RESEARCH ARTICLE

 

Synthesis, characterization and activity of sulphate-modified V₂O₅/SnO₂ catalysts

 

 

Sreejarani K. Pillai; Omanakutty Gheevarghese^*

Department of Chemistry, Tshwane University of Technology, Pretoria 0001, South Africa

 

 

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ABSTRACT

Sulphate-modified V₂O₅/SnO₂ catalysts were prepared by a simple impregnation method and characterized using different physicochemical techniques, such as EDX, BET-SA, XRD, FT-IR, TGA and ⁵¹V NMR spectroscopy. A simple, effective and environmentally friendly method for the gas phase conversion of cyclohexanone oxime to E-caprolactam by these modified catalysts is presented. The optimal protocol allows ε-caprolactam to be synthesized in excellent yields. NH₃-TPD and cumene conversion reactions were used to determine the acid structural properties of the catalysts. Definite correlation was observed between the concentration of medium strength acid sites or Bronsted sites and the E-caprolactam selectivity. Time-on-stream studies showed fast decline in the activity of the catalyst resulting from the basic nature of the reactant and product molecules.

Keywords: Sulphated V₂O₅/SnO₂ catalysts, acidity, vapour phase Beckmann rearrangement

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Received 19 July 2007
Revised 8 February 2008
Accepted 13 February 2008

 

 

* To whom correspondence should be addressed: E-mail: gheevargheseo@tut.ac.za