A method for efficient desorption of ammonia assisted by visible light

Abstract

The present invention discloses a method for efficient, visible-light-assisted ammonia desorption. The method comprises: subjecting an ammonia-adsorbing adsorbent material to visible light irradiation to achieve efficient ammonia desorption. The adsorbent material is prepared by freeze-drying and high-temperature calcination of a metal-organic framework (MOF-303(Al)) and graphene oxide, with the graphene oxide comprising 5% to 30% by weight, and the balance being the MOF-303(Al) material. The present invention enables efficient and low-energy ammonia desorption under visible light irradiation. The adsorbent material prepared under optimal process conditions exhibits excellent desorption performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy gas desorption methods, and in particular relates to a visible light assisted high-efficiency desorption method for ammonia. Background Art

[0002] Ammonia is a new energy gas with a high hydrogen content. It has important applications in hydrogen production through cracking and fuel cells, and is considered a highly efficient, carbon-free energy source. Due to its high corrosiveness, ammonia requires specialized media for its storage and transportation. However, due to its high toxicity and corrosiveness, its utilization requires the development of novel NH3 storage media with high adsorption capacity and low desorption energy. Porous materials have recently emerged as a highly effective medium for ammonia storage. However, adsorbents with high adsorption capacity typically interact strongly with NH3, resulting in low desorption efficiency or increased energy requirements. In typical desorption processes, heating and decompression are the most commonly used techniques to enhance NH3 desorption. However, these methods require significant energy input and are not compatible with the necessary conditions for sustainable development. For example, temperatures of 150-200°C and vacuum conditions are often used to desorb NH3 from porous materials. Therefore, low-energy release, or desorption, of ammonia from porous materials is a prerequisite for its effective utilization. To address these challenges, developing efficient and energy-efficient ammonia desorption methods is crucial. Summary of the Invention

[0003] The technical problem solved by the present invention is to provide a method for efficiently desorbing ammonia with the assistance of visible light with high efficiency and low energy consumption.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solution, which is a method for efficient desorption of ammonia assisted by visible light, characterized in that the specific process is: an adsorption material that adsorbs ammonia is irradiated with visible light to achieve efficient desorption of ammonia, and the adsorption material is prepared by freeze-drying and high-temperature calcination of a metal-organic framework material MOF-303 (Al) and graphene oxide, wherein the weight percentage of graphene oxide is 5% to 30%, and the balance is the metal-organic framework material MOF-303 (Al).

[0005] It is further defined that visible light is natural sunlight or simulated sunlight, wherein the illumination intensity of simulated sunlight is 300mW / cm 2 .

[0006] It is further defined that the desorption process is completed under vacuum conditions.

[0007] It is further defined that the vacuum condition is -1 bar.

[0008] It is further defined that the weight percentage of graphene oxide is 7% to 10%.

[0009] It is further defined that the weight percentage of graphene oxide is 8%.

[0010] It is further defined that the specific preparation process of the adsorption material is: ultrasonically dispersing graphene oxide in deionized water, then adding MOF-303 (Al) to the above solution in multiple times, and continuing ultrasonic treatment for more than 3 hours, wherein the weight percentage of graphene oxide is 8%, and then placing the mixed system in liquid nitrogen for rapid freezing, and then placing it in a freeze dryer for freeze drying, and then calcining it at 200°C in an argon atmosphere for 2 hours to obtain the adsorption material. The adsorption material has a high ammonia adsorption capacity and can be regenerated and recycled. The ammonia desorption efficiency of the adsorption material after saturation with ammonia adsorption reaches more than 42% under natural sunlight for 2 hours; the ammonia desorption efficiency of the adsorption material after saturation with ammonia adsorption reaches more than 70% under simulated sunlight for 2 hours; the ammonia desorption efficiency of the adsorption material after saturation with ammonia adsorption reaches more than 90% under vacuum assistance and simulated sunlight for 2 hours.

[0011] Compared with existing technologies, the present invention has the following advantages and beneficial effects: It can achieve efficient and low-energy ammonia desorption under visible light irradiation. The adsorbent material prepared under optimal process conditions has excellent desorption performance. After saturating the adsorbent with ammonia adsorption, the ammonia desorption efficiency of the adsorbent material under natural sunlight irradiation for 2 hours reaches over 42%; after saturating the adsorbent with ammonia adsorption, the ammonia desorption efficiency of the adsorbent material under simulated sunlight irradiation for 2 hours reaches over 70%; and after saturating the adsorbent with ammonia adsorption, the ammonia desorption efficiency of the adsorbent material under vacuum-assisted and simulated sunlight irradiation for 2 hours reaches over 90%. The present invention has the advantages of simplicity, low energy consumption, high efficiency, and strong operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the curve showing the influence of different raw material compositions on the absorption properties of the adsorption material under the same calcination time conditions.

[0013] Figure 2 This is the light heating curve of the adsorption material prepared with different raw material compositions at the same calcination time.

[0014] Figure 3 This is the light heating curve of the adsorption material prepared with the same raw material composition and different calcination times. DETAILED DESCRIPTION

[0015] The above contents of the present invention are further described in detail below through examples, but this should not be understood as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above contents of the present invention fall within the scope of the present invention. Example 1

[0016] 2.5g of graphene oxide and 28.75g of the metal-organic framework MOF-303(Al) were ultrasonically mixed, rapidly frozen in liquid nitrogen, and freeze-dried in a freeze dryer for 24 hours to produce the MOF-GO-8% material. The MOF-GO-8% material was then calcined at 200°C for 2 hours in an argon atmosphere to produce the adsorbent material MOF-GO-8%-2h. This adsorbent has an ammonia adsorption capacity of 17.0mmol / g and exhibits excellent ammonia absorption under simulated sunlight (light intensity of 300mW / cm 2 , the same below) can heat the adsorption material to 75°C under illumination, and the ammonia desorption efficiency can reach 71.4% after 2 hours of illumination. Example 2

[0017] 2.5g of graphene oxide and 28.75g of the metal-organic framework MOF-303(Al) were ultrasonically mixed, rapidly frozen in liquid nitrogen, and freeze-dried in a freeze dryer for 24 hours to produce the MOF-GO-8% material. MOF-GO-8% was then calcined at 200°C for 3 hours in an argon atmosphere to produce the adsorbent MOF-GO-8%-3h. Under simulated sunlight, the adsorbent was able to heat to 67°C and achieve a 60% ammonia desorption efficiency after 2 hours of illumination. Example 3

[0018] 2.5g of graphene oxide and 28.75g of the metal-organic framework MOF-303(Al) were ultrasonically mixed, rapidly frozen in liquid nitrogen, and freeze-dried in a freeze dryer for 24 hours to produce the MOF-GO-8% material. MOF-GO-8% was then calcined at 200°C for one hour in an argon atmosphere to produce the adsorbent MOF-GO-8%-1h. Under simulated sunlight, the adsorbent was able to heat to 66°C and achieve an ammonia desorption efficiency of 59% after two hours of illumination. Example 4

[0019] 1.75g of graphene oxide and 33.25g of the metal-organic framework MOF-303(Al) were ultrasonically mixed, rapidly frozen in liquid nitrogen, and freeze-dried in a freeze dryer for 24 hours to produce the MOF-GO-5% material. MOF-GO-5% was then calcined at 200°C for 2 hours in an argon atmosphere to produce the adsorbent MOF-GO-5%-2h. This adsorbent exhibited an ammonia adsorption capacity of 17.2mmol / g. Under simulated sunlight, the material could be heated to 65°C, and the ammonia desorption efficiency reached 58% after 2 hours of illumination. Example 5

[0020] 3.0g of graphene oxide and 17.0g of the metal-organic framework MOF-303(Al) were ultrasonically mixed, rapidly frozen in liquid nitrogen, and freeze-dried in a freeze dryer for 24 hours to produce the MOF-GO-15% material. MOF-GO-15% was then calcined at 200°C for 2 hours in an argon atmosphere to produce the adsorbent MOF-GO-15%-2h. Under simulated sunlight, the adsorbent was able to heat to 75°C and achieve a 70% ammonia desorption efficiency after two hours of illumination. Example 6

[0021] 2.5g of graphene oxide and 28.75g of the metal-organic framework MOF-303(Al) were ultrasonically mixed, rapidly frozen in liquid nitrogen, and freeze-dried in a freeze dryer for 24 hours to produce the MOF-GO-8% material. MOF-GO-8% was then calcined at 200°C for 2 hours in an argon atmosphere to produce the adsorbent MOF-GO-8%-2h. This adsorbent exhibited an ammonia adsorption capacity of 17.0mmol / g. Under natural sunlight, the material could be heated to 65°C, and the ammonia desorption efficiency reached 42.1% after 2 hours of illumination. Example 7

[0022] 2.5g of graphene oxide and 28.75g of the metal-organic framework MOF-303(Al) were ultrasonically mixed, rapidly frozen in liquid nitrogen, and freeze-dried in a freeze dryer for 24 hours to produce MOF-GO-8%. MOF-GO-8% was then calcined at 200°C for 2 hours in an argon atmosphere to produce the adsorbent MOF-GO-8%-2h. This adsorbent exhibited an ammonia adsorption capacity of 17.0 mmol / g, and achieved an ammonia desorption efficiency of 53.1% at -1 bar under natural sunlight for 2 hours. Example 8

[0023] 2.5g of graphene oxide and 28.75g of the metal-organic framework MOF-303(Al) were ultrasonically mixed, rapidly frozen in liquid nitrogen, and freeze-dried in a freeze dryer for 24 hours to produce MOF-GO-8%. MOF-GO-8% was then calcined at 200°C for 2 hours in an argon atmosphere to produce the adsorbent MOF-GO-8%-2h. This adsorbent exhibited an ammonia adsorption capacity of 17.0 mmol / g, and achieved an ammonia desorption efficiency of 92.0% at -1 bar under simulated sunlight for 2 hours.

[0024] The core of the impact on the desorption performance of the adsorbent material in the present invention lies in the degree of temperature rise of the adsorbent material under visible light irradiation. The core of the impact on this performance comes from the adsorbent material's absorption of light. Studies have shown that under the same conditions, the absorbance of the adsorbent material is closely related to the raw material composition and calcination time. Figure 1 As shown in the figure, after adding graphene oxide, the light absorption performance of the sample can be significantly increased through calcination and reduction, laying the foundation for light heating. Figure 1 It can be seen that under the same calcination time conditions, the raw material composition has a greater influence on the light absorption properties of the adsorption material.

[0025] like Figure 1 As shown in Figure 2, under the same calcination time conditions, different raw material compositions have a greater impact on the light absorption properties of the adsorption material. To this end, the present invention measured the light heating of the adsorption material prepared under different composition conditions, and the results are as follows: Figure 2 As shown. Figure 2 It can be seen that the photothermal adsorption performance of the adsorbent materials prepared under the conditions of 15wt% and 8wt% graphene oxide raw material composition is basically the same, and is significantly higher than that of the 5wt% graphene oxide raw material composition. Considering the economic efficiency, the present invention uses 8wt% graphene oxide raw material composition to test the heating performance under different lighting conditions. The results are as follows Figure 3 As shown. Figure 3 It can be seen that under the same raw material composition conditions, the heating effect of the adsorption material prepared by calcination for 2 hours is significantly higher than that of the adsorption material prepared by calcination for 1 hour and 3 hours. The reason is that the shorter calcination time leads to incomplete reduction of graphene oxide, resulting in poor heating performance of the prepared adsorption material. If the calcination time is too long, the loss of reduced graphene will be caused, which will adversely affect the heating effect of the prepared adsorption material.

[0026] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A visible light assisted method for efficient ammonia desorption, characterized in that The specific process is: the adsorption material that adsorbs ammonia achieves efficient desorption of ammonia under visible light irradiation. The adsorption material is made of metal-organic framework material MOF-303 (Al) and graphene oxide through freeze drying and high-temperature calcination. The weight percentage of graphene oxide is 5% to 30%, and the balance is metal-organic framework material MOF-303 (Al). The desorption process is completed under vacuum conditions. The specific preparation process of the adsorption material is as follows: ultrasonically dispersing graphene oxide in deionized water, then adding MOF-303 (Al) to the above solution in multiple times, continuing ultrasonic treatment for more than 3 hours, then placing the mixed system in liquid nitrogen for rapid freezing, then placing it in a freeze dryer for freeze drying, and then calcining it at 200°C in an argon atmosphere for 2 hours to obtain the adsorption material. The adsorption material has a high ammonia adsorption capacity and can be regenerated and reused. After the adsorption material is saturated with ammonia adsorption, the ammonia desorption efficiency of the adsorption material under natural sunlight for 2 hours reaches more than 42%; the ammonia desorption efficiency of the adsorption material under simulated sunlight for 2 hours after the adsorption material is saturated with ammonia adsorption reaches more than 70%; the ammonia desorption efficiency of the adsorption material under vacuum assistance and simulated sunlight for 2 hours after the adsorption material is saturated with ammonia adsorption reaches more than 90%.

2. The method for efficient visible light assisted ammonia desorption according to claim 1, characterized in that: Visible light is natural sunlight or simulated sunlight, where the intensity of simulated sunlight is 300mW / cm 2 .

3. The method for efficient visible light assisted ammonia desorption according to claim 1, characterized in that: The vacuum condition during the desorption process was -1 bar.

4. The method for efficient visible light assisted ammonia desorption according to claim 1, characterized in that: The weight percentage of graphene oxide is 7%~10%.

5. The method for efficient visible light assisted ammonia desorption according to claim 1, characterized in that: The weight percentage of graphene oxide is 8%.

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