Studies on the catalytic oxidation of alkanes and alkenes by titanium silicates

Journal Article · Thu Sep 01 04:00:00 EDT 1994 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1994.1285· OSTI ID:110988

Khouw, C B; Dartt, C B; Labinger, J A ^[1]

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1. 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, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 149; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

10 SYNTHETIC FUELS
40 CHEMISTRY
ALKANES
ALKENES
CATALYST SUPPORTS
CATALYTIC EFFECTS
LIFETIME
OXIDATION
RADICALS
TITANIUM SILICATES