Meng Yuan, Ju Tongyao, Meng Fanzhi, Han Siyu, Song Mengzhu, Jiang Jianguo
School of Environment, Tsinghua University, Beijing 100084, China.
ACS Appl Mater Interfaces. 2021 Nov 17;13(45):54018-54031. doi: 10.1021/acsami.1c17132. Epub 2021 Nov 3.
The emerging polyethylenimine (PEI)-functionalized solid adsorbents have witnessed significant development in the implementation of CO capture and separation because of their decent adsorption capacity, recyclability, and scalability. As an indispensable substrate, the importance of selecting porous solid supports in PEI functionalization for CO adsorption was commonly overlooked in many previous investigations, which instead emphasized screening amine types or developing complex porous materials. To this end, we scrutinized the critical role of different commercial porous supports (silica, alumina, activated carbon, and polymeric resins) in PEI impregnation in this study, taking into account multiple perspectives. Hereinto, the present results identified that abundant larger pore structures and surface functional groups were conducive to loading a considerable amount of PEI molecules. Various supports after PEI functionalization had great differences in adsorption capacities, amine efficiencies, and the corresponding optimal temperatures. In addition, more attention was paid to the role of porous supports in long-term stability during the consecutive adsorption-regeneration cycles, while N and CO purging as regeneration strategies, respectively. Especially, CO-induced degradation due to urea species formation was specifically recognized in a SiO-based adsorbent, which would induce serious concerns in CO cyclic capture. On the other side, we also confirmed that adopting conventional porous supports, for example, HP20, could achieve superior adsorption performance (above 4 mmol CO/g) and cyclic stability (around 1% loss after 30 cycles) rather than the ones synthesized through complex approaches, which ensured the availability and scalability of PEI-functionalized CO adsorbents.
新兴的聚乙烯亚胺（PEI）功能化固体吸附剂因其良好的吸附能力、可回收性和可扩展性，在二氧化碳捕集与分离领域取得了显著进展。作为不可或缺的基质，在许多先前的研究中，人们普遍忽视了在PEI功能化用于二氧化碳吸附时选择多孔固体载体的重要性，这些研究反而侧重于筛选胺类或开发复杂的多孔材料。为此，本研究从多个角度审视了不同商业多孔载体（二氧化硅、氧化铝、活性炭和聚合物树脂）在PEI浸渍中的关键作用。在此，目前的结果表明，丰富的较大孔结构和表面官能团有利于负载大量的PEI分子。PEI功能化后的各种载体在吸附容量、胺效率和相应的最佳温度方面存在很大差异。此外，在连续的吸附-再生循环中，更加关注多孔载体在长期稳定性中的作用，同时分别采用氮气和二氧化碳吹扫作为再生策略。特别是，在基于二氧化硅的吸附剂中特别认识到由于脲类物质形成导致的二氧化碳诱导降解，这将在二氧化碳循环捕集中引起严重关注。另一方面，我们还证实，采用传统的多孔载体，例如HP20，能够实现优于通过复杂方法合成的载体的吸附性能（高于4 mmol CO/g）和循环稳定性（30次循环后损失约1%），这确保了PEI功能化二氧化碳吸附剂的可用性和可扩展性。
