Direct measurement of transient concentration profiles in adsorbent particles and chromatographic columns by MRI

Magnetic resonance imaging (MRI) was applied as an in situ imaging technique to study transient adsorption/desorption and chromatographic processes in microporous adsorbents. Transient concentration profiles were measured for several different types of systems: the diffusion of water vapor into a bed of 4A zeolite, the movement of pulses of light hydrocarbons through a chromatographic column of 5A or 13X zeolite, and the transient adsorption/desorption of propane or water vapor in a single extrudate of 13X zeolite. The profiles are approximately as predicted from nonlinear diffusion theory and the effect of isotherm nonlinearity on the form of the transient profiles is clearly apparent. The possibility of distinguishing between the concentration profiles in the gaseous and adsorbed phases by MRI methods is also examined.