Production of unsaturated aldehydes

An oxidation catalyst comprises cobalt molybdate and a tellurium compound additive. The catalyst may be used on a support, e.g. silica.ALSO:Acrolein or methacrolein is produced by reacting propylene or isobutene at elevated temperature in the vapour phase with molecular oxygen in the presence of an oxidation catalyst, the reaction being effected in a series of adiabatic stages with interstage cooling of the reactants and the reaction temperature in each stage being controlled by the residence time in each stage and/or the inlet temperature of the reactant mixture to that stage. Suitable catalysts, for example, are bismuth molybdate, bismuth phosphomolybdate, antimony molybdate, tin antimonate and/or cobalt molybdate which may also contain tellurium. If desired the catalyst may be used on a support such as silica. Specifications 821,999, 839,808 and 878,803 are referred to.