甲醇制烯烃体系的热力学计算与分析

Calculation and Analysis of Thermodynamics of Methanol to Olefins

根据甲醇制烯烃(MTO)的反应机理,建立了包括10个主副反应的热力学模型。采用四参数法对MTO反应进行热力学计算,得到各反应的焓变、吉布斯自由能变和平衡常数随温度的变化规律。利用Aspen Plus软件对MTO反应的热力学体系进行了模拟,并从热力学角度研究了温度、压力和水含量对MTO反应平衡组成的影响。实验结果表明,MTO的大多数反应为强放热反应,且各反应均能自发进行;四参数法的计算值与Aspen Plus模拟值吻合良好;温度对反应平衡组成的影响最大,高温有利于低碳烯烃的生成,可以通过控制温度调节乙烯与丙烯的产出比;压力和水含量对平衡组成的影响不大,增加压力和水含量均不利于低碳烯烃的生成。

Thermodynamic models for 10 reactions in methanol to olefins（MTO） was established based on the reaction mechanisms. The thermodynamic calculation for the MTO process was carried out by the four parameters method, and the relationships of the enthalpy changes, Gibbs free energy changes and equilibrium constant changes with temperature were obtained. The thermodynamics of the MTO process were also studied by means of the Aspen Plus software. The effects of temperature, pressure and water content on the reactions were investigated according to the thermodynamic calculation. It was showed that most of the reactions in the MTO process were strong exothermic reactions and all the reactions could occur spontaneously. The results calculated by the four parameters method was in accordance with the results simulated by the Aspen Plus software. High temperature is beneficial to the formation of light olefins and the ratio of ethylene to propylene in the products can be adjusted by controlling the temperature. The pressure and water content have less effect on the reactions than that of temperature. High pressure and high water content are unfavourable to the formation of light olefins.