Cu含量对Cu/Al-Ce-PILC上丙烯选择性催化还原NO反应的影响

Effect of Cu Loading 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粘土Al-Ce-PILC,经SO42-改性后,以浸渍法制备了用于C3H6选择性还原NO反应的铜基交联粘土催化剂Cu/Al-Ce-PILC.用XRD,XPS和TPR等技术对催化剂进行了表征,并考察了Cu含量对催化剂性能的影响.结果表明,Cu负载未改变Al-Ce-PILC的结构;w(Cu)=2%时,Cu物种以Cu+和Cu2+两种形式存在,催化剂具有最高的催化活性和较宽的操作温度范围,在反应气组成为0·22%NO-0·12%C3H6-2·0%O2-97·66%He,空速为24000h-1和温度为350℃的条件下,NO转化率可达56·4%,700℃下仍可达22·3%;w(Cu)=5%时,催化剂中有明显的CuO物相存在,该物相促进C3H6的深度氧化,从而降低了NO选择性还原反应的性能.

The selective catalytic reduction （SCR） of NO by hydrocarbon is an efficient way to remove NO emission from lean-burn gasoline and diesel exhausts where the noble-metal three-way catalysts are not effective. The montmorillonite was pillared by multi oligomeric hydroxyl cation to synthesize pillared interlayered clay （Al-Ce-PILC） and then modified by SO4^2- to increase its acidity. Cu-based pillared clay catalyst was prepared by impregnation and applied to the SCR of NO by propylene in the presence of oxygen. The influence of Cu loading on its catalytic performance was investigated, and the support and the catalyst were characterized by XRD, XPS and TPR. The results showed that the framework of Al-Ce-PILC impregnated with copper was nearly the same as the one without impregnation. The catalyst with 2 % Cu loading expressed good performance in a broad temperature range, and the NO conversion to N2 reached its maximum of 56.4% at 350 ℃ and remained 22.3% at 700 ℃ as the feed composition was 0.22% NO-0.12% C3H6-2.0% O2-He balance at space velocity of 24 000 h^-1. Cu^＋ and Cu^2＋ species were observed on the optimal catalyst, while another species CuO formed as the Cu loading increased to 5%. Since CuO species facilitated propylene combustion, the NO conversion to N2 decreased.