Decomposition of Ethanol Over Ni-Al Catalysts: Effect of Copper Addition

A series of Ni-Al hydrotalcite-type samples modified with copper was prepared and evaluated for use in the decomposition of ethanol. The partial substitution of Ni by Cu has small influence on the specific surface area and on the structure (XRD). However, it has a strong influence on the degree of reducibility (shifts to lower temperatures) and on the selectivity of reaction. The selectivity towards H2 and CO increases for reactions conducted at a higher temperature, which is followed by a decrease in the amount of carbon formed. Catalysts with a high Cu content exhibit lower selectivity for H2 and CO. SEM images show that carbon nanotubes with greater and more variable diameters and lengths were formed by Cu-loaded catalysts, possibly due to the sintering of copper. Nevertheless, the Raman spectra suggest that the nanotubes produced by the Cu-containing samples have higher purities and fewer defects.