Sulfur compounds represent one of the most common impurities present in the crude oil. Sulfur in liquid fuel oil leads directly to the emission of SO2 and sulfate particulate matter (SPM) that endangers public health and community property; and reduces the life of the engine due to corrosion. Furthermore, the sulfur compounds in the exhaust gases of diesel engines can significantly impair the emission control technology designed to meet NOx and SPM emission standards. The research efforts for developing conventional hydrodesulfurization and alternative desulfurization methods such as selective adsorption, biodesulfurization, oxidation/extraction (oxidative desulfurization), etc. for removing these refractory sulfur compounds from petroleum products are on the rise. Research laboratories and refineries are spending huge amounts of money in finding a viable and feasible solution to reduce sulfur to a concentration of less than 10 mg l−1. This paper reviews the current status in detail of various desulphurization techniques being studied worldwide. It presents an overview of novel emerging technologies for ultra-deep desulfurization so as to produce ultra-low-sulfur fuels.

An evaluation of desulfurization technologies for sulfur removal from liquid fuels

Hydrodesulfurization (HDS), a widely employed method in industries for the desulfurization of fuel oils, such as gasoline and diesel fuel is faced with the challenge of producing lower-sulfur or sulfur-free fuel oils, which are required by more and more countries. However, HDS is not very effective for the removal of thiophenic sulfur compounds due to sterically-hindered adsorption on the catalyst surface, unless operated under harsh conditions, such as high temperature, high pressure, and requirement of a noble catalyst and hydrogen. Extractive desulfurization (EDS) of fuel oils using ionic liquids (ILs) has been intensively studied in recent decades and has a good future as an alternative or complementary method to HDS. In this review, we reviewed the research results of EDS using ILs and provided comprehensive discussions on diverse factors, which influence desulfurization, such as the IL species, IL–oil mass ratio, initial sulfur content, temperature, time, mutual solubility, multiple extractions and regeneration. Potential problems or shortcomings were also stated. Some other desulfurization methods currently under study, such as extraction, oxidation, adsorption and biodesulfurization were also briefly outlined. It can be inferred that ILs remain a class of ideal solvents to realize clean fuel oil in the near future because of their desirable physiochemical properties, which are lacking in molecular organic solvents, while there are possible challenges, such as relatively high viscosity and low efficiency.

A review of extractive desulfurization of fuel oils using ionic liquids

Sulfur compounds in transportation fuels are a pressing issue currently due to the more stringent limits of sulfur content. Sulfur compounds lead to SOx emissions which cause many environmental and health problems. The conventional refinery desulfurization process, hydrodesulfurization (HDS), is conducted at elevated temperatures and pressures, using expensive hydrogen gas and catalysts. This review aims to discuss the merits and drawbacks of the major areas of alternative desulfurization technologies, including biodesulfurization, adsorption, extractive and oxidative desulfurization, with special emphasis on the role of ionic liquids (ILs) as distinctive multi-task fluids. With the rapid development of ILs in the last decades, more effective and reliable desulfurization techniques are foreseeable.

The role of ionic liquids in desulfurization of fuels: A review

Ionic liquids on desulfurization of fuel oils

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.

Yufeng Hu

Papers

Desulfurization of Diesel Fuel by Extraction with [BF4]−-based Ionic Liquids

Densities and Viscosities of the Quaternary System Mannitol-Sorbitol-D-Glucose-H2O and Its Ternary Subsystems at 298.15K

Decomposition Kinetics for Formation of CO2 Hydrates in Natural Silica Sands

Prediction of Activity Coefficients for Mixed Aqueous Electrolyte Solutions from the Data of Their Binary Solutions

Viscosities of ternary systems Y(NO3)3+La(NO3)3+H2O, La(NO3)3+Ce(NO3)3+H2O,La(NO3)3+Nd(NO3)3+H2O and their binary subsystems at different temperatures