YSZ monoliths promoted with Co as catalysts for the production of H2 by steam reforming of ethanol

Abstract

Steam reforming of ethanol was investigated between 400°C and 600°C over 3mol% Y2O3 doped ZrO2 monolith infiltrated with Co, known as an effective catalyst for this reaction. Monoliths were fabricated by implementing the freeze-casting technique in order to obtain hierarchical, vertical and highly ordered porous microstructure resulting in very low pressure drop, high surface area and accessibility to active sites. Catalytic monoliths were firstly loaded with 3wt% of Co. Catalytic activity of Co-containing monolith was compared with the catalytic activity of a powdered material with the same chemical composition than the catalytic monolith. The results show a clear improvement all over the temperature range of the ethanol conversion and H2 yield and a decrease of the by-products contents when using a freeze-cast monolith support. The incorporation of La enabled a strong decrease in coke deposition over the activated monolith. The effect of the addition of 0.25wt.% of Pt was also studied. Pt makes possible to inhibit carbon deposition but has a detrimental effect on ethanol conversion at temperatures above 500°C and on H2 selectivity at low temperature. A higher Pt loading of 0.8wt% did not bring any beneficial effect and was even detrimental at low temperature. Finally, the beneficial effect of the implementation of freeze-cast monolith in comparison with the not structured fixed-bed configuration is explained by the difference of packing since and improved fluid dynamics at similar GHSV, the former one promotes in a higher proportion the Water Gas Shift Reaction (WGSR) further in the monolith length.