MOSSBAUER STUDY OF Fe-Cu-K CATALYST FOR FISCHER-TROPSCH SYNTHESIS

摘要

Mossbauer spectroscopy (MES) has been used to study the characteristics of iron catalysts pretreated in different ways for Fischer-Tropsch (F-T) synthesis. The Mossbauer spectrum results showed that the fine particle of α-Fe_2O_3 is the main phase of oxide catalyst. Catalysts pretreated in H_2:CO ratio of 2.1 syngas at 250℃ and under 0.5 MPa with the gas hourly space velocity of 1500 h~(-1) for 32 h in a fixed-bed reactor resulted in the reduction of 91% of iron to Fe_3O_4, FeO and χ-Fe_5C_2. The χ-Fe_5C_2 content of reacted catalyst increased greatly as compared with reduced catalyst, while FeO and Fe_3O_4 contents decreased. The Fe_3O_4 content of catalyst poisoned by oxygen increased as compared with reduced catalyst. FeS_2 is the main phase of catalyst poisoned at high COS concentration, while FeS is the main phase of catalyst poisoned by COS at low concentration. The Fe_3O_4 content decreased with the increase of sulfur fed to catalyst. The deactivation rate is related to the composition of the catalyst treated in concentrations.