A process for the production of ethylenically unsaturated carboxylic acid esters and a catalyst therefor

A process for the production of an ethylenically unsaturated carboxylic acid ester, preferably an α,ß ethylenically unsaturated carboxylic acid ester is described. The process takes place by the reaction of formaldehyde or a suitable source thereof with a carboxylic acid ester in the presence of a basic metal methyl carbonate co-reactant, wherein the process produces a second basic metal salt and wherein the process includes the step of contacting the second basic metal salt with: a)carbon dioxide (CO2) and optionally, methanol, and/or b)dimethyl carbonate, to regenerate the basic metal methyl carbonate co-reactant. The invention includes use of carbon dioxide and/or dimethyl carbonate to regenerate a basic metal methyl carbonate.