Desulfurization Performance of Choline Chloride-Based Deep Eutectic Solvents in the Presence of Graphene Oxide

Abstract

Extractive catalytic oxidative desulfurization (ECODS) is the one of the recent methods used in fuel desulfurization which involved the use of catalyst in the oxidative desulfurization of diesel fuel. This study is aimed to test the effectiveness of synthesized choline chloride (ChCl) based deep eutectic solvent (DES) in fuel desulfurization via ECODS method, with the presence of graphene oxide (GO) as catalyst and hydrogen peroxide (H2O2) as oxidant. In this study, 16 DESs based on choline chloride were synthesized using glycerol (GLY), ethylene glycol (EG), tetraethylene glycol (TEG) and polyethylene glycol (PEG). The characterization of the synthesized DES was carried out via Fourier transform infrared spectroscopy (FTIR) analysis, density, and viscosity determination. According to the screening result, ChCl-PEG (1:4) was found to be the most effective DES for desulfurization using ECODS method, with a removal of up to 47.4% of sulfur containing compounds in model oil in just 10 min per cycle after the optimization of the reaction parameters, and up to 95% desulfurization efficiency could be achieved by six cycles of desulfurization. It is found that the addition of GO as catalyst does not increase the desulfurization performance drastically; hence, future studies for the desulfurization performance of DESs made up from ChCl and PEG and its derivatives can be done simply by using extraction desulfurization (EDS) method instead of ECODS method, for cost reduction purpose and easier regulation of DES waste into environment.

Time‐Dependent Hydrogen Bond Network Formation in Glycerol‐Based Deep Eutectic Solvents

“…Properties of glyceline differ from the consistent behaviour of reline and ethaline, [23–25] due to the larger number of hydroxy (OH) groups in Gly, causing the oversaturation of the HBA by 50 % in comparison with ethylene glycol [26,27] . Moreover, the ionic character of ChCl can change the overall electrochemical properties of glyceline, in comparison with amino acids‐ or organic acid‐based HBAs in equivalent DES [28] .…”

“…[20,21] Thus, the most popular examples of type III DESs are reline (ChCl:U), ethaline (ChCl:EG) and glyceline (ChCl:Gly), all synthesized using 1 : 2 molar ratio of HBA:HBD. [22] Properties of glyceline differ from the consistent behaviour of reline and ethaline, [23][24][25] due to the larger number of hydroxy (OH) groups in Gly, causing the oversaturation of the HBA by 50 % in comparison with ethylene glycol. [26,27] Moreover, the ionic character of ChCl can change the overall electrochemical properties of glyceline, in comparison with amino acids-or organic acid-based HBAs in equivalent DES.…”

“…[28] Consequently, Gly will firstly solvate Ch + and Cl À [29,30] and the excess glycerol will self-aggregate via the intermolecular HBs, [31] although the HBA -HBD interaction remains unaffected upon increased number of Gly molecules. [23] Due to its physicochemical properties, glyceline can improve the liquid membrane's permeability, [32][33][34] serve as an extraction medium for biodiesel and biomass, [14,21,[35][36][37] or low-corrosive lubricant. [38] Regardless of the similar ChCl and Gly behaviour upon glycerol addition, the overall thermophysical properties of the solvent are influenced by the varying HBA:HBD ratio.…”

“…For example, 1 : 1 (ChCl:Gly) DES demonstrates the highest viscosity and lowest density in comparison with 1 : 2 (glyceline), 1 : 3 or 1 : 4 (glycholine). [23,39] This effect can be used in different ways. For example, reduction of the HBA:HBD ratio to 1 : 1 can increase the extraction yield for biodiesel products, [14,39] whereas more dense DES 1 : 3 can reduce the crude oil interfacial tension.…”

“…Moreover, the ionic character of ChCl can change the overall electrochemical properties of glyceline, in comparison with amino acids‐ or organic acid‐based HBAs in equivalent DES [28] . Consequently, Gly will firstly solvate Ch + and Cl −[29,30] and the excess glycerol will self‐aggregate via the intermolecular HBs, [31] although the HBA – HBD interaction remains unaffected upon increased number of Gly molecules [23] . Due to its physicochemical properties, glyceline can improve the liquid membrane‘s permeability, [32–34] serve as an extraction medium for biodiesel and biomass, [14,21,35–37] or low‐corrosive lubricant [38] …”