Particulate Matter Chemical Characteristics from a Light-Duty Diesel Engine Fueled with PODE/Diesel Blends

To evaluate the Influence of polyoxymethylene dimethyl ethers (PODE) on particulate matter (PM) chemical features, PM samples emitted from diesel fuel and PODE/diesel blends at volume ratios of 10 %, 20 %, and 30 % (P10, P20, and P30) were characterized using gas chromatography-mass spectrometry, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopic (FT-IR). Results showed that adding PODE in diesel fuel could increase the proportions of the lower carbon-atom-number components and the contents of oxygen-containing compounds in the soluble organic fractions extracted from PM samples. The ratio of oxygen to carbon (O/C), the functional groups, and the nanostructure of dry soot obtained from XPS showed that the O/C rose as the PODE volume ratio increased. The graphitization degree of dry soot decreased in the order: diesel fuel > P10 > P30 > P20. The relative content of hydroxyl functional groups exhibited the same trend, while the relative content of carbonyl functional groups exhibited an opposite trend with the graphitization degree. Moreover, according to FT-IR, both the branching degree and the relative content of hydrocarbon functional groups of aliphatics are influenced by the graphitization degree of dry soot. A turning point at P20 observed by analysis results above indicated that the chemical characteristics of PM could be affected not only by fuel properties but also by the process of fuel combustion and PM formation.