草酸二乙酯和草酸二甲酯加氢反应热力学对比分析

Comparative Thermodynamic Analysis of Hydrogenations of Diethyl Oxalate and Dimethyl Oxalate

采用Benson基团贡献法、Constantinou—Gani法和Rihani—Dorasiwamy法计算了草酸二乙酯（DEO）、乙醇酸乙酯、草酸二甲酯（DMO）和乙醇酸甲酯等物质的标准生成焓、标准生成吉布斯自由能和摩尔定压热容。在473～513K和1．0～3．5MPa下，分别计算了DEO和DMO加氢反应的焓变、吉布斯自由能变和平衡常数。计算结果表明，除在低压高温条件下乙醇酸甲酯加氢生成乙二醇的反应为非自发反应外，DEO和DMO加氢都是自发进行的放热反应；低温高压有利于生成乙二醇；与DMO的加氢反应相比，DEO加氢反应具有更高的平衡常数。

Standard enthalpies of formation △Hf, standard Gibbs free energies of formation △fG298 and molar heat capacities at constant pressure Cρ m of diethyl oxalate （DEO）, ethyl glycolate, dimethyl oxalate（DMO） and methyl glycollate（MG） etc. , and further the enthalpy changes △rHT, Gibbs free energy changes ArGT and equilibrium constants Kp in hydrogenations of DEO and DMO under 473 - 513 K and 1.0 -3.5 MPa were calculated by different methods, including Benson group contribution method, Constantinou-Gani method and Rihani-Dorasiwamy method. The results show that the hydrogenations of DEO and DMO are spontaneous exothermic reactions, except for the production of ethylene glycol from MG, which is not spontaneous at low pressure and high temperature. Low temperature and high pressure are propitious to synthesis of ethylene glycol. Kp of DEO hydrogenation is higher than that of DMO hydrogenation.