Abstract:

Mixed matrix membranes combine the advantages of polymers with inorganic materials, which can outperform polymer membranes and have a wide range of applications in gas separation. To obtain high-performance CO₂/N₂ separation membranes, sulfonated CAU-1 (CAU-1@BS) was prepared by the ring-opening reaction of the epoxy group of prop-1-ene-1,3-sultone (BS) with the primary amine group of CAU-1. Then, CAU-1@BS was added to polyvinylamine (PVAm) to prepare a casting solution, which was coated on a hydrophilic modified polysulfone ultrafiltration membrane to obtain a mixed matrix composite membrane. The chemical structure and pore structure of CAU-1@BS were characterized by XPS, FTIR and BET, and the morphological structure of the membrane was characterized by SEM. Furthermore, the effects of preparation and test conditions of mixed matrix composite membranes on gas separation were investigated. The results showed that as-prepared mixed matrix composite membranes exhibited excellent separation performance with a CO₂ permeance of 505 GPU and a CO₂/N₂ selectivity of 67, when the content of CAU-1@BS was 7% (mass). Their values were improved by 70.6% and 71.8%, respectively, compared with those of pristine PVAm membranes (CO₂ permeance: 296 GPU; CO₂/N₂ selectivity: 39). On the one hand, this is due to the fact that the sulfonic acid groups introduced through the ring-opening reaction not only act as Lewis basic sites for acid-base interactions with CO₂, but also adsorb water molecules to enhance the facilitated transport of CO₂ in the membrane. On the other hand, the gas separation performance of the membrane was improved by the synergic effect of the amine groups and porous structure of CAU-1@BS. In addition, under the condition of using CO₂/N₂ mixed gas as feed gas, the prepared mixed matrix composite membrane maintained good stability for up to 360 h, and its average CO₂ permeance and CO₂/N₂ selectivity were 527 GPU and 70, respectively, which shows that the membrane has good application prospects.

Key words: mixed matrix composite membranes, CO₂ capture, separation, sulfonated CAU-1, transport processes

摘要：

混合基质膜结合了聚合物和无机材料的优点，性能可超过聚合物膜，在气体分离方面具有广泛的应用前景。为了获得高性能的CO₂/N₂分离膜，利用丙烯基-1，3-磺酸内酯（BS）的环氧基团与CAU-1的伯胺基团开环反应制备磺化CAU-1（CAU-1@BS）。然后，将CAU-1@BS添加到聚乙烯胺（PVAm）中制备制膜液，将其涂覆在亲水性改性聚砜超滤膜上制备得到混合基质复合膜。借助XPS、FTIR和BET表征了CAU-1@BS的化学结构和孔隙结构，并通过SEM表征了膜的形貌结构。此外，还研究了混合基质复合膜的制备条件和测试条件对气体分离性能的影响。研究结果表明，当CAU-1@BS的含量为7%（质量分数）时，制备的混合基质复合膜表现出优异的分离性能，其CO₂渗透速率为505 GPU（1 GPU=3.38×10^-10 mol·m^-2·S^-1·Pa^-1），CO₂/N₂选择性为67，与纯PVAm膜（CO₂渗透速率为296 GPU；CO₂/N₂选择性为39）相比，分别提高了70.6%和71.8%。一方面，这是因为通过开环反应引入的磺酸基团不仅可以作为Lewis碱性位点与CO₂发生酸碱相互作用，而且能够吸附水分子从而增强CO₂在膜中的促进传递效果。另一方面，PVAm中的氨基与CAU-1@BS的多孔结构协同作用提高膜的气体分离性能。此外，在以CO₂/N₂混合气为原料气的条件下，制备的混合基质复合膜在长达360 h的时间内保持了良好的稳定性，其平均CO₂渗透速率和CO₂/N₂选择性分别为527 GPU和70，这表明该膜具有较好的应用前景。

关键词: 混合基质复合膜, 二氧化碳捕集, 分离, 磺化CAU-1, 传递过程