Amphiphilic acid carbon catalysts produced by bio-oil sulfonation for solvent-free glycerol ketalization

Herein, an efficient amphiphilic carbon catalyst produced by the reaction of bio-oil with sulfuric acid was used for the first time for the solvent-free glycerol ketalization with 2-propanone for solketal production (2,2-dimethyl-1,3-dioxolane-4-methanol) at room temperature. The catalyst synthesis, described previously, led to an amphiphilic carbon due to hydrophobic nanostructures, e.g. graphene, nanotube, nano-onions, nanographite, embedded in an amorphous carbon containing high concentration of hydrophilic oxygen and sulfonic surface groups with strong acid sites (ca. 0.3 mmol g−1). The amphiphilic catalyst promoted the formation of an emulsion from the two immiscible phases, glycerol and 2-propanone, which had a strong effect on the reaction interface and solketal yield. Glycerol ketalization at 25 °C and solvent-free showed conversions higher than 90%, using 0.6 wt% catalyst, 1:10 glycerol:2-propanone after 2 h. The catalyst can be recovered and reused four times without any significant activity loss.