Bamboo biomass carbon material with low Si content as well as preparation method and application of bamboo biomass carbon material

Abstract

The invention discloses a low-Si-content bamboo biomass carbon material as well as a preparation method and application thereof. The preparation method of the bamboo biomass carbon material comprises the following steps: (1) washing fresh bamboos with water, and then adding the washed bamboos into a KOH solution for pretreatment to obtain a pretreated material; (2) carbonizing the pretreated material to obtain a carbonized material; (3) activating the carbonized material by adopting an alkali metal compound, and then roasting to obtain powder carbon; (4) carrying out acid pickling treatment on the powder carbon; and (5) washing the acid-washed powder carbon with water, and drying to obtain the bamboo biomass carbon material with low Si and K contents. The invention provides the application of the bamboo biomass carbon material as a supercapacitor electrode material, and the bamboo biomass carbon material has good double-electric-layer capacitance performance. The invention also provides a Pd-based selective hydrogenation catalyst with the bamboo biomass carbon material as a carrier, and provides application of the Pd-based selective hydrogenation catalyst in a parachloronitrobenzene hydrogenation reaction, and the Pd-based selective hydrogenation catalyst has excellent catalytic reaction performance.

Description

Technical Field

[0001] This invention belongs to the field of biomass resource utilization technology, specifically relating to a bamboo biomass carbon material, its preparation method, and its application. Background Technology

[0002] Biomass, as a renewable carbon-containing resource, can not only reduce greenhouse gas emissions when effectively utilized [Mohanty A K, et al. Nature Reviews Methods Primers, 2024, 4:19], but also effectively improve the utilization efficiency and value of carbon resources. Among many biomass resources, bamboo biomass has advantages such as concentrated planting areas and low cost. Therefore, converting bamboo biomass into activated carbon materials is an economical, clean, and efficient biomass utilization method. However, bamboo is a typical silicon-accumulating plant [Zhang YM, et al. Bioresources. 2017, 12(3), 4652-4669.], and existing research results show that the Si component in biomass has a negative impact on the properties of the resulting carbon materials. For example, in the production of activated carbon, most of the Si components have an adverse effect on pore formation during the activation process (blocking some pores) and reduce the solid carbon content, affecting the adsorption performance of activated carbon [Wang G, et al. Clean Coal Technology, 2018, 24: 88-91.]; and the silica contained in biomass can hinder electron conduction [Wang M, et al. Applied Surface Science. 2023, 636: 157820.]; the research results of MaW et al. show that the volume change of Si is very large (>300%) during repeated charge and discharge, which can lead to electrode disintegration and persistent side reactions with electrolyte [MaW, et al. Small, 2024, 20, 2308109.]. Secondly, Si in biomass carbon materials generally exists in the form of silicates and SiO2, which usually requires the use of HF for removal. This increases the requirements for processing equipment and leads to environmental pollution problems [Xiong SX, et al. Energy & Fuels, 2020, 34(6):7591-7599.]. On the other hand, the current method of converting bamboo biomass into high specific surface area carbon materials is mainly through chemical activation, which leads to the residue of alkali metal elements [Zhou XX, et al. Chemical Paper. 2023, 77:7361-7377.]. The above problems make it difficult to prepare carbon materials with high specific surface area and low Si and metal ion (ppm level) content from high Si biomass using existing methods, thus affecting the application of biomass carbon materials in the field of high-value carbon materials (e.g., capacitive carbon, carbon supports for noble metal catalysts).

[0003] To address the aforementioned challenges encountered in the preparation of biomass carbon materials, this invention reports a method for preparing carbon materials with high specific surface area and low Si and metal ion (ppm-level) content based on bamboo biomass as raw material, and its application in supercapacitors and carbon-supported Pd-based p-chloronitrobenzene (p-CNB) hydrogenation catalysts. Summary of the Invention

[0004] To address the issues of high levels of residual Si and alkali metal elements in bamboo biomass carbon materials, this invention provides a method for preparing bamboo biomass carbon materials with high specific surface area and low Si and metal ion (ppm level) content, the resulting carbon materials, and their applications.

[0005] The technical solutions adopted to solve the above-mentioned technical problems are described below.

[0006] In a first aspect, the present invention provides a method for preparing bamboo biomass carbon materials, the method comprising the following steps:

[0007] (1) Take fresh bamboo, rinse the surface of the bamboo with deionized water to remove impurities, then add it to KOH solution for pretreatment, and then obtain the pretreated material by filtration, washing and drying.

[0008] (2) The above pretreated material is placed in a tube furnace for carbonization treatment, and after cooling to room temperature, it is taken out to obtain carbonized material.

[0009] (3) The carbonized material is activated by alkali metal compounds and then roasted in a tube furnace to obtain powdered carbon.

[0010] (4) The powdered carbon is acid washed;

[0011] (5) The acid-washed powdered carbon is washed with water until neutral, and then dried to obtain bamboo biomass carbon material with a specific surface area of ​​3000-3300 m². 2 ·g -1 The Si element content is <0.1%, and the alkali metal element (K) content is below 50 ppm.

[0012] Preferably, in step (1), the mass ratio of bamboo to KOH is 1:1-3, preferably 1:2; the mass fraction of the KOH solution is 15-25wt%, preferably 20wt%; the pretreatment temperature is 80-110℃, preferably 100℃; and the pretreatment time is 1-3h, preferably 2h.

[0013] Preferably, in step (2), the atmosphere inside the tubular furnace is a nitrogen atmosphere, the carbonization temperature is 500-600℃, preferably 600℃, and the heating rate is 5-10℃ / min. -1Carbonize at a constant temperature for 2-3 hours.

[0014] Preferably, in step (3), the activation treatment involves grinding and mixing the carbonized material with an alkali metal compound, wherein the alkali metal compound is preferably solid KOH, and the mass ratio of KOH to the carbonized material is 3-5:1, preferably 3:1; the tubular furnace atmosphere is nitrogen, the calcination temperature is 700-900℃, preferably 800℃, and the heating rate is 5-10℃ / min. -1 Calcination at a constant temperature for 2-3 hours.

[0015] Preferably, in step (4), the powdered carbon is subjected to acid washing, wherein the acid used for acid washing is nitric acid with a concentration of 1-2 mol / L. -1 Preferably 1 mol L -1 The pickling temperature is 70-90℃, preferably 80℃; the pickling time is 3-4 hours.

[0016] Preferably, in step (5), the drying temperature is 80-100℃ and the drying time is 10-12h.

[0017] Secondly, the present invention provides a bamboo biomass carbon material prepared according to the preparation method described in the first aspect, wherein the bamboo biomass carbon material has a specific surface area of ​​3000-3300 m². 2 ·g -1 The Si element content is <0.1%, and the alkali metal element (K) content is below 50 ppm.

[0018] Thirdly, this invention provides the application of the bamboo biomass carbon material described in the second aspect as an electrode material for supercapacitors. The electrode material exhibits good double-layer capacitance performance, demonstrating excellent specific capacitance and good conductivity.

[0019] Fourthly, the present invention provides a Pd-based selective hydrogenation catalyst, the Pd-based selective hydrogenation catalyst comprising a support and an active component Pd, wherein the support is the bamboo biomass carbon material described in the second aspect.

[0020] Preferably, the Pd-based selective hydrogenation catalyst is prepared by the following method: a mixed aqueous solution of PEG and palladium precursor is prepared, added dropwise to bamboo biomass carbon material, impregnated at room temperature for 3-5 hours, then treated in a water bath at 70-90°C for 1-2 hours, dried, and placed in a tube furnace for calcination at 300-500°C under an inert atmosphere for 3-5 hours, and then cooled to room temperature to obtain the Pd-based selective hydrogenation catalyst. More preferably, the mass ratio of PEG, palladium precursor, and bamboo biomass carbon material is 0.15-0.2:0.01-0.02:3, wherein the mass of the palladium precursor is based on the mass of palladium element contained therein.

[0021] Fifthly, the present invention provides the application of the Pd-based selective hydrogenation catalyst described in the fourth aspect in the hydrogenation reaction of p-chloronitrobenzene (p-CNB). The Pd-based selective hydrogenation catalyst exhibits excellent reactivity and selectivity for the p-chloroaniline product during the catalytic hydrogenation reaction of p-chloronitrobenzene.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The preparation method reported in this invention only requires simple pretreatment to reduce the Si content in carbon materials, avoiding complex processing technology and reducing the requirements for processing equipment.

[0024] (2) The low Si and K content carbon material prepared by this invention has good double-layer capacitance performance when used as an electrode material, exhibiting excellent specific capacitance and low resistance.

[0025] (3) The low Si and K content carbon material prepared by the present invention can be used as a support to prepare a supported Pd-based catalyst, which has excellent catalytic performance in the catalytic hydrogenation of p-chloronitrobenzene. Attached Figure Description

[0026] Figure 1 Figures (a) and (b) show the cyclic voltammetry curves of electrode sheets prepared using carbon materials A and B, respectively. Figure (a) and (b) represent the CV curves of electrode sheets prepared using carbon materials A and B at the same cycle and different scan rates, respectively.

[0027] Figure 2 The constant current charge-discharge curves of the electrode sheet prepared using carbon material A are obtained by scanning at different currents.

[0028] Figure 3 The figures show the specific capacitance curves of electrode sheets prepared using carbon materials A and B under different currents. a and b represent electrode sheets prepared using carbon materials A and B, respectively.

[0029] Figure 4 The figures show the AC impedance curves of electrode sheets prepared using carbon materials A and B, respectively. a and b represent electrode sheets prepared using carbon materials A and B, respectively. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0031] Example 1:

[0032] First, the fresh bamboo was rinsed with deionized water to remove surface impurities. 10g of KOH solid was mixed with 40g of deionized water to prepare a 20wt% KOH solution, which was then mixed with 5g of bamboo. After water bath treatment at 100℃ for 2 hours, the mixture was filtered while hot, and then washed with deionized water until the filtrate pH≈7. The treated bamboo was then placed in an oven and dried at 100℃ for 12 hours.

[0033] The pretreated material was placed in a tube furnace and calcined at 600°C in a nitrogen atmosphere for two hours (heating rate of 5°C / min). -1 After cooling to room temperature, the carbonized material is removed.

[0034] The carbonized material and KOH solid were mixed at a mass ratio of 1:3 and ground in a mortar for 5 minutes. The mixed sample was then placed in a tube furnace and calcined at a constant temperature of 800℃ in a nitrogen atmosphere for two hours (heating rate of 5℃ / min). -1 To obtain powdered carbon materials.

[0035] After washing the activated powdered carbon material once with deionized water, add 100 mL of 1 mol L... -1 The HNO3 solution was treated in a water bath at 80°C for 3 hours, then filtered while hot, and washed with deionized water until the pH of the filtrate was approximately 7. The treated carbon material was then dried in an oven at 100°C for 12 hours to obtain the desired carbon material A.

[0036] Comparative Example 1

[0037] First, the fresh bamboo is rinsed with deionized water to remove surface impurities. Then, it is placed in a tube furnace and roasted at a constant temperature of 600°C in a nitrogen atmosphere for two hours (heating rate of 5°C / min). -1 After cooling to room temperature, the carbonized material is removed.

[0038] The carbonized material and KOH solid were mixed at a mass ratio of 1:3 and ground in a mortar for 5 minutes. The mixed sample was then placed in a tube furnace and calcined at a constant temperature of 800℃ in a nitrogen atmosphere for two hours (heating rate of 5℃ / min). -1 To obtain powdered carbon materials.

[0039] After washing the activated carbon powder once with deionized water, add 100 mL of HNO3 solution (1 mol / L). -1 After being treated in a water bath at 80℃ for 3 hours, the carbon material was filtered while hot and then washed with deionized water until the pH of the filtrate was approximately 7. The treated carbon material was then placed in an oven and dried at 100℃ for 12 hours to obtain the desired carbon material B.

[0040] Table 1 shows the texture and elemental content data for carbon materials A and B. Table 1 reveals that the method reported in Example 1 can effectively reduce the Si content in carbon materials, but has little impact on the specific surface area, pore volume, and pore structure of the carbon materials.

[0041] Table 1

[0042]

[0043] a Calculate using the Brunauer-Emmett-Teller (BET) equation

[0044] b Calculated from the Dubinin-Astakhov equation

[0045] c Determined by relative pressure and P / P0 = 0.99

[0046] d Micropore volume (V) mic ) Determined using t-Plot method

[0047] Example 3 (Three-electrode electrochemical performance test):

[0048] Weigh approximately 0.035g of carbon material A or B, approximately 0.01g of acetylene black, and approximately 0.005g of PVDF, place them in a mortar, and grind them evenly. Then, spread the mixture evenly on a 1.5×1.5cm surface. 2 Electrode sheets A and B were fabricated on nickel foam, pressed for 1 minute under 10 MPa pressure, and then dried in an 85°C oven for 12 hours. The electrode material loading was approximately 5-7 mg. Electrode sheet A or B was used as the working electrode, a platinum sheet electrode as the auxiliary electrode, and Hg / HgO as the reference electrode. A 2 mol L... -1 Using KOH solution as the electrolyte, the electrochemical performance of carbon materials A and B was determined using a three-electrode testing system with a KOSTER CS03104 electrochemical workstation.

[0049] Figure 1 The figures show the CV curves of electrode sheets made from carbon materials A and B (a is the CV curve of electrode sheet A at different scan rates; b is the CV curve of electrode sheet B at different scan rates). It can be seen from the figures that, compared to electrode sheet B, the CV curves of electrode sheet A at different scan rates are more rectangular. This indicates that carbon material A with low Si content is closer to an ideal double-layer capacitor material, and therefore has superior charge and electrolyte ion migration capabilities.

[0050] Figure 2The image shows the GCD curves of electrode A obtained under different currents. The graphs reveal that its charge-discharge curves approximate isosceles triangles, indicating that carbon material A possesses excellent double-layer capacitance characteristics.

[0051] Figure 3 The figure shows the specific capacitance of electrode A and electrode B under different currents (A is the specific capacitance value of electrode A under different currents; B is the specific capacitance value of electrode B under different currents). It can be seen from the figure that the specific capacitance of carbon material A with low Si content is consistently higher than that of carbon material B with high Si content under different currents.

[0052] Figure 4 The Nyquist spectra of electrodes A and B are shown (A is the Nyquist spectrum of electrode A; B is the Nyquist spectrum of electrode B). In the high-frequency region, the intercept between the impedance curve and the horizontal axis represents the equivalent series resistance Rs, reflecting the internal resistance of the electrochemical system. The internal resistance Rs of carbon material A is 0.5Ω, while that of carbon material B is 0.76Ω, a reduction of approximately 33%. This indicates that reducing the Si content helps improve the conductivity of the biomass carbon material. Furthermore, the vertical line in the low-frequency region represents the Warburg impedance related to the diffusion resistance of electrolyte ions in the electrode pores. The slope of the line for carbon material A is closer to 90°, indicating that it has lower diffusion resistance than carbon material B, suggesting a faster diffusion rate between the electrolyte and the carbon material.

[0053] Based on the test results of the carbon material in the three-electrode system, it can be found that the low-Si content bamboo biomass carbon material prepared by the method described in Example 1 of this invention has good double-layer capacitance performance, exhibiting excellent specific capacitance and good conductivity, and therefore has good application prospects in supercapacitors.

[0054] Example 4 (Preparation of Pd-based catalyst):

[0055] Solution A was prepared by mixing 0.1750 g of PEG-1000 with 3 mL of deionized water. Solution B was prepared by mixing 1.5 mL of deionized water with 1.5 mL of palladium nitrate solution (0.2590 g of palladium nitrate dihydrate was uniformly mixed with 10 mL of deionized water). Solutions A and B were mixed thoroughly, and the mixture was then added dropwise to 3.0 g of carbon support A or B and impregnated at room temperature for 4 h. After treatment in an 80 °C water bath for 1 h, the mixture was dried in a 100 °C oven for 4 h. The resulting solid was then placed in a tube furnace and dried under a 99.999% N2 atmosphere (N2 flow rate = 100 mL / min). -1Carbon-supported Pd-based catalysts were obtained by calcination treatment for 4 hours (calcination temperature 400℃). The catalysts using carbon materials A and B as supports were named Pd / AC and Pd / BC catalysts, respectively.

[0056] Example 5 (Catalytic hydrogenation reaction):

[0057] Use 100cm 3 The performance of the Pd-based catalyst prepared in Example 4 for the catalytic hydrogenation of p-chloronitrobenzene was evaluated using a stainless steel high-pressure reactor. First, 50 mL of anhydrous ethanol, 1.0 g of p-chloronitrobenzene (p-CNB), and 0.05 g of catalyst were added to the high-pressure reactor. Before the hydrogenation reaction, the reactor system was first purged with 99.999% H2 six times, and then the catalytic hydrogenation reaction was carried out under magnetic stirring conditions of 60 °C, 1.1 MPa, and 1000 rpm. The hydrogenation products were qualitatively and quantitatively analyzed using a gas chromatograph (Agilent GC7890B) equipped with a flame ionization detector. The catalytic hydrogenation experiment results showed that with the Pd / AC catalyst, the p-CNB conversion reached ~99.5% in 150 minutes, and the p-CAN selectivity was ~99.8%. However, with the Pd / BC catalyst, the p-CNB conversion was only achieved to ~100% after a reaction time extended to 240 minutes, and the p-CAN selectivity was only ~95.4%.

[0058] The above experimental results show that the Pd-based catalyst prepared using low-Si bamboo biomass carbon material as a support by the method described in Example 1 of this invention exhibits higher p-CNB catalytic hydrogenation activity and p-CAN selectivity in the hydrogenation reaction of p-chloronitrobenzene than the Pd-based catalyst prepared using high-Si carbon material as a support. Therefore, the low-Si bamboo biomass carbon material prepared by the method described in this invention also shows good application prospects in supported Pd-based catalytic hydrogenation catalysts.

Claims

1. A method for preparing bamboo biomass carbon material, characterized in that: The preparation method comprises the following steps: (1) taking fresh bamboo, washing impurities on the bamboo surface with deionized water, then adding it into a KOH solution for pretreatment, and then filtering, washing, and drying to obtain a pretreated material; (2) placing the pretreated material in a tubular furnace for carbonization treatment, and taking it out after cooling to room temperature to obtain a carbonized material; (3) activating the carbonized material with an alkali metal compound and then calcining it in a tubular furnace to obtain powdered carbon; (4) acid washing the powdered carbon; (5) washing the acid-washed powdered carbon with water until it is neutral, and then drying it to obtain a bamboo biomass carbon material, wherein the specific surface area of ​​the bamboo biomass carbon material is 3000-3300m 2 ·g -1 , the Si element content is <0.1%, and the alkali metal element K content is below 50 ppm.

2. The preparation method according to claim 1, characterized in that: In the step (1), the mass ratio of bamboo to KOH is 1:1-3; the mass fraction of the KOH solution is 15-25wt%; the pretreatment temperature is 80-110°C; and the pretreatment time is 1-3h.

3. The preparation method according to claim 1, characterized in that: In step (2), the atmosphere in the tube furnace is nitrogen atmosphere, the carbonization temperature is 500-600°C, preferably 600°C; the heating rate is 5-10°C min -1 , carbonize at constant temperature for 2-3h.

4. The preparation method according to claim 1, characterized in that: In the step (3), the activation treatment is to grind and mix the carbonized material with the alkali metal compound, the alkali metal compound is KOH solid, the mass ratio of KOH to the carbonized material is 3-5:1, preferably 3:1; the atmosphere of the tubular furnace is nitrogen atmosphere, the roasting temperature is 700-900°C, preferably 800°C; the heating rate is 5-10°C min -1 , calcine at constant temperature for 2-3h.

5. The preparation method according to claim 1, characterized in that: In step (4), the powdered carbon is pickled with nitric acid at a concentration of 1-2 mol L -1 ; The pickling temperature is 70-90℃; The pickling time is 3-4h.

6. A bamboo biomass carbon material obtained according to the preparation method according to any one of claims 1 to 5.

7. Use of the bamboo biomass carbon material as claimed in claim 6 as a supercapacitor electrode material.

8. A Pd-based selective hydrogenation catalyst, characterized in that: The Pd-based selective hydrogenation catalyst comprises a carrier and an active component Pd, and the carrier is the bamboo biomass carbon material according to claim 6.

9. The Pd-based selective hydrogenation catalyst according to claim 8, characterized in that: The Pd-based selective hydrogenation catalyst is prepared by the following method: preparing a mixed aqueous solution of PEG and palladium precursor, dropping the mixed aqueous solution onto a bamboo biomass carbon material, immersing the mixture at room temperature for 3-5 hours, then treating the mixture in a water bath at 70-90° C. for 1-2 hours, drying the mixture and placing the mixture in a tubular furnace, calcining the mixture at 300-500° C. for 3-5 hours under an inert atmosphere, and cooling the mixture to room temperature to obtain a Pd-based selective hydrogenation catalyst.

10. Use of the Pd-based selective hydrogenation catalyst as claimed in claim 8 or 9 in the hydrogenation reaction of p-chloronitrobenzene.

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