Preparation method of salt-tolerant and high-temperature-resistant rapid-response polyacrylamide flocculant

Abstract

The application provides a preparation method of a salt-resistant and high-temperature-resistant fast-response polyacrylamide flocculant, which comprises the following steps: using purified acrylamide as a polymerization monomer, using strong hydration functional monomer 2-acrylamide-2-methylpropanesulfonic acid and rigid functional monomer itaconic acid as copolymerization monomers, and using nano-silicon dioxide modified by a silane coupling agent to prepare the flocculant through one-step in-situ polymerization reaction. The one-step in-situ polymerization method ensures that the modified nano-silicon dioxide is uniformly dispersed in the reaction system before polymerization, and a uniform and stable organic-inorganic hybrid network structure is formed in the polymerization process. The application has high process integration degree, low cost, can realize large-scale industrial production, and significantly improves the thermal stability, salt resistance, solubility and flocculation performance of the polyacrylamide flocculant in a high-temperature and high-mineralization environment. Meanwhile, the prepared flocculant is stable at 120 DEG C, has a salt resistance of 20000 ppm mineralization degree, can be dissolved in 15 seconds, and has a flocculation time of 7 seconds.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a method for preparing a salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant. Background Technology

[0002] Polyacrylamide (PAM) is a linear, water-soluble polymer, a general term for acrylamide homopolymers and copolymers. With molecular weights reaching tens of millions, it is one of the most widely used, consumed, and rapidly developing water-soluble polymers. Besides its crucial advantage of water solubility, various polyacrylamide derivatives, obtained through structural design, also possess excellent properties such as flocculation, thickening, shear resistance, and dispersibility. Polyacrylamide flocculants are widely used in oil extraction, mineral processing, chemical industry, and agricultural production, and are known as a green and environmentally friendly "all-industry auxiliary agent," playing a vital role in national economic development.

[0003] In recent years, constrained by global industrial transformation, environmental policies, and changes in market demand, the development of polyacrylamide flocculants has faced a series of complex problems and challenges. As oil and gas resource development extends to complex formations (high temperature, high salinity, low permeability, unconventional oil and gas, etc.), new challenges are posed to the flocculation performance of flocculants under high salinity and high temperature conditions. In highly saline solutions, divalent cations neutralize the carboxyl anions of polymer molecules, causing polymer molecules to coil up. Furthermore, at high temperatures, acrylamide groups undergo hydrolysis, reducing the viscosity of the polymer solution and severely impacting the flocculation efficiency of polyacrylamide. Simultaneously, the catalytic effect of metal ions makes it difficult to precisely control the reaction initiation point, potentially leading to side reactions, localized overheating, and explosive polymerization, severely affecting the stability of the polymerization process. Existing technologies such as recrystallization and activated carbon adsorption can effectively remove polymerization inhibitors from acrylamide, but trace metal ions remain difficult to remove. To improve the overall performance of polyacrylamide flocculants, polyacrylamide synthesis engineers are optimizing multiple dimensions, including raw material purification, formulation design, process adaptation, cost control, and environmental friendliness.

[0004] Among them, the patent publication number "CN 119285824 A" discloses "A method for producing high molecular weight polyacrylamide by adding alkali before homopolymerization," which improves the product's molecular weight and salt resistance by utilizing technological innovations such as the pre-polymerization alkali addition process, post-hydrolysis process, and the preparation of sodium hydroxide particles encapsulated in a thermosensitive material. However, industrial acrylamide monomers contain trace amounts of metal ions, which can act as catalysts to promote the decomposition of the thermosensitive material, leading to problems such as uncontrollable polymerization reactions.

[0005] Patent publication number CN119038719B discloses a "Composite Flocculant Containing Polyacrylamide," which introduces amino acid-modified graphene oxide and triazine amino acids to enhance the adsorption bridging effect of polyacrylamide and improve its flocculation performance. However, the preparation steps are cumbersome and the conditions are harsh, resulting in high production costs and hindering large-scale application.

[0006] The patent publication number "CN119613612A" discloses "A branched polyacrylamide polymer resistant to ultra-high salt and ultra-high temperature". The polyacrylamide prepared by this method meets the requirements of salt and high temperature resistance, but the raw materials such as pentaethylenehexamine and formaldehyde are hazardous chemicals, which greatly increases the environmental protection pressure of large-scale production.

[0007] In summary, developing a high-performance polymer that can synergistically address the dual challenges of high temperature and high salinity from the perspectives of molecular structure design and material composites, and which is also technologically feasible, has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0008] This invention provides a method for preparing a salt-resistant, high-temperature-resistant, and fast-response polyacrylamide flocculant, which overcomes the problems of uncontrollable polymerization reaction, complicated preparation steps, harsh conditions, high production costs, and increased environmental pressure caused by large-scale production in the prior art.

[0009] To achieve the above objectives, the technical solution adopted in this invention is as follows: a method for preparing a salt-resistant, high-temperature-resistant, and fast-response polyacrylamide flocculant, which uses purified acrylamide as the polymerizing monomer, and the strong hydration functional monomer 2-acrylamide-2-methylpropanesulfonic acid and the rigid functional monomer itaconic acid as comonomers, and is prepared by one-step in-situ polymerization with nano-silica modified by a silane coupling agent.

[0010] Furthermore, the above preparation method includes the following steps: Step 1: Add purified acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, itaconic acid and modified nano silica to a container, add deionized water, and stir until the system is evenly dispersed to obtain a monomer mixture. Step 2: Add NaOH to adjust the pH to 5-7; Step 3: Under nitrogen protection, add the composite initiator ammonium persulfate and tetramethylethylenediamine, and polymerize at 20-50℃ for 4-8 hours to obtain a white flocculent substance; Step 4: Dry the white flocculent material in a drying oven at 60°C for 24 hours, then grind it into powder to obtain a salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant.

[0011] Furthermore, in step one above, the mass ratio of purified acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and itaconic acid is 10:4:1, and the amount of modified nano silica added is 0.5-5% of the total mass of the three monomers.

[0012] Furthermore, in step three above, the mass ratio of ammonium persulfate to tetramethylethylenediamine is 1:1, and the amount of composite initiator added is 0.06% of the total mass of the three monomers.

[0013] Furthermore, in step three above, the one-step in-situ polymerization reaction is carried out at 20-50℃ for 4-8 hours.

[0014] Furthermore, the above-mentioned method for preparing purified acrylamide involves preparing a 40% (w / w) ethanol solution of acrylamide in a container, and under nitrogen protection and stirring, slowly adding an organophosphorus chelating agent ethanol solution dropwise using a microsyringe or pipette, with the addition amount being 0.1% of the acrylamide mass; reacting at 25°C for 3 hours; after the reaction is complete, adding 1% (w / w) of activated carbon from the total mass of the solution, and reacting at 50°C in the dark for 1 hour; filtering out insoluble impurities from the solution while hot, and then allowing the filtrate to stand in the dark for 24 hours before slowly cooling to precipitate crystals; collecting the crystals by vacuum filtration using a Buchner funnel, drying under vacuum at 40°C, and then sealing and storing in the dark.

[0015] Furthermore, the above-mentioned modified nano-silica (SiO2) is prepared by drying silica at 100 °C for 2 h, preparing a 2% (w / w) ethanol solution of silane coupling agent KH550, and then ultrasonically dispersing it for 10 min; adding the dried silica at room temperature, mixing it evenly, ultrasonically dispersing it for 30 min, performing a coupling grafting reaction at 80 °C for 5 h, and drying it to obtain modified nano-SiO2.

[0016] 1. This invention utilizes a one-step in-situ polymerization process to prepare a salt-resistant, high-temperature-resistant, and rapidly responsive terpolymer polyacrylamide flocculant. The one-step in-situ polymerization method ensures uniform dispersion and simultaneous reaction of all components in the reaction system to generate the composite material. This method avoids the problems of uneven pre-dispersion of nanoparticles and poor compatibility in subsequent blending, resulting in high process integration, low cost, and suitability for large-scale industrial production.

[0017] 2. This invention innovatively combines a ternary functional monomer of sulfonic acid-based strong hydration (AMPS), a rigid cyclic structure (IA), and a main-chain acrylamide (AM). The introduced 2-acrylamido-2-methylpropanesulfonic acid, with its strongly hydrating functional group sulfonic acid (-SO3H), enhances the charge stability of the ternary copolymer system, which is beneficial for polyacrylamide to maintain the hydration layer in high-mineralization environments, thereby maintaining solution viscosity. The introduced itaconic acid, with its rigid side group, can effectively inhibit the chain segment movement of the ternary copolymer molecular chain at high temperatures, thereby effectively improving the high-temperature resistance of the polyacrylamide flocculant. The combination of these three elements simultaneously enhances charge stability, spatial rigidity, and chain flexibility at the molecular synergistic design level, providing a structural basis for salt and temperature resistance.

[0018] 3. This invention proposes an "organic-inorganic" nano-reinforcement mechanism. Modified nano-SiO2 is introduced into the system for one-step in-situ polymerization, making it an organic component of the polymer network. The "one-step in-situ polymerization method" used in the preparation of the introduced modified nano-SiO2 ensures that the nanoparticles are uniformly dispersed in the reaction system before polymerization. During polymerization, a uniform and stable organic-inorganic hybrid network structure is formed through chemical bonds or strong hydrogen bonds, fundamentally solving the problem of dispersion and compatibility of nanomaterials in polymer materials. Therefore, the modified SiO2 nanoparticles can provide additional adsorption sites, enhancing flocculation and bridging capabilities. This invention utilizes molecular synergistic design and "organic-inorganic" nano-reinforcement to significantly improve the thermal stability, salt resistance, solubility, and flocculation performance of polyacrylamide flocculants under high temperature and high mineralization environments.

[0019] 4. This invention introduces organophosphorus compounds with excellent chelating effects, utilizing the synergistic effect of "coordination-charge-steric hindrance" to efficiently remove Cu metal ions from AM. 2+ The purified acrylamide obtained in this way can effectively avoid adverse factors such as overheating and explosive polymerization. Meanwhile, the silica introduced in this invention, modified with a silane coupling agent, can further improve structural dispersibility and stability. Through research, this invention has determined that the amount of silane coupling agent-modified nano-silica added should be 0.5-5% of the total mass of the three monomers. Too low an addition amount cannot effectively improve the system's dispersibility and adsorption bridging effect, while too high an addition amount is detrimental to the formation of high molecular weight terpolymers. Compared with traditional nano-silica whose surface only contains hydroxyl functional groups, the modified surface grafted with organic functional groups can form strong hydrogen bonds, ionic bonds, or covalent bonds with the polyacrylamide molecular chains, acting as physical cross-linking points. This greatly enhances the rigidity and stability of the entire molecular network, effectively resisting the thermal motion of molecular chains caused by high temperatures and the compression effect of salt ions on the chain segments.

[0020] 5. The salt-resistant, high-temperature-resistant, and fast-response polyacrylamide flocculant of this invention exhibits stable performance at 120℃, with a salt resistance of 20,000 ppm mineralization. It dissolves in 15 seconds and flocculates in 7 seconds, making it a fast-response flocculant capable of rapid dissolution. It is particularly suitable for use in extreme environments such as high-temperature and high-mineralization conditions. Attached Figure Description

[0021] Figure 1 SEM image of polyacrylamide flocculant prepared by free radical polymerization.

[0022] Figure 2 This is a SEM image of the salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant prepared according to an embodiment of the present invention. Detailed Implementation

[0023] 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.

[0024] This invention uses purified acrylamide (AM) as the polymerizing monomer, and the strong hydration functional monomer 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and the rigid functional monomer itaconic acid (IA) as comonomers, and obtains the product through a one-step in-situ polymerization reaction with nano-silica (SiO2) modified with a silane coupling agent.

[0025] Example: This invention provides a method for preparing a salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant, comprising the following steps: Step 1: Add purified acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, itaconic acid, and modified nano-silica to a three-necked flask, add deionized water, and stir until the system is uniformly dispersed to obtain a monomer mixture; the mass ratio of purified acrylamide (AM), 2-acrylamide-2-methylpropanesulfonic acid, and itaconic acid is 10:4:1, and the amount of modified nano-silica added is 2.5% of the total mass of the three monomers; The method for preparing modified silica is as follows: Silica was dried at 100 °C for 2 h to remove adsorbed water from its surface. 5% by mass of silane coupling agent KH550 was weighed and prepared into a 2% by mass ethanol solution. The solution was then ultrasonically dispersed for 10 min. The dried silica was added at room temperature and mixed evenly. The mixture was then ultrasonically dispersed for 30 min and subjected to a coupling grafting reaction at 80 °C for 5 h. The resulting sample was dried to obtain modified nano-SiO2.

[0026] The method for preparing purified acrylamide is as follows: Acrylamide was prepared into a 40% (w / w) ethanol solution in a three-necked flask. Under nitrogen protection and stirring, an organophosphorus chelating agent ethanol solution was slowly added dropwise using a microsyringe or pipette. The amount of organophosphorus chelating agent added was 0.1% of the mass of acrylamide. The reaction was carried out at 25°C for 3 hours. After the reaction was completed, 1% (w / w) of activated carbon was added to the solution, and the reaction was carried out at 50°C in the dark for 1 hour. Insoluble impurities in the solution were filtered off while hot. The filtrate was allowed to stand in the dark for 24 hours and then slowly cooled to precipitate crystals. The crystals were then collected by vacuum filtration using a Buchner funnel, dried under vacuum at 40°C, and stored in a sealed, light-protected container.

[0027] Step 2: Add NaOH to adjust the pH to 6; Step 3: Under nitrogen protection, add the composite initiator ammonium persulfate and tetramethylethylenediamine, and react at 30°C for 4 hours to obtain a white flocculent substance through a one-step in-situ polymerization reaction; wherein, the amount of composite initiator added is 0.06% of the total mass of the three monomers, and the mass ratio of ammonium persulfate to tetramethylethylenediamine is 1:1; Step 4: Dry the white flocculent material in a drying oven at 60°C for 24 hours, then grind it into powder to obtain a salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant.

[0028] See Figure 2 The salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant prepared in the embodiments of the present invention, and Figure 1 Compared with the polyacrylamide flocculant prepared by free radical polymerization, the surface is smoother and more uniform, indicating that the components are uniformly dispersed in the reaction system and react synchronously to form the composite material.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. All equivalent structural changes made based on the description and drawings of the present invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant, characterized in that: The product was prepared by one-step in-situ polymerization of purified acrylamide as the polymerization monomer, 2-acrylamido-2-methylpropanesulfonic acid (a strongly hydrated functional monomer) and itaconic acid (a rigid functional monomer) as comonomers, and nano-silica modified with silane coupling agent.

2. The preparation method of the salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant according to claim 1, characterized in that: Includes the following steps Step 1: Add purified acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, itaconic acid and modified nano silica to a container, add deionized water, and stir until the system is evenly dispersed to obtain a monomer mixture. Step 2: Add NaOH to adjust the pH to 5-7; Step 3: Under nitrogen protection, add the composite initiator ammonium persulfate and tetramethylethylenediamine, and polymerize at 20-50℃ for 4-8 hours to obtain a white flocculent substance; Step 4: Dry the white flocculent material in a drying oven at 60°C for 24 hours, then grind it into powder to obtain a salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant.

3. The preparation method of the salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant according to claim 2, characterized in that: In step one, the mass ratio of purified acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and itaconic acid is 10:4:1, and the amount of modified nano silica added is 0.5-5% of the total mass of the three monomers.

4. The preparation method of the salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant according to claim 2, characterized in that: In step three, the mass ratio of ammonium persulfate to tetramethylethylenediamine is 1:1, and the amount of composite initiator added is 0.06% of the total mass of the three monomers.

5. The preparation method of the salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant according to claim 2, characterized in that: In step three, the one-step in-situ polymerization reaction is carried out at 20-50°C for 4-8 hours.

6. The preparation method of the salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant according to claim 2, characterized in that: The method for preparing purified acrylamide is as follows: acrylamide is prepared into a 40% (w / w) ethanol solution in a container. Under nitrogen protection and stirring, an organophosphorus chelating agent ethanol solution is slowly added dropwise using a microsyringe or pipette, with the amount added being 0.1% of the mass of acrylamide. The reaction is carried out at 25°C for 3 hours. After the reaction is completed, 1% (w / w) of activated carbon is added to the solution and the reaction is carried out at 50°C in the dark for 1 hour. Insoluble impurities in the solution are filtered while hot. The filtrate is then allowed to stand in the dark for 24 hours and slowly cooled to precipitate crystals. The crystals are then collected by vacuum filtration using a Buchner funnel, dried under vacuum at 40°C, and then sealed and stored in the dark.

7. The preparation method of a salt-resistant, high-temperature-resistant, fast-response polyacrylamide flocculant according to claim 2, characterized in that: The modified nano-silica (SiO2) is prepared by drying silica at 100 °C for 2 h, preparing a 2% (w / w) ethanol solution of silane coupling agent KH550, and then ultrasonically dispersing it for 10 min; adding the dried silica at room temperature, mixing it evenly, ultrasonically dispersing it for 30 min, performing a coupling grafting reaction at 80 °C for 5 h, and drying it to obtain modified nano-SiO2.

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