Magnetic resonance imaging as an emerging tool for studying the preparation of supported catalysts

Abstract

Several magnetic resonance imaging (MRI) approaches are presented that can be used to study transport processes when supported catalysts are prepared by impregnating mm-sized porous support bodies. Both diamagnetic and paramagnetic components of an impregnation solution such as the solvent, the metal-containing precursors of an active component, and various organic and inorganic additives can be visualized with MRI. Their spatial distributions within a catalyst support body and the evolution of these distributions in time can be characterized not only qualitatively but also quantitatively, if calibration procedures are used to convert the images into corresponding concentration profiles. In particular, the physicochemical interactions between γ-Al2O3 support bodies and the aqueous solutions containing Cu, Co, Mo, citrate and phosphate ions are investigated upon pore volume impregnation as a function of concentration and solution pH. Furthermore, it is shown that multinuclear and solid state MRI can be used to map the solid phase distribution of the active component precursors and additives within the impregnated support bodies after their drying. Based on the case studies discussed, it can be concluded that MRI is an emerging versatile tool for studying the transport processes in support bodies upon their impregnation and the distribution of the key components after drying of the impregnated bodies.