Physicochemical characteristics of particulate matter emitted from the oxygenated fuel/diesel blend engine

The physicochemical characteristics of particulate matter (PM) produced by polyoxymethylene dimethyl ethers (PODE_2-4)/diesel blended fuel at different blend ratios was characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). TEM analysis indicated that the overall size of PM decreased with an increasing PODE_2-4 concentration. TEM images using fractal theory showed that the fractal dimension of PM increased as the PODE_2-4 blending ratio increased. These trends increased the oxidation activity. FTIR was used to analyze the aliphatic C-H on the surface of PM and found that the ratio I_C-H/I_C=_C and the aliphatic C-H functional group on the surface of PM decreased with an increasing PODE_2-4 blending ratio. According to XPS data, with increments of the PODE_2-4 blending ratio, the contents of O/C, sp³/sp², C-OH, C=O and total oxygen-containing functional groups of the PM increased, demonstrating that the oxygen-containing functional group and disorder of the PM nanostructure was correlated with a faster oxidation rate. Results thus demonstrated that the addition of PODE_2-4 can affect the nanostructure and oxidation activity of PM, making it easier to oxidize to reduce environmental pollution.