Acid functionalized carbon–silica composite and its application for solketal production

Abstract

Various sulfonated carbon–silica-meso composite materials have been synthesized by adopting a novel concept of using glucose as a carbon source as well as precursor for the structure directing agent. The change in concentration of glucose in the initial gel mixture and the nature of treatment of the gel (thermal or hydrothermal methods) influenced the properties of the resultant composite material such as surface area, porosity and acidity. All the samples have been characterized by XRD, SEM, FT-IR, TPD, N2 adsorption–desorption, CHNS elemental analysis and were used for acetalization of glycerol reaction to produce 2,2-dimethyl-1,3-dioxolane-4-methanol, also known as solketal. Among the various catalysts, the highly acidic composite gave the higher glycerol conversion (82%) and solketal selectivity. The activity achieved with sulfonated carbon–silica-meso composite was observed to be comparable with the reported results of known sulfonated catalyst Amberlyst-15. Optimal production of solketal over sulfonated carbon–silica-meso composite has been established at 70°C reaction temperature after 30min reaction time under reflux and the catalyst exhibited comparable activity at least up to the studied number of four cycles.