Glycerol oxidehydration into acrolein and acrylic acid over W–V–Nb–O bronzes with hexagonal structure

This paper deals with an investigation of hexagonal W–Nb–O and W–V–Nb–O bronzes as catalysts for the one-pot oxidehydration of glycerol into acrylic acid. In a previous work, we reported that the best yield to acrylic acid obtained with the W–V–O bronze was 25%; in the current work, the incorporation of Nb in the tri-component bronze structure allowed us to obtain the best acrylic acid yield of 34%. The W–Nb–O bronze was an efficient acid catalyst for the dehydration of glycerol into acrolein – more selective than WO3 at temperatures lower than 300 °C –, whereas in the tri-component system the presence of V conferred to the catalyst the redox properties for the partial oxidation of acrolein into acrylic acid. The characterization of the catalysts confirmed the incorporation of Nb5+ in the hexagonal structure, and the generation of acid sites with enhanced strength compared to the bi-component W–V–O system. This also enhanced the stability of catalytic performance during short-term lifetime experiments.

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► W–V–Nb oxides with the hexagonal tungsten bronze structure were prepared hydrothermally.
► These systems possess both acid and redox features, for the oxidehydration of glycerol into acrylic acid.
► The best yield of 34% to acrylic acid was obtained with W–V–Nb–O bronze.
► The selectivity to acrolein and acrylic acid was greatly affected by the reaction conditions.