Aromatic heavy oil asphaltene inhibitor, preparation method and application thereof

Abstract

The present application relates to a kind of aromatic heavy oil asphaltene inhibitor, preparation method and its application, belong to the technical field of asphaltene aggregation inhibition in heavy oil.The preparation method of the aromatic heavy oil asphaltene inhibitor includes the following steps: according to the molar ratio of beta-D-pyranose glucose unit and sodium periodate 1:1.1, sodium periodate is added to microcrystalline cellulose water dispersion, oxidation reaction is carried out under 30 DEG C for 48h under light protection, then temperature is increased to 50 DEG C, and oxidation reaction is continued for 48h, and dialdehyde group cellulose is obtained.Titration is obtained in dialdehyde group cellulose aldehyde group content.According to the molar ratio of amido and aldehyde group 1:1, dodecylamine is added to dialdehyde group cellulose aqueous solution, and grafting reaction is carried out at 60 DEG C for 6h, and dodecylamine modified cellulose is obtained.Dodecylamine modified cellulose is dissolved in toluene, and aromatic heavy oil asphaltene inhibitor is obtained.The aromatic heavy oil asphaltene inhibitor has long-acting and stable inhibiting effect on asphaltene deposition, and can achieve inhibiting effect at lower dosage.

Description

Technical Field

[0001] This invention belongs to the field of asphaltenes aggregation inhibition technology in heavy oil, and particularly relates to an aromatic heavy oil asphaltenes inhibitor, its preparation method and its application. Background Technology

[0002] Asphaltene is a complex mixture defined by its solubility. It generally refers to petroleum components that are soluble in aromatic solvents (such as toluene or benzene) but insoluble in low molecular weight n-alkanes (C5-C7). At room temperature, it is a dark brown to black amorphous solid with a glossy appearance and is hard and brittle. It has a relatively large molecular weight with no fixed value and a relative density slightly greater than 1.

[0003] Asphaltenes have a strong tendency to polymerize, leading to their instability and deposition in crude oil. This deposition can negatively impact the performance of crude oil transportation equipment and refining facilities. Numerous factors, including crude oil properties (such as composition and viscosity), temperature, pressure, and reservoir properties, affect the stability of asphaltenes in crude oil, resulting in deposition. Adding chemical dispersants to crude oil as asphaltenes inhibitors, which interact with the asphaltenes to achieve uniform dispersion within the crude oil and inhibit precipitation, is currently the most effective method for solving the problem of asphaltenes deposition in crude oil. Currently, commonly used asphaltenes inhibitors are mainly sulfonic acid-based inhibitors, such as dodecylbenzenesulfonic acid. However, dodecylbenzenesulfonic acid readily undergoes acid-base neutralization reactions with alkaline components in the formation, generating negatively charged anionic head groups (-SO3). - Sulfonates, with their anionic head groups following the solubility product (Ksp) rule, undergo irreversible complexation reactions extremely rapidly, generating flocculent precipitates of calcium or magnesium petroleum sulfonate that are extremely insoluble in both oil and water phases. This affects the inhibitory effect of dodecylbenzene sulfonic acid on asphaltene deposition. Moreover, when dodecylbenzene sulfonic acid is introduced into a crude oil system containing asphaltene, it can only inhibit asphaltene deposition when the amount of dodecylbenzene sulfonic acid added exceeds 1% (see the literature "Goual L, Firoozabadi A. Effect of resins and DBSA on asphaltene precipitation from petroleum fluids. Aiche Journal, 2004, 50(2):470-479.DOI:10.1002 / aic.10041"). Therefore, when dodecylbenzene sulfonic acid is used as an asphaltene inhibitor in heavy oil extraction, the required amount added is relatively large, resulting in high processing costs.

[0004] Therefore, how to provide a heavy oil asphaltene inhibitor that can achieve asphaltene inhibition at a low dosage and has a long-lasting and stable inhibition effect is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing asphaltene inhibitors, this invention provides an aromatic heavy oil asphaltene inhibitor, its preparation method, and its application. This aromatic heavy oil asphaltene inhibitor exhibits a long-lasting and stable inhibitory effect on asphaltene deposition and can achieve the inhibitory effect at a low dosage, which helps to reduce processing costs.

[0006] This invention provides a method for preparing an aromatic heavy oil asphaltenes inhibitor, comprising the following steps: S1. According to the molar ratio of β-D-pyranose units to sodium periodate in microcrystalline cellulose of 1:1.1, sodium periodate was added to the aqueous dispersion of microcrystalline cellulose. Under the dark, the reaction was first carried out at 30°C for 48 hours, and then the temperature was raised to 50°C to continue the oxidation reaction for 48 hours. The oxidation reaction product was collected to obtain dialdehyde cellulose. S2. The aldehyde content in dialdehyde cellulose was obtained by hydroxylamine hydrochloride titration. S3. Adjust the pH of the dialdehyde cellulose aqueous solution to 9, add dodecylamine dissolved in ethanol to the dialdehyde cellulose aqueous solution at a molar ratio of amine to aldehyde of 1:1, and perform the grafting reaction at 60°C for 6 hours. Collect the grafting reaction product to obtain dodecylamine modified cellulose. S4. Dissolve dodecylamine-modified cellulose in toluene to obtain an aromatic heavy oil asphaltenes inhibitor.

[0007] In some embodiments, in step S1, the concentration of the microcrystalline cellulose aqueous dispersion is 1 wt%.

[0008] In some embodiments, the specific steps for collecting the oxidation reaction products in step S1 are as follows: the reaction solution after oxidation reaction is dialyzed with deionized water to remove periodate ions, the dialyzed reaction solution is refluxed at 80°C for 6 hours and centrifuged at 10,000 r / min for 15 minutes, and the supernatant is retained to remove unoxidized cellulose.

[0009] In some embodiments, the specific steps for collecting the grafting reaction product in step S3 are as follows: centrifuge the reaction solution after the grafting reaction, collect the precipitate, and obtain crude dodecylamine modified cellulose product; mix hydrochloric acid aqueous solution with pH=3 and ethanol at a volume ratio of 1:1 to obtain a washing acid solution, and use the washing acid solution to wash the crude dodecylamine modified cellulose product to remove unreacted dodecylamine.

[0010] The present invention also provides an aromatic heavy oil asphaltenes inhibitor, which is prepared by the preparation method of the aromatic heavy oil asphaltenes inhibitor described in any of the above technical solutions.

[0011] The present invention further provides the application of the aromatic heavy oil asphaltene inhibitor described in any of the above technical solutions in inhibiting asphaltene deposition. In application, the aromatic heavy oil asphaltene inhibitor is directly added to the asphaltene dissolved in heavy oil or toluene.

[0012] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. The method for preparing aromatic heavy oil asphaltenes inhibitor provided by the present invention firstly oxidizes cellulose with sodium periodate to obtain dialdehyde cellulose, then performs a Schiff base reaction between the amino group of dodecylamine and the aldehyde group of dialdehyde cellulose to graft dodecylamine onto cellulose to obtain dodecylamine-modified cellulose, and finally dissolves the dodecylamine-modified cellulose with toluene as a solvent to obtain aromatic heavy oil asphaltenes inhibitor. The preparation steps are simple and the cost is low. The aromatic heavy oil asphaltenes inhibitor obtained can effectively inhibit asphaltenes deposition through the combined action of the long dodecyl chain of dodecylamine-modified cellulose and the hydroxyl, aldehyde and imine groups on the cellulose backbone with toluene solvent. Its inhibitory effect is long-lasting and stable, and it can achieve the inhibitory effect at a low dosage, which is beneficial to reducing the processing cost. 2. In the preparation method of the aromatic heavy oil asphaltenes inhibitor provided by the present invention, microcrystalline cellulose is used as raw material. The ratio of microcrystalline cellulose to sodium periodate is controlled according to the molar ratio of β-D-glucopyranose units in microcrystalline cellulose to sodium periodate is 1:1.1. The temperature gradient segmented oxidation method is adopted to obtain dialdehyde cellulose with appropriate aldehyde content, which is beneficial to the subsequent dense grafting of dodecylamine. 3. In the preparation method of the aromatic heavy oil asphaltenes inhibitor provided by the present invention, the aldehyde content of dialdehyde cellulose is accurately obtained by the hydroxylamine hydrochloride titration method, and the amount of dodecylamine is controlled according to the molar ratio of amine to aldehyde group of 1:1. This ensures that dodecylamine is densely grafted onto the cellulose backbone of dialdehyde cellulose, thereby utilizing the densely grafted dodecyl long chain to form effective steric hindrance and prevent asphaltenes molecules from stacking. 4. The aromatic heavy oil asphaltenes inhibitor provided by this invention, compared with traditional asphaltenes inhibitors such as dodecylbenzenesulfonic acid, can effectively and stably inhibit asphaltenes deposition with a lower dosage when applied to inhibit asphaltenes deposition. In addition, it contains toluene as a solvent and can be directly added to heavy oil without additional preparation steps, making it convenient to use. Attached Figure Description

[0013] Figure 1 This is a flowchart illustrating the preparation method of the aromatic heavy oil asphaltenes inhibitor provided in the embodiments of the present invention; Figure 2 This is a schematic diagram illustrating the preparation process of dodecylamine-modified cellulose in the aromatic heavy oil asphaltenes inhibitor provided in this embodiment of the invention. Figure 3These are photographs of blank group samples B1-B8 in Example 2 of the present invention, wherein (a) is a photograph of the sample after 24 hours of static settling, and (b) is a photograph of the sample after one week of static settling. Figure 4 The images are of samples C0-C8 of the dodecylamine-modified cellulose group in Example 2 of the present invention, wherein (a) is a sample photo after 24 hours of static settling, (b) is a sample photo after one week of static settling, and (c) is a sample photo after 90 days of static settling. Figure 5 These are photographs of samples D0-D8 in the dodecylbenzenesulfonic acid comparative group in Example 2 of the present invention, wherein (a) is a photograph of the sample after standing for 24 hours, and (b) is a photograph of the sample after standing for one week. Figure 6 These are photographs of samples E0-E8 of the octylamine modified cellulose group in Example 2 of the present invention, wherein (a) is a photograph of the sample after standing for 24 hours, and (b) is a photograph of the sample after standing for one week. Figure 7 Photographs of the dodecylamine control group samples in Example 2 of this invention; Figure 8 This is a graph showing the change in asphaltene concentration as a function of n-heptane mass fraction before static settling in Example 2 of the present invention. Figure 9 This is a graph showing the change in asphaltene concentration as a function of the mass fraction of n-heptane after the sample was left to stand for one week in Example 2 of this invention. Figure 10 These are photographs of the experimental groups in Example 3 of the present invention, wherein (a) is the blank group, (b) is the dodecylbenzenesulfonic acid control group, (c) is the octylamine modified cellulose group, (d) is the dodecylamine modified cellulose group, and (e) is the dodecylamine control group. Figure 11 This is the transmission spectrum of the blank sample in Example 3 of the present invention; Figure 12 This is the transmission spectrum of the dodecylbenzenesulfonic acid comparative group sample in Example 3 of the present invention; Figure 13 The transmission spectrum of the octylamine-modified cellulose group sample in Example 3 of this invention is shown below. Figure 14 The transmission spectrum of the dodecylamine-modified cellulose sample in Example 3 of this invention is shown below. Figure 15 This is the transmission spectrum of the dodecylamine control group sample in Example 3 of the present invention; Figure 16 The TSI data graphs for the blank group, dodecylbenzenesulfonic acid control group, octylamine modified cellulose group, dodecylamine modified cellulose group, and dodecylamine control group samples in Example 3 of the present invention are shown. Figure 17These are photographs of the dodecylamine-modified cellulose samples in Example 4 of the present invention, wherein (a) is a photograph of the sample after standing for 24 hours, (b) is a photograph of the sample after standing for one week, and (c) is a photograph of the sample after standing for 90 days. Figure 18 These are photographs of the dodecylbenzenesulfonic acid comparative group samples in Example 4 of the present invention, wherein (a) is a photograph of the sample after standing for 24 hours, and (b) is a photograph of the sample after standing for one week. Figure 19 This is a graph showing the change in asphaltene concentration as a function of asphaltene inhibitor concentration in the sample of Example 4 of the present invention. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] like Figure 1 As shown, this embodiment of the invention provides a method for preparing an aromatic heavy oil asphaltenes inhibitor, comprising the following steps: S1. According to the molar ratio of β-D-pyranose units to sodium periodate in microcrystalline cellulose of 1:1.1, sodium periodate was added to the aqueous dispersion of microcrystalline cellulose. Under the dark, the reaction was first carried out at 30°C for 48 hours, and then the temperature was raised to 50°C to continue the oxidation reaction for 48 hours. The oxidation reaction product was collected to obtain dialdehyde cellulose. S2. The aldehyde content in dialdehyde cellulose was obtained by hydroxylamine hydrochloride titration. S3. Adjust the pH of the dialdehyde cellulose aqueous solution to 9, add dodecylamine dissolved in ethanol to the dialdehyde cellulose aqueous solution at a molar ratio of amine to aldehyde of 1:1, and perform the grafting reaction at 60°C for 6 hours. Collect the grafting reaction product to obtain dodecylamine modified cellulose. S4. Dissolve dodecylamine-modified cellulose in toluene to obtain an aromatic heavy oil asphaltenes inhibitor.

[0016] The preparation process of dodecylamine-modified cellulose is as follows: Figure 2As shown in the figure, the above-mentioned method for preparing aromatic heavy oil asphaltenes inhibitor involves first oxidizing cellulose with sodium periodate to obtain dialdehyde cellulose, then performing a Schiff base reaction between the amino group of dodecylamine and the aldehyde group of dialdehyde cellulose to graft dodecylamine onto cellulose to obtain dodecylamine-modified cellulose, and finally dissolving the dodecylamine-modified cellulose in toluene to obtain the aromatic heavy oil asphaltenes inhibitor. The preparation steps are simple and the cost is low. The aromatic heavy oil asphaltenes inhibitor obtained can effectively inhibit asphaltenes deposition through the combined action of the long dodecyl chain of the dodecylamine-modified cellulose and the hydroxyl, aldehyde, and imine groups on the cellulose backbone with the toluene solvent. Its inhibitory effect is long-lasting and stable, and it can achieve the inhibitory effect at a low dosage, which is beneficial to reducing the processing cost.

[0017] The specific mechanism by which aromatic heavy oil asphaltenes inhibitors suppress asphaltenes deposition is explained below: (1) Toluene, as a good solvent for dodecylamine-modified cellulose and asphaltenes, can increase the probability of contact between asphaltenes and dodecylamine-modified cellulose. (2) The cellulose skeleton of dodecylamine modified cellulose has abundant hydroxyl groups, aldehyde groups and electron-rich imine groups generated through grafting reaction, which can form hydrogen bonds or Lewis acid-base interactions with heteroatoms (such as N, S, O) and polar functional groups in asphaltene molecules, so that dodecylamine modified cellulose is bound to the surface of asphaltene particles. (3) The densely grafted dodecyl long chains on the cellulose skeleton can be entangled with the aliphatic hydrocarbon side chains of the asphaltene molecule by van der Waals forces, forming a stable weakly polar alkyl chain adsorption layer around the asphaltene. The densely grafted dodecyl long chains on the cellulose skeleton have excellent compatibility with the saturated hydrocarbon components in crude oil. According to the principle of like dissolves like, the adsorption of the weakly polar alkyl chain adsorption layer on the surface of asphaltene plays a "bridge effect", resulting in higher dispersion stability of asphaltene in crude oil. (4) The rigid cellulose macromolecular skeleton in dodecylamine modified cellulose can build a "rigid protective layer" around the asphaltene. The presence of the "rigid protective layer" causes two asphaltene particles to be bounced away by elastic collision when they approach each other, instead of agglomerating. At the same time, the dense dodecyl long chains extending outward make the spatial repulsion between asphaltene molecules greater than the π-π attraction that causes them to aggregate, thereby preventing further stacking of asphaltene molecules and avoiding the formation of large asphaltene flocs.

[0018] Meanwhile, in the above-mentioned method for preparing aromatic heavy oil asphaltenes inhibitors, microcrystalline cellulose is used as the raw material. The ratio of microcrystalline cellulose to sodium periodate is controlled according to a molar ratio of β-D-glucopyranose units to sodium periodate of 1:1.1. A temperature gradient staged oxidation method is employed to obtain dialdehyde cellulose with a suitable aldehyde content, which is beneficial for subsequent dense grafting of dodecylamine. Furthermore, in the above-mentioned method for preparing aromatic heavy oil asphaltenes inhibitors, the aldehyde content of dialdehyde cellulose is accurately obtained by hydroxylamine hydrochloride titration, and the amount of dodecylamine is controlled according to a molar ratio of amine to aldehyde of 1:1. This ensures dense grafting of dodecylamine onto the cellulose backbone of dialdehyde cellulose, thereby utilizing the densely grafted dodecyl long chains to form effective steric hindrance and prevent asphaltenes molecule stacking.

[0019] In a preferred embodiment, in step S1, the concentration of the microcrystalline cellulose aqueous dispersion is 1 wt%. Using this concentration of microcrystalline cellulose aqueous dispersion helps to ensure that the microcrystalline cellulose is fully oxidized, obtaining dialdehyde cellulose with a suitable aldehyde group content, which facilitates subsequent dense grafting of dodecylamine.

[0020] In an optional embodiment, step S1, specifically the collection of oxidation reaction products, involves: dialysis of the reaction solution after oxidation with deionized water to remove periodate ions; refluxing the dialyzed reaction solution at 80°C for 6 hours and centrifuging at 10,000 r / min for 15 minutes; retaining the supernatant to remove unoxidized cellulose. Dialysis and high-temperature centrifugation effectively remove unreacted substances, ensuring the purity of the obtained dialdehyde cellulose.

[0021] In an optional embodiment, step S3, specifically the collection of the grafting reaction product, involves: centrifuging the reaction solution after the grafting reaction, collecting the precipitate, and obtaining crude dodecylamine-modified cellulose; mixing hydrochloric acid aqueous solution with pH=3 and ethanol at a volume ratio of 1:1 to obtain a washing acid solution, and using the washing acid solution to wash the crude dodecylamine-modified cellulose product to remove unreacted dodecylamine. Through centrifugation and washing with the washing acid solution, unreacted dodecylamine can be effectively removed, ensuring the purity of the obtained dodecylamine-modified cellulose.

[0022] This invention provides an aromatic heavy oil asphaltenes inhibitor, prepared using the method described above. Compared to traditional asphaltenes inhibitors such as dodecylbenzenesulfonic acid, this aromatic heavy oil asphaltenes inhibitor, through the dodecyl chain of dodecylamine-modified cellulose and the hydroxyl, aldehyde, and imine groups on the cellulose backbone, combined with toluene solvent, can stably inhibit asphaltenes deposition for a long time at a lower dosage. Furthermore, the aromatic heavy oil asphaltenes inhibitor itself contains toluene solvent and can be directly added to heavy oil without additional preparation steps, making it convenient to use. Preferably, the concentration of dodecylamine-modified cellulose in the aromatic heavy oil asphaltenes inhibitor is 100~10000 ppm. Controlling the concentration of dodecylamine-modified cellulose in the aromatic heavy oil asphaltenes inhibitor within the range of 100~10000 ppm ensures that the dodecylamine-modified cellulose is uniformly dispersed in toluene, ensuring stable product performance.

[0023] Furthermore, embodiments of the present invention provide the application of the above-mentioned aromatic heavy oil asphaltenes inhibitor in inhibiting asphaltenes deposition. In application, the aromatic heavy oil asphaltenes inhibitor is directly added to the asphaltenes dissolved in heavy oil or toluene.

[0024] To provide a clearer and more detailed description of the aromatic heavy oil asphaltenes inhibitor, its preparation method, and its application provided in the embodiments of the present invention, the following description will be based on specific embodiments.

[0025] It should be noted that the heavy oil sample used in the following specific embodiments comes from the Tahe Oilfield in Xinjiang. The contents of saturated fraction, aromatic fraction, gum, and asphaltenes in the heavy oil sample are shown in Table 1. The asphaltenes used in the following specific embodiments are asphaltenes obtained by precipitation of the heavy oil sample with n-heptane. The contents of each element in the asphaltenes are shown in Table 2. The average molecular weight of the asphaltenes was measured to be 3875 g / mol.

[0026] Table 1. Contents of saturated fractions, aromatic fractions, resins, and asphaltenes in Tarim River heavy oil samples.

[0027] Table 2. Elemental composition of asphaltenes in Tarim River heavy oil samples

[0028] Example 1 A method for preparing an aromatic heavy oil asphaltenes inhibitor includes the following steps: (1) Sodium periodate was added to a 1 wt% microcrystalline cellulose aqueous dispersion according to the molar ratio of β-D-glucopyranose units to sodium periodate of 1:1.1. Under the dark, the reaction was first oxidized at 30°C for 48 h, and then the temperature was raised to 50°C for another 48 h. After the reaction, the reaction solution was dialyzed with deionized water using an MD34-3500 dialysis bag to remove periodate ions. The dialyzed reaction solution was refluxed at 80°C for 6 h and centrifuged at 10000 r / min for 15 min. The supernatant was retained to remove unoxidized cellulose and dialdehyde cellulose aqueous solution was obtained. (2) Take 5g of the dialdehyde cellulose solution after dialysis and centrifugation in step (1), and adjust the pH of the dialdehyde cellulose solution to 3.5 using HCl; take 5g of hydroxylamine hydrochloride solution with a concentration of 0.1mmol / g, and adjust the pH of the hydroxylamine hydrochloride solution to 3.5 using HCl; mix the pH-adjusted dialdehyde cellulose solution with the hydroxylamine hydrochloride solution, and titrate with 0.1mol / L NaOH until the pH of the mixed solution is 3.5. Based on the amount of NaOH added, calculate that the aldehyde content in the dialdehyde cellulose prepared in step (1) is 0.064 mmol / g; (3) Adjust the pH of the dialdehyde cellulose aqueous solution obtained in step (1) to 9 with NaOH aqueous solution, add dodecylamine dissolved in ethanol to the dialdehyde cellulose aqueous solution obtained in step (1) according to the molar ratio of amino groups to aldehyde groups of 1:1, and perform grafting reaction at 60℃ for 6h; after the reaction, centrifuge the reaction solution after grafting reaction, collect the precipitate, and obtain crude dodecylamine modified cellulose product; mix hydrochloric acid aqueous solution with pH=3 and ethanol at a volume ratio of 1:1 to obtain washing acid solution, use washing acid solution to wash the crude dodecylamine modified cellulose product to remove unreacted dodecylamine, place the washed product in a vacuum drying oven at 60℃ and dry to obtain dodecylamine modified cellulose product; (4) Dissolve the dodecylamine-modified cellulose product obtained in step (3) in toluene to obtain an aromatic heavy oil asphaltenes inhibitor.

[0029] Comparative Example 1 The difference between this comparative example and Example 1 is that octylamine is used instead of dodecylamine, and the octylamine-modified cellulose is obtained in step (3).

[0030] Example 2 – Experiment on the Inhibition of Asphaltenes Deposition in Asphaltenes-Toluene Solution by Asphaltenes Inhibitor 1. Prepare experimental group samples (1) Blank group: Prepare 1g of toluene solution with a concentration of 2000ppm asphaltene, then add 1g of pure toluene, and make up to 10g with toluene-heptane solutions with mass ratios of 7:1, 6:2, 5:3, 4:4, 3:5, 2:6, 1:7 and 0:8 respectively to obtain samples B1-B8. After standing for 24h, the sample photos are as follows. Figure 3 As shown in Figure (a); (2) Dodecylamine-modified cellulose group: 1g of a toluene solution of dodecylamine-modified cellulose with a concentration of 2000ppm prepared in Example 1 (i.e., aromatic heavy oil asphaltenes inhibitor) was added to 1g of a toluene solution of asphaltenes with a concentration of 2000ppm. The solution was then diluted to 10g with toluene-heptane solutions at mass ratios of 8:0, 7:1, 6:2, 5:3, 4:4, 3:5, 2:6, 1:7, and 0:8, respectively, to obtain samples C0-C8. The sample photographs after standing for 24h are shown below. Figure 4 As shown in Figure (a); (3) Dodecylbenzenesulfonic acid control group: 1g of a 2000ppm toluene solution of dodecylbenzenesulfonic acid was prepared as an asphaltene inhibitor and added to 1g of a 2000ppm toluene solution of asphaltene. The solution was then diluted to 10g with toluene-heptane solutions at mass ratios of 8:0, 7:1, 6:2, 5:3, 4:4, 3:5, 2:6, 1:7, and 0:8, respectively, to obtain samples D0-D8. The sample photos after standing for 24 hours are shown below. Figure 5 As shown in Figure (a); (4) Octylamine-modified cellulose group: 1g of toluene solution of octylamine-modified cellulose with a concentration of 2000ppm prepared in Comparative Example 1 was used as an asphaltenes inhibitor and added to 1g of toluene solution of asphaltenes with a concentration of 2000ppm. The solution was then diluted to 10g with toluene-heptane solutions at mass ratios of 8:0, 7:1, 6:2, 5:3, 4:4, 3:5, 2:6, 1:7 and 0:8, respectively, to obtain samples E0-E8. The sample photos after standing for 24h are shown below. Figure 6 As shown in Figure (a).

[0031] (5) Dodecylamine control group: 1g of a toluene solution of dodecylamine with a concentration of 2000ppm was prepared as an asphaltenes inhibitor and added to a toluene solution of asphaltenes with a concentration of 2000ppm. The solution was then diluted to 10g with n-heptane and allowed to stand for 24 hours. The sample photograph is shown below. Figure 7 As shown; 2. Asphalt deposition inhibition effect test For samples B1-B8, C0-C8, D0-D8, and E0-E8 after standing for 24 hours, the asphaltene concentration in the sample supernatant was determined by ultraviolet light. A graph showing the change in asphaltene concentration as a function of the mass fraction of n-heptane was plotted, as shown below. Figure 8As shown in Table 3. It should be noted that during the UV test, the UV absorbance of toluene solutions of asphaltene at different concentrations was first measured to plot a standard curve of absorbance versus asphaltene concentration, and the asphaltene concentration in each sample was determined based on the standard curve. Based on the UV test results, the amount of asphaltene aggregation was calculated using the following formula (1), and the results are shown in Table 3.

[0032] Formula (1).

[0033] It should be noted that, based on the sample preparation process of each experimental group, the initial asphaltene concentration for each experimental group sample was taken as 200 ppm during the calculation.

[0034] Samples B1-B8, C0-C8, D0-D8, and E0-E8 were left to stand for one week to allow the asphalt to continue settling. The sample photographs are shown below. Figure 3 Figure (b) in the middle Figure 4 Figure (b) in the middle Figure 5 Figure (b) in the middle and Figure 6 As shown in Figure (b). The asphaltenes concentration in the supernatant of each sample was again measured using ultraviolet light, and a graph showing the change in asphaltenes concentration versus the mass fraction of n-heptane after one week of settling was plotted, as shown in Figure (b). Figure 9 As shown in Table 3. Based on the UV test results, the amount of asphalt aggregate was calculated according to formula (1), and the results are shown in Table 3. Among them, samples C0-C8 were left to stand for 90 days, and the sample photos after standing are shown in Table 3. Figure 4 As shown in Figure (c).

[0035] Table 3. Calculation results of asphaltene aggregation in samples B1-B8, C0-C8, D0-D8, and E0-E8.

[0036] Depend on Figure 3 , Figure 8 , Figure 9 As shown in Table 3, without the addition of asphaltenes inhibitors, significant asphaltenes precipitation began after 24 hours of settling at a heptane mass fraction of 30%. Ultraviolet analysis revealed that the asphaltenes concentration in the sample was only 31.5 ppm at a heptane mass fraction of 80%, with an asphaltenes aggregation rate of 84.3%. After one week of settling, asphaltenes precipitation intensified, with a heptane mass fraction of 20% marking the turning point for asphaltenes deposition. At a heptane mass fraction of 80%, the asphaltenes concentration in the sample was only 17.8 ppm, while the asphaltenes aggregation rate increased to 91.1%.

[0037] Depend on Figure 5 , Figure 8 , Figure 9As shown in Table 3, when dodecylbenzenesulfonic acid, a traditional asphaltene inhibitor, was added, no asphaltene aggregation occurred after standing for 24 hours when the mass fraction of n-heptane was 80%, corresponding to an asphaltene concentration of 181 ppm and an asphaltene aggregation amount of 9.5%. However, after one week of settling, asphaltene precipitation began to occur when the mass fraction of n-heptane was 60%. As the mass fraction of n-heptane increased, the asphaltene concentration decreased rapidly, and when the mass fraction of n-heptane was 80%, the asphaltene concentration of the sample decreased to 104.8 ppm, and the asphaltene aggregation amount reached 47.6%.

[0038] Depend on Figure 4 , Figure 8 , Figure 9 As shown in Table 3, when the toluene solution of dodecylamine-modified cellulose (i.e., aromatic heavy oil asphaltenes inhibitor) prepared in Example 1 of this invention was added, no precipitation occurred after standing for 24 hours at a heptane mass fraction of 80%, corresponding to an asphaltenes concentration of 171.1 ppm and an asphaltenes aggregation amount of 14.5%. Although this is slightly higher than the corresponding result of the traditional asphaltenes inhibitor dodecylbenzenesulfonic acid, no precipitation occurred after standing for one week. After standing for one week, the asphaltenes concentration of the sample at a heptane mass fraction of 80% was 173.5 ppm, and the asphaltenes aggregation amount was only 13.3%. After standing for 90 days, no significant asphaltenes deposition occurred. This indicates that the aromatic heavy oil asphaltenes inhibitor prepared in Example 1 of this invention can effectively inhibit asphaltenes deposition, and its inhibitory effect is long-lasting and stable.

[0039] Depend on Figure 6 , Figure 8 , Figure 9 As shown in Table 3, when the toluene solution of octylamine-modified cellulose prepared in Comparative Example 1 was added as an asphaltenes inhibitor, precipitation began to occur after standing for 24 hours at a heptane mass fraction of 60%, and the asphaltenes concentration of the sample was 32.2 ppm at a heptane mass fraction of 80%, with an asphaltenes aggregation rate of 83.9%. After standing for one week, precipitation began to occur at a heptane mass fraction of 50%, and the asphaltenes concentration of the sample was only 7.1 ppm at a heptane mass fraction of 80%, with the asphaltenes aggregation rate increasing to 96.5%.

[0040] Depend on Figure 7 It is evident that when a toluene solution containing dodecylamine is used as an asphaltenes inhibitor, after standing for 24 hours, asphaltenes exhibit severe aggregation and precipitation at a heptane mass fraction of 80%, indicating that toluene solution containing dodecylamine alone cannot inhibit asphaltenes precipitation.

[0041] Example 3 – Experiment on the Inhibition of Asphaltenes Deposition in Heavy Oil by Asphaltenes Inhibitors 1. Prepare experimental group samples (1) Blank group: 1g of toluene was added to 1g of heavy oil from Xinjiang Tahe River, and then 23ml of n-heptane was added to induce asphaltene sedimentation. The sample photo is shown below. Figure 10 As shown in Figure (a); (2) Dodecylbenzenesulfonic acid control group: 1g of toluene solution with a concentration of 10000ppm dodecylbenzenesulfonic acid was prepared as an asphaltene inhibitor and added to 1g of Xinjiang Tahe heavy oil. Then, 23ml of n-heptane was added to induce asphaltene sedimentation. The sample photos are as follows. Figure 10 As shown in Figure (b); (3) Octylamine-modified cellulose group: 1g of toluene solution of octylamine-modified cellulose with a concentration of 10000ppm prepared in Comparative Example 1 was used as an asphaltene inhibitor and added to 1g of Xinjiang Tahe heavy oil. Then, 23ml of n-heptane was added to induce asphaltene sedimentation. The sample photos are as follows. Figure 10 As shown in Figure (c); (4) Dodecylamine-modified cellulose group: 1g of a toluene solution of dodecylamine-modified cellulose with a concentration of 10000ppm prepared in Example 1 (i.e., aromatic heavy oil asphaltenes inhibitor) was added to 1g of Xinjiang Tahe heavy oil, and then 23ml of n-heptane was added to induce asphaltenes sedimentation. The sample photos are as follows. Figure 10 As shown in Figure (d); (5) Dodecylamine control group: 1g of toluene solution of dodecylamine with a concentration of 10000ppm was prepared as an asphaltene inhibitor and added to 1g of Xinjiang Tahe heavy oil. Then, 23ml of n-heptane was added to induce asphaltene sedimentation. The sample photos are as follows. Figure 10 As shown in Figure (e).

[0042] 2. Asphalt deposition inhibition effect test The TSI values ​​of the blank group, dodecylbenzenesulfonic acid control group, octylamine-modified cellulose group, dodecylamine-modified cellulose group, and dodecylamine control group were determined using a Turbiscan LAB Expert multiple light scattering spectrometer to characterize the inhibitory effects of each asphaltenes inhibitor on asphaltenes deposition in heavy oil. During measurement, scans were performed every 1 minute for a total of 30 minutes. The transmission spectra of the blank group, dodecylbenzenesulfonic acid control group, octylamine-modified cellulose group, dodecylamine-modified cellulose group, and dodecylamine control group are shown below. Figures 11-15 As shown, the measured TSI results are as follows: Figure 16 As shown.

[0043] Depend on Figure 10 (a) Figure 11 , Figure 16It is evident that adding a large amount of n-heptane to a heavy oil sample will cause the asphaltene in the sample to precipitate rapidly. After half an hour of measurement and sedimentation, the blank group without asphaltene inhibitor showed obvious asphaltene deposition at the bottom of the sample. The light transmittance of the upper layer of the sample increased rapidly to around 35%, and the TSI value eventually stabilized at around 20, indicating that the oil sample was extremely unstable and asphaltene was deposited rapidly.

[0044] Depend on Figure 10 (b) Figure 12 , Figure 16 As can be seen, when toluene solution containing dodecylbenzenesulfonic acid is added as an asphaltene inhibitor, after half an hour of sedimentation, obvious asphaltene precipitate appears at the bottom of the sample, the transmittance of the upper layer of the sample stabilizes at around 19.7%, and the TSI value eventually stabilizes at around 13.

[0045] Depend on Figure 10 (c) Figure 13 , Figure 16 As can be seen, when the toluene solution of octylamine modified cellulose prepared in Comparative Example 1 was added as an asphaltenes inhibitor, asphaltenes precipitated at the bottom of the sample after half an hour of sedimentation measurement. The transmittance of the upper layer of the sample stabilized at around 12.8%, and the TSI value finally stabilized at around 6.5.

[0046] Depend on Figure 10 (d) Figure 14 , Figure 16 As can be seen, when the toluene solution of dodecylamine-modified cellulose (i.e., the aromatic heavy oil asphaltenes inhibitor) prepared in Example 1 was added as an asphaltenes inhibitor, no asphaltenes precipitated at the bottom of the sample after half an hour of sedimentation measurement, and the transmittance of the upper layer of the sample was also low, only 2.3%, with the TSI value eventually stabilizing at around 1.6. This indicates that, compared with traditional asphaltenes inhibitors such as dodecylbenzenesulfonic acid and toluene solution of octylamine-modified cellulose, the aromatic heavy oil asphaltenes inhibitor prepared in Example 1 of this invention, when added to heavy oil, can greatly improve the stability of the oil sample and effectively inhibit asphaltenes deposition.

[0047] Depend on Figure 10 (e) Figure 15 , Figure 16 As can be seen, when toluene solution with added dodecylamine was used as an asphaltene inhibitor, asphaltene precipitated at the bottom of the sample after half an hour of sedimentation. The transmittance of the upper layer of the sample stabilized at around 26%, and the TSI value finally stabilized at around 20.5, which was close to that of the blank group. This proves that the use of dodecylamine alone has almost no inhibitory effect on the aggregation of asphaltene.

[0048] Example 4 – Experiment on the Inhibition of Asphaltene Deposition by Different Concentrations of Asphaltene Inhibitors 1. Prepare experimental group samples (1) Dodecylamine-modified cellulose group: 1g of toluene solutions of dodecylamine-modified cellulose (i.e., aromatic heavy oil asphaltenes inhibitors) prepared in Example 1 with concentrations of 1400ppm, 1000ppm, 600ppm, 200ppm and 100ppm were prepared as asphaltenes inhibitors and added to 1g of toluene solution of asphaltenes with a concentration of 2000ppm. Then 8g of n-heptane was added to obtain samples H2, H4, H6, H8 and H10. At the same time, sample C8 prepared in Example 2 was also used as a sample of the dodecylamine-modified cellulose group in this example. The photos of each sample after standing for 24h are shown below. Figure 17 As shown in Figure (a), the sample photograph after one week of settling is as follows. Figure 17 As shown in Figure (b), the sample photograph after 90 days of standing is as follows. Figure 17 As shown in Figure (c); (2) Dodecylbenzenesulfonic acid control group: 1g of toluene solutions of dodecylbenzenesulfonic acid with concentrations of 1400ppm, 1000ppm, 600ppm, 200ppm and 100ppm were prepared as asphaltenes inhibitors and added to 1g of toluene solution of asphaltenes with a concentration of 2000ppm. Then 8g of n-heptane was added to obtain samples L1, L2, L3, L4 and L5. Sample D8 prepared in Example 2 was also used as a sample in the dodecylbenzenesulfonic acid control group of this example. The photos of each sample after standing for 24 hours are shown below. Figure 18 As shown in Figure (a), the sample photograph after one week of settling is as follows. Figure 18 As shown in Figure (b).

[0049] 2. Asphalt deposition inhibition effect test For each sample in the dodecylamine-modified cellulose group and the dodecylbenzenesulfonic acid control group, the asphaltenes concentration in the supernatant was measured by ultraviolet light after 24 hours of standing and after one week of standing sedimentation. The changes in asphaltenes concentration as a function of inhibitor concentration were plotted, as shown in the figure. Figure 19 As shown in Table 4, the amount of asphalt aggregate was calculated using the above formula (1) based on the ultraviolet test results.

[0050] Table 4. Calculation results of asphaltenes aggregation in each sample of the dodecylamine-modified cellulose group and the dodecylbenzenesulfonic acid comparison group.

[0051] Depend on Figure 18 , Figure 19As shown in Table 4, when dodecylbenzenesulfonic acid was used as an asphaltene inhibitor, after standing for 24 hours, when the concentration of dodecylbenzenesulfonic acid was below 140 ppm, the concentration of asphaltene in the corresponding sample decreased rapidly, indicating severe asphaltene aggregation. When the concentration decreased to 10 ppm, the asphaltene concentration in the corresponding sample was only 33.3 ppm, and the asphaltene aggregation rate was 83.4%. After standing for one week, when the concentration was below 140 ppm, the concentration of asphaltene in the corresponding sample decreased rapidly, and the asphaltene aggregation worsened. When the concentration was as low as 10 ppm, the asphaltene aggregation rate was as high as 91.7%.

[0052] Depend on Figure 17 , Figure 19 As shown in Table 4, when the toluene solution of dodecylamine-modified cellulose (i.e., aromatic heavy oil asphaltenes inhibitor) prepared in Example 1 of this invention was added, after standing for 24 hours, the concentration of asphaltenes in the corresponding samples did not fluctuate significantly with the decrease in the concentration of the aromatic heavy oil asphaltenes inhibitor. When the concentration of the aromatic heavy oil asphaltenes inhibitor decreased to 10 ppm, the asphaltenes aggregation was only 7.3%. After standing for one week, the asphaltenes concentration also did not change significantly. When the concentration of the aromatic heavy oil asphaltenes inhibitor was 10 ppm, the asphaltenes aggregation was only 8%. After standing for 90 days, no asphaltenes aggregation was observed. Therefore, compared with the traditional asphaltenes inhibitor dodecylbenzenesulfonic acid, the aromatic heavy oil asphaltenes inhibitor provided in Example 1 of this invention, when added to oil samples to inhibit asphaltenes deposition, can achieve a significant inhibitory effect at a lower concentration, which can greatly reduce the cost of oil sample processing.

[0053] The influence of cellulose type was further examined below.

[0054] Comparative Example 2 Cellulose nanocrystals were used instead of microcrystalline cellulose in Example 1. Dialdehyde cellulose was prepared according to the same steps as in Example 1 (1). The aldehyde group of the dialdehyde cellulose prepared by cellulose nanocrystals was titrated according to the same steps as in Example 1 (2). The aldehyde group content was 0.046 mmol / g, which was lower than that in Example 1, which was not conducive to further grafting dodecylamine.

[0055] Comparative Example 3 Cellulose nanofibers were used instead of microcrystalline cellulose in Example 1. Dialdehyde cellulose was prepared according to the same steps as in Example 1 (1). The aldehyde group of the dialdehyde cellulose prepared by cellulose nanofibers was titrated according to the same steps as in Example 1 (2). The aldehyde group content was 0.057 mmol / g, which was lower than that in Example 1, which was not conducive to further grafting dodecylamine.

[0056] Finally, the effects of oxidation temperature and time on microcrystalline cellulose were investigated.

[0057] Comparative Example 4 According to the molar ratio of β-D-glucopyranose units to sodium periodate in microcrystalline cellulose being 1:1.1, sodium periodate was added to a 1% microcrystalline cellulose aqueous dispersion and oxidized at 30°C for 48 hours. The reaction solution after the reaction was treated with the same dialysis and centrifugation method as in step (1) of Example 1 to obtain a dialdehyde cellulose aqueous solution. The aldehyde group of the obtained dialdehyde cellulose was titrated according to the same steps as in step (2) of Example 1, and the aldehyde group content was found to be 0.035 mmol / g. The aldehyde group content was significantly lower than that in Example 1, which is not conducive to further grafting of dodecylamine.

Claims

1. A method for preparing an aromatic heavy oil asphaltenes inhibitor, characterized in that, Includes the following steps: S1. According to the molar ratio of β-D-pyranose units to sodium periodate in microcrystalline cellulose of 1:1.1, sodium periodate was added to the aqueous dispersion of microcrystalline cellulose. Under the dark, the reaction was first carried out at 30°C for 48 hours, and then the temperature was raised to 50°C to continue the oxidation reaction for 48 hours. The oxidation reaction product was collected to obtain dialdehyde cellulose. S2. The aldehyde content in dialdehyde cellulose was obtained by hydroxylamine hydrochloride titration. S3. Adjust the pH of the dialdehyde cellulose aqueous solution to 9, add dodecylamine dissolved in ethanol to the dialdehyde cellulose aqueous solution at a molar ratio of amine to aldehyde of 1:1, and perform the grafting reaction at 60°C for 6 hours. Collect the grafting reaction product to obtain dodecylamine modified cellulose. S4. Dissolve dodecylamine-modified cellulose in toluene to obtain an aromatic heavy oil asphaltenes inhibitor.

2. The method for preparing the aromatic heavy oil asphaltenes inhibitor according to claim 1, characterized in that, In step S1, the concentration of the microcrystalline cellulose aqueous dispersion is 1 wt%.

3. The method for preparing the aromatic heavy oil asphaltenes inhibitor according to claim 1, characterized in that, In step S1, the specific steps for collecting the oxidation reaction products are as follows: the reaction solution after oxidation reaction is dialyzed with deionized water to remove periodate ions, the dialyzed reaction solution is refluxed at 80°C for 6 hours and centrifuged at 10000 r / min for 15 minutes, and the supernatant is retained to remove unoxidized cellulose.

4. The method for preparing the aromatic heavy oil asphaltenes inhibitor according to claim 1, characterized in that, In step S3, the specific steps for collecting the grafting reaction product are as follows: centrifuge the reaction solution after the grafting reaction, collect the precipitate, and obtain the crude product of dodecylamine modified cellulose; mix hydrochloric acid aqueous solution with pH=3 and ethanol at a volume ratio of 1:1 to obtain a washing acid solution, and use the washing acid solution to wash the crude product of dodecylamine modified cellulose to remove unreacted dodecylamine.

5. An aromatic heavy oil asphaltenes inhibitor, characterized in that, It was prepared by the method for preparing aromatic heavy oil asphaltenes according to any one of claims 1-4.

6. The application of the aromatic heavy oil asphaltenes inhibitor according to claim 5 in inhibiting asphaltenes deposition, characterized in that, When applying, aromatic heavy oil asphaltenes inhibitors are added directly to heavy oil or toluene-dissolved asphaltenes.

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