Mutual Influence of Furfural and Furancarboxylic Acids on Their Solubility in Aqueous Solutions: Experiments and Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) Predictions

Furan compounds are of mounting global interest due to their biorenewable nature and their potential to replace petroleum-based compounds as feedstocks in manufacturing. In this work the solubilities of furfural and the furancarboxylic acids 2-furoic acid (FA), 5-formyl-2-furancarboxylic acid (FFA), and 2,5-furandicarboxylic acid (FDCA) in aqueous solutions and organic solvents were investigated experimentally and by modeling with perturbed-chain statistical associating fluid theory (PC-SAFT). The PC-SAFT pure-component parameters of the solutes FA, FFA, and FDCA and one binary parameter between each solute and each solvent were adjusted to fit experimentally determined solubilities of each solute in each organic solvent or in water. Pure-component parameters of furfural were fitted to experimental density data and vapor-pressure data, and a binary interaction parameter was fitted to capture the solubility behavior of furfural in water. Modeling of pH effects enhanced predictions of the mutual influences of the acids on their solubilities in ternary aqueous systems. Mutual solubility influences of furfural and the furancarboxylic acids were accurately modeled with one constant binary parameter for the acid furfural mixtures. All PC-SAFT modeling results were validated with new experimental solubility data at 35 degrees C, which were measured by HPLC analysis of equilibrated saturated solutions.