Investigation on nanostructure, surface functional groups, and oxidation activity of particulate along the exhaust after-treatment of a diesel engine fueled with waste cooking oil biodiesel blends.

In this study, the nanostructure, surface functional groups, and oxidation activity of soot particulate along the exhaust after-treatment system of a heavy-duty diesel engine fueled with waste cooking oil (WCO) biodiesel blends are investigated by TEM, XPS, and TGA respectively. The main findings are as follows: Along the exhaust after-treatment system, fringe length of primary particles of soot particulate emitted from tested heavy-duty diesel engine fueled with B0, B10, B20, and B100, i.e., 0%, 10%, 20%, and 100% ratio of WCO biodiesel blended into petroleum diesel in volume respectively increases, while fringe tortuosity and separation distance of primary particles reduces. The fringe length of B10, B20, and B100 is smaller, but the fringe tortuosity and separation distance are larger than that of B0. The O/C ratio of soot particulate tends to increase firstly and then decrease as the exhaust passes through DOC+cDPF and SCR+ASC in sequence. The O/C ratio of B10, B20, and B100 are also higher than that of B0. Soot particulate at cDPF outlet contains carborundum and biuret is found at SCR+ASC outlet. The sp3/sp2 ratio decreases along the exhaust after-treatment system, and B10, B20, and B100 tend to get higher sp3/sp2 ratio than B0. The C-OH and C=O content of soot particulate from different WCO biodiesel blends show generally similar trends along the exhaust after-treatment system, while the activation energy of soot particulate keeps increasing along the exhaust after-treatment system, but decreases with the increasing of blend ratio. These findings can provide useful references for optimizing the after-treatment system for WCO biodiesel blends.