WO2007123356A1

WO2007123356A1 - The facilitated olefin transporting composite membrane comprising nanosized metal and ionic liquid

Info

Publication number: WO2007123356A1
Application number: PCT/KR2007/001991
Authority: WO
Inventors: Yong-Soo Kang; Sang-Wook Kang; Kook-Heon Char; Jong-Ho Kim
Original assignee: Industry-University Cooperation Foundation Hanyang University
Priority date: 2006-04-26
Filing date: 2007-04-24
Publication date: 2007-11-01
Also published as: JP2009535193A

Abstract

Disclosed is a composite membrane, comprising metal nanoparticles and ionic liquid. In the composite membrane, the metal nanoparticles are partially cationized (polarized) by the anions of the ionic liquid to act as carriers enabling the facilitated transport of olefin. Thus, the composite membrane enables the selective facilitated transport of olefin in the separation of a mixed gas of olefin and paraffin.

Description

THE FACILITATED OLEFIN TRANSPORTING COMPOSITE MEMBRANE COMPRISING NANOSIZED METAL AND IONIC

LIQUID

Technical Field

[1] The present invention relates to a composite membrane enabling the separation of olefin from paraffin, which have similar molecular weights, and more particularly to a composite membrane, comprising ionic liquid and metal nanoparticles. Background Art

[2] The present invention relates to a composite membrane, comprising ionic liquids

(ILs) and metal nanoparticles, characterized in that the metal nanoparticles polarized by the anions of the ionic liquids act as carriers for facilitated transport carriers, to enable the separation of olefin from paraffin.

[3] Methods for separating various mixtures into components using polymer membranes have been applied mainly for the separation of carbon dioxide from methane, oxygen from air, organic vapor from air, and the like. However, in the case of the separation of olefin from paraffin, for example, propylene from propane, and butylene from butane, the use of traditional polymer membranes cannot achieve sufficient separation performance, because olefin and paraffin have very similar molecular weights and physical properties. Since the concept of facilitated transport was introduced as a solution to the problem in which the separation of olefin from paraffin, having similar molecular weight, is difficult to achieve using such traditional polymer membranes, studies on the application of polymer membranes for the separation of olefin from paraffin have been actively conducted.

[4] If a carrier capable of reversibly reacting with the specific component of a mixture to be separated into components is present in a membrane, not only mass transfer, attributable to a simple concentration gradient according to Fick's law, but also facilitated transport, induced by the carrier, will occur due the reversible reaction between the carrier and the specific component of the mixture, thus increasing selectivity and permeability.

[5] Examples of polymer membranes for use in such facilitated transport separation include technologies relating to supported or immobilized liquid membranes made by loading, as carriers, silver salts such as AgBF or AgCF SO . However, such

4 3 3 technologies have a shortcoming in that the activity of silver salts decreases with the increase in separation time. To overcome this shortcoming, technologies using phthalate compounds or surfactants have been proposed. [6] The present inventors have conducted interesting studies on facilitated transport, which use metal nanoparticles as carriers, instead of using the prior metal salt- type carriers, and, as a result, have developed a composite membrane comprising metal nanoparticles, which enables the separation of olefin from paraffin.

[7] Meanwhile, ionic liquids are present in the liquid state at a temperature lower than

100 ⁰C, unlike conventional metal salt compounds comprising metallic cations and non-metallic anions. The ionic liquid consists of organic cations and anions. The cations of the ionic liquids include dialkylimidazolium, alkylpyridinium, quaternary ammonium and quaternary phosphonium, and the anions thereof NO , BF , CF SO , PF 6 ^", AlCl 4 ^", Al 2Cl 7 ^", AcO^", TfO^" (trifluoromethanesulfonate), Tf 2 N^"

(trifluoromethanesulfonylamide), CH CH(OH)CO (L-lactate) and the like. [8] Due to the unique physical and chemical properties thereof, the ionic liquids are also used as catalysts for heterogeneous catalytic reactions, catalysts substituting for hazardous materials such as HF, cell electrolytes, and mediators of gas-gas separation or liquid-liquid separation. [9] The present inventors paid attention to the activity of metal nanoparticles and the function of ionic liquids as separation mediators, thereby completing the present invention.

Disclosure of Invention

Technical Problem

[10] It is an object of the present invention to provide a composite membrane, which uses metal nanoparticles to enable the facilitated transport of olefin so as to enable the separation of olefin and paraffin, which were difficult to separate using the prior method due to similar molecular weights and physical properties. Technical Solution

[11] To achieve the above object, the present invention provides a facilitated olefin transport composite membrane, comprising metal nanoparticles and ionic liquid.

[12] Preferably, the metal nanoparticles are selected from the group consisting of silver nanoparticles, gold nanoparticles and copper nanoparticles.

[13] The facilitated olefin transport composite membrane preferably further comprises a porous support.

[14] The porous support is preferably a poly sulf one porous support.

[15] The metal nanoparticles are preferably contained in an amount of 0.05-1 part by weight based on one part by weight of the ionic liquid.

[16] The metal nanoparticles preferably have a particle size of less than 100 nm.

[17] The ionic liquid is preferably one selected from the group consisting of BMIM⁺BF

, BMIM⁺NO 3 and BMIM⁺CF 3 SO 3 . [18] The technical characteristic of the present invention resides in that the metal nanoparticles are cationized (polarized) by the ionic liquid and thus act as carriers for facilitated transport. In the present invention, there are no limitations on the kind of metal nanoparticles and the kind of ionic liquids, because various ionic liquids are applied for various metal nanoparticles, so that partial cationization of the metal nanoparticles is achieved according to the same mechanism.

[19] The interaction between the ionic liquid and the metal nanoparticles in the present invention is as follows. FIG. 1 is an illustrative view showing the mechanism by which the surface of a metal nanoparticle is partially cationized by BMIM⁺BF as an ionic liquid. As shown in FIG. 1, the anion BF of BMIM⁺BF approaches the surface of a metal nanoparticle to partially cationize the metal nanoparticle, such that the metal nanoparticle will act as an olefin carrier capable of reversibly reacting with the π-bond of olefin.

[20] FIGS. 2 and 3 show the partial cationization mechanisms of metal nanoparticles in the cases of using BMIM⁺CF SO and BMIM⁺NO , respectively, as ionic liquids. As shown in the mechanisms in FIGS. 1 to 3, the partial cationization of metal nanoparticles is possible using all conventional ionic liquids, and hence, the present invention does not impose any particular limitation on the kind of ionic liquid or metal nanoparticle. Examples below are given to promote a better understanding of the present invention, and the scope of the present invention is not limited to the ionic liquids and metal nanoparticles used in these examples.

Advantageous Effects

[21] The present invention provides a composite membrane, comprising metal nanoparticles and a liquid, which allows the facilitated transport of olefin by the metal nanoparticles. The composite membrane according to the present invention uses a facilitated transport mechanism and allows the easy separation of materials, which are difficult to separate, due to the similar molecular weights and physical properties thereof, for example, olefin/paraffin mixtures such as a propane/propylene mixture. Thus, the composite membrane of the present invention can be used in various separation processes. Brief Description of the Drawings

[22] FIG. 1 is an illustrative view showing the interaction between ionic liquid BMIM⁺

BF and metal nanoparticles in a composite membrane of the present invention.

[23] FIG. 2 is an illustrative view showing the interaction between ionic liquid BMIM⁺

CF SO and metal nanoparticles in the inventive composite membrane.

[24] FIG. 3 is an illustrative view showing the interaction between ionic liquid BMIM⁺

NO and metal nanoparticles in the inventive composite membrane. [25] FIG. 4 is a graphic diagram showing the pure gas permeances of propane and propylene through the composite membranes of Examples 1 to 6, measured in Test Example 1.

[26] FIG. 5 shows Raman spectra for composite membranes of Comparative Example and Examples 2, 4 and 6, measured in Test Example 3.

[27] FIG. 6 shows deconvoluted Raman spectra for the composite membranes of

Comparative Example and Examples 2, 4 and 6, measured in Test Example 3.

[28] FIG. 7 is a graphic diagram showing the pure gas permeances of propane and propylene through the composite membranes of Examples 7 to 12, measured in Test Example 4.

[29] FIG. 8 is a graphic diagram showing the pure gas permeances of propane and propylene through the composite membranes of Examples 15 to 20, measured in Test

Example 6.

Best Mode for Carrying Out the Invention

[30]

[31] Examples 1 to 6: Composite membranes comprising BMIM⁺BF ^" as ionic liquid

[32]

[33] Silver nanoparticles (70-nm size and 99.5% pure) were purchased from Aldrich

Chemical Co., Inc. and BMIM⁺BF (l-butyl-3-methylimidazolium tetrafluoroborate) was purchased from C-TRI Co., Ltd., Korea. The purchased materials were used in experiments without any further treatment.

[34] The preparation of composite membranes, comprising ionic liquid (IL) and silver nanoparticles, was performed by dispersing the silver nanoparticles in the ionic liquid. Because BMIM⁺BF has a very high viscosity of 234 cP (at 25 ⁰C), the preparation of the composite membranes became possible only when the silver nanoparticles and the ionic liquid were used.

[35] As a support to be coated with a mixture of the ionic liquid and the silver nanoparticles, a microporous polysulfone support (Sanhan Industry Co., Ltd., Korea) was used, and the polymer mixture solution was coated on the support using an RK control coater (Model 101, Control Coater RK Print-Coat Instruments, Ltd., UK).

[36] The composite membranes of Examples 1 to 6 were prepared by changing the weight ratio of the ionic liquid BMIM⁺BF ^" to the silver nanoparticles within the range from 1:0.1 to 1:1, as shown in Table 1 below.

[37] Table 1

[38] [39] Examples 7 to 12: Use of BMIM⁺NO as ionic liquid [40] [41] Silver nanoparticles (70-nm size and 99.5% pure) were purchased from Aldrich Chemical Co., Inc. and BMIM⁺NO (l-butyl-3-methylimidazolium nitrate) was purchased from C-TRI Co., Ltd., Korea. The purchased materials were used in experiments without any further treatment. The preparation of composite membranes, comprising silver nanoparticles and BMIM⁺NO , was performed in the same manner as in Example 1.

[42] Composite membranes of Examples 7 to 12 were prepared by changing the weight ratio of the ionic liquid BMIM⁺NO to the silver nanoparticles within the range from 1:0.1 to 1:1, as shown in Table 2 below.

[43] Table 2

[44] [45] Example 13: Composite membrane comprising copper nanoparticles and BMIM⁺BF ^" as ionic liquid

[46] [47] Copper nanoparticles (70-nm average particle size) were purchased from Aldrich Chemical Co., Inc., and BMIM⁺BF ^~ (l-butyl-3-methylimidazolium tetrafluoroborate) was purchased from C-TRI Co., Ltd., Korea. The purchased materials were used in experiments without any further treatment.

[48] The preparation of a composite membrane, comprising ionic liquid and copper nanoparticles, was performed by dispersing the copper nanoparticles in the ionic liquid. Herein, the weight ratio of BMIM⁺BF ^" to the copper nanoparticles was 1 : 0.4.

4

The remaining process conditions were the same as in Example 1.

[49]

[50] Example 14: Composite membrane comprising gold nanoparticles and BMIM⁺BF as ionic liquid

[51]

[52] A composite membrane was prepared in the same manner as in Example 13, except that gold nanoparticles (50-130-nm average particle size) purchased from Aldrich Chemical Co., Inc., and the weight ratio of BMIM⁺BF to gold nanoparticles was 1: 0.1.

[53]

[54] Examples 15 to 20: Composite membranes comprising BMIM⁺Tf as ionic liquid

[55]

[56] Composite membranes were prepared using silver nanoparticles and BMIM⁺CF SO

(l-butyl-3-methylimidazolium triflate, also referred to as BMIM⁺Tf) as an ionic liquid. The remaining process conditions and the content ratio of silver nanoparticles were the same as in Examples 1 to 6. That is, the prepared composite membranes were comprised of silver nanoparticles at ratios of 0.1, 0.25, 0.5, 0.7, 0.8 and 1.0 parts by weight based on one part by weight of BMIM⁺CF SO .

[57]

[58] Comparative Example

[59]

[60] A membrane was prepared by coating only BMIM⁺BF ^" on a polysulfone support.

[61]

[62] Test Example 1 : Test of total permeance and selectivity of Comparative Example and Example 4

[63]

[64] The membrane of Comparative Example, comprising only BMIM⁺BF , and the membrane of Example 4, comprising BMIM⁺BF and silver nanoparticles at a weight ratio of 1: 0.7, were tested for the total permeance and selectivity of a mixed gas of propylene and propane (1:1 v/v).

[65] The test of total permeance was performed using a mass flow meter (MFM). Gas permeance is expressed in GPU, and 1 GPU is 1 x 10 cm (STP)/(cm sec cmHg). In the case of a mixed gas of propylene and propane, because it is impossible to measure the permeance of each component thereof using only an MFM, the permeances of propylene and propane were measured using a gas chromatograph together with the MFM. The gas chromatograph that was used was a gas chromatograph (G 1530A, Hewlett Packard), equipped with a TCD detector and a unibead 2S 60/80 packing column.

[66] Table 3 shows the results of Test Example 1. As can be seen in Table 3, the membrane of Comparative Example, comprising only BMIM⁺BF ^", showed a

4 propylene selectivity of only 0.9 and a total permeance of 0.5 GPU, suggesting that it would not be used as a membrane for the separation of propylene from propane. However, the composite membrane of Example 4 according to the present invention had a propylene selectivity of 17 and a total permeance of 2.7, and thus showed the characteristics of a typical facilitated transport membrane, showing increased selectivity and total permeance. That is, it could be seen that the improvement in the performance of the facilitated olefin transport composite membrane of Example 4 according to the present invention was because the silver nanoparticles were partially cationized by the ionic liquid to make the facilitated transport of olefin possible.

[67] Table 3

[68] [69] Test Example 2 [70] [71] In Test Example 2, unlike Test Example 2, the pure gas permeance of each of propylene and propane gases through the membranes of Examples 1 to 6 was measured. The measurement results are shown in FIG. 4. As can be seen in the graphs of FIG. 4, the permeance of propane was almost constant, but the permeance of propylene gas abruptly increased with an increase in the content of silver nanoparticles, and then decreased. Examples 1 to 6 showed the permeance of propylene, which was much higher than the permeance of propane gas, suggesting that the facilitated transport of olefin through the membranes of Examples 1 to 6 occurred.

[72] Particularly, when the weight ratio of the silver nanoparticles to the ionic liquid was in the range of 0.5-0.7: 1, the facilitated transport of olefin clearly appeared. However, when the weight ratio of the silver nanoparticles to the ionic liquid was more than 0.7:1, the permeance of propylene decreased instead of increased. This is considered to be because the aggregation of the silver nanoparticles occurred when the content of the silver nanoparticles was excessively high. [73]

[74] Test Example 3

[75]

[76] The interaction between silver nanoparticles and BF ^" ions in the BMIM⁺BF /silver

4 4 nanoparticle composite membrane was observed using FT-Raman spectroscopy. FIG. 5 shows Raman spectra for the composite membranes of Examples 2, 4 and 6 in the stretching band region of BMIM⁺BF ^~. In FIG. 5, the wavenumbers of free ions, ion pairs and higher ion aggregates are 765 cm^" , 770 cm^" and 774 cm^" , respectively. As can be seen in FIG. 5, the fraction of free ions increased until a weight ratio of silver nanoparticles to ionic liquid of 0.7: 1 (Example 4), but the peak decreased at a wavenumber of 774 cm corresponding to BF ion aggregates.

4

[77] FIG. 6 shows deconvoluted Raman spectra for composite membranes of

Comparative Example and Examples 2, 4 and 6, measured in Test Example 3. As can be seen in FIG. 6, the fraction of free ions increased from 0.07 for BMIM⁺BF (Comparative Example) to 0.29 for BMIM⁺BF 4 /Ag (Example 4), and the fraction of ion aggregates also decreased from 0.41, for Comparative Example, to 0.28 for Example 4.

[78] Putting the results of FIGS. 5 and 6 together, (1) BMIM⁺BF is present as ion pairs or ion aggregates, and (2) BF 4 ions react with silver nanoparticles, thus weakening the bond between BMIM⁺ and BF 4 . That is, it can be concluded that the surface of the silver nanoparticles is partially cationized by BF ^" to further activate the complexion of silver-olefin.

[79]

[80] Test Example 4

[81]

[82] The pure gas permeances of propylene and propane through the composite membranes of Examples 7 to 12 were measured. Specifically, pure gas permeances through the composite membranes, comprising, as the ionic liquid, BMIM⁺NO instead of BMIM⁺BF as used in Examples 1 to 6, were measured. The measurement results are shown in FIG. 7. These results were slightly different from the results of Test Example 2 for the composite membranes comprising BMIM⁺BF and silver

4 nanoparticles (Examples 1 to 6). It could be seen that the permeance of propylene started to increase abruptly from a weight ratio of BMIM⁺NO : silver nanoparticle of 1 : 0.7, and that the permeance of propane started to increase from a weight ratio of BMIM⁺NO : silver nanoparticle of 1 : 0.8. From these results, it could be found that, although the facilitated transport of silver nanoparticles occurred even when BMIM⁺ NO was used as the ionic liquid, the composite membranes, comprising BMIM⁺NO , must have a larger content of silver nanoparticles than the composite membranes comprising BMIM⁺BF ^". From the results of Test Example 4, it could be found that the use of BMIM⁺BF ^" as the ionic liquid would be preferable to the use of BMIM⁺NO in view of the permeance, selectivity and economy required for the facilitated transport of olefin.

[83]

[84] Test Example 5: Measurement of total permeance and selectivity for Comparative

Example and Examples 13 and 14

[85]

[86] The membrane of Comparative Example, comprising only BMIM⁺BF , and the composite membranes of Examples 13 and 14, comprising BMIM⁺BF and copper

4 nanoparticles (1:0.4) or BMIM⁺BF and silver nanoparticles (1:0.1), were tested for the permeance and selectivity of a mixed gas of propylene and propane (1:1 v/v).

[87] In the results of Test Example 5, the composite membranes of Examples 13 and 14 showed propylene selectivities of 16 and 12, respectively, and total permeances of 5.2 and 5.5, respectively, and had the characteristics of a typical facilitated transport membrane, showing highly increased selectivity and total permeance. This suggests that the copper nanoparticles and the metal nanoparticles were also cationized by the ionic liquid, as in the case of the silver nanoparticles.

[88]

[89] Test Example 6

[90]

[91] The composite membranes of Examples 15 to 20 were measured for the pure gas permeances of propylene and propane. The measurement results are shown in FIG. 8.

[92] As can be seen in FIG. 8, the permeance of propylene abruptly increased from a weight ratio of silver nanoparticles to ionic liquid of about 0.25: 1, and the permeance of propane was maintained at a low value without change. The permeance of propane also increased from a weight ratio of silver nanoparticles to ionic liquid of about 0.7: 1, resulting in a decrease in selectivity. This is because the silver nanoparticles aggregate when they are used in a given amount. As can be seen from Test Examples 2 and 4, the content of silver nanoparticles at which they aggregated varied depending on the kind of ionic liquid.

[93] In consideration of various kinds of ionic liquid, the present inventors propose that the silver nanoparticles be used in an amount of 0.05-1.0 parts by weight based on one part by weight of the ionic liquid. The weight ratio of silver nanoparticles to ionic liquid is determined within the specified range depending on the kind of ionic liquid.

[94] As described above, the present invention provides a facilitated transport composite membrane, comprising ionic liquid and metal nanoparticles, which enables the separation of olefin from paraffin through the facilitated transport of olefin. Such fa- cilitated transport of olefin is possible because the metal nanoparticles are polarized by the ionic liquid.

[95] Although the above Examples and Test Examples suggested only the use of BMIM⁺

BF ^", BMIM⁺NO ^" and BMIM⁺CF SO ^" as ionic liquids and the use of silver

4 3 3 3 ⁿ nanoparticles, gold nanoparticles and copper nanoparticles as metal nanoparticles, these Examples are merely examples for illustrating the present invention, and the technical characteristics of the present invention reside in that the metal nanoparticles are used as carriers for facilitated transport, and the ionic liquids are used to activate the metal nanoparticles as carriers. Accordingly, it is to be understood that the scope of the present invention is not limited to any kind of ionic liquid or metal nanoparticle. Industrial Applicability

[96] The present invention can be used in a process for the separation of olefin and paraffin, which were difficult to separate in the prior art because their molecular weights are similar. For example, even the separation of olefin and paraffin, like the separation of propylene and propane, having very similar molecular weights, can be achieved through the facilitated transport mechanism according to the present invention. Accordingly, the present invention can be used in various separation processes.

[97]

[98]

Claims

[1] A facilitated olefin transport composite membrane, comprising metal nanoparticles and ionic liquid.

[2] The facilitated olefin transport composite membrane of Claim 1, wherein the metal nanoparticles are selected from the group consisting of silver nanoparticles, gold nanoparticles and copper nanoparticles.

[3] The facilitated olefin transport composite membrane of Claim 1 or 2, which further comprises a microporous support.

[4] The facilitated olefin transport composite membrane of Claim 3, wherein the microporous support is a polysulfone porous support.

[5] The facilitated olefin transport composite membrane of Claim 1 or 2, wherein the metal nanoparticles are contained in an amount of 0.05-1 part by weight based on one part by weight of the ionic liquid.

[6] The facilitated olefin transport composite membrane of Claim 1 or 2, wherein the metal nanoparticles have a particle size of less than 100 nm.

[7] The facilitated olefin transport composite membrane of Claim 1 or 2, wherein the ionic liquid is any one selected from the group consisting of BMIM⁺BF

4

(l-butyl-3-methylimidazolium tetrafluoroborate), BMIM⁺NO (l-butyl-3-methylimidazolium nitrate) and BMIM⁺CF SO ( 1 -butyl- 3 -methylimidazolium triflate) .