Surface Characterization and Reactivity in Ammoxidation Reactions of Vanadium Antimonate Catalysts

Research output: Contribution to journalArticle

Abstract

Unsupported vanadium antimonate catalysts with Sb/V ratios of 1 and 5 and samples with the latter ratio supported on alumina were studied in toluene and propane ammoxidation to benzonitrile and acrylonitrile, respectively, and were characterized by X-ray photoelectron spectroscopy (XPS) analysis before and after catalytic tests. Activity data for toluene ammoxidation suggest that excess antimony with respect to the stoichiometric amount required for forming the VSbO4 rutile phase affects the dispersion of the latter phase giving smaller particles. Vanadium sites are involved both in the activation of toluene and in the insertion of nitrogen in this reaction, whereas antimony does not play a specific role in the reaction mechanism. In propane ammoxidation, on the other hand, due to a higher reaction temperature with respect to toluene (500°C vs. 370°C), free vanadia on the surface of the catalyst has a negative influence on the selectivity because it promotes the conversion of ammonia to nitrogen, decreasing the surface nitrogenous species required for the selective formation of acrylonitrile. Excess antimony is thus necessary for completing the reaction between antimony and vanadium oxides, but antimony also participates in the reaction mechanism. In propane ammoxidation, in fact, XPS data show that both vanadium and antimony sites are reduced. Tentatively, vanadium sites are involved in the activation of propane, while antimony sites insert nitrogen. The differences between the toluene and propane ammoxidation mechanisms are interpreted to be primarily related to the different reaction temperatures.

Details

Authors
  • Arne Andersson
  • S L T Andersson
  • G Centi
  • R K Graselli
  • Mehri Sanati
  • F Trifirò
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Chemical Engineering
  • Production Engineering, Human Work Science and Ergonomics

Keywords

  • acrylonitrile, antimony, benzonitrile, propane ammoxidation, toluene ammoxidation, vanadium, x-ray photoelectron spectroscopy
Original languageEnglish
Pages (from-to)43-57
JournalApplied Analysis A: General
Volume113
Issue number1
Publication statusPublished - 1994
Publication categoryResearch
Peer-reviewedYes