具有均一吸收性质的多位点SO2离子液体吸收剂的设计与合成

Removing toxic components such as SO2 from flue gas is crucial to our sustainable development, therefore, it is an important research area to develop desulfurization agents that are environmentally friendly, highly efficient, and reusable. Due to their unique properties including low vapor pressure, high thermal stability, and virtually unlimited functional tunability, etc., ionic liquids have shown great potential in the application of acidic gas absorption and separation. In consideration of the problems of the recently reported multi-site SO2 capture ionic liquids, which may be caused by the large difference in the interaction strength of each site, this proposal aims at design and synthesis of novel ionic liquids with multiple absorption sites that can chemically absorb SO2 and the sites are of nearly uniform absorption properties. The latter feature ensures a synchronized and universal control of absorption (desorption) under the same conditions over all the absorption sites. Consequently, under practical and feasible absorption and desorption conditions, these ionic liquids should be able to achieve higher SO2 effective uptakes than other ionic liquids. This research includes utilizing quantum chemistry calculations and Langmuir-type macroscopic models to help select desirable ionic liquids, synthesize and characterize the target ionic liquids, and measure their actual performance in SO2 absorption, desorption, and capture cycles, and finally obtain the correlation between the ionic liquid structure and the absorption performance. This project will provide a research foundation for the search of novel industrially applicable SO2 absorption and separation materials.

除去烟气中的SO2等有害气体对人类的可持续发展至关重要，开发环保、高效、可重复使用的脱硫剂是亟待解决的重要课题。离子液体因蒸汽压低、热稳定性高、功能可调等特性在酸气吸收分离方面具有广阔的应用前景。本项目分析了近期文献报道的能多位点吸收SO2的离子液体因各吸收位点与SO2作用强度差异较大可能引起的问题，并在此基础上提出设计合成具有均一吸收性质、多位点化学吸收SO2的新型离子液体。均一的吸收性质可保证在相同条件下，对多个吸收位点的吸收（脱除）进行同步、统一的控制。在现实可行的吸收与脱除条件下，达到比其他离子液体对烟气中SO2更高的有效吸收载荷。本课题将通过量子化学计算与兰缪尔宏观吸附模型模拟，辅助筛选离子液体，制备和表征目标离子液体，测试其对SO2的吸收、脱除及循环使用效果，最终获得吸收性能与离子液体结构之间的构-效关系。本项目将为寻找可工业应用的SO2气体吸收分离新材料奠定研究基础。

对于传统的能够多位点吸收SO2的离子液体来说，其各吸收位点与SO2的作用强度往往差异较大，从而引起在循环使用时的有效吸收载荷降低。针对这一问题，我们设计、合成了一系列由多(唑)硼酸根阴离子与咪唑鎓阳离子匹配形成的离子液体，并将它们应用于SO2的化学吸收中。在通过量子化学计算确定多(唑)硼酸根阴离子给电子能力可调的基础上，我们研究了它们与多个SO2之间的各级作用的焓变。结果表明它们可以多位点吸收SO2，并且各个位点与SO2之间的作用强度适中。实验中，我们采用盐交换反应合成了目标离子液体，对于它们的热稳定性、玻璃态转化温度、粘度和电导率等物化性质与其结构之间的关联及趋势进行了全面的考察。经测试，合成的离子液体能够在20 oC，0.1 MPa SO2条件下多位点吸收SO2，最高吸收摩尔比可达到5.8 mol SO2/mol IL或1.05 g SO2/g IL。在循环使用（五次）中，被测离子液体可保持最初的吸收能力，但由于在温度较高条件下离子液体与SO2作用比较复杂，仍有少量被吸收的SO2未能在解吸条件下脱除。尽管多(唑)硼酸根衍生离子液体与工业应用还有一段距离，但此工作丰富和拓展了基于多(唑)硼酸根离子液体的研究。本项目还对阳离子在酸性气体吸收分离过程中的影响、由多(唑)硼酸根均裂产生的硼负自由基的稳定性及多种硼自由基的亲电亲核属性进行了理论方面的研究。