Green fuel through green route by using a task-specific and neutral 0 CrossMark phosphonium ionic liquid: A joint experimental and theoretical study

Extractive desulfurization (EDS) is one of the most important techniques for the removal of the sulfur compounds (present in liquid fuels), which are one of the main sources to produce air pollutions, for instance: SO.. Because of environmental considerations, the use of organic solvents is limited for this process. Ionic liquids have unique properties, which broaden the applications of these types of solvents for EDS. In continuation of our previous work on the application of task-specific and acidic phosphonium ionic liquids (PIL) for EDS, tri-n-butyl-(2-hydroxyethyl)phosphonium bromide (ITBHEN[Br]) was synthesized, then, the EDS performance of it, as a neutral PIL with alcoholic moiety, was studied in details. At first, the effect of various parameters, such as: the reaction time, temperature, the volume ratio of [TBHEP][Br]ifuel, the initial concentration of sulfur in the liquid fuel and the types of the sulfur compounds on the extraction efficiency were investigated. The obtained results of experimental investigations show that [TBHEP][Br] (with the values of the extraction efficiency about 56, 70 and 41% for benzothiophene (BT), dibenzothiophene (DBT) and dimethyldibenzothiophene (DMDBT), respectively) acts as a suitable extractant for removal of the sulfur compounds from liquid fuel. Also, the theoretical calculations demonstrate that hydrogen of alcohol, as well as alpha-hydrogens of the methylene groups, connecting to phosphonium, can provide interaction between dibenzothiophene and PIL in the extraction process. However, it is concluded that [TBHEP][Br] is more suitable extractant than our previous report, PIL with acetic acid tag for EDS of the liquid fuel, because of low corrosivity and price. So, the results of this work support the idea of rational design, synthesis and application of task-specific ionic liquids for the green EDS. (C) 2016 Elsevier B.V. All rights reserved.