CN117208927A - High-efficiency capturing low-concentration CO in humid environment 2 High-silicon LTA molecular sieve as well as preparation method and application thereof - Google Patents

High-efficiency capturing low-concentration CO in humid environment 2 High-silicon LTA molecular sieve as well as preparation method and application thereof Download PDF

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CN117208927A
CN117208927A CN202311254359.7A CN202311254359A CN117208927A CN 117208927 A CN117208927 A CN 117208927A CN 202311254359 A CN202311254359 A CN 202311254359A CN 117208927 A CN117208927 A CN 117208927A
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molecular sieve
lta
silicon
adsorption
humid environment
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卢晗锋
方国楠
柯权力
潘鹏云
陈竞
熊峰
徐振涛
卢予妍
陆帝
洪良骏
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Zhejiang University of Technology ZJUT
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Zhejiang University of Technology ZJUT
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/40—Capture or disposal of greenhouse gases of CO2

Abstract

The invention relates to a method for efficiently capturing low-concentration CO in a humid environment 2 The molecular sieve has LTA molecular sieve configuration, and the chemical composition molar ratio is aAl 2 O 3 ：bSiO 2 The elemental composition contains more tetravalent element Si and less trivalent element Al, the molar ratio of oxides (m=sio 2 /Al 2 O 3 ) The numerical value is 2-10. The molecular sieve adopts an initial gel prepared from an inorganic structure guiding agent, water, a silicon source and an aluminum source, adjusts the charge density of a double organic template agent, assembles different cage structures of the LTA molecular sieve for synthesis, and simultaneously realizes high silicon-aluminum ratio and high water resistance. Compared with commercial molecular sieve, the high-silicon LTA molecular sieve in the invention can be used for CO with water vapor 2 /N 2 Preferential CO adsorption in a large amount in the system 2 . In application to 97%The molecular sieve of the present invention can maintain more than about 90% CO in a humid environment of relative humidity 2 Adsorption capacity and good cyclic regeneration capacity.

Description

High-efficiency capturing low-concentration CO in humid environment 2 High-silicon LTA molecular sieve as well as preparation method and application thereof
Technical Field
The invention relates to a method for efficiently capturing low-concentration CO in a humid environment 2 High-silicon LTA molecular sieve, preparation method and application thereof, and CO of high-silicon LTA molecular sieve in a wet gas environment 2 /N 2 Preferential CO adsorption in a large amount in the system 2 And has good cyclic regeneration capability.
Background
The increase in the concentration of carbon dioxide in the atmosphere causes a series of problems as to how to reduce atmospheric CO 2 The concentration is of great importance. Carbon Capture Utilization and Storage (CCUS) is the treatment of CO 2 An efficient method of emissions. Selective separation of CO from natural gas 2 Capturing low concentration CO from the atmosphere 2 Of technical importance for improving gas purity and preventing corrosion of industrial facilities, in proposed technology to address these challenges, adsorption of various kinds of ordered nanoporous materials drives CO due to low energy required for regeneration and non-corrosiveness 2 Capture is considered an alternative to current commercial processes using aqueous amine solutions (chem. Soc. Rev.,2020,49,8584-8686). Zeolites have advantages in terms of physicochemical stability and synthesis costs compared to other solid adsorbents such as metal organic frameworks.
Zeolites are a representative adsorbent due to the nature of their porous structure. The zeolite is formed to contain mainly oxygen, silicon and aluminumThe aluminosilicate solid with the three-dimensional framework has larger pore volume and pore diameter and more regular pore structure, and good adsorption capacity is revealed. And CO 2 Dynamic diameter of (2)And N 2 />There is a great interest in small pore zeolites because their effective size of the 8-membered ring (8 MRs) can be adjusted to limit the larger N 2 Molecular ingress while allowing smaller CO 2 And (5) molecular adsorption. Zeolite 13X has been found to remove some carbon dioxide from flue gas at low temperatures and the surface can be controlled by post-modification of the zeolite, such as ion exchange (Applied Energy,2017, 191:87-98).
The pore size of conventional zeolite a (framework LTA, si/al=1.0) can be adjusted to the pore size by changing the type of counter cation of the framework introducedTo->To change between and thereby at CO 2 Significant changes in adsorption capacity and selectivity occur. However, classical LTA zeolites are currently commercially available as type a molecular sieves for use as desiccants, water absorbents due to their low hydrothermal stability and low hydrophobicity. Patent CN110467196A reports a preparation method without a template agent, and the preparation method is obtained by crystallization for 7 hours at 40 ℃, and is simple and convenient; patent CN110498423A reports a method for producing an A-type molecular sieve by using a gelatinization additive, crystallizing for 1-6 hours at 70-100 ℃, and obtaining a 400-800nm nanoscale molecular sieve which is smaller than the 2 mu m A-type molecular sieve on the market after ultrasonic treatment; patent CN107986296B reports that a high silica-alumina ratio type a molecular sieve with a silica-alumina ratio of 1.5-8 can achieve the effects of shortening the synthesis period, improving the yield and reducing the use of an organic template agent by adding seed crystals, and is mainly applied to the field of SCR denitration.
To prepare molecular sieves with high silica to alumina ratios, the Moscoso et al charge density mismatch process appears to work well for small pore zeolite synthesis (US 6713041,2004.) because LTA, ERI and UFI zeolites can be prepared in this manner immediately thereafter. Corma et al propose that they produce so-called ITQ-29 in fluoride medium synthesis. Although primarily directed to the germanosilicate and pure silicate forms of LTA, the authors also showed aluminosilicate LTA by using TMA to bind to a large supramolecular OSDA complex of two identical large aromatic pi-pi stacking cations. This moiety self-assembles in solution and is incorporated into a large cage (Nature 2004,431,287-290.). Suk Bong Hong teaches that 1, 2-dimethyl-3- (4-methylbenzyl) imidazolium and tetramethylammonium are added to a silica-alumina solution followed by Hydrogen Fluoride (HF) to show LTA zeolite with a different Si/Al ratio of 8.3 (Acs Catalysis,2016,6 (4)), and that a Cu/LTA catalyst with Si/Al ratio of 17 is synthesized with a similar organic structure directing agent for selective catalytic reduction of NH in ammonia 3 Exhibits excellent high temperature activity and heat resistance in SCR (Applied Catalysis, B.environmental,2019,243.). Na-ZK-4 with Si/al=1.3 by the Niklas Hedin team was K + Ion exchange to obtain NaK-ZK-4 molecular sieve (K) + Ion content 26%) at 15% CO 2 +85％N 2 At 273K and 101Kpa of test temperature and pressure, gives an adsorption capacity of 3.4mmol/g and a selectivity of greater than 800 (Langmuir, 2014,30 (32)); corma synthesized LTA molecular sieves with Si/Al=5 in CO with Si/Al ratio of 1,2, 3.5, 5, respectively 2 /CH 4 A capacity of adsorption of 5.58mmol/g was achieved at 500kpa,303K under gas conditions of He=48:48:4 (Langmuir, 2010,26 (3): 1910-7). However, the existing LTA zeolite molecular sieves with high silica-alumina ratio cannot achieve the simultaneous improvement of water resistance and adsorption performance, so that we need to obtain higher exposed active site proportion by adjusting the formulation, and meanwhile, in order to commercialize the catalyst, we need to find an inexpensive organic guiding agent and a more environment-friendly and economical synthesis method.
The invention aims to provide an aluminum for producing LTA structure with high silicon-aluminum ratioA process for silicate zeolite which uses economical synthetic raw materials compared to existing products. In view of the current CO capture in humid environments with respect to high silicon LTA-type molecular sieves 2 Almost no report is found, the LTA molecular sieve with high silica alumina ratio is obtained through one-step synthesis by adjusting the double organic templates with different charge densities and directionally assembling different cage structures of the LTA molecular sieve, and finally the LTA molecular sieve is applied to low-concentration CO in a humid environment 2 Adsorption separation of CO 2 /N 2 Preferential adsorption of CO by the system 2 And has good cyclic regeneration performance.
Disclosure of Invention
Aiming at the technical problems existing in the prior art, the invention aims to provide a method for efficiently capturing low-concentration CO in a humid environment 2 High silicon LTA molecular sieve of (2), and preparation method and application thereof.
According to the invention, through adjusting the double organic templates with different charge densities, different cage structures of the LTA molecular sieve are assembled directionally, the LTA molecular sieve with high silicon-aluminum ratio is synthesized at one time, and finally the LTA molecular sieve is applied to CO in a wet environment 2 /N 2 In the system, and preferentially adsorb a large amount of CO 2 . The molecular sieve of the present invention can maintain more than about 90% CO when applied in a humid environment (rh=97%) 2 Adsorption capacity and good cyclic regeneration capacity.
In order to achieve the aim, the invention adopts the silicon-containing compound and the aluminum-containing compound to prepare the initial gel, successfully synthesizes the LTA molecular sieve with high silicon-aluminum ratio by adjusting the composition of templates with different charge densities and selecting proper synthesis conditions, obtains the LTA molecular sieve with high specific surface area and can still adsorb a large amount of CO in a humid environment 2 And adsorption test experiments of low-concentration carbon dioxide are carried out.
1. The technical scheme of the invention is that CO with low concentration is efficiently trapped in a humid environment 2 The high silicon LTA molecular sieve has the chemical composition molar ratio of aAl 2 O 3 ：bSiO 2 The element composition contains more tetravalent element Si and less trivalent element Al, wherein a is more than or equal to 0.1 and less than or equal to 0.B is more than or equal to 5 and is more than or equal to 5, and oxide SiO 2 /Al 2 O 3 The molar ratio of (2) is m, m is more than or equal to 2 and less than or equal to 10;
when the X-ray diffraction measurement is performed, characteristic peaks are present in at least the following 4 interplanar spacings d: first interplanar spacing d=12.09±0.2, second interplanar spacing d=8.55±0.2, third interplanar spacing d=6.98±0.2, and fourth interplanar spacing d=6.04±0.2.
2. The molecular sieves described herein have an LTA molecular sieve configuration as defined by the international molecular sieve society (IZA). The characteristics were confirmed by X-ray diffraction measurement.
3. The X-ray diffraction measuring light source is not limited to CuK alpha, co K alpha, mo K alpha and Ag K alpha, and can be used as a light source for phase analysis. The raw material form tested may be a powder, emulsion or solid particles.
4. The molecular sieve is synthesized by adopting macromolecular organic template agents with different charge densities, so that a synthesized molecular sieve precursor after the hydrothermal reaction is completed needs to be heated and calcined to remove the macromolecular organic template agents.
5. In the composition of the LTA molecular sieve, the molar ratio of the oxide m=sio 2 /Al 2 O 3 The numerical value is 5.4-8.6.
[ method for synthesizing molecular sieves ]
The invention provides a method for efficiently capturing low-concentration CO in a humid environment 2 The preparation method of the high-silicon LTA molecular sieve comprises the following specific preparation steps of:
(a) Sequentially adding an Al source, deionized water, an Si source, an inorganic structure directing agent and LTA seed crystals into a reaction kettle, then adding double organic template agents with different charge densities, uniformly stirring, aging to obtain initial gel, transferring into a polytetrafluoroethylene pressure-resistant container for sealing, transferring the polytetrafluoroethylene pressure-resistant container into an oven for hydrothermal synthesis, and assembling different cage structures of the LTA molecular sieve by the organic template agents with different charge densities to obtain a molecular sieve precursor;
(b) Filtering, washing and drying the molecular sieve precursor after the reaction in the step (a), calcining, heating and activating in a tube furnace to remove organic matters in the molecular sieve precursor, cooling after the calcining is finished, taking out and preserving to obtain the finished product.
< raw materials for molecular sieve Synthesis >
The Al source in step (a) includes, but is not limited to, one or more of aluminum alkoxide, aluminum salt, activated alumina, pseudo-boehmite, or pseudo-boehmite, preferably aluminum alkoxide, aluminum salt, activated alumina, or pseudo-boehmite, and more preferably aluminum alkoxide or aluminum salt.
The Si source in step (a) includes, but is not limited to, one or more of silica sol, silica gel, activated silica or orthosilicate, preferably silica sol, silica gel or activated silica, more preferably silica sol or silica gel.
The inorganic structure directing agent in the step (a) comprises one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, sodium chloride, potassium chloride and cesium chloride, preferably sodium hydroxide, potassium hydroxide, sodium chloride or potassium chloride, more preferably sodium hydroxide or sodium chloride.
The LTA seed described in step (a) has a SAR value of 2 to 10, preferably a SAR value of 2.
The organic template agent in the step (a) comprises one or a mixture of a plurality of N, N-dimethyl-3, 5-dimethyl piperidine hydroxide, choline, tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide or tetrabutyl ammonium hydroxide.
The initial gel of step (a) has a mass concentration of Al source of 2-8%, preferably 2.5-5%; the mass concentration of Si source is 5-30%, preferably 5-22%; the mass concentration of the double organic template agent is 10-19%, preferably 12-18%; the mass concentration of the inorganic structure directing agent is 2-5%, preferably 3-4%; the mass concentration of LTA seed crystal is 0.35-1%, preferably 0.39-0.7%.
< formulation of initial gel >
The initial gel preparation process in step (a) of the invention is affected by the dissolution sequence and dissolution conditions. Typically, an Al source, deionized water, si source, inorganic structure directing agent, and LTA seed are added, and then the dual organic templating agent is dissolved in water to obtain the initial gel. The aging time is selected from 12 to 60 hours, preferably from 40 to 48 hours.
< hydrothermal Synthesis >
In the hydrothermal synthesis process of the step (a), the initial gel and a reaction kettle are moved into a polytetrafluoroethylene pressure-resistant container, and after being screwed up, the initial gel is heated and reacted in a rotary reaction furnace by hot air or is kept stand in an oven to react at a certain temperature. The reaction temperature of the hydrothermal synthesis is usually controlled to be 100 ℃ or higher, preferably 120 ℃ or higher; the upper limit temperature of the reaction is controlled to 180℃or less, preferably 150℃or less, more preferably 130℃or less. The reaction time is usually controlled to be 3d or more, preferably 6d or more; the upper limit of the reaction time is usually controlled to 20d or less, preferably 14d or less.
< post-treatment of hydrothermal Synthesis >
In the filtration, washing and drying process in step (b), the drying process temperature is selected to be 60-200 ℃, preferably 80-100 ℃. The drying time is selected to be 12-36 hours, preferably 12 hours. The dried molecular sieve needs to be heated and calcined to remove the template agent in the molecular sieve so as to have adsorption and catalytic properties, and the calcining temperature is selected to be 400-800 ℃, preferably 500-600 ℃. The calcination time is selected from 0.5 to 12 hours, preferably from 2 to 8 hours.
[ use of the invention ]
The high silica alumina ratio LTA molecular sieve of the invention can be used for CO in a wet gas environment 2 /N 2 Preferential CO adsorption in a large amount in the system 2 . The molecular sieve of the present invention can maintain more than about 90% CO when applied in a wet environment 2 Adsorption capacity and good cyclic regeneration capacity.
The LTA molecular sieve adsorption separation gas can be operated at 273-353K, preferably 293-323K.
The LTA molecular sieve can adsorb and separate gas in CO 2 The concentration was lower than 10000ppm.
[ advantageous effects of the invention ]
(1) The high silicon-aluminum ratio LTA molecular sieve has high acid site proportion exposed, can obtain balance between water resistance and adsorption performance, and has high cyclic test adsorption capacity.
(2) Compared with commercial A-type molecular sieves, the high silica alumina ratio LTA molecular sieve synthesis method provided by the invention adopts double-template agents with different charge densities, has higher specific surface area, still has higher adsorption capacity in a humid environment, and has better water resistance.
(3) The high silicon-aluminum ratio LTA molecular sieve provided by the invention has the advantages of small polarity, strong hydrophobicity, good adsorption effect in a wet environment and easiness in cyclic regeneration.
(4) The organic template agent for preparing the LTA molecular sieve is easy to obtain and low in price, and the organic structure guiding agent for the conventional high-silicon LTA molecular sieve is high in cost and high in toxicity, and the method can effectively reduce the manufacturing cost in industrial production.
Drawings
Table 1 shows the characteristic interplanar spacings of Na-LTA-1 of example 1;
table 2 shows the characteristic interplanar spacings of Na-LTA-2 of example 2;
table 3 shows the characteristic interplanar spacings of Na-LTA-3 of example 3;
table 4 shows the characteristic interplanar spacings of Na-LTA-4 of example 4;
table 5 shows the 10% CO at 313K for dry gas, wet gas (RH=97%) environment for the different molecular sieves of examples 1-4 and comparative example 1 2 Is a reduction in adsorption capacity and amplitude;
table 6 shows the molecular sieves of example 1 and comparative example 1 for low concentration CO 2 Is a result of adsorption cycle test; table 7 is a table of specific surface areas, micropore ratios, total pore volumes and micropore volumes for the different molecular sieves of examples 1-4 and comparative example 2;
table 8 shows the amounts of B acid, L acid and total acid for the different molecular sieves of examples 1-4 and comparative example 2;
FIG. 1 is a schematic representation of XRD test results for Na-LTA-1 of example 1;
FIG. 2 is a schematic representation of XRD test results for Na-LTA-2 of example 2;
FIG. 3 is a schematic representation of XRD test results for Na-LTA-3 of example 3;
FIG. 4 is a schematic representation of XRD test results for Na-LTA-4 of example 4;
FIG. 5 is a schematic diagram showing the results of adsorption cycle test of Na-LTA-1 of example 1.
Detailed Description
The present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
[ Instrument characterization ]
< X-ray diffraction measurement >
The X-ray diffraction measuring instrument is a Panalytical X' Pert PRO, the detecting light source CuK alpha, the tube voltage is 40kV, the tube current is 40mA, the detecting angle range is 5-50 degrees, and the detecting time is 10min. According to the invention, the phase structure of the synthesized molecular sieve is determined by X-ray diffraction, the ground sample powder is added into square holes on a glass plate, then the glass plate is inserted into the axis position of a goniometer, and the probe rotates at a 2 theta/min speed under the irradiation of a Cu K alpha light source. In addition, the light source is not limited to Cu kα, co kα, mo kα, ag kα, and may be used as a light source for phase analysis. The raw material form tested may be a powder, emulsion or solid particles.
< inductively coupled plasma Spectrometry >
Inductively coupled plasma spectroscopy (ICP) measurements were performed using PerkinElmer Optima x00. The invention determines the content of tetravalent element Si, trivalent element Al and monovalent element or monovalent cation M in the synthesized molecular sieve by inductively coupled plasma spectroscopy. And (5) diluting the standard sample, and then making a concentration gradient absorption curve. The sample is dissolved by hydrofluoric acid, diluted by water and then the concentration of each element in the sample is determined by absorption peak intensity.
< static adsorption test >
The specific surface area of the material was measured at a temperature of 77K using the size of the nitrogen molecules. The adsorption/desorption curve and pore size distribution curve were obtained using a fully automatic specific surface and porosity analyzer (3-Flex). The specific surface area and pore volume of the material were calculated by Brunauer-Emmett-Teller (BET), T-Plot and Density Functional Theory (DFT) algorithms.
< dynamic adsorption test >
Gas suctionThe adsorption test was performed with an Agilent 8860 gas chromatograph, with a TCD detector, a HayeSep Q column. The present invention tests gas adsorption selectivity by gas adsorption assays. CO 2 /N 2 The adsorption isotherm is measured at 288-313K, about 1000mg of sample is taken and placed in a sample tube, then placed in a set constant temperature water bath, and the steel cylinder gas is prepared by adopting 10% CO 2 And 90% N 2 The standard gas was prepared at a gas flow rate of 5ml/min. All samples were activated for more than 6 hours at 350 ℃ before adsorption testing.
< determination of molecular sieve acid amount >
The molecular sieve active acid sites were analyzed using pyridine adsorption and FT-IR spectroscopy (Nicolet 6700 spectrometer equipped with DTGS detector). The sample was pressed into a free standing wafer and degassed under vacuum at 400 ℃ for 1 hour prior to adsorption measurement. After cooling to 50 ℃,25 mbar of gas phase pyridine was introduced into the sample cell until saturated. Thermal desorption was performed at 150 ℃ to remove weakly adsorbed pyridine species. By passing through the two layers at 1455 and 1554cm respectively -1 Quantification of Lewis acid and by integration of the area of the absorption bandThe amount of acid sites. Absorption extinction coefficient: ε (B) =1.67 cm. Mu. Mol -1 And ε (L) =2.22 cm. Mu. Mol -1 。
[ example ]
LTA seed crystals in the examples of the present invention were purchased from Tianjin southbound catalyst Co., ltd., model NKF-4A.
Example 1 ]
2.6g NaAlO 2 (NaAlO 2 The mass percentage content>98%) into 25g of water, followed by the sequential addition of 2.5g of NaCl (mass% sodium chloride)>99.5%), 30.5g tetraethylammonium hydroxide (35% aquos), 2.5g tetramethylammonium chloride (mass percent tetramethylammonium chloride)>99 percent of the mixture is stirred uniformly. After the solution was clear, 13g of ludox as-40 (40% aquous silicon solution) was added dropwise and stirring continued until the solution was thoroughly mixed; 0.3g of LTA seed (sar=2) was charged and aged for 48 hours to give an initial gel. Transferring the gel mixture into a polytetrafluoroethylene pressure-resistant containerSealing, and dynamically crystallizing for 6d at 130 ℃ reaction temperature and autogenous pressure. After the hydrothermal reaction is finished, the reaction liquid is cooled, filtered and washed to obtain a crystal product. The resulting crystals were dried at 100℃for 12h to give the product as a powder.
The obtained powdery product was calcined in a muffle furnace at 550℃for 6 hours to obtain a powdery product Na-LTA-1. The obtained product is subjected to phase analysis by XRD, the interplanar spacing of characteristic peaks in Na-LTA-1 is shown in table 1, and a schematic diagram of XRD test results is shown in figure 1, so that the synthesized molecular sieve has an LTA molecular sieve structure confirmed by IZA. The above samples were subjected to elemental composition analysis by ICP, and the analysis result showed that the SAR value of Na-LTA-1 was 6.6.
The Na-LTA-1 is used for low concentration CO 2 Adsorption test experiment. The adsorption capacity of the sample was measured on an 8860 gas chromatograph from Agilent company, the detector being TCD, the column being a HayeSep Q column. Measurement parameters: the sample inlet was 150 ℃, the column box 120 ℃, the detector 250 ℃, the column box temperature was raised to 120 ℃ at a heating rate of 40 ℃/min, then maintained at 120 ℃ for 2min, and the gas mixture flow rate was 5ml/min during the chromatographic operation.
The gas used for the adsorption test was 10% CO 2 Adding 90% of N 2 The prepared mixed gas (the mixed gas is bubbled through a water vapor bottle to simulate the moisture environment of RH=97% when moisture is detected), 1g of prepared Na-LTA-1 is weighed and added into a U-shaped pipe, activation treatment is carried out for 6 hours at 350 ℃, then the U-shaped pipe is placed in a 40 ℃ constant temperature water bath for adsorption test experiment, and the inlet flow of the U-shaped pipe is 5ml/min when the test experiment is carried out. In order to avoid the influence of too fine particle size of the molecular sieve on pressure drop, the prepared molecular sieve is required to be sieved by a sieve with 40-60 meshes; in order to avoid the influence of dead volume in a pipeline, the empty U-shaped pipe without the molecular sieve is subjected to empty pipe adsorption test to serve as the dead volume of an instrument before adsorption test, and then the dead volume is corrected by subtracting the dead volume from the adsorption quantity of the detected molecular sieve. Testing to obtain Na-LTA-1 for CO under moisture 2 The adsorption capacities of (C) are 2.87mmol/g respectively for CO under dry gas 2 The adsorption capacity of (2) is shown in Table 5.
TABLE 1 characteristic interplanar spacing of Na-LTA-1
Interplanar spacing (d)
1 12.096
2 8.486
3 6.937
4 6.005
5 5.377
6 4.922
7 4.264
8 4.019
Example 2 ]
3.55g of aluminum sec-butoxide (the mass percentage of the aluminum sec-butoxide is more than 96%) is added into 25g of water for dissolution, then 2.5g of NaCl (the mass percentage of sodium chloride is more than 99.5%), 27.4g of tetraethylammonium hydroxide (25% aquos) and 3g of tetramethylammonium chloride (the mass percentage of tetramethylammonium chloride is more than 99%) are sequentially added, and the mixture is stirred uniformly. After the solution was clear, 13g of ludox as-40 (40% aquous silicon solution) was added dropwise and stirring continued until the solution was thoroughly mixed; 0.5g of LTA seed (sar=2) was charged and aged for 48 hours to give an initial gel. The gel mixture is transferred into a polytetrafluoroethylene pressure-resistant container for sealing, and is dynamically crystallized for 6d at the reaction temperature of 130 ℃ and under autogenous pressure. After the hydrothermal reaction is finished, the reaction liquid is cooled, filtered and washed to obtain a crystal product. The resulting crystals were dried at 100℃for 12h to give the product as a powder.
The obtained powdery product is calcined in a muffle furnace at 550 ℃ for 6 hours to obtain a powdery product Na-LTA-2. The obtained product was subjected to XRD phase analysis, the interplanar spacing of characteristic peaks in Na-LTA-2 is shown in Table 2, and a schematic diagram of XRD test results is shown in FIG. 2, which shows that the synthesized molecular sieve has an LTA molecular sieve configuration identified by IZA. The above samples were subjected to elemental composition analysis by ICP, and the analysis result showed that the SAR value of Na-LTA-2 was 5.8.
The Na-LTA-2 is used for low concentration CO 2 Adsorption test experiment. The adsorption capacity of the sample was measured on an 8860 gas chromatograph from Agilent company, the detector being TCD, the column being a HayeSep Q column. Measurement parameters: the sample inlet was 150 ℃, the column box 120 ℃, the detector 250 ℃, the column box temperature was raised to 120 ℃ at a heating rate of 40 ℃/min, then maintained at 120 ℃ for 2min, and the gas mixture flow rate was 5ml/min during the chromatographic operation.
The gas used for the adsorption test was 10% CO 2 Adding 90% of mixed gas prepared by N2 (bubbling the mixed gas through a water vapor bottle to simulate RH=97% of wet gas environment when measuring wet gas), weighing 1g of prepared Na-LTA-2, adding into a U-shaped tube, performing activation treatment at 350 ℃ for 6 hours, then placing into a 40 ℃ constant temperature water bath kettle for adsorption test, and performing the mixed gas with the inlet flow of 5ml/min of the U-shaped tube during the test. In order to avoid the influence of too fine particle size of the molecular sieve on pressure drop, the prepared molecular sieve is required to be sieved by a sieve with 40-60 meshes; in order to avoid the influence of dead volume in the pipeline, the empty U-shaped pipe without the molecular sieve is used for empty pipe adsorption test as the dead volume of the instrument before adsorption test,dead volume correction was then performed by subtracting the dead volume from the adsorption of the molecular sieve measured. Testing to obtain Na-LTA-2 for CO under moisture 2 The adsorption capacity of (C) is 2.74mmol/g respectively for CO under dry gas 2 The adsorption capacity of (2) is shown in Table 5.
TABLE 2 characteristic interplanar spacing of Na-LTA-2
Example 3 ]
2.58g of aluminum sec-butoxide (mass percentage of aluminum sec-butoxide)>96%) into 25g of water, then 2g of tetramethyl ammonium chloride (tetramethyl ammonium chloride mass percent) are added in turn>99%), 25g tetraethylammonium hydroxide (25% aquos), 2.5g NaCl (sodium chloride mass percent)>99.5%) and after the solution had clarified, 16g of ethyl orthosilicate (as SiO) were added stepwise 2 Calculating the mass percentage content>28 percent of the mixture is stirred uniformly. 0.5g of LTA seed (sar=2) was charged and aged for 48 hours to give an initial gel. The gel mixture is transferred into a polytetrafluoroethylene pressure-resistant container for sealing, and is dynamically crystallized for 6d at the reaction temperature of 130 ℃ and under autogenous pressure. After the hydrothermal reaction is finished, the reaction liquid is cooled, filtered and washed to obtain a crystal product. The resulting crystals were dried at 100℃for 12h to give the product as a powder.
The obtained powdery product was calcined in a muffle furnace at 550℃for 6 hours to obtain a powdery product Na-LTA-3. The obtained product was subjected to XRD phase analysis, the interplanar spacing of characteristic peaks in Na-LTA-3 is shown in Table 3, and a schematic diagram of XRD test results is shown in FIG. 3, which shows that the synthesized molecular sieve has an LTA molecular sieve configuration identified by IZA. The above samples were subjected to elemental composition analysis by ICP, and the analysis result showed that the SAR value of Na-LTA-3 was 5.6.
The Na-LTA-3 is used for low concentration CO 2 Adsorption test experiment. The adsorption capacity of the sample was measured on a 8860 gas chromatograph from Agilent corporationThe assay was performed with TCD as detector and a HayeSep Q column as column. Measurement parameters: the sample inlet was 150 ℃, the column box 120 ℃, the detector 250 ℃, the column box temperature was raised to 120 ℃ at a heating rate of 40 ℃/min, then maintained at 120 ℃ for 2min, and the gas mixture flow rate was 5ml/min during the chromatographic operation.
The gas used for the adsorption test was 10% CO 2 Adding 90% of N 2 The prepared mixed gas (the mixed gas is bubbled through a water vapor bottle to simulate the moisture environment of RH=97% when moisture is detected), 1g of prepared Na-LTA-3 is weighed and added into a U-shaped pipe, activation treatment is carried out for 6 hours at 350 ℃, then the U-shaped pipe is placed in a 40 ℃ constant temperature water bath for adsorption test experiment, and the inlet flow of the U-shaped pipe is 5ml/min when the test experiment is carried out. In order to avoid the influence of too fine particle size of the molecular sieve on pressure drop, the prepared molecular sieve is required to be sieved by a sieve with 40-60 meshes; in order to avoid the influence of dead volume in a pipeline, the empty U-shaped pipe without the molecular sieve is subjected to empty pipe adsorption test to serve as the dead volume of an instrument before adsorption test, and then the dead volume is corrected by subtracting the dead volume from the adsorption quantity of the detected molecular sieve. Testing to obtain Na-LTA-3 for CO under moisture 2 The adsorption capacity of (C) is 2.56mmol/g respectively for CO under dry gas 2 The adsorption capacity of (2) is shown in Table 5.
TABLE 3 characteristic interplanar spacing of Na-LTA-3
Interplanar spacing (d)
1 12.102
2 8.513
3 6.895
4 6.015
5 5.406
6 4.899
7 4.251
8 4.082
Example 4 ]
2g of aluminium hydroxide (aluminium hydroxide mass percentage)>99%) into 20g of water, followed by the sequential addition of 29.1g of tetramethylammonium hydroxide (40% aquos), 2g of tetramethylammonium chloride (mass% tetramethylammonium chloride)>99%), 2.5g NaCl (sodium chloride mass percent)>99.5%) and after the solution had clarified, 16g of ethyl orthosilicate (as SiO) were added stepwise 2 Calculating the mass percentage content>28 percent of the mixture is stirred uniformly. 0.5g of LTA seed (sar=2) was charged and aged for 48 hours to give an initial gel. The gel mixture is transferred into a polytetrafluoroethylene pressure-resistant container for sealing, and is dynamically crystallized for 6d at the reaction temperature of 130 ℃ and under autogenous pressure. After the hydrothermal reaction is finished, the reaction liquid is cooled, filtered and washed to obtain a crystal product. The resulting crystals were dried at 100℃for 12h to give the product as a powder.
The obtained powdery product was calcined in a muffle furnace at 550℃for 6 hours to obtain a powdery product Na-LTA-4. The obtained product was subjected to XRD phase analysis, the interplanar spacing of characteristic peaks in Na-LTA-4 is shown in Table 4, and a schematic diagram of XRD test results is shown in FIG. 4, which shows that the synthesized molecular sieve has an LTA molecular sieve configuration identified by IZA. The above samples were subjected to elemental composition analysis by ICP, and the analysis result showed that the SAR value of Na-LTA-4 was 5.4.
The Na-LTA-4 is used for low concentration CO 2 Adsorption test experiment. The adsorption capacity of the sample was measured on an 8860 gas chromatograph from Agilent company, the detector being TCD, the column being a HayeSep Q column. Measurement parameters: the sample inlet was 150 ℃, the column box 120 ℃, the detector 250 ℃, the column box temperature was raised to 120 ℃ at a heating rate of 40 ℃/min, then maintained at 120 ℃ for 2min, and the gas mixture flow rate was 5ml/min during the chromatographic operation.
The gas used for the adsorption test was 10% CO 2 Adding 90% of N 2 The prepared mixed gas (the mixed gas is bubbled through a water vapor bottle to simulate the moisture environment of RH=97% when moisture is detected), 1g of prepared Na-LTA-4 is weighed and added into a U-shaped pipe, activation treatment is carried out for 6 hours at 350 ℃, then the U-shaped pipe is placed in a 40 ℃ constant temperature water bath for adsorption test experiment, and the inlet flow of the U-shaped pipe is 5ml/min when the test experiment is carried out. In order to avoid the influence of too fine particle size of the molecular sieve on pressure drop, the prepared molecular sieve is required to be sieved by a sieve with 40-60 meshes; in order to avoid the influence of dead volume in a pipeline, the empty U-shaped pipe without the molecular sieve is subjected to empty pipe adsorption test to serve as the dead volume of an instrument before adsorption test, and then the dead volume is corrected by subtracting the dead volume from the adsorption quantity of the detected molecular sieve. Testing to obtain Na-LTA-4 for CO under moisture 2 The adsorption capacity of (C) is 2.30mmol/g respectively for CO under dry gas 2 The adsorption capacity of (2) is shown in Table 5.
Table 4 Na-LTA-4 characteristic interplanar spacing
Comparative example 1 ]
Taking three commercial molecular sieves of a certain amount of 4A type molecular sieves (silicon-aluminum ratio is 1) of Nanka chemical reagent field, 4A type molecular sieves (silicon-aluminum ratio is 1) of Zhuo environmental protection Co., ltd., shen Tanhuan A type molecular sieves (silicon-aluminum ratio is 1) of Nanka chemical reagent field and a high silicon LTA molecular sieve with silicon-aluminum ratio of 5 prepared by referencing Croma literature (Langmuir, 2010,26 (3): 1910-7), the obtained molecular sieves are named Na-LTA-5, na-LTA-6, na-LTA-7 and Na-LTA-8 in sequence, taking out dried samples and storing the dried samples in a drying dish.
The above Na-LTA-5, na-LTA-6, na-LTA-7 and Na-LTA-8 were used for low concentration CO 2 Adsorption test experiment. The adsorption capacity of the sample was measured on an 8860 gas chromatograph from Agilent company, the detector being TCD, the column being a HayeSep Q column. Chromatographic determination parameters: the sample inlet was 150 ℃, the column box 120 ℃, the detector 250 ℃, the column box temperature was raised to 120 ℃ at a heating rate of 40 ℃/min, then maintained at 120 ℃ for 2min, and the gas mixture flow rate was 5ml/min during the chromatographic operation.
The gas used for the adsorption test was 10% CO 2 Adding 90% of N 2 The prepared mixed gas (the mixed gas is bubbled through a water vapor bottle to simulate the moisture environment of RH=97% when moisture is detected), 1g of prepared Na-LTA-5, na-LTA-6, na-LTA-7 and Na-LTA-8 are respectively weighed and added into a U-shaped pipe, activation treatment is carried out for 6 hours at 350 ℃, then the mixed gas is placed in a water bath for adsorption test, and the inlet flow rate of the U-shaped pipe is 5ml/min when the test is carried out. In order to avoid the influence of too fine particle size of the molecular sieve on pressure drop, the prepared molecular sieve is required to be sieved by a sieve with 40-60 meshes; in order to avoid the influence of dead volume in a pipeline, the empty U-shaped pipe without the molecular sieve is subjected to empty pipe adsorption test to serve as the dead volume of an instrument before adsorption test, and then the dead volume is corrected by subtracting the dead volume from the adsorption quantity of the detected molecular sieve. Various molecular sieves low concentration CO 10% at 40 ℃ for dry gas, wet gas environment (rh=97%) 2 The adsorption amount of (2) is shown in Table 5.
Subsequently, adsorption cycle test experiments were performed on Na-LTA-1, na-LTA-5 and Na-LTA-8, and the adsorption capacity of the samples was measured on a 8860 gas chromatograph from Agilent corporation, the detector was TCD, and a HayeSep Q column was used as the chromatographic column. Gas used in adsorption testCO in 10% 2 Adding 90% of N 2 The mixture was configured and bubbled through a water vapor bottle to simulate an rh=97% moisture environment. 1g of prepared Na-LTA-1, na-LTA-5 and Na-LTA-8 are respectively weighed and added into a U-shaped tube, activation treatment is carried out for 6 hours at 350 ℃, then the U-shaped tube is placed in a water bath kettle at 40 ℃ for adsorption test, and the inlet flow of the U-shaped tube is 5ml/min of mixed gas during the test. In order to avoid the influence of too fine particle size of the molecular sieve on pressure drop, the prepared molecular sieve is required to be sieved by a sieve with 40-60 meshes; in order to avoid the influence of dead volume in a pipeline, the empty U-shaped pipe without the molecular sieve is subjected to empty pipe adsorption test to serve as the dead volume of an instrument before adsorption test, and then the dead volume is corrected by subtracting the dead volume from the adsorption quantity of the detected molecular sieve. Chromatographic determination parameters: the sample inlet was 150 ℃, the column box 120 ℃, the detector 250 ℃, the column box temperature was raised to 120 ℃ at a heating rate of 40 ℃/min, then maintained at 120 ℃ for 2min, and the gas mixture flow rate was 5ml/min during the chromatographic operation. The desorption temperature is still 40 ℃, and the gas flow rate is purged by adopting 20ml/min nitrogen until CO in the chromatograph 2 The peak area of (2) is reduced to almost 0, then the second adsorption experiment at 40 ℃ is carried out, the parameters used in the second adsorption experiment are as above, finally the second desorption experiment and the third adsorption experiment … … are sequentially repeated for a plurality of times, and the adsorption cycle performance of the molecular sieve at 40 ℃ is detected. The adsorption cycle performance of the molecular sieves is shown in table 6 and fig. 5.
Comparative example 2 ]
Taking three commercial molecular sieves of a certain amount of 4A type molecular sieves (silicon-aluminum ratio is 1) of Nanka chemical reagent field, 4A type molecular sieves (silicon-aluminum ratio is 1) of Zhuo environmental protection Co., ltd., shen Tanhuan A type molecular sieves (silicon-aluminum ratio is 1) of Nanka chemical reagent field and a high silicon LTA molecular sieve with silicon-aluminum ratio of 5 prepared by referencing Croma literature (Langmuir, 2010,26 (3): 1910-7), the obtained molecular sieves are named Na-LTA-5, na-LTA-6, na-LTA-7 and Na-LTA-8 in sequence, taking out dried samples and storing the dried samples in a drying dish.
About 0.2-0.3g of sample is weighed, and the specific surface area of the material is measured at 77K by using the size of nitrogen molecules. The adsorption or adsorption/desorption curves and pore size distribution curves were obtained using a fully automated specific surface and porosity analyzer (3-Flex). The specific surface area, pore volume of the material was calculated by the Brunauer-Emmett-Teller (BET), T-Plot and Density Functional Theory (DFT) algorithms. The specific surface area and pore volume of the different molecular sieves are shown in table 7.
The molecular sieves and commercial molecular sieves prepared above were subjected to acid measurements. The sample was pressed into a free standing wafer and degassed under vacuum at 400 ℃ for 1 hour prior to adsorption measurement. After cooling to 50 ℃,25 mbar of gas phase pyridine was introduced into the sample cell until saturated. Thermal desorption was performed at 150 ℃ to remove weakly adsorbed pyridine species. By passing through the two layers at 1455 and 1554cm respectively -1 Quantification of Lewis acid and adsorption zone by integrating the area of the adsorption zoneThe amount of acid sites. The acid amounts of the different molecular sieves are shown in table 8.
Table 5 different molecular sieves 10% co in 313K for dry gas, wet gas (rh=97%) environment 2 Adsorption capacity and reduction of amplitude of (2)
Table 6 different molecular sieves low concentration CO for moisture (rh=97%) conditions 2 Adsorption cycle test of (2)
TABLE 7 specific surface area, micropore ratio, total pore volume and micropore volume of different molecular sieves
Molecular sieve designation S BET (m 2 g -1 ) S mic (m 2 g -1 ) V t (cm 3 g -1 ) V mic (cm 3 g -1 )
Na-LTA-1 734 719 0.278443 0.278512
Na-LTA-2 721 705 0.269254 0.268452
Na-LTA-3 705 690 0.264542 0.262538
Na-LTA-4 698 687 0.260387 0.259873
Na-LTA-5 362 342 0.152325 0.132195
Na-LTA-6 380 361 0.160391 0.139236
Na-LTA-7 301 292 0.152423 0.131456
Na-LTA-8 725 692 0.254833 0.238000
TABLE 8B acid, L acid and Total acid size for different molecular sieves
What has been described in this specification is merely an enumeration of possible forms of implementation for the inventive concept and may not be considered limiting of the scope of the present invention to the specific forms set forth in the examples.

Claims (8)

1. High-efficiency capturing low-concentration CO in humid environment 2 The high silicon LTA molecular sieve has the chemical composition molar ratio of aAl 2 O 3 ：bSiO 2 The element composition contains more tetravalent element Si and less trivalent element Al, wherein a is more than or equal to 0.1 and less than or equal to 0.5, and 1 is more than or equal to 1b is less than or equal to 5, oxide SiO 2 /Al 2 O 3 The molar ratio of (2) is m, m is more than or equal to 2 and less than or equal to 10;
when the X-ray diffraction measurement is performed, characteristic peaks are present in at least the following 4 interplanar spacings d: first interplanar spacing d=12.09±0.2, second interplanar spacing d=8.55±0.2, third interplanar spacing d=6.98±0.2, and fourth interplanar spacing d=6.04±0.2.
2. A method for efficiently capturing CO of low concentration in a humid environment according to claim 1 2 The high silicon LTA molecular sieve is characterized in that: LTA molecular sieve configuration identified by IZA of International molecular sieve society; the molar ratio of the oxides m=sio 2 /Al 2 O 3 The numerical value is 5.4-8.6.
3. A method for efficiently capturing CO of low concentration in a humid environment according to claim 1 2 The preparation method of the high-silicon LTA molecular sieve is characterized by comprising the following steps:
(a) Sequentially adding an Al source, deionized water, an Si source, an inorganic structure directing agent and LTA seed crystals into a reaction kettle, adding double organic template agents with different charge densities, uniformly stirring, aging to obtain initial gel, transferring into a polytetrafluoroethylene pressure-resistant container for sealing, transferring the polytetrafluoroethylene pressure-resistant container into an oven for hydrothermal synthesis, and assembling different cage structures of the LTA molecular sieve by the organic template agents with different charge densities to obtain a molecular sieve precursor;
(b) Filtering, washing and drying the molecular sieve precursor after the reaction in the step (a), calcining, heating and activating in a tube furnace to remove organic matters in the molecular sieve precursor, cooling after the calcining is finished, taking out and preserving to obtain the finished product.
4. A method of efficiently capturing low concentration CO in a humid environment according to claim 3 2 The preparation method of the high-silicon LTA molecular sieve is characterized in that the Al source in the step (a) comprises one or more than two of aluminum alkoxide, aluminum salt, activated alumina, pseudo-boehmite or pseudo-boehmite, preferably aluminum alkoxide and aluminumSalts, activated alumina or pseudo-boehmite, more preferably aluminum alkoxides or aluminum salts;
the Si source in the step (a) comprises one or more of silica sol, silica gel, active silica or tetraethoxysilane, preferably silica sol, silica gel or active silica, more preferably silica sol or silica gel;
the bi-organic template agent in the step (a) is one or a mixture of a plurality of N, N-dimethyl-3, 5-dimethyl piperidine hydroxide, choline, tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide or tetrabutyl ammonium hydroxide;
the inorganic structure directing agent in the step (a) comprises one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, sodium chloride, potassium chloride and cesium chloride, preferably sodium hydroxide, potassium hydroxide, sodium chloride or potassium chloride, more preferably sodium hydroxide or sodium chloride;
the LTA seed of step (a) has a SAR value of 2-10, preferably a SAR value of 2;
the ageing time in the step (a) is selected to be 12-60h, preferably 40-48h, the temperature of the hydrothermal synthesis reaction is 100-130 ℃, and the reaction time is 3-20 d, preferably 6-14 d.
5. A method of efficiently capturing low concentration CO in a humid environment according to claim 3 2 The preparation method of the high-silicon LTA molecular sieve is characterized in that the mass concentration of an Al source in the initial gel in the step (a) is 2-8%, preferably 2.5-5%; the mass concentration of Si source is 5-30%, preferably 5-22%; the mass concentration of the double organic template agent is 10-19%, preferably 12-18%; the mass concentration of the inorganic structure directing agent is 2-5%, preferably 3-4%; the mass concentration of LTA seed crystal is 0.35-1%, preferably 0.39-0.7%.
6. A method of efficiently capturing low concentration CO in a humid environment according to claim 3 2 The preparation method of the high-silicon LTA molecular sieve is characterized in that the calcining and heating activation temperature in the step (b) is 500-600 ℃, and the heating activation time is 2-8h.
7. The high silicon LTA molecular sieve of claim 1, which efficiently traps low concentration CO in a humid environment 2 Is used in the application of (a).
8. Use according to claim 7, characterized in that the CO in the gas to be separated 2 Is less than 10000ppm.
CN202311254359.7A 2023-09-27 2023-09-27 High-efficiency capturing low-concentration CO in humid environment 2 High-silicon LTA molecular sieve as well as preparation method and application thereof Pending CN117208927A (en)

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