Insights into the synergistic effect of catalyst acidity and solvent basicity for effective production of pentose from glucose

Controllable and effective transformation of glucose to high value-added products by regulating catalysts and solvents is significant and challenging. Herein, sodium lignosulfonate (SL) as a by-product of papermaking industry, was directly employed to convert glucose into pentose and formic acid (FA) with high efficiency due to the presence of both Lewis acid and weak Brønsted acid on the -SO3- group. The synergistic effect of catalyst and solvent on selective conversion of glucose to pentose, hydroxymethylfurfural (HMF) and furfural was innovatively revealed and it demonstrated that the product distribution can be regulated by varying the Brønsted acid strength and solvent basicity. The 13C-isotope labelling experiments suggested that glucose was firstly isomerized into fructose, the C1-C2 bond of which was then selectively breaking to form pentose and FA. Being consistent with the 13C-isotope experiment results, molecular dynamics simulation indicated that γ-butyrolactone-H2O (GBL-H2O) (19:1, w/w) changed SL arrangement around glucose predominantly to C1-OH and C6-OH, whose change contributed to the isomerization of glucose into fructose starting at C1-OH, and thus inhibited the dehydration of glucose to HMF starting at C2-OH, C3-OH and C4-OH. The degradation of pentose was also inhibited due to solvent regulation for SL distribution around glucose instead of pentose. The highest yield reached 86.5% pentose (60.2% xylose, 26.3% arabinose) and 93.1% FA with the aid of microwave (400 W, 413 K, 1 h). This strategy offered new insights into high-efficient production of platform chemicals from glucose and facilitated the green and sustainable development of modern bio-refinery and papermaking industry.