High-temperature-resistant long-chain gemini imidazole ionic liquid corrosion inhibitor and preparation method and application thereof

Abstract

The application discloses a high-temperature-resistant long-chain gemini imidazole ionic liquid corrosion inhibitor and a preparation method and application thereof, and relates to the technical field of metal corrosion inhibition. The application solves the technical problem of low corrosion inhibition efficiency caused by poor thermal stability and non-dense film formation of the corrosion inhibitor in the prior art under a high-temperature and strong-acid environment. The preparation method of the carbon steel corrosion inhibitor comprises the following steps: firstly, 2-methyl imidazole and 1-bromododecane are dissolved in acetonitrile at a molar ratio of 1:1, and then the mixture is refluxed at 85°C for 24 hours; secondly, after the reaction is completed, the solvent is removed by rotary evaporation, the precipitate is washed with ether for multiple times, and then the precipitate is dried in vacuum to obtain an intermediate; and finally, the intermediate and 1,6-dibromohexane are added into acetonitrile at a molar ratio of 2:1, and then the mixture is refluxed at 85°C for 24 hours; after the reaction is completed, the target product C6(2-MI 12 )2Br2 is obtained through rotary evaporation, ether washing and vacuum drying. The long-chain gemini corrosion inhibitor prepared by the application has high corrosion inhibition efficiency and excellent stability under a high-temperature and strong-acid environment through double-center anchoring and dense self-assembly.

Description

Technical Field

[0001] This invention relates to the field of metal corrosion inhibition technology, specifically to a high-temperature resistant and strong acid-resistant long-chain gemini imidazole ionic liquid corrosion inhibitor, its preparation method, and its application. Background Technology

[0002] In deep-well acidizing operations in oil extraction, metal tubing is frequently exposed to extreme corrosive environments of high temperatures and strong acids. N80 steel, a commonly used downhole tubing material, is prone to severe corrosion under these conditions. Existing organic corrosion inhibitors (such as monomeric imidazoline or quaternary ammonium salts) face the following technical problems under extreme conditions: 1. Insufficient thermal stability; the molecular structure is easily degraded at high temperatures; 2. Limited adsorption capacity; high temperatures accelerate the desorption of molecules from the metal surface; 3. Non-dense film formation; the spatial repulsion between single-chain molecules allows water molecules and corrosive ions to easily penetrate. The compound corrosion inhibitor disclosed in application number 201410061809.5 requires mixing multiple substances, resulting in complex compatibility issues. Therefore, there is an urgent need to develop a corrosion inhibitor with a structure possessing multiple protective mechanisms and stable properties under high-temperature and strong acid conditions. Summary of the Invention

[0003] A long-chain twin imidazole ionic liquid corrosion inhibitor is provided, whose molecular structure integrates two adsorption centers and two hydrophobic long chains. Through multi-site anchoring and dense self-assembly, it solves the problems of low efficiency and poor stability of existing corrosion inhibitors under high temperature and strong acid.

[0004] To achieve the above objectives, the present invention employs the following technical solution: a method for preparing a high-temperature resistant long-chain gemini-type imidazole ionic liquid corrosion inhibitor, comprising the following steps:

[0005] a. Dissolve 2-methylimidazole and 1-bromododecane in acetonitrile at a molar ratio of 1:1 and reflux at 85°C for 24 hours.

[0006] b. After the reaction is complete, the solvent is removed by rotary evaporation, the precipitate is washed several times with diethyl ether, and dried under vacuum to obtain the intermediate.

[0007] c. Add the intermediate and 1,6-dibromohexane to acetonitrile at a molar ratio of 2:1, and reflux at 85°C for 24 hours.

[0008] d. After the reaction is complete, the solvent is removed by rotary evaporation, the precipitate is washed several times with diethyl ether, and dried under vacuum to obtain the target product C6(2-MI). 12 )2Br2

[0009] The reaction mechanism and synergistic mechanism of this invention are as follows: Chemisorption: The nitrogen atoms of the two 2-methylimidazolium rings provide lone pairs of electrons, forming stable coordinate bonds (N-Fe) with the d orbitals of Fe, achieving multi-site "chelate" anchoring. Physicosorption: The quaternized cation centers are rapidly adsorbed onto the negatively charged metal interface through Coulomb forces. Hydrophobic barrier: The long didodecyl (C12) chain forms a dense hydrophobic barrier through self-assembly, effectively repelling water molecules.

[0010] The above-mentioned high-temperature resistant long-chain gemini-type imidazole ionic liquid corrosion inhibitor, its preparation method and application, in step a, 2-methylimidazolium is ultrasonically dissolved in acetonitrile.

[0011] In the above-mentioned high-temperature resistant long-chain gemini imidazole ionic liquid corrosion inhibitor, its preparation method and application, in step a, the ultrasonic power is 700-800W and the ultrasonic time is 3-8min.

[0012] In the above-mentioned high-temperature resistant long-chain gemini imidazole ionic liquid corrosion inhibitor, its preparation method and application, in step b, the rotary evaporation temperature is 40-50℃, the rotary evaporation rate is 100-150 r / min, and the rotary evaporation time is 20 min.

[0013] In the above-mentioned high-temperature resistant long-chain gemini imidazole ionic liquid corrosion inhibitor, its preparation method and application, in step b, the vacuum drying temperature is 60℃ and the drying time is 12h.

[0014] In the above-mentioned high-temperature resistant long-chain gemini imidazole ionic liquid corrosion inhibitor, its preparation method and application, in step c, the rotary evaporation temperature is 40-50℃, the rotary evaporation rate is 100-150 r / min, and the rotary evaporation time is 20 min.

[0015] In the above-mentioned high-temperature resistant long-chain gemini imidazole ionic liquid corrosion inhibitor, its preparation method and application, in step c, the vacuum drying temperature is 60℃ and the drying time is 12h.

[0016] The reaction mechanism of this invention is as follows.

[0017] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0018] (1) The 2-methylimidazolium ionic liquid prepared by the present invention has a corrosion inhibition efficiency of 91.68% under extreme conditions of 15% HCl and 363 K, which is increased to 99.34% after compounding with propynyl alcohol ethoxylate (PME).

[0019] (2) Gemini 2-methylimidazolium ionic liquid has a decomposition temperature as high as 232℃, which far exceeds the temperature requirements for deep well operations. The gemini structure has an extremely low critical micelle concentration and can self-assemble into a more compact molecular film than ordinary monomers.

[0020] (3) The raw materials of this invention are easy to obtain, the method is simple to operate, the reaction conditions are mild, and the gemini-type 2-methylimidazolium ionic liquid can be prepared without complicated equipment, which is conducive to industrial promotion.

[0021] (4) The 2-methylimidazolium ionic liquid prepared by the present invention can be adapted to the existing petroleum and chemical acid processes without the need for additional equipment modification, and has strong compatibility. Attached Figure Description

[0022] Figure 1 The image shows the infrared spectrum of a gemini-type 2-methylimidazole ionic liquid.

[0023] Figure 2 The 1H NMR spectrum of the geminal 2-methylimidazole ionic liquid is shown.

[0024] Figure 3 The thermogravimetric curve of the gemini-type 2-methylimidazolium ionic liquid.

[0025] Figure 4 The zeta potential diagram for a gemini-type 2-methylimidazolium ionic liquid.

[0026] Figure 5 The graph shows the corrosion rates of different concentrations of Gemini 2-methylimidazolium ionic liquids under corrosion conditions of 15% HCl and 363 K.

[0027] Figure 6 Electrochemical impedance spectroscopy (EIS) diagrams of different concentrations of Gemini 2-methylimidazolium ionic liquids under corrosion conditions of 15% HCl and 363 K.

[0028] Figure 7 Images showing the surface morphology of steel sheets subjected to corrosion at 15% HCl and 363 K with or without the addition of a gemini-type 2-methylimidazolium ionic liquid.

[0029] Figure 8 Corrosion rate diagrams of different proportions of Gemini 2-methylimidazolium ionic liquids and propynyl alcohol ethoxy compounds under corrosion conditions of 15% HCl and 363 K. Detailed Implementation

[0030] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0031] All the raw materials mentioned in this invention can be purchased through commercial channels.

[0032] The technical concept of this invention lies in addressing the insufficient protective efficacy of traditional corrosion inhibitors under extreme high-temperature and strong acid environments such as deep well acidification. A high-temperature resistant gemini-type 2-methylimidazolium ionic liquid was designed and synthesized via a two-step reaction method. This molecule constructs an interfacial barrier through dual-center anchoring and self-assembly of long alkyl chains. Experimental evaluation showed that it exhibited excellent stability under extreme corrosion conditions of 15% HCl and 363 K, with a single-agent corrosion inhibition efficiency of approximately 91%. Furthermore, by implementing a "skeleton-filling" synergistic strategy with propynyl alcohol ethoxylate, the corrosion inhibition efficiency of the system was ultimately increased to 99.34%, achieving near-complete protection for the metal substrate.

[0033] Example 1: This invention discloses a high-temperature resistant long-chain gemini-type imidazole ionic liquid corrosion inhibitor, its preparation method, and its application, specifically including the following steps:

[0034] Step 1, Primary Quaternization (Intermediate Synthesis): Dissolve 1.0 g (0.012 mol) of 2-methylimidazole and 3.04 g (0.012 mol) of 1-bromododecane in 30 mL of acetonitrile. Reflux at 85 °C for 24 hours.

[0035] Step 2: After the reaction is complete, the solvent is removed using a rotary evaporator. Purification pretreatment: The crude product is repeatedly washed with diethyl ether to thoroughly remove unreacted raw materials and byproducts, and then dried again by rotary evaporation to obtain the purified mono-head imidazolium intermediate.

[0036] Step 3, Secondary Quaternization (Gemini Structure Construction): The above intermediate was redissolved in 30 mL of acetonitrile, followed by the addition of 1,6-dibromohexane (1.49 g, 0.006 mol) at a molar ratio of intermediate to linker of 2:1. The reaction was continued under reflux at 85 °C for 24 hours. Post-treatment and drying: After the reaction was complete, the acetonitrile was removed by rotary evaporation. The solid product was precipitated with diethyl ether and washed three times. Finally, the product was placed in a vacuum drying oven and dried at 60 °C to constant weight to obtain the target gemini-type ionic liquid corrosion inhibitor.

[0037] Example 2: A systematic evaluation of the structure, thermal stability, and application performance of the prepared gemini-type 2-methylimidazolium ionic liquid corrosion inhibitor under extreme acidification conditions:

[0038] 1. Characterization of the product's physicochemical properties and verification of its structure and purity: This was achieved through infrared spectroscopy (IR spectroscopy). Figure 1 Analysis showed that the product was at 2930 cm⁻¹ -1 and 2850 cm -1 A distinct alkyl long-chain characteristic peak appears at [location], and the characteristic absorption peak of the imidazole ring is retained; 1H NMR spectrum ( Figure 2The results show that the proton displacements perfectly match the theoretical structure, confirming the successful synthesis of the twin-type structure. Thermal stability analysis: Thermogravimetric curves (…) Figure 3 Tests showed that the corrosion inhibitor did not exhibit significant mass loss below 232°C, and its decomposition temperature was much higher than that of deep well acidizing operations, ensuring its chemical stability in high-temperature formations. Interfacial electrical property testing: Zeta potential diagram ( Figure 4 The results show that the corrosion inhibitor is positively charged in the acidic medium, which is conducive to its anchoring on the negatively charged metal surface by electrostatic attraction, forming an initial physical adsorption layer.

[0039] 2. Evaluation of macroscopic corrosion inhibition efficiency of protective performance under extreme conditions (15% HCl, 363 K): Under the extreme conditions of 15% HCl and 363 K, the corrosion rate of N80 steel decreased significantly with increasing corrosion inhibitor concentration. Figure 5 Electrochemical impedance spectroscopy (EIS) Figure 6 The results showed that the charge transfer resistance was significantly improved after the addition of the corrosion inhibitor, and the calculated highest single-agent corrosion inhibition efficiency reached 91.68%. Microscopic morphology protection effect: The surface morphology of the corroded steel sheet was observed using scanning electron microscopy (SEM). Figure 7 The blank control group showed severe honeycomb-like ulcer corrosion on the surface; however, after adding the corrosion inhibitor of this invention, the steel sheet surface was smooth and the original wear marks were clearly visible, proving that the corrosion inhibitor constructed a strong molecular barrier at the interface.

[0040] 3. Synergistic Effect of Compound Formulation (“Skeleton-Filling” Synergistic Strategy): To further enhance the protective capability at extremely high acid concentrations, this gemini ionic liquid was combined with propynyl alcohol ethoxylate (PME) for testing. Figure 8 Technical efficacy verification: Experimental results show that due to the large volume of the twin molecules, microscopic gaps inevitably exist within the adsorption layer, while small-molecule PME can penetrate and seal these gaps through the "skeleton filling" effect. When the two are in the optimal ratio (7:3), the total corrosion inhibition efficiency under 15% HCl and 363 K conditions increases from 91.68% for the single agent to 99.34%, achieving near-complete protection for the metal substrate.

[0041] Comparative Example 1: A choline amino acid monomeric ionic liquid with good biodegradability was selected as a reference. This type of corrosion inhibitor performed well under mild conditions of 298 K and 1 M HCl, with a maximum efficiency of 94.9%. However, its stability was drastically affected by temperature, and the efficiency dropped significantly to 74.8% at 328 K. In contrast, the gemini-type 2-methylimidazole ionic liquid prepared in this invention maintained a single-agent efficiency of 91.68% even under extreme conditions of approximately 5 times increased acid strength and a temperature of 363 K, demonstrating that its gemini structure design has stronger film-forming stability under extreme thermodynamic environments.

[0042] Comparative Example 2: Brominated cucurbita supramolecular ionic liquid was used as a reference. This supramolecular system exhibited a corrosion inhibition efficiency of 97.54% under 333 K and 1 M NaCl saturated CO2 / H2S conditions. However, its adsorption equilibrium under high-temperature, strong acid conditions was easily disrupted by hydrogen ion competition, and the measured performance stability at 100 mg / L at 333 K remained limited. This invention, through a synergistic strategy of "dual-center anchoring" combined with "skeleton filling," significantly improved the efficiency from 91.68% for a single agent to 99.34% under even more stringent conditions of 15% HCl and 363 K, successfully addressing the technical challenge of desorption in supramolecular or monomeric structures at extremely high acid concentrations.

[0043] Comparative Example 3: A symmetrical geminal quaternary ammonium salt (N1) was used as a reference. This corrosion inhibitor achieved a maximum efficiency of 90.6% at 298 K and 1 M HCl, and its molecular design is primarily targeted at room temperature and low acid environments. The geminal 2-methylimidazolium ionic liquid designed in this invention significantly enhances the desorption resistance of the molecule at 363 K by introducing a more coordinating imidazolium ring and a specific C12 alkyl long chain. Experimental comparisons show that even with a 15-fold increase in acid strength and a 65 K increase in temperature, the protective efficacy of this invention (91.68%) still surpasses that of Comparative Example 3 (90.6%) under dilute acid conditions at room temperature, demonstrating the precise control advantage of the molecular structure of this invention under extreme operating conditions.

[0044] A comprehensive analysis of the embodiments and comparative examples of this invention clearly highlights its innovativeness and technical advantages:

[0045] (1) Performance Advantages: The gemini-type 2-methylimidazolium ionic liquid corrosion inhibitor prepared in this invention exhibits unexpectedly high protective capabilities under extreme environments. Under extremely harsh conditions of 15% HCl and 363 K (90°C), the single-agent corrosion inhibition efficiency reaches 91.68%, significantly better than the performance of conventional gemini quaternary ammonium salts in Comparative Example 3 under dilute acid conditions at room temperature (90.6%). More significantly, through synergistic compounding with propynyl alcohol ethoxylate, the corrosion inhibition efficiency of the system in this invention leaps to 99.34%. In contrast, the efficiency of the monomeric ionic liquid in Comparative Example 1 drops sharply to 74.8% when the temperature increases to 328 K, and the corrosion inhibition efficiency of Comparative Example 2 at 333 K is only about 83.06%. This proves that this invention can still maintain a near-full-efficiency protection level under the dual impact of extremely high acid strength and high temperature.

[0046] (2) Mechanism Advantages: The technological advancement of this invention stems from its precise molecular structure design and innovative "skeleton filling" synergistic strategy. Unlike the monomer structure of Comparative Example 1, this invention adopts a symmetrical Gemini structure with a bisimidazole active center, forming a stronger bond with the metal surface through a dual anchoring effect, significantly improving its resistance to thermal desorption. Addressing the intermolecular gap problem commonly found in the comparative examples, this invention utilizes a macromolecular Gemini ionic liquid to construct the "main core skeleton" and introduces a small molecule alkynol derivative to fill the gaps. This synergistic assembly fills the microscopic channels within the adsorption layer, constructing a denser and more continuous hydrophobic barrier than Comparative Example 2 (supramolecular system), completely blocking the penetration of corrosive ions into the substrate from a physical perspective.

[0047] (3) Comprehensive Performance: While ensuring ultimate protective performance, this invention also possesses excellent stability and engineering applicability. Thermogravimetric analysis confirms that the product decomposition temperature is as high as 232°C, overcoming the technical pain point that traditional imidazoline derivatives or the supramolecular structure in Comparative Example 2 are prone to degradation or failure under high temperature and strong acid. Surface morphology analysis shows that this invention can form a highly kinetically stable protective layer at the metal interface, solving the problem that the monomeric ionic liquid efficiency in Comparative Example 1 decreases sharply with increasing temperature. In addition, compared with the complex synthesis route of Comparative Example 2, this invention can obtain a stable product through a simple two-step quaternization method, and is highly compatible with existing oilfield acidizing processes, thus having significant industrial promotion value.

[0048] In summary, the gemini-type 2-methylimidazolium ionic liquid corrosion inhibitor provided by this invention exhibits significant comprehensive advantages in terms of efficiency, stability, breadth of applicable conditions, and synergistic mechanism of action. It is a novel high-efficiency corrosion inhibitor with excellent performance and suitable for harsh working conditions.

[0049] Any parts not mentioned in this invention can be achieved by referring to existing technologies.

[0050] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.

Claims

1. The application of a high-temperature resistant long-chain gemini imidazole ionic liquid corrosion inhibitor, characterized in that, The preparation method of the carbon steel corrosion inhibitor includes the following steps in sequence: (1) Dissolve 2-methylimidazole and 1-bromododecane in acetonitrile, and then sonicate to obtain a solution. (2) The solution was refluxed at 85°C for 24 h. After the reaction was completed, the solvent was removed by rotary evaporation. The precipitate was washed with diethyl ether and dried under vacuum to obtain the intermediate. (3) The intermediate and 1,6-dibromohexane were added to acetonitrile and refluxed at 85°C for 24 h. After the reaction was completed, the solvent was removed by rotary evaporation, the precipitate was washed with diethyl ether and dried under vacuum to obtain the target product C6(2-MI). 12 )2Br2.

2. The applications include: N80 steel was pretreated, and the pretreated N80 steel was placed in a composite corrosion inhibition system containing the target product and propynyl alcohol ethoxylate, and immersed in 15% HCl at 363K. The composite corrosion inhibition system utilizes the synergistic effect of multi-site anchoring of gemini imidazole cations and "skeleton filling" of propynyl alcohol ethoxylate, and achieves the best corrosion inhibition efficiency on the metal substrate within 4 hours at a ratio of 7:

3.

3. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of 2-methylimidazole to 1-bromododecane is 1:1, and it is dissolved in 30 mL of acetonitrile.

4. The preparation method according to claim 1, characterized in that: In step (1), the ultrasonic power is 700-800W and the ultrasonic time is 3-8min.

5. The preparation method according to claim 1, characterized in that: In steps (2) and (3), the rotary evaporation temperature is 40-50°C, the rotary evaporation speed is 100-150 r / min, and the rotary evaporation time is 20 min.

6. The preparation method according to claim 1, characterized in that: In steps (2) and (3), the vacuum drying temperature is 60°C and the drying time is 12h.

7. The preparation method according to claim 1, characterized in that: In step (3), the molar ratio of the intermediate to 1,6-dibromohexane is 2:

1.

8. The application according to claim 2, characterized in that: In the aforementioned composite corrosion inhibition system, the target product C6(2-MI) 12 The ratio of 2Br2 to propynyl alcohol ethoxylate is 0:10, 3:7, 5:5, 7:3 and 10:0, and the ratio is a mass ratio.

9. The application according to claim 2, characterized in that: The N80 steel test piece was polished sequentially with sandpaper of different grits, and then cleaned with acetone and ethanol.

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