Dispersion of Nano Nickel Particles over SBA-15 Modified by Carbon Films on Pore Walls
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Dispersion of Nano Nickel Particles over SBA-15 Modified by Carbon Films on Pore Walls Haiyan Zhu • Mingwei Xue • Hui Chen Jianyi Shen
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Received: 18 October 2009 / Accepted: 16 November 2009 / Published online: 1 December 2009 Ó Springer Science+Business Media, LLC 2009
Abstract Mesoporous SBA-15 was prepared by using P123 as a template. The precursor with the template was calcined in an inert atmosphere so that carbon films might be formed in pores of SBA-15 due to the decomposition of template. The SBA-15C thus formed contained 3% C and exhibited similar pore structures as the SBA-15. Both SBA-15 and SBA-15C were used to support 20% nickel (by weight) via impregnation. It was found that doping with carbon films enhanced the dispersion of supported nickel. However, calcination at high temperatures before the reduction had a negative effect on the dispersion of nickel. The un-calcined 20%Ni/SBA-15C after the reduction in H2 at 673 K exhibited the highest dispersion of nickel (42%) and smallest average particle size of about 2.4 nm, in the catalysts studied in this work. It was also the most active catalyst for the hydrogenation of toluene to methyl cyclohexane. Conversion of toluene could be detected even at room temperature and atmospheric pressure for the catalyst in a fix-bed reactor, and 100% conversion of toluene was reached when temperature was raised to 358 K. Keywords SBA-15 Pore wall modification Carbon film Supported Ni Hydrogenation of toluene
Electronic supplementary material The online version of this article (doi:10.1007/s10562-009-0229-z) contains supplementary material, which is available to authorized users. H. Zhu M. Xue H. Chen J. Shen (&) Lab of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, 210093 Nanjing, China e-mail: [email protected]
1 Introduction The hydrogenation of benzene and toluene are usually used to probe the activity of catalysts for reactions taking place on metal sites [1–10]. Metallic nickel and noble metals (such as Pt and Pd) are usually used as catalysts for the hydrogenation of aromatic compounds. Since nickel is much cheaper than noble metals, it is more desirable than noble metals if they work similarly well for the hydrogenation reactions. In fact, both Ni and Pt have been used for the hydrogenation of benzene in industry. Highly active nickel catalysts with high nickel surface areas are needed to improve the catalytic activity. Supported nickel catalysts with high loading, reducibility and dispersion are the basic requirements to obtain the high nickel surface areas. The supported catalysts are usually prepared by the co-precipitation [11, 12], impregnation [12, 13] and ion exchange [14] methods. High dispersion of Ni may be achieved by the ion exchange method, but the loading is usually low with this method. Impregnation method can be used to prepare the supported nickel catalysts with high loadings, but the dispersion may not be high at the high loading with the method. The catalysts prepared by the co-precipi
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