Studies on effective catalytic conversion of xylose to furfural using green sulfonated carbon catalysts: Process optimization by Taguchi approach

Herein, furfural was synthesized via dehydration of xylose with γ-valerolactone (GVL) in the presence of sulfonated carbon catalysts prepared from eucalyptus activated carbon (EAC) and sulfonating agents (H2SO4 and TsOH). Influences of pure and mixed sulfonating agents on physicochemical attributes of the obtained sulfonated carbon catalysts were explored using different characterization techniques (BET, FTIR, NH3-TPD, CHNS, XRD, TGA, SEM and total acid density). The process input variables (temperature, solvent/substrate ratio, time and catalyst loading) influencing the dehydration process were optimized using Taguchi design approach. The best H2SO4 (H)/TsOH (T) molar ratio for the mixed acid sulfonated EAC (EAC-H-T) material to catalyze xylose conversion to furfural was 3:2. The total acid density (0.79 ± 0.08 mmol/g), specific surface area (711.9 m2/g) and sulfur concentration (9.77%) of the EAC-3H-2T catalyst were higher compared to other sulfonated EAC materials. Taguchi optimization approach revealed that highest furfural yield (74.61 ± 0.05 %) was achieved at the optimum conditions of 180 °C dehydration temperature, 1.5 wt% catalyst loading, 3.0 h dehydration time and 3 mL/g GVL/xylose ratio. 1H- and 13C NMR analyses conducted on isolated product obtained under optimum conditions confirmed the formation of furfural. In addition, the EAC-3H-2T catalyst exhibited sustained activity after it was reused for six times.

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