Extracting agent and method for separating aromatic hydrocarbon in catalytic cracking diesel oil

Abstract

The invention provides an extraction agent and a method for separating aromatic hydrocarbons in catalytic cracking diesel oil. The extraction agent comprises 55 to 80 wt% of 1-butyl-3-methylimidazolium tetrafluoroborate, 10 to 25 wt% of 1-ethyl-3-methylimidazoline diimine, 5 to 15 wt% of ethanolamine and 4 to 6 wt% of a hydroxyl-containing compound. The extraction agent has extremely high selectivity on aromatic hydrocarbons, can effectively extract bicyclic aromatic hydrocarbons in oil products, and realizes conversion of high value-added chemicals.

Description

Technical Field

[0001] This invention belongs to the field of aromatic hydrocarbon extraction technology in catalytic cracking diesel, specifically relating to an extractant and method for separating aromatic hydrocarbons from catalytic cracking diesel. Background Technology

[0002] In today's era of rapid development of new energy sources, the growth in diesel demand is slow, and diesel prices continue to decline. This presents new challenges for refining structures, with refineries facing the difficult question of how to better handle aromatics in petroleum products to improve quality or transform them into high-value-added products. Catalytic cracking diesel contains over 70% total aromatics, rich in bicyclic aromatics (such as methylnaphthalene and dimethylnaphthalene). Utilizing the high aromatic content of catalytic cracking diesel, reducing its aromatic content, and simultaneously making rational use of aromatics can improve the economic efficiency of enterprises.

[0003] Liquid-liquid extraction has a wide range of applications in diesel fuel dearomatics. Currently, industrially, single solvents are commonly used as extractants, such as sulfolane and dimethyl sulfoxide. The Udex and Sulfoane processes are well-developed industrially and achieve ideal separation results. However, these technologies are primarily designed for the separation of monocyclic aromatic hydrocarbons (BTX). In catalytic cracking diesel fuel systems, which contain polycyclic aromatic hydrocarbons (PAHs) and exhibit polarity differences, extractants struggle to efficiently separate all aromatic hydrocarbons.

[0004] Traditional organic solvents have the following drawbacks: (1) They have a certain degree of miscibility with alkanes in oil products, causing cross-contamination between the extractant and the oil products; (2) They have the disadvantages of poor thermal stability and poor chemical stability, and are prone to side reactions such as decomposition and oxidation, which remain in the oil products and cause oil pollution; (3) The boiling point of the target product in catalytic cracking diesel is generally between 220-300℃. The boiling point of these organic solvents is exactly within the boiling point range of the product to be extracted, making it difficult to separate the extractant from the product, which is not conducive to the regeneration of the extractant and increases the energy consumption for extractant regeneration.

[0005] Ionic liquids, as a novel type of extractant, offer advantages such as negligible vapor pressure, thermal stability, and structural designability. These advantages not only enhance the selectivity of extractants for aromatics but also simplify separation devices and reduce energy consumption due to their unique physicochemical properties.

[0006] CN115703023A provides a composite solvent for separating ethylbenzene from C8 aromatics. This composite solvent, used for separating ethylbenzene from C8 aromatics, exhibits a certain ethylbenzene separation efficiency. The composite solvent for separating ethylbenzene from C8 aromatics provided by this invention comprises 75-96 wt% of a main solvent and 4-25 wt% of a co-solvent. The main solvent is selected from trichlorobenzene, and the co-solvent is selected from C10-C18 alkanes or C10-C13 aromatics. This method is only suitable for separating monocyclic aromatics and is not suitable for separating polycyclic aromatics in catalytic cracking diesel fuel. Furthermore, the additive is easily miscible with the oil, making aromatic separation difficult.

[0007] CN112552951A discloses a composite extractant and its application method suitable for the removal of aromatics from straight-run naphtha with low aromatic content. The raw materials for this composite extractant, by weight, are: 80 parts N,N-dimethyl sulfoxide, 10-20 parts N,N-dimethylformamide (DMF), and 8-15 parts propylene carbonate (PC). This method can control the solubility and selectivity of aromatics between two phases. A disadvantage of this method is that the boiling points of DMF and propylene carbonate are within the boiling point range of catalytic cracking diesel fuel, which is not conducive to the recovery of the extractant during the extraction process, increasing the extraction cost.

[0008] CN112795397A provides a composite solvent for separating cycloalkanes and aromatics from naphtha, composed of N,N-dimethylformamide, cyclodextrin, and 1-butyl-3-methylimidazolium dicyandiamide salt. The weight composition is 80-90 wt% N,N-dimethylformamide, 10-20 wt% cyclodextrin, and 1 wt% 1-butyl-3-methylimidazolium dicyandiamide salt. The composite solvent achieves a selectivity and removal rate of 37.0% and 95% for aromatics in naphtha, respectively. This composite solvent has adjustable characteristics, meaning the extraction performance for cycloalkanes and aromatics in naphtha can be adjusted by changing the formulation ratio of the components. A drawback of this method is the use of cyclodextrin as an adjuvant. Because the hydroxyl groups on the outer layer of cyclodextrin can form hydrogen bonds with neighboring water molecules, the water solubility of cyclodextrin is generally low, making it difficult to recover during solvent recovery and back-extraction, thus increasing extraction energy consumption.

[0009] CN104945328A provides a composite solvent and its application method for extracting and separating aromatics and alkanes from diesel fractions. The composite solvent comprises an ionic liquid and an organic solvent, wherein the cation is an alkyl-substituted imidazole or pyridine cation, and the anion is BF4. - PF6 -The additives, including p-toluenesulfonate, bis(trifluoromethanesulfonyl)imide, nonafluorobutyrate, dodecyl sulfonate, acetate, or sulfate, are used with an ionic liquid as the main solvent and a conventional organic solvent as a co-solvent. The organic solvent is N,N-dimethylformamide, N,N-dimethylacetamide, or sulfolane. By adjusting the carbon number on the cation substituents of the ionic liquid, the selective solubility of aromatics in diesel fuel can be increased, resulting in a lower aromatic content and a higher cetane number in the raffinate. The disadvantage of this invention is that while the addition of additives can effectively improve the solubility of aromatics, the selected organic solvents used as additives are easily miscible with alkanes in the oil, making separation difficult.

[0010] CN108003915A discloses a composite solvent and method for extracting and separating aromatics and alkanes from diesel fractions. The method comprises 60–99 wt% of a main solvent A and 1–40 wt% of a co-solvent B. Both main solvent A and co-solvent B are ionic liquids. The main solvent A and co-solvent B have the same cation, selected from alkyl-substituted imidazole or pyridine cations, and different anions, selected from hexafluorophosphate, tetrafluoroborate, or bis(trifluoromethanesulfonyl)imide, respectively. Although this method more effectively separates aromatic components from diesel fractions and improves the properties of diesel products, the use of ionic liquids as the composite solvent does not solve the problems of high viscosity and high cost associated with ionic liquids, and requires high-temperature extraction to ensure mass transfer efficiency. Summary of the Invention

[0011] The purpose of this invention is to provide an extractant for separating aromatics from catalytic cracking diesel oil. This extractant has extremely high selectivity for aromatics and can effectively extract bicyclic aromatics from oil products, thereby realizing the conversion of high-value-added chemicals.

[0012] Another objective of this invention is to provide a method for separating aromatics from catalytic cracking diesel fuel.

[0013] To achieve the above objectives, the present invention provides an extractant for separating aromatics from catalytic cracking diesel fuel, comprising 55-80 wt% of 1-butyl-3-methylimidazolium tetrafluoroborate, 10-25 wt% of 1-ethyl-3-methylimidazoline diimide, 5-15 wt% of ethanolamine and 4-6 wt% of a hydroxyl-containing compound.

[0014] The extractant for separating aromatics from catalytic cracked diesel fuel according to the present invention comprises one or more of methanol, ethanol, and water containing hydroxyl compounds.

[0015] The extractant for separating aromatics from catalytic cracked diesel fuel according to the present invention comprises 60-80 wt% of 1-butyl-3-methylimidazolium tetrafluoroborate, 10-20 wt% of 1-ethyl-3-methylimidazoline diimide, 5-15 wt% of ethanolamine and 4-5 wt% of a hydroxyl-containing compound.

[0016] To achieve the above objectives, the present invention also provides a method for separating aromatics from catalytic cracking diesel, wherein the extractant described above is used to extract the catalytic cracking diesel by mixing the extractant with the catalytic cracking diesel, wherein the mass ratio of the extractant to the catalytic cracking diesel is 1 to 3:1.

[0017] The method for separating aromatics from catalytic cracking diesel fuel according to the present invention uses an extraction temperature of 25–100°C.

[0018] The method for separating aromatics from catalytic cracking diesel fuel according to the present invention has an extractant to catalytic cracking diesel fuel mass ratio of 2 to 3:1.

[0019] The method for separating aromatics from catalytic cracking diesel fuel according to the present invention uses an extraction temperature of 55–75°C.

[0020] The method for separating aromatics from catalytic cracking diesel fuel according to the present invention is wherein the content of bicyclic aromatics in the catalytic cracking diesel fuel is 35-50 wt%.

[0021] The method for separating aromatics from catalytic cracked diesel fuel according to the present invention, wherein the boiling point of the catalytic cracked diesel fuel is 180-350°C.

[0022] Beneficial effects of this invention:

[0023] (1) The extractant used in this invention is a common substance with low toxicity and low corrosivity. It can effectively reduce the viscosity of the composite solvent, has good miscibility between components, and is inexpensive and readily available, thus reducing costs and increasing the yield of aromatics.

[0024] (2) The present invention uses ethanolamine, which can significantly improve the solubility of ionic liquids. The selected hydroxyl-containing compounds can form hydrogen bonds with ionic liquids or ethanolamine, increase the solubility with aromatics, enhance the polarity of the extractant, and thus increase the selectivity for aromatics. In particular, methylnaphthalene and dimethylnaphthalene have better extraction effects. At the same time, they are immiscible with the alkanes contained in catalytic cracking diesel oil and have better separation effects.

[0025] (3) The extractant of the present invention enhances the solubility and selectivity of bicyclic aromatic hydrocarbons and improves the recovery rate of aromatic hydrocarbons. At the same time, the catalytic cracked diesel oil obtained has a high cetane number, which improves the quality of diesel oil.

[0026] (4) The addition of ethanolamine and hydroxyl-containing compounds can treat raw materials with a wide boiling point range and low aromatic content. Detailed Implementation

[0027] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0028] Table 1. Raw material feed composition of the examples

[0029]

[0030]

[0031] Example 1

[0032] The catalytic diesel feedstock, the composition of which is listed in Table 1, was used. The extractant used contained 65 wt% 1-butyl-3-methylimidazolium tetrafluoroborate, 20 wt% 1-ethyl-3-methylimidazoline diimide, 10 wt% ethanolamine, and 5% methanol. The extraction temperature was 75°C, and the extractant-to-oil ratio was 3.0.

[0033] Example 2

[0034] The catalytic diesel feedstock, the composition of which is listed in Table 1, was used. The extractant used contained 70 wt% 1-butyl-3-methylimidazolium tetrafluoroborate, 20 wt% 1-ethyl-3-methylimidazoline diimide, 5 wt% ethanolamine, and 5% ethanol. The extraction temperature was 100°C, and the extractant-to-oil ratio was 3.0.

[0035] Example 3

[0036] The catalytic diesel feedstock, the composition of which is listed in Table 1, was used. The extractant used contained 60 wt% 1-butyl-3-methylimidazolium tetrafluoroborate, 20 wt% 1-ethyl-3-methylimidazoline diimide, 15 wt% ethanolamine, and 5% water. The extraction temperature was 55°C, and the extractant-to-oil ratio was 3.0.

[0037] Example 4

[0038] The catalytic diesel feedstock, the composition of which is listed in Table 1, was used. The extractant used contained 80 wt% 1-butyl-3-methylimidazolium tetrafluoroborate, 10 wt% 1-ethyl-3-methylimidazoline diimide, 5 wt% ethanolamine, and 5% methanol. The extraction temperature was 75°C, and the extractant-to-oil ratio was 3.0.

[0039] Comparative Example 1

[0040] The catalytic diesel feedstock, the composition of which is listed in Table 1, was used. The extractant used contained 65 wt% 1-butyl-3-methylimidazolium tetrafluoroborate, 20 wt% 1-ethyl-3-methylimidazoline diimide, and 15 wt% ethanolamine. The extraction temperature was 75°C, and the extractant-to-oil ratio was 3.0.

[0041] Comparative Example 2

[0042] The catalytic diesel feedstock, the composition of which is listed in Table 1, was used. The extractant used contained 65 wt% 1-butyl-3-methylimidazolium tetrafluoroborate, 20 wt% 1-ethyl-3-methylimidazoline diimide, and 15 wt% methanol. The extraction temperature was 75 °C, and the extractant-to-oil ratio was 3.0.

[0043] Comparative Example 3

[0044] The catalytic diesel feedstock, the composition of which is listed in Table 1, was used. The extractant used contained 65 wt% 1-butyl-3-methylimidazolium tetrafluoroborate, 20 wt% 1-ethyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide, 10 wt% ethanolamine, and 5% methanol. The extraction temperature was 25°C, and the extractant-to-oil ratio was 1.0.

[0045] The extraction results in the examples and comparative examples are shown in Table 2.

[0046] The contents of mixed aromatic hydrocarbons and methylnaphthalene + dimethylnaphthalene were determined by GC-MS chromatography-mass spectrometry.

[0047] Mixed aromatics yield = (mass of extract oil after extraction × total aromatics content in extract oil) / (mass of feed oil × total aromatics content in feed oil).

[0048] Table 2

[0049] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Mixed aromatics content, wt% 98.5 97.3 99.75 95.2 80.7 76.5 86.5 Mixed aromatics yield, % 92.6 95.2 90.3 96.8 89.4 89.1 90.11 Methylnaphthalene + dimethylnaphthalene, wt% 91.95 94.86 89.49 95.05 70.2 65.6 82.18

[0050] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. An extractant for separating aromatics from catalytic cracking diesel fuel, characterized in that, It includes 55–80 wt% of 1-butyl-3-methylimidazolium tetrafluoroborate, 10–25 wt% of 1-ethyl-3-methylimidazoline diimide, 5–15 wt% of ethanolamine and 4–6 wt% of hydroxyl-containing compounds.

2. The extractant for separating aromatics from catalytic cracking diesel oil according to claim 1, characterized in that, The hydroxyl-containing compound is one or more of methanol, ethanol, and water.

3. The extractant for separating aromatics from catalytic cracking diesel oil according to claim 1, characterized in that, It includes 60–80 wt% of 1-butyl-3-methylimidazolium tetrafluoroborate, 10–20 wt% of 1-ethyl-3-methylimidazoline diimide, 5–15 wt% of ethanolamine and 4–5 wt% of hydroxyl-containing compounds.

4. A method for separating aromatics from catalytic cracking diesel fuel, characterized in that, Using the extractant according to any one of claims 1 to 3, the extractant and catalytic cracked diesel are mixed and extracted, wherein the mass ratio of the extractant to the catalytic cracked diesel is 1 to 3:

1.

5. The method for separating aromatics from catalytic cracking diesel oil according to claim 4, characterized in that, The extraction temperature is 25–100℃.

6. The method for separating aromatics from catalytic cracking diesel oil according to claim 4, characterized in that, The mass ratio of the extractant to the catalytic cracked diesel is 2 to 3:

1.

7. The method for separating aromatics from catalytic cracking diesel oil according to claim 5, characterized in that, The extraction temperature is 55–75℃.

8. The method for separating aromatics from catalytic cracking diesel oil according to claim 4, characterized in that, The catalytic cracked diesel fuel contains 35-50 wt% bicyclic aromatic hydrocarbons.

9. The method for separating aromatics from catalytic cracking diesel oil according to claim 4, characterized in that, The boiling point of the catalytic cracked diesel oil is 180–350°C.

Images