An oil-based hydrate nucleation inhibitor, its preparation method and application

Abstract

The application discloses an oil-based hydrate nucleation inhibitor and a preparation method and application thereof. The preparation method of the inhibitor comprises the following steps: (1) heating ethylene tar to a molten state; (2) loading the ethylene tar heated in the step (1) into a reaction kettle, and performing oxidative heat treatment under stirring by inputting an oxidizing gas; (3) stopping inputting of the oxidizing gas, replacing the oxidizing gas in the reaction kettle by using a protective gas, and then performing closed heat treatment on the material obtained in the step (2) under the protective gas to obtain an oil-based inhibitor component; and (4) after cooling the oil-based inhibitor component obtained in the step (3), placing the oil-based inhibitor component in a solvent, and mixing the oil-based inhibitor component with light oil to obtain the oil-based hydrate nucleation inhibitor. The oil-based hydrate nucleation inhibitor prepared by the method can obviously prolong a hydrate induction period and inhibit hydrate nucleation.

Description

Technical Field

[0001] This invention relates to the field of hydrate inhibitors, and particularly to an oil-based hydrate nucleation inhibitor, its preparation method, and its application. Background Technology

[0002] During subsea oil extraction, produced fluids containing crude oil, natural gas, and water need to be transported to onshore processing facilities via subsea pipelines. The low-temperature environment and high-pressure conditions inside the pipelines greatly increase the risk of gas hydrate formation. The formation of hydrates increases fluid viscosity, increases pipeline pressure drop, and in severe cases, can block the pipeline, causing a shutdown and resulting in significant economic losses.

[0003] When the environment of a multiphase system meets the conditions for hydrate formation, the hydrate will remain in a metastable state for a certain period before forming. The hydrate induction period is often defined as the difference between the hydrate formation time and the time when the system enters a three-phase equilibrium state. Once hydrates begin to appear, they grow rapidly in a short time, easily leading to safety accidents. To prolong the hydrate formation time and increase the hydrate formation induction period, hydrate nucleation inhibitors have been widely used. In recent years, with the development of the South China Sea oilfield and the rapid development of offshore oil and gas extraction, the demand for hydrate nucleation inhibitors has been increasing. Traditional thermodynamic inhibitors are mainly composed of methanol and ethylene glycol, but they need to be added in large quantities, typically at a mass fraction of 30% to 50% of the liquid phase, which greatly affects crude oil quality and pollutes the environment.

[0004] CN116083065A discloses a low-dose natural gas hydrate inhibitor and its preparation method. The inhibitor is obtained by compounding organic solvents such as poly(N-vinylcaprolactam), dimethyl sulfoxide, formate, and gemini quaternary ammonium salts, which can inhibit hydrate nucleation and prolong the time for hydrate formation. However, this method requires the addition of multiple chemical reagents, making the operation complex and costly. Furthermore, in practical applications, the addition of large amounts of poly(N-vinylcaprolactam) and quaternary ammonium salts increases the viscosity of the liquid phase and the emulsion interface strength within the pipeline, increasing pipeline operation and crude oil processing pressure.

[0005] CN114276793A discloses an environmentally friendly natural gas hydrate inhibitor and its application. This method primarily uses nisin as the main component of the hydrate inhibitor, which is obtained by compounding it with chitosan oligosaccharide and alcohol-based thermodynamic hydrate inhibitors. However, this hydrate inhibitor is mainly suitable for pure water systems, requires a large amount of reagent, and when applied to crude oil pipelines, the addition of non-crude oil components such as nisin increases the difficulty of subsequent crude oil separation.

[0006] To reduce the dosage of inhibitors, low-dose hydrate nucleation inhibitors are gaining increasing attention. Low-dose inhibitors can prolong the hydrate induction period and delay hydrate formation. In recent years, oil-based hydrate inhibitors have attracted widespread attention from researchers due to their low dosage, significant effects, and minimal impact on crude oil quality. However, current oil-based hydrate nucleation inhibitors suffer from low production efficiency, a small proportion of effective components in the feedstock, and the inhibitory effect on hydrate nucleation can be further enhanced. Summary of the Invention

[0007] The purpose of this invention is to provide an oil-based hydrate nucleation inhibitor, its preparation method, and its application. The oil-based hydrate inhibitor prepared by this invention can significantly prolong the hydrate induction period and inhibit hydrate nucleation. The method of this invention is simple, uses readily available and inexpensive raw materials, requires small amounts of chemical reagents, and has a significant effect when applied.

[0008] This invention provides a method for preparing an oil-based hydrate nucleation inhibitor, comprising the following steps:

[0009] (1) Heat the ethylene tar to a molten state;

[0010] (2) The heated ethylene tar from step (1) is loaded into a reaction vessel and oxidized under stirring by introducing oxidizing gas;

[0011] (3) Stop the input of oxidizing gas, replace the oxidizing gas in the reactor with protective gas, and then perform closed heat treatment on the material obtained in step (2) under protective gas to obtain oil-based inhibitor components.

[0012] (4) After cooling the oil-based inhibitor component obtained in step (3), place it in a solvent and mix it with light oil to obtain an oil-based hydrate nucleation inhibitor.

[0013] Further, in step (1), the ethylene tar has the following properties: a density of 1.05 g / cm³ at 20°C. 3 ~1.10g / cm 3 The residual carbon has a mass content of 10.1 wt% to 18.0 wt%, an initial boiling point of 150 to 180 °C, a carbon content of 91 wt% to 93 wt%, a hydrogen content of 6.2 wt% to 8.1 wt%, and by mass fraction, saturated components of 0.1 wt% to 15.0 wt%, aromatic components of 30.5 wt% to 68.5 wt%, gums of 20.1 wt% to 35.8 wt%, asphaltenes of 8.5 wt% to 20.5 wt%, and ash content of less than 0.01 wt%.

[0014] Further, in step (1), the temperature at which the material is heated to a molten state is 130-180°C, preferably 130-150°C, and the heating time is preferably 1-3 hours.

[0015] Furthermore, in step (1), it is preferable to distill the ethylene tar heated to a molten state to remove light components.

[0016] Furthermore, the distillation can be atmospheric distillation and / or vacuum distillation, and the distillation temperature is 150–480°C, preferably 200–450°C.

[0017] Furthermore, the content of light components distilled is 10 wt% to 60 wt% of the initial feed mass, preferably 10 wt% to 50 wt% of the initial feed mass.

[0018] Furthermore, in step (2), the reactor is a high-pressure reactor.

[0019] Further, in step (2), the temperature of the oxidation heat treatment is 300–400℃, preferably 350–380℃, and the heating is performed using a programmed temperature rise rate of 0.5–2.5℃ / min. The oxidation heat treatment time is 0.2–2h, preferably 0.5–1.5h. The stirring speed is 100–400rpm, preferably 100–300rpm.

[0020] Further, in step (2), the oxidizing gas is oxygen-enriched air (oxygen volume content of 25v% to 60v%), and the gas flow rate is 0.05 to 0.5 m³ / h. 3 / kg / h.

[0021] Furthermore, in step (2), the oxidizing gas maintains the pressure inside the reactor at 0.2 to 0.7 MPa.

[0022] Further, in step (3), the protective gas is at least one of nitrogen and an inert gas; the flow rate of the protective gas is 0.05–0.5 m³ / s. 3 / kg / h.

[0023] Further, in step (3), the temperature of the closed heat treatment is 360–450°C, preferably 380–420°C; the pressure of the closed heat treatment is 0.5–4.5 MPa, preferably 2–4 MPa; and the time of the closed heat treatment is 2–8 h, preferably 3–6 h. During the closed heat treatment, continuous stirring is performed at a speed of 100–300 rpm.

[0024] Further, in step (4), the cooling is simply cooling to room temperature. The solvent is one or more of toluene, xylene, and quinoline. The light oil is one or more of diesel, mineral oil, and condensate oil. The mass ratio of solvent to light oil is 1:0.5-2, and the mass ratio of oil-based inhibitor component to solvent is 2-5:95-98.

[0025] Further, in step (4), after the oil-based inhibitor obtained in step (3) is cooled, it is placed in a solvent and subjected to ultrasonic vibration to fully disperse it. The ultrasonic frequency of the ultrasonic vibration process is 20KHz~60KHz, the ultrasonic vibration time is 20~40min, and the ultrasonic vibration temperature is preferably 20~60℃.

[0026] Furthermore, in step (4), the mixing with light oil is preferably carried out under ultrasonic vibration, with an ultrasonic frequency of 20KHz to 60KHz, an ultrasonic vibration time of 20 to 40 min, and an ultrasonic vibration temperature of 20 to 60℃.

[0027] This invention provides an oil-based hydrate nucleation inhibitor prepared by the above method.

[0028] This invention provides the application of an oil-based hydrate nucleation inhibitor prepared by the above method in the field of multiphase pipeline transportation.

[0029] When the oil-based hydrate nucleation inhibitor is used, the volume of the aqueous phase is less than 60% of the total volume of the oil and water phases, preferably 10% to 50%. The mass of the oil-based hydrate nucleation inhibitor added accounts for 1% to 5% of the mass of the oil phase. The operating temperature range is -10 to 50°C, and the operating pressure range is 0.1 to 30 MPa.

[0030] Compared with the prior art, the oil-based hydrate nucleation inhibitor of the present invention has the following advantages:

[0031] (1) This invention uses ethylene tar as raw material, which is itself a low-value by-product in the petroleum refining process. Its application as a raw material for nucleation inhibitors of oil-based hydrates broadens its uses, increases its added value, and has economic benefits.

[0032] (2) The oil-based hydrate nucleation inhibitor of the present invention has the advantages of simple preparation method, readily available raw materials, low price, small amount of chemical reagents, small impact on crude oil quality, and small amount used in application. The oil-based hydrate nucleation inhibitor prepared by the present invention has significant effects and can significantly prolong the hydrate formation time, which is of great significance to pipeline safety.

[0033] (3) In the preparation method of the present invention, the oxidative heat treatment and the closed heat treatment can cause the raw materials to undergo condensation, oxidation and other reactions in a high temperature and high pressure environment, thereby increasing the content of the effective components of the hydrate inhibitor in the raw materials and enhancing the effect of the inhibitor. Attached Figure Description

[0034] Figure 1 This is the method for determining the hydrate formation time in Example 1. Detailed Implementation

[0035] The present invention will be further described in detail below through specific embodiments. The described embodiments are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0036] In a specific implementation, the effect of hydrates in inhibiting nucleation was evaluated using a high-pressure stirred tank reactor experiment. The method for determining the hydrate formation time was as follows: Figure 1 As shown, during hydrate formation, the system temperature rises rapidly due to the exothermic reaction of hydrate formation, while the pressure decreases significantly due to gas consumption. The evaluation experimental steps are as follows:

[0037] (1) After cleaning the high-pressure reactor with petroleum ether, pour in 2L of oil-water emulsion, the volume of the aqueous phase is 400mL, add oil-based hydrate inhibitor and then seal the reactor.

[0038] (2) Turn on the stirring paddle and set the speed to 300 rpm. Collect the temperature and pressure parameters inside the vessel in real time through the data acquisition system. Open the gas cylinder and the air inlet valve to introduce carbon dioxide gas into the high-pressure stirring vessel to replace the residual air inside the vessel.

[0039] (3) After the gas is replaced, the reaction gas is continuously introduced into the stirred tank to increase the pressure inside the tank to 2.3 MPa, in order to create a high-pressure environment to generate carbon dioxide hydrate.

[0040] (4) The temperature of the fluid in the stirred tank was gradually reduced from 15℃ to 2.6℃ by adjusting the temperature-controlled water bath, and the temperature was maintained until hydrates were formed. The time point of hydrate formation was identified by the abrupt change point of the temperature and pressure curves, and the nucleation induction period of hydrates was calculated by the time point of hydrate formation and the time point of three-phase equilibrium.

[0041] (5) When the system temperature does not change within 30 minutes, the hydrate formation experiment is terminated and the high-pressure stirred tank is cleaned with petroleum ether.

[0042] During the cooling process of the system, the temperature of the fluid in the stirred tank will gradually decrease to the equilibrium temperature, and then continue to decrease to 2.6℃ and remain constant. Once the system temperature is below the equilibrium temperature, there is a possibility of hydrate formation. Therefore, hydrate may occur during both the cooling process and the constant temperature process in the experiment.

[0043] Example 1

[0044] (1) Heat 200g of ethylene tar (properties shown in Table 2) in an oven at 140℃ for 2 hours until it reaches a molten state;

[0045] (2) The molten ethylene tar in step (1) was heated to 224°C and distilled under atmospheric pressure using an atmospheric distillation apparatus to distill off 30 wt% of the initial raw material mass and remove the low-boiling light components from the ethylene tar.

[0046] (3) The distilled material from step (2) is loaded into a high-pressure reactor, and oxygen-enriched air (oxygen volume content of 45%) is introduced under stirring at 100 r / min to perform oxidative heat treatment on the material. The gas flow rate during the heat treatment is 0.1 m³ / min. 3 / kg / h, the pressure inside the reactor is maintained at 0.6MPa, the oxidation heat treatment temperature is 370℃, the heating rate is 2.0℃ / min, and the oxidation time is 0.8h.

[0047] (4) Stop adding oxygen-enriched air, and bring the temperature to 0.1m. 3 Nitrogen gas is introduced into the reactor at a flow rate of / kg / h to replace the residual oxygen-rich air in the reactor. After the replacement is completed, the exhaust valve is closed and nitrogen gas is continuously introduced to increase the pressure to 3.0MPa. The temperature is raised to 400℃ and the stirring speed is kept at 100rpm / min. The material obtained in step (3) is then heat-treated in a sealed manner for 4h.

[0048] (5) After the closed heat treatment process is completed, open the exhaust valve to discharge the gas in the reactor. Cool the material in the reactor to room temperature in a room temperature environment. Take 20g of the material and put it into 40g of o-xylene. Shake it at 40℃ and 40KHz for 30min. Then add 40g of diesel oil and continue to sonicate in the environment for 20min to obtain an oil-based hydrate nucleation inhibitor.

[0049] 26.8 g (2% of the mass of the oil phase) of the hydrate inhibitor prepared in Example 1 was added to an oil-water emulsion (the volume of the aqueous phase was 20% of the total volume of the oil and water phases), and a hydrate formation experiment was conducted using a high-pressure stirred tank (final stable temperature was 2.6℃, and the operating pressure was 2.3 MPa). The hydrate formation results are shown in Table 3.

[0050] Example 2

[0051] (1) Heat 200g of ethylene tar (properties shown in Table 2) in an oven at 140℃ for 2 hours until it reaches a molten state;

[0052] (2) The molten ethylene tar in step (1) was heated to 224°C and distilled under atmospheric pressure using an atmospheric distillation apparatus to distill off 30 wt% of the initial raw material mass and remove the low-boiling light components from the ethylene tar.

[0053] (3) The distilled material from step (2) is loaded into a high-pressure reactor, and oxygen-enriched air (oxygen volume content of 45%) is introduced under stirring at 100 r / min to perform oxidative heat treatment on the material. The gas flow rate during the heat treatment is 0.1 m³ / min. 3 The oxidation rate was 0.6 MPa / kg / h, the pressure inside the reactor was maintained at 0.6 MPa, the oxidation temperature was 370℃, the heating rate was 2.0℃ / min, and the oxidation time was 0.5 h.

[0054] (4) Stop adding oxygen-enriched air, and bring the temperature to 0.1m. 3 Nitrogen gas is introduced into the reactor at a flow rate of / kg / h to replace the residual oxygen-rich air in the reactor. After the replacement is completed, the exhaust valve is closed and nitrogen gas is continuously introduced to increase the pressure to 2.0MPa. The temperature is raised to 380℃ and the stirring speed is kept at 100rpm / min. The material obtained in step (3) is then heat-treated in a sealed manner for 3h.

[0055] (5) After the closed heat treatment process is completed, open the exhaust valve to discharge the gas in the reactor. Cool the material in the reactor to room temperature in a room temperature environment. Take 20g of the material and put it into 40g of o-xylene. Shake it at 40℃ and 40KHz for 30min. Then add 40g of diesel oil and continue to sonicate in the environment for 20min to obtain an oil-based hydrate nucleation inhibitor.

[0056] 26.8 g (2% of the mass of the oil phase) of the hydrate inhibitor prepared in Example 2 was added to an oil-water emulsion (the volume of the aqueous phase was 20% of the total volume of the oil and water phases), and a hydrate formation experiment was conducted using a high-pressure stirred tank (final stable temperature was 2.6℃, and the operating pressure was 2.3 MPa). The hydrate formation results are shown in Table 3.

[0057] Example 3

[0058] (1) Heat 200g of ethylene tar (properties shown in Table 2) in an oven at 140℃ for 2 hours until it reaches a molten state;

[0059] (2) The molten ethylene tar in step (1) was heated to 349°C and distilled under atmospheric pressure using an atmospheric distillation apparatus to distill off 50 wt% of the initial raw material mass and remove the low-boiling light components from the ethylene tar.

[0060] (3) The distilled material from step (2) is loaded into a high-pressure reactor, and oxygen-enriched air (oxygen volume content of 45%) is introduced under stirring at 200 r / min to perform oxidative heat treatment on the material. The gas flow rate during the heat treatment is 0.1 m³ / min. 3 / kg / h, the pressure inside the reactor is maintained at 0.6MPa, the oxidation temperature is 380℃, the heating rate is 2.0℃ / min, and the oxidation time is 1h.

[0061] (4) Stop adding oxygen-enriched air, and bring the temperature to 0.1m. 3 Nitrogen gas is introduced into the reactor at a flow rate of / kg / h to replace the residual oxygen-rich air in the reactor. After the replacement is completed, the exhaust valve is closed and nitrogen gas is continuously introduced to increase the pressure to 4.0MPa. The temperature is raised to 420℃ and the stirring speed is kept at 100rpm / min. The material obtained in step (3) is then heat-treated in a sealed manner for 5h.

[0062] (5) After the closed heat treatment process is completed, open the exhaust valve to discharge the gas in the reactor. Cool the material in the reactor to room temperature in a room temperature environment. Take 20g of the material and put it into 40g of o-xylene. Shake it at 40℃ and 40KHz for 30min. Then add 40g of diesel oil and continue to sonicate in the environment for 30min to obtain an oil-based hydrate nucleation inhibitor.

[0063] 26.8 g (2% of the mass of the oil phase) of the hydrate inhibitor prepared in Example 3 was added to an oil-water emulsion (the volume of the aqueous phase was 20% of the total volume of the oil and water phases), and a hydrate formation experiment was conducted using a high-pressure stirred tank (final stabilization temperature was 2.6℃, and the operating pressure was 2.3MPa). The hydrate formation results are shown in Table 3.

[0064] Example 4

[0065] (1) Heat 200g of ethylene tar (properties shown in Table 2) in an oven at 140℃ for 2 hours until it reaches a molten state;

[0066] (2) The molten ethylene tar in step (1) was heated to 349°C and distilled under atmospheric pressure using an atmospheric distillation apparatus to distill off 50 wt% of the initial raw material mass and remove the low-boiling light components from the ethylene tar.

[0067] (3) The distilled material from step (2) is loaded into a high-pressure reactor, and oxygen-enriched air (oxygen volume content of 45%) is introduced under stirring at 100 r / min to perform oxidative heat treatment on the material. The gas flow rate during the heat treatment is 0.1 m³ / min. 3 The oxidation rate was 0.6 MPa, the pressure inside the reactor was maintained at 0.6 MPa, the oxidation temperature was 370 °C, the heating rate was 2.0 °C / min, and the oxidation time was 0.8 h.

[0068] (4) Stop adding oxygen-enriched air, and bring the temperature to 0.1m. 3 Nitrogen gas is introduced into the reactor at a flow rate of / kg / h to replace the residual oxygen-rich air in the reactor. After the replacement is completed, the exhaust valve is closed and nitrogen gas is continuously introduced to increase the pressure to 3.0MPa. The temperature is raised to 400℃ and the stirring speed is kept at 100rpm / min. The material obtained in step (3) is then heat-treated in a sealed manner for 3h.

[0069] (5) After the closed heat treatment process is completed, open the exhaust valve to discharge the gas in the reactor. Cool the material in the reactor to room temperature in a room temperature environment. Take 20g of the material and put it into 40g of o-xylene. Shake it at 40℃ and 40KHz for 30min. Then add 40g of diesel oil and continue to sonicate in the environment for 20min to obtain an oil-based hydrate nucleation inhibitor.

[0070] 26.8 g (2% of the mass of the oil phase) of the hydrate inhibitor prepared in Example 4 was added to an oil-water emulsion (the volume of the aqueous phase was 20% of the total volume of the oil and water phases), and a hydrate formation experiment was conducted using a high-pressure stirred tank (final stable temperature was 2.6℃, and the operating pressure was 2.3 MPa). The hydrate formation results are shown in Table 3.

[0071] Example 5

[0072] (1) Heat 200g of ethylene tar (properties shown in Table 2) in an oven at 140℃ for 2 hours until it reaches a molten state;

[0073] (2) The molten ethylene tar was directly loaded into a high-pressure reactor, and oxygen-enriched air (oxygen volume content of 45%) was introduced under stirring at 100 r / min to perform oxidative heat treatment on the material. The gas flow rate during the heat treatment was 0.1 m³ / min. 3 The oxidation rate was 0.6 MPa, the pressure inside the reactor was maintained at 0.6 MPa, the oxidation temperature was 370 °C, the heating rate was 2.0 °C / min, and the oxidation time was 0.8 h.

[0074] (3) Stop adding oxygen-enriched air, and bring the temperature to 0.1m. 3 Nitrogen gas is introduced into the reactor at a flow rate of / kg / h to replace the residual oxygen-rich air in the reactor. After the replacement is completed, the exhaust valve is closed and nitrogen gas is continuously introduced to increase the pressure to 3.0MPa. The temperature is raised to 400℃ and the stirring speed is kept at 100rpm / min. The material obtained in step (3) is then heat-treated in a sealed manner for 4h.

[0075] (4) After the closed heat treatment process is completed, open the exhaust valve to discharge the gas in the reactor. Cool the material in the reactor to room temperature in a room temperature environment. Take 20g of the material and put it into 40g of o-xylene. Shake it at 40℃ and 40KHz for 30min. Then add 40g of diesel oil and continue to sonicate in the environment for 20min to obtain an oil-based hydrate nucleation inhibitor.

[0076] 26.8 g (2% of the mass of the oil phase) of the hydrate inhibitor prepared in Example 5 was added to an oil-water emulsion (the volume of the aqueous phase was 20% of the total volume of the oil and water phases), and a hydrate formation experiment was conducted using a high-pressure stirred tank (final stable temperature was 2.6℃, and the operating pressure was 2.3 MPa). The hydrate formation results are shown in Table 3.

[0077] Comparative Example 1

[0078] (1) Heat 200g of ethylene tar (properties shown in Table 2) in an oven at 140℃ for 2 hours until it reaches a molten state;

[0079] (2) The molten ethylene tar in step (1) was heated to 224°C and distilled under atmospheric pressure using an atmospheric distillation apparatus to distill off 30 wt% of the initial raw material mass and remove the low-boiling light components from the ethylene tar.

[0080] (3) Without undergoing oxidative heat treatment and closed heat treatment, 20g of the distilled material in step (2) is directly placed in 40g of o-xylene and shaken at 40℃ and 40KHz for 30min. Then, 40g of diesel is added and ultrasonic shaking is continued in the same environment for 20min to obtain an oil-based hydrate nucleation inhibitor.

[0081] 26.8 g (2% of the mass of the oil phase) of the hydrate inhibitor prepared in Comparative Example 1 was added to an oil-water emulsion (the volume of the aqueous phase was 20% of the total volume of the oil and water phases), and a hydrate formation experiment was conducted using a high-pressure stirred tank. The hydrate formation results are shown in Table 3.

[0082] Comparative Example 2

[0083] Compared with Example 1, the difference is that the oil-based inhibitor component obtained in the component dissolution stage is not compounded with reagents and light oils, but is used directly after cooling at room temperature (i.e. step (5) is not included). The hydrate formation results are shown in Table 3.

[0084] Comparative Example 3

[0085] Compared to Example 1, the difference lies in that 20g of ethylene tar was directly added to 40g of o-xylene, and the mixture was shaken at 40°C and 40kHz for 30 minutes. Then, 40g of diesel oil was added, and the mixture was ultrasonically shaken for another 20 minutes in the same environment to obtain an oil-based hydrate inhibitor. Subsequently, 26.8g (2% of the oil phase mass) of the hydrate inhibitor was added to the oil-water emulsion, and a hydrate formation experiment was conducted using a high-pressure stirred tank reactor. The hydrate formation results are shown in Table 3.

[0086] Comparative Example 4

[0087] No oil-based hydrate nucleation inhibitor was added to the oil-water emulsion. Hydrate formation experiments were conducted using a high-pressure stirred tank reactor. The hydrate formation results are shown in Table 3.

[0088] Table 1. Oil properties of the oil-water emulsions used in the examples and comparative examples.

[0089] <![CDATA[Density (20 °C) / g / cm 3 > 0.83 Pour point / °C -5 Flash point / °C 76.5 Ash content / wt% 0.003 Polycyclic aromatic hydrocarbons / wt% 4.5 <![CDATA[Kinematic viscosity (20 °C) / mm 2 / s]]> 4.1 Sulfur content (mg / kg) 2.8 Carbon residue value / wt% 0.04

[0090] Table 2 Properties of the ethylene tar used in the examples and comparative examples

[0091] <![CDATA[Density (20 °C) / g / cm 3 > 1.07 Carbon residue value / wt% 15.6 Initial boiling point / °C 162.1 Carbon content / wt% 92.7 Hydrogen content / wt% 6.4 Saturated fraction / wt% 14.0 Aromatic components / wt% 38.6 Gel / wt% 32.2 Asphalt / wt% 15.2 Ash content / wt% 0.008

[0092] Table 3. Results of hydrate formation experiments in the examples and comparative examples.

[0093] project Generation temperature / °C Generation time / min Induction period / min Example 1 2.6 141.0 85.7 Example 2 2.6 125.2 69.9 Example 3 2.6 195.7 140.4 Example 4 2.6 167.3 112.0 Example 5 2.6 123.4 68.1 Comparative Example 1 3.1 89.6 34.3 Comparative Example 2 3.0 97.3 42.0 Comparative Example 3 3.5 75.6 20.3 Comparative Example 4 4.3 62.6 7.3

[0094] As shown in Table 3, the preparation method of the oil-based hydrate nucleation inhibitor provided by the present invention can further prolong the hydrate formation time and increase the hydrate formation induction period after heating and melting ethylene tar, distilling light components, oxidative heat treatment, closed heat treatment and component dissolution, and significantly enhance the effect of the oil-based hydrate inhibitor. This is of great significance for the management of hydrates and the safety of multiphase pipelines.

[0095] The scope of protection of this invention is not limited to the above embodiments, but is defined by the claims. Those skilled in the art can make appropriate modifications to these embodiments without departing from the technical concept and spirit of this invention, and these modified embodiments are also included within the scope of protection of this invention.

Claims

1. A method for preparing an oil-based hydrate nucleation inhibitor, characterized by: The method comprises the following steps: (1) heating ethylene tar to a molten state; (2) loading the heated ethylene tar of step (1) into a reaction kettle, and introducing an oxidizing gas to perform oxidative heat treatment under stirring; (3) stopping the input of the oxidizing gas, replacing the oxidizing gas in the reaction kettle with a protective gas, and then performing closed heat treatment on the material obtained in step (2) under the protective gas to obtain an oil-based inhibitor component; (4) after cooling the oil-based inhibitor component obtained in step (3), placing it in a solvent, and mixing it with a light oil product to obtain an oil-based hydrate nucleation inhibitor. In step (1), the properties of the ethylene tar include: a density of 1.05 g / cm 3 1.10 g / cm 3 at 20°C, a carbon residue of 10.1 wt% to 18.0 wt%, an initial boiling point of 150 to 180°C, a carbon content of 91 wt% to 93 wt%, a hydrogen content of 6.2 wt% to 8.1 wt%, a saturated fraction of 0.1 wt% to 15.0 wt%, an aromatic fraction of 30.5 wt% to 68.5 wt%, a gum of 20.1 wt% to 35.8 wt%, an asphaltene of 8.5 wt% to 20.5 wt%, and an ash content of less than 0.01 wt%. In step (2), the temperature of the oxidative heat treatment is 300-400°C, and a programmed temperature rise is adopted during heating, with a temperature rise rate of 0.5-2.5°C / min, and the oxidative heat treatment time is 0.2-2h. In step (2), the pressure in the reaction kettle is maintained at 0.2-0.7MPa by the oxidizing gas. In step (3), the protective gas is at least one of nitrogen and an inert gas. In step (3), the temperature of the closed heat treatment is 360-450°C, the closed heat treatment pressure is 0.5-4.5MPa, and the closed heat treatment time is 2-8h. In step (4), the solvent is one or more of toluene, xylene and quinoline; and the light oil product is one or more of diesel oil, mineral oil and condensate oil.

2. The method of claim 1, wherein: In step (1), the ethylene tar heated to a molten state is distilled to remove light components.

3. The method of claim 2, wherein: The content of the distilled light components is 10wt%-60wt% of the mass of the initial raw material.

4. The method of claim 3, wherein: The content of the distilled light components is 10wt%-50wt% of the mass of the initial raw material.

5. The method of claim 1, wherein: In step (2), the temperature of the oxidative heat treatment is 350-380°C, and the oxidative heat treatment time is 0.5-1.5h; and the stirring speed is 100-400rpm.

6. The method of claim 5, wherein: In step (2), the stirring speed is 100-300rpm.

7. The method of claim 1, wherein: The oxidizing gas is oxygen-enriched air, the oxygen volume content is 25v%~60v%, the gas flow is 0.05~0.5m 3 / kg / h.

8. The method of claim 1, wherein: In step (3), the gas flow rate of the protective gas is 0.05 to 0.5 m 3 / kg / h.

9. The method of claim 1, wherein: In step (3), the temperature of the closed heat treatment is 380-420°C, the closed heat treatment pressure is 2-4MPa, and the closed heat treatment time is 3-6h; and stirring is continuously performed during the closed heat treatment, with a stirring speed of 100-300rpm.

10. The method of claim 1, wherein: In step (4), the mass ratio of the solvent to the light oil product is 1:0.5-2, and the mass ratio of the oil-based inhibitor component to the solvent is 2-5:95-98.

11. The method of claim 1, wherein: In step (4), the mixing with the light oil product is performed under ultrasonic oscillation, with an ultrasonic frequency of 20KHz-60KHz, an ultrasonic oscillation time of 20-40min, and an ultrasonic oscillation temperature of 20-60°C.

12. An oil-based hydrate nucleation inhibitor prepared by the method according to any one of claims 1-11.

13. Use of the oil-based hydrate nucleation inhibitor prepared by the method according to any one of claims 1-11 in the field of multiphase pipeline transportation.

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