Control of micropore formation in the carbonized ion exchange resin by utilizing pillar effect

A new method is presented for controlling the micropore structure of porous carbon by use of pillar effect of metal and/or sulfur compounds. An ion exchange resin having sulfonic acid groups as ion exchangeable functional groups was used as a raw material. Resins having various cations of H+, K+, Na+, Ca2+, Zn2+, Cu2+, Fe2+, Ni2+ and Fe3+ were prepared from the ion exchange resin. They were carbonized at 500-900 degrees C in a nitrogen stream to prepare porous carbons. The micropore distributions of all the resins carbonized at 500 degrees C were rather sharp and their average diameters varied in the range of 0.38 to 0.45 nm depending on the kind of cations exchanged. At the carbonization temperature of 900 degrees C, the carbonized resins prepared from the resins with di- or trivalent cations maintained sharp pore distributions, whereas those prepared from the resins with univalent cations lost most of the pores. The difference was brought about, because di- or trivalent cations can form ionic crosslinkings connecting two or three functional groups in the resins, but univalent cations cannot. The crosslinking functional groups and cations are converted to highly dispersed metal sulfides or elemental metals etc. during the carbonization, which would form a kind of pillar to maintain pores in the carbonized resins. The micropore distributions could be controlled by changing the kind of di- or trivalent cations. (C) 1999 Elsevier Science Ltd. All rights reserved.