电厂烟气脱硝催化剂V2O5-WO3/TiO2失活机理研究

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。

Deactivation mechanism of de-NOx catalyst (V2O5-WO3/TiO2) used in coal fired power plant

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, FT-IR, XRD and TG. The results showed that the used catalyst was seriously deactivated. The NO_x 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 Al₂(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.