The simultaneous isomorphous substitution of Al(III) and P(V) ions, in an aluminophosphate framework, with redox active Co(III) and Ti(IV) metal ions, generates highly active single-site heterogeneous catalysts that exhibit considerable synergy, compared to their corresponding monometallic analogues, in the catalytic epoxidation of olefins.

Probing multifunctional acid centres in nanoporous architectures through in situ spectroscopy affords a strategy for predictive design of novel catalysts.

A combination of time-resolved synchrotron μ-X-ray diffraction computed tomography (μ-XRD-CT) and μ-pair distribution function computed tomography (μ-PDF-CT) has been applied for the study of an individual Co/γ-Al2O3 catalyst pellet during reduction and the early stages of the Fischer–Tropsch synthesis (FTS) reaction, revealing insight into the solid-state changes occurring from within such crystalline materials. Both sets of data were of sufficient quality so as to be able to follow the spatial dependency of Co speciation evolution from Co3O4 to CoO to face-centered cubic (fcc) Co metal nanoparticles. These data revealed the samples to be highly heterogeneous and contain two types of Co species: small (≤6.5 nm) nanoparticles that interact strongly with the γ-Al2O3 support which are difficult to reduce (remaining as CoO) and nanoparticles that agglomerate and have little interaction or else are weakly interacting with the support but readily reduce in H2. The Co phase evolution under FTS conditions shows a strong dependence on the Co nanoparticle location; the complementarity between the observations made using μ-XRD-CT vs μ-PDF-CT allowed us to conclude that at the sample periphery a significant amount of agglomerated, weakly interacting with the support, small fcc Co metal nanoparticles (≤7.5 nm) oxidize to CoO/Co3O4 during FTS, most likely due to the presence of water vapor produced during the reaction. Catalytic tests demonstrated that this oxidation coincided with a decrease in CH4 selectivity and increased water-gas shift (WGS) activity. This oxidation of fcc Co nanoparticles (i.e., the removal of the contribution to the XRD signal) also explains the observation of sintering previously reported for such catalysts in the early stages of the FTS reaction.

Abstract[VOF3(MeCN)], obtained by dissolving VOF3 in dry acetonitrile, is a useful synthon for the preparation of complexes of the oxide‐fluoride, and the reaction with 2,2′‐bipyridyl, 1,10‐phenanthroline, Me2N(CH2)2NMe2 and Ph2P(O)CH2P(O)Ph2 (L–L), or Ph3PO, Me3PO, Ph3AsO, pyridine and pyridine N‐oxide (L), produces the complexes [VOF3(L–L)] or [VOF3(L)2] respectively. These were characterised by microanalysis, IR, UV/Vis and multinuclear NMR [51V, 19F{1H}, 31P{1H}, 1H] spectroscopy, the data showing them to besix‐coordinate with trans F–V–F units and the neutralligands trans to O and F, respectively. X‐ray crystal structures of [VOF3(1,10‐phenanthroline)], [VOF3(Ph3PO)2] and [VOF3(pyNO)2] confirm the geometry, although the first two exhibit O/F disorder trans to the neutral ligand. Unstable complexes with ether and thioether ligands including [VOF3{MeO(CH2)2OMe}], [VOF3{MeS(CH2)2SMe}] and [VOF3(15‐crown‐5)] are also described; these decompose rapidly even in the solid state, with fluorination of the ligands. The [VOF3(Ph3AsO)2] also decomposes in solutionto a mixture of products including Ph3AsF2 and [V6O12F4(Ph3AsO)2(Ph2AsO2)2] identified crystallographically. Comparisons with complexes of VOCl3 are also described.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)