Nb-doped vanadium phosphorus oxide
catalysts were prepared and
characterized using a variety of methods, including XRD, FT-IR, XPS,
TPD and BET. The catalysts were examined for their ability to promote
the aldol condensation of acetic acid with formaldehyde to acrylic
acid. Catalyst composition and the conditions used to prepare the
catalysts were investigated for their effects on catalytic activity.
The addition of Nb changes the properties and catalytic properties
of the catalyst to some extent, especially the surface acidity of
catalyst and the average valence of surface V atoms, which have the
greatest influence on the catalyst. When Nb/V = 0.06, the catalyst
surface has the greatest acidity, the valence of surface V atoms is
the lowest, and the selectivity (83.4%) and yield of acrylic acid
(18.1%) are maximized.