Molecular Sieve Catalysts for the Regioselective and Shape- Selective Oxyfunctionalization of Alkanes in Air

• Published in: Accounts of chemical research Vol. 34; no. 3; pp. 191 - 200
• Main Authors: Thomas, John Meurig, Raja, Robert, Sankar, Gopinathan, Bell, Robert G
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.03.2001
• Subjects: Aerobiosis; Air - analysis; Alkanes - chemistry; Catalysis; Oxygen - chemistry
• ISSN: 0001-4842; 1520-4898
• DOI: 10.1021/ar970020e

Framework-substituted, molecular-sieve, aluminophosphate, microporous solids are the centerpieces of a new approach to the aerobic oxyfunctionalization of saturated hydrocarbons. The sieves, and the few percent of the AlIII sites within them that are replaced by catalytically active, transition-metal ions in high oxidation states (CoIII, MnIII, FeIII), are designed so as to allow free access of oxygen in to and out of the interior of these high-area solids. Certain metal-substituted, molecular sieves permit only end-on approach of linear alkanes to the active centers, thereby favoring enhanced reactivity of the terminal methyl groups. By optimizing cage dimension, with respect to that of the hydrocarbon reactant, as well as adjusting the average separation of active centers within a cage, and by choosing the sieve with the appropriate pore aperture, highly selective conversions such as n-hexane to hexanoic acid or adipic acid, and cyclohexane to cyclohexanol, cyclohexanone, or adipic acid, may be effected at low temperature, heterogeneously in air.