A low-toxicity thiopyrimidine-based high-temperature acid corrosion inhibitor, its preparation method and application

Abstract

This invention provides a low-toxicity thiopyrimidine-based high-temperature acid corrosion inhibitor, its preparation method, and its application, belonging to the field of metal corrosion protection technology. This invention uses thiourea, ethyl propionate, and pyridine-4-carboxaldehyde as main raw materials to prepare a thiopyrimidine derivative, which is then used as the main agent in combination with N,N-dimethylformamide and Triton X-100 to form a high-temperature acid corrosion inhibitor. By introducing pyridine rings, pyrimidine rings, and a large number of nitrogen, oxygen, and sulfur heteroatoms into the corrosion inhibitor molecule, this invention improves the adsorption capacity and number of adsorption sites on the metal surface, thereby enhancing the film-forming performance of the corrosion inhibitor on the metal surface under high-temperature and strong acid conditions. The dense and complete corrosion inhibitor adsorption film can effectively prevent contact between the metal surface and the corrosive medium, ensuring that the corrosion inhibitor provides effective corrosion protection for wellbore in an environment with a temperature of 140℃-180℃ and a hydrochloric acid concentration of 20%, and is low in toxicity and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of metal corrosion protection technology, specifically relating to a low-toxicity thiopyrimidine-based high-temperature acid corrosion inhibitor, its preparation method, and its application. Background Technology

[0002] Metals are widely used in the petroleum industry, but they are susceptible to corrosion due to environmental factors such as high temperatures at the bottom of wells, highly salinized formation water, bacteria, and acidizing operations. This not only shortens the service life of metal materials and causes economic losses, but in severe cases, it can also lead to sudden accidents that endanger life and property.

[0003] Currently, common methods for metal protection include modifying the internal structure of the metal, electrochemical protection, surface coating, and adding corrosion inhibitors. Among these, adding corrosion inhibitors has advantages such as ease of use, low cost, wide applicability, and good corrosion inhibition effect, so this method is widely used in oil and gas extraction and transportation. Corrosion inhibitor molecules can be rapidly adsorbed onto the metal surface through electrostatic forces, and then form covalent bonds by donating lone pairs of electrons to metal atoms. Corrosion inhibitor molecules containing benzene rings can enhance the adsorption strength between the corrosion inhibitor molecules and the metal surface through π bonds, forming a dense protective film that prevents the metal from contacting the corrosive medium and slows down metal corrosion.

[0004] Due to the increasingly complex international energy situation and huge energy consumption demands in recent years, the oil and gas industry has gradually shifted towards unconventional, deep, and ultra-deep oil and gas reservoirs. Acidizing technology is widely used in the development of unconventional reservoirs, but as the extraction depth increases, the bottom-hole temperature also rises, with some oilfield reservoirs averaging over 160°C. Acidizing operations at such high temperatures cause severe corrosion to downhole metal equipment and tubing, making corrosion control difficult and resulting in economic losses as well as serious safety hazards for production operations. To avoid or reduce the corrosion of metal equipment and pipelines by acid, corrosion inhibitors are often added to the acid solution. Patent CN 110105943 A (A High-Temperature Acidification Corrosion Inhibitor and Its Preparation Method) uses imidazoline-type Mannich base as the main agent, compounded with synergistic corrosion inhibitors propynyl alcohol and KI, dispersant OP-10, and mixed solvents N,N-dimethylformamide, diethylene glycol, and deionized water to form a high-temperature acidification corrosion inhibitor. It has the characteristics of low freezing point, high flash point, good solubility and dispersibility at high temperature, and superior corrosion inhibition effect.

[0005] Patent CN107418548A (A High-Temperature Acidification Corrosion Inhibitor Combining Pyridine Derivative and Mannich Base) reports a high-temperature acidification corrosion inhibitor combining a pyridine derivative and a Mannich base. The inhibitor is composed of dimethylaminomethylphenyltriazole Mannich base, 1,3-pyridine-2-hydroxypropane dichloroisocyanurate, hexamethylenetetramine, a synergist, a surfactant, a dispersant, a solvent, triethanolamine, and formic acid. This high-temperature acidification corrosion inhibitor combining a pyridine derivative and a Mannich base is suitable for temperatures of 120-160℃ and features good compatibility, high safety, convenient transportation and storage, and low cost.

[0006] Patent CN103571448A (A corrosion inhibitor suitable for high-temperature acidizing at 160℃-180℃ and its preparation and application) reports a corrosion inhibitor suitable for high-temperature acidizing at 160℃-180℃. It consists of two components, A and B. Component A is made from polycyclic aromatic hydrocarbon chloromethyl pyridine quaternary ammonium salt, 3-methyl-1-pentyn-3-ol, 2,4-pentanedione, dodecyl pyridine bromide, cinnamaldehyde, potassium fluoride, WH-9603 thickener, and methanol. Component B is made from antimony glycolate, bismuth trichloride, cuprous oxide, and 1+1 hydrochloric acid. This corrosion inhibitor is applied to production enhancement operations in deep wells at 160℃-180℃ and in oil and gas wells acidized with 15%-28% concentrated hydrochloric acid or terrine. It has a low freezing point, good dispersibility in acidizing fluids, and excellent corrosion inhibition performance against high-temperature concentrated hydrochloric acid and terrine corrosion. The corrosion inhibition rate is ≥98%, and the corrosion rate is lower than the industry standard for first-grade products.

[0007] The literature (Li Xiaoke et al., Preparation and performance evaluation of a new type of high temperature acid corrosion inhibitor [J]. Applied Chemical Industry, 2014, 43(06): 1105-1107) synthesized an oleic acid thiourea-based imidazoline by dehydration condensation using thiourea, polyethylene polyamine and oleic acid as raw materials, and then compounded it with surfactants, pyridine, aldehydes, alkynols and other ingredients to obtain a new type of high temperature acid corrosion inhibitor.

[0008] The literature (Wu Wengang et al., Research and application of ultra-high temperature acidizing corrosion inhibitors [C]. Proceedings of the 2016 National Natural Gas Academic Conference, 2016: 2896-2900) describes the formulation of ultra-high temperature acidizing corrosion inhibitors by compounding Mannich base with formic acid derivatives and antimonate complexes, and the field application of the inhibitors in Heshen 1 well (bottom hole temperature 180℃) and Shuangtan 1 well (bottom hole temperature 170℃).

[0009] In summary, many scholars have conducted extensive theoretical and experimental research on high-temperature acid corrosion inhibitors, but current research results still have certain shortcomings. For example, most high-temperature acid corrosion inhibitors require the formulation of many different additives to achieve satisfactory results, which is inconvenient to use; or the inhibitor system may contain components such as hexamethylenetetramine, alkynyl alcohols, and heavy metal salt ions, which are harmful to human health and the environment, thus significantly limiting their field application.

[0010] Therefore, there is still considerable room for research in the field of high-temperature acid corrosion inhibitors, and the development of green and efficient high-temperature acid corrosion inhibitors will undoubtedly become one of the key research focuses in the future. Pyrimidine compounds themselves possess the characteristics of low toxicity and multiple adsorption sites. By synthesizing suitable pyrimidine derivatives, their adsorption capacity on metal surfaces can be further enhanced, enabling them to provide good corrosion protection for metals under high-temperature acidification environments. This will have a positive impact on the research of existing corrosion inhibitor systems. Summary of the Invention

[0011] This invention addresses the problems existing in the prior art by providing a low-toxicity thiopyrimidine-based high-temperature acid corrosion inhibitor, its preparation method, and its application. Using thiourea, ethyl propionate, and pyridine-4-carboxaldehyde as main raw materials, this invention prepares a thiopyrimidine derivative, which is then used as the main agent in combination with N,N-dimethylformamide and Triton X-100 to form a high-temperature acid corrosion inhibitor. By introducing pyridine rings, pyrimidine rings, and a large number of nitrogen, oxygen, and sulfur heteroatoms into the corrosion inhibitor molecule, this invention improves the adsorption capacity and number of adsorption sites on the metal surface, thereby enhancing the film-forming performance of the corrosion inhibitor on the metal surface under high-temperature and strong acid conditions. The dense and complete corrosion inhibitor adsorption film effectively prevents contact between the metal surface and the corrosive medium, ensuring that the corrosion inhibitor provides effective corrosion protection for the wellbore at temperatures of 140℃-180℃ and a hydrochloric acid concentration of 20%. In addition, due to the low toxicity of pyrimidine compounds, the invented thiopyrimidine-based high-temperature acid corrosion inhibitors are more environmentally friendly and have a wider range of application prospects under increasingly stringent environmental regulations.

[0012] To achieve the above objectives, in a first aspect, this application provides a low-toxicity thiopyrimidine-based high-temperature acidification corrosion inhibitor, which is prepared by using thiopyrimidine derivatives as the main agent and compounding them with N,N-dimethylformamide and Triton X-100;

[0013] The structure of the thiopyrimidine derivative is shown in formula (I):

[0014]

[0015] Preferably, the mass ratio of the thiopyrimidine derivative, N,N-dimethylformamide and Triton X-100 is (0.2-0.4):(0.2-0.4):(0.2-0.4), more preferably 0.3:0.4:0.3.

[0016] Secondly, this application provides a method for preparing a low-toxicity thiopyrimidine-based high-temperature acid corrosion inhibitor, comprising the following steps:

[0017] 1) Add solvent to a three-necked flask, add thiourea and pyridine-4-carboxaldehyde at room temperature, and stir magnetically to prepare a homogeneous solution. Then add ethyl propionate dropwise to the prepared homogeneous solution and stir until homogeneous.

[0018] 2) Heat the well-mixed solution in a water bath to 50-75℃, and stir magnetically for 5-20 hours under reflux until the solution becomes oily;

[0019] 3) Cool the obtained oily substance to room temperature, and then extract it twice with diethyl ether to obtain the thiopyrimidine derivative, the main component of the high-temperature acidification corrosion inhibitor.

[0020] 4) The obtained thiopyrimidine derivatives as the main corrosion inhibitors can be compounded with N,N-dimethylformamide and Triton X-100 in a certain proportion to obtain thiopyrimidine high-temperature acidification corrosion inhibitors.

[0021] Preferably, the solvent in step 1) is anhydrous ethanol; the molar ratio of thiourea, pyridine-4-carboxaldehyde and ethyl propionate in step 1) is (0.9-1.1):1:(0.9-1.1), more preferably 1:1:1.

[0022] Preferably, in step 2), the temperature is heated to 65°C and the reaction is carried out for 10 hours.

[0023] Thirdly, the present invention provides the application of the above-mentioned low-toxicity thiopyrimidine-based high-temperature acidification corrosion inhibitors in high-temperature acidification environments.

[0024] Furthermore, the low-toxicity thiopyrimidine-based high-temperature acidification corrosion inhibitor is suitable for environments with temperatures ranging from 140℃ to 180℃ and a hydrochloric acid concentration of 20%.

[0025] The present invention has the following beneficial effects:

[0026] 1. The low-toxicity thiopyrimidine-based high-temperature acid corrosion inhibitor of the present invention exhibits a corrosion rate of N80 steel that is superior to the requirements in "SY / T 5405-2019 Test Methods and Evaluation Indicators for Performance of Acid Corrosion Inhibitors" under the conditions of 140℃-180℃ and 20% hydrochloric acid concentration.

[0027] 2. The pyrimidine compounds of this invention have low toxicity, and the thiopyrimidine high-temperature acidification corrosion inhibitors invented are more environmentally friendly, with broader application prospects under increasingly stringent environmental regulations. Attached Figure Description

[0028] Figure 1 The synthetic route of the low-toxicity thiopyrimidine-based high-temperature acidification corrosion inhibitor of the present invention.

[0029] Figure 2 Corrosion inhibition performance of the low-toxicity thiopyrimidine-based high-temperature acidification corrosion inhibitor in Example 1 at different temperatures.

[0030] Figure 3 Corrosion inhibition performance of low-toxicity thiopyrimidine-based high-temperature acid corrosion inhibitors of different mass concentrations in Example 1. Detailed Implementation

[0031] It is worth noting that the raw materials used in this invention are all commercially available products, and their sources are not specifically limited. The technical solution of this invention is illustrated below through specific examples.

[0032] Example 1

[0033] A method for preparing a low-toxicity thiopyrimidine-based high-temperature acid corrosion inhibitor includes the following steps:

[0034] 1) Add 30 mL of anhydrous ethanol to a three-necked flask as a solvent, add 0.1 mol of thiourea and 0.1 mol of pyridine-4-carboxaldehyde at room temperature, stir magnetically for 5 min to prepare a homogeneous solution, and then add 0.1 mol of ethyl propionate dropwise to the prepared homogeneous solution and stir until homogeneous.

[0035] 2) Heat the well-mixed solution in a water bath to 65°C, and stir magnetically for 10 hours under reflux until the solution becomes oily;

[0036] 3) Cool the obtained oily substance to room temperature, and then extract it twice with diethyl ether to obtain the thiopyrimidine derivative, the main component of the high-temperature acidification corrosion inhibitor.

[0037] 4) The obtained corrosion inhibitor main agent is compounded with N,N-dimethylformamide and Triton X-100 in a mass ratio of 0.3:0.4:0.3 to obtain a thiopyrimidine-based high-temperature acidification corrosion inhibitor.

[0038] Example 2

[0039] A method for preparing a low-toxicity thiopyrimidine-based high-temperature acid corrosion inhibitor includes the following steps:

[0040] 1) Add 30 mL of anhydrous ethanol to a three-necked flask as a solvent, add 0.1 mol of thiourea and 0.1 mol of pyridine-4-carboxaldehyde at room temperature, stir magnetically for 5 min to prepare a homogeneous solution, and then add 0.1 mol of ethyl propionate dropwise to the prepared homogeneous solution and stir until homogeneous.

[0041] 2) Heat the well-mixed solution in a water bath to 60°C, and stir magnetically for 12 hours under reflux until the solution becomes oily;

[0042] 3) Cool the obtained oily substance to room temperature, and then extract it twice with diethyl ether to obtain the thiopyrimidine derivative, the main component of the high-temperature acidification corrosion inhibitor.

[0043] 4) The obtained corrosion inhibitor main agent is compounded with N,N-dimethylformamide and Triton X-100 at a mass ratio of 0.4:0.3:0.3 to obtain a thiopyrimidine-based high-temperature acidification corrosion inhibitor.

[0044] Example 3

[0045] A method for preparing a low-toxicity thiopyrimidine-based high-temperature acid corrosion inhibitor includes the following steps:

[0046] 1) Add 30 mL of anhydrous ethanol to a three-necked flask as a solvent, add 0.1 mol of thiourea and 0.1 mol of pyridine-4-carboxaldehyde at room temperature, stir magnetically for 5 min to prepare a homogeneous solution, and then add 0.1 mol of ethyl propionate dropwise to the prepared homogeneous solution and stir until homogeneous.

[0047] 2) Heat the well-mixed solution to 70°C in a water bath and stir magnetically for 8 hours under reflux until the solution becomes oily;

[0048] 3) Cool the obtained oily substance to room temperature, and then extract it twice with diethyl ether to obtain the thiopyrimidine derivative, the main component of the high-temperature acidification corrosion inhibitor.

[0049] 4) The obtained corrosion inhibitor main agent is compounded with N,N-dimethylformamide and Triton X-100 at a mass ratio of 0.35:0.35:0.3 to obtain a thiopyrimidine-based high-temperature acidification corrosion inhibitor.

[0050] Comparative Example 1

[0051] The main agent of the high-temperature acidification corrosion inhibitor, a thiopyrimidine derivative, was replaced with the pyrimidine thionone corrosion inhibitor in the existing technology (synthesis and performance evaluation of pyrimidine thionone corrosion inhibitor, Tu Sheng et al., Journal of Southwest University (Natural Science Edition), Vol. 40, No. 11, pp. 168-174), that is, the pyrimidine thionone corrosion inhibitor prepared by 3-pyridinecarboxaldehyde, ethyl acetoacetate and thiourea, and the rest is the same as in Example 1.

[0052] Comparative Example 2

[0053] The thiopyrimidine derivative of the high-temperature acid corrosion inhibitor prepared in Example 1 was compounded with N,N-dimethylformamide at a mass ratio of 0.6:0.4 to obtain a thiopyrimidine-based high-temperature acid corrosion inhibitor.

[0054] Comparative Example 3

[0055] A thiopyrimidine-based high-temperature acidification corrosion inhibitor was obtained by compounding Triton X-100 and N,N-dimethylformamide at a mass ratio of 0.6:0.4.

[0056] Test case

[0057] 1) The solubility and dispersibility of the developed thiopyrimidine-based high-temperature acid corrosion inhibitor were evaluated at room temperature. Following the requirements of industry standard SY / T 5405-2019, a 6% (w / w) concentration of the corrosion inhibitor was added to 20% hydrochloric acid. After thorough mixing, the system was observed at regular intervals. The results are shown in Table 1.

[0058] Table 1. Dispersion of corrosion inhibitors in acid in Examples 1-3 and Comparative Examples 1-3.

[0059]

[0060] 2) Under conditions of 20% hydrochloric acid concentration, 4 hours of corrosion, and 16 MPa nitrogen pressure, the corrosion inhibition performance of the corrosion inhibitor at different temperatures was evaluated by calculating the corrosion rate of N80 steel at different temperatures. Specifically, the corrosion inhibitor concentration was 3% at 140℃, 3.5% at 150℃, 4% at 160℃, 4.5% at 170℃, and 5% at 180℃. The results for the corrosion inhibitor in Example 1 are shown in the appendix. Figure 2 From the appendix Figure 2 It can be seen that the developed thiopyrimidine-based high-temperature acid corrosion inhibitors exhibit corrosion inhibition performance at 140℃-180℃ that is superior to the requirements of the industry standard SY / T5405-2019.

[0061] 3) Under the conditions of experimental temperature 180℃, hydrochloric acid concentration 20%, corrosion time 4h, and nitrogen pressure 16MPa, the corrosion inhibition performance of the corrosion inhibitor at different concentrations was evaluated by calculating the corrosion rate of N80 steel at different inhibitor mass concentrations. The results of the corrosion inhibitor in Example 1 are shown in the appendix. Figure 3 .from Figure 3 It can be seen that, at a concentration of 5% or higher, the corrosion rate of N80 steel by the developed thiopyrimidine-based high-temperature acid corrosion inhibitor is less than 60 g·m⁻¹. -2 ·h -1 It can provide good corrosion protection for metals in acidic environments.

[0062] 4) The comparison results of the corrosion inhibition performance of the corrosion inhibitors of Examples 1-3 and Comparative Examples 1-3 are shown in Table 2. The specific test methods are the same as above.

[0063] Table 2 shows the corrosion inhibition performance of Example 1 corrosion inhibitor with a mass concentration of 5% at 140-180°C.

[0064] Temperature / °C Example 1 140 32.86 150 36.91 160 44.75 170 51.38 180 59.74

[0065] Table 3 shows the corrosion inhibition performance of the corrosion inhibitors of Examples 1-3 and Comparative Examples 1-3 at a mass concentration of 5% at 140°C and 180°C.

[0066]

[0067]

[0068] As shown in Tables 2-3, the corrosion inhibitors of Examples 1-3 exhibit superior slow-release performance. Specifically, the corrosion rates of Examples 2 and 3 at 140℃ and 180℃ are higher than that of Example 1 to varying degrees, indicating that the synthesis temperature and compounding ratio of Example 1 are superior to those of Examples 2-3, and the corrosion inhibitor prepared in Example 1 has the best slow-release performance. Furthermore, the corrosion rate of Comparative Example 1 at both experimental temperatures is significantly higher than that of Example 1, indicating that the thiopyrimidine derivative of this invention, as the main agent of the high-temperature acidification corrosion inhibitor, can achieve a better corrosion inhibition effect than the pyrimidine thione in Comparative Example 1. The experimental results of Comparative Example 2 show that poor solubility and dispersion performance severely affects the corrosion inhibition effect of the inhibitor. Therefore, in Example 1, compounding the prepared thiopyrimidine derivative with a suitable proportion of solubilizer (Traraton, a corrosion inhibitor that also has a solubilizing effect on thiopyrimidine derivatives) is necessary and feasible for improving the corrosion inhibition performance. The experimental results of Comparative Example 3 show that although Triton X-100 and N,N-dimethylformamide have certain corrosion inhibition effects, at high temperatures, the thiopyrimidine derivatives of this invention still play a major role.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A thiopyrimidine-based high-temperature acidification corrosion inhibitor, characterized in that, It was prepared by using thiopyrimidine derivatives as the main agent, combined with N,N-dimethylformamide and Triton X-100; the high temperature was 140℃-180℃. The structure of the thiopyrimidine derivative is shown in formula (I): Formula (I).

2. The thiopyrimidine-based high-temperature acidification corrosion inhibitor as described in claim 1, characterized in that, The mass ratio of the thiopyrimidine derivative, N,N-dimethylformamide, and Triton X-100 is (0.2-0.4):(0.2-0.4):(0.2-0.4).

3. The thiopyrimidine-based high-temperature acidification corrosion inhibitor as described in claim 1, characterized in that, The mass ratio of the thiopyrimidine derivative, N,N-dimethylformamide, and Triton X-100 is 0.3:0.4:0.

3.

4. The method for preparing the thiopyrimidine-based high-temperature acid corrosion inhibitor according to any one of claims 1-3, characterized in that, Includes the following steps: 1) Add solvent to a three-necked flask, add thiourea and pyridine-4-carboxaldehyde at room temperature, stir magnetically to prepare a homogeneous solution, and then add ethyl propionate dropwise to the prepared homogeneous solution and stir until homogeneous. 2) Heat the well-mixed solution in a water bath to 50-75℃, and stir magnetically for 5-20 hours under reflux until the solution becomes oily; 3) Cool the obtained oily substance to room temperature, and then extract it twice with diethyl ether to obtain the thiopyrimidine derivative, the main component of the high-temperature acid corrosion inhibitor. 4) The obtained thiopyrimidine derivatives as the main corrosion inhibitors can be compounded with N,N-dimethylformamide and Triton X-100 in a certain proportion to obtain thiopyrimidine high-temperature acidification corrosion inhibitors.

5. The preparation method according to claim 4, characterized in that, The solvent in step 1) is anhydrous ethanol.

6. The preparation method according to claim 4, characterized in that, In step 1), the molar ratio of thiourea, pyridine-4-carboxaldehyde and ethyl propionate is (0.9-1.1):1:(0.9-1.1).

7. The preparation method according to claim 6, characterized in that, In step 1), the molar ratio of thiourea, pyridine-4-carboxaldehyde and ethyl propionate is 1:1:

1.

8. The preparation method according to claim 4, characterized in that, In step 2), heat to 65°C and react for 10 hours.

9. The application of the thiopyrimidine-based high-temperature acidification corrosion inhibitor as described in any one of claims 1-3 or the thiopyrimidine-based high-temperature acidification corrosion inhibitor prepared by the preparation method described in any one of claims 4-8 in a high-temperature acidification environment.

10. The application as described in claim 9, characterized in that, The thiopyrimidine-based high-temperature acidification corrosion inhibitor is suitable for use in environments with a temperature of 140℃-180℃ and a hydrochloric acid concentration of 20%.

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