Microstructural control of a SSZ-13 zeolite film via rapid thermal processing

A SSZ-13 zeolite (CHA type zeolite having a pore size of 0.37 × 0.42 nm2) can separate CO2 (0.33 nm) from larger molecules (N2 (0.364 nm) or CH4 (0.38 nm)) because of the molecular size differences. However, methods to control the non-zeolitic defects of SSZ-13 membranes are lacking. Here, we demonstrate that rapid thermal processing (RTP) of as-synthesized SSZ-13 films tunes their microstructural defect properties and increases their CO2 separation ability. The maximum CO2/N2 separation factor (SF) at 30 °C increased from ~2.9 to ~4.8 due to RTP because the defective region was reduced. Furthermore, the addition of water vapor (the third main component of coal-fired power plant flue gas) to the feed markedly improved the CO2/N2 SF of the RTP-treated SSZ-13 membrane; from ~4.3 at 50 °C (a representative flue gas stream temperature) under dry conditions to ~10.1 under wet conditions (vs. ~1.6 across the conventionally calcined counterpart). Furthermore, the less-defective RTP-treated SSZ-13 membranes achieved a CO2/CH4 SF as high as ~43.7 under wet conditions at 50 °C. Fluorescence confocal optical microscopy analyses complemented with the permeation modeling revealed that the reduced defect size after RTP (~2.2 nm against ~3.9 nm for the conventionally calcined counterpart) improved the CO2 permselectivity, even though the defect porosities were low (~0.1%). [Display omitted] •Rapid thermal processing (RTP) of SSZ-13 films improved the CO2 permselectivities.•The improved separation performance was attributed to the reduced defect size.•Despite the comparable degree of defects, their size determined the performance.•Such improvement was pronounced with respect to water vapor-containing feeds.•Robust CO2 permselectivities were achieved using the RTP-treated SSZ-13 membranes.