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MATERIALS AND INTERFACES Vapor Permeation Properties of an NaY-Type Zeolite Membrane for Normal and Branched Hexanes Byeong-Heon Jeong, Yasuhisa Hasegawa, Ken-Ichiro Sotowa, Katsuki Kusakabe,* and Shigeharu Morooka Department of Applied Chemistry, Kyushu University, Fukuoka 812-8581, Japan
An FAU-type zeolite contains pores which are larger than those of an MFI-type zeolite. Thus, membranes that are synthesized from these zeolites behave differently in terms of the separation of hydrocarbon vapors. This study describes an investigation of the vapor permeation of singlecomponent 3-methylpentane (MP) and 2,2-dimethylbutane (DMB), as well as equimolar binary mixtures of n-hexane (n-C6), benzene, and branched hexanes, through an NaY-type zeolite membrane, as a function of the permeation temperature. For the single-component systems, the permeances were in the order of n-C6 . MP > DMB, which are in good agreement with the extent of chain branching (i.e., molecular width). Adsorption isotherms for single-component n-C6, MP, and DMB were fundamentally the same. Thus, the permeation of these components is based on differences in diffusion rates in the zeolitic channels. For the case of binary systems of n-C6/MP and n-C6/DMB, however, the presence of branched hexanes led to a significant decrease in the permeance to n-C6, whereas the presence of n-C6 had only a small effect on branched hexane permeation. The separation factors for the mixtures were close to unity, while the ideal separation factors were higher than 10. This suggests that a single-file transport mechanism prevailed. Introduction Inorganic membranes are stable in the presence of aromatic solvents, which often cause swelling of polymeric membranes. Thus, inorganic membranes can be used for the separation of organic compounds. Zeolite membranes have a variety of framework structures such as well-defined channels and nonzeolitic pores. A number of investigators have attempted to separate hydrocarbons using MFI-type zeolite membranes. Gump et al.1 reported on the separation of butane isomers using two types of ZSM-5 zeolite membranes. In the case of a membrane, which has small nonzeolitic pores, separation was achieved by selective adsorption and pore blocking effects, and that of the other membrane was achieved by selective diffusion through zeolitic pores. Tuan et al.2 prepared ZSM-5 zeolite membranes substituted with Al, Fe, B, or Ge for Si atoms in the framework structure and investigated the permeation mechanism of butane isomers. The B-ZSM-5 membrane showed the highest n-C4H10/i-C4H10 separation factor, which they attributed to differences in the diffusion rates. Funke et al.3 investigated the permeation properties of n-octane, isooctane, and n-hexane vapors through silicalite membranes. Although isooctane permeated at an approximately 5 times higher rate than n-octane for single-component systems, noctane permeated faster in the case of binary systems. Gade et al.4 investigated the permeation properties of * To whom correspondence should be addressed. Tel: 81-92-642-3552. Fax: 81-92-651-5606. E-mail: kusaktcf@ mbox.nc.kyushu-u.ac.jp.
n-hexane (n-C6) and 2,2-dimethylbutane (DMB) through boron-substituted ZSM-5 zeolite membranes. n-C6 permeance was found to be high, and DMB permeance was low. The separation was based on the selective adsorption of n-C6. In contrast, Flanders et al.5 reported that the separation between n-C6 and DMB through protonated ZSM-5 zeolite membranes was based on molecular sieving. Keizer et al.6 and Giroir-Fendler et al.7 investigated the separation of n-C6 and DMB through silicalite membranes. The n-C6 flux increased with permeation temperature, while the DMB flux remained relatively unchanged, suggesting that the membranes had few defects. They concluded that DMB was substantially rejected by a molecular sieving effect. Funke et al.8 also separated n-C6 from MP or DMB using a silicalite membrane. However, the ideal separation factors were less than two for both systems. The separation was due to the preferential adsorption of n-C6, which inhibited the permeation of the branched isomers. Thus, the membranes described by Funke et al.8 showed a permeation mechanism which was different from that for the membranes described Keizer et al.6 and Giroir-Fendler et al.7 Only a few studies on the permeation properties of hydrocarbons using FAU-type zeolite membranes have been published. Kita et al.9 investigated the vapor permeation properties of methanol and methyl tert-butyl ether (MTBE) using a NaY-type zeolite membrane and obtained a high separation factor for methanol over MTBE. Nikolakis et al.10 and Jeong et al.11 measured permeances to benzene and cyclohexane and obtained a high separation factor for benzene (Bz) over cyclohex-
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ane (Ch) using NaX- and NaY-type zeolite membranes, respectively. Moreover, Jeong et al.12 separated Bz from n-alkanes with high separation factors using a membrane prepared by the same method as that reported by Kusakabe et al.13,14 and Hasegawa et al.15,16 To our knowledge, no studies on the permeation of branched hydrocarbons through FAU-type zeolite membranes have been reported to date. Thus, an investigation of the permeation properties of branched hydrocarbons would be relevant for further optimization of the permeation properties of FAU-type zeolite membranes. In the present study, therefore, the vapor permeation properties of an NaY-type zeolite membrane were investigated. Permeation experiments were performed with single-component 3-methylpentane (MP) and DMB, binary mixtures of n-C6 and branched hexanes, and mixtures of Bz and branched hexanes. To compare these data with the results of our previous studies,11,12 an identical NaY-type zeolite membrane was employed in these studies. The permeation and separation mechanisms are discussed on the basis of adsorption isotherms, which were determined under the same conditions as those used for the permeation, and the results are compared to those of MFI-type zeolite membranes, as described in the literature. Experimental Section The procedures used for the membrane preparation, as well as the permeation and adsorption tests, are the same as those reported in a previous paper.11 An NaYtype zeolite membrane was prepared on the outer surface of a porous R-Al2O3 support tube (NOK Corp., Japan) by means of hydrothermal synthesis. The dimensions of the support tube were outside diameter ) 2.1 mm, inside diameter ) 1.7 mm, void fraction ) 0.40, and pore size ) 120-150 nm. For implantation of seeds for nucleation, the outer surface of the support tube was rubbed with NaY zeolite crystals (Tosoh Corp., HSM320NAA, Si/Al ) 2.8, crystal size ) 0.5 µm). The support was then placed in a tubular autoclave, which was maintained in a horizontal position. An aqueous solution of water glass, sodium aluminate, and sodium hydroxide was homogenized by stirring at room temperature for 240 min. The initial composition was Al2O3:SiO2:Na2O: H2O ) 1:12.8:17:975 on a molar basis. The hydrothermal synthesis was performed at 363 K for 24 h. The outer surface of the synthesized NaY-type zeolite membrane, except for the permeating portion, was sealed with a polytetrafluorocarbon tube. An NaY-type zeolite powder was also prepared by the same procedure as that used for the membrane. The synthesized NaY-type zeolite membrane and powder were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The vapor permeation properties of the membrane were determined using single-component MP and DMB and binary mixtures of n-C6 and branched hexanes, as well as binary mixtures of Bz and branched hexanes, at permeation temperatures in the range of 358-413 K. The hydrocarbon vapor was diluted in a flow of nitrogen and introduced onto the feed side. Nitrogen was also used as the sweep on the permeate side, and the sweep flow rate, Qs, was varied over the range of 10100 cm3/min. The total pressure on both sides was maintained at 101.3 kPa throughout the experiments. The permeance to permeant i, πi, is defined as moles of the component permeated per unit time and unit
Figure 1. Permeances to single-component systems as a function of the permeation temperature. Qs ) 10 cm3/min.
membrane area divided by the partial pressure difference between the feed and permeate sides. The separation factor, R(i/j), is defined as the ratio of the permeances, πi/πj. Adsorption isotherms of single-component branched hexanes and Bz, as well as binary mixtures of Bz and each branched hexane, were determined for the NaYtype zeolite powder at 373 K, using an adsorption apparatus (BEL Japan, FMS-BG-H50). This unit was equipped with a magnetically suspended thermobalance and precision pressure sensors and was capable of evaluating the isotherms of two components. Results Membrane Structure and Quality. The SEM photographs of the synthesized membrane showed the presence of two zeolite layers; an inner layer formed in the voids of the support (ca. 5 µm in thickness) and an outer layer formed on the support (ca. 3 µm in thickness). Crystal growth was not observed on the inside of the support. The XRD pattern of the synthesized powder was identical with that of the NaY zeolite structure. Details have been reported in a previous paper.17 The quality of the membrane was evaluated based on the permeances of n-C6, MP, and DMB for singlecomponent systems at 358 K. The ratios of permeances for n-C6/MP and n-C6/DMB were approximately 10 and 21, respectively. This suggests that the permeation through the nonzeolitic pores was not considerable. Permeation of Single Components. Figure 1 shows the permeances to single-component MP and DMB as a function of the permeation temperature. The results were compared to the permeances to Bz and n-C6 obtained in a previous study.12 The partial pressure on the feed side was 9.5 kPa for MP and 7.3 kPa for DMB. The sweep flow rate was maintained at 10 cm3/min, and the partial pressure on the permeate side was 0.22 kPa for MP and 0.06 kPa for DMB. The partial pressures on the permeate side were much lower than the partial pressures on the feed side. The permeances to branched hexanes were much lower than the permeance to n-C6 or Bz over the entire temperature range. All of the permeances increased with increasing temperature, indicating that an activated transport mechanism was operative. The separation factors for single-component systems were 9 for n-C6/MP and 20 for n-C6/DMB over the entire permeation temperature range, and for Bz/ MP and Bz/DMB, those values were 4 and 10, respectively, at 373 K. Permeation of Binary Mixtures. Figures 2 and 3 show the permeances and separation factors for binary systems of n-C6/MP and n-C6/DMB, respectively, as a
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Figure 2. Permeances and separation factors for a binary system composed of n-C6 and MP. Partial pressures: n-C6 ) 3.9 kPa and MP ) 3.7 kPa on the feed side; n-C6 ) 0.05 kPa and MP ) 0.04 kPa on the permeate side. Qs ) 10 cm3/min.
Figure 4. Permeances and separation factors for a binary system composed of Bz and MP. Partial pressures: Bz ) 4.4 kPa and MP ) 4.0 kPa on the feed side; Bz ) 0.13 kPa and MP ) 0.02 kPa on the permeate side. Qs ) 10 cm3/min.
Figure 3. Permeances and separation factors for a binary system composed of n-C6 and DMB. Partial pressures: n-C6 ) 3.5 kPa and DMB ) 3.3 kPa on the feed side; n-C6 ) 0.03 kPa and DMB ) 0.02 kPa on the permeate side. Qs ) 10 cm3/min.
Figure 5. Permeances and separation factors for a binary system composed of Bz and DMB. Partial pressures: Bz ) 5.2 kPa and DMB ) 4.7 kPa on the feed side; Bz ) 0.11 kPa and DMB ) 0.02 kPa on the permeate side. Qs ) 10 cm3/min.
function of the permeation temperature. The sweep flow rate was also maintained at 10 cm3/min. Partial pressures for the mixture of n-C6/MP were 3.9 kPa for n-C6 and 3.7 kPa for MP on the feed side and 0.05 kPa for n-C6 and 0.04 kPa for MP on the permeate side. Similarly, the partial pressures for the mixture of n-C6/ DMB were 3.5 kPa for n-C6 and 3.3 kPa for DMB on the feed side and 0.03 kPa for n-C6 and 0.02 kPa for DMB on the permeate side. The partial pressures on the permeate side were also much lower than the partial pressures on the feed side. For the mixtures, the permeances to branched hexanes were the same as the value determined for the single-component systems. However, the n-C6 permeance for the mixtures decreased to the values of branched hexanes. As a result, no substantial separation was observed over the entire permeation temperature range. Furthermore, the permeances to all components were not significantly affected by the permeation temperature. Figures 4 and 5 show the permeances and separation factors for binary systems of Bz/MP and Bz/DMB, respectively, as a function of the permeation temperature. The sweep flow rate was maintained at 10 cm3/ min. Partial pressures for the mixture of Bz/MP were 4.4 kPa for Bz and 4.0 kPa for MP on the feed side and 0.13 kPa for Bz and 0.02 kPa for MP on the permeate side. Similarly, the partial pressures for the mixture of Bz/DMB were 5.2 kPa for Bz and 4.7 kPa for DMB on the feed side and 0.11 kPa for Bz and 0.02 kPa for DMB on the permeate side. The partial pressures on the permeate side were much lower than those on the feed side. For the mixtures, the permeances to both Bz and branched hexanes were slightly decreased, compared to the value for the single-component systems, and increased with increasing temperature. The separation
Figure 6. Adsorption isotherms for single-component systems on NaY-type zeolite at 373 K.
factors for both the Bz/MP and Bz/DMB mixtures slightly increased with increasing temperature. In addition, for both the Bz/MP and Bz/DMB mixtures, the Bz permeances increased slightly with increasing sweep flow rate, whereas the permeances to branched hexanes decreased slightly. Therefore, the separation factors increased slightly with increasing sweep flow rate, and as a result, the highest separation factors were found to be 12 and 14 for the Bz/MP and Bz/DMB mixtures, respectively, when the sweep flow rate was 100 cm3/ min. In previous papers,11,12 the highest separation factors of 107, 57, 70, 63, and 27 were reported for Bz/ Ch, Bz/n-C4, Bz/n-C5, Bz/n-C6, and Bz/n-C7, respectively, under similar conditions. Adsorption. Figure 6 shows the adsorption isotherms for single-component hexane isomers (n-C6, MP, and DMB) on the NaY-type zeolite at 373 K. The Bz adsorption isotherm was obtained from a previous study11 in which an identical zeolite sample was used. For all components, the adsorption increased with increasing pressure. The capacity of hexane isomers for
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coefficient decreased with increasing molecular size because large molecules interact more strongly with segments of the zeolites than small molecules. The activation energies for the diffusion of n-C6 and MP were 34.7 and 50.0 kJ/mol, respectively. Thus, larger molecules diffuse through the zeolite pores at lower rates than small-sized molecules. The n-C6 permeance through the FAU-type zeolite membrane was similar to that through the MFI-type zeolite membrane. However, the permeances to branched hexanes through the FAU-type zeolite membrane were 20-100 times higher than those through the MFI-type zeolite membrane. This behavior appears to be due to the fact that the size of branched hexane molecules is similar to or larger than the MFI-type zeolite pore size ()0.55 nm), whereas the size of branched hexane molecules is much smaller than the pore size of the FAU-type zeolite ()0.74 nm). Permeance through a membrane is dependent on the sorption coefficient, as well as on the diffusion coefficient. The adsorption of branched hexanes on the NaY-type zeolite was similar, as shown in Figure 6. For the single-component permeation, therefore, the permeation mechanism of branched hexanes through the FAU-type zeolite membrane appears to be based on the differences in diffusion rates in the zeolite channels. Separation. The FAU-type zeolite membrane was unsuitable for use in the separation of n-C6 from binary mixtures with MP or DMB, as shown in Table 3. For binary systems composed of n-C6/MP and n-C6/DMB, the branched hexanes inhibited the permeation of n-C6 and the permeance to n-C6 was equal to that of the branched hexanes, although the diffusivity of n-C6 was much higher than that of branched hexanes for singlecomponent systems. Thus, the slowly permeating species restrained the diffusion of the other species, and the membrane failed to show any separation. This behavior appears to be due to the single-file transport mechanism. In contrast to the FAU-type zeolite membrane, the MFI-type zeolite membrane5 was highly selective for n-C6 permeation in the mixtures, indicating that the separation was primarily due to molecular sieving at the entrance. The separation factor for n-C6/
Table 1. Amounts Adsorbed for Equimolar Binary Systems at 373 K system
total pressure [kPa]
amount adsorbed [mol kg-1]
adsorption selectivity
Bz/MP Bz/DMB
9.5 9.4
1.9/0.5 2.2/0.2
4 11
adsorption on the NaY-type zeolite was similar and half the value of Bz over the entire pressure range tested. Table 1 shows adsorption values for equimolar binary systems of Bz/MP and Bz/DMB on the NaY-type zeolite at 373 K. The adsorption selectivities were then calculated from the two-component adsorption isotherms, which were determined under the same conditions as those for the permeation of binary systems. The values were found to be approximately the same as the separation factors, shown in Table 2. Discussion Permeation. The molecular dimensions,8,18,19 permeances, and separation factors through FAU- and MFI-type zeolite membranes at 373 K are listed in Table 3. Data on the MFI-type zeolite membrane are cited from a report by Flanders et al.5 For the permeation of single-component systems, the permeances through both of the FAU- and MFI-type zeolite membranes were in the order of n-C6 . MP > DMB and were in good agreement with the extent of chain branching (i.e., molecular width) of the components as shown in Table 3. The permeants n-C6, MP, and DMB were similar in adsorptivity and different in diffusivity. Thus, the higher permeance of n-C6 can be ascribed to its larger diffusivity. Matsufuji et al.20 studied the permeation properties of n-C6, MP, and DMB through an MFI membrane by pervaporation at 303 K and concluded that the fluxes followed the order of n-C6 . MP > DMB for single-component systems. Millot et al.21 examined the diffusion of n-C6 and MP in ZSM-5-supported membranes based on the Maxwell-Stefan equations and calculated the diffusion coefficients and diffusion activation energies. The diffusion coefficients were determined to be 1.0 × 10-11 and 5.0 × 10-14 m2/s for n-C6 and MP, respectively, at 373 K. The diffusion
Table 2. Permeation Properties of an NaY-Type Zeolite Membrane at 373 K
a
permeance [mol m-2 s-1 Pa-1] single binary
widtha [nm]
lengtha [nm]
Bz MP
0.585 0.50
0.75 0.90
1.2 × 10-7 2.7 × 10-8
DMB
0.62
0.78
1.2 × 10-8
hydrocarbon (i)
separation factor R(Bz/i) mixture ideal
Bz: 2.9 × 10-8 MP: 5.1 × 10-9 Bz: 2.5 × 10-8 DMB: 5.1 × 10-9
6
4
5
10
Values of width and length are taken from Funke et al.,8 Breck,18 and Masuda et al.19
Table 3. Permeances and Separation Factors through FAU- and MFI-Type Zeolite Membranes at 373 K permeance [mol m-2 s-1 Pa-1] hydrocarbon (i)
widtha [nm]
lengtha [nm]
single 10-7
n-C6 MP
0.43 0.50
1.02 0.90
2.5 × 2.7 × 10-8
DMB
0.62
0.78
1.2 × 10-8
separation factor R(n-C6/i)
MFIb
FAU binary n-C6: 1.9 × 10-8 MP: 1.5 × 10-8 n-C6: 1.9 × 10-8 DMB: 1.0 × 10-8
single 10-7
1.0 × 1.2 × 10-9 1.3 × 10-10
a Values of width and length are taken from Funke et al.,8 Breck,18 and Masuda et al.19 et al.5
b
MFIb
binary
FAU
n-C6: 3.6 × 10-8 MP: 7.0 × 10-10 n-C6: 8.0 × 10-8 DMB: 7.0 × 10-11
1.3
>500
1.9
>1000
MFI data are cited from a report by Flanders
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DMB was 2 times higher than that for n-C6/MP. The molecular diameter of DMB ()0.62 nm) is significantly larger than the pore size of the MFI zeolite ()0.55 nm), whereas the molecular diameter of MP ()0.5 nm) is approximately the same as the pore size of the MFI zeolite. The differences in separation of n-C6 from branched hexanes between the FAU- and MFI-type zeolite membranes appear to be due to differences in the zeolite structures or the orientation of the polycrystalline layers. On the other hand, for the separation of Bz from binary mixtures with MP or DMB, the FAU-type zeolite membrane was quite selective for Bz permeation although both the Bz and branched hexane permeances for mixtures were lower than the values for singlecomponent systems. This behavior indicates that the Bz permeance was inhibited somewhat by the branched hexane molecules. In this case, the presence of a component having a lower diffusivity than Bz decreased the permeance of both of the components without changing the selectivity. This is significantly different from our earlier results,11,12 the findings of which indicated that the Bz permeance was not changed, for either single-component systems or binary mixture systems for the case of Ch and n-alkanes (C4-C7). This difference can be attributed to the larger molecular size and the shape of the branched molecules, which are different from linear or cyclic molecules. In addition, the DMB permeance was the same as that for the MP permeance, when mixed with Bz, regardless of the difference in molecular width. This behavior appears to be due to the fact that the diffusion rates of branched molecules through the window region, between two supercages, are affected by the movement of Bz molecules as the result of strong interactions between the hydrogen atoms of Bz and the oxygen atoms of the window, as well as the π electrons of Bz and the cations of the window. Table 1 indicates that selective adsorption does not play an important role in the separation mechanism because selective adsorption did not occur for mixtures of Bz/MP or Bz/DMB. The separation factors for the Bz/MP and Bz/DMB systems were higher than those for the n-C6/MP and n-C6/DMB systems. This difference can be attributed to the differences in adsorption properties of Bz and n-C6, but an understanding of the detailed mechanism will require additional investigation. Conclusions An NaY-type zeolite membrane was hydrothermally prepared on the outer surface of a porous R-Al2O3 support tube. The vapor permeation properties of the membrane were determined using single-component MP and DMB and binary mixtures of n-C6 and branched hexanes, as well as binary mixtures of Bz and branched hexanes, at permeation temperatures in the range of 358-413 K. For the single-component systems, the permeances were in the order of n-C6 . MP > DMB, in good agreement with the extent of chain branching (i.e., molecular width) of the components. The single-component n-C6, MP, and DMB adsorptions were similar to each other. Thus, the permeation mechanism appears to involve differences in diffusion rates. For the binary systems of n-C6/MP and n-C6/DMB, however, the presence of branched hexanes significantly decreased the n-C6 permeance, whereas the presence of n-C6 did not strongly affect the branched hexane permeations for the
mixtures. The separation factors for the mixtures were almost unity, whereas the ideal separation factors were 10-20. Thus, the separation appears to be controlled by the single-file transport mechanism. For the binary systems of Bz/MP and Bz/DMB, on the other hand, both the Bz and MP or DMB permeances decreased somewhat, compared to the values for the single-component systems. The separation factors for the Bz/MP and Bz/ DMB systems were higher than those for the n-C6/MP and n-C6/DMB systems. A further study on the permeation model based on the experimental data reported herein is now underway. Acknowledgment This work was supported by the Japan Society for the Promotion of Science (JSPS) and the New Energy and IndustrialTechnologyDevelopmentOrganization(NEDO) of Japan. We also sincerely acknowledge the support of the NOK Corp., Japan, and the Tosoh Corp., Japan. Literature Cited (1) Gump, C. J.; Lin, X.; Falconer, J. L.; Noble, R. D. Experimental Configuration and Adsorption Effects on the Permeation of C4 Isomers through ZSM-5 Zeolite Membranes. J. Membr. Sci. 2000, 173, 35. (2) Tuan, V. A.; Falconer, J. L.; Noble, R. D. Isomorphous Substitution of Al, Fe, B, and Ge into MFI-zeolite Membranes. Microporous Mesoporous Mater. 2000, 41, 269. (3) Funke, H. H.; Kovalchick, M. G.; Falconer, J. L.; Noble, R. D. Separation of Hydrocarbon Isomer Vapors with Silicalite Zeolite Membranes. Ind. Eng. Chem. Res. 1996, 35, 1575. (4) Gade, S. K.; Tuan, V. A.; Gump, C. J.; Noble, R. D.; Falconer, J. L. Highly Selective Separation of n-Hexane from Branched, Cyclic and Aromatic Hydrocarbons Using B-ZSM-5 Membranes. Chem. Commun. 2001, 601. (5) Flanders, C. L.; Tuan, V. A.; Noble, R. D.; Falconer, J. L. Separation of C6 Isomers by Vapor Permeation and Pervaporation through ZSM-5 Membranes. J. Membr. Sci. 2000, 176, 43. (6) Keizer, K.; Burggraaf, A. J.; Vroon, Z. A. E. P.; Verweij, H. Two Component Permeation through Thin Zeolite MFI Membranes. J. Membr. Sci. 1998, 147, 159. (7) Giroir-Fendler, A.; Peureux, J.; Mozzanega, H.; Dalmon, J. A. Characterization of a Zeolite Membrane for Catalytic Membrane Reactor Application. Stud. Surf. Sci. Catal. 1996, 101, 127. (8) Funke, H. H.; Argo, A. M.; Falconer, J. L.; Noble, R. D. Separations of Cyclic, Branched, and Linear Hydrocarbon Mixtures through Silicalite Membranes. Ind. Eng. Chem. Res. 1997, 36, 137. (9) Kita, H.; Inoue, T.; Asamura, H.; Tanaka, K.; Okamoto, K. NaY Zeolite Membrane for the Pervaporation Separation of Methanol-Methyl tert-Butyl Ether Mixtures. Chem. Commun. 1997, 45. (10) Nikolakis, V.; Xomeritakis, G.; Abibi, A.; Dickson, M.; Tsapatsis, M.; Vlachos, D. G. Growth of a Faujasite-type Zeolite Membrane and its Application in the Separation of Saturated/ Unsaturated Hydrocarbon Mixtures. J. Membr. Sci. 2001, 184, 209. (11) Jeong, B.-H.; Hasegawa, Y.; Kusakabe, K.; Morooka, S. Separation of Benzene and Cyclohexane Mixtures Using an NaYtype Zeolite Membrane. Sep. Sci. Technol. 2002, 37, 1225. (12) Jeong, B.-H.; Hasegawa, Y.; Sotowa, K.-I.; Kusakabe, K.; Morooka, S. Separation of Mixtures of Benzene and n-Alkanes Using an FAU-type Zeolite Membrane. J. Chem. Eng. Jpn. 2002, in press. (13) Kusakabe, K.; Kuroda, T.; Morooka, S. Separation of Carbon Dioxide from Nitrogen Using Ion-Exchanged Faujasitetype Zeolite Membranes Formed on Porous Support Tubes. J. Membr. Sci. 1998, 148, 13. (14) Kusakabe, K.; Kuroda, T.; Uchino, K.; Hasegawa, Y.; Morooka, S. Gas Permeation Properties of Ion-Exchanged Faujasite-Type Zeolite Membranes. AIChE J. 1999, 45, 1220.
Ind. Eng. Chem. Res., Vol. 41, No. 7, 2002 1773 (15) Hasegawa, Y.; Watanabe, K.; Kusakabe, K.; Morooka, S. The Separation of CO2 Using Y-type Zeolite Membranes Ionexchanged with Alkali Metal Cations. Sep. Purif. Technol. 2001, 22-23, 319. (16) Hasegawa, Y.; Kusakabe, K.; Morooka, S. Effect of Temperature on the Gas Permeation Properties of NaY-type Zeolite Formed on the Inner Surface of a Porous Support Tube. Chem. Eng. Sci. 2001, 56, 4273. (17) Hasegawa, Y.; Tanaka, T.; Watanabe, K.; Jeong, B.-H.; Kusakabe, K.; Morooka, S. Separation of CO2-CH4 and CO2-N2 Systems Using Ion-exchanged FAU-type Zeolite Membranes with Different Si/Al Ratios. Korean J. Chem. Eng. 2002, in press. (18) Breck, D. W. Zeolite Molecular Sieves; John Wiley and Sons: New York, 1974.
(19) Masuda, T.; Fukada, K.; Fujikata, Y.; Ikeda, H.; Hashimoto, K. Measurement and Prediction of the Diffusivity of Y-type Zeolite. Chem. Eng. Sci. 1996, 51, 1879. (20) Matsufuji, T.; Watanabe, K.; Nishiyama, N.; Egashira, Y.; Matsukata, M.; Ueyama, K. Permeation of Hexane Isomers through an MFI Membrane. Ind. Eng. Chem. Res. 2000, 39, 2434. (21) Millot, B.; Me´thivier, A.; Jobic, H.; Moueddeb, H.; Dalmon, J. A. Permeation of Linear and Branched Alkanes in ZSM-5 Supported Membranes. Microporous Mesoprous Mater. 2000, 38, 85.
Received for review September 24, 2001 Revised manuscript received January 3, 2002 Accepted January 9, 2002 IE010792L
