Alteration of molecular sieving properties of microporous carbons by heat treatment and carbon gasification

Abstract

The effect of thermal treatment on the porosity of microporous carbons, of pore structure ranging between that of a carbon molecular sieve (CMS) and an activated carbon (AC), was investigated by adsorption and diffusion of O 2 and Ar. Sieving behavior was improved in the case of carbons containing molecular sieving pores. Selectivity for separation of O 2 and Ar was enhanced by heat treatment of a CMS at ~1100 K. No useful molecular sieving properties were developed by the thermal treatment of an AC. Pore opening by controlled carbon gasification was also demonstrated as a method to adjust the size of the sieving pores of carbons containing an appropriate pore structure. In some cases, the net effect of carbon gasification was shrinkage of pores in a particular size range, which introduced interesting possibilities for production of highly selective CMS.