The selective oxidation of 1-butene over a multicomponent molybdate catalyst. Influences of various elements on structure and activity

Structures, activities and selectivities were investigated of catalysts with the general formula: MeaIIMebIIIBicModOe, in which MeII is Ni, Co, Mg or Mn and MeIII is Fe, Cr, Al or Ce. The structural and catalytic properties lead to division into two categories, one when MeIII is Fe, Cr or Al and the other when MeIII is Ce. In the first group catalytic activity and selectivity is connected with Bi2MoO6 and Bi2Mo3O12, present as an outer layer on a nucleus formed by MeIIMoO4 (with β-CoMoO4 structure) and Me2III(MoO4)3. The formation of Bi2MoO6 is promoted by MeIII in the sequence Fe > Cr > Al. Moreover Bi2MoO6 is activated by use of Fe. Me2III(MoO4)3 has been proved to be a stabilizer of the β-CoMoO4 structure. In the second group the promoter effect seems to be connected with an incorporation of Bi3+ in the Ce-molybdate and there is no specific preference for the β-CoMoO4 structure.