Experimental Study of Thermal Aging on Catalytic Diesel Particulate Filter Performance

In this paper, a methodology is presented to study the influence of thermal aging on catalytic DPF performance using small scale coated filter samples and side-stream reactor technology. Different mixed oxide catalytic coating families are examined under realistic engine exhaust conditions and under fresh and thermally aged state. This methodology involves the determination of filter physical (flow resistance under clean and soot loaded conditions and filtration efficiency) and chemical properties (reactivity of catalytic coating towards direct soot oxidation). Thermal aging led to sintering of catalytic nanoparticles and to changes in the structure of the catalytic layer affecting negatively the filter wall permeability, the clean filtration efficiency and the pressure drop behavior during soot loading. It also affected negatively the catalytic soot oxidation activity of the catalyzed samples. Based on the characterization results, feedback to the catalyst synthesis process can be provided and improved aging-tolerant catalytic formulations can be developed that exhibit minimal degradation after thermal aging. A set of relevant physicochemical properties of the fresh and aged DPFs is derived by analyzing mathematically the results permitting the extrapolation of this study to larger filter systems.