Copper Doping Promotion on Ce/CAC-CNT Catalysts with High Sulfur Dioxide Tolerance for Low-Temperature NH3–SCR

The stumbling block to the ever-increasing need for improving air quality remains nitrogen oxides (NOx). The copper-introduced Ce/CAC-CNT (CuxCe/CAC-CNTs) catalyst using the in situ-growth-prepared activated carbon and carbon-nanotube composite (CAC-CNT) carrier with high sulfur dioxide tolerance was successfully applied to low-temperature NH3–SCR in this study. The findings indicate that the CuxCe/CAC-CNTs obtained at a 0.2 Cu/Ce molar ratio and the calcination temperature of 450 °C showed the highest 100% NO conversion with 95.8% N2 selectivity at 150 °C and 10 000 h–1. The incorporation of Cu improved the Cu0.2Ce/CAC-CNTs in Lewis acid, lattice oxygen (31.99%), and Ce3+ (26.03%). The accelerated NH3 adsorption on acid sites, the encouraging electron transfer by the Ce4+ + Cu+ ↔ Ce3+ + Cu2+ redox circle, and the more surface chemisorbed oxygen (Oβ) improved the catalytic activity of Cu0.2Ce/CAC-CNTs. The NH3–SCR of Cu0.2Ce/CAC-CNTs largely follows the L–H mechanism, together with a certain degree of "Fast SCR." The added Cu species effectively prevented surface SO2 adsorption and oxidation, and the Cu0.2Ce/CAC-CNTs restored more than 94% SCR activity after 8 h of poisoning in 50 ppm SO2 and 5 vol % H2O.