Effects of 2,5-dimethylfuran addition on morphology, nanostructure and oxidation reactivity of diesel exhaust particles

As an oxygenated additive, 2, 5-dimethylfuran (DMF) addition is a method to reduce effectively the diesel particulate matter (PM) emissions. However, the influences of DMF addition on oxidation behavior and nanostructure of PM produced from diesel engines are not well understood. This study explores the effects of DMF addition on morphology, nanostructure and oxidation reactivity of diesel exhaust particles. Experiments were conducted in a high pressure common-rail diesel engine fueled with pure diesel, DMF10 (90% diesel and 10% DMF, by vol.), DMF20 (80% diesel and 20% DMF, by vol.), under two different engine loads at the same engine speed (1800 r/min). Particulate samples were collected from engine exhaust tailpipe and further characterized by transmission electron microscope (TEM), Raman spectroscopy (RS) and thermogravimetric analysis (TGA). Results showed that the physicochemical features of diesel exhaust particles can be influenced by both engine load and DMF blending ratio. Under the given engine load condition, soot particle from DMF20 was more reactive to oxidation, followed by samples from DMF10 and diesel. With a rise of DMF blending ratio, both primary particle diameter and fringe length decreased while fringe tortuosity increased. Similar with the results obtained by TEM, the larger D1-FWHM and I-D1/I-G for blended fuels demonstrated less graphitic structure. Specially, the fringe separation distance and A(D1)/A(G) did not show statistically significant differences between various tested fuels in this study. The more disordered structures explained the higher reactivity of soot from blended fuels. Independently of tested fuel, soot particles exhibited larger primary particle diameter and more graphitic structure under higher engine loads, indicating a lower soot oxidation reactivity.