(600cl) The Effects of Catalysts Pore Structure on Intraparticle Diffusion in Cobalt-based Fischer-Tropsch Synthesis

Intraparticle diffusion in Fischer-Tropsch synthesis not only decreases the overall efficiency, but also changes the reaction behaviors via affecting syngas diffusion, olefin’s second reactions and so on. Due to the capillary effect, the Fischer-Tropsch catalysts pores are always filled with liquid products under steady-state conditions. Always，the process is supposed to depend on the characteristics of molecular diffusion in liquid^[1-2]. According to Fick law, intraparticle diffusion rate and . In that case, pore structure is closely related to the diffusion, embodying by particle porosity ε and tortuosity factor τ. We prepared two kinds of ZrO₂-supported catalysts, whose reaction behaviors were similar, but greatly different in pore network, especially in structure regularity. Based the relationship between pore structure and surface fractal dimensions, we compared quantitatively the differences in the catalysts pore network via considering coordination number Z, which characterizes particle pore network connectivity. Then, the effects of catalysts pore structure on intraparticle diffusion and following Fischer-Tropsch synthesis reaction behaviors were revealed from a new perspective.

For Fischer-Tropsch synthesis, the results showed the more porous, the worse connectivity, the gap between D_e and D_A should be narrower. The smaller Z, pore network connectivity would be worse. However, its variation effects would be limited when the Z absolute value was high. The calculation also indicated that Z scarcely varied with the pore structure regularity. Considering high Z is common for porous materials, it might not be a good idea to improve the mass-transfer by adjusting the pore structure in the case of certain porosity, especially increasing the pore regularity.

Keywords: Fischer-Tropsch synthesis, Intraparticle diffusion, Pore structure

Reference：

[1] M. F. M. Post, A. C. Hoog.VAN'T, J. K. Minderhoud et al,  AIChE Journal, 1989, 35(7):1107-1114.

[2] E. Iglesia, Applied Catalysis A: General, 1997, 161(1-2):59-78.

Supported by:

(1) Strategic Priority Research Program, Chinese Academy of Sciences, Grant No. XDA07070700

(2) National Natural Science Foundation of China, Grant No. 21273265