The synergy effect between gamma and beta phase of bismuth molybdate catalysts: Is there any relation between conductivity and catalytic activity?

This work aims to clarify the postulate that the catalytic activity of bismuth molybdates (β-Bi2Mo2O9 and γ-Bi2MoO6) and their mixtures is related to their conductivity. Mixtures of these pure bismuth molybdate phases have been recognized to possess high catalytic activities owing to the synergy effect. Pure bismuth molybdate phases and their mixtures were synthesized using sol–gel method. This method has been considered as one of the best methods to result in stoichiometric bismuth molybdate products. Conductivities of these samples were recorded at the catalytic reaction temperature (300–450 °C). The comparison of the measured conductivities allows us to conclude that the high number of active sites to abstract the α-hydrogen is more important factor than the influence of conductivity in the mechanism of the selective oxidation of propylene.