New Insights into the Role of the Synthesis Procedure on the Performance of Co-Based Catalysts for Ethanol Steam Reforming

Co/SiO₂ catalysts with two Co contents of 10 and 30 mol% were prepared and used in ethanol steam reforming. With the aim of tailoring the materials features by varying the synthesis parameters, two different sol–gel procedures were designed, namely a modified hydrolytic alkoxide sol–gel synthesis and a (non-ionic) surfactant assisted one. Effect of the synthesis procedure on the physico-chemical properties of the prepared catalysts is in the focus of the present investigation. The obtained Co/SiO₂ catalysts were characterized by means of X-rays powder diffraction, diffuse reflectance UV–Vis spectroscopy, N₂ adsorption/desorption isotherms at − 196 °C, field emission scanning electron microscopy equipped with energy dispersive X-ray probe, temperature-programmed reduction and CO adsorption at nominal − 196 °C as followed by IR spectroscopy. The oxidation state of Co species within the SiO₂ matrix was affected by the synthesis method. In particular, the non-ionic surfactant, acting both as pores template and as chelating agent of Co ions during the synthesis, prevented the formation of Co₃O₄ phase leading to a higher dispersion and higher temperature reducibility of Co species with respect to samples with same Co content synthesized without surfactant. The fine balance between Co dispersion and reducibility was the fundamental parameter governing the activity of the Co/SiO₂ catalysts in terms of H₂ production, CO/CO₂ ratio and C balance during ethanol steam reforming.