Crude oil pour point depressant and preparation method thereof

Abstract

The invention belongs to the technical field of crude oil pour point depressants, and particularly relates to a crude oil pour point depressant and a preparation method thereof. The crude oil pour point depressant comprises a lauryl methacrylate-maleic anhydride-(alpha-methylstyrene) terpolymer, 50-60 parts of a modified ethylene-vinyl acetate copolymer, 10-20 parts of an inorganic nano pour point depressant a, 10-15 parts of an inorganic nano pour point depressant b, 0.5-1.5 parts of an antioxidant and 1-3 parts of a lubricant, the preparation method comprises the following steps: adding the terpolymer, the modified ethylene-vinyl acetate copolymer, the inorganic nano pour point depressant a, the inorganic pour point depressant b, the antioxidant and the lubricant into the solvent oil, and stirring to obtain the crude oil pour point depressant. According to the crude oil pour point depressant disclosed by the invention, an efficient, stable and environment-friendly solution is provided for long-distance wax-bearing crude oil pipeline transportation through nano hybridization, multi-component synergy and the like.

Description

Technical Field

[0001] The present application belongs to the technical field of crude oil pour point depressants, and specifically relates to a crude oil pour point depressant and a preparation method thereof. Background Art

[0002] Waxy crude oil exists worldwide, particularly in regions like China, India, Egypt, and the North Sea, where it has been mined for decades. The high wax content in crude oil leads to a high pour point and high viscosity, creating numerous serious challenges in its extraction and pipeline transportation, including high energy consumption, difficult transportation, and prone to pipe congestion. As the temperature drops, the wax in the crude oil precipitates, crystallizes, and interacts to form a three-dimensional network structure, reducing its fluidity and potentially causing pipeline blockages and other accidents.

[0003] Therefore, it is necessary to use certain technical means to prevent or remove the deposited paraffin. These technologies can be divided into four categories: physical, chemical, and biological. Among them, although the physical method is fast in removing paraffin and does not cause chemical pollution, and although the physical method can effectively ensure the normal transportation of crude oil, it consumes a lot of energy and has safety risks. The biological method is environmentally friendly, but the activity of the bacterial community is inhibited by the mineralization degree, making industrial expansion difficult. The chemical method mainly reduces the pour point and viscosity of crude oil by adding chemical depressants to the crude oil, so that it can still flow freely at low temperatures. It is a commonly used method at present. Compared with the physical method, adding chemical depressants to waxy crude oil is more in line with the requirements of environmental protection, economy, and safety.

[0004] Commonly used pour point depressants in chemical processes are copolymers of various compounds, such as octadecyl acrylate-maleic anhydride-styrene terpolymer, ethylene-vinyl acetate copolymer, and styrene-maleic anhydride copolymer. Octadecyl acrylate-maleic anhydride-styrene terpolymer and ethylene-vinyl acetate copolymer are particularly common. However, these chemical processes are sensitive to crude oil composition (one depressant may have a good depressing effect on one crude oil but poor or no effect on another). Furthermore, during long-distance transportation in pipelines, the depressant's shear resistance decreases, leading to a weakening of its effectiveness. Therefore, with the development of society and changes in crude oil transportation methods, new requirements have been placed on the depressing effect of depressants. To further improve the depressing effect of chemical depressants and develop more cost-effective, efficient, and universal depressants, depressants are often modified.

[0005] Nanomaterials, due to their unique small size, surface, and quantum tunneling effects, hold immense promise for widespread application across various sectors of the national economy. Within the petroleum industry, nanomaterials have been applied in lubricants, road asphalt, catalysts in oil processing, and the plastics processing industry, aiming to improve the friction and wear resistance of lubricants and the high-temperature stability of road asphalt, respectively. Nanosilica, nanotitanium dioxide, and nanohalloysite are widely used in polymer modification and reinforcement, as well as for reducing crude oil viscosity and pour point.

[0006] For example, Chinese patent publication number CN115960597B discloses a composite crude oil pour point depressant and its preparation method. This technical solution modifies an EVA pour point depressant with nano-halloysite and mixes it with a polyester pour point depressant to produce a composite crude oil pour point depressant. This composite crude oil depressant effectively inhibits the aggregation of wax crystals and the formation of a gel network, reducing the yield stress and viscosity of waxy crude oil, thereby improving the fluidity of crude oil at low temperatures. Another example is Chinese patent publication number CN114989373B, which discloses a copolymer pour point depressant based on halloysite nanotubes and its preparation method. The main monomers of the copolymer are first embedded into the internal space of the halloysite nanotubes through the halloysite nanotubes to form a higher alcohol ester. Based on this, the copolymer is reacted with a styrene derivative and maleic anhydride to produce a block copolymer, the latter two ends of which are then extended to the exterior of the halloysite nanotubes. However, in both of these technical solutions, the nanomaterials are not modified and easily agglomerate in the pour point depressant, thus affecting the pour point depressant effect.

[0007] To address these issues, Chinese Patent Publication No. CN107448777B discloses a crude oil nanoparticle viscosity and pour point depressant composition, its preparation method, and its application. This technical solution comprises solid particles prepared by melt blending an inorganic nanoparticle pour point depressant, an organic pour point depressant, a graft polymer, a coupling agent, and a polymer processing aid. The graft polymer in the blended particles is essentially modified EVA (the modified EVA is essentially modified with a nonionic surfactant), the organic pour point depressant is essentially a multi-component copolymer, and the inorganic nanoparticle pour point depressant is essentially surface-modified inorganic nanoparticles or is directly unmodified. This technical solution only tests the pour point and apparent viscosity. However, crude oil is affected by many factors during transportation, especially long-distance pipeline transportation, which requires a high shear resistance of the pour point depressant. However, the large amounts of graft copolymer and organic pour point depressant added in this technical solution, combined with the relatively small amount of inorganic nanoparticle pour point depressant, do not necessarily guarantee a pour point depressant effect for long-distance pipeline transportation.

[0008] However, in the technical documents mentioned above, due to the addition of nanomaterials, it is difficult to disperse them evenly due to the characteristics of the nanomaterials themselves, which may lead to loose wax crystal structure and reduce the low-temperature fluidity of crude oil.

[0009] In summary, chemical pour point depressants have poor shear resistance during long-distance pipeline transportation. After inorganic nanohybrid modification, the inorganic nanomaterials are prone to agglomeration or the component addition amount is unreasonable, resulting in a loose wax crystal structure, which can easily cause the fluidity of crude oil to deteriorate under low temperature conditions. It is urgent to propose a composite pour point depressant with good shear resistance, reasonable component addition amount, and low-temperature guaranteed crude oil fluidity to improve the solutions in the existing technology. Summary of the Invention

[0010] In view of the problems that chemical pour point depressants in the existing technology have poor shear resistance during long-distance pipeline transportation, and after inorganic nano hybrid modification, the inorganic nano materials are prone to agglomeration or the component addition amount is unreasonable, the wax crystal structure is loose, and the crude oil fluidity is easily deteriorated under low temperature conditions. This application proposes a crude oil pour point depressant with good shear resistance, reasonable component addition amount, and guaranteed crude oil fluidity at low temperatures.

[0011] The technical solution of this application is as follows:

[0012] In one aspect, the present application provides a crude oil pour point depressant comprising the following components in parts by weight:

[0013] 8-13 parts of lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer, 50-60 parts of modified ethylene-vinyl acetate copolymer, 10-20 parts of inorganic nano-pour point depressant a, 10-15 parts of inorganic pour point depressant b, 0.5-1.5 parts of antioxidant and 1-3 parts of lubricant;

[0014] The preparation method of the lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer is as follows: lauryl methacrylate, maleic anhydride and (α-methylstyrene) are added to toluene, azobisisobutyronitrile is added, the temperature is raised to 75-80° C., polymerization reaction is carried out under a nitrogen atmosphere for 6-7 hours, and finally washing with anhydrous ethanol and drying to obtain the lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer.

[0015] Preferably, the mass ratio of lauryl methacrylate, maleic anhydride and (α-methylstyrene) is (3-5:):1:1; the mass ratio of toluene to lauryl methacrylate is (5-6):1; and the amount of azobisisobutyronitrile is 1-2% of the mass of lauryl methacrylate.

[0016] Preferably, the modified ethylene-vinyl acetate copolymer is copolymerized with oleic acid and acrylic acid, and the specific preparation method is as follows:

[0017] Step S1: adding an initiator to ethylene-vinyl acetate copolymer, heating to 80-90° C., and stirring until completely dissolved to obtain a mixed solution A;

[0018] Step S2. Add oleic acid to the mixed component A, maintain the temperature at 80-90°C, stir and react for 1-2 hours, then add acrylic acid, raise the temperature to 90-95°C, continue stirring and react for 2-3 hours, terminate the reaction and cool the reaction system to 60°C to obtain a mixed solution B;

[0019] Step S3: adding ethanol to the mixed solution B to separate out the precipitate, and centrifugally drying the precipitate to obtain a modified ethylene-vinyl acetate copolymer.

[0020] Preferably, the mass ratio of the ethylene-vinyl acetate copolymer, the initiator, oleic acid and acrylic acid is 1:5:(0.2-0.5):(0.1-0.3).

[0021] Preferably, the initiator is any one of p-toluenesulfonic acid, dibenzoyl peroxide or aminosulfonic acid.

[0022] Preferably, the inorganic nano-pour point depressant a is any one of nano-silicon dioxide or natural nano-silicate materials; nano-silicon dioxide or natural nano-silicate materials are modified by a silane coupling agent; the natural nano-silicate material is montmorillonite, attapulgite or sepiolite.

[0023] Preferably, the inorganic pour point depressant b is oleic acid modified ferrosoferric oxide, and the specific operation method is:

[0024] The ferrosoferric oxide nanoparticles were dispersed in an ethanol solution, ultrasonically treated for 10 to 20 minutes, oleic acid was added, the temperature was raised to 70 to 80° C. with stirring, the reaction was carried out for 1 hour, the solution was washed with ethanol three times and dried to obtain oleic acid-modified ferrosoferric oxide.

[0025] Preferably, the mass ratio of the ferroferric oxide to oleic acid is 1:(80-150); the mass ratio of the ferroferric oxide to ethanol is 1:(50-100).

[0026] Preferably, the antioxidant is butylated hydroxytoluene, and the lubricant is calcium stearate.

[0027] In another aspect, the present application provides a method for preparing a crude oil pour point depressant. Specifically, 8 to 13 parts of lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer, 50 to 60 parts of modified ethylene-vinyl acetate copolymer, 10 to 20 parts of inorganic nanoparticle pour point depressant a, 10 to 15 parts of inorganic pour point depressant b, 0.5 to 1.5 parts of an antioxidant, and 1 to 3 parts of a lubricant are added to solvent oil and stirred for 20 to 40 minutes to obtain the crude oil pour point depressant. The solvent oil is any one of D70, D80, or D90. The ratio of the mass of the modified ethylene-vinyl acetate copolymer, inorganic nanoparticle pour point depressant a, inorganic pour point depressant b, antioxidant, and lubricant to the solvent oil after mixing is 1:(5-10).

[0028] Beneficial effects of this application:

[0029] The crude oil pour point depressant proposed in this application improves the crude oil pour point depressing effect through the synergistic effect of the multi-components of the terpolymer, the modified ethylene-vinyl acetate copolymer, the inorganic nano-pour point depressant a, and the inorganic pour point depressant b, especially in terms of shear resistance, component dispersibility, and low-temperature fluidity, as follows:

[0030] (1) Traditional octadecyl acrylate-maleic anhydride-styrene terpolymers have problems such as uneven low-temperature fluidity and poor stability due to the easy hydrolysis of the anhydride group. This application replaces octadecyl acrylate with lauryl methacrylate. The α-methyl side chain of lauryl methacrylate, through the steric hindrance effect, is more effective than the straight-chain octadecyl acrylate in destroying the close arrangement of wax crystals, inhibiting the formation of large flake / needle-shaped wax crystals, and reducing chain transfer side reactions; α-methylstyrene replaces styrene. The α-methyl group of α-methylstyrene increases the glass transition temperature of the polymer, reduces molecular chain breakage during high-temperature transportation or repeated heating, and maintains the long-term effectiveness of the pour point depressant. The polar groups of the terpolymer interact and combine with the nano pour point depressant to jointly promote the formation of small and uniform wax crystals; the residual carboxyl groups (from maleic anhydride) of the terpolymer and the acrylic acid carboxyl groups of the modified EVA jointly anchor the wax crystal surface, forming a dense solvation layer, which inhibits the aggregation of wax crystals; the rigid α-methylstyrene segments of the terpolymer combine with Fe3O4 nanoparticles through van der Waals forces to improve shear resistance.

[0031] (2) This application copolymerizes ethylene-vinyl acetate copolymers with oleic acid and acrylic acid to introduce long-chain alkyl and carboxylic acid groups into the molecular chains of the ethylene-vinyl acetate copolymers. The hydrophobic chain of oleic acid is similar to the structure of wax crystals and can be embedded in the surface of wax crystals, while the polar groups of acrylic acid enhance the adsorption capacity of wax crystals, forming a denser solvation layer; the modified ethylene-vinyl acetate copolymer disrupts the arrangement of wax molecules through eutectic action, transforming wax crystals from large-sized flakes or needles into fine particles, destroying their cross-linked network, and reducing yield stress and viscosity. The introduced long-chain alkyl and carboxylic acid groups form a network through physical cross-linking, enhancing the mechanical strength of the molecular chain and reducing the breakage of the molecular chain caused by shear force, thereby maintaining the durability of the pour point depression effect.

[0032] (3) The inorganic nanoparticle pour point depressant a of the present application is treated with a silane coupling agent and then grafted with organic groups on its surface, thereby improving its dispersibility in crude oil and preventing agglomeration. The nanoparticles act as nucleation sites, promoting the preferential crystallization of wax molecules on their surface, forming smaller, more evenly distributed wax crystals and inhibiting the growth of large crystals. The inorganic nanoparticle pour point depressant a binds to the modified ethylene-vinyl acetate copolymer through hydrogen bonds or van der Waals forces, enhancing the coating ability of the wax crystals and improving the thermal stability of the system.

[0033] (4) The magnetic nanoparticle pour point depressant b of the present application is oleic acid-modified ferroferric oxide. The oleic acid molecules coordinate with the surface of Fe3O4 through carboxyl groups to form a hydrophobic layer, which makes it uniformly dispersed in the organic phase and reduces the phase separation caused by polarity differences. On the one hand, the material's own magnetism will further induce wax crystals to form an ordered and compact structure on the surface of the body, inhibiting the formation of a gel structure, thereby reducing the viscosity of crude oil; the oleic acid-coated Fe3O4 and the modified nanomaterial both have hydrophobic surfaces, and the two form composite agglomerates through the entanglement of the long oleic acid chains to increase the adsorption capacity. Fe3O4 can also form a "rigid and flexible" structure with the flexible chain of ethylene-vinyl acetate copolymer. Under the action of shear force, the nanoparticles absorb energy by sliding or rotating, thereby increasing the shear resistance of crude oil. On the other hand, if the magnetic nanoparticles can be arranged along the direction of the oil pipeline under an external magnetic field to form a chain structure, it can not only locally increase the temperature through the magnetocaloric effect, but also improve the low-temperature fluidity.

[0034] In summary, the composite pour point depressant of the present application provides an efficient, stable and environmentally friendly solution for long-distance waxy crude oil pipeline transportation through multi-component synergy. DETAILED DESCRIPTION

[0035] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with preferred embodiments.

[0036] It should be noted that the raw materials involved in this application can all be obtained commercially, among which the VA content in ethylene-vinyl acetate copolymer (EVA) is 28%, and the inorganic nano-pour point depressant a is any one of nano-silica or natural nano-silicate materials; the nano-silica or natural nano-silicate materials are modified with a silane coupling agent, and the applicant obtains them with reference to the common solution stirring modification in the prior art, while the lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer, modified ethylene-vinyl acetate copolymer and oleic acid-modified ferrosoferric oxide material are obtained by the applicant through literature review and years of work experience.

[0037] Preparation Examples 1 to 4 provide a method for preparing a modified ethylene-vinyl acetate copolymer.

[0038] Preparation Example 1

[0039] This preparation example provides a modified ethylene-vinyl acetate copolymer, and the specific operation is as follows:

[0040] Step S1. Nitrogen was introduced into the reaction apparatus to displace oxygen to prevent oxidative degradation of the EVA main chain. This is because the presence of oxygen may trigger a cross-linking side reaction. The nitrogen flow rate was 0.5 L / min. 10 g of ethylene-vinyl acetate copolymer and 50 g of p-toluenesulfonic acid were heated to 85° C. and stirred until completely dissolved to obtain a mixed solution A. At 85° C., the initiator rapidly decomposed, efficiently initiating a chain scission reaction of the EVA main chain, providing active sites for subsequent grafting.

[0041] Step S2. 3 g of oleic acid was added to the mixed component A, and the mixture was maintained at 85°C with stirring for 1.2 h. Subsequently, 2 g of acrylic acid was added, and the temperature was raised to 93°C. The mixture was stirred for 2.5 h. Oleic acid was preferentially grafted onto the EVA backbone, utilizing the hydrophobicity of its long alkyl chain to occupy backbone sites, thereby reducing the competitive polymerization of acrylic acid and oleic acid and improving the orderliness of the grafting. Finally, the reaction was terminated and the reaction system was cooled to 60°C to obtain a mixed solution B.

[0042] Step S3. Add ethanol in an amount 5 times the volume of the mixed solution B to precipitate, centrifuge at 3000 rpm for 10 min, and then dry at 50° C. for 24 h to obtain a modified ethylene-vinyl acetate copolymer.

[0043] Preparation Example 2

[0044] This preparation example provides a modified ethylene-vinyl acetate copolymer, and the specific operation is as follows:

[0045] Step S1. Nitrogen was introduced into the reaction apparatus to displace oxygen to prevent oxidative degradation of the EVA main chain. This is because the presence of oxygen may trigger a cross-linking side reaction. The nitrogen flow rate was 0.5 L / min. 10 g of ethylene-vinyl acetate copolymer and 50 g of dibenzoyl peroxide were heated to 80° C. and stirred until completely dissolved to obtain a mixed solution A. At 80° C., the initiator rapidly decomposed, efficiently initiating a chain scission reaction of the EVA main chain, providing active sites for subsequent grafting.

[0046] Step S2. 2 g of oleic acid was added to the mixed component A, and the mixture was stirred at 80°C for 1.5 hours. Subsequently, 3 g of acrylic acid was added, and the temperature was raised to 95°C. The mixture was stirred for 3 hours. Oleic acid was preferentially grafted onto the EVA backbone, utilizing the hydrophobicity of its long alkyl chain to occupy backbone sites, thereby reducing the competitive polymerization of acrylic acid and oleic acid and improving the orderliness of the grafting. Finally, the reaction was terminated and the reaction system was cooled to 60°C to obtain a mixed solution B.

[0047] Step S3. Add ethanol in an amount 5 times the volume of the mixed solution B to precipitate, centrifuge at 3000 rpm for 10 min, and then dry at 50° C. for 24 h to obtain a modified ethylene-vinyl acetate copolymer.

[0048] Preparation Example 3

[0049] This preparation example provides a modified ethylene-vinyl acetate copolymer, and the specific operation is as follows:

[0050] Step S1. Nitrogen was introduced into the reaction apparatus to displace oxygen to prevent oxidative degradation of the EVA main chain. This is because the presence of oxygen may trigger a cross-linking side reaction. The nitrogen flow rate was 0.5 L / min. 10 g of ethylene-vinyl acetate copolymer and 50 g of aminosulfonic acid were heated to 90° C. and stirred until completely dissolved to obtain a mixed solution A. At 90° C., the initiator rapidly decomposed, efficiently initiating a chain scission reaction of the EVA main chain, providing active sites for subsequent grafting.

[0051] Step S2. 5 g of oleic acid was added to the mixed component A, the mixture was maintained at 90°C, and the reaction was stirred for 1 hour. Subsequently, 1 g of acrylic acid was added, and the mixture was maintained at 90°C and stirred for 2 hours. Oleic acid was preferentially grafted onto the EVA backbone, utilizing the hydrophobicity of its long alkyl chain to occupy backbone sites, thereby reducing the competitive polymerization of acrylic acid and oleic acid and improving the orderliness of the grafting. Finally, the reaction was terminated and the reaction system was cooled to 60°C to obtain a mixed solution B.

[0052] Step S3. Add ethanol in an amount 5 times the volume of the mixed solution B to precipitate, centrifuge at 3000 rpm for 10 min, and then dry at 50° C. for 24 h to obtain a modified ethylene-vinyl acetate copolymer.

[0053] Preparation Example 4

[0054] This preparation example provides a modified ethylene-vinyl acetate copolymer, and the specific operation is as follows:

[0055] Step S1. Nitrogen was introduced into the reaction apparatus to displace oxygen to prevent oxidative degradation of the EVA main chain. This is because the presence of oxygen may trigger a cross-linking side reaction. The nitrogen flow rate was 0.5 L / min. 10 g of ethylene-vinyl acetate copolymer and 50 g of p-toluenesulfonic acid were heated to 85° C. and stirred until completely dissolved to obtain a mixed solution A. At 85° C., the initiator rapidly decomposed, efficiently initiating a chain scission reaction of the EVA main chain, providing active sites for subsequent grafting.

[0056] Step S2. 4 g of oleic acid was added to the mixed component A, and the mixture was maintained at 85°C with stirring for 2 h. Subsequently, 2 g of acrylic acid was added, and the temperature was raised to 91°C. The mixture was stirred for 2.5 h. Oleic acid was preferentially grafted onto the EVA backbone, utilizing the hydrophobicity of its long alkyl chain to occupy backbone sites, thereby reducing the competitive polymerization of acrylic acid and oleic acid and improving the orderliness of the grafting. Finally, the reaction was terminated and the reaction system was cooled to 60°C to obtain a mixed solution B.

[0057] Step S3. Add ethanol in an amount 5 times the volume of the mixed solution B to precipitate, centrifuge at 3000 rpm for 10 min, and then dry at 50° C. for 24 h to obtain a modified ethylene-vinyl acetate copolymer.

[0058] Preparation Examples 5 to 7 provide an oleic acid-modified ferrosoferric oxide.

[0059] Preparation Example 5

[0060] This preparation example provides an oleic acid-modified ferroferric oxide, and the specific operation method is as follows:

[0061] Before use, Fe3O4 nanoparticles were vacuum dried at 60°C for 2 hours to remove adsorbed moisture. 2 g of ferrosoferric oxide nanoparticles were dispersed in 150 g of ethanol solution and ultrasonically treated at 600 W for 20 min. 250 g of oleic acid was added, and the temperature was raised to 80°C with stirring. The reaction was carried out for 1 hour, and the solution was washed with ethanol three times and dried at 60°C for 24 hours to obtain oleic acid-modified ferrosoferric oxide.

[0062] Preparation Example 6

[0063] This preparation example provides an oleic acid-modified ferroferric oxide, and the specific operation method is as follows:

[0064] Before use, Fe3O4 nanoparticles were vacuum dried at 60°C for 2 hours to remove adsorbed moisture. 2 g of ferrosoferric oxide nanoparticles were dispersed in 100 g of ethanol solution, ultrasonically treated at 600 W for 15 min, 300 g of oleic acid was added, and the temperature was raised to 70°C with stirring. The reaction was carried out for 1 hour, and the mixture was washed with ethanol three times and dried at 60°C for 24 hours to obtain oleic acid-modified ferrosoferric oxide.

[0065] Preparation Example 7

[0066] This preparation example provides an oleic acid-modified ferroferric oxide, and the specific operation method is as follows:

[0067] Before use, Fe3O4 nanoparticles were vacuum dried at 60°C for 2 hours to remove adsorbed moisture. 2 g of ferroferric oxide nanoparticles were dispersed in 200 g of ethanol solution and ultrasonically treated at 600 W for 20 min. 160 g of oleic acid was added, and the temperature was raised to 75°C with stirring. The reaction was carried out for 1 hour, and the mixture was washed with ethanol three times and dried at 60°C for 24 hours to obtain oleic acid-modified ferroferric oxide.

[0068] Preparation Examples 8 and 9 provide a method for preparing a lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer.

[0069] Preparation Example 8

[0070] This preparation example provides a method for preparing a lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer, which is specifically as follows: 8.2 g of lauryl methacrylate, 2.0 g of maleic anhydride, and 2.0 g of (α-methylstyrene) are added to 47.0 g of toluene, 0.123 g of azobisisobutyronitrile is added, the temperature is raised to 77° C., and polymerization is carried out under a nitrogen atmosphere for 6.5 hours. Finally, the mixture is washed three times with anhydrous ethanol and vacuum dried at 50° C. for 24 hours to obtain a lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer.

[0071] Preparation Example 9

[0072] This preparation example provides a method for preparing a lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer, which is specifically as follows: 6.0 g of lauryl methacrylate, 2.0 g of maleic anhydride, and 2.0 g of (α-methylstyrene) are added to 36.0 g of toluene, 0.12 g of azobisisobutyronitrile is added, the temperature is raised to 75° C., and polymerization reaction is carried out under a nitrogen atmosphere for 7 hours. Finally, the mixture is washed three times with anhydrous ethanol and vacuum dried at 50° C. for 24 hours to obtain a lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer.

[0073] Preparation Example 10

[0074] This preparation example provides a method for preparing a lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer, which is specifically as follows: 10 g of lauryl methacrylate, 2.0 g of maleic anhydride, and 2.0 g of (α-methylstyrene) are added to 50.0 g of toluene, 0.10 g of azobisisobutyronitrile is added, the temperature is raised to 80° C., and polymerization is carried out under a nitrogen atmosphere for 6 hours. Finally, the mixture is washed three times with anhydrous ethanol and vacuum dried at 50° C. for 24 hours to obtain a lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer.

[0075] Example 1

[0076] This embodiment provides a method for preparing a crude oil pour point depressant, which is as follows:

[0077] 62 parts of the modified ethylene-vinyl acetate copolymer prepared in Preparation Example 1, 8 parts of the lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer prepared in Preparation Example 8, 15 parts of inorganic nano-pour point depressant a (KH550 modified nano-silica), 12 parts of inorganic pour point depressant b (oleic acid-modified ferrosoferric oxide prepared in Preparation Example 5), 1 part of butylated hydroxytoluene and 2 parts of calcium stearate were mixed and added to 600 parts of solvent oil D70 and stirred for 30 minutes to obtain a crude oil pour point depressant.

[0078] Example 2

[0079] This embodiment provides a method for preparing a crude oil pour point depressant, which is as follows:

[0080] 50 parts of the modified ethylene-vinyl acetate copolymer prepared in Preparation Example 2, 12 parts of the lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer prepared in Preparation Example 8, 20 parts of inorganic nano-pour point depressant a (KH550 modified nano-silica), 15 parts of inorganic pour point depressant b (oleic acid-modified ferrosoferric oxide prepared in Preparation Example 6), 0.5 parts of butylated hydroxytoluene and 2.5 parts of calcium stearate were mixed and added to 800 parts of solvent oil D70 and stirred for 30 minutes to obtain a crude oil pour point depressant.

[0081] Example 3

[0082] This embodiment provides a method for preparing a crude oil pour point depressant, which is as follows:

[0083] 58 parts of the modified ethylene-vinyl acetate copolymer prepared in Preparation Example 3, 9 parts of the lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer prepared in Preparation Example 9, 19 parts of inorganic nano-pour point depressant a (KH550 modified nano-silica), 11.5 parts of inorganic pour point depressant b (oleic acid-modified ferrosoferric oxide prepared in Preparation Example 7), 1.5 parts of butylated hydroxytoluene and 1 part of calcium stearate were mixed and added to 1000 parts of solvent oil D80 and stirred for 20 minutes to obtain a crude oil pour point depressant.

[0084] Example 4

[0085] This embodiment provides a method for preparing a crude oil pour point depressant, which is as follows:

[0086] 54 parts of the modified ethylene-vinyl acetate copolymer prepared in Preparation Example 4, 15 parts of the lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer prepared in Preparation Example 10, 17 parts of an inorganic nanopour point depressant a (KH550 modified attapulgite), 10 parts of an inorganic pour point depressant b (oleic acid-modified ferrosoferric oxide prepared in Preparation Example 7), 1.2 parts of butylated hydroxytoluene, and 2.8 parts of calcium stearate were mixed and added to 600 parts of solvent oil D80 and stirred for 40 minutes to obtain a crude oil pour point depressant.

[0087] Example 5

[0088] This embodiment provides a method for preparing a crude oil pour point depressant, which is as follows:

[0089] 60 parts of the modified ethylene-vinyl acetate copolymer prepared in Preparation Example 4, 13 parts of the lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer prepared in Preparation Example 8, 10 parts of inorganic nanopour point depressant a (KH550 modified montmorillonite), 13 parts of inorganic pour point depressant b (oleic acid-modified ferrosoferric oxide prepared in Preparation Example 7), 1.7 parts of butylated hydroxytoluene, and 2.3 parts of calcium stearate were mixed and added to 500 parts of solvent oil D90 and stirred for 25 minutes to obtain a crude oil pour point depressant.

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 1 is that the ethylene-vinyl acetate copolymer in this comparative example is not modified with oleic acid and acrylic acid.

[0092] Comparative Example 2

[0093] The difference between this comparative example and Example 1 is that the ethylene-vinyl acetate copolymer in this comparative example is not modified with oleic acid.

[0094] Comparative Example 3

[0095] The difference between this comparative example and Example 1 is that the ethylene-vinyl acetate copolymer in this comparative example is not modified with acrylic acid.

[0096] Comparative Example 4

[0097] The difference between this comparative example and Example 1 is that the terpolymer used in this comparative example is octadecyl acrylate-maleic anhydride-styrene. The reference material for the preparation method is: Luo Xiaowen et al. <Preparation and Performance Evaluation of Nano-montmorillonite Composite Pour Point Depressant>.

[0098] Comparative Example 5

[0099] The difference between this comparative example and Example 1 is that the nano-silica in this comparative example has not been modified.

[0100] Comparative Example 6

[0101] The difference between this comparative example and Example 1 is that the nano-ferrosoferric oxide in this comparative example is not modified with oleic acid.

[0102] Comparative Example 7

[0103] The difference between this comparative example and Example 1 is that the inorganic nano-pour point depressant a (KH550 modified attapulgite) is not added in this comparative example.

[0104] Comparative Example 8

[0105] The difference between this comparative example and Example 1 is that the inorganic pour point depressant b (oleic acid-modified ferrosoferric oxide prepared in Preparation Example 7) is not added in this comparative example.

[0106] Comparative Example 9

[0107] The difference between this comparative example and Example 1 is that the ethylene-vinyl acetate copolymer, the inorganic nano-pour point depressant a, and the inorganic pour point depressant b in this comparative example are not modified.

[0108] The crude oil used for the pour point depressants prepared in Examples 1 to 5 and Comparative Examples 1 to 9 had a wax content of 19% and was sourced from the Daqing Oilfield. The effects of the pour point of the crude oil depressants added in the same amounts and the effects of the pour point depressants on the yield strength of the crude oil at 20°C were tested, and the results are shown in Table 1.

[0109] Table 1

[0110]

[0111]

[0112] From Table 1, in combination with Examples 1 to 5, and in comparison with waxy crude oil, it can be seen that the crude oil pour point depressant prepared by the method of the present application can reduce the pour point by up to 18.2° C., and the yield stress can be reduced to a maximum of 8.32 Pa. This is because the crude oil pour point depressant proposed in the present application enhances the adsorption strength of wax crystals and improves the crude oil pour point depressing effect through the synergistic effect of the multi-components of the terpolymer, the modified ethylene-vinyl acetate copolymer, the inorganic nano pour point depressant a, and the inorganic pour point depressant b.

[0113] From Table 1 and in combination with Example 1 and Comparative Examples 1 to 9, it can be seen that the pour point depression effect of the crude oil in Comparative Examples 1 to 9 is worse than that in Example 1, especially in Comparative Examples 7 and 8. Due to the lack of the addition of nanoparticles and the lack of crystallization nuclei, the pour point depression effect and yield stress decrease significantly. In Comparative Examples 1 to 6 and Comparative Example 9, since some components have not been modified, the components cannot fully play their role and the synergistic effect is reduced.

[0114] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A crude oil pour point depressant, characterized in that: The composition comprises the following components in parts by weight: 8-13 parts of lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer, 50-60 parts of modified ethylene-vinyl acetate copolymer, 10-20 parts of inorganic nano-pour point depressant a, 10-15 parts of inorganic pour point depressant b, 0.5-1.5 parts of antioxidant and 1-3 parts of lubricant; The preparation method of the lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer is as follows: lauryl methacrylate, maleic anhydride and (α-methylstyrene) are added to toluene, azobisisobutyronitrile is added, the temperature is raised to 75-80° C., polymerization reaction is carried out under a nitrogen atmosphere for 6-7 hours, and finally washing with anhydrous ethanol and drying to obtain the lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer.

2. A crude oil pour point depressant according to claim 1, characterized in that: The mass ratio of lauryl methacrylate, maleic anhydride and (α-methylstyrene) is (3-5:):1:1; the mass ratio of toluene and lauryl methacrylate is (5-6):1; and the amount of azobisisobutyronitrile is 1-2% of the mass of lauryl methacrylate.

3. The crude oil pour point depressant according to claim 1, characterized in that: The modified ethylene-vinyl acetate copolymer is copolymerized with oleic acid and acrylic acid, and the specific preparation method is as follows: Step S1: adding an initiator to ethylene-vinyl acetate copolymer, heating to 80-90° C., and stirring until completely dissolved to obtain a mixed solution A; Step S2. Add oleic acid to the mixed component A, maintain the temperature at 80-90°C, stir and react for 1-2 hours, then add acrylic acid, raise the temperature to 90-95°C, continue stirring and react for 2-3 hours, terminate the reaction and cool the reaction system to 60°C to obtain a mixed solution B; Step S3: adding ethanol to the mixed solution B to separate out the precipitate, and centrifugally drying the precipitate to obtain a modified ethylene-vinyl acetate copolymer.

4. A crude oil pour point depressant according to claim 3, characterized in that: The mass ratio of the ethylene-vinyl acetate copolymer, the initiator, oleic acid and acrylic acid is 1:5:(0.2-0.5):(0.1-0.3).

5. The crude oil pour point depressant according to claim 3, characterized in that: The initiator is any one of p-toluenesulfonic acid, dibenzoyl peroxide or aminosulfonic acid.

6. The crude oil pour point depressant according to claim 1, characterized in that: The inorganic nano pour point depressant a is any one of nano silicon dioxide or natural nano silicate materials; the nano silicon dioxide or natural nano silicate materials are modified by a silane coupling agent; the natural nano silicate material is montmorillonite, attapulgite or sepiolite.

7. The crude oil pour point depressant according to claim 1, characterized in that: The inorganic pour point depressant B is oleic acid modified ferrosoferric oxide, and the specific operation method is: The ferrosoferric oxide nanoparticles were dispersed in an ethanol solution, ultrasonically treated for 10 to 20 minutes, oleic acid was added, the temperature was raised to 70 to 80° C. with stirring, the reaction was carried out for 1 hour, the solution was washed with ethanol three times and dried to obtain oleic acid-modified ferrosoferric oxide.

8. The crude oil pour point depressant according to claim 7, characterized in that: The mass ratio of the ferroferric oxide to oleic acid is 1:(80-150); the mass ratio of the ferroferric oxide to ethanol is 1:(50-100).

9. The crude oil pour point depressant according to claim 1, characterized in that: The antioxidant is butylated hydroxytoluene, and the lubricant is calcium stearate.

10. The method for preparing a crude oil pour point depressant according to any one of claims 1 to 9, characterized in that: The specific operation is as follows: 8 to 13 parts of lauryl methacrylate-maleic anhydride-(α-methylstyrene) terpolymer, 50 to 60 parts of modified ethylene-vinyl acetate copolymer, 10 to 20 parts of inorganic nano-pour point depressant a, 10 to 15 parts of inorganic pour point depressant b, 0.5 to 1.5 parts of antioxidant and 1 to 3 parts of lubricant are added to solvent oil and stirred for 20 to 40 minutes to obtain a crude oil pour point depressant, wherein the solvent oil is any one of D70, D80 or D90, and the ratio of the mass of the modified ethylene-vinyl acetate copolymer, inorganic nano-pour point depressant a, inorganic pour point depressant b, antioxidant and lubricant after mixing to the solvent oil is 1:(5 to 10).

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