Preparation of carbon black for rubber by biomass multistage pyrolysis coupling catalytic graphitization and method and application thereof

Abstract

This disclosure presents a method and application for preparing carbon black for rubber from biomass through multi-stage pyrolysis coupled catalytic graphitization, belonging to the fields of carbon black material preparation and green tire manufacturing technology. The method includes selecting agricultural and forestry waste biomass rich in cellulose, hemicellulose, or lignin, washing with deionized water, acid washing, isothermal drying, and then mechanically pulverizing to obtain biomass powder; subjecting the biomass powder to a first isothermal treatment in a protective atmosphere furnace, resulting in preliminary carbonization of the biomass to obtain a pre-carbonized product; mixing the pre-carbonized product with a catalyst precursor solution, drying, and then subjecting it to a second isothermal treatment in a protective atmosphere to obtain a catalytic reforming product; subjecting the catalytic reforming product to a third isothermal treatment to obtain a graphitized product; immersing the graphitized product in an inorganic acid solution with stirring, washing to neutrality, and drying to obtain carbon black for rubber. This method achieves precise control of the structure and surface chemistry of biomass carbon black.

Description

Technical Field

[0001] This disclosure belongs to the field of carbon black material preparation and green tire manufacturing technology, specifically relating to a method and application of preparing carbon black for rubber by biomass multi-stage pyrolysis coupled catalytic graphitization. Background Technology

[0002] With the transformation of the global energy structure and increasing pressure on environmental protection, developing efficient and clean energy conversion technologies has become a focus of contemporary scientific research. In the tire industry, the EU's Tire Labelling Regulation mandates the labeling of rolling resistance, wet grip, and noise levels, and green tires now account for over 60% of the market share. Under China's "dual carbon" goals, the tire industry faces enormous pressure to reduce emissions; traditional oil furnace carbon black production emits 2.5-3.5 tons of CO2 per ton. International tire giants (Michelin, Bridgestone, Goodyear) have pledged to use 40%-100% sustainable materials by 2030.

[0003] Biomass carbon black technology offers significant advantages: its lifecycle carbon emissions are reduced by 80%-90% compared to traditional carbon black; the cost of biomass raw materials is only 30%-50% of that of petroleum / natural gas raw materials; and its unique oxygen-containing functional groups enhance interfacial bonding with rubber. However, existing technologies suffer from significant bottlenecks: direct pyrolysis biomass carbon black has low structure (DBP oil absorption value <80 mL / 100g), failing to meet tire reinforcement requirements; high ash content (>5%) affects rubber's aging resistance; and insufficient graphitization results in electrical and thermal conductivity inferior to N300 / N500 series industrial carbon black.

[0004] Therefore, developing a method for precisely constructing high-structure rubber carbon black by utilizing the endogenous characteristics of biomass is of significant academic and engineering importance for promoting the green transformation of the tire industry. Summary of the Invention

[0005] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a method and application for preparing carbon black for rubber by biomass multi-stage pyrolysis coupled catalytic graphitization.

[0006] One aspect of this disclosure provides a method for preparing carbon black for rubber by multi-stage pyrolysis coupled with catalytic graphitization of biomass, the method comprising: Agricultural and forestry waste biomass rich in cellulose, hemicellulose or lignin is selected, and after being washed with deionized water, acid-washed to remove some metal impurities, dried at constant temperature and then mechanically crushed to obtain biomass powder. The biomass powder is placed in a protective atmosphere furnace for a first constant temperature treatment to cause preliminary carbonization of the biomass, retaining the natural pore structure template, and obtaining a pre-carbonized product. The pre-carbonized product was mixed with the catalyst precursor solution, dried, and then placed in a protective atmosphere for a second isothermal treatment. A mesoporous network structure was formed by metal catalytic etching to obtain the catalytic reforming product. The catalytic reforming product was subjected to a third isothermal treatment to construct a conductive graphite microcrystalline structure, thereby obtaining the graphitized product. The graphitized product was immersed in an inorganic acid solution and stirred. After repeated washing until neutral and vacuum drying, carbon black for rubber was obtained.

[0007] Optionally, the constant temperature drying temperature is 100-110℃, and the particle size D50 of the biomass powder is 100μm-500μm.

[0008] Optionally, the temperature of the first isothermal treatment is 300-500℃, the time is 1-3h, and the heating rate is 2-5℃ / min.

[0009] Optionally, the second isothermal treatment is performed at a temperature of 600-900℃ for 1-2 hours, with a heating rate of 5-10℃ / min.

[0010] Optionally, the catalyst precursor is selected from one or more of alkali metal nitrates, alkali metal carbonates, alkaline earth metal nitrates, alkaline earth metal carbonates, transition metal nitrates, and transition metal carbonates, and the total metal loading is controlled at 0.5-2.0 wt%.

[0011] Optionally, the temperature of the third isothermal treatment is 1200-1600℃, the time is 1-4h, and the heating rate is 5-10℃ / min.

[0012] Optionally, the inorganic acid solution is selected from hydrochloric acid, nitric acid, or sulfuric acid; The acid treatment process of immersing the graphitized product in an inorganic acid solution and stirring is repeated 1 to 2 times to ensure that the metal impurity content is below 500 ppm.

[0013] Optionally, after obtaining the carbon black for rubber, the method further includes: The carbon black used for rubber is subjected to surface oxidation treatment or coupling agent treatment to regulate the content of oxygen-containing functional groups on the surface or enhance the interfacial bonding with the rubber.

[0014] In another aspect of this disclosure, a type of carbon black for rubber is provided, which is prepared by the method described above.

[0015] Optionally, the carbon black for rubber has a typical three-dimensional hierarchical porous structure with a BET specific surface area of ​​60-150 m². 2 / g, DBP oil absorption value is 80-120 mL / 100g, graphitization degree I_D / I_G is 0.8-1.2, and metal impurity content is <500 ppm.

[0016] In another aspect of this disclosure, a type of carbon black for rubber is proposed, which is used in green tire tread compound by employing the aforementioned carbon black for rubber.

[0017] This disclosure presents a method and application for preparing carbon black for rubber by multi-stage pyrolysis coupled with catalytic graphitization of biomass. The method includes: selecting agricultural and forestry waste biomass rich in cellulose, hemicellulose, or lignin; washing with deionized water, acid washing to remove some metal impurities, drying at a constant temperature, and then mechanically pulverizing to obtain biomass powder; placing the biomass powder in a protective atmosphere furnace for a first isothermal treatment to induce preliminary carbonization of the biomass, retaining the natural pore structure template to obtain a pre-carbonized product; mixing the pre-carbonized product with a catalyst precursor solution, drying, and then placing it in a protective atmosphere for a second isothermal treatment to form a mesoporous network structure using metal catalytic etching to obtain a catalytic reforming product; subjecting the catalytic reforming product to a third isothermal treatment to construct a conductive graphite microcrystalline structure to obtain a graphitized product; immersing the graphitized product in an inorganic acid solution with stirring, repeatedly washing until neutral, and vacuum drying to obtain carbon black for rubber. This invention employs a three-stage pyrolysis strategy of "low-temperature pre-carbonization - medium-temperature catalytic reforming - high-temperature graphitization," combined with an alkali metal / alkaline earth metal catalytic system, to achieve precise control over the structure and surface chemistry of biomass carbon black. The resulting carbon black exhibits a DBP oil absorption value of 80-120 mL / 100g and a nitrogen adsorption specific surface area of ​​60-150 m². 2 / g, can completely or partially replace N200 / N300 series industrial carbon black for green tire manufacturing. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating a method for preparing carbon black for rubber by biomass multi-stage pyrolysis coupled with catalytic graphitization, which is a specific embodiment of this disclosure. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0020] As shown in Figure 1, one aspect of this disclosure provides a method S100 for preparing carbon black for rubber by multi-stage pyrolysis coupled with catalytic graphitization of biomass, specifically including the following steps S110~S150: S110. Raw material pretreatment: Select agricultural and forestry waste biomass rich in cellulose, hemicellulose or lignin, wash with deionized water, remove some metal impurities by acid washing, dry at constant temperature and then mechanically crush to obtain biomass powder.

[0021] In step S110, the agricultural and forestry waste biomass rich in cellulose, hemicellulose or lignin is selected from at least one or a combination of several of rice husks, coconut shells, pine lignin, crop straw or bamboo.

[0022] In step S110, the temperature for constant temperature drying is 100-110°C, for example, preferably 105°C.

[0023] In step S110, the particle size D50 of the biomass powder is 100μm-500μm.

[0024] This embodiment reduces the ash content of the final product by purifying the raw materials to remove surface salts, dust, and some metallic impurities. Furthermore, by pulverizing the raw materials to a specific particle size, it ensures uniform heat and mass transfer and controllable reaction during the subsequent pyrolysis process.

[0025] S120, Low-temperature pre-carbonization: The biomass powder is placed in a protective atmosphere furnace for the first constant temperature treatment to cause preliminary carbonization of the biomass, retaining the natural pore structure template, and obtaining the pre-carbonized product.

[0026] In step S120, the temperature of the first isothermal treatment is 300-500℃, the time is 1-3h, and the heating rate is 2-5℃ / min.

[0027] In step S120, the protective atmosphere is selected from high-purity nitrogen (N2) or high-purity argon (Ar).

[0028] This embodiment first performs pre-carbonization treatment at low temperature, which causes the unstable components in biomass (such as hemicellulose and some lignin) to undergo preliminary pyrolysis, but retains its natural cellulose skeleton and pore structure as a "hard template" for the subsequent formation of hierarchical pores. At the same time, most of the volatile components and water are removed to form a stable carbon skeleton, preventing drastic shrinkage or pore collapse in the subsequent high-temperature stage.

[0029] S130, Intermediate-temperature catalytic reforming: The pre-carbonized product is mixed with the catalyst precursor solution, dried, and then placed in a protective atmosphere for a second isothermal treatment. A mesoporous network structure is formed by metal catalytic etching to obtain the catalytic reforming product.

[0030] In step S130, the temperature of the second isothermal treatment is 600-900℃, the time is 1-2h, and the heating rate is 5-10℃ / min.

[0031] In step S130, the protective atmosphere is selected from high-purity nitrogen (N2), high-purity argon (Ar), or a nitrogen-hydrogen mixture containing 5-10 vol% hydrogen.

[0032] In step S130, the catalyst precursor is selected from one or more of the following: alkali metal nitrates (e.g., KNO3, NaNO3), alkali metal carbonates (e.g., K2CO3, Na2CO3), alkaline earth metal nitrates (e.g., Ca(NO3)2, Mg(NO3)2), alkaline earth metal carbonates (e.g., CaCO3, MgCO3), transition metal nitrates and transition metal carbonates (e.g., Fe(NO3)3, Ni(NO3)2, Co(NO3)2), and the total metal loading is controlled at 0.5-2.0 wt%.

[0033] It should be noted that the catalyst precursor described in this embodiment is mainly used to construct a mesoporous network in the intermediate temperature range, and the metal species (such as K) formed by the decomposition of the precursor at high temperatures are... + Fe 3+ Ni 2+ Plasma or nanoparticles have the ability to activate carbon atoms and can selectively react with disordered and unstable amorphous carbon in the biomass carbon skeleton. In the high-temperature range, they are mainly used to construct conductive networks. They can achieve effective graphitization at a relatively low temperature of 1200-1600℃. The resulting graphite microcrystals are interconnected to form a continuous conductive and thermally conductive network. The two work together to solve the industry bottleneck of insufficient performance of biomass carbon black.

[0034] This embodiment further improves the structure of carbon black by catalytic reforming at medium temperature, activating the catalyst precursor at high temperature, selectively etching amorphous carbon, and catalytically forming a rich mesoporous (2-50nm) network on the pre-carbonized framework, thereby providing more entanglement and bonding space for rubber molecular chains.

[0035] S140, Intermediate-temperature catalytic reforming: The catalytic reforming product is subjected to a third isothermal treatment to construct a conductive graphite microcrystalline structure, thereby obtaining a graphitized product.

[0036] In step S140, the protective atmosphere is selected from high-purity nitrogen (N2), high-purity argon (Ar), or a nitrogen-hydrogen mixture containing 5-10 vol% hydrogen.

[0037] In step S140, the temperature of the third isothermal treatment is 1200-1600℃, the time is 1-4h, and the heating rate is 5-10℃ / min.

[0038] This embodiment also uses high-temperature graphitization treatment, under the promotion of a catalyst, to transform amorphous carbon into an ordered graphite microcrystalline structure, forming a conductive network, which significantly improves the conductivity, thermal conductivity and stability of carbon black, thereby reducing the rolling resistance and heat generation of rubber composite materials.

[0039] S150. Purification and surface modification: The graphitized product is immersed in an inorganic acid solution and stirred. After repeated washing until neutral and vacuum drying, carbon black for rubber is obtained.

[0040] In step S150, the inorganic acid solution is selected from hydrochloric acid, nitric acid or sulfuric acid, with a preferred concentration of 1-3 mol / L. The treatment temperature is 70-80℃ and the treatment time is 6-8h. The above acid treatment process is repeated 1 to 2 times to ensure that the content of metal impurities is less than 500 ppm.

[0041] This embodiment can completely remove residual metal catalysts introduced in the process and ash from the raw materials through purification, ensuring that the content of metal impurities is <500 ppm, thus avoiding affecting the vulcanization and aging performance of rubber. Oxygen-containing functional groups are introduced through acid washing, or surface chemical properties are regulated through subsequent oxidation / coupling agent treatment, thereby enhancing the interfacial compatibility and bonding force between carbon black and the rubber matrix.

[0042] In some preferred embodiments, after obtaining the carbon black for rubber, the method further includes: The carbon black used for rubber is subjected to surface oxidation treatment or coupling agent treatment to regulate the content of oxygen-containing functional groups on the surface or enhance the interfacial bonding with the rubber.

[0043] It should be noted that this embodiment mainly prepares rubber carbon black with high structure and low rolling resistance based on the following three synergistic levels: First, the hierarchical pore structure control technology. In the low-temperature range (300-500℃), the natural pore template of biomass is preserved; in the medium-temperature range (600-900℃), catalytic etching forms a mesoporous network; and in the high-temperature range (1200-1600℃), graphitization constructs a conductive network. This hierarchical pore structure allows rubber molecular chains to effectively entangle, enhancing the reinforcing effect.

[0044] Second, the in-situ catalytic graphitization mechanism. Endogenous minerals (K, Ca, Mg) from biomass are used as autocatalysts, while exogenous transition metal salts (Fe, Ni, Co) are added to form a synergistic catalysis. The catalyst amount is <2 wt%, avoiding the impact of metal residues on rubber performance. Catalytic graphitization significantly improves the electrical and thermal conductivity of carbon black, reducing tire rolling resistance.

[0045] Third, directional modification of surface functional groups. By controlling the degree of oxidation, carboxyl groups and phenolic hydroxyl groups can be introduced, or pretreatment with coupling agents can enhance entanglement with rubber molecular chains, thereby optimizing dynamic mechanical properties and reducing hysteresis loss.

[0046] This embodiment utilizes agricultural and forestry waste biomass as raw material. By exploring the chemical structural potential of agricultural and forestry waste, and using the natural cellulose, hemicellulose, and lignin on its molecular chain as carbon precursors, a three-stage pyrolysis strategy of "low-temperature pre-carbonization - medium-temperature catalytic reforming - high-temperature graphitization" is adopted. Combined with an alkali metal / alkaline earth metal catalytic system, the structure and surface chemistry of biomass carbon black are precisely controlled to prepare rubber carbon black with high structure and low rolling resistance.

[0047] In another aspect of this disclosure, a type of carbon black for rubber is provided, which is prepared by the method described above.

[0048] In this embodiment, the carbon black for rubber has a typical three-dimensional hierarchical porous structure, including macropores (>50nm), mesopores (2-50nm), and micropores (<2nm). Among them, micropores provide a large internal surface area for storing active sites and are the main sites for strong physical-chemical interactions (such as van der Waals forces) between carbon black and rubber molecules. Mesopores provide space for rubber molecular chain entanglement, and have high reinforcing properties and high DBP oil absorption value. The hierarchical pore structure of macropores promotes stress dispersion and serves as a fast channel for rubber molecular chains and processing aids to enter the carbon black aggregates, which helps to reduce the mixing viscosity, improve processing performance, and disperse stress under stress.

[0049] In this embodiment, the BET specific surface area of ​​the carbon black for rubber is 60-150 m². 2 / g, DBP oil absorption value is 80-120 mL / 100g, graphitization degree I_D / I_G is 0.8-1.2 (determined by Raman spectroscopy), and metal impurity content is <500 ppm.

[0050] In another aspect of this disclosure, a type of carbon black for rubber is proposed, which is used in green tire tread compound by employing the aforementioned carbon black for rubber.

[0051] The carbon black prepared in this embodiment can completely or partially replace N200, N300 or N500 series industrial carbon black in green tire tread compound to reduce tire rolling resistance and improve wear resistance.

[0052] The preparation method of carbon black for rubber will be further explained below with reference to specific embodiments: Example 1: Rice husk-based high-structure carbon black used in green tire treads for passenger cars (1) Raw material pretreatment: Rice husks (containing 15-20% SiO2 and 3-5% endogenous K2O) were collected from rice processing waste and washed three times with deionized water and 0.1M dilute hydrochloric acid to remove surface salts and some metal impurities. After drying at 105℃, the husks were pulverized using a high-speed universal pulverizer to obtain rice husk powder with an average particle size of about 200μm.

[0053] (2) Low-temperature pre-carbonization: Rice husk powder is spread evenly in a quartz boat and placed in a tube furnace. Under the condition of continuous introduction of high-purity nitrogen (200 mL / min), the temperature is increased to 400℃ at a rate of 3℃ / min and maintained for 2h to allow the rice husk to undergo preliminary carbonization while retaining the organosilicon framework structure.

[0054] (3) Intermediate-temperature catalytic reforming: The pre-carbonized product was mixed with a K2CO3 solution (loading 1.0 wt% K), vacuum dried, and then placed in a tube furnace. Under nitrogen protection, the temperature was increased to 750℃ at a rate of 5℃ / min and held for 1 h. The K2CO3 solution was then used to catalyze the reforming. + Catalytic etching forms a rich mesoporous network.

[0055] (4) High-temperature graphitization: The catalytic reforming product was heated to 1400℃ at a rate of 5℃ / min and held at the same temperature for 2h to construct a graphite microcrystalline structure. During this process, the in-situ generated SiC whiskers played a role in enhancing graphitization.

[0056] (5) Washing and purification: After grinding the graphitized product, it was added to a 2 mol / L hydrochloric acid solution and stirred at 80°C for 8 hours. Then, it was filtered and washed with deionized water until the filtrate was neutral. The filtrate was then vacuum dried at 80°C to obtain rice husk-based rubber carbon black (RHC-1400).

[0057] Furthermore, this embodiment characterizes the performance of the prepared rubber carbon black and its application in tires, and the performance data are as follows: 1. Pore size distribution: BET test results show that the specific surface area of ​​this material is 112 m² / g, and the total pore volume is 0.85 cm³. 3 / g, with a mesoporous content of 48%. The DBP oil absorption value is 105 mL / 100g, which belongs to high-structure carbon black.

[0058] 2. Physicochemical properties: Ash content 2.8% (mainly SiO2), volatile matter 1.2%, pH value 7.5, total metal impurities <300 ppm.

[0059] 3. Rubber application performance: In a natural rubber / styrene-butadiene rubber (60 / 40) blend system, the carbon black content is 50 phr. The compound has a 300% tensile stress of 18.5 MPa (superior to N234 carbon black's 16.2 MPa), tensile strength of 26.8 MPa, tear strength of 45 kN / m, and DIN abrasion index of 115.

[0060] 4. Tire dynamic performance: Rolling resistance coefficient of vulcanized rubber is 8.2 (label grade A, traditional N234 carbon black is grade BC), wet grip index is 1.15 (baseline = 1.0), heat generation coefficient (60℃) is 105 (N234 is 125).

[0061] Commercial value: This carbon black is used in the tread of green tires for passenger cars and can obtain an EU tire label rating of A / A / 72dB, with an export premium of 15%-20%.

[0062] Example 2: Coconut shell-based abrasion-resistant carbon black used in truck and bus tire treads (1) Raw material pretreatment: Select imported coconut shells from Southeast Asia (high-density lignin, ash content <3%), wash them with deionized water and dilute hydrochloric acid, dry them at 105℃, and then crush them with a high-speed universal pulverizer to obtain coconut shell powder with an average particle size of about 500μm.

[0063] (2) Spread the coconut shell powder evenly in a quartz boat and place it in a tube furnace. Under high-purity nitrogen (200 mL / min) conditions, raise the temperature to 400℃ at a rate of 3℃ / min and hold for 2 hours to prestabilize and reduce the volatile content.

[0064] (3) Catalytic impregnation: The pre-stabilized coconut shell was mixed with Fe(NO3)3 solution (loading 1.5 wt% Fe), impregnated at room temperature for 12 h, and then vacuum dried.

[0065] (4) Continuous pyrolysis: Pyrolysis is carried out in a continuous rotary kiln. The first stage is 900℃×3h (nitrogen protection, Fe catalyzes the formation of mesopores), and the second stage is 1500℃×1h (high temperature graphitization).

[0066] (5) Purification treatment: The pyrolysis product was treated with 3 mol / L nitric acid at 70℃ for 6 h to remove metal impurities, washed until neutral and then dried.

[0067] Furthermore, this embodiment characterizes the performance of the prepared rubber carbon black and its application in tires, and the performance data are as follows: 1. Particle size distribution: Primary particle size 25-35nm (TEM statistics), aggregate size 100-200nm.

[0068] 2. Surface roughness: RMS 2.1 nm (measured by AFM).

[0069] 3. Rubber bond content: 42% (35% for traditional N330).

[0070] 4. Dynamic compression heat generation: ΔT 18℃ (28℃ for N330).

[0071] 5. Tire Application: Used in the tread compound of all-steel radial truck tires, achieving a 22% improvement in mileage compared to the N330 compound, increasing retreading cycles by 1-2 times, and improving total lifespan by 30%. Meets the TCO (Total Cost of Ownership) optimization needs of long-haul logistics fleets, saving approximately 200 RMB per tire.

[0072] Example 3: Pine-based low-hysteresis carbon black for high-performance racing tires (1) Raw material preparation: Pine lignin (high purity, containing methoxy groups) produced by the papermaking industry was selected, washed three times with deionized water and dilute hydrochloric acid, and then dried at 105℃. It was then pulverized using a high-speed universal pulverizer to obtain pine powder with an average particle size of about 300μm.

[0073] (2) Low-temperature pre-carbonization: Same as in Example 1.

[0074] (3) Medium-temperature catalytic reforming: The pre-carbonized product was mixed with Ca(NO3)2 solution (2.0 wt% Ca loading), dried under vacuum, and placed in a tube furnace. Under nitrogen protection, the temperature was increased to 700℃ at a rate of 5℃ / min and held for 1h.

[0075] (4) High-temperature graphitization: The catalytic reforming product is heated to 1500℃ at a rate of 5℃ / min and kept at a constant temperature for 2h.

[0076] (5) Washing and purification: Same as in Example 1.

[0077] (6) Plasma activation: Pyrolytic carbon black is treated with oxygen plasma (power 100W, time 30min) to introduce nitrogen-containing functional groups (nitrogen content 1.8 wt%).

[0078] Furthermore, this embodiment characterizes the performance of the prepared rubber carbon black and its application in tires, and the performance data are as follows: 1. Surface energy: 45 mJ / m² (matched with solution-polymerized styrene-butadiene rubber).

[0079] 2. Payne effect: Low strain modulus decrease rate <15% (conventional carbon black >25%).

[0080] 3. Glass transition temperature: -45℃ (DMA determination).

[0081] 4.0℃ tanδ: 0.25 (wetland grip index).

[0082] 5. Tire Applications: Used in Formula One slick tire formulations, with a dry grip coefficient of 1.45 (compared to 1.0 for standard N330) and a heat fade temperature threshold of 180℃ (compared to 150℃ for conventional formulations). It replaces imported specialty carbon black (priced at 80-120 RMB / kg), reducing costs by 40%.

[0083] Example 4: Straw-based low-cost carbon black used in inner tube / pad belt rubber compounds (1) Raw material pretreatment: wheat / corn straw (agricultural waste, cost <200 yuan / ton) was selected, washed with deionized water and dilute hydrochloric acid, dried at 105℃, and then crushed with a high-speed universal pulverizer to obtain straw powder with an average particle size of about 200μm.

[0084] (2) Low-temperature pre-carbonization: Same as in Example 1.

[0085] (3) Medium-temperature catalytic reforming: The pre-carbonized product was mixed with MgCO3 (0.5 wt% Mg), dried under vacuum, and placed in a tube furnace. Under nitrogen protection, the temperature was increased to 800℃ at a rate of 5℃ / min and held for 1h.

[0086] (4) High-temperature graphitization: The catalytic reforming product is heated to 1500℃ at a rate of 5℃ / min and kept at a constant temperature for 2h.

[0087] (5) Washing and purification: Same as in Example 1.

[0088] (6) CO2 activation: The pyrolytic carbon was activated at 800℃ for 1h in a CO2 atmosphere to adjust the specific surface area to 70 m² / g.

[0089] (7) Magnetic separation to remove impurities: Ferromagnetic impurities are removed by high-intensity magnetic separation, reducing the ash content to <8%.

[0090] Furthermore, this embodiment characterizes the performance of the prepared rubber carbon black and its application in tires, and the performance data are as follows: 1. Specific surface area: 72 m² 2 / g.

[0091] 2.300% constant elongation stress: 12 MPa (meets inner tube standard ≥10 MPa).

[0092] 3. Air tightness: Air permeability coefficient 2.5×10 -17 m 2 / (s·Pa) (better than standard 3.0×10) -17 ).

[0093] 4. Production cost: 50% lower than that of carbon black produced by oil furnace process.

[0094] 5. Tire Applications: Used in bicycle / motorcycle inner tubes and truck tire strips, reducing formulation costs by 800 RMB per ton of rubber compound. Excellent processing performance, stable Mooney viscosity, and smooth extrusion surface. Targeting price-sensitive markets in Southeast Asia and Africa, with an annual production capacity of 100,000 tons, it offers economic viability.

[0095] Example 5: Bamboo-based conductive-reinforcing bifunctional carbon black for smart tires (1) Raw material preparation: Select bamboo processing residue (high crystalline cellulose), wash it three times with deionized water and dilute hydrochloric acid, dry it at 105℃, and then crush it with a high-speed universal pulverizer to obtain bamboo powder with an average particle size of about D50=150μm.

[0096] (2) Low-temperature pre-carbonization: Same as in Example 1.

[0097] (3) Medium-temperature catalytic reforming: The pre-carbonized product was mixed with Ni(NO3)2 solution (1.0 wt% Ni), dried under vacuum, and placed in a tube furnace. Under nitrogen protection, the temperature was increased to 750℃ at a rate of 5℃ / min and held for 1h.

[0098] (4) High-temperature graphitization: The catalytic reforming product is heated to 1550℃ at a rate of 5℃ / min and kept at a constant temperature for 2h.

[0099] (5) Washing and purification: Same as in Example 1.

[0100] Furthermore, this embodiment characterizes the performance of the prepared rubber carbon black and its application in tires, and the performance data are as follows: 1. Specific surface area: 450 m² 2 / g (60% mesoporous).

[0101] 2. Electrical conductivity: 15 S / m (30% by volume in rubber matrix).

[0102] 3. Dynamic modulus E' (60℃): 8.5 MPa (low hysteresis).

[0103] 4. Surface resistivity: 10 6 Ω (meets the requirements for explosion-proof tires).

[0104] 5. Temperature coefficient of resistance: -0.3% / ℃ (temperature sensing characteristics).

[0105] 6. Tire Applications: Used for integrating sensors (RFID, pressure monitoring) in smart tires to achieve static electricity dissipation to prevent fuel vapor ignition and supports real-time tread temperature monitoring. Supports the development of Tire IoT, adding 50-100 yuan to each tire, aligning with the trend of smart mobility.

[0106] Comparative Example 1: Traditional direct pyrolysis method (without staged pyrolysis) (1) Raw materials: Take the same mass of rice husk powder as in Example 1.

[0107] (2) Process: Carbonization is carried out directly at 10℃ / min to 1400℃ without low-temperature pre-carbonization and medium-temperature catalytic reforming.

[0108] (3) Results: The specific surface area of ​​the obtained carbon black was only 45 m². 2 / g, DBP oil absorption value 65 mL / 100g, low structure; graphitization degree I_D / I_G=1.35, poor electrical conductivity; poor dispersion in rubber, with a 300% constant tensile stress of only 9.5 MPa.

[0109] Conclusion: Compared with the above embodiments, it can be seen that the "multi-stage pyrolysis" adopted in this disclosure is crucial for constructing high-structure carbon black. The lack of staged pyrolysis leads to the collapse of the pore structure and insufficient graphitization.

[0110] Comparative Example 2: Excessive use of catalyst (excessive metal residue) (1) Process: Same as in Example 1, but the K2CO3 loading is increased to 5 wt%.

[0111] (2) Results: Although the degree of graphitization was increased to I_D / I_G=0.75, the metal residue reached 2000 ppm, which led to delayed rubber vulcanization and deterioration of aging performance (tensile strength retention rate of only 60% at 100℃×72h).

[0112] Conclusion: This study demonstrates that the amount of catalyst used must be strictly controlled within the range of this invention (<2 wt%) to balance the graphitization effect and the performance of rubber applications.

[0113] This disclosure presents a method and application for preparing carbon black for rubber by multi-stage pyrolysis coupled with catalytic graphitization of biomass, which has the following advantages compared to the prior art: 1. Advantages of hierarchical pore structure: This disclosure achieves a hierarchical pore structure through a three-stage pyrolysis strategy, in which micropores (<2nm) store active sites, mesopores (2-50nm) provide space for rubber molecular chain entanglement, and macropores (>50nm) promote stress dispersion, thus taking into account both reinforcing performance and processing performance.

[0114] 2. Synergistic effect of catalytic graphitization: This disclosure achieves effective graphitization at a lower temperature (1200-1600℃) through the synergistic catalysis of endogenous alkali metals and exogenous transition metals, reducing energy consumption by 30% compared with traditional graphitization processes (>2000℃).

[0115] 3. Green and low-carbon benefits: The carbon footprint of this disclosure is reduced by more than 80% compared with that of carbon black produced by oil furnace method, which meets the requirements of EU regulations on carbon footprint of batteries and tires and has green premium capabilities.

[0116] 4. Cost competitive advantage: The raw material cost of this method is reduced by 50-70%, and the equipment investment is lower than that of the oil furnace method (no high-temperature combustion furnace is required), making it suitable for distributed layout in biomass resource-rich areas.

[0117] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for preparing carbon black for rubber by biomass multi-stage pyrolysis coupled with catalytic graphitization, characterized in that, The method includes: Agricultural and forestry waste biomass rich in cellulose, hemicellulose or lignin is selected, and after being washed with deionized water, acid washed, dried at constant temperature and then mechanically crushed, biomass powder is obtained. The biomass powder is placed in a protective atmosphere furnace for a first constant temperature treatment to cause preliminary carbonization of the biomass, retaining the natural pore structure template, and obtaining a pre-carbonized product. The pre-carbonized product was mixed with the catalyst precursor solution, dried, and then placed in a protective atmosphere for a second isothermal treatment. A mesoporous network structure was formed by metal catalytic etching to obtain the catalytic reforming product. The catalytic reforming product was subjected to a third isothermal treatment to construct a conductive graphite microcrystalline structure, thereby obtaining the graphitized product. The graphitized product was immersed in an inorganic acid solution and stirred. After repeated washing until neutral and vacuum drying, carbon black for rubber was obtained.

2. The method according to claim 1, characterized in that, The constant temperature drying temperature is 100-110℃, and the particle size D50 of the biomass powder is 100μm-500μm.

3. The method according to claim 1, characterized in that, The first isothermal treatment is performed at a temperature of 300-500℃ for 1-3 hours, with a heating rate of 2-5℃ / min.

4. The method according to claim 1, characterized in that, The second isothermal treatment is performed at a temperature of 600-900℃ for 1-2 hours, with a heating rate of 5-10℃ / min.

5. The method according to claim 1, characterized in that, The catalyst precursor is selected from one or more of alkali metal nitrates, alkali metal carbonates, alkaline earth metal nitrates, alkaline earth metal carbonates, transition metal nitrates, and transition metal carbonates, and the total metal loading is controlled at 0.5-2.0 wt%.

6. The method according to claim 1, characterized in that, The third isothermal treatment is performed at a temperature of 1200-1600℃ for 1-4 hours, with a heating rate of 5-10℃ / min.

7. The method according to claim 1, characterized in that, The inorganic acid solution is selected from hydrochloric acid, nitric acid, or sulfuric acid; The acid treatment process of immersing the graphitized product in an inorganic acid solution and stirring is repeated 1 to 2 times to ensure that the metal impurity content is below 500 ppm.

8. The method according to any one of claims 1-7, characterized in that, After obtaining the carbon black for rubber, the method further includes: The carbon black used for rubber is subjected to surface oxidation treatment or coupling agent treatment to regulate the content of oxygen-containing functional groups on the surface or enhance the interfacial bonding with the rubber.

9. A type of carbon black for rubber, characterized in that, The carbon black for rubber is prepared by the method according to any one of claims 1-8; wherein... The carbon black for rubber has a typical three-dimensional hierarchical porous structure, with a BET specific surface area of ​​60-150 m². 2 / g, DBP oil absorption value is 80-120 mL / 100g, graphitization degree I_D / I_G is 0.8-1.2, and metal impurity content is <500 ppm.

10. A type of carbon black for rubber, characterized in that, The carbon black for rubber described in claim 9 is used in green tire tread compound.

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