ANALYSIS OF SORPTION HYSTERESIS IN MESOPOROUS SOLIDS USING A PORE NETWORK MODEL

We consider sorption hysteresis in mesoporous solids using a network model of the pore space. In this model, adsorption is an equilibrium process (described by a variant of the Kelvin equation) and both primary and secondary desorption are percolation processes. Hysteresis is thus a consequence of the interconnectivity of the pore network. Extensive Monte Carlo simulations of primary and secondary desorption have been carried out on a three-dimensional simple cubic lattice. The simulation results are used to interpret experimental measurements of the adsorption and desorption of nitrogen on a sample of alumina. The pore size distribution is calculated from the adsorption isotherm, while the mean coordination number and the size of the pore network are estimated from an analysis of the primary desorption isotherm. The simulation results are then used to predict (with no adjustable parameters) the secondary desorption isotherms. Agreement with experimental data is generally good, and the deviations between theory and experiment are consistent with the existence of a single-pore contribution to the observed hysteresis. © 1993 Academic Press, Inc.