Nature of the β-phase of bismuth molybdate

Abstract

Infrared and Raman spectroscopies, X-ray diffraction and d.s.c. analysis have confirmed that the β-phase (B mixture) is different from an equimolar mixture of the α- and γ-phase (A mixture) of bismuth molybdate. A comparison of the catalytic properties between A and B mixtures in the partial oxidation of propene and the dehydrogenation–dehydration of isopropanol also confirms this difference. The β-phase is a defined phase of the bismuth molybdate system and is metastable at room temperature, but is stable enough to be used in catalytic tests. The enthalpy of transformation of mixture A to mixture B at 560 °C was found to be 6330 J mol^–1.