Applied Catalysis A: General, Vol.269, No.1-2, 53-61, 2004
Synthesis of Mo/V mixed oxide catalysts via crystallisation and spray drying - a novel approach for controlled preparation of acrolein to acrylic acid catalysts
Technical catalysts for partial oxidation of acrolein to acrylic acid are based on MoN mixed oxides. Different preparation steps are characterised starting from solutions of ammonium-heptamolybdate and -metavanadate. These were dried, employing spray drying and crystallisation method followed by calcination. The materials formed at each preparation step were studied using X-ray powder diffraction, thermal decomposition, TG/DTA-MS and temperature programmed reduction (with H-2 and acrolein). X-ray diffraction revealed that the drying method affects structural composition of the binary Mo/V-oxides. Spray drying results preferably in a hexagonal MoO3-type phase, whereas crystallisation leads to V2O5-type structure. A correlation of the applied drying method and therefore of structural composition with catalytic performance is discussed by means of TPR investigation comparing the activation process of the two probe molecules H-2 and acrolein. Generally, spray dried samples are more active. The preparation variant via spray drying of precursor solution establishes a highly reproducible as well as promising basis for a specific focussing on the genesis of mostly metastable structure parts, which play a crucial role in heterogeneous catalysis. (C) 2004 Elsevier B.V. All rights reserved.