The functions of Pt located at different positions of HZSM-5 in H-2-SCR

Series of Pt/HZSM-5 catalysts (x = 0.1-0.5) were prepared by impregnating H2PtCl6 or Pt(NO3)(2) on HZSM-5 and characterized by FTIR and XPS. It was found that Pt is predominantly located on the zeolite outside surface for the catalysts prepared from H2PtCl6, whereas large portion of Pt existed in the zeolite channels for the catalysts prepared from Pt(NO3)(2). In the H-2-SCR, the Pt on the zeolite outside surface plays the role of activating H-2, while that in the zeolite channels merely adsorbs NOx species for the reaction. For the catalysts, proper NOx adsorption capacity matching the property activating H-2 is indispensable for increasing the H-2 efficiency and the N-2 selectivity. Some cations such as Al3+ capable of accepting more NOx species in the zeolite channels effectively improved the catalytic performance.