Biomass-based catalyst based on acid-base impregnation-high temperature combined process, preparation method and application thereof

Abstract

The invention belongs to the technical field of environment and energy material synthesis, and particularly relates to a biomass-based catalyst based on an acid-base impregnation-high temperature combined process, and a preparation method and application thereof. The preparation method comprises the following steps: firstly, preparing waste biomass treated by acid dipping, calcining, and further dipping by alkali liquor to form the biomass-based catalyst which takes a furan structure as a main body framework and has no inorganic impurity load on the surface. Active sites on the surface of the catalyst are exposed through removal of inorganic impurities, and adsorption and activation of reactants are facilitated. Meanwhile, multifunctional functional groups can be formed on the surface of the catalyst in the impregnation process, and in addition, the step-by-step calcination process in the carbon dioxide atmosphere can slow down the structural evolution rate of the catalyst in the calcination process, so that inorganic impurities are more thoroughly removed under the condition that the biochar structure is not influenced, the concentration of the functional groups on the surface of the catalyst is higher, and the catalyst has higher catalytic activity. And finally, the waste biomass is converted into the photocatalyst with low cost and high activity.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst preparation, specifically a biomass-based catalyst based on an acid-base impregnation-high temperature combined process, its preparation method, and its application. Background Technology

[0002] Photocatalysis is a green energy conversion technology that can convert environmentally friendly and readily available solar energy into high-energy chemicals. To date, researchers have made significant progress in the field of semiconductor photocatalysis through in-depth research into the mechanisms of photocatalysis. However, traditional photocatalysts, such as titanium dioxide (TiO2) and zinc oxide (ZnO), suffer from high electron-hole recombination rates and low activity. Novel high-performance photocatalysts, such as heterojunction photocatalysts and covalent organic frameworks (COFs), often require loading noble metal sites, resulting in high costs and complex synthesis processes. Therefore, developing low-cost, simple-to-synthesize, and highly active photocatalysts is beneficial for the industrialization of photocatalysis.

[0003] Waste biomass generated in daily life, such as sugarcane bagasse and corn cobs, can be converted into catalysts for reuse through simple synthesis processes such as calcination and hydrothermal treatment. The principle is that calcination of these biomass materials forms polymerized biomass-based char, which has proven to be significant in simplifying synthesis processes and reusing resources. However, to date, these biomass-modified char materials exhibit low catalytic activity. This is because most inorganic impurities generated during biomass synthesis cannot be easily removed by heating. These impurities coat the char surface, covering the active sites on the catalyst surface, thus hindering the adsorption of reactants on the catalyst surface and the migration of photogenerated electrons and holes to the target analytes. Summary of the Invention

[0004] To address the problem that inorganic impurities cover the active sites of waste biomass modified carbon materials, resulting in low catalytic activity, this invention provides a biomass-based catalyst, its preparation method, and its application based on an acid-base impregnation-high temperature combined process.

[0005] This invention discloses a method for preparing a biomass-based catalyst based on an acid-base impregnation-high temperature combined process, comprising the following steps: Step 1: Dry waste biomass is ground into powder, and the ground biomass powder is impregnated in a hydrofluoric acid solution of a certain concentration. After impregnation for a period of time, the biomass residue is collected and continuously calcined in a stepwise manner under a CO2 atmosphere. After calcination, the sample is collected, washed several times with deionized water, and dried to obtain an acid-impregnated intermediate; Step 2: A certain amount of H-BS is placed in a sodium hydroxide solution of a certain concentration, impregnated at room temperature for a period of time, and then further impregnated at a higher temperature. Subsequently, the product is collected by centrifugation, washed several times with deionized water, and dried to obtain the product, which is the biomass-based catalyst.

[0006] Furthermore, the waste biomass is one or more of sugarcane bagasse and corn cobs.

[0007] Furthermore, in step one: the ratio of biomass powder to hydrofluoric acid is 1 g : (10-40) mL; the concentration of the hydrofluoric acid solution is 2-4 mol / L.

[0008] Furthermore, in step one: the biomass powder is soaked in the hydrofluoric acid solution for 1-2 hours; the continuous step-by-step calcination is divided into two steps, the first step calcination temperature is 200℃ and the calcination time is 6 hours, the second step calcination temperature is 300℃ and the calcination time is 6 hours; the washing is performed 3-5 times.

[0009] Furthermore, in step two: the ratio of acid impregnation intermediate to sodium hydroxide solution is 1 g : (10-40) mL; the concentration of sodium hydroxide solution is 1-4 mol / L.

[0010] Furthermore, in step two: the room temperature immersion time is 1-2 hours; the heated immersion time is 12 hours, and the temperature after heating is 60°C.

[0011] Furthermore, in step two: the number of washing cycles is 3-5, the drying time is 12 hours, and the drying temperature is 80℃.

[0012] The biomass-based catalyst prepared by the aforementioned method is photoexciteable. After acid-base impregnation and high-temperature calcination, the organic matter in the waste gas biomass is transformed into a carbon-containing semiconductor polymer structure, which can be photoexcited. This biomass-based catalyst can be used as a photocatalyst for the photocatalytic production of H₂O₂.

[0013] Beneficial effects: (1) In the preparation method of biomass-based catalyst of the present invention, the hydrofluoric acid impregnation treatment can remove some inorganic impurities on the surface of biomass and load halogen groups (-F) on the surface of the catalyst, providing proton binding force for the oxygen reduction reaction. (2) In the preparation method of biomass-based catalyst of the present invention, the sodium hydroxide impregnation treatment can load hydroxyl functional groups (-OH) on the surface of the material. This group reduces the energy barrier of intermediate *OOH in the oxygen reduction reaction, confirming the optimization effect of acid and base impregnation on the rate-limiting step. (3) In the preparation method of biomass-based catalyst of the present invention, a stepwise calcination process is adopted. In the first stage, the waste gas biomass is converted into biochar. In the second stage, the calcination temperature is increased to remove inorganic impurities. At the same time, the CO2 atmosphere slows down the structural evolution rate of the catalyst during the calcination process, resulting in better biochar conversion and more thorough removal of inorganic impurities. (4) The waste biomass-based catalyst prepared by the present invention has its surface inorganic impurities deeply removed, so that inorganic impurities do not cover the sites, the active sites are exposed, which is conducive to the adsorption of oxygen molecules and further ordered electron-hole transfer and enrichment.

[0014] (5) The waste biomass-based catalyst (H-OH-BS) prepared in this invention, as a new photocatalytic material, has multifunctional functional groups on its surface, which effectively improves the separation efficiency of photogenerated electron-hole pairs and is also beneficial to ·O 2- The formation of [a specific catalyst] effectively improves the yield of H2O2. The H2O2 yield of the waste biomass-based catalyst H-OH-BS prepared in this invention can reach 943.29 μmol / g, which is 6.3 times higher than that of unmodified BS (149.42 μmol / g). Attached Figure Description

[0015] Figure 1 The images show the Fourier transform infrared spectra of different samples; the samples are H-BS and H-OH-BS, respectively.

[0016] Figure 2 These are transmission maps of different samples; the samples are H-BS and H-OH-BS, respectively.

[0017] Figure 3 The images show the X-ray photoelectron spectra of different samples; the samples are H-BS and H-OH-BS, respectively.

[0018] Figure 4 The graph shows the photocatalytic H2O2 production yield of different samples; the samples are BS, H-BS and H-OH-BS, respectively.

[0019] Figure 5 This is the in-situ infrared image of the H-OH-BS sample. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Example 1: (1) Preparation of BS: 2g of dried sugarcane bagasse was ground into powder and placed in a tube furnace for calcination under a CO2 atmosphere. The calcination temperature was 200℃ and held for 6h. Then, the temperature was raised to 300℃ and held for 6h. The sample was collected after calcination, washed with deionized water, and dried to obtain BS.

[0024] (2) Preparation of H-BS: 2g of dried sugarcane bagasse was ground into powder. The powder was then immersed in 30mL of 3mol / L hydrofluoric acid solution for 2h. After immersion, the bagasse was collected and placed in a tube furnace for stepwise calcination under a CO2 atmosphere. The first stage of calcination was carried out at 200℃ for 6h, and the second stage was carried out at 300℃ for 6h. After calcination, the sample was collected, washed with deionized water, and dried to obtain the acid-impregnated intermediate H-BS.

[0025] (3) Preparation of H-OH-BS: H-BS was placed in 30 mL of 2 mol / L sodium hydroxide solution and soaked at room temperature for 2 h. Then, the temperature was raised to 60℃ and maintained for 12 h. The product was then collected by centrifugation, washed with deionized water, and dried to obtain the modified biochar material, which is denoted as H-OH-BS.

[0026] Figure 1 The figure shows the Fourier transform infrared (FT-IR) spectra of different samples. As shown in the figure, no obvious Si-O-Si characteristic vibrational peaks were observed in the FT-IR spectra of H-OH-BS, further confirming the effectiveness of acid-base impregnation in removing Si from inorganic components. Simultaneously, H-OH-BS was observed to exhibit a peak at 1026 cm⁻¹. -1 and 1216 cm -1 The peak belongs to the COC tensile vibration, 1612 cm⁻¹ -1 and 1505cm -1 The peak at 1705 cm⁻¹ is classified as a C=C stretching vibration. -1 The peak at 2924 cm⁻¹ is due to the stretching vibration of C=O. A peak at 2924 cm⁻¹ was also observed for CH. -1 The stretching and -OH at 3423 cm -1 The stretching effect was significant. Of particular note was the presence of a significantly enhanced -OH stretching vibration peak in H-OH-BS, confirming the successful modification of the hydroxyl functional groups on the material surface. These results demonstrate that H-OH-BS material can achieve deep removal of inorganic impurities through a combined acid-base impregnation and high-temperature process.

[0027] Figure 2The images show TEM images of different samples. As shown in the figure, SEM observation revealed that both materials exhibit a microsphere structure with a particle size of 1-3 μm. Among them, H-OH-BS treated with the mixed solution maintained its complete spherical morphology while significantly reducing its surface roughness, indicating that the treatment process achieved deep removal of inorganic impurities on the surface while preserving the main structure of the material.

[0028] Figure 3 The images show X-ray photoelectron spectroscopy (XPS) spectra of different samples. The characteristic C 1s peak of the H-OH-BS spectrum corresponds to the characteristic peaks of the C-C, CO, and C=O bonds, respectively. The CN characteristic peak in the N 1s spectrum may originate from amino structures grafted onto the carbon skeleton edge. The characteristic peaks in the O 1s spectrum correspond to the C=O and CO bonds, respectively. Furthermore, the weak characteristic peak at 536.57 eV is attributed to CO-Si, while the newly appearing C-OH characteristic peak at 530.84 eV further confirms the successful modification of the hydroxyl group. Figure 3 The Si 2p spectrum in .3e shows that the intensity of the CO-Si bond characteristic peak is significantly weakened and disappears compared to H-BS after alkali treatment. These results demonstrate the successful modification of the hydroxyl group in the material. Combined with the C 1s and O 1s spectral characteristics and infrared spectral analysis, this further confirms the successful preparation of H-OH-BS.

[0029] Evaluation method for photocatalytic hydrogen peroxide production activity: 20 mg of material was uniformly dispersed in a photochemical reaction vessel containing 100 mL of deionized water, and magnetic stirring was turned on under air conditions. Under xenon lamp irradiation (300 W power), 1 mL of reaction solution was sampled every 15 min. After each sample, it was immediately filtered through a 0.22 μm microporous membrane. The entire photocatalytic process lasted 60 min, during which the reaction system temperature was maintained constant at 20℃ using external condenser water. Figure 4 The graph shows the photocatalytic H2O2 production yield of different samples. Notably, the H-OH-BS material treated with the acid-base impregnation-high temperature combined process exhibits a significantly enhanced H2O2 production performance compared to the untreated sample, reaching 943.29 μmol / g, which is 6.31 times that of the base material BS. This strongly confirms that the acid-base impregnation-high temperature combined process can effectively promote the photocatalytic synthesis of H2O2.

[0030] Figure 5This study investigated the detection of H₂O₂ in an aqueous solution using in-situ Fourier transform infrared spectroscopy (FTIR), further elucidating the mechanism by which the H-OH-BS catalyst promotes H₂O₂ formation. First, a trace amount of catalyst was applied to the instrument's detection substrate using a cotton swab. During the detection period, oxygen was continuously introduced into the detection container, and the system was continuously illuminated with a 365 nm lamp for 20 minutes. The lines from bottom to top represent the dynamic changes in the infrared spectrum from 0 min to 20 min. The results are shown in the figure; the peak value of evaporated water (EW) appeared at 1630 cm⁻¹. -1 The sample is approximately 1262 cm². -1 and 1454 cm -1 The characteristic peak appearing at [location] is attributed to the characteristic vibrational mode of the *OOH intermediate adsorbed on the catalyst surface. Meanwhile, at 1395 cm⁻¹... -1 The intensity of the *HOOH vibrational characteristic peak detected at the location showed a significant increasing trend with the extension of illumination time. This dynamic change process is the two-electron oxygen reduction reaction (2e... - The ORR pathway-dominated H2O2 formation mechanism provides direct evidence, accompanied by a free hydrogen peroxide (OH) signal peak at 3647 cm⁻¹. -1 The enhancement at the catalyst surface implies continuous and efficient production of H2O2.

[0031] This invention first prepares waste biomass through acid impregnation, followed by calcination and further impregnation with alkaline solution to form a biomass-based catalyst with a furan structure as the main framework and no inorganic impurities loaded on the surface. The removal of inorganic impurities from the surface of the biomass-based catalyst exposes the active sites, which is beneficial for the adsorption and activation of reactants. Simultaneously, the impregnation process forms multifunctional functional groups (-F, -OH) on the catalyst surface. These functional groups provide a hydrophilic surface for the catalytic conversion of O2 to H2O2 during the oxygen reduction reaction, and also provide an alkaline reaction microenvironment to reduce the decomposition efficiency of the product H2O2. Furthermore, the stepwise calcination process under a carbon dioxide atmosphere slows down the structural evolution rate of the catalyst during calcination, allowing for more thorough removal of inorganic impurities without affecting the biochar structure, resulting in a higher concentration of functional groups on the catalyst surface. Ultimately, this enables the conversion of waste biomass into a low-cost, highly active photocatalyst.

[0032] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention.

Claims

1. A method for preparing a biomass-based catalyst based on an acid-base impregnation-high temperature combined process, characterized in that, Includes the following steps: Step 1: Grind the dried waste biomass into powder. Place the ground biomass powder into a solution containing a certain concentration of hydrofluoric acid for impregnation. After impregnation for a period of time, collect the biomass residue and continuously calcine it in a stepwise manner under a CO2 atmosphere. After calcination, collect the sample, wash it several times with deionized water, and dry it to obtain the acid-impregnated intermediate. Step 2: Place a certain amount of H-BS into a solution containing a certain concentration of sodium hydroxide and impregnate it at room temperature for a period of time. Then, further increase the temperature for impregnation, centrifuge to collect the product, wash it several times with deionized water, and dry it to obtain the product, which is the biomass-based catalyst.

2. The preparation method according to claim 1, characterized in that, The waste biomass is one or more of sugarcane bagasse and corn cobs.

3. The preparation method according to claim 1, characterized in that, In step one: the ratio of biomass powder to hydrofluoric acid is 1 g : (10-40) mL; the concentration of hydrofluoric acid solution is 2-4 mol / L.

4. The preparation method according to claim 1, characterized in that, In step one: the biomass powder is soaked in the hydrofluoric acid solution for 1-2 hours; the continuous step-by-step calcination is divided into two steps: the first step calcination temperature is 200℃ and the calcination time is 6 hours, and the second step calcination temperature is 300℃ and the calcination time is 6 hours; the washing is performed 3-5 times.

5. The preparation method according to claim 1, characterized in that, In step two: the ratio of acid impregnation intermediate to sodium hydroxide solution is 1 g : (10-40) mL; the concentration of sodium hydroxide solution is 1-4 mol / L.

6. The preparation method according to claim 1, characterized in that, In step two: the immersion time at room temperature is 1-2 hours; the immersion time at elevated temperature is 12 hours, and the temperature after elevation is 60°C.

7. The preparation method according to claim 1, characterized in that, In step two: the number of washing cycles is 3-5, the drying time is 12 hours, and the drying temperature is 80℃.

8. A biomass-based catalyst prepared by the preparation method according to any one of claims 1-6.

9. The application of the preparation method of the biomass-based catalyst according to claim 8 in photocatalytic H2O2 production.

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