甲醇-乙二醇及乙醇-乙二醇脱水制乙二醇醚反应体系的非均相热力学对比OA

In response to the overcapacity of bulk chemicals such as ethylene glycol,methanol,and ethanol in the coal chemical industry,the development of high-value-added ethylene glycol ether products has emerged as an important technological pathway.Due to the differences in molecular structure and physicochemical properties between methanol and ethanol,the thermodynamic behaviors of their dehydration reactions with ethylene glycol may vary,which in turn affects the product distribution and the selection of process conditions.To reveal the intrinsic differences in the two reaction systems,a systematic heterogeneous thermodynamic calculation was conducted for the methanol-ethylene glycol and ethanol-ethylene glycol dehydration systems based on the Gibbs free energy minimization principle.The UNIFAC activity coefficient model was employed to correct for liquid-phase non-ideality,and the genetic algorithm was utilized for global optimization.The effects of operating parameters on the equilibrium conversion rate,product selectivity,and phase equilibrium composition of the two reaction systems were investigated under the conditions of 100 mol of ethylene glycol feed,temperatures ranging from 20 to 300 ℃,pressures from 0.1 to 0.7 MPa,and the feed molar ratio of methanol or ethanol to ethylene glycol ranging from 1∶1 to 7∶1.The results show that there are significant differences in the heterogeneous temperature ranges of the two systems.At 0.3 MPa and a feed molar ratio of 4∶1,the heterogeneous temperature range of the methanol-ethylene glycol system is 50～110℃(low starting point,wide range),while that of the ethanol-ethylene glycol system is 100～120℃(high starting point,narrow range).Pressure mainly exerts an indirect influence on reaction equilibrium by affecting the temperature range of phase transitions,and it has a negligible effect on equilibrium conversions rate and product selectivities.With the increase of the feed molar ratio,both systems mainly produce diethers,the selectivities of ethylene glycol dimethyl ether and ethylene glycol diethyl ether continuously increase and approach 100%.