Comparative Investigation of Three-Way Conversion over Palladium-Based Catalysts Supported on Phosphorus-Doped and Phosphorus-Free Ceria-Zirconia-Alumina

The combined route of stoichiometric combustion + three-way catalysis (TWC) is an era choice for natural gas vehicles (NGVs) to actively respond to the environmental protection requirements of gradual pressurization. However, synergistic and efficient purification of exhaust gas in a humid atmosphere is still one of the key challenges. The catalytic performance of phosphorus-doped and phosphorus-free CeO2-ZrO2-Al2O3 (CZA)-supported Pd-based model catalysts for CH4, NO, and CO was evaluated in a practical operating environment close to stoichiometric combustion. Phosphorus doping induces the formation of abundant surface lattice oxygen, promotes the active migration of interface charges, and improves the catalytic activity of the Pd/CeO2-ZrO2-P2O5-Al2O3 (Pd/CZPA) catalyst for CH4 and NO conversion. However, the catalytic oxidation of CO strongly depends on the dispersion of Pd nanoparticles, regardless of whether phosphorus is added or not. This research provides a useful guidance for the development of new pure palladium TWC for NGVs, regional environmental governance, as well as re-examining the value of phosphorus.