EXTRACTIVE DESULFURIZATION OF FUEL OIL USING GLYCOL-BASED DEEP EUTECTIC SOLVENT MEDIATED BY HYDROGEN PEROXIDE AND GRAPHENE OXIDE
Sulfur-containing compounds in fuel oil is one of the major pollutants that contributes to air pollution. To solve this issue, separation of sulfurs is crucial to produce ultra-clean fuel oil according to Euro V standard. Conventional method uses hydrodesulfurization to separate sulfur, however the system requires harsh conditions to operate in a separation unit. Morever, it is inefficient to remove sterically hindered sulfur compounds such as dibenzothiophene, benzothiophene and 4, 6-dimethyldibenzothiophene. An alternative to the current technology is using integrated extractive and catalytic-oxidative desulfurization. Many researchers has attempted to use ionic liquid as the extractant, however due to its complexity of synthesis and expensive starting material, the analogue of ionic liquid which is deep eutectic solvent (DES) could be a promising candidate to desulfurize fuel oil. In this work, four types of glycol-based DES (glycerol, ethylene glycol, tetraethylene glycol and poly(ethylene glycol) 400 (PEG)) with tetrabutylammonium chloride (TBAC) as salt have been synthesized in different mole ratios to study the effect of glycols towards desulfurization efficiency. Higher desulfurization can be achieved when using DES compared to glycol itself as solvent due to the synergistic effect of salt and glycols. The performance of desulfurization can reach as high as 66.24% when using TBAC:PEG in 1:2 mole ratio in ambient condition in the presence of hydrogen peroxide as oxidant and graphene oxide as catalyst. The hydrogen peroxide helps to oxidize dibenzothiphene into high polar dibenzothiophene sulfone so that it be easily extracted into the layer of DES and the process is mediated by the graphene oxide. The main reason for the enhanced performance is longer repeating ethoxy chains of polyethylene glycol which favoured the oxidized sulfur species to be extracted.
Keywords: sulfur, desulfurization, deep-eutectic solvent, glycol, graphene oxide, oxidation
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