Patent ID: 8729288

Claim:
A method for producing 2-hydroxy-4-(methylthio)-butyronitrile, comprising: reacting 3-methylmercaptopropionaldehyde with hydrogen cyanide in the presence of a base as catalyst in a main reaction zone of a multizone reactor to form a reaction mixture comprising the 2-hydroxy-4-(methylthio)butyronitrile, unreacted 3-methylmercaptopropionaldehyde, the catalyst and residual amounts of gaseous hydrogen cyanide; removing the residual gaseous hydrogen cyanide from the main reaction zone to an absorption and post-reaction zone of the reactor which comprises a mixture of 3-methylmercaptopropionaldehyde and the catalyst; and further reacting the gaseous hydrogen cyanide with the 3-methylmercaptopropionaldehyde in the absorption and post reaction zone.