Stable molybdenum catalyst for converting C3- and C4-olefins into unsaturated aldehydes and acids

摘要

A stabilised heteropolymolybdate catalyst starting material in calcined form, which contains anionic molybdenum in the defect state, is impregnated on its surface with certain metal cations. The stabilised starting material is obtained by incorporating an aqueous chloride ion-containing solution and a phosphorus tungstate, silicon tungstate, vanadium arsenate, silicon arsenate, phosphorus vanadate or silicon vanadate compound into the reaction product of a molybdate and a soluble phosphate, silicate or arsenate, and then carrying out drying and calcination. During the chloride ion stabilisation step, other metals can be incorporated in the preparation of the stabilised starting material. The starting material obtained is catalytically active in the conversion of unsaturated aldehydes into the corresponding unsaturated carboxylic acids with or without incorporation of the metal cation during the chloride ion stabilisation step. If the calcined starting material obtained is impregnated on the surface with a metal cation of Group VIII, preferably with cobalt and/or iron, and with a selenium or tellurium compound, the catalysts obtained have high activity and are capable of converting C3- and C4-monoolefins in a single stage into the corresponding unsaturated carboxylic acids.