Solvent Optimization in Reactive Extraction for Process Intensification in Biomass Upgrade

In chemical processes when desired products are reactive intermediates, reactive separations (i.e. simultaneous reaction and product separation) are essential for process intensification toward high yields and selectivities. The focus on limited sets of common solvents for liquid-phase extraction of such products leads to non-optimal results and a systematic framework for solvent selection in biphasic systems is lacking at present. In this work, we have explored the reactive solvent extraction of 5-hydroxymethylfurfural (HMF), a biomass-derived platform chemical and a reactive intermediate in hexose hydrolysis.

A multifaceted study was conducted starting with in silico solvent screening using the multiscale COSMO-RS model that identified potential high-performing solvents to maximize HMF extraction from a water-organic biphasic system. This was followed by experimental determination of HMF partition coefficients (PHMF) of selected solvents both at room temperature and reaction temperature. To preserve phase compositions at elevated reaction temperatures, an in-situ sampling and subsequent sample handling procedure was established. For biphasic systems, substituted phenols predicted by COSMO-RS exhibit order-of-magnitude increase in PHMF compared to conventional solvents. However, predicted high-performing anilines were determined to be reactive with HMF, highlighting the importance of combining in silico screening with reactivity and stability experiments. This comprehensive study considers solvent-HMF reactivity, solvent-water miscibility, solvent stability at reaction temperature, partitioning of the substrate (fructose), acid (HCl) and other reaction products (levulinic acid (LA), and formic acid (FA)) in fructose dehydration and provides the first systematic framework of solvent selection for reactive extractions, which can be extended to other biomass derived products such as furfural.