两性离子用于强化固定载体膜CO2传递机制的研究

Design and fabrication of fixed carrier membrane based on CO2 facilitated transport chemistry lies in the frontier of carbon capture & membrane field. There are three key factors in CO2 facilitated transport chemistry: alkaline carrier, water, and cation/anion, of which the latter two have been seldom explored. In this project, preparation of novel fixed carrier membrane with zwitterion compound as modifier is proposed, with the purpose of intensifying CO2 facilitated transport mechanism based on the ion-conductive capacity and salting-out effect of zwitterion at the presence of water. In particular, by borrowing the charge-separated characteristic of zwitterion, the charge separation of H+ and HCO3–, which are produced from CO2 hydration and dissociation, is expected to be greatly promoted. In this manner, transmembrane channels for rapid transport of H+ and HCO3– are expected to be simultaneously constructed, resulting in ion transfer-dominating facilitated transport mechanism. By varying the anion type, cation type, electric dipole moment, and doping level of zwitterion, the effect on ionic conductivity, gas adsorption capacity, water state and physical structure of membrane will be studied, and the intensification of CO2 facilitated transport mechanism will be evaluated. The aims of this project encompass: to develop anovel method of fixed carrier membrane preparation; to establisha novel theory of CO2 transport mechanism; and to open novel pathways of membrane CO2 capture intensification.

基于CO2促进传递化学设计和制备固定载体膜是碳捕集与膜科学技术领域的前沿。碱性载体、水和阴阳离子是CO2促进传递化学的三个关键要素，但关于水和阴阳离子两个要素的研究较少。本项目提出将两性离子化合物作为修饰剂制备固定载体膜的方法，基于两性离子的离子传递能力及其与水协同产生的盐析效应，强化膜促进CO2传递的机制。特别地，借助两性离子化合物正负电荷分离的特点，促进质子和HCO3–的电荷分离，在膜内同时构建出质子和HCO3–的快速传递通道，形成以离子传递机制为主导的促进传递机制。通过调节两性离子修饰剂的阴阳离子类型、正负电荷间距以及在膜中的含量，研究膜离子传递特性、气体吸附量、水状态和物理结构的变化规律，研究膜CO2促进传递机制的强化效果。期望通过本项目的实施，形成固定载体膜制备的新方法，建立CO2传递机制的新理论，开拓膜法捕碳过程强化的新途径。

基于CO2促进传递化学设计和制备固定载体膜是碳捕集与膜科学技术领域的前沿。本项目提出将两性离子化合物作为修饰剂制备固定载体膜的方法，基于两性离子的离子传递能力及其与水协同产生的盐析效应，强化膜促进CO2传递的机制。首先，在橡胶态高分子Pebax中简单填充两性离子，验证了其通过水和电荷起作用的促进传递机制，并发现了提高膜自由体积对促进传递机制显著的增强效应。特别地，合成了季铵化氧化石墨烯并引入磺化聚醚醚酮膜中，构筑了荷双电的复合镶嵌膜。借助于其正负电荷分离的特点，在高分子-无机界面附近模拟了两性离子化合物的结构特征，促进质子和碳酸氢根的分离，因而膜内同时构建出质子和碳酸氢根的快速传递通道，形成以离子传递机制为主导的促进传递机制，佐证了碱性载体、水、阴阳离子是CO2促进传递化学三个关键要素的论断。本研究所制备的均质膜，CO2渗透系数最高达到1300 barrer，选择性达到120，超过了2008年的Robeson上限。为更好地发挥两性离子的作用，本研究还尝试开发了薄膜复合膜的制备技术，对两性离子在薄膜内的高量负载作了初步探讨。本项目的研究成果对研发超高通量、高选择性的CO2分离膜具有较强的指导意义，使膜技术有望在对CO2脱除有特殊要求的敏感场合（如载人航天空间站）与分子筛脱附技术竞争，进而获得应用。