A method for preparing cyclopentadiene by depolymerization of dicyclopentadiene

Abstract

The present invention discloses a method for preparing cyclopentadiene by depolymerizing dicyclopentadiene. Dicyclopentadiene is mixed with a solvent and a polymerization inhibitor and fed into a reactive distillation tower equipped with a falling film depolymerizer in a stripping section for falling film depolymerization and fractionation separation. Cyclopentadiene is obtained at the top of the tower. The present invention provides a method for preparing cyclopentadiene by depolymerizing dicyclopentadiene. The method effectively suppresses the autopolymerization reaction during the depolymerization of dicyclopentadiene at a relatively low cost, thereby obtaining cyclopentadiene with high yield and high purity.

Description

Technical Field

[0001] The invention belongs to the technical field of cyclopentadiene preparation, and particularly relates to a method for preparing cyclopentadiene by depolymerizing dicyclopentadiene. Background Art

[0002] Cyclopentadiene is an important by-product of the ethylene industry. It is widely used in the fields of rubber, pesticides, resins, etc. and has very high application value. Cyclopentadiene is also the main raw material for preparing MMT. MMT full name is methylcyclopentadiene trihydroxy manganese. It is a kind of unleaded gasoline antiknock agent with excellent performance and an alternative product to tetraethyl lead. Cyclopentadiene is prone to dimerization at room temperature to form dicyclopentadiene. Therefore, when using cyclopentadiene, dicyclopentadiene first needs to be depolymerized. Dicyclopentadiene is a colorless crystal at room temperature. When containing impurities, it is a light yellow oily liquid with camphor smell. It is soluble in most organic solvents and needs to be depolymerized into cyclopentadiene at high temperature. Because dicyclopentadiene has self-polymerization phenomenon in the high-temperature depolymerization process, it forms coking blockage due to self-polymerization, and is also accompanied by side reactions to produce impurities, thereby bringing negative impact to the yield and purity of the product.

[0003] At present, the method for depolymerization of dicyclopentadiene has liquid phase depolymerization method and gas phase depolymerization method. The conversion rate of gas phase depolymerization method DCPD is higher, but because the temperature is too high, the material is prone to coking phenomenon, blocking the reactor, and bringing great difficulties to operation. Liquid phase depolymerization is carried out in a distillation tower still, and its shortcoming is that DCPD will produce polymers when heated for a long time in the still, and the cyclopentadiene of depolymerization is prone to self-polymerization when separated, causing the CPD yield to be low. CN 109704905A reports that in order to improve the yield and purity of cyclopentadiene prepared by liquid phase depolymerization of dicyclopentadiene, hydroquinone, o-nitrophenol or aniline are added as inhibitors during the depolymerization process, and n-hexadecane and n-hexane are added as diluents. Although this process is conducive to the yield and purity of cyclopentadiene, it increases the cost of the dicyclopentadiene depolymerization process and the process of the subsequent separation of dicyclopentadiene. Summary of the Invention

[0004] The present invention aims to overcome the problems of the prior art in that autopolymerization occurs during the high-temperature depolymerization of dicyclopentadiene, as well as the low purity and yield of cyclopentadiene and the high cost. A method for preparing cyclopentadiene by depolymerizing dicyclopentadiene is provided. The method effectively suppresses the autopolymerization during the depolymerization of dicyclopentadiene at a relatively low cost, thereby obtaining cyclopentadiene with a high yield and high purity.

[0005] In order to achieve the above object, the present invention provides a method for preparing cyclopentadiene by depolymerizing dicyclopentadiene. Dicyclopentadiene is mixed with a solvent and a polymerization inhibitor and sent into a reaction distillation tower equipped with a falling film depolymerizer in a stripping section for falling film depolymerization and distillation separation, and cyclopentadiene is obtained at the top of the tower.

[0006] The solvent is at least one of alkanes and aromatic hydrocarbons with a boiling point of 175-260° C., preferably at least one of n-butylbenzene, cyclopentylbenzene, and cyclohexylbenzene.

[0007] Wherein, relative to 100 parts by weight of dicyclopentadiene, the amount of the solvent used is 5-50 parts by weight, preferably 20-40 parts by weight.

[0008] The polymerization inhibitor is selected from at least one of aromatic nitro polymerization inhibitors, quinone polymerization inhibitors, phenol polymerization inhibitors and amine polymerization inhibitors; preferably at least one of m-di-tert-butyl-p-cresol, p-tert-butylcatechol and p-nonylphenol.

[0009] Wherein, relative to 100 parts by weight of dicyclopentadiene, the amount of the polymerization inhibitor is 0.001-0.03 parts by weight, preferably 0.01-0.02 parts by weight.

[0010] Among them, the distillation section of the reactive distillation tower is packing separation, and the number of tower plates is 8-10.

[0011] In the falling film depolymerization and distillation separation process, the outer wall temperature of the falling film depolymerizer is 170-240°C, preferably 180-220°C; the bottom temperature is 35-160°C, preferably 80-140°C; the top temperature is 41-45°C, preferably 41-42°C; the condensation temperature is -10-20°C, preferably -5 to 10°C; the reflux ratio is 2-6:1, preferably 3-5:1, the bottom circulation flow rate to the feed flow rate ratio is 0.5:1-5:1, preferably 1:1-3:1, and the operating pressure of the distillation tower is 0.001-0.05 MPaG, preferably 0.01 to 0.03 MPaG.

[0012] Process of the present invention:

[0013] A mixed solution of dicyclopentadiene, solvent and polymerization inhibitor enters a reactive distillation tower and is evenly added to a liquid distribution plate of a falling film depolymerizer through a feed distributor. The liquid distribution plate is provided with a plurality of sieve holes, the aperture of which is 2 to 3 mm larger than the outer diameter of the falling film tube. The mixed solution flows from top to bottom along the outer wall of the falling film tube through the sieve holes, forming a falling film evaporation and depolymerization reaction. The generated cyclopentadiene can quickly enter the gas phase, reducing the self-polymerization rate. In addition, the dicyclopentadiene can quickly flow through the falling film tube wall, reducing the side reaction of the dicyclopentadiene polymerization and the heavy components, and improving the yield of cyclopentadiene.

[0014] In the present invention, a falling film depolymerizer is arranged in the stripping section of a reactive distillation tower, and falling film depolymerization is adopted to reduce the tower bottom temperature, thereby effectively reducing the self-polymerization of dicyclopentadiene. Adding a solvent to the reaction material can increase the flowability of the material and prevent the depolymerization temperature from being too high. Adding a polymerization inhibitor can further reduce the self-polymerization of dicyclopentadiene and reduce the generation of heavy components in the tower bottom material. A smaller number of distillation plates reduces the residence time of the distillation, and the condensation temperature of the tower top material is low, thereby preventing cyclopentadiene from re-polymerizing to produce dicyclopentadiene, thereby effectively improving the yield of cyclopentadiene and the purity of the cyclopentadiene product. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a schematic structural diagram of a reaction distillation tower for preparing cyclopentadiene by depolymerizing dicyclopentadiene.

[0016] Figure 2 It is a schematic structural diagram of the falling film depolymerizer of the present invention;

[0017] Among them: 1. Reaction distillation tower; 2. Distillation section; 3. Falling film depolymerizer; 4. Tower kettle; 5. Condenser; 6. Reflux ratio controller; 7. Feed distributor; 8. Circulating oil bath; 9. Cooling water coil; 10. Feed liquid circulation pump; 11. Oil bath inlet pipe; 12. Liquid distribution plate; 13. Falling film tube; 14. Oil bath outlet pipe; 15. Sieve hole. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below with reference to the embodiments and the accompanying drawings, but the embodiments do not limit the present invention.

[0019] The equipment used in the embodiment of the present invention is as follows Figure 1 As shown, the specific parameters and materials are:

[0020] In the reaction distillation tower 1, the upper section is the DN80×800mm distillation section 2 equipped with 5mm metal titanium θ ring, and the lower section is the DN380×1000mm stripping section and the tower kettle 4, in which the stripping section is equipped with 0.6m 2 The falling film depolymerizer 3 has a large contact area. The falling film depolymerizer 3 is heated by a circulating oil bath 8, and the tower kettle 4 is equipped with a cooling water coil 9; the top of the tower is equipped with a condenser 5 and a reflux ratio controller 6, and the condenser 5 uses a refrigerant to cool the tower; the discharge from the tower kettle is mixed with the raw material dicyclopentadiene through a liquid circulation pump 10 and sent to a feed distributor 7.

[0021] The structure of the falling film depolymerizer is as follows Figure 2As shown, there are several vertically arranged falling film tubes 13, the tops of the falling film tubes 13 are connected to the upper cavity, the bottoms of the falling film tubes 13 are connected to the lower cavity, the upper cavity is connected to the oil bath outlet pipe, and the lower cavity is connected to the oil bath inlet pipe. The falling film tubes 13 are provided with a liquid distribution plate 12 near the upper cavity, and the liquid distribution plate 12 is provided with a sieve hole 15. The aperture of the sieve hole 15 is 2 to 3 mm larger than the outer diameter of the falling film tube 13. The feed liquid flows from the outer wall of the falling film tube from top to bottom through the sieve hole, forming a falling film evaporation and depolymerization reaction.

[0022] Implementation Plan

[0023] Under normal pressure, dicyclopentadiene, a solvent, and a polymerization inhibitor are mixed and added to a distillation tower to establish a bottom liquid level; a circulating oil bath of a falling film depolymerizer is opened to increase the temperature, and a feed liquid circulation pump is started to circulate and increase the temperature of the feed liquid; dicyclopentadiene is depolymerized on the outer wall of the falling film tube to generate cyclopentadiene, which is condensed in a condenser at the top of the tower through a distillation section; the refrigerant temperature of the condenser is controlled to ensure that the temperature of the cyclopentadiene in the condenser at the top of the tower is -10-20°C; a reflux ratio controller is started to perform continuous reflux and discharge; dicyclopentadiene is continuously added to ensure a stable bottom liquid level; and the cooling water flow in the cooling water coil is controlled to ensure that the bottom temperature is 35-160°C.

[0024] Example 1

[0025] According to the implementation plan, dicyclopentadiene, cyclopentylbenzene, and p-tert-butylcatechol were mixed in a mass ratio of 100:30:0.02, and a 50% bottom liquid level was established. The circulating oil bath of the falling film depolymerizer was opened and heated to 180°C. The feed liquid circulation pump was started at a circulation rate of 2kg / h to circulate the material and increase the temperature. The generated cyclopentadiene was condensed in the overhead condenser through the distillation section. The condenser refrigerant temperature was controlled to maintain the cyclopentadiene temperature at 5°C. The operating pressure of the distillation column was 0.001MPa gauge pressure, and the top temperature was 41°C. The reflux ratio controller was started to control the reflux ratio to 3:1, and continuous reflux and discharge were performed. Dicyclopentadiene was continuously added at 1kg / h to ensure a stable bottom liquid level. The bottom circulation flow rate to feed rate ratio was 2:1. The cooling water flow in the cooling water coil was controlled to ensure the bottom temperature was 100°C. The yield and purity of cyclopentadiene obtained are shown in Table 1.

[0026] Example 2

[0027] According to the implementation plan, dicyclopentadiene, cyclohexylbenzene, and p-nonylphenol were mixed in a mass ratio of 100:50:0.03, and a 50% bottom liquid level was established. The circulating oil bath of the falling film depolymerizer was opened and heated to 240°C. The feed liquid circulation pump was started at a circulation rate of 5kg / h to circulate the material and heat it up. The generated cyclopentadiene was condensed in the overhead condenser through the distillation section. The condenser refrigerant temperature was controlled to keep the cyclopentadiene temperature at 20°C. The operating pressure of the distillation tower was 0.05MPa gauge pressure, and the tower top temperature was 43°C. The reflux ratio controller was started to control the reflux ratio to 6:1, and continuous reflux and discharge were performed. 1kg / h of dicyclopentadiene was continuously added to ensure a stable bottom liquid level. The bottom circulation flow rate to feed rate ratio was 5:1. The cooling water flow in the cooling water coil was controlled to ensure the bottom temperature was 160°C. The obtained cyclopentadiene yield and purity are shown in Table 1.

[0028] Example 3

[0029] According to the implementation plan, dicyclopentadiene, n-butylbenzene, and m-di-tert-butyl-p-cresol were mixed in a mass ratio of 100:10:0.001, a 50% bottom liquid level was established, the falling film depolymerizer circulating oil bath was opened and heated to 170°C, and the feed liquid circulation pump was started at a circulation rate of 0.5kg / h to circulate the material and heat it up. The generated cyclopentadiene was condensed in the top condenser of the distillation section. The condenser refrigerant temperature was controlled to keep the cyclopentadiene temperature at -10°C. The operating pressure of the distillation tower was 0.01MPa gauge pressure, and the top temperature was 42°C. The reflux ratio controller was started to control the reflux ratio to 2:1, and continuous reflux and discharge were performed. 1kg / h of dicyclopentadiene was continuously added to ensure a stable bottom liquid level. The bottom circulation flow rate to feed rate ratio was 0.5:1. The cooling water flow in the cooling water coil was controlled to ensure a bottom temperature of 35°C. The yield and purity of cyclopentadiene obtained are shown in Table 1.

[0030] Comparative Example 1

[0031] In Example 1, a falling film depolymerizer was not used, and the kettle temperature was controlled at 180° C. Dicyclopentadiene was depolymerized in the kettle. The yield and purity of the obtained cyclopentadiene are shown in Table 1.

[0032] Comparative Example 2

[0033] In Example 1, no solvent was used. The yield and purity of cyclopentadiene obtained are shown in Table 1.

[0034] Comparative Example 3

[0035] In Example 1, no polymerization inhibitor was used. The yield and purity of cyclopentadiene obtained are shown in Table 1.

[0036] Comparative Example 4

[0037] In Example 1, the tower top condensation temperature was controlled at 30° C. The yield and purity of cyclopentadiene obtained are shown in Table 1.

[0038] Table 1

[0039] serial number Cyclopentadiene yield / % Cyclopentadiene purity / % Example 1 98.5 99.5 Example 2 97.8 99.1 Example 3 98.8 99.8 Comparative Example 1 85.2 99.6 Comparative Example 2 95.1 99.6 Comparative Example 3 92.3 99.6 Comparative Example 4 97.1 93.5

[0040] As can be seen from the above embodiments and comparative examples, the present invention adopts falling film depolymerization of dicyclopentadiene, which reduces the residence time of dicyclopentadiene at high temperature and reduces the further polymerization degree of dicyclopentadiene; the addition of an alkane or aromatic solvent with a boiling point of 175-260° C. and an aromatic nitro polymerization inhibitor, a quinone polymerization inhibitor, a phenol polymerization inhibitor, or an amine polymerization inhibitor further improves the yield of cyclopentadiene; the overhead condenser controls the condensation temperature at a low level, reduces the self-polymerization of cyclopentadiene, and improves the purity of cyclopentadiene.

Claims

1. A method for preparing cyclopentadiene by depolymerizing dicyclopentadiene, characterized in that: Dicyclopentadiene is mixed with a solvent and a polymerization inhibitor and fed into a reaction distillation tower equipped with a falling film depolymerizer in a stripping section for falling film depolymerization and distillation separation, to obtain cyclopentadiene at the tower top. The distillation section of the reaction distillation tower is a packing separation tower with 8 to 10 plates. During the falling film depolymerization and distillation separation, the outer wall temperature of the falling film depolymerizer is 170 to 240° C.; the tower bottom temperature is 35 to 160° C.; the tower top temperature is 41 to 45° C.; the condensation temperature is -10 to 20° C.; the reflux ratio is 2 to 6:1, the ratio of the tower bottom circulation flow rate to the feed flow rate is 0.5:1 to 5:1, and the operating pressure of the distillation tower is 0.001 to 0.05 MPaG.

2. The method for preparing cyclopentadiene by depolymerizing dicyclopentadiene according to claim 1, wherein: The solvent is at least one of alkanes and aromatic hydrocarbons having a boiling point of 175-260°C.

3. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 2, wherein: The solvent is at least one of n-butylbenzene, cyclopentylbenzene and cyclohexylbenzene.

4. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 1, wherein: The amount of the solvent used is 5 to 50 parts by weight relative to 100 parts by weight of dicyclopentadiene.

5. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 1, wherein: The polymerization inhibitor is selected from at least one of aromatic nitro polymerization inhibitors, quinone polymerization inhibitors, phenol polymerization inhibitors and amine polymerization inhibitors.

6. The method for preparing cyclopentadiene by depolymerizing dicyclopentadiene according to claim 5, wherein: The polymerization inhibitor is at least one of m-di-tert-butyl-p-cresol, p-tert-butylcatechol and p-nonylphenol.

7. The method for preparing cyclopentadiene by depolymerizing dicyclopentadiene according to claim 1, wherein: The amount of the polymerization inhibitor is 0.001 to 0.03 parts by weight relative to 100 parts by weight of dicyclopentadiene.

8. The method for preparing cyclopentadiene by depolymerizing dicyclopentadiene according to claim 1, wherein: The distillation section of the reactive distillation tower is packing separation, and the number of tower plates is 8 to 10.

9. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 1, wherein: During the falling film depolymerization and distillation separation process, the outer wall temperature of the falling film depolymerizer is 180-220° C.; the tower bottom temperature is 80-140° C.; the tower top temperature is 41-42° C.; the condensation temperature is -5-10° C.; the reflux ratio is 3-5:1, the tower bottom circulation flow rate to feed flow rate ratio is 1:1-3:1, and the operating pressure of the distillation tower is 0.01-0.03 MPaG.

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