Preparation method of vinyl norbornene and ethylidene norbornene mixture

Abstract

The invention relates to a preparation method of a mixture of vinyl norbornene and ethylidene norbornene, which comprises the following steps: mixing 1, 3-butadiene, cyclopentadiene, a mixed solvent and a polymerization inhibitor, adding a nickel-based isomerization catalyst into a reactor for reaction, and after the reaction is finished, separating and purifying to obtain the mixture of vinyl norbornene and ethylidene norbornene. And refining and separating the reaction liquid to obtain a mixture of vinyl norbornene and ethylidene norbornene. According to the method, the conversion rate and the selectivity of 1, 3-butadiene are greatly increased, so that a mixture of vinyl norbornene and ethylidene norbornene is obtained at a relatively high yield, and the high-purity ethylidene norbornene can be prepared after the vinyl norbornene in the mixture is further isomerized.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and particularly relates to a method for preparing a mixture of vinyl norbornene and ethylidene norbornene. Background Art

[0002] As an important third monomer of ethylene-propylene rubber (EPDM), ethylidene norbornene (ENB) occupies an important position in the rubber industry because it gives EPDM excellent vulcanizability, high reactivity, fast vulcanization speed, and good chemical resistance, water vapor resistance, and ozone resistance. Although significant progress has been made in the preparation technology of ENB, it still faces many challenges, such as improving yield, selectivity, and reducing production costs. At present, the process of synthesizing ENB is to first use 1,3-butadiene as a dienophile and cyclopentadiene (CPD) to generate vinyl norbornene (VNB) through Diels-Alder reaction, and then VNB is catalytically isomerized to obtain ENB. The main by-products of the VNB synthesis process are vinyl cyclohexene, cyclooctadiene, tetrahydroindene, some oligomers and 1,3-butadiene polymers. Such as in Chinese patents CN1580015, CN 104744201, CN103980084, CN104058912, CN104692994, U.S. Patent US4777309 and Japan Sumitomo Chemical Co., Ltd. (Sumitomo Chemical, 1990 (2): 4-11) reported. The main reaction is as follows:

[0003]

[0004] CN105461505B provides a method for producing ethylidene norbornene, which uses a kettle reactor to crack dicyclopentadiene (DCPD) into cyclopentadiene (CPD), and then reacts with 1,2-butadiene (BD) to convert it into ENB through Diels-Alder reaction. The method uses acetone as a solvent and significantly improves the conversion rate and selectivity of ENB by optimizing reaction conditions such as temperature, pressure, time, etc. The disadvantage is that the industrialization level of 1,2-butadiene is very low, the price is expensive, the production cost is significantly increased, and the economic benefit of industrialization is low.

[0005] CN103483135A relates to a method for preparing high-purity ENB, wherein CPD is prepared from the cracked carbon nine bicyclic segment fraction, and then VNB is generated by a dead volume-free series tubular reactor with 1,3-butadiene, and high-purity ENB is obtained through dehydration, isomerization, and distillation. The process route of this method is simple and reliable, and it is suitable for large-scale production, but the utilization rate and selectivity of 1,3-butadiene are low, and there is a problem of recycling a large amount of DCPD, which increases the cost of DCPD and solvent recovery.

[0006] At present, the method of adding 1,3-butadiene to cyclopentadiene to generate vinyl norbornene and then catalytically isomerizing vinyl norbornene to prepare ethylidene norbornene has the following problems: during the reaction, the selectivity of butadiene to generate the target product is 75%, and 1,3-butadiene dimerization generates more vinyl cyclohexene and cyclooctadiene, accounting for 20-30%, and the butadiene conversion rate and selectivity need to be improved; although increasing the cyclopentadiene concentration is beneficial to the formation of vinyl norbornene and increasing the yield of vinyl norbornene to about 35% within a certain range, the yield is still low. The main reason is that as the reaction proceeds, the concentration of vinyl norbornene gradually increases, which is not conducive to the main reaction. Therefore, the product needs to be removed in time, but at the same time, the raw material utilization rate is also reduced. On the other hand, cyclopentadiene self-polymerizes quickly and forms a large amount of DCPD at high concentrations; because of the presence of a large amount of by-product DCPD, the energy consumption of subsequent separation will be significantly increased, resulting in high costs for product refining and solvent recycling. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing a mixture of vinyl norbornene and ethylidene norbornene, which greatly increases the conversion rate and selectivity of 1,3-butadiene, thereby obtaining a mixture of vinyl norbornene and ethylidene norbornene with a higher yield, and further isomerizing the vinyl norbornene therein to prepare high-purity ethylidene norbornene. At the same time, because the conversion rate and selectivity of 1,3-butadiene are improved, it is beneficial to reduce the reflux ratio during distillation separation, thereby reducing energy consumption.

[0008] The present invention provides a method for preparing a mixture of vinyl norbornene and ethylidene norbornene, comprising the following steps:

[0009] After mixing 1,3-butadiene, cyclopentadiene, a mixed solvent and a polymerization inhibitor in a mass ratio of 1: (0.5-2.0): (1.0-10.0): (0.0001-0.01), a nickel-based isomerization catalyst is added to a reactor to react. After the reaction is completed, the reaction liquid is purified and separated to obtain a mixture of vinyl norbornene and ethylidene norbornene.

[0010] Preferably, the 1,3-butadiene is of industrial grade with a purity greater than 99.5%. The purity of cyclopentadiene is greater than 99.2%, and can be prepared by depolymerization of DCPD.

[0011] Preferably, the mixed solvent consists of solvent A and solvent B in a mass ratio of 1:(0.1-100).

[0012] Preferably, the solvent A is at least one of acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, and dioxane; the solvent B is at least one of C5-C10 alkanes, cycloalkanes, and aromatic hydrocarbons, and may be at least one of C6 solvent oil, cyclohexane, cyclopentane, n-hexane, n-heptane, toluene, and xylene.

[0013] Preferably, the polymerization inhibitor is a mixture of sodium nitrite and p-tert-butylcatechol, wherein the mass ratio of sodium nitrite to p-tert-butylcatechol is 1:(0.5-3).

[0014] Preferably, the nickel-based isomerization catalyst comprises a nickel source and a ligand; wherein the nickel source is at least one of bis(1,5-cyclooctadiene)nickel Ni(cod)2, (1,5,9-cyclododecatriene)nickel, and allyl nickel complex Ni(π-C3H5)2; the ligand is one of 1,1'-bis(diphenylphosphino)ferrocene, tricyclohexylphosphine tetrafluoroborate, tricyclohexylphosphine, triphenylphosphine, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)ethane, bis(diphenylphosphino)methane, and 1,3-bis(diphenylphosphino)propane (dppp); the molar ratio of the nickel source to the ligand is 1:(0.5-10); the mass ratio of the nickel-based isomerization catalyst to 1,3-butadiene is (0.001-0.1):1.

[0015] Preferably, the reaction temperature is 160-190° C., the reaction pressure is 1-8 MPa, and the reaction time is 1-5 h.

[0016] Preferably, the mass ratio of vinyl norbornene to ethylidene norbornene in the mixture of vinyl norbornene and ethylidene norbornene is 1:(1-100). The sum of the purity of the two is greater than or equal to 98.0%, and the impurities mainly include light component tetrahydroindene, heavy component dicyclopentadiene DCPD and trace water.

[0017] The order of adding the raw materials is not limited. 1,3-butadiene, cyclopentadiene, mixed solvent, and polymerization inhibitor can be added in sequence. Solvent and polymerization inhibitor can also be added first, and then 1,3-butadiene and cyclopentadiene are added. When feeding intermittently, this scheme is preferred. 1,3-butadiene can be mixed with a mixed solvent first and then mixed evenly with cyclopentadiene, a mixed solvent, and a polymerization inhibitor; 1,3-butadiene, a polymerization inhibitor, and a mixed solvent can also be mixed first, and cyclopentadiene, a mixed solvent, and a polymerization inhibitor can be mixed, and then the mixture is mixed and introduced into the reactor. This scheme is preferred when feeding continuously. The mixing method can be a static mixer, a dynamic mixer, stirring, and the like.

[0018] The present invention also provides a method for preparing high-purity ethylidene norbornene, comprising the following steps:

[0019] The obtained vinyl norbornene and ethylidene norbornene mixture is dried and dehydrated, and then introduced into an isomerization reactor, and an isomerization catalyst is added to react to obtain crude ethylidene norbornene; after refining, high-purity ethylidene norbornene can be obtained.

[0020] Preferably, the drying controls the water content to be less than 20 ppm, and the drying medium comprises one or both of 5A molecular sieve or γ-alumina.

[0021] Preferably, the isomerization catalyst is K-Na2O / γ-Al2O3, and the amount of the isomerization catalyst is 0.1-1.5% of the total mass of vinyl norbornene and ethylidene norbornene. The isomerization catalyst can also be other super base systems, such as Na-NaOH / γ-Al2O3, Na-Na2CO3 / γ-Al2O3, and Na / γ-Al2O3 super base systems, which can also achieve good isomerization effects, but the alkalinity needs to be strictly controlled.

[0022] Preferably, the reaction temperature is 5-35° C., the reaction pressure is 0.01-0.05 MPa, and the reaction time is 0.5-4 h.

[0023] Preferably, the purity of the high-purity ethylidene norbornene is greater than 99.0%, the vinyl norbornene is less than 0.5%, the light component is less than 0.8%, the heavy component is less than 0.8%, and the water content is less than 50ppm. A polymerization inhibitor may be added, and the content does not exceed 200ppm.

[0024] Beneficial Effects

[0025] (1) The present invention adopts a mixed solvent system, which improves the selectivity of the reaction of 1,3-butadiene and cyclopentadiene, reduces the generation of butadiene self-polymerization and cyclopentadiene self-polymerization products, and is conducive to reducing the reflux ratio during distillation separation, thereby reducing energy consumption.

[0026] (2) The present invention uses a nickel-based isomerization catalyst to in-situ isomerize vinyl norbornene to ethylidene norbornene, which significantly reduces the concentration of vinyl norbornene in the addition reaction system, helps promote the main reaction, and thus improves the yield.

[0027] (3) The nickel-based isomerization catalyst used in the present invention has good tolerance to organic matter, and the polar solvent used can coordinate with the metal, which is beneficial to the stability of the catalyst. The catalyst has a long life and can be recycled to reduce costs.

[0028] (4) The addition of the polar solvent of the present invention can completely dissolve the sodium nitrite in the inhibitor, avoiding the appearance of flocs, thereby avoiding clogging of filters and other equipment. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0030] Example 1

[0031] The raw materials 1,3-butadiene 675g, cyclopentadiene 825g, mixed solvent 1500g (dioxane 750g, cyclohexane 750g), inhibitor 0.3g (sodium nitrite 0.15g, TBC 0.15g) were added to the reactor and mixed evenly, and the mass of nickel-based isomerization catalyst was added 2.26g [Ni(cod)2 0.75g, dppf 1.51g]. In the reactor, the reaction temperature was 178°C, the reaction system pressure was 5.1MPa, and the reaction time was 4h. After the reaction was completed, the reaction liquid was separated by vacuum distillation to obtain a mixture of vinyl norbornene and ethylidene norbornene, and the purity of the sum of the two was 98.6%.

[0032] The basic reaction steps of Examples 2-6 and Comparative Examples 1-3 are the same, and the specific feed and process conditions are according to Table 1. The corresponding 1,3-BD conversion rate, VNB selectivity, ENB selectivity, CPD conversion rate, (VNB+ENB) total yield and (VNB+ENB) purity after purification are shown in Table 2.

[0033] Table 1

[0034]

[0035]

[0036] Table 2

[0037]

[0038] 1,3-BD conversion rate = (mass of 1,3-butadiene reacted) / (mass of 1,3-butadiene in raw materials) × 100%;

[0039] VNB selectivity = (mass of 1,3-butadiene consumed to generate VNB) / (mass of 1,3-butadiene reacted) × 100%;

[0040] ENB selectivity = (mass of 1,3-butadiene consumed to generate ENB) / (mass of 1,3-butadiene reacted) × 100%;

[0041] CPD conversion rate = (mass of CPD consumed by generating VNB and ENB) / (mass of CPD in raw materials) × 100%;

[0042] Total yield of (VNB+ENB)=(mass of ENB+mass of VNB) / (total mass of reaction raw materials)×100%.

[0043] Comparative Example 1 is a scheme for preparing VNB by addition reaction of conventional CPD and 1,3-butadiene. The obtained reaction solution is recycled by raw materials and solvents, light components are removed, and heavy components are removed to prepare high-purity VNB. Then, VNB is isomerized to ENB using superbase as a catalyst, and high-purity ENB can be obtained after distillation. However, the conversion rate of 1,3-butadiene is low, and the selectivity of VNB is about 70%. The main side reaction is 1,3-butadiene dimer vinyl cyclohexene, accounting for about 25%. Other small amounts of by-products mainly include tetrahydroindene and butadiene polymers. Comparative Example 2 uses a mixed solvent of dioxane / cyclohexane, and the conversion rate of 1,3-butadiene is increased from 72.8% to 87.4%, but the selectivity is significantly reduced. Overall, the total yield of (VNB+ENB) (ENB is basically 0 here) increased by 7%, but it was not significant. The results of Comparative Example 3 show that the addition of an isomerization catalyst further promotes the conversion of 1,3-butadiene, and part of VNB is in situ isomerized to ENB, and the total yield of (VNB+ENB) is further increased to 29.3%. However, the ratio of VNB to ENB in ​​the single solvent acetonitrile is 28.6:35.4. The nickel-based isomerization catalyst has a certain effect, but the selectivity needs to be improved. In addition, although the conversion of 1,3-butadiene and CPD is significantly improved, the total yield of (VNB+ENB) is not significantly improved, which means that a large amount of by-product vinyl cyclohexene is formed, resulting in a decrease in raw material utilization and an increase in cost.

[0044] Compared with Comparative Example 1, after replacing the cyclohexane solvent with a mixed solvent of dioxane and cyclohexane, the conversion rate of 1,3-butadiene was significantly improved, and the total yield of (VNB+ENB) was increased from 25.5% to 33.4%. Compared with Comparative Examples 2 and 3, although the conversion rate of 1,3-butadiene decreased to a certain extent, the degree of isomerization was significantly improved, thereby increasing the total yield of (VNB+ENB) to 33.4%, which was nearly 20% higher than that of a single solvent system.

[0045] The comparison of Examples 1-3 shows that the presence of 20% or even 10% of dioxane in the mixed solvent also has a positive effect on the conversion rate of 1,3-butadiene and the total yield of (VNB+ENB), and has a wide range of applications.

[0046] Examples 4-6 used an acetonitrile-toluene mixed solvent system and an acetonitrile-heptane solvent system, and also showed a high 1,3-butadiene monomer conversion rate. In the acetonitrile-toluene mixed solvent system, the total yield of (VNB+ENB) reached 37.7%. It can also be seen from the selectivity of VNB and ENB in ​​Examples 1-6 that the higher the ENB selectivity, the higher the overall yield, indicating that the conversion of VNB to ENB is conducive to the further main reaction of 1,3-butadiene.

[0047] From the perspective of CPD conversion rate, there is little difference between the example and the comparative example, because even if CPD does not undergo addition reaction with butadiene to generate VNB, it will rapidly self-polymerize, so that the conversion rate is maintained between 96-98%.

[0048] When polar solvents such as acetonitrile or dioxane are introduced into the reaction system, the boiling points thereof are similar to those of cyclohexane, or even lower than those of solvents such as heptane and toluene, and the cost of solvent recycling will not be increased. From the comparison between Examples 1-7 and the comparative example, it can be seen that the selection of a suitable mixed solvent improves the selectivity of the reaction of 1,3-butadiene and cyclopentadiene, and reduces the generation of butadiene self-polymerization and cyclopentadiene self-polymerization products.

[0049] Example 7

[0050] The raw materials 1,3-butadiene 675g, acetonitrile 750g and sodium nitrite 0.15g were mixed evenly, cyclopentadiene 825g and cyclohexane 750g were mixed, TBC 0.15g was mixed, and then all were added to the reactor and mixed evenly, and nickel source Ni (cod) 21.5g and dppf 3.02g were added. In the reactor, the reaction system temperature was 182 ° C, the reaction system pressure was 5.5MPa, and the reaction time was 3h. After the reaction was completed, the reaction solution was separated by vacuum distillation to obtain a mixture of vinyl norbornene and ethylidene norbornene. Example 8-11 Example 7 The basic reaction steps are consistent, and the specific feeding and process conditions are carried out according to Table 3. The corresponding 1,3-BD conversion rate, VNB selectivity, ENB selectivity, (VNB + ENB) total yield and (VNB + ENB) purity after refining are shown in Table 4.

[0051] The results of Example 7 show that when the acetonitrile-cyclohexane system is used and the amount of isomerization catalyst is increased, the total yield of (VNB+ENB) can be increased to 40.6%, with an outstanding 1,3-butadiene conversion rate. From the ratio of ENB and VNB, it can be seen that the increase in the amount of catalyst is conducive to the isomerization of VNB to ENB. Example 8 changed the ratio of 1,3-butadiene and cyclopentadiene, and also achieved a good total yield of (VNB+ENB). In Example 9, tricyclohexylphosphine tetrafluoroborate (Cy3P·HBF4) was used as a ligand, which showed a conversion rate of up to 91.5% of 1,3-butadiene. The in-situ conversion of VNB to ENB was good, ENB:VNB=15.8, so VNB is not easy to accumulate in the reaction system and the content is low, which helps to improve the conversion rate of 1,3-butadiene and the total yield of VNB+ENB). Its disadvantage is that the ligand is a fluorine-containing compound, and hydrogen fluoride may be present during the reaction process, which poses a risk of corrosion to steel reactors.

[0052] Example 10 also achieved good results by using triphenylphosphine as a ligand. The triphenylphosphine ligand used in Example 11 was 5 times that of Example 10, which could increase the total yield of (VNB+ENB) from 37.7 to 39.33%.

[0053] Table 3

[0054]

[0055] Table 4

[0056] Example 7 Example 8 Example 9 Example 10 Embodiment 11 1,3-BD conversion rate (%) 87.6 90.5 91.5 81.8 84.4 VNB selectivity (%) 9.2 10.5 5.6 10.6 10.1 ENB selectivity (%) 83.5 82.1 88.7 81.5 83.1 (VNB+ENB) total yield % 40.6 37.2 43.14 37.7 39.33 (VNB+ENB) purity (%) 98.6 98.7 98.6 98.8 98.7

[0057] Examples 12-14

[0058] After the vinyl norbornene VNB and ethylidene norbornene mixture ENB are dried and dehydrated by molecular sieve, 60g is added to the dehydration and deoxygenation reactor, and 0.3g of isomerization catalyst K-Na2O / γ-Al2O3 is added. The reaction temperature is 28°C, the operating pressure is 0.015MPa, and the reaction time is 3h. Vinyl norbornene is isomerized to ethylidene norbornene to obtain crude ethylidene norbornene, and the ENB and VNB contents are analyzed by gas chromatography. The crude ethylidene norbornene can be obtained by alkali washing, drying and rectification to obtain high-purity ethylidene norbornene. Examples 12-14 are tested using the vinyl norbornene and ethylidene norbornene mixture (VNB+ENB) in Examples 1, 2 and 11 respectively. Comparative Example 4 is tested using the vinyl norbornene and ethylidene norbornene mixture (VNB+ENB) in Comparative Example 1. The specific results are shown in Table 5.

[0059] Table 5

[0060]

[0061] The dehydrated vinyl norbornene VNB and ethylidene norbornene mixture ENB, 0.5% of the super base isomerization catalyst K-Na2O / γ-Al2O3 can isomerize VNB to ethylidene norbornene ENB with a very high conversion rate, while the ENB content in the comparative example is only 92%. The reason is that the VNB content in the raw materials used in Examples 12-14 is 10%-15%, while the comparative example is basically all VNB. Comparative Example 4 prolongs the reaction time or increases the amount of catalyst, and the VNB conversion rate can also be increased to more than 99%. Although the terminal olefin isomerization catalyst nickel source and ligand are introduced when vinyl norbornene and ethylidene norbornene are prepared by addition of 1,3-butadiene and cyclopentadiene, the amount of super base is also reduced when vinyl norbornene is further isomerized to ethylidene norbornene, and the super base isomerization time is shortened, thereby improving production efficiency. Therefore, the addition of the nickel-based isomerization catalyst does not increase the catalyst cost.

Claims

1. A method for preparing a mixture of vinyl norbornene and ethylidene norbornene, comprising the following steps: After mixing 1,3-butadiene, cyclopentadiene, a mixed solvent and a polymerization inhibitor in a mass ratio of 1: (0.5-2.0): (1.0-10.0): (0.0001-0.01), a nickel-based isomerization catalyst is added to a reactor to react. After the reaction is completed, the reaction liquid is purified and separated to obtain a mixture of vinyl norbornene and ethylidene norbornene.

2. The preparation method according to claim 1, characterized in that: The mixed solvent consists of solvent A and solvent B in a mass ratio of 1:(0.1-100).

3. The preparation method according to claim 2, characterized in that: The solvent A is at least one of acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone and dioxane; the solvent B is at least one of C5-C10 alkanes, cycloalkanes and aromatic hydrocarbons.

4. The preparation method according to claim 1, characterized in that: The polymerization inhibitor is a mixture of sodium nitrite and p-tert-butylcatechol, wherein the mass ratio of the sodium nitrite to the p-tert-butylcatechol is 1:(0.5-3).

5. The preparation method according to claim 1, characterized in that: The nickel-based isomerization catalyst includes a nickel source and a ligand; wherein the nickel source is at least one of bis(1,5-cyclooctadiene)nickel Ni(cod)2, (1,5,9-cyclododecatriene)nickel, and allyl nickel complex Ni(π-C3H5)2; the ligand is one of 1,1'-bis(diphenylphosphino)ferrocene, tricyclohexylphosphine tetrafluoroborate, tricyclohexylphosphine, triphenylphosphine, 1,4-bis(diphenylphosphino)butane, 1,2-bis(diphenylphosphino)ethane, bis(diphenylphosphino)methane, and 1,3-bis(diphenylphosphino)propane; the molar ratio of the nickel source to the ligand is 1:(0.5-10); the mass ratio of the nickel-based isomerization catalyst to 1,3-butadiene is (0.001-0.1):

1.

6. The preparation method according to claim 1, characterized in that: The reaction temperature is 160-190° C., the reaction pressure is 1-8 MPa, and the reaction time is 1-5 h.

7. The preparation method according to claim 1, characterized in that: The mass ratio of vinyl norbornene to ethylidene norbornene in the mixture of vinyl norbornene and ethylidene norbornene is 1:(1-100).

8. A method for preparing high-purity ethylidene norbornene, comprising the following steps: The mixture of vinyl norbornene and ethylidene norbornene obtained in claim 1 is dried and dehydrated, and then introduced into an isomerization reactor, and an isomerization catalyst is added to react to obtain crude ethylidene norbornene; after refining, high-purity ethylidene norbornene can be obtained.

9. The preparation method according to claim 8, characterized in that: The isomerization catalyst is K-Na2O / γ-Al2O3, and the dosage of the isomerization catalyst is 0.1-1.5% of the total mass of vinyl norbornene and ethylidene norbornene; the reaction temperature is 5-35°C, the reaction pressure is 0.01-0.05MPa, and the reaction time is 0.5-4h.

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