GB743933A - Improvements in or relating to synthesis of carboxylic acids - Google Patents

Abstract

Carboxylic acids are synthesized by the catalytic addition of carbon monoxide to an alcohol, or of carbon monoxide and water to an olefin, ether or carboxylic acid ester in the presence of a catalyst containing an element of the iron sub-group and chlorine, bromine or iodine, at a temperature of from 200 DEG to 350 DEG C. and a pressure of 2000 to 15,000 p.s.i., in which the reaction is conducted in a reactor, the inner surfaces of which consist of, or which is lined with, a metal containing at least 90 per cent titanium or zirconium. Alcohols specified are methanol, ethanol, propanol, isopropanol, butanol, amyl alcohol, cyclohexanol, terpinol, fenchyl alcohol and benzyl alcohol. An acrylic or alicyclic olefine, or an aromatic hydrocarbon with an olefinic side chain may be used, e.g. ethylene, propylene, isobutylene, pentenes, hexenes, cyclohexene, menthene, camphene or styrene. The reaction is applicable to any alkyl, cycloalkyl, aralkyl or aryl ether, either simple or mixed. Thus acetic acid is obtained from dimethyl ether and propionic acid from diethyl ether. Dicarboxylic acids are obtained from cyclic ethers, e.g. adipic acid from tetrahydrofuran. The ester used may be any alkyl, cycloalkyl, aralkyl, mono or polyhydric alcohol ester of any alkanoic, cycloalkanoic, aryl or aralkyl carboxylic acid. In the catalyst, iron, cobalt or nickel may be used as free metal, or as a compound, e.g. carbonyl, acetate, or halide. The halogen may also be free or in the form of an inorganic salt or organic halide, such as methyl or ethyl iodide. A combination of nickel and iodine, either as free elements, as nickel iodide, or a combination of, e.g., nickel acetate or carbonyl with bismuth iodide, cuprous iodide or hydrogen iodide, is preferred. According to examples: (a) acetic acid, with methyl acetate as by-product, is produced by reaction of methanol, dimethyl ether, or methyl acetate with carbon monoxide and water, in a titanium-lined reactor, using as catalyst nickel iodide, nickel chloride, or nickel bromide, or a combination of nickel acetate, nickel carbonyl, nickel powder or cobalt acetate with methyl iodide, or nickel acetate with iodine; (b) pentene-1 is similarly converted to 2-methyl-pentanoic acid and n-hexanoic acid, and hexenes are converted to heptanoic acids, using nickel acetate-hydriodic acid as catalyst; (c) camphene is similarly converted to an acid using nickel iodide and bismuth triiodide as catalyst; (d) using a platinum-lined reactor in which strips of zirconium are hung, methanol is reacted with carbon monoxide and water, using a nickel iodide catalyst, to give acetic acid. Specification 628,161 is referred to.ALSO:A reactor, the inner surfaces of which consist of, or which is lined with, a metal containing at least 90 per cent titanium or zirconium is used for the synthesis of organic carboxylic acids by the catalytic addition of carbon monoxide to an alcohol, or of carbon monoxide and water to an olefin, ether or carboxylic acid ester, in the presence of a catalyst containing an element of the iron subgroup and chlorine, bromine or iodine, at a temperature of 200 DEG to 350 DEG C. and a pressure of 2000 to 15,000 p.s.i. Titanium and zirconium are resistant to the highly corrosive conditions of these syntheses. All parts of the apparatus coming into direct contact with the reactants or products at high temperatures and pressures are made of, plated with, or inner-lined with a metal containing at least 90 per cent titanium or zirconium. Such a plating or inner lining may be held in place by other materials capable of withstanding the temperature and pressure.