DENSITY-FUNCTIONAL THEORY MODEL FOR CALCULATING PORE-SIZE DISTRIBUTIONS - PORE STRUCTURE OF NANOPOROUS CATALYSTS

Using the example of nanoporous catalysts, we discuss the non-local de nsity functional theory (NLDFT) model applied to physical adsorption o f nitrogen and argon. The model has been used for predicting adsorptio n/desorption isotherms in nanopores of different geometries over a wid e range of pore sizes (0.5-100 nm), and for calculating pore size dist ributions from adsorption isotherms based on given intermolecular flui d-fluid and fluid-solid potentials. The development of new nanoporous catalysts requires reliable characterization methods. We critically an alyze different methods which are currently used for pore structure ch aracterization in the range of nanometers. Calculations of the pore si ze distributions from nitrogen and argon adsorption isotherms are pres ented. Our primary method is based on the NLDFT model of adsorption on MCM-41, developed earlier. The results obtained with the NLDFT model are compared with other methods. It is shown, that the pore structure of nanoporous catalysts can be quite complex, and that Ar and N-2, iso therms contain complimentary information. The NLDFT model is recommend ed for evaluation of pore size distributions in nanoporous catalysts a nd other MCM-41 based materials. (C) 1998 Elsevier Science B.V. All ri ghts reserved.