GB795287A - Improvements in or relating to the production of vinyl esters - Google Patents

Abstract

Vinyl esters are prepared by reacting acetylene and a carboxylic acid using standard fluidized-bed technique, the catalyst, consisting of at least one metallic salt known to activate the reaction and which is capable of regeneration by combustion, being continuously removed from the reaction zone, a deposit of catalytic particles being formed at the lower end of the reactor acting as a substantially water-impermeable pad, regenerated by combustion and recycled to the reactor. The rate of flow of reactants is greater than that which would permit complete reaction. The catalyst is used as a powder, alone or on a support such as silica gel or clay. The particle size may vary from 40-200 microns, 95 per cent of the particles being from 50-150 microns. Zinc and cadmium silicates are the preferred catalysts. The reactants may be used in stoichiometric proportions or one reactant, preferably the acetylene, may be in excess. The gaseous mixture leaving the reaction zone is freed from entrained catalyst by, for example, cyclone separators, filters or electrical precipitators and cooled to condense the vinyl ester, the unreacted reactants being recycled to the reaction zone. The vinyl ester is fractionally distilled to eliminate impurities, dissolved acetylene and unreacted acid, the last two being recycled. The reaction temperature is generally 150-300 DEG C. The reaction zone is preferably surrounded by a cooling jacket. Examples describe the preparation of vinyl acetate and vinyl butyrate, but the process is stated to be applicable generally to vaporizable, acyclic or cyclic, mono- or polycarboxylic, substituted or unsubstituted acids.