Hydrogen production by the steam reforming of ethanol over K-promoted Co/Al2O3–CaO xerogel catalysts

Abstract A series of K-promoted cobalt catalysts supported on Al2O3–CaO xerogel supports with different K loading (Co–xK/Al2O3–CaO, x = 0, 5, 10, and 15 wt.%, at fixed Co loading of 15 wt.%) were prepared to apply for ethanol steam reforming (ESR). K-promoted catalysts showed higher hydrogen yield and lower methane selectivity than did unpromoted catalyst. The promotion effect of K was investigated using various analyses, such as N2 adsorption–desorption, X-ray Diffraction (XRD), H2–Temperature-Programmed Reduction (H2–TPR), X-ray Photoelectron Spectroscopy (XPS), and Temperature-Programmed Surface Reaction (TPSR). Also, the catalysts were applied to methanation reaction, which is the main undesired reaction. It was found that lower methane selectivity during ESR over K-promoted catalysts was explained by the suppression effect of K on the methanation reaction. Also, TPSR study revealed that after K doping, starting temperature of the ESR shifted to lower temperature. However, excess amount of K doping blocked small pores of the alumina–calcium support, resulting in deterioration of the textural property of the catalysts. In addition, XPS analysis showed that as the amount of K doping increased, amount of surface concentration of cobalt decreased. Therefore, 10 wt.% K was found to be optimum loading for the ESR.