Abstract Increase in energy demand and consumption has been accompanied by a corresponding increase in sulfur emissions. These pollutants have both health and economic consequences. Furthermore, it significantly reduces the efficiency of advanced emission control systems of diesel engines, thereby indirectly causing more harm to the environment. This resulted in stringent sulfur emission limit down to about 15 ppm or less and in turn served as an incentive for research into alternative sulfur reduction technologies. Although feasible improvements to hydrodesulfurization are currently under investigation, adsorptive, extractive, oxidative and biodesulfurization have also been studied in recent years. Oxidative desulfurization appears to be one of the most promising desulfurization technologies due to its broadness and compatibility with other technologies such as extractive, adsorptive and biodesulfurization. The advent of ionic liquids as extraction solvents has made this even more so. This work, therefore, reviews the different approaches and investigations carried out on oxidative desulfurization while identifying research gaps and giving important recommendations.

Deep oxidative desulfurization of liquid fuels

Extractive oxidation, wherein aromatic sulfurcontaining compounds are extracted and subsequently oxidized to their corresponding sulfones, has proven to be one of the most effective desulfurization methods for producing ultra-low sulfur content fuels. As non-volatile and highly designable solvents, ionic liquids (ILs) have attracted considerable attention for the oxidative desulfurization of fuels. In this review, we systematically discuss the utility of ILs in catalytic and extractive oxidation, including their role as extractant, catalyst, or both. We also discuss the challenges facing the use of ILs in this regard, including their relatively high cost and excessive viscosity, as well as their efficiency and stability as catalyst. 
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Oxidative desulfurization of fuels using ionic liquids: A review? ?

Direct synthesis of mesoporous H3PMo12O40/SiO2 and its catalytic performance in oxidative desulfurization of fuel oil

An eco-friendly magnetic mesoporous silica iron oxide (MS@Fe3O4) nanoparticles with a high surface area was fabricated using a colloidal chemical method. Hereafter, polyaniline (PANI) was conjugated into the pores of MS@Fe3O4 to obtain PANI–MS@Fe3O4 nanocomposites. The nanocomposites were essentially monodispersed and highly efficient for the adsorption of methyl orange (MO). In addition, the rate of the adsorption reaction followed pseudo-second-order kinetics and the adsorption isotherm fitted well to the Langmuir isotherm model. The negative values for the change in Gibbs energy (ΔG) and positive value of the change in enthalpy (ΔH) indicated that the overall adsorption process was spontaneous and endothermic in nature. The density functional theory calculation using the Gaussian 09 and GaussView 5.0 programs also supported the electrostatic interaction phenomena between PANI and MO, which is mainly responsible for the adsorption.

Wenlong Zhen

Papers

Phosphotungstic acid containing ionic liquid immobilized on magnetic mesoporous silica rod catalyst for the oxidation of dibenzothiophene with H2O2