Lignosulfonate-based heterogeneous sulfonic acid catalyst for hydrolyzing glycosidic bonds of polysaccharides

•Novel and reusable lignosulfonate-based heterogeneous acid catalyst was reported.•High activities in hydrolysis of polysaccharides to monosaccharides were achieved.•Better accessibility of substrate to active site accounts for superior performance.•The catalyst can be reused four times.

We report a novel lignosulfonate-based heterogeneous sulfonic acid catalyst (LF) which offered high yields of monosaccharides (75–98%) in hydrolysis of polysaccharides, such as cellobiose, maltose, d-melezitose, sucrose, inulin, and starch. Specific activity in cellobiose hydrolysis was 5.6 ± 0.3 mol glucose per mol SO3H. Kinetic analysis showed that the apparent activation energy of cellobiose hydrolysis over the LF catalyst is 98.5 kJ mol−1, which was less than 110–138 kJ mol−1 for mineral acids, organic acid homogeneous catalysts or grafted sulfonic acids. The catalyst was recycled by filtration and reused four times in cellobiose hydrolysis without apparent loss of catalytic activity. NMR characterization suggests that the better accessibility of cellobiose to SO3H sites and multiple bindings of hydroxyls of cellobiose on COOH and OH sites may account for its superior performance. This is a new method of utilizing pulp industry waste as sulfonic acid precursor; otherwise sulfonation process is required for preparing heterogeneous sulfonic acid catalysts.

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