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已往的工作指出,顆粒熔鉄催化剂在合成过程中活性有随时間下降的現象,认为主要是由于腊液堵塞孔隙的关系,应用成型方法构成大孔,能够有利于腊液的流出,延緩了活性下降的时間,但当腊液堵滿孔隙时,活性下降的水平仍与未成型的顆粒催化剂相近。本文根据活性方面的数据,进行了宏观动力学的分析,由动力学計算再次指明:当腊液未堵塞孔隙吋,合成反应是化学反应控制,此时表面有效利用系数达0.98(空速1000,CO轉化90％以上)。而当腊液堵塞孔隙后,轉为液相扩散控制,对362-1大顆粒催化剂言,此时表面有效利用系数为0.082,并求得气体通过液柱的扩散系数为2.4×10~(-5)厘米~2/秒。在扩散控制的情况下,由动力学分析指明,能影响活性水平的主要是Deff、Ks、Sg。有效扩散系数Deff在液相扩散情况下的改变是不大的,增大孔径并不能提高扩散控制时的活性水平。因此,孔径的增大在合成烃情况下仅起延緩腊液的积聚作用,而不能提高終活性的水平。由动力学分析指出,沉淀剂由于有大的表面积(較熔鉄剂大数倍以至数十倍),因此,可能适用于高速固定床操作而不須进行再生。实驗也驗証了这个看法。
Previous work has pointed out that the activity of granular melts catalyst in the synthesis process decreased over time, that is mainly due to blocking the pores of the wax, the application of molding methods constitute a large hole, can be conducive to the flow of wax liquid, delaying the activity Decline time, but when the wax block pore, the level of activity decline is still similar to the unformed pellet catalyst. Based on the data of activity, macroscopical kinetic analysis was carried out. According to the kinetic calculation, it was pointed out again that the synthetic reaction was controlled by chemical reaction when the wax liquid did not block the pores, and the effective utilization coefficient of the surface reached 0.98 (space velocity 1000, CO conversion of more than 90%). When the wax blocked the pore, the liquid diffusion control was changed. For the 362-1 large particle catalyst, the surface effective utilization coefficient was 0.082 and the diffusion coefficient of the gas through the liquid column was 2.4 × 10 ~ (- 5) cm ~ 2 / sec. In the case of diffusion control, as indicated by the kinetic analysis, Deff, Ks, Sg, which can influence the activity level, are mainly. The effective diffusion coefficient Deff does not change much in the case of liquid phase diffusion. Increasing the pore size does not improve the activity level during diffusion control. Therefore, an increase in pore size in the case of synthetic hydrocarbons only retards the accumulation of waxy fluid without increasing the level of viability. Kinetic analysis indicates that precipitants may be suitable for high-speed, fixed-bed operation without regeneration due to their large surface area (many times their number of units and tens of magnifications). Experiments also verify this view.