High-temperature corrosion inhibitor for diverting acid and preparation method of high-temperature corrosion inhibitor

Abstract

The invention discloses a high-temperature corrosion inhibitor for diverting acid and a preparation method thereof, and relates to the technical field of acidizing corrosion inhibitors, the high-temperature corrosion inhibitor comprises 20-40 parts of a modified heterocyclic quaternary ammonium salt main corrosion inhibitor, 10-20 parts of a high-temperature synergist, and 30-50 parts of a solvent; the modified heterocyclic quaternary ammonium salt main corrosion inhibitor is a compound with an amphiphilic structure, and the molecular structure is characterized in that the modified heterocyclic quaternary ammonium salt main corrosion inhibitor simultaneously comprises a quaternized nitrogen-containing heterocyclic ring serving as a hydrophilic head group, C14-C18 long-chain alkyl serving as a hydrophobic tail chain, and an alkynyl unsaturated group, a benzene ring rigid linking group or a hydroxyl-containing aliphatic hydrocarbon linking group which are used for high-temperature anchoring; the modified heterocyclic quaternary ammonium salt main corrosion inhibitor is prepared by firstly carrying out N-alkylation reaction on a nitrogen-containing heterocyclic compound and long-chain halogenated alkane and then carrying out quaternization reaction with a quaternization reagent. By introducing a high-temperature anchoring group, a stable adsorption film can be formed on the metal surface at high temperature, and the corrosion rate is effectively reduced; meanwhile, the compatibility with a viscoelastic surfactant system is good, the viscosity of the acid liquor is not reduced, and the construction performance of the diverting acid is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of acid corrosion inhibitors, specifically to a high-temperature corrosion inhibitor for acid reversal and its preparation method. Background Technology

[0002] Currently, in oil and gas field development, acid fracturing technology is an important production enhancement measure to remove formation blockage and improve reservoir permeability. Among them, viscosity-modifying acid or diverting acid systems are widely used in the stimulation of heterogeneous carbonate reservoirs because they utilize viscoelastic surfactants to automatically increase viscosity during acid-rock reactions, achieving temporary plugging, diversion, and uniform acid distribution. To prevent acid from corroding the downhole tubing during construction, corrosion inhibitors are usually added to the acid system. These corrosion inhibitors are typically composed of organic corrosion inhibitors, synergists, and solvents, aiming to form a protective film on the metal surface to isolate acid corrosion.

[0003] In the field of oil and gas well acidizing, as well depth increases, existing conventional corrosion inhibitors often exhibit unstable adsorption films and easy desorption under high-temperature environments, leading to a sharp increase in corrosion rates and failing to meet the safety requirements of deep well operations. More critically, many conventional cationic corrosion inhibitors have poor compatibility with viscoelastic surfactant acid systems. The addition of corrosion inhibitors often disrupts the micelle structure of the acid system, causing an abnormal and sharp decrease in acid viscosity. This results in the diverting acid losing its intended viscosity-shifting function, making it difficult to achieve the expected acidizing effect. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature corrosion inhibitor for acid reversal and its preparation method, thereby solving the problems existing in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides a high-temperature corrosion inhibitor for acid refraction, comprising the following components in parts by mass: 20-40 parts of modified heterocyclic quaternary ammonium salt main corrosion inhibitor, 10-20 parts of high-temperature synergist, and 30-50 parts of solvent; the modified heterocyclic quaternary ammonium salt main corrosion inhibitor is a compound with an amphiphilic structure, characterized by simultaneously containing a quaternized nitrogen-containing heterocycle as a hydrophilic head group, a C14-C18 long-chain alkyl group as a hydrophobic tail chain, and an alkyne unsaturated group, a benzene ring rigid linking group, or a hydroxyl-containing aliphatic hydrocarbon linking group for high-temperature anchoring; the modified heterocyclic quaternary ammonium salt main corrosion inhibitor is prepared by first reacting a nitrogen-containing heterocyclic compound with a long-chain haloalkane in an N-alkylation reaction, and then reacting it with a quaternizing agent in a quaternization reaction.

[0006] Preferably, in the raw materials for preparing the modified heterocyclic quaternary ammonium salt main corrosion inhibitor: the nitrogen-containing heterocyclic compound is one or more of 2-methylbenzimidazole and benzimidazole; the long-chain haloalkanes are one or more of 1-bromotetradecane, 1-bromohexadecane, and 1-bromooctadecane; and the quaternizing agent is one or more of 3-bromopropyne, 3-chloropropyne, 1,4-bis(chloromethyl)benzene, and 1,3-dichloro-2-propanol.

[0007] Preferably, the high-temperature synergist is one or more of propargyl alcohol, 1-hexyn-3-ol, and cinnamaldehyde; the solvent is one or more of methanol, ethanol, isopropanol, ethylene glycol, and water.

[0008] Preferably, the modified heterocyclic quaternary ammonium salt primary corrosion inhibitor is selected from one of the following compounds: 3,3'-(1,4-phenylenebis(methylene))bis(1-hexadecyl-2-methyl-1H-benzimidazole-3-onium) dichloride, 1-hexadecyl-3-(2-propynyl)-1H-benzimidazole-3-onium bromide.

[0009] A method for preparing a high-temperature corrosion inhibitor for acid reversal is also provided, comprising the following steps: (1) Synthesis of N-alkylation intermediate: The nitrogen-containing heterocyclic compound was dissolved in the first organic solvent, and a base was added. Long-chain haloalkanes were added dropwise under constant pressure with stirring. After the addition was completed, the temperature was raised to 70-90℃ and refluxed for 6-12 h. After the reaction was completed, the solvent was removed by rotary evaporation under reduced pressure. The residue was washed with deionized water to remove inorganic salts and dried to obtain the N-alkylation intermediate. (2) Quaternization modification: The N-alkylation intermediate obtained in step (1) is dissolved in a second organic solvent, a quaternization reagent is added, and under nitrogen atmosphere protection, the temperature is raised to 75-90℃ for reflux condensation reaction for 12-24h; the reaction mixture is cooled to room temperature, and unreacted raw materials and by-products are removed by recrystallization purification, and the modified heterocyclic quaternary ammonium salt main corrosion inhibitor is obtained after vacuum drying; (3) Compounding: Add the prepared modified heterocyclic quaternary ammonium salt main corrosion inhibitor and high temperature synergist to the solvent, and mechanically stir at 300-500 rpm for 30-60 minutes under water bath conditions of 40-60℃ until the system forms a homogeneous transparent solution, thus obtaining the high temperature corrosion inhibitor for acid conversion.

[0010] Preferably, in step (1), the molar ratio of nitrogen-containing heterocyclic compound, long-chain haloalkane and base is 1:(1.0~1.2):(1.0~1.5); the first organic solvent is anhydrous ethanol or N,N-dimethylformamide; and the base is potassium hydroxide, sodium hydroxide or potassium carbonate.

[0011] Preferably, the molar ratio of the N-alkylation intermediate to the quaternizing agent in step (2) is controlled as follows: When the quaternizing agent is 3-bromopropyne or 3-chloropropyne, the molar ratio is 1:(1.0~1.2); When the quaternizing agent is 1,4-bis(chloromethyl)benzene or 1,3-dichloro-2-propanol, the molar ratio is 2:(1.0~1.1).

[0012] Preferably, the second organic solvent in step (2) is acetonitrile, isopropanol or ethyl acetate; the solvent used for recrystallization purification is a mixture of acetone and anhydrous ethanol, and the recrystallization is performed 2 to 3 times.

[0013] Preferably, the vacuum drying conditions in step (2) are: vacuum degree (gauge pressure) ≤ -0.08MPa, temperature 50-60℃, and drying time 12-24h.

[0014] Compared with the prior art, the present invention has the following beneficial effects: By introducing specific high-temperature anchoring groups and rigid connection structures, the corrosion inhibitor molecules can form a strong chemical adsorption film on the metal surface under high-temperature conditions. This effectively overcomes the defect of traditional corrosion inhibitors that are prone to thermal desorption under high-temperature and high-flow-rate conditions, ensuring long-term protection of metal pipes under extreme working conditions. It also exhibits excellent film-forming performance in high-temperature and acidic environments, effectively inhibiting pitting and uniform corrosion, thereby extending the service life of downhole tubing and equipment and reducing operational risks.

[0015] The corrosion inhibitor and viscoelastic surfactant acid system exhibit excellent compatibility. Unlike conventional additives that easily disrupt the micelle structure of the acid and lead to viscosity loss, corrosion inhibitor molecules can coexist synergistically with surfactant molecules in the acid and even help maintain the rheological properties of the system. The acid system can still maintain high viscosity and good shear stability at high temperatures, ensuring that the diverting acid can play a normal role in temporary plugging and diversion during reservoir modification, thus achieving a balance between the functionality and protection of the acid system.

[0016] Through multi-step purification and solvent optimization, reaction byproducts and inorganic salt impurities were effectively removed. The high-purity product not only improved its solubility and dispersion in acid, avoiding precipitation or stratification caused by impurity accumulation, but also further reduced the potential interference of foreign ions on the performance of the acid system. The process conditions were stable, the product quality was uniform, and it could adapt to complex field operation environments, providing a reliable chemical additive guarantee for acid fracturing operations in deep and ultra-deep wells. Detailed Implementation

[0017] Example 1: This embodiment aims to prepare a modified corrosion inhibitor with a basic C14 chain length. In step (1), the molar ratio of benzimidazole, 1-bromotetradecane, and potassium hydroxide is precisely set to 1:1.0:1.0, and anhydrous ethanol is selected as the first organic solvent. In this step, a strongly polar aprotic solvent or ethanol is selected as the medium to promote the dissociation of active hydrogen on benzimidazole to form negative ions, which is more conducive to nucleophilic attack on 1-bromotetradecane. Strict control of the equimolar ratio is to prevent excessive haloalkanes from initiating disubstituted side reactions and to ensure that the product is mainly an N1-monosubstituted structure. That is, the N-alkylation intermediate; in step (2), the molar ratio of the N-alkylation intermediate to 3-bromopropyne is controlled at 1:1.0, and the second organic solvent is acetonitrile; acetonitrile, as a dipolar solvent, can effectively stabilize the charge separation in the reaction transition state and significantly reduce the activation energy of the quaternization reaction; at the same time, the nitrogen protection environment effectively prevents the alkyne group from undergoing oxidative coupling or self-polymerization at high temperature, and retains its high reactivity as a high-temperature anchoring point; the crude product is purified by recrystallization twice using a mixture of acetone and anhydrous ethanol at a volume ratio of 3:1, utilizing the impurities and product in the mixture The significant difference in solubility in the solvent removes unreacted raw materials and byproducts, ensuring the solubility and interfacial activity of the final product in the acid solution; the vacuum drying conditions are controlled at -0.08MPa, 50℃, and 12h, which prevents the quaternary ammonium salt from thermally degrading during solvent removal; in step (3), 30 parts of the modified heterocyclic quaternary ammonium salt main corrosion inhibitor and 15 parts of the high-temperature synergist are weighed and added to 45 parts of solvent, which is a mixture of methanol and water in a mass ratio of 1:1. This specific ratio ensures the co-solubility of the organic phase and the inorganic salt in the system; Under 40°C water bath conditions, the mixture was mechanically stirred at 300 rpm for 30 min until a homogeneous transparent solution was formed, thus obtaining the high-temperature corrosion inhibitor for acid conversion. The corrosion inhibitor prepared in this example has a C14 chain length that gives the molecule appropriate surface activity, enabling it to coexist with VES molecules in the acid system and reducing damage to the micelle structure. All raw materials used in this example are commercially available analytical grade reagents. According to calculations, the yield of the N-alkylation intermediate in step (1) was 91.5%, and the yield of the final product in step (2) was 86.2%, and the product was a white powder.

[0018] Example 2: This embodiment is a specific preparation of a gemini structure corrosion inhibitor; in step (1), the molar ratio of 2-methylbenzimidazole, 1-bromohexadecane and sodium hydroxide is set to 1:1.1:1.2, the solvent is N,N-dimethylformamide, the reaction temperature is 80℃, and the time is 9h; after the reaction is completed, the reaction solution is poured into ice water to precipitate the solid, filtered and washed with water until neutral to remove the generated inorganic salt and residual alkali, and dried to obtain the N-alkylation intermediate 1-hexadecyl-2-methylbenzimidazole, with a yield of 93.2%; in step (2), the molar ratio of the N-alkylation intermediate to 1,4-bis(chloromethyl)benzene is controlled to 2:1.0, the solvent is isopropanol, and the reaction temperature is 80℃. The solution was refluxed at 2℃ for 18 h. The crude product was recrystallized three times using an acetone-ethanol (4:1 volume ratio) mixed solvent. Taking advantage of the characteristic that quaternary ammonium salt products precipitate in a cold mixed solvent while impurities dissolve, monosubstituted byproducts and residual raw materials were thoroughly removed. Vacuum drying was performed at -0.08 MPa, 60℃, and for 12 h. The final product obtained was 3,3'-(1,4-phenylenebis(methylene))bis(1-hexadecyl-2-methyl-1H-benzimidazole-3-onium) dichloride, a pale yellow powder with a yield of 84.5%. The target product structure was confirmed by ¹H NMR and IR spectroscopy, with the characteristic peaks assigned as follows: ; ; The rigid benzene ring linking group introduced in this structure forms a strong adsorption on the metal surface through π-d orbital hybridization at a high temperature of 160℃; in the compounding process of step (3), 40 parts of the modified heterocyclic quaternary ammonium salt main corrosion inhibitor and 15 parts of the high temperature synergist are weighed and added to 45 parts of solvent. The solvent is prepared by mixing ethanol and ethylene glycol at a mass ratio of 2:1. The addition of ethylene glycol effectively increases the boiling point of the solvent system and reduces the volatilization loss at high temperature; under the condition of 50℃ water bath, the system is mechanically stirred at a speed of 400 rpm for 45 min until a homogeneous transparent solution is formed, which is the high temperature corrosion inhibitor for acid conversion; the corrosion inhibitor prepared in this embodiment has a special molecular configuration that not only does not destroy VES micelles, but also promotes the growth and entanglement of VES micelles as a linking unit, thereby maintaining or even increasing the viscosity of the acid solution, showing excellent dual functions of thickening and corrosion inhibition; all raw materials used in this embodiment are commercially available analytical grade reagents.

[0019] Example 3: This embodiment aims to explore the ultimate performance combination of C18 ultralong hydrophobic chains and high-temperature crosslinking synergists; in step (1), the molar ratio of benzimidazole, 1-bromooctadecane and potassium carbonate is 1:1.2:1.5, the reaction temperature is 90℃, and the time is 12h; since C18 haloalkanes have low reactivity and large steric hindrance, increasing the reaction temperature and extending the reaction time are necessary means to overcome kinetic obstacles; potassium carbonate, as a mild base, avoids the elimination reaction byproducts that may be caused by strong bases at high temperatures; in step (2), the molar ratio of N-alkylation intermediate to 3-chloropropyne is 1:1.2, the solvent is ethyl acetate, and the reaction temperature is refluxed at 77℃ for 24h; since the reflux temperature of ethyl acetate is low, in order to ensure the complete quaternization reaction, this embodiment deliberately extends the reaction time to 24h; 3-chloropropyne is chosen instead of bromopropyne, although the reactivity is slightly lower, the introduction of chloride ions can produce a stronger synergistic adsorption effect in the subsequent acid system; in step (3), the prepared 25 parts of modified heterocyclic quaternary ammonium salt main corrosion inhibitor and 20 parts of high-temperature synergist cinnamaldehyde were added to 50 parts of solvent, which was isopropanol. Under the conditions of 60°C water bath, the mixture was mechanically stirred at 500 rpm for 60 min. Cinnamaldehyde readily polymerized in situ on the metal surface under high-temperature acidic conditions, forming a dense polymer protective film. The system was stirred until a homogeneous transparent solution was formed, and the high-temperature corrosion inhibitor for acid was obtained. The corrosion inhibitor prepared in this example has C18 ultra-long chain that maximizes the van der Waals interaction with the hydrophobic tail chain of the VES system. Combined with the high-temperature crosslinking characteristics of cinnamaldehyde, it exhibits the best ability to inhibit pitting corrosion and uniform corrosion at an extreme high temperature of 160°C. Although its preparation cost is slightly higher, it is suitable for deep well operations with extremely harsh working conditions. All raw materials used in this example are commercially available analytical grade reagents. The yield of intermediate in step (1) was calculated to be 88.6%, and the yield of final product in step (2) was 80.3%. The product is a white solid.

[0020] Example 4: This embodiment focuses on adjusting the water solubility and adsorption sites of molecules by introducing hydrophilic linking groups; in step (1), the reaction temperature is 85℃ and the time is 10h to obtain an N-alkylated intermediate; in step (2), the molar ratio of the N-alkylated intermediate to 1,3-dichloro-2-propanol is 2:1.1, the solvent is acetonitrile, and the reaction temperature is 82℃ under reflux for 20h; 1,3-dichloro-2-propanol is selected as the linker here, and a hydroxyl group -OH is introduced at the molecular center; the introduction of this hydroxyl group has a dual significance: on the one hand, it increases the solubility of the modified main corrosion inhibitor in acid through hydrogen bonding, and improves the fluidity at low temperature; on the other hand, the hydroxyl group, as an additional lone pair electron donor, works synergistically with the benzimidazole ring and long-chain alkyl group to construct a multi-center adsorption mode on the metal surface; in the compounding process of step (3), the obtained modified 35 parts of heterocyclic quaternary ammonium salt main corrosion inhibitor and 12 parts of high-temperature synergist propargyl alcohol were added to 40 parts of solvent, which was a mixture of methanol and ethanol in a mass ratio of 1:1. This compound combination further enhanced the homogeneous stability of the system. Under the condition of 45℃ water bath, the system was mechanically stirred at 350 rpm for 40 min until a homogeneous transparent solution was formed, which yielded the high-temperature corrosion inhibitor for acid conversion. The corrosion inhibitor prepared in this embodiment, under the premise of ensuring good compatibility with VES acid, provided reliable corrosion protection in high-temperature and high-shear environment by utilizing the synergistic effect of multiple adsorption centers. It also had strong process adaptability and was not prone to phase separation. All raw materials used in this embodiment were commercially available analytical grade reagents. According to calculation, the yield of N-alkylation intermediate in step (1) was 90.4%, and the yield of final product in step (2) was 82.1%. The product was a light brown viscous solid.

[0021] Example 5: This embodiment is a comprehensive optimization of the C16 single-chain structure and its preparation process parameters; in step (1), the molar ratio of benzimidazole, 1-bromohexadecane and potassium carbonate is 1:1.15:1.4, the solvent is DMF, and the reaction is carried out at 75℃ for 8 hours to obtain the N-alkylation intermediate; in step (2), the molar ratio of the N-alkylation intermediate to 3-bromopropyne is 1:1.1, the solvent is isopropanol, and the reaction is carried out at 90℃ for 16 hours; the recrystallization time is increased to 3 times, the vacuum drying temperature is 58℃, and the time is 20 hours; by finely controlling the recrystallization and drying parameters, the trace amounts of inorganic salts and unreacted monomers that may damage the VES micelles are removed to the maximum extent; in step (3), when compounding, 28 parts of the prepared modified heterocyclic quaternary ammonium salt main corrosion inhibitor and 18 parts of the high-temperature synergist cinnamaldehyde are weighed and added to 48 parts of solvent, the solvent being isopropanol and A mixture of water at a mass ratio of 3:1, cinnamaldehyde and the purified main corrosion inhibitor formed a stable microemulsion structure in the alcohol-water system; under a water bath at 55°C, the mixture was mechanically stirred at 450 rpm for 50 min until a homogeneous transparent solution was formed, thus obtaining the high-temperature corrosion inhibitor for acid conversion; the product prepared in this embodiment has high purity and complete structure. The combination of C16 alkyl chain and propargyl group achieves a perfect balance between micelle embedding and surface film formation at the microscopic level, effectively solving the technical problem of acid viscosity reduction caused by conventional corrosion inhibitors. Moreover, the production process is stable and suitable for large-scale industrial production; all raw materials used in this embodiment are commercially available analytical grade reagents; according to calculations, the yield of the N-alkylation intermediate in step (1) is 94.1%, the yield of the final product in step (2) is 88.7%, and the product is a white crystal.

[0022] Comparative Example 1: This comparative example provides a conventional acid corrosion inhibitor with a composition similar to that of Example 2, except that the main corrosion inhibitor used is dodecyl dimethyl benzyl ammonium chloride 1227, which does not contain the specific structure of the modified heterocyclic quaternary ammonium salt main corrosion inhibitor of this application, i.e., it does not contain benzimidazole heterocycles or alkynyl groups or rigidly linked twin structures for high-temperature anchoring; the remaining high-temperature synergists and solvent components are consistent with those of Example 2. This comparative example aims to verify the fundamental influence of the specific nitrogen-containing heterocyclic skeleton and anchoring groups of this application on high-temperature corrosion inhibition and VES compatibility, serving as a blank control of the prior art.

[0023] Comparative Example 2: This comparative example provides a modified acid corrosion inhibitor with a composition similar to that of Example 2, except that in step (1) of preparing the main corrosion inhibitor, iodomethane is used instead of 1-bromohexadecane for N-alkylation reaction, thereby obtaining a short-chain methyl modified benzimidazole quaternary ammonium salt without C14-C18 long-chain hydrophobic alkyl groups; this comparative example aims to demonstrate the necessity of C14-C18 long-chain alkyl groups for maintaining the viscosity of acid systems, i.e., compatibility, and to verify the key role of hydrophobic chain intercalation micelle mechanism.

[0024] Comparative Example 3: This comparative example provides a modified acid corrosion inhibitor with a composition similar to that of Example 2, except that in step (2) of preparing the main corrosion inhibitor, 1-chlorobutane is used instead of 1,4-bis(chloromethyl)benzene for quaternization reaction, thereby obtaining a single long-chain benzimazole quaternary ammonium salt without high-temperature anchoring groups such as alkynyl or benzene ring rigid linkage groups; this comparative example aims to verify the contribution of high-temperature anchoring groups to reducing the corrosion rate at 160°C, and to prove that long-chain alkyl groups alone are insufficient to resist high-temperature desorption.

[0025] Comparative Example 4: This comparative example provides a modified acid corrosion inhibitor with a composition similar to that of Example 2. The only difference is that after step (2) of preparing the main corrosion inhibitor, the recrystallization purification step is omitted, and the crude product after rotary evaporation is directly used for compounding. This comparative example aims to verify the effect of high purity on the rheological properties of the VES acid system and to reveal the potential interference effect of impurities such as residual inorganic salts and unreacted halogenated hydrocarbons on the micelle structure.

[0026] Verification experiment: To verify the performance of the high-temperature corrosion inhibitor for acid in this invention, a verification experiment was set up to comprehensively evaluate the performance of the corrosion inhibitors prepared in Examples 1-5 and Comparative Examples 1-4.

[0027] Testing standards: Corrosion testing standard: Refer to SY / T5405-2019 "Performance Indicators and Test Methods for Corrosion Inhibitors for Acidification", and adopt a combination of static and dynamic rotating plate methods; Viscosity testing standard: Use a HAAKEMARS60 high-temperature and high-pressure rheometer, referring to the rheological performance testing method in SY / T6376-2008 "General Technical Conditions for Fracturing Fluids".

[0028] Specific testing process: Preparation of corrosive media: A diversion acid-based solution was prepared using 20 wt% hydrochloric acid and 4 wt% erucamide propyl betaine (VES). Corrosion inhibitor dosage: 2.0% of the total acid mass; Corrosion test procedure: After grinding, degreasing, and weighing, the N80 steel test piece is placed in a high-temperature and high-pressure autoclave containing corrosive medium. The temperature is raised to 160℃, the pressure is increased to 10MPa, and the rotation speed is set to 60r / min to simulate dynamic shear. The corrosion time is 4h. After the experiment, the test piece is removed, cleaned, degreased, dried, and weighed. The corrosion rate is calculated. Each group of experiments is measured in parallel 3 times, and the average value is taken. Viscosity test procedure: Place the prepared acid solution containing corrosion inhibitor into the rheometer measurement system, and at a constant temperature of 160℃, measure the viscosity at a rate of 170s. -¹ Shearing at a constant shear rate, and recording the apparent viscosity after stabilization; as a benchmark, the viscosity of blank VES acid solution without corrosion inhibitor under the same conditions was measured to be 45 mPa·s; each group of samples was tested three times, and the data were averaged.

[0029] Data table: Table 1 Performance test results of each embodiment and comparative example

[0030] Note: The surface tension test temperature is 25℃, which is used to assist in characterizing the surface activity of molecules.

[0031] Result analysis components: As can be seen from the test results in Table 1, the high-temperature corrosion inhibitor for acid conversion prepared in this invention has achieved a significant breakthrough in balancing high-temperature corrosion protection and VES compatibility. The corrosion rates of Examples 1-5 were strictly controlled below 20 g / (m²·h), and the acid viscosity was maintained above 45 mPa·s, i.e., above the blank baseline, confirming the effectiveness of the molecular design of nitrogen-containing heterocyclic + long-chain alkyl + high-temperature anchoring group; in particular, Example 2 with a twin structure had a viscosity as high as 52.30 mPa·s, which was significantly higher than the blank sample. This is attributed to the special bi-headed and bi-tailed chain structure of the molecule, which can connect adjacent VES micelles like a bridge, promote the formation of longer worm-like micelles, and achieve the anomalous effect of corrosion inhibitor thickening. Compared with Comparative Example 1, which uses conventional 1227, Comparative Example 1 showed a sharp drop in viscosity to 12.10 mPa·s and severe corrosion. This is because the small-molecule strong cationic head group of 1227 drastically compressed the electric double layer of VES micelles, leading to micelle disintegration. At the same time, it lacks high-temperature anchoring groups and cannot be stably adsorbed on metal surfaces at 160°C. This indicates that the modified structure of the present invention is the key to solving the compatibility problem. Compared with Comparative Example 2, which does not contain long chains, the viscosity of Comparative Example 2 decreased to 28.40 mPa·s, indicating that molecules lacking C14~C18 long chains cannot be embedded in the VES micelles and can only be free in water to destroy the micelle structure; at the same time, its corrosion rate increased, confirming that the hydrophobic film formed by the hydrophobic long chains makes an important contribution to blocking acid attack. Compared with Comparative Example 2 and Comparative Example 3 without anchoring groups, although Comparative Example 3 maintained a good viscosity of 44.20 mPa·s due to its long chain, its corrosion rate was as high as 89.70 g / (m²·h). This strongly proves that simple physical adsorption achieved by alkyl chains cannot withstand the impact of high temperature and high flow rate at 160°C. It is necessary to introduce alkynyl or benzene ring rigid connecting groups to form chemical bonds, i.e., π-d coordination, in order to anchor the protective film at high temperature. Compared with the unpurified Comparative Example 4, the presence of impurities caused the viscosity to drop to 36.50 mPa·s, indicating that the synthesis byproducts interfere with the self-assembly of VES micelles, highlighting the necessity of a high-purity preparation process through recrystallization. In summary, this invention has successfully constructed a high-temperature corrosion inhibitor that can withstand high temperatures of 160℃ through chemical anchoring and can coexist perfectly with the VES system through a long-chain embedding mechanism by precisely tailoring the molecular structure and strictly controlling the preparation process.

[0032] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A high-temperature corrosion inhibitor for acid reversal, characterized in that, The product comprises the following components in parts by weight: 20-40 parts of modified heterocyclic quaternary ammonium salt main corrosion inhibitor, 10-20 parts of high-temperature synergist, and 30-50 parts of solvent. The modified heterocyclic quaternary ammonium salt main corrosion inhibitor is a compound with an amphiphilic structure. Its molecular structure is characterized by simultaneously containing a quaternized nitrogen-containing heterocycle as a hydrophilic head group, a C14-C18 long-chain alkyl group as a hydrophobic tail chain, and an alkyne unsaturated group, a benzene ring rigid linking group, or a hydroxyl-containing aliphatic hydrocarbon linking group for high-temperature anchoring. The modified heterocyclic quaternary ammonium salt main corrosion inhibitor is prepared by first reacting a nitrogen-containing heterocyclic compound with a long-chain haloalkane in an N-alkylation reaction, and then reacting it with a quaternizing agent in a quaternization reaction.

2. The high-temperature corrosion inhibitor for diverting acid as described in claim 1, characterized in that, The raw materials for preparing the modified heterocyclic quaternary ammonium salt main corrosion inhibitor include: nitrogen-containing heterocyclic compounds such as 2-methylbenzimidazole and benzimidazole; long-chain halogenated alkanes such as 1-bromotetradecane, 1-bromohexadecane, and 1-bromooctadecane; and quaternizing agents such as 3-bromopropyne, 3-chloropropyne, 1,4-bis(chloromethyl)benzene, and 1,3-dichloro-2-propanol.

3. The high-temperature corrosion inhibitor for diverting acid as described in claim 1, characterized in that, The high-temperature synergist is one or more of propargyl alcohol, 1-hexyn-3-ol, and cinnamaldehyde; the solvent is one or more of methanol, ethanol, isopropanol, ethylene glycol, and water.

4. The high-temperature corrosion inhibitor for diverting acid as described in claim 2, characterized in that, The modified heterocyclic quaternary ammonium salt primary corrosion inhibitor is selected from one of the following compounds: 3,3'-(1,4-phenylenebis(methylene))bis(1-hexadecyl-2-methyl-1H-benzimidazole-3-onium) dichloride, 1-hexadecyl-3-(2-propynyl)-1H-benzimidazole-3-onium bromide.

5. A method for preparing a high-temperature corrosion inhibitor for diverting acid as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Synthesis of N-alkylation intermediate: The nitrogen-containing heterocyclic compound was dissolved in the first organic solvent, and a base was added. Long-chain haloalkanes were added dropwise under constant pressure with stirring. After the addition was completed, the temperature was raised to 70-90℃ and refluxed for 6-12 h. After the reaction was completed, the solvent was removed by rotary evaporation under reduced pressure. The residue was washed with deionized water to remove inorganic salts and dried to obtain the N-alkylation intermediate. (2) Quaternization modification: The N-alkylation intermediate obtained in step (1) is dissolved in a second organic solvent, a quaternization reagent is added, and under nitrogen atmosphere protection, the temperature is raised to 75-90℃ for reflux condensation reaction for 12-24h; the reaction mixture is cooled to room temperature, and unreacted raw materials and by-products are removed by recrystallization purification, and the modified heterocyclic quaternary ammonium salt main corrosion inhibitor is obtained after vacuum drying; (3) Compounding: Add the prepared modified heterocyclic quaternary ammonium salt main corrosion inhibitor and high temperature synergist to the solvent, and mechanically stir at 300-500 rpm for 30-60 minutes under water bath conditions of 40-60℃ until the system forms a homogeneous transparent solution, thus obtaining the high temperature corrosion inhibitor for acid conversion.

6. The method for preparing a high-temperature corrosion inhibitor for diverting acid as described in claim 5, characterized in that, In step (1), the molar ratio of nitrogen-containing heterocyclic compound, long-chain haloalkanes and base is 1:(1.0~1.2):(1.0~1.5); the first organic solvent is anhydrous ethanol or N,N-dimethylformamide; the base is potassium hydroxide, sodium hydroxide or potassium carbonate.

7. The method for preparing a high-temperature corrosion inhibitor for diverting acid as described in claim 5, characterized in that, In step (2), the molar ratio of the N-alkylation intermediate to the quaternizing agent is controlled as follows: When the quaternizing agent is 3-bromopropyne or 3-chloropropyne, the molar ratio is 1:(1.0~1.2); When the quaternizing agent is 1,4-bis(chloromethyl)benzene or 1,3-dichloro-2-propanol, the molar ratio is 2:(1.0~1.1).

8. The method for preparing a high-temperature corrosion inhibitor for diverting acid as described in claim 5, characterized in that, In step (2), the second organic solvent is acetonitrile, isopropanol or ethyl acetate; the solvent used for recrystallization purification is a mixture of acetone and anhydrous ethanol, and the recrystallization is performed 2 to 3 times.

9. The method for preparing a high-temperature corrosion inhibitor for diverting acid as described in claim 5, characterized in that, The conditions for vacuum drying in step (2) are: vacuum degree (gauge pressure) ≤ -0.08MPa, temperature 50-60℃, and drying time 12-24h.

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