Carbon dioxide reforming of methane over La 2 NiO 4 as catalyst precursor—Characterization of carbon deposition Germa ´n Sierra Gallego a,b , Fanor Mondrago ´n b , Jean-Michel Tatiboue ¨t a , Joe ¨l Barrault a , Catherine Batiot-Dupeyrat a, * a Laboratoire de Catalyse en Chimie Organique, UMR CNRS 6503, Universite ´ de Poitiers, Ecole Supe ´rieure d’Inge ´nieurs de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex, France b Institute of Chemistry, University of Antioquia, A.A. 1226, Medellı ´n, Colombia Available online 1 February 2008 Abstract La 2 NiO 4 -type perovskites were prepared by the ‘‘self-combustion’’ method and were used as catalyst precursor for the CO 2 reforming of CH 4 reaction at 700 8C. The catalysts were used in reduced and non-reduced form. High CH 4 and CO 2 conversions were obtained with a H 2 /CO ratio lower than 1. This result was explained by the occurrence of the RWGS (reverse water gas shift) reaction. The reduction of the perovskite La 2 NiO 4 leads to the formation of small nickel particles (average diameter: 7 nm), consequently the catalytic activity is higher than that obtained with 5% Ni/La 2 O 3 (average diameter: 11 nm). The use of the perovskite La 2 NiO 4 without reductive treatment prior to the reaction shows that the catalyst is composed of a mixture of Ni, La 2 O 2 CO 3 and La 2 NiO 4 during the first hours of the reaction. The catalytic activity is thus lower than that obtained with the reduced perovskite. The reaction performed using the non-reduced perovskite is accompanied by carbon deposition. TEM and Raman analysis showed that multiwalled carbon nanotubes are formed under those experimental conditions. # 2007 Elsevier B.V. All rights reserved. Keywords: CO 2 reforming of CH 4 ; Perovskite La 2 NiO 4 ; Auto combustion method 1. Introduction In recent years, the carbon dioxide reforming of methane process has received considerable attention from both academic and industrial sectors. This reaction converts the cheapest carbon containing gases (CH 4 and CO 2 ) in synthesis gas with aH 2 /CO ratio of 1. This process is particularly interesting environmentally when gas fields contain a significant amount of methane and carbon dioxide, both gases being undesirable greenhouse gases. The low H 2 /CO ratio is preferentially used for the production of liquid hydrocarbons in the Fischer– Tropsch synthesis and for the production of formaldehyde and polycarbonates [1,2]. Because of the high endothermicity of the reaction, the process can be used in energy transfer from solar energy to chemical energy, in energy storage in the form of CO and H 2 and chemical energy transmission systems (CETS) [3]. The main drawbacks of the process are: (1) requirement of temperatures as high as 800 8C for high conversions and (2) catalyst deactivation due to carbon deposition. The two main reasons for coke formation are: methane decomposition (reaction (7)) and the Boudouard reaction (reaction (6)). The first reaction is favored at high temperatures and low pressures, whereas the second one is favored at low temperatures and high pressures. The carbon dioxide reforming of methane is accompanied by some side reactions [4]: CH 4 þ CO 2 , 2CO þ 2H 2 ðcarbon dioxide reformingÞ (1) H 2 þ CO 2 , CO þ H 2 O ðreverse water gas shiftÞ (2) CO 2 þ 4H 2 , CH 4 þ 2H 2 O ðCO 2 methanationÞ (3) CO þ 3H 2 , CH 4 þ H 2 O ðCO methanationÞ (4) CH 4 þ 2H 2 O , CO þ 3H 2 ðsteam reformingÞ (5) www.elsevier.com/locate/cattod Available online at www.sciencedirect.com Catalysis Today 133–135 (2008) 200–209 * Corresponding author. Tel.: +33 549453540. E-mail address: catherine.batiot.dupeyrat@univ-poitiers.fr (C. Batiot-Dupeyrat). 0920-5861/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cattod.2007.12.075