Patent ID: 7128813

Claim:
A process for the preparation of high purity methacrylic acid with minimization of decomposition of hydroxy isobutyric acid (HIBA), said process comprising: (i) using a first distillation column, a second distillation column and a third distillation column; (ii) feeding a crude methacrylic acid, which was formed by hydrolyzing acetone cyanohydrin, to an upper section of said first distillation column, said crude methacrylic acid comprising methacrylic acid, light ends and heavy ends, said light ends comprising water and acetone and said heavy ends comprising HIBA; (iii) distilling said crude methacrylic acid in said first distillation column, at a pressure between 50 and 80 mmHg and a temperature between 70 and 10° C., to form a first overhead vapor stream comprising light ends and a first bottom liquid stream comprising methacrylic acid and heavy ends; (iv) feeding said first bottom liquid stream to a center section of said second distillation column; (v) distilling said first bottom liquid stream in said second distillation column, at a pressure between 60 and 100 mmHg and a temperature between 75 and 115° C., to form a second overhead vapor stream comprising methacrylic acid and light ends and a second bottom liquid stream comprising heavy ends; (vi) feeding at least a portion of said second overhead vapor stream to an upper section of said third distillation column; (vii) distilling said at least a portion of said second overhead vapor stream in said third distillation column, at a pressure between 50 and 80 mmHg and a temperature between 70 and 110° C., to form a third overhead vapor stream comprising light ends and a third bottom liquid stream comprising methacrylic acid wherein said methacrylic acid has an impurity level of not more than 1% by weight wherein no more than 0.05% by weight is water, such that the decomposition of HIBA to water and acetone is minimized.