Alkali Metal Deactivation on the Low Temperature Selective Catalytic Reduction of NOx with NH3 over MnOx-CeO2: A Mechanism Study

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• 作者：Shangchao Xiong ; Jingxia Weng ; Yong Liao ; Bo Li ; Sijie Zou ; Yang Geng ; Xin Xiao ; Nan Huang ; Shijian Yang
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：July 21, 2016
• 年：2016
• 卷：120
• 期：28
• 页码：15299-15309
• 全文大小：673K
• 年卷期：0
• ISSN：1932-7455

文摘

The application of MnO<sub>xsub>-CeO<sub>2sub> as the low temperature selective catalytic reduction (SCR) catalyst to control NO<sub>xsub> emission from coal-fired power plants is extremely restricted due to the unrecoverable deactivation by SO<sub>2sub>. There is little SO<sub>2sub> in the flue gas from biomass-fired power plants, and the concentration of alkali metals in the flue gas after the electrostatic precipitator is very low, so the application of MnO<sub>xsub>-CeO<sub>2sub> may be possible to control NO<sub>xsub> emission from biomass-fired power plants. However, a very small amount of alkali metals showed a seriously negative effect on NO reduction over MnO<sub>xsub>-CeO<sub>2sub> such that both NO<sub>xsub> conversion and N<sub>2sub> selectivity obviously decreased. In this work, the mechanism of NO reduction over MnO<sub>xsub>-CeO<sub>2sub> and K-MnO<sub>xsub>-CeO<sub>2sub> was investigated by the transient reaction study and the kinetic parameters of NO reduction were obtained from the steady-state kinetic study. After comparison of the kinetic parameters, the mechanism of potassium deactivation on NO reduction over MnO<sub>xsub>-CeO<sub>2sub> was discovered. The decrease of the SCR activity of MnO<sub>xsub>-CeO<sub>2sub> after potassium deactivation was mainly attributed to the decrease of acid site and Mn<sup>4+sup> concentration on the surface, and the increase of N<sub>2sub>O selectivity was mainly related to the occurrence of N<sub>2sub>O formation over K-MnO<sub>xsub>-CeO<sub>2sub> through the Langmuir–Hinshelwood mechanism.