助剂对铁基费托合成催化剂氧化行为的影响:H2O作用的解读

以纯Fe催化剂为研究对象,采用XRD、Raman和TPH等手段考察了催化剂的碳化程度、还原程度对H_2O氧化过程的影响,获得了H_2O氧化过程与催化剂中碳物种转变之间的相互影响规律;系统考察了典型的费托合成助剂K和SiO_2存在时对催化剂物化性质以及H_2O氧化行为的影响,发现催化剂的碳化程度越高,碳化铁的抗H_2O氧化能力越强,氧化过程使得碳物种的石墨化程度增加。适量K助剂可促进碳化铁和催化剂表面石墨碳的形成,提高了碳化铁在H_2O氧化过程中的稳定性;SiO_2助剂的加入显著抑制了催化剂的碳化,但可有效提高碳化铁以及碳物种的稳定性。

Effect of the promoters on oxidation behavior of Fe-based Fischer-Tropsch catalyst: Deciphering the role of H2O

The effect of carburization and reduction degree on H₂O oxidation behaviour for the iron carbides in Fe-based FTS catalyst were firstly investigated using a combination method including X-ray diffraction (XRD), Raman and temperature-programmed-hydrogenation (TPH). The relationship between carbon species transformation and H₂O oxidation behaviour of iron carbides was investigated simultaneously. Based on these observations, the influence of typical promoters like K and SiO₂ on the structure and H₂O oxidation behaviour of Fe-based FTS catalysts was further studied. The results indicated that, for the iron catalyst, the stability of iron carbides against H₂O oxidation was increased with the increase of iron carbides content, and the H₂O oxidation process led to the formation of more graphitic carbon. The carburization ability was effectively enhanced when certain amount of K promoter was incorporated. Addition of K into Fe-based FTS catalyst increased the number of graphitic carbons, which increased the stability of iron carbides toward H₂O oxidation ultimately. It was also found that promotion of SiO₂ greatly degraded the carburization degree of the catalyst, while their tendency to be oxidized to form Fe₃O₄ in the H₂O atmosphere was obviously hindered.