A Comparative Study of Supercritical Petroleum Ether and Carbon Dioxide Drying in the Preparation of Carbon Aerogels

Organic and carbon aerogels were synthesized from sol-gel polymerization of phenolic resole and methylolated melamine followed by supercritical drying and pyrolysis. Supercritical petroleum ether (30℃-60℃) drying (SPD) and supercritical carbon dioxide drying (SCD) were employed and compared for the preparation of organic and carbon aerogels. It was found that SPD, which was carried out at 240℃ and 6.0MPa for 1h, produced organic aerogels with lower BET surface areas and mesopore volumes than SCD, which was carried out at 60℃ and 10.0MPa for 7d. However, the porous structure of SPD organic aerogels is more stable during pyrolysis than that of SCD organic aerogels, and as a result, BET surface areas and mesopore volumes of SPD carbon aerogels are all larger than those of SCD carbon aerogels, indicating that SPD, whose drying process is substantially shorter than with SCD, can be used as an alternative method for the preparation of carbon aerogels.