High-efficiency corrosion inhibitor and preparation method thereof

Abstract

The application relates to the technical field of corrosion inhibitors, and particularly discloses a high-efficiency corrosion inhibitor and a preparation method thereof. The high-efficiency corrosion inhibitor is prepared from the following raw materials in parts by weight: 30-50 parts of a bifunctional modified aromatic polybasic ester, 15-25 parts of a sulfonated styrene-maleic anhydride copolymer, 5-10 parts of modified nano-alumina, 15-45 parts of octadecyl naphthalene, 5-15 parts of dipropylene glycol methyl ether and 1-2 parts of an antioxidant; the bifunctional modified aromatic polybasic ester is a thioureido-imidazoline bifunctional modified diisooctyl phthalate; and the modified nano-alumina is nano-alumina modified by a silane coupling agent on the surface. The corrosion inhibitor has the advantages of high corrosion inhibition efficiency and good salt resistance.

Description

Technical Field

[0001] This application relates to the field of corrosion inhibitor technology, and more specifically, to a highly efficient corrosion inhibitor and its preparation method. Background Technology

[0002] Corrosion is a significant problem in petroleum refining. Equipment corrosion not only poses potential safety risks but also increases production and maintenance costs, ultimately reducing plant efficiency. In refineries, crude oil is the primary cause of metal equipment corrosion. Small amounts of inorganic salts, sulfur- or nitrogen-containing compounds, CO2, acids, and water in crude oil are themselves corrosive substances. During petroleum processing, other impurities, though not inherently corrosive, can react and transform into corrosive media that damage equipment. While these impurities may be present in small quantities, they pose a significant potential threat to the safety of refinery metal equipment. Various additives and acidic / alkaline substances added during petroleum refining can also form corrosive media, further exacerbating metal corrosion. Therefore, corrosion prevention measures are essential to ensure the long-term operation of the equipment. Currently, in addition to material corrosion protection, corrosion prevention primarily relies on the addition of additives for process corrosion protection. Commonly added additives include demulsifiers, neutralizers, and corrosion inhibitors. Corrosion inhibitors are substances that can prevent or slow down metal corrosion under certain conditions. Compared with other protection methods, corrosion inhibitors have advantages such as being able to prevent corrosion without changing the corrosive environment; not requiring increased investment in anti-corrosion equipment; and the type and dosage of corrosion inhibitors can be varied according to changes in corrosion conditions to achieve the best corrosion inhibition effect. Currently, more than 90% of oil refineries in my country use the addition of different corrosion inhibitors to reduce corrosion in different parts of different units.

[0003] Corrosion inhibitors are characterized by high selectivity, leaching, contamination, and toxicity. Their protective ability for equipment is affected by various factors, such as the chemical composition and properties of the inhibitor, injection concentration and temperature, ambient pH, and system flow rate. Commonly used corrosion inhibitors can be classified into oxidation-type film corrosion inhibitors, adsorption-type film corrosion inhibitors, precipitation-type film corrosion inhibitors, and reaction-conversion-type film corrosion inhibitors. Among them, oxidation-type film corrosion inhibitors directly or indirectly oxidize the protected metal, forming a metal oxide film on its surface. This film has good density and strong adhesion to the metal. When the oxide film reaches a certain thickness, the oxidation reaction slows down; therefore, excessive corrosion inhibitors will not cause scaling or ferruginous deposits. Adsorption-type film corrosion inhibitors adsorb onto the metal surface through the physical or chemical adsorption of polar groups on the inhibitor molecules. This increases the activation energy of the corrosion reaction, hinders the transfer of charges or substances related to corrosion, and reduces the corrosion rate. Precipitation-type film corrosion inhibitors react with ions in the corrosive medium to form a water-insoluble or poorly soluble deposit film, which protects the metal. Precipitated films have poorer density and adhesion than passivation films, so their effectiveness is slightly lower than that of oxide films. Furthermore, the accumulation of precipitated films as the reaction progresses may cause scaling as a side effect. Reactive conversion corrosion inhibitors, on the other hand, form a reactive conversion film through interfacial reactions or transformations between the corrosion inhibitor, the corrosive medium, and the metal surface, thus protecting the metal device.

[0004] To address key issues such as naphthenic acid corrosion in petroleum refining processes, various corrosion inhibitor formulations have been developed. Among these, Chinese invention patent CN112391632A discloses a corrosion inhibitor, its preparation method, and a method for inhibiting naphthenic acid corrosion in oil products. This technical solution proposes a corrosion inhibitor with 25%-65% aromatic polyester as the main agent, combined with 1%-40% corrosion inhibitors selected from olefin-maleic anhydride copolymers and oil-soluble magnesium compounds, compounded with 20%-60% organic solvent. This corrosion inhibitor can function at high temperatures of 240℃-480℃, inhibiting naphthenic acid corrosion through the adsorption of aromatic polyesters and the film-forming synergistic effect of magnesium compounds. Furthermore, the absence of phosphorus reduces the risk of poisoning subsequent hydrogenation catalysts. Due to its relatively environmentally friendly nature and high-temperature adaptability, this corrosion inhibitor has been applied in some high-acid crude oil processing units.

[0005] However, these aromatic polyester-based corrosion inhibitors still have significant performance limitations in complex real-world operating conditions. The core problem lies in the substantial decrease in corrosion inhibition efficiency under high-salt environments. The abundant anions present in high-salt environments compete with the polar groups of the aromatic polyesters in the inhibitor for adsorption sites on the metal surface, while simultaneously disrupting the loose protective film formed by oil-soluble magnesium compounds. This leads to the loss of the corrosion film's continuity, resulting in a significant decrease in corrosion inhibition efficiency. While increasing the dosage to compensate for these performance defects can improve the corrosion inhibition rate, it doubles the reagent consumption and easily triggers emulsification problems in the tower top system, adding extra costs to subsequent oil-water separation. In summary, the corrosion inhibitors in these technologies suffer from poor salt resistance. Summary of the Invention

[0006] To improve the salt resistance of corrosion inhibitors, this application provides a high-efficiency corrosion inhibitor and its preparation method.

[0007] This application provides a high-efficiency corrosion inhibitor and its preparation method, which adopts the following technical solution:

[0008] A highly efficient corrosion inhibitor comprises the following raw materials in parts by weight:

[0009] 30-50 parts of bifunctional modified aromatic polyester;

[0010] 15-25 parts of sulfonated styrene-maleic anhydride copolymer;

[0011] 5-10 parts of modified nano-alumina;

[0012] 15-45 parts of octadecylnaphthalene;

[0013] 5-15 parts of dipropylene glycol methyl ether;

[0014] 1-2 parts antioxidant;

[0015] The bifunctional modified aromatic polyester is thiourea-imidazoline bifunctional modified diisooctyl phthalate;

[0016] The modified nano-alumina is nano-alumina with a surface modified by a silane coupling agent.

[0017] By adopting the above technical solution, existing corrosion inhibitors based on aromatic polyesters rely solely on the polarity of a single ester group for physical adsorption. The binding force between the molecule and the metal surface is weak, and in high-salt media, adsorption sites are easily replaced by anions such as chloride and sulfate ions, which is the core reason for the degradation of salt resistance. This application proposes a solution using thiourea-imidazoline bifunctional modified diisooctyl phthalate as the main agent, overcoming this limitation at the molecular adsorption mechanism level. This bifunctional structure can form an "NS-cooperative coordination adsorption system." The N atom in the imidazoline ring and the N and S atoms in the thiourea group simultaneously form stable chelate bonds with the empty d orbitals of Fe on the metal surface through lone pair electrons. Compared to the physical adsorption of a single ester group, the binding energy of chemical chelation is significantly improved, greatly enhancing the adsorption strength of the main agent molecule on the metal surface. Even in high-salt environments, it can resist competitive corrosion by anions, fundamentally blocking the path of adsorption site loss.

[0018] The introduction of sulfonated styrene-maleic anhydride copolymer constructs a second barrier against salt damage, forming a synergistic effect with the bifunctional main agent. The copolymer's molecular structure is rich in sulfonyl (-SO3) groups. － The sulfonated copolymer exhibits strong polarity and, upon adsorption onto a metal surface, forms a negatively charged repulsive layer. This layer, through electrostatic repulsion, hinders the migration and diffusion of anions from the high-salt medium to the metal surface, reducing the probability of contact between anions and the main agent molecules. This dual "adsorption-repulsion" mechanism overcomes the shortcomings of existing technologies that rely solely on the main agent's adsorption and lack an active anti-interference mechanism, significantly improving the corrosion inhibition system's tolerance to anions. Simultaneously, the oil-soluble structure of the sulfonated copolymer demonstrates excellent compatibility with the main agent and solvent system, allowing for uniform dispersion and participation in film formation, thus preventing localized protective failures caused by component separation.

[0019] The combination of modified nano-alumina with composite solvents and antioxidants improves salt resistance from the perspectives of membrane structure and adaptability to operating conditions. Unmodified nanoparticles are prone to agglomeration and have poor compatibility with oil-phase systems. However, after modification with silane coupling agents, their surface oleophilicity is enhanced, allowing them to be uniformly dispersed and fill the pores of the adsorption membrane formed by the main agent and copolymer. This effectively improves the problem of loose and porous protective films formed by oil-soluble magnesium compounds in existing technologies, enhances the density and continuity of the membrane, and prevents anions from penetrating to the metal surface through the membrane pores.

[0020] In summary, the above technical solution, through the combination of bifunctional modified aromatic polyesters, sulfonated styrene-maleic anhydride copolymers, modified nano-alumina, and other raw materials, effectively enhances the salt resistance of the corrosion inhibitor and extends its effective corrosion inhibition period while ensuring the high corrosion inhibition performance of the provided corrosion inhibitor.

[0021] Optionally, the thiourea-imidazoline bifunctional modified diisooctyl phthalate is prepared by the following method:

[0022] A1. Add phthalic anhydride and isooctyl alcohol to a reaction vessel, heat to 100-120℃ and stir until completely dissolved, then add tetrabutyl titanate catalyst, heat to 130-150℃ and react for 2-3 hours to obtain diisooctyl phthalate prepolymer.

[0023] A2. Add a mixture of oleyl hydroxyethyl imidazoline and pyridine-3-isothiocyanate to the diisooctyl phthalate prepolymer at a dropping rate of 0.5-1 mL / min. After the addition is complete, keep the reaction at 80-100℃ for 1-2 h. After cooling, thiourea-imidazoline bifunctional modified diisooctyl phthalate is obtained.

[0024] By employing the above technical solution, step A1 first prepares a structurally stable diisooctyl phthalate prepolymer, avoiding the molecular chain crosslinking or functional group grafting disorder that may result from direct modification. Step A2 controls the acceleration rate of the mixed droplets, preventing excessively vigorous local reactions from generating byproducts and ensuring that the thiourea group and imidazoline ring can be orderly and fully grafted onto the prepolymer molecular chain. This stepwise preparation strategy guarantees the structural integrity and modification efficiency of the bifunctional main agent, avoids the problem of insufficient adsorption sites due to insufficient modification of the main agent, and enables the main agent molecule to stably exert a synergistic chelate adsorption effect, providing a material basis for the stability of the corrosion inhibitor's salt resistance.

[0025] Optionally, in step A1, the mass ratio of phthalic anhydride to isooctyl alcohol is 1:(1.8-2.0).

[0026] By adopting the above technical solution, this mass ratio ensures the structural integrity of the prepolymer, providing a prerequisite for the sufficiency of subsequent bifunctional modification, and ensuring that the main agent molecule has sufficient synergistic adsorption sites, thereby enhancing the adsorption stability of the corrosion inhibitor in high-salt media.

[0027] Optionally, in step A1, the amount of tetrabutyl titanate catalyst added is 0.1%-0.3% of the total mass of phthalic anhydride and isooctyl alcohol.

[0028] By adopting the above technical solution, an addition amount of 0.1%-0.3% falls within the optimal range for catalytic activity. This effectively reduces the activation energy of the esterification reaction, promoting the rapid and complete reaction of phthalic anhydride and isooctyl alcohol at 130-150℃, thus shortening the reaction cycle. It also avoids side reactions caused by excessive catalyst, such as prepolymer chain degradation due to catalyst residue or abnormal crosslinking during subsequent thiourea modification. Insufficient catalyst leads to incomplete esterification; residual phthalic anhydride in the prepolymer can undergo non-target reactions with oleoyl hydroxyethyl imidazoline, occupying modifying reagents and reducing the bifunctional grafting rate, indirectly weakening salt resistance. This dosage range ensures the purity of the esterification product, guaranteeing the performance of the bifunctional main agent.

[0029] Optionally, in step A2, the mass ratio of diisooctyl phthalate prepolymer, oleoyl hydroxyethyl imidazoline, and pyridine-3-isothiocyanate is 10:(1-1.5):(0.8-1.2).

[0030] Optionally, the modified nano-alumina is prepared by the following method:

[0031] The silane coupling agent KH-550 was mixed with an ethanol solution and stirred at 40-60℃ for 30-60 min to obtain a hydrolysate. Then, nano-alumina was added, the temperature was raised to 80-100℃, and the mixture was stirred at 200-300 r / min for 1-2 h. The mixture was then centrifuged, the precipitate was collected, washed 3-5 times with anhydrous ethanol, and then dried in a drying oven at 50-60℃ for 2-3 h to obtain modified nano-alumina.

[0032] By employing the above technical solution, the dispersion problem of nanoparticles is solved through a continuous "hydrolysis-grafting-purification" process, providing support for membrane densification. The silane coupling agent KH-550 is first hydrolyzed in an ethanol solution to generate active silanol groups, creating conditions for the condensation reaction with hydroxyl groups on the surface of nano-alumina. A reaction temperature of 80-100℃ and a specific stirring rate promote sufficient contact of the active groups, ensuring uniform grafting of the coupling agent onto the nanoparticle surface. Centrifugation and washing with anhydrous ethanol remove ungrafted free coupling agent, preventing it from becoming a source of membrane defects. The nano-alumina modified by this method exhibits significantly improved surface oleophilicity, allowing it to be uniformly dispersed in the oil-phase corrosion inhibitor system instead of agglomerating into large particles. This effectively fills the pores in the membrane formed by the main agent and copolymer, improving the porous nature of existing protective films, reducing anion permeation channels, and enhancing the protective stability of the membrane under salt-resistant environments.

[0033] Optionally, the mass concentration of the ethanol solution is 30%-40%, and the mass ratio of the silane coupling agent KH-550 to the ethanol solution is 1:(10-15).

[0034] Optionally, the mass ratio of the nano-alumina to the silane coupling agent KH-550 is (5-8):1.

[0035] Optionally, the antioxidant is any one of antioxidant 1076, antioxidant 264, and antioxidant 1010.

[0036] Secondly, this application provides a method for preparing a highly efficient corrosion inhibitor, employing the following technical solution:

[0037] A method for preparing a highly efficient corrosion inhibitor includes the following steps:

[0038] S1. Add octadecylnaphthalene and dipropylene glycol methyl ether to a mixing vessel, heat to 40-60℃, add antioxidant and stir for 10-15 min until completely dissolved, then add sulfonated styrene-maleic anhydride copolymer and modified nano alumina in sequence, stir at 300-500 r / min for 30-60 min to obtain a premixed solution.

[0039] S2. Slowly add the bifunctional modified aromatic polyester to the premixed solution, stir at 200-300 r / min for 1-2 h at 50-70℃, cool to room temperature, and filter through a 5μm polytetrafluoroethylene filter membrane to obtain a high-efficiency corrosion inhibitor.

[0040] By designing a reasonable process, the synergistic effect of each component is fully utilized, indirectly improving salt resistance. Step S1 first dissolves the antioxidant in the composite solvent, then sequentially adds the sulfonated copolymer and modified nano-alumina. This avoids uneven dispersion of the antioxidant due to solubility issues and ensures that the copolymer and nanoparticles are fully dissolved and dispersed in the solvent, preventing localized film defects caused by agglomeration. Step S2 controls the addition rate and stirring conditions of the main agent, promoting uniform mixing of the main agent and the premix, allowing the main agent molecules, copolymer, and nanoparticles to form an ordered adsorption and filling structure. Uneven dispersion of components during preparation can lead to localized pores or insufficient adsorption sites in the film, allowing anions to easily penetrate and cause corrosion. This method ensures the homogeneity of the corrosion inhibitor system, enabling the functional components to synergistically form a dense and stable protective film, thereby fully utilizing salt resistance.

[0041] In summary, this application has the following beneficial effects:

[0042] 1. This application uses thiourea-imidazoline bifunctional modified diisooctyl phthalate as the main agent to construct an NS synergistic coordination adsorption system. Through the lone pair electrons of multiple atoms in the imidazoline ring and thiourea group, stable chelate bonds are formed with the metal surface. This chemical chelation significantly improves the binding energy compared to physical adsorption, greatly enhancing the adsorption strength of the main agent molecule on the metal surface. Even in high-salt environments, it can firmly occupy adsorption sites, blocking adsorption failure caused by anion competition at the molecular level. This provides core support for salt resistance and fundamentally strengthens the salt resistance of the corrosion inhibitor.

[0043] 2. To address the shortcomings of existing corrosion inhibitor films, such as their porous structure and lack of active anti-interference mechanisms, this application utilizes a sulfonated styrene-maleic anhydride copolymer to form a negatively charged repulsive layer. This layer, through electrostatic repulsion, hinders the migration of anions to the metal surface, reducing the probability of contact between the main agent and anions. Nano-alumina modified with a silane coupling agent, with its enhanced oleophilicity, can uniformly fill the pores of the film layer, solving the porosity problem of traditional magnesium compound protective films and blocking anion penetration channels. Antioxidants ensure the structural stability of functional components under high-temperature conditions, preventing a decrease in adsorption capacity due to oxidative degradation. The synergistic effect of multiple components significantly improves the corrosion inhibitor system's tolerance to high-salt environments. This multi-component synergy constructs a three-dimensional protective layer, effectively enhancing the corrosion inhibitor's salt resistance and anti-interference capabilities. Detailed Implementation

[0044] The present application will be further described in detail below with reference to the embodiments.

[0045] Preparation example of thiourea-imidazoline bifunctional modified diisooctyl phthalate

[0046] Preparation Example 1

[0047] The preparation method of thiourea-imidazoline bifunctional modified diisooctyl phthalate is as follows:

[0048] A1. Mix 10 kg of phthalic anhydride and 18 kg of isooctanol and add them to a reaction vessel. Heat the mixture to 100°C and stir until completely dissolved. Then add 0.028 kg of tetrabutyl titanate catalyst and heat the mixture to 130°C for 2 hours to obtain diisooctyl phthalate prepolymer.

[0049] A2. Add 1 kg of oleoyl hydroxyethyl imidazoline and 0.8 kg of pyridine-3-isothiocyanate to 10 kg of diisooctyl phthalate prepolymer at a dropping rate of 0.5 mL / min. After the addition is complete, keep the reaction at 80 °C for 1 h. After cooling, thiourea-imidazoline bifunctional modified diisooctyl phthalate is obtained.

[0050] Preparation Example 2

[0051] The preparation method of thiourea-imidazoline bifunctional modified diisooctyl phthalate is as follows:

[0052] A1. Mix 10 kg of phthalic anhydride and 19 kg of isooctanol and add them to the reactor. Heat the mixture to 110°C and stir until completely dissolved. Then add 0.058 kg of tetrabutyl titanate catalyst and heat the mixture to 140°C for 2.5 h to obtain diisooctyl phthalate prepolymer.

[0053] A2. Add 1.2 kg of oleoyl hydroxyethyl imidazoline and 1.0 kg of pyridine-3-isothiocyanate to 10 kg of diisooctyl phthalate prepolymer at a dropping rate of 0.5 mL / min. After the addition is complete, keep the reaction at 90 °C for 1.5 h. After cooling, thiourea-imidazoline bifunctional modified diisooctyl phthalate is obtained.

[0054] Preparation Example 3

[0055] The preparation method of thiourea-imidazoline bifunctional modified diisooctyl phthalate is as follows:

[0056] A1. Mix 10 kg of phthalic anhydride and 20 kg of isooctanol and add them to the reactor. Heat the mixture to 120°C and stir until completely dissolved. Then add 0.09 kg of tetrabutyl titanate catalyst and heat the mixture to 150°C for 3 hours to obtain diisooctyl phthalate prepolymer.

[0057] A2. Add a mixture of 1.5 kg of oleoyl hydroxyethyl imidazoline and 1.2 kg of pyridine-3-isothiocyanate to 10 kg of diisooctyl phthalate prepolymer at a dropping rate of 1 mL / min. After the addition is complete, keep the mixture at 100 °C for 2 h. After cooling, thiourea-imidazoline bifunctional modified diisooctyl phthalate is obtained.

[0058] Preparation Example 4

[0059] The difference between the imidazoline-modified diisooctyl phthalate and Preparation Example 3 is that pyridine-3-isothiocyanate was not added in step A2 of this Preparation Example.

[0060] Preparation example of modified nano-alumina

[0061] Preparation Example 5

[0062] Modified nano-alumina was prepared using the following method:

[0063] 1 kg of silane coupling agent KH-550 was mixed with 10 kg of 30% ethanol solution and stirred at 40 °C for 30 min to obtain a hydrolysate. Then, 5 kg of nano alumina was added, the temperature was raised to 80 °C, and the mixture was stirred at 200 r / min for 1 h. The mixture was then centrifuged, the precipitate was collected, washed 5 times with anhydrous ethanol, and then dried in a 50 °C drying oven for 2 h to obtain modified nano alumina.

[0064] Preparation Example 6

[0065] Modified nano-alumina was prepared using the following method:

[0066] 1 kg of silane coupling agent KH-550 was mixed with 12 kg of 35% ethanol solution and stirred at 50 °C for 45 min to obtain a hydrolysate. Then, 6.5 kg of nano-alumina was added, the temperature was raised to 90 °C, and the mixture was stirred at 250 r / min for 1.5 h. The mixture was then centrifuged, the precipitate was collected, washed 5 times with anhydrous ethanol, and then dried in a 55 °C drying oven for 2.5 h to obtain modified nano-alumina.

[0067] Preparation Example 7

[0068] Modified nano-alumina was prepared using the following method:

[0069] 1 kg of silane coupling agent KH-550 was mixed with 15 kg of 40% ethanol solution and stirred at 60 °C for 60 min to obtain a hydrolysate. Then, 8 kg of nano-alumina was added, the temperature was raised to 100 °C, and the mixture was stirred at 300 r / min for 2 h. The mixture was then centrifuged, the precipitate was collected, washed 5 times with anhydrous ethanol, and then dried in a 60 °C drying oven for 3 h to obtain modified nano-alumina.

[0070] The sulfonated styrene-maleic anhydride copolymer used in the embodiments of this application was prepared in-house. Specifically, the sulfonated styrene-maleic anhydride copolymer was prepared by the following method:

[0071] (1) First, wash 10 kg of styrene twice with 2 kg of 5% NaOH solution to remove the polymerization inhibitor, then wash with deionized water until the pH of the aqueous phase is 7, and add 0.02 kg of hydroquinone to prevent self-polymerization for later use; add 30 kg of toluene to a reactor equipped with a stirrer and reflux condenser and heat to 80 °C, mix the pretreated styrene, 5 kg of maleic anhydride and 0.15 kg of BPO evenly, and drop it into the reactor at a rate of 3 mL / min (to be completed in about 1.5 hours), then keep the reflux reaction at 80-85 °C for 4 hours until the solution is light yellow and viscous and a white solid is precipitated when a sample is dropped into ethanol, thus obtaining SMA toluene solution.

[0072] (2) Cool the SMA toluene solution to 50°C, and slowly add 6 kg of 98% concentrated sulfuric acid at a rate of 1 mL / min while stirring. Control the system temperature to not exceed 60°C by circulating cold water through the jacket of the reactor. After the addition is complete, raise the temperature to 65°C and keep it at that temperature for 2 hours. When the solution color deepens to light brown and the pH test paper shows strong acidity, it proves that the sulfonation reaction is complete and the sulfonated mixture is obtained.

[0073] (3) Slowly pour the sulfonated mixture into 20 kg of ice water and stir vigorously. After the brown flocculent precipitate is precipitated, let it stand for 30 minutes, filter and collect the precipitate, and wash it with deionized water until the pH of the washing solution is 4-5. Then soak and wash it once with 15 kg of ethanol to remove impurities. Put the washed precipitate into a vacuum drying oven and dry it at 60℃ and 0.08 MPa for 6 hours to finally obtain brown powder sulfonated styrene-maleic anhydride copolymer (SSMA).

[0074] Example

[0075] Example 1

[0076] A highly efficient corrosion inhibitor, the raw material components and formulation of which are shown in Table 1, wherein the bifunctional modified aromatic polyester is the thiourea-imidazoline bifunctional modified diisooctyl phthalate prepared in Preparation Example 1; the modified nano alumina is the modified nano alumina prepared in Preparation Example 5; and the antioxidant is antioxidant 1076.

[0077] A highly efficient corrosion inhibitor is prepared as follows:

[0078] S1. Add octadecylnaphthalene and dipropylene glycol methyl ether to a mixing vessel, heat to 40°C, add antioxidant and stir for 10 min until completely dissolved, then add sulfonated styrene-maleic anhydride copolymer and modified nano alumina in sequence, stir at 300 r / min for 30 min to obtain a premixed solution.

[0079] S2. The bifunctional modified aromatic polyester was slowly added to the premixed solution and stirred at 200 r / min for 1 h at 50 °C. After cooling to room temperature, the solution was filtered through a 5 μm polytetrafluoroethylene filter membrane to obtain a high-efficiency corrosion inhibitor.

[0080] Example 2

[0081] A highly efficient corrosion inhibitor, the raw material components and formulation of which are shown in Table 1, wherein the bifunctional modified aromatic polyester is the thiourea-imidazoline bifunctional modified diisooctyl phthalate prepared in Preparation Example 1; the modified nano alumina is the modified nano alumina prepared in Preparation Example 6; and the antioxidant is antioxidant 1010.

[0082] A highly efficient corrosion inhibitor is prepared as follows:

[0083] S1. Add octadecylnaphthalene and dipropylene glycol methyl ether to a mixing vessel, heat to 50°C, add antioxidant and stir for 12 min until completely dissolved, then add sulfonated styrene-maleic anhydride copolymer and modified nano alumina in sequence, stir at 400 r / min for 45 min to obtain a premixed solution.

[0084] S2. The bifunctional modified aromatic polyester was slowly added to the premixed solution and stirred at 250 r / min for 1.5 h at 60 °C. After cooling to room temperature, the solution was filtered through a 5 μm polytetrafluoroethylene filter membrane to obtain a high-efficiency corrosion inhibitor.

[0085] Example 3

[0086] A highly efficient corrosion inhibitor, the raw material components and formulation of which are shown in Table 1, wherein the bifunctional modified aromatic polyester is the thiourea-imidazoline bifunctional modified diisooctyl phthalate prepared in Preparation Example 1; the modified nano alumina is the modified nano alumina prepared in Preparation Example 7; and the antioxidant is antioxidant 1010.

[0087] A highly efficient corrosion inhibitor is prepared as follows:

[0088] S1. Add octadecylnaphthalene and dipropylene glycol methyl ether to a mixing vessel, heat to 50°C, add antioxidant and stir for 12 min until completely dissolved, then add sulfonated styrene-maleic anhydride copolymer and modified nano alumina in sequence, stir at 400 r / min for 45 min to obtain a premixed solution.

[0089] S2. The bifunctional modified aromatic polyester was slowly added to the premixed solution and stirred at 250 r / min for 1.5 h at 60 °C. After cooling to room temperature, the solution was filtered through a 5 μm polytetrafluoroethylene filter membrane to obtain a high-efficiency corrosion inhibitor.

[0090] Table 1. Raw material components and proportions (kg) of the corrosion inhibitors in Examples 1-3

[0091]

[0092] Example 4

[0093] A highly efficient corrosion inhibitor, which differs from Example 3 in that the antioxidant used in this example is antioxidant 264.

[0094] Example 5

[0095] A highly efficient corrosion inhibitor, which differs from Example 3 in that the bifunctional modified aromatic polyester in this example is the thiourea-imidazoline bifunctional modified diisooctyl phthalate obtained in Preparation Example 2.

[0096] Example 6

[0097] A highly efficient corrosion inhibitor, which differs from Example 3 in that the bifunctional modified aromatic polyester in this example is the thiourea-imidazoline bifunctional modified diisooctyl phthalate obtained in Preparation Example 3.

[0098] Comparative Example

[0099] Comparative Example 1

[0100] A corrosion inhibitor was prepared according to the method in Example 1-1 of the patent application document with publication number CN112391632A entitled "A Corrosion Inhibitor and its Preparation Method and a Method for Inhibiting Naphthenic Acid Corrosion in Oil".

[0101] Comparative Example 2

[0102] A highly efficient corrosion inhibitor, which differs from Example 3 in that an equal amount of imidazoline-modified diisooctyl phthalate prepared in Preparation Example 4 is used in this comparative example instead of thiourea-imidazoline bifunctional modified diisooctyl phthalate.

[0103] Comparative Example 3

[0104] A highly efficient corrosion inhibitor, which differs from Example 3 in that an equal amount of unmodified nano-alumina is used instead of modified nano-alumina in this comparative example.

[0105] Comparative Example 4

[0106] A highly efficient corrosion inhibitor, which differs from Example 3 in that sulfonated styrene-maleic anhydride copolymer was not added in this comparative example, and the difference was made up by thiourea-imidazoline bifunctional modified diisooctyl phthalate of Preparation Example 1.

[0107] Performance testing

[0108] 1. Test substrate and medium

[0109] In this experiment, a fixed dosage of 10 ppm corrosion inhibitor was used for all tests to ensure data comparability;

[0110] Substrate: Q235 steel sheet (size 20mm×10mm×2mm, polished to mirror finish, degreased with acetone, weighing accuracy 0.0001g).

[0111] Normal operating medium: Simulated crude oil atmospheric and vacuum distillation tower top water (pH=6.5, containing 500mg / L naphthenic acid, temperature 80℃);

[0112] High-salt working medium: 5% NaCl + 1% Na2SO4 (simulating a high-salt crude oil processing environment) are added to the conventional medium. － SO4 2－ (The main interfering anion), temperature 80℃.

[0113] 2. Test Methods

[0114] (1) Corrosion inhibition efficiency (η)

[0115] Weight loss method: The steel sheet is immersed in the medium for 24 hours and the corrosion rate (v) is calculated. η=(v0-v) / v0×100% (v0 is the corrosion rate of the blank group).

[0116] (2) Cl － SO4 2－ Permeation rate

[0117] Ion-selective electrode method: The concentration of anions in the adsorption layer on the surface of the steel sheet was detected after 24 hours, and the permeation rate was calculated.

[0118] 3. The test results are shown in Table 2.

[0119] Table 2 Experimental Results

[0120]

[0121] As can be seen from the experimental results in Table 2, the high-efficiency corrosion inhibitors prepared in this application exhibit significantly better salt resistance than the comparative examples under high-salt conditions. Specifically, the corrosion inhibition efficiency of Examples 1-6 remained above 85.6% under high-salt conditions, while the anion permeation rate was controlled at 2.3 μg / (cm²). 2 ·h) and below, especially in Example 6, the corrosion inhibition efficiency reached 93.5% under high salt conditions, and the anion permeation rate was as low as 1.2 μg / (cm). 2 The results (h) indicate that the technical solution of this application significantly improves the corrosion inhibitor's resistance to anionic competitive corrosion in high-salt environments through the multiple effects of the bifunctional modified main agent, the synergistic effect of the sulfonated copolymer, and the filling of the pores in the modified nano-alumina film. In contrast, Comparative Example 1 (corrosion inhibitor based on existing technology) showed a sharp drop in corrosion inhibition efficiency to 48.2% under high-salt conditions, with an anion penetration rate as high as 8.9 μg / (cm³). 2 This is mainly attributed to the fact that its single ester physical adsorption mechanism is easily replaced by anions in a high-salt environment, leading to the loss of adsorption sites and the disruption of membrane continuity.

[0122] Further comparison of the differences between the examples and Comparative Examples 2-4 reveals the contribution of each component to the salt resistance performance. Comparative Example 2, using an imidazoline-modified main agent without thiourea groups, showed a significantly lower corrosion inhibition efficiency (65.3%) under high salt conditions compared to the examples, indicating that the mechanism by which the "NS synergistic coordination adsorption system" enhances adsorption strength through chemical chelation is the core of the improved salt resistance performance. Comparative Example 3, using unmodified nano-alumina, achieved a high salt corrosion inhibition efficiency of 72.1% and an anion permeation rate of 4.5 μg / (cm³). 2The results (h) were inferior to those of the examples, indicating that the modification with silane coupling agents is crucial for blocking anion permeation channels by enhancing the oleophilicity of nanoparticles and uniformly filling the pores of the film. Comparative Example 4, without the addition of the sulfonated copolymer, exhibited a high-salt corrosion inhibition efficiency of 70.5% and an anion permeation rate of 5.1 μg / (cm²). 2 The significant decrease in ·h) verifies the synergistic effect of the sulfonated copolymer on salt resistance through the "adsorption-repulsion" dual action mode of hindering anion migration by electrostatic repulsion.

[0123] Furthermore, a comparison between Examples 5-6 and Examples 1-3 shows that optimizing the preparation process of the bifunctional main agent (such as adjusting the mass ratio of phthalic anhydride to isooctanol, the amount of catalyst, and the proportion of modifying reagents) can further improve salt resistance. For example, Example 6, using a phthalic anhydride to isooctanol mass ratio of 1:2.0 and a catalyst dosage of 0.3%, exhibited a 3.7% increase in high-salt corrosion inhibition efficiency compared to Example 3, and a 0.6 μg / (cm²) decrease in anion permeation rate. 2 This is attributed to the superior prepolymer structural integrity and bifunctional group grafting rate, which enhances the synergistic chelation adsorption capacity of the main agent molecules. In summary, the technical solution of this application achieves a breakthrough improvement in the salt resistance of corrosion inhibitors through innovative molecular adsorption mechanisms, multi-component synergistic enhancement, and process optimization, providing an efficient solution for metal corrosion protection under high-salt conditions.

[0124] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A corrosion inhibitor, characterized in that, The raw materials include the following parts by weight: 30-50 parts of bifunctional modified aromatic polyester; 15-25 parts of sulfonated styrene-maleic anhydride copolymer; 5-10 parts of modified nano-alumina; 15-45 parts of octadecylnaphthalene; 5-15 parts of dipropylene glycol methyl ether; 1-2 parts antioxidant; The bifunctional modified aromatic polyester is thiourea-imidazoline bifunctional modified diisooctyl phthalate; The modified nano-alumina is nano-alumina with a surface modified by a silane coupling agent; The thiourea-imidazoline bifunctional modified diisooctyl phthalate was prepared by the following method: A1. Add phthalic anhydride and isooctyl alcohol to a reaction vessel, heat to 100-120℃ and stir until completely dissolved, then add tetrabutyl titanate catalyst, heat to 130-150℃ and react for 2-3 hours to obtain diisooctyl phthalate prepolymer. A2. Add a mixture of oleyl hydroxyethyl imidazoline and pyridine-3-isothiocyanate to the diisooctyl phthalate prepolymer at a dropping rate of 0.5-1 mL / min. After the addition is complete, keep the reaction at 80-100℃ for 1-2 h. After cooling, thiourea-imidazoline bifunctional modified diisooctyl phthalate is obtained.

2. The corrosion inhibitor according to claim 1, characterized in that: In step A1, the mass ratio of phthalic anhydride to isooctyl alcohol is 1:(1.8-2.0).

3. The corrosion inhibitor according to claim 1, characterized in that: In step A1, the amount of tetrabutyl titanate catalyst added is 0.1%-0.3% of the total mass of phthalic anhydride and isooctyl alcohol.

4. The corrosion inhibitor according to claim 1, characterized in that: In step A2, the mass ratio of diisooctyl phthalate prepolymer, oleoyl hydroxyethyl imidazoline, and pyridine-3-isothiocyanate is 10:(1-1.5):(0.8-1.2).

5. The corrosion inhibitor according to claim 1, characterized in that, The modified nano-alumina was prepared using the following method: The silane coupling agent KH-550 was mixed with an ethanol solution and stirred at 40-60℃ for 30-60 min to obtain a hydrolysate. Then, nano-alumina was added, the temperature was raised to 80-100℃, and the mixture was stirred at 200-300 r / min for 1-2 h. The mixture was then centrifuged, the precipitate was collected, washed 3-5 times with anhydrous ethanol, and then dried in a drying oven at 50-60℃ for 2-3 h to obtain modified nano-alumina.

6. The corrosion inhibitor according to claim 5, characterized in that, The mass concentration of the ethanol solution is 30%-40%, and the mass ratio of the silane coupling agent KH-550 to the ethanol solution is 1:(10-15).

7. The corrosion inhibitor according to claim 5, characterized in that, The mass ratio of the nano-alumina to the silane coupling agent KH-550 is (5-8):

1.

8. The corrosion inhibitor according to claim 1, characterized in that, The antioxidant is any one of antioxidant 1076, antioxidant 264 and antioxidant 1010.

9. A method for preparing a corrosion inhibitor according to any one of claims 1-8, characterized in that, The steps include the following: S1. Add octadecylnaphthalene and dipropylene glycol methyl ether to a mixing vessel, heat to 40-60℃, add antioxidant and stir for 10-15 min until completely dissolved, then add sulfonated styrene-maleic anhydride copolymer and modified nano alumina in sequence, stir at 300-500 r / min for 30-60 min to obtain a premixed solution. S2. Slowly add the bifunctional modified aromatic polyester to the premixed solution, stir at 200-300 r / min for 1-2 h at 50-70℃, cool to room temperature, and filter through a 5μm polytetrafluoroethylene filter membrane to obtain a high-efficiency corrosion inhibitor.

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