Mixing-assisted oxidative desulfurization of model sulfur compounds using ferrate derived from drinking water treatment sludge

With the impacts of using fossil fuel-derived oils, there is a pressing need to explore the use of alternative fuels in the industrial field. Pyrolysis oil from waste tires is explored as an alternative fuel, however, it contains high levels of sulfur compounds, rendering it unsuitable for direct use. In this study, mixing-assisted oxidative desulfurization was examined to achieve the maximum sulfur conversion in dibenzothiophene (DBT) and benzothiophene (BT) model fuels. Crude K2FeO4 or Fe(VI) from drinking water treatment sludge was successfully prepared and utilized in the oxidation process to convert sulfur compounds in model fuels. Optimization studies were performed considering Fe(VI) concentration, phase transfer agent (PTA) concentration, agitation speed, and mixing temperature. The optimized MAOD parameters for DBT were found to be 537 ppm Fe(VI), 114 mg PTA/50-mL model fuel, 8,157 rpm agitation speed, and 41.7 °C, resulting in a sulfur conversion of 99.7%. Meanwhile, for BT, the optimized parameters were 600 ppm Fe(VI), 101 mg PTA/50-mL model fuel, 10,800 rpm agitation speed, and 40.0 °C, yielding a sulfur conversion of 88.1%. The optimal parameters were applied to a pyrolysis oil sample with an initial sulfur concentration of 8,804 ppm and desulfurization was achieved at 53.2% using the DBT optimal parameters and at 54.7% under the BT optimal parameters. Kinetic analyses revealed that both systems fit a pseudo-first order model, with DBT having a higher rate constant than BT. Results confirm the effectiveness of MAOD in sulfur conversion using milder operating conditions compared to conventional desulfurization methods. Additionally, this research demonstrates the potential of MAOD in producing cleaner fuels through waste recovery for industrial applications.