Structure and selectivity changes in vanadia-titania catalysts used to promote the reduction of nitric oxide with ammonia

Studies on Dispersion and Reactivity of Vanadium Oxide Catalysts Supported on Titania

“…The anatase is a low-temperature modification of titania, and the phase transition to rutile generally occurs above 973 K. The vanadia supported on anatase TiO 2 is a classical example of support enhancement of active phase, especially if the vanadium oxide is applied to titania as a monomolecular layer. The optimal catalytic activity and selectivity is achieved when one monolayer of vanadia is dispersed on anatase phase of TiO 2 . , The structure of highly dispersed VO x species present on the TiO 2 surface in V 2 O 5 /TiO 2 catalysts has been studied extensively in the recent past by various spectroscopic techniques including laser Raman spectra, − 51 V NMR, , ESR, − , EXAFS, and ESCA. − The V 2 O 5 /TiO 2 catalyst system has been employed in selective oxidation and ammoxidation of aromatic hydrocarbons and alcohols. − In environmental catalytic applications V 2 O 5 /TiO 2 catalysts in combination with WO 3 have been successfully employed for selective catalytic reduction of NO x reactions. − …”

“…[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] In environmental catalytic applications V 2 O 5 /TiO 2 catalysts in combination with WO 3 have been successfully employed for selective catalytic reduction of NO x reactions. [37][38][39][40][41][42][43][44] In the present investigation we report the characterization of vanadium oxide catalysts supported on various modifications of TiO 2 (anatase, rutile, and titania containing anatase and rutile) by XRD, ESR, and oxygen chemisorption methods. We also report the differences in catalytic properties exhibited by these catalysts during vapor-phase ammoxidation of 3-picoline to nicotinonitrile.…”

Structure and Reactivity of Vanadium Oxide Catalysts Supported on Anatase TiO2

“…Supported vanadium oxide catalysts have been widely investigated as they represent an important group of catalysts for a number of selective oxidation reactions − as well as the reduction of NO with NH 3 . − The bulk oxides cannot generally be employed in industrial applications because of their lack of thermal/mechanical strength. In addition, the surface structure of vanadia dispersed on supported oxides is very different from that of bulk phase and consequently exhibits a unique role in catalytic activity and selectivity.…”

Selective Catalytic Reduction of Nitric Oxide over Vanadia/Titania Catalysts: Temperature-Programmed Desorption and Isotopically Labeled Oxygen-Exchange Studies

“…Vanadia-based catalysts are being used commercially to reduce NO* levels as prescribed by Clean Air Act Amendments (CAAA) of 1990. Due to their high NO* removal efficiencies and SO2 resistant properties these catalysts have received a great deal of attention in the past few years (Bosch et al, 1986; Bauerle et al, 1975; Bauerle et al, 1978;Morikawa et al, 1981;Nam et al, 1986; Haber et al, 1986;Inomata et al, 1982;Janssen, 1988;Hotter et al, 1989). While our understanding of the catalytic phenomena involved in the SCR reaction network has significantly increased through some of the recent studies (Haber et al, 1986;Janssen, 1988; Odriozola et al, 1989; Ramis et al, 1990;Topsoe, 1991; Went et al, 1992a,b,c), there still remain questions in the literature regarding the nature of active sites, the elementary steps that take place on the catalyst surfaces, the adsorption/desorption behavior of nitric oxide and ammonia, and the role of the support material.…”