The calcination of the precursor compositions to produce the actual catalytically active multimetal oxide compositions is generally carried out, regardless of whether it is before or after shaping, at from 250 to 600??? C., preferably from 300 to 450??? C. Calcination can be carried out under inert gas, e.g. nitrogen, a mixture of inert gas and oxygen, e.g. air, reducing gases such as hydrocarbons