Manganese-Biochar Catalyst for Sustainable Glycolic\nAcid Production from Biomass-Derived Glucose and Oligosaccharides

Production\nof glycolic acid from renewable resources is a significant\nchallenge considering its extensive market and the depletion of fossil\nresources. This study accomplished sustainable glycolic acid production\nfrom biomass-derived saccharides using a microwave-assisted aerobic\noxidation system. Various Mn-biochar catalysts were synthesized using\ndifferent precursors (MnCl<sub>2</sub> and KMnO<sub>4</sub>) and synthesis\ntemperatures (400–850 °C). Glycolic acid yield from glucose\ncould reach 62.8 Cmol % within 20 min at 180 °C over MnBC-VII-700\n(i.e., catalyst derived from Mn(VII) precursor and synthesized at\n700 °C). Mn(III) was identified as the catalytically active state\nby correlation with the catalytic performance. Biochar support is\nvital for reactant adsorption, electron transfer, and microwave absorption.\nTransformation from glucose to glycolic acid would experience retro-aldol\nand oxidation reactions, while oxidation-hydrolysis of the glycosidic\nbond could be achieved for one-pot oligosaccharide conversion. The\nyields of glycolic acid reached 43.1, 29.2, and 33.3 Cmol % within\n30 min, when the substrates were cellobiose, maltose, and maltotriose,\nrespectively. This study developed a low-cost Mn-biochar catalyst\nfor biomass valorization. The study presents valuable mechanistic\ninsights that can serve as a critical reference for the sustainable\nproduction of chemical building blocks in heterogeneous catalysis.