Complementary study of microporous adsorbents with DFT and LBET

Abstract

Results of pore structure analysis based on two essentially different interpretations of adsorption mechanisms and resultant mathematical models are discussed. The first model, exploiting the density functional theory (DFT), allows evaluating pore volume distribution with a presumed pore shape. The second, referred to as the LBET model, provides information on distribution of adsorbate clusters in micropores, which may be used to deduce the pore structure. To improve reliability of the structure evaluations, both models were fitted simultaneously to a set of adsorption isotherms of different probing adsorbates. Results of the analysis obtained, for two microporous carbons, by fitting their adsorption isotherms of Ar, N 2, and H 2 are discussed. Both DFT and LBET models gave relatively good fit to the experimental isotherms. The pore size distribution evaluated with the DFT model is qualitatively consistent with a picture of pore structure provided by the LBET description. The LBET approach yields less explicit information on the properties of pores, but it provides more detailed information about particular shapes of the isotherms.