Evaluation of mercury porosimeter experiments using a network pore structure model

Abstract

A square network model has been developed to interpret mercury penetration and retraction behaviour in the widely employed mercury porosimetry technique for investigating pore structure and pore size distribution. A network of arbitrary size is constructed by assembling cylindrical pore segments of equal length and pseudo-random number generation is used to assign pore diameters according to any stipulated size distribution function. Application of the simple Washburn equation then predicts movement of mercury into the network under increasing pressure (penetration) and the corresponding withdrawal under reducing pressure (retraction) The network model is superior to the classical parallel bundle model, since it implicitly produces hysteresis between penetration and retraction, predicts that mercury entrapment on retraction is a result of interconnectedness of pore segments and provides a better estimate of the intrinsic distribution of segment sizes. Comparison with porosimeter experiments on a commercial hydrodesulphurisation catalyst show that the approach can be applied to practical measurements and the model may provide an improved basis for the study of diffusion, reaction and deactivation in catalyst pellets.