Catalytic Remove Of Soot Over Cu,Ce Or Mn Metal Oxides Supported HZSM-5 Zeolite Catalysts

Continuous renewable trap?CRT?is the most effective technology to eliminate soot particles in diesel exhaust.Development of high-performance catalytic combustion catalyst is the key factor of this technology.In this paper,the Cu,Mn and Ce metal oxide catalysts supported by HZSM-5 zeolite were studied.The catalysts were characterized by XRD,BET,TEM,SEM,NH3-TPD,H2-TPR,XPS,NO₂-TPD and in situ DRIFTS.The activities of the catalysts were investigated under different conditions.Moreover,the TOF values of the catalysts were calculated by isothermal anaerobic titration,and the apparent activation energys?Ea?of catalytic soot combustion on the catalysts were calculated by TG/DTA testing.The catalysts loaded with different types of Cu species over HZSM-5 zeolite were prepared by cuprammonium evaporation method,and the referential sample was prepared by incipient wetness impregnation method.The effect of different Cu species in the soot catalytic combustion was investigated.In the loose contact mode,the isolated Cu?II?inside the zeolite,as the main active sites,has the strong oxidation ability of NO to NO₂.In the tight contact mode,because the CuO particles on the external surface of zeolite can cantact with soot,it can directly provide reactive oxygen species for soot combustion.Compared with the catalyst of SiO₂ loading CuO,the catalyst 9.5Cu-Z shows the superior catalytic activity.On the one hand,the isolated Cu?II?inside the HZSM-5 has a strong oxidation ability of NO to NO₂.On the other hand,the acidicity of HZSM-5 inhibits NO₂ adsorption on the catalyst,leading to a preferential adsorption of NO₂ on the surface of soot and providing more chances for NO₂-soot reactions.Moreover,the storage pathways of NO₂ and the NO₂-soot reaction mechanisms were discussed by situ DRIFTS.Moreover,the Mn,Ce and Mn-Ce metal oxides loaded HZSM-5 catalysts were prepared by incipient wetness impregnation method.The results show that compared with MnOx,the tempertature of hydrogen reduction of MnOx-CeO₂ shifts toward lower temperatures due to the interaction of MnOx and CeO₂.It demonstrates that the mixture of the MnOx-CeO₂ metal oxides possesses better oxidizability.Furthermore,the interaction of MnOx and CeO₂ also increases the chemisorbed oxygen species on the surface of the catalyst,which is considered to conducive to soot combustion.Finally,by NaOH etching of HZSM-5 zeolite,the Cu/Ce metal oxides loaded catalyst?CuCe/DZ?with the mesoporous structure was prepared.Compared with the catalyst of Cu/Ce metal oxides loaded untreated HZSM-5 zeolite?CuCe/Z?,the CuCe/DZ catalyst with the mesoporous structure presents the higher catalytic activity for soot combustion.Its T50 value decreases from 401 °C to 390 °C.Because of the interaction between CuO and CeO₂,the oxidation ability of the catalyst is enhanced.In addition,the catalyst with the mesoporous structure can increase the effective contact between soot and the catalyst and promote the mass transport?...