A nuclear magnetic resonance microscopy study of mass transport in porous materials

The H-1 nuclear magnetic resonance (NMR) microimaging is employed to study the mass transport processes in porous materials, including individual cata lyst support pellets and beds comprised of porous grains. Drying and adsorp tion are investigated by detecting the temporal evolution of the one-dimens ional spatial profiles or two-dimensional maps of liquid content without in terrupting the process under study. The characteristic features of these pr ocesses, such as the main mechanisms and the limiting stages of mass transp ort, and some factors which can alter the efficiency of mass transport are considered. The problems associated with the relaxation weighting of the NM R signals, often unavoidable for liquids permeating mesoporous solids, and the possibilities to overcome these problems are discussed.