Methacrylic acid and derivs from methacry- - lonitrile and hcn

摘要

Methacrylic acid and its derivatives are made by reacting a mixt. of HCN, acetonitrile and methacrylonitrile with acetone in the presence of an alkali metal hydroxide catalyst, neutralising the product with an inorg. acid, distilling off the acetonitrile and reacting the residue (comprising a binary mixture of methacrylonitrile and acetone cyanohydrin) with conc. H2SO4 in the pres. of CuSO4 or hydroquinone, and separating the product from the reaction mass. Pref. starting material is the product obt. by oxidative ammonolysis of isobutene, reacted with acetone at 15-20 degrees C. After distilling off the acetonitrile, the residue is treated with the H2SO4/CuSO4 at ca.100 degrees C and the methacrylic acid recovered by diluting the mass with water, distilling off a water/methacrylic acid azeotrope, and subjecting this to extractive distillation in the presence of dichloroethane. Acrylamide can be formed by neutralising the mass with ammonium carbonate, filtering off the ppt. and extracting with diethyl ether. Methacrylic esters are made by cooling the mass to 40 degrees C, adding an aliphatic alcohol R-OH where R = 1-4 C alkyl grp., heating to 100 degrees C and fractionating the product. High yield obt; uses less H2SO4 than known processes.