Pour point depressants and methods for their preparation
By preparing polythiol-silanoxane microspheres and grafting them with high-carbon acrylic acid esters, combined with ethylene-vinyl acetate copolymer, the problem of poor pour point depressing effect of high-wax crude oil was solved, achieving better rheological properties and reduced energy consumption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM PIPELINE ENG CO LTD
- Filing Date
- 2024-12-23
- Publication Date
- 2026-06-23
AI Technical Summary
Existing pour point depressants are not very effective at reducing the pour point of high-wax crude oil, making it difficult to effectively lower the pour point and low-temperature viscosity of paraffin-based crude oil, resulting in high energy consumption during extraction and transportation.
Using mercaptopropyltrimethoxysilane as the silicon source, polythiol silanol microspheres were prepared by the sol-gel method, and high carbon acrylate was grafted onto the surface of the microspheres by the mercapto-olefin click method to prepare a grafted pour point depressant. Subsequently, it was blended with ethylene-vinyl acetate copolymer to form a composite pour point depressant.
It improves the pour point reduction effect on high-wax crude oil, improves rheological properties, promotes the formation of wax crystal particles, reduces pour point and viscosity, and reduces transportation energy consumption.
Smart Images
Figure CN122255479A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of oilfield development technology, and in particular to a pour point depressant and its preparation method. Background Technology
[0002] Paraffin-based crude oil has a high paraffin content, characterized by a high pour point, poor low-temperature fluidity, difficult extraction, and high energy consumption during transportation. When the ambient temperature decreases, wax crystals precipitate from the crude oil. These crystals gradually grow, and as the number of precipitated crystals increases, the crude oil's fluidity deteriorates, eventually gelling and ceasing to flow, causing significant losses in oil production and transportation. Adding pour point depressants to waxy crude oil can effectively reduce its pour point and viscosity at low temperatures.
[0003] The pour point depressants in related technologies mainly include EVA (Ethylene Vinyl Acetate Copolymer), poly(meth)acrylate copolymer, maleic anhydride copolymer, nitrogen-containing polymers, etc. However, these pour point depressants are mainly suitable for low-wax crude oil, and their pour point depressing effect is generally poor for high-wax crude oil. Summary of the Invention
[0004] This application provides a pour point depressant and its preparation method, wherein the pour point depressant has a good pour point depressing effect on high-wax crude oil. The technical solution is as follows:
[0005] On the one hand, a method for preparing a pour point depressant is provided, the method comprising:
[0006] Polymerized mercaptosilane microspheres were prepared by sol-gel method using mercaptopropyltrimethoxysilane as the silicon source and deionized water as the solvent.
[0007] The polythiol-based silanol microspheres, high-carbon acrylate, and reaction solvent are added to the first container, and the first container is then subjected to ultrasonic treatment.
[0008] Continue adding initiator to the first container, seal the first container, turn on the circulating water bath, control the water bath temperature, and stir continuously during the reaction;
[0009] The first container is irradiated with ultraviolet light for a first duration. Then, excess methanol is added to the solution in the first container, and stirring is continued until flocculent precipitate appears.
[0010] After the flocculent material is precipitated, filtered, washed, and dried, a grafted pour point depressant is obtained.
[0011] In one possible implementation, the higher carbon acrylate includes at least one of octadecyl acrylate, dodecyl acrylate, and hexadecyl acrylate.
[0012] In another possible implementation, the preparation method further includes:
[0013] The grafted pour point depressant is blended with ethylene-vinyl acetate copolymer using a melt blending method to obtain a composite pour point depressant; wherein the content of ethylene-vinyl acetate copolymer in the composite pour point depressant is 1wt% to 20wt%.
[0014] In another possible implementation, the grafted pour point depressant is blended with an ethylene-vinyl acetate copolymer using a melt blending method to obtain a composite pour point depressant, comprising:
[0015] The grafted pour point depressant and the ethylene-vinyl acetate copolymer were blended using a melt blending method to obtain a mixture;
[0016] The mixture is added to a twin-screw extruder in batches;
[0017] After discharge, the material is cooled and pulverized to obtain the composite pour point depressant.
[0018] In another possible implementation, the preparation of polythiol-silanol microspheres via a sol-gel method using mercaptopropyltrimethoxysilane as the silicon source and deionized water as the solvent includes:
[0019] At the first temperature, the deionized water and emulsifier are added to the second container;
[0020] The emulsion formed by mixing mercaptopropyltrimethoxysilane with water is added dropwise to the second container at a preset rate;
[0021] Under stirring conditions, hydrochloric acid is continuously added dropwise to the second container to adjust the pH value of the solution in the second container to acidic.
[0022] After the mercaptopropyltrimethoxysilane is hydrolyzed in an acidic environment for a second time, ammonia water is added dropwise to the second container to adjust the pH value of the solution in the second container to alkaline, so that the hydrolysis product undergoes a condensation reaction in an alkaline environment.
[0023] After the third reaction time, the reaction product was obtained;
[0024] The reaction product was washed, centrifuged, and dried to obtain the polythiol silanol microspheres.
[0025] In another possible implementation, the mass ratio of the mercaptopropyltrimethoxysilane to the deionized water is 1:10 to 100.
[0026] In another possible implementation, the pH of the acidic environment is 2.5;
[0027] The pH value of the alkaline environment is 11;
[0028] The first temperature is 25°C;
[0029] Both the second duration and the third duration are 4 hours;
[0030] The stirring rate is 300 r / min.
[0031] In another possible implementation, the molar ratio of the high carbon acrylate to the thiol groups in the polythiol silanol microspheres is 1:4, 2:4, 3:4, 4:4, or 5:1.
[0032] In another possible implementation, the mass of the initiator is 0 to 6% of the total mass of the high carbon acrylate and the polythiol silanol microspheres.
[0033] On the other hand, a pour point depressant is provided, which is prepared by any of the preparation methods described above.
[0034] This application provides a method for preparing a pour point depressant. The method first prepares polythiol-silicon semioxane microspheres using a sol-gel method with mercaptopropyltrimethoxysilane as the silicon source and deionized water as the solvent. Then, a high-carbon acrylate is grafted onto the surface of the polythiol-silicon semioxane microspheres using a mercapto-olefin click method to obtain a grafted pour point depressant. This method grafts high-carbon acrylate onto the surface of the polythiol-silicon semioxane microspheres, modifying the surface of the microspheres and thus improving the pour point depressant effect on high-wax crude oil. Furthermore, the mercapto-olefin click reaction has advantages such as high reactivity, simple reaction conditions, more regular polymers, and easy product separation and purification. Therefore, grafting high carbon acrylates onto the surface of polythiol silanol microspheres via the mercapto-olefin click method is beneficial for preparing pour point depressants with high purity and high grafting density. After dispersing this pour point depressant in crude oil, it is beneficial for promoting the formation of larger and more compact wax crystal particles, thereby improving the rheological properties of high wax crude oil and further enhancing the pour point depressant effect on high wax crude oil.
[0035] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this disclosure. Attached Figure Description
[0036] Figure 1 This is a flowchart of a method for preparing a pour point depressant provided in an embodiment of this application;
[0037] Figure 2 This is a flowchart illustrating the preparation of polythiol-based silanolane microspheres, provided in an embodiment of this application.
[0038] Figure 3 This is a diagram illustrating the formation mechanism of polythiol-based silanol microspheres provided in the embodiments of this application;
[0039] Figure 4 This is a PMPAQ microsphere morphology diagram with different polycondensation reaction times provided in the embodiments of this application;
[0040] Figure 5 This is a PMPAQ microsphere morphology diagram provided in an embodiment of this application for different mass ratios of silicon source and deionized water;
[0041] Figure 6 This is a PMPAQ microsphere morphology diagram provided in an embodiment of this application at different reaction speeds;
[0042] Figure 7 These are PMPAQ microsphere morphology images provided in the embodiments of this application at different reaction temperatures;
[0043] Figure 8 This is a PMPAQ microsphere morphology diagram provided in the embodiments of this application under different acidic pH values;
[0044] Figure 9 This is a PMPAQ microsphere morphology diagram provided in the embodiments of this application at different alkaline pH values;
[0045] Figure 10 This is a SEM image of a grafted pour point depressant provided in an embodiment of this application;
[0046] Figure 11 This is an infrared spectrum of PMPSQ microspheres, OA monomers, and PMPSQ-OA provided in the embodiments of this application;
[0047] Figure 12 This is a DSC curve of a grafted pour point depressant provided in an embodiment of this application;
[0048] Figure 13 This is a flowchart illustrating the preparation of a composite pour point depressant, as provided in an embodiment of this application.
[0049] Figure 14 This application provides an embodiment of PMPSQ microspheres and TGA curves of PMPSQ-OA-1 to PMPSQ-5;
[0050] Figure 15 This application provides TGA curves for EVA, EVA / PMPSQ, and EVA / PMPSQ-OA-1 to 5.
[0051] Figure 16 This is a schematic diagram showing the adsorption amount of EVA on the surface of PMPSQ microspheres and PMPSQ-OA-1 to PMPSQ-5 provided in the embodiments of this application;
[0052] Figure 17 This is a DSC curve of a composite pour point depressant provided in the embodiments of this application;
[0053] Figure 18 This application provides an embodiment of the yield stress before and after adding different initiator concentrations to a grafted pour point depressant synthesized from Changqing crude oil;
[0054] Figure 19 This application provides rheological curves of grafted pour point depressants synthesized from Changqing crude oil with different initiator concentrations before and after addition.
[0055] Figure 20 This application provides DSC curves of grafted pour point depressants synthesized from Changqing crude oil with different initiator concentrations before and after addition;
[0056] Figure 21 This is a polarized light micrograph of wax crystals before and after adding different initiator concentrations to Changqing crude oil to synthesize a grafted pour point depressant, as provided in the embodiments of this application.
[0057] Figure 22 This application provides an embodiment of the yield stress of Changqing crude oil before and after the addition of PMPSQ and PMPSQ-OA-1 to 5;
[0058] Figure 23 This application provides rheological curves of Changqing crude oil before and after the addition of PMPSQ and PMPSQ-OA-1 to PMPSQ-5;
[0059] Figure 24 This application provides an embodiment of the DSC curves of Changqing crude oil before and after the addition of PMPSQ and PMPSQ-OA-1 to PMPSQ-5.
[0060] Figure 25 This is a polarized light micrograph of wax crystals before and after adding PMPSQ and PMPSQ-OA-1 to 5 to Changqing crude oil, as provided in the embodiments of this application.
[0061] Figure 26 This application provides a rheological curve of Qinghai crude oil before and after adding PMPSQ-OA-4;
[0062] Figure 27 This application provides an embodiment of the DSC curves of Qinghai crude oil before and after the addition of PMPSQ-OA-4;
[0063] Figure 28 This is a polarized light micrograph of wax crystals before and after adding PMPSQ-OA-4 to Qinghai crude oil, provided in an embodiment of this application.
[0064] Figure 29 This application provides an embodiment of the yield stress of Qinghai crude oil before and after adding EVA and EVA / PMPSQ-OA-1 to 5;
[0065] Figure 30 This application provides rheological curves of Qinghai crude oil before and after adding EVA and EVA / PMPSQ-OA-1 to 5;
[0066] Figure 31 This application provides an embodiment of the DSC curves of Qinghai crude oil before and after adding EVA and EVA / PMPSQ-OA-1 to 5;
[0067] Figure 32 This is a polarized light micrograph of wax crystals before and after adding EVA and EVA / PMPSQ-OA-1 to 5 to Qinghai crude oil, as provided in the embodiments of this application. Detailed Implementation
[0068] To make the technical solution and advantages of this application clearer, the embodiments of this application will be described in further detail below.
[0069] Figure 1 This is a flowchart of a method for preparing a pour point depressant provided in an embodiment of this application. See also... Figure 1 The preparation method includes:
[0070] Step 101: Using mercaptopropyltrimethoxysilane as the silicon source and deionized water as the solvent, polythiol-silanoxane microspheres were prepared by sol-gel method.
[0071] See Figure 2 The process for preparing polythiol-silanol semioxane microspheres (PMPAQ) can be achieved through the following steps 1011 to 1016, including:
[0072] Step 1011: At the first temperature, add deionized water and emulsifier to the second container.
[0073] The type and volume of the second container can be set and changed as needed, and there are no specific limitations. For example, the second container is a beaker with a volume of 250 mL.
[0074] The emulsifier can be set and changed as needed, and there are no specific limitations on this. For example, the emulsifier could be sodium dodecylbenzenesulfonate.
[0075] The first temperature can be 10℃, 25℃, 40℃, 55℃ or 70℃. In this embodiment, only the first temperature of 25℃ is used as an example for illustration.
[0076] Accordingly, step (1) can be: at 25°C, add a certain amount of deionized water and sodium dodecylbenzenesulfonate to a beaker, where the concentration of sodium dodecylbenzenesulfonate can be its critical micelle concentration.
[0077] It should be noted that a magnetic rotor can be added to the first container, which can be continuously stirred during the subsequent reaction process, thus facilitating the reaction.
[0078] Step 1012: The emulsion formed by mixing mercaptopropyltrimethoxysilane with water is added dropwise to the second container at a preset rate.
[0079] The preset rate can be set and changed as needed, and there is no specific limitation on it. For example, the preset rate is 1 mL / min.
[0080] Accordingly, step (2) can be: mixing a certain amount of mercaptopropyltrimethoxysilane (MPTMS) with water, stirring it with a high-speed dispersing emulsifier to form a uniformly dispersed milky white emulsion, and then adding it dropwise to the second container at a rate of 1 mL / min.
[0081] In this embodiment, the mass ratio of mercaptopropyltrimethoxysilane to deionized water in step (1) can be set and changed as needed, and is not specifically limited thereto. For example, the mass ratio of mercaptopropyltrimethoxysilane to deionized water is 1:10 to 100. Specifically, the mass ratios of mercaptopropyltrimethoxysilane to deionized water are 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, and 1:100. In this embodiment, only a mass ratio of 1:20 of mercaptopropyltrimethoxysilane to deionized water is used as an example for illustration.
[0082] Step 1013: Under stirring conditions, continue to add hydrochloric acid dropwise to the second container to adjust the pH value of the solution in the second container to acidic.
[0083] The stirring rate of the magnetic rotor can be set and changed as needed, and is not specifically limited thereto. For example, the stirring rate of the magnetic rotor can be 100 r / min, 300 r / min, 500 r / min, 700 r / min, or 900 r / min. In this embodiment, only a stirring rate of 300 r / min is used as an example for illustration.
[0084] The concentration of hydrochloric acid can be set and changed as needed, and there is no specific limitation. For example, the concentration of hydrochloric acid can be 37 wt%.
[0085] The pH value of an acidic environment can be set and changed as needed, and there is no specific limitation. For example, the pH value of an acidic environment can be 2, 2.5, 3, or 4. In this embodiment, only an acidic environment with a pH value of 2.5 is used as an example for illustration.
[0086] Accordingly, step (3) can be: controlling the stirring speed of the magnetic rotor to 300 r / min, continuing to add 37 wt% hydrochloric acid to the second container, and adjusting the pH value of the solution in the second container to 2.5 by using hydrochloric acid.
[0087] See Figure 3 In the initial stage of the reaction, due to the poor compatibility between deionized water and the silicon source, the high-speed stirring of the emulsifier stably disperses mercaptopropyltrimethoxysilane in the deionized water as small droplets, increasing the reaction interface and accelerating the hydrolysis rate. After the addition of hydrochloric acid, in the acidic environment, mercaptopropyltrimethoxysilane first hydrolyzes to form silanol and its dimer. The silanol and its dimer dissolve in water, forming a transparent solution.
[0088] Step 1014: After the second hydrolysis time of mercaptopropyltrimethoxysilane in an acidic environment, ammonia water is added dropwise to the second container to adjust the pH value of the solution in the second container to alkaline, so that the hydrolysis product undergoes a condensation reaction in an alkaline environment.
[0089] The second duration can be set and changed as needed, and there is no specific limitation on it. For example, the second duration can be 4 hours.
[0090] The concentration of ammonia can be set and changed as needed, and there is no specific limitation. For example, the concentration of ammonia can be 25 wt%.
[0091] The pH value of an alkaline environment can be set and changed as needed, and there is no specific limitation. For example, the pH value of an alkaline environment is 8, 9, 10, or 11. In the embodiments of this application, only an alkaline environment with a pH value of 11 is used as an example for illustration.
[0092] Accordingly, step (4) can be: after the mercaptopropyltrimethoxysilane is hydrolyzed in an acidic environment for 4 hours, 25wt% ammonia water is added dropwise to the second container to adjust the pH value of the solution in the second container to alkaline, so that the hydrolysis product undergoes a condensation reaction in an alkaline environment.
[0093] Step 1015: After the third reaction time, the reaction product is obtained.
[0094] The third duration can be set and changed as needed, and there is no specific limitation on it. For example, the third duration can be 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours. In this embodiment, only a third duration of 4 hours is used as an example for illustration.
[0095] See also Figure 3 Upon addition of ammonia, silanols condense to form oligomers with Si-O-Si bonds and numerous hydroxyl groups on their surface. Nucleation occurs when the critical degree of polymerization is reached. The rapid condensation of silanols in ammonia is caused by the attack of deprotonated silanols (SiO—) on the Si atoms of the Si-OH group. These nuclei, with their large specific surface area, continuously absorb silanols from the solution and undergo condensation reactions, causing the particles to gradually grow into spheres, ultimately forming polythiol-based silanyl oxyalkylene microspheres.
[0096] Step 1016: After washing, centrifuging and drying the reaction product, polythiol silanol microspheres are obtained.
[0097] The reaction product is a white opaque solution. The white opaque solution is washed 3-4 times with anhydrous ethanol to remove residual ammonia and unreacted monomers. The solution is centrifuged at 10000 r / min for 30 min, the supernatant is discarded, and the precipitate is dried in a vacuum drying oven for 10 hours to obtain a white powder, which is polythiol silanol microspheres.
[0098] This application employs a two-step acid-base catalyzed sol-gel method to prepare PMPAQ microspheres. The sol-gel method uses compounds containing highly chemically active components as reaction precursors and adds emulsifiers to ensure uniform mixing of these raw materials in the liquid phase to form a stable, transparent sol system. Under alkali catalysis, the colloidal particles can further undergo a condensation reaction to form a gel, which, after drying, yields micro / nano-scale materials.
[0099] This application uses deionized water as a solvent, sodium dodecylbenzenesulfonate (SDBS) as an emulsifier, and mercaptopropyltrimethoxysilane (MPTMS) as a silicon source. By controlling reaction conditions such as polycondensation reaction time, pH value of acidic environment, pH value of alkaline environment, reaction speed, reaction temperature, and mass ratio of mercaptopropyltrimethoxysilane to deionized water, PMPAQ microspheres are synthesized.
[0100] See Figure 4 , Figure 4 The morphology of PMPAQ microspheres at different polycondensation reaction times: (a) 1 hour; (b) 2 hours; (c) 3 hours; (d) 4 hours; (e) 5 hours. Figure 4 It can be seen that a complete spherical morphology is achieved only after a polycondensation reaction of 4 hours or more. Specifically, for different polycondensation reaction times, the pH value of the acidic environment was 2.5, the pH value of the alkaline environment was 11, the reaction temperature was 25℃, the mass ratio of silicon source to deionized water was 1:20, and the reaction speed was 300 r / min.
[0101] See Figure 5 , Figure 5Morphology of PMPAQ microspheres with different mass ratios of silicon source to deionized water: (a) 1:10; (b) 1:20; (c) 1:40; (d) 1:60; (e) 1:80; (f) Variation in average particle size of microspheres. Figure 5 It can be seen that as the mass ratio of silicon source to deionized water decreases, the average particle size of the microspheres gradually decreases. Specifically, for different mass ratios of silicon source to deionized water, the pH value in the acidic environment was 2.5, the pH value in the alkaline environment was 11, the reaction temperature was 25℃, the reaction speed was 300 r / min, and the polycondensation reaction time was 4 hours.
[0102] See Figure 6 , Figure 6 The morphology of PMPAQ microspheres at different reaction speeds: (a) 100 r / min; (b) 300 r / min; (c) 500 r / min; (d) 700 r / min; (e) 900 r / min; (f) variation in average particle size of the microspheres. Figure 6 It can be seen that the average particle size of the microspheres gradually decreases with increasing reaction speed. Specifically, the reaction speeds were adjusted as follows: acidic environment pH 2.5, alkaline environment pH 11, reaction temperature 25℃, silicon source to deionized water mass ratio 1:20, and polycondensation reaction time 4 hours.
[0103] See Figure 7 , Figure 7 The morphology of PMPAQ microspheres at different reaction temperatures: (a) 10℃; (b) 25℃; (c) 40℃; (d) 55℃; (e) 70℃; (f) variation in average particle size of the microspheres. Figure 7 It can be seen that the average particle size of the microspheres first decreases and then increases with increasing reaction temperature. Specifically, at different reaction temperatures, the pH value of the acidic environment was 2.5, the pH value of the alkaline environment was 11, the reaction speed was 300 r / min, the mass ratio of silicon source to deionized water was 1:20, and the polycondensation reaction time was 4 hours.
[0104] See Figure 8 , Figure 8 The morphology of PMPAQ microspheres under different acidic pH conditions: (a) pH = 2; (b) pH = 2.5; (c) pH = 3; (d) pH = 4. Figure 8 It can be seen that when the pH value of the acidic environment is 2.5, the generated microspheres are similar in size and relatively uniform. Among them, the reaction temperature is 25℃, the alkaline environment pH value is 11, the reaction speed is 300r / min, the mass ratio of silicon source to deionized water is 1:20, and the polycondensation reaction time is 4 hours.
[0105] See Figure 9 , Figure 9The morphology of PMPAQ microspheres under different alkaline pH values: (a) pH=8; (b) pH=9; (c) pH=10; (d) pH=11. Figure 9 It can be seen that PMPAQ microspheres with a complete spherical morphology cannot be formed when the pH value of the alkaline environment is less than 11. Specifically, the reaction temperature was 25℃, the acidic environment pH value was 2.5, the reaction speed was 300 r / min, the mass ratio of silicon source to deionized water was 1:20, and the polycondensation reaction time was 4 hours for different alkaline pH values.
[0106] In conclusion, the following conclusions can be drawn:
[0107] ① The condensation reaction takes 4 hours or more to form a complete spherical morphology. The reaction must be carried out in a strong acid or strong alkali environment. When the pH value of the acidic environment is greater than 4 or the pH value of the alkaline environment is less than 11, PMPAQ microspheres with a complete spherical morphology cannot be formed.
[0108] ② Different reaction conditions all affect the average particle size of PMPAQ microspheres. As the mass ratio of silicon source to deionized water decreases, the average particle size of microspheres gradually decreases; as the reaction speed increases, the average particle size of microspheres gradually decreases; as the reaction temperature increases, the average particle size of microspheres first decreases and then increases.
[0109] ③ Considering factors such as spherical morphology, particle size, and synthesis loss, this application determines the optimal reaction conditions as follows: acidic environment pH 2.5, alkaline environment pH 11, reaction temperature 25℃, reaction speed 300 r / min, mass ratio of silicon source to deionized water 1:20, and polycondensation reaction time 4 hours.
[0110] Step 102: Add polythiol-siloxane microspheres, high carbon acrylate and reaction solvent to the first container, and then sonicate the first container.
[0111] The reaction solvent can be set and changed as needed, and there are no specific limitations. For example, the reaction solvent can be tetrahydrofuran.
[0112] The molar ratio of thiol groups in the high-carbon acrylic ester to the polythiol-silicon semioxane microspheres can be set and changed as needed, and there is no specific limitation on it. For example, the molar ratio of thiol groups in the high-carbon acrylic ester to the polythiol-silicon semioxane microspheres can be 1:4, 2:4, 3:4, 4:4, or 5:1.
[0113] It should be noted that when the mercaptopropyltrimethoxysilane reacts completely, the molar amount of thiol groups in the polythiol silanol microspheres is the same as the molar amount of thiol groups in the mercaptopropyltrimethoxysilane. Therefore, this application uses the molar amount of thiol groups in the mercaptopropyltrimethoxysilane as the molar amount of thiol groups in the polythiol silanol microspheres.
[0114] In one possible implementation, the higher carbon acrylate includes at least one of octadecyl acrylate, dodecyl acrylate, and hexadecyl acrylate. In the embodiments of this application, only octadecyl acrylate is used as an example for illustration.
[0115] Accordingly, step 102 can be: weigh 147 mg of PMPAQ microspheres and a certain mass of octadecyl acrylate and add them to the first container, then add 29.4 g of tetrahydrofuran, and sonicate in an ultrasonic cleaner for 30 min to fully disperse the PMPAQ microspheres and octadecyl acrylate in the reaction solvent.
[0116] It should be noted that before adding PMPAQ microspheres and octadecyl acrylate to the first container, the airtightness of the first container should be checked first. If the airtightness is good, N2 should be continuously introduced into the first container to purge the air in the first container.
[0117] Step 103: Continue adding initiator to the first container, seal the first container, turn on the circulating water bath, control the water bath temperature, and stir continuously during the reaction.
[0118] The initiator can be set and changed as needed, and there are no specific limitations. For example, the initiator could be benzoin dimethyl ether.
[0119] The mass of the initiator can be set and changed as needed, and there is no specific limitation. For example, the mass of the initiator can be 0% to 6% of the total mass of the high-carbon acrylate and polythiol silanol microspheres. Specifically, the mass of the initiator can be 0%, 1%, 2%, 3%, 4%, 5%, or 6% of the total mass of the two.
[0120] Accordingly, step 103 can be: continue adding dimethyl benzoate to the first container, seal the first container, turn on the circulating water bath, control the water bath temperature at 30°C, and apply mechanical stirring at a constant rate of 400 r / min to ensure a more complete reaction. The mass of dimethyl benzoate can be 0%, 1%, 2%, 4%, or 6% of the total mass of both.
[0121] Step 104: Irradiate the first container with ultraviolet light for a first duration, then add excess methanol to the solution in the first container and continue stirring until flocculent precipitate appears.
[0122] Turn on a 36W ultraviolet lamp (λ=365nm) and let the ultraviolet lamp shine vertically on the first container. The distance between the light source and the first container is 10cm.
[0123] The initial duration can be set and changed as needed, and there is no specific limit to it. For example, the initial duration can be 2 hours.
[0124] After the first time has elapsed, turn off the UV lamp, pour the solution from the first container into a 500mL beaker, add excess methanol and continue stirring until flocculent precipitate appears at the bottom of the beaker.
[0125] Step 105: After precipitating, filtering, washing, and drying the flocculent material, a grafted pour point depressant is obtained.
[0126] After filtering the flocculent precipitate, it was washed repeatedly with methanol and finally dried in a vacuum oven at 60°C for 12 hours to obtain the grafted pour point depressant. This grafted pour point depressant is obtained by grafting octadecyl acrylate (OA) onto the surface of PMPAQ microspheres.
[0127] In the embodiments of this application, grafting was performed with OA to -SH (thiol) molar ratios of 1:4, 2:4, 3:4, 4:4, and 5:1 to synthesize pour point depressants with different grafting concentrations, which were named PMPSQ-OA-1, PMPSQ-OA-2, PMPSQ-OA-3, PMPSQ-OA-4, and PMPSQ-OA-5, respectively.
[0128] Refer to Table 1, which shows the grafting rate of PMPSQ-OA at different initiator concentrations. Table 1 shows that the pour point depressant yield is highest when the initiator concentration is 6%. Specifically, at different initiator concentrations, the total mass of PMPSQ microspheres and OA is 10% of the solution mass.
[0129] Table 1
[0130] Initiator concentration 0 1％ 2％ 4％ 6％ Yield / g 1.3827 2.27107 2.62808 2.86777 2.96413 Grafting rate / % 35.45 58.23 67.387 73.53 76.00
[0131] Refer to Table 2, which shows the grafting rate of PMPSQ-OA at different molar ratios of OA and -SH. Table 2 shows that when the OA content is very low (PMPSQ-OA-1), the grafting rate of the pour point depressant is only 39.2%. As the molar amount of OA increases, the grafting rate gradually increases. When the molar ratio of OA to -SH is 2:4, 3:4, and 4:4, the grafting rates become 50.32%, 68.24%, and 78.53%, respectively. When OA is in excess, the grafting rate continues to increase to 85.22%, but the change is very small. The initiator concentration is 6% for different molar ratios of OA and -SH.
[0132] Table 2
[0133] reaction products PMPSQ-OA-1 PMPSQ-OA-2 PMPSQ-OA-3 PMPSQ-OA-4 PMPSQ-OA-5 Grafting rate / % 39.20 50.32 68.24 78.53 85.22
[0134] See Figure 10 , Figure 10 This is a scanning electron microscope (SEM) image of a grafted pour point depressant. From... Figure 10As can be seen, the grafted pour point depressant basically maintains the spherical morphology, but its surface is no longer smooth and flat, but uneven, and the particle size of the spheres has also increased. This is because the thiol functional groups on the PMPSQ microspheres are successfully linked to the acrylic acid double bonds through ultraviolet light irradiation, and octadecyl acrylate is successfully grafted onto the surface of the PMPSQ microspheres.
[0135] See Figure 11 , Figure 11 Infrared spectra of PMPSQ microspheres, OA monomers, and PMPSQ-OA. From Figure 11 As can be seen from the data, the characteristic peaks of PMPSQ-OA correspond to the characteristic peaks of PMPSQ microspheres and OA monomers, respectively, which also indicates that octadecyl acrylate was successfully grafted onto the surface of PMPSQ microspheres.
[0136] See Figure 12 , Figure 12 DSC (Differential Scanning Calorimetry) curves for grafted pour point depressants: (a) different initiator concentrations; (b) different molar ratios of OA and -SH. Figure 12 As shown in (a), the initial crystallization temperature of the grafted pour point depressant synthesized without initiator is 41℃, and the peak crystallization temperature is 39℃. When the initiator concentration is 1%, the initial crystallization temperature is 44℃, and the peak crystallization temperature is 37℃. When the initiator concentration is 2%, the initial crystallization temperature is 44℃, and the peak crystallization temperature is 41℃. When the initiator concentration is 4%, the initial crystallization temperature is 46℃, and the peak crystallization temperature is 42℃. It is evident that with increasing initiator concentration, both the initial crystallization temperature and the peak crystallization temperature increase, indicating improved crystallization performance of the grafted pour point depressant. However, when the initiator concentration is 6%, both the initial crystallization temperature and the peak crystallization temperature of the grafted pour point depressant decrease significantly, with the initial crystallization temperature dropping to 43℃ and the peak crystallization temperature to 39℃, indicating poorer crystallization performance. The DSC curve is the crystallization exothermic curve obtained from a differential scanning calorimeter.
[0137] from Figure 12 As shown in (b), PMPSQ microspheres have almost no crystallization peaks. With increasing OA monomer concentration, the heat release per unit mass increases significantly, the crystallization peak value increases, and the initial crystallization temperature rises. The initial crystallization temperatures of PMPSQ-OA-1 to 5 are 42, 42, 43, 44, and 45℃, respectively, and the crystallization peak temperature also gradually increases. Therefore, it can be concluded that PMPSQ microspheres are not crystallizable, but they acquire crystallization properties after OA monomer grafting onto their surface, and the crystallization properties are enhanced with increasing OA monomer concentration.
[0138] This application provides a method for preparing a pour point depressant. The method first prepares polythiol-silicon semioxane microspheres using a sol-gel method with mercaptopropyltrimethoxysilane as the silicon source and deionized water as the solvent. Then, a high-carbon acrylate is grafted onto the surface of the polythiol-silicon semioxane microspheres using a mercapto-olefin click method to obtain a grafted pour point depressant. This method grafts high-carbon acrylate onto the surface of the polythiol-silicon semioxane microspheres, modifying the surface of the microspheres and thus improving the pour point depressant effect on high-wax crude oil. Furthermore, the mercapto-olefin click reaction has advantages such as high reactivity, simple reaction conditions, more regular polymers, and easy product separation and purification. Therefore, grafting high carbon acrylates onto the surface of polythiol silanol microspheres via the mercapto-olefin click method is beneficial for preparing pour point depressants with high purity and high grafting density. After dispersing this pour point depressant in crude oil, it is beneficial for promoting the formation of larger and more compact wax crystal particles, thereby improving the rheological properties of high wax crude oil and further enhancing the pour point depressant effect on high wax crude oil.
[0139] The above mainly describes the preparation process of grafted pour point depressants. In the embodiments of this application, a melt blending method can also be used to blend the grafted pour point depressant with ethylene-vinyl acetate copolymer to prepare a composite pour point depressant. The preparation method of the composite pour point depressant will be described next; see [link to relevant documentation]. Figure 13 The preparation method includes:
[0140] Step 1301: The grafted pour point depressant is blended with the ethylene-vinyl acetate copolymer using a melt blending method to obtain a mixture.
[0141] In this implementation, the content of ethylene-vinyl acetate copolymer (EVA) in the mixture is 1 wt% to 20 wt%. Specifically, the content of ethylene-vinyl acetate copolymer can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 15 wt%, 17 wt%, 18 wt%, or 20 wt%. In this embodiment, only an EVA content of 10 wt% is used as an example for illustration.
[0142] The content of vinyl acetate (VA) in the ethylene-vinyl acetate copolymer can be 12%, 18%, 28% or 33%, and the melt index is 6.
[0143] The grafted pour point depressant can be PMPSQ-OA-1, PMPSQ-OA-2, PMPSQ-OA-3, PMPSQ-OA-4, or PMPSQ-OA-5. Accordingly, step 1301 can be: blending EVA with each of the five grafted pour point depressants (PMPSQ-OA-1, PMPSQ-OA-2, PMPSQ-OA-3, PMPSQ-OA-4, and PMPSQ-OA-5) to obtain five mixtures. The content of EVA is 10 wt%.
[0144] Step 1302: Add the mixture to the twin-screw extruder in batches.
[0145] Adjust the operating temperature of the twin-screw extruder to 130℃ and preheat for 15 minutes.
[0146] For each mixture, it is added to the twin-screw extruder in small batches, according to the mass of the mixture.
[0147] Step 1303: After discharge, the material is cooled and crushed to obtain a composite pour point depressant.
[0148] During the feeding process, the feeding time, blending time, and screw speed are kept constant. After discharge, the material is cooled and pulverized to obtain different types of primary pour point depressants, also known as composite pour point depressants.
[0149] For the composite pour point depressant, this application first synthesizes polythiol silanyl semioxane microspheres (PMPSQ) via the sol-gel method, then grafts octadecyl acrylate (OA) onto the surface of the synthesized PMPSQ microspheres via the mercapto-olefin click method to obtain a grafted pour point depressant, and finally blends the grafted pour point depressant with ethylene-vinyl acetate copolymer (EVA) via melt blending to obtain the composite pour point depressant.
[0150] This application tested the adsorption capacity of EVA on the surface of a grafted pour point depressant. The test procedure was as follows: A certain amount of EVA was placed in n-dodecane and mechanically stirred in a 60°C constant temperature water bath until completely dissolved and dispersed, preparing a 5wt% EVA-n-dodecane mixed solution. Then, 0.25wt% of PMPSQ microspheres or PMPSQ-OA-1 to 5 pour point depressants were added to the mixed solution. The mixed solution containing EVA / PMPSQ or EVA / PMPSQ-OA-1 to 5 pour point depressants was stirred for a period of time and then allowed to stand at 60°C for 6 hours. Finally, the mixed solution was centrifuged at 10000 r / min, and the obtained sediment was dried in a vacuum drying oven. The thermogravimetric analysis (TGA) was then used to test the thermogravimetric curve of the sediment under a nitrogen atmosphere, and the percentage of mass loss of the sediment at 600°C was calculated and denoted as f. cSimultaneously, under the same conditions, the thermogravimetric curves of pure PMPSQ microspheres or PMPSQ-OA-1~5 pour point depressants were measured, and the percentage of mass loss at 600℃ was recorded as f. n The adsorption percentage f of EVA on the surface of PMPSQ microspheres or PMCSQ-OA-1 to PMCSQ-5 pour point depressant particles was calculated using the following formula. ads :
[0151]
[0152] See Figure 14 and Figure 15 , Figure 14 Thermogravimetric analysis (TGA) curves of PMPSQ microspheres and PMPSQ-OA-1 to PMPSQ-5 are shown. Figure 15 TGA curves for EVA, EVA / PMPSQ, and EVA / PMPSQ-OA-1 to 5. From... Figure 14 and Figure 15 It can be seen from the data that PMPSQ microspheres and PMPSQ-OA-1~5 at 600℃... n The concentrations of PMPSQ and PMPSQ-OA-1 to 5 after adsorbing EVA in dodecane solution were 45.66%, 65.27%, 71.84%, 79.75%, 82.79%, and 95.85%, respectively, at 600℃. n The percentages of EVA adsorption on the surfaces of PMPSQ microspheres and PMPSQ-OA-1 to PMPSQ-5 were 86.44%, 92.59%, 93.61%, 94.79%, 95.54%, and 96.35%, respectively. The adsorption percentages f of EVA on PMPSQ microspheres and PMPSQ-OA-1 to PMPSQ-5 were calculated using the above formulas. ads ,like Figure 16 As shown. From Figure 16 As can be seen, EVA has the highest adsorption capacity on the surface of PMPSQ-OA-1 pour point depressant. With the increase of the surface mass of nanoparticles, the surface polarity decreases, the adsorption capacity of EVA on its surface weakens, and the adsorption capacity decreases. For PMPSQ, the low adsorption capacity of EVA may be due to its strong surface polarity, but it is easy to agglomerate in the organic phase, which reduces the specific surface area, thus the adsorption capacity of EVA is not high.
[0153] See Figure 17 , Figure 17 The DSC curve of the composite pour point depressant is shown in the image. Figure 17The results show that the initial crystallization temperature of EVA is 65.1℃, and the peak crystallization temperature is 50.17℃. After EVA is combined with PMPSQ microspheres, the initial crystallization temperature decreases to 64.06℃, and the peak crystallization temperature is 50.11℃, indicating that the crystallinity of EVA / PMPSQ is worse than that of pure EVA. After EVA is combined with PMPSQ-OA-1~5, the initial crystallization temperatures become 66.1℃, 66.08℃, 66.08℃, 66.07℃, and 66.11℃ respectively, all higher than the initial crystallization temperature of pure EVA. However, the EVA / PMPSQ-OA-4~5 composite pour point depressants all show two crystallization peaks, which may be due to the large number of nonpolar alkanes grafted on the surface of PMPSQ-OA-4~5, resulting in poor binding ability with EVA and thus the appearance of two crystallization peaks.
[0154] This application provides a method for preparing a composite pour point depressant. This method further composites a grafted pour point depressant with an ethylene-vinyl acetate copolymer to obtain a composite pour point depressant. When this composite pour point depressant is dispersed in crude oil, it can act as a template for wax crystallization, promoting the formation of larger, more compact wax crystals. This further improves the rheological properties of waxy crude oil based on the ethylene-vinyl acetate copolymer, thereby further enhancing the pour point depressant effect on waxy crude oil.
[0155] The technical solution of this application will be described in detail below through specific embodiments.
[0156] In the following specific embodiments, unless otherwise specified, all operations shall be performed under normal conditions or conditions recommended by the manufacturer.
[0157] See Table 3, which shows the physical properties of Changqing crude oil and Qinghai crude oil.
[0158] Table 3
[0159]
[0160] in, This indicates the density of crude oil relative to water at 4°C at 20°C.
[0161] Example 1
[0162] This embodiment mainly tests the effect of grafted pour point depressant on improving the rheological properties of Changqing crude oil.
[0163] (1) The total mass of PMPSQ microspheres and OA in the grafted pour point depressant was controlled to be 10% of the solution mass. Grafted pour point depressants synthesized with different initiator concentrations of 500 ppm were added to Changqing crude oil to test the effect of initiator dosage on product performance. The initiator was benzoin dimethyl ether.
[0164] ①Pour point and gelling properties test
[0165] See Table 4, which shows the pour point and gel point of grafted pour point depressants synthesized with different initiator concentrations in Changqing crude oil before and after addition.
[0166] Table 4
[0167]
[0168] Wherein, G′ is the energy storage modulus and G″ is the loss modulus, both of which represent the structural strength of crude oil.
[0169] ② Yield value test at 5℃
[0170] See Figure 18 , Figure 18 The yield stress of grafted pour point depressants synthesized from Changqing crude oil with different initiator concentrations is shown. Figure 18 It can be seen that the yield stress of Changqing crude oil is 450.68 Pa. As the initiator concentration increases (0% to 4%), the yield stress of Changqing crude oil gradually decreases. If the initiator concentration is further increased, the yield stress of Changqing crude oil will increase instead.
[0171] ③ Rheological property test at 5℃
[0172] See Figure 19 , Figure 19 Rheological curves of grafted pour point depressants synthesized from Changqing crude oil before and after the addition of different initiator concentrations. Figure 19 It can be seen that as the initiator concentration increases (0% to 4%), the apparent viscosity of Changqing crude oil gradually decreases. However, if the initiator concentration is further increased (6%), the apparent viscosity of Changqing crude oil actually increases.
[0173] ④ Test of exothermic crystallization characteristics
[0174] See Figure 20 , Figure 20 The DSC curves of grafted pour point depressants synthesized from Changqing crude oil with different initiator concentrations are shown. Figure 20As can be seen, the wax precipitation point of Changqing crude oil is 28.2℃. After adding a grafted pour point depressant with an initiator concentration of 0% to Changqing crude oil, the wax precipitation point increases to 29.4℃. This is because the added grafted pour point depressant provides a large number of heterogeneous nucleation sites, promoting the crystallization and precipitation of wax molecules. With the increase of initiator concentration (0%~4%), the number of free radicals generated during the grafting process increases, resulting in an increase in the grafting amount on the surface of the microspheres. Octadecyl acrylate (OA) grafted onto the surface of the microspheres can undergo eutectic reaction with wax crystals, solubilizing wax molecules. The polar groups on the OA chain can increase the interfacial tension between the wax crystals and the oil phase, thereby raising the nucleation barrier for wax molecule crystallization, making it difficult for wax molecules to crystallize and precipitate, thus lowering the wax precipitation point of the crude oil. Therefore, with the increase of initiator dosage, the wax precipitation point of the wax oil gradually decreases, but the decrease is very small. The wax precipitation points of crude oils with initiator concentrations of 1%, 2%, and 4% decreased to 29.3℃, 29.2℃, and 28.7℃, respectively. As the initiator concentration was further increased (6%), the effective free radicals were saturated, the amount of OA monomer grafting did not change significantly, and the wax precipitation point of the wax oil remained unchanged.
[0175] ⑤ Microscopic images of wax crystals
[0176] See Figure 21 , Figure 21 Polarized light micrographs of wax crystals before and after adding different initiator concentrations to grafted pour point depressants synthesized from Changqing crude oil: (a) Changqing crude oil; (b) 0% initiator; (c) 1% initiator; (d) 2% initiator; (e) 4% initiator; (f) 6% initiator. Figure 21 As can be seen, after adding pour point depressants to Changqing crude oil, the wax crystal volume increases, and varying degrees of agglomeration occur. These agglomerates form relatively large wax crystal flocs, which are less likely to stack and form a three-dimensional network structure. Therefore, at low temperatures, the rheological properties of the crude oil are improved after adding pour point depressants. Compared to crude oil without pour point depressants, when the initiator concentration is 0%, the wax crystal volume increases slightly, but it remains uniformly dispersed in the oil phase. When the initiator concentration is 1%, a small number of wax crystal flocs begin to appear. With the increase of initiator concentration (2%–6%), the wax crystals agglomerate more, and the floc size further increases.
[0177] In summary, the test results from ① to ⑤ show that grafted pour point depressants with different initiator concentrations can significantly improve the rheological properties of crude oil. With increasing initiator dosage (0%–6%), the pour point of Changqing crude oil first decreases and then increases, indicating a trend of improved and then worsened rheological properties. In particular, the addition of 500 ppm of grafted pour point depressant at a 4% initiator concentration resulted in the largest decrease in pour point (14℃), along with the lowest yield value and apparent viscosity, demonstrating the best rheological improvement effect.
[0178] (2) The amount of initiator in the grafted pour point depressant was controlled to be 4%. 500 ppm of PMPSQ-OA-1, PMPSQ-OA-2, PMPSQ-OA-3, PMPSQ-OA-4, and PMPSQ-OA-5 were added to Changqing crude oil respectively, and the effect of the molar ratio of OA to -SH on the product performance was tested.
[0179] ①Pour point and gelling properties test
[0180] See Table 5, which shows the pour point and gel point of Changqing crude oil after adding PMPSQ and PMPSQ-OA-1 to 5.
[0181] Table 5
[0182]
[0183] ② Yield value test at 5℃
[0184] See Figure 22 , Figure 22 The yield stress of Changqing crude oil before and after adding PMPSQ and PMPSQ-OA-1 to 5 is calculated. Figure 22 It can be seen that the yield stress of Changqing crude oil is 450.68 Pa. After adding PMPSQ, the yield stress of crude oil drops to 371.98 Pa. With the changes of PMPSQ-OA-1 to 4, the yield stress of crude oil gradually decreases. When PMPSQ-OA-5 is added, the yield stress of crude oil actually increases.
[0185] ③ Rheological property test at 5℃
[0186] See Figure 23 , Figure 23 Rheological curves of Changqing crude oil before and after the addition of PMPSQ and PMPSQ-OA-1 to PMPSQ-5. Figure 23 As can be seen, the apparent viscosity of crude oil decreased slightly after adding PMPSQ, but the decrease was not significant. The apparent viscosity of crude oil gradually decreased with the changes in PMPSQ-OA-1 to PMPSQ-OA-5. Specifically, the apparent viscosity of crude oil corresponding to PMPSQ-OA-4 and PMPSQ-OA-5 was similar.
[0187] ④ Test of exothermic crystallization characteristics
[0188] See Figure 24 , Figure 24 DSC curves of Changqing crude oil before and after adding PMPSQ and PMPSQ-OA-1 to 5. From Figure 24The results show that the wax separation point of Changqing crude oil is 28.2℃. After adding PMPSQ, the wax separation point of the crude oil increases to 31.1℃. With the changes in PMPSQ-OA-1 to PMPSQ-OA-5, the wax separation point of the crude oil gradually decreases. Among them, the changes in the wax separation point of the crude oil corresponding to PMPSQ-OA-4 and PMPSQ-OA-5 are relatively small.
[0189] ⑤ Microscopic images of wax crystals
[0190] See Figure 25 , Figure 25 Polarized light micrographs of wax crystals before and after adding PMPSQ and PMPSQ-OA-1 to OA-5 to Changqing crude oil: (a) Changqing crude oil; (b) PMPSQ; (c) PMPSQ-OA-1; (d) PMPSQ-OA-2; (e) PMPSQ-OA-3; (f) PMPSQ-OA-4; (g) PMPSQ-OA-5. Figure 25 It can be seen that after adding PMPSQ, the volume of wax crystals increases slightly; as PMPSQ-OA-1 to 5 change, wax crystal flocs gradually appear, and the size of the flocs further increases.
[0191] In summary, the test results from ① to ⑤ show that when the molar ratio of OA to -SH is appropriate, the grafted pour point depressant (PMPSQ-OA-1 to 4) gradually improves the rheological properties of Changqing crude oil as the OA concentration increases. When OA is excessive (PMPSQ-OA-5), the improvement in crude oil rheological properties is not significantly enhanced. Overall, the grafted pour point depressant corresponding to PMPSQ-OA-4 has the best effect on improving crude oil rheological properties.
[0192] Example 2
[0193] This embodiment mainly tests the effect of grafted pour point depressant on improving the rheology of Qinghai crude oil.
[0194] Add 500 ppm of the grafted pour point depressant corresponding to PMPSQ-OA-4 to the crude oil from Qinghai.
[0195] ①Pour point and gelling properties test
[0196] See Table 6, which shows the pour point and gel point of Qinghai crude oil before and after the addition of PMPSQ-OA-4.
[0197] Table 6
[0198]
[0199] ② Rheological property test at 20℃
[0200] See Figure 26 , Figure 26Rheological curves of Qinghai crude oil before and after the addition of PMPSQ-OA-4. From Figure 26 As can be seen, the apparent viscosity of crude oil decreased significantly after adding PMPSQ-OA-4.
[0201] ③ Test of exothermic crystallization characteristics
[0202] See Figure 27 , Figure 27 DSC curves before and after adding PMPSQ-OA-4 to Qinghai crude oil. From Figure 27 It can be seen that the wax precipitation point of Qinghai crude oil is 48.1℃, and after adding PMPSQ-OA-4, the wax precipitation point becomes 48.2℃.
[0203] ④ Microscopic images of wax crystals
[0204] See Figure 28 , Figure 28 Polarized light micrographs of wax crystals before and after adding PMPSQ-OA-4 to Qinghai crude oil: (a) Qinghai crude oil; (b) PMPSQ-OA-4. Figure 28 As can be seen, wax crystal flocs appeared after adding PMPSQ-OA-4.
[0205] The test results from ① to ④ show that PMPSQ-OA-4 applied to Qinghai crude oil also has good pour point depressant and viscosity reduction effects.
[0206] Example 3
[0207] This embodiment mainly tests the effect of composite pour point depressant on improving the rheological properties of Qinghai crude oil.
[0208] 100 ppm of EVA and a composite pour point depressant were added to Qinghai crude oil, and the performance of the composite pour point depressant and EVA was compared. The composite pour point depressant consisted of EVA / PMPSQ-OA-1 to 5.
[0209] ①Pour point and gelling properties test
[0210] See Table 7, which shows the pour point and gel point of Qinghai crude oil after adding EVA and EVA / PMPSQ-OA-1 to 5.
[0211] Table 7
[0212]
[0213] ② Yield value test at 20℃
[0214] See Figure 29 , Figure 29 The yield stress of Qinghai crude oil before and after adding EVA and EVA / PMPSQ-OA-1 to 5 was determined. Figure 29It can be seen that the yield stress of Qinghai crude oil is 1855.15 Pa. After adding EVA, the yield stress of crude oil decreased to some extent, but the decrease was not as significant as that of crude oil with EVA / PMPSQ-OA-1 added. In addition, the yield stresses of EVA / PMPSQ-OA-1 to 4 are similar, while the yield stress of EVA / PMPSQ-OA-5 actually increased.
[0215] ③ Rheological property test at 20℃
[0216] See Figure 30 , Figure 30 Rheological curves of Qinghai crude oil before and after adding EVA and EVA / PMPSQ-OA-1 to 5. Figure 30 As can be seen, although the apparent viscosity of Qinghai crude oil decreased to some extent after adding EVA, the decrease was not as significant as that of crude oil after adding EVA / PMPSQ-OA-1. Furthermore, among EVA / PMPSQ-OA-1 to 5, EVA / PMPSQ-OA-1 showed the largest decrease.
[0217] ④ Test of exothermic crystallization characteristics
[0218] See Figure 31 , Figure 31 DSC curves of Qinghai crude oil before and after adding EVA and EVA / PMPSQ-OA-1 to 5. Figure 31 It can be seen that the wax separation point of Qinghai crude oil is 48.1℃. After adding EVA, the wax separation point of crude oil is reduced to 46.0℃. Compared with EVA, the wax separation point of crude oil is higher after adding EVA / PMPSQ-OA-1 to 5.
[0219] ⑤ Microscopic images of wax crystals
[0220] See Figure 32 , Figure 32 Polarized light micrographs of wax crystals before and after adding EVA and EVA / PMPSQ-OA-1 to OA-5 to Qinghai crude oil: (a) Qinghai crude oil; (b) EVA; (c) EVA / PMPSQ-OA-1; (d) EVA / PMPSQ-OA-2; (e) EVA / PMPSQ-OA-3; (f) EVA / PMPSQ-OA-4; (g) EVA / PMPSQ-OA-5. Figure 32 As can be seen, the volume of wax crystals increases after adding EVA. Compared to EVA alone, the wax crystal particles precipitated after adding EVA / PMPSQ-OA-1 to 3 are more compactly aggregated.
[0221] ⑥ The effect of pour point depressant concentration on setting point and gel point
[0222] See Table 8, which shows the pour point and gel point of Qinghai crude oil after adding EVA and EVA / PMPSQ-OA-1.
[0223] Table 8
[0224]
[0225] The test results from ① to ⑥ show that the composite pour point depressants prepared from EVA and PMPSQ-OA-1 to 5 are superior to pure EVA in terms of thermal stability and exothermic crystallization characteristics. Taking EVA / PMPSQ-OA-1 as an example, compared with pure EVA, the addition of EVA / PMPSQ-OA-1 lowers the gel point of crude oil, increases the wax precipitation point, and the precipitated wax crystal particles agglomerate more compactly, resulting in a better effect on improving the rheological properties of crude oil. Furthermore, the optimal concentration is very low, only 500 ppm, lower than the optimal concentration of EVA (100 ppm). For EVA / PMPSQ-OA-1 to 5, as the amount of alkyl branches on the surface of the nanospheres increases, the adsorption capacity of EVA on the nanoparticle surface weakens, the adsorption amount decreases, and the pour point depressant effect of the prepared composite pour point depressant deteriorates. The adsorption between EVA and PMPSQ-OA-1 to 5 is an important factor affecting the effect of the composite pour point depressant. Grafted pour point depressants with a small amount of organic alkyl chains on their surface, when combined with EVA, have a better effect on improving the rheological properties of crude oil.
[0226] In summary, both the grafted pour point depressant and the composite pour point depressant provided in this application have good pour point and viscosity depressant properties. Among them, the composite pour point depressant can further reduce the pour point and viscosity of waxy crude oil based on EVA. It is stable, easy to transport, and has a simple and safe synthesis process, which can meet the requirements of pipeline transportation.
[0227] The above description is only for the purpose of enabling those skilled in the art to understand the technical solution of this application, and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for preparing a pour point depressant, characterized in that, The preparation method includes: Polymerized mercaptosilane microspheres were prepared by sol-gel method using mercaptopropyltrimethoxysilane as the silicon source and deionized water as the solvent. The polythiol-based silanol microspheres, high-carbon acrylate, and reaction solvent are added to the first container, and the first container is then subjected to ultrasonic treatment. Continue adding initiator to the first container, seal the first container, turn on the circulating water bath, control the water bath temperature, and stir continuously during the reaction; The first container is irradiated with ultraviolet light for a first duration. Then, excess methanol is added to the solution in the first container, and stirring is continued until flocculent precipitate appears. After the flocculent material is precipitated, filtered, washed, and dried, a grafted pour point depressant is obtained.
2. The preparation method according to claim 1, characterized in that, The higher carbon acrylates include at least one of octadecyl acrylate, dodecyl acrylate, and hexadecyl acrylate.
3. The preparation method according to claim 1, characterized in that, The preparation method further includes: The grafted pour point depressant is blended with ethylene-vinyl acetate copolymer using a melt blending method to obtain a composite pour point depressant; wherein the content of the ethylene-vinyl acetate copolymer in the composite pour point depressant is 1wt% to 20wt%.
4. The preparation method according to claim 3, characterized in that, The grafted pour point depressant is blended with an ethylene-vinyl acetate copolymer using a melt blending method to obtain a composite pour point depressant, comprising: The grafted pour point depressant and the ethylene-vinyl acetate copolymer were blended using a melt blending method to obtain a mixture; The mixture is added to a twin-screw extruder in batches; After discharge, the material is cooled and pulverized to obtain the composite pour point depressant.
5. The preparation method according to claim 1, characterized in that, The preparation of polythiol-based silanol microspheres using mercaptopropyltrimethoxysilane as the silicon source and deionized water as the solvent via a sol-gel method includes: At the first temperature, the deionized water and emulsifier are added to the second container; The emulsion formed by mixing mercaptopropyltrimethoxysilane with water is added dropwise to the second container at a preset rate; Under stirring conditions, hydrochloric acid is continuously added dropwise to the second container to adjust the pH value of the solution in the second container to acidic. After the mercaptopropyltrimethoxysilane is hydrolyzed in an acidic environment for a second time, ammonia water is added dropwise to the second container to adjust the pH value of the solution in the second container to alkaline, so that the hydrolysis product undergoes a condensation reaction in an alkaline environment. After the third reaction time, the reaction product was obtained; The reaction product was washed, centrifuged, and dried to obtain the polythiol silanol microspheres.
6. The preparation method according to claim 1 or 5, characterized in that, The mass ratio of mercaptopropyltrimethoxysilane to deionized water is 1:10 to 100.
7. The preparation method according to claim 5, characterized in that, The pH value of the acidic environment is 2.5; The pH value of the alkaline environment is 11; The first temperature is 25°C; Both the second duration and the third duration are 4 hours; The stirring rate is 300 r / min.
8. The preparation method according to claim 1, characterized in that, The molar ratio of the high carbon acrylate to the thiol groups in the polythiol-silanolane microspheres is 1:4, 2:4, 3:4, 4:4, or 5:
1.
9. The preparation method according to claim 1, characterized in that, The mass of the initiator is 0-6% of the total mass of the high carbon acrylate and the polythiol silanol microspheres.
10. A pour point depressant, characterized in that, The pour point depressant is prepared by the preparation method according to any one of claims 1 to 9.