SiO_2掺杂对V_2O_5-WO_3/TiO_2脱硝催化性能的影响

Effect of SiO_2 doped over V_2O_5-WO_3/TiO_2 catalyst for selective catalytic reduction of NO by NH_3

采用溶胶凝胶法制备TiO_2-SiO_2载体,浸渍法制备出V_2O_5-WO_3/TiO_2-SiO_2催化剂,利用BET、FESEM、XRD、TGA和激光拉曼对催化剂进行表征,研究催化剂的理化性质。以NH_3为还原剂,考察反应温度、SiO_2掺杂量、焙烧温度、空速和使用时间对SCR催化还原NO的性能影响。结果表明,V_2O_5-WO_3/TiO_2-SiO_2催化剂最佳反应温度在250~350℃。SiO_2掺杂能提高活性组分V_2O_5和WO_3在载体表面的分散性,制备出的催化剂具有更大的比表面积和更宽的温度区间,提高脱硝活性及稳定性。SiO_2掺杂量对催化剂性能影响较大,制备的催化剂中,TiO_2/SiO_2=2显示了最大催化活性,脱硝率均在60%以上,TiO_2/SiO_2=0.5制备的催化剂稳定性最差。焙烧温度对催化剂性能也有影响,焙烧温度在500和600℃时,最低脱硝率为58%和23%,最佳焙烧温度为400℃,脱硝率均在80%以上,具有优越的脱硝性能。实验结果还表明,空速对V_2O_5-WO_3/TiO_2-SiO_2催化剂的影响不大,在20 000 h^(-1)空速下催化剂的使用时间对脱硝率的影响也不大,48 h内能保持在99%左右,非常稳定。

The catalyst V2O5-WO3/TiO2-SiO2 was prepared by impregnation with TiO2-SiO2 carrier,which was prepared as the support using the sol-gel method. The catalyst was characterized using BET,FESEM,XRD,TGA,and Raman analysis,to study its physicochemical properties. In the present study,the influence of the reaction temperature,SiO2 doped component,calcination temperature,space velocity,and time used were investigated for the selective reduction of NO with NH3. The results indicated that the best reaction temperature was250 to 350 ℃. The active components V2O5 and WO3 were shown to have improved dispersibility on the carrier surface supported on SiO2. A series of results revealed that the introduction of SiO2 greatly increased the specific surface and temperature range,and also increased its catalytic activity and stability. The doping of the SiO2 component had a marked influence on the NO removal efficiency. The greatest catalytic activity of TiO2/SiO2 occurred at a ratio of ‘2＇（ denitrification rate above 60%）; while at the ratio of 0. 5,it had the worst stability.The calcination temperature also affected catalyst performance. With calcination temperature at 500 and 600 ℃,the denitration was the lowest（ 58% and 23%）. The best calcination temperature was 400 ℃,which resulted in a denitration rate 80%,with excellent denitration performance. The results also showed that space velocity had little effect on V2O5-WO3/TiO2-SiO2 catalyst,and the time used also had little influence at 20 000 h^-1 on the denitration rate,which reached approximately 99% within 48 h and remained steady afterward.