SMAI法制备的Co/SiO2催化剂及La3+促进Co/SiO2催化剂的比较

实验证明,钴基催化剂是非常有效的F-T合成催化剂. 由于钴基催化剂对形成长链烷烃具有高活性和高选择性,故它尤其适用于天然气间接转换为液态燃料和蜡的过程1～5]. F-T合成用钴基催化剂由四个主要成分组成: 主金属(Co)、第二过渡金属、氧化物助剂(碱金属、稀土金属或过渡金属氧化物)及大比表面积氧化物载体(氧化硅或氧化铝)5]. La对钴基催化剂的促进效果因其被加入到催化剂前体中的方式和顺序以及载体的性质和金属钴的状态等参数的变化而有所不同. 为了评价La对Co/SiO2催化CO加氢作用的促进效果,本文对溶剂化金属原子浸渍法(SMAI)制备的Co/SiO2和Co/La-SiO2进行了对比研究. 在保持某些参数(如载体的性质和金属钴的价态等)不变的情况下,评价了La的助催化效果,取得了一些有益的结果.

Comparison between Co/SiO2 and Co/La-SiO2 Catalyst Samples Prepared via Solvated Metal Atom Impregnation Method

The solvated metal atom impregnation (SMAI) method was used to prepare Co/SiO 2 and Co/La SiO 2 catalyst samples with 5%Co content. The XPS results showed that the cobalt particles both in SiO 2 and in La SiO 2 existed in zero valent state (Co\+0). The CO chemisorption results showed that the cobalt particle size (5 3 nm) of Co/La SiO 2 sample was much smaller than that (8 1 nm) of Co/SiO 2 sample. The turnover frequency (TOF) of CO on Co/La SiO 2 sample was higher than that on Co/SiO 2 sample in F T reaction (CO hydrogenation), which was probably due to the fact that the cobalt particle size in Co/La SiO 2 sample was much smaller than that in Co/SiO 2 sample. The experimental results also showed that the selectivity of Co/La SiO 2 sample for long chain paraffins was higher than that of Co/SiO 2 sample.