Development of Diesel Hydrocarbon Oxidation Catalysts Aimed at Reducing Platinum Group Metals Usage

Highly active diesel oxidation catalyst for the oxidation of diesel hydrocarbons, with minimal use of platinum group metals, was developed. Pt/Al2O3 showed the highest activity for total oxidation of a mixture of n-decane and 1-methylnaphthalene as model fuel-originated hydrocarbons even after high temperature aging at 750 degrees C for 5 h in air. The surface density of acid sites on Al2O3 was found to be important to stabilize the Pt surface in the active metallic state, resulting in high hydrocarbon oxidation activity. The catalytic activity of Pt/Al2O3 was strongly dependent on the Pt dispersion. Based on the findings of in-situ FT-IR spectroscopy, a reaction mechanism was proposed, in which acrylate species as reaction intermediate formed on Pt migrates to the acid-base centers of the Al2O3 surface and then reacts with 02 to form CO2. On the basis of these findings, we successfully developed highly active diesel oxidation catalyst by the addition of Pd with Pt/Pd weight ratio of 3/1 and the use of Al2O3 support modified with acidic additives such as WO3.