CO_2加氢合成低碳烯烃反应热力学分析

Thermodynamics Analyses of Hydrogenation of Carbon Dioxide to Light Olefins

本文使用Gibbs自由能最小化法和熵最大化法对考虑催化剂效应下的CO_2加氢合成低碳烯烃反应进行了热力学分析,系统研究了反应温度、压力、进料气摩尔比和不同的化学和工业手段对平衡状态的影响。结果表明,CO_2加氢合成低碳烯烃符合"两步合成机制"的反应机理,CO_2平衡转化率随温度增大先减少后增大。向合成气中添加CO能提高烯烃的选择性,同时,与不考虑催化剂效应的结果不同,除去反应中生成的。H_2O可提高烯烃的选择性与产量。使用熵最大法对平衡温度的计算显示,反应压力不影响反应体系的平衡温度,但过高的进料气氢碳比会增加反应的放热量,适当增高进料气温度可在一定程度上降低平衡温度,防止反应器过热形成热点。

Gibbs free energy minimization method and entropy maximization method are used to conduct thermodynamic analyses of hydrogenation of C02 to light olefins with considering effect of catalyst in this paper. The effects of reaction temperature, pressure, feed gas mole ratio and different chemical and industrial approaches on equilibrium state are studied systematically. The results show that hydrogenation of C02 to light olefins accords with the two-step reaction mechanism and the equilibrium conversion rate of carbon dioxide increases at first and then decreases with temperature. The addition of CO into syngas can increase the selectivity of olefins. Unlike the results without considering the effect of the catalyst, the removal of water can increase the selectivity and yield of olefins. The results of the equilibrium temperature based on the entropy maximization method show that the equilibrium temperature is not affected by pressure, but excessive ratio of hydrogen to carbon dioxide can augment the heat released from reactions. Appropriate increase of the initial temperature of feed gas can decrease the equilibrium temperature to some extent, and prevent the formation of hot spots in the reactor.