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

The deactivation mechanism by different types of sulfate was investigated for the selective catalytic reduction of NOx on Cu/SAPO-34 catalyst. A Cu/SAPO-34 catalyst was treated with 50 ppm SO2 alone at 150 and 250 degrees C or in the presence of a SCR feed at 250 and 350 degrees 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 degrees C. In situ DRIFTs results show that both copper sulfate and ammonia sulfate species are formed on the isolated Cu2+ sites. All sulfated catalysts have lower NOx conversions compared with the Unsulfated catalysts due to reduced number of active sites. However, their apparent activation energies fot 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 degrees C, resulting in a larger extent of activity recovery. (C) 2016 Elsevier B.V. All rights reserved.