费托合成反应体系的热力学计算与分析

利用Benson基团贡献法和ABWY法估算了费托合成产物的标准生成焓、标准熵和摩尔定压热容,对费托合成反应体系的热力学性质进行了详尽的计算,得到不同反应温度下的反应焓、吉布斯自由能以及反应平衡常数等热力学性质。分析了不同反应步骤的热力平衡与限度,对反应生成烷烃、烯烃、含氧有机化合物的热力学可能性与生成顺序进行了判断,考察了温度和H2与CO摩尔比对合成气平衡转化率的影响。结果表明:费托合成反应是放热反应,低温时大部分反应在热力学上都能够自发地进行,并运行到很高的程度;高温时(大于635 K)生成烷烃、烯烃、醇及酸的大部分反应在热力学上不能自发进行;随着温度的升高,平衡转化率降低,随着H2与CO摩尔比的增大,平衡转化率升高;且所获的热力学数据对费托合成工艺研究及相关催化剂研发等具有重要的参考价值。

Thermodynamic calculation and analysis of Fischer-Tropsch synthesis system

By using Benson group contribution method and ABWY method,the standard enthalpy of formation,standard entropy and isobaric molar heat capacity of Fischer-Tropsch(F-T) synthesis products were estimated.The enthalpy change,Gibbs free energy change and equilibrium constant of F-T synthesis reaction system were calculated in detail as a function of temperature.The thermodynamic equilibrium and the limit of different reaction steps were analyzed.The thermodynamic feasibility and formation sequence of alkane,alkene,and oxygen-containing organic compounds were judged.The effects of temperature and mole ratio of H2 to CO on the equilibrium conversion were investigated.The results show that F-T synthesis is an exothermic reaction;most F-T synthesis reactions are spontaneous at low temperature and can reach to a deep extent,while most reactions generating alkane,alkene,alcohol and acid can not go along spontaneously at high temperature(more than 635 K).The equilibrium conversion increases with the increase of mole ratio of H2 to CO,and decreases with the increase of temperature.The thermodynamic data obtained have important reference value to the study of F-T synthesis process and catalyst development.