In situ NMR imaging studies of the drying kinetics of porous catalyst support pellets

The proton NMR imaging (microscopy) technique is employed to study the process of drying of alumina and titania porous catalyst support pellets impregnated with various liquids. Despite the short spin-spin relaxation times usually exhibited by liquids that permeate porous solids, the possibility to monitor their evaporation in real time by detecting one-dimensional liquid concentration profiles along the diameter of a cylindrical sample is demonstrated. Ln the qualitative discussion of the results, it is shown that the experiment is sensitive to the fine details of the drying process, such as the efficiency of liquid transport and peculiar profile shape transformations in the course of drying. A simple experiment is proposed that yields an empirical relation between the detected profile intensity and the actual liquid content, which allows one to correct the detected profiles for the inevitable T-2-weighting effects.