253 1. INTRODUCTION Ethanol possesses diverse advantages over the derived hydrocar- bons from fossil sources: it is a renewable source and neutral with respect to emissions of CO 2 , it is less toxic; it can be more easily stored and without handling risk and it can be obtained in large quantities from biomass; in comparison with methanol and the gasoline[1-2]. In order to produce hydrogen and its potential use in fuel cells, it has been proposed the bio-ethanol as a renewable source using the catalytic steam reforming. The reaction of ethanol with steam is strongly endothermic and it only produces H 2 and CO 2 if the ethanol reacts in the most desir- able way. However, other undesirable products as CO and CH 4 are also formed during the reaction [1]. Other reactions occur such as dehydrogenation of ethanol to CH 3 CHO, dehydration to CH 2 =CH 2 , decomposition to CO and CH 4 or CO 2 , CH 4 and H 2 . The CH 3 CHO and the CH 2 =CH 2 are intermediary products that could be formed during the reaction at relatively low temperatures before the for- mation of H 2 and CO 2 and finally the formation of coke in the surface of the catalyst. In this type of reaction, the production of CO and CO 2 is very low, since the reaction produce hydrogen [3-4]. An energetic analysis has shown that only the 30% of total energy is required to produce hydrogen using the ethanol steam reforming [5]. Hydrotalcites are materials consisting of positively charged two- dimensional sheets with water and exchangeable charge- compensation anions in the interlayer region. The nature of both the layer cations and the interlayer anions can be changed and when it occurs, the compounds are known as hydrotalcite-like compounds. They have the general molecular formula [M 1-x 2+ M x 3+ (OH) 2 ] x+ (A x/n n- ) mH 2 O where: M 2+ and M 3+ are divalent and trivalent metal cations in the brucite-type layers respectively, A n- is the interlayer charge-compensating n-valent anion, x is the molar ratio of M III /(M II + M III ) and can take values from 0.1 to 0.5 and m is the water of crystallization [6]. We have studied the hy- drotalcites because they have a high surface area, a good basic site distribution, and a memory effect [7-9]. The addition of W to hy- drotalcite is interesting because the addition of this metal to Pt/Al 2 O 3 catalysts has shown a high stability [10]. Besides this, the *To whom correspondence should be addressed: Email: jlcl@correo.azc.uam.mx Phone: 53189065 ext 116 , fax 53947378 Tungsten Effect Over Co-hydrotalcite Catalysts to Produce Hydrogen from Bio-ethanol J.L. Contreras 1,* , M.A. Ortiz 1 , G.A. Fuentes 2 , R. Luna 1 , J. Salmones 3 , B. Zeifert 3 , L. Nuno 1 and A.Vazquez 4 1 Universidad Autónoma Metropolitana-Azcapozalco Depto. de Energía, CBI, Av. Sn.Pablo 180 Col.Reynosa, Azcapotzalco C.P.02200 México D.F., México. 2 Universidad Autónoma Metropolitana-Iztapalapa, Depto. de IPH, CBI,México, D.F., México 3 Instituto Politécnico Nacional, ESIQIE,Unidad Prof. ALM, México, D. F., 07738, México 4 Instituto Mexicano del Petróleo, Eje Central 152, México, D.F.México. Received: November 10, 2009, Accepted: February 04, 2010 Abstract: A great stabilization effect of tungsten over the Co-hydrotalcite catalysts to produce H 2 from ethanol in steam reforming was found. The catalysts were characterized by N 2 physisorption (BET area), X-ray diffraction, Infrared ,Raman and UV-vis spectroscopies. Catalytic evaluations were performed in a fixed bed reactor using a water/ethanol mol ratio of 4, at 450°C, and the W concentration stud- ied was from 0.5 to 3 wt%. As W concentration increases, the intensity of crystalline reflections of the Co-hydrotalcite catalysts decreases. There were found porous with the shape of parallel layers with a monomodal mesoporous distribution. Superficial chemical groups as: - OH, H 2 O, Al-OH, Mg-OH, W-O-W and CO 3 2- were found by infrared spectroscopy. Catalyst with low amounts of W (1%) showed both, the highest H 2 production and the best catalytic stability. The smallest pore volume of this catalyst could be related with long residence times of ethanol in the pores. Tungsten promoted the conversion for the Co-hydrotalcite catalysts. The reaction products were: H 2 , CO 2, CH 3 CHO, CH 4 and C 2 H 4 and the catalysts did not produce CO. Keywords: Hydrogen, Pt, WOx,Co-Hydrotalcite, Ethanol Journal of New Materials for Electrochemical Systems 13, 253-259 (2010) © J. New Mat. Electrochem. Systems