Recovery of Homogeneous Polyoxometallate Catalysts from Aqueous and Organic Media by a Mesoporous Ceramic Membrane without Loss of Catalytic Activity

Authors

  • Sankhanilay Roy Chowdhury Dr.,

    1. University of Twente, MESA+ Institute for Nanotechnology, P.O. Box 217, 7500 AE Enschede, The Netherlands, Fax: (+31) 53-489-4683
    2. Current address: Ecole Nationale Supérieure de Chimie Mulhouse, 3, rue Alfred Werner, 68093 Mulhouse Cedex, France
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  • Peter T. Witte Dr.,

    1. DSM Pharma Chemicals, Advanced Synthesis, Catalysis, and Development, P.O. Box 18, 6160 MD Geleen, The Netherlands, Fax: (+31) 46-476-7604
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  • Dave H. A. Blank Prof.,

    1. University of Twente, MESA+ Institute for Nanotechnology, P.O. Box 217, 7500 AE Enschede, The Netherlands, Fax: (+31) 53-489-4683
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  • Paul L. Alsters Dr.,

    1. DSM Pharma Chemicals, Advanced Synthesis, Catalysis, and Development, P.O. Box 18, 6160 MD Geleen, The Netherlands, Fax: (+31) 46-476-7604
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  • Johan E. ten Elshof Dr.

    1. University of Twente, MESA+ Institute for Nanotechnology, P.O. Box 217, 7500 AE Enschede, The Netherlands, Fax: (+31) 53-489-4683
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Abstract

The recovery of homogeneous polyoxometallate (POM) oxidation catalysts from aqueous and non-aqueous media by a nanofiltration process using mesoporous γ-alumina membranes is reported. The recovery of Q12[WZn3(ZnW9O34)2] (Q=[MeN(n-C8H17)3]+) from toluene-based media was quantitative within experimental error, while up to 97 % of Na12[WZn3(ZnW9O34)2] could be recovered from water. The toluene-soluble POM catalyst was used repeatedly in the conversion of cyclooctene to cyclooctene oxide and separated from the product mixture after each reaction. The catalytic activity increased steadily with the number of times that the catalyst had been recycled, which was attributed to partial removal of the excess QCl that is known to have a negative influence on the catalytic activity. Differences in the permeability of the membrane for different liquid media can be attributed to viscosity differences and/or capillary condensation effects. The influence of membrane pore radius on permeability and recovery is discussed.

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