Applied Catalysis A: General 468 (2013) 250–259 Contents lists available at ScienceDirect Applied Catalysis A: General j ourna l h omepa ge: www.elsevier.com/locate/apcata Sol-derived AuNi/MgAl 2 O 4 catalysts: Formation, structure and activity in dry reforming of methane A. Horváth a,∗ , L. Guczi a,1 , A. Kocsonya a , G. Sáfrán b , V. La Parola c , L.F. Liotta c , G. Pantaleo c , A.M. Venezia c,∗ a Department of Surface Chemistry and Catalysis, Centre for Energy Research, HAS, P.O. Box 49, H-1525 Budapest, Hungary b Institute for Technical Physics and Materials Science, Research Centre for Natural Sciences, HAS, P.O. Box 49, H-1525 Budapest, Hungary c ISMN - CNR, Via Ugo la Malfa 153, Palermo I-90146, Italy a r t i c l e i n f o Article history: Received 13 May 2013 Received in revised form 27 August 2013 Accepted 30 August 2013 Available online 8 September 2013 Keywords: Dry reforming Methane Nickel catalysts MgAl2O4 support Gold effect a b s t r a c t Ni nanoparticles doped with different amount of gold were supported on MgAl 2 O 4 by deposition from aqueous metal sol producing a series of catalysts with different Au content. The sol procedure was allowed to obtain dispersed metal particles with different composition. The particle size and the particle compo- sition of the sol were maintained even after being deposited on the support. The catalysts, characterized by several techniques such as TPR, XPS, XRD, TEM, HRTEM and EELS at the different stages of their life exhibited significant structural modification. In particular, thermal treatments in reducing and oxidizing environment produced NiAu alloy phases and NiO surface segregation, respectively. When testing for methane dry reforming with CO 2 in temperature ramped reaction, the monometallic nickel catalyst was more active at lower temperature whereas the bimetallic catalysts were more active at higher temper- ature. The presence of gold slightly affected the CO/H 2 ratio due to the occurrence of parallel reactions such as the reverse water gas shift reaction (RWGS). Both types of catalysts, monometallic and bimetallic ones, deactivated a little with time but the degree of activity loss was not in straightforward relation with Au content due to the different effect of gold on the stability and on the amount of carbon formation. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Reforming of methane with CO 2 , known also as dry reforming (DRM), is a convenient and feasible process to produce synthesis gas and at the same time to remove two powerful greenhouse gases like CO 2 and CH 4 , from the environment [1–3]. As compared to the steam reforming of methane, producing syngas with a H 2 /CO ratio of 3, the DRM produces a synthesis gas with the H 2 /CO molar ratio close to unity, making it useful feed for the Fisher Tropsch syntheses to liquid hydrocarbons and for the syntheses of oxygenates [4]. The DRM reaction (1) is endothermic and requires high temperatures to attain good conversion levels. CH 4 + CO 2 → 2CO + 2H 2 , H ◦ 700 ◦ C = 258 kJ/mol (1) At high temperatures the following endothermic reactions (2) and (3) referred as decomposition of methane and reverse water gas shift (RWGS), respectively, are also favored. CH 4 → C + 2H 2 , H ◦ 700 ◦ C = 85 kJ/mol (2) ∗ Corresponding author. Tel.: +39 0916809372; fax: +39 0916809399. E-mail addresses: horvath.anita@energia.mta.hu (A. Horváth), venezia@pa.ismn.cnr.it (A.M. Venezia). 1 Prof. L. Guczi passed away on December 20th, 2012. CO 2 + H 2 → CO + H 2 O, H ◦ 700 ◦ C = 38 kJ/mol (3) For the dry reforming of methane, noble metals have been suc- cessfully used providing stable and active catalysts at the lowest as possible temperatures [5]. However, because of their high cost and low availability, most of the applications are based on the use of the group VIII transition metals [6]. Among these, Ni has been stud- ied extensively, being the most active, cheap and available metal [7–9]. However, its main drawback is represented by the produc- tion of significant amount of carbon and by the sintering at the high temperatures of the reaction. Carbon deposits are formed when the rate of methane dissociation is faster than the oxidation of carbon, occurring with the surface oxygen species arising from CO 2 disso- ciation on the metal component or from carbonates formed at the metal support interface. Both, the amount and the type of carbon deposited from methane decomposition during the dry reforming, would affect the activity/stability of the Ni based catalysts [9,10]. Researchers, through the use of several surface techniques have shown different types of carbon deposits such as, polymeric, fil- amentous, graphitic carbon and bulk nickel carbide [10–14]. The strategies adopted to decrease the carbon poisoning include the support formulation, the support morphology and the doping of the nickel catalysts with other elements such as alkali metals, sulfur and also gold. 0926-860X/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apcata.2013.08.053