Abstract: The invention refers to the use of a particulate catalyst containing 60.0 to 99.5 wt. % ZrO2 stabilised with an oxide of the element Hf and at least one oxide of the element M, wherein M=Ce, Si, Ti, or Y, for the hydrolysis reaction of methionine amide to methionine, wherein the median particle size x50 of the particulate catalyst is in the range of from 0.8 to 9.0 mm, preferably of from 1.0 to 7.0 mm. The invention also refers to a process for preparing methionine comprising a step of contacting a solution or suspension comprising methionine amide and water with said particulate catalyst to provide a reaction mixture comprising methionine and/or its ammonium salt from which methionine can be isolated.

Abstract: The invention refers to the use of a particulate catalyst containing 60.0 to 99.5 wt. % ZrO2 stabilised with an oxide of the element Hf and at least one oxide of the element M, wherein M=Ce, Si, Ti, or Y, for the hydrolysis reaction of methionine amide to methionine, wherein the median particle size x50 of the particulate catalyst is in the range of from 0.8 to 9.0 mm, preferably of from 1.0 to 7.0 mm. The invention also refers to a process for preparing methionine comprising a step of contacting a solution or suspension comprising methionine amide and water with said particulate catalyst to provide a reaction mixture comprising methionine and/or its ammonium salt from which methionine can be isolated.

Abstract: The invention relates to a process for preparing 2,6-bis(methionyl)-1,4-dketopiperazine, comprising the following steps: a) heating a reaction mixture comprising methionine and polar protic solvent at a temperature of less than 170.0° C., while passing an inert gas stream over or through the reaction mixture; b) obtaining 2,6-bis(methionyl)-1,4-diketopiperazine.