The Phase Structural Evolution and Gas Separation Performances of Cellulose Acetate/Polyimide Composite Membrane from Polymer to Carbon Stage

Abstract

Blending and heat-treatment play significant roles in adjusting gas separation performances of membranes, especially for incorporating thermally labile polymers into carbon molecular sieve membranes (CMSMs). In this work, cellulose acetate (CA) is introduced into polyimide (PI) as a sacrificial phase to adjust the structure and gas separation performance from polymer to carbon. A novel result is observed that the gas permeability is reduced, even when the immiscible CA phase decomposes and forms pores after heat treatment at 350 °C. After carbonization at 600 °C, the miscible CA has changed without contribution, while the role of the immiscible CA phase has changed from original hindrance to facilitation, the composite-based CMSM at a CA content of 10 wt.% shows highest performances, a H2 permeability of ~5300 Barrer (56% enhancement) with a similar H2/N2 permselectivity of 42. The structural analyses reveal that the chain interactions and phase separation behaviors between CA and PI play critical roles on membrane structures and gas diffusion, and the corresponding phase structural evolutions during heat treatment and carbonization determine gas separation properties.

A review on recent advances of cellulose acetate membranes for gas separation

“…22 The incorporation of CA into PI to enhance membrane structure led to remarkable H 2 permeability of 5300 Barrer in high-temperature H 2 /N 2 separation experiments. 23 Membranes are fabricated by incorporating CA with different acetyl concentrations, CA-39 and CA-56. 58 The results demonstrate an improvement in performance as compared to pure CA.…”

“… 22 The incorporation of CA into PI to enhance membrane structure led to remarkable H 2 permeability of 5300 Barrer in high-temperature H 2 /N 2 separation experiments. 23 …”

“…CA/Pebax, there is an approximate 25% and 59% increase in CO 2 /N 2 selectivity and CO 2 permeability, respectively. [21][22][23] Each blend presents a unique gas permeability sequence, emphasizing their application-specic advantages.…”