Synthesis of chabazite/polymer composite membrane for CO2/N2 separation

Abstract

There is considerable interest in using zeolite membranes for gas separations. For CO2 and N2 separation, much research has focused on faujasitic (FAU) membranes. Simulations suggest that chabazite (CHA) membranes can also be good at CO2 and N2 separation. In this study, we have focused on CHA membranes grown on porous polymeric polyethersulfone (PES) supports. Recently, we have reported on a dehydration rehydration hydrothermal (DRHT) process for FAU membrane growth on PES supports, which results in rapid crystallization. It is well known that FAU can be converted to CHA by an interzeolite conversion method, and is our choice for CHA synthesis in this study. A synthesis method for isolated CHA nanocrystals with size of 50–100 nm is reported. Rapid DRHT-based CHA powder synthesis and CHA/PES membrane growth are also being reported, all made by the interzeolite conversion of FAU. The CHA/PES membranes of ∼4 μm thickness were coated with polydimethylsiloxane (PDMS), and at 25 °C, CO2 permeance of 1243 GPU with CO2/N2 selectivity of 19 was observed. The porosity of the PES support was critical to enhancing the formation and stability of the CHA membrane, since the CHA membrane on the PES surface was bonded to interconnected CHA crystals that grew within the PES from the seed crystals.