Efficient sugarcane leaf-derived biochar-based acid catalyst for sorbitol dehydration into isosorbide

Abstract

Biomass-derived solid acid catalysts provide a sustainable and environmentally friendly approach for producing isosorbide (ISB) via sorbitol dehydration in line with green chemistry principles. In this study, a biochar-based acid catalyst was synthesized from sugarcane leaf (SL) through carbonization at 500 ºC, followed by sulfonation at 140 – 180 ºC using different CSL (carbonized SL):H<inf>2</inf>SO<inf>4</inf> ratios ranging from 1:10–1:30 (g: mL). The catalyst characteristics were comprehensively explored using elemental analysis, acid–base titration, BET surface area, TPD, TGA, XPS, FTIR, XRD, Raman, SEM, and TEM. Catalytic activity was evaluated for ISB production at varying temperatures (160 – 240 ºC), reaction times (12 – 24 h), and catalyst loadings (0 – 45 wt%). Among all catalysts, the sample sulfonated at 160 ºC with a CSL:H<inf>2</inf>SO<inf>4</inf> ratio of 1:20 (160–20-SCSL) exhibited the maximum activity, achieving an ISB yield of 55.77 mol%, selectivity of 56.75%, and sorbitol conversion of 98.26% at 220 °C for 21 h with 25 wt% catalyst loading. The superior performance was due to its dominant surface area and high acid site density. Moreover, the 160–20-SCSL catalyst exhibited strong thermal and structural stability and maintained activity over multiple cycles. Compared with the commercial Amberlyst-15 catalyst, 160–20-SCSL exhibited comparable efficiency, highlighting its potential as a competitive catalyst support for scalable and sustainable ISB production.