A low-silica CHA-type molecular sieve, its preparation method and application
By preparing low-silica CHA-type molecular sieves, the problems of complex and high cost of CO2 separation processes in existing technologies have been solved. This method enables efficient selective adsorption of CO2 and resource utilization of FCC waste catalysts, simplifies the process flow, and reduces energy consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JILIN UNIVERSITY
- Filing Date
- 2024-05-21
- Publication Date
- 2026-05-26
Smart Images
Figure CN118579805B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of adsorption materials technology, specifically relating to a low-silica CHA-type molecular sieve, its preparation method, and its application. Background Technology
[0002] Acetylene (C2H2) has wide industrial applications, used to produce various chemical materials and fine chemicals. C2H2 is mainly produced by petroleum cracking and partial combustion of methane. Its byproduct, carbon dioxide (CO2), can reach a concentration of up to 50% of the C2H2 in the gas stream. Therefore, removing CO2 from the C2H2 stream is crucial for obtaining high-purity C2H2. Based on the similar physical properties of C2H2 and CO2, adsorption separation using porous adsorbents has attracted great interest from academia and industry. Ethylene (C2H4) is a precursor to various bulk products and can also be used to produce bulk chemicals. C2H4 is typically prepared through steam cracking of hydrocarbon feedstocks, dehydrogenation and oxidative dehydrogenation of alkanes, and dehydration of ethanol. C2H4 prepared by these processes usually contains impurities such as CO2. Considering both economic feasibility and product quality, adsorption separation technology is a good choice.
[0003] Zeolite molecular sieves are a class of crystalline inorganic microporous aluminosilicates with regular pore structures, good thermal stability, and modifiability, making them important inorganic porous materials. They have wide applications in catalysis fields such as the adsorption and separation of small molecule gases, the removal of heavy metal ions from wastewater, the preparation of petroleum products, and denitrification reactions. To date, the International Zygote Association (IZA) Structure Committee has included more than 256 different molecular sieve framework structures. Currently, various molecular sieves are used as adsorbent materials. For example, Chinese patent CN 116920791 A provides a method for preparing ion-exchange M-MOR molecular sieves, which mainly solves the problem of removing trace amounts of carbon dioxide and acetylene in the purification of ethylene production by ion exchange of Na-type MOR molecular sieves. However, the above method requires ion exchange of the molecular sieve, making the process relatively complex. Summary of the Invention
[0004] The purpose of this invention is to provide a low-silica CHA-type molecular sieve, its preparation method, and its application. The preparation method provided by this invention does not require an ion exchange process, and the resulting low-silica CHA-type molecular sieve exhibits significant selectivity for carbon dioxide adsorption.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] This invention provides a method for preparing low-silica CHA-type molecular sieves, comprising the following steps:
[0007] An alkali source, an aluminum source, a silicon source, and water are mixed to obtain a mixture; the alkali source includes sodium hydroxide and potassium hydroxide; the aluminum source includes boehmite or FCC waste catalyst; the silicon source and aluminum source, respectively, are calculated based on the effective components SiO2 and Al2O3, with a molar ratio of 2 to 4:1;
[0008] The mixture was subjected to hydrothermal crystallization to obtain the low-silica CHA-type molecular sieve;
[0009] The preparation method does not include metal ion exchange.
[0010] Preferably, the molar ratio of sodium hydroxide to potassium hydroxide is 0.082–0.5:0.9–1.12.
[0011] Preferably, the silicon source is silica sol;
[0012] The silicon source and sodium hydroxide, calculated as effective components SiO2 and Na2O respectively, have a molar ratio of 2-4:0.082-0.5.
[0013] Preferably, the mass percentage of SiO2 in the silica sol is 30-40%;
[0014] When the aluminum source is boehmite, the silicon source is alkaline silica sol;
[0015] When the aluminum source is an FCC waste catalyst, the silicon source is a neutral silica sol or an acidic silica sol.
[0016] Preferably, the molar ratio of the silicon source (based on the effective component SiO2) to water is 2-4:160-180.
[0017] Preferably, the hydrothermal crystallization temperature is 90–160°C and the time is 48–96 h.
[0018] The present invention also provides a low-silicon CHA-type molecular sieve obtained by the preparation method described above, wherein the silicon-to-aluminum ratio of the low-silicon CHA-type molecular sieve is 1 to 2.1.
[0019] Preferably, the particle size of the low-silica CHA-type molecular sieve is 1–5 μm.
[0020] This invention also provides the application of the low-silica CHA-type molecular sieve described above in carbon dioxide separation.
[0021] Preferably, the application is for separating carbon dioxide from a mixture containing acetylene and / or ethylene.
[0022] This invention provides a method for preparing a low-silica CHA-type molecular sieve, comprising the following steps: mixing an alkali source, an aluminum source, a silicon source, and water to obtain a mixture; the alkali source includes sodium hydroxide and potassium hydroxide; the aluminum source includes boehmite or FCC waste catalyst; the silicon source and aluminum source, respectively calculated as effective components SiO2 and Al2O3, have a molar ratio of 2-4:1; the mixture is then subjected to hydrothermal crystallization to obtain the low-silica CHA-type molecular sieve; the preparation method does not include metal ion exchange. The preparation method provided by this invention directly crystallizes low-silica CHA zeolite in one step without activation pretreatment, and eliminates the need for any metal ion exchange process. This not only ensures product purity and crystallinity but also eliminates the need for excessively high crystallization temperatures, simplifying the process and reducing energy consumption. The resulting low-silica CHA-type molecular sieve exhibits a crystalline morphology and excellent carbon dioxide gas separation performance.
[0023] Furthermore, the preparation method provided by this invention achieves the first-ever preparation of low-silica CHA zeolite using FCC waste catalyst as raw material. The added FCC waste catalyst has a high utilization rate, replacing pure chemical reagents. Low-silica CHA zeolite with good crystallinity and purity can be synthesized at a relatively low temperature. This solves the problems of FCC waste catalyst treatment and storage, significantly reduces production costs, and yields a high-value-added low-silica CHA zeolite product with excellent carbon dioxide separation performance. In summary, the preparation method provided by this invention simultaneously achieves the resource utilization of FCC waste catalyst, the reduction of zeolite material costs, and the synthesis of a fully crystalline, high-efficiency CO2 removal zeolite material. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0025] Figure 1 The X-ray diffraction patterns of the products obtained in Examples 1-5 and Comparative Examples 1-2 are shown below.
[0026] Figures 2-6 SEM images of the low-silica CHA-type molecular sieves obtained in Examples 1-5;
[0027] Figure 7 This is the isothermal adsorption curve of the low-silica CHA-type molecular sieve obtained in Example 1;
[0028] Figure 8 The image shows the isothermal adsorption curve of the low-silica CHA-type molecular sieve obtained in Example 2. Detailed Implementation
[0029] This invention provides a method for preparing low-silica CHA-type molecular sieves, comprising the following steps:
[0030] An alkali source, an aluminum source, a silicon source, and water are mixed to obtain a mixture; the alkali source includes sodium hydroxide and potassium hydroxide; the aluminum source includes boehmite or FCC waste catalyst; the silicon source and aluminum source, respectively, are calculated based on the effective components SiO2 and Al2O3, with a molar ratio of 2 to 4:1;
[0031] The mixture was subjected to hydrothermal crystallization to obtain the low-silica CHA-type molecular sieve;
[0032] The preparation method does not include metal ion exchange.
[0033] In this invention, unless otherwise specified, all raw materials are commercially available products well known to those skilled in the art.
[0034] The present invention mixes an alkali source, an aluminum source, a silicon source and water to obtain a mixture; the alkali source includes sodium hydroxide and potassium hydroxide.
[0035] In this invention, the molar ratio of sodium hydroxide to potassium hydroxide is preferably 0.082-0.5:0.9-1.12, more preferably 0.1-0.4:0.95-1.1.
[0036] In this invention, the silicon source is preferably a silica sol; the mass percentage of SiO2 in the silica sol is preferably 30-40%; when the aluminum source is boehmite, the silicon source is preferably an alkaline silica sol; the manufacturer of the silicon source is preferably Sigma-Aldrich; the mass percentage of SiO2 is more preferably 35-40%; the type of the silica sol is preferably AS-40. When the aluminum source is FCC waste catalyst, the silicon source is preferably a neutral silica sol or an acidic silica sol; the manufacturer of the silicon source is preferably Luoyang Jianlong Micro-Nano New Materials Co., Ltd.; the mass percentage of SiO2 is more preferably 30-35%; the molar ratio of the silicon source and sodium hydroxide, respectively calculated as effective components SiO2 and Na2O, is preferably 2-4:0.082-0.5, more preferably 2.5-3.5:0.1-0.4.
[0037] In this invention, the silicon source is selected from the above-mentioned types because the silica sol from Luoyang Jianlong Micro-Nano New Materials Co., Ltd. is Na. + Stable, with a neutral or slightly acidic pH; Sigma-Aldrich silica sol is NH4+. + It is stable and has an alkaline pH, making it suitable for various reaction systems.
[0038] In this invention, the aluminum source includes boehmite or FCC waste catalyst, preferably FCC waste catalyst; the elemental content is determined by X-ray fluorescence spectroscopy, and the FCC waste catalyst is preferably converted into the effective component molar ratio with SiO2 content of 40-45% and Al2O3 content of 50-55%, more preferably with SiO2 content of 41.13% and Al2O3 content of 52.30%.
[0039] In this invention, the aluminum source is either boehmite or FCC waste catalyst. The main components of the FCC waste catalyst are rare earth metal modified Y-type zeolite, inert alumina matrix, and a small amount of ZSM-5 zeolite catalyst promoter, of which SiO2+Al2O3 (which can be used as raw material for zeolite molecular sieve synthesis) accounts for more than 90% of the total mass fraction.
[0040] In this invention, the components of the FCC waste catalyst can promote the crystallization process of the molecular sieve, enabling it to be synthesized at a lower temperature and with a lower silicon-to-aluminum ratio.
[0041] In this invention, the silicon source and aluminum source are calculated as effective components SiO2 and Al2O3, respectively, and the molar ratio is 2 to 4:1, preferably 2.5 to 3.5:1.
[0042] In this invention, the molar ratio of the silicon source (based on the effective component SiO2) to water is preferably 2-4:160-180, more preferably 2.5-3.5:165-175.
[0043] In this invention, the preferred order of adding the alkali source, aluminum source, silicon source and water is to first dissolve the alkali source in water, and then add the aluminum source and silicon source in sequence; the preferred method of dissolving the alkali source in water is stirring; the addition of the aluminum source also preferably includes stirring; the stirring time is preferably 2 to 6 hours, more preferably 2 to 4 hours.
[0044] In this invention, the mixing method is stirring; the stirring speed is preferably 300-500 rpm, more preferably 350-450 rpm; the stirring time is preferably 0.5-1 h, more preferably 0.5 h.
[0045] After obtaining the mixture, the present invention performs hydrothermal crystallization on the mixture to obtain the low-silicon CHA type molecular sieve.
[0046] In this invention, the hydrothermal crystallization temperature is preferably 90–160°C, more preferably 90–120°C; the time is preferably 48–96 h, more preferably 60–80 h; the hydrothermal crystallization equipment is preferably a stainless steel reactor; the stainless steel reactor preferably includes a polytetrafluoroethylene liner.
[0047] In this invention, the hydrothermal crystallization process preferably includes sequential filtration, washing, and drying; the pH value of the washed product is preferably 7-10, more preferably 7-8; the drying temperature is preferably 75-100℃, more preferably 75-80℃, and the drying time is preferably 12-24h, more preferably 20-24h.
[0048] The present invention also provides a low-silicon CHA-type molecular sieve obtained by the preparation method described above, wherein the silicon-to-aluminum ratio of the low-silicon CHA-type molecular sieve is 1 to 2.1, preferably 1.5 to 2.1.
[0049] In this invention, the particle size of the low-silica CHA-type molecular sieve is preferably 1-5 μm, more preferably 2-4 μm.
[0050] The low-silica CHA-type molecular sieve provided by this invention is composed of composite building units d6r and cha cages, possessing a three-dimensional pore structure. The pore diameter of the CHA molecular sieve in the (001) direction is... It is a typical eight-membered ring small-pore molecular sieve. Under the condition of no template agent addition, a CHA-type molecular sieve with a low silicon-to-aluminum ratio (Si / Al = 2-4) is obtained, also known as chalcogenide, which has wide and important applications in the fields of radioactive ion adsorption and CO2 capture.
[0051] This invention also provides the application of the low-silica CHA-type molecular sieve described above in carbon dioxide separation.
[0052] Preferably, the application is preferred for separating carbon dioxide from a mixture containing acetylene and / or ethylene.
[0053] The present invention does not impose any special limitations on the application process of the low-silicon CHA-type molecular sieve in carbon dioxide separation; any method known to those skilled in the art can be used.
[0054] To further illustrate the present invention, the low-silica CHA-type molecular sieve, its preparation method, and its application provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.
[0055] Example 1
[0056] 0.023 g of sodium hydroxide and 0.457 g of potassium hydroxide were added to 8.83 g of water and stirred until uniformly dissolved. After the solution cooled to room temperature, 0.456 g of boehmite was added and stirred for 2 h. 1.94 g of Sigma-Aldrich silica sol AS-40 was added to the resulting suspension and stirred at 300 rpm for 0.5 h at room temperature. The molar ratio of effective components in the raw materials was 0.092 Na₂O:Al₂O₃:3.99 SiO₂:1.067 K₂O:171 H₂O.
[0057] The resulting mixture was transferred to a stainless steel reactor with a polytetrafluoroethylene liner for hydrothermal crystallization at a temperature of 160°C for 96 hours.
[0058] The crystallized product was collected by filtration, washing and drying. After washing, the pH value was 8, the drying temperature was 75℃ and the drying time was 24h to obtain a low-silica CHA type molecular sieve, denoted as A1.
[0059] Example 2
[0060] 0.11g of sodium hydroxide and 0.32g of potassium hydroxide were added to 7g of water and stirred until dissolved. After the solution cooled to room temperature, 0.488g of spent FCC catalyst was added and stirred for 2 hours. 0.58g of silica sol (30% SiO2 mass fraction) from Luoyang Jianlong Micro-Nano New Materials Co., Ltd. was added to the resulting suspension and stirred at 300 rpm for 0.5 hours at room temperature. The molar ratio of effective components in the raw materials was 0.5Na2O:0.9K2O:Al2O3:2.5SiO2:165H2O.
[0061] The resulting mixture was transferred to a stainless steel reactor with a polytetrafluoroethylene liner for hydrothermal crystallization at a temperature of 90°C for 72 hours.
[0062] The crystallized product was collected by filtration, washing and drying. After washing, the pH value was 8, the drying temperature was 75℃ and the drying time was 24h to obtain a low-silica CHA type molecular sieve, denoted as A2.
[0063] Example 3
[0064] 0.11g of sodium hydroxide and 0.32g of potassium hydroxide were added to 7g of water and stirred until dissolved. After the solution cooled to room temperature, 0.488g of spent FCC catalyst was added and stirred for 2 hours. 0.84g of silica sol (30% SiO2 mass fraction) from Luoyang Jianlong Micro-Nano New Materials Co., Ltd. was added to the resulting suspension and stirred at 300 rpm for 0.5 hours at room temperature. The molar ratio of effective components in the raw materials was 0.5Na2O:0.9K2O:Al2O3:3SiO2:165H2O.
[0065] The resulting mixture was transferred to a stainless steel reactor with a polytetrafluoroethylene liner for hydrothermal crystallization at a temperature of 90°C for 72 hours.
[0066] The crystallized product was collected by filtration, washing and drying. After washing, the pH value was 8, the drying temperature was 75℃ and the drying time was 24h, and a low-silica CHA type molecular sieve was obtained, which was denoted as A3.
[0067] Example 4
[0068] 0.11g of sodium hydroxide and 0.32g of potassium hydroxide were added to 7g of water and stirred until dissolved. After the solution cooled to room temperature, 0.488g of spent FCC catalyst was added and stirred for 2 hours. 0.58g of silica sol (30% SiO2 mass fraction) from Luoyang Jianlong Micro-Nano New Materials Co., Ltd. was added to the resulting suspension and stirred at 300 rpm for 0.5 hours at room temperature. The molar ratio of effective components in the raw materials was 0.5Na2O:0.9K2O:Al2O3:2.5SiO2:165H2O.
[0069] The resulting mixture was transferred to a stainless steel reactor with a polytetrafluoroethylene liner for hydrothermal crystallization at a temperature of 100°C for 72 hours.
[0070] The crystallized product was collected by filtration, washing and drying. After washing, the pH value was 8, the drying temperature was 75℃ and the drying time was 24h to obtain a low-silica CHA type molecular sieve, denoted as A4.
[0071] Example 5
[0072] 0.11g of sodium hydroxide and 0.32g of potassium hydroxide were added to 7g of water and stirred until dissolved. After the solution cooled to room temperature, 0.488g of spent FCC catalyst was added and stirred for 2 hours. 0.58g of silica sol (30% SiO2 mass fraction) from Luoyang Jianlong Micro-Nano New Materials Co., Ltd. was added to the resulting suspension and stirred at 300 rpm for 0.5 hours at room temperature. The molar ratio of effective components in the raw materials was 0.5Na2O:0.9K2O:Al2O3:2.5SiO2:165H2O.
[0073] The resulting mixture was transferred to a stainless steel reactor with a polytetrafluoroethylene liner for hydrothermal crystallization at a temperature of 90°C for 48 hours.
[0074] The crystallized product was collected by filtration, washing and drying. After washing, the pH value was 8, the drying temperature was 75℃ and the drying time was 24h to obtain a low-silica CHA type molecular sieve, denoted as A5.
[0075] Comparative Example 1
[0076] The technical solution described in Comparative Example 1 differs from that in Example 1 in that it uses silica sol (SiO2 mass fraction 30%) from Luoyang Jianlong Micro-Nano New Materials Co., Ltd. instead of Sigma-Aldrich silica sol AS-40, as detailed below:
[0077] 0.023 g of sodium hydroxide and 0.457 g of potassium hydroxide were added to 8.18 g of water and stirred until uniformly dissolved. After the solution cooled to room temperature, 0.456 g of boehmite was added and stirred for 2 h. 2.59 g of silica sol (30% SiO2 by mass) was added to the resulting suspension and stirred at 300 rpm for 0.5 h at room temperature. The molar ratio of effective components in the raw materials was 0.092 Na2O:Al2O3:3.99 SiO2:1.067 K2O:171 H2O.
[0078] The resulting mixture was transferred to a stainless steel reactor with a polytetrafluoroethylene liner for hydrothermal crystallization at a temperature of 160°C for 96 hours.
[0079] The crystallized product was collected by filtration, washing and drying. After washing, the pH value was 8. The drying temperature was 80℃ and the drying time was 24h. The resulting product was designated as B1.
[0080] Comparative Example 2
[0081] The technical solution described in Comparative Example 2 differs from that in Example 2 in that sodium aluminate is used instead of the spent FCC catalyst, as detailed below:
[0082] Add 0.03g sodium hydroxide and 0.298g potassium hydroxide to 7g water and stir until dissolved. After the solution cools to room temperature, add 0.533g sodium aluminate and stir for 2 hours. Add 1.25g of silica sol (SiO2 mass fraction 30%) from Luoyang Jianlong Micro-Nano New Materials Co., Ltd. to the resulting suspension and stir at 300 rpm for 0.5 hours at room temperature. The molar ratio of effective components in the raw materials is 0.5Na2O:0.9K2O:Al2O3:2.5SiO2:165H2O.
[0083] The resulting mixture was transferred to a stainless steel reactor with a polytetrafluoroethylene liner for hydrothermal crystallization at a temperature of 90°C for 72 hours.
[0084] The crystallized product was collected by filtration, washing and drying. After washing, the pH value was 8, the drying temperature was 80℃ and the drying time was 24h. The resulting product was designated as B2.
[0085] Test Example 1
[0086] XRD tests were performed on the products obtained in Examples 1-5 and Comparative Examples 1-2, and scanning electron microscopy was performed on the low-silica CHA-type molecular sieves obtained in Examples 1-5. The XRD test results are shown in the figure. Figure 1 The SEM images of the products obtained in Examples 1-5 are shown below. Figures 2-6 .
[0087] Depend on Figure 1 It can be seen that the low-silica CHA-type molecular sieves obtained in Examples 1-5 are consistent with the standard spectra, are pure phases, and have high crystallinity; the products obtained in Comparative Examples 1-2 are amorphous substances.
[0088] Depend on Figures 2-6 It can be seen that the low-silica CHA-type molecular sieves obtained in Examples 1 to 5 have crystalline morphology.
[0089] Test Example 2
[0090] The adsorption isotherms of CO2, C2H4, and C2H2 of the low-silica CHA-type molecular sieve obtained in Example 1 were tested at 298 K. The test results are as follows: Figure 7 As shown.
[0091] Depend on Figure 7 It can be seen that, under conditions of 298 K, with P / P0 = 1.0 bar in the high-pressure zone, the CO2 adsorption capacity of the low-silica CHA molecular sieve in Example 1 is 71.41464 cm⁻¹. 3 / g, far exceeding the adsorption capacity of C2H2 (13.23477cm). 3 The adsorption capacity of / g and C2H4 was 8.40624cm. 3 / g. The separation coefficients CO2 / C2H2(50 / 50,v / v) and CO2 / C2H4(50 / 50,v / v) are 7.7 and 11.4, respectively, demonstrating that the low-silica CHA molecular sieve in Example 1 has potential application value in the field of CO2 separation.
[0092] Test Example 3
[0093] The adsorption isotherms of CO2, C2H4, and C2H2 of the low-silica CHA-type molecular sieve obtained in Example 2 were tested at 298K. The test results are as follows: Figure 7 As shown.
[0094] Depend on Figure 8 It can be seen that, under conditions of 298K, with P / P0 = 1.0 bar in the high-pressure zone, the CO2 adsorption capacity of the low-silica CHA molecular sieve in Example 2 is 57.22498 cm⁻¹. 3 / g, far exceeding the adsorption capacity of C2H2 (19.02302cm³). 3 The adsorption capacity of / g and C2H4 was 8.16531cm. 3 / g. The separation coefficients CO2 / C2H2(50 / 50,v / v) and CO2 / C2H4(50 / 50,v / v) are 3.8 and 8.1, respectively, demonstrating that the low-silica CHA molecular sieve in Example 1 has potential application value in the field of CO2 separation.
[0095] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method for preparing a low-silica CHA-type molecular sieve, characterized in that, Includes the following steps: An alkali source, an aluminum source, a silicon source, and water are mixed to obtain a mixture; the alkali source includes sodium hydroxide and potassium hydroxide; the aluminum source includes boehmite or FCC waste catalyst; the silicon source and aluminum source are calculated as active ingredients SiO2 and Al2O3, respectively, with a molar ratio of 2~4:1; the silicon source is silica sol. The silica sol contains 30-40% SiO2 by mass. When the aluminum source is boehmite, the silicon source is alkaline silica sol; When the aluminum source is an FCC waste catalyst, the silicon source is a neutral silica sol or an acidic silica sol; The mixture was subjected to hydrothermal crystallization to obtain the low-silica CHA-type molecular sieve; The preparation method does not include metal ion exchange.
2. The preparation method according to claim 1, characterized in that, The molar ratio of sodium hydroxide to potassium hydroxide is 0.082~0.5:0.9~1.
12.
3. The preparation method according to claim 1 or 2, characterized in that, The silicon source and sodium hydroxide, calculated as effective components SiO2 and Na2O respectively, have a molar ratio of 2~4:0.082~0.
5.
4. The preparation method according to claim 1, characterized in that, The silicon source, calculated as the effective component SiO2, has a molar ratio of 2~4:160~180 with water.
5. The preparation method according to claim 1, characterized in that, The hydrothermal crystallization temperature is 90~160℃, and the time is 48~96h.
6. The low-silica CHA-type molecular sieve obtained by the preparation method according to any one of claims 1 to 5, characterized in that, The silica-to-alumina ratio of the low-silicon CHA-type molecular sieve is 1 to 2.
1.
7. The low-silica CHA-type molecular sieve according to claim 6, characterized in that, The low-silica CHA-type molecular sieve has a particle size of 1~5μm.
8. The application of the low-silica CHA-type molecular sieve according to claim 6 or 7 in carbon dioxide separation.
9. The application according to claim 8, characterized in that, The application is to separate carbon dioxide from a mixture of acetylene and / or ethylene.