High-efficiency paraffin inhibitor for heavy crude oil and preparation method thereof

Abstract

The present application provides a heavy crude oil efficient wax removal and prevention agent and a preparation method thereof, and belongs to the technical field of oil field chemistry, and comprises the following steps: step S1, surface modification of hollow mesoporous silica microspheres by KH-570 to obtain a carrier with a methacrylate double bond on the surface; step S2, preparation of a composite carrier with a surface grafted copolymer layer; step S3, preparation of an amphoteric functionalized composite carrier; and step S4, D-limonene loading of the amphoteric functionalized composite carrier to obtain a heavy crude oil efficient wax removal and prevention agent. The present application can solve the problems of the prior art, such as the difficulty in simultaneously achieving wax removal and prevention, the insufficient release sustainability of active components, and the poor dispersion stability in complex oil phases.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical technology, specifically to a high-efficiency dewaxing and anti-waxing agent for heavy crude oil and its preparation method. Background Technology

[0002] During the extraction, gathering, and storage of heavy crude oil and high-wax crude oil, the phase equilibrium between n-alkanes, isoalkanes, and some resin and gum components is disrupted due to temperature decreases, pressure fluctuations, and changes in local shear conditions. Paraffin components gradually precipitate, grow, and overlap, eventually forming an adhesive wax layer on the walls of wellbores, tubing, gathering pipelines, and storage tanks. Once formed, this wax layer not only increases flow resistance, pump pressure, and energy consumption, but also reduces the effective flow cross-section, increases testing instrument errors, and may even lead to well shutdown and production stoppage. For heavy crude oil, due to the high content of high-molecular-weight hydrocarbons, gums, and asphaltenes, wax crystals tend to form a dense framework more easily, further increasing the difficulty of peeling off the existing wax layer and the tendency for redeposition.

[0003] To address the issue of wax deposition, existing technologies typically employ three methods: mechanical wax removal, hot washing wax removal, and chemical wax removal and prevention agents. Mechanical and hot washing wax removal can restore local channels in a short time, but require frequent operations, resulting in high on-site costs. Furthermore, they often only treat existing wax deposits and do not provide sustained inhibition of subsequent re-deposition. Chemical wax removal and prevention agents have become an important technical approach in oilfields due to their ease of application and continuous action; however, chemical agents themselves have issues such as different focuses on wax removal and prevention, and significant differences in on-site compatibility.

[0004] Patent application CN103805279A discloses a wax-removing and anti-waxing agent with aromatic solvents, weighting agents, and anionic surfactants as the main components. This type of solution relies on the rapid dissolution of waxes and asphaltenes by the solvent to achieve short-term wax removal and has a certain removal effect on low-temperature solidified wax layers. However, the active ingredients of this type of free-state solvent-based system are all exposed in the oil phase, which easily leads to problems such as volatilization loss, rapid instantaneous consumption, and short duration of action; at the same time, its technical focus is biased towards the dissolution of already deposited wax layers, and its long-term inhibition ability on wax crystal nucleation, growth, and redeposition is limited.

[0005] Patent application CN109370553A discloses an oilfield crude oil anti-wax agent and its preparation method. This method uses a compound of ethylene-vinyl acetate copolymer, pinene, and surfactants to improve the wax crystal structure and fluidity of high-wax crude oil. This type of polymer-based anti-wax system is beneficial for adjusting wax crystal morphology and reducing viscosity; however, its main function is still during wax crystal formation and growth. For aged wax layers that are already firmly attached to metal surfaces, it typically lacks sufficiently strong rapid peeling and removal capabilities, thus limiting its application in continuous scenarios where cleaning precedes anti-wax treatment.

[0006] Patent application CN114763469A discloses an oil-soluble wax-removing and anti-waxing agent and its preparation method. This type of solution takes into account both oil solubility and wax-removing and anti-waxing properties, and has certain applicability to wax-containing heavy oil systems. However, its active components still mainly exist in the medium in a free dispersion manner, which is easily affected by wellbore temperature gradient, flow rate and residence time, resulting in local concentration decay. When the wax-removing component and the wax-preventing component lack spatial distribution and interfacial structure, it is often difficult to simultaneously take into account the rapid weakening of the existing wax layer, the inhibition of secondary aggregation of wax crystals and the dispersion stability in complex oil phase environments.

[0007] Therefore, there is a need to provide a high-efficiency dewaxing agent for heavy crude oil and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0008] In view of this, the present invention provides a high-efficiency wax remover and wax preventer for heavy crude oil and its preparation method, so as to solve the problems of difficulty in achieving both wax removal and wax prevention in the prior art, insufficient continuous release of active components, and poor dispersion stability in complex oil phases.

[0009] To achieve the above objectives, the present invention provides a method for preparing a high-efficiency dewaxing agent for heavy crude oil, comprising the following steps:

[0010] Step S1: Dissolve CTAB in water and add ethanol. After adjusting the pH, add solid silica spheres, disperse by ultrasonication, and add TEOS dropwise for heating and stirring reaction. Then, etch with sodium carbonate solution and extract with acid to obtain hollow mesoporous silica microspheres. Then, use KH-570 to modify the surface of the hollow mesoporous silica microspheres to obtain a carrier with methacrylate double bonds on the surface.

[0011] Step S2: The carrier is dispersed in a mixed solvent of anisole and DMF, and grafted copolymerized with GMA and ODMA in the presence of an initiator to obtain a composite carrier with a surface grafted copolymer layer.

[0012] Step S3: Disperse the composite carrier in a mixed solvent of isopropanol and DMF, react it first with N,N-dimethylaminoethylenediamine, and then with 1,3-propanesulfonyl lactone to obtain an amphoteric functionalized composite carrier.

[0013] Step S4: After vacuum drying, the amphoteric functionalized composite carrier is loaded with D-limonene by vacuum adsorption and pressure impregnation to obtain a high-efficiency dewaxing agent for heavy crude oil.

[0014] This invention first constructs hollow mesoporous silica microspheres as a carrier, where the hollow structure provides a liquid storage cavity and the mesoporous shell provides a mass transfer channel, which is beneficial for the efficient loading and continuous release of subsequent active components. Then, polymerizable double bonds are introduced through KH-570, enabling the carrier surface to undergo graft copolymerization with GMA and ODMA to form an interface layer with both reaction sites and oleophobic segments. Subsequently, N,N-dimethylaminoethylenediamine undergoes a ring-opening reaction with the epoxy groups in GMA, and further an amphoteric functional layer is constructed on the carrier surface through 1,3-propanesulfonyl lactone. Finally, D-limonene is efficiently loaded into the pores and hollow cavities by vacuum adsorption and pressure impregnation, thereby forming a composite system with both rapid wax removal and continuous wax prevention functions.

[0015] D-Limonene can swell and dissolve hydrocarbon components in waxy deposits; hollow mesoporous carriers can delay the volatilization and loss of D-limonene, increasing the residence time of effective components in wellbores and pipelines; surface-grafted ODMA long-chain oleophobic groups can interact with the wax crystal surface, interfering with the orderly growth of wax crystals; the amphoteric functional layer can form a stable adsorption layer at the wax crystal / crude oil interface, weakening the adhesion between wax crystals and between wax crystals and metal walls, thereby achieving synergistic effects of wax removal, dispersion, and anti-redeposition.

[0016] The internally loaded D-limonene preferentially penetrates and weakens the existing wax layer, while the external wax-repellent long chains disturb the nucleation and growth of newly formed wax crystals around the brush layer. The amphoteric interface layer ensures the stable dispersion of microspheres near the oil phase and solid-liquid interface. The synergistic effect of these three components simultaneously improves wax removal efficiency, redeposition inhibition capability, and duration of action, making it more suitable for continuous wax removal and prevention under complex conditions involving heavy crude oil.

[0017] Preferably, the preparation of the solid silica spheres includes the following steps:

[0018] Anhydrous ethanol, deionized water, and ammonia were mixed and stirred at 30-32℃ and 390-430 rpm. TEOS was added dropwise at a rate of 0.45-0.51 g / min. After the addition was completed, the reaction was continued for 3.9-4.3 h. The mixture was then centrifuged, washed with ethanol, and dried to obtain solid silica spheres.

[0019] The solid silica spheres prepared under the above conditions have relatively uniform particle size, which is beneficial for the subsequent formation of a mesoporous shell layer with controllable thickness.

[0020] Preferably, in step S1, the pH is adjusted to 10.4-10.6; the ultrasonic dispersion time is 28-32 min; the temperature for heating and stirring is 44-46℃, and the speed is 580-630 rpm.

[0021] It facilitates the synergistic assembly of CTAB micelle templates and silica precursors, resulting in a more uniform shell pore structure.

[0022] Preferably, in step S1, the concentration of the sodium carbonate solution is 0.075-0.09 mol / L, the etching temperature is 79-82℃, and the etching time is 7.2-8.5 h.

[0023] It is beneficial to selectively remove the kernel and effectively remove the template to obtain a complete hollow mesoporous structure.

[0024] Preferably, the carrier comprises the following components in parts by weight:

[0025] Hollow mesoporous silica 1.8-2.2 parts, anhydrous toluene 65.9-71.1 parts, and KH-570 2.8-3.4 parts.

[0026] Preferably, the composite carrier of the surface-grafted copolymer layer comprises the following components in parts by weight:

[0027] 0.9-1.1 parts of carrier, 2.2-2.8 parts of GMA, 3.8-4.4 parts of ODMA and 0.09-0.11 parts of AIBN.

[0028] Preferably, the amphoteric functionalized composite carrier comprises the following components in parts by weight: 1.4-1.6 parts of the composite carrier with a surface grafted copolymer layer, 22.6-24.5 parts of isopropanol, 0.9-1.1 parts of N,N-dimethylaminoethylenediamine, and 0.7-0.9 parts of 1,3-propanesulfonyl lactone.

[0029] Preferably, in step S4, the amphoteric functionalized composite carrier is vacuum dried at 58-62°C to constant weight, and then evacuated to 18-25 Pa and held for 2.0-2.5 h.

[0030] It helps to remove gas and residual solvent from the pores, thereby improving the subsequent absorption efficiency of D-limonene.

[0031] Preferably, in step S4, the weight of D-limonene is 32.0-35.3 parts; the pressure for impregnation is 1.4-1.6 MPa, and the time is 9-11 h.

[0032] This facilitates the full entry of D-limonene into the pores and hollow cavities, achieving a higher loading capacity and a better sustained-release effect.

[0033] To achieve the above objectives, the present invention also provides a high-efficiency dewaxing agent for heavy crude oil prepared by the above-described method for preparing a high-efficiency dewaxing agent for heavy crude oil.

[0034] The high-efficiency wax remover and wax inhibitor for heavy crude oil prepared by the method of this invention can solve the problems of difficulty in achieving both wax removal and wax prevention in the prior art, insufficient continuous release of active components, and poor dispersion stability in complex oil phases.

[0035] The above-described technical solution of the present invention has at least the following beneficial effects:

[0036] 1. This invention uses hollow mesoporous silica as a carrier, which has both hollow cavity and mesoporous channels. It can provide a large space for the active components and construct a release path that gradually migrates from the internal reservoir to the external interface. Compared with traditional free-state wax removers, it can slow down the instantaneous loss of active components. Compared with simple dense microspheres or non-porous materials, it can significantly improve loading efficiency and diffusion utilization.

[0037] 2. After ring-opening of N,N-dimethylaminoethylenediamine and reaction with 1,3-propanesulfonyl lactone, a sulfobetaine-type amphoteric interface layer is constructed on the surface of the carrier. On the one hand, this improves the stable dispersion of the composite microspheres in complex oil phases with high wax, gum and asphaltenes content, and reduces particle agglomeration and sedimentation. On the other hand, it forms a more uniform distribution of action on the wax crystal surface and near the metal interface, reducing the redeposition problem caused by insufficient local reagent concentration.

[0038] 3. The internally loaded D-limonene preferentially penetrates and weakens the existing wax layer, while the external wax-repellent long chains disturb the nucleation and growth of newly formed wax crystals around the brush layer. The amphoteric interface layer ensures that the microspheres are dispersed stably near the oil phase and solid-liquid interface. The synergistic effect of the three can simultaneously improve the wax removal efficiency, redeposition inhibition ability, and on-site continuous action time, thereby achieving efficient wax removal and prevention. Detailed Implementation

[0039] The technical solution will now be clearly and completely described in conjunction with the embodiments of the present invention.

[0040] In Examples 1-6 and Comparative Examples 1-4 below, TEOS is tetraethyl orthosilicate, CTAB is hexadecyltrimethylammonium bromide, AIBN is azobisisobutyronitrile, DMF is N,N-dimethylformamide, GMA is glycidyl methacrylate, and ODMA is octadecyl methacrylate.

[0041] Example 1:

[0042] 110.5 g of anhydrous ethanol, 20.0 g of deionized water and 5.4 g of 28% ammonia solution were added to a 500 mL three-necked flask. 9.3 g of TEOS was added dropwise at a rate of 0.47 g / min under stirring at 30 °C and 400 rpm. After the addition was complete, the reaction was continued for 4 h. The resulting product was centrifuged, washed three times in ethanol and dried at 60 °C to obtain solid silica spheres.

[0043] 3.0 g CTAB was dissolved in 160.0 g deionized water, 11.8 g ethanol was added, and the pH was adjusted to 10.5 with 28% ammonia. Solid silica spheres were added, and the mixture was sonicated for 30 min to ensure thorough dispersion. 11.2 g TEOS was slowly added dropwise at 45 °C and 600 rpm, and the reaction was carried out for 10 h to obtain core-shell particles. After centrifugation and washing, the particles were dispersed in 200.0 g of 0.08 mol / L sodium carbonate solution and etched at 80 °C for 8.0 h. Subsequently, the particles were placed in a mixture of 75.0 g ethanol and 1.2 g concentrated hydrochloric acid and extracted by heating and stirring at 60 °C for 8 h. After centrifugation, washing with ethanol three times, and drying, hollow mesoporous silica microspheres were obtained.

[0044] 2.0 g of hollow mesoporous silica was vacuum dried at 110 °C for 4 h, dispersed in 69.4 g of anhydrous toluene, sonicated for 20 min, and then 3.1 g of KH-570 was added. The mixture was reacted at 110 °C for 8 h under nitrogen protection, centrifuged, washed three times each with toluene and ethanol, and vacuum dried at 50 °C to obtain a carrier with methacrylate double bonds on its surface.

[0045] 1.0 g of the carrier was dispersed in a mixed solvent of 29.9 g anisole and 28.3 g DMF, and sonicated for 20 min. Then, 2.5 g GMA, 4.0 g ODMA and 0.1 g AIBN were added. After three vacuum-nitrogen-purging deoxygenation cycles, the mixture was reacted at 70 °C and 400 rpm for 8 h. After the reaction was completed, the mixture was centrifuged, washed with DMF until the supernatant was clear, washed three times with ethanol, and dried under vacuum at 50 °C to obtain the composite carrier with the surface grafted copolymer layer.

[0046] 1.5 g of the composite carrier was dispersed in a mixed solvent of 23.6 g isopropanol and 18.9 g DMF, and sonicated for 15 min. 1.0 g N,N-dimethylaminoethylenediamine was added, and the mixture was stirred at 50 °C for 10 h. After centrifugation and washing, the precipitate was redispersed in 37.8 g DMF, and 0.8 g 1,3-propanesulfonyl lactone was added. The mixture was reacted at 55 °C for another 10 h. After centrifugation, the mixture was washed three times each with DMF and ethanol, and then dried under vacuum at 50 °C to obtain the amphoteric functionalized composite carrier.

[0047] 1.0 g of amphoteric functionalized composite carrier was vacuum dried at 60 °C to constant weight, vacuumed to 20 Pa and maintained for 2 h, and 33.6 g of D-limonene was drawn into the carrier under vacuum to impregnate it. Then nitrogen gas was introduced to pressurize to 1.5 MPa, and the carrier was allowed to stand for 10 h. After centrifugation at 3000 rpm for 5 min, the surface was dried to obtain a high-efficiency dewaxing agent for heavy crude oil loaded with D-limonene.

[0048] Example 2:

[0049] 107.3 g of anhydrous ethanol, 18.5 g of deionized water and 4.7 g of 28% ammonia solution were added to a 500 mL three-necked flask. 9.0 g of TEOS was added dropwise at a rate of 0.45 g / min under stirring at 30 °C and 390 rpm. After the addition was complete, the reaction was continued for 4 h. The product was centrifuged, washed three times in ethanol and dried at 58 °C to obtain solid silica spheres.

[0050] 2.8 g CTAB was dissolved in 156.0 g deionized water, 10.3 g ethanol was added, and the pH was adjusted to 10.4 with 28% ammonia. Solid silica spheres were added, and the mixture was sonicated for 28 min to ensure complete dispersion. 10.6 g TEOS was slowly added dropwise at 44 °C and 585 rpm, and the reaction was allowed to proceed for 9.2 h to obtain core-shell particles. After centrifugation and washing, the particles were dispersed in 190.0 g of 0.075 mol / L sodium carbonate solution and etched at 79 °C for 7.2 h. Subsequently, the particles were placed in a mixture of 75.0 g ethanol and 1.1 g concentrated hydrochloric acid and extracted by heating and stirring at 58 °C for 7 h. After centrifugation, washing with ethanol three times, and drying, hollow mesoporous silica microspheres were obtained.

[0051] 1.8 g of hollow mesoporous silica was vacuum dried at 110 °C for 4 h, dispersed in 65.9 g of anhydrous toluene, sonicated for 20 min, and then 2.8 g of KH-570 was added. The mixture was reacted at 109 °C for 7.5 h under nitrogen protection, centrifuged, washed three times each with toluene and ethanol, and vacuum dried at 50 °C to obtain a support with methacrylate double bonds on its surface.

[0052] 0.9 g of the carrier was dispersed in a mixed solvent of 28.9 g anisole and 27.4 g DMF, and sonicated for 20 min. Then, 2.2 g GMA, 3.8 g ODMA and 0.1 g AIBN were added. After three vacuum-nitrogen-purging deoxygenation cycles, the mixture was reacted at 68 °C and 400 rpm for 7.5 h. After the reaction was completed, the mixture was centrifuged, washed with DMF until the supernatant was clear, washed three times with ethanol, and dried under vacuum at 50 °C to obtain the composite carrier with the surface grafted copolymer layer.

[0053] 1.4 g of the composite carrier was dispersed in a mixed solvent of 22.6 g isopropanol and 18.1 g DMF, and sonicated for 15 min. 0.9 g N,N-dimethylaminoethylenediamine was added, and the mixture was stirred at 48 °C for 9 h. After centrifugation and washing, the precipitate was redispersed in 37.8 g DMF, and 0.7 g 1,3-propanesulfonyl lactone was added. The mixture was reacted at 53 °C for another 9 h. After centrifugation, the mixture was washed three times each with DMF and ethanol, and then dried under vacuum at 50 °C to obtain the amphoteric functionalized composite carrier.

[0054] 0.9 g of amphoteric functionalized composite carrier was vacuum dried at 58 °C to constant weight, vacuumed to 25 Pa and maintained for 2 h, and 32.0 g of D-limonene was drawn in to impregnate the carrier while maintaining vacuum. Then nitrogen gas was introduced to pressurize to 1.4 MPa, and the carrier was allowed to stand for 9 h. After centrifugation at 3000 rpm for 5 min, the surface was dried to obtain a high-efficiency dewaxing agent for heavy crude oil loaded with D-limonene.

[0055] Example 3:

[0056] 113.6 g of anhydrous ethanol, 21.0 g of deionized water, and 5.4 g of 28% ammonia solution were added to a 500 mL three-necked flask. 9.7 g of TEOS was added dropwise at a rate of 0.51 g / min under stirring at 32 °C and 430 rpm. After the addition was complete, the reaction was continued for 4.2 h. The resulting product was centrifuged, washed three times in ethanol, and dried at 62 °C to obtain solid silica spheres.

[0057] 3.2 g CTAB was dissolved in 165.0 g deionized water, 13.4 g ethanol was added, and the pH was adjusted to 10.6 with 28% ammonia. Solid silica spheres were added, and the mixture was sonicated for 32 min to ensure thorough dispersion. 11.4 g TEOS was slowly added dropwise at 46 °C and 630 rpm, and the reaction was carried out for 10.5 h to obtain core-shell particles. After centrifugation and washing, the particles were dispersed in 205.0 g of 0.090 mol / L sodium carbonate solution and etched at 82 °C for 8.5 h. Subsequently, the particles were placed in a mixture of 78.9 g ethanol and 1.3 g concentrated hydrochloric acid and extracted by heating and stirring at 61 °C for 8 h. After centrifugation, washing with ethanol three times, and drying, hollow mesoporous silica microspheres were obtained.

[0058] 2.2 g of hollow mesoporous silica was vacuum dried at 110 °C for 4 h, dispersed in 71.1 g of anhydrous toluene, sonicated for 20 min, and then 3.4 g of KH-570 was added. The mixture was reacted at 110 °C for 8.5 h under nitrogen protection, centrifuged, washed three times each with toluene and ethanol, and vacuum dried at 50 °C to obtain a support with methacrylate double bonds on its surface.

[0059] 1.1 g of the carrier was dispersed in a mixed solvent of 30.8 g anisole and 29.3 g DMF, and sonicated for 20 min. Then, 2.8 g GMA, 4.4 g ODMA and 0.1 g AIBN were added. After three vacuum-nitrogen-purging deoxygenation cycles, the mixture was reacted at 72 °C and 400 rpm for 8.5 h. After the reaction was completed, the mixture was centrifuged, washed with DMF until the supernatant was clear, washed three times with ethanol, and dried under vacuum at 50 °C to obtain the composite carrier with the surface grafted copolymer layer.

[0060] 1.6 g of the composite carrier was dispersed in a mixed solvent of 24.5 g isopropanol and 19.6 g DMF, and sonicated for 15 min. 1.1 g of N,N-dimethylaminoethylenediamine was added, and the mixture was stirred at 52 °C for 10 h. After centrifugation and washing, the precipitate was redispersed in 37.8 g DMF, and 0.9 g of 1,3-propanesulfonyl lactone was added. The mixture was reacted at 56 °C for another 10 h. After centrifugation, the mixture was washed three times each with DMF and ethanol, and then dried under vacuum at 50 °C to obtain the amphoteric functionalized composite carrier.

[0061] 1.1 g of amphoteric functionalized composite carrier was vacuum dried at 62 °C to constant weight, then evacuated to 18 Pa and maintained for 2.5 h. Under vacuum, 35.3 g of D-limonene was drawn in to impregnate the carrier, followed by nitrogen gas to pressurize to 1.6 MPa, and allowed to stand for 11 h. After centrifugation at 3000 rpm for 5 min, the surface was dried to obtain a high-efficiency dewaxing agent for heavy crude oil loaded with D-limonene.

[0062] Example 4:

[0063] 108.9 g of anhydrous ethanol, 19.0 g of deionized water and 4.9 g of 28% ammonia solution were added to a 500 mL three-necked flask. 9.1 g of TEOS was added dropwise at a rate of 0.47 g / min under stirring at 31 °C and 410 rpm. After the addition was complete, the reaction was continued for 4.1 h. The resulting product was centrifuged, washed three times in ethanol and dried at 60 °C to obtain solid silica spheres.

[0064] 2.9 g CTAB was dissolved in 158.0 g deionized water, 11.0 g ethanol was added, and the pH was adjusted to 10.5 with 28% ammonia. Solid silica spheres were added, and the mixture was sonicated for 29 min to ensure complete dispersion. 10.8 g TEOS was slowly added dropwise at 45 °C and 590 rpm, and the reaction was allowed to proceed for 9.6 h to obtain core-shell particles. After centrifugation and washing, the particles were dispersed in 195.0 g of 0.080 mol / L sodium carbonate solution and etched at 80 °C for 7.5 h. Subsequently, the particles were placed in a mixture of 75.7 g ethanol and 1.2 g concentrated hydrochloric acid and extracted by heating and stirring at 59 °C for 7.5 h. After centrifugation, washing with ethanol three times, and drying, hollow mesoporous silica microspheres were obtained.

[0065] 1.9 g of hollow mesoporous silica was vacuum dried at 110 °C for 4 h, dispersed in 67.6 g of anhydrous toluene, sonicated for 20 min, and then 3.0 g of KH-570 was added. The mixture was reacted at 110 °C for 8 h under nitrogen protection, centrifuged, washed three times each with toluene and ethanol, and vacuum dried at 50 °C to obtain a carrier with methacrylate double bonds on its surface.

[0066] 1.0 g of the carrier was dispersed in a mixed solvent of 29.4 g anisole and 27.8 g DMF, and sonicated for 20 min. Then, 2.4 g GMA, 4.1 g ODMA and 0.1 g AIBN were added. After three vacuum-nitrogen-purging deoxygenation cycles, the mixture was reacted at 69 °C and 400 rpm for 8 h. After the reaction was completed, the mixture was centrifuged, washed with DMF until the supernatant was clear, washed three times with ethanol, and dried under vacuum at 50 °C to obtain the composite carrier with the surface grafted copolymer layer.

[0067] 1.5 g of the composite carrier was dispersed in a mixed solvent of 23.1 g isopropanol and 18.5 g DMF, and sonicated for 15 min. 1.0 g N,N-dimethylaminoethylenediamine was added, and the mixture was stirred at 49 °C for 10 h. After centrifugation and washing, the precipitate was redispersed in 37.8 g DMF, and 0.8 g 1,3-propanesulfonyl lactone was added. The mixture was reacted at 54 °C for 9.5 h, centrifuged, and washed three times each with DMF and ethanol. The mixture was then vacuum dried at 50 °C to obtain the amphoteric functionalized composite carrier.

[0068] 1.0 g of amphoteric functionalized composite carrier was vacuum dried at 59 °C to constant weight, vacuumed to 22 Pa and maintained for 2 h, and 32.8 g of D-limonene was drawn into the carrier under vacuum. Then nitrogen gas was introduced to pressurize to 1.5 MPa, and the carrier was allowed to stand for 10 h. After centrifugation at 3000 rpm for 5 min, the surface was dried to obtain a high-efficiency dewaxing agent for heavy crude oil loaded with D-limonene.

[0069] Example 5:

[0070] 112.0 g of anhydrous ethanol, 20.5 g of deionized water and 5.2 g of 28% ammonia solution were added to a 500 mL three-necked flask. 9.5 g of TEOS was added dropwise at a rate of 0.49 g / min under stirring at 30 °C and 400 rpm. After the addition was complete, the reaction was continued for 4.3 h. The resulting product was centrifuged, washed three times in ethanol and dried at 61 °C to obtain solid silica spheres.

[0071] 3.1 g CTAB was dissolved in 162.0 g deionized water, 12.6 g ethanol was added, and the pH was adjusted to 10.6 with 28% ammonia. Solid silica spheres were added, and the mixture was sonicated for 31 min to ensure thorough dispersion. 11.1 g TEOS was slowly added dropwise at 46 °C and 620 rpm, and the reaction was carried out for 10.2 h to obtain core-shell particles. After centrifugation and washing, the particles were dispersed in 202.0 g of 0.085 mol / L sodium carbonate solution and etched at 81 °C for 8.2 h. Subsequently, the particles were placed in a mixture of 77.3 g ethanol and 1.2 g concentrated hydrochloric acid and extracted by heating and stirring at 60 °C for 7.8 h. After centrifugation, washing with ethanol three times, and drying, hollow mesoporous silica microspheres were obtained.

[0072] 2.1 g of hollow mesoporous silica was vacuum dried at 110 °C for 4 h, then dispersed in 70.2 g of anhydrous toluene, sonicated for 20 min, and 3.3 g of KH-570 was added. The mixture was reacted at 110 °C for 8.2 h under nitrogen protection, centrifuged, washed three times each with toluene and ethanol, and vacuum dried at 50 °C to obtain a support with methacrylate double bonds on its surface.

[0073] 1.0 g of the carrier was dispersed in a mixed solvent of 30.3 g anisole and 28.8 g DMF, and sonicated for 20 min. Then, 2.7 g GMA, 3.9 g ODMA and 0.1 g AIBN were added. After three vacuum-nitrogen-purging deoxygenation cycles, the mixture was reacted at 70 °C and 400 rpm for 8.2 h. After the reaction was completed, the mixture was centrifuged, washed with DMF until the supernatant was clear, washed three times with ethanol, and dried under vacuum at 50 °C to obtain the composite carrier with the surface grafted copolymer layer.

[0074] 1.6 g of the composite carrier was dispersed in a mixed solvent of 24.0 g isopropanol and 19.3 g DMF, and sonicated for 15 min. 1.1 g N,N-dimethylaminoethylenediamine was added, and the mixture was stirred at 51 °C for 9.5 h. After centrifugation and washing, the precipitate was redispersed in 37.8 g DMF, and 0.9 g 1,3-propanesulfonyl lactone was added. The mixture was reacted at 55 °C for 10 h, centrifuged, and washed three times each with DMF and ethanol. The mixture was then vacuum dried at 50 °C to obtain the amphoteric functionalized composite carrier.

[0075] 1.1 g of amphoteric functionalized composite carrier was vacuum dried at 61 °C to constant weight, then evacuated to 19 Pa and maintained for 2.3 h. Under vacuum, 34.5 g of D-limonene was drawn in to impregnate the carrier, followed by nitrogen gas to pressurize to 1.6 MPa, and allowed to stand for 10.5 h. After centrifugation at 3000 rpm for 5 min, the surface was dried to obtain a high-efficiency dewaxing agent for heavy crude oil loaded with D-limonene.

[0076] Example 6:

[0077] 109.7 g of anhydrous ethanol, 19.5 g of deionized water, and 5.0 g of 28% ammonia solution were added to a 500 mL three-necked flask. 9.2 g of TEOS was added dropwise at a rate of 0.46 g / min under stirring at 31 °C and 420 rpm. After the addition was complete, the reaction was continued for 3.9 h. The resulting product was centrifuged, washed three times in ethanol, and dried at 59 °C to obtain solid silica spheres.

[0078] 3.0 g CTAB was dissolved in 159.0 g deionized water, 11.8 g ethanol was added, and the pH was adjusted to 10.5 with 28% ammonia. Solid silica spheres were added, and the mixture was sonicated for 30 min to ensure thorough dispersion. 10.9 g TEOS was slowly added dropwise at 45 °C and 605 rpm, and the reaction was allowed to proceed for 9.8 h to obtain core-shell particles. After centrifugation and washing, the particles were dispersed in 198.0 g of 0.080 mol / L sodium carbonate solution and etched at 80 °C for 7.8 h. Subsequently, the particles were placed in a mixture of 76.5 g ethanol and 1.2 g concentrated hydrochloric acid and extracted by heating and stirring at 59 °C for 7.3 h. After centrifugation, washing with ethanol three times, and drying, hollow mesoporous silica microspheres were obtained.

[0079] 2.0 g of hollow mesoporous silica was vacuum dried at 110 °C for 4 h, dispersed in 68.5 g of anhydrous toluene, sonicated for 20 min, and then 3.1 g of KH-570 was added. The mixture was reacted at 110 °C for 8 h under nitrogen protection, centrifuged, washed three times each with toluene and ethanol, and vacuum dried at 50 °C to obtain a carrier with methacrylate double bonds on its surface.

[0080] 1.0 g of the carrier was dispersed in a mixed solvent of 29.9 g anisole and 28.3 g DMF, and sonicated for 20 min. Then, 2.3 g GMA, 4.2 g ODMA and 0.1 g AIBN were added. After three vacuum-nitrogen-purging deoxygenation cycles, the mixture was reacted at 69 °C and 400 rpm for 8 h. After the reaction was completed, the mixture was centrifuged, washed with DMF until the supernatant was clear, washed three times with ethanol, and dried under vacuum at 50 °C to obtain the composite carrier with the surface grafted copolymer layer.

[0081] 1.5 g of the composite carrier was dispersed in a mixed solvent of 23.6 g isopropanol and 18.9 g DMF, and sonicated for 15 min. 1.0 g N,N-dimethylaminoethylenediamine was added, and the mixture was stirred at 50 °C for 9.5 h. After centrifugation and washing, the precipitate was redispersed in 37.8 g DMF, and 0.8 g 1,3-propanesulfonyl lactone was added. The reaction was continued at 54 °C for 9.5 h. After centrifugation, the mixture was washed three times each with DMF and ethanol, and then vacuum dried at 50 °C to obtain the amphoteric functionalized composite carrier.

[0082] 1.0 g of amphoteric functionalized composite carrier was vacuum dried at 60 °C to constant weight, vacuumed to 21 Pa and maintained for 2.2 h, and 33.6 g of D-limonene was drawn in to impregnate the carrier while maintaining vacuum. Then nitrogen gas was introduced to pressurize to 1.5 MPa, and the carrier was allowed to stand for 10 h. After centrifugation at 3000 rpm for 5 min, the surface was dried to obtain a high-efficiency dewaxing agent for heavy crude oil loaded with D-limonene.

[0083] The present invention also includes comparative examples and related experiments.

[0084] Comparative Example 1:

[0085] The only difference between Comparative Example 1 and Example 1 is that after preparing hollow mesoporous silica microspheres, D-limonene was directly loaded. The other components and preparation methods were the same as in Example 1, and a high-efficiency dewaxing agent for heavy crude oil was prepared.

[0086] Comparative Example 2:

[0087] The difference between Comparative Example 2 and Example 1 is that 1,3-propanesulfonyl lactone was not used when preparing the amphoteric functionalized composite carrier. The other components and preparation methods were the same as in Example 1, and a high-efficiency dewaxing agent for heavy crude oil was prepared.

[0088] Comparative Example 3:

[0089] The difference between Comparative Example 3 and Example 1 is that ODMA was not used when preparing the composite carrier with the surface grafted copolymer layer. The other components and preparation methods are the same as in Example 1, and a high-efficiency dewaxing agent for heavy crude oil is prepared.

[0090] Comparative Example 4:

[0091] The difference between Comparative Example 4 and Example 1 is that D-limonene loading was not performed, but the other components and preparation methods were the same as in Example 1, and a high-efficiency dewaxing agent for heavy crude oil was prepared.

[0092] Performance testing

[0093] 1. The D-limonene loading and heat retention rate of the high-efficiency dewaxing agents for heavy crude oil prepared in Examples 1-6 and Comparative Examples 1-4 were determined.

[0094] The D-limonene content was determined by thermogravimetric analysis. The sample was heated from 30℃ to 300℃ under nitrogen protection at a heating rate of 10℃ / min. The D-limonene loading was calculated using an empty support as a reference. The loading was calculated according to the following formula:

[0095] Load (wt%) = (m1 - m0) / m1 × 100%;

[0096] Where m1 is the mass of the sample after loading, and m0 is the mass of the corresponding empty carrier.

[0097] The heat retention rate test method is as follows: Weigh the sample, keep it at 60℃ for 6 hours, and then measure the residual amount of D-limonene again. Calculate the retention rate using the following formula:

[0098] Retention rate (%) = m2 / m3 × 100%;

[0099] Where m2 is the mass of D-limonene in the sample after isothermal treatment, and m3 is the mass of D-limonene in the sample before isothermal treatment.

[0100] In summary, the test results are shown in Table 1.

[0101] Table 1. Test results of D-limonene loading and retention rate

[0102]

[0103] As shown in Table 1, the D-limonene loading of Examples 1-6 was 63.9-66.2 wt%, and the retention rate after incubation at 60℃ for 6 hours was 87.4%-89.3%, both significantly better than Comparative Examples 1, 2, and 3. This indicates that the present invention, through the synergistic design of hollow mesoporous silica support, surface grafted copolymer layer, and amphoteric functionalization, not only improves the loading capacity of D-limonene but also enhances its thermal stability retention. Comparative Example 1 relied solely on hollow mesoporous silica for physical loading, resulting in significantly lower loading and retention rates, indicating that relying solely on the mesoporous structure itself is insufficient to achieve the loading effect of the present invention. Comparative Example 2, without amphoteric treatment, had a lower retention rate than Examples 1-6, indicating that the zwitterionic structure is beneficial for improving the surface interface environment and enhancing the constraint on D-limonene. Comparative Example 3, lacking the ODMA long-chain copolymer segment, also showed a decrease in loading and retention performance, indicating that the long-chain oleophobic segment helps to create a more suitable environment for the existence of D-limonene.

[0104] 2. The wax-removing and wax-preventing performance of the high-efficiency heavy crude oil dewaxing and anti-waxing agents prepared in Examples 1-6 and Comparative Examples 1-4 was tested. The crude oil used for testing was high-wax heavy crude oil, and its main indicators for blank oil samples were as follows: wax precipitation point 42.6℃, pour point 31.8℃, apparent viscosity at 30℃ 13150 mPa·s, and yield value at 25℃ 47.8 Pa. The addition amount for each sample was 1000 mg / kg (based on the total sample mass, relative to the crude oil mass), and the test method was as follows:

[0105] 1) Add the sample to the crude oil and stir at 60℃ for 30 min to disperse it evenly. After standing for 4 h, determine the wax precipitation point and pour point of the crude oil. The wax precipitation point is determined by microscopic observation and the pour point is determined by conventional low temperature cooling method.

[0106] 2) Add the sample to crude oil and stir at 60℃ for 30 min. Then cool to the test temperature and use a rotational rheometer to determine the apparent viscosity at 30℃ and the yield value at 25℃.

[0107] 3) The anti-wax performance of the samples was evaluated using the cold finger deposition method. The crude oil after adding the sample was kept at a constant temperature of 45℃, and the cold finger temperature was controlled at 20℃. After deposition for 4 hours, the cold finger was removed, and free oil on the surface was removed. The amount of wax deposited was weighed under the same conditions, and the deposition inhibition rate was calculated using the following formula:

[0108] Deposition inhibition rate (%) = (m4-m5) / m4×100%, where m4 is the amount of wax deposition in the blank oil sample and m5 is the amount of wax deposition in the oil sample after sample addition;

[0109] 4) The wax removal ability of the sample was evaluated using a standard wax deposition layer removal experiment. An initial wax deposition layer was first prepared on the surface of a metal sheet, which was then placed in crude oil containing the sample and stirred at 35°C for 60 minutes. The metal sheet was then removed and the residual wax content was weighed. The wax removal rate was calculated using the following formula:

[0110] Wax removal rate (%) = (m6-m7) / m6×100%, where m6 is the amount of wax deposited before treatment and m7 is the amount of residual wax after treatment;

[0111] Each group was measured in parallel three times, and the average value of the results was taken. The test results are shown in Table 2.

[0112] Table 2 Results of wax removal and anti-wax performance tests

[0113]

[0114] As shown in Table 2, after treatment with the wax-preventing and dewaxing agents prepared in Examples 1-6, the wax precipitation point of crude oil decreased to 33.8-35.2℃, the pour point decreased to 18.9-21.0℃, the apparent viscosity at 30℃ decreased to 4470-5180 mPa·s, and the yield value at 25℃ decreased to 18.9-23.5 Pa, indicating that the samples of this invention can significantly improve the low-temperature fluidity of high-wax heavy crude oil. Meanwhile, the wax deposition amount in Examples 1-6 was only 0.34-0.49 g, the deposition inhibition rate reached 74.5%-82.3%, and the wax removal rate reached 82.9%-89.8%, indicating that the samples possess both excellent wax-preventing and wax-removing capabilities.

[0115] Compared with Comparative Example 1, Example 1 showed significantly better performance in all indicators, including wax precipitation point, pour point, low-temperature rheology, wax prevention, and wax removal. This indicates that the effectiveness of the present invention is not solely due to the physical loading of D-limonene onto the hollow mesoporous silica, but is closely related to the surface grafted copolymer layer and amphoteric functionalization. Compared with Comparative Example 2, Example 1 further improved in all aspects, indicating that the zwitterionic groups introduced by 1,3-propanesulfonyl lactone can improve the dispersion stability and interfacial compatibility of the sample in crude oil, thereby enhancing the wax removal and prevention effect. Compared with Comparative Example 3, Example 1 showed significant advantages in reducing the wax precipitation point, decreasing viscosity, and inhibiting wax deposition, indicating that the long-chain segments of ODMA played an important role in interfering with wax crystal nucleation, growth, and aggregation. Comparative Example 4, an empty amphoteric functionalized composite carrier, showed significantly lower wax removal and prevention rates than Example 1, indicating that the introduction of D-limonene makes a significant contribution to achieving efficient wax removal and improving the overall wax prevention effect.

Claims

1. A method for preparing a high-efficiency dewaxing and anti-waxing agent for heavy crude oil, characterized in that, Includes the following steps: Step S1: Dissolve hexadecyltrimethylammonium bromide in water and add ethanol. After adjusting the pH, add solid silica spheres, disperse by ultrasonication, and add tetraethyl orthosilicate dropwise for heating and stirring reaction. Then, etch with sodium carbonate solution and extract with acid to obtain hollow mesoporous silica microspheres. Then, use KH-570 to modify the surface of the hollow mesoporous silica microspheres to obtain a carrier with methacrylate double bonds on the surface. Step S2: Disperse 0.9-1.1 parts by weight of the carrier in a mixed solvent of anisole and N,N-dimethylformamide, and graft copolymerize it with 2.2-2.8 parts by weight of glycidyl methacrylate, 3.8-4.4 parts by weight of octadecyl methacrylate and 0.09-0.11 parts by weight of azobisisobutyronitrile in the presence of an initiator to obtain a composite carrier with a surface graft copolymer layer; Step S3: Disperse 1.4-1.6 parts by weight of the composite carrier with surface grafted copolymer layer in a mixed solvent of 22.6-24.5 parts by weight of isopropanol and N,N-dimethylformamide, react it first with 0.9-1.1 parts by weight of N,N-dimethylaminoethylenediamine, and then react it with 0.7-0.9 parts by weight of 1,3-propanesulfonyl lactone to obtain the amphoteric functionalized composite carrier; Step S4: After vacuum drying, the amphoteric functionalized composite carrier is loaded with D-limonene by vacuum adsorption and pressure impregnation to obtain a high-efficiency dewaxing agent for heavy crude oil.

2. The preparation method of a high-efficiency dewaxing agent for heavy crude oil according to claim 1, characterized in that, The preparation of the solid silica spheres includes the following steps: Anhydrous ethanol, deionized water, and ammonia were mixed and stirred at 30-32℃ and 390-430 rpm. Tetraethyl orthosilicate was added dropwise at a rate of 0.45-0.51 g / min. After the addition was completed, the reaction was continued for 3.9-4.3 h. The mixture was then centrifuged, washed with ethanol, and dried to obtain solid silica spheres.

3. The preparation method of a high-efficiency dewaxing agent for heavy crude oil according to claim 1, characterized in that, In step S1, the pH is adjusted to 10.4-10.6; the ultrasonic dispersion time is 28-32 min; the temperature for heating and stirring is 44-46℃, and the speed is 580-630 rpm.

4. The preparation method of a high-efficiency dewaxing agent for heavy crude oil according to claim 1, characterized in that, In step S1, the concentration of the sodium carbonate solution is 0.075-0.09 mol / L, the etching temperature is 79-82℃, and the etching time is 7.2-8.5 h.

5. The preparation method of a high-efficiency dewaxing agent for heavy crude oil according to claim 1, characterized in that, The carrier comprises the following components in parts by weight: Hollow mesoporous silica 1.8-2.2 parts, anhydrous toluene 65.9-71.1 parts, and KH-570 2.8-3.4 parts.

6. The preparation method of a high-efficiency dewaxing agent for heavy crude oil according to claim 1, characterized in that, In step S4, the amphoteric functionalized composite carrier is vacuum dried at 58-62℃ to constant weight, and then evacuated to 18-25 Pa and held for 2.0-2.5 h.

7. The preparation method of a high-efficiency dewaxing agent for heavy crude oil according to claim 1, characterized in that, In step S4, the weight of D-limonene is 32.0-35.3 parts; the pressure for impregnation is 1.4-1.6 MPa, and the time is 9-11 h.

8. A high-efficiency dewaxing and anti-waxing agent for heavy crude oil, characterized in that, It is prepared by the method described in any one of claims 1-7 for a high-efficiency dewaxing agent for heavy crude oil.

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