这是早期比较原始的那篇关于HK吸附模型,里面给出了一下比较原始的解释。相关人员可以研究一下

Adsorption,1, 18%196(1995) 1995KluwerAcademicPublishers,Boston.Manufacturedin The Netherlands.

Predicting Isotherms in Micropores for Different Molecules and Temperatures from a Known Isotherm by Improved Horvath-Kawazoe Equations LINDA S. CHENG AND RALPH T. YANG* Department of Chemical Engineering, State University of New York at Buffalo, Buffalo, NY 14260

Abstract. Our improved Horvath-Kawazoe (H-K) equations (by considering the isotherm nonlinearity) for three pore geometries are first summarized. These equations apply to adsorption in microporous materials at subcritical temperatures. From a known isotherm at a given temperature, these equations are used to predict isotherms of the same adsorbate molecules at other temperatures, and also to predict isotherms for other adsorbate molecules at the same (or any subcritical) temperature. A reasonable agreement is obtained between predictions and experimental data. Since the H-K formulation only involves dispersion forces, it underpredicts for gas-solid systems in which other forces also exist. The N2-zeolite system is one of these systems. Keywords: Introduction Study of equilibrium adsorption in microporous solids, such as carbons, zeolites and pillared clays, is of both fundamental and practical importance. Monte Carlo simulations have been conducted for adsorption in zeolites under supercritical conditions (Soto et al., 1981; Woods and Rowlinson, 1989; Razmus and Hall, 1991). Nitrogen and/or argon adsorption isotherms at subcritical temperatures have been routinely applied to studies of the surface and pore structures of sorbents (Gregg and Sing, 1982). Starting from ultramicropores, adsorption progresses by pore filling as the pressure is increased. For mesopores (20-500 A), the Kelvin equation, which considers capillary condensation, is applicable for calculating the corresponding pore sizes. On the other hand, for ultramicropores where pore sizes approach a few molecular dimensions, the potential energy fields from neighboring surfaces overlap and the total interaction energy with the adsorbate molecules is substantially enhanced. Here, Kelvin equation is no longer valid. A theoretical framework combining the microscopic and macroscopic formulation was developed by Horvath and Kawazoe (1983) (H-K) for calculating micropore size distribution of carbon molecular sieve from nitrogen isotherm at the liquid nitrogen temperature. Although simple, it catches the essential feature of progressive pore tilling. The H-K model provides a one-to-one correspondence between the pore sizes micropore size distribution, Horvath-Kawazoe equation, isotherms from pore size distribution and the relative pressure at which the pore is filled. It has since been widely applied for micropore size distribution analysis of zeolites (e.g., Venero and Chiou, 1988; Davis etal., 1989; Beck et al., 1992). Extension of the slit-pore H-K model to cylindrical and spherical pores models has been made (Saito and Foley, 1991; B

aksh and Yang, 1991; Cheng and Yang, 1994) considering the curvature effects of pore walls. Recently, Kaminsky etal. (1994) made an assessment of the mean-field methods approach used in H-K model. Improvement of the H-K formulation has also been made by taking into consideration of the nonlinearity of the adsorption isotherm (Cheng and Yang, 1994), resulting in significant improvements while still preserving the simplicity of the calculation. The experimental measurements of isotherms on microporous sorbents at subcritical temperatures are difficult due to slow diffusion and very low relative pressures needed (e.g., 10-7 tO 10-4). The goal of this work is to explore the possibility of applying our improved H-K formulations to derive isotherms at other temperatures and also of other molecules at subcritical temperatures.

Theoretical

(1) Improved Horvath-Kawazoe Equations for Three Pore Geometries Details of the derivation are available elsewhere (Cheng and Yang, 1994). The following is a brief summary.

*Addressco~Tespondence R.T.Yang. to