A poly-alpha-olefin drag reducer suspension and its direct method of preparation and use

Abstract

The application discloses a kind of poly-alpha olefin drag reduction agent suspensions and its direct preparation method and application, the method includes the following steps: in the coordination polymerization of alpha-olefin in hydrocarbon solvent to obtain low viscosity, flowable polymer solution;Then slowly inject the polymer solution into alcoholic dispersion medium under stirring, and polymer is precipitated in the form of microgel particles and uniformly suspended in liquid phase;Subsequently, remove and recover hydrocarbon solvent by vacuum distillation, to obtain stable suspension with alcohol as continuous phase, polymer microgel particles as dispersed phase;The application does not go through acidification precipitation, filtration, washing and vacuum drying and other steps throughout the process, eliminates the long time swelling and dissolution process necessary for traditional solid drag reduction agent, and the obtained suspension can be directly injected into oil pipeline by pump, instantaneously diluted and dissolved in oil flow and play a role in drag reduction. The method is simple, low in energy consumption, the obtained suspension has good storage stability, the drag reduction rate can reach more than 50%, and has significant industrial application advantages.

Description

Technical Field

[0001] This invention belongs to the field of oil drag-reducing agent preparation and application technology, specifically relating to a polyalphaolefin drag-reducing agent suspension and its direct preparation method and application, particularly relating to a suspension-type drag-reducing agent with alcohol as the dispersion medium and ultra-high molecular weight polyalphaolefin as the active component, as well as a method for directly preparing the suspension from the polymerization reaction liquid and its application in oil pipeline transportation drag reduction. Background Technology

[0002] Pipeline transportation is the most economical and efficient method for transporting crude oil and refined petroleum products. However, turbulence is generated when oil flows in pipelines, and the radial pulsation of fluid elements causes a large amount of energy to be dissipated as frictional heat, resulting in increased pressure drop along the pipeline and higher pumping energy consumption. To suppress turbulence and reduce transportation resistance, the industry commonly uses drag-reducing agents to add to the oil. Adding a very small amount (usually at the ppm level) of high molecular weight polymer can significantly reduce pipeline friction resistance, achieving "drag reduction and increased transportation," with significant economic benefits.

[0003] Among various drag-reducing agents, ultra-high molecular weight polyalphaolefin (PAO), which is prepared by coordination polymerization of long-chain alpha-olefins, is the most widely used and consumed drag-reducing agent for oil pipelines due to its outstanding advantages such as good oil solubility, low addition amount, high drag reduction efficiency, and no adverse effects on oil quality.

[0004] Currently, commercially available PAO drag reducers are mainly supplied in suspension form. The mainstream production process is as follows: First, high-purity α-olefins (such as 1-hexene, 1-octene, 1-decene, 1-dodecene, etc.) are used as monomers and subjected to low-temperature solution polymerization under a Ziegler-Natta catalytic system to obtain polymers with weight-average molecular weights reaching millions or even tens of millions. After polymerization, acidified alcohols are added to the reaction solution to precipitate the polymer, which is then filtered, washed, and vacuum dried to obtain a solid block polymer. Subsequently, the obtained solid polymer is freeze-brittled in liquid nitrogen and mechanically pulverized into fine powder at low temperature. Finally, this powder is dispersed and suspended in a mixture of an alcohol medium (such as isopropanol, ethylene glycol, or an alcohol-water mixture) and a small amount of stabilizer to obtain a pumpable suspension-type drag reducer. When this suspension is injected into pipelines, the polymer particles dissolve rapidly upon contact with the oil and exert their drag-reducing effect, making it convenient and quick to use.

[0005] However, the traditional preparation process of suspension-type drag reducers has significant shortcomings. First, the process route is lengthy, requiring multiple independent unit operations from polymerization to finished product, including precipitation, filtration, washing, drying, freezing, pulverization, and redispersion. This results in large equipment investments and long production cycles. Second, the drying and freeze-pulverization processes are extremely energy-intensive: drying requires vacuum and heating conditions, freezing requires a large amount of liquid nitrogen to keep the polymer below its glass transition temperature, and pulverization requires specialized low-temperature grinding equipment, leading to high overall production costs. More importantly, the thermal history during drying causes irreversible conformational rearrangement and physical entanglement between ultra-high molecular weight polymer chains, forming a dense aggregated structure. This dense structure is difficult to completely destroy during subsequent freeze-pulverization, and the molecular chain entanglement remaining inside the microparticles dissociates slowly during the dissolution stage, reducing the dissolution rate and effective utilization of the drag reducer. Summary of the Invention

[0006] This invention addresses the problems of lengthy processes, high costs, and irreversible polymer chain entanglement caused by the multiple energy-intensive steps involved in the production of suspension-type polyalphaolefin drag-reducing agents, such as precipitation, drying, and freeze-drying. It provides a polyalphaolefin drag-reducing agent suspension, its direct preparation method, and its applications. The method directly prepares alcohol-based suspension drag-reducing agents from the polymerization reaction solution. Specifically, this method creatively combines solution polymerization with a reverse-phase feeding-solvent displacement process, eliminating any steps such as acidification precipitation, filtration, washing, vacuum drying, liquid nitrogen freezing, and mechanical pulverization. It directly converts the polymerization reaction solution into a stable suspension with alcohol as the continuous phase and polymer microgel particles as the dispersed phase, significantly shortening the process flow and substantially reducing energy consumption and production costs.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for preparing a polyα-olefin drag-reducing agent suspension, comprising the following steps: (1) In a hydrocarbon solvent, α-olefin monomers are subjected to coordination polymerization in a Ziegler-Natta catalytic system containing a main catalyst and a co-catalyst; wherein the total molar concentration of the α-olefin monomers is 0.05 to 0.5 mol / L; after the reaction is completed, the reaction is terminated to obtain a polymer solution containing polyα-olefins; (2) Under stirring conditions, the polymer solution is slowly added to an alcohol dispersion medium, so that the poly-α-olefin precipitates out in the form of microgel particles and is suspended in the liquid phase to obtain a suspension containing hydrocarbon solvent; (3) The suspension containing hydrocarbon solvent obtained in step (2) is subjected to vacuum distillation to remove and recover the hydrocarbon solvent. At the same time, an alcohol dispersion medium is optionally added to adjust the solid content, so as to obtain the poly-α-olefin drag reducer suspension.

[0008] Further, in step (1), the total molar concentration of the monomer is 0.05 to 0.5 mol / L, preferably 0.1 to 0.2 mol / L; The hydrocarbon solvent is selected from at least one of toluene, xylene, n-hexane, n-heptane, cyclohexane, and methylcyclohexane, preferably n-hexane; The main catalyst is a TiCl4 catalyst supported on MgCl2; the co-catalyst is an alkyl aluminum, selected from at least one of triethylaluminum, triisobutylaluminum, and trimethylaluminum, preferably triisobutylaluminum.

[0009] Further, in step (1), the temperature of the coordination polymerization reaction is -30 to 0 °C, preferably -20 to -10 °C; the reaction time is 4 to 36 hours, preferably 12 to 24 hours; The reaction is terminated by introducing air into the reaction system.

[0010] Further, the alcohol dispersion medium in step (2) is isopropanol, and its amount is 1 to 5 times the volume of the polymer solution, preferably 2 to 3 times; The stirring is performed using a high-speed mixer or a high-shear homogenizer, with a stirring speed of 500–5000 rpm.

[0011] Further, in step (3), the temperature of the vacuum distillation is 40 to 70 °C and the pressure is -0.06 to -0.095 MPa. The distillation conditions are such that a large amount of isopropanol is distilled off. The removed hydrocarbon solvent is condensed and separated and then recycled for the coordination polymerization reaction in step (1).

[0012] Furthermore, the method further includes a step of adding a stabilizer to the obtained poly-α-olefin drag-reducing agent suspension, wherein the stabilizer is selected from at least one of polyvinylpyrrolidone, hydroxypropyl cellulose, and polyvinyl alcohol, and the amount added is 0.1 to 2 wt% of the total mass of the suspension.

[0013] Secondly, the present invention provides a polyalphaolefin drag-reducing agent suspension prepared according to the method, comprising: an ultra-high molecular weight polyalphaolefin polymer having a weight-average molecular weight greater than 300 × 10⁻⁶. 4 g / mol, with a molecular weight distribution index of 1.5 to 3.0; an alcohol dispersion medium selected from ethanol, isopropanol, or mixtures thereof; the poly-α-olefin polymer is dispersed in the alcohol dispersion medium in the form of microgel particles to form a poly-α-olefin drag-reducing agent suspension; the poly-α-olefin drag-reducing agent suspension is obtained directly without undergoing the steps of precipitating, filtering, and drying the polymer from the solution.

[0014] Further, the poly-α-olefin polymer is a homopolymer or copolymer of at least one α-olefin selected from 1-hexene, 1-octene, 1-decene, and 1-dodecene; the solid content of the poly-α-olefin drag-reducing agent suspension is 5-30 wt%, preferably 15-25 wt%; and the average particle size of the microgel particles in the poly-α-olefin polymer is 10-500 μm.

[0015] Thirdly, the present invention also provides an application of the aforementioned polyα-olefin drag-reducing agent suspension in drag reduction during oil pipeline transportation.

[0016] Furthermore, the poly-α-olefin drag-reducing agent suspension is directly injected into the oil pipeline through a metering pump. The polymer microgel particles in the poly-α-olefin drag-reducing agent suspension dissolve rapidly after contact with the oil and exert drag-reducing effects. In a No. 0 diesel solution diluted to a polymer concentration of 20 ppm, the drag reduction rate measured according to the SY / T 6578-2016 standard is greater than 50%.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects: (1) The method of this invention starts from the polymerization reaction liquid and directly obtains alcohol suspension drag-reducing agents through an innovative combination of solution polymerization and reverse feeding-solvent replacement process, without going through any of the steps of acid precipitation, filtration, washing, vacuum drying, liquid nitrogen freezing and mechanical pulverization. Compared with the traditional "precipitation-drying-freeze pulverization-redispersion" process, the process flow is greatly shortened, the number of unit operations is reduced, and the equipment investment is significantly reduced.

[0018] (2) The method of the present invention eliminates the two most energy-intensive processes: drying and cryogenic pulverization. The vacuum and heating energy consumption of the drying process, and the liquid nitrogen consumption and mechanical power consumption of the cryogenic pulverization process are all eliminated, which significantly reduces the overall production energy consumption and cost. At the same time, the hydrocarbon solvent is recovered and recycled through vacuum distillation, which further improves the utilization rate of raw materials and the economy of the process.

[0019] (3) The polymer microgel particles in the suspension obtained by the method of the present invention have a loose structure, and the internal molecular chain conformation is close to its original state in the solution, without undergoing irreversible entanglement and densification caused by the drying heat history. Therefore, when the microgel particles come into contact with oil in the injection pipeline, they can quickly dissociate and dissolve, and fully exert their drag-reducing effect. The dissolution rate is significantly better than that of the dense powder obtained by the traditional cryogenic pulverization method, which effectively improves the utilization efficiency of the drag-reducing agent and the convenience of on-site operation.

[0020] (4) This invention solves the technical problem of ultra-high molecular weight poly-α-olefins forming blocky gels during polymerization, making them unmanageable, by employing a solution polymerization strategy. The extremely low monomer concentration ensures that the system remains a flowable viscous liquid after polymerization, providing the necessary operability for subsequent reverse-phase feeding and solvent displacement.

[0021] (5) The present invention uses a reverse-phase feeding strategy, with alcohol as the continuous phase and polymer solution as the dispersed phase, to make the polymer precipitate in the form of loose microgel particles rather than in block form, thus successfully achieving a balance between good dispersibility and particle uniformity, and solving the inherent defects of polymer agglomeration and clumping in the traditional precipitation method. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The high-temperature GPC curve of the polymer in the example is shown. Figure 2 The DSC secondary heating curve of the polymer in the example is shown. Figure 3 This is a particle size distribution diagram of the polymer suspension in Example 2; Figure 4 The TGA diagram is shown for the polymer in the example. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0027] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0029] This invention provides a poly(α-olefin) drag-reducing agent suspension, its direct preparation method, and its application. The key innovation of this invention lies in its innovative combination of solution polymerization and reverse-phase feeding-solvent replacement processes, starting from the polymerization reaction solution, to directly obtain a stable suspension with an alcohol as the continuous phase and polymer microgel particles as the dispersed phase, without undergoing any of the steps involved in acid precipitation, filtration, washing, vacuum drying, liquid nitrogen freezing, or mechanical pulverization. Specifically, this invention first performs α-olefin solution polymerization in a hydrocarbon solvent at an extremely low monomer concentration, ensuring that the system remains a flowable, low-viscosity polymer solution rather than a blocky gel after polymerization. Subsequently, using a reverse-phase feeding method, the polymer solution is slowly injected into an alcohol dispersion medium under high-speed stirring, causing the polymer to precipitate uniformly in the form of loose microgel particles. Finally, the hydrocarbon solvent is removed by vacuum distillation and recycled, while an alcohol medium is added to adjust the solid content, directly obtaining the product.

[0030] Compared to traditional processes, this invention integrates polymerization, precipitation, dispersion, and solvent recovery into a continuous flow line, eliminating the most energy-intensive drying and cryogenic pulverization steps. This significantly shortens the process route and reduces equipment investment and production costs. Simultaneously, because the polymer has never undergone drying heat or mechanochemical degradation, the microgel particles maintain a loose molecular chain conformation, allowing for instantaneous dissociation and dissolution upon contact with oil in the injection pipeline, fully leveraging its drag-reduction efficiency. The economics, operability, and product performance of this invention surpass existing technologies, demonstrating promising prospects for industrial application.

[0031] In a first aspect, the present invention provides a method for preparing a polyα-olefin drag-reducing agent suspension, comprising the following steps: S1: In a hydrocarbon solvent, α-olefin monomers undergo coordination polymerization in a Ziegler-Natta catalytic system containing a main catalyst and a co-catalyst, wherein the total molar concentration of the monomers is 0.05–0.5 mol / L; The α-olefin monomer is at least one selected from 1-hexene, 1-octene, 1-decene, and 1-dodecene. When two or more monomers are used for copolymerization, the crystallinity of the polymer decreases, which is beneficial for improving drag reduction performance and solubility in oils. The total molar concentration of the α-olefin monomer is preferably 0.1–0.2 mol / L. Within this concentration range, the polymer concentration in the system after polymerization is approximately 1–2 wt%, which is lower than the critical chain entanglement concentration of ultra-high molecular weight polyα-olefins. The entire reaction solution remains a flowable viscous liquid and does not form elastic gels or lumps that encapsulate the solvent, providing the necessary flowability and pumpability for subsequent reverse-phase feeding operations.

[0032] Furthermore, the hydrocarbon solvent is selected from at least one of toluene, xylene, n-hexane, n-heptane, cyclohexane, and methylcyclohexane, preferably n-hexane. n-Hexane has good solubility for polyα-olefins, and its boiling point (69 °C) differs from that of isopropanol (82 °C) by approximately 13 °C. Therefore, the two do not form an azeotrope, and clear separation can be easily achieved in the subsequent vacuum distillation desolventizing step, avoiding loss of the alcohol medium.

[0033] Furthermore, the main catalyst is a TiCl4 catalyst supported on MgCl2; the co-catalyst is an alkylaluminum selected from at least one of triethylaluminum, triisobutylaluminum, and trimethylaluminum, preferably triisobutylaluminum.

[0034] Furthermore, the temperature of the coordination polymerization reaction is -30 to 0 °C, preferably -20 to -10 °C; the reaction time is 4 to 36 hours, preferably 12 to 24 hours. Low-temperature polymerization helps to suppress chain transfer reactions and can obtain polymers with ultra-high molecular weight and narrow molecular weight distribution.

[0035] S2: After the polymerization reaction is completed, the reaction is terminated to obtain a polymer solution containing polyα-olefin; Furthermore, the reaction can be terminated by introducing air into the reaction system. The oxygen and water vapor in the air can rapidly oxidize and hydrolyze the co-catalyst, thus deactivating it. This method is simple and does not introduce additional chemical reagents.

[0036] S3: Under stirring conditions, the polymer solution obtained in step S2 is slowly added to the alcohol dispersion medium, so that the polyα-olefin precipitates out in the form of microgel particles and is suspended in the liquid phase, thus obtaining a suspension containing hydrocarbon solvent. The alcohol dispersion medium is selected from ethanol, isopropanol, or mixtures thereof, preferably isopropanol.

[0037] This step is one of the key steps in the method of this invention. This invention employs a reverse-phase feeding method, where the polymer solution is slowly added to the alcohol dispersion medium under stirring, rather than adding the alcohol dispersion medium directly to the polymer solution. During this process, the polymer solution enters the continuous alcohol phase in the form of fine droplets. The polymer within the droplets precipitates slowly due to the gradual dilution of the hydrocarbon solvent by the alcohol, forming loose, porous microgel particles. Since alcohols are poor solvents for polyα-olefins, the particle surface quickly solidifies, preventing particle adhesion and fusion, ultimately resulting in a uniform and stable suspension. Conversely, if a normal-phase feeding method is used (adding the alcohol to the polymer solution), the polymer solution acts as the continuous phase. Upon local contact with the alcohol, a large amount of polymer precipitates instantaneously and agglomerates into lumps, making dispersion difficult.

[0038] Furthermore, the amount of the alcohol dispersion medium is 1 to 5 times the volume of the polymer solution, preferably 2 to 3 times. Sufficient alcohol content ensures that polymer particles are fully extracted from the solution and provides a sufficient liquid buffer volume for subsequent distillation.

[0039] Furthermore, the stirring is carried out using a high-speed stirrer or a high-shear homogenizer, with a stirring rate of 500 to 5000 rpm, to ensure that the polymer solution is rapidly dispersed into uniform microdroplets in the alcohol dispersion medium.

[0040] S4: The suspension obtained in step S3 is subjected to vacuum distillation to remove and recover hydrocarbon solvents. An alcohol dispersion medium is optionally added to adjust the solid content, thereby obtaining the polyα-olefin drag reducer suspension.

[0041] The vacuum distillation is performed at a temperature of 40–70 °C and a pressure of -0.06–-0.095 MPa. The vacuum distillation is designed to effectively remove hydrocarbon solvents while avoiding the excessive evaporation of alcohol dispersion media. When hexane (boiling point 69 °C) is used as the polymerization solvent and isopropanol (boiling point 82 °C) as the dispersion medium, within the aforementioned temperature and pressure range, hexane preferentially vaporizes and is condensed and recovered, while isopropanol, due to its higher boiling point (which remains above 40 °C under the vacuum conditions described in this invention), has a limited evaporation rate. The removed hydrocarbon solvents, after condensation and drying, can be recycled for the polymerization reaction in step S1, further reducing production costs and organic solvent emissions.

[0042] Further, the process may include adding a stabilizer to the suspension obtained in step S4. The stabilizer is selected from at least one of polyvinylpyrrolidone, hydroxypropyl cellulose, and polyvinyl alcohol, and is added in an amount of 0.1–2 wt% of the total mass of the suspension. The stabilizer adsorbs onto the surface of the polymer microgel particles, providing steric hindrance and preventing the particles from settling and agglomerating during long-term storage.

[0043] Secondly, the present invention also provides a polyα-olefin drag-reducing agent suspension prepared by any of the above preparation methods. The suspension comprises: (a) A high molecular weight polyalphaolefin with a solid content of 5–30 wt%, wherein the weight-average molecular weight of the polyalphaolefin is greater than 300 × 10⁻⁶. 4 g / mol, with a molecular weight distribution index of 1.5–3.0, exists in the form of microgel particles, with an average particle size of 10–500 μm; (b) An alcohol-based dispersion medium, selected from ethanol, isopropanol, or mixtures thereof, preferably isopropanol. The suspension shows no hard settling after standing at room temperature for 3 months, and can be restored to homogeneity with slight agitation, and can be transported using a conventional gear pump or screw pump.

[0044] After the suspension is injected into the oil pipeline, the polymer microgel particles can dissociate and dissolve within minutes of contact with the oil. When diluted to a polymer concentration of 20 ppm, the drag reduction rate measured according to the SY / T 6578-2016 standard is greater than 50%.

[0045] Thirdly, the present invention also provides the application of the poly-α-olefin drag-reducing agent suspension in drag reduction during oil pipeline transportation. In use, the suspension is directly injected into the oil pipeline via a metering pump, without the need for pre-swelling or dissolving.

[0046] It should be noted that all solvents involved in this invention are anhydrous and oxygen-free solvents after post-treatment. In the process of preparing poly-α-olefin drag-reducing polymers, all operations sensitive to moisture and oxygen are performed by professionals skilled in this field under nitrogen protection in an MBraun glove box or using standard Schlenk techniques.

[0047] The obtained polymer was subjected to relevant tests. The particle size and particle size distribution were determined by a laser particle size analyzer. An appropriate amount of suspension was diluted with isopropanol to a light-blocking degree of 10% to 15% and then injected into the sample cell. Isopropanol was used as the dispersion medium and the refractive index was set to 1.49. The D10, D50, D90 values ​​and particle size distribution curve were recorded. According to the industry standard SY / T 6578-2016 "Technical Specification for Adding Drag Reducing Agent to Oil Pipeline", the drag-reducing polymer to be tested was mixed with No. 0 diesel oil to make a 20 ppm solution. After the polymer was completely dissolved and uniformly distributed, it was measured using an indoor loop drag reduction test device. The frictional pressure drop of the indoor loop test pipe section was measured before and after the addition of drag reducing agent to the liquid under the same conditions. The drag reduction rate was calculated according to formula (1): (1) Where DR represents the drag reduction effect (%), ΔP0 represents the pressure drop (kPa) caused by friction in the test instrument tubing of the solvent without drag reduction agent under certain temperature conditions, and ΔP DRA To prepare a drag-reducing agent solution of a certain concentration, the solution was passed through the same pipeline to obtain the pressure drop (KPa) of the oil after the drag-reducing agent was added.

[0048] A portion of the hydrocarbon solvent suspension obtained in step (3) was taken, and excess ethanol was added to completely precipitate the polymer. After filtration, washing, and vacuum drying, a solid polymer sample was obtained for characterization. The thermal properties of the polymer were characterized using differential scanning calorimetry (DSC), and the molecular weight and molecular weight distribution of the polymer were characterized using high-temperature gel permeation chromatography (GPC). The thermal properties of the polymer were measured using a differential scanning calorimeter (Q2000 DSC). The test procedure was as follows: heating to 100 °C at a rate of 20 °C / min, holding for 3 min to eliminate the thermal history of the material, then cooling to -70 °C at a rate of 10 °C / min, holding for 3 min to obtain the cooling curve; finally, heating to 100 °C at a rate of 10 °C / min, holding for 3 min to obtain the secondary heating curve. Thermogravimetric analysis (TGA) was performed under a nitrogen atmosphere, with a heating rate of 10 °C / min and a test temperature range from room temperature to 600 °C. Gel permeation chromatography was performed using a PLGPC-220 gel permeation chromatograph at 150 °C, with 1,2,4-trichlorobenzene as the mobile phase and a flow rate of 1.0 mL / min. The standard sample was Easi-Cal PS-1 (PL Ltd.) polystyrene standard sample.

[0049] The Ti-Mg catalyst of this invention, designated LP-21-S01, along with co-catalysts such as triethylaluminum and triisobutylaluminum, and polymerizable monomers such as 1-hexene, 1-octene, 1-decene, and 1-dodecene, were all purchased from Anaiji Chemical Co., Ltd., China. Hydrocarbon solvents such as n-hexane, cyclohexane, and toluene were of analytical grade and dried using an MBraun solvent purification system before use. Isopropanol, ethanol, and other conventional reagents were all of analytical grade and purchased from Tianjin Jiangtian Chemical Co., Ltd., and were used directly without further purification.

[0050] Example 1 (1) Preparation of polyα-olefin solution: Coordination polymerization was carried out using a Ti-Mg catalyst / triisobutylaluminum catalyst system. All operations were conducted under anhydrous and oxygen-free conditions. In a 250 mL stainless steel magnetically coupled mechanically stirred reactor, 1-octene (40 mmol), 1-decene (40 mmol), and n-hexane were added under nitrogen purging to achieve a total monomer concentration of 0.2 mol / L and a total liquid volume of 400 mL. The reactor was cooled to -15 °C, and a toluene solution of triisobutylaluminum co-catalyst (0.24 mmol Al) and an 8 μmol Ti-Mg catalyst n-hexane suspension were added sequentially. The reaction was carried out at -15 °C and 400 rpm for 12 h with mechanical stirring. After polymerization, the reaction was terminated by bubbling dried and purified air into the reactor for 30 min, yielding a polymer solution containing polyα-olefins. This solution was a colorless, transparent to slightly turbid viscous liquid, free-flowing, and without obvious lumps or gels.

[0051] (2) Preparation of suspension by reverse phase feeding: 800 mL of isopropanol was added to a 1000 mL jacketed glass reactor, and a high-shear homogenizer (3000 rpm) was turned on at room temperature. The entire polymer solution (approximately 400 mL) obtained in step (1) was slowly injected into the isopropanol via a capillary tube at a rate of 10 mL / min using a peristaltic pump. During the injection, the polymer solution dispersed into fine droplets in the isopropanol, and the polymer gradually precipitated within the droplets to form microgel particles. After all the solution had been injected, stirring was continued for 30 min to obtain a white to milky white suspension with a volume of approximately 1200 mL. Microscopic observation showed that the polymer particles were spherical or amorphous loose microparticles with a particle size ranging from 20 to 150 μm.

[0052] (3) Solvent removal and solid content adjustment: The suspension obtained in step (2) was transferred to a 2000 mL three-necked flask equipped with a vacuum distillation apparatus and distilled under vacuum conditions of a 60 °C water bath and a vacuum degree of -0.08 MPa. The distillate was collected by condensation and mainly consisted of n-hexane and a small amount of isopropanol. Fresh isopropanol was added as needed during distillation to maintain the liquid volume based on the drop in liquid level. Distillation was stopped when no obvious droplets were distilled out of the condenser outlet. Finally, a white, homogeneous suspension with isopropanol as the continuous phase was obtained. The solid content was adjusted to 20 wt% with isopropanol, and the total volume was approximately 300 mL.

[0053] The suspension obtained in this embodiment showed no obvious stratification after standing at room temperature for 3 months. The suspension sample obtained in step (3) was diluted with isopropanol to a suitable concentration and then subjected to particle size analysis using a laser particle size analyzer. Figure 3As shown, the test results indicate that the volume average particle size D[4,3] of the polymer microgel particles in the suspension is 185 μm, the median particle size D50 is 172 μm, D10 = 8.5 μm, D90 = 256 μm, and the Span value is 1.78, indicating that the particle size distribution is narrow and the suspension has good uniformity.

[0054] After precipitating a portion of the suspension sample with ethanol and drying it, the polymer properties were tested: weight-average molecular weight. M w = 5.17×10 6 g / mol, PDI = 1.82, such as Figure 1 As shown in the attached diagram. DSC testing showed no melting peak. Figure 2 As shown. The TGA reading indicates the polymer decomposition temperature is greater than 350 °C, as... Figure 4 As shown. After dilution to a concentration of 20 ppm, a drag reduction test was performed on the loop, and the drag reduction rate was 53.8%.

[0055] Example 2 The difference from Example 1 is that the polymerization solvent was changed from n-hexane to cyclohexane, the dispersion medium was changed from isopropanol to a mixture of isopropanol and ethanol, and the polymerization temperature was adjusted to -20 °C.

[0056] In step (1), cyclohexane was used as the solvent, with 1-octene (40 mmol) and 1-decene (40 mmol) as the monomers, a total monomer concentration of 0.2 mol / L, and a total volume of 400 mL. Triisobutylaluminum toluene solution (0.24 mmol Al) and 8 μmol Ti-Mg catalyst were added sequentially at -20 °C, and the reaction was allowed to proceed for 12 h. The reaction was terminated by purging with air to obtain a polymer cyclohexane solution.

[0057] In step (2), the obtained polymer solution is slowly injected into 800 mL of isopropanol / ethanol mixture (volume ratio 80:20) under stirring at 3000 rpm to form a suspension.

[0058] In step (3), cyclohexane is removed by vacuum distillation at 65 °C and -0.08 MPa, while a small amount of ethanol is distilled off with the cyclohexane-ethanol azeotrope. An isopropanol / ethanol mixture is added as needed to adjust the solid content to 18 wt%. Figure 3 As shown, the laser particle size analyzer test results show that the volume average particle size D[4,3] of the polymer microgel particles in the suspension is 270 μm, the median particle size D50 is 283 μm, D10 = 9.4 μm, D90 = 501 μm, and the Span value is 1.89.

[0059] Compared to Example 1, the particle size is slightly larger and the distribution is slightly wider. This may be due to the difference in the diffusion rate of cyclohexane in the isopropanol / ethanol mixture compared to that of n-hexane in pure isopropanol, resulting in a difference in the solvent exchange rate inside the droplets during polymer precipitation.

[0060] The resulting suspension was a milky white, homogeneous slurry, and showed no obvious stratification after standing at room temperature for 3 months. (Polymer) M w = 4.89×10 6 g / mol, PDI = 1.95, such as Figure 1 As shown. DSC testing showed no melting peak, as indicated. Figure 2 As shown. The TGA reading indicates the polymer decomposition temperature is greater than 350 °C, as... Figure 4 As shown, the drag reduction rate is 51.2%.

[0061] Example 3 The difference from Example 1 is that only 1-octene is used as the homopolymer monomer, and the polymerized solution is diluted with n-hexane before the reverse phase feeding.

[0062] In step (1), 1-octene (80 mmol) was added to hexane as solvent, with a total monomer concentration of 0.2 mol / L and a total volume of 400 mL. Triisobutylaluminum (0.24 mmol Al) and 8 μmol Ti-Mg catalyst were added sequentially at -15 °C, and the reaction was terminated by purging with air.

[0063] The reverse feeding operation in step (2) is the same as in Example 1.

[0064] Step (3) involves solvent removal and solid content adjustment as in Example 1, with a final solid content of 20 wt%. Figure 3 As shown, the laser particle size analyzer test results show that the volume average particle size D[4,3] of the polymer microgel particles in the suspension is 232 μm, the median particle size D50 is 215 μm, D10 = 45 μm, D90 = 365 μm, and the Span value is 1.91.

[0065] Compared to Examples 1 and 2, the particle size of the particles obtained by homopolymerization of 1-octene in this example is significantly larger. This may be because the homopolymer molecular chains have higher chemical uniformity, resulting in stronger inter-segment interactions when precipitated in alcohol media, tending to form denser and larger particles.

[0066] The resulting suspension was a white, homogeneous slurry, and showed no obvious stratification after standing at room temperature for 3 months. (Polymer) M w = 3.96×10 6 g / mol, PDI = 2.04, such as Figure 1 As shown. DSC testing showed no melting peak, as indicated. Figure 2 As shown. The TGA reading indicates the polymer decomposition temperature is greater than 350 °C, as... Figure 4 As shown, the drag reduction rate is 44.7%.

[0067] Example 4 The difference from Example 1 is that the dispersion medium was changed from isopropanol to ethanol, and the polymerization temperature was adjusted to -10 °C.

[0068] Step (1) is the same as in Example 1, to obtain a polymer n-hexane solution.

[0069] In step (2), the obtained polymer solution is slowly injected into 800 mL of anhydrous ethanol under mechanical stirring at 2000 rpm to form a suspension.

[0070] In step (3), n-hexane is removed by vacuum distillation at 50 °C and -0.09 MPa. Since there is still a certain difference between the boiling point of ethanol (78 °C) and that of n-hexane (69 °C), n-hexane is preferentially removed under controlled low distillation temperature. Ethanol is added as needed during distillation, and the final solid content is adjusted to 22 wt%. Figure 3 As shown, the laser particle size analyzer test results show that the volume average particle size D[4,3] of the polymer microgel particles in the suspension is 68 μm, the median particle size D50 is 55 μm, D10 = 8.1 μm, D90 = 128 μm, and the Span value is 2.00.

[0071] Compared to Example 1, which used isopropanol as the dispersion medium, the average particle size of the particles obtained when using ethanol was smaller, but the particle size distribution was slightly increased. This may be because ethanol has a weaker solubility for poly-α-olefins, and the polymer solution droplets precipitate and solidify more quickly upon contact with ethanol, forming a finer but slightly wider particle size distribution.

[0072] The resulting suspension was a white, homogeneous slurry, and showed no obvious stratification after standing at room temperature for 3 months. (Polymer) M w = 5.03×10 6 g / mol, PDI = 1.88, such as Figure 1 As shown. DSC testing showed no melting peak, as indicated. Figure 2 As shown. The TGA reading indicates the polymer decomposition temperature is greater than 350 °C, as... Figure 4 As shown, the drag reduction rate is 52.1%.

[0073] In summary, the method of this invention, through an innovative combination of solution polymerization and reverse feeding-solvent displacement processes, directly produces polyα-olefin drag-reducing agent alcohol suspensions without precipitation, filtration, drying, freezing, and pulverization. The process route is short, energy consumption is low, and the drag reduction rate of the resulting suspension can reach over 50%. This process avoids the steps of liquid nitrogen freezing and mechanical pulverization required in traditional processes, thus avoiding both energy waste and the chain entanglement caused by solidification and the thermal history during the recovery process from freezing. It has excellent prospects for industrial application, provides a high-performance solution for drag-reducing agent preparation, and has significant research value.

[0074] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a polyα-olefin drag-reducing agent suspension, characterized in that, Includes the following steps: (1) In a hydrocarbon solvent, α-olefin monomers are subjected to coordination polymerization in a Ziegler-Natta catalytic system containing a main catalyst and a co-catalyst; wherein the total molar concentration of the α-olefin monomers is 0.05 to 0.5 mol / L; after the reaction is completed, the reaction is terminated to obtain a polymer solution containing polyα-olefins; (2) Under stirring conditions, the polymer solution is slowly added to an alcohol dispersion medium, so that the poly-α-olefin precipitates out in the form of microgel particles and is suspended in the liquid phase to obtain a suspension containing hydrocarbon solvent; (3) The suspension containing hydrocarbon solvent obtained in step (2) is subjected to vacuum distillation to remove and recover the hydrocarbon solvent. At the same time, an alcohol dispersion medium is optionally added to adjust the solid content, so as to obtain the poly-α-olefin drag reducer suspension.

2. The preparation method according to claim 1, characterized in that, In step (1), the total molar concentration of the monomer is 0.05–0.5 mol / L, preferably 0.1–0.2 mol / L; The hydrocarbon solvent is selected from at least one of toluene, xylene, n-hexane, n-heptane, cyclohexane, and methylcyclohexane, preferably n-hexane; The main catalyst is a TiCl4 catalyst supported on MgCl2; the co-catalyst is an alkyl aluminum, selected from at least one of triethylaluminum, triisobutylaluminum, and trimethylaluminum, preferably triisobutylaluminum.

3. The preparation method according to claim 1, characterized in that, In step (1), the temperature of the coordination polymerization reaction is -30 to 0 °C, preferably -20 to -10 °C; the reaction time is 4 to 36 hours, preferably 12 to 24 hours. The reaction is terminated by introducing air into the reaction system.

4. The preparation method according to claim 1, characterized in that, The alcohol dispersion medium in step (2) is isopropanol, and its amount is 1 to 5 times the volume of the polymer solution, preferably 2 to 3 times. The stirring is performed using a high-speed mixer or a high-shear homogenizer, with a stirring speed of 500–5000 rpm.

5. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the vacuum distillation is 40 to 70 °C and the pressure is -0.06 to -0.095 MPa. The distillation conditions are designed to prevent a large amount of isopropanol from being distilled out. The removed hydrocarbon solvent is condensed and separated and then recycled for the coordination polymerization reaction in step (1).

6. The preparation method according to any one of claims 1 to 5, characterized in that, The method further includes the step of adding a stabilizer to the obtained poly-α-olefin drag-reducing agent suspension, wherein the stabilizer is selected from at least one of polyvinylpyrrolidone, hydroxypropyl cellulose, and polyvinyl alcohol, and the amount added is 0.1 to 2 wt% of the total mass of the suspension.

7. A poly-α-olefin drag-reducing agent suspension prepared according to any one of claims 1 to 6, characterized in that, include: Ultra-high molecular weight polyalphaolefin polymers with a weight-average molecular weight greater than 300 × 10⁻⁶ 4 g / mol, with a molecular weight distribution index of 1.5 to 3.0; an alcohol dispersion medium selected from ethanol, isopropanol, or mixtures thereof; the poly-α-olefin polymer is dispersed in the alcohol dispersion medium in the form of microgel particles to form a poly-α-olefin drag-reducing agent suspension; the poly-α-olefin drag-reducing agent suspension is obtained directly without undergoing the steps of precipitating, filtering, and drying the polymer from the solution.

8. The poly-α-olefin drag-reducing agent suspension according to claim 7, characterized in that, The poly-α-olefin polymer is a homopolymer or copolymer of at least one α-olefin selected from 1-hexene, 1-octene, 1-decene, and 1-dodecene; the solid content of the poly-α-olefin drag-reducing agent suspension is 5-30 wt%, preferably 15-25 wt%; the average particle size of the microgel particles in the poly-α-olefin polymer is 10-500 μm.

9. The application of a polyalphaolefin drag-reducing agent suspension according to any one of claims 7 or 8 in drag reduction during oil pipeline transportation.

10. The application according to claim 9, characterized in that, The polyalphaolefin drag reducer suspension is directly injected into the oil pipeline through a metering pump. The polymer microgel particles in the polyalphaolefin drag reducer suspension dissolve rapidly after contact with the oil and exert drag reduction effect. In a No. 0 diesel solution diluted to a polymer concentration of 20 ppm, the drag reduction rate measured according to the SY / T6578-2016 standard is greater than 50%.

Images