Ce-HPW-TiO2催化剂利用C3H6选择性催化还原NO反应的机理

Mechanism of C3H6 selective catalytic reduction reaction of NO by Ce-HPW-TiO2 catalyst

为提高C3H6-SCR脱硝催化剂的低温脱硝性能,采用浸渍法合成了几种由铈和Keggin型磷钨酸改性的TiO2催化剂。在模拟烟气的实验条件下,考察了不同催化剂在150~350℃的脱硝活性,通过XRD、FT-IR和SEM对催化剂的理化性质进行了分析,并且通过原位FT-IR探究并对比了不同催化剂在吸附NO和C3H6时产生的吸附物种。结果表明:铈和磷钨酸的共掺杂大大提高了TiO2催化剂在中低温区的脱硝效率;Ce和H3PW12O40(HPW)成功负载于TiO2上,负载的HPW也保留了其Keggin结构,而且负载后的催化剂表面更加光滑,形态更加规则,分散性更好;原位FT-IR结果显示:Ce和HPW的掺杂可以促进催化剂表面硝酸盐物质和丙烯吸附物种的形成;同时发现无论是在预吸附NO还是在预吸附C3H6的情况下,Ce-HPW-TiO2(CM)催化剂表面发生的反应活性最高。由此提出了Ce-HPW-TiO2(CM)催化剂的反应机理,发现其反应中间体主要为无机硝酸盐、甲酸盐、乙酸盐和有机氮化合物。

In order to improve the low-temperature denitration performance of C3 H6-SCR denitration catalyst,several modified TiO2 catalysts with ceria and Keggin-type tungstophosphoric acid were synthesized by impregnation method.Under the experimental conditions of simulated flue gas,the denitrification activities of different catalysts at 150~350℃was investigated.The physicochemical properties of these catalysts were analyzed by XRD,FT-IR and SEM.In situ FT-IR was used to investigate and compare the adsorbed species produced on different catalysts when they absorbed NO and C3 H6.The results showed that the co-doping of cerium and phosphotungstic acid greatly improved the denitration efficiency of TiO2 catalyst in the middle and low temperature regions.Ce and H3 PW12O40(HPW)were successfully supported on TiO2,and the supported HPW also retained its Keggin structure,and the catalysts after loading had more smooth surface,more regular shape,and better dispersion.The in situ FTIR spectra showed that the doping of Ce and HPW could promote the formation of nitrate and propylene adsorbed species on the surface of catalysts.At the same time,the surface of Ce-HPW-TiO2(CM)catalyst had the highest reactivity whether it was pre-adsorbed with NO or C3 H6.Therefore,the reaction mechanism of Ce-HPW-TiO2(CM)catalyst was proposed,and the reaction intermediates were mainly inorganic nitrate,formate,acetate and organic nitrogen compounds.