Hydrolysis of disaccharides via carbon-based solid acids with binding and catalytic domains: Glycosidic bond fracture properties and reaction kinetics

A multifunctional carbon solid acid with binding and catalytic domains was prepared by co-carbonisation of 8-cyclodextrin and polyvinyl chloride followed by sulfonation. The abundant -OH group on the surface of 8-cyclodextrin cavity increased the hydrophilicity and dispersibility of catalyst, and the grafting of -Cl group collectively promoted its adsorption performance (45.8% within 6 h). Additionally, the oxidation and substitution of alkyl chains and aliphatic bridges in carbon precursors were responsible to introduce catalytic functional -SO3H group. The catalyst directionally facilitated disaccharide hydrolysis with strong bond-breaking effects on alpha-1, 4 and 8-1, 4-glycosidic bonds; the hydrolysis rates ranged 72.7%-84.3%, and the monosaccharide yields ranged 68.7%-78.2%. However, the destruction of alpha-1, 1-glycosidic bond was weak, and the fracture of alpha, 8-1, 2-glycosidic bond was likely to cause fructose decomposition. The reaction rate constants of glucose production and decomposition increased with the increase of temperature. The apparent activation energy of glucose production was 98.6 kJ/mol, decreased by 25.9% and 10.4% compared with homogeneous dilute acids and conventional carbon solid acids. The binding domains of catalyst not only played important role in enhancing the surface hydrolysis reaction of saccharides, but also decreased the activation energies.