Laser Raman characterization of tungsten oxide supported on alumina: Influence of calcination temperatures

• Published in: Journal of catalysis Vol. 92; no. 1; pp. 1 - 10
• Main Authors: Chan, Shirley S., Wachs, Israel E., Murrell, Lawrence L., Dispenziere, Nick C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.03.1985; Elsevier
• Subjects: Catalysis; Catalysts: preparations and properties; Catalytic reactions; Chemistry; Exact sciences and technology; General and physical chemistry; General. Nomenclature, chemical documentation, computer chemistry; Theory of reactions, general kinetics; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Alumina; Phase transitions; Tungsten VI Oxides; Supported catalyst
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/0021-9517(85)90231-3

The influence of calcination temperature upon the solid state chemistry of WO 3 on Al 2O 3 was examined with laser Raman spectroscopy. Laser Raman spectroscopy revealed the amorphous and crystalline structural transformations occurring in the WO 3 on Al 2O 3 oxide system. Below monolayer coverage of tungsten oxide on alumina, the tungsten oxide phase is present as a highly dispersed and amorphous surface complex on the support. A close-packed monolayer of the tungsten oxide surface complex on alumina is formed as the surface area of the alumina support decreases at high calcination temperatures. The lower the tungsten oxide loading, the more severe the calcination temperature must be to reach the close-packed monolayer. The close-packed tungsten oxide monolayer accommodates the further desurfacing at still higher temperatures by forming the bulk tungsten oxide phases WO 3 and Al 2(WO 4) 3. The Al 2(WO 4) 3 phase is formed from the reaction of WO 3 crystallites with the Al 2O 3 support. The parameter controlling the phases present in the WO 3 on Al 2O 3 system is the surface density of the tungsten oxide species on the alumina surface.