Studies On The Preparation And Molding Additives Of Mn-Ce/TiO₂ Low-temperature SCR Catalyst

Mn-Ce/TiO₂catalyst showed excellent performance in laboratory-scale works.And the study of forming is the key link from the laboratory to the application stage.However,the present forming process is suitable for commercial V/TiO₂based catalyst at high-temperature,and the catalysts at low-temperature are still a long way from commercial applications.Therefore,it is significant practical value to develop the forming study of low-temperature catalysts with perfect shapes,high mechanical strength and high de-NO_xefficiency at low temperature.In this article,the preparation method and preparation conditions for the Mn-Ce/TiO₂catalyst were selected to obtain an economical preparation method;The optimal preparation method and preparation conditions were used to obtain the granular Mn-Ce/TiO₂catalyst.By adding different additives,the catalyst molding process and the effects of different additives on the catalyst molding effect were studied.At the same time,the activity and physico-chemical properties of catalysts were compared before and after molding;The effects of operating conditions during SCR reaction for forming catalyst,including the reaction temperature,space velocity,concentration of O₂and ammonia nitrogen ratio,were studied.The following conclusions were reached:（1）Among the three methods,co-precipitation method,impregnation method,and sol-gel method,the impregnation method was a suitable method for preparing a granular catalyst in consideration of the performance and economics of the catalyst.The experimental study showed that the optimal preparation conditions for the preparation of Mn-Ce/TiO₂catalysts by impregnation method were:（Mn+Ce）/Ti=0.2,Mn:Ce=0.85:0.15,simultaneous loading,calcination condition was 450℃,3h.（2）Adding an appropriate amount of pseudo-boehmite could not only adhere the catalyst particles to each other,but also increase the mechanical strength of the forming catalyst;adding an appropriate amount of activated carbon could increase the specific surface area of the catalyst.Comparing the catalyst before and after molding,the appearance of hydroxyl absorption peaks on the surface of the monolithic catalyst was conducive to the progress of the redox reaction;the specific surface area and pore volume of the catalyst after molding were reduced;the surface acidity sites and the reduction of the redox capacity of the catalyst would affect the denitration performance.Therefore,the low-temperature activity of the catalyst after molding was poor.（3）The monolithic catalyst has good low-temperature denitration performance.In the temperature range of 180℃-250℃,the NO_xconversion rate was maintained at100%.When the temperature was higher than 180℃,the NO_xconversion rate of the catalyst was basically unchanged as the space velocity increased from 8000h^-1to 40,000h^-1.At 120℃,the optimal O₂concentration was above 5%;at 150℃,the optimal O₂concentration was above 3%.The NO_xconversion rate increased first and then decreased with the increased of the ammonia-nitrogen ratio.When the ammonia-nitrogen ratio was equal to 1,the NO_xconversion rate reached the maximum.