An inhibitor chemical and a method of making the same

Abstract

This invention belongs to the field of crude oil corrosion inhibition technology, specifically relating to a corrosion-inhibiting chemical and its preparation method. The corrosion-inhibiting chemical, by weight percentage, comprises the following components: 5-25% polyacid compound, 55-80% ionic liquid, 5-15% dispersant, and 2-8% stabilizer. The polyacid-ionic liquid compound corrosion-inhibiting chemical of this invention exhibits high slow-release efficiency and stability. The ionic liquid forms an adsorption film on the metal surface through adsorption, while the excellent redox properties of the polyacid can form a dense metal oxide passivation film at the metal interface. The electrostatic interaction between the polyacid anions and the ionic liquid improves the solubility and dispersibility of the polyacid in crude oil media. The synergistic effect of these two components forms a double protective film, further enhancing the corrosion inhibition effect in high-salt, acidic, and sulfur-containing media. The corrosion-inhibiting chemical synthesized in this invention is environmentally friendly and meets the requirements of green chemical development.

Description

Technical Field

[0001] This invention belongs to the field of crude oil corrosion inhibition technology, specifically relating to a corrosion-inhibiting chemical and its preparation method. Background Technology

[0002] As the "arteries" of my country's energy transportation, the safe and stable operation of crude oil pipelines is crucial to national economic development and energy security. The main component of crude oil pipelines is carbon steel. During long-term service, the presence of corrosive media such as water, salts, sulfides, and organic or inorganic acids in crude oil can cause severe corrosion of the pipeline's inner wall. This not only shortens the pipeline's lifespan and increases maintenance costs but also may lead to crude oil leaks, causing serious environmental pollution and safety accidents. Therefore, developing efficient, stable, and environmentally friendly corrosion-resistant chemicals for crude oil pipelines has significant industrial application value and practical importance.

[0003] Currently, commonly used corrosion inhibitors for crude oil pipelines mainly include organic amines, imidazolines, and quaternary ammonium salts. However, these chemicals have drawbacks such as limited corrosion inhibition efficiency, poor resistance to high temperatures and high salt concentrations, volatility, and environmental pollution, making them unsuitable for meeting the corrosion protection requirements under complex operating conditions (such as transporting high-temperature, high-salt, and sulfur-containing crude oil). Ionic liquids, as a novel green solvent and functional material, possess characteristics such as low vapor pressure, good thermal stability, excellent solubility, and strong designability, showing promising application prospects in the field of metal corrosion prevention and inhibition. Polyoxometalates (polyacids) are a class of polyoxometalate cluster compounds formed by the bridging of central and coordinating atoms through oxygen atoms. They possess strong acidity and excellent redox properties, and can induce the formation of a dense metal oxide passivation film on the metal surface, thus playing a corrosion inhibition role. However, traditional polyoxometalates suffer from problems such as small specific surface area, poor dispersibility in crude oil media, and difficulty in recovery, limiting their large-scale application.

[0004] While there are reports of ionic liquids or metal oxometalate corrosion inhibitors in the prior art (the ionic liquid corrosion inhibitor composition disclosed in Chinese invention patent CN119980245A and the molybdate-containing composite corrosion inhibitor disclosed in Chinese invention patent CN110885981A), there are still no highly efficient synergistic corrosion inhibitors that precisely combine polyacids and ionic liquids and are specifically designed for the complex corrosive environment of crude oil pipelines (containing sulfur, high salt, and wide temperature range). Furthermore, there is still room for improvement in the corrosion inhibition efficiency, stability, and environmental friendliness of existing corrosion inhibitors. Summary of the Invention

[0005] This invention addresses the problems of low corrosion inhibition efficiency, poor resistance to high salt, sulfur, and acid, and insufficient environmental friendliness of existing crude oil corrosion inhibitors. It provides a corrosion inhibitor and its preparation method. The corrosion inhibitor has the advantages of high corrosion inhibition efficiency, good stability, high salt and acid resistance, and green environmental protection. It can effectively inhibit the corrosion of the inner wall of long-distance crude oil pipelines, extend the service life of the pipelines, and the preparation method is simple, low-cost, and easy to industrialize.

[0006] The specific technical solution is as follows: The first objective of this invention is to provide a corrosion inhibitory chemical comprising, by weight percentage: 5-25% polyacid compound, 55-80% ionic liquid, 5-15% dispersant, and 2-8% stabilizer.

[0007] This invention combines polyacid compounds with ionic liquids to prepare polyacid-ionic liquid compound corrosion inhibitors, which can fully leverage the synergistic advantages of both and overcome their respective limitations. The positively charged component of the ionic liquid binds to the polyacid anions through electrostatic interactions, enhancing the interaction between them. Furthermore, the ionic liquid can serve as a dispersion medium and carrier for the polyacids, improving their solubility and dispersibility in crude oil media, while simultaneously enhancing the corrosion inhibition effect through its own adsorption properties; the polyacids, on the other hand, can further strengthen the stability and density of the corrosion-inhibiting film through their excellent redox properties and acid resistance.

[0008] Furthermore, the polyacid compound is a Keggin-type heteropolyacid, selected from one or more of phosphomolybdic acid, silicotungstic acid, phosphomolybdic acid, and silicotungstic acid.

[0009] Furthermore, the ionic liquid is an imidazole-type ionic liquid, selected from one or more of 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-dodecyl-3-methylimidazolium tetrafluoroborate, and 1-hexadecyl-2,3-dimethylimidazolium hexafluorophosphate, or a mixture thereof.

[0010] Furthermore, the dispersant is one or a mixture of polyethylene glycol 600, Tween 80, and Span 80.

[0011] Furthermore, the stabilizer is one or a mixture of sodium sulfite, disodium EDTA, and citric acid.

[0012] Furthermore, the corrosion inhibitory chemical comprises, by weight percentage: 5-25% polyacid compound, 55-75% ionic liquid, 5-12% dispersant, and 3-8% stabilizer.

[0013] Furthermore, the polyacid compound is a mixture of molybdenum-based polyacid and tungsten-based polyacid in a weight ratio of 1:1-3.

[0014] Furthermore, the ionic liquid is a mixture of 1-dodecyl-3-methylimidazolium tetrafluoroborate and 1-hexadecyl-2,3-dimethylimidazolium hexafluorophosphate in a weight ratio of 2:1, or the ionic liquid is a mixture of 1-hexyl-3-methylimidazolium hexafluorophosphate and 1-dodecyl-3-methylimidazolium tetrafluoroborate in a weight ratio of 2:1.

[0015] In this invention, polyacid compounds, as one of the main components of the corrosion inhibitor, possess strong oxidizing capabilities due to their polymetallic oxygen cluster structure. They can undergo redox reactions with metal pipelines, inducing the formation of a dense metal oxide passivation film. This passivation film effectively blocks contact between the corrosive medium and the metal. Simultaneously, its acid resistance and redox properties inhibit anodic dissolution and cathodic hydrogen evolution reactions in crude oil pipelines, thus playing a corrosion inhibitor role. Ionic liquids, as another major component of the corrosion inhibitor, have their cationic portion forming coordinate bonds with empty d orbitals of the metal through π electrons on the imidazole ring, thereby chemically adsorbing onto the metal substrate interface. Long-chain alkyl groups can form a hydrophobic and dense physical adsorption film at the metal substrate interface, protecting the substrate material. Ionic liquids not only possess good solubility and dispersibility, uniformly dispersing polyacid compounds in the crude oil medium, but their cationic portion can also form a synergistic adsorption film on the metal surface with polyacid anions through electrostatic adsorption, enhancing the film's density and stability. Meanwhile, the low volatility and high stability of ionic liquids ensure the stable performance of corrosion inhibitors in high-salt, sulfur-containing, and acidic environments; the polyacids, with a size of approximately 1 nm, form a protective film on the metal surface with the ionic liquids, compensating for microscopic defects and pores in the adsorption film, thereby reducing active sites for metal corrosion and improving corrosion inhibition efficiency; dispersants further improve the dispersibility of polyacid compounds and ionic liquids in crude oil, preventing agglomeration and ensuring that corrosion inhibitors act uniformly on the inner wall of the pipeline; stabilizers prevent the decomposition of polyacid compounds and the degradation of ionic liquids, extending the service life of corrosion inhibitors while suppressing the interference of impurities in the medium on the corrosion inhibition effect.

[0016] A second objective of this invention is to provide a method for preparing the aforementioned corrosion-inhibiting chemicals for crude oil pipelines, comprising the following steps: S1. Weigh out the polyacid compound, ionic liquid, dispersant, and stabilizer according to the above weight percentages, and set aside for later use; S2. Add the ionic liquid to the reaction vessel, and under the protection of an inert atmosphere, heat it to 40-70℃ and stir it at a rate of 200-300r / min for 10-20 min to make the ionic liquid uniformly dispersed and maintain a stable state. S3. Slowly add the polyacid compound to the ionic liquid in step S2, and continue stirring at 40-70℃ and 200-300r / min for 30-60 min. At the same time, use ultrasonic-assisted dispersion to ensure that the polyacid compound is completely dissolved and uniformly dispersed in the ionic liquid to obtain mixture A. S4. Add the dispersant and stabilizer to mixture A, heat to 50-80℃, and stir at a rate of 300-400 r / min for 40-80 min to completely dissolve the dispersant and stabilizer and to ensure that all components are thoroughly mixed to obtain mixture B. S5. Cool the mixture B obtained in step S4 to room temperature (25±5℃) and let it stand for 10-20 min to obtain the corrosion inhibitor.

[0017] Furthermore, in step S2, the inert atmosphere is nitrogen or argon, and the heating rate is 2-5 °C / min to avoid excessively rapid heating that could lead to the decomposition of the ionic liquid.

[0018] Furthermore, in step S3, the addition rate of the polyacid compound is 0.5-1 g / min. Slow addition can prevent excessive local concentration from causing agglomeration and ensure sufficient dissolution. The ultrasonic-assisted dispersion power is 200-300 W and the time is 15-25 min. Ultrasonic-assisted dispersion can effectively break the agglomeration of the polyacid compound, improve the dispersion uniformity, and shorten the stirring time.

[0019] Furthermore, in step S4, the stirring time is 50-70 minutes, which ensures that the synergistic effect of each component is fully utilized.

[0020] The corrosion inhibitors of this invention exhibit excellent slow-release efficiency and stability. Ionic liquids form an adsorption film on the metal surface through adsorption, while the excellent redox properties of polyacids allow for the formation of a dense metal oxide passivation film at the metal interface. The electrostatic interaction between polyacid anions and the ionic liquid enhances the solubility and dispersibility of the polyacids in crude oil. The synergistic effect of these two factors creates a dual protective film that further strengthens the corrosion inhibition effect in acidic, high-salt media. The corrosion inhibitors synthesized in this invention are environmentally friendly and meet the requirements of green chemical development. Furthermore, the preparation process is simple, energy-efficient, and allows for large-scale industrial production.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention combines polyacid compounds with ionic liquids, which work synergistically to inhibit corrosion. The chemical adsorption of polyacid compounds and the electrostatic adsorption of ionic liquids combine to form a dense and stable double protective film on the metal surface of the pipeline, effectively inhibiting anodic dissolution and cathodic hydrogen evolution reaction of the metal. In simulated crude oil media, its corrosion inhibition rate can reach more than 92%, which is significantly better than existing single-type corrosion inhibitors.

[0022] (2) In this invention, the ionic liquid has good chemical and thermal stability. The polyacid compounds are evenly dispersed in the ionic liquid and are not easily decomposed. With the help of the stabilizer, the corrosion inhibitor can maintain stable performance under high salt and acid conditions. It is suitable for corrosion protection of crude oil pipelines under high salt, high sulfur and acid conditions, and solves the problem of performance degradation of existing corrosion inhibitors under harsh environments.

[0023] (3) The present invention adds a special dispersant, which can ensure that the polyacid compound and ionic liquid are uniformly dispersed in crude oil, without agglomeration or precipitation, and can fully cover the inner wall of the pipeline; the selected ionic liquid is green and environmentally friendly and non-volatile, and the polyacid compound, dispersant and stabilizer are all environmentally friendly reagents, which meet the requirements of green chemical development.

[0024] (4) The preparation method of the present invention does not require complex equipment and harsh reaction conditions. It can be completed by simple steps such as heating, stirring and ultrasonic assistance. The reaction time is short, the energy consumption is low, the cost is low, and the raw materials of each component are easy to obtain (such as phosphomolybdic acid and imidazole ionic liquids are commercially available conventional reagents), which can realize large-scale industrial production.

[0025] (5) The stabilizer in the corrosion inhibitor of the present invention can effectively prevent the decomposition of polyacid compounds and the degradation of ionic liquids. At the same time, the corrosion inhibitor film has high density and stability and is not easy to fall off. The corrosion inhibitor can be used for corrosion protection of X65 steel crude oil pipeline material, significantly extending the service life of the pipeline, reducing maintenance costs and leakage risks, and has good economic and social benefits. Detailed Implementation

[0026] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0027] Example 1 A corrosion inhibitory chemical comprising, by weight percentage: 15% phosphomolybdic acid, 70% 1-dodecyl-3-methylimidazolium tetrafluoroborate, 12% polyethylene glycol 600, and 3% citric acid.

[0028] A method for preparing a corrosion inhibitor includes the following steps: S1. Weigh out 15g of phosphomolybdic acid, 70g of 1-dodecyl-3-methylimidazolium tetrafluoroborate, 12g of polyethylene glycol 600, and 3g of citric acid according to the above weight percentages, and set aside. S2. Add 1-dodecyl-3-methylimidazolium tetrafluoroborate to the reaction vessel, purge with nitrogen for protection, heat to 45°C at a rate of 3°C / min, stir at a rate of 220 r / min for 15 min to ensure uniform dispersion of the ionic liquid and maintain a stable state. S3. Slowly add phosphomolybdic acid to the ionic liquid in step S2 at a rate of 0.8 g / min, continue stirring at 45℃ and 220 r / min for 45 min, and simultaneously use 250 W ultrasonic-assisted dispersion for 20 min to obtain mixture A. S4. Add polyethylene glycol 600 and citric acid to mixture A, heat to 65°C, adjust the stirring speed to 350 r / min, and stir for 60 min to ensure that all components are fully mixed and homogeneous, thus obtaining mixture B. S5. Cool the mixture B to 25°C and let it stand for 10 minutes to obtain the corrosion inhibitor.

[0029] Example 2 A corrosion inhibitory chemical comprises, by weight percentage, the following components: 10% of a compound polyacid consisting of phosphomolybdic acid and silicotungstic acid in a weight ratio of 1:2; 75% of a compound ionic liquid consisting of 1-dodecyl-3-methylimidazolium tetrafluoroborate and 1-hexadecyl-2,3-dimethylimidazolium hexafluorophosphate in a weight ratio of 2:1; 10% of Tween 80; 2% of sodium sulfite; and 3% of citric acid.

[0030] A method for preparing a corrosion inhibitor includes the following steps: S1. Weigh out 10g of the compound polyacid (including 3.3g of phosphomolybdic acid and 6.7g of silicotungstic acid), 75g of the compound ionic liquid (including 50g of 1-dodecyl-3-methylimidazolium tetrafluoroborate and 25g of 1-hexadecyl-2,3-dimethylimidazolium hexafluorophosphate), 10g of Tween 80, 2g of sodium sulfite, and 3g of citric acid according to the above weight percentages, and set aside. S2. Add the compound ionic liquid to the reaction vessel, purge with nitrogen for protection, heat to 70°C at a rate of 2°C / min, stir at a stirring rate of 300 r / min for 20 min, so that the ionic liquid is uniformly dispersed and kept in a stable state. S3. The compound polyacid is slowly added to the ionic liquid in step S2 at a rate of 0.5 g / min, and the mixture is stirred at 70℃ and 300 r / min for 60 min. At the same time, it is dispersed with ultrasonic assistance at 300 W for 25 min to obtain mixture A. S4. Add Tween 80, sodium sulfite and citric acid to mixture A, heat to 80℃, adjust the stirring speed to 400 r / min, stir for 80 min to ensure that all components are fully mixed and homogeneous, and obtain mixture B. S5. Cool the mixture B to 20°C and let it stand for 20 minutes to obtain the corrosion inhibitor.

[0031] Example 3 A corrosion inhibitory chemical comprises, by weight percentage, the following components: 25% of a compound polyacid consisting of molybdic acid and phosphotungstic acid in a 1:1 weight ratio; 55% of a compound ionic liquid consisting of 1-hexyl-3-methylimidazolium hexafluorophosphate and 1-dodecyl-3-methylimidazolium tetrafluoroborate in a 2:1 weight ratio; 12% of Span 80; 3% of disodium EDTA; and 5% of citric acid.

[0032] A method for preparing a corrosion inhibitor includes the following steps: S1. Weigh out 25g of the compound polyacid (including 12.5g of silylic acid and 12.5g of phosphotungstic acid), 55g of the compound ionic liquid (including 36.7g of 1-hexyl-3-methylimidazolium hexafluorophosphate and 18.3g of 1-dodecyl-3-methylimidazolium tetrafluoroborate), 12g of Span 80, 3g of disodium EDTA, and 5g of citric acid according to the above weight percentages, and set aside. S2. Add the compound ionic liquid to the reaction vessel, introduce argon gas for protection, heat to 65℃ at a rate of 5℃ / min, stir at a stirring rate of 300 r / min for 10 min to make the ionic liquid uniformly dispersed and kept in a stable state. S3. The compound polyacid is slowly added to the ionic liquid in step S2 at a rate of 1 g / min, and the mixture is stirred at 65℃ and 300 r / min for 30 min. At the same time, it is dispersed with ultrasonic assistance at 300W for 15 min to obtain mixture A. S4. Add Span 80, disodium EDTA, and citric acid to mixture A, heat to 80°C, adjust the stirring speed to 400 r / min, and stir for 50 min to ensure thorough mixing of all components, thus obtaining mixture B. S5. Cool the mixture B to 30°C and let it stand for 10 minutes to obtain the corrosion inhibitor.

[0033] Example 4 A corrosion inhibitory chemical comprising, by weight percentage: 10% molybdic acid, 72% 1-hexyl-3-methylimidazolium hexafluorophosphate, 12% Span 80, 2% disodium EDTA, and 4% citric acid.

[0034] A method for preparing a corrosion inhibitor includes the following steps: S1. Weigh out 10g of molybdic acid, 72g of 1-hexyl-3-methylimidazolium hexafluorophosphate, 12g of Span 80, 2g of disodium EDTA, and 4g of citric acid according to the above weight percentages, and set aside. S2. Add 1-hexyl-3-methylimidazolium hexafluorophosphate to the reaction vessel, purge with argon gas for protection, heat to 65°C at a rate of 5 °C / min, stir at a stirring rate of 300 r / min for 10 min to ensure uniform dispersion of the ionic liquid and maintain a stable state. S3. Slowly add molybdic acid to the ionic liquid in step S2 at a rate of 1 g / min, continue stirring at 65℃ and 300 r / min for 30 min, and simultaneously use 300W ultrasonic-assisted dispersion for 15 min to obtain mixture A. S4. Add Span 80, disodium EDTA and citric acid to mixture A, heat to 80℃, adjust the stirring speed to 400 r / min, stir for 50 min to ensure that all components are fully mixed and homogeneous, and obtain mixture B. S5. Cool the mixture B to 30°C and let it stand for 10 minutes to obtain the corrosion inhibitor.

[0035] Example 5 A corrosion inhibitory chemical comprising, by weight percentage: 6% molybdic acid, 72% 1-hexyl-3-methylimidazolium hexafluorophosphate, 14% Span 80, 3% disodium EDTA, and 5% citric acid.

[0036] A method for preparing a corrosion inhibitor includes the following steps: S1. Weigh out 6g of molybdic acid, 72g of 1-hexyl-3-methylimidazolium hexafluorophosphate, 14g of Span 80, 3g of disodium EDTA, and 5g of citric acid according to the above weight percentages, and set aside. S2. Add 1-hexyl-3-methylimidazolium hexafluorophosphate to the reaction vessel, purge with argon gas for protection, heat to 65°C at a rate of 5 °C / min, stir at a stirring rate of 300 r / min for 10 min to ensure uniform dispersion of the ionic liquid and maintain a stable state. S3. Slowly add molybdic acid to the ionic liquid in step S2 at a rate of 1 g / min, continue stirring at 65℃ and 300 r / min for 30 min, and simultaneously use 300W ultrasonic-assisted dispersion for 15 min to obtain mixture A. S4. Add Span 80, disodium EDTA and citric acid to mixture A, heat to 80°C, adjust the stirring speed to 400 r / min, and stir for 50 min to ensure that all components are fully mixed. S5. Cool the mixture to 30°C and let it stand for 10 minutes to obtain the corrosion inhibitor.

[0037] Comparative Example 1 An ionic liquid corrosion inhibitor chemical comprises, by weight percentage: 82% 1-hexyl-3-methylimidazolium hexafluorophosphate, 12% Span 80, 2% disodium EDTA, and 4% citric acid.

[0038] A method for preparing an ionic liquid corrosion inhibitor includes the following steps: S1. Weigh out 82g of 1-hexyl-3-methylimidazolium hexafluorophosphate, 12g of Span 80, 2g of disodium EDTA, and 4g of citric acid according to the above weight percentages, and set aside. S2. Add 1-hexyl-3-methylimidazolium hexafluorophosphate to the reaction vessel, purge with argon gas for protection, heat to 65°C at a rate of 5 °C / min, stir at a stirring rate of 300 r / min for 10 min to ensure uniform dispersion of the ionic liquid and maintain a stable state. S3. Add Span 80, disodium EDTA and citric acid to the ionic liquid in step S2, continue to raise the temperature to 80°C, adjust the stirring rate to 400 r / min, stir for 50 min, so that the components are fully mixed and homogeneous, and obtain mixture B. S4. Cool the mixture B to 30°C and let it stand for 10 minutes to obtain the ionic liquid corrosion inhibitor.

[0039] Comparative Example 2 A polyacid corrosion inhibitor, comprising the following components by weight percentage: 25% of a compound polyacid mixture of molybdic acid and phosphotungstic acid in a 1:1 weight ratio, 12% of Span 80, 55% of ethanol, 3% of disodium EDTA, and 5% of citric acid.

[0040] A method for preparing a polyacid corrosion inhibitor includes the following steps: S1. Weigh out 25g of the compound polyacid (including 12.5g of silymolybdic acid and 12.5g of phosphotungstic acid), 12g of Span 80, 55g of ethanol, 3g of disodium EDTA, and 5g of citric acid according to the above weight percentages, and set aside. S2. Add the compound polyacid slowly to the reaction vessel at a rate of 1 g / min. Add Span 80, ethanol, disodium EDTA and citric acid to the reaction vessel. Heat to 80℃, adjust the stirring rate to 400 r / min, and stir for 50 min to ensure that all components are fully mixed and homogeneous to obtain mixture B. S3. Cool the mixture B to 30°C and let it stand for 10 minutes to obtain the polyacid corrosion inhibitor.

[0041] Comparative Example 3 A polyacid ionic liquid corrosion inhibitor comprises the following components by weight percentage: 10% molybdic acid, 84% 1-hexyl-3-methylimidazolium hexafluorophosphate, 2% disodium EDTA, and 4% citric acid.

[0042] A method for preparing a polyacid ionic liquid corrosion inhibitor includes the following steps: S1. Weigh out 10g of molybdic acid, 84g of 1-hexyl-3-methylimidazolium hexafluorophosphate, 2g of disodium EDTA, and 4g of citric acid according to the above weight percentages, and set aside. S2. Add 1-hexyl-3-methylimidazolium hexafluorophosphate to the reaction vessel, purge with argon gas for protection, heat to 65°C at a rate of 5 °C / min, stir at a stirring rate of 300 r / min for 10 min to ensure uniform dispersion of the ionic liquid and maintain a stable state. S3. Slowly add molybdic acid to the ionic liquid in step S2 at a rate of 1 g / min, continue stirring at 65℃ and 300 r / min for 30 min, and simultaneously use 300W ultrasonic-assisted dispersion for 15 min to obtain mixture A. S4. Add disodium EDTA and citric acid to mixture A, heat to 80℃, adjust the stirring speed to 400 r / min, stir for 50 min to ensure that all components are fully mixed and homogeneous, and obtain mixture B. S5. Cool the mixture B to 30°C and let it stand for 10 minutes to obtain the polyacid ionic liquid corrosion inhibitor.

[0043] test: Based on the methods in SY / T 5273-2014 "Performance Indicators and Evaluation Methods for Corrosion Inhibitors Used in Oilfield Produced Water Treatment" and the literature ("Corrosion of 20 Steel by Crude Oil Emulsion", Zhang Zhihong et al., Corrosion and Protection, Vol. 45, No. 2, 2024), and after optimization for corresponding working conditions, the corrosion inhibitors prepared in Examples 1-5 and Comparative Examples 1-3 were tested for corrosion resistance.

[0044] The corrosion test was conducted on the steel sheet samples using the hanging plate method. The corrosion rate was recorded and compared with the corrosion standard (≤0.076 mm / a) by simulating the application conditions of each embodiment and comparative example.

[0045] Corrosion rate ( v Calculation formula: (1) Sustained release rate ( or Calculation formula: (2) In the formula v The corrosion rate is expressed in mm / year. w The mass loss of the metal before and after corrosion is expressed in grams (g). S The area of ​​the metal hanging piece is expressed in cm². 2 ; tTest time, in hours (h); The sustained-release rate is expressed in % (%). v 0 represents the corrosion rate without the addition of corrosion inhibitors, in mm / a; v 1 represents the corrosion rate of the added corrosion inhibitor, in mm / a.

[0046] Experimental conditions: Simulated crude oil medium from an oilfield in my country (composition shown in Table 1), carbon dioxide 0.3 MPa. Pipeline material was X65 steel, corrosion inhibitor dosage was 60 mg / L, test temperature was 80℃, and test time was 72 h. The surfaces of the metal pads were polished to a bright finish using sandpaper (200~1500#), then rinsed with distilled water, degreased with acetone, and wiped with anhydrous ethanol, and dried in an oven before use. The simulated crude oil medium was added to a corrosion reaction evaluation device, and high-purity N2 was introduced to remove oxygen from the device to evaluate the corrosion of the X65 pads. The sample test results are shown in Table 2 below. Table 1 Composition of Crude Oil Simulation Medium

[0047] Table 2. Sample test data for each embodiment and comparative example.

[0048] Comparing the test data in Table 2, it can be seen that the polyacid ionic liquid corrosion inhibitor prepared in this invention achieves a corrosion inhibition rate of over 92%, with a corrosion rate far lower than the comparative example, and exhibits excellent stability and dispersibility. Comparing Example 4 with Comparative Example 1, replacing molybdenum silylate with an equal amount of 1-hexyl-3-methylimidazolium hexafluorophosphate ionic liquid resulted in a certain degree of reduction in the release rate due to the lack of a passivation film induced by molybdenum silylate. Comparing Example 3 with Comparative Example 2, the absence of the composite ionic liquid of 1-hexyl-3-methylimidazolium hexafluorophosphate and 1-dodecyl-3-methylimidazolium tetrafluoroborate significantly reduced the release performance of the inhibitory compound, indicating that the ionic liquid is the main functional component of the corrosion inhibitor. Comparing Example 4 with Comparative Example 3, the lack of a dispersant significantly reduced the release efficiency and stability.

[0049] The above results indicate that the polyacid compound and ionic liquid composite system can effectively leverage their synergistic anti-corrosion properties. The redox properties of the polyacid compound can induce the formation of a dense oxide passivation film on the metal surface, thereby blocking the corrosion of the metal by the corrosive medium. The imidazole-based ionic liquid can utilize the π electrons on its cationic moiety (imidazolium) to form coordinate bonds with the empty d orbitals of the metal, thus chemically adsorbing onto the metal surface. Furthermore, the alkane groups in the ionic liquid can adsorb onto the metal surface, forming a hydrophobic organic adsorption film that inhibits anodic dissolution, effectively isolating the corrosive ions in the crude oil aqueous medium from corrosive effects on the metal pipeline. Moreover, the polyacid compound exhibits excellent acid resistance and a small size (approximately 1 nm). Under acidic conditions, after forming a double protective film with the ionic liquid, it can effectively fill the microscopic defects on the adsorption film surface, thereby reducing the sites that induce metal corrosion. This not only provides good acid resistance but also delays metal corrosion. Therefore, the polyacid compound and ionic liquid composite system can effectively meet the anti-corrosion requirements of crude oil pipelines and has promising application prospects.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A corrosion inhibitor chemical, characterized in that, By weight percentage, it includes the following components: 5-25% polyacid compounds, 55-80% ionic liquids, 5-15% dispersants, and 2-8% stabilizers.

2. The corrosion inhibitor according to claim 1, characterized in that, The polyacid compound is a Keggin-type heteropolyacid, selected from one or more of phosphomolybdic acid, silicotungstic acid, phosphomolybdic acid, and silicotungstic acid.

3. The corrosion inhibitor according to claim 1, characterized in that, The ionic liquid is an imidazole-type ionic liquid, selected from one or more of 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-dodecyl-3-methylimidazolium tetrafluoroborate, and 1-hexadecyl-2,3-dimethylimidazolium hexafluorophosphate, or a mixture thereof.

4. The corrosion inhibitor according to claim 1, characterized in that, The dispersant is one or a mixture of polyethylene glycol 600, Tween 80, and Span 80.

5. The corrosion inhibitor according to claim 1, characterized in that, The stabilizer is one or a mixture of sodium sulfite, disodium EDTA, and citric acid.

6. The corrosion inhibitor according to claim 1 or 2, characterized in that, The polyacid compound is a mixture of molybdenum-based polyacid and tungsten-based polyacid in a weight ratio of 1:1-3.

7. The corrosion inhibitor according to claim 1 or 3, characterized in that, The ionic liquid is a mixture of 1-dodecyl-3-methylimidazolium tetrafluoroborate and 1-hexadecyl-2,3-dimethylimidazolium hexafluorophosphate in a weight ratio of 2:1, or the ionic liquid is a mixture of 1-hexyl-3-methylimidazolium hexafluorophosphate and 1-dodecyl-3-methylimidazolium tetrafluoroborate in a weight ratio of 2:

1.

8. A method for preparing a corrosion inhibitory chemical as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Weigh out the polyacid compound, ionic liquid, dispersant, and stabilizer by weight percentage and set aside. S2. Add the ionic liquid to the reaction vessel, and under an inert atmosphere, heat it to 40-70℃ and stir it at a rate of 200-300 r / min for 10-20 min. S3. Add the polyacid compound to the ionic liquid in step S2, and continue stirring at 40-70℃ and 200-300 r / min for 30-60 min, while using ultrasonic-assisted dispersion to obtain mixture A; S4. Add the dispersant and stabilizer to mixture A, heat to 50-80℃, and stir at a rate of 300-400 r / min for 40-80 min to ensure that all components are fully mixed and homogeneous, thus obtaining mixture B. S5. Cool the mixture B obtained in step S4 to room temperature and let it stand for 10-20 minutes to obtain the corrosion inhibitor.

9. The method for preparing the corrosion inhibitor chemical according to claim 8, characterized in that, In step S2, the inert atmosphere is nitrogen or argon, and the heating rate is 2-5 °C / min.

10. The method for preparing the corrosion inhibitor chemical according to claim 8, characterized in that, In step S3, the addition rate of the polyacid compound is 0.5-1 g / min; the power of the ultrasonic-assisted dispersion is 200-300 W, and the time is 15-25 min.

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