Experimental study and reaction mechanism of anti-poisoning of high KCl content in NH3-SCR over Zr(HPO4)2-based catalyst

Catalysts for NH 3 selective catalytic reduction (NH 3 -SCR) suffer from severe alkali metal poisoning, particularly by potassium (K). In this study, a series of K-resistant zirconium phosphate supported CeO 2 -SnO 2 catalysts (CeSn/ZrPs) were prepared by a hydrothermal-impregnation method and the simulated poisoning process with K loading amounts ranging from 1 wt% to 10 wt% was achieved by impregnating the catalysts with a KCl solution. The catalyst that contained 20 wt% Ce and 1 wt% Sn exhibited excellent SCR activity and K-poisoning resistance. The NO conversion over the CeSn/ZrP catalyst achieved 91.6% at 350 °C after 5 wt% K poisoning, and even retained 80.2% when the K content was increased to 8 wt%. The resistance mechanism of CeSn/ZrP against K-poisoning was studied by a series of characterizations. The results demonstrate that CeSn/ZrP exhibits a high surface area, strong acidity and enhanced redox properties due to Sn doping. The abundant Brønsted acid sites provided by the zirconium phosphate support played a crucial role in resisting K poisoning. In-situ DRIFTS revealed that KCl poisoning primarily suppresses the SCR reaction by occupying acid sites and reducing NH3 adsorption. The abundant acid sites of CeSn/ZrP can ensure that the catalyst retains a certain NH 3 adsorption capacity under high KCl loading.