Patent ID: 6670501
Filing Date: 2003-12-30
Classification: C07C

Abstract:
A process for the production of methyl methacrylate, which process comprises the steps of:(i) reacting propionic acid or an ester thereof with formaldehyde or a precursor thereto in a condensation reaction to produce a gaseous product stream comprising methyl methacrylate, residual reactant, methanol and byproducts; (ii) processing at least a portion of the gaseous product stream to form a liquid product stream comprising substantially all of the methyl methacrylate and at least one impurity which melts at a temperature greater than that of methyl methacrylate; and subjecting said liquid product stream to at least one fractional crystallisation stage which comprises the steps of:(a) cooling said liquid product stream to between the freezing temperature of methyl methacrylate and about âˆ’95Â° C. such that said liquid product stream forms crystals of solid methyl methacrylate and mother liquor, said crystals containing a higher proportion of methyl methacrylate than does said liquid product stream or mother liquor, (b) separating said crystals of solid methyl methacrylate from said mother liquor and (c) melting said crystals to form liquid methyl methacrylate which contains a lower concentration of said at least one impurity than said liquid product stream.