Catalysts and Catalytic Processes Studied by MRI

Abstract

MRI can provide all sorts of useful information about the internal properties of heterogeneous catalysts and catalytic reactors and various processes within them. The morphology of porous solids, heat and mass transport processes, chemical composition, conversion, etc. can be visualized and quantified with MRI noninvasively and with spatial resolution. Most studies are performed under nonreactive conditions and address the morphology of various porous materials including individual catalyst and support bodies and packed catalyst beds, and micro- and macroscopic fluid transport in porous materials, and model reactors. Examples include the preparation and characterization of catalysts and catalyst supports, deactivation and regeneration of catalysts, single- and two-phase flow, filtration of fluids in porous media, and transport of granular solids. However, some features such as catalytic conversion and selectivity, heat transport, etc. have to be studied under reactive conditions, and examples of such applications do exist. They include spectroscopy, thermometry, and imaging studies of catalysts and model catalytic reactors performed during the actual heterogeneous catalytic processes. Homogeneous autocatalytic reactions that exhibit spatial patterns of concentration or temperature can be also addressed with MRI. Finally, catalytic hydrogenation with parahydrogen is a promising route towards a significant enhancement of sensitivity in magnetic resonance. Keywords: heterogeneous catalysis; catalysts and catalyst supports; packed catalyst bed; porous materials; mass and heat transport; flow and filtration; spatially resolved NMR spectroscopy; spatially resolved NMR thermometry; hyperpolarization; MRI