Method for desulfurizing crude benzene

Abstract

The invention relates to the technical field of desulfurization, and discloses a crude benzene desulfurization method, which comprises: (1) carrying out first mixing on a ternary eutectic solvent and a crude benzene solution to obtain a solution I; (2) sequentially carrying out first extraction, second extraction and third extraction on the solution I to obtain a product I; and (3) carrying out rotary distillation on the product I to obtain a benzene-containing solution. The method is simple in operation process, low in cost and low in energy consumption, and the crude benzene desulfurization efficiency and the eutectic solvent recovery rate can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of desulfurization, in particular to a method for desulfurization of crude benzene. BACKGROUND

[0002] With the increasing shortage of petroleum resources, coking crude benzene as another important source of pure benzene, its position gradually highlights. However, the sulfides contained in the crude benzene, especially carbon disulfide and thiophene, not only will corrode the hydrogenation equipment, shorten the service life of the catalyst, but also affect the processing and use of subsequent products. Therefore, the desulfurization of crude benzene becomes an indispensable part of the coking industry. The content of sulfides in crude benzene is about 0.6%~2.0%, among which carbon disulfide and thiophene are the main components, and although the content of sulfides such as mercaptan in crude benzene is low, it cannot be ignored. These sulfides may be oxidized to monomer sulfur during the storage of crude benzene, further affecting the product quality. With the continuous development of desulfurization technology, hydrogenation and extractive distillation are the two most commonly used methods in the process of refining crude benzene into refined benzene.

[0003] At present, the main crude benzene refining process at home and abroad adopts hydrogenation method, and the representative processes are: Japan's high temperature and high pressure gas phase hydrogenation Litol technology, extractive distillation low temperature hydrogenation method (K.K method), and solvent extraction low temperature hydrogenation method (using sulfolane as an extractant to remove non-aromatic hydrocarbons). At present, the domestic hydrogenation technology is mainly improved on the basis of foreign countries, and low temperature hydrogenation method is mostly used. The new extractive refining process is a new refining technology independently developed by China, which can produce three kinds of benzene products at a lower temperature and under normal pressure / reduced pressure, and recover high value-added product thiophene.

[0004] CN102911003A discloses a method for removing thiophene sulfur from coking benzene, which uses NHDS-8 hydrogenation desulfurization adsorption catalyst to convert thiophene into hydrogen sulfide by hydrogenation, and then the hydrogen sulfide is adsorbed on the catalyst to complete the desulfurization of benzene.

[0005] CN106916044A discloses a coking crude benzene refining method, in which sulfolane is used as an extractant to obtain heavy benzene product.

[0006] CN104844559A discloses a device and method for extracting thiophene before hydrogenation of coking crude benzene, which includes crude benzene fraction cutting, extractive distillation and thiophene refining units. The device couples the two pre-separation processes of benzene light removal and heavy removal together by using a partition tower, and then recovers thiophene in benzene by extractive distillation method, which optimizes the existing benzene hydrogenation process, reduces hydrogen consumption, obtains thiophene with purity of more than 99.6%, and reduces the content of thiophene in benzene to below 0.1%.

[0007] In the extractive distillation desulfurization process, the extractant is directly related to the desulfurization efficiency, product quality and environmental friendliness and many other aspects. The research and development of the extractant has experienced the evolution process from traditional organic solvents to ionic liquids, and then to eutectic solvents. Although traditional organic solvents such as sulfolane have certain application effects in crude benzene desulfurization, they are volatile and toxic; the emergence of ionic liquids provides a new idea for extractive desulfurization with the advantages of high thermal stability, low volatility and designability. However, the complex synthesis process, high cost and long cycle of ionic liquids limit their large-scale industrialization. SUMMARY

[0008] The purpose of the present application is to solve the problem of low desulfurization efficiency of crude benzene in the prior art.

[0009] In order to achieve the above purpose, the present application provides a method for desulfurizing crude benzene, which comprises: (1) mixing a ternary eutectic solvent with a crude benzene solution to obtain solution I; (2) sequentially performing first extraction, second extraction and third extraction on the solution I to obtain product I; (3) performing rotary distillation on the product I to obtain a benzene-containing solution; Wherein, the temperature of the first extraction, the second extraction and the third extraction is T1, T2 and T3 respectively; and T1 < T2 < T3, T1 is 10-30℃ lower than T2; The ternary eutectic solvent contains an amide compound, a metal salt and a fatty acid in a molar ratio of 1:0.3-1.2:1-3.

[0010] The method for desulfurizing crude benzene provided by the present application can improve the desulfurization efficiency of crude benzene and the recovery rate of eutectic solvent. The method has simple operation process, low cost and low energy consumption. In addition, most of the raw materials for preparing eutectic solvent are derived from renewable resources, which reduces the dependence on fossil resources and reduces carbon emissions. Secondly, eutectic solvent does not produce harmful substances such as volatile organic compounds (VOCs) during use, which can reduce environmental pollution. Compared with traditional solvents, eutectic solvent can reduce the negative impact on the environment during the extraction process, which meets the concept of sustainable development. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a flowchart of the method for desulfurizing crude benzene of the present application. DETAILED DESCRIPTION

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] As mentioned above, the present invention provides a method for desulfurizing crude benzene, the method comprising: (1) The ternary eutectic solvent and the crude benzene solution are mixed for the first time to obtain solution I; (2) The solution I was subjected to a first extraction, a second extraction, and a third extraction in sequence to obtain product I; (3) The product I was subjected to rotary distillation to obtain a benzene-containing solution; The temperatures of the first extraction, the second extraction, and the third extraction are T1, T2, and T3, respectively; and T1 < T2 < T3, with T1 being 10-30°C lower than T2. The ternary eutectic solvent contains amide compounds, metal salts, and fatty acids in a molar ratio of 1:0.3-1.2:1-3.

[0014] The method for extracting crude benzene solution by using specific ternary eutectic solvent can improve the desulfurization efficiency of crude benzene, because the hydrogen bond network in the eutectic solvent provides an environment conducive to the dissolution of thiophene, carbon disulfide and mercaptan in sulfides. The formation of the hydrogen bond network can not only enhance the solubility of sulfides in the eutectic solvent, but also promote the transmission process of sulfide molecules in the eutectic solvent. Among the sulfide molecules (thiophene, carbon disulfide and mercaptan) in the crude benzene solution, the sulfur atom has a negative charge, and the hydrogen atom has a positive charge. These sulfide molecules can form additional hydrogen bonds with the hydrogen bond donors or acceptors (such as amide oxygen atoms or other oxygen-containing functional groups) in the eutectic solvent, thereby enhancing their solubility and stability in the eutectic solvent. In addition, the amide group can have pi-pi interaction and C-H-pi interaction with the sulfur atom of thiophene, carbon disulfide and mercaptan through the polarization or induction effect of the electron cloud, and the empty d orbitals of the metal ions in the metal salt can accept the lone pair electrons of the sulfur atom, polarize the C-S bond, and make it easy to break. There are various intermolecular interactions between the eutectic solvent and the sulfides, including van der Waals force, dipole-dipole interaction and charge transfer interaction. These interactions lead to an increase in the solubility of thiophene, carbon disulfide and mercaptan in the eutectic solvent, and a decrease in their solubility in crude benzene, making them more easily enter the eutectic solvent, thereby further improving the desulfurization efficiency of crude benzene. Moreover, the eutectic solvent has a low melting point, high thermal stability and chemical stability, and can maintain stable performance during the extraction process without being easily decomposed or deteriorated, thereby improving the recycling rate of the eutectic solvent.

[0015] The present application provides a method for desulfurizing crude benzene. Figure 1 The present application provides a method for desulfurizing crude benzene.

[0016] According to a preferred embodiment, in step (3), the step of rotary distillation includes: performing first distillation on the product I at T4℃, and performing second distillation at T5℃ to obtain a benzene-containing solution; T5 is 10-50℃ higher than T4, preferably, T5 is 25-40℃ higher than T4.

[0017] The inventors of the present application found in research that the method of gradient temperature rising rotary distillation can fully separate the eutectic solvent and improve the recycling rate and desulfurization efficiency of the eutectic solvent.

[0018] Preferably, T4 is 20-50℃, and T5 is 40-80℃.

[0019] Preferably, the method further includes: naturally cooling the product I to room temperature before performing the rotary distillation.

[0020] More preferably, the first distillation time is 1-2h, and the second distillation time is 2-3h.

[0021] According to another preferred embodiment, the rotation distillation is performed at a rotation speed of 300-800 r / min.

[0022] According to still another preferred embodiment, the rotation distillation can also be performed in an environment of no more than 50 Pa, and the inventors have found that under this preferred condition, the cost and energy consumption can be reduced.

[0023] Preferably, the amide compound is selected from at least one of N-methyl acetamide, caprolactam, and urea.

[0024] Preferably, the metal salt is selected from at least one of AlCl3, CuCl2, FeCl3, LiCl, and ZnCl2.

[0025] Preferably, the fatty acid is selected from at least one of propionic acid, lauric acid, lactic acid, and palmitic acid.

[0026] The present application does not have special requirements for the preparation method of the ternary eutectic solvent, and those skilled in the art can use the methods known in the art to prepare it. Illustratively, the amide compound, metal salt, and fatty acid are weighed in proportion, vacuum dried at 70-90°C for 20-30 hours to remove moisture, then placed in a round-bottom flask, stirred in an 80-100°C oil bath for 0.5-2h, and then cooled to room temperature to obtain a colorless transparent ternary eutectic solvent.

[0027] Preferably, in step (2), T1 is 20-50°C, T2 is 55-70°C, and T3 is 80-110°C. The inventors have found that under this preferred condition, the eutectic solvent can selectively bind with sulfides, efficiently dissolve and extract thiophene, carbon disulfide, and mercaptan in the crude benzene solution, and further improve the desulfurization efficiency of the crude benzene.

[0028] Preferably, in step (2), the first extraction, the second extraction, and the third extraction are all performed in a closed environment.

[0029] Preferably, the conditions of the first extraction include a time of 10-30 min and a stirring speed of 600-800 r / min.

[0030] Preferably, the conditions of the second extraction include a time of 0.5-1h and a stirring speed of 600-800 r / min.

[0031] More preferably, the conditions of the third extraction include a time of 5-15 min and a stirring speed of 600-800 r / min.

[0032] According to a preferred embodiment, the mass ratio of the DES to the crude benzene solution is 0.1-1:1; preferably 0.4-0.7:1. The inventors have found that under the preferred conditions, the desulfurization efficiency of the crude benzene can be further improved.

[0033] Preferably, the crude benzene solution contains 73-76wt% benzene, 13-16wt% toluene, 3.2-3.5wt% xylene, 1.1-1.5wt% styrene, 1.6-2.1wt% naphthalene, 0.1-0.3wt% chloride, and 2000-5000ppm sulfide in terms of sulfur element.

[0034] More preferably, the sulfide is at least one selected from thiophene, carbon disulfide and mercaptan.

[0035] According to a preferred embodiment, in step (1), the rotation speed of the first mixing is 600-800r / min, and the time is 0.5-3h.

[0036] The present application does not have special requirements for the sequence and specific manner of the first mixing, and those skilled in the art can select according to the known technical means in the art. Illustratively, the DES and the crude benzene solution are mixed in a round-bottom flask at room temperature. The present application will not be described in detail here, and those skilled in the art should not be construed as a limitation on the present application.

[0037] The present application will be described in detail by way of examples below. When the specific experimental procedures or conditions are not specified in the following examples, the known experimental procedures described in the literature in the art can be used. When the manufacturer of the raw materials or instruments is not specified, they can be obtained by commercial purchase. When the reaction temperature is not specifically mentioned in the following examples, it is carried out at room temperature, which refers to 22±2℃.

[0038] The crude benzene solution in the following examples is derived from Cangzhou Xuyang Chemical Co., Ltd., which contains 74.4wt% benzene, 13.4wt% toluene, 3.3wt% xylene, 1.1wt% styrene, 1.7wt% naphthalene, 0.3wt% chloride, and 5000ppm sulfide in terms of sulfur element (including thiophene, carbon disulfide and mercaptan).

[0039] Preparation Example 1 1mol of caprolactam was weighed, vacuum dried at 80℃ for 24h with ZnCl2 and lauric acid in a ratio of 1:0.5:2, then placed in a round-bottom flask, stirred in an 80℃ oil bath for 1h, and naturally cooled to room temperature to obtain a colorless transparent DES A1.

[0040] Preparation Example 2 Take 1 mol of N-methylacetamide, with FeCl3, lactic acid according to the proportion of 1:0.5:1.5 molar ratio under vacuum drying at 80℃ for 24h, placed in a round bottom flask, stirring in the oil bath pot at 80℃ for 1h, natural cooling to room temperature to get colorless transparent ternary eutectic solvent A2.

[0041] Preparation Example 3 Take 1 mol of caprolactam, with ZnCl2, lactic acid according to the proportion of 1:0.5:1 molar ratio under vacuum drying at 80℃ for 24h, placed in a round bottom flask, stirring in the oil bath pot at 80℃ for 1h, natural cooling to room temperature to get colorless transparent ternary eutectic solvent A3.

[0042] Preparation Example 4 Take 1 mol of caprolactam, with AlCl3, lauric acid according to the proportion of 1:1:1 molar ratio under vacuum drying at 80℃ for 24h, placed in a round bottom flask, stirring in the oil bath pot at 80℃ for 1h, natural cooling to room temperature to get colorless transparent ternary eutectic solvent A4.

[0043] Preparation Example 5 Take 1 mol of caprolactam, with FeCl3, lauric acid according to the proportion of 1:0.5:1.5 molar ratio under vacuum drying at 80℃ for 24h, placed in a round bottom flask, stirring in the oil bath pot at 80℃ for 1h, natural cooling to room temperature to get colorless transparent ternary eutectic solvent A5.

[0044] Preparation Example 6 Take 1 mol of urea, with lauric acid, tetrabutylammonium chloride according to the proportion of 1:1:0.5 molar ratio under vacuum drying at 80℃ for 24h, placed in a round bottom flask, stirring in the oil bath pot at 80℃ for 1h, natural cooling to room temperature to get colorless transparent ternary eutectic solvent A6.

[0045] Preparation Example 7 Take 1 mol of caprolactam, with ZnCl2 according to the proportion of 1:0.5 molar ratio under vacuum drying at 80℃ for 24h, placed in a round bottom flask, stirring in the oil bath pot at 80℃ for 1h, natural cooling to room temperature to get colorless transparent binary eutectic solvent A7.

[0046] Preparation Example 8 Take 1 mol of caprolactam, with lauric acid according to the proportion of 1:2 molar ratio under vacuum drying at 80℃ for 24h, placed in a round bottom flask, stirring in the oil bath pot at 80℃ for 1h, natural cooling to room temperature to get colorless transparent binary eutectic solvent A8.

[0047] Preparation Example 9 Take 1 mol of ZnCl2, and lauric acid in a proportion of 1:3 of the molar ratio of the dosage after vacuum drying at 80°C for 24h, placed in a round-bottom flask, stirred in an oil bath at 80°C for 1h, and naturally cooled to room temperature to obtain a colorless transparent binary eutectic solvent A9.

[0048] Preparation Example 10 Take 1 mol of caprolactam, and ZnCl2, lactic acid in a proportion of 1:0.2:0.5 of the molar ratio of the dosage after vacuum drying at 80°C for 24h, placed in a round-bottom flask, stirred in an oil bath at 80°C for 1h, and naturally cooled to room temperature to obtain a colorless transparent ternary eutectic solvent A10.

[0049] Preparation Example 11 Take 1 mol of caprolactam, and ZnCl2, tetrabutylammonium chloride in a proportion of 1:0.5:2 of the molar ratio of the dosage after vacuum drying at 80°C for 24h, placed in a round-bottom flask, stirred in an oil bath at 80°C for 1h, and naturally cooled to room temperature to obtain a colorless transparent ternary eutectic solvent A11.

[0050] Example 1 (1) 50g of the ternary eutectic solvent A1 was mixed with 100g of the crude benzene solution at a rotation speed of 600r / min for 1h to obtain solution I; (2) The solution I was sequentially extracted at 40°C and 600r / min for 20min, at 60°C and 600r / min for 30min, and at 80°C and 600r / min for 10min to obtain product I; (3) The product I was subjected to rotary distillation: first distillation at 30°C and 600r / min for 1h, and second distillation at 60°C and 600r / min for 3h to obtain a benzene-containing solution.

[0051] Examples 2-5 and Comparative Examples 1-6 The similar method of Example 1 was used, except that the eutectic solvent and its dosage were different, and the dosage of the crude benzene solution was different, as shown in Table 1, to obtain a benzene-containing solution.

[0052] Table 1

[0053] Example 6 The similar method of Example 1 was used, except that in step (3), the temperature of the first distillation was kept unchanged, and the temperature of the second distillation was adjusted to 50°C to obtain a benzene-containing solution.

[0054] Example 7 The method similar to that in Example 1 was adopted, except that gradient temperature rising rotary distillation was not performed, specifically, in step (3), the solution I was distilled at 60℃, 600r / min for 4h to obtain the product I; The other steps were the same as those in Example 1 to obtain the benzene-containing solution.

[0055] Comparative Example 7 The method similar to that in Example 1 was adopted, except that gradient temperature rising extraction was not performed, specifically, in step (2), the solution I was extracted at 80℃, 600r / min for 1h to obtain the product I; The other steps were the same as those in Example 1 to obtain the benzene-containing solution.

[0056] Comparative Example 8 The method similar to that in Example 1 was adopted, except that in step (2), the temperature of the second extraction was adjusted to 45℃ while the temperatures of the first and third extractions were kept unchanged to obtain the benzene-containing solution.

[0057] Test Example 1 The light component (i.e. the benzene-containing solution) and the heavy component after gradient temperature rising rotary distillation in the examples were taken respectively, and the light component, the heavy component and the crude benzene solution were diluted 4000 times by the purified benzene solution for sulfur content analysis (instrument: fluorescence sulfur analyzer, manufacturer: Shenzhen Tianlu Metrology and Testing Co., Ltd., model: HYS-YS-01) to obtain the sulfur contents in the benzene-containing solution, the heavy component and the crude benzene solution.

[0058] The desulfurization efficiency of the crude benzene = 1-(sulfur content in the benzene-containing solution / sulfur content in the crude benzene solution) x 100%; The desulfurization efficiency of the crude benzene solution was calculated, and the results are shown in Table 2.

[0059] Table 2

[0060] As can be seen from the results in Table 2, the method for desulfurizing crude benzene provided by the present application can improve the desulfurization efficiency of the crude benzene solution.

[0061] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for desulfurizing crude benzene, characterized in that, The method includes: (1) The ternary eutectic solvent and the crude benzene solution are mixed for the first time to obtain solution I; (2) The solution I was subjected to a first extraction, a second extraction, and a third extraction in sequence to obtain product I; (3) The product I was subjected to rotary distillation to obtain a benzene-containing solution; The temperatures of the first extraction, the second extraction, and the third extraction are T1, T2, and T3, respectively; and T1 < T2 < T3, with T1 being 10-30°C lower than T2. The ternary eutectic solvent contains amide compounds, metal salts, and fatty acids in a molar ratio of 1:0.3-1.2:1-3.

2. The method according to claim 1, characterized in that, In step (3), the rotary distillation step includes: performing a first distillation on product I at T4°C and a second distillation at T5°C to obtain a benzene-containing solution; T5 is 10-50°C higher than T4.

3. The method according to claim 2, characterized in that, The T4 temperature is 20-50℃, and the T5 temperature is 40-80℃; And / or, the first distillation time is 1-2 hours, and the second distillation time is 2-3 hours.

4. The method according to any one of claims 1-3, characterized in that, The amide compound is selected from at least one of N-methylacetamide, caprolactam, and urea; And / or, the metal salt is selected from at least one of AlCl3, CuCl2, FeCl3, LiCl, and ZnCl2.

5. The method according to any one of claims 1-3, characterized in that, The fatty acid is selected from at least one of propionic acid, lauric acid, lactic acid, and palmitic acid.

6. The method according to any one of claims 1-3, characterized in that, In step (2), T1 is 20-50℃, T2 is 55-70℃, and T3 is 80-110℃.

7. The method according to any one of claims 1-3, characterized in that, The mass ratio of the ternary eutectic solvent to the crude benzene solution is 0.1-1:

1.

8. The method according to any one of claims 1-3, characterized in that, The crude benzene solution contains 73-76 wt% benzene, 13-16 wt% toluene, 3.2-3.5 wt% xylene, 1.1-1.5 wt% styrene, 1.6-2.1 wt% naphthalene, 0.1-0.3 wt% chloride, and 2000-5000 ppm sulfides based on elemental sulfur. The sulfide is selected from at least one of thiophene, carbon disulfide, and thiols.

9. The method according to any one of claims 1-3, characterized in that, In step (1), the rotation speed of the first mixing is 600-800 r / min, and the time is 0.5-3 h.

10. The method according to any one of claims 1-3, characterized in that, In step (2), the conditions for the first extraction include: a time of 10-30 min and a stirring speed of 600-800 r / min; And / or, the conditions for the second extraction include: a time of 0.5-1 h and a stirring speed of 600-800 r / min; And / or, the conditions for the third extraction include: a time of 5-15 min and a stirring speed of 600-800 r / min.

Images