Abstract:

In order to obtain high-performance mixed matrix membrane to effectively capture CO₂ in flue gas, this paper designed a N,S co-doped porous carbon sphere with excellent diffusion and adsorption selectivity for CO₂ as an additive to achieve the efficient separation of CO₂/N₂ from flue gas. Glucose with rich oxygen groups as the carbon source and thiourea as nitrogen and sulfur source are selected to prepare the nitrogen and sulfur co-doped carbons (NSC) by hydrothermal method. The porous structure of NSPC is produced by the activation of NSC with KOH. FTIR, XRD and BET tests indicate the successful synthesis of NSPC, which has high specific surface area and microporosity. The optimal ratio of glucose to thiourea, the optimal ratio of NSC to KOH in the synthesis of NSPC, the effect of NSPC content, feed pressure, test temperature on the performance of the membrane are studied. It proves that the nitrogen, sulfur-containing CO₂ affinity sites and micropores in NSPC have beneficial effects on the gas separation performance of the membrane. The results show that when the NSPC content is 3%(mass), the performance of membrane is the best at 25℃ and 0.2 MPa. The CO₂ permeability is 589 Barrer, and the CO₂/N₂ selectivity is 64. The performance of the membrane in the mixed gas is slightly lower than that in the pure gas, and it can remain stable for 360 h, which has good industrial application prospects.

Key words: mixed matrix membrane, activated carbon, CO₂ capture, flue gas, PEBA

摘要：

为了获得高性能的混合基质膜，有效捕集烟道气中的CO₂，设计了对CO₂有优异的扩散选择性和吸附选择性的氮硫共掺杂多孔碳球添加剂，实现了烟道气中CO₂/N₂的高效分离。选用表面含氧基团丰富的葡萄糖作为碳源，硫脲作为氮源和硫源，通过水热法制备了氮硫共掺杂碳球（NSC），并用KOH活化，获得了具有多孔结构的氮硫共掺杂碳球（NSPC），再加入聚醚嵌段酰胺（PEBA）中制备出PEBA/NSPC混合基质膜。采用FTIR、XRD和BET表征了材料的化学结构和孔结构，借助力学性能表征了膜的两相界面相容性。系统研究了PEBA/NSPC混合基质膜中葡萄糖与硫脲的质量比、NSC和KOH的质量比、NSPC的添加量、操作压力、操作温度，以及模拟烟道气条件对膜CO₂渗透性、CO₂/N₂选择性的影响。结果表明：NSPC材料成功实现了氮、硫元素的共掺杂，而且具有较好的孔结构。在操作温度25℃、操作压力0.2 MPa的条件下，混合基质膜中NSPC添加量为3%（质量）时气体分离性能最优，CO₂渗透系数和CO₂/N₂选择性分别为589 Barrer和64，相比纯PEBA膜分别提高了244%和139%。这是因为多孔碳球的微孔结构显著提高了CO₂的扩散选择性，同时氮、硫元素的掺杂因为酸碱相互作用和良好亲和性有效提高了CO₂的吸附选择性。稳定性实验表明，PEBA/NSPC混合基质膜在360 h连续运行过程中气体分离性能稳定，具有较好的工业应用前景。

关键词: 混合基质膜, 活性炭, CO₂捕集, 烟道气, 聚醚嵌段酰胺