Application Of Cu-SAPO-34 Catalyst For Selective Catalytic Reduction Of No_x

The problem of environmental pollution caused by the increasing nitrogen oxides（NO_X）and particulate matter（PM）emissions from diesel vehicles must be paid great attention.As the way of combustion of diesel vehicles and the state for the escalation of emissions regulations,the major OEMs have been difficult to solve the NOX and PM emissions issues only through the machine purification technology.so NH₃-SCR technology emerge in response to the needs of times.However,the short film of the technology is poor NH₃-SCR activity in the low temperature,the narrow temperature range,the poor hydrothermal stability,the sulfur and propene poisoning resistance.Considering this problems,it is particularly important to develop a catalyst that meets the requirements of national regulatory emissions.In this paper,the molecular sieve catalyst named Cu-SAPO-34,which has excellent catalytic performance and strong hydrothermal stability,is successfully synthesized by adjusting the ratio of raw materials of the catalyst and optimization of the technological conditions.First,morphine,diethylamine and triethylamine is used as template to synthesize H-SAPO-34 molecular sieves.At the same time,Cu-SAPO-34 catalyst was prepared by ion exchange solution under the same process conditions.Based on the performance at the fresh and aging condition,the catalyst which is prepared by morphine as a template is perfect choice,and then by the standard of the crystallinity,the hydrothermal resistance and the acidity to confirm the optimum template ratio.Cu-SAPO-34_（MOR）catalyst’s conversion reach more than 90%in the temperature range of 235-500°C,Cu-SAPO-34_（DEA）catalyst has a conversion of 90%in the temperature range of 300-450°C.what’s more,Cu-SAPO-34_（TEA）catalyst do not reach more than 90%of the whole temperature window.On the basis of this,morpholine was used as the template to synthetise SAPO-34.then,changing the feeding ratio of the template to research the performance of the molecular sieve.At MOR/Al₂O₃=2.08,the conversion at 200°C is only 60%,and there is no low temperature advantage at all comparing the 80%conversion of catalyst which is synthesized at MOR/Al₂O₃=2.8.At the same time,when the amount of template material is too high,such as MOR/Al₂O₃=4.2,its maximum conversion in the entire temperature window is only 80%.Regardless of the type of template or the amount of template,it mainly affects the activity,crystallinity and acidity of the catalyst by the skeletal structure of the molecular sieve and the silicon content of the molecular sieve structure and the loading of copper under the same process conditionsSecondly,taking into account the synthesis of the catalyst is a multi-faceted process and based on the type of template or the amount of template which has been summarized,we further explore the ratio of molecular sieve other raw materials such as phosphoric acid,the content of water and the feed ratio of silica.The properties,structure and acidity of Cu-SAPO-34 is tested.The results show that the change of each feed ratio is mainly through the influence of molecular sieve skeleton structure and silicon content and the distribution of copper.What is more,it is proposed that the feed ratio is suitable for the synthesis of excellent activity,which is in favor for the optimization of process conditionsFinally,this paper further optimized the technological conditions of molecular sieve synthesis,mainly through the time and temperature of crystallization during the synthesis of H-SAPO-34,the regulation of pH in ammonia exchange,the way of loading copper and the precursor type of Cu-SAPO-34.we optimize the best process conditions based on the fresh and aging activity.For the subsequent application of the production of Cu-SAPO-34provides a large number of theoretical basis data.