EFFECT OF DRYING METHOD ON MESOPOROSITY OF RESORCINOL–FORMALDEHYDE DRYGEL AND CARBON GEL

Abstract

Resorcinol–formaldehyde hydrogels were synthesized by sol–gel polycondensation of resorcinol with formaldehyde in a slightly basic aqueous solution. RF cryogels, RF xerogels, and RF xerogels (MW gels) were respectively prepared from RF hydrogels by freeze drying, hot air drying, and microwave drying. Carbon cryogels, carbon xerogels and carbon MW gels were subsequently obtained by pyrolyzing RF drygels in an inert atmosphere. Freeze drying and microwave drying were effective to prepare mesoporous RF drygels and carbon gels. RF cryogels and carbon cryogels showed high mesoporosity over wide ranges of the molar ratio of resorcinol to catalyst (R/C) and the ratio of resorcinol to water (R/W) used in sol–gel polycondensation. Although RF xerogels had a few mesopores, carbon xerogels had no mesopores. RF MW gels and carbon MW gels showed mesoporosity if appropriate values of R/C and R/W were selected.

Keywords:

• BET surface area
• Freeze drying
• Hot air drying
• Microwave drying
• Pore size distribution
• Pyrolysis
• Sol–gel polycondensation

ACKNOWLEDGMENTS

This research was partially supported by the Ministry of Education, Science, Sports and Culture of Japan, Grant-in Aid for Scientific Research on Priority Area (Carbon Alloys), No. 11124227 (1999), and by the Mazda Foundation's Research Grant (1998).