The NMR microimaging studies of the interplay of mass transport and chemical reaction in porous media

Abstract

PFG NMR is employed to perform a comparative study of the filtration of water and propane through model porous media. It is shown that the dispersion coefficients for water are dominated by the holdup effects even in a bed of nonporous glass beads. It is demonstrated that correlation experiments such as VEXSY are applicable to gas flow despite the large diffusivity values of gases. The PFG NMR technique is applied to study the gravity driven flow of liquid-containing fine solid particles through a porous bed. The NMR imaging technique is employed to visualize the propagation of autocatalytic waves for the Belousov-Zhabotinsky reaction which is carried out in a model porous medium. It is demonstrated that the wave propagation velocity decreases as the wave crosses the boundary between the bulk liquid and the flooded bead pack. The images detected during the catalytic hydrogenation of α-methylstyrene on a single catalyst pellet at elevated temperatures have revealed that the reaction and the accompanying phase transition alter the distribution of the liquid phase within the pellet.