WO2012010069A1

WO2012010069A1 - Synthesis method of naa zeolite molecular sieve membrane on macropore carrier

Info

Publication number: WO2012010069A1
Application number: PCT/CN2011/077183
Authority: WO
Inventors: 王金渠; 杨建华; 盛春光; 周志辉; 陈赞; 鲁金明; 殷德宏; 张艳
Original assignee: 大连理工大学
Priority date: 2010-07-19
Filing date: 2011-07-15
Publication date: 2012-01-26
Also published as: CN101890306B; CN101890306A

Abstract

A synthesis method of NaA zeolite molecular sieve membrane on macropore carrier comprises coating a continuous and uniform crystal seed layer on the surface of the macropore carrier by using thermo-dipping and brush-coating method. The growth and separation performance of the synthesized membrane can be regulated with different grain sizes of the crystal seeds. A synthesis liquid is prepared according to the molar ratio of Na₂O:SiO₂:Al₂O₃:H₂O=1-20:2-5:1:100-1000. Dynamically hydrothermal crystallization is performed in a rotary oven to synthesize the NaA zeolite molecular sieve membrane with excellent separation performance. The synthesized NaA molecular sieve membrane has excellent separation performance, high reusability and suitability for large-scale application.

Description

Method for synthesizing NaA zeolite molecular sieve membrane on macroporous support

技术领域 Technical field

The invention relates to a method for synthesizing a zeolite molecular sieve membrane, in particular to preparing a NaA with excellent performance after pre-coating a seed crystal by a hot dipping method on a macroporous carrier. Zeolite molecular sieve membrane.

背景技术 Background technique

Pervaporation (PV Is a membrane separation technology that has been rapidly developed in the past two decades. It utilizes the adsorption (or dissolution or sieving) and diffusion properties of the components in a binary or multi-component liquid mixture on the separation membrane to achieve separation of the mixture. It is known from the principle of pervaporation that the pervaporation membrane separation process is not limited by the vapor-liquid equilibrium, and therefore has unique advantages for the separation of near-boiling and azeotrope which are difficult to handle by conventional separation means. In addition, for the removal of some trace components in the mixture, pervaporation shows higher separation efficiency, and compared with traditional separation methods such as distillation, absorption, extraction, etc., pervaporation has incomparable advantages, such as equipment. It has the advantages of simple operation, low pollution, low energy consumption and high separation efficiency. However, the pervaporation membranes used today are mostly organic polymer membranes, and such materials have the disadvantages of poor chemical stability, thermal stability and mechanical stability, and it is difficult to obtain high flux and selectivity, thereby making their application fields subject to The limit.

The zeolite molecular membrane uses a porous material as a carrier to grow a zeolite molecular sieve on its surface. It has a uniform pore size and a pore size similar to the molecular size, adjustable surface characteristics, high temperature resistance, good chemical stability, solvent resistance and microbial corrosion. High performance, high strength, wear resistance, easy cleaning, etc., making it high temperature , a large pressure gradient, and use in harsh operating environments such as acid-base media or bio-erosion with a certain intensity, Has a unique advantage. Zeolite molecular sieve membrane has become one of the most promising membranes, and its preparation and application research have become the research hotspot and frontier of membrane science and technology.

The NaA zeolite molecular sieve membrane has a three-dimensional eight-membered ring channel system with a crystal channel diameter of 4.1 Å × 4.1 Å, and the composition of Si/Al Ratio (referred to as the molar ratio) is 1:1 It is extremely hydrophilic, and it exhibits excellent ideal molecular sieve selectivity and extremely high permeation flux for dehydration of organic matter over a wide range of concentrations, thus separating the organic solvent mixture. NaA The component that is permeated through the membrane is only water, and the permeate flux is two orders of magnitude larger than the organic membrane 1-2, which makes NaA When the organic membrane is dehydrated, the zeolite membrane can be efficiently separated in a wide concentration range including an azeotrope, and the application range is wide, so that the purity of the product can reach a higher demand. It is also important that the molecular sieve itself has excellent physical properties such as high temperature resistance, good chemical stability, solvent resistance and microbial corrosion resistance. The NaA zeolite membrane can be used in conditions such as high temperature, strong solvent, and strong biocorrosion. NaA These excellent properties of zeolite molecular sieves are unmatched by organic membranes, making them widely used in the removal of water and refined organics from various organic materials.

发明内容 Summary of the invention

The technical problem to be solved by the present invention is to provide a macroporous carrier for the market. High performance, highly reproducible NaA was prepared on the surface of macroporous supports by providing a novel seed coating method, a two-step seed-assisted secondary growth method. Zeolite molecular sieve membranes are applied to water by pervaporation to remove ethanol.

NaOH, NaAlO ₂ , silica sol and deionized water are added in order, and the synthetic liquid is obtained by vigorous stirring and aging, and then the treated carrier tube is firstly subjected to a two-step seeding method, that is, firstly, the NaA crystal is thermally dipped. Apply to the surface of the carrier, then apply NaA seed crystals to the macroporous support such as α-Al ₂ O ₃ , stainless steel or mullite by lift or spin coating; or apply large crystal The high-performance NaA zeolite molecular sieve membrane is obtained by a secondary repair synthesis method without applying a small seed crystal. The NaA zeolite molecular sieve membrane with excellent separation performance was synthesized by dynamic hydrothermal crystallization in a rotary oven by controlling the growth of the synthetic membrane and the separation performance of the membrane by the difference in the grain size of the seed crystal. The grain size of the large seed crystal is slightly smaller than the average pore size of the carrier. The seed crystal serves to modify the macropore pore size to reduce the pore size of the carrier, so that the NaA zeolite can form a uniform and continuous NaA zeolite membrane on the surface of the carrier, while preventing a large amount of NaA zeolite. Molecular sieves are formed in the pores of the carrier, resulting in a decrease in the flux of the membrane and at the same time inducing the growth of the NaA zeolite molecular sieve. The small seed crystals mainly induce NaA zeolite which induces uniformity and separation performance of the NaA zeolite molecular sieve on the surface of the carrier. Molecular sieve membrane. The prepared membrane was characterized by scanning electron microscopy and XRD, and the separation performance of the membrane was evaluated by pervaporation separation of water in ethanol using a NaA membrane.

The technical solution of the present invention is as follows:

The treated carrier tube is passed through a two-step seeding method, that is, first, a NaA seed crystal is applied to the surface of the carrier by hot dipping, and then the NaA seed crystal is applied to α-Al _{2 by} lift or spin coating. On a macroporous support such as O ₃ , stainless steel or mullite; or by applying a large seed crystal, without applying a small seed crystal, the other synthesis conditions remain the same as the two-step seed method of simultaneously applying the size seed crystal method. Then, a high performance NaA zeolite molecular sieve membrane was obtained by secondary repair synthesis; the NaA zeolite molecular sieve membrane was prepared as follows: Al ₂ O ₃ :SiO ₂ :Na ₂ O:H ₂ O=1:2.5-5:25-50 : 500-1000 molar ratio is prepared into synthetic liquid, which is prepared by hydrothermal synthesis on macroporous support; synthesis temperature is 80-100 °C, synthesis time is 3-6h; for secondary repair synthesis, secondary repair The crystallization temperature and crystallization time are 90-100 ° C, _2-4 h, and the molar ratio formula is: Al ₂ O ₃ : SiO ₂ : Na ₂ O: H ₂ O = 1: 2: 2: 100-150, A high performance NaA zeolite membrane is also finally obtained. The prepared NaA molecular sieve membrane is soaked in neutralized water with deionized water. The synthesized membrane is repeatedly rinsed with deionized water to neutrality and then naturally dried. It can also be dried in an oven at 20-100 °C for 6-24 hours. use.

The pore size of the carrier tube may be from 0.1 μm to 4 μm and the porosity is from 30 to 50%. NaA The large seed crystal refers to a NaA zeolite molecular sieve crystal grain having a size of 1 - 3 μm. The NaA small seed crystal refers to a NaA zeolite molecular sieve grain having a size of 50 - 600 nm.

The hot dipping method refers to putting a carrier tube preheated at a temperature of 50-200 ° C into a prepared large seed crystal solution, and the immersion time is 10-50s, the concentration of seed crystals in the seed solution is 2-10wt.%, The seed crystal is applied to the surface of the carrier; the method is to form a negative pressure by rapid cooling of the hot air in the carrier tube, so that the seed crystal in the seed liquid is adsorbed into the surface channel of the carrier tube.

The synthesized NaA zeolite molecular sieve membrane is pervaporated to carry out ethanol dehydration, and the concentration in ethanol is 50-99 wt.%. In the range of the separation, the separation performance is excellent, the repeatability is high, and it is suitable for large-scale applications.

The effect of the present invention is to provide a method for seeding a seed on a macroporous support, and to regulate the growth of the NaA zeolite membrane by the size of the seed crystal, thereby overcoming the difficulty of film formation on the macroporous support. A dense continuous high-performance NaA zeolite membrane is prepared on the surface of a carrier having a macroporous α-Al ₂ O ₃ having a length of 5 to 120 cm, which is available on the domestic market, and the membrane is pervaporated to carry out ethanol dehydration in ethanol. The concentration is in the range of 50-99wt.%, the separation performance is excellent, the repeatability is high, and it is suitable for large-scale application, and has important industrial application value and practical significance.

附图说明 DRAWINGS

Figure 1 is a surface view a and a cross-sectional view b of an SEM image of an α-Al ₂ O ₃ carrier tube.

Figure 2 is a surface view a and a cross-sectional view b of the SEM image of the synthesized NaA film.

Figure 3 is a surface view a and a cross-sectional view b of the SEM image of the synthesized NaA film.

Figure 4 is an XRD picture of a synthetic NaA film.

In the figure: * is the characteristic peak of the carrier tube Al ₂ O ₃ .

Figure 5 is a flow chart of pervaporation.

具体实施方式 detailed description

实施例 1 Example 1

Step 1, carrier tube pretreatment

The carrier tube used in the embodiment of the present invention is provided by Nanjing University of Technology with a nominal pore size of 2-3 μm and a porosity of 30-40% α-Al ₂ O ₃ tube, or Guangdong Foshan Ceramic Research Institute or Jiexi Smooth Technology Co., Ltd. An α-Al ₂ O ₃ tube having a nominal pore size of 2-3 μm and a porosity of 30-40% is provided, and the tube length is 80 cm.

The surface of the carrier tube is sequentially used 600# and 800# The waterproof sandpaper is sanded until the surface of the carrier is smooth, and then ultrasonically shaken with acid and alkali to remove the residue in the carrier pores, washed with deionized water until neutral, and then dried naturally, and finally at 150 °C. Dry at room temperature for use.

Step 2, preparation of carrier seed layer

(1) Applying a large seed crystal on the treated carrier tube by hot dipping: a self-made NaA molecular sieve having a grain size of 1 to 3 μm is used. The temperature of 1K/min is raised to 550 °C for 4h to remove the organic template in the molecular sieve, and then it is configured as a 10% aqueous solution of the seed crystal, which is quickly dried at 180 °C. 4h of the carrier tube is immersed in the above seed solution, the immersion time is 20s, then the carrier tube coated with the seed crystal is placed in an oven at 50~100 °C for drying, and finally the excess molecular sieve on the surface of the carrier is gently wiped off with absorbent cotton. .

(2) Secondary application of the small seed crystal to the above carrier tube by the pulling method: the self-made NaA molecular sieve with a small average grain size of 400 nm is also The temperature of 1K/min is raised to 550 °C for 4h to remove the templating agent from the molecular sieve and then formulated into 2% The seed crystal aqueous solution is then immersed in the seed crystal solution with the large seed crystal carrier, the immersion time is 20 s, and finally the carrier is dried in an oven at 50 to 100 ° C for synthesis.

Step 3, Preparation of NaA Zeolite Molecular Sieve Membrane

Weigh 1.9 g of NaAlO ₂ and 35.6 g of NaOH dissolved in 156.5 g of deionized water. After clarification, slowly add 9.3 g of silica sol (SiO ₂ wt.% = 26.0, Na ₂ O wt.% = 0.05). Stir well until it becomes a clear solution, which is the mother liquor for the synthesis membrane, and its composition is Al ₂ O ₃ : SiO ₂ : Na ₂ O: H ₂ O = 1: 5: 50: 1000. Thereafter, the two ends of the seeded carrier were blocked with a Teflon plug and placed vertically into a stainless steel reaction vessel, and the above-mentioned configured synthetic liquid was added, and after sealing, the kettle was fixed in a rotary oven at 80 ° C for heating. After crystallization for 5 h, it was taken out, cooled to room temperature, and the membrane tube was taken out and washed with deionized water until neutral, and dried. The crystal structure and film surface morphology of the dried NaA zeolite molecular sieve membrane were confirmed by SEM photograph (Fig. 2) and XRD (Fig. 4), and the obtained NaA membrane was counted as M1.

实施例 2 Example 2

Step 1. The carrier tube is pretreated in the same manner as in step 1 of Example 1.

Step 2: Preparation of carrier seed layer: The large seed crystal is applied to the surface of the carrier only by hot dipping-wiping method, and no small seed crystal is coated. Steps are the same as the embodiment Step 1 in step 2 of the procedure (1).

Step 3, Preparation of NaA Zeolite Molecular Sieve Membrane

In the same manner as in the third step of the first embodiment, the NaA film obtained is M2, that is, M2 before the repair. Since only a large seed crystal is coated, the separation selectivity of the one-step crystallized NaA zeolite membrane needs to be improved, and in order to further improve the separation performance of the NaA zeolite membrane, a two-step crystallization synthesis is employed. As described above, the first step of the synthesis process is exactly the same as in step 3 of the embodiment 1. In the second step, the conditions and formulation were changed. The specific process was as follows: 6.80 g of NaAlO ₂ and 2.072 g of NaOH were thoroughly dissolved in 107.875 g of water in a 200 ml beaker, stirred vigorously for 1 h, and then 15.385 g of silica sol ( SiO ₂ wt.% = 26.0 wt.%, Na ₂ O = 0.05%) was slowly added to the above stirred aluminate, and then stirred for 3 h to prepare a white emulsion sol synthetic liquid, the composition of each component was Al ₂ O ₃ : SiO ₂ : Na ₂ O: H ₂ O = 1: 2: 2: 120 . The two ends of the membrane tube synthesized in the first step were blocked with a Teflon plug and placed vertically in a stainless steel reaction vessel, and then the above synthetic liquid was transferred to a crystallization vessel, and then the kettle was fixed in a rotary oven at 100 °C. After crystallization for a certain period of time, it was taken out, cooled to room temperature, and the film tube was taken out and washed with deionized water until neutral, and dried. The surface morphology of the dried NaA zeolite molecular sieve membrane was confirmed by SEM photograph (Fig. 3), and the obtained NaA membrane was repaired M2. It can be seen from the figure that the second step of the synthesis is only to repair the defects existing in the first unsynthesized film.

实施例 3 Example 3

The treated NaA zeolite molecular sieve membrane is installed in a membrane separator, and both ends are sealed with a corrosion-resistant fluorine rubber O-type gasket, and an aqueous solution of ethanol or an aqueous solution of isopropanol having a concentration of 50.0-99.0 wt.% is separated and supplied to the mixture. The shell of the membrane is evacuated from the tube side of the membrane. The flux and separation factor of the membrane were measured at a temperature of 70 ° C and a vacuum of 200-400 Pa on the permeate side. The raw material component, the permeation component and the retentate component are analyzed by gas chromatography, and the flux of the membrane is determined by collecting the permeate condensed by liquid nitrogen for 10 to 60 minutes at a specific time to determine the composition of the weight and the permeation component. Calculated. The pervaporation performance of the membrane is represented by the permeation flux J and the separation factor α, respectively. The composition of the raw material liquid and the permeate was analyzed by HP6890+ gas chromatograph produced by Agilent. The column HP-5, the stationary phase was benzylsilane, the column length was 30 m, the inner diameter was 0.32 mm, and H ₂ was the carrier gas. Thermal conductivity detection. Permeate flux J Separation coefficient α Calculated as follows:

(1)

(2)

Where M is the total weight (kg) collected on the permeate side of the membrane for a certain period of time Δt (h), A is the effective area of the membrane (m ² ), J is the total permeate flux of the membrane, and the composition The permeate flux is calculated from the total permeate flux and its composition. i is the component water, j is the mass percentage of the material side and the permeate side material which are not easily permeated through the component ethanol or isopropanol, and α is a separation coefficient, indicating the water-to-alcohol separation coefficient of the membrane.

The membrane tubes synthesized in Example 1 and Example 2 were respectively subjected to pervaporation performance of an ethanol/water system or an isopropanol/water system, and the flow thereof is shown in Fig. 3, wherein (a) a magnetic stirrer (b) constant temperature oil Bath (c) membrane tube (d) membrane module (e) ethanol/water raw material liquid (f) cold trap (g) liquid nitrogen (h) silicon vacuum tube (i) vacuum buffer bottle (j) iron frame (k) vacuum gauge ( l ) Vacuum pump. For ethanol/water systems with an ethanol or isopropanol mass fraction of 90 wt.%, the operating temperature is 70 °C, the M1 of the permeate side is 200-400 Pa, and the separation factor of the M2 after the second repair is Between 5000 and ∞, the permeate flux is between 1.45-1.81 kg/m ² h. It exhibits good separation performance and has important industrial application value and practical significance.

Table 1 Separation performance of synthetic NaA membrane M1 pervaporation ethanol aqueous solution

Concentration [ wt.% ] Concentration [ wt.% ]	Separation Temperature [ ℃ ]Separation Temperature [ °C ]	Water Flux [kg·m^-2·h^-1]Water Flux [kg·m ^-2 ·h ^-1 ]	Separation factor αH2O/EtOH [-]Separation factor αH2O/EtOH [-]
85.0 85.0	70 70	2.87 2.87	∞ ∞
90.0 90.0	70 70	1.81 1.81	46246 46246
95.0 95.0	70 70	1.00 1.00	37886 37886

Table 2 Separation performance of synthetic NaA membrane M1 pervaporation aqueous solution of isopropanol

Concentration [ wt.% ] Concentration [ wt.% ]	Separation Temperature [ ℃ ]Separation Temperature [ °C ]	Flux [kg·m^-2·h^-1]Flux [kg·m ^-2 ·h ^-1 ]	Separation factor αH2O/IPA [-]Separation factor αH2O/IPA [-]
85.0 85.0	70 70	2.15 2.15	∞ ∞
90.0 90.0	70 70	1.60 1.60	∞ ∞
95.0 95.0	70 70	0.88 0.88	10458 10458

Table 3 Separation performance of synthetic NaA membrane M2 pervaporation ethanol aqueous solution

Concentration [ wt.% ] Concentration [ wt.% ]	Separation Temperature [ ℃ ]Separation Temperature [ °C ]	Flux [kg·m^-2·h^-1]Flux [kg·m ^-2 ·h ^-1 ]	Separation factor α_{H2O/ EtOH} [-]Separation factor α _{H2O/ EtOH} [-]
修补前 Before patching
90.0 90.0	70 70	2.18 2.18	200 200
修补后 After patching
90.0 90.0	70 70	1.45 1.45	5000 5000

Claims

What is claimed is: 1. A method for preparing a NaA zeolite molecular sieve membrane on a macroporous support, characterized by the following steps,

(1) Pre-coating the seed crystals with the two-step seeding method to obtain high performance NaA Zeolite molecular sieve membrane; or coating large crystal seeds, not coating small seed crystals, and then obtaining high performance NaA zeolite molecular sieve membrane by secondary repair synthesis;

(2) The NaA zeolite molecular sieve membrane is prepared as follows: Al ₂ O ₃ :SiO ₂ :Na ₂ O:H ₂ O=1:2.5-5:25-50:500-1000 molar ratio is formulated into a synthetic liquid, using water The thermal synthesis was carried out on a macroporous support; the crystallization of the NaA zeolite membrane was carried out dynamically in a rotary oven at a temperature of 80-100 ° C and a synthesis time of 3-6 h;

For the case of secondary repair synthesis, the crystallization temperature and crystallization time of the secondary repair are 90-100 ° C, _2-4 h, and the molar ratio formulas are: Al ₂ O ₃ : SiO ₂ : Na ₂ O: H ₂ O=1:2:2:100-150;

(3) The prepared NaA molecular sieve membrane is soaked in neutralized water with deionized water and dried.

2. The preparation method according to claim 1, wherein the carrier tube has a pore size of from 0.1 μm to 4 μm. The porosity is 30-50%.

The method according to claim 1 or 2, wherein the two-step seeding method has different NaA seed crystal sizes, and the large crystal seed crystal has a size of 1 to 3 μm. NaA zeolite molecular sieve grains, small crystal seeds are NaA zeolite molecular sieve grains with a size of 50-600 nm.

A method according to claim 1 or 2, wherein the two-step seeding method is a hot dipping method, and the temperature of the impregnated carrier tube is 50 to 200 ° C. The immersion time is 10-50 s, and the concentration of the seed crystal in the seed solution is 2-10 wt.%.

A method according to claim 3, wherein the two-step seeding method is a hot dipping method, and the temperature of the impregnated carrier tube is 50-200 ° C, and the immersion time is 10-50 s , the concentration of seed crystals in the seed crystal is 2-10 wt.%.

The preparation method according to claim 1 or 2, wherein the prepared NaA zeolite membrane is pervaporated to carry out ethanol dehydration, and the concentration in ethanol is In the range of 50.0-99.0wt.%, the separation performance is excellent and the repeatability is high, which is suitable for large-scale applications.