Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/ijhydene Ni–Mg and Ni–Cu–Mg catalysts for simultaneous production of hydrogen and carbon nanofibers The effect of calcination temperature R. Moliner a , Y. Echegoyen a , I. Suelves a,Ã , M.J. La ´ zaro a , J.M. Palacios b a Instituto de Carboquı´mica, CSIC, Miguel Luesma 4, 50018 Zaragoza, Spain b Instituto de Cata ´ lisis y Petroleoquı ´mica, CSIC, Campus UAM, Cantoblanco, 28049 Madrid, Spain article info Article history: Received 9 November 2007 Received in revised form 14 January 2008 Accepted 15 January 2008 Available online 4 March 2008 Keywords: TCD Hydrogen production Ni–Mg catalysts Calcination temperature abstract In this paper, we studied the thermocatalytic decomposition of methane using NiMg and NiCuMg catalysts prepared by fusion of the corresponding nitrates in a fixed-bed reactor. The effects of calcination temperature (450, 600, 800 and 1000 1C) and the effect of copper on the hydrogen yields, as well as the properties of both the catalyst before and after use and the deposited carbon, were studied. In all cases, NiCuMg catalysts showed a high and almost constant hydrogen production yield without signs of catalyst deactivation after 8 h on-stream. The performance of NiMg catalysts without Cu became highly influenced by the calcination temperature used. At calcination temperatures higher than 600 1C, a solid solution NiO  MgO was apparently formed in high extension, leading to a fast catalyst deactivation. The structural properties of the obtained carbon nanofilaments were highly dependent on the presence of Cu and on the calcination temperature, as the presence of copper and low calcination temperatures promote the formation of a well-ordered graphitic carbon. Conversely, NiMg catalysts without Cu and, especially, high calcination temperatures enhanced the formation of a disordered turbostratic carbon. & 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. 1. Introduction The environmental pollution produced by the delivery of massive energy through the combustion of fossil fuels has made it necessary to develop new alternatives based on sustainable power carriers. Hydrogen, as an energy vector, is an attractive choice since it is a clean energy source that may be used either for feeding conventional or non-conventional engines, such as low-temperature fuel cells [1]. The production of high-purity hydrogen is extremely desir- able for its use in proton exchange membrane fuel cells (PEMFC) since its performance is highly affected by the presence of minor impurities, especially CO. Consequently, the thermal catalytic decomposition (TCD) of methane has recently received great attention as a process for the production of CO-free hydrogen [2–12]. Additionally, the methane decom- position (reaction 1) CH 4 ðgÞ! C ðsÞþ 2H 2 ðgÞ; DH 0 298 K ¼ 74:52 kJ=mol (1) is a single reaction occurring without other secondary reac- tions, and is slightly endothermic with no emissions of CO 2 to the atmosphere. Comparatively, it is a more environmentally benign process for hydrogen production than the conventional steam reforming of methane, which must be followed by other processes, such as CO shift reaction, CO 2 scrubbing and CO ARTICLE IN PRESS 0360-3199/$ - see front matter & 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2008.01.005 Ã Corresponding author. Tel.: +34 976733977; fax: +34 976733318. E-mail address: isuelves@icb.csic.es (I. Suelves). INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 33 (2008) 1719– 1728