Nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor, preparation method and application
By preparing a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor, the problem of poor performance of existing corrosion inhibitors in H2SO4 and H2S media was solved, achieving high-efficiency corrosion protection for oil and gas gathering and transportation pipelines with a corrosion inhibition rate of over 97%.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-09
- Publication Date
- 2026-03-10
AI Technical Summary
Existing corrosion inhibitors are not very effective in H2SO4 and/or H2S media, and are difficult to effectively protect oil and gas gathering and transportation pipelines from corrosion.
A method for preparing nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitors was adopted. Through a three-step heating reaction and a specific solvent system, carbon quantum dot corrosion inhibitors with nitrogen-sulfur co-doped graphene structures were prepared. These inhibitors were used in H2SO4 and H2S media, and their excellent water solubility and surface organic ligand adsorption characteristics were utilized to achieve corrosion inhibition.
It exhibits excellent corrosion inhibition effects in H2SO4 and H2S media, effectively suppressing metal corrosion and achieving corrosion protection for oil and gas gathering and transportation pipelines, with a corrosion inhibition rate of over 97%.
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Figure CN121629403A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of corrosion protection technology for oil and gas gathering and transportation pipelines, specifically to a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor, its preparation method, and its application. Background Technology
[0002] Hydrogen sulfide-containing natural gas reservoirs are a crucial component of global natural gas resources, possessing enormous reserves. During the exploration, production, transportation, and processing of this gas, metal facilities are chronically exposed to corrosive media containing H2S, CO2, inorganic salts, and corrosive well fluids, facing severe corrosion problems. The highly toxic and corrosive H2S not only causes economic damage due to the corrosion of metal facilities but also poses a threat to human life. Therefore, controlling metal corrosion in oil and gas fields is a continuous and crucial need. Appropriate measures must be taken to control corrosion during oil and gas development.
[0003] Corrosion inhibitors are widely used in oil and gas field development to suppress metal corrosion due to their effectiveness, cost-effectiveness, and simple application processes. In recent years, organic corrosion inhibitors have gained popularity due to their excellent performance; however, the synthesis of these organic compounds is complex and they often exhibit high toxicity, making it difficult to meet the requirements of "green chemistry" and sustainable development. Therefore, an increasing number of researchers are focusing on the research of environmentally friendly corrosion inhibitors. Carbon quantum dot corrosion inhibitors have been extensively studied due to their excellent biocompatibility, stability, and low toxicity. Furthermore, their significant fluorescence properties allow for more convenient measurement of their concentration in corrosive media.
[0004] However, although many researchers have successfully synthesized various types of carbon quantum dots using a variety of precursors and conducted extensive research in various industrial applications, they are mostly used in hydrochloric acid environments. Their application in H2SO4 and / or H2S media is not very effective, and existing technologies are relatively scarce for corrosion inhibitors that have good effects in H2SO4 and / or H2S media. Summary of the Invention
[0005] This invention aims to address the technical problem that existing corrosion inhibitors are mostly used in hydrochloric acid environments but have poor performance in H2SO4 and / or H2S media. The purpose is to provide a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor, its preparation method, and its application. This corrosion inhibitor exhibits excellent corrosion inhibition effects in both H2SO4 and H2S media, and can effectively achieve corrosion protection for oil and gas gathering and transportation pipelines.
[0006] This invention is achieved through the following technical solution:
[0007] The first objective of this invention is to provide a method for preparing a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor, wherein the corrosion inhibitor is used in an H2SO4 and / or H2S medium environment, and the method includes the following preparation steps:
[0008] Nitrogen source precursor and sulfur source precursor were added to solvent 1 and solvent 2 in proportion, respectively. After complete dissolution, they were mixed and added to a hydrothermal reactor for a three-step heating reaction to obtain a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor.
[0009] The nitrogen source precursor is at least one of urea and 4-aminosalicylic acid, and the sulfur source precursor is at least one of L-cysteine and thiourea.
[0010] Furthermore, the molar ratio of the nitrogen source precursor to the sulfur source precursor is 1.0-3.0.
[0011] Furthermore, the volume ratio of solvent 1 to solvent 2 is 0.2 to 5.0.
[0012] Furthermore, solvent 1 is at least one of water and ethanol, and solvent 2 is at least one of water and ethanol.
[0013] Furthermore, the three-step heating reaction process is as follows:
[0014] The first step involves heating the reaction at a temperature of 60℃~100℃ for 1 hour.
[0015] The second step involves heating the reaction at a temperature of 140℃ to 180℃ for 4 to 6 hours.
[0016] The third step involves heating the reaction at a temperature of 180℃ to 220℃ for 4 to 16 hours.
[0017] Furthermore, the following steps are included after the three-step heating reaction:
[0018] After cooling the product obtained from the reaction to room temperature, it was filtered using a microporous membrane, and then evaporated and concentrated at 40℃~60℃ until no obvious bubbles were generated. After freeze-drying, a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor was obtained.
[0019] The second objective of this invention is to provide a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor, which is prepared by the aforementioned method.
[0020] Furthermore, the particle size of the corrosion inhibitor is 2–10 nm.
[0021] The third objective of this invention is to provide an application of a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor in the corrosion protection of oil and gas gathering and transportation pipelines.
[0022] Furthermore, the corrosion inhibitor is used to inhibit corrosion of metals in H2SO4 or H2S-containing media environments.
[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0024] 1. The present invention provides a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor, which has a carbon quantum dot core with a nitrogen-sulfur co-doped graphene structure and surface organic ligands. It has excellent water solubility, can be rapidly adsorbed onto metal surfaces, and exhibits excellent corrosion inhibition effects in both H2SO4 and H2S media, effectively achieving corrosion protection for oil and gas gathering and transportation pipelines.
[0025] 2. The nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor prepared by this invention has a high specific surface area. Its surface can adsorb a large number of organic ligands, including -COOH, -NH2, -SH, and -OH. It also has multiple nitrogen, sulfur, and oxygen adsorption sites, which can form coordination bonds and feedback bonds with iron atoms, promoting the adsorption of the corrosion inhibitor on the metal surface and effectively inhibiting corrosion. The nitrogen-sulfur co-doped carbon quantum dot core with graphene structure has hydrophobic properties, which can effectively block corrosive media.
[0026] 3. This invention utilizes a two-solvent system and a three-step heating reaction to prepare a nitrogen- and sulfur-co-doped carbon quantum dot corrosion inhibitor, which features high yield and uniform particle size distribution. Specifically, the first heating reaction increases the solubility of the precursor in the solvent, thereby increasing the yield; the second heating reaction utilizes the solvothermal effect generated by the solvent to create high temperature and pressure, promoting the conversion of the precursor to carbon quantum dots and enabling rapid nucleation of the carbon quantum dots; the third heating reaction allows the carbon quantum dot nuclei to continue epitaxial growth, preventing them from maturing and thus increasing the particle size distribution. Attached Figure Description
[0027] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:
[0028] Figure 1 Nyquist plot of a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor provided in Example 1 of the present invention in 0.5 M H₂SO₄ solution;
[0029] Figure 2 Fourier transform infrared spectrum of a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor provided in Embodiment 1 of the present invention;
[0030] Figure 3The UV-Vis absorption spectrum, fluorescence excitation spectrum, and fluorescence emission spectrum of a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor provided in Example 1 of this invention are shown below.
[0031] Figure 4 X-ray diffraction pattern of a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor provided in Embodiment 1 of the present invention;
[0032] Figure 5 This is a transmission electron microscope (TEM) image of a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor provided in Embodiment 1 of the present invention.
[0033] Figure 6 This is a size distribution diagram of a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor provided in Embodiment 1 of the present invention;
[0034] Figure 7 This is a high-resolution transmission electron microscope image of a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor provided in Embodiment 1 of the present invention. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.
[0036] The following detailed description, with appropriate reference to the accompanying drawings, outlines embodiments of a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor, its preparation method, and its applications. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions may be omitted. This is to avoid unnecessarily lengthy explanations and to facilitate understanding by those skilled in the art.
[0037] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.
[0038] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.
[0039] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.
[0040] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other substances not listed may also be included, or that only the listed substances may be included.
[0041] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.
[0042] To address the technical problem that existing corrosion inhibitors are mostly used in hydrochloric acid environments and have poor performance in H2SO4 and / or H2S media, the present invention provides a method for preparing a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor. This corrosion inhibitor is used to inhibit the corrosion of metals in H2SO4 or H2S-containing environments, and includes the following preparation steps:
[0043] Nitrogen source precursor and sulfur source precursor were added to solvent 1 and solvent 2 in proportion, respectively. After complete dissolution, they were mixed and added to a hydrothermal reactor for a three-step heating reaction to obtain a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor.
[0044] The nitrogen source precursor is at least one of urea and 4-aminosalicylic acid, and the sulfur source precursor is at least one of L-cysteine and thiourea.
[0045] The preparation method of this invention yields a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor, which has a carbon quantum dot core with a nitrogen-sulfur co-doped graphene structure and surface organic ligands. It has excellent water solubility, can be rapidly adsorbed onto metal surfaces, and exhibits excellent corrosion inhibition effects in both H2SO4 and H2S media, effectively achieving corrosion protection for oil and gas gathering and transportation pipelines.
[0046] The nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor prepared by this invention has a high specific surface area. Its surface can adsorb a large number of organic ligands, including -COOH, -NH2, -SH, and -OH. It also has multiple nitrogen, sulfur, and oxygen adsorption sites, which can form coordination bonds and feedback bonds with iron atoms, promoting the adsorption of the corrosion inhibitor on the metal surface and effectively inhibiting corrosion. The nitrogen-sulfur co-doped carbon quantum dot core with graphene structure has hydrophobic properties, which can effectively block corrosive media.
[0047] In a preferred embodiment, the molar ratio of the nitrogen source precursor to the sulfur source precursor is 1.0-3.0. For example, the molar ratio of the nitrogen source precursor to the sulfur source precursor can be 1.0, 1.5, 2, 2.5, 3, etc.
[0048] In a preferred embodiment, the volume ratio of solvent 1 to solvent 2 is 0.2 to 5.0, for example, the volume ratio of solvent 1 to solvent 2 can be 0.2, 0.5, 1, 2, 3, 4, or 5.
[0049] In a preferred embodiment, solvent 1 is at least one of water and ethanol, and solvent 2 is at least one of water and ethanol. The present invention uses water and / or ethanol as solvents to fully dissolve the reactants and generate solvothermal activity, creating high temperature and pressure to promote the conversion of precursors into carbon quantum dots.
[0050] As a preferred embodiment, the three-step heating reaction process is as follows:
[0051] The first step involves heating the reaction at a temperature of 60℃~100℃ for 1 hour.
[0052] The second step involves heating the reaction at a temperature of 140℃ to 180℃ for 4 to 6 hours.
[0053] The third step involves heating the reaction at a temperature of 180℃ to 220℃ for 4 to 16 hours.
[0054] This invention utilizes a two-solvent system and a three-step heating reaction to prepare a nitrogen- and sulfur-co-doped carbon quantum dot corrosion inhibitor, characterized by high yield and uniform particle size distribution. Specifically, the first heating reaction increases the solubility of the precursor in the solvent, thereby increasing yield; the second heating reaction utilizes the solvothermal effect of the solvent to create high temperature and pressure, promoting the conversion of the precursor to carbon quantum dots and enabling rapid nucleation of the carbon quantum dots; the third heating reaction allows the carbon quantum dot nuclei to continue epitaxial growth, preventing them from maturing and thus increasing the particle size distribution.
[0055] In a preferred embodiment, the following steps are included after the three-step heating reaction:
[0056] After cooling the product obtained from the reaction to room temperature, it was filtered using a microporous membrane, and then evaporated and concentrated at 40℃~60℃ until no obvious bubbles were generated. After freeze-drying, a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor was obtained.
[0057] Based on the above preparation method, the present invention obtains a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor, wherein the particle size of the corrosion inhibitor is 2-10 nm and the particle size distribution is uniform.
[0058] The present invention discloses a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor used in corrosion protection of oil and gas gathering and transportation pipelines. Specifically, the corrosion inhibitor is used to inhibit the corrosion of metals in H2SO4 or H2S-containing media environments.
[0059] The technical solution of the present invention will be further described in detail below with reference to the embodiments.
[0060] It should be noted that, unless otherwise specified, the experimental methods used in the embodiments are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.
[0061] Example 1
[0062] A method for preparing a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor includes the following steps:
[0063] (1) Dissolve 4 mmol of 4-aminosalicylic acid and 2.5 mmol of L-cysteine in 15 mL of ethanol and 55 mL of distilled water respectively, mix them and add them to a hydrothermal reactor for a three-step heating reaction: keep at 80 °C for 1 h, then raise the temperature to 150 °C and keep at 150 °C for 4 h, and then raise the temperature to 200 °C again and keep at 200 °C for 16 h.
[0064] (2) After cooling the product obtained in step (1) to room temperature, filter it using a 0.22 μm microporous membrane, then evaporate and concentrate it at 40 °C until no obvious bubbles are generated. After freeze drying, nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor is obtained.
[0065] Example 2
[0066] A method for preparing a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor includes the following steps:
[0067] (1) Dissolve 2.5 mmol 4-aminosalicylic acid and 2.5 mmol L-cysteine in 15 mL ethanol and 55 mL distilled water respectively, mix them and add them to a hydrothermal reactor for a three-step heating reaction: keep at 60 °C for 1 h, then raise the temperature to 140 °C and keep at 140 °C for 5 h, and then raise the temperature to 180 °C again and keep at 180 °C for 10 h.
[0068] (2) After cooling the product obtained in step (1) to room temperature, filter it using a 0.22 μm microporous membrane, then evaporate and concentrate it at 40 °C until no obvious bubbles are generated. After freeze drying, nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor is obtained.
[0069] Example 3
[0070] A method for preparing a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor includes the following steps:
[0071] (1) Dissolve 4 mmol of 4-aminosalicylic acid and 2 mmol of thiourea in 15 mL of ethanol and 55 mL of distilled water respectively, mix them and add them to a hydrothermal reactor for a three-step heating reaction: keep at 80℃ for 1 h, then raise the temperature to 140℃ and keep at 6 h, then raise the temperature again to 220℃ and keep at 16 h.
[0072] (2) After cooling the product obtained in step (1) to room temperature, filter it using a 0.22 μm microporous membrane, then evaporate and concentrate it at 40 °C until no obvious bubbles are generated. After freeze drying, nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor is obtained.
[0073] Example 4
[0074] A method for preparing a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor includes the following steps:
[0075] (1) Dissolve 6 mmol urea and 2 mmol thiourea in 35 mL of distilled water respectively, mix them and add them to a hydrothermal reactor for a three-step heating reaction: keep at 100℃ for 1 h, then raise the temperature to 160℃ and keep at 6 h, then raise the temperature to 220℃ again and keep at 16 h.
[0076] (2) After cooling the product obtained in step (1) to room temperature, filter it using a 0.22 μm microporous membrane, then evaporate and concentrate it at 50 °C until no obvious bubbles are generated. After freeze drying, nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor is obtained.
[0077] Example 5
[0078] A method for preparing a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor includes the following steps:
[0079] (1) Dissolve 6 mmol of urea and 2 mmol of L-cysteine in 35 mL of distilled water respectively, mix them and add them to a hydrothermal reactor for a three-step heating reaction: keep at 100℃ for 1 h, then raise the temperature to 160℃ and keep at 6 h, then raise the temperature again to 220℃ and keep at 16 h.
[0080] (2) After cooling the product obtained in step (1) to room temperature, filter it using a 0.22 μm microporous membrane, then evaporate and concentrate it at 60 °C until no obvious bubbles are generated. After freeze drying, nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor is obtained.
[0081] Comparative Example 1
[0082] The difference between this comparative example and Example 1 is that a one-step synthesis reaction is used, and the synthesis temperature is 200°C, specifically:
[0083] 4 mmol of 4-aminosalicylic acid and 2.5 mmol of L-cysteine were dissolved in 15 mL of ethanol and 55 mL of distilled water, respectively. The mixture was added to a hydrothermal reactor, heated to 200 °C, and kept at that temperature for 16 h.
[0084] The obtained nitrogen and sulfur co-doped carbon quantum dot corrosion inhibitor was cooled to room temperature and filtered using a 0.22 μm microporous membrane. It was then evaporated and concentrated at 40 °C until no obvious bubbles were generated. After freeze-drying, the nitrogen and sulfur co-doped carbon quantum dot corrosion inhibitor was obtained.
[0085] The following are the testing experiments of the products prepared in Examples 1-5 and Comparative Example 1.
[0086] Experimental Example 1
[0087] The corrosion inhibition performance of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitors prepared in Examples 1-5 and Comparative Example 1 in an H2S-containing oil and gas gathering and transportation pipeline environment was tested using the weight loss method.
[0088] The testing process was as follows: The nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitors prepared in Examples 1-5 and Comparative Example 1 were subjected to corrosion tests under high-pressure environments containing H2S and CO2, respectively. The corrosion test procedure was performed in accordance with the American Society for Testing and Materials (ASTM) standard G111, "Standard Guide for Corrosion Tests in High Temperature or High Pressure Environment, or Both." The test specimens were made of 20# steel, the material used in surface gathering and transportation systems for sulfur-containing gas fields. The corrosion test medium was an aqueous solution containing 50,000 ppm NaCl. The concentration of the corrosion inhibitor was 1000 ppm (based on 100% of the total mass of the corrosion test medium). The partial pressure of H2S was 0.6 MPa, the partial pressure of CO2 was 3.0 MPa, the total pressure was 10 MPa, the temperature was 50°C, and the oxygen environment was oxygen-free. After 72 hours of corrosion under these conditions, the corrosion inhibition rate η was determined based on the difference in specimen mass before and after the test, as shown in the following formula:
[0089]
[0090] In the formula: η is the corrosion inhibition rate, %; Δm0 is the weight loss of the coupon in the blank test, in grams (g); Δm1 is the weight loss of the coupon after adding the corrosion inhibitor, in grams (g).
[0091] The corrosion inhibition rates of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitors prepared in Examples 1-5 and Comparative Example 1 were statistically analyzed in an H2S-containing oil and gas gathering and transportation pipeline environment. The results are shown in Table 1.
[0092] Table 1 shows the corrosion inhibition rate data of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitors prepared in Examples 1-5 and Comparative Example 1 in an H2S-containing oil and gas gathering and transportation pipeline environment.
[0093] sample Corrosion inhibition rate / % Example 1 91.2 Example 2 87.6 Example 3 90.4 Example 4 62.5 Example 5 74.9 Comparative Example 1 85.3
[0094] As can be seen from the data in Table 1, the corrosion inhibitor prepared in the embodiments of the present invention has excellent corrosion inhibition performance in the environment of oil and gas gathering and transportation pipelines containing H2S, with a corrosion inhibition efficiency of over 62%. Under the conditions of H2S partial pressure of 0.6 MPa, CO2 partial pressure of 3.5 MPa, and corrosion inhibitor dosage of 1000 ppm, the corrosion inhibition rate can reach 91.2%.
[0095] Compared to Example 1, Comparative Example 1 showed that replacing the three-step synthesis method with a one-step synthesis method significantly reduced the corrosion inhibition rate and decreased the corrosion inhibition performance, indicating that the three-step synthesis method has a promoting effect on improving product performance.
[0096] Experimental Example 2
[0097] The corrosion inhibition performance of the nitrogen- and sulfur co-doped carbon quantum dot corrosion inhibitors provided in Examples 1-5 and Comparative Example 1 under H2SO4 conditions was tested using the weight loss method.
[0098] The testing process was as follows: The nitrogen- and sulfur-co-doped carbon quantum dot corrosion inhibitors provided in Examples 1-5 and Comparative Example 1 were subjected to corrosion tests in a 0.5M H2SO4 environment. The corrosion test procedure was performed in accordance with the petroleum and natural gas industry standard SY / T5405-2019 "Performance Test Methods and Evaluation Indicators for Acidizing Corrosion Inhibitors". The test specimens were made of 20# steel used in surface gathering and transportation systems for sulfur-containing gas fields. The concentration of the corrosion inhibitor was 150 ppm (based on 100% of the total mass of the corrosion test medium), and the temperature environment was 25℃. After 24 hours of corrosion under the above conditions, the corrosion inhibition rate η was determined according to the mass difference of the test specimens before and after the test, as shown in the following formula:
[0099]
[0100] In the formula: η is the corrosion inhibition rate, %; Δm0 is the weight loss of the coupon in the blank test, in grams (g); Δm1 is the weight loss of the coupon after adding the corrosion inhibitor, in grams (g).
[0101] The corrosion inhibition rates of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitors prepared in Examples 1-5 and Comparative Example 1 under H2SO4 conditions were statistically analyzed, and the results are shown in Table 2.
[0102] Table 2 shows the corrosion inhibition performance data of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitors prepared in Examples 1-5 and Comparative Example 1 under H2SO4 conditions.
[0103] sample Corrosion inhibition rate / % Example 1 97.0 Example 2 92.6 Example 3 96.0 Example 4 82.5 Example 5 81.6 Comparative Example 1 87.2
[0104] As can be seen from the data in Table 2, the corrosion inhibitor prepared in the embodiments of the present invention has excellent corrosion inhibition performance under H2SO4 conditions, with a corrosion inhibition efficiency of over 81%. Under the conditions of 0.5M H2SO4 solution and 150ppm corrosion inhibitor dosage, the corrosion inhibition rate can reach 97%.
[0105] Compared to Example 1, Comparative Example 1 showed that replacing the three-step synthesis method with a one-step synthesis method significantly reduced the corrosion inhibition rate and decreased the corrosion inhibition performance, indicating that the three-step synthesis method has a promoting effect on improving product performance.
[0106] Experimental Example 3
[0107] The nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor prepared in Example 1 of this invention was evaluated using an electrochemical method. The electrochemical workstation was a CS2350M, and the test employed a three-electrode system: the working electrode was made of 20# steel with an exposed area of 1 cm². 2 Except for the exposed surface in contact with the solution, all other end faces are encapsulated within a PEEK support. The exposed surfaces are sequentially polished with 400, 800, 1000, and 1200 grit sandpaper. The reference electrode is a saturated calomel electrode, and the auxiliary electrode is a platinum electrode. The experiment was conducted in a 0.5M H₂SO₄ solution at 25℃, with a corrosion inhibitor concentration of 0–150 ppm. After the open-circuit voltage stabilized, AC impedance testing was performed at a frequency of 10 Hz. -1 ~10 5 The amplitude is 10mV. The corrosion inhibition efficiency is calculated using the following formula, obtained by fitting the AC impedance spectrum through the equivalent circuit diagram:
[0108]
[0109] In the formula, η is the corrosion inhibition efficiency, %; R ct,0 The charge transfer resistance for the blank group; R ct,i The charge transfer resistance after adding a corrosion inhibitor.
[0110] The AC impedance spectrum obtained from the test is as follows Figure 1 As shown, the data fitted by the equivalent circuit is shown in Table 3.
[0111] Table 3. Data for equivalent circuit fitting
[0112]
[0113] In Table 3, R s For the solution resistance, Y is a constant phase angle element, and R is... ct It is a charge transfer resistor.
[0114] When different concentrations of nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitors are added, the charge transfer resistance increases significantly with increasing inhibitor concentration. Figure 1 The diameter of the capacitor ring also gradually increases, indicating that metal corrosion is effectively suppressed. When the corrosion inhibitor concentration is greater than 50 ppm, the corrosion inhibition efficiency exceeds 84.6%, and when the corrosion inhibitor concentration is 150 ppm, the corrosion inhibition efficiency reaches 97.9%.
[0115] Experiment Example 4
[0116] The nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor prepared in Example 1 was characterized by Fourier transform infrared spectroscopy, ultraviolet-visible absorption spectroscopy / fluorescence excitation spectroscopy / fluorescence emission spectroscopy, X-ray diffraction, transmission electron microscopy, size distribution statistics, and high-resolution transmission electron microscopy. The results are as follows: Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 As shown.
[0117] like Figure 2 The image shows the Fourier transform infrared (FTIR) spectrum of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor in Example 1. The image shows the 3700 cm⁻¹ spectrum. -1 -3000cm -1 The broad, strong absorption band is attributed to the stretching vibrations of the OH and NH bonds, 1693 cm⁻¹. -1 The characteristic peak at 1574 cm⁻¹ is attributed to the symmetric vibration of the C=N bond. -1 The single peak at 1406 cm⁻¹ is attributed to the stretching vibration of the NC=O group in the amide. -1 The splitting peak at 1248 cm⁻¹ is attributed to the stretching vibration of the CN bond. -1 The small, sharp peak at that point is a characteristic peak of the CS bond.
[0118] like Figure 3 The images show the UV-Vis absorption spectrum, fluorescence excitation spectrum, and fluorescence emission spectrum of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor in Example 1.
[0119] In the UV-Vis absorption spectrum, three weak absorption bands appear around 237 nm, 238 nm, and 334 nm, corresponding to the core, edge, and surface states, respectively. The absorption band at 237 nm is attributed to the π-π* transition (core state) of the aromatic C-C bonds in the graphene structure, while the absorption band at 283 nm can be attributed to the sp... 2 The π-π* charge transfer transition (edge state) at the nuclear edge corresponds to the n-π* transition (surface state) at the carbon quantum dot surface, while the absorption band at 334 nm corresponds to the n-π* transition (surface state) at the carbon quantum dot surface.
[0120] At a wavelength of 520 nm, the absorption value of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor in Example 1 for the wavelength range of 250-500 nm was detected to obtain its fluorescence excitation spectrum, which showed strong selective absorption for light sources with wavelengths of 330-450 nm.
[0121] The nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor in Example 1 was irradiated with a light source of 365 nm wavelength, and its fluorescence signal intensity was detected in the range of 400 nm-650 nm to obtain the fluorescence emission spectrum, with the fluorescence emission peak located at a wavelength of 511 nm.
[0122] Figure 4 The image shows the X-ray diffraction pattern of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor in Example 1. Figure 4 The results show sharp, narrow diffraction peaks at 2θ = 29.8951, 32.0109, and 45.8367, indicating the presence of a graphene structure.
[0123] Figure 5 The image shown is a transmission electron microscope (TEM) image of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor in Example 1. It can be seen that the prepared carbon quantum dot corrosion inhibitor exhibits an approximately spherical structure and is monodisperse.
[0124] Figure 6 The size distribution statistics of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor in Example 1 show that the average size of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor in Example 1 is 2.4 nm, and the standard deviation is ±0.6 nm.
[0125] Figure 7 The image shows a high-resolution transmission electron microscope (TEM) image of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor in Example 1. It shows obvious lattice fringes with an interplanar spacing of 0.32 nm, indicating a highly crystalline structure, which is consistent with the values of the graphene (100) plane.
[0126] Finally, it should be noted that the above specific embodiments are only used to describe the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation of the present invention and is not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions or improvements can be made to some or all of the technical features. These modifications, equivalent substitutions, and improvements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.
Claims
1. A preparation method of nitrogen-sulfur co-doped carbon quantum dots corrosion inhibitor, characterized in that, The corrosion inhibitor is used in H2SO4 and / or H2S medium environment, comprising the following preparation steps: The nitrogen source precursor and the sulfur source precursor are added into solvent 1 and solvent 2 respectively in proportion, and after complete dissolution, they are mixed and added into a hydrothermal reaction kettle to perform three-step heating reaction, thereby preparing a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor. The nitrogen source precursor is at least one of urea and 4-amino salicylic acid, and the sulfur source precursor is at least one of L-cysteine and thiourea.
2. The preparation method of the nitrogen and sulfur co-doped carbon quantum dots corrosion inhibitor according to claim 1, characterized in that, The molar ratio of the nitrogen source precursor and the sulfur source precursor is 1.0-3.
0.
3. The preparation method of the nitrogen and sulfur co-doped carbon quantum dots corrosion inhibitor according to claim 1, characterized in that, The volume ratio of the solvent 1 to the solvent 2 is 0.2-5.
0.
4. The preparation method of the nitrogen and sulfur co-doped carbon quantum dots corrosion inhibitor according to claim 1, characterized in that, The solvent 1 is at least one of water and ethanol, and the solvent 2 is at least one of water and ethanol.
5. The preparation method of the nitrogen and sulfur co-doped carbon quantum dots corrosion inhibitor according to claim 1, characterized in that, The three-step heating reaction process is as follows: The first-step heating reaction temperature is 60-100℃, and the reaction time is 1h; The second-step heating reaction temperature is 140-180℃, and the reaction time is 4-6h; The third-step heating reaction temperature is 180-220℃, and the reaction time is 4-16h.
6. The preparation method of the nitrogen and sulfur co-doped carbon quantum dots corrosion inhibitor according to claim 1, characterized in that, After the three-step heating reaction, the following steps are further included: After the product obtained by reaction is cooled to room temperature, it is filtered using a microporous filter membrane, and then it is evaporated and concentrated at 40-60℃ until no obvious bubbles are generated, and after freeze-drying, a nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor is prepared.
7. A nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor prepared by the method of any one of claims 1-6. 8.The nitrogen and sulfur co-doped carbon quantum dots corrosion inhibitor according to claim 7, characterized in that, The particle size of the corrosion inhibitor is 2-10nm.
9. Application of the nitrogen-sulfur co-doped carbon quantum dot corrosion inhibitor of claim 7 in corrosion protection of oil and gas gathering and transportation pipelines.
10. Use according to claim 9, characterized in that, The corrosion inhibitor is used for corrosion inhibition of metals in H2SO4 or H2S-containing medium environment.