Impact of Humidity on the CO<sub>2</sub>/N<sub>2</sub> Separation Performance of Pebax-MOF Mixed Matrix Membranes
Zikang Qin, Xuan Feng, Dengguo Yin, Bingru Xin, Ziheng Jin, Yi Deng, Lin Yang, Lu Yao, Wenju Jiang, Chong Liu, Zhongde Dai
Abstract
Postcombustion capture has been an important field for CO 2 capture, but its high H 2 O content has been a significant barrier to the performance of mixed matrix membranes (MMMs). In this study, a series of humidity values were established, and two types of MOFs (SUM-1 and SUM-9) were used in Pebax 2533 (poly(ether- block -amide)) to prepare MMMs to explore CO 2 /N 2 separation performance. At 35 °C and 2 bar, the CO 2 permeability of Pebax-SUM-1 was 380.9, 433.1, 405.4, and 401.7 Barrer, respectively, when the relative humidity (RH) changed from 0, 30, 60, to 100%, and the CO 2 /N 2 selectivity was 20.5, 19.0, 18.1, and 17.0, respectively. The CO 2 permeability of Pebax-SUM-9 was 390.9, 387.4, 412.5, and 452.4 Barrer, with the CO 2 /N 2 selectivities being 18.5, 19.9, 20.0, and 19.7, respectively. The CO 2 /N 2 selectivity had no significant fluctuations. A hypothesis has been proposed that the large-pore MOFs could only provide transport channels and could not screen CO 2, and the CO 2 /N 2 selectivity would mainly be provided by the polymer matrix. Under high humidity conditions, the CO 2 transport channels with large-pore MOFs might fail due to competition between H 2 O and CO 2 . This study investigated the influence of a series of RH on MMMs separation performance. The proposed theory suggests that there might be an optimal humidity range for the CO 2 permeability of MMMs in humid conditions, which can be useful to guide the design of porous fillers for future MMMs development.