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Abstract:
Metal-doped hexagonal tungsten oxide bronzes (h-WVOx and h-WNbOx) and metal-doped orthorhombic molybdenum oxide bronzes-M1 type (MoVOx, MoVTeOx and MoVTeNbOx) have been synthesized hydrothermally and heat-treated at 400, 550 or 600 °C in N2. The catalysts were characterized by several techniques and tested in the one-pot aerobic transformation of glycerol at 350 °C. From all of them, h-WNbOx resulted as the most selective to acrolein (80 % yield), whereas both h-WVOx and MoVTeNbOx were more effective to acrylic acid (with a yield lower than 25 %). Subsequently, a double-bed reactor comparative study was conducted, with h-WNbOx acting as the first catalytic bed. In this case, the yield to acrylic acid decreased as follows: MoVTeNbOx > MoVTeOx > MoVOx> h-WVOx. IR spectroscopy of acrolein adsorbed on these catalysts allows to explain the catalytic performance of these catalysts.