Thermodynamics of Dimethyl Carbonate and Ethylene Carbonate Generation During the Conversion of Syngas to Ethylene Glycol

Despite recent progress in the coal-to-ethylene glycol (EG) technology, some indicators show that the obtained products are still different from those produced by the petroleum route method. Therefore, it is of great significance to improve the thermodynamic performance of the system to obtain an enhanced process technology. In this paper, thermodynamic data related to uncommon substances in coal-to-EG reactions were estimated using the Benson group contribution method, and the values of the reaction enthalpy, Gibbs free energy, and the equilibrium constant of each reaction in the system were calculated. We systematically analyzed the temperature influence on the main product, DMO (dimethyl oxalate), and the main by-product, DMC (dimethyl carbonate), in the DMO synthesis reaction and the influence of the DMC content on the spontaneous formation of EC (ethylene carbonate) in the DMO hydrogenation reaction. The obtained results demonstrated that elevated temperatures are favorable for the generation of DMC. In the DMO hydrogenation reaction, the mass fraction of DMC should be less than 0.05678 % when the feeding proportion is based on industrial data. When pure DMO is fed, the mass fraction of DMC should be less than 0.0335 %. Finally, no special treatment is required for EC separation in these cases.

Automated summary

Despite progress in coal-to-ethylene glycol technology, the obtained products differ from those produced by petroleum methods. Improving the thermodynamic performance of the system is important, and this study estimated thermodynamic data using the Benson group contribution method and calculated the values of reaction enthalpy, Gibbs free energy, and equilibrium constant in the system. Temperature was found to influence the production of dimethyl carbonate (DMC) in the dimethyl oxalate (DMO) synthesis reaction, and the DMC content affected the spontaneous formation of ethylene carbonate (EC) in the DMO hydrogenation reaction. The results showed that higher temperatures favored DMC generation, and certain limits on DMC content were identified.