A Comparative Study of the Adsorption and Reaction of Nitrogen Oxides on 12-Tungstophosphoric, 12-Tungstosilicic, and 12-Molybdophosphoric Acids

• Published in: Journal of catalysis 1995-03, Vol.152 (1), p.179-188
• Main Authors: Belanger, R., Moffat, J.B.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; General and physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1006/jcat.1995.1071

The sorption and conversion of NO and NO 2 on the three heteropoly acids (metal-oxygen cluster compounds), 12-tungstophosphoric (HPW) 12-molybdophosphoric (HPMo), and 12-tungstosilicic (HSiW) acids are investigated and compared. Substantial quantities of NO 2 are taken up by the tungsten-containing acids. In contrast, relatively small amounts of NO 2 are sorbed by HPMo. In the absence of presorbed NO 2 comparatively small quantities of NO are sorbed by any of the three solids. However, HPW and HSiW with presorbed NO 2 sorb substantial quantities of NO. No evidence for reduction of either NO or NO 2 is found. Temperature-programmed desorption, thermal gravimetry, infrared spectroscopy, and X-ray diffraction are employed to provide interpretive data. The results are interpreted as indicative of the formation of HNO 3 from the reaction of NO 2 and water as well as the substitution of the protons by NO + 2 in establishing a charge balance mechanism.