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Science 10 January 1997:
Vol. 275. no. 5297, pp. 191 - 193
DOI: 10.1126/science.275.5297.191
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Reports

The Kinetic Significance of V5+ in n-Butane Oxidation Catalyzed by Vanadium Phosphates

George W. Coulston, * Simon R. Bare, Harold Kung, Kari Birkeland, dagger Gregory K. Bethke, Richard Harlow, Norman Herron, Peter L. Lee

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 alpha I-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.

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.
*   To whom correspondence should be addressed.

dagger    Present address, Dow Chemical Company, Midland, MI 48674, USA.

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