GB750538A - Improvements in the production of acrylic acid - Google Patents

Abstract

Acrylic acid is produced by the catalytic reaction of acetylene with carbon monoxide and water at raised temperature and under elevated pressure using an inert oxygen-containing organic solvent in excess and in the presence of a catalyst containing a soluble compound of a carbonyl-forming metal of the iron group and halogen either in free or combined form and in the presence of an activator consisting of a small amount of a soluble copper compound. The catalyst is used in such small amount that it is homogeneously dissolved. Preferred solvents are cyclic ethers such as tetrahydrofurane, -pyrane and 1,4-dioxane, and saturated ketones such as acetone, methyl ethyl and diethyl ketone. Cyclic esters and amides such as butyrolactone or N-alkyl-lactones such as N-methyl and -ethyl pyrrolidones may also be used. The preferred catalysts are nickel chloride and bromide. Carbonyls of metals of the iron group with free halogens, hydrogen halides, or other metal halides may also be used. Preferred activators are copper halides but other water-soluble salts such as the sulphate, acetate or propionate may be used. Powdered copper may also be added. The preferred temperatures are in the range 150 DEG to 250 DEG C. and the preferred pressures are in the range 20 to 60 atmospheres. The process may be carried out batchwise or continuously. In the examples acrylic acid is prepared by reacting acetylene with carbon monoxide using (a) nickel bromide as catalyst and copper chloride as activator; (b) nickel carbonyl and hydrogen bromide as catalyst and copper bromide as activator; (c) nickel chloride as catalyst and copper chloride as activator; (d) iron carbonyl and bromine as catalyst and copper bromide as activator; (e) nickel carbonyl, iron carbonyl and bromine as catalyst and copper bromide as activator; (f) cobalt bromide as catalyst and copper bromide as activator; and (g) nickel bromide as catalyst and copper chloride as activator.