Solvent-free conversion of glycerol to solketal catalysed by activated carbons functionalised with acid groups

Activated carbons prepared from agricultural waste were modified to introduce surface acid sites by treatment with HNO3 or H2SO4. These acid-functionalised materials were studied as heterogeneous catalysts for the solvent-free acetalisation of acetone with glycerol to produce 2,2-dimethyl-1,3-dioxolane-4-methanol (solketal). The best catalyst was prepared by treatment with concentrated sulphuric acid and achieved 97% conversion of glycerol with high selectivity towards solketal by reaction with acetone at room temperature. The catalytic behaviour of the activated carbons was correlated with their physicochemical properties through characterization by N2-physisorption, XPS, elemental analysis, TGA and Boehm titration of the acid sites.