GB815835A - Improvements in the production of aromatic carboxylic acids, their esters and salts - Google Patents

Abstract

Aromatic carboxylic acids, their esters or salts, are made by reacting a halogen-substituted aromatic hydrocarbon which may be further substituted by carboxylic acid or ether groups with at least the equivalent amount of a formate of an alkali or alkaline-earth metal or of ammonium or of a mixture thereof, or a corresponding quantity of the corresponding hydroxide and carbon monoxide, at elevated temperature and under increased pressure, the reaction being conducted in the presence of an alcohol if the ester is desired or of a basic-reacting compound if the salt is desired. The reaction may be conducted continuously or discontinuously by heating the mixture of halogen compound and formate in a closed vessel, if desired in the presence of nitrogen or carbon monoxide. When hydroxides are used a portion of the hydroxide may be replaced by the corresponding carbonate. Catalysts comprising metal carbonyl compounds such as carbonyl compounds of nickel, cobalt, iron, molybdenum and chromium, metal carbonyl hydrides such as that of cobalt, or compounds of the formul Fe(CO)4Br2, (R3P)2Ni(CO)2 or (R3P)Ni(CO)3 where R is a hydrocarbon radical such as alkyl, may be used. When a pressure of carbon monoxide is used the carbonyl-forming metals themselves may be used as catalysts. Other catalysts are copper or silver metals and halides of copper, silver, nickel, cobalt and iron. Halogen-substituted aromatic hydrocarbons mentioned are mono- or poly-halogen substituted benzene, toluene, xylene, diphenyl, naphthalene or anthracene or mixtures thereof. Alkali or alkaline-earth metals specified as formates or hydroxides are sodium, potassium, magnesium, calcium, barium and strontium. Alcohols for use in obtaining esters are methanol, ethanol or propanol. Basic-reacting substances for use in obtaining salts are oxides, hydroxides, carbonates or salts of weak organic acids and alkali or alkaline-earth metals, ammonia, alkylamines, pyridine or quinoline. Examples 1 to 7 illustrate the preparation of terephthalic acid from p-dichlorobenzene under various conditions, p-chlorobenzoic acid being sometimes obtained as a by-product; other examples illustrate the making of (8) 4 : 41-diphenyl dicarboxylic acid from 4 : 41-dichlorodiphenyl, (9) terephthalic acid and bromobenzoic acid from p-dibromobenzene, (10) o-phthalic acid from o-dichlorobenzene, (11) disodium terephthalate from p-chlorobenzoic acid, (12) anisic acid from p-chloroanisole, (13) dimethyl terephthalate and terephthalic acid from p-dichlorobenzene and methanol, and (14) disodium terephthalate and sodium chlorobenzoate from p-dichlorobenzene in the presence of soda.