GB754877A - Improvements in the production of carboxylic acids, their anhydrides and esters - Google Patents

Abstract

Aliphatic carboxylic acids, their anhydrides or esters are obtained by the carbonylation of aliphatic olefines in the presence of water and/or a saturated aliphatic alcohol and/or the fatty acid to be produced, under superatmospheric pressure and at elevated temperatures using as catalyst a complex salt derived from nickel or cobalt and an aliphatic mono-, di-, or polycarboxylic acid containing at least one hydroxy or keto group. Specified complex-forming acids are lactic, 2-hydroxypropionic, propionyl propionic, tartronic, mesoxalic, hydroxysuccinic, tartaric, citric, acetone dicarboxylic, and saccharic acids. When using salts derived from di- or polycarboxylic acids it is preferred to replace one of the carboxylic hydrogen atoms of the acid by an equivalent of nickel or cobalt and the remaining hydrogen by another cation particularly an alkali metal cation e.g. sodium or potassium, or an ammonium cation which may be substituted by an organic radical. The ammonium or substituted ammonium ion may be derived from ammonia or an amine such as mono-, di- or tri-alkyl amines containing saturated C1-C6 hydrocarbon radicals. Specified amines are trimethyl and triethyl amines, diaminoalkanes such as ethylene, propylene, and butylene diamine and their N-alkyl derivatives, e.g. tetramethyl or tetra-ethyl derivatives. Pyrrolidine, piperidine and their N-alkyl derivatives such as N-methyl, N-propyl, or N-butyl polymethylene imines, pyridine, pyrrole, and their homologues may also be used. The catalysts may be prepared by heating together in aqueous medium nickel or cobalt carbonate with the complex-forming acid. The preferred catalysts are obtained by heating together in an aqueous medium about 2 molecular proportions of a hydroxy or keto dicarboxylic acid alkali metal salt with one molecular proportion of nickel or cobalt carbonate and the solution obtained may be used directly as the catalyst. The catalysts may also be obtained by reacting the dicarboxylic acid, an amine, and nickel or cobalt carbonate in a solvent, e.g. water. The catalysts may alternatively be formed in situ by adding the various constituents of the catalyst to the starting mixture, thus propionic acid may be prepared by adding pyridine or triethylamine, the complex-forming acid, and nickel or cobalt carbonate to water and then treating with ethylene and carbon monoxide. The carbonylation is preferably effected in the liquid phase and the reaction may be carried out batchwise or continuously and is preferably effected at 170-290 DEG C. and at 150-800 atmospheres pressure. Additional solvents such as saturated hydrocarbons or the reaction products themselves particularly the acid to be produced or other inert solvents, e.g. carboxylic acid esters or lactones, may be used. Specified olefines are ethylene, propylene, and butylenes, octene, octadecene and mixtures of hydrocarbons such as are obtained by cracking paraffin wax or by reacting carbon monoxide and hydrogen. When saturated aliphatic alcohols, e.g. methanol, ethanol, n- and iso-propanol or the butanols are used instead of water, esters are formed and when carboxylic acids are used anhydrides are formed. Examples are given for the production of propionic acid and its anhydride from ethylene, carbon monoxide and propionic acid, using as catalyst (1) a solution prepared by heating to boiling a mixture of nickel carbonate and acid potassium tartrate dissolved in water in a molecular ratio of 1 to 2 and then allowing to cool; (2) using the same catalyst solution as in (1) or using an aqueous potassium cobalt tartrate solution; (3) using either an aqueous pyridinium nickel tartrate solution prepared by dissolving nickel carbonate, pyridine and tartaric acid in a molecular ratio of 1 : 2 : 2 in water and heating or a solution of methyl pyrrolidinium nickel tartrate or dimethyl butyl ammonium nickel tartrate; (4) by adding nickel acetate and propionyl propionic acid (or lactic acid) to a mixture of propionic acid and water and reacting the mixture with ethylene and carbon monoxide; in other examples: (5) propionic acid is obtained by treating a mixture of water, propionic acid, nickel acetate (or cobalt propionate) and citric acid with ethylene and carbon monoxide; (6) propionic acid is obtained by reacting ethylene and carbon monoxide with a mixture of water, propionic acid, cobalt acetate and propionyl propionic acid; (7) propionic acid propyl ester and some propionic acid are obtained by treating a mixture of n-propanol, propionic acid, water, cobalt acetate, pyridine, and tartaric acid with an ethylene-carbon monoxide mixture. The distillation residue remaining after removing the product may be used without purification to catalyse a new batch of starting materials.