基于热力学计算的CO_(2)催化加氢制二甲醚流程分析

Process analysis of catalytic hydrogenation of CO_(2) to dimethyl ether based on thermodynamic calculation

二甲醚是一种理想的发动机清洁燃料,在碳中和背景下,国内外积极开展了以二氧化碳(CO_(2))为原料制备二甲醚的研究。CO_(2)催化加氢制二甲醚的方法主要包括一步法和两步法,对基于不同方法的工艺流程展开热力学分析,可为工艺流程优化和相关催化剂开发提供参考。基于一步法构建了流程一,基于两步法分别构建了流程二(以甲醇为中间体)和流程三(以CO为中间体),在原料气组成为n(H_(2)):n(CO_(2))=3:1的条件下,对反应温度(150~350℃)与反应压力(1.0~9.0 MPa)对各流程中相应的平衡常数、CO_(2)平衡转化率和二甲醚收率的影响进行了研究。结果表明,在150℃、9.0 MPa下,与其他两种流程相比,流程一更具优势,其CO_(2)平衡转化率为94.61%,二甲醚收率为85.31%。对于以CO为中间体的两步法工艺,未来需加强高效逆水煤气低温催化剂的开发。对于一步法工艺,将反应体系与分离体系进行耦合的复合体系是未来主要的研究方向。

Dimethyl ether is an ideal engine clean fuel.Under the background of carbon neutrality,the preparation of dimethyl ether from CO_(2) has been actively carried out at home and abroad.The methods of catalytic hydrogenation of CO_(2) to dimethyl ether mainly include one-step and two-step method.The thermodynamic analysis of the processes based on different methods can provide reference for process optimization and related catalyst development.Process one was constructed based on the one-step method,and process two(with methanol as the intermediate)and process three(with CO as the intermediate)were respectively constructed based on the two-step method.Under the condition that the composition of raw gas is n(H_(2)):n(CO_(2))=3:1,the effects of reaction temperatures(from 150℃to 350℃)and reaction pressures(from 1.0 MPa to 9.0 MPa)on the corresponding equilibrium constants,CO_(2) equilibrium conversion rates and dimethyl ether yields in each process were studied.The results show that at 150℃and 9.0 MPa,the process one is superior to the other two processes,with CO_(2) equilibrium conversion rate of 94.61%and dimethyl ether yield of 85.31%.For the two-step method process with CO as the intermediate,the development of high efficiency reverse water gas low temperature catalyst should be strengthened in the future.For the one-step method process,the composite system coupling reaction system and separation system is the main research direction in the future.