Structural characterization of high-performance catalysts for partial oxidation—the high-resolution and analytical electron microscopy approach

Abstract

A set of Mo, V, and W mixed-oxide samples with additives P and Cs showing high performance in selective partial oxidation of propene is studied by means of elemental mapping and crystal structure determination using scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and electron energy loss spectroscopy (EELS) as supplement to XRD measurements which are insufficient for phase determination. The set is divided into two subsets of samples denoted A and B, where subset A samples show the highest performance in selective partial oxidation of propene.These high-performance catalysts are all predominated by structures of the Mo 5 O 14 type in contrast to a negligible amount of the orthorhombic MoO 3 , which is known to favor total oxidation.

Active Sites for Propane Oxidation: Some Generic Considerations

“…This pentameric site is located within the motif of M1 as the bridge between two adjacent heptagonal channels. Figure 2 illustrates that in agreement with experimental derivations [42,49,53,71] the assumed active site does not only occur on the basal plane (001) but also on the stepped large prism faces of the oxide needles if we assume a low-energy process for creating a surface in the M1 structure. Figure 2a reminds us on the basal plane projection of the orthorhombic structure of M1.…”

“…Silica or alumina are thus no optimal supports for partial oxidation catalysts but molybdenum oxide (in the form of the M1 phase) or other reducible mixed oxides with a stable geometric structure [65][66][67][68][69][70][71][72] are suitable choices for reactions involving both C-H activation and oxygen transfer. The in situ analytical results described above and the concept of site isolation preclude, however, the view that a reactive dimer ''antenna site'' may be connected to the bulk of the M1 phase acting as collective electron storage unit.…”

Aiding the Self‐Assembly of Supramolecular Polyoxometalates under Hydrothermal Conditions To Give Precursors of Complex Functional Oxides

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The activation of small alkane molecules originating from natural gas or renewable resources will offer alternative pathways to functionalized hydrocarbons in a post-petroleum era. [3] The crystal structures of these oxides show common structural attributes. [3] The crystal structures of these oxides show common structural attributes.

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Aiding the Self‐Assembly of Supramolecular Polyoxometalates under Hydrothermal Conditions To Give Precursors of Complex Functional Oxides

“…The activation of small alkane molecules originating from natural gas or renewable resources will offer alternative pathways to functionalized hydrocarbons in a post‐petroleum era. Crystalline or nanocrystalline molybdenum–vanadium‐based multimetal oxides have been identified as versatile heterogeneous catalysts for selective oxidation of ethane,1 propane,2 and propene 3…”