Pore Diffusion in the Fischer–Tropsch Synthesis : Limitation or Advantage in Multi-Tubular Reactors?

The Fischer–Tropsch synthesis (FTS) is a highly exothermic reaction often conducted in multi-tubular fixed-bed reactors. Pore diffusion limitations within the catalyst particles are typically viewed as detrimental due to reduced reaction rates. However, this study demonstrates that these limitations can provide significant benefits in terms of reactor stability and performance. Using a 2D numerical reactor model, we explore the influence of pore diffusion on temperature profiles, conversion, and thermal runaway behavior under realistic operating conditions. Results reveal that pore diffusion reduces the apparent activation energy, effectively mitigating thermal sensitivity and increasing the allowable level of reaction temperature. Consequently, higher CO conversions can be achieved safely compared to an idealized scenario without pore diffusion limitations. Hence, pore diffusion limitations, rather than being a disadvantage, act as a stabilizing factor in FTS reactors.