Comparison of ethanol steam reforming using Co and Ni catalysts supported on SBA-15 modified by Ca and Mg

• Mg- and Ca-modified Co/SBA-15 for ethanol steam reforming as novel application.
• Mg and Ca in Co/SBA-15 promote metal properties in greater degree than in Ni/SBA-15.
• Mg- and Ca-promoted Co/SBA-15 need high temperatures (> 700 °C) to be H2-reduced.
• Better catalytic behavior of promoted Ni catalysts than Ni/SBA-15 sample at 700 °C.
• Ni/Ca/SBA-15 keeps 100 % conversion and H2 selectivity > 88 mol% for 50 h at 700 °C.

Cobalt catalysts supported on SBA-15 and modified by Mg and Ca incorporation were tested in the steam reforming of ethanol as a novel application and compared to analogous nickel catalysts. The prepared materials were characterized by N2 physisorption, ICP-AES, XDR, H2-TPR and TGA. Tests on ethanol steam reforming were performed at 600 and 700 °C, using high space velocity. Incorporation of both Mg and Ca promotes the metal dispersion and the interaction between metallic species and the modified SBA-15 support, but this effect is significantly more pronounced in the case of the Co catalysts. As a consequence, Mg- and Ca-promoted Co samples needed higher temperatures to be reduced and were not able to maintain enough active Co0 species under reaction conditions to convert C2 intermediate compounds. Thus, these modified Co catalysts lead to lower ethanol conversion and hydrogen selectivity than a Co/SBA-15 catalyst. Meanwhile, Mg- and Ca-promoted Ni catalysts have intermediate reduction temperatures and achieve higher hydrogen production than a Ni/SBA-15 sample at 700 °C. In this sense, the best catalytic results were obtained with the Ni/Ca/SBA-15 catalyst (complete ethanol conversion and 90.8 mol% of hydrogen selectivity), which was stable for 50 h. Coke formation is also diminished by Ca and Mg addition, but while for Co catalysts this effect is more evident using Mg, in the case of Ni samples, the highest coke formation reduction is achieved by Ca addition. Again, the Ni/Ca/SBA-15 sample obtained the lowest carbon deposition, despite the general tendency of Co samples to form less coke.

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