不同孔结构CeTiO_(x)催化剂的制备及其NH_(3)-SCR脱硝性能研究

Preparation and NH3-SCR catalytic performance of CeTiOx catalysts with different pore structures

为探究催化剂的孔结构对催化剂脱硝活性的影响,采用溶胶凝胶法分别制备了三维有序大孔-介孔(3DOM-m) CeTiO_(x)、三维有序大孔(3DOM) CeTiO_(x)、三维有序介孔(3DOm) CeTiO_(x)及无序孔(DM) CeTiO_(x)等四种不同孔结构的催化剂。NH3-SCR测试结果表明,催化剂活性依次为3DOM-m CeTiO_(x)>3DOm CeTiO_(x)>3DOM CeTiO_(x)>DM CeTiO_(x), 3DOM-m CeTiO_(x)表现出更优异的催化活性,NO转化率在60000 h^(-1)、250–400℃时超过90%。通过XRD、SEM、BET、NH_(3)-TPD、in-situ DRIFTS等技术对催化剂进行表征分析。结果表明,催化剂的比表面积并不是决定CeTiO_(x)脱硝活性的主导因素。3DOM-m CeTiO_(x)具有高度有序的大孔-介孔结构、丰富的Bronsted酸酸性位点,进而提高了催化剂的脱硝活性。3DOM-m CeTiO_(x)催化剂在NH_(3)-SCR反应过程中同时遵循E-R机理和L-H机理。

To investigate the influence of pore structure on the catalytic activity of catalysts,four catalysts including three-dimensionally ordered macroporous-mesoporous(3DOM-m)CeTiO_(x),three-dimensionally ordered macroporous(3DOM)CeTiO_(x),three-dimensionally ordered mesoporous(3DOm)CeTiO_(x)and disordered mesoporous(DM)CeTiO_(x) were synthesized by the sol-gel method.The NH3-SCR denitration testing results show that the performance of the catalysts with different pore structures follows the sequence of 3DOM-m CeTiO_(x)>3DOm CeTiO_(x)>3DOM CeTiO_(x)>DM CeTiO_(x),and the 3DOM-m CeTiO_(x) shows an excellent catalytic activity,with more than 90%NO conversion in the range of 250–400℃ at a GHSV of 60000 h^(-1).The characterization of catalysts by XRD,SEM,BET,NH3-TPD and in-situ DRIFTS indicates that the surface area is not the dominant factor determining the catalytic activity of CeTiO_(x).3DOM-m CeTiO_(x) has a highly ordered macroporous-mesoporous structure and abundant Bronsted acidic sites,thereby improving the denitrification activity.The NH_(3)-SCR reaction over the 3DOM-m CeTiO_(x) mainly follows the L-H and E-R mechanisms.