GB2155921A - Process for producing 4-alkyl-4'-formylbiphenyl - Google Patents

Abstract

4-alkyl-4'-formylbiphenyl is simply produced from 4-alkylbiphenyl as a readily available raw material by carbonylation of 4-alkylbiphenyl in the presence of a hydrogen fluoride-boron fluoride catalyst. 4-alkyl-4'-formylbiphenyl is easily oxidized to 4,4'-biphenyldicarboxylic acid as a useful material for polyester resin and aramide resin.

Description

SPECIFICATION Process for producing 4-alkyl-4'-formylbiphenyl Background of the invention This invention relates to a process for producing 4-alkylA'-formylbiphenyl.

4-Alkyl-4'-formylbiphenyl is easily oxidized to 4,4'- biphenyldicarboxylic acid, which will be hereinafter referred to as BPDC, a useful raw material for high performance polyester resin or aramide resin having a good heat resistance and a high strength, and various processes have been proposed for its production. However, the so far proposed processes are complicated or low in yield, and are actually not economical processes for producing BPDC.

The present inventors have studied carbonylation reaction of aromatic compounds with carbon monoxide, using a hydrogen fluoride-boron fluoride catalyst, and have found that, contrary to the original presumption that the aromatic nucleus having an alkyl group is carbonylated in the carbonylation reaction of alkylbiphenyl, the 4'- position of other aromatic nucleus is very selectively carbonylated, and further that BPDC can be obtained in high yield by oxidizing the carbonylated product with a gas containing molecular oxygen, and have established the present invention.

Summary of the invention An object of the present invention is to provide a process for producing 4-alkyl-4'-formylbiphenyl which comprises allowing a 4-alkylbiphenyl to react with carbon monoxide in the presence of a hydrogen fluoride-boron fluoride catalyst.

The 4-alkylbiphenyl for use in the present invention as the starting materials includes, for example, 4- methylbiphenyl, 4-ethybiphenyl, 4-isopropylbiphenyl, etc. which can be prepared according to various methods. For example, 4-methylbiphenyl can be recovered from the by-product high boiling oil obtained in a process for producing benzene by demethylation of toluene, or can be readily obtained by hydrogenating 4-formylbiphenyl (4-biphenyl aldehyde) obtained by carbonylating biphenyl with carbon monoxide in the presence of a hydrogen fluoride-boron fluoride catalyst, where 4-methylbiphenyl can be obtained from biphenyl in yield of at least 95%.Biphenyl can be carboxylated with carbon monoxide to 4-formylbiphenyl, for example, in the presence of a solvent such as benzene, etc. under a carbon monoxide partial pressure of 5 to 30 kg/cm2 gage, preferably 10 to 20 kg/cm2 gage at a reaction temperature of 5" to 20"C, preferably 5" to 10"C in a molar ratio of hydrogen fluoride: boron fluoride as catalyst components: biphenyl as the starting material of 4 to 10 1 to 1.5 1, preferably 5 to 6 1.2 to 1.3 :1.4formylbiphenyl can be hydrogenated to 4-alkylbiphenyl, for example, in the presence of a palladium catalyst su ported on activated carbon under a hydrogen pressure of 5 to 50 kg/cm2 gage at a reaction temperature of 100" to 200"C, preferably 120" to 150"C.

4-Ethylbiphenyl and 4-isopropylbiphenyl are now produced for use as heating oil, etc. by alkylating biphenyl with ethylene and propylene, respectively, and can be readily recovered from the heating oil by physical means such as distillation, crystallization, etc.

4-Alkylbiphenyl is carbonylated with carbon monoxide under a carbon monoxide partial pressure of 10 to 20 kgicm2 gage at a reaction temperature of 0" to 20 C in a molar ratio of alkylbiphenyl boron fluoride : hydrogen fluoride of 1:1.1 to 1.7 : 5 to 10 for 15 to 30 minutes, where the reaction proceeds smoothly and whereby the desired 4-alkyl-4'-formylbiphenyl (4,4'-alkylbiphenyl aldehyde) can be obtained in very high yield with high selectivity.

When the alkyl group at 4-position such as ethyl group is readily transferably in the presence of a hydrogen fluoride-boron fluoride catalyst by disproportionnation reaction, etc., it is preferable to select reaction conditions to carry out the carbonylation reaction while suppressing the disproportionation reaction. It is also effective to add thereto an inhibitor for the alkyl group transfer such as methylcyclopentane, etc.

BPDC can be readily derived from 4-alkyl-4'-formylbiphenyl by oxidation, and can be obtained in high yield in the presence of various solvents such as acetic acid, etc. and various catalyst systems, such as cobalt or manganese and bromine.

The present invention provides a process of rationally producting useful 4-alkyl-4'-formylbiphenyl from readily available raw materials through simple steps, and has a high industrial significance.

Preferred embodiments of the invention Example 1 Carbonylation of alkylbiphenyl (1) 4-methylbiphenyl prepared by carbonylating biphenyl with CO in the presence of a HF-BF3 catalyst, thereby obtaining 4-biphenyl aldehyde (selectively: 99%) and reducing the aldehyde group of the 4-biphenylaldehyde to methyl group in the presence of a Pd/carbon catalyst was carbonylated in the following manner, using an autoclave of 5 t capacity with a stirrer as a carbonylation reactor.

The reactor could be cooled with a cooling medium passing through the jacket on the reactor.

1,136 g (6.73 moles) of 4-methylbiphenyl with a purity of 99.6%, as dissolved in 568 g (7.3 moles) of benzene, was charged into the reactor, and then 1,200 g (60 moles) of HF and 640 g (9.4 moles) of BF3 gas were charged into the reactor with stirring and cooling to prepare a HF-BF3 complex solution of 4-methylbiphenyl. Then, a CO gas was introduced thereto with stirring and cooling to conduct carbonylation while maintaining the reactor under a pressure of 20 kg/cm2 gage. CO absorption with heat release was discontinued about 15 minutes after the CO introduction, while keeping the reaction temperature at about 10"C. After the completion of the reaction, the reaction solution was poured into ice water, and the oil layer was recovered therefrom, washed with an aqueous alkaline solution and then with water.Then, 4,4' methylbiphenyl aldehyde (boiling point: 170"C/4 mmHg) was recovered therefrom by distillation.

Conversion of 4-methylbiphenyl to aldehyde was 80%, and selectively to 4,4'-isomer in the aldehyde- was 97%.

(2) 4-ethylbiphenyl contained at a concentration of 52% by weight in Therm S 600 (heating oil made by Shin Nittetsu Kagaku K.K., Japan) was recovered and purified by distillation and crystallization and used as the starting material for carbonylation.

An autoclave of 2 e capacity was used as a carbonylation reactor.

1,100 g (55 moles) of HF was charged into the reactor, and then the reactor was maintained under a pressure of 20 kg/cm2 gage with a CO gas with stirring and cooling: 70 g (0.38 moles)/min. of 4ethylbiphenyl was fed to the reactor in that state as a 70 wt.% solution in benzene through a metering pump, and at the same time 39 g (0.58 moles)/min.

of BF2 gas was fed thereto under the cylinder pressure for 15 minutes to conduct the reaction. After the discontinuation to feed the CO gas, the reaction was further continued for 5 minutes. Then, the reaction solution was treated in the same manner as in (1).

During the reaction, the heat of reaction was removed by the cooling medium passing through the jacket on the reactor to keep the inside temperature at 5"C. Yield of aldehyde to the charged 4ethylbiphenyl was 78%, and the selectivity to 4,4'ethylbiphenyl aldehyde was 98%.

Example 2 Oxidation of 4,4'-methylbiphenyl aldehyde 40 g of 4,4'-methylbiphenyl aldehyde, 0.44 g of cobalt bromide hexahydrate, and 0,33 g of manganese acetate tetrahydrate, together with 200 g of 95% acetic acid, were charged into a titanium autoclave with a high speed electromagnetic stirrer and a gas inlet, and air was fed into the reactor, while keeping the reaction temperature at 200 C and the pressure under 20 kg/cm2 gage.

The reaction took place immediately with rapid oxygen absorption. The reaction was continued even after no substantial oxygen absorption was shown. The reaction time was 1.5 hours in total.

The reaction solution was filtered, washed with acetic acid and then with water, and dried, whereby 45 g of crude 4,4'-biphenyldicarboxylic acid was obtained as solid powder.

Example 3 Oxidation of 4,4'-ethylbiphenyl aldehyde 40 g of 4,4'-diethylbiphenyl aldehyde and 40 g of cobalt acetate tetrahydrate, together with 200 g of 95% acetic acid, were charged into the same reactor as used in Example 2, and air was fed into the reactor, while keeping the reaction temperature at 150"C and the pressure under 20 kg/cm2 gage.

The reaction took place immediately with rapid oxygen absorption and continued for 1.5 hours.

The reaction solution was treated in the same manner as in Example 2, whereby 41 g of crude 4,4'-biphenyldicarboxylic acid was obtained as solid powder.

Claims (8)

1. A process for producing 4-alkyl-4'-formylbi- phenyl, which reacting a 4-alkylbiphenyl with carbon monoxide in the presence of a hydrogen fluoride-boron fluoride catalyst.

2. A process according to Claim 1, wherein the reaction of 4-alkylbiphenyl with carbon monoxide is carried out under a carbon monoxide partial pressure of 10 to 20 kg/cm2 gage at a reaction temperature of 0" to 20 C in a molar ratio of alkylbiphenyl : boron fluoride : hydrogen fluoride of 1: 1.1 to 1.7 : 5 to 10.

3. A process according to either of Claims 1 to 2, wherein the 4-alkylbiphenyl is 4-methylbiphenyl, 4-ethylbiphenyl or 4-isopropylbipheny.

4. A process for producing a 4,4'-biphenyldicar- boxylic acid, which comprises reacting a 4-alkylbiphenyl with carbon monoxide in the presence of a hydrogen fluoride- boron fluoride catalyst, and oxidising the resulting alkyl-4'-formylbiphenyl, with a gas containing molecular oxygen.

5. A process for producing 4-alkyl-4'-formylbi- phenyl substantially as hereinbefore described with particular reference to Example 1.

6. A process for the production of 4,4'- biphenyldicarboxylic acid substantially as hereinbefore described with particular reference to Examples 2 and 3.

7. 4-alkyl-4'-formylbiphenyl when produced by a process according to any one of Claims 1 to 3 and 5.

8. 4,4'-biphenyldicarboxylic acid when produced by a process according to any one of claims 4 and 6.