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Improvement of ethanol selectivity of silicalite membrane in pervaporation by silicone rubber coating
Journal of Membrane Science 210 (2002) 433–437
Short communication
Improvement of ethanol selectivity of silicalite membrane in pervaporation by silicone rubber coating H. Matsuda a , H. Yanagishita b,∗ , H. Negishi b , D. Kitamoto b , T. Ikegami b , K. Haraya b , T. Nakane b , Y. Idemoto a , N. Koura a , T. Sano c b
a Science University of Tokyo, 2641 Yamazaki, Noda, Chiba 278-8510, Japan National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba Central 5, Ibaraki 305-8565, Japan c Japan Advanced Institute of Science and Technology, Tatsunokuchi, Ishikawa 923-1292, Japan
Received 30 November 2001; received in revised form 20 April 2002; accepted 10 June 2002
Abstract In order to improve the pervaporation performance of silicalite membrane, two types of silicone rubber, KE45 and KE108, were coated on the membrane surface. The initial molecular weight of KE108 is high and vulcanizing starts when it comes into contact with moisture in air, whereas the initial molecular weight of KE45 is low and vulcanizing starts when it is mixed with a catalyst. KE108 was found to be more effective than KE45 in enhancing the ethanol selectivity of silicalite membranes. A membrane coated using a 3 wt.% KE108 hexane solution showed separation factor of α = 125 with a total flux of 0.14 kg/m2 h. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Silicalite; Pervaporation; Ethanol selectivity; Silicone rubber; Coating
1. Introduction In recent years, zeolite membranes have been great attention as candidates for molecular sieving separation membranes and membrane reactors [1–5]. Silicalite, one of zeolite, is more hydrophobic than any other zeolite. We successfully prepared separation membranes consisting of silicalite polycrystals on a stainless steel support by hydrothermal synthesis. The silicalite membrane showed high ethanol selectivity with a separation factor α of 60 for a 5 vol.% ethanol aqueous solution at 30 ◦ C on pervaporation [6,7]. Furthermore, we established the preparation condi∗ Corresponding author. Tel.: +81-298-61-4659; fax: +81-298-61-4674. E-mail address: [email protected] (H. Yanagishita).
tions for a silicalite membrane with high ethanol selectivity (α = 120) [8]. During calcination, defects or pores between silicalite grains may be generated due to the difference in thermal expansion between the silicalite membrane and the support. The separation of ethanol and water is not being generated only through the pores of zeolite. Xomeritakis et al. have reported to improve separation performance of xylene by filling up the cracks of MFI membrane formed on the surface of alumina support disks after annealing with using sol–gel process [9]. By closing only defects or pores between silicalite grains, the silicalite membrane should show higher ethanol selectivity. On the other hand, silicone rubber has also been used for covering defects in organic and inorganic membrane. When Mohammadi et al. coated silicone rubber on an asymmetric aromatic polyamide membrane, the gas selectivity of the coated membrane
0376-7388/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 6 - 7 3 8 8 ( 0 2 ) 0 0 3 6 4 - 2
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H. Matsuda et al. / Journal of Membrane Science 210 (2002) 433–437
improved [10]. Petersen et al. coated the surface of carbon membranes with silicone rubber. They also reported that the gas separation performance of coated membranes improved [11]. In this study, silicalite membranes were coated with silicone rubber in order to improve ethanol selectivity in pervaporation. Two types of silicone rubber were used. This paper describes the effect of silicone rubber coating on the separation performance of silicalite membranes. 2. Experimental 2.1. Membrane preparation Silicalite membranes were prepared on a stainless steel support (pore diameter: 2 m) by hydrothermal synthesis. The starting solution consisted of colloidal silica (Cataloid SI-30, Shokubai Kasei Co.; 30.4 wt.% SiO2 , 0.38 wt.% Na2 O and 69.22 wt.% water), tetrapropylammonium bromide (TPABr), sodium hydroxide and distilled water. Hydrothermal synthesis was performed at 170 ◦ C for 24–144 h, and calcination of the membrane was performed at 375 ◦ C for 60 h. Details of these processes are described elsewhere [8,12]. Two types of silicone rubber supplied by Shinetsu Kagaku Co. were used: KE45, whose molecular weight is high and which starts vulcanizing when it comes into contact with air and KE108, whose molecular weight is low and which starts vulcanizing when it comes into contact with a catalyst. We prepared 1–10 wt.% hexane solutions of these silicone rubbers and stirred them using a magnetic stirrer until they were homogeneously mixed. The silicalite membrane coating process was as follows. Cellophane tape was fixed to the rear side of the membrane to prevent that side from being coated. The membrane was then immersed in the coating solution for 10 s and dried at room temperature for 2 days. The morphology of the membrane was observed by a scanning electron microscope (SEM: S-800, Hitachi). 2.2. Separation performance measurement The pervaporation performance of the membrane was measured using a 5 vol.% ethanol aqueous solu-
tion at 30 ◦ C as a feed, and was evaluated by the separation factor α(EtOH/H2 O) as well as total flux. These parameters are calculated from following equations: Flux (kg/m2 h) weight of permeate (kg) = membrane area (m2 ) × permeation time (h) Separation factor α =
[CEtOH /CH2 O ] permeate [CEtOH /CH2 O ] feed
where the CEtOH and CH2 O are the volume fraction of alcohols and water, respectively. The concentrations of the permeate and the feed were analyzed by gas chromatography. A stainless steel cell previously developed in our laboratory was used for pervaporation measurements [13]. The membranes were evacuated in a vacuum oven at 80 ◦ C.
3. Results and discussion 3.1. Silicone rubber coating on silicalite membranes In order to utilize the hydrophobicity and adsorption properties of silicalite membranes, only defects or pores except zeolitic pores should be covered, while the surface of the membrane should not be coated with silicone rubber. From this standpoint, dilute coating solutions were used in which the silicone rubber concentration was less than 3 wt.%. Table 1 shows the pervaporation performance of membranes with coating of silicone rubber. The flux of membrane no. 1 was 0.17 kg/m2 h before coating. After coating with silicone rubber (KE45), the flux decreased although the separation factor increased slightly. Similar results were obtained for membranes nos. 2 and 3. The separation factor of membrane no. 4 improved only slightly although the flux decreased drastically. This suggests that the silicone rubber (KE45) formed a thin layer of silicone rubber on the surface of the membrane because of its high viscosity, although only partially rather than on the entire surface because of rough surface of the membrane. On the other hand, the membranes coated with the silicone rubber (KE108) showed high ethanol selectivity. For example, membrane no. 6 showed a high separation factor α of 125 after coating. This value
H. Matsuda et al. / Journal of Membrane Science 210 (2002) 433–437
435
Table 1 Pervaporation performance of membranes coated with silicone rubber Membrane
Silicone rubber
Silicone rubber concentration (wt.%)
Silicalitea [8] Silicone rubberb [13] Silicone rubberc [14]
Total flux (kg/m2 h)
EtOH concentration of permeate (vol.%)
0.29 0.039 0.022
Separation factor α 120 5.5 6.5
Silicalite No. 1
KE45
0 1
0.17 0.07
67 71
39 47
No. 2
KE45
0 2
0.21 0.16
70 74
44 54
No. 3
KE45
0 3
0.40 0.19
71 72
47 49
No. 4
KE45
0 3
0.33 0.052
58 79
26 71
No. 5
KE108
0 2
0.19 0.093
59 81
27 81
No. 6
KE108
0 3
0.15 0.14
73 88
51 125
Feed: 5 vol.% ethanol aqueous solution at 30 ◦ C. Feed: 6.0% (w/v) ethanol aqueous solution at 25 ◦ C. c Feed: 8.2 wt.% ethanol aqueous solution at 35 ◦ C. a
b
of separation factor α is similar to or higher than the value for a pure silicalite membrane we previously reported, which is higher than any other value reported by other researchers for pure silicalite membranes. From the above results, it was found that the silicone
rubber (KE108) covered only defects or pores except zeolitic pores without forming a thin layer on the entire surface of the silicalite membrane. The above difference between the behavior of two types of silicone rubbers was seen in SEM observation
Fig. 1. SEM images of the surface of the silicalite membranes before and after coating with silicone rubber (3000×).
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H. Matsuda et al. / Journal of Membrane Science 210 (2002) 433–437
aration factor decreased when they passed through silicalite. The apparent activation energy of ethanol and water were 34.0 and 40.8 kJ/mol/K, respectively. These values were similar to those obtained for the pure silicalite membrane with a separation factor α of 120 that we previously reported [8]. From the above results, it was concluded that in the case of a silicalite membrane coated with silicone rubber (KE108), ethanol and water do not pass through the silicone rubber but through the silicalite in pervaporation. Fig. 2. Effect of feed temperature on pervaporation performance of silicalite membrane coated with silicone rubber (KE108). Feed: 5 vol.% EtOH aqueous solution.
of the membrane surface. Fig. 1 shows SEM images of the surface of the silicalite membranes before and after silicone rubber coating. Using KE45, the surface of the membrane was partially covered with silicone rubber. This feature was marked with black circle in Fig. 1b. Using KE108, silicone rubber could not be observed as could be in one liquid type. Silicone rubber should penetrate into defects or pores except zeolitic pores. It is considered that this difference in coating is attributable to the different viscosities of coating solutions due to the properties of the initial silicone rubber (before vulcanizing). 3.2. Effect of temperature on pervaporation performance Fig. 2 shows the effect of feed temperature on pervaporation performance using a silicalite membrane coated with silicone rubber (KE108). The flux increased with increasing feed temperature, but separation factor decreased slightly. This result agrees well with that for the pure silicalite membrane previously reported [7,8]. On the contrary, other researchers have reported that the flux and the separation factor increased with increasing feed temperature [14]. A similar result was reported using a silicalite–silicone rubber composite membrane [15]. It was suggested that separation factor increased with increasing feed temperature when ethanol and water passed through silicone rubber, while the sep-
References [1] J. Olsson, G. Tragardh, Influence of temperature on membrane permeability during pervaporation aroma recovery, Sep. Sci. Tech. 34 (1999) 1643. [2] K. Wegner, J. Dong, Y.S. Lin, Polycrystalline MFI zeolite membranes: xylene pervaporation and its implication on membrane microstructure, J. Membr. Sci. 158 (1999) 17. [3] H. Kita, T. Inoue, H. Asamura, K. Tanaka, K. Okamoto, NaY zeolite membrane for the pervaporation separation of methanol-methyl tert-butyl ether mixtures, Chem. Commun. 45 (1997). [4] C.J. Gump, R.D. Noble, J.L. Falconer, Separation of hexane isomers through nonzeolite pores in ZSM-5 zeolite membranes, Ind. Eng. Chem. Res. 38 (1999) 2775. [5] N. Qureshi, H.P. Blaschek, Buthanol recovery from model solution/fermentation broth by pervaporation: evaluation of membrane performance, Biomass Bioenergy 17 (1999) 175. [6] T. Sano, H. Yanagishita, Y. Kiyozumi, D. Kitamoto, F. Mizukami, Separation of ethanol/water mixture by silicalite membrane, Chem. Lett. (1992) 2413. [7] T. Sano, H. Yanagishita, Y. Kiyozumi, F. Mizukami, K. Haraya, Separation of ethanol/water mixture by silicalite membrane on pervaporation, J. Membr. Sci. 95 (1994) 221. [8] H. Matsuda, H. Yanagishita, D. Kitamoto, T. Nakane, K. Haraya, N. Koura, T. Sano, Preparation of silicalite pervaporation membrane with high ethanol permselectivity, Membrane 23 (1998) 259. [9] G. Xomeritakis, Z. Lai, M. Tsapatsis, Separatopn of xylene isomer vapors with oriented MFI membranes made by seeded growth, Ind. Eng. Chem. Res. 40 (2001) 544. [10] A.T. Mohammadi, T. Matsuura, S. Sourirajan, Gas separation by silicone-coated dry asymmetric aromatic polyamide membranes, Gas. Sep. Purif. 9 (1995) 181. [11] J. Petersen, M. Matsuda, K. Haraya, Capillary carbon molecular sieve membranes derived from Kapton for high temperature gas separation, J. Membr. Sci. 131 (1997) 85. [12] H. Matsuda, H. Yanagishita, D. Kitamoto, K. Haraya, T. Nakane, T. Takada, N. Koura, T. Sano, Effects of preparation methods of silicalite membrane in the hydrothermal synthesis,
H. Matsuda et al. / Journal of Membrane Science 210 (2002) 433–437 in: Proceedings of the 1999 International Congress on Membranes and Membrane Processes, Toronto, 1999. [13] H. Yanagishita, C. Maejima, D. Kitamoto, T. Nakane, Preparation of asymmetric polyimide membrane for water/ ethanol separation in pervaporation by the phase inversion process, J. Membr. Sci. 86 (1994) 231.
437
[14] S. Kimura, T. Nomura, Pervaporation of organic substance water system with silicone rubber membrane, Maku 8 (1983) 177. [15] X. Chen, Z. Ping, Y. Long, Separation properties of alcohol– water mixture through silicalite-1-filled silicone rubber membranes by pervaporation, J. Appl. Poly. Sci. 67 (1998) 629.
Short communication
Improvement of ethanol selectivity of silicalite membrane in pervaporation by silicone rubber coating H. Matsuda a , H. Yanagishita b,∗ , H. Negishi b , D. Kitamoto b , T. Ikegami b , K. Haraya b , T. Nakane b , Y. Idemoto a , N. Koura a , T. Sano c b
a Science University of Tokyo, 2641 Yamazaki, Noda, Chiba 278-8510, Japan National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba Central 5, Ibaraki 305-8565, Japan c Japan Advanced Institute of Science and Technology, Tatsunokuchi, Ishikawa 923-1292, Japan
Received 30 November 2001; received in revised form 20 April 2002; accepted 10 June 2002
Abstract In order to improve the pervaporation performance of silicalite membrane, two types of silicone rubber, KE45 and KE108, were coated on the membrane surface. The initial molecular weight of KE108 is high and vulcanizing starts when it comes into contact with moisture in air, whereas the initial molecular weight of KE45 is low and vulcanizing starts when it is mixed with a catalyst. KE108 was found to be more effective than KE45 in enhancing the ethanol selectivity of silicalite membranes. A membrane coated using a 3 wt.% KE108 hexane solution showed separation factor of α = 125 with a total flux of 0.14 kg/m2 h. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Silicalite; Pervaporation; Ethanol selectivity; Silicone rubber; Coating
1. Introduction In recent years, zeolite membranes have been great attention as candidates for molecular sieving separation membranes and membrane reactors [1–5]. Silicalite, one of zeolite, is more hydrophobic than any other zeolite. We successfully prepared separation membranes consisting of silicalite polycrystals on a stainless steel support by hydrothermal synthesis. The silicalite membrane showed high ethanol selectivity with a separation factor α of 60 for a 5 vol.% ethanol aqueous solution at 30 ◦ C on pervaporation [6,7]. Furthermore, we established the preparation condi∗ Corresponding author. Tel.: +81-298-61-4659; fax: +81-298-61-4674. E-mail address: [email protected] (H. Yanagishita).
tions for a silicalite membrane with high ethanol selectivity (α = 120) [8]. During calcination, defects or pores between silicalite grains may be generated due to the difference in thermal expansion between the silicalite membrane and the support. The separation of ethanol and water is not being generated only through the pores of zeolite. Xomeritakis et al. have reported to improve separation performance of xylene by filling up the cracks of MFI membrane formed on the surface of alumina support disks after annealing with using sol–gel process [9]. By closing only defects or pores between silicalite grains, the silicalite membrane should show higher ethanol selectivity. On the other hand, silicone rubber has also been used for covering defects in organic and inorganic membrane. When Mohammadi et al. coated silicone rubber on an asymmetric aromatic polyamide membrane, the gas selectivity of the coated membrane
0376-7388/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 6 - 7 3 8 8 ( 0 2 ) 0 0 3 6 4 - 2
434
H. Matsuda et al. / Journal of Membrane Science 210 (2002) 433–437
improved [10]. Petersen et al. coated the surface of carbon membranes with silicone rubber. They also reported that the gas separation performance of coated membranes improved [11]. In this study, silicalite membranes were coated with silicone rubber in order to improve ethanol selectivity in pervaporation. Two types of silicone rubber were used. This paper describes the effect of silicone rubber coating on the separation performance of silicalite membranes. 2. Experimental 2.1. Membrane preparation Silicalite membranes were prepared on a stainless steel support (pore diameter: 2 m) by hydrothermal synthesis. The starting solution consisted of colloidal silica (Cataloid SI-30, Shokubai Kasei Co.; 30.4 wt.% SiO2 , 0.38 wt.% Na2 O and 69.22 wt.% water), tetrapropylammonium bromide (TPABr), sodium hydroxide and distilled water. Hydrothermal synthesis was performed at 170 ◦ C for 24–144 h, and calcination of the membrane was performed at 375 ◦ C for 60 h. Details of these processes are described elsewhere [8,12]. Two types of silicone rubber supplied by Shinetsu Kagaku Co. were used: KE45, whose molecular weight is high and which starts vulcanizing when it comes into contact with air and KE108, whose molecular weight is low and which starts vulcanizing when it comes into contact with a catalyst. We prepared 1–10 wt.% hexane solutions of these silicone rubbers and stirred them using a magnetic stirrer until they were homogeneously mixed. The silicalite membrane coating process was as follows. Cellophane tape was fixed to the rear side of the membrane to prevent that side from being coated. The membrane was then immersed in the coating solution for 10 s and dried at room temperature for 2 days. The morphology of the membrane was observed by a scanning electron microscope (SEM: S-800, Hitachi). 2.2. Separation performance measurement The pervaporation performance of the membrane was measured using a 5 vol.% ethanol aqueous solu-
tion at 30 ◦ C as a feed, and was evaluated by the separation factor α(EtOH/H2 O) as well as total flux. These parameters are calculated from following equations: Flux (kg/m2 h) weight of permeate (kg) = membrane area (m2 ) × permeation time (h) Separation factor α =
[CEtOH /CH2 O ] permeate [CEtOH /CH2 O ] feed
where the CEtOH and CH2 O are the volume fraction of alcohols and water, respectively. The concentrations of the permeate and the feed were analyzed by gas chromatography. A stainless steel cell previously developed in our laboratory was used for pervaporation measurements [13]. The membranes were evacuated in a vacuum oven at 80 ◦ C.
3. Results and discussion 3.1. Silicone rubber coating on silicalite membranes In order to utilize the hydrophobicity and adsorption properties of silicalite membranes, only defects or pores except zeolitic pores should be covered, while the surface of the membrane should not be coated with silicone rubber. From this standpoint, dilute coating solutions were used in which the silicone rubber concentration was less than 3 wt.%. Table 1 shows the pervaporation performance of membranes with coating of silicone rubber. The flux of membrane no. 1 was 0.17 kg/m2 h before coating. After coating with silicone rubber (KE45), the flux decreased although the separation factor increased slightly. Similar results were obtained for membranes nos. 2 and 3. The separation factor of membrane no. 4 improved only slightly although the flux decreased drastically. This suggests that the silicone rubber (KE45) formed a thin layer of silicone rubber on the surface of the membrane because of its high viscosity, although only partially rather than on the entire surface because of rough surface of the membrane. On the other hand, the membranes coated with the silicone rubber (KE108) showed high ethanol selectivity. For example, membrane no. 6 showed a high separation factor α of 125 after coating. This value
H. Matsuda et al. / Journal of Membrane Science 210 (2002) 433–437
435
Table 1 Pervaporation performance of membranes coated with silicone rubber Membrane
Silicone rubber
Silicone rubber concentration (wt.%)
Silicalitea [8] Silicone rubberb [13] Silicone rubberc [14]
Total flux (kg/m2 h)
EtOH concentration of permeate (vol.%)
0.29 0.039 0.022
Separation factor α 120 5.5 6.5
Silicalite No. 1
KE45
0 1
0.17 0.07
67 71
39 47
No. 2
KE45
0 2
0.21 0.16
70 74
44 54
No. 3
KE45
0 3
0.40 0.19
71 72
47 49
No. 4
KE45
0 3
0.33 0.052
58 79
26 71
No. 5
KE108
0 2
0.19 0.093
59 81
27 81
No. 6
KE108
0 3
0.15 0.14
73 88
51 125
Feed: 5 vol.% ethanol aqueous solution at 30 ◦ C. Feed: 6.0% (w/v) ethanol aqueous solution at 25 ◦ C. c Feed: 8.2 wt.% ethanol aqueous solution at 35 ◦ C. a
b
of separation factor α is similar to or higher than the value for a pure silicalite membrane we previously reported, which is higher than any other value reported by other researchers for pure silicalite membranes. From the above results, it was found that the silicone
rubber (KE108) covered only defects or pores except zeolitic pores without forming a thin layer on the entire surface of the silicalite membrane. The above difference between the behavior of two types of silicone rubbers was seen in SEM observation
Fig. 1. SEM images of the surface of the silicalite membranes before and after coating with silicone rubber (3000×).
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H. Matsuda et al. / Journal of Membrane Science 210 (2002) 433–437
aration factor decreased when they passed through silicalite. The apparent activation energy of ethanol and water were 34.0 and 40.8 kJ/mol/K, respectively. These values were similar to those obtained for the pure silicalite membrane with a separation factor α of 120 that we previously reported [8]. From the above results, it was concluded that in the case of a silicalite membrane coated with silicone rubber (KE108), ethanol and water do not pass through the silicone rubber but through the silicalite in pervaporation. Fig. 2. Effect of feed temperature on pervaporation performance of silicalite membrane coated with silicone rubber (KE108). Feed: 5 vol.% EtOH aqueous solution.
of the membrane surface. Fig. 1 shows SEM images of the surface of the silicalite membranes before and after silicone rubber coating. Using KE45, the surface of the membrane was partially covered with silicone rubber. This feature was marked with black circle in Fig. 1b. Using KE108, silicone rubber could not be observed as could be in one liquid type. Silicone rubber should penetrate into defects or pores except zeolitic pores. It is considered that this difference in coating is attributable to the different viscosities of coating solutions due to the properties of the initial silicone rubber (before vulcanizing). 3.2. Effect of temperature on pervaporation performance Fig. 2 shows the effect of feed temperature on pervaporation performance using a silicalite membrane coated with silicone rubber (KE108). The flux increased with increasing feed temperature, but separation factor decreased slightly. This result agrees well with that for the pure silicalite membrane previously reported [7,8]. On the contrary, other researchers have reported that the flux and the separation factor increased with increasing feed temperature [14]. A similar result was reported using a silicalite–silicone rubber composite membrane [15]. It was suggested that separation factor increased with increasing feed temperature when ethanol and water passed through silicone rubber, while the sep-
References [1] J. Olsson, G. Tragardh, Influence of temperature on membrane permeability during pervaporation aroma recovery, Sep. Sci. Tech. 34 (1999) 1643. [2] K. Wegner, J. Dong, Y.S. Lin, Polycrystalline MFI zeolite membranes: xylene pervaporation and its implication on membrane microstructure, J. Membr. Sci. 158 (1999) 17. [3] H. Kita, T. Inoue, H. Asamura, K. Tanaka, K. Okamoto, NaY zeolite membrane for the pervaporation separation of methanol-methyl tert-butyl ether mixtures, Chem. Commun. 45 (1997). [4] C.J. Gump, R.D. Noble, J.L. Falconer, Separation of hexane isomers through nonzeolite pores in ZSM-5 zeolite membranes, Ind. Eng. Chem. Res. 38 (1999) 2775. [5] N. Qureshi, H.P. Blaschek, Buthanol recovery from model solution/fermentation broth by pervaporation: evaluation of membrane performance, Biomass Bioenergy 17 (1999) 175. [6] T. Sano, H. Yanagishita, Y. Kiyozumi, D. Kitamoto, F. Mizukami, Separation of ethanol/water mixture by silicalite membrane, Chem. Lett. (1992) 2413. [7] T. Sano, H. Yanagishita, Y. Kiyozumi, F. Mizukami, K. Haraya, Separation of ethanol/water mixture by silicalite membrane on pervaporation, J. Membr. Sci. 95 (1994) 221. [8] H. Matsuda, H. Yanagishita, D. Kitamoto, T. Nakane, K. Haraya, N. Koura, T. Sano, Preparation of silicalite pervaporation membrane with high ethanol permselectivity, Membrane 23 (1998) 259. [9] G. Xomeritakis, Z. Lai, M. Tsapatsis, Separatopn of xylene isomer vapors with oriented MFI membranes made by seeded growth, Ind. Eng. Chem. Res. 40 (2001) 544. [10] A.T. Mohammadi, T. Matsuura, S. Sourirajan, Gas separation by silicone-coated dry asymmetric aromatic polyamide membranes, Gas. Sep. Purif. 9 (1995) 181. [11] J. Petersen, M. Matsuda, K. Haraya, Capillary carbon molecular sieve membranes derived from Kapton for high temperature gas separation, J. Membr. Sci. 131 (1997) 85. [12] H. Matsuda, H. Yanagishita, D. Kitamoto, K. Haraya, T. Nakane, T. Takada, N. Koura, T. Sano, Effects of preparation methods of silicalite membrane in the hydrothermal synthesis,
H. Matsuda et al. / Journal of Membrane Science 210 (2002) 433–437 in: Proceedings of the 1999 International Congress on Membranes and Membrane Processes, Toronto, 1999. [13] H. Yanagishita, C. Maejima, D. Kitamoto, T. Nakane, Preparation of asymmetric polyimide membrane for water/ ethanol separation in pervaporation by the phase inversion process, J. Membr. Sci. 86 (1994) 231.
437
[14] S. Kimura, T. Nomura, Pervaporation of organic substance water system with silicone rubber membrane, Maku 8 (1983) 177. [15] X. Chen, Z. Ping, Y. Long, Separation properties of alcohol– water mixture through silicalite-1-filled silicone rubber membranes by pervaporation, J. Appl. Poly. Sci. 67 (1998) 629.