Asphalt regenerant based on straw supercritical fluid liquefaction product as well as preparation method and application of asphalt regenerant

Abstract

The invention discloses an asphalt regenerant based on a straw supercritical fluid liquefaction product as well as a preparation method and application of the asphalt regenerant, and belongs to the technical field of asphalt regeneration. According to the method, the straw biomass is liquefied by adopting the supercritical fluid to obtain a liquefied product rich in phenols, ethers and light aromatic structures, and the liquefied product is used as a regenerant to supplement the loss of light components caused by oxidation and volatilization of the aged asphalt and reconstruct the colloid structure of the aged asphalt. According to the method, the needle penetration, softening point, ductility and high and low temperature rheological properties of the regenerated asphalt can be remarkably improved, the anti-aging stability of the regenerated asphalt is improved, and synergistic recovery of the asphalt in the aspects of components, structures and properties is realized. The method is mild in process and good in repeatability, the obtained regenerant is derived from renewable straw resources, good environmental benefits are achieved, and the method can be widely applied to the fields of road asphalt regeneration and waste material recycling.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of asphalt regeneration, and particularly relates to an asphalt regenerant based on a supercritical fluid liquefaction product of straw and a preparation method and application thereof. BACKGROUND

[0002] Petroleum asphalt is an organic cementing material with very complex components, which is mainly derived from the residue after distillation of crude oil and is widely used as a paving material for roads and bridges. Under long-term service conditions, asphalt will undergo repeated effects of ultraviolet radiation, oxidation, thermal aging and vehicle load, causing the volatilization of light components in asphalt and the gradual transformation of the light components into polar macromolecular oxidation products, resulting in the hardening and embrittlement of aged asphalt, the increase in viscosity and the decrease in rheological properties. Asphalt regenerants can partially restore the performance of aged asphalt, improve the hardening and embrittlement of aged asphalt, and thus increase the incorporation ratio and utilization layer of waste asphalt mixture. However, most of the current asphalt regenerants are extracted from petroleum derivatives such as aromatic oil, plasticizer, tackifying resin and anti-aging agent, and excessively rely on non-renewable resources. Studies have shown that biomass resources such as straw can obtain liquid products containing phenols, lipids and light aromatics through supercritical fluid liquefaction. Due to the similar molecular structure of the liquid products to the light components of asphalt and the rich oxygen-containing functional groups, the liquid products are considered as a potential way to replace petroleum-based regenerants. However, the compatibility of the liquid products with aged asphalt is poor under conventional conditions, and the diffusion speed is slow, making it difficult to fully exert the chemical repair capacity.

[0003] Supercritical fluid is a special state of matter between liquid and gas, which has the permeability and mass transfer rate close to gas and the solubility and extraction capacity close to liquid, and can significantly improve the penetration efficiency of the liquefaction product in asphalt, realizing the directional repair of the structure of aged asphalt. Therefore, it is of great significance to construct an asphalt regeneration technology based on supercritical liquefaction products. SUMMARY

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

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is to provide a preparation method of an asphalt regenerant based on a supercritical fluid liquefaction product of straw, comprising the following steps: S1: drying the straw biomass to a water content of not higher than 5%, crushing it to 40-80 mesh, and then pretreating it; S2: liquefying the pretreated straw biomass under a protective gas with a supercritical fluid as a liquefaction solvent to obtain a liquefaction product; S3: cooling, separating and drying the liquefaction product to obtain a light oil phase; S4: mixing and stirring the light oil phase with the compatibility improver, plasticizer and antioxidant to obtain the asphalt rejuvenator based on the straw supercritical fluid liquefaction product.

[0006] Further, the straw biomass is one or more of corn stalk, wheat stalk, rice straw, microcrystalline cellulose and pure lignin.

[0007] Further, the pretreatment includes alkali treatment, steam explosion treatment or dilute acid treatment, wherein the alkali treatment is that the crushed straw biomass is added into 1-5wt% sodium hydroxide, potassium hydroxide, sodium carbonate or ammonia solution, and treated at 60-90℃ for 30-120min; the steam explosion treatment is that the crushed straw biomass is placed in saturated steam at 1.0-2.5MPa for 3-10min; and the dilute acid treatment is that the crushed straw biomass is placed in 0.5-2wt% dilute sulfuric acid, and treated at 100-145℃ for 20-60min.

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

[0009] Further, the liquefaction reaction process is that the flow rate of the supercritical fluid is controlled to be 40-120mL / min, and the stirring reaction is carried out at 260-300℃ and 15-22MPa for 3-5h.

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

[0011] Further, the compatibility improver is alkyl phenol resin, SBS or EVA; the plasticizer is phthalate plasticizer or fatty acid ester plasticizer; and the antioxidant is hindered phenolic antioxidant or hindered amine antioxidant.

[0012] The application further provides the asphalt rejuvenator based on the straw supercritical fluid liquefaction product prepared by the preparation method.

[0013] Further, the viscosity of the asphalt rejuvenator based on the straw supercritical fluid liquefaction product is 0.2-1.0Pa s at 60℃.

[0014] The application further provides the application of the asphalt rejuvenator based on the straw supercritical fluid liquefaction product in aged asphalt rejuvenation, and the addition amount of the asphalt rejuvenator based on the straw supercritical fluid liquefaction product is 10-15% of the mass of the aged asphalt.

[0015] The beneficial effects of the present application are: the present application realizes the directional separation of aged asphalt components and the precise supply of regenerant by constructing a "supercritical fluid + straw liquefaction product" composite system, breaks through the inherent contradiction in the prior art that only relying on single supercritical CO2 or high-temperature light hydrocarbon cannot balance the solubility and selectivity, and brings the following effects: 1. Excellent performance recovery ability: the present application takes the light oil phase obtained by liquefying straw with supercritical fluid as the core component, which is rich in phenolic, ether and light aromatic structures, and is highly similar to the missing light components of aged asphalt, which can effectively supplement the saturated components and aromatic components lost due to aging, and participate in the reconstruction of colloidal structure. The penetration of the prepared regenerated asphalt can be restored to more than 80% of the original unaged asphalt, the softening point change is controllable, the low-temperature ductility is significantly improved, the rheological performance indexes such as complex modulus, phase angle and low-temperature bending modulus are well recovered, and the synchronous and balanced repair of high and low temperature performance is realized.

[0016] 2. Significantly improved aging resistance and durability: the antioxidants compounded in the regenerant can synergistically act with the active components in the straw liquefaction product to effectively inhibit the secondary oxidation of the regenerated asphalt during use. After the thin film oven aging test, the residual penetration ratio of the regenerated asphalt (for example, up to 72%-78%) is much higher than the specification requirement.

[0017] 3. Mild process and stable product: the supercritical fluid liquefaction technology is relatively mild compared with traditional thermal cracking, avoiding excessive condensation and coking caused by high temperature, and the obtained liquefaction product has a narrower molecular weight distribution and better chemical stability. The subsequent compounding process is simple and easy to scale up, and the prepared regenerant has moderate viscosity (0.2-1.0 Pa·s at 60°C), good compatibility with aged asphalt, high penetration and diffusion efficiency.

[0018] 4. Green and environmentally friendly and sustainable resources: the present application uses agricultural wastes such as corn stalks, wheat stalks and straw as the main raw material, replacing the traditional non-renewable petroleum-based aromatic hydrocarbon oil, greatly reducing the dependence on fossil resources (estimated to reduce 30%-60% of petroleum resource consumption), realizing the high-value utilization of straw and the resource utilization of solid waste, and meeting the green and circular development direction of road materials.

[0019] In summary, the present application forms a systematic innovation technology chain from solvent system selection, phase equilibrium control, structure adaptability regulation to sustainable resource utilization, and provides a more efficient, more stable and wider applicable technology approach for asphalt regeneration than the prior art. DETAILED DESCRIPTION

[0020] The specific embodiments of the present application will be described in detail below in conjunction with the examples.

[0021] Example 1 A preparation method of a bitumen regenerant based on straw supercritical fluid liquefaction product, comprising the following steps: S1: dry the corn stalks to a moisture content of ≤5%, then crush them to 40-80 mesh, then add the crushed corn stalks to a 3wt% sodium hydroxide solution (solid-liquid ratio 1g:10mL), treat at 75°C for 90min, then wash with water until pH≈7, and then dry to a moisture content of ≤5%; S2: put the pretreated corn stalks into a liquefaction kettle, vacuumize, then protect with nitrogen, use a mixture of supercritical CO2 and supercritical methanol (volume ratio 1:1) as the liquefaction solvent, control the solvent flow rate to be 80mL / min, heat to 280°C, pressure 18MPa, stir for 4h to obtain a liquefaction product; S3: cool the liquefaction product to room temperature, reduce the pressure in the liquefaction kettle to 1MPa, then further remove residual solvent by vacuum drying to obtain a light oil phase; S4: mix the light oil phase, SBS, DOP (phthalate plasticizer) and BHT (hindered phenolic antioxidant) according to a mass ratio of 85:5:4:0.6, stir at 140°C for 90min to obtain a bitumen regenerant based on straw supercritical fluid liquefaction product.

[0022] The bitumen regenerant prepared in this example has a viscosity of 0.6Pa s.

[0023] Add 12% of the bitumen regenerant prepared in this example to the aged bitumen, first stir at a speed of 300rpm for 30min, then shear at a speed of 3000rpm for 30min, and finally homogenize and mix at a speed of 500rpm for 45min to obtain the finished product, regenerant bitumen.

[0024] Example 2 A preparation method of a bitumen regenerant based on straw supercritical fluid liquefaction product, comprising the following steps: S1: dry the corn stalks to a moisture content of ≤5%, then crush them to 40-80 mesh, then add the crushed corn stalks to a 3wt% sodium hydroxide solution (solid-liquid ratio 1g:10mL), treat at 75°C for 90min, then wash with water until pH≈7, and then dry to a moisture content of ≤5%; S2: put the pretreated corn stalks into a liquefaction kettle, vacuumize, then protect with nitrogen, use a mixture of supercritical CO2 and supercritical methanol (volume ratio 1:1) as the liquefaction solvent, control the solvent flow rate to be 80mL / min, heat to 280°C, pressure 18MPa, stir for 4h to obtain a liquefaction product; S3: cool the liquefaction product to room temperature, reduce the pressure in the liquefaction kettle to 1MPa, then further remove 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 test of the reclaimed asphalt: the finished reclaimed asphalt prepared in Examples 1-3 was subjected to performance test, and the results are shown in Table 1. The penetration recovery rate of the reclaimed asphalt in Examples 1-3 all reached 88% or more, and the low-temperature ductility at 5℃ was greatly recovered from less than 3cm of the aged asphalt to more than 25cm, which indicates that the rejuvenator of the present application can effectively supplement the light oil fraction lost by the aged asphalt, and significantly improve the workability and ease of use and low-temperature crack resistance of the asphalt; the softening point of the reclaimed asphalt is maintained at 42.6-44.1℃, which is not much different from that of the unaged asphalt (46℃), and the change is controllable, which indicates that while the flexibility is recovered, the high-temperature stability is not excessively weakened. The significant reduction in stiffness modulus and the significant improvement in creep rate together confirm that the low-temperature rheological performance is fundamentally improved, and the crack resistance is enhanced; after short-term aging in a thin film oven, the residual penetration ratio of the reclaimed asphalt is as high as 72%-78%, which is much higher than the conventional requirement of ≥60% for reclaimed asphalt in the Technical Code for Recycling of Highway Asphalt Pavement (JTG / T 5521) and other standards, which directly proves that the active components from the straw liquefaction product and the antioxidants contained in the rejuvenator of the present application can effectively delay the secondary aging process of the asphalt; the dynamic stability test results show that the high-temperature anti-rutting ability of the reclaimed asphalt is extremely outstanding (3500-4200 times / mm), which is improved by orders of magnitude compared with that of the aged asphalt (about 850 times / mm).

[0031] Table 1. Asphalt performance statistics

[0032] In summary, the rejuvenator prepared by taking the supercritical fluid liquefaction product of straw as the core not only can comprehensively and evenly recover the key physical and rheological performance indicators of the aged asphalt, but also exhibits advantages over traditional recycling technologies in terms of anti-aging durability and high-temperature stability. This is due to the active product obtained by the supercritical liquefaction process, which is highly compatible with the components of asphalt, and the synergistic effect of the product and the selected additives, which realizes deep regeneration from component supplementation to structure reconstruction.

[0033] Although the specific embodiments of the present application are described in detail in combination with the examples, it should not be understood as limiting the protection scope of the present patent. Various modifications and variations made by those skilled in the art within the scope described in the claims are still within the protection scope of the present patent.

Claims

1. A method for preparing a bitumen rejuvenator based on supercritical fluid liquefaction products of straw, characterized in that, The method comprises the following steps: S1: drying the straw biomass to a moisture content of not higher than 5%, then crushing to 40-80 mesh, and then pretreating; S2: performing a liquefaction reaction on the pretreated straw biomass under a protective gas and using a supercritical fluid as a liquefaction solvent to obtain a liquefaction product; S3: performing cooling, separation and drying treatment on the liquefaction product to obtain a light oil phase; S4: mixing and stirring the light oil phase with a compatibility improver, a plasticizer and an antioxidant to obtain the asphalt rejuvenator based on the straw supercritical fluid liquefaction product.

2. The method of claim 1, wherein: The straw biomass is one or more of corn stalks, wheat stalks, rice straw, microcrystalline cellulose and pure lignin.

3. The method of claim 1, wherein: The pretreatment comprises alkali treatment, steam explosion treatment or dilute acid treatment, wherein the alkali treatment is adding the crushed straw biomass into a 1-5wt% sodium hydroxide, potassium hydroxide, sodium carbonate or ammonia solution, and treating at 60-90°C for 30-120min; the steam explosion treatment is placing the crushed straw biomass under saturated steam at 1.0-2.5MPa for 3-10min; and the dilute acid treatment is placing the crushed straw biomass in 0.5-2wt% dilute sulfuric acid, and treating at 100-145°C for 20-60min.

4. The method of claim 1, wherein: The supercritical fluid is one or more of supercritical CO2, supercritical methanol, supercritical ethanol and supercritical water.

5. The method of claim 1, wherein: The liquefaction reaction process is stirring and reacting at 260-300°C and 15-22MPa for 3-5h with the supercritical fluid flow controlled at 40-120mL / min.

6. The method of claim 1, wherein: The mass ratio of the light oil phase, the compatibility improver, the plasticizer and the antioxidant is 80-90:3-8:2-6:0.4-0.

8.

7. The method of claim 1 or 6, wherein: The compatibility improver is an alkyl phenol resin, SBS or EVA; the plasticizer is a phthalate plasticizer or a fatty acid ester plasticizer; and the antioxidant is a hindered phenol antioxidant or a hindered amine antioxidant.

8. The asphalt rejuvenator based on the straw supercritical fluid liquefaction product prepared by the method of any one of claims 1-7.

9. The straw supercritical fluid liquefaction product based asphalt recycling agent according to claim 8, characterized in that: The viscosity of the straw supercritical fluid liquefaction product-based asphalt regenerant is 0.2-1.0 Pa at 60℃ s.

10. Use of the asphalt regenerant based on the supercritical fluid liquefaction product of straw according to claim 9 for the regeneration of aged asphalt, characterized in that: The addition amount of the asphalt rejuvenator based on the straw supercritical fluid liquefaction product is 10-15% of the mass of the aged asphalt.

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