H 2 production by methane decomposition: Catalytic and technological aspects F. Frusteri a, *, G. Italiano b , C. Espro b , C. Cannilla a , G. Bonura a a Istituto CNR-ITAE “Nicola Giordano”, Via S. Lucia Sopra Contesse 5, 98126 Messina, Italy b Dip. Chimica Industriale ed Ing. Dei Materiali, Universita ` di Messina, Viale F. Stagno D’Alcontres 31, 98166 Messina, Italy article info Article history: Received 11 November 2011 Received in revised form 27 February 2012 Accepted 29 February 2012 Available online 29 March 2012 Keywords: Methane decomposition Hydrogen production Ni and Co catalysts Coke formation mechanism abstract Ni and Co supported on SiO 2 and Al 2 O 3 silica cloth thin layer catalysts have been investi- gated in the catalytic decomposition of natural gas (CDNG) reaction. The influence of carrier nature and reaction temperature was evaluated with the aim to individuate the key factors affecting coke formation. Both Ni and Co silica supported catalysts, due to the low metal support interaction (MSI), promotes the formation of carbon filament with particles at tip. On the contrary, in case alumina was used as support, metals strongly interact with surface thus depressing both the metal sintering and the detachment of particles from catalyst surface. In such cases, carbon grows on metal particle with a “base mechanism” while particles remain well anchored on the catalyst surface. This allowed to realize a cyclic dual-step process based on methane decomposition and catalyst oxygen regen- eration without deactivation of catalyst. Technological considerations have led to conclude that the implement of a process based on decomposition and regeneration of catalyst by oxidation requires the development of a robust catalytic system characterized by both a strong MSI and a well defined particle size distribution. In particular, the catalyst should be able to operate at high temperature, necessary to reach high methane conversion values (> 90%), avoiding at the same time the formation of both the carbon filaments with metal at tip or the encapsulating carbon which drastically deactivate the catalyst. Copyright ª 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction The catalytic decomposition of natural gas (CDNG) into hydrogen and carbon is drawing great interest since it appears to be a direct, mildly endothermic, attractive way for producing highly “pure” hydrogen with reduced CO 2 emis- sions. Although the CDNG reaction has been extensively studied in the last decades, the main technological drawbacks associated with catalyst lifetime or regeneration and separa- tion of carbon still remain unsolved. Several catalysts have already been investigated and Ni- based systems have attracted particular attention since they are active and stable under mild reaction conditions. On the other hand, unfortunately, their use has also met some draw- backs as the window of working temperature at which they are active is very narrow and moreover they are unstable during the oxidative treatment (burn-off with O 2 /air, gasification with H 2 O/CO 2 ) normally used for coke removal. Therefore, to over- come the problems encountered by using nickel as catalyst, the doping with different promoters was proposed. NieMgeAl [1], NieCu [2,3], NieCueFe [4] catalysts were prepared and tested under different reaction conditions. Even if the promoters contribute to improve the Ni stability by lowering its cracking activity, the detachment of active particles from carrier * Corresponding author. Tel.: þ39 090624233; fax: þ39 090624247. E-mail address: francesco.frusteri@itae.cnr.it (F. Frusteri). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 16367 e16374 0360-3199/$ e see front matter Copyright ª 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2012.02.192