The effect of sulfate species on the activity of NH3-SCR over Cu/SAPO-34

Abstract The deactivation mechanism by different types of sulfate was investigated for the selective catalytic reduction of NO x on Cu/SAPO-34 catalyst. A Cu/SAPO-34 catalyst was treated with 50 ppm SO 2 alone at 150 and 250 °C or in the presence of a SCR feed at 250 and 350 °C. Copper sulfate was found on all sulfated catalysts, but ammonia sulfate was found only on the catalyst sulfated in the SCR feed at 250 °C. In situ DRIFTs results show that both copper sulfate and ammonia sulfate species are formed on the isolated Cu 2+ sites. All sulfated catalysts have lower NO x conversions compared with the unsulfated catalysts due to reduced number of active sites. However, their apparent activation energies for the SCR reaction remain the same, and their turnover frequencies are identical. This suggests that the deactivation mechanism is similar regardless of the type of sulfate species. On the other hand, it was found that ammonia sulfate was easier to remove than copper sulfate by a desulfation treatment at 600 °C, resulting in a larger extent of activity recovery.