Probing the structure of porous pellets: an NMR study of drying

Partially saturated porous catalyst support pellets have been studied using NMR relaxation, PGSE, and imaging techniques. Spatially nonresolved PGSE data were acquired as a function of the fractional saturation of the pellets during drying. Combination of these data with an estimate of the width of the pore-size distribution, as determined by mercury porosimetry, and the results of numerical simulations of diffusion in a random pore network enabled predictions of the connectivity of the pore structure to be determined. NMR imaging was shown to be effective in discriminating between different models of drying; even when the bulk drying curves are similar, significantly different moisture redistribution phenomena are seen to occur.