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富铝Cu-Beta分子筛具有优异的低温NH_3-SCR性能,在汽车尾气脱硝中具有潜在的应用前景.我们考察了H_2O、CO_2、丙烯等气氛对富铝Cu-Beta分子筛NH_3-SCR反应性能的影响.发现H_2O会降低催化剂的低温活性,CO_2则提高低温活性,丙烯对中、低温活性均有明显抑制作用.固体13C核磁共振显示丙烯在分子筛上形成链状脂肪烃积碳,导致催化剂的活性降低.Pt修饰使丙烯存在下低温NH_3-SCR活性有所提高,但在中高温度下会催化NH_3氧化产生大量的N_2O和NO,从而降低了NO转化率.电子顺磁共振(EPR)和紫外-可见(UV-Vis)光谱研究表明,Pt的引入使部分孤立铜离子转化为簇状多聚态铜离子,会进一步加剧高温NH_3氧化反应的发生,进而降低了催化剂的活性.
Al-rich Cu-Beta zeolite has excellent low-temperature NH 3-SCR performance and potential applications in automotive exhaust gas denitrification.We investigated the effect of H 2 O, CO 2, and propylene on the performance of NH 3-SCR reaction of aluminum-rich Cu-Beta zeolite .H 2 O was found to reduce the activity of the catalyst at low temperature, while CO 2 increased the activity at low temperature, and the activity of propylene at medium and low temperature was significantly inhibited.The solid 13 C NMR showed that propylene formed carbon chain on the molecular sieve and led to the decrease of catalyst activity .Pt modification improved the activity of NH_3-SCR at low temperature in the presence of propylene, but it also catalyzed the oxidation of NH_3 to produce a large amount of N_2O and NO at middle and high temperatures, thus reducing the NO conversion.Electron paramagnetic resonance (EPR) and UV-Vis (UV-Vis) spectroscopy studies show that the introduction of Pt to some isolated copper ions into clusters of copper ions will further exacerbate the occurrence of high-temperature oxidation of NH_3, thereby reducing the activity of the catalyst.