Corrosion inhibitor capable of resisting carbon dioxide corrosion as well as preparation method and application of corrosion inhibitor

Abstract

The invention provides a corrosion inhibitor capable of resisting carbon dioxide corrosion as well as a preparation method and application thereof, and relates to the technical field of corrosion protection of oil and gas fields. The invention provides a corrosion inhibitor which is prepared from the following raw materials: alpha-lipoic acid, diethylenetriamine, formaldehyde, 2-acetophenone and benzyl chloride in a molar ratio of (1.0 to 1.2) to (0.8 to 1.2) to (1.2 to 2.0) to (1.0 to 1.4) to (1.0 to 1.4). The preparation method comprises the following steps: taking raw materials according to a molar ratio, mixing the alpha-lipoic acid and the diethylenetriamine, and reacting to obtain a first product; mixing formaldehyde, 2-acetophenone and the first product, and reacting to obtain a second product; and mixing benzyl chloride and the second product, and reacting to obtain the finished product corrosion inhibitor. The invention also provides application of the corrosion inhibitor in prevention of carbon dioxide corrosion. The corrosion inhibitor is good in corrosion inhibition effect, simple in preparation method, stable in structure and still excellent in corrosion inhibition effect in a high-salinity environment.

Description

Technical Field

[0001] This invention relates to the field of corrosion protection technology for oil and gas fields, and in particular to a corrosion inhibitor for carbon dioxide corrosion, its preparation method and application. Background Technology

[0002] CO2 enhanced oil recovery technology is widely used in oil and gas field development. After CO2 is injected into the reservoir, it can expand the volume of crude oil, reduce crude oil viscosity, reduce oil-water interfacial tension, and reduce capillary pressure, thereby improving crude oil recovery rate.

[0003] However, in the oil and gas extraction process, the surface and underground equipment used are primarily made of metal. CO2, when dissolved in formation water, can cause corrosion and perforation of oil pipes and mechanical equipment failure. Furthermore, at the same pH level, carbonic acid has a higher total acidity than hydrochloric acid, making it more corrosive to oil well pipes and surface gathering and transportation systems. This can lead to significant economic losses and safety accidents.

[0004] In actual production and transportation, CO2 corrosion protection is often achieved through methods such as proper material selection, coatings, plating, process improvement, and the addition of corrosion inhibitors. Equipment made with corrosion-resistant materials or coatings is prohibitively expensive, significantly increasing operating costs during oil extraction.

[0005] Therefore, adding corrosion inhibitors during the injection-extraction process can form one or more protective films on the metal surface, blocking the contact between acid and metal, reducing the corrosion rate, and protecting the metal material. Currently, corrosion inhibitors used for carbon dioxide corrosion mainly include imidazoline, Mannich base, and pyridine inhibitors. However, these inhibitors still need improvement in terms of performance and stability, especially since their effectiveness decreases significantly in high-salinity environments. Summary of the Invention

[0006] The purpose of this invention is to address the problem that existing corrosion inhibitors for carbon dioxide corrosion are not stable enough, and their corrosion inhibition effect decreases significantly in high-salinity environments. The aim is to provide a corrosion inhibitor that effectively resists carbon dioxide corrosion and maintains superior corrosion inhibition performance in high-salinity environments, along with its preparation method and applications. The corrosion inhibitor provided by this invention has a stable structure, good corrosion inhibition effect, a simple preparation method, and a corrosion inhibition rate >80%.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: Firstly, in a first aspect, the present invention provides a corrosion inhibitor for resisting carbon dioxide corrosion, wherein the raw materials of the corrosion inhibitor include α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride; The molar ratio of α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride is 1.0~1.2:0.8~1.2:1.2~2.0:1.0~1.4:1.0~1.4.

[0008] Secondly, in a second aspect, the present invention provides a method for preparing the corrosion inhibitor as described above, comprising the following steps: S1. Take the raw materials in molar ratio, mix α-lipoic acid and diethylenetriamine, and react to obtain the first product; S2. Formaldehyde, 2-naphthyl ethyl ketone, and the first product are mixed and reacted to give the second product. S3. Mix benzyl chloride and the second product, and react to obtain the finished corrosion inhibitor.

[0009] Furthermore, in step S1, the reaction includes reacting at 140~160℃ for 2~5 hours, and then reacting at 190~210℃ for 2~5 hours.

[0010] Furthermore, in step S1, xylene is used as a water-carrying agent and the reaction is carried out in a nitrogen atmosphere.

[0011] Furthermore, in step S2, the reaction temperature is 60~90℃ and the reaction time is 3~8h.

[0012] Furthermore, in step S2, ethanol is used as the solvent during mixing.

[0013] Furthermore, in step S3, the reaction temperature is 90~110℃ and the reaction time is 2~6h.

[0014] Furthermore, step S3 also includes vacuum drying after the reaction.

[0015] Furthermore, the vacuum drying process is carried out at a temperature of 70-90°C for 0.5-1 hour.

[0016] Furthermore, in a third aspect, the present invention also provides the application of the corrosion inhibitor described above in preventing carbon dioxide corrosion.

[0017] The beneficial effects of this invention compared to the prior art are as follows: 1. The present invention provides a corrosion inhibitor for resisting carbon dioxide corrosion. First, diethylenetriamine is selected as a raw material to prepare the corrosion inhibitor, enabling the inhibitor molecules to form imidazoline rings, thereby adsorbing onto the metal surface. Further, α-lipoic acid monomer is introduced to enhance the hydrophobicity of the corrosion inhibitor, and the introduction of sulfur further enhances the adsorption capacity of the corrosion inhibitor molecules. Simultaneously, the addition of 2-naphthyl ethylone monomer, with its naphthalene ring, further enhances the hydrophobic properties of the corrosion inhibitor molecules, increasing the coverage area of ​​the corrosion inhibitor and further enhancing its corrosion inhibition performance. The introduction of benzyl chloride monomer modifies the corrosion inhibitor molecules, enhancing the water solubility, film-forming properties, and corrosion inhibition performance of the corrosion inhibitor, further achieving the purpose of slowing down corrosion.

[0018] The corrosion inhibitor of this invention has the following structural formula: Figure 2 It has an imidazoline Mannich base quaternary ammonium salt structure and contains multiple cyclic structures, therefore the corrosion inhibitor of the present invention has good film-forming properties.

[0019] See further Figure 2 The imidazoline structure of the corrosion inhibitor of the present invention has a nitrogen-containing heterocyclic structure, which can effectively enhance the adsorption of the corrosion inhibitor.

[0020] See also further details Figure 2 The corrosion inhibitor of this invention possesses a Mannich base structure. The amino group (—N—) in the Mannich base molecule forms an electron-rich conjugated system with the benzene ring, coordinating with empty orbitals on the metal surface via lone pairs of electrons to form a robust chemisorption layer. This adsorption layer remains stable even in highly salinized environments, effectively blocking Cl-. - SO4 2- This allows corrosive ions to come into contact with the metal. Therefore, this structure can enhance the corrosion inhibition performance of corrosion inhibitors in highly salinized media.

[0021] In summary, the corrosion inhibitor provided by this invention can effectively resist carbon dioxide corrosion, has stable performance, and still has excellent corrosion inhibition effect in high salinity environments.

[0022] 2. The present invention provides a method for preparing a corrosion inhibitor against carbon dioxide corrosion. The method is relatively simple and easy to apply widely. The preparation method effectively enhances the water solubility, film-forming properties, and corrosion inhibition performance of the corrosion inhibitor through a quaternization reaction, and the corrosion inhibition effect remains excellent even in high salinity environments.

[0023] The prepared corrosion inhibitor exhibits excellent performance. It possesses an imidazoline Mannich base quaternary ammonium salt structure, and the presence of multiple ring structures enhances its film-forming properties. The prepared corrosion inhibitor also has a nitrogen-containing heterocyclic structure, which effectively enhances its adsorption capacity. Furthermore, the prepared corrosion inhibitor's Mannich base structure enhances its corrosion inhibition performance in highly salinized media.

[0024] 3. The corrosion inhibitor against carbon dioxide corrosion provided by this invention has a wide range of applications and strong advantages in preventing corrosion of equipment and / or pipelines containing carbon dioxide. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 Infrared spectrum of a corrosion inhibitor against carbon dioxide corrosion provided by the present invention; Figure 2 The present invention provides a structural formula for a corrosion inhibitor that resists carbon dioxide corrosion. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] Firstly, in a first aspect, the present invention provides a corrosion inhibitor for resisting carbon dioxide corrosion, wherein the raw materials of the corrosion inhibitor include α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride; the molar ratio of α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride is 1.0~1.2:0.8~1.2:1.2~2.0:1.0~1.4:1.0~1.4. The structural formula of the corrosion inhibitor is shown below. Figure 2 .

[0033] The preferred molar ratio of α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride is 1.1:0.9~1.1:1.4~1.8:1.1~1.3:1.1~1.3; more preferably 1.1:1.0:1.5:1.2:1.2.

[0034] It is understood that the corrosion inhibitor of the present invention, using diethylenetriamine as a raw material, enables the inhibitor molecules to form imidazoline rings, allowing them to adsorb onto the steel surface. The introduction of α-lipoic acid monomer enhances the hydrophobicity of the corrosion inhibitor, and the introduction of sulfur further enhances the adsorption capacity of the inhibitor molecules. Simultaneously, the naphthalene ring of the 2-naphthyl ethylone monomer further enhances the hydrophobic properties of the corrosion inhibitor molecules, increasing the coverage area and further strengthening the corrosion inhibition performance. The introduction of benzyl chloride monomer modifies the corrosion inhibitor molecules, enhancing their water solubility, film-forming properties, and corrosion inhibition performance, further achieving the goal of slowing down corrosion.

[0035] See Figure 2 The corrosion inhibitor of the present invention has an imidazoline Mannich base quaternary ammonium salt structure and contains multiple cyclic structures, thus the corrosion inhibitor of the present invention has good film-forming properties.

[0036] See further Figure 2 The imidazoline structure of the corrosion inhibitor of the present invention has a nitrogen-containing heterocyclic structure, which can effectively enhance the adsorption of the corrosion inhibitor.

[0037] See also further details Figure 2 The corrosion inhibitor of this invention possesses a Mannich base structure. The amino group (—N—) in the Mannich base molecule forms an electron-rich conjugated system with the benzene ring, coordinating with empty orbitals on the metal surface via lone pairs of electrons to form a robust chemisorption layer. This adsorption layer remains stable even in highly salinized environments, effectively blocking Cl-. - SO4 2- This allows corrosive ions to come into contact with the metal. Therefore, this structure can enhance the corrosion inhibition performance of corrosion inhibitors in highly salinized media.

[0038] Secondly, in a second aspect, the present invention provides a method for preparing the corrosion inhibitor as described above, comprising the following steps: S1. Take the raw materials in molar ratio, mix α-lipoic acid and diethylenetriamine, and react to obtain the first product; S2. Formaldehyde, 2-naphthyl ethyl ketone, and the first product are mixed and reacted to give the second product. S3. Mix benzyl chloride and the second product, and react to obtain the finished corrosion inhibitor.

[0039] It is understood that the preparation method of the carbon dioxide corrosion inhibitor provided by this invention is relatively simple and easy to apply widely. The preparation method effectively enhances the water solubility, film-forming properties, and corrosion inhibition performance of the inhibitor through a quaternization reaction. The prepared inhibitor exhibits excellent performance; it possesses an imidazoline Mannich base quaternary ammonium salt structure, and the presence of multiple ring structures enhances its film-forming properties; the nitrogen-containing heterocyclic structure effectively enhances its adsorption capacity; and the Mannich base structure enhances its corrosion inhibition performance in highly salinized media.

[0040] In some embodiments of the present invention, in step S1, the molar ratio of α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride is 1.0~1.2:0.8~1.2:1.2~2.0:1.0~1.4:1.0~1.4.

[0041] The preferred molar ratio of α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride is 1.1:0.9~1.1:1.4~1.8:1.1~1.3:1.1~1.3; more preferably 1.1:1.0:1.5:1.2:1.2.

[0042] In some embodiments of the present invention, step S1 includes reacting at 140-160°C for 2-5 hours, and then reacting at 190-210°C for 2-5 hours.

[0043] In step S1, the reaction is further preferably carried out by reacting at 145~155℃ for 3~4 hours, and then at 195~205℃ for 3~4 hours.

[0044] Furthermore, preferably, the reaction is carried out at 150°C for 3.5 hours first, and then at 200°C for 3.5 hours.

[0045] In some embodiments of the present invention, in step S1, xylene is used as a water-carrying agent and the reaction is carried out in a nitrogen atmosphere.

[0046] In some embodiments of the present invention, step S1 is used to prepare an imidazoline ring structure.

[0047] In some embodiments of the present invention, in step S2, the reaction temperature is 60~90°C and the reaction time is 3~8h.

[0048] In step S2, the reaction is preferably carried out at a temperature of 65~80℃, and more preferably at 70℃. In step S2, the reaction time is preferably 3-8 hours, more preferably 4-6 hours, and even more preferably 5 hours.

[0049] In some embodiments of the present invention, ethanol is used as a solvent during step S2.

[0050] In some embodiments of the present invention, step S2 is a Mannich base reaction.

[0051] In some embodiments of the present invention, in step S3, the reaction temperature is 90~110℃ and the reaction time is 2~6h.

[0052] In step S3, the reaction is a quaternization reaction.

[0053] In step S3, the reaction temperature is further preferably 95~105℃, and even more preferably 100℃.

[0054] In step S3, the reaction time is further preferably 3-5 hours, and even more preferably 4 hours.

[0055] In some embodiments of the present invention, step S3 further includes vacuum drying after the reaction.

[0056] In some embodiments of the present invention, the vacuum drying process is carried out at a temperature of 70-90°C for 0.5-1 hour.

[0057] The processing temperature for the vacuum drying treatment is further preferably 75~85℃, and even more preferably 80℃. The processing time for the vacuum drying treatment is further preferably 0.6~0.8h, and even more preferably 0.7h.

[0058] Furthermore, in a third aspect, the present invention also provides the application of the corrosion inhibitor described above in preventing carbon dioxide corrosion.

[0059] It is understood that the application of the corrosion inhibitor against carbon dioxide corrosion provided by this invention has a wide range of applications and strong advantages in preventing corrosion of equipment and / or pipelines containing carbon dioxide.

[0060] Example 1 A corrosion inhibitor resistant to carbon dioxide corrosion is composed of the following raw material components: α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride in a molar ratio of 1.1:1.0:1.5:1.2:1.2.

[0061] Example 2 A corrosion inhibitor resistant to carbon dioxide corrosion is composed of the following raw material components: α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride in a molar ratio of 1.0:1.2:1.2:1.4:1.0.

[0062] Example 3 A corrosion inhibitor resistant to carbon dioxide corrosion is composed of the following raw material components: α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride in a molar ratio of 1.2:0.8:2.0:1.0:1.4.

[0063] Example 4 A method for preparing a corrosion inhibitor resistant to carbon dioxide corrosion, comprising the following steps: (1) Dissolve 5.16g α-lipoic acid and 2.58g diethylenetriamine in a three-necked flask, add 40ml xylene as a water-carrying agent, and react at 150℃ for 2h in a nitrogen atmosphere, then react at 200℃ for 2h to remove xylene and obtain the first product. (2) Add the first product to a three-necked flask, add 30 ml of ethanol to dissolve it, add 1.50 g of formaldehyde and 5.11 g of 2-naphthyl ethyl ketone, and continue the reaction at 70 °C for 5 h to obtain the second product; (3) Mix 3.80g of benzyl chloride with the second product, quaternize at 100℃ for 3h, transfer to a vacuum oven, and vacuum dry at 80℃ for 0.5h to obtain corrosion inhibitor 1.

[0064] Example 5 A method for preparing a corrosion inhibitor resistant to carbon dioxide corrosion, comprising the following steps: (1) Dissolve 5.16g α-lipoic acid and 3.10g diethylenetriamine in a three-necked flask, add 40ml xylene as a water-carrying agent, and react at 150℃ for 2h in a nitrogen atmosphere, then react at 200℃ for 2h to remove xylene and obtain the first product. (2) Add the first product to a three-necked flask, add 30 ml of ethanol to dissolve it, add 1.50 g of formaldehyde and 5.11 g of 2-naphthyl ethyl ketone, and continue the reaction at 70 °C for 5 h to obtain the second product; (3) Mix 3.80g of benzyl chloride with the second product, quaternize at 100℃ for 3h, transfer to a vacuum oven, and vacuum dry at 80℃ for 0.5h to obtain corrosion inhibitor 2.

[0065] Example 6 A method for preparing a corrosion inhibitor resistant to carbon dioxide corrosion, comprising the following steps: (1) Dissolve 5.16g α-lipoic acid and 2.58g diethylenetriamine in a three-necked flask, add 40ml xylene as a water-carrying agent, and react at 150℃ for 2h in a nitrogen atmosphere, then react at 200℃ for 2h to remove xylene and obtain the first product. (2) Add the first product to a three-necked flask, add 30 ml of ethanol to dissolve it, add 1.50 g of formaldehyde and 4.26 g of 2-naphthyl ethyl ketone, and continue the reaction at 70 °C for 5 h to obtain the second product; (3) Mix 3.80g of benzyl chloride with the second product, quaternize at 100℃ for 3h, transfer to a vacuum oven, and vacuum dry at 80℃ for 0.5h to obtain corrosion inhibitor 3.

[0066] Example 7 A method for preparing a corrosion inhibitor resistant to carbon dioxide corrosion, comprising the following steps: (1) Dissolve 5.16g α-lipoic acid and 3.10g diethylenetriamine in a three-necked flask, add 40ml xylene as a water-carrying agent, and react at 150℃ for 2h in a nitrogen atmosphere, then react at 200℃ for 2h to remove xylene and obtain the first product. (2) Add the first product to a three-necked flask, add 30 ml of ethanol to dissolve it, add 1.50 g of formaldehyde and 4.26 g of 2-naphthyl ethyl ketone, and continue the reaction at 70 °C for 5 h to obtain the second product; (3) Mix 3.80g of benzyl chloride with the second product, quaternize at 100℃ for 3h, transfer to a vacuum oven, and vacuum dry at 80℃ for 0.5h to obtain corrosion inhibitor 4.

[0067] Example 8 A method for preparing a corrosion inhibitor resistant to carbon dioxide corrosion, comprising the following steps: (1) Dissolve 5.16g α-lipoic acid and 3.10g diethylenetriamine in a three-necked flask, add 40ml xylene as a water-carrying agent, and react at 150℃ for 2h in a nitrogen atmosphere, then react at 200℃ for 2h to remove xylene and obtain the first product. (2) Add the first product to a three-necked flask, add 30 ml of ethanol to dissolve it, add 1.50 g of formaldehyde and 4.26 g of 2-naphthyl ethyl ketone, and continue the reaction at 70 °C for 5 h to obtain the second product; (3) Mix 3.16g of benzyl chloride with the second product, quaternize at 100℃ for 3h, transfer to a vacuum oven, and vacuum dry at 80℃ for 0.5h to obtain corrosion inhibitor 5.

[0068] Example 9 A method for preparing a corrosion inhibitor resistant to carbon dioxide corrosion, comprising the following steps: (1) Dissolve 5.16g α-lipoic acid and 3.10g diethylenetriamine in a three-necked flask, add 40ml xylene as a water-carrying agent, and react at 150℃ for 2h in a nitrogen atmosphere, then react at 200℃ for 2h to remove xylene and obtain the first product. (2) Add the first product to a three-necked flask, add 30 ml of ethanol to dissolve it, add 0.90 g of formaldehyde and 4.26 g of 2-naphthyl ethyl ketone, and continue the reaction at 70 °C for 5 h to obtain the second product; (3) Mix 3.80g of benzyl chloride with the second product, quaternize at 100℃ for 3h, transfer to a vacuum oven, and vacuum dry at 80℃ for 0.5h to obtain corrosion inhibitor 6.

[0069] Example 10 A method for preparing a corrosion inhibitor resistant to carbon dioxide corrosion, comprising the following steps: (1) Dissolve 5.16g α-lipoic acid and 2.58g diethylenetriamine in a three-necked flask, add 40ml xylene as a water-carrying agent, and react at 150℃ for 2h in a nitrogen atmosphere, then react at 200℃ for 2h to remove xylene and obtain the first product. (2) Add the first product to a three-necked flask, add 30 ml of ethanol to dissolve it, add 0.90 g of formaldehyde and 4.26 g of 2-naphthyl ethyl ketone, and continue the reaction at 70 °C for 5 h to obtain the second product; (3) Mix 3.80g of benzyl chloride with the second product, quaternize at 100℃ for 3h, transfer to a vacuum oven, and vacuum dry at 80℃ for 0.5h to obtain corrosion inhibitor 7.

[0070] Experimental Example 1 1.1 Experimental Design The corrosion inhibitors prepared in Examples 4 to 10 were used as samples, and the corrosion inhibition performance of each group of samples was measured. A blank control was set up: no corrosion inhibitor was added.

[0071] The specific experimental procedure is as follows: The test medium was self-prepared simulated water, and the content of each component of the simulated water is shown in Table 1.

[0072] Prepare simulated water according to Table 1, and introduce carbon dioxide until saturated to obtain simulated water; use N80 steel sheet for the test piece with external dimensions of 50mm×10mm×3mm; use a 1L volumetric flask for the test container.

[0073] First, wipe the test piece clean with filter paper, then place it in petroleum ether with a boiling range of 60°C. After removing the surface grease with degreased cotton, immerse it in anhydrous ethanol for about 5 minutes for further degreasing and dehydration. Remove the test piece, place it on filter paper, dry it with cold air, then wrap it in filter paper and store it in a desiccator. After 1 hour, measure the size and weigh it, accurate to 0.1 mg.

[0074] Add the prepared corrosion inhibitor solution to the test container using a pipette according to the designed mass concentration value.

[0075] Purge the test container with nitrogen to remove air. Then, use rubber tubing to introduce the test medium into the container. During introduction, the rubber tubing should be inserted below the liquid surface and flush against the container wall to prevent air from entering. Gradually raise the rubber tubing as the liquid level rises, adding the required volume of test medium. Hang the test pieces in the container and tighten the stopper to seal. Simultaneously perform a blank test without corrosion inhibitor. Hang three test pieces in each container. The test pieces must not contact the container wall, the spacing between them should be at least 1 cm, and the top of the test piece should be at least 3 cm above the liquid surface.

[0076] Place the test apparatus in a water bath and keep it at the set temperature for 72 hours. After the test period has ended, remove the test piece, observe and record the surface corrosion state and the adhesion of corrosion products, then immediately rinse off the test medium with clean water and wipe it dry with filter paper.

[0077] Place the test piece in a container of petroleum ether or acetone with a boiling range of 60-90℃. Remove the oil from the surface of the test piece with degreased cotton, then soak it in anhydrous ethanol for 5 minutes for further degreasing and dehydration. Remove the test piece and soak it in the acid cleaning solution prepared according to Appendix A (the standard appendix) for 5 minutes, while gently wiping the corrosion products on the surface of the test piece with a small amount of degreased cotton using tweezers. Remove the test piece from the cleaning solution, rinse off the residual acid with tap water, and immediately immerse the test piece in a sodium hydroxide solution (60 g / L) for 30 seconds, then rinse with tap water, and then soak it in anhydrous ethanol for about 5 minutes, washing and dehydrating twice. Remove the test piece, place it on filter paper, and dry it with cold air. Then wrap the test piece with filter paper, store it in a desiccator, and weigh it after 1 hour, accurate to 0.1 mg. Observe and record the corrosion condition of the test piece surface. Calculate the corrosion rate and corrosion inhibition rate according to Formula I and Formula II.

[0078] , Formula I; , Formula II; In Formula I, r corr The uniform corrosion rate is expressed in mm / year; m represents the mass of the specimen before the test, in g; m t S1 represents the mass of the test specimen after the test, in grams; S2 represents the total area of ​​the test specimen, in centimeters. 2 ρ represents the density of the sample material, in g / cm³. 2 t represents the test time, h.

[0079] In Formula II, η1 represents the corrosion inhibition rate (%), Δm0 represents the mass loss of the test piece in the blank test (g), and Δm1 represents the mass loss of the test piece in the dosing test (g).

[0080] Table 1. Content of various components in simulated water

[0081] 1.2 Test Results The measurement results are shown in Table 2.

[0082] Table 2. Slow-release performance of the corrosion inhibitors prepared in Examples 4 to 10

[0083] 1.3 Results Analysis Referring to the measurement results in Table 2, the corrosion rate of the blank control group was 0.891, while the corrosion inhibitors of the present invention were all below 0.148. The corrosion rates of corrosion inhibitors 1-7 prepared in Examples 4-10 of the present invention were all lower than those of the blank control group. Furthermore, the corrosion inhibition rates of corrosion inhibitors 1-7 of the present invention were all greater than 80%.

[0084] It is evident that the corrosion inhibitor provided by this invention exhibits excellent resistance to carbon dioxide corrosion.

[0085] Experimental Example 2 2.1 Experimental Design The corrosion inhibitor 5 prepared in Example 8 was used as a sample, and its structural composition was determined using an infrared spectrometer.

[0086] 2.2 Test Results The measurement results are as follows Figure 1 As shown.

[0087] 2.3 Results Analysis See Figure 1 According to the test results, the corrosion inhibitor 5 provided by this invention, at 3419 cm⁻¹, -1 The peak at 2931 cm⁻¹ is attributed to the stretching vibration of the NH bond. -1 The peak at 1673 cm⁻¹ is attributed to the asymmetric vibration of CH₂. -1 The peak at 1602 cm⁻¹ is attributed to the stretching vibration of the C=O bond; -1 The peaks at 1359 cm⁻¹ are attributed to the stretching vibrations of the C=N bonds. -1 The peaks at 1280 and 989 cm⁻¹ belong to the bending vibration of the CH₂ bond. -1 The peaks at 700 cm⁻¹ belong to the absorption peaks of the CH bending vibration of the naphthalene ring and the absorption peaks of the SS bond, respectively; -1 The peak at that point is attributed to the out-of-plane bending vibration of the monosubstituted CH ring.

[0088] visible, Figure 1 Infrared results show that the corrosion inhibitor provided by the present invention matches the chemical structure of the expected target product.

[0089] In summary, based on the measurements in Experimental Examples 1 and 2, the corrosion inhibitor provided by this invention possesses a stable chemical structure and excellent resistance to carbon dioxide corrosion. It is evident that the imidazoline ring in the corrosion inhibitor enables it to adsorb onto the steel surface; the presence of the ss ring enhances the hydrophobicity of the inhibitor, and the introduction of S further enhances the adsorption capacity of the inhibitor molecules; simultaneously, the presence of the naphthalene ring further enhances the hydrophobicity of the inhibitor molecules, increasing the inhibitor's coverage area and further strengthening its corrosion inhibition performance; and the modification of the benzyl chloride monomer enhances the water solubility, film-forming properties, and corrosion inhibition performance of the inhibitor, further achieving the goal of slowing down corrosion.

[0090] As can be seen from the above embodiments, the present invention provides a corrosion inhibitor for resisting carbon dioxide corrosion, its preparation method and application. The corrosion inhibitor has the advantages of good corrosion inhibition effect and stable structure, and its corrosion inhibition rate is >80%.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A corrosion inhibitor resistant to carbon dioxide corrosion, characterized in that, The raw materials for the corrosion inhibitor include α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride; The molar ratio of α-lipoic acid, diethylenetriamine, formaldehyde, 2-naphthyl ethyl ketone, and benzyl chloride is 1.0~1.2:0.8~1.2:1.2~2.0:1.0~1.4:1.0~1.

4.

2. A method for preparing the corrosion inhibitor as described in claim 1, characterized in that, Includes the following steps: S1. Take the raw materials in molar ratio, mix α-lipoic acid and diethylenetriamine, and react to obtain the first product; S2. Formaldehyde, 2-naphthyl ethyl ketone, and the first product are mixed and reacted to give the second product. S3. Mix benzyl chloride and the second product, and react to obtain the finished corrosion inhibitor.

3. The preparation method according to claim 2, characterized in that, In step S1, the reaction includes reacting at 140~160℃ for 2~5 hours, and then reacting at 190~210℃ for 2~5 hours.

4. The preparation method according to claim 2, characterized in that, In step S1, xylene is used as a water-carrying agent and the reaction is carried out in a nitrogen atmosphere.

5. The preparation method according to claim 2, characterized in that, In step S2, the reaction temperature is 60~90℃ and the reaction time is 3~8h.

6. The preparation method according to claim 2, characterized in that, In step S2, ethanol is used as the solvent during mixing.

7. The preparation method according to claim 2, characterized in that, In step S3, the reaction temperature is 90~110℃ and the reaction time is 2~6h.

8. The preparation method according to claim 2, characterized in that, Step S3 further includes vacuum drying after the reaction.

9. The preparation method according to claim 8, characterized in that, The vacuum drying process is carried out at a temperature of 70-90°C for 0.5-1 hour.

10. The application of the corrosion inhibitor as described in claim 1 in preventing carbon dioxide corrosion.

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