Abstract:

Xylene isomer are crucial chemical intermediates, but traditional production methods and yield increasing strategies result in significant differences in isomer content. The content of para-xylene (PX) can be changed from the thermodynamic equilibrium (about 23.8%) to more than 90%, which poses a great challenge for low-carbon and efficient separation strategies. Addressing variations in isomer content from different process sources, this paper focuses on the separation efficiency, energy consumption, and techno-economic feasibility of three separation strategies such as simulated moving bed (SMB) adsorption, cryogenic crystallization and reactive distillation. As the PX content in xylene isomers increases to over 90% from thermodynamic equilibrium compositions, the energy consumption, equipment costs, and utility requirements of the SMB adsorption process significantly increase, leading to decreased economic viability. Conversely, reactive distillation and cryogenic crystallization processes exhibit opposite trends. SMB adsorption demonstrates significant techno-economic feasibility when PX content is low, whereas reactive distillation achieves higher separation efficiency at higher PX contents. Cryogenic crystallization shows lower energy consumption and superior techno-economic performance when PX content ranges among 45.49%—72.57%.

Key words: xylene isomer, simulated moving bed adsorption, cryogenic crystallization, reactive distillation, technical-economic evaluation

摘要：

二甲苯异构体是重要的化工中间体产品，但传统生产方法和增产技术获得的异构体含量差异较大，对二甲苯（PX）的含量可由热力学平衡组成（约23.8%）上升至90%以上，对低碳高效的分离策略提出了巨大挑战。针对不同工艺来源二甲苯异构体含量差异，重点探究模拟移动床吸附、深冷结晶、反应精馏3种分离策略的分离效率、能耗和技术经济性，对3种分离策略的关键因素进行灵敏度分析。结果表明，当异构体中PX含量由热力学平衡组成增加至90%以上时，模拟移动床分离效率先降低后增加，过程能耗、设备成本和公用工程都在显著增加，经济性逐渐变差；而反应精馏和结晶分离的分离效率逐渐升高，能耗降低、经济性增加。当二甲苯异构体中PX含量较低时，模拟移动床具有显著的技术经济性；PX含量较高时，反应精馏分离效率较高；当PX含量位于45.49%~72.57%时，结晶分离工艺具有较低的能耗和较优的技术经济性。

关键词: 二甲苯异构体, 模拟移动床吸附, 深冷结晶, 反应精馏, 技术经济评价