B ENVlRChlMENTAL ELSEVTER Applied Catalysis B: Environmental 7 ( 1995) I-18 Physico-chemical study of selective catalytic reduction vanadia-titania catalysts prepared by the equilibrium adsorption method Paolo Ciambelli a,*, Luciana Lisi b, Gennaro Russo b, Jean Claude Volta ’ ’ Dipartimento di Ingegneria Chimica e Alimentare. Universitir di Salerno. via Ponte Don Me/ilk). 84084 Fisciano, Salerno, Ita!\ ’ Dipurtimento di Ingegneriu Chimica, Universith di Napoli ‘Federico II’, P. Ir Tecchio 80. 8012.5, Naples, Italy ’ Institut de Recherches sur la CatalweKNRS. 2 Av. A. Einstein. 69626, Villeurbanne. France Received I4 November 1994; revised 7 July 1995; accepted 9 July 1995 Abstract Sub-monolayer V,Os/TiO, catalysts were prepared by the equilibrium adsorption method using a high surface area TiO, anatase powder. They were characterized by the following techniques: X-ray diffraction, BET surface area measurements, electrical conductivity, electron paramagnetic resonance, UV-VIS, laser-Raman spectroscopy and “V solid state nuclear magnetic resonance (NMR). The physico-chemical characterization shows that vanadium is present in the 5 + oxidation state and that the vanadium oxide phase is well dispersed on the surface of the support. The conditions of preparation markedly influence the nature of the surface species: alkaline pH promotes the formation of isolated tetrahedral species, whereas with acidic pH more condensed vanadium oxide species, containing octahedrally coordinated vanadium, are formed. The calcination gives rise to a further aggregation of the surface vanadium oxide phase. The activity of the catalysts in the selective reduction of NO by NH, in the presence of O2 was determined. The analysis of kinetic data combined with the results of physico-chemical characterization leads to a good relationship between the reaction rate and the amount of octahedrally coordinated vanadium, as evaluated by NMR spectra under ambient condi- tions. Krywords: Catalyst preparation (adsorption); Nitrogen oxides; Reduction; Vanadiaititania 1. Introduction V20,/Ti0, catalysts are widely used for the selective catalytic reduction (SCR) of nitrogen oxides by ammonia in flue gases from stationary sources [ 11. Both the * Corresponding author. E-mail ciambelli@vaxsa.csied.unisa.it. tel. ( + 39-89) 96415 I, fax. ( + 39-89) 964057. 0926-3373/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDIO926-3373(95)00033-X