Permselectivity improvement in membranes for CO2/N2 separation

Abstract

In this work, small-pore zeolites of different topology (CHA, LTA5, Rho), all with Si/Al ratio of 5, have been added to highly permeable poly(1-trimethylsilyl-1-propyne) (PTMSP) to increase its selectivity and thermal and mechanical stability. Membranes were characterized by TGA, XRD, SEM and CO2 and N2 single gas permeation measurements at different temperatures. TGA reveal that the thermal resistance of the membranes is as good as pure PTMSP polymer. XRD and SEM results reflect that there is good interaction between the fillers and the membrane matrix, at 5 and 10 wt. % zeolite loadings, while at 20 wt.% a dual layer stucture is formed, when Rho zeolite is the filler, because the particle size of Rho is higher than those of LTA5 or CHA, and voids appear that limit the permselectivity performance. In single gas permeation of N2 and CO2, the influence of temperature, zeolite loading and type is analyzed. The selectivity of pure PTMSP is considerably enhanced with the addition of the zeolites and the increase of temperature, and the MMM loaded with 5 wt. % zeolite surpassed the Robeson's upper bound for CO2/N2 separation, without decreasing the permeability too much. Upon increasing temperature from 298 to 333 K, the permselectivity is enhanced even further without loss of permeability. The 5 wt% loaded membranes were tested in CO2/N2 mixed gas separation experiments at 333 K and 12.5 wt. % CO2 in the feed, and the permselectivity of LTA5-and Rho-PTMSP membranes was further enhanced, compared with the single gas permeation experiments.

Mixed Matrix Membranes for O2/N2 Separation: The Influence of Temperature

“…The thermal resistance of the MMMs is as high as that of pristine PTMSP membranes, up to 573 K, which accounts for the potential use of these MMMs at industrial levels where separation processes are carried out at elevated temperatures [21]. The real zeolite loading of the MMMs was determined from the residual weight after TGA experiments, as reported in a previous work [21].…”

“…The real zeolite loading of the MMMs was determined from the residual weight after TGA experiments, as reported in a previous work [21]. In all cases, the real zeolite loading agreed with nominal values, being 7.58 ± 3.30 wt %, 8.48 ± 3.55 wt %, 7.65 ± 2.72 wt %, and 28.6 ± 8.84 wt % for 5 wt % CHA-PTMSP, 5 wt % LTA5-PTMSP, 5 wt % Rho-PTMSP, and 20 wt % LTA1-PTMSP MMMs, respectively.…”

“…Poly (1-trimethylsilyl-1propyne) (PTMSP) has been proposed in previous works [20,21] as the continuous polymeric matrix in the CO 2 /N 2 gas pair separation due to its high permeability, which determines the minimum separation performance. Small-pore zeolites with different frameworks (CHA, LTA and Rho), Si/Al ratios (1, 5 and ∞), and zeolite loadings (5, 10 and 20 wt %) were selected as fillers.…”

Development of Polysulfone Hollow Fiber Porous Supports for High Flux Composite Membranes: Air Plasma and Piranha Etching

“…Low-temperature plasma treatment with non-polymer-forming gases has been used in recent years as a useful tool to modify the surface properties of different materials, including PSf porous membranes [9][10][11][12][13][14][15][16][17][18][19]. Plasma allows to improve adhesion or wettability, as it generates the active species, capable of activating the upper surface molecular layers without involving the polymer bulk.…”

“…The thin film composite membranes using poly[1-(trimethylsilyl)-1-propyne] (PTMSP) as a non-porous selective layer and air plasma etched PSf porous hollow fiber membranes as a support were prepared and selective layer integrity was confirmed by gas permeation testing. The membrane selectivity can be improved by coating PTMSP on porous supports, even if this polymer is not greatly selective and many attempts have been reported to increase this [10,11].…”