The role of surface properties of silicotungstic acid doped CeO2 for selective catalytic reduction of NOx by NH3: Effect of precipitant

The present work elucidated the precipitants effect of pure CeO2 on the activity of silicotungstic acid supported on CeO2 catalysts toward NO. reduction. The results implied that the silicotungstic acid doped CeO2 prepared by the NH3 center dot H2O precipitant showed the best SCR performance and nearly 100% NO. conversion was obtained at 225-450 degrees C. Silicotungstic acid doped CeO2 prepared by NH3 center dot H2O (Cat-A) was enclosed by (1 1 1) and (2 2 0) planes; the catalyst with (NH4)(2)CO3 (Cat -B) predominantly exposed (2 2 0) and (2 00) surfaces, and the catalyst with the mixture of NH3 center dot H2O and (NH4)(2)CO3 (Cat-C) merely exhibited the (2 0 0) planes. Moreover, the aggregated WO3 was observed over the Cat-B and Cat-C, the BET surface areas and total pore volume of the two samples significantly decreased compared with Cat-A. Besides, the Bronsted (B) acid sites only appeared on the Cat-A catalyst and the intensity of Lewis acid was visibly stronger than that of Cat -B and Cat-C. Importantly, the Cat-A possessed its higher concentration of Ce3+ and surface chemisorbed oxygen Oa. As a result, the structure geometry and surface acidity were different on the (I I 1) and (2 0 0) surfaces of CeO2, which were dependence on the different precipitants. (C) 2015 Elsevier B.V. All rights reserved.