GB630279A - Improvements in or relating to the synthesis of carboxylic acids - Google Patents

Abstract

Carboxylic acids are produced by reaction at above 150 DEG C. and under superatmospheric pressure of a compound containing non-aromatic olefinic unsaturation with carbon monoxide and water in the presence of a preformed nickel or cobalt carbonyl catalyst and in the absence of inorganic acidic substances. Olefinic compounds used include hydrocarbons, e.g. ethylene, propylene, butene-2, isobutene, pentene-1, tetramethyl ethylene, diisobutene, cracked or dehydrogenated petroleum fractions, cyclohexene, butadiene, isoprene, polymerized dienes, rubber, styrene, a -methyl styrene, vinyl cyclohexene, pinene, limonene, cyclohexadiene and dicyclopentadiene, allyl alcohol, acetate, and ethers, methallyl alcohol, vinyl acetate, furane, methyl acrylate and methacrylate, methallyl propionate, methyl oleate, oleic acid, methyl vinyl ketone and ether, cyclohexene carboxylic acids and their esters, methallyl methacrylate, acrolein and, generally, olefinic esters, ethers, carboxylic acids, amides, aldehydes, and ketones. Polymerization inhibitors may be employed. The amount of carboxyl catalyst is generally about 0.05-30 per cent by weight of the reaction mixture. It may be combined with inert materials or promoters, e.g. thoria or manganese. Pressure may be 50-3000 atm. or more. Products additional to carboxylic acids may be formed. Thus, ethylene yields diethyl ketone, and oleic acid yields products containing alcoholic hydroxyl as well as carboxyl. Preferably 0.1-10, especially 0.8-2 moles. of olefin, and 0.1-20, especially 0.8-5 moles. of carbon monoxide are used per mole. of water. If the amount of water is less than that required for formation of carboxylic acids, other oxygenated products may be produced also. Temperature is generally 150-500 DEG C., preferably 175-375 DEG C. Inert liquid reaction media such as carboxylic acids, dialkyl ethers, dioxane, cyclohexane, aromatic and saturated hydrocarbons, may be present. Carbon dioxide may be added to suppress the water/gas reaction. In continuous operation, tubular converters with temperature and pressure gradients, and introduction of reactants at spaced points may be used. The carboxyl may be recovered by distillation under a blanket of carbon monoxide. In examples, ethylene is converted to propionic acid, propylene to butyric acid, and oleic acid yields a product of high acid and hydroxyl number, nickel carboxyl being the catalyst.