Method for synthesis of p-terphenyl-2',5'-dicarboxylic acid

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method for synthesis of p-terphenyl-2',5'-dicarboxylic acid through akylation of p-xylene with a cyclohexanol alkylation agent in the presence of a catalyst - sulphuric acid and then dehydrogenation of the obtained 2,5-dicyclohexyl-p-xylene in liquid phase at atmospheric pressure and temperature 260-290°C on aluminium-palladium catalysts, with extraction of 2',5'-dimethyl-p-terphenyl during cooling and then its oxidation with oxygen in a solution of glacial acetic acid at high temperature in the presence of a dissolved cobalt-manganese-bromine catalyst and extraction of p-terphenyl-2',5'-dicarboxylic acid crystals from the reaction mixture after cooling, where alkylation is carried out in molar ratio of p-xylene, cyclohexanol and sulphuric acid equal to 2-5:2-5:2-4 and temperature 0-5°C while adding the first half of cyclohexanol and raising temperature to 10-20°C until the end of the alkylation process, and oxidation of 2',5'-dimethyl-p-terphenyl is carried out at 105-110°C.

EFFECT: method enables to increase output of the said product by several times.

3 ex

 

The invention relates to a method for producing a p-terphenyl-2',5'-dicarboxylic acid, which is a valuable monomer for obtaining a heat-resistant liquid-crystalline polymers.

Known and loved to the present invention is a method of obtaining a p-terphenyl-2',5'-dicarboxylic acid by alkylation of p-xylene alkylating agent cyclohexanol at a molar ratio of p-xylene, cyclohexanol and sulfuric acid 2-5: 1: 2-4 and a temperature of 0-5°C in the presence of a catalyst is sulfuric acid, followed by dehydration of the obtained 2,5-DICYCLOHEXYL-p-xylene in the liquid phase at atmospheric pressure and a temperature of 260-290°C on aluminium oxide-platinum or alumapalooza catalysts and separation when cooled 2',5'-dimethyl-p-terphenyl and subsequent the oxidation in a solution of glacial acetic acid with oxygen at a temperature of 95°C in the presence of a soluble cobalt-manganese-bromine catalyst for 4-5 hours to complete oxidation. After cooling of the reaction mixture to separate the precipitated crystals of p-terphenyl-2',5'-dicarboxylic acid (Kuznetsova E.A. Synthesis of terphenyl and its derivatives based on petrochemical raw materials. The dissertation on competition of a scientific degree of candidate of chemical Sciences: 05.17.04. Yaroslavl, AGTU, 2004, pages 84-104).

However, the yield of product obtained in this way is very low and is on adca 10% of the loaded material.

The technical objective of this invention is to improve product yield.

This technical problem is solved using the method of producing p-terphenyl-2',5'-dicarboxylic acid by alkylation of p-xylene alkylating agent cyclohexanol in the presence of a catalyst is sulfuric acid, followed by dehydration of the obtained 2,5-DICYCLOHEXYL-p-xylene in the liquid phase at atmospheric pressure and a temperature of 260-290°C in alumapalooza catalysts and separation when cooled 2',5'-dimethyl-p-terphenyl and its subsequent oxidation in a solution of glacial acetic acid with oxygen at elevated temperature in the presence of a soluble cobalt-manganese-bromine catalyst to complete oxidation and allocation after cooling of the reaction mixture of crystals of p-terphenyl-2',5'-dicarboxylic acid, and the alkylation is carried out at a molar ratio of p-xylene, cyclohexanol and sulfuric acid 2-5: 2-5: 2-4 and a temperature of 0-5°C with the introduction of the first half of cyclohexanol and raising the temperature to 10-20°C until the end of the process, alkylation, and oxidation of 2',5'-dimethyl-p-terphenyl is carried out at 105-110°C.

Example 1.

Alkylation. To a mixture of p-xylene 212,4 g (2 mol) and sulfuric acid 98% 196 g (2 mol) at the initial temperature 0°C with stirring dropwise within one hour add half the CEC is hexanol of 100.2 g (1 mol), then the temperature of the reaction mass was raised to 10°C, zakapyvat within an hour, the other half of the cyclohexanol of 100.2 g (1 mol) and the mass is maintained with stirring for one hour. Then separated from the hydrocarbon layer is washed with water, 10%solution of sodium hydroxide and again with water until neutral, dried with calcium chloride and fractionary under vacuum to precipitation 162 g of 2,5-DICYCLOHEXYL-p-xylene.

The dehydrogenation. Obtained 2,5-DICYCLOHEXYL-p-xylene is subjected to dehydrogenation in the presence of 10 g of 2%palladium on alumina (catalyst CNG) at 260-290°C for approximately three hours prior to the selection of theoretically calculated amount of hydrogen. Filtered hot produce from the catalyst, cooled and extracted with benzene 152 g (0,588 mol) of 2',5'-dimethyl-p-terphenyl.

The oxidation. Crystals of 2',5'-dimethyl-p-terphenyl dissolved in glacial acetic acid, in the presence of a soluble cobalt-manganese-bromine catalyst is passed through a solution of oxygen at a temperature of 105-110°C for approximately 4 hours to complete oxidation. After cooling of the reaction mixture to separate the precipitated crystals 112 g (0,350 mol) p-terphenyl-2',5'-dicarboxylic acid. Yield: 35%.

Example 2.

Alkylation. To a mixture of p-xylene 531 g (5 mol) and sulfuric acid 98% 392 g (4 mol) at initial temp is the temperature 5°C with stirring dropwise within one hour add half of cyclohexanol of 100.2 g (1 mol), then the temperature of the reaction mass was raised to 20°C, zakapyvat within an hour, the other half of the cyclohexanol of 100.2 g (1 mol) and the mass is maintained with stirring for another half an hour. Then separated from the hydrocarbon layer is washed with water, 10%sodium hydroxide solution and again with water until neutral, dried with calcium chloride and fractionary under vacuum to precipitation 135 g (0.50 mol) of 2,5-DICYCLOHEXYL-p-xylene.

The dehydrogenation. Obtained 2,5-DICYCLOHEXYL-p-xylene is subjected to dehydrogenation in the presence of 10 g of 2%palladium on alumina (catalyst MA-15) at 260-290°C for approximately three hours prior to the selection of theoretically calculated amount of hydrogen. Filtered hot produce from the catalyst, cooled and extracted with benzene 125 g (0,485 mol) of 2',5'-dimethyl-p-terphenyl.

The oxidation. Crystals of 2',5'-dimethyl-p-terphenyl dissolved in glacial acetic acid, in the presence of a soluble cobalt-manganese-bromine catalyst is passed through a solution of oxygen at a temperature of 105-110°C for approximately 4 hours to complete oxidation. After cooling of the reaction mixture to separate the precipitated crystals 89,5 g (0,280 mol) p-terphenyl-2',5'-dicarboxylic acid. Yield: 28%.

Example 3.

Alkylation. To a mixture of p-xylene 318,6 g (3 mol) and sulfuric acid 98% 294 g (3 mol) started when the Noah temperature 5°C with stirring dropwise within one hour add half of cyclohexanol 250,05 g (2.5 mol), then the temperature of the reaction mass was raised to 20°C, zakapyvat within an hour, the other half of cyclohexanol 250 g (2.5 mol) and the mass is maintained with stirring for another half an hour. Then separated from the hydrocarbon layer is washed with water, 10%sodium hydroxide solution and again with water until neutral, dried with calcium chloride and fractionary under vacuum to precipitation 438,75 g of 2,5-DICYCLOHEXYL-p-xylene.

The dehydrogenation. Obtained 2,5-DICYCLOHEXYL-p-xylene is subjected to dehydrogenation in the presence of 10 g of 2%palladium on alumina (catalyst MA-15) at 260-290°C for approximately three hours prior to the selection of theoretically calculated amount of hydrogen. Filtered hot produce from the catalyst, cooled and extracted with benzene 410,9 g of 2',5'-dimethyl-p-terphenyl.

The oxidation. Crystals of 2',5'-dimethyl-p-terphenyl dissolved in glacial acetic acid, in the presence of a soluble cobalt-manganese-bromine catalyst is passed through a solution of oxygen at a temperature of 105-110°C for approximately 4 hours to complete oxidation. After cooling of the reaction mixture to separate the precipitated crystals 318 g of p-terphenyl-2',5'-dicarboxylic acid.

Yield: 40%.

The product yield in comparison with the prototype has increased four times.

A method of obtaining a p-terphenyl-2',5'-dicarboxylic key is lots by alkylation of p-xylene alkylating agent cyclohexanol in the presence of catalyst sulfuric acid, followed by dehydration of the obtained 2,5-DICYCLOHEXYL-p-xylene in the liquid phase at atmospheric pressure and a temperature of 260-290°C in alumapalooza catalysts and separation when cooled 2',5'-dimethyl-p-terphenyl and its subsequent oxidation in a solution of glacial acetic acid with oxygen at elevated temperature in the presence of a soluble cobalt-manganese-bromine catalyst and allocation after cooling of the reaction mixture of crystals of p-terphenyl-2',5'-dicarboxylic acid, characterized in that the alkylation is carried out at a molar ratio of p-xylene, cyclohexanol and sulfuric acid 2-5: 2-5: 2-4 and a temperature of 0-5°C with the introduction of the first half of cyclohexanol with increasing temperature 10-20°C until the end of the process, alkylation, and oxidation of 2',5'-dimethyl-p-terphenyl is carried out at 105-110°C.



 

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16 cl, 5 dwg, 7 ex, 8 tbl

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EFFECT: design of an efficient method of obtaining carboxylic acids.

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EFFECT: higher efficiency.

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