Method and system for extracting high-purity norbornene

Abstract

The invention relates to the technical field of separation and purification, and discloses a method and a system for extracting high-purity norbornene. The norbornene product obtained by the method provided by the invention has high purity and is suitable for COC synthesis. Moreover, the method also has the advantages of high treatment efficiency, easiness in control and management of the treatment process and the like, and is very suitable for large-scale industrial production and application.

Description

Technical Field

[0001] The present invention relates to the technical field of separation and purification, and in particular to a method and system for extracting high-purity norbornene. Background Art

[0002] Cycloolefin copolymers (COC) have good heat resistance, chemical stability, high transparency, dimensional stability, melt fluidity, moisture barrier properties and extremely low dielectric constant, which makes them widely used in food, medicine, electronics, chemical industry and other fields. Norbornene is an important comonomer required for the preparation of COC, which is usually prepared by Diels-Alder cycloaddition reaction of cyclopentadiene and ethylene under high temperature and high pressure conditions. In order to obtain high-quality COC products, high purity requirements are placed on norbornene as one of the raw materials.

[0003] The synthesis of norbornene can be divided into two methods: solvent-free and solvent-containing. Since the solvent-containing synthesis method has more advantages in terms of safety and economy, it has become the main production method currently used in industry. However, the composition of the synthetic solution of norbornene obtained by the solvent method is complex. In addition to norbornene and solvent, there are also unreacted raw materials, new components produced by the reaction, impurities introduced by the raw materials and their products, and impurities produced by side reactions. Moreover, some of the impurities will transform into each other during the separation process, making it difficult to efficiently obtain high-purity norbornene.

[0004] Moreover, the current research on norbornene mainly focuses on the synthesis method, and there is little research on how to separate and obtain high-purity norbornene in the future, especially there is almost no report on the norbornene purification process that can be applied industrially. Although CN1284051A discloses a method for separating and obtaining norbornene from a norbornene synthesis liquid, it is aimed at the separation and purification of a norbornene synthesis liquid obtained by a solvent-free synthesis method, and has limited help in obtaining a method for separating and obtaining high-purity norbornene from a norbornene synthesis liquid obtained by a solvent synthesis method. Moreover, the norbornene synthesis liquid used in it is also greatly different from the actual industrial norbornene synthesis liquid, and has limited guiding role in industrial application.

[0005] Therefore, it is very important for norbornene production and COC production and other related downstream industries to develop a method that is easy to industrialize, energy-saving and environmentally friendly, and can efficiently separate the norbornene synthesis liquid obtained by a solvent synthesis method to obtain a high-purity norbornene product. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of the prior art that are not suitable for industrial application, and to provide a method and system for extracting high-purity norbornene for the method of efficiently separating the norbornene synthesis liquid obtained by solvent synthesis to obtain high-purity norbornene. The method provided by the present invention has the advantages of high processing efficiency, high purity of norbornene product, easy control and management of the processing process, and easy industrialization.

[0007] In order to achieve the above object, the first aspect of the present invention provides a method for extracting high-purity norbornene, the method comprising:

[0008] (1) De-weighting: The norbornene synthesis liquid is introduced into a de-weighting tower for first distillation to obtain a de-weighting tower bottom stream and a de-weighting tower top stream.

[0009] The conditions of the first distillation are such that no more than 15 wt% of norbornene in the norbornene synthesis liquid enters the de-weighting tower bottom stream, and the toluene content in the de-weighting tower top stream does not exceed 1 wt%;

[0010] (2) removing light substances: introducing the overhead stream of the heavy removal tower obtained in step (1) into a light removal tower for secondary distillation to obtain a light removal tower bottom stream and a light removal tower overhead stream;

[0011] Wherein, the conditions of the second distillation are such that the total content of cyclopentadiene and dicyclopentadiene in the light-removal tower bottom stream does not exceed 10 ppm.

[0012] A second aspect of the present invention provides a system for extracting high-purity norbornene, the system comprising a heavy removal tower and a light removal tower;

[0013] The material inlet and outlet of the de-weighting tower include: the inlet of the material to be de-weighted, the outlet of the bottom logistics of the de-weighting tower and the outlet of the top logistics of the de-weighting tower;

[0014] The material inlet and outlet of the light-removal tower include: the inlet of the material to be removed, the outlet of the bottom logistics of the light-removal tower and the outlet of the top logistics of the light-removal tower;

[0015] The top logistics outlet of the deheaving tower is connected to the inlet of the light material to be removed, and the bottom logistics outlet of the deheaving tower is connected to the inlet of the material to be refined of the refining tower. Preferably, the bottom logistics outlet of the refining tower is connected to the inlet of the material to be pre-deheavy removed.

[0016] Through the above technical solution, the present invention can at least achieve the following beneficial effects:

[0017] (1) The method provided by the present invention can achieve one-step removal of heavy components in the norbornene synthesis liquid by allowing part of the norbornene to enter the bottom stream of the de-heavy tower during the de-heavy process. At the same time, by controlling the treatment method and conditions of the de-heavy process, a high-purity norbornene product can be efficiently obtained. In addition, by adopting the method of the present invention, since part of the norbornene is allowed to enter the bottom stream of the de-heavy tower during the de-heavy process, the requirements and difficulty of controlling and managing the operating conditions are reduced, and the energy consumption of the distillation process is also effectively controlled, thereby improving the economy and environmental protection of the overall process, which is conducive to industrial promotion.

[0018] (2) In the preferred embodiment of the present invention, the bottom stream of the deheaving tower is further separated, and the norbornene, toluene, and some heavy components that can be used as raw materials for norbornene synthesis are recovered and recycled, thereby further improving the yield of norbornene, reducing resource waste, and reducing the cost of the overall process of norbornene synthesis and purification, which is more in line with the requirements of green and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the system for separating and purifying norbornene used in Example 1 of the present invention.

[0020] Description of Reference Numerals

[0021] T-1: heavy removal tower; T-2: light removal tower; T-3: norbornene recovery tower; T-4: solvent recovery tower;

[0022] S-1: norbornene synthesis liquid; S-2: deheavy tower top logistics; S-3: deheavy tower bottom logistics; S-4: delight tower top logistics; S-5: delight tower bottom logistics (norbornene product); S-6: norbornene recovery tower top logistics; S-7: norbornene recovery tower bottom logistics; S-8: solvent recovery tower top logistics; S-9: solvent recovery tower bottom logistics. DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] In the present invention, unless otherwise specified, "heavy components" refer to components in the norbornene synthesis liquid having a boiling point greater than that of norbornene, including solvents (mainly toluene) and intermediate products / by-products (such as dicyclopentadiene, tricyclopentadiene, tetracyclododecene, etc.); "light components" refer to components in the norbornene synthesis liquid having a boiling point less than that of norbornene, mainly including raw materials remaining in the norbornene synthesis liquid, and impurities (such as cyclopentadiene, isoprene, isoprene, etc.) generated by the conversion of the raw materials or entrained in the raw materials; "polymerization grade norbornene" refers to norbornene with high purity and low impurity content, so as to meet the production requirements of COC with norbornene as one of the main raw materials (purity ≥ 98% by weight, and the contents of cyclopentadiene and dicyclopentadiene are both less than 10 ppm, preferably less than 5 ppm, for example, 1 ppm, 2 ppm, 3 ppm, 4 ppm, 5 ppm, or any intermediate value between any two of the above values).

[0025] In the present invention, unless otherwise specified, the theoretical plate number is obtained by experiments using a general determination method in the separation field.

[0026] In the present invention, unless otherwise specified, the operation numbers (such as "first", "second", etc. in the first distillation and the second distillation) are only used to make it easier to distinguish the same treatment in different steps in the description, and have no limiting effect on the specific operation method, conditions and sequence.

[0027] When norbornene is synthesized in a solvent-containing manner, the obtained norbornene synthesis liquid contains, in addition to norbornene and a solvent (usually toluene), unreacted raw material cyclopentadiene and heavy components with a boiling point higher than that of norbornene, such as dicyclopentadiene, tetracyclododecene, tricyclopentadiene, etc. From the perspective of separation and purification, it is best to separate and remove the heavy components at one time. However, since cyclopentadiene and dicyclopentadiene can be mutually converted under certain conditions during the separation process, the distillation process is actually a reactive distillation process, and the boiling point of cyclopentadiene is lower than that of norbornene, and the boiling point of dicyclopentadiene is higher than that of norbornene, it is difficult to completely remove impurities such as cyclopentadiene and dicyclopentadiene when purifying and separating the norbornene synthesis liquid, resulting in the problem that the purity of the norbornene product is insufficient and cannot meet the production needs.

[0028] The inventor of the present invention cleverly discovered during the research process that when removing the solvent and heavy component impurities in the norbornene synthesis liquid, if a small amount of norbornene is extracted together with the solvent and the heavy component, the solvent and the heavy component impurities can be removed in one step, and the remaining norbornene and the mixture of light component impurities are further separated to obtain a norbornene product, which has the advantages of simple process and suitability for industrial promotion. Moreover, some norbornene is allowed to be carried in the bottom stream of the de-weighting tower, which can reduce the energy consumption of the de-weighting tower and reduce the refining requirements. The de-weighting tower only needs to ensure that the components with a boiling point higher than that of norbornene at the top of the tower are qualified, which reduces the requirements for operation and management. At the same time, by controlling the operation mode and conditions when further separating the mixture of norbornene and light component impurities, a higher purity norbornene product can be obtained to meet the needs of COC synthesis. This method can greatly simplify the separation and purification process of norbornene, reduce the operational and management inconvenience caused by repeatedly removing some of the convertible light / heavy impurities, reduce energy consumption, and improve the feasibility of the separation and purification process in industrial applications.

[0029] Based on the above findings, the first aspect of the present invention provides a method for extracting high-purity norbornene, the method comprising:

[0030] (1) De-weighting: The norbornene synthesis liquid is introduced into a de-weighting tower for first distillation to obtain a de-weighting tower bottom stream and a de-weighting tower top stream.

[0031] The conditions of the first distillation are such that no more than 15 wt% of norbornene in the norbornene synthesis liquid enters the de-weighting tower bottom stream, and the toluene content in the de-weighting tower top stream does not exceed 1 wt%;

[0032] (2) removing light substances: introducing the overhead stream of the heavy removal tower obtained in step (1) into a light removal tower for secondary distillation to obtain a light removal tower bottom stream and a light removal tower overhead stream;

[0033] Wherein, the conditions of the second distillation are such that the total content of cyclopentadiene and dicyclopentadiene in the light-removal tower bottom stream does not exceed 10 ppm.

[0034] The method provided by the present invention can separate and purify the norbornene synthesis liquid obtained by any prior art process of synthesizing norbornene in a solvent-free manner. Generally, the norbornene synthesis liquid contains norbornene and toluene (i.e., the solvent used in the synthesis), and at least one of cyclopentadiene, dicyclopentadiene, tricyclopentadiene, tetracyclododecene, pentene, pentadiene, 3-methylcyclohexene, santalen, methylnorbornene, etc. Preferably, the norbornene synthesis liquid includes cyclopentadiene, norbornene, toluene, dicyclopentadiene, tricyclopentadiene, tetracyclododecene and santalen.

[0035] In the present invention, the purpose of step (1) is to (completely) remove the heavy components in the norbornene synthesis liquid. Since a solvent is also required in the subsequent COC production process, a small amount of toluene remaining in the norbornene product does not affect its quality and subsequent use. However, the content of heavy components such as dicyclopentadiene and tetracyclododecene should be strictly controlled to prevent them from entering the bottom stream of the light removal tower and affecting the quality of the norbornene product.

[0036] In the present invention, a certain amount of norbornene is allowed to enter the de-weighting tower bottom stream, thereby ensuring that the heavy components in the norbornene synthesis liquid can be removed as much as possible in the first distillation process. At the same time, considering the yield of the norbornene product and avoiding the loss of norbornene, the amount of norbornene entering the de-weighting tower bottom stream should be controlled not to be too high. The inventor cleverly discovered in the study that when a specific proportion of norbornene in the synthetic liquid enters the de-weighting tower bottom stream, the yield and quality of the norbornene product can reach a high level.

[0037] According to some preferred embodiments of the present invention, in step (1), the conditions of the first distillation are such that no more than 10 wt % of norbornene in the norbornene synthesis liquid enters the bottom flow of the deweighting tower, and preferably, 1-10 wt % (for example, 1 wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, or any intermediate value between any two of the above values) of norbornene in the norbornene synthesis liquid enters the bottom flow of the deweighting tower.

[0038] In order to further improve the purity of the norbornene product, preferably, the conditions of the first distillation are such that the toluene content in the weight removal tower top stream does not exceed 0.7 wt %.

[0039] In order to achieve the above control of the content of norbornene, toluene and other substances in the deweighting tower top stream and the deweighting tower bottom stream, according to a preferred embodiment of the present invention, the number of theoretical plates of the deweighting tower is 15-55, preferably 20-40.

[0040] Dicyclopentadiene and tetracyclododecene will undergo depolymerization reaction at a higher temperature, dicyclopentadiene will depolymerize into cyclopentadiene, tetracyclododecene will depolymerize into cyclopentadiene and norbornene, cyclopentadiene will react with the substance containing carbon-carbon double bonds in the heavy component to produce a Diels-alder diene synthesis reaction, which will easily cause coking and blockage of the equipment. Therefore, the deweighting tower is preferably operated under reduced pressure or normal pressure, more preferably under reduced pressure. In addition, in order to reduce the reaction of impurity components in the first distillation process, it is preferred to control the tower bottom temperature not to be too high.

[0041] According to some preferred embodiments of the present invention, the conditions of the first distillation include: a tower top pressure of 20-101 kPa, and a tower top temperature of 45-110°C.

[0042] Preferably, the conditions of the first distillation include: a tower top pressure of 40-100 kPa, and a tower top temperature of 60-100°C.

[0043] Preferably, the conditions of the first distillation also include: the tower bottom temperature is 75-120°C, preferably 80-115°C, more preferably 90-115°C.

[0044] According to the theoretical plate number of the deweighting tower and the composition of the synthetic liquid used, more preferably, the reflux ratio of the first distillation is 1-7, preferably 2-5.

[0045] According to a preferred embodiment of the present invention, the norbornene synthesis liquid is fed into the lower part of the deweighting tower, that is, the feed port can be set below 1 / 2 position of the packing or tray from the upper end, preferably below 1 / 3 position.

[0046] According to a preferred embodiment of the present invention, the deheavy tower top stream obtained in step (1) contains norbornene, light components (such as cyclopentadiene, etc.) and (a very small amount of) toluene.

[0047] According to a preferred embodiment of the present invention, the deheavy tower bottom stream obtained in step (1) contains: (a small amount of) norbornene, toluene and heavy components.

[0048] In the present invention, the purpose of step (2) is to remove the light components in the deweighting tower top stream obtained in step (1) to obtain a (high purity) norbornene product. The light components contained in the norbornene synthesis liquid mainly include unreacted cyclopentadiene and components with lower boiling points brought in by the dicyclopentadiene raw material, and may also be components produced by reactions of some components in the dicyclopentadiene raw material, such as polymers of isoprene and cyclopentadiene, polymers of isoprene and cyclopentadiene, etc. These polymers will also depolymerize to produce isoprene or isoprene during the process of dicyclopentadiene depolymerization to cyclopentadiene. The specific composition of the light components in the norbornene synthesis liquid is closely related to the composition of the dicyclopentadiene raw material. In step (2), the light components should be removed as much as possible, so that the content of light component impurities in the norbornene product obtained by purification using the method of the present invention meets the COC production requirements.

[0049] In order to achieve the above object, according to a preferred embodiment of the present invention, in step (2), the conditions of the second distillation are such that the content of cyclopentadiene in the light removal tower bottom stream does not exceed 10 ppm, preferably does not exceed 5 ppm, and more preferably does not exceed 2 ppm.

[0050] In order to make the content of components contained in the bottom stream of the light-removal tower meet the above requirements, according to a preferred embodiment of the present invention, the number of theoretical plates of the light-removal tower is 25-70.

[0051] In the method provided by the present invention, the lightness removal tower can be operated under reduced pressure or normal pressure.

[0052] According to some preferred embodiments of the present invention, the conditions of the second distillation include: a tower top pressure of 20-101 kPa, and a tower top temperature of 45-90°C.

[0053] Preferably, the conditions of the second distillation include: a tower top pressure of 40-100 kPa, and a tower top temperature of 50-100°C.

[0054] For example, the top pressure of the second distillation tower can be 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa, 100 kPa, or any intermediate value between any two of the above values.

[0055] For example, the top temperature of the second distillation tower can be: 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or any intermediate value between any two of the above values.

[0056] In order to prevent the light component impurities from reacting in the light component removal tower, especially from converting them into heavy component impurities, the bottom temperature of the second distillation should not be too high. Preferably, the conditions of the second distillation also include: the bottom temperature is 60-105°C, preferably 70-100°C.

[0057] For example, the bottom temperature of the second distillation tower can be 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or any intermediate value between any two of the above values.

[0058] Generally speaking, the relative volatility of the light components contained in the norbornene synthesis liquid is quite different from that of norbornene, and they are easy to separate. However, in order to reduce the content of the light components in the bottom extraction stream as much as possible so that it meets the requirements of COC synthesis, a certain reflux ratio is still required to control the content of the light components brought into the norbornene product and improve the purity and quality of the obtained norbornene product. In order to achieve the above purpose, preferably, the reflux ratio of the second distillation is 20-60, preferably 25-45.

[0059] According to a preferred embodiment of the present invention, the light components such as cyclopentadiene, pentene, and pentadiene are contained in the light-removal tower top stream obtained in step (2).

[0060] According to a preferred embodiment of the present invention, the de-light tower bottom stream obtained in step (2) contains norbornene, and its purity is relatively high, which can meet the requirements for preparing COC, and can be directly packaged and used as a high-purity norbornene product. There may also be a very small amount of toluene in the de-light tower bottom stream. According to actual production needs, in order to further reduce the impurity content in the norbornene product, step (2) may further include an operation of removing toluene from the de-light tower bottom stream.

[0061] Since in the method of the present invention, the deweighting tower bottom stream obtained in step (1) contains part of norbornene, in order to avoid waste of resources, it should be considered to recover this part of norbornene, so as to improve the overall yield of norbornene. In addition, considering that the solvent and part of the heavy components (such as dicyclopentadiene, tetracyclododecene, etc.) are raw materials in the production process of norbornene, in order to improve resource utilization and production efficiency, these components can also be recovered and recycled. Therefore, according to some preferred embodiments of the present invention, wherein the method further includes the step of recovering at least one of the norbornene, solvent and heavy components in the deweighting tower bottom stream obtained in step (1).

[0062] In the present invention, any method known in the art that can achieve separation of the desired target substance can be used to recover norbornene, solvent, and some of the usable heavy components in the deweighting tower bottom stream. Those skilled in the art can choose to recover and recycle one or some of the components according to the needs.

[0063] In order to obtain higher resource utilization and make the production process more in line with the requirements of green and sustainable development, according to a preferred embodiment of the present invention, the method may further include:

[0064] (3) norbornene recovery: introducing the deweighting tower bottom stream obtained in step (1) into a norbornene recovery tower for third distillation to obtain a norbornene recovery tower bottom stream and a norbornene recovery tower top stream;

[0065] (4) solvent recovery: introducing the norbornene recovery tower bottom stream obtained in step (3) into a solvent recovery tower, performing a fourth distillation to obtain a solvent recovery tower bottom stream and a solvent recovery tower top stream, and recycling the solvent recovery tower top stream as a recovery solvent; and

[0066] Optionally, (5) intermediate product recovery: separating and recovering tetracyclododecene and / or dicyclopentadiene in the solvent recovery tower bottom stream obtained in step (4), preferably, the separation method is selected from distillation and / or depolymerization reaction distillation.

[0067] In the present invention, the purpose of step (3) is to recover the norbornene remaining in the bottom stream of the deweighting tower, thereby increasing the overall yield of norbornene and reducing the loss of norbornene.

[0068] In order to further reduce the loss of norbornene, according to a preferred embodiment of the present invention, the conditions of the third distillation are such that the content of norbornene in the bottom stream of the norbornene recovery tower does not exceed 1% by weight, preferably does not exceed 0.5% by weight, and more preferably does not exceed 0.3% by weight.

[0069] In order to maximize the amount of norbornene that enters the norbornene recovery tower top stream through the third distillation, part of the toluene may be allowed to enter the norbornene recovery tower top stream. Preferably, the third distillation conditions allow 15-30 wt% of the toluene in the weight removal tower bottom stream to enter the norbornene recovery tower top stream.

[0070] In order to reduce equipment coking, tetracyclododecene and other heavy components should be avoided as much as possible from entering the norbornene recovery tower overhead stream. Preferably, the conditions of the third distillation are such that the total content of heavy components (with a boiling point above toluene) in the norbornene recovery tower overhead stream does not exceed 100 ppm. Preferably, it does not exceed 75 ppm. For example, it can be 75 ppm, 65 ppm, 55 ppm, 45 ppm, 35 ppm, 25 ppm, 15 ppm, 5 ppm, 1 ppm, 0, or any intermediate value between any two of the above values.

[0071] In order to make the content of components contained in the norbornene recovery tower top stream and the norbornene recovery tower bottom stream meet the above requirements, preferably, the number of theoretical plates of the norbornene recovery tower is 15-60, preferably 20-40. It is preferred to feed at the top of the norbornene recovery tower. That is, the feed port position can be set at more than 1 / 2 position of the packing or tower plate from the upper end, preferably at 1 / 6-1 / 2 position.

[0072] In order to prevent the heavy components in the deheaving tower bottom stream from reacting during the third distillation process and reduce equipment coking, the third distillation is preferably operated under reduced pressure or normal pressure.

[0073] Preferably, the conditions of the third distillation include: a tower top pressure of 20-101 kPa, and a tower top temperature of 70-120°C.

[0074] More preferably, the conditions of the third distillation include: a tower top pressure of 50-100 kPa, and a tower top temperature of 80-110°C.

[0075] More preferably, the conditions of the third distillation further include: a tower bottom temperature of 80-130°C, preferably a tower bottom temperature of 90-120°C.

[0076] More preferably, the reflux ratio of the third distillation is 2-12, preferably 3-6.

[0077] According to a preferred embodiment of the present invention, the top stream of the norbornene recovery tower obtained in step (3) contains: (a small amount of) toluene and norbornene.

[0078] According to a preferred embodiment of the present invention, the bottom stream of the norbornene recovery tower obtained in step (3) contains: toluene and heavy components.

[0079] Toluene is usually used to dissolve dicyclopentadiene in the norbornene production process. Therefore, when toluene is recovered in step (4), dicyclopentadiene in the logistics can also be separated out together with toluene. Moreover, even if dicyclopentadiene is depolymerized to generate cyclopentadiene during this logistics separation process, it is allowed. However, if tetracyclododecene enters toluene again, heavier components will be generated in the next norbornene synthesis process. Therefore, the conditions of the fourth distillation should be controlled to avoid tetracyclododecene and the like from entering the solvent recovery tower overhead logistics as much as possible.

[0080] According to a preferred embodiment of the present invention, the conditions of the fourth distillation are such that the content of tetracyclododecene in the solvent recovery weight removal tower overhead stream does not exceed 1% by weight, preferably does not exceed 0.5% by weight.

[0081] Preferably, the fourth distillation is carried out under conditions such that the content of dicyclopentadiene in the solvent recovery tower bottom stream does not exceed 10 wt %, for example, 10 wt %, 9 wt %, 8 wt %, 7 wt %, 6 wt %, 5 wt %, 4 wt %, 3 wt %, 2 wt %, 1 wt %, 0.5 wt %, 0.1 wt %, 0.05 wt %, 0.01 wt %, 0, or any intermediate value between any two of the above values.

[0082] In order to ensure that the contents of components in the solvent recovery tower top stream and the solvent recovery tower bottom stream meet the aforementioned requirements, preferably, the number of theoretical plates of the solvent recovery tower is 5-25.

[0083] In order to avoid the reaction of the heavy components and the resulting coking of the equipment, the fourth distillation is preferably carried out under reduced pressure or normal pressure.

[0084] According to a preferred embodiment of the present invention, the conditions of the fourth distillation include: a tower top pressure of 20-101 kPa, and a tower top temperature of 70-120°C.

[0085] Preferably, the conditions of the fourth distillation include: a tower top pressure of 50-100 kPa, and a tower top temperature of 80-115°C.

[0086] More preferably, the conditions of the fourth distillation further include: a tower bottom temperature of 160-250°C, preferably a tower bottom temperature of 180-230°C.

[0087] More preferably, the reflux ratio of the fourth distillation is 0.2-3, preferably 0.3-1.

[0088] According to a preferred embodiment of the present invention, the solvent recovery tower top stream obtained in step (4) contains toluene and may also contain cyclopentadiene and dicyclopentadiene.

[0089] According to a preferred embodiment of the present invention, the solvent recovery tower bottom stream obtained in step (4) contains heavy components such as tetracyclododecene.

[0090] In the present invention, in order to reduce the loss of norbornene, part of the toluene is allowed to enter the norbornene recovery tower overhead stream obtained by the third distillation, resulting in a lower purity of this stream. It cannot be used directly as a high-purity norbornene product. However, further separation will bring additional costs and energy consumption. Therefore, considering the economic and environmental costs of the entire process, it is more preferred to recycle the norbornene recovery tower overhead stream rather than directly purifying the high-purity norbornene product from the norbornene recovery tower overhead stream.

[0091] Based on the above purpose, according to a preferred embodiment of the present invention, the method further comprises:

[0092] (6) Material circulation: introducing the top stream of the norbornene recovery tower obtained in step (3) into a de-weighting tower, and / or introducing 40-60 wt % of the top stream of the light-removal tower obtained in step (2) into a de-weighting tower.

[0093] The above-mentioned method is used for material circulation. On the one hand, the overall yield of norbornene is improved and resource waste is avoided. On the other hand, the production cost and energy consumption are reduced, which is conducive to improving production efficiency.

[0094] The second aspect of the present invention provides a system for extracting high-purity norbornene (using the above method), the system comprising a heavy removal tower and a light removal tower;

[0095] The material inlet and outlet of the de-weighting tower include: the inlet of the material to be de-weighted, the outlet of the bottom logistics of the de-weighting tower and the outlet of the top logistics of the de-weighting tower;

[0096] The material inlet and outlet of the light-removal tower include: the inlet of the material to be removed, the outlet of the bottom logistics of the light-removal tower and the outlet of the top logistics of the light-removal tower;

[0097] The top logistics outlet of the deheaving tower is connected to the inlet of the light material to be removed, and the bottom logistics outlet of the deheaving tower is connected to the inlet of the material to be refined of the refining tower. Preferably, the bottom logistics outlet of the refining tower is connected to the inlet of the material to be pre-deheavy removed.

[0098] According to a preferred embodiment of the present invention, the number of theoretical plates of the deweighting tower is 15-55.

[0099] Preferably, the inlet of the material to be deweighted divides the deweighting tower into a distillation section and a stripping section, and the number of theoretical plates of the stripping section of the pre-deweighting tower does not exceed 1 / 2 of the total theoretical plates, preferably does not exceed 1 / 3.

[0100] According to a preferred embodiment of the present invention, the number of theoretical plates of the lightness removal tower is 25-70.

[0101] Preferably, the inlet for the light material to be removed divides the light-removing tower into a distillation section and a stripping section, and the number of theoretical plates of the distillation section of the light-removing tower does not exceed 1 / 2 of the total theoretical plates, preferably does not exceed 1 / 3.

[0102] Preferably, the outlet of the top stream of the light-removal tower is divided into two outlets, one of which is connected to the inlet of the heavy-removal tower for the heavy-removal material to be removed.

[0103] According to some preferred embodiments of the present invention, the system further comprises a norbornene recovery tower (for recovering norbornene from the deweighting tower bottom stream);

[0104] The material inlet and outlet of the norbornene recovery tower include: an inlet I for materials to be recovered, a bottom logistics outlet of the norbornene recovery tower, and a top logistics outlet of the norbornene recovery tower;

[0105] Among them, the deweighting tower bottom logistics outlet of the deweighting tower is connected to the material inlet I to be recovered of the norbornene recovery tower.

[0106] Preferably, the norbornene recovery tower has 15-60 theoretical plates.

[0107] Preferably, the material inlet I to be recovered divides the norbornene recovery tower into a distillation section and a stripping section, and the number of theoretical plates of the distillation section of the norbornene recovery tower does not exceed 1 / 2 of the total theoretical plates, preferably 1 / 6-1 / 2 of the total theoretical plates.

[0108] According to some preferred embodiments of the present invention, the system further comprises a solvent recovery tower (for recovering toluene, dicyclopentadiene, cyclopentadiene and other components in the bottom stream from norbornene);

[0109] The material inlets and outlets of the solvent recovery tower include: an inlet II for materials to be recovered, a bottom stream outlet of the solvent recovery tower, and a top stream outlet of the solvent recovery tower;

[0110] The norbornene recovery tower bottom stream outlet of the norbornene recovery tower is connected to the to-be-recovered material inlet II of the solvent recovery tower.

[0111] Preferably, the number of theoretical plates of the solvent recovery tower is 5-25.

[0112] According to some preferred embodiments of the present invention, the system further comprises an optional solvent recovery device and an optional intermediate product recovery device. "Optional" means that the device can be selectively added to the system provided by the present invention according to actual conditions and needs, and when the optional device is not added, the system can already achieve the purpose of the present invention, and after the optional device is added, a better effect can be obtained, or a new effect can be obtained on the basis of (substantially without affecting) the original effect.

[0113] Preferably, the solvent recovery tower top stream outlet is connected to a solvent recovery device.

[0114] Preferably, the solvent recovery tower bottom stream outlet is connected to an intermediate product recovery device. Preferably, the intermediate product recovery device contains a device for separating and recovering tetracyclododecene and / or dicyclopentadiene. For example, the intermediate product recovery device may include: a distillation device and / or a depolymerization reaction distillation device.

[0115] The present invention will be described in detail below by way of examples. It should be understood that the following examples are only used to further explain and illustrate the content of the present invention by way of example, and are not intended to limit the present invention.

[0116] In the following examples, unless otherwise specified, the reagents used were all commercial products obtained from regular chemical suppliers, and the purity was analytically pure. The flow rate of each step was detected by a mass flow meter, and the top / bottom flow components obtained in each step were analyzed by gas chromatography and the weight proportion of each component was calculated (in Tables 1-9, " / " represents not detected).

[0117] Example 1

[0118] use Figure 1 The system shown in the figure is used to separate norbornene from the norbornene synthesis liquid according to the following method. The norbornene synthesis liquid used in this embodiment is a simplified simulated norbornene synthesis liquid prepared according to the proportion of logistics S-1 in Table 1 with reference to the composition of the industrially produced norbornene synthesis liquid. The logistics flow and composition of each step are detailed in Table 1.

[0119] (1) De-weighting: The norbornene synthesis liquid S-1 is introduced into the de-weighting tower T-1 for the first distillation to obtain the de-weighting tower bottom stream S-3 and the de-weighting tower top stream S-2.

[0120] The number of theoretical plates of the deweighting tower T-1 is 30, and the inlet of the norbornene synthesis liquid is arranged at the 20th theoretical plate from top to bottom.

[0121] The conditions of the first distillation include: top pressure 49 kPa, top temperature 70° C., bottom temperature 94° C., and reflux ratio 3.

[0122] According to the calculation of the flow rate, about 4.53 wt % of norbornene in the norbornene synthesis liquid enters the bottom flow of the deweighting tower.

[0123] (2) Light removal: The top stream S-2 of the heavy removal tower is introduced into the light removal tower T-2 for secondary distillation to obtain the light removal tower bottom stream S-5 and the light removal tower top stream S-4.

[0124] The number of theoretical plates of the light-removal tower T-2 is 40, and the inlet for the light-removal material is set at the 15th theoretical plate from top to bottom.

[0125] The conditions of the second distillation include: top pressure 50 kPa, top temperature 61° C., bottom temperature 76° C., and reflux ratio 30.

[0126] (3) Norbornene recovery: The deheaving tower bottom stream S-3 is introduced into the norbornene recovery tower T-3 for the third distillation to obtain the norbornene recovery tower bottom stream S-7 and the norbornene recovery tower top stream S-6.

[0127] The number of theoretical plates of the norbornene recovery tower is 30, and the inlet I for the material to be recovered is set at the 5th theoretical plate from top to bottom.

[0128] The conditions of the third distillation include: top pressure 50 kPa, top temperature 84° C., bottom temperature 95.7° C., and reflux ratio 4.

[0129] According to the calculation of the flow rate of the logistics, about 21.4 wt % of the toluene in the bottom logistics of the deweighting tower enters the top logistics of the norbornene recovery tower.

[0130] (4) Solvent recovery: The norbornene recovery tower bottom stream S-7 is introduced into the solvent recovery tower T-4 for fourth distillation to obtain the solvent recovery tower bottom stream S-9 and the solvent recovery tower top stream S-8.

[0131] The number of theoretical plates of the solvent recovery tower is 10, and the inlet II for the material to be recovered is arranged at the 5th theoretical plate from top to bottom.

[0132] The conditions of the fourth distillation include: top pressure 50 kPa, top temperature 89° C., bottom temperature 207.7° C., and reflux ratio 0.5.

[0133] The solvent recovery tower top stream S-8 can be collected and reused as the recovery solvent in the norbornene synthesis process. The solvent recovery tower bottom stream S-9 can be further separated and the tetracyclododecene and dicyclopentadiene therein can be recovered and reused in the norbornene synthesis process.

[0134] Table 1

[0135] Logistics components S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 <![CDATA[Mass flow rate / kg·h -1 > 1024 627.7 521.9 6.22 621.5 125.6 396.3 372 24.3 Cyclopentadiene / wt.% 0.04 0.07 / 6.56 2ppm / / / / Toluene / wt.% 36.00 0.70 88.67 2ppm 0.71 78.41 91.92 97.92 1ppm Norbornene / wt.% 60.95 99.23 5.42 93.44 99.29 21.59 0.30 0.32 / Tetracyclododecene / wt.% 2.15 / 4.22 / / / 5.55 0.17 88.17 Dicyclopentadiene / wt.% 0.58 / 1.14 / / / 1.50 1.60 / Tricyclopentadiene / wt.% 0.28 / 0.55 / / / 0.72 / 11.82

[0136] From the data in Table 1, it can be seen that there is very little toluene in the top stream of the de-heavy tower, so the toluene content of the norbornene product extracted at the bottom of the light tower will be very low, which improves the purity of the norbornene product. There is very little material extracted from the top of the light tower, indicating that the separation effect of the light tower is very good, and the norbornene product can be obtained at a high yield. The purity of norbornene in the bottom stream of the light tower is 99.29%, which can be directly used as a high-purity norbornene product, in which the impurities contain only 2ppm cyclopentadiene, and the balance is toluene, which can meet the COC production requirements.

[0137] The above method returns the top stream of the norbornene recovery tower to the deweighting tower, which not only recovers the norbornene therein, but also reduces the separation load of the deweighting tower and reduces its separation effect. By controlling the content of norbornene in the bottom stream of the norbornene recovery tower, the overall yield of norbornene is further improved.

[0138] The solvent recovery tower further separates the solvent and heavy components in the bottom stream of the norbornene recovery tower, and can recover the solvent and reuse it in the norbornene production process, thereby reducing resource waste, and also recovering a small amount of norbornene therein, further improving the overall yield of norbornene.

[0139] According to the calculation of the flow rate of the logistics, the yield of norbornene in this embodiment is 98.88%, and the recovery rate of the solvent is 98.81%.

[0140] Example 2

[0141] The method in Example 1 is adopted, except that the toluene content in the deheaving tower top stream is controlled to be 0.3%, and the cyclopentadiene content in the deheaving tower bottom stream is controlled to be 1 ppm. The process and feed position are the same as those in Example 1, and the other operations and conditions are as follows. The stream flow and composition of each step are detailed in Table 2. The norbornene synthetic liquid used in this example is a simulated norbornene synthetic liquid prepared according to the proportion of stream S-1 in Table 2 with reference to the composition of the industrially produced norbornene synthetic liquid.

[0142] (1) Weight removal: tower top pressure 49 kPa, tower top temperature 69.8°C, tower bottom temperature 92.5°C, reflux ratio 3. The toluene content in the tower top stream was controlled to be 0.30% by adjusting the tower top extraction flow rate. According to the flow rate calculation, about 9.03 wt% of norbornene in the norbornene synthesis liquid entered the weight removal tower bottom stream.

[0143] (2) Light removal: tower top pressure 50 kPa, tower top temperature 50.9 °C, tower bottom temperature 76.4 °C, reflux ratio 30, and the CPD content in the tower bottom flow is controlled to be 1 ppm by adjusting the tower top extraction volume.

[0144] (3) Norbornene recovery: tower top pressure 50 kPa, tower top temperature 81.1°C, tower bottom temperature 95.7°C, reflux ratio 4, adjust the tower top flow to control the norbornene content in the tower bottom stream to 0.30%. According to the stream flow calculation, about 20.5 wt% of the toluene in the deweighting tower bottom stream enters the norbornene recovery tower top stream.

[0145] (4) Solvent recovery: tower top pressure 50 kPa, tower top temperature 88.8°C, tower bottom temperature 197.8°C, reflux ratio 0.5.

[0146] Table 2

[0147]

[0148] It can be seen from the data in Table 2 that the method of the present invention can reduce the cyclopentadiene content in the norbornene product to about 1 ppm, and the toluene content is controllable, making it particularly suitable for COC production.

[0149] According to the calculation of the flow rate of the logistics, the yield of norbornene in this example is 98.95%, and the recovery rate of the solvent is 99.49%.

[0150] Example 3

[0151] The method in Example 2 was used, except that the reflux ratio of the deweighting tower was controlled to be 4, so that the norbornene entering the bottom stream of the deweighting tower accounted for 1.61% by weight of the norbornene in the synthetic liquid. The other conditions were basically the same as in Example 2, as follows. The flow rate and composition of the streams in each step are detailed in Table 3.

[0152] (1) Weight removal: tower top pressure 50 kPa, tower top temperature 70.4°C, tower bottom temperature 95°C, reflux ratio 4, and the toluene content in the tower top stream was controlled to be 0.30% by adjusting the tower top extraction flow rate.

[0153] (2) Light removal: tower top pressure 50 kPa, tower top temperature 51 °C, tower bottom temperature 76.4 °C, reflux ratio 30, and the CPD content in the tower bottom flow is controlled to be 1 ppm by adjusting the tower top extraction volume.

[0154] (3) Norbornene recovery: tower top pressure 50 kPa, tower top temperature 86.7°C, tower bottom temperature 95.7°C, reflux ratio 4, adjust the tower top flow to control the norbornene content in the tower bottom stream to 0.30%. According to the stream flow calculation, about 19.97 wt% of toluene in the deweighting tower bottom stream enters the norbornene recovery tower top stream.

[0155] (4) Solvent recovery: tower top pressure 50 kPa, tower top temperature 88.8°C, tower bottom temperature 197.8°C, reflux ratio 0.5.

[0156] Table 3

[0157] Logistics components S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 <![CDATA[Mass flow rate / kg·h -1 > 1024 625.11 499.27 6.24 618.88 100.39 398.89 372 26.89 2-Methyl-1-butene / wt.% 0.03 0.0491 / 4.92 / / / / / Isoprene / wt.% 0.01 0.0164 / 1.64 / / / / / Cyclopentadiene / wt.% 0.04 0.0655 / 6.56 1ppm / / / / Toluene / wt.% 36.00 0.30 91.79 0.9ppm 0.30 91.17 91.95 98.59 0.02 Norbornene / wt.% 60.90 99.57 2.01 86.88 99.70 8.82 0.30 0.32 / Tetracyclododecene / wt.% 2.15 / 4.41 / / / 5.52 1.8ppm 81.88 Dicyclopentadiene / wt.% 0.58 / 1.19 / / 16ppm 1.49 1.06 7.43 Tanrene / wt.% 0.01 / 0.02 / / 49ppm 0.0257 0.03 1.8ppm Tricyclopentadiene / wt.% 0.28 / 0.57 / / / 0.72 / 10.66

[0158] It can be seen from the data in Table 3 that the method of the present invention can allow a small amount of norbornene to enter the deweighting tower bottom stream, reduce the cyclopentadiene content in the norbornene product to about 1 ppm, and control the toluene content, making it particularly suitable for COC production.

[0159] According to the calculation of the flow rate of the logistics, the yield of norbornene in this example is 98.94%, and the recovery rate of the solvent is 99.49%.

[0160] Example 4

[0161] The method of Example 3 is adopted, except that the operating pressure at the top of the four distillation towers is 80 kPa, and the top temperature and bottom temperature are as follows. The flow rate and composition of the logistics in each step are detailed in Table 4.

[0162] (1) Weight removal: Tower top pressure 80 kPa, tower top temperature 93.9°C, tower bottom temperature 111.1°C, reflux ratio 4, and the toluene content in the tower top stream was controlled to be 0.30% by adjusting the tower top extraction flow rate. According to the flow rate calculation, about 8.51 wt% of norbornene in the norbornene synthesis liquid entered the weight removal tower bottom stream.

[0163] (2) Light removal: Tower top pressure 80 kPa, tower top temperature 67.9 °C, tower bottom temperature 90.3 °C, reflux ratio 30, and the CPD content in the tower bottom flow is controlled to be 1 ppm by adjusting the tower top extraction volume.

[0164] (3) Norbornene recovery: Tower top pressure 80 kPa, tower top temperature 97.8°C, tower bottom temperature 109.4°C, reflux ratio 4, adjust the tower top flow to control the norbornene content in the tower bottom stream to be 0.30%. According to the flow rate calculation, about 24.71 wt% of toluene in the deweighting tower bottom stream enters the norbornene recovery tower top stream.

[0165] (4) Solvent recovery: tower top pressure 80 kPa, tower top temperature 104.1°C, tower bottom temperature 215.7°C, reflux ratio 0.5.

[0166] Table 4

[0167]

[0168] It can be seen from the data in Table 4 that the method of the present invention can allow a small amount of norbornene to enter the deweighting tower bottom stream, reduce the cyclopentadiene content in the norbornene product to about 1 ppm, and control the toluene content, making it particularly suitable for COC production.

[0169] According to the calculation of the flow rate of the logistics, the yield of norbornene in this example is 98.94%, and the recovery rate of the solvent is 99.49%.

[0170] Example 5

[0171] The method of Example 3 was adopted, except that the operating pressure at the top of the four distillation towers was controlled to be 100 kPa, and the top temperature and bottom temperature were as follows. The flow rate and composition of the logistics in each step are detailed in Table 5.

[0172] (1) Weight removal: tower top pressure 100 kPa, tower top temperature 93.9°C, tower bottom temperature 114.7°C, reflux ratio 5. According to the flow rate calculation, about 6.5 wt% of norbornene in the norbornene synthesis liquid enters the weight removal tower bottom flow.

[0173] (2) Light removal: tower top pressure 100 kPa, tower top temperature 76.5 °C, tower bottom temperature 97.6 °C, reflux ratio 30, and the CPD content in the tower bottom flow is controlled to be 1 ppm by adjusting the tower top extraction volume.

[0174] (3) Norbornene recovery: The tower top pressure was 100 kPa, the tower top temperature was 107.2°C, the tower bottom temperature was 116.7°C, the reflux ratio was 4, and the tower top flow rate was adjusted to control the norbornene content in the tower bottom stream to be 0.30%. According to the flow rate calculation, about 26.97 wt% of the toluene in the deweighting tower bottom stream entered the norbornene recovery tower top stream.

[0175] (4) Solvent recovery: tower top pressure 100 kPa, tower top temperature 111.8°C, tower bottom temperature 224.6°C, reflux ratio 0.5.

[0176] Table 5

[0177] Logistics components S-1 S-2 S-3 S-4 S-5 S-6 S-7 S-8 S-9 <![CDATA[Mass flow rate / kg·h -1 > 1024 625.00 573.85 7.45 617.56 174.85 399.0 372 27.00 2-Methyl-1-butene / wt.% 0.03 0.0492 / 4.13 / / / / / Isoprene / wt.% 0.01 0.0164 / 5.49 / / / / / Cyclopentadiene / wt.% 0.04 0.0655 / 5.82 1ppm / / / / Toluene / wt.% 36.00 0.28 87.54 3.4ppm 0.29 77.49 91.95 98.62 0.05 Norbornene / wt.% 60.90 99.59 7.06 89.01 99.71 22.50 0.30 0.32 / Tetracyclododecene / wt.% 2.15 / 3.84 / / / 5.52 4.8ppm 81.54 Dicyclopentadiene / wt.% 0.58 / 1.04 / / 16ppm 1.49 1.03 7.79 Tanrene / wt.% 0.01 / 0.02 / / 26ppm 0.0257 0.03 5.8ppm Tricyclopentadiene / wt.% 0.28 / 0.50 / / / 0.72 / 10.62

[0178] It can be seen from the data in Table 5 that the method of the present invention can allow a small amount of norbornene to enter the deweighting tower bottom stream, reduce the cyclopentadiene content in the norbornene product to about 1 ppm, and control the toluene content, making it particularly suitable for COC production.

[0179] According to the calculation of the flow rate of the logistics, the yield of norbornene in this example is 98.75%, and the recovery rate of the solvent is 99.52%.

[0180] Example 6

[0181] The method in Example 2 was used, except that the pressure at the top of the de-heavy tower was 50 kPa, the temperature at the top was 70.4°C, and the temperature at the bottom was 94.2°C; the pressure at the light tower was 50 kPa, the temperature at the top was 50.4°C, and the temperature at the bottom was 76.4°C. Only the bottom stream of the de-heavy tower was collected, and steps (3) and (4) were not performed. The remaining operations and conditions were the same as those in Example 2. The flow composition of the streams in each step is shown in Table 6.

[0182] Table 6

[0183] Logistics components S-1 S-2 S-3 S-4 S-5 <![CDATA[Mass flow rate / kg·h -1 > 1024 599.49 424.51 5.98 593.51 2-Methyl-1-butene / wt.% 0.03 0.0512 / 5.14 / Isoprene / wt.% 0.01 0.0171 / 1.71 / Cyclopentadiene / wt.% 0.04 0.0683 / 6.84 1ppm Toluene / wt.% 36.00 0.30 86.42 0.9ppm 0.30 Norbornene / wt.% 60.90 99.56 6.30 86.31 99.70 Tetracyclododecene / wt.% 2.15 / 5.19 / / Dicyclopentadiene / wt.% 0.58 / 1.40 / / Tanrene / wt.% 0.01 / 0.02 / / Tricyclopentadiene / wt.% 0.28 / 0.68 / /

[0184] By comparing the data in the above table with those in Table 2, it can be seen that although the purity of norbornene extracted from the bottom of the light removal tower can be very high by changing the top extraction amount of the heavy removal tower and the light removal tower, the yield of norbornene is 94.88%. Obviously, such a treatment method causes the loss of norbornene and discards toluene, and the economic efficiency is not as good as that of Example 2. If the collected heavy removal tower bottom stream is directly treated harmlessly and then discarded, on the one hand, the cost of environmental protection treatment is increased, and on the other hand, norbornene and a large amount of toluene are wasted, which increases the overall cost of norbornene production.

[0185] Example 7

[0186] The method of Example 2 is adopted, except that the top stream of the light-removing tower is divided into two streams, so that about 50% of the original flow, 3kg / h, is returned to the inlet of the pre-deweighting tower for circulation, and the rest is extracted as S-4. Other operations, control indicators and conditions are basically the same as those of Example 2. The flow rate and composition of the streams in each step are shown in Table 7.

[0187] Table 7

[0188]

[0189] Comparing the data in Table 2 and Table 7, it can be seen that in the method of the present invention, 50% of the original flow rate of the overhead stream from the light-removal tower is recycled, and the rest is removed, which not only avoids the accumulation of these light components in the system, but also increases the content of light components in the overhead stream of the light-removal tower, thereby reducing the content of norbornene in the overhead stream, thereby improving the yield of norbornene.

[0190] According to the calculation of the logistics flow rate, the yield of norbornene in this example is 99.43%, and the product quality remains unchanged.

[0191] Comparative Example 1

[0192] This comparative example is used to illustrate the effect of allowing only a small amount of norbornene in the synthesis liquid to enter the deweighting tower bottom stream.

[0193] By adopting the method in Example 2, the extraction amount of toluene in the overhead stream is maintained at about 0.3% by weight, except that the content of norbornene in the bottom stream of the de-weighting tower is 0.26%, which requires a reflux ratio of 8 for the de-weighting tower, and a flow rate of 625kg / h for the overhead stream, accounting for 61% of the feed amount of the de-weighting tower. Such a large reflux ratio and reflux rate will make the energy consumption of the de-weighting tower very high, and will undoubtedly extend the residence time of the material in the tower body, so that the cyclopentadiene dimerization of the material in the distillation section generates dicyclopentadiene and is brought into the overhead stream, resulting in a higher content of dicyclopentadiene in the bottom stream of the de-lighting tower. The remaining operations and conditions are the same as in Example 2. The composition of the stream flow rate of each step is shown in Table 8.

[0194] Table 8

[0195] Logistics components S-1 S-2 S-3 S-4 S-5 <![CDATA[Mass flow rate / kg·h -1 > 1024 625.40 413.60 6.18 619.22 2-Methyl-1-butene / wt.% 0.03 0.0491 / 4.97 / Isoprene / wt.% 0.01 0.0164 / 1.66 / Cyclopentadiene / wt.% 0.04 0.0643 / 6.62 1ppm Toluene / wt.% 36.00 0.30 92.26 0.9ppm 0.30 Norbornene / wt.% 60.90 99.57 0.26 86.76 99.70 Tetracyclododecene / wt.% 2.15 / 5.32 / / Dicyclopentadiene / wt.% 0.58 12ppm 1.44 / 12ppm Tanrene / wt.% 0.01 / 0.03 / / Tricyclopentadiene / wt.% 0.28 / 0.69 / /

[0196] It can be seen from the data in Table 8 that if toluene and norbornene are completely separated in the de-weighting tower, a larger reflux ratio and reflux amount will be required, causing cyclopentadiene to dimerize to form dicyclopentadiene, and the heavy components extracted from the top of the de-weighting tower will be brought into the norbornene product, affecting the quality of the norbornene product.

[0197] Comparative Example 2

[0198] The method in Example 2 was adopted, except that the conditions of the first distillation were controlled so that approximately 15 wt%, 20 wt%, and 25 wt% of the norbornene in the synthetic liquid entered the deweighting tower bottom stream, respectively. The remaining operations and conditions were the same as in Example 2. The specific stream flow rates and compositions are listed in Table 9.

[0199] Table 9

[0200]

[0201]

[0202] By comparing the data in Table 9 and Table 2, it can be seen that when the proportion of norbornene in the synthetic liquid entering the de-weighting tower bottom stream is increased, the norbornene flow rate in the norbornene recovery tower top stream also increases. For example, when about 15% by weight of norbornene in the synthetic liquid enters the de-weighting tower bottom stream, the norbornene flow rate in the norbornene recovery tower top stream is 91.80 kg / h, which is about 66.6% higher than 55.11 kg / h in Example 2. This shows that in the method of this comparative example, more norbornene has been circulating in the distillation system, which will inevitably cause the loss of norbornene by side reactions. In addition, it can be seen from Table 9 that the de-weighting tower bottom stream contains too much norbornene and does not improve and enhance the quality of the norbornene product. Combined with the results of Comparative Example 1, it can be seen that only when the proportion of norbornene entering the bottom flow of the deweighting tower is within the preferred range of the present invention can the effect of simultaneously improving the norbornene yield and product quality be obtained. When the proportion of norbornene entering the bottom flow of the deweighting tower exceeds or is lower than this range, it will have an adverse effect on the product quality or yield.

[0203] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for extracting high-purity norbornene, characterized in that: The method comprises: (1) De-weighting: The norbornene synthesis liquid is introduced into a de-weighting tower for first distillation to obtain a de-weighting tower bottom stream and a de-weighting tower top stream. The conditions of the first distillation are such that no more than 15 wt% of norbornene in the norbornene synthesis liquid enters the de-weighting tower bottom stream, and the toluene content in the de-weighting tower top stream does not exceed 1 wt%; (2) removing light substances: introducing the overhead stream of the heavy removal tower obtained in step (1) into a light removal tower for secondary distillation to obtain a light removal tower bottom stream and a light removal tower overhead stream; Wherein, the conditions of the second distillation are such that the total content of cyclopentadiene and dicyclopentadiene in the light-removal tower bottom stream does not exceed 10 ppm.

2. The method according to claim 1, wherein: In step (1), the conditions of the first distillation are such that no more than 10 wt % of norbornene in the norbornene synthesis liquid enters the bottom stream of the deweighting tower, preferably such that 1-10 wt % of norbornene in the norbornene synthesis liquid enters the bottom stream of the deweighting tower; Preferably, the conditions of the first distillation are such that the toluene content in the weight removal tower top stream does not exceed 0.7 wt%.

3. The method according to claim 1 or 2, wherein: The number of theoretical plates of the deweighting tower is 15-55, and the conditions of the first distillation preferably include: the tower top pressure is 20-101 kPa, and the tower top temperature is 45-110°C; Preferably, the conditions of the first distillation further include: the tower bottom temperature is 75-120°C, preferably 80-115°C; More preferably, the reflux ratio of the first distillation is 1-7, preferably 2-5.

4. The method according to claim 1, wherein: In step (2), the conditions of the second distillation are such that the cyclopentadiene content in the light-removal tower bottom stream does not exceed 5 ppm, preferably does not exceed 2 ppm.

5. The method according to claim 1 or 4, wherein: The number of theoretical plates of the light removal tower is 25-70, and the conditions of the second distillation preferably include: the tower top pressure is 20-101 kPa, and the tower top temperature is 45-90°C; Preferably, the conditions of the second distillation further include: a tower bottom temperature of 60-105°C, preferably 70-100°C; More preferably, the reflux ratio of the second distillation is 20-60, preferably 25-45.

6. The method according to any one of claims 1 to 5, wherein: The method further comprises the step of recovering at least one of norbornene, solvent and heavy components in the deheavy tower bottom stream obtained in step (1); Preferably, the method further comprises: (3) norbornene recovery: introducing the deweighting tower bottom stream obtained in step (1) into a norbornene recovery tower for third distillation to obtain a norbornene recovery tower bottom stream and a norbornene recovery tower top stream; (4) solvent recovery: introducing the norbornene recovery tower bottom stream obtained in step (3) into a solvent recovery tower, performing a fourth distillation to obtain a solvent recovery tower bottom stream and a solvent recovery tower top stream, and recycling the solvent recovery tower top stream as a recovery solvent; and Optionally, (5) intermediate product recovery: separating and recovering tetracyclododecene and / or dicyclopentadiene in the solvent recovery tower bottom stream obtained in step (4), preferably, the separation method is selected from distillation and / or depolymerization reaction distillation.

7. The method according to claim 6, wherein: The conditions of the third distillation are such that the content of norbornene in the bottom stream of the norbornene recovery tower does not exceed 1 wt %, preferably does not exceed 0.5 wt %, and more preferably does not exceed 0.3 wt %; Preferably, the conditions of the third distillation are such that 15-30 wt % of toluene in the bottom stream of the weight removal tower enters the top stream of the norbornene recovery tower; Preferably, the number of theoretical plates of the norbornene recovery tower is 15-60, and the third distillation is preferably operated under reduced pressure or normal pressure conditions; More preferably, the conditions of the third distillation include: the tower top pressure is 20-101 kPa, and the tower top temperature is 70-120° C.; More preferably, the conditions of the third distillation further include: a tower bottom temperature of 80-130°C, preferably a tower bottom temperature of 90-120°C; More preferably, the reflux ratio of the third distillation is 2-12, preferably 3-6.

8. The method according to claim 6, wherein: The fourth distillation is performed under conditions such that the content of tetracyclododecene in the solvent recovery tower overhead stream does not exceed 1 wt %; Preferably, the conditions of the fourth distillation are such that the content of dicyclopentadiene in the solvent recovery tower bottom stream does not exceed 10 wt %; Preferably, the number of theoretical plates of the solvent recovery tower is 5-25, and preferably the conditions of the fourth distillation include: the tower top pressure is 20-101 kPa, and the tower top temperature is 70-120° C.; More preferably, the conditions of the fourth distillation further include: a tower bottom temperature of 160-250°C, preferably a tower bottom temperature of 180-230°C; More preferably, the reflux ratio of the fourth distillation is 0.2-3, preferably 0.3-1.

9. The method according to any one of claims 1 to 8, wherein: The method further comprises: (6) Material circulation: introducing the top stream of the norbornene recovery tower obtained in step (3) into a de-weighting tower, and / or introducing 40-60 wt % of the top stream of the light-removal tower obtained in step (2) into a de-weighting tower.

10. A system for extracting high-purity norbornene, characterized in that: The system includes a heavy removal tower and a light removal tower; The material inlet and outlet of the de-weighting tower include: the inlet of the material to be de-weighted, the outlet of the bottom logistics of the de-weighting tower and the outlet of the top logistics of the de-weighting tower; The material inlet and outlet of the light-removal tower include: the inlet of the material to be removed, the outlet of the bottom logistics of the light-removal tower and the outlet of the top logistics of the light-removal tower; The top logistics outlet of the deheaving tower is connected to the inlet of the light material to be removed, and the bottom logistics outlet of the deheaving tower is connected to the inlet of the material to be refined of the refining tower. Preferably, the bottom logistics outlet of the refining tower is connected to the inlet of the material to be pre-deheavy removed.

11. The system according to claim 10, wherein: The number of theoretical plates of the deweighting tower is 15-55; Preferably, the inlet of the material to be deweighted divides the deweighting tower into a rectifying section and a stripping section, and the number of theoretical plates of the stripping section of the pre-deweighting tower does not exceed 1 / 2 of the total theoretical plates, preferably does not exceed 1 / 3; And / or, the number of theoretical plates of the lightness removal tower is 25-70; Preferably, the inlet of the light material to be removed divides the light-removing tower into a rectifying section and a stripping section, and the number of theoretical plates of the rectifying section of the light-removing tower does not exceed 1 / 2 of the total theoretical plates, preferably does not exceed 1 / 3; Preferably, the outlet of the top stream of the light removal tower is divided into two outlets, one of which is connected to the inlet of the heavy removal tower for the material to be removed.

12. The system according to claim 10, wherein: The system also includes a norbornene recovery tower; The material inlet and outlet of the norbornene recovery tower include: an inlet I for materials to be recovered, a bottom logistics outlet of the norbornene recovery tower, and a top logistics outlet of the norbornene recovery tower; Wherein, the deweighting tower bottom stream outlet of the deweighting tower is connected to the inlet I of the material to be recovered of the norbornene recovery tower; Preferably, the number of theoretical plates of the norbornene recovery tower is 15-60; Preferably, the material inlet I to be recovered divides the norbornene recovery tower into a rectification section and a stripping section, and the number of theoretical plates of the rectification section of the norbornene recovery tower does not exceed 1 / 2 of the total theoretical plates, preferably 1 / 6-1 / 2 of the total theoretical plates; And / or, the system further comprises a solvent recovery tower; The material inlets and outlets of the solvent recovery tower include: an inlet II for materials to be recovered, a bottom stream outlet of the solvent recovery tower, and a top stream outlet of the solvent recovery tower; Wherein, the norbornene recovery tower bottom stream outlet of the norbornene recovery tower is connected to the to-be-recovered material inlet II of the solvent recovery tower; Preferably, the number of theoretical plates of the solvent recovery tower is 5-25.

13. The system according to any one of claims 10 to 12, wherein: The system also includes an optional solvent recovery unit and an optional intermediate product recovery unit; Preferably, the solvent recovery tower top stream outlet is connected to a solvent recovery device; Preferably, the bottom stream outlet of the solvent recovery tower is connected to an intermediate product recovery device. Preferably, the intermediate product recovery device contains a device for separating and recovering tetracyclododecene and / or dicyclopentadiene. Preferably, the intermediate product recovery device includes: a distillation device and / or a depolymerization reaction distillation device.

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