Composite solvents, methods and apparatus for simultaneously separating naphthenes and aromatics from naphtha

Abstract

The application discloses a composite solvent, a method and a device suitable for simultaneously separating naphthenes and aromatics from naphtha, wherein the composite solvent is composed of dimethyl sulfoxide (I), cucurbituril (II) and 1-ethyl-3-methyl imidazole ethyl sulfate salt (III), the mass ratio of the three is I:II:III=(85-96):(3-14):1, the selectivity of the composite solvent to naphthenes can reach 6.27, the mass removal rate of naphthenes can reach 71.34%, the selectivity to aromatics can reach 36.16, and the mass removal rate of aromatics is 91.51%. The application has the characteristics that the special structure and properties of cucurbituril are used to enrich the naphthenes and aromatics and other cyclic compounds in the naphtha at the bottom of a reactor, and a filter is arranged at the bottom of an extraction tower to achieve the effect of rapid separation.

Description

Technical Field

[0001] This invention relates to the technical field of separating cycloalkanes and aromatics from naphtha, and more particularly to a composite solvent for simultaneously separating cycloalkanes and aromatics from naphtha, as well as a method and apparatus for using the composite solvent. Background Technology

[0002] Naphtha is an important chemical feedstock in petrochemical production. It is mainly composed of n-alkanes, isoalkanes, cycloalkanes, and aromatics. Among these, n-alkanes and isoalkanes yield relatively high ethylene production through cracking, making them ideal feedstocks for ethylene cracking. Cycloalkanes can yield high yields of propylene and butadiene after cracking, but the ethylene yield is low, requiring careful control of their proportion in the ethylene cracking feedstock. Furthermore, cycloalkanes are easily converted into aromatics under reforming conditions; therefore, cycloalkanes are suitable as feedstocks for both ethylene cracking and catalytic reforming. Aromatics do not contribute to the yield of ethylene during cracking and are prone to coking, shortening the unit's production cycle; therefore, aromatics are unsuitable as feedstocks for ethylene cracking.

[0003] Currently, the main industrial method for separating hydrocarbon mixtures is light-heavy cutting. The disadvantage of this method is that it cannot effectively separate components and cannot achieve the desired separation of aromatics and olefins, thus resulting in the raw materials not being fully utilized.

[0004] Furthermore, existing technologies have studied the adsorption and extraction separation of naphtha. CN1476474A and CN1710030A disclose methods for selectively separating n-alkanes from naphtha via adsorption separation. Although these methods can yield ethylene cracking feedstock rich in n-alkanes, they mainly separate n-alkanes or aromatics from naphtha and cannot simultaneously separate cycloalkanes / aromatics from naphtha.

[0005] CN104945328A discloses a method for separating aromatics from diesel fuel using ionic liquids; CN101265152A discloses a method for separating cyclohexane and benzene using ionic liquids; and CN102405084A discloses a method for separating aromatic isomers using ionic liquids. These technologies demonstrate that using ionic liquids to separate mixtures of substances has the advantages of high targeting and efficiency. Developing a composite solvent containing ionic liquids to simultaneously separate cycloalkanes / aromatics from naphtha, tailored to the compositional characteristics of naphtha, is feasible. To this end, CN110229692A discloses a method for simultaneously separating cycloalkanes / aromatics from naphtha using a composite solvent containing ionic liquids. However, in actual operation, it has been found that some ionic liquids are still entrained in the raffinate, potentially leading to the loss of ionic liquids during subsequent separation processes. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention aims to provide a composite solvent, method, and apparatus for simultaneously separating cycloalkanes and aromatics from naphtha. The composite solvent of the present invention, by adding cucurbita and ionic liquids to form a composite solvent, utilizes the special structure and properties of cucurbita to enrich cyclic compounds such as cycloalkanes and aromatics in naphtha, thereby enhancing the effect of simultaneously separating cycloalkanes and aromatics from naphtha and minimizing the loss and leakage problems that may be caused by ionic liquids entering subsequent separation processes.

[0007] To achieve the above objectives, this invention provides a composite solvent for simultaneously separating cycloalkanes and aromatics from naphtha. The composite solvent is composed of dimethyl sulfoxide (DMSO), cucurbita, and ethyl 1-ethyl-3-methylimidazolium sulfate, with a mass ratio of 85–96:3–14:1. The composite solvent for simultaneously separating cycloalkanes / aromatics from naphtha in this invention uses DMSO (component I) as the main solvent, and its primary function is to separate aromatics from naphtha. Adding appropriate proportions of cucurbita (component II) and ethyl 1-ethyl-3-methylimidazolium sulfate (component III) to DMSO (component I) primarily serves to simultaneously separate cycloalkanes / aromatics from naphtha, and the separation ratio of cycloalkanes can be flexibly adjusted. The composite solvent of this invention has adjustable characteristics, meaning that the extraction performance for separating cycloalkanes and aromatics can be adjusted by changing the formulation ratio of the components. The composite solvent is prepared at a constant temperature within the range of 40–100°C. The composite solvent can extract and separate naphtha at 60–100℃ and 0.01–1.0MPa, separating some or all of the cycloalkanes / aromatics from the naphtha as needed.

[0008] The present invention also provides a method for simultaneously separating cycloalkanes and aromatics from naphtha, the method comprising the following steps: mixing the above-mentioned composite solvent with naphtha and then filtering, the filtered stream being rich in cycloalkanes and aromatics.

[0009] In the method of the present invention, the mass ratio of the composite solvent to the naphtha is 2 to 8:1, preferably 2 to 6:1.

[0010] In the method of the present invention, the mixing temperature is 60-100°C and the pressure is 0.01-1.0 MPa.

[0011] In the method of the present invention, the mixing temperature is 70-90°C and the pressure is 0.02-0.5 MPa.

[0012] The method of the present invention further includes the following steps: the filtered stream is separated from cycloalkanes and aromatics by vacuum distillation to obtain a regenerated composite solvent, which is then recycled.

[0013] In the method of the present invention, the temperature of the vacuum distillation is 60-100°C, preferably 70-90°C, and the pressure is -0.01--0.08 MPa, preferably -0.02--0.06 MPa.

[0014] The present invention provides an apparatus for simultaneously separating cycloalkanes and aromatics from naphtha, characterized in that it includes an extraction tower and a vacuum distillation tower. The extraction tower has a raffinate oil outlet and a feed outlet at its top and bottom, respectively. A filter is provided above the feed outlet. The upper and lower parts of the extraction tower have a composite solvent inlet and a feed oil inlet, respectively. The top and bottom of the vacuum distillation tower have an extracted oil outlet and a regenerated composite solvent outlet, respectively. The middle part of the vacuum distillation tower has a mixture inlet, which is connected to the feed outlet.

[0015] The apparatus of the present invention further includes a mixer, the outlet of which is connected to the composite solvent inlet or the regenerated composite solvent outlet.

[0016] In the apparatus of the present invention, the mixer is a static mixer, and the operating temperature of the static mixer is constant at 40 to 100°C.

[0017] The composite solvent of this invention, by adding cucurbitacin and combining it with ionic liquids, enriches cyclic compounds such as cycloalkanes and aromatics in naphtha using the special structure and properties of cucurbitacin. This enhances the simultaneous separation of cycloalkanes and aromatics from naphtha while minimizing the loss and runoff that might occur when ionic liquids enter subsequent separation processes. The composite solvent of this invention achieves selective and mass removal rates of 6.27% and 71.34% for cycloalkanes and 36.16% and 91.51% for aromatics from naphtha, respectively. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the apparatus for simultaneously separating cycloalkanes and aromatics from naphtha according to the present invention.

[0019] in,

[0020] 1. Extraction tower,

[0021] 11. Residual oil outlet,

[0022] 12. Composite solvent inlet

[0023] 13. Naphtha feed inlet,

[0024] 14. Filter,

[0025] 2. Vacuum distillation column,

[0026] 21. Drain the oil outlet.

[0027] 22. Inlet for cycloalkane-rich materials,

[0028] 3. Static mixer,

[0029] 31. Dimethyl sulfoxide inlet,

[0030] 32. Cucurbita urine ingested.

[0031] 33. 1-Ethyl-3-methylimidazolium sulfate ethyl ester salt ingested. Detailed Implementation

[0032] The following provides a detailed description of the embodiments of the present invention: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions.

[0033] Reference Figure 1 As shown, Figure 1 This is a schematic diagram of the apparatus for simultaneously separating cycloalkanes and aromatics from naphtha according to the present invention. The apparatus includes an extraction column 1 and a vacuum distillation column 2. The top of the extraction column 1 is provided with a raffinate oil outlet 11 and a composite solvent inlet 12, the bottom of the extraction column is provided with a filter 14, and the lower part of the extraction column is provided with a naphtha feed inlet 13. The top of the vacuum distillation column 2 is provided with a raffinate oil outlet 21, and the middle part of the vacuum distillation column is provided with a cycloalkane-rich material inlet 22, which is connected to the outlet of the extraction column 1. The apparatus also includes a static mixer 3, the outlet of which is connected to the composite solvent inlet 12.

[0034] Reference Figure 1As shown, the method for simultaneously separating cycloalkanes and aromatics from naphtha provided by the present invention includes the following steps: dimethyl sulfoxide (component I) enters static mixer 3 from dimethyl sulfoxide inlet 31, cucurbita (component II) from cucurbita inlet 32, and 1-ethyl-3-methylimidazolium sulfate ethyl salt (component III) from 1-ethyl-3-methylimidazolium sulfate ethyl salt inlet 33, respectively. After thorough mixing, the mixture is introduced into extraction tower 1 from composite solvent inlet 12 at the top of extraction tower 1, and reacts with the carbon hydrocarbon mixture feedstock entering from naphtha feed inlet 13 at the bottom of extraction tower 1. The process involves liquid-liquid extraction, resulting in a liquid-liquid contact flow. The top stream of extraction tower 1 is raffinate oil from which some cycloalkanes and aromatics have been removed. Most of the cycloalkanes, aromatics, and all the complex solvents are concentrated in the lower part of extraction tower 1. Unlike traditional processes, a filter 14 is installed above the bottom outlet of extraction tower 1, dividing the bottom of extraction tower 1 into two zones: a cucurbitacin-rich zone above filter 14 and a cucurbitacin-lean zone below filter 14. This separation of the cucurbitacin-rich and cucurbitacin-lean zones prevents cucurbitacin from entering the vacuum distillation tower and causing unnecessary blockage. The stream in the lean cucurbit urea zone below the bottom filter 14 of extraction tower 1 is rich in cycloalkanes and aromatics. It is led out through the outlet to vacuum distillation tower 2. After vacuum distillation in vacuum distillation tower 2, the stream (regenerated composite solvent) flowing out from the bottom of vacuum distillation tower 2 is recycled to the composite solvent inlet 12 of extraction tower 1. It is mixed with the fresh composite solvent coming out from static mixer 3 and then enters extraction tower 1 together. The stream at the top of vacuum distillation tower 2 is the extracted oil (a mixture of cycloalkanes and aromatics). The extracted oil can be used as a feedstock for catalytic reforming or for other purposes.

[0035] The extraction and separation performance of composite solvents refers to the solubility of composite solvents in naphtha for cycloalkanes and aromatics under certain solvent-to-oil ratio conditions, and is characterized by selectivity and removal rate parameters.

[0036] The following formula can be used selectively for calculation:

[0037]

[0038] In the formula, S represents selectivity, and C i 抽出油 and C j 抽出油 C represents the mass concentrations of components i and j in the extracted oil, respectively. i 抽余油 and C j 抽余油 These represent the mass concentrations of components i and j in the raffinate oil, respectively.

[0039] The removal rate is calculated using the following formula:

[0040]

[0041] In the formula, P% represents the removal rate, and Ci 抽出油 C represents the mass concentration of component i in the extracted oil. i 原料油 β represents the mass concentration of component i in the feedstock oil, and β represents the yield of the raffinate oil.

[0042] Example 1

[0043] Dimethyl sulfoxide (component I), cucurbita (component II), and 1-ethyl-3-methylimidazolium sulfate ethyl ester salt (component III) were mixed in static mixer 3 at a ratio of component I:component II:component III = 85:14:1 (mass), according to... Figure 1 The process involves the extraction and separation of naphtha, wherein the mass ratio of the composite solvent to the naphtha feedstock is 2:1; the operating conditions of the static mixer 3 are: temperature 60℃; the operating conditions of the extraction tower 1 are: temperature 80℃ and pressure 0.20MPa; and the operating conditions of the vacuum distillation tower 2 are: temperature 70℃ and pressure 0.04MPa.

[0044] The composition of the naphtha used is shown in Table 1, the extraction operation parameters are shown in Table 2, and the composition of the raffinate and extracted oil are shown in Table 3.

[0045] Example 2

[0046] Dimethyl sulfoxide (component I), cucurbita (component II), and 1-ethyl-3-methylimidazolium sulfate ethyl ester salt (component III) were mixed in static mixer 3 at a ratio of component I:component II:component III = 91:8:1 (by mass). The naphtha was then mixed according to... Figure 1 The extraction and separation process is carried out in the following manner: the mass ratio of the composite solvent to the naphtha feedstock is 2:1; the operating conditions of the static mixer 3 are: temperature 60℃; the operating conditions of the extraction tower 1 are: temperature 80℃ and pressure 0.20MPa; the operating conditions of the vacuum distillation tower 2 are: temperature 70℃ and pressure 0.04MPa.

[0047] The composition of the naphtha used is shown in Table 1, the extraction operation parameters are shown in Table 2, and the composition of the raffinate and extracted oil are shown in Table 3.

[0048] Example 3

[0049] Dimethyl sulfoxide (component I), cucurbita (component II), and 1-ethyl-3-methylimidazolium sulfate ethyl ester salt (component III) were mixed in static mixer 3 at a ratio of component I:component II:component III = 96:3:1 (by mass). The naphtha was then mixed according to... Figure 1The extraction and separation process is carried out in the following manner: the mass ratio of the composite solvent to the naphtha feedstock is 2:1; the operating conditions of the static mixer 3 are: temperature 60℃; the operating conditions of the extraction tower 1 are: temperature 80℃ and pressure 0.20MPa; the operating conditions of the vacuum distillation tower 2 are: temperature 70℃ and pressure 0.04MPa.

[0050] The composition of the naphtha used is shown in Table 1, the extraction operation parameters are shown in Table 2, and the composition of the raffinate and extracted oil are shown in Table 3.

[0051] Comparative Example 1

[0052] This comparative example is basically the same as Example 2, except that:

[0053] The composite solvent is a mixture of dimethyl sulfoxide (component I) and 1-ethyl-3-methylimidazolium sulfate ethyl ester salt (component III) in a ratio of component I:component III = 99:1 (mass). The mass ratio of the composite solvent to the naphtha feedstock is 2:1. The operating conditions for static mixer 3 are: temperature 60℃; the operating conditions for extraction tower 1 are: temperature 80℃ and pressure 0.30 MPa; and the operating conditions for vacuum distillation tower 2 are: temperature 70℃ and pressure 0.04 MPa.

[0054] The composition of the naphtha used is shown in Table 1, the extraction operation parameters are shown in Table 2, and the composition of the raffinate and extracted oil are shown in Table 3.

[0055] Comparative Example 2

[0056] This comparative example is basically the same as Example 2, except that:

[0057] Sulfolane (component I) and ethyl 1-ethyl-3-methylimidazolium sulfate (component III) are compounded in a ratio of I:II = 99:1 (mass), wherein the mass ratio of the compound solvent to the naphtha feedstock is 2:1; the operating conditions of static mixer 3 are: temperature 60℃; the operating conditions of extraction tower 1 are: temperature 100℃ and pressure 0.30MPa; the operating conditions of vacuum distillation tower 2 are: temperature 80℃ and pressure 0.05MPa.

[0058] The composition of the naphtha used is shown in Table 1, the extraction operation parameters are shown in Table 2, and the composition of the raffinate and extracted oil are shown in Table 3.

[0059] Table 1 Naphtha Composition

[0060] project Alkanes Cycloalkanes Olefins Aromatics PIONA value, mass % 55.4 30.4 0.1 14.1

[0061] Table 2 Extraction process conditions

[0062]

[0063]

[0064] Table 3 Extraction results

[0065]

[0066] As shown in Table 3, the present invention utilizes the special structure and properties of cucurbituril to enrich cyclic compounds such as cycloalkanes and aromatics in naphtha at the bottom of the reactor for rapid separation. Compared with the control group without cucurbituril, the composite solvent of the present invention achieves a selectivity of 6.27 for cycloalkanes and a mass removal rate of 71.34% for cycloalkanes. At the same time, the composite solvent of the present invention achieves a selectivity of 36.16 for aromatics and a mass removal rate of 91.51% for aromatics.

[0067] In addition, the present invention adds a filter above the lower outlet of the extraction tower 1, which reduces the possibility of heavy components causing blockage in subsequent equipment pipelines to a certain extent while ensuring the normal operation of the extraction tower.

[0068] 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 present invention.

Claims

1. A composite solvent for simultaneously separating cycloalkanes and aromatics from naphtha, characterized in that, The composite solvent is composed of dimethyl sulfoxide, cucurbita and ethyl 1-ethyl-3-methylimidazolium sulfate, in a mass ratio of 85-96:3-14:

1.

2. A method for simultaneously separating cycloalkanes and aromatics from naphtha, characterized in that, The process includes the following steps: mixing the composite solvent of claim 1 with naphtha and then filtering the mixture, the filtered stream being rich in cycloalkanes and aromatics.

3. The method for simultaneously separating cycloalkanes and aromatics from naphtha according to claim 2, characterized in that, The mass ratio of the composite solvent to the naphtha is 2 to 8:

1.

4. The method for simultaneously separating cycloalkanes and aromatics from naphtha according to claim 2, characterized in that, The mass ratio of the composite solvent to the naphtha is 2 to 6:

1.

5. The method for simultaneously separating cycloalkanes and aromatics from naphtha according to claim 2, characterized in that, The mixing temperature is 60–100°C, and the pressure is 0.01–1.0 MPa.

6. The method for simultaneously separating cycloalkanes and aromatics from naphtha according to claim 5, characterized in that, The mixing temperature is 70–90°C, and the pressure is 0.02–0.5 MPa.

7. The method for simultaneously separating cycloalkanes and aromatics from naphtha according to claim 2, characterized in that, It also includes the following steps: The filtered stream is separated into cycloalkanes and aromatics by vacuum distillation to obtain a regenerated composite solvent, which is then recycled.

8. The method for simultaneously separating cycloalkanes and aromatics from naphtha according to claim 7, characterized in that, The vacuum distillation is carried out at a temperature of 60–100°C and a pressure of -0.01–-0.08 MPa.

9. The method for simultaneously separating cycloalkanes and aromatics from naphtha according to claim 7, characterized in that, The temperature for vacuum distillation is 70–90°C.

10. The method for simultaneously separating cycloalkanes and aromatics from naphtha according to claim 7, characterized in that, The pressure of the vacuum distillation is -0.02 to -0.06 MPa.

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