A desulfurization catalyst bamboo activated carbon and a preparation method thereof

Abstract

The application belongs to the field of purification materials, and particularly relates to a desulfurization catalyst bamboo active carbon. The method comprises the following steps: 1) crushing bamboo, and performing pretreatment to obtain a bamboo base; 2) performing biological pretreatment on the bamboo base, and performing stabilization treatment to obtain a precursor; and 3) performing segmented activation on the precursor to prepare the desulfurization catalyst bamboo active carbon. The application realizes directional construction of multi-stage pores through a biological-chemical composite process, forms a "micropore-mesopore-macropore" high-efficiency interconnected hierarchical pore system, greatly improves diffusion and mass transfer effects of a desulfurization catalysis process, has excellent desulfurization catalysis effects and stable physical and chemical properties, and still has good desulfurization effects under a wet and hot condition.

Description

Technical Field

[0001] This invention belongs to the field of purification materials, specifically relating to a desulfurization catalyst made of bamboo-based activated carbon. Background Technology

[0002] Desulfurization catalysts are key materials used to remove sulfur dioxide produced during combustion and are widely used in industries such as petrochemicals and coal chemicals. Common desulfurization catalysts include vanadium oxide catalysts and nickel oxide catalysts, and their catalytic mechanisms mainly include adsorption-dissociation mechanisms and insertion-removal mechanisms. Desulfurization catalysts convert sulfur-containing compounds in waste gas into harmless substances through chemical adsorption, thereby effectively reducing environmental pollution.

[0003] While desulfurization catalysts can significantly improve desulfurization efficiency in industrial flue gas and fuel desulfurization processes, they still suffer from the following major technical drawbacks due to limitations in material properties, process conditions, and application environment: 1. Catalytic activity is significantly affected by operating conditions, exhibiting poor adaptability. The activity of desulfurization catalysts is highly dependent on operating conditions and is easily constrained by factors such as temperature, sulfur concentration, and flue gas composition. 2. Insufficient stability and lifespan, leading to easy deactivation. 3. Catalysts may alter the properties of desulfurization products, resulting in limited utilization of by-product resources, requiring stockpiling, occupying land, and posing a risk of leakage. Summary of the Invention

[0004] This invention addresses the technical challenges of traditional catalysts, such as poor adaptability, insufficient stability, and limited utilization of by-products, by providing a desulfurization catalyst made of bamboo-based activated carbon.

[0005] The main objective of this invention is to: 1. provide a bio-based desulfurization catalyst and improve the temperature adaptability of the catalyst.

[0006] II. Reduce catalyst abnormalities caused by sulfur concentration fluctuations.

[0007] III. Constructing a hierarchical porous structure to achieve soluble desorption of byproducts.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] A method for preparing bamboo-based activated carbon as a desulfurization catalyst, the method comprising: 1) crushing bamboo and pretreating it to obtain bamboo substrate.

[0010] 2) The bamboo substrate is subjected to biological pretreatment and stabilization treatment to obtain the precursor.

[0011] 3) The precursor is activated in stages to prepare bamboo-based activated carbon as a desulfurization catalyst.

[0012] Preferably, the bamboo material in step 1) is pulverized to 20-30 mesh.

[0013] Preferably, the pretreatment in step 1) is: blasting treatment for 150-170 s under environmental conditions of 210-220 ℃ and saturated vapor pressure of 1.9-2.1 MPa, and the fiber length-to-diameter ratio after steam blasting is 20-30:1.

[0014] Preferably, the biological pretreatment in step 2) involves inoculating the bamboo substrate with a bacterial solution concentration of 1×10⁻⁶. 7 ~5×10 7 CFU / g of *Phanerochaete chrysosporium* was inoculated at a rate of 25–35 mL / 100 g bamboo substrate and cultured for 96–144 h at a temperature of 25–30 °C and a humidity of 70–80% RH.

[0015] Preferably, the stabilization treatment in step 2) is as follows: the filtered and sterilized biologically pretreated bamboo substrate is completely immersed in the impregnation solution and impregnated for 3 to 4 hours under environmental conditions of 63 to 67 ℃ and vacuum degree of -0.1 to -0.05 MPa.

[0016] Preferably, the impregnation solution comprises 4-6 wt% nano-silica sol, 3-5 wt% sodium citrate, 0.8-1.2 wt% potassium dihydrogen phosphate, 0.3-0.5 wt% ethylenediaminetetramethylenephosphonic acid, and the balance being deionized water.

[0017] Preferably, the nano-silica sol has a nano-silica particle size of 8–12 nm, a silica content of 15–25 wt%, and a viscosity of 4–6 mPa·s at 25 °C.

[0018] Preferably, the segmented activation in step 3) is as follows: the first stage is carbonized for 30 to 60 min under nitrogen atmosphere and a heating rate of 10 ℃ / min to 480 to 520 ℃.

[0019] The second stage involves activation for 45–75 min under conditions of carbon dioxide gas flow rate of 1.2–1.8 L / min and temperature of 850–900 ℃.

[0020] A desulfurization catalyst made of bamboo-based activated carbon.

[0021] The core of this invention lies in the three-pronged approach of bio-enzyme directional etching, inorganic-organic synergistic stabilization, and precise control of carbon dioxide activation kinetics, which enables precise structural design and significant performance improvement of bamboo-based activated carbon desulfurization catalysts.

[0022] This invention employs *Phanerochaete chrysosporium* as a biological pretreatment agent, utilizing its secreted lignin peroxidase and manganese peroxidase to selectively modify the structure of bamboo fibers. These specific enzyme systems preferentially attack β-O-4 ether bonds and Cα-Cβ bonds in bamboo fibers, achieving directional breakage of the lignin skeleton. Under conditions of pH 4.5 and 45 °C, the selective cleavage rate of lignin peroxidase on β-O-4 bonds is several times higher than that of other bond types, ensuring a highly directional etching process. Unlike traditional chemical etching, this bio-enzymatic etching proceeds along the original axial structure of plant cells, forming axially penetrating tunnels with a diameter of 8–15 μm, preserving the original ordered microstructure of the bamboo. Simultaneously, oxalic acid produced during mycelial metabolism acts on the fiber surface, selectively dissolving hemicellulose and exposing cellulose nanofibers. These high-density hydroxyl functional groups create ideal anchoring sites for subsequent silicon species loading, improving upon traditional activation methods.

[0023] To address the structural collapse problem of traditional activated carbon under high-temperature conditions, this invention develops an inorganic-organic synergistic stabilization strategy. First, nano-silica sol is in-situ loaded with citric acid through complexation, forming an "organic acid-silicon species" complex. Citric acid forms complexes with silicon species through its carboxyl groups, reducing the hydrolytic sensitivity of silicon-oxygen bonds and significantly improving colloidal stability. This allows the silica sol to penetrate deep into the bamboo matrix through axial channels formed by bio-etching. During heat treatment, silicon species and hydroxyl groups on the bamboo charcoal surface form ≡Si-OC≡ covalent bonds through dehydration condensation, while adjacent silicon species form Si-O-Si bonds, constructing a highly cross-linked silicon-oxygen framework covering the carbon skeleton. Potassium dihydrogen phosphate, as a secondary protective agent, transforms into potassium pyrophosphate at high temperatures, exhibiting a molten state. At the microscale, these molten salts fill the microporous structure, inhibiting sintering densification at high temperatures. The modified bamboo charcoal exhibits lower graphitization and smaller aromatic lamellar stacking height, indicating a more disordered microstructure, which is beneficial for subsequent activation processes.

[0024] This invention uses carbon dioxide as an activator and achieves precise control of the pore structure through precise control of reaction kinetics. A two-stage temperature program is employed: first, preliminary carbonization is performed at a relatively low temperature, retaining some oxygen-containing functional groups as preferred sites for subsequent activation; then, carbon dioxide activation is performed in a high-temperature range, achieving selective gasification within the confined environment of the silicon-oxygen network. Carbon dioxide preferentially reacts with the active sites in the disordered carbon regions, while the microporous structure protected by the silicon-oxygen network remains largely intact. This "confined gasification effect" gradually thins the tunnel walls formed by the original biological enzyme etching, forming mesoporous channels while retaining a large number of micropores. The final product forms a unique three-level pore structure of "micropore-mesopore-macropore," with micropores mainly concentrated in the surface region and mesopores concentrated in a deeper layer. This distribution is extremely beneficial for the desulfurization reaction.

[0025] The axial tunnels formed by the bio-enzyme etching of this invention provide an effective channel for the deep penetration of silica sol; the organic acid complexation ensures the uniform distribution of silicon species at the microscale; the silicon-oxygen network and phosphate melt work together to protect the microporous structure; the carbon dioxide vaporization process achieves precise expansion of mesopores, ultimately forming a hierarchical pore system with efficient interconnection of "micropores-mesopores-macropores".

[0026] This hierarchical pore structure has a decisive influence on the desulfurization catalytic performance. Micropores provide high specific surface area and abundant active sites; mesopores promote the diffusion and mass transfer of reactant molecules; and macropores ensure the rapid transport of reactants and products.

[0027] The beneficial effects of this invention are as follows: This invention achieves the directional construction of multi-level channels through a bio-chemical composite process, forming a hierarchical channel system of "micropores-mesopores-macropores" with high efficiency, which greatly improves the diffusion and mass transfer effect of the desulfurization catalytic process, has excellent desulfurization catalytic effect and stable physicochemical properties, and still has good desulfurization effect under humid and hot conditions. Detailed Implementation

[0028] The present invention will be further described clearly and in detail below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0029] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available or obtainable by those skilled in the art; unless otherwise specified, all methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0030] Unless otherwise specified, the nano-silica sol used in the embodiments of the present invention is a commercially available nano-silica sol with the grade 20 nano-silica, wherein the average particle size of the nano-silica is 10-12 nm, the silica content is 20±0.5 wt%, and the viscosity at 25 ℃ is 4.6-4.7 mPa·s.

[0031] Unless otherwise specified, the bamboo used in the embodiments of this invention is all thorny bamboo.

[0032] Example 1: A desulfurization catalyst made of bamboo activated carbon, the method comprising: 1) crushing bamboo into 20 mesh, and blasting it for 170 s under an environment of 210 ℃ and 1.9 MPa saturated vapor pressure, the fiber length-to-diameter ratio after steam blasting is 20:1, and bamboo matrix is ​​prepared.

[0033] 2) The concentration of the inoculum for inoculating bamboo substrate is 1×10⁻⁶. 7 CFU / g of *Phanerochaete chrysosporium* bacterial suspension was inoculated at a rate of 30 mL / 100 g bamboo substrate and cultured for 144 h at 25 ℃ and 70% RH. Biological pretreatment was then performed, with the filtered and sterilized bamboo substrate completely immersed in the impregnation solution for 4 h at 63 ℃ and -0.1 MPa vacuum. Stabilization was then carried out to obtain the precursor. The impregnation solution consisted of 4 wt% nano-silica sol, 3 wt% sodium citrate, 0.8 wt% potassium dihydrogen phosphate, 0.3 wt% ethylenediaminetetramethylenephosphonic acid, and the remainder being deionized water.

[0034] 3) The precursor was activated in stages. The first stage was carbonized for 60 min under nitrogen atmosphere and heating rate of 10 ℃ / min to 480 ℃. The second stage was activated for 75 min under carbon dioxide gas flow rate of 1.2 L / min and temperature of 850 ℃ to prepare bamboo activated carbon desulfurization catalyst.

[0035] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are as follows.

[0036] Desulfurization performance testing: The bamboo-based activated carbon desulfurization catalyst prepared in this example was evaluated for its desulfurization kinetic performance using a fixed-bed reactor with an inner diameter of 20 mm and a constant temperature zone of not less than 100 mm, in accordance with GB / T 30202-2013 "Test Method for Desulfurization Performance of Desulfurizing Agents". The experiment used nitrogen-balanced simulated flue gas with a sulfur dioxide concentration of 200–2000 ppm for 3000 h⁻¹. -1 The desulfurization process was conducted under conditions of high space velocity and a bed height-to-diameter ratio of 3:1. During the desulfurization process, the sulfur dioxide concentration was monitored in real time using an ultraviolet fluorescence analyzer. The breakthrough time when the outlet sulfur dioxide concentration reached 5% of the inlet concentration was recorded, and the catalyst saturated sulfur capacity and desulfurization rate were also measured.

[0037] Table 1: Characterization results of saturated sulfur capacity and desulfurization rate of catalyst sample in Example 1:

[0038] In addition, the catalyst material prepared in this example was tested for its adaptability to extreme operating conditions, and the specific characterization results are as follows.

[0039] Temperature adaptability: Before testing, the samples were dried for 2 hours under a nitrogen atmosphere at 120 ℃, with the compaction density controlled at 0.65 g / cm³. Low-temperature testing involved introducing simulated flue gas containing 500 ppm sulfur dioxide and 5% oxygen at 80 ℃, with a space velocity of 3000 h⁻¹. -1The desulfurization rate was recorded for 120 minutes, and the average desulfurization rate was recorded for the following 60 minutes. In the high-temperature test, a heating rate of 15℃ / min was used to simulate the start-up and shutdown process of the catalytic cracking unit. After reaching 450℃, 1500 ppm sulfur dioxide flue gas was introduced, and the same space velocity was maintained while recording the desulfurization rate for 60 minutes after temperature stabilization. The desulfurization rate fluctuation was calculated through 10 rapid temperature cycles.

[0040] Sulfur concentration suitability: Initially, a baseline of 200 ppm sulfur dioxide was introduced at 350 ℃. After the desulfurization rate stabilized at over 99%, the sulfur dioxide concentration was precisely controlled using a mass flow meter to instantaneously jump to 2000 ppm, while continuously monitoring the outlet sulfur dioxide concentration change at a sampling frequency of 1 Hz. Recovery capability was assessed by recording the recovery time required for the outlet concentration to drop back to 5% of the inlet concentration.

[0041] Humidity adaptability: Humidity was controlled using a saturated steam generator with an accuracy of ±2%RH, and the flue gas dew point temperature was set to 85℃ to simulate 90% relative humidity conditions at 90℃. In the hydrothermal synergy experiment, humid flue gas containing 1000 ppm sulfur dioxide (90℃, 90%RH) was introduced, and the space velocity was maintained for 3000 h⁻¹. -1 The test was conducted for 6 hours, with the desulfurization rate recorded every 30 minutes. After the test, the BET surface area decay rate of the samples was measured, and the failure criterion was set as a desulfurization rate of less than 90% for three consecutive tests.

[0042] Table 2: Temperature adaptation time and sulfur shock recovery time of catalyst samples in Example 1, and characterization results of high-humidity desulfurization:

[0043] The key parameters of the hole structure are shown in Table 3 below.

[0044] Table 3: Characterization results of pore structure parameters:

[0045] Regeneration performance testing: The catalyst regeneration performance was evaluated using a 0.5 mol / L NH4Cl solution simulating industrial conditions. The regeneration procedure included ultrasonic treatment of the saturated adsorption catalyst at 40 kHz for 30 min, followed by drying at 105 ℃ for 2 h. The cyclic stability of the material was evaluated through at least 10 adsorption-regeneration cycle tests to assess the catalyst's regeneration performance and lifespan.

[0046] Table 4: Regeneration performance characterization results:

[0047]

[0048] Analysis of the characterization results in Tables 1-4 shows that the prepared bamboo-based activated carbon desulfurization catalyst exhibits excellent desulfurization performance. Under simulated flue gas conditions, it demonstrates a long breakthrough time, high saturated sulfur capacity, and a desulfurization rate approaching 100%, exhibiting good desulfurization kinetics. Furthermore, the catalyst demonstrates excellent temperature adaptability, sulfur concentration suitability, and humidity adaptability, maintaining stable desulfurization efficiency even under extreme operating conditions. Analysis of key pore structure parameters reveals that the catalyst possesses a large BET specific surface area, moderate micropore volume, and a high proportion of mesopores; this unique pore structure is beneficial for the desulfurization reaction. Regeneration performance testing results indicate that after multiple adsorption-regeneration cycles, the catalyst maintains a high capacity retention rate and a low pore volume decay rate, exhibiting good cycle stability and service life.

[0049] Example 2: A desulfurization catalyst made of bamboo activated carbon, the method comprising: 1) crushing bamboo into 5 mesh, and blasting it for 160 s under an environment of 215 ℃ and 2.0 MPa saturated vapor pressure, the fiber length-to-diameter ratio after steam blasting is 25:1, and bamboo matrix is ​​prepared.

[0050] 2) The concentration of the inoculum for inoculating bamboo substrate is 3×10⁻⁶. 7 The *Phanerochaete chrysosporium* bacterial suspension (CFU / g) was inoculated at a rate of 30 mL / 100 g bamboo substrate and cultured for 120 h at 27 ℃ and 75% RH. Biological pretreatment was then performed, with the filtered and sterilized bamboo substrate completely immersed in the impregnation solution for 3.5 h at 65 ℃ and -0.07 MPa vacuum. Stabilization was then carried out to obtain the precursor. The impregnation solution consisted of 5 wt% nano-silica sol, 4 wt% sodium citrate, 1 wt% potassium dihydrogen phosphate, 0.4 wt% ethylenediaminetetramethylenephosphonic acid, and the remainder being deionized water.

[0051] 3) The precursor was activated in stages. The first stage was carbonized for 45 min under nitrogen atmosphere and heating rate of 10 ℃ / min to 500 ℃. The second stage was activated for 60 min under carbon dioxide gas flow rate of 1.5 L / min and temperature of 870 ℃ to prepare bamboo activated carbon desulfurization catalyst.

[0052] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are as follows.

[0053] Desulfurization performance testing: The bamboo-based activated carbon desulfurization catalyst prepared in this example was evaluated for its desulfurization kinetic performance using a fixed-bed reactor with an inner diameter of 20 mm and a constant temperature zone of not less than 100 mm, in accordance with GB / T 30202-2013 "Test Method for Desulfurization Performance of Desulfurizing Agents". The experiment used nitrogen-balanced simulated flue gas with a sulfur dioxide concentration of 200–2000 ppm for 3000 h⁻¹. -1 The desulfurization process was conducted under conditions of high space velocity and a bed height-to-diameter ratio of 3:1. During the desulfurization process, the sulfur dioxide concentration was monitored in real time using an ultraviolet fluorescence analyzer. The breakthrough time when the outlet sulfur dioxide concentration reached 5% of the inlet concentration was recorded, and the catalyst saturated sulfur capacity and desulfurization rate were also measured.

[0054] Table 5: Characterization results of saturated sulfur capacity and desulfurization rate of catalyst sample in Example 2:

[0055] In addition, the catalyst material prepared in this example was tested for its adaptability to extreme operating conditions, and the specific characterization results are as follows.

[0056] Temperature adaptability: Before testing, the samples were dried for 2 hours under a nitrogen atmosphere at 120 ℃, with the compaction density controlled at 0.65 g / cm³. Low-temperature testing involved introducing simulated flue gas containing 500 ppm sulfur dioxide and 5% oxygen at 80 ℃, with a space velocity of 3000 h⁻¹. -1 The desulfurization rate was recorded for 120 minutes, and the average desulfurization rate was recorded for the following 60 minutes. In the high-temperature test, a heating rate of 15℃ / min was used to simulate the start-up and shutdown process of the catalytic cracking unit. After reaching 450℃, 1500 ppm sulfur dioxide flue gas was introduced, and the same space velocity was maintained while recording the desulfurization rate for 60 minutes after temperature stabilization. The desulfurization rate fluctuation was calculated through 10 rapid temperature cycles.

[0057] Sulfur concentration suitability: Initially, a baseline of 200 ppm sulfur dioxide was introduced at 350 ℃. After the desulfurization rate stabilized at over 99%, the sulfur dioxide concentration was precisely controlled using a mass flow meter to instantaneously jump to 2000 ppm, while continuously monitoring the outlet sulfur dioxide concentration change at a sampling frequency of 1 Hz. Recovery capability was assessed by recording the recovery time required for the outlet concentration to drop back to 5% of the inlet concentration.

[0058] Humidity adaptability: Humidity was controlled using a saturated steam generator with an accuracy of ±2%RH, and the flue gas dew point temperature was set to 85℃ to simulate 90% relative humidity conditions at 90℃. In the hydrothermal synergy experiment, humid flue gas containing 1000 ppm sulfur dioxide (90℃, 90%RH) was introduced, and the space velocity was maintained for 3000 h⁻¹. -1The test was conducted for 6 hours, with the desulfurization rate recorded every 30 minutes. After the test, the BET surface area decay rate of the samples was measured, and the failure criterion was set as a desulfurization rate of less than 90% for three consecutive tests.

[0059] Table 6: Temperature adaptation time of catalyst samples in Example 2, recovery time from sulfur shock, and characterization results of high-humidity desulfurization:

[0060] The key parameters of the hole structure are shown in Table 7 below.

[0061] Table 7: Characterization results of pore structure parameters:

[0062]

[0063] Regeneration performance testing: The catalyst regeneration performance was evaluated using a 0.5 mol / L NH4Cl solution simulating industrial conditions. The regeneration procedure included ultrasonic treatment of the saturated adsorption catalyst at 40 kHz for 30 min, followed by drying at 105 ℃ for 2 h. The cyclic stability of the material was evaluated through at least 10 adsorption-regeneration cycle tests to assess the catalyst's regeneration performance and lifespan.

[0064] Table 8: Regeneration performance characterization results:

[0065]

[0066] Analysis of the characterization results in Tables 5-8 shows that the prepared bamboo-based activated carbon desulfurization catalyst also exhibits excellent desulfurization performance. In simulated flue gas testing, its breakthrough time reached 242 min, its saturated sulfur capacity was as high as 205.7 mg / g, and its desulfurization rate remained stable at 98.5%, further verifying the excellent desulfurization kinetics of this catalyst. Compared with Example 1, although the preparation conditions were adjusted, the desulfurization efficiency was not affected, but rather slightly improved. This may be related to the optimization of the bamboo powder mesh size, the explosion treatment conditions, and the composition of the impregnation solution.

[0067] The catalyst also performed excellently in extreme operating condition adaptability tests. Temperature adaptability tests showed that the desulfurization rate remained stable with minimal fluctuations under both low and high temperature conditions, indicating that the catalyst has a wide operating temperature window. Sulfur concentration adaptability tests demonstrated that the catalyst can respond rapidly to instantaneous changes in sulfur dioxide concentration with a short recovery time, exhibiting good resistance to sulfur shocks. Humidity adaptability tests further confirmed the catalyst's stability under high humidity conditions, with the desulfurization rate remaining at a high level.

[0068] Analysis of key pore structure parameters showed that the catalyst's BET specific surface area, micropore volume, and mesopore ratio were all within the ideal range. This optimized pore structure not only facilitates the desulfurization reaction but also improves the catalyst's adsorption efficiency and regeneration performance. Regeneration performance testing results indicated that after multiple adsorption-regeneration cycles, the catalyst's capacity retention rate and pore volume decay rate remained within acceptable ranges, demonstrating that the catalyst possesses good cycle stability and a long service life.

[0069] Example 3: A desulfurization catalyst made of bamboo activated carbon, the method comprising: 1) crushing bamboo into 30 mesh, and blasting it for 150 s under an environment of 220 ℃ and 2.1 MPa saturated steam pressure, the fiber length-to-diameter ratio after steam blasting is 30:1, and bamboo matrix is ​​prepared.

[0070] 2) The concentration of the inoculum for inoculating bamboo substrate was 5×10⁻⁶. 7 The *Phanerochaete chrysosporium* bacterial suspension (CFU / g) was inoculated at a rate of 30 mL / 100 g bamboo substrate and cultured for 96 h at 30 ℃ and 80% RH. Biological pretreatment was then performed, with the filtered and sterilized bamboo substrate completely immersed in the impregnation solution for 3 h at 67 ℃ and -0.05 MPa vacuum. Stabilization was then carried out to obtain the precursor. The impregnation solution consisted of 6 wt% nano-silica sol, 5 wt% sodium citrate, 1.2 wt% potassium dihydrogen phosphate, 0.5 wt% ethylenediaminetetramethylenephosphonic acid, and the remainder being deionized water.

[0071] 3) The precursor was activated in stages. The first stage was carbonized for 30 min under nitrogen atmosphere and heating rate of 10 ℃ / min to 520 ℃. The second stage was activated for 45 min under carbon dioxide gas flow rate of 1.8 L / min and temperature of 900 ℃ to prepare bamboo activated carbon desulfurization catalyst.

[0072] The materials prepared in the examples were subjected to performance testing, and the specific characterization results are as follows.

[0073] Desulfurization performance testing: The bamboo-based activated carbon desulfurization catalyst prepared in this example was evaluated for its desulfurization kinetic performance using a fixed-bed reactor with an inner diameter of 20 mm and a constant temperature zone of not less than 100 mm, in accordance with GB / T 30202-2013 "Test Method for Desulfurization Performance of Desulfurizing Agents". The experiment used nitrogen-balanced simulated flue gas with a sulfur dioxide concentration of 200–2000 ppm for 3000 h⁻¹. -1 The desulfurization process was conducted under conditions of high space velocity and a bed height-to-diameter ratio of 3:1. During the desulfurization process, the sulfur dioxide concentration was monitored in real time using an ultraviolet fluorescence analyzer. The breakthrough time when the outlet sulfur dioxide concentration reached 5% of the inlet concentration was recorded, and the catalyst saturated sulfur capacity and desulfurization rate were also measured.

[0074] Table 9: Characterization results of saturated sulfur capacity and desulfurization rate of catalyst sample in Example 3:

[0075] In addition, the catalyst material prepared in this example was tested for its adaptability to extreme operating conditions, and the specific characterization results are as follows.

[0076] Temperature adaptability: Before testing, the samples were dried for 2 hours under a nitrogen atmosphere at 120 ℃, with the compaction density controlled at 0.65 g / cm³. Low-temperature testing involved introducing simulated flue gas containing 500 ppm sulfur dioxide and 5% oxygen at 80 ℃, with a space velocity of 3000 h⁻¹. -1 The desulfurization rate was recorded for 120 minutes, and the average desulfurization rate was recorded for the following 60 minutes. In the high-temperature test, a heating rate of 15℃ / min was used to simulate the start-up and shutdown process of the catalytic cracking unit. After reaching 450℃, 1500 ppm sulfur dioxide flue gas was introduced, and the same space velocity was maintained while recording the desulfurization rate for 60 minutes after temperature stabilization. The desulfurization rate fluctuation was calculated through 10 rapid temperature cycles.

[0077] Sulfur concentration suitability: Initially, a baseline of 200 ppm sulfur dioxide was introduced at 350 ℃. After the desulfurization rate stabilized at over 99%, the sulfur dioxide concentration was precisely controlled using a mass flow meter to instantaneously jump to 2000 ppm, while continuously monitoring the outlet sulfur dioxide concentration change at a sampling frequency of 1 Hz. Recovery capability was assessed by recording the recovery time required for the outlet concentration to drop back to 5% of the inlet concentration.

[0078] Humidity adaptability: Humidity was controlled using a saturated steam generator with an accuracy of ±2%RH, and the flue gas dew point temperature was set to 85℃ to simulate 90% relative humidity conditions at 90℃. In the hydrothermal synergy experiment, humid flue gas containing 1000 ppm sulfur dioxide (90℃, 90%RH) was introduced, and the space velocity was maintained for 3000 h⁻¹. -1 The test was conducted for 6 hours, with the desulfurization rate recorded every 30 minutes. After the test, the BET surface area decay rate of the samples was measured, and the failure criterion was set as a desulfurization rate of less than 90% for three consecutive tests.

[0079] Table 10: Temperature adaptation time of catalyst samples in Example 3, recovery time from sulfur shock, and characterization results of high-humidity desulfurization:

[0080] The key parameters of the hole structure are shown in Table 11 below.

[0081] Table 11: Characterization results of pore structure parameters:

[0082]

[0083] Regeneration performance testing: The catalyst regeneration performance was evaluated using a 0.5 mol / L NH4Cl solution simulating industrial conditions. The regeneration procedure included ultrasonic treatment of the saturated adsorption catalyst at 40 kHz for 30 min, followed by drying at 105 ℃ for 2 h. The cyclic stability of the material was evaluated through at least 10 adsorption-regeneration cycle tests to assess the catalyst's regeneration performance and lifespan.

[0084] Table 12: Regeneration performance characterization results:

[0085]

[0086] Analysis of the characterization results in Tables 9-12 shows that the prepared bamboo-based activated carbon desulfurization catalyst once again exhibited excellent performance in the desulfurization performance test. Its breakthrough time reached 241 min, its saturated sulfur capacity was as high as 205.3 mg / g, and its desulfurization rate remained stable at 98.4%. These data fully demonstrate the high efficiency and stability of the catalyst in the desulfurization reaction. Compared with Example 2, although the preparation process parameters were slightly adjusted, the desulfurization efficiency did not decrease significantly; on the contrary, it remained highly consistent, further verifying the reliability and flexibility of the preparation method.

[0087] In terms of extreme operating condition adaptability testing, the catalyst also demonstrated satisfactory adaptability. Temperature adaptability testing results showed that the desulfurization rate remained stable under both low and high temperature conditions, with minimal fluctuations. This fully demonstrates that the catalyst has a wide temperature operating window and can adapt to desulfurization requirements under different temperature conditions. Sulfur concentration adaptability testing indicated that the catalyst can rapidly respond to instantaneous changes in sulfur dioxide concentration with a short recovery time, which is of great significance in practical applications, as the sulfur dioxide concentration in flue gas often fluctuates due to changes in operating conditions. Humidity adaptability testing further confirmed the catalyst's stability under high humidity conditions, with the desulfurization rate remaining at a high level.

[0088] Analysis of key pore structure parameters shows that the catalyst's BET specific surface area, micropore volume, and mesopore ratio are all within the ideal range. This optimized pore structure not only facilitates the desulfurization reaction but also improves the catalyst's adsorption efficiency and regeneration performance. The larger BET specific surface area provides more adsorption sites, the moderate micropore volume promotes the diffusion and adsorption of sulfur dioxide molecules, and the higher mesopore ratio contributes to the desorption of reaction products and catalyst regeneration.

[0089] The regeneration performance test results show that after multiple adsorption-regeneration cycles, the catalyst's capacity retention rate and pore volume decay rate remain within acceptable ranges. This indicates that the catalyst has good cycle stability and a long service life, meeting the requirements for long-term operation.

[0090] Comparative Example 1: Based on Example 2, this example only modifies the biological pretreatment process; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0091] Table 13: Experimental grouping and process adjustments for Comparative Example 1:

[0092] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0093] Table 14: Characterization results of Comparative Example 1 (I):

[0094] Analysis of the characterization results in Table 14 shows that group D1-1 exhibits significantly deteriorated desulfurization performance: shortened penetration time, desulfurization rate of only 82.2%, decreased BET specific surface area, decreased mesoporous proportion, and lack of a continuous hierarchical pore structure, exhibiting only an irregular micropore distribution. More importantly, the penetration depth of silicon in the bamboo charcoal matrix of D1-1 is reduced, and the distribution of silicon species in D1-1 is highly uneven, with most concentrated in the outer layer, forming a "core-shell" structure rather than an ideal homogeneous distribution. This phenomenon directly verifies the core hypothesis that "biological channels are a prerequisite for deep loading of nano-silicon." Without the axial tunnels formed by bio-etching, silica sol cannot efficiently penetrate into the interior of the material, leading to uneven distribution of active components, ultimately resulting in a significant decrease in catalytic performance.

[0095] Groups D1-2 and D1-3 exhibited different degrees of performance defects, revealing the critical regulatory effect of inoculation density parameters. In D1-2, the tunnel pore breakage rate was as high as 32%, the silica loading depth was low, and the pore connectivity was significantly reduced, resulting in a desulfurization rate of only 73.6%. Low-density inoculation led to sparse mycelial distribution and discontinuous biological channels, exhibiting an alternating state of "breakage-connection-breakage," which restricted the subsequent deep penetration of silica sol.

[0096] In contrast, while D1-3 exhibited a longer penetration time, its desulfurization rate and BET specific surface area were both lower than those of Example 2, demonstrating a typical "ultra-high density negative effect." Firstly, the ultra-high density hyphae formed a tightly intertwined network, and electron microscopy revealed that some pores were completely filled by the overgrown hyphae. Secondly, the excessively high concentration of organic acids produced by the metabolism of the high-density hyphae led to excessive etching, causing the microstructure to shift from ordered degradation to disordered corrosion, thus disrupting the original anisotropic channel structure of the bamboo. These two effects combined resulted in D1-3 exhibiting a structural characteristic of "abundant micropores but reduced mesopores," which is detrimental to the mass transfer and diffusion of large sulfide molecules.

[0097] Group D1-4 exhibited a unique structure-performance correlation: its breakthrough time was higher than D1-1 but significantly lower than that of Example 2, and its desulfurization rate decreased. This phenomenon reflects the differences in the degradation mechanisms of different fungal enzyme systems. *Phanerochaete chrysospora* primarily secretes lignin peroxidase and manganese peroxidase, achieving selective degradation of lignin; while *Trametes versicolor* uses laccase as its dominant enzyme system. Laccase can only directly oxidize phenolic lignin units with low redox potentials, requiring indirect action through mediators for non-phenolic structures. In D1-4, the laccase activity was 4.5 times that of lignin peroxidase and manganese peroxidase, causing the degradation mode to shift from "selective bond breaking" to "surface oxidation." This degradation mode generates a large number of micropores rather than an ideal mesoporous network. Although micropores provide a high specific surface area, the diffusion of sulfur dioxide molecules in these narrow pores is severely restricted, with a diffusion coefficient only about 15% of that in mesopores, ultimately resulting in lower desulfurization efficiency.

[0098] In addition, the desulfurization performance of the materials prepared in Example 2 and this example will be tested under high temperature and high humidity environments, and the specific characterization results are as follows.

[0099] High-temperature desulfurization performance testing: The stability of the material was evaluated using a fixed-bed reactor with an inner diameter of 20 mm and a constant temperature zone of 100 mm. Simulated flue gas containing 1500 ppm SO2 and 5% O2 in N2 was used to simulate the flue gas. The temperature was increased from room temperature to 450 °C at a rate of 15 °C / min, and then maintained at 450 °C for 3000 h. -1 The air velocity was recorded and the desulfurization rate was recorded within 60 minutes after the temperature stabilized. Each group was tested 5 times, and the fluctuation value of the desulfurization rate was calculated.

[0100] High-humidity desulfurization performance testing: Humidity was controlled using a saturated steam generator with an accuracy of ±2%RH, and the flue gas dew point temperature was set to 85℃, simulating an environment of 90% relative humidity under 90℃ operating conditions. A solution containing 1000 ppm SO₂ was used. 2 The N2 equilibrium flue gas with 10% H2O was reacted at a reaction temperature of 90 °C for 3000 h. -1Under air velocity conditions, the desulfurization rate was recorded every 30 minutes for 6 hours, and the desulfurization rate at the end of the first 6 hours was calculated. The test was terminated when the desulfurization rate was below 90% for three consecutive times, and the BET specific surface area decay rate at this time was calculated.

[0101] Table 15: Characterization results of Comparative Example 1 (II):

[0102] Analysis of the characterization results in Table 15 shows that the comparative examples suffer from poor high-temperature resistance due to insufficient exposure of active sites caused by uneven silicon distribution. At the same time, the varying degrees of pore blockage in each group of the comparative examples lead to water molecule retention, which in turn affects the desulfurization effect in high humidity environments.

[0103] Compared to Example 2, all comparative groups D1-1 to D1-4 showed varying degrees of performance degradation in high-temperature desulfurization performance testing. Specifically, group D1-1, due to insufficient silicon penetration depth and highly uneven distribution of active components, achieved a high-temperature desulfurization rate of only 65.3%, with a desulfurization fluctuation value as high as 16.2%, indicating poor thermal stability and consistency in desulfurization performance. While groups D1-2 and D1-3 showed reduced desulfurization fluctuation values, their high-temperature desulfurization rates remained lower than in Example 2. This is related to defects in their pore structure; further observation revealed tunnel pore breakage, reduced pore connectivity, and structural disorder caused by excessive etching. Group D1-4, due to its structure characterized by abundant micropores and reduced mesopores resulting from differences in degradation modes, limited the mass transfer and diffusion of sulfur dioxide molecules, leading to a lower high-temperature desulfurization rate than in Example 2.

[0104] In the high-humidity desulfurization performance test, all comparative groups showed a trend of performance degradation. Group D1-1, due to the irregularity of its pore structure and the uneven distribution of silicon, easily retained water molecules, affecting the desulfurization effect. Its high-humidity desulfurization rate was only 80.1%, and its BET decay rate was as high as 32.7%, indicating that its structure was easily damaged under high humidity. Although the BET decay rates of groups D1-2 and D1-3 decreased, their high-humidity desulfurization rates remained low, which is related to their high degree of pore blockage. Group D1-4, due to its microporous structure restricting the diffusion of sulfur dioxide molecules, and the surface oxide layer produced by the laccase degradation mode easily absorbing water, further affected its desulfurization performance, resulting in unsatisfactory high-humidity desulfurization rate and BET decay rate.

[0105] Comparative Example 2: Based on Example 2, this example only modifies the stabilization process; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0106] Table 16: Experimental Grouping and Process Adjustments for Comparative Example 2:

[0107] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0108] Table 17: Characterization results of Comparative Example 2 (I):

[0109] Analysis of the characterization results revealed significant structural and performance degradation in group D2-1: after 10 regenerations, the capacity retention decreased to 73.5%, and the pore volume decay rate increased sharply to 32.4%. Simultaneously, the catalyst exhibited significant performance fluctuations within the temperature range of 250–450 °C. D2-1 experienced severe micropore collapse after multiple regenerations, with the micropore proportion decreasing from the initial 41.5% to 22.8%. This phenomenon stems from the multiple protective mechanisms of phosphate during heat treatment. Potassium dihydrogen phosphate transforms into a molten state within the temperature range of 590–610 °C, forming a liquid protective layer covering the carbon skeleton. This molten salt acts as a physical barrier at the carbon-gas interface, preventing excessive activation of the micropore walls by carbon dioxide. Furthermore, KOP bonds form a stable interfacial structure with the carbon surface, and this surface modification further enhances the oxidation resistance of the carbon skeleton.

[0110] Group D2-3 showed acceptable initial desulfurization performance, but after 10 regenerations, the capacity retention rate dropped to 82.0%, and the pore volume decay rate increased to 10.4%. This performance difference reflects the fundamental difference between nano-silica sol and diatomaceous earth in microstructure regulation. Nano-silica sol has a significant "penetration advantage," allowing nano-silica particles to penetrate deep into the bamboo charcoal through axial tunnels formed by biological pretreatment, forming a uniformly distributed "carbon-silicon" composite framework. Nano-silica particles form a "bridging structure" at the micropore-mesopore interface, providing additional framework support and preventing pore wall collapse at high temperatures. This difference in microstructure directly explains the higher pore volume decay rate of D2-3 after multiple regenerations compared to Example 2. The silica-oxygen network formed by the silica sol not only provides thermal stability but also provides highly dispersed loading sites for the active phase.

[0111] A comparison between groups D2-4 and D2-2 reveals the crucial role of organic acid complexation in silicon network formation. While group D2-4 exhibited a higher regeneration capacity retention rate, its pore volume decay rate was still significantly higher than in Example 2. This is mainly due to the decreased cross-linking degree of the silicon-oxygen network. Citric acid, with three carboxyl groups and one hydroxyl group, can form multi-site coordination complex structures; while acetic acid has only a single carboxyl group, limiting its complexing ability. Group D2-2 showed a moderate degree of performance degradation. The absence of ethylenediaminetetramethylenephosphonic acid (EDTA), an auxiliary stabilizer, led to a slight decrease in silicon network stability. Furthermore, the absence of EDTA also affected the dispersion state of metal ions, reducing the utilization efficiency of the catalytically active phase.

[0112] The stabilization treatment of the bamboo-based activated carbon desulfurization catalyst of this invention is a complex system with multiple components working synergistically: phosphate provides microporous thermal protection, nano-silica sol constructs a uniformly distributed supporting framework, and organic acid complexation ensures the uniform formation and high cross-linking degree of the silicon network. This triple synergistic mechanism of "thermal protection-structural support-molecular regulation" is the key technological foundation for achieving high-performance desulfurization catalysts that are stable at high temperatures and capable of multiple regenerations.

[0113] In addition, the desulfurization performance of the materials prepared in Example 2 and this example will be tested under high temperature and high humidity environments, and the specific characterization results are as follows.

[0114] High-temperature desulfurization performance testing: The stability of the material was evaluated using a fixed-bed reactor with an inner diameter of 20 mm and a constant temperature zone of 100 mm. Simulated flue gas containing 1500 ppm SO2 and 5% O2 in N2 was used to simulate the flue gas. The temperature was increased from room temperature to 450 °C at a rate of 15 °C / min, and then maintained at 450 °C for 3000 h. -1 The air velocity was recorded and the desulfurization rate was recorded within 60 minutes after the temperature stabilized. Each group was tested 5 times, and the fluctuation value of the desulfurization rate was calculated.

[0115] High-humidity desulfurization performance testing: Humidity was controlled using a saturated steam generator with an accuracy of ±2%RH, and the flue gas dew point temperature was set to 85℃, simulating an environment of 90% relative humidity under 90℃ operating conditions. A solution containing 1000 ppm SO₂ was used. 2 The N2 equilibrium flue gas with 10% H2O was reacted at a reaction temperature of 90 °C for 3000 h. -1 Under air velocity conditions, the desulfurization rate was recorded every 30 minutes for 6 hours, and the desulfurization rate at the end of the first 6 hours was calculated. The test was terminated when the desulfurization rate was below 90% for three consecutive times, and the BET specific surface area decay rate at this time was calculated.

[0116] Table 18: Characterization results of Comparative Example 2 (II):

[0117] Analysis of the above characterization results shows that the high-temperature resistance of the material in this case is significantly reduced due to the thermal collapse of micropores caused by the lack of molten salt and the obstruction of heat conduction by large particles of diatomaceous earth. At the same time, the enrichment of hydrophilic metal ions leads to an accelerated desulfurization rate decline.

[0118] In the high-temperature desulfurization performance test, group D2-1, due to the lack of phosphate, experienced a microporous structure that was prone to collapse at high temperatures. Furthermore, the lack of a physical barrier effect from molten salt led to excessive activation of the micropore walls by carbon dioxide, resulting in a high-temperature desulfurization rate of only 65.3% and a desulfurization fluctuation value as high as 16.7%, demonstrating poor thermal stability and consistency in desulfurization performance. Although group D2-3 used diatomaceous earth instead of nano-silica sol, the large particles of diatomaceous earth hindered heat conduction, leading to a lower high-temperature desulfurization rate than in Example 2, and an increased desulfurization fluctuation value. In contrast, while groups D2-2 and D2-4 showed a lower high-temperature desulfurization rate, their desulfurization fluctuation values ​​were relatively smaller, exhibiting relatively stable desulfurization performance.

[0119] In the high-humidity desulfurization performance test, group D2-1 also showed significant performance degradation, with a high-humidity desulfurization rate of only 82.0% and a BET decay rate as high as 32.4%. This is mainly due to the collapse of its microporous structure and pore blockage, which makes it easy for water molecules to be retained, affecting the desulfurization effect. Group D2-3, due to the low degree of cross-linking of the silicon network formed by diatomaceous earth, had a high pore volume decay rate, and its high-humidity desulfurization rate was also lower than that of Example 2. Groups D2-2 and D2-4, on the other hand, had relatively better high-humidity desulfurization rates and BET decay rates because they retained some key components of the stabilization process.

[0120] Comparative Example 3: Based on Example 2, this example only modifies the segmented activation process; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0121] Table 19: Experimental grouping and process adjustments for Comparative Example 3:

[0122] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0123] Table 20: Characterization results of Comparative Example 3 (I):

[0124] Analysis of the above characterization results shows that group D3-1 exhibits significant structural and performance defects. Due to direct high-temperature activation and the lack of pre-adjustment of the bamboo structure by the low-temperature carbonization stage, group D3-1 suffers from a significant reduction in micropore volume and a slight decrease in the proportion of mesopores. This structural change directly affects desulfurization performance, significantly shortening the penetration time and reducing the saturated sulfur capacity. Although the capacity retention rate after 10 regeneration cycles remains at a high level, the overall desulfurization efficiency is lower than that of Example 2. This significant deterioration stems from the premature decomposition of oxygen-containing functional groups, leading to the failure of the "micropore protection mechanism." The CO and C=O bond content in D3-1 is lower than that in Example 2. These oxygen-containing functional groups act as "micropore incubation points" in normal two-stage activation. The presence of these oxygen-containing functional groups provides a high-density reaction initiation site for subsequent carbon dioxide activation, allowing the gasification process to occur more selectively in specific regions, forming an ordered micropore-mesopore hierarchical structure. Although D3-1 maintains a high regeneration capacity retention rate, this is related to its low initial desulfurization capacity, reflecting the characteristics of "fewer active sites but a more stable framework structure". Direct high-temperature activation promotes partial graphitization, reducing active sites but increasing structural stability.

[0125] Groups D3-2 and D3-3 represent two extreme activation medium strategies, leading to different pore structure development paths. Due to the lack of activating gas, D3-2 exhibits a micropore volume of only 0.2 cm³ / g, displaying a typical "pure pyrolysis structure": the pores mainly originate from the release of volatiles from the bamboo material, rather than selective vaporization. The pore size distribution in D3-2 is extremely uneven, with micropores concentrated primarily in the surface region. This directly affects the adsorption kinetics of sulfur dioxide molecules, limiting mass transfer due to the lack of vaporization.

[0126] In contrast, the proportion of mesopores in group D3-3 increased dramatically, while the micropore volume increased slightly, exhibiting a "over-expansion" characteristic. This stems from the chemical nature of water vapor activation, which results in a faster and less selective reaction rate, leading to pore wall fractures and channel merging in some areas. More critically, water vapor activation causes partial disruption of the silicon-oxygen network, with water vapor undergoing hydrolysis with silicon-oxygen species during activation. This structural change leads to a decrease in saturated sulfur capacity, lower than in Example 2, causing uncontrolled gasification kinetics and resulting in structural deterioration.

[0127] Group D3-4 exhibited the most significant degradation in regeneration performance: after 10 regeneration cycles, the capacity retention rate was only 30.6%. This phenomenon stems from "thermal stress cracking" caused by rapid heating. Thermal stress in the microstructure cannot be released in time, leading to a cumulative effect, and the accumulation of internal stress causes lattice distortion. The D3-4 samples contain a high density of microcracks, which become the starting point for structural collapse during regeneration. Rapid heating creates a temperature gradient within the sample, generating a significant stress field between regions with high differences in thermal expansion coefficients, exceeding the material's mechanical strength threshold and leading to microcrack formation. Rapid heating in D3-4 results in more frequent microscopic damage events. This microscopic damage may not immediately manifest as performance degradation in a single activation, but it gradually expands during multiple regeneration cycles, eventually leading to structural collapse. This explains the extremely low regeneration capacity retention rate of D3-4.

[0128] In addition, the desulfurization performance of the materials prepared in Example 2 and this example will be tested under high temperature and high humidity environments, and the specific characterization results are as follows.

[0129] High-temperature desulfurization performance testing: The stability of the material was evaluated using a fixed-bed reactor with an inner diameter of 20 mm and a constant temperature zone of 100 mm. Simulated flue gas containing 1500 ppm SO2 and 5% O2 in N2 was used to simulate the flue gas. The temperature was increased from room temperature to 450 °C at a rate of 15 °C / min, and then maintained at 450 °C for 3000 h. -1 The air velocity was recorded and the desulfurization rate was recorded within 60 minutes after the temperature stabilized. Each group was tested 5 times, and the fluctuation value of the desulfurization rate was calculated.

[0130] High-humidity desulfurization performance testing: Humidity was controlled using a saturated steam generator with an accuracy of ±2%RH, and the flue gas dew point temperature was set to 85℃, simulating an environment of 90% relative humidity under 90℃ operating conditions. A solution containing 1000 ppm SO₂ was used. 2 The N2 equilibrium flue gas with 10% H2O was reacted at a reaction temperature of 90 °C for 3000 h. -1 Under air velocity conditions, the desulfurization rate was recorded every 30 minutes for 6 hours, and the desulfurization rate at the end of the first 6 hours was calculated. The test was terminated when the desulfurization rate was below 90% for three consecutive times, and the BET specific surface area decay rate at this time was calculated.

[0131] Table 21: Characterization results of Comparative Example 3 (II):

[0132] Analysis of the characterization results shows that the lack of oxygen-containing functional groups in the material prepared in this example weakens its adsorption activity, and the accompanying thermal stress cracking further reduces the material's high-temperature resistance. Furthermore, in this example, the material exhibits poor moisture resistance because the silicon-oxygen network collapses in high-humidity environments, leading to surface structure damage.

[0133] In the high-temperature desulfurization performance test, group D3-1, due to direct high-temperature activation and lack of pre-adjustment in the low-temperature carbonization stage, suffered from insufficient microporous structure development, resulting in a high-temperature desulfurization rate of only 76.4% and a desulfurization fluctuation value of 10.8%, exhibiting characteristics of structural instability and large fluctuations in desulfurization performance. Although group D3-2 had a smaller desulfurization fluctuation value, its high-temperature desulfurization rate was lower than that of Example 2, which is related to its pores primarily originating from volatile matter release rather than selective gasification. Group D3-3, due to excessive activation by water vapor, experienced pore structure deterioration, resulting in a high-temperature desulfurization rate of only 72.5% and a relatively high desulfurization fluctuation value. In contrast, although group D3-4's high-temperature desulfurization rate was close to that of Example 2, its desulfurization fluctuation value was as high as 19.3%, reflecting the impact of thermal stress caused by rapid heating on the stability of desulfurization performance.

[0134] In the high-humidity desulfurization performance test, group D3-1 also showed a significant performance decline, with a high-humidity desulfurization rate of 83.2% and a BET decay rate of 27.9%. This is mainly due to the insufficient microporous structure and uneven distribution of pores, which makes water molecules easy to be retained, affecting the desulfurization effect. The high-humidity desulfurization rate of group D3-2 was slightly higher than that of group D3-1, but the BET decay rate also reached 15.8%, indicating that its pore structure was still damaged to some extent under high-humidity conditions. Due to the partial damage to the silicon-oxygen network, the high-humidity desulfurization rate of group D3-3 dropped sharply to 68.2%, and the BET decay rate was as high as 41.7%. Group D3-4, on the other hand, had unsatisfactory high-humidity desulfurization rate and BET decay rate due to the presence of thermal stress cracks.

[0135] Comparative Example 4: Based on Example 2, this example only modifies the components of the impregnation solution in the segmented activation process; the remaining steps are the same as in Example 2. The specific settings are as follows:

[0136] Table 22: Experimental grouping and process adjustments for Comparative Example 4:

[0137] The performance testing method for the comparative product is completely consistent with that of Example 1. Partial performance characterization was performed, and the characterization results are shown in the table below.

[0138] Table 23: Characterization results of Comparative Example 4 (I):

[0139] Analysis of the above characterization results shows that the ternary synergistic control of the concentration, viscosity and particle size of nano-silica sol is the key to maintaining the hierarchical pore structure of bamboo activated carbon in this scheme. Deviation of any parameter will trigger a cascade reaction from permeation failure to structural collapse.

[0140] The characterization results of the D4 series comparative examples demonstrate the precise control of the concentration, viscosity, and particle size parameters of nano-silica sol on the pore structure of biomass-based catalysts. The use of high-concentration silica sol in the D4-1 group resulted in an exponential increase in the viscosity of the impregnation solution; when the volume fraction of silicon particles exceeded a critical value, the viscosity of the suspension increased sharply. High viscosity hinders the capillary penetration of silica sol within the bio-etching channels; the penetration depth is limited by viscosity, and an increase in viscosity directly reduces the penetration rate. Simultaneously, the accumulation of excess silicon species on the material surface forms a dense "silica shell." This non-uniform distribution disrupts the original hierarchical pore connectivity, forming a thick, high-density silicon-oxygen network. This shell structure not only hinders the mass transfer of reactant molecules but also generates internal stress during heat treatment due to differences in thermal expansion coefficients, leading to microcrack formation and pore collapse.

[0141] The high-viscosity silica sol in group D4-2 exhibited significant flow resistance during vacuum impregnation. The shear-thinning effect was insufficient to overcome the flow resistance caused by high viscosity. In the micron-scale axial tunnels, viscous forces dominated, and the high viscosity degraded the flow rate, resulting in the silica network only covering the shallow region. Deep micropores lacked the skeletal support of the silica network, making them prone to over-vaporization and structural collapse during subsequent CO2 activation. The surface region, due to the protective effect of silica, maintained a relatively intact microporous structure, resulting in significant radial inhomogeneity and a markedly reduced regeneration capacity.

[0142] The large-diameter silicon particles in group D4-3 cannot pass through the micron-sized channels formed by bio-etching, resulting in physical blockage at the pore openings. This "sieving effect" causes the silicon particles to accumulate mainly on the material surface, while the internal channels exhibit "cavitation" characteristics. The accumulation of large particles also disrupts the geometry of the pore openings, turning the originally regular circular openings into irregular shapes, further increasing flow resistance, forming a large number of dead-end pores, and severely affecting mass transfer efficiency and catalytic performance.

[0143] The comprehensive parameter breakthrough in group D4-4 led to the most severe performance degradation. The sharp drop in BET specific surface area and the decrease in regeneration capacity retention to 61.3% reflect the cumulative effect of multiple failure mechanisms. The synergistic effect of high concentration, high viscosity, and large particle size makes it difficult for silica sol to penetrate deeply and easy to clog the surface, forming an extremely non-uniform distribution of "surface overload - deep deficiency". Under this distribution mode, the material loses its original "micropore-mesopore-macropore" hierarchical structure and transforms into a non-connected isolated pore system. The loss of pore connectivity prevents reactant molecules from effectively reaching the active sites, and the catalytic efficiency drops sharply. At the same time, the non-uniform silicon distribution generates differential thermal stress during thermal cycling, accelerating the structural degradation process.

[0144] In addition, the desulfurization performance of the materials prepared in Example 2 and this example will be tested under high temperature and high humidity environments, and the specific characterization results are as follows.

[0145] High-temperature desulfurization performance testing: The stability of the material was evaluated using a fixed-bed reactor with an inner diameter of 20 mm and a constant temperature zone of 100 mm. Simulated flue gas containing 1500 ppm SO2 and 5% O2 in N2 was used to simulate the flue gas. The temperature was increased from room temperature to 450 °C at a rate of 15 °C / min, and then maintained at 450 °C for 3000 h. -1 The air velocity was recorded and the desulfurization rate was recorded within 60 minutes after the temperature stabilized. Each group was tested 5 times, and the fluctuation value of the desulfurization rate was calculated.

[0146] High-humidity desulfurization performance testing: Humidity was controlled using a saturated steam generator with an accuracy of ±2%RH, and the flue gas dew point temperature was set to 85℃, simulating an environment of 90% relative humidity under 90℃ operating conditions. A solution containing 1000 ppm SO₂ was used. 2 The N2 equilibrium flue gas with 10% H2O was reacted at a reaction temperature of 90 °C for 3000 h. -1 Under air velocity conditions, the desulfurization rate was recorded every 30 minutes for 6 hours, and the desulfurization rate at the end of the first 6 hours was calculated. The test was terminated when the desulfurization rate was below 90% for three consecutive times, and the BET specific surface area decay rate at this time was calculated.

[0147] Table 24: Characterization results of Comparative Example 4 (II):

[0148] Analysis of the above characterization results shows that the large-diameter silicon particles in the material prepared in this example block the pores, resulting in a sharp reduction in the effective specific surface area. The isolated pores also hinder the diffusion of reactants, severely affecting the material's efficiency in high-temperature environments. Furthermore, the shallow silicon network accelerates water molecule erosion, causing the main "silicon shell" to peel off, resulting in the material lacking good moisture resistance.

[0149] In the high-temperature desulfurization performance test, group D4-1 experienced a decrease in high-temperature desulfurization rate to 86.7% due to increased viscosity caused by excessively high silica sol concentration, which affected the penetration depth of silica sol in bamboo activated carbon. Although the desulfurization fluctuation was relatively small, the overall desulfurization performance was still lower than that of Example 2. Group D4-2 had a slightly higher high-temperature desulfurization rate than group D4-1, but due to the high viscosity of silica sol, a silicon-oxygen network was only formed in the shallow region, resulting in instability of the deep microporous structure and a small desulfurization fluctuation. Group D4-3 experienced a significant decrease in high-temperature desulfurization rate to 72.1% due to the clogging effect of large-diameter silica particles, and a significant increase in desulfurization fluctuation, indicating that pore blockage has a significant impact on the stability of desulfurization performance. Group D4-4, due to breakthroughs in comprehensive parameters, had the lowest high-temperature desulfurization rate at only 61.3%, with a desulfurization fluctuation as high as 26.4%, showing severe structural instability and desulfurization performance fluctuation.

[0150] In the high-humidity desulfurization performance test, the high-humidity desulfurization rate of group D4-1 was similar to that of high-temperature desulfurization, but the BET decay rate still reached 16.8%, indicating that its pore structure was still damaged to some extent under high humidity. The high-humidity desulfurization rate of group D4-2 decreased significantly to only 75.8%, and the BET decay rate was as high as 28.1%, which is related to the instability of its shallow silica network under high humidity. The high-humidity desulfurization rate of group D4-3 was slightly higher than that of group D4-2, but the BET decay rate was still high, reflecting the adverse effect of pore blockage on the material's moisture resistance. Group D4-4, due to the extreme uneven distribution of "surface overload - deep deficiency", had unsatisfactory high-humidity desulfurization rate and BET decay rate, at 68.5% and 42.9% respectively, indicating that its pore structure was severely degraded under high humidity.

Claims

1. A method for preparing bamboo-based activated carbon as a desulfurization catalyst, characterized in that, The method includes: 1) Shred the bamboo material and pre-treat it to obtain bamboo substrate; 2) The bamboo substrate is subjected to biological pretreatment and stabilization treatment to obtain the precursor; 3) The precursor is activated in stages to prepare bamboo-based activated carbon as a desulfurization catalyst; Step 2) the biological pretreatment is inoculating Phanerochaete chrysosporium with a concentration of 1 x 10 7 ~ 5 x 10 7 CFU / g in the bamboo base, the inoculation amount is 25-35 mL / 100 g bamboo base, and the culture is carried out at an environmental condition of a temperature of 25-30 °C and a humidity of 70-80 %RH for 96-144 h. Step 2) The stabilization process is as follows: The filtered and sterilized biologically pretreated bamboo substrate was completely immersed in the impregnation solution and impregnated for 3 to 4 hours under environmental conditions of 63 to 67 ℃ and vacuum degree of -0.1 to -0.05 MPa. The impregnation solution consists of 4-6 wt% nano-silica sol, 3-5 wt% sodium citrate, 0.8-1.2 wt% potassium dihydrogen phosphate, 0.3-0.5 wt% ethylenediaminetetramethylenephosphonic acid, and the balance being deionized water.

2. The method for preparing bamboo-based activated carbon as a desulfurization catalyst according to claim 1, characterized in that, Step 1) The bamboo material is pulverized to 20-30 mesh.

3. The method for preparing bamboo-based activated carbon as a desulfurization catalyst according to claim 1 or 2, characterized in that, Step 1) The preprocessing is as follows: The fiber aspect ratio was 20–30:1 after steam explosion under an environment of 210–220 ℃ and saturated vapor pressure of 1.9–2.1 MPa for 150–170 s.

4. The method for preparing bamboo-based activated carbon as a desulfurization catalyst according to claim 1, characterized in that, The nano-silica sol has a particle size of 8–12 nm, a silica content of 15–25 wt%, and a viscosity of 4–6 mPa·s at 25 °C.

5. The method for preparing bamboo-based activated carbon as a desulfurization catalyst according to claim 1, characterized in that, Step 3) The segmented activation is as follows: The first stage involves carbonization for 30–60 minutes under nitrogen atmosphere and a heating rate of 10 °C / min to 480–520 °C. The second stage involves activation for 45–75 min under conditions of carbon dioxide gas flow rate of 1.2–1.8 L / min and temperature of 850–900 ℃.

6. A desulfurization catalyst made of bamboo-based activated carbon prepared by any one of claims 1 to 5.

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