Preparation method and application of amine-functionalized hierarchical pore NaX zeolite

Abstract

The invention discloses a preparation method and application of amine-functionalized hierarchical pore NaX zeolite, and belongs to the technical field of material preparation and environment purification. Under the condition of not adding any template and other auxiliaries, only an aluminum source, a silicon source and a sodium source are adopted as raw materials, a long-time aging process is omitted, the hierarchical porous Kazaku type NaX zeolite is prepared through simple hydrothermal crystallization, and then the amine-functionalized hierarchical porous NaX zeolite is obtained through amino loading. The NaX zeolite prepared by the method is high in crystallinity and has a Kazaku-shaped morphology, a large specific surface area and a micro-mesoporous structure are obtained, the amido loading capacity is improved, and the obtained amido composite material can be used for efficiently and selectively adsorbing SO2 gas and has good water resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation and environmental purification, and relates to a preparation technology and application of a Kayu-type NaX zeolite adsorbent, and specifically to a method for preparing a multi-level pore Kayu-type zeolite by a template-free method and its application in highly selective removal of SO 2 Application in this area. Background Art

[0002] Sulfur dioxide (SO 2 ) is a typical atmospheric pollutant mainly produced by human activities, which is prone to cause acid rain and atmospheric particulate matter. Therefore, reducing SO 2 Emissions are one of the key goals in the pursuit of global environmental sustainability. In recent decades, China has been committed to reducing anthropogenic SO 2 However, low concentrations of SO 2 Removal remains a challenge.

[0003] Adsorption technology is currently recognized as an economical and effective technology for removing sulfur-containing gases. Metal oxides, metal organic frameworks (MOFs), activated carbon and zeolites are commonly used as solid adsorbents. Zeolites are widely used in the adsorption field due to their adjustable structure, good thermal stability and non-flammability. In the 1970s, NaX was used for air separation (Natl. Sci. Rev. 2022, 9). In addition, NaX has a high affinity for SO 2 With CO 2 、N 2 It also shows a certain selective adsorption capacity in mixed environments (J.Hazard. Mater., 2012, 203-204). However, most of the reported FAU zeolites have low selectivity for SO 2 The adsorption capacity and selectivity of adsorbents are generally not ideal, which may be due to limited adsorption sites or microporous structure limitations. Therefore, it is necessary to develop adsorbent materials with excellent adsorption performance and high selectivity.

[0004] Studies have shown that the introduction of additional adsorption sites (such as amine groups) on porous materials can enhance the adsorption of SO 2 However, the microporous structure of FAU zeolites limits the accessibility of adsorption sites. Therefore, it is necessary to alleviate the diffusion limitation of molecules within zeolite materials, which can be achieved by constructing a multi-level pore structure. In addition, the porous structure can also promote the attachment of macromolecules to the zeolite channels, thereby facilitating the immobilization of amines.

[0005] At present, hierarchical pore zeolites with a house-of-cards (HCL) structure have been reported. For example, a triangular nanosheet-assembled HCL zeolite NaX (Angew. Chem. Int. Ed., 2012, 1962-1965) was prepared by using soft templates such as 3-(trimethoxysilyl)propyl hexadecyldimethylammonium chloride (TPHAC). Alternatively, inorganic salts (such as Li 2 CO 3 or Zn(NO 3 ) 2 ), can prepare NaX zeolite with layered morphology (Chemical Communications, 2015, 279-281). However, considering the additional cost and potential environmental hazards of removing these templates and inorganic salt additives, the above methods are not conducive to the promotion of industrial applications. In addition, the currently reported synthesis route of HCL structure FAU type zeolite usually requires a long aging (1-3 days) and hydrothermal crystallization time due to its slow crystallization at low temperature, which also increases the time cost of zeolite synthesis. Therefore, it is necessary to design a simple and green strategy for the rapid synthesis of NaX hierarchical pore zeolite. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing hierarchical pore casa-shaped NaX zeolite by an amine-loaded template-free method and its application. This method obtains a casa-shaped NaX carrier through a simple precursor mixing strategy, introduces an additional mesoporous structure, and further immobilizes an amine-based ionic liquid CT into NaX to obtain a composite solid adsorbent. The adsorbent prepared by this method has abundant amine base adsorption sites and can achieve SO at low temperature and low pressure. 2 High selective adsorption and good water resistance.

[0007] To achieve the above object, the present invention adopts the following technical solution: A method for preparing amine-functionalized hierarchical pore Kayu-type NaX zeolite by a template-free method, comprising the following steps: Step 1: Add water to the silicon source, aluminum source, and sodium source, and stir at room temperature for 2 h to allow the materials to fully contact; Step 2: The material obtained in step 1 is transferred to a Telfon reactor and placed in an oven for hydrothermal crystallization; Step 3: After the Telfon reactor is cooled, the solid product obtained after the crystallization in step 2 is washed with deionized water until it is neutral, and then centrifuged, filtered, and dried to obtain the multi-level pore Kayu-type NaX zeolite.

[0008] Step 4: By adjusting the raw material ratio, aging time, hydrothermal crystallization temperature and time of the above steps 1-3, a traditional microporous NaX material can be obtained.

[0009] Step 5: The raw materials caprolactam (CPL) and tetrabutylammonium bromide (TBAB) were mixed and reacted at 90 °C. The reaction product was vacuum dried at 120 °C for 2 h to obtain amine-based ionic liquid CT.

[0010] Step 6: Disperse NaX and CT in a certain proportion in methanol solvent, stir continuously at room temperature for 24 h, and dry in a vacuum oven overnight to obtain an amine-loaded NaX adsorbent.

[0011] Furthermore, the aluminum source in step 1 is sodium aluminate (NaAlO 2 ).

[0012] Furthermore, the silicon source in step 1 is a sodium silicate solution.

[0013] Furthermore, the sodium source in step 1 is sodium aluminate (NaAlO 2 ), at least one of sodium silicate and sodium hydroxide (NaOH).

[0014] Further, the silicon source SiO used in step 1 2 、Sodium source Na 2 O, aluminum source Al 2 O 3 The molar ratio of SiO to water is 2 :Na 2 O:Al 2 O 3 :H 2 O = 2.51:2.58:1.0:70.5.

[0015] Furthermore, the hydrothermal crystallization temperature in step 2 is 60-75°C and the time is 6-48 h.

[0016] Furthermore, the drying temperature in step 3 is 60-75° C. and the drying time is 12-24 h.

[0017] Further, the molar ratio of the raw materials used in step 4 is SiO 2 :Na 2 O:Al 2 O 3 :H 2 O = 2.51:3.52:1.0:151.5.

[0018] Furthermore, the hydrothermal crystallization temperature in step 4 is 75° C. and the time is 72 h.

[0019] Furthermore, the drying temperature in step 4 is 75° C. and the drying time is 12-24 h.

[0020] Furthermore, the mass ratio of CT to NaX in step 6 is 1.2:1.0.

[0021] The specific surface area of ​​the prepared Kayu-type NaX zeolite is 645 m 2 / g, and the micropore volume is 0.28 cm 3 / g, and the mesopore volume is 0.17 cm 3 / g, amine-supported NaX adsorbent at 25 °C and 1.0 bar pressure, SO 2 The adsorption capacity is 10.58 mmol / g in SO 2 / N 2 and SO 2 / CO 2 SO adsorption in binary atmosphere 2 The selectivities were as high as 1673 and 219 respectively.

[0022] The significant advantages of the present invention are: The preparation method of the present invention is simple, green, economical, energy-saving and efficient. The obtained NaX zeolite has a house-like morphology and a multi-level pore structure, high crystallinity, high amine utilization rate, and can achieve SO under normal temperature and pressure conditions. 2 The highly selective adsorption of gases, and it was recycled 6 times, 2 The adsorption rate can still be maintained above 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the SEM image of the zeolite sample prepared in Example 1-2.

[0024] Figure 2 XRD spectra of the adsorbent samples prepared in Examples 1-4.

[0025] Figure 3 XRD spectra and crystallization curves of the adsorbent samples prepared in Example 1 at different crystallization times.

[0026] Figure 4 XRD diagrams of the adsorbent samples prepared in Example 1 with different raw material ratios.

[0027] Figure 5 These are SEM images of the adsorbent samples prepared in Example 1 with different raw material ratios.

[0028] Figure 6 N is the N of the adsorbent samples prepared in Examples 1-4 2 -Absorption and removal of attached pictures.

[0029] Figure 7 The pore size distribution diagram of the adsorbent samples prepared in Examples 1-4.

[0030] Figure 8 is the SO of the adsorbent samples prepared in Examples 1-4 2 Static adsorption curve.

[0031] Fig. 9 is the SO of the adsorbent samples prepared in Examples 1-4 2 Selective graph. DETAILED DESCRIPTION

[0032] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0033] Example 1 The template-free hydrothermal method is used to synthesize the Kayu-type NaX zeolite, which specifically includes the following steps: Weigh 1.2 g NaAlO 2 , added to a solution consisting of 0.5 g NaOH and 6.7 g deionized water, and then 3.9 g sodium silicate solution (27.8% SiO 2 , 8.4% Na 2 O, 63.8% H 2 O), stirred at room temperature for 2 h to allow the components to fully contact and obtain the initial gel. The initial gel was transferred to the Telfon kettle lining, and the kettle was placed in an oven for hydrothermal crystallization at 70 °C for 24 h. After the crystallization, the solid product was washed, filtered, and dried at 70 °C for 24 h. The prepared zeolite sample was named X-HCL.

[0034] Example 2 (Traditional) Weigh 1.2 g NaAlO 2 , added to a solution consisting of 1.0 g NaOH and 17 g deionized water, and then added 3.9 g sodium silicate solution, stirred at room temperature for 2 h to allow the components to fully contact, and an initial gel was obtained. After aging the initial gel for 1 day, it was transferred to the Telfon kettle lining, and the kettle was placed in an oven for hydrothermal crystallization at 75 ° C for 72 h. Other operations were the same as in Example 1, and the prepared zeolite sample was named XT.

[0035] Example 3 The raw materials CPL and TBAB were added to the flask in a molar ratio of 2:1, heated to 90 °C, and stirred until a uniform liquid phase was formed. After vacuum drying at 120 °C for 2 h, an amine-based ionic liquid product was obtained, named CT. 1.0 g of X-HCL carrier and 1.2 g of CT were placed in 10 mL of methanol solvent, stirred continuously at room temperature for 24 h, and dried in a vacuum oven at 60 °C overnight to obtain an amine-based supported NaX (CT / X-HCL) adsorbent.

[0036] Example 4 The zeolite carrier in Example 3 was changed to XT, and other operations were the same as in Example 3. The prepared amine-loaded NaX adsorbent was named CT / XT.

[0037] Figure 1 The scanning electron microscope images of the zeolite samples prepared in Examples 1-2 are shown. As can be seen from the images, the zeolite sample synthesized in Example 1 exhibits a crisscrossed house-like morphology, which is significantly different from the traditional octahedral morphology of Example 2.

[0038] Figure 2 The XRD spectra of the adsorbent samples prepared in Examples 1-4 are shown. As can be seen from the figure, the characteristic peaks of the samples synthesized in Examples 1-4 are basically consistent with the PDF standard card of pure NaX (JCPSD NO.38-0237). This proves that the NaX zeolite was successfully prepared by the template-free method. After loading the amine ionic liquid, the crystallinity was reduced, but the good crystal phase structure was still maintained.

[0039] Figure 3 The XRD spectra and crystallization curves of the adsorbent prepared in Example 1 at different crystallization times (only the crystallization time is different, and the rest of the operations are the same as in Example 1). The material begins to nucleate after 3 h of crystallization and forms a complete crystalline phase after 24 h.

[0040] Figure 4 The XRD patterns of the adsorbent samples prepared in Example 1 with different raw material ratios (only the raw material ratio is different, and the rest of the operations are the same as in Example 1). 2 O / Al 2 O 3 The molar ratio is too high and H 2 O / Al 2 O 3 A molar ratio that is too high or too low can easily lead to a decrease in the crystallinity of NaX and even the appearance of impurity peaks.

[0041] Figure 5 The SEM images of the adsorbent samples prepared in Example 1 with different raw material ratios (only the raw material ratio is different, and the rest of the operations are the same as in Example 1). 2 O / Al 2 O 3 The molar ratio gradually decreases, and too low Na 2 O / Al 2 O 3 The molar ratio resulted in the failure of the complete construction of the sample's card house morphology ( Figure 5 The particle size of the sample changes with H. 2 O / Al 2 O 3The molar ratio increases gradually. 2 O / Al 2 O 3 The molar ratio leads to the transformation of the sample morphology to octahedral ( Figure 5 (see the four small pictures below).

[0042] Figure 6 N is the N of the adsorbent prepared in Examples 1-4 2 Adsorption-desorption curves. According to the IUPAC classification, the XT sample shows a type I adsorption isotherm, that is, it has a good microporous structure, while the X-HCL sample shows a type IV adsorption isotherm, showing the characteristics of a mesoporous structure.

[0043] Figure 7 The pore size distribution diagram of the zeolite samples prepared in Examples 1 to 4 shows that the prepared X-HCL retains the microporous structure of NaX while also introducing a mesoporous structure. After loading CT, the pore size distribution of the sample decreases.

[0044] Figure 8 is the SO of the adsorbent samples prepared in Examples 1-4 2 Static adsorption curve. From the results obtained, it can be seen that the prepared X-HCL sample is better than the traditional XT for SO 2 The adsorption effect of CT / X-HCL on SO is better. 2 The adsorption enhancement effect is also significantly better than CT / XT.

[0045] Table 1 shows the textural property parameters and adsorption capacity of the zeolite samples prepared in Examples 1-4 of the present invention.

[0046] Table 1 Structural parameters and adsorption capacity of samples in Example As shown in Table 1, the specific surface area and micropore volume of the X-HCL sample synthesized in Example 1 are basically the same as those of the XT conventional NaX zeolite synthesized in Example 2, but the mesopore volume is significantly increased to 0.17 cm 3 / g, indicating that the synthesized card house-type X-HCL material has an improved multi-level pore structure and SO 2 In addition, the specific surface area and pore structure of CT / X-HCL (Example 3) and CT / XT (Example 4) materials were greatly reduced due to the CT loading entering or blocking the pores of some zeolites. However, the introduced amine base adsorption sites significantly increased the SO 2 Adsorption, the adsorption amount can reach 10.58 mmol / g.

[0047] Fig. 9 is the SO of the adsorbent samples prepared in Examples 1-42 / CO 2 Selectivity diagram, it can be seen that with SO 2 The molar partial pressure increases, and compared with the original NaX carrier, the adsorbent loaded with CT has a higher SO 2 The selectivity of CT / X-HCL materials is gradually improved. 2 The strongest selection ability.

[0048] In summary, the X-HCL zeolite prepared by the present invention is simple in process and has a multi-level pore structure, which is more conducive to the loading of amino groups. 2 It has excellent performance in adsorption and removal. In addition, it has good water resistance and cyclic stability (the adsorption performance can still be maintained at more than 90% after 6 cycles), and has great application potential.

[0049] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing an amine-functionalized hierarchical pore NaX zeolite, characterized in that: The following steps are involved: 1) Add water to the silicon source, aluminum source and sodium source and mix them, and stir them at room temperature for 2 h to allow the materials to fully contact; 2) subjecting the material obtained in step 1) to hydrothermal crystallization; 3) washing the solid product obtained after the crystallization in step 2) with deionized water until it is neutral, and then centrifuging, filtering and drying to obtain the multi-level pore Kayu-type NaX zeolite; 4) caprolactam and tetrabutylammonium bromide were mixed and reacted at 90 °C, and the reaction product was vacuum dried at 120 °C for 2 h to obtain amine-based ionic liquid CT; 5) NaX zeolite and amine-based ionic liquid CT were dispersed in a methanol solvent in a certain proportion, stirred continuously for 24 h at room temperature, and dried in a vacuum oven overnight to obtain amine-functionalized hierarchical pore NaX zeolite.

2. The method according to claim 1, characterized in that The aluminum source in step 1) is sodium aluminate.

3. The method according to claim 1, characterized in that The silicon source in step 1) is a sodium silicate solution.

4. The method according to claim 1, characterized in that: The sodium source in step 1) is at least one of sodium aluminate, sodium silicate and sodium hydroxide.

5. The method according to claim 1, characterized in that The raw materials silicon source, aluminum source, sodium source and water used in step 1) are configured in a molar ratio of SiO2: Al2O3: Na2O: H2O = 2.51: 1.0: 2.58: 70.

5.

6. The method according to claim 1, characterized in that The temperature of the hydrothermal crystallization in step 2) is 60-75°C and the time is 6-48 h.

7. The method according to claim 1, characterized in that The drying temperature in step 3) is 60-75°C and the drying time is 12-24 hours.

8. The method according to claim 1, characterized in that In step 4), the molar ratio of caprolactam to tetrabutylammonium bromide is 2:

1.

9. The method according to claim 1, characterized in that: In step 5), the mass ratio of the amine-based ionic liquid CT to the NaX zeolite is 1.2:1.

0.

10. An application of the amine-functionalized hierarchical pore NaX zeolite prepared by the method of claim 1 in the adsorption and removal of SO2, characterized in that: At 25°C and 0-1 bar, the amine-functionalized hierarchical pore NaX zeolite is used as an adsorbent for adsorbing SO2 gas.

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