CN108117089B

CN108117089B - Chabazite molecular sieve and application thereof

Info

Publication number: CN108117089B
Application number: CN201611070989.9A
Authority: CN
Inventors: 王树东; 郭亚; 孙天军; 赵生生; 乌荣光
Original assignee: Dalian Wanlin Garments Co ltd; Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Wanlin Garments Co ltd; Dalian Institute of Chemical Physics of CAS
Priority date: 2016-11-29
Filing date: 2016-11-29
Publication date: 2021-08-27
Anticipated expiration: 2036-11-29
Also published as: CN108117089A

Abstract

The invention relates to a chabazite molecular sieve and application thereof, belonging to the field of preparation of molecular sieve inorganic microporous materials. The molecular sieve is an inorganic porous material with a CHA topological structure formed by self-assembly of silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron, the Si/Al molar ratio is between 4 and 8, and the BET specific surface area is 400-²The grain size is 0.8-20 microns. In the preparation of the molecular sieve, alkyl ammonium hydroxide and adamantyl ammonium hydroxide are used as double templates, so that the use amount of expensive adamantyl ammonium hydroxide is reduced, and the preparation cost is reduced. The molecular sieve has larger specific surface area and pore volume, and the eight-membered ring small pore window is favorable for improving CO₂/N₂Separation performance, and the balance cation outside the framework is beneficial to improving N₂/O₂Separation performance.

Description

Chabazite molecular sieve and application thereof

Technical Field

The present invention belongs to the preparation of molecular sieve microporous material and its application in CO₂/N₂And N₂/O₂The technical field of mixed gas separation, in particular to a chabazite molecular sieve and application thereof.

Background

Chabazite has the CHA topology, and the framework is formed into an ellipsoidal cage structure by the staggered connection of double six-membered rings. The theoretical diameter of the eight-membered ring window is 0.38nm multiplied by 0.38nm, and the eight-membered ring window belongs to a typical small-pore molecular sieve. High silicon to aluminum ratio (Si/Al)>20) The chabazite has good hydrophobicity and hydrothermal stability, and simultaneously has large specific surface area and pore volume, so that a certain adsorption and separation performance can be still maintained under the condition of the presence of water vapor. In addition, the eight-membered ring small pore window is beneficial to playing the role of sieving the mixed gas. Such as CO₂/N₂Separation and N₂/O₂Separation, and the like. CO 2₂/N₂The effective separation of the carbon has important significance for carbon capture, and CO₂Than N₂Has a small dynamic diameterCan be preferentially diffused into the pores of the chabazite molecular sieve, and CO is simultaneously diffused into the pores₂Has high polarizability and quadrupole moment, and is preferentially adsorbed. N is a radical of₂/O₂The effective separation has important significance on the air separation by the pressure swing adsorption method, and N is₂Has larger quadrupole moment and is preferentially absorbed.

Naturally occurring chabazite is generally intergrown with other zeolites and requires pre-treatment to remove impurities to obtain high purity chabazite, which increases its production cost and is not conducive to industrial applications. The artificially synthesized chabazite is generally obtained by uniformly mixing a silicon source, an aluminum source and an alkali source by a hydrothermal method, adding a proper organic template agent, and reacting under a certain hydrothermal condition. Patent CN 104163434a discloses a method for synthesizing chabazite molecular sieve with high silica-alumina ratio by using seed crystal method, which is to mix a certain amount of silica sol, potassium hydroxide, sodium hydroxide, aluminum sulfate and N, N-trimethylammonamantadine hydroxide uniformly, then to obtain the product through crystallization, roasting and ammonium exchange. Patent CN 105236440a discloses a method for synthesizing CHA molecular sieve by using USY molecular sieve as silicon source and aluminum source and tetraethylammonium hydroxide as template agent. The USY molecular sieve is used as a silicon source and an aluminum source, so that the silicon-aluminum ratio of the raw material and the silicon-aluminum ratio of the product cannot be effectively regulated. US patent US 4544538 discloses a method for synthesizing high-silicon (Si/Al 15-30) chabazite, using N, N-trimethyl-1-adamantammonium as a template. The synthetic method of chabazite reported in the literature at present mostly uses an organic template, and the commonly used organic template is amantadine. The chabazite synthesized without using an organic template has low crystallinity and is difficult to meet the requirements of practical application.

Disclosure of Invention

The invention aims to provide a chabazite molecular sieve, a preparation method and application thereof, and the method has the advantages of low synthesis cost, good thermal stability and hydrothermal stability of the product and the like, and can be used for CO₂/N₂And N₂/O₂The adsorption separation of (3).

A chabazite molecular sieve is an inorganic porous material with CHA topological structure formed by self-assembly of silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron, and Si/Al molar ratio is mediumBetween 4 and 8, the BET specific surface area is 400-800m²The crystal grain is 0.8-20 microns, ion exchange modification is carried out by using different metal cations, and a binary composite template agent is prepared by the following specific steps:

(1) dissolving a proper amount of sodium hydroxide and an aluminum source in a certain amount of water, and cooling to room temperature;

(2) slowly adding a mixture consisting of a proper amount of a template agent R1 and a template agent R2 under stirring, and continuously stirring for 0.5-1 hour to fully mix the components;

(3) slowly adding a proper amount of silicon source under vigorous stirring, continuously stirring and aging for 5-24 hours at room temperature, and then dynamically crystallizing for 2-5 days at the temperature of 120-;

(4) after the reaction is finished, carrying out vacuum filtration to separate out a solid product, washing until the pH is less than 8, drying at 100 ℃ for 6-12 hours, roasting at 500 ℃ and 600 ℃ for 4-10 hours, wherein the roasting atmosphere is air;

(5) exchanging the obtained molecular sieve raw powder with different metal ions at the temperature of 40-100 ℃;

(6) and (3) activating the ion-exchanged molecular sieve powder in vacuum or inert atmosphere to obtain the chabazite molecular sieve with excellent adsorption performance.

In the step (2), alkyl ammonium hydroxide (R1) and adamantyl ammonium hydroxide (R2) are used as double templates, and the molar ratio of R1 to R2 is 0.5: 1-2: 1.

The template R1 in the step (2) is selected from one of tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide and tetrabutyl ammonium hydroxide; r2 is selected from one of adamantane, amantadine, 1, 3-adamantanediamine, 2-methyladamantane and N, N, N-trimethyl-1-adamantylammonium hydroxide.

The silicon source is selected from one of silica sol with the mass fraction of 30% and sodium silicate nonahydrate; the aluminum source is one or more selected from aluminum hydroxide, sodium aluminate, aluminum sol, aluminum sulfate octadecahydrate or aluminum nitrate nonahydrate, one of the aluminum hydroxide and the aluminum hydroxide in the aluminum source is more than 10% by weight.

The preparation method comprises the following raw materials: SiO 2₂/Al₂O₃In a molar ratio of 40:1 to 120:1, Na₂O/Al₂O₃The molar ratio of (A) to (B) is 2: 1-12: 1, (R1+ R2)/Al₂O₃In a molar ratio of 2:1 to 20:1, H₂O/Al₂O₃The molar ratio of (A) to (B) is 1000:1 to 5000: 1.

The metal ions used for ion exchange are selected from Ag⁺、Li⁺、Ca²⁺One or a combination thereof.

The specific conditions for exchanging with different metal ions in the step (5) are as follows: the metal salt is selected from one of nitrate, acetate and chloride corresponding to corresponding metal ions, preferably chloride; the concentration of the used metal ions is 0.1-2 mol/L, the target cations are excessive by 2-8 times, and the exchange temperature is 40-100 ℃; the exchange time is 2-5 hours each time, and the exchange is repeated for 2-4 times.

The cation exchange degree is more than 95%.

Application of chabazite molecular sieve for CO₂/N₂/O₂Separation of gas mixture, in which CO is present at room temperature and pressure₂The adsorption capacity is 2-8 mmol/g, N₂The adsorption amount is 0.5 to 1.2mmol/g, O₂The adsorption amount is 0.2 to 0.5 mmol/g.

The aim of the invention is achieved by the following measures that chabazite molecular sieve raw powder is prepared by a hydrothermal method, then the template agent is removed by high-temperature roasting, then different metal cations are used for ion exchange, and finally the modified chabazite molecular sieve adsorbent is obtained by vacuum activation or inert atmosphere activation. The metal ions used for the ion exchange modification include Ca²⁺、Li⁺And Ag⁺. The template agent is a mixture of alkyl ammonium hydroxide (R1) and adamantyl ammonium hydroxide (R2), and the use of cheap alkyl ammonium hydroxide can reduce the use amount of expensive adamantyl ammonium hydroxide and reduce the production cost.

The synthesis method of the zeolite molecular sieve comprises a hydrothermal method, a solid-phase synthesis method, a microwave-assisted synthesis method, an ultrasonic-assisted synthesis method, a hydroxyl radical accelerated crystallization method and the like. Hydrothermal method is the most commonly used method for synthesizing molecular sieves, and generally refers to the synthesis of molecular sieve crystals by high temperature and high pressure reaction in the presence of water or other solvents. Based on this, solvothermal and ionothermal processes have been derived. Factors affecting the synthesis of molecular sieves include alkali concentration, charge Si/Al, temperature, template species, and the like.

In a raw material reaction system, the molar ratio of the double templates is R1/R2 is 0.5: 1-2: 1, the addition of R1 effectively reduces the dosage of R2, and meanwhile, the product crystallinity is not greatly influenced, so that the production cost is reduced.

The silicon source used in the invention is one of silica sol and sodium silicate nonahydrate with the mass fraction of 30%; the aluminum source is one or more of aluminum hydroxide, sodium aluminate, aluminum sol, aluminum sulfate octadecahydrate and aluminum nitrate nonahydrate, wherein one of the aluminum source is aluminum hydroxide. The proportion of each component in the raw material mixed liquor is crucial to the specific structure of the chabazite, and the proportion of each component in the raw material mixed liquor is as follows: SiO 2₂/Al₂O₃In a molar ratio of 40:1 to 120:1, Na₂O/Al₂O₃The molar ratio of (A) to (B) is 2: 1-12: 1, (R1+ R2)/Al₂O₃In a molar ratio of 2:1 to 20:1, H₂O/Al₂O₃The molar ratio of (A) to (B) is 1000:1 to 5000: 1.

The ion exchange modification of the synthesized molecular sieve raw powder is a main means for making the molecular sieve have excellent adsorption and separation performance. The metal ions used in the present invention include Ca²⁺、Li⁺And Ag⁺The metal salt is selected from one of nitrate, acetate and chloride corresponding to corresponding metal ions. The ion exchange sequence is Ca first²⁺Exchange, then respectively carry out Li⁺And Ag⁺And exchanging to obtain the chabazite molecular sieve exchanged with different metal ions. Since the ion exchanged molecular sieve contains a certain amount of moisture, which affects the adsorption performance of the molecular sieve, it is necessary to activate the modified molecular sieve to remove the moisture therefrom. The activation method adopted by the invention comprises a vacuum heating activation method and an inert atmosphere heating activation method, and the activation temperature is 300-600 ℃.

The present invention providesThe preparation method of chabazite has the advantages of low production cost, good thermal stability and hydrothermal stability of the product and the like. The BET specific surface area of the modified chabazite is 400-800m²The pore distribution is between 0.3 and 0.8nm, and the Si/Al molar ratio is between 4 and 8. The uniform micropore distribution and the strong polar surface are beneficial to improving the CO₂/N₂And N₂/O₂Separation performance.

Drawings

FIG. 1 is an XRD spectrum of the crystalline product at 25.3 and 51.5 feeds Si/Al, respectively.

FIG. 2 is a scanning electron micrograph of the crystalline product at a magnification of 1000 times and 5000 times, respectively, at a charge Si/Al of 51.5.

FIG. 3 shows Na prepared in example 1⁺Exchanged chabazite for CO at 298K₂、N₂And O₂Adsorption isotherm (P) of₀At standard atmospheric pressure).

Detailed Description

The invention is further illustrated by the following description of specific embodiments in conjunction with the accompanying drawings, which are not to be construed as limiting the invention. All numbers appearing in the description and claims of the invention are not to be understood as absolute precise values which are within the tolerances understood by those skilled in the art and allowed by the common general knowledge.

Example 1

(1) 0.4167g NaOH and 0.164g NaAlO₂Dissolved in 26.2g of deionized water, and 10.55g N, N, N-trimethyl-1-adamantyl ammonium hydroxide was added with stirring. Stirring was continued until the solid was completely dissolved and cooled to room temperature, 10.1g of 30% silica sol were slowly added dropwise with vigorous stirring and stirring was continued for 6 hours. Transferring the mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, and dynamically crystallizing for 4 days at 160 ℃. And naturally cooling to room temperature after the reaction is finished, filtering out a solid product in vacuum, and washing with a large amount of deionized water until the pH value of the filtrate is less than 8. Drying the product at 100 ℃ for 12 hours to obtain white powder, and then roasting at 550 ℃ for 12 hours to remove the template agent, wherein the roasting atmosphere is air.

(2) Weighing 1g of molecular sieve raw powder, adding the molecular sieve raw powder into a round-bottom flask, and adding 60ml of 1mol/L CaCl₂The solution was ion exchanged for 5 hours with heating in a water bath at 80 ℃ and magnetic stirring. After the reaction is finished, filtering and separating out a solid, and washing until chloride ions can not be detected in the filtrate. The above procedure was repeated twice and the product was dried at 100 ℃ for 12 hours. The dried product was activated by heating to 300 ℃ under vacuum for 6 hours.

The XRD pattern of the prepared chabazite molecular sieve raw powder is shown as a diffraction pattern corresponding to 25.3 Si/Al in figure 1, and the morphology of the raw powder is shown as figure 2.

Example 2

(1) 0.4167g NaOH and 0.156g Al (OH)₃Dissolved in 21.36g of deionized water, and 10.55g N, N, N-trimethyl-1-adamantyl ammonium hydroxide was added with stirring. Stirring was continued until the solid was completely dissolved and cooled to room temperature, 10.1g of 30% silica sol were slowly added dropwise with vigorous stirring and stirring was continued for 6 hours. Transferring the mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, and dynamically crystallizing for 4 days at 160 ℃. And naturally cooling to room temperature after the reaction is finished, filtering out a solid product in vacuum, and washing with a large amount of deionized water until the pH value of the filtrate is less than 8. Drying the product at 100 ℃ for 12 hours to obtain white powder, and then roasting at 550 ℃ for 12 hours to remove the template agent, wherein the roasting atmosphere is air.

(2) Weighing 1g of molecular sieve raw powder, adding the molecular sieve raw powder into a round-bottom flask, adding 60ml of 1mol/L NaCl solution, and carrying out ion exchange for 5 hours under the conditions of water bath heating at 80 ℃ and magnetic stirring. After the reaction is finished, filtering and separating out a solid, and washing until chloride ions can not be detected in the filtrate. The above procedure was repeated twice and the product was dried at 100 ℃ for 12 hours. The dried product was activated by heating to 300 ℃ under vacuum for 6 hours.

Prepared Na⁺CO of exchanged chabazite molecular sieves₂、N₂And O₂The adsorption performance of (2) is shown in FIG. 3.

Example 3

(1) 0.4167g NaOH and 0.078g Al (OH)₃Dissolved in 21.22g of deionized water and stirredNext, 10.55g N, N, N-trimethyl-1-adamantyl ammonium hydroxide was added. Stirring was continued until the solid was completely dissolved and cooled to room temperature, 10.3g of 30% silica sol were slowly added dropwise with vigorous stirring and stirring was continued for 6 hours. Transferring the mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, and dynamically crystallizing for 4 days at 160 ℃. And naturally cooling to room temperature after the reaction is finished, filtering out a solid product in vacuum, and washing with a large amount of deionized water until the pH value of the filtrate is less than 8. Drying the product at 100 ℃ for 12 hours to obtain white powder, and then roasting at 550 ℃ for 12 hours to remove the template agent, wherein the roasting atmosphere is air.

(2) Weighing 1g of molecular sieve raw powder, adding the molecular sieve raw powder into a round-bottom flask, adding 60ml of 2mol/L LiCl solution, and carrying out ion exchange for 5 hours under the conditions of water bath heating at 80 ℃ and magnetic stirring. After the reaction is finished, filtering and separating out a solid, and washing until chloride ions can not be detected in the filtrate. The above procedure was repeated twice and the product was dried at 100 ℃ for 12 hours. The dried product was activated by heating to 300 ℃ under vacuum for 6 hours.

The XRD pattern of the prepared chabazite molecular sieve raw powder is shown as a diffraction pattern corresponding to Si/Al 51.5 in figure 1.

Example 4

(1) 0.4167g NaOH and 0.164g NaAlO₂Dissolved in 24g of deionized water, and a mixture of 5.28g N, N, N-trimethyl-1-adamantyl ammonium hydroxide and 2.1g tetraethylammonium hydroxide was added with stirring. Stirring was continued until the solid was completely dissolved and cooled to room temperature, 10.1g of 30% silica sol was slowly added dropwise with vigorous stirring and stirring was continued for 6 hours. Transferring the mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, and dynamically crystallizing for 4 days at 160 ℃. And naturally cooling to room temperature after the reaction is finished, filtering out a solid product in vacuum, and washing with a large amount of deionized water until the pH value of the filtrate is less than 8. Drying the product at 100 ℃ for 12 hours to obtain white powder, and then roasting at 550 ℃ for 12 hours to remove the template agent, wherein the roasting atmosphere is air.

Example 5

(1) 0.4167g NaOH and 0.164g NaAlO₂Dissolved in 24g of deionized water, and a mixture of 5.28g N, N, N-trimethyl-1-adamantyl ammonium hydroxide and 2.1g tetraethylammonium hydroxide was added with stirring. Stirring was continued until the solid was completely dissolved and cooled to room temperature, 10.1g of 30% silica sol were slowly added dropwise with vigorous stirring and stirring was continued for 6 hours. Transferring the mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, and dynamically crystallizing for 4 days at 160 ℃. And naturally cooling to room temperature after the reaction is finished, filtering out a solid product in vacuum, and washing with a large amount of deionized water until the pH value of the filtrate is less than 8. Drying the product at 100 ℃ for 12 hours to obtain white powder, and then roasting at 550 ℃ for 12 hours to remove the template agent, wherein the roasting atmosphere is air.

(2) Weighing 1g of Na⁺The exchanged molecular sieves were added to a round bottom flask, 60ml of 0.1mol/L AgNO was added₃The solution was ion exchanged for 5 hours with heating in a water bath at 80 ℃ and magnetic stirring. After the reaction is finished, filtering and separating out a solid, and washing until chloride ions can not be detected in the filtrate. The above procedure was repeated twice and the product was dried at 100 ℃ for 12 hours. The dried product was activated by heating to 300 ℃ under vacuum for 6 hours.

Example 6

(1) 0.4167g NaOH and 0.164g Al (OH)₃Dissolved in 24g of deionized water, and a mixture of 5.28g N, N, N-trimethyl-1-adamantyl ammonium hydroxide and 2.1g tetraethylammonium hydroxide was added with stirring. Stirring was continued until the solid was completely dissolved and cooled to room temperature, 10.1g of 30% silica sol was slowly added dropwise with vigorous stirring and stirring was continued for 6 hours. Transferring the mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene lining, and dynamically crystallizing for 4 days at 160 ℃. Naturally cooling to room temperature after the reaction is finished, filtering out a solid product in vacuum, and removing a large amount of solid productThe seed water is washed until the filtrate pH is less than 8. Drying the product at 100 ℃ for 12 hours to obtain white powder, and then roasting at 550 ℃ for 12 hours to remove the template agent, wherein the roasting atmosphere is air.

Claims

1. For CO₂/N₂/O₂The chabazite molecular sieve for the adsorption separation of the mixed gas is characterized in that: the molecular sieve is an inorganic porous material with a CHA topological structure formed by self-assembly of silicon-oxygen tetrahedron and aluminum-oxygen tetrahedron, the Si/Al molar ratio is between 4 and 8, and the BET specific surface area is 400-²The crystal grain is 0.8-20 microns, ion exchange modification is carried out by using different metal cations, and a binary composite template agent is prepared in the preparation process, wherein the preparation method comprises the following specific steps:

(2) slowly adding a mixture consisting of a proper amount of a template agent R1 and a template agent R2 as a double template agent under stirring, and continuously stirring for 0.5-1 hour to fully mix the components; the molar ratio of the template agent R1 to R2 is 0.5: 1-2: 1;

(6) the ion exchanged molecular sieve powder is activated in vacuum or inert atmosphere to obtain the chabazite molecular sieve with excellent adsorption performance;

the metal ion used for ion exchange is Ag⁺、Li⁺、Ca²⁺(ii) a The ion exchange sequence is Ca first²⁺Exchange, then respectively carry out Li⁺And Ag⁺Exchanging to obtain chabazite molecular sieves exchanged by different metal ions;

the raw materials meet the following requirements: SiO 2₂/Al₂O₃In a molar ratio of 40:1 to 120:1, Na₂O/Al₂O₃The molar ratio of (A) to (B) is 2: 1-12: 1, (R1+ R2)/Al₂O₃In a molar ratio of 2:1 to 20:1, H₂O/Al₂O₃The molar ratio of (A) to (B) is 1000:1 to 5000: 1.

2. A chabazite molecular sieve according to claim 1, wherein said templating agent R1 in step (2) is selected from the group consisting of one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; r2 is selected from one of adamantane, amantadine, 1, 3-adamantanediamine, 2-methyladamantane and N, N, N-trimethyl-1-adamantylammonium hydroxide.

3. A chabazite molecular sieve according to claim 1, wherein the silicon source used is selected from the group consisting of 30% by weight silica sol and sodium silicate nonahydrate; the aluminum source is a mixture of aluminum hydroxide or aluminum hydroxide and one or more of sodium aluminate, aluminum sol, aluminum sulfate octadecahydrate or aluminum nitrate nonahydrate, and the weight ratio of the aluminum hydroxide in the aluminum source is more than 10%.

4. A chabazite molecular sieve according to claim 1, characterized in that the specific conditions for the exchange with different metal ions in step (5) are: the used metal salt is selected from one of nitrate, acetate and chloride corresponding to corresponding metal ions, the concentration of the used metal ions is 0.1-2 mol/L, the target cation is excessive by 2-8 times, and the exchange temperature is 40-100 ℃; the exchange time is 2-5 hours each time, and the exchange is repeated for 2-4 times.

5. A chabazite molecular sieve according to claim 1, characterized in that said cation exchange degree is greater than 95%.

6. Use of a chabazite molecular sieve according to claim 1, characterized in that said molecular sieve is used for CO₂/N₂/O₂Separation of gas mixture, in which CO is present at room temperature and pressure₂The adsorption capacity is 2-8 mmol/g, N₂The adsorption amount is 0.5 to 1.2mmol/g, O₂The adsorption amount is 0.2 to 0.5 mmol/g.