V_2O_5-WO_3-TiO_2催化体系中V的取代对催化性能的影响

Effect of Vanadia Substitution in V_2O_5-WO_3-TiO_2 Catalysts on Catalytic Performance

采用浸渍法制备了不同比例Fe2O3和50%CuO、50%LaOx分别替代催化体系中V的V2O5-WO3-TiO2催化剂,并对其理化性能和催化活性进行了表征.结果表明:质量分数为9%的WO3能够保证500℃煅烧后的替代和未替代V2O5-WO3-TiO2催化剂具有较高的比表面积和较纯净的锐钛矿晶型,而氧化物替代对比表面积影响不大;当活性氧化物负载量的质量分数不高于3%时,Fe2O3替代对V2O5-WO3-TiO2催化剂的SCR催化性能影响不大;而LaOx替代使得催化剂的低温活性有所提高,同时高活性温度窗口也有一定程度的拓宽;CuO替代催化剂的活性明显低于其他几种催化剂;空气流速增加,Fe2O3替代催化剂的活性首先缓慢下降,在空气流速超过80 000 h-1以后,转化效率急速下降;水蒸气使Fe2O3替代催化剂的温度-转化率曲线向高温方向移动约50℃,但最高活性和高活性温度窗口变化不大.

Substituted by Fe2 O3 of different proportion, 50% CuO or 50 % LaOx, a series of V2O5-WO3-TiO2 catalysts were prepared by wet-impregnation method for selective catalytic reduction of NO, with NH3 as a reductant. A combination of various techniques was used to characterize the physical-chemical and catalytic performance of these catalysts. After calcined at 500 ℃, the catalysts loaded 9% of WO3 resulted in pure anatase area and high surface at 500 ℃ in spite of the substitution of active oxide. When the loading of active oxide was low, the substitution of Fe2 O3 seemed not to have effect on catalytic activity of V2 O5-WO3-TiO2 catalysts. However, the substitution of LaOx contributed to better catalytic activity under low reactive temperature （ 〈 300 ℃ ）, and temperature window of high activity grew wider. Activity of the catalyst substituted by CuO tended to be lower than those substituted by others. The catalyst activity substituted by Fe2O3 decreased with GHSV increasing. And the reduction efficiency of NOx decreased remarkably when GHSV went beyond 80 000 h^-1. When the catalyst was substituted by Fe2 O3, the influence of vapor was taken into account in this paper. The existence of vapor resulted in the temperature-reduction curve moving to the high temperature field by nearly 50 ℃, but the highest activity and temperature window of high activity almost held the line.