The Rhodium-Molybdenum Interaction in Rh/Mo/Alumina

• Published in: Journal of catalysis Vol. 141; no. 2; pp. 478 - 485
• Main Authors: Storm, D.A., Mertens, F.P., Cataldo, M.C., Decanio, E.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.06.1993; Elsevier
• Subjects: 400201 - Chemical & Physicochemical Properties; ABSORPTION SPECTROSCOPY; ALUMINIUM COMPOUNDS; ALUMINIUM OXIDES; CARBON COMPOUNDS; CARBON MONOXIDE; CARBON OXIDES; Catalysis; CATALYST SUPPORTS; Catalysts: preparations and properties; CHALCOGENIDES; CHEMICAL ANALYSIS; CHEMICAL REACTIONS; CHEMISORPTION; Chemistry; ELEMENTS; Exact sciences and technology; General and physical chemistry; HYDROGEN; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ION MICROPROBE ANALYSIS; MASS SPECTROSCOPY; METALS; MICROANALYSIS; MOLYBDENUM; NONDESTRUCTIVE ANALYSIS; NONMETALS; OXIDATION; OXIDES; OXYGEN COMPOUNDS; PARTICLES; PLATINUM METALS; RHODIUM; SEPARATION PROCESSES; SORPTION; SPECTROSCOPY; STRUCTURAL CHEMICAL ANALYSIS; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; TRANSITION ELEMENTS; Mixed catalyst; Hydrogen; Secondary ion mass spectrometry; Transition metal; Experimental study; Molybdenum; Supported catalyst; Characterization; Infrared spectrometry; Gas solid adsorption; Heterogeneous catalysis; Gamma form; Impregnation; Rhodium; Preparation; Carbon monoxide; Alumina; Platinoid
• DOI: 10.1006/jcat.1993.1156
• ISSN: 0021-9517

Rhodium and molybdenum form mixed metal particles when supported on alumina. Results of chemisorption, IR, and SIMS measurements indicate that the composition of the surface of these particles is sensitive to the environment in which the measurements are made. Molybdenum appears concentrated in the surface when the atmosphere is nonreducing, while rhodium appears concentrated in the surface when hydrogen is adsorbed. Chemisorption and infrared results indicate that molybdenum reduces the surface available for the chemisorption of carbon monoxide and hydrogen. The band for the linear carbonyl is shifted 8-11 cm−1 higher when molybdenum is present, which may indicate oxidation of the rhodium by the molybdenum or increased dipolar interactions between carbon monoxide molecules adsorbed on the smaller surface. Chemisorption and infrared results also suggest that adsorbed hydrogen increases electronic density at the rhodium sites. Bands for both the gem dicarbonyl and the linear carbonyl are shifted 7-10cm−1 lower in either Rh/alumina or Rh/Mo/alumina when hydrogen is adsorbed.