pH-responsive nano-bio-based corrosion inhibitor, and preparation method and application thereof

Abstract

This application discloses a pH-responsive nanobio-based corrosion inhibitor, its preparation method, and its application, belonging to the field of oil and gas field corrosion protection technology. It comprises nanospheres composed of chitosan derivatives and pH-responsive nanoparticles; wherein the pH-responsive nanoparticles are encapsulated within the nanospheres. This corrosion inhibitor can rapidly respond and release its corrosion-inhibiting components in an acidic environment with CO2-induced oil displacement, effectively suppressing CO2-induced electrochemical corrosion. The product of this invention is environmentally friendly, highly responsive, and has a simple preparation process, solving the problems of poor performance and lack of responsiveness of existing corrosion inhibitors in acidic environments.

Description

Technical Field

[0001] This application relates to a pH-responsive nano-bio-based corrosion inhibitor, its preparation method, and its application, belonging to the field of oil and gas field corrosion protection technology. Background Technology

[0002] CO2 enhanced oil recovery (EOR) is currently a core tertiary oil recovery technology for improving oil recovery and achieving carbon sequestration. It boasts advantages such as high oil displacement efficiency, controllable costs, and a green, low-carbon approach, and has been widely applied in major oil and gas fields both domestically and internationally. However, in actual CO2 EOR operations, the injected CO2 reacts with formation water and produced fluids to form carbonic acid, which can easily cause severe electrochemical corrosion of oil and gas equipment and steel pipelines. This significantly shortens the service life of oil and gas extraction equipment, increases oilfield operation and maintenance costs, and poses safety hazards, thus hindering the large-scale promotion and application of CO2 EOR technology.

[0003] Currently, commonly used corrosion inhibitors in oilfields are mostly traditional inhibitors such as organic amines, imidazolines, and inorganic phosphates. However, these inhibitors suffer from poor water solubility, high dosage requirements, environmental unfriendliness, and short action time. Existing bio-based corrosion inhibitors are mostly single chitosan-modified materials, such as patent CN118879300B, which lack intelligent responsive structures, have poor slow-release performance, low corrosion inhibition efficiency, and cannot adapt to the dynamic acidic corrosion conditions of CO2 flooding. Therefore, developing a green and environmentally friendly nano-bio-based corrosion inhibitor with intelligent pH response, excellent slow-release properties, and adaptability to the complex conditions of CO2 flooding is currently a key research focus and a pressing technological need in this field. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a pH-responsive nano-bio-based corrosion inhibitor. Based on a bio-based chitosan derivative, a nano-coating structure is constructed, and pH-responsive nanoparticles and composite corrosion-inhibiting active components are introduced. This achieves intelligent triggering and slow release in acidic environments and stable storage in neutral environments, while also taking into account the advantages of being green and environmentally friendly, highly stable, and having high corrosion inhibition efficiency.

[0005] According to the first aspect of this application, this application provides a pH-responsive nanobio-based corrosion inhibitor, comprising nanospheres composed of chitosan derivatives and pH-responsive nanoparticles. The pH-responsive nanoparticles are encapsulated within the nanospheres.

[0006] This invention constructs a smart corrosion inhibitor with a "core-shell" structure by encapsulating pH-responsive nanoparticles inside chitosan derivative nanospheres. This corrosion inhibitor maintains the stability of the microsphere structure in neutral or weakly alkaline environments, thereby encapsulating the internal active components. When the environmental pH decreases (e.g., in a CO2-driven oil recovery environment where CO2 dissolves and becomes acidic), the microsphere structure undergoes slight swelling, triggering the activation of the internal pH-responsive particles and releasing the active substances to exert their corrosion-inhibiting effect. This design enables the on-demand release of the corrosion inhibitor in acidic corrosive environments, improving the corrosion inhibition efficiency and utilization.

[0007] Meanwhile, chitosan derivative nanospheres can enhance the adsorption performance of corrosion inhibitors on metal surfaces, forming uniform and dense films that can significantly improve long-term corrosion inhibition capabilities.

[0008] Optionally, the chitosan derivative is carboxymethyl chitosan or a chitosan quaternary ammonium salt.

[0009] Compared to chitosan, carboxymethyl chitosan and chitosan quaternary ammonium salts exhibit significantly improved water solubility, being completely soluble in aqueous systems without the need for organic solvents. They can also be uniformly dispersed in oilfield produced and injected fluids, making them suitable for aqueous flooding operations. Furthermore, the carboxyl or quaternary ammonium groups on the molecular chains of carboxymethyl chitosan and chitosan quaternary ammonium salts can form stronger coordination or electrostatic adsorption with metal surfaces, enhancing the corrosion-inhibiting film and thus improving protective capabilities.

[0010] Optionally, the pH-responsive nanoparticles are at least one of nano-ZnO, nano-CaCO3, and nano-Mg(OH)2.

[0011] The aforementioned nanoparticles can rapidly dissolve and release Zn under acidic conditions. 2+ Ca 2+ Mg 2+ Plasma can disrupt the microsphere structure, and these metal ions themselves have a certain cathodic corrosion inhibition effect.

[0012] Optionally, the average particle size of the pH-responsive nanoparticles is 5-50 nm.

[0013] This average particle size range is beneficial for the uniform dispersion of nanoparticles within the nanospheres, preventing agglomeration and enabling rapid response.

[0014] Optionally, the amount of pH-responsive nanoparticles is 10-30% of the mass of the nanospheres.

[0015] This filling amount ensures that the microsphere structure is effectively disrupted in an acidic environment, enabling rapid release, while avoiding excessive filling that could affect the sphericity and stability of the microspheres.

[0016] Optionally, the nanospheres are further loaded with a second corrosion-inhibiting active component, the loading amount being 5-8% of the mass of the chitosan derivative.

[0017] Optionally, the second corrosion-inhibiting active component is at least one of tannic acid, phytic acid, and vanillin.

[0018] These secondary corrosion-inhibiting active components are all green and highly efficient organic corrosion inhibitors. They can chelate with metal ions to form a multi-layered, dense protective film on the metal surface, inhibiting electrochemical corrosion. Simultaneously, they can synergistically work with chitosan derivatives to enhance the adsorption and film-forming properties of the nanospheres. In the early stages, before the pH-responsive particles have completely dissolved, the secondary corrosion-inhibiting active components can slowly seep out from the surface or shallow layer of the microspheres, providing advanced protection and eliminating the initial corrosion risk that may result from delayed response.

[0019] When the loading of the second corrosion inhibitor active component is too low, the content of organic corrosion inhibitor component is insufficient, and the synergistic corrosion inhibition effect is weak; when the loading is too high, the excessive organic component will block the pores of the nanospheres, hinder the pH response triggering mechanism, and at the same time, the component is prone to separation, reducing the stability and dispersibility of the corrosion inhibitor.

[0020] Optionally, the average particle size of the nanospheres is 120-200 nm.

[0021] In oilfield produced water or injected water systems, micron-sized particles easily settle or clog formation pores. Nanoparticles in the 120-200 nm range can form a stable colloidal dispersion system, which can be smoothly transported with the injected fluid to the metal surface of wells thousands of meters deep without causing formation blockage.

[0022] Meanwhile, the nanospheres have an extremely high specific surface area, providing more active adsorption sites per unit mass, which significantly improves their initial adhesion efficiency and coverage on metal surfaces.

[0023] According to a second aspect of this application, this application provides a method for preparing the pH-responsive nano-bio-based corrosion inhibitor described in any of the above claims, comprising the following steps: Chitosan derivatives were dissolved in water to obtain an aqueous solution with a mass concentration of 1.5-5%. pH-responsive nanoparticles and a crosslinking agent were added, and the mixture was reacted at 20-60℃ for 1-4 hours with continuous stirring. After the reaction was completed, the mixture was washed and dried to obtain the final product.

[0024] pH-responsive particles are directly added to a chitosan derivative solution, and then nanospheres are formed around the particles through a cross-linking reaction. This achieves simultaneous spheroidization and encapsulation, avoiding the problems of active component leakage or uneven loading in multi-step methods. Continuous stirring during the reaction process prevents nanoparticle aggregation, ensuring uniform dispersion and encapsulation.

[0025] Optionally, a second corrosion-inhibiting active component is also added when the pH-responsive nanoparticles are added.

[0026] Optionally, the crosslinking agent is sodium tripolyphosphate or glutaraldehyde.

[0027] Sodium tripolyphosphate or glutaraldehyde can promote the cross-linking of chitosan derivative molecular chains to form a stable nanosphere coating structure.

[0028] Optionally, the amount of crosslinking agent added is 0.5-2% of the mass of the chitosan derivative.

[0029] According to a third aspect of this application, this application provides the application of the pH-responsive nanobio-based corrosion inhibitor described in any one of the above claims, or the nanobio-based corrosion inhibitor prepared by the preparation method of the pH-responsive nanobio-based corrosion inhibitor described in any one of the above claims, in CO2 flooding processes.

[0030] The beneficial effects of this application include, but are not limited to: 1. According to the pH-responsive nanobio-based corrosion inhibitor of this application, pH-responsive nanoparticles are encapsulated inside chitosan derivative nanospheres, successfully constructing a stable core-shell intelligent response structure, realizing intelligent response and on-demand release of the corrosion inhibitor.

[0031] 2. According to the pH-responsive nano-bio-based corrosion inhibitor of this application, modified bio-based raw materials such as carboxymethyl chitosan and chitosan quaternary ammonium salt are used as microsphere matrix, and inorganic pH-responsive nanoparticles and organic second corrosion inhibitor active components are combined to construct a compound synergistic system, which effectively blocks water, oxygen, carbonic acid corrosion media from contacting the metal matrix.

[0032] 3. The pH-responsive nano-bio-based corrosion inhibitor of this application is mainly composed of chitosan derivatives and inorganic mineral pH-responsive particles, all of which have good environmental compatibility and meet the requirements of green and environmentally friendly oilfield chemicals.

[0033] 4. According to the preparation method of the pH-responsive nano-bio-based corrosion inhibitor of this application, a one-step process is adopted to directly disperse pH-responsive nanoparticles in an aqueous solution of chitosan derivative and add a crosslinking agent for crosslinking, which effectively solves the problems of uneven component distribution and large performance dispersion in the traditional stepwise modification process. Detailed Implementation

[0034] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0035] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application were all purchased commercially.

[0036] Unless otherwise specified, the methods used in the embodiments and comparative examples of this application are conventional methods in the prior art.

[0037] Example 1 This embodiment relates to a method for preparing a pH-responsive nano-bio-based corrosion inhibitor, including the following steps: Carboxymethyl chitosan was dissolved in water to obtain an aqueous solution with a mass concentration of 1.5%. 10% (by mass) of pH-responsive nano-ZnO particles (average particle size of 50 nm) were added to the solution, along with 0.5% (by mass) of sodium tripolyphosphate, a crosslinking agent. The mixture was stirred continuously and reacted at 20 °C for 4 h. After the reaction, the mixture was repeatedly washed with deionized water and dried at 80 °C for 2 h to obtain a pH-responsive nano-bio-based corrosion inhibitor with an average particle size of 120 nm.

[0038] Example 2 This embodiment relates to a method for preparing a pH-responsive nano-bio-based corrosion inhibitor, including the following steps: Chitosan quaternary ammonium salt was dissolved in water to obtain a 5% aqueous solution. 30% (by weight of chitosan quaternary ammonium salt) of pH-responsive nano-CaCO3 particles (average particle size 5 nm) and 5% (by weight of chitosan quaternary ammonium salt) of tannic acid were added. 2% (by weight of chitosan quaternary ammonium salt) of glutaraldehyde, a crosslinking agent, was added. The mixture was stirred continuously and reacted at 60°C for 1 hour. After the reaction, the mixture was repeatedly washed with deionized water and dried at 80°C for 2 hours to obtain a pH-responsive nano-bio-based corrosion inhibitor with an average particle size of 200 nm.

[0039] Example 3 This embodiment relates to a method for preparing a pH-responsive nano-bio-based corrosion inhibitor, including the following steps: Chitosan quaternary ammonium salt was dissolved in water to obtain a 3% aqueous solution. 20% (by weight of chitosan quaternary ammonium salt) of pH-responsive nano-Mg(OH)2 particles (average particle size 25 nm) and 8% (by weight of chitosan quaternary ammonium salt) of vanillin were added. 1% (by weight of chitosan quaternary ammonium salt) of glutaraldehyde, a crosslinking agent, was added. The mixture was stirred continuously and reacted at 40°C for 3 hours. After the reaction, the mixture was repeatedly washed with deionized water and dried at 80°C for 2 hours to obtain a pH-responsive nano-bio-based corrosion inhibitor with an average particle size of 150 nm.

[0040] Example 4 This embodiment relates to a method for preparing a pH-responsive nano-bio-based corrosion inhibitor, including the following steps: Carboxymethyl chitosan was dissolved in water to obtain a 2.5% aqueous solution. 24% (by weight of carboxymethyl chitosan) of pH-responsive nano-ZnO particles (average particle size of 35 nm) and 6.5% (by weight of carboxymethyl chitosan) of vanillin were added. 1.5% (by weight of carboxymethyl chitosan) of sodium tripolyphosphate, a crosslinking agent, was added. The mixture was stirred continuously and reacted at 45°C for 2.5 h. After the reaction, the mixture was repeatedly washed with deionized water and dried at 80°C for 2 h to obtain a pH-responsive nano-bio-based corrosion inhibitor with an average particle size of 130 nm.

[0041] Example 5 The difference between this embodiment and Embodiment 4 is that the amount of pH-responsive nano-ZnO particles added is 34% of the mass of carboxymethyl chitosan, while the rest are the same.

[0042] Example 6 The difference between this embodiment and Embodiment 4 is that the amount of vanillin added is 10% of the mass of carboxymethyl chitosan, while the rest are the same.

[0043] Example 7 The difference between this embodiment and embodiment 4 is that vanillin is not added; all other aspects are the same.

[0044] Comparative Example 1 The difference between this comparative example and Example 4 is that chitosan is used instead of carboxymethyl chitosan; all other aspects are the same.

[0045] Comparative Example 2 The difference between this comparative example and Example 4 is that no crosslinking agent was added; all other aspects are the same.

[0046] Comparative Example 3 The difference between this comparative example and Example 4 is that no continuous stirring was performed during the reaction; all other aspects are the same.

[0047] Test Example 1 The corrosion inhibition performance of the corrosion inhibitors obtained in the above embodiments and comparative examples was tested, and the test results are shown in Table 1. The test methods are as follows: Test specimen: N80 carbon steel, size 50mm×25mm×2mm, surface gradually polished to 800# sandpaper, degreased with acetone, dried and weighed.

[0048] Corrosive medium: Simulated CO2-enhanced oil recovery fluid, composed of: NaCl 20 g / L, CaCl2 2 g / L, MgCl2 1 g / L, NaHCO3 0.5 g / L. High-purity CO2 was introduced to saturate the fluid before the experiment (30 min), with an initial pH of 4.2 ± 0.1. A neutral control group was also set up (with the same composition but without CO2 introduction, and the pH adjusted to 7.5 with NaOH).

[0049] Test temperature: 60℃ (constant temperature water bath).

[0050] Test duration: 72 hours.

[0051] Corrosion inhibitor dosage: All solid corrosion inhibitors were added at 200 mg / L (based on total solution volume).

[0052] Evaluation indicators: The corrosion rate (mm / a) was calculated using the weight loss method: v = 8.76 × 10⁻⁶ 4 × m / (S·t·ρ), where Δm: weight loss (g), S: area (cm²) 2 ), t: time (h), ρ: density (7.85 g / cm³) 3 ) The corrosion inhibition rate η = (v0-v) / v0×100%, where v0 is the corrosion rate of the blank test (without corrosion inhibitor), and the corrosion rate of the blank test (without corrosion inhibitor) in a pH=4.2 CO2 saturated solution is v0 = 1.82 mm / a.

[0053] Parallel experiments: 3 parallel samples in each group, and the average value is taken.

[0054] Table 1

[0055] As shown in the data of the examples in Table 1, the corrosion inhibitor prepared in this application has excellent corrosion inhibition ability under acidic conditions. However, Comparative Example 1 uses chitosan instead of carboxymethyl chitosan. Due to the poor solubility of chitosan in water, it is difficult to form uniform microspheres during preparation, and there are problems of too rapid dissolution and poor film formation under acidic conditions, resulting in a low corrosion inhibition rate. In Comparative Example 2, no crosslinking agent was added, and only simple mechanical mixing was performed, so nanospheres could not be formed, and a uniform protective film could not be formed under acidic conditions. In Comparative Example 3, no continuous stirring was performed during the reaction, resulting in particle agglomeration, uneven microsphere particle size, and poor encapsulation effect, so the corrosion inhibition rate was significantly lower than that of Example 4.

[0056] The corrosion inhibition rate at pH 7.5 represents the degree of "passive consumption" of the corrosion inhibitor in a neutral environment. The lower the rate, the more stable the structure of the nanospheres, the less ineffective release occurs in a neutral environment, and the better the response selectivity. As shown in Table 1, the corrosion inhibitor prepared in this application has a low ineffective release rate under neutral conditions, indicating good pH responsiveness.

[0057] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A pH-responsive nano-bio-based corrosion inhibitor, characterized in that, This includes nanospheres composed of chitosan derivatives and pH-responsive nanoparticles; The pH-responsive nanoparticles are encapsulated within the nanospheres.

2. The pH responsive nanobiobased corrosion inhibitor according to claim 1, wherein, The chitosan derivative is carboxymethyl chitosan or chitosan quaternary ammonium salt.

3. The pH responsive nanobiobased corrosion inhibitor according to claim 1, wherein, The pH-responsive nanoparticles are at least one of nano ZnO, nano CaCO3, and nano Mg(OH)2; The average particle size of the pH-responsive nanoparticles is 5-50 nm.

4. The pH responsive nanobiobased corrosion inhibitor of claim 1, wherein, The amount of pH-responsive nanoparticles is 10-30% of the mass of the nanospheres.

5. The pH-responsive nano-bio-based corrosion inhibitor according to claim 1, characterized in that, The nanospheres are also loaded with a second corrosion-inhibiting active component, the loading amount of which is 5-8% of the mass of the chitosan derivative; The second corrosion-inhibiting active component is at least one of tannic acid, phytic acid, and vanillin.

6. The pH-responsive nano-bio-based corrosion inhibitor according to claim 1, characterized in that, The average particle size of the nanospheres is 120-200 nm.

7. The method for preparing the pH-responsive nano-bio-based corrosion inhibitor according to any one of claims 1-6, characterized in that, Includes the following steps: Chitosan derivatives were dissolved in water to obtain an aqueous solution with a mass concentration of 1.5-5%. pH-responsive nanoparticles and a crosslinking agent were added, and the mixture was reacted at 20-60℃ for 1-4 hours with continuous stirring. After the reaction was completed, the mixture was washed and dried to obtain the final product.

8. The method for preparing the pH-responsive nano-bio-based corrosion inhibitor according to claim 7, characterized in that, A second corrosion inhibitory active component is also added when the pH-responsive nanoparticles are added.

9. The method for preparing the pH-responsive nano-bio-based corrosion inhibitor according to claim 7, characterized in that, The crosslinking agent is sodium tripolyphosphate or glutaraldehyde; The amount of crosslinking agent added is 0.5-2% of the mass of the chitosan derivative.

10. The application of the pH-responsive nanobio-based corrosion inhibitor according to any one of claims 1-6 or the preparation method of the pH-responsive nanobio-based corrosion inhibitor according to any one of claims 7-9 in CO2 flooding processes.

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