Drying of resorcinol-formaldehyde gels with CO2 medium

Erik Geissler (1) , Orsolya Czakkel (2) , Edit Székely (3) , Béla Koczka (4) , Krisztina Laszlo (5)

1 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]
2 ESRF - European Synchrotron Radiation Facility
3 Department of Chemical and Environmental Process Engineering
4 Department of Inorganic and Analytical Chemistry
5 Department of Physical Chemistry and Materials Science

The effect of using real supercritical conditions in the CO2 drying process on the structure and texture of resorcinol-formaldehyde networks is investigated by low temperature nitrogen adsorption, scanning electron microscopy and by small and wide angle X-ray scattering. If supercritical conditions are maintained throughout the whole extraction process the resulting networks exhibit much more developed porosity. The surface area of the supercritically dried gel, in excess of 500 m2/g, is more than twice that of the sample dried with liquid CO2. Pore volumes are also significantly higher in all pore classes. In the supercritical region the applied pressure strongly affects the porosity, while the effect of temperature is limited. Drying time also influences the total pore volume of the samples, but not the mesopore and micropore volumes. The volume filling character of the molecular adsorption process in this system is illustrated by the difference in surface areas measured by small angle X-ray scattering and that by nitrogen adsorption.

Mots clés: supercritical drying; rf gels; porosity; structure

Domaines: Chimie-Physique [physics.chem-ph]

Erik Geissler, Orsolya Czakkel, Edit Székely, Béla Koczka, Krisztina Laszlo. Drying of resorcinol-formaldehyde gels with CO2 medium. Microporous and Mesoporous Materials, 2012, 148, pp.34-42. ⟨10.1016/j.micromeso.2011.07.008⟩. ⟨hal-00634657⟩