Vinyl copolymer pour point depressant as well as preparation method and application thereof

Abstract

The invention discloses a vinyl copolymer pour point depressant as well as a preparation method and application thereof, and relates to the technical field of vinyl copolymer pour point depressants. Acrylamide, a methacrylate compound, a fumaric acid compound and alkyl coupling agent modified nano silicon dioxide are used as monomers, and the prepared copolymer pour point depressant has the characteristics and characteristic chemical bonds of copolymer macromolecules; due to the specific molecular chain and structure of the copolymer, the flexibility and flexibility variation range of copolymer molecules in the presence of dissolution or a solution is extremely large, crude oil can be quickly and effectively dispersed, the fluidity of the crude oil can be enhanced, blockage is reduced, and the oil production amount is increased; and the condensation point and the viscosity of crude oil can be obviously reduced under the condition of a very small amount (such as 500ppm).

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority of a Chinese patent application with the application number 2024115972368, titled "A Vinyl Copolymer Pour Point Depressant, Its Preparation Method and Application", filed with the Chinese Patent Office on November 11, 2024, the entire content of which is incorporated herein by reference. Technical field

[0003] The present invention relates to the technical field of vinyl copolymer pour point depressants, and more particularly, to a vinyl copolymer pour point depressant, its preparation method and application. Background technique

[0004] Energy is a necessity for human survival and development, and petroleum obtained from crude oil processing is an important part of human production and life. Therefore, the exploitation, transportation, and storage of crude oil are particularly important. However, the high wax content in crude oil leads to a high freezing point and high viscosity, which in turn causes problems such as difficult oil extraction, low efficiency, and difficult transportation. Pour point depressants are commonly used additives in the process of crude oil exploitation and transportation. By adding a small amount of pour point depressant, the freezing point of crude oil can be significantly reduced, the viscosity can be significantly decreased, and no special post - treatment process is required. Using pour point depressants has advantages such as less dosage, convenient use, good effect, and low cost compared with heating and dilution methods.

[0005] The principle of adding a small amount of pour point depressant to crude oil to achieve significant effects is as follows: The pour point depressant can solubilize the wax, change the nucleation and growth of wax crystals, inhibit the formation of reticulated fine crystals, or play a good dispersing role. Currently discovered pour point depressants all have polar groups (such as carbonyl groups, etc.) and non - polar groups (long - chain alkyl groups, phenyl groups, etc.), and are typical surfactants with relatively special structures. Due to the extremely complex composition of crude oil and the complex and variable nature of oil well geological structures, different oil wells in different regions and crude oil exploitation at different stages require different pour point depressants, that is, general pour point depressants do not have universality. The common defects of currently used pour point depressants are: they cannot be quickly and effectively dispersed in crude oil while ensuring efficiency, and the dosage is still relatively high (generally 800 ppm - 1800 ppm).

[0006] Therefore, there is an urgent need to develop a pour point depressant that can not only significantly reduce the freezing point and viscosity of crude oil but also quickly and effectively disperse crude oil.

[0007] In view of this, the present invention is specifically proposed. Summary of the invention

[0008] The purpose of the present invention is to provide a vinyl copolymer pour point depressant, its preparation method and application, aiming to improve the effect of reducing pour point and viscosity on the premise of significantly reducing the dosage of the pour point depressant.

[0009] The present invention is implemented as follows:

[0010] In a first aspect, the present invention provides a vinyl copolymer pour point depressant, which is obtained by polymerizing monomers including acrylamide, methacrylate compounds, fumaric acid compounds, and nano-silica modified with an alkyl coupling agent;

[0011] The weight ratio of the fumaric acid compounds, acrylamide, and methacrylate compounds is (1 - 2):(1 - 2):(3 - 7);

[0012] The weight ratio of the total amount of the fumaric acid compounds, acrylamide, and methacrylate compounds to the nano-silica modified with an alkyl coupling agent is (20 - 45):1.

[0013] In an optional embodiment, the fumaric acid compounds are selected from at least one of fumaric acid, monoethyl fumarate, and diethyl fumarate.

[0014] In an optional embodiment, in the fumaric acid compounds, the weight ratio of fumaric acid, monoethyl fumarate, and diethyl fumarate is (1 - 3):(0 - 1):(0 - 1).

[0015] In an optional embodiment, the methacrylate compounds are selected from at least one of octadecyl methacrylate and hexadecyl methacrylate.

[0016] In an optional embodiment, in the methacrylate compounds, the weight ratio of octadecyl methacrylate and hexadecyl methacrylate is (1 - 3):(0 - 1).

[0017] In a second aspect, the present invention provides a preparation method of the vinyl copolymer pour point depressant according to any one of the foregoing embodiments, including: using acrylamide, methacrylate compounds, fumaric acid compounds, and nano-silica modified with an alkyl coupling agent as monomers to carry out a polymerization reaction.

[0018] In an optional embodiment, it includes: mixing the monomers with a solvent and heating to 55°C - 95°C, adding an initiator and polymerizing for 4h - 9h;

[0019] Wherein, the initiator is selected from at least one of potassium persulfate, sodium persulfate, ammonium persulfate, azobisisobutyronitrile, and azobisisovaleronitrile; the mass ratio of the initiator to the total amount of the monomers is (0.1 - 0.5):100;

[0020] The solvent is selected from at least one of toluene, xylene, butanol, isobutanol, propanol, isopropanol, and ethanol;

[0021] After the polymerization reaction is completed, the solvent is distilled to obtain a solid material, and the solid material is washed and dried.

[0022] In an alternative embodiment, the preparation process of the alkyl coupling agent-modified nano-silica includes:

[0023] Hydrolyze the silane coupling agent for 0.5 h - 4 h under the conditions of a pH value of 4 - 7 and a temperature of 30°C - 65°C to obtain a hydrolysis reaction material;

[0024] Carry out a coupling grafting reaction on the nano-silica and the hydrolysis reaction material, and control the reaction temperature to be 55°C - 95°C and the reaction time to be 4 h - 9 h.

[0025] In an alternative embodiment, the silane coupling agent is selected from at least one of A171, A173, ZQ172, and KH570;

[0026] And / or, the mass ratio of the nano-silica to the silane coupling agent is (3 - 5):1.

[0027] In a third aspect, the present invention provides the application of the vinyl copolymer pour point depressant in any of the foregoing embodiments or the vinyl copolymer pour point depressant prepared by the preparation method in any of the foregoing embodiments in treating waxy crude oil;

[0028] Among them, the addition amount of the vinyl copolymer pour point depressant is 400 ppm - 600 ppm.

[0029] The present invention has the following beneficial effects: The present invention uses acrylamide, fumaric acid compounds, methacrylate compounds, and alkyl coupling agent-modified nano-silica as monomers, and the prepared copolymer pour point depressant has the characteristics of copolymer macromolecules and characteristic chemical bonds. Due to the unique molecular chain and structure of the copolymer, the flexibility and extensibility of the copolymer molecules vary greatly in the dissolved or solution state, and it can quickly and effectively disperse crude oil, and can significantly reduce the pour point and viscosity of crude oil under the condition of a very small dosage (such as 500 ppm). BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is the infrared characterization diagram of the vinyl copolymer pour point depressant prepared in Example 1 of the present invention; (a) represents SiO2; (b) represents OSiO2; (c) represents the product of Example 1 of the present application;

[0032] Figure 2SEM images of the raw material silica, graft-modified nano-silica, and the copolymer obtained in Step (2) in Example 1; among them, (a) represents silica; (b) represents nano-silica modified with an alkyl coupling agent; (c) represents the copolymer. Detailed implementation manners

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0034] Aiming at the problems of high dosage and unsatisfactory crude oil dispersion effect existing in the existing pour point depressants, the embodiments of the present invention improve the monomer types and ratios of the vinyl copolymer pour point depressant, so that the prepared vinyl copolymer pour point depressant can significantly reduce the pour point and viscosity of crude oil under the condition of very little dosage (such as 500 ppm), and the pour point of crude oil can be reduced by about 30 °C, and the pour point depressing effect is very remarkable.

[0035] The embodiments of the present invention provide a preparation method of a vinyl copolymer pour point depressant, which is obtained by polymerizing acrylamide, methacrylate compounds, fumaric acid compounds, and nano-silica modified with an alkyl coupling agent as monomers. The specific steps are as follows:

[0036] S1. Prepare nano-silica modified with an alkyl coupling agent

[0037] The nano-silica modified with an alkyl coupling agent is obtained by modifying nano-silica with an alkyl coupling agent. Due to the introduction of the alkyl coupling agent, the nano-silica modified with an alkyl coupling agent can participate in the subsequent polymerization reaction, introducing large groups at the nanoscale (20 - 60 nm) into the main chain of the polymer molecule. This large group also has certain structures and polar and non-polar groups, which can further adjust the molecular structure, the ratio and distribution of polar and non-polar groups of the copolymer.

[0038] In some embodiments, the preparation process of the nano-silica modified with an alkyl coupling agent includes: first, hydrolyze the silane coupling agent sufficiently, and then perform an coupling grafting reaction with the nano-silica. In the actual operation process, it includes the following steps: hydrolyze the silane coupling agent under the conditions of a pH value of 4 - 7 and a temperature of 30 °C - 65 °C for 0.5 h - 4 h to obtain a hydrolysis reaction material; perform an coupling grafting reaction on the nano-silica and the hydrolysis reaction material, and control the reaction temperature at 55 °C - 95 °C and the reaction time at 4 h - 9 h. By regulating the hydrolysis conditions of the silane coupling agent (such as the stirring intensity - rate and the form of the stirring paddle), the purpose of sufficient hydrolysis is achieved to improve the grafting rate with the nano-silica.

[0039] Specifically, the pH value of the hydrolysis reaction of the silane coupling agent can be 4.0, 5.0, 6.0, 7.0, etc., the hydrolysis temperature can be 30°C, 40°C, 50°C, 60°C, 65°C, etc., and the hydrolysis time can be 0.5 h, 1.0 h, 2.0 h, 3.0 h, 4.0 h, etc.; the reaction temperature during the coupling grafting of nano-silica and the hydrolysis reaction material can be 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, etc., and the reaction time can be 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, etc. After the coupling grafting reaction is completed, solid-liquid separation can be carried out by means such as filtration, and the obtained solid material is washed and dried to obtain nano-silica modified by an alkyl coupling agent for subsequent use as a monomer in synthesizing a pour point depressant.

[0040] In some embodiments, the silane coupling agent is selected from at least one of A171, A173, ZQ172, and KH570, and the silane coupling agent can be any one or several of the above. The mass ratio of nano-silica to the silane coupling agent is (3 - 5):1, such as 3:1, 4:1, 5:1, etc. By regulating the mass ratio of nano-silica to the silane coupling agent to control the introduction amount of the silane coupling agent, and further regulating the structure of the vinyl copolymer pour point depressant, the effect of reducing pour point and viscosity can be further improved. The particle size of the nano-silica is at the nano level, and the specific particle size can be 20 nm - 60 nm.

[0041] S2. Polymerization reaction

[0042] Using acrylamide, methacrylate compounds, fumaric acid compounds, and nano-silica modified by an alkyl coupling agent as monomers, a polymerization reaction is carried out.

[0043] It should be noted that in the embodiments of the present invention, a variety of comonomers are used, so that the vinyl copolymer pour point depressant product has a rich, adjustable and three-dimensional molecular configuration adapted to complex crude oils, with polar groups and non-polar groups; and because a large group at the nano scale is introduced into the main chain of the polymer molecule by grafting, this large group also has a certain structure and polar groups and non-polar groups, which can further adjust the molecular structure of the copolymer and the ratio and distribution of polar groups and non-polar groups. This vinyl copolymer pour point depressant with a brand-new molecular structure has excellent oil solubility and water solubility with a wide adaptation range, and the molecular flexibility and stretchability are greatly improved. It can not only increase the solubility of crude oil wax in the system and change the nucleation and growth characteristics of wax crystals, but also be quickly and effectively dispersed in the crude oil system (due to the simultaneous presence of polar and non-polar substances in crude oil and the presence of dispersed microemulsion water phases, etc.), which makes the pour point depressant have excellent pour point and viscosity reduction effects.

[0044] In some embodiments, the weight ratio of the fumaric acid compound, acrylamide, and methacrylate compound is (1 - 2):(1 - 2):(3 - 7); the weight ratio of the total amount of the fumaric acid compound, acrylamide, and methacrylate compound to the alkyl-coupling agent-modified nano-silica is (20 - 45):1. By regulating the dosages of several monomers, the three-dimensional molecular configuration of the vinyl copolymer pour point depressant is further regulated to enhance its compatibility with complex crude oil and improve the pour point depressing and viscosity reducing effects of the pour point depressant.

[0045] Specifically, the weight ratio of the fumaric acid compound, acrylamide, and methacrylate compound can be 1.0:1.0:3.0, 1.3:1.3:4.0, 1.5:1.5:5.0, 1.8:1.8:6.0, 2.0:2.0:7.0, etc.; the weight ratio of the total amount of the fumaric acid compound, acrylamide, and methacrylate compound to the alkyl-coupling agent-modified nano-silica can be 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, etc.

[0046] In some embodiments, the fumaric acid compound is selected from at least one of fumaric acid, monoethyl fumarate, and diethyl fumarate, and the fumaric acid compound can be any one or several of the above. In a preferred embodiment, in the fumaric acid compound, the weight ratio of fumaric acid, monoethyl fumarate, and diethyl fumarate is (1 - 3):(0 - 1):(0 - 1), such as 1.0:0:0, 1.5:0.1:0.1, 2.0:0.3:0.3, 2.5:0.5:0.5, 2.8:0.8:0.8, 3.0:1.0:1.0, etc.

[0047] In some embodiments, the methacrylate compound is selected from at least one of octadecyl methacrylate and hexadecyl methacrylate, and the methacrylate compound can be any one or several of the above. In the methacrylate compound, the weight ratio of octadecyl methacrylate and hexadecyl methacrylate is (1 - 3):(0 - 1), such as 1.0:0.0, 1.5:0.3, 2.0:0.5, 2.5:0.8, 3.0:1.0, etc.

[0048] In some embodiments, the specific operating steps of the polymerization reaction include: mixing the monomer and the solvent and heating to 55°C - 95°C (such as 55°C, 60°C, 70°C, 80°C, 90°C, 95°C, etc.), adding a radical initiator under reflux conditions and polymerizing for 4 h - 9 h (such as 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, etc.). By controlling the polymerization temperature and time, the reaction proceeds sufficiently. The initiator is selected from at least one of potassium persulfate, sodium persulfate, ammonium persulfate, azodiisobutyronitrile, and azodiisooctanenitrile. The initiator can be any one or several of the above; the mass ratio of the initiator to the total amount of the monomer is (0.1 - 0.5):100, such as 0.1:100, 0.2:100, 0.3:100, 0.4:100, 0.5:100, etc. It is appropriate within this dosage range to promote the polymerization reaction.

[0049] Further, the solvent is selected from at least one of toluene, xylene, butanol, isobutanol, propanol, isopropanol, and ethanol. The solvent can be any one or several of the above.

[0050] Further, after the polymerization reaction is completed, the solvent is distilled to obtain a solid material, and the solid material is washed and dried to obtain the copolymer product pour point depressant. The washing method is not limited and can be multiple water washes to fully remove unreacted raw materials, and then the washing solvent is removed by drying to obtain the final product.

[0051] The embodiment of the present invention also provides a vinyl copolymer pour point depressant, which is obtained by polymerizing monomers including acrylamide, methacrylate compounds, fumaric acid compounds, and alkyl-coupled agent-modified nano-silica; wherein, the alkyl-coupled agent-modified nano-silica is obtained by modification with an alkyl-coupled agent. The ratio of each monomer can refer to the description in the above preparation method and will not be repeated here.

[0052] It should be noted that the vinyl copolymer pour point depressant provided by the embodiment of the present invention has excellent oil solubility and water solubility with a wide adaptability range, and the molecular flexibility and stretchability are greatly improved. It can not only increase the solubility of crude oil wax in the system and change the wax crystal nucleation and growth characteristics, but also be quickly and effectively dispersed in the crude oil system, and can have excellent pour point and viscosity reduction effects even with a very small dosage.

[0053] The embodiment of the present invention also provides the application of the above vinyl copolymer pour point depressant in treating waxy crude oil. The unique molecular chain and structure of the vinyl copolymer pour point depressant enable the flexibility and stretchability of the copolymer molecules to vary greatly in the dissolved or solution state, and it can be quickly and effectively dispersed in the crude oil, and can significantly reduce the pour point and viscosity of the crude oil even with a very small dosage.

[0054] In some embodiments, the addition amount of the vinyl copolymer pour point depressant is 400 ppm - 600 ppm, such as 400 ppm, 450 ppm, 500 ppm, 550 ppm, 600 ppm, etc., and preferably 500 ppm.

[0055] The features and properties of the present invention will be further described in detail below in conjunction with the embodiments.

[0056] Example 1

[0057] This example provides a preparation method of a vinyl copolymer pour point depressant, and the steps are as follows:

[0058] (1) Prepare alkyl coupling agent-modified nano-silica

[0059] Weigh 4.00 g of nano-silica with an average particle size of 37 nm, and weigh 1.00 g of silane coupling agent (KH570).

[0060] Mix and stir the silane coupling agent and 1.5 mL of deionized water, adjust the pH value to 5 with a 10% by mass dilute hydrochloric acid solution, and hydrolyze for 1 h at 39 °C to obtain a hydrolysis reaction material.

[0061] Mix and stir the nano-silica and 40 mL of propanol, heat to 70 °C, mix and stir with the hydrolysis reaction material, and carry out a grafting reaction at 70 °C for 8 h. After the reaction is completed, carry out separation, and obtain alkyl coupling agent-modified nano-silica after washing with water and drying (100 °C, 5 h) for use in synthesizing the pour point depressant.

[0062] (2) Polymerization reaction

[0063] Weigh 14.29 g of acrylamide, 28.57 g of octadecyl methacrylate, 7.14 g of fumaric acid, and 2.00 g of modified nano-silica monomer.

[0064] Add the monomers of the above weights into a four-necked flask containing a total volume of 120 mL of xylene and butanol (volume ratio 1:1, the same below), stir and heat up to reflux, and dropwise add 20 mL of azobisisoheptonitrile solution at 65 °C. The dropping time is 100 min, and continue to keep the temperature for reaction for 5 h after the dropping is completed. After the reaction is completed, distill the solvent, and then wash with water and dry (100 °C, 3 h).

[0065] Example 2

[0066] This example provides a preparation method of a vinyl copolymer pour point depressant, and the steps are as follows:

[0067] (1) Prepare alkyl coupling agent-modified nano-silica

[0068] For the specific steps, refer to Example 1.

[0069] (2) Polymerization reaction

[0070] Weigh 14.29 g of acrylamide, 28.57 g of octadecyl methacrylate, 5.9 g of fumaric acid, 2.00 g of monoethyl fumarate, and 2.00 g of modified nano-silica monomer.

[0071] Add the monomers of the above weights into a four-necked flask containing 120 mL of xylene and butanol respectively, stir and heat up to reflux, and dropwise add 20 mL of azodiisooctanenitrile solution at 65 °C. The dropping time is 100 min. After the dropping is completed, continue to keep the temperature for reaction for 5 h. After the reaction is completed, distill the solvent, and then wash with water and dry (at 100 °C for 3 h).

[0072] Example 3

[0073] The difference from Example 1 is only that: in step (2), the type of monomer methacrylate is different. Weigh 14.29 g of acrylamide, 28.57 g of hexadecyl methacrylate, 7.14 g of fumaric acid, and 2.00 g of modified nano-silica monomer.

[0074] Example 4

[0075] The difference from Example 1 is only that: in step (2), the dosage of the monomer is different. Weigh 21.44 g of acrylamide, 42.86 g of octadecyl methacrylate, 11.85 g of fumaric acid, and 2.00 g of modified nano-silica monomer.

[0076] Note: In this example, the weight ratio of the total amount of fumaric acid compounds, acrylamide, and methacrylate compounds to the weight of nano-silica modified by alkyl coupling agent is 38:1, and the weight ratio of fumaric acid compounds, acrylamide, and methacrylate compounds is 1:1.8:3.61.

[0077] Example 5

[0078] The difference from Example 1 is only that: in step (1), the dosage of nano-silica is 4.00 g, the dosage of silane coupling agent is 1.3 g, and the weight ratio of nano-silica to silane coupling agent is 3:1.

[0079] Comparative Example 1

[0080] The pour point depressant provided in this comparative example is an octadecyl acrylate-maleic anhydride copolymer pour point depressant, and the preparation method is as follows: refer to Example 1 of Patent 201910527927.3.

[0081] Comparative Example 2

[0082] The pour point depressant provided in this comparative example refers to an aniline aminated pour point depressant of octadecyl acrylate-maleic anhydride copolymer, and the preparation method is as follows: Refer to Example 3 of Patent 201910527927.3.

[0083] Comparative Example 3

[0084] The difference from Example 1 is only that: in step (2), the dosages of the monomers are different. Weigh 14.29 g of acrylamide, 17.86 g of octadecyl methacrylate, 7.14 g of fumaric acid, and 2.00 g of modified nano-silica monomer.

[0085] Note: In this comparative example, the weight ratio of the total amount of fumaric acid compounds, acrylamide, and methacrylate compounds to the alkyl-coupling agent-modified nano-silica is 19.6:1, and the weight ratio of fumaric acid compounds, acrylamide, and methacrylate compounds is 1:2.0:2.5.

[0086] Comparative Example 4

[0087] The difference from Example 1 is only that: in step (2), the dosages of the monomers are different. Weigh 9.52 g of acrylamide, 19.05 g of octadecyl methacrylate, 5.27 g of fumaric acid, and 2.00 g of modified nano-silica monomer.

[0088] Note: In this comparative example, the weight ratio of the total amount of fumaric acid compounds, acrylamide, and methacrylate compounds to the alkyl-coupling agent-modified nano-silica is 16.92:1, and the weight ratio of fumaric acid compounds, acrylamide, and methacrylate compounds is 1:1.8:3.6.

[0089] Comparative Example 5

[0090] The difference from Example 1 is only that: do not add the modified nano-silica monomer; 14.29 g of acrylamide, 28.57 g of octadecyl methacrylate, and 7.14 g of fumaric acid.

[0091] Comparative Example 6

[0092] The difference from Example 1 is only that: do not add fumaric acid; 14.29 g of acrylamide, 28.57 g of octadecyl methacrylate, and 2.00 g of modified nano-silica monomer.

[0093] Comparative Example 7

[0094] The difference from Example 1 is only that: do not add acrylamide; 28.57 g of octadecyl methacrylate, 7.14 g of fumaric acid, and 2.00 g of modified nano-silica monomer.

[0095] Test Example 1

[0096] The ethylene copolymer pour point depressant prepared in Example 1 was characterized by infrared spectroscopy, and the results are as follows Figure 1 shown.

[0097] Figure 1 As shown in (a), the anti-symmetric stretching vibration peak and symmetric stretching vibration of Si-O-Si are around 1056 cm -1 and 800 cm -1 respectively, and the absorption peak at 474 cm -1 is the bending vibration of Si-O-Si. (a) is the raw material of nano-SiO2. Figure 1 After organic grafting in (b), the vibration peak appearing at 1703 cm -1 may be the carbon-carbon double bond, or the stretching vibration of the carboxyl group bond (C=O) on the silane coupling agent, or the result of the joint reflection of the carbon-carbon double bond and the carbon-oxygen double bond, that is, the stronger stretching vibration of the carboxyl group (C=O) and the weaker stretching vibration of the carbon-carbon double bond (C=C) affect each other, resulting in the offset, interlacing and masking of these two characteristic peaks, and thus showing a peak at 1703 cm -1 . Whether the vibration peak appearing at 1703 cm -1 is attributed to the carbon-carbon double bond or the stretching vibration of the carboxyl group bond, it can prove that the silane coupling agent of this application has been successfully grafted onto nano-silica. (b) is the graft-modified nano-SiO2.

[0098] Figure 1 As shown in (c), for the ethylene copolymer product of this application, the stretching vibration absorption peak of Si-O-Si is around 1044 cm -1 , and the bending vibration absorption peak of Si-O-Si is around 465 cm -1 . The rest are the absorption peaks of the polymer. The stretching vibration absorption peak of the primary amine -NH2 is observed at the high wavenumbers of 3200 cm -1 and 3343 cm -1 . The characteristic stretching vibration absorption peaks of -CH3 and -CH2 appear at 2917 cm -1 and 2850 cm -1 . The characteristic bending vibration absorption peak of -(CH) n - appears at 723 cm -1 . At 1670 - 1640 cm -1 , the stretching vibration absorption peak of the C=C bond disappears, indicating that there are no unreacted monomers in the copolymer. The absorption peak of C=O is also observed at 1708 cm -1 , from the carboxylic acid dimer. The peak intensity and absorption band width increase with the increase of the molar fraction of the carboxylic acid dimer at 1708 - 1724 cm -1 . It fully proves the structural characteristics of the vinyl copolymer nano pour point depressant of the monomers of this application product. (c) is the pour point depressant product containing graft-modified nano-SiO2.

[0099] Test Example 2

[0100] The pour point depressing and viscosity reducing effects of the pour point depressants prepared in the test examples and comparative examples were tested, and the test results are shown in Table 1.

[0101] High wax-containing crude oil was used as the experimental oil. The wax content of this experimental oil was 9%, the resin and asphaltene content was 8.3% (by weight), the pour point was 12 °C, and the viscosity was 82.6 Pa·s (20 °C).

[0102] Test method: The viscosity in this example was the measured value of the crude oil added with 500 ppm of the pour point depressant at 20 °C.

[0103] Table 1 Pour point depressing and viscosity reducing effects of the pour point depressants prepared in the examples and comparative examples

[0104]

[0105]

[0106] It can be seen that there are huge differences in the viscosity reducing and pour point depressing effects of different pour point depressants, which may be due to: the differences in the structures of the pour point depressant molecules (largely depending on the differences in monomer molecules and structures); the reason for the excellent performance of the nano pour point depressant provided in the examples of the present invention is also that nano silica large groups are introduced by the grafting method in the copolymer molecular chain, so that the pour point depressant further improves and enriches the hydrophilic and lipophilic groups from the perspective of molecular structure. Therefore, when the pour point depressant provided in the examples of the present invention is used in the crude oil system, it can be effectively and rapidly dispersed and distributed, and is more compatible with various substances in the crude oil system, and can act together in solubilization, dispersion and crystal modification.

[0107] Test Example 3

[0108] The pour point depressing and viscosity reducing effects of the vinyl copolymer pour point depressant provided in Test Example 1 under different dosages were tested, and the results are shown in Table 2.

[0109] Table 2 Pour point depressing and viscosity reducing effects of the vinyl copolymer pour point depressant in Example 1 under different dosages

[0110] Dosage Pour Point (°C) Drop (°C) Viscosity (Pa.s) Drop (Pa.s) 250 ppm -14.0 26.0 26.1 56.5 400 ppm -16.5 28.5 20.9 61.7 500 ppm -18.0 30.0 17.4 65.2 600 ppm -17.0 29.0 19.6 63.0 700 ppm -16.5 29.0 20.9 61.7

[0111] It can be seen that under the condition of a dosage of 500 ppm, the pour point depressing and viscosity reducing effects are the best.

[0112] Test Example 4

[0113] The SEM images of the raw material silica, the nano silica modified by an alkyl coupling agent and the copolymer obtained in step (2) in Test Example 1 are as Figure 2 shown.

[0114] Figure 2 Shows the scanning electron microscope images of the original nano-silica and the nano-silica after organic grafting. Nano-silica is spherical, but due to surface effects, van der Waals forces, and hydrogen bonding, it is prone to aggregation, clustering, and difficult to disperse in organic solvents. After modification with KH570, the tendency of nano-particles to agglomerate is weakened, the particle size becomes smaller, and the distribution distance is more uniform. This is because the siloxane bonds on the surface of OSiO2 particles are incorporated with organic groups, reducing the number of active siloxane bonds and the attraction strength between particles. At the same time, the grafted long carbon chains increase the distance between particles. The copolymer picture shows that the organic silica is evenly distributed in the polymer matrix, without spherical or flaky structures, proving that the nano-silica is evenly dispersed in the polymer matrix. (a) is the raw material nano-SiO2; (b) is the nano-SiO2 after grafting modification; (c) is the pour point depressant product containing the grafted modified nano-SiO2.

[0115] Test Example 5

[0116] Using the nano-particle size and Zeta potential analyzer of Malvern Instruments Limited in the UK, the Zeta potential of the raw material silica and the nano-silica modified by alkyl coupling agent (OSiO2) in Example 1 was tested, and the results are shown in Table 3.

[0117] Table 3 Zeta potential of raw material silica and nano-silica modified by alkyl coupling agent

[0118]

[0119] Among them, avg represents the average value.

[0120] It can be seen from Table 3 that the unmodified SiO2 has a strong electronegativity, and the Zeta potential value reaches -40.4 mV, indicating that the silica surface contains a lot of silanol groups, and after ionization, SiO2 carries a lot of negative charges. When surface grafting modification reaction is carried out on it with KH570, the electronegativity decreases. This may be because: the silanol formed by the hydrolysis of the methoxy group of KH570 reacts with the silanol groups on the silica surface to form Si—O—Si covalent bonds and thus grafts onto the silica surface, reducing the H that can be ionized on the silica surface and decreasing the electronegativity. The measured Zeta potential value of the modified sample OSiO2 in Table 3 is -11 mV, close to electrical neutrality. It shows that the number of hydrophilic silanol groups on the SiO2 surface has been greatly reduced, and the grafting effect is very good.

[0121] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A vinyl copolymer pour point depressant, characterized in that, It is obtained by polymerizing monomers including acrylamide, methacrylate compounds, fumaric acid compounds and alkyl-coupling agent-modified nano-silica; The weight ratio of the fumaric acid compounds, the acrylamide and the methacrylate compounds is (1-2):(1-2):(3-7); The weight ratio of the total amount of the fumaric acid compounds, the acrylamide and the methacrylate compounds to the alkyl-coupling agent-modified nano-silica is (20-45):

1.

2. The pour point depressant of the vinyl copolymer according to claim 1, characterized in that, The fumaric acid compounds are selected from at least one of fumaric acid, monoethyl fumarate and diethyl fumarate.

3. The vinyl copolymer pour point depressant according to claim 2, wherein In the fumaric acid compounds, the weight ratio of fumaric acid, monoethyl fumarate and diethyl fumarate is (1-3):(0-1):(0-1).

4. The vinyl copolymer pour point depressant according to claim 1, wherein The methacrylate compounds are selected from at least one of octadecyl methacrylate and hexadecyl methacrylate.

5. The vinyl copolymer pour point depressant according to claim 4, wherein In the methacrylate compounds, the weight ratio of octadecyl methacrylate and hexadecyl methacrylate is (1-3):(0-1).

6. A preparation method of the vinyl copolymer pour point depressant according to any one of claims 1-5, characterized in that, It includes: Using the acrylamide, the methacrylate compounds, the fumaric acid compounds and the alkyl-coupling agent-modified nano-silica as monomers to carry out a polymerization reaction.

7. The preparation method according to claim 6, characterized in that, It includes: Mixing the monomers with a solvent and heating to 55°C - 95°C, adding an initiator and polymerizing for 4h - 9h; Among them, the initiator is selected from at least one of potassium persulfate, sodium persulfate, ammonium persulfate, azodiisooctylonitrile and azodiisobutyronitrile; the mass ratio of the initiator to the total amount of monomers is (0.1-0.5):100; The solvent is selected from at least one of toluene, xylene, butanol, isobutanol, propanol, isopropanol and ethanol; After the polymerization reaction is completed, distill the solvent to obtain a solid material, and wash and dry the solid material.

8. The preparation method according to claim 6, characterized in that, The preparation process of the alkyl-coupling agent-modified nano-silica includes: Hydrolyzing a silane coupling agent under the conditions of a pH value of 4-7 and a temperature of 30°C - 65°C for 0.5h - 4h to obtain a hydrolysis reaction material; Carrying out an azo-coupling graft reaction on the nano-silica and the hydrolysis reaction material, controlling the reaction temperature at 55°C - 95°C and the reaction time at 4h - 9h.

9. The preparation method according to claim 8, wherein The silane coupling agent is selected from at least one of A171, A173, ZQ172 and KH570; And / or, the mass ratio of the nano-silica to the silane coupling agent is (3-5):

1.

10. Application of the vinyl copolymer pour point depressant according to any one of claims 1-5 or the vinyl copolymer pour point depressant prepared by the preparation method according to any one of claims 6-9 in treating waxy crude oil; Among them, The addition amount of the vinyl copolymer pour point depressant is 400ppm - 600ppm.

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