Development of an accelerated ash loading protocol for diesel particulate filters

The accelerated ash loading of diesel particulate filters (DPFs) with diesel oxidation catalysts (DOCs) mounted upstream by lube-oil derived products was investigated using a single cylinder diesel engine and fuel blended with 5% lube oil. An ash loading protocol is developed which combines soot loading, active soot regeneration, and periodic shutdowns for filter weighing. Active regeneration is accomplished by exhaust injection of diesel fuel, initiated by a backpressure criteria and providing DPF temperatures up to 700°C. In developing this protocol, five DPFs of various combinations of substrates (cordierite, silicon carbide, and mullite) and washcoats (none, low PGM, and high PGM) are used and evaluated. The initial backpressure and rate of backpressure increase with ash varied with each of the DPFs and ash was observed to have an effect on the active soot light-off temperature for the catalyzed DPFs. Multiple characterization techniques are performed on the ash layers and ash distribution was found to be weighted towards the back of the DPFs with ash layer topography a function of channel wall topography. Ash balances indicate an average recovery of 65% for calcium and zinc and 10% for sulfur and phosphorous and CaSO₄ and Zn(PO₃)₂ account for a large portion of the total ash.