Mixed Matrix Membranes Incorporated with Aminosilane-Functionalized SAPO-34 for Upgrading CO<sub>2</sub>/CH<sub>4</sub> Separation Performances
Xiaonan Zhao, Wei Liu, Xiu-Feng Liu, Baoquan Zhang
Abstract
Mixed matrix membranes (MMMs) are challenged by the poor compatibility between fillers and a polymer matrix that leads to the weakened performance for gas separation. The surface modification of fillers with aminosilane should be an effective approach to improve their compatibility within the polymer matrix. 3-(2-Aminoethylamino)propyl-dimethoxymethylsilane (APDS) was used as a silane coupling agent for modification of sheet-like silicoaluminophosphate-34 (SAPO-34) crystal grains, and novel MMMs were fabricated by incorporating APDS-modified SAPO-34 crystal grains into a Pebax MH 1657 polymer. Based on characterization using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and mechanical tests, the incorporation of an APDS-modified SAPO-34 into Pebax matrix led to much enhanced interfacial adhesion within the MMM. In addition, the effect of the filler content in the MMM on the separation performance of a CO2/CH4 gas mixture and pure gases (CO2 and CH4) was investigated. Compared with available Pebax-based MMMs in the literature, the prepared MMM containing 8 wt % APDS-modified SAPO-34 exhibited the satisfactory CO2 permeability of ca. 137 Barrer and the highest selectivity of 34.7 for the CO2/CH4 gas mixture. It was believed that the excellent separation performance and good stability of the prepared MMM in this study should be due to the good interfacial compatibility of APDS–SAPO-34 fillers together with their strong affinity for CO2 within the MMM.