Ionic Liquids in Selective Oxidation: Catalysts and Solvents

Abstract

Selective oxidation has an important role in environmental and green chemistry (e.g., oxidative desulfurization of fuels and oxidative removal of mercury) as well as chemicals and intermediates chemistry to obtain high-value-added special products (e.g., organic sulfoxides and sulfones, aldehydes, ketones, carboxylic acids, epoxides, esters, and lactones). Due to their unique physical properties such as the nonvolatility, thermal stability, nonexplosion, high polarity, and temperature-dependent miscibility with water, ionic liquids (ILs) have attracted considerable attention as reaction solvents and media for selective oxidations and are considered as green alternatives to volatile organic solvents. Moreover, for easy separation and recyclable utilization, IL catalysts have attracted unprecedented attention as "biphasic catalyst" or "immobilized catalyst" by immobilizing metal- or nonmetal-containing ILs onto mineral or polymer supports to combine the unique properties of ILs (chemical and thermal stability, capacity for extraction of polar substrates and reaction products) with the extended surface of the supports. This review highlights the most recent outcomes on ILs in several important typical oxidation reactions. The contents are arranged in the series of oxidation of sulfides, oxidation of alcohols, epoxidation of alkenes, Baeyer-Villiger oxidation reaction, oxidation of alkanes, and oxidation of other compounds step by step involving ILs as solvents, catalysts, reagents, or their combinations.

Optical and XPS evidence for the electrochemical generation of an N-heterocyclic carbene and its CS2adduct from the ionic liquid [bmim][PF6]

“…In summary, we present direct optical and X-ray photoelectron spectroscopic evidence for the electrochemical generation of an N-heterocyclic carbene and its CS 2 (1) in the presence of CS 2 resulted in the formation of the dithiocarboxylate adduct 3, supported optically by the formation of red color and through XP spectroscopy exhibiting the expected S2p peak. To the best of our knowledge, this is the first example of the formation of a CS 2 adduct via an electrochemically generated N-heterocyclic carbene.…”

“…[1][2][3][4][5][6][7] ILs have found widespread use as reaction solvents in the area of green chemistry due to their unique properties such as extremely low vapor pressure, structural tunability, and thermal stability. 8 Being composed of purely anions and cations and having a reasonable ionic conductivity (10 À2 S cm À1 ) together with an enlarged electrochemical window, ILs have also found a unique place in the field of electrochemistry, notably in energy storage, such as batteries, supercapacitors, etc.…”

A novel strategy to utilize ethylene glycol‐ionic liquids for the selective precipitation of polysaccharides

“…to volatile and hazardous organic solvents, ILs have been widely applied in separation science [10][11][12], analytical chemistry [8,13,14], biomass transformation [15], and organic synthesis [16], among others. Over the past years, carbohydrate chemists have witnessed the use of ILs in a wide variety of aspects [6,7,12].…”

Morphology‐Controlled Synthesis of CuO, CuO Rod/MWW Composite for Advanced Oxidation of Indole and Benzothiophene

“…On the other hand, sulfur compounds are Benzothiophene (BT), Dibenzothiophene (DBT), 3‐methyl thiophen (3‐MT), Thiophen (T), 2‐methyl thiophene (2‐MT), 4,6‐dimethyl dibenzothiophene (4, 6‐DMDBT), Sulfone dibenzothiophene (DBTO), and 4‐methyl dibenzothiophene (4‐MDBT) . For removal, the most effective methods are oxidative denitrogenation (ODN) and oxidative desulfurization (ODS) by catalysts. Meanwhile, zeolite matrixes are a group of catalysts with a high selectivity and a desirable activity to break down the recently introduced C−N and C−S bonds .…”