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Systematic Study of Ionic Liquids Based Coal Extraction: Selectivity in Extract Molecular Weights and Targeted Functional Groups
journal contribution
posted on 2020-03-25, 02:43 authored by Shuai Tan, Mitchell Ross Helling, Franco Basile, Katie Dongmei Li-OakeyIonic liquids (ILs) are environmentally
friendly solvents that
have been used to extract valuable compounds from coal and biomass.
In this work, eight methylimidazolium-based ionic liquids were selected
based on their different capabilities of interactions with solutes.
ζ-Potential characterization was used as a descriptor to reveal
the type of interactions (e.g., hydrogen bonding, π–π
interaction, and dispersion force) between the chosen ILs and coal
particles. Consequently, the different interactions with certain strengths
between the selected cations/anions and coal particles provide unprecedented
selectivity of ILs in coal extraction. For aromatic-rich bituminous
coal, the ILs associated with Cl– preferably extracted
polycyclic aromatic hydrocarbons (PAHs). In contrast, for the same
cations, BF4– and SbF6– anions did not show significant PAH extraction for
bituminous coal. On the other hand, for oxygen-rich subbituminous
coal, the fatty acids (FAs) with more than 20 carbon atoms were found
to be rich in the extracts from the ILs associated with Cl–, whereas the same C4mim+ cation with BF4–, PF6–, and
SbF6– anions extracted unique tricyclic
diterpanes. As such, this study provides systematic experimental results
demonstrating that ILs may be custom designed to extract targeted
compounds from coal or other complex feedstock such as lignocellulosic
biomass.