Method for preparing modified molecular sieve adsorbent and modified molecular sieve adsorbent

Abstract

The application provides a preparation method of a modified molecular sieve adsorbent and the modified molecular sieve adsorbent. The preparation method of the modified molecular sieve adsorbent comprises the following steps: Cu-Zn-Al-LDH preparation: a mixed solution is prepared by preparing a salt solution of Cu, Zn and Al, a soluble carbonate solution with a pH value of 9-10 is prepared, and the mixed solution is added dropwise into the soluble carbonate solution to obtain Cu-Zn-Al-LDH; wherein the ratio of the sum of the moles of Cu and Zn n(Cu+Zn) to the mole of Al n(Al) is 3:1; molecular sieve treatment: the molecular sieve ZSM-5 is treated by hydrochloric acid; and modified molecular sieve adsorbent preparation: the Cu-Zn-Al-LDH is deposited on the molecular sieve ZSM-5, and the modified molecular sieve adsorbent is obtained by drying and calcining.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a method for preparing a modified molecular sieve adsorbent and the modified molecular sieve adsorbent itself. Background Technology

[0002] As an important industrial raw material and clean energy source, the choice of hydrogen production technology is crucial. Compared with methods such as water electrolysis and membrane separation, pressure swing adsorption (PSA) has significant advantages in hydrogen production, including high purity, large gas production, low energy consumption, and a simple process.

[0003] 5A molecular sieves are commonly used in pressure swing adsorption (PSA) for hydrogen production, H2 and CO purification, and petroleum dewaxing. Traditional production processes involve mixing 4A molecular sieve powder with kaolin, granulating the mixture, and then subjecting it to drying, calcination, alkali washing and crystallization, CaCl2 exchange, and activation. However, this method results in high chloride ion content in the wastewater due to the use of calcium chloride, which negatively impacts the activity of microorganisms in wastewater treatment systems, posing environmental challenges.

[0004] ZSM-5 molecular sieve, with its regular micropores, tunable surface polarity, and excellent stability, represents a leap from traditional size sieving to polar-selective adsorption. It transforms a basic adsorbent material into a high-performance, specialized adsorbent capable of handling complex conditions (such as high humidity, multi-component, and macromolecular applications) through functional modification (e.g., metal loading, acid treatment), playing an irreplaceable role, especially in VOCs treatment and petrochemical separation.

[0005] Although ion exchange modification is a conventional strategy for molecular sieves and has been extensively studied in the field of adsorption, its practical application is significantly limited due to inherent drawbacks such as complex operation procedures, low exchange efficiency, and limited applicable systems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a modified molecular sieve adsorbent and the modified molecular sieve adsorbent itself, so as to solve the problems in the prior art.

[0007] To solve the above-mentioned technical problems, the present invention provides a method for preparing a modified molecular sieve adsorbent, comprising the following steps:

[0008] Preparation of Cu-Zn-Al-LDH: Prepare salt solutions of Cu, Zn and Al to obtain a mixed solution, prepare a soluble carbonate solution with a pH of 9-10, and add the mixed solution dropwise to the soluble carbonate solution to obtain Cu-Zn-Al-LDH; wherein the ratio of the sum of the moles of Cu and Zn n(Cu+Zn) to the moles of Al n(Al) is 3:1; Treatment of molecular sieves: ZSM-5 molecular sieves were treated with hydrochloric acid; Preparation of modified molecular sieve adsorbent: Cu-Zn-Al-LDH was deposited onto molecular sieve ZSM-5, and then dried and calcined to obtain the modified molecular sieve adsorbent.

[0009] In one embodiment, the modified molecular sieve adsorbent comprises, by mass percentage, 1%-15% Cu-Zn-Al-LDH and 85%-99% ZSM-5 molecular sieve.

[0010] In one embodiment, the salt solution of Cu, Zn and Al is at least one of nitrate, chloride, bromide or sulfate; The soluble carbonate solution is at least one of potassium carbonate, potassium bicarbonate, sodium bicarbonate, ammonium carbonate, or ammonium bicarbonate.

[0011] In one embodiment, the molar ratio of Cu to Zn is (5%~95%):(95%~5%).

[0012] In one embodiment, the molecular sieve ZSM-5 has a n(SiO2):n(Al2O3) ratio of 50 to 100.

[0013] In one embodiment, the volume ratio of the hydrochloric acid to the weight of the molecular sieve ZSM-5 is 20-30 mL / g, and the amount of hydrochloric acid used is 2-3 mmol / g ZSM-5. The hydrochloric acid treatment time for molecular sieve ZSM-5 is 1~2 h.

[0014] In one embodiment, the treatment of the molecular sieve includes the following steps: Weigh out molecular sieve ZSM-5 and place it in a container, then add deionized water and sonicate to fully disperse the powder and obtain molecular sieve ZSM-5 suspension; Slowly add the HCl solution to the container containing the ZSM-5 molecular sieve suspension and stir for 30-60 minutes. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. The washed solid was dried at 80~110 ℃ to obtain acid-treated molecular sieve ZSM-5.

[0015] In one embodiment, the preparation of the modified molecular sieve adsorbent includes the following steps: Weigh the acid-treated molecular sieve ZSM-5 obtained in the previous step, and then dry it at 100~120 ℃ for 4~6 h to remove adsorbed water; then add the molecular sieve ZSM-5 to deionized water and ultrasonically disperse it evenly at 40~60 ℃ to obtain ZSM-5 molecular sieve dispersion. Slowly add the Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 2-4 hours, then adjust the pH to 8-9 and allow the deposition time to be 1-6 hours. The loaded solid is separated by filtration and washed with deionized water to remove free salts until the washing liquid is nearly neutral. The wet filter cake is dried at 100~120 ℃ for 10~16 h to obtain dry powder. The dried powder is calcined and naturally cooled to obtain the modified molecular sieve adsorbent.

[0016] In one embodiment, the calcination time is 2-6 h; The calcination temperature is 400 ℃~550 ℃; The calcination heating rate is 2~4 °C / min.

[0017] The present invention also provides a modified molecular sieve adsorbent, which is prepared by the preparation method described above.

[0018] As can be seen from the above technical solution, the advantages and positive effects of the present invention are as follows: The preparation method of this invention first prepares SiO2 nanocrystal seeds, then uses these seeds as nucleation sites to effectively control the initiation of crystallization and suppress disordered growth. Simultaneously, the structural template agent, through its guiding effect, ensures uniform crystal growth at the nanoscale. The two work synergistically to guarantee the high controllability, excellent uniformity, and long-term stability of the microcrystalline material formation. Through the synergistic effect of multiple template agents—mesoporous template agents, structurally confined template agents, and microporous template agents—a hierarchical porous structure of micropores and mesopores is simultaneously constructed during crystal formation, resulting in the hierarchical porous microcrystalline adsorbent aluminum silicate. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of the preparation method of the modified molecular sieve adsorbent in this invention.

[0020] Figure 2 These are the XRD patterns of the modified molecular sieve adsorbents prepared in Examples 1 to 4 of this invention and Comparative Example 1.

[0021] Figure 3 These are Fourier transform infrared spectra of the modified molecular sieve adsorbents prepared in Examples 1 to 4 of this invention and Comparative Example 1.

[0022] Figure 4Here are SEM images of different samples from this invention: (a) Unmodified ZSM-5, (b) Cu-Zn-Al-LDH precursor, (c) Cu-Zn-ZSM-5 molecular sieve prepared in Example 1 and (d) Example 3.

[0023] Figure 5 These are the adsorption-desorption curves of the modified molecular sieve adsorbents prepared in Examples 1 to 4 of this invention and Comparative Example 1. Detailed Implementation

[0024] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations herein are for illustrative purposes only and not intended to limit the present invention.

[0025] To further illustrate the principles and structure of the present invention, preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0026] This invention provides a method for preparing a modified molecular sieve adsorbent, which improves the selectivity and adsorption capacity of molecular sieve ZSM-5 by modifying it with Cu and Zn, and exhibits good adsorption capacity for hydrocarbons.

[0027] In this preparation method, Cu-Zn-Al-LDH can be prepared to achieve high dispersion and uniform distribution of Cu and Zn. Acid treatment of molecular sieve ZSM-5 creates secondary mesopores and increases the specific surface area. Nanoscale mesopores are etched on the micropore walls to form a multi-level "micropore-mesopore" pore structure. Cu-Zn-Al-LDH is deposited on molecular sieve ZSM-5 through interfacial bonding, physical coverage, and local coordination to form a tight interface, thereby obtaining a modified molecular sieve adsorbent.

[0028] The preparation method of this modified molecular sieve adsorbent is described in detail below.

[0029] See Figure 1 The preparation method of modified molecular sieve adsorbent includes the following steps: Preparation of S100 and Cu-Zn-Al-LDH: Prepare salt solutions of Cu, Zn and Al to obtain a mixed solution, prepare a soluble carbonate solution with a pH of 9-10, and add the mixed solution dropwise to the soluble carbonate solution to obtain Cu-Zn-Al-LDH; wherein, the ratio of the sum of the moles of Cu and Zn n(Cu+Zn) to the moles of Al n(Al) is 3:1.

[0030] Specifically, it includes the following: S101. Weigh out copper salt, zinc salt and aluminum salt according to the ratio of n(Cu+Zn):n(Al) of 3:1 and n(Cu):n(Zn) of (5%~95%): (95%~5%), and add them to a container containing deionized water to obtain a mixed solution.

[0031] The salt solutions of Cu, Zn, and Al are nitrate solutions.

[0032] In the LDH coprecipitation system, the metal salt should meet the following requirements: good water solubility, no anion participating in precipitation or competing for coordination, no affecting the precise control of pH, and no generating "difficult-to-remove" strongly adsorbed anions in the LDH interlayer.

[0033] Nitrates do not participate in precipitation, are easily eluted, and have minimal interference with the LDH crystal form and interlayer structure. Chlorides and bromides react with Cu. 2+ Zn 2+ It has complexing properties, easily remains on the surface of LDH or ZSM-5, forms metal chlorides / chloride oxides after calcination, and is extremely unfriendly to PSA hydrogen production and the environment. SO4 in sulfates 2- It can enter the LDH interlayer, be difficult to wash off, alter the LDH interlayer spacing and thermal decomposition behavior, and affect metal dispersion and valence state regulation. Therefore, nitrates are selected as the metal salt in this application.

[0034] S102. In another container, prepare an appropriate amount of soluble carbonate solution. Further, place the soluble carbonate solution on a stirrer and stir at 40~60 °C.

[0035] A soluble carbonate solution is at least one of potassium carbonate, potassium bicarbonate, sodium bicarbonate, ammonium carbonate, or ammonium bicarbonate. The function of soluble carbonates is as follows: to provide CO3. 2- (LDH interlayer anion), provides mild alkalinity and precisely maintains pH at 9-10.

[0036] S103. The mixed solution is added dropwise to a soluble carbonate solution to obtain Cu-Zn-Al-LDH.

[0037] Specifically, during the dropwise addition of the mixed solution to the soluble carbonate solution, the pH of the solution is maintained at 9–10. The solution temperature is maintained at 40–60 °C during the dropwise addition, and stirring continues for 2 hours after the addition is complete.

[0038] After stirring for 2 hours, the precipitate was collected by filtration and washed with deionized water until the pH of the washing solution was approximately 7. The wet, muddy Cu-Zn-Al-LDH suspension was retained for later use. The Cu-Zn-Al-LDH precursor was obtained at this point.

[0039] LDH is short for Layered Double Hydroxide, which is chemically composed of positively charged metal hydroxide layers, intercalated anions, and water molecules. The general formula for LDH can be represented as [M... 2 + 1-x M 3+ x (OH)2] z+ [A n- ] z / n mH2O, x is M 3+ / (M 2+ + M 3+ The molar ratio of M to M 2+ M represents a divalent metal cation. 3+ Represents a trivalent metal cation, A n- is the interlayer anion, and m is the number of interlayer water molecules.

[0040] Cu-Zn-Al-LDH is a ternary bilayer metal hydroxide. The divalent metal cations are copper and zinc ions, and the trivalent metal cation is aluminum ion.

[0041] The co-precipitation method for synthesizing Cu-Zn-Al-LDH achieves high dispersion and uniform distribution of Cu and Zn, avoiding aggregation or excessively high local concentrations that may result from single-metal modification. The formation of the LDH precursor essentially locks Cu, Zn, and Al within the same layered lattice, ensuring controllable metal ratios and spatial positions, resulting in an ordered layered structure for subsequent loading. Zn, as a metal additive, not only enhances the dispersion of CuO on the molecular sieve, thereby increasing the number of active sites, but also strengthens the intermetallic interactions, making it easier for reactant molecules to adsorb, thus improving the reaction conversion rate.

[0042] S200, molecular sieve treatment: ZSM-5 molecular sieve is treated with hydrochloric acid.

[0043] In the ZSM-5 molecular sieve, the n(SiO2):n(Al2O3) ratio is 50~100. This refers to the molar ratio.

[0044] The volume ratio of hydrochloric acid to the weight of molecular sieve ZSM-5 is 20-30 mL / g, and the amount of hydrochloric acid used is 2-3 mmol / g ZSM-5. That is, the molar amount of hydrochloric acid to the weight of ZSM-5 is 2-3 mmol / g.

[0045] The treatment time for ZSM-5 molecular sieve with hydrochloric acid is 1-2 hours.

[0046] The specific steps are as follows: S201. Weigh out molecular sieve ZSM-5 and place it in a container. Then add deionized water and sonicate to fully disperse the powder and obtain molecular sieve ZSM-5 suspension.

[0047] The ultrasound time is 2 to 10 minutes. The specific time can be set according to the actual situation.

[0048] S202. Slowly add the HCl solution to the container containing the ZSM-5 molecular sieve suspension and stir for 30-60 minutes.

[0049] Specifically, take concentrated hydrochloric acid and prepare it into an HCl solution with a concentration of 0.1 ~ 0.2 mol / L.

[0050] The temperature during stirring is 25℃.

[0051] S203. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral.

[0052] Specifically, vacuum filtration can be used to separate solids.

[0053] S204. The washed solid is dried at 80~110 ℃ to obtain the acid-treated molecular sieve ZSM-5.

[0054] Preparation of S300 modified molecular sieve adsorbent: Cu-Zn-Al-LDH was deposited onto molecular sieve ZSM-5, and then dried and calcined to obtain the modified molecular sieve adsorbent.

[0055] Specifically, the steps include: S301. Weigh the acid-treated molecular sieve ZSM-5 obtained in the previous step, and then dry it at 100~120 ℃ for 4~6 h to remove adsorbed water. Next, add the molecular sieve ZSM-5 to deionized water and ultrasonically disperse it evenly at 40~60 ℃ to obtain a ZSM-5 molecular sieve dispersion.

[0056] S302. Slowly add the Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring, so that Cu-Zn-Al-LDH is deposited on the surface of the ZSM-5 molecular sieve. Continue stirring for 2-4 h, then adjust the pH to 8-9 and allow the deposition time to be 1-6 h.

[0057] The purpose of this step is to ensure that the metal in the LDH is uniformly deposited on the zeolite surface and at the pore inlet.

[0058] S303. Filter to separate the loaded solids, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100 ℃~120 ℃ for 10~16 h to obtain dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5.

[0059] The calcination time is 2-6 hours. The calcination temperature is 400℃-550℃. The calcination heating rate is 2-4 °C / min.

[0060] In the prepared modified molecular sieve adsorbent, Cu-Zn-Al-LDH accounts for 1%-15% by mass percentage, and molecular sieve ZSM-5 accounts for 85%-99%.

[0061] The preparation method of this application involves preparing Cu-Zn-Al-LDH by co-precipitation. Cu-Zn-Al-LDH is used as a metal precursor. The molecular sieve ZSM-5 is acid-treated to induce the structural tunability of ZSM-5. Then, Cu-Zn-Al-LDH is deposited on the acid-treated molecular sieve ZSM-5 to obtain a modified molecular sieve adsorbent, thereby achieving effective control over the introduction of metal components.

[0062] Modified molecular sieve adsorbents possess both microporous and mesoporous structural characteristics, which facilitates the diffusion and adsorption of gas molecules, resulting in a significant improvement in adsorption capacity. The preparation method described in this application has significant advantages in both structural regulation and adsorption performance, making it particularly suitable for industrial separation applications such as pressure swing adsorption.

[0063] This application also provides a modified molecular sieve adsorbent. This modified molecular sieve adsorbent is prepared using the method described above.

[0064] The inventors of this application have achieved the preparation of modified molecular sieve adsorbents by strictly designing the content of each component and the parameters in each step. The preparation method of modified molecular sieve adsorbents is described below through various embodiments.

[0065] Example 1 The preparation method of the modified molecular sieve adsorbent in this embodiment includes the following steps: Preparation of S11, Cu-Zn-Al-LDH: Dissolve 0.48 g Zn(NO3)2·6H2O, 0.19 g Cu(NO3)2·3H2O, and 0.3 g Al(NO3)3·9H2O in 250 mL of deionized water to obtain a mixed solution, such that the concentration of Zn(NO3)2 in the solution is [missing information]. 2+ +Cu 2+ ): n(Al 3+ )=3:1, and n(Cu): n(Zn)=1:2.

[0066] Prepare a 1.0 M Na₂CO₃ solution in another container. Place the solution on a stirrer and stir at 40 °C.

[0067] The mixed solution was added dropwise to the Na₂CO₃ solution to maintain the pH at 9–10. The temperature was kept at 40 °C, and stirring was continued for 2 h after the addition was complete.

[0068] Filter and collect the precipitate, wash with deionized water until the pH of the washing solution is approximately 7, and retain the wet mud-like LDH suspension for later use.

[0069] S12. Molecular sieve treatment: Weigh 10 g of molecular sieve ZSM-5 and place it in a container. Then add 300 mL of deionized water and sonicate to fully disperse the powder, obtaining a molecular sieve ZSM-5 suspension. Slowly add 300 mL of 0.1 mol / L HCl solution to the container containing the molecular sieve ZSM-5 suspension and stir for 30 min. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. Dry the washed solid at 80 ℃ to obtain acid-treated molecular sieve ZSM-5.

[0070] In molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 100.

[0071] S13. Preparation of Modified Molecular Sieve Adsorbent: Weigh 5g of acid-treated molecular sieve ZSM-5 and dry it at 120℃ for 6 h to remove adsorbed water. Then, add ZSM-5 to deionized water and ultrasonically disperse it evenly at 50℃ to obtain a ZSM-5 molecular sieve dispersion. Slowly add a Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 4 h, then adjust the pH to 8-9 and allow the deposition time to 1 h. Filter to separate the loaded solid, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100℃ for 10 h to obtain a dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5. During calcination, the temperature was raised from 25°C to 120°C and held for 1 hour; then raised to 300°C and held for 1 hour; finally, raised to 500°C and held for 4 hours. The heating rate was 2 °C / min. After calcination, the sample was allowed to cool naturally to 25°C and then removed; this result was Cu–Zn–ZSM-5.

[0072] In this embodiment, Cu-Zn-Al-LDH accounts for 10% of the modified molecular sieve adsorbent.

[0073] Example 2 The difference between this embodiment and Embodiment 1 is that Cu-Zn-Al-LDH accounts for 1% of the modified molecular sieve adsorbent.

[0074] The preparation method of the modified molecular sieve adsorbent in this embodiment includes the following steps: Preparation of S21, Cu-Zn-Al-LDH: Dissolve 0.048 g Zn(NO3)2·6H2O, 0.019 g Cu(NO3)2·3H2O, and 0.03 g Al(NO3)3·9H2O in 250 mL of deionized water to obtain a mixed solution, such that n(Zn)2·6H2O is dissolved in the solution. 2+ +Cu 2+ ):n(Al 3+ )=3:1, and n(Cu): n(Zn)=1:2.

[0075] Prepare a 1.0 M Na₂CO₃ solution in another container. Place the solution on a stirrer and stir at 40 °C.

[0076] The mixed solution was added dropwise to the Na₂CO₃ solution to maintain the pH at 9–10. The temperature was kept at 40 °C, and stirring was continued for 2 h after the addition was complete.

[0077] Filter and collect the precipitate, wash with deionized water until the pH of the washing solution is approximately 7, and retain the wet mud-like LDH suspension for later use.

[0078] S22. Molecular sieve treatment: Weigh 10g of molecular sieve ZSM-5 and place it in a container. Then add 300mL of deionized water and sonicate to fully disperse the powder, obtaining a molecular sieve ZSM-5 suspension. Slowly add 300mL of 0.1mol / L HCl solution to the container containing the molecular sieve ZSM-5 suspension and stir for 30min. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. Dry the washed solid at 80℃ to obtain acid-treated molecular sieve ZSM-5.

[0079] In molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 100.

[0080] S23. Preparation of Modified Molecular Sieve Adsorbent: Weigh 5g of acid-treated molecular sieve ZSM-5 and dry it at 120℃ for 6 h to remove adsorbed water. Then, add ZSM-5 to deionized water and ultrasonically disperse it evenly at 50℃ to obtain a ZSM-5 molecular sieve dispersion. Slowly add a Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 4 h, then adjust the pH to 8-9 and allow the deposition time to 1 h. Filter to separate the loaded solid, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100℃ for 10 h to obtain a dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5. During calcination, the temperature was raised from 25°C to 120°C and held for 1 hour; then raised to 300°C and held for 1 hour; finally, raised to 500°C and held for 4 hours. The heating rate was 2 °C / min. After calcination, the sample was allowed to cool naturally to 25°C and then removed; this result was Cu–Zn–ZSM-5.

[0081] Example 3 The difference between this embodiment and Embodiment 1 is that Cu-Zn-Al-LDH accounts for 5% of the modified molecular sieve adsorbent.

[0082] The preparation method of the modified molecular sieve adsorbent in this embodiment includes the following steps: Preparation of S31, Cu-Zn-Al-LDH: Dissolve 0.024 g Zn(NO3)2·6H2O, 0.095 g Cu(NO3)2·3H2O, and 0.15 g Al(NO3)3·9H2O in 250 mL of deionized water to obtain a mixed solution, such that the concentration of Zn(NO3)2 in the solution is... 2+ +Cu 2+ ):n(Al 3+ )=3:1, and n(Cu): n(Zn)=1:2.

[0083] Prepare a 1.0 M Na₂CO₃ solution in another container. Place the solution on a stirrer and stir at 40 °C.

[0084] The mixed solution was added dropwise to the Na₂CO₃ solution to maintain the pH at 9–10. The temperature was kept at 40 °C, and stirring was continued for 2 h after the addition was complete.

[0085] Filter and collect the precipitate, wash with deionized water until the pH of the washing solution is approximately 7, and retain the wet mud-like LDH suspension for later use.

[0086] S32. Molecular sieve treatment: Weigh 10g of molecular sieve ZSM-5 and place it in a container. Then add 300mL of deionized water and sonicate to fully disperse the powder, obtaining a molecular sieve ZSM-5 suspension. Slowly add 300mL of 0.1mol / L HCl solution to the container containing the molecular sieve ZSM-5 suspension and stir for 30min. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. Dry the washed solid at 80℃ to obtain acid-treated molecular sieve ZSM-5.

[0087] In molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 100.

[0088] S33. Preparation of Modified Molecular Sieve Adsorbent: Weigh 5g of acid-treated molecular sieve ZSM-5 and dry it at 120 ℃ for 6 h to remove adsorbed water. Then, add ZSM-5 to deionized water and ultrasonically disperse it evenly at 50 ℃ to obtain a ZSM-5 molecular sieve dispersion. Slowly add a Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 4 h, then adjust the pH to 8-9 and allow the deposition time to 1 h. Filter to separate the loaded solid, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100 ℃ for 10 h to obtain a dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5. During calcination, the temperature was raised from 25°C to 120°C and held for 1 hour; then raised to 300°C and held for 1 hour; finally, raised to 500°C and held for 4 hours. The heating rate was 2 °C / min. After calcination, the sample was allowed to cool naturally to 25°C and then removed; this result was Cu–Zn–ZSM-5.

[0089] Example 4 The difference between this embodiment and Embodiment 1 is that Cu-Zn-Al-LDH accounts for 15% of the modified molecular sieve adsorbent.

[0090] The preparation method of the modified molecular sieve adsorbent in this embodiment includes the following steps: Preparation of S41, Cu-Zn-Al-LDH: Dissolve 0.72 g Zn(NO3)2·6H2O, 0.285 g Cu(NO3)2·3H2O, and 0.45 g Al(NO3)3·9H2O in 250 mL of deionized water to obtain a mixed solution, such that the concentration of Zn(NO3)2 in the solution is... 2+ +Cu 2+ ):n(Al 3+ )=3:1, and n(Cu): n(Zn)=1:2.

[0091] Prepare a 1.0 M Na₂CO₃ solution in another container. Place the solution on a stirrer and stir at 40 °C.

[0092] The mixed solution was added dropwise to the Na₂CO₃ solution to maintain the pH at 9–10. The temperature was kept at 40 °C, and stirring was continued for 2 h after the addition was complete.

[0093] Filter and collect the precipitate, wash with deionized water until the pH of the washing solution is approximately 7, and retain the wet mud-like LDH suspension for later use.

[0094] S42. Molecular sieve treatment: Weigh 10g of molecular sieve ZSM-5 and place it in a container. Then add 300mL of deionized water and sonicate to fully disperse the powder, obtaining a molecular sieve ZSM-5 suspension. Slowly add 300mL of 0.1mol / L HCl solution to the container containing the molecular sieve ZSM-5 suspension and stir for 30min. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. Dry the washed solid at 80℃ to obtain acid-treated molecular sieve ZSM-5.

[0095] In molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 100.

[0096] S43. Preparation of Modified Molecular Sieve Adsorbent: Weigh 5g of acid-treated molecular sieve ZSM-5 and dry it at 120℃ for 6 h to remove adsorbed water. Then, add ZSM-5 to deionized water and ultrasonically disperse it evenly at 50℃ to obtain a ZSM-5 molecular sieve dispersion. Slowly add a Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 4 h, then adjust the pH to 8-9 and allow the deposition time to 1 h. Filter to separate the loaded solid, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100℃ for 10 h to obtain a dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5. During calcination, the temperature was raised from 25°C to 120°C and held for 1 hour; then raised to 300°C and held for 1 hour; finally, raised to 500°C and held for 4 hours. The heating rate was 2 °C / min. After calcination, the sample was allowed to cool naturally to 25°C and then removed; this result was Cu–Zn–ZSM-5.

[0097] Example 5 The difference between this embodiment and Embodiment 1 is that the molar ratio of Cu and Zn is different.

[0098] The preparation method of the modified molecular sieve adsorbent in this embodiment includes the following steps: Preparation of S51, Cu-Zn-Al-LDH: Dissolve 0.48 g Zn(NO3)2·6H2O, 0.19 g Cu(NO3)2·3H2O, and 0.3 g Al(NO3)3·9H2O in 250 mL of deionized water to obtain a mixed solution, such that the concentration of Zn(NO3)2 in the solution is... 2+ +Cu 2+ ): n(Al 3+ )=3:1, and n(Cu): n(Zn)=5:95.

[0099] Prepare a 1.0 M Na₂CO₃ solution in another container. Place the solution on a stirrer and stir at 40 °C.

[0100] The mixed solution was added dropwise to the Na₂CO₃ solution to maintain the pH at 9–10. The temperature was kept at 40 °C, and stirring was continued for 2 h after the addition was complete.

[0101] Filter and collect the precipitate, wash with deionized water until the pH of the washing solution is approximately 7, and retain the wet mud-like LDH suspension for later use.

[0102] S52. Molecular sieve treatment: Weigh 10g of molecular sieve ZSM-5 and place it in a container. Then add 300mL of deionized water and sonicate to fully disperse the powder, obtaining a molecular sieve ZSM-5 suspension. Slowly add 300mL of 0.1mol / L HCl solution to the container containing the molecular sieve ZSM-5 suspension and stir for 30min. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. Dry the washed solid at 80℃ to obtain acid-treated molecular sieve ZSM-5.

[0103] In molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 100.

[0104] S53. Preparation of Modified Molecular Sieve Adsorbent: Weigh 5g of acid-treated molecular sieve ZSM-5 and dry it at 120℃ for 6 h to remove adsorbed water. Then, add ZSM-5 to deionized water and ultrasonically disperse it evenly at 50℃ to obtain a ZSM-5 molecular sieve dispersion. Slowly add a Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 4 h, then adjust the pH to 8-9 and allow the deposition time to 1 h. Filter to separate the loaded solid, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100℃ for 10 h to obtain a dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5. During calcination, the temperature was raised from 25°C to 120°C and held for 1 hour; then raised to 300°C and held for 1 hour; finally, raised to 500°C and held for 4 hours. The heating rate was 2 °C / min. After calcination, the sample was allowed to cool naturally to 25°C and then removed; this result was Cu–Zn–ZSM-5.

[0105] Example 6 The difference between this embodiment and Embodiment 1 is that the molar ratio of Cu and Zn is different.

[0106] The preparation method of the modified molecular sieve adsorbent in this embodiment includes the following steps: Preparation of S61, Cu-Zn-Al-LDH: Dissolve 0.48 g Zn(NO3)2·6H2O, 0.19 g Cu(NO3)2·3H2O, and 0.3 g Al(NO3)3·9H2O in 250 mL of deionized water to obtain a mixed solution, such that the concentration of Zn(NO3)2 in the solution is equal to the concentration of Cu(NO3)2·6H2O. 2+ +Cu 2+ ): n(Al 3+ )=3:1, and n(Cu): n(Zn)=95:5.

[0107] Prepare a 1.0 M Na₂CO₃ solution in another container. Place the solution on a stirrer and stir at 40 °C.

[0108] The mixed solution was added dropwise to the Na₂CO₃ solution to maintain the pH at 9–10. The temperature was kept at 40 °C, and stirring was continued for 2 h after the addition was complete.

[0109] Filter and collect the precipitate, wash with deionized water until the pH of the washing solution is approximately 7, and retain the wet mud-like LDH suspension for later use.

[0110] S62. Molecular sieve treatment: Weigh 10g of molecular sieve ZSM-5 and place it in a container. Then add 300mL of deionized water and sonicate to fully disperse the powder, obtaining a molecular sieve ZSM-5 suspension. Slowly add 300mL of 0.1mol / L HCl solution to the container containing the molecular sieve ZSM-5 suspension and stir for 30min. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. Dry the washed solid at 80℃ to obtain acid-treated molecular sieve ZSM-5.

[0111] In molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 100.

[0112] S63. Preparation of Modified Molecular Sieve Adsorbent: Weigh 5g of acid-treated molecular sieve ZSM-5 and dry it at 120℃ for 6 h to remove adsorbed water. Then, add ZSM-5 to deionized water and ultrasonically disperse it evenly at 50℃ to obtain a ZSM-5 molecular sieve dispersion. Slowly add a Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 4 h, then adjust the pH to 8-9 and allow the deposition time to 1 h. Filter to separate the loaded solid, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100℃ for 10 h to obtain a dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5. During calcination, the temperature was raised from 25°C to 120°C and held for 1 hour; then raised to 300°C and held for 1 hour; finally, raised to 500°C and held for 4 hours. The heating rate was 2 °C / min. After calcination, the sample was allowed to cool naturally to 25°C and then removed; this result was Cu–Zn–ZSM-5.

[0113] Example 7 The difference between this embodiment and Embodiment 1 is that several parameters are different.

[0114] The preparation method of the modified molecular sieve adsorbent in this embodiment includes the following steps: Preparation of S71, Cu-Zn-Al-LDH: Dissolve 0.48 g Zn(NO3)2·6H2O, 0.19 g Cu(NO3)2·3H2O, and 0.3 g Al(NO3)3·9H2O in 250 mL of deionized water to obtain a mixed solution, such that the concentration of Zn(NO3)2 in the solution is equal to the concentration of Cu(NO3)2·6H2O. 2+ +Cu 2+ ): n(Al 3+ )=3:1, and n(Cu): n(Zn)=1:2.

[0115] Prepare a 1.0 M NaHCO3 solution in another container. Place the solution on a stirrer and stir at 40 °C.

[0116] The mixed solution was added dropwise to the NaHCO3 solution to maintain the pH at 9–10. The temperature was kept at 40 °C, and stirring was continued for 2 h after the addition was complete.

[0117] Filter and collect the precipitate, wash with deionized water until the pH of the washing solution is approximately 7, and retain the wet mud-like LDH suspension for later use.

[0118] S72. Molecular sieve treatment: Weigh 10 g of molecular sieve ZSM-5 and place it in a container. Then add 200 mL of deionized water and sonicate to fully disperse the powder, obtaining a molecular sieve ZSM-5 suspension. Slowly add 200 mL of 0.1 mol / L HCl solution to the container containing the molecular sieve ZSM-5 suspension and stir for 30 min. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. Dry the washed solid at 80 ℃ to obtain acid-treated molecular sieve ZSM-5.

[0119] In molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 50.

[0120] S73. Preparation of Modified Molecular Sieve Adsorbent: Weigh 5g of acid-treated molecular sieve ZSM-5 and dry it at 120℃ for 6 h to remove adsorbed water. Then, add ZSM-5 to deionized water and ultrasonically disperse it evenly at 40℃ to obtain a ZSM-5 molecular sieve dispersion. Slowly add a Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 4 h, then adjust the pH to 8-9 and allow the deposition time to 1 h. Filter to separate the loaded solid, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100℃ for 10 h to obtain a dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5. During calcination, the temperature was raised from 25°C to 120°C and held for 1 hour; then raised to 300°C and held for 1 hour; finally, raised to 550°C and held for 2 hours. The heating rate was 4°C / min. After calcination, the sample was allowed to cool naturally to 25°C and then removed; this result was Cu–Zn–ZSM-5.

[0121] Example 8 The difference between this embodiment and Embodiment 1 is that several parameters are different.

[0122] The preparation method of the modified molecular sieve adsorbent in this embodiment includes the following steps: Preparation of S81, Cu-Zn-Al-LDH: Dissolve 0.48 g Zn(NO3)2·6H2O, 0.19 g Cu(NO3)2·3H2O, and 0.3 g Al(NO3)3·9H2O in 250 mL of deionized water to obtain a mixed solution, such that the concentration of Zn(NO3)2 in the solution is... 2+ +Cu 2+ ): n(Al 3+ )=3:1, and n(Cu): n(Zn)=1:2.

[0123] Prepare a 1.0 M (NH4)2CO3 solution in another container. Place the solution on a stirrer and stir at 40 °C.

[0124] The mixed solution was added dropwise to the (NH4)2CO3 solution to maintain the pH at 9–10. The temperature was kept at 40 °C, and stirring was continued for 2 h after the addition was complete.

[0125] Filter and collect the precipitate, wash with deionized water until the pH of the washing solution is approximately 7, and retain the wet mud-like LDH suspension for later use.

[0126] S82. Molecular sieve treatment: Weigh 10 g of molecular sieve ZSM-5 and place it in a container. Then add 250 mL of deionized water and sonicate to fully disperse the powder, obtaining a molecular sieve ZSM-5 suspension. Slowly add 250 mL of 0.1 mol / L HCl solution to the container containing the molecular sieve ZSM-5 suspension and stir for 30 min. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. Dry the washed solid at 80 ℃ to obtain acid-treated molecular sieve ZSM-5.

[0127] In molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 80.

[0128] S83. Preparation of Modified Molecular Sieve Adsorbent: Weigh 5g of acid-treated molecular sieve ZSM-5 and dry it at 120 ℃ for 6 h to remove adsorbed water. Then, add molecular sieve ZSM-5 to deionized water and ultrasonically disperse it uniformly at 60 ℃ to obtain a ZSM-5 molecular sieve dispersion. Slowly add a Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 4 h, then adjust the pH to 8-9 and allow the deposition time to 1 h. Filter to separate the loaded solid, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100 ℃ for 10 h to obtain a dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5. During calcination, the temperature was raised from 25°C to 120°C and held for 1 hour; then raised to 300°C and held for 1 hour; finally, raised to 400°C and held for 6 hours. The heating rate was 3 °C / min. After calcination, the sample was allowed to cool naturally to 25°C and then removed; this result was Cu–Zn–ZSM-5.

[0129] Example 9 The difference between this embodiment and Embodiment 1 is that several parameters are different.

[0130] The preparation method of the modified molecular sieve adsorbent in this embodiment includes the following steps: Preparation of S91, Cu-Zn-Al-LDH: Dissolve 0.48 g Zn(NO3)2·6H2O, 0.19 g Cu(NO3)2·3H2O, and 0.3 g Al(NO3)3·9H2O in 250 mL of deionized water to obtain a mixed solution, such that n(Zn)2·6H2O is dissolved in the solution. 2+ +Cu 2+ ): n(Al 3+ )=3:1, and n(Cu): n(Zn)=1:2.

[0131] Prepare a 1.0 M K₂CO₃ solution in another container. Place the solution on a stirrer and stir at 40 °C.

[0132] The mixed solution was added dropwise to the K2CO3 solution to maintain the pH at 9–10. The temperature was kept at 40 °C, and stirring was continued for 2 h after the addition was complete.

[0133] Filter and collect the precipitate, wash with deionized water until the pH of the washing solution is approximately 7, and retain the wet mud-like LDH suspension for later use.

[0134] S92. Molecular sieve treatment: Weigh 10 g of molecular sieve ZSM-5 and place it in a container. Then add 300 mL of deionized water and sonicate to fully disperse the powder, obtaining a molecular sieve ZSM-5 suspension. Slowly add 300 mL of 0.1 mol / L HCl solution to the container containing the molecular sieve ZSM-5 suspension and stir for 30 min. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. Dry the washed solid at 80 ℃ to obtain acid-treated molecular sieve ZSM-5.

[0135] In molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 100.

[0136] S93. Preparation of Modified Molecular Sieve Adsorbent: Weigh 5g of acid-treated molecular sieve ZSM-5 and dry it at 120℃ for 6 h to remove adsorbed water. Then, add ZSM-5 to deionized water and ultrasonically disperse it evenly at 45℃ to obtain a ZSM-5 molecular sieve dispersion. Slowly add a Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 4 h, then adjust the pH to 8-9 and allow the deposition time to 6 h. Filter to separate the loaded solid, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100℃ for 10 h to obtain a dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5. During calcination, the temperature was raised from 25°C to 120°C and held for 1 hour; then raised to 300°C and held for 1 hour; finally, raised to 500°C and held for 4 hours. The heating rate was 2 °C / min. After calcination, the sample was allowed to cool naturally to 25°C and then removed; this result was Cu–Zn–ZSM-5.

[0137] Example 10 The preparation method of the modified molecular sieve adsorbent in this embodiment includes the following steps: Preparation of S101 and Cu-Zn-Al-LDH: Dissolve 0.48 g Zn(NO3)2·6H2O, 0.19 g Cu(NO3)2·3H2O and 0.3 g Al(NO3)3·9H2O in 250 mL of deionized water to obtain a mixed solution, so that the concentration of Zn(NO3)2 in the solution is equal to the concentration of Cu(NO3)2·6H2O. 2+ +Cu 2+ ): n(Al 3+ )=3:1, and n(Cu): n(Zn)=1:2.

[0138] Prepare a 1.0 M Na₂CO₃ solution in another container. Place the solution on a stirrer and stir at 40 °C.

[0139] The mixed solution was added dropwise to the Na₂CO₃ solution to maintain the pH at 9–10. The temperature was kept at 40 °C, and stirring was continued for 2 h after the addition was complete.

[0140] Filter and collect the precipitate, wash with deionized water until the pH of the washing solution is approximately 7, and retain the wet mud-like LDH suspension for later use.

[0141] S102. Molecular sieve treatment: Weigh 10 g of molecular sieve ZSM-5 and place it in a container. Then add 300 mL of deionized water and sonicate to fully disperse the powder, obtaining a molecular sieve ZSM-5 suspension. Slowly add 300 mL of 0.1 mol / L HCl solution to the container containing the molecular sieve ZSM-5 suspension and stir for 30 min. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. Dry the washed solid at 80 ℃ to obtain acid-treated molecular sieve ZSM-5.

[0142] In molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 100.

[0143] S103. Preparation of Modified Molecular Sieve Adsorbent: Weigh 5g of acid-treated molecular sieve ZSM-5 and dry it at 120℃ for 6 h to remove adsorbed water. Then, add ZSM-5 to deionized water and ultrasonically disperse it evenly at 45℃ to obtain a ZSM-5 molecular sieve dispersion. Slowly add a Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 4 h, then adjust the pH to 8-9 and allow the deposition time to 6 h. Filter to separate the loaded solid, wash with deionized water to remove free salts until the washing solution is nearly neutral. Dry the wet filter cake at 100℃ for 10 h to obtain a dry powder. Calcine the dried powder and allow it to cool naturally to obtain the modified molecular sieve adsorbent, Cu-Zn-ZSM-5. During calcination, the temperature was raised from 25°C to 120°C and held for 1 hour; then raised to 300°C and held for 1 hour; finally, raised to 500°C and held for 4 hours. The heating rate was 2 °C / min. After calcination, the sample was allowed to cool naturally to 25°C and then removed; this result was Cu–Zn–ZSM-5.

[0144] Comparative Example 1 Without Cu-Zn modification, the other steps are the same as in Example 1, and the resulting molecular sieve is ZSM-5.

[0145] Comparative Example 2 Without using Zn, with n(Cu):n(Al) ratio of 3:1, and other steps being the same as in Example 1, molecular sieve ZSM-5 modified only with Cu was obtained.

[0146] Comparative Example 3 Without using Cu, the ratio of n(Zn):n(Al) is 3:1, and the other steps are the same as in Example 1, resulting in ZSM-5 molecular sieve modified only with Zn.

[0147] The adsorption performance of the modified molecular sieve adsorbents in Examples 1-10 and Comparative Examples 1-5 was evaluated using the following methods: The adsorption amounts of N2, O2, CO, and CH4 for each molecular sieve were determined by volumetric adsorption at 25 °C and 101.325 × 103 Pa. The data obtained are shown in Table 1.

[0148] Table 1 Adsorption performance of molecular sieves

[0149] As shown in Table 1, the adsorption performance of the modified molecular sieve adsorbents in the examples is better than that in Comparative Example 1.

[0150] Figure 2 The XRD patterns of the modified molecular sieve adsorbent Cu-Zn-ZSM-5 prepared in Examples 1 to 4 and Comparative Example 1 are shown. All the major diffraction peaks appearing in the figures, such as those at 2θ of approximately 7.9°, 8.8°, 23.1°, 23.9° and 24.4°, are completely consistent with the characteristic diffraction peaks of the pentasilicone ring zeolite topology of the standard ZSM-5 molecular sieve. Therefore, the modification process in this application did not destroy the core framework structure of the ZSM-5 molecular sieve itself.

[0151] Figure 3 The Fourier transform infrared (FT-IR) spectra of the modified molecular sieve adsorbent Cu-Zn-ZSM-5 prepared in Examples 1 to 4 and Comparative Example 1 are shown. Figure 2 Middle, 1220 cm - ¹ and -1100 cm - ¹Attributable to the asymmetric stretching vibration of the silicon-oxygen tetrahedron (Si-O-Si). The position and shape of the peak remained essentially unchanged in all samples, indicating that the framework structure of ZSM-5 remained intact after copper-zinc modification. 550 cm⁻¹ - The peak at ¹ is a characteristic double-ring vibrational peak of the pentasilicone ring zeolite structure and a characteristic fingerprint peak of ZSM-5 molecular sieve. Its stable presence in all samples further demonstrates the preservation of the host crystal structure after modification. (1630 cm⁻¹) - ¹H HOH bending vibrations attributed to adsorbed water.

[0152] Figure 4SEM images of different samples are shown. The crystals shown in the images exhibit a very regular hexagonal prismatic structure, which is a very classic and common crystal morphology of ZSM-5 zeolite. The crystal sizes in the samples are highly uniform, and the lengths of most crystals are concentrated between 2-3 μm.

[0153] Figure 5 The adsorption and desorption curves of the modified molecular sieve adsorbents prepared in Examples 1 to 4 and Comparative Example 1 are shown. As can be seen from the figure, all the adsorbents exhibit a type I and type IV composite isotherm. When P / P0 is less than 0.2, the curve is type I, and when 0.2 < P / P0 < 1, it is type IV and the curve shows a hysteresis loop, indicating that there are certain mesopores in the adsorbent.

[0154] Although the present invention has been described with reference to several exemplary embodiments, it should be understood that the terms used are illustrative and exemplary, rather than restrictive. Since the present invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above-described embodiments are not limited to any of the foregoing details, but should be broadly construed within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A method for preparing a modified molecular sieve adsorbent, characterized by, Includes the following steps: Preparation of Cu-Zn-Al-LDH: Prepare salt solutions of Cu, Zn and Al to obtain a mixed solution, prepare a soluble carbonate solution with a pH of 9-10, and add the mixed solution dropwise to the soluble carbonate solution to obtain Cu-Zn-Al-LDH; wherein the ratio of the sum of the moles of Cu and Zn n(Cu + Zn) to the moles of Al n(Al) is 3:1; Treatment of molecular sieves: ZSM-5 molecular sieves were treated with hydrochloric acid; Preparation of modified molecular sieve adsorbent: Cu-Zn-Al-LDH was deposited onto molecular sieve ZSM-5, and then dried and calcined to obtain the modified molecular sieve adsorbent.

2. The method for preparing the modified molecular sieve adsorbent according to claim 1, characterized in that, By mass percentage, the modified molecular sieve adsorbent contains 1%-15% Cu-Zn-Al-LDH and 85%-99% ZSM-5 molecular sieve.

3. The method for preparing the modified molecular sieve adsorbent according to claim 1, characterized in that, The salt solution of Cu, Zn and Al is a nitrate solution; The soluble carbonate solution is at least one of potassium carbonate, potassium bicarbonate, sodium bicarbonate, ammonium carbonate, or ammonium bicarbonate.

4. The method for preparing the modified molecular sieve adsorbent according to claim 1, characterized in that, The molar ratio of Cu to Zn is (5%~95%):(95%~5%).

5. The method for preparing the modified molecular sieve adsorbent according to claim 1, characterized in that, In the molecular sieve ZSM-5, the ratio of n(SiO2):n(Al2O3) is 50~100.

6. The method for preparing the modified molecular sieve adsorbent according to claim 1, characterized in that, The volume ratio of the hydrochloric acid to the weight of the molecular sieve ZSM-5 is 20-30 mL / g, and the amount of hydrochloric acid used is 2-3 mmol / g ZSM-5; The hydrochloric acid treatment time for molecular sieve ZSM-5 is 1~2 h.

7. The method for preparing the modified molecular sieve adsorbent according to claim 1, characterized in that, The processing of the molecular sieve includes the following steps: Weigh out molecular sieve ZSM-5 and place it in a container, then add deionized water and sonicate to fully disperse the powder and obtain molecular sieve ZSM-5 suspension; Slowly add the HCl solution to the container containing the ZSM-5 molecular sieve suspension and stir for 30-60 minutes. After stirring, separate the solid and wash it repeatedly with deionized water until the pH of the filtrate is close to neutral. The washed solid was dried at 80~110 ℃ to obtain acid-treated molecular sieve ZSM-5.

8. The method for preparing the modified molecular sieve adsorbent according to claim 1, characterized in that, The preparation of the modified molecular sieve adsorbent includes the following steps: Weigh the acid-treated molecular sieve ZSM-5 obtained in the previous step, and then dry it at 100~120 ℃ for 4~6 h to remove adsorbed water; then add the molecular sieve ZSM-5 to deionized water and ultrasonically disperse it evenly at 40~60 ℃ to obtain ZSM-5 molecular sieve dispersion. Slowly add the Cu-Zn-Al-LDH wet mud suspension to the ZSM-5 molecular sieve dispersion while stirring to allow Cu-Zn-Al-LDH to deposit on the surface of the ZSM-5 molecular sieve. Continue stirring for 2-4 hours, then adjust the pH to 8-9 and allow the deposition time to be 1-6 hours. The loaded solid is separated by filtration and washed with deionized water to remove free salts until the washing liquid is nearly neutral. The wet filter cake is dried at 100~120 ℃ for 10~16 h to obtain dry powder. The dried powder is calcined and naturally cooled to obtain the modified molecular sieve adsorbent.

9. The method for preparing the modified molecular sieve adsorbent according to claim 1, characterized in that, The calcination time is 2-6 h; The calcination temperature is 400 ℃~550 ℃; The calcination heating rate is 2~4 °C / min.

10. A modified molecular sieve adsorbent, characterized in that, The modified molecular sieve adsorbent is prepared by the preparation method according to any one of claims 1 to 9.

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