焙烧条件对Fe-Mo/ZSM-5催化剂上NO选择性催化还原性能的影响

采用共浸渍法制备了m(Fe):m(Mo)=1的Fe-Mo/ZSM-5催化剂,并对其在不同焙烧条件所得样品上NO选择性催化还原反应活性进行了测试。结果表明,焙烧条件对Fe-Mo/ZSM-5催化性能影响明显,600℃焙烧6 h的样品在低温范围具有较好的催化性能,随着焙烧时间或焙烧温度的增加,其NOx转化率依次向高温方向移动,在800℃焙烧后的样品催化活性明显下降。采用XRD和BET对Fe-Mo/ZSM-5样品的体相结构和表面性能进行了研究。结果表明,不同焙烧条件下Fe-Mo/ZSM-5催化剂的晶胞参数和比表面积产生了差别,特别是焙烧温度达到800℃时,其比表面积显著减小,这可能是导致Fe-Mo/ZSM-5催化性能突然下降的主要原因。焙烧过程中残留在的表面含氮物种对Fe-Mo/ZSM-5催化剂上NO选择性催化还原反应活性影响较大。

Effects of calcination conditions on catalytic performance of Fe-Mo/ZSM-5 catalyst for SCR reaction of NO

Fe-Mo/ZSM-5 catalyst with m （Fe） ： m （ Mo ） = 1 was prepared by co-impregnation method under different calcination conditions. Their catalytic performance for selective catalytic reduction （SCR） for nitrogen oxides was investigated. The results showed that the calcination conditions had evident influ- ence on the performance of Fe-Mo/ZSM-5 catalyst. The catalyst calcinated at 600 ~C for 6 h exhibited bet- ter performance for SCR of nitrogen oxides;the curve of NOx conversion was shifted to higher temperature with the increase of calcination time and calcination temperature. The catalytic activity of the catalyst cal- cined at 800 ℃ was dropped obviously. The bulk phase and surface properties of Fe-Mo/ZSM-5 catalyst were also characterized by XRD and BET techniques. The results indicated that the lattice constants and the surface area of Fe-Mo/ZSM-5 catalysts were changed under different calcination conditions. When cal-canation temperature was 800 ~C, the surface area was reduced obviously, which could be the main cause of activity reduction of the catalyst. The residual nitrous species on the catalyst surface after calcination had important influence on the activity of Fe-Mo/ZSM-5 catalyst for the selective catalytic reduction of nitrogen oxides.