Desulfurising Fuels Using Alcohol-Based Deep Eutectic Solvents Using Extractive Catalytic Oxidative Desulfurisation Method

Abstract

A special awareness has been given worldwide to clean the polluted environment. The environment is polluted mainly by greenhouse gases, emissions from transportation fuels, etc. Among them, sulfur compounds emitted from the emission of transported fuels significantly impact environmental pollution. It requires the removal of these sulfur compounds from transportation fuels. Refineries use the hydrodesulfurization (HDS) process to reduce these sulfur compounds from fuels. However, the HDS process requires high hydrogen pressure and temperature, making it cost-effective. An alternative to the HDS process is oxidative desulfurization via solvent extraction, which requires low-temperature operating conditions. In this regard, deep eutectic solvents (DESs) are attractive for researchers to desulfurize transportation fuels via solvent extraction due to their low-cost synthesis method. In our study, DESs were synthesized using phenylacetic acid and salicylic acid as hydrogen bond acceptors (HBAs) and tetraethylene glycol as hydrogen bond donor (HBD) in the mole ratio of 1:2. DESs were characterized by using FTIR spectra. Physico-chemical properties of DESs, such as density, viscosity, and refractive Index, were also measured. The synthesized DESs were performed to extract organosulfur compounds from model fuel and actual diesel. An oxidation study was carried out for model fuel and diesel, followed by solvent extraction using these synthesized DESs. The extraction efficiency for PAA/TTEG(1:2) and SAA/TTEG(1:2) was achieved as 50.16% and 38.89% for model fuel at a temperature of 30oC using a solvent to feed ratio of 1.0 while for diesel, it was 38% and 37%. However, it increased to 77%, 68%, and 54%, 73%, respectively, for PAA/TTEG(1:2) and SAA/TTEG(1:2) when the feedstocks were oxidized. These results showed better extraction performance of DES PAA/TTEG(1:2) than that of SAA/TTEG(1:2) at low-temperature 30oC using extractive combined oxidative desulfurization (ECODS). Hence, the DES synthesized using SAA and TTEG in the mole ratio of 1:2 works better as an extraction solvent for removing the organic sulfur compounds from fuels at low temperatures.