Activation of Mo and V oxides supported on ZSM-5 zeolite catalysts followed by in situ XAS and XRD and their uses in oxydehydration of glycerol

ACEVEDO, MAURO D.; PASSOS, ALINE R.; MARTINS, LEANDRO; PADRÓ, CRISTINA L.; PULCINELLI, SANDRA H.; POSSATO, LUIZ G.; BRIOIS, VALÉRIE; SANTILLI, CELSO V.

Molecular Catalysis

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Lugar: AMSTERDAM; Año: 2020 vol. 481

2468-8231

This paper describes the activation and catalytic performance of a Multifunctional catalyst consisting of mixed oxides of vanadium and molybdenum supported on an acidic ZSM-5 zeolite. The zeolite was wet-impregnatedwith an aqueous solution containing a mixture of NH⁠4VO⁠3 and (NH⁠4)⁠6Mo⁠7O⁠24 precursors at a V/(Mo+V) molar ratio of 0.6. Evolution of the phases during activation (by calcination under 20% O⁠2/He) was followed by synchrotron X-ray diffraction (XRD), but detection of mixed oxides of Mo⁠xV⁠yO⁠z was difficult, due to the high degree of dispersion on the zeolite surface. On the other hand, X-ray absorption spectroscopy (XAS) performed simultaneously at the Mo and V K-edges enabled confirmation of formation of the MoV⁠2O⁠8 phase on the acidic ZSM-5 zeolite. The combination of the MoV⁠2O⁠8 phase and the zeolite acid sites produced a highly active catalyst for gas phase glycerol dehydration-oxidation coupled reactions in which acrylic acid was the main product. Themultifunctional catalyst presented only 6% of deactivation during a period of 8h under glycerol stream, while the activities of the bulk mixed oxide and the pure ZSM-5 zeolite decreased by almost 20 and 31%, respectively.