酯交换法合成碳酸二甲酯反应热力学研究

Study on the Thermodynamics of Synthesizing Dimethyl Carbonate by Transesterification

以甲醇钠为催化剂,实验测定了碳酸丙烯酯与甲醇酯交换合成碳酸二甲酯(DMC)的反应平衡数据,采用最小二乘法,分别拟合得到了25℃、35℃、45℃和55℃下的平衡常数K和反应Gibbs自由能,并利用Van’t Hoff方程式求得恒压下反应焓变和⊿rS值。结果反应焓变为⊿rH=-32.324kJ/mol,表明酯交换反应为一弱放热反应,提高温度不利于提高酯交换反应的平衡转化率。

With using CH3ONa as catalyst, the thermodynamic data of dimethyl carbonate synthesis by transesterification of propylene carbonate with methanol were measured experimentally. The reaction equilibrium constants K and the Gibbs reaction free energies rG at 25℃, 35℃, 45℃ and 55℃ were correlated respectively by the least square method. The reaction enthalpy △rH and △rS at different temperature were calculated according to the Van＇t Hoff Equation. The results showed that △rH=-32.324 kJ/mol, which indicated that the trmasesterification was a weak exothermic reaction, therefore increasing reaction temperature was unfavorable for the enhancement of the equilibrium conversion.