FTIR and Kinetic Studies of the Mechanism of Fe3+-Exchanged TiO2-Pillared Clay Catalyst for Selective Catalytic Reduction of NO with Ammonia
FTIR and Kinetic Studies of the Mechanism of Fe3+-Exchanged TiO2-Pillared Clay Catalyst for Selective Catalytic Reduction of NO with Ammonia
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DOI：
10.1006/jcat.1999.2737
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发表时间：
2000-02
影响因子：
7.3
通讯作者：
R. Q. Long;R. T. Yang
中科院分区：
文献类型：
--
作者：
R. Q. Long;R. T. Yang
研究了Fe~(3+)离子交换的TiO2柱撑粘土(Fe-TiO2PILC)催化剂上氨气选择性催化还原一氧化氮(SCR)的红外光谱和动力学。结果表明，NO分子被吸附在新鲜的Fe-TiO2PILC催化剂上，然后被O2氧化为吸附的NO2和硝酸盐物种。在高温下，NH3可以还原这些NOx吸附物种。NH3分子还可以吸附在Fe-TiO2PILC催化剂上的Bronsted酸和Lewis酸位上，分别生成NH+4离子和配位NH3物种。这些NH3吸附物种对NO、NO+O2和NO2的反应都很活跃，但NH3+NO+O2和NH3+NO2的反应速率远高于NO+NH3。而在反应条件下，Fe-TiO2PILC的表面主要被NH+4离子和配位NH3覆盖，没有检测到NOx的存在。这与SCR反应相对于NH3的零级一致。提出了一种在Fe-TiO2PILC上SCR反应的可能反应方案。NO还原首先涉及NO2与成对NH3吸附物种反应生成活性中间体，再与气态或弱吸附的NO反应生成N_2和H_2O。
A series of FTIR spectroscopic and kinetic studies of the selective catalytic reduction (SCR) of nitric oxide by ammonia were conducted on Fe3+-exchanged TiO2-pillared clay (Fe-TiO2-PILC) catalyst. It was found that NO molecules were adsorbed on the fresh Fe-TiO2-PILC catalyst and then oxidized by O2 to adsorbed NO2 and nitrate species. These NOx adspecies could be reduced by NH3 at high temperatures. NH3 molecules could also be adsorbed on the Bronsted acid and Lewis acid sites on the Fe-TiO2-PILC catalyst to generate, respectively, NH+4 ions and coordinated NH3 species. These NH3 adspecies were active in reacting with NO, NO+O2 and NO2, but the reaction rates of NH3+NO+O2 and NH3+NO2 were much higher than that of NO+NH3. However, under reaction conditions, the surface of Fe-TiO2-PILC was mainly covered by NH+4 ions and coordinated NH3, and no NOx adspecies were detected. This is in agreement with the zero-order for the SCR reaction with respect to NH3. A possible reaction scheme for the SCR reaction on Fe-TiO2-PILC was proposed. NO reduction initially involved the reaction between NO2 and pairs of NH3 adspecies to form an active intermediate, which finally reacted with gaseous or weakly adsorbed NO to produce N2 and H2O.