新型炭基固体胺吸附剂孔结构对CO2吸附行为影响及其机理研究

Amine-supported sorbents, combined with the advantages of adsorbent and amine, have been shown their promising prospects for the capture of CO2 from purified flue gas after FGD process. To meet industrial needs, further improvement in CO2 capacity and adsorption rate of these sorbents are necessary. The porous supports of choice are of great importance in the CO2 adsorption properties of the resulting amine-supported sorbents. These sorbents using mesoporous materials show higher capacity and faster kinetics, compared with those using microporous supports. This was attributed to better diffusion condition of these porous structures with increased pore diameter and pore volume. However, CO2 diffusion limitation due to increased amine-loading still exists in the sorbents even using mesoporous supports such as silicas (5-20nm), curbing further improvement of their CO2 adsorption performance. If further increasing the pore size and pore volume, would amine-supported sorbents possess even better CO2 capacity and kinetics. Is there a limit for this improvement? What factors affect and what mechanism govern the proposed changes in the CO2 adsorption performance of these sorbents? To answer these related open questions, carbon areogel, with an array of controllable pore sizes in mesoporous range (2-50nm), will be synthesized and used as a suitable support for amine-loading. Using vacuum impregnation, with the increase of amine loading, the changes in both the CO2 adsorption capacity and kinetic behaviors of the resulting amine-supported sorbents will be systematically studied through breakthrough curves measured on a lab-scale packed bed. The changes in CO2 diffusion of these sorbents will be analyzed from both the available pore space and the thickness of amine film. A model about the relationship between the pore structure and the CO2 adsorption performance will then be proposed. This work would provide insight into the mechanism underlining the changes in the adsorption behaviors and the support structure, and would be helpful in designing a sorbent with superior properties.

固体胺吸附法烟气CO2捕集技术具有良好的工业应用前景，进一步提高吸附剂的吸附容量和吸附速率是推进该法工业应用的关键，也是当前国内外的研究热点和难点。载体材料的孔结构对固体胺吸附剂的吸附性能影响很大，增大载体的孔径和孔容能改善传质过程，可提高吸附速率和动态吸附容量。然而，已有研究中载体的孔径变化范围较窄(5-20nm)，能否通过进一步增加孔径和孔容来提高吸附性能尚不清楚，载体的孔结构对吸附性能的影响机理也待深入研究。碳气凝胶是一种新型纳米多孔碳材料，其孔隙发达，孔径在2-50nm范围内可调，可作为研究上述问题的合适载体。本项目拟以碳气凝胶为载体，采用真空浸渍的方法负载有机胺制备固体胺吸附剂，在介孔范围内考察孔径和孔容变化时的有机胺负载量、胺基分布、CO2吸附容量及扩散阻力的变化规律，研究孔结构对CO2吸附行为的影响及其机理，建立数学模型，从而为设计出性能更优的固体胺吸附剂提供理论依据。