Reactivity of V2O5 catalysts for the selective catalytic reduction of NO by NH3: Influence of vanadia loading, H2O, and SO2
Reactivity of V2O5 catalysts for the selective catalytic reduction of NO by NH3: Influence of vanadia loading, H2O, and SO2
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DOI：
10.1006/jcat.1996.0182
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发表时间：
1996-06-01
影响因子：
7.3
通讯作者：
Kim, DS
中科院分区：
文献类型：
--
作者：
Amiridis, MD;Wachs, IE;Kim, DS
在623 K下，对不同钒负载量的V_2O_5/TiO_2催化剂上NH_3选择性催化还原NO进行了系统的研究。动力学研究在存在和不存在H_2O和SO_2的情况下进行。各种催化剂的结构以及存在于其表面上的吸附物种通过原位拉曼和红外光谱表征。在干燥和无SO_2的条件下，发现SCR反应的转换频率在约半个单层的氧化钒表面覆盖度处经历最大值，在氧化钒表面覆盖率超过半个单层的SCR营业额频率中观察到的减少可以归因于与TiO 2支持相关的强酸位点的损失。向反应气体混合物中添加H2O导致SCR转换频率降低约40- 50%，这与氧化钒表面覆盖率无关。原位拉曼结果表明，这种降低可以归因于H2O在活性氧化钒位点上的竞争吸附。在SCR反应期间，气相中SO2的存在导致在低氧化钒表面覆盖度下的转换频率显著增加，而在氧化钒表面覆盖度超过半个单层时没有影响。拉曼和红外光谱的结果表明，SO2的影响可以归因于表面硫酸盐物种的形成，这是只存在于二氧化钛表面低于半个单层覆盖，由于表面氧化钒和硫酸盐物种之间的排斥相互作用。(C)出版社：Academic Press，Inc.
A systematic investigation of the selective catalytic reduction (SCR) of NO by NH3 over V2O5/TiO2 catalysts of variable vanadia loading has been carried out at 623 K. Kinetic studies were conducted both in the presence and in the absence of H2O and SO2, The structure of the various catalysts, as well as adsorbed species present on their surface, was characterized by in situ Raman and infrared spectroscopies, Under dry and SO2-free conditions, the turnover frequency of the SCR reaction was found to go through a maximum with vanadia surface coverage at approximately half a monolayer, The observed decrease in the SCR turnover frequency at vanadia surface coverages exceeding half a monolayer can be attributed to the loss of strong acid sites which are associated with the TiO2 support. Addition of H2O to the reacting gas mixture results in a decrease in the SCR turnover frequency of approximately 40-50%, which is independent of the vanadia surface coverage. In situ Raman results suggest that such a decrease can be attributed to the competitive adsorption of H2O on the active vanadia sites, The presence of SO2 in the gas phase during the SCR reaction results in a significant increase of the turnover frequency at low vanadia surface coverages, while it has no effect at vanadia surface coverages above half a monolayer, Raman and infrared results suggest that the effect of SO2 can be attributed to the formation of surface sulfate species, which are only present on the titania surface below half a monolayer coverage due to repulsive interactions between the surface vanadia and sulfate species. (C) 1996 Academic Press, Inc.