Efficient corrosion inhibitor and preparation method thereof

Abstract

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

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of corrosion inhibitors, and more particularly to a high-efficiency corrosion inhibitor and a preparation method thereof. BACKGROUND

[0002] There are many corrosion problems in the oil refining process. The corrosion of equipment not only has potential safety problems, but also increases the production and maintenance costs, and overall reduces the efficiency of the plant. In the oil refinery, crude oil is the main factor causing corrosion of metal equipment. A small amount of inorganic salts, S or N-containing compounds, CO2, acid and water impurities in crude oil are corrosive substances themselves; and in the oil processing process, other impurities that are not corrosive can also be converted into corrosive media that corrode equipment due to reactions. These impurities, although in small amounts, pose a great potential threat to the safety of metal equipment in oil refineries. In the oil refining process, various additives and acidic and basic substances added can also form corrosive media, thereby exacerbating the corrosion of metal equipment. Therefore, corrosion protection measures must be taken to ensure long-term operation of the device. Among the current corrosion protection measures, in addition to material corrosion protection, process corrosion protection is mainly achieved by adding additives. Commonly added additives include demulsifiers, neutralizing agents 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 the advantages of not changing the corrosion environment, not needing to increase corrosion protection equipment investment, and the type and amount of corrosion inhibitors can be changed with the change of corrosion conditions to achieve the best corrosion inhibition effect. At present, more than 90% of oil refineries in China use the measure of adding different corrosion inhibitors to reduce the corrosion of different parts in different devices.

[0003] Corrosion inhibitors have high selectivity, loss, pollution, toxicity and other characteristics, and the protection ability of the equipment is affected by various factors, such as the chemical composition and properties of the corrosion inhibitor, the injection concentration and temperature, the environmental pH value, the system flow rate and the like. The commonly used corrosion inhibitors can be divided into oxidation type film corrosion inhibitor, adsorption type film corrosion inhibitor, precipitation type film corrosion inhibitor and reaction conversion type film corrosion inhibitor and the like. Among them, the oxidation type film corrosion inhibitor directly or indirectly oxidizes the protected metal, and forms a thin film of metal oxide on the surface of the metal, which has good density and strong adhesion to the metal. When the oxidation film reaches a certain thickness, the oxidation reaction slows down, so that excessive corrosion inhibitor will not cause scale formation or iron scale. The adsorption type film corrosion inhibitor is adsorbed on the metal surface through the physical adsorption or chemical adsorption of the polar groups on the corrosion inhibitor molecules, increases the activation energy of the corrosion reaction, hinders the transfer of charges or substances related to corrosion, and reduces the corrosion rate. The precipitation type film corrosion inhibitor reacts with ions in the corrosion medium to form a precipitate film that is difficult to dissolve in water or insoluble in water, which protects the metal. The density and adhesion of the precipitate film are poorer than those of the passivation film, so the effect is slightly worse than that of the oxidation film type. Moreover, the precipitate film will continuously increase with the reaction, which may cause the side effect of fouling. The reaction conversion type film corrosion inhibitor forms a reaction conversion film by interfacial reaction or conversion of the corrosion inhibitor, corrosion medium and metal surface to protect the metal device.

[0004] In view of the key problems such as naphthenic acid corrosion in the petroleum refining process, the existing technology has developed various corrosion inhibitor formulations. In the related technology, a kind of corrosion inhibitor and its preparation method and method for inhibiting naphthenic acid corrosion in oil products are disclosed in Chinese patent application No. CN112391632A. The corrosion inhibitor provided in the technical solution is mainly composed of 25%-65% aromatic polyesters by mass fraction, 1%-40% corrosion auxiliary agent, the corrosion auxiliary agent is selected from olefin-maleic anhydride copolymer and oil-soluble magnesium compound, and 20%-60% organic solvent is compounded. The corrosion inhibitor provided by the technical solution can work at a high temperature condition of 240-480℃, realizes the inhibition of naphthenic acid corrosion through the adsorption of aromatic polyesters and the film forming synergistic effect of magnesium compounds, and reduces the poisoning risk of subsequent hydrogenation catalysts due to the absence of phosphorus element. The corrosion inhibitor provided by the technical solution has been applied in some high-acid crude oil processing devices due to its relative environmental protection and high temperature adaptability.

[0005] However, the aromatic polybasic ester-based corrosion inhibitor still has significant performance limitations in actual complex working conditions. The core problem is the significant attenuation of corrosion inhibition efficiency in high-salt medium. A large number of anions in high-salt environment compete with the polar groups of the aromatic polybasic ester in the corrosion inhibitor for the adsorption sites on the metal surface, and at the same time, destroy the loose protective film formed by the oil-soluble magnesium compound, resulting in loss of continuity of the corrosion inhibition film, and then leading to significant attenuation of the corrosion inhibition efficiency. If the addition amount is increased to compensate for the performance defects, the corrosion inhibition rate can be increased, but the single consumption of the agent is increased by 2 times, and the emulsification problem of the tower top system is easily caused, which increases the additional cost of subsequent oil-water separation. In summary, the corrosion inhibitor in the related art has the defect of poor salt tolerance. SUMMARY

[0006] In order to improve the salt tolerance of the corrosion inhibitor, the application provides a high-efficiency corrosion inhibitor and a preparation method thereof.

[0007] The high-efficiency corrosion inhibitor and the preparation method thereof provided by the application adopt the following technical scheme: A high-efficiency corrosion inhibitor comprises 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-aluminum oxide; 15-45 parts of octadecylnaphthalene; 5-15 parts of dipropylene glycol methyl ether; 1-2 parts of an antioxidant; The bifunctional modified aromatic polybasic ester is a thioureido-imidazoline bifunctional modified diisooctyl phthalate; The modified nano-aluminum oxide is nano-aluminum oxide modified by a silane coupling agent on the surface.

[0008] By adopting the above technical scheme, the existing corrosion inhibitor based on the aromatic polybasic ester relies only on the polarity of a single ester group to achieve physical adsorption, and the binding force between the molecule and the metal surface is weak. In a high-salt medium, the adsorption sites are easily replaced by anions such as chloride ions and sulfate ions, which is the core reason for the attenuation of salt tolerance. The technical scheme of the application proposes to use a thioureido-imidazoline bifunctional modified diisooctyl phthalate as a main agent, which breaks through this limitation from the aspect of molecular adsorption mechanism. The bifunctional structure can form an “N-S synergistic coordination adsorption system”. The N atom in the imidazoline ring and the N and S atoms in the thioureido group form stable chelate bonds with the empty d orbitals of the metal surface Fe through lone pair electrons. Compared with physical adsorption of a single ester group, the binding energy of chemical chelation is significantly improved, so that the adsorption firmness of the main agent molecule on the metal surface is greatly enhanced, and even in a high-salt environment, the corrosion inhibitor can resist the erosion of anions. This fundamentally blocks the path of loss of adsorption sites.

[0009] The introduction of sulfonated styrene-maleic anhydride copolymer builds a second barrier for salt resistance, and forms a synergistic effect with the bifunctional main agent. The sulfonic group (-SO3 － ) in the molecular structure of the copolymer is highly polar, and can form a negatively charged repulsive layer after adsorbing on the metal surface, thereby hindering the migration and diffusion of anions to the metal surface in a high-salt medium through electrostatic repulsion effect, and reducing the contact probability of anions with the main agent molecules. This dual action mode of "adsorption-repulsion" solves the defect in the prior art that only relies on the single adsorption of the main agent and lacks an active anti-interference mechanism, so that the resistance of the corrosion inhibitor system to anions is significantly improved. At the same time, the oil-soluble structure of the sulfonated copolymer has excellent compatibility with the main agent and the solvent system, and can be uniformly dispersed and involved in the film layer construction, avoiding the local failure of protection caused by component separation.

[0010] The modification of nano-aluminum oxide with composite solvents and antioxidants improves the salt resistance from the aspects of film structure and working condition adaptability. The unmodified nanoparticles are prone to agglomeration and have poor compatibility with the oil phase system, but after modification by silane coupling agent, the surface lipophilicity is improved, and the nanoparticles can be uniformly dispersed and filled in the adsorption film pores formed by the main agent and the copolymer, effectively improving the problem of loose and porous protective film formed by the oil-soluble magnesium compound in the prior art, and improving the film density and continuity to prevent anions from penetrating through the film pores to the metal surface.

[0011] In summary, the above technical scheme cooperates the bifunctional modified aromatic polybasic ester, the sulfonated styrene-maleic anhydride copolymer, the modified nano-aluminum oxide, and other raw materials, effectively enhances the salt resistance of the corrosion inhibitor on the basis of ensuring that the provided corrosion inhibitor has high corrosion inhibition performance, and prolongs the action period of the corrosion inhibitor.

[0012] Optionally, the thioureido-imidazoline bifunctional modified diisooctyl phthalate is prepared by the following method: A1, mix phthalic anhydride and isooctanol into a reaction kettle, heat to 100-120℃, stir until completely dissolved, then add tetrabutyl titanate catalyst, heat to 130-150℃, react for 2-3h, to obtain diisooctyl phthalate prepolymer; A2, add a mixed solution of oil-based hydroxyethyl imidazoline and pyridine-3-isothiocyanate to the diisooctyl phthalate prepolymer dropwise at a rate of 0.5-1mL / min, and after the dropwise addition is completed, heat at 80-100℃ for 1-2h, and then cool to obtain the thioureido-imidazoline bifunctional modified diisooctyl phthalate.

[0013] By adopting the technical scheme, the diisooctyl phthalate prepolymer with stable structure is prepared in the A1 step, avoiding crosslinking of molecular chains or confusion of functional group grafting caused by direct modification; the dropping speed of the mixed solution is controlled in the A2 step, preventing the production of by-products caused by too intense local reaction, and ensuring that the thioureido group and the imidazoline ring can be orderly and sufficiently grafted on the molecular chains of the prepolymer. The step-by-step preparation strategy ensures the structural integrity and modification efficiency of the bifunctional main agent, avoids the problem of insufficient adsorption sites caused by insufficient modification of the main agent, enables the main agent molecules to stably play a synergistic chelation and adsorption role, and provides a material basis for the stability of the salt resistance of the corrosion inhibitor.

[0014] Optionally, in the A1 step, the mass ratio of the phthalic anhydride and the isooctanol is 1: (1.8-2.0).

[0015] By adopting the technical scheme, the mass ratio ensures the structural integrity of the prepolymer, provides a prerequisite for the sufficiency of the subsequent bifunctional modification, ensures that the main agent molecules have sufficient synergistic adsorption sites, and thus enhances the adsorption stability of the corrosion inhibitor in the high-salt medium.

[0016] Optionally, in the A1 step, the addition amount of the tetrabutyl titanate catalyst is 0.1%-0.3% of the total mass of the phthalic anhydride and the isooctanol.

[0017] By adopting the technical scheme, the addition amount of 0.1%-0.3% is in the optimal interval of catalytic activity, which can effectively reduce the activation energy of esterification reaction, promote the rapid reaction of phthalic anhydride and isooctanol at 130-150℃, and shorten the reaction period; and can avoid side reactions caused by excessive catalyst, such as degradation of the molecular chains of the prepolymer caused by catalyst residues, or abnormal crosslinking in the subsequent thiouronium modification process. Insufficient catalyst dosage will lead to incomplete esterification reaction, and the residual phthalic anhydride in the prepolymer will cause non-target reactions with oil-based hydroxyethyl imidazoline, occupy the modification reagent, and reduce the bifunctional grafting rate, which indirectly weakens the salt resistance. The dosage range ensures the purity of the esterification product, and provides protection for the performance of the bifunctional main agent.

[0018] Optionally, in the A2 step, the mass ratio of the diisooctyl phthalate prepolymer, the oil-based hydroxyethyl imidazoline, and the pyridine-3-isothiocyanate is 10: (1-1.5): (0.8-1.2).

[0019] Optionally, the modified nano-aluminum oxide is prepared by the following method: Mix silane coupling agent KH-550 with ethanol solution, stir at 40-60℃ for 30-60min to obtain hydrolysis solution, then add nano-alumina, heat to 80-100℃, stir at 200-300r / min for 1-2h, then centrifugal separation, collect the precipitate, wash with anhydrous ethanol for 3-5 times, then place in 50-60℃ drying oven to dry for 2-3h, to obtain modified nano-alumina.

[0020] By adopting the above technical scheme, the dispersibility problem of nanoparticles is solved through the consecutive "hydrolysis-grafting-purification" steps, and support is provided for the densification of the film layer. The silane coupling agent KH-550 is first hydrolyzed in the ethanol solution to generate active silicon hydroxyl groups, which creates conditions for the condensation reaction with the surface hydroxyl groups of the nano-alumina. The reaction temperature of 80-100℃ and the specific stirring rate promote the full contact of the active groups, ensuring that the coupling agent is uniformly grafted on the surface of the nanoparticles. The centrifugal separation and anhydrous ethanol washing remove the ungrafted free coupling agent, avoiding it from becoming a defect source of the film layer. The nano-alumina modified by this method has significantly improved lipophilicity on the surface, and can be uniformly dispersed in the oil phase corrosion inhibitor system instead of agglomerating into large particles, thereby effectively filling the pores of the film layer formed by the main agent and the copolymer, improving the defect of the loose protective film in the prior art, reducing the anion penetration channel, and improving the stability of the film layer in the salt environment.

[0021] 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).

[0022] Optionally, the mass ratio of the nano-alumina to the silane coupling agent KH-550 is (5-8):1.

[0023] Optionally, the antioxidant is any one of antioxidant 1076, antioxidant 264, and antioxidant 1010.

[0024] In a second aspect, the application provides a preparation method of a high-efficiency corrosion inhibitor, which adopts the following technical scheme: A preparation method of a high-efficiency corrosion inhibitor includes the following steps: S1, octadecylnaphthalene and dipropylene glycol methyl ether are added to a mixing kettle, heated to 40-60℃, first add antioxidant and stir for 10-15min until completely dissolved, then add sulfonated styrene-maleic anhydride copolymer and modified nano-alumina in sequence, stir at 300-500r / min for 30-60min to obtain a premix; S2, slowly add the bifunctional modified aromatic polybasic ester to the premix, stir at 200-300r / min for 1-2h at 50-70℃, cool to room temperature, filter through a 5μm polytetrafluoroethylene filter membrane to obtain a high-efficiency corrosion inhibitor.

[0025] The rational step design ensures the full play of the synergistic effect of each component, indirectly improving the salt tolerance. In the S1 step, the antioxidant is dissolved in the composite solvent, and then the sulfonated copolymer and modified nano-aluminum oxide are added in sequence, which can avoid uneven dispersion of the antioxidant due to solubility problems, while ensuring the full dissolution and dispersion of the copolymer and nanoparticles in the solvent, preventing local film layer defects caused by agglomeration; the S2 step controls the addition speed and stirring conditions of the main agent, which can promote the uniform mixing of the main agent and the pre-mixed solution, and make the main agent molecules form an ordered adsorption and filling structure with the copolymer and nanoparticles. If the components are not uniformly dispersed during preparation, it will cause local film layer to have pores or insufficient adsorption sites, and anions are easy to penetrate from the defects to cause corrosion. This method ensures the uniformity of the corrosion inhibitor system, so that each functional component synergistically forms a dense and stable protective film, thereby fully exerting the salt tolerance.

[0026] In summary, the present application has the following beneficial effects: 1. The present application uses thioureido-imidazoline bifunctional modified diisooctyl phthalate as the main agent to construct an N-S synergistic coordination adsorption system, and forms stable chelate bonds with the metal surface through the lone pair electrons of multiple atoms in the imidazoline ring and the thioureido group. This chemical chelation can significantly improve the physical adsorption binding energy, greatly enhance the adsorption firmness of the main agent molecules on the metal surface, and firmly occupy the adsorption sites even in a high salt environment, thereby blocking the adsorption failure caused by anion competition from the molecular interaction level, providing core support for salt tolerance, and strengthening the salt tolerance of the corrosion inhibitor from the root.

[0027] 2. In view of the defects of the existing corrosion film, such as loose and lack of active anti-interference mechanism, the present application forms a negative electric repulsion layer after adsorption of the sulfonated styrene-maleic anhydride copolymer, hinders the migration of anions to the metal surface through electrostatic repulsion, and reduces the contact probability of the main agent and anions; the nano-aluminum oxide modified by the silane coupling agent can uniformly fill the film layer pores after the oil affinity is improved, solving the problem of porous protective film of traditional magnesium compounds and blocking the anion penetration channel. The antioxidant ensures the stability of the functional component structure under high temperature conditions, avoids the decrease of adsorption capacity caused by oxidative degradation, and the multi-component synergy significantly improves the tolerance of the corrosion system to high salt environment, and the multi-component synergy establishes a solid protection, effectively strengthening the salt resistance and anti-interference ability of the corrosion inhibitor. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below in conjunction with the examples.

[0029] Preparation example of thioureido-imidazoline bifunctional modified diisooctyl phthalate Preparation example 1 The preparation method of the thioureido-imidazoline bifunctional modified diisooctyl phthalate is as follows: A1. Mix 10 kg of phthalic anhydride and 18 kg of isooctanol and add them to the reactor. 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. 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.

[0030] Preparation Example 2 The preparation method of thiourea-imidazoline bifunctional modified diisooctyl phthalate is as follows: 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. 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.

[0031] Preparation Example 3 The preparation method of thiourea-imidazoline bifunctional modified diisooctyl phthalate is as follows: 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. A2. A mixture of 1.5 kg of oleoyl hydroxyethyl imidazoline and 1.2 kg of pyridine-3-isothiocyanate was added dropwise to 10 kg of diisooctyl phthalate prepolymer at a dropping rate of 1 mL / min. After the addition was complete, the mixture was kept at 100 °C for 2 h. After cooling, thiourea-imidazoline bifunctional modified diisooctyl phthalate was obtained.

[0032] Preparation Example 4 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.

[0033] Preparation example of modified nano-alumina Preparation Example 5 Modified nano-alumina was prepared using the following method: 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.

[0034] Preparation Example 6 Modified nano-alumina was prepared using the following method: 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.

[0035] Preparation Example 7 Modified nano-alumina was prepared using the following method: 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.

[0036] 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: (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.

[0037] (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.

[0038] (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).

[0039] Example Example 1 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.

[0040] A highly efficient corrosion inhibitor is prepared as follows: 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. 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.

[0041] Example 2 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.

[0042] A highly efficient corrosion inhibitor is prepared as follows: 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. 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.

[0043] Example 3 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.

[0044] A highly efficient corrosion inhibitor is prepared as follows: 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. 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.

[0045] Table 1. Raw material components and proportions (kg) of the corrosion inhibitors in Examples 1-3

[0046] Example 4 A highly efficient corrosion inhibitor, which differs from Example 3 in that the antioxidant used in this example is antioxidant 264.

[0047] Example 5 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.

[0048] Example 6 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.

[0049] Comparative Example Comparative Example 1 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".

[0050] Comparative Example 2 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.

[0051] Comparative Example 3 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.

[0052] Comparative Example 4 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.

[0053] Performance testing 1. Test substrate and medium In this experiment, a fixed dosage of 10 ppm corrosion inhibitor was used for all tests to ensure data comparability; Substrate: Q235 steel sheet (size 20mm×10mm×2mm, polished to mirror finish, degreased with acetone, weighing accuracy 0.0001g). Normal operating medium: Simulated crude oil atmospheric and vacuum distillation tower top water (pH=6.5, containing 500mg / L naphthenic acid, temperature 80℃); 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℃.

[0054] 2. Test Methods (1) Corrosion inhibition efficiency (η) 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).

[0055] (2) Cl － SO4 2－ Permeation rate 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.

[0056] 3. The test results are shown in Table 2.

[0057] Table 2 Experimental Results

[0058] 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) demonstrate 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 anionic penetration rate as high as 8.9 μg / (cm²). 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.

[0059] 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). 2 The 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.

[0060] 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.

[0061] 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 high efficiency corrosion inhibitor characterized in that, Comprise the following raw materials by weight: Bifunctional modified aromatic polybasic ester 30-50 parts; Sulfonated styrene-maleic anhydride copolymer 15-25 parts; Modified nano alumina 5-10 parts; Octadecylnaphthalene 15-45 parts; Dipropylene glycol methyl ether 5-15 parts; Antioxidant 1-2 parts; The bifunctional modified aromatic polybasic ester is thioureido-imidazoline bifunctional modified diisooctyl phthalate; The modified nano alumina is nano alumina modified by silane coupling agent on the surface.

2. The high efficiency corrosion inhibitor according to claim 1, characterized in that, The thioureido-imidazoline bifunctional modified diisooctyl phthalate is prepared by the following method: A1, phthalic anhydride and isooctanol are mixed and added to the reaction kettle, heated to 100-120℃ and stirred until completely dissolved, then tetrabutyl titanate catalyst is added, heated to 130-150℃ and reacted for 2-3h to obtain diisooctyl phthalate prepolymer; A2, drop the mixture of oil-based hydroxyethyl imidazole and pyridine-3-isothiocyanate into the diisooctyl phthalate prepolymer, the drop rate is 0.5-1mL / min, after drop completion, heat at 80-100℃ for 1-2h reaction, cool and obtain thioureido-imidazoline bifunctional modified diisooctyl phthalate.

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

4. The high efficiency corrosion inhibitor according to claim 2, 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 isooctanol.

5. The high efficiency corrosion inhibitor according to claim 2, wherein: In step A2, the mass ratio of diisooctyl phthalate prepolymer, oil-based hydroxyethyl imidazole and pyridine-3-isothiocyanate is 10:(1-1.5):(0.8-1.2).

6. The high efficiency corrosion inhibitor of claim 1, wherein, The modified nano alumina is prepared by the following method: Mix silane coupling agent KH-550 with ethanol solution, stir at 40-60℃ for 30-60min to obtain hydrolyzate, then add nano alumina, heat to 80-100℃, stir at 200-300r / min for 1-2h, then centrifugal separation, collect the precipitate, wash with anhydrous ethanol for 3-5 times, then place in a 50-60℃ drying oven for 2-3h to obtain modified nano alumina.

7. The high efficiency corrosion inhibitor according to claim 6, wherein The mass concentration of the ethanol solution is 30%-40%, the mass ratio of silane coupling agent KH-550 to ethanol solution is 1:(10-15).

8. The high efficiency corrosion inhibitor of claim 6, wherein, The mass ratio of nano alumina to silane coupling agent KH-550 is (5-8):

1.

9. The high efficiency corrosion inhibitor of claim 1, wherein, The antioxidant is any one of antioxidant 1076, antioxidant 264 and antioxidant 1010.

10. A method for preparing a highly efficient corrosion inhibitor according to any one of claims 1-9, characterized in that, Comprise the following steps: S1, octadecylnaphthalene and dipropylene glycol methyl ether are added to the mixing kettle, heated to 40-60℃, first add antioxidant and stir for 10-15min until completely dissolved, then add sulfonated styrene-maleic anhydride copolymer, modified nano alumina in sequence, stir at 300-500r / min for 30-60min to obtain a premix; S2, slowly add the bifunctional modified aromatic polybasic ester into the premixing solution, stir at 200-300 r / min for 1-2 h at 50-70 ℃, cool to room temperature, filter through a 5 μm polytetrafluoroethylene filter membrane to obtain the high-efficiency corrosion inhibitor.

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