Patent ID: 6137001
Filing Date: 2000-10-24
Classification: C01B,C07C,Y02P

Abstract:
A continuous process for preparing aromatic acid from a corresponding methyl substituted aromatic compound by catalytic liquid-phase oxidation of the methyl groups with a dioxygen-containing gas in a solvent comprising a lower aliphatic monocarboxylic acid at an elevated temperature and pressure and in the presence of an oxidation catalyst comprising a heavy metal component and a source of bromine, which process comprises:(11-a) oxidizing a methyl substituted aromatic compound to an aromatic carboxylic acid in a liquid-phase reaction mixture comprising water, aliphatic monocarboxylic acid of 2 to about 6 carbon atoms, an oxidation catalyst comprising a heavy metal component and a source of bromine and a source of dioxygen, under reaction conditions which produce a gaseous high pressure stream comprising dioxygen, carbon monoxide, carbon dioxide, steam, aliphatic monocarboxylic acid, methyl ester thereof, and one or more volatile organic bromide compounds;(11-b) contacting counter-currently in a high efficiency, continuous separation apparatus the gaseous stream with an aqueous liquid phase in the presence of solid hydrolysis-promoting catalyst material which does not disintegrate in less than one month under conditions employed in the separation apparatus to form products of the hydrolysis comprising an alcohol and hydrogen bromide, and separating aqueous hydrogen bromide and the less volatile aliphatic monocarboxylic acid from the more volatile alcohol in the high efficiency separation apparatus by volatility, the aqueous hydrogen bromide and aliphatic monocarboxylic acid being contained in the aqueous liquid phase withdrawn from the separation apparatus in a liquid bottoms stream and the alcohol being carried up and out of the separation apparatus in a gaseous high pressure overhead stream, the hydrolysis and separation being carried out coextensively in the continuous separation apparatus.