GB809496A - Improvements in or relating to the preparation of carboxylic acid esters - Google Patents

Abstract

Catalysts for use in the preparation of esters (Group IV (b)) by reacting an unsaturated hydrocarbon with carbon monoxide and an alcohol consist of a combination of an alcohol-soluble salt of tin or germanium with an alcohol-soluble salt of a noble metal from Group 8 of the Periodic Table. Suitable tin and germanium salts are, for example, stannous and stannic chlorides, bromides, fluorides, iodides and sulphates, germanium di- and tetrachlorides, tetraiodide and tetrafluoride. Suitable salts of noble metals are, for example, ruthenium tri-and tetrachloride and tribromide; rhodium trichloride tetrahydrate; palladium dichloride, dibromide and nitrate; osmium di- and trichloride; iridium tetrabromide and tetrachloride; and plastinic bromide, chloride and sulphate. For the purposes of the invention compounds such as chloroplatinic acid and osmic acid are considered as salts. In the examples, catalysts are prepared by mixing (a) platinous chloride, stannous chloride dihydrate and aqueous hydrogen chloride; (b) a solution of stannous chloride dihydrate in methanol and a solution of chlorplatinic acid in methanol; (c) a solution of stannous chloride dihydrate in methanol and a solution of osmic acid in methanol; (d) a solution of bromoplatinic acid in methanol and a solution of stannous bromide in methanol; (e) chlorplatinic acid and stannous chloride dihydrate in n-butyl alcohol solution; (f) methanol, germanium tetrachloride and platinic chloride; (g) methanol, germanium tetrachloride and ruthenium trichloride; (h) methanol, rhodium chloride and germanium tetrachloride; (j) methanol, iridium chloride and germanium tetrachloride; (k) methanol, iridium trichloride and stannous chloride; (l) methanol, palladium dichloride and germanium tetrachloride; (m) methanol, palladium chloride and stannous chloride; and (n) methanol, ruthenium and ribromide and stannous bromide. In one example the catalyst is prepared by reacting an aqueous solution of platinic chloride with sulphuric acid, evaporating the product to dryness, dissolving the residue in methanol and adding to this solution an aqueous solution of stannous sulphate.ALSO:Carboxylic acid esters are prepared by a process comprising reacting carbon monoxide, a non-aromatic unsaturated hydrocarbon in which each of the plurally-bonded carbon atoms is bound directly to not more than one other carbon atom, and a monohydric primary or secondary alcohol, in the presence of a catalyst (see Group III) which is a combination of an alcohol-soluble salt of tin or germanium with an alcohol-soluble salt of a noble metal from Group VIII of the periodic Table at a temperature of from 30 DEG to 325 DEG C. and under a pressure of from 100 to 3000 atmospheres. In one method of carrying out the process a pressure reactor is charged with a primary or secondary alcohol and catalyst and the unsaturated hydrocarbon and carbon monoxide are injected into the mixture. In the examples: (a) methyl, ethyl, propyl, butyl and cyclohexyl alcohols are reacted with ethylene and carbon monoxide to give the corresponding esters of propionic acid; (b) methyl alcohol and carbon monoxide are reacted with propene, cyclohexene, allene, methyl acetylene and cis-2-butene to give respectively the methyl esters of butyric acid, cyclohexane carboxylic acid, methacrylic acid (with some methyl crotonate) and ethyl-acetic acid; and ethyl alcohol and carbon monoxide react with butadiene to give ethyl pentenoate. In all cases the catalyst consisted of a salt, e.g. chloride or sulphate, of tin or germanium with a salt, for example the chloride or bromide, of a noble metal, e.g. platinum, osmium, ruthenium, rhodium, iridium or palladium. In some cases diethyl ketone is also obtained.