合成气在超临界流体及F-T重质烃中的扩散行为研究

A Study on Diffusion of Syngas in Supercritical Fluid and in Heavy Paraffinic F-T Products

对CO和H2 在 4 83K、3.5MPa条件下 ,在充满F T合成产物 (平均相对分子质量 4 0 0 )或超临界正戊烷的催化剂微孔内的扩散速率、孔内气体浓度分布以及催化剂的内表面利用率进行了模拟计算 .结果表明合成气在F T产物中的扩散速率比超临界介质中低很多 ,从而造成了气相反应中从催化剂孔口到孔内显著的合成气浓度梯度及催化剂内表面利用率的下降 ,从理论上解释了超临界条件下CO转化率和烃收率优于气相反应的原因 .

Diffusion coefficients of H 2 and CO in the catalyst pores filled with either supercritical n pentane or heavy paraffinic Fischer Tropsch products (mean relative molecular mass,400) at 483 K and 3.5 MPa,gas concentration profiles within catalyst pores and the inner surface effectiveness factor of the catalyst were simulated and calculated.It was found that diffusion of CO and H 2 in F T products was significantly slower than in supercritical fluid which led to a marked gradient of syngas concentration inside the catalyst pores and to a decrease in effectiveness factor for gas phase reaction at which catalyst pores are filled with F T products.The calculated results gave a satisfactory explanation for the superior F T reaction behavior in supercritical phase to that in gas phase.