Removal of lead from organic diaryl carbonate reaction mixtures

摘要

A method for efficient removal of lead co-catalyst species from organic process streams arising from diaryl carbonate synthesis, by contacting the organic reaction mixtures with an aqueous acid, salt, or acid/salt solution, thereby extracting the treated mixture into an aqueous phase, or by treating the organic reaction mixtures with solid oxalic acid or oxalic acid salt, or an aqueous solution of oxalic acid or oxalic acid salt, thereby resulting in precipitation of the lead. The precipitated lead may then be calcined to provide a lead compound that is catalytically active in the carbonylation of phenol to yield diary carbonates. Use of these methods will substantially reduce both financial and environmental concerns for the preparation of diaryl carbonates.