The role of Ti and lewis acidity in manganese oxide octahedral molecular sieves impregnated with titanium in oxidation reactions
Octahedral manganese oxide molecular sieves (OMS-2) was prepared by precipitation method and modified by impregnation of titanium with different titanium/manganese (Ti/Mn) ratio. It was discov-ered that Ti/Mn ratio of less than 0.5 still retains the original pure cryptomelane structure of OMS-2. How...
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| Main Authors: | , , , |
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| Format: | Article |
| Published: |
Diponegoro University
2014
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| Subjects: | |
| Online Access: | http://eprints.utm.my/id/eprint/63019/ http://dx.doi.org/10.9767/bcrec.9.1.5603.28-38 |
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| Institution: | Universiti Teknologi Malaysia |
| Summary: | Octahedral manganese oxide molecular sieves (OMS-2) was prepared by precipitation method and modified by impregnation of titanium with different titanium/manganese (Ti/Mn) ratio. It was discov-ered that Ti/Mn ratio of less than 0.5 still retains the original pure cryptomelane structure of OMS-2. However, for sample with Ti/Mn ratio of more than 0.5, some rutile phases of titania (TiO2) can be de-tected together with the cryptomelane phase. Lewis acid sites were also observed in the titanium modi-fied OMS-2 (Ti-OMS-2). Ti-OMS-2 was then used as catalysts for the oxidation of cyclohexane, cyclo-hexene and styrene, where Ti-OMS-2 with Ti/Mn ratio of 0.67 was most active in all three of the oxida-tion reactions as compared to TiO2 and OMS-2. The results suggest that both titanium sites in frame-work and non-framework and the Lewis acidity created by the impregnation of Ti, increased the activi-ty of OMS-2 in oxidation reactions. |
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