Alkylation of phenols. Friedel-Crafts Alkylation and Acylation of Phenols Phenol Alkylation

Alkylation of phenol with epichlorohydrin

The addition reaction of phenol to epichlorohydrin can proceed in a neutral, acidic or alkaline medium.

In a neutral medium, epichlorohydrin and phenol must be heated for several hours at 155-160°, otherwise the reaction does not proceed. Chlorohydrin phenyl ester is obtained, but in poor yield.

When comparing the action of acidic and alkaline catalysts, it was found that the latter give the best yields.

Marple, Shokal and Evans, using stannous chloride as an acid catalyst, developed a technical process for the preparation of aromatic ethers of chlorohydrin, especially esters of substituted phenols. Instead of tin tetrachloride, it is more expedient to use it in a complex with isopropyl alcohol SnCl4(C8H7OH)4.

Lefebvre and Loeva found that BF3 is a particularly effective catalyst for the reaction of epichlorohydrin with phenol. In its presence, the addition proceeds already at 0°, which minimizes the formation of high molecular weight products. In a benzene solution with a 4-fold excess of phenol and a reaction temperature of 0 °, chlorohydrin esters with phenol, o-, m- and p-cresol, p-bromophenol and thymol are obtained (yield 50%).

The reaction of epichlorohydrin with phenols in the presence of alkali can proceed in two directions.

1) When using catalytic amounts of alkali metal hydroxide, the degree of conversion to phenyl ester of chlorohydrin is 35%.

2) When using equimolecular amounts of alkali metal hydroxide, phenol and epichlorohydrin, the intermediate chlorohydrin phenyl ester is converted to glycidol ester:

Aryl esters of glycidol, obtained by heating equimolecular amounts of epichlorohydrin, phenol, and an aqueous solution of alkali, were first obtained and described by Lindemann.

The addition of epichlorohydrin to a solution of sodium phenolate at 40--70°C leads to a low yield of glycidol phenyl ester. On the contrary, Marlet obtained aromatic esters of glycidol in a satisfactory yield by reacting epichlorohydrin, phenol, and the calculated amount of sodium hydroxide at ordinary temperature for several days.

Davis, Nant, and Skinner studied the preparation of aromatic chlorohydrin esters by replacing caustic alkalis with alkaline earth metal hydroxides. Of the hydroxides of magnesium, calcium, barium, the best results were obtained with calcium hydroxide.

The method for the synthesis of glycidic esters of phenols with a yield of 55--65% of the theoretical one consists in the fact that first equimolecular amounts of epichlorohydrin and phenol are subjected to short-term heating, and then, when heated, an excess of an aqueous solution of caustic alkali is introduced.

In the interaction of glycidic esters of substituted phenols with salts of tertiary amines, quaternary ammonium compounds are formed. For example, in the case of trimethylamine hydrochloride, the reaction proceeds as follows:

To obtain polyglycide esters of polyhydric phenols, it is recommended to use 1.5 mol of epichlorohydrin for each hydroxyl group of the phenol. At the same time, 92--97% of alkali from the calculated one is taken. After separating the excess of epichlorohydrin, the resulting chlorohydrin groups are converted by an excess of alkali into epoxy groups.

Alkylation of phenols under IFC conditions

For the alkylation of phenols, interfacial catalysis can be successfully used [ 17]. This method uses a two-phase system, such as water-methylene chloride: an alkyl halide is added to phenol in the presence of a catalytic amount of quaternary ammonium salts, and the phase equilibrium is maintained by effective mixing. In summary, the process can be represented as a diagram:

The phenolate ion and the quaternary ammonium salt is in equilibrium with the quaternary ammonium phenoxide, which is extracted into the organic phase where alkylation occurs. Quaternary ammonium halide, in turn, goes into equilibrium with its hydroxide in the aqueous phase.

The advantage of this synthesis method is that:

The phenolate ion is less solvated in the organic phase, the reaction rate is reduced to a lesser extent by steric effects, and only O-alkylation is achieved, and the rate increases;

The main one is only the aqueous phase, which protects the alkylating agent (halide, sulfate, etc.) from destruction due to hydrolysis;

Non-stoichiometric amounts of ammonium salt are used.

Quaternary ammonium and phosphonium salts such as benzyltriethylammonium chloride (TEBAC), tetrabutylammonium hydrogen sulfate (TBAGS), etc. can be used as a catalyst, polymer-bound crown ethers and cryptans can also be used.

The interfacial method is applicable to a wide range of phenols with electron-withdrawing and electron-donating substituents, P naphthols, and hindered phenols. In most cases, when using various alkylating agents, the yields of esters are high (70-95%).

This method can be successfully used in the synthesis of aryl ethers of glycols, as well as in the preparation of monoalkyl ether dihydric phenols.

The reaction of epichlorohydrin with aromatic hydroxy compounds has been studied in particular detail, since technically valuable products are formed as a result. Most often, phenols are used as starting compounds, especially polyhydric, mono- or multinuclear ones.

For the alkylation of phenols, protic acids (H 2 SO 4, H 3 PO 4) or catalytic oxides of the type A1 2 O 3 or aluminosilicates are used. AlCl 3 is not used, since phenols form inactive ArOAlCl 2 salts with it, which do not catalyze the process. The activity of the catalyst decreases in the series H 2 SO 4 > H 3 PO 4 > p-toluenesulfonic acid.

When H 2 SO 4 is used as a catalyst at temperatures of 50–120 °C, the formation of sulfonated phenols is possible in the system. If the catalyst is p-toluenesulfonic acid, then the process proceeds under milder conditions, which makes it possible to obtain a high yield of p-alkyl derivatives and a decrease in the amount of polymerization products.

A common disadvantage of using acid catalysts in liquid form is the need to wash the products from the catalyst and the significant formation of wastewater.

Heterogeneous catalysts are devoid of this disadvantage, but their activity is significantly lower, which implies that the process is carried out at higher temperatures: the liquid-phase process using KU-2 ion-exchange resins as a catalyst proceeds at temperatures of 120 ° C, and the alkylation of o-cresol and xylene in the vapor-gas phase in the presence of aluminosilicates - at 200-400 °C.

Tertiary alcohols and olefins are used as alkylating agents. The mechanism is similar to the alkylation of benzene with acids.

The phenol hydroxyl group increases the electron density in the ring and facilitates the introduction of the o- and p-position alkyl groups. The p-isomer is the most stable (o-isomers undergo isomerization with the migration of the alkyl group to the p-position). The ratio of isomers depends on the process conditions. Increasing the temperature and duration of the reaction leads to an increase in the content of p-isomers from 60-80% to 95%.

Alkylation to the core can proceed sequentially with the formation of mono-, di- and trialkylphenols. Of the dialkylphenols, 2,4-dialkyl derivatives predominate.

During the alkylation of phenols, the rate of each subsequent stage decreases (the introduction of the first alkyl group occurs quickly, the second - slowly, the third - even more slowly). The composition of the products depends on the rate of transalkylation: with an increase in temperature, catalyst activity, and reaction time, the content of monoalkylphenols increases.

The process conditions are similar to the alkylation of benzene, but unlike benzene, for which high selectivity for the monoalkyl derivative is provided only with a large excess of benzene, monoalkylphenols are obtained with small excesses of phenol relative to the alkene and the selectivity for monoalkylphenol increases mainly due to the transalkylation reaction . To obtain di- and trialkyl derivatives, an excess of an alkylating agent is used.

By-products formed are polymerization products of alkenes and longer side chain alkylphenols. When phenols are alkylated with higher alkenes, especially with branched chains, a side chain depolymerization reaction is observed with the formation of a shorter alkyl group. To reduce the yield of by-products, it is advisable to lower the temperature, use a less active catalyst or reduce its concentration, or dose alkene into the reaction mass.

Formation of ethers of phenols by alkylation of phenolates

Alkylation formation of ethers of phenols). Alkylation of phenols produced in most cases using dimethyl or diethyl sulfate or diazomethane. Methylation with diazomethane proceeds especially smoothly under mild conditions. Methyl and ethyl esters of phenols almost always have sharp melting and boiling points.95

Significant research has been carried out on the development of protective additives for sour diesel fuels, for which the problem of reducing corrosion in the presence of moisture is most acute. For this purpose, compounds from a number of amines, phenols (alkylated pyrocatechol) and others have been studied. 36, 46, 49, 50 consider sufficient. The protective effect of antioxidants and metal deactivators in sour diesel fuel can be seen from the following data 36, 50

The use of alcohols and alkyl halides is justified only in cases where they are not can be replaced by alkenes. Examples of such processes are the methylation of phenols, alkylation with benzyl chloride, triphenylchloromethane, and other similar reactions.

To obtain phenols alkylated exclusively in the ortho position, the attack of the alkylating agent must be carried out from the side of the hydroxyl group, as, for example, in the Kolky method 4, 5 (Example 6.1).309

Alkylation of phenols. Alkylation of phenols produces alkoxy compounds of the Ar-O-Alk type. For alkylation, as in the case of amines, alcohols and alkyl halides (in most cases ethyl chloride) can be used.

Synthetic depressants, which proved to be rather highly effective and have gained wide technical distribution, include the condensation product of naphthalene with chlorinated paraffin (AzNII depressant, paraflow), as well as condensation products of phenol alkylated with chlorinated paraffin and phthalyl chloride, produced by foreign industry under the name santonur.73

The action of complex organic inhibitors, which are the product of the condensation of ethylene oxide with a light fraction of crude coal phenols alkylated with shale gasoline, both individually and in combination with chromates, is shown in Table. 19.22. The effectiveness of these inhibitors is not very high, since the maximum value of y is about 6.332
Copolymer of butadiene with styrene, phenol Phenol alkylated with polymer Clay in xylene, 50-60 C, 20 h 4

Alkylation of alcohols and phenols. Alkylation of a hydroxy group by the action of alcohol and mineral acid has limited application, mainly for compounds of the naphthalene and anthracene series. In the benzene series, alcohol in an acidic medium can be resorcinol and phloroglucinum are especially easily alkylated. Dimethyl sulfate and methyl esters of benzene- and p-toluenesulfonic acids are widely used for alkylation and, in particular, for methylation of hydroxy compounds. The process is usually carried out with an excess of alkali

Synthesis of p-tert. octi.l, phenols (alkylation with increased te.shge-469

The method is not suitable for O-alkylated phenols, alkylated anilines and unsaturated compounds. In all these cases, due to the addition of bromine, improved results are obtained.363

Phenols alkylated in both the ortho and para positions, especially with tertiary alkyls, can be oxidized with silver oxide or potassium ferricyanide to aroxyls - substances with the properties of free radicals (E. Müller)

In the presence of zeolites, other organic compounds capable of interacting with acid sites also undergo alkylation. One such compound is phenol.

Alkylation of phenol on a conventional acid catalyst is complicated by the formation of side products - esters and complexes of the catalyst-phenol hydroxyl groups. However, when phenol is alkylated with olefins on the rare earth form of zeolite X at -°C, these side processes are not observed 61.

As in the case of other benzene derivatives, phenol alkylation results mainly in substitution in the para and o/7o positions, which corresponds to Brown's selectivity rule. The formation of l/ta-isomers occurs either after prolonged contact of the alkylation products with the catalyst, or with an increase in the reaction temperature. It has been established that the appearance of n/exa isomers in the products of phenol alkylation with isobutylene is associated with the isomerization of ortho- and ap-isomers via transalkylation 54.393

Based on the research carried out, A. A. Petrov proposed the demulsifier OlPASFE (oxyethylated synthetic phenol, alkylated with a-olefins from paraffin cracking). For its synthesis, it was proposed to use olefins with a chain of medium length C12-C13, which seems somewhat illogical, since it does not fit with the author's conclusions about the optimal length of the alkyl chain (Cd). The content of ethylene oxide in the demulsifier OlPASFE should be 30-40 mol per 1 mol of alkylphenol or 80-85 wt. % of the finished product.

The raw material for its production was coal phenol alkylated with a fraction of cracked kerosene with a boiling range of -°. The UFE demulsifier was also made on the basis of coal tar phenol, but it was subjected only to oxyethylation (without alkylation) with 7–8 moles of oxyethylene.

Demulsifiers OP-7 and OP-10 were reaction products of mono- and dialkylphenols obtained on the basis of synthetic phenol with ethylene oxide. The degree of oxyethylation was 6-7 and 9-10, respectively.

The demulsifier OP-10 was tested on an industrial scale during the dehydration of Zolnenskaya, Zhiguli and Kalinovskaya oils. During these tests, conditioned oil was obtained at the following flow rates OP-10 (g/t): Zolnenskaya oil - 100 Zhigulevskaya - Kalinovskaya - 80. The consumption of the NCHK demulsifier during the dehydration of these oils was 3-5 kg/t.77

At present, the world scientific practice has accumulated significant factual material on the directed alkylation of phenols. Alkylation can be carried out in the direction of preferential formation of n-monoalkylphenols, as well as o,p- and o,o-dialkylphenols.91

A number of sterically hindered phenols are alkylated with dimethyl sulfate under the conditions of interfacial catalysis. When replacing methyl iodide with dimethyl sulfate, it turned out that a stoichiometric amount of catalyst 5 is required for complete reaction. 5.4 shows the results of alkylation of several

Phenol homologues can be obtained by analogous reactions from sulfo-, halogen-, or amine derivatives of benzene homologues. However, there are also methods for introducing an alkyl group into the phenol core. Alkylation of phenols is easier than the alkylation of benzene and its homologues due to the activating action of the hydroxyl group. Zinc chloride can be used as a catalyst, and alcohols can be used as alkylating agents 346

It is also possible to obtain higher phenols by alkylating lower phenols from acid catalysts. Substitution goes in para-position

With this modification, solubility in aromatic hydrocarbons is achieved faster than compatibility with other additives. Here the latest data pointing to the stepwise nature of the transition deserve attention. radical. However, for compatibility with neutral substances (hydroxy fatty acid glycerides, coumarone resins, resin esters, butyric alkyds), it is necessary to increase the chain length of the substituent radical. An even greater elongation is necessary for compatibility with fatty oils, hard oils, pitches, mineral oils, stearin pitch, rubber, etc. Thus, it is most difficult to obtain the properties most valuable for varnishes.436

Alkylation of 2,6-dialkylphenols. Some examples of the use of reactions of 2,6-dialkylphenols with olefins and dienes have already been noted before. Before the advent of the ortho-alkylation method, this method was limited to only a few examples. However, in the last decade, 2,6-dialkylphenols have been increasingly used to obtain 4-substituted hindered phenols. Alkylation of 2,6-dialkylphenols proceeds under milder conditions than alkylation of unsubstituted phenol and is possible even when interacting with cyclopropenyl, cycloheptatrienyl and other stable ions41

Of the 15 surfactant samples, the KA),2UFE16,4 reagent (condensation product of the 44-° fraction at 2 mm Hg of coal phenols, the alkylated fraction -° of cracked gasoline with 16 molecules of ethylene oxide) proved to be the most effective demulsifier for Devonian oil. Based on laboratory studies of demulsifying properties in terms of the amount of settled water and residual water in oil, we recommended this reagent for industrial testing.

Compounds of the G-16 type are widely represented by sulfonates of phenol alkylated with tri- or tetraisobutylene or tetra- or pentapropylene. Most of the relevant patents relate to methods for alkylating phenol with these olefins. Several unusual catalysts for this process include stannous chloride, phosphotungstic and phosphomolybdic acids, phosphoric acid-activated silica, and acid-activated clays. Sulfuric acid is also used, but in this case, unless special precautions are taken 47, significant depolymerization occurs, which reduces the yield of the product.

Phenol and its homologues are alkylated even more easily than naphthalene. It is especially easy to introduce the radical decyl-, keryl (see page) and other radicals. Examples of obtaining low molecular weight alkyl derivatives are contained in the patents of a number of companies. High-quality detergents are obtained from phenols alkylated with normal hydrocarbons. A similar product was described by Flett

To complete the reaction, an excess of polymer distillate (% of phenol) is used. Alkylation is carried out at °C and completed with a phenol content of not more than 0.5%. The duration of the process is 10-12 hours. The main disadvantage of the process is its duration, as well as the use of a large amount of a corrosive catalyst.83

Course project for the discipline:

"Theory of chemical processes of organic synthesis"

Alkylation of phenol with olefins

Supervisor: Associate Professor, Ph.D. n. Nesterova T.N.

1. Thermodynamic analysis

When analyzing the process of alkylation of phenol with olefins, it is necessary, first of all, to determine which substances will be formed. There are two reaction centers in the phenol molecule: an aromatic ring and a hydroxyl group. When an alkene reacts with an OH group, ethers are formed, which can easily rearrange into alkylphenols. It has been established that alkylphenols are predominantly formed by direct alkylation to the core. Let us consider the influence of the hydroxyl group in the phenol molecule on the aromatic ring. The substituent is characterized by a large positive conjugation effect compared to a negative inductive effect. It strongly activates the ortho and para positions, so 3-alkylphenols will be found in products in very small quantities. The process can go further with the formation of mono-, di- and trialkylphenols. Because Since we are interested in mono-substituted phenols, it is necessary to carry out the process with a small excess of phenol.

The process proceeds through the formation of an intermediate carbocation from the alkene, which is an easily isomerized and active particle. The following is possible: positional and structural isomerization, cracking reaction, interaction with unsaturated hydrocarbons, oligomerization. The isomerization reaction, as a rule, is ahead of all other transformations, therefore, during alkylation with olefins, we obtain all kinds of isomers. Under relatively non-rigid conditions, only positional isomerization reactions occur.

Considering the above, we will select substances that are most likely to be in an equilibrium mixture:

(a)-2-(2-hydroxyphenyl)tetradecane; (b)-3-(2-hydroxyphenyl)tetradecane;

(c)-4-(2-hydroxyphenyl)tetradecane; (d)-5-(2-hydroxyphenyl)tetradecane;

(i)-6-(2-hydroxyphenyl)tetradecane; (f)-7-(2-hydroxyphenyl)tetradecane;

(g)-2-(4-hydroxyphenyl)tetradecane; (h)-3-(4-hydroxyphenyl)tetradecane;

(m)-4-(4-hydroxyphenyl)tetradecane; (n)-5-(4-hydroxyphenyl)tetradecane;

(o)-6-(4-hydroxyphenyl)tetradecane; (p)-7-(4-hydroxyphenyl)tetradecane.

We choose (n-1) independent reactions, where n is the number of formed components:

ab; bc; cd; di; if; ag; gh; hm;

We write the reaction rate constants:

Kx a =; Kx b =; Kx c =; Kx d =; Kx i =; Kx g =; Kx h =;

Kx m =; Kx n =; Kx o =; Kx p =.

Let us express the concentration of each component in terms of the reaction constants and the concentration of the component g:

=; =; =; =;

=; =; =

For systems obeying Raoult's law, we can write for:

In its turn:

= - =

In thermodynamic analysis, to calculate the reaction constants, accurate enthalpy and entropy data are required, and if the process is in the liquid phase, then critical parameters for calculating the saturated vapor pressure are desirable if these are experimental data.

Enthalpies and entropies. Benson's method will not give exact values in our case. For example, consider 2-(4-hydroxyphenyl)tetradecane and 3-(4-hydroxyphenyl)tetradecane. These substances will have the same contributions: Cb-(O)-1; Cb-(H)-4; Cb-(C)-1; O-(H,Cb)-1; CH-(2C,Cb)-1; CH 2 -(2C)-11; CH 3 -(C)-2. Therefore =0 and =0. An exception is the reaction (a)(g). =-9.9 kJ/mol due to ortho-interaction in the molecule (a); =-Rln2 kJ/(mol K) due to the rotation of the aromatic nucleus in the molecule (g).

Saturated steam pressure. Using the Liedersen or Jobak method, you can calculate the critical parameters, and then and . But the contributions for all substances are the same, so the critical parameters are equal, therefore, equal, they can be ignored, =. Pressure has no effect on the reaction. The use of a diluent will adversely affect the reaction rate.

Temperature dependence of the reaction rate constant.

Kx a	Kxb	Kx c	Kx d	Kx i	Kxg	Kx h	Kx m	Kx n	Kxo
298	1	1	1	1	1	27,23829	1	1	1	1
350	1	1	1	1	1	15,03934	1	1	1	1
400	1	1	1	1	1	9,827575	1	1	1	1
450	1	1	1	1	1	7,058733	1	1	1	1
500	1	1	1	1	1	5,416903	1	1	1	1
600	1	1	1	1	1	3,641561	1	1	1	1
700	1	1	1	1	1	2,742201	1	1	1	1
800	1	1	1	1	1	2,216706	1	1	1	1
900	1	1	1	1	1	1,878661	1	1	1	1
1000	1	1	1	1	1	1,645737	1	1	1	1

The sum of the mole fractions of all components is 0.95, because The reaction is carried out in excess of phenol.

Dependence of the mole fraction of components on temperature.

T, K	N	a	b	c	d	i	f	g	h	m	n	o	p
298	0,95	0,0056	0,0056	0,0056	0,0056	0,0056	0,0056	0,1527	0,1527	0,1527	0,1527	0,1527	0,1527
350	0,95	0,0099	0,0099	0,0099	0,0099	0,0099	0,0099	0,1485	0,1485	0,1485	0,1485	0,1485	0,1485
400	0,95	0,0146	0,0146	0,0146	0,0146	0,0146	0,0146	0,1437	0,1437	0,1437	0,1437	0,1437	0,1437
450	0,95	0,0196	0,0196	0,0196	0,0196	0,0196	0,0196	0,1387	0,1387	0,1387	0,1387	0,1387	0,1387
500	0,95	0,0247	0,0247	0,0247	0,0247	0,0247	0,0247	0,1337	0,1337	0,1337	0,1337	0,1337	0,1337
600	0,95	0,0341	0,0341	0,0341	0,0341	0,0341	0,0341	0,1242	0,1242	0,1242	0,1242	0,1242	0,1242
700	0,95	0,0423	0,0423	0,0423	0,0423	0,0423	0,0423	0,1160	0,1160	0,1160	0,1160	0,1160	0,1160
800	0,96	0,0497	0,0497	0,0497	0,0497	0,0497	0,0497	0,1103	0,1103	0,1103	0,1103	0,1103	0,1103
900	0,95	0,0550	0,0550	0,0550	0,0550	0,0550	0,0550	0,1033	0,1033	0,1033	0,1033	0,1033	0,1033
1000	0,95	0,0598	0,0598	0,0598	0,0598	0,0598	0,0598	0,0985	0,0985	0,0985	0,0985	0,0985	0,0985

We build a graph of the “mole fraction - temperature” dependence for two substances (g) and (a), because paraalkylphenols will merge into one line, the same will happen with orthoalkylphenols.

It can be seen from the graph that as the temperature increases, the mole fraction of paraalkylphenols decreases. Therefore, the process should be carried out at low temperatures.

As a rule, paraalkylphenols are used as an intermediate product for the synthesis of nonionic surfactants by their oxyethylation:

To obtain products with better biodegradability, a less branched alkyl is needed.

2. Adiabatic temperature difference in the reactor

(there is an error in the calculation of the enthalpy of alkylphenol, the reaction is exothermic)

Let us calculate the thermal effect of the reaction and the temperature of the mixture at the end of the reaction in the adiabatic reactor. Let us assume that the alkylation of phenol with tetradecene-1 yields 7-(4'-hydroxyphenyl)tetradecane.

The amount of heat entering the reactor is the sum of the heat introduced with phenol and olefin. Phenol consumption 1.1 mol/hour, olefin consumption 1 mol/hour.

Q in = =

141911.6 (J/h)

It is necessary to find the temperature of the outgoing mixture from the reactor, for this it is necessary to know the temperature of the incoming mixture. After mixing phenol and olefin, their average temperature will be equal to T in, cf. Thus Q in is equal to:

Using the Microsoft Excel program and the “selection of parameters” function, as well as the previously determined dependences of the heat capacity on temperature and the amount of heat entering the reactor, we find T in, cf.

T in, cf = 315.13 K, while = 110.45 (J / mol), = 328.84 (J / mol).

The enthalpy of reaction from the corollary of Hess's law is:

= - =

= - ( + )

229297 + (98386.5 + 227532) = 96621.5 (J/mol)

The reaction is endothermic, proceeding with a decrease in the amount of heat in the entire system.

Assume that the degree of conversion of the olefin is 100%.

The amount of heat leaving the pre-contact zone with the mixture is:

Q out \u003d Q in - Q reactions

Q out \u003d 141911.6 - 96621.5 \u003d 45290.1 (J / h)

Also, the amount of heat leaving with the mixture can be calculated through T out, cf.

Thus T out, cf = 171.26 K.

3. Process kinetics

Reaction mechanism:

1. Olefin protonation occurs with the formation of a carbocation:

2. A -complex is formed:

3. A -complex is formed. This stage is limiting.

4. Detachment of a proton from an aromatic nucleus:

The separated proton can interact with the olefin, and the process will start again or with the catalyst, then the reaction will stop.

Sulfuric acid is most often used in industry as catalysts - protic acids. It is the most active among other available and cheap acids, but at the same time it also catalyzes side reactions, additionally leading to phenol sulfonation and olefin sulfonation and forming phenol sulfonic acids HOC 6 H 4 SO 2 OH and monoalkyl sulfates ROSO 2 OH, which also participate in catalysis. process. With sulfuric acid, alkylation with n-olifins occurs at 100-120ºС. Another catalyst that does not cause side reactions of sulfonation and is milder in its action is p-toluenesulfonic acid CH 3 C 6 H 4 SO 2 OH. However, it has less activity and greater cost than H 2 SO 4 .

With these catalysts, phenol alkylation proceeds as a homogeneous reaction according to the following equation:

It can be seen from the equation that with an increase in the concentration of one of the substances, the reaction rate will increase linearly. In production, they work with a relatively small excess of phenol relative to olefin, and even with their equimolar amount. If H 2 SO 4 is taken as a catalyst, then it is used in an amount of 3-10% (wt.). An increase in temperature will have a positive effect on the reaction rate, because. the process is endothermic.

4. Process Technology

For the alkylation of phenols, a batch process is used. The reaction is carried out in an apparatus with a stirrer and a jacket for heating with steam or cooling with water. Phenol and a catalyst are loaded into it, heated to 90 ºС, after which liquid tetradecene-1 is fed with stirring and cooling at a temperature of 25 ºС (melting point -12.7 ºС). They do it this way because if you first load the catalyst with an olefin, then oligo- and polymerization reactions can take place there. In the second half of the reaction, on the contrary, it is necessary to heat the reaction mass. The total duration of the operation is 2-4 hours. After that, the reaction mass is neutralized in the mixer with 5% alkali, taken in an equivalent amount to the acid-catalyst, heating the mixture with live steam. The neutralized organic layer of crude alkylphenols is separated from the aqueous salt solution and sent to vacuum distillation, when water, olefin residues and unconverted phenol are distilled off.

Task number 1

During the oxidative ammonolysis of propylene, a reaction mass of the following composition was obtained (% wt.): - propylene - 18.94, acrylic acid nitrile - 54.85, acetonitrile - 13.00, acetaldehyde - 1.15, propionaldehyde - 5.07, hydrocyanic acid - 4.99, formaldehyde - 0.80, CO 2 - 1.20. Calculate the degree of conversion of the reagents, the selectivity of the process for each of the reaction products per each reagent, and the yield per passed raw material of each of the reaction products per one reagent.

Solution: the most probable scheme of transformations during oxidative ammonolysis:

Let's make a distribution table. share ref. substances:

Component	% wt.	M	G	Number of mol. ref. in-va
Component	% wt.	M	G	propylene	ammonia	oxygen
propylene	18.94	42.08	0.4501	b1 = 0.4501	0	0
acrylonitrile	54.85	53.06	1.0337	b 2 \u003d 1.0337	d 1 \u003d 1.0337	0
acetonitrile	13.00	41.05	0.3167	b 3 \u003d 0.3167	d 2 \u003d 0.3167	0
acetaldehyde	1.15	44.05	0.0261	b 4 \u003d 0.0261	0	e 1 \u003d 0.0261
propionaldehyde	5.07	58.08	0.0873	b 5 \u003d 0.0873	0	e 2 \u003d 0.0873
hydrocyanic acid	4.99	27.03	0.1846	b 6 \u003d 0.1846	d 3 \u003d 0.1846
formaldehyde	0.80	30.03	0.0266	b 7 \u003d 0.0266	0	e 3 \u003d 0.0266
carbon dioxide	1.20	44.01	0.0273	b 8 \u003d 0.0273	0	e 4 \u003d 0.0273

The degree of propylene conversion is determined by the formula:

The degree of conversion of ammonia: and oxygen.

Selectivity for propylene is calculated by the formula: , for ammonia: , for oxygen: . The calculation results are given in Table. one.

Table 1

Examination: , .

Yield per passed raw material in terms of propylene is calculated by the formula: . The results are presented in table. 2:

table 2

Task 2.

For the isomerization of n-pentane to isopentane, calculate the temperature difference in the reaction zone for the adiabatic process. The process proceeds at a pressure of 1 atm. The reactor is fed with 10 t/h of n-pentane at 650K and 25 moles of hydrogen per 1 mole of pentane at 900K. The degree of conversion of n-pentane 10, 20, 50, 70%. The selectivity of the process is 100%. The heat loss to the environment is 3% of the heat input to the reactor. Carry out a graphical and analytical dependence of the adiabatic temperature difference on the degree of conversion of n-pentane. Argue the technological methods used in the implementation of the industrial isomerization of hydrocarbons.

Solution: The reaction scheme is shown in fig. one:

Rice. 1. Isomerization of n-pentane.

The scheme of the reactor is shown in fig. 2.

Rice. 2. Scheme of the thermal balance of the reactor.

The heat entering the reactor is determined by the formula:

, (1) here:

Determined for T = 650K from a polynomial equation obtained from tabular data;

Determined for Tin from the polynomial equation for Ср n-pentane using the function "Search for a solution" of the program "Microsoft Excel";

For 900K determined from tabular data;

Determined for Tin from a polynomial equation for Cp of water using the "Search for a solution" function of the Microsoft Excel program;

, ,

Using the "Search for a solution" function of the Microsoft Excel program, the value of Tin = 685K was determined using the least squares method.

Enthalpy of reaction at a given T in:

The heat of reaction is determined by the enthalpy of the reaction, the mass flow rate of the reactant, and the degree of conversion of the reactant.

Consider an example where the conversion rate is .

According to the heat balance equation:

Here: ,

Determined for T out of a polynomial equation using the "Search for a solution" function of the Microsoft Excel program;

Determined for T out of the polynomial equation for Ср n-pentane using the function "Search for a solution" of the program "Microsoft Excel";

Determined for T out of the polynomial equation for Ср and-pentane using the function "Search for a solution" of the program "Microsoft Excel";

Using the function "Search for a solution" of the program "MicrosoftExcel" by the method of least squares, the value of Tout = 687K was determined.

Similarly, we determine the values of T out for different values of the degree of conversion. The obtained values are presented in table 3.

Table 3

α	T out
0,1	662
0,2	663
0,5	667
0,7	669

The graphical dependence of the temperature difference at the inlet and outlet on the degree of conversion is shown in Figure 3.

Rice. 3. Dependence of the adiabatic temperature difference on the degree of conversion.

As the degree of conversion increases, the temperature drop in the reaction zone decreases linearly.

Copyright JSC "Central Design Bureau "BIBCOM" & LLC "Agency Book-Service" Ministry of Education and Science of Russia Federal State Budgetary Educational Institution of Higher Professional Education "Kazan National Research Technological University" E.N. Cherezov, G.N. Nugumanova, D.P. Shalyminova ALKYLATION OF PHENOL WITH OLEFINS AS A METHOD OF SYNTHESIS OF STABILIZERS FOR POLYMERS Monograph Kazan KNRTU 2013 Copyright OJSC Central Design Bureau BIBCOM & LLC Agency Book-Service UDC 541.64:66 (076.5) Cherezova E.N. Alkylation of phenol with olefins as a method for the synthesis of stabilizers for polymers: monograph / E.N. Cherezov, G.N. Nugumanova, D.P. Shalimynov; M-in the image. and Science of Russia, Kazan. nat. research technol. un-t. - Kazan: Publishing House of KNRTU, 2013. - 80 p. ISBN 978-5-7882-1435-1 A review of literature data on the methods of alkylation of phenol and its derivatives with olefins is presented. The catalytic systems and process conditions are given, as well as some technological schemes for the production of substituted phenols by the alkylation method. The monograph is intended for graduate students, masters studying the discipline "Chemistry and Technology of Additives for Polymers", "Aging and Stabilization of Polymers", as well as scientists. Prepared by the Department of Synthetic Rubber Technology. Published by decision of the editorial and publishing council of the Kazan National Research Technological University Reviewers: Ph.D. tech. Sciences, Assoc. KSPEU Yu.A. Averyanova, Ph.D. chem. Sciences, Assoc. K(P)FU S.R. Egorova ISBN 978-5-7882-1435-1 Cherezova E.N., Nugumanova G.N., Shalyminova D.P., 2013 Kazan National Research Technological University, 2013 Service» INTRODUCTION The protective effect of compounds of the class of shielded (sterially hindered) phenols (SFP) has been known for more than a hundred years (the first patent was filed in 1870), but they found wide application about fifty years ago. This is due to the introduction of polymeric materials into many areas of human activity - technology, healthcare, everyday life. In particular, PZF occupy a leading position in the stabilization of polymers, and their share is increasing by 2-3% annually, which is explained by the tightening of sanitary and hygienic standards and environmental safety requirements both for the stabilizers themselves and for their production, and the refusal in connection with this in some cases from the use of toxic arylamine antioxidants. In addition, phenolic antioxidants have little effect on the color of the polymer and make it possible to obtain white or brightly colored products. A number of phenolic antioxidants can be used in products that come into contact with food and other biological media. To a large extent, this is the reason for the surge of attention of well-known additive manufacturing companies such as Chemtura (USA), Songwon Industrial Co (USA), Sumitomo (Japan) to the search for new structures and the development of more technological methods for the synthesis of known phenolic antioxidants. (FAO). As alkylating agents, olefins, alcohols and alkyl halides can be used. Of particular interest in terms of the possibilities of FAO synthesis is the method consisting in the alkylation of phenol with olefins, one of the key reactions of organic synthesis. Olefins are preferred primarily due to their availability and lower cost; moreover, in the vast majority of cases, the mechanism of alkylation with alcohols goes through the stage of formation of the corresponding alkenes, and, thus, the use of alcohols does not have any advantages in terms of organization of production, its simplicity and yields. Book-Service Agency» products. The use of alcohols and alkyl halides is justified only in cases where they cannot be replaced by alkenes. At present, the technology of alkylation of phenol with isobutylene, which is used to obtain such well-known PAOs as 2,6-di-tert.-butyl-4methylphenol (Agidol 1, Ionol), 3,5-di-tert.-butyl-4hydroxyphenylpropionic ester acid and pentaerythritol (Irganoks 1010, Phenozan 23) and a number of others. The processes of alkylation of phenol with olefins of a different structure are used very limitedly. At the same time, there is evidence of a rather high efficiency of the stabilizing effect of methylbenzylated phenols (MBF), shown in the works of Ya.A. Gurvich. It should be noted that MBFs are low-viscosity liquids. This state of aggregation of stabilizers is necessary for introduction into latexes and liquid polymers. This monograph presents a review of the literature on methods for the production of FAO by the reaction of alkylation of phenol with olefins. 4 Copyright JSC "Central Design Bureau "BIBCOM" & OOO "Agency Kniga-Service" 1 CONDITIONS AND MECHANISM OF THE REACTION OF PHENOL ALKYLATION 1.1 Thermal alkylation of phenol with olefins Phenols are capable of entering into various chemical reactions, both at the hydroxyl group and at the aromatic ring. The chemical properties of phenols are determined to a large extent by the existence of a static effect of interaction between the phenolic hydroxyl and the aromatic ring. The stabilization energy of phenol is 40 kcal/mol. Table 1 Distribution of the total (σ + π) electronic charge in different positions of the benzene ring of phenol Phenol Position in the ring relative to the OH group 2 -0.110 3 -0.028 4 -0.079 5 -0.028 6 -0.110 associated with the delocalization of the lone pair of electrons. The stabilization effect of the phenolate anion is even greater. The growth of electron density in the molecule of phenol (and its derivatives) (Table 1), and especially in the phenolate ion, leads to the fact that these substances are prone to electrophilic substitution reactions. 5 Copyright OJSC Central Design Bureau BIBCOM & LLC Agency Kniga-Service In this case, all positions of the benzene ring are activated, but especially ortho- and para-positions, which is the result of the coordinated action of static (facilitation from the point of view of energy approach to ortho- and parapositions) and dynamic (lower energy of the transition state with ortho- and para-substitution) factors. The main electrophilic substitution reactions characteristic of phenols are: halogenation, sulfonation, nitration, nitrosation, azo coupling, carboxylation, carbonylation, reactions with sulfur and its compounds, hydrogenation, dealkylation, disproportionation, alkylation. One of the widely used technological methods in organic synthesis is the alkylation of phenols with alcohols and olefins in the presence of acid catalysts and Lewis acids. The phenol alkylation reaction is one of the most important in the synthesis of phenolic stabilizers. Of greatest practical importance is the process of alkylation of phenols with olefins and cycloolefins, which includes a number of sequential and parallel reactions. According to the data presented in the work, a mixture of mono-, di-, trialkylated phenols is formed during the main phenol alkylation reaction. The authors of the work proposed a probable mechanism for the non-catalytic reaction of alkylation of phenol with olefins through the intermediate formation of a quinoid complex according to the following schemes: a) with the production of ortho-alkylphenol with an attached oxyphenyl radical to the first carbon atom of the aliphatic chain: Agency Kniga-Service "b) to obtain ortho-alkylphenol with an attached hydroxyphenyl radical to the second carbon atom of the aliphatic chain. In the case of thermal non-catalytic alkylation of phenol with higher olefins, as well as in the case of alkylation with lower olefins, alkylphenols with substituents are formed almost exclusively in the ortho position. In this case, the yield of ortho-alkylphenols and the selectivity of the alkylation process depend on many factors: reaction temperature, contact time, pressure, ratio of reagents, etc. In general, increasing the process temperature increases the yield of ortho-alkylphenols. However, an excessive increase in temperature leads to a shift in equilibrium towards the formation of initial reagents (table 2). This fact is confirmed by the values of the Gibbs energies and the equilibrium constant of the alkylation process, which decrease as the temperature of the process increases. In the absence of catalysts in the alkylation of phenol with olefins, it is not desirable to increase the process temperature above 400°C. An example is the thermal orthoalkylation of phenol with α-olefins in a flow reactor. During the alkylation of phenol with n-nonene-1 at constant temperature (370°C), pressure (42.2 MPa) and molar ratio of reagents (6.7:1), an increase in the reaction time from 1.25 to 1.8 h is accompanied by an increase in the conversion olefin from 65 to 85;6 (Table 3). However, an increase in the reaction time is accompanied by a decrease in the yield of monoalkylphenols from 79 to 60%. There is also a decrease in the selectivity of the alkylation process for "extremely attached" alkylphenols. 7 Copyright JSC "Central Design Bureau "BIBCOM" & OOO "Agency Kniga-Service" Table 2 Equilibrium constants of reactions, isomerization of some alkylphenols at different temperatures Alkylphenol initial final ortho-isomer meta-isomer ortho-isomer para-isomer para-isomer meta-isomer 300 3.22 1.08 2.97 Temperature, ºС 350 400 450 2.93 2.70 2.52 1.08 1.07 1.07 2.72 2.53 2.37 500 2.38 1.06 2 ,24 At a temperature of 370°C, an increase in the pressure of phenol alkylation with nonene from 4.2 to 5.3 MPa, i.e. by 1.1 MPa leads to a decrease in the conversion of the olefin from 48 to 41% and an increase in the yield of monoalkylphenols from 58 to 69%. Comparison of the results of alkylation of phenol with n-nonene-1 and n-decene-1 under the same conditions (370°C, 5.3 MPa, phenol:olefin"=6.7:1, 0.3 h) shows that the greater the molecular weight of the alkylating agent, the higher your yield of monoalkylphenols and the selectivity of the reaction for "extremely attached" isomers, but the lower the degree of conversion of the olefin. More clear relationships between the degree of conversion of olefins, selectivity, and some factors influencing the process of thermal alkylation were obtained by reacting phenol with a fraction of C8-C10 olefins. The degree of conversion of these olefins is significantly affected by the ratio of reactants and temperature. Thus, during the alkylation of phenol with olefins of the C8-C10 fraction, taken in a molar ratio (1-5): 1, and temperatures of 325-425 ° C, the higher the conversion of unsaturated compounds, the higher the molar ratio and the higher the temperature. At a constant temperature in the range from 325 to 410 °C, there is a directly proportional relationship between the degree of conversion of olefins and the molar ratio. Increasing the temperature to 425 °C violates the directly proportional relationship. This is especially noticeable when the ratio of phenol:olefin (C8-C10) above 3:1. 8 Copyright JSC "TsKB "BIBCOM" & OOO "Agency Kniga-Service" At different reaction times at each selected pressure, the degree of conversion of the C8-C10 olefin increases with increasing contact time. Under conditions of thermal alkylation of phenol with olefins, the reaction products are unstable, especially when exposed to high temperatures for a long time. Thus, when pure ortho-tert-butyl-phenol was heated at a temperature of 315-332°C for 5 hours, the pressure in the isolated system increased by 49 MPa. Analysis of the products showed that 27% of ortho-tert-butylphenol decomposes into phenol and isobutylene. It was shown that in the presence of an excess of phenol at a temperature of 370°C and a contact time of 2 h, ortho-(1methyloctyl)phenol was converted into ortho-nonylphenols with an hydroxyphenyl radical attached to the 3, 4, and 5 carbon atoms of the alkyl chain of the substituent. And when dialkylphenols, isolated from the VAT residue of thermal alkylation, were heated at a temperature of 370 ° C with a fourfold excess of phenol, a decrease in their number was observed over time. At the same time, there was an increase in the content of monoalkylphenols. After 5 h of heating, the dialkylphenols were completely converted to monoalkylphenols. At the same time, the newly formed products contained a significant amount of monosubstituted "internally attached" alkylphenols. These data show that in each individual case, in order to obtain a high yield of products, it is necessary to find the optimal values between the reaction time, sufficient for a good degree of conversion, and time. Table 3 Results of thermal alkylation of phenol with n-nonene-1, n-decene-1 and their mixtures in a flow reactor , phenol: alkylated, olefin, phenols, isomers, agents, % mol % % С9-10 370 4.2 0.3 1.4:1 21 71 92 С9-10 370 4.2 1, 2 1.4:1 55 60 95 С9-10 370 4.2 0.3 2.8:1 19 64 96 С9-10 325 2.5 1.4 6.7:1 34 86 96 С9 295 2.5 1.5 6.7:1 23 80 93 C9 315 5.3 1.5 6.7:1 39 71 92 C9 370 4.2 0.3 6.7:1 48 58 93 C9 370 5.3 0.3 6.7 :1 41 69 92 С9 370 4.2 1.25 6.7:1 65 79 84 С9 370 4.2 1.8 6.7:1 85 60 81 С9 400 6.0 0.4 6.7:1 52 74 С9 400 6.0 1.1 6.7:1 77 - 87 - С10 370 5.3 0.3 6.7:1 31 86 95 indicates that temperatures of 300-450°C are required for this reaction to proceed. The latter lie far beyond the temperatures of thermodynamic irreversibility of the process of alkylation of phenol with olefins. Therefore, to obtain acceptable yields of ortho-alkyl-phenols, the reaction is carried out under a pressure of 3.0 - 15.0 MPa. 10 Copyright OJSC Central Design Bureau BIBCOM & LLC Agency Kniga-Service 1.2 Acid-catalyzed alkylation of phenol with olefins Acid catalysts were used to soften the process conditions, increase yield and selectivity. Such reactions proceed by the mechanism of electrophilic substitution in the aromatic nucleus. The paper presents the general mechanism of acid-catalyzed reactions of phenol alkylation with olefins, which includes the following stages: 1) the olefin interacts with the catalyst (HX), forming a polarized complex: in the form of an ion pair) attacks the phenol molecule, forming a π-complex with it, in which the alkyl group can relatively easily move from one part of the aromatic molecule to another. OH OH R2 + R1 C + R2 + C R1 CH3 CH3 When the π-complex is rearranged into the δ-complex, a covalent bond appears between the alkyl substituent entering the aryl nucleus and one from the carbon atoms of the aromatic ring. δ-Complex is not stable; it easily rearranges into a π-complex of an alkylaromatic compound, and the latter, donating a proton, stabilizes into an alkylphenol: OH OH OH + H + R2 OH H R2 + H C R1 CH3 R1 C R2 CH3 R1 C R 2 CH3 + C R1 CH3 OH H + OH R2 OH C R1 C R1 CH3 R2 CH3 R2 C R1 + H CH3 + H Although the intermediates are of low stability, the existence of a number of them has been proven. In some cases, it was possible to isolate the δ-complex formed by the addition of a carbocation to an aromatic ring. The orientation of the alkyl group when introduced into the aromatic nucleus is determined by the electron-donating properties of the hydroxyl group: due to the strong (+) mesomeric effect, the electron density increases in the ortho- and para-position to the hydroxyl group, and when the π-complex is rearranged into the σ-complex, the alkyl group is fixed in ortho or para position. The process of alkylation of phenol is complicated by the fact that, along with mono-substituted phenols, di- and tri-substituted phenols can be formed. 12 Copyright JSC "Central Design Bureau "BIBCOM" & OOO "Agency Kniga-Service" Of the monoalkylphenols, according to the data of the work during catalysis with protic acids, the para-isomer predominates. With an increase in the activity of the catalyst, the temperature and duration of the reaction, the proportion of this isomer among the monosubstituted ones can increase from 60-80 to 95% or more due to the isomerization of the ortho-isomer. The paper also points to the dominance of the process of alkylation of phenol with branched olefins (especially higher ones) in the para position, which is explained by the steric effect of the substituent. Of the disubstituted ones, 2,4-dialkylphenol predominates, the proportion of which increases with an increase in temperature and catalyst activity. With the sequential introduction of alkyl groups into the phenol molecule, the first stage proceeds faster than the second, and the second, in turn, faster than the third. A decrease in the reactivity of phenols upon the introduction of alkyl groups in the ortho and para positions with respect to the phenolic hydroxyl was also noted by other authors. 13 Copyright OJSC Central Design Bureau BIBCOM & LLC Agency Kniga-Service The composition of the products of sequential substitution is also affected by the reversible transalkylation reaction H R 2 C 6 H 3 OH + C 6 H 5 OH + 2 RC 6 H 4 OH equilibrium , which is significantly shifted to the right. Therefore, with an increase in the activity of the catalyst, temperature, and duration of the reaction in the resulting mixture, a significant increase in the content of monoalkylphenol is possible. Similar reactions can proceed through the stage of formation of a simple ether, which is then rearranged to alkylphenol. According to the authors of the work, the ortho-alkylation reaction proceeds through the formation of ethers and consists of a series of successive stages: OR OH I OH OH II R III R OH R IV R R R up to 100 ° C, therefore it is recommended to carry out the process at higher temperatures. During the alkylation of phenols with higher olefins using cation exchange resins, which were used as KU-2, KU-23, the formation of alkylphenyl ethers was not recorded. This may indicate the predominant alkylation to the core or the complete conversion of the resulting esters into alkylphenols. The rearrangement of alkylphenyl ethers to alkylphenols under the action of cation exchangers occurs very easily. Even very stable phenoxyoctane in the presence of KU-2 resin isomerized by 80% to octylphenols. The reaction is accompanied by the decomposition of phenoxyoctane into phenol and octene, which indicates to a certain extent the predominant role in the mechanism of dissociation rearrangement by alkylation into the nucleus: ether followed by OH O-CH2(CH2 )6-CH3 + + CH2-(CH2)6-CH3 + CH2=CH-(CH2)5-CH3 CH2-(CH2)6-CH3 OH CH2=CH-(CH2)5-CH3 OH + CH3-CH- (CH2)5-CH3 Alkylphenyl ethers containing secondary or tertiary aliphatic radicals (the formation of just such esters should be expected in the alkylation of phenols with branched olefins) isomerize to alkylphenols much more easily than phenoxyoctane. This explains their absence in the alkylate. According to the data given in the work, an increase in the molecular weight of the alkene and branching of its carbon chain contributes to the reaction and an increase in the yield of alkylphenols. So, if ethylene alkylates phenol at a noticeable rate only at temperatures above 2000 C, then isobutylene and higher olefins can carry out the reaction already at room temperature. The optimum temperatures for alkylation of phenol with ethylene, propylene, isobutylene and isoamylene in the presence of an aluminosilicate catalyst at a molar ratio of initial reagents of 2.5:1 and a space velocity of 0.2 h-1 are, respectively, 400; 275; 250 and 2200 C. The dependence of the yield of alkylphenols on the molecular weight of the alkylating agent can be illustrated by the example of alkylation of phenol with normal olefins in the presence of the KU-2 cation exchanger (molar ratio 15 olefin = 2:1, catalyst - 20% by weight of phenol, 1301450 С, reaction time 2-3.5 h): Olefin Propene Butene-1 Penthene-1 Hexene-1 Yield, % 65 81 83 84 Olefin Heptene-1 Nonene -1 Decene-1 Yield, % 86 89 88 The highest yield of alkyl derivatives is usually observed when individual phenol is used as a raw material. The use of technical mixtures of phenols in almost all cases reduces the yield and quality of the product. The alkylation process is complicated by side reactions: isomerization of alkylphenols, dealkylation, disproportionation and transalkylation. According to the data of the work, with an increase in temperature, the equilibrium constant of the alkylation process increases, i.e. more favorable conditions for the occurrence of side reactions are created. The use of acid catalysts accelerates another side reaction, olefin polymerization. It also proceeds by the mechanism of electrophilic substitution and is accelerated by acidic alkylation catalysts. R3 R3 t R 1 CH=C CH-C R2 R 1 R2 n Side reactions significantly complicate the directed synthesis of alkylphenols. A common method for suppressing these side reactions is to lower the temperature, since alkylation has the lowest activation energy, on the order of 20 kJ/mol (compared to the transalkylation reaction, which requires an energy of 63 kJ/mol). Olefin polymerization can be avoided by reducing its concentration in the liquid, which is achieved by gradual (dosed) introduction of olefin into the reaction mass. The reactions of phenols with isoolefins are largely reversible, and heating the corresponding alkylphenols with an acid catalyst leads to the isolation of the olefin. H+ (CH3)2=CH2+ C6H5OH (CH3)3-C6H4OH Isomerization and transalkylation partly occur due to this reaction. The percentage of alkylated phenols formed in this case depends both on the type of catalyst and on the ratio of the main reagents phenol: olefin, on the process temperature. 1.2.1 Catalysts of the phenol alkylation process and their effect on the composition and structure of products Mineral acids (sulphuric, hydrochloric, phosphoric), arylsulfonic acids, cation exchange resins are described as a catalyst for the alkylation of phenol with various olefins; boron fluoride, aluminum chloride and aluminosilicates. The alkylation processes in the presence of each class have their own characteristics, which must be taken into account in order to lead the process in a given direction. The first catalyst used to produce alkylphenols was sulfuric acid. As early as 1890, Koenigs carried out the alkylation of phenol with isoamylene in her presence. The mechanism of action of sulfuric acid is usually associated with the formation of olefin sulfates, which alkylate phenols with oxygen, and also form carbonium ions: CH3-C=CH2. (CH3)2C-OSO 3H C6H5OH . (CH3)2C-O-C 6H5 - H2SO4 R R + . (CH3)2C(+) . (CH3)2C-OSO 3H HSO4(-) Carbonium ions can also be formed directly from an olefin upon addition of a proton: R R . CH3-C=CH2+. (CH3)2C(+) H2SO4 + HSO4(-) The resulting alkylphenyl ethers under the action of H2SO4 are usually completely rearranged into alkylphenols, apparently through intermediate quinoid structures. Another mechanism of ether rearrangement is also possible - decomposition into initial phenol and olefins with subsequent alkylation into the core. The phenol and olefin found in the ester conversion products confirm the possibility of such a reaction. As already mentioned, the reaction of phenols with olefins is reversible. In accordance with this mechanism, the ease of elimination of alkyl groups should be proportional to the stability of carbonium ions, i.e. tertiary > secondary > primary. In the same sequence, the rate of conversion of the corresponding alkylphenyl ethers also increases. The catalytic activity of H2SO4 begins to manifest itself already at low temperatures. As the temperature rises, the rate of alkylation increases, and if the optimal ratios of catalyst and olefin are observed, the yields of alkylphenols remain high (90–98%). In table. Figure 4 shows the yields of octylphenols formed at 122°C as a function of the amount of catalyst and the phenol:diisobutylene molar ratio. It should be noted that along with an increase in the rate of alkylation, an increase in temperature contributes to the occurrence of side processes, in particular, the destruction of higher olefins and alkylphenols. In this case, alkylphenols with short side chains are formed. So. in the alkylation of phenol with diisobutylene at 130-140°C, para-tert-butylphenol is formed mainly. An increase in the amount of H2SO4, as well as an elongation of the carbon chain of the alkylating agent, contributes to the occurrence of such destructive reactions. In practice, most of the processes of alkylation of phenols with olefins in the presence of concentrated H2SO4 are usually carried out in the range of 60-1200 C. Due to the fact that the optimum temperature depends on many factors, including the composition and structure of the feedstock and reaction products, it should be specified for each specific process experimentally. According to the literature, the amount of H2SO4 used for alkylation is very different and ranges from 0.0005 - 20%. However, 1-3% is more commonly recommended. Using the example of ortho-cresol alkylation, it was shown that the use of an acid in an amount of more than 5% causes a decrease in the yield of products and, first of all, monoalkyl derivatives. This dependence is usually well observed in alkylation. phenols at elevated temperatures. H2SO4 as a catalyst for the alkylation of phenols has significant drawbacks. It has already been indicated above that it contributes to the flow of destructive processes. In addition, H2SO4 favors the polymerization of olefins and the formation of phenol sulfonic acids and alkyl sulfonic esters, which reduce the yield of target products, make it difficult to wash off the catalyst and further process the alkylate. Therefore, in a number of processes, instead of H2SO4, it is often recommended to use benzene- and toluenesulfonic acids, in the presence of which the above disadvantages are manifested to a lesser extent. The yield of alkylphenols in this case reaches 90%. Preference is given to toluenesulfonic acids, which are easily removed from the alkylate by centrifugation (after conversion to ammonium salts), which makes it possible to exclude wastewater pollution with sulfonic acids. Table 4 Alkylation of phenol in the presence of H2SO4 . Effect of the amount of H2SO4 and the molar ratio of phenol:isobutylene on the composition of the resulting alkylphenols (Temperature 1220 C) diisobutylene 1:1 1:1 1:1 1:1 1:1 2:1 6.7:1 Monooctyl-phenols 36 60 65 78 35 84 89 Yield, % Dicotylphenols 4 12 10 10 61 4 2 Total 40 72 75 88 96 88 91 Other catalysts are of lesser use. Hydrogen fluoride is used in the alkylation of phenol with propylene, isobutylene, and higher olefins. High yields of alkylphenols in the presence of HF are observed only with an excess of catalyst. The effect of the phenol:isobutylene molar ratio on phenol alkylation in the presence of HF is illustrated in Table 1. 5. The optimal conditions for this process are - temperature 20°C, molar ratio of HF: phenol >2.5:1, phenol: isobutylene 1:1. The yield of para-tert-butylphenol is 67%. A significant increase in the yield can be achieved if the butylphenol formed in the di-tert20 process is returned for alkylation. With this design of the process, a decrease in the yield of by-products occurs both as a result of a shift in the equilibrium of the alkylation reaction towards the formation of monoalkyl derivatives, and due to disproportionation of the formed ditert-butylphenol. Table 5 Alkylation of phenol in the presence of HF. Effect of phenol:isobutylene ratio on alkylate composition (HF:phenol molar ratio 2:1) Phenol:isobutylene molar ratio Phenol 10:1 5:1 2.5:1 1.54:1 1.16:1 1:1 1, 25:1 84.0 68.0 48.1 28.0 21.0 10.0 - Composition of alkylate, % para 0 3.6 61.0 7.7 3.3 65.9 10.0 3.1 65.0 20.0 5.0 65.0 26.0 9.0 Phosphoric and polyphosphoric acids are used for phenol alkylation with styrene, α-methylstyrene, cyclohexene. Alkylation of phenol in the presence of polyphosphoric acid with low molecular weight olefins (C2-C4) proceeds only at sufficiently high temperatures, as a result of which these reactions are recommended to be carried out in the vapor phase at 250–450 °C, and the catalyst to be applied to a support. The mechanism of acid-catalyzed phenol alkylation has been studied in most detail for the case of using aluminum phenolate (homogeneous catalysis). It includes the following stages: 21 Copyright OJSC Central Design Bureau BIBCOM & LLC Agency Kniga-Service - formation of phenoxyaluminic acid Al(OC 6H5)3 + C 6H5OH OH Al(OC6H5)3 - formation of the "catalyst-olefin" complex, in in which the attacking electrophilic particle and the attacked aromatic nucleus are combined: CH3 R1 + OH C=CH2 R2 C O Al(OC6 H5)3 R1 R2 Al(OC6H5)3 - formation of a π-complex and rearrangement into a σ-complex: R1 O CH3 CH3 C C R1 R2 Al(OC6H5)3 O C(CH3)R2 R1 R2 Al(OC6 H5)3 + H O Al(OC6 H5)3 decomposition of the "catalyst-olefin" complex with the formation of a carbonium ion. The latter attacks the phenol molecule by the mechanism of conventional alkylation with the predominant formation of a para-substituted one. This explains the increase in the yield of para-substituted and the decrease in the yield of ortho-substituted at elevated temperatures. The mechanism of the catalytic action of solid acid catalysts (supported heteropoly acids, zeolites, cation exchange resins, etc.) in the alkylation reaction is similar to the proton mechanism of acid catalysis. However, in terms of the mobility of dissociated protons, cation exchange resins are significantly inferior to mineral and low molecular weight organic sulfonic acids. Ion-catalytic processes occur mainly inside the granules, which is facilitated by the swelling of the resins in the reacting components. In a swollen cation exchanger, the network polymer chains move away from each other, and it is able to pass molecules of very large sizes. Alkylation on cation-exchange resins is generally represented in the work by the following stages: - sorption of phenol and olefin on the surface of the catalyst and their diffusion into the granules to the active centers; - dissociation of functional groups under the influence of water residues (strongly retained by sulfo groups even after prolonged drying of cation exchangers), as well as polar reagents that associate protons by reactions. cation exchanger-SO3H + CH2 =СR1-R2 → cation exchanger-SO-3 + CH3 –R1С+-R2 cation exchanger-SO3H + Н2О → cation exchanger-SO-3 + Н3О+ Note that in the literature there is another point of view on the role of water, indicating that the presence of moisture hinders the sorption of reacting molecules on the catalyst. - transfer of protons from hydroxonium and phenoxonium ions to olefins: + H + CH2=C-R2 R1 HO + CH3-C-R2 + HO R1 + H3O + CH3-C-R 2 + OH2 CH2=C-R 2 R1 R1 BIBCOM" & LLC "Agency Kniga-Service" - interactions of carbonium ion and phenol with the formation of alkylphenol and the elimination of a proton that reduces the catalyst; - migration of alkylphenol molecules to the surface of the granules and their desorption. The probability of these reactions occurring is confirmed by the data on the electrical conductivity of phenol and its mixtures with KU-23 and propene trimer. Peculiarities of alkylation of phenols with olefins in the presence of metal halides. AlCl3 is one of the most active catalysts for aromatic substitution reactions. However, the alkylation of phenols in the presence of AlCl3 is accompanied by intense side reactions: olefin polymerization and dealkylation; in most cases, it has to be abandoned. When alkylating propylene С15-С30 with trimers using AlCl2H2SO4 (20% by weight of phenol), the maximum yield of alkylphenols (80%) is achieved at a temperature of 80ºС. Like aluminum chloride, boron fluoride catalyzes the phenol alkylation reaction very effectively, and in its presence the process proceeds faster; in addition, this catalyst is more easily separated from the reaction products. At low temperatures, alkylphenyl ethers are predominantly formed; an increase in temperature contributes to their decomposition into the starting substances, the interaction of which produces alkylphenols. It is also hypothesized that alkylphenyl ethers isomerize to alkylphenols via intermediate quinoid structures. The yield of alkylphenols up to 93.5% is already achieved in the temperature range of 25-30O C. At temperatures above 40-50O C, favorable conditions are created for direct alkylation into the core, however, due to the dealkylation processes and the formation of dialkylphenols, the yield decreases. » & LLC «Agency Book-Service» of monoalkylphenols. To prevent the formation of polymers and dialkylphenols, a large excess of olefin in the reaction mixture should be avoided. It is expedient to add olefin to the mixture of phenol with the catalyst during alkylation at such a rate that the concentration of olefin in the reaction mass does not exceed 5%. At too low a rate, dealkylation of alkylphenols can occur, at too high, olefin polymerization. The use of boron fluoride is especially effective in cases where it promotes subsequent processing of alkylphenols, for example, obtaining additives, and there is no need to carefully remove it from the alkylate. Molecular compounds of boron fluoride have a high catalytic activity in the alkylation reaction. However, with their participation, a mixture of alkylphenols and alkylphenyl ethers is obtained in a ratio of approximately 2:1, the separation of which is possible by treatment with liquid ammonia. In terms of activity, catalysts containing BF3 are located in the series BF3, (C2H5)2OBF3, H3PO4BF3, H2OBF3. Using H3PO4 BF3 as a catalyst for phenol alkylation with diisobutylene H3PO4 BF3, it is possible to obtain isooctyl-substituted phenols in the temperature range of 50100 ° C with a catalyst amount of 1-5 wt.% and a reaction time of 2-4 hours with a yield of 48-54.5%. Under the same alkylation conditions, but with the use of BF3 monohydrate, the yield of alkylphenols was only 38%. Boron fluoride is a better catalyst than its molecular compounds. In its presence, the rate of alkylation is higher, and the formation of alkylphenyl ethers can be virtually eliminated. It should be noted that the catalytic role of tin tetrachloride is due to acids corresponding to 2- or 2- complex ions. These ions are formed under the action of water on SnCl4 through complex hybridization of electrons of tin atoms with the inclusion of 3d orbits. 25 Copyright OJSC Central Design Bureau BIBCOM & LLC Agency Kniga-Service Metal chlorides can be used both independently and together with hydrogen chloride. The latter reacts with alkenes to form chloroparaffins, which also react with phenols. In the presence of zinc chloride, alkylation proceeds satisfactorily only at 160-1900 C. The addition of hydrogen chloride at an elevated temperature of 1400 C makes it possible to obtain 75% of alkylphenols; the yield of the latter increases with decreasing temperature 60-800 C. The alkylation of phenol and m-cresol with diisobutylene using FeCl3 and HCl is characterized by high intensity, the yield of octyl derivatives of phenol and m-cresol is 92 and 78%. Peculiarities of phenol alkylation in the presence of alkyl and arylsulfonic acids. Alkyl and arylsulfonic acids have milder catalytic action. However, in this case, the process is also accompanied by the polymerization of olefins. In the presence of benzenesulfonic acid (BSA), phenol is alkylated by n-olefins predominantly in the ortho position, with the yield reaching 60-80%. The composition of orthoalkylphenol (up to 60%) also includes dialkylated phenols formed as a result of the reaction (15%). When the BSA content is above 5%, the dealkylation processes are significantly accelerated. When using BSC, an increase in the molar ratio of phenol: olefins does not affect the reaction rate. When using toluenesulfonic acid (TSA), the yield of alkylphenols reaches 90%. To remove TSC from the reaction products, it was proposed to neutralize it with aqueous ammonia and separate the salt by centrifugation. Peculiarities of phenol alkylation in the presence of superacids, supported heteropolyacids and zeolites. The method for obtaining alkylphenols consists in gas-phase alkylation of phenol in the presence of solid catalysts (magnesium or aluminum oxides). More complex catalysts, as a rule, are modified or mixed oxide systems, however, the main component of such systems is magnesium oxide. Aluminosilicates, copper-aluminum hydrocalcites, zeolites, metal phosphates are also used. However, all of the mentioned catalysts make it possible to carry out the selective C-alkylation of phenol only at high temperatures (>350°C); at low temperatures, they are inactive, or anisoles predominate in the reaction products. . In the literature, there are two points of view on the nature of the active centers of such catalysts: on the one hand, it is argued that the presence of strong acidic sites on the catalyst surface provides C-alkylation, while the basic ones (at low temperatures) lead to the O-alkylation process; on the other hand, on the contrary, it is believed that for the selective alkylation of phenol at the aromatic ring, it is necessary that strong basic or weak acid centers be present in the catalyst. High activity in phenol alkylation at low temperatures is shown by systems with strong acidic and superacid properties. These can be solid superacids based on TiO2 and ZrO2 oxides promoted by SO42- and WO42- anions, and phosphorus-containing heteropolyacids. The use of these systems makes it possible to reduce the temperature of the reaction and increase its selectivity, which, of course, is of great practical importance. Studies show that heteropolyacids deposited on oxides or zeolites are more preferable. A number of recent works have shown the high activity of zeolite catalysts in alkylation reactions. 27 Copyright OAO Central Design Bureau BIBCOM & LLC Agency Kniga-Service With the help of such catalysts, along with an increase in the conversion of phenol, it is possible to achieve an increase in the selectivity of the formation of o-cresol compared to anisole. The catalytic properties of zeolite and zeolite-containing catalysts significantly depend on the conditions of their pretreatment. The appearance on the surface of a zeolite and a zeolite-containing catalyst, along with protic centers, also stabilizes the activity of the catalyst. Peculiarities of phenol alkylation in the presence of sulfonic cation exchangers. Of domestic cation exchangers, sulfonated coal, sulfonated phenol-formaldehyde resin KU-4, sulfonated polymer of styrene with divinylbenzene KU-23, sulfonated styrene-butadiene rubbers SBS and their modifications based on rubbers are described as phenol alkylation catalysts. Characteristic of the listed cation exchangers is a greater or lesser degree of three-dimensionality of the carbon skeleton of macromolecules, which prevents the dissolution of the cation exchanger in organic substances and ensures their resistance to chemical, thermal and mechanical influences. The different efficiency of cation exchangers is due to their different exchange capacity, thermal stability, degree of swelling in the reaction mixture, sorption capacity, mechanical strength, particle size and other factors. The dependence of the yield of alkylphenols on the molecular weight of the alkylating agent can be illustrated by the example of alkylation of phenol with olefins in the presence of KU-2 (Table 6). The yield of octylphenols on sulfonated carbon, for example, is only 10%, on cation-exchange resin KU-1 - up to 56.3%, on KU-2 - up to 80%. -2. Table 6 Dependence of the yield of alkylphenols on the type of alkylating agent (phenol:olefin molar ratio 2:1, catalyst 20% of the phenol weight, 130-145ºС, reaction time 2- 3.5 hours) Olefin Propene Butene-1 Penthene-1 Yield, % 65 81 83 Olefin Hexene1 Nonene-1 Decene-1 Yield, % 84 89 88 The catalyst humidity significantly influences the process. Air-dry Amberlite IR-112 practically does not catalyze the reaction. The AF yield on the KU-1 cation exchanger with a moisture content of 20–30% is approximately 1.5 times lower than the yield on the cation exchanger dried to a constant weight. The authors of the work attribute this to the fact that in the presence of moisture, the sorption of reacting molecules on the catalyst becomes more difficult. The catalyst is dried under vacuum at a temperature of 60900 C or by azeotropic distillation with benzene. Such dehydration methods make it possible to avoid the elimination of functional groups, i.e. maintain the exchange capacity of the catalyst. One of the decisive factors in the efficiency of alkylation on cation exchangers is temperature. When cation exchange resins are heated above 1200 C, their activity decreases. In hydrocarbon media at this temperature, desulfurization is not observed; it starts only at 1500 С. Зависимость выхода алкилфенолов от применяемого катализатора 30 Олефин Катализатор Температура, ºС Этилен Изобутилен Изобутилен Изобутилен Изобутилен Изобутилен Изоамилен Изоамилен Изобутилен Изобутилен Al2Cl62SO4 H3PO4 H3PO4·BF3 BF3 BF3·(С2Н5)2О Al2Cl6 Al2Cl6·HCl SiO2/Al2O3 275 275 100 100 100 100 90-110 90-100 110 130 Isobutylene (CH3)2SO4 150 Yield, % of converted phenol 2,42,62,4,6o-alkyl- n-alkyldialkyl-dialkyl-trialkyl-ether phenol phenol phenol phenol phenol 20 15 27 25 65 19 60 28 81 15 83 13 89 6 64 25 87 25 75 5 30 30 2 5 25 8 9 which is explained by an increase in the rate of diffusion of reagents into the granules of cation exchangers and an increase in the mobility of protons of functional groups with increasing temperature. The optimal temperature for the alkylation of phenols in the presence of 0 cation exchange resins should be considered 120-135 C; at 150-2000 C, dealkylation reactions are intensified. The conversion of phenols to alkylphenols accelerates with an increase in the catalyst concentration, which is in good agreement with the concept of the proton reaction mechanism; with an increase in the number of functional sulfo groups, the concentration of carbonium ions formed per unit time increases. When using cation exchangers in an amount of 20% by weight of phenol, a relatively high yield of alkylphenols is provided and there are no particular difficulties in filtering the alkylate. However, with an increase in the concentration of KU-23 resin in the reaction mass by more than 20%, the reaction rate practically does not increase. 1.2.2 Peculiarities of alkylation of phenol and its derivatives with vinylbenzene using various catalysts Syntheses of α-methylbenzylphenols in the presence of hydrogen halides, phosphoric and perchloric acids, boron fluoride or its complexes, arylsulfonic acid, solid superacids, supported heteropolyacids and zeolites, some cation exchange resins are known. The features of these reactions are discussed below. The conditions for their occurrence are summarized in Table 1.6. Alkylation of phenol with vinylbenzene in the presence of sulfuric acid. One of the first phenol alkylation reactions was carried out by Koenigs in 1890 in the presence of a solution of sulfuric acid in acetic acid (1:9). From the alkylate obtained at room temperature, only monosubstituted phenols were isolated in 2–3 days. With an increase in the amount of VB over the stoichiometric amount, along with mono-, di- and trisubstituted ones are formed, and the process of polymerization of VB also becomes noticeable. According to the work, during the alkylation of phenol WB in the presence of sulfuric acid, seven fractions were isolated with different boiling points from 150 to 280 ºС. The composition of the fractions was studied using IR spectroscopy. A comparison of the spectra showed that the fractions are mixtures with a predominance of isomers of one or another type of substitution: mono-, di-, tri-substituted. The use of sulfuric acid provides a high yield of condensed products only when diluted with WB with a suitable solvent, for example, toluene. This in turn reduces polymerization. The presence of polystyrene impurities leads to a significant increase in the viscosity of the mixture. Sulfuric acid, being an active catalyst for the alkylation of phenol WB, also catalyzes to a large extent the side reaction of sulfonation of phenols. However, sulfuric acid as a catalyst has been used in industrial production for many years, but the inability to overcome the above disadvantages has led to the termination of industrial installations. Various modifications of this technology did not give a significant positive effect: the binding of sulfuric acid to the salt-like complex AlCl2H2SO4, the use of acid sodium sulfate, tetrapolyphosphoric acid as a catalyst. Alkylation of phenols with vinylbenzene in the presence of phosphoric acid derivatives. In the presence of catalytic amounts of phosphoric acid, the alkylation of phenol and WB cresols proceeds in high yield, and almost exclusively monosubstituted ones are formed; increasing the ratio of phenol: WB does not increase the yield of disubstituted. When used as a catalyst 75% H3PO4 saturated with BF3. methylbenzylation reactions are accompanied by the polymerization of (aryl)olefins. In this case, the main process is VB polymerization, so the yield of products, even when the temperature drops to -6 0C, does not exceed 33% of the theoretical one. In the presence of the BF3O(C2H5)2 catalyst and 75% H3PO4, phenol with vinylbenzene, in contrast to olefins, forms mono- and diarylalkyl-substituted phenols, and with α-methylvinylbenzene one product: n-oxydiphenyldimethylmethane. The yield of the latter ranges from 4 to 57% (from theoretical). Styrene polymers obtained with the BF3O(C2H5)2 catalyst are a black or brown viscous adhesive mass that does not distill above 300 0C and quickly hardens at room temperature. The 75% H3PO4 and BF3 obtained with the catalyst are a solid mass, triturating into a white or grayish powder. Using polyphosphoric acid as a catalyst, a mixture of mono- and di-(α-methylbenzyl)phenols was obtained. The predominance of the para-isomer in the mixture of mono-substituted ones is due to the isomerization of 2-α-methylbenzylphenol, which occurs under alkylation conditions. Studying the kinetics of the process of phenol methylbenzylation, it was found that the reaction of phenol alkylation with VB in the presence of these catalysts is an irreversible second-order reaction. Instead of phosphoric acids in the alkylation of phenol with styrene, it is recommended to use oxalic acid. In this case, α-methylbenzylphenols are obtained in higher yields, since the reaction is not accompanied by dealkylation and disproportionation, and the rate of styrene polymerization is not high. 33 Copyright JSC "Central Design Bureau "BIBCOM" & LLC "Agency Kniga-Service" Alkylation of phenols with vinylbenzene in the presence of aluminum phenolate. The substitution of phenol occurs mainly in the ortho position, while the yield of 2,6-di-α-MBF is 46% wt. Monoalkylphenols, 2,4- and 2,4,6-tri-α-MBF are obtained in a small amount, and an undistilled resinous mass is left in the residue. Alkylation of phenols with vinylbenzene in the presence of organic acids. In the presence of oxalic acid, alkylation of phenol WB (130-135 0C) at a ratio of 1:1.5 gives a mixture of isomeric mono- and di-α-methylbenzylphenol and 2,4,6-tri-α-methylbenzylphenol. When carrying out this reaction under production conditions, a product was obtained with the following ratio of isomers. Isomers Monosubstituted: 2- and 4-α-MBF Disubstituted 2,4- and 2,6-di-α-MBF Trisubstituted Content, % 32-35 30-33 30-35 The product contains 2-3% polystyrene impurities. Attempts to increase the content of disubstituted products in the reaction mass by increasing the reaction temperature or increasing the ratio of vinylbenzene to phenol led to an increase in the content of polystyrene impurities in the reaction mass and a noticeable increase in the content of the trisubstituted product. A modified method for obtaining the above products is possible with sequential conduct of the reaction with a strict molar ratio of reagents phenol: vinylbenzene=1: (1.75-1.8) . Due to the fact that in the reaction mass until the end of the reaction there is an excess of reactive α-MBF, which reacts with vinylbenzene at a high rate, polystyrene is practically not formed, while the yield of mono-, di- and trisubstituted ones is, respectively, 18-20, 55 -60 and 21-23%. 34 Copyright OJSC "Central Design Bureau "BIBCOM" & LLC "Agency Kniga-Service" The work shows that the use of oxalic acid dihydrate as a catalyst at 90-150 0C and the fractional addition of it and vinylbenzene to a technical mixture of phenols accelerates the reaction. This increases the yield of target products, suppresses the occurrence of side and secondary processes, including WB polymerization. The reaction products are mainly phenols monosubstituted in one position; side and initial reaction products are not detected in the reaction mixture. When studying the alkylation of phenol with vinylbenzene in the presence of carboxylic acids, a relationship was shown between the catalytic activity of the studied acids and their pKa. On fig. Figure 1 shows the kinetic curves for the alkylation of phenol with styrene in the presence of various carboxylic acids. Trichloroacetic and oxalic acids turned out to be the most active catalysts (the rate constants are 10.4.10-3 and 7.4.10-3 L/mol×s, respectively). In the presence of oxalic acid, the rate of alkylation of phenol with vinylbenzene exceeds the rate of polymerization of vinylbenzene so much that polystyrene is practically absent in the reaction mass. Rice. 1 - Kinetic curves of phenol alkylation with styrene in the presence of different acids: 1-trichloroacetic; 2- oxalic; 3 - dichloroacetic; 4 - monochloroacetic; 5- - fumaric; 6 - maleic; 7-malonic 35 Copyright OAO Central Design Bureau BIBCOM & LLC Agency Kniga-Service It should be noted that, along with vinylbenzene, the process of production of para-methylbenzylphenols by alkylation of phenol with α-methylvinylbenzene or a fraction containing α-methylstyrene is described. As a catalyst, sulfonic acid type cation exchangers are used in the form of a gel (wofatite KPS) or a macroporous structure (amberlist-15, wofatite OK-80). The report indicates that the selectivity of the reaction does not depend on the system of the catalyst lattice and is ~90-92%. The resulting product with a purity of ≥ 85% is suitable as a fungicide and wood impregnator. Another way to obtain this product is to alkylate phenol with α-methylvinylbenzene in the presence of a solid inorganic acid, for example, activated clay (Silton SCL brand) at 30-2000C and distillation of the formed para-methylbenzylphenol on a distillation column of periodic action with the introduction of an inert gas (N2) into the column. , water vapor) as 0.001-1 mol per 1 mol of para-methylbenzylphenol vapor. The catalyst is used as 1-50% by weight of p-methylbenzylphenol. A known method of alkylation of phenol with α-methylstyrene on aluminum-zirconium catalyst, consisting of a mixture of oxides of aluminum and zirconium and sulfated oxides of aluminum and zirconium. The reaction is carried out at 80-1100C and the volumetric feed rate of 1-3 h-1. The catalyst contains sulfates in the amount of 5-15% wt. (in terms of SO42-), oxides 5-30% (in terms of Al2O3). For the preparation of the catalyst, a mixture of boehmite and pseudoboehmite is used as aluminum hydroxide (ratio from 1: 3 to 3: 1 by weight). Table 8 Processes of phenol alkylation with various olefins Catalyst Olefin Conditions 1 BF3О(С2Н5)2 and 75% H3PO4 2 α-methylvinylbenzene 3 Al(OC6H5)3 Vinylbenzene Т =90-120°С AlCl2H2SO4 HCl 37 FeCl3 and HCl Propene trimers Propene trimers Propene trimers BSA n-olefin n-TSA n-olefin Sulfuric acid Vinylbenzene - Yield of products (alkylphenols),% 4 4-57 (oxydiphenyldimethylmethane) 46 (2, 6-di-methylbenzylphenols) T=80°C, catalyst 80 (composition not shown) 20% wt. T=80°C T=80-140°C T=90-130°C, 5% wt. catalyst 75 (composition not shown) 92 (phenol octyl derivatives) 60-80 (15-20 dialkylphenols, 45-60 monoalkylphenols) Literature 5 42, 43 50 17 17 17 19, 20 , 20 90 (composition not shown) wt. catalyst Т=90°С, [phenol]: 82-87 8 [styrene]= 1: 1.7 mol (composition not shown) 8 1 2 Oxalic acid Vinylbenzene Oxalic acid Vinylbenzene Oxalic acid dihydrate Vinylbenzene Wofatite KPS 38 °С, [phenol]: [styrene]= 1: 1.5 mol Т=130-135°С, [phenol]: [styrene]= 1: 1.75-1.8 mol Т=90-150°С , 0.2-4% mass 4 32-35 (mono-substituted); 30-33 (disubstituted); 3035 (trisubstituted) 18 (mono-substituted); 55 (disubstituted); 21 (trisubstituted) 90 (composition not shown) 5 46, 47 46, 47 47 51 Т=185°С [phenol]: [olefin]= 2:1 85 (composition not shown) 50-70 (composition not shown) 92.5 (88.4) (composition not shown) 52 53 38 38 Central Design Bureau "BIBKOM" & LLC "Agency Kniga-Service" Thus, a large number of acid catalysts, both heterogeneous and homogeneous, are known for the processes of alkylation of phenol with olefins. A characteristic feature of the phenol alkylation process proceeding in the presence of acid catalysts is that as a result of the reaction mixtures of para- and ortho-isomers are usually obtained. In this case, side reactions of alkylation (isomerization and disproportionation) can occur, in particular polymerization of an unsaturated agent, which is typical for processes catalyzed by mineral and organic acids, metal chlorides and halides, and complex compounds of boron fluoride. There are problems of separation of catalysts, regeneration of spent catalyst mass and corrosion of equipment. To a greater extent, the alkylation method using solid acid systems is free in this regard. There is an opinion that the actual absence of stabilizers of methylbenzylated phenols on the market is due to two groups of problems. First, the lack of appropriate synthetic approaches. The synthesis conditions described in the literature, leading to the formation of a mixture of differently substituted (MB)F, are costly and hardly acceptable for implementation due to the low conversion of phenol; A rather detailed study of the possibility of inhibiting the vinylbenzene oligomerization process using polymerization inhibitors of various classes was carried out in this work (Tables 9–11). Table 9 Induction periods of WB thermopolymerization in the presence of various inhibitors (Т=120ºС, Cing.=0.025 wt.%) change By change in volume By dry residue of the refractive index of the reaction mass of the polymer Induction periods (τ)**, min 2,6-Di-tert-butyl-4-methylphenol 80 3.00 80 3.00 85 3.25 I (Agidol 1) Bis-(2-hydroxy-5-methyl-3-tert-butyl85 3, 25 85 3.25 90 3.50 II phenyl)-methane)) (Agidol 2) 75 2.75 75 2.75 80 3.00 III 2,6-Di-tert.-butylphenol (Agidol 0) 140 6, 00 140 6.00 130 5.50 IV Mixture of 2,4- and 2,6-di(MB)P 80 3.00 80 3.00 85 3.25 V Mixture of (MB)P* N,N-dimethyl- (3,5-di-tert.-butyl-4160 7.00 160 7.00 150 6.50 VI hydroxybenzyl)amine 2, mono(MB)F - 22.42; di(MB)F - 52.26; tri(MB)F - 23.32; **τ - induction period of VB thermopolymerization in the presence of an inhibitor; τ0 is the induction period of WB thermopolymerization in the absence of an inhibitor; p=0.96 (confidence interval) Copyright JSC Central Design Bureau "BIBCOM" & LLC "Agency Kniga-Service" Inhibitor I -tert-butylphenol (Agidol 0) Mixture of 2,4- and 2,6-dimethylbenzylphenols Mixture of methylbenzylated phenols* 41 - II III IV V Induction period (τ), min Constant** of vinylbenzene polymerization rate, Ki ×106, s- 1 (СIn=0.025%) 20 (p) 6.586 Dark maroon 100 0.025 0.05 0.1 6.586 Dark maroon 100 140 170 210 3.509 Cream 15 80 120 160 4.609 Cream 20 41 Inhibitor 0.025 0.05 0.1 Induction period (τ), min -tert-butyl-4120 160 200 2.944 VII yellow hydroxybenzyl)amine * Composition of the MBF mixture, %: phenol - 2, mono(MB)F - 22.42; di(MB)F - 52.26; tri(MB)F - 23.32; ** The integral method for determining the rate constant was used; *** GOST 14871-76; p=0.96 (confidence interval) VI 42 Constant** Color of the reaction rate Index of polymerization of the mass after coloring, vinylbenzene, thermostatic scores *** 6 -1 Ki ×10 , curing (СIn=0.025%) Dark2.585 60 yellow 42 60 Copyright JSC "Central Design Bureau "BIBCOM" & OOO "Agency Kniga-Service" = 0.025% wt.) In the presence of a cation exchanger In the presence of Lewatit K-2629 n-TSA (5% wt.) (15% wt.) Rel. Relates out τ***, τ0***, min τ***, min change τ, change τ, min %** %** 20 15 -25.00 15 Without catalyst Comm. - Inhibitor 43 2,6-Di-tert-butyl-4-methylphenol 80 75 -6.25 75 I (Agidol 1) Bis-(2-hydroxy-5-methyl-3-tert-butyl85 80 -5, 88 85 II phenyl)-methane)) (Agidol 2) 2,6-Di-tert.-butylphenol (Agidol 0) 75 65 -13.3 70 III Mixture of 2,4- and 2.6140 135 -3.57 135 IV dimethylbenzylphenols* Mixture of methylbenzylated phenols 80 70 -12.50 75 V N,N-dimethyl(3.5-di-tert.-butyl-4160 150 -6.25 155 VI hydroxybenzyl)amine * Composition of the MBF mixture, %: phenol – 2, mono(MB)F - 22.42; di(MB)F - 52.26; tri(MB)F - 23.32; **[τwithout cat.-τcat.]/ τwithout. cat ×100; ***р=0.95 (confidence interval) 43 -6.25 -5.88 -20.0 -3.57 -6.25 -3.25 Service" A number of literary sources indicated the possibility of preserving the color of the reaction mass when organic acids, for example, adipic, citric acids, were introduced into the system, while an increase in the inhibitory effectiveness of the action of N-FAO (VI) in the processes of inhibiting the polymerization of monomers was recorded. In patents [55, 56, 57], there is information about the high stabilizing effect of compositions of N-FAO (VI) with synthetic fatty acids (FFA). In later rather numerous works of researchers, a pattern was established for the non-additive enhancement of a large number of properties of polymers and polymeric materials by mixtures of saturated and unsaturated carboxylic acids: oleic and stearic. Based on the available data, compositions of N-FAO (VI) with a mixture of stearic (StAt (VIII)) and oleic (OlKt (IX)) acids in various ratios were tested as inhibitors of spontaneous thermal polymerization of VB. From a numerous series of experiments, it was revealed that the compositions: N-FAO (VI): (a mixture of StKt and OLT) (70:30; 60:40; 50:50% wt.) in the ratios (1:2) ÷ (2:1 ) more effectively prevent the thermopolymerization process. However, the problem of the appearance of color in the reaction system was not removed (Table 12). A generalization of the set of experimental data and fairly stringent requirements for the color of the target product shows that the use of 2,6-di-tert.-butyl-4-methylphenol (I) or a mixture of 2,4-di - and 2,6-di(MB)phenols. However, the latter requires an additional technological operation to separate the MBF mixture formed in the course of methylbenzylation of phenol, which is quite costly. Table 12 Induction periods (τ) of thermopolymerization of vinylbenzene (Т=120 ºС, Cing=0.05% wt.) in the presence of inhibitory composition N-FAO / ( STKt+OlKt) (dilatometric method, Т=120º С) [] Ratio of inhibitor components, wt.h. N-FAO Inhibitor: (StKt+OlKt (50:50; wt %)) N-FAO: (StKt+OlKt (60:40; wt %)) N-FAO: (StKt+OlKt (70:30; % wt)) N-FAO: (StKt+OlKt (40:60; % wt.)) N-PAO StKt+OlKt (70:30; % wt.) StKt OLT 0:2 2:0 2:1 1: 1 1:2 Color index, points τ, min. - - 205 195 170 50 - - 270 250 150 50 - - 390 320 300 50 - - 260 240 110 50 130 160 - - - - - - - 60 - 85 75 - - - - - below, was carried out in the presence of FAO (I). 1.2.3 Study of the interaction of phenol with vinylbenzene in the presence of p-toluenesulfonic acid To identify the main patterns of the influence of reaction conditions on the features of the interaction of phenol with WB, the process was studied in detail using steam as a catalyst45 TSC, which is distinguished by low corrosion aggressiveness. The reaction scheme can be represented as follows: Three main components – mono-, di-, tri(MB)F (Tables 13, 14) In all cases, the formation of compounds not identified by LC with high retention times and a significant amount of residual phenol after 2-3 hours from the start of the reaction were observed. catalyst showed that it is most expedient to use 5% p-TSA (from phenol), because further increase in its amount has little effect on phenol conversion, and its content after 2 h remains quite high (more than 8%) (Table 13). Table 13 Effect of the amount of nara-TSK catalyst on the composition of the reaction product of phenol with vinylbenzene (phenol:WB=1:1.75 mol, T=120°C, τ =2 h, LC) Composition of the product, % wt Cata p-TSA lyzer, % Phenol mono(MB)P di(MB)P tri(MB)P 2 5 7 10.17 8.57 7.99 28.12 30.76 30.71 36.09 40.86 41 .74 24.44 18.48 18.22 Σ Other 1.17 1.33 1.34 from phenol, Т=120° С, τ= 2 h, LC) Composition of the product, % wt. Phenol/WB ratio, mol Phenol mono(MB) F di(MB) F tri(MB) F 1:1.25 1:1.5 1:1.75 1:2 20.52 15.56 8, 57 8.21 38.48 45.59 30.76 32.79 17.50 18.66 40.86 41.01 17.41 17.93 18.48 15.91 Σ Other 6.09 2.26 1 ,33 2.08 A noticeable increase in the reaction rate, fixed by residual phenol, was observed with an increase in the amount of WB to 1.75 mol per 1 mol of phenol (Table fourteen). For the specified ratio, an increase in the synthesis time to 4 hours made it possible to reduce the residual amount of phenol to 1.56%, however, the share of by-products increased (Fig. 2). 47 Copyright JSC "Central Design Bureau "BIBCOM" & OOO "Agency Book-Service" Pic. 2 - The effect of the process time on the content of residual phenol (1) and unidentified compounds (2) in the product of phenol methylbenzylation (amount of para-TSA 5% wt., phenol:WB = 1:1.75 mol, T=120 °C, LC ) Thus, the conduct of the process of methylbenzylation of phenol in the presence of a homogeneous p-TSA catalyst leads to the fact that either a sufficiently large amount of unreacted phenol remains in the system, or a significant amount of by-products is formed with an increase in the reaction time. 1.2.4 Reaction of phenol with vinylbenzene in the presence of sulfonic cation exchangers The reaction mechanism is similar to the proton mechanism of homogeneous acid catalysis. As heterogeneous catalysts, sulfonic cation exchangers (SFCs) activated according to the standard procedure, which differ in exchange capacity, pore volume, and specific surface area, were studied: KU-23, Purolite St-151, Lewatit K-2629, Lewatit K-2431. The reaction was carried out in temperature conditions established by gradual dosing of WB. for p-TSA c capacity, congestion (meq/ml) Lewatit 1.9 K-2629 Lewatit 1.2 K-2431 Purolite 5.1 CT-151 KU-23 4.8 Pore volume, cm3/g Composition of the bottom product, % Phenol Mono(MB )F Di(MB)F Tri(MB)F Σ Other 0.3 2.00 22.42 52.26 23.32 - 0.3 2.68 32.04 49.37 15.91 - 0.15 6 .45 32.29 38.40 22.86 - - - 26.29 20.94 18.55 34.02 It has been established that the use of KU-23 leads to a large number (up to 34%) of unidentified products. When using other studied catalysts, the formation of unidentified products was not observed. The most complete conversion of phenol (~98%) was recorded using Lewatit (Fig. 3). The amount of di(MB)F was ~49–52%. With a high residual phenol content (6.45%), Purolite ST-151 led to a shift in the process towards the formation of monosubstituted phenols, the amount of di(MB)F decreased to 38% (Table 15). Due to the highest conversion of phenol in the presence of Lewatit K- 2629 further studies on optimizing the synthesis conditions were carried out in its presence (Fig. 3). 49 Copyright JSC "Central Design Bureau "BIBCOM" & OOO "Agency Book-Service" Pic. 3 - The effect of the catalyst on the conversion of phenol in the process of methylbenzylation (phenol:WB=1:1.75, mol, Т=90-120 °С, catalyst - 20% of the mass of phenol): 1 - KU-23, 2 - Lewatit K -2629, 3 – Lewatit K-2431, 4 – Purolite ST-151 T=90°C T=110°C 4 – Influence of the ratio of initial reagents on the content of residual phenol and di(MB)F in the product (MB)F obtained at different temperatures (τ=2h, catalyst Lewatit K 2629 20% wt.) From a technological point of view, it is more favorable to carry out processes at more low temperatures, which would increase the -MBF, % phenol conversion, % catalyst life and reduced energy costs. To test the feasibility and feasibility of carrying out the process under milder conditions, a series of experiments was carried out at limiting temperatures of 90, 100, and 110 °C. In these series, with varying the ratio of reagents and the amount of catalyst, it was not possible to achieve a high conversion of phenol: the minimum phenol content remains at the level of 6% (T= 110 °C, 2 h, phenol:WB=1:1.75, mol) (Fig. 4 , Table 15). 20 15 10 5 phenol:WB ratio, phenol:WB mole ratio, m a b in the process of methylbenzylation of phenol To optimize the reaction conditions of methylbenzylation at a temperature of 120 °C and evaluate their effect on the conversion of phenol, statistical methods of experimental search for the optimum were used. The full factorial experiment carried out indicates that the maximum achieved response in terms of phenol conversion corresponds to the molar ratio of phenol: WB = 1:1.75, and the amount of SFC is 15-20% wt. (Fig. 5). Under these conditions, the amount of di(MB)F was maximum. 51 Copyright JSC "Central Design Bureau "BIBCOM" & LLC "Agency Kniga-Service" Evaluation of the possibility of repeated use of the catalyst Lewatit K-2629 showed that up to 20 cycles the activity of the catalyst changes slightly, the conversion of phenol after 10 cycles decreases from 98% to 96.5% and then remains at the specified level. The share of disubstituted MBFs decreases from 52% to 49.3% (Fig. 6). Rice. 6 – Influence of the number of reaction cycles using the Lewatit K-2629 catalyst (phenol:WB =1:1.75 mol, Т=90-120°С, τ=2 h, amount of catalyst 20% wt.): 1 - on phenol conversion ; 2 - for di(MB)F content , T=120°C). 52 Copyright OJSC Central Design Bureau BIBCOM & LLC Agency Kniga-Service 2 TECHNOLOGIES FOR THE PRODUCTION OF PHENOL STABILIZERS The main raw materials for the production of PAO are phenol and paracresol. Phenol is mainly produced from benzene via isopropylbenzene hydroperoxide (cumene method). The production of phenolic stabilizers consumes 3-4% of the total phenol produced. para-Cresol is obtained in limited quantities by sulfonation of toluene and alkaline melting of para-toluenesulfonic acid. As alkylating agents, isobutylene, styrene, cyclohexene are used: OH HO + 2 olefin OH R cat. + R R R _ _ R = C(CH3)3; CH Ph; CH3. Isobutylene, a monomer in the production of polyisobutylene and raw material for the production of isoprene, is isolated from the butane-butylene fraction of petroleum product pyrolysis gases or obtained by dehydrogenation of isobutane. Styrene, which is widely used in the production of polystyrene and rubbers, is produced by the catalytic dehydrogenation of ethylbenzene. 2,6-Di-tert-butylphenol is the most important intermediate in the synthesis of sterically hindered phenolic stabilizers. To obtain 2,6-di-tert-butylphenol, the "ortho-alkylation" method is used using aluminum phenolate as a catalyst. The catalyst is prepared by treating phenol with aluminum metal. 2 Al(OPh)3 + 3 H2 6 PhOH + 2 Al phenoxyaluminum acid "catalyst-olefin" complex Alkylation is carried out in an autoclave (batch scheme) or a column reactor (continuous scheme), feeding isobutylene into molten phenol, in which the catalyst is dissolved. The main stages of the process of obtaining 2,6-di-tert-butylphenol: preparation of a catalyst, alkylation of phenol with isobutylene, destruction and separation of the catalyst, isolation of 2,6-di-tert-butylphenol. The technological scheme of the process is shown in fig. 7. Phenol and aluminum are introduced into the reactor 1 at the rate of 5-10 g of aluminum per 1 kg of phenol. At a temperature of 150-160°C, aluminum reacts with phenol to form complex phenoxyaluminic acid. The resulting solution is fed into reactor 2 for alkylation with isobutylene. Alkylation is carried out at a temperature not exceeding 100°C. Then the reaction mass enters the apparatus 3 for the decomposition of the catalyst. The resulting aluminum hydroxide is filtered off, and the alkylate is fed to the isolation of 2,6-di-tert-butylphenol. In distillation columns 5, 6 and 7, 2-tert-butylphenol and phenol are isolated first, and then 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol and 2,4,6-tri-tert-butylphenol. water Al 2-TBP + PhOH 8 10 2,4-di-TBP PhOH 2,6-di-TBP 9 3 7 4 1 5 2 6 isobutylene 2,4,6-tri-TBP Al(OH)3 Fig. 7. Technological scheme for the production of 2,6-di-tert-butylphenol: 1 - reactor for the preparation of a catalyst; 2 – alkylation reactor; 3 – apparatus for catalyst decomposition; 4 - filter; 5, 6, 7 - distillation columns; 8, 9, 10 - refrigerators The yield of 2,6-di-tert-butylphenol in one pass is 70-72% with a selectivity of its formation from phenol 90%. By-products of alkylation can be converted into starting materials and returned to the process: 55 + 3 5 t-Bu In this case, the yield of 2,6-di-tert-butylphenol increases to 95-97%. Rice. 8 - Technological scheme for obtaining Ionol: 1 - mixer; 2 – aminoalkylation reactor; 3, 5 - distillation columns; 4 - columns of hydrogenolysis; 6 - crystallizer; 7 - filter; 8 - dryer; 9, 10, 11 - heat exchangers 56 Copyright JSC Central Design Bureau "BIBCOM" & LLC "Agency Kniga-Service" fuels and other petroleum products 2,6-li-tert-butyl-4-methylphenol (Ionol, Agidol 1). The main method of obtaining Ionol in the world is the catalytic alkylation of 4-methylphenol (Fig. 8). Sulfuric acid can serve as a catalyst. Oleum, polyphosphoric acid, cation exchange resins, alkyl sulfonic acids, etc. In addition to isobutylene, mixtures of hydrocarbons are used for alkylation, for example, the butane-butylene fraction. Instead of 4-methylphenol, you can use the cresol fraction of coal tar, which is a mixture of 3- and 4-methylphenols. In Russia, a process has been developed for obtaining 2,6-di-tert-butyl-4methylphenol from phenol through 2,6-di-tert-butylphenol. The latter is subjected to aminoalkylation, the resulting Mannich base is reduced according to the scheme: t-Bu HO t-Bu + H2C=O + HN(CH3)2 _H O 2 t-Bu CH2N(CH3)2 t-Bu t-Bu HO HO t-Bu CH2N(CH3)2 H2, cat. t-Bu HO t-Bu 57 CH3 + HN(CH3)2 Copyright OJSC Central Design Bureau BIBCOM & LLC Agency Kniga-Service Dimethylamine and formalin are mixed in mixer 1 (Fig. 9). The mixture is fed into the aminoalkylation reactor 2, where the melt of 2,6-di-tert-butylphenol and the solvent (methanol) also enter. volatile products 10 HCHO HN(CH3)2; H2 11 CH3OH NH(CH3)2 6 1 5 3 2 CH3OH 4 8 7 2,6-di-TBP secondary alkylphenols 9 hydrogen Ionol filtrate 9 - Technological scheme for the production of Agidol 1: 1 - mixer; 2 – aminoalkylation reactor; 3, 5 - distillation columns; 4 – hydrogenolysis column; 6 - crystallizer; 7 - filter; 8 - dryer; 9, 10, 11 - heat exchangers. Aminoalkylation proceeds at 100°C; in 30 min almost complete conversion of 2,6-di-tert-butylphenol is achieved. Then the reaction mass enters column 3 to separate the solvent, dimethylamine and low-boiling by-products. 2,6-Di-tert-butyl-4dimethylaminomethylphenol (Mannich base) is sent to column 4 for hydrogenolysis. Hydrogenolysis is carried out on an alloy catalyst (Ni+Al, Ni+Cr or Ni+Cu) at 140-160°C with an excess of hydrogen. The resulting dimethylamine is removed from excess hydrogen. The reaction mass after hydrogenolysis is sent to a distillation column 5. The crude product is taken from the top of the column and fed to recrystallization. The recrystallized (from methanol) product is sent for filtration and drying. The solvent goes to regeneration. VAT residue from column 5 is used as an antioxidant for petroleum products. 2-tert-Butyl-4-methylphenol. This compound is formed by catalytic alkylation of 4-methylphenol with an equimolar amount of isobutylene in the presence of sulfuric acid or cation exchangers: OH OH + C(CH 3) 3 H 3C CH 2 H 3C CH 3 CH 3 Preparation scheme. A continuously operating pressurized alkylation plant is described. A mixture of liquid isobutylene and 4-methylphenol at 2-2.5 MPa is fed into a flow reactor with a fixed bed of cation exchanger; alkylation temperature 85-950 C. To increase the selectivity and reduce dealkylation, some excess of 4-methylphenol is taken. 6-tert-Butyl-3-methylphenol. The simplest way to obtain is the catalytic alkylation of 3-methylphenol with isobutylene: OH OH + CH2 H3C H3C The reaction is carried out by catalysts. C(CH3)3 H3C in H3C in the presence of 59 common acid acids mono- or dialkylation; its preparation is often combined with the production of 2,6-di-tert-butyl-4-methylphenol or 2-tert-butyl-4-methylphenol. With monoalkylation of the cresol fraction containing 60% 3-methyl-phenol (800 C, catalyst - 3.5% sulfuric acid), and subsequent separation, the target product is obtained with a yield of 60%. Tetrakis-methylene-3-(3',5'-ditrabutyl-4-hydroxypropyl) propionate methane. The alkaline alkylation reaction of 2,6-di-tert-butylphenol is of great importance in the synthesis of phenol stabilizers. Under the action of alkaline catalysts on this compound, a mesomeric phenolate anion is formed, which can add to the molecules of activated olefins. _ t-Bu HO HO t-Bu t-Bu _ O t-Bu t-Bu t-Bu _ O + H2O CH2=CHA _ _ HO t-Bu HO CH2CH2A , t-Bu where A is an electron-withdrawing substituent Alkaline alkylation reaction used in the synthesis of a number of industrial stabilizers and, in particular, Irganox 1010: OH t-Bu 4 t-Bu + 4 CH2=CHCOCH3 _ HO O OH t-Bu t-Bu 4 C(CH2OH)4 _ 4 CH3OH CH 2CH2COCH3 O 60 Copyright OJSC "Central Design Bureau "BIBCOM" & LLC "Agency Kniga-Service" t-Bu HO CH2 CH2COCH 2 O t-Bu C Irganox 1010 4 α-Methylbenzylphenols are a product of catalytic alkylation of phenol with styrene. It was first obtained in 1890, sulfuric acid was used as a catalyst. OH OH + C 6 H 5 -CH CH 2 OH + C6 H5 -CH CH 2 H 3C C H C 6H 5 OH H C C6 H5 + CH 3 C 6 H 5 -CH CH 2 H C C6H5 + CH3 CH 3 CH 3 C6H5-CH CH2 OH H3C OH C H OH C H C6H5 H C C6H 5 CH3 H3 C C H C6H 5 OH H C C6H5 CH3 C H C6H5-CH CH2 C 6H5 + H C6H5 C C6H5-CH CH2 61 H C C6H5 CH3 CH3 H3C C6H5 H C C6H5 CH3 H3C + H C C6 H5 H C 6H5 C OH OH H3C C6H5 CH 3 OH OH H C C H C6H5 10 - Technological scheme for the production of methylbenzylphenols: 1 - measuring tank, 2 - condenser, 3 - separator, 4 - reactor, 5 - distillation column The lower part of the apparatus (1) is loaded with molten phenol (T=70°C), mixed with a polymerization inhibitor, then SFC. Further, with stirring, an equimolar amount of styrene is introduced into the reactor (1) from the measuring tank (2) by injection through the nozzles for 1 hour, maintaining the temperature at 90 ± 5 ºС. The remaining amount of styrene (0.75 mol per 1 mol of phenol) is introduced with a gradual increase in temperature to 120 ºС. The reaction mass is stirred at 120 ºС for 1 hour, after which the reaction mass is pumped into the 62 Copyright JSC "TsKB" BIBCOM " & LLC "Agency Kniga-Service" batch distillation column (4) for the distillation of unreacted phenol. Distillation is carried out at a residual pressure (P=10 kPa, T=70 ºС). The MBF mixture remains in the cube, which is unloaded from the bottom of the column (4) onto the package. Rice. 11 - Schematic diagram of the production of MBF in the presence of Lewatit K-2629: 1 - reactor; 2 - measuring stick; 3- pump; 4 distillation column of periodic action At the end of the process, the heterogeneous catalyst settles in the lower part of the apparatus (1) on the caps of steel pipes. After 10-15 cycles, the spent catalyst is washed out of the apparatus with an alcohol solution and removed by means of a pump through a hatch in the middle part of the apparatus for regeneration. SOME ASPECTS OF AGING AND STABILIZATION OF POLYMERS 3.1 The mechanism of polymer oxidation and its inhibition Modern ideas about the aging of organic substrates are based on the theory of chain branching and degenerate-branched reactions developed in the works N.N. Semenova, N.M. Emanuel, E.T. Denisova, A.L. Buchachenko, A.S. Kuzmina. The main types of aging of carbon chain polymers are oxidation and thermal oxidation. The oxidation of carbochain polymers proceeds by the mechanism of an autoinitiated chain reaction with the participation of alkyl and peroxide radicals in the chain propagation reaction and chain termination in a bimolecular reaction. The similarity of kinetic patterns in liquid and solid phases gives grounds to describe the mechanism of solid-phase oxidation by the same scheme that is adopted in liquid-phase oxidation and in general can be represented by the following main reactions: RH O2  R+HOO R + O2  ROO ROO  + RH k2 ROOH + R (0) (1) (2) According to reaction (1), peroxide radicals ROO are formed, which attack the polymer chain according to reaction (2). The overall oxidation process depends on the concentration of these radicals and the rate of reaction (2). As ROOH hydroperoxide accumulates, it decomposes to form free radicals (degenerate branching reaction) capable of generating new oxidation chains (reactions 3, 4, 5). 64 Copyright OJSC Central Design Bureau BIBCOM & OOO Agency Kniga-Service The rate of this reaction already at the earliest stages of the process significantly exceeds the rate of primary initiation. The main branching agent is hydroperoxide. The decomposition of hydroperoxide proceeds according to reactions (3, 4, 5). ROOH  RO + HO 2ROOH  ROO + H2O + RO ROOH + RH  ROO + H2O + R (3) (4) (5) As a rule, the death of kinetic chains occurs by quadratic termination: R + R  → R-R (6)   R + ROO → ROOR (6.1)   ROO + ROO → ROOR + O2 (6.2) The kinetic regularities of the autocatalytic process are typical for the oxidation of many polymers (all polymers containing C-H bonds). The chain process can be stopped either by increasing the rate of termination of kinetic chains, or by reducing the rates of chain nucleation and branching by destroying initiators and branching products. For this purpose, stabilizers-antioxidants are introduced into the polymer. The action of stabilizers is usually reduced to the destruction of intermediate products that are a source of active radicals. Reactions proceeding in the presence of an inhibitor (inhibited oxidation) are presented below by reactions (711), the main of which is reaction (7). ROO+InOH k7ROOH+ InO ROO+ InO  Quinolide peroxides InO + InO  InO products + RH k10 InOH + R 65 (7) (8) (9) (10) Copyright JSC « Central Design Bureau "BIBCOM" & LLC "Agency Kniga-Service" InOH + ROOH → molecular products (11) Interacting with the peroxide radical according to reaction (7), the inhibitor (stabilizer) reduces the concentration of peroxide radicals and slows down oxidation. The resulting radical can react with other free radicals to give molecular products. At the same time, this radical should be low active and should not enter into reaction (10), so that new oxidation chains do not arise [66]. For an effective stabilizer, the ratio of the rate constants k10/k2 of reactions (10) and (2) should be very small, while the ratio k7/k2 should be large. Of practical importance for protecting polymers from oxidation are, first of all, inhibitors that terminate chains by reaction with peroxide radicals, and inhibitors that destroy hydroperoxides. The first type of inhibitors includes the most effective and widely used in practice phenolic compounds and aromatic amines. 3.2 Factors determining the antioxidant activity of sterically hindered phenols Among phenolic stabilizers, there are: 1. Mononuclear alkylphenols: a) monobasic t-Bu t-Bu CH3 OH OH OH t-Bu t-Bu CH2OCH3 t-Bu t-Bu CH2CH2COC18H37 O 66 Copyright JSC "Central Design Bureau" BIBCOM " & LLC "Agency Book-Service" b) dibasic OH t-Bu t-Bu OH 2. Binuclear (bisphenols): OH OH S t-Bu t-Bu t-Bu t-Bu HO t- Bu CH3 CH3 OH t-Bu 3. Polynuclear: CH3 RH2C t-Bu CH2R ; H3C CH3 CH2R (RCH2CH2COCH2)4C R= OH t-Bu 4. o-Hydroxyphenyl ketones: CO HO OC8H17 The mechanism of inhibition of the processes of oxidation of organic media by substituted phenols has now been studied in detail. The reaction of PAO with peroxide radicals (reaction (7)) determines the ability of phenolic compounds to inhibit chain oxidation. The reaction product is the phenoxy radical PhO . The effectiveness of phenolic stabilizers will be determined primarily by the parameter k7. In the works of Ya.A. Gurvich, it was shown that when substituents are introduced in the ortho-position to the OH group of phenol (or pcresol), the compound loses its typical "phenolic" properties (solubility in water, acid reaction, ease of formation of phenolates). More acceptable with the introduction of ortho-substituents is the homolytic cleavage of the OH bond with the formation of a phenoxy radical. The decrease in acidity is influenced by the positive inductive effect of alkyl substituents, leading to electronic saturation of the O-H bond; violation of the coplanarity of the aromatic ring of the OH group, and steric obstacles to solvation. In addition, alkyl groups in the phenol molecule lower its effective dielectric constant, which increases the electrostatic energy of the anion and leads to a decrease in the dissociation constant (Table 16). Especially strong changes are observed when the ortho-positions are replaced by bulky groups, for example, tert.-alkyl, creating spatial obstacles. The deviation (albeit insignificant) of the OH group in 2,6-dialkylphenols from coplanarity is caused by the interaction of the electron shells of the OH and bulky tert-alkyl groups. When studying the molecular model of 2,6di-tert.-butylphenol, it was shown that the effective radii of the hydrogen atom of the OH group and each of the equivalent hydrogen atoms of neighboring tert-butyl groups in the most convenient conformation overlap. The effect of the volume of ortho-alkyl substituents on the reactivity of phenols is twofold. On the one hand, an increase in the volume of ortho-alkyl substituents leads to an increase in the activity of phenols in radical substitution reactions involving the hydrogen atom of the OH group. On the other hand, the shielding of the reaction center increases the steric hindrance for such reactions. In this regard, the most active in the processes of radical substitution are phenols with intermediate ortho-alkyl substitution. Table 16 Dissociation constants of 4-substituted phenols in water pKa para-substituent CH3 C(CH3)3 H Unsubstituted phenol 10.26 10.23 9.99 2, 6-di-tert-butylphenol 12.23 12.19 11.70 The reactivity and properties of phenols are also affected by the distribution of electron and spin densities ). It follows from the experimental data that the linear dependence of the value of the constant rate k7 with DOH and, therefore, with the thermal effect of reaction (1) is actually absent: the value of DOH continuously decreases as an increase in the effective volume of orthoalkyl substituents, and the rate constant k7 reaches its maximum value at the intermediate ortho-alkyl substitution of phenol, after which it decreases. Table 17 Values of interaction constants of peroxide radicals of different structure with 2,4,6-tri-tert.-butylphenol (Т=70 °С) Radical ROO. M-Xylolol Isopropylbenzene Cyclohexanone Ethylbenzene Styrene Cyclohexene Cyclohexanol Dioxane Methoxycyclohexane k7 10-4, l/(mol×s) 2.0 ± 0.08 2.0 ± 0.09 1.0 ± 0.05 1.7 ± 0, 07 2.2 ± 0.10 2.2 ± 0.08 0.9 ± 0.03 0.9 ± 0.05 1.0 ± 0.04 Attention should be paid to the influence of the electron density distribution in the phenol molecule on the value of k7 and the steric factor. Both factors operate independently. The steric factor is due to the nature of the o-alkyl substituent; electron density distribution by the electron-donating (acceptor) ability of the 4-substituent. An analysis of the rate constants k7 ] indicates that the introduction of ortho-bulky alkyl substituents decreases the k7 value. As can be seen from Table. 18, the weaker the HO bond in the phenol molecule, the faster it reacts with the peroxide radical. 70 Copyright OJSC "Central Design Bureau "BIBCOM" & LLC "Agency Kniga-Service" A large amount of experimental material on the AOA of phenols of various structures in polymers and polymeric materials has been accumulated in the literature.]. Table 18 Reactivity of the interaction of ortho-substituted phenols with peroxide radicals (k7 rel. units) on the strength of the attacked OH bond C(CH3)3, 4-C(CH3)3 2,6-C(CH3)3, 4-C6H5 2,4,6-C(CH3) 2,6-C(CH3)3, 4-CH3 2 ,6-C(CH3)3, 4-OCH3 DOH, kcal/mol 88.2 83.9 84.9 84.9 85.1 k7 (60°C), l/(mol s) 4.8× 103 4.6×104 2.0×104 1.6×104 2.2×104 A1×107, l/(mol s) 1.6 1.6 1.6 1.6 1.6 E1, kcal /mol 3.82 3.87 4.42 4.56 4.35 78.9 4.9×104 3.5 4.35 80.6 1.9×104 3.1 4.90 81.1 1, 6×104 0.8 4.09 81.8 2.0×104 3.4 4.90 76.3 1.6×105 3.0 3.49 favorable conditions for their evaporation, for example at high temperatures. This explains the higher AOA of high molecular weight phenols, including bisphenols. 71 Copyright OJSC "Central Design Bureau "BIBCOM" & LLC "Agency Kniga-Service" OH R2 R6 R2 R5 OH R3 R1 HO OH R3 C OH C R5 R6 R1 R4 I R6 R4 II R2 R4 III the period before the onset of polymer oxidation (τind) for bisphenols (II, III) during polymer oxidation allows us to conclude that the AOA of bisphenols II and III with the same substituents are approximately equal. The maximum AOA is observed in bisphenols with one or two t-alkyl groups, further shielding leads to a decrease in AOA, especially in the case of phenol III, which are very sensitive to n-position shielding. Similar patterns are also observed for monophenols. Replacing hydrogen atoms in the methylene bridge with methyl and phenyl groups reduces AOA if all o- and n-positions are occupied by alkyl groups. The longest and most effective inhibition of the chain oxidation process can be provided by PAOs with moderately bulky alkyl substituents located in the orthoortho- and ortho-para-positions. These, in turn, include methylbenzylated phenols. 72 Copyright OJSC Central Design Bureau BIBCOM & OOO Agency Kniga-Service ACCEPTIONS AND SYMBOLS AO – antioxidant; AOA - antioxidant activity; VB, vinylbenzene; MBF, methylbenzylated phenol; SFC - sulfonic cation exchanger; Tri(MB)F, tri(methylbenzyl)phenol; n-TSA, p-toluenesulfonic acid; FAO, phenolic antioxidant; N-FAO is a nitrogen-containing phenolic antioxidant. 73 Copyright JSC "Central Design Bureau "BIBCOM" & OOO "Agency Book-Service" REFERENCES 1 . Gurvich A.Ya., Kumok S.T. Intermediates, organic dyes and chemicals for polymeric materials: Proc. allowance.-3 ed. revised and add.-M.: High school, 1989.-304s. 2. Gorbunov, B.N. Chemistry and technology of stabilizers of polymeric materials / B.N. Gorbunov, Ya.A. Gurvich, I.P. 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Emmanuel N.M., Denisov E.T., Mayzus Z.K. Chain reactions of hydrocarbons oxidation in liquid phase. M.: Nauka, 1965. - 270s. 90 . Voigt, I. Stabilization of synthetic polymers against the action of light and heat / And Voigt. L.: Chemistry, 1972. - 650 p. 91 . Roginsky V.A. Hindered phenols antioxidants for polyolefins. Communication of antioxidant activity with the structure / V.A. Roginsky // High-molecular compounds. 1982.- Vol. 24- No. 9 - S. 1802-1827. 92 . Shlyapnikov, Yu.A. Antioxidant stabilization of polymers / Shlyapnikov Yu.A., Kiryushkin G.A., Maryin A.P. - M.: Chemistry.-1986.256 p. 82 Copyright JSC "Central Design Bureau "BIBCOM" & OOO "Agency Book-Service" 93 . Roginsky, V.A. Oxidation of polyolefins inhibited by sterically hindered phenols: dis…. dr. chem. Sciences. M.: Institute of chem. Physics. - 1982. 426s. 94 . Kovtun, G.A. Reactivity of the interaction of phenolic antioxidants with peroxyl radicals / G.A. Kovtun //Catalysis and petrochemistry.-2000.-№4.-С.1-9. 95 . Pospisil J. // Degradation and stabilization of polymers. Amsterdam etc.: Elsevier, 1983. Vol. 4.- P. 194-234 96 . Dolgoplosk, B.A. Questions of chemical kinetics, catalysis and reactivity / B.A. Dolgoplosk, G.V. Karpukhina, M.A. Meskina.- M.: AN SSSR, 1985. -387p. 83 Copyright OJSC "Central Design Bureau "BIBCOM" & LLC "Agency Kniga-Service" CONTENTS INTRODUCTION 1. Conditions and mechanism of the reaction of phenol alkylation 1.1. Thermal alkylation of phenol with olefins 1.2. Acid-catalyzed alkylation of phenol with olefins 2. Technologies for the production of phenolic stabilizers 3. Some aspects of aging and stabilization of polymers 3.1. The mechanism of polymer oxidation and its inhibition 3.2. Factors that determine the antioxidant activity of sterically hindered phenols Accepted abbreviations and designations References 3 5 5 11 53 64 64 66 73 74 Responsible for issue М.А. Ibragimov License No. 020404 dated March 6, 1997 Signed for publication on June 26, 2013 Offset paper 5.0 ed. l. Print Riso Circulation 100 copies. Format 60×84/16 4.65 arb. oven l. Order "C" 113 Publishing house of the Kazan National Research Technological University Offset laboratory of the Kazan National Research Technological University 420015, Kazan, K. Marksa, 68 84

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