Patent ID: 8426637

Claim:
A process for preparation of pure methacrylic acid, comprising: a) carrying out gas phase oxidation of a C 4 compound to obtain a methacrylic acid-comprising gas phase, b) condensing the methacrylic acid-comprising gas phase to obtain an aqueous methacrylic acid solution, c) separating at least a part of the methacrylic acid from the aqueous methacrylic acid solution to obtain at least one crude methacrylic acid-comprising product; and d) separating at least a part of the methacrylic acid from the at least one crude methacrylic acid-comprising product by a thermal separation process to obtain a pure methacrylic acid; wherein said thermal separation process is a distillation or rectification; wherein in d), the methacrylic acid is separated by rectification from at least a part of the at least one crude methacrylic acid-comprising product, wherein the pure methacrylic acid is removed in a side outlet from a column used for the rectification; and wherein the amount of pure methacrylic acid removed in a defined time interval is 40 to 80% of the amount of the amount of crude methacrylic acid-comprising product introduced into the rectification column in the same time interval.