Guta Yoseph A, Carneiro Juliana, Li Sichi, Innocenti Giada, Pang Simon H, Sakwa-Novak Miles A, Sievers Carsten, Jones Christopher W
School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Dr., Atlanta, Georgia 30332, United States.
Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States.
ACS Appl Mater Interfaces. 2023 Oct 11;15(40):46790-46802. doi: 10.1021/acsami.3c08140. Epub 2023 Sep 29.
Aminopolymer-based sorbents are preferred materials for extraction of CO from ambient air [direct air capture (DAC) of CO] owing to their high CO adsorption capacity and selectivity at ultra-dilute conditions. While those adsorptive properties are important, the stability of a sorbent is a key element in developing high-performing, cost-effective, and long-lasting sorbents that can be deployed at scale. Along with process upsets, environmental components such as CO, O, and HO may contribute to long-term sorbent instability. As such, unraveling the complex effects of such atmospheric components on the sorbent lifetime as they appear in the environment is a critical step to understanding sorbent deactivation mechanisms and designing more effective sorbents and processes. Here, a poly(ethylenimine) (PEI)/AlO sorbent is assessed over continuous and cyclic dry and humid conditions to determine the effect of the copresence of CO and O on stability at an intermediate temperature of 70 °C. Thermogravimetric and elemental analyses in combination with in situ horizontal attenuated total reflection infrared (HATR-IR) spectroscopy are performed to measure the extent of deactivation, elemental content, and molecular level changes in the sorbent due to deactivation. The thermal/thermogravimetric analysis results reveal that incorporating CO with O accelerates sorbent deactivation using these sorbents in dry and humid conditions compared to that using CO-free air in similar conditions. The in situ HATR-IR spectroscopy results of PEI/AlO sorbent deactivation under a CO-air environment show the formation of primary amine species in higher quantity (compared to that in conditions without O or CO), which arises due to the C-N bond cleavage at secondary amines due to oxidative degradation. We hypothesize that the formation of bound CO species such as carbamic acids catalyzes C-N cleavage reactions in the oxidative degradation pathway by shuttling protons, resulting in a low activation energy barrier for degradation, as probed by metadynamics simulations. In the cyclic experiment after 30 cycles, results show a gradual loss in stability (dry: 29%, humid: 52%) under CO-containing air (0.04% CO/21% O balance N). However, the loss in capacity during cyclic studies is significantly less than that during continuous deactivation, as expected.
基于氨基聚合物的吸附剂因其在超稀释条件下具有高CO吸附容量和选择性，是从环境空气中提取CO（CO的直接空气捕获，即DAC）的首选材料。虽然这些吸附性能很重要，但吸附剂的稳定性是开发可大规模部署的高性能、经济高效且持久的吸附剂的关键因素。除了工艺故障外，诸如CO、O和H₂O等环境成分可能导致吸附剂长期不稳定。因此，揭示这些大气成分在环境中对吸附剂寿命的复杂影响，是理解吸附剂失活机制以及设计更有效吸附剂和工艺的关键一步。在此，对聚（乙烯亚胺）（PEI）/Al₂O₃吸附剂在连续和循环的干燥及潮湿条件下进行评估，以确定在70℃的中间温度下CO和O共存对稳定性的影响。结合原位水平衰减全反射红外（HATR-IR）光谱进行热重分析和元素分析，以测量吸附剂因失活导致的失活程度、元素含量和分子水平变化。热/热重分析结果表明，与在类似条件下使用无CO空气相比，在干燥和潮湿条件下将CO与O结合使用会加速这些吸附剂的失活。PEI/Al₂O₃吸附剂在CO-空气环境下失活的原位HATR-IR光谱结果表明，与没有O或CO的条件相比，伯胺物种的形成量更高，这是由于仲胺处的C-N键因氧化降解而断裂所致。我们假设，诸如氨基甲酸等结合态CO物种的形成通过质子穿梭催化氧化降解途径中的C-N裂解反应，导致降解的活化能垒较低，这已通过元动力学模拟得到证实。在30次循环后的循环实验中，结果表明在含CO空气（0.04% CO/21% O，其余为N）下稳定性逐渐丧失（干燥：29%，潮湿：52%）。然而，正如预期的那样，循环研究期间的容量损失明显小于连续失活期间的损失。
