Oxygenation of aromatic compounds in diesel as a novel technique to reduce its sooting tendency during combustion

To address the rising demand for cost-effective and eco-friendly transportation fuels, the blending of fossil fuels with oxygenated biofuels presents a promising solution to reduce our dependence on fossil fuels as well the emission of pollutants such as CO, soot, and NOx. However, biofuels have limited availability and are generally expensive to produce. To achieve low pollutant emissions due to the existence of fuel-bound oxygen, in this study, a portion of sooting aromatics existing in diesel is replaced with oxygenated-aromatics to validate if a clean fuel formulation strategy, where a hydrocarbon stream in a refinery rich in aromatics is catalytically oxygenated to obtain oxygenated aromatics before blending it with other hydrocarbons to produce diesel, could be beneficial. For reproducibility, a diesel surrogate fuel containing n-decane, n-hexadecane, and toluene was formulated that had properties such as molecular weight, density, threshold sooting index, and cetane index similar to that of commercial diesel. In line with the above fuel formulation strategy, a portion of aromatics (toluene) in diesel surrogate fuel is changed with oxygenated aromatics, benzyl alcohol and anisole that have structural similarity with toluene. The threshold sooting indices of the diesel surrogate and the oxygenated fuel blends indicate reduced sooting propensity of the latter in comparison to the former fuel. The characterization of soot particles, produced from the combustion of diesel surrogate and oxygenated blends, using TGA, XRD, HRTEM, and EDS elemental analysis indicates higher soot reactivity with smaller particle and crystallite sizes with oxygenated blends. Thus, the fuel formulation strategy discussed in this study can decrease diesel soot emission by hampering soot growth and accelerating oxidation and can enhance soot reactivity to diminish its lifespan in the environment.