n -Butane Dehydrogenation on PtSn/Carbon Modified MgO Catalysts
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n-Butane Dehydrogenation on PtSn/Carbon Modified MgO Catalysts Veldurthi Shashikala • Heon Jung • Chae-Ho Shin • Hyoung-Lim Koh • Kwang-Deog Jung
Received: 28 January 2013 / Accepted: 14 April 2013 / Published online: 27 April 2013 Ó Springer Science+Business Media New York 2013
Abstract Carbon modified magnesium oxides (CMgO600, CMgO-700 and CMgO-800) were prepared from pyrolyzing n-hexane vapors at 600, 700 and 800 °C, respectively, on the surface of the MgO. Modification of magnesium oxide (CMgO) with carbon increased the covalent character of the Mg–O bond, consequently decreasing the basicity. TEM and H2 chemisorption showed that the average metal particle size on CMgO was ca. 3.0 nm and the HRTEM images showed that the metal particles consisted of Pt–Sn alloys with different Pt/Sn composition. PtSn/CMgO catalysts showed much higher activity and selectivity than PtSn/MgO for the butane dehydrogenation, because a high metal dispersion on PtSn/ CMgO resulted from preventing MgO dissolution during the impregnation step of metal salts on the support. The PtSn/CMgO-600 catalyst among the prepared catalysts gave the highest butenes yield. Keywords CMgO PtSn/CMgO PtSn alloy n-Butane dehydrogenation
V. Shashikala H. Jung K.-D. Jung (&) Clean Energy Research Centre, Korea Institute of Science and Technology, P.O. Box 131, Cheongryyang, Seoul 136-791, South Korea e-mail: [email protected] C.-H. Shin Department of Chemical Engineering, Chungbuk National University, Cheongju 361-763, Chungbuk, South Korea H.-L. Koh Department of Chemical Engineering, Hankyong National University, Anseong 456-749, Kyunggido, Korea
1 Introduction Synthesis of light olefins from dehydrogenation of lower alkanes (C1–C4) is an industrially important reaction. n-Butane dehydrogenation has been studied on PtSn catalysts supported on Al2O3 and ZnAl2O4 [1–3]. Various undesired reactions such as cracking, isomerization and polymerization were intensified with an increase in the acidity of the supports [4–6]. Thus, an attempt was made to select the supports with the base property such as alkali earth metal oxides to reduce the side reactions. MgO with Lewis and Bro¨nsted (O2- and OH-) basic sites has been considered as an important solid base catalyst for many organic transformations in heterogeneous catalysis [7, 8], which has been used as supports to disperse active metal components such as Pt, Pd, Rh, and Ni [9–15]. However, the inherent properties of MgO such as dissolution and reprecipitation in an aqueous solution and the strong metal support interactions limited its applications to heterogeneous catalysis [9, 15–18]. In the process of the catalyst preparation using MgO support, it was observed that the active metal particles could be encapsulated by the support [16, 17]. The strong metal support interactions and formation of Pt–MgO complex were also reported [9, 18]. Thus, the above drawbacks of MgO support must be suppressed to enhance the applications of MgO as support in heterogeneous catalysis. In this paper, we discuss the sy
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