Investigation of controlling factor for combustion of diesel soot

- Effect of oxygen containing functional groups

抄録

DPF (Diesel Particulate Filter) is effective for trapping diesel soot from diesel engines. The trapped diesel soot is removed by combustion above 600 °C using excess fuels, which results in reduction of fuel economy. An effective design of DPF is strongly required to improve DPF regeneration efficiency and fuel economy; however, the internal phenomenon of diesel soot combustion on DPF is still not clarified. For an effective design of DPF, in this study, we investigated the effect of diesel soot structure on combustion temperature using real diesel soot. Soot samples were characterized by means of various physicochemical techniques: XPS (X-ray photoelectron spectroscopy), EELS (Electron Energy Loss Spectroscopy), Raman spectroscopy, TEM (transmission electron microscopy), and elemental analysis. TEM images and Raman spectra of real diesel soot showed that the difference in the crystallinity of soot was small. XPS, EELS, and elemental analysis revealed that oxygen content, which is derived from surface functional groups of -COOH, -OH, and -C=O at defect sites, was strongly affected by the engine operating conditions. The ignition temperature of diesel soot was dependent on O/C ratio measured by elemental analysis. With the increase in oxygen content of diesel soot, combustion temperatures of soot became lower. It was concluded that the concentration of oxygen containing functional groups is an essential factor for the control of the ignition temperature of diesel soot.