GB742740A - Improvements in the production of carboxylic acids, their esters and anhydrides - Google Patents

Abstract

Carboxylic acids, anhydrides and esters are made by treating saturated aliphatic alcohols or their ethers or aliphatic monocarboxylic acid esters with CO, optionally in admixture with H2, at elevated temperatures and pressures in the presence of a complex compound of nickel bromide or iodide with a quaternary ammonium and/or phosphonium halide. Complex compounds used may be of formula [A4N]2.Ni.X4, where A is a saturated hydrocarbon radicle of 1-4 C atoms, an aralkyl or cycloalkyl radicle or 2 of the A's form an alkylene radicle of 5-7 C atoms and X is Br or I or the quat. ammonium radicle may be replaced by a benzyl or alkyl pyridinium radicle. Typical of specified ammonium complexes are triethyl butyl ammonium nickel bromide iodide, diethyl dibutyl ammonium nickel iodide, trimethyl cyclohexyl ammonium nickel bromide, benzyl pyridinium nickel iodide and diethyl pyrrolidinium nickel iodide. Phosphonium complexes described are triaryl alkyl phosphonium nickel bromides where the alkyl radicle has 1-6 C atoms and the aryl group is a benzene residue, e.g. phenyl, tolyl or xylyl. The complexes may be formed during the reaction from the nickel bromide or iodide or nickel and the free halogen and the quat. ammonium or phosphonium halide. Preferred temperatures are 70-250 DEG C. and pressures over 50, especially 200-700 atmospheres are preferred. The CO used may be pure or contain other gases such as N2, H2, CO2 or CH4. When mixed gases are used the minimum concentration of CO is 10 per cent. With an excess of CO over H2, e.g. with at least 60 volumes of CO and at most 40 volumes of H2 the main products are carboxylic acids, esters and anhydrides. With higher concentrations of hydrogen a greater tendency to the production of aldehydes is observed. The feed gases should be substantially free of H2S. Products may be worked up in conventional fashion the complex being recovered unchanged and suitable for reuse. Preferably 0.01-2 per cent of Ni in the complex form calculated on starting material is used. Solvents, e.g. hydrocarbons, esters, ethers, N-alkyl lactams or reaction products, may be present. Specified alcohols are methanol, ethanol, propanols, butanols, ethylene glycol, propylene glycol, butanediols and mixtures of alcohols obtained by olefine hydration. Specified ethers are dimethyl and dipropyl ether. Acetates and propionates are mentioned as suitable esters. In examples (1) methyl acetate with CO in the presence of a mixture of triphenyl butyl phosphonium nickel tetrabromide or triphenyl ethyl phosphonium nickel tetra iodide or tritolyl butyl phosphonium nickel tetra bromide or iodide and N-methyl pyrrolidone yield acetic anhydride; (2) dimethyl ether with CO in the presence of triphenyl n-propyl phosphonium nickel tetra bromide or tritolyl butyl phosphonium nickel bromide or the corresponding iodides admixed with N-methyl pyrrolidone yields acetic anhydride; methyl acetate with CO in the presence of (3) tetramethyl ammonium nickel iodide; (4) tetraethyl ammonium nickel iodide; (5) tetraethyl ammonium nickel bromo iodide; (6) tetraethyl ammonium nickel bromide; (7), (8) and (9) trimethyl butyl ammonium nickel iodide; and (10) tetramethyl ammonium nickel iodide + triphenyl butyl phosphonium nickel bromide admixed with N-methyl pyrrolidone yield acetic anhydride; (11) methanol with CO and triphenyl ethyl phosphonium nickel iodide or triphenyl butyl phosphonium nickel bromo iodide or tritolyl ethyl phosphonium nickel iodide or triphenyl butyl phosphonium nickel bromide or tetraethyl ammonium nickel iodide or trimethyl propyl ammonium nickel bromo iodide or trimethyl butyl ammonium nickel iodide yield methyl acetate and acetic acid; (12) methyl acetate with CO and H2 and a mixture of tetramethyl ammonium iodide, nickel iodide and N-methyl pyrrolidone yields acetic anhydride; (13) butane diol 1,4 with CO and tetramethyl ammonium nickel iodide yields mainly adipic acid with some d -valero-lactone and valeric acid and in (14) butane diol-1,4 with CO and a mixture of nickel, iodine, bismuth, triethylamine and ethyl iodide yields adipic acid.