School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control, Southern University of Science and Technology, Shenzhen 518055, China.
School of Environment, Harbin Institute of Technology, Harbin 150090, China.
Environ Sci Technol. 2021 Apr 20;55(8):5236-5247. doi: 10.1021/acs.est.0c07973. Epub 2021 Mar 28.
Solid amine adsorbents are among the most promising CO adsorption technologies for biogas upgrading due to their high selectivity toward CO, low energy consumption, and easy regeneration. However, in most cases, these adsorbents undergo severe chemical inactivation due to urea formation when regenerated under a realistic CO atmosphere. Herein, we demonstrated a facile and efficient synthesis route, involving the synthesis of nano-AlO support derived from coal fly ash with a CO flow as the precipitant and the preparation of polyethylenimine (PEI)-impregnated AlO-supported adsorbent. The optimal 55%PEI@2%AlO adsorbent showed a high CO uptake of 139 mg·g owing to the superior pore structure of synthesized nano-AlO support and exhibited stable cyclic stability with a mere 0.29% decay per cycle even under the realistic regenerated CO atmosphere. The stabilizing mechanism of PEI@nano-AlO adsorbent was systematically demonstrated, namely, the cross-linking reaction between the amidogen of a PEI molecule and nano-AlO support, owing to the abundant Lewis acid sites of nano-AlO. This cross-linking process promoted the conversion of primary amines into secondary amines in the PEI molecule and thus significantly enhanced the cyclic stability of PEI@nano-AlO adsorbents by markedly inhibiting the formation of urea compounds. Therefore, this facile and efficient strategy for PEI@nano-AlO adsorbents with anti-urea properties, which can avoid active amine content dilution from PEI chemical modification, is promising for practical biogas upgrading and various CO separation processes.
固体胺吸附剂是最有前途的沼气升级 CO 吸附技术之一，因为它们对 CO 具有高选择性、低能耗和易于再生。然而，在大多数情况下，这些吸附剂在实际 CO 气氛下再生时会因尿素形成而遭受严重的化学失活。在此，我们展示了一种简便有效的合成途径，涉及以 CO 流为沉淀剂合成源自粉煤灰的纳米 AlO 载体，以及制备聚乙烯亚胺（PEI）浸渍的 AlO 负载吸附剂。最佳的 55%PEI@2%AlO 吸附剂由于合成的纳米 AlO 载体的优越孔结构，表现出高的 CO 吸收量 139mg·g，并且即使在实际再生的 CO 气氛下，其循环稳定性也很稳定，每个循环仅衰减 0.29%。系统地证明了 PEI@纳米 AlO 吸附剂的稳定机制，即 PEI 分子中的酰胺基与纳米 AlO 载体之间的交联反应，这归因于纳米 AlO 丰富的路易斯酸位。这个交联过程促进了 PEI 分子中伯胺向仲胺的转化，从而显著提高了 PEI@纳米 AlO 吸附剂的循环稳定性，显著抑制了尿素化合物的形成。因此，这种具有抗尿素性能的简便有效的 PEI@纳米 AlO 吸附剂策略，可以避免 PEI 化学修饰导致的活性胺含量稀释，有望用于实际的沼气升级和各种 CO 分离过程。
