镧改性铜基铝铈交联蒙脱土的制备及其对丙烯选择性还原NO的催化性能

Preparation of La-Modified Cu-Based Al-Ce Pillared Montmorillonite and Its Catalytic Properties for Selective Reduction of NO by Propylene

制备了镧改性铜基铝铈交联蒙脱土催化剂La/Cu/SO2 -4/AlCe PILM ,研究了它在富氧条件下对丙烯选择还原NO的催化性能 ,考察了镧的添加方法、添加量及催化剂焙烧温度对La/Cu/SO2 -4/AlCe PILM催化性能的影响 .结果表明 ,采用分步浸渍法引入镧能显著提高催化剂对NO选择还原反应的催化活性和高温稳定性 ,镧的添加量为 1 0 %时 ,经 5 0 0℃焙烧制得的La/Cu/SO2 -4/AlCe PILM催化剂性能较佳 ,NO最大转化率由未加镧时的 4 9 1%提高到加镧时的 5 7 2 % ,在 6 5 0℃反应时La/Cu/SO2 -4/AlCe PILM上的NO转化率仍高达 2 0 % .XRD ,TPR和XPS表征分析结果表明 ,镧物种和铜物种均呈分散状态 ,镧的引入可能促进了活性中心Cu2 + 的氧化还原催化循环过程 ,从而提高了催化剂对丙烯选择还原NO反应的催化活性 .

The purpose of this work is to prepare a new and effective catalyst for the selective catalytic reduction (SCR) of NO x with hydrocarbon, and to find out the relationship between the catalyst properties and the preparation conditions. By using montmorillonite pillared with Al-Ce bipillaring agent as support and introducing SO 2- 4 to modify the support acidity, the Cu-based Al-Ce pillared montmorillonite catalyst modified by La, La/Cu/SO 2- 4/AlCe-PILM, was prepared and its catalytic properties for the selective reduction of NO by propylene in the presence of excess oxygen were studied. The influences of the La introduction methods, La content and calcination temperature on the catalytic properties of the catalyst were also investigated. The results showed that the catalytic activity for the selective reduction of NO and the thermal stability of the catalyst at high temperatures could be significantly enhanced by introducing La through two-step wet impregnation. The optimal catalytic activity was achieved with a La content of 1% at a calcination temperature of 500 ℃. The catalyst made under these conditions was able to increase the maximum NO conversion by 8 1% higher than that made without introducing La. Even at a reaction temperature of 650 ℃, a NO conversion as high as 20% could still be obtained. The characterization of the catalyst by means of XRD, TPR and XPS revealed that both La and Cu species existed in the form of dispersion states, which was probably due to that the introduction of La improved the redox cycle of Cu 2+ active centers, resulting in the enhancement of the catalyst activity for the selective reduction of NO.