Enhancing oxidative desulfurization using sludge-derived ferrate (VI) for dibenzothiophene: An optimization study

Abstract

Sulfur emissions pose a substantial threat to human health and the environment. To address this, stringent regulations limit sulfur content in fuels, and innovative desulfurization technologies are under active investigation. Oxidative desulfurization (ODS) employs oxidants to convert sulfur compounds into more readily recoverable sulfones. This study explores high-shear mixing in ODS, known as mixing-assisted oxidative desulfurization (MAOD), focusing on dibenzothiophene (DBT) oxidation in model fuels and pyrolysis oil. Fe(VI) derived from drinking water treatment sludge via wet oxidation is utilized in the MAOD process. The research evaluates the impact of ferrate concentration (400–600 ppm), phase transfer agent (PTA) concentration (100–300 mg per 50 mL of fuel), agitation speed (4,400 to 10,800 rpm), and temperature (40–60 °C) on % DBT conversion. Experimental sulfur conversions range from 63.4 % to 99.6 %. Through response surface methodology, optimal parameters of 537 ppm Fe(VI), 114 mg PTA per 50 mL of model fuel, 8,157 rpm agitation speed, and 41.7 °C are determined. These parameters are applied to pyrolysis oil, achieving a desulfurization efficiency of 53.2 %. Notably, increasing Fe(VI) concentration, agitation speed, and temperature significantly enhances sulfur reduction. The study underscores the potential of using potassium ferrate derived from drinking water treatment sludge in MAOD for effective desulfurization and provides insights into the impact of operating conditions on desulfurization efficiency. Ultimately, the research contributes to advancing environmentally friendly and cost-effective desulfurization technologies.