An asphalt rejuvenator based on straw supercritical fluid liquefaction products, its preparation method and application

Abstract

This invention discloses an asphalt regenerator based on supercritical fluid liquefaction products of straw, its preparation method, and its application, belonging to the field of asphalt regeneration technology. This invention utilizes supercritical fluid liquefaction of straw-based biomass to obtain liquefied products rich in phenols, ethers, and light aromatic compounds. These products serve as regenerators to replenish the loss of lightweight components in aged asphalt due to oxidation and volatilization, and to rebuild its colloidal structure. This method can significantly improve the penetration, softening point, ductility, and high- and low-temperature rheological properties of regenerated asphalt, enhance its anti-aging stability, and achieve synergistic recovery of asphalt composition, structure, and properties. The process of this invention is mild and highly reproducible. The resulting regenerator is derived from renewable straw resources, has good environmental benefits, and can be widely applied in the fields of road asphalt regeneration and waste material resource utilization.

Description

Technical Field

[0001] This invention belongs to the field of asphalt recycling technology, specifically relating to an asphalt recycler based on straw supercritical fluid liquefaction products, its preparation method, and its application. Background Technology

[0002] Petroleum asphalt is a complex organic cementitious material, primarily derived from the residue after crude oil distillation, and is widely used in road and bridge paving. Under long-term service conditions, asphalt undergoes repeated exposure to ultraviolet radiation, oxidation, thermal aging, and vehicle loads, causing its lighter components to volatilize and gradually transform into polar macromolecular oxidation products. This leads to hardening, embrittlement, increased viscosity, and decreased rheological properties in aged asphalt. Asphalt rejuvenators can partially restore the properties of aged asphalt, improving the hardening and embrittlement problems after aging, thereby increasing the proportion of waste asphalt mixtures and their utilization in strata. However, currently, most asphalt rejuvenators are extracted from petroleum derivatives, such as aromatic oils, plasticizers, tackifying resins, and anti-aging agents, resulting in over-reliance on non-renewable resources. Research indicates that supercritical fluid liquefaction of biomass resources such as straw can yield liquid products containing phenols, lipids, and light aromatics. Due to the similarity in molecular structure to the lighter components of asphalt and the abundance of oxygen-containing functional groups in these liquefied products, they are considered a potential alternative to petroleum-based rejuvenators. However, under normal conditions, the liquefied products have poor compatibility with aged asphalt and diffuse slowly, making it difficult to fully utilize the chemical repair capabilities.

[0003] Supercritical fluids are a special state of matter between liquid and gas, possessing permeability and mass transfer rates approaching those of gases, as well as dissolving and extracting capabilities approaching those of liquids. This allows for a significant improvement in the penetration efficiency of liquefied products within asphalt, enabling the targeted repair of aged asphalt structures. Therefore, developing an asphalt regeneration technology based on supercritical liquefied products is of great importance. Summary of the Invention

[0004] In view of the above-mentioned prior art, the present invention provides an asphalt rejuvenator based on the supercritical fluid liquefaction product of straw, its preparation method and application, which realizes the comprehensive restoration and improvement of the performance of aged asphalt, and promotes the high-value utilization of straw.

[0005] To achieve the above objectives, the technical solution adopted by this invention is: to provide a method for preparing an asphalt rejuvenator based on straw supercritical fluid liquefaction products, comprising the following steps: S1: Dry straw biomass to a moisture content of no more than 5%, then pulverize it to 40-80 mesh, and then perform pretreatment; S2: The pretreated straw biomass is liquefied under a protective gas atmosphere using a supercritical fluid as the liquefaction solvent to obtain the liquefied product. S3: Cool, separate and dry the liquefied products to obtain a light oil phase; S4: Mix the light oil phase with compatibility improver, plasticizer and antioxidant to obtain asphalt regenerator based on straw supercritical fluid liquefaction products.

[0006] Furthermore, straw-based biomass includes one or more of corn stalks, wheat stalks, rice straw, microcrystalline cellulose, and pure lignin.

[0007] Furthermore, the pretreatment includes alkali treatment, steam explosion treatment, or dilute acid treatment. Alkali treatment involves adding the crushed straw biomass to a 1-5 wt% solution of sodium hydroxide, potassium hydroxide, sodium carbonate, or ammonia solution and treating it at 60-90°C for 30-120 min. Steam explosion treatment involves placing the crushed straw biomass under saturated steam at 1.0-2.5 MPa for 3-10 min. Dilute acid treatment involves placing the crushed straw biomass in a 0.5-2 wt% solution of dilute sulfuric acid and treating it at 100-145°C for 20-60 min.

[0008] Furthermore, the supercritical fluid is one or more of supercritical CO2, supercritical methanol, supercritical ethanol, and supercritical water.

[0009] Furthermore, the liquefaction reaction process involves controlling the supercritical fluid flow rate at 40–120 mL / min and stirring the reaction at 260–300 °C and 15–22 MPa for 3–5 hours.

[0010] Furthermore, the mass ratio of light oil phase, compatibility improver, plasticizer and antioxidant is 80~90:3~8:2~6:0.4~0.8.

[0011] Furthermore, the compatibility improver is an alkylphenol resin, SBS, or EVA; the plasticizer is a phthalate plasticizer or a fatty acid ester plasticizer; and the antioxidant is a hindered phenolic antioxidant or a hindered amine antioxidant.

[0012] The present invention also provides an asphalt regenerator based on straw supercritical fluid liquefaction products prepared by the above preparation method.

[0013] Furthermore, the asphalt rejuvenator based on the supercritical fluid liquefaction products of straw has a viscosity of 0.2~1.0 Pa at 60℃. s.

[0014] The present invention also provides the application of asphalt rejuvenator based on straw supercritical fluid liquefaction products in the regeneration of aged asphalt, wherein the amount of asphalt rejuvenator based on straw supercritical fluid liquefaction products added is 10-15% of the mass of aged asphalt.

[0015] The beneficial effects of this invention are as follows: By constructing a composite system of "supercritical fluid + straw liquefaction products", this invention achieves the directional separation of aged asphalt components and the precise replenishment of regenerator, overcoming the inherent contradiction in existing technologies where relying solely on supercritical CO2 or high-temperature light hydrocarbons makes it difficult to simultaneously achieve both solubility and selectivity, and brings the following benefits: 1. Excellent performance recovery capability: This invention uses the light oil phase obtained by supercritical fluid liquefaction of straw as the core component. Its rich phenolic, etheric, and light aromatic structures are highly similar to the light components lost in aged asphalt, effectively replenishing the saturated and aromatic components lost due to aging and participating in the reconstruction of colloidal structures. The resulting recycled asphalt can recover its penetration to more than 80% of the original unaged asphalt, with controllable changes in softening point, significantly improved low-temperature ductility, and good recovery of rheological properties such as complex modulus, phase angle, and low-temperature flexural modulus, achieving simultaneous and balanced restoration of high and low temperature performance.

[0016] 2. Significantly improved anti-aging durability: The antioxidants compounded in the regenerator work synergistically with the active components in straw liquefaction products to effectively inhibit secondary oxidation of recycled asphalt during use. After aging tests in a thin-film oven, the residual penetration ratio of the recycled asphalt (e.g., reaching 72%-78%) is far higher than the standard requirements.

[0017] 3. Mild process and stable product: Utilizing supercritical fluid liquefaction technology, the reaction conditions are milder than traditional pyrolysis, avoiding excessive condensation and coking caused by high temperatures. The resulting liquefied product has a narrower molecular weight distribution and better chemical stability. Subsequent compounding processes are simple and easy to scale up for production. The resulting regenerator has a moderate viscosity (0.2~1.0 Pa·s at 60℃), good compatibility with aged asphalt, and high penetration and diffusion efficiency.

[0018] 4. Green and environmentally friendly and sustainable resources: This invention uses agricultural waste such as corn stalks, wheat stalks, and rice straw or lignocellulose as the main raw materials, replacing traditional non-renewable petroleum-based aromatic oils, which greatly reduces dependence on fossil resources (it is expected to reduce petroleum resource consumption by 30%-60%), realizes the high-value utilization of straw and the resource utilization of solid waste, and is in line with the green and circular development direction of road materials.

[0019] In summary, this invention forms a systematic and innovative technology chain from solvent system selection, phase balance control, structural compatibility regulation to sustainable resource utilization, providing a more efficient, stable, and widely applicable technical approach for asphalt recycling than existing technologies. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in detail below with reference to examples.

[0021] Example 1 A method for preparing an asphalt rejuvenator based on straw supercritical fluid liquefaction products includes the following steps: S1: Dry the corn stalks to a moisture content of ≤5%, then crush them to 40-80 mesh. Add the crushed corn stalks to a 3wt% sodium hydroxide solution (solid-liquid ratio 1g:10mL), treat at 75℃ for 90min, wash with water until pH≈7, and then dry to a moisture content of ≤5%. S2: The pretreated corn stalks are put into the liquefaction kettle, and after vacuuming, nitrogen is introduced for protection. A mixture of supercritical CO2 and supercritical methanol (volume ratio of 1:1) is used as the liquefaction solvent. The solvent flow rate is controlled at 80 mL / min. The temperature is raised to 280℃ and the pressure is 18 MPa. The reaction is stirred for 4 hours to obtain the liquefied product. S3: Cool the liquefied product to room temperature and reduce the pressure in the liquefaction vessel to 1 MPa. Then, further remove the residual solvent by vacuum drying to obtain a light oil phase. S4: Light oil phase, SBS, DOP (phthalate plasticizer) and BHT (hindered phenolic antioxidant) are mixed in a mass ratio of 85:5:4:0.6 and stirred at 140℃ for 90 min to obtain asphalt regenerator based on straw supercritical fluid liquefaction products.

[0022] The asphalt recycling agent prepared in this embodiment has a viscosity of 0.6 Pa at 60°C. s.

[0023] Add 12% of the aged asphalt mass to the asphalt recycling agent prepared in this example, stir at 300 rpm for 30 minutes, shear at 3000 rpm for 30 minutes, and finally homogenize and mix at 500 rpm for 45 minutes to obtain the finished recycled asphalt.

[0024] Example 2 A method for preparing an asphalt rejuvenator based on straw supercritical fluid liquefaction products includes the following steps: S1: After drying wheat straw to a moisture content of ≤5%, mix it with pure lignin at a mass ratio of 2:1, then pulverize it to 40~80 mesh, and then subject the pulverized mixture to steam explosion treatment (steam pressure 1.8MPa, temperature 190℃, pressure holding for 120s, instantaneous pressure release rate of 12MPa / s). S2: The pretreated mixture is put into the liquefaction vessel, vacuumed and protected with nitrogen, using supercritical water as the liquefaction solvent, controlling the solvent flow rate at 40 mL / min, heating to 300℃ and pressure at 22 MPa, stirring and reacting for 3 hours to obtain the liquefied product. S3: Cool the liquefied product to room temperature and reduce the pressure in the liquefaction vessel to 1 MPa. Then, further remove the residual solvent by vacuum drying to obtain a light oil phase. S4: Light oil phase, alkylphenol resin, epoxidized soybean oil ESBO (fatty acid ester plasticizer) and antioxidant 770 (hindered amine antioxidant) are mixed in a mass ratio of 80:3:2:0.4 and stirred at 150℃ for 80 min to obtain asphalt regenerator based on straw supercritical fluid liquefaction products.

[0025] The asphalt recycling agent prepared in this embodiment has a viscosity of 0.2 Pa at 60°C. s.

[0026] Add 10% of the aged asphalt mass to the asphalt recycling agent prepared in this example, stir at 300 rpm for 30 minutes, shear at 3000 rpm for 30 minutes, and finally homogenize and mix at 500 rpm for 45 minutes to obtain the finished recycled asphalt.

[0027] Example 3 A method for preparing an asphalt rejuvenator based on straw supercritical fluid liquefaction products includes the following steps: S1: After drying the rice straw to a moisture content of ≤5%, mix it with microcrystalline cellulose at a mass ratio of 3:1, then pulverize it to 40~80 mesh. Then add the pulverized mixture to a 1wt% dilute sulfuric acid solution (solid-liquid ratio 1g:10mL), treat it at 110℃ for 40min, wash it with water until pH≈7 after treatment, and then dry it to a moisture content of ≤5%. S2: The pretreated mixture is put into a liquefaction vessel, vacuumed and protected with nitrogen, using supercritical ethanol as the liquefaction solvent, controlling the solvent flow rate at 80 mL / min, heating to 260 °C and pressure at 15 MPa, and stirring for 5 h to obtain the liquefied product. S3: Cool the liquefied product to room temperature and reduce the pressure in the liquefaction vessel to 1 MPa. Then, further remove the residual solvent by vacuum drying to obtain a light oil phase. S4: Light oil phase, EVA, DBP (phthalate plasticizer) and BHA (hindered phenolic antioxidant) are mixed in a mass ratio of 90:8:6:0.8 and stirred at 140℃ for 90 min to obtain asphalt regenerator based on straw supercritical fluid liquefaction products.

[0028] The asphalt recycling agent prepared in this embodiment has a viscosity of 1.0 Pa at 60°C. s.

[0029] Add 15% of the aged asphalt mass to the asphalt recycling agent prepared in this example, stir at 300 rpm for 30 minutes, shear at 3000 rpm for 30 minutes, and finally homogenize and mix at 500 rpm for 45 minutes to obtain the finished recycled asphalt.

[0030] Experimental Example Performance testing of recycled asphalt: The finished recycled asphalts obtained in Examples 1-3 were subjected to performance testing. The results are shown in Table 1. The penetration recovery rate of the recycled asphalts in Examples 1-3 all reached over 88%, and the low-temperature ductility at 5℃ recovered significantly from less than 3cm in the aged asphalt to over 25cm. This indicates that the regenerator of the present invention can effectively replenish the light oil content lost in the aged asphalt and significantly improve its workability and low-temperature crack resistance. The softening point of the recycled asphalt was maintained between 42.6-44.1℃, which is not much different from that of the unaged asphalt (46℃), and the change is controllable. This indicates that while restoring flexibility, its high-temperature stability was not excessively weakened. The significant reduction in stiffness modulus and the substantial increase in creep rate jointly demonstrate that its low-temperature rheological properties have been fundamentally improved, and its crack resistance has been enhanced. After short-term aging in a thin-film oven, the residual penetration ratio of the recycled asphalt is as high as 72%-78%, far exceeding the conventional requirement of ≥60% for recycled asphalt in standards such as the "Technical Specification for Recycling Asphalt Pavement of Highway" (JTG / T 5521). This directly proves that the active components from straw liquefaction products and the compounded antioxidants contained in the regenerator of this invention can effectively delay the secondary aging process of asphalt. The dynamic stability test results show that the high-temperature rutting resistance of the recycled asphalt is extremely outstanding (3500-4200 times / mm), which is an order of magnitude improvement compared with aged asphalt (about 850 times / mm).

[0031] Table 1. Statistics on Asphalt Performance

[0032] In summary, the regenerator prepared by supercritical fluid liquefaction of straw products not only comprehensively and evenly restores the key physical and rheological properties of aged asphalt, but also demonstrates advantages over traditional regeneration technologies in terms of anti-aging durability and high-temperature stability. This is due to the active products obtained by the supercritical liquefaction process, which are highly compatible with asphalt components, and their synergistic effect with carefully selected additives, achieving deep regeneration from component replenishment to structural reconstruction.

[0033] While specific embodiments of the present invention have been described in detail, they should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

Claims

1. A method for preparing an asphalt rejuvenator based on straw supercritical fluid liquefaction products, characterized in that, Includes the following steps: S1: Dry straw biomass to a moisture content of no more than 5%, then pulverize it to 40-80 mesh, and then perform pretreatment; S2: The pretreated straw biomass is liquefied under a protective gas atmosphere using a supercritical fluid as the liquefaction solvent to obtain liquefied products. The supercritical fluid is one or more of supercritical CO2, supercritical methanol, supercritical ethanol, and supercritical water. The liquefaction process involves controlling the supercritical fluid flow rate to 40-120 mL / min and stirring the reaction at 260-300℃ and 15-22 MPa for 3-5 hours. S3: Cool, separate and dry the liquefied products to obtain a light oil phase; S4: Mix and stir the light oil phase with the compatibility improver, plasticizer and antioxidant to obtain the asphalt regenerator based on the supercritical fluid liquefaction product of straw. The mass ratio of the light oil phase, compatibility improver, plasticizer and antioxidant is 80~90:3~8:2~6:0.4~0.

8.

2. The preparation method according to claim 1, characterized in that: The straw-based biomass is one or more of corn stalks, wheat stalks, rice straw, microcrystalline cellulose, and pure lignin.

3. The preparation method according to claim 1, characterized in that: The pretreatment includes alkali treatment, steam explosion treatment, or dilute acid treatment. Alkali treatment involves adding the crushed straw biomass to a 1-5 wt% solution of sodium hydroxide, potassium hydroxide, sodium carbonate, or ammonia solution and treating it at 60-90°C for 30-120 min. Steam explosion treatment involves placing the crushed straw biomass under saturated steam at 1.0-2.5 MPa for 3-10 min. Dilute acid treatment involves placing the crushed straw biomass in a 0.5-2 wt% solution of dilute sulfuric acid and treating it at 100-145°C for 20-60 min.

4. The preparation method according to claim 1, characterized in that: The compatibility improver is an alkylphenol resin, SBS, or EVA; the plasticizer is a phthalate plasticizer or a fatty acid ester plasticizer; and the antioxidant is a hindered phenolic antioxidant or a hindered amine antioxidant.

5. The asphalt regenerator based on straw supercritical fluid liquefaction products prepared by the method according to any one of claims 1 to 4.

6. The asphalt rejuvenator based on straw supercritical fluid liquefaction products according to claim 5, characterized in that: The asphalt rejuvenator based on the supercritical fluid liquefaction product of straw has a viscosity of 0.2~1.0 Pa·s at 60℃.

7. The application of the asphalt rejuvenator based on straw supercritical fluid liquefaction products as described in claim 6 in the regeneration of aged asphalt, characterized in that: The amount of asphalt rejuvenator added based on the supercritical fluid liquefaction product of straw is 10-15% of the mass of aged asphalt.

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