In situ DRIFTS and DFT studies of SO2 poisoning over Cu-exchanged X zeolite catalyst for NH3-SCR

Abstract

Nitrogen oxides (NOx) emitted from diesel engines induces various environmental problems. Selective catalytic reduction with NH3 is an efficient technology for NOx emissions reduction. In this study, copper ion exchanged zeolite catalysts (Cu-X) were prepared from blast furnace slag. Cu-X showed excellent catalytic activity and SO2 tolerance with 84% NO conversion in the presence of 50 ppm SO2. Excessive Cu inhibited the SO2 chemisorption on the active site of zeolite X to some extent. In situ DRIFTS showed that the increase of Cu exchanged amount affected the quantity distribution of bridged hydroxyl group (Si-OH-Al), terminal hydroxyl group (SiOH) and Cun+-L, and the different reaction paths and barriers of the active centers to the chemical adsorption of SO2 led to the different sulfur resistance. DFT kinetic adsorption simulation module was used to simulate the adsorption of gas components on γ -Cu-X catalyst and the transition state of active center. The results showed that the amount of Cu in the adsorption system affected the average local chemical potential during the reaction process, leading to the change of the adsorption heat of SO2 gas in the component of γ-Cu-X catalyst, and the change of the load of SO2 in the Cu-X catalyst cell.