Reaction Engineering From Catalyst to Reactor

With respect to in situ spectroscopy, there is no attempt here to give a detailed overview of the ongoing activities in this field. The interested reader is directed to excellent articles describing applications of MR spectroscopy in catalysis that have been published elsewhere (Baba and Ono, 1999 Dybowski et al., 1991 Fraissard, 1999 Haw, 1999 Hunger and Weitkamp, 2001 Packer, 1996 Parker 2000 Roe et al., 1998 van der Klink, 2000). Instead, we focus on the nature of 

A review of this field has been given by Haw (1999). Reactions can be followed either in sealed glass ampoules or flow-through cells constructed within the spectrometer. The formation of intermediates can be studied in real time. An elegant example of this was shown in an early study of methanol to gasoline conversion over HZSM-5 zeolites. As a result of the shape selectivity of the catalyst, spectroscopic evidence of reaction intermediates, which were not seen as reaction products, was observed (Anderson and Klinowski, 1990). 

Most studies of molecular diffusion within catalysts have been performed on the as-prepared (i.e. powder form) of the catalyst and focus predominantly on zeolites and related catalytic materials. A recent review of this field has been given by Karger and Freude (2002). In situ studies of molecular diffusion during reaction include 13C-PFG-MR studies of diffusion and reaction of isopropanol 

Micro-imaging and Molecular Diffusion Studies of Formed Catalyst 

The majority of the early MR imaging studies specific to catalysis addressed the heterogeneity in structure and transport within catalyst pellets. In-plane spatial resolution was 30 pm, and the pellets themselves were typically 1-5 mm in size. In the majority of cases, studies have addressed the pure, usually oxide, support so that the quantitative nature of the data obtained is not sacrificed by the presence of metal, which can introduce an unknown extent of nuclear spin-relaxation time contrast into the images. 

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