Preparation of carbon aerogels from 5-methylresorcinol–formaldehyde gels

The systematics of the preparation of low density carbon aerogels from 5-methylresorcinol–formaldehyde (MR/F) organic aerogels dried in CO2 under supercritical conditions is reported. The synthesis of organic aerogels involves a doubly catalysed process: at first, in basic medium using a sodium carbonate catalyst and second, in acidic medium. The aquagels were obtained at room temperature within an hour. The carbonization of the organic aerogel to get a carbon aerogel was carried out at 973 K and 1273 K in the flow of dry nitrogen. Carbon aerogels with a density of 0.13 g/cm3 and specific surfaces of over 500 m2/g were obtained. The optimization of the ratio of the components was carried out in order to achieve minimum shrinkage of the organic aerogel after drying. Regarding to the pore size distribution, it was found that the porosity of obtained the materials obtained could be easily tailored by changing the synthesis conditions. Thus, the conditions for obtaining materials with a preferential micro- or mesoporous structure were determined.