Ionic liquids for coal dissolution, extraction and liquefaction

Abstract

Coal is the most abundant fossil fuel. Direct combustion of low‐ and medium‐rank coals causes alarming environmental impacts. Therefore, it is crucial for coal to undergo pretreatments before its efficient utilization [such as coal to liquid (CTL) processes]. Conventional pretreatment methods suffer from several limitations including the use of volatile organic solvents, environmental hazards, strong reaction conditions (e.g. high temperature and pressure), consumption of large quantities of nonrecoverable chemicals (e.g. bases used in aqueous alkaline digestion), or being only effective for specific coals. On the other hand, coal pretreatment by nonvolatile ionic liquids (ILs) could lead to partial coal dissolution/swelling and structure disruption, which is a critical step before coal liquefaction, hydrogenation, pyrolysis or the inhibition of oxidation/combustion. In addition, ILs are suitable solvents for extracting sulfur compounds from coal, asphaltenes from Direct Coal Liquefaction Residues (DCLR) and phenolic compounds from coal tar. This review will discuss these aspects of coal pretreatments by ILs, and identify how ILs could lead to a cleaner and more efficient utilization of coal resources. © 2020 Society of Chemical Industry

Extraction performance evaluation and theoretical analysis of removal of phenol from oil mixture using a dual‐functionalized ionic liquid: 1‐hydroxyethyl‐3‐methylimidazolium propionate

“…Because the Cl − anion provides higher electronegativity, 44 the RE values of the ILs containing Cl − are higher than that of the IL with the BF 4 − anion. 45 However, ILs containing the Cl − anion are usually corrosive, so such ILs can be detrimental to the equipment. Because there are two functional sites in the prepared [EtOHmim][Pro], the IL displays better extraction performance.…”

Recovery of Rare Earth Elements (REEs) Using Ionic Solvents

“…Coal and coal combustion by-products have been studied as potential sources of REEs. The dissolution of coal in ILs has been recently reviewed [90] and the possibility of recovering REEs has been investigated using an IL and a DES, respectively 1-butyl-3methylimidazolium chloride [C 1 C 4 im] [Cl] and a mixture of choline chloride:urea (molar ratio 1:2) [91].…”

Waste to Treasure: Preparation of Functional Polymeric Particles from Waste Olefins in Carbolic Oil by Self-Stabilized Precipitation Polymerization

“…, hydrogen, solar, and wind) and making greater use of fossil resources ( e.g. , coal and petroleum) as feedstock for chemical production has become an important trend for the sustainable development. , Coal is the most abundant fossil resource, and it is an important raw material for fuels and chemicals. − One of the most important routes from coal to chemicals is coal coking, whose product, coke, is usually used as a reducing agent for iron oxides in the iron and steel industry. , Meanwhile, there are a great amount of by-product, coal tar, producing in the process of coke production . In China alone, the annual output of coal tar is about 25 million tons .…”