Fischer-Tropsch synthesis (FTS) was carried out with an industrial iron-based catalyst (100Fe/5Cu/6K/16SiO2,by weight) at the baseline conditions in a continuous stirred tank slurry reactor (CSTR).The impact of activation pressure on the catalyst bulk compositions and on the long-term (>500 h) activity and selectivity of the catalyst was investigated.It was found that the BET surface area of the catalyst decreases with the increase of reduction pressure.The iron phase compositions,textural properties,and FTS performances of the catalysts were strongly dependent on pretreatment pressure.The high reduction pressure clearly retards the carburization.MES results indicated that the content of the iron carbides clearly decreases with the increase of reduction pressure,especially for the reduction pressure increasing from 1.0 MPa pressure to 1.5 MPa pressure,and the reverse trend is observed for superparamagnetic Fe3+ (spm).The higher amount of CO2 in tail gas results in the higher content of Fe3+ (spm) when the catalyst is reduced at higher pressure.The catalyst activity decreases with the increase of reduction pressure.The high quantity of iron carbides is the necessary for high FTS to be obtained.However,the activity of the catalyst activating in syngas can not be predicted solely from the fraction of the carbides,and the phase equilibrium of oxidation-reduction of the iron phases may be responsible for FTS activity when the total of carbides reaches the required level.With the increase of the reduction pressure,the product distribution shifted towards440the higher molecular weight products.It is concluded that activation with syngas at the lower pressure was the most desirable on the catalyst activity and stability.