Method for regenerating aged bitumen based on waste cooking oil

Abstract

This invention discloses a method for regenerating aged asphalt based on waste cooking oil, belonging to the field of road engineering technology. The method includes the following steps: First, the waste cooking oil is esterified by mixing sodium hydroxide solution, methanol, and waste cooking oil; then, the esterified waste cooking oil is epoxidized by mixing hydrogen peroxide, glacial acetic acid, concentrated sulfuric acid, and the esterified waste cooking oil; finally, the esterified and epoxidized waste cooking oils are simply mixed to prepare a regenerating agent, which is used to regenerate aged asphalt to obtain regenerated asphalt. The road-use regenerated asphalt prepared by this invention has excellent high-temperature performance, low-temperature performance, rheological properties, and shear resistance, essentially restoring the performance indicators of the base asphalt. It can be used in road engineering construction, providing a useful reference for the resource utilization of waste cooking oil and aged asphalt.

Description

Technical Field

[0001] This invention belongs to the field of road engineering technology, specifically relating to a method for regenerating aged asphalt based on waste cooking oil. Background Technology

[0002] Asphalt binder is one of the main materials used in road construction. Every year, a large amount of recycled asphalt pavement material is generated during the maintenance of old road surfaces. Statistics show that in China alone, 50 to 80 million tons of waste asphalt mixtures are generated annually from road maintenance, and this figure continues to grow. If these waste asphalt mixtures are not properly disposed of, they will not only place a huge burden on the environment but also result in a significant waste of resources (asphalt originates from petroleum). Therefore, given the shortage of crude oil resources and the urgent need for highway construction, recycled asphalt pavement has become a choice that offers both economic and environmental benefits.

[0003] Asphalt mainly consists of alkanes, cycloalkanes, and condensed aromatic hydrocarbons. Modern colloid theory generally considers asphalt to be mainly composed of asphaltenes and solubles, which can be further divided into oil (aromatics and saturated components) and resins. After asphalt ages, the asphalt content increases significantly, while the aromatic and resin content decreases, and the saturated components do not change much because their molecules are in a relatively stable state. Currently, petroleum-based regenerators are mainly used in road engineering, but the following technical problems exist when regenerating aged asphalt: (1) The light components of the regenerator are easily volatilized at high temperatures, resulting in poor regeneration efficiency; (2) Petroleum-based regenerators usually have higher aromatic content and more unsaturated bonds, which are easily oxidized at high temperatures. Therefore, developing green, environmentally friendly, and efficient regenerators is of great significance. Ran Longfei used different waste oils as base oils and prepared asphalt regenerators with plasticizers, tackifying resins, etc., and developed an environmentally friendly regenerator to regenerate aged SBS modified asphalt (Ran Longfei. Study on the aging mechanism of SBS modified asphalt under coupled heat, light and water conditions and development of high-performance regenerators [D]. Chongqing: Chongqing Jiaotong University, 2016.). The results showed that the regenerator could restore the various properties of aged asphalt to the original asphalt level, and had good economic value and environmental protection effect. Jie et al. used waste vegetable oils (corn oil and soybean oil) as asphalt regenerators to study their regeneration effect. The results showed that vegetable oils could significantly reduce the viscosity and hardness of aged asphalt, and improve the fatigue performance and low-temperature crack resistance of aged asphalt (Jie J, Yao H, Suo Z, et al. Journal of Materials in Civil Engineering, 2017, 29(3):3-12.). Researchers at Southeast University, including Gong Minghui, conducted a study on the regeneration of aged asphalt using bio-oil obtained from biodiesel residue (Gong M, Yang J, Zhang J, et al. Construction and Building Materials, 2016, 105:35-45.). The results showed that bio-oil could restore the physical and rheological properties of aged asphalt, improving its viscosity and low-temperature crack resistance. Although adding bio-oil significantly improved the penetration and softening point of aged asphalt, the ductility of the regenerated aged asphalt remained unsatisfactory.

[0004] The discharge of waste cooking oil increases the pressure on wastewater and waste oil treatment, posing a certain threat to environmental protection. It is worth noting that the main component of waste cooking oil is fatty acids, belonging to aromatic oils, similar in structure to the aromatic components missing in aged asphalt. Furthermore, modifying waste cooking oil can lower its acid value, making it exhibit a low-saturation effect, which can further improve the high-temperature performance, shear resistance, and rheological properties of aged asphalt. Therefore, using waste cooking oil to replace the base oil of conventional waste asphalt regeneration agents can turn waste into treasure, improving environmental and economic benefits, and has received widespread attention. Although waste cooking oil can restore some indicators of aged asphalt to the level of the base asphalt, its ductility is significantly reduced, which seriously affects the regeneration effect of asphalt. To address this problem, researchers have synthesized regeneration agents by mixing waste cooking oil with chemical reagents such as acetyl tributyl citrate, dibutyl phthalate, and C5 petroleum resin, but this method still has problems such as high cost and complex synthesis process.

[0005] In view of this, the present invention modifies waste cooking oil in two steps. The regenerator can be prepared by simply mixing the two modified waste cooking oils. This regenerator can restore the various indicators of aged asphalt to the level of the base asphalt, especially the ductility to the level of road use, which is of great significance for the regeneration of aged asphalt. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method for regenerating aged asphalt based on waste cooking oil, so as to improve the performance of aged asphalt and reduce the problems of waste asphalt waste and waste cooking oil discharge.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: Step S1, Esterification modification of waste cooking oil: Mix sodium hydroxide solution with methanol and waste cooking oil, place in an oil bath, heat while stirring, and finally let stand to separate into layers. The lower liquid obtained is the esterified waste cooking oil.

[0008] Step S2, epoxidative modification of waste cooking oil: Hydrogen peroxide, glacial acetic acid, concentrated sulfuric acid and esterified modified cooking oil are mixed together and placed in an oil bath. While stirring, the mixture is heated and then distilled at high temperature to obtain epoxidative modified waste cooking oil.

[0009] Step S3, preparation of regenerator: The waste edible oil obtained by esterification modification in step S1 and the waste edible oil obtained by epoxidation modification in step S2 are mixed and stirred to obtain asphalt regenerator.

[0010] Step S4, Regeneration of Aged Asphalt: Place the aged asphalt in an oven and heat it until it has good fluidity. Pour it into a mixing container, start the electric mixer, add the recycling agent to the aged asphalt, and shear at a uniform speed to obtain recycled asphalt.

[0011] Preferably, the waste cooking oil mentioned in step S1 is cooking oil discarded by regular restaurants, hotels and other catering establishments, and its main component is soybean oil.

[0012] Preferably, the concentration of the sodium hydroxide solution in step S1 is 0.8~1.2 mol / L, the amount of sodium hydroxide added is 0.5~2% of the volume of waste cooking oil, the volume ratio of methanol to waste cooking oil is (4~8):1, and the amount of waste cooking oil used is 90~110mL.

[0013] Preferably, the heating temperature in step S1 is 60~70℃, the stirring speed is 30~50 r / min, the stirring is continued for 0.5~2 h, and the standing time is 5~24 h.

[0014] Preferably, the amount of esterified modified waste edible oil used in step S2 is 9-11 g, glacial acetic acid 2.3-2.6 g, hydrogen peroxide 3.4-3.6 g, and concentrated sulfuric acid 14-16 μL.

[0015] Preferably, the oil bath heating temperature in step S2 is 45~55℃, the stirring speed is 30~50 r / min, the stirring is continued for 3~6 h, and the distillation temperature is 119~125℃.

[0016] Preferably, the ratio of esterified modified waste edible oil to epoxidized modified waste edible oil in step S3 is (0~10):1.

[0017] Preferably, the amount of recycler added in step S4 is 3-5% of the asphalt, and it is added in three parts with an interval of 10 minutes between each addition, in order to avoid poor modification effect due to uneven mixing.

[0018] Preferably, the stirring speed of the aged asphalt regeneration process in step S4 is 700~900 r / min, the heating temperature is 130~140℃, and the process is uniformly sheared for 50~70 min.

[0019] The beneficial effects of this invention are as follows: (1) This invention utilizes modified waste edible oil to modify aged asphalt. The regenerated aged asphalt can be basically restored to the level of the base asphalt and has excellent high temperature and anti-aging properties, which is beneficial to road construction and reduces the supply pressure of base asphalt.

[0020] (2) The aged asphalt modifier of the present invention is waste cooking oil, which turns waste into treasure and is cheap and readily available.

[0021] (3) The process of this invention is simple, the equipment requirements are low, and it is easy to mass-produce. Attached Figure Description

[0022] Figure 1 This is an infrared comparison image of epoxidized waste cooking oil and waste cooking oil.

[0023] Figure 2 The figure shows the ductility test results for different asphalt samples.

[0024] Figure 3 The figure shows the experimental results of the softening point of different asphalt samples.

[0025] Figure 4 The figure shows the penetration test results for different asphalt samples.

[0026] Figure 5 The graph shows the test results for different asphalt samples.

[0027] Figure 6 The figure shows the ductility test results of different ratios of esterified modified waste edible oil and epoxidized modified waste edible oil.

[0028] Figure 7 The figure shows the softening point test results of different ratios of esterified modified waste edible oil and epoxidized modified waste edible oil.

[0029] Figure 8 Figure 1 shows the penetration test results of different ratios of esterified modified waste edible oil and epoxidized modified waste edible oil.

[0030] Figure 9 The figure shows the viscosity test results of esterified modified waste edible oil and epoxidized modified waste edible oil with different proportions.

[0031] Figure 10 The results of composite shear modulus tests for different dosages of esterified and epoxidized waste edible oils are presented. Detailed Implementation

[0032] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0033] Example 1 A method for regenerating aged asphalt based on waste cooking oil, comprising the following steps: Step S1, Esterification and Modification of Waste Edible Oil: Prepare a sodium hydroxide solution with a concentration of 1 mol / L. Mix the sodium hydroxide solution with methanol and waste edible oil, wherein the volume ratio of methanol to waste edible oil is 6:1, and the amount of sodium hydroxide added is 1% of the volume of waste edible oil. Place the resulting mixture in an oil bath with magnetic stirring at a stirring speed of 45 r / min and react at 65℃ for 1 h. After the reaction is complete, let it stand overnight until it separates into layers. The lower layer is the esterified and modified waste edible oil, which can be collected.

[0034] Step S2, Epoxidation Modification of Waste Edible Oil: Mix 10 g of esterified modified waste edible oil, 2.5 g of glacial acetic acid, 3.5 g of hydrogen peroxide, and 15 μL of concentrated sulfuric acid together, place them in an oil bath at 50°C and stir for 3 h. After stirring, raise the temperature to 125°C to evaporate excess components to obtain epoxidation modified edible oil.

[0035] Step S3, preparation of regenerator: The waste edible oil obtained by esterification modification in step S1 and the waste edible oil obtained by epoxidation modification in step S2 are mixed and stirred to obtain asphalt regenerator, with a ratio of 4:6.

[0036] Step S4, Regeneration of Aged Asphalt: Place the aged asphalt in an oven and heat it until it has good fluidity. Pour it into a mixing container, start the electric mixer, and add the recycling agent to the aged asphalt in three batches, with each batch 10 minutes apart, to ensure the asphalt sample is thoroughly mixed. Increase the speed to 800 r / min and maintain the asphalt temperature at 135℃. Shear at a uniform speed for 60 minutes to obtain recycled asphalt. The amount of recycling agent added is 3%, 4%, or 5% of the mass of the aged asphalt.

[0037] Comparative Example 1 (using waste cooking oil directly) The aged asphalt was regenerated directly using unmodified waste cooking oil, and the regeneration method was the same as step S4 in Example 1.

[0038] Comparative Example 2 (Esterification modification of waste cooking oil only) The aged asphalt was regenerated using the same method as in Example 1, except that steps S2 and S3 were omitted, i.e., esterified modified waste edible oil was used directly to regenerate the aged asphalt.

[0039] Example 2 (Regenerants with different ratios) The aged asphalt was regenerated using the same method as in Example 1, except that the ratio of the regenerator was 9:1, 8:2, 7:3, 6:4, 5:5, 3:7, 2:8, 1:9, or 0:10, and the amount of regenerator added was 5% of the mass of the aged asphalt.

[0040] Figure 1 The results are infrared comparisons between epoxidized waste cooking oil and waste cooking oil. The wavelengths of 838 cm-1 and 3490 cm-1 are the characteristic peaks of the three-membered ring ether (COC) and hydroxyl group (OH), respectively, indicating that step S2 successfully introduced epoxy groups into the waste cooking oil.

[0041] According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering", the asphalt prepared in the examples and comparative examples was tested, and the results are as follows: (1) The viscosity test is rotational viscosity, using a Brookfield viscometer, and the test temperature is 135℃.

[0042] (2) The short-term aging test was conducted by heating in a rotating thin film oven for asphalt. The mass of each asphalt sample was 50±0.5 g, the heating temperature was 163±0.5℃, and the total rotating heating time was 5 h.

[0043] (3) The long-term aging test is a pressure aging test. The mass of each asphalt sample is 50±0.5 g, the air pressure is 2.1±0.1 MPa, the test temperature is 100℃, and the aging time is 20 h.

[0044] (4) The ductility test temperature is 15℃, the asphalt sample cooling time is at least 1.5 h, and the tensile speed is 5 cm / min.

[0045] (5) In the penetration test, all asphalt samples were placed in multiple penetration test dishes in sequence, the samples were cooled for at least 1.5 h at a temperature of 25°C, the insertion time was 5 s, and each sample was measured 3 times and the average value was taken.

[0046] (6) In the softening point determination test, all asphalt samples are placed in multiple softening point molds in sequence. The samples are cooled for at least 15 minutes at a temperature of 5°C. In one embodiment, two samples are tested at a time, and the average value is taken.

[0047] Based on macroscopic experimental data, a comparative analysis of the road performance of the regenerated aged asphalt was conducted with that of unmodified waste edible oil and waste edible oil modified only by esterification, demonstrating the practicality and rationality of the regenerator prepared by the two-step modification method of this invention for the regeneration of aged asphalt.

[0048] Short-term aging (RTFOT) and long-term aging (PAV) were performed on 70# base asphalt. The resulting aged asphalt was then subjected to penetration, softening point, ductility, and viscosity tests on recycled asphalt prepared in Example 1, Comparative Example 1, Comparative Example 2, and Example 2. The high-temperature, shear deformation resistance, and low-temperature properties of the recycled asphalt were also tested.

[0049] Example 1 and Comparative Example 1 and Comparative Example 2, the experimental results are as follows: Figures 1-4 As shown, the softening point of the base asphalt is 48.4℃, the penetration is 63 dmm, and the viscosity is 484 CP, while the softening point of the long-term aged asphalt is 63℃, the penetration is 28.7 dmm, and the viscosity is 5258 CP. Figure 2Ductility tests showed that the improvement in ductility was poor when waste cooking oil was directly recycled into aged asphalt, and when only esterification-modified waste cooking oil was used to regenerate aged asphalt, with a maximum improvement of no more than 23.3 cm. However, the ductility of aged asphalt was significantly improved after regenerating it with a recycling agent obtained by mixing esterification modification and epoxidation modification in a certain proportion, with a maximum improvement of up to 115.4 cm. This may be due to the formation of epoxy bonds, which provides a good lubrication effect within the molecules of the asphalt during the deformation process.

[0050] Figure 3 The softening point test results showed that the softening point of the asphalt was significantly improved after adding waste cooking oil and esterified waste cooking oil compared with that of aged asphalt. The addition of epoxidized waste cooking oil on the basis of esterified waste cooking oil further reduced the softening point of the asphalt to a level closer to that of the base asphalt, indicating that epoxidized waste cooking oil also has a certain effect on softening aged asphalt.

[0051] Figure 4 The penetration test results showed that the penetration gradually increased with the addition of waste cooking oil. Higher admixture levels also resulted in softer physical properties in the recycled asphalt, reaching a maximum of 76.8 dmm. The highest penetration of esterified modified waste cooking oil was 61.7 dmm. When both esterified and epoxidized modified waste cooking oil were added simultaneously, the highest penetration was 59.6 dmm, a slight decrease. This may be because the epoxidized modified waste cooking oil has a lower aromatic content, resulting in less dissolved asphaltenes, but it is still close to the level of the base asphalt.

[0052] from Figure 5 In terms of viscosity, the viscosity gradually decreased with the increasing amount of waste cooking oil and esterified waste cooking oil. The chemically treated esterified waste cooking oil showed an even lower viscosity, which was also closer to the base asphalt's 484 CP. When esterified and epoxidized waste cooking oil were mixed and added, the viscosity decreased from 5258 CP to 597 CP. Compared to adding only esterified waste cooking oil, the viscosity increased slightly, but it still showed a significant improvement.

[0053] Figure 6-9 Example 2 presents the results of ductility, softening point, penetration, and viscosity of recycled asphalt with different ratios. By comparison, it can be found that when the ratio of esterified modified waste edible oil to epoxidized modified waste edible oil is 4:6, the ductility of the recycled aged asphalt is 115.4 cm, the softening point is 50℃, the penetration is 59.6 dmm, and the viscosity is 597 CP. The ductility shows the greatest improvement, and the softening point, penetration, and viscosity also show significant improvements, indicating a superior recycling effect.

[0054] Figure 10 The composite shear modulus results for different amounts of recycling agent in Example 1 show that after adding the recycling agent, the composite shear modulus recovered to the level of the base asphalt and was slightly higher than that of the base asphalt, indicating that the recycling agent has good recycling performance and also improves the deformation resistance of the asphalt.

[0055] Based on the above tests of ductility, softening point, penetration, and viscosity, the recycled asphalt prepared by mixing esterified modified waste edible oil and epoxidized modified waste edible oil in a 4:6 ratio with a dosage of 5% exhibits the best results, almost reaching the level of base asphalt. This solves the problem of a significant decrease in ductility when using only bio-oil to recycle asphalt. This bio-based regenerator is environmentally friendly and easily degradable, solving the problem of petroleum-based regenerators being environmentally unfriendly. It fully meets the needs of road construction materials, with significant economic, social, and environmental benefits and broad application prospects.

[0056] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for regenerating aged asphalt based on waste cooking oil, characterized in that: Includes the following steps: (1) Esterification modification of waste cooking oil: Sodium hydroxide solution, methanol and waste cooking oil are mixed, heated while stirring, and allowed to stand to separate into layers. The lower liquid is the esterified waste cooking oil. (2) Epoxidation modification: Hydrogen peroxide, glacial acetic acid, concentrated sulfuric acid and esterified waste edible oil are mixed, heated while stirring, and distilled at high temperature to obtain epoxidized waste edible oil; (3) Preparation of regenerator: Esterified waste edible oil and epoxidized waste edible oil are mixed and stirred to obtain asphalt regenerator; (4) Regeneration of aged asphalt: The aged asphalt is heated until it has good fluidity, and asphalt recycling agent is added while stirring. The asphalt is sheared at a uniform speed to obtain recycled asphalt. In step (3), the volume ratio of esterified waste edible oil to epoxidized waste edible oil is 4:

6.

2. The method according to claim 1, characterized in that: In step (1), the main component of the waste cooking oil is soybean oil.

3. The method according to claim 1, characterized in that: In step (1), the concentration of sodium hydroxide solution is 0.8~1.2 mol / L, the amount of sodium hydroxide added is 0.5~2% of the volume of waste cooking oil, and the volume ratio of methanol to waste cooking oil is 4~8:

1.

4. The method according to claim 1, characterized in that: In step (1), the heating temperature is 60~70℃, the stirring speed is 30~50 r / min, the stirring is continued for 0.5~2 h, and the standing time is 5~24 h.

5. The method according to claim 1, characterized in that: In step (2), 9-11 g of esterified waste cooking oil, 2.3-2.6 g of glacial acetic acid, 3.4-3.6 g of hydrogen peroxide, and 14-16 μL of concentrated sulfuric acid are used; the heating temperature is 45-55℃, the stirring speed is 30-50 r / min, the stirring is continued for 3-6 h, and the distillation temperature is 119-125℃.

6. The method according to claim 1, characterized in that: In step (4), the amount of recycling agent added is 3 to 5% of the mass of aged asphalt, and it is added in three parts with an interval of 10 minutes between each addition.

7. The method according to claim 1, characterized in that: In step (4), the stirring speed is 700~900 r / min, the heating temperature is 130~140℃, and the shearing is performed at a constant speed for 50~70 min.

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