Solid–liquid equilibria predictions for the dissolution of brown coal in ionic liquids using a continuum solvation model

• Dissolution and dispersion of brown coal using ionic liquids.
• Negative value of Gibb's free energy at infinite dilution of brown coal.
• Solubility of brown coal increases with increase in temperature.
• [BMPYR][CH3CO3] having small cation structure has the highest solubility.

Ionic Liquids (IL) are green solvents and has shown immense potential recently for the solubilisation and dispersion of certain coals. However, the choice of IL is cumbersome owing to its infinite cation and anion combination. Continuum Solvation Models (CSM) can theoretically predict the solvation phenomena of a component in solution. In this work, the continuum solvation model namely Conductor like Screening Model (COSMO) was used to predict the Solid (brown coal) — Liquid (IL) behaviour. Taking the process economics and the nature of ionic liquids into account, 18 ILs were selected from the Sigma Aldrich Catalogue to predict the Solid–liquid Equilibria (SLE) of brown coal in ionic liquid. Initially, the model was benchmarked qualitatively using the data available in literature for coal and conventional solvents such as pyridine and NMP. Thereafter, Gibb's Free Energy of solvation and SLE predictions were performed for these 18 ILs. IL showing the highest solubility was chosen as potential solvent which can disrupt the hydrogen bonding of brown coal and the same was used to predict the solid–liquid-equilibrium. The IL namely 1-butyl-1-methylpyrrolidinium methylcarbonate [BMPYR][CH3CO3] and brown coal gave complementary behaviour in sigma profile which proved that this IL is highly miscible in brown coal.