Characteristics and Catalytic Properties of Mesocellular Foam Silica Supported Pd Nanoparticles in the Liquid-Phase Sele
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Characteristics and Catalytic Properties of Mesocellular Foam Silica Supported Pd Nanoparticles in the Liquid-Phase Selective Hydrogenation of Phenylacetylene Chayanin Na-Chiangmai • Napaporn Tiengchad • Prathan Kittisakmontree • Okorn Mekasuwandumrong Jonathan Powell • Joongjai Panpranot
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Received: 17 November 2010 / Accepted: 24 March 2011 / Published online: 7 April 2011 Ó Springer Science+Business Media, LLC 2011
Abstract An ultra-large pore mesocellular foam silica (MCF) was employed as a support for preparation of supported Pd catalysts for the liquid-phase selective hydrogenation of phenylacetylene. The catalysts were prepared by three different routes: (i) incipient wetness impregnation using Pd(II)acetate solution (Pd/MCF-imp), (ii) impregnation of colloidal Pd nanoparticles obtained by the solvent reduction method (Pd/MCF-col), and (iii) in situ synthesis of MCF in the presence of the Pd colloid (Pd/MCF-ss). The conventional impregnation method resulted in more agglomeration of Pd particles and partial collapse of MCF structure, hence the Pd/MCF-imp exhibited the lowest selectivity towards styrene at total conversion of phenylacetylene. Only the Pd/MCF-ss, in which most of the Pd nanoparticles were encapsulated by the silica matrix, was found to retain high styrene selectivity ([80%) after complete conversion of phenylacetylene. Comparing to the other highly efficient Pd catalysts reported in the literature under similar reaction conditions, it can be emphasized that coverage of Pd surface by the support produces great
C. Na-Chiangmai N. Tiengchad P. Kittisakmontree J. Panpranot (&) Department of Chemical Engineering, Faculty of Engineering, Center of Excellence on Catalysis and Catalytic Reaction Engineering, Chulalongkorn University, Bangkok 10330, Thailand e-mail: [email protected] O. Mekasuwandumrong Department of Chemical Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakhon Pathom 73000, Thailand J. Powell International School of Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand
beneficial effect for enhancing styrene selectivity, regardless of the type of supports used (i.e., TiO2, carbon nanotubes, or mesostructured silica). Keywords Mesocellular foam silica Pd nanoparticles Phenylacetylene Hydrogenation
1 Introduction Hydrogenation is such a fast and highly exothermic reaction, severe diffusion limitations may be induced due to small pore diameters of the catalyst support. To overcome diffusion resistance, large pore supports are usually preferred especially for the three-phase catalytic systems. Much attention has focused on the use of ordered mesoporous materials such as MCM-41 [1], SBA-x [2], and HMS [3]. The regular mesoporous structure not only improved the hydrogenation activity but was also enhance the selectivity of certain species. For example, the confinement of homogeneous chiral catalyst within MCM-41 has been found to improve the enantioselectivity of asymmetric epoxidation and hydroformy
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