(383al) Polyorganosilica Membranes Structure Tightening and Hydrothermal Stabilization Via Few Cycle Atomic Layer Deposition for Hydrogen Purification Process
AIChE Annual Meeting
2024
2024 AIChE Annual Meeting
Separations Division
Poster Session: Separations Division
Tuesday, October 29, 2024 - 3:30pm to 5:00pm
Polyorganosilica (POSi) membranes with excellent H2 separation properties can be rapidly prepared via 2-minute oxygen plasma treatment of polydimethylsiloxane (PDMS)-based thin-film composite (TFC) membranes. However, POSi membranes are subject to hydrothermal instability, decreasing H2 permeance and H2/CO2 selectivity. In this study, we employ few-cycle atomic layer deposition (ALD) of aluminum oxide to induce metal-siloxane covalent linkage, which can simultaneously stabilize POSi networks and tighten porous structures to improve H2/CO2 separation performance. First, oxygen plasma treatment induces an ultrathin (<10 nm) POSi top layer with abundant silanol (Si-OH) groups, as confirmed by XPS and SEM images. Second, the hydroxide groups enable the ALD process, where exposure to trimethylaluminum (TMA) forms Al-O-Si covalent linkages. The effect of the ALD parameters on the POSi network structure, gas transport properties at 150oC, and hydrothermal stability are thoroughly examined. For example, exposing POSi membranes to 3-cycle ALD improves H2/CO2 selectivity from 67 to 110 but decreases H2 permeance from 380 to 240 GPU. When challenged with roughly 0.6 mol% water vapor, the pristine POSi membrane exhibits an irreversible drop of H2/CO2 selectivity to 55 while a 3-cycle of ALD retains the selectivity, suggesting improved hydrothermal stability with the ALD treatment. The superior H2/CO2 separation properties and robust hydrothermal stability coupled with the facile fabrication processes demonstrate the potential of the POSi membranes for practical H2 purification and CO2 capture.