Physicochemical properties of exhaust soot from lower and higher alcohols: Characterizations and impact on soot oxidation behavior

• Published in: Fuel (Guildford) 2022-03, Vol.311, p.122524, Article 122524
• Main Authors: Wang, Yuke, Pan, Mingzhang, Huang, Haozhong, Zhou, Xiaorong, Wei, Jiangjun, Chen, Hao
• Format: Article
• Language: English
• Subjects: Activation energy; Alcohol fuels; Alcohols; Aliphatic compounds; Aliphatic C–H functional groups; Butanol; Carbon; Carbon atom hybridization; Diesel; Diesel engines; Different alcohols-diesel fuels; Emissions; Fourier analysis; Fourier transforms; Functional groups; Graphitization; Graphitization degree; Hybridization; Infrared analysis; Infrared spectroscopy; Internal combustion engines; Molecular chains; O/C ratio; Octanol; Oxidation; Oxygen content; Photoelectron spectroscopy; Photoelectrons; Physicochemical properties; Raman spectroscopy; Soot; Spectroscopy; Spectrum analysis
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2021.122524

•The addition of alcohol fuels increases the graphitization degree of particles.•The C–H/C = C ratio increases with the use of low- to high-carbon chain alcohols.•The sp3/sp2 ratio are consistent with the changing trend of AD1/AG for particles.•The D1-FWHM has an important effect on the oxidation activity of the particles. Alcohol fuels can effectively reduce particle emissions of diesel engines. However, the effects of lower and higher alcohols on the microscopic physicochemical properties of the particles, such as the graphitization degree, surface aliphatic C–H functional groups, O/C ratio, and the carbon atom hybridization is still unclear. Moreover, the relationship between microscopic physicochemical properties and particle oxidation activity has not been systematically studied. Therefore, the alcohol-diesel mixtures with different carbon chain lengths and the same oxygen content were used as the fuel for commercial diesel engines in this research, such as methanol/diesel mixture (M10), n-butanol/diesel mixture (NB25), and n-octanol/diesel mixture (NO45), and the pure diesel (D100) was used as a reference. The physicochemical properties of different fuel particles under two loads were analyzed using Raman spectroscopy, Fourier Transform Infrared, and X-ray photoelectron spectroscopy. The results showed that as the load increased, the AD1/AG of the particles decreased, which meant that the graphitization degree increased. Moreover, the addition of alcohol fuel will increase the graphitization degree of the particles. In addition, the addition of alcohol fuel will reduce the aliphatic C–H functional groups and the O/C ratio on the surface of the particles. However, with the use of M10 to NO45, the aliphatic C–H functional groups continued to increase, while the O/C ratio first decreased and then increased, and the NB25 particle had the smallest O/C ratio. Through the Partial Least Square analysis, it was found that the fringe length and fringe separation distance had the most significant impact on the activation energy of the particles. Interestingly, among the characteristic parameters of Raman spectroscopy, the D1-full width at half maximum had the largest contribution to the activation energy.