Investigations of the mechanism and kinetics of catalyzed reactions are most informative when all sites are virtually the same. However, the creation of an ensemble of identical sites in the field of heterogeneous catalysis is extremely difficult. The best opportunities are afforded by cations exchanged into zeolites, but even here there are issues of the locations of the charge exchange site or sites within the zeolite framework. This talk will illustrate this point by addressing the challenges of creating isolate cationic Ga sites in MFI. It will be shown that isolated Ga<sup>3+</sup> can be produced but only at relatively low Ga/Al ratios, and even then diversity of these sites arise because of the distribution of proximate charge-exchange sites that are the preferred locations for such cations. Characterization of the ligands associated with the Ga requires careful combination of experimental and theoretical methods. It will also be shown that despite great efforts not all of the isolate sites have equivalent activity for propane dehydrogenation, the differences in the site activity can be measured and the relationship of the observed activity to the local structure of the site can be interpreted with the aid an analysis of the reaction free energy.<br/>

The challenge of creating well-defined cation sites in zeolite: A study of propane dehydrogenation on Ga/H-MFI

256th National Meeting (2018)

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