Impact of non-precious metal additives on the performance and hydrothermal stability of DOC coatings

Abstract

The diesel oxidation catalyst (DOCs) doped with six additives (La, Ce, Ba, Fe, Mn, Co) were selected. Based on X-ray diffraction (XRD) analysis, the influence of different additives on the crystal form of the alumina support in the catalyst was studied. Based on X-ray photoelectron spectroscopy (XPS) analysis, the influence of different additives on the aluminum coordination state on the surface of alumina was investigated. Based on H₂ temperature-programmed reduction (H₂-TPR) and CO pulse reduction experiments, the influence of different additives on the redox performance of DOC was explored. Based on CO pulse adsorption, the influence of different additives on the precious metal dispersion of DOC was studied. Based on a small-scale evaluation device, the influence rules of different additives and their contents on the performance and hydrothermal stability of DOC were investigated. The experimental results show that among the six additives, La and Ba have the best effect on improving the hydrothermal stability of DOC. Further research shows that when the doping amount of La is 5 % and that of Ba is 3 %, La and Ba have the best effect on improving the performance and hydrothermal stability of DOC. Compared with the La additive, the Ba additive has a stronger effect on improving the hydrothermal stability of DOC. Characterization analysis experiments confirm that La and Ba stabilize and disperse Pt and Pd particles through the La–O–Al and Ba–O–Al interfaces formed on the surface of alumina, increasing the number of active centers and their hydrothermal aging resistance.