Facilitating CO2 transport across mixed matrix membranes containing

Subscriber access provided by Kaohsiung Medical University

Applications of Polymer, Composite, and Coating Materials

Facilitating CO2 transport across mixed matrix membranes containing multifunctional nanocapsules Haiyang Zhang, Ruili Guo, Jinli Zhang, and Xueqin Li ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b15269 • Publication Date (Web): 19 Nov 2018 Downloaded from http://pubs.acs.org on November 20, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Facilitating CO2 transport across mixed matrix membranes containing multifunctional nanocapsules Haiyang Zhang,† Ruili Guo,† Jinli Zhang,†, ‡ Xueqin Li,† †School

of Chemistry and Chemical Engineering/Key Laboratory for Green

Processing of Chemical Engineering of Xinjiang Bingtuan, Shihezi University, Shihezi, Xinjiang, 832003, China ‡Key

Laboratory for Green Chemical Technology of Ministry of Education, School of

Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China ABSTRACT: Mixed matrix membranes (MMMs) have exhibited advantages in overcoming the trade-off effect, although it is still intensively demanded in the design of multifunctional fillers to improve CO2 separation performance. At present, MMMs with transport channels present an effective strategy to obtain ultrahigh CO2 permselectivity. In this work, Pebax-based MMMs was fabricated by incorporating nanocapsules (NCs), whose exterior, interior and transverse shell surfaces contained abundant carboxylic acid groups. NCs, similar to vesicles in cells, provide favourable physical and chemical microenvironments to the constructed CO2 transport channels, enhancing the CO2 permselectivity via both a facilitated transport mechanism and a solution-diffusion mechanism. CO2 permselectivity of MMMs doped with 20 wt% NCs surpassed the 2008 Robeson limit; an increase in CO2 permeability was up to 1431 ± 35 Barrer for pure gas, which was a 362% enhancement from the pure membrane, and an increase of the CO2/CH4 and CO2/N2 ideal selectivities to 46 ± 1.4 and 69 ± 2.7, corresponding to 44% and 23% enhancements from the pure membrane, 1

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

respectively. This study provides an ingenious strategy to enhance the gas permselectivity of MMMs. KEYWORDS: Pebax, nanocapsule, mixed matrix membrane, channel, CO2 capture

2


Page 2 of 42

Page 3 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1. INTRODUCTION On the basis of the CO2 removal from natural gas for energy utilisation and carbon capture from flue gas for environment issues, fast and selective CO2 separation membranes have attracted enormous interest because of their high energy efficiency, environment friendly nature and low energy consumption.1-2 New membrane materials are required to further develop highly efficient membranes.3-6 In nature, selective CO2 channels are abundant in biological systems.7 A cell, and its membrane offers efficient channels to control the CO2 exchange. Biological membranes represent a wonderful prototype with unusually high efficiency for CO2 transport. To comprehend the selective permeation mechanism in biological membranes and imitate their separation mechanism, the corresponding models have been researched.8-9 The ultrafast CO2 transport behaviour of biological membranes arises from favourable physical and chemical channel microenvironments and from multiple transport mechanisms.10-12 Inspired by CO2 transport in biological membranes, synthetic membranes can be designed by mimicking their structure and composition to construct CO2 transport channels and achieve multiple transport mechanisms, thus improving their CO2 separation performance. Within the last few years, mixed matrix membranes (MMMs) have been considered as excellent materials for such systems because of their advantages given by combining a filler and a polymer matrix phase.13-19 3



Page 4 of 42

Designing the fillers can endow these MMMs with efficient CO2 transport channels, which are mainly constituted by channel-containing nanofillers. However, researchers have been devoting to tailor the physical and chemical microenvironments of the transport channels to achieve selective and fast CO2 transport. The physical microenvironments of CO2 transport channels depend mainly on the channel structure, distribution and connectivity. For example, hollow fillers offer hollow channels, which simultaneously reduce CO2 transport distance and resistance.20-22 By regulating their distribution, highly ordered and interconnected channels favourable to rapid CO2 transport can be obtained. On the other hand, the regulation of the chemical microenvironments primarily focuses on the dissolution and the facilitated transport processes of CO2 molecules.23-25 When selecting the functional groups for channel decoration, their interactions with water should be primarily considered since water serves as both important medium and efficient carrier for CO2 transport. When it is present, water acts as a CO2 carrier and a Brønsted base. It can also efficiently catalyse the conversion of CO2 to HCO3−, as shown in Equations (1) and (2). Since HCO3− is transported faster than CO2 through the hydrated channels, CO2 transport is considerably facilitated.10 CO2 + H2O ⇋ H2CO3

(1)

H2CO3 ⇋ H+ + HCO3−

(2)

4


Page 5 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Moreover, functional groups usually act as affinity reagents for the surface modification of fillers. The functional sites on the interior and exterior surfaces of the channels greatly influence the CO2 transport behaviour of the membranes. The functional sites (such as –COOH, –NH2, ethylene oxide units) inside MMMs are expected to interact with CO2 and water to provide optimal chemical microenvironments in the channels, facilitating the CO2 dissolution process and transport through MMMs.26-28 Given the water absorbability and retention of different functional groups, we discuss and focus on a selection of carboxyl groups for the optimisation of the chemical microenvironments of CO2 transport channels because of their higher CO2 sorption and water absorbability compared to other groups (amines and hydroxyl groups).29-31 In this study, the rational design of MMMs from the viewpoints of constructing CO2 transport channels and regulating their microenvironments is proposed. For the first time, nanocapsules (NCs) with carboxyl group loading on their exterior, interior and transverse shell surfaces were synthesised. Then, they were doped into a Pebax polymer to fabricate MMMs. The NCs, similarly to vesicles in cells, play the following roles. Their hollow structure acts as the ultrahigh channels, simultaneously reducing CO2 transport distance and resistance. The carboxyl groups on their exterior, interior and transverse shell surfaces can absorb large amounts of water, which acts as a CO2 carrier, enhancing the CO2 transport via a facilitated transport mechanism. With the aid of these multifunctional NCs, we can achieve an efficient CO2 transport by 5



constructing CO2 transport channels and regulating channel microenvironments. To intensify this effect, we choose Pebax MH 1657 as the membrane matrix, because of its good affinity with CO2, hydrophilicity and good stability.32-33 2. EXPERIMENTAL PROCEDURES 2.1. Materials. Pebax MH 1657 (Pebax) was supplied by Shanghai Rongtian Chemical Co., Ltd. Tetraethyl orthosilicate (TEOS), N, N’-methylenebisacrylamide (MBAAm), methacrylic acid (MAA), 2,2’-azobisisobutyronitrile (AIBN), acetonitrile, 40% hydrofluoric acid (HF) solution and 25% ammonium aqueous solution were purchased from Aladdin Chemistry Co., Ltd. 2.2. Synthesis of NCs. Silica spheres were synthesised by the classical Stöber method.34 TEOS (14 mL) was dropped into a mixed solution of ethanol (250 mL), water (25 mL) and 25% ammonium aqueous solution (6 mL) and stirred at 25 °C for 24 h. Then, resultant silica spheres were purified by repeated centrifugation, followed by the desiccation at 50 °C to a constant weight. The synthesised silica spheres (0.02 g) were suspended in acetonitrile (40 mL). MBAAm (0.10 g), MAA (0.14 g) and AIBN (0.005 g) were dropped into the above suspension in a flask attached to a Liebig condenser, a fractionating column and a receiver, and then the suspension was boiled. After removing the solvent (20 mL), the resultant composite spheres with –COOH groups on their shell layers were purified by repeated centrifugation, followed by the desiccation at 50 °C to a constant weight. 6


Page 6 of 42

Page 7 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The resultant composite spheres were immersed in the 40% HF aqueous solution for 2 h. The final NCs were obtained by centrifuging and washing in water until pH of 7 and successive drying at 50 °C to a constant weight. 2.3. Fabrication of MMMs. Pebax pellets (0.6 g) were dissolved into a 70 wt% ethanol aqueous solution (14.4 g) under stirring (80 °C) for at least 2 h. Simultaneously, a given mass of NCs was put into Pebax solution and dispersed by ultrasonic treatment; then, the solution was mixed under stirring for other 6 h (25 °C). The detail procedure of fabricating MMMs was the same as that in our previous work.17 The NCs-containing MMM series produced was labelled as Pebax–NC-X, where X (0–30 wt%) is the mass percentage of NCs relative to the mass of polymer matrix. The controlled thicknesses were located in the range of 75–95 μm for the membranes. 2.4. Characterisation of MMMs. Transmission electron microscopy (TEM) measurement was conducted using Tecnai G2 F20 S-TWIN.35 Fourier transform infrared (FTIR) spectra (400–4000 cm−1) were recorded using a Vertex 70 Bruker spectrometer. Scanning electron microscopy (SEM) characterisation was carried out by a Hitachi S-4800 microscope; the microstructure of the membranes was observed after being sputtered with a gold layer. The glass transition temperature (Tg) was obtained by differential scanning calorimetry (DSC) attached to a Netzsch DSC 200 F3 apparatus; the membrane samples were preheated under N2 atmosphere from room temperature to 100 °C, then cooled down to −75 °C and finally reheated up to 7



Page 8 of 42

250 °C at 10 °C/min. X-ray diffractometry (XRD) was carried out in the 3°–90° range using a Rigaku D/MAX 2500 diffractometer.36-37 2.5. Permeation experiments. A set of experimental equipment for gas tests shown in Scheme 1 was set up to evaluate the gas permselectivity of the fabricated membranes with a conventional constant pressure/variable volume method.16 The diffusivity and solubility of all membranes were tested using the time-lag method.16 Pure gases or mixed-gas with a 10/90 volume ratio for CO2/CH4 (or CO2/N2) were supplied as feed gas. Gas permeation experiments were conducted under dried or humidified gas. The detailed procedure of measurement was described in our previous reported works.17, 38 The flow rate of feed gas was 85 mL/min and that of sweep gas was 31 mL/min. The permeate gas composition was analysed using a gas chromatograph (Agilent 7820). All of the as-prepared membranes were measured at least three times to guarantee the reproducibility and reliability. The

gas

permeability

(Pi,

in

Barrer;

1

Barrer

=

10−10

(cm3STP · cm)/(cm2 · s · cmHg)) was calculated as follows:

Pi =

Qi l ΔP i A

(3)

where Qi is the volumetric flow rate of gas “i” (in cm3STP/s), l is the membrane thickness (in cm), Δpi is the partial pressure difference of gas “i” (in cmHg), and A is the effective membrane area (in cm2, 12.90 cm2 in this study). The selectivity (αij, ideal selectivity, separation factor) of the membranes was calculated as the permeability ratio between fast gas “i” and slow gas “j”:

8


Page 9 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


αij=

Pi Pj

(4)

Scheme 1. A schematic diagram of the equipment for gas test. 3. RESULTS AND DISCUSSION 3.1. Characterisation of Multifunctional NCs. The morphology and size of the synthesised NCs were characterised by TEM. The TEM image shown in Figure 1a clearly reveals well-defined capsular structures for all NCs, which were quite uniform and had a lumen diameter of ~260 nm. The thickness of shell was around 90 nm, resulting in enough robustness to maintain the hollow structure. The chemical structures of the synthesised NCs were characterised by FTIR analysis. The peak situated at 1685 cm−1 in NCs (Figure 1b) is due to the stretching vibration of the carbonyl units of –COOH groups.

9



Figure 1. TEM images of NCs (a) and FTIR spectra of NCs (b). 3.2. Characterisation of MMMs. The cross-sectional morphologies can be obviously observed from SEM images (Figure 2). Pure Pebax membrane had a smooth and dense cross-sectional structure. NCs maintained their pristine structure and were homogeneously mixed with the Pebax matrix without apparent filler aggregations under a maximum filler loading amount of up to 20 wt%, above which some aggregation phenomenon was observed (Figure 2 and Figure S1). As shown in Figure 2i, the NCs aggregated in some regions circled by yellow ellipses in the MMMs. However, NCs have good interfacial compatibility with membrane matrix, and they can be observed in SEM images at high magnification (Figure 2d, f, h and j). Additionally, the holes in SEM images resulted from the broken NCs during freeze-fracturing in liquid nitrogen for membrane samples. Besides, some whole NCs can also be clearly observed and they have been circled by two red circles in Figure 2h.

10


Page 10 of 42

Page 11 of 42


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 11



Figure 2. SEM images of cross-sections of (a, b) Pebax, (c, d) Pebax-NC-5, (e, f) Pebax-NC-10, (g, h) Pebax-NC-20 and (i, j) Pebax-NC-30 membranes (HM represents the SEM images observed under high magnification. The red circles indicate some whole NCs existed in MMMs, and the positions of yellow ellipses indicate the agglomeration of NCs in MMMs). The compatibility between Pebax and NCs was analysed by DSC at temperatures between −65 °C and 250 °C (Figure S2). As shown in Table 1, the melting temperatures (Tms) of the polyethylene oxide (PEO) blocks in the Pebax–NC MMMs shifted towards a higher temperature region (at about 35 °C) than those in pure Pebax membrane. This suggests that NCs have a strong interaction with PEO blocks, decreasing the mobility of polymer chains. As displayed in Table 1, the Tg of pure membrane was −51.3 °C, and those of the Pebax–NC MMMs increased to −44.9 °C upon increasing the content of NCs up to 30 wt%, indicating a good interfacial compatibility between the Pebax matrix and NC fillers, probably because of their hydrogen bonds. Such bonds were formed between −OH in the Pebax chain and −COOH in the NC surface and between the ether oxygen units in Pebax and NCs, as revealed by FTIR analysis (Figure S3). NCs provided superior interfacial compatibility with matrix, which is a requisite for the realisation of the high selective MMMs. Table 1. DSC results of the membranes

12


Page 12 of 42

Page 13 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Membrane sample

Tg (°C)

Tm of PEO (°C)

Tm of PA (°C)

Pure Pebax

-51.3

16.8

207.5

Pebax-NC-5

-50.9

17.8

207.8

Pebax-NC-10

-50.2

22.4

207.8

Pebax-NC-20

-47.8

27.5

207.4

Pebax-NC-30

-44.9

35.7

205.3

3.3. Structure–Property Relationships. The water uptakes of samples were summarized, as shown in Figure S4, to pursue an explanation for the transport mechanisms of the synthesised Pebax–NC MMMs. Figure 3 exhibits the relationship between the CO2 separation performance of Pebax–NC MMMs and their water uptake. As can be seen from Figure 3, the greater the water uptake, the higher the CO2 permeability and CO2/gas selectivity. Furthermore, CO2 permselectivities increased simultaneously upon increasing the NC loading. This could be tentatively interpreted the favourable physical and chemical microenvironments of transport channels, which were constructed by introducing multifunctional NCs in the MMMs.

13


Page 14 of 42

2400

90

2100

80

CO2/N2

1800

70 60

1500

CO2/CH4

1200

50 40

900

30

600

20

300 0

Ideal selectivity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

CO2 permeability (Barrer)


10 5

10

15

20

25

30

0 35

Water uptake (%) Figure 3. Correlations between CO2 separation performance and water uptake of the MMMs. The physical microenvironments of the channels were mainly regulated by the hollow structure of the NCs. MMMs with NCs are schematically represented in Figure 4. The homogeneous dispersion of NCs in the membrane matrix formed the channels for CO2 transport. When a hollow filler was added, its hollow parts reduced the effective thickness of the MMMs (lE), which is equal to its total thickness (l) minus the hollow parts of the NCs (d*n) (Figure 4). Hollow NCs can increase the inner space of membrane matrix, thus increasing the gas permeability. Hence, introducing hollow fillers reduces both CO2 transport distance and resistance. In addition, NCs exhibited superior interfacial compatibility with Pebax matrix because of the formed hydrogen bonds between the –COOH on their surface and –O– units in Pebax polymer 14


Page 15 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


chains (Figure S3). NCs also decreased crystallinity of Pebax matrix (Figure S5), which is favourable to improve CO2 permeability.

Figure 4. Schematic representation of a MMM with NCs. The total thickness and effective thickness of a MMM are indicated by l and lE, respectively. d is the inner diameters of a NC. n represents the number of the NCs. The schematic illustration of the chemical microenvironments of the CO2 transport channels is shown in Figure 5. Their mainly exhibited details were as follows. (i) The addition of NCs improved the water uptake of MMMs (Figure 5), and water could dissociate acid groups as well as form a continuous water network microenvironment. (ii) Water acted as a CO2 carrier by forming HCO3− ions and transporting them faster than CO2 molecules, being able to pass through the MMMs with a low barrier. Therefore, the high water content of MMMs had CO2 transport resistance relatively lower than CH4 and N2. Considering the abundant water uptake in Pebax–NC MMMs, the water within the membranes may form facilitated CO2 transport channels. (iii) The NCs homogeneously dispersed within membrane matrix would open a new CO2 transport channel with the help of –COOH groups on their exterior, interior and transverse shell surfaces due to their good affinity with CO2. The intrinsic CO2 15



affinity of NCs can provide facilitated channels for CO2 transport across MMMs. This phenomenon can also be found in the reported literatures.39-41 It can be concluded that the introduction of NCs in MMMs played a positive role for CO2 transport, as expected.

Figure 5. Schematic illustration of the chemical microenvironments in a MMM. 3.4. The permselectibity of membranes. 3.4.1. Pure-gas. Permeations of pure-gas were performed on the synthesised Pebax–NC MMMs (Figure 6). The permeability for the target molecule (CO2) and the ideal selectivities of pure membrane were greatly improved by incorporating the NCs in the MMMs. A considerably higher CO2 permeability, beyond the current performance limits of various hollow filler- and Pebax-based MMMs (Table 2), was achieved. Moreover, the CO2 permselectivity of the Pebax–NC MMMs systematically increased upon increasing the NC loading up to 30 wt%. Compared with pure membrane, CO2 permeability increased by 362% for MMMs, up to 1431 ± 35 Barrer, at 20 wt% loading, together with a slight increase in CO2/CH4 and CO2/N2 ideal selectivities, respectively, up to 46 and 69. The notable increase of CO2 permeability was interpreted as follows: the hollow space in NC filler 16


Page 16 of 42

Page 17 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


simultaneously reduced the CO2 transport distance and resistance, thus increasing the CO2 permeation; meanwhile, the abundant carboxylic acid groups from the NCs promoted water uptake in the MMMs, favouring the CO2 transport via both a facilitated transport mechanism and a solution-diffusion mechanism. NC loading is considered a key factor in improving CO2 permselectivity of the MMMs. To clearly explain the transport mechanism of MMMs, the diffusivity and solubility of membranes were measured and the results are displayed in Figure S6. Figure S6 indicated that MMMs exhibited a higher diffusivity and solubility than pure membrane, and the diffusion coefficients (D) and solubility coefficients (S) of MMMs increased with the increasing NCs loading. The hollow structure of NCs provided accessible channels for all penetrant gases. Additionally, the affinitive groups endowed MMMs with strong affinity and increased the gas solubility of the membranes. NCs can also provide suitable physical and chemical microenvironments to construct CO2 transport channels, enhancing the CO2 permselectivity of the MMMs.

17



100

2400

CO2 permeability CO2/CH4


2100 1800

80

CO2/N2

1500

60

1200 40

900 600

Ideal selectivity

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 42

20

300 0

0

5

10

15

20

25

30

0

NCs content (wt%) Figure 6. The effect of NCs content on CO2 permselectivity under pure gas at 2 bar and 25 °C. 3.4.2. Mixed-gas. Figure 7 presented CO2 permselectivity of Pebax–NC MMMs for mixed gases. CO2 permselectivity with mixed-gas was lower than that observed with pure gases. The differences between pure- and mixed-gas originated from the different competitive sorption interactions for different gases (Table S1). However, the differences in separation factor and ideal selectivity between pure membrane and MMMs were small for mixed-gas. The main reason was that the incorporation of NCs offered favourable physical and chemical microenvironments of CO2 transport channel within the MMMs, increasing CO2 permselectivity, as explained in Section 3.3. Additionally, the preferential CO2 solubility of MMMs can increase more CO2 permeability than that of pure membrane, and it would hinder CH4 or N2 transport. 18


Page 19 of 42


a

2400

60

2100

50

1800 40

1500 1200

30

900

20

600 10

300 0

0

5

10

15

20

25

30

CO2/CH4 separation factor

0

NCs content (wt%)


b

100

2400 2100

80

1800 1500

60

1200 40

900 600

20

300 0

0

5

10

15

20

25

30

CO2/N2 separation factor

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0

NCs content (wt%) Figure 7. The effect of NCs content on CO2 permselectivity under mixed-gas at 2 bar and 25 °C (a) CO2/CH4 system and (b) CO2/N2 system.

19



3.4.3. Effect of feed gas pressure on CO2 permselectivity. The influence of feed gas pressure on CO2 permselectivity was studied for the membranes. In both cases, CO2 permselectivity decreased with the increase of feed gas pressure, and the decreased CO2 permeability suggested that it was a typical phenomenon in facilitated transport processes. It indicated that the CO2 transport through MMMs followed a facilitated transport mechanism. Moreover, the decrease for the pure membrane was higher than that for the Pebax–NC-20 MMM. The decrease of CO2 permeability for the pure Pebax membrane (Figure 8) with the pressure stemed from the decreasing solubility of the polymer (based on the dual-mode sorption model).42-43 The decrease of CO2 permeability showed by Pebax–NC-20 MMM at higher pressures is the same as that previously observed in literature and is usually attributed to the saturation of the CO2 carriers.44-45

20


Page 20 of 42

Page 21 of 42


a

90

1800

Pebax Pebax-NC-20

1500

80 70 60

1200

50 900 40 30

600

20 300 10 0

2

4

6

8

10


0

Feed pressure (bar)


b

1800

100

Pebax Pebax-NC-20

1500

80

1200 60 900 40 600 20

300 0

2

4

6

8

10


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0

Feed pressure (bar) Figure 8. The effect of feed pressure on CO2 permselectivity at 25 °C: (a) CO2/CH4 system and (b) CO2/N2 system.

21



3.4.4. Effect of operation temperature on CO2 permselectivity. Figure 9 shows the evolution of CO2 permselectivity for the membranes at various operation temperatures. For both samples, the separation factors declined with the increasing temperature, while CO2 permeability increased with the increasing temperature because of the resultant increase in polymer chains flexibility and gas diffusivity. The enhancement of CO2 permeability for Pebax–NC-20 MMM from 25 °C to 75 °C was more prominent than that for the pure membrane. This can be ascribed to the high water content of MMMs because of the presence of NCs.

22


Page 22 of 42

Page 23 of 42

a

3600

60

Pebax Pebax-NC-20


3200

50

2800 2400

40

2000 30 1600 1200

20

800 10 400 0 20

30

40

50

60

70


0 80

Temperature (o C)

b

100

3600

Pebax Pebax-NC-20


3200 2800

80

2400 60

2000 1600

40

1200 800

20

400 0 20

30

40

50

60

70


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0 80

Temperature (o C) Figure 9. The effect of operation temperature on CO2 permselectivity at 2 bar: (a) CO2/CH4 system and (b) CO2/N2 system.

23



3.4.5. Long-term stability of MMMs. The long-term stability of Pebax–NC-15 MMM was determined by continuous permeation for 120 h under the test conditions of 2 bar and 25 °C (Figure 10). Both CO2 permselectivity retained their initial values during the 120 h continuous permeation, demonstrating that the presence of NCs within MMMs maintained a favourable effect on the membrane structure during the assessment period, which is a critical aspect for membranes used in industrial applications.

24


Page 24 of 42

Page 25 of 42

a

80

2000


1800

70

1600

60

1400

50

1200

40

1000 800

30

600

20

400

10

200 0

0

10

20

30

40

50

60

70

80


0 90 100 110 120 130

Time (h)

b

2000

140


1800

120

1600 100

1400 1200

80

1000 60

800 600

40

400 20

200 0

0

10

20

30

40

50

60

70

80


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0 90 100 110 120 130

Time (h) Figure 10. The long-term assessment of the membranes under the test conditions of 2 bar and 25 °C: (a) CO2/CH4 system and (b) CO2/N2 system.

25



3.5. Comparison of CO2 permselectivity in this work with that in the related literatures. The CO2 permselectivity of the membranes are shown as Robeson upper bound lines in Figure 11. Membranes with CO2 separation performance closed to these lines were suitable for commercialisation. It clearly shows that the increase of NC loading has a beneficial effect on the CO2 permselectivity, surpassing the 2008 Robeson limit of 10 wt% NC loading. CO2 permeability increased at higher filler loadings because of the fast CO2 diffusion in the presence of transport channels.

a

1000

CO2/CH4 and CO2/N2 selectivities

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 42

2008 CO2/N2 upper bound 2008 CO2/CH4 upper bound

100

Pebax-SG Pure Pebax

10

Pebax-SG Pure Pebax 1

1

10

CO2/CH4 1991 CO2/CH4

CO2/N2 100

upper bound

1000

10000

CO2 permeability (Barrer) Figure 11. Robeson curves of the relationship between the mixed-gas selectivity and CO2 permeability for the CO2/CH4 and CO2/N2 systems. To better understand how NCs work within the MMMs, the results of this work were compared with those for other representative MMMs with hollow fillers or Pebax polymer matrix reported in literature (Table 2). 26


Page 27 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


After such comparison, the MMMs described here placed themselves among the best performing in terms of CO2 separation. Therefore, it can be inferred that the efficient CO2 channels were formed by the NCs in the MMMs. These results highlighted the key factor of NCs for CO2 separation in MMMs. Hence, the strategy of filler design presented in this work was indeed an ingenious inspiration to the development of high separation performance MMMs.

27


ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

Page 28 of 42

Table 2. CO2 permselectivity of various hollow filler- and Pebax-based MMMs fillers

Polymer

Loading (wt%)

P (atm)

T (°)

Test gas

Test state

PCO2(Barrer)

αCO2/CH4

αCO2/N2

Ref.

HZSs

PSF

8

2.7

35

Mixed gas

Dry

7.2

37.5

41.7

46

HZSs

PI

8

—

35

Mixed gas

Dry

18.7

87.7

39.8

46

ZIF-8

PVC-g-POEM

30

—

35

Pure gas

Dry

623.0

11.2

—

20

Ag/IL

Pebax 1657

0.5/50

10

35

Pure gas

Dry

180

61.0

187.5

32

MoS2

Pebax 1657

0.15

0.2

30

Pure gas

Dry

64

—

93

47

ATP

Pebax 1657

1.7

—

35

Pure gas

Wet

~180

—

~55

33

CNTs

Pebax 1657

2.5

2

25

Pure gas

Dry

~140

~18

—

48

zeolite

Pebax 1657

30

5

25

Pure gas

Dry

155.8

7.9

12.9

49

NaX

Pebax 1657

20

7

25

Pure gas

Dry

35.2

—

121.5

50

NaX

Pebax 1657

10

8

25

Pure gas

Dry

95

45

—

51

ZIF-7

Pebax 1657

8

3.8

25

Pure gas

Dry

145

23

68

52

28


Page 29 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46


ZIF-8

Pebax 1657

10

3

25

Pure gas

Dry

~180

19

41

53

PDA

Pebax 1657

5

2

25

Mixed gas

Wet

450.4

27.5

—

54

NC

Pebax 1657

20

2

25

Pure gas

Wet

1431

46

69

This work

NC

Pebax 1657

30

2

25

Pure gas

Wet

1993

39

60

This work

29



Page 30 of 42

4. CONCLUSIONS MMMs with high separation performance were fabricated by incorporating novel NCs into a Pebax matrix. The MMM performance was improved by the rational design of the NCs. The homogeneously dispersed fillers within the membrane matrix produced a facilitated CO2 transport channel with the assistance of the hollow structure of NCs, the carboxylic acid groups and the adsorbed water. Hence, NCs can provide favourable physical and chemical microenvironments of the constructed channels in MMMs, and CO2 will be able to permeate unhindered through their hollow structure. In addition, the absorbed water acts as CO2 carrier and forms interconnected networks for constructing CO2 transport channels, giving the MMMs both a facilitated transport

mechanism

and

a

solution-diffusion

mechanism.

The

CO2

permselectivity of Pebax–NC MMMs surpassed the upper bound limit with a reduced trade-off effect, and such high performance remained stable under humid state and after a 120 h continuous permeation. Consequently, the high CO2 permselectivity combined with good stability makes Pebax–NC MMMs feasible membrane materials for CO2 separations. ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Supporting Information contains Figure S1. SEM images of cross-sections of (a) 30


Page 31 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Pebax, (b) Pebax-NC-5, (c) Pebax-NC-10, (d) Pebax-NC-20 and (e) Pebax-NC-30 membranes under low magnification; Figure S2. DSC curves of membranes at temperatures between −65 °C and 250 °C; Figure S3. FTIR spectra of membranes: (a) the full wavenumber range (4000-500 cm-1) and (b) the low wavenumber range (1800–600 cm−1); Figure S4. Water uptake of membranes; Figure S5. XRD patterns of membranes; Figure S6. Diffusivity (a) and solubility (b) of gases for membranes at 2 bar and 25 °C.; Table S1. Kinetic diameters, critical temperatures and reactivity of various investigated gaseous species and REFERENCES. AUTHOR INFORMATION Corresponding author *X.

Li.

Tel.:

86-993-2057277.

Fax:

86-993-2057210.

E-mail

address:

[email protected]. ORCID Xueqin Li: 0000-0002-1501-4371 Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS We gratefully acknowledge the support from the National Natural Science Foundation for Young Scientists of China (Grant No. 21706166 and 21706167), the Fok Ying Tung Education Foundation (Grant No. 161108), the Program for Changjiang Scholars and Innovative Research Team in University (Grant No.

31



IRT_15R46) and Yangtze River scholar research project of Shihezi University (Grant No. CJXZ201601).

32


Page 32 of 42

Page 33 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


REFERENCES (1) Liu, G.; Chernikova, V.; Liu, Y.; Zhang, K.; Belmabkhout, Y.; Shekhah, O.; Zhang, C.; Yi, S.; Eddaoudi, M.; Koros, W. J. Mixed Matrix Formulations with MOF Molecular Sieving for Key Energy-Intensive Separations. Nat. Mater. 2018, 17 (3), 283-289. (2) Ding, L.; Wei, Y.; Li, L.; Zhang, T.; Wang, H.; Xue, J.; Ding, L. X.; Wang, S.; Caro, J.; Gogotsi, Y. Mxene Molecular Sieving Membranes for Highly Efficient Gas Separation. Nat. Commun. 2018, 9 (1), 155. (3) Fu, Y.; Jiang, Y. B.; Dunphy, D.; Xiong, H.; Coker, E.; Chou, S.; Zhang, H.; Vanegas, J. M.; Croissant, J. G.; Cecchi, J. L.; Rempe, S. B.; Brinker, C. J. Ultra-Thin Enzymatic Liquid Membrane for CO2 Separation and Capture. Nat. Commun. 2018, 9 (1), 990. (4) Zhou, F.; Tien, H. N.; Xu, W. L.; Chen, J.-T.; Liu, Q.; Hicks, E.; Fathizadeh, M.; Li, S.; Yu, M. Ultrathin Graphene Oxide-Based Hollow Fiber Membranes with Brush-Like CO2-Philic Agent for Highly Efficient CO2 Capture. Nat. Commun. 2017, 8 (1), 2107. (5) Molavi, H.; Shojaei, A.; Mousavi, S. A. Improving Mixed-Matrix Membrane Performance Via Pmma Grafting from Functionalized NH2–Uio-66. J. Mater. Chem. A 2018, 6, 2775-2791. (6) Park, H. B.; Kamcev, J.; Robeson, L. M.; Elimelech, M.; Freeman, B. D. Maximizing the Right Stuff: The Trade-off between Membrane Permeability and Selectivity. Science 2017, 356 (6343), eaab0530. 33



(7) K. Renggli; P. Baumann; K. Langowska; O. Onaca; N. Bruns; Meier, W. Selective and Responsive Nanoreactors. Adv. Funct. Mater. 2011, 21 (7), 1241-1259. (8) P. Tanner; P. Baumann; R. Enea; O. Onaca; C. Palivan; Meier, W. Polymeric Vesicles: From Drug Carriers to Nanoreactors and Artificial Organelles. Acc. Chem. Res. 2011, 44 (10), 1039-1049. (9) Midda, M. O.; Suresh, A. K. Some Mechanistic Insights into the Action of Facilitating Agents on Gas Permeation through Glassy Polymeric Membranes. AIChE J. 2018, 64 (1), 186-199. (10) Cao, L.; He, X.; Jiang, Z.; Li, X.; Li, Y.; Ren, Y.; Yang, L.; Wu, H. Channel-Facilitated Molecule and Ion Transport across Polymer Composite Membranes. Chem. Soc. Rev. 2017, 46, 6725-6745. (11) Wang, S.; Li, X.; Wu, H.; Tian, Z.; Xin, Q.; He, G.; Peng, D.; Chen, S.; Yin, Y.; Jiang, Z.; Guiver, M. D. Advances in High Permeability Polymer-Based Membrane Materials for CO2 Separations. Energy Environ. Sci. 2016, 9, 1863-1890. (12) Wang, S.; Xie, Y.; He, G.; Xin, Q.; Zhang, J.; Yang, L.; Li, Y.; Wu, H.; Zhang, Y.; Guiver, M. D.; Jiang, Z. Graphene Oxide Membranes with Heterogeneous Nanodomains for Efficient CO2 Separations. Angew. Chem. Int. Ed. 2017, 56, 14246 -14251.

34


Page 34 of 42

Page 35 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(13) Gao, Y.; Qiao, Z.; Zhao, S.; Wang, Z.; Wang, J. In Situ Synthesis of Polymer Grafted ZIFs and Application in Mixed Matrix Membrane for CO2 Separation. J. Mater. Chem. A 2018, 6 (7), 3151-3161. (14) Ebadi Amooghin, A.; Sanaeepur, H.; Omidkhah, M.; Kargari, A. “Ship-in-a-Bottle”, a New Synthesis Strategy for Preparing Novel Hybrid Host–Guest Nanocomposites for Highly Selective Membrane Gas Separation. J. Mater. Chem. A 2018, 6 (4), 1751-1771. (15) Zhu, X.; Hua, Y.; Tian, C.; Abney, C. W.; Zhang, P.; Jin, T.; Liu, G.; Browning, K. L.; Sacci, R. L.; Veith, G. M.; Zhou, H.C.; Jin, W.; Dai, S. Accelerating Membrane-Based CO2 Separation by Soluble Nanoporous Polymer Networks Produced Via Mechanochemical Oxidative Coupling. Angew. Chem. Int. Ed. 2017, 57 (11), 2816-2821. (16) Li, X.; Ma, L.; Zhang, H.; Wang, S.; Jiang, Z.; Guo, R.; Wu, H.; Cao, X.; Yang, J.; Wang, B. Synergistic Effect of Combining Carbon Nanotubes and Graphene Oxide in Mixed Matrix Membranes for Efficient CO2 Separation. J. Membr. Sci. 2015, 479, 1-10. (17) Zhang, H.; Guo, R.; Hou, J.; Wei, Z.; Li, X. Mixed-Matrix Membranes Containing Carbon Nanotubes Composite with Hydrogel for Efficient CO2 Separation. ACS Appl. Mater. Interfaces 2016, 8 (42), 29044-29051. (18) Wu, H.; Li, X.; Li, Y.; Wang, S.; Guo, R.; Jiang, Z.; Wu, C.; Xin, Q.; Lu, X. Facilitated Transport Mixed Matrix Membranes Incorporated with Amine

35



Page 36 of 42

Functionalized MCM-41 for Enhanced Gas Separation Properties. J. Membr. Sci. 2014, 465, 78-90. (19) Wang, Z.; Wang, D.; Zhang, S.; Hu, L.; Jin, J. Interfacial Design of Mixed Matrix Membranes for Improved Gas Separation Performance. Adv. Mater. 2016, 28 (17), 3399-3405. (20) Hwang, S.; Chi, W. S.; Lee, S. J.; Im, S. H.; Kim, J. H.; Kim, J. Hollow ZIF-8 Nanoparticles Improve the Permeability of Mixed Matrix Membranes for CO2/CH4 Gas Separation. J. Membr. Sci. 2015, 480, 11-19. (21) Vanherck, K.; Aerts, A.; Martens, J.; Vankelecom, I. Hollow Filler Based Mixed Matrix Membranes. Chem. Commun. 2010, 46 (14), 2492-2494. (22) Hou, J.; Li, X.; Guo, R.; Zhang, J.; Wang, Z. Mixed Matrix Membranes with Fast and Selective Transport Pathways for Efficient CO2 Separation. Nanotechnology 2018, 29 (12), 125706-125706. (23) Fu, X.; Li, X.; Guo, R.; Zhang, J.; Cao, X. Block Copolymer Membranes Based on Polyetheramine and Methyl-Containing Polyisophthalamides Designed for Efficient CO2 Separation. High Perform. Polym. 2017, 1-11. (24) Lin, R.; Hernandez, B. V.; Ge, L.; Zhu, Z. Metal Organic Framework Based Mixed Matrix Membranes: An Overview on Filler/Polymer Interfaces. J. Mater. Chem. A 2018, 6, 293-312. (25) Yu, L.; Kanezashi, M.; Nagasawa, H.; Ohshita, J.; Naka, A.; Tsuru, T. Fabrication

and

Microstructure

Tuning

of

36


a

Pyrimidine-Bridged

Page 37 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Organoalkoxysilane Membrane for CO2 Separation. Ind. Eng. Chem. Res. 2017, 56 (5), 1316-1326. (26) Li, X.; Jiang, Z.; Wu, Y.; Zhang, H.; Cheng, Y.; Guo, R.; Wu, H. High-Performance Composite Membranes Incorporated with Carboxylic Acid Nanogels for CO2 Separation. J. Membr. Sci. 2015, 495, 72-80. (27) Xiang, L.; Sheng, L.; Wang, C.; Zhang, L.; Pan, Y.; Li, Y. Amino-Functionalized Zif-7 Nanocrystals: Improved Intrinsic Separation Ability and Interfacial Compatibility in Mixed-Matrix Membranes for CO2/CH4 Separation. Adv. Mater. 2017, 29 (32), 1606999. (28) Seipp, C. A.; Williams, N. J.; Kidder, M. K.; Custelcean, R. CO2 Capture from Ambient Air by Crystallization with a Guanidine Sorbent. Angew. Chem. Int. Ed. 2017, 56 (4), 1042-1045. (29) Dawson, R.; Adams, D. J.; Cooper, A. I. Chemical Tuning of CO2 Sorption in Robust Nanoporous Organic Polymers. Chem. Sci. 2011, 2, 1173-1177. (30) Calle, M.; Jo, H. J.; Doherty, C. M.; Hill, A. J.; Lee, Y. M. Cross-Linked Thermally Rearranged Poly(Benzoxazole-Co-Imide) Membranes Prepared from Ortho-Hydroxycopolyimides Containing Pendant Carboxyl Groups and Gas Separation Properties. Macromolecules 2015, 48 (8), 2603-2613. (31) Yoon, K. W.; Kang, S. W. Highly Permeable and Selective CO2 Separation Membrane to Utilize 5-Hydroxyisophthalic Acid in Poly(Ethylene Oxide) Matrix. Chem. Engineer. J. 2018, 334, 1749-1753. 37



Page 38 of 42

(32) Ehsan, G. E.; Mohammadreza, O.; Amooghin, A. E. Interfacial Design of Ternary

Mixed

Matrix

Membranes

1657/Silver-Nanopowder/[Bmim][BF4]

for

Containing

Improved

CO2

Pebax Separation

Performance. ACS Appl. Mater. Interfaces 2017, 9 (11), 10094-10105. (33) Xiang, L.; Pan, Y.; Zeng, G.; Jiang, J.; Chen, J.; Wang, C. Preparation of Poly(Ether-Block-Amide)/Attapulgite Mixed Matrix Membranes for CO2/N2 Separation. J. Membr. Sci. 2016, 500, 66-75. (34) Stöber, W.; Fink, A.; E., B. Controlled Growth of Monodisperse Silica Spheres in the Micron Size Range. J. Colloid Interface Sci. 1968, 26, 62-69. (35) Zhang, H.; Dai, B.; Li, W.; Wang, X.; Zhang, J.; Zhu, M.; Gu, J. Non-Mercury

Catalytic

Acetylene

Hydrochlorination

over

Spherical

Activated-Carbon-Supported Au-Co(III)-Cu(II) Catalysts. J. Catal. 2014, 316, 141-148. (36) Zhang, H.; Li, W.; Li, X.; Zhao, W.; Gu, J.; Qi, X.; Dong, Y.; Dai, B.; Zhang, J. Non-Mercury Catalytic Acetylene Hydrochlorination over Bimetallic Au–Ba(II)/AC Catalysts. Catal. Sci. Technol. 2015, 5, 1870-1877. (37) Zhang, H.; Dai, B.; Wang, X.; Li, W.; Han, Y.; Gu, J. Non-Mercury Catalytic Acetylene Hydrochlorination over Bimetallic Au-Co(III)/SAC Catalysts for Vinyl Chloride Monomer Production. Green Chem. 2013, 15 (3), 829-836. (38) Zhang, H.; Tian, H.; Zhang, J.; Guo, R.; Li, X. Facilitated Transport Membranes with an Amino Acid Salt for Highly Efficient CO2 Separation. Int. J. Greenh. Gas Con. 2018, 78, 85-93. 38


Page 39 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(39) Wang, M.; Wang, Z.; Wang, J.; Zhu, Y.; Wang, S. An Antioxidative Composite Membrane with the Carboxylate Group as a Fixed Carrier for CO2 Separation from Flue Gas. Energy Environ. Sci. 2011, 4, 3955-3959. (40) Li, Y.; Wang, S.; He, G.; Wu, H.; Pan, F.; Jiang, Z. Facilitated Transport of Small Molecules and Ions for Energy-Efficient Membranes. Chem. Soc. Rev. 2015, 44, 103-118. (41) Wang, M.; Wang, Z.; Li, S.; Zhang, C.; Wang, J.; Wang, S. A High Performance Antioxidative and Acid Resistant Membrane Prepared by Interfacial Polymerization for CO2 Separation from Flue Gas. Energy Environ. Sci. 2013, 6 (2), 539-551. (42) Stannett, V. The Transport of Gases in Synthetic Polymeric Membranes an Historic Perspective. J. Membr. Sci. 1978, 3 (2), 97-115. (43) Shahid, S.; Nijmeijer, K. High Pressure Gas Separation Performance of Mixed-Matrix Polymer Membranes Containing Mesoporous Fe(BTC). J. Membr. Sci. 2014, 459, 33-44. (44) Li, X.; Cheng, Y.; Zhang, H.; Wang, S.; Jiang, Z.; Guo, R.; Wu, H. Efficient CO2 Capture by Functionalized Graphene Oxide Nanosheets as Fillers to Fabricate Multi-Permselective Mixed Matrix Membranes. ACS Appl. Mater. Interfaces 2015, 7, 5528-5537. (45) Zhang, X. M.; Tu, Z. H.; Li, H.; Li, L.; Wu, Y. T.; Hu, X. B. Supported Protic-Ionic-Liquid Membranes with Facilitated Transport Mechanism for the Selective Separation of CO2. J. Membr. Sci. 2017, 527, 60-67. 39



Page 40 of 42

(46) Zornoza, B.; Esekhile, O.; Koros, W. J.; Téllez, C.; Coronas, J. Hollow Silicalite-1 Sphere-Polymer Mixed Matrix Membranes for Gas Separation. Sep. Purif. Technol. 2011, 77 (1), 137-145. (47) Shen, Y.; Wang, H.; Zhang, X.; Zhang, Y. MoS2 Nanosheets Functionalized Composite Mixed Matrix Membrane for Enhanced CO2 Capture Via Surface Drop-Coating Method. ACS Appl. Mater. Interfaces 2016, 8 (35), 23371-23378. (48) Azizi, N.; Arzani, M.; Mahdavi, H. R.; Mohammadi, T. Synthesis and Characterization of Poly(Ether-Block-Amide) Copolymers/Multi-Walled Carbon Nanotube Nanocomposite Membranes for CO2/CH4 Separation. Korean J. Chem. Eng. 2017, 34 (9), 2459-2470. (49) Surya Murali, R.; Ismail, A. F.; Rahman, M. A.; Sridhar, S. Mixed Matrix Membranes of Pebax-1657 Loaded with 4A Zeolite for Gaseous Separations. Sep. Purif. Technol. 2014, 129, 1-8. (50) Zarshenas, K.; Raisi, A.; Aroujalian, A. Mixed Matrix Membrane of Nano-Zeolite Nax/Poly (Ether-Block-Amide) for Gas Separation Applications. J. Membr. Sci. 2016, 510, 270-283. (51) Mahmoudi, A.; Asghari, M.; Zargar, V. CO2/CH4 Separation through a Novel

Commercializable

Three-Phase

PEBA/PEG/NaX

Membrane. J. Ind. Eng. Chem. 2015, 23, 238-242.

40


Nanocomposite

Page 41 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(52) Li, T.; Pan, Y.; Peinemann, K.-V.; Lai, Z. Carbon Dioxide Selective Mixed Matrix Composite Membrane Containing ZIF-7 Nano-Fillers. J. Membr. Sci. 2013, 425-426, 235-242. (53) Sutrisna, P. D.; Hou, J.; Li, H.; Zhang, Y; Chen, V. Improved Operational Stability of Pebax-Based Gas Separation Membranes with ZIF-8: A Comparative Study of Flat Sheet and Composite Hollow Fibre Membranes. J. Membr. Sci. 2017, 524, 266-279. (54) Chen, S.; Zhou, T.; Wu, H.; Wu, Y.; Jiang, Z. Embedding Molecular Amine

Functionalized

Polydopamine

Submicroparticles

into

Polymeric

Membrane for Carbon Capture. Ind. Eng. Chem. Res. 2017, 56 (28), 8103-8110.

41



Table of Contents

42


Page 42 of 42

Facilitating CO2 transport across mixed matrix membranes containing

Recommend Documents