Enhanced catalytic performance of lignin-derived carbon supported SnOx via lignin fractionation in the conversion of glucose to 5-hydroxymethylfurfural

As a high-quality carbon source, this study employed the gradient acid precipitation method to separate and extract bamboo lignin (BL) fractions from alkaline pulping black liquor, aiming to investigate the influence of BL fraction on the yield of lignin-derived carbon supported tin oxide (SnO x /LC) and its catalytic performance in the conversion of glucose to 5-hydroxymethylfurfural (5-HMF), utilizing various testing methods for detailed characterization. The characterization results revealed that SnO x /LC-2 was thermally stable with both Lewis acid and Brønsted acid sites, and the Sn element was uniformlmly dispersed on carbon carrier surface. In addition, with decreasing pH of black liquor, the molecular weight and polydispersity of BL fraction were significantly reduced, and its structural homogeneity was effectively improved. More importantly, the relative content of syringl unit and the content difference between phenolic hydroxyl and carboxylic acid groups in the structure of BL fractions both showed linear negative correlations with 5-HMF yield, which revealed the constitutive relationship between the molecular structural features of lignin and the catalytic performance of SnO x /LC, thus contributing to the high-value utilization of industrial lignin.