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Abstract: The kind and percentage of point defects in commercial as well as laboratory prepared hemihydrate VPO precursors have been analysed using a combination of electron diffraction experiments and diffraction pattern simulation. Experimental patterns reveal the systematic existence of kinematically forbidden reflections that are attributed to vacant lattice sites in the VOHPO4·1/2H2O matrix. The vacancies are associated with vanadium ions and are distributed into the bulk and surface of hemihydrate in an ordered fashion. The amount of vacancies is in similar proportion between the two precursors studied. A considerable enhancement in the forbidden reflections intensity in doped hemihydrate samples has been experimentally observed, which is attributed to the partial substitution of dopant ions into V vacant sites. The beneficial effect of such a modified hemihydrate structure on the resulting VPO catalyst performance is demonstrated, since the facilitation of promoter incorporation in V-based vacant active sites brings upon an enhanced activity and selectivity for the catalyst. [Copyright &y& Elsevier]

A novel reactor configuration is proposed to study the kinetics of heterogeneous catalytic reactions. It is based on the bubbling fluidization regime; gas velocities are sufficiently low to minimize bypassing but high enough to ensure solids backmixing and a uniform temperature gradient. The reactor is equipped with a gas manifold designed to operate the reactor either under steady-state feed conditions or with cyclical feeds. By cycling VPO catalyst between a reducing environment with butane and an oxidizing environment, we quantify the lattice oxygen contribution to the reaction. Furthermore, we show that carbon can build up on the VPO surface and this phenomenon increases with an increase in the severity of the reducing environment. We propose a simple kinetic model involving three sites—V5+, V4+ and VC4. The model adequately characterizes the transient partial oxidation of butane but further research is required to create a generalized model that fits all reaction environments. [Copyright &y& Elsevier]

Prepared unique mesh-hole structure of VPO catalyst by POM-ILs anions-cations synergetic Interaction for promoting C H bond activation. • Design a single-component additive POM-ILs with dual-function to enhance the activity of VPO catalyst. • The synergistic interaction of anions and cations of POM-ILs was illuminated. • POM-ILs@VPO shows unique mesh-hole structure and forms more oxygen vacancies and crystal defects. • POM-ILs@VPO exhibits high activation ability of C–H bond. • Finely divide the poly-acids (α , β , γ -acid) sites to describe the acidic properties. Vanadyl pyrophosphate (VPO) catalyst exhibits a unique ability to activate C H bond and selectively oxidize n- butane to maleic anhydride (MA). Here, a novel "function-oriented design" strategy was proposed to design and develop single-component additive polyoxometalate-ionic liquids (POM-ILs) with dual-function to enhance the activity of VPO catalyst. And the synergistic interaction of anions and cations of POM-ILs was illuminated combined with characterizations. The IL-cations guide the growth of the catalyst precursor to ordered nanolamellar structure rather than three-dimensional disordered rose-like. Correspondingly, it makes the catalyst exhibit a unique mesh-hole structure and benefit exposure of the active surface (200) of (VO) 2 P 2 O 7. The POM-anions decompose into the defective O P Mo compound and cause more oxygen vacancies and crystal defects formed on the surface of VPO after activation. Besides, we established a specific method to divide the poly-acids (α , β , γ -acid) sites to describe the acidic properties on the surface of VPO by NH 3 -TPD in qualitatively and quantitatively and related with catalytic performance. [ABSTRACT FROM AUTHOR]