Deep oxidative desulfurization by sulfated alumina catalyst using ferrate (Fe(VI)) oxidant derived from scrap iron

A new efficient and environmentally friendly approach using ferrate (Fe (VI)) and SO42−/γ-Al2O3 solid super-acid catalyst was proposed for deep oxidative desulfurization in this work. Fe (VI) was produced via electrolyzing of scrap iron as an affordable industrial feed. The SO42−/γ-Al2O3 catalysts were synthesized by impregnation method and then characterized by XRF, XRD, BET, N2-adsorption desorption, SEM-EDX, FTIR, and NH3-TPD analysis. Relatively, impacts of reaction temperature and tetra butyl ammonium chloride (TBAC) as a mass transfer agent on dibenzothiophene (DBT) oxidation ability of ferrate, was positive; however, a very more significant promotion in the ferrate performance was achieved using the SO42−/γ-Al2O3 catalyst. It can be interpreted that acidic sites of this catalyst were beneficial for generating protonated ferrates as strong oxidant reagents. However, a high amount of sulfuric acid concentration during impregnation, was not in favor of its catalytic effects. It led to aggregation of sulfate over the catalyst surface which induced a low dispersion and decreased acidic sites. The best efficiency of DBT elimination by ferrate was found to be 91.7% at temperature of 40 °C by 0.2 g/mL of SO42−/γ-Al2O3 catalyst at 3 wt.% S loading. Accumulations of impurities on the catalyst during ODS reaction caused a slight reduction in the catalyst performance after 4 consecutive recycling.