Abstract:

Crude propylene oxide (PO) produced from propylene epoxidation contains contaminations such as acetaldehyde, methanol, methyl formate, water and so on. It is difficult to remove them by using simple distillation because the relative volatilities of these components to PO are close to 1. Meanwhile, the PO is easy to react with water and 1,2-propanediol (PG) that will affect the extractive efficiency is then produced. Therefore, a process flowsheet combined extractive distillation and liquid-liquid extraction is proposed here to effectively remove these contaminations and improve PO product yield, in which the PO hydrolysis reaction (non-catalytic reactive distillation) and the processes of water washing for PO recover and side-drawing for the removal of PG are considered. The whole process is then simulated by using process simulation software Aspen Plus, in which the NRTL thermodynamic model is employed to character the thermodynamic properties. The effects of major design parameters of the separation process, such as the solvent ratio, the theoretical stage number of extractive distillation column, the location of feed, and the temperature of solvent, are investigated. The results show that the process is reasonable, reliable, and economical superior to existing processes, which can guide industrial process design and operation optimization.

Key words: propyleneoxide, extractive distillation, azeotrope, separation, optimal design

摘要：

丙烯环氧化反应获得的粗环氧丙烷(PO)中含有乙醛、甲醇、甲酸甲酯和水等杂质，由于这些杂质与PO相对挥发度接近于1，普通精馏难以提纯PO；同时，分离过程中PO易发生水解生成1,2-丙二醇(PG)，而PG又导致萃取剂萃取性能下降。据此，结合萃取精馏和液液萃取技术，同时考虑PO水解反应，开发了水洗回收PO和侧线采出共沸物脱除PG流程，在有效脱除杂质的同时，提高了PO的回收率和萃取剂的萃取效率，获得了高纯度PO产品。采用流程模拟软件Aspen Plus对上述流程进行了全流程模拟计算，借助NRTL热力学方法，分析了萃取精馏塔的溶剂比、理论塔板数、原料进料位置、溶剂进料温度等主要工艺参数对分离过程的影响。结果表明该工艺流程合理、可靠，经济性优于现有工艺，可指导工业过程设计和操作优化。

关键词: 环氧丙烷, 萃取精馏, 共沸混合物, 分离, 优化设计