Effects of La addition to Ni/Al 2 O 3 catalysts on rates and carbon deposition during steam reforming of n-dodecane Masanori Sugisawa a , Kazuhiro Takanabe a , Makoto Harada b,c , Jun Kubota a , Kazunari Domen a, ⁎ a Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan b INPEX Corporation, 5-3-1 Akasaka, Minato-ku, Tokyo 107-6332, Japan c Department of Chemistry, Nagaoka University of Technology, 1603-1 Kamitomioka-cho, Nagaoka, Niigata 940-2188, Japan abstract article info Article history: Received 22 June 2010 Received in revised form 14 August 2010 Accepted 26 August 2010 Keywords: n-dodecane Steam reforming Hydrogen Ni catalyst Lanthanum Steam reforming of n-dodecane on La–Ni/γ-Al 2 O 3 catalysts was investigated at a relatively low temperature (773 K) to elucidate the catalytic behavior at the inlet of a practical reformer. The addition of lanthanum to the Ni/γ-Al 2 O 3 formulation completely suppressed carbon deposition, which otherwise occurs to a significant extent on unmodified Ni/γ-Al 2 O 3 . Modification with La also enhanced the initial turnover rates of hydrogen formation. The La–Ni/γ-Al 2 O 3 catalysts, however, deactivated with increased time-on-stream at a high steam-to-carbon ratio of 3.5, because of oxidation of the active Ni metal. Reduction at 873 K almost fully regenerated the catalytic activity, indicating that the deactivation was not primarily a result of sintering or carbon deposition, but was due to the oxidation of active Ni metal. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Hydrogen production is one of the most important technologies for the chemical industry, power generation, and fuel cell applications. Fuel cell systems have been commercialized, and some currently use easily- transportable hydrocarbons, such as propane and kerosene, as fuels [1]. Kerosene is a liquid at ambient temperature, which is beneficial for its handling and transportation, and is widely used in residential areas as a heating fuel. Kerosene is therefore a promising candidate source for on- site hydrogen production in a residential fuel cell system. Kerosene is composed of saturated hydrocarbons with typical carbon numbers between 6 and 16. Catalytic steam reforming of kerosene is an attractive method for hydrogen production [2–7], especially in residential fuel cell systems. However, because of its high carbon number, deposition of carbon species on the catalyst surface causes deactivation of the catalysts and plugging of the reactor, which must be completely avoided. Thermal decomposition of kerosene at high temperatures leads directly to carbonaceous deposits (pyrolytic carbon) and to the formation of olefins, which then become an additional source of carbon deposits (whisker or polymeric carbon) [1,8]. In large-scale industrial hydrogen production, an adiabatic pre- reformer is used to convert higher hydrocarbons at lower temperatures (700–800 K) [8]. However, in fuel cell systems, a single reformer is preferred, in order to avoid the use of multiple reactors. It is thus required that the inlet of the reformer is maintained at a relatively low temperature (typically ~773 K) to avoid thermal decomposition of the hydrocarbons. After scission of C–C bonds to generate C 1 compounds (CH 4 , CO, and CO 2 ), the temperature is shifted higher (~1000 K) in later parts of the reformer to convert the remaining CH 4 for a higher H 2 yield. Noble metals, such as ruthenium [3] and rhodium [7], have been reported to exhibit high activity and stability in the steam reforming of kerosene. With respect to the cost and availability of most noble metals, the use of these catalysts in large-scale commercial applica- tions involves economic limitations. Ni-based catalysts are thus preferred due to their low cost [4–6]. Nickel is a well-known active metal, used in industry for steam reforming of methane and pre- reforming of naphtha [1,8]. However, Ni-based catalysts are more prone to coking than noble metal catalysts [1]. Many studies have focused on suppressing carbon deposition during reforming. It has been suggested that carbon deposition can be suppressed when the metal is supported on a metal oxide with a strong Lewis basicity [8–10], which increases the ability of the catalyst to chemisorb oxidants (H 2 O and CO 2 ). Several commercial reforming catalysts therefore contain alkaline earth metal oxides, such as MgO or CaO [10,11]. Although some reports have claimed that a strong interaction between Ni and an oxidic support results in a high tolerance to carbon formation during reforming [7–9,12], the reactions of metallic nickel with MgO or Al 2 O 3 to form NiMgO 2 or NiAl 2 O 4 are known to lead to deactivation [1]. It has been reported that the addition of lanthanum species onto Ni-based catalysts can effectively improve the activity and stability in the steam reforming of kerosene [4,5], but no information on carbon Fuel Processing Technology 92 (2011) 21–25 ⁎ Corresponding author. E-mail address: domen@chemsys.t.u-tokyo.ac.jp (K. Domen). 0378-3820/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.fuproc.2010.08.014 Contents lists available at ScienceDirect Fuel Processing Technology journal homepage: www.elsevier.com/locate/fuproc