Metal-Based Ionic Liquids in Oxidative Desulfurization: A Critical Review

Abstract

Ionic liquids (ILs) as novel functional desulfurization materials have attracted increasing attentions. Metal-based ionic liquids (MILs) are classified into three types of metal chloride ILs, metal oxide ILs, and metal complex ILs based on the definition and basic structure of MILs in this critical review. On the basis of the properties of ILs such as structure designability, super dissolution performance, good thermal and chemical stability, nonflammability, and wide electrochemical window, MILs exhibit unique advantages on hydrophobicity, oxidation performance, and Bronsted−Lewis acidity. Therefore, MILs possess both the absorption and oxidation centers for the intramolecular adsorption and oxidation to improve the oxidative desulfurization (ODS) process. During the novel nonaqueous wet oxidative desulfurization process (Nasil), H 2 S can be oxidized into elemental sulfur with hydrophobic MILs, which can be regenerated by oxygen for recycle, to solve the problems of low sulfur capacity, low sulfur quality, and severe secondary pollution in the aqueous Lo-Cat wet oxidative desulfurization process. Another outstanding feature of MILs in ODS is biomimetic catalysis, which has the function of activating molecular oxygen and improving the oxidation performance. Metal oxide ILs and metal complex ILs are used in combination with hydrogen peroxide or oxygen with the existing water to generate a Fenton-like reaction to convert hydrophobic organic sulfur or SO 2 into hydrophilic sulfoxide/sulfone or sulfur acid, respectively. However, the corrosion of Cl − to the equipment and emulsification phenomenon in the extraction process of sulfoxide/sulfone separation still need further study. Furthermore, the promising strategies to construct highly efficient and green desulfurization processes for large-scale applications are provided.

A current overview of the oxidative desulfurization of fuels utilizing heat and solar light: from materials design to catalysis for clean energy

“…27 The catalytic performances of various homogeneous and heterogeneous ODS catalysts have also been critically discussed and compared in several reports. [28][29][30] The applications of ionic liquids (ILs), [31][32][33] polyoxometalates (POMs), 34 metalorganic frameworks (MOFs) 35,36 and graphene 11 in ODS have also been individually reviewed. Although these scientific reviews have encapsulated a wide panorama of the innumerable ODS applications, the structure-activity connection of multiple materials, which is of vital importance to direct material engineering for shaping catalysts with extraordinary catalytic activity and stability in ODS, has not yet been completely unraveled.…”

Effective absorption of SO2 by imidazole‐based protic ionic liquids with multiple active sites: Thermodynamic and mechanical studies

“…It has been widely studied and applied as a functional liquid due to the good chemical stability and adjust‐ability, low vapor pressure, and good thermal stability. In recent 10 years, ILs are widely used in the field of gas treatment 12–15 . The successively developed guanidyl, 15,16 imidazole, 17,18 phenolic, 19 tertiary amine‐functionalized, 16,20 hydroxyl ammonium, 21,22 and ether‐functionalized ILs 23–25 were developed for SO 2 absorption, especially ether‐functionalized and amine‐functionalized ILs demonstrate remarkable SO 2 uptake through multi‐site interaction.…”

Unravelling the Interactions of Magnetic Ionic Liquids by Energy Decomposition Schemes: Towards a Transferable Polarizable Force Field

“…For instance, [Bmim] [ZnCl 3 ] was reused six times, without losing efficiency in PET conversion, reaching up to 97.9% [ 19 ]. In the last decade, several experimental studies exhibit also the potential of applying MILs in DNA extractions [ 20 ], CO 2 , NH 3 and SO 2 separation [ 8 , 21 , 22 ], energy harvesting [ 23 ] as well as in catalysis applications [ 24 , 25 ]. Rare-earth-based MILs, in addition to their high response to the magnetic field, show high luminescence too, which makes them suitable to use in optical applications [ 26 ].…”