Tungstated zirconia is a robust solid acid catalyst for light alkane (C(4)-C(8)) isomerization. Several structural models for catalytically active sites have been proposed, but the topic remains controversial, partly because of the absence of direct structural imaging information on the various supported WO(x) species. High-angle annular dark-field imaging of WO(3)/ZrO(2) catalysts in an aberration-corrected analytical electron microscope allows, for the first time, direct imaging of the various species present. Comparison of the relative distribution of these WO(x) species in materials showing low and high catalytic activities has allowed the deduction of the likely identity of the catalytic active site--namely, subnanometre Zr-WO(x) clusters. This information has subsequently been used in the design of new catalysts, in which the activity of a poor catalyst has been increased by two orders of magnitude using a synthesis procedure that deliberately increases the number density of catalytically relevant active species.

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A series of supported 1-60% TiO(2)/SiO(2) catalysts were synthesized and subsequently used to anchor surface VO(x) redox and surface WO(x) acid sites. The supported TiO(x), VO(x), and WO(x) phases were physically characterized with TEM, in situ Raman and UV-vis spectroscopy, and chemically probed with in situ CH(3)OH-IR, CH(3)OH-TPSR and steady-state CH(3)OH dehydration. The CH(3)OH chemical probe studies revealed that the surface VO(x) sites are redox in nature and the surface WO(x) sites contain acidic character. The specific catalytic activity of surface redox (VO(4)) and acidic (WO(5)) sites coordinated to the titania nanoligands are extremely sensitive to the degree of electron delocalization of the titania nanoligands. With decreasing titania domain size, <10 nm, acidic activity increases and redox activity decreases due to their inverse electronic requirements. This is the first systematic study to demonstrate the ability of oxide nanoligands to tune the electronic structure and reactivity of surface metal oxide catalytic active sites.

Double‐supported metal oxide catalysts, in which an oxide support material with a high surface area is modified by the presence of a second metal oxide surface species added to control the distribution and activity of a third active oxide component, represent a significant challenge in terms of structural characterization. In this study the various components in a double‐supported WO3/TiO2/SiO2 catalyst system are effectively visualized by using complementary high‐angle annular dark field (HAADF) and bright field (BF) imaging within an aberration‐corrected scanning transmission electron microscope (STEM). Furthermore, if combined with chemical analysis by electron energy‐loss spectroscopy (EELS) and X‐ray energy‐dispersive spectroscopy (XEDS) within the same STEM instrument, it is possible to map out the relative spatial distribution of all the metal oxide components within the WO3/TiO2/SiO2 catalysts. By comparing the structures of a systematic set of WO3/TiO2/SiO2 samples that display high, intermediate and low activity for the methanol dehydration reaction, new insight is provided into the structure‐performance relationships that exist in this double supported catalyst system.