Solubility of bio-sourced feedstocks in ‘green’ solvents

Abstract

A group of 14 different bio-sourced, renewable feedstocks (homoserine, 1; glutamic acid, 2; aspartic acid, 3; 2,5-furandicarboxylic acid, 4; fumaric acid, 5; oxalacetic acid, 6; tartaric acid, 7; malic acid, 8; succinic acid, 9; levulinic acid, 10; γ-hydroxybutyrolactone, 11; xylitol, 12; mannitol, 13; sorbitol, 14) have been examined for their solubility/miscibility in a variety of ‘green’ solvents, including water, supercritical carbon dioxide (scCO₂), and ionic liquids. Two other bio-based compounds 5-hydroxymethylfurfural, 15, and D-xylose, 16, were studied in selected solvents. Trends in solubility have been assessed so that these data may be extrapolated to help predict solubilities of other related compounds. For example, 10, 11 and 15 all demonstrated appreciable solubility in scCO₂, as they possess weak intermolecular interactions. The dicarboxylic acids studied (4–9) all proved soluble in modified scCO₂ (by use of MeOH as a cosolvent). While the polyols (12–14) and 1 were insoluble in scCO₂ but water of various pHs and ionic liquids proved adept at their dissolution. Some of the amino acids studied (2 and 3) were only soluble in water with an adjustment of pH.