离子液体－近/超临界CO2双相分离噻吩类硫的实验及分子模拟研究

Supercritical CO2 fluids extraction using cosolvents is an important technique in the field of supercritical separation. Supercritical CO2 fluids with room temperature ionic liquids as cosolvents have potential applications on removing thiophene and its derivatives from oils. To design and prepare the sub/supercritical fluids which can separate thiophene and its derivatives, the main obstacle focus on how to select a specific function cosolvent. However, there are two important problems on using supercritical CO2 fluids with ionic liquids to separate thiophene and its derivatives: 1. For a great variety of ionic liquids, there are a lack of theoretical guidance and practical difficulties how to select an appropriate ionic liquid which has high solubility and selectivity to thiophene and its derivatives; 2. It is particularly important to insight the separation mechanism applying the molecular level theories to investigate interaction relationship between thiophene derivatives, ionic liquid cosolvents and liquid phases. This project uses the experimental combining multiscale theories to study the thermodynamic properties of thiophene and its derivatives in the sub/supercritical systems, so that we can obtain the fundamental principles between sulfur compounds, the ionic liquid co-solvents and fluid phases. We will intensely expore the nature of ionic liquids and micro-chemical surroundings of the guest molecules distributions in the fluid phase to achieve the quantitative relationship between these factors and solubility of sulfur compounds. We expect to provide a theoretical basis of molecular level on designing and preparation of sub/supercritical CO2 with ionic liquid cosolvents for separation of thiophene and its derivatives.

添加共溶剂的超临界CO2萃取是超临界分离领域的一种重要方法。以离子液体为共溶剂的超临界CO2双相分离噻吩类硫具有潜在应用价值。对于分离噻吩类硫的含共溶剂的近/超临界流体设计与制备，主要问题是能选择特定功能的共溶剂。然而采用含离子液体的超临界CO2相分离噻吩类硫存在以下两方面问题：1.离子液体种类繁多，怎样选择特定对噻吩类硫具有高溶解性和选择性的离子液体缺乏理论指导和现实困难；2.怎样从分子水平理论研究噻吩类硫与共溶剂、流体相间作用关系，这对于解释相分离噻吩类硫机理尤为重要。本项目采用实验结合多种尺度模拟方法，研究噻吩类硫在近/超临界体系中热力学性质，获得其与共溶剂、流体相之间的关系。并探索在近/超临界条件下，离子液体特性、客体分子在流体相中分布的微结构特征，找出这些因素与噻吩类硫溶解性能之间定量关系。希望从分子水平上为设计和制备离子液体-近/超临界CO2体系相分离噻吩类硫化物提供理论基础。

添加共溶剂的超临界CO2萃取是超临界分离领域的一种重要方法。而以室温离子液体为共溶剂的超临界CO2相分离噻吩类硫具有重要意义。分离噻吩类硫的室温离子液体-近/超临界流体设计，需要获得噻吩类硫与室温离子液体-近/超临界CO2体系溶解性能之间的关系。本项目采用经典和量子的不同尺度分子模拟方法，研究了噻吩在近/超临界体系中热力学性质，获得了其与室温离子液体、高压CO2流体相之间的关系。并研究了在近/超临界条件下，离子液体特性、噻吩在流体相中分布的微结构特征，获得了这些因素与噻吩类硫溶解性能之间的定量关系。1）根据经典蒙特卡洛模拟和量子Car-Parrinello分子动力学（CPMD）理论方法，从分子水平上解释了几种离子液体和CO2混合物对噻吩类硫化物的溶解机理，并阐明了吸收溶解的分子机制；2）构建了几种室温离子液体和超临界CO2的理论模型，研究了噻吩类硫在这几种体系中的溶解规律，探寻了影响溶解性能的重要因素，建立起了对噻吩类硫吸收溶解性能间的关系。并采用CPMD分子动力学方法，揭示了硫化物在溶液相中的分布规律；3）通过诱导偶极子方法，构建了苯并噻吩的可极化力场，将原子极化描述的噻吩类硫模型应用于模拟汽油中，热力学性质计算的精确性得到提高，这些理论方法有助于构建理想的溶剂体系方法。