Effect of cobalt loading on reducibility, dispersion and crystallite size Co/Al2O3Fischer-Tropsch catalyst①
来源期刊:中南大学学报(英文版)2004年第4期
论文作者:熊海峰 张煜华 李金林 古映莹
文章页码:414 - 418
Key words:Fischer-Tropsch synthesis; cobalt/alumina catalyst; temperature programmed reduction; hydrogen temperature programmed desorption
Abstract: Co/Al2O3 Fischer-Tropsch synthesis catalysts with different cobalt loadings were prepared using incipient wetness impregnation method. The effects of cobalt loading on the properties of catalysts were studied by means of X-ray diffraction (XRD), temperature programmed reduction (TPR), hydrogen temperature programmed desorption (H2-TPD) and O2 titration. Co-support compound formation can be detected in catalyst system by XRD. For the Co/Al2O3 catalysts with low cobalt loading, Co/Al2O4 phase appears visibly. Two different reduction regions can be presented for Co/Al2O3 catalysts, which belong to Co3O4 crystallites (reduction at 320℃) and cobalt oxide-alumina interaction species (reduction at above 400℃). Increasing Co loading results in the increase of Co3O4 crystallite size. The reduced Co/Al2O3catalysts have two adsorption sites, and cobalt loading greatly influences the adsorption behavior. With the increase of cobalt loading, the amount of low temperature adsorption is increased, the amount of high temperature adsorption is decreased, and the percentage reduction and cobalt crystallite size are increased.