助剂添加对CuO/TiO_(2)催化剂NH_(3)-SCO性能的影响研究

Effect of additives and SO_(2)on selective catalytic oxidation of NH3 over CuO/TiO_(2)catalysts

采用浸渍法制备了一系列CuO-MO_(x)/TiO_(2)(M=W,Zr,La)催化剂用于NH_(3)选择性催化氧化(NH_(3)-SCO),同时探究了SO_(2)中毒对NH_(3)氧化性能的影响.结果表明,过渡金属氧化物的添加使Cu/TiO_(2)催化剂NH_(3)转化率降低,但显著提高N_(2)选择性.其中,W03具有最好的促进效果,在300℃下催化剂N_(2)选择性提高了36%.通过H_(2)-TPR和NH_(3)-TPD表征发现,WO_(3)的添加增加了Cu/TiO_(2)催化剂表面酸性位点的数量,促进NH_(3)的吸附,但降低催化剂氧化还原性能,抑制NH_(3)氧化为NOx.经SO_(2)中毒处理后,CuO-MO_(x)/TiO_(2)催化剂N_(2)选择性进一步提高,表征结果表明,酸性位点的增加和氧化氧化还原性的降低是提高催化剂N_(2)选择性的关键.

A series of CuO-MO_(x)/TiO_(2)(M=W,Zr,La)catalysts were prepared by impregnation method for the selective catalytic oxidation of NH_(3),and the effects of SO_(2)poisoning on the oxidation of NH_(3)over Cu/Ti-based catalysts were investigated.The results show that adding of transition metal oxides decreased the NH_(3)conversion efficiency of Cu/Ti catalyst slightly,but significantly improved the N_(2)selectivity.WO_(3)was the best promoter among those additives,with an increase of N_(2)selectivity by 36%at 300℃in comparison to Cu/Ti catalyst.The H_(2)-TPR and NH_(3)-TPD results indicate that adding of WO_(3)significantly increased the number of acid sites on the surface of Cu/Ti catalyst,and promoted the adsorption of NH_(3).But it affected the redox performance of the catalyst and inhibited the oxidation of NH_(3)to NOx.After SO_(2)poisoning,the N_(2)selectivity of CuO-MO_(x)/TiO_(2)catalyst was further improved.The characterization results shows that the increase of acid sites and the reduction of redox performance are the key factors to improve the N_(2)selectivity.