Method for synthesizing norbornene by using C9 fraction as raw material

Abstract

The invention relates to the field of chemical synthesis, and discloses a method for synthesizing norbornene by taking C9 fraction as a raw material, which comprises the following steps: (1) cracking the C9 fraction containing dicyclopentadiene; and (2) in the presence of a solvent, the cyclopentadiene-containing product obtained in the step (1) is contacted with ethylene for a reaction, the reaction temperature is not higher than 270 DEG C, and the pressure is not lower than 10 MPa. When the method is used for preparing the norbornene, the C9 fraction in the ethylene industry can be fully utilized, the production difficulty of the norbornene is reduced, and a high-purity norbornene product is continuously generated.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis, and more specifically, to a method for synthesizing norbornene using C9 fraction as a raw material. Background Technology

[0002] Norbornene (2-norbornene, NB) is a basic raw material for the production of cyclic polyolefin copolymers and an important comonomer. Norbornene is synthesized from ethylene and cyclopentadiene (CPD) via the Diels-Adel reaction. CPD is not easily stored at room temperature and readily undergoes dimerization to form dicyclopentadiene (DCPD). Therefore, industrially, DCPD is typically used as a raw material; it is first depolymerized to CPD before NB is synthesized.

[0003] The depolymerization of DCPD to CPD is a reversible reaction. High temperatures can promote the depolymerization of DCPD to CPD, but at high temperatures, in addition to depolymerization, DCPD will also undergo polymerization to form polymers. Furthermore, the remaining undepolymerized DCPD will further react with CPD and ethylene during NB synthesis to generate byproducts, thereby reducing the selectivity of NB.

[0004] Current synthesis processes for norbornene all use dicyclopentadiene as the initial raw material, conducting the reaction at relatively high temperatures and pressures. However, these high temperatures and pressures pose safety risks during production. Furthermore, due to the difficulty in purifying cyclopentadiene, commercially available cyclopentadiene has a purity of only around 80%. Impurities may affect the cracking of dicyclopentadiene, leading to a decrease in cyclopentadiene purity. Moreover, these impurities may react with ethylene or the generated cyclopentadiene to produce byproducts, further complicating norbornene purification. Additionally, high concentrations of cyclopentadiene can cause coking and clogging of the reactor.

[0005] Therefore, there is an urgent need to develop a production process for norbornene to reduce the generation of byproducts, lower the reaction difficulty, and simplify product purification. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem of low purity of norbornene in the prior art and to provide a method for synthesizing norbornene using C9 fraction as a raw material.

[0007] To achieve the above objectives, the present invention provides a method for synthesizing norbornene from C9 fraction as a raw material, the method comprising:

[0008] (1) Crack the C9 fraction containing dicyclopentadiene;

[0009] (2) In the presence of a solvent, the product containing cyclopentadiene obtained in step (1) is brought into contact with ethylene for reaction, wherein the temperature of the reaction is not higher than 270°C and the pressure is not lower than 10 MPa.

[0010] The above technical solution can make full use of the C9 fraction in the ethylene industry, reduce the production difficulty of norbornene, and continuously produce norbornene products with higher purity. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of a process for synthesizing norbornene using C9 fraction as a raw material, according to a preferred embodiment of the present invention. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] This invention provides a method for synthesizing norbornene from C9 fraction, the method comprising:

[0014] (1) Crack the C9 fraction containing dicyclopentadiene;

[0015] (2) In the presence of a solvent, the product containing cyclopentadiene obtained in step (1) is brought into contact with ethylene for reaction, wherein the temperature of the reaction is not higher than 270°C and the pressure is not lower than 10 MPa.

[0016] In this invention, the C9 fraction used to synthesize norbornene can be derived from the cracking product of ethylene production from petroleum cracking. The product is separated to obtain the C8 and lower light fractions, thus yielding the C9 fraction used in this invention. The dicyclopentadiene content in the C9 fraction can be 0.01-30 mol%, preferably 15-25 mol%. Generally, the C9 fraction may also contain at least one of cyclopentadiene (CPD), methyl-1,3-cyclopentadiene, styrene, methylstyrene, indene, methylcyclopentadiene dimer, 1-n-propylnaphthalene, 1-methylindene, and 1-methylnaphthalene. Compared to the commonly used cracked C5 fraction in norbornene synthesis, the C9 fraction has a lower dicyclopentadiene content. However, the inventors of this invention have discovered that a specific dicyclopentadiene content is more conducive to direct cracking at lower temperatures, atmospheric pressure, and without catalyst catalysis, without the need for dilution gas (such as hydrogen) and without the generation of polymers or other substances that clog the reactor, thereby further improving production efficiency. Moreover, compared to C5 fractions, C9 fractions are easier to separate from the product, facilitating the acquisition of norbornene with higher purity and a more uniform impurity composition. This improves the selectivity, yield, and purity of norbornene. Therefore, due to its composition, C9 fractions are particularly suitable for the production of norbornene, and can be used without complex purification before production, significantly reducing production difficulty and increasing efficiency. Using C9 fractions as a raw material not only improves the overall utilization rate of C9 fractions, increases product added value and economic benefits, but also yields high-quality norbornene for further industrial production, which has significant economic implications.

[0017] In this invention, the pyrolysis temperature is preferably 180-250℃.

[0018] The cracking reaction of dicyclopentadiene can be carried out in any temperature-controlled reactor. After cracking, the cyclopentadiene is purified using a suitable distillation apparatus and directly used for the subsequent synthesis of norbornene. Typically, the cracking reaction of dicyclopentadiene can be carried out in a depolymerization reactor or reaction vessel under hydrogen protection. The inventors of this invention have discovered that when the C9 fraction used in this invention is cracked in a reactive distillation column, by using optimized conditions, without the use of catalysts, polymerization inhibitors, or other additives, the operation is further simplified, the reaction cost is reduced, and high-purity cyclopentadiene can be obtained continuously and uninterruptedly. Furthermore, since the formation and distillation of cyclopentadiene occur simultaneously in the reactive distillation column, norbornene synthesis can be carried out immediately after cyclopentadiene formation, thereby significantly reducing the probability of self-polymerization and improving the purity of the subsequent norbornene.

[0019] According to a preferred embodiment of the present invention, the pyrolysis is carried out in a reactive distillation column. Preferably, the reactive distillation column can be a plate column, with a theoretical plate number of 20-50, a reflux ratio of 1-20, a top temperature of 30-120°C, and a bottom temperature of 180-250°C.

[0020] In this invention, after the C9 fraction containing dicyclopentadiene is cracked in a reactive distillation column, the cyclopentadiene-containing product is mainly present at the top of the column. Therefore, according to one embodiment of the invention, the cyclopentadiene-containing product is drawn from the top of the reactive distillation column and contacted with ethylene.

[0021] In this invention, the boiling point of the solvent is preferably 100-200℃.

[0022] In this invention, in order to more smoothly distill norbornene, the type of solvent used in the synthesis reaction can be adjusted and optimized according to the type of impurities in the norbornene-containing product. The solvent is preferably toluene, xylene, n-decane and decahydronaphthalene. In order to minimize energy consumption while ensuring the distillation effect, toluene is more preferred as the solvent.

[0023] In this invention, the amount of each raw material can be adjusted according to the reaction requirements, but preferably, the molar ratio of cyclopentadiene, solvent and ethylene in the cyclopentadiene-containing product is 1:(1-5):(2-40).

[0024] Theoretically, the higher the concentration of reactants, the faster the reaction rate. Therefore, when the amount of cyclopentadiene is constant, reducing the amount of solvent and increasing the amount of ethylene will increase the reaction rate. However, too low a amount of solvent will increase the self-aggregation of cyclopentadiene, and too high a amount of ethylene will increase the production cost. Therefore, according to the most preferred embodiment of the present invention, the highest purity cyclopentadiene can be obtained when the molar ratio of cyclopentadiene, solvent and ethylene is 1:(1.5-2.5):(3-5).

[0025] In this invention, the reaction temperature is preferably 210-270℃, more preferably 220-250℃, and the reaction pressure is preferably 10-18MPa.

[0026] According to the present invention, those skilled in the art know that the synthesis of norbornene from the reaction of cyclopentadiene and ethylene requires high temperatures. However, the inventors of the present invention have discovered that controlling the temperature at 210-270°C when the pressure is within 10-18 MPa can significantly improve the purity of norbornene. According to the most preferred embodiment of the present invention, the purity of norbornene prepared at a temperature of 220-230°C and a pressure of 14-16 MPa reaches 99.7 mol%.

[0027] In this invention, the reaction time is preferably 5-120 min.

[0028] According to the present invention, a method for contacting a cyclopentadiene-containing product with ethylene may include: first, thoroughly mixing cyclopentadiene and a solvent and pressurizing and preheating them, while simultaneously pressurizing and preheating the ethylene, and then thoroughly mixing the treated ethylene with the mixture of cyclopentadiene and the solvent at the reactor inlet, wherein the pressure of the system after pressurizing the ethylene is preferably 10-18 MPa.

[0029] According to the present invention, the optimized tubular reactor internals (refer to patent CN117658760A) are more suitable for the synthesis of norbornene compared to conventional tubular reactors and reaction vessels.

[0030] In this invention, to obtain a purer product, the method may further include: performing gas-liquid separation and distillation on the product after the reaction. The gas-liquid separation and distillation can be performed in a conventional manner.

[0031] Preferably, the distillation is carried out in a distillation column, such as a plate column or a packed column, and preferably, the distillation column is a packed column.

[0032] According to the present invention, during the distillation process, one or more distillation columns can be used for single or multiple distillations. When only one distillation is performed, ethylene can be distilled off at the top of the distillation column, and norbornene can be distilled off on the side stream of the distillation column. Alternatively, multiple distillation columns can be connected in series for multiple distillations. Depending on the substances recovered, substances can be distilled off sequentially in different distillation processes in any manner, such as increasing boiling point, decreasing boiling point, decreasing boiling point followed by increasing boiling point, or increasing boiling point followed by decreasing boiling point.

[0033] In this invention, norbornene can be obtained by two distillations, including a first distillation and a second distillation. Preferably, the first distillation uses a distillation column with 20-40 theoretical plates, a reflux ratio of 4-20, a top temperature of 1-35°C, and a bottom temperature of 60-100°C. The second distillation uses a distillation column with 40-70 theoretical plates, a reflux ratio of 4-15, a top temperature of 90-110°C, and a bottom temperature of 120-150°C.

[0034] According to the present invention, after the second distillation, a third distillation can be performed to recover the solvent, wherein the theoretical plate number can be 10-30, the reflux ratio can be 1-8, the top temperature of the third distillation column can be 100-120°C, and the bottom temperature can be 120-200°C.

[0035] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials and equipment used in the following examples and comparative examples are commercially available.

[0036] The key devices and parameters in this invention are as follows:

[0037] R1 - Reactive distillation column: Plate column, theoretical plate number 35, reflux ratio 13, temperature 68℃ (top) / 226℃ (bottom);

[0038] V1 - Raw material mixing tank;

[0039] P1 - Raw material booster pump;

[0040] C1 - Compressor;

[0041] M1 - Synthetic raw material mixer;

[0042] R2-Synthesis Reactor: Tubular reactor;

[0043] V2 - Gas-liquid phase separator;

[0044] T1-NB coarse separator: packed tower, theoretical number of trays 25, reflux ratio 10, temperature 19℃ (top) / 95℃ (bottom);

[0045] T2-NB purification tower: packed tower, theoretical number of trays 48, reflux ratio 10, temperature 102℃ (top) / 145℃ (bottom);

[0046] T3 - Solvent Recovery Tower: Packed tower with 20 theoretical plates, a reflux ratio of 4, and temperatures of 105℃ (top) / 177℃ (bottom).

[0047] CPD conversion rate: (Amount of CPD before reaction - Amount of CPD after reaction) / Amount of CPD before reaction × 100%;

[0048] NB selectivity: (Amount of NB after reaction - Amount of NB before reaction) / (Amount of CPD before reaction - Amount of CPD after reaction) × 100.

[0049] Example 1

[0050] like Figure 1 As shown, norbornene was synthesized according to the following specific operating procedure:

[0051] 1. Formation of cyclopentadiene:

[0052] The C9 fraction feedstock enters the reactive distillation column R1 through S1, generating CPD with a concentration of 99.5 mol%. After being condensed by the condenser in R1, S2 is drawn from the top of the column and sent to the feed mixing tank V1, where it is mixed with the solvent (toluene) in S3 and S17. The molar ratio of solvent to CPD is 2:1. The heavy fraction S4 at the bottom of the R1 column is sent out of the boundary area.

[0053] 2. Synthesis of norbornene:

[0054] While the synthetic raw materials containing CPD are fully mixed with the solvent in V1, S6, pressurized to 12MPa and preheated to 170℃ by the raw material booster pump P1 from the bottom of V1, is sent to the synthetic raw material mixer M1. S5, which is a mixture of S7 and S11, is pressurized by the compressor C1, and S8, which is pressurized to 12MPa and preheated to 150℃, is sent to the synthetic raw material mixer M1. S9, after the gas and liquid phases in M1 are fully mixed, is sent to the synthesis reactor R2 to synthesize norbornene. The pressure of R2 is 12MPa (g), the temperature is 230℃, the molar ratio of ethylene to CPD is 14:1, and the residence time of the materials is 10min.

[0055] 3. Purification of norbornene:

[0056] After the reaction in R2 is completed, the gas-liquid mixture is condensed to obtain S10 and sent to the gas-liquid phase separator V2. The gas phase S11 at the top of V2 is mixed with S7 (fresh ethylene) and recycled, while the liquid phase S12 at the bottom of the tank is sent to the NB coarse separator T1 for purification.

[0057] The liquid phase S14 at the bottom of the NB coarse fractionation column T1 is sent to the NB purification column T2, and the light component S13 at the top of the column is sent out of the boundary area. S15 (qualified product norbornene NB) distilled from the top of column T2 is collected, and the heavy component S16 at the bottom of column T2 is sent to the solvent recovery column T3. The solvent S17 distilled from the top of column T3 is mixed with S3 (fresh solvent) and recycled. The heavy component S18 at the bottom of column T3 is sent out of the boundary area.

[0058] After 0.5 h of reaction, the composition and content of each stream except streams 6, 8 and 9 were determined by liquid chromatography and gas chromatography (unit: mol% mixed gas). The composition and content of streams S6, S8 and S9 were calculated based on the relative volume of each stream and the content of each substance therein, as shown in Tables 1 and 2.

[0059] Table 1

[0060]

[0061] Note: Data “0” indicates two situations: (1) the content of the substance is below the detection limit and is not detected, (2) the substance is not present at all.

[0062] Table 2

[0063]

[0064]

[0065] Note: The data “0” indicates two situations: (1) the content of the substance is below the detection limit and is not detected, (2) the substance is not present at all; the data “0.0001” not only represents the actual content as 0.0001, but also represents the content as approximately tens to hundreds of ppm. Due to the limitation of the detection limit and the rounding during data processing, its value is ultimately represented as 0.0001.

[0066] Example 2

[0067] The synthesis of norbornene was carried out in accordance with Example 1, except that the reaction temperature and reaction pressure were 225°C and 15 MPa, respectively. The contents of each substance in S10 and the product norbornene (S15) after the synthesis reaction are shown in Table 3. For comparison, the contents of each substance in S10 and S15 of Example 1 are also given in Table 3.

[0068] Comparative Example 1

[0069] The process was carried out in accordance with Example 1, except that the feedstock for pyrolysis was C5 fraction / commercially available dicyclopentadiene. According to petrochemical standard SH / T1806-2016, the high-purity dicyclopentadiene had a purity greater than 97% (superior grade), and the polyester-grade dicyclopentadiene had a purity greater than 85% (superior grade). The contents of each substance in S10 and the product norbornene S15 are shown in Table 3.

[0070] Table 3

[0071]

[0072] Note: The data “0” indicates two situations: (1) the content of the substance is below the detection limit and is not detected, (2) the substance is not present at all; the data “0.0001” not only represents the actual content as 0.0001, but also represents the content as approximately tens to hundreds of ppm. Due to the limitation of the detection limit and the rounding during data processing, its value is ultimately represented as 0.0001.

[0073] As can be seen from the results in Tables 1-3, the norbornene product synthesized using the process provided by this invention, with pyrolyzed C9 as raw material, has higher purity and lower content of cyclopentadiene and heavy components (dicyclopentadiene, tetracyclododecene, and cyclopentadiene trimer). Furthermore, the CPD conversion rate reaches 98%, and the NB selectivity reaches 99.8%. It can be observed that using the method provided by this invention to prepare norbornene can achieve higher CPD conversion and higher norbornene selectivity, thereby improving the quality of norbornene 1240683.

[0074] I96550BHY

[0075] The quality of olefin products.

[0076] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for synthesizing norbornene from C9 fraction, characterized in that, The method includes: (1) Crack the C9 fraction containing dicyclopentadiene; (2) In the presence of a solvent, the product containing cyclopentadiene obtained in step (1) is brought into contact with ethylene for reaction, wherein the temperature of the reaction is not higher than 270°C and the pressure is not lower than 10 MPa.

2. The method according to claim 1, wherein, The content of dicyclopentadiene in the C9 fraction is 0.01-30 mol%, preferably 15-25 mol%. And / or, the pyrolysis temperature is 180-250°C.

3. The method according to claim 1, wherein, The cracking is carried out in a reactive distillation column, which is a plate column with a theoretical number of 20-50 plates, a reflux ratio of 1-20, a top temperature of 30-120℃, and a bottom temperature of 180-250℃.

4. The method according to claim 3, wherein, The cyclopentadiene-containing product is drawn from the top of the reactive distillation column and brought into contact with ethylene.

5. The method according to claim 1, wherein, The solvent has a boiling point of 100-200℃; And / or, the solvent is at least one selected from toluene, xylene, n-decane, and decahydronaphthalene, preferably toluene.

6. The method according to claim 1, wherein, The molar ratio of cyclopentadiene, solvent and ethylene in the cyclopentadiene-containing product is 1:(1-5):(2-40).

7. The method according to claim 1, wherein, The reaction temperature is 210-270℃, preferably 220-250℃, and the reaction pressure is 10-18MPa; And / or, the reaction time is 5-120 min.

8. The method according to claims 1-7, wherein, The method also includes: gas-liquid separation and distillation of the products after the reaction is completed.

9. The method according to claim 8, wherein, The distillation is carried out in a distillation column, preferably a packed column; And / or, the distillation includes a first distillation and a second distillation. Preferably, the first distillation uses a distillation column with 20-40 theoretical plates, a reflux ratio of 4-20, a top temperature of 1-35°C, and a bottom temperature of 60-100°C; the second distillation uses a distillation column with 40-70 theoretical plates, a reflux ratio of 4-15, a top temperature of 90-110°C, and a bottom temperature of 120-150°C.

10. The method according to claims 1-7, wherein, The C9 fraction also contains at least one of cyclopentadiene, methyl-1,3-cyclopentadiene, styrene, methylstyrene, indene, methylcyclopentadiene dimer, 1-n-propylnaphthalene, 1-methylindene, and 1-methylnaphthalene.

Images