Design and synthesis of lignosulfonate-derived carbon-based solid acid with dual-acid sites for directional and...

The efficient conversion of cellulose into levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) represents a promising pathway toward sustainable alternatives to petroleum-based resources. However, several challenges persist, including limited catalyst activity and stability, as well as the difficulty in achieving high selectivity for HMF. Herein, a "catalyst-solvent" synergistic strategy was proposed to fabricate Al-Zr/BC and Al-Si/BC solid acid catalysts featuring Brønsted and Lewis dual-acid sites through the calcination of mechanical activation-treated precursors, in which metal species were loaded into lignosulfonate-derived biomass carbon. These catalysts demonstrated high efficiency in promoting the conversion of cellulose to produce HMF and LA in aqueous and water/γ-valerolactone (GVL) systems. The formation of stable metal-support interactions within the catalysts contributed to their excellent activity and stability. In the aqueous system with the Al-Si/BC catalyst, cellulose conversion reached 93.0% with an LA yield of 61.8%. In the water/GVL biphasic system with the Al-Zr/BC catalyst, cellulose conversion achieved 94.0% with an HMF yield of 62.5%. The synergistic modulation of catalyst surface acidity and the reaction microenvironment, enabled by the interfacial region and the polar solvent environment, significantly enhanced HMF selectivity. Based on these research findings, reaction pathways for cellulose conversion in both aqueous and biphasic systems were proposed. This study provides valuable insights for the rational design of efficient and environmentally benign catalysts, as well as for the optimization of solvent systems for biomass conversion.