Silica-alumina-supported acidic molybdenum catalysts - TPR and XRD characterization

Journal Article · Wed Jun 01 00:00:00 EDT 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1159· OSTI ID:7174147

Rajagopal, S; Marini, H J; Marzari, J A; Miranda, R ^[1]

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1. Univ. of Louisville, KY (United States)

A series of silica-aluminas with controlled composition has been synthesized and used as supports for Mo oxide catalysts. X-ray diffraction (XRD) and temperature-programmed reduction (TPR) were used to study the role of support composition upon the stability of various oxidic species, including products of solid state reaction between Mo oxide and silica-alumina. In general, the reducibility of Mo increases with increasing Mo loading, regardless of support composition. For a fixed Mo loading, however, extent of reduction increases with SiO[sub 2] content and shows a maximum at a composition SiO[sub 2]:Al[sub 2]O[sub 3] = 75:25 (wt%). Except for silica-rich catalysts, the average oxidation state of Mo does not reach below +4 at the conditions used for TPR (maximum temperature: 550[degrees]C). Most of the support compositions yield XRD-amorphous Mo oxide. Only Mo-rich and silica-rich catalysts (MoO[sub 3] [ge] 12 wt%; SiO[sub 2] [ge] 50 wt%) contain crystalline phases of Mo: orthorhombic MoO[sub 3] on 100% SiO[sub 2], and MoO[sub 3] and Al[sub 2](MoO[sub 4])[sub 3] on silica-aluminas. 62 refs., 11 figs., 5 tabs.

• DOE Contract Number: FG22-89PC89771
• OSTI ID: 7174147
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 147:2; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CATALYST SUPPORTS
CATALYSTS
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
CONCENTRATION RATIO
DIFFRACTION
MINERALS
MOLYBDENUM COMPOUNDS
MOLYBDENUM OXIDES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
REDUCTION
REFRACTORY METAL COMPOUNDS
SCATTERING
SILICA
SILICON COMPOUNDS
SILICON OXIDES
STRUCTURAL CHEMICAL ANALYSIS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TRANSITION ELEMENT COMPOUNDS
VALENCE
X-RAY DIFFRACTION