PdAu Alloy Nanoparticles Encapsulated by PPI-g-MWCNTs as a Novel Catalyst for Chemoselective Hydrogenation of Alkenes Un
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PdAu Alloy Nanoparticles Encapsulated by PPI-g-MWCNTs as a Novel Catalyst for Chemoselective Hydrogenation of Alkenes Under Mild Conditions Ahmad Shaabani • Mojtaba Mahyari
Received: 5 May 2013 / Accepted: 1 July 2013 Ó Springer Science+Business Media New York 2013
Abstract The synthesis, characterization and catalytic applications of bimetallic PdAu encapsulated on polypropylene imine grafted multi-wall carbon nanotubes hybrid materials have been reported. The results show that the catalyst induces a highly activity and chemoselective hydrogenation of less hindered alkenes to the corresponding alkanes using hydrogen gas in environmentally friendly solvents H2O/EtOH at 50 °C with high yields. The characterization of catalyst was confirmed by FT-IR, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray powder diffraction. Keywords Bimetallic Polypropylene imine Multi-wall carbon nanotubes Chemoselective hydrogenation
1 Introduction The selective hydrogenation is a critical step in the synthesis of chemical intermediates that have wide applications in many fields such as foods, pharmaceuticals, cosmetics, plastics, and lubricants industries [1–3]. Encapsulated noble metals are industrial and academic important catalytic for the selective hydrogenation [4, 5]. Bimetallic nanoparticles (NPs) have appeared as an important class of catalysts. Bimetallic nanoparticles based on the mixing pattern, can be Electronic supplementary material The online version of this article (doi:10.1007/s10562-013-1063-x) contains supplementary material, which is available to authorized users. A. Shaabani (&) M. Mahyari Department of Chemistry, Shahid Beheshti University, G. C., P.O. Box 19396-4716, Tehran, Iran e-mail: [email protected]
divided into three main types [6]. Heterostructures, core– shell structures, and intermetallic or alloyed structures. Among these types, bimetallic alloy NPs are very important nanomaterials because of their applications in large variety of catalytic reactions, including catalytic alcohol oxidation, reforming reactions, and pollution control [7–11]. The addition of a second metal is an important approach for tailoring the geometric and electronic structures of NPs to promote their catalytic activity and selectivity. Carbon nanotubes (CNTs) are attractive solid supports for heterogeneous catalysts due to their unique properties and surface structures [12], but there are some difficulties in dispersing metal nanoparticles on the surface of pristine CNTs. In this work, a well-defined polymer known as dendrimer [13, 14] is used as template to control the size, stability, and solubility of nanoparticles ranging in diameter from\1 to 5 nm. Dendrimers are suitable for hosting metal nanoparticles especially for catalytic systems due to the following reasons: (i) the nanoparticles are stabilized by encapsulation within the dendrimer, and they do not agglomerate [15–21]; (ii) the encapsulated nanoparticles are confined by steric effects, and therefore a substantial fraction of th
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