Beneficial effect of steam on synthesis of hierarchically porous zeolite-templated carbons

Hierarchically meso-/microporous carbons were synthesized using nanocrystalline beta zeolite as a sacrificial template. The zeolite template possessed intercrystalline mesopores in addition to ordered micropores of the nanocrystals. Various amounts of steam were used with a carbon source, such as ethylene, propylene or acetonitrile, to generate a carbon structure inside the template. The synthesis results showed that adding a suitable amount of steam gave rise to faithful replication of the ordered microporous structure, while the intercrystalline mesopores were retained. That is, the carbon structure was formed selectively inside nanocrystalline zeolites rather than at the exterior by the steam addition. Microscopic observation and thermogravimetric analysis revealed that steam oxidized the carbon species deposited at the external surface of zeolite nanocrystals, and hence inhibited the undesirable carbon deposition. Furthermore, such a beneficial effect of steam could be applied for the carbon synthesis using other type zeolite templates.