整体式含氮分级孔炭质CO2吸附剂的设计制备及变电吸附性能研究

The development of highly efficient CO2 adsorbents and the adsorption separation process with low energy consumption are the key to the adsorption technology. This proposal provides a new concept of designed synthesis of nitrogen doped hierarchical porous carbon monoliths for CO2 capture and development of the electrical swing adsorption (ESA) process. The nitrogen doped hierarchical porous carbon monoliths will be prepared by a low-cost approach based on the fiber reinforced method. The pore structure, morphology and surface chemistry of the carbon monoliths will be carefully controlled to optimize the adsorbents. The CO2 adsorption capacity of the carbon monoliths will be investigated to understand how the structural feature and surface chemistry of the adsorbents influence the adsorption parameters. The feasibility and efficiency for CO2 capture on the carbon monoliths by electrical swing adsorption (ESA) process will be evaluated. The coordinated control technology of the best cycle will be explored from the cycle experiment. The key concepts in the project are including: (i) The macropores and mesopores could facilitate the CO2 diffusion, while the micropores could increase the CO2 adsorption capacity and sever as the storage for CO2. (ii) The nitrogen doping could improve the adsorption potential for CO2 adsorption. (iii) The carbon monoliths have good electrical conductivity and homogenized structure which could be used in the low-energy consumption electrical swing adsorption (ESA) process to desorb CO2 rapidly. The successfully implementation of this program will make great contribution to the design of high performance adsorbent and guide the further development of CO2 adsorption separation process for industrial application.

高效CO2吸附剂的制备及低能耗吸附过程是吸附法捕集CO2的关键。本项目提出结构设计及制备整体式含氮分级孔炭质CO2吸附剂，并建立与之相匹配的变电吸附过程的新思路。拟采用基于纤维增强的复合方法制备整体式含氮分级孔炭，定向控制材料的宏观形貌、孔隙结构和表面化学组成，通过对CO2吸附分离性能的深入研究，揭示吸附剂结构与CO2吸附性能的构-效关系，并建立与之相匹配的低能耗变电吸附过程，探索出最佳循环过程协同控制技术。本思路的核心在于：（i）串联分级孔结构的设计，中大孔有利于CO2的扩散传输，微孔有利于CO2的吸附存储；（ii）碱性含氮基团的引入能够增强吸附剂对CO2的吸附势；（iii）整体式炭具有各向同性的微结构和良好的导电导热性，可采用变电吸附实现快速升温脱附，降低再生能耗。本项目的实施对高效CO2吸附剂的理性设计及吸附法的工业应用具有重要的科学意义和指导价值。

本项目结构设计并制备了整体式含氮分级孔炭质CO2吸附剂，并建立与之相匹配的变电吸附过程。采用纤维增强的复合方法以预氧化聚丙烯腈纤维毡为增强体制备整体式含氮分级孔炭，材料的宏观形貌、孔隙结构和表面化学组成可通过反应条件进行定向控制，材料具有分级孔结构，弯曲强度在5.0-13.0 MPa范围内，比表面积在170-1870 m2/g范围内可控，建立了整体式含氮分级孔炭质吸附剂结构和表面化学与制备条件的对应关系；系统研究了吸附剂的CO2吸附分离性能，分级孔结构的存在，中大孔有利于二氧化碳分子的扩散传输，微孔有利于二氧化碳的吸附，碱性含氮基团的引入能够增强吸附剂对CO2的吸附势，使分级孔炭具有高效的二氧化碳吸附性能，整体式分级孔炭经聚乙烯亚胺修饰后，在75 oC下对15%的CO2化学吸附性能可达到3.73 mmol/g；整体式含氮分级孔炭在75 oC常压下对于二氧化碳的物理吸附性能为3.80 mmol/g，25 bar下吸附量可达到15.9 mmol/g，CO2/N2选择性为13，同时，阐明了吸附剂结构和表面化学与吸附性能的构-效关系；整体式炭具有各向同性的微结构，允许轴向和径向均匀的气体流动，而且独特的整体式结构和良好的导电、导热性，可采用变电再生实现快速升温脱附，通入6 V电压吸附剂的温度迅速升高到150 oC，使二氧化碳快速脱附，将其浓度富集到50%以上，吸附剂的再生效率达92%以上，并在吸/脱附循环中基本保持稳定，通过对吸附循环周期和循环时间的合理优化，建立了与吸附剂相匹配的变电吸附过程；本项目发展了整体式含氮分级孔炭质吸附剂的低成本可控制备技术，对高效CO2吸附剂的理性设计及吸附法的工业应用具有重要的科学意义和指导价值。