In “good” solvents such as pyridine, coal particles swell and fracture to some degree as soluble material is extracted, but they remain as more-or-less coherent particles. It is shown here that certain ionic liquids (ILs) are capable of solubilizing, disintegrating, and dispersing certain coals as very fine particles to a remarkable extent. The solubility of two coals, a Powder River Basin coal and an Illinois No. 6 coal, also increased significantly in IL/N-methyl pyrrolidinone (NMP) and IL/pyridine mixtures, relative to the solubility of the coals in NMP and pyridine. A third coal, Upper Freeport, gave yields that were lower than those obtained in pyridine alone. This coal may be anomalous in its behavior. It is suggested that many if not most coals are densely cross-linked networks where a portion of soluble material remains trapped, even upon swelling in good solvents, which fracture and only partially fragment coals at ambient temperatures. Certain ILs fragment and disperse some coals to a much greater extent, however, apparently releasing much of this trapped material.

It is demonstrated that bitumen can be separated from "water-wet" Alberta oil sands and "oil-wet" Utah oil sands using a so-called analogue ionic liquid (IL) based on deep eutectic mixtures of choline chloride and urea (ChCl/U) together with a diluent such as naphtha. Unlike conventional ILs, these eutectics are relatively cheap and environmentally friendly. The process is straightforward and involves simply mixing the components at ambient temperatures followed by standard solid/liquid and liquid/liquid separation steps. The ChCl/U mixture appears to reduce the adhesion of bitumen to sand, facilitating separation. It is also immiscible with hydrocarbons such as bitumen or oil. Coupled with a large density difference, this results in a sharp phase separation of hydrocarbons from the ChCl/U mixture. The ChCl/U deep eutectic essentially acts as a separating fluid, keeping the naphtha-diluted bitumen and extracted sand apart, facilitating subsequent separations and solvent recovery steps. However, ChCl/U mixtures are highly viscous at ambient temperatures, but high concentrations of this deep eutectic in water also work well. Initial scale-up work suggests that this approach may form the basis for a viable large-scale process.

It is well-known that dispersing catalysts to obtain good contact with coal particles enhances coal liquefaction. This is often accomplished using soluble catalyst precursors that are then converted to an active form. In this study, it is shown that certain ionic liquids can be used to fragment, disperse, and partially dissolve coal to such an extent that good contact can be made with commercially obtained, micrometer-size molybdenum disulfide particles by simply mixing these particles with the ionic liquid/coal dispersion. Good liquefaction yields under standard conditions are obtained using this approach.

No abstract

Certain ionic liquids can fragment coals to a remarkable degree at temperatures below 100 °C. Here, it is shown that when Illinois No. 6 coal is mixed with the ionic liquid 1-butyl-3-methylimidazolium tetrafluoromethanesulfonate and tetralin and held at temperatures of 300 °C or less under hydrogen, a dramatic increase in pyridine solubility is obtained. The highest yield of soluble material was in excess of 90% [dry and ash-free (daf) basis], but the results were very variable, partly as a result of the small sample sizes used.