Hydrogen production in membrane reactors using Rh catalysts on binary supports Carlos Carrara a , Alejandro Roa a , Laura Cornaglia a, * , Eduardo A. Lombardo a , Cecilia Mateos-Pedrero b , Patricio Ruiz b a Instituto de Investigaciones en Cata ´lisis y Petroquı ´mica (FIQ, UNL-CONICET), Sgo del Estero 2829-3000 Santa Fe, Argentina b Unite ´ de Catalyse et Chimie des Mate ´riaux Divise ´s, Universite ´ Catholique de Louvain, Place Croix du Sud 2/17, 1348 Louvain-la Neuve, Belgium Available online 24 January 2008 Abstract The binary supports employed in this work were prepared by different methods. The Ti(7%)–MgO and the Ti(13%)–SiO 2 were obtained using the grafting technique. The La(27%)–SiO 2 was obtained through the incipient wetness impregnation with La(NO 3 ) 3 of Aerosil 300, previously calcined at 1173 K. The Rh was incorporated to these supports by wet impregnation. The catalysts were first evaluated for the CH 4 + CO 2 reaction in a fixed-bed reactor. They were found to be active and stable as to justify their use in the membrane reactor, which was operated at 823 K achieving methane conversions up to twice as much as the equilibrium values. In all cases, the activity of the Rh solids remained constant after 120 h on stream with very little formation of carbonaceous residues only detected through LRS. The catalysts were characterized through either hydrogen or carbon monoxide chemisorption, TPR, XRD, LRS and XPS. The Rh(0.6)/La–SiO 2 catalyst showed a high metal dispersion that remained constant after use and the highest capacity to restore the CH 4 + CO 2 equilibrium when H 2 was permeated out of the reaction section. The Rh(0.8)/Ti–MgO showed the highest Rh/oxide interaction associated with the lowest capacity to restore the reaction equilibrium. The Rh(0.8)/Ti– SiO 2 exhibited an intermediate activity due in part to the partial segregation of the TiO 2 upon calcinations and the subsequent appearance of small Rh8 crystallites in the used catalysts. # 2007 Elsevier B.V. All rights reserved. Keywords: Dry reforming; Methane; Ti–MgO; Ti–SiO 2 ; La–SiO 2 1. Introduction In previous papers, it was shown that Rh-containing catalysts can be used to obtain ultrapure hydrogen through the CH 4 + CO 2 reaction using membrane reactors [1,2]. For this application the catalyst should be active and stable at ca. 823 K with no carbon formation. In the case of Rh/La 2 O 3 the stability of this active catalyst is due to the strong interaction between the metal and the oxide. Besides, the very low amount of carbon deposited on this catalyst is due to the presence of oxycarbonates that remove most of the carbon formed from methane decomposition [1,3]. The use of mixed supports for this type of catalysts is very attractive in view of the good results obtained for the partial oxidation of methane with TiO 2 –MgO and TiO 2 –SiO 2 [4]. In the same vein, Vidal et al. [5] reported values of up to 100% dispersion for Rh supported on La 2 O 3 –SiO 2 . Different types of materials have been used in membrane reactors to obtain hydrogen, among them silica modified alumina [6] and thin palladium films [7]. In previous studies, we reported [1,2] that both hydrogen production and methane conversion could be greatly improved by removing the H 2 formed using a stable and 100% selective Pd–Ag dense 50 mm thick membrane. In this work, Ti–MgO, Ti–SiO 2 and La–SiO 2 were used as Rh supports. In the first two cases the surfaces of both oxides were modified by grafting Ti on them. In the latter case, the lanthanum salt was impregnated on the oxide. Hydrogen and CO chemisorption, TPR, XRD, LRS and XPS were used to www.elsevier.com/locate/cattod Available online at www.sciencedirect.com Catalysis Today 133–135 (2008) 344–350 * Corresponding author. E-mail address: lmcornag@fiqus.unl.edu.ar (L. Cornaglia). 0920-5861/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cattod.2007.12.016