Synthesis of alumina supported nickel nanoparticle catalysts and evaluation of nickel metal dispersions by temperature programmed desorption |
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| Institution: | 1. AGH University of Science and Technology, Faculty of Energy and Fuels, Al. A. Mickiewicza 30, 30-059 Cracow, Poland;2. Sorbonne Universités, UPMC, Univ. Paris 6, CNRS, UMR 7190, Institut Jean Le Rond d’Alembert, 2 place de la gare de ceinture, 78210 Saint-Cyr-L’Ecole, France;1. Chemical Engineering Program, Texas A&M University at Qatar, Doha, Qatar;2. Department of Chemistry, Northwestern University, Evanston, IL, USA;3. Gas and Fuels Research Center, Texas A&M Engineering Experiment Station, College Station, TX 77843, USA;1. Department of Chemical and Biochemical Engineering, Missouri University of Science and Technology, Rolla, MO 65409, United States;2. Gas Technology Institute, 1700 S Mount Prospect Road, Des Plaines, IL 60018, United States;3. Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, PR China;1. Department de Química Física i Inorgànica, Universitat Rovira i Virgili, 43007 Tarragona, Spain;2. Institute of Energy Technologies and Centre for Research in Nanoengineering, Universitat Politècnica de Catalunya, Avda. Diagonal 647, ed. ETSEIB, 08028 Barcelona, Spain;1. Department of Science, Roma Tre University, Via della Vasca navale 79, 00146 Roma, Italy;2. Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL Research, Monte Porzio Catone, 00040 Rome, Italy |
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| Abstract: | The purpose of this study was to synthesize highly dispersed Ni/Al2O3 catalysts and to develop a suitable hydrogen-temperature programmed desorption (H2-TPD) method for the determination of nickel metal surface area, dispersion, and crystallite sizes. Several highly dispersed Ni/Al2O3 catalysts with a Ni loading between 15 and 25 wt.% were synthesized. The reducibility of catalysts was determined by temperature programmed reduction (TPR) experiments. All catalysts exhibited a single reduction peak with a maximum rate of H2 consumption (Tmax in TPR) occurring below 450 °C. Three different H2-TPD methods were employed to determine the amount of H2 chemisorbed. In TPD-1, a 10% H2/Ar mixture was used for catalyst pre-reduction and surface saturation by cooling down from Tmax in TPR to room temperature. In TPD-2, the catalyst surface after pre-reduction was flushed with Ar at Tmax in TPR + 10 °C. The TPD-3 was similar to the TPD-2, but used 100% H2 instead of 10% H2/Ar mixture. In all three TPD methods, the profiles exhibited 2 domains of H2 desorption peaks, one below 450 °C, referred to as type-1 peaks, and attributed to H2 desorbed from exposed fraction of Ni atoms, and the other above 450 °C, denoted as type-2 peaks, and assigned to the desorption of H2 located in the subsurface layers and/or to spillover H2. Flushing the reduced catalyst surface in Ar at Tmax in TPR + 10 °C in TPD-2 and TPD-3 removed most of the H2 located in the subsurface layers/ spillover H2. The amount of H2 chemisorbed to form a monolayer on the reduced Ni/Al2O3 catalysts was determined quantitatively from the TPD peak areas of type-1 peaks in TPD-1, and from both type-1 and type-2 peaks in TPD-2 and TPD-3. The Ni metal surface area, dispersions and crystallite sizes were calculated from the chemisorption data and the values were compared with those obtained using the static chemisorption method. Both TPD-2 and TPD-3 gave chemisorption results similar to that obtained from the static method. |
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