A method of separating naphtha

Abstract

The present disclosure relates to a method for separating naphtha, comprising: feeding naphtha and a first desorbent into a first adsorption separation tower for first adsorption separation to obtain a first extract and a first raffinate; feeding the first raffinate into a first rectifying tower for first rectification treatment to obtain a first stream mainly containing cycloalkanes and alkanes; feeding the first stream and a second desorbent into a second adsorption separation tower for second adsorption separation to obtain a second extract and a second raffinate; feeding the second raffinate into a second rectifying tower for second rectification treatment to obtain a second stream mainly containing alkanes; feeding the first extract and the second extract into a third rectifying tower for third rectification treatment to obtain a third stream mainly containing aromatic hydrocarbons and cycloalkanes; wherein the first desorbent is selected from heavy aromatic hydrocarbon components, and the second desorbent is selected from light hydrocarbon components. The method of the present disclosure has low cost, simple process, high separation purity and high yield.

Description

Technical Field

[0001] This disclosure relates to the field of aromatic hydrocarbon separation technology, and more specifically, to a method for separating naphtha. Background Technology

[0002] Separating petroleum fractions based on their molecular structure and processing them separately enables the efficient and high-value utilization of hydrocarbon resources. This is of great significance for promoting the transformation of fraction refining to component refining and for refining enterprises to transform from traditional energy-based to more refined and efficient integrated refining and chemical production.

[0003] In traditional refining processes, cycloalkanes in naphtha are readily converted into aromatics under catalytic reforming conditions, making them high-quality reforming feedstocks. Alkanes, on the other hand, yield high amounts of ethylene and propylene during thermal cracking, making them excellent ethylene cracking feedstocks. Therefore, separating and processing alkanes and cycloalkanes from naphtha separately is of great practical significance for further improving naphtha utilization efficiency and reducing energy and material consumption in subsequent catalytic reforming and ethylene cracking processes. Aromatics in naphtha are also an important feedstock for the production of paraxylene. Therefore, component separation of aromatics, cycloalkanes, and alkanes from naphtha, with the resulting products that can be further optimized for utilization, resource integration, and improved feedstock adaptability, is of great value.

[0004] Existing technologies can separate naphtha into aromatics and non-aromatics (cycloalkanes, n-alkanes, branched alkanes); or into n-alkanes and non-n-alkanes (aromatics, cycloalkanes, and branched alkanes). CN101759513A discloses a method for utilizing naphtha, which separates naphtha into n-alkanes and non-n-alkanes, cuts the n-alkanes, and uses the C5 and C6 components as isomerization feedstocks, while the larger C7 n-alkanes are used as catalytic cracking feedstocks. Simultaneously, because the non-n-alkanes are rich in cycloalkanes and isoalkanes, under mild reforming reaction conditions, cycloalkanes readily dehydrogenate to form aromatics. The resulting oil after catalytic reforming can be used as a high-octane gasoline blending component, or it can undergo aromatic extraction to separate aromatics and non-aromatics. After reforming, the non-aromatics in the resulting oil are mainly alkanes, which are then fed into a catalytic cracking unit. This combination of processes can significantly improve the yield of low-carbon olefins and aromatics, increase gasoline yield, reduce benzene content in gasoline, reduce energy consumption, improve naphtha utilization efficiency, and achieve rational resource allocation.

[0005] CN111826197A discloses a method for producing gasoline from naphtha, which involves hydrorefining naphtha feedstock to obtain refined oil; extracting aromatics from the refined oil to obtain extracted oil and raffinate oil; hydroisomerizing the raffinate oil to obtain isomerized oil; and mixing the aromatic-rich oil from the extracted oil with the isomerized oil to obtain the gasoline product.

[0006] There are currently no reported technologies for separating naphtha into alkanes and non-alkanes (including aromatics and cycloalkanes). Summary of the Invention

[0007] The purpose of this disclosure is to provide a method for separating naphtha, which efficiently separates naphtha into alkanes and non-alkanes. The method is low-cost, simple, and achieves high purity and high yield, with alkanes reaching a purity of over 85%.

[0008] To achieve the above objectives, this disclosure provides a method for separating naphtha, the method comprising the following steps: (1) Naphtha and the first desorbent are fed into the first adsorption separation tower for the first adsorption separation to obtain the first extract and the first raffinate, which mainly contain aromatics; the first raffinate is fed into the first distillation tower for the first distillation treatment to obtain the first stream, which mainly contains cycloalkanes and alkanes, and the regenerated first desorbent. (2) The first stream and the second desorbent are fed into the second adsorption separation tower for the second adsorption separation to obtain the second extract and the second raffinate; the second raffinate is fed into the second distillation tower for the second distillation treatment to obtain the regenerated second desorbent and the second stream mainly containing alkanes. (3) The first extract and the second extract are sent to the third distillation column for third distillation treatment to obtain the regenerated second desorbent, the regenerated first desorbent and the third stream mainly containing aromatics and cycloalkanes. The first desorbent comprises heavy aromatic hydrocarbon components with more than C10 carbon atoms, and the second desorbent comprises light hydrocarbon components with less than C6 carbon atoms.

[0009] Optionally, the first desorbent comprises a C11-C13 heavy aromatic hydrocarbon, and the boiling point of the first desorbent is 220-330°C; preferably, the first desorbent comprises methylnaphthalene and / or 1-methyl-1,2,3,4-tetrahydronaphthalene.

[0010] Optionally, the second desorbent is a C5-C6 light hydrocarbon component, and the boiling point of the second desorbent is 30-100°C; preferably, the second desorbent includes n-pentane and / or cyclopentane.

[0011] Optionally, in step (1), the conditions for the first adsorption separation include: being carried out in a simulated moving bed, with a temperature of 40~200℃, preferably 80~100℃, a pressure of 0.5~3MPa, preferably 0.8~1.2MPa, and a feed mass hourly space velocity (WHSV) of 0.35~2.0h for the naphtha. -1 ; The first adsorbent used in the first adsorption separation is selected from one or more of silica gel, modified silica gel, or X-type molecular sieve.

[0012] Optionally, in step (1), the conditions for the first distillation treatment include: the top temperature of the column is 85~95℃ and the bottom temperature of the column is 240~250℃; The method includes: obtaining the first stream, which mainly contains cycloalkanes and alkanes, from the top of the first distillation column, and obtaining the regenerated first desorbent from the bottom of the first distillation column.

[0013] Optionally, in step (2), the conditions for the second adsorption separation include: being carried out in a simulated moving bed, with a temperature of 40~200℃, preferably 80~120℃, a pressure of 0.5~3MPa, preferably 0.8~1.2MPa, and a feed mass hourly space velocity of the first stream of material of 0.15~1.0h. -1 ; The second adsorbent used in the second adsorption separation is selected from one of X-type molecular sieve or Y-type molecular sieve, wherein the X-type molecular sieve and the Y-type molecular sieve each independently contain alkali metals, including Cs and / or Rb; based on the weight of the second adsorbent, the weight content of the alkali metal is 50-95%, preferably 80-95%.

[0014] Optionally, in step (2), the conditions for the second distillation treatment include: the top temperature of the column is 30~40℃ and the bottom temperature of the column is 90~100℃; The method includes: obtaining the regenerated second desorbent from the top of the second distillation column, and obtaining the second stream mainly containing alkanes from the bottom of the second distillation column.

[0015] Optionally, in step (3), the conditions for the third distillation process include: the top temperature of the column is 30~40℃ and the bottom temperature of the column is 240~250℃; The method includes: obtaining the regenerated second desorbent from the top of the third distillation column, obtaining the regenerated first desorbent from the bottom of the third distillation column, and obtaining the third stream mainly containing aromatics and cycloalkanes from the side stream of the third distillation column.

[0016] Optionally, the naphtha comprises C6~C 10 Hydrocarbons.

[0017] Optionally, the method includes: returning the regenerated first desorbent obtained in step (1) and the regenerated first desorbent obtained in step (3) to the first adsorption separation tower for continued use; and returning the regenerated second desorbent obtained in step (2) and the regenerated second desorbent obtained in step (3) to the second adsorption separation tower for continued use.

[0018] Through the above technical solution, this disclosure involves a first adsorption separation of naphtha using heavy aromatics as the first desorbent to obtain a first extract mainly containing aromatics and a first raffinate mainly containing alkanes and cycloalkanes. After removing the desorbent from the first raffinate, a second adsorption separation is performed using light aromatics as the second desorbent to obtain a second extract mainly containing cycloalkanes and a second raffinate mainly containing alkanes. The second raffinate is then distilled to obtain a second stream mainly containing alkanes. The first and second extracts are then distilled to obtain a third stream mainly containing aromatics and cycloalkanes, and the first and second desorbents are recovered. This method efficiently separates naphtha; the separated alkanes can be used for ethylene cracking, and the separated cycloalkanes and aromatics can be used for catalytic reforming, achieving efficient utilization and component classification management of naphtha. This method is low-cost, simple, and produces high-purity and high-yield naphtha, with alkanes purity reaching over 85%.

[0019] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0020] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0021] This disclosure provides a method for separating naphtha, the method comprising the following steps: (1) Naphtha and the first desorbent are fed into the first adsorption separation tower for first adsorption separation to obtain the first extract and the first raffinate; the first raffinate is fed into the first distillation tower for first distillation treatment to obtain the first stream mainly containing cycloalkanes and alkanes and the regenerated first desorbent. (2) The first stream and the second desorbent are fed into the second adsorption separation tower for the second adsorption separation to obtain the second extract and the second raffinate; the second raffinate is fed into the second distillation tower for the second distillation treatment to obtain the regenerated second desorbent and the second stream mainly containing alkanes. (3) The first extract and the second extract are sent to the third distillation column for third distillation treatment to obtain the regenerated second desorbent, the regenerated first desorbent and the third stream mainly containing aromatics and cycloalkanes. The first desorbent comprises heavy aromatic hydrocarbon components with more than C10 carbon atoms, and the second desorbent comprises light hydrocarbon components with less than C6 carbon atoms.

[0022] This disclosure involves a first adsorption separation of naphtha using heavy aromatics as the first desorbent, yielding a first extract mainly containing aromatics and a first raffinate mainly containing alkanes and cycloalkanes. After removing the first desorbent from the first raffinate, a second adsorption separation is performed using light aromatics as the second desorbent, yielding a second extract mainly containing cycloalkanes and a second raffinate mainly containing alkanes. The second raffinate is then distilled to obtain a second stream mainly containing alkanes. The first and second extracts are then distilled again to obtain a third stream mainly containing aromatics and cycloalkanes, and both the first and second desorbents are recovered. This method efficiently separates naphtha, allowing the separated alkanes to be used for ethylene cracking, and the separated cycloalkanes and aromatics to be used for catalytic reforming. This achieves efficient utilization of naphtha and component classification management. The method is low-cost, simple, and produces high-purity and high-yield naphtha, with alkanes achieving a purity of over 85%.

[0023] According to one embodiment of this disclosure, the first desorbent comprises a C11-C13 heavy aromatic hydrocarbon component, and the boiling point of the first desorbent is 220-330°C. Preferably, the first desorbent comprises methylnaphthalene and / or 1-methyl-1,2,3,4-tetrahydronaphthalene. The above embodiment is beneficial for separating aromatic hydrocarbons from naphtha, and for improving the purity and yield of aromatic hydrocarbons.

[0024] According to one embodiment of this disclosure, the second desorbent comprises a C5-C6 light hydrocarbon component, and the boiling point of the second desorbent is 30-100°C; preferably, the second desorbent comprises n-pentane and / or cyclopentane. The above embodiments facilitate the separation of cycloalkanes, improving the purity and yield of cycloalkanes.

[0025] According to one embodiment of this disclosure, the difference between the boiling point of the first desorbent and the boiling point of the second desorbent is 150°C or higher, preferably 170-300°C. Exemplarily, the boiling point difference can be 155°C, 160°C, 170°C, 180.8°C, 184.06°C, 185°C, 190°C, 195.8°C, 205°C, 209°C, 210°C, 220°C, 250°C, or 252.25°C. This embodiment is beneficial for saving energy consumption, and the first and second desorbents can be recovered simultaneously during desorbent recovery.

[0026] According to one embodiment of this disclosure, in step (1), the conditions for the first adsorption separation include: being carried out in a simulated moving bed at a temperature of 40~200℃, preferably 80~100℃, and a pressure of 0.5~3MPa, preferably 0.8~1.2MPa; the first adsorbent used in the first adsorption separation is selected from one or more of silica gel, modified silica gel, or X-type molecular sieves, and the feed mass hourly space velocity of the naphtha is 0.35~2.0h. -1 The above-described embodiments are beneficial for separating aromatics from naphtha, and for improving the purity and yield of aromatics.

[0027] In one embodiment, this disclosure does not specifically limit the silica gel; for example, commercially available silica gel typically exhibits selective adsorption of aromatics, achieving the effects described in this application. This disclosure also does not specifically limit the modified silica gel; for example, silica gel can be modified by acids, alkalis, or metal salts, or its selectivity can be modulated by introducing various groups through reaction with hydroxyl groups on the silica gel surface. The modified silica gel is typically in the form of spherical particles. In a further embodiment, the modification process requires preheating to remove free moisture from the silica gel, but without damaging the surface silanol groups.

[0028] In one embodiment, this disclosure does not specifically limit the preparation method of X-type molecular sieves, which can be synthesized by conventional methods in the art. For example, the preparation method of NaX molecular sieves may include: mixing molecular sieve powder with a binder and performing a molding process; calcining the resulting molded product to obtain a molecular sieve pre-product; and contacting the molecular sieve pre-product with an alkaline solution for alkaline treatment to obtain a sodium-type molecular sieve. The preparation method of CsX or RbX molecular sieves using adsorbents may include: mixing molecular sieve powder with a binder and performing a molding process; calcining the resulting molded product to obtain a molecular sieve pre-product; contacting the molecular sieve pre-product with an alkaline solution for alkaline treatment to obtain a sodium-type molecular sieve; and subjecting the sodium-type molecular sieve to ion exchange with an ion exchange liquid to obtain a modified molecular sieve; wherein the ion exchange liquid includes metal active ions, and the metal active ions include Rb. + and / or Cs + .

[0029] In one embodiment, the simulated moving bed adsorption tower includes a desorption zone, a purification zone, an adsorption zone, and an isolation zone. Each zone includes at least two adsorption columns. Along the material flow direction within the adsorption tower, the adsorbent bed between the desorbent injection and the extractant collection constitutes the desorption zone; the adsorbent bed between the extractant collection and the feed injection constitutes the purification zone; the adsorbent bed between the feed injection and the raffinate collection constitutes the adsorption zone; and the adsorbent bed between the raffinate collection and the desorbent injection constitutes the isolation zone. The number of simulated moving bed layers is 10 to 16.

[0030] According to one embodiment of this disclosure, in step (1), the conditions for the first distillation treatment include: a column top temperature of 85~95℃, preferably 88~91℃, and a column bottom temperature of 240~250℃, preferably 242~245℃. This embodiment facilitates the removal of the first desorbent from the first raffinate, allowing the first desorbent to be regenerated and recycled, thus reducing production costs.

[0031] According to one embodiment of the present disclosure, in step (1), the first stream mainly containing cycloalkanes and alkanes is obtained from the top of the first distillation column, and the regenerated first desorbent is obtained from the bottom of the first distillation column.

[0032] According to one embodiment of this disclosure, in step (2), the conditions for the second adsorption separation include: being carried out in a simulated moving bed, with a temperature of 40~200℃, preferably 80~120℃, a pressure of 0.5~3MPa, preferably 0.8~1.2MPa, and a feed mass hourly space velocity of the first stream of material of 0.15~1.0h. -1 The above-described embodiments facilitate the separation of alkanes and cycloalkanes.

[0033] According to one embodiment of this disclosure, in step (2), the second adsorbent used for the second adsorption separation is selected from one of X-type molecular sieves or Y-type molecular sieves, wherein each of the X-type and Y-type molecular sieves independently contains an alkali metal, wherein the alkali metal is Cs and / or Rb; based on the weight of the second adsorbent, the weight content of the alkali metal is 50-95%, preferably 80-95%. The X-type or Y-type molecular sieves used in this disclosure are ion-exchange modified X-type or Y-type molecular sieves, which have significantly higher selectivity for cycloalkanes than for alkanes. The above embodiment is beneficial for separating cycloalkanes and alkanes, and improving the purity and yield of cycloalkanes. This disclosure does not limit the method of ion modification; those skilled in the art can obtain the X-type or Y-type molecular sieves of this disclosure through conventional ion exchange.

[0034] According to one embodiment of this disclosure, in step (2), the conditions for the second distillation treatment include: a column top temperature of 36-40°C, preferably 35-37°C, and a column bottom temperature of 85-95°C, preferably 90-93°C. This embodiment facilitates the removal of the second desorbent from the second raffinate, allowing for the regeneration and recycling of the second desorbent, which helps reduce production costs; it also facilitates the obtaining of alkanes with higher purity and yield.

[0035] According to one embodiment of the present disclosure, in step (2), the regenerated second desorbent is obtained from the top of the second distillation column, and the second stream mainly containing alkanes is obtained from the bottom of the second distillation column.

[0036] According to one embodiment of this disclosure, in step (3), the conditions for the third distillation treatment include: a column top temperature of 30~40℃, preferably 35~37℃, and a column bottom temperature of 240~250℃, preferably 244~247℃. This embodiment facilitates the simultaneous regeneration of the first and second desorbents in the same distillation column, thereby reducing production costs.

[0037] According to one embodiment of the present disclosure, in step (3), the regenerated second desorbent is obtained from the top of the third distillation column, the regenerated first desorbent is obtained from the bottom of the third distillation column, and the third stream mainly containing aromatics and cycloalkanes is obtained from the side stream of the third distillation column.

[0038] According to one embodiment of this disclosure, the naphtha comprises C6~C 10 Hydrocarbons. The main components of hydrocarbons are aromatics, cycloalkanes, and alkanes; among them, the components classified as aromatics are mainly benzene, toluene, and xylene; the components classified as cycloalkanes are mainly monocycloalkanes and bicycloalkanes; and the components classified as alkanes are mainly n-alkanes and isoalkanes.

[0039] According to one embodiment of this disclosure, the method includes: returning the regenerated first desorbent obtained in step (1) and the regenerated first desorbent obtained in step (3) to the first adsorption separation tower for continued use; and returning the regenerated second desorbent obtained in step (2) and the regenerated second desorbent obtained in step (3) to the second adsorption separation tower for continued use. The above embodiment is beneficial for reducing production costs.

[0040] The present disclosure will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present disclosure, but do not limit the disclosure in any way. Unless otherwise specified, all other goods are commercially available.

[0041] In this disclosure, the adsorbents, type A silica gel and type B silica gel, are commercially available silica gels. The type A silica gel has an average pore size of 1~3 nm and a specific surface area of ​​600~650 m². 2 / g; Type B silica gel has an average pore size of 6~8nm and a specific surface area of ​​500~550m². 2 / g; The specific surface area of ​​X-type molecular sieves is 555~570m². 2 / g, with a silica-to-alumina ratio of 2.0~2.5; the specific surface area of ​​the Y-type molecular sieve is 540~580m². 2 / g, with a silica-alumina ratio of 3.3~3.4. The composition of the naphtha used is shown in Table 1.

[0042] Table 1

[0043] Example 1 The simulated moving bed device in this embodiment consists of 12 identical adsorption columns (33mm inner diameter and 156mm long) forming an adsorption chamber with a total dosage of 1.6L. These columns are evenly installed around the rotating disc of the rotary valve. The 12 adsorption columns are connected into a ring system with the ends connected by the rotary valve and the circulating pump. The rotating disc rotates the adsorption columns periodically under the action of the transmission mechanism. The lower plate is fixed and has five inlets and outlets: raw material, desorbent, evaporator, circulating liquid outlet, and circulating liquid inlet. Another stream of material is drawn out from the circulating liquid outlet as the evaporator outlet. The method in this embodiment includes: adsorption tower A is loaded with approximately 950g of adsorbent, and adsorption tower B is loaded with approximately 1620g of adsorbent. Naphtha feedstock is fed into adsorption tower A. The adsorbent is type B silica gel, and the first desorbent is methylnaphthalene (boiling point 245℃). The conditions for the first adsorption separation include: temperature 80℃, pressure 1.2 MPa, a mass flow rate ratio of naphtha feedstock to the first desorbent of 1:2, and a naphtha feed mass hourly space velocity of 0.41 h⁻¹. -1 The process yields a first extract and a first raffinate. The first extract mainly contains aromatics with the first desorbent, while the first raffinate contains non-aromatics with the first desorbent. The simulated moving bed naphtha feed rate is 392 g / h, the first desorbent feed rate is 780 g / h, and the flow rates of the first extract and the first raffinate are 345 g / h and 828 g / h, respectively. The first raffinate, after the first adsorption step, is fed into a first distillation column for first distillation treatment. A first stream mainly containing cycloalkanes and alkanes is obtained from the top of the first distillation column, and the regenerated first desorbent is obtained from the bottom of the first distillation column. The first stream is fed into adsorption tower B for secondary adsorption separation. The adsorbent is CsX molecular sieve, in which the weight content of cesium metal is 85%. The second desorbent is n-pentane (boiling point 36℃). The boiling point difference between the first and second desorbents is 209℃, resulting in a second effluent and a second raffinate. The conditions for the secondary adsorption separation include: temperature 100℃, pressure 1.2 MPa, mass flow rate ratio of the first stream to the second desorbent 1:3, simulated moving bed feed rate of 439 g / h for the first stream, 1979 g / h for the second desorbent, and feed mass hourly space velocity (WHSV) of the first stream 0.27 h⁻¹. -1 The flow rates of the second extract and the second raffinate are 1200 g / h and 1218 g / h, respectively. The second extract consists of cycloalkanes containing the second desorbent, and the second raffinate consists of alkanes containing the second desorbent. The second raffinate is sent to the second distillation column for second distillation treatment. The regenerated second desorbent is obtained from the top of the second distillation column, and the second stream mainly containing alkanes is obtained from the bottom of the second distillation column. The first and second extracts are fed into a third distillation column for third distillation. The regenerated second desorbent is obtained from the top of the third distillation column, the regenerated first desorbent is obtained from the bottom of the third distillation column, and the third stream, mainly containing aromatics and cycloalkanes, is obtained from the side stream of the third distillation column. Specific conditions are shown in Table 2, and the simulated moving bed evaluation results are shown in Table 3.

[0044] Example 2 The method in this embodiment includes: adsorption tower A is loaded with approximately 1300g of adsorbent, and adsorption tower B is loaded with approximately 1620g of adsorbent. Naphtha feedstock is fed into adsorption tower A. The adsorbent is type A silica gel, and the first desorbent is 1-methyl-1,2,3,4-tetrahydronaphthalene (boiling point 220.06℃). The conditions for the first adsorption separation include: temperature 80℃, pressure 1.2MPa, mass flow rate ratio of naphtha feedstock to the first desorbent 1:2, and naphtha feed mass hourly space velocity (MHV) 0.33h. -1 The process yields a first extract and a first raffinate. The first extract consists of aromatics containing the first desorbent, and the first raffinate consists of non-aromatics containing the first desorbent. The simulated moving bed naphtha feed rate is 434 g / h, the first desorbent feed rate is 709 g / h, and the flow rates of the first extract and the first raffinate are 221 g / h and 922 g / h, respectively. The first raffinate, after the first adsorption step, is fed into a first distillation column for first distillation treatment. A first stream mainly containing cycloalkanes and alkanes is obtained from the top of the first distillation column, and the regenerated first desorbent is obtained from the bottom of the first distillation column. The first stream is fed into adsorption tower B for secondary adsorption separation. The adsorbent is CsX molecular sieve, in which the weight content of cesium metal is 85%. The second desorbent is n-pentane (boiling point 36℃). The boiling point difference between the first and second desorbents is 184.06, resulting in a second effluent and a second raffinate. The conditions for the second adsorption separation include: temperature 100℃, pressure 1.2 MPa, mass flow rate ratio of the first stream to the second desorbent 1:3, and feed mass hourly space velocity (HHSV) of the first stream 0.27 h⁻¹. -1 The simulated moving bed has a first feed rate of 439 g / h, a second desorbent feed rate of 1979 g / h, and second evaporate and second raffinate flow rates of 1200 g / h and 1218 g / h, respectively. The second evaporate consists of cycloalkanes containing the second desorbent, and the second raffinate consists of alkanes containing the second desorbent. The second raffinate is fed into a second distillation column for second distillation treatment. The regenerated second desorbent is obtained from the top of the second distillation column, and the second stream, mainly containing alkanes, is obtained from the bottom of the second distillation column. The first and second extracts are fed into a third distillation column for third distillation. The regenerated second desorbent is obtained from the top of the third distillation column, the regenerated first desorbent is obtained from the bottom of the third distillation column, and the third stream, mainly containing aromatics and cycloalkanes, is obtained from the side stream of the third distillation column. Specific conditions are shown in Table 2, and the simulated moving bed evaluation results are shown in Table 3.

[0045] Example 3 In this embodiment, adsorption tower A is filled with approximately 1100g of adsorbent, and adsorption tower B is filled with approximately 1620g of adsorbent. The method in this embodiment includes: feeding naphtha feedstock into adsorption tower A; the adsorbent is NaX molecular sieve; the first desorbent is methylnaphthalene; and the conditions for the first adsorption separation include: a temperature of 80℃, a pressure of 1.2 MPa, a mass flow rate ratio of naphtha feedstock to the first desorbent of 1:2, and a naphtha feed mass hourly space velocity of 0.47 h⁻¹. -1 The process yields a first extract and a first raffinate. The first extract mainly contains aromatics with the first desorbent, while the first raffinate contains non-aromatics with the first desorbent. The simulated moving bed naphtha feed rate is 521 g / h, the first desorbent feed rate is 775 g / h, and the flow rates of the first extract and the first raffinate are 414 g / h and 882 g / h, respectively. The first raffinate, after the first adsorption step, is fed into a first distillation column for first distillation treatment. A first stream mainly containing cycloalkanes and alkanes is obtained from the top of the first distillation column, and the regenerated first desorbent is obtained from the bottom of the first distillation column. The first stream is fed into adsorption tower B for a second adsorption separation. The adsorbent is CsX molecular sieve, in which the weight content of cesium metal is 85%. The second desorbent is n-pentane, yielding a second extract and a second raffinate. The conditions for the second adsorption separation include: a temperature of 80℃, a pressure of 1.2 MPa, a mass flow rate ratio of the first stream to the second desorbent of 1:3, and a feed mass hourly space velocity (WHSV) of 0.63 h⁻¹. -1 The simulated moving bed has a first feed rate of 694 g / h, a second desorbent feed rate of 1952 g / h, and second evaporate and second raffinate flow rates of 1318 g / h and 1328 g / h, respectively. The second evaporate is n-alkanes containing the second desorbent, and the second raffinate is alkanes containing the second desorbent. The second raffinate is sent to a second distillation column for second distillation treatment. The regenerated second desorbent is obtained from the top of the second distillation column, and the second stream mainly containing alkanes is obtained from the bottom of the second distillation column. The first and second extracts are fed into a third distillation column for third distillation. The regenerated second desorbent is obtained from the top of the third distillation column, the regenerated first desorbent is obtained from the bottom of the third distillation column, and the third stream, mainly containing aromatics and cycloalkanes, is obtained from the side stream of the third distillation column. Specific conditions are shown in Table 2, and the simulated moving bed evaluation results are shown in Table 3.

[0046] Example 4 In this embodiment, adsorption tower A is filled with approximately 1100g of adsorbent, and adsorption tower B is filled with approximately 1570g of adsorbent. The method in this embodiment includes: Naphtha feedstock is fed into adsorption tower A. The adsorbent is NaX molecular sieve, and the first desorbent is 1-methyl-1,2,3,4-tetrahydronaphthalene. The conditions for the first adsorption separation are: temperature 100℃, pressure 1.2 MPa, naphtha to first desorbent mass flow rate ratio 1:2, and naphtha feed mass hourly space velocity (MHV) 0.56 h⁻¹. -1 The process yields a first extract and a first raffinate. The first extract mainly contains aromatics with the first desorbent, while the first raffinate contains non-aromatics with the first desorbent. The simulated moving bed naphtha feed rate is 624 g / h, the first desorbent feed rate is 834 g / h, and the flow rates of the first extract and the first raffinate are 557 g / h and 901 g / h, respectively. The first raffinate, after the first adsorption step, is fed into a first distillation column for first distillation treatment. A first stream mainly containing cycloalkanes and alkanes is obtained from the top of the first distillation column, and the regenerated first desorbent is obtained from the bottom of the first distillation column. The first stream is fed into adsorption tower B for a second adsorption separation. The adsorbent is RbX molecular sieve, in which the weight content of rubidium metal is 84%. The second desorbent is cyclopentane (boiling point 49.2℃), yielding a second effluent and a second raffinate. The conditions for the second adsorption separation include: a temperature of 100℃, a pressure of 1.2 MPa, a mass flow rate ratio of the first stream to the second desorbent of 1:3, and a feed mass hourly space velocity (WHSV) of 0.27 h⁻¹. -1 The simulated moving bed has a first feed rate of 422 g / h, a second desorbent feed rate of 1967 g / h, and second evaporate and second raffinate flow rates of 1104 g / h and 1285 g / h, respectively. The second evaporate is cycloalkanes containing the second desorbent, and the second raffinate is alkanes containing the second desorbent. The second raffinate is sent to a second distillation column for second distillation treatment. The regenerated second desorbent is obtained from the top of the second distillation column, and the second stream mainly containing alkanes is obtained from the bottom of the second distillation column. The first and second extracts are fed into a third distillation column for third distillation. The regenerated second desorbent is obtained from the top of the third distillation column, the regenerated first desorbent is obtained from the bottom of the third distillation column, and the third stream, mainly containing aromatics and cycloalkanes, is obtained from the side stream of the third distillation column. Specific conditions are shown in Table 2, and the simulated moving bed evaluation results are shown in Table 3.

[0047] Example 5 In this embodiment, adsorption tower A is filled with approximately 1100g of adsorbent, and adsorption tower B is filled with approximately 1620g of adsorbent. The method in this embodiment includes: feeding naphtha feedstock into adsorption tower A; the adsorbent is NaX molecular sieve; the first desorbent is methylnaphthalene (boiling point 245℃); and the conditions for the first adsorption separation include: temperature 100℃, pressure 1.2 MPa, a naphtha to first desorbent mass flow rate ratio of 1:2, and a naphtha feed mass hourly space velocity (MHV) of 0.54 h⁻¹. -1 The process yields a first extract and a first raffinate. The first extract consists mainly of aromatics containing the first desorbent, while the first raffinate consists of non-aromatics containing the first desorbent. The simulated moving bed naphtha feed rate is 597 g / h, the first desorbent feed rate is 882 g / h, and the flow rates of the first extract and first raffinate are 478 g / h and 1001 g / h, respectively. The first raffinate, after adsorption in the first step, is fed into a first distillation column for first distillation treatment. A first stream mainly containing cycloalkanes and alkanes is obtained from the top of the first distillation column, and the regenerated first desorbent is obtained from the bottom of the first distillation column. The first stream is fed into adsorption tower B, with CsX molecular sieve as the adsorbent, containing 85% cesium metal by weight. The second desorbent is cyclopentane (boiling point 49.2℃), and the boiling point difference between the first and second desorbents is 195.8℃, yielding a second effluent and a second raffinate. The conditions for the second adsorption separation include: a temperature of 120℃, a pressure of 1.2 MPa, a mass flow rate ratio of the first stream to the second desorbent of 1:3, and a feed mass hourly space velocity (WHSV) of 0.22 h⁻¹. -1 The simulated moving bed has a first feed rate of 358 g / h, a second desorbent feed rate of 1907 g / h, and second evaporate and second raffinate flow rates of 997 g / h and 1268 g / h, respectively. The second evaporate consists of cycloalkanes containing the second desorbent, and the second raffinate consists of alkanes containing the second desorbent. The second raffinate is fed into a second distillation column for second distillation treatment. The regenerated second desorbent is obtained from the top of the second distillation column, and the second stream, mainly containing alkanes, is obtained from the bottom of the second distillation column. The first and second extracts are fed into a third distillation column for third distillation. The regenerated second desorbent is obtained from the top of the third distillation column, the regenerated first desorbent is obtained from the bottom of the third distillation column, and the third stream, mainly containing aromatics and cycloalkanes, is obtained from the side stream of the third distillation column. Specific conditions are shown in Table 2, and the simulated moving bed evaluation results are shown in Table 3.

[0048] Example 6 The method in this embodiment is the same as in embodiment 1, except that the first adsorbent used in the first adsorption separation is NaY. The specific conditions are shown in Table 2, and the evaluation results of the simulated moving bed are shown in Table 3.

[0049] Example 7 The method in this embodiment is the same as in embodiment 1, except that the second adsorbent used in the second adsorption separation is BaX. The specific conditions are shown in Table 2, and the evaluation results of the simulated moving bed are shown in Table 3.

[0050] Example 8 The method in this embodiment is the same as in embodiment 1, except that the second adsorbent used is CsX molecular sieve, wherein the weight content of alkali metal Cs is 40%.

[0051] Example 9 The method in this embodiment is the same as in Embodiment 1, except that the first desorbent used is 1,4,6,7-tetramethylnaphthalene, and the second desorbent is n-pentane.

[0052] Table 2

[0053] Table 3

[0054] In Table 3, the purity of cycloalkane is calculated as 100% × (mass fraction of cycloalkane in the second extract of the cycloalkane-rich material / mass fraction of the material in the second extract). Cycloalkanes yield = 100% × (flow rate of the second extract of the cycloalkanes-rich feedstock × mass fraction of cycloalkanes in the second extractstock) / (flow rate of naphtha feedstock × mass fraction of cycloalkanes in the naphtha feedstock).

[0055] Aromatic purity = 100% × (mass fraction of aromatics in the first extract of aromatic-rich material / mass fraction of material in the first extract); Aromatics yield = 100% × (flow rate of the first extract of aromatics-rich material × mass fraction of aromatics in the first extract) / (flow rate of naphtha feedstock × mass fraction of aromatics in naphtha feedstock).

[0056] Alkane purity = 100% × (mass fraction of alkanes in the second stream rich in alkanes / mass fraction of materials in the second stream); Alkane yield = 100% × (second stream flow rate rich in alkane × mass fraction of alkane in second stream) / (naphtha feedstock flow rate × mass fraction of alkane in naphtha feedstock).

[0057] As shown in Table 3, the method of this disclosure can efficiently separate naphtha into alkanes and non-alkanes. The method is low-cost, simple, and achieves high purity and yield, with aromatic purity reaching over 98% and alkanes purity reaching over 85%. A comparison of Examples 1 and 6 shows that within the conditions of the preferred first adsorbent of this disclosure, both aromatic purity and yield are higher. A comparison of Examples 1 and 7 / 8 shows that within the conditions of the preferred second adsorbent of this disclosure, both aromatic purity and alkanes purity and yield are higher. A comparison of Examples 1 and 9 shows that within the conditions of the preferred first desorbent of this disclosure, both aromatic purity and yield are higher.

[0058] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0059] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0060] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for separating naphtha, characterized in that, The method includes the following steps: (1) Naphtha and the first desorbent are fed into the first adsorption separation tower for the first adsorption separation to obtain the first extract and the first raffinate, which mainly contain aromatics; the first raffinate is fed into the first distillation tower for the first distillation treatment to obtain the first stream, which mainly contains cycloalkanes and alkanes, and the regenerated first desorbent. (2) The first stream and the second desorbent are fed into the second adsorption separation tower for the second adsorption separation to obtain the second extract and the second raffinate. The second raffinate is sent to the second distillation column for a second distillation process to obtain a regenerated second desorbent and a second stream mainly containing alkanes. (3) The first extract and the second extract are sent to the third distillation column for third distillation treatment to obtain the regenerated second desorbent, the regenerated first desorbent and the third stream mainly containing aromatics and cycloalkanes. The first desorbent comprises heavy aromatic hydrocarbon components with more than C10, and the second desorbent comprises light hydrocarbon components with less than C6.

2. The method according to claim 1, wherein, The first desorbent comprises a C11-C13 heavy aromatic hydrocarbon, and the boiling point of the first desorbent is 220-330°C; preferably, the first desorbent comprises methylnaphthalene and / or 1-methyl-1,2,3,4-tetrahydronaphthalene.

3. The method according to claim 2, wherein, The second desorbent is a C5-C6 light hydrocarbon component, and the boiling point of the second desorbent is 30-100℃; preferably, the second desorbent includes n-pentane and / or cyclopentane.

4. The method according to claim 1, wherein, In step (1), the conditions for the first adsorption separation include: being carried out in a simulated moving bed at a temperature of 40~200℃, preferably 80~100℃, a pressure of 0.5~3MPa, preferably 0.8~1.2MPa, and a feed mass hourly space velocity (WHSV) of 0.35~2.0h for the naphtha. -1 ; The first adsorbent used in the first adsorption separation is selected from one or more of silica gel, modified silica gel, or X-type molecular sieve.

5. The method according to claim 1, wherein, In step (1), the conditions for the first distillation process include: the top temperature of the column is 85~95℃ and the bottom temperature of the column is 240~250℃; The method includes: obtaining the first stream, which mainly contains cycloalkanes and alkanes, from the top of the first distillation column, and obtaining the regenerated first desorbent from the bottom of the first distillation column.

6. The method according to claim 1, wherein, In step (2), the conditions for the second adsorption separation include: being carried out in a simulated moving bed, with a temperature of 40~200℃, preferably 80~120℃, a pressure of 0.5~3MPa, preferably 0.8~1.2MPa, and a feed mass hourly space velocity of the first stream of material of 0.15~1.0h. -1 ; The second adsorbent used in the second adsorption separation is selected from one of X-type molecular sieve or Y-type molecular sieve, wherein the X-type molecular sieve and the Y-type molecular sieve each independently contain alkali metals, including Cs and / or Rb; based on the weight of the second adsorbent, the weight content of the alkali metal is 50-95%, preferably 80-95%.

7. The method according to claim 1, wherein, In step (2), the conditions for the second distillation process include: the top temperature of the column is 30~40℃ and the bottom temperature of the column is 90~100℃; The method includes: obtaining the regenerated second desorbent from the top of the second distillation column, and obtaining the second stream mainly containing alkanes from the bottom of the second distillation column.

8. The method according to claim 1, wherein, In step (3), the conditions for the third distillation process include: the top temperature of the column is 30~40℃ and the bottom temperature of the column is 240~250℃; The method includes: obtaining the regenerated second desorbent from the top of the third distillation column, obtaining the regenerated first desorbent from the bottom of the third distillation column, and obtaining the third stream mainly containing aromatics and cycloalkanes from the side stream of the third distillation column.

9. The method according to claim 1, wherein, The naphtha comprises C6~C 10 Hydrocarbons.

10. The method according to claim 1, wherein, The method includes: returning the regenerated first desorbent obtained in step (1) and the regenerated first desorbent obtained in step (3) to the first adsorption separation tower for continued use; and returning the regenerated second desorbent obtained in step (2) and the regenerated second desorbent obtained in step (3) to the second adsorption separation tower for continued use.

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