Thermal and Chemical Aging of Diesel Particulate Filters 2007-01-1266
The effects of thermal and chemical aging on the performance of cordierite-based and high-porosity mullite-based diesel particulate filters (DPFs), were quantified, particularly their filtration efficiency, pressure drop, and regeneration capability.
Both catalyzed and uncatalyzed core-size samples were tested in the lab using a diesel fuel burner and a chemical reactor. The diesel fuel burner generated carbonaceous particulate matter with a pre-specified particle-size distribution, which was loaded in the DPF cores. As the particulate loading evolved, measurements were made for the filtration efficiency and pressure drop across the filter using, respectively, a Scanning Mobility Particle Sizer (SMPS) and a pressure transducer. In a subsequent process and on a different bench system, the regeneration capability was tested by measuring the concentration of CO plus CO2 evolved during the controlled oxidation of the carbonaceous species previously deposited on the DPF samples.
Similar tests were carried out on fresh samples as well as on thermally and chemically aged DPFs. Thermal aging consisted of subjecting the samples to a continuous flow of moist air for 100 hours at 550°C plus 100 hours at 650°C. Chemical aging consisted of exposing the filters to the equivalent of 8 and 16 grams of phosphorous per liter of DPF by submitting the samples to exhaust generated from diesel containing phosphorous.
The results indicate that the thermal aging conditions used in this experiment yielded only a minor effect on the performance of DPFs. Conversely, chemical aging by phosphorous had a significant effect on the regeneration capability of the filters. After exposure to phosphorous, the peaks representing the concentrations of CO plus CO2 flattened out and shifted towards higher temperatures, indicating a decrease in the soot regeneration activity.
Results from this study can be used to improve the DPF and catalyst formulations and to optimize filter sizing and operating conditions.