Deasphalting and oxidative desulfurization of heavy fuel oil followed by liquid-liquid extraction

Abstract

ABSTRACT Heavy fuels usually contain very high amounts of complex sulfur compounds such as benzothiophenes and dibenzothiophenes leading to emission of SOx and sulfate particulate matter, which cause environmental problems such as air pollution and acid rains. Using oxidative desulfurization (ODS) process, sulfur compounds can be oxidized to sulfoxides and sulfones that can be removed using liquid-liquid extraction due to their high polarity, under mild conditions. In this study, oxidative desulfurization of a heavy fuel (Mazut, 3.1 wt% S) has been studied, with hydrogen peroxide as the oxidant and acetic acid as the catalyst. Applying ODS to Mazut commonly results in high viscosity and gum formation in the fuel. Therefore, in this study, a novel ODS procedure was developed and combined with an upgrading method to avoid this problem. The appropriate extraction solvent and the adequate solvent-to-fuel and oxidant to fuel ratios were also determined. The oxidized sulfur compounds were extracted by liquid-liquid extraction using a solvent, dimethylformamide (DMF). By using a pre-treatment method followed by a desulfurization process involving two rounds of oxidation and extraction, viscosity of fuel decreased about 87% and the sulfur content of the heavy fuel was decreased to 0.91 wt%, which means achieving 70.83% desulfurization.