| abstract |
The invention relates to an improved process for synthesizing alkyl methacrylates, in particular methyl methacrylate (MMA), involving reacting acetone cyanohydrin (ACH) and sulfuric acid in a first reaction stage (amidation) and heating the first reaction mixture in a second reaction stage (conversion) such that methacrylamide (MAA) is obtained, and then esterifying methacrylamide (MAA) with alcohol and water, preferably methanol and water, in a third reaction stage such that alkyl methacrylate is formed, wherein the sulfuric acid used has a concentration of 98.0 wt% to 100.0 wt%, and wherein the subsequent working up of the third reaction mixture involves least two distillation steps in which the byproducts methacrylonitrile (MeAN) and acetone are obtained as an aqueous heteroazeotrope at least in part in the top fraction, and at least some of the aqueous heteroazeotrope is removed from the process and at least partially reintroduced into the third reaction stage. |