STRUCTURAL, SURFACE, AND CATALYTIC PROPERTIES OF BISMUTH MOLYBDOVANADATES CONTAINING FOREIGN ATOMS .5. OXIDATIVE DEHYDROGENATION OF 1-BUTENE ON IRON-CONTAINING BISMUTH MOLYBDOVANADATE CATALYSTS

The oxidative dehydrogenation of 1-butene has been studied over catalysts with the scheelite structure and general formula Bi1-x/3squarex/3-yMey[V1-xMOx-yFey]O4 with x = 0.45; y = 0, 0.10, or 0.15; Me = Fe or Bi. Experiments were carried out in a pulse microreactor in the temperature range 473-673 K. The trend of total conversion with catalyst composition is similar to that found previously for the same catalysts in propene oxidation. Moreover, the total conversion was identical in the presence and in the absence of gaseous oxygen in the pulse (first pulse with 1-butene alone). On the other hand, the production of butadiene was markedly different from that of acrolein in the propene reaction for the catalyst in which the cationic vacancies were completely filled with bismuth ions (y = 0.15, Me = Bi). This finding points to a differing importance of the cationic vacancies depending on whether the selective reaction occurs with oxygen insertion. Also the oxidation to isomerization ratios and the reduction-oxidation properties changed with catalyst composition. The results are discussed in terms of participation of cationic vacancies and iron ions in the steps of the allylic oxidation. (C) 1994 Academic Press, Inc.