A Novel Chemical Surface Modification for the Fabrication of PEBA

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A Novel Chemical Surface Modification for Fabrication of PEBA/SiO2 Nanocomposite Membranes to Separate CO2 from Syngas and Natural Gas Streams Ali Ghadimi, Toraj Mohammadi, and Norallah Kasiri Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie503216p • Publication Date (Web): 11 Oct 2014 Downloaded from http://pubs.acs.org on October 15, 2014

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Industrial & Engineering Chemistry Research

A Novel Chemical Surface Modification for Fabrication of PEBA/SiO2 Nanocomposite Membranes to Separate CO2 from Syngas and Natural Gas Streams Ali Ghadimi, Toraj Mohammadi*, Norollah kasiri Research Centre for Membrane Separation Processes, Chemical Engineering Department Iran University of Science and Technology (IUST), Narmak, Tehran, Iran Tel: +98 21 77240496, Fax: +98 21 77240495 [email protected]

Abstract: In this work, a novel chemical modification is introduced to fabricate poly (ether block amide)/silica, (PEBA/SiO2), nanocomposite membranes for separation of CO2 from syngas and natural gas streams. Cis-9-octadecenoic acid (OA) was utilized for surface modification of the nanoparticles to restrict their agglomeration within the polymeric matrix. To our best knowledge, there is no evidence about application of this modifier agent for fabrication of nanocomposite membranes. Separation performance of the fabricated membranes was investigated by pure and mixed gas permeation experiments. Incorporation of the modified nanoparticles into the polymeric matrix improved separation performance of the fabricated nanocomposite membranes. For instance, by increasing loading content of the SiO2 nanoparticles from 0 wt. % (the neat PEBA membrane) to 8 wt. %, at 25 °C and 2 bar, ideal selectivity values of CO2/H2, CO2/CH4 and CO2/N2 were improved from (9, 18 and 61) to (17, 45 and 137), respectively.

Keywords: Nanocomposite membrane; Surface modification; Pure and mixed gas permeation.

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1. Introduction

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Emission of greenhouse gases, particularly carbon dioxide (CO2), is considered as one of the most serious causes of global warming. Consequently, separation of CO2 from different sources is the aim of many investigations1-3. Among different proposed methods, membrane separation processes have recently attracted more attention of investigators due to their advantages over other traditional separation techniques. Membrane separation processes are currently used in different commercial gas separation fields, such as CO2 removal from syngas and natural gas streams4-8. Some of the most notable advantages of the membrane-based separation processes are their small footprint, mechanical simplicity, low investment and operational cost, and relatively low energy requirements9-14.

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Dense polymeric membranes have been widely used for gas separation purposes with dominant transport mechanism of solution-diffusion, governing the transport of penetrants7, 15, 16. Indeed, this mechanism makes these membranes capable of separating the larger gas molecules from the smaller ones. According to this mechanism, gas sorption initially takes place at the high pressure side of the membrane, followed by molecules diffusion, and then the diffused molecules are desorbed from the downstream side of the membrane 17, 18.

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Most of the utilized polymers for fabrication of dense membranes are in their rubbery state which has high gas diffusion rate, and consequently low diffusion selectivity. Thus, to enhance their separation performance, preferential sorption of one species over other penetrants should be improved.

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Solubility of gases within a polymeric matrix is essentially affected by chemical structure of the polymer19. Lin et al. 20 investigated effect of different polar moieties of polymers, (ether oxygens, acetates, nitriles, and carbonates), on CO2 solubility. They found that polymeric membranes with ether oxygen moieties in their backbone have a significant affinity to organic vapors and acid gases. Therefore, these polymers are one of the best candidates for fabrication of reverse selective membranes to separate CO2 from light gases. Additionally, they justified that polymers with a Hansen solubility parameter 21 equal to 22 , have the lowest FloryHuggins interaction parameter with CO2 molecules and thereby the highest solubility coefficient for CO2. 22 Therefore, based on the mentioned points, it can be concluded that, polymers with a solubility parameter equal to 22 and ether oxygen linkage in their backbones are capable options for CO2 removal purposes.

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poly (ether block amide) (PEBA) is a block copolymer composed of polyamide (PA) and polyether (PE) into the hard and the soft segments of the polymer chains, respectively 10, 23, 24. Different types of polyamides and polyethers are used for synthesis and controlling mechanical and chemical properties of PEBA copolymers 10, 25. PEBA1657 has been found to be a promising membrane material for separation of polar gases such as CO2 from light gases 26. This copolymer has ether oxygen linkages in its backbone and a solubility parameter equal to 22.5 which 2 ACS Paragon Plus Environment

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enhance solubility of CO2 into the polymeric matrix 27. Moreover, because of the spatial shape of the ether oxygen linkages in PEBA, i.e. having a bond angle of 110°, free fractional volume (FFV) and the diffusion coefficient of sorbed gases through the polymeric matrix of the membrane is increased. Therefore, in the present work, PEBA1657, was chosen for separation of CO2 from light gases, such as hydrogen (H2), nitrogen (N2) and methane (CH4). In addition it should be noted that, there are different studies about using PEBA membranes for gas separation and pervaporation aims in the literature10, 26-29.

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Although polymeric membranes, like PEBA, have outstanding separation characteristics, they are still limited by the trade-off trend between gas permeability and selectivity30. Therefore improving separation performance of polymeric membranes for gas separation purposes is one of the attractive research topics for many of investigators31, 32. Incorporation of an inorganic phase into the matrix of polymeric membranes not only improves their mechanical and thermal properties but also may enhance separation performance of the filled membranes 33. As a result, a number of researchers have tried to improve properties of PEBA membrane by incorporation of an inorganic phase into the polymeric matrix 33-39.

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In this paper, three different approaches, including sol-gel, physical surface modification of the SiO2 nanoparticles with poly (ethylene glycol) (PEG) macro-monomers, and chemical surface modification of the SiO2 nanoparticles with cis-9-octadecenoic acid (OA), were employed to prepare PEBA/SiO2 nanocomposite membranes. The obtained results showed that chemical surface modification of the nanoparticles can be considered as a promising technique for preparation PEBA/SiO2 nanocomposite membranes with satisfactory separation and structural properties among the other methods. Therefore, for improving dispersion of SiO2 nanoparticles into the polymeric matrix, their surface was chemically modified using OA. This chemical surface modification efficiently eliminated agglomeration, and resulted in excellent dispersion of the SiO2 nanoparticles. In addition, pure and mixed gas permeation experiments were carried out through the modified nanocomposite membranes. It was found that incorporation of the modified SiO2 nanoparticles into the PEBA matrix decreases permeability coefficients of H2, N2, and CH4, and conversely increases that of CO2. Therefore CO2/H2, CO2/N2 and CO2/CH4 selectivity values of the nanocomposite membranes were improved compared to those of the neat PEBA membrane.

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2. Experiments 2.1. Materials

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PEBA1657, HO-[(C2H4-O)x-CO-(NH-C5H10-CO)y]n-OH, was purchased from Arkema Inc. in the form of elliptic pellets. PEG (MW=400 gr/mol), tetraethyl orthosilicate, (TEOS), cis-9octadecenoic acid (OA), tetrahydrofuran, (THF), and formic acid, (HCOOH), were obtained from Sigma-Aldrich company. The hydrophilic SiO2 nanoparticles (primary particle size = 7 nm) were provided by US-Nano company. Absolute ethanol was supplied by Merck company, and 3 ACS Paragon Plus Environment


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CO2, CH4, H2, and N2 gases (99.995% purity) were purchased from Farafan Gas Tehran Company.

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2.2.

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2.2.1. Experimental set up

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To measure gas permeation coefficients through the fabricated membranes, a simple apparatus was designed and constructed, as schematically illustrated in Figure 1. Operating conditions of the preformed experiments, i.e. temperature and pressure, were adjusted by means of a ballast volume placed into an oven and pressure regulators, respectively. All of the permeation experiments were performed with constant volume (CV) method.

Gas permeation experiments

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2.2.2. Calculation of permeation values

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As mentioned earlier, permeation coefficients of the penetrants were determined with CV

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method. To do so, the steady state rate of the downstream-pressure increments

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was used for

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calculation of permeability coefficients according to the following equation : [

(

)]

[ [

( (

)] )][

[ ]

(

)

]

[

[

( (

) )

]

[

15

]

(1)

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where represents the permeability coefficient of component i. , , and designate the volume of the permeation chamber, the film thickness, the membrane effective area, and the experimental temperature, respectively. The pressure of upstream and downstream are denoted by and . In addition, mole fraction of components in the feed and the permeate streams are indicated by and , respectively. One should note that, in the case of pure gas experiments, and are considered equal to 1.

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2.2.3. Measurement of mixed gas composition

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Gas composition in the permeate stream was measured using maMoS-200 analyzer, a 2-channel gas analyzer system with NDIR sensors, supplied by Madur Electronics Company. Initially about one liter of the permeate stream was collected into a tedlar sample bag (Cat No: 232-01, supplied by SKC Company), and then its composition was determined by the analyzer.

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2.3. Nanocomposite membranes 2.3.1. Fabrication of nanocomposite membranes via sol-gel approach

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Sol-gel method is known as a convenient and promising approach for synthesis of the organicinorganic networks such as nanocomposite membranes41. Fundamentally, the name of the “solgel process” has come from the transition from a liquid (solution) into a solid (gel) state. In 4 ACS Paragon Plus Environment

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principle, this process is formation of an inorganic phase through a chemical reaction in the solution state at low temperature, followed by fine dispersion (even at the molecular level) of the formed inorganic phase in the organic matrix.

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Indeed, this method consists of two successive steps: (a) hydrolysis of alkoxides for producing hydroxyl groups, and then (b) polycondensation of the hydroxyl groups to form a threedimensional inorganic network41. In the literature, there are different comprehensive studies on the sol–gel method providing detailed information about preparation of organic–inorganic hybrid materials 42-45.

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In the present work, initially, a 6 wt.% PEBA solution was prepared in a (1/1 wt/wt) mixture of THF/HCOOH under stirring condition. Then, different amounts of TEOS (15, 30, 45 wt.%), based on the polymer weight, were added into the polymeric solution. In the next step, deionized water was added, so the resulting H2O/TEOS molar ratio be 2. Thereafter, the solution was poured into the Teflon flat-bottomed Petri dishes, and the reaction was allowed to continue for 24 hours. The fabricated nanocopmposite films were dried at 60 for 48 hours, and placed under vacuum for 3 days to remove residual solvent. Table 1, presents more information on each one of the prepared solutions based on, 100 gr solvent.

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2.3.2. Fabrication of nanocomposite membranes after surface modification approaches

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Agglomeration of nanoparticles into a host polymeric matrix can be considered as a major problem for preparation of polymeric nanocomposites. Although SiO2 nanoparticles are widely applied for preparation of different nanocomposite membranes, they suffer from high tendency to agglomerate. In fact, presence of the -OH groups on surface of the SiO2 nanoparticles and their capability to form hydrogen bondings, causes poor dispersion of these nanoparticles and increases their agglomeration 46.

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To overcome this shortcoming, in this work surface of the SiO2 nanoparticles was modified by physical and chemical approaches and then the modified nanoparticles were used to fabricate nanocomposite membranes.

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2.3.2.1.

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Adsorption of macro-monomers on surface of the SiO2 nanoparticles is one of the surface modification approaches which is based on the physical interactions47. Oxyethylene-based macro-monomer such as PEG covers the surface of SiO2 nanoparticles due to the presence of ethylene oxide groups, which are able to form hydrogen bonds with surficial -OH groups on the nanoparticles. Figure 2 illustrates a covered SiO2 nanoparticle with PEG macro-monomers, schematically. Indeed, in this study, PEG macro-monomers were applied for surface coverage of the SiO2 nanoparticles because of two main reasons: (a) surface coverage of the nanoparticles with PEG macro-monomers can restrict formation of hydrogen bonding between SiO2

Physical surface modification



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nanoparticles and reduce their agglomeration; (b) positive interactions between PEG macromonomers and PEO blocks in PEBA can enhance dispersion of the modified nanoparticles within the polymeric matrix. This physical surface modification was carried out as follows: (a) a silica suspension was prepared in deionized water; (b) PEG was added into the prepared suspension at the preset concentration; (c) adsorption was performed at 25 °C for 36 hour; (d) the modified nanoparticles were dried in a rotary set. Table 2 presents the applied concentrations for both SiO2 nanoparticles and PEG macro-monomers.

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2.3.2.2.

Chemical surface modification

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To eliminate the agglomeration of the SiO2 nanoparticles and thereby improving their dispersion in the polymeric matrix, their surface was chemically modified to reduce the surface density of OH groups. The utilized modifier agent was cis-9-octadecenoic acid (OA) in normal Hexane medium. This chemical surface modification was performed in the following steps:

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(a) a 3 wt.% mixture of the SiO2 nanoparticles/n-Hexane was prepared; (b) a specific amount of modifier agent (OA) was added into the mixture (20, 40 and 60 wt.% based on the weight of the existing nanoparticles); (c) the mixture was vigorously mixed for 5 hours at 60 °C; and (d) the modified nanoparticles were obtained after complete evaporation of the liquid medium in a rotary set.

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This chemical modification can be simply expressed by following reaction:

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SiO2(OH)n + yHOOCC17H33 → SiO2(OH)n-y(OOCC17H33)y + yH2O

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Based on this reaction, the –COOH group of OA, reacts with the –OH group on surface of the SiO2 nanoparticles. The product of this reaction is carboxylate; so by reduction of the –OH groups on the surface of the SiO2 nanoparticles, their tendency for agglomeration would be decreased.

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2.3.2.3. Fabrication of nanocomposite membrane with surface modified SiO2 nanoparticles

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To fabricate the nanocomposite membranes with the surface modified nanoparticles, a 6 wt. % PEBA solution was prepared using a (70/30 w/w) mixture of ethanol/water at 80-90 °C after mixing for 6 hours (under reflux). At the end of the mixing, a certain weight of the physical or chemical modified nanoparticles, prepared as mentioned in sections 2.3.2.1 and 2.3.2.2, (2, 4, 6, and 8 wt.%, based on the polymer weight), were added into the polymeric solution, and thereupon magnetically stirred at 80 °C for 1 hour. Thereafter, the prepared solution was filtered through a steel filter to obtain a clear and homogenous solution. Then, it was poured within the Teflon flat-bottomed Petri dishes. After the first drying step, at 60 °C for 24 hour, the cast films were removed from the Teflon Petri dishes and were placed in an oven at 50 °C for 6 hours under vacuum to completely remove the residual solvent. 6 ACS Paragon Plus Environment

(2)

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2.4.

Membrane characterization

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The fabricated neat and nanocomposite membranes were investigated with differential scanning calorimetry (DSC), fourier transform infrared (FTIR), and scanning electron microscopy (SEM). Technical features of the applied instruments can be found in our previous work 48

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3. Results and discussion

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3.1. Selecting the proper approach for fabrication of the PEBA/SiO2 nanocomposite membranes

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3.1.1. Sol-gel approach

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The fabricated PEBA/SiO2 nanocomposite membranes via sol-gel method were translucent, nonadherent and easy to handle. SEM and DSC analysis techniques were applied to investigate their morphological and thermal properties, respectively. The obtained information from DSC analysis has been outlined in Table 3. The distribution of SiO2 nanoparticles in the cross section of the membranes has been evaluated by mapping the particles. The SEM-EDX images, Figure 3, approved the formation and the excellent dispersion of SiO2 nanoparticles into the polymeric matrix. Then, gas permeation tests were carried out on the fabricated nanocomposite membranes by sol-gel approach. The obtained results showed that the fabricated membranes have lower separation performance in comparison to that of the neat PEBA membrane. Table 4 presents permeability and selectivity values for CO2, H2, N2 and CH4 at 25 °C and 2 bar. As it is clear, incorporation of the SiO2 nanoparticles, synthesized via sol-gel method, has decreased the permeability and selectivity values of the fabricated nanocomposite membranes.

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The observed reduction in the permeability values can be attributed to high compatibility of the synthesized inorganic phase within the organic polymeric matrix and also adhesion of the inert fillers within a polymeric matrix. In this way, the tortuous path of penetration is increased and the cross-section of the transportation is decreased, leading to the slower penetration of the penetrants. Therefore, regarding to the poor separation performance of the fabricated nanocomposite membranes via sol-gel approach, further investigation on this approach was not pursued.

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3.1.2. Physical surface modification of SiO2 nanoparticles

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Influence of physical modification on surface of the SiO2 nanoparticles, was investigated by means of the attenuated total reflectance (ATR) analysis. Figure 4 illustrates ATR spectrums of the unmodified and modified SiO2 nanoparticles. The observed peak at 3490 cm-1 is assigned to hydroxyl groups, -OH, existing on surface of the SiO2 nanoparticles. The increased intensity of this peak for the modified nanoparticles, can be related to the presence of the hydroxyl terminated PEG macro-monomers on the surface of the SiO2 nanoparticles. Another peak at 2940 cm-1 is relegated to long alkyl chains of PEG and confirms surface coverage of the nanoparticles by the applied surface modifier. 7 ACS Paragon Plus Environment


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To investigate dispersion of the modified SiO2/PEG nanoparticles into to the polymeric matrix, morphology of the fabricated nanocomposite membranes was examined with SEM analysis. Figure 5 shows dispersion of the modified nanoparticles within the PEBA matrix. As can be seen, in contrast to the expectations, the applied physical modification could not prevent agglomeration of the SiO2 nanoparticles. This observation can be explained as follows: (a) it is possible that the PEG macro-monomer fails to efficiently prevent the formation of hydrogen bonds between the nanoparticles; (b) it is also possible that interactions of PEG macromonomers placed on the surface of the nanoparticles with each other are more than the probable interactions between PEG macro-monomers with PEO blocks in PEBA. Whereas, agglomeration of nanoparticles is one of the major defects of nanocomposite membranes, all the fabricated membranes with the introduced physical treatment in this work were defective. Therefore, investigation on these membranes was stopped due to their structural defects and their separation performances were not investigated.

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3.1.3. Chemical surface modification of SiO2 nanoparticles

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The fabricated nanocomposite membranes, with the discussed chemical modification approach in sections 2.3.2.2, were found as promising nanocomposite membranes. Therefore, the fabricated membranes with this approach were selected for more investigation. Following sections present characterization results of these nanocomposite membranes.

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3.2.

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3.2.1. FTIR analysis The influence of the applied chemical modification on the surface of the SiO2 nanoparticles, was investigated via comparing FTIR spectra of the un-modified and modified SiO2 nanoparticles, as shown in Figure 6. The observed peak at 3490 cm-1 is assigned to the hydroxyl groups, -OH, existing on the surface of the SiO2 nanoparticles. As can be seen, this peak is more intense for the unmodified SiO2 nanoparticles. However, appearance of this peak in the spectra of the modified nanoparticles shows that the –OH groups on the surface of SiO2 nanoparticles are not completely reacted with OA. Additionally, the observed peak at 1720 cm−1 corresponds to the – COOH groups in OA and the peaks at 2860 and 2940 cm-1 refer to the long alkyl chains which are present on the modified SiO2 nanoparticles. As stated before, this chemical modification attempts to reduce the density of –OH groups on the surface of SiO2 nanoparticles and limits their agglomeration into the polymeric matrix. As can be seen in Figure 6, all of the applied OA contents for the modification, i.e., 20, 40 and 60 wt.%, have approximately the same effect on the surficial –OH groups; therefore to avoid the side effects of the presence of modifier agent, the modified SiO2 nanoparticles with 20% OA were selected to be used for fabrication of the ultimate nanocomposite membranes. 3.2.2. DSC analysis

Characterization of the PEBA/SiO2OA nanocomposite membranes


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Thermal properties of the neat and the nanocomposite membranes were investigated using DSC analysis. The obtained values for thermal properties of the neat PEBA, summarized in Table 5, are in accordance with the reported values by other investigators11, 25, 49, 50. For the neat PEBA membrane, based on Bernardo investigations, maximum crystallinity of PEO and PA blocks are approximately within the ranges of 14–22% and 21–31%, respectively 49, which are in excellent agreement with the achieved values in this study (17.6% for PEO block and 29.8% for PA block). According to the obtained results, incorporation of the nanoparticles into the polymeric matrix slightly increases their Tg values; though, it does not have considerable effect on other thermal properties of the prepared membranes. The same thermal behavior for the PEBA nanocomposite membranes has been reported by Yu et al. 34. 3.2.3. SEM analysis Dispersion of the unmodified and the chemically modified nanoparticles into the polymeric matrix was examined with SEM analysis. As can be observed in Figure 7, the unmodified SiO2 nanoparticles intensely agglomerate into the polymeric matrix, whereas the modified nanoparticles show an excellent dispersion, see Figures 8a-8e. Therefore, it can be concluded that the proposed chemical surfaces modification in this work reduces the surficial –OH groups of the nanoparticles, and enhances their dispersion into the polymeric matrix.

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In addition, it is worthy to be noted that, modification of the nanoparticles with the applied chemical modifier agent, OA, has also a negative side effect. This modifier agent increases the surface hydrophobicity of the modified nanoparticles which may make dispersion of the modified nanoparticles into the polymeric matrix difficult. However, based on the observed enhancement in dispersion of the modified nanoparticles into the polymeric matrix it can be concluded that, the restriction of hydrogen bonding formation between the nanoparticles which is the positive effect of the proposed chemical modification compensates the mentioned negative side effect.

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3.2.4. Pure and mixed gas permeation Permeation coefficients of pure gases, i.e., CO2, H2, CH4 and N2, thorough the fabricated neat and nanocomposite membranes were investigated at 25 °C and 2 bar. Figures 9a and 9b illustrate permeation coefficients and ideal permeation selectivity values, respectively. The obtained permeability coefficients for CO2, H2, CH4, and N2 through the neat PEBA membrane are 70.3, 7.7, 3.8, and 1.1 Barrer, respectively. As can be seen, CO2 and N2 have the lowest and the highest activation energy of permeation, respectively; which is in agreement with the literature 48. For instance, Car et al. 51 have reported values of 22.2, 33.5, 37.6 and 40.1 kJ/mol for the activation energy of permeation of CO2, H2, CH4 and N2, respectively.

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As can be seen in Figure 9a, incorporation of the SiO2 nanoparticles into the polymeric matrix increases permeability of CO2, while permeability values of the other gases are slightly decreased. Consequently, the ideal permeation selectivity values for CO2/H2, CO2/CH4 and CO2/N2 are increased by increasing the loading content of the nanoparticles, see Figure 9b. For 9 ACS Paragon Plus Environment


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instance, by increasing the loading content of the SiO2 nanoparticles from 0 wt.% (the neat PEBA membrane) to 8 wt.%, the ideal permeation selectivity values for CO2/H2, CO2/CH4 and CO2/N2 are increased from [9, 18 and 61] to [17, 45 and 137], respectively. The observed permeation behavior through the nanocomposite membranes, can be explained by the following two points: (a) incorporation of the SiO2 nanoparticles into the polymeric matrix decreases diffusivity of the penetrants, mainly due to the reduction of the transport cross-section, as well as increment of the tortuous paths of penetration, and (b) the diffusivity reduction of H2, CH4 and N2 decreases their permeability; while, the solubility increment of CO2, caused by the SiO2 nanoparticles, overcomes its decreased diffusivity and consequently its permeability is increased. It should be mentioned that the residual -OH groups on the surface of the nanoparticles after chemical modification, have positive interactions with polar CO2 molecules and these interactions lead to solubility enhancement of CO2 molecules into the polymeric matrix35.

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Additionally, Separation performance of the fabricated nanocomposite membranes, was compared with the Robeson’s upper bound line52. As can be seen in Figure 10, the fabricated membranes lay close or even above the Robeson’s upper bound line. This comparison confirms improvement of separation performance of the fabricated nanocomposite membranes in comparison with that of the neat membrane, and also other polymeric membranes which have been considered for determination of the upper limits. .

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To investigate permeation of one component in the presence of other penetrants, mixed gas permeation experiments for the neat and the nanocomposite membranes were carried out. The experiments were performed with three different feed compositions of 20/80 mol.% for CO2/H2, 40/60 mol.% for CO2/N2 and 50/50 mol.% for CO2/CH4. The first two mixtures are relegated to the syngas and the last one is related to the natural gas streams. It should be mentioned that, the composition of syngas streams in some ammonia producer companies is almost equal to 15/25/60 mol.% for CO2/N2/H2. Consequently, the applied compositions in this work for CO2/H2 and CO2/N2 pairs were selected regarding to this composition with neglecting the third component. Operating conditions of the experiments were also chosen regarding to the industrial conditions. For instance, some of the industrial units which remove CO2 from syngas streams in ammonia producer companies operate at 65 °C and 26 bar; therefore, the related experiments for the CO2/H2, CO2/N2 mixtures were carried out at this operating condition. While, CO2/CH4 mixed gas experiments were performed at 45 °C and 44 bar which is the probable operating condition of the pre-treated natural gas which should be sent to the membrane units for CO2 removal.

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Figures 11a, 12a and 13a illustrate pure and mixed gas permeation of CO2/H2, CO2/N2 and CO2/CH4 pairs through the neat and the nanocomposite membranes at the assigned operating conditions, i.e. (65 °C and 26 bar) for syngas, and (45 °C and 44 bar) for natural gas. Moreover, the related ideal and mixed permeation selectivity values are presented in Figures 11b, 12b and 13b. As can be seen, the pure and the mixed permeability values for CO2, are enhanced by increasing the loading content of the SiO2 nanoparticles into the polymeric matrix. As mentioned 10 ACS Paragon Plus Environment

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earlier, the observed increment for CO2 permeability values through the nanocomposite membranes, in comparison with the neat membrane, can be related to the positive effect of the nanoparticles on enhancing the solubility increment of CO2 molecules. While, the observed reduction in permeability values of H2, N2 and CH4 is duo to the reduction of their diffusion coefficients through the nanocomposite membranes in comparison to those of the neat membrane.

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In addition, as can be seen in Figures 11a 12a and 13a, for all loading contents of the nanoparticles, the mixed CO2 permeability decreases respect to the pure CO2 permeability. In contrast, the mixed permeability values of H2, N2 and CH4 improve in comparison with the pure permeability values. The observed decline in mixed CO2 permeability can be related to the prevented plasticization effect of CO2 due to the presence of the second component in the feed stream (i.e. H2, N2 or CH4). While, the detected increment in permeability values of H2, N2 and CH4 can be relegated to the plasticization effect of CO2. Regarding to the observed mixed permeability values, it is expectable that the mixed permeation selectivity values decrease in comparison with the pure permeation selectivity values, cf. Figures 11b 12b and 13b. However, the important point is that, the fabricated nanocomposite membranes in this work could also enhance separation performance for the all investigated mixed gas streams in comparison with the neat membrane.

19 20 21 22 23 24 25 26 27 28 29 30 31 32

4. Conclusions This study tried to fabricate PEBA/SiO2 nanocomposite membranes for separation CO2 from light gases, i.e. H2, CH4 and N2. To do so, three different approaches including sol-gel, physical and chemical surface modification of the nanoparticles, were investigated. The results showed that, the fabricated nanocomposite membranes with the sol-gel approach have a lower separation performance in comparison with that of the neat membrane, and the applied physical surface modification could not eliminate the agglomeration of SiO2 nanoparticles within the polymeric matrix. Whereas, the presented chemical surface modification eliminated agglomeration of the nanoparticles by reduction of the –OH groups on surface of the nanoparticles. Additionally, the obtained result from the pure and mixed gas permeation experiments showed that the fabricated nanocomposite membranes with this chemical modification have a better separation performance in comparison with that of the neat membrane. Therefore, it can be concluded that, the introduced chemical modification in this work is a promising approach to fabricate PEBA/SiO2 nanocomposite membranes for separation of CO2 from syngas and natural gas streams.



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1 2

Notes

3 4 5 6

ACKNOWLEDGMENTS

The authors declare no completing financial interest.

The authors gratefully acknowledge the financial support of this project by Iran Nanotechnology Initiative Council and Petrochemical Research and Technology Co. of Iran (Grant 0870289106).


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References: (1) Hwang, H. Y.; Nam, S. Y.; Koh, H. C.; Ha, S. Y.; Barbieri, G.; Drioli, E. The Effect of Operating Conditions on the Performance of Hollow Fiber Membrane Modules for CO2/N2 Separation. J. Ind. Eng. Chem. 2012, 18, (1), 205. (2) Ghasem, N.; Al-Marzouqi, M.; Duaidar, A. Effect of Quenching Temperature on the Performance of Poly(Vinylidene Fluoride) Microporous Hollow Fiber Membranes Fabricated via Thermally Induced Phase Separation Technique on the Removal of CO2 from CO2-Gas Mixture. Int. J. Greenh. Gas Con. 2011, 5, (6), 1550. (3) Razavi, S. M. R.; Razavi, S. M. J.; Miri, T.; Shirazian, S. CFD Simulation of CO2 Capture from Gas Mixtures in Nanoporous Membranes by Solution of 2-Amino-2-Methyl-1-Propanol and Piperazine. Int. J. Greenh. Gas Con. 2013, 15, 142. (4) Cong, H.; Radosz, M.; Towler, B. F.; Shen, Y. Polymer–Inorganic Nanocomposite Membranes for Gas Separation. Sep. Purif. Technol. 2007, 55, (3), 281. (5) Scholes, C. A.; Bacus, J.; Chen, G. Q.; Tao, W. X.; Li, G.; Qader, A.; Stevens, G. W.; Kentish, S. E. Pilot Plant Performance of Rubbery Polymeric Membranes for Carbon Dioxide Separation from Syngas. J. Membr. Sci. 2012, 389, 470. (6) Zamani Pedram, M.; Omidkhah, M.; Ebadi Amooghin, A. Synthesis and Characterization of Diethanolamine-Impregnated Cross-Linked Polyvinylalcohol/Glutaraldehyde Membranes for CO2/CH4 Separation. J. Ind. Eng. Chem. 2014, 20, (1), 74. (7) Rajabi, Z.; Moghadassi, A. R.; Hosseini, S. M.; Mohammadi, M. Preparation and Characterization of Polyvinylchloride Based Mixed Matrix Membrane Filled with Multi Walled Carbon Nano Tubes for Carbon Dioxide Separation. J. Ind. Eng. Chem. 2013, 19, (1), 347. (8) Ahmad, A. L.; Sunarti, A. R.; Lee, K. T.; Fernando, W. J. N. CO2 Removal Using Membrane Gas Absorption. Int. J. Greenh. Gas Con.2010, 4, (3), 495. (9) Barillas, M. K.; Enick, R. M.; O’Brien, M.; Perry, R.; Luebke, D. R.; Morreale, B. D. The CO2 Permeability and Mixed Gas CO2/H2 Selectivity of Membranes Composed of CO2-Philic Polymers. J. Membr. Sci. 2011, 372, (1–2), 29. (10) Bondar, V. I.; Freeman, B. D.; Pinnau, I. Gas Transport Properties of Poly(Ether-B-Amide) Segmented Block Copolymers. J. Polym. Sci., Part B: Polym. Phys. 2000, 38, (15), 2051. (11) Car, A.; Stropnik, C.; Yave, W.; Peinemann, K.-V. PEG Modified Poly(Amide-B-Ethylene Oxide) Membranes for CO2 Separation. J. Membr. Sci. 2008, 307, (1), 88. (12) Park, H. B.; Kim, C. K.; Lee, Y. M. Gas Separation Properties of Polysiloxane/Polyether Mixed Soft Segment Urethane Urea Membranes. J. Membr. Sci. 2002, 204, (1–2), 257. (13) Tocci, E.; Gugliuzza, A.; De Lorenzo, L.; Macchione, M.; De Luca, G.; Drioli, E. Transport Properties of a Co-Poly(Amide-12-B-Ethylene Oxide) Membrane: A Comparative Study Between Experimental and Molecular Modelling Results. J. Membr. Sci. 2008, 323, (2), 316. (14) Liu, L.; Chakma, A.; Feng, X. Preparation of Hollow Fiber Poly(Ether Block Amide)/Polysulfone Composite Membranes for Separation of Carbon Dioxide from Nitrogen. Chem. Eng. J. 2004, 105, (1–2), 43. (15) Reijerkerk, S. R.; Jordana, R.; Nijmeijer, K.; Wessling, M. Highly Hydrophilic, Rubbery Membranes for CO2 Capture and Dehydration of Flue Gas. Int. J. Greenh. Gas Con. 2011, 5, (1), 26. (16) Zhang, Y.; Sunarso, J.; Liu, S.; Wang, R. Current Status and Development of Membranes for CO2/CH4 Separation: A Review. Int. J. Greenh. Gas Con. 2013, 12, 84. (17) Lau, C. H.; Li, P.; Li, F.; Chung, T.-S.; Paul, D. R. Reverse-Selective Polymeric Membranes for Gas Separations. Prog. Polym. Sci. 2013, 38, (5), 740. (18) Sridhar, S.; Smitha, B.; Aminabhavi, T. M. Separation of Carbon Dioxide from Natural Gas Mixtures Through Polymeric Membranes—A Review. Sep. Purif. Rev. 2007, 36, (2), 113. 13 ACS Paragon Plus Environment


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 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 14 of 35

(19) Muñoz, D. M.; Maya, E. M.; de Abajo, J.; de la Campa, J. G.; Lozano, A. E. Thermal Treatment of Poly(Ethylene Oxide)-Segmented Copolyimide Based Membranes: An Effective Way to Improve the Gas Separation Properties. J. Membr. Sci. 2008, 323, (1), 53. (20) Lin, H.; Freeman, B. D. Materials Selection Guidelines for Membranes That Remove CO2 from Gas Mixtures. J. Mol. Struct. 2005, 739, (1–3), 57. (21) Hansen, C. M. Hansen Solubility Parameters-A User’s Handbook; Second Edition; Taylor & Francis Group: Boca Raton London New York, 2007. (22) Van Krevelen, D. W. Properties of Polymers-Their Correlation with Chemical Structure; Their Numerical Estimation and Prediction from Additive Group Contributions; Fourth completely Revised Edition; Elsevier, 2009. (23) Feng, S.; Ren, J.; Li, Z.; Li, H.; Hua, K.; Li, X.; Deng, M. Poly(Amide-12-B-Ethylene Oxide)/Glycerol Triacetate Blend Membranes for CO2 Separation. Int. J. Greenh. Gas Con. 2013, 19, 41. (24) Choi, M.-C.; Jung, J.-Y.; Yeom, H.-S.; Chang, Y.-W. Mechanical, Thermal, Barrier, and Rheological Properties of Poly(Ether-Block-Amide) Elastomer/Organoclay Nanocomposite Prepared by Melt Blending. Polym. Eng. Sci. 2013, 53, (5), 982. (25) Kim, J. H.; Ha, S. Y.; Lee, Y. M. Gas Permeation of Poly(Amide-6-B-Ethylene Oxide) Copolymer. J. Membr. Sci. 2001, 190, (2), 179. (26) Ren, X.; Ren, J.; Deng, M. Poly(Amide-6-B-Ethylene Oxide) Membranes for Sour Gas Separation. Sep. Purif. Technol. 2012, 89, 1. (27) Ren, X.; Ren, J.; Li, H.; Feng, S.; Deng, M. Poly (Amide-6-B-Ethylene Oxide) Multilayer Composite Membrane for Carbon Dioxide Separation. Int. J. Greenh. Gas Con. 2012, 8, 111. (28) Sridhar, S.; Suryamurali, R.; Smitha, B.; Aminabhavi, T. M. Development of Crosslinked Poly(Ether-Block-Amide) Membrane for CO2/CH4 Separation. Colloids Surf., A Physicochem. Eng. Asp. 2007, 297, (1–3), 267. (29) Gu, J.; Shi, X.; Bai, Y.; Zhang, H.; Zhang, L.; Huang, H. Silicalite-Filled PEBA Membranes for Recovering Ethanol from Aqueous Solution by Pervaporation. Chem. Eng. Technol. 2009, 32, (1), 155. (30) Moghadassi, A. R.; Rajabi, Z.; Hosseini, S. M.; Mohammadi, M. Fabrication and Modification of Cellulose Acetate Based Mixed Matrix Membrane: Gas Separation and Physical Properties. J. Ind. Eng. Chem. 2014, 20, (3), 1050. (31) Rafiq, S.; Man, Z.; Maulud, A.; Muhammad, N.; Maitra, S. Separation of CO2 from CH4 Using Polysulfone/Polyimide Silica Nanocomposite Membranes. Sep. Purif. Technol. 2012, 90, 162. (32) Feng, S.; Ren, J.; Li, H.; Hua, K.; Li, X.; Deng, M. Polyvinyl Acetate/Poly(Amide-12-B-Ethylene Oxide) Blend Membranes for Carbon Dioxide Separation. Journal of Energy Chemistry 2013, 22, (6), 837. (33) Zoppi, R. A.; das Neves, S.; Nunes, S. P. Hybrid Films of Poly(Ethylene Oxide-B-Amide-6) Containing Sol–Gel Silicon or Titanium Oxide as Inorganic Fillers: Effect of Morphology and Mechanical Properties on Gas Permeability. Polymer 2000, 41, (14), 5461. (34) Yu, B.; Cong, H.; Li, Z.; Tang, J.; Zhao, X. S. Pebax-1657 Nanocomposite Membranes Incorporated with Nanoparticles/Colloids/Carbon Nanotubes for CO2/N2 and CO2/H2 Separation. J. Appl. Polym. Sci. 2013, 130, 2867. (35) Kim, J. H.; Lee, Y. M. Gas Permeation Properties of Poly(Amide-6-B-Ethylene Oxide)–Silica Hybrid Membranes. J. Membr. Sci. 2001, 193, (2), 209. (36) Murali, R. S.; Sridhar, S.; Sankarshana, T.; Ravikumar, Y. V. L. Gas Permeation Behavior of Pebax1657 Nanocomposite Membrane Incorporated with Multiwalled Carbon Nanotubes. Ind. Eng. Chem. Res. 2010, 49, (14), 6530. (37) Zoppi, R. A.; de Castro, C. R.; Yoshida, I. V. P.; Nunes, S. P. Hybrids of SiO2 and Poly(Amide 6-BEthylene Oxide). Polymer 1997, 38, (23), 5705.


Page 15 of 35

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 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


(38) Zoppi, R. A.; Soares, C. G. A. Hybrids of Poly(Ethylene Oxide-B-Amide-6) and ZrO2 Sol–Gel: Preparation, Characterization, and Application in Processes of Membranes Separation. Adv. Polym. Tech. 2002, 21, (1), 2. (39) Zhao, D.; Ren, J.; Li, H.; Hua, K.; Deng, M. Poly(Amide-6-B-Ethylene Oxide)/Sapo-34 Mixed Matrix Membrane for CO2 Separation. Journal of Energy Chemistry 2014, 23, (2), 227. (40) Shangguan, Y. Intrinsic Properties of Poly(Ether-B-Amide) (Pebax®1074) for Gas Permeation and Pervaporation. M.Sc. Dissertation, University of Waterloo, 2011. (41) Irani, M.; Keshtkar, A. R.; Moosavian, M. A. Removal of Cadmium from Aqueous Solution Using Mesoporous PVA/TEOS/APTES Composite Nanofiber Prepared by Sol–Gel/Electrospinning. Chem. Eng. J. 2012, 200–202, 192. (42) Pomogailo, A. D. Hybrid Polymer-Inorganic Composite. Russ. Chem. Rev. 2000, 69, 53. (43) Schottner, G. Hybrid Sol-Gel-Derived Polymers: Applications of Multi-Functional Materials. Chem Mater. 2001, 13, 3422. (44) Mammeri, F.; Le Bourhis, E.; Rozes, L.; Sanchez, C. Mechanical Properties of Hybrid OrganicInorganic Materials. J.Mater.Chem. 2005, 15, 3787. (45) Sanchez, C.; Julián, B.; Belleville, P.; Popall, M. Applications of Hybrid Organic-Inorganic Nanocomposites. J.Mater.Chem.2005, 15, 3559. (46) Zou, H.; Wu, S.; Shen, J. Polymer/Silica Nanocomposites: Preparation, Characterization, Properties, and Applications. Chem. Rev. 2008, 108, 3893. (47) Reculusa, S.; Poncet-Legrand, C.; Ravaine, C.; Mingotaud, C.; Duguet, E.; Bourgeat-Lami, E. Syntheses of Raspberrylike Silica/Polystyrene Materials. Chem. Mater. 2002, 14, 2354. (48) Ghadimi, A.; Amirilargani, M.; Mohammadi, T.; Kasiri, N.; Sadatnia, B. Preparation of Alloyed Poly(Ether Block Amide)/Poly(Ethylene Glycol Diacrylate) Membranes for Separation of CO2/H2(Syngas Application). J. Membr. Sci. 2014, 458, 14. (49) Bernardo, P.; Jansen, J. C.; Bazzarelli, F.; Tasselli, F.; Fuoco, A.; Friess, K.; Izák, P.; Jarmarová, V.; Kačírková, M.; Clarizia, G. Gas Transport Properties of Pebax®/Room Temperature Ionic Liquid Gel Membranes. Sep. Purif. Technol. 2012, 97, 73. (50) Yave, W.; Car, A.; Peinemann, K.-V. Nanostructured Membrane Material Designed for Carbon Dioxide Separation. J. Membr. Sci. 2010, 350, (1–2), 124. (51) Car, A.; Stropnik, C.; Yave, W.; Peinemann, K.-V. Pebax®/Polyethylene Glycol Blend Thin Film Composite Membranes for CO2 Separation: Performance with Mixed Gases. Sep. Purif. Technol. 2008, 62, (1), 110. (52) Rowe, B. W.; Robeson, L. M.; Freeman, B. D.; Paul, D. R. Influence of Temperature on the Upper Bound: Theoretical Considerations and Comparison with Experimental Results. J. Membr. Sci. 2010, 360, (1–2), 58.

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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

Table captions:

2 3

Table 1: The amount of TEOS and water and theoretical calculation of SiO2 weight percent into the 6wt. % PEBA/ THF:HCOOH, based on 100gr solvent

4

Table 2: The applied condition for physical modification of the SiO2 nanoparticles

5 6

Table 3: Thermal properties of the fabricated nanocomposite membranes via sol-gel approach, DSC analysis

7

Table 4: Gas permeability of the fabricated nanocomposite membranes via sol-gel approach

8 9

Table 5: Thermal properties of the fabricated neat and nanocomposite membranes via chemical modification approach, DSC analysis


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1

Figure captions:

2 3 4

Figure 1. Schematic view of the experimental setup CP (Constant Pressure Section), CV (Constant Volume Section) (1): Ballast volume, (2): membrane module, (3): Permeate vessels, (4): Thermocouple

5

Figure 2. Schematic view of the surface modified SiO2 nanoparticles with PEG macromolecules

6 7

Figure 3. Distribution of SiO2 nanoparticles in cross-section of the fabricated nanocomposite membranes via sol-gel approach obtained by SEM-mapping.(a) 15wt. %, (b) 30wt. %, and (c) 45wt. %

8

Figure 4. FT-IR spectra of the physically modified and unmodified SiO2 nanoparticles

9 10

Figure 5. SEM images of the physically modified nanocomposite membranes: (a) 2wt. %, (b) 4wt. %, and (c) 6wt. %

11

Figure 6. FT-IR spectra of the chemically modified and unmodified SiO2 nanoparticles

12

Figure 7. SEM image of the 2wt. % unmodified nanocomposite membrane

13 14

Figure 8. SEM images of the chemically modified nanocomposite membranes: (a) 0wt. % (neat PEBA), (b) 2wt. % (c) 4wt. %, (c) 6wt. %, and (d) 8wt. %

15

Figure 9. Pure permeability and ideal permeation selectivity of gases, at 25 °C and 2 bar

16

Figure 10. Robeson diagram for the CO2/CH4, CO2/H2 and CO2/N2 pairs

17 18

Figure 11. Pure and mixed permeability and permeation selectivity of CO2/H2, at 65 °C and 26 bar

19 20

Figure 12. Pure and mixed permeability and permeation selectivity of CO2/N2, at 65 °C and 26 bar

21 22

Figure 13. Pure and mixed permeability and permeation selectivity of CO2/CH4, at 45 °C and 44 bar



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Table 1. The amount of TEOS and water and theoretical calculation of SiO2 weight percent into the 6wt. % PEBA/ THF:HCOOH, based on 100gr solvent samples TEOS/PEBA 15% TEOS/PEBA 30% TEOS/PEBA 45%

TEOS (mole) 0.0051 0.0123 0.0236

Water (mole) 0.0102 0.0247 0.471

SiO2 (gr) 0.3054 0.7416 1.4159

19 20


SiO2/PEBA (wt%) 4.8 11.0 19.1

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Table 2. The applied condition for physical modification of the SiO2 nanoparticles SiO2 Particle diameter (nm) 7-20

SiO2 Concentration (gr/L) 10

PEG Concentration (gr/L) 3.7

18


Temperature ( )

Time (hr)

25

36


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Table 3. Thermal properties of the fabricated nanocomposite membranes via sol-gel approach, DSC analysis Sample PEBA (previous work) 48

∆Hf,PEO ∆Hf,PA (j/g) (j/g)

Tg °C

Tm(PE) Tm(PA) °C °C

PEO

PA

(%)

(%)

68.64 77.53

-51.09

13.66

204.99

17.6

29.8

TEOS/PEBA 15%

29.29 33.82

-51.69

10.44

200.09

20.32

33.70

TEOS/PEBA 30%

17.07

41.97

-54.36

9.95

193.86

10.26

18.25

TEOS/PEBA 45%

10.16

17.53

-55.47

17.7

179.39

6.10

7.62

16 17


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Table 4. Gas permeability of the fabricated nanocomposite membranes via sol-gel approach

Gas permeability CO2

N2

H2 CH4 CO2/N2 CO2/H2 CO2/CH4

PEBA TEOS/PEBA 15% TEOS/PEBA 30% TEOS/PEBA 45%

1.1 0.89 0.65 0.53

7.7 6.5 5.1 3.5

70.3 50.3 41.8 23.7

3.8 3.1 2.6 1.7

63.91 56.52 64.31 44.72

18


9.13 7.74 8.20 6.77

18.50 16.23 16.08 13.94


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Table 5. Thermal properties of the fabricated neat and nanocomposite membranes via chemical modification approach, DSC analysis Sample PEBA (previous work) 2% SiO2OA/PEBA 4% SiO2OA/PEBA 6% SiO2OA/PEBA 8% SiO2OA/PEBA

48

∆Hf,PEO ∆Hf,PA (j/g) (j/g) 29.29 68.64 31.75 67.33 30.49 62.26 28.25 67.34 28.56 68.57

Tg Tm(PE) Tm(PA) °C °C °C -51.09 13.66 204.99 -50.56 12.41 204.51 -49.83 12.4 204.52 -49.04 12.67 205.07 -48.03 12.53 205.03

18


PEO

PA

(%) 17.6 19.1 18.3 16.9 17.1

(%) 29.8 29.3 27.1 29.3 29.8

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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


Figure 1. Schematic view of the experimental setup CP (Constant Pressure Section), CV (Constant Volume Section) (1): Ballast volume, (2): membrane module, (3): Permeate vessels, (4): Thermocouple



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Figure 2. Schematic view of the surface modified SiO2 nanoparticles with PEG macromolecules


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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


(a)

(b)

(c)

Figure 3. Distribution of SiO2 nanoparticles in cross-section of the fabricated nanocomposite membranes via sol-gel approach obtained by SEM-mapping.

(a) 15wt. %, (b) 30wt. %, and (c) 45wt. %



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Figure 4. FT-IR spectra of the physically modified and unmodified SiO2 nanoparticles


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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


(a)

(b)

(c)

Agglomerated SiO2 Nanoparticles

Agglomerated SiO2 Nanoparticles Agglomerated SiO2 Nanoparticles

Figure 5. SEM images of the physically modified nanocomposite membranes: (a) 2wt. %, (b) 4wt. %, and (c) 6wt. %



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Figure 6. FT-IR spectra of the chemically modified and unmodified SiO2 nanoparticles


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23


Agglomerated SiO2 Nanoparticles

Figure 7. SEM image of the 2wt. % unmodified nanocomposite membrane



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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

a

b

c

dd

e

Figure 8. SEM images of the chemically modified nanocomposite membranes: (a) 0wt. % (neat PEBA), (b) 2wt. % (c) 4wt. %, (c) 6wt. %, and (d) 8wt. %


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Figure 9. Pure permeability and ideal permeation selectivity of gases, at 25 °C and 2 bar



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Figure 10. Robeson diagram for the CO2/CH4, CO2/H2 and CO2/N2 pairs


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Figure 11. Pure and mixed permeability and permeation selectivity of CO2/H2, at 65 °C and 26 bar



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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

Figure 12. Pure and mixed permeability and permeation selectivity of CO2/N2, at 65 °C and 26 bar


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Figure 13. Pure and mixed permeability and permeation selectivity of CO2/CH4, at 45 °C and 44 bar


A Novel Chemical Surface Modification for the Fabrication of PEBA

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