A method for realizing fine separation of aromatic hydrocarbons in oil products based on a combined simulated moving bed process

Abstract

The present application relates to a kind of methods for realizing fine separation of aromatic hydrocarbons in oil product based on combined simulated moving bed process.The method uses porous carbon material, molecular sieve and its metal modified material as adsorbent, and the aromatic hydrocarbon-containing oil product is first subjected to a simulated moving bed, and the aromatic hydrocarbon components in diesel oil are separated by adsorption, to obtain two categories of high-purity mixed aromatic hydrocarbons and non-aromatic hydrocarbons.Then, the high-purity mixed aromatic hydrocarbon components are sequentially subjected to two-stage simulated moving bed containing high-selectivity adsorption material, to sequentially obtain monocyclic, bicyclic and tricyclic aromatic hydrocarbon components.Through the combination of three simulated moving bed devices, the fine separation of multi-component aromatic hydrocarbons in diesel oil is efficiently realized, and high-purity aromatic hydrocarbon components and low-aromatic high-quality gasoline and diesel oil are finally obtained.The multi-component aromatic hydrocarbon separation process provided by the present application has the characteristics of low energy consumption, low adsorption-regeneration temperature, good operation continuity, strong regulation ability, and the adsorption process can obtain multiple aromatic hydrocarbon products in one step, and has wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of separation and purification technology of mixed aromatics in oil products, specifically involving a method for fine separation of aromatics in oil products based on a combined simulated moving bed process. Background Technology

[0002] For my country's oil refining industry, crude oil quality is generally poor, mainly consisting of heavy and low-quality oil. Secondary processing primarily involves catalytic cracking and coking. However, catalytic cracked diesel and coking diesel have high aromatic content, resulting in low cetane numbers and poor combustion performance. Meanwhile, the demand for downstream diesel derivatives (aromatics, olefins, etc.) is growing much faster than that for refined oil products. If the components in diesel could be separated to obtain high-purity alkanes, cycloalkanes, monocyclic aromatics, and polycyclic aromatics, these high-purity aromatics could serve as high-quality aromatic solvents or high-quality BTX (benzene, toluene, xylene) production-enhancing feedstocks. This would not only achieve classified management of diesel components, providing feedstocks for efficient diesel conversion and accurate processing, but also reduce the diesel-to-gasoline ratio in refineries, improving both economic and social benefits for enterprises.

[0003] The separated non-aromatic hydrocarbons can serve as high-quality diesel blending components and high-quality olefin production feedstocks; while the high-purity aromatic hydrocarbons, as high-quality aromatic solvents or high-quality BTX (benzene, toluene, xylene) production feedstocks, will undoubtedly help resolve the contradiction between oil product overcapacity and chemical production shortage, while simultaneously enabling the classified management of diesel components. This is of paramount importance not only for improving the quality and efficiency of oil products in my country's petrochemical industry but also for promoting industrial transformation and upgrading.

[0004] Industrially, the main technologies for separating mixed aromatic hydrocarbon components include precision distillation, membrane separation, and adsorption separation. Precision distillation utilizes the differences in boiling points of the components to achieve separation and purification, but it has a narrow separation range and is complex and difficult to operate. Membrane separation technology mainly utilizes the differences in diffusion coefficients of different components as they pass through the membrane to separate mixed components. Although it has advantages such as low energy consumption and simple process, the fabrication of the separation membrane is relatively complex and costly, and it is difficult to achieve a balance between high throughput and high selectivity, which restricts its industrial application. CN107774143A discloses a hydrotalcite tubular hybrid membrane for separating aromatic hydrocarbons / alkanes and its preparation method. The prepared hybrid membrane is used for the separation of aromatic hydrocarbons / alkanes in the pervaporation field. The pervaporation membrane performance is: permeate flux of 400-600 g·m³. -2 ·h -1 The permeate contained approximately 70% toluene, and the separation factor was 2–5. This demonstrated good separation performance and showed potential for future applications.

[0005] Existing adsorption separation technologies suffer from problems such as low purity of aromatic and non-aromatic components, large desorbent usage, and low yield of target products. CN109022020A discloses a method for multi-component adsorption separation of diesel fuel. This method uses a metal-modified MCM-41 molecular sieve as an aromatic adsorbent to adsorb monocyclic and polycyclic aromatic components, yielding cycloalkane components. Methylcyclohexane is used as the desorbent. The adsorption temperature is 25–150℃, the adsorption pressure is 0.1–2.0 MPa, the desorption temperature is 50–200℃, and the desorption pressure is 0.1–1.5 MPa. After adsorption separation, the alkane component has a alkane content of over 85%, the cycloalkane component has a cycloalkane content of over 95%, the monocyclic aromatic component has a monocyclic aromatic content of over 95%, and the polycyclic aromatic component has a polycyclic aromatic content of over 90%. CN 109022020B describes a method combining extraction and adsorption to separate aromatics. Silica gel is used as the adsorbent, and alkylbenzene as the desorbent. The adsorption temperature is 60–100℃, the desorption temperature is 10–50℃, and the desorption time is 20–60 min. After adsorption and separation, the aromatic content of the diesel fuel component is reduced to below 20%, and the separated aromatic component has an aromatic content greater than 90%.

[0006] Currently, there are few reports on the fine separation of mixed aromatic components in petroleum products. The non-aromatic components separated by the adsorption separation technology in this invention can not only be used as high-quality diesel blending components but also as high-quality olefin production feedstock, and of course, can also be sold directly as non-aromatic solvents. The separated high-purity monocyclic aromatics can be used as high-quality feedstock for the lightening of heavy aromatics; polycyclic aromatics can be blended into high-aromatic solvent oils for sale. Summary of the Invention

[0007] In view of this, and to overcome the shortcomings of the prior art, the present invention provides a method for the fine separation of multi-component aromatics in oil products based on a simulated moving bed process. This method uses activated carbon, molecular sieves, or metal-modified materials as aromatic adsorbents, and achieves the fine separation of monocyclic, bicyclic, and tricyclic aromatics through three simulated moving bed processes. The present invention features environmental friendliness, mild reaction conditions, low investment, low energy consumption, and ease of control.

[0008] The technical solution of this invention is as follows.

[0009] A method for fine separation of aromatics in oil based on a combined simulated moving bed process includes a separation method using a combined simulated moving bed and functional adsorbent materials within the bed, with each adsorption column filled with functional adsorbent materials, wherein the functional adsorbent materials include one or more of activated carbon, molecular sieves, or metal-modified materials.

[0010] The steps are as follows: Three simulated moving bed adsorption devices are connected in series. Each of the three simulated moving bed devices is a four-zone simulated moving bed adsorption device, including adsorption zone I, isolation zone IV, desorption zone III, and purification zone II. Each adsorption bed contains inlet and outlet pipelines and periodically switching valves, and each forms a closed loop through a circulating pump (see Appendix). Figure 1 ).

[0011] The aromatic oil first passes through a simulated moving bed to adsorb and separate the aromatic components, yielding two main categories: high-purity mixed aromatics and non-aromatics. Then, the high-purity mixed aromatic components pass through a second and third simulated moving bed device to adsorb monocyclic, bicyclic, and tricyclic aromatic components, respectively, thereby efficiently achieving the fine separation of multiple aromatic components in the oil.

[0012] Furthermore, the simulated moving bed device is divided into adsorption zone I, isolation zone IV, desorption zone III, and refining zone II in sequence along the material flow direction, with at least one adsorption column allocated to each zone; wherein adsorption zone I uses an aromatic adsorbent to adsorb the aromatic components in the oil to obtain high-purity mixed aromatics and non-aromatics; each adsorption column is equipped with a multi-position valve, which contains four inlet and outlet pipelines, corresponding to raw material, desorbent, extractant, and raffinate; the periodic switching of each material valve realizes the simulated moving bed continuous adsorption-regeneration process.

[0013] Furthermore, the oil product to be processed is one or more of the following: catalytic gasoline, catalytic diesel, coking gasoline, coking diesel, straight-run gasoline, and straight-run diesel.

[0014] Furthermore, the adsorption separation method described above can change the order of aromatic hydrocarbon separation by changing the type of adsorbent in the adsorption bed and the feed position, including two processes: separating the light components (monocyclic aromatic hydrocarbons) first and separating the heavy components (tricyclic aromatic hydrocarbons) first.

[0015] Further, the aromatic hydrocarbon adsorbent is a porous carbon material or a metal-modified molecular sieve material, wherein the modified metal is one or more of Mg, Ni, Cu, K, Co, Cr, and Fe, with a content of 0.5–10 wt%, and the molecular sieve is one of NaY, 13X, MCM-41, and ZSM-5; the tricyclic aromatic hydrocarbon adsorbent is a porous carbon material or its metal-modified material, wherein the modified metal is one or more of Mg, Ni, Cu, Mn, Fe, Cr, and Zn, with a content of 0.5–10 wt%; the monocyclic or bicyclic aromatic hydrocarbon adsorbent is one of a metal-modified molecular sieve material or a porous carbon material, wherein the metal ion is any one or two of Mg, Ca, Ba, Cu, Ni, Mn, Zn, Fe, Co, and Cr, with a content of 0.5–10 wt%.

[0016] Furthermore, the combination of aromatic adsorbents in each simulated moving bed can achieve the adjustment of aromatic separation performance; that is, by changing the type of adsorbent and the feed position of the adsorption bed, the separation order of aromatics can be changed. For example, in the adsorption zone, the aromatic adsorbent first separates the light components (monocyclic aromatics) and then separates the heavy components (tricyclic aromatics), while in the desorption zone, the aromatic components are regenerated by the desorbent. The regenerated adsorbent is then recycled in the refining zone, ultimately achieving the fine separation of aromatics in the oil.

[0017] The desorption agent used in the desorption zone is one or more of toluene, methylcyclohexane, ethylbenzene, n-dodecane, ethylnaphthalene, and cyclohexane.

[0018] Furthermore, the adsorbent bed temperature in adsorption zone I is 20–150℃, and the adsorption pressure is 0.1–2.0 MPa; during regeneration in desorption zone III, the bed temperature is 40–150℃, the regeneration pressure is 0.1–2.0 MPa, the cycle switching time is 200–1500 s, the mass flow rate ratio of mixed aromatic feedstock to desorbent is 1:1.5–1:4, and the volume flow rate ratio of feedstock to circulating volume is 1:2–1:5.

[0019] Furthermore, the order of adsorption and separation of materials is based on the adsorbent types of the second and third adsorption beds, and the separation order includes two types: separating the heavy component tricyclic aromatic hydrocarbons first and separating the light component monocyclic aromatic hydrocarbons first.

[0020] An application of a highly efficient porous carbon-based adsorbent in the adsorption and separation of mixed aromatics in oil products, for the recovery of aromatics from aromatic-rich oil products; or for the removal of aromatics from aromatic-rich oil products.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. This invention employs a highly efficient and environmentally friendly simulated moving bed (SMB) process. Through a three-stage SMB unit, mixed aromatic hydrocarbon components in oil products can be adsorbed and separated. Both the adsorption and regeneration processes are carried out at low temperature and low pressure, resulting in mild reaction conditions. It offers advantages such as being environmentally friendly, pollution-free, energy-efficient, and easy to control.

[0023] 2. By adjusting the type of adsorption material in the adsorption bed, the separation sequence of aromatics can be controlled, greatly improving the process's adaptability to raw materials. Furthermore, the high-purity monocyclic aromatics obtained through separation can serve as a high-quality raw material for the lightening of heavy aromatics; polycyclic aromatics can be blended into high-aromatic solvent oils for sale. This objective is achieved through the following technical solutions. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a simulated moving bed adsorption device containing four functional zones;

[0025] Figure 2A simplified process flow diagram for the fine separation of multi-component aromatics from petroleum products;

[0026] Figure 3 This is a schematic diagram of a 24-column simulated moving bed adsorption separation device. Detailed Implementation

[0027] This invention relates to a method for the fine separation of multi-component aromatic hydrocarbons, including a metal-modified adsorbent and relevant process parameters for the adsorption and separation of aromatic hydrocarbons using a simulated moving bed. The metal-modified adsorbent uses one of activated carbon, molecular sieve, alumina, and silica as its carrier, and the modified metal used is one or more of Mg, Ni, Cu, Mn, Fe, Cr, Zn, and Ca.

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of this invention.

[0029] Combined with appendix Figure 3 The aromatic oil and three desorbents are connected to 24 adsorption towers via rotary valves. The adsorption towers can be divided into three functional zones by switching the valves: an aromatic removal zone, a heavy aromatic removal zone, and a light aromatic removal zone. Figure 2 As shown. Each functional area consists of 8 towers, which respectively serve as zones 1-4 of the moving bed, as follows. Figure 1 As shown, the three functional zones are connected upstream and downstream via two pipelines: one for light aromatics liquid and one for heavy aromatics liquid. The extract from the dearomatization zone is directly discharged into the lower low-aromatics oil pipeline. The eluent from the dearomatization zone and the extract from the de-heavy or de-light aromatics zone are connected to the two light / heavy aromatics liquid pipelines, and then controlled by valves to enter the subsequent separation zone. Finally, the separated products are fed into the downstream distillation unit through monocyclic, bicyclic, and tricyclic aromatics product lines for further distillation, yielding a series of high-purity aromatic products. Furthermore, the number of adsorption towers can be expanded according to actual needs, while the function of each zone remains unchanged.

[0030] The following examples will further illustrate the present invention.

[0031] The diesel fuel used in the examples was hydrotreated catalytic diesel from a certain refinery, with an aromatic hydrocarbon content of 10%–70%, containing various compounds such as toluene, ethylnaphthalene, hexadecane, dodecylbenzene, naphthalene, tetrahydronaphthalene, and phenanthrene. The content of polycyclic aromatic hydrocarbons was determined by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS).

[0032] Example 1

[0033] (1) The aromatic adsorbent in SMB1 is a porous carbon material derived from coconut shell. The tricyclic aromatic adsorbent in SMB2 is a metal-modified wood-based activated carbon material, and the modified metal used is Ni, with Ni(NO3)2 content of 0.5wt%. The bicyclic aromatic adsorbent in SMB3 is a metal-modified Y molecular sieve material, and the metal ions are Mg and Ca, with MgO content of 0.5wt% and CaO content of 0.5wt%.

[0034] (2) The mass flow rate ratio of mixed aromatic feedstock to desorbent is 1:2; the volume flow rate ratio of feedstock to circulation volume is 1:3; and the switching time is 400s.

[0035] (3) Adsorbent Evaluation: Using hydrotreated catalytic diesel from a certain refinery as feedstock, with an aromatic component mass fraction of 30%, the adsorbent was loaded into three simulated moving bed devices. The adsorption and separation process was a countercurrent simulated moving bed adsorption and separation process, with an adsorption and separation temperature of 40℃. The desorbents were cyclohexane and ethylbenzene, with ethylbenzene having a mass fraction of 60%. The aromatic-rich oil first passed through a simulated moving bed SMB1 to adsorb and separate the aromatic components in the diesel, obtaining two main categories: high-purity mixed aromatics and non-aromatics. Then, the high-purity mixed aromatic components passed through a simulated moving bed device SMB2 to adsorb tricyclic and higher-level heavy aromatics, obtaining high-purity tricyclic and higher-level heavy aromatic components and light aromatics (monocyclic and bicyclic); or adsorbing monocyclic aromatics, obtaining high-purity monocyclic aromatic components and polycyclic aromatics (bicyclic and tricyclic). If light aromatic hydrocarbons (monocyclic and bicyclic aromatic hydrocarbons) enter the simulated moving bed SMB3, the bicyclic aromatic hydrocarbons are adsorbed, resulting in high-purity bicyclic aromatic hydrocarbon raffinate and monocyclic aromatic hydrocarbon extract. If polycyclic aromatic hydrocarbons (bicyclic and tricyclic aromatic hydrocarbons) enter the simulated moving bed SMB3, the tricyclic aromatic hydrocarbons are adsorbed, resulting in high-purity tricyclic aromatic hydrocarbon raffinate and bicyclic aromatic hydrocarbon extract. Through three stages of the simulated moving bed device, the fine separation of multiple aromatic hydrocarbon components in the oil is achieved efficiently. Finally, high-purity monocyclic, bicyclic, and tricyclic aromatic hydrocarbon components are obtained. The separation process employs... Figure 3 The 24-tower model shown is divided into 8-8-8 sections. The distribution of adsorption towers in each section and the evaluation results are shown in Table 1.

[0036] Example 2

[0037] (1) The aromatic adsorbent in SMB1 is a metal-modified ZSM-5 material, the modified metal is Mg, and the content of Mg(NO3)2 is 0.5wt%. The tricyclic aromatic adsorbent in SMB2 is coconut shell activated carbon material. The bicyclic aromatic adsorbent in SMB3 is a metal-modified X molecular sieve material, the metal ions are Cu and Ni, and the content of Cu(NO3)2 is 1wt% and the content of Ni(NO3)2 is 1wt%.

[0038] (2) The mass flow rate ratio of mixed aromatic feedstock to desorbent is 1:1.5; the volume flow rate ratio of feedstock to circulation volume is 1:3; and the switching time is 200s.

[0039] (3) Adsorbent Evaluation: Using hydrotreated catalytic diesel from a certain refinery as feedstock, with an aromatic component mass fraction of 40%, the adsorbents were loaded into three simulated moving bed devices. The adsorption separation was a countercurrent simulated moving bed adsorption separation process, with an adsorption separation temperature of 60℃. The desorbents used were methylcyclohexane and ethylbenzene, with ethylbenzene having a mass fraction of 80%. The aromatic-rich oil first passed through SMB1 to adsorb and separate the aromatic components in the diesel, obtaining two main categories: high-purity mixed aromatics and non-aromatics. Then, the high-purity mixed aromatic components passed through SMB2 again to adsorb tricyclic and higher-level heavy aromatics, obtaining high-purity tricyclic and higher-level heavy aromatic components and light aromatics (monocyclic and bicyclic); or adsorbing monocyclic aromatics, obtaining high-purity monocyclic aromatic components and polycyclic aromatics (bicyclic and tricyclic). If light aromatic hydrocarbons (monocyclic and bicyclic aromatic hydrocarbons) enter the simulated moving bed SMB3, the bicyclic aromatic hydrocarbons are adsorbed, resulting in high-purity bicyclic aromatic hydrocarbon raffinate and monocyclic aromatic hydrocarbon extract. If polycyclic aromatic hydrocarbons (bicyclic and tricyclic aromatic hydrocarbons) enter the simulated moving bed SMB3, the tricyclic aromatic hydrocarbons are adsorbed, resulting in high-purity tricyclic aromatic hydrocarbon raffinate and bicyclic aromatic hydrocarbon extract. Through three simulated moving bed processes, the fine separation of multiple aromatic hydrocarbon components in diesel fuel is achieved efficiently. Ultimately, high-purity monocyclic, bicyclic, and tricyclic aromatic hydrocarbon components are obtained. The separation process employs the following... Figure 3 The 24-tower model shown is divided into 8-8-8 sections. The distribution of adsorption towers in each section and the evaluation results are shown in Table 1.

[0040] Example 3

[0041] (1) The aromatic adsorbent in SMB1 is a metal-modified NaY material, with Co and Ba as the modified metals, and the content of Co(NO3)2 is 2wt% and the content of Ba(NO3)2 is 2wt%. The tricyclic aromatic adsorbent in SMB2 is a metal-modified coconut shell activated carbon material, with Mg as the modified metal, and the content of Mg(NO3)2 is 1.5wt%. The bicyclic aromatic adsorbent in SMB3 is a metal-modified MCM-41 molecular sieve material, with Cu as the metal ion, and the content of CuO is 1.5wt%.

[0042] (2) The mass flow rate ratio of mixed aromatic feedstock to desorbent is 1:2; the volume flow rate ratio of feedstock to circulation volume is 1:4; and the switching time is 500s.

[0043] (3) Adsorbent Evaluation: Using hydrotreated catalytic diesel from a certain refinery as raw material, with an aromatic component mass fraction of 50%, the adsorbent was loaded into three simulated moving bed devices. The adsorption separation was carried out using a countercurrent simulated moving bed adsorption separation process, with an adsorption separation temperature of 80℃. Pure ethylbenzene was used as the desorbent. The aromatic-rich oil first passed through SMB1 to adsorb and separate the aromatic components in the diesel, obtaining two main categories: high-purity mixed aromatics and non-aromatics. Then, the high-purity mixed aromatic components passed through SMB2 again to adsorb tricyclic and higher-level heavy aromatics, obtaining high-purity tricyclic and higher-level heavy aromatic components and light aromatics (monocyclic and bicyclic); or adsorbing monocyclic aromatics, obtaining high-purity monocyclic aromatic components and polycyclic aromatics (bicyclic and tricyclic). If light aromatic hydrocarbons (monocyclic and bicyclic aromatic hydrocarbons) enter the simulated moving bed SMB3, the bicyclic aromatic hydrocarbons are adsorbed, resulting in high-purity bicyclic aromatic hydrocarbon raffinate and monocyclic aromatic hydrocarbon extract. If polycyclic aromatic hydrocarbons (bicyclic and tricyclic aromatic hydrocarbons) enter the simulated moving bed SMB3, the tricyclic aromatic hydrocarbons are adsorbed, resulting in high-purity tricyclic aromatic hydrocarbon raffinate and bicyclic aromatic hydrocarbon extract. Through three simulated moving bed processes, the fine separation of multiple aromatic hydrocarbon components in diesel fuel is achieved efficiently. Ultimately, high-purity monocyclic, bicyclic, and tricyclic aromatic hydrocarbon components are obtained. The separation process employs the following... Figure 3 The 24-tower model shown is divided into 8-8-8 sections. The distribution of adsorption towers in each section and the evaluation results are shown in Table 1.

[0044] Example 4

[0045] (1) The aromatic hydrocarbon adsorbent in SMB1 is a metal-modified molecular sieve material, the modified metal is Cu, and the content of Cu(NO3)2 is 3wt%. The tricyclic aromatic hydrocarbon adsorbent in SMB2 is a metal-modified wood-based activated carbon material, the modified metal is Ni, and the content of Ni(NO3)2 is 3wt%. The bicyclic aromatic hydrocarbon adsorbent in SMB3 is a metal-modified X molecular sieve material, the metal ions are Ca and Ba, and the content of CaO is 2.5wt% and the content of BaO is 2.5wt%.

[0046] (2) The mass flow rate ratio of mixed aromatic feedstock to desorbent is 1:2; the volume flow rate ratio of feedstock to circulation volume is 1:1.5; and the switching time is 1200s.

[0047] (3) Adsorbent Evaluation: Using hydrotreated catalytic diesel from a certain refinery as feedstock, with an aromatic component mass fraction of 60%, the adsorbents were loaded into three simulated moving bed devices. The adsorption separation was a countercurrent simulated moving bed adsorption separation process, with an adsorption separation temperature of 80℃. The desorbents used were methylcyclohexane and toluene, with toluene having a mass fraction of 80%. The aromatic-rich oil first passed through SMB1 to adsorb and separate the aromatic components in the diesel, obtaining two main categories: high-purity mixed aromatics and non-aromatics. Then, the high-purity mixed aromatic components passed through SMB2 again to adsorb tricyclic and higher-level heavy aromatics, obtaining high-purity tricyclic and higher-level heavy aromatic components and light aromatics (monocyclic and bicyclic); or adsorbing monocyclic aromatics, obtaining high-purity monocyclic aromatic components and polycyclic aromatics (bicyclic and tricyclic). If light aromatic hydrocarbons (monocyclic and bicyclic aromatic hydrocarbons) enter the simulated moving bed SMB3, the bicyclic aromatic hydrocarbons are adsorbed, resulting in high-purity bicyclic aromatic hydrocarbon raffinate and monocyclic aromatic hydrocarbon extract. If polycyclic aromatic hydrocarbons (bicyclic and tricyclic aromatic hydrocarbons) enter the simulated moving bed SMB3, the tricyclic aromatic hydrocarbons are adsorbed, resulting in high-purity tricyclic aromatic hydrocarbon raffinate and bicyclic aromatic hydrocarbon extract. Through three simulated moving bed processes, the fine separation of multiple aromatic hydrocarbon components in diesel fuel is achieved efficiently. Ultimately, high-purity monocyclic, bicyclic, and tricyclic aromatic hydrocarbon components are obtained. The separation process employs the following... Figure 3 The 24-tower model shown is divided into 8-8-8 sections. The distribution of adsorption towers in each section and the evaluation results are shown in Table 1.

[0048] Example 5

[0049] (1) The aromatic adsorbent in SMB1 is a porous carbon material derived from fruit shells. The tricyclic aromatic adsorbent in SMB2 is a metal-modified coconut shell activated carbon material with Zn as the modified metal and Zn(NO3)2 content of 5wt%. The bicyclic aromatic adsorbent in SMB3 is a metal-modified Y molecular sieve material with Ni as the modified metal and Ni(NO3)2 content of 5wt%.

[0050] (2) The mass flow rate ratio of mixed aromatic feedstock to desorbent is 1:2.5; the volume flow rate ratio of feedstock to circulation volume is 1:3.5; and the switching time is 600s.

[0051] (3) Adsorbent Evaluation: Using hydrotreated catalytic diesel from a certain refinery as raw material, with an aromatic component mass fraction of 70%, the adsorbent was loaded into three simulated moving bed devices. The adsorption separation was carried out using a countercurrent simulated moving bed adsorption separation process at a temperature of 100℃. The desorbents used were n-hexadecane and ethylbenzene, with ethylbenzene having a mass fraction of 60%. The aromatic-rich oil first passed through SMB1 to adsorb and separate the aromatic components in the diesel, obtaining two main categories: high-purity mixed aromatics and non-aromatics. Then, the high-purity mixed aromatic components passed through SMB2 again to adsorb tricyclic and higher-level heavy aromatics, obtaining high-purity tricyclic and higher-level heavy aromatic components and light aromatics (monocyclic and bicyclic); or adsorbing monocyclic aromatics, obtaining high-purity monocyclic aromatic components and polycyclic aromatics (bicyclic and tricyclic). If light aromatic hydrocarbons (monocyclic and bicyclic aromatic hydrocarbons) enter the simulated moving bed SMB3, the bicyclic aromatic hydrocarbons are adsorbed, resulting in high-purity bicyclic aromatic hydrocarbon raffinate and monocyclic aromatic hydrocarbon extract. If polycyclic aromatic hydrocarbons (bicyclic and tricyclic aromatic hydrocarbons) enter the simulated moving bed SMB3, the tricyclic aromatic hydrocarbons are adsorbed, resulting in high-purity tricyclic aromatic hydrocarbon raffinate and bicyclic aromatic hydrocarbon extract. Through three simulated moving bed processes, the fine separation of multiple aromatic hydrocarbon components in diesel fuel is achieved efficiently. Ultimately, high-purity monocyclic, bicyclic, and tricyclic aromatic hydrocarbon components are obtained. The separation process employs the following... Figure 3 The 24-tower model shown is divided into 8-8-8 sections. The distribution of adsorption towers in each section and the evaluation results are shown in Table 1.

[0052] Table 1. Analysis data of multi-component aromatics in diesel fuel separated by adsorption.

[0053]

[0054]

[0055] To further illustrate the superiority of the proposed solution, the following comparative examples are provided.

[0056] Comparative Example 1

[0057] Compared to Example 1, Comparative Example 1 differs in that the aromatic adsorbent in SMB1 is an unmodified molecular sieve material. Other conditions are the same as in Example 1. It was found that after the aromatic-rich oil first passed through a simulated moving bed SMB1, the aromatic content in the extract was higher than 40%, while the aromatic content in the eluent was lower than 80%, indicating that aromatics could not be well separated from aromatic components. This is because the unmodified molecular sieve material has a weak adsorption force on aromatic components and poor selectivity, making it difficult to achieve aggregate adsorption of aromatics.

[0058] Comparative Example 2

[0059] Compared to Example 2, Comparative Example 2 differs in that the mass flow rate ratio of the mixed aromatic feedstock to the desorbent is 1:5, while other conditions remain the same as in Example 2. It was found that after the aromatic-rich oil passed through three simulated moving bed processes, the contents of the corresponding monocyclic, bicyclic, and tricyclic aromatic components in the three products were 74%, 66%, and 79%, respectively, failing to achieve fine separation of the multi-component aromatics in the oil. This is because at excessively high flow rates, the fluid spends a short time passing through the adsorption column, insufficiently contacting and separating the components in the mixture. Simultaneously, high-speed flow also makes it difficult for the components in the mixture to stably stratify within the adsorption column, leading to increased mixing and lower separation, thus hindering fine separation of aromatics.

[0060] Comparative Example 3

[0061] Compared to Example 3, Comparative Example 3 differs in that the tricyclic aromatic hydrocarbon adsorbent in SMB2 is a metal-modified mesoporous silica material, and the bicyclic aromatic hydrocarbon adsorbent in SMB3 is a molecular sieve material. Other conditions are the same as in Example 3. It was found that after changing the adsorbents in SMB2 and SMB3, the purity of the monocyclic, bicyclic, and tricyclic aromatic hydrocarbon components obtained from the aromatic hydrocarbon-rich oil after three simulated moving bed processes decreased significantly by more than 30%. This is because the unmodified molecular sieve and metal-modified silica have similar adsorption forces for both tricyclic and bicyclic aromatic hydrocarbons, resulting in poor selectivity and making it difficult to achieve fine separation of aromatic hydrocarbons.

[0062] The specific embodiments described above illustrate the technical solution and beneficial effects of the present invention in detail. It should be understood that the above description is only the most preferred embodiment of the present invention and is not intended to limit the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for fine separation of aromatics in oil products based on a combined simulated moving bed process, characterized in that, It includes a separation method that combines a simulated moving bed and functional adsorbent materials within the bed, with each adsorption column filled with functional adsorbent materials; The separation method of the combined simulated moving bed includes the following steps: three simulated moving bed adsorption devices connected in series are used, wherein the three simulated moving bed devices are four-zone simulated moving bed adsorption devices, including adsorption zone I, isolation zone IV, desorption zone III and purification zone II. Each adsorption bed contains inlet and outlet pipelines and periodic switching valves, and each forms a closed loop through a circulation pump. The specific process is as follows: First, the aromatic oil is fed into the first simulated moving bed adsorption device. The adsorption columns of the first simulated moving bed adsorption device are arranged side-by-side and connected end-to-end, forming a closed loop via a circulating pump. The simulated moving bed adsorption device is divided into four zones, sequentially labeled Adsorption Zone I, Isolation Zone IV, Desorption Zone III, and Refining Zone II, following the material flow direction. Each zone is assigned at least one adsorption column. In Adsorption Zone I, aromatic components in the oil are adsorbed using an aromatic adsorbent to obtain two main categories: high-purity mixed aromatics and non-aromatics. Subsequently, the high-purity mixed aromatic components are sequentially passed into the second and third simulated moving bed devices for adsorption and separation. The arrangement of each adsorption column is the same as that of the first simulated moving bed device, but the aromatic adsorbent used in Adsorption Zone I is different. Finally, high-purity monocyclic, bicyclic, and tricyclic aromatic components are obtained, achieving fine separation. The aromatic hydrocarbon adsorbent in the first simulated moving bed adsorption device is a porous carbon material derived from coconut shell. The tricyclic aromatic hydrocarbon adsorbent in the second simulated moving bed adsorption device is a metal-modified wood-based activated carbon material, with Ni as the modified metal and Ni(NO3)2 content of 0.5 wt%. The bicyclic aromatic hydrocarbon adsorbent in the third simulated moving bed adsorption device is a metal-modified Y molecular sieve material, with Mg and Ca as the modified metals, MgO content of 0.5 wt% and CaO content of 0.5 wt%.

2. The method for fine separation of aromatics in oil products based on a combined simulated moving bed process as described in claim 1, characterized in that, The aromatic hydrocarbon adsorbent in the first simulated moving bed adsorption device is a metal-modified ZSM-5 material, with Mg as the modified metal and 0.5 wt% Mg(NO3)2 content. The tricyclic aromatic hydrocarbon adsorbent in the second simulated moving bed adsorption device is coconut shell activated carbon material. The bicyclic aromatic hydrocarbon adsorbent in the third simulated moving bed adsorption device is a metal-modified X molecular sieve material, with Cu and Ni as the modified metals, and 1 wt% Cu(NO3)2 content and 1 wt% Ni(NO3)2 content.

3. The method for fine separation of aromatics in oil products based on a combined simulated moving bed process as described in claim 1, characterized in that, The aromatic hydrocarbon adsorbent in the first simulated moving bed adsorption device is a metal-modified NaY material, with Co and Ba as the modifying metals, wherein the content of Co(NO3)2 is 2wt% and the content of Ba(NO3)2 is 2wt%. The tricyclic aromatic hydrocarbon adsorbent in the second simulated moving bed adsorption device is a metal-modified coconut shell activated carbon material, with Mg as the modifying metal, wherein the content of Mg(NO3)2 is 1.5wt%. The bicyclic aromatic hydrocarbon adsorbent in the third simulated moving bed adsorption device is a metal-modified MCM-41 molecular sieve material, with Cu as the modifying metal, wherein the content of CuO is 1.5wt%.

4. The method for fine separation of aromatics in oil products based on a combined simulated moving bed process as described in claim 1, characterized in that, The aromatic hydrocarbon adsorbent in the first simulated moving bed adsorption device is a metal-modified molecular sieve material, with Cu as the modified metal and Cu(NO3)2 content of 3wt%. The tricyclic aromatic hydrocarbon adsorbent in the second simulated moving bed adsorption device is a metal-modified wood-based activated carbon material, with Ni as the modified metal and Ni(NO3)2 content of 3wt%. The bicyclic aromatic hydrocarbon adsorbent in the third simulated moving bed adsorption device is a metal-modified X molecular sieve material, with Ca and Ba as the modified metals, CaO content of 2.5wt% and BaO content of 2.5wt%.

5. The method for fine separation of aromatics in oil products based on a combined simulated moving bed process as described in claim 1, characterized in that, The aromatic adsorbent in the first simulated moving bed adsorption device is a porous carbon material derived from fruit shells. The tricyclic aromatic adsorbent in the second simulated moving bed adsorption device is a metal-modified coconut shell activated carbon material with Zn as the modified metal and Zn(NO3)2 content of 5wt%. The bicyclic aromatic adsorbent in the third simulated moving bed adsorption device is a metal-modified Y molecular sieve material with Ni as the modified metal and Ni(NO3)2 content of 5wt%.

6. The method for fine separation of aromatics in oil products based on a combined simulated moving bed process as described in claim 1, characterized in that, The oil product to be processed is one or more of the following: catalytic gasoline, catalytic diesel, coking gasoline, coking diesel, straight-run gasoline, and straight-run diesel.

7. The method for fine separation of aromatics in oil products based on a combined simulated moving bed process as described in claim 1, characterized in that, The desorption agent used in the desorption zone is one or more of toluene, methylcyclohexane, ethylbenzene, n-dodecane, ethylnaphthalene, and cyclohexane.

8. The method for fine separation of aromatics in oil products based on a combined simulated moving bed process as described in claim 1, characterized in that, The adsorbent bed temperature in adsorption zone I is 20~150℃, and the adsorption pressure is 0.1~2.0 MPa; the bed temperature during regeneration in desorption zone III is 40~150℃, and the regeneration pressure is 0.1~2.0 MPa.

9. The method for fine separation of aromatics in oil products based on a combined simulated moving bed process as described in claim 1, characterized in that, The periodic switching valve enables continuous adsorption and separation in the simulated moving bed device, with a switching time of 200~1500s.

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