A silica scale inhibitor and its preparation method

Abstract

This invention relates to a silica scale inhibitor and its preparation method, belonging to the field of industrial water treatment technology. The preparation method of the silica scale inhibitor includes the following steps: hydrophobic modification: under nitrogen protection, polyethyleneimine and a hydrophobic group donor in a mass ratio of 4-5:1 are heated to 70-80°C and stirred continuously for 1-3 hours to obtain solution A; silanization modification: while maintaining the temperature at 70-80°C, a silane coupling agent is slowly added dropwise to solution A and the reaction continues for 1-3 hours to obtain solution B, wherein the mass ratio of polyethyleneimine to silane coupling agent is 2.5-3.5:1; alkaline hydrolysis: while maintaining the temperature at 70-80°C, a 6 g / L sodium hydroxide solution is added to solution B and stirred for 0.5-1.5 hours, wherein the molar ratio of sodium hydroxide to silane coupling agent is 2-4:1. After stirring, the solution is cooled to room temperature to obtain the silica scale inhibitor. The silica scale inhibitor of this invention exhibits excellent scale inhibition, dispersibility, adsorption, and stability under strongly alkaline conditions.

Description

Technical Field

[0001] This invention relates to the field of industrial water treatment technology, and in particular to a silica scale inhibitor and its preparation method. Background Technology

[0002] In circulating water systems across numerous industrial sectors, including oil fields, steam boilers, geothermal energy utilization, seawater desalination, papermaking, and thermal power plants, silica in the raw or circulating water easily deposits on equipment surfaces, forming silica scale. Silica scale is hard and difficult to remove, not only corroding equipment but also severely impacting production efficiency, becoming a prominent problem restricting the operation of many industries. For example, in the alumina industry, the Bayer process is used to produce alumina from bauxite. Bauxite typically contains various forms and amounts of silica. Some silica is chemically inert and therefore does not dissolve, remaining as a solid within the Bayer loop. Other forms of silica, when added to the Bayer process liquid, dissolve in caustic alkali, thus increasing the silica concentration in the liquid. As the liquid repeatedly flows through the Bayer process loop, the silica concentration in the liquid further increases, eventually reaching the point where insoluble aluminosilicate particles form silica scale. The scaling that occurs during alumina production is caused by the crystallization of supersaturated bauxite slurry at high temperatures, resulting in the precipitation of Al(OH)3 and sodium silicate slag, which then deposit on the inner wall of the pipes. Higher temperatures lead to more scaling, reducing the flow area within the pipes and increasing energy consumption in alumina production. Alumina scaling is formed by the dissolution of gibbsite or boehmite from the bauxite slurry at high temperatures in the pipes. The dissolution temperatures and conditions differ for different crystalline phases; for example, gibbsite can dissolve at 125–140°C, while boehmite can dissolve at 240–260°C with the addition of 3%–7% lime. In alumina production, it is necessary to reduce the SiO2 content in the bauxite during the pre-desiliconization stage to increase the silica-alumina ratio and thus improve the final quality of the bauxite. However, scaling mainly occurs during the pre-desiliconization process. To perform this pre-desiliconization, the bauxite slurry needs to be retained in a desiliconization tank at 95-100℃ for 8-10 hours to dissolve the kaolinite in the bauxite and generate sodium aluminosilicate. In other words, the SiO2 in the slurry is converted into sodalite-type hydrated sodium aluminosilicate crystals, which, over time, easily form scale on the inner wall of the pipe, affecting the production efficiency and functional losses of alumina.

[0003] Traditional descaling methods primarily rely on hydraulic flushing or dissolution with strong acids (such as sulfuric acid, oxalic acid, and hydrofluoric acid). Chemical treatment methods involve using one or more chemical agents to first dissolve and soften the scale, then physically breaking down the remaining precipitates, and finally using the liquid flow in the pipeline to carry away the precipitates. Sulfuric acid or hydrochloric acid of a certain concentration is commonly used to dissolve the scale inside the pipeline. Since the pipeline cannot be disassembled, chemical treatment can avoid disassembling the equipment. Chemical agents can penetrate into small crevices and corners in the equipment that are inconvenient for mechanical cleaning. However, chemical treatment often uses strong acids as solvents for scale, requiring careful control of the dosage and cleaning intensity; otherwise, it will severely corrode the inner wall of the pipeline.

[0004] Scale inhibitors and dispersants show even greater application potential. The difference between scale inhibitor technology and traditional methods lies in the fact that the former inhibits and disperses scale, while the latter passively removes scale. Adding scale inhibitors and dispersants to alumina slurry disperses scale as soon as it begins to precipitate, ensuring no scale adheres to the equipment pipelines. This increases the internal surface area of ​​the pipelines, allowing the slurry to flow smoothly without interference. Simultaneously, it improves heat transfer efficiency and production efficiency, extends equipment life, and reduces energy consumption.

[0005] Chinese invention patent CN100545212A discloses a composite silica scale inhibitor for preventing silica scale deposition in industrial water treatment systems. It comprises an adipic acid / amino-terminated polyether / diethylenetriamine copolymer and sodium polyaspartate in a weight ratio of 10:1 to 2:1. The sodium polyaspartate used in this composite silica scale inhibitor significantly improves the silica scale inhibition effect of the adipic acid / amino-terminated polyether / diethylenetriamine copolymer. However, existing silica scale inhibitors exhibit significant performance variations, particularly in their generally poor inhibition of amorphous colloidal silica scale. Therefore, there is an urgent need to research and develop a new silica scale inhibitor. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a silica scale inhibitor and its preparation method. The silica scale inhibitor of this invention exhibits excellent scale inhibition, dispersibility, adsorption, and stability under strongly alkaline conditions.

[0007] In a first aspect, the present invention provides a method for preparing a silica scale inhibitor, the method comprising the following steps:

[0008] Hydrophobic modification: Polyethyleneimine and hydrophobic group donors in a mass ratio of 4-6:1 are heated to 70-80℃ under nitrogen protection and stirred continuously for 1-3 hours to obtain solution A;

[0009] Silanization modification: While maintaining a temperature of 70-80℃, slowly add silane coupling agent dropwise to solution A and continue the reaction for 1-3 hours to obtain solution B. The mass ratio of polyethyleneimine to silane coupling agent is 2.5-3.5:1.

[0010] Alkaline hydrolysis: Maintain a temperature of 70-80℃, add 6g / L sodium hydroxide solution to solution B and stir for 0.5-1.5h. The molar ratio of sodium hydroxide to silane coupling agent is 2-4:1. After stirring, cool to room temperature to obtain the silica scale inhibitor.

[0011] In the above technical solution, the primary and secondary amine groups on the polyethyleneimine molecular chain, under non-catalytic conditions, attack the epoxy groups of the hydrophobic group donor, undergoing a ring-opening reaction. The long-chain alkyl group of the hydrophobic group donor is covalently grafted onto the polyethyleneimine backbone via stable CN bonds, achieving hydrophobic modification. The hydrophobic long chains are strongly adsorbed onto the surface of hydrophobic or partially hydrophobic equipment and pipes through van der Waals forces. The long chains extend in the solution, forming a physical barrier that prevents scale particles from approaching.

[0012] After the addition of the silane coupling agent, the remaining amine groups in solution A continue to attack the epoxy groups in the silane coupling agent molecule, causing it to open its ring. The silane methoxy end group (-Si(OCH3)3) of the silane coupling agent is introduced into the polymer chain, giving the polymer an affinity for the inorganic silica scale surface.

[0013] Sodium hydroxide solution hydrolyzes the -Si(OCH3)3 groups introduced by the silane coupling agent into hydrophilic silanol groups (-Si(OH)3). These silanol groups not only enhance the water solubility of the scale inhibitor but can also further condense to form strong Si-O-Si or Si-OM (M is a metal) chemical bonds on the equipment surface, achieving strong anchoring adsorption. Sodium hydroxide simultaneously converts the carboxyl groups (-COOH) on the grafted polyacrylic acid chains into sodium carboxylate (-COONa), giving it better solubility and stronger electronegativity in water. The strong Si-O- chemical bonds formed by the silanol groups on the equipment surface make the scale inhibitor film more durable and less prone to erosion.

[0014] Optionally, the molecular weight of the polyethyleneimine is 1200-2000; the hydrophobic group donor is any one of nonylphenyl glycidyl ether, octyl glycidyl ether, and chlorooctane; and the silane coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane.

[0015] In the above technical solution, polyethyleneimine is a highly branched polymer with a large number of primary, secondary, and tertiary amine groups on its molecular chain. The amine groups are the reaction sites for subsequent chemical modification. Polyethyleneimine with a molecular weight of 1200-2000 has a chain length sufficient to provide enough reaction sites, ensuring that the scale inhibitor can be grafted with a sufficient number of functional groups. If the molecular weight is too high, the water solubility of polyethyleneimine itself will decrease, and the molecular chains will become too coiled or entangled in the solution, potentially leading to excessively high viscosity of the scale inhibitor, which is not conducive to uniform dispersion and diffusion in the system. Polyethyleneimine with a molecular weight of 1200-2000 can dissolve well in water, ensuring that the scale inhibitor molecules can quickly reach the action site.

[0016] Hydrophobic donors enable polymers to be strongly anchored to the metal surface of equipment or the surface of scale particles through hydrophobic interactions and planar adsorption effects, forming an initial protective film.

[0017] The epoxy groups of γ-glycidoxypropyltrimethoxysilane react efficiently and stably with the remaining amine groups of polyethyleneimine to form strong covalent bonds. This ensures that the silane functional groups are firmly attached to the polymer chain. In the final alkaline hydrolysis step, the (-Si(OCH3)3)3 groups hydrolyze to generate highly reactive silanol groups (-Si-OH). These silanol groups can undergo dehydration condensation with the hydroxyl groups on the surface of the protected equipment (usually metal oxides such as Fe2O3, Al2O3) or on the surface of silica particles (SiO2) to form strong Si-OM (M=Fe, Al, Si) covalent bonds.

[0018] Optionally, the method for preparing the silica scale inhibitor includes the following steps:

[0019] Hydrophobic modification: Polyethyleneimine and hydrophobic group donors in a mass ratio of 4-6:1 are heated to 70-80℃ under nitrogen protection and stirred continuously for 1-3 hours to obtain solution A;

[0020] Silanization modification: While maintaining a temperature of 70-80℃, slowly add silane coupling agent dropwise to solution A and continue the reaction for 1-3 hours to obtain solution B. The mass ratio of polyethyleneimine to silane coupling agent is 2.5-3.5:1.

[0021] Monomer grafting: Cool solution B to 55-65℃, add 0.1 g / ml of a mixed solution of carboxyl-containing olefin monomer and water to solution B, wherein the mass ratio of the carboxyl-containing olefin monomer to polyethyleneimine is 1:8-12, and add an initiator, wherein the mass ratio of the initiator to the carboxyl-containing olefin monomer is 1:18-22, and react at 55-65℃ for 1-2 h to obtain solution C;

[0022] Alkaline hydrolysis: The temperature is then raised to 70-80℃, and a 6g / L sodium hydroxide solution is added to solution C and stirred for 0.5-1.5h. The molar ratio of sodium hydroxide to silane coupling agent is 2-4:1. After stirring, the mixture is cooled to room temperature to obtain the silica scale inhibitor.

[0023] In the above technical solution, through free radical graft copolymerization, the double bonds of carboxyl-containing olefin monomers are activated under the action of a free radical initiator. The activated carboxyl-containing olefin monomer molecules connect to each other, forming shorter chains. These activated chains abstract hydrogen atoms from the α-carbon positions of the polyethyleneimine backbone, thus forming active sites on the polyethyleneimine skeleton, initiating chain growth, and ultimately introducing carboxyl-containing olefin monomer chains into the polymer side chains. Under a high-pH alkaline environment, -COONa is completely ionized, and the chain segments unfold with a strong negative charge, efficiently dispersing negatively charged colloidal silica and aluminosilicate particles through electrostatic repulsion. The carboxyl groups can chelate Ca in water. 2+ Mg 2+ Plasma prevents the formation of complex scale such as calcium carbonate. Polyelectrolyte segments can form a thick hydration layer, generating a strong steric hindrance effect.

[0024] Optionally, the carboxyl-containing olefin monomer is any one of acrylic acid, itaconic acid, and maleic acid; the initiator is ammonium persulfate.

[0025] In the above technical solution, the selected carboxyl-containing alkene monomers possess strong water solubility, ensuring good compatibility and uniform reaction with the aqueous system during the grafting reaction. They all possess abundant carboxyl functional groups, which ionize into carboxylate ions (-COO-) under alkaline conditions. - This gives the polymer chains a strong negative charge. Both exhibit moderate reactivity; their carbon-carbon double bonds can be activated by free radical initiators without being overly reactive, leading to uncontrollable aggregation.

[0026] Optionally, the method for preparing the silica scale inhibitor includes the following steps:

[0027] Hydrophobic modification: Polyethyleneimine and hydrophobic group donors in a mass ratio of 4-6:1 are heated to 70-80℃ under nitrogen protection and stirred continuously for 1-3 hours to obtain solution A;

[0028] Silanization modification: While maintaining a temperature of 70-80℃, slowly add silane coupling agent dropwise to solution A and continue the reaction for 1-3 hours to obtain solution B. The mass ratio of polyethyleneimine to silane coupling agent is 2.5-3.5:1.

[0029] Monomer grafting: Cool solution B to 55-65℃, add 0.1 g / ml of a mixed solution of carboxyl-containing olefin monomer and water to solution B, wherein the mass ratio of the carboxyl-containing olefin monomer to polyethyleneimine is 1:8-12, and add an initiator, wherein the mass ratio of the initiator to the carboxyl-containing olefin monomer is 1:18-22, and react at 55-65℃ for 1-2 h to obtain solution C;

[0030] Alkaline hydrolysis: The temperature is then raised to 70-80℃, and a 6g / L sodium hydroxide solution is added to solution C and stirred for 0.5-1.5h. The molar ratio of sodium hydroxide to silane coupling agent is 2-4:1. After stirring, the solution is cooled to room temperature to obtain solution D.

[0031] Complexation and crosslinking: Cool solution D to 45-55℃, mix guar gum with a small amount of deionized water to form a paste, then add hot water to completely dissolve it to prepare a 2% solution. While stirring, slowly add the guar gum solution to solution D, then add the crosslinking agent. The mass ratio of guar gum to polyethyleneimine is 0.1-0.3:1, and the mass ratio of the crosslinking agent to guar gum is 1:5-10. Continue the reaction at 45-55℃ for 25-35 minutes to obtain the silica scale inhibitor.

[0032] In the above technical solution, the crosslinking agent complexes with guar gum, forming ion bridges through ion coordination or by forming stable covalent bonds, thus connecting two or more guar gum molecular chains. The main molecular chain of guar gum is mannose, which is structurally rich in cis-ortho-hydroxyl groups. The polymer surface in solution D contains numerous silanol and carboxyl groups. The guar gum molecular chains intertwine and tightly bind with the polymer chains through hydrogen bonds and van der Waals forces. Ultimately, through the strong complexation of the crosslinking agent and the physical entanglement between molecular chains, guar gum and the polymer form a complete, unified, and loose three-dimensional network structure.

[0033] Guar gum itself is a natural water-soluble polymer with certain thickening and dispersing abilities, which synergistically inhibits scale formation with the polymer. The formed three-dimensional network can load other highly efficient functional polymer molecules within it, enabling slow release under fluid action, thereby extending the effective action time and improving agent utilization. Simultaneously, in the relatively static environment of the equipment surface, the dynamic network temporarily disrupted by water flow can quickly reconstruct, forming a dense, tough, and continuous gel-like protective film. This effectively prevents scale-forming ions (such as silicate and aluminum ions) and microcrystalline particles from directly contacting the equipment's metal surface, inhibiting scale nucleation and growth at its source.

[0034] Optionally, the crosslinking agent is any one of borate, zirconium salt, aluminum salt, glutaraldehyde, glyoxal, and ethylene glycol diglycidyl ether; preferably, the crosslinking agent is sodium tetraborate.

[0035] In the above technical solution, the reversible complexation between the borate ions in sodium tetraborate and the cis-hydroxyl groups of guar gum and the silanol groups of polymer hydrolysis constructs a loose, dynamic three-dimensional supramolecular network.

[0036] Secondly, the present invention provides a silica scale inhibitor, which is prepared by the above-mentioned method for preparing silica scale inhibitors.

[0037] Thirdly, the present invention provides a method for preparing a silica scale inhibitor, and the silica scale inhibitor prepared by the method is used in circulating water systems of the steel industry, petrochemical industry, chemical industry, thermal power plant industry, and in the production of alumina.

[0038] In summary, the present invention has at least one of the following beneficial technical effects:

[0039] 1. This application uses a silane coupling agent to modify polyethyleneimine. By introducing Si-(OR) end groups into its macromolecular chain segments, hydrophobic modification is achieved, so that the polymer can maintain good scale inhibition and dispersion ability while possessing certain negative charge properties, which greatly improves the scale inhibition efficiency of the silica scale inhibitor.

[0040] 2. This application introduces carboxyl-containing olefin monomer chains into the polymer side chains through a monomer grafting step. Under a high-pH alkaline environment, -COONa is completely ionized, and the chain segments extend and carry a strong negative charge. This allows for the efficient dispersion of negatively charged colloidal silica and aluminosilicate particles through electrostatic repulsion. The carboxyl groups can chelate Ca in water. 2+ Mg 2+ Plasma prevents the formation of complex scale such as calcium carbonate. Polyelectrolyte segments can form a thick hydration layer, generating a strong steric hindrance effect.

[0041] 3. This application incorporates a complexation and crosslinking step. Through the strong complexation of the crosslinking agent and the physical entanglement between molecular chains, guar gum and the polymer form a complete, unified, and loose three-dimensional network structure. In a relatively static environment on the equipment surface, the dynamic network temporarily disrupted by water flow can be rapidly reconstructed, forming a dense, tough, and continuous gel-like protective film. This film effectively prevents scale-forming ions (such as silicate and aluminum ions) and microcrystalline particles from directly contacting the metal surface of the equipment, thus inhibiting scale nucleation and growth at the source. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the embodiments.

[0043] All materials used in the following examples are available for purchase on the market.

[0044] Example 1: A silica scale inhibitor #1 and its preparation method.

[0045] The preparation method includes the following steps:

[0046] S1. Hydrophobic modification: Polyethyleneimine with a molecular weight of 1800 and octyl glycidyl ether in a mass ratio of 4:1 were heated to 75°C under nitrogen protection and stirred continuously for 2 hours to obtain solution A.

[0047] S2. Silanization modification: While maintaining a temperature of 75°C, γ-glycidoxypropyltrimethoxysilane was slowly added dropwise to solution A and the reaction was continued for 2 hours to obtain solution B. The mass ratio of polyethyleneimine to γ-glycidoxypropyltrimethoxysilane was 2.5:1.

[0048] S3. Alkaline hydrolysis: Maintain a temperature of 75°C, add 6 g / L sodium hydroxide solution to solution B and stir for 1 h. The molar ratio of sodium hydroxide to γ-glycidoxypropyltrimethoxysilane is 2:1. After stirring, cool to room temperature to obtain the silica scale inhibitor #1.

[0049] Example 2: A silica scale inhibitor #2 and its preparation method.

[0050] The preparation method includes the following steps:

[0051] S1. Hydrophobic modification: Polyethyleneimine with a molecular weight of 1200 and chlorooctane in a mass ratio of 6:1 were heated to 75°C under nitrogen protection and stirred continuously for 2 hours to obtain solution A.

[0052] S2. Silanization modification: While maintaining a temperature of 75°C, γ-glycidoxypropyltrimethoxysilane was slowly added dropwise to solution A and the reaction was continued for 2 hours to obtain solution B. The mass ratio of polyethyleneimine to γ-glycidoxypropyltrimethoxysilane was 3.5:1.

[0053] S3. Alkaline hydrolysis: Maintain a temperature of 75°C, add 6 g / L sodium hydroxide solution to solution B and stir for 1 h. The molar ratio of sodium hydroxide to γ-glycidoxypropyltrimethoxysilane is 4:1. After stirring, cool to room temperature to obtain the silica scale inhibitor #2.

[0054] Example 3: A silica scale inhibitor #3 and its preparation method.

[0055] The preparation method includes the following steps:

[0056] S1 hydrophobic modification: Polyethyleneimine with a molecular weight of 2000 and nonylphenyl glycidyl ether in a mass ratio of 4.5:1 were heated to 75°C under nitrogen protection and stirred continuously for 2 hours to obtain solution A.

[0057] S2 silanization modification: While maintaining a temperature of 75℃, γ-glycidoxypropyltrimethoxysilane was slowly added dropwise to solution A and the reaction was continued for 2 hours to obtain solution B. The mass ratio of polyethyleneimine to γ-glycidoxypropyltrimethoxysilane was 3:1.

[0058] S3 Alkaline Hydrolysis: Maintain a temperature of 75°C, add 6 g / L sodium hydroxide solution to solution B and stir for 1 h. The molar ratio of sodium hydroxide to γ-glycidoxypropyltrimethoxysilane is 3:1. After stirring, cool to room temperature to obtain the silica scale inhibitor #3.

[0059] Example 4: A silica scale inhibitor #4 and its preparation method.

[0060] The preparation method includes the following steps:

[0061] S1. Hydrophobic modification: Polyethyleneimine with a molecular weight of 2000 and nonylphenyl glycidyl ether in a mass ratio of 4.5:1 were heated to 75°C under nitrogen protection and stirred continuously for 2 hours to obtain solution A.

[0062] S2. Silanization modification: While maintaining a temperature of 75°C, γ-glycidoxypropyltrimethoxysilane was slowly added dropwise to solution A and the reaction was continued for 2 hours to obtain solution B. The mass ratio of polyethyleneimine to γ-glycidoxypropyltrimethoxysilane was 3:1.

[0063] S3. Monomer grafting: Cool solution B to 60℃, add a mixed solution of itaconic acid and water at a ratio of 0.1 g / ml to 1 ml (mass ratio of itaconic acid to polyethyleneimine is 1:8), and add ammonium persulfate (mass ratio of ammonium persulfate to itaconic acid is 1:18). React at 60℃ for 1.5 h to obtain solution C.

[0064] S4. Alkaline hydrolysis: Maintain a temperature of 75°C, add a 6 g / L sodium hydroxide solution to solution C and stir for 1 hour. The molar ratio of sodium hydroxide to γ-glycidoxypropyltrimethoxysilane is 3:1. After stirring, cool to room temperature to obtain the silica scale inhibitor #4.

[0065] Example 5: A silica scale inhibitor #5 and its preparation method.

[0066] The preparation method includes the following steps:

[0067] S1. Hydrophobic modification: Polyethyleneimine with a molecular weight of 2000 and nonylphenyl glycidyl ether in a mass ratio of 4.5:1 were heated to 75°C under nitrogen protection and stirred continuously for 2 hours to obtain solution A.

[0068] S2. Silanization modification: While maintaining a temperature of 75°C, γ-glycidoxypropyltrimethoxysilane was slowly added dropwise to solution A and the reaction was continued for 2 hours to obtain solution B. The mass ratio of polyethyleneimine to γ-glycidoxypropyltrimethoxysilane was 3:1.

[0069] S3. Monomer grafting: Cool solution B to 60℃, add a mixed solution of maleic acid and water at a ratio of 0.1 g / ml to 1:12, and add ammonium persulfate at a ratio of 1:22 to 1:22. React at 60℃ for 1.5 h to obtain solution C.

[0070] S4. Alkaline hydrolysis: Maintain a temperature of 75°C, add a 6 g / L sodium hydroxide solution to solution C and stir for 1 hour. The molar ratio of sodium hydroxide to γ-glycidoxypropyltrimethoxysilane is 3:1. After stirring, cool to room temperature to obtain the silica scale inhibitor #5.

[0071] Example 6: A silica scale inhibitor #6 and its preparation method.

[0072] The preparation method includes the following steps:

[0073] S1. Hydrophobic modification: Polyethyleneimine with a molecular weight of 2000 and nonylphenyl glycidyl ether in a mass ratio of 4.5:1 were heated to 75°C under nitrogen protection and stirred continuously for 2 hours to obtain solution A.

[0074] S2. Silanization modification: While maintaining a temperature of 75°C, γ-glycidoxypropyltrimethoxysilane was slowly added dropwise to solution A and the reaction was continued for 2 hours to obtain solution B. The mass ratio of polyethyleneimine to γ-glycidoxypropyltrimethoxysilane was 3:1.

[0075] S3. Monomer grafting: Cool solution B to 60℃, add a mixed solution of acrylic acid and water at a ratio of 0.1 g / ml to 10:10, and add ammonium persulfate at a ratio of 1:20:20. React at 60℃ for 1.5 h to obtain solution C.

[0076] S4. Alkaline hydrolysis: Maintain a temperature of 75°C, add a 6 g / L sodium hydroxide solution to solution C and stir for 1 hour. The molar ratio of sodium hydroxide to γ-glycidoxypropyltrimethoxysilane is 3:1. After stirring, cool to room temperature to obtain the silica scale inhibitor #6.

[0077] Example 7: A silica scale inhibitor #7 and its preparation method.

[0078] The preparation method includes the following steps:

[0079] S1. Hydrophobic modification: Polyethyleneimine with a molecular weight of 2000 and nonylphenyl glycidyl ether in a mass ratio of 4.5:1 were heated to 75°C under nitrogen protection and stirred continuously for 2 hours to obtain solution A.

[0080] S2. Silanization modification: While maintaining a temperature of 75°C, γ-glycidoxypropyltrimethoxysilane was slowly added dropwise to solution A and the reaction was continued for 2 hours to obtain solution B. The mass ratio of polyethyleneimine to γ-glycidoxypropyltrimethoxysilane was 3:1.

[0081] S3. Monomer grafting: Cool solution B to 60℃, add a mixed solution of acrylic acid and water at a ratio of 0.1 g / ml to 10:10, and add ammonium persulfate at a ratio of 1:20:20. React at 60℃ for 1.5 h to obtain solution C.

[0082] S4. Alkaline hydrolysis: Maintain a temperature of 75°C, add 6 g / L sodium hydroxide solution to solution C and stir for 1 h. The molar ratio of sodium hydroxide to γ-glycidoxypropyltrimethoxysilane is 3:1. After stirring, cool to room temperature to obtain solution D.

[0083] S5. Complexation and crosslinking: Cool solution D to 50°C, mix guar gum with a small amount of deionized water to form a paste, then add hot water to completely dissolve it to prepare a 2% solution. While stirring, slowly add the guar gum solution to solution D, then add zirconium oxychloride. The mass ratio of guar gum to polyethyleneimine is 0.1:1, and the mass ratio of zirconium oxychloride to guar gum is 1:5. Continue the reaction at 50°C for 30 minutes to obtain the silica scale inhibitor #7.

[0084] Example 8: A silica scale inhibitor #8 and its preparation method.

[0085] The preparation method includes the following steps:

[0086] S1. Hydrophobic modification: Polyethyleneimine with a molecular weight of 2000 and nonylphenyl glycidyl ether in a mass ratio of 4.5:1 were heated to 75°C under nitrogen protection and stirred continuously for 2 hours to obtain solution A.

[0087] S2. Silanization modification: While maintaining a temperature of 75°C, γ-glycidoxypropyltrimethoxysilane was slowly added dropwise to solution A and the reaction was continued for 2 hours to obtain solution B. The mass ratio of polyethyleneimine to γ-glycidoxypropyltrimethoxysilane was 3:1.

[0088] S3. Monomer grafting: Cool solution B to 60℃, add a mixed solution of acrylic acid and water at a ratio of 0.1 g / ml to 10:10, and add ammonium persulfate at a ratio of 1:20:20. React at 60℃ for 1.5 h to obtain solution C.

[0089] S4. Alkaline hydrolysis: Maintain a temperature of 75°C, add 6 g / L sodium hydroxide solution to solution C and stir for 1 h. The molar ratio of sodium hydroxide to γ-glycidoxypropyltrimethoxysilane is 3:1. After stirring, cool to room temperature to obtain solution D.

[0090] S5. Complexation and crosslinking: Cool solution D to 50°C. Mix guar gum with a small amount of deionized water to form a paste, then add hot water to completely dissolve it to prepare a 2% solution. While stirring, slowly add the guar gum solution to solution D, then add ethylene glycol diglycidyl ether. The mass ratio of guar gum to polyethyleneimine is 0.3:1, and the mass ratio of ethylene glycol diglycidyl ether to guar gum is 1:10. Continue the reaction at 50°C for 30 minutes to obtain the silica scale inhibitor #8.

[0091] Example 9: A silica scale inhibitor #9 and its preparation method.

[0092] The preparation method includes the following steps:

[0093] S1. Hydrophobic modification: Polyethyleneimine with a molecular weight of 2000 and nonylphenyl glycidyl ether in a mass ratio of 4.5:1 were heated to 75°C under nitrogen protection and stirred continuously for 2 hours to obtain solution A.

[0094] S2. Silanization modification: While maintaining a temperature of 75°C, γ-glycidoxypropyltrimethoxysilane was slowly added dropwise to solution A and the reaction was continued for 2 hours to obtain solution B. The mass ratio of polyethyleneimine to γ-glycidoxypropyltrimethoxysilane was 3:1.

[0095] S3. Monomer grafting: Cool solution B to 60℃, add a mixed solution of acrylic acid and water at a ratio of 0.1 g / ml to 10:10, and add ammonium persulfate at a ratio of 1:20:20. React at 60℃ for 1.5 h to obtain solution C.

[0096] S4. Alkaline hydrolysis: Maintain a temperature of 75°C, add 6 g / L sodium hydroxide solution to solution C and stir for 1 h. The molar ratio of sodium hydroxide to γ-glycidoxypropyltrimethoxysilane is 3:1. After stirring, cool to room temperature to obtain solution D.

[0097] S5. Complexation and cross-linking: Cool solution D to 50°C, mix guar gum with a small amount of deionized water to form a paste, then add hot water to completely dissolve it to prepare a 2% solution. While stirring, slowly add the guar gum solution to solution D, then add glutaraldehyde. The mass ratio of guar gum to polyethyleneimine is 0.2:1, and the mass ratio of glutaraldehyde to guar gum is 1:7. Continue the reaction at 50°C for 30 minutes to obtain the silica scale inhibitor #9.

[0098] Example 10: A silica scale inhibitor #10 and its preparation method.

[0099] The preparation method includes the following steps:

[0100] S1. Hydrophobic modification: Polyethyleneimine with a molecular weight of 2000 and nonylphenyl glycidyl ether in a mass ratio of 4.5:1 were heated to 75°C under nitrogen protection and stirred continuously for 2 hours to obtain solution A.

[0101] S2. Silanization modification: While maintaining a temperature of 75°C, γ-glycidoxypropyltrimethoxysilane was slowly added dropwise to solution A and the reaction was continued for 2 hours to obtain solution B. The mass ratio of polyethyleneimine to γ-glycidoxypropyltrimethoxysilane was 3:1.

[0102] S3. Monomer grafting: Cool solution B to 60℃, add a mixed solution of acrylic acid and water at a ratio of 0.1 g / ml to 10:10, and add ammonium persulfate at a ratio of 1:20:20. React at 60℃ for 1.5 h to obtain solution C.

[0103] S4. Alkaline hydrolysis: Maintain a temperature of 75°C, add 6 g / L sodium hydroxide solution to solution C and stir for 1 h. The molar ratio of sodium hydroxide to γ-glycidoxypropyltrimethoxysilane is 3:1. After stirring, cool to room temperature to obtain solution D.

[0104] S5. Complexation and crosslinking: Cool solution D to 50°C, mix guar gum with a small amount of deionized water to form a paste, then add hot water to completely dissolve it to prepare a 2% solution. While stirring, slowly add the guar gum solution to solution D, then add sodium tetraborate. The mass ratio of guar gum to polyethyleneimine is 0.2:1, and the mass ratio of sodium tetraborate to guar gum is 1:8. Continue the reaction at 50°C for 30 minutes to obtain the silica scale inhibitor #10.

[0105] Comparative Example 1: This comparative example provides a method for preparing a comparative silica scale inhibitor and a comparative silica scale inhibitor D1, which is the same as the preparation method of Example 10, except that polyacrylamide is used instead of polyethyleneimine.

[0106] Comparative Example 2: This comparative example provides a method for preparing a comparative silica scale inhibitor and a comparative silica scale inhibitor D2, which are the same as the preparation method in Example 10, except that nonylphenol polyoxyethylene ether glycidyl ester is used instead of nonylphenyl glycidyl ether.

[0107] Comparative Example 3: This comparative example provides a method for preparing a comparative silica scale inhibitor and a comparative silica scale inhibitor D3, which is the same as the preparation method of Example 10, except that γ-aminopropyltriethoxysilane is used instead of γ-glycidoxypropyltrimethoxysilane.

[0108] Comparative Example 4: This comparative example provides a method for preparing a comparative silica scale inhibitor and a comparative silica scale inhibitor D4, which are the same as the preparation method in Example 10, except that methacrylic acid is used instead of acrylic acid.

[0109] The performance of the silica scale inhibitors #1-#10 in Examples 1-10 and the comparative silica scale inhibitors D1-D3 in Comparative Examples 1-3 were tested, including scale inhibition performance test, dispersion performance test and adsorption performance test. The test results are shown in Table 1.

[0110] Test 1: Scale Inhibition Performance

[0111] Using deionized water, a certain amount of sodium silicate, aluminum chloride, and sodium hydroxide are added to the solution to neutralize SiO2 and Al. 3+ The concentration reached a supersaturated state. The prepared test solution was placed in clean, capped glass bottles, 200 mL per bottle, divided into three groups. 10 ppm of the aforementioned silica scale inhibitor from the examples and comparative examples was added to the first group; 20 ppm of the same inhibitor was added to the second group; and the third group was a blank group with no silica scale inhibitor sample added. All bottles were sealed and placed in a constant temperature oven at 105°C for 16 hours. The 0.45 μm microporous filter membrane was dried at 105°C for 2 hours to constant weight, cooled in a desiccator, and weighed using an analytical balance, recorded as m1. The bottles were removed from the oven and cooled to room temperature. The solution in the bottles was then vacuum filtered through the pre-weighed filter membrane. The scale on the filter membrane was washed 2-3 times with a small amount of deionized water to remove soluble salts. The filter membrane with scale was dried again in a 105℃ oven for 2 hours until constant weight. It was then removed, cooled in a desiccator, and accurately weighed, recorded as m2. The scale mass deposited in a single bottle is m = m2 - m1. The scale inhibition rate (η) is calculated using the formula: η(%) = [1 - (m / m0)] × 100%, where m: scale mass deposited in the chemically treated group (g); m0: scale mass deposited in the blank control group (g).

[0112] Test 2: Dispersion Performance

[0113] Weigh out a certain amount of kaolin and sodium aluminosilicate, add them to deionized water, and stir thoroughly to prepare a 1 g / L suspension. Take a series of stoppered colorimetric tubes and add 50 mL of the above suspension to each. Add 20 ppm of the scale inhibitor sample from the above examples and comparative examples to one group, and use the other group as a blank control without adding scale inhibitor. Tighten the stopper and shake vigorously to mix. Let all colorimetric tubes stand at room temperature for 4 hours. The better the dispersibility of the sample, the slower the solid particles settle and the more turbid the supernatant. After standing, use a pipette to take a certain amount of supernatant from 2 cm below the liquid surface. Use a UV spectrophotometer to measure the transmittance of the supernatant at 600 nm.

[0114] Test 3: Adsorption Performance

[0115] The adsorption performance of the silica scale inhibitor samples in the above examples and comparative examples was tested using the adsorption isotherm method, and the adsorption amount was finally calculated.

[0116] Table 1

[0117]

[0118] The test data obtained from Examples 1-3 in Table 1, especially the test data from Example 3, show that modifying polyethyleneimine with a silane coupling agent and introducing Si-(OR) end groups into its macromolecular chain segments achieves hydrophobic modification, enabling the polymer to maintain good scale inhibition and dispersion capabilities while possessing certain negative charge properties, thus greatly improving the scale inhibition efficiency of the silica scale inhibitor.

[0119] Compared to Example 3, Examples 4-6 added a monomer grafting step to Example 3. In particular, the test data from Example 6 shows that the double bonds of acrylic acid are activated under the action of ammonium persulfate. The activated acrylic acid molecules connect to each other, forming shorter polyacrylic acid chains. These activated polyacrylic acid chains abstract hydrogen atoms from the α-carbon positions of the polyethyleneimine backbone, thus forming active sites on the polyethyleneimine skeleton, initiating the growth of the acrylic acid chains, and ultimately grafting the polyacrylic acid chains onto the polymer. Under alkaline conditions, -COONa is completely ionized, and the chain segments extend and carry a strong negative charge, efficiently dispersing negatively charged colloidal silica and aluminosilicate particles through electrostatic repulsion. The carboxyl groups can also chelate Ca in water. 2+ Mg 2+ Plasma helps prevent the formation of complex scale such as calcium carbonate.

[0120] Compared to Example 6, Examples 7-10 added a complexation and cross-linking step to the basics of Example 6. In particular, the test data from Example 10 shows that the reversible complexation between borate ions in sodium tetraborate and the cis-hydroxyl groups of guar gum and the hydrolyzed silanol groups of the polymer forms a complete, unified, and loose three-dimensional network structure. This effectively prevents scale-forming ions (such as silicate and aluminum ions) and microcrystalline particles from directly contacting the metal surface of the equipment, thus inhibiting scale nucleation and growth at the source.

[0121] Compared to Example 10, Comparative Example 1 used polyacrylamide instead of polyethyleneimine, and the resulting comparative silica scale inhibitor D1 performed significantly worse than the silica scale inhibitor #10 in Example 10. This is because although both polyacrylamide and polyethyleneimine are water-soluble polymers, the amine groups of polyacrylamide are mainly located on the quaternary ammonium salt, and its reactivity is much lower than that of the primary and secondary amines of polyethyleneimine. This makes it difficult for polyacrylamide to undergo efficient and quantitative nucleophilic ring-opening substitution reactions with hydrophobic group donors (epoxides, halogenated hydrocarbons) and silane coupling agents, thus hindering subsequent modification.

[0122] Compared to Example 10, Comparative Example 2 used nonylphenol polyoxyethylene ether glycidyl ester instead of nonylphenyl glycidyl ester. The resulting comparative silica scale inhibitor D2 exhibited significantly lower performance than silica scale inhibitor #10 in Example 10. This is because the polyoxyethylene chain of nonylphenol polyoxyethylene ether glycidyl ester is hydrophilic, which severely weakens the hydrophobic modification effect.

[0123] Compared to Example 10, Comparative Example 3 used γ-aminopropyltriethoxysilane instead of γ-glycidoxypropyltrimethoxysilane. The resulting comparative scale inhibitor D3 exhibited significantly lower performance than the scale inhibitor #10 in Example 10. This is because, although both are silane coupling agents, their terminal organic functional groups differ. The γ-aminopropyltriethoxysilane molecule itself contains both a highly reactive amino group (-NH2) and a hydrolyzable methoxy group (-Si(OCH3)3). Under reaction conditions, the amino group of one γ-aminopropyltriethoxysilane molecule can attack the methoxy group of another γ-aminopropyltriethoxysilane molecule, undergoing a condensation reaction to generate a siloxane (Si-O-Si) structure and release methanol. This results in a complex and unstable scale inhibitor structure, affecting the stability of the scale inhibitor's performance.

[0124] Compared to Example 10, Comparative Example 4 used methacrylic acid instead of acrylic acid, and the resulting comparative silica scale inhibitor D4 exhibited significantly lower performance than the silica scale inhibitor #10 of Example 10. This is because although methacrylic acid and acrylic acid have similar structures, differing only by a methyl group (-CH3), and both can undergo free radical polymerization to provide a carboxyl group, the α-methyl group in methacrylic acid creates significant steric hindrance, resulting in a significantly lower polymerization rate and grafting efficiency compared to acrylic acid. Furthermore, the polymethacrylic acid segments formed after polymerization are more rigid than the polyacrylic acid segments, leading to a weakened steric hindrance effect and thus affecting the final dispersion effect.

[0125] Therefore, the absence or substitution of materials will not play a role in the silica scale inhibitor, but will instead reduce the effectiveness of the silica scale inhibitor. Thus, each component cannot be arbitrarily replaced by other materials.

[0126] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a silica scale inhibitor, characterized in that, The preparation method of the silica scale inhibitor, by weight percentage, includes the following steps: Hydrophobic modification: Polyethyleneimine and hydrophobic group donors in a mass ratio of 4-6:1 are heated to 70-80℃ under nitrogen protection and stirred continuously for 1-3 hours to obtain solution A; Silanization modification: While maintaining a temperature of 70-80℃, slowly add silane coupling agent dropwise to solution A and continue the reaction for 1-3 hours to obtain solution B. The mass ratio of polyethyleneimine to silane coupling agent is 2.5-3.5:

1. Alkaline hydrolysis: Maintain a temperature of 70-80℃, add 6g / L sodium hydroxide solution to solution B and stir for 0.5-1.5h. The molar ratio of sodium hydroxide to silane coupling agent is 2-4:

1. After stirring, cool to room temperature to obtain the silica scale inhibitor. The molecular weight of the polyethyleneimine is 1200-2000; the hydrophobic group donor is any one of nonylphenyl glycidyl ether, octyl glycidyl ether and chlorooctane; the silane coupling agent is γ-glycidyl etheroxypropyltrimethoxysilane.

2. A method for preparing a silica scale inhibitor, characterized in that, The method for preparing the silica scale inhibitor, by weight percentage, includes the following steps: Hydrophobic modification: Polyethyleneimine and hydrophobic group donors in a mass ratio of 4-6:1 are heated to 70-80℃ under nitrogen protection and stirred continuously for 1-3 hours to obtain solution A; Silanization modification: While maintaining a temperature of 70-80℃, slowly add silane coupling agent dropwise to solution A and continue the reaction for 1-3 hours to obtain solution B. The mass ratio of polyethyleneimine to silane coupling agent is 2.5-3.5:

1. Monomer grafting: Cool solution B to 55-65℃, add 0.1 g / ml of a mixed solution of carboxyl-containing olefin monomer and water to solution B, wherein the mass ratio of the carboxyl-containing olefin monomer to polyethyleneimine is 1:8-12, and add an initiator, wherein the mass ratio of the initiator to the carboxyl-containing olefin monomer is 1:18-22, and react at 55-65℃ for 1-2 h to obtain solution C; Alkaline hydrolysis: The temperature is then raised to 70-80℃, and a 6g / L sodium hydroxide solution is added to solution C and stirred for 0.5-1.5h. The molar ratio of sodium hydroxide to silane coupling agent is 2-4:

1. After stirring, the mixture is cooled to room temperature to obtain the silica scale inhibitor. The carboxyl-containing olefin monomer is any one of acrylic acid, itaconic acid, and maleic acid; the initiator is ammonium persulfate; the molecular weight of the polyethyleneimine is 1200-2000; the hydrophobic group donor is any one of nonylphenyl glycidyl ether, octyl glycidyl ether, and chlorooctane; and the silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

3. A method for preparing a silica scale inhibitor, characterized in that, The method for preparing the silica scale inhibitor, by weight percentage, includes the following steps: Hydrophobic modification: Polyethyleneimine and hydrophobic group donors in a mass ratio of 4-6:1 are heated to 70-80℃ under nitrogen protection and stirred continuously for 1-3 hours to obtain solution A; Silanization modification: While maintaining a temperature of 70-80℃, slowly add silane coupling agent dropwise to solution A and continue the reaction for 1-3 hours to obtain solution B. The mass ratio of polyethyleneimine to silane coupling agent is 2.5-3.5:

1. Monomer grafting: Cool solution B to 55-65℃, add 0.1 g / ml of a mixed solution of carboxyl-containing olefin monomer and water to solution B, wherein the mass ratio of the carboxyl-containing olefin monomer to polyethyleneimine is 1:8-12, and add an initiator, wherein the mass ratio of the initiator to the carboxyl-containing olefin monomer is 1:18-22, and react at 55-65℃ for 1-2 h to obtain solution C; Alkaline hydrolysis: The temperature is then raised to 70-80℃, and a 6g / L sodium hydroxide solution is added to solution C and stirred for 0.5-1.5h. The molar ratio of sodium hydroxide to silane coupling agent is 2-4:

1. After stirring, the solution is cooled to room temperature to obtain solution D. Complexation and crosslinking: Cool solution D to 45-55℃, mix guar gum with a small amount of deionized water to form a paste, then add hot water to completely dissolve it to prepare a 2% solution. While stirring, slowly add the guar gum solution to solution D, then add the crosslinking agent. The mass ratio of guar gum to polyethyleneimine is 0.1-0.3:1, and the mass ratio of the crosslinking agent to guar gum is 1:5-10. Continue the reaction at 45-55℃ for 25-35 minutes to obtain the silica scale inhibitor. The carboxyl-containing olefin monomer is any one of acrylic acid, itaconic acid, and maleic acid; the initiator is ammonium persulfate; the molecular weight of the polyethyleneimine is 1200-2000; the hydrophobic group donor is any one of nonylphenyl glycidyl ether, octyl glycidyl ether, and chlorooctane; and the silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

4. The method for preparing a silica scale inhibitor according to claim 3, characterized in that, The crosslinking agent is any one of borate, zirconium salt, aluminum salt, glutaraldehyde, glyoxal, and ethylene glycol diglycidyl ether.

5. The method for preparing a silica scale inhibitor according to claim 4, characterized in that, The crosslinking agent is sodium tetraborate.

6. A silica scale inhibitor, characterized in that, It is prepared using the method for preparing the silica scale inhibitor according to any one of claims 1-5.

7. The application of a silica scale inhibitor in circulating water systems of the steel, petrochemical, chemical, and thermal power industries, as well as in alumina industrial production, characterized in that... The scale inhibitor prepared using the method for preparing the scale inhibitor as described in any one of claims 1-5, or the scale inhibitor as described in claim 6.

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