CN111573692B

CN111573692B - CHA molecular sieve membrane and preparation method and application thereof

Info

Publication number: CN111573692B
Application number: CN202010285547.6A
Authority: CN
Inventors: 李子宜; 李俊; 刘应书; 章佳佳; 杨雄; 刘文海
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2020-04-13
Filing date: 2020-04-13
Publication date: 2022-04-01
Anticipated expiration: 2040-04-13
Also published as: CN111573692A

Abstract

The invention belongs to the field of molecular sieve membrane material preparation and gas separation application, and particularly relates to a CHA molecular sieve membrane and a preparation method and application thereof. The preparation method is to synthesize ordered pore channels, acid resistance, corrosion resistance and high SO on the surface of the porous carrier₂/NO₂A CHA molecular sieve membrane with selectivity and long-term stability. The CHA molecular sieve membrane with the weight ratio of silicon to aluminum of 5-1000 or pure silicon has high acid resistance and stability. The CHA molecular sieve membrane is used for SO₂/NO₂The separation coefficient reaches 8 to 45, SO₂The permeation flux reaches 5-60 multiplied by 10^‑8mol·m^‑2·Pa^‑1·s^‑1. The CHA molecular sieve membrane has proper pore size and surface polarity, and can form SO at low temperature₂/NO₂Sieving effect and promotion of SO₂The adsorption selectivity of (1).

Description

CHA molecular sieve membrane and preparation method and application thereof

Technical Field

The invention belongs to the field of molecular sieve membrane material preparation and gas separation application, and particularly relates to a CHA molecular sieve membrane and a preparation method and application thereof.

Background

SO in industrial flue gas₂And NO_XIs the main reason for forming air pollution and acid rain, and according to statistics, China has annual average SO₂And NO_xThe emission amount is over 2000 ten thousand tons and is at the top of the world. In recent years, the synergistic adsorption removal and resource technology of multiple pollutants in flue gas is well accepted and widely applied, for example, the technology can be used for simultaneously adsorbing and removing SO in the United states in a large scale₂And NO_x(removal rate can reach 90 percent) and realizes regenerated NOXSO technology and Japanese Rokkasho nuclear waste disposal companyRecovering NO_x(the recovery rate is 95 percent, and the purity is 99.8 percent) by adopting a vacuum pressure swing adsorption technology and the like. Therefore, the purification and recycling by the adsorption method are important methods for comprehensively treating the smoke pollutants.

SO₂Besides being used as basic raw materials for producing sulfuric acid and fertilizers, the sulfuric acid and the fertilizers are widely used in the fields of agricultural product processing (soaking liquid and safety liquid), papermaking industry (bleaching agent), petrifaction (refining agent), chemical industry (glue and gelatin production) and the like. NO₂The product is used as an oxidant in rocket fuels and is often used for preparing industrial reagents such as nitric acid, nitrating agents, oxidants, catalysts, acrylate polymerization inhibitors and the like in industry. Thus, high purity SO₂With NO₂The method has important application value, so that the oxidizing gases are collected, recovered and recycled, waste is changed into valuable, the problem of environmental pollution is solved, and the two purposes are achieved.

NO in flue gas_xWith NO and NO₂Contains a small amount of N as main component₂O₃，N₂O and N₂O₅And the like. In the process of adsorption purification, because NO is a permanent gas, the adsorption amount is usually extremely low, and NO is oxidized into NO₂Can be effectively adsorbed with NO₂Can be adsorbed in a large amount in a wide temperature and humidity range. Many studies have shown that NO₂Stripping NO from gas for adsorbent regeneration_xThe main component (c). Therefore, in the process of adsorbing and purifying the multiple pollutants in the flue gas, the pollutant gas in the desorbed gas is mainly SO₂With NO₂If the two are to be recovered, enriched and recycled without damage, SO₂/NO₂Is of great importance. However, SO₂With NO₂The boiling point and the molecular diameter of the polymer are-10 ℃, 21 ℃ and

the boiling points and the molecular sizes of the two are relatively close, and the traditional rectification method or the temperature change/pressure change adsorption method has great difficulty.

The utilization of molecular sieve membrane for gas separation is a hot spot of molecular sieve membrane research in recent yearsDue to the special size effect and the adsorption characteristic, different gases can be effectively separated, energy is saved to a greater extent, and the continuity of the separation process is ensured. Zeolites with smaller pores may be provided for the separation of light gases because the pore size of these zeolites is smaller than

Approaching the kinetic diameter of many light molecules. CHA is a copolymer having a porosity of 17.3% and

a porous three-dimensional zeolite. The pores have the same diameter as the light gas molecules and are used for hydrocarbon and CO₂、H₂And the mixture with other small molecules has larger screening effect, and can realize higher selectivity and permeability.

At present, most researchers apply the aspects of focusing on air separation, hydrogen recovery, aromatic extraction, natural gas purification, flue gas and synthesis gas decarburization and the like of molecular sieve membrane separation to SO in industrial flue gas₂With NO₂Reports on the preparation of molecular sieve membranes for gas separation have not yet been made. In addition, there are few reports on the ordered growth of CHA zeolite membranes.

Disclosure of Invention

In order to solve the problems, the invention provides a CHA molecular sieve membrane and a preparation method and application thereof. The preparation method is to synthesize ordered pore channels, acid resistance, corrosion resistance and high SO on the surface of the porous carrier₂/NO₂A CHA molecular sieve membrane with selectivity and long-term stability.

The invention is realized by the following technical scheme:

a CHA molecular sieve membrane is a silicon-aluminum type CHA molecular sieve membrane or a pure silicon type molecular sieve membrane;

the ratio of the amount of silicon to aluminum in the silicon-aluminum type CHA molecular sieve membrane is 5 to 1000;

adding metal cation (K) into the CHA molecular sieve membrane during preparation⁺) Thereby promoting the ordered growth of CHA crystals;

the higher the ratio of the amount of the silicoaluminophosphate species of the CHA molecular sieve membrane, the higher the acid resistance and stability.

Further, the CHA molecular sieve membrane conforms to the requirements of separating SO in industrial flue gas from molecular diameter, physical properties and surface polarity₂And NO₂(ii) a Has stronger thermal stability and acid resistance, and can realize SO under harsh conditions₂With NO₂The gas separation of (2).

Another objective of the present invention is to provide a preparation method of the CHA molecular sieve membrane, wherein the preparation method adopts the original CHA molecular sieve as a seed crystal to induce and synthesize a dense high-silicon CHA molecular sieve membrane: seed spreading is realized on a carrier by using a seed crystal suspension, seed crystals are fixed in a high-temperature drying mode, a compact and smooth CHA molecular sieve membrane is induced and synthesized, and a template agent in the CHA molecular sieve membrane is removed by high-temperature calcination to open a molecular sieve pore channel;

the crystal size of the seed crystal is 0.1-10 mu m;

the seed crystal is pure silicon or the quantity ratio of the silicon and aluminum in the seed crystal is 5-100;

the preparation method is carried out by adding metal cation (such as K) into the original CHA molecular sieve⁺) The purpose of promoting the ordered growth of the crystal in the growth process is achieved, and the permeability and the selectivity of the gas are improved.

Further, the preparation method comprises the following specific steps:

s1, preparing a seed crystal suspension: mixing the seed crystal with deionized water, and stirring after ultrasonic treatment to obtain the uniformly dispersed seed crystal suspension; stirring can be continuously carried out on a magnetic stirrer for 1-6 h;

s2, preparing a molecular sieve seed crystal carrier: standing the seed crystal suspension, spreading seeds on a carrier, and finally drying and fixing to obtain the molecular sieve seed crystal carrier; standing for 3-20 minutes;

s3, preparing precursor gel: stirring a silicon source, a metal hydroxide, an aluminum source, trimethyl amantadine hydroxide (TMADAOH) and water at the temperature of 0-100 ℃ to obtain precursor gel; stirring for 4-72 h;

s4, preparing a CHA molecular sieve membrane: mixing the molecular sieve seed crystal carrier obtained in the step S2 with the precursor gel obtained in the step S3, and performing hydrothermal reaction at 100-220 ℃ to obtain a CHA molecular sieve membrane containing a template agent; the hydrothermal reaction time is 12-144 h;

s5, calcining: calcining and activating the CHA molecular sieve membrane at the temperature of 300-600 ℃ to finally obtain the CHA molecular sieve membrane; the calcination can be carried out in a tube furnace at 300-600 ℃.

Further, several drops of strong acid are added dropwise after the seed crystals and deionized water are mixed before sonication in S1 to stabilize the seed crystals and allow the seed crystals to be more uniformly suspended in the solvent.

Further, the strong acid is hydrochloric acid with a concentration of 5 wt%.

Further, the mass concentration of the seed crystal in the seed crystal suspension in S1 is 0.05-1%.

Further, in the step S2, the drying and fixing are carried out for 2-24 hours at the temperature of 100-600 ℃.

Further, the metal hydroxide in the mixed solution A is KOH and NaOH;

the molar ratio of the mixed solution A is silicon source: sodium hydroxide: potassium hydroxide: an aluminum source: trimethyl amantadine hydroxide: water 1 (0.1-0.4), (0.04-0.2), (0.001-0.2), (0.05-0.4), (20-200); double alkali metal hydroxide is adopted, one is to create an alkaline environment which is favorable for defect-free growth of the film; the second is by adding K⁺Enabling ordered growth of film crystals; NaOH creates an alkaline environment which is favorable for the defect-free growth of the film; added K⁺Enabling the film crystal to grow directionally.

Further, the silicon source is one, two or three of fumed silica, 10-80 wt% of silica sol and 3.1-3.6M of sodium silicate. Further, the aluminum source is aluminum hydroxide, sodium metaaluminate or pseudo-boehmite.

Further, the molar ratio of the mixed solution B is as follows:

silicon source: hydrofluoric acid: trimethyl amantadine hydroxide: water is 1 (0.1 to 0.8) to 0.1 to 0.6 to 10 to 100.

Furthermore, the porosity of the carrier is 30-60%, and the pore diameter is 0.8-10 μm.

Further, the carrier is stainless steel, mullite, cordierite, alumina, zirconia or silica.

Further, the calcination in S5 is performed by conventional calcination, staged calcination or rapid thermal treatment;

the conventional calcination is to keep the calcination temperature of 300-600 ℃ for 2-24 h at the temperature rise and fall rate of 0.1-4K/min;

the step of sectional calcination is to heat the material to 100-300 ℃ at a heating rate of 0.1-4K/min and keep the material for 2-12 h, continue heating the material to 300-600 ℃ and keep the material for 2-24 h, and cool the material to normal temperature at a cooling rate of 0.1-4K/min;

the rapid heat treatment is to put the CHA molecular sieve membrane into a 600-1000 ℃ tubular furnace to be kept for 1-60 min, then directly put into a 300-600 ℃ furnace to be kept for 2-24 h, and then the temperature is reduced to the normal temperature at a cooling rate of 0.1-4K/min, or put the CHA molecular sieve membrane into a 600-1000 ℃ tubular furnace to be kept for 1-60 min, and then conventional calcination is carried out.

The invention also aims to provide a CHA molecular sieve membrane for removing SO in flue gas₂With NO₂Application in separation and recovery.

Further, the CHA molecular sieve membrane is used for separating SO in the flue gas₂With NO₂The temperature condition is-100 to 200 ℃. At this temperature, SO₂With NO₂Separation is easier to occur; over-high temperature, NO₂Not dimerisable to form N₂O₄Decrease SO₂And NO₂The sieving effect of (a); too low a temperature will cause SO₂And NO₂The competitive adsorption effect on the surface of the molecular sieve membrane is reduced.

Further, the CHA molecular sieve membrane is used for separating SO in the flue gas₂With NO₂The pressure drop condition of (A) is 0.01 to 5 MPa. Under the pressure drop condition, SO₂With NO₂Separation occurs more easily.

Further, the CHA molecular sieve membrane separation smokeSO in gas₂With NO₂During the preparation of the gas, SO is removed₂、NO₂In addition, the balance gas is selected from nitrogen, Ar and CO₂One, two or three of them. The dynamic diameters of the balance gases are smaller than the pore diameter of the CHA molecular sieve membrane, so that the balance gases can play a role of balance gases in the gas separation process, and the pore channels cannot be blocked in the molecular sieving process to influence the experiment.

Further, SO in the flue gas₂The gas concentration range is 100-200000 ppm; NO₂The gas concentration is 100 to 200000 ppm. In this concentration range, SO₂With NO₂Separation occurs more easily.

The invention has the following beneficial technical effects:

(1) the CHA molecular sieve membrane prepared by the invention is used for SO in flue gas₂With NO₂When separated and recovered, SO₂Has a kinetic diameter of

Less than main pore diameter of CHA molecular sieve

Readily passing through the CHA molecular sieve membrane, NO₂Will be converted into N greatly due to dimerization at low temperature and high pressure₂O₄Not readily pass through the CHA molecular sieve membrane; and SO₂Compare NO₂Or N₂O₄Has higher polarizability and dipole moment, is easier to adsorb on the membrane surface and is beneficial to SO₂/N₂O₄Separation of (4). For gas separation of molecular sieve membrane at low temperature, molecular diffusion mechanism is weakened, adsorption mechanism contributes obviously to membrane separation, and SO₂There is a greater advantage in that the adsorption selectivity will be further increased, contributing to the SO₂/N₂O₄Separation of (4).

(2) The CHA molecular sieve membrane is used for separating SO in flue gas₂With NO₂The two gases can be recycled. At-100 to 200 ℃, a pressure drop of 0.01 to 5MPa and SO₂、NO₂(when preparing gas, adding different balance gases, wherein the balance gases are selected from nitrogen, Ar and CO₂Etc.) and a concentration of 100 to 200000ppm, SO as to be 8 to 45%₂/NO₂Separation coefficient and 5 to 60X 10^-8mol·m^-2·Pa^-1·s^-1SO of (A)₂The permeate flux.

(3) According to the preparation method disclosed by the invention, the prepared CHA molecular sieve membrane can adjust the mass ratio of 5-1000 silicon-aluminum substances, and can also obtain a pure silicon CHA molecular sieve membrane, so that high acid resistance and stability are achieved, and K is added⁺Can adjust the ordered growth of CHA crystals on the carrier to obtain the CHA molecular sieve membrane.

(4) The CHA molecular sieve membrane has proper pore size and surface polarity, and can form SO at low temperature₂/NO₂Sieving effect and promotion of SO₂The adsorption selectivity, high acid resistance, long-term stability and pore channel order are simultaneously achieved, and the method is applied to SO₂/NO₂Separating a material with great potential.

(5) CHA molecular sieve membranes of the invention are selective for SO₂/NO₂The separation coefficient reaches 8 to 45, SO₂The permeation flux reaches 5-60 multiplied by 10^-8mol·m^-2·Pa^-1·s^-1。

Drawings

FIG. 1(a) is a SEM photograph of the membrane surface of the CHA zeolite membrane in example 1 of the present invention.

FIG. 1(b) is a sectional SEM photograph of the CHA zeolite membrane in example 1 of the present invention.

FIG. 2(a) is a SEM photograph of the membrane surface of the CHA zeolite membrane in example 2 of the present invention.

FIG. 2(b) is a SEM cross-section of CHA zeolite membrane of example 2.

FIG. 3(a) is a SEM photograph of the membrane surface of the CHA zeolite membrane in example 3 of the present invention.

FIG. 3(b) is a SEM cross-section of CHA zeolite membrane of example 3.

FIG. 4(a) is a SEM photograph of the membrane surface of the CHA zeolite membrane in example 4 of the present invention.

FIG. 4(b) is a SEM cross-section of CHA zeolite membrane of example 4.

FIG. 5 is a schematic view of a gas separation test stand used in an embodiment of the present invention.

FIG. 6 is a schematic flow chart of a method for preparing a CHA molecular sieve membrane in an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

On the contrary, the invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, certain specific details are set forth in order to provide a better understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details.

Example 1

0.002g of CHA seed crystal is dissolved in 20mL of deionized water, 4 drops of 5 wt% hydrochloric acid solution are added, the mixture is stirred for 1 hour on a magnetic stirrer, and the mixture is kept still for 10 minutes to obtain uniform and stable seed crystal suspension. Pretreating a stainless steel carrier before seed spreading, immersing the stainless steel carrier into a seed crystal suspension through the steps of polishing, acid-base soaking, cleaning and drying, swinging for 10s from side to enable the stainless steel carrier to fully contact the seed crystal in the suspension, and repeating the step for 4 times; after the seed is laid, the seed crystal is better fixed on the alpha-Al₂O₃Drying the ceramic surface at 120 ℃ for 4 h.

According to 1SiO₂:0.4NaOH:0.04KOH:0.2Al₂O₃:0.2TMAdaOH:40H₂Preparing gel according to the molar ratio of O, stirring fumed silica, aluminum hydroxide, sodium hydroxide, potassium hydroxide, TMADAOH and water in an oil bath at 25 ℃ for 4h to obtain precursor gel, putting the carrier with the CHA molecular sieve seed crystal and the precursor gel into a reaction kettle, and reacting at 140 ℃ for 144h under the hydrothermal condition to obtain the productThe CHA molecular sieve membrane is subjected to conventional calcination in a tubular furnace at 400 ℃ for 24 hours, and the temperature rise and fall rate is 2K/min. The membrane surface diagram and the cross-sectional diagram of the CHA molecular sieve membrane are respectively shown in fig. 1(a) and fig. 1(b), CHA molecular sieve crystals are mutually crosslinked and highly intergrown on the surface of a carrier, crystal grains are grown in a staggered mode, the surface of the carrier is covered with cubic crystals with the size of 5-10 mu m, the phenomenon that the size and the shape of the crystals on the surface of the membrane are greatly different is avoided, and the relatively smooth and complete CHA molecular sieve membrane with the membrane thickness of about 20 mu m is formed. The permeability and separability of the CHA molecular sieve membranes, which were located in the membrane module units, were measured using a gas separation test rig as shown in fig. 5. SO of the film under the conditions of 0.15MPa and 25 DEG C₂/NO₂The separation coefficient can reach 31, SO₂The permeation flux reaches 3.72 multiplied by 10^-7·mol·m^-2·Pa^-1·s^-1。

Example 2

0.05g of CHA seed crystal is dissolved in 20mL of deionized water, 2 drops of 20 wt% hydrochloric acid solution are added, the mixture is stirred for 1 hour on a magnetic stirrer, and the mixture is kept still for 10 minutes to obtain uniform and stable seed crystal suspension. The seed-spreading treatment was the same as in example 1, and the seed crystal was fixed to the α -Al layer after the seed-spreading treatment₂O₃Drying the ceramic surface at 120 ℃ for 4 h.

According to 1SiO₂:0.1NaOH:0.12KOH:0.05Al₂O₃:0.1TMAdaOH:80H₂Preparing gel according to the molar ratio of O, stirring 3.1M of sodium silicate, pseudo-boehmite, sodium hydroxide, potassium hydroxide, TMADAOH and water in an oil bath at 40 ℃ for 6h to obtain precursor gel, putting the carrier with the CHA molecular sieve seed crystal and the precursor gel into a reaction kettle, reacting at 150 ℃ for 96h under the hydrothermal condition, heating the obtained CHA molecular sieve membrane to 250 ℃ for 2h, continuously heating to 450 ℃ for calcining for 18h, wherein the heating and cooling rate is 2K/min. The membrane surface diagram and the cross-sectional diagram of the CHA molecular sieve membrane are respectively shown in fig. 2(a) and fig. 2(b), CHA molecular sieve crystals are cross-linked and intergrown on the surface of a carrier, and grow in a staggered manner, the surface of the carrier is covered with cubic crystals with the size of 5-10 mu m, the surface is uneven, and the complete CHA molecular sieve membrane with the membrane thickness of about 10-25 mu m is also formed. The CHA molecular sieve membrane permeability and separability were measured using the gas separation test rig shown in figure 5,the CHA molecular sieve membrane is positioned in a membrane group unit. SO of the film under the conditions of 0.3MPa and 25 DEG C₂/NO₂The separation coefficient can reach 45, SO₂The permeation flux reaches 1.04X 10^-7·mol·m^-2·Pa^-1·s^-1。

Example 3

Dissolving 0.08g of CHA seed crystal into 20mL of deionized water, adding 4 drops of 5 wt% hydrochloric acid solution, stirring for 5h on a magnetic stirrer, and standing for 15min to obtain uniform and stable seed crystal suspension. The seed-spreading treatment was the same as in example 1, and the seed crystal was fixed to the α -Al layer after the seed-spreading treatment₂O₃Drying the ceramic surface for 4h at 160 ℃.

According to 1SiO₂:0.2NaOH:0.08KOH:0.01Al₂O₃:0.3TMAdaOH:120H₂Preparing gel according to the molar ratio of O, stirring fumed silica, pseudo-boehmite, sodium hydroxide, potassium hydroxide, TMADAOH and water in an oil bath at the temperature of 80 ℃ for 8 hours to obtain precursor gel, putting the carrier with the CHA molecular sieve seed crystal and the precursor gel into a reaction kettle, reacting at the temperature of 180 ℃ for 48 hours under the hydrothermal condition, and conventionally calcining the obtained CHA molecular sieve membrane in a tubular furnace at the temperature of 500 ℃, wherein the temperature rising and falling rate is 0.5K/min. The membrane surface diagram and the cross-sectional diagram of the CHA molecular sieve membrane are respectively shown in fig. 3(a) and fig. 3(b), CHA molecular sieve crystals are cross-linked and intergrown on the surface of a carrier, the crystals on the surface of the carrier are mainly 2-5 μm in size, a small amount of cubic crystals with the size of about 10 μm are distributed on the membrane, and the CHA molecular sieve membrane with the thickness of about 5 μm and smooth and flat is formed. The CHA molecular sieve membranes were measured for permeability and separability using a gas separation test rig as shown in fig. 5, with the CHA molecular sieve membranes located in membrane module units. SO of the film under the conditions of 0.2MPa and 25 DEG C₂/NO₂The separation coefficient can reach 28, SO₂The permeation flux reaches 3.63 multiplied by 10^-7·mol·m^-2·Pa^-1·s^-1。

Example 4

0.15g of CHA seed crystal is dissolved in 20mL of deionized water, 3 drops of 10 wt% hydrochloric acid solution are added, the mixture is stirred for 5 hours on a magnetic stirrer, and a uniform and stable seed crystal suspension is obtained after standing for 15 min. Seed treatment and phase 1Meanwhile, after the seed is paved, the seed crystal is better fixed on the alpha-Al₂O₃Drying the ceramic surface for 24h at 200 ℃.

According to 1SiO₂:0.4NaOH:0.2KOH:0.005Al₂O₃:0.4TMAdaOH:160H₂Preparing gel according to the molar ratio of O, stirring 3.6M sodium silicate, aluminum hydroxide, sodium hydroxide, potassium hydroxide, TMADAOH and water in an 80 ℃ oil bath for 6h to obtain precursor gel, putting the carrier with the CHA molecular sieve seed crystal and the precursor gel into a reaction kettle, reacting for 12h at 220 ℃ under the hydrothermal condition, heating the obtained CHA molecular sieve membrane to 300 ℃ and keeping the temperature for 4h, continuously heating to 550 ℃ and calcining for 6h, wherein the heating and cooling rate is 0.4K/min. The film surface diagram and the cross-sectional diagram of the CHA molecular sieve film are respectively shown in fig. 4(a) and fig. 4(b), CHA molecular sieve crystals are mutually crosslinked and highly intergrown on the surface of a carrier, cubic crystals with the size of 2-10 mu m are covered on the surface of the carrier, large and small crystals are grown in a staggered mode, and the CHA molecular sieve film with the film thickness of about 25 mu m and smooth and flat is formed. The CHA molecular sieve membranes were measured for permeability and separability using a gas separation test rig as shown in fig. 5, with the CHA molecular sieve membranes located in membrane module units. SO of the film under the conditions of 0.15MPa and 25 DEG C₂/NO₂The separation coefficient can reach 37, SO₂The permeation flux reaches 1.82 multiplied by 10^-7·mol·m^-2·Pa^-1·s^-1。

Example 5

0.06g of CHA seed crystal is dissolved in 20mL of deionized water, 3 drops of 10 wt% hydrochloric acid solution are added, the mixture is stirred for 4 hours on a magnetic stirrer, and a uniform and stable seed crystal suspension is obtained after the mixture is kept stand for 5 min. The seed-spreading treatment was the same as in example 1, and the seed crystal was fixed to the α -Al layer after the seed-spreading treatment₂O₃Drying the ceramic surface for 2h at 200 ℃.

According to 1SiO₂:0.2HF:0.2TMAdaOH:30H₂Preparing gel according to the molar ratio of O, stirring 40% silica sol, hydrofluoric acid, TMADAOH and water in an oil bath at 25 ℃ for 6h to obtain precursor gel, putting the carrier with the CHA molecular sieve seed crystal and the precursor gel into a reaction kettle, reacting at 155 ℃ for 48h under the hydrothermal condition, quickly treating the obtained CHA molecular sieve membrane in a 800 ℃ tubular furnace for 8min, and directly putting the CHA molecular sieve membrane into a tube furnace at 450 DEG CThe temperature in the furnace is kept for 12 hours, and the temperature is reduced to the normal temperature at the cooling rate of 1K/min.

Example 6

According to 1SiO₂:0.2NaOH:0.01Al₂O₃:0.3TMAdaOH:120H₂Preparing gel according to the molar ratio of O, stirring fumed silica, pseudo-boehmite, sodium hydroxide, TMADAOH and water in an oil bath at the temperature of 80 ℃ for 8 hours to obtain precursor gel, putting the carrier with the CHA molecular sieve seed crystal and the precursor gel into a reaction kettle, reacting for 48 hours at the temperature of 180 ℃ under the hydrothermal condition, and conventionally calcining the obtained CHA molecular sieve membrane in a tubular furnace at the temperature of 500 ℃, wherein the heating and cooling rate is 0.5K/min. The CHA molecular sieve membranes were measured for permeability and separability using a gas separation test rig as shown in fig. 5, with the CHA molecular sieve membranes located in membrane module units. SO of the film under the conditions of 0.2MPa and 25 DEG C₂/NO₂The separation coefficient can reach 8, SO₂The permeation flux reaches 3.54 multiplied by 10^-7mol·m^-2·Pa^-1·s^-1。

The CHA molecular sieve membrane provided by the embodiments of the present invention, and the preparation method and application thereof are described in detail above. The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core ideas; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

As used in the specification and claims, certain terms are used to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. "substantially" means within an acceptable error range, and a person skilled in the art can solve the technical problem within a certain error range to substantially achieve the technical effect. The following description is of the preferred embodiment for carrying out the invention, and is made for the purpose of illustrating the general principles of the invention and not for the purpose of limiting the scope of the invention. The scope of the present invention is defined by the appended claims.

It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a good or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such good or system. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a commodity or system that includes the element.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

The foregoing description shows and describes several preferred embodiments of the invention, but as aforementioned, it is to be understood that the invention is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the inventive concept as expressed herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A CHA molecular sieve membrane is characterized in that the CHA molecular sieve membrane is a silicon-aluminum type CHA molecular sieve membrane; the mass ratio of silicon to aluminum of the silicon-aluminum type CHA molecular sieve membrane is 50;

the CHA molecular sieve membrane is prepared by adding metal cations during preparation so as to promote ordered growth of CHA crystals;

the preparation method of the CHA molecular sieve membrane comprises the following steps of adopting an original CHA molecular sieve as a seed crystal to induce and synthesize a compact high-silicon CHA molecular sieve membrane: seed spreading is realized on a carrier by using a seed crystal suspension, seed crystals are fixed in a high-temperature drying mode, a compact and smooth CHA molecular sieve membrane is induced and synthesized, and a template agent in the CHA molecular sieve membrane is removed by high-temperature calcination to open a molecular sieve pore channel;

the crystal size of the seed crystal is 0.1-10 mu m;

the quantity ratio of the silicon and aluminum in the seed crystal ranges from 5 to 100;

the preparation method comprises the following specific steps:

s1, preparing a seed crystal suspension: mixing the seed crystal with deionized water, and stirring after ultrasonic treatment to obtain the uniformly dispersed seed crystal suspension;

s2, preparing a molecular sieve seed crystal carrier: standing the seed crystal suspension, spreading seeds on a carrier, and finally drying and fixing to obtain the molecular sieve seed crystal carrier;

s3, preparing precursor gel: stirring a mixed solution A containing a silicon source, a metal hydroxide, an aluminum source, trimethyl adamantanamine hydroxide and water at the temperature of 80 ℃ to obtain precursor gel;

s4, preparing a CHA molecular sieve membrane: mixing the molecular sieve seed crystal carrier obtained in the step S2 with the precursor gel obtained in the step S3, and carrying out hydrothermal reaction for 48 hours at 180 ℃ to obtain a CHA molecular sieve membrane containing a template agent;

s5, calcining: calcining and activating the CHA molecular sieve membrane at the temperature of 500 ℃ to finally obtain the CHA molecular sieve membrane;

the mixture A comprises the following components in percentage by mass: 1SiO₂: 0.2NaOH:0.08KOH:0.01Al₂O₃:0.3TMAdaOH:120H₂O；

The film thickness of the CHA molecular sieve film is 5 mu m;

the CHA molecular sieve membrane is used for treating SO under the conditions of 0.2MPa and 25 DEG C₂/NO₂The separation coefficient reaches 28, SO₂The permeation flux reaches 3.63 multiplied by 10^-7 mol•m^-2•Pa^-1•s^-1。

2. The CHA molecular sieve membrane of claim 1 in flue gas SO₂With NO₂The separation and recovery of (1).