Abstract:

The composite oxide precursors containing Mo-V were prepared by solution method，and the precursors after spray drying were calcined under different atmospheres（5%H₂+95%N₂，N₂，5%O₂+95%N₂，air and O₂） to obtain Mo-V-W-Sb series composite metal oxide catalysts.And they were applied to the vapor phase oxidation of acrolein to acrylic acid.The catalysts were characterized by inductively coupled plasma-optical emission spectrometer（ICP-OES），X-ray fluorescence spectrometer（XRF），X-ray diffractometer（XRD），nitrogen physical adsorption analyzer，transmission electron microscope（TEM），temperature program reduction（H₂-TPR） and potentiometric titrator.The experimental results indicated that the calcination atmosphere had a significant impact on the crystal structure，physicochemical properties，and catalytic performance of the Mo-V-W-Sb series catalysts.When the precursor was thermotreated in a weakly oxidizing atmosphere（5%O₂+95%N₂），it was beneficial to prepare a catalyst with pure Mo₃VO_11+x active phase，relatively larger specific surface area（6.8 m²/g），moderate crystallinity and reduction temperature（about 415 ℃），and the most suitable n（V⁵⁺）/［n（V³⁺）+n（V⁴⁺）+ n（V⁵⁺）］=0.019.Furthermore，this catalyst exhibited the best reaction performance in the oxidation of acrolein to acrylic acid，with a conversion rate of 99.5% acrolein and a yield of 88.7% acrylic acid.

Key words: composite oxides, vapor phase oxidation, acrylic acid, catalytic performance