Probing the Transport of Paramagnetic Complexes inside Catalyst Bodies in a Quantitative Manner by Magnetic Resonance Imaging

摘要

Supported metal and metal oxide catalysts form an important class of functional materials, owing to their role in oil refining, the manufacturing of bulk and fine chemicals, and as automotive catalysts.[1] As the first step in the industrial preparation of supported catalysts, regardless of the nature of the active phase, a metal-precursor salt is usually applied to the mm-sized support bodies by pore-volume impregnation with a suitable precursor solution, after which drying, calcination, and in some cases reduction or sulfidation, is carried out to obtain the active catalyst. To maximize the metal loading in the final catalyst, metal salts with a high solubility, such as nitrates, are often used as the precursor in industrial impregnation solutions.[2] For example, the impregnation solutions used in copper-based methanol-synthesis catalysts, nickel-based hydrogenation catalysts, cobalt-based Fischer-Tropsch catalysts, and iron-based ammonia synthesis catalysts, contain paramagnetic Cu2+ (d9), Ni2+ (d8), Co2+ (d7), and Fe3+ (d5) ions, respectively.[1]