Effect of solvent in the sol-gel synthesis of layered double hydroxides as catalysts for the ethanol steam reforming reaction

Full text: Production of H₂ from ethanol has been stimulated by the search for renewable sources to replace fossil fuels. The ethanol steam reforming (ESR) reaction stands out because it allows to high conversion rates. The use of layered double hydroxides (LDH) in heterogeneous catalysis allows the choice of cations according to the final application, as well as its low cost and facility to obtain [1]. The sol-gel route provides a wide variety of LDH systems with hierarchical structure of macro and mesopores, facilitating the mass transport and the exposure of the catalytic sites. In this work, the influence of solvent (ethanol/glycerol) in the synthesis of the Ni(0,3)Cu(0,15)Al(1,0)/Cl type LDH and its catalytic efficiency in the ESR reaction were evaluated. X-ray diffraction results showed the 003 and 006 characteristic peaks of LDH formation, and a basal distance of 7.8 Å. Scattering electron microscopy images showed the materials presented a rough surface before the ESR due to the presence of LDH platelets, while after this reaction, the images show carbon filaments accumulated on transition metal catalysts such as Ni and Cu. The broad band between 1500-1200 cm-1 in the infrared spectra characterizes the presence of glycerol [2]. In summary, the ethanol conversion rate, from mass spectroscopy during ESR, is higher for LDH prepared without glycerol, as expected due to its higher surface area and pore volume determined by N2 adsorption/desorption isotherms. (author)