The Effect of Preparation Parameters of MCM-41 Supported Pt/Ni Catalysts and their Hydrogenation Properties
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The Effect of Preparation Parameters of MCM-41 Supported Pt/Ni Catalysts and their Hydrogenation Properties N. H. H. Abu Bakar Æ M. M. Bettahar Æ M. Abu Bakar Æ S. Monteverdi Æ J. Ismail
Received: 19 December 2008 / Accepted: 25 February 2009 / Published online: 17 March 2009 Ó Springer Science+Business Media, LLC 2009
Abstract A series of Pt50Ni50 supported on MCM-41 catalysts were prepared via wet co-impregnation of the metal salts H2PtCl6 and NiSO46H2O. The metal salts were reduced using NaBH4 and catalytic activities of the catalysts were investigated for the hydrogenation of benzene to cyclohexane. The effect of various reduction conditions such as reduction temperature, NaBH4 concentration and the medium in which reduction was carried out was investigated. Results show that optimum catalytic activity occurs when catalysts are synthesized at 273 K using 0.3 M of NaBH4 in a medium of ethanol. The variation in reduction rate with reduction conditions influenced the metal particle morphology which effected catalytic activity. Further comparison of the reactivity of Pt50Ni50 with that of the respective monometallic catalysts synthesized at optimum conditions, show that the Pt50Ni50 exhibited superior reactivity. Surface properties of the catalysts were characterized using H2-TPR, H2-adsorprtion and H2-TPD analyzes. Studies on the morphology of the metal particles and composition were obtained via TEM and SEM equipped with elemental analysis. Keywords Pt/Ni NaBH4 reduction MCM-41 Hydrogenation N. H. H. Abu Bakar M. M. Bettahar (&) S. Monteverdi UMR CNRS-UHP 7565, ICPCJB, Faculte´ des Sciences, Universite´ Henri Poincare, Nancy 1, BP 239, 54506 Vandoeuvre Cadex, France e-mail: [email protected] N. H. H. Abu Bakar e-mail: [email protected] N. H. H. Abu Bakar M. Abu Bakar J. Ismail School of Chemical Sciences, Universiti Sains Malaysia, 11800 Gelugor, P. Pinang, Malaysia
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1 Introduction The high cost of monometallic Pt catalysts has encouraged scientists to find less expensive alternatives with improved activity. One of such alternatives that have attracted increasing attention in recent years is supported bimetallic Pt/Ni catalysts [1–9]. It has been shown that the methods employed to prepare catalysts have a considerable influence on the catalyst properties and activities. In fact, several research groups have investigated the factors that influence the various preparation stages [3, 10–12]. As an example, Machek et al. [12] described the solvent affect on the adsorption of chloroplatinic acid and indirectly the Pt dispersion on activated carbon. They found that polar solvents such as water resulted in sintering and a nonuniform distribution of Pt while less polar solvents such as ketone gave rise to a uniform distribution of the metal phase. Manipulating the reduction parameters is also an important aspect in the synthesis of catalysts. A wide range of reducing agents such as H2 [13, 14], sodium borohydride (NaBH4) [15–17], hydrazine [18, 19] and alcohol [20] have been emplo
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