Selective HDO · Selective sustainable hydrodeoxygenation of bioaromatics

Selective sustainable hydrodeoxygenation of bioaromatics

The development of effective processes to transform non-edible biomass into base chemicals and fuels is one of the key societal challenges to achieve a low-carbon economy. Lignocellulose is an ideal renewable carbon source given its abundance on Earth. State-of-the-art lignin-first processes enable the abstract and depolymerization of lignin, delivering polyoxygenated aromatic compounds (guaiacols and syringols) with up to near-to-theoretical yields considering the percentage of the β-O-4 linkages present, and carbohydrate pulp residue which is amenable to biobased sugars. These compounds could potentially serve for the future production of bio-based aromatic and aliphatic platform chemicals. However, on one hand, accessing lower oxygen content arenes required for the chemical industry, which are traditionally obtained through oxidation of petroleum-based arenes, requires selective hydrodeoxygenation (HDO) of these bio-based polyoxygenated aromatics. Although hydrodemethoxylation can be achieved, selective hydrodehydroxylation of the OH groups while leaving the OMe group intact with high yields is only possible after converting the hydroxy into better leaving groups (–OR). However, all the known examples used traditional activating reactants (e.g. isocyanates, sulfonyl, carbamoyl or acyl chlorides, dimethoxymethylsilane), which are non-renewable, expensive, and problematic based on Environmental, Health, and Safety (EHS) criteria. Importantly, more challenging syringols, featuring 2 ortho MeO, have not yet been tackled. Selective removal of one hydroxy group in Ar-(OH)n is also unprecedented. On the other hand, current biorefineries of sugars have focused more on the energy sector by producing biofuels such as ethanol, GVL, etc, scarifying the unique enantio-enriched stereocenters, which are challenging to build artificially, gifted by nature. Selective deoxygenation of polyols with retention of stereochemistry is thus of significant importance for the further valorization of biomass. Conventional methods that meet this purpose rely on selectively transforming the hydroxy into radical precursors with unbenign activating reagents such as O-thiocarbonyl chlorides. Herein this project aims at strategies combining green activation (low cost and benign reagent) with cheap base metal catalysis featuring improved green metrics to transform biobased platform compounds selectively into functional chemicals.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз