Applied Catalysis B: Environmental 144 (2014) 846–854 Contents lists available at ScienceDirect Applied Catalysis B: Environmental jo ur nal home p ag e: www.elsevier.com/locate/apcatb Effect of gold on a NiLaO 3 perovskite catalyst for methane steam reforming S. Palma ∗ , L.F. Bobadilla, A. Corrales, S. Ivanova, F. Romero-Sarria, M.A. Centeno, J.A. Odriozola Departamento de Química Inorgánica e Instituto de Ciencia de Materiales de Sevilla, Av. Américo Vespucio, 49, 41092 Sevilla, Spain a r t i c l e i n f o Article history: Received 21 May 2013 Received in revised form 17 July 2013 Accepted 23 July 2013 Available online xxx Keywords: Au–Ni catalyst Steam reforming of methane Carbon nanotubes Surface alloy a b s t r a c t The effect of gold addition to a supported Ni SRM catalyst has been studied in this work in order to determine the influence of gold on both the amount and type of carbon species formed during the reaction. The structure of the support, a mixed La–Al perovskite, determines the catalyst reducibility and Ni particle size. Gold addition affects the metal particle size increasing metal dispersion on increasing the gold content. Therefore, although gold blocks step Ni sites, the more active sites for C H activation, and increases electron density on nickel, the higher dispersion results in an apparently higher activity upon gold addition. Moreover, gold addition increases the catalyst stability by decreasing the rate of growth of carbon nanotubes. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Crude oil and natural gas, according to 2010 data, account for the 57% of the total energy consumed in the world and 60% of the produced hydrogen comes from natural gas [1]. Apart from the large reserves, huge amounts of natural gas are present in a wide variety of sources that can be grouped as non-conventional gas, including natural gas confined in low-permeability geological deposits, associated gas, biogas produced by anaerobic digestion of residues and product gas a result of biomass and tar gasification. Recent trends in the use of syngas are forecast the conversion in compact GTL units of inexpensive remote natural gas into liquid fuels of easier storage and transportation [2–4]. The production of hydrogen or synthesis gas from methane by partial oxidation, dry reforming and steam-reforming processes are widely studied [1]. According to the stoichiometry of the reforming reaction, steam- reforming is the most advisable process to produce hydrogen rich currents from methane. The methane steam reforming (SRM) is strongly endothermic since the high stability of the CH 4 molecule. Thus, this process requires high temperatures and the use of cat- alysts to achieve high methane conversion at appreciable rates [5]. The active phase of the catalysts typically used contains noble metals (Rh, Ru, Pt, Pd and Ir), cobalt, nickel or iron. High activity and resistance to the formation of carbonaceous deposits are the ∗ Corresponding author. E-mail address: sandra.palma@icmse.csic.es (S. Palma). main advantages of noble metal containing catalysts [1], although the elevated price of these metals has led to the use of cost-effective nickel-based catalysts. The activity of the catalysts is related to the activation of the C H bond that is enhanced by small metallic nickel particles [5]. A successful strategy for the preparation of active SRM catalysts con- sists in using nanoparticles precursors with well-defined chemical structures such as perovskites, spinels, or hydrotalcites [6–8]. The reduction of these precursors results in well dispersed nickel parti- cles on an oxide support that usually shows high catalytic activity in reforming reactions, especially combined with oxygen gener- ators (e.g. rare earths: Ce, Pr or others), which allow controlled formation of nanoparticles, good catalytic behavior in the SRM reac- tion and stability of the catalyst under strong reaction conditions [9,10]. A major drawback, despite the good activity in the SRM of nickel- based catalysts, is the strong tendency of nickel to form surface coke. This may results in the total deactivation of the catalyst. Methane decomposition on the metal particle results in the for- mation of surface C species. The built-up of the carbonaceous layer continues until a critical concentration is reached, then carbon dif- fusion through the nickel particle or surface diffusion of carbon species starts driven by the carbon concentration gradient. This process results in the nucleation of carbon whiskers in the opposite side of the nickel particle. The time required to initiate the nuclea- tion of the carbon whiskers is named induction time. The limiting step of the whole process is diffusion. Therefore, the best strategy to obtain robust catalysts is to increase the induction time to the 0926-3373/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apcatb.2013.07.055