Gas separation membranes use up to 90% less energy in gas processing compared to distillation and absorption based technologies. Beyond the environmental ramifications of energy savings, membranes are also widely studied for the sequestration of CO2 in post-combustion flue gas streams. Unfortunately, the latter application faces challenges due to low gas permeabilities of commercialized membranes, such as cellulose acetate (CA), which also shows a decline in gas selectivity in aggressive mixed gas feeds. This talk describes a facile sub-Tg modification of dense CA films by simultaneously silanating and crosslinking the membrane. FTIR and solid-state NMR (13C and 29Si) confirmed the silanation, while SEM/EDS confirmed that the reaction homogeneously occurred throughout the entire membrane. Pure gas testing indicated that silanated membranes had 5-6 times higher CO2 permeabilities compared to neat CA with modest losses in gas selectivity. However, binary mixed gas tests at 800 psi demonstrated enhanced plasticization resistance of the silanated films that led to the same selectivity as neat CA while still demonstrating the same large permeability enhancement. We probed the scalability of this technology by treating hollow fibers and showed a successful retention of the dense skin layer and underlying porous microstructure. Finally, we show that the improved gas separation performance of these modified membranes are maintained in aggressive, sour-gas feeds containing up to 20% of toxic, corrosive H2S.

Silanated cellulose acetate membranes with enhanced gas permeabilities and plasticization resistance in pure and mixed gas feeds

2019 Fall National Meeting

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