GB743597A - Production of carboxylic acids - Google Patents

Abstract

Carboxylic acids are obtained by reacting olefines or olefinic compounds and carbon monoxide in the presence of a catalyst consisting of sulphuric acid of at least 90 per cent strength or anhydrous hydrogen fluoride alone or with addition of boron fluoride, the reaction being first carried out in the liquid phase without addition of water and the reaction product taken up in water from which the carboxylic acids are then recovered. Specified olefines are aliphatic olefines, such as ethylene, propene, butene, isobutene, nonene, hexadecene, and mixtures thereof, e.g. the olefin-rich products of the Fischer-Tropsch synthesis carried out under moderate pressure in the presence of iron catalysts. Cyclic olefines such as cyclohexene, olefinic compounds such as unsaturated carboxylic acids, e.g. oleic acid, and diolefines, e.g. butadiene and 4-vinyl-cyclohexene-1, may also be used. The reaction can be carried out at ordinary temperatures and pressures although in some cases it may be advantageous to operate at an elevated temperature of up to 100 DEG C. and at elevated pressure, e.g. at 20-50 atmospheres pressure. The reaction is preferably carried out in such a manner that the olefin is added to the catalyst after the catalyst and the catalyst space have been saturated with carbon monoxide. The reaction product is taken up in water and the carboxylic acid formed floats on the surface and can often be separated as such or it may be separated by steam distillation or extraction. Examples are given for the conversion of (I) iso butene to a mixture of carboxylic acids including trimethylacetic acid, 97 per cent sulphuric acid being used; (2) propene to isobutyric acid, the yields obtained by using various temperature conditions, various pressures of carbon monoxide and different concentrations of sulphuric acid (from 89 to 100 per cent) being compared; (3) isobutene to a mixture containing fatty acids consisting of trimethylacetic acid and higher molecular weight acids, hydrogen fluoride being used as catalyst; (4) isobutene to trimethylacetic acid using 97 per cent sulphuric acid and a carbon monoxide pressure of 50 atmospheres; (5) ethylene to propionic acid using a mixture of hydrofluoric acid and boron trifluoride as catalyst; (6) 2-ethyl-hexene-1 to a mixture of carboxylic acids containing mainly a -methyla -ethyl-caproic acid, the reaction being carried out in the presence of n-hexane as diluent and with 97 per cent sulphuric acid; (7a) an olefin-paraffin mixture containing 52 per cent olefins, being a C5 cut from the product of the Fischer-Tropsch synthesis carried out at moderate pressure in the presence of iron catalysts, to a mixture of fatty acids consisting mainly of C6 acids; (7b) a 1:1 mixture of pentene-1 and n-pentane to form a mixture of C6 acids, diethyl acetic acid and methyl-n-propylacetic acid, in (7a) 97.6 per cent sulphuric acid is used and in (7b) 97.5 per cent sulphuric acid is used; (8) a C12 cut containing 60 per cent of olefins derived from the Fischer-Tropsch synthesis to form tridecane carboxylic acids, 97 per cent sulphuric acid being used; (9) cyclohexene diluted with n-hexane to form a mixture of methylcyclopentane- and cyclohexane carboxylic acids, 97 per cent sulphuric acid being used; (10) oleic acid diluted with n-hexane to form a mixture of the C19 acids a -nonyl sebacic acid and a -octyl nonanedicarboxylic acids, 97 per cent sulphuric acid being used. The acids obtained in the examples are generally purified via their alkali metal salts. Specification 5599/46, as open to inspection under Sect. 91, is referred to.