Oxidation of Carbon Monoxide Over SBA-15-Confined Copper, Palladium and Iridium Nanocatalysts
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Oxidation of Carbon Monoxide Over SBA-15-Confined Copper, Palladium and Iridium Nanocatalysts Vanessa S. Garcia-Cuello • Liliana Giraldo Juan Carlos Moreno-Piraja´n
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Received: 15 July 2011 / Accepted: 22 August 2011 / Published online: 7 September 2011 Ó Springer Science+Business Media, LLC 2011
Abstract Copper, palladium and iridium nanoparticles were synthesised within the pore channels of selectively grafted mesoporous silica SBA-15. The support and catalysts were characterised by different techniques. The synthesized catalyst were able to catalyse oxidation of carbon monoxide with activity values as high as 7.0 9 10-3 mmol g-1 cat s-1 at 353 K. Carbon monoxide conversion was found to increase with decreasing nano particle size. Keywords SBA-15 Nanocatalyst Oxidation Carbon monoxide Adsorption calorimetry
1 Introduction The recent discovery of mesoporous silicas, such as M41s [1] and SBA-15 [2], has sparked intensive investigations into the ‘‘hostguest’’ chemistry occurring inside their channels [3–6]. Mesoporous silicas have numerous potential applications in catalysis and medicine, and may be useful as selective adsorbents [7], sensors [8, 9], and in the fabrication of nanomaterials. In addition, because of their uniform mesostructure, high surface area, and tunable pore size [2], ordered mesoporous silicas have been used as templates to control the size and shape of metal
V. S. Garcia-Cuello L. Giraldo Faculty of Science, Department of Chemistry, National University of Colombia, Bogota, Colombia J. C. Moreno-Piraja´n (&) Faculty of Science, Department of Chemistry, Research Group on Porous Solids and Calorimetry, Universidad de los Andes, Carrera 1 No. 18 A 10, Bogota, Colombia e-mail: [email protected]
nanoparticles [10–16]. The molecular properties of nanoparticles confined in various molecular sieves have been well-documented [17–19]. In addition, surface modifications of ordered mesoporous silicas have been described [17, 18]. Traditionally, two major methods have been reported for modification of mesoporous materials, via covalent linkage between functional groups and the silica framework: (1) grafting (post-synthesis); and (2) co-condensation (direct incorporation) [20]. In grafting, organic functional groups can be introduced onto pre-synthesised mesoporous silicas by direct reaction of organosilanes with the silica surface. Depending on the downstream application, other functionalities can be added, including amino, thiol, and alkyl groups, via covalent bonding and/or molecular recognition of the original modification(s) [20–23]. The distribution and concentration of functional groups are influenced by the reactivity of the organosilane, and the accessibility of surface silanols, which are limited by diffusion and steric factors. Chao et al. [6, 11] prepared SBA15 functionalised with (CH3O)3Si(CH2)3N(CH3)3Cl (TPTAC), and synthesised metal nanoparticles using anion exchange between grafted SBA-15 and metal precursors inside the channels, as well as through reduction of the precurs
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