Cycloolefin purification method and application thereof

Abstract

The invention provides a cycloolefin purification method and application thereof, and the purification method comprises the following steps: heavy component removal: carrying out first rectification on a cycloolefin crude product in a heavy component removal tower to obtain a heavy component removal tower bottom material flow and a heavy component removal tower top material flow; light component removal: carrying out second rectification on the heavy component removal tower top material flow in a light component removal tower to obtain a light component removal tower bottom material flow and a light component removal tower top material flow; the light component removal tower top material flow comprises a light component removal tower top gas phase material flow and a light component removal tower top liquid phase material flow, the light component removal tower top liquid phase material flow is returned to the heavy component removal tower for cyclic utilization, and the mass percentage content of cyclopentadiene in the light component removal tower top liquid phase material flow is 5-20%; the light component removal tower bottom material flow is subjected to third rectification in a refining tower, a refining tower bottom material flow and a refining tower top material flow are obtained, and the refining tower top material flow is purified cycloolefin. According to the purification method, dynamic conversion of cyclopentadiene and dicyclopentadiene can be inhibited, the impurity removal rate is increased, high-purity and high-yield cycloolefin is obtained, and the cost is low.

Description

Technical Field

[0001] This invention belongs to the field of separation and purification technology, specifically relating to a purification method for cyclic olefins and its application. Background Technology

[0002] Cyclic olefin copolymers are high-performance thermoplastics with high transparency, low water absorption, excellent heat resistance and chemical stability, and are widely used in high-end fields such as optical devices, medical packaging, and electronic components.

[0003] Cyclic olefin copolymers are typically polymerized from cyclic olefin monomers and olefin monomers. The purity and stability of the raw materials directly affect the performance of the copolymers. Therefore, to obtain high-performance cyclic olefin copolymers, high purity is required for the synthetic monomers, especially for cyclic olefin monomers used in coordination polymerization. To avoid affecting reactivity, the monomers must have even higher purity. For example, norbornene (NB), a commonly used core monomer for synthesizing cyclic olefin copolymers (COCs), can be prepared from dicyclopentadiene and olefins, requiring a purity of over 99.5%. However, the composition of its synthesis solution is complex, containing not only unreacted raw materials and byproducts, but also impurities and oligomers carried by the raw materials. Furthermore, dicyclopentadiene easily decomposes into cyclopentadiene at high temperatures, and cyclopentadiene repolymerizes back into dicyclopentadiene at low temperatures. This leads to a dynamic transformation between dicyclopentadiene (DCPD) and cyclopentadiene (CPD) during distillation. This depolymerization-polymerization cycle results in repeated impurity generation, forming closed-loop interference, making separation difficult. Conventional separation and purification processes struggle to stably control impurity content. Furthermore, existing purification methods can only separate and purify systems with low concentrations of cyclopentadiene and dicyclopentadiene. High concentrations of cyclopentadiene and dicyclopentadiene further exacerbate their dynamic transformation, thus increasing the difficulty of separation. Therefore, using existing purification methods to separate systems with high concentrations of cyclopentadiene and dicyclopentadiene is not conducive to obtaining high-purity cycloolefin monomers while simultaneously achieving high yields, and it also consumes a large amount of energy.

[0004] Therefore, developing a purification method that can suppress the dynamic transformation between cyclopentadiene and dicyclopentadiene, and can be used to separate and purify crude cycloolefins containing high contents of cyclopentadiene and dicyclopentadiene, to obtain cycloolefins with high purity and high yield, is an urgent problem to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a purification method for cyclic olefins and its application. This purification method can be used to separate and purify crude cyclic olefin products containing high levels of cyclopentadiene and dicyclopentadiene. It can inhibit the dynamic transformation between cyclopentadiene and dicyclopentadiene, improve the impurity removal rate, and obtain high-purity and high-yield cyclic olefin monomers. Furthermore, the process is reliable, easy to control, operates under mild conditions, and has low energy consumption.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for purifying cyclic olefins, the purification method comprising the following steps: (1) Removal of heavy substances: the crude cyclic olefin product is subjected to a first distillation in a removal column to obtain a bottom stream and a top stream of the removal column; the impurities in the crude cyclic olefin product include cyclopentadiene and dicyclopentadiene, and the total mass percentage of cyclopentadiene and dicyclopentadiene in the crude cyclic olefin product is ≥1%; (2) Removal of light substances: the top stream of the removal column obtained in step (1) is subjected to a second distillation in a removal column to obtain a bottom stream and a top stream of the removal column; the top stream of the removal column includes a gaseous stream and a liquid stream, the liquid stream of the removal column is returned to the removal column for recycling, and the mass percentage of cyclopentadiene in the liquid stream of the removal column is 5~20%; (3) Refining: the bottom stream of the removal column obtained in step (2) is subjected to a third distillation in a refining column to obtain a bottom stream and a top stream of the refining column, the top stream of the refining column being the purified cyclic olefin.

[0008] In this invention, the purification method controls the mass percentage of cyclopentadiene in the liquid stream from the top of the light cyclopentadiene removal tower within a specific range. This inhibits the conversion between cyclopentadiene and dicyclopentadiene, thus suppressing the generation and fall of dicyclopentadiene and preventing its decomposition into cyclopentadiene, thereby reducing the cyclopentadiene content and increasing the impurity removal rate. Furthermore, it prevents the entrainment of large amounts of cycloolefins, leading to cycloolefin loss. The return of the liquid stream from the top of the light cyclopentadiene removal tower to the heavy cyclopentadiene removal tower further reduces cycloolefin loss and improves the overall yield of cycloolefins. Moreover, the combined use of heavy cyclopentadiene removal, light cyclopentadiene removal, and purification processes results in a high yield, high purity, and high impurity removal rate of the final cycloolefins. This method is reliable, easy to control, operates under mild conditions, and has low energy consumption, making it suitable for separating and purifying crude cycloolefin products with high cyclopentadiene and dicyclopentadiene content.

[0009] In this invention, the total mass percentage of cyclopentadiene and dicyclopentadiene in the crude cycloolefin product is ≥1%, for example, it can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.2%, 2.5%, 2.8%, 3% or any of the above values, more preferably 1.1~2%.

[0010] Preferably, the mass percentage of cyclopentadiene in the crude cycloolefin product of step (1) is ≥0.5%, for example, it can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% or any of the above values, more preferably 0.6~1.2%.

[0011] Preferably, the mass percentage of dicyclopentadiene in the crude cycloolefin product of step (1) is ≥0.5%, for example, it can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% or any of the above values.

[0012] Preferably, the impurities in the crude cycloolefin product in step (1) further include tetracyclododecene, and the mass percentage of tetracyclododecene in the crude cycloolefin product is ≥3%, for example, it can be 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5% or any of the above values, more preferably 3.5~4.5%.

[0013] Preferably, the crude cyclic olefin product in step (1) includes crude products of norbornene and / or its derivatives.

[0014] Preferably, the crude cyclic olefin product in step (1) is prepared from a toluene solution of dicyclopentadiene and an olefin compound as raw materials.

[0015] In this invention, the crude cyclic olefin product can be prepared from raw materials or it can be prepared by simulating the composition of crude cyclic olefin products through various impurities.

[0016] In this invention, the crude cyclic olefin product, by mass percentage, comprises 45-55% norbornene, 35-55% toluene, 0.5-2% cyclopentadiene, 0.1-1% ethylene, 0.1-2% dicyclopentadiene, and 3-6% tetracyclododecene.

[0017] Preferably, the mass percentage of norbornene and / or its derivatives in the bottom stream of the deweighting tower in step (1) is ≤20%, preferably ≤15%, and more preferably ≤10%.

[0018] Preferably, the theoretical number of plates in the deweight removal tower in step (1) is 10 to 35, for example, it can be 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34 or any of the above values.

[0019] Preferably, the top temperature of the deweight removal tower in step (1) is ≥50℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃ or any of the above values, more preferably 60~90℃.

[0020] Preferably, the pressure at the top of the deweighting tower in step (1) is 35~75 kPa, for example, it can be 35 kPa, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa, 65 kPa, 70 kPa, 75 kPa or any of the above values.

[0021] Preferably, the bottom temperature of the deweight removal tower in step (1) is 70~130℃, for example, it can be 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃ or any of the above values, more preferably 80~120℃.

[0022] Preferably, the reflux ratio of the de-weighting tower in step (1) is 0.01 to 5, for example, it can be 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.4, 0.6, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or any of the above values, preferably 0.02 to 0.8.

[0023] In this invention, the mass percentage of cyclopentadiene in the liquid stream from the top of the light-light-removal tower is 5-20%, for example, it can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 17%, 18%, 19%, 20%, or any of the above values, more preferably 8-15%.

[0024] Preferably, the theoretical number of plates in the light removal tower in step (2) is 8 to 36, for example, it can be 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 35 or any of the above values, more preferably 12 to 30.

[0025] Preferably, the top temperature of the light-light removal tower in step (2) is ≥50℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃ or any of the above values, more preferably 60~90℃.

[0026] Preferably, the pressure at the top of the light-weight removal tower in step (2) is 35~75 kPa, for example, it can be 35 kPa, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa, 65 kPa, 70 kPa, 75 kPa or any of the above values.

[0027] Preferably, the bottom temperature of the light-removal tower in step (2) is ≤120℃, for example, it can be 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃ or any of the above values, more preferably 70~105℃.

[0028] Preferably, the reflux ratio of the light-light tower in step (2) is 5 to 52, for example, it can be 5, 6, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 48 or any of the above values, preferably 10 to 30.

[0029] Preferably, the content of light components in the bottom stream of the light removal tower in step (2) is ≤50ppm, more preferably ≤30ppm, and even more preferably ≤15ppm.

[0030] Preferably, the content of cyclopentadiene in the bottom stream of the light-removal tower in step (2) is ≤30ppm, more preferably ≤20ppm, more preferably ≤15ppm, and particularly preferably ≤5ppm.

[0031] In this invention, the content of dicyclopentadiene in the bottom stream of the light-removal tower in step (2) is ≤20ppm, and more preferably ≤15ppm.

[0032] In this invention, the dicyclopentadiene concentration in the bottom stream of the light-light removal tower is low before entering the refining tower, so that it will not decompose and produce cyclopentadiene in the refining tower. This helps to avoid the cycloolefins from being unqualified due to excessive cyclopentadiene content.

[0033] Preferably, the theoretical number of plates in the refining tower in step (3) is 20 to 45, for example, it can be 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44 or any of the above values.

[0034] Preferably, the top temperature of the refining tower in step (3) is 50~90℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃ or any of the above values.

[0035] Preferably, the top pressure of the refining column in step (3) is 35~75 kPa, for example, it can be 35 kPa, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa, 65 kPa, 70 kPa, 75 kPa or any of the above values.

[0036] Preferably, the bottom temperature of the refining tower in step (3) is 70~120℃, for example, it can be 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃ or any of the above values, more preferably 78~100℃.

[0037] Preferably, the reflux ratio of the refining tower in step (3) is 1 to 40, for example, it can be 1, 2, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40 or any of the above values, preferably 2 to 25.

[0038] Preferably, the temperature difference between the top and bottom temperatures of the refining column in step (3) is 2~23℃, for example, it can be 2℃, 3℃, 4℃, 5℃, 6℃, 7℃, 8℃, 9℃, 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, 21℃, 22℃, 23℃ or any of the above values, more preferably 8~18℃.

[0039] Preferably, the content of cyclopentadiene in the purified top stream of step (3) is ≤5ppm, more preferably ≤2ppm.

[0040] In this invention, the first distillation, the second distillation, and the third distillation are all vacuum distillation, which not only reduces the distillation temperature and energy consumption, but also helps to reduce the reactivity of cyclopentadiene and dicyclopentadiene, thereby inhibiting the interconversion of cyclopentadiene and dicyclopentadiene.

[0041] In this invention, the overhead stream from the heavy removal column includes a liquid stream and a gaseous stream from the heavy removal column; the liquid stream from the heavy removal column undergoes a second distillation in the light removal column; the overhead stream from the purification column includes a liquid stream and a gaseous stream from the purification column; wherein the liquid stream from the purification column is the purified cyclic olefin; the bottom stream from the heavy removal column, the gaseous stream from the heavy removal column, the gaseous stream from the light removal column, the gaseous stream from the purification column, and the bottom stream from the purification column can be collected to avoid discharge and waste.

[0042] In this invention, the top temperature of the first, second, and third distillations is higher than the melting point of norbornene, which can prevent the gaseous solidified stream from clogging the pipeline.

[0043] In this invention, the apparatus used in the purification method is not limited in too much. Any apparatus that can achieve the purpose of this invention is acceptable. For example, the apparatus includes a heavy removal tower, a light removal tower, a purification tower, and a heat exchanger.

[0044] The heavy removal tower, light removal tower, and refining tower are all equipped with inlets and outlets; the outlet of the heavy removal tower includes a bottom stream outlet, a top liquid stream outlet, and a top gaseous stream outlet; the top liquid stream outlet of the heavy removal tower is connected to the inlet of the light removal tower; the outlet of the light removal tower includes a bottom stream outlet, a top liquid stream outlet, and a top gaseous stream outlet; the heavy removal tower... The bottom flow outlet of the light tower is connected to the inlet of the refining tower, and the top liquid flow outlet of the light removal tower is connected to the inlet of the heavy removal tower; the outlets of the refining tower include the bottom flow outlet, the top gas flow outlet, and the top liquid flow outlet; the bottom flow outlet of the refining tower is preferably connected to the inlet of the heavy removal tower; the top gas flow outlets of the heavy removal tower, the light removal tower, and the refining tower are all connected to a vacuum pipeline.

[0045] The bottom and top outlets of the heavy removal tower, light removal tower, and refining tower are all equipped with heat exchangers for cooling, extraction, and reflux.

[0046] In this invention, the feed inlet of the deweight removal tower divides the deweight removal tower into a rectification section and a stripping section. The number of theoretical plates in the rectification section of the deweight removal tower is not less than 1 / 2 of the total number of theoretical plates, preferably not less than 3 / 4.

[0047] Preferably, the feed inlet of the light-light removal tower divides the light-light removal tower into a rectification section and a stripping section, and the number of theoretical plates in the rectification section of the light-light removal tower does not exceed 2 / 3 of the total number of theoretical plates.

[0048] Preferably, the feed inlet of the refining column divides the refining column into a rectification section and a stripping section, and the number of theoretical plates in the rectification section of the refining column is not less than 1 / 2 of the total number of theoretical plates, preferably not less than 2 / 3 of the total number of theoretical plates.

[0049] In a second aspect, the present invention provides an application of the purification method described in the first aspect in the preparation of cyclic olefins.

[0050] In this invention, the cyclic olefins obtained by the purification method can be used for coordination polymerization, meeting the monomer purity requirements of coordination polymerization.

[0051] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0053] In this invention, the purification method, by controlling the mass percentage of cyclopentadiene in the liquid stream from the light olefin removal tower within a specific range and returning the liquid stream from the light olefin removal tower to the heavy olefin removal tower for recycling, and by employing a specific combination of steps and a specific process, can suppress the dynamic conversion between cyclopentadiene and dicyclopentadiene, improve the impurity removal rate, and obtain high-purity and high-yield cycloolefin monomers to meet the needs of subsequent industrial applications. Moreover, the method provided by this invention is simple and easy to implement, with relatively mild conditions, low energy consumption, and is easy to promote industrially. Attached Figure Description

[0054] Figure 1 The apparatus system used in the purification method provided by this invention;

[0055] Among them, T-1 is the heavy removal tower; T-2 is the light removal tower; T-3 is the refining tower; and H-4 is the heat exchanger.

[0056] S-1 is the norbornene synthesis liquid; S-2 is the gaseous stream from the top of the heavy removal column; S-3 is the liquid stream from the top of the heavy removal column; S-4 is the bottom stream from the heavy removal column; S-5 is the gaseous stream from the top of the light removal column; S-6 is the liquid stream from the top of the light removal column; S-7 is the bottom stream from the light removal column; S-8 is the liquid stream from the top of the refining column; S-9 is the bottom stream from the refining column; S-10 is the gaseous stream from the top of the refining column. Detailed Implementation

[0057] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0058] In this invention, unless otherwise specified, "heavy components" refer to components in the norbornene synthesis solution with boiling points higher than toluene, including intermediate products (such as dicyclopentadiene, tetracyclododecene, etc.); "light components" refer to components in the norbornene synthesis solution with boiling points lower than norbornene, mainly including raw materials remaining in the norbornene synthesis solution, as well as impurities generated from the conversion of raw materials or carried in the raw materials (such as cyclopentadiene, etc.); high-purity norbornene refers to norbornene with high purity and low impurity content, thus meeting the needs of COC production with norbornene as one of the main raw materials (purity ≥ 99.5 wt%, and the content of cyclopentadiene and dicyclopentadiene does not exceed 5 ppm).

[0059] In this invention, unless otherwise specified, the theoretical plate number is obtained experimentally using a method commonly used in the field of separation.

[0060] In this invention, unless otherwise specified, the operation numbers (such as "first" and "second" in "first distillation" and "second distillation") are only used to facilitate the differentiation of the same process in different steps in the description, and do not limit the specific operation method, conditions and order.

[0061] In this invention, unless otherwise specified, "ppm" refers to one part per million by mass, and 100ppm = 0.01wt%.

[0062] All materials used in this invention can be purchased commercially or prepared using conventional methods. Unless otherwise specified, the materials used in this invention are as follows.

[0063] The norbornene product, namely the norbornene synthetic solution, is prepared with reference to the composition of the norbornene synthetic solution produced industrially using dicyclopentadiene toluene solution and ethylene as raw materials. Specifically, by mass percentage, the norbornene synthetic solution comprises 53.2% norbornene, 41.33% toluene, 0.87% cyclopentadiene, 0.4% ethylene, 0.5% dicyclopentadiene, and 3.7% tetracyclododecene, and is labeled as S-1.

[0064] Example 1

[0065] This embodiment provides a purification method for norbornene, and the purification method uses the following apparatus system: Figure 1 As shown, it includes heavy removal tower T-1, light removal tower T-2, purification tower T-3, and heat exchanger H-4; the specific purification method is as follows:

[0066] (1) De-heavy: The norbornene synthesis liquid S-1 is introduced into the de-heavy column from the feed inlet of the de-heavy column for the first distillation. After cooling by a heat exchanger, the bottom stream of the de-heavy column (marked as S-4) and the top stream of the de-heavy column are obtained. The top stream of the de-heavy column includes the top gas stream of the de-heavy column (marked as S-2) and the top liquid stream of the de-heavy column (marked as S-3). The top liquid stream S-3 of the de-heavy column is sent into the light removal column.

[0067] Specific process parameters of the deweight removal tower: The deweight removal tower has 21 theoretical plates, and the feed inlet is located at the 17th theoretical plate from top to bottom; the top pressure of the deweight removal tower is 55 kPa, the top temperature is 82℃, the bottom temperature is 106℃, and the reflux ratio is 0.12.

[0068] (2) Light Distillation: The liquid stream S-3 from the top of the heavy distillation tower is introduced into the light distillation tower through the feed inlet of the light distillation tower for a second distillation. After cooling by a heat exchanger, the bottom stream (marked as S-7) and the top stream of the light distillation tower are obtained. The top stream of the light distillation tower includes the gas stream (marked as S-5) and the liquid stream (marked as S-6) from the top of the light distillation tower. The liquid stream S-6 from the top of the light distillation tower is returned to the heavy distillation tower for recycling, and the bottom stream S-7 from the light distillation tower is sent to the purification tower.

[0069] Specific process parameters for the light-light weight removal tower: The light-light weight removal tower has 20 theoretical plates, and the feed inlet is located at the 10th theoretical plate from top to bottom; the top pressure of the light-light weight removal tower is 53 kPa, the top temperature is 69℃, the bottom temperature is 80℃, and the reflux ratio is 13; the mass percentage of cyclopentadiene in the liquid stream S-6 at the top of the light-light weight removal tower is 9.48%.

[0070] (3) Refining: The bottom stream S-7 of the light distillation tower is fed into the refining tower through the feed port of the refining tower for the third distillation. After cooling by a heat exchanger, the bottom stream (marked as S-9) and the top stream of the refining tower are obtained. The top stream of the refining tower includes the liquid stream (marked as S-8) and the gas stream (marked as S-10) of the refining tower. Among them, the liquid stream S-8 is the purified norbornene.

[0071] Specific process parameters of the refining tower: The refining tower has 30 theoretical plates, and the feed inlet is located at the 20th theoretical plate from the top; the top pressure of the refining tower is 50 kPa, the top temperature is 72℃, the bottom temperature is 87℃, and the reflux ratio is 6.

[0072] The purification methods for norbornene provided in Examples 2-14 and Comparative Examples 1-3 differ from those in Example 1 in that the specific process parameters are different, as shown in Tables 1-3.

[0073] In the purification method provided in Comparative Example 3, the liquid phase stream from the top of the light phase removal tower is not returned to the heavy phase removal tower for recycling, and the bottom stream S-9 of the purification tower is returned to the heavy phase removal tower for recycling. Other parameters are the same as in Example 1.

[0074] It should be noted that in Tables 1-3, "Inlet Plate Number" indicates which theoretical plate the feed inlet is located on from top to bottom. For example, if the inlet plate number is 17, it means that the feed inlet is located on the 17th theoretical plate from top to bottom. The section above the feed inlet is the rectification section, and the section below it is the stripping section. "Cyclopentadiene (wt%)" indicates the mass percentage of cyclopentadiene in the liquid stream S-6 at the top of the light-light removal tower.

[0075] Table 1

[0076]

[0077] Table 2

[0078]

[0079] Table 3

[0080]

[0081] Performance testing

[0082] 1. In this invention, the composition of each stream in the purification method can be determined by gas chromatography. Specifically, an Agilent 6890-5973 GC-MS and a GC9790 GC are used for detection. The gas chromatography parameters are as follows: HP-1 capillary column (50m × 0.2mm × 0.5mm); flame ionization detector; split ratio of 100:1; nitrogen carrier gas flow rate of 0.5mL / min; vaporization chamber temperature of 220℃; column oven temperature program of initial temperature 70℃, held for 2min, heating rate of 10℃ / min, final temperature 220℃, held for 5min; injection volume of 0.5μL. The mass spectrometry parameters are as follows: chromatographic-mass spectrometry interface temperature of 280℃; ion source temperature of 230℃; quadrupole temperature of 150℃; ionization mode of EI; ionization energy of 70eV; solvent-free delay time.

[0083] 2. In this invention, the yield of norbornene is calculated based on the flow rate of the feed stream, and the calculation formula is as follows: Yield = S-8 norbornene content / norbornene content in the feed stream; S-8 norbornene content = S-8 norbornene mass percentage × mass flow rate; Norbornene content in the feed stream = norbornene mass percentage in the norbornene synthesis liquid × mass flow rate (1000 kg / h).

[0084] The purification methods provided in the embodiments and comparative examples of this invention, and the specific test results of the composition of each stream, namely S-3, S-7, S-8 and the yield of norbornene, are shown in Tables 4 and 5. Among them, taking Examples 1-4 and Comparative Example 2 as examples, the composition and yield of streams S-3, S-7, and S-8 are shown in Table 4; the composition and yield of S-8 in Examples 5-14 and Comparative Example 1 are shown in Table 5.

[0085] The composition of S-1 is as described above, and the mass flow rate of S-1 is 1000 kg / h.

[0086] Table 4

[0087]

[0088] Table 5

[0089]

[0090] As shown in Tables 4 and 5, the purification method provided by this invention, by controlling the mass percentage of cyclopentadiene in the liquid stream from the light olefin removal tower within a specific range and returning the liquid stream from the light olefin removal tower to the heavy olefin removal tower for recycling, and by employing a specific combination of steps and a specific process, can suppress the dynamic conversion between cyclopentadiene and dicyclopentadiene, improve the impurity removal rate, and obtain cyclic olefin monomers with high purity and high yield. The purity of norbornene obtained by the purification method is ≥99.7%, which meets the production requirements of COC, and the yield is ≥89%, while also ensuring a high yield.

[0091] As can be seen from Examples 1 and 8-10, using a reflux ratio within a specific range in the deweighting tower is beneficial for obtaining norbornene products with higher purity and yield, and lower cyclopentadiene and dicyclopentadiene content.

[0092] As can be seen from Examples 1 and 11-12, the temperature difference between the top and bottom of the refining column is within a specific range, which is beneficial to obtaining a higher yield of norbornene product.

[0093] As can be seen from Examples 1 and 14, and Comparative Example 2, if the cyclopentadiene content in the liquid stream from the top of the light-light product removal tower is too low, the yield of norbornene will decrease; if the cyclopentadiene content in the top liquid stream from the light-light product removal tower is too high, it will dimerize to form dicyclopentadiene, which will fall back into the light-light product removal tower, resulting in an excessively high dicyclopentadiene content in the bottom stream of the light-light product removal tower. When this dicyclopentadiene enters the purification tower, it will decompose to produce cyclopentadiene, resulting in an excessively high cyclopentadiene content in norbornene, which does not meet the production requirements of COC. In the examples, the purification method provided by the present invention is used, resulting in a lower dicyclopentadiene content in the bottom stream of the light-light product removal tower. This reduces the chance of dicyclopentadiene decomposition to produce cyclopentadiene when it enters the purification tower, thus obtaining norbornene with a lower cyclopentadiene content, which meets the production requirements of COC.

[0094] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for purifying cyclic olefins, characterized in that, The purification method includes the following steps: (1) De-weighting: The crude cyclic olefin product is subjected to a first distillation in a de-weighting column to obtain the bottom stream and the top stream of the de-weighting column; The impurities in the crude cyclic olefin product include cyclopentadiene and dicyclopentadiene, and the total mass percentage of cyclopentadiene and dicyclopentadiene in the crude cyclic olefin product is ≥1%; (2) Light removal: The overhead stream obtained in step (1) is subjected to a second distillation in the light removal column to obtain the bottom stream and the overhead stream of the light removal column; The overhead stream from the light-weight removal tower includes a gaseous overhead stream and a liquid overhead stream. The liquid overhead stream is returned to the heavy-weight removal tower for recycling. The mass percentage of cyclopentadiene in the liquid overhead stream is 5-20%. (3) Refining: The bottom stream obtained in step (2) is subjected to a third distillation in a refining column to obtain a bottom stream and a top stream, which are the purified cyclic olefins.

2. The purification method according to claim 1, characterized in that, In step (1), the crude cycloolefin product contains ≥0.5% cyclopentadiene by mass. The mass percentage of dicyclopentadiene in the crude cycloolefin product of step (1) is ≥0.5%.

3. The purification method according to claim 1, characterized in that, The crude cyclic olefin product in step (1) includes crude products of norbornene and / or its derivatives; The crude cyclic olefin product in step (1) is prepared from a toluene solution of dicyclopentadiene and olefin compounds as raw materials.

4. The purification method according to claim 1, characterized in that, The theoretical number of plates in the deweight removal tower described in step (1) is 10 to 35. The top temperature of the deweight removal tower in step (1) is ≥50℃; The pressure at the top of the deweight removal tower in step (1) is 35~75 kPa.

5. The purification method according to claim 1, characterized in that, The bottom temperature of the deweight removal tower in step (1) is 70~130℃; The reflux ratio of the de-weighting tower in step (1) is 0.01~5.

6. The purification method according to claim 1, characterized in that, The mass percentage of cyclopentadiene in the liquid stream from the top of the light-light-removal tower is 8-15%. The theoretical number of plates in the light-light removal tower described in step (2) is 8 to 36. The number of theoretical plates in the light-light distillation section does not exceed 2 / 3 of the total number of theoretical plates; The temperature at the top of the light-weight removal tower in step (2) is ≥50℃; The pressure at the top of the light-light removal tower in step (2) is 35~75 kPa.

7. The purification method according to claim 1, characterized in that, The bottom temperature of the light-light removal tower in step (2) is ≤120℃; The reflux ratio of the light-light tower in step (2) is 5~52; The content of light components in the bottom stream of the light removal tower in step (2) is ≤50ppm; The content of cyclopentadiene in the bottom stream of the light-removal tower in step (2) is ≤30ppm.

8. The purification method according to claim 1, characterized in that, The theoretical number of plates in the refining column described in step (3) is 20 to 45. The temperature at the top of the refining tower in step (3) is 50~90℃; The pressure at the top of the refining column in step (3) is 35~75 kPa; The bottom temperature of the refining column in step (3) is 70~120℃; The reflux ratio of the refining tower in step (3) is 1 to 40.

9. The purification method according to claim 1, characterized in that, The temperature difference between the top and bottom of the refining column in step (3) is 2~23℃; The content of cyclopentadiene in the purified column top stream in step (3) is ≤5ppm.

10. The application of the purification method according to any one of claims 1 to 9 in the preparation of cyclic olefins.

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