邻甲氧基环己醇液相脱氢制备愈创木酚的热力学分析

Thermodynamic analysis of liquid phase dehydrogenation of 2-methoxycyclohexanol to guaiacol

采用Benson基团贡献法计算了邻甲氧基环己醇和愈创木酚的标准摩尔生成焓、标准摩尔熵和摩尔等压热容,确定了反应焓变、吉布斯自由能变和平衡常数与温度的函数式;利用UNIFAC基团贡献模型建立了邻甲氧基环己醇-愈创木酚-水三元体系液相活度系数关联式;考察了氢分压、温度及水醇比对脱氢平衡转化率的影响。实验结果表明,对邻甲氧基环己醇催化脱氢制备愈创木酚的液相反应体系,随温度的升高,平衡常数逐渐增大,在温度低于458 K时,平衡常数远小于1;降低氢分压、增加水醇比均可提高反应的平衡转化率。为邻甲氧基环己醇脱氢制备愈创木酚反应过程研究及生产工艺开发提供了理论依据。

The standard molar enthalpies of formation, standard molar entropies and molar heat capacities of 2-methoxycyclohexanol and guaiacol were calculated based on the Benson group contribution method, and the enthalpy changes, Gibbs free energy changes and equilibrium constants of the liquid phase dehydrogenation reaction of 2-methoxycyclohexanol to guaiacol were obtained as functions of temperature. The liquid phase activity coefficients of the 2-methoxycyclohexanol- guaiacol-water system were predicted by means of the UNIFAC group contribution model. The effects of hydrogen partial pressure, temperature and molar ratio of water to 2-methoxycyclohexanol on the reaction equilibrium conversion were investigated. The results showed that the equilibrium constants of the dehydrogenation reaction increased with temperature rise and was far less than 1 below 458 K. It was indicated that decreasing the hydrogen partial pressure and increasing the molar ratio of water to 2-methoxycyclohexanol could improve the reaction equilibrium conversion.