Fuel oxygenation as a novel method to reduce sooting propensity of fuels: An investigation with gasoline surrogate fuels

• A novel method for gasoline fuel formulation is studied through aromatics oxygenation by replacing a portion of aromatics with oxygenated ones. • A reduction in threshold soot index with negligible effect on octane number is observed. • Soot is collected from flames of gasoline surrogate and fuels with benzyl alcohol and anisole. • Soots from oxygenated fuels had significantly lower crystallite lengths and higher reactivity. Blending transportation fuels like gasoline with biofuels reduce our reliance on fossil fuels and pollutant emission due to the presence of fuel-bound oxygen. However, biofuel availability is limited to regions with an abundance of biomass and land for energy crops. To gain the advantage of fuel-bound oxygen on emission reduction, this work explores the effect of replacing a fraction of soot-producing aromatics present in gasoline with oxygenated aromatics to check if a fuel formulation strategy, where a fraction of aromatics-rich stream in a refinery is catalytically oxygenated to form oxygenated aromatics before blending with other hydrocarbon streams to produce gasoline, could be advantageous in producing clean fuels. A gasoline surrogate containing 17% n- heptane, 47% isooctane, and 36% toluene, which closely predicted gasoline properties such as density, molecular weight, threshold sooting index, and octane number, is used for the experiments. To mimic the above fuel formulation strategy, a fraction of toluene in gasoline surrogate is replaced with oxygenated aromatics, benzyl alcohol and anisole that are structurally similar to toluene. The oxygenated blends showcased lower sooting tendency than the surrogate fuel. Soot particles, collected from the three fuel blends, are analyzed using TGA, XRD, HRTEM, and elemental analyzer, where soots from oxygenated blends are found to have higher reactivity with lower particle diameter and crystallite size. The results indicate that such fuel formulation can not only reduce soot emission, but also improve soot physicochemical properties to reduce its lifetime in the environment.