Heterogeneously catalysed partial oxidation of acrolein to acrylic acid—structure, function and dynamics of the V–Mo–W mixed oxides

Philip Kampe; Lars Giebeler; Dominik Samuelis; Jan Kunert; Alfons Drochner; Frank Haaß; Andreas H. Adams; Joerg Ott; Silvia Endres; Guido Schimanke; Thorsten Buhrmester; Manfred Martin; Hartmut Fuess; Herbert Vogel

doi:10.1039/B700098G

Heterogeneously catalysed partial oxidation of acrolein to acrylic acid—structure, function and dynamics of the V–Mo–W mixed oxides†

Philip Kampe,^a Lars Giebeler,^b Dominik Samuelis,^c Jan Kunert,^a Alfons Drochner,^a Frank Haaß,^bc Andreas H. Adams,^b Joerg Ott,^a Silvia Endres,^a Guido Schimanke,^c Thorsten Buhrmester,^b Manfred Martin,*^c Hartmut Fuess*^b and Herbert Vogel*^a

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* Corresponding authors

^a Darmstadt University of Technology, Faculty of Chemistry, Technical Chemistry, Petersenstr. 20, Darmstadt, Germany
E-mail: vogel@ct.chemie.tu-darmstadt.de
Fax: +49 6151 163465
Tel: +49 6151 162165

^b Darmstadt University of Technology, Institute for Materials Science Structure Research, Petersenstr. 23, Darmstadt, Germany
E-mail: hfuess@tu-darmstadt.de
Fax: +49 6151 166023
Tel: +49 6151 164373

^c RWTH Aachen University, Institute of Physical Chemistry, Landoltweg 2, Aachen, Germany
E-mail: martin@pc.rwth-aachen.de
Fax: +49 241 80992128
Tel: +49 241 8094712

Abstract

The major objective of this research project was to reach a microscopic understanding of the structure, function and dynamics of V–Mo–(W) mixed oxides for the partial oxidation of acrolein to acrylic acid. Different model catalysts (from binary and ternary vanadium molybdenum oxides up to quaternary oxides with additional tungsten) were prepared via a solid state preparation route and hydrochemical preparation of precursors by spray-drying or crystallisation with subsequent calcination. The phase composition was investigated ex situ by XRD and HR-TEM. Solid state prepared samples are characterised by crystalline phases associated to suitable phase diagrams. Samples prepared from crystallised and spray-dried precursors show crystalline phases which are not part of the phase diagram. Amorphous or nanocrystalline structures are only found in tungsten doped samples. The kinetics of the partial oxidation as well as the catalysts’ structure have been studied in situ by XAS, XRD, temperature programmed reaction and reduction as well as by a transient isotopic tracing technique (SSITKA). The reduction and re-oxidation kinetics of the bulk phase have been evaluated by XAS. A direct influence not only of the catalysts’ composition but also of the preparation route is shown. Altogether correlations are drawn between structure, oxygen dynamics and the catalytic performance in terms of activity, selectivity and long-term stability. A model for the solid state behaviour under reaction conditions has been developed. Furthermore, isotope exchange experiments provided a closer image of the mechanism of the selective acrolein oxidation. Based on the in situ characterisation in combination with micro kinetic modelling a detailed reaction model which describes the oxygen exchange and the processes at the catalyst more precisely is discussed.

Physical Chemistry Chemical Physics

Heterogeneously catalysed partial oxidation of acrolein to acrylic acid—structure, function and dynamics of the V–Mo–W mixed oxides†

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Heterogeneously catalysed partial oxidation of acrolein to acrylic acid—structure, function and dynamics of the V–Mo–W mixed oxides

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