工业Fe-Mn催化剂上基于详细反应机理的F-T合成动力学模型 Ⅱ. 不同校正方法的动力学模型分析

 通过平衡闪蒸模拟催化剂孔道液体组成、烯烃物理吸附和虚拟烯烃分压等方法,考察了化学反应以外的非本征因素对F-T合成动力学模型的校正. 平衡闪蒸模拟催化剂孔道中烯烃组成的校正计算结果表明,在烯烃浓度出现峰值前,溶解度效应对烯烃再吸附及参与二次反应起主导作用,而在烯烃浓度出现峰值后,烯烃的扩散和物理吸附等效应可能起主导作用. 分析烯烃添加的反应器模拟结果发现,考虑烯烃物理吸附作用的动力学模型校正方法不能够正确反映烯烃添加实验的定性规律,而虚拟烯烃分压校正方法能够正确反映烃分布规律并可定量预测烯烃添加对产物分布规律的影响,这对需要尾气循环的F-T合成工业操作具有重要意义.

Detailed Kinetics Model of Fischer-Tropsch Synthesis over an Industrial Fe-Mn Catalyst Ⅱ. Kinetics Model Analysis Regressed by Different Correction Methods

A detailed kinetics model for Fischer-Tropsch synthesis (FTS) in which the bulk effect is not included cannot predict the deviation of hydrocarbons from the ASF distribution and the decrease in olefin/paraffin ratio with increasing carbon number. In this paper three methods were used to correct the FTS kinetics model: the flash distillation of the FTS products to simulate the liquid composition in the catalyst pores, the olefin physisorption and the fictitious olefin pressure. The kinetics calculation results regressed by the correction of the FTS product flash distillation show that the solubility effect dominates the olefin readsorption and secondary reactions before the maximum of the olefin molar fraction in the catalyst pores, and the olefin diffusion and physisorption effects become significant after the maximum of the olefin molar fraction. The reactor simulation of the olefin addition indicates that the method regressed by the olefin physisorption cannot predict the reasonable product distribution, while the method regressed by the fictitious olefin pressure can predict the product distribution well. Therefore, the latter method is a promising way to quantitatively predict the olefin addition effect on the product distribution, which is very important for the industrial operation where the reaction tail gas recycle is needed.