(663a) A New Class of Xylose-Based Green Solvents Produced from Renewable Biomass

Organic solvents represent more than half the mass of all raw materials required for the production of chemicals. Concurrently, solvent use in industry is facing increasing regulatory and commercial pressure due to tightening legislation and an evolving awareness of health and safety issues. In parallel, growing environmental concerns over the source and life cycle of common solvents encourage the development of bio-based alternatives that can compete with petroleum-derived counterparts.

Lignocellulosic biomass is a promising feedstock for the production of renewable solvents since it is available in large quantities and does not compete with food crops. Several biomass-derived solvents have been developed and commercialized so far. However, their use in industry is still considered problematic due to various reasons such as high production cost (GVL, Dimethyl isosorbide), high flammability (2-Me-THF), instability in harsh conditions (Cyrene, cyclic carbonates). Newly emerging candidates that aim to replace hazardous analogs are also facing challenges. In this regard, acetal-stabilized xylose derivatives that can be inexpensively produced directly from biomass at over 90% yield (on a xylan basis) by aldehyde-assisted fractionation (AAF) technology developed in our lab could be interesting candidates for use as solvents¹.

In this work, we explored diformylxylose (DFX) and its derivatives isolated during AAF of biomass as potential solvents by assessing their performance in model reactions, as well as measuring their physical and solvatochromic parameters. DFX was found to have similar solvation properties to conventional polar aprotic solvents such as NMP, DMF, DMAc, while DFX’s derivatives, for example, dipropylxylose (DPX) and dibutylxylose (DBX) were closer to medium-polarity solvents such as acetone and THF, according to a comparison of Kamlet-Abboud-Taft parameters. The high polarity and high hydrogen-bond accepting ability of DFX also make it a promising component of deep eutectic solvents, several of which were prepared in this work as demonstrations. In addition, determined Hansen Solubility Parameters indicate that DFX is the most similar to Dimethyl Isosorbide while being potentially much less expensive. At the same time, DPX and DBX can complement the list of conventional ethers and ketones like di-n-butyl ether, methyl isobutyl ketone (MIBK), but bringing new physical properties and, possibly, a safer profile.

Notably, we demonstrated that DFX’s performance in alkylation, cross-coupling, and hydrogenation reactions was comparable with conventional problematic analogs and in some cases outperforming existing green alternatives². DBX and DPX also possessed the right solvation properties to promote some of the model reactions. DFX was also found to have potential in many other applications including preparation of electrodes, synthesis of metal-organic frameworks, polymer synthesis, solid-phase peptide synthesis, biomass processing, liquid exfoliations, microfiltration membrane preparation, etc.

A preliminary toxicological assessment (bacterial Ames test) performed on DFX showed that this molecule is unable to cause mutations both directly and indirectly and cannot be considered a mutagenic compound. This shows that DFX is a good candidate for follow-up in-depth toxicology assessment (e.g. in vivo) needed for the approval of the compound for public use.

Finally, we demonstrated that DFX and its derivatives can be produced sustainably from biomass, specifically corn cobs in a kg-scale. This shows an excellent example of how waste biomass can be valorized into valuable chemicals with relatively low cost and high efficacy. A life cycle assessment has been performed, which demonstrated high competitiveness of this new class of solvents against conventional analogs.