NaCl与Hg0对V2O5-WO3/TiO2SCR脱硝催化剂的协同作用研究

制备了纳米级V₂O₅-WO₃/TiO₂脱硝催化剂,采用浸渍法模拟催化剂NaCl中毒,吸附法模拟单质汞Hg⁰作用于催化剂,运用X射线衍射分析(XRD)、扫描电镜(SEM)、比表面积分析(BET)、NH₃程序升温脱附(NH₃-TPD)、傅里叶变换红外光谱分析(FT-IR)等技术表征分析了NaCl和Hg⁰对催化剂性能的影响。同时,结合已有的研究分析,提出两者对催化剂的作用机理。实验结果表明,NaCl的添加会造成催化剂表面团聚黏结,催化剂比表面积减小,且NaCl负载量越大,对催化剂毒害作用越大。Na会中和催化剂的Brønsted酸性位(V-OH),最终形成-V-O-Na及Cl-V-O-Na,造成催化剂失活。Hg⁰对催化剂的表面形貌及物相组成没有影响,并主要通过吸附在催化剂的V活性位上使其脱硝性能有所减弱。当NaCl和Hg⁰同时存在时,吸附的Hg会与NaCl中引入的Cl结合,形成HgCl、HgCl₂,并部分取代-Na,最终形成-V-O…Hg及-V-O-Hg-Cl。

Synergy of NaCl and Hg0 on V2 O5-WO3/TiO2 SCR catalysts

The nano V₂O₅-WO₃/TiO₂ catalysts were prepared. NaCl was loaded on the catalysts by impregnation and Hg⁰ was loaded by adsorption. The samples were characterized by XRD, SEM, BET, NH₃-TPD and FT-IR measurements to investigate the effect of NaCl and Hg⁰ on the performance of V₂O₅-WO₃/TiO₂ SCR catalysts. Besides, the functional mechanism was proposed combining with previous conclusions. The results indicate that NaCl causes the agglomeration of catalysts, leading to the decrease of BET surface area. For NaCl poisoning catalysts, the deactivation is observed obviously with the increase of NaCl loadings. Brønsted acid sites (-V-OH) are neutralized by Na to ultimately form -V-O-Na and Cl-V-O-Na, resulting in the decline of catalytic activity. Hg⁰ shows no influence on the microstructure and phase composition of the catalysts. However, it can be adsorbed on the V active sites to weaken the De-NO_x activities slightly. When NaCl and Hg⁰ exist simultaneously, Hg⁰ will combine with Cl that is introduced from NaCl to form HgCl or HgCl₂ and partly replace Na, and -V-O…Hg or-V-O-Hg-Cl is produced finally.