电厂烟气脱硝催化剂V_2O_5-WO_3/TiO_2失活机理研究

Deactivation mechanism of de-NOx catalyst(V_2O_5-WO_3/TiO_2) used in coal fired power plant

分别以某电厂失活和新鲜的烟气选择性催化还原(SCR)脱硝催化剂为研究对象,模拟测试催化剂的脱硝效率,并采用扫描电子显微镜-能量色散X射线光谱(SEM-EDX)、X荧光光谱(XRF)、X光电子能谱(XPS)、氮气吸脱附、傅里叶红外光谱(FT-IR)、X射线衍射(XRD)和热重分析(TG)等手段对催化剂的微观结构和表面形态进行表征,探讨了SCR催化剂的失活机制。结果表明,380℃下失活催化剂的脱硝效率(35.0%)和比表面积(1.05 m2/g)明显低于新鲜催化剂(88.2%,72.50 m2/g)。与新鲜催化剂相比,失活催化剂中V5+的比例由17.4%升高到32.2%,并且表面出现了大量的Al2(SO4)3。另外,SEM和XRD结果表明,失活催化剂出现了烧结。催化剂表面V价态的改变、高温烧结和表面Al2(SO4)3相的大量生成是催化剂失活的主要原因。

The fresh and deactivated Selective Catalytic Reduction （SCR） catalysts used in a coal fired power plant were studied in a fixed bed reactor. The physical-chemical properties of the catalysts were characterized by means of SEM-EDX, XRF, XPS, N2 adsorption/desorption, FF-IR, XRD and TG. The results showed that the used catalyst was seriously deactivated. The NOx removal efficiency and the specific surface area of the used catalyst （35.0%, 1.05 m2/g） were obviously less than those of the fresh catalyst （88.2%, 72.50 m2/g）. The V5＋ content in the deactivated catalyst was increased from 17.4% to 32.2% compared with the fresh one, and large quantities of AlE（ SO4 ）3 can be found over the surface of the deactivated catalyst. The results of SEM and XRD showed that the thermal sintering occurred in the deactivated catalyst. Generally, the V2O5-WO3/TiO2 catalyst deactivation can be interpreted by the valence change of V atoms, thermal sintering and aluminum sulfate formation over catalyst surface.