Preparation and properties of sulfonated carbon-silica composites from sucrose dispersed on MCM-48

Sulfonated carbon-silica composites with surface areas of over 600 m²/g and pore sizes of 1.5-2.2 nm were prepared by incompletely carbonizing sucrose dispersed on MCM-48 and sulfonating the obtained carbon/MCM-48 composites. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, N₂ adsorption, energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy. The catalytic activities of these composites were studied in the esterification of acetic acid with n-butyl alcohol. The pore sizes and catalytic activities of the sulfonated carbon-silica composites were adjustable by changing the amount of sucrose loadings, and the composites exhibited enhanced hydrothermal stability and amphiphilic property. When the sucrose loading was close to the monolayer dispersion capacity of sucrose on MCM-48 (1.1 g sucrose/g MCM-48), the resulting sulfonated carbon-silica composites exhibited surface areas of 700-724 m²/g and n-butyl acetate yields of 90.4-98.7% in the esterification of acetic acid with n-butyl alcohol. They also showed obvious catalytic activities in the esterification of long-chain fatty acids with ethanol. The expensive MCM-48 could be easily recycled by simply calcining the sulfonated carbon-silica composites in air.