Synthesis Of Fe-Beta Molecular Sieve NH Without Template Route3 - SCR Reaction Performance Exploration

The pollutant emissions of Diesel vehicle is one of the main reasons for the formation of atmospheric haze and photochemical smog,so it is very important to control and reduce diesel NOx emissions from the source for improving the urban air pollution situation.Selective catalytic reduction of NO using NH₃ or urea?NH₃-SCR?as reductant is the most efficient technologies for the removal of NOx in Diesel vehicle at present,and the NH₃-SCR catalyst is the essential factor of the technology.Therefore,designing efficient,stable and environment friendly NH₃-SCR catalyst is of great significance for improve the efficiency of diesel exhausts purification of NOx.In this paper,through developing one-step synthesis to prepare Fe-Beta-OP catalyst,and then Cu-Fe-Beta catalyst were prepared by ion-exchange method based on the Fe-Beta-OP.They are used in NH₃-SCR activity test at last.This chapter has four chapters,the first chapter is the foreword,the second chapter is the experimental part,and the research results are mainly in the third and the fourth chapter.In the third chapter,on the basis of template-free and seed-oriented synthetic route,we prepare Fe-Beta-OP catalyst by one-step synthesis and Fe-Beta-IE by ion exchange method.By comparing the NH₃-SCR reaction properties,Fe-Beta-OP catalyst can completely convert NO and NH₃ at 175?.At the same time,the performance of the catalyst decreases slowly at high temperature,and at 500?,the NO conversion is about 50%,while the NH₃ conversion is about 100%,showing a wide temperature windows.NO conversion of the Fe-Beta-IE catalyst is about 65% at175?,the initial conversion temperature is 200?,and the performance of catalyst reduces rapidly at high temperature,showing a relatively narrow temperature window.The concentration of N2 O is less than 30 ppm in the two catalysts test,indicating good N2 selectivity.In the fourth chapter,through introducing a certain amount of Cu species into Fe-Beta zeolite catalyst by ion exchange method on the basis of one-step synthesis of Fe-Beta and testing NH₃-SCR reaction performance of the modified catalyst,the results show that the catalytic performance of Cu-Fe-Beta catalyst prepared by adding Cu in Fe-Beta catalyst system has been improved remarkably.In the low temperature section,at 150?,NO conversion rate of up to 80%,while that of Fe-Beta catalyst is only about 35%.In the high temperature section,at 350?,it can still maintain the complete conversion of NO,and with the temperature further increased,its performance decreases very slow.The NO conversion rate can still be maintainedabove 80% at 500?,while that of the Fe-Beta catalyst has been reduced to 50%.In addition,the NH₃ transformation trend is consistent with that of NO.The concentration of N2 O produced is slightly increased compared with Fe-Beta during the reaction,but it decreases with the increase of temperature.In summary,Cu species may reduce the N2 selectivity of the catalyst to a certain extent.