二甲氧基甲烷合成反应的热力学分析

Thermodynamic analysis of dimethoxymethane synthesis reaction

用Benson基团贡献法估算了二甲氧基甲烷的标准摩尔生成焓ΔfHmθ、标准摩尔熵Smθ和摩尔等压热容Cp,m,计算了缩醛化合成二甲氧基甲烷的标准摩尔焓变ΔrHmθ、吉布斯自由能变ΔrGmθ以及反应平衡常数K与温度T的关联式;用UNIFAC基团贡献模型关联甲醛-甲醇-水-二甲氧基甲烷四元体系液相活度系数。考察了反应温度T以及原料醇醛物质的量比M对甲醛平衡转化率Xe的影响,并与实验数据比较。本热力学分析为二甲氧基甲烷合成的实验研究及生产工艺优化提供了理论指导,并为后续聚甲氧基二甲醚的研究开发奠定了基础。

The standard enthalpy of formation, entropy and heat capacity of dimethoxymethane were calculated by using Benson group contribution method. The mole enthalpy changes, the Gibbs free energies and the equilibrium constants of the reaction of dimethoxymethane synthesis from methanol and formaldehyde were calculated as a function of temperature. The liquid activity coefficients of formaldehyde-methanol-water-dimethoxymethane system were predicted with UNIFAC group contribution model. The effects of temperature and the formaldehyde/methanol mole ratio on formaldehyde equilibrium conversion were studied as well, and the results were compared with the experimental data. The results provided a thermodynamic basis for the synthesis of dimethoxymethane and laid a solid foundation for study of polyoxymethylene dimethyl ethers.