Molecular sieve for CO2 adsorption based on ternary ion modification and preparation method thereof

Abstract

The invention discloses a preparation method of a molecular sieve for CO2 adsorption based on ternary ion modification, which comprises the following steps: drying pretreatment: placing a molecular sieve matrix in a drying box to obtain a dried molecular sieve; first ion exchange; carrying out secondary ion exchange; performing ion exchange for the third time; washing and drying: taking out the molecular sieve subjected to the third ion exchange, washing the molecular sieve with deionized water until the molecular sieve is neutral, and drying the molecular sieve; roasting and activating at high temperature, namely roasting and activating the molecular sieve subjected to ion exchange for three times and drying treatment in a nitrogen atmosphere; the metal cation in the first metal salt solution is Na < + >, the metal cation in the second metal salt solution is Li < + >, and the metal cation in the third metal salt solution is one of Zn < 2 + >, Ca < 2 + > and K < + >. The molecular sieve provided by the invention has high specific surface area, optimized pore structure and good cycle stability.

Description

Technical Field

[0001] The present invention relates to the field of adsorption materials, and in particular to a method for preparing a ternary ion-modified molecular sieve, and is suitable for the preparation method and application of adsorption materials for CO2 adsorption. Background Art

[0002] With the development of industrialization, carbon dioxide (CO2) emissions have increased year by year. As one of the main greenhouse gases, the continued accumulation of CO2 has become an important driving factor for global climate change. Molecular sieves have been widely used in the field of CO2 capture and separation due to their regular pore structure, high specific surface area and good thermal stability. However, traditional molecular sieves have some limitations in CO2 adsorption performance, such as insufficient adsorption capacity, low selectivity and poor recycling performance, which limit their further promotion in industrial-scale applications.

[0003] In order to overcome the above problems, the modification of molecular sieves by ion exchange has become a research hotspot. By introducing metal ions, the acidity and alkalinity of the molecular sieve surface, polarity and charge distribution in the pores can be effectively regulated, which can improve the CO2 adsorption performance of the molecular sieve. However, the traditional single ion modification method can usually only improve certain specific properties, and the overall performance improvement in adsorption capacity and cycle stability is limited.

[0004] Multi-ion synergistic modification is an emerging research direction. Its core is to optimize the surface properties and pore environment of molecular sieves through the synergistic effect of different ions, increase the diversity of adsorption sites, and thus improve the adsorption performance of molecular sieves for CO2. Summary of the invention

[0005] In view of the problems existing in the prior art, in order to solve the problem of low CO2 adsorption capacity of traditional molecular sieve adsorbents, the present invention provides a molecular sieve modified by ternary ions and a preparation method thereof, which can improve the adsorption performance of molecular sieves for CO2, specifically including the following contents:

[0006] Specifically, the molecular sieve is a 5A molecular sieve modified by a ternary metal cation.

[0007] Specifically, the molecular sieve matrix has a particle diameter of 1.6 to 2.5 mm and a specific surface area of ​​300 to 500 m 2 / g, pore volume 0.1~0.5cc / g.

[0008] Specifically, the first metal cation is Na + , the second metal cation is Li + , the third metal cation is Zn 2 + , Ca 2+ , K+ One of them.

[0009] Specifically, the modified molecular sieve preparation steps include:

[0010] S1 Drying pretreatment: placing the molecular sieve substrate in a drying oven to obtain a dry molecular sieve;

[0011] S2: First ion exchange: The original dry molecular sieve is replaced with the first metal ion solution by heating and stirring in a water bath;

[0012] S3 washing and drying: taking out the molecular sieve that has completed the first ion exchange, washing it with deionized water until it is neutral, and then drying it;

[0013] S4 Second ion exchange: transfer the dried molecular sieve after the first ion exchange to the second metal ion solution for a second water bath heating and stirring replacement;

[0014] S5 washing and drying: taking out the molecular sieve that has completed the second ion exchange, washing it with deionized water until it is neutral, and then drying it;

[0015] S6 The third ion exchange: the dried molecular sieve after the second ion exchange is transferred to the third metal ion solution for the third water bath heating and stirring replacement;

[0016] S7 washing and drying: taking out the molecular sieve that has completed the third ion exchange, washing it with deionized water until it is neutral, and then drying it;

[0017] S8 high temperature calcination activation: the molecular sieve which has been ion exchanged three times and dried is placed in an inert atmosphere for calcination activation;

[0018] Specifically, the molecular sieve in step S1 is 5A molecular sieve.

[0019] Specifically, the pH value of the ion exchange liquid in steps S2, S4 and S6 is 4-6.

[0020] Specifically, in steps S2, S4, and S6, the molar ratio of the first metal cation, the second metal cation, and the third metal cation is 1:0.5:(0.2-0.4).

[0021] Specifically, the molar concentration of the first metal ion solution in steps S2, S4 and S6 is 0.5-1 mol / L, and the solid-liquid ratio of the three ion exchange solutions is 1:(10-15).

[0022] Specifically, in steps S1, S3, S5 and S7, the drying temperature is 110-130°C, and the drying time is 10-12 hours.

[0023] Specifically, in steps S2, S4 and S6, the ion exchange temperature is 80-90°C and the time is 1-3 hours.

[0024] Specifically, the inert gas in step S8 is nitrogen, the calcination temperature is 300-500° C., and the calcination time is 1-4 hours.

[0025] Beneficial effects of the present invention:

[0026] (1) The present invention discloses the synergistic modification of ternary metal ions, and introduces multiple active sites on the surface and inside of the pores of the molecular sieve, which can enhance the adsorption capacity of CO2 molecules by regulating the charge balance and surface acidity and alkalinity. In addition, the synergistic effect between different metal ions can significantly increase the adsorption energy of CO2 molecules, especially under low pressure or room temperature conditions, the modified molecular sieve shows an adsorption capacity far higher than that of the unmodified molecular sieve, which has obvious advantages in industrial applications.

[0027] (2) The present invention utilizes the synergistic modification of multiple metal ions to adjust the surface charge distribution and polarity of the molecular sieve, so that it exhibits a higher affinity for CO2 molecules. Specifically, the molecular sieve after ion exchange can not only enhance the chemical adsorption of CO2 molecules, but also reduce the non-selective adsorption of other gas molecules. This characteristic enables the modified molecular sieve to exhibit higher selectivity in the mixed gas separation process, which can effectively improve the separation efficiency.

[0028] (3) The present invention can greatly improve the structural stability and thermal shock resistance of the molecular sieve by optimizing the ion exchange process and the calcination process. In multiple adsorption-desorption cycles, the modified molecular sieve can maintain efficient adsorption performance without pore collapse or loss of active sites. This stability is mainly due to the uniform distribution of various metal ions in the molecular sieve structure and the stable chemical bonds formed during the calcination process. In addition, the modified molecular sieve has a strong tolerance to water vapor and other impurities, which can further improve its service life and performance stability in actual industrial operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the principle of preparing modified molecular sieves by ternary ion exchange disclosed in the present invention. Figure 2 This is the process flow chart of molecular sieve modification. Figure 3 The XRD test diagrams of the implementation case and the original 5A molecular sieve. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be particularly noted that the embodiments described below are only used to more clearly explain the content of the present invention, are not limited to the best embodiment, and do not limit the content and protection scope of the present invention. In addition, all the constituent contents described in these embodiments are not essential components of the inventive solutions in the claims.

[0031] Example 1

[0032] This example provides Na + , Li + , Zn 2+ The method for preparing a ternary ion-modified molecular sieve comprises:

[0033] S1 Drying pretreatment: Place the 5A molecular sieve substrate in a drying oven and dry it at 120°C for 10 hours to obtain a dry molecular sieve;

[0034] S2: First ion exchange: The original dry molecular sieve is heated in a water bath with a first metal salt solution NaCl solution with a concentration of 0.5 mol / L and stirred for replacement at a temperature of 90°C for 2 hours.

[0035] S3 washing and drying: take out the molecular sieve that has completed the first ion exchange, rinse it with deionized water until the pH value is neutral, and dry the rinsed molecular sieve at 120°C for 12 hours to ensure that the moisture is removed and the molecular sieve structure is stabilized;

[0036] S4 Second ion exchange: transfer the dried molecular sieve after the first ion exchange to a second metal salt solution LiCl solution with a concentration of 0.25 mol / L for a second water bath heating and stirring replacement, the ion exchange temperature is 90°C, and the time is 2h;

[0037] S5 washing and drying: take out the molecular sieve that has completed the second ion exchange, rinse it with deionized water until the pH value is neutral, and dry the rinsed molecular sieve at 120°C for 12 hours to ensure that the moisture is removed and the molecular sieve structure is stabilized;

[0038] S6 The third ion exchange: the dried molecular sieve after the second ion exchange is transferred to the third metal salt solution ZnCl2 solution with a concentration of 0.1 mol / L for the third water bath heating and stirring replacement, the ion exchange temperature is 90 ° C, and the time is 2h;

[0039] S7 washing and drying: take out the molecular sieve that has completed the third ion exchange, rinse it with deionized water until the pH value is neutral, and dry the rinsed molecular sieve at 120°C for 12 hours to ensure that the moisture is removed and the molecular sieve structure is stabilized;

[0040] S8 high temperature calcination activation: the molecular sieve which has undergone three ion exchange and drying treatment is placed in a nitrogen atmosphere for calcination activation at a calcination temperature of 450°C and a calcination time of 1h;

[0041] The prepared Li + , Na + , Zn 2+ The XRD diffraction peaks of the ternary ion modified molecular sieve did not change significantly after modification, indicating that the crystal structure did not change before and after modification. The XRD test results are as follows: Figure 3 The adsorption capacity of Example 1 was tested at three temperature conditions: 25°C, 35°C, and 45°C, and the pressure was set in the range of 0 to 1 MPa. The isothermal adsorption line of Na + , Li + , Zn 2+ The CO2 adsorption capacity of the ternary ion modified molecular sieve is 16% higher than that of the original 5A molecular sieve. After 50 cycles of adsorption-desorption, the adsorption capacity decreases by less than 5%, maintaining efficient adsorption performance.

[0042] Example 2

[0043] This example provides Na + , Li + , Ca 2+ Preparation method of ternary ion modified molecular sieve

[0044] S1 Drying pretreatment: Place the 5A molecular sieve substrate in a drying oven and dry it at 110°C for 10 hours to obtain a dry molecular sieve;

[0045] S2: First ion exchange: The original dry molecular sieve is heated in a water bath with a first metal salt solution NaCl solution with a concentration of 0.6 mol / L and stirred for replacement at a temperature of 80°C for 3 hours.

[0046] S3 washing and drying: take out the molecular sieve that has completed the first ion exchange, rinse it with deionized water until the pH value is neutral, and dry the rinsed molecular sieve at 110°C for 12 hours to ensure that the moisture is removed and the molecular sieve structure is stabilized;

[0047] S4 Second ion exchange: transfer the dried molecular sieve after the first ion exchange to a second metal salt solution LiCl solution with a concentration of 0.3 mol / L for a second water bath heating and stirring replacement, the ion exchange temperature is 80°C, and the time is 1h;

[0048] S5 washing and drying: take out the molecular sieve that has completed the second ion exchange, rinse it with deionized water until the pH value is neutral, and dry the rinsed molecular sieve at 110°C for 12 hours to ensure that the moisture is removed and the molecular sieve structure is stabilized;

[0049] S6 The third ion exchange: the dried molecular sieve after the second ion exchange is transferred to the third metal salt solution ZnCl2 solution with a concentration of 0.2 mol / L for the third water bath heating and stirring replacement, the ion exchange temperature is 80 ° C, and the time is 1 hour;

[0050] S7 washing and drying: take out the molecular sieve that has completed the third ion exchange, rinse it with deionized water until the pH value is neutral, and dry the rinsed molecular sieve at 110°C for 12 hours to ensure that the moisture is removed and the molecular sieve structure is stabilized;

[0051] S8 high temperature calcination activation: the molecular sieve which has been ion exchanged three times and dried is placed in a nitrogen atmosphere for calcination activation at a temperature of 500°C and a calcination time of 1 hour;

[0052] The prepared Na + , Li + , Ca 2+ The XRD diffraction peaks of the ternary ion modified molecular sieve did not change significantly after modification, indicating that the crystal structure did not change before and after modification. The XRD test results are as follows: Figure 3 The adsorption capacity of Example 1 was tested at three temperature conditions: 25°C, 35°C, and 45°C, and the pressure was set in the range of 0 to 1 MPa. The isothermal adsorption line of Na + , Li + , Ca 2+ The CO2 adsorption capacity of the ternary ion modified molecular sieve is 20% higher than that of the original 5A molecular sieve. After 50 cycles of adsorption-desorption, the adsorption capacity decreases by less than 7%, maintaining efficient adsorption performance.

[0053] Example 3

[0054] This example provides Na + , Li + , K + Preparation method of ternary ion modified molecular sieve

[0055] S1 Drying pretreatment: Place the 5A molecular sieve substrate in a drying oven and dry it at 90°C for 10 hours to obtain a dry molecular sieve;

[0056] S2: First ion exchange: The original dried molecular sieve is heated in a water bath with a first metal salt solution NaCl solution with a concentration of 0.8 mol / L and stirred for replacement at a temperature of 80°C for 2 h.

[0057] S3 washing and drying: take out the molecular sieve that has completed the first ion exchange, rinse it with deionized water until the pH value is neutral, and dry the rinsed molecular sieve at 130°C for 10 hours to ensure that the moisture is removed and the molecular sieve structure is stabilized;

[0058] S4 Second ion exchange: transfer the dried molecular sieve after the first ion exchange to a second metal salt solution LiCl solution with a concentration of 0.4 mol / L for a second water bath heating and stirring replacement, the ion exchange temperature is 80°C, and the time is 1h;

[0059] S5 washing and drying: take out the molecular sieve that has completed the second ion exchange, rinse it with deionized water until the pH value is neutral, and dry the rinsed molecular sieve at 130°C for 10 hours to ensure that the moisture is removed and the molecular sieve structure is stabilized;

[0060] S6 The third ion exchange: the dried molecular sieve after the second ion exchange is transferred to the third metal salt solution ZnCl2 solution with a concentration of 0.2 mol / L for the third water bath heating and stirring replacement, the ion exchange temperature is 80 ° C, and the time is 1 hour;

[0061] S7 washing and drying: take out the molecular sieve that has completed the third ion exchange, rinse it with deionized water until the pH value is neutral, and dry the rinsed molecular sieve at 130°C for 10 hours to ensure that the moisture is removed and the molecular sieve structure is stabilized;

[0062] S8 high temperature calcination activation: the molecular sieve which has undergone three ion exchange and drying treatment is placed in a nitrogen atmosphere for calcination activation at a calcination temperature of 350°C and a calcination time of 4h;

[0063] The prepared Na + , Li + , K + The XRD diffraction peaks of the ternary ion modified molecular sieve did not change significantly after modification, indicating that the crystal structure did not change before and after modification. The XRD test results are as follows: Figure 3 The adsorption capacity of Example 1 was tested at three temperature conditions: 25°C, 35°C, and 45°C, and the pressure was set in the range of 0 to 1 MPa. The isothermal adsorption line of Na + , Li + , K + The CO2 adsorption capacity of the ternary ion modified molecular sieve is 25% higher than that of the original 5A molecular sieve. After 50 cycles of adsorption-desorption, the adsorption capacity decreases by less than 7%, maintaining efficient adsorption performance.

[0064] Through the above description of the disclosed embodiments, professionals in the field can use and implement the present invention. Various modifications to these embodiments are apparent to professionals in the field. The general principles defined herein can be applied to other embodiments without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments described herein, but covers the broadest range consistent with the principles and innovative features disclosed herein.

Claims

1. A method for preparing a molecular sieve for CO2 adsorption based on ternary ion modification, characterized in that The following steps are involved: S1 Drying pretreatment: placing the molecular sieve substrate in a drying oven for drying to obtain a dry molecular sieve; S2: First ion exchange: Place the original dry molecular sieve and the first metal ion solution in a water bath and perform heating and stirring for ion exchange; S3 washing and drying: taking out the molecular sieve that has completed the first ion exchange, washing it with deionized water until it is neutral, and then drying it; S4 Second ion exchange: transfer the dried molecular sieve after the first ion exchange to the second metal ion solution for a second water bath heating and stirring replacement; S5 washing and drying: taking out the molecular sieve that has completed the second ion exchange, washing it with deionized water until it is neutral, and then drying it; S6 The third ion exchange: the dried molecular sieve after the second ion exchange is transferred to the third metal ion solution for the third water bath heating and stirring replacement; S7 washing and drying: taking out the molecular sieve that has completed the third ion exchange, washing it with deionized water until it is neutral, and then drying it; S8 high temperature calcination activation: the molecular sieve which has been ion exchanged three times and dried is placed in an inert atmosphere for calcination activation; The first metal cation is Na + , the second metal cation is Li + , the third metal cation is Zn 2+ , Ca 2+ , K + One of the above; the molecular sieve in step S1 is 5A molecular sieve; The pH value of the ion exchange liquid in steps S2, S4 and S6 is 4 to 6; In the steps S2, S4 and S6, the molar ratio of the first metal cation, the second metal cation and the third metal cation is 1:0.5:(0.2-0.4); The molar concentration of the first metal ion solution in steps S2, S4 and S6 is 0.5-1 mol / L, and the solid-liquid ratio of the three ion exchange solutions is 1:(10-15); In the steps S2, S4 and S6, the ion exchange temperature is 80-90°C and the time is 1-3h; The inert gas in step S8 is nitrogen, the calcination temperature is 300-500° C., and the calcination time is 1-4 hours.

2. The preparation method according to claim 1, characterized in that: In the steps S1, S3, S5 and S7, the drying temperature is 110-130° C. and the drying time is 10-12 hours.

3. A molecular sieve prepared by the method according to claim 1.

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