Extractive performance of an acidic phosphonium-based deep eutectic solvent for simultaneous desulfurization and denitrogenation of real gasoline

Abstract

Hydrodesulfurization and hydrodenitrification in petroleum refinery are often associated with certain limitations of a huge energy consumption and restricted efficacy in removing total sulfur and nitrogen content. This study elucidates employing a selective liquid–liquid extraction process for desulfurization and denitrogenation of real gasoline using an efficient deep eutectic solvent (DES), obtained from methyltriphenylphosphonium bromide and para-toluensulfonic acid in a 3:7 molar ratio. The results show remarkable extraction efficiencies of 50.5% for the total sulfur compounds and 93.5% for the total nitrogen compounds in a single extraction step. After five extraction steps, these efficiencies were improved to 89.3% and 99.3%, respectively, using DES:gasoline volume ratio of 1:1 at 45 ^ºC. In solvent regeneration via vacuum evaporation, 86.5% of its performance was retained after three stages in extracting sulfur and 91.0% in extracting nitrogen compounds. From NMR analysis, detailed information was obtained regarding the dominant interactions and the extraction mechanism involving acid-base interaction and π– π bonding, dominant for pyridine, and C–H⋯O hydrogen bonding for thiophene, examined by using the DES with a synthetic gasoline. The results totally demonstrate the benefits of utilizing such ecofriendly solvents for purifying fuels.