Patent ID: 7423173

Claim:
A process for preparing methacrylic acid comprising: a) reacting acetone cyanohydrin with a maximum of 1.2 equivalents of sulphuric acid in the presence of 0.05-1.0 equivalent of water; wherein said reacting occurs in the presence of an inert polar solvent at a temperature below 80° C. and forms a stirrable solution of the corresponding amide sulphate(s) in the inert solvent, b) adding water to the stirrable solution of a) and removing the inert polar solvent to produce a solution containing water, ammonium hydrogensulphate and alpha-hydroxyisobutyric acid, c) adding an extractant to remove the hydroxyisobutyric acid from the solution produced by b) and recovering a solution containing alpha-hydroxyisobutyric acid in the presence of a metal salt of alpha-hydroxyisobutyric acid d) converting in liquid phase the solution containing alpha-hydroxyisobutyric acid obtained by c) at a temperature between 160-300° C. to a mixture substantially comprising methacrylic acid and water, and e) recovering the methacrylic acid.