The Preparation Of The Cu-SAPO-34Catalyst And Its C₃H₆-SCR Performance

Selective catalytic reduction (SCR) technology is an effective method for NOxemission of lean-burn engines. Due to its small pore structure, strong acid and goodhydrothermal stability, Cu-SAPO-34is a promising candidate for SCR catalysts. Thispaper is aimed to synthesize and modify the SAPO-34molecular sieve. A number offacts on the structure of SAPO-34and C3H6-SCR performance were investigated. TheXRD, SEM and NH3-TPD were used to characterize the structures of SAPO-34.It was better to use silica sol as silica source, crystallize48h and not add glycolduring the preparation of Cu-SAPO-34catalysts to achieve the best catalytic activity.It can ensure both high conversion of NOxand high selectivity for CO2. In addition,the influences of SiO2/Al2O3ratio as well as the template were the main targets tostudy. Our results showed that with the increase of SiO2/Al2O3ratio the particle sizeof SAPO-34became more uniform, and the NOxelimination over Cu-SAPO-34wasmore efficient. It is easier to synthesize the completed SAPO-34molecular sieve,whose particle size was large, with either MOR or TEA as template. With the TEAOHtemplate, the particle size of SAPO-34was less than5μm and a lot of amorphousmaterial coexisted on. There were large differences among Cu-SAPO-34withdifferent templates in the SCR performance: the Cu-MOR catalyst showed the bestNOxremoval efficiency and CO2selectivity, while the Cu-TEAOH catalyst wascatalytically inactive in the whole temperature range.The effects of metal ions on SCR performance of SAPO-34were carried out. Theresults showed that the Cu-SAPO-34catalysts synthesized with Cu(AC)2by ionexchange method showed the best catalytic activity in the temperature range from200to450°C. The catalytic performance of the synthesized ionCu-hydCo catalystdepended on a good deal of facts such as cobalt source, Co content and ion exchangetime. With the Co(NO3)2·6H2O as cobalt source, the conversion of NOxwas higher,but the more the Co content, the worse the SCR catalytic property. What’s more, theNOxconversion of1-ionCu-hydCo caytalyst was around20%higher than2-ionCu-hydCo catalyst, which may be caused by the reduction of Br nsted acid sites.