Process for producing methyl methacrylate having reduced biacetyl content

摘要

This invention provides a process for reducing biacetyl in alpha-, beta-unsaturated carboxylic acid esters, particularly in acrylic or methacrylic (hereinafter “(meth)acrylic”) esters, which comprise low levels of weak acid.

主权项

1. A process for removing biacetyl from an alpha-, beta-unsaturated carboxylic acid ester, comprising:
a) treating a crude alpha-, beta-unsaturated carboxylic acid ester to produce said alpha-, beta-unsaturated carboxylic acid ester which comprises biacetyl and has a weak acid content of between 0.001% and 5.0% by weight, based on the total weight of said alpha-, beta-unsaturated carboxylic acid ester; wherein the weak acid comprises carboxylic acid selected from the group consisting of acrylic acid and methacrylic acid, and b) adding to said alpha-, beta-unsaturated carboxylic acid ester, at a temperature of from 40 to 120° C., from 1 to 10 molar ratio of an aromatic ortho-diamine, based upon moles of biacetyl, to produce an amine-treated ester mixture, said aromatic ortho-diamine having the formula: where X is NR3R4 and R1, R2, R3, R4, and Y are independently selected from hydrogen, alkyl, phenyl, and naphthyl.