添加WO3提高铈锆固溶体的氨选择性催化还原NOx反应活性

Tungsta Promotion of Selective Catalytic Reduction of NO_x by NH_3 over Ceria-Zirconia Catalyst

采用程序升温氨脱附、程序升温还原和X射线光电子能谱分析手段表征了加入WO3前后CeO2-ZrO2颗粒催化剂的表面性能变化.结果表明,WO3一方面增加了催化剂的酸性,另一方面略微提高了催化剂的氧化还原性能.在氨选择性催化还原氮氧化物反应中,当NH3/NO=1,空速为90000h-1的条件下,CeO2-ZrO2催化剂上氮氧化物转化率低于65%,而10%WO3/CeO2-ZrO2催化剂催化活性大于80%,所对应的温度区间为220～420℃.通入10%CO2和10%H2O后,由于竞争吸附,CeO2-ZrO2催化剂上的氮氧化物转化率低于46%,而10%WO3/CeO2-ZrO2催化剂上的氮氧化物转化率大于80%的温度区间移至230～500℃.

CeO2-ZrO2 and 10 % WO3/CeO2-ZrO2 catalysts were characterized by NH3 temperature-programmed desorption, H2-temperature-programmed reduction, and X-ray photoelectron spectroscopy. Their activity in the selective catalytic reduction （SCR） of NOx with NH3 was compared. The results show that the promotion effect of WO3 may be related to the increase of acidity and redox properties of the catalyst. CeO2-ZrO2 shows less than 65 % and 10 % WO3/CeOe-ZrO2 shows more than 80 % NO, conversion in the temperature range of 220-420℃ at NH3/NO = 1 and space velocity of 90 000 h 1. The addition of 10 % H20 and 10 % CO2 decreases the catalyst activity at low temperature by competitive adsorption on the catalyst surface and improves the NOx conversion at high temperature. The CeO2-ZrO2 catalyst shows less than more than 80 % NOx conversion in the temperature range of 46% and the 10%WO3/CeO2-ZrO2 catalyst shows 230-500℃.