Sodium lignin sulfonate-based multifunctional scale inhibitor as well as preparation method and application thereof

Abstract

The invention discloses a sodium lignin sulfonate-based multifunctional scale inhibitor as well as a preparation method and application thereof, and belongs to the technical field of macromolecular water treatment. The scale inhibitor has a structural general formula shown in the specification. In addition, the invention also provides a preparation method of the scale inhibitor, which comprises the following steps: S1, mixing maleic anhydride with the first solvent, then continuously mixing with sodium lignin sulfonate, and then reacting in a water bath at 60-70 DEG C to obtain an SL-MA solution; s2, adding imidazoline and formaldehyde into the SL-MA solution, and reacting at 40 to 50 DEG C to obtain an SL-MA-KIL solution; and S3, adding itaconic acid and an initiator into the SL-MA-KIL solution, and reacting at 80-90 DEG C to obtain the scale inhibitor. The scale inhibitor provided by the invention has excellent scale inhibition performance.

Description

A sodium lignosulfonate-based multifunctional scale inhibitor, its preparation method and application Technical Field

[0001] This invention relates to the field of polymer water treatment technology, specifically to a sodium lignosulfonate-based multifunctional scale inhibitor, its preparation method, and its application. Background Technology

[0002] As oilfield exploitation gradually enters the medium-to-high water-cut stage, reservoir conditions become increasingly complex and demanding: reservoir temperature rises, formation water salinity increases, and there are significant differences in compatibility between injected water and formation water, leading to frequent scaling phenomena on formation pores, wellbore, oil pipelines, and the surface of oil production equipment.

[0003] Currently, oilfields mainly rely on adding chemical scale inhibitors to prevent scale buildup. However, existing products have significant limitations under complex operating conditions: single scale inhibitors are too targeted and cannot simultaneously inhibit multiple scale types such as calcium carbonate, calcium sulfate, and barium sulfate (strontium), especially for insoluble scale such as barium sulfate (strontium). Some traditional scale inhibitors contain phosphorus and are difficult to biodegrade after use, which can easily lead to eutrophication of water bodies and does not meet the requirements of environmental protection and "dual carbon" development.

[0004] Given the complex problems of high temperature, high salinity, and excessive scaling in existing technologies, this invention aims to develop a multifunctional and highly efficient scale inhibitor to better address the scaling challenges in oilfield development. This has significant practical implications for improving oil recovery, reducing production and maintenance costs, and achieving green and safe production. Summary of the Invention

[0005] To address the aforementioned issues, this invention, based on the concept of high-value utilization of biomass resources, selects sodium lignosulfonate as the base material. While sodium lignosulfonate possesses certain scale inhibition potential, its active functional groups are insufficient in number and variety, and its molecular spatial configuration lacks sufficient chelation and dispersion sites, making it difficult to adapt to the high-temperature, high-salinity, and high-mineralization oilfield produced water environment. This invention, through modification, can significantly improve its scale inhibition performance: on the one hand, it can simultaneously address various scale types such as calcium carbonate, calcium sulfate, and barium (strontium) sulfate, especially showing significant inhibition efficiency against barium (strontium) sulfate scale; on the other hand, the raw material is derived from renewable biomass, featuring good biodegradability, wide availability, and low cost, balancing environmental protection and economic efficiency, and better meeting the needs of green and sustainable oilfield development.

[0006] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a sodium lignosulfonate-based multifunctional scale inhibitor, its preparation method and application, thereby solving the technical problem of how to improve the scale inhibition performance of scale inhibitors in the prior art.

[0007] To achieve the above-mentioned technical objectives, the present invention provides a sodium lignosulfonate-based multifunctional scale inhibitor with the following general structural formula: Where x and y are any integers from 1 to 10, and lignin represents the aromatic structural skeleton of sodium lignin sulfonate molecule derived from lignin parent.

[0008] Furthermore, the present invention also proposes a method for preparing the above-mentioned sodium lignosulfonate-based multifunctional scale inhibitor, comprising the following steps: S1, mixing maleic anhydride and a first solvent, then mixing with sodium lignosulfonate, and then reacting in a water bath at 60~70℃ to obtain an SL-MA solution; S2, adding imidazoline and formaldehyde to the SL-MA solution and reacting at 40~50℃ to obtain the SL-MA-KIL solution; S3, adding itaconic acid to the SL-MA-KIL solution and reacting at 80~90℃ to obtain the sodium lignosulfonate-based multifunctional scale inhibitor.

[0009] In any embodiment, in step S1, the reaction time in a water bath at 60~70°C is 6-8 hours.

[0010] In any embodiment, in step S1, the molar ratio of the lignin sulfonic acid to the maleic anhydride is 1:(6~9).

[0011] In any embodiment, in step S2, the imidazoline is added at a molar ratio of 1:(0.7-0.8) of imidazoline to sodium lignosulfonate.

[0012] In any embodiment, in step S2, the reaction time at 40-50°C is 3-4 hours.

[0013] In any embodiment, in step S3, the molar ratio of the lignin sulfonic acid to the itaconic acid is 1:(10 ~ 14).

[0014] In any embodiment, in step S3, the reaction time at 80-90°C is 4-5 hours.

[0015] In any embodiment, in step S1, the first solvent is pyridine.

[0016] In any embodiment, in step S1, the molar ratio of the first solvent to the maleic anhydride is (1-2):1.

[0017] In any embodiment, in step S2, the molar ratio of formaldehyde to imidazoline is (0.5~1):(2~5).

[0018] In any embodiment, in step S3, the initiator is ammonium persulfate.

[0019] In any embodiment, in step S3, the total mass ratio of the initiator, maleic anhydride, itaconic acid, and formaldehyde is (0.5~1):10.

[0020] Furthermore, this invention also proposes the application of the above-mentioned sodium lignosulfonate-based multifunctional scale inhibitor or the sodium lignosulfonate-based multifunctional scale inhibitor prepared by the above preparation method in oilfield water treatment.

[0021] Compared with existing technologies, the beneficial effects of this invention include: the sodium lignosulfonate-based multifunctional scale inhibitor molecule proposed in this invention introduces structural units such as carboxyl groups, benzene rings, and nitrogen-containing five-membered heterocycles. These functional groups significantly enhance scale inhibition efficiency through synergistic effects. Carboxyl groups can chelate scale-forming ions in water, inhibiting crystal nucleation; benzene rings interfere with the orderly growth of scale crystals through steric hindrance; and the nitrogen-containing five-membered heterocycles, with their multiple adsorption centers, expand their interaction sites with scale crystals and enhance their binding with scale crystals through intermolecular and intramolecular hydrogen bonds, further hindering their aggregation and deposition. The complementary and synergistic effects of each unit give the synthesized compound the characteristics of high scale inhibition efficiency, low cost, and ease of application, effectively meeting the scale control needs under complex oilfield conditions.

[0022] Beneficial effects also include: the introduction of maleic anhydride as a modified monomer in this invention, directionally introducing active functional groups such as carboxyl groups into the product molecule, effectively chelating scale-forming ions in oilfield water and enhancing the dispersion of already formed microcrystals, inhibiting the nucleation, growth, and deposition of scale from the source, and ensuring the scale inhibition effect of the system under high temperature and high salinity conditions; the introduction of formaldehyde and imidazoline promotes the formation of a synergistic configuration of benzene ring and nitrogen-containing five-membered aromatic heterocycle (such as imidazoline ring) in the molecular structure. This structure not only interferes with the orderly arrangement of scale crystals through steric hindrance, but its nitrogen-containing heterocycle can also provide multiple adsorption sites and strengthen the binding with the scale crystal surface through interactions such as hydrogen bonding, further hindering crystal aggregation and deposition; sodium lignosulfonate, as a biomass-based framework, enhances the chemical stability and durability of the product under high temperature and high salinity environments with its stable aromatic ring structure; at the same time, this component is derived from renewable resources, has good biodegradability, meets the requirements of green chemistry and sustainable development, and the sodium lignosulfonate-based multifunctional scale inhibitor proposed in this invention has excellent and sufficient performance. Attached Figure Description

[0023] Figure 1 is the infrared spectrum of the sodium lignosulfonate-based multifunctional scale inhibitor prepared in Example 3 of the present invention. Detailed Implementation

[0024] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0025] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0026] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0027] This specific embodiment provides a sodium lignosulfonate-based multifunctional scale inhibitor with the following general structural formula: Where x and y are any integers from 1 to 10, and lignin represents the aromatic structural skeleton of sodium lignin sulfonate molecule derived from lignin parent.

[0028] This specific embodiment also proposes a method for preparing the above-mentioned sodium lignosulfonate-based multifunctional scale inhibitor, comprising the following steps: S1, mixing maleic anhydride and a first solvent, then continuing to mix with sodium lignosulfonate, and then reacting in a water bath at 60~70℃ for 6-8h to obtain an SL-MA solution; the molar ratio of the lignosulfonic acid to the maleic anhydride is 1:(6~9); the first solvent is pyridine; the molar ratio of the first solvent to the maleic anhydride is (1-2):1; S2, adding imidazoline and formaldehyde to the SL-MA solution at 40~ The SL-MA-KIL solution is obtained by reacting at 50℃ for 3-4 hours; the imidazoline is added according to the molar ratio of imidazoline to sodium lignosulfonate 1:(0.7-0.8); the molar ratio of formaldehyde to imidazoline is (0.5-1):(2-5); S3, itaconic acid and initiator are added to the SL-MA-KIL solution and reacted at 80-90℃ for 4-5 hours to obtain the sodium lignosulfonate-based multifunctional scale inhibitor; the molar ratio of lignosulfonic acid to itaconic acid is 1:(12-15); the initiator is ammonium persulfate; the total mass ratio of the initiator, maleic anhydride, itaconic acid and formaldehyde is (0.3-1):10.

[0029] The reaction formula is as follows: .

[0030] This specific embodiment also proposes the application of a sodium lignosulfonate-based multifunctional scale inhibitor or a sodium lignosulfonate-based multifunctional scale inhibitor prepared by the above preparation method in oilfield water treatment.

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] In this invention, the terms "some embodiments," "this embodiment," and examples are used to describe a subset of all possible embodiments. However, it is understood that "some embodiments" can be the same subset or different subsets of all possible embodiments and can be combined with each other without conflict.

[0033] If the application documents contain similar descriptions such as "first / second", the following explanation shall be added: In the following description, the terms "first / second / third" are used only to distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first / second / third" may be interchanged in a specific order or sequence where permitted, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0034] In this embodiment, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, object A and / or object B can represent three situations: object A exists alone, object A and object B exist simultaneously, and object B exists alone.

[0035] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0036] Example 1 This example proposes a sodium lignosulfonate-based multifunctional scale inhibitor, the structural formula of which is: Where x and y are any integers from 1 to 10, and lignin represents the aromatic structural skeleton of sodium lignin sulfonate molecule derived from lignin parent.

[0037] This embodiment also proposes a method for preparing the above-mentioned sodium lignosulfonate-based multifunctional scale inhibitor, including the following steps: S1, a certain amount of maleic anhydride (i.e., MA) and pyridine are added to a three-necked flask equipped with a thermometer, a reflux condenser and a stir bar, and stirred at a uniform speed until completely dissolved, and then sodium lignosulfonate (i.e., SL) is added. In step S1, lignin sulfonic acid and maleic anhydride were reacted in a 60°C water bath at a molar ratio of 1:6 for 6 hours to obtain a brown viscous SL-MA solution. In step S2, imidazoline (KIL) and formaldehyde were added to the SL-MA solution and reacted at 40°C for 3 hours, with a molar ratio of SL to KIL of 1:0.7 and a molar ratio of formaldehyde to imidazoline of 0.5:2, to obtain a brown SL-MA-KIL solution. In step S3, itaconic acid (IA) and an initiator (APS) were added to the SL-MA-KIL solution and reacted at 80°C for 4 hours, with a molar ratio of SL to IA of 1:12 and a molar ratio of APS to the total mass of the monomers (maleic anhydride, itaconic acid, and formaldehyde) of 0.3:10. After the reaction was completed, the solution was cooled to obtain the reaction product solution. The product was purified by dialysis to remove unreacted small molecule monomers, and then freeze-dried to obtain a sodium lignin sulfonate-based multifunctional scale inhibitor.

[0038] Example 2 This example proposes a sodium lignosulfonate-based multifunctional scale inhibitor, which is prepared by the following steps: S1, a certain amount of maleic anhydride and pyridine are added to a three-necked flask equipped with a thermometer, a reflux condenser and a stir bar, and stirred at a uniform speed until completely dissolved, and then sodium lignosulfonate is added. In step S1, lignin sulfonate and maleic anhydride were reacted in a 65°C water bath at a molar ratio of 1:7 for 6 hours to obtain a brown viscous SL-MA solution. Step S2: Imidazoline and formaldehyde were added to the SL-MA solution and reacted at 45°C for 4 hours, with the molar ratio of SL to KIL being 1:0.7 and the molar ratio of formaldehyde to the imidazoline being 1:5, to obtain a brown SL-MA-KIL solution. Step S3: Itaconic acid (IA) and an initiator (APS) were added to the SL-MA-KIL solution and reacted at 80°C for 4 hours, with the molar ratio of SL to IA being 1:13 and the ratio of APS to the total mass of the monomers (maleic anhydride, itaconic acid, and formaldehyde) being 0.4:10. After the reaction was completed, the mixture was cooled to obtain a product solution. The product was purified by dialysis to remove unreacted small molecule monomers and then freeze-dried to obtain a sodium lignin sulfonate-based multifunctional scale inhibitor.

[0039] Example 3 This example proposes a sodium lignosulfonate-based multifunctional scale inhibitor, which is prepared by the following steps: S1, a certain amount of maleic anhydride and pyridine are added to a three-necked flask equipped with a thermometer, a reflux condenser and a stir bar, and stirred at a uniform speed until completely dissolved, and then sodium lignosulfonate is added. In step S1, lignin sulfonate and maleic anhydride were reacted in a 65°C water bath at a molar ratio of 1:8 for 6 hours to obtain a brown viscous SL-MA solution. In step S2, imidazoline and formaldehyde were added to the SL-MA solution and reacted at 50°C for 3 hours, with a molar ratio of SL to KIL of 1:0.7 and a molar ratio of formaldehyde to imidazoline of 2:5, resulting in a brown SL-MA-KIL solution. In step S3, itaconic acid (IA) and an initiator (APS) were added to the SL-MA-KIL solution and reacted at 80°C for 4 hours, with a molar ratio of SL to IA of 1:14 and a ratio of APS to the total mass of the monomers (maleic anhydride, itaconic acid, and formaldehyde) of 0.5:10. After the reaction was completed, the mixture was cooled to obtain a product solution. The product was purified by dialysis to remove unreacted small molecule monomers and then freeze-dried to obtain a sodium lignin sulfonate-based multifunctional scale inhibitor.

[0040] Figure 1 shows the infrared spectrum of the sodium lignosulfonate-based multifunctional scale inhibitor prepared in Example 3 of this invention. As can be seen from the curve in Figure 1, the value is 3433.32 cm⁻¹. -1 The absorption peak is the stretching vibration absorption peak of the OH bond in the carboxyl group, at 2926.89 cm⁻¹. -1The absorption peak at 1724.63 cm⁻¹ represents the asymmetric stretching vibration of the CH bond, indicating the presence of alkyl structural units in the product molecule. The scale inhibitor molecule prepared in this study contains a carboxylic acid group. -1 The absorption peak at the specified wavenumber corresponds to the stretching vibration of the C=O bond in the carboxylic acid group. (1632.92 cm⁻¹) -1 This wavenumber is related to the stretching vibration of C=C and originates from the carbon-carbon double bond in maleic anhydride. 1395.65 cm⁻¹ -1 The absorption peak near this wavenumber is related to the bending vibration of C-H, at 1489.36 cm⁻¹. -1 The characteristic absorption peak for the stretching vibration of the CN bond confirms the presence of carbon-nitrogen covalently bonded structural units in the molecule. 1186.31 cm⁻¹ -1 The wavenumber corresponds to the stretching vibration absorption peak at S=O, 755.65 cm⁻¹. -1 and 683.87 cm -1 The two characteristic absorption peaks are stretching vibration peaks of the CS bond in the sulfonic acid group, further indicating that the sulfonic acid functional group was successfully introduced into the product molecule. The above infrared spectral characterization results prove the successful preparation of the LS-MA-KIL compound, and that the molecule contains multiple functional groups such as carboxyl groups, carbon-carbon double bonds, carbon-nitrogen bonds, and sulfonic acid groups, indicating that it has scale inhibition activity.

[0041] Example 4 This example proposes a sodium lignosulfonate-based multifunctional scale inhibitor, which is prepared by the following steps: S1, a certain amount of maleic anhydride and pyridine are added to a three-necked flask equipped with a thermometer, a reflux condenser and a stir bar, and stirred at a uniform speed until completely dissolved, and then sodium lignosulfonate is added. In step S1, lignin sulfonate and maleic anhydride were reacted in a 70°C water bath at a molar ratio of 1:9 for 6 hours to obtain a brown, viscous SL-MA solution. In step S2, imidazoline and formaldehyde were added to the SL-MA solution and reacted at 50°C for 3 hours, with a SL to KIL molar ratio of 1:0.7 and a formaldehyde to imidazoline molar ratio of 0.5:5, resulting in a brown SL-MA-KIL solution. In step S3, itaconic acid (IA) and an initiator (APS) were added to the SL-MA-KIL solution and reacted at 80°C for 4 hours, with a SL to IA molar ratio of 1:15 and an APS to the total mass of the monomers (maleic anhydride, itaconic acid, and formaldehyde) ratio of 1:10. After the reaction, the mixture was cooled to obtain a product solution. The product was purified by dialysis to remove unreacted small molecule monomers and then freeze-dried to obtain a sodium lignin sulfonate-based multifunctional scale inhibitor.

[0042] Comparative Example 1: This comparative example discloses a scale inhibitor prepared by the following steps: A certain amount of maleic anhydride and pyridine are added to a three-necked flask equipped with a thermometer, a reflux condenser, and a stirrer. The mixture is stirred at a uniform speed until completely dissolved, and then sodium lignosulfonate is added. The molar ratio of lignosulfonate to maleic anhydride is 1:8. The mixture is reacted in a water bath at 65°C for 6 hours to obtain a brown viscous solution. Imidazoline and formaldehyde are added to the brown viscous solution and reacted at 50°C for 3 hours. The molar ratio of SL to KIL is 1:0.7, and the molar ratio of formaldehyde to imidazoline is 2:5. After the reaction is completed, the mixture is cooled to obtain a reaction product solution. The product is purified by dialysis to remove unreacted small molecule monomers, and then freeze-dried to obtain a multifunctional, high-efficiency scale inhibitor.

[0043] Comparative Example 2: This comparative example presents a scale inhibitor prepared by the following steps: A certain amount of maleic anhydride and pyridine are added to a three-necked flask equipped with a thermometer, a reflux condenser, and a stirrer. The mixture is stirred at a uniform speed until completely dissolved, and then sodium lignosulfonate is added. The molar ratio of lignosulfonic acid to maleic anhydride is 1:8. The mixture is reacted in a water bath at 65°C for 6 hours to obtain a brown viscous solution. Itaconic acid and an initiator are added to the brown viscous solution, and the mixture is reacted at 80°C for 4 hours. The molar ratio of SL to IA is 1:14, and the mass ratio of APS to the total monomers is 0.5:10. After the reaction is completed, the mixture is cooled to obtain a reaction product solution. The product is purified by dialysis to remove unreacted small molecule monomers, and then freeze-dried to obtain a multifunctional, high-efficiency scale inhibitor.

[0044] The performance of the calcium carbonate scale inhibitor was tested using a static scale inhibition evaluation method. The performance of the synthesized compound prepared in the examples in inhibiting calcium carbonate scale was tested, and the test results are recorded in Table 1.

[0045] Accurately weigh 0.50 g of scale inhibitor, dissolve it in a small amount of pure water, and transfer it to a 250 mL volumetric flask. Dilute to the mark to obtain the scale inhibitor solution. Take 200 mL of pure water into a 250 mL volumetric flask, add the pre-prepared CaCl2 solution, and prepare the Ca... 2+ The content is 96.00 mg·L. -1 Add 7.5 mL of scale inhibitor solution to the calcium chloride solution, let it stand for 10 minutes, and then add the pre-prepared Na2CO3 solution while shaking, so that the CO32-... 2- The content is 150.72 mg·L. -1 Then dilute with pure water to the mark, pour into a ground glass joint Erlenmeyer flask, place in a 50℃±1℃ water bath for half an hour, and let stand for 16 hours.

[0046] After the reaction was complete, the solution was cooled to room temperature and filtered using quantitative filter paper. The filtrate of CaCO3 was titrated with a standard solution of ethylenediaminetetraacetic acid (EDTA) to determine the Ca2+ content. 2+At the same concentration, a blank test was conducted simultaneously, and the scale inhibition rate was calculated using the following formula: Where η (100%) is the scale inhibition rate, and V blank2 V represents the volume of EDTA consumed by all calcium ions in the solution. blank1 V represents the volume of EDTA consumed by calcium ions in the solution without added scale inhibitor; final This represents the volume of EDTA consumed by calcium ions present after the addition of scale inhibitor to the solution.

[0047] Table 1. Scale inhibition performance test results of the scale inhibitors in Examples 1-4 and Comparative Examples 1-2 As shown in Table 1, the sodium lignosulfonate-based multifunctional scale inhibitor provided by the present invention has good inhibition performance against calcium carbonate, and a scale inhibition efficiency of 92.89% can be achieved with a scale inhibitor concentration of 30 mg / L.

[0048] The performance of the compound prepared in the examples in inhibiting calcium sulfate scale was tested using a static scale inhibition evaluation method. The results are recorded in Table 2.

[0049] Accurately weigh 0.50 g of scale inhibitor, dissolve it in a small amount of pure water, and transfer it to a 250 mL volumetric flask. Dilute to the mark to obtain the scale inhibitor solution. Take 150 mL of pure water into a 250 mL volumetric flask, add the pre-prepared CaCl2 solution, and prepare the Ca... 2+ The content is 30.00 mg·L. -1 Add 7.5 mL of scale inhibitor solution to the calcium chloride solution, let it stand for 10 minutes, and then add the pre-prepared Na2SO4 solution while shaking, so that the SO42-... 2- The content is 73.35 mg·L. -1 Then dilute with pure water to the mark, pour into a ground glass stoppered Erlenmeyer flask, place in a 50℃±1℃ water bath for half an hour, and let stand for 24 hours.

[0050] After the reaction was complete, the solution was cooled to room temperature and filtered through quantitative filter paper. The filtrate of CaSO4 was titrated with a standard ethylenediaminetetraacetic acid (EDTA) solution to determine the Ca content. 2+ At the same concentration, a blank test was conducted simultaneously, and the scale inhibition rate was calculated using the following formula: Where η (100%) is the scale inhibition rate, and V blank2 V represents the volume of EDTA consumed by all calcium ions in the solution. blank1 V represents the volume of EDTA consumed by calcium ions in the solution without added scale inhibitor; final This represents the volume of EDTA consumed by calcium ions present after the addition of scale inhibitor to the solution.

[0051] Table 2. Scale inhibition performance test results of the scale inhibitors in Examples 1-4 and Comparative Examples 1-2. As shown in Table 2, the sodium lignosulfonate-based multifunctional scale inhibitor provided by this invention has good inhibition performance against calcium sulfate, and a scale inhibition efficiency of 96.52% can be achieved with a scale inhibitor concentration of 30 mg / L.

[0052] The barium sulfate scale inhibition performance was tested using a static scale inhibition evaluation method. The performance of the synthesized compound prepared in the examples in inhibiting barium sulfate scale was tested, and the test results are recorded in Table 3.

[0053] Accurately weigh 0.50 g of scale inhibitor, dissolve it in a small amount of pure water, and transfer it to a 250 mL volumetric flask. Dilute to the mark to obtain the scale inhibitor solution. Take 200 mL of pure water into a 250 mL volumetric flask, add the pre-prepared BaCl2 solution, and prepare the BaCl2 solution. 2+ The content is 2.80 mg·L. -1 The barium chloride solution. Accurately add 7.5 mL of scale inhibitor solution to the barium chloride solution, let stand for 10 minutes, then add the pre-prepared Na2SO4 solution while shaking, so that SO42-... 2- The content is 2.06 mg·L. -1 Then dilute with pure water to the mark, pour into a ground glass stoppered Erlenmeyer flask, place in a 50℃±1℃ water bath for half an hour, and let stand for 24 hours.

[0054] After the reaction was complete, the solution was cooled to room temperature and filtered through quantitative filter paper. The filtrate of BaSO4 was titrated with ethylenediaminetetraacetic acid (EDTA) standard solution to determine Ba. 2+ At the same concentration, a blank test was conducted simultaneously, and the scale inhibition rate was calculated using the following formula: Where η (%) is the scale inhibition rate, V blank2 V represents the volume of EDTA consumed by all barium ions in the solution. blank1 V represents the volume of EDTA consumed by barium ions in a solution without added scale inhibitor; final This represents the volume of EDTA consumed by barium ions present in the solution after the addition of a scale inhibitor.

[0055] Table 3. Scale inhibition performance test results of the scale inhibitors in Examples 1-4 and Comparative Examples 1-2 As shown in Table 3, the sodium lignosulfonate-based multifunctional scale inhibitor provided by the present invention has good inhibition performance against barium sulfate, and a scale inhibition efficiency of 94.9% can be achieved with 30 mg / L of scale inhibitor.

[0056] In summary, the sodium lignosulfonate-based multifunctional scale inhibitor prepared in this invention exhibits excellent scale inhibition performance: at a dosage of 30 mg / L, the scale inhibition efficiencies for calcium carbonate, calcium sulfate, and barium sulfate reach 92.89%, 96.52%, and 94.9%, respectively, with particularly outstanding inhibition effects on calcium sulfate and barium sulfate. The performance advantages of this scale inhibitor align with the core development trend of modern water treatment agents—"multi-element grafting, green and efficient"—providing a high-performance, novel biomass-based scale inhibition solution that conforms to industry development trends for complex water treatment scenarios such as oilfield produced water.

[0057] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A sodium lignosulfonate-based multifunctional scale inhibitor, characterized in that, It has the following general structural formula: Where x and y are any integers from 1 to 10, and lignin represents the aromatic structural skeleton of sodium lignin sulfonate molecule derived from lignin parent.

2. A method for preparing the sodium lignosulfonate-based multifunctional scale inhibitor according to claim 1, characterized in that, Includes the following steps: S1. Maleic anhydride and a first solvent are mixed, followed by further mixing with sodium lignosulfonate, and then reacted in a water bath at 60-70°C to obtain an SL-MA solution; S2. Imidazoline and formaldehyde are added to the SL-MA solution and reacted at 40-50°C to obtain an SL-MA-KIL solution; S3. Itaconic acid and an initiator are added to the SL-MA-KIL solution and reacted at 80-90°C to obtain the sodium lignosulfonate-based multifunctional scale inhibitor.

3. The preparation method of the sodium lignosulfonate-based multifunctional scale inhibitor according to claim 2, characterized in that, In step S1, the reaction time in a water bath at 60~70℃ is 6-8 hours.

4. The preparation method of the sodium lignosulfonate-based multifunctional scale inhibitor according to claim 2, characterized in that, In step S1, the molar ratio of the lignin sulfonic acid to the maleic anhydride is 1:(6~9).

5. The method for preparing the sodium lignosulfonate-based multifunctional scale inhibitor according to claim 2, characterized in that, In step S2, the imidazoline is added at a molar ratio of 1:(0.7-0.8) to sodium lignosulfonate; and / or, in step S2, the reaction time is 3-4 h at 40-50°C.

6. The method for preparing the sodium lignosulfonate-based multifunctional scale inhibitor according to claim 2, characterized in that, In step S3, the molar ratio of lignin sulfonic acid to itaconic acid is 1:(10~14); and / or, in step S3, the reaction time at 80~90°C is 4~5h.

7. The method for preparing the sodium lignosulfonate-based multifunctional scale inhibitor according to claim 2, characterized in that, In step S1, the first solvent is pyridine; and / or, in step S1, the molar ratio of the first solvent to the maleic anhydride is (1-2):1; and / or, in step S2, the molar ratio of the formaldehyde to the imidazoline is (0.5~1):(2~5).

8. The method for preparing the sodium lignosulfonate-based multifunctional scale inhibitor according to claim 2, characterized in that, In step S3, the initiator is ammonium persulfate.

9. The method for preparing the sodium lignosulfonate-based multifunctional scale inhibitor according to claim 2, characterized in that, In step S3, the total mass ratio of the initiator, maleic anhydride, itaconic acid, and formaldehyde is (0.5 ~ 1):

10.

10. The application of a sodium lignosulfonate-based multifunctional scale inhibitor according to claim 1 or a sodium lignosulfonate-based multifunctional scale inhibitor prepared by any one of claims 2-9 in oilfield water treatment.

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