Universal crude oil desalting agent and preparation method thereof

Abstract

The invention discloses a universal crude oil decalcifying agent and a preparation method thereof. The crude oil decalcifying agent comprises the following components: an inorganic salt, a polymer modified clay mineral and polyether, and the polymer modified clay mineral comprises a clay mineral and a polymer chemically bonded to the surface of the clay mineral; the polymer is a copolymer and includes a quaternary ammonium group. The desalting agent plays a role in combining metal ions based on a complexation method and a precipitation method at the same time, can remove various metal elements (including Ni, Ca, Fe and the like) in crude oil, further improves the polarity of a water phase so as to improve the dehydration rate of the crude oil, and can improve the dehydration speed and the dehydration degree when being applied to an electric desalting system.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum desalting agents, and more particularly, to a universal crude oil desalting agent and a preparation method thereof. Background Art

[0002] Compared with conventional crude oil, the metal content in inferior crude oil is several times that of conventional crude oil. Although the content of some metal elements is not high, they are very harmful in the primary and secondary processing of crude oil. For example, metal salts such as calcium and iron deposit and scale in heat exchangers and heating furnace tubes, affecting heat transfer and causing corrosion; inorganic salts such as calcium, magnesium, and sodium cause corrosion of the distillation unit top condensation and cooling systems; metals such as nickel and vanadium reduce the activity of catalytic cracking catalysts, seriously affecting the product distribution of catalytic cracking, and can also poison hydrogenation catalysts and block the bed layer. Therefore, exploring new methods for efficiently removing heavy metals from crude oil has become an urgent challenge in the petrochemical field. At present, most desalting agents only have a desalting effect on calcium and cannot effectively remove other metal elements. In addition, the key to crude oil desalting is dehydration, and the key to dehydration is demulsification. Therefore, the existing technology requires the combined use of desalting agents and demulsifying agents to improve the dehydration rate and thus the desalting rate. However, there is little research on the compatibility of current desalting agents and demulsifying agents, and it is difficult to play a synergistic role, so the dehydration and desalting efficiency is low.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The present invention provides a universal crude oil desalting agent and a preparation method thereof, aiming to remove various metal elements in crude oil and improve the crude oil desalting rate and desalting and dehydration efficiency.

[0005] The present invention is implemented as follows:

[0006] The present invention provides a universal crude oil desalting agent, comprising the following components: inorganic salts, polymer-modified clay minerals, polyethers, wherein the polymer-modified clay minerals include clay minerals and polymers chemically bonded to the surfaces of the clay minerals; the polymers are copolymers and include the following repeating units (a)-(c);

[0007] Among them, R1 and R2 are independently selected from H or CH3, R3 is H or an alkyl group with 1-3 carbon atoms; X is one of Cl, Br, and OH, and * is the site for linking other repeating units.

[0008] In the desalting agent provided by the present invention, the addition of inorganic salts can increase the polarity of the aqueous phase, thereby facilitating the improvement of the dehydration efficiency of electro-dehydration; the polymer-modified clay mineral simultaneously has the advantages of clay minerals and copolymers, and the two can exert synergistic effects in dehydration and desalting through chemical bonding. Specifically, the clay mineral has a high specific surface area, and the mechanical strength of the oil-water interface film is reduced through mechanisms such as adsorption and charge neutralization, thereby realizing demulsification; after grafting the polymer, the lipophilicity of the clay mineral is enhanced, which is conducive to dispersion in the crude oil emulsion, thereby promoting the rupture of the oil-water interface film; in addition, quaternary ammonium salt functional groups are grafted in the polymer chain, and demulsification is achieved through the synergy of charge neutralization and hydrophobic adsorption, and the positive charges carried by it can adjust the system conductivity during the electro-desalting process, enhancing the polarization effect of the electric field on water droplets. Therefore, polymer modification significantly improves the demulsification ability and dehydration ability of clay minerals. Further, the polymer-modified clay mineral can simultaneously exert the functions of adsorption flocculation and complexation. As the polymer-modified clay mineral complexes metal ions, aggregates can be formed and settle, improving the desalting effect.

[0009] In some embodiments, the polymer also contains catechol groups; the catechol groups can provide a stable complex structure for metal ions, thereby improving the complexation ability with metal ions and enhancing its desalting effect.

[0010] In some embodiments, the universal crude oil desalting agent further includes an oxidant and / or an organic phosphonic acid.

[0011] Preferably, the oxidant is selected from at least one of hydrogen peroxide, ammonium persulfate, and sodium persulfate.

[0012] Preferably, the organic phosphonic acid is selected from at least one of aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid or its salts, hydroxyethylethylenediphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, diethylenetriamine pentamethylenephosphonic acid, and sodium 2-phosphonopropionate.

[0013] In the desalting agent provided by the present invention, an oxidant is further added. The oxidant can oxidize the metal ions in the crude oil to a higher valence state, thereby reducing their complexation ability with other organic substances and transferring them to the aqueous phase; the organic phosphonic acid has a stronger complexation ability with nickel ions compared to other acid groups (such as sulfonic acid groups, carboxyl groups, etc.); therefore, adding an oxidant and / or an organic phosphonic acid is beneficial to improving the removal rate of nickel metal.

[0014] In some embodiments, the inorganic salt includes at least one of ammonium chloride, ammonium nitrate, and ammonium sulfate.

[0015] In some embodiments, the polyether includes polyoxyethylene ether, polyoxypropylene ether, or a block copolymer of the two.

[0016] In some embodiments, the universal crude oil desalting agent, calculated by mass parts, comprises the following components: 5-10 parts of oxidant, 6-10 parts of organic phosphonic acid, 4-10 parts of inorganic salt, 10-20 parts of polymer-modified clay mineral, 20-40 parts of polyether, and 20-50 parts of solvent 1.

[0017] In some embodiments, solvent 1 is at least one of water and ethanol.

[0018] In some embodiments, the clay mineral is at least one of attapulgite clay, montmorillonite or bentonite.

[0019] In some embodiments, the particle size of the polymer-modified clay mineral is 50-150 μm; at this particle size, it is beneficial to balance the dispersibility and sedimentation of the polymer-modified clay mineral. If the particle size is too large, the sedimentation is too fast, and if the particle size is too small, it is difficult to sediment and easy to agglomerate.

[0020] In some embodiments, the preparation method of the polymer-modified clay mineral comprises the following steps:

[0021] (1) Synthesize small molecule RAFT agent

[0022] Drop 2-mercaptoethyltriethoxysilane into the ethanol solution of sodium methoxide and stir for reaction 1, then drop carbon disulfide and stir for reaction 2, and finally drop methyl 4-(bromomethyl)phthalate or benzyl bromide and stir for reaction 3. After purification and drying, the small molecule RAFT agent is obtained;

[0023] (2) Synthesize small molecule RAFT agent modified clay mineral

[0024] Treat the clay mineral with acid, then disperse it in an aqueous alcohol solution, add the small molecule RAFT agent and the base agent and stir for reaction 4. After filtration, washing and drying, the small molecule RAFT agent modified clay mineral is obtained;

[0025] (3) Prepare polymer-modified clay mineral

[0026] Disperse the small molecule RAFT agent modified clay mineral in solvent 2, add the polymer monomer and the initiator and stir for reaction 5. After filtration, washing and drying, an intermediate is obtained; after quaternization of the intermediate, filter, wash, dry and crush to obtain the polymer-modified clay mineral.

[0027] In some embodiments, the reaction temperature of the stirring reaction 1 in step (1) is 10-25 °C, and the reaction time is 2 h;

[0028] In some embodiments, the reaction temperature of the stirring reaction 2 is 10-25 °C, and the reaction time is 4 h;

[0029] In some embodiments, the reaction temperature of the stirring reaction 3 is 10-25 °C, and the reaction time is 12 h;

[0030] In some embodiments, the molar ratio of sodium methoxide, 2-mercaptoethyltriethoxysilane, carbon disulfide, and methyl 4-(bromomethyl)phthalate is 1:1:1:1;

[0031] In some embodiments, the purification means that after the solvent of the reaction solution obtained from the stirring reaction 3 is evaporated to dryness, it is dissolved in dichloromethane, washed with water, repeated three times, and the organic phase is collected;

[0032] In some embodiments, the drying means that the organic phase obtained by purification is dried with magnesium sulfate and then the solvent is evaporated by vacuum distillation.

[0033] In some embodiments, the acid treatment in step (2) means that the clay mineral is dispersed in 0.2 mol / L hydrochloric acid, stirred for 12 h, then filtered, washed with water and dried to obtain;

[0034] In some embodiments, the aqueous alcohol solution is a 20 vt% aqueous ethanol solution;

[0035] In some embodiments, the base agent is selected from sodium hydroxide or potassium hydroxide;

[0036] In some embodiments, the reaction temperature of the stirring reaction 4 is 40-60 °C, and the reaction time is 10-12 h;

[0037] In some embodiments, the clay mineral is selected from at least one of attapulgite clay, montmorillonite, or bentonite.

[0038] In some embodiments, the solvent 2 in step (3) is selected from at least one of N,N-dimethylformamide, toluene, and dioxane;

[0039] In some embodiments, the polymer monomer includes at least one of 4-vinylbenzoic acid, methacrylic acid, acrylic acid, 2-hydroxyethyl acrylate, 2-(dimethylamino)ethyl acrylate, and 2-(dimethylamino)ethyl methacrylate;

[0040] In some embodiments, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptonitrile, and dimethyl 2,2'-azobis(2-methylpropionate);

[0041] In some embodiments, the reaction temperature of the stirring reaction 5 is 60-80 °C, the reaction time is 24-48 h, and the reaction atmosphere is an anaerobic environment;

[0042] In some embodiments, the quaternization means that the intermediate is subjected to a stirring reaction with an alkyl halide.

[0043] The present invention has the following beneficial effects:

[0044] The present invention provides a crude oil desalting agent, which plays the role of binding metal ions based on the complexation method and the precipitation method, can remove various metal elements (including Ni, Ca, Fe, etc.) in crude oil, and in addition, the desalting agent also improves the polarity of the aqueous phase, thereby increasing the dehydration rate of crude oil. When applied to an electric desalting system, it can improve the dehydration speed and degree. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. 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 be obtained based on these drawings without creative efforts.

[0046] Figure 1 It is a schematic diagram of the route for preparing polymer-modified clay minerals in Example 1.

[0047] Figure 2 It is a thermogravimetric analysis diagram of unmodified attapulgite, clay minerals modified with small molecule RAFT agents, and polymer-modified clay minerals in Test Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] 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. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.

[0049] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary-secondary relationship of the indicated technical features.

[0050] The mention of "embodiment" in this article means that the specific features, structures, or characteristics described in connection with the embodiment may be included in at least one embodiment of the present application. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0051] In the embodiments of the present application, the term "or / and" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A or / and B can represent: A exists alone, A and B exist simultaneously, and B exists alone.

[0052] In addition, in this text, the character " / " generally indicates an "or" relationship between the associated objects before and after.

[0053] In the embodiments of the present application, the meaning of "a plurality of" refers to two or more (including two). Similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of layers" refers to two or more layers (including two layers), unless otherwise clearly specified and limited.

[0054] In the embodiments of the present application, the meaning of "at least one" refers to one or more than one.

[0055] Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application according to specific circumstances.

[0056] The features and performance of the present invention will be further described in detail below in conjunction with embodiments.

[0057] Embodiment 1

[0058] A general-purpose crude oil desalting agent, calculated by mass fraction, comprises the following components: 10 parts of inorganic salt, 15 parts of polymer-modified clay mineral, 35 parts of polyether, 25 parts of water, and 15 parts of ethanol; wherein, the inorganic salt is ammonium nitrate, and the polyether is octadecylamine polyoxyethylene ether (MOA-3, purchased from Jiangsu Haian Petrochemical Factory); the preparation method of the polymer-modified clay mineral is as follows:

[0059] (1) Synthesize small molecule RAFT agent

[0060] Drop 2-mercaptoethyltriethoxysilane into the ethanol solution of sodium methoxide, stir and react at 25°C for 2 h, then drop in carbon disulfide and stir and react for 4 h, and finally drop in methyl 4-(bromomethyl)phthalate and stir and react for 12 h. After the obtained reaction solution is evaporated to dryness of the solvent, it is redissolved with dichloromethane, and washed with an equal volume of water, and the washing is repeated three times. The organic phase is collected, dried with magnesium sulfate, and then evaporated to dryness of the solvent under reduced pressure to obtain the small molecule RAFT agent with the structure of Formula I. 1 H-NMR(400MHz,CDCl3): δ1.22(t,CH3,9H),1.28(t,SiCH2,2H),2.85(t,S-CH2,2H),3.81~3.89(m,OCHx,12H), 4.51(s,SCH2,2H),7.62~7.94(ArH,3H).

[0061]

[0062] Among them, the molar ratio of sodium methoxide, 2-mercaptoethyltriethoxysilane, carbon disulfide, and methyl 4-(bromomethyl)phthalate is 1:1:1:1.

[0063] (2) Modification of clay minerals with small molecule RAFT agents

[0064] Disperse attapulgite in 0.2 mol / L hydrochloric acid and stir for 12 h, then filter and wash with water until the washing liquid is neutral, and then redisperse it in a 20 vt% aqueous alcohol solution. Add a small molecule RAFT agent and sodium hydroxide, heat up to 50 °C and stir for 10 h. After filtration, washing with water and drying, the clay minerals modified with small molecule RAFT agents are obtained.

[0065] Among them, the feeding mass ratio of attapulgite to the small molecule RAFT agent is 1:1; sodium hydroxide is added according to adjusting the pH of the reaction solution to 8.

[0066] (3) Preparation of polymer-modified clay minerals

[0067] Disperse the clay minerals modified with small molecule RAFT agents in N,N-dimethylformamide (DMF), add polymer monomers and initiators, heat up to 70 °C and stir in an anaerobic environment for 48 h. After filtration, washing with DMF and drying, an intermediate is obtained; disperse the intermediate in DMF, dropwise add bromoethane, react at room temperature for 12 h, wash with DMF, dry and then perform airflow crushing to obtain polymer-modified clay minerals with a particle size of 50 - 150 μm.

[0068] Among them, the polymer monomers are a mixture of 4-vinylbenzoic acid, methacrylic acid, and dimethylaminoethyl methacrylate with a molar ratio of 1:1:10; the initiator is azobisisobutyronitrile, and the addition amount is 3% of the total mass of the polymer monomers; the mass ratio of the clay minerals modified with small molecule RAFT agents to the polymer monomers is 1:5; the mass ratio of the intermediate to bromoethane is 1.5:1.

[0069] Example 2

[0070] The difference from Example 1 is that in the preparation method of the polymer-modified clay minerals, the polymer monomers are a mixture of 4-vinylbenzoic acid, methacrylic acid, and dimethylaminoethyl methacrylate with a molar ratio of 1:1:5.

[0071] Example 3

[0072] The difference from Example 1 is that in the preparation method of the polymer-modified clay minerals, the polymer monomers are a mixture of 4-vinylbenzoic acid, methacrylic acid, and dimethylaminoethyl methacrylate with a molar ratio of 1:1:15.

[0073] Example 4

[0074] A universal crude oil desalting agent, calculated by mass fraction, includes the following components: 8 parts of oxidant, 8 parts of inorganic salt, 14 parts of polymer-modified clay mineral (the same as in Example 1), 30 parts of polyether, 25 parts of water, and 15 parts of ethanol; wherein, the oxidant is ammonium persulfate, the inorganic salt is ammonium nitrate, and the polyether is polyoxyethylene ether.

[0075] Example 5

[0076] A universal crude oil desalting agent, calculated by mass fraction, includes the following components: 8 parts of organic phosphonic acid, 8 parts of inorganic salt, 14 parts of polymer-modified clay mineral (the same as in Example 1), 30 parts of polyether, 25 parts of water, and 15 parts of ethanol; wherein, the organic phosphonic acid is diethylenetriamine pentamethylene phosphonic acid, the inorganic salt is ammonium nitrate, and the polyether is polyoxyethylene ether.

[0077] Example 6

[0078] A universal crude oil desalting agent, calculated by mass fraction, includes the following components: 5 parts of oxidant, 6 parts of organic phosphonic acid, 5 parts of inorganic salt, 15 parts of polymer-modified clay mineral (the same as in Example 1), 29 parts of polyether, 25 parts of water, and 15 parts of ethanol; wherein, the oxidant is ammonium persulfate, the organic phosphonic acid is diethylenetriamine pentamethylene phosphonic acid, the inorganic salt is ammonium nitrate, and the polyether is oxyethylene ether.

[0079] Example 7

[0080] A universal crude oil desalting agent, calculated by mass fraction, includes the following components: 16 parts of oxidant, 10 parts of organic phosphonic acid, 4 parts of inorganic salt, 10 parts of polymer-modified clay mineral (the same as in Example 1), 26 parts of polyether, 19 parts of water, and 15 parts of ethanol; wherein, the oxidant is 30wt% hydrogen peroxide aqueous solution, the organic phosphonic acid is hydroxyethylidene diphosphonic acid, the inorganic salt is ammonium sulfate, and the polyether is nonylphenol polyoxyethylene ether (NP-5, purchased from Jiangsu Haian Petrochemical Factory).

[0081] Example 8

[0082] A universal crude oil desalting agent, calculated by mass fraction, includes the following components: 16 parts of oxidant, 6 parts of organic phosphonic acid, 4 parts of inorganic salt, 20 parts of polymer-modified clay mineral (the same as in Example 1), 20 parts of polyether, 19 parts of water, and 15 parts of ethanol; wherein, the oxidant is 30wt% hydrogen peroxide aqueous solution, the organic phosphonic acid is a mixture of aminotrimethylene phosphonic acid and ethylenediaminetetra(methylene phosphonic acid) with a mass ratio of 1:1, the inorganic salt is ammonium sulfate, and the polyether is polyoxypropylene ether.

[0083] Example 9

[0084] The difference from Example 6 is that the preparation method of the polymer-modified clay mineral is as follows:

[0085] (1) Synthesis of small molecule RAFT agent

[0086] 2-Mercaptoethyltriethoxysilane was added dropwise to an ethanol solution of sodium methoxide, and the mixture was stirred at 25 °C for 2 h. Then, carbon disulfide was added dropwise and the mixture was stirred for 4 h. Finally, benzyl bromide was added dropwise and the mixture was stirred for 10 h. After the solvent of the resulting reaction solution was evaporated, it was redissolved in dichloromethane and washed with an equal volume of water. The washing was repeated three times. The organic phase was collected, dried with magnesium sulfate, and then the solvent was evaporated under reduced pressure to obtain the small molecule RAFT agent with the following structure of Formula II. 1 H-NMR (400 MHz, CDCl3): δ 1.22 (t, CH3, 9H), 1.26 (t, SiCH2, 2H), 2.83 (t, SCH2, 2H), 3.84 (m, OCH2, 6H), 4.55 (s, SCH2, 2H), 7.22 - 7.28 (ArH, 4H).

[0087]

[0088] Among them, the molar ratio of sodium methoxide, 2-mercaptoethyltriethoxysilane, carbon disulfide, and benzyl bromide is 1:1:1:1.

[0089] (2) The same as Example 1.

[0090] (3) The same as Example 1.

[0091] Comparative Example 1

[0092] A desalting agent, which is different from that of Example 1 in that an equal amount of citric acid is used instead of the polymer-modified clay mineral.

[0093] Comparative Example 2

[0094] A desalting agent, which is different from that of Example 1 in that a mixture of unmodified attapulgite and polymer with a mass ratio of 1:5 is used instead of the polymer-modified clay mineral; the preparation method of the polymer is as follows:

[0095] (1) Synthesis of small molecule RAFT agent

[0096] 2-Mercaptoethyltriethoxysilane was added dropwise to an ethanol solution of sodium methoxide, and the mixture was stirred at 25 °C for 2 h. Then, carbon disulfide was added dropwise and the mixture was stirred for 4 h. Finally, methyl 4-(bromomethyl)phthalate was added dropwise and the mixture was stirred for 12 h. After the solvent of the resulting reaction solution was evaporated, it was redissolved in dichloromethane and washed with an equal volume of water. The washing was repeated three times. The organic phase was collected, dried over magnesium sulfate, and the solvent was evaporated under reduced pressure to obtain a small molecule RAFT agent containing an ester group. Further, the small molecule RAFT agent containing an ester group was dispersed in an aqueous alcohol solution of 20 vt%, and sodium hydroxide was added to adjust the pH to 8. The temperature was raised to 50 °C and the mixture was stirred for 10 h for hydrolysis reaction. After the reaction solution was concentrated to 1 / 3 volume, it was purified by silica gel column chromatography and dried to obtain a small molecule RAFT agent with the following structure of formula III. 1 H-NMR (400 MHz, CDCl3): δ 1.24 (t, CH3, 9H), 1.28 (t, SiCH2, 2H), 2.86 (t, SCH2, 2H), 3.84 (m, OCH2, 6H), 4.57 (s, SCH2, 2H), 7.80 - 8.05 (ArH, 3H), 12.84 (s, COOH, 2H).

[0097]

[0098] Among them, the molar ratio of sodium methoxide, 2-mercaptoethyltriethoxysilane, carbon disulfide, and methyl 4-(bromomethyl)phthalate is 1:1:1:1.

[0099] (2) Synthesis of polymer

[0100] The small molecule RAFT agent was dispersed in N,N-dimethylformamide (DMF), and the polymer monomer and initiator were added. The temperature was raised to 70 °C and the mixture was stirred in an anaerobic environment for 48 h. After the reaction solution was cooled to room temperature, bromoethane was added dropwise and the reaction was carried out at room temperature for 12 h. The reaction solution was concentrated and then purified by dialysis against water and dried to obtain the polymer.

[0101] Among them, the molar ratio of the small molecule RAFT agent, 4-vinylbenzoic acid, methacrylic acid, dimethylaminoethyl methacrylate, and bromoethane is 1:5:5:50:60; the initiator is azobisisobutyronitrile, and the addition amount is 3% of the total mass of the polymer monomer.

[0102] Comparative Example 3

[0103] A desalting agent, which is different from Example 6 in that a mixture of unmodified attapulgite and polymer (the same as in Comparative Example 2) with a mass ratio of 1:5 is used to replace the polymer-modified clay mineral.

[0104] Test Example 1 Thermogravimetric analysis test

[0105] The thermal stability and organic matter content of the samples were tested using a Pyris Diamond TG / DTA 6300 thermogravimetric analyzer from Perkin Elmer Instruments in the United States. The heating rate was 10 °C / min, the nitrogen atmosphere was used, and the test temperature range was from room temperature to 800 °C. The samples included the raw attapulgite clay of Example 1, the clay mineral modified with a small molecule RAFT agent, and the polymer-modified clay mineral. The results are as Figure 2 shown.

[0106] It can be seen from Figure 2 that the weight loss within 100 °C is about 4% - 8%, which is caused by the water volatilization of attapulgite and is recorded as Stage I; the maximum weight loss occurs within 100 - 650 °C, which is caused by the decomposition and gasification of organic matter and is recorded as Stage II; the weight loss within 200 - 650 °C is statistically counted to evaluate the organic matter content. The weight loss rates of the raw attapulgite clay, the clay mineral modified with a small molecule RAFT agent, and the polymer-modified clay mineral are 9.87%, 10.94%, and 22.36% respectively. This shows that the small molecule RAFT agent has been successfully grafted onto the surface of attapulgite, and polymerization has been successfully initiated on the surface of the clay mineral modified with the small molecule RAFT agent.

[0107] Test Example 2 Dehydration Rate Test

[0108] The crude oil used was Shengli Gudao crude oil, with a density of 0.9125 g / mL, a viscosity (at 50 °C) of 956 MPa·s, an S content of 1.22%, an acid value of 7.53 mg KOH / g, and a salt content of 62.1 mg NaCl / L.

[0109] According to the industry standard SY / T 5281-2000 "Test Method for the Performance of Crude Oil Demulsifiers" (bottle test method) to evaluate the dehydration performance, the dehydration temperature was 40 °C, the dosage of the desalting agent was 90 mg / L, the water dehydration amounts at different times were recorded, and at the same time, the interface and the dehydrated water situation were observed, and the dehydration rate = (dehydration amount / water content of the crude oil emulsion) × 100% was calculated. The results are listed in Table 1.

[0110] Table 1

[0111]

[0112]

[0113] As can be seen from Table 1, the desalting agent provided by the embodiments of the present invention has a better dehydration rate compared with the comparative examples. In Comparative Example 1, no polymer-modified clay mineral was added, and in Comparative Example 2, an unmodified clay mineral and a RAFT polymer were added, resulting in a lower dehydration rate for both. Clay minerals have a high specific surface area and can adsorb natural emulsifiers (such as asphaltenes and resins) in crude oil. This adsorption directly weakens the mechanical strength of the oil-water interface film, thus achieving demulsification. Further, the hydrophobic main chain in the polymer long chain of the polymer-modified clay mineral covers the clay surface, reducing its hydrophilicity, enhancing its compatibility with the oil phase, and promoting the rupture of the oil-water interface film. In addition, quaternary ammonium salt functional groups are grafted onto the polymer chain, achieving demulsification through the synergistic effect of charge neutralization and hydrophobic adsorption. The positive charges carried by them can adjust the system conductivity during the electro-desalting process, enhancing the polarization effect of the electric field on water droplets, which is closely related to the clay particles acting as charge carriers to promote the compression of the double electric layer. Therefore, polymer modification significantly improves the demulsification ability and dehydration ability of clay minerals. In Examples 1 to 3, different specifications of polymers were used to modify the clay minerals. From the results, it can be seen that the more the number of quaternary ammonium salt repeating units, the dehydration ability first increases and then decreases. The reason is that the more quaternary ammonium salt units, the stronger the charge neutralization ability, but the lower the hydrophobicity, resulting in a decrease in the synergistic demulsification ability. In Example 4, an oxidant was added compared with Example 1, and it had little effect on the dehydration efficiency. In Example 5, the dehydration rate decreased slightly after adding organic phosphonic acid. The reason is that organic phosphoric acid or its complex with metal reduced the polarization effect of water droplets to a certain extent. In Example 7, the content of inorganic salts or / and polymer-modified clay minerals in the desalting agent decreased, resulting in a decrease in its dehydration rate. In Example 8, the content of polymer-modified clay minerals in the desalting agent increased, so the dehydration effect was improved compared with Example 7 and was similar to that of Example 1.

[0114] Desalting Rate Test of Test Example 3

[0115] The YS-3 type electric desalting tester was adopted; the test oils included Tahe crude oil (with a density of 936.7 kg / m3, an S content of 2.1%, and a salt content of 274.5 mg NaCl / L), Shengli Gudao crude oil (with a density of 0.9125 g / mL, an S content of 1.22%, and a salt content of 62.1 mg NaCl / L), and Xinjiang Northwest crude oil (with a density of 0.8952 g / mL, an S content of 1.41%, and a salt content of 45.5 mg NaCl / L); the crude oil and water were mixed at a volume ratio of 285:15 to obtain an emulsion and put into the electric desalting tester. The oil temperature was 100 °C and the electric field strength was 800 V / cm for secondary desalting. When performing primary desalting, the addition amount of the desalting agent was 1200 μg / L. When performing secondary desalting, an equal amount of water was supplemented and the desalting agent was supplemented at 600 μg / L. Inductively coupled plasma emission spectrometry was used to measure the metal elements before and after electric desalting, and the metal removal rate was calculated as = (content before desalting - content after desalting) / content before desalting × 100%. The results are listed in Tables 2 to 4.

[0116] Table 2: Tahe Crude Oil

[0117]

[0118] It can be seen from the results that the desalting agent provided in the embodiments of the present invention has a removal effect on various metals and has universality. Specifically, in Comparative Example 3, unmodified clay minerals and RAFT polymers were added compared to Example 6. Due to the poor dehydration effect, the desalting efficiency was also low; in Comparative Example 9, the polymer-modified clay minerals added compared to Example 6 did not have catechol groups, resulting in a lower iron element removal rate, indicating that the coordination space provided by the catechol groups can better complex iron ions, thereby increasing the iron element removal rate. In Example 4, an oxidant was further added compared to Example 1, resulting in an increase in the removal rates of nickel and iron elements, indicating that the addition of the oxidant is beneficial to the oxidation of nickel ions from the low valence state to the high valence state and reduces their complexing ability with other organic substances; in Example 5, an organic phosphonic acid was further added compared to Example 1, resulting in an increase in the removal rate of nickel elements, indicating that the addition of organic phosphoric acid has a stronger complexing ability with carboxyl groups and nickel ions; in Example 6, an oxidant and an organic phosphonic acid were added simultaneously, so the comprehensive metal removal rate was the highest.

[0119] Table 3: Shengli Gudao Crude Oil

[0120]

[0121] Table 4: Xinjiang Northwest Crude Oil

[0122]

[0123] Based on the results of Tables 1 to 3, it can be seen that the desalting agent provided by the present invention is applicable to crude oils with various salt contents, has a removal effect on various metals, and has universality.

[0124] 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 within the protection scope of the present invention.

Claims

1. A universal crude oil desalting agent and its preparation method, characterized in that, The invention comprises the following components: an inorganic salt, a polymer-modified clay mineral, and a polyether, wherein the polymer-modified clay mineral comprises a clay mineral and a polymer chemically bonded to the surface of the clay mineral; the polymer is a copolymer and comprises the following repeating units (a) to (c); Wherein, R1 and R2 are independently selected from H or CH3, R3 is H or an alkyl group having 1 to 3 carbon atoms; X is one of Cl, Br and OH, and * is a site for linking other repeating units.

2. The universal crude oil desalting agent according to claim 1, characterized in that, The polymer also contains catechol groups.

3. The universal crude oil desalting agent according to claim 1 or 2, characterized in that, The universal crude oil desalter further comprises an oxidant and / or an organic phosphonic acid; Preferably, the oxidant is selected from at least one of hydrogen peroxide, ammonium persulfate and sodium persulfate; Preferably, the organic phosphonic acid is selected from at least one of aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid or its salt, hydroxyethylenediphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, diethylenetriaminepenta(methylenephosphonic acid) and sodium diphosphonopropionylphosphonate.

4. The universal crude oil desalting agent according to any one of claims 1 to 3, characterized in that The inorganic salt includes at least one of ammonium chloride, ammonium nitrate and ammonium sulfate; And / or, the polyether includes polyoxyethylene ether, polyoxypropylene ether or a block copolymer thereof.

5. The universal crude oil desalting agent according to any one of claims 1 to 4, characterized in that, The universal crude oil desalter comprises the following components, calculated by weight: 5 to 10 parts of an oxidant, 6 to 10 parts of an organic phosphonic acid, 4 to 10 parts of an inorganic salt, 10 to 20 parts of a polymer-modified clay mineral, 20 to 40 parts of a polyether, and 20 to 50 parts of solvent 1.

6. The universal crude oil desalting agent according to claim 5, characterized in that, The solvent 1 is at least one of water and ethanol; And / or, the clay mineral is at least one of attapulgite, montmorillonite or bentonite; And / or, the particle size of the polymer-modified clay mineral is 50 to 150 μm.

7. The universal crude oil desalting agent according to any one of claims 1 to 6, characterized in that, The preparation method of the polymer-modified clay mineral comprises the following steps: (1) Synthesis of small molecule RAFT agents 2-mercaptoethyltriethoxysilane is added dropwise to an ethanol solution of sodium methoxide to carry out a stirring reaction 1, followed by a stirring reaction 2, and finally a stirring reaction 3 by adding methyl 4-(bromomethyl)phthalate or benzyl bromide. After purification and drying, a small molecule RAFT agent is obtained. (2) Synthesis of small molecule RAFT agents to modify clay minerals The clay mineral is treated with acid, then dispersed in an alcohol aqueous solution, a small molecule RAFT agent and an alkaline agent are added and stirred for reaction 4, and the small molecule RAFT agent-modified clay mineral is obtained after filtering, washing, and drying; (3) Preparation of polymer-modified clay minerals A small molecule RAFT agent modified clay mineral is dispersed in a solvent 2, a polymer monomer and an initiator are added and stirred for reaction 5, and an intermediate is obtained by filtering, washing, and drying. After quaternization of the intermediate, the intermediate is filtered, washed, dried, and crushed to obtain a polymer-modified clay mineral.

8. The universal crude oil desalting agent according to claim 7, characterized in that, The reaction temperature of the stirring reaction 1 in step (1) is 10-25° C. and the reaction time is 2 h; And / or, the reaction temperature of the stirring reaction 2 is 10-25° C. and the reaction time is 4 h; And / or, the reaction temperature of the stirring reaction 3 is 10-25° C. and the reaction time is 12 h; And / or, the molar ratio of sodium methoxide, 2-mercaptoethyltriethoxysilane, carbon disulfide, and methyl 4-(bromomethyl)phthalate is 1:1:1:1; And / or, the purification means that after evaporating the solvent from the reaction solution obtained from Stirring Reaction 3, dissolving it in dichloromethane, adding water for washing, repeating three times, and collecting the organic phase.

9. The universal crude oil desalting agent according to claim 7, characterized in that The acid treatment in step (2) means that the clay mineral is dispersed in 0.2 mol / L hydrochloric acid and stirred for 12 h, then filtered, washed with water, and dried to obtain; And / or, the aqueous alcohol solution is a 20 vt% ethanol aqueous solution; And / or, the base agent is selected from sodium hydroxide or potassium hydroxide; And / or, the reaction temperature of Stirring Reaction 4 is 40 - 60 °C, and the reaction time is 10 - 12 h; And / or, the clay mineral is selected from at least one of attapulgite clay, montmorillonite, or bentonite.

10. The universal crude oil desalting agent according to claim 7, characterized in that, The solvent 2 in step (3) is selected from at least one of N,N-dimethylformamide, toluene, and dioxane; And / or, the polymer monomer includes at least one of 4-vinylbenzoic acid, methacrylic acid, acrylic acid, 2-hydroxyethyl acrylate, dimethylaminoethyl acrylate, and dimethylaminoethyl methacrylate; And / or, the initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptonitrile, and dimethyl 2,2'-azobis(2-methylpropionate); And / or, the reaction temperature of Stirring Reaction 5 is 60 - 80 °C, the reaction time is 24 - 48 h, and the reaction atmosphere is an anaerobic environment; And / or, the quaternization means that the intermediate is subjected to a stirring reaction with an alkyl halide.

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