Methane cracking using Ni supported on porous and non-porous alumina catalysts Ashraf M. Amin a , Eric Croiset b, *, Crystle Constantinou b , William Epling b a Chemical Engineering & Pilot Plant Department, National Research Centre, Dokki, Giza, Egypt b Chemical Engineering Department, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1 article info Article history: Received 29 July 2011 Received in revised form 23 January 2012 Accepted 1 February 2012 Available online 13 April 2012 Keywords: Hydrogen Methane cracking Nickel catalyst abstract Porous and non-porous alumina catalysts were used as nickel supports to catalyze methane cracking. Different operating parameters were studied in a thermal gravimetric analyzer, including methane and hydrogen partial pressures, temperature and flow rate. During CH 4 cracking, carbon builds up on the catalyst surface and therefore the catalyst requires periodic regeneration. Cycling tests were performed, using air during the regen- eration phase to burn off the carbon. The results showed that the non-porous catalyst performed better than the porous catalyst in terms of cracking during the first cycle. Full regeneration of the catalysts by oxidizing the deposited carbon was achieved at 550  C, while oxidation was very slow at 500  C. After full regeneration, the performance of the porous catalyst became considerably better than the non-porous. The porous catalyst kept its activity for 24 cracking/regeneration cycles, while the non-porous catalyst lost half of its activity by the second cracking cycle and almost all of its activity after six cycles. NiAl 2 O 4 formation and Ni sintering caused the non-porous catalyst activity loss. TPO results showed that two carbon types were deposited on the catalysts, namely Cb and Cg, where Cb is more active than Cg. Copyright ª 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Hydrogen is the most abundant element in the universe, but is not naturally available in its pure form. H 2 is widely used in industrial applications and is a promising fuel in the auto- motive sector, especially if PEM fuel cells penetrate this market. The annual global hydrogen consumption in 2006 was about 50 million tons, including industrial applications and merchant use [1e6]. The average annual increase in hydrogen demand was 4% from 1997 to 2006, and 9.5e10% for carbon monoxide free hydrogen from 1997 to 2006 [1]. Currently, hydrogen is mostly produced from hydrocarbon sources, and mainly from methane, which has the highest hydrogen/ carbon ratio of all hydrocarbons [7]. Steam reforming is widely used for producing hydrogen, but the CO produced is poisonous for many hydrogen-based catalytic applications [8e11]. Alternatively, methane catalytic cracking can produce a 90% concentrated stream of CO-free hydrogen, mixed with residual methane [12]. In addition to producing CO-free hydrogen, methane catalytic cracking produces a significant amount of carbon filaments, which have wide industrial applications, or which alternatively could be burned to provide the heat necessary for the cracking process [13e16]. Nickel is widely used as a catalyst for methane cracking due to its high activity [17e20]. But a persistent problem associated with methane cracking is a rapid catalyst * Corresponding author. E-mail address: ecroiset@uwaterloo.ca (E. Croiset). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 9038 e9048 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.2012.02.001