Characteristics and Catalytic Properties of Pd/SiO 2 Synthesized by One-step Flame Spray Pyrolysis in Liquid-phase Hydro
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Characteristics and Catalytic Properties of Pd/SiO2 Synthesized by One-step Flame Spray Pyrolysis in Liquid-phase Hydrogenation of 1-Heptyne Sirima Somboonthanakij Æ Okorn Mekasuwandumrong Æ Joongjai Panpranot Æ Tarit Nimmanwudtipong Æ Reto Strobel Æ Sotiris E. Pratsinis Æ Piyasan Praserthdam
Received: 10 June 2007 / Accepted: 2 August 2007 / Published online: 7 September 2007 Springer Science+Business Media, LLC 2007
Abstract In this study, Pd/SiO2 catalysts with 0.5– 10 wt.% Pd loadings were prepared by one-step flame spray pyrolysis (FSP) and characterized by N2 physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), CO chemisorption, and X-ray photoelectron spectroscopy (XPS). The average cluster/particles size of Pd as revealed by TEM were ca. 0.5–3 nm. The turnover frequencies (TOFs) of the flame-made catalysts decreased from 66.2 to 4.3 per s as Pd loading increased from 0.5 to 10 wt.%, suggesting that the catalytic activity was dependent on Pd particle/cluster size. However, there were no appreciable influences on 1-heptene selectivity. The flame-made Pd/SiO2 showed better properties than the conventional prepared catalysts. Their advantages are not only the presence of large pores that facilitates diffusion of the reactants and products, but also the high-catalytic activity of as-synthesized catalysts so that further pretreatment is not necessary.
S. Somboonthanakij J. Panpranot (&) T. Nimmanwudtipong P. Praserthdam Center of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand e-mail: [email protected] O. Mekasuwandumrong Department of Chemical Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakorn Pathom 73000, Thailand R. Strobel S. E. Pratsinis Particle Technology Laboratory, Department of Mechanical and Process Engineering, ETH Zentrum, Swiss Federal Institute of Technology, CH-8092 Zurich, Switzerland
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Keywords Flame spray pyrolysis Pd/SiO2 Liquid phase hydrogenation 1-Heptyne hydrogenation Pd nanoparticle
1 Introduction The selective hydrogenation of alkynes to alkenes is an important reaction in the synthesis of biologically active compounds such as insect sex pheromones (pest control) and vitamins [1]. Palladium (Pd) is the most selective of the noble metal catalysts for alkyne semihydrogenation with respect to over all alkene formation [2]. The classic Lindlar catalyst, consisting of metallic Pd on calcium carbonate support modified with lead(II) acetate, is the well known commercially available catalyst for such reaction. As reported by several authors, high activity and selectivity may be obtained over other catalyst systems in which modifiers are not necessary such as supported Pd complexes [3–5], bimetallic Pd–Cu/SiO2 [6], Pd/montmorillonite [7], Pd/pumice [8], Pd/MCM-41 [9], Pd/activated carbon, and Pd/Al2O3 [10]. The advantages of the reaction in heterogeneous conditions are easy se
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