黏结剂对柴油车用V_2O_5-WO_3/TiO_2催化剂选择性催化还原性能的影响

采用偏NH_4VO_3和TiO_2为前驱体制备选择性催化还原(SCR)催化剂涂层所需浆料,将浆料浸涂在蜂窝陶瓷载体上,得到整体涂覆式SCR催化剂。研究了SiO_2溶胶、H_3PO_4及H_3NO_3对催化剂涂层耐久性及活性的影响。在模拟评价装置上对催化剂活性进行了评价。结果表明,SiO_2溶胶和H_3PO_4对催化剂涂层耐久性具有明显改善作用,质量分数8%的SiO_2溶胶和4%的H_3PO_4使催化剂涂层脱落率从32.71%降至4.08%和17.89%;V_2O_5-WO_3/TiO_2-4%SiO_2溶胶催化剂表现出较高的活性和选择性,新鲜催化剂NO的起燃温度(T_(50))为205℃,随着H_3PO_4添加量的增加,催化剂低温活性逐渐降低,高H_3PO_4添加量时,催化剂表面被H_3PO_4覆盖,大部分与钛及钒键连接的羟基基团被P—OH所取代,催化剂SCR活性降低。

Effects of binders on SCR performance of V2O5-WO3/TiO2catalysts for emission control of diesel vehicle

V2O5-WO3/TiO2 catalysts were prepared using ceramic honeycomb as the carrier and NH4VO3 and TiO2 as the precursors. The influence of SiO2-sol, H3PO4 and H3NO3 on durability and catalytic activ- ity of V2Os-WO3/TiO2 catalysts was investigated. The activity of V2Os-WO3/TiO2 catalysts for NO selec- tive catalytic reduction（SCR） with NH3 was evaluated in a simulated evaluation unit. The results showed that the durability of catalyst coating was obviously improved by adding SiO2-sol and H3 PO4, and the coat- ing lossing rate of the catalyst with 8wt% SiO2-sol or 4wt% H3PO4 decreased from 32.71% to 4.08% and 17. 89%, respectively. V2Os-WO3/TiO2-4% SiO2-sol exhibited the highest catalytic activity and selectivity. The light-off temperature of NO （50% conversion efficiency）of the fresh catalyst was 205 ℃. With the increase of H3 PO4 dosage, the low-temperature activity of V205 （4%）-WO3/TiO2-H3PQ gradu- ally decreased. When H3 PO4 dosage was high, the catalyst surface was covered with H3 PO4, the bonds between titanium and vanadium with the hydroxyl groups were replaced by P--OH, which made the SCR activity of the catalyst reduce.