Pore morphology and fractal dimension of ash deposited in catalyst diesel particulate filter

Diesel particle filter (DPF) has been widely acknowledged as the most effective way to mitigate particulate matter emitted from diesel engines. Over time, ash mainly derived from lubricating oil will deposit in DPF, showing negative influence to engine performance, fuel economy, service life of DPF, and so on. Recently, the investigation about DPF backpressure characteristics and DPF regeneration process considering ash has gained attention. As a porous material, ash will play a key role in the DPF permeability. Thus, the pore morphology and fractal dimension of ash derived from three kinds of lube are addressed in this work. The results show that the changing tendency of the micropore specific surface and pore volume is consistent with the ash content in lubricant oil, which is owing to the chemical interaction of Ca and S contained in the oil during the complex DPF regeneration. There is no significant changing tendency of the mesopore and macropore properties because of the heterogeneity and complexity of ash. According to the fractal analyses, the Avnir equation shows excellent predictive accuracy for the pore surface fractal dimension of ash, which reflects that the ash pore surfaces are irregular.