Sulfur-containing low-temperature molten salts and their application in removing aromatic sulfides from fuel oil

Abstract

The present invention provides a sulfur-containing low-temperature molten salt and its application in removing aromatic sulfides from fuel oil. The sulfur-containing low-temperature molten salt is obtained by a chemical reaction of a thiophene compound, a benzothiophene compound, a dibenzothiophene compound, or a naphthothiophene compound with a sulfuric acid diester, a trifluoromethanesulfonate, a phosphoric acid triester, a trifluoroacetate, or a sulfonate in a molar ratio of 1:1 to 1.05, and the product has high purity and stability. By using the sulfur-containing low-temperature molten salt as an extractant, aromatic sulfides in fuel oil can be removed at room temperature and atmospheric pressure, and the removal rate is higher than 99.9%. The reaction process is mild, the operation is simple, and the time is short. There is no need for high temperature and high pressure, catalyst, oxidant, and inert gas protection, and it can avoid using hydrogen peroxide, acids and bases, and media containing heavy metal components. The regenerated sulfur-containing low-temperature molten salt can be recycled to remove aromatic sulfides from fuel oil, further reducing the reaction cost and waste emissions.

Description

Technical Field

[0001] The present invention belongs to the field of fuel desulfurization, and particularly relates to a sulfur-containing low-temperature molten salt and a method for removing aromatic sulfides from fuel. Background Art

[0002] Since modern times, with the rapid development of industrial production and social economy and the continuous improvement of the living standards of human beings, the demand for energy has been increasing day by day. At present, fuel resources represented by gasoline, diesel, etc. are still one of the most important forms of energy production and consumption in various countries around the world. The extensive use of fuel has brought convenience to production and life, but it has also caused certain pollution. Among them, the sulfides contained in fuel generate harmful substances such as sulfur dioxide after combustion, which has an adverse impact on the natural environment and life health. Therefore, fuel desulfurization technology research and application have been widely emphasized and strengthened at home and abroad.

[0003] To date, the fuel desulfurization process mostly proceeds through catalytic hydrogenation reaction. Although this method is convenient for removing relatively simple organic and inorganic sulfides, it is difficult to remove aromatic sulfides in fuel. In response to this problem, other types of desulfurization methods have been continuously developed, such as adsorption desulfurization, oxidation desulfurization, and extraction desulfurization. Among them, the extraction desulfurization method has the characteristics of low energy consumption and mild conditions, and is widely used. However, the organic solvents and other media used in the extraction desulfurization method are prone to volatilization and have poor stability, reducing the reaction efficiency. In this case, it is necessary to further develop a new type of high-efficiency medium for extraction desulfurization.

[0004] Low-temperature molten salts, usually also known as ionic liquids, are generally composed of organic cations and conventional anions. The special structure endows this system with excellent properties such as a low melting point, strong structural tunability, and stability, making it a new type of medium with broad application prospects. Research in recent years has shown that low-temperature molten salts can be used as extractants or catalysts for fuel desulfurization, achieving certain results. It should be noted that the preparation processes of related systems are mostly complex and require two-step or even multi-step chemical reactions to complete. Secondly, some systems need to be combined with additives such as hydrogen peroxide to achieve the extraction effect, which increases the reaction cost and makes the operation process more complex. In addition, some systems contain heavy metal components or strong acidity and alkalinity, which are not conducive to environmental protection and recycling. Among them, Chinese invention patent (CN103626706A) proposed a preparation method for a desulfurization-functional ionic liquid. This method first reacts N-methylimidazole with 3-chloropropionic acid to generate an imidazole-type chloride salt, and then the imidazole-type chloride salt is mixed with ferric chloride to obtain the target ionic liquid. This system is obtained through two-step chemical reactions, contains heavy metal components, and has strong acidity. The preparation process needs to be completed in a glove box under argon protection, and the operation is relatively complex. In addition, Chinese invention patent (CN110229693A) discloses a method for fuel extraction oxidative desulfurization using a solid acid coupled with an ionic liquid. This method requires mixing substances such as ionic liquid, solid acid, and hydrogen peroxide and heating for 1-5 h to complete fuel desulfurization. The composition and reaction operation of such systems are relatively complex, the extraction time is long, and it is not convenient for large-scale application.

[0005] In the above background, in order to improve the extraction efficiency of fuel desulfurization, simplify the operation process, reduce environmental pollution, and promote the recycling of the system, it is necessary to continue to develop media with more excellent performance and their application methods for removing aromatic sulfides in fuels. Summary of the Invention

[0006] In order to overcome the above technical defects, the present invention provides a sulfur-containing low-temperature molten salt and a method for removing aromatic sulfides in fuels, aiming to achieve efficient removal of aromatic sulfides in fuels under mild conditions, simplify the operation, reduce energy consumption, and at the same time avoid using hydrogen peroxide, acids and bases, and media containing heavy metal components, reduce environmental pollution, and promote the recycling of the system.

[0007] The sulfur-containing low-temperature molten salt of the present invention is obtained by reacting a thiophene-based, benzothiophene-based, dibenzothiophene-based, or naphthothiophene-based compound with a sulfuric acid diester, trifluoromethanesulfonate, phosphoric acid triester, trifluoroacetate, or sulfonate in a molar ratio of 1:1 to 1.05.

[0008] Further, the molecular structure of the thiophene-based compound is The molecular structure of the benzothiophene-based compound is The molecular structure of the dibenzothiophene compound is The molecular structure of the naphthothiophene compound is Among them, R1-R8 are each independently selected from hydrogen, a C1-C8 saturated alkyl group, a C2-C8 alkyl group with a C═C double bond, a phenyl group, or a phenyl-substituted C1-C4 alkyl group.

[0009] Furthermore, the molecular structure of the sulfate ester is The molecular structure of the trifluoromethanesulfonate ester is The molecular structure of the triphosphate ester is The molecular structure of the trifluoroacetate ester is The molecular structure of the sulfonate ester is Among them, R, R1-R3 are each independently selected from a C1-C8 saturated alkyl group, a C2-C8 alkyl group with a C═C double bond, a phenyl group, or a phenyl-substituted C1-C4 alkyl group.

[0010] Furthermore, the molten salt is obtained by mixing a thiophene compound, a benzothiophene compound, a dibenzothiophene compound, or a naphthothiophene compound and an ester at 10-30 °C and 0.1 MPa for 0.5-4 h, and then performing vacuum distillation at 30-100 °C and 1-20 kPa.

[0011] Meanwhile, the present invention also provides the application of the aforementioned sulfur-containing low-temperature molten salt in removing aromatic sulfides from fuel oil.

[0012] Furthermore, the fuel oil is gasoline or diesel.

[0013] Furthermore, the aromatic sulfides include one or more of thiophene compounds, benzothiophene compounds, dibenzothiophene compounds, and naphthothiophene compounds, and the total mass content of the aromatic sulfides in the fuel oil is 0.05-0.5%.

[0014] Furthermore, the molecular structure of the thiophene compound is The molecular structure of the benzothiophene compound is The molecular structure of the dibenzothiophene compound is The molecular structure of the naphthothiophene compound is Among them, R1-R8 are each independently selected from hydrogen, a C1-C8 saturated alkyl group, a C2-C8 alkyl group with a C═C double bond, a phenyl group, or a phenyl-substituted C1-C4 alkyl group.

[0015] Furthermore, the application of the sulfur-containing low-temperature molten salt of the present invention in removing aromatic sulfides from fuel oil includes the following steps:

[0016] 1) At room temperature and normal pressure, mix the aforementioned sulfur-containing low-temperature molten salt with fuel oil containing aromatic sulfides and stir for 0.1-0.5 h to extract the sulfides into the sulfur-containing low-temperature molten salt;

[0017] 2) After the reaction system in step 1) stands still and layers, separate the upper and lower systems. Among them, the upper system is the fuel oil after removing aromatic sulfides. The lower system is purified by vacuum distillation to obtain the regenerated sulfur-containing low-temperature molten salt and the corresponding aromatic sulfides.

[0018] Further, the room temperature in step 1) is 10 - 30°C, the normal pressure is 0.1 MPa, and the mass ratio of the sulfur-containing low-temperature molten salt to the fuel oil is 1:5 - 10.

[0019] Further, the pressure of the vacuum distillation in step 2) is 0.5 - 20 kPa, and the temperature is 30 - 150°C.

[0020] The chemical composition of the sulfur-containing low-temperature molten salt is determined by nuclear magnetic resonance spectroscopy and mass spectrometry, and the chemical composition of the aromatic sulfides is determined by nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy. The corresponding mass contents are obtained according to the test results.

[0021] Research shows that the cations of the sulfur-containing low-temperature molten salt have relatively close chemical compositions and structures to the aromatic sulfides. The π bonds in the cations can have a strong complexation effect with the π bonds in the sulfides. At the same time, the anions and cations can also have a strong electrostatic attraction with the sulfur atoms in the sulfides, promoting the full extraction of aromatic sulfides into the molten salt on the basis of immiscibility, so as to achieve the purpose of highly efficient desulfurization under relatively mild conditions and in a short time.

[0022] Compared with the existing technology, the following technical effects can be achieved by using the present invention:

[0023] 1) A sulfur-containing low-temperature molten salt proposed by the present invention has easily available raw materials for preparation. The preparation process can be completed by one-step chemical reaction at room temperature and normal pressure, without multiple-step chemical reactions and inert gas protection. Through the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is higher than 99.9%, and it has high purity and stability.

[0024] 2) The present invention uses the sulfur-containing low-temperature molten salt as an extractant to remove aromatic sulfides in fuel oil at room temperature. The reaction process is mild, the operation is simple, and the time is short. It does not require high temperature and high pressure, catalysts, oxidants, and inert gas protection, and can avoid using hydrogen peroxide, acids and bases, and media containing heavy metal components, which is beneficial to environmental protection.

[0025] 3) The test results of ultraviolet absorption spectroscopy and nuclear magnetic resonance spectroscopy prove that the mass content of aromatic sulfides in the desulfurized fuel oil is lower than 0.0005%, and the removal rate of aromatic sulfides is higher than 99.9%, showing good desulfurization effect.

[0026] 4) After regeneration, the mass content of the sulfur-containing low-temperature molten salt is higher than 99.8%, and it can be recycled for removing aromatic sulfides in fuel oil, further reducing the reaction cost and waste emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 1H NMR spectrum of 5-methyldibenzothiophenium trifluoromethanesulfonate prepared in Example 1 according to the present invention.

[0028] Figure 2 Positive ion mass spectrum of 5-methyldibenzothiophenium trifluoromethanesulfonate prepared in Example 1 of the present invention.

[0029] Figure 3 Negative ion mass spectrum of 5-methyldibenzothiophenium trifluoromethanesulfonate prepared in Example 1 of the present invention.

[0030] Figure 4 Ultraviolet absorption spectrum of the aromatic sulfide - thiophene separated in Example 1 of the present invention, and the wavelength of the maximum absorption peak is 231 nm. DETAILED DESCRIPTION OF THE INVENTION

[0031] The specific embodiments of the present invention will be described in detail with the following examples. However, the present invention is not limited to the following examples, and all embodiments that meet the above-mentioned purpose are within the technical protection scope of the present invention.

[0032] Example 1

[0033] A method for preparing a sulfur-containing low-temperature molten salt: At 10 °C and 0.1 MPa, dibenzothiophene and methyl trifluoromethanesulfonate are mixed and reacted at a molar ratio of 1:1.01 for 0.5 h, and then the system is subjected to vacuum distillation at 20 kPa and 60 °C to finally obtain 5-methyldibenzothiophenium trifluoromethanesulfonate. Through the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is 99.94%, and the molecular structure is

[0034] A method for removing aromatic sulfides in fuel oil using a sulfur-containing low-temperature molten salt, comprising the following steps:

[0035] 1) At 20 °C and 0.1 MPa, 5-methyldibenzothiophenium trifluoromethanesulfonate and gasoline containing thiophene are mixed at a mass ratio of 1:10, and then stirred for 0.2 h for extraction. Among them, the total mass content of thiophene in gasoline is 0.3%;

[0036] 2) After the reaction system in step 1) is allowed to stand and separate into layers, the upper and lower systems are separated. Among them, the upper system is gasoline from which aromatic sulfides have been removed. In addition, the lower system is purified by vacuum distillation at 5 kPa and 30 °C, and regenerated thiophene is obtained from the distillate, and the remaining substance is regenerated 5-methyldibenzothiophenium trifluoromethanesulfonate.

[0037] The test results of nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy show that the total mass content of thiophene in the desulfurized gasoline is 0.00009%, and the removal rate of aromatic sulfides is 99.97%. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the regenerated 5-methyldibenzothiophenium trifluoromethanesulfonate is 99.91%, and it can be recycled for removing aromatic sulfides in fuel oil.

[0038] Example 2

[0039] A preparation method of a sulfur-containing low-temperature molten salt: At 20 °C and 0.1 MPa, benzothiophene and diethyl sulfate are mixed and reacted for 1 h in a molar ratio of 1:1.02, then the system is subjected to vacuum distillation at 5 kPa and 80 °C, and finally 1-ethylbenzothiophenium ethyl sulfate is obtained. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is 99.93%, and the molecular structure is

[0040] A method for removing aromatic sulfides in fuel oil using a sulfur-containing low-temperature molten salt includes the following steps:

[0041] 1) At 15 °C and 0.1 MPa, 1-ethylbenzothiophenium ethyl sulfate is mixed with gasoline containing benzothiophene and dibenzothiophene in a mass ratio of 1:8, and then stirred for 0.3 h for extraction. Among them, the total mass content of benzothiophene and dibenzothiophene in the gasoline is 0.35%;

[0042] 2) After the reaction system in step 1) is allowed to stand and separate into layers, the upper and lower systems are separated. Among them, the upper system is gasoline from which aromatic sulfides have been removed. In addition, the lower system is purified by vacuum distillation at 1 - 5 kPa and 80 - 120 °C, and regenerated benzothiophene and dibenzothiophene are obtained from the distillate using different pressures and temperatures, and the remaining substance is regenerated 1-ethylbenzothiophenium ethyl sulfate.

[0043] The test results of nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy show that the total mass content of benzothiophene and dibenzothiophene in the desulfurized gasoline is 0.00015%, and the removal rate of aromatic sulfides is 99.96%. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the regenerated 1-ethylbenzothiophenium ethyl sulfate is 99.84%, and it can be recycled for removing aromatic sulfides in fuel oil.

[0044] Example 3

[0045] A preparation method of sulfur-containing low-temperature molten salt: At 30 °C and 0.1 MPa, 2-n-octylthiophene and trimethyl phosphate are mixed and reacted at a molar ratio of 1:1 for 4 h, and then the system is subjected to vacuum distillation at 8 kPa and 70 °C, and finally 1-methyl-2-n-octylthiophenium dimethyl phosphate salt is obtained. After characterization by nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is 99.91%, and the molecular structure is

[0046] A method for removing aromatic sulfides from fuel oil using sulfur-containing low-temperature molten salt includes the following steps:

[0047] 1) At 10 °C and 0.1 MPa, 1-methyl-2-n-octylthiophenium dimethyl phosphate salt and diesel containing 3-methylthiophene, benzothiophene, and 4,6-dimethyldibenzothiophene are mixed at a mass ratio of 1:6, and then stirred for 0.4 h for extraction. Among them, the total mass content of 3-methylthiophene, benzothiophene, and 4,6-dimethyldibenzothiophene in diesel is 0.42%;

[0048] 2) After the reaction system in step 1) is allowed to stand and separate into layers, the upper and lower layer systems are separated. Among them, the upper layer system is diesel from which aromatic sulfides have been removed. In addition, the lower layer system is purified by vacuum distillation at 1-20 kPa and 30-120 °C, and regenerated 3-methylthiophene, benzothiophene, and 4,6-dimethyldibenzothiophene are obtained from the distillate at different pressures and temperatures, and the remaining substance is regenerated 1-methyl-2-n-octylthiophenium dimethyl phosphate salt.

[0049] The test results of nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy show that the total mass content of 3-methylthiophene, benzothiophene, and 4,6-dimethyldibenzothiophene in the desulfurized diesel is 0.00024%, and the removal rate of aromatic sulfides is 99.94%. After characterization by nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the regenerated 1-methyl-2-n-octylthiophenium dimethyl phosphate salt is 99.85%, and it can be recycled for removing aromatic sulfides from fuel oil.

[0050] Example 4

[0051] A preparation method of sulfur-containing low-temperature molten salt: At 25 °C and 0.1 MPa, 5-methylbenzothiophene and ethyl trifluoroacetate are mixed and reacted at a molar ratio of 1:1.05 for 3 h, and then the system is subjected to vacuum distillation at 3 kPa and 30 °C, and finally 1-ethyl-5-methylbenzothiophenium trifluoroacetate salt is obtained. After characterization by nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is 99.93%, and the molecular structure is

[0052] A method for removing aromatic sulfides from fuel oil using a sulfur-containing low-temperature molten salt, comprising the following steps:

[0053] 1) At 25 °C and 0.1 MPa, 1-ethyl-5-methylbenzo[b]thiophenium trifluoroacetate is mixed with diesel oil containing 2-benzylthiophene and 3-methylbenzo[b]thiophene in a mass ratio of 1:7, and then stirred for 0.3 h for extraction. Among them, the total mass content of 2-benzylthiophene and 3-methylbenzo[b]thiophene in the diesel oil is 0.15%;

[0054] 2) After the reaction system in step 1) stands and layers, the upper and lower systems are separated. Among them, the upper system is the diesel oil from which aromatic sulfides have been removed. In addition, the lower system is purified by vacuum distillation at 5-10 kPa and 40-90 °C, and regenerated 2-benzylthiophene and 3-methylbenzo[b]thiophene are obtained from the distillate at different pressures and temperatures, and the remaining substance is regenerated 1-ethyl-5-methylbenzo[b]thiophenium trifluoroacetate.

[0055] The test results of nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy show that the total mass content of 2-benzylthiophene and 3-methylbenzo[b]thiophene in the desulfurized diesel oil is 0.00008%, and the removal rate of aromatic sulfides is 99.95%. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the regenerated 1-ethyl-5-methylbenzo[b]thiophenium trifluoroacetate is 99.87%, and it can be recycled for removing aromatic sulfides from fuel oil.

[0056] Example 5

[0057] A preparation method of a sulfur-containing low-temperature molten salt: 4,6-dimethyldibenzothiophene and n-butyl methanesulfonate are mixed and reacted at a molar ratio of 1:1.02 at 15 °C and 0.1 MPa for 2.5 h, and then the system is vacuum distilled at 10 kPa and 85 °C, and finally 4,6-dimethyl-5-n-butyldibenzothiophenium methanesulfonate is obtained. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is 99.91%, and the molecular structure is

[0058] A method for removing aromatic sulfides from fuel oil using a sulfur-containing low-temperature molten salt, comprising the following steps:

[0059] 1) At 20 °C and 0.1 MPa, 4,6-dimethyl-5-n-butyldibenzothiophenium methanesulfonate is mixed with diesel oil containing 2-ethylbenzothiophene in a mass ratio of 1:9, and then stirred for 0.1 h for extraction. Among them, the total mass content of 2-ethylbenzothiophene in the diesel oil is 0.05%;

[0060] 2) After the reaction system in step 1) stands still and layers, separate the upper and lower systems. Among them, the upper system is diesel oil from which aromatic sulfides have been removed. In addition, the lower system is purified by vacuum distillation at 5 kPa and 100 °C, and regenerated 2-ethylbenzothiophene is obtained from the distillate, and the remaining substance is regenerated 4,6-dimethyl-5-n-butyldibenzothiophenium methanesulfonate.

[0061] The test results of nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy show that the total mass content of 2-ethylbenzothiophene in the desulfurized diesel oil is 0.00004%, and the removal rate of aromatic sulfides is 99.92%. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of regenerated 4,6-dimethyl-5-n-butyldibenzothiophenium methanesulfonate is 99.86%, and it can be recycled for removing aromatic sulfides in fuel oil.

[0062] Example 6

[0063] A preparation method of a sulfur-containing low-temperature molten salt: At 20 °C and 0.1 MPa, mix 2-phenylthiophene and dipropyl sulfate in a molar ratio of 1:1.03 and react for 1.5 h, then perform vacuum distillation on the system at 15 kPa and 80 °C, and finally obtain 1-n-propyl-2-phenylthiophenium propyl sulfate salt. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is 99.95%, and the molecular structure is

[0064] A method for removing aromatic sulfides in fuel oil using a sulfur-containing low-temperature molten salt includes the following steps:

[0065] 1) At 30 °C and 0.1 MPa, mix 1-n-propyl-2-phenylthiophenium propyl sulfate salt with gasoline containing 3-phenylthiophene, 5-methylbenzothiophene, dibenzothiophene, and naphthothiophene in a mass ratio of 1:5, and stir for 0.5 h for extraction. Among them, the total mass content of 3-phenylthiophene, 5-methylbenzothiophene, dibenzothiophene, and naphthothiophene in the gasoline is 0.5%;

[0066] 2) After the reaction system in step 1) stands still and layers, separate the upper and lower systems. Among them, the upper system is gasoline from which aromatic sulfides have been removed. In addition, the lower system is purified by vacuum distillation at 0.5 - 10 kPa and 50 - 150 °C, and regenerated 3-phenylthiophene, 5-methylbenzothiophene, dibenzothiophene, and naphthothiophene are obtained from the distillate at different pressures and temperatures respectively, and the remaining substance is regenerated 1-n-propyl-2-phenylthiophenium propyl sulfate salt.

[0067] The test results of nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy show that the total mass content of 3-phenylthiophene, 5-methylbenzothiophene, dibenzothiophene, and naphthothiophene in the desulfurized gasoline is 0.00047%, and the removal rate of aromatic sulfides is 99.91%. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the regenerated 1-n-propyl-2-phenylthiophenium propyl sulfate salt is 99.88%, which can be recycled to remove aromatic sulfides from fuel.

[0068] Example 7

[0069] A preparation method of a sulfur-containing low-temperature molten salt: At 25 °C and 0.1 MPa, benzothiophene and phenethyl methanesulfonate are mixed and reacted at a molar ratio of 1:1.02 for 2 h, and then the system is subjected to vacuum distillation at 1 kPa and 100 °C, and finally 1-phenethylbenzothiophenium methanesulfonate is obtained. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is 99.92%, and the molecular structure is

[0070] A method for removing aromatic sulfides from fuel using a sulfur-containing low-temperature molten salt includes the following steps:

[0071] 1) At 25 °C and 0.1 MPa, 1-phenethylbenzothiophenium methanesulfonate is mixed with diesel containing benzothiophene, 4-methyldibenzothiophene, and naphthothiophene at a mass ratio of 1:6, and then stirred for 0.4 h for extraction. Among them, the total mass content of benzothiophene, 4-methyldibenzothiophene, and naphthothiophene in the diesel is 0.27%;

[0072] 2) After the reaction system in step 1) stands and separates into layers, the upper and lower systems are separated. Among them, the upper system is the diesel from which aromatic sulfides have been removed. In addition, the lower system is purified by vacuum distillation at 0.5 - 5 kPa and 100 - 150 °C, and the regenerated benzothiophene, 4-methyldibenzothiophene, and naphthothiophene are obtained from the distillate at different pressures and temperatures, and the remaining substance is the regenerated 1-phenethylbenzothiophenium methanesulfonate.

[0073] The test results of nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy show that the total mass content of benzothiophene, 4-methyldibenzothiophene, and naphthothiophene in the desulfurized diesel is 0.00025%, and the removal rate of aromatic sulfides is 99.91%. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the regenerated 1-phenethylbenzothiophenium methanesulfonate is 99.87%, which can be recycled to remove aromatic sulfides from fuel.

[0074] Example 8

[0075] Preparation method of sulfur-containing low-temperature molten salt: At 20 °C and 0.1 MPa, naphthothiophene and allyl trifluoroacetate are mixed and reacted at a molar ratio of 1:1.03 for 3 h, and then the system is subjected to vacuum distillation at 10 kPa and 80 °C. Finally, 1-allylnaphthothiophenium trifluoroacetate is obtained. After characterization by nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is 99.92%, and the molecular structure is

[0076] Method for removing aromatic sulfides from fuel oil using sulfur-containing low-temperature molten salt, comprising the following steps:

[0077] 1) At 30 °C and 0.1 MPa, 1-allylnaphthothiophenium trifluoroacetate and gasoline containing 3-octylthiophene, benzothiophene, 4,6-dimethyldibenzothiophene, and naphthothiophene are mixed at a mass ratio of 1:5 and stirred for 0.5 h for extraction. Among them, the total mass content of 3-octylthiophene, benzothiophene, 4,6-dimethyldibenzothiophene, and naphthothiophene in gasoline is 0.41%;

[0078] 2) After the reaction system in step 1) stands and layers, the upper and lower systems are separated. Among them, the upper system is gasoline from which aromatic sulfides have been removed. In addition, the lower system is purified by vacuum distillation at 0.5-10 kPa and 50-150 °C, and regenerated 3-octylthiophene, benzothiophene, 4,6-dimethyldibenzothiophene, and naphthothiophene are obtained from the distillate at different pressures and temperatures, and the remaining substance is regenerated 1-allylnaphthothiophenium trifluoroacetate.

[0079] The test results of nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy show that the total mass content of 3-octylthiophene, benzothiophene, 4,6-dimethyldibenzothiophene, and naphthothiophene in the desulfurized gasoline is 0.00033%, and the removal rate of aromatic sulfides is 99.92%. After characterization by nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the regenerated 1-allylnaphthothiophenium trifluoroacetate is 99.83%, and it can be recycled for removing aromatic sulfides from fuel oil.

[0080] Example 9

[0081] Preparation method of sulfur-containing low-temperature molten salt: At 15 °C and 0.1 MPa, 2-benzylthiophene and phenyl trifluoromethanesulfonate are mixed and reacted at a molar ratio of 1:1.04 for 1.5 h, and then the system is subjected to vacuum distillation at 5 kPa and 60 °C. Finally, 1-phenyl-2-benzylthiophenium trifluoromethanesulfonate is obtained. After characterization by nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is 99.94%, and the molecular structure is

[0082] A method for removing aromatic sulfides from fuel oil using a sulfur-containing low-temperature molten salt, comprising the following steps:

[0083] 1) At 25 °C and 0.1 MPa, 1-phenyl-2-benzylthiophenium trifluoromethanesulfonate is mixed with diesel oil containing 3-(2-butenyl)thiophene and 2-n-butyldibenzothiophene in a mass ratio of 1:7, and then stirred for 0.3 h for extraction. Among them, the total mass content of 3-(2-butenyl)thiophene and 2-n-butyldibenzothiophene in the diesel oil is 0.26%;

[0084] 2) After the reaction system in step 1) stands and layers, the upper and lower systems are separated. Among them, the upper system is diesel oil from which aromatic sulfides have been removed. In addition, the lower system is purified by vacuum distillation at 2-10 kPa and 50-120 °C, and the regenerated 3-(2-butenyl)thiophene and 2-n-butyldibenzothiophene are obtained from the distillate at different pressures and temperatures, and the remaining substance is the regenerated 1-phenyl-2-benzylthiophenium trifluoromethanesulfonate.

[0085] The test results of nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy show that the total mass content of 3-(2-butenyl)thiophene and 2-n-butyldibenzothiophene in the desulfurized diesel oil is 0.00019%, and the removal rate of aromatic sulfides is 99.93%. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the regenerated 1-phenyl-2-benzylthiophenium trifluoromethanesulfonate is 99.91%, and it can be recycled for removing aromatic sulfides from fuel oil.

[0086] Example 10

[0087] A preparation method of a sulfur-containing low-temperature molten salt: 2-vinylthiophene and n-hexyl benzenesulfonate are mixed and reacted at a molar ratio of 1:1.03 at 25 °C and 0.1 MPa for 2 h, and then the system is subjected to vacuum distillation at 10 kPa and 70 °C, and finally 1-n-hexyl-2-vinylthiophenium benzenesulfonate is obtained. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the product is 99.92%, and the molecular structure is

[0088] A method for removing aromatic sulfides from fuel oil using a sulfur-containing low-temperature molten salt, comprising the following steps:

[0089] 1) At 30 °C and 0.1 MPa, 1-n-hexyl-2-vinylthiophenium benzenesulfonate is mixed with gasoline containing 5-tert-butylbenzothiophene in a mass ratio of 1:8, and then stirred for 0.2 h for extraction. Among them, the total mass content of 5-tert-butylbenzothiophene in the gasoline is 0.23%;

[0090] 2) After the reaction system in step 1) is allowed to stand for stratification, the upper and lower systems are separated. Among them, the upper system is gasoline from which aromatic sulfides have been removed. In addition, the lower system is purified by vacuum distillation at 2 kPa and 130 °C, and regenerated 5-tert-butylbenzothiophene is obtained from the distillate, and the remaining substance is regenerated 1-n-hexyl-2-vinylthiophenium benzenesulfonate.

[0091] The test results of nuclear magnetic resonance spectroscopy and ultraviolet absorption spectroscopy show that the total mass content of 5-tert-butylbenzothiophene in the desulfurized gasoline is 0.00019%, and the removal rate of aromatic sulfides is 99.92%. After the characterization of nuclear magnetic resonance spectroscopy and mass spectrometry, the mass content of the regenerated 1-n-hexyl-2-vinylthiophenium benzenesulfonate is 99.89%, and it can be recycled for removing aromatic sulfides in fuel oil.

Claims

1. Application of sulfur-containing low-temperature molten salt in removing aromatic sulfides from fuel oil, characterized in that: The sulfur-containing low-temperature molten salt is obtained by a chemical reaction of a thiophene-based, benzothiophene-based, dibenzothiophene-based or naphthothiophene-based compound with a sulfuric acid diester, a trifluoromethanesulfonate, a phosphoric acid triester, a trifluoroacetate or a sulfonate in a molar ratio of 1:1 to 1.05; specifically, it includes the following steps: 1) At room temperature and atmospheric pressure, the sulfur-containing low-temperature molten salt is mixed with an aromatic sulfur-containing fuel and stirred to extract the sulfide into the sulfur-containing low-temperature molten salt; the room temperature is 10 to 30 °C, the atmospheric pressure is 0.1 MPa, and the mass ratio of the sulfur-containing low-temperature molten salt to the fuel is 1:5 to 10; 2) After the reaction system in step 1) is allowed to stand and separate into layers, the upper and lower systems are separated; among them, the upper system is the fuel after removing the aromatic sulfur-containing compounds; the lower system is purified by vacuum distillation to obtain the regenerated sulfur-containing low-temperature molten salt and the corresponding aromatic sulfur-containing compounds; the pressure of the vacuum distillation is 0.5 to 20 kPa and the temperature is 30 to 150 °C.

2. Use of the sulfur-containing low-temperature molten salt according to claim 1 in removing aromatic sulfides from fuel oil, characterized in that: In step 1), the fuel is gasoline or diesel, the aromatic sulfur-containing compounds include one or more of thiophene-based, benzothiophene-based, dibenzothiophene-based, naphthothiophene-based compounds, and the total mass content of the aromatic sulfur-containing compounds in the fuel is 0.05 to 0.5%.

3. Use of the sulfur-containing low-temperature molten salt according to claim 2 in removing aromatic sulfides from fuel oil, characterized in that: The molecular structure of the thiophene compound is The molecular structure of the benzothiophene compound is The molecular structure of the dibenzothiophene compound is The molecular structure of the naphthothiophene compound is Among them, R1-R8 are each independently selected from hydrogen, C1-C8 saturated alkyl groups, C2-C8 alkyl groups with C=C double bonds, phenyl groups, or phenyl-substituted C1-C4 alkyl groups.

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