High temperature corrosion inhibitor for diverting acid and preparation method thereof

Abstract

The application discloses a high-temperature corrosion inhibitor for diverting acid and a preparation method thereof, and relates to the technical field of acidification corrosion inhibitors, and comprises the following components: 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 amphiphilic structure, and the molecular structure features are that the compound simultaneously contains a quaternized nitrogen-containing heterocyclic ring 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 subjecting a nitrogen-containing heterocyclic compound to N-alkylation reaction with a long-chain halogenated alkane, and then subjecting the product to quaternization reaction with a quaternization reagent. The high-temperature anchoring group is introduced, a stable adsorption film can be formed on the metal surface at high temperature, the corrosion rate is effectively reduced, the compatibility with a viscoelastic surfactant system is good, the acid liquid viscosity is not reduced, and the construction performance of the diverting acid is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acidizing corrosion inhibitor, in particular to a high-temperature corrosion inhibitor for diverting acid and a preparation method thereof. BACKGROUND

[0002] At present, in the development process of oil and gas fields, acidizing and fracturing technology is an important stimulation measure to remove formation blockage and improve reservoir permeability. Among them, the viscous acid or diverting acid system is widely used in the reconstruction of heterogeneous carbonate reservoirs because it can automatically increase the viscosity during acid-rock reaction by using viscoelastic surfactants, thereby achieving temporary plugging, diversion and uniform acid distribution. In order to prevent corrosion of downhole string by acid during operation, corrosion inhibitors are usually added to the acid system. These corrosion inhibitors are usually compounded by organic corrosion inhibitor main agent, synergist and solvent, aiming to form a protective film on the metal surface to isolate the acid corrosion.

[0003] In the field of oil and gas well acidizing, with the increase of well depth, the existing conventional corrosion inhibitors often have the phenomenon of unstable adsorption film and easy desorption in high temperature environment, which leads to a sharp increase in corrosion rate and cannot meet the safety needs of deep well operation. More importantly, many conventional cationic corrosion inhibitors have poor compatibility with viscoelastic surfactant acid systems. After adding the corrosion inhibitor, the micellar structure of the acid system is often disturbed, which causes the viscosity of the acid to abnormally decrease sharply, so that the diverting acid loses its viscosity diversion function and cannot achieve the expected acidizing effect. SUMMARY

[0004] The purpose of the present application is to provide a high-temperature corrosion inhibitor for diverting acid and a preparation method thereof, which solves the problems in the background art.

[0005] To solve the above technical problems, the present application provides a high-temperature corrosion inhibitor for diverting acid, which comprises the following components in mass fraction: modified heterocyclic quaternary ammonium salt main corrosion inhibitor 20-40 parts, high-temperature synergist 10-20 parts, and solvent 30-50 parts. The modified heterocyclic quaternary ammonium salt main corrosion inhibitor is a compound with amphiphilic structure, and its molecular structure features include a quaternized nitrogen-containing heterocyclic ring 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 N-alkylating reaction of a nitrogen-containing heterocyclic compound with a long-chain halogenated alkane, and then quaternization reaction with a quaternization reagent.

[0006] Preferably, the raw materials for preparing the modified heterocyclic quaternary ammonium salt main corrosion inhibitor are: the nitrogen-containing heterocyclic compound is one or more of 2-methylbenzimidazole and benzimidazole; the long-chain halogenated alkane is one or more of 1-bromotetradecane, 1-bromohexadecane and 1-bromooctadecane; and the quaternization reagent is one or more of 3-bromopropynyl, 3-chloropropynyl, 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; and the solvent is a mixture of one or more of methanol, ethanol, isopropanol, ethylene glycol and water.

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

[0009] Also provided is a method for preparing a high-temperature corrosion inhibitor for diverting acid, comprising the following steps:

[0010] (1) N-alkylated intermediate synthesis: the nitrogen-containing heterocyclic compound is dissolved in a first organic solvent, a base is added, and the long-chain halogenated alkane is added dropwise under stirring at constant pressure, after the dropwise addition is completed, the reaction is carried out under reflux condensation at 70-90°C for 6-12 h; after the reaction is completed, the solvent is removed by rotary evaporation under reduced pressure, the residue is washed with deionized water to remove inorganic salts, and then dried to obtain the N-alkylated intermediate;

[0011] (2) quaternization modification: the N-alkylated intermediate obtained in step (1) is dissolved in a second organic solvent, and a quaternization reagent is added, and then the reaction is carried out under reflux condensation at 75-90°C for 12-24 h under the protection of nitrogen atmosphere; the reaction mixture is cooled to room temperature, and then purified by recrystallization to remove unreacted raw materials and byproducts, and then vacuum dried to obtain the modified heterocyclic quaternary ammonium salt main corrosion inhibitor;

[0012] (3) compounding: the prepared modified heterocyclic quaternary ammonium salt main corrosion inhibitor and high-temperature synergist are added to a solvent, and then stirred at a speed of 300-500 rpm under water bath at 40-60°C for 30-60 min until a homogeneous transparent solution is formed, thereby obtaining the high-temperature corrosion inhibitor for diverting acid.

[0013] Preferably, in step (1), the molar ratio of the nitrogen-containing heterocyclic compound, the long-chain halogenated alkane and the 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.

[0014] Preferably, the molar ratio of the N-alkylated intermediate to the quaternary ammonium reagent in step (2) is controlled as follows:

[0015] When the quaternary ammonium reagent is 3-bromopropynyl or 3-chloropropynyl, the molar ratio is 1:(1.0~1.2);

[0016] When the quaternary ammonium reagent is 1,4-bis(chloromethyl)benzene or 1,3-dichloro-2-propanol, the molar ratio is 2:(1.0~1.1).

[0017] Preferably, the second organic solvent in step (2) is acetonitrile, isopropanol or ethyl acetate; the solvent used for recrystallization is a mixture of acetone and anhydrous ethanol, and the recrystallization is performed 2~3 times.

[0018] Preferably, the vacuum drying conditions in step (2) are as follows: vacuum degree (gauge pressure) ≤-0.08 MPa, temperature 50-60℃, and drying time 12-24h.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] By introducing specific high-temperature anchoring groups and rigid connecting structures, the corrosion inhibitor molecules can form a firm chemisorption film on the metal surface under high-temperature conditions, effectively overcoming the defect that traditional corrosion inhibitors are prone to thermal desorption under high-temperature and high-flow rate conditions, ensuring the long-term protection of metal pipes under extreme working conditions, and exhibiting excellent film-forming performance in high-temperature acidic environments, which can effectively inhibit the occurrence of pitting corrosion and uniform corrosion, thereby prolonging the service life of downhole pipe strings and equipment and reducing the operation risk.

[0021] The corrosion inhibitor and the viscoelastic surfactant acid system have excellent compatibility performance, unlike conventional additives that can easily destroy the micelle structure of the acid system, leading to viscosity loss. The corrosion inhibitor molecules can coexist with the surfactant molecules in the acid system, 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 normally play a temporary plugging and diverting role during reservoir reconstruction, and realizing the unity of functionality and protection of the acid system.

[0022] Through multi-step purification and solvent optimization, the reaction byproducts and inorganic salt impurities are effectively removed. The high-purity product not only improves its solubility and dispersion ability in the acid system, avoiding precipitation or stratification caused by impurity accumulation, but also further reduces the potential interference of external ions on the performance of the acid system. The process conditions are stable, the product quality is uniform, and it can adapt to complex field operation environments, providing reliable chemical additive support for acidizing and fracturing construction in deep and ultra-deep wells. DETAILED DESCRIPTION

[0023] Example 1:

[0024] The present 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 accurately set to 1:1.0:1.0, and anhydrous ethanol is selected as the first organic solvent; in this step, a strong polar aprotic solvent or ethanol is selected as the medium to promote the dissociation of active hydrogen on benzimidazole to form a negative ion, thereby facilitating the nucleophilic attack of 1-bromotetradecane; strict control of the equimolar ratio is to prevent excessive halogenated alkanes from causing double substitution side reactions and ensure that the product is mainly N1-monosubstituted structure, i.e. N-alkylated intermediate; in step (2), the molar ratio of N-alkylated intermediate to 3-bromopropyne is controlled to 1:1.0, and acetonitrile is selected as the second organic solvent; acetonitrile as a dipolar solvent can effectively stabilize the charge separation in the reaction transition state, significantly reducing the activation energy of quaternary ammonium reaction; at the same time, the nitrogen protection environment effectively prevents the oxidation coupling or self-polymerization of alkynyl groups at high temperature, retaining its high reactivity as an anchoring point at high temperature; the crude product is recrystallized twice using a mixture of acetone and anhydrous ethanol with a volume ratio of 3:1, which takes advantage of the significant difference in solubility of impurities and products in the mixed solvent to remove unreacted raw materials and by-products, ensuring the solubility and interfacial activity of the final product in acid solution; the vacuum drying conditions are controlled at -0.08 MPa, 50°C, and 12h, which prevents thermal degradation of quaternary ammonium salts during solvent removal; in step (3), 30 parts of the prepared modified heterocyclic quaternary ammonium salt main corrosion inhibitor and 15 parts of 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 cosolvency of organic phase and inorganic salts in the system; under the condition of 40°C water bath, mechanical stirring is carried out at a speed of 300 rpm for 30 min until a homogeneous transparent solution is formed, and a high-temperature corrosion inhibitor for reverse acid is obtained; the C14 chain length of the corrosion inhibitor prepared in this embodiment gives the molecule a moderate surface activity, allowing it to coexist with VES molecules in the acid system and reduce the damage to the micellar structure; all the raw materials used in this embodiment are commercially available analytical pure reagents; by calculation, the yield of N-alkylated intermediate in step (1) is 91.5%, and the yield of the final product in step (2) is 86.2%, and the product is a white powder.

[0025] Example 2:

[0026] This embodiment is the specific preparation of the twin 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°C, and the reaction time is 9h; after the reaction is completed, the reaction liquid is poured into ice water to precipitate the solid, which is filtered and washed with water until it is neutral to remove the generated inorganic salt and residual alkali, and dried to obtain the N-alkylated intermediate 1-hexadecyl-2-methylbenzimidazole with a yield of 93.2%; in step (2), the molar ratio of the N-alkylated intermediate and 1,4-bis(chloromethyl)benzene is controlled to be 2:1.0, the solvent is selected to be isopropyl alcohol, the reaction temperature is 82°C reflux for 18h; the crude product is recrystallized 3 times using a mixed solvent of acetone-ethanol (volume ratio 4:1), and the single-substituted by-product and residual raw material are completely removed by using the characteristics that the quaternary ammonium salt product precipitates in the cold mixed solvent while the impurities dissolve; the vacuum drying conditions are vacuum degree-0.08MPa, 60°C, and 12h; the final product prepared is 3,3'-(1,4-phenylenebis(methylene))bis(1-hexadecyl-2-methyl-1H-benzimidazol-3-ium) dichloride, which is a light yellow powder with a yield of 84.5%; the structure of the target product is correct, which is confirmed by nuclear magnetic resonance hydrogen spectrum (1H-NMR) and infrared spectrum (IR), and the characteristic peaks are as follows:

[0027] ;

[0028] ;

[0029] The benzene ring rigid linker introduced in the structure forms strong adsorption with the metal surface through π-d orbital hybridization at high temperature of 160°C; in step (3), 40 parts of the prepared modified heterocyclic quaternary ammonium salt main corrosion inhibitor and 15 parts of the high-temperature synergist are weighed and added to 45 parts of the solvent, and the solvent is prepared by mixing ethanol and ethylene glycol at a mass ratio of 2:1, and the addition of ethylene glycol effectively raises the boiling point of the solvent system and reduces the volatilization loss at high temperature; under the condition of 50°C water bath, mechanical stirring is carried out at a speed of 400rpm for 45min until a homogeneous transparent solution is formed, and the high-temperature corrosion inhibitor for diversion acid is obtained; the special molecular configuration of the corrosion inhibitor prepared in this embodiment not only does not destroy the VES micelle, but also promotes the growth and winding of the VES micelle as a connecting unit, so as to maintain or even improve the viscosity of the acid liquid, and excellent viscosity increasing and corrosion inhibition dual functions are exhibited; the raw materials used in this embodiment are all commercially available analytical pure reagents.

[0030] Example 3:

[0031] The present embodiment aims to explore the limit performance combination of C18 super-long hydrophobic chain and high-temperature cross-linking synergist; in step (1), the molar ratio of benzimidazole, 1-bromooctadecane and potassium carbonate is 1:1.2:1.5, the reaction temperature is 90°C, and the reaction time is 12h; due to the low reactivity and large steric hindrance of C18 halogenated alkanes, increasing the reaction temperature and prolonging the reaction time are necessary means to overcome the kinetic barrier; potassium carbonate as a mild base avoids the elimination reaction by-product that may be caused by strong base at high temperature; in step (2), the molar ratio of N-alkylated intermediate and 3-chloropropargyl is 1:1.2, the solvent is ethyl acetate, the reaction temperature is 77°C reflux for 24h; in order to ensure the complete quaternary ammonium reaction, the reaction time is specially extended to 24h in this embodiment; 3-chloropropargyl is selected instead of bromopropargyl, although the reaction activity is slightly lower, but the introduction of chloride ion can produce a stronger synergistic adsorption effect in the subsequent acid system; in step (3), 25 parts of the prepared modified heterocyclic quaternary ammonium salt main corrosion inhibitor and 20 parts of high-temperature synergist cinnamaldehyde are weighed and added into 50 parts of solvent, and the solvent is isopropanol; under the condition of 60°C water bath, mechanical stirring is carried out at a speed of 500rpm for 60min, cinnamaldehyde is easily polymerized in situ on the metal surface under high-temperature acidic environment, forming a dense polymer protective film; until the system forms a homogeneous transparent solution, the high-temperature corrosion inhibitor for turning to acid is obtained; the corrosion inhibitor prepared in this embodiment, C18 super-long chain maximally enhances the van der Waals force interaction with the hydrophobic tail chain of the VES system, combined with the high-temperature cross-linking characteristics of cinnamaldehyde, it shows the best ability to inhibit pitting and uniform corrosion at an extreme high temperature of 160°C, although its preparation cost is slightly high, but it is suitable for deep well operation under extremely harsh working conditions; the raw materials used in this embodiment are all commercially available analytical pure reagents; by calculation, the intermediate yield in step (1) is 88.6%, and the final product yield in step (2) is 80.3%, and the product is a white solid.

[0032] Example 4:

[0033] The present embodiment focuses on adjusting the water solubility and adsorption sites of the molecule by introducing a hydrophilic linker; in step (1), the reaction temperature is 85°C and the time is 10h, and the N-alkylated intermediate is prepared; in step (2), the molar ratio of N-alkylated intermediate to 1,3-dichloro-2-propanol is 2:1.1, the solvent is acetonitrile, the reaction temperature is 82°C reflux for 20h; 1,3-dichloro-2-propanol is selected as a linker, which introduces a hydroxyl group -OH at the center of the molecule; the introduction of the hydroxyl group has a double meaning: on the one hand, it increases the solubility of the modified main corrosion inhibitor in the acid solution through hydrogen bonding, and improves the flowability at low temperature; on the other hand, the hydroxyl group as an additional lone pair electron donor cooperates with the benzimidazole ring and long chain alkyl to construct a multi-center adsorption mode on the metal surface; in the compounding process of step (3), 35 parts of the prepared modified heterocyclic quaternary ammonium salt main corrosion inhibitor and 12 parts of high-temperature synergist propargyl alcohol are weighed and added to 40 parts of solvent, and the solvent is a mixture of methanol and ethanol in a mass ratio of 1:1; the further compounding of the system further strengthens the homogeneous stability of the system; under the condition of 45°C water bath, mechanical stirring at a speed of 350rpm for 40min until a homogeneous transparent solution is formed, a high-temperature corrosion inhibitor for diversion acid is obtained; the corrosion inhibitor prepared in the present embodiment provides reliable corrosion protection in high-temperature and high-shear environment under the premise of ensuring good compatibility with VES acid, and has strong process adaptability and is not prone to phase separation; the raw materials used in the present embodiment are all commercially available analytical pure reagents; by calculation, the yield of N-alkylated intermediate in step (1) is 90.4%, and the yield of the final product in step (2) is 82.1%, and the product is a light brown viscous solid.

[0034] Example 5:

[0035] The present embodiment is a comprehensive optimization of 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, the reaction is carried out at 75°C for 8h, and the N-alkylated intermediate is prepared; in step (2), the molar ratio of N-alkylated intermediate and 3-bromopropyne is 1:1.1, the solvent is isopropanol, and the reaction is carried out at 90°C for 16h; the recrystallization times are increased to 3 times, the vacuum drying temperature is 58°C, and the time is 20h; by fine tuning the recrystallization and drying parameters, the trace amount of inorganic salt and unreacted monomer that may damage the VES micelle are removed to the maximum extent; in step (3) of compounding, 28 parts of the prepared modified heterocyclic quaternary ammonium salt main corrosion inhibitor and 18 parts of high-temperature synergist cinnamaldehyde are weighed and added to 48 parts of solvent, and the solvent is a mixture of isopropanol and water in a mass ratio of 3:1; cinnamaldehyde and the purified main corrosion inhibitor form a stable microemulsion structure in the alcohol-water system; under the condition of water bath at 55°C, mechanical stirring is carried out at a speed of 450rpm for 50min until a homogeneous transparent solution is formed, and a high-temperature corrosion inhibitor for diversion acid is obtained; the product prepared in the present embodiment has high purity and complete structure, the combination of C16 alkyl chain and propargyl group realizes perfect balance of micelle embedding and surface film forming in microcosm, effectively solves the technical problem of viscosity reduction of acid liquid caused by conventional corrosion inhibitor, and the production process is stable and suitable for large-scale industrial production; the raw materials used in the present embodiment are all commercially available analytical pure reagents; by calculation, the yield of N-alkylated intermediate in step (1) is 94.1%, and the yield of the final product in step (2) is 88.7%, and the product is a white crystal.

[0036] Comparative Example 1

[0037] The present comparative example provides a conventional acidizing corrosion inhibitor, which has a similar composition to Example 2, and the only difference is 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 the present application, i.e. does not contain benzimidazole heterocycle and alkyne group or rigid connecting geminal structure for high-temperature anchoring; the remaining high-temperature synergist and solvent components remain the same as Example 2; this comparative example aims to verify the fundamental influence of the specific nitrogen-containing heterocyclic skeleton and anchoring group on high-temperature corrosion and VES compatibility, serving as a blank control of prior art.

[0038] Comparative Example 2

[0039] The present comparative example provides a modified acidizing corrosion inhibitor, which has a similar composition to Example 2, and the only difference is that in step (1) of preparing the main corrosion inhibitor, methyl iodide is used instead of 1-bromohexadecane for N-alkylation reaction, thereby preparing a short-chain methyl-modified benzimidazole quaternary ammonium salt without C14-C18 long-chain hydrophobic alkyl group; this comparative example aims to disprove the necessity of C14-C18 long-chain alkyl group for viscosity maintenance of diversion acid system, i.e. compatibility, and to verify the key role of hydrophobic chain embedding micelle mechanism.

[0040] Comparative Example 3:

[0041] This comparative example provides a modified acidizing corrosion inhibitor, which has a similar composition to Example 2, with the only difference being that in step (2) of preparing the main corrosion inhibitor, 1-chlorobutane is used instead of 1,4-bis(chloromethyl)benzene for the quaternary ammonium reaction, thereby preparing a single long-chain benzimidazole quaternary ammonium salt without high-temperature anchoring groups such as alkynyl or benzene ring rigid linking groups; this comparative example aims to verify the contribution of high-temperature anchoring groups to reducing the corrosion rate under the condition of 160°C, and to prove that only long-chain alkyl groups are insufficient to resist high-temperature desorption.

[0042] Comparative Example 4:

[0043] This comparative example provides a modified acidizing corrosion inhibitor, which has a similar composition to Example 2, with the only difference being 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 influence of high purity on the rheological properties of the VES acidizing fluid system, and to reveal the potential interference of impurities such as residual inorganic salts and unreacted halogenated hydrocarbons on the micellar structure.

[0044] Verification test:

[0045] In order to verify the performance of the high-temperature corrosion inhibitor for diversion acid according to the present application, verification experiments are specially set up to evaluate the comprehensive performance of the corrosion inhibitors prepared in Examples 1-5 and Comparative Examples 1-4.

[0046] Test standards:

[0047] Corrosion test standards: refer to SY / T 5405-2019 "Performance indicators and test methods for corrosion inhibitors for acidizing", using a combination of static coupon method and dynamic rotating coupon method;

[0048] Viscosity test standards: use HAAKE MARS60 high-temperature high-pressure rheometer, refer to the rheological property test method in SY / T 6376-2008 "General technical conditions for fracturing fluid".

[0049] Test specific process:

[0050] Corrosion medium preparation: use 20wt% hydrochloric acid and 4wt% erucylamidepropylbetaine VES to prepare the diversion acid base fluid;

[0051] Corrosion inhibitor addition: all at 2.0% of the total mass of the acid fluid;

[0052] Corrosion test operation: after the surface of the N80 steel test piece polished, degreased and weighed, it was placed in a high temperature and high pressure kettle containing corrosion medium, heated to 160 DEG C, pressurized to 10 MPa, the speed was set to 60 r / min to simulate dynamic shear, and the corrosion time was 4 h; after the experiment, the test piece was taken out, washed, film removed, dried, weighed, and the corrosion rate was calculated; each group of experiments was measured in triplicate, and the average value was taken;

[0053] Viscosity test operation: the prepared acid liquid containing corrosion inhibitor was placed in the rheometer measurement system, sheared at a constant shear rate of 170 s - at 160 DEG C, and the apparent viscosity after stabilization was recorded; as a reference, the viscosity of the blank VES acid liquid without corrosion inhibitor was 45 mPa·s under the same conditions; each sample was tested in triplicate, and the data was averaged.

[0054] Data table:

[0055] Table 1 performance test results of each example and comparative example

[0056]

[0057] Note: the surface tension test temperature is 25 DEG C, which is used to assist in characterizing the surface activity of the molecule.

[0058] Result analysis group:

[0059] From the test results in Table 1, the high-temperature corrosion inhibitor for diverting acid prepared by the application has made a significant breakthrough in considering high-temperature corrosion prevention and VES compatibility;

[0060] The corrosion rate of examples 1-5 is strictly controlled below 20 g / (m²·h), and the viscosity of the acid liquid is maintained above 45 mPa·s, i.e. the blank reference, which confirms the effectiveness of the molecular design of nitrogen-containing heterocyclic ring + long-chain alkyl + high-temperature anchoring group; in particular, example 2 with a gemini structure, its viscosity is as high as 52.30 mPa·s, which is significantly higher than the blank sample, which is due to the special double-headed and double-tailed chain structure of the molecule, which can connect adjacent VES micelles like a bridge, promoting the formation of longer worm-like micelles, achieving the abnormal effect of increasing the viscosity of the corrosion inhibitor;

[0061] Comparative example 2 and comparative example 1 using conventional 1227, the viscosity of comparative example 1 dropped to 12.10 mPa·s and the corrosion was serious; this is because the small molecule strong cationic head group of 1227 compresses the double electric layer of VES micelles, causing the micelles to disintegrate; at the same time, it lacks a high-temperature anchoring group and cannot be stably adsorbed on the metal surface at 160 DEG C; this shows that the modified structure of the application is the key to solving the compatibility problem;

[0062] Comparative Example 2 and Comparative Example 2 without long chain, the viscosity of Comparative Example 2 is reduced to 28.40 mPa·s, which indicates that the molecules lacking C14-C18 long chain cannot be embedded in the VES micelle and can only be free in water to destroy the micelle structure; at the same time, the corrosion rate increases, which confirms that the hydrophobic membrane formed by the hydrophobic long chain has an important contribution to blocking the attack of acid;

[0063] Comparative Example 2 and Comparative Example 3 without anchoring groups, although Comparative Example 3 relies on long chains to maintain a good viscosity of 44.20 mPa·s, but the corrosion rate is as high as 89.70 g / (m²·h); this strongly proves that simple physical adsorption relying on alkyl chains cannot resist the high temperature and high flow rate impact of 160℃, and it is necessary to introduce alkyne or benzene ring rigid linking groups to form chemical bonding, i.e. π-d coordination, to anchor the protective film at high temperature;

[0064] Comparative Example 2 and Comparative Example 4 without purification, the presence of impurities causes the viscosity to drop to 36.50 mPa·s, which indicates that synthesis by-products will interfere with the self-assembly of VES micelles, emphasizing the necessity of high-purity preparation process through recrystallization;

[0065] In summary, the present application successfully constructs a high-temperature corrosion inhibitor that can not only resist 160℃ high temperature through chemical anchoring, but also coexist perfectly with the VES system through long-chain embedding mechanism, by fine tailoring of molecular structure and strict control of preparation process.

[0066] The above is only a preferred embodiment of the present application, and does not limit the form of the present application, any skilled person in the art can use the disclosed technical content to make changes or modifications to equivalent embodiments applied to other fields, but any simple modification, equivalent change and modification made in accordance with the technical essence of the present application to the above embodiments, without departing from the technical solution content of the present application, still belongs to the protection scope of the technical solution of the present application.

Claims

1. A high temperature corrosion inhibitor for use in diverting acid, characterized by, The composition comprises the following components in mass fraction: modified heterocyclic quaternary ammonium salt main corrosion inhibitor 20-40 parts, high-temperature synergist 10-20 parts, and solvent 30-50 parts; the modified heterocyclic quaternary ammonium salt main corrosion inhibitor is a compound with amphiphilic structure, and the molecular structure is characterized in that it simultaneously contains a quaternized nitrogen-containing heterocyclic ring 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 subjecting a nitrogen-containing heterocyclic compound to N-alkylation reaction with a long-chain halogenated alkane, and then subjecting the N-alkylated intermediate to quaternization reaction with a quaternization reagent; In the preparation of 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 halogenated alkane is one or more of 1-bromotetradecane, 1-bromohexadecane and 1-bromooctadecane; and the quaternization reagent is one or more of 3-bromopropynyl, 3-chloropropynyl, 1,4-bis(chloromethyl)benzene and 1,3-dichloro-2-propanol.

2. A high temperature corrosion inhibitor for diverting acid according to claim 1, wherein The high-temperature synergist is one or more of propargyl alcohol, 1-hexyn-3-ol and cinnamyl aldehyde; and the solvent is a mixture of one or more of methanol, ethanol, isopropanol, ethylene glycol and water.

3. A high temperature corrosion inhibitor for diverting acid according to claim 1, wherein The modified heterocyclic quaternary ammonium salt main corrosion inhibitor is selected from one of the following compounds: 3,3'-(1,4-phenylenebis(methylene))bis(1-hexadecyl-2-methyl-1H-benzimidazol-3-ium) dichloride and 1-hexadecyl-3-(2-propynyl)-1H-benzimidazol-3-ium bromide.

4. A process for the preparation of a high temperature corrosion inhibitor for diverting acids as claimed in any one of claims 1 to 3, characterized in that, The method comprises the following steps: (1) N-alkylation intermediate synthesis: the nitrogen-containing heterocyclic compound is dissolved in a first organic solvent, an alkali is added, and the long-chain halogenated alkane is added dropwise under stirring at constant pressure, and then the reaction mixture is heated to 70-90 DEG C for reflux condensation reaction for 6-12 hours; after the reaction is completed, the solvent is removed by rotary evaporation under reduced pressure, the inorganic salt is removed by washing the residue with deionized water, and the N-alkylation intermediate is obtained after drying; wherein the nitrogen-containing heterocyclic compound is one or more of 2-methylbenzimidazole and benzimidazole; the long-chain halogenated alkane is one or more of 1-bromotetradecane, 1-bromohexadecane and 1-bromooctadecane; and the quaternization reagent is one or more of 3-bromopropynyl, 3-chloropropynyl, 1,4-bis(chloromethyl)benzene and 1,3-dichloro-2-propanol; (2) quaternization modification: the N-alkylation intermediate obtained in step (1) is dissolved in a second organic solvent, and the quaternization reagent is added, and then the reaction mixture is heated to 75-90 DEG C for reflux condensation reaction for 12-24 hours under nitrogen atmosphere; the reaction mixture is cooled to room temperature, and the 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: the prepared modified heterocyclic quaternary ammonium salt main corrosion inhibitor and high-temperature synergist are added to the solvent, and the mixture is stirred at a speed of 300-500 rpm in a water bath at 40-60 DEG C for 30-60 minutes until a homogeneous transparent solution is formed, thereby obtaining the high-temperature corrosion inhibitor for acid diversion.

5. A process for the preparation of high temperature corrosion inhibitors for diverting acids as claimed in claim 4 wherein, The molar ratio of the nitrogen-containing heterocyclic compound, the long-chain halogenated alkane and the base in step (1) 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.

6. A process for the preparation of high temperature corrosion inhibitors for diverting acids as claimed in claim 4 wherein, In step (2), the molar ratio of the N-alkylated intermediate and the quaternary ammonium reagent is controlled as follows: When the quaternary ammonium reagent is 3-bromopropynyl or 3-chloropropynyl, the molar ratio is 1:(1.0-1.2); When the quaternary ammonium reagent is 1,4-bis(chloromethyl)benzene or 1,3-dichloro-2-propanol, the molar ratio is 2:(1.0-1.1).

7. A process for the preparation of high temperature corrosion inhibitors for diverting acids as claimed in claim 4 wherein, In step (2), the second organic solvent is acetonitrile, isopropanol or ethyl acetate; the solvent used for recrystallization is a mixture of acetone and anhydrous ethanol, and the recrystallization is performed for 2-3 times. ​ 8. A process for the preparation of high temperature corrosion inhibitors for diverting acids as claimed in claim 4 wherein, In step (2), the vacuum drying conditions are as follows: vacuum degree (gauge pressure) ≤-0.08 MPa, temperature 50-60℃, and drying time 12-24 h. ​

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