1. Introduction
Anthropogenic activities are one of the primary causes of global warming. The primary cause of climate change is the combustion of fossil fuels, which results in enormous CO
2 concentration in the atmosphere. Recently, the CO
2 levels in the atmosphere were recorded as 414 parts per million, which is several folds higher than before the industrial revolution
[1][2]. This increasing level of CO
2 causes the greenhouse effect, contributes to respiratory disease, acts as asphyxiant, causes ocean acidification, and acts as a major source of energy imbalance due to a rise in earth temperature. Several approaches have been developed to mitigate CO
2 in the atmosphere, including geological sequestration, catalytic conversion to useful products, adsorption, and membrane separation
[3][4][5][6]. One approach is to separate and capture CO
2 from air and its originating sources.
Several gas separation strategies have been independently researched for CO
2 capture and separation, including cryogenic distillation and post-combustion processes such as absorption, adsorption, hydrated-based systems, and membrane separation techniques
[7][8][9]. Cryogenic distillation necessitates huge distillation columns and is a high-energy process. Due to its compact footprint, simplicity, and great energy efficiency, membrane gas separation technology has been considered to be one of the most promising technologies to replace older technologies such as amine scrubbing. The membrane separation technique has considerable advantages over other separation technologies because it is a continuous separation process that consumes less energy, and the materials can be recycled. Recently, as compared with polymeric membranes, the incorporation of zeolites into polymers has been shown to improve CO
2 separation performance significantly.
In 1756, Swedish scientist Axel Fredrik Cronstedt invented the term “zeolite”
[10]. Zeolites have a unique chemical composition, distinctive pore size distribution, and chemical, thermal, and ion exchange properties
[11][12][13][14][15][16][17][18][19][20][21]. These materials have been employed for a range of applications, including capture, purification, and catalysis
[22][23][24][25][26][27][28][29][30]. Among zeolites, Lok et al.
[31] introduced the family of SAPO zeolite materials. The SAPO-34 unit cell has chabazite (CHA)-type topology related to other aluminophosphates (such as SAPO-15, SAPO-11, SAPO-16, and SAPO-31), aluminosilicate (low-silica CHA and high-silica SSZ-13) and pure silicate (all-silica CHA). All these low and high-silica zeolite materials have been explored for gas separation applications
[32][33][34][35][36].
The SAPO-34 zeolite has intra-crystalline pore volumes and pore sizes ranging from 0.18 to 0.48 cm
3/g and from 0.3 to 0.8 nm, respectively. The SAPO-34 structure is made up of eight-membered rings with a diameter of 9.4 (3.8 × 3.8), as shown in
Figure 1. In addition to distinct pore size and volume, SAPO-34 material exhibits moderate to high hydrophobicity and has high thermal and hydrothermal stability. Due to these characteristic features, SAPO-34 has been extensively used in the methanol to olefin (MTO) process
[37][38][39][40][41][42][43][44][45][46][47][48]. In recent years, SAPO-34 has been investigated for CO
2 remediation, including CO
2 capture
[49][50][51], conversion
[52][53][54], and separation
[49]. Several studies have already covered a vast area of SAPO-34 materials research. Askari et al.
[43] examined several synthetic procedures of SAPO-34. Ahmadi et al. summarized the deactivation of SAPO-34. Sun et al. looked at how to increase MTO performance in SAPO-34 by reducing the size of the zeolite using crystals and pore engineering. There has been a lot of research done on SAPO-34 membranes for CO
2 separation, but no recent paper has been written about the role of SAPO-34 membranes in CO
2 separation, especially from air (N
2) and natural gas (CH
4). Therefore, as a result of the rapidly developing research on SAPO-34, as shown in
Figure 2, and its role in CO
2 mitigation.
Figure 1. Schematic presentation of SAPO-34 membranes in CO2 separation.
Figure 2. Histograms of SAPO-34 zeolite literature since 1990. Data were taken from SciFinder using keywords “SAPO-34” and “SAPO-34 and CO2”.
2. SAPO-34 Membranes for CO2 Separation
A crystalline hydrate aluminosilicate is distinguished by its uniform pore size (0.3–1.3 nm), as well as superior thermal, chemical, and mechanical stability. Zeolite is an ideal material for different applications, such as adsorption, ion exchange, and catalysis. Recently, it has become attractive for membrane applications due to its unique structure and excellent physicochemical properties
[55]. Among more than 190 zeolite frameworks, a few have been distinguished for their promising separation performances. SAPO-34 is one of these structures that exhibits a significant separation performance, specifically removing CO
2 from CH
4 and N
2 mixture. As shown in
Figure 3, SAPO-34 membranes are mainly classified into two types: (1) Mixed matrix membranes (MMMs) where the SAPO-34 is incorporated in the polymer. These membranes are fabricated via various methods, including solution casting, phase inversion, solvent evaporation, and dip coating. (2) Pure SAPO-34 membranes where a substrate such as alumina, stainless steel, and silica are used as a support for the SAPO-34 membranes. Secondary seeded growth and in situ crystallization methods are the most frequent routes to fabricate these membrane types.
Figure 3. Schematic of fabrication method and performance advancement approaches for SAPO-34 membranes.
2.1. SAPO-34-Based Mixed Matrix Membranes
Several gas separation technologies have been investigated for CO2 capture, including cryogenic distillation, post-combustion process, and membrane separation processes. Membrane separation technology shows significant merits as compared with other separation technologies because it is a continuous separation process, requires low energy consumption, and the materials can be regenerated. As compared with the polymeric membranes, MMMs that combine the advantages of both polymeric and inorganic materials have become the focus for a next-generation gas separation membrane. MMMs could provide a solution to the permeability and selectivity trade-off in polymeric membranes and bridge the gap with pure inorganic membranes. MMMs also offer the physicochemical stability of a ceramic material while ensuring the desired morphology with higher permeability, selectivity, hydrophilicity, fouling resistance, as well as greater thermal, mechanical, and chemical strength over a wider temperature and pH range. In MMMs where the flexibility, processability, and scalability of polymeric membranes meet the exceptional separation performance, the chemical and thermal stability of inorganic fillers have become a trending focus of academia and industry.
Since the first report of MMMs in 1970
[56], extensive research has been conducted to improve the separation performance and industrial implementation for a range of applications such as hydrogen recovery, treatment of natural gas, and air separation
[57][58][59]. Different types of polymer matrices have been reported with various fillers, such as MOFs
[60][61][62][63][64], COFs
[65][66][67][68][69], carbon materials
[70], zeolites
[56], and other materials
[71][72]. Zeolite materials with their sieving properties and cost-effectiveness on a large scale make them better candidates for gas separation. The most suitable zeolite filler for CO
2 separation is SAPO-34 due to its unique structure and CO
2 adsorption affinity
[73].
2.1.1. SAPO-34 MMMs
Peydayesh et al.
[74] fabricated SAPO-34/Matrimid 5218 MMMs. They showed 55% and 97% enhancements in CO
2 permeability and CO
2/CH
4 selectivity, respectively, indicating the good adhesion of the filler in the polymer matrix. Wu et al.
[75] reported an MMMs obtained by the inclusion of SAPO-34 nanoparticles within a polyethersulfone (PESU) polymer. The separation performance increased with increasing SAPO-34 loading. In addition, the nanoparticle size was investigated, where 100 nm particles resulted in defective membranes. In contrast, 200 nm SAPO-34 showed fewer defects with a continuous interface and higher permselectivity than smaller particles. Carter et al.
[76] reported three types of filler: SAPO-34, silica, and ZIF-8. Among all the fabricated MMMs, ZIF-8 showed the best performance owing to the strong interaction between the filler and polymer matrix and surface diffusion transport. In addition, the study claimed that pore size was the most influential factor in gas permeability, as it increased permeability. As a result of the reduced interfacial voids and chain mobility, the SPAO-34 MMMs showed high ideal selectivity. Messaoud et al.
[77] reported a dip-coating route for fabricating SAPO-34/polyetherimide MMMs. This study investigated the effects of two solvents, N-methyl-2-pyrrolidone (NMP) and dichloroethane (DCE), on membrane fabrication. DCE resulted in better performance properties related to the entrapping of small DCE molecules in SAPO-34 particles, which induced the sealing of SAPO-34 pores. The best molecular sieving performance was achieved with 5 wt% SAPO-34 MMMs with 4.41 × 10
−10 mol m
−2 s
−1 Pa
−1 and 60 CO
2/CH
4 selectivity. Particle agglomeration was observed with 10 wt% MMMs. Zhao et al.
[78] reported SAPO-34/Pebax1657 MMMs fabricated by solvent evaporation. The inclusion of SAPO significantly enhanced the CO
2 permeability as compared with that of the neat membrane, whereas the selectivity remained constant. The effect of pressure was studied, and as a reason for plasticization, the permeation of MMMs increased with pressure. Junaidi et al.
[79] conducted two studies on MMMs. First, asymmetric SAPO-34/PSf MMMs were prepared using the phase inversion method. The highest performance was achieved with 10 wt% MMMs with ideal selectivity 28.1 and 26.2 for CO
2/CH
4 and CO
2/N
2, respectively. When the filler loading was increased to >20 wt%, it led to poor interaction between filler and matrix which caused interfacial voids. They modified the SAPO-34 particles with the coupling agent APMS using two solvents, isopropanol and ethanol, before being added to the polymer matrix to overcome the previously reported challenge. The study showed that modified SAPO-34 MMMs exhibited better performance than unmodified and neat membranes owing to the reduction in interfacial voids
[80]. An experimental and modeling study was reported by Santaniello et al.
[73] where 200 nm SAPO-34 was incorporated, for the first time, in a polyhexafluoropropylene PHFP matrix. The MMMs with 24.6 v% and 36 v% showed an enhancement in the permeability and CH
4/CO
2 selectivity as compared with the neat membrane, which was ascribed to the increased polymer-free volume. The modeling part of gas transport confirmed the experimental results that 200 nm SAPO-34 particles provoked a polymer-free volume of 24.6 v%.
2.1.2. SAPO-34 Functionalized MMMs
The functionalization strategy offers the prospect of enhancing membrane performance. Cakal et al.
[81] reported the influence of compatibilizer additives on the permeation performance of SAPO-34/HMA/PES membranes. The elimination of interfacial voids in the membrane is the main role of the HMA compatibilizer. The improvement in CO
2/CH
4 selectivity for SAPO-34 (20 wt%)/HMA (10%)/PES as compared with neat PES was attributed to the reduction in the diffusion pathway of CH
4. The effect of temperature was expected, as the permeability of all gases was enhanced as the temperature increased
[82]. The effect of the functionalization of SAPO-34 with ethylenediamine (EDA) and hexylamine (HA) organic amino cations on the gas permeation, morphology, and pore size of SAPO-34/PES MMMs was investigated. The MMMs fabricated with modified SAPO-34 with the EDA agent showed better performance than the HA agent owing to higher amino grafting, which enhanced the filler/polymer adhesion, resulting in a better CO
2/CH
4 ideal selectivity
[83]. Amino functionalization and ionic liquid inclusion were studied by Nasir et al.
[84]. The study revealed that the improvement of the particles/polymer interphase was due to the incorporation of [emim][Tf
2N] ionic liquids. Simultaneously, the amino functionalization of the SAPO-34 surface by EDA and HA enhanced the thermal stability of the MMMs. In addition, the membrane with the modified SAPO-34 and [emim][Tf
2N] IL exhibited the best CO
2/CH
4 selectivity as compared with that of the neat membrane. The hydrophobicity of MMMs is a key factor for industrial applications. Functionalization of SAPO-34 using 1H,1H,2H,2H-perflourodecyltriethoxysilane (HFDS) fluorocarbons was reported by Junaidi et al.
[85]. In this study, functionalized SAPO-34 particles were embedded in a PSf polymer to overcome the competitive adsorption of moisture under wet conditions. Among the fabricated MMMs, the SAPO-34 10 wt% + 0.1 HFDS/PSF membrane showed the best performance (CO
2 permeance = 278 GPU) and (CO
2/CH
4 = 38.9) as compared with a bare polymer. The incorporation of modified SAPO-34 enhanced the membrane 17.64% hydrophobicity and showed better filler/polymer adhesion. In addition, SAPO-34 10 wt% + 0.1 HFDS/PSf membrane showed excellent stability for long-term stability tests under wet and dry conditions, whereas the unmodified membrane lost 90% of its performance under wet conditions.
Incorporating the third component in the MMM plays a vital role in improving SAPO-34 membrane performance. Nawar et al. reported the synergetic influence of ionic liquid (IL) inclusions on the separation of SAPO-34 MMMs
[86]. In this study, 5 wt% SAPO-34 particles were incorporated into the polysulfone matrix, and the resulting membrane was immersed in 1-ethyl-3-methylimidazolium bis(tri-fluoromethylsulfonyl)imide IL. The membrane with the 0.2 M ionic liquid showed enhanced membrane performance as compared with the unmodified membrane, which was ascribed to interfacial defect reduction due to ionic liquid inclusion. Increasing the amount of ionic liquid caused a reduction in permeance and selectivity owing to pore and filler blockage. Ahmad et al.
[87] used an [emim][TF2N] IL. Increasing the immersion time of SAPO-34 membranes led to an enhancement in the adsorption affinity of SAPO-34 for CO
2 and filler/polymer interfacial adhesion, and SAPO-34 + IL/PSF showed the best performance as compared with neat PSF, with ideal selectivity of 20.35 and 18.82 for CO
2/CH
4 and CO
2/N
2, respectively. Mohshim et al.
[88] reported the use of Tf2N in SAPO-34/PES. This work also proved that ionic liquids improve interfacial adhesion and function as wetting agents. The performance of the modified MMMs was significantly enhanced as compared with bare PES. A modeling study was conducted to study the effect of incorporating (emim [Tf
2N]) and (emim[CF
3SO
3]) ionic liquids in a polymer matrix using the Maxwell, Lewis–Nielson, and Maxwell–Wagner–Sillar (MWS) gas separation models. The study showed a local agglomeration of SAPO-34 particles and a high deviation from the experimental results. Modification of the MWS model to include the wet phase factor showed good agreement with the experimental results
[89]. Sen et al.
[90] investigated the impregnation of carbon in polyetherimide using in situ carbonization to tailor SAPO-34 MMMs. Owing to the incompatibility, the impregnated carbon particles redecorated the interfacial pores formed between the filler and polymer. This approach minimized the interfacial pores/defects, which enhanced membrane performance.
2.1.3. SAPO-34 MMMs and Operating Conditions
The operating conditions are one of the key factors affecting membrane performance. Sodeifian et al.
[91] investigated the influence of pressure and inclusion of SAPO-34 nanoparticles. The study showed that increasing the pressure (0.4–1.4 MPa) caused an increase in CO
2 permeability, whereas CH
4 and N
2 permeability remained constant. Increasing SAPO-34 within the polyurethane matrix decreases the permeability of CO
2 and CH
4 and enhanced the ideal selectivity of CO
2/N
2 and CO
2/CH
4, which indicated the benefit of SAPO-34 particle incorporation in the PU matrix, as shown in
Figure 4.
Figure 4. Effect of SAPO-34 content in the gas permeation properties of polyurethane–SAPO-34 membranes on the permeability of CO
2, CH
4, and N
2 gases in 1.2 MPa pressure and selectivity of CO
2/CH
4 and CO
2/N
2 gases in 1.2 MPa pressure.
Adapted with permission from Ref. [91]. Copyright 2019 Elsevier.
Rabiee et al.
[92] investigated the effects of temperature and pressure on the separation performance of SAPO-34/Pebax MMMs. The study showed that the incorporation of SAPO-34 led to an enhancement in gas permeability
, and the membranes exhibited diffusion-dominant behavior, and indicated the molecular sieving effect of SAPO-34. An increase in operating conditions and pressure (4–24 bar) led to an enhancement in gas permeation, increasing the driving force and solution diffusion mechanism. The temperature alternation also showed the same behavior, which increased the Pebax chain mobility around the filler. The above discussions are summarized in
Table 1.
Table 1. Summary of separation performance for SAOP-34 MMMs.
Filler |
Substrate |
CO | 2 | Permeance |
CO | 2 | /CH | 4 | Selectivity |
CO | 2 | /N | 2 | Selectivity |
Ref. |
Neat |
Matrimid 5218 |
4.4 Barrer |
34 |
- |
[74] |
SAPO-34 2 wt% |
Matrimid 5218 |
4.5 Barrer |
41.98 |
- |
[74] |
SAPO-34 5 wt% |
Matrimid 5218 |
4.6 Barrer |
44.24 |
- |
[74] |
SAPO-34 10 wt% |
Matrimid 5218 |
5.3 Barrer |
50.82 |
- |
[74] |
SAPO-34 15 wt% |
Matrimid 5218 |
5.9 Barrer |
58.14 |
- |
[74] |
SAPO-34 20 wt% |
Matrimid 5218 |
6.9 Barrer |
66.99 |
- |
[74] |
Neat |
Polyethersulfone (PESU) |
6.7 Barrer |
37.8 |
- |
[75] |
SAPO-34 NP 20 wt% |
Polyethersulfone (PESU) |
8.2 Barrer |
42.6 |
- |
[75] |
SAPO-34 NP 30 wt% |
Polyethersulfone (PESU) |
8.9 Barrer |
48.3 |
- |
[75] |
Neat |
Matrimid 5218 |
9.5 ± 1.07 GPU |
29.81 |
13.63 |
[76] |
SAPO-34 10 wt% uncalcined |
Matrimid 5218 |
7.63 ± 0.81 GPU |
31.79 |
26.31 |
[76] |
SAPO-34 10 wt% calcined |
Matrimid 5218 |
12.5 ± 1.3 GPU |
9.32 |
10.50 |
[76] |
Neat |
Polyetherimide |
6 × 10 | −10 | mol/(m | 2 | s Pa) |
0.02 |
- |
[77] |
SAPO-34 5 wt% |
Polyetherimide |
4.4 × 10 | −10 | mol/(m | 2 | s Pa) |
60 |
- |
[77] |
SAPO-34 10 wt% |
Polyetherimide |
6 × 10 | −10 | mol/(m | 2 | s Pa) |
8 |
- |
[77] |
Neat |
Pebax 1657 |
100 Barrer |
16.7 |
53.8 |
[78] |
SAPO-34 23 wt% |
Pebax 1657 |
134 Barrer |
21.7 |
55.2 |
[78] |
SAPO-34 33 wt% |
Pebax 1657 |
252 Barrer |
17 |
55 |
[78] |
SAPO-34 50 wt% |
Pebax 1657 |
339 Barrer |
16.8 |
53.2 |
[78] |
Neat |
Polysulfone (Asymmetric) |
22.0 ± 3.42 GPU |
17.3 |
16.5 |
[79] |
SAPO-34 5 wt% |
Polysulfone (Asymmetric) |
205.9 ± 7.26 GPU |
22.5 |
21.4 |
[79] |
SAPO-34 10 wt% |
Polysulfone (Asymmetric) |
314.0 ± 4.65 GPU |
28.2 |
26.1 |
[79] |
SAPO-34 20 wt% |
Polysulfone (Asymmetric) |
281.18 ± 6.92 GPU |
10.9 |
10.7 |
[79] |
SAPO-34 30 wt% |
Polysulfone (Asymmetric) |
232. ± 3.21 GPU |
3 |
2.9 |
[79] |
Neat |
Polysulfone (Asymmetric) |
105 GPU |
15 |
13 |
[80] |
SAPO-34 10 wt% |
Polysulfone (Asymmetric) |
459 GPU |
27 |
21 |
[80] |
SAPO-34E 10 wt% |
Polysulfone (Asymmetric) |
706 GPU |
31 |
28 |
[80] |
SAPO-34I 10 wt% |
Polysulfone (Asymmetric) |
775 GPU |
28 |
22 |
[80] |
Neat |
Polyhexafluoropropylene (PHFP) |
290 Barrer |
14.1 |
- |
[73] |
SAPO-34 NP 24.6 v% |
Polyhexafluoropropylene (PHFP) |
468 Barrer |
15.8 |
- |
[73] |
SAPO-34 NP 36 v% |
Polyhexafluoropropylene (PHFP) |
437 Barrer |
17.5 |
- |
[73] |
Neat |
PES |
4.45 Barrer |
33.2 |
- |
[81] |
HMA 10% |
PES |
0.8 Barrer |
32.3 |
- |
[81] |
SAPO-34 20 wt% |
PES |
5.7 Barrer |
37 |
- |
[81] |
SAPO-34 20 wt% + HMA 10% |
PES |
1.3 Barrer |
44.7 |
- |
[81] |
HMA 4% |
PES |
5.1 Barrer |
39.3 |
- |
[82] |
SAPO-34 20 wt% |
PES |
13.8 Barrer |
32.7 |
- |
[82] |
SAPO-34 20 wt% + HMA 4% |
PES |
7.8 Barrer |
41.6 |
- |
[82] |
SAPO-34 |
PES |
18 GPU |
1.2 |
- |
[83] |
SAPO-34 20 wt% |
PES |
30 GPU |
1.3 |
- |
[83] |
SAPO-34 20 wt% m-EDA |
PES |
10.0 GPU |
12.14 |
- |
[83] |
SAPO-34 20 wt% |
PES |
50 GPU |
2.5 |
- |
[84] |
SAPO-34 20 wt%/IL |
PES |
0.03 GPU |
4.9 |
- |
[84] |
SAPO-34 20 wt% m-EDA/IL |
PES |
0.09 GPU |
26.5 |
- |
[84] |
SAPO-34 20 wt% m-HA/IL |
PES |
0.045 GPU |
37.2 |
- |
[84] |
Neat |
Polysulfone (PSf) |
21.3 ± 2.8 GPU |
17.2 |
- |
[85] |
SAPO-34 10 wt% |
Polysulfone (PSf) |
317.0 ± 3.5 GPU |
27.9 |
- |
[85] |
SAPO-34 20 wt% |
Polysulfone (PSf) |
283.0 ± 2.2 GPU |
10.8 |
- |
[85] |
SAPO-34 10 wt% + 0.5 wt%HFDS |
Polysulfone (PSf) |
310.4 ± 1.7 GPU |
30.4 |
- |
[85] |
SAPO-34 10 wt% + 1 wt%HFDS |
Polysulfone (PSf) |
278.8 ± 2.1 GPU |
38.9 |
- |
[85] |
SAPO-34 10 wt% + 1.5 wt%HFDS |
Polysulfone (PSf) |
259.7 ± 4.2 GPU |
37.3 |
- |
[85] |
SAPO-34 20 wt% + 0.5 wt%HFDS |
Polysulfone (PSf) |
332.1 ± 5.5 GPU |
11.9 |
- |
[85] |
SAPO-34 20 wt% + 1 wt%HFDS |
Polysulfone (PSf) |
293.7 ± 4.9 GPU |
27.5 |
- |
[85] |
SAPO-34 20 wt% + 1.5 wt%HFDS |
Polysulfone (PSf) |
306.8 ± 5.2 GPU |
24.8 |
- |
[85] |
SAPO-34 5 wt% |
Polysulfone (PSf) |
6.1 GPU |
4.9 |
5.1 |
[87] |
SAPO-34 5 wt%/IL(0.2 M) |
Polysulfone (PSf) |
24.89 GPU |
35.06 |
40.15 |
[87] |
Neat |
Polysulfone (PSf) |
5.60 ± 0.75 GPU |
3.24 |
6.15 |
[88] |
SAPO-34 5 wt% |
Polysulfone (PSf) |
6.53 ± 1.22 GPU |
3.47 |
5.67 |
[88] |
SAPO-34 5 wt%/IL(0.4 M) |
Polysulfone (PSf) |
4.82 ± 1.28 GPU |
4.86 |
8.04 |
[88] |
SAPO-34 5 wt%/IL(0.6 M) |
Polysulfone (PSf) |
7.24 ± 1.78 GPU |
20.35 |
18.82 |
[88] |
SAPO-34 20 wt% |
Polyethersulfone (PES) |
85.7 GPU |
20.67 |
- |
[89] |
SAPO-34 20 wt% + IL 5 wt% |
Polysulfone (PSf) |
230.8 GPU |
- |
46.20 |
[89] |
SAPO-34 20 wt% + IL 10 wt% |
Polysulfone (PSf) |
255.69 GPU |
- |
58.83 |
[89] |
SAPO-34 20 wt% + IL 15 wt% |
Polysulfone (PSf) |
279.2 GPU |
- |
60.62 |
[89] |
SAPO-34 20 wt% + IL 20 wt% |
Polysulfone (PSf) |
300.0 GPU |
- |
62.58 |
[89] |
Neat |
Polyetherimide |
3.8 × 10 | −10 | mol/(m | 2 | s Pa) |
- |
2.23 |
[91] |
SAPO-34 10 wt% |
Polyetherimide |
2.8 × 10 | −8 | mol/(m | 2 | s Pa) |
- |
2.54 |
[91] |
SAPO-34 25 wt% + Carbonization |
Polyetherimide |
8.42 × 10 | −8 | mol/(m | 2 | s Pa) |
- |
6.47 |
[91] |
SAPO-34 40 wt% |
Polyetherimide |
9.1 × 10 | −7 | mol/(m | 2 | s Pa) |
- |
5.05 |
[91] |
Neat |
Polyurethane |
30.05 Barrer |
21.93 |
36.64 |
[86] |
SAPO-34 NP 5 wt% |
Polyurethane |
29.41 Barrer |
22.97 |
44.56 |
[86] |
SAPO-34 NP 10 wt% |
Polyurethane |
28.43 Barrer |
23.89 |
54.67 |
[86] |
SAPO-34 NP 20 wt% |
Polyurethane |
28.71 Barrer |
25.63 |
58.59 |
[86] |
Neat |
Pebax 1074 |
120 Barrer |
17.5 |
60.3 |
[92] |
SAPO-34 5 wt% |
Pebax 1074 |
123 Barrer |
18.5 |
61 |
[92] |
SAPO-34 10 wt% |
Pebax 1074 |
130 Barrer |
22 |
62.5 |
[92] |
SAPO-34 20 wt% |
Pebax 1074 |
152 Barrer |
29 |
68 |
[92] |
SAPO-34 30 wt% |
Pebax 1074 |
156 Barrer |
35 |
69 |
[92] |