Effects of hydrothermal aging at high and low temperatures on the selective catalytic reduction of NOx with NH3 over Cu/SAPO-34
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Effects of hydrothermal aging at 80 and 850 °C on catalytic performance and stability of Cu/SAPO-34 catalysts with different Cu loadings were examined, and their catalytic activities were investigated for the selective catalytic reduction (SCR) of NOx with ammonia. Over the fresh catalysts, the NH3-SCR activity increased with the loading of copper in the low-temperature range and decreased in the high-temperature range. Both of the isolated Cu2+ ions and CuO synergistically influenced the SCR behavior of the Cu/SAPO-34 catalysts, which gave rise to the distinct trends of catalytic activity in the two temperature ranges. Structural damage and dealumination, however, were observed in the aged samples, leading to a severely decreased amount in acid site and a loss in crystallinity. After hydrothermal aging at 850 °C, there was some aggregation in Cu species and the redox capacity of the 0.8Cu/SAPO-34-850 catalyst was improved. It is found that the isolated Cu2+ ions were transformed into the Cu–AlOx species after hydrothermal aging at 80 °C. These results clearly demonstrate that the change in the state of copper species and the damage in structure led to different catalytic activity of the sample.
KeywordsSAPO-34 Supported copper catalyst Selective catalytic reduction NOx removal Hydrothermal aging
This work was supported by the National Natural Science Foundation of China (Grant Nos. 21277008 and 20777005), the National Key Research and Development Program of China (Grant No. 2017YFC0209905), and the Natural Science Foundation of Beijing (Grant No. 8082008). We also thank Prof. Ralph T. Yang (University of Michigan) for his helpful discussion and encouragement.
- 26.Y. Cao, L. Lan, X. Feng, Z. Yang, S. Zou, H. Xu, Z. Li, M. Gong, Y. Chen, Catal. Sci. Technol. 5, 4511 (2015)Google Scholar