Study on effect of different calcination atmospheres on properties of acrylic acid catalysts
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 perfor-mance 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 Mo3VO11+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.
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