The selective oxidation of propane on Mo-V-Te-Nb-O catalysts: The influence of Te-precursor

Abstract Mo-V-Te-Nb-O catalysts have been prepared by hydrothermal synthesis and have been tested in the selective oxidation of propane to acrylic acid. The catalysts have been prepared by using different Te- and Mo-starting compounds. Both the catalyst characterization results (XRD, SEM–EDX, FTIR and XPS) and the catalytic tests show important differences depending on the Te- and Mo-starting compounds used in the hydrothermal synthesis. The most active and selective catalysts for the oxidation of propane to acrylic acid were those prepared from Te(VI)-compounds, i.e. telluric acid or an Anderson-type telluromolybdate. However, catalysts prepared from Te(IV)-compounds, i.e. TeO 2 or (NH 4 ) 4 TeMo 6 O 22 ·2H 2 O, presented both low activity and low selectivity to acrylic acid. In the best catalysts, several crystalline phases were observed: Mo 5 TeO 16 , (Mo 0.93 V 0.07 ) 5 O 14 , and/or Nb 0.09 Mo 0.91 O 2.80 and new Te-V-Nb-Mo-oxide crystalline phases. The presence of small crystals of MoO 3 in active and selective catalysts can also be proposed. The different catalytic performance of these catalysts could be related to the different incorporation of Te, V and Nb ions, which depends strongly on the Te-compound introduced in the synthesis gel.

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