Method of preparing vinyl esters of carboxylic acids

摘要

Vinyl esters are produced by reacting a carboxylic acid and a vinyl ester reactant in the presence of a mercury-acid salt vinyl inter-change catalyst, neutralizing the co-catalyst acid with a neutralizing agent comprising an alkaline earth metal base which is insoluble in the reaction product mixture to form an insoluble salt of the catalyst acid, removing the resulting insoluble material from said reaction product mixture, separating the vinyl ester product and mercury-containing residue and repeating said reaction using the mercury-containing residue with a corresponding amount of strong acid catalyst. The neutralization and removal of insoluble material may be effected at about 60 DEG C., filtration being aided by adding a finely divided diatomaceous earth. Low-boiling constituents may then be removed by distillation, and the vinyl ester product separated, e.g. by distillation or by extraction, for example as described in Specification 869,830. The carboxylic acid may be an aliphatic monocarboxylic acid, aliphatic dicarboxylic acid, half ester of an aliphatic or aromatic dicarboxylic acid, an alicyclic acid or aromatic acid. Vinyl acetate is the preferred ester but vinyl esters up to the heptanoate are specified. Mercury salt-strong acid catalysts are most effective including mercuric oxide or acelate with sulphuric, phosphoric, p-toluene sulphonic or trifluoroacetic acid. During the reaction, the vinyl ester reactant by-product acid may be continuously removed as described in Specification 869,829. Examples describe the preparation of vinyl stoarate, divinyl sebacate, vinyl benzoate, methyl vinyl succinate, vinyl cyclohexane carboxylate, and methyl vinyl phthalate.