Tungsten effect over co-hydrotalcite catalysts to produce hydrogen from bio-ethanol

A great stabilization effect of tungsten over the Co-hydrotalcite catalysts to produce H2 from ethanol in steam reforming was found. The catalysts were characterized by N₂ 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 studied 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 ₂O, Al-OH, Mg-OH, W-O-W and CO₃ 2- were found by infrared spectroscopy. Catalyst with low amounts of W (1%) showed both, the highest H2 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: H₂, CO₂, CH₃CHO, CH₄ and C2H4 and the catalysts did not produce CO.