The role of cationic additions in molybdate multi-component catalysts

In order to determine the role and the influence of added cations in the industrial catalysts of mild oxidation of olefins, several mechanical mixtures have been prepared. Ferric molybdate Fe2(MoO4)3 was mixed with Cobalt molybdate CoMoO4, nickel molybdate NiMoO4 and magnesium molybdate MgMoO4 and the resulting mixtures were annealed at different temperatures over different periods. Analysis of the prepared materials by Mössbauer spectroscopy and XRD show that iron occurs in solid solution in the molybdate structures similarly to that of solid samples prepared by coprecipitation method. Further investigation shows evidence of reduction of initial Fe3 +  species into Fe2 +  by substitution of M2 +  ions to form M(Fe2 + )MoO4 solid solution and the process is greatly enhanced by increasing the annealing time and temperature.