Oxygen depletion of bismuth molybdates

L K YONG, Russell Francis Howe, G W KEULKS, W K HALL

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Abstract

Pure ..cap alpha..-phase bismuth molybdate (Bi/sub 2/Mo/sub 3/O/sub 12/), which is known to be weakly active for selective oxidation, and pure ..gamma..-phase bismuth molybdate (Bi/sub 2/MoO/sub 6/), which has good activity, were subjected to oxidation-reduction cycles with known amounts of hydrogen and oxygen, at 300/sup 0/-570/sup 0/C and with evacuation steps between treatments. The volume of oxygen consumed during reoxidation was equal to half the hydrogen consumed during the reduction on the ..cap alpha..-phase, which indicated that no hydrogen was retained during reduction. For the ..gamma..-phase, the oxygen consumption was greater than half of the hydrogen consumption and it increased with extent of reduction. The excess oxygen was apparently consumed by filling anion vacancies formed during outgassing subsequent to the reduction step. ESR spectroscopy and temperature-programed oxidation-reduction indicated that lattice oxide ions which bridge between bismuth and molybdenum layers of the koechlinite structure become more labile when the catalyst is in a partially reduced state, and that this effect is greater in the ..gamma..- than the ..cap alpha..-phase. Table and 15 references.
Original languageEnglish
Pages (from-to)544-546
Number of pages3
JournalJournal of Catalysis
Volume52
Issue number3
Publication statusPublished - 1 May 1978

Cite this

YONG, L. K., Howe, R. F., KEULKS, G. W., & HALL, W. K. (1978). Oxygen depletion of bismuth molybdates. Journal of Catalysis, 52(3), 544-546.