A preparation method of 5-ethylidene-2-norbornene

Abstract

The present invention relates to a method for preparing 5-ethylidene-2-norbornene, comprising: cyclopentadiene, 1,3-butadiene, and a solvent are mixed as raw materials, lanthanide sulfonate is used as a catalyst, and 5-vinyl-2-norbornene is obtained by Diels-Alder polymerization in a jacketed reactor with stirring in series; and high-purity 5-ethylidene-2-norbornene is obtained by processes such as catalyst removal, refined separation, and isomerization reaction. The present invention realizes a highly selective D-A reaction at a relatively low reaction temperature, reduces the generation of by-products, improves the overall yield of 5-ethylidene-2-norbornene, and has a good economic benefit prospect.

Description

Technical Field

[0001] The invention belongs to the field of modified materials, and particularly relates to a method for preparing 5-ethylidene-2-norbornene. Background Art

[0002] 5-Ethylene-2-norbornene (ENB), also known as ethylidene norbornene, is the key third monomer of ethylene propylene diene monomer (EPDM), and is often used as a modified material for rubber products around engines, waterproof boards and other building materials and impact-resistant plastics. Currently, 1,3-butadiene (BD) and cyclopentadiene (CPD) are mainly used as raw materials to generate 5-vinyl-2-norbornene (VNB) through the Diels-Alder reaction (abbreviated as: DA reaction), and then the thermal polymerization method of ENB is obtained through isomerization. The main reaction equation and side reaction equation are as follows:

[0003] Ⅰ) Main reaction:

[0004]

[0005] Ⅱ) Side effects:

[0006]

[0007] The competitive polymerization rates of BD and CPD in the above-mentioned thermal free radical polymerization are not much different, so a large number of by-products such as dicyclopentadiene (DCPD), 5-vinyl-2-cyclohexene (VCH), tetrahydroindene (THI) and their polymers will be produced during the reaction, resulting in a low conversion rate of the main products such as VNB and ENB.

[0008] In patent CN201310393790.X, CPD and BD are reacted in a dead volume-free series tubular reactor to generate VNB through Diels-Alder reaction, and then isomerized to generate crude ENB and then purified; this patent reduces the generation of by-products in high-temperature reactions by adding polymerization inhibitors. In patent CN02108265.0, crude DCPD raw material is used, decomposed into CPD, and reacted with BD to generate VNB through Diels-Alder reaction, and then isomerized to generate ENB; its technical scheme is similar to the previous patent. In patent 201510893647.6, ENB is synthesized using a kettle reactor, which is characterized by using acetone as a solvent, which can significantly enhance the reaction conversion rate and ENB selectivity at relatively low temperature and pressure. The above patents all utilize the traditional DA reaction principle, improve the reaction selectivity through different process technologies, reduce the generation of by-products, and thus improve the economic efficiency of ENB synthesis. However, the above process technology has the defects of high reaction temperature and high CPD self-polymerization rate, resulting in low single-pass conversion rate. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a method for preparing 5-ethylidene-2-norbornene, which realizes a highly selective DA reaction at a relatively low reaction temperature, reduces the generation of by-products, improves the overall yield of 5-ethylidene-2-norbornene, and has a good economic benefit prospect.

[0010] The present invention provides a method for preparing 5-ethylidene-2-norbornene, comprising:

[0011] (1) Cyclopentadiene CPD, 1,3-butadiene BD, and a solvent are uniformly mixed in a mass ratio of 1:(0.4-1):(1-4) as raw materials, and are pre-cooled to -20-10° C. by a heat exchanger, and then transported into a first polymerization reactor with a stirring and jacket, and a catalyst is added, and the mixture is reacted at 80-110° C. and a pressure of 2.0-5.0 MPa for 0.5-1.5 h; wherein the catalyst is a lanthanide sulfonate;

[0012] (2) The product of step (1) is transported into a second polymerization reactor with stirring and jacket, reacted at 120-160° C. and a pressure of 2.0-5.0 MPa for 0.1-0.5 h, and then enters a flash tower with a top operating temperature of -10-15° C. and an operating pressure of 0.03-0.3 MPa. Unreacted CPD and BD are recovered from the top of the tower and recycled to the batching tank. The bottom material enters a decatalyst reactor to be stirred;

[0013] (3) adding 0.2-1.0% of the total mass of alkali solution to the decatalytic reaction kettle, removing the catalyst at 10-50° C. for a residence time of 5-30 min, and the bottom material of the kettle is discharged from the alkali solution and then enters the first distillation tower;

[0014] (4) In the first distillation tower, the top operating temperature is 30-70° C., the operating pressure is 5-20 kPa, the reflux ratio is 0.25-2, the crude VCH product is obtained at the top of the tower, and the bottom material enters the second distillation tower;

[0015] (5) In the second distillation tower, the tower top operating temperature is 40-80° C., the operating pressure is 5-20 kPa, the reflux ratio is 1-5, and VNB is obtained at the tower top;

[0016] (6) The VNB obtained in the second distillation tower is subjected to adsorption on a molecular sieve packing bed to remove moisture, and then enters an isomerization reactor, where it is reacted for 2 to 5 hours at a temperature of 0 to 25° C. and an operating pressure of 0.05 to 0.15 MPa under the action of an alkali catalyst to obtain a crude ENB mixture;

[0017] (7) The crude ENB mixture enters a third distillation tower, with a tower top operating temperature of 40 to 80° C., an operating pressure of 5 to 20 kPa, and a reflux ratio of 3 to 6, and 5-ethylidene-2-norbornene ENB is obtained at the tower top.

[0018] The solvent in step (1) is at least one of C6-C10 saturated cycloalkane solvents, which may be cyclohexane, methylcyclohexane, dimethylcyclohexane, etc.

[0019] The lanthanide sulfonate in step (1) is at least one of ytterbium trifluoromethanesulfonate and scandium trifluoromethanesulfonate, and the added amount is 0.1-0.75% of the total mass of CPD and BD.

[0020] The first polymerization reactor in step (1) uses saturated hot water (≥80°C) as the heat transfer medium; the second polymerization reactor in step (2) uses medium-temperature heat transfer oil as the heat transfer medium, the pour point of which is -40 to -30°C, and the kinematic viscosity at 40°C is 5 to 40 mm 2 / s.

[0021] The alkali solution in step (3) is a NaOH aqueous solution with a mass concentration of 15%; the water content of the bottom material of the kettle after the alkali solution is removed is ≤1000ppm.

[0022] In the step (5), the bottom of the second distillation tower obtains a mixture A, which includes tetrahydroindene, DCPD and other polymer products with a boiling point of ≥143°C.

[0023] The molecular sieve filler in step (6) is sodium X-type molecular sieve 13X, and the water content of the material entering the isomerization reactor is controlled to be ≤25ppm.

[0024] The base catalyst in step (6) is Na2O-NaOH / γ-Al2O3, the base strength thereof is 38-43, and the amount of the base catalyst used is 4.0-6.0 mmol / g.

[0025] The ENB obtained in the step (7) has a purity of ≥98.5wt%, a Pt / Co color number of ≤50, and a moisture content of ≤50ppm.

[0026] In the step (7), the bottom of the third distillation tower obtains a mixture B, which includes ENB and VNB with a mass percentage of ≤5%, and other polymer products, and can be further refined and recycled.

[0027] The Diels-Alder reaction of CPD and BD is a cycloaddition reaction, and the reaction of conjugated diene and monoenophile can generate 5-vinyl-2-norbornene (VNB) and tetrahydroindene (THI). However, as the DA reaction initiated by the free radical increases with the reaction temperature, the reaction reactivity of side reactions such as CPD and BD self-dimerization will be greatly enhanced, resulting in a decrease in monomer conversion. The lanthanide sulfonate used in the present invention is a Lewis acid, which can effectively enhance the selectivity of the DA reaction, reduce the requirements for reaction conditions, and reduce side reaction products, thereby improving the monomer conversion rate.

[0028] Beneficial Effects

[0029] (1) The present invention uses lanthanide sulfonate as a catalyst to improve the selectivity of the Diels-Alder synthesis reaction of 5-ethylidene-2-norbornene and reduce the generation of by-products;

[0030] (2) The present invention adopts a series of tank reactors to carry out DA reaction, improves heat transfer efficiency by stirring, and effectively reduces the isomerization of VNB to THI caused by back mixing, thereby improving the product yield;

[0031] (3) The present invention uses saturated hot water with large flow rate and large heat capacity as the heating and heat removal medium in the DA polymerization reactor to ensure that the reaction system is basically kept at a constant temperature, thereby reducing the occurrence of CPD dimerization and various side reactions;

[0032] (4) The present invention sets a molecular sieve drying bed in front of the VNB isomerization reactor to remove trace moisture, thereby increasing the life of the isomerization catalyst and reducing the catalyst unit consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0034] 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.

[0035] Example 1

[0036] Cyclopentadiene (CPD), 1,3-butadiene (BD) and methylcyclohexane are uniformly mixed in a mass ratio of 1:0.75:2.25 as raw materials, and are pre-cooled to -5°C by a heat exchanger E101, and then transported into a first polymerization reactor R201 with stirring and a jacket, and 0.15% of the total material mass of scandium trifluoromethanesulfonate Sc(OTF)3 is added, and the reaction is carried out at 95°C and a pressure of 2.7MPa for 1.0h; then the reaction materials are transported into a second polymerization reactor R202 with stirring and a jacket, and reacted at 150°C and a pressure of 3.8MPa for 0.2h, and then enter a flash tower T201, with a top operating temperature of 5°C and an operating pressure of 0.12MPa. Unreacted CPD and BD are recovered from the top of the tower and recycled to the batching tank V101, and the bottom material enters a decatalyst reactor R203 to be stirred.

[0037] Add 15% NaOH aqueous solution of 0.5% of the total material mass to the decatalytic reactor R203, remove the catalyst at 20°C, and the residence time is 15min. The bottom material of the reactor first removes the alkali solution and then enters the first distillation tower T202. The top operating temperature of the tower is 35°C, the operating pressure is 10kPa, and the reflux ratio is 1. The crude VCH product is obtained at the top of the tower, and the bottom material enters the second distillation tower T203; the top operating temperature of the second distillation tower T203 is 70°C, the operating pressure is 15kPa, and the reflux ratio is 2. The bottom of the tower obtains the mixture A, and the top of the tower obtains VNB and enters the molecular sieve packing bed T301 for adsorption and dehydration. After dehydration, the VNB with a water content of 10ppm enters the isomerization reactor R301, and reacts for 2.0h at a temperature of 10°C and an operating pressure of 0.11MPa under the action of the Na2O-NaOH / γ-Al2O3 catalyst with a basicity of 42 to generate a crude ENB mixture.

[0038] The crude ENB enters the third distillation tower T401, with a top operating temperature of 55°C, an operating pressure of 15 kPa, and a reflux ratio of 3. ENB with a purity of 99.06 wt%, a Pt / Co color number of 15, and a moisture content of 26 ppm is obtained at the top of the tower, and a mixture B is obtained at the bottom of the tower.

[0039] Embodiments 2 to 5

[0040] In Examples 2 to 5, only the lanthanide sulfonate catalyst and the addition amount were changed, and the other process conditions were the same as those in Example 1, that is, ENB with different physical and chemical properties and the target conversion rate of the monomer were obtained.

[0041]

[0042]

[0043] * Target monomer conversion rate: Statistics of the actual yield of BD and CPD converted into the final ENB product.

[0044] It can be seen from the above examples that increasing the amount of catalyst added can significantly improve the target conversion rate of monomers in the Diels-Alder reaction, but has little effect on the purity and moisture index of the final ENB product.

[0045] When high concentrations of Sc(OTF)3 and Yb(OTF)3 catalysts were used respectively, the former could obtain a lighter ENB product color, while the latter was more effective in improving the target monomer conversion rate.

[0046] Embodiments 6 to 9

[0047] Cyclopentadiene (CPD), 1,3-butadiene (BD) and methylcyclohexane are uniformly mixed in a mass ratio of 1:1:2 as raw materials, and are pre-cooled to -5°C by a heat exchanger E101, and then transported into a first polymerization reactor R201 with stirring and a jacket, and 0.3% of the total material mass of scandium trifluoromethanesulfonate Sc(OTF)3 is added, and the reaction is carried out at 95°C and a pressure of 2.7MPa for 1.0h; then the reaction materials are transported into a second polymerization reactor R202 with stirring and a jacket, and reacted at 150°C and a pressure of 3.8MPa for 0.2h, and then enter a flash tower T201 with a top operating temperature of 5°C and an operating pressure of 0.12MPa. Unreacted CPD and BD are recovered from the top of the tower and recycled to the batching tank V101. The materials in the bottom of the tower enter the decatalytic reactor R203 to be stirred.

[0048] Add 15% NaOH aqueous solution of 0.5% of the total material mass to the decatalytic reactor R203, remove the catalyst at 20°C, and stay for 15 minutes. The bottom material of the reactor first removes the alkali solution and then enters the first distillation tower T202. The top operating temperature is 35°C, the operating pressure is 10kPa, and the reflux ratio is 1. The crude VCH product is obtained at the top of the tower, and the bottom material enters the second distillation tower T203; the top operating temperature of the second distillation tower T203 is 70°C, the operating pressure is 15kPa, and the reflux ratio is 2. The bottom of the tower obtains the mixture A, and the top of the tower obtains VNB and enters the molecular sieve packing bed T301 for adsorption and dehydration. VNB is reacted in the isomerization reactor R301 under the action of Na2O-NaOH / γ-Al2O3 catalyst with a basicity of 42, with an amount of 5.5mmol / g, at a temperature of 10°C and an operating pressure of 0.11MPa for 2.0h to generate a crude ENB mixture. The crude ENB enters the third distillation tower T401, with a top operating temperature of 55°C, an operating pressure of 15 kPa, and a reflux ratio of 3. High-purity ENB is obtained at the top of the tower, and a mixture B is obtained at the bottom of the tower.

[0049] The following examples show the effects of VNB with different trace water contents on isomerization single-pass conversion and ENB product performance.

[0050] Example 6 Example 7 Example 8 Example 9 Trace water, ppm 5 10 25 50 ENB purity, wt% 99.05 99.14 98.87 97.69 Pt / Co Color Number 15 20 20 20 Moisture, ppm 10 15 30 75 One-way conversion rate 98.6 96.5 90.4 75.6

[0051] *Isomerization reaction single-pass conversion rate: the conversion rate of VNB isomerization to ENB in ​​a single-pass reaction.

[0052] It can be seen from the above Examples 6 to 9 that as the trace water content of VNB increases, the water content of the ENB product will increase accordingly; the excess water in VNB causes the catalytic efficiency of the base catalyst to be greatly reduced, and the single-pass conversion rate of the isomerization reaction will be significantly reduced.

[0053] Embodiments 10 to 11

[0054] Cyclopentadiene (CPD), 1,3-butadiene (BD) and methylcyclohexane are uniformly mixed in a mass ratio of 1:0.5:2 as raw materials, and are pre-cooled to -5°C through a heat exchanger, and then transported into a first polymerization reactor R201 with stirring and a jacket, and 0.4% of the total material mass of scandium trifluoromethanesulfonate Yb (OTF)3 is added, and the reaction is carried out at 110°C and a pressure of 4.0 MPa for 1.0 h; then the reaction materials are transported into a second polymerization reactor R202 with stirring and a jacket, and reacted at 140°C and a pressure of 3.0 MPa for 0.2 h, and then enter a flash tower T201 with a top operating temperature of 5°C and an operating pressure of 0.12 MPa. Unreacted CPD and BD are recovered from the top of the tower and recycled to the batching tank V101. The materials in the tower bottom enter the decatalyst reactor R203 to be stirred.

[0055] Add 15% NaOH aqueous solution of 0.8% of the total material mass to the decatalytic reactor R203, remove the catalyst at 25°C, and the residence time is 30min. The bottom material of the reactor first removes the alkali solution and then enters the first distillation tower T202. The top operating temperature of the tower is 35°C, the operating pressure is 10kPa, and the reflux ratio is 1. The crude VCH product is obtained at the top of the tower, and the bottom material enters the second distillation tower T203; the top operating temperature of the second distillation tower T203 is 70°C, the operating pressure is 15kPa, and the reflux ratio is 2. The bottom of the tower obtains the mixture A, and the top VNB ​​enters the molecular sieve packing bed T301 for adsorption and dehydration to 20ppm. VNB is reacted in the isomerization reactor R301 under the action of Na2O-NaOH / γ-Al2O3 catalyst with a basicity of 42, with an amount of 6.0mmol / g, at a temperature of 15°C and an operating pressure of 0.12MPa for 3.0h to generate a crude ENB mixture.

[0056] Examples 10-11 show the effects of different operating conditions of the third distillation tower T401 on the performance of the ENB product.

[0057] Example 10 Embodiment 11 Tower top temperature, °C 40 80 Operating pressure, kPa 5 20 Reflux ratio 6 3 ENB purity, % 99.70 98.60 Pt / Co Color Number 30 30 Moisture, ppm 10 25

[0058] It can be seen from the above embodiments that under the conditions of low operating pressure, top distillation temperature and high reflux ratio of the third distillation tower T401, the physical and chemical properties of the ENB product are better.

[0059] Comparative Example 1

[0060] Cyclopentadiene (CPD), 1,3-butadiene (BD) and methylcyclohexane are uniformly mixed in a mass ratio of 1:0.75:2.25 as raw materials, pre-cooled to -5°C by a heat exchanger, and then transported into a polymerization reactor R201 with stirring and a jacket. No catalyst is added, and the reaction is carried out at 120°C and a pressure of 5.5MPa for 1.0h; then the reaction materials are transported into a polymerization reactor R202 with stirring and a jacket, and reacted at 150°C and a pressure of 3.8MPa for 0.2h, and then enter a flash tower T201 with a top operating temperature of 5°C and an operating pressure of 0.12MPa. Unreacted CPD and BD are recovered from the top of the tower and recycled to the V101 tank for batching. The materials in the bottom of the tower enter the decatalyst reactor R203 to be stirred.

[0061] Add 0.5% of the total material mass of 15% NaOH aqueous solution to R203, stir for 15 minutes, remove alkali solution from the bottom of the kettle and then enter the distillation tower T202, the top operating temperature is 35°C, the operating pressure is 10kPa, the reflux ratio is 1, the crude VCH is obtained at the top of the tower, and the bottom of the tower enters the distillation tower T203; the top operating temperature of T203 tower is 70°C, the operating pressure is 15kPa, the reflux ratio is 2, the bottom of the tower obtains mixture A, and the top of the tower obtains VNB and enters the molecular sieve packing bed T301 for adsorption and dehydration. After dehydration, the VNB with a water content of 50ppm enters the isomerization reactor R301, and reacts for 2.0 hours at a temperature of 10°C and an operating pressure of 0.11MPa under the action of a Na2O-NaOH / γ-Al2O3 catalyst with a basicity of 38 to generate a crude ENB mixture.

[0062] The crude ENB enters the distillation tower T401, the tower top operating temperature is 65°C, the operating pressure is 50kPa, the reflux ratio is 2, and the ENB product with a purity of 95.0wt%, a Pt / Co color number of 70, and a water content of 112ppm is obtained at the tower top. The target monomer conversion rate is ≤50%, and there are a lot of by-products such as DCPD and VCH.

Claims

1. A method for preparing 5-ethylidene-2-norbornene, comprising: (1) Cyclopentadiene CPD, 1,3-butadiene BD, and a solvent are uniformly mixed in a mass ratio of 1:(0.4-1):(1-4) as raw materials, and are pre-cooled to -20-10°C by a heat exchanger (E101), and then transported into a first polymerization reactor (R201) with stirring and a jacket, and a catalyst is added to react at 80-110°C and a pressure of 2.0-5.0 MPa for 0.5-1.5 h; wherein the catalyst is ytterbium trifluoromethanesulfonate, and the amount added is 0.1-0.75% of the total mass of CPD and BD; and the solvent is at least one of C6-C10 saturated cycloalkane solvents; (2) The product of step (1) is transported into a second polymerization reactor (R202) with stirring and jacketing, and reacts at 120-160°C and a pressure of 2.0-5.0 MPa for 0.1-0.5 h, and then enters a flash tower (T201) with a top operating temperature of -10-15°C and an operating pressure of 0.03-0.3 MPa. Unreacted CPD and BD are recovered from the top of the tower and recycled to the batching tank (V101). The bottom material of the tower enters a decatalyst reactor (R203) to be stirred; (3) Add 0.2-1.0% of the total mass of alkali solution to the catalyst removal reactor (R203), remove the catalyst at 10-50 °C, and retain it for 5-30 min. After the alkali solution is removed from the bottom of the reactor, the material enters the first distillation tower (T202); (4) In the first distillation tower (T202), the top operating temperature is 30-70°C, the operating pressure is 5-20 kPa, the reflux ratio is 0.25-2, and crude VCH is obtained at the top of the tower. The bottom material enters the second distillation tower (T203). The structural formula of VCH is ; (5) In the second distillation tower (T203), the tower top operating temperature is 40-80°C, the operating pressure is 5-20 kPa, the reflux ratio is 1-5, and VNB is obtained at the tower top. The structural formula of the VNB is ; (6) The VNB obtained from the second distillation tower (T203) is adsorbed on a molecular sieve packing bed (T301) to remove moisture, and then enters an isomerization reactor (R301). Under the action of an alkali catalyst, the reaction is carried out for 2 to 5 hours at a temperature of 0 to 25 °C and an operating pressure of 0.05 to 0.15 MPa to obtain a crude ENB mixture. The structural formula of the ENB is ; (7) The crude ENB mixture enters the third distillation tower (T401) with a top operating temperature of 40 to 80 °C, an operating pressure of 5 to 20 kPa, and a reflux ratio of 3 to 6, and 5-ethylidene-2-norbornene ENB is obtained at the top of the tower.

2. The preparation method according to claim 1, characterized in that: The first polymerization reactor (R201) in step (1) uses saturated hot water as the heat transfer medium; the second polymerization reactor (R202) in step (2) uses medium-temperature heat transfer oil as the heat transfer medium, the pour point of which is -40 to -30 °C, and the kinematic viscosity at 40 °C is 5 to 40 mm 2 / s.

3. The preparation method according to claim 1, characterized in that: The alkali solution in step (3) is a NaOH aqueous solution with a mass concentration of 15%; the water content of the bottom material after the alkali solution is removed is ≤1000 ppm.

4. The preparation method according to claim 1, characterized in that: In the step (5), the bottom of the second distillation tower (T203) obtains a mixture A, which includes tetrahydroindene with a boiling point ≥143°C, dicyclopentadiene DCPD and other polymer products.

5. The preparation method according to claim 1, characterized in that: The molecular sieve filler in step (6) is sodium X-type molecular sieve 13X, and the water content of the material entering the isomerization reactor (R301) is controlled to be ≤25 ppm.

6. The preparation method according to claim 1, characterized in that: The base catalyst in step (6) is Na2O-NaOH / γ-Al2O3, the base strength thereof is 38-43, and the amount of the base catalyst used is 4.0-6.0 mmol / g.

7. The preparation method according to claim 1, characterized in that: The ENB obtained in the step (7) has a purity of ≥98.5wt%, a Pt / Co color number of ≤50, and a moisture content of ≤50 ppm.

8. The preparation method according to claim 1, characterized in that: In the step (7), the bottom of the third distillation tower (T401) obtains a mixture B, wherein the mixture B includes ENB and VNB in ​​a mass percentage of ≤5%, and other polymer products.

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