Effects of reduction conditions on fused iron catalyst for high temperature Fischer-Tropsch synthesis

In order to investigate the phase change of fused iron catalyst during the reduction process and its effect on the performance in high temperature Fischer-Tropsch reaction, the catalyst was characterized by SEM, EDS, BET and in-situ XRD. The performance of Fischer-Tropsch reaction was evaluated in a fixed-bed reactor under 340℃, 2.4MPa, and H2/CO=3.8, similar to industrial conditions. The effects of different heating processes, hydrogen partial pressure, reduction space velocity and reduction time on the phase structure, crystal size and reduction degree of the fused iron catalysts were analyzed. The results showed that the initial heating rate was quite significant. When the initial heating rate was over 2.4℃/min, reduction rate was too fast, and the α -Fe grains grown and agglomerated rapidly. The influence of hydrogen partial pressure on the reduction degree was not monotonical, and the change trend of reduction degree is the same when it is >70%.α-Fe was more stable at low hydrogen partial pressure, which, under 40%H2/Ar, increased only by 1nm within 40h. The high reduction space velocity of 10000h-1 made the catalyst surface pore distribution and pore size more uniform, and the reduction efficiency and limit reduction degree higher. The low reduction space velocity 1000—2000h-1 gave the reduction catalyst stable surface/bulk structure, more stable crystal size and higher reaction activity. After reduced at 420℃ to the limiting reduction degree, the α-Fe continued to grow slowly with the increase of reduction time. The suitable reduction conditions were obtained as: reduction heating rate in between 0.4℃/min(200—350℃)—0.8℃/min(-1, and reduction time less than 30h. © 2022 Chemical Industry Press. All rights reserved.