RU2189963C1 - Method of synthesis of unsaturated dimers of alpha-methylstyrene - Google Patents

Abstract

FIELD: petroleum chemistry. SUBSTANCE: method involves the dimerization reaction of α-methylstyrene that is carried out in the presence of zeolite Y in NaH-form as a catalyst with degree of an ionic exchange 40-60%. The amount of catalyst is 5-20 wt.-%, temperature of reaction is 60-140 C. EFFECT: enhanced selectivity, simplified technology of synthesis of α- methylstyrene. 1 tbl

Description

 The invention relates to the field of petrochemical synthesis, and in particular to a method for producing linear unsaturated α-methylstyrene dimers.

 The linear dimers of α-methylstyrene - 4-methyl-2,4-diphenylpentene-1 (I) and 4-methyl-2,4-diphenylpentene-2 (II) are used as solvents for varnishes, dielectric fluids, modifiers in the production of various polymers.

 A known method of producing unsaturated α-methylstyrene dimers by oligomerizing it on acidic clays such as montmorillonite, bentonite, attapulchite or montmorillonite treated with sulfuric acid [patent 1530430, UK]. The composition of the reaction products is largely dependent on the conditions. For a more selective formation of unsaturated dimers, the reaction is carried out in the presence of additives of aldehydes, ketones, alcohols. Without these additives, a predominantly (up to 95 wt.%) Cyclic saturated α-methylstyrene dimer 1,1,3-trimethyl-3-phenylindane (III) is formed. The maximum conversion of α-methylstyrene in the experiments was 95 wt.%, While the yield of the fraction of dimers obtained by distillation of the reaction mass was 87 wt.%. The fraction contains 98 wt.% Unsaturated dimers I, II and 2 wt.% Cyclic dimer III. In other experiments, the yield of the dimeric fraction was 77-82 wt.%, The content of the cyclic dimer in it was from 2 to 10 wt.%. The residue after distillation is a polymer, its amount is 12 wt.% Or more.

 A significant disadvantage of this method is the presence in the reaction mass of an additional component (aldehydes, ketones, alcohols), which then must be removed and preferably regenerated and which may be present in the target product, contaminating it.

Closest to the proposed invention, the technical solution, selected as a prototype, is a method for producing unsaturated dimers of α-methylstyrene, carried out by oligomerizing it on zeolite Y in the presence of a solvent - methylene chloride [V.P. Talsi, V.P. Doronin, T.P. Sorokina et al. On some methods of oligomerization of α-methylstyrene. // ZhPKh. 2000. T. 13. 5. S. 787]. The conversion of α-methylstyrene is 98.4-99.9 wt.%, The selectivity of the formation of linear unsaturated dimers reaches 76.1-87.0%. The concentration of α-methylstyrene in CH ₂ Cl ₂ is about 30%, the amount of catalyst is 60-90 wt.% Per α-methylstyrene. The reaction was carried out at a temperature of 25-40 ^o C for 1-2 hours. The solvent CH ₂ Cl ₂ can not only be excluded, but also replaced by some other solvent due to the low conversion of α-methylstyrene.

The disadvantages of this method include:
1. The presence of solvent CH ₂ Cl ₂ , quite expensive and used in large quantities - 70 wt.%. Carrying out the reaction in a solvent complicates the technology of oligomerization, as the rectification stage becomes necessary, and therefore, additional equipment and additional energy consumption appear.

 2. In the process of rectification, the reaction mass is exposed to temperature, which can lead to a change in the composition of the reaction mass and deterioration in the quality of the target product.

 3. High consumption of catalyst (60-90 wt.% For raw materials) due to insufficiently high activity.

 4. The low selectivity of the formation of unsaturated dimers is 76.1-87%.

 The aim of the present invention is to increase the selectivity and simplification of the method for producing unsaturated dimers of α-methylstyrene.

This goal is achieved in that the method of producing unsaturated dimers of α-methylstyrene by oligomerization of α-methylstyrene is carried out according to the invention, in the presence of zeolite Y in NaH form with a degree of exchange of Na ions equal to 40-60%, at a reaction temperature of 60-140 ^o With and the amount of catalyst 5-20 wt.%.

A comparative analysis of the proposed solution with the prototype shows that the claimed method differs from the prototype in that in the process of oligomerization of α-methylstyrene to unsaturated linear dimers, zeolite Y in NaH form with a degree of exchange of sodium ions of 40-60% is used as a catalyst. The oligomerization process is carried out at a temperature of 60-140 ^o C, the amount of catalyst is 5-20 wt.%. The selectivity of the formation of unsaturated dimers of α-methylstyrene I and II reaches 87.0-96.9% with a feed conversion of 94.9-100 wt.%.

 The resulting reaction mass contains 0-5.1 wt.% Unreacted α-methylstyrene, 83.5-96.9 wt.% Dimers I and II, 0.9-6.7 wt.% Cyclic dimer III, 2.2- 8.6 wt.% Trimers. Tetramers of α-methylstyrene and higher molecular weight compounds are absent. The reaction mass of this composition without any additional processing can be used, for example, as a modifier in the production of polymers. Consequently, additional capital and energy-intensive operations will not be required to remove any reagents (for example, solvent), to distill off unreacted monomer, to isolate the target fraction, to remove and utilize bottoms.

 The proposed method is as follows.

The oligomerization of α-methylstyrene is carried out by a periodic method. Zeolite Y in Na-form manufactured by Salavatnefteorgsintez JSC is used in the work. The NaH form of the zeolite is obtained after processing the samples with a solution of NH ₄ NO ₃ at 60 ^{° C.} to a certain residual Na ₂ O content and calcining them at 500 ^{° C.} for 4 hours.

The feed (α-methylstyrene) is loaded into the reactor and at a reaction temperature of 60-140 ^{° C., the} catalyst is loaded in portions. The suspension is stirred at the reaction temperature for 1-2 hours. At certain intervals, samples are taken and analyzed by GLC on a Chrom-5 chromatograph. Analysis conditions: glass capillary column 0.2-0.25 mm • 20 m with a stationary liquid phase SE-30, linear programming of temperature from 60 to 270 ^o C at a speed of 6 ^o C / min. Carrier gas helium, carrier gas velocity 1-2 ml / min, ratio of carrier gas flow through the column and bypass 1: 100.

 The proposed method is illustrated by the following examples (see table).

Example 1. In a glass heated reactor with a stirrer, reflux condenser and thermometer, 100 g of α-methylstyrene are charged and begin to heat. At a temperature of 100 ^{° C.,} 5 g of zeolite in NaH form are charged in portions with a degree of ion exchange of 60%. The suspension is stirred at 100 ^{° C.} for 1 hour. After cooling and filtering off the catalyst, 98.7 g of the reaction mass of the composition are obtained, wt.%:
α-Methylstyrene - 4.8
4-Methyl-2,4-diphenylpenten-1 - 66.0
4-Methyl-2,4-diphenylpenten-2 - 20.5
1,1,3-Trimethyl-3-phenylindane - 4.5
Trimers - 4.2
Examples 2-14. Analogously to example 1. The conditions and results of the examples are presented in the table.

Claims (1)

A method of producing unsaturated α-methylstyrene dimers by oligomerization of α-methylstyrene in the presence of a zeolite Y catalyst, characterized in that zeolite Y in NaH form is used as a catalyst, with a degree of ion exchange of 40-60% in an amount of 5-20 wt. %, and the reaction is carried out at a temperature of 60-140 ^o C.

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