Patent GB-490334-A (GB)
Title: Improvement in the production of vinyl esters
IPC: B63B23/58
Filed: 1937-10-15
Abstract: Catalytic agents for use in the preparation of vinyl esters and ethylidene diesters from acetylene and carboxylic acids consist of mercury compounds of heteropoly acids which may be prepared by (a) passing acetylene into a solution of mercuric carboxylate in the corresponding acid and adding the heteropoly acid; (b) saturating a solution of the heteropoly acid with acetylene and adding a solution of the mercuric carboxylate in the carboxylic acid; (c) dissolving mercuric oxide in the carboxylic acid, adding the heteropoly acid and stirring under acetylene.  Heteropoly acids specified are silicotungstic, phosphotungstic, silicomolybdic, phosphomolybdic, tungstomolybdophosphoric and borotungstic acids. Carboxylic acids specified are formic, acetic, propionic, butyric and 2-ethylbutyric acids.  The spent catalyst may be recovered by separating it from the liquid by filtration, centrifuging or distillation, distilling the solid at low pressures to recover the mercury and treating the residue with sodium hydroxide yielding a solution from which the heteropoly acid is obtained in the usual manner.ALSO:<PICT:0490334/IV/1> Vinyl esters and ethylidene diesters are prepared by reacting acetylene with a carboxylic acid in the presence of a mercury compound of a heteropoly acid.  These catalysts may be prepared by (a) passing acetylene into a solution of mercuric carboxylate in the corresponding acid and adding the heteropoly acid; (b) saturating a solution of the heteropoly acid in the carboxylic acid with acetylene and adding a solution of the mercuric carboxylate in the carboxylic acid; (c) dissolving mercuric oxide in the carboxylic acid, adding the heteropoly acid and stirring under acetylene.  Heteropoly acids specified are silicotungstic, phosphotungstic, silicomolybdic, phosphomolybdic, tungstomolybdophosphoric and borotungstic acids.  Carboxylic acids specified are formic, acetic, propionic, butyric and 2-ethylbutyric acids.  The esters may be prepared by any of the known methods using the above catalysts, the following continuous method being preferred. Acetylene is passed into the carboxylic acid containing the catalyst in the reaction vessel R, at about 35 DEG  C., a portion of the reaction mixture being withdrawn continuously or periodically and passed to the still S, where the vinyl ester is distilled off, while fresh carboxylic acid is added via C.  A part of the residue from S is returned to R and the remainder passed to the still SS, where the carboxylic acid is distilled off and returned to R, the residual ethylidene diester, if not desired for use as such, being hydrolysed in F, to give the carboxylic acid (which is returned to R) and acetaldehyde, which is oxidized in G to acetic acid.  The spent catalyst may be recovered by separating it from the liquid by filtration, centrifuging or distillation, distilling the solid at low pressures to recover the mercury and treating the residue with sodium hydroxide to give a solution from which the heteropoly acid is obtained.  When higher carboxylic acid esters are being prepared, the catalyst is made in the presence of a lower acid and then added to the higher acid.  In the examples, details of preparing vinyl acetate at different temperatures with different catalysts are given.