Effect of PdSx on Sulfur Resistance of Pd-Based Catalysts for CO Oxidation

Carbon monoxide (CO) is one of the most widely spread and enormous pollutants in the atmosphere, and CO catalytic oxidation is the primary method for reducing CO levels. Pd catalysts show excellent catalytic performance in CO catalytic oxidation, yet the majority of Pd-based catalysts are weakly resistant to sulfur. SO2, which is particularly harmful to the catalyst, is frequently present in industrial exhaust gases. Therefore, in this report, we have used a H2S-pretreated Pd-based catalyst for CO catalytic oxidation with outstanding catalytic activity, sulfur resistance, and high stability. A series of characterizations were carried out on the fresh and used catalysts, revealing that the catalytic activity is determined by Pd0 and the sulfur resistance is dependent on PdSx species. The PdSx content is adjusted by changing the concentration of H2S in the gas sulfidation process. The catalytic activity of the PdSx catalyst is much superior to that of other Pd-based catalysts, enabling complete oxidation of CO at around 200 °C. For the long-term test, the PdSx catalyst showed good ability and the conversion of CO was maintained at 94.93% in the presence of 500 ppm SO2 for 300 h, indicating the excellent stability. At last, CO catalytic oxidation and sulfur resistance mechanisms are presented and discussed, which will provide an insight in the design of sulfur-resistant catalysts.