Application of a hydrogen-substituted graphene in the adsorption and removal of gaseous elemental mercury

Abstract

The application discloses application of hydrogen-substituted graphdiyne in adsorption and removal of gaseous elemental mercury, and belongs to the technical field of nano adsorption materials. The application of hydrogen-substituted graphdiyne in adsorption and removal of gaseous elemental mercury. It is found that the hydrogen-substituted graphdiyne adsorbent has a large conjugated pi bond, an oversized pore structure and a high-activity diacetylene bond, and through coupling and electron transfer (Hg 0 → hydrogen-substituted graphdiyne) of H1s and C2p in the rich diacetylene bond of the hydrogen-substituted graphdiyne with the Hg5d electron layer of an adsorbed mercury atom, high-efficiency capture of Hg 0 is realized, and conversion of Hg 0 into Hg 2+ is realized without an additional oxidant.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-adsorption materials, and in particular to application of hydrogen-substituted graphyne in the adsorption and removal of gaseous elemental mercury. Background Art

[0002] Mercury (Hg) pollution has attracted widespread attention due to its strong bioaccumulation and high toxicity. The Minamata Convention came into effect in 2017, aiming to control and reduce mercury emissions worldwide. Coal flue gas is one of the main sources of mercury emissions in my country. Generally speaking, there are three forms of mercury in the flue gas produced by coal combustion: elemental mercury (Hg 0 ), oxidized mercury (Hg 2+ ) and particulate mercury (Hg p ). Due to Hg p and Hg 2+ Due to its physical properties, conventional air pollution control devices such as particulate matter control devices (PMCDs) and wet flue gas desulfurization systems (WFGDs) can effectively remove Hg p and Hg 2+ However, due to Hg 0 Due to its low solubility and high volatility, 66-94% of mercury in flue gas is difficult to be captured by the above-mentioned device.

[0003] At present, the technologies for removing mercury from coal-fired flue gas include catalytic oxidation, photochemical oxidation, electrocatalytic oxidation, electrochemical oxidation and adsorbent injection. Among them, adsorbent is used to capture Hg 0 It is considered to be an effective and feasible method for removing mercury from flue gas. Activated carbon has been widely explored and commercially used for Hg removal from flue gas. 0 Remove. For example, Hg LH EXTRA is a commercial Br-modified activated carbon adsorbent that was found to be effective in removing Hg from real flue gases. 0 Its porous structure can promote Hg 0 However, other traditional carbon materials such as activated carbon and graphene generally show poor Hg adsorption due to their limited surface active sites. 0 Removal activity. Additional chemical modification (such as metal oxides, halogens, sulfur) is required to increase the active sites of carbon materials. This will lead to an increase in the cost of the adsorbent. In addition, due to the loss of active substances, the performance of the modified adsorbent will significantly decrease after several thermal regeneration cycles. Therefore, there is an urgent need to develop a high-performance regenerable carbon adsorbent and supporting processes to ensure efficient removal of Hg from flue gas. 0 . Summary of the Invention

[0004] The application aims to overcome the above technical deficiencies, and provides an application of hydrogen-substituted graphdiyne in adsorbing and removing gaseous elemental mercury, so as to solve the technical problems of poor mercury adsorption effect or difficult regeneration of carbon adsorbents in the prior art.

[0005] To achieve the above technical purpose, the technical scheme of the application provides an application of hydrogen-substituted graphdiyne in adsorbing and removing gaseous elemental mercury.

[0006] Further, the application of hydrogen-substituted graphdiyne in adsorbing and removing gaseous elemental mercury in coal-fired flue gas.

[0007] Further, the hydrogen-substituted graphdiyne is placed in a gas pipe, and then a gas is passed through the gas pipe to react.

[0008] Further, the temperature of the reaction is 100-200 DEG C.

[0009] Further, the temperature is raised at a temperature raising rate of 5-10 DEG C / min to 100-200 DEG C.

[0010] Further, the reaction atmosphere of the gas is: 340-360 mu g / m 3 Hg 0 , N2 balance gas, and the space velocity is 18000 h -1 .

[0011] Further, after the gas is passed, the hydrogen-substituted graphdiyne is further incubated at 100-200 DEG C. for 100-200 min.

[0012] Further, the amount of the hydrogen-substituted graphdiyne is 100 mg-200 mg.

[0013] Further, after the reaction, the hydrogen-substituted graphdiyne is further subjected to regeneration treatment: the hydrogen-substituted graphdiyne is incubated at 400-450 DEG C.

[0014] Further, the regeneration treatment further includes: nitrogen atmosphere, temperature raising at a temperature raising rate of 2-4 DEG C / min to 400-450 DEG C, and incubation at 400-450 DEG C. for 10-20 min.

[0015] Compared with the prior art, the application has the following beneficial effects: the application of hydrogen-substituted graphdiyne in adsorbing and removing gaseous elemental mercury. The capture of gaseous elemental mercury is different from the adsorption of heavy metal ions in water, and the gaseous elemental mercury is volatile, so the contact time is shorter when the gaseous elemental mercury is captured in the gas phase, and thus the difficulty is greater. At the same time, the gaseous elemental mercury needs to be oxidized at the same time of adsorption to enhance the stability of the adsorbent surface in capturing mercury. We found that the hydrogen-substituted graphdiyne adsorbent has a large conjugated pi bond, a large pore structure, and a high active diacetylene bond. The hydrogen-substituted graphdiyne is an extended pi conjugated carbon material composed of butadiyne bonds and benzene rings. The pore diameter of the hydrogen-substituted graphdiyne is 0.6-0.7 nm, which is larger than that of the carbon nanotube (0.38 nm) and the graphene (0.34 nm). In comparison, the pore size of hydrogen-substituted graphdiyne is expanded to The hydrogen-substituted graphdiyne material provides a favorable environment for the rapid diffusion of mercury atoms inside it, and on the other hand, through the coupling of H1s, C2p in its abundant diacetylene bonds with the Hg5d electron layer of the adsorbed mercury atom and the electron transfer effect (Hg 0 → hydrogen-substituted graphdiyne) realizes the efficient capture of Hg 0 , and at the same time, without the need for an external oxidizing agent to realize the conversion of Hg 0 to Hg 2+ .

[0016] Through simple thermal desorption regeneration, the mercury-enriched hydrogen-substituted graphdiyne converts the mercury adsorbed by the hydrogen-substituted graphdiyne into Hg 2+ through reverse electron transfer, and can be restored to the initial state. The hydrogen-substituted graphdiyne has strong mercury capture ability, excellent regeneration performance, and good application potential. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a scanning electron microscope image of the hydrogen-substituted graphdiyne of Example 1 of the present application capturing mercury.

[0018] Figure 2 It is an element scanning and distribution image of the hydrogen-substituted graphdiyne of Example 1 of the present application capturing mercury.

[0019] Figure 3 It is an XPS Hg4f spectrum of the hydrogen-substituted graphdiyne of Example 1 of the present application capturing mercury.

[0020] Figure 4 It is a Raman spectrum of the hydrogen-substituted graphdiyne of Example 1 of the present application capturing mercury and the hydrogen-substituted graphdiyne.

[0021] Figure 5 It is an x-ray powder diffraction spectrum of the hydrogen-substituted graphdiyne of Example 8 of the present application capturing mercury and the hydrogen-substituted graphdiyne after regeneration. DETAILED DESCRIPTION

[0022] The present detailed description provides an application of hydrogen-substituted graphdiyne in adsorbing and removing gaseous elemental mercury. Further, it is adsorbing and removing gaseous elemental mercury in coal-fired flue gas.

[0023] The application in the present detailed description includes placing 100mg-200mg of hydrogen-substituted graphdiyne in a gas pipe, then heating to 100-200℃ at a heating rate of 5-10℃ / min, then reacting for 100-200min at 100-200℃ by passing a gas through the gas pipe; the reaction atmosphere of the gas is: 340-360μg / m 3 Hg 0N2 balance gas, space velocity 18000h -1 .

[0024] In some embodiments, the reaction is followed by a regeneration treatment of the hydrogen-substituted graphdiyne: the hydrogen-substituted graphdiyne is incubated at 400-450℃ for 10-20min, and the regeneration treatment further comprises: nitrogen atmosphere, and heating to 400-450℃ at a heating rate of 2-4℃ / min.

[0025] The hydrogen-substituted graphdiyne used in the present specific embodiment is prepared from the hydrogen-substituted graphdiyne proposed in the application file with publication number CN115888640A by the following steps:

[0026] S1, adding a tetrabutylammonium fluoride solution to a 1,3,5-tri[(trimethylsilyl)ethynyl]benzene solution, stirring at 2-10℃ under light shielding conditions for 15-45min, and then obtaining triethynylbenzene by extraction and rotary evaporation treatment. Specifically, the ratio between 1,3,5-tri[(trimethylsilyl)ethynyl]benzene and tetrabutylammonium fluoride is 200mg:(1.5-1.8)mmol.

[0027] S2, dissolving triethynylbenzene in pyridine to obtain a first mixed solution. The concentration of the triethynylbenzene solution is 1-3mg / mL.

[0028] S3, placing a copper foil into pyridine, preheating at 80-100℃ for 30min to obtain a second mixture.

[0029] S4, adding the first mixed solution to the second mixture containing the copper foil, and reacting at 90-110℃ to generate a solid powder, which is calcined after washing to obtain a hydrogen-substituted graphdiyne nanometer powder material.

[0030] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0031] The hydrogen-substituted graphdiyne used in the following examples is prepared by the following steps:

[0032] S1, 200 mg of 1,3,5-tri[(trimethylsilyl)ethynyl]benzene was dissolved in 60 mL of THF, and TBAF (1 M THF solution, 1.65 mL, 1.65 mmol) was added to the solution. The mixture was stirred at 6 °C for 30 min under light protection. After the reaction, the solution was extracted with dichloromethane, washed with distilled water, dried over anhydrous sodium sulfate, filtered and the solvent was rotary evaporated to obtain 1,3,5-triethynylbenzene. 150 mg of 1,3,5-triethynylbenzene was dissolved in 100 mL of pyridine to form a 1.5 mg / ml solution.

[0033] S2, Copper foils (1 cm wide, 10 cm long, 0.1 cm thick, 20 pieces) were ultrasonically treated in 1 M hydrochloric acid, water and acetone respectively for 5 min, dried in a nitrogen stream and immersed in 80 ml of pyridine, preheated at 100 °C for 30 min to obtain mixture A.

[0034] S3, The pyridine solution of triethynylbenzene prepared in step S1 was slowly added to mixture A, and the reaction was maintained at 100 °C for 5 days. The reaction solution was ultrasonically treated, and the solvent was evaporated to obtain a powder.

[0035] S4, The powder prepared in step S3 was centrifuged with N,N-dimethylformamide (DMF) and acetone respectively until the supernatant was colorless to remove oligomers. Then it was refluxed with 20 mL of hydrochloric acid (HCl, 1 M) at 80 °C for 3 h, filtered, washed with pure water until neutral. Then it was refluxed with 20 mL of sodium hydroxide (NaOH, 1 M) at 80 °C for 3 h, filtered, washed with pure water until neutral. Then it was dried at 80 °C under vacuum for 24 h, and finally the obtained powder was calcined in a tube furnace at 300 °C for 2 h at a rate of 5 °C per minute under a protective atmosphere to obtain a yellow-brown powder, which is the hydrogen-substituted graphdiyne nanometer powder material.

[0036] Example 1

[0037] This example proposes the application of four adsorbents, carbon nanotubes, graphdiyne, graphene and hydrogen-substituted graphdiyne, to adsorb and remove elemental mercury. Specifically, 100 mg of each of the four adsorbent powders was first loaded into the middle of four quartz tubes with an inner diameter of 12 mm, then the quartz tubes loaded with the adsorbents were placed in the correct position in the tube furnace, and a programmed temperature mode was adopted to heat from 20 °C to 100 °C at a rate of 10 °C / min, and the temperature was maintained at 100 °C for 100 min. The reaction atmosphere was 340 μg / m 3 Hg 0 , N2 balance gas, with a space velocity of 18000 h -1 , and a total flow rate of 400 mL / min. The mercury removal efficiencies of carbon nanotubes, graphdiyne, graphene and hydrogen-substituted graphdiyne were 42.4%, 8.5%, 0% and 87.5%, respectively.Figure 1 The scanning electron microscope image of the hydrogen-substituted graphdiyne adsorbing gaseous mercury in this embodiment can show that the hydrogen-substituted graphdiyne maintains a porous nanostructure. Figure 2 The element scanning and distribution image of the hydrogen-substituted graphdiyne capturing mercury in this embodiment can show that the mercury element is uniformly distributed on the surface of the hydrogen-substituted graphdiyne. Figure 3 The XPS Hg4f spectrum of the hydrogen-substituted graphdiyne capturing mercury in this embodiment can show that the characteristic peak at the binding energy of 104 eV is attributed to Hg 2+ . Figure 4 The Raman spectrum of the hydrogen-substituted graphdiyne capturing mercury and the hydrogen-substituted graphdiyne in this embodiment can show that the Raman peak of the hydrogen-substituted graphdiyne after adsorbing mercury is shifted, indicating that there is an interaction between Hg and the hydrogen-substituted graphdiyne.

[0038] In addition, it should be noted that in the test of removing lead ions in the liquid phase, 5 mg of graphdiyne, carbon nanotubes and activated carbon were added to 30 mL of lead ion solution with a concentration of 200 mg / L and stirred for 2 hours. The sample was taken by a syringe with a microfiltration membrane, and the lead ion concentration in the solution was determined by ICP-AES, and then the adsorption capacity of each material was obtained. The adsorption capacities of graphdiyne, carbon nanotubes and activated carbon are all high, which are 422 mg / g, 213 mg / g and 120 mg / g respectively, but these materials are difficult to adsorb gaseous mercury, which also proves that adsorbing heavy metals in the liquid phase and adsorbing mercury in the gas phase are two different things.

[0039] Example 2

[0040] This embodiment proposes an application of hydrogen-substituted graphdiyne in adsorbing and removing gaseous elemental mercury. The elemental mercury adsorption and oxidation activity of hydrogen-substituted graphdiyne at a temperature of 100℃ is tested, specifically including: in a quartz tube fixed bed reactor with an inner diameter of 12 mm, 100 mg of adsorbent powder is first loaded in the middle of the quartz tube, then the quartz tube loaded with the adsorbent is placed in the correct position in the tube furnace, and a programmed heating mode is adopted, with a heating rate of 10℃ / min from 20℃ to 100℃, and the temperature is kept at 100℃ for 100 min. The reaction atmosphere is 340 μg / m 3 Hg 0 , N2 balance gas, and the space velocity is 18000 h -1 , and the total flow rate is 400 mL / min. Under this condition, the mercury removal efficiency is 87.5%.

[0041] Example 3

[0042] The embodiment provides application of hydrogen-substituted graphdiyne in adsorption and removal of gaseous elemental mercury, tests elemental mercury adsorption and oxidation activity of the hydrogen-substituted graphdiyne at 150 DEG C, and specifically, includes the following steps: 100 mg of adsorbent powder is firstly loaded in the middle of a quartz tube fixed bed reactor with an inner diameter of 12 mm, then the quartz tube loaded with the adsorbent is placed in a tube furnace in a correct position, a programmed temperature mode is adopted, the temperature is raised from 20 DEG C to 150 DEG C at a temperature raising rate of 10 DEG C / min, and the temperature is kept at 150 DEG C for 100 min, the reaction atmosphere is 340 μg / m 3 Hg 0 , N2 balance gas, the space velocity is 18000 h -1 , and the total flow is 400 mL / min. Under the condition, the mercury removal efficiency is 97.4%.

[0043] Example 4

[0044] The embodiment provides application of hydrogen-substituted graphdiyne in adsorption and removal of gaseous elemental mercury, tests elemental mercury adsorption and oxidation activity of the hydrogen-substituted graphdiyne at 200 DEG C, and specifically, includes the following steps: 100 mg of adsorbent powder is firstly loaded in the middle of a quartz tube fixed bed reactor with an inner diameter of 12 mm, then the quartz tube loaded with the adsorbent is placed in a tube furnace in a correct position, a programmed temperature mode is adopted, the temperature is raised from 20 DEG C to 200 DEG C at a temperature raising rate of 10 DEG C / min, and the temperature is kept at 200 DEG C for 100 min, the reaction atmosphere is 340 μg / m 3 Hg 0 , N2 balance gas, the space velocity is 18000 h -1 , and the total flow is 400 mL / min. Under the condition, the mercury removal efficiency is 84.3%.

[0045] Example 5

[0046] The embodiment provides application of hydrogen-substituted graphdiyne in adsorption and removal of gaseous elemental mercury, tests elemental mercury adsorption and oxidation activity of the hydrogen-substituted graphdiyne at 150 DEG C, and specifically, includes the following steps: 200 mg of adsorbent powder is firstly loaded in the middle of a quartz tube fixed bed reactor with an inner diameter of 12 mm, then the quartz tube loaded with the adsorbent is placed in a tube furnace in a correct position, a programmed temperature mode is adopted, the temperature is raised from 20 DEG C to 150 DEG C at a temperature raising rate of 10 DEG C / min, and the temperature is kept at 150 DEG C for 100 min, the reaction atmosphere is 340 μg / m 3 Hg 0 , N2 balance gas, the space velocity is 18000 h -1 , and the total flow is 400 mL / min. Under the condition, the mercury removal efficiency is 100%.

[0047] Example 6

[0048] The embodiment provides application of hydrogen-substituted graphdiyne in adsorption and removal of gaseous elemental mercury, tests elemental mercury adsorption and oxidation activity of the hydrogen-substituted graphdiyne at 150 DEG C, and specifically comprises the following steps: 100 mg of adsorbent powder is first loaded in the middle of a quartz tube fixed bed reactor with an inner diameter of 12 mm, then the quartz tube loaded with the adsorbent is placed in a tube furnace in a correct position, a programmed temperature mode is adopted, the temperature is raised from 20 DEG C to 150 DEG C at a temperature raising rate of 5 DEG C / min, and the temperature is kept at 150 DEG C for 100 min, the reaction atmosphere is 340 μg / m 3 Hg 0 , N2 balance gas, the space velocity is 18000 h -1 , and the total flow rate is 400 mL / min. Under the condition, the mercury removal efficiency is 97.4%.

[0049] Example 7

[0050] The embodiment provides application of hydrogen-substituted graphdiyne in adsorption and removal of gaseous elemental mercury, tests elemental mercury adsorption and oxidation activity of the hydrogen-substituted graphdiyne at 150 DEG C, and specifically comprises the following steps: 100 mg of adsorbent powder is first loaded in the middle of a quartz tube fixed bed reactor with an inner diameter of 12 mm, then the quartz tube loaded with the adsorbent is placed in a tube furnace in a correct position, a programmed temperature mode is adopted, the temperature is raised from 20 DEG C to 150 DEG C at a temperature raising rate of 10 DEG C / min, and the temperature is kept at 150 DEG C for 300 min, the reaction atmosphere is 340 μg / m 3 Hg 0 , N2 balance gas, the space velocity is 18000 h -1 , and the total flow rate is 400 mL / min. Under the condition, the mercury removal efficiency is 97.4%.

[0051] Example 8

[0052] The embodiment provides a regeneration process and performance of hydrogen-substituted graphdiyne after adsorption and removal of gaseous elemental mercury, tests elemental mercury adsorption and oxidation activity of the hydrogen-substituted graphdiyne at 150 DEG C, and specifically comprises the following steps: 100 mg of adsorbent powder after adsorption of mercury is first loaded in the middle of a quartz tube fixed bed reactor with an inner diameter of 12 mm, then the quartz tube loaded with the adsorbent is placed in a tube furnace in a correct position, a programmed temperature mode is adopted, the temperature is raised from 20 DEG C to 400 DEG C at a temperature raising rate of 2 DEG C / min, and the temperature is kept at 400 DEG C for 20 min, during which N2 balance gas is continuously introduced, the space velocity is 18000 h -1, the total flow rate was 400 mL / min. The mercury removal efficiencies of the hydrogen-substituted graphdiyne after 1-time regeneration, 2-time regeneration and 3-time regeneration according to the regeneration treatment method of Example 8 were 97.5%, 96.3% and 96.8%, respectively, indicating that the hydrogen-substituted graphdiyne had excellent regeneration performance and could repeatedly adsorb mercury. It should be noted that before each regeneration treatment, the hydrogen-substituted graphdiyne was subjected to mercury adsorption according to the procedure of Example 7. From Figure 5 As can be seen from the x-ray powder diffraction pattern of the hydrogen-substituted graphdiyne after capturing mercury and regeneration, the structure of the hydrogen-substituted graphdiyne did not change significantly after adsorption and regeneration.

[0053] It should be noted that although the gas in the examples of the present application does not use coal-fired flue gas, it should be understood that the application can also adsorb and remove gaseous elemental mercury in coal-fired flue gas.

[0054] The specific embodiments of the present application described above do not constitute a limitation on the scope of protection of the present application. Any various other corresponding changes and modifications made according to the technical concept of the present application shall be included in the scope of protection of the claims of the present application.

Claims

1. Application of hydrogen-substituted graphyne in the adsorption and removal of gaseous elemental mercury. Hydrogen-substituted graphyne captures Hg 0 , and no external oxidant is required to achieve Hg 0 Xiang Hg 2+ The reaction temperature is 100~200℃; The hydrogen-substituted graphyne is prepared by the following steps: S1. Dissolve 200 mg of 1,3,5-tris[(trimethylsilyl)ethynyl]benzene in 60 mL of THF, and add 1.65 mL of 1M TBAF to the solution. Stir the mixture at 6°C for 30 minutes in the dark. After the reaction, extract the solution with dichloromethane, wash with distilled water, dry over anhydrous sodium sulfate, filter, and rotary evaporate the solvent to obtain 1,3,5-triethynylbenzene. Dissolve 150 mg of 1,3,5-triethynylbenzene in 100 mL of pyridine to form a 1.5 mg / ml solution. S2. Ultrasonicate the copper foil in 1 M hydrochloric acid, water, and acetone for 5 minutes, dry it in a nitrogen stream, immerse the copper foil in 80 ml of pyridine, and preheat at 100°C for 30 minutes to obtain a mixture A. S3, slowly adding the pyridine solution of triethynylbenzene prepared in step S1 to mixture A, maintaining the reaction temperature at 100° C. for 5 days; ultrasonically treating the reaction solution, and evaporating the solvent to obtain a powder; S4. The powder obtained in step S3 was centrifuged with N,N-dimethylformamide and acetone until the supernatant was colorless to remove oligomers, and then refluxed with 20 mL of 1 M hydrochloric acid at 80° C. for 3 hours, filtered, and washed with pure water until the pH was neutral. Then, refluxed with 20 mL of 1 M sodium hydroxide at 80° C. for 3 hours, filtered, and washed with pure water until the pH was neutral. Then, vacuum dried at 80° C. for 24 hours, and finally, the obtained powder was heated at a rate of 5° C. per minute in a tube furnace and calcined at 300° C. for 2 hours under a protective atmosphere to obtain a yellowish-brown powder, which is the hydrogen-substituted graphyne nanopowder material.

2. The use according to claim 1, characterized in that The hydrogen-substituted graphyne is used in the adsorption and removal of gaseous elemental mercury in coal-fired flue gas.

3. The use according to claim 1, characterized in that The method comprises placing hydrogen-substituted graphyne in a vent tube, and then passing gas into the vent tube to react.

4. The use according to claim 3, characterized in that The temperature was raised to 100-200°C at a heating rate of 5-10°C / min.

5. The use according to claim 3, characterized in that The reaction atmosphere through which the gas passes is: 340-360 μg / m 3 Hg 0 , N2 balance gas, space velocity 18000 h -1 .

6. The use according to claim 3, characterized in that After passing the gas, it also includes keeping warm at 100~200℃ for 100-200min.

7. The use according to claim 3, characterized in that The amount of hydrogen-substituted graphyne used is 100 mg-200 mg.

8. The use according to claim 3, characterized in that After the reaction, the method further includes regenerating the hydrogen-substituted graphyne: the hydrogen-substituted graphyne is kept at 400-450°C.

9. The use according to claim 8, characterized in that The regeneration treatment conditions also include: nitrogen atmosphere, heating to 400-450° C. at a heating rate of 2-4° C. / min, and holding at 400-450° C. for 10-20 minutes.

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