离子液体-金属有机骨架协同强化低浓度煤层气吸附分离及相平衡研究

Adsorption separation of CH4/N2 mixture is an important method for efficient utilization of low-concentration coal bed methane. To solve the problem of low N2 adsorption quantity and selectivity in traditional pressure swing adsorption, this project proposes ionic liquid supported metal-organic frameworks (IL@MOF) can be used as an efficient adsorbent, base on the strong interaction between N2 molecules and metal ions with empty electron orbital. By controlling topology, surface properties, species of ligands and metal ions of metal-organic frameworks, enchancing the interaction between N2 molecules and adsorbent, thus increasing the N2 adsorption quantity. Furthermore, the pore structures of adsorbent are finely controlled by adjusting IL loading, which increase the diffusion resistance of CH4 molecules and decrease its adsorption quantity, so as to realize the efficient separation of CH4/N2 mixture. On the basis of the phase equilibrium data, this project focuses on exploring the influence of various factors on the phase equilibrium properties of low-concentration coal bed methane, revealing the influence mechanism of synergy effect of IL-MOF on the separation properties of low-concentration coal bed methane, establishing the phase equilibrium equation with synergy effect of IL-MOF, illuminating the internal relations among the structural properites of the IL@MOF, synergy effect of IL-MOF and separation properties of CH4/N2 mixture. This project shows the intercross and coalescence among multi-subjects, the achievements will promote the development of pressure swing adsorption in the separation of low-concentration coal bed methane.

吸附分离CH4/N2是实现低浓度煤层气高效利用的重要手段。针对目前变压吸附存在N2吸附量和选择性低的问题，本项目基于N2分子与具有空电子轨道的金属离子间的强相互作用，提出以离子液体负载型金属有机骨架(IL@MOF)为吸附剂。通过调控MOF拓扑结构、表面特性、有机配体及金属离子种类，强化N2与吸附剂间的相互作用，提升N2吸附量；进一步调节IL负载量对吸附剂孔隙结构进行精细调控，提高CH4分子扩散阻力，降低其吸附量，从而实现CH4/N2的高效分离。从低浓度煤层气吸附相平衡数据出发，研究各因素对低浓度煤层气吸附相平衡特性的影响规律，揭示IL-MOF协同作用对低浓度煤层气分离性能的影响机制，建立考虑两者协同作用的气体吸附相平衡方程，阐明IL@MOF结构特性—IL-MOF协同作用—CH4/N2分离性能之间的内在联系。本项目体现了多学科的交叉融合，其成果将为变压吸附分离低浓度煤层气技术的发展奠定基础。

合理开发利用低浓度煤层气对我国能源结构优化、大气环境保护具有重要意义。而吸附分离CH4/N2是实现低浓度煤层气高效利用的重要手段，但是由于CH4与N2具有相似的物理性质和分子动力学直径，导致目前变压吸附分离低浓度煤层气存在吸附量和选择性低的问题。针对该问题，本项目通过将客体分子封装至金属有机骨架孔隙内的方法调控了吸附剂的孔隙结构和表面特性。采用密度泛函理论、分子模拟、实验表征及理论分析方法，从微观到宏观角度详细研究了不同复合材料对CH4, N2组分及混合物的吸附分离性能。基于CH4, N2组分吸附相平衡数据，研究了温度、压力等因素对低浓度煤层气吸附分离的影响规律；揭示了客体封装分子强化CH4/N2混合气体吸附分离的作用机制；阐明了吸附剂结构特性—主客体协同作用—CH4/N2分离性能之间的内在联系。本项目体现了多学科的交叉融合，其成果将为变压吸附分离低浓度煤层气技术的发展奠定基础。项目实施期间发表学术论文8篇，其中SCI/EI论文6篇，会议论文1篇；申请国家发明专利1项；培养硕士研究生5名；参加基金委组织的学术会议4人次。