Studies on the catalytic oxidation of alkanes and alkenes by titanium silicates
- California Institute of Technology, Pasadena, CA (United States); and others
Titanium containing, aluminum-free ZSM-5 (TS-1) and amorphous TiO{sub 2}-SiO{sub 2} coprecipitate are investigated as catalysts for the selective oxidation of alkanes and alkenes using a variety of oxidants at temperatures below 100{degrees}C. Comparisons between the activities of TS-1 and and TiO{sub 2}-SiO{sub 2} coprecipitate for alkane oxidation and alkene epoxidation using nonaqueous H{sub 2}O{sub 2} indicate that the absence of water is crucial for the catalytic activity of silica-supported titanium. Due to the hydrophobicity of TS-1, the concentration of water surrounding the titanium is maintained at a low value, and thus TS-1 can be used as an oxidation catalysts with aqueous H{sub 2}O{sub 2} as oxidant. Alkyl hydroperoxides are active as oxidants for alkene epoxidation on the TiO{sub 2}-SiO{sub 2} coprecipitate but not for alkane oxidation reactions on both TS-1 and the TiO{sub 2}-SiO{sub 2} coprecipitate. A plausible explanation for the above results is provided. The presence of stereoscrambling without any {open_quotes}radical clock{close_quotes} rearrangement during alkane oxidation on TS-1 indicates that the radicals formed may have a very short lifetime, or their movements are restricted such that no rearrangement can occur. A proposal for the mechanism of alkane oxidation on TS-1 is given and compared to a mechanism suggested for alkene epoxidation on TS-1 and the TiO{sub 2}-SiO{sub 2} coprecipitate. 47 refs., 10 figs., 9 tabs.
- OSTI ID:
- 110988
- Journal Information:
- Journal of Catalysis, Vol. 149, Issue 1; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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