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Abstract

Thermal Hysteresis of Palladium encaged inside Mesoporous Silica catalyst for Low Temperature CO oxidation Rola Al Soubaihi 1,2, Joydeep Dutta2 Liberal Arts and Science Program, Virginia Commonwealth University-Qatar, Doha, Qatar Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden Carbon Monoxide (CO) is colorless, odorless gas produced from incomplete combustion of carbon fuel under conditions with a limited supply of oxygen. Catalytic oxidation is one of the effective methods of removing CO and convert it to CO2. [1] Catalyzed CO oxidation reaction finds applications in many fields such as environmental protection, air purification for buildings or cars, orbiting, closed-cycle CO2 lasers, gas masks for mining applications, CO detectors[2-3]. Depending on their size, shape, and preparation conditions, Nanocatalysts can exhibit unique properties (electrical, optical, magnetic, and catalytic) which are different from their bulk material properties [4-6]. The surface of nanomaterials contains large number of high energy defects such as surface and edge atoms that can provide active sites for catalyzing surface reactions by lowering the activation energy [7-8]. Supported Palladium catalysts are known for their high activity, recyclability, and their cheap cost when compared to platinum catalysts. Support plays a crucial role in the synthesis of such catalysts. In this regard support can reduce the amounts of the metal and ensure a good dispersion, and increase their thermal stability. Mesoporous materials with large internal surface areas (>1000 m2/g) and narrow pore size distributions can be an ideal support for Palladium based catalysts [9-10]. Silica are well known for structural and thermal properties and allow anchoring of catalytically palladium active species onto their surfaces. Silica can provide enormous beneficial features to enhance the catalytic activity such as high surface area, high porous, high thermal insulation, and local heating and heat retention [11-13]. Here, we report for the first time exceptional catalytic CO oxidation on Pd supported on mesoporous SiO2 with good stability and recycling behavior under heating and cooling conditions with wide CO Thermal hysteresis (close to 200 °C). We attribute our results to the phase transformation of Palladium to palladium oxide intermediate at different temperatures during the heating and cooling cycles and the structure and the local environment of the palladium since Pd clusters are small and highly dispersed on the silica surfaces and encaged inside the pores. References [1] S. Biswas, K. Mullick, S. Y. Chen, A. Gudz, D. M. Carr, C. Mendoza, et al., «Facile access to versatile functional groups from alcohol by single multifunctional reusable catalyst,» Applied Catalysis B-Environmental, vol. 203, pp. 607–614, Apr 2017. [2] X. Zhang, Zhenping Qu, Xinyong Li, Meng Wen, Xie Quan, Ding Ma, and Jingjing Wu., «Studies of silver species for low-temperature CO oxidation on Ag/SiO 2 catalysts.,» Separation and Purification Technology, vol. 3, pp. 395–400., 2010. [3] P. A. Wright, Srinivasan Natarajan, John M. Thomas, and Pratibha L. Gai-Boyes, «Mixed-metal amorphous and spinel phase oxidation catalysts: characterization by x-ray diffraction, x-ray absorption, electron microscopy, and catalytic studies of systems containing copper, cobalt, and manganese,» Chemistry of materials vol. 5 pp. 1053–1065., 1992. [4] A. Cubo, J. Iglesias, G. Morales, J. A. Melero, J. Moreno, and R. Sanchez-Vazquez, «Dehydration of sorbitol to isosorbide in melted phase with propyl-sulfonic functionalized SBA-15: Influence of catalyst hydrophobization,» Applied Catalysis a-General, vol. 531, pp. 151–160, Feb 2017. [5] W. Fang, Y. C. Deng, L. Tang, G. M. Zeng, Y. Y. Zhou, X. Xie, et al., «Synthesis of Pd/Au bimetallic nanoparticle-loaded ultrathin graphitic carbon nitride nanosheets for highly efficient catalytic reduction of p-nitrophenol,» Journal of Colloid and Interface Science, vol. 490, pp. 834–843, Mar 2017. [6] M. V. D. Fernandes and L. R. D. da Silva, «Structural analysis of mesoporous vermiculite modified with lanthanum,» Materials Letters, vol. 189, pp. 225–228, Feb 2017. [7] A. K. Herrmann, P. Formanek, L. Borchardt, M. Klose, L. Giebeler, J. Eckert, et al., «Multimetallic Aerogels by Template-Free Self-Assembly of Au, Ag, Pt, and Pd Nanoparticles,» Chemistry of Materials, vol. 26, pp. 1074–1083, Jan 2014. [8] R. Muller, S. H. Zhang, B. Neumann, M. Baumer, and S. Vasenkov, «Study of Carbon Dioxide Transport in a Samaria Aerogel Catalyst by High Field Diffusion NMR,» Chemie Ingenieur Technik, vol. 85, pp. 1749–1754, Nov 2013. [9] Al-Oweini, S. Aghyarian, and H. El-Rassy, «Immobilized polyoxometalates onto mesoporous organically-modified silica aerogels as selective heterogeneous catalysts of anthracene oxidation,» Journal of Sol-Gel Science and Technology, vol. 61, pp. 541–550, Mar 2012. [10] B. N. Bhadra, P. W. Seo, J. W. Jun, J. H. Jeong, T. W. Kim, C. U. Kim, et al., «Syntheses of SSZ-39 and mordenite zeolites with N,N-dialkyl-2,6-dimethyl-piperidinium hydroxide/iodides: Phase-selective syntheses with anions,» Microporous and Mesoporous Materials, vol. 235, pp. 135–142, Nov 2016. [11] S. Dilger, C. Hintze, M. Krumm, C. Lizandara-Pueyo, S. Deeb, S. Proch, et al., «Gas phase synthesis of titania with aerogel character and its application as a support in oxidation catalysis,» Journal of Materials Chemistry, vol. 20, pp. 10032–10040, 2010. [12] A. K. Herrmann, P. Formanek, L. Borchardt, M. Klose, L. Giebeler, J. Eckert, et al., «Multimetallic Aerogels by Template-Free Self-Assembly of Au, Ag, Pt, and Pd Nanoparticles,» Chemistry of Materials, vol. 26, pp. 1074–1083, Jan 2014. [13] R. Muller, S. H. Zhang, B. Neumann, M. Baumer, and S. Vasenkov, «Study of Carbon Dioxide Transport in a Samaria Aerogel Catalyst by High Field Diffusion NMR,» Chemie Ingenieur Technik, vol. 85, pp. 1749–1754, Nov 2013.

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2018-03-12
2020-06-01
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