Separate/simultaneous catalytic reduction of sulfur dioxide and/or nitric oxide by carbon monoxide over titanium-tin solid solution catalysts

Titanium-tin solid solutions prepared by coprecipitation were studied for the separate and simultaneous catalytic reduction of SO2 and/or NO by CO. Physicochemical characterizations of the solid solutions before and after reactions with different SnO2 contents were conducted to disclose the reaction mechanism by means of XRD, CO-TPR, XPS and transient MS techniques. It is found that TiO2-SnO2 solid solutions were very active towards the reduction of SO2 by CO at a low temperature and space velocity. There existed a strong synergistic promoted effect. which can be explained based on an enhanced redox mechanism proposed in the work. Furthermore, TiO2-SnO2 solid solutions would show a pronounced increase in catalytic activity during the reduction of NO by CO after the catalysts finished SO2 + CO reactions, or by introducing SO2 into the reaction feed. This promoting effort is due to the formation of tin sulfide species as a product of the reduction of SO2 by CO on the catalyst surface. A NO decomposition mechanism with the formation of SO2 by-product was proposed. The produced SO2 was in situ catalytically reduced to sulfur to regenerate tin sulfide. Lastly, simultaneous catalytic reduction of SO2 and NO using CO as a reducing agent was carried out on TiO2-SnO2 solid solution catalysts. Experimental results showed that at a temperature above 350 degreesC. SO2 and NO conversions are greater than 91 and 99%, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.