The role of Ti and lewis acidity in manganese oxide octahedral molecular sieves impregnated with titanium in oxidation reactions

• Main Authors: Fitri, Hayati, Chandren, Sheela, Hamdan, Halimaton, Hadi, Nur
• Format: Article
• Published: Diponegoro University 2014
• Subjects: Q Science
• Online Access: http://eprints.utm.my/id/eprint/63019/; http://dx.doi.org/10.9767/bcrec.9.1.5603.28-38
• Institution: Universiti Teknologi Malaysia

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.