Effects of Oxygenated Additives on Pollutant Formation During Fuel Combustion

Abstract

This research investigates the use of fuels containing oxygen as a novel approach to shrink sooting tendency of fuels by using gasoline and diesel surrogate fuels (diesel fuel containing combination of isooctane, along with toluene, and little amount of heptane and a mixture of toluene and n-hexadecane) and by replacing a part of toluene with its oxygenated counterparts, benzyl alcohol and anisole. The surrogate fuel and the two oxygenated fuel blends have been tested for their sooting propensity and octane rating. Soot fragments, gathered from the fuel mixture have been investigated via HRTEM, TGA, SEM, elemental analyzer, and XRD, Where the results of the oxygenated soots showed higher reactivity with decreased crystallite size and particle diameter. The study findings revealed that such fuel approach can not only decrease soot emission, but also enhance soot physicochemical properties to minimize its lifetime in the surroundings. The composition of gasoline surrogate has been determined (36% toluene, 47% isooctane, and 17% n-heptane) that could mimic the target properties of commercial ULG91 gasoline (density, threshold sooting index, molecular weight, and cetane number). The composition of diesel surrogate has been determined (70% n-heptane, and 30% toluene) that could mimic the target properties of commercial diesel. Moreover, the research had shown that the replacement of toluene in the surrogate fuel with 10% oxygenated compound (benzyl alcohol or anisole) has a noticeable contraction in the sooting tendency (fuel), where the emission of the smoke is observed to be increased. Furthermore, soot particles from the fuels containing oxygen have been found to be more active as compared to soot from the diesel surrogates, and gasoline. Moreover, the fundamental particles found in the surrogate fuel soot were larger than those found in soots from the oxygenated fuels, which indicates a slower growth rate and/or a higher oxidation rate of soot molecules in the fire of fuels oxygenated with benzyl alcohol, and anisole. The elemental analysis revealed that the oxygen/ carbon proportion is the highest for gasoline, and diesel surrogate soot explaining its higher oxidative reactivity at very low oxidation levels in TGA experiments and lower in-flame oxidation of soot in the surrogate flame that usually causes a loss of oxygenated groups on soot. The study reveals that that oxygenating the sooting components (aromatics) of fuels can aid in decreasing emissions of soot from the fuel and they can also help in enhancing the oxidative reactivity of soot fragments to enhance their in-cylinder burning or to support faster regeneration of particulate filters used for their collection.

Date of Award	Dec 2022
Original language	American English
Supervisor	Mirella El-Kadi (Supervisor)