Heteropolioxomethalates Supported on Zeolite ZSM-5 as Catalysts in Selective Oxidation Reactions

Abstract

Heteropolycompounds (HPC) catalysis is becoming increasingly important since their acidic properties, redox and bifunctional character are extremely interesting, however these compounds are quite soluble in water and organic solvents and have low surface area which restrict their use as heterogeneous catalysts. A way to overcome these disadvantages is to anchor them on porous supports. Zeolites are microporous crystalline materials. They have structures with regular periodic arrays of channels and cavities. So, zeolites seem to be suitable supports for HPC, ensuring the heterogeneity and increasing their surface area.
Supported K_6CoW_12O_40(HPC) were obtained by wet impregnation of ZSM-5 zeolite synthesized by the hydrothermal method. The materials thus prepared were characterized by different experimental techniques.
These materials were tested as solid catalysts for the follow selective oxidations with hydrogen peroxide:
- Styrene to benzaldehyde;
-2,3,5-Trimethylphenol to 2,3,5-trimethylbenzoquinone and 2,3,5-trimethylhydroquinone;
- 2-(methylthio)-benzothiazol to its corresponding sulfoxide and sulfone.