Pretreatment Studies with a Precipitated Iron Catalyst for Fischer-Tropsch Synthesis Under Different Reaction Conditions

Fischer-Tropsch Synthesis (FTS) is a catalyzed chemical reaction in which synthesis gas (H₂ +CO) is converted to clean fuels and chemicals. Catalyst pretreatment is an important stage in FT synthesis, which consists of reducing the catalyst using appropriate reducing agent, such as H₂, CO or syngas.  Several papers have reported the effects of reducing agents on the catalytic performance under a fixed reaction condition.  However, only limited work has been done on the comparison of the catalyst activity and selectivity under different FT reaction conditions for the catalyst activated by H₂, CO and syngas. With the aim of investigating the effect of the reducing agents on the catalyst performance under different reaction conditions, three fixed bed reactors, each loaded with 1 gram of the same iron based catalyst, were set in parallel and simultaneously reduced with H₂, CO and syngas (CO/H₂) for 48 hrs at 250 °C, at atmospheric pressure and a flowrate of 60 (NTP)ml/min. After the reduction, the FT reactions were performed at 250 ^oC, pressures of 1, 10 and 20 bar (gauge) and flowrates of 15, 30 and 60 (NTP)ml/min for a total time on stream (TOS) of 1000-hrs.The experimental data demonstrated that the CO consumption rate increased with increasing the feed flowrate and the following trend was obtained: CO < Syngas < H₂ reduced catalyst. The results showed that the CO reduced catalyst produced more olefins followed by H₂ and lastly syngas reduced, which indicated that the CO could be used as a reducing agent in the process aimed at producing mainly olefinic products. More experimental results, such as the effect of pressure on the reactant consumption rate and product formation rate as well as paraffin to olefin ratios were also measured and compared.