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 in the formula (I), when the corrosion inhibitor is applied to a seawater pipeline, the corrosion inhibitor can be adsorbed on the surface of metal through various ways such as electrostatic adsorption and coordinate bond formation, a layer of protective film is formed on the surface of the metal, contact of the metal with oxygen and salt ions is blocked, and the purpose of corrosion resistance is achieved.

Description

Technical Field

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

[0002] Seawater plays a vital role as a circulating cooling medium in ship operations and many marine engineering applications. However, the high salt content and complex composition of seawater, including dissolved minerals, organic matter, and microorganisms, pose a serious corrosion threat to metal pipes and heat exchange systems. This corrosion phenomenon not only leads to a significant decline in equipment performance and shortens its service life, but may also cause leakage accidents, pollute the environment, and even bring significant economic losses and safety risks.

[0003] Specifically, the corrosive effect of seawater is mainly reflected in the following aspects: first, electrochemical corrosion caused by high salinity accelerates the oxidation process of the metal surface; second, corrosive ions such as chloride ions dissolved in seawater erode the metal surface; third, the attachment of marine organisms such as shellfish and algae, and the formation of biological scale aggravates the corrosion process; fourth, changes in physical factors such as seawater temperature and flow rate also affect the corrosion rate.

[0004] In order to solve the problem of seawater corrosion on metal pipes and equipment, researchers have been exploring effective anti-corrosion methods. Among them, corrosion inhibitors, as a chemical substance or compound that can effectively prevent or alleviate material corrosion, have been widely used in the field of seawater corrosion protection due to their low cost, high efficiency, and simple operation. The mechanism of action of corrosion inhibitors is mainly to form a protective film on the metal surface, isolating the direct contact between seawater and metal, thereby slowing down or preventing the occurrence of corrosion.

[0005] However, traditional corrosion inhibitors have also exposed some problems during use, such as high toxicity and serious environmental pollution, which is contrary to the current requirements of enhanced environmental protection awareness and sustainable development. Therefore, the development of a green corrosion inhibitor that can effectively inhibit seawater corrosion and meet environmental protection requirements has become a technical problem that needs to be solved urgently.

[0006] In addition, with the continuous expansion of seawater utilization, from industrial cooling water to seawater desalination, marine engineering, shipbuilding and other fields, there is an urgent need for efficient and environmentally friendly seawater pipeline corrosion inhibitors. Only by solving the corrosion problem of metal materials in seawater can we ensure the normal operation of equipment, extend its service life, and promote the comprehensive utilization and sustainable development of seawater resources. Summary of the invention

[0007] 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. The corrosion inhibitor can form a complex with metal ions and block the contact between the metal and oxygen and salt ions by adsorbing on the metal surface, thereby achieving an anti-corrosion effect.

[0008] In order to achieve the above-mentioned object and other related objects, the present invention provides a corrosion inhibitor, the structural formula of the corrosion inhibitor is shown in formula (I):

[0009]

[0010] The present application also provides a method for preparing the above-mentioned corrosion inhibitor, the method comprising:

[0011] (1) dissolving 4-cyanophenol and propyne bromide in a first solvent, adding a base catalyst, and carrying out a nucleophilic substitution reaction under the protection of an inert gas, and performing post-treatment to obtain a compound represented by formula (II);

[0012] (2) dissolving the compound represented by formula (II) in anhydrous tetrahydrofuran, slowly adding lithium aluminum hydride dropwise in an ice bath, removing the ice bath after the lithium aluminum hydride is added, and conducting a hydrogenation reduction reaction at room temperature. After the reaction is completed, quenching the reaction and post-treatment are performed to obtain a compound represented by formula (III);

[0013] (3) mixing 5-methyl-1,1′-phenanthroline and selenium dioxide in a dry environment, and suspending them in an o-dichlorobenzene solvent for reaction. After the reaction is completed, post-treatment is performed to obtain a compound represented by formula (IV);

[0014] (4) dissolving the compound represented by formula (III) and the compound represented by formula (IV) in a second solvent, and reacting them under heating reflux; adding sodium borohydride dropwise under ice bath conditions to carry out a reduction reaction, and after the reaction is completed, quenching the reaction and post-processing; and then acidifying, salifying and purifying in sequence to obtain the target compound represented by formula (I);

[0015] in,

[0016] Optionally, the molar ratio of 4-cyanophenol to propyne bromide is 1:1.5;

[0017] The molar ratio of the compound represented by formula (II) to lithium aluminum hydride is (4.9-5):1;

[0018] The molar ratio of 5-methyl-1,1′-phenanthroline to selenium dioxide is (1.9-2):1;

[0019] The molar ratio of the compound represented by formula (III), the compound represented by formula (IV) and sodium borohydride is 1:1:5.

[0020] Optionally, the first solvent in step (1) is acetone; the alkaline catalyst is potassium carbonate;

[0021] The molar ratio of 4-cyanophenol, propyne bromide and potassium carbonate is 1:1.5:3.

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

[0023] After the reaction is completed, the insoluble solid impurities in the reaction system are removed by filtering, and then the filtrate is subjected to vacuum compression treatment;

[0024] Using dichloromethane as an extractant, extracting the concentrated solution multiple times, retaining the organic phase, and adding magnesium sulfate to the organic phase for drying;

[0025] After drying, the magnesium sulfate solid is removed by filtering, and the obtained organic solution is then distilled under reduced pressure;

[0026] The concentrated product is recrystallized using a mixed solvent of ethyl acetate and hexane as a recrystallization solvent to obtain a pure white compound represented by formula (II).

[0027] Optionally, the reaction quenching and post-treatment in step (2) specifically include:

[0028] After the reaction is completed, water, 15% sodium hydroxide aqueous solution, and water are sequentially added to the reaction system for quenching. After the quenching is completed, the generated solid by-product is removed by filtering;

[0029] The filtered filtrate was transferred to a separatory funnel, and ethyl acetate was used as an extractant for multiple extractions. The organic phases were combined and dried by adding magnesium sulfate;

[0030] After drying, the mixture was filtered again to remove magnesium sulfate, and the filtrate was then concentrated in vacuo to obtain the compound represented by formula (III).

[0031] Optionally, the post-processing in step (3) specifically includes:

[0032] After the reaction is completed, the reaction system is naturally cooled to room temperature, and the insoluble solid impurities therein are removed by filtering;

[0033] Add citric acid solution to the filtrate for acidification, and collect the aqueous phase;

[0034] Add dichloromethane to the aqueous phase for multiple washing operations, and then add 10 mol / L sodium hydroxide solution to the aqueous phase until the solution becomes alkaline;

[0035] Using dichloromethane as an extractant, extracting the neutralized aqueous phase multiple times, combining the organic phases, and adding magnesium sulfate for drying;

[0036] After drying, the magnesium sulfate is removed by filtering, and the filtrate is concentrated in vacuo to evaporate the solvent to dryness to obtain the compound represented by formula (IV).

[0037] Optionally, the second solvent is methanol.

[0038] Optionally, the reaction quenching and post-treatment in step (4) specifically include:

[0039] After the reaction is completed, water is added to the reaction system to terminate the reaction;

[0040] removing the second solvent by vacuum distillation to obtain a solid residue;

[0041] Dissolving the solid residue in dichloromethane to form an organic solution, washing the organic solution with water, and collecting the organic phase;

[0042] Add magnesium sulfate to the organic phase for drying;

[0043] The dichloromethane solvent is removed by vacuum concentration technology to obtain a concentrated product;

[0044] Acidification, salification and purification specifically include:

[0045] The concentrated product is redissolved in a second solvent, and concentrated hydrochloric acid is added to adjust the pH value of the solution to less than 2 for acidification, and the second solvent is evaporated under reduced pressure to obtain an acidified concentrated residue;

[0046] The concentrated residue was suspended in acetone and saturated NH 4 PF 6 aqueous solution, precipitate out; after evaporating the acetone solvent under vacuum conditions, continue to add methanol;

[0047] The precipitate was removed by filtration, and the target compound was obtained after washing and filtration were repeated several times.

[0048] The present application also provides the use of the above corrosion inhibitor, or the corrosion inhibitor prepared by the above preparation method, in seawater pipelines.

[0049] As described above, a corrosion inhibitor and a preparation method and application thereof of the present application have the following beneficial effects:

[0050] The corrosion inhibitor provided in the present application is used in seawater pipelines. The corrosion inhibitor can be adsorbed on the metal surface through various means such as electrostatic adsorption and formation of coordination bonds, forming a protective film on the metal surface to block the contact between the metal and oxygen and salt ions, thereby achieving the purpose of corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is the protonated hydrogen nuclear magnetic resonance spectrum of the corrosion inhibitor in the examples of this application.

[0052] Figure 2 This is a diagram of the complexation process between the corrosion inhibitor and the metal iron ions in the embodiment of the present application. DETAILED DESCRIPTION

[0053] The present application is further described below in conjunction with 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.

[0054] The following describes the implementation of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application.

[0055] Unless otherwise specified, the raw materials, solvents and reagents in the examples of this application were purchased from commercial sources.

[0056] The structural formula of the corrosion inhibitor provided in the present application is shown in formula (I):

[0057]

[0058] The reaction route of the corrosion inhibitor provided in this application is as follows:

[0059]

[0060] Example 1

[0061] This embodiment provides a method for preparing a corrosion inhibitor, comprising the following steps:

[0062] (1) 25.2 mmol of 4-cyanophenol and 37.8 mmol of propyne bromide were dissolved in acetone, and then 75.6 mmol of potassium carbonate (K2CO3) was added to the mixed solution. 2 CO 3 ); in an inert environment protected by an inert gas (such as nitrogen), heating the mixture to reflux temperature, and maintaining this condition overnight to ensure that the nucleophilic substitution reaction between 4-cyanophenol and bromopropyne is fully carried out;

[0063] After the reaction is completed, the insoluble solid impurities in the reaction system are removed by filtering; the filtrate is then vacuum concentrated to reduce the volume of the solvent for subsequent operations;

[0064] Dichloromethane (DCM) was used as the extractant to extract the concentrated solution several times (100 mL each time, three times in total) to effectively separate the organic phase; magnesium sulfate (MgSO 4 ) to remove any trace amount of water that may remain;

[0065] After drying, the magnesium sulfate solid is removed by filtering, and then the obtained organic solution is distilled under reduced pressure to further concentrate to a suitable volume;

[0066] Finally, the concentrate from the previous step was recrystallized using a mixed solvent of ethyl acetate and hexane as a recrystallization solvent to obtain a pure white compound of formula (II) with a yield of 83%.

[0067] (2) 0.637 mmol of the compound represented by formula (II) was dissolved in anhydrous tetrahydrofuran (THF) to form a uniform solution; then, 3.184 mmol of lithium aluminum hydride (LiAlH4) was slowly added dropwise to the solution under ice bath conditions, and the temperature was closely monitored to prevent local overheating; after the addition was completed, the ice bath was removed, and the reaction system was continuously stirred at room temperature for 8 hours to ensure that the hydrogenation reduction reaction was fully carried out;

[0068] After the reaction is completed, water (120 μL), 15% sodium hydroxide aqueous solution (120 mL), and water (240 mL) are sequentially and slowly added to the reaction system for quenching. During this process, the liquid addition speed must be strictly controlled to avoid the occurrence of violent reaction. After the quenching is completed, the generated solid by-product is removed by filtering;

[0069] The filtered filtrate was transferred to a separatory funnel and extracted several times with ethyl acetate as the extractant until the organic phase no longer contained soluble impurities of the target product; the organic phases were combined and magnesium sulfate (MgSO 4 ) to dry the product to effectively remove any trace moisture that may remain;

[0070] After drying, the mixture is filtered again to remove magnesium sulfate, and the filtrate is then vacuum concentrated until the solvent is substantially evaporated to obtain a crude product of the compound represented by formula (III). The purity of the product is relatively high, and therefore, the crude product can be directly used for subsequent reactions or analysis without further purification.

[0071] (3) 1.03 mmol of 5-methyl-1,1′-phenanthroline and 2.0 mmol of selenium dioxide (SeO2 ) are thoroughly mixed in a dry environment, and then the mixture is suspended in 30 mL of o-dichlorobenzene solvent to form a reaction suspension;

[0072] After the reaction was completed, the reaction system was naturally cooled to room temperature, and the insoluble solid impurities therein were removed by filtering; then, 20 mL of 5 mol / L citric acid solution was added to the filtrate for acidification, and the resulting aqueous phase was collected;

[0073] In order to remove the organic impurities that may remain in the aqueous phase, dichloromethane (DCM) was used for multiple washing operations; then, 30 mL of 10 mol / L sodium hydroxide solution was slowly added to the aqueous phase while stirring until the solution became alkaline to neutralize the remaining acidic substances;

[0074] Dichloromethane (DCM) was used as the extractant to extract the neutralized aqueous phase several times (100 mL each time, for a total of five times) to fully extract the organic components therein; all organic phases were combined and magnesium sulfate (MgSO 4 ) to remove any trace amount of water that may remain;

[0075] After drying, magnesium sulfate is removed by filtering, and the filtrate is then vacuum concentrated until the solvent is completely evaporated to obtain a crude product of the compound represented by formula (IV). The structure of the crude product is characterized by nuclear magnetic resonance analysis (NMR), and it is confirmed that the chemical structure of the product is consistent with the chemical structure represented by formula (IV). After testing, the crude product has a high purity and can be directly used in subsequent experiments or applications without further purification.

[0076] (4) 0.310 mmol of the compound represented by formula (III) and 0.310 mmol of the compound represented by formula (IV) were mixed and dissolved in 10 mL of methanol; the solution was then placed in a reflux device and stirred for 16 hours under heating conditions to promote the chemical reaction between the two;

[0077] After the reaction volume was cooled to room temperature naturally, 1.55 mmol of sodium borohydride (NaBH 4 ) to start the reduction reaction; then, the reaction mixture was stirred at room temperature for 6 hours to ensure that the reduction reaction was complete;

[0078] After the reaction is completed, an appropriate amount of water is added to the reaction system to terminate the reaction; then, the methanol solvent is removed by vacuum distillation technology, and the solid residue is collected;

[0079] The solid residue was dissolved in 100 mL of dichloromethane (CH 2 Cl2 ) to form an organic solution; in order to remove possible water-soluble impurities, the organic solution was washed twice with 50 mL of water, and the washed organic phase was collected; then, magnesium sulfate (MgSO 4 ) is dried and the dichloromethane solvent is removed by vacuum concentration technology;

[0080] The concentrated product was redissolved in 30 mL of methanol, and concentrated hydrochloric acid (cocn.HCl) was slowly added to adjust the pH value of the solution to less than 2 for acidification; then, the methanol solvent was evaporated under reduced pressure to obtain an acidified concentrated residue; the concentrated residue was suspended in 30 mL of acetone, and saturated NH 4 PF 6 aqueous solution; stirring continuously at room temperature for 3 hours to promote the formation and precipitation of the target product;

[0081] After evaporating the acetone solvent under vacuum conditions, methanol is added to the residue to promote and assist the precipitation of excess salts. The precipitate is removed by filtration, and this washing and filtration process is repeated several times until all residual salts are completely removed. The pure product obtained will be further analyzed and applied. The obtained product was subjected to protonation nuclear magnetic resonance analysis, and the results are as follows Figure 1 As shown, it is confirmed that the chemical structure of the product is consistent with the structure of the compound shown in formula (I).

[0082] Example 2

[0083] This embodiment also provides a method for preparing a corrosion inhibitor, comprising the following steps:

[0084] (1) 50.4 mol of 4-cyanophenol and 75.6 mol of propyne bromide were dissolved in acetone, and then 151.2 mol of potassium carbonate (K2CO3) was added to the mixed solution. 2 CO 3 ); in an inert environment protected by an inert gas (such as nitrogen), heating the mixture to reflux temperature, and maintaining this condition overnight to ensure that the nucleophilic substitution reaction between 4-cyanophenol and bromopropyne is fully carried out;

[0085] After the reaction is completed, the insoluble solid impurities in the reaction system are removed by filtering; the filtrate is then vacuum concentrated to reduce the volume of the solvent for subsequent operations;

[0086] Dichloromethane (DCM) was used as the extractant to extract the concentrated solution for multiple times (200 L each time, three times in total) to effectively separate the organic phase; magnesium sulfate (MgSO 4) to remove any trace amount of water that may remain;

[0087] After drying, the magnesium sulfate solid is removed by filtering, and then the obtained organic solution is distilled under reduced pressure to further concentrate to a suitable volume;

[0088] Finally, the concentrate from the previous step was recrystallized using a mixed solvent of ethyl acetate and hexane as a recrystallization solvent to obtain a pure white compound of formula (II) with a yield of 82%.

[0089] (2) 1.274 mol of the compound represented by formula (II) was dissolved in anhydrous tetrahydrofuran (THF) to form a uniform solution; then, 6.368 mol of lithium aluminum hydride (LiAlH4) was slowly added dropwise to the solution under ice bath conditions, and the temperature was closely monitored to prevent local overheating; after the addition was completed, the ice bath was removed, and the reaction system was continuously stirred at room temperature for 8 hours to ensure that the hydrogenation reduction reaction was fully carried out;

[0090] After the reaction is completed, water (240 mL), 15% sodium hydroxide aqueous solution (240 L), and water (480 L) are sequentially and slowly added to the reaction system for quenching. During this process, the liquid addition rate must be strictly controlled to avoid the occurrence of violent reaction. After the quenching is completed, the generated solid by-product is removed by filtering;

[0091] The filtered filtrate was transferred to a separatory funnel and extracted several times with ethyl acetate as the extractant until the organic phase no longer contained soluble impurities of the target product; the organic phases were combined and magnesium sulfate (MgSO 4 ) to dry the product to effectively remove any trace moisture that may remain;

[0092] After drying, the mixture is filtered again to remove magnesium sulfate, and the filtrate is then vacuum concentrated until the solvent is substantially evaporated to obtain a crude product of the compound represented by formula (III). The purity of the product is relatively high, and therefore, the crude product can be directly used for subsequent reactions or analysis without further purification.

[0093] (3) 2.06 mol of 5-methyl-1,1′-phenanthroline and 4.0 mol of selenium dioxide (SeO 2 ) are thoroughly mixed in a dry environment, and then the mixture is suspended in 60 L of o-dichlorobenzene solvent to form a reaction suspension;

[0094] After the reaction was completed, the reaction system was naturally cooled to room temperature, and the insoluble solid impurities therein were removed by filtering; then, 40 L of 5 mol / L citric acid solution was added to the filtrate for acidification, and the resulting aqueous phase was collected;

[0095] In order to remove organic impurities that may remain in the aqueous phase, dichloromethane (DCM) is used for multiple washing operations; then, 60 L of 10 mol / L sodium hydroxide solution is slowly added to the aqueous phase while stirring until the solution becomes alkaline to neutralize the remaining acidic substances;

[0096] Dichloromethane (DCM) was used as the extractant to extract the neutralized aqueous phase several times (200 L each time, for a total of five times) to fully extract the organic components therein; all organic phases were combined and magnesium sulfate (MgSO 4 ) to remove any trace amount of water that may remain;

[0097] After drying, magnesium sulfate is removed by filtering, and the filtrate is then vacuum concentrated until the solvent is completely evaporated to obtain a crude product of the compound represented by formula (IV). The structure of the crude product is characterized by nuclear magnetic resonance analysis (NMR), and it is confirmed that the chemical structure of the product is consistent with the chemical structure represented by formula (IV). After testing, the crude product has a high purity and can be directly used in subsequent experiments or applications without further purification.

[0098] (4) 0.620 mol of the compound represented by formula (III) and 0.620 mol of the compound represented by formula (IV) were mixed and dissolved in 20 L of methanol; the solution was then placed in a reflux device and stirred for 16 hours under heating conditions to promote the chemical reaction between the two;

[0099] After the reaction volume was cooled to room temperature naturally, 3.10 mol of sodium borohydride (NaBH 4 ) to start the reduction reaction; then, the reaction mixture was stirred at room temperature for 6 hours to ensure that the reduction reaction was complete;

[0100] After the reaction is completed, an appropriate amount of water is added to the reaction system to terminate the reaction; then, the methanol solvent is removed by vacuum distillation technology, and the solid residue is collected;

[0101] The solid residue was dissolved in 200 L of dichloromethane (CH 2 Cl 2 ) to form an organic solution; in order to remove possible water-soluble impurities, the organic solution was washed twice with 100 L of water, and the washed organic phase was collected; then, magnesium sulfate (MgSO 4 ) is dried and the dichloromethane solvent is removed by vacuum concentration technology;

[0102] The concentrated product was redissolved in 60 L of methanol, and concentrated hydrochloric acid (cocn.HCl) was slowly added to adjust the pH value of the solution to less than 2 for acidification; then, the methanol solvent was evaporated under reduced pressure to obtain an acidified concentrated residue; the concentrated residue was suspended in 60 L of acetone, and saturated NH 4 PF 6 aqueous solution; stirring continuously at room temperature for 3 hours to promote the formation and precipitation of the target product;

[0103] After evaporating the acetone solvent under vacuum conditions, methanol is added to the residue to promote and assist the precipitation of excess salts. The precipitate is removed by filtration, and this washing and filtration process is repeated several times until all residual salts are completely removed. The pure product obtained will be further analyzed and applied. The obtained product was subjected to protonation nuclear magnetic resonance analysis, and the results are as follows Figure 1 As shown, it is confirmed that the chemical structure of the product is consistent with the structure of the compound shown in formula (I).

[0104] The preparation method of the corrosion inhibitor provided in this embodiment is applicable to large-scale production.

[0105] In the preparation method of the corrosion inhibitor provided in Example 1 and Example 2, not only the secondary amine is protonated, but also the o-phenanthroline group is protonated. The final product is dissolved in the aqueous phase after protonation, so a mild acid is selected to acidify the secondary amine and keep the o-phenanthroline group in a neutral state, thereby reducing the pollution of the corrosion inhibitor to the water environment.

[0106] Example 3

[0107] This embodiment provides the application of the corrosion inhibitor prepared in the above embodiment in seawater pipelines. The N on the heterocyclic alkyl pyridine ring in the corrosion inhibitor molecule has a lone pair of electrons. Combined with the benzene ring structure, N becomes an active group and can be adsorbed on the metal surface through various means such as electrostatic adsorption and formation of coordination bonds, so that the corrosion inhibitor molecules form a protective film on the metal surface. Figure 2 As shown, the corrosion inhibitor molecules and metal iron ions form a protective film on the surface of the ship pipeline through complexation.

[0108] 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 familiar with 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still 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 4-cyanophenol and propyne bromide in a first solvent, adding a base catalyst, and carrying out a nucleophilic substitution reaction under the protection of an inert gas, and performing post-treatment to obtain a compound represented by formula (II); (2) dissolving the compound represented by formula (II) in anhydrous tetrahydrofuran, slowly adding lithium aluminum hydride dropwise in an ice bath, removing the ice bath after the lithium aluminum hydride is added, and conducting a hydrogenation reduction reaction at room temperature. After the reaction is completed, quenching the reaction and post-treatment are performed to obtain a compound represented by formula (III); (3) mixing 5-methyl-1,1′-phenanthroline and selenium dioxide in a dry environment, and suspending them in an o-dichlorobenzene solvent for reaction. After the reaction is completed, post-treatment is performed to obtain a compound represented by formula (IV); (4) dissolving the compound represented by formula (III) and the compound represented by formula (IV) in a second solvent, and reacting them under heating reflux; adding sodium borohydride dropwise under ice bath conditions to carry out a reduction reaction, and after the reaction is completed, quenching the reaction and post-processing; and then acidifying, salifying and purifying in sequence to obtain the target compound represented by formula (I); in, 3. The method according to claim 2, characterized in that The molar ratio of 4-cyanophenol to propyne bromide is 1:1.5; The molar ratio of the compound represented by formula (II) to lithium aluminum hydride is (4.9-5):1; The molar ratio of 5-methyl-1,1′-phenanthroline to selenium dioxide is (1.9-2):1; The molar ratio of the compound represented by formula (III), the compound represented by formula (IV) and sodium borohydride is 1:1:

5.

4. The method according to claim 2, characterized in that: The first solvent in step (1) is acetone; the alkaline catalyst is potassium carbonate; The molar ratio of 4-cyanophenol, propyne bromide and potassium carbonate is 1:1.5:

3.

5. The method according to claim 2, characterized in that: The post-processing in step (1) specifically includes: After the reaction is completed, the insoluble solid impurities in the reaction system are removed by filtering, and then the filtrate is subjected to vacuum compression treatment; Using dichloromethane as an extractant, extracting the concentrated solution multiple times, retaining the organic phase, and adding magnesium sulfate to the organic phase for drying; After drying, the magnesium sulfate solid is removed by filtering, and the obtained organic solution is then distilled under reduced pressure; The concentrated product is recrystallized using a mixed solvent of ethyl acetate and hexane as a recrystallization solvent to obtain a pure white compound represented by formula (II).

6. The method according to claim 2, characterized in that The reaction quenching and post-treatment in step (2) specifically include: After the reaction is completed, water, 15% sodium hydroxide aqueous solution, and water are sequentially added to the reaction system for quenching. After the quenching is completed, the generated solid by-product is removed by filtering; The filtered filtrate was transferred to a separatory funnel, and ethyl acetate was used as an extractant for multiple extractions. The organic phases were combined and dried by adding magnesium sulfate; After drying, the mixture was filtered again to remove magnesium sulfate, and the filtrate was then concentrated in vacuo to obtain the compound represented by formula (III).

7. The method according to claim 2, characterized in that: The post-processing in step (3) specifically includes: After the reaction is completed, the reaction system is naturally cooled to room temperature, and the insoluble solid impurities therein are removed by filtering; Add citric acid solution to the filtrate for acidification, and collect the aqueous phase; Dichloromethane was added to the aqueous phase for multiple washing operations, and then 10 mol / L sodium hydroxide solution was added to the aqueous phase. until the solution becomes alkaline; Using dichloromethane as an extractant, extracting the neutralized aqueous phase multiple times, combining the organic phases, and adding magnesium sulfate for drying; After drying, the magnesium sulfate is removed by filtering, and the filtrate is concentrated in vacuo to evaporate the solvent to dryness to obtain the compound represented by formula (IV).

8. The method according to claim 2, characterized in that: The second solvent is methanol.

9. The method according to claim 2 or 8, characterized in that: The reaction quenching and post-treatment in step (4) specifically include: After the reaction is completed, water is added to the reaction system to terminate the reaction; removing the second solvent by vacuum distillation to obtain a solid residue; Dissolving the solid residue in dichloromethane to form an organic solution, washing the organic solution with water, and collecting the organic phase; Add magnesium sulfate to the organic phase for drying; The dichloromethane solvent is removed by vacuum concentration technology to obtain a concentrated product; Acidification, salification and purification specifically include: The concentrated product is redissolved in a second solvent, and concentrated hydrochloric acid is added to adjust the pH value of the solution to less than 2 for acidification, and the second solvent is evaporated under reduced pressure to obtain an acidified concentrated residue; The concentrated residue is suspended in acetone, and a saturated NH4PF6 aqueous solution is gradually added to precipitate; after evaporating the acetone solvent under vacuum conditions, methanol is continuously added; The precipitate was removed by filtration, and the target compound was obtained after washing and filtration were repeated several times.

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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