A carbon dioxide corrosion inhibitor based on mannich base and a preparation method and application thereof

Abstract

The application discloses a kind of carbon dioxide corrosion inhibitor based on mannich base and its preparation method and application, belong to petroleum chemical industry metal material protection technical field.Main agent mannich base is with 3-amino crotonitrile, 3-hydrazine quinoline, phenylacetone, cinnamaldehyde as main, it is prepared by condensation, mannich two-step reaction, its structure is as shown in formula A.The inhibitor includes by mass percentage:mannich base A 30~40%, alkylamine 8~16%, potassium iodide 0.3~0.6%, surfactant 10~20%, organic solvent 30~60%.Mannich base A synthesis is simple, post-treatment is convenient, molecule contains quinoline, pyrazole, carbonyl, double bond, phenyl functional group simultaneously, can be well adsorbed on carbon steel surface and form dense protective film to prevent the invasion of corrosive medium.Add alkylamine, potassium iodide, surfactant, organic solvent, water solubility increases after compounding, corrosion inhibition effect is enhanced.The corrosion inhibitor has the characteristics such as small amount, high efficiency, wide application range, and has wide application prospect in oil and gas production.

Description

Technical Field

[0001] This invention belongs to the field of petrochemical metal material protection technology, specifically relating to a carbon dioxide corrosion inhibitor based on Mannich base, its preparation method, and its application. Background Technology

[0002] Carbon steel, with its high mechanical strength and low cost, is a key engineering material in the oil and gas pipeline industry. In oil and gas extraction, carbon dioxide is a common associated corrosive gas and can also be used as an oil displacement additive to improve oil recovery. This leads to a surge in carbon dioxide levels in formation water and produced water. Carbon dioxide dissolves in water to form carbonic acid, causing severe electrochemical corrosion of carbon steel. The corrosion is exacerbated when the solution contains chloride ions or organic acids.

[0003] Adding corrosion inhibitors is one of the most common methods to suppress corrosion of oil and gas metal pipelines, offering advantages such as speed, efficiency, and ease of operation. Imidazolium derivatives can adsorb onto carbon steel surfaces through strong coordination or non-covalent interactions, forming a protective barrier to slow corrosion and are currently the most widely used carbon dioxide corrosion inhibitors. However, imidazoline cationic surfactants form numerous micro-anodic zones on carbon steel surfaces, exacerbating localized corrosion and creating pitting. Furthermore, the corrosion inhibition effect of imidazoline corrosion inhibitors decreases rapidly under medium- and high-temperature conditions, limiting their application range. The presence of chloride ions or organic acids in the solution further intensifies corrosion, increasing the safety risks and economic costs of oil and gas extraction. Therefore, researchers have been dedicated to developing more efficient carbon dioxide corrosion inhibitors for complex operating conditions. Introducing amino, heterocyclic, carbonyl, and conjugated segments into the molecular structure can effectively inhibit carbon steel corrosion, but currently, carbon dioxide corrosion inhibitors often have simple molecular structures, frequently containing only one or two of these functional groups, resulting in relatively low corrosion inhibition efficiency. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a carbon dioxide corrosion inhibitor based on Mannich base, its preparation method and application. The main agent molecule contains multiple functional groups, has strong adsorption capacity on the metal matrix surface, good temperature resistance, and is simple and convenient to synthesize. When compounded with alkylamine, potassium iodide, surfactant and organic solvent, its water solubility increases and its effect is enhanced, which can effectively slow down the corrosion rate of carbon steel in carbon dioxide, chloride ion and organic acid media at medium and high temperatures.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] The present invention provides a carbon dioxide corrosion inhibitor based on Mannich base, wherein the carbon dioxide corrosion inhibitor comprises, by mass percentage, 30-40% Mannich base A, 8-16% alkylamine, 0.3-0.6% potassium iodide, 10-20% surfactant, and 30-60% organic solvent.

[0007] Furthermore, the alkylamine is one of rosin amine, octadecylamine, and dodecylamine; the surfactant is one of Triton X-100 and Tween 80; and the organic solvent is one of N,N-dimethylformamide and isopropanol.

[0008] Furthermore, the structural formula of the Mannich base A is as follows:

[0009]

[0010] Furthermore, the method for preparing Mannich base A includes the following steps:

[0011] S11. Mix and stir 3-aminocrotonitrile, 3-hydrazinoquinoline and hydrochloric acid solution to dissolve them, and heat to carry out a condensation reaction to obtain a mixed liquid;

[0012] S12. Pour the mixed liquid into ethyl acetate, wash and combine the organic layers, dry, and distill under reduced pressure to obtain a light brown intermediate;

[0013] S13. Add cinnamaldehyde, anhydrous ethanol, and hydrochloric acid to the intermediate and stir to obtain a homogeneous mixture. Then add acetophenone and heat to carry out the Mannich reaction. After the Mannich reaction is completed, cool and precipitate yellow crystals. Filter under reduced pressure to obtain Mannich base A.

[0014] In a further embodiment of the present invention, in S11, the molar ratio of 3-aminocrotonitrile, 3-hydrazinoquinoline to hydrochloric acid solution is 1:(1.0-1.1):(1.4-1.6).

[0015] In a further step of the present invention, in S11, the reaction temperature of the condensation reaction is 110-130℃; and the reaction time of the condensation reaction is 18-19h.

[0016] In a further step of the present invention, in S13, the molar ratio of 3-aminocrotonitrile, cinnamaldehyde, hydrochloric acid and acetophenone in the intermediate is 1:(0.9-1.1):(0.1-0.15):(1.0-1.1).

[0017] In a further step of the present invention, in S13, the temperature of the Mannich reaction is 90-100°C; and the reaction time of the Mannich reaction is 5-6 hours.

[0018] The present invention provides a method for preparing the carbon dioxide corrosion inhibitor described in any one of the above-mentioned methods, wherein 30-40% Mannich base A, 8-16% alkylamine, 0.3-0.6% potassium iodide, 10-20% surfactant and 30-60% organic solvent are taken by mass percentage and stirred evenly at room temperature to obtain the carbon dioxide corrosion inhibitor.

[0019] The application of any one of the carbon dioxide corrosion inhibitors in oil and gas field development.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] This invention provides a carbon dioxide corrosion inhibitor based on Mannich bases. The Mannich base A molecule contains multiple functional groups. In acidic solutions, the quinoline, pyrazole, and secondary amine groups are protonated, which not only improves the dispersibility of the inhibitor molecules in aqueous solutions but also allows them to adsorb onto the metal substrate surface through electrostatic interactions, forming a protective film that prevents corrosive media in the solution from contacting the metal surface, thus protecting the metal material from corrosion. The molecule also contains rigid conjugated structures such as benzene rings and double bonds, which can form coordinate bonds with the metal, increasing the adhesion of the inhibitor molecules to the metal surface. The outermost orbitals of the N and O heteroatoms in the molecule are not fully occupied, allowing them to accept outer electrons from metal elements to form conjugated structures, reducing the metal's tendency to lose electrons. The combined alkylamine, potassium iodide, and Mannich base A have a synergistic effect. The large size of the Mannich base A molecule forms a large pore in the adsorption film, reducing the size gradient between the alkylamine and iodide ions, which can fill pore defects of different sizes, improving the density of the protective film of the corrosion inhibitor.

[0022] The corrosion inhibitor provided by this invention exhibits significant anti-corrosion effects and is suitable for corrosion inhibition of carbon steel under conditions of high temperature and coexistence of chloride ions, organic acids, and carbon dioxide. Introducing multiple functional groups into the same molecular structure can greatly enhance the adsorption capacity of the corrosion inhibitor and improve its corrosion inhibition efficiency.

[0023] This invention synthesizes multiple functional group-modified Mannich base molecules through rational molecular design. The corrosion inhibitor formed by compounding alkylamines, potassium iodide, surfactants, organic solvents and other auxiliaries has good dispersibility, strong temperature resistance and high corrosion inhibition efficiency. The synthesis of Mannich base A is simple, has a high yield and is easy to industrialize. It has broad application prospects in the field of metal corrosion protection under the combined conditions of carbon dioxide, chloride ions and organic acids and in oil and gas field development. Attached Figure Description

[0024] Figure 1 A schematic flowchart of the preparation method of the main agent Mannich base A provided for embodiments of the present invention;

[0025] Figure 2 The synthetic route for Mannich base A of the present invention is shown below. Detailed Implementation

[0026] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0027] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0028] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0029] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0030] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0031] This invention provides a carbon dioxide corrosion inhibitor based on Mannich base, its preparation method, and its application.

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0033] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0034] The first objective of this invention is to provide a carbon dioxide corrosion inhibitor based on Mannich base, comprising, by weight percentage: 30-40% Mannich base A, 8-16% alkylamine, 0.3-0.6% potassium iodide, 10-20% surfactant, and 30-60% organic solvent;

[0035] The alkylamine is one of rosin amine, octadecylamine, and dodecylamine; the surfactant is one of Triton X-100 and Tween 80; and the organic solvent is one of N,N-dimethylformamide and isopropanol.

[0036] The molecular structure and synthetic route of the Mannich base A are shown below:

[0037]

[0038]

[0039] The preparation method of Mannich base A is as follows:

[0040] S11. Add 3-aminocrotonitrile, 1 mol / L hydrochloric acid solution, and 3-hydrazinoquinoline to a round-bottom flask, stir to dissolve, connect an external reflux condenser, heat to 110-130℃, react for 18-19 h, and obtain a reddish-brown mixed liquid. Let it cool to room temperature.

[0041] S12. Pour the above mixed liquid into ethyl acetate, wash three times with deionized water, combine the organic layers, dry with anhydrous sodium sulfate for 10-15 min, and then remove excess solvent by vacuum distillation to obtain a light brown intermediate.

[0042] S13. Transfer the concentrated intermediate to a round-bottom flask, add cinnamaldehyde, anhydrous ethanol, and 1 mol / L hydrochloric acid. Stir the mixture at room temperature for 10-15 min, then slowly add acetophenone. Heat to 90-100℃ and react for 5-6 h. After the reaction is complete, cool to room temperature. Yellow crystals precipitate. Remove excess solvent by vacuum filtration to obtain a yellow solid, which is Mannich base A.

[0043] Specifically, in steps S11 and S12, the amounts of 3-aminocrotonitrile, 3-hydrazinoquinoline, hydrochloric acid solution (step S11), cinnamaldehyde, hydrochloric acid (step S13), and acetophenone, based on 1 mole, are 1.0–1.1 moles, 1.4–1.6 moles, 0.9–1.1 moles, 0.1–0.15 moles, and 1.0–1.1 moles, respectively.

[0044] Specifically, in step S12, the weight ratio of ethyl acetate to 3-aminocrotonitrile is 35:1, and the weight ratio of deionized water to 3-aminocrotonitrile is 70:1. These are added in three portions for extraction and separation.

[0045] The second objective of this invention is to provide a method for preparing a carbon dioxide corrosion inhibitor based on Mannich bases, as follows:

[0046] Weigh out Mannich base A, alkylamine, potassium iodide, surfactant, and organic solvent by mass percentage and stir until homogeneous at room temperature.

[0047] The application of the multifunctional modified Mannich base carbon dioxide corrosion inhibitor in the field of oil and gas field development.

[0048] The corrosion rate of the corrosion inhibitor prepared according to the present invention was determined by means of:

[0049] S21. Simulated water preparation: 90.375g / L NaCl + 2.241g / L KCl + 2.930g / L MgCl2 + 0.425g / L Na2SO4 + 17.309CaCl2 + 0.498g / L NaHCO3 + 0.183g / L CH3COOH.

[0050] S22. Test conditions are as follows: First, polish the oil pipe with a steel sheet (grade N80 or P110) until bright, then remove the protective oil from the surface with anhydrous degreasing cotton in acetone, followed by cleaning and drying with anhydrous ethanol. Measure the length, thickness, and width using vernier calipers, weigh and record the data, and then place the steel sheet into an autoclave. Add the corrosion inhibitor to the prepared simulated aqueous solution, stir evenly, transfer to the autoclave, and seal the lid. First, purge with CO2 gas for 1 hour to remove dissolved oxygen, close the outlet valve, raise the temperature to a specific temperature, then purge with high-purity CO2 and maintain the CO2 partial pressure at 5 MPa. After stabilizing under these conditions for 72 hours, remove the sample, remove the corrosion product film from the sample surface, dry, weigh, and calculate the corrosion rate.

[0051] Corrosion rate calculation method:

[0052]

[0053] In the formula: r c - Corrosion rate, in mm / a; m - Weight of specimen before test, in g; m1 - Weight of specimen after test, in g; S - Specimen area, in cm² 2 ρ – Density of the material, in g / cm³ 3 t – test time, in hours (h).

[0054] The steps for synthesizing Mannich base A are as follows:

[0055] S11. Add 80.04 g of 3-aminocrotonitrile, 1460 mL of 1 mol / L hydrochloric acid solution, and 156.42 g of 3-hydrazinoquinoline to a round-bottom flask, stir to dissolve, connect an external reflux condenser, heat to 120 °C, react for 19 h, and obtain a reddish-brown mixed liquid. Let it cool to room temperature.

[0056] S12. Pour the above mixed liquid into 2400g of ethyl acetate, then add 1860g of deionized water to wash three times, combine the organic layers, dry with 41.12g of anhydrous sodium sulfate for 10min, and then remove excess solvent by vacuum distillation to obtain a light brown intermediate.

[0057] S13. Transfer the concentrated intermediate to a round-bottom flask, add 132.06 g of cinnamaldehyde, 90 mL of anhydrous ethanol, and 98 mL of hydrochloric acid solution (1 mol / L). Stir the mixture at room temperature for 15 min, then slowly add 123.64 g of acetophenone. Heat to 90 °C and react for 6 h. After the reaction is complete, cool to room temperature. Yellow crystals precipitate. Remove excess solvent by vacuum filtration to obtain a yellow solid, which is Mannich base A. The two-step yield is 85%.

[0058] High-resolution mass spectrometry (HRMS) (ESI): Measurements were performed using a Bruker Solarix XR Fourier transform mass spectrometer in positive ion mode.

[0059] HRMS (ESI) results for Mannich base A: C 30 H 27 N4O[M+H] + The theoretical value is 458.21, while the actual value is 458.22.

[0060] The method for using carbon dioxide corrosion inhibitors with multifunctional modified Mannich bases as the main agent is to add the corrosion inhibitor to the simulated corrosive medium solution and stir evenly. The amount of corrosion inhibitor added accounts for 1-3% of the mass fraction of the mixture.

[0061] Example 1

[0062] Weigh out 30.15g of Mannich base A, 15.93g of rosin amine, 0.60g of potassium iodide, 10.11g of surfactant Triton X-100, and 43.21g of N,N-dimethylformamide, mix and stir until homogeneous to obtain the corrosion inhibitor. The amount of corrosion inhibitor added is 2% by weight, the test temperature is 60℃, the test steel sheet is N80, and other test conditions are as described in steps S21 and S22.

[0063] Example 2

[0064] Weigh out 34.97g of Mannich base A, 12.12g of rosin amine, 0.45g of potassium iodide, 14.95g of surfactant Triton X-100, and 37.51g of N,N-dimethylformamide, mix and stir until homogeneous to obtain the corrosion inhibitor. The amount of corrosion inhibitor added is 2% by weight, the test temperature is 60℃, the test steel sheet is N80, and other test conditions are as described in steps S21 and S22.

[0065] Example 3

[0066] Weigh 35.10g of Mannich base A, 12.04g of rosin amine, 0.45g of potassium iodide, 15.13g of surfactant Tween 80, and 37.28g of isopropanol, mix and stir thoroughly to obtain the corrosion inhibitor. The amount of corrosion inhibitor added is 2% by weight, the test temperature is 60℃, the test steel sheet is N80, and other test conditions are as described in steps S21 and S22.

[0067] Example 4

[0068] Weigh out 39.98g of Mannich base A, 8.05g of rosin amine, 0.31g of potassium iodide, 19.97g of surfactant Tween 80, and 31.69g of isopropanol, mix and stir thoroughly to obtain the corrosion inhibitor. The amount of corrosion inhibitor added is 2% by weight, the test temperature is 60℃, the test steel sheet is N80, and other test conditions are as described in steps S21 and S22.

[0069] Example 5

[0070] Weigh 40.11g of Mannich base A, 8.07g of octadecylamine, 0.31g of potassium iodide, 20.01g of surfactant Tween 80, and 31.50g of isopropanol, mix and stir thoroughly to obtain the corrosion inhibitor. The amount of corrosion inhibitor added is 2% by weight, the test temperature is 60℃, the test steel sheet is N80, and other test conditions are as described in steps S21 and S22.

[0071] Example 6

[0072] Weigh out 39.98g of Mannich base A, 7.95g of dodecylamine, 0.30g of potassium iodide, 19.94g of surfactant Tween 80, and 31.83g of isopropanol, mix them thoroughly to obtain the corrosion inhibitor. The amount of corrosion inhibitor added is 2% by weight, the test temperature is 60℃, the test steel sheet is N80, and the other test conditions are the same as in steps S21 and S22.

[0073] The composition of each corrosion inhibitor in Examples 1-6 is summarized in Table 1, and the corrosion rates measured in Examples 1-6 are shown in Table 2.

[0074] Table 1 Corrosion inhibitor composition and dosage for each implementation case

[0075]

[0076] Table 2 Corrosion rates for each implementation case

[0077]

[0078] The test results from Examples 1 to 6 show that the developed corrosion inhibitor with multifunctional Mannich base A as the main agent exhibits excellent corrosion inhibition performance under conditions containing chloride ions, organic acids, and carbon dioxide, protecting N80 carbon steel from corrosion. Furthermore, the combination of Mannich base A with rosin amine, potassium iodide, Tween 80, and isopropanol, with a mass percentage close to 40:8:0.3:20:30 (Example 4), shows the best effect, with a corrosion rate as low as 0.0721 mm / a.

[0079] Based on the above embodiments, the protective effect of the corrosion inhibitor on steel sheet samples of different materials at different temperatures was further verified.

[0080] Example 7

[0081] The corrosion inhibitor composition is the same as in Example 4, with the amount of corrosion inhibitor added being 2% by weight. The test temperatures are 60℃, 90℃, 120℃, and 150℃, and the test steel sheet is N80. The other test conditions are the same as in steps S21 and S22.

[0082] The corrosion rates of N80 at different temperatures after adding the corrosion inhibitor provided in this patent are shown in Table 3.

[0083] Table 3 Corrosion rates of N80 specimens at different temperatures

[0084]

[0085] Example 8

[0086] The corrosion inhibitor composition is the same as in Example 4, with the corrosion inhibitor dosage being 2% by weight. The test temperatures are 60℃, 90℃, 120℃, and 150℃, and the test steel sheet is P110. The other test conditions are the same as in steps S21 and S22.

[0087] The corrosion rates of P110 at different temperatures after adding the corrosion inhibitor provided by this invention are shown in Table 4.

[0088] Table 4 Corrosion rates of P110 specimens at different temperatures

[0089]

[0090] As can be seen from Examples 7 and 8, the corrosion inhibitor provided by the present invention has good temperature resistance. Even at temperatures as high as 150°C, it can still effectively protect N80 and P110 steel sheets from corrosion.

[0091] This invention discloses a method for preparing a carbon dioxide corrosion inhibitor based on Mannich bases and its application. The main agent, Mannich base, is prepared from 3-aminocrotonitrile, 3-hydrazinoquinoline, acetophenone, and cinnamaldehyde as primary raw materials through a two-step reaction involving condensation and Mannich reaction, and its structure is shown in Formula A.

[0092]

[0093] Example 9

[0094] The steps for synthesizing Mannich base A are as follows:

[0095] S11. Add 80.10g of 3-aminocrotonitrile, 1466mL of 1 mol / L hydrochloric acid solution, and 174.99g of 3-hydrazinoquinoline to a round-bottom flask, stir to dissolve, connect an external reflux condenser, heat to 110℃, react for 18h, and obtain a reddish-brown mixed liquid. Let it cool to room temperature.

[0096] S12. Pour the above mixed liquid into 2450g of ethyl acetate, then add 1800g of deionized water to wash three times, combine the organic layers, dry with 41.21g of anhydrous sodium sulfate for 10min, and then remove excess solvent by vacuum distillation to obtain a light brown intermediate.

[0097] S13. Transfer the concentrated intermediate to a round-bottom flask, add 118.85 g of cinnamaldehyde, 95 mL of anhydrous ethanol, and 95 mL of 1 mol / L hydrochloric acid solution. Stir the mixture at room temperature for 15 min, then slowly add 132.17 g of acetophenone. Heat to 100 °C and react for 5 h. After the reaction is complete, cool to room temperature. Yellow crystals precipitate. Remove excess solvent by vacuum filtration to obtain a yellow solid, which is Mannich base A. The two-step yield is 80%.

[0098] Example 10

[0099] The steps for synthesizing Mannich base A are as follows:

[0100] S11. Add 80.12g of 3-aminocrotonitrile, 1430mL of 1 mol / L hydrochloric acid solution, and 155.43g of 3-hydrazinoquinoline to a round-bottom flask, stir to dissolve, connect an external reflux condenser, heat to 130℃, react for 19h, and obtain a reddish-brown mixed liquid. Let it cool to room temperature.

[0101] S12. Pour the above mixed liquid into 2500g of ethyl acetate, then add 1800g of deionized water to wash three times, combine the organic layers, dry with 43.32g of anhydrous sodium sulfate for 10min, and then remove excess solvent by vacuum distillation to obtain a light brown intermediate.

[0102] S13. Transfer the concentrated intermediate to a round-bottom flask, add 135.21 g of cinnamaldehyde, 95 mL of anhydrous ethanol, and 95 mL of 1 mol / L hydrochloric acid solution. Stir the mixture at room temperature for 15 min, then slowly add 126.02 g of acetophenone. Heat to 90 °C and react for 6 h. After the reaction is complete, cool to room temperature. Yellow crystals precipitate. Remove excess solvent by vacuum filtration to obtain a yellow solid, which is Mannich base A. The two-step yield is 82%.

[0103] Example 11

[0104] The steps for synthesizing Mannich base A are as follows:

[0105] S11. Add 80.04 g of 3-aminocrotonitrile, 1460 mL of 1 mol / L hydrochloric acid solution, and 156.42 g of 3-hydrazinoquinoline to a round-bottom flask, stir to dissolve, connect an external reflux condenser, heat to 110 °C, react for 18 h, and obtain a reddish-brown mixed liquid. Let it cool to room temperature.

[0106] S12. Pour the above mixed liquid into 2400g of ethyl acetate, then add 1860g of deionized water to wash three times, combine the organic layers, dry with 41.12g of anhydrous sodium sulfate for 10min, and then remove excess solvent by vacuum distillation to obtain a light brown intermediate.

[0107] S13. Transfer the concentrated intermediate to a round-bottom flask, add 195.82 g of cinnamaldehyde, 90 mL of anhydrous ethanol, and 98 mL of 1 mol / L hydrochloric acid solution. Stir the mixture at room temperature for 15 min, then slowly add 123.64 g of acetophenone. Heat to 100 °C and react for 5 h. After the reaction is complete, cool to room temperature. Yellow crystals precipitate. Remove excess solvent by vacuum filtration to obtain a yellow solid, which is Mannich base A. The two-step yield is 85%.

[0108] The Mannich base A provided by this invention is simple to synthesize and easy to post-process. Its molecule simultaneously contains quinoline, pyrazole, carbonyl, double bond, and phenyl functional groups, allowing it to effectively adsorb onto carbon steel surfaces to form a dense protective film and prevent the intrusion of corrosive media. Adding alkylamine, potassium iodide, surfactant, and organic solvent increases its water solubility and enhances its corrosion inhibition effect. This corrosion inhibitor features low dosage, high efficiency, and wide applicability, making it promising for application in oil and gas production and extraction.

[0109] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A carbon dioxide corrosion inhibitor based on Mannich base, characterized in that, The carbon dioxide corrosion inhibitor comprises, by mass percentage, 30-40% Mannich base A, 8-16% alkylamine, 0.3-0.6% potassium iodide, 10-20% surfactant, and 30-60% organic solvent, with the sum of the mass percentages of all components being 100%. The structural formula of Mannich base A is as follows: ； The preparation method of the Mannich base A includes the following steps: S11. Mix and stir 3-aminocrotonitrile, 3-hydrazinoquinoline and hydrochloric acid solution to dissolve them, and heat to carry out a condensation reaction to obtain a mixed liquid; S12. Pour the mixed liquid into ethyl acetate, wash and combine the organic layers, dry, and distill under reduced pressure to obtain a light brown intermediate; S13. Add cinnamaldehyde, anhydrous ethanol, and hydrochloric acid to the intermediate and stir to obtain a homogeneous mixture. Then add acetophenone and heat to carry out the Mannich reaction. After the Mannich reaction is completed, cool and precipitate yellow crystals. Filter under reduced pressure to obtain Mannich base A.

2. The carbon dioxide corrosion inhibitor according to claim 1, characterized in that, The alkylamine is one of rosin amine, octadecylamine, and dodecylamine; the surfactant is one of Triton X-100 and Tween 80; and the organic solvent is one of N,N-dimethylformamide and isopropanol.

3. The carbon dioxide corrosion inhibitor according to claim 1, characterized in that, In S11, the molar ratio of 3-aminocrotonitrile, 3-hydrazinoquinoline to hydrochloric acid solution is 1:(1.0~1.1):(1.4~1.6).

4. The carbon dioxide corrosion inhibitor according to claim 1, characterized in that, In step S11, the reaction temperature of the condensation reaction is 110-130 °C; the reaction time of the condensation reaction is 18-19 h.

5. The carbon dioxide corrosion inhibitor according to claim 1, characterized in that, In S13, the molar ratio of 3-aminocrotonitrile, cinnamaldehyde, hydrochloric acid and acetophenone in the intermediate is 1:(0.9~1.1):(0.1~0.15):(1.0~1.1).

6. The carbon dioxide corrosion inhibitor according to claim 1, characterized in that, In step S13, the temperature of the Mannich reaction is 90-100 °C; the reaction time of the Mannich reaction is 5-6 h.

7. A method for preparing the carbon dioxide corrosion inhibitor according to any one of claims 1 to 6, characterized in that, Take 30-40% Mannich base A, 8-16% alkylamine, 0.3-0.6% potassium iodide, 10-20% surfactant and 30-60% organic solvent by mass percentage, and stir evenly at room temperature to obtain carbon dioxide corrosion inhibitor.

8. The application of the carbon dioxide corrosion inhibitor according to any one of claims 1 to 6 in oil and gas field development.

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