The influence of phosphorus on the catalytic properties, durability, sulfur resistance and kinetics of Cu-SSZ-13 for NOx reduction by NH3-SCR

The influence of phosphorus on the catalytic properties, durability, sulfur resistance and kinetics of Cu-SSZ-13 for NOx reduction by ammonia selective catalytic reduction (NH3-SCR) were systematically investigated to obtain a deeper understanding of the deactivation of Cu-SSZ-13 in the presence of phosphorus-containing impurities in diesel exhaust. An enhanced effect on NO conversion at low phosphorus loading was found above 450 ℃, probably due to the reduction of copper oxides that promote NH3 oxidation at high temperatures. As the phosphorus loading reached 0.4 mmol/gcatal, the framework dealumination and decrease of the BET specific surface area, acidity, and isolated Cu2+ ions accounted for the decrease in activity and hydrothermal stability over the entire temperature range. Simultaneously, the activity of phosphorus-impregnated samples tested in the presence of SO2 indicates that phosphorus accelerates the deactivation of Cu-SSZ-13 in the presence of SO2 at low temperatures, primarily due to the severe decrease of the Cu2+ ion content and partial coverage of the acid sites and active sites by phosphate and sulfate species. Additionally, kinetic analysis further demonstrated that phosphorus has an inhibitory effect on the SCR reaction rates at low temperatures and high phosphorus addition changes the NH3-SCR reaction kinetic parameters. The data presented herein provide a comprehensive picture of the interaction between phosphorus and Cu-SSZ-13.