Dynamic investigation of the role of the surface sulfates in NO{sub x} reduction and SO{sub 2} oxidation over V{sub 2}O{sub 5}-WO{sub 3}/TiO{sub 2} catalysts

Journal Article · Mon Jun 01 04:00:00 EDT 1998 · Industrial and Engineering Chemistry Research

DOI:https://doi.org/10.1021/ie970734t· OSTI ID:651192

Orsenigo, C; Lietti, L; Tronconi, E; Forzatti, P ^[1]; Bregani, F ^[2]

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1. Politecnico di Milano, Milan (Italy). Dipt. di Chimica Industriale e Ingegneria Chimica
2. ENEL-DSR, Milan (Italy). Centro di Ricerca Ambiente e Materiali

Transient experiments performed over synthesized and commercial V{sub 2}O{sub 5}-WO{sub 3}/TiO{sub 2} catalysts during catalyst conditioning and during step changes of the operating variables (SO{sub 2} inlet concentration and temperature) show that conditioning of the catalyst is required to attain significant and reproducible steady-state data in both the reduction of NO{sub x} and the oxidation of SO{sub 2}. The response time of conditioning for NO{sub x} reduction is of a few hours and that for SO{sub 2} oxidation is of several hours. Fourier transform infrared spectroscopy temperature programmed decomposition, and thermogravimetric measurements showed that catalyst conditioning is associated with a slow process of buildup of sulfates: the different characteristic conditioning times observed in the reduction of NO{sub x} and in the oxidation of SO{sub 2} suggest that the buildup of sulfates occurs first at the vanadyl sites and later on at the exposed titania surface. Formation of sulfates at or near the vanadyl sites increases the reactivity in the de-NO{sub x} reaction, possibly due to the increase in the Broensted and Lewis acidity of the catalyst, whereas the titania surface acts as SO{sub 3} acceptor and affects the outlet SO{sub 3} concentration during catalyst conditioning for the SO{sub 2} oxidation reaction. The response time to step changes in SO{sub 2} concentration and temperature is of a few hours in the case of SO{sub 2} oxidation and much shorter in the case of NO{sub x} reduction. The different time responses associated with conditioning and with step changes in the settings of the operating variables have been rationalized in terms of the different extent of perturbation of the sulfate coverage experienced by the catalyst.

• OSTI ID: 651192
• Journal Information: Industrial and Engineering Chemistry Research, Journal Name: Industrial and Engineering Chemistry Research Journal Issue: 6 Vol. 37; ISSN IECRED; ISSN 0888-5885
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
CHEMICAL REACTION KINETICS
NITROGEN OXIDES
OXIDATION
SELECTIVE CATALYTIC REDUCTION
SULFUR DIOXIDE
SULFUR TRIOXIDE
TITANIUM OXIDES
TUNGSTEN OXIDES
VANADIUM OXIDES