Synthesis of Cobalt Doped Porous Titania-Silica Prepared by Using the Rice Husks as Both Silicon Source and Template and
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Synthesis of Cobalt Doped Porous Titania-Silica Prepared by Using the Rice Husks as Both Silicon Source and Template and its Catalytic Oxidation of 4-Methyl Pyridine Zhongbiao Zhai Æ Yingchun Miao Æ Qiaoli Sun Æ Huiwang Tao Æ Wei Wang Æ Jiaqiang Wang
Received: 19 December 2008 / Accepted: 26 March 2009 / Published online: 10 April 2009 Ó Springer Science+Business Media, LLC 2009
Abstract Cobalt doped porous titania-silica with Ti/Si molar ratio of 0.2 synthesized by using rice husks as both silicon source and template presented good product (4-pyridinecarboxylic acid) selectivity (91%) and high substrate conversion rate (96%) for the catalytic oxidation of 4-methyl pyridine. Fast hot catalyst filtration experiment proved that it acted as a heterogeneous one and can be used a number of times with almost the same activity. Keywords 4-Methyl pyridine 4-Pyridinecarboxylic acid Rice husk Co doped porous titania-silica
1 Introduction 4-Pyridinecarboxylic acid (4-PCA), is a valuable intermediate of vitamins, food additives and pharmaceuticals. The classical synthesis method is based on the oxidation of alkylpyridines by air, nitric acid, ozone, KMnO4, etc., [1–3]. However, these methods always need critical conditions, and they are expensive, polluting, and risky. Since heterogeneous catalysts with significant advantages for Z. Zhai Y. Miao Q. Sun H. Tao W. Wang J. Wang (&) Department of Applied Chemistry, Key Laboratory of Medicinal Chemistry for Natural Resource Ministry of Education, Yunnan University, 650091 Kunming, People’s Republic of China e-mail: [email protected] Z. Zhai Technology Center of Yunnan Metallurgy Group Company, 650031 Kunming, People’s Republic of China Y. Miao Faculty of Chemical and Life Sciences, Qujing Normal University, 655000 Qujing, People’s Republic of China
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recovery and stabilities are more desirable than the soluble catalysts, quite a few formulations for the vapor-phase oxidations of picoline have been investigated [4–10]. For example, crystalline CrV0.95P0.05O4 was found to be highly active for the vapor-phase oxidation of picoline with a high yield (84.3%) of 4-PCA at 570 K [9, 10]. However, the heterogeneous catalytic liquid phase oxidation of picoline is very few and there is still rather limited study of the application of porous materials in the oxidation of picoline. For instance, there is a synergetic effect of a V2O5 layer supported by TiO2 as a catalyst carrier for the vapor phase oxidation of b-picoline [6]. Moreover, it has been reported that the addition of silica in Titania not only enhances the thermal stability for the phase transformation of Titania particles from anatase to rutile but also increases the surface area and exhibit interesting properties related to the generation of new catalytic sites for selective oxidation reactions [11–14]. For example, we synthesized cobalt doped mesoporous titania-silica with Ti/Si molar ratio of 0.5 (Co–TiO2–SiO2 (CTAB)) by using hexadecyltrimethylammonium bromide (CTAB) as template and tetraethyl orthosilicate
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