Corrosion inhibitor and preparation method and application thereof

Abstract

The invention provides a corrosion inhibitor and a preparation method and application thereof. The structural formula of the corrosion inhibitor is shown as a formula (I), when the corrosion inhibitor is applied to a seawater pipeline, phenolic hydroxyl groups of corrosion inhibitor molecules can be subjected to a complexation reaction with a metal surface to form a stable hexa-coordinated complex structure, and formation of the hexa-coordinated complex has remarkable significance on corrosion resistance of the metal pipeline. Due to the strong chemical stability, the complex can tightly and uniformly cover the surface of the metal pipeline to form a layer of uniform and compact protective film. The protective film effectively isolates direct contact between the metal pipeline and the external environment, and corrosion of a corrosive medium to the metal pipeline is prevented; in addition, the six-coordinate complex also has excellent adhesion and durability, can be firmly attached to the surface of the metal pipeline, resists water flow scouring and mechanical wear, and can still keep excellent corrosion resistance in the long-time use process.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion inhibitors, and in particular to a corrosion inhibitor, a preparation method thereof and an application thereof. Background Art

[0002] With the in-depth development and utilization of global marine resources and the rapid development of the shipbuilding industry, the reliability and durability of seawater pipeline systems, as a key component connecting various important components of ships, are directly related to the overall performance and safe operation of ships. However, seawater pipelines are exposed to highly corrosive environments for a long time, including the combined effects of high concentrations of salt water, dissolved oxygen, microorganisms, and other complex chemicals, making the pipeline surface extremely susceptible to severe corrosion and damage.

[0003] This corrosion not only damages the ship's exterior integrity but, more importantly, seriously threatens the overall strength and functionality of the hull structure, leading to premature aging and performance degradation. In the long term, this will significantly increase the cost of ship maintenance and repair, shorten the ship's service life, and potentially lead to serious safety accidents, posing a potential threat to the safety of crew members and property.

[0004] Seawater pipeline corrosion is a complex, multidisciplinary problem encompassing electrochemical corrosion principles, chemical corrosion reactions, physical erosion mechanisms, and biological factors. The complexity and variability of the corrosion process make accurate prediction and effective prevention and control particularly challenging.

[0005] To address this challenge, the industry has implemented a range of anti-corrosion measures, with surface treatment technology being considered a crucial preventative measure. Common surface treatment technologies include anti-corrosion coatings, phosphating and oxidation treatments, galvanizing, and sherardizing. These technologies effectively enhance the corrosion resistance of seawater pipelines by improving the chemical and physical properties of the material surface.

[0006] In addition, corrosion inhibitors, as a highly effective anti-corrosion additive, are also widely used in seawater pipeline systems. Traditional corrosion inhibitors are mainly divided into two categories: inorganic corrosion inhibitors and organic corrosion inhibitors. Although inorganic corrosion inhibitors, such as nitrites and phosphates, were widely used in the early days, they are highly toxic and have poor effects in acidic environments, which limits their further application and development. In contrast, organic corrosion inhibitors, such as chain organic amines, imidazoline derivatives and quaternary ammonium salts, can form a dense protective barrier on the metal surface due to their good adsorption and film-forming properties, effectively slowing down the corrosion rate. They are widely used in fields such as oil, natural gas, petrochemicals and marine engineering.

[0007] However, although existing corrosion inhibitors have alleviated the corrosion problem of seawater pipelines to a certain extent, they still have many limitations in terms of anti-corrosion effect, environmental performance and economic cost. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a corrosion inhibitor and its preparation method and application, which are used to solve the problems that the corrosion inhibitors in the prior art still have many limitations in terms of anti-corrosion effect, environmental performance and economic cost.

[0009] To achieve the above-mentioned and other related purposes, the present invention provides a corrosion inhibitor, the structural formula of which is shown in formula (I):

[0010]

[0011] The present application also provides a method for preparing the above-mentioned corrosion inhibitor, the method comprising:

[0012] (1) dissolving 1,4-cyclohexanedione in a first solvent, adding o-phthalaldehyde at a first temperature to form a first mixed solution; slowly adding a saturated sodium hydroxide solution dropwise to the first mixed solution until the color of the first mixed solution gradually turns black and then dark green, then stopping the addition; after the reaction is completed at a second temperature, post-processing is performed to obtain a compound represented by formula (II);

[0013] (2) Under the protection of inert gas, carbon tetrabromide and triphenylphosphine are added to anhydrous toluene. After the reaction is completed, the compound represented by formula (II) is added, and the mixture is heated under reflux. After the reaction is completed, the compound represented by formula (III) is obtained by post-treatment.

[0014] (3) dissolving the compound represented by formula (III), 4-hydroxyphenylboronic acid, sodium carbonate and tetrakis(triphenylphosphine)palladium in a mixed solvent, and after the reaction is complete, post-processing to obtain the target compound;

[0015] in,

[0016] Optionally, the molar ratio of 1,4-cyclohexanedione to o-phthalaldehyde is 1:(2-2.5);

[0017] The molar ratio of carbon tetrabromide, triphenylphosphine and the compound represented by formula (II) is (4-4.5):(8-8.5):1;

[0018] The molar ratio of the compound represented by formula (III), 4-hydroxyphenylboric acid, sodium carbonate and tetrakis(triphenylphosphine) is (20-21):(96-97):(161-162):1.

[0019] Optionally, the first solvent is ethanol;

[0020] The first temperature is 50° C.

[0021] The second temperature is 85°C.

[0022] Optionally, the post-processing in step (1) includes the following steps:

[0023] The reaction system was cooled to room temperature;

[0024] removing the first solvent by vacuum filtration to obtain a filter cake;

[0025] The filter cake is washed with the first solvent and dried to obtain the compound represented by formula (II).

[0026] Optionally, during heating under reflux in step (2), the reaction temperature is maintained at 110°C.

[0027] Optionally, the post-processing in step (2) includes the following steps:

[0028] Removing toluene from the reaction system by distillation under reduced pressure;

[0029] The product was recrystallized using a mixed solvent of dichloromethane and methanol;

[0030] The mixed solvent is removed by vacuum filtration to obtain the compound represented by formula (III).

[0031] Optionally, the mixed solvent in step (3) consists of toluene, methanol and water;

[0032] The reaction temperature of step (3) is 90°C.

[0033] Optionally, the post-processing in step (3) includes the following steps:

[0034] The reaction system was cooled to room temperature;

[0035] Removing the organic solvent from the reaction system by distillation under reduced pressure;

[0036] The residue was extracted with dichloromethane, the organic phases obtained from the extraction were combined, and the combined organic phases were dried using anhydrous sodium sulfate;

[0037] The dichloromethane solvent was removed by distillation under reduced pressure to obtain a crude product;

[0038] The crude product is separated and purified by column chromatography to obtain the target compound.

[0039] The present application also provides a use of the above-mentioned corrosion inhibitor, or the corrosion inhibitor prepared by the above-mentioned preparation method, in seawater pipelines.

[0040] As described above, the corrosion inhibitor of the present application, its preparation method and application have the following beneficial effects:

[0041] The corrosion inhibitor provided by the present application forms a complex with metallic iron to build a dense and uniform protective film on the metal surface, significantly slowing down or preventing the corrosion rate of the metal in corrosive media. This protective mechanism makes the corrosion inhibitor provided by the present application perform well in corrosion resistance. Compared with traditional corrosion inhibitors, the corrosion inhibitor molecules of the present application have the advantages of small dosage and good corrosion inhibition effect, which reduces the cost of use and improves the corrosion inhibition efficiency. The corrosion inhibitor molecules of the present application have timely replenishment and can quickly replenish and form a new protective film when the metal surface is damaged, effectively overcoming the shortcomings of traditional coating protection that is difficult to repair after damage and may aggravate corrosion, and provides a strong guarantee for the long-term stable operation of metal materials. The hexacoordinate complex formed by the corrosion inhibitor molecules of the present application has a compact structure and strong chemical stability. It can cover the metal surface tightly and evenly, effectively isolating the metal from direct contact with the external environment and preventing erosion by corrosive media. The hexacoordinate complex exhibits excellent adhesion and durability, can firmly adhere to the metal surface, resist water erosion and mechanical wear, and ensure that it can maintain excellent corrosion resistance during long-term use.

[0042] The preparation method of the corrosion inhibitor provided in the application adopts cheap, easily available and widely available raw materials for synthesis, which greatly reduces the production cost and improves the market competitiveness of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the principle of applying the corrosion inhibitor according to an embodiment of the present application in a seawater pipeline. DETAILED DESCRIPTION

[0044] The present application is further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present application and are not used to limit the scope of protection of the present application.

[0045] The following describes the embodiments of the present application through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present application from the disclosure herein. The present application may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present application.

[0046] Unless otherwise specified, the raw materials, solvents and reagents in the examples of this application were purchased from commercial sources.

[0047] The structural formula of the corrosion inhibitor provided in this application is shown in formula (I):

[0048]

[0049] The reaction scheme of the corrosion inhibitor provided in this application is as follows:

[0050]

[0051]

[0052] Example 1

[0053] This embodiment provides a method for preparing a corrosion inhibitor, comprising the following steps:

[0054] (1) 89.5 mmol of 1,4-cyclohexanedione was dissolved in 600 mL of ethanol, stirred evenly, and then heated to 50°C. At this temperature, 223.7 mmol of o-phthalaldehyde was added and stirred until completely dissolved; a saturated sodium hydroxide solution was slowly added dropwise while observing the color change of the reaction solution. When the color of the reaction solution gradually turned black and finally turned dark green, the addition of the saturated sodium hydroxide solution was stopped; the temperature was raised to 85°C and the reaction was maintained at this temperature overnight to ensure that the reaction was complete; after the reaction was completed, the reaction system was cooled to room temperature and the solvent was removed by vacuum filtration to obtain a filter cake; the filter cake was washed with ethanol and dried to obtain 26.1 g of a yellow solid product;

[0055] (2) Under the protection of inert gas, 129.7 mmol of carbon tetrabromide (CBr4) and 259.5 mmol of triphenylphosphine (PPh3) were added to 600 mL of anhydrous toluene. The two were reacted under stirring in an inert gas atmosphere for 40 minutes to ensure that the reaction was fully carried out; 32.4 mmol of the compound represented by formula (II) was added to the reaction system and continued to stir. The reaction solution was heated to 110°C and maintained at this temperature for 12 hours to promote the full reaction between the compounds; after the reaction was completed, the toluene in the reaction system was removed by vacuum distillation, and the product was recrystallized using a mixed solvent of dichloromethane (DCM) and methanol (MeOH) to improve the purity and yield of the product; finally, the solvent was removed by vacuum filtration to obtain 18.1 g of a white solid product;

[0056] (3) 1.61 mmol of the compound represented by formula (III), 7.74 mmol of 4-hydroxyphenylboronic acid, 12.90 mmol of sodium carbonate and 0.08 mmol of tetrakis(triphenylphosphine)palladium were dissolved in a mixed solvent consisting of 20 mL of toluene, 5 mL of methanol and 5 mL of water, and the mixture was stirred and reacted at 90°C for 24 hours. After the reaction was completed, the reaction system was cooled to room temperature and the organic solvent in the reaction system was removed by vacuum distillation. The residue was extracted with 30 mL of dichloromethane for a total of 3 times to ensure complete extraction. The organic phases obtained from the 3 extractions were combined and dried with anhydrous sodium sulfate. After drying, the dichloromethane solvent was removed again by vacuum distillation to obtain a crude product. Finally, the crude product was separated and purified by column chromatography to obtain a white target compound (i.e., the compound represented by formula (I), u-HBC-4COOCH3).

[0057] Example 2

[0058] This embodiment provides a method for preparing a corrosion inhibitor, comprising the following steps:

[0059] (1) 89.5 mol of 1,4-cyclohexanedione was dissolved in 600 L of ethanol, stirred evenly, and then heated to 50 ° C. At this temperature, 223.7 mol of o-phthalaldehyde was added and stirred until completely dissolved; a saturated sodium hydroxide solution was slowly added dropwise while observing the color change of the reaction solution. When the color of the reaction solution gradually turned black and finally turned dark green, the addition of the saturated sodium hydroxide solution was stopped; the temperature was raised to 85 ° C. and the reaction was maintained at this temperature overnight to ensure that the reaction was complete; after the reaction was completed, the reaction system was cooled to room temperature, and the solvent was removed by vacuum filtration to obtain a filter cake; the filter cake was washed with ethanol and dried to obtain 26.1 kg of a yellow solid product;

[0060] (2) Under the protection of inert gas, 129.7 mol of carbon tetrabromide (CBr4) and 259.5 mol of triphenylphosphine (PPh3) were added to 600 L of anhydrous toluene. The two were reacted under stirring in an inert gas atmosphere for 40 minutes to ensure that the reaction was fully carried out; 32.4 mol of the compound represented by formula (II) was added to the reaction system and continued to stir. The reaction solution was heated to 110°C and the reaction was maintained at this temperature for 12 hours to promote the full reaction between the compounds; after the reaction was completed, the toluene in the reaction system was removed by vacuum distillation, and the product was recrystallized using a mixed solvent of dichloromethane (DCM) and methanol (MeOH) to improve the purity and yield of the product; finally, the solvent was removed by vacuum filtration to obtain 18.1 kg of a white solid product;

[0061] (3) 1.61 mol of the compound represented by formula (III), 7.74 mol of 4-hydroxyphenylboronic acid, 12.90 mol of sodium carbonate and 0.08 mol of tetrakis(triphenylphosphine)palladium were dissolved in a mixed solvent consisting of 20 L of toluene, 5 L of methanol and 5 L of water, and the mixture was stirred and reacted at 90°C for 24 hours. After the reaction was completed, the reaction system was cooled to room temperature and the organic solvent in the reaction system was removed by vacuum distillation. The residue was extracted with 3 mL of dichloromethane for a total of 3 times to ensure complete extraction. The organic phases obtained from the 3 extractions were combined and dried with anhydrous sodium sulfate. After drying, the dichloromethane solvent was removed again by vacuum distillation to obtain a crude product. Finally, the crude product was separated and purified by column chromatography to obtain a white target compound (i.e., the compound represented by formula (I), u-HBC-4COOCH3).

[0062] Example 2 is an amplified reaction of Example 1. The yields of the compound of formula (II) obtained in step (1) of Example 1 and Example 2 both reached 95%; the yields of the compound of formula (III) obtained in step (2) were both 90%; and the yields of the target compound obtained in step (3) were both 86%.

[0063] Example 3

[0064] This embodiment provides an application of a corrosion inhibitor in seawater pipelines, such as Figure 1 shown.

[0065] The working principle of the corrosion inhibitor of this embodiment in the seawater pipeline is as follows: the corrosion inhibitor of this embodiment contains 4 hydroxyl polar groups, which can be adsorbed by the surface charge of the metal to form a monomolecular film in the entire anode and cathode areas, thereby preventing or slowing down the corresponding electrochemical reaction.

[0066] The corrosion inhibitor of this embodiment forms a complex with metallic iron to achieve effective adsorption on the metal surface, constructing a dense and uniform protective film, which significantly slows down or prevents the corrosion rate of the metal in the corrosive medium. The corrosion inhibitor molecules have the ability to be replenished in a timely manner, effectively overcoming the shortcomings of traditional coating protection that is difficult to repair after damage and may aggravate corrosion, and becomes a key chemical protection means to ensure the long-term and stable operation of metal materials.

[0067] Specifically, the phenolic hydroxyl groups of the corrosion inhibitor molecules of this embodiment can react with the metal surface to form a stable six-coordinate complex structure, such as Figure 1As shown, the complex consists of a metal atom and six phenolic hydroxyl groups in the corrosion inhibitor molecules as ligands. A strong coordination bond is formed through electron sharing between the metal atom and the oxygen atom in the phenolic hydroxyl groups. As the reaction proceeds, the phenolic hydroxyl groups in the six corrosion inhibitor molecules gradually coordinate with the same metal atom, forming a tight and stable hexacoordinate complex. This complex has a compact structure, and the coordination bonds tightly connect the metal and corrosion inhibitor molecules, forming a strong protective layer.

[0068] The formation of this hexacoordinate complex is of significant importance for the corrosion resistance of metal pipes. Its strong chemical stability enables the complex to tightly and evenly coat the surface of the metal pipe, forming a uniform and dense protective film. This protective film effectively isolates the metal pipe from direct contact with the external environment, preventing erosion by corrosive media. Furthermore, the hexacoordinate complex exhibits excellent adhesion and durability, firmly adhering to the metal pipe surface and resisting water erosion and mechanical wear. This ensures that the excellent corrosion resistance is maintained during long-term use, providing long-lasting and stable protection for the metal pipe.

[0069] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A corrosion inhibitor, characterized in that: The structural formula of the corrosion inhibitor is shown in formula (I):

2. A method for preparing the corrosion inhibitor according to claim 1, characterized in that: The method comprises: (1) dissolving 1,4-cyclohexanedione in a first solvent, adding o-phthalaldehyde at a first temperature to form a first mixed solution; slowly dropping a saturated sodium hydroxide solution into the first mixed solution until the color of the first mixed solution gradually turns black and then dark green, then stopping the dropping; after the reaction is completed at a second temperature, post-treating to obtain a compound represented by formula (II); (2) under the protection of inert gas, adding carbon tetrabromide and triphenylphosphine to anhydrous toluene, after the reaction is completed; adding the compound represented by formula (II), heating under reflux, after the reaction is completed, post-treating to obtain the compound represented by formula (III); (3) dissolving the compound represented by formula (III), 4-hydroxyphenylboronic acid, sodium carbonate and tetrakis(triphenylphosphine)palladium in a mixed solvent, and after the reaction is complete, post-treating to obtain the target compound; in, 3. The method according to claim 2, characterized in that The molar ratio of 1,4-cyclohexanedione to o-phthalaldehyde is 1: (2～2.5)； The molar ratio of carbon tetrabromide, triphenylphosphine and the compound represented by formula (II) is (4-4.5):(8-8.5):1; The molar ratio of the compound represented by formula (III), 4-hydroxyphenylboric acid, sodium carbonate and tetrakis(triphenylphosphine) is (20-21): (96～97)：(161～162)：1。 4. The method according to claim 2, characterized in that: The first solvent is ethanol; The first temperature is 50°C; The second temperature is 85°C.

5. The method according to any one of claims 2 to 4, characterized in that: The post-processing in step (1) comprises the following steps: Cool the reaction system to room temperature; Removing the first solvent by vacuum filtration to obtain a filter cake; The filter cake is washed with the first solvent and dried to obtain the compound represented by formula (II).

6. The method according to claim 2, characterized in that During heating under reflux in step (2), the reaction temperature was maintained at 110°C.

7. The method according to claim 2 or 6, characterized in that: The post-processing in step (2) comprises the following steps: Removing toluene from the reaction system by distillation under reduced pressure; The product is recrystallized using a mixed solvent of dichloromethane and methanol; The mixed solvent is removed by vacuum filtration to obtain a compound represented by formula (III).

8. The method according to claim 2, characterized in that: The mixed solvent in step (3) consists of toluene, methanol and water; The reaction temperature of step (3) is 90°C.

9. The method according to claim 2 or 8, characterized in that: The post-processing in step (3) comprises the following steps: Cool the reaction system to room temperature; Removing the organic solvent in the reaction system by distillation under reduced pressure; The residue is extracted with dichloromethane, the organic phases obtained by the extraction are combined, and the combined organic phases are dried with anhydrous sodium sulfate; The dichloromethane solvent is removed by distillation under reduced pressure to obtain a crude product; The crude product is separated and purified by column chromatography to obtain the target compound.

10. Use of the corrosion inhibitor according to claim 1 or the corrosion inhibitor prepared by the preparation method according to any one of claims 2 to 9 in seawater pipelines.

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