Molecular adsorption coating for in-situ encapsulation of metal particles in graded FAU zeolite through ALD and preparation method of molecular adsorption coating

Abstract

The invention discloses a molecular adsorption coating for in-situ encapsulation of metal particles in graded FAU zeolite through ALD and a preparation method of the molecular adsorption coating, and belongs to the field of special functional coatings. The invention aims to solve the problems that a molecular sieve adsorption coating lacks effective chemical adsorption sites and is easy to desorb after adsorbing pollution molecules. According to the invention, metal particles are packaged in situ in graded FAU zeolite through an ALD technology, and a molecular adsorption coating with high adsorption binding force and stability is prepared; the coating comprises a functional filler and a binder, the binder is prepared silica sol, and the composite coating is formed through a spraying process; the coating has two action modes of physical adsorption and chemical adsorption when interacting with pollutant molecules, the adsorption capacity of the coating can be remarkably improved, and the long-term stable adsorption effect is achieved. The method can be applied to the fields of spacecraft thermal control systems, air purification, sewage treatment, pollution protection and the like, and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of special functional coatings, and specifically, relates to a molecular adsorption coating for in-situ encapsulation of metal particles in graded FAU zeolite by atomic layer deposition (ALD) technology and a preparation method thereof. The technology can be widely used in the fields of spacecraft thermal control systems, air purification, sewage treatment and pollution protection, and has broad application prospects. Background Art

[0002] With the continuous improvement of the accuracy of spacecraft optical and thermal control systems, higher requirements are placed on the control of space molecular pollutants. Space molecular pollutants mainly come from the gassing effect of spacecraft materials. These pollutants will form a film on the surface of the spacecraft, affecting the performance of sensitive devices such as optical devices, thermal control coatings, and solar panels. Traditional zeolite molecular sieve materials have been widely used to adsorb volatile organic compounds (VOCs) due to their large specific surface area and pore size. However, the surface of traditional zeolite materials exhibits a certain degree of hydrophilicity, which limits its adsorption capacity for small organic molecule pollutants. In addition, the adsorption performance of zeolite molecular sieves will drop significantly in low-pressure environments, making it difficult to meet the pollution control needs of spacecraft in extreme environments.

[0003] Although traditional molecular sieve modification methods (such as acid etching, alkaline etching, etc.) can regulate the pore structure, they easily lead to the destruction of the molecular sieve skeleton structure and the reduction of specific surface area. In addition, traditional coatings lack strong binding force to pollutants, resulting in easy desorption of adsorbed pollutants, affecting the long-term performance of the coating. Therefore, it is of great significance to develop a molecular adsorption coating that can improve the adsorption and binding force of the coating through the synergistic effect of chemical adsorption and physical adsorption. Summary of the invention

[0004] At this stage, the present invention aims to solve the problem that the molecular sieve adsorption coating lacks effective chemical adsorption sites and is easy to desorb after adsorbing pollutant molecules. This patent provides a preparation method of a molecular adsorption coating of graded FAU zeolite in-situ encapsulated metal particles using ALD technology, which increases the adsorption and binding capacity of the molecular sieve adsorption coating through the synergistic effect of chemical adsorption and physical adsorption.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The object of the present invention is to provide a method for preparing a molecular adsorption coating for in-situ encapsulation of metal particles in a graded FAU zeolite by ALD, characterized in that it comprises the following steps:

[0007] Step 1: synthesizing and preparing hierarchical pore FAU zeolite by hydrothermal method;

[0008] Step 2, pre-treating the graded FAU zeolite at a certain temperature;

[0009] Step 3: ALD technology is then used to in-situ encapsulate metal particles (functional fillers) on the surface of the pretreated FAU zeolite;

[0010] Step 4: then mix evenly with silica sol to form a slurry;

[0011] Step 5: Then apply it to the surface of the substrate, heat and cure it to obtain the molecular adsorption coating.

[0012] It is further defined that in step 1, the graded pore FAU zeolite is prepared according to the following steps:

[0013] Step 1, 2.4 g of sodium hydroxide, 7.5 g of 40 wt% silica sol and 20 g of water were stirred and dissolved at 90° C. for 15 minutes to prepare solution A;

[0014] Step 2, 2.73 g of sodium aluminate, 1.1 g of sodium hydroxide and 20 g of water were stirred at room temperature for 30 minutes, and 1.66 g of CTAB was added after dissolution, and stirring was continued for 30 minutes to obtain solution B;

[0015] Step 3, under vigorous stirring, slowly add solution A to solution B until a uniform gel is formed, crystallize at 90°C for 12 hours, centrifuge, wash the solid with distilled water 3-5 times until the pH value reaches 7-8, and then dry at 80°C for 3 hours;

[0016] Step 4: Then, the temperature is raised to 550° C. within 0.5 hours, kept at that temperature for 8 hours, and then naturally cooled to room temperature to obtain graded pore FAU zeolite.

[0017] It is further defined that in step 2, the pretreatment is to place the zeolite molecular sieve powder into a tubular furnace, heat it at a rate of 200°C-300°C within 0.5h, then evacuate it to -0.1MPa, keep it at this temperature and pressure for 2h-5h, and finally cool it naturally to room temperature.

[0018] Further, in step 3, the in-situ encapsulated metal particles are CoOx, TiO 2 , one of ZnO, CuO, and FeOx.

[0019] Further, in step 3, the ALD technology in-situ encapsulation of metal particles is specifically performed as follows: the pre-treated graded pore FAU zeolite powder is placed in the deposition chamber of the atomic layer deposition instrument, and the chamber is first evacuated to 4×10 -3 Up to 6×10 -3 Torr, then introduce carrier gas to raise the chamber pressure to 0.1 Torr; adjust the source bottle temperature to 70℃-85℃ and the chamber temperature to 200℃-320℃, and the cycle period is 10cycle-70cycle.

[0020] It is further defined that the pigment-to-base ratio of the functional filler to the silica sol in step 4 is (0.2-1):1, and the mixing and stirring time is 2h-3h.

[0021] It is further defined that the base material of the coating in step five can be selected from metal materials such as aluminum alloy, or non-metallic bases such as resins and organic-inorganic composite materials.

[0022] It is further defined that the preparation process of the coating in step five covers a variety of methods such as spraying, brushing, scraping, and spin coating, and the specific method can be selected according to actual needs; the process parameters such as spraying pressure, spraying speed, and spray gun distance can be adjusted according to actual needs.

[0023] It is further defined that in step five, the curing is first heated to 60° C. and kept warm for 1 hour; then the temperature is further heated to 80° C. and kept warm for 8 hours.

[0024] The present invention also aims to provide a molecular adsorption coating prepared by any of the above methods.

[0025] The present invention provides a molecular adsorption coating for in-situ encapsulation of metal particles by graded FAU zeolite constructed by ALD technology. The coating has both physical adsorption and chemical adsorption when interacting with pollutant molecules, which can significantly improve the adsorption capacity of the coating and achieve a long-term stable adsorption effect. The coating includes a functional filler and a binder. The functional coating is synthesized by a template method to synthesize multi-level porous FAU zeolite and then encapsulates metal particles on its surface by ALD technology. The binder is a prepared silica sol, and the composite coating is formed by a spraying process. By providing chemical adsorption sites, the adsorption binding force of the coating is improved, so that it can stably adsorb pollutants.

[0026] The present invention uses ALD technology to in-situ encapsulate metal particles in graded FAU zeolite to prepare a molecular adsorption coating with high adsorption binding force and stability. The present invention has the following beneficial effects:

[0027] The FAU zeolite prepared by the template method of the present invention has a multi-level pore structure of micropores and mesopores, can provide more adsorption sites under a low-pressure environment, and improves the low-pressure adsorption performance of the coating.

[0028] The present invention uses ALD technology to in-situ encapsulate metal particles (such as TiO 2 , CoOx, ZnO, CuO, FeOx, etc.), the metal particles form stable chemical bonds with the hydroxyl groups on the surface of the zeolite, providing chemical adsorption sites and enhancing the binding ability of the coating with pollutants.

[0029] The present invention uses the synergistic effect of chemical adsorption and physical adsorption, so that the coating can stably adsorb space molecular pollutants for a long time, reduce the desorption phenomenon of pollutants, and improve adsorption stability.

[0030] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the attached drawings are only provided for reference and illustration and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a SEM image of the graded pore FAU zeolite prepared by the method of Example 1;

[0032] Figure 2 1 is the XRD diagram of the graded pore FAU zeolite molecular sieve prepared by the method of Example 1 and the FAU zeolite molecular sieve in situ encapsulated with metal particles by ALD technology;

[0033] Figure 3 The nitrogen isotherm adsorption-desorption curve of the graded pore FAU zeolite molecular sieve prepared by the method of Example 1;

[0034] Figure 4 This is the adsorption amount graph of the coating prepared by the method of Example 1 for 88 hours;

[0035] Figure 5 This is a graph of the adsorption amount of the coating prepared by the method of Example 2 for 88 hours. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, and do not limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0037] Example 1

[0038] (1) Preparation of hierarchical pore FAU zeolite

[0039] The hierarchical FAU zeolite was synthesized by a hydrothermal method, and the specific steps are as follows: first, 2.4 g of sodium hydroxide, 7.5 g of silica sol (40% wt) and 20 g of water were stirred at 90°C for 15 minutes to dissolve to prepare solution A. Secondly, 2.73 g of sodium aluminate, 1.1 g of sodium hydroxide and 20 g of water were stirred at room temperature for 30 minutes, and 1.66 g of CTAB was added after dissolution, and stirring was continued for 30 minutes to obtain solution B. Subsequently, solution A was slowly added to solution B under vigorous stirring until a uniform gel was formed. The final composition of the gel was 3.5 Na 2 O:1Al 2 O3 :3SiO 2 :180H 2 O:0.7CTAB. The mixture was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and crystallized at 90°C for 12 hours. After crystallization, the solid product was separated by centrifugation, washed with distilled water 3-5 times until the pH value reached 7-8, and then dried at 80°C for 3 hours. Finally, the dried product was calcined in a tubular furnace to remove the template, and the heating program was set to heat to 550°C within 0.5 hours, and then naturally cooled to room temperature after 8 hours of heat preservation to obtain the graded pore FAU zeolite.

[0040] (2) Graded pore FAU zeolite pretreatment

[0041] Load the prepared graded pore FAU molecular sieve into a magnetic boat dedicated to the tube furnace and place it in the heating area of ​​the tube furnace. Then, close both ends of the tube furnace, connect one end to the mechanical pump, and tighten the valve at the other end. Start the mechanical pump, vacuum for 30 minutes, and then turn it off. Set the heating program to heat to 200°C within 30 minutes, keep it at this temperature for 2 hours, and finally cool it naturally to room temperature.

[0042] (3) ALD technology for in-situ encapsulation of metal particles

[0043] The pretreated graded FAU zeolite was placed in the ALD reaction chamber and heated by C 12 H 28 O 4 Ti (titanium tetraisopropoxide) and deionized water were used as precursors, nitrogen was used as the load gas, the deposition temperature was set to 220 °C, the source bottle temperature was 80 °C, the pulse time was 0.2 s, the cycle was 50 cycles, and TiO was in situ encapsulated on the graded pore FAU zeolite. 2 .

[0044] (4) Configuration of molecular adsorption coating spray slurry

[0045] The functional filler and silica sol are accurately weighed according to a preset ratio and placed in a mixing container. At room temperature, a mechanical stirrer is used to stir at a constant speed for 30 minutes to ensure that the functional filler and silica sol are fully mixed and form a uniform suspension system to obtain a spray slurry.

[0046] (5) Spraying of molecular adsorption coating

[0047] This embodiment uses aluminum alloy thin plate as the substrate material. First, the substrate surface is polished with 500-mesh sandpaper, and then placed in anhydrous ethanol for ultrasonic cleaning for 30 minutes to remove surface impurities. The prepared spray diluent is evenly sprayed on the surface of the aluminum alloy substrate. The specific spraying parameters are as follows: the nozzle diameter is 2.5mm, the spray gun pressure is 1.5MPa, the spray gun moving speed is 80cm / s, and the spray distance is 20cm. In order to ensure the uniformity and density of the coating, multiple spraying processes are adopted. After each spraying, the coating surface is naturally air-dried before the next spraying. After the spraying is completed, the coating sample is placed in a vacuum oven for programmed temperature curing treatment to enhance the bonding force between the coating and the substrate. The curing program is set as follows: first, the temperature is raised to 60°C at a set rate and kept warm for 1 hour; then the temperature is continued to rise to 80°C and kept warm for 8 hours. After the above process treatment, an adsorption coating with excellent adsorption performance and good stability is finally obtained.

[0048] The test results of the scanning electron microscope of the hierarchical pore FAU zeolite molecular sieve obtained in this example are as follows: Figure 1 As shown, after template synthesis, the surface of the zeolite presents an irregular morphology of stacked layers, indicating that the addition of the template has caused a significant change in the morphology of the FAU zeolite.

[0049] The XRD test results of the graded pore FAU zeolite molecular sieve obtained in this example and the FAU zeolite molecular sieve in situ encapsulated with metal particles by ALD technology are shown in Figure 2. Figure 2 As shown, the diffraction peak positions of the zeolite synthesized by the template method and the zeolite after deposition of metal particles are basically consistent with those of the FAU zeolite characterization card, and the zeolite has good crystallinity, indicating that the addition of the template and the in-situ encapsulation of metal particles have no effect on the crystal structure of the FAU zeolite.

[0050] The test results of the 77.3K nitrogen adsorption-desorption curve of the graded pore FAU zeolite molecular sieve obtained in this example are as follows: Figure 3 As shown in the figure, the hierarchical pore FAU zeolite molecular sieve has a small hysteresis loop in the range of p / p0 of 0.7-0.9, indicating that it has a small amount of mesoporous structure. The hierarchical pore structure of micropores and mesopores can provide more adsorption sites. According to the BET method, its specific surface area is 13X (816.76 m 2 / g) increased (904.05m 2 / g), and the large specific surface area is conducive to the adsorption of pollutant molecules.

[0051] Adsorption performance test was conducted under vacuum environment using dioctyl phthalate as the target pollutant. The specific experimental steps are as follows: the molecular adsorption coating material obtained in Example 1 was placed together with dioctyl phthalate in a space molecular contamination vacuum test system, and the temperature of the heating table was set to 60°C. The adsorption experiment was conducted under heating conditions, sampling was performed every 60 minutes, and then the samples were transferred to a precision balance for weighing. The adsorption amount was determined by calculating the mass difference before and after weighing. The experimental results are shown in the following table:

[0052] Table 1

[0053] Adsorption time (min) <![CDATA[吸附量(mg / cm 2 )]]> 60 1.1429 120 1.8761 180 2.4733 240 2.8714 300 3.1857

[0054] As shown in Table 1, the adsorption amount of the molecular adsorption coating material obtained in Example 1 gradually increases within 300 min, and the adsorption amount can reach 3.1857 mg / cm within 300 min. 2 .

[0055] The molecular adsorption coating material obtained in Example 1 and the typical molecular pollutant dioctyl phthalate were placed in a space molecular pollution vacuum test system, and the temperature of the heating table was set to 60°C. The adsorption experiment was carried out on the heating table, and after 88 hours, the precision balance in the glove box was placed for weighing, and the adsorption amount was obtained by calculating the difference before and after weighing. The results are shown in Figure 4 As shown, the adsorption amount is 3.7132 mg / cm 2 Increased to 6.5698mg / cm 2 , proving that the adsorption coating prepared by this method has a significant improvement in the adsorption capacity.

[0056] Example 2

[0057] (1) Preparation of hierarchical pore FAU zeolite

[0058] The hierarchical FAU zeolite was synthesized by a hydrothermal method, and the specific steps are as follows: first, 2.4 g of sodium hydroxide, 7.5 g of silica sol (40% wt) and 20 g of water were stirred at 90°C for 15 minutes to dissolve to prepare solution A. Secondly, 2.73 g of sodium aluminate, 1.1 g of sodium hydroxide and 20 g of water were stirred at room temperature for 30 minutes, and 1.66 g of CTAB was added after dissolution, and stirring was continued for 30 minutes to obtain solution B. Subsequently, solution A was slowly added to solution B under vigorous stirring until a uniform gel was formed. The final composition of the gel was 3.5 Na 2 O:1Al 2 O 3 :3SiO 2 :180H 2O:0.7CTAB. The mixture was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and crystallized at 90°C for 12 hours. After crystallization, the solid product was separated by centrifugation, washed with distilled water 3-5 times until the pH value reached 7-8, and then dried at 80°C for 3 hours. Finally, the dried product was calcined in a tubular furnace to remove the template, and the heating program was set to heat to 550°C within 0.5 hours, and then naturally cooled to room temperature after 8 hours of heat preservation to obtain the graded pore FAU zeolite.

[0059] (2) Graded pore FAU zeolite pretreatment

[0060] Load the prepared graded pore FAU molecular sieve into a magnetic boat dedicated to the tube furnace and place it in the heating area of ​​the tube furnace. Then, close both ends of the tube furnace, connect one end to the mechanical pump, and tighten the valve at the other end. Start the mechanical pump, vacuum for 30 minutes, and then turn it off. Set the heating program to heat to 200°C within 30 minutes, keep it at this temperature for 2 hours, and finally cool it naturally to room temperature.

[0061] (3) ALD technology for in-situ encapsulation of metal particles

[0062] The pretreated graded FAU zeolite was placed in an atomic layer deposition reaction chamber, with ferrocene and deionized water as precursors and nitrogen as carrier gas. The deposition temperature was set to 300°C, the source bottle temperature to 80°C, the pulse time to 0.5 seconds, and the cycle to 10 times. Through the above process, FeOx nanoparticles were in-situ encapsulated in the pores of the graded pore FAU zeolite.

[0063] (4) Configuration of molecular adsorption coating spray slurry

[0064] The functional filler and silica sol are accurately weighed according to a preset ratio and placed in a mixing container. At room temperature, a mechanical stirrer is used to stir at a constant speed for 30 minutes to ensure that the functional filler and silica sol are fully mixed and form a uniform suspension system to obtain a spray slurry.

[0065] (5) Spraying of molecular adsorption coating

[0066] This embodiment uses aluminum alloy thin plate as the substrate material. First, the substrate surface is polished with 500-mesh sandpaper, and then placed in anhydrous ethanol for ultrasonic cleaning for 30 minutes to remove surface impurities. The prepared spray diluent is evenly sprayed on the surface of the aluminum alloy substrate. The specific spraying parameters are as follows: the nozzle diameter is 2.5mm, the spray gun pressure is 1.5MPa, the spray gun moving speed is 80cm / s, and the spray distance is 20cm. In order to ensure the uniformity and density of the coating, multiple spraying processes are adopted. After each spraying, the coating surface is naturally air-dried before the next spraying. After the spraying is completed, the coating sample is placed in a vacuum oven for programmed temperature curing treatment to enhance the bonding force between the coating and the substrate. The curing program is set as follows: first, the temperature is raised to 60°C at a set rate and kept warm for 1 hour; then the temperature is continued to rise to 80°C and kept warm for 8 hours. After the above process treatment, an adsorption coating with excellent adsorption performance and good stability is finally obtained.

[0067] Using dioctyl phthalate as the target pollutant, the adsorption performance of the molecular adsorption coating material was tested under a vacuum environment. The specific experimental steps are as follows: Place the molecular adsorption coating material prepared in Example 2 together with dioctyl phthalate in a space molecular contamination vacuum test system, and set the temperature of the heating table to 60°C. Carry out the adsorption experiment under heating conditions, take samples every 60 minutes, and then transfer the samples to a precision balance for weighing. Determine the adsorption amount by calculating the mass difference before and after weighing. The experimental results are shown in the following table:

[0068] Table 2

[0069] Adsorption time (min) <![CDATA[吸附量(mg / cm 2 )]]> 60 0.9823 120 1.6547 180 2.1235 240 2.4568 300 2.7891

[0070] From the data in Table 2, it can be seen that the adsorption amount of the molecular adsorption coating material prepared in Example 2 shows a continuous growth trend within 300 min, and the final adsorption amount reaches 2.7891 mg / cm 2 , showing excellent adsorption performance.

[0071] The molecular adsorption coating material prepared in Example 2 was placed in a space molecular contamination vacuum test system together with a typical molecular pollutant, dioctyl phthalate, and the temperature of the heating stage was set to 60°C. The adsorption experiment was carried out under heating conditions for 88 hours, and then the sample was transferred to a precision balance in the glove box for weighing. The adsorption amount was obtained by calculating the mass difference before and after weighing. The experimental results are shown in the figure. Figure 5 As shown in the figure, the adsorption capacity after modification increased from 3.6815 mg / cm 2 Significantly increased to 6.0321mg / cm 2 , which fully proves that the adsorption coating prepared by this method has a significant improvement effect in adsorption performance.

[0072] The above describes the specific embodiments of the present invention. It should be noted that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the essential content of the present invention.

Claims

1. A method for preparing a molecular adsorption coating for in-situ encapsulation of metal particles in a graded FAU zeolite by ALD, characterized in that: The following steps are involved: Step 1: synthesizing and preparing hierarchical pore FAU zeolite by hydrothermal method; Step 2, pre-treating the graded FAU zeolite at a certain temperature; Step 3: ALD technology is then used to in-situ encapsulate metal particles on the surface of the pretreated FAU zeolite; Step 4: then mix evenly with silica sol to form a slurry; Step 5: Then apply it to the surface of the substrate, heat and cure it to obtain the molecular adsorption coating.

2. The method according to claim 1, characterized in that: The graded pore FAU zeolite is prepared according to the following steps: Step 1, 2.4 g of sodium hydroxide, 7.5 g of 40 wt% silica sol and 20 g of water were stirred and dissolved at 90° C. for 15 minutes to prepare solution A; Step 2, 2.73 g of sodium aluminate, 1.1 g of sodium hydroxide and 20 g of water were stirred at room temperature for 30 minutes, and 1.66 g of CTAB was added after dissolution, and stirring was continued for 30 minutes to obtain solution B; Step 3, under vigorous stirring, slowly add solution A to solution B until a uniform gel is formed, crystallize at 90°C for 12 hours, centrifuge, wash the solid with distilled water 3-5 times until the pH value reaches 7-8, and then dry at 80°C for 3 hours; Step 4: Then, the temperature is raised to 550° C. within 0.5 hours, kept at that temperature for 8 hours, and then naturally cooled to room temperature to obtain graded pore FAU zeolite.

3. The method according to claim 1, characterized in that: The pretreatment is to heat at a rate of 200°C-300°C within 0.5h, then evacuate to -0.1MPa, keep the temperature and pressure for 2h-5h, and finally cool naturally to room temperature.

4. The method according to claim 1, characterized in that: The in-situ encapsulated metal particles are CoOx, TiO2, ZnO, CuO or FeOx.

5. The method according to claim 1, characterized in that: In-situ packaging: The pretreated graded pore FAU zeolite powder was placed in the deposition chamber of the atomic layer deposition instrument. The chamber was first evacuated to 4×10 -3 Up to 6×10 -3 Torr, then introduce carrier gas to raise the chamber pressure to 0.1 Torr; adjust the source bottle temperature to 70℃-85℃ and the chamber temperature to 180℃-240℃, and the cycle period is 10-70 cycles.

6. The method according to claim 1, characterized in that: The pigment-to-base ratio in step 4 is (0.2-1):

1.

7. The method according to claim 1, characterized in that: The base materials are aluminum alloy, resin, and organic-inorganic composite materials.

8. The method according to claim 1, characterized in that: The coating is carried out by spraying, brushing, scraping or spin coating.

9. The method according to claim 1, characterized in that: The curing process is to first heat the temperature to 60°C and keep it at that temperature for 1 hour; then continue to heat the temperature to 80°C and keep it at that temperature for 8 hours.

10. A molecular adsorption coating prepared by the method according to any one of claims 1 to 9.

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