Interaction of HCI and HBr with a Molybdena-Alumina Catalyst

S ABDO, A KAZUSAKA, Russell Francis Howe

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Abstract

The interaction of HC1 and HBr with molybdena-alumina catalysts has been investigated by using EPR, infrared,
and Raman spectroscopy. Exposure of reduced catalysts to HCl or HBr causes a 3-fold increase in Mo(V) spin
concentration which is reversed on subsequent outgassing. The changes in g and hyperfine tensor components
of the MOW) signal indicate that halide ions replace oxide ions in the coordination sphere of Mo(V). The increase
in Mo(V) spin concentration is attributed to removal of bridging oxide ligands between adjacent Mo(V) ions.
Oxidized catalysts are reduced by initial exposure to HCl or HBr but thereafter undergo the same reversible
changes seen with prereduced catalysts. A model is developed to account for the EPR results, as well as the
infrared and Raman spectra of HC1-treated catalysts. Reaction of reduced catalysts with HX is proposed to
be a useful test for the presence of coupled Mo(V) species.
Original languageEnglish
Pages (from-to)1380-1386
Number of pages7
JournalJournal of Physical Chemistry
Volume85
Issue number10
Publication statusPublished - 1981

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