Influence of M-Doped (M = Ba, Zr, La, and Ce) for Enhanced CO and C₃H₆ Catalytic Oxidation over Pd/Al₂O₃ Catalysts

In this study, the effect of M-doping (M= Ba, Zr, La, Ce) on the catalytic oxidation of Pd/Al2O3 CO and C3H6 was investigated using a simulated gas test bed. The physicochemical properties of Pd-M/Al2O3 catalysts were thoroughly investigated using transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2-TPR, and CO2-TPD. Comparative analytical performance tests and characterization results indicated that doping with Ba and La significantly improved the catalytic activity of Pd/Al2O3 for both CO and C3H6 oxidation, attributed to the improved dispersion of Pd on the catalyst surface and favorable electronic modifications ratio i.e higher Pd2+/Pd0. The addition of these metals decreased the comprehensive oxidation index (S) and peak temperature (Tp) of Pd/Al2O3 catalysts, with La-doped catalysts showing the highest stability (Rw) during combustion. The order for S and Rw values from highest to lowest was La > Ba > Zr > Ce, while the Tp order was Zr > Ce > Ba > La. In contrast, Zr and Ce doping did not enhance catalytic performance; specifically, Pd–Ce/Al2O3 exhibited lower electron density, and Pd–Zr/Al2O3 showed decreased reducibility, both factors detrimental to catalytic activity. For C3H6 oxidation, metal doping reduced the Rw of Pd/Al2O3 catalysts, with only Pd–Zr/Al2O3 showing a slight increase in S. Additionally, Pd dispersion increased upon loading Ba, La, Zr, and Ce, with La showing the most pronounced effect. This study provides a new idea for designing efficient and stable palladium-based catalysts and offers new insights into understanding the effect of interfacial interactions on catalytic performance, which has potential applications.