Abstract
The influence of coprecipitated cobalt on the catalytic, redox and textural properties of βVPO5 is reported. Four catalysts were prepared in which the Co/V ratio was varied between 0 and 0.05 and the P/V ratio was held at unity. Cobalt strongly reduced the surface area of βVPO5 and diminished reactivity toward hydrogen was observed as a monotonous feature as the cobalt content increased. By contrast this material showed complex kinetic behaviour during reoxidation from reduced states. When reoxidation was confined to surface layers a maximum in rate was observed for Co/V ratios of ca. 0.02. Bulk reoxidation was strongly sensitive to small amounts of cobalt but it was independent of cobalt content above Co/V = 0.01. Results of catalytic testing for n-butane partial oxidation to maleic anhydride indicate that conversion was at a maximum for the undoped material but selectivity showed an optimum value for Co/V of ca. 0.02. Above this value a sharp drop in selectivity was observed. A strong increase in areal reoxidisability was observed for Co/V above 0.02. X.P.S. data indicated that some surface segregation of cobalt had occured for Co/V = 0.05. Two domains of influence by cobalt on the catalytic activity of βVPO5 were identified; one in which it influenced the solid state properties and increased selectivity, the other in which a surface enrichment in cobalt provoked total oxidation of n-butane.
Original language | English |
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Pages (from-to) | 245-259 |
Number of pages | 15 |
Journal | Applied Catalysis |
Volume | 6 |
Issue number | 2 |
DOIs | |
Publication status | Published - 13 May 1983 |
Externally published | Yes |