Influence of cobalt on the textural, redox and catalytic properties of stoichiometric vanadium phosphate

B. K. Hodnett, B. Delmon

Research output: Contribution to journalArticlepeer-review

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 languageEnglish
Pages (from-to)245-259
Number of pages15
JournalApplied Catalysis
Volume6
Issue number2
DOIs
Publication statusPublished - 13 May 1983
Externally publishedYes

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