Abstract: The thermodynamic model for the initial activation reaction of n-heptane before and after adding methanol is established according to the reaction mechanism of methanol activating n-alkanes. The enthalpy change, Gibbs free energy change, and equilibrium constant of each reaction at different temperatures are calculated using the five-parameter method. The thermodynamic system of methanol coupled n-heptane catalytic pyrolysis reaction is simulated using Aspen Plus software, and the effects of methanol addition amount, temperature, and pressure on the equilibrium composition of the coupled reaction are studied. The calculation results show that: compared with the initial activation cracking reaction of n-heptane, the methanol activation of n-heptane reaction has lower energy consumption, the heat absorption is about 15 kJ/mol, and the reaction is irreversible. Adding an appropriate amount of methanol is beneficial to improve the equilibrium yield of olefins. When the molar ratio of methanol to n-heptane is 1:1, the equilibrium yield of propylene is increased by about 15 percentage points. Compared with alkane products, the changes of temperature and pressure have a greater effect on the equilibrium composition of olefin products. The equilibrium yield of propylene has a maximum value with temperature changes, and low pressure is conducive to the formation of propylene.

Key words: font-family:-apple-system, blinkmacsystemfont, ", font-size:14px, background-color:#FFFFFF, ">methanol, n-heptane, catalytic pyrolysis, Gibbs free energy, equilibrium constant, reaction conversion, olefin products, equilibrium yield

摘要： 根据甲醇活化正构烷烃反应机理，建立了添加甲醇前后正庚烷初始活化反应热力学模型。采用五参数法计算了不同温度下各反应的反应焓变、吉布斯自由能变和反应平衡常数。利用Aspen Plus软件对甲醇耦合正庚烷催化裂解反应的热力学体系进行了模拟，探讨了甲醇添加量、反应温度和压力对耦合反应平衡组成的影响。计算结果表明：相比于正庚烷初始活化裂解反应，甲醇活化正庚烷反应的能耗较低，吸热量约为１５ｋＪ／ｍｏｌ，且反应不可逆；添加适量甲醇有利于提高烯烃的平衡收率，当甲醇和正庚烷摩尔比为１∶１时，丙烯的平衡收率提高约１５百分点；相比于烷烃产物，温度、压力的变化对烯烃产物平衡组成影响较大，丙烯平衡收率随温度的变化存在最大值，且低压有利于丙烯的生成。

关键词: font-family:-apple-system, blinkmacsystemfont, ", font-size:14px, background-color:#FFFFFF, ">甲醇, 正庚烷, 催化裂解, 吉布斯自由能, 平衡常数, 反应转化率, 烯烃产物, 平衡收率