Direct Formation of Phenolic/Furfural Aerogel Microspheres in Supercritical CO2 †

Abstract

P/F aerogel microspheres were successfully produced in one-step method by sol-emulsion-gel technique in supercritical CO2. The solubility of alcohol in supercritical CO2 varied with temperature and pressure of the system. When the dispersion phase is insoluble in supercritical CO2, it could be emulsified in CO2 by means of a CO2-soluble stabilizer with high temperature and low pressure, phase separation occurred and led to the formation of phenolic/furfural (P/F) gel microspheres. At the inversion of process condition, alcohol in the P/F gel microspheres was then exchanged with supercritical CO2 continuously, which was supercritically dried to obtain organic aerogel microspheres. CO2-soluble poly(-dimethylsiloxane) (PDMS) was used as the stabilizer in this system. Spherical morphology of the gel microspheres was confirmed by scanning electron microscopy. Particle size and particle size distribution of P/F aerogel microspheres can be modified upon variation of the solids and the stabilizer content. The resultant P/F aerogel microspheres have average particle size in the range of 1–6μm. The pore surface area of P/F aerogel microspheres can be modified upon variation of the solids content and phenolic/catalyst (P/C) weight ratio. † Part of this paper was presented at 74th Colloid and Surface Science Symposium, June 2000, Pennsylvania, U.S.A.