TiO_2-ZrO_2基催化剂SO_2中毒机理研究

SO_2 Poisoning Mechanism over TiO_2-ZrO_2 Based Catalyst for Selective Catalytic Reduction of NO_x by NH_3

利用原位漫反射红外光谱仪,设计多种进气工况的单吸附/共吸附实验,并结合SO_2中毒前后的BET、XRD、XRF表征和性能实验,研究了V_2O_5-WO_3/TiO_2-ZrO_2催化剂的SO_2中毒机理。原位漫反射红外实验表明NH_3和SO_2都可吸附在催化剂的表面,产生竞争吸附,且两者的竞争吸附能力不相上下;NO在催化剂表面无吸附,SO_2和NO不存在竞争吸附;不论气相中是否有O_2,催化剂表面都不会有吸附态的SO_3出现。BET的结果显示,催化剂在SO_2中毒前后的孔径分布结果基本相同,表明SO_2对于催化剂孔隙结构的影响较小。XRD的结果显示,催化剂在SO_2中毒前后的谱图基本相同,表明SO_2对于催化剂晶体结构的影响较小。XRF的结果显示,当催化剂在SO_2中毒后,催化剂表面会有极少量的S元素检出,表明SO_2的存在确实会导致金属氧化物的硫酸盐化。性能实验的结果显示,随着SO_2含量逐渐增加,催化剂的脱硝率逐渐降低。这些研究说明催化剂的SO_2中毒主要体现在SO_2与NH_3的竞争吸附。

The adsorption experiments of single or mixing feeding gases were designed based on in situ diffuse reflectance infrared Fourier transform spectroscopy（in situ DRIFTS） and the combination of characterization techniques like BET,XRD,XRF were employed as well as the catalytic performance measurement were carried out to investigate the SO2 poisoning mechanism over V2O5-WO3/TiO2-ZrO2 catalyst. In situ DRIFTS analysis showed that both SO2 and NH3 can be absorbed on the surface of the catalyst competitively and the adsorption capacity of both gas are equally matched. There is no adsorption of NO on the surface and no competitive absorption between SO2 and NO. No SO3 can be detected in the adsorption state on the surface of the catalyst with or without O2 in the feeding gas. BET and XRD results show that the pore size distributions and the XRD patterns of the catalyst before and after SO2 poisoning are basically the same,indicating that SO2 has little influence on the pore structure and the crystal structure of the catalyst. The results of XRF show that after SO2 poisoning,a very small amount of S element can be observed on the surface of the catalyst,implying that SO2 can cause the sulfuric acid salinization of metal oxides. Furthermore,NO conversion decreased gradually with the increase of SO2 content. All these findings conclude that the competitive adsorption between SO2 and NH3 accounts for the SO2 poisoning over V2O5-WO3/TiO2-ZrO2 catalyst.