Redox chemistry of molybdena-silica catalysts: 2. Photoreduction

S R SEYEDMONIR, Russell Francis Howe

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Abstract

An EPR study of Mo5+ species formed on photoreduction of MoO3---SiO2 catalysts in H2 is reported. The major product of photoreduction at -253 °C is a tetrahedrally coordinated Mo5+OH- species showing 1H hyperfine splitting formed by reaction of H2 with a hole—electron pair. At higher temperatures this is converted to an octahedral Mo5+OH- also showing 1H hyperfine splitting, and ultimately to a distorted octahedral Mo5+O2- species which has no bound protons and which resembles the Mo5+ formed on thermal reduction of the same catalysts in H2 above 300 °C. A CO adduct of the tetrahedral Mo5+OH- has been characterized by its EPR spectrum. The chemistry of photoreduction is compared with that of thermal reduction, and it is suggested that both may occur via similar pathways.

Original languageEnglish
Pages (from-to)229-242
Number of pages14
JournalJournal of Catalysis
Volume110
Issue number2
DOIs
Publication statusPublished - Apr 1988

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