Synthesis and characterization of VPO catalysts

The procedures for synthesizing the catalysts have a marked effect on their activity. The active VPO catalyst phases are produced as follows. 

For high performance industrial catalysts capable of activating butane, organic media are used for the synthesis of VPO, which results in a large area of active (010) orientations. VPO catalysts synthesized in organic media are therefore used in the present chapter to elucidate dynamic butane catalysis by in situ ETEM. The other methods of preparation can be multi-phasic, which can result in the modification of the reactivity of the catalyst (Centi 1993, Kiely et al 1996). 

1 Precursor to active catalyst transformation VHPO to active VPO catalysts and dynamic electron diffraction 

Dynamic atomic-resolution ETEM and diffraction studies provide fundamental insights into the catalyst precursor transformation mechanism. The studies reveal that the temperature regimes are critical to the formation of active catalysts. They show that the nature of the VHPO - VPO transformation is topotac-tic. Topotaxy is defined as the conversion of a single crystal to a pseudomorph 

During the activation of VHPO, very small concentrations of minor VOPO4 phases are occasionally present and these minor amounts may be below the XRD detection limit. This has implications in understanding the redox couple active in the butane oxidation reaction. These aspects are discussed later. 

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