A corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments and its preparation method

Abstract

This invention belongs to the field of anti-corrosion materials technology, specifically relating to a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments and its preparation method. The preparation method of the corrosion inhibitor includes the following steps: mixing an emulsifier and deionized water, heating, adding surface-modified nitrogen-containing carbon dots and stirring, then adding a corrosion inhibitor auxiliary and a corrosion inhibitor synergist and heating and stirring to obtain a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments. The preparation method of the surface-modified nitrogen-containing carbon dots is as follows: first, nitrogen-containing carbon dots are prepared using citric acid and isopropanolamine as raw materials, and then the nitrogen-containing carbon dots are surface-modified using urea to obtain surface-modified nitrogen-containing carbon dots. This invention improves the corrosion inhibition rate of the corrosion inhibitor through the synergistic effect of its components and ensures good low-temperature storage stability, making it suitable for low-temperature, high-pressure carbon dioxide environments.

Description

Technical Field

[0001] This invention belongs to the field of corrosion-resistant materials technology, specifically relating to a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments and its preparation method. Background Technology

[0002] Steel oil pipelines, as core infrastructure for global energy transmission, are constantly exposed to high temperatures, high pressures, multiphase flow, and environments containing carbon dioxide, H2S, and Cl. - In extreme environments with corrosive media, corrosion failure has become a major challenge restricting the sustainable development of the oil and gas industry. In acidic environments, steel materials not only suffer damage themselves but also experience significant impacts on their structure and mechanical strength, resulting in substantial economic losses and resource waste. To effectively prevent steel corrosion, a series of targeted measures have been adopted, such as improving material corrosion resistance, electrochemical protection, surface coating protection, the use of corrosion-resistant alloys, and the addition of corrosion inhibitors. Corrosion inhibitors, due to their excellent availability, high efficiency, and ease of use, have become a widely adopted anti-corrosion method.

[0003] Corrosion inhibitors are chemical substances that, when added in small doses to corrosive media, can effectively mitigate or prevent the corrosion of metals and other materials. They are widely used in various industries such as construction, electrical engineering, aerospace, energy, and transportation. They work by adsorbing onto the surface of metal materials or forming a passivation film, creating an effective barrier layer to inhibit the penetration of corrosive media and achieve corrosion inhibition. Compared to other corrosion prevention methods, such as coatings and electrochemical protection, using corrosion inhibitors is simpler to operate, takes effect faster, and reduces costs. Therefore, corrosion inhibitors are widely used in industrial production and other fields to mitigate corrosion.

[0004] Existing corrosion inhibitors may crystallize or flocculate and precipitate their active ingredients under low-temperature, high-pressure carbon dioxide conditions. Once these phenomena occur, it is difficult to restore uniformity and stability through simple shaking, thus affecting the normal use of the corrosion inhibitor. Chinese patent (publication number CN110093609B) mentions that imidazoline-based corrosion inhibitors synthesized from industrial oleic acid are prone to precipitation and stratification at lower ambient temperatures, such as in winter. Furthermore, as the temperature decreases or storage time at lower temperatures increases, the sediment layer becomes viscous and difficult to flow, increasing the concentration gradient between the upper and lower layers, causing inconvenience to users.

[0005] Chinese patent (publication number CN120924255A) discloses a corrosion inhibitor for oil and gas fields. This inhibitor primarily consists of benzotriazole, polycarboxylic acid, sodium phosphate, polymaleic anhydride, zinc oxide nanoparticles, chitosan, phytic acid, and water. Through the synergistic effect of these multiple components, it significantly improves corrosion inhibition performance and stability. Its unique composition allows it to form a stable protective film under high temperature and pressure conditions, effectively preventing metal corrosion and significantly improving the long-term stability of the inhibitor. This provides a safer and more durable protection solution for oil and gas field equipment. However, research on the effectiveness of this technology under low-temperature, high-pressure carbon dioxide environments is lacking, and there is room for further improvement in the corrosion inhibition rate.

[0006] Therefore, how to modify the components of corrosion inhibitors and improve their corrosion inhibition rate through synergistic effects of the components, while ensuring good low-temperature storage stability so that they can be used in low-temperature, high-pressure carbon dioxide environments, has become a direction that needs to be studied. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments and its preparation method. The invention first prepares nitrogen-containing carbon dots using citric acid and isopropanolamine as raw materials, then uses urea to perform surface modification treatment on the nitrogen-containing carbon dots to obtain surface-modified nitrogen-containing carbon dots. These surface-modified nitrogen-containing carbon dots are used as the main corrosion inhibitor, modified imidazoline as an auxiliary corrosion inhibitor, and methylbutynol and propynol propoxylated derivatives as corrosion inhibitor synergists. Combined with the effects of emulsifiers and deionized water, this ensures the corrosion inhibitor can be stably stored at low temperatures while simultaneously improving the corrosion inhibition rate, making it suitable for low-temperature, high-pressure carbon dioxide environments.

[0008] In a first aspect, the present invention provides a method for preparing a corrosion inhibitor suitable for a low-temperature, high-pressure carbon dioxide environment, comprising the following steps: mixing an emulsifier and deionized water, heating and adding nitrogen-containing carbon dots to the surface-modified mixture, stirring and mixing, and then adding a corrosion inhibitor and a corrosion inhibitor synergist for heating and stirring to obtain a corrosion inhibitor suitable for a low-temperature, high-pressure carbon dioxide environment.

[0009] As a preferred embodiment of the present invention, each component comprises, by weight: 40-50 parts of surface-modified nitrogen-containing carbon dots, 16-20 parts of corrosion inhibitor, 8-12 parts of emulsifier, 6-9 parts of corrosion inhibitor synergist, and 60-80 parts of deionized water.

[0010] As a preferred embodiment of the present invention, the weight percentage of the surface-modified nitrogen-containing carbon dots can be 40 parts, 42 parts, 44 parts, 46 parts, 48 ​​parts, or 50 parts, etc.

[0011] As a preferred technical solution of the present invention, the weight parts of the corrosion inhibitor can be 16 parts, 17 parts, 18 parts, 19 parts or 20 parts, etc.

[0012] As a preferred embodiment of the present invention, the emulsifier may be present in parts by weight of 8, 9, 10, 11 or 12, etc.

[0013] As a preferred embodiment of the present invention, the corrosion inhibitor can be present in 6, 7, 8 or 9 parts by weight.

[0014] As a preferred technical solution of the present invention, the weight parts of the deionized water can be 60 parts, 65 parts, 70 parts, 75 parts or 80 parts, etc.

[0015] As a preferred technical solution of the present invention, the method for preparing the surface-modified nitrogen-containing carbon dots is as follows: firstly, nitrogen-containing carbon dots are prepared using citric acid and isopropanolamine as raw materials, and then the nitrogen-containing carbon dots are surface-modified using urea to obtain surface-modified nitrogen-containing carbon dots.

[0016] As a preferred technical solution of the present invention, the preparation steps of the nitrogen-containing carbon dots are as follows: by weight, 4-5 parts of citric acid and 3.5-4.5 parts of isopropanolamine are added to 300-400 parts of N,N-dimethylformamide and stirred evenly. Then, the mixture is transferred to a reaction vessel and heated at 180-190°C for 8-10 hours. After the reaction is completed, the mixture is centrifuged at 8000-9000 r / min for 30-40 minutes. The supernatant is collected, dialyzed, and vacuum dried to obtain nitrogen-containing carbon dots.

[0017] As a preferred technical solution of the present invention, the surface modification treatment step is as follows: by weight, 6-8 parts of urea are added to 100-120 parts of deionized water, then 2-4 parts of the nitrogen-containing carbon dots are added and stirred for 20-30 minutes, heated to 170-180°C for surface modification treatment for 5-7 hours, cooled to room temperature, and ground to obtain surface-modified nitrogen-containing carbon dots.

[0018] In this invention, citric acid undergoes dehydration and carbonization in the high-temperature environment of N,N-dimethylformamide to form a carbon core. The amino and hydroxyl groups of isopropanolamine undergo amidation and other reactions with the carboxyl groups and other groups on the surface of the carbon core, thereby achieving nitrogen doping and surface passivation to obtain nitrogen-containing carbon dots. Subsequently, urea is covalently modified on the surface of the nitrogen-containing carbon dots under high-temperature hydrothermal conditions, ultimately obtaining urea surface-modified nitrogen-containing carbon dots.

[0019] As a preferred embodiment of the present invention, the corrosion inhibitor is a modified imidazoline. As a preferred technical solution of the present invention, the modified imidazoline is prepared by: preparing oleic acid imidazoline from oleic acid and diethylenetriamine as raw materials, and then modifying the oleic acid imidazoline with 1,3,5-trioxane to obtain the modified imidazoline.

[0020] As a preferred technical solution of the present invention, the preparation steps of the oleic acid imidazoline are as follows: by weight, 120-130 parts of oleic acid and 50-60 parts of diethylenetriamine are added to 60-70 parts of xylene, reacted at 170-180°C for 2-4 hours, then heated to 210-220°C and kept at that temperature for 3-5 hours, and then distilled under reduced pressure to obtain oleic acid imidazoline.

[0021] As a preferred embodiment of the present invention, the modification treatment steps are as follows: by weight, 80-100 parts of the oleic acid imidazoline, 8-10 parts of deionized water and 8-10 parts of 1mol / L hydrochloric acid solution are mixed to obtain a mixture; 12-16 parts of 1,3,5-trioxane are added to 50-60 parts of acetophenone and stirred for 20-30 minutes; then added dropwise to the mixture; the temperature is raised to 100-110℃ for modification treatment for 2-4 hours; the mixture is cooled to room temperature; and the mixture is distilled under reduced pressure and recrystallized to obtain the modified imidazoline.

[0022] This invention uses oleic acid and diethylenetriamine as raw materials and employs a two-step heating process to prepare oleic acid imidazoline. First, oleic acid reacts with a primary amino group of diethylenetriamine at 170-180°C to generate an amide. Then, the temperature is raised to 210-220°C to induce the nitrogen atom on the amide to attack the adjacent carbon of another secondary amino group, forming a five-membered ring of imidazoline through intramolecular cyclization and dehydration, thereby obtaining oleic acid imidazoline. Finally, 1,3,5-trioxane is used to hydroxyalkylate the imidazoline to introduce a hydrophilic hydroxymethyl group onto the imidazoline skeleton, thus preparing the modified imidazoline.

[0023] As a preferred embodiment of the present invention, the corrosion inhibitor is methylbutynol and propynol propoxylated derivative.

[0024] As a preferred embodiment of the present invention, the mass ratio of methylbutynol to propynol propoxylated derivative is (1~2):1.

[0025] This invention selects methylbutynol and propynol propoxylated derivatives as compound corrosion inhibitors and achieves good compounding effect by controlling the mass ratio of the two, thereby improving the corrosion inhibition rate and low-temperature storage stability of the corrosion inhibitor system.

[0026] As a preferred embodiment of the present invention, the emulsifier is sodium dodecyl sulfonate or sodium dodecylbenzene sulfonate.

[0027] As a preferred embodiment of the present invention, the heating temperature is 60~70℃; the heating and stirring temperature is 85~95℃, and the stirring time is 50~60min.

[0028] A second aspect of the present invention provides a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments, prepared by the preparation method described in the first aspect.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) The surface-modified nitrogen-containing carbon dots of the present invention can fill the micro-pores and defects on the metal surface caused by corrosion or inhomogeneity, forming an ultra-thin and dense physical isolation film to effectively block the diffusion path of the corrosive medium. Nitrogen doping changes the electronic structure of the carbon dots, which can increase the electron density on the metal surface and inhibit the loss of electrons by metal atoms, thereby slowing down corrosion from the electrochemical root. In addition, the carbon dots can be adsorbed around other corrosion inhibitor molecules, preventing them from agglomerating and precipitating at low temperatures through the steric hindrance effect. The surface modification of urea endows the carbon dots with abundant hydrophilic functional groups, giving them good hydration ability and dispersibility, making them less prone to agglomeration and precipitation due to strong intermolecular forces, thereby significantly improving the storage stability of corrosion inhibitors under low temperature and high pressure carbon dioxide environment.

[0030] (2) The benzene ring introduced by the modified imidazoline of the present invention can interact with the metal surface through π-electron interaction to form a stronger physicochemical adsorption. At the same time, the large side chain makes the molecules more compact when arranged on the surface, forming a thicker physical barrier layer, thereby significantly improving the corrosion inhibition rate. In addition, the benzene ring and branched structure make it difficult for the molecules to be arranged in a regular manner, effectively destroying the molecular symmetry and reducing the tendency to crystallize. The introduced strong polar carbonyl group can greatly improve the solubility of the molecules in the aqueous phase, improve the low-temperature storage stability of the corrosion inhibitor, and enable it to be used in low-temperature and high-pressure carbon dioxide environments.

[0031] (3) In the compound corrosion inhibitor of the present invention, methylbutyninol utilizes its strong chemical adsorption capacity to quickly and firmly occupy the active sites on the metal surface to form the first tight molecular film. The long-chain polyether of propyninol propoxylated derivative can be interwoven laterally to build a loose but large-volume three-dimensional covering layer on the anchoring point formed by methylbutyninol. Through double protection, the integrity and anti-permeability of the corrosion inhibitor film are greatly enhanced, thereby improving the corrosion inhibition rate. At the same time, propyninol propoxylated derivative improves the solubilization capacity of the system for short-chain alkynols, so that it can still maintain uniformity and stability at low temperature and prevent the occurrence of stratification or precipitation. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0033] Figure 1 The infrared spectrum of nitrogen-containing carbon dots on the surface modified in Example 1 of the present invention is shown. Detailed Implementation

[0034] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0035] The sources of some components in the examples and comparative examples are as follows: Citric acid, CAS No. 77-92-9, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Isopropanolamine, CAS No. 78-96-6, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Urea, CAS No. 57-13-6, purchased from Sinopharm Chemical Reagent Co., Ltd. Oleic acid, CAS No. 112-80-1, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Diethylenetriamine, CAS No. 111-40-0, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. 1,3,5-Trioxane, CAS No. 110-88-3, purchased from Sinopharm Chemical Reagent Co., Ltd. Methylbutynol, CAS No. 115-19-5, purchased from Sinopharm Chemical Reagent Co., Ltd. Propylene alcohol propoxylated derivative, model PT-PP-1, was purchased from Wuhan Boli New Materials Co., Ltd. Sodium dodecyl sulfonate, CAS No. 2386-53-0, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Sodium dodecylbenzenesulfonate, CAS No. 25155-30-0, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. The commercially available imidazoline, product number I422098, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Example

[0036] This embodiment provides a method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments, comprising the following steps: mixing 12 parts of emulsifier sodium dodecyl sulfonate and 80 parts of deionized water, heating to 70°C, adding 50 parts of surface-modified nitrogen-containing carbon dots and stirring, then adding 20 parts of corrosion inhibitor modified imidazoline and 9 parts of corrosion inhibitor synergist (6 parts of methylbutynol and 3 parts of propynol propoxylated derivative) and heating and stirring at 95°C for 50 minutes, and naturally cooling to obtain a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments.

[0037] Preparation of the surface-modified nitrogen-containing carbon dots: By weight, 5 parts of citric acid and 4.5 parts of isopropanolamine were added to 400 parts of N,N-dimethylformamide and stirred evenly. Then, the mixture was transferred to a reaction vessel and heated at 190°C for 8 hours. After the reaction was completed, the mixture was centrifuged at 9000 r / min for 30 minutes. The supernatant was collected, dialyzed, and vacuum dried to obtain nitrogen-containing carbon dots. First, 8 parts of urea were added to 120 parts of deionized water, and then 4 parts of the nitrogen-containing carbon dots were added and stirred for 30 minutes. The mixture was heated to 180°C for surface modification treatment for 5 hours. After cooling to room temperature, the mixture was ground to obtain surface-modified nitrogen-containing carbon dots.

[0038] Preparation of the modified imidazoline: 130 parts by weight of oleic acid and 60 parts by weight of diethylenetriamine were added to 70 parts by weight of xylene. The mixture was reacted at 180°C for 2 hours, then heated to 220°C and kept at that temperature for 3 hours. The mixture was then distilled under reduced pressure to obtain oleic acid imidazoline. 100 parts by weight of the oleic acid imidazoline, 10 parts by weight of deionized water and 10 parts by weight of 1 mol / L hydrochloric acid solution were mixed to obtain a mixture. 16 parts by weight of 1,3,5-trioxane were added to 60 parts by weight of acetophenone and stirred for 30 minutes. The mixture was then added dropwise to the mixture. The mixture was heated to 110°C for 2 hours for modification treatment. The mixture was cooled to room temperature, distilled under reduced pressure, and recrystallized to obtain the modified imidazoline. Example

[0039] This embodiment provides a method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments, comprising the following steps: mixing 8 parts of emulsifier sodium dodecylbenzenesulfonate and 60 parts of deionized water, heating to 60°C, adding 40 parts of surface-modified nitrogen-containing carbon dots and stirring, then adding 16 parts of corrosion inhibitor modified imidazoline and 6 parts of corrosion inhibitor synergist (3 parts of methylbutynol and 3 parts of propynol propoxylated derivative) and heating and stirring at 85°C for 60 minutes, and naturally cooling to obtain a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments.

[0040] Preparation of the surface-modified nitrogen-containing carbon dots: By weight, 4 parts of citric acid and 3.5 parts of isopropanolamine were added to 300 parts of N,N-dimethylformamide and stirred evenly. Then, the mixture was transferred to a reaction vessel and heated at 180°C for 10 hours. After the reaction was completed, the mixture was centrifuged at 8000 r / min for 40 minutes. The supernatant was collected, dialyzed, and vacuum dried to obtain nitrogen-containing carbon dots. 6 parts of urea were added to 100 parts of deionized water, and then 2 parts of the nitrogen-containing carbon dots were added and stirred for 20 minutes. The mixture was heated to 170°C for surface modification treatment for 7 hours. After cooling to room temperature, the mixture was ground to obtain surface-modified nitrogen-containing carbon dots.

[0041] Preparation of the modified imidazoline: 120 parts by weight of oleic acid and 50 parts by weight of diethylenetriamine were added to 60 parts by weight of xylene. The mixture was reacted at 170°C for 4 hours, then heated to 210°C and kept at that temperature for 5 hours. The mixture was then distilled under reduced pressure to obtain oleic acid imidazoline. 80 parts by weight of the oleic acid imidazoline, 8 parts by weight of deionized water and 8 parts by weight of 1 mol / L hydrochloric acid solution were mixed to obtain a mixture. 12 parts by weight of 1,3,5-trioxane were added to 50 parts by weight of acetophenone and stirred for 20 minutes. The mixture was then added dropwise to the mixture. The mixture was heated to 100°C for 4 hours for modification treatment. The mixture was cooled to room temperature, distilled under reduced pressure, and recrystallized to obtain the modified imidazoline. Example

[0042] This embodiment provides a method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments, comprising the following steps: mixing 10 parts of emulsifier sodium dodecyl sulfonate and 70 parts of deionized water, heating to 65°C, adding 45 parts of surface-modified nitrogen-containing carbon dots and stirring, then adding 18 parts of corrosion inhibitor modified imidazoline and 8 parts of corrosion inhibitor synergist (5 parts of methylbutynol and 3 parts of propynol propoxylated derivative) and heating and stirring at 88°C for 55 minutes, and naturally cooling to obtain a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments.

[0043] Preparation of the surface-modified nitrogen-containing carbon dots: By weight, 4.5 parts of citric acid and 4.2 parts of isopropanolamine were added to 350 parts of N,N-dimethylformamide and stirred evenly. Then, the mixture was transferred to a reaction vessel and heated at 185°C for 9 hours. After the reaction was completed, the mixture was centrifuged at 8500 r / min for 35 minutes. The supernatant was collected, dialyzed, and vacuum dried to obtain nitrogen-containing carbon dots. First, 7 parts of urea were added to 110 parts of deionized water, and then 3 parts of the nitrogen-containing carbon dots were added and stirred for 25 minutes. The mixture was heated to 175°C for surface modification treatment for 6 hours. After cooling to room temperature, the mixture was ground to obtain surface-modified nitrogen-containing carbon dots.

[0044] Preparation of the modified imidazoline: 125 parts by weight of oleic acid and 55 parts by weight of diethylenetriamine were added to 65 parts by weight of xylene. The mixture was reacted at 175°C for 3 hours, then heated to 215°C and kept at that temperature for 4 hours. The mixture was then distilled under reduced pressure to obtain oleic acid imidazoline. 90 parts by weight of the oleic acid imidazoline, 9 parts by weight of deionized water, and 9 parts by weight of 1 mol / L hydrochloric acid solution were mixed to obtain a mixture. 14 parts by weight of 1,3,5-trioxane were added to 55 parts by weight of acetophenone and stirred for 25 minutes. The mixture was then added dropwise to the mixture. The mixture was heated to 105°C for modification treatment for 3 hours. After cooling to room temperature, the mixture was distilled under reduced pressure and recrystallized to obtain the modified imidazoline.

[0045] Comparative Example 1 The difference between this comparative example and Example 1 is that nitrogen-containing carbon dots are used instead of surface-modified nitrogen-containing carbon dots.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 is that commercially available imidazoline (product number I422098) was used instead of modified imidazoline.

[0047] Comparative Example 3 The difference between this comparative example and Example 1 is that the corrosion inhibitor is replaced entirely with methylbutynol.

[0048] Comparative Example 4 The difference between this comparative example and Example 1 is that the corrosion inhibitor is replaced entirely with propynyl alcohol propoxylated derivatives. The performance of the corrosion inhibitors provided in the above embodiments and comparative examples was tested using the following methods: (1) Corrosion inhibition rate: The test was conducted in accordance with the "SY / T5405-2019 Test method and evaluation index of corrosion inhibitor for acidification". The steel sheet material was Q235, the test temperature was 90℃, the test time was 4h, the amount of corrosion inhibitor added was 0.1% of the acid volume, and the acid was 5wt% hydrochloric acid.

[0049] (2) Low temperature storage stability: The corrosion inhibitors of the examples and comparative examples were stored in a 25% hydrochloric acid solution at -10°C for 48 hours, and it was observed whether stratification, flocculation or precipitation occurred.

[0050] The performance test data above are shown in Table 1.

[0051] Table 1 Performance Test Results Corrosion inhibition rate (%) Low-temperature storage stability (whether stratification, flocculation, or precipitation occurs). Example 1 94.5 no Example 2 93.8 no Example 3 94.1 no Comparative Example 1 85.3 yes Comparative Example 2 86.6 yes Comparative Example 3 89.7 yes Comparative Example 4 89.1 yes As can be seen from the above, the present invention first prepares nitrogen-containing carbon dots using citric acid and isopropanolamine as raw materials, and then uses urea to perform surface modification treatment on the nitrogen-containing carbon dots to obtain surface-modified nitrogen-containing carbon dots. The surface-modified nitrogen-containing carbon dots are used as the main corrosion inhibitor, modified imidazoline is used as the auxiliary corrosion inhibitor, and methylbutynol and propynol propoxylated derivatives are used as corrosion inhibitor synergists. The corrosion inhibitors (Examples 1 to 3) are prepared in combination with emulsifiers and deionized water. The corrosion inhibitors have the best comprehensive performance and can be applied to low-temperature and high-pressure carbon dioxide environments.

[0052] Compared to Example 1, using nitrogen-containing carbon dots instead of surface-modified nitrogen-containing carbon dots resulted in a lack of surface modification effect from urea, leading to a decrease in the corrosion inhibition rate and poorer low-temperature storage stability of the corrosion inhibitor (Comparative Example 1). Compared to Example 1, using commercially available imidazoline (product number I422098) instead of modified imidazoline resulted in a lack of the effect of modified imidazoline, leading to a decrease in the corrosion inhibition rate and poorer low-temperature storage stability of the corrosion inhibitor (Comparative Example 2). Compared to Example 1, replacing the corrosion inhibitor with methylbutynol resulted in a lack of the compounding effect of propynol propoxylated derivatives, leading to a decrease in the corrosion inhibition rate and poorer low-temperature storage stability of the corrosion inhibitor (Comparative Example 3). Compared to Example 1, replacing the corrosion inhibitor with propynol propoxylated derivatives resulted in a lack of the compounding effect of methylbutynol, leading to a decrease in the corrosion inhibition rate and poorer low-temperature storage stability of the corrosion inhibitor (Comparative Example 4).

Claims

1. A method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments, characterized in that, Includes the following steps: The emulsifier and deionized water were mixed evenly, and after heating, nitrogen-containing carbon dots were added to the surface-modified mixture and stirred. Then, corrosion inhibitors and corrosion inhibitors were added and heated and stirred to obtain a corrosion inhibitor suitable for low-temperature and high-pressure carbon dioxide environments. The method for preparing the surface-modified nitrogen-containing carbon dots is as follows: first, nitrogen-containing carbon dots are prepared using citric acid and isopropanolamine as raw materials, and then the nitrogen-containing carbon dots are surface-modified using urea to obtain surface-modified nitrogen-containing carbon dots.

2. The method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments according to claim 1, characterized in that, The components, by weight, include: 40-50 parts of surface-modified nitrogen-containing carbon dots, 16-20 parts of corrosion inhibitor, 8-12 parts of emulsifier, 6-9 parts of corrosion inhibitor synergist, and 60-80 parts of deionized water.

3. The method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments according to claim 1, characterized in that, The preparation steps of the nitrogen-containing carbon dots are as follows: by weight, 4-5 parts of citric acid and 3.5-4.5 parts of isopropanolamine are added to 300-400 parts of N,N-dimethylformamide and stirred evenly. Then, the mixture is transferred to a reaction vessel and heated at 180-190°C for 8-10 hours. After the reaction is completed, the mixture is centrifuged at 8000-9000 r / min for 30-40 minutes. The supernatant is collected, dialyzed, and vacuum dried to obtain nitrogen-containing carbon dots.

4. The method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments according to claim 1, characterized in that, The surface modification treatment steps are as follows: by weight, 6-8 parts of urea are added to 100-120 parts of deionized water, then 2-4 parts of the nitrogen-containing carbon dots are added and stirred for 20-30 minutes. The temperature is raised to 170-180℃ for surface modification treatment for 5-7 hours, cooled to room temperature, and ground to obtain surface-modified nitrogen-containing carbon dots.

5. The method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments according to claim 1, characterized in that, The corrosion inhibitor is a modified imidazoline; The modified imidazoline is prepared by using oleic acid and diethylenetriamine as raw materials to prepare oleic acid imidazoline, and then modifying the oleic acid imidazoline with 1,3,5-trioxane to obtain the modified imidazoline.

6. The method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments according to claim 5, characterized in that, The preparation steps of the oleic acid imidazoline are as follows: by weight, 120-130 parts of oleic acid and 50-60 parts of diethylenetriamine are added to 60-70 parts of xylene, reacted at 170-180℃ for 2-4 hours, then heated to 210-220℃ and kept at that temperature for 3-5 hours, and then distilled under reduced pressure to obtain oleic acid imidazoline.

7. The method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments according to claim 5, characterized in that, The modification process is as follows: by weight, 80-100 parts of the oleic acid imidazoline, 8-10 parts of deionized water and 8-10 parts of 1mol / L hydrochloric acid solution are mixed to obtain a mixture. 12-16 parts of 1,3,5-trioxane are added to 50-60 parts of acetophenone and stirred for 20-30 minutes. Then, the mixture is added dropwise to the mixture. The temperature is raised to 100-110℃ for modification treatment for 2-4 hours. After cooling to room temperature, the mixture is distilled under reduced pressure and recrystallized to obtain the modified imidazoline.

8. The method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments according to claim 1, characterized in that, The corrosion inhibitor is methylbutynol and propynol propoxylated derivative; The mass ratio of methylbutynol to propynol propoxylated derivative is (1~2):

1.

9. The method for preparing a corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments according to claim 1, characterized in that, The emulsifier is sodium dodecyl sulfonate or sodium dodecylbenzene sulfonate.

10. A corrosion inhibitor suitable for low-temperature, high-pressure carbon dioxide environments, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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