SUBSTRATE HAVING AT LEAST ONE PARTIALLY OR ENTIRELY FLAT SURFACE AND USE THEREOF

Abstract

A method for preparing a thin or thick film, including the aligning non-spherical seed crystals on a flat portion of at least one surface of the substrate such that an a-axis, a b-axis, and/or a c-axis are oriented according to a certain rule; and exposing the aligned seed crystals to a solution for enabling the growth of the seed crystals to thereby form and grow a film from the seed crystals using a secondary growing technique.

Claims

1. A method of preparing a substrate, at least one surface of which is partially or entirely flat, the method comprising: forming a substrate by first substrate-forming particles; placing a second substrate-forming particles on the surface of the substrate formed by the first substrate-forming particles; applying pressure to the second substrate-forming particles to be insert into the first pores formed among the first substrate-forming particles, followed by calcinations; coating the surface of the calcined substrate with a solution of the polymer, thereby filling some or all of second pores remaining in a portion filled with the second substrate-forming particles; and heating the polymer-coated substrate to evaporate the solvent or cure the polymer.

2. The method of claim 1, wherein at least one surface of the substrate is flat to allow non-spherical seed crystals to be aligned such that one or more or all of a-axes, b-axes and c-axes of the seed crystals are oriented according to a predetermined rule.

3. The method of claim 1, wherein the first substrate-forming particles have an average particle size greater than that of the second substrate-forming particles.

4. The method of claim 1, wherein one or more second substrate-forming particles are filled in each of the first pores generated by the first substrate-forming particles.

5. The method of claim 1, wherein the first substrate-forming particles and the second substrate-forming particles are independently selected from ordered porous materials.

6. The method of claim 1, wherein the first substrate-forming particles and the second substrate-forming particles are independently porous silica.

7. The method of claim 1, wherein the polymer has a hydroxyl group or is treatable to have a hydroxyl group on a surface thereof.

8. A method of preparing a substrate complex, the method comprising: preparing a substrate according to claim 1; and aligning non-spherical seed crystals on a flat portion of at least one surface of the substrate such that one or more or all of a-axes, b-axes, and c-axes of the seed crystals are oriented according to a predetermined rule.

9. A method for preparing a thin film or a thick film, the method comprising: (1) preparing a substrate according to claim 1; (2) aligning non-spherical seed crystals on a flat portion of at least one surface of the substrate such that one or more or all of a-axis, b-axis and c-axis of the seed crystals are oriented according to a predetermined rule; and (3) exposing the aligned seed crystals to a solution for seed crystal growth, and forming and growing the film from the seed crystals by a secondary growth method.

10. The method of claim 9, wherein the solution for seed crystal growth used in step (3) comprises a structure-directing agent.

11. The method of claim 9, wherein the seed crystals in step (3) grow vertically from the surface thereof by secondary growth to form a three-dimensional structure while being connected to one another two-dimensionally, thereby forming the film.

12. The method of claim 9, wherein the seed crystals are selected from ordered porous materials.

13. The method of claim 9, wherein the seed crystals in step (2) are aligned such that all the a-axes of the seed crystals are oriented parallel to one another, all the b-axes of the seed crystals are oriented parallel to one another, all the c-axes of the seed crystals are oriented parallel to each other, or a combination thereof.

14. The method of claim 13, wherein the a-axis, b-axis or c-axis of the seed crystals is oriented normal to the substrate surface in step (2).

15. The method of claim 9, wherein the film, formed in an area in which the orientations of the axes of seed crystals adjacent to one another are uniform, has : (a) channels that are continuously connected to one another and extend in an axial direction parallel to the substrate surface; or (b) channels that are continuously connected to one another and extend in an axial direction perpendicular or inclined with respect to the substrate surface; or (c) both the channels of (a) and the channels of (b).

16. The method of claim 9, wherein the seed crystals and the formed film is a zeolite or a zeotype molecular sieve.

17. The method of claim 9, wherein step (2) is achieved by placing the seed crystals on the substrate, and then aligning the orientation of the a-axis, b-axis, or c-axis of the seed crystals by physical pressure.

18. A film prepared according to a method set forth in claim 9.

19. The film of claim 18, wherein the substrate comprises the second substrate-forming particles filling some or all of the first pores generated among the first substrate-forming particles on at least one surface of the substrate formed by the first substrate-forming particles, but the polymer filling some or all of the second pores was removed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0092] FIG. 1 is schematic illustrations of (A) leaflet-shaped and (B) coffin-shaped SL crystals and (C) truncated bipyramidal BEA crystals and their channel systems, as well as their respective (D) a-oriented, (E) b-oriented, and (F) a-oriented monolayers. (G) to (I) shows that secondary growth on these monolayers produces uniformly oriented films.

[0093] FIG. 2 is a schematic drawing illustrating a process for preparing a substrate according to the present invention.

[0094] FIG. 3 shows SEM images of leaflet shaped SL seed crystals (A) and the SL crystals grown from the SL seed crystals by secondary growths in Gel-2 (B). (C) represents XRD diffraction patterns of leaflet shaped SL seed crystals and the SL crystals grown from the seed crystals by secondary growth in Gel-2. (D) illustrates the plots of the average length increases of the SL crystals vs. reaction time during the secondary growths of leaflet SL crystals in Gel-2. (E) is an illustration of the morphology change of SL seed crystals after secondary growth.

[0095] FIG. 4 shows (A) top SEM views of a typical porous substrate (3 mm) composed of a 1:1 mixture of 350 nm and 600 nm silica beads prepared by pressing (150 kgf cm') for 30 s and calcining at 1,020° C. for 2 h (A) after surface polishing and (B) after additional rubbing its surface with 70-nm silica beads followed by calcination at 550° C. for 8 h. (C) shows SEM images of b-oriented SL monolayer assembled on porous silica supports and (D) shows b-oriented continuous SL film supported on porous silica supports prepared by the secondary growth of the monolayer in Gel-2 at 165° C. for 18 h.

[0096] FIG. 5 is a schematic illustration of the set-up used in our work to test the p-/o-xylene separation performance of the membranes.

[0097] FIG. 6 shows (A) structure of HC-n dyes and (B) Plots of the number of HC-n dyes incorporated in a single channel (Nc).sub.n of the SL film versus the alkyl chain length n of the HC-n dye. (C) shows plots of the relative second harmonic intensity (rel-I.sub.2ω) of the HC-n-incorporating SL films (of indicated thickness) with respect to a reference (3-mm-thick Y-cut quartz) versus the alkyl chain length n of the HC-n dye. Below are plots of permeances of p-(open circle) and o-xylene (open square) and the SF with time for the two operation temperatures, (D) 80° C. and (E) 150° C.

DETAILED DESCRIPTION

[0098] Hereinafter, the present invention will be described in more detail with reference to examples. However, these examples are for illustrative purposes only, and the scope of the present invention is not limited to these examples.

EXAMPLE 1

Preparation of Porous Silica Substrates

[0099] Porous silica substrates were prepared from 50-550 nm sized silica beads which were synthesized according to the Stöber method. For this, 10 g of 350-nm SiO.sub.2 beads and 10 g of 550-nm SiO.sub.2 beads were mixed together using food mixer. Into the mixed silica beads 0.6 mL of aqueous solution of Na.sub.2SiO.sub.3 (0.5% in DDW) was added drop wise and the silica bead mixture was ground for 10 min in food mixer. Porous silica supports were prepared by placing 1.8 g of the above mixture in a home-made stainless steel mold and pressing at the pressure of 150 kgf/cm.sup.2. The resulting silica dishes were calcined at 1,020° C. for 2 h with the heating rate of 100° C./h. After cooling to room temperature, both sides of the porous silica disc were polished using a SiC sandpaper (Presi, grit size P800). To make the surface smooth, one side was polished again using a SiC sandpaper (Presi, grit size P1200). The diameter and thickness of the porous silica disc were 20 and 3 mm, respectively. The porosity measured by a mercury porosimeter is 45.5% with the average pore size of 250 nm.

[0100] One drop of DDW was dropped onto a porous silica support. Independently, 70-nm silica beads were prepared and calcined at 550° C. for 24 h. The calcinced 70-nm silica beads were gently rubbed on the porous silica supports until the surface became shiny. The shiny porous silica supports were dried overnight at room temperature and sintered at 550° C. for 8 h on a muffle furnace. The temperature was increased to 550° C. during the 8 h period and cooled to room temperature during the period of 4 h. An acetone solution of epoxy resin (10 wt %) was spin coated onto the porous silica at the speed of 3,000 rpm for 15 sec and cured at 80° C. for 30 min.

EXAMPLE 2

Assembly of SL Monolayers on Porous Silica Substrates

[0101] Onto the epoxy-coated porous silica supports an ethanol solution of polyethyleneimine (PEI, 0.1%) was spin-coated with the spin rate of 2,500 rpm for 15 sec. Perfect boriented SL crystals (1.0×0.5×1.4 μm.sup.3) were assembled on the porous supports by rubbing them onto the supports using a finger. The SL crystal monolayer supported on porous silica is denoted as b-SL.sub.m/p-SiO.sub.2. The b-SL.sub.m/p-SiO.sub.2 plates were calcined at 550° C. for 24 h in air on a tubular furnace to remove the organic polymer layers as well as to fix the SL monolayers on the silica supports through the formation of Si—O—Si bonding. The rate of temperature increase was 65° C./h. The rate of temperature decrease was 100° C./h.

[0102] The calcined b-SL.sub.m/p-SiO.sub.2 plates were kept in a constant humidity chamber overnight to allow the plates to absorb H.sub.2O. The hydrated b-SL.sub.m/p-SiO.sub.2 plates were then immersed into an aqueous NH4F solution (0.2 M) for 5 h. The NH4F-treated b-SL.sub.m/p-SiO.sub.2 plates were immersed in fresh DDW for 1 h and dried at room temperature for 24 h

EXAMPLE 3

Secondary Growth of b-SL.SUB.m./g Plates in Gel-2 (Preparation of Perfect b-oriented SL Film on Porous SiO.SUB.2

[0103] A gel consisting of TEOS, TEAOH, (NH.sub.4).sub.2SiF.sub.6, and H.sub.2O (denoted Gel-2) was prepared, where the molar ratio of the gel was 4.00:1.92:0.36:n2, where nz=40-80. The gel was prepared as follows:

[0104] (I) Preparation of the TEOS/TEAOH solution (solution I): TEAOH (35%, 20.2 g) and DDW (22.2 g) were sequentially added into a plastic beaker containing 31.8 g of TEOS (98%). This beaker containing the above solution was tightly covered using plastic wrap and magnetically stirred for about 30 min until the solution became clear.

[0105] (II) Preparation of the TEAOH/(NH.sub.4).sub.2SiF.sub.6 solution (solution II): TEAOH (35%, 10.1 g), (NH.sub.4).sub.2SiF.sub.6 (2.45 g), and DDW (11.1 g) were introduced into a plastic beaker and stirred until all (NH.sub.4).sub.2SiF.sub.6 became dissolved.

[0106] Solution II was quickly poured into the solution I with vigorous stirring. The mixture solidified immediately. The solidified mixture was stirred for an additional 2 min using a plastic rod, and aged under a static condition for 6 h. After aging, the semisolid gel was ground using a food mixer and transferred into a Teflon-lined autoclave.

[0107] b-SL.sub.m/p-SiO.sub.2 plates were placed vertically in Gel-2. The hydrothermal reactions were carried out at 165° C. for 18 h. After the reaction, the perfectly b-oriented SL films supported on porous SiO.sub.2 substrates (denoted as b-SL.sub.f/p-SiO.sub.2) was produced and then washed with copious amounts of DDW. To remove the alkali in the porous SiO.sub.2 support, the b-SL.sub.f/p-SiO.sub.2 membranes were immersed in DDW for 2 h and subsequently in a NH4F solution (0.2 M) for 4 h. The membranes were then washed with DDW, dried by blowing N2 gas, and kept at room temperature for 24 h. Finally they were calcined at 440° C. for 8 h in air to remove TEAOH template. The heating rate was 60° C./h and the cooling rate was 90° C./h. The calcined membranes were kept in a desiccator for permeation test.

EXPERIMENTAL EXAMPLE 1

Laser Scanning Confocal Microscope (LSCM) Measurement

[0108] The LSCM measurements were carried out with two types of membrane including random oriented silicalite-1 films supported on porous silica substrates (denoted as r-SL.sub.Fp-SiO.sub.2) and b-SL.sub.f/p-SiO.sub.2. The calcined membranes were mounted on a home-made permeance cell. The zeolite site was contacted to pure MeOH while the support site was contacted to fluorescein (see below) solution 0.1 M in MeOH. The contact areas were sealed by O-ring. After 4 days for dye inclusion at room temperature, the membranes were removed and washed with copious amount of MeOH, dried by blowing N.sub.2 gas, and kept at room temperature for 12 h.

[0109] The LSCM measurements were conducted using LSM-710 (Carl Zeiss) with Argon laser source (488 nm) and z-stack scan mode. The r-SL.sub.F/p-SiO.sub.2 membrane was measured at laser power of 3.5% using Plan-Apochromat 40x/0.95 Korr M27 objective lens with a zoom value of 0.6 and a master gain value of 547. The b-SL.sub.f/p-SiO.sub.2 membrane was measured at a laser power of 6.5% using Plan-Apochromat 40x/0.95 Korr M27 objective lens with a zoom value of 2.0 and the master gain value of 700. The 3D images were built using ZEN 2009 Light Edition software (Carl Zeiss).

##STR00002##

[0110] [2-(6-hydroxy-3-oxo-(3H)-xanthen-9-yl) benzoic acid]

[0111] Absorption maximum: 496 nm

EXPERIMENTAL EXAMPLE 2

Separation of the o-/p-xylene Mixture with b-SL.SUB.f./p-SiO.SUB.2

[0112] The separation of the xylene mixture was carried out according to the Wicke-Kallenbach method (FIG. 5). A b-SL.sub.f/p-SiO.sub.2 membrane was mounted on a home-made stainless steel cell. AS-568A O-rings (Kalrez, DuPont Performance Elastomers) were used as the sealing materials. The active area was 2.0 cm.sup.2. Helium was passed through the xylene mixture placed in a container whose temperature was kept at 25° C. This vapor stream was mixed with a second He stream in a mixer. This xylene vapor was fed into the feed side of the membrane. The total flow rate in the feed side was maintained at 60 mL/min. The p- and o-xylene vapor pressures in the feed side were 0.32, and 0.31 kPa, respectively. Helium with a flow rate of 15 mL/min was used to sweep the permeate side. The total pressure on both sides was atmospheric pressure. The separation cell was mounted in a convection oven. To prevent the condensation, all the lines of the system were kept at 110° C. by tape heater. The permeance tests were conducted at a desired temperature to which the temperature was increased slowly at the rate of 1° C./min from room temperature. A fresh membrane was used for each test at different temperatures. During the temperature increase, pure He gas was passed to both sides of the membrane.

[0113] For permeance measurements, the gas stream of the permeate side was passed to a GC through a 6-port valve. The concentrations of the components (p- and o-xylene) were analyzed by the GC chromatogram areas. The area-concentration curve was obtained before the membrane tests for each component by passing reference streams of He with different concentrations of each component.

[0114] The permeance (P in mole s.sup.−1m.sup.−2Pa.sup.−1) is defined as the flux (F in mole s.sup.−1m.sup.−2) of a component M over the difference in the partial pressure of M between the feed and permeate sides (eq. 1).

P=F/Δp   (1)

[0115] The separation factor (α.sub.P/O) is defined as the ratio of the mole fractions of the para isomer (f.sub.p) with respect to the ortho isomer (f.sub.o) at the feed and permeate sides (eq. 2).

α.sub.P/O=[(f.sub.p/f.sub.o)].sub.permeate/[(f.sub.p/f.sub.o)].sub.feed   (2)

Experimental Results

[0116] Zeolite films prepared according to the specific embodiment of the present invention can be used in membrane-mediated separation of small molecule mixtures into pure components. To investigate the performance of uniformly b-oriented SL films as separation membranes for xylene mixture, we prepared monolayers of rounded coffin-shaped SL crystals on porous silica supports and subsequently grew 1.0-μm thick uniformly b-oriented SL films in gel-2 (FIG. 4). The use of porous silica supports is necessary to maintain uniform b-orientation of the SL films, because aluminum-containing porous supports suppress the film growth. The porous silica supports were readily prepared by the method described in Example 1. The separation of the o- and p-xylene mixture was conducted at two different temperatures (80° C. and 150° C.) under standard reported conditions (FIG. 5).

[0117] The initially measured permeance of p-xylene at 80° C. was much higher than that of o-xylene, giving rise to a high (>1900) separation factor (SF) (FIG. 6D). However, the permeance continuously decreased over a period of 216 hours and reached a steady state. The steady-state permeance of p-xylene and o-xylene were 0.7×10.sup.−8 and 0.0092×10.sup.−8 mol s.sup.−1m.sup.−2Pa.sup.−1, respectively, giving rise to a steady-state SF of 71. We attribute the continuous decreases of p-xylene permeance and the SF value to gradual adsorption of o-xylene into the channels, leading to a gradual increase in the degree of channel blockage, which in turn decreases the diffusion rate of p-xylene molecules. The fact that the permeance decreases to near zero also indicates that the b-oriented SL film does not have cracks.

[0118] At 150° C., the p-xylene permeance also continuously decreased from 21.6×10.sup.−8 to 5×10.sup.−8 mol s.sup.−1m.sup.−2Pa.sup.−1 over a period of 400 hours (FIG. 6E). During the same period, the o-xylene permeance decreased from 0.0097×10.sup.−8 to 0.0068×10.sup.−8 mol s.sup.−1m.sup.−2Pa.sup.−1. The gradual decrease of p-xylene permeance even at 150° C. indicates that the channel blocking by o-xylene still continues at 150° C., and the b-oriented SL film does not undergo crack formation during operation. During the period from 20 to 370 hours, the SF value remained nearly constant at 1000. Although this steady-state SF value is lower than the highest value observed from randomly oriented tubular SL films, it is about two times higher than those of randomly oriented non-tubular SL films with similar thickness (table 1).

TABLE-US-00001 TABLE 1 p-xylene permeance Thickness [10.sup.−10 mol s.sup.−1 m.sup.−2 Temp. Calcination Orientation [μm] Pa.sup.−1] SF [° C.] method random (Ref. 1) 0.5 2,700 17 400 C b (Ref. 2) 1.0 2,460 378 150 C b (Ref. 2) 1.0 1,960 483 200 C random (Ref. 3) — 270 60 150 C random (Ref. 4) — — ~5,000 200 — b (the present 1.0 2,100-500 ~1,000 150 C invention) (Ref. 1) J. Hedlund, F. Jareman, A. J. Bons, M. Anthonis, J. Membr. Sci. 222, 163 (2003). (Ref. 2) Z. P. Lai, M. Tsapatsis, J. R. Nicolich, Adv. Funct. Mater. 14, 716 (2004). (Ref. 3) C. J. Gump, V. A. Tuan, R. D. Noble, J. L. Falconer, Ind. Eng. Chem. Res. 40, 565 (2001). (Ref. 4) M. O. Daramola et, al., Sep. Sci. Technol. 45, 21 (2009).

[0119] Reference 1. J. Hedlund, F. Jareman, A. J. Bons, M. Anthonis, J. Membr. Sci. 222, 163 (2003).

[0120] Reference 2. Z. P. Lai, M. Tsapatsis, J. R. Nicolich, Adv. Funct. Mater. 14, 716 (2004).

[0121] Reference 3. C. J. Gump, V. A. Tuan, R. D. Noble, J. L. Falconer, Ind. Eng. Chem. Res. 40, 565 (2001).

[0122] Reference 4. M. O. Daramola et al., Sep. Sci. Technol. 45, 21 (2009).

[0123] Table 1 indicates the comparison of the characteristics and performance of the uniformly b-oriented SL membranes prepared by method of the present invention with the SL membranes prepared by other groups. SF represents Separation factor, and the conventional slow temperature rising and slow temperature cooling method is used as Calcination method (C).

[0124] Although the present invention has been described in detail with reference to the specific features, it will be apparent to those skilled in the art that this description is only for a preferred embodiment and does not limit the scope of the present invention. Thus, the substantial scope of the present invention will be defined by the appended claims and equivalents thereof.