反应条件对Cu/Al-Ce-PILC上丙烯选择性催化还原NO反应的影响

Effect of Reaction Conditions on Catalytic Performance of Cu/Al-Ce-PILC for Selective Catalytic Reduction of NO by Propylene

采用聚合羟基复合阳离子合成交联黏土Al-Ce-PILC,经SO42-改性后,以浸渍法制备了铜基交联黏土催化剂Cu/Al-Ce-PILC,并将其应用于C3H6选择性还原NO的反应,考察了预处理气氛、O2和C3H6浓度、空速、水蒸气和SO2等反应条件对催化剂性能的影响.结果表明,He预处理后催化剂表面的Cu物种以Cu+和Cu2+两种形式存在,而H2预处理后仅以Cu+存在,NO转化率最大值由23%升至56%.反应体系中适当的O2和C3H6浓度可促进NO还原为N2,但过高的浓度反而可降低NO的还原活性,O2同时可起到抑制积炭、清洁催化剂表面的作用.NO转化率随着空速的增大而降低.10%水蒸气的存在可抑制NO的还原和C3H6的氧化,其转化率曲线向高温方向位移.但是,由于金属氧化物交联柱表面的疏水特性,Cu/Al-Ce-PILC较Cu/ZSM-5具有较强的耐湿热稳定性,NO和C3H6最大转化率仅分别下降13%和5%.SO2的存在明显抑制了催化剂的低温活性,但对高温活性有一定促进作用.

Montmorillonite was pillared by multi-oligomeric hydroxyl cations to synthesize Al-Ce-PILC （PILC- pillared interlayer clay）, which was modified by SO4^2- and then was used as a catalyst support to prepare the Cu/ Al-Ce-PILC catalyst by impregnation. The influence of pretreatment atmosphere, concentration of O2 and C3H6, space velocity, water vapor, and SO2 on the conversion of NO and C3H6 over Cu/Al-Ce-PILC was investigated. The results showed that both Cu^＋ and Cu^2 ＋ species were observed on Cu/Al-Ce-PILC pretreated in He, while only Cu^＋ existed after being pretreated in H2, and the maximum NO conversion was enhanced from 23 % to 56 %. Proper concentration of O2 and C3H6 promoted the reduction of NO to N2, and the formation of coke was distinctly suppressed by excess oxygen. NO conversion decreased with increasing space velocity. The presence of 10% water vapor in the feed restrained the selective catalytic reduction （SCR） of NO, the temperature for the maximum conversion increased, and the maximum conversion of NO and C3H6 decreased by 13% and 5 %, respectively. Compared with Cu-ZSM-5, Cu/Al-Ce-PILC showed better resistance to water vapor owing to the hydrophobic nature of the oxide pillar surface. SO2 greatly inhibited the SCR activity of Cu/Al-Ce-PILC at low temperature and slightly promoted it at high temperature.