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

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

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。

The effect of carburization and reduction degree on H 2O 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 H 2O oxidation behaviour of iron carbides was investigated simultaneously.Based on these observations,the influence of typical promoters like K and SiO 2 on the structure and H 2O oxidation behaviour of Fe-based FTS catalysts was further studied.The results indicated that,for the iron catalyst,the stability of iron carbides against H 2O oxidation was increased with the increase of iron carbides content,and the H 2O 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 H 2O oxidation ultimately.It was also found that promotion of SiO 2 greatly degraded the carburization degree of the catalyst,while their tendency to be oxidized to form Fe 3O 4 in the H 2O atmosphere was obviously hindered.