Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Patent
1985-08-15
1986-06-17
Williams, Howard S.
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
B01J 1912
Patent
active
045954704
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for the preparation of benzene polycarboxylic acids.
BACKGROUND ART
With respect to the preparation of aromatic polycarboxylic acids, it has hitherto been proposed to synthetize benzoic acid and terephthalic acid respectively from chlorobenzene and 4-chlorobenzoic acid, for example, by the CO-insertion reaction at high temperature and under high pressure in the presence of a carbonylation catalyst such as cobalt carbonyl or by the phase-transfer catalyst method. However, it has not yet been reported that the desired product may be obtained with a high yield. Also it has not yet been reported that, for example, 4-chlorophthalic acid, 5-chlorotrimellitic and the like may be converted to the corresponding polycarboxylic acids such as trimellitic acid, pyromellitic acid and the like by the CO-insertion reaction.
Recently, studies on the photocarbonylation of chlorobenzene in the presence of a catalyst have been reported and moreover a study on the preparation of terephthalic acid by photocarbonylation of 4-chlorobenzoic acid in the presence of a cobalt carbonyl has been reported (Jean-Jacques Brunet, Christian Sidot & Paul Caubere, J. Org. Chem., 1983, 48, 1166-1171).
It was previously known in the art that, in the synthesis of aromatic carboxylic acids, the reaction becomes more difficult and the amount of by-products increases in accordance with the increase of the number of carboxyl groups.
It has now unexpectedly found that, by subjecting a monochloro-polycarboxylic acid to the photocarbonylation reaction in a homogeneous aqueous solution, the reaction proceeds smoothly and the reaction velocity becomes considerably faster than the corresponding velocity of the photocarbonylation reaction of 4-chlorobenzoic acid, and that by-product is scarcely formed.
DISCLOSURE OF INVENTION
The present invention relates to a process for the preparation of a benzene polycarboxylic acid represented by the formula: ##STR3## (wherein n is an integer of 2 or 3) which comprises reacting a monochlorobenzene polycarboxylic acid represented by the formula: ##STR4## (wherein n is as hereinbefore defined) or an alkali metal salt thereof with carbon monoxide in an aqueous solution of an alkali metal compound in the presence of a carbonylation catalyst with irradiation of ray of 340-400 nm, and then acidifying the resultant reaction solution.
The present reaction can be carried out in a homogeneous solution under mild reaction conditions without the use of organic solvent and corrosive substance, and thus the present reaction is practically advantageous.
Preferred examples of the benzene polycarboxylic acids which may be prepared by the present invention include trimellitic acid (benzene 1,2,4-tricarboxylic acid), pyromellitic acid (benzene-1,2,4,5-tetracarboxylic acid) and the like.
Preferred examples of monochlorobenzene polycarboxylic acids include 4-chlorophthalic acid, 5-chlorotrimellitic acid and the like, and alkali metal salts thereof are exemplified by sodium salt, potassium salt, lithium salt and the like.
Preferred alkali metal compounds include, for example, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and the like, alkali metal carbonates such as sodium carbonate, potassium carbonates and alkali metal bicarbonates such as sodium bicarbonate, potassium bicarbonate and the like. The concentration of the aqueous solution of the alkali metal compound may be within a range of 0.5 to 10 (preferably 4-6) normal. When the concentration is not higher than 0.8 normal, the decrease of the yield of the desired product may sometimes be noted.
Examples of the carbonylation catalysts which may be used in the present invention include cobalt carbonyls (e.g. dicobalt octacarbonyl), nickel carbonyls, manganese carbonyls, iron carbonyls and the like. They may be used alone or in combination. The amount of the catalyst used may preferably, for example, 1/200 to 1/2 mol on the basis of the carboxylic acid used as raw material.
The reaction according to
REFERENCES:
patent: 2563820 (1951-08-01), Darragh et al.
Chem. Abs., vol. 68 (17) 77910h.
Kudo Kiyoshi
Nagaoka Koichi
Sugita Nobuyuki
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