Diffusion Behavior of Synthesis Gas

The apparent activation energies were 23 kcal/mol for the gas phase reaction, 21 kcal/mol for the supercritical phase reaction and 17 kcal/mol for the liquid phase reaction. These results lead to the conclusion that the mass transfer efficiency in the supercritical phase reaction is higher than that in the liquid-phase reaction and is close to that in the gas phase reaction. 

The lower catalytic activity and the smaller apparent activation energy in the liquid phase reaction should be attributed to the lower rate of synthesis gas diffusion inside the catalyst particles compared to the rate of the surface reaction, because the activation energy of diffusion should be smaller than intrinsic reaction activation energy. As a result, the reactant concentrations inside the catalyst particles were so low that the effectiveness factor of the catalyst dropped. 

---