Effect Of Titanium Exchange On Cu-SSZ-13 Zeolite For Catalytic Removal Of NO_x In Vehicle Exhaust

Vehicle exhaust has become one of the main causes of air pollution in the city,in which nitrogen oxides?NO_x?are the important factors for the formation of photochemical smog and acid rain.NH₃-SCR technology is considered to be one of the most perspective technologies for removing NO_x from vehicle exhaust gas.The key is to develop efficient and stable catalysts.Because of its excellent catalytic activity,selectivity and hydrothermal stability,Cu-SSZ-13 zeolite become a significant research object of zeolite catalysts reducing NO_x from diesel vehicles in recent years.With introducing into the framework of Cu-SSZ-13 zeolite,heteroatom element can enrich the skeleton structure of the zeolite and endow the catalysts with excellent electromagnetic properties,resulting in enhancing the activity,selectivity and hydrothermal stability of catalyst.Ti is an element often used to modify molecular sieves.In this paper,Cu-SSZ-13 zeolites were prepared by in-situ synthesis method and traditional hydrothermal synthesis method.Then the Ti was introduced via ion exchange method.The TiCl₄ concentration,ion exchange time and temperature,and the exchange order of Cu and Ti were investigated.Meanwhile,we systematically studied the effects of these factors on catalytic activity,selectivity and hydrothermal stability.This work will also provide a theoretical basis data for optimizing Cu/Ti-SSZ-13 catalysts for removing NOx performance.?1?The Cu-SSZ-13 catalyst prepared by in-situ hydrothermal synthesis method was modified by titanium ion exchange.The optimal concentration of TiCl₄ solution was 0.075 mol/L and the exchange temperature and time was 35 ? and 6 h respectively.At this exchange condition,the sample has relatively better denitration activity and higher hydrothermal stability.After aging,specific surface area of the sample increased,and the low temperature activity was the same as fresh samples.?2?The SSZ-13 catalyst was prepared by the traditional hydrothermal synthesis method.The concentration of TiCl₄ solution was 0.075 mol/L,and the ion exchange was carried out at 35 ? for 6 h.The copper exchange was carried out with a 0.025 mol/L copper sulfate solution under 80 ? water baths for 1 h.The results show that the addition of titanium atoms enhances the high temperature activity of SSZ-13 catalyst.The samples with the first exchange of titanium and the then exchange of copper have relatively good hydrothermal stability.