Predicting the Solubilities of Furancarboxylic Acids in Water with PC-SAFT

As CO₂ levels continue to rise to unprecedented levels, it becomes ever-more important to consider the substitution of petroleum feedstocks with bio-based, or plant-derived alternatives. Whereas the breakdown of petroleum-derived products introduces ‘new’ CO₂ into the atmosphere, the use of plant-based feeds may help to close the carbon cycle- only releasing at end-of-life inorganic carbon which had already been in the atmosphere prior to its incorporation into biomass via the Calvin-Benson-Bassham cycle. Furthermore, as bio-based chemical intermediates tend to resemble native substrates of catalytic enzymes, their use as feedstocks is amenable to the development of biocatalytic manufacturing processes which tend to operate at very mild conditions.

One of the US Department of Energy’s Top Value Added Chemicals from Biomass is 2,5-furandicarboxylic acid (FDCA), which can be produced by the enzymatic oxidation of 5-formyl-2-furancarboxylic acid (FFA), an oxidation product of 5-hydroxymethylfurfural. (1) (2) Therefore, we consider the thermodynamic properties of FDCA and FFA at biologically relevant conditions of pH and temperature, and most importantly, under aqueous conditions which are agreeable to enzyme catalysis.

Perturbed-Chain SAFT (PC-SAFT) (3) was used to model the solubility behavior of FDCA and FFA in complex media. For this, in a first step the pure-component PC-SAFT parameters for FDCA and FFA were estimated based on solubility data in non-aqueous media. Using these parameters, the solubilities of FDCA and FFA in aqueous media could be predicted with good agreement to the experimental data. PC-SAFT allowed predicting the influence of co-solvents (ethanol) and the effect of temperature and pH on the solubility of FDCA and FFA.

1. Aden, ; Bozell, J.; Holladay, J.; White, J.; Manheim, A. Top value added chemicals from biomass; Technical Report; US Department of Energy: Oakridge, TN, 2004.

2. Dijkman, W. P.; Binda, C.; Fraaije, M. W.; Mattevi, A. Structure-based enzyme tailoring of 5-hydroxymethylfurfural oxidase. ACS Catal. 2015, 5, 1833-1839.

3. Gross, J.; Sadowski, G. Perturbed-Chain SAFT: an equation of state based on a perturbation theory for chain molecules. Ind. Eng. Chem. Res. 2001, 40 (4), 1244-1260.