The Kinetic Significance of V5 in n-Butane Oxidation Catalyzed by Vanadium Phosphates
Maleic anhydride, a precursor to polyester resins, is made by oxidation of n-butane over vanadium phosphate catalysts. This system is of general interest because it is the only heterogeneously catalyzed, alkane-selective oxidation reaction in commercial use. Time-resolved in situ x-ray absorption spectroscopy shows that when either alphaI-VOPO4/SiO2 or (VO)2P2O7/SiO2 catalysts are exposed to n-butane, the rate of maleic anhydride formation is proportional to the rate of decay of V5+ species in the catalyst. Thus V5+ species are kinetically significant for the production of maleic anhydride and not just for the production of by-products. The results also suggest that V5+ species may play a role in the initial hydrogen abstraction from n-butane, the rate-determining step in the reaction sequence. V4+ sites appear to be responsible for by-product formation.
Coulston
GW
G. W. Coulston, R. Harlow, N. Herron, DuPont Company, Wilmington, DE 19880-0262, USA. S. R. Bare, Dow Chemical Company, Midland, MI 48674, USA. H. Kung, K. Birkeland, G. K. Bethke, Ipatieff Laboratory, Northwestern University, Evanston, IL 60208-3000, USA. P. L. Lee, Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
Bare
SR
Kung
H
Birkeland
K
Bethke
GK
Harlow
R
Herron
N
Lee
PL