The microstructural and chemical characterization of catalysts is not only integral to their initial development but also to understanding and controlling their behavior over time. To better elucidate the morphology of these materials and relate physical properties to catalytic properties (e.g., activity, selectivity, etc.), “ex-situ” methods for studying catalysts under reactive conditions have been developed.

Because conventional transmission electron microscopy (CTEM) is conducted under high vacuum conditions, it is difficult to replicate the exact chemical environment of a catalyst (e.g., high pressure, variable gas mixtures, etc) within the TEM. Consequently, most analyses focus on comparing “fresh” and “spent” materials. In general, this methodology provides useful structural information albeit with limitations associated with the comparison of dissimilar regions and the effects of sampling inhomogenieties.