Bagasse-derived 3D nitrogen-rich carbon aerogel as well as preparation method and application thereof

Abstract

The invention discloses bagasse-derived 3D nitrogen-rich carbon aerogel as well as a preparation method and application thereof. The preparation method specifically comprises the following steps: (1) sequentially performing hydrothermal pretreatment, alkalization treatment, bleaching treatment and cellulose extraction on dried bagasse powder; (2) mixing with a cross-linking agent, and freeze-drying; and (3) nitrogen doping and activating treatment, high-temperature carbonization, washing and drying are carried out, and the composite material is obtained. The bagasse-derived 3D nitrogen-rich carbon aerogel has rich pore structures, defect sites and Lewis alkaline sites, H2S can be converted into valuable sulfur elements with high selectivity under mild conditions and recycled, and meanwhile resource utilization of waste biomass bagasse and toxic and harmful gas H2S is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural and forestry solid waste biomass resource utilization and air pollution control, and more specifically to a bagasse-derived 3D nitrogen-rich carbon aerogel and a preparation method and application thereof. Background Art

[0002] H2S is considered one of the most harmful and smelly sulfur-containing gases, and it originates from a variety of industrial processes (e.g., industrial waste streams, natural gas refining, biogas purification, and coal chemistry), landfills, and indoor environments (e.g., food decay and bacterial decomposition of human and animal feces). H2S has the potential to corrode transportation pipelines and buildings, promote the formation of acid rain in the atmosphere, degrade the environment, and pose a health risk to humans. Due to the very low olfactory threshold of H2S, which is only 0.0008 mg / m 3 , so even at low concentrations, H2S can cause discomfort. Therefore, reducing H2S emission levels below the olfactory threshold is critical to minimizing its impact on the environment and human health.

[0003] At present, many methods have been developed for the removal of H2S, such as adsorption, membrane separation, Claus process and selective catalytic oxidation. Among them, selective catalytic oxidation (SCO) provides an efficient method for completely converting H2S into sulfur, which makes it particularly suitable for the effective and thorough removal of H2S, making SCO a hot topic and considered to be the most promising method for purifying H2S. However, the previously reported metal oxide-based catalysts and carbon-based catalysts have insufficient specific surface area and limited pore structure in the process of H2S catalytic oxidation, which affects the H2S removal efficiency. In addition, due to the high temperature and high oxygen content, the byproduct SO2 is generated, causing secondary pollution, which is not conducive to the green cycle development of industry. Therefore, it is urgent to develop a green, environmentally friendly, cost-effective catalyst that can avoid the above disadvantages for the conversion of H2S-SCO to sulfur.

[0004] Bagasse is a typical agricultural and forestry solid waste with Yunnan regional characteristics. Yunnan Province is the second largest sugar cane production base in the country, and its total sugarcane output accounts for more than 20% of the total sugar production in the country, which is an important support for the country's sugar supply security. The "Three-Year Action Plan for Agricultural Modernization in Yunnan Province (2022-2024)" issued in 2022 lists the sugarcane industry as a key industry in the province, and vigorously promotes the promotion of improved sugarcane varieties and methods. The ensuing problem is how to deal with the by-product bagasse formed in the sugar production process.

[0005] At present, the resource utilization technology of bagasse is limited, and the mainstream treatment methods are still mainly open-air stacking (accounting for more than 60%) and extensive burning (CO2 emission intensity reaches 1.8 tons / ton of residue), resulting in serious biomass resource waste and carbon emission problems. Although there have been studies on exploring the preparation of carbon-based materials from bagasse cellulose, there are still significant gaps in the field of functional modification.

[0006] It is understood that there is no report in the international community on the realization of the directional conversion of H2S and the recovery of sulfur resources by 3D porous nitrogen-functionalized carbon aerogel based on bagasse. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a bagasse-derived 3D nitrogen-rich carbon aerogel and its preparation method and application to solve the deficiencies in the prior art.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A preparation method of a bagasse-derived 3D nitrogen-rich carbon aerogel specifically includes the following steps:

[0010] (1) Subject the dried bagasse powder to hydrothermal pretreatment, alkalization treatment, bleaching treatment in sequence, and extract cellulose;

[0011] (2) Mix the cellulose and the cross-linking agent, and perform freeze-drying to obtain an aerogel;

[0012] (3) Subject the aerogel to nitrogen doping and activation treatment in sequence, perform high-temperature carbonization, washing, and drying to obtain the bagasse-derived 3D nitrogen-rich carbon aerogel.

[0013] Further, in the above step (1), the temperature of the hydrothermal pretreatment is 150°C and the time is 8h.

[0014] The beneficial effect of adopting the above is that subjecting the dried bagasse powder to hydrothermal pretreatment can remove the carbohydrates, fungi, and bacteria therein.

[0015] Further, in the above step (1), the alkalization reagent for the alkalization treatment is a NaOH solution with a concentration of 0.5 mol / L; the bleaching reagent for the bleaching treatment is a NaClO2 solution with a concentration of 9 wt%; the mass ratio of the bagasse powder, NaOH, and NaClO2 is (2 - 8):(1 - 6):(6 - 15), preferably (3 - 6):(2 - 4):(8 - 12), and more preferably 3:2:12.

[0016] The further beneficial effects of the above are as follows. The main function of alkalizing the bagasse powder after hydrothermal pretreatment is to destroy the lignin structure, reduce the crystallinity of cellulose, increase the purity of cellulose, improve the physical properties of cellulose, and enhance the processability of cellulose. The main function of bleaching the alkalized bagasse powder is to increase the whiteness of cellulose, remove residual lignin, improve chemical stability, enhance processability, and reduce pollutants. In addition, the present invention selects NaOH solution and NaClO2 solution as the alkalizing reagent and bleaching reagent for extracting cellulose from bagasse, which can not only improve the extraction efficiency and purity of cellulose, improve its physical properties, but also have significant environmental benefits and the effect of improving product quality.

[0017] Furthermore, in the above step (1), the time for both alkalizing treatment and bleaching treatment is 1 - 4 h.

[0018] Furthermore, in the above step (2), the crosslinking agent is a polyvinyl alcohol solution with a concentration of 1 wt%. The mass ratio of cellulose to polyvinyl alcohol is (1 - 5):(1 - 4), preferably (2 - 4):(1 - 3), and more preferably 2:1.

[0019] The further beneficial effects of the above are as follows. The present invention selects polyvinyl alcohol as the crosslinking agent for the aerogel, which can significantly improve the mechanical properties, water resistance, and adjustability of the aerogel, and at the same time has the advantages of environmental protection and multifunctionality.

[0020] Furthermore, in the above step (2), the temperature for freeze-drying is -40 to -80 °C, and the time is 12 - 72 h.

[0021] The further beneficial effects of the above are as follows. Freeze-drying plays a key role in the synthesis of the aerogel. It can not only effectively remove the solvent, maintain the nanoporous structure, but also reduce the loss of thermosensitive substances, improve the stability of the material, and facilitate subsequent processing and application.

[0022] Furthermore, in the above step (3), the nitrogen source for nitrogen doping and activation treatment is urea, and the activator is KOH. The mass ratio of the aerogel, urea, and KOH is (1 - 2):(1 - 4):(0.5 - 2), preferably 1:(1 - 2):(0.5 - 1), and more preferably 1:1:0.5.

[0023] The further beneficial effects of the above are as follows. Nitrogen doping treatment can introduce nitrogen atoms into the carbon skeleton. These nitrogen atoms, as electron donors, improve the conductivity of the material, modify the surface chemical properties of the carbon material to increase active sites, and facilitate the formation of more micro-mesopores in the carbon material, thereby increasing the specific surface area of the carbon aerogel. The activation treatment is mainly to increase the specific surface area of the carbon aerogel and optimize the pore size distribution. In addition, since urea contains a high nitrogen element, is inexpensive and widely available, and the nitrogen doping ratio can be controlled by a simple mass ratio to precisely regulate the degree of nitrogen doping, it is selected as the nitrogen source. KOH can effectively etch the carbon material to form a rich microporous structure to increase the specific surface area and the carbon yield. Moreover, compared with other strong bases, KOH may have better environmental compatibility and lower corrosivity in some cases, meeting the principles of green chemistry and sustainable development.

[0024] Further, in the above step (3), the atmosphere for high-temperature carbonization is an inert atmosphere or a carbon dioxide atmosphere, the heating rate is 5 - 10 °C / min, preferably 10 °C / min, the temperature is 500 - 900 °C, and the time is 2 - 4 h.

[0025] The further beneficial effects of the above are as follows. Appropriate high-temperature carbonization can fully exert the pore-expanding effect of KOH, which helps to achieve internal nitrogen self-doping so that nitrogen elements are evenly distributed inside the carbon skeleton rather than just staying on the surface.

[0026] The present invention also claims a bagasse-derived 3D nitrogen-rich carbon aerogel prepared by the above preparation method, with a specific surface area of 480 m 2 / g or more, I D / I G being 0.8 or more, and the nitrogen content being 3.5 at.% or more.

[0027] The present invention also claims an application of the bagasse-derived 3D nitrogen-rich carbon aerogel prepared by the above preparation method in removing H2S.

[0028] The bagasse-derived 3D nitrogen-rich carbon aerogel of the present invention is applied to the H2S-SCO reaction under mild conditions (180 °C, C O2 / C H2S = 1:2), and specifically includes the following steps:

[0029] (1) Place the 40 - 60 mesh bagasse-derived 3D nitrogen-rich carbon aerogel in a quartz reaction tube, heat the quartz reactor to 180 °C through a tube furnace, and purge with N2 for 30 min to remove possible impurities on the surface of the aerogel;

[0030] (2) preparing a mixed gas of O2, N2 and H2S by a dynamic gas distribution method, passing the mixed gas into a quartz reaction tube, and controlling the temperature of the quartz reaction tube at 60 to 240°C (preferably 120 to 190°C, more preferably 180°C) by a tube furnace to perform a gas-solid catalytic oxidation reaction. When the concentration of H2S in the tail gas at the outlet of the quartz reaction tube reaches a certain value, the reaction is completed;

[0031] (3) The temperature of the tubular furnace is lowered to room temperature, and the resulting catalytic oxidation product is taken out to cool the aggregated elemental sulfur and aerogel.

[0032] Furthermore, in the above step (1), the mass of the bagasse-derived 3D nitrogen-rich carbon aerogel is 0.1 to 0.4 g, preferably 0.1 to 0.3 g, and more preferably 0.1 g.

[0033] Furthermore, in the above step (2), in the mixed gas, the concentration of H2S gas is 0.1 vol.%, the concentration of O2 is 0.05 vol.%, and the remainder is N2; the flow rate of the mixed gas is 80 to 200 mL / min, preferably 100 to 150 mL / min, and more preferably 100 mL / min.

[0034] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. Aiming at the problem of solid waste management of about 3 to 4 million tons of bagasse produced in Yunnan Province every year, the present invention innovatively developed a directional conversion technology based on bagasse fiber, which is converted into a 3D nitrogen-rich carbon aerogel with a hierarchical porous structure through a green activation-self-assembly process. The material has a broad-spectrum purification capability for H2S waste gas of all concentrations (50ppm to 1vol%) by virtue of its unique defect-nitrogen active site synergistic mechanism, converting low-value agricultural waste into high-value carbon-based materials, and successfully constructing a closed-loop system of "bagasse resource utilization-H2S harmlessness-sulfur resource recycling", providing an innovative paradigm for the efficient utilization of regional characteristic biomass.

[0036] 2. The present invention uses sugarcane bagasse, a cellulose-rich agricultural and forestry solid waste, as a precursor, extracts cellulose through delignification treatment, uses polyvinyl alcohol (PVA) as a green crosslinker, combines freeze-drying technology, and cooperates with KOH activation to achieve multi-level pore structure regulation. The urea pyrolysis nitridation strategy is used to achieve directional nitrogen doping of the carbon skeleton to form nitrogen-rich active sites, and high-temperature carbonization under a specific atmosphere to obtain 3D nitrogen-rich carbon aerogel. This material has shown significant application value in the field of H2S purification. Its unique hierarchical pore structure effectively promotes the mass transfer of reactants, and the rich pyridinic nitrogen active sites significantly improve the H2S oxidation kinetics, providing an efficient and economical solution for industrial desulfurization technology.

[0037] 3. The bagasse-derived 3D nitrogen-rich carbon aerogel of the present invention has a rich pore structure, defect sites, and Lewis basic sites, and can selectively convert H2S into valuable sulfur elements and recycle them under mild conditions. At the same time, the resource utilization of waste biomass bagasse and toxic and harmful gas H2S is realized.

[0038] 4. The synthesis cycle of the preparation method of the present invention is short, the cost is low, and it is green and environmentally friendly.

[0039] 5. The bagasse-derived 3D nitrogen-rich carbon aerogel of the present invention uses inexpensive and easily available raw materials, can be mass-produced on a large scale in various chemical industries, and has high H2S conversion rate, high sulfur selectivity, and good stability at 180 °C.

[0040] 6. Compared with traditional nitrogen-rich carbon catalysts, the bagasse-derived 3D nitrogen-rich carbon aerogel of the present invention can not only be used for H2S-SCO, but also in the fields of supercapacitors and adsorption of organic pollutants.

[0041] 7. The bagasse-derived 3D nitrogen-rich carbon aerogel of the present invention can purify H2S in various chemical industry tail gases, has a wide range of applications, and can also recycle elemental sulfur as raw materials for various chemical products (such as sulfuric acid, vulcanized rubber, and gunpowder), realizing waste treatment with waste and promoting green circular development.

[0042] 8. The bagasse-derived 3D nitrogen-rich carbon aerogel of the present invention can be used for efficient and stable purification and removal of H2S in the desulfurization tail gas during natural gas extraction, the hydrodesulfurization process of crude oil refining and coal processing, wastewater treatment, and papermaking systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Raman spectra of the NCA-700 prepared in Example 1 and the CA-700 prepared in Comparative Example 1;

[0044] Figure 2 N2-adsorption / desorption isotherm diagrams of the NCA-700 prepared in Example 1 and the CA-700 prepared in Comparative Example 1;

[0045] Figure 3 H2S conversion rates of the NCA-700 prepared in Example 1 and the CA-700 prepared in Comparative Example 1 at a temperature gradient of 60-210 °C;

[0046] Figure 4 Comparison diagrams of S selectivity of the NCA-700 prepared in Example 1 and the CA-700 prepared in Comparative Example 1 at a temperature gradient of 60-210 °C;

[0047] Figure 5Test chart of the stability of the NCA-700 material prepared in Example 1 during the H2S-SCO reaction. Detailed implementation mode

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] Example 1

[0050] A preparation method of bagasse-derived 3D nitrogen-rich carbon aerogel specifically includes the following steps:

[0051] (1) First, add 10 g of dry bagasse powder pretreated by hydrothermal treatment at 150 °C for 8 h to 250 mL of 0.5 mol / L NaOH solution for alkalization treatment. Magnetically stir at a constant temperature of 90 °C for 3 h. After completion, add 0.5 mol / L HCl solution to adjust the pH to neutral, then add 200 mL of neutral 9 wt% NaClO2 solution for bleaching treatment. The obtained bleached cellulose is washed 3 times with ethanol and deionized water respectively, and dried to obtain cellulose;

[0052] (2) First, place 2 g of cellulose and 1 g of polyvinyl alcohol in 100 mL of deionized water, stir at 60 °C for 3 h to form a uniform suspension, then ultrasonically treat for 30 min to remove internal bubbles to form a uniform hydrogel, and finally freeze-dry the hydrogel at -70 °C for 72 h to obtain an aerogel;

[0053] (3) Mix the aerogel, urea and KOH in a mass ratio of 1:1:0.5 for nitrogen doping and activation treatment. After ultrasonic impregnation for 1 h, dry it. Place the obtained activated product in a tubular furnace with a CO2 atmosphere, heat it to 700 °C at a rate of 10 °C / min for high-temperature carbonization for 2 h, cool to room temperature, wash the obtained black whole material 3 times with deionized water to neutral, and dry it to obtain bagasse-derived 3D nitrogen-rich carbon aerogel.

[0054] Example 2

[0055] A preparation method of bagasse-derived 3D nitrogen-rich carbon aerogel specifically includes the following steps:

[0056] (1) First, add 10 g of dry sugarcane bagasse powder pretreated by hydrothermal treatment at 150 °C for 8 h into 250 mL of 0.5 mol / L NaOH solution for alkalization treatment. Magnetically stir for 3 h under the constant temperature condition of 90 °C. After completion, add 0.5 mol / L HCl solution to adjust the pH to neutral. Then, add 200 mL of neutral 9 wt% NaClO2 solution for bleaching treatment. The obtained bleached cellulose is washed 3 times with ethanol and deionized water respectively, and then dried to obtain cellulose;

[0057] (2) First, put 2 g of cellulose and 4 g of polyvinyl alcohol into 100 mL of deionized water, stir at 60 °C for 3 h to form a uniform suspension, then ultrasonically treat for 30 min to remove internal bubbles to form a uniform hydrogel. Finally, freeze-dry the hydrogel at -70 °C for 72 h to obtain an aerogel;

[0058] (3) Mix the aerogel, urea and KOH in a mass ratio of 1:1:0.5 for nitrogen doping and activation treatment. After ultrasonic impregnation for 1 h, dry it. The obtained activated product is placed in a tubular furnace with a CO2 atmosphere, heated to 700 °C at a rate of 10 °C / min for high-temperature carbonization for 2 h, cooled to room temperature. The obtained black bulk material is washed 3 times with deionized water to neutrality, and then dried to obtain sugarcane bagasse-derived 3D nitrogen-rich carbon aerogel.

[0059] Example 3

[0060] A preparation method of sugarcane bagasse-derived 3D nitrogen-rich carbon aerogel, specifically including the following steps:

[0061] (1) First, add 10 g of dry sugarcane bagasse powder pretreated by hydrothermal treatment at 150 °C for 8 h into 250 mL of 0.5 mol / L NaOH solution for alkalization treatment. Magnetically stir for 3 h under the constant temperature condition of 90 °C. After completion, add 0.5 mol / L HCl solution to adjust the pH to neutral. Then, add 200 mL of neutral 9 wt% NaClO2 solution for bleaching treatment. The obtained bleached cellulose is washed 3 times with ethanol and deionized water respectively, and then dried to obtain cellulose;

[0062] (2) First, put 2 g of cellulose and 1 g of polyvinyl alcohol into 100 mL of deionized water, stir at 60 °C for 3 h to form a uniform suspension, then ultrasonically treat for 30 min to remove internal bubbles to form a uniform hydrogel. Finally, freeze-dry the hydrogel at -70 °C for 72 h to obtain an aerogel;

[0063] (3) Mix aerogel, urea, and KOH in a mass ratio of 1:1:0.5 for nitrogen doping and activation treatment. After ultrasonic impregnation for 1 h, dry it. Place the obtained activated product in a tube furnace with a CO₂ atmosphere and heat it to 900 °C at a rate of 10 °C / min for high-temperature carbonization for 2 h. Cool it to room temperature. Wash the obtained black bulk material 3 times with deionized water until neutral, and finally dry it to obtain bagasse-derived 3D nitrogen-rich carbon aerogel.

[0064] Comparative Example 1

[0065] A preparation method of bagasse-derived 3D carbon aerogel specifically includes the following steps:

[0066] (1) First, add 10 g of dry bagasse powder pretreated by hydrothermal treatment at 150 °C for 8 h to 250 mL of 0.5 mol / L NaOH solution for alkalization treatment. Magnetically stir it for 3 h under the constant temperature condition of 90 °C. After completion, add 0.5 mol / L HCl solution to adjust the pH to neutral, and then add 200 mL of neutral 9 wt% NaClO₂ solution for bleaching treatment. Wash the obtained bleached cellulose 3 times with ethanol and deionized water respectively, and dry it to obtain cellulose.

[0067] (2) First, place 2 g of cellulose and 1 g of polyvinyl alcohol in 100 mL of deionized water, stir at 60 °C for 3 h to form a uniform suspension, then ultrasonically treat for 30 min to remove internal bubbles to form a uniform hydrogel, and finally freeze-dry the hydrogel at -70 °C for 72 h to obtain aerogel.

[0068] (3) Place the aerogel in a tube furnace with a CO₂ atmosphere and heat it to 700 °C at a rate of 10 °C / min for high-temperature carbonization for 2 h. Cool it to room temperature. Wash the obtained black bulk material 3 times with deionized water until neutral, and finally dry it to obtain bagasse-derived 3D carbon aerogel.

[0069] Performance Test

[0070] 1. Physical and Chemical Characterization

[0071] Conduct physical and chemical characterization analysis on the bagasse-derived 3D nitrogen-rich carbon aerogel (named NCA-700) prepared in Example 1 and the bagasse-derived 3D carbon aerogel (named CA-700) prepared in Comparative Example 1 respectively.

[0072] Among them, determine the defect degree by measuring the intensity ratio of the D band and the G band of the material with a Raman spectrometer (Thermo Scientific K-Alpha, USA). The excitation wavelength is 532 nm and the power is 5 mW. Use a full-automatic specific surface area and pore analyzer (Quantachrome Autosorb IQ). Before sample detection and analysis, degas at 150 °C for 12 h, and then conduct BET specific surface area test.

[0073] The results are as Figure 1-2 shown.

[0074] It can be seen from Figure 1 that compared with Comparative Example 1, the nitrogen-doped and chemically activated nitrogen-rich carbon aerogel obtained in Example 1 has a higher degree of defects, which is more conducive to the anchoring of nitrogen species.

[0075] It can be seen from Figure 2 that compared with Comparative Example 1, the nitrogen-rich carbon aerogel obtained in Example 1 after nitrogen doping and chemical activation has more abundant micropores, and the specific surface area increases from 23.5 m 2 / g to 485.3 m 2 / g.

[0076] 2. H2S-SCO reaction performance

[0077] 0.1 g of NCA-700 prepared in Example 1 and 0.2 g of CA-700 prepared in Comparative Example 1 were respectively subjected to the H2S-SCO reaction, which specifically included the following steps:

[0078] (1) Place the 40-60 mesh aerogel in a quartz reaction tube, heat the quartz reactor to 180 °C through a tube furnace, and purge with N2 for 30 min to remove possible impurities on the surface of the aerogel;

[0079] (2) Prepare a mixed gas (containing 0.1 vol.% H2S, 0.05 vol.% O2, and N2 as the balance gas) by the dynamic gas mixing method, and introduce the mixed gas into the quartz reaction tube. The total flow rate of the mixed gas is 100 mL / min. The mass space velocity corresponding to NCA-700 is 60000 mL / g·h, and the mass space velocity corresponding to CA-700 is 30000 mL / g·h. Control the temperature of the quartz reaction tube at 60 °C, 90 °C, 120 °C, 150 °C, 180 °C, and 210 °C respectively through a tube furnace for gas-solid catalytic oxidation reaction. Detect the H2S concentration in the gas at the outlet of the reactor through a hydrogen sulfide detector. When the outlet concentration of H2S reaches 0.01 vol.%, the reaction is completed;

[0080] (3) Lower the temperature of the tube furnace to room temperature, and take out the obtained catalytic oxidation product to cool and collect the elemental sulfur and aerogel.

[0081] Record and calculate their conversion rates and S selectivities for H2S respectively. The results are as Figures 3-5 shown.

[0082] It can be seen from Figures 3-4It can be seen that, compared with Comparative Example 1, the conversion rate of the nitrogen-rich carbon aerogel obtained after nitrogen doping and chemical activation in Example 1 increases in a volcanic shape with the increase of the reaction temperature. The conversion rate of H2S can reach 100% at 180 °C, while the S selectivity decreases to 95%.

[0083] It can be seen from Figure 5 that after continuous reaction at 180 °C for 30 h, the conversion rate of H2S of the nitrogen-rich carbon aerogel obtained after nitrogen doping and chemical activation in Example 1 remains at 100%. Due to the peroxidation reaction, the S selectivity slightly decreases to 94%.

[0084] In addition, the bagasse-derived 3D nitrogen-rich carbon aerogel prepared in Example 2 was subjected to the H2S-SCO reaction. The results show that its conversion rate of H2S remains at 88% at 180 °C, and the S selectivity is 85.2%.

[0085] The bagasse-derived 3D nitrogen-rich carbon aerogel prepared in Example 3 was subjected to the H2S-SCO reaction. The results show that both its conversion rate of H2S and S selectivity remain at 91% at 180 °C.

[0086] The above tests show that the bagasse-derived 3D nitrogen-rich carbon aerogels prepared in Examples 1-3 of the present invention have good performance in the H2S-SCO reaction, can efficiently and stably purify the toxic and harmful gas H2S under low-temperature and micro-oxygen conditions and recover sulfur resources, which is beneficial to solving the emission problem of various industrial tail gases containing H2S and the treatment problem of a large amount of bagasse generated every year. The present invention provides a method for purifying the toxic and harmful gas H2S while realizing the recovery and utilization of sulfur resources and the resource utilization of the waste biomass bagasse. The raw materials of this material are cheap and easy to obtain, the synthesis method is simple and the cycle is short. Moreover, it has high selectivity and few by-products in the process of H2S catalytic oxidation, avoiding secondary pollution and being easy to realize large-scale application in actual industry.

[0087] The bagasse-derived 3D nitrogen-rich carbon aerogel developed by the present invention exhibits excellent performance in H2S-SCO. Through a unique defect-nitrogen site synergistic action mechanism, this material can achieve a conversion rate of nearly 100% for the toxic H2S gas under medium-temperature (180 °C) and low-oxygen concentration conditions, and the sulfur element selectivity reaches more than 90%, effectively avoiding secondary pollution such as SO2. It converts H2S in industrial tail gas into high-purity sulfur resources (S0), and highly utilizes the agricultural waste bagasse to achieve dual resource utilization. The present invention synchronously solves the two major problems of the "high-energy-consuming catalytic system" in the industrial desulfurization field and the "bagasse accumulation pollution" in the agricultural solid waste field, providing an innovative solution for constructing a sustainable development model of "waste gas treatment-solid waste utilization-sulfur resource cycle".

[0088] The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing bagasse-derived 3D nitrogen-rich carbon aerogel, characterized in that: The specific steps include: (1) subjecting dried bagasse powder to hydrothermal pretreatment, alkalization treatment, bleaching treatment, and cellulose extraction; (2) mixing cellulose and a cross-linking agent, and freeze-drying the mixture to obtain an aerogel; (3) The aerogel is sequentially subjected to nitrogen doping and activation treatment, high-temperature carbonization, washing, and drying to obtain the bagasse-derived 3D nitrogen-rich carbon aerogel.

2. The method for preparing a bagasse-derived 3D nitrogen-rich carbon aerogel according to claim 1, characterized in that: In step (1), the temperature of the hydrothermal pretreatment is 150° C. and the time is 8 hours.

3. The method for preparing a bagasse-derived 3D nitrogen-rich carbon aerogel according to claim 1, characterized in that: In step (1), the alkalizing agent for the alkalization treatment is a NaOH solution with a concentration of 0.5 mol / L; the bleaching agent for the bleaching treatment is a NaClO2 solution with a concentration of 9 wt%; the mass ratio of the bagasse powder, NaOH and NaClO2 is (2-8):(1-6):(6-15).

4. The method for preparing bagasse-derived 3D nitrogen-rich carbon aerogel according to claim 1, characterized in that: In step (1), the duration of the alkalization treatment and the bleaching treatment is 1 to 4 hours.

5. The method for preparing a bagasse-derived 3D nitrogen-rich carbon aerogel according to claim 1, characterized in that: In step (2), the cross-linking agent is a polyvinyl alcohol solution with a concentration of 1 wt %; the mass ratio of cellulose to polyvinyl alcohol is (1-5):(1-4).

6. The method for preparing bagasse-derived 3D nitrogen-rich carbon aerogel according to claim 1, characterized in that: In step (2), the freeze-drying temperature is -40 to -80°C and the time is 12 to 72 hours.

7. The method for preparing bagasse-derived 3D nitrogen-rich carbon aerogel according to claim 1, characterized in that: In step (3), the nitrogen source for the nitrogen doping and activation treatment is urea, and the activator is KOH; the mass ratio of the aerogel, urea and KOH is (1-2):(1-4):(0.5-2).

8. The method for preparing bagasse-derived 3D nitrogen-rich carbon aerogel according to claim 1, characterized in that: In step (3), the high-temperature carbonization atmosphere is an inert atmosphere or a carbon dioxide atmosphere, the heating rate is 5 to 10°C / min, the temperature is 500 to 900°C, and the time is 2 to 4h.

9. A bagasse-derived 3D nitrogen-rich carbon aerogel prepared by the preparation method according to any one of claims 1 to 8.

10. Use of bagasse-derived 3D nitrogen-rich carbon aerogel prepared by the preparation method according to any one of claims 1 to 8 in removing H2S.

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