Porosity and surface area of monolithic carbon aerogels prepared using alkaline carbonates and organic acids as polymerization catalysts

Abstract

Carbon aerogels were prepared by polymerization of a resorcinol–formaldehyde mixture using different polymerization catalysts such as: sodium or potassium carbonates, oxalic acid or para-toluenesulfonic acid. The carbon aerogel obtained with this last acid was further CO 2-activated to 8.5% and 22% burn-off. All samples were characterized by N 2 and CO 2 adsorption at −196 and 0 °C, respectively, and by mercury porosimetry, scanning electron microscopy, and thermogravimetric analysis. Samples prepared using Na 2CO 3 were denser than those prepared using K 2CO 3. In addition, the density of samples prepared under acidic conditions was greater than that of samples prepared using alkaline carbonates as catalysts. Most of the carbon aerogels prepared were mesoporous with narrow pore size distributions. Results obtained showed that the nature of the acid used in the preparation of these aerogels only affected the gelation process. Finally, it is noteworthy that CO 2 activation of the carbon aerogel prepared with para-toluenesulfonic acid as catalyst only increased and widened the microporosity and had virtually no effect on the mesoporosity.