Ferrierite-poly(vinyl acetate) mixed matrix membranes for gas separation: A comparative study

Ferrierite/PVAc mixed matrix membranes (MMMs) were prepared for O-2/N-2, CO2/CH4, and CO2/N-2 separations and their performances were compared to those of silicalite-1, 4A, and 5A-filled PVAc membranes. The MMMs were characterized by XRD, SEM, and single gas permeation. The MMMs with 20% zeolite content was prepared without visible defects at the zeolite-polymer interface. Priming was employed at 40% zeolite loading to enhance zeolite-polymer adhesion except in the case of silicalite-1; silicalite-1 filled MMMs exhibited no significant defects even at 40 wt% loading without priming. Ferrierite addition into the PVAc matrix improved CO2 and CH4 permeabilities and CO2/N-2 ideal selectivity with respect to the neat polymer, while O-2 and N-2 permeabilities decreased and O-2/N-2 and CO2/CH4 selectivities slightly increased with ferrierite addition. Ferrierite-PVAc MMMs at 40% loading yielded a CO2 permeability of 4 Barrer and a remarkably high CO2/N-2 ideal selectivity of 80, possibly due to the strong interaction of CO2 molecules with the framework cations in ferrierite. Although the highest ideal O-2/N-2 selectivity was obtained for 4A-PVAc membranes, Si-PVAc membranes also exhibited high selectivity (8.1) towards O-2 that was accompanied by a relatively higher O-2 permeability, possibly due to solvent being trapped in the pores of the organophilic silicalite-1. This study shows that ferrierite, a zeolite more hydrophobic than zeolites 4A and 5A and with a pore aperture smaller than 5A and silicalite-1, is a promising candidate to be used as the dispersed phase in MMM fabrication for gas separation, in particular, separation of CO2 from industrial streams. Ferrierite may be promising especially in the case of humid feeds where hydrophilic zeolites and MOFs may fail or do not exhibit satisfactory performance. (C) 2017 Elsevier Inc. All rights reserved.