Preparation method and application of super high specific surface area porous lignin based on zinc source template-hydrothermal carbonization

Abstract

The application discloses a preparation method of superhigh specific surface area porous lignin based on a zinc source template-hydrothermal carbonization and application thereof, and belongs to the technical field of biomass material modification. The preparation method comprises the following steps: material fusion: mixing sodium lignosulfonate with a solid content of 10-30 wt% and a zinc source according to a molar ratio of 1:0.5-2, and pouring the mixed product into a reaction kettle; ion exchange reaction: stirring and reacting at 60-80 DEG C for 2-4 hours, and forming zinc-lignin complex precipitate in the reaction kettle. The obtained material has superhigh specific surface area (>=2500 m2 / g) and various pore structure characteristics, is suitable for supercapacitor electrodes, adsorbents and catalyst carriers, has better pore structure characteristics and higher specific surface area than commercially available products, has good effects whether used for electrodes or adsorbents, and is free of alkali in the whole process, and is more environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of biomass material modification technology, specifically involving a method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization and its application. Background Technology

[0002] Porous carbon materials possess excellent electrical conductivity, strong skeletal rigidity, and high specific surface area, exhibiting distinct structures and properties compared to traditional graphite electrodes, carbon black, and activated carbon. Asphalt, coke, polymers, and biomass are commonly used precursors for the preparation of porous carbon, with the use of widely available and abundant biomass becoming a research hotspot in recent years. Lignin, an important component of plant biomass, is the world's most abundant natural aromatic polymer, typically produced by the pulp and paper industry. Lignin's abundant sources, high carbon content, and low cost provide a low-cost, sustainable carbon precursor for the preparation of high-performance porous carbon electrode materials.

[0003] Existing porous carbon materials typically use activated carbon, graphite, and carbon black as raw materials. Traditional activated carbon usually has a specific surface area of ​​<2000 m² / g, and its preparation process often relies on highly corrosive chemical activators (such as KOH and ZnCl2), which not only requires sophisticated equipment but also easily causes environmental pollution. Meanwhile, although biomass carbon precursors, represented by lignin, have advantages such as renewability, low cost, and high carbon content, carbon materials obtained by direct heat treatment generally suffer from low porosity (<500 m² / g) and insufficient specific surface area. In addition, hard template methods (such as silica templates) require subsequent etching removal steps using hazardous chemicals such as hydrofluoric acid, posing safety and environmental risks. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization and its application.

[0005] The technical solution adopted to solve the above technical problems is:

[0006] A method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization includes the following steps;

[0007] (1) Material fusion: Mix the lignin sulfonate solution with the zinc source at a molar ratio of 1:0.5-2, and pour the mixed product into the reaction vessel;

[0008] (2) Ion exchange reaction: The mixture in the reaction vessel is stirred, and a zinc-lignin complex precipitate is formed in the reaction vessel;

[0009] (3) Hydrothermal carbonization: The reactants obtained in step (2) are transferred into a high-pressure reactor and reacted at 180-220℃ for 6-12 hours;

[0010] (4) Reaction condition control: The heating rate in the high-pressure reactor is controlled at 5-10℃ / min, and the reaction pressure is maintained at 2-4MPa;

[0011] (5) Post-processing: After the reaction product in the autoclave is cooled, it is filtered, acid washed to remove residual zinc, and finally vacuum dried to obtain black porous powder, namely porous lignin.

[0012] Through the above technical solution, the present invention uses a zinc source synthesis method, which innovatively utilizes several unique properties of the zinc source: low-temperature hydrolysis, moderate reduction temperature (can be reduced by biomass carbon at 220℃), and the spontaneous pore-forming ability of gaseous products (different from solid templates). This reaction path successfully avoids the etching process required by the traditional template method.

[0013] Furthermore, the zinc source is selected from one of zinc oxide, zinc acetate, or zinc nitrate.

[0014] Through the above technical solution, the purpose of fusing the two materials in steps 1 and 2 is to exchange ions between sodium lignosulfonate and zinc source, with Zn²⁺ replacing Na⁺, thereby forming a zinc-lignin complex precipitate. The lignin sulfonate molecule has sulfonic acid groups, phenolic hydroxyl groups, carboxyl groups, etc., which can serve as metal ion complexation sites and can form chelate / complex structures with Zn²⁺. Zinc acetate and zinc nitrate are themselves soluble zinc salts and can directly provide Zn²⁺ in the aqueous phase, which is conducive to rapid ion exchange / complexation with lignin sulfonate. Although zinc oxide is difficult to dissolve, it can participate in the formation of zinc-containing intermediates / nanoparticle templates in a hydrothermal system and is easily removed during subsequent acid washing.

[0015] Furthermore, the zinc source has a particle size of 50-200 nm.

[0016] A common problem with the above technical solutions for nano-zinc oxide is that the smaller the particle size, the larger the specific surface area or surface energy, and the easier it is to spontaneously agglomerate. This leads to a larger effective particle size participating in the reaction and poorer dispersion, resulting in uneven template effect and unstable pore structure. Therefore, setting the lower limit above 50 nm is to avoid strong agglomeration and batch instability caused by extremely small particle size. The direct consequence of increasing particle size is a decrease in specific surface area per unit mass, a reduction in solid-liquid interface contact, and a slowdown in related processes, resulting in insufficient pore formation and poor uniformity.

[0017] Furthermore, the acid washing in the post-treatment step uses a hydrogen chloride solution with a concentration of 0.1–0.2 mol / L, and the washing is performed 1–3 times.

[0018] Through the above technical solution, a certain amount of zinc components will remain in the product after hydrothermal carbonization, such as ZnO, Zn²⁺ complex residues or zinc-containing intermediates. If these residues are not removed, they will occupy the pores and block the micropores / mesopores, directly reducing the specific surface area and pore structure quality. Hydrogen chloride and zinc oxide can be directly synthesized into soluble zinc chloride. 0.1–0.2 mol / L is sufficient to provide the dissolution driving force without being too strong.

[0019] Furthermore, the lignin sulfonate is sodium lignin sulfonate, and the solid content of the lignin sulfonate solution is 10–30 wt%.

[0020] Through the above technical solutions, lignin sulfonate is essentially a polyelectrolyte with hydrophilic groups such as sulfonate and carboxyl groups, which can ensure its solubility in the aqueous phase. This is the basis for its use as a reaction substrate and metal complex carrier. Among them, sodium lignin sulfonate has good solubility and is easier to prepare into a stable solution and participate in the reaction in engineering. At the same time, lignin sulfonate solution has colloidal properties, and the solution viscosity increases with the increase of concentration. The higher the concentration, the easier it is to have a stronger aggregation effect, which brings the risk of inhomogeneity in stirring, mass transfer, filtration and forming. Therefore, it is necessary to control its solid content.

[0021] Furthermore, the temperature in the reactor is 60-80℃, and the stirring reaction lasts for 2-4 hours.

[0022] Through the above technical solution, ion complexation essentially relies on the contact and coordination between Zn²⁺ and the sulfonic acid and carboxyl groups on lignin sulfonate. Heating can accelerate diffusion, reduce solution viscosity, and increase molecular motion rate, thereby increasing the reaction propulsion speed. At the same time, lignin sulfonate belongs to a polyelectrolyte system, and its conformation, colloidal state, and complexation behavior in aqueous solution are affected by parameters such as temperature. The temperature window should be selected in a range that is conducive to the reaction and will not cause the system to run away from control. Raising the temperature to 60–80℃ is usually to make the system easier to stir evenly, so that Zn²⁺ can contact and exchange more evenly on the lignin sulfonate chain, thereby obtaining a more uniform zinc-lignin precursor.

[0023] Furthermore, the mass of the hydrogen chloride solution is 2-4 times the theoretical solids.

[0024] The reason for setting the amount of hydrogen chloride solution to 2–4 times the theoretical solids in the above technical solution is not that the stoichiometry must be so high, but to take into account the reaction stoichiometry, mass transfer and diffusion, impurity consumption and process fluctuations in the real system, to ensure that the washing is clean, stable and repeatable, while avoiding unnecessary overdosing that would lead to a surge in cost or waste liquid or unnecessary impact on the materials.

[0025] Based on the application of ultra-high specific surface area porous lignin formed by zinc source template-hydrothermal carbonization, the porous lignin is used to prepare supercapacitor electrodes, dye adsorbents or catalyst supports.

[0026] The lignin produced by the above-mentioned technical solution and preparation method has ultra-high specific surface area, hierarchical pore structure with micropore-mesopore synergy, good chemical stability and carbon skeleton load-bearing characteristics, thus possessing typical high-performance porous carbon common properties.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) The present invention found that zinc oxide converted from zinc source has dual functions in lignin sulfonate system: firstly, it acts as a template agent, complexing with sulfonic acid groups to form micro-nano structures; secondly, it acts as a self-sacrificing pore-forming agent, decomposing and volatilizing in situ during hydrothermal process, and zinc oxide decomposes to produce ZnO nanoparticles and gaseous byproducts (CO2 / H2O). Its escape process forms hierarchical pores (micropore / mesopore synergy) in carbon skeleton, giving lignin a mesoporous-microporous structure. The resulting material has an ultra-high specific surface area (≥2500 m² / g) and diverse pore structure characteristics.

[0029] (2) The present invention uses a zinc source synthesis method, which innovatively utilizes several unique properties of the zinc source: 1. Low-temperature hydrolysis, 2. Moderate reduction temperature (can be reduced by biomass carbon at 220℃), 3. Spontaneous pore-forming ability of gaseous products (different from solid templates). This reaction path successfully avoids the etching process required by traditional template methods, such as HF etching of SiO2, and is the first time that in-situ self-sacrificial pore-forming-carbonization integration has been achieved in lignin modification. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0031] Example 1: A method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization, comprising the following steps:

[0032] (1) 5340g of sodium lignosulfonate with a content of 10% and 162.78g of zinc oxide with a particle size of 50nm were stirred at 60℃ for 2h to obtain complex A;

[0033] (2) Transfer material A into a high-pressure reactor, heat it at a rate of 5℃ / min, pressurize it at 2MPa, and react it at 180℃ for 12h to obtain material B;

[0034] (3) Filter material B to remove some water, remove residual zinc with 1394g of hydrogen chloride solution containing 0.1mol, wash once, and vacuum dry to obtain black porous powder.

[0035] Example 2: A method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization, comprising the following steps:

[0036] (1) 3560g of sodium lignosulfonate with a content of 15% and 81.39g of zinc oxide with a particle size of 50nm were stirred at 80℃ for 3h to obtain complex A;

[0037] (2) Transfer material A into a high-pressure reactor, heat it at a rate of 10℃ / min, pressurize it at 3MPa, and react it at 200℃ for 8 hours to obtain material B;

[0038] (3) Filter material B to remove some water, remove residual zinc with 1847g of hydrogen chloride solution containing 0.1mol, and vacuum dry to obtain black porous powder.

[0039] Example 3: A method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization, comprising the following steps:

[0040] (1) 1780g of sodium lignosulfonate with a content of 30% and 40.7g of zinc oxide with a particle size of 50nm were stirred at 70℃ for 4h to obtain complex A;

[0041] (2) Transfer material A into a high-pressure reactor, heat it at a rate of 5℃ / min, pressurize it at 4MPa, and react it at 220℃ for 6 hours to obtain material B;

[0042] (3) Filter material B to remove some water, remove residual zinc with 1575g of hydrogen chloride solution containing 0.2mol, wash twice, and vacuum dry to obtain black porous powder.

[0043] Example 4: A method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization, comprising the following steps:

[0044] (1) 5340g of sodium lignosulfonate with a content of 10% and 184g of zinc acetate were stirred at 70℃ for 3h to obtain complex A;

[0045] (2) Transfer material A into a high-pressure reactor, heat it at a rate of 10℃ / min, pressurize it at 2.5MPa, and react it at 200℃ for 8 hours to obtain material B;

[0046] (3) Filter material B to remove some water, remove residual zinc with 1394g of hydrogen chloride solution containing 0.1mol, wash once, and vacuum dry to obtain black porous powder.

[0047] Comparative Example 1:

[0048] This comparative example differs from Example 1 only in that zinc oxide is not added in step 1.

[0049] Comparative Example 2

[0050] This comparative example differs from Example 1 only in that the autoclave is not moved in step 2.

[0051] Comparative Example 3

[0052] Compared to Example 1, this comparative example only omits cleaning in step 3.

[0053] Comparative Example 4

[0054] This comparative example differs from Example 1 only in that zinc oxide is replaced with zinc chloride in step 1.

[0055] Performance testing:

[0056] Pore ​​structure characteristics and specific surface area testing:

[0057] The pore structure characteristics and specific surface area of ​​the samples were tested using a low-temperature nitrogen adsorption-desorption method. The specific test method is as follows:

[0058] (1) Sample pretreatment

[0059] Take 50-100 mg of the vacuum-dried sample and put it into a sample tube for the surface area analyzer. Degas the sample at 200°C for 8 hours under vacuum to remove adsorbed moisture and volatile impurities from the sample surface and pores. After degassing, allow the sample tube to cool to room temperature and seal it for transfer to the analysis station for later use.

[0060] (2) Adsorption-desorption isotherm test

[0061] The sample was placed in the liquid nitrogen temperature range of 77K for N2 adsorption-desorption isotherm testing. The relative pressure P / P0 ranged from 0.01 to 0.995. The adsorption and desorption data of the sample were collected point by point under different relative pressures to obtain a complete adsorption-desorption isotherm.

[0062] (3) Calculation of specific surface area

[0063] The BET method was used to calculate the specific surface area of ​​the sample; the BET fitting interval was selected as the linear interval that satisfies the Rouquerol criterion, and the relative pressure P / P0 used for fitting was in the range of 0.05 to 0.30.

[0064] (4) Calculation of pore volume and pore size distribution

[0065] The total pore volume was calculated based on the nitrogen adsorption capacity when P / P0=0.99; the micropore volume and micropore specific surface area were calculated using the t-plot method; the pore size distribution was analyzed using the NLDFT carbon slit pore model to obtain the micropore and mesopore distribution results of the sample.

[0066] (5) Criteria for judging the characteristics of pore structure

[0067] According to the IUPAC pore size classification standard: pores < 2 nm are micropores, 2–50 nm are mesopores, and > 50 nm are macropores. The pore structure type of a sample is determined according to the following principles:

[0068] When the proportion of micropore volume to total pore volume is ≥60% and the proportion of mesopore volume to total pore volume is <20%, it is judged as "micropore";

[0069] When the proportion of micropore volume to total pore volume is ≥30% and the proportion of mesopore volume to total pore volume is ≥20%, it is judged as "micropore-mesopore";

[0070] When the BET specific surface area of ​​a sample is <500m² / g and the total pore volume is <0.10cm³ / g, it is judged as "almost non-porous".

[0071] When the nitrogen adsorption isotherm shows no significant increase in adsorption amount in the low-pressure region, and scanning electron microscopy shows that there are pores with a diameter greater than 50 nm on the sample surface, it is judged as "macropore".

[0072] When a sample is predominantly macropores with a wide pore size distribution and uneven pore shape, it is classified as "irregular macropores".

[0073] (6) Morphological auxiliary characterization

[0074] To further verify the pore structure characteristics determined by the nitrogen adsorption method, and to intuitively confirm the unique morphology, internal pore network, and compositional purity of the material of the present invention at the microscopic level, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS) were used to characterize the samples.

[0075] a) Surface morphology and macroscopic pore structure analysis:

[0076] The surface morphology of the samples was observed using field emission scanning electron microscopy (FE-SEM). A small amount of vacuum-dried sample powder was fixed to the sample stage with conductive tape and then subjected to ion sputtering gold plating to enhance conductivity. The test conditions were set as follows: accelerating voltage 5-15 kV, working distance 8-12 mm, and imaging in secondary electron (SE) mode. By observing at different magnifications (500x-100,000x), the presence of an open and uniform porous structure on the sample surface was determined. Simultaneously, the sample from the example was compared with the sample from Comparative Example 3 (un-acid-washed) to confirm the effectiveness of the acid washing step in removing residues clogging the pores and releasing the porous structure. The sample from the example was expected to have a clean surface and clearly visible pores, while the sample from Comparative Example 3 showed obvious granular or blocky residues on its surface.

[0077] b) Verification of the internal fine-pore structure:

[0078] High-resolution transmission electron microscopy (HR-TEM) was used to directly observe the microporous and mesoporous structures within the samples. A very small amount of sample was ultrasonically dispersed in ethanol and dropped onto an ultrathin carbon-supported copper grid. After the solvent evaporated, the sample was tested at an accelerating voltage of 200 kV. By observing the bright-field image, it was determined whether an interconnected microporous-mesoporous hierarchical network structure had formed within the material, with the carbon framework appearing as darker areas and the pores as brighter areas. At high magnification, the presence of microporous regions with pore sizes less than 2 nm and mesoporous channels with pore sizes in the range of 2-50 nm was confirmed in the sample, providing direct visual evidence for the "microporous-mesoporous" synergistic structure calculated by the NLDFT model.

[0079] c) Confirmation of elemental composition:

[0080] The elemental composition and distribution of selected microregions in the sample were analyzed using an energy dispersive spectroscopy (EDS / EDX) instrument coupled with a scanning electron microscope or a transmission electron microscope. The core purpose of this step is to confirm the thoroughness of the acid washing process in the post-processing steps. Elemental analysis of the final product (e.g., Examples 1-4) should show only strong carbon (C) peaks and moderate oxygen (O) peaks in the spectrum, with the zinc (Zn) signal peak below the instrument's detection limit or completely absent. In contrast, a significant zinc (Zn) peak must be detectable when analyzing the sample of Comparative Example 3 (unwashed). By comparing the elemental signals before and after acid washing, it can be irrefutably proven that the zinc, acting as a template agent, has been completely removed, and the resulting material is high-purity porous carbon.

[0081] Overall judgment:

[0082] Combining the three microscopic analysis methods described above, a complete chain of evidence for the microstructure can be constructed. SEM confirms the open porous morphology of the material surface, TEM visually reveals its rich micropore-mesopore hierarchical network, and EDS confirms the high purity of the material. These visual and compositional evidences are in high agreement with nitrogen adsorption data, collectively and conclusively demonstrating that the method described in this invention can successfully prepare pure porous lignin materials with ultra-high specific surface area and hierarchical pore structure.

[0083] Table 1. Summary of experimental data from Examples 1-4 and Comparative Examples 1-4

[0084]

[0085] Data Analysis:

[0086] As can be seen from Table 1, (1) the method of the present invention can stably prepare porous lignin materials with hierarchical pore structure and significantly improve the specific surface area. Using the process route of "zinc source ion exchange complexation - hydrothermal carbonization - acid washing to remove zinc" described in the present invention, the pore structure of the products obtained in Examples 1 to 4 all showed the synergistic characteristics of "micropore-mesopore", and the specific surface areas were 2534, 2589, 2566 and 2506 m² / g, respectively. The overall level reached and remained stable above 2500 m² / g, demonstrating excellent structural construction effect and repeatability;

[0087] (2) Compared with commercially available activated carbon, the material of the present invention has significant advantages in terms of specific surface area and pore structure. Commercially available activated carbon samples are mainly microporous with a specific surface area of ​​1258 m² / g; while the specific surface area of ​​the material in the embodiments of the present invention is increased to 2506-2589 m² / g and forms a hierarchical pore structure of "micropore-mesopore". This shows that the present invention can still obtain a higher specific surface area and a better pore structure without relying on the traditional strong corrosion activator / hard template etching process;

[0088] (3) Comparative Example 1 demonstrates that the introduction of a zinc source is a key and necessary condition for obtaining a high specific surface area and hierarchical pore structure. When zinc oxide is not added in step 1 (Comparative Example 1), the resulting product has an "irregular macropore" pore structure with a specific surface area of ​​only 389 m² / g. Compared with the "micropore-mesopore, 2500+ m² / g" of Examples 1-4, the technical effect is significantly deteriorated, proving that the zinc source plays a decisive role in pore structure construction and specific surface area improvement.

[0089] (4) Comparative Example 2 demonstrates that the hydrothermal carbonization step is a necessary process for forming a porous structure and achieving a high specific surface area. When hydrothermal carbonization is not carried out in the autoclave in step 2 (Comparative Example 2), the resulting product is "almost non-porous" with a specific surface area of ​​only 329 m² / g. This result is in stark contrast to the example where "micropores-mesopores" were formed under hydrothermal conditions and a specific surface area of ​​2500+ m² / g was obtained, further illustrating that hydrothermal carbonization conditions are indispensable for the formation and solidification of the porous structure.

[0090] (5) Comparative Example 3 demonstrates that pickling / washing to remove residual zinc is an important step in releasing effective pores and increasing the measurable specific surface area. When step 3 is not washed (Comparative Example 3), the resulting product exhibits a "macropore" pore structure with a specific surface area of ​​1167 m² / g. Although this is close to the level of commercially available activated carbon, it is still significantly lower than the 2500+ m² / g of the example. This indicates that if residual zinc and related components are not removed, the pores will not be fully opened or the contribution of effective pores will be limited, thereby weakening the technical effect of the material of the present invention.

[0091] (6) The zinc source is replaceable to a certain extent, but the core technical effect of the present invention can still be maintained. In Example 4, after replacing the zinc source with zinc acetate, a "microporous-mesoporous" pore structure was still obtained and the specific surface area reached 2506 m² / g, which shows that under the overall process framework of the present invention, the type of zinc source can be selected within a certain range without affecting the core effect of obtaining a high specific surface area integral pore structure;

[0092] (7) Comparative Example 4 further demonstrates that not all zinc-containing compounds can achieve the pore structure construction effect of the present invention. When zinc oxide in step (1) is replaced by zinc chloride (Comparative Example 4), the pore structure of the obtained product is only "micropores", with a specific surface area of ​​1684 m² / g. Although this is higher than that of commercially available activated carbon, it is significantly lower than the 2500+ m² / g level of Examples 1-4. This indicates that although zinc chloride can provide Zn²⁺, it is difficult to achieve the same micropore / mesopore synergistic construction effect as the zinc oxide template-hydrothermal carbonization system. The resulting material has insufficient mesopore development and therefore cannot achieve the core technical effect of the present invention.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization, characterized in that: Includes the following steps; (1) Material fusion: Mix the lignin sulfonate solution with the zinc source at a molar ratio of 1:0.5-2, and pour the mixed product into the reaction vessel; (2) Ion exchange reaction: Stir the mixture in the reaction vessel to form a zinc-lignin complex precipitate in the reaction vessel; (3) Hydrothermal carbonization: The reactants obtained in step (2) are transferred into a high-pressure reactor and reacted at 180-220℃ for 6-12 hours; (4) Reaction condition control: The heating rate in the high-pressure reactor is controlled at 5-10℃ / min, and the reaction pressure is maintained at 2-4MPa; (5) Post-processing: After the reaction product in the autoclave is cooled, it is filtered, acid washed to remove residual zinc, and finally vacuum dried to obtain black porous powder, namely porous lignin.

2. The method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization according to claim 1, characterized in that, The zinc source is selected from one of zinc oxide, zinc acetate, or zinc nitrate.

3. The method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization according to claim 1, characterized in that, The zinc source has a particle size of 50-200 nm.

4. The method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization according to claim 1, characterized in that, The acid washing in the post-treatment step uses a hydrogen chloride solution with a concentration of 0.1–0.2 mol / L, and the washing is performed 1–3 times.

5. The method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization according to claim 1, characterized in that, The lignin sulfonate is sodium lignin sulfonate, and the solid content of the lignin sulfonate solution is 10–30 wt%.

6. The method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization according to claim 1, characterized in that, The temperature in the reactor is 60-80℃, and the stirring reaction lasts for 2-4 hours.

7. The method for preparing ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization according to claim 4, characterized in that, The mass of the hydrogen chloride solution is 2-4 times the theoretical solids.

8. An application of the ultra-high specific surface area porous lignin based on zinc source template-hydrothermal carbonization as described in claim 1, characterized in that, The porous lignin is used to prepare supercapacitor electrodes, dye adsorbents, or catalyst supports.

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