Comparison of precursors for the synthesis of Cu-SSZ-39 zeolite catalysts for NH3-SCR reaction

Cu-SSZ-39 zeolites are noted for excellent NH3-SCR activity and hydrothermal stability for applications on diesel vehicles. In this study, Cu-SSZ-39 zeolites were prepared using four precursors. The results showed that the Cu-SSZ-39 prepared using ZSM-5 as precursor (Cu2.5-SSZ-39-Z) has high atomic utilization and the largest particle size, comparing with those using Y, beta and colloidal silica. The Si/Al ratio of Cu2.5-SSZ-39-Z is 9.0, and over 32% of Cu ions are Cu(OH)+ species. Cu2.5-SSZ-39-Z exhibited the best low-temperature NH3-SCR activity and hydrothermal stability. Over 90% of NOx conversion was achieved in the temperature range of 200–550 oC; meanwhile, over 90% NOx conversion could be obtained between 225 oC and 450 oC after hydrothermal aging at 850 oC for 16 h or 900 oC for 5 h. The excellent activity and hydrothermal stability make ZSM-5 the preferred precursor for industrial preparation of Cu-SSZ-39 zeolite.