Functionalized Biomass-Waste-Derived Porous Carbon Catalyst for Selective Synthesis of Biomass-Derived Fuel Additives

Leveraging renewable, non-edible lignocellulosic biomass (cellulose, hemicellulose, and lignin) as a carbon source for synthesizing materials, biofuels, and chemicals can replace fossil feedstock in the chemical industry toward carbon neutrality. This study showed the utilization of lignin to develop a highly active and recyclable porous carbon catalyst for synthesizing fuel additives from readily available cellulose- and hemicellulose-derived ethylene glycol and furfural, respectively. The lignin was extracted with more than 90% yield from waste lignocellulose (neem sawdust) using an organosolv process (1,4-dioxane:H2O = 8:2, v/v), followed by boron doping (BLC: boron-doped lignin-carbon) featuring hierarchical pores, superior surface area (713 m2/g), and abundant defect sites. The XPS study of the BLC catalyst unveils the presence of diverse boron-based species (BC3, BCO2, and BC2O), which could act as acid sites, as elucidated by NH3-TPD analysis. Thus, the BLC catalyst showed a 94% yield of 2-(furan-2-yl)-1,3-dioxolane (FDL) from acetalization of ethylene glycol with furfural, whereas lower yields of FDL (28 and 38%) were obtained over the lignin-carbon (LC) and nitrogen-doped lignin-carbon (NLC), respectively. The high stability of the BLC catalyst, as confirmed by a hot filtration test, facilitated phenomenal reusability with 94% and 93% yields of FDL in the 1st and 10th cycles, respectively. The versatile efficiency of the BLC catalyst was demonstrated for synthesizing about 20 diverse fuel additives. The hierarchical porous structure, higher surface area, and strong acidic sites with efficient catalytic reusability and process scalability emphasize the practical application of BLC-based catalysts in the biorefinery industry.