Add time:08/11/2019         Source:sciencedirect.com

The present work elucidated the precipitants effect of pure CeO2 on the activity of silicotungstic acid (cas 12363-31-4) supported on CeO2 catalysts toward NOx reduction. The results implied that the silicotungstic acid doped CeO2 prepared by the NH3·H2O precipitant showed the best SCR performance and nearly 100% NOx conversion was obtained at 225–450 °C. Silicotungstic acid doped CeO2 prepared by NH3·H2O (Cat-A) was enclosed by (1 1 1) and (2 2 0) planes; the catalyst with (NH4)2CO3 (Cat-B) predominantly exposed (2 2 0) and (2 0 0) surfaces, and the catalyst with the mixture of NH3·H2O and (NH4) 2CO3 (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 Brönsted (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 Oα. As a result, the structure geometry and surface acidity were different on the (1 1 1) and (2 0 0) surfaces of CeO2, which were dependence on the different precipitants.

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