E mail borjarodriguezusces The conventional method used to remove S compounds

E mail borjarodriguezusces the conventional method

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E-mail: [email protected] The conventional method used to remove S-compounds in fuel oils is hydrodesulfurization (HDS), 4 a process in which the S-compounds react with hydrogen and are converted into H 2 S and the corresponding hydrocarbons. However, HDS requires high temperatures (300–400 C) and pressures (20– 100 atm of H 2 ), and presents difficulties in removing aromatic heterocyclic S-compounds such as thiophene, benzothiophene, dibenzothiophene (DBT) or their derivatives, because of the sterically-hindered adsorption of these compounds on the catalyst surface. 5 To overcome these drawbacks, it is essential to explore novel approaches to improve HDS technology, and certain alternative deep-desulfuration processes such as absorption, 6 biodesulfurization, 7 extraction 8 and oxidation 9 have been investigated. Among them, extractive desulfurization (EDS) has been revealed as one of the most promising techniques because it does not involve hydrogen consumption, catalyst, high temperature or high pressure, and operates with mild and simple conditions. A few molecular solvents, such as polyalkylene glycol, imidazolidinone, pyrymidinone and dimethylsulfoxide, were tested in EDS but the results were undesirable, and their mutual solubility led to cross-contamination. Furthermore, these extractants are usually flammable and volatile organic compounds, which result in additional safety and environmental problems. There is an urgent need to find alternative and effective extractants for EDS. Over the past decade, ionic liquids (ILs) have attracted great interest and their potential and applications as environmentally benign alternative solvents have been extensively reviewed. 10 2768 | Green Chem. , 2011, 13 , 2768–2776 This journal is © The Royal Society of Chemistry 2011 Published on 18 August 2011. Downloaded by Memorial University of Newfoundland on 12/22/2018 10:10:24 PM. View Article Online / Journal Homepage / Table of Contents for this issue
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Most ILs have several advantages over organic solvents such as chemical and thermal stability, extensive liquid range, non- flammability, compatibility with oxidizing and reducing agents, ability to dissolve a wide range of materials and their negligible vapour pressure, which is the most attractive property from an environmental point of view, allowing its easy regeneration. The extraction of fuels using ILs to remove S-compounds has been recently reviewed. 11 Since 2001, 12 works on EDS using ILs have shown their potential to achieve ultra-low sulfur diesels (ULSDs). The principal focus of these studies is the extraction of S-containing aromatics, such as thiophene, dibenzothiophene (DBT) or 4,6-dimethyldibenzothiophene from heptane or dode- cane as a model oil system. By applying NMR studies, Su et al. have demonstrated that thiophene molecules are accommodated into the ionic par structure of the IL in significantly high molar ratios, enabling the selective and extractive removal of aromatic sulfur compounds from fuels.
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