Catalytic performance of bimetallic PtPd/Al2O3 for diesel hydrocarbon oxidation and its implementation by acidic additives

• Activity of Pt/Al2O3 for hydrocarbon oxidation was promoted by addition of Pd.
• Formation of PtPd alloy was confirmed, resulting in sintering suppression of Pt.
• Creation of Pt-enriched surface is responsible for high oxidation activity.
• Addition of W into PtPd/Al2O3 causes an enhancement of oxidation activity.
• W additive can create strong Lewis acidic sites on Al2O3 surface.

The effect of Pd additive on the catalytic performance of Pt/Al2O3 for the total oxidation of a mixture of n-decane and 1-methylnaphthalene as model hydrocarbons was investigated to develop a highly active diesel oxidation catalyst. Bimetallic Pt–Pd diesel oxidation catalyst showed higher catalytic activity for the total oxidation of hydrocarbons even after high temperature ageing than monometallic Pt and Pd catalysts. The optimum Pt/Pd weight ratio was 3/1. Catalyst characterizations such as XRD, CO-TPR and FT-IR spectroscopy following CO adsorption revealed that an enrichment of Pt on the surface of alloyed Pt–Pd particles in PtPd/Al2O3 is responsible for high hydrocarbon oxidation activity. The catalytic activity of PtPd/Al2O3 was also found to be effectively improved by modification of Al2O with 1 wt% WO3 as acidic additives. The role of WO3 additive was considered to create strong Lewis acidic sites by interaction with Al2O3, leading to a stabilization of PtPd sites in highly active metallic state.

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