Tuning Task-Specific Ionic Liquids for the Extractive Desulfurization of Liquid Fuel

Abstract

Extractive desulfurization of liquid fuel is a simple process that requires minimum energy input and can be operated via existing liquid−liquid extraction apparatuses. In particular, to achieve deep desulfurization, the conventional hydrodesulfurization (HDS) process has shown limitations in the removal of aromatic sulfur compounds. Recently, extractive desulfurization using a new type of nonvolatile solvent, ionic liquids (ILs), has yielded promising results. However, there is a lack of systematic evaluation of the effect of IL structure on desulfurization efficiency, and a lack of mechanistic understanding regarding how ILs lead to the partition of aromatic sulfur compounds from fuel to the IL phase. The present study examines a total of 71 ILs and two deep eutectic solvents (DESs) with combinations representing various cations and anions. We identify a number of ILs that yield high partition coefficients [up to 1.85 mg(S) kg (IL) −1 /mg(S) kg (oil) −1 ] for the partition of aromatic sulfur compounds between ILs and n-octane or n-dodecane as surrogates for gasoline or diesel, respectively. We find that the high sulfur partition coefficient correlates with a high dipolarity/polarizability (π*) or a low solvent polarizability (SP) of ILs carrying the same cation and different anions, but correlates with a low dipolarity/polarizability (π*) for ILs carrying the same anion paired to cations bearing different alkyl chain lengths. We further demonstrate that a four-step extraction using ILs can achieve 99% dibenzothiophene (DBT) removal (i.e., an initial sulfur content of 500 ppm is reduced to <5 ppm following extraction).

Catalytic oxidative desulfurization of fuels in acidic deep eutectic solvents with [(C6H13)3P(C14H29)]3PMo12O40 as a catalyst

“…Extractive desulfurization is a feasible approach because of its simple and mild conditions (Nejad and Beigi 2015). The common extractants are organic solvents, ionic liquids and deep eutectic solvents (DESs) (Jiang et al 2015;Li et al 2016a, b, c;Zhao et al 2016;Jiang et al 2016;Zhang et al 2018). Among the three types of solvent, DESs, a eutectic mixture of two or more components, are the most promising extractants due to their low cost and biodegradability.…”

Water distribution at the electrified interface of deep eutectic solvents

“…They can be prepared from sustainable and inexpensive materials with less demanding preparation methods (no purication is required) and they are non-toxic. [4][5][6]9,10 Due to these compelling unusual physicochemical properties, DESs have been increasingly used in a vast number of applications with success, including solvent extraction, 11,12 biodiesel production, 13 organic synthesis, 5,10,14,15 lubrication, 5 nanoporous carbon synthesis, 16,17 fuel treatment, 10,11,18 gas capture [19][20][21] and DNA stabilization. 22,23 Besides, they have also been extensively used as solvents for many electrochemical purposes such as electrodeposition, [24][25][26][27][28][29] energy conversion, 30 energy storage, [31][32][33][34] etc.…”

Synthesis of Morpholine-Based Ionic Liquids for Extractive Desulfurization of Diesel Fuel

“…In addition, according to Domańska e Wlazio (2014), the extraction efficiency of non-aromatic cation morpholinium-based ILs is significantly influenced by hydrogen bonding of the hetero-atoms of sulfur compounds with the IL cation. In addition, the kinetics are significantly affected by the specific volume and shape of the IL (Zhao et al, 2016).…”