Pore structure and swelling character of porous carbon beads prepared from esterified silica gels

Porous carbon beads have been prepared by a replica method using five silica gels with surface areas ranging from 70 to 765 m(2) g(-1). The replica method consists of esterification of silica gel with 4-phenyl-1,2-dihyroxybenzene, pyrolysis of the esterified silica gel, dissolution of the silica gel, and drying of the porous carbon from water or, in some cases, from benzene. Porous carbon beads, at maximum, shrank to about 33% of the size of silica gel beads used as a substrate during drying in the preparation. The extent of shrinkage was increased with decreasing surface area of the silica gels. The porous carbons prepared from different silica gels showed a similar pore size distribution, although the distribution became somewhat broader when a silica gel with a small surface area was used. The percentage of expansion of porous carbon beads on adsorbing benzene varied to some extent with the kind of silica gel, and the porous carbon prepared from the silica gel with the surface area of 470 m(2) g(-1) showed a maximum expansion, 31%. Porous carbon beads dried from benzene showed about 10% higher percentages of expansion on average compared with that from water. Furthermore, in the carbon beads from benzene, a small number of carbon beads showed enormously large expansion, and the expansion was found to be related to the extent of shrinkage during drying in the preparation. (C) 1999 Kluwer Academic Publishers.