Process and apparatus for the depolymerization of dicyclopentadiene to produce cyclopentadiene and uses thereof

Abstract

This invention relates to the chemical industry and discloses a method and apparatus for preparing cyclopentadiene from dicyclopentadiene through depolymerization, as well as its applications. The method includes: mixing dicyclopentadiene and a polymerization inhibitor and performing depolymerization distillation separation in a reactive distillation column; the product obtained at the top of the column is then rapidly cooled to obtain cyclopentadiene; wherein the rapid cooling temperature is 0-30°C. This invention, by adding a rapid cooling device to the depolymerization equipment, rapidly cools the depolymerized cyclopentadiene to a low temperature, preventing the cyclopentadiene from repolymerizing to form dicyclopentadiene. Therefore, it effectively improves the yield and selectivity of dicyclopentadiene while reducing the production cost of cyclopentadiene.

Description

Technical Field

[0001] This invention relates to the field of chemical engineering, specifically to a method and apparatus for preparing cyclopentadiene by depolymerization of dicyclopentadiene and its application. Background Technology

[0002] Cyclopentadiene is an important byproduct of the ethylene industry, widely used in rubber, pesticides, resins, and other fields, and has high application value. Cyclopentadiene is also a major raw material for the preparation of MMT (methylcyclopentadiene trihydroxymanganese), a high-performance unleaded gasoline antiknock agent and a substitute for tetraethyl lead. Cyclopentadiene readily undergoes dimerization at room temperature to form dicyclopentadiene; therefore, dicyclopentadiene must first be depolymerized before using cyclopentadiene. Dicyclopentadiene is a colorless crystal at room temperature, but when containing impurities, it is a pale yellow oily liquid with a camphor odor. It is soluble in most organic solvents and requires high-temperature depolymerization to form cyclopentadiene. Due to the self-polymerization phenomenon during the high-temperature depolymerization of dicyclopentadiene, coking and blockage can occur, along with side reactions that produce impurities, negatively impacting the product yield and purity.

[0003] Currently, there are two methods for depolymerizing dicyclopentadiene: liquid-phase depolymerization and gas-phase depolymerization. Gas-phase depolymerization of DCPD has a high conversion rate, but due to the high temperature, the material is prone to coking, clogging the reactor and causing significant operational difficulties. Liquid-phase depolymerization is carried out in the reboiler of a distillation column. Its disadvantages include the formation of polymers from prolonged heating of DCPD in the reboiler, and the tendency for depolymerized cyclopentadiene to undergo self-polymerization during separation, resulting in low CPD yield. CN 109704905A reports that to improve the yield and purity of cyclopentadiene prepared from liquid-phase depolymerization of dicyclopentadiene, hydroquinone, o-nitrophenol, or aniline are added as polymerization inhibitors during the depolymerization process, along with n-hexadecane and n-hexane as diluents. While this process improves the yield and purity of cyclopentadiene, it increases the cost of the dicyclopentadiene depolymerization process and the subsequent separation process. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of self-polymerization reaction during the high-temperature depolymerization of dicyclopentadiene, as well as the low purity and yield of cyclopentadiene and high cost in the existing technology. This invention provides a method and equipment for preparing cyclopentadiene by depolymerization of dicyclopentadiene. This method effectively suppresses the self-polymerization reaction during the depolymerization process of dicyclopentadiene at a lower cost, and obtains cyclopentadiene with high efficiency and high purity.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for preparing cyclopentadiene by depolymerization of dicyclopentadiene, the method comprising: mixing dicyclopentadiene and a polymerization inhibitor and carrying out depolymerization and distillation separation in a reactive distillation column, wherein the product obtained at the top of the column is rapidly cooled to obtain cyclopentadiene;

[0006] The temperature of the rapid cooling is 0-30℃.

[0007] A second aspect of the present invention provides an apparatus for the depolymerization of dicyclopentadiene to prepare cyclopentadiene, the apparatus comprising a reactive distillation column and a quenching device assembled at the top of the reactive distillation column;

[0008] In the reactive distillation column, dicyclopentadiene depolymerizes to form cyclopentadiene;

[0009] The quenching device is used to quench the depolymerization product of dicyclopentadiene.

[0010] A third aspect of the present invention provides the application of the apparatus described above in the depolymerization of dicyclopentadiene to prepare cyclopentadiene.

[0011] The method described in this invention does not use a diluent when preparing cyclopentadiene from dicyclopentadiene through depolymerization, thereby reducing energy consumption in the depolymerization process and subsequent cyclopentadiene separation process.

[0012] By adding a quenching device to the depolymerization equipment, the depolymerized cyclopentadiene is rapidly cooled to a low temperature, preventing the cyclopentadiene from repolymerizing to form dicyclopentadiene. This effectively improves the yield of cyclopentadiene, increases the purity of the cyclopentadiene product, and reduces the production cost of cyclopentadiene. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the equipment used in this invention to prepare cyclopentadiene by depolymerizing dicyclopentadiene.

[0014] Explanation of reference numerals in the attached figures

[0015] 01 Reactive distillation column 02 Quenching unit Detailed Implementation

[0016] 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.

[0017] The first aspect of this invention provides a method for preparing cyclopentadiene by depolymerization of dicyclopentadiene, the method comprising: mixing dicyclopentadiene and a polymerization inhibitor and carrying out depolymerization and distillation separation in a reactive distillation column, wherein the product obtained at the top of the column is rapidly cooled to obtain cyclopentadiene;

[0018] The temperature of the rapid cooling is 0-30℃.

[0019] During their research, the inventors of this invention discovered that even in the presence of a polymerization inhibitor, when preparing cyclopentadiene from dicyclopentadiene through depolymerization, the cyclopentadiene obtained at the top of the reactive distillation column still undergoes a vigorous self-polymerization reaction, negatively impacting the yield and purity of cyclopentadiene. The inventors addressed this by rapidly quenching the cyclopentadiene obtained at the top of the column, preventing further dimerization and significantly improving the yield and purity of cyclopentadiene, thus obtaining polymer-grade cyclopentadiene. The reason for this improvement is likely that the absence of a polymerization inhibitor or a significantly reduced inhibitor concentration at the top of the reactive distillation column allows the cyclopentadiene to still undergo self-polymerization, resulting in a substantial decrease in the yield and purity of the obtained cyclopentadiene.

[0020] In this invention, depolymerization and distillation separation in a reactive distillation column means that dicyclopentadiene is first depolymerized in the reactive distillation column, and the product rises in the distillation column for distillation separation, thereby achieving both reaction (depolymerization) and separation (distillation) in one reactor (reactive distillation column).

[0021] In this invention, the quenching temperature is 0-30°C, for example, it can be 0, 10, 15, 20, 30°C or any value between two points. Within this range, a high yield and purity of cyclopentadiene can be guaranteed. Preferably, the quenching temperature is 0-10°C. Within this preferred range, the yield and purity of cyclopentadiene can be further improved. In this invention, quenching refers to rapidly cooling the depolymerized material in the aforementioned quenching environment (0-30°C, preferably 0-10°C) within a range of 1-40 seconds. For example, the depolymerized material is brought into contact with a coolant at 0-5°C within a range of 5-15 seconds, so that the temperature of the depolymerized material is rapidly reduced to obtain cyclopentadiene.

[0022] In this invention, the operating conditions of the reactive distillation column in the depolymerization and distillation separation steps can be conventional operating conditions in the art. Preferably, in the depolymerization and distillation separation steps, the bottom temperature is controlled at 170-190°C, the top temperature at 41-43°C, the reflux volume ratio at 2:1-6:1, and the operating pressure of the distillation column at gauge pressure from -0.1 MPa to 0.6 MPa. Under these preferred conditions, the yield and purity of cyclopentadiene can be further improved.

[0023] In this invention, the residence time of the material in the depolymerization and distillation separation step can be selected within a wide range, as long as the reaction proceeds normally, preferably 80-210 min. Under these preferred conditions, the yield and purity of cyclopentadiene can be further improved. The residence time can be controlled by controlling the feed rate of the continuous feed.

[0024] In this invention, the cracking conversion rate of dicyclopentadiene can be adjusted by controlling the feed rate. Those skilled in the art can adjust the feed rate according to the size of the reactive distillation column; for example, in a 0.5m reactive distillation column... 3 When feeding, the preferred feed rate is 0.5-2 L / h.

[0025] In this invention, in order to ensure the depolymerization effect of dicyclopentadiene, a polymerization inhibitor is added to dicyclopentadiene. It should be understood that the mixture of dicyclopentadiene and polymerization inhibitor should be fully mixed before entering the reactive distillation column.

[0026] In this invention, the polymerization inhibitor can be a polymerization inhibitor conventionally used in the art, such as at least one selected from aromatic nitro polymerization inhibitors, quinone polymerization inhibitors, phenolic polymerization inhibitors, and amine polymerization inhibitors. Preferably, the polymerization inhibitor is a phenolic polymerization inhibitor.

[0027] The aromatic nitro polymerization inhibitor can be an aromatic nitro polymerization inhibitor commonly used in the art, preferably 4-butylnitrobenzene, p-tert-butylnitrobenzene and 2,6-di-tert-butyl-p-nitrobenzene.

[0028] The quinone polymerization inhibitor can be a quinone polymerization inhibitor conventionally used in the art, preferably p-benzodiquinone, 1,4-naphthoquinone, and p-dioxanone.

[0029] The phenolic polymerization inhibitor can be a conventionally used phenolic polymerization inhibitor in the art, preferably m-di-tert-butyl-p-cresol, p-tert-butylcatechol, and nonylphenol.

[0030] The amine polymerization inhibitor can be a conventionally used amine polymerization inhibitor in the art, preferably toluidine, diphenylamine, benzidine, p-phenylenediamine and N-nitrosodiphenylamine.

[0031] In a preferred embodiment of the present invention, the polymerization inhibitor is selected from at least one of m-di-tert-butyl-p-cresol, p-tert-butylcatechol, and nonylphenol. Under these preferred conditions, the yield and purity of cyclopentadiene can be further improved.

[0032] In this invention, the amount of the polymerization inhibitor can be selected within a wide range. Preferably, relative to 100 parts by weight of dicyclopentadiene, the amount of the polymerization inhibitor is 0.001-0.02 parts by weight, for example, 0.001, 0.002, 0.004, 0.006, 0.008, 0.01, 0.012, 0.014, 0.016, 0.018, 0.02 parts by weight, and any range between any two points. Under these preferred conditions, the yield and purity of cyclopentadiene can be further improved.

[0033] In this invention, preferably, the material separated by depolymerization distillation does not contain a diluent. The inventors have discovered that when preparing cyclopentadiene from dicyclopentadiene by depolymerization without using a diluent, the reaction time can be shortened, the reaction efficiency improved, the separation steps reduced, and the purity and yield of cyclopentadiene increased.

[0034] The diluent can be a conventional diluent in the art, for example, the diluent is selected from one of the C6-C16 n-alkanes, such as n-hexane and n-hexadecane.

[0035] In this invention, the purity determination of cyclopentadiene is described in “Jiang Liwen. Purity determination of cyclopentadiene - gas chromatography [J]. Yanshan Oil Chemical, 1987(01):33-35.”.

[0036] A second aspect of the present invention provides an apparatus for the depolymerization of dicyclopentadiene to prepare cyclopentadiene, such as... Figure 1 As shown, the equipment includes a reactive distillation column 01 and a quenching device 02 assembled at the top of the reactive distillation column;

[0037] In the reactive distillation column 01, dicyclopentadiene depolymerizes to form cyclopentadiene.

[0038] The rapid cooling device 02 is used to rapidly cool the depolymerization product of dicyclopentadiene.

[0039] like Figure 1 As shown, the equipment includes a reactive distillation column 01 and a quench device 02 mounted at the top of the column. By mounting the quench device 02 at the top of the reactive distillation column, the depolymerized material can be rapidly cooled, achieving rapid cooling treatment of the depolymerized material. Dicyclopentadiene material (containing a polymerization inhibitor) enters the reactive distillation column 01 through a pipeline. After depolymerization and distillation separation, cyclopentadiene is obtained at the top of the column. The obtained cyclopentadiene enters the quench device 02 for rapid cooling to prevent self-polymerization, and high-purity cyclopentadiene liquid is collected at the bottom of the quench device. The bottom product flows out through the bottom pipeline of the reactive distillation column 01.

[0040] In this invention, the reactive distillation column 01 can be a reactive distillation column commonly used in the chemical industry. Those skilled in the art can choose according to the circumstances, and will not elaborate further here.

[0041] In this invention, the rapid cooling device 02 can be a rapid cooling device conventionally used in the art, such as a device that rapidly cools using a coolant.

[0042] In this invention, the quenching device 02 can be installed at any position above the middle section of the reactive distillation column 01, preferably at a position near the material outlet at the top of the column.

[0043] In this invention, the coolant in the quenching device 02 can be a conventional coolant in the art, as long as it enables the quenching device to provide a quenching temperature. Preferably, the coolant is selected from at least one of sodium chloride aqueous solution, calcium chloride aqueous solution, ethylene glycol aqueous solution, and aqueous solution containing C3-C6 polyols, and more preferably sodium chloride aqueous solution and / or calcium chloride aqueous solution.

[0044] The operating conditions of the reactive distillation column 01 and the quenching device 02 have been described in detail in the first aspect and will not be repeated here.

[0045] A third aspect of the present invention provides the application of the apparatus described above in the depolymerization of dicyclopentadiene to prepare cyclopentadiene.

[0046] The present invention will be described in detail below through embodiments.

[0047] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0048] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0049] In the embodiments of the present invention, the purity determination of cyclopentadiene is described in “Jiang Liwen. Purity determination of cyclopentadiene - gas chromatography [J]. Yanshan Oil Chemical, 1987(01):33-35.”.

[0050] The following examples are in Figure 1 The reaction takes place in the apparatus shown, wherein the reactive distillation column 01 has a size of 0.5m. 3 The tower is 3 meters high (vertical distance from the inner wall of the tower bottom to the outlet at the top), and the quenching device is located 0.5 meters above the top of the tower. During the quenching process, the coolant in the quenching device circulates to maintain a constant temperature.

[0051] Example 1

[0052] This embodiment illustrates the method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to the present invention.

[0053] First, m-di-tert-butyl-p-cresol and cyclopentadiene are mixed evenly, with m-di-tert-butyl-p-cresol accounting for 0.005% of the weight of cyclopentadiene. Then, the mixture is pumped into a reactive distillation column for depolymerization and distillation separation. The bottom temperature of the column is controlled at 170-173℃, the top temperature at 41-43℃, the reflux volume ratio at 3:1, the operating pressure of the distillation column at gauge pressure of 0.2MPa, the feed rate at 0.5L / h, and the temperature of the quench device at 10℃ (the coolant is an aqueous sodium chloride solution). Cyclopentadiene at 11.2℃ is collected at the bottom of the quench device.

[0054] Example 2

[0055] This embodiment illustrates the method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to the present invention.

[0056] First, p-tert-butylcatechol and cyclopentadiene are mixed evenly, with m-di-tert-butyl-p-cresol accounting for 0.01% of the weight of cyclopentadiene. Then, the mixture is pumped into a reactive distillation column for depolymerization and distillation separation. The bottom temperature of the column is controlled at 179-182℃, the top temperature at 41-43℃, the reflux volume ratio at 3:1, the operating pressure of the distillation column at gauge pressure of 0.2MPa, the feed rate at 1.2L / h, and the temperature of the quench device at 5℃ (the coolant is a calcium chloride aqueous solution). Cyclopentadiene at 6.8℃ is collected at the bottom of the quench device.

[0057] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0058] Example 3

[0059] This embodiment illustrates the method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to the present invention.

[0060] First, m-di-tert-butyl-p-cresol and cyclopentadiene are mixed evenly, with m-di-tert-butyl-p-cresol accounting for 0.015% of the weight of cyclopentadiene. Then, the mixture is pumped into a reactive distillation column for depolymerization and distillation separation. The bottom temperature of the column is controlled at 175-183℃, the top temperature at 41-43℃, the reflux volume ratio at 3:1, the operating pressure of the distillation column at gauge pressure of 0.2MPa, the feed rate at 2L / h, and the temperature of the quench device at 0℃ (the coolant is an aqueous solution of ethylene glycol). Cyclopentadiene at 2.6℃ is collected at the bottom of the quench device.

[0061] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0062] Example 4

[0063] This embodiment illustrates the method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to the present invention.

[0064] The method described in Example 3 is followed, except that the temperature of the quenching device is 15°C (the coolant is an aqueous sodium chloride solution).

[0065] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0066] Example 5

[0067] This embodiment illustrates the method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to the present invention.

[0068] The method described in Example 3 is followed, except that the temperature of the quenching device is 20°C (the coolant is an aqueous sodium chloride solution).

[0069] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0070] Example 6

[0071] This embodiment illustrates the method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to the present invention.

[0072] The operation is carried out according to the method described in Example 3, except that the temperature of the column bottom is controlled at 252-260℃.

[0073] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0074] Example 7

[0075] This embodiment illustrates the method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to the present invention.

[0076] The method described in Example 3 is followed, except that the polymerization inhibitor is p-benzodiquinone.

[0077] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0078] Example 8

[0079] This embodiment illustrates the method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to the present invention.

[0080] The procedure was performed according to the method described in Example 3, except that a diluent was added to cyclopentadiene and m-di-tert-butyl-p-cresol. The diluent consisted of n-hexadecane and n-hexane in a 7:2 mass ratio, diluting the cyclopentadiene to a mass fraction of 53%.

[0081] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0082] Example 9

[0083] This embodiment illustrates the method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to the present invention.

[0084] The procedure was performed according to the method described in Example 3, except that the m-tert-butyl-p-cresol was 0.15% of the weight of cyclopentadiene.

[0085] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0086] Example 10

[0087] This embodiment illustrates the method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to the present invention.

[0088] The procedure was performed according to the method described in Example 3, except that the m-tert-butyl-p-cresol was 0.0008% of the weight of cyclopentadiene.

[0089] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0090] Comparative Example 1

[0091] This comparative example is used to illustrate the method for preparing cyclopentadiene by depolymerization of a reference dicyclopentadiene.

[0092] First, add the diluent and polymerization inhibitor to the raw material and mix them evenly. Let it stand for 40 minutes. Then, carry out depolymerization and distillation separation in a reactive distillation column. Control the bottom temperature of the column to be 252-260℃, the top temperature of the column to be 41-43℃, the top pressure of the column to be 15-16KPaG, the reflux ratio to be 8, and the feed rate to be 10mL / min. Cyclopentadiene is collected at the top of the column.

[0093] The diluent is composed of n-hexadecane and n-hexane in a 7:2 mass ratio, which dilutes the raw material to a mass fraction of 53%.

[0094] The polymerization inhibitor is composed of hydroquinone, o-nitrophenol and aniline in a mass ratio of 5:11:1, and the amount added is 0.011% of the mass of the raw materials before dilution.

[0095] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0096] Comparative Example 2

[0097] This comparative example is used to illustrate the method for preparing cyclopentadiene by depolymerization of a reference dicyclopentadiene.

[0098] The method described in Example 3 was followed, except that the top product was cooled naturally without a quenching device, and was collected at atmospheric pressure.

[0099] The yield and purity of cyclopentadiene were determined and calculated, and the results are shown in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] As can be seen from the results in Table 1, by adding a rapid cooling device to the depolymerization equipment, the cyclopentadiene obtained from depolymerization is rapidly cooled to a low temperature, which effectively improves the yield and purity of cyclopentadiene.

[0104] By employing the preferred operating conditions, the temperature of the quenching device, and the type and amount of polymerization inhibitor of the present invention, the yield and purity of cyclopentadiene can be further improved.

[0105] The method described in this invention does not require a diluent when preparing cyclopentadiene from dicyclopentadiene through depolymerization, which can further improve the yield and purity of cyclopentadiene, while also reducing the energy consumption of the depolymerization process and subsequent cyclopentadiene separation process.

[0106] 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 preparing cyclopentadiene by depolymerization of dicyclopentadiene, characterized in that, The method includes: mixing dicyclopentadiene and a polymerization inhibitor and carrying out depolymerization and distillation separation in a reactive distillation column, and quenching the product obtained at the top of the column to obtain cyclopentadiene; The temperature of the rapid cooling is 0-30℃; The materials separated by depolymerization and distillation do not contain a diluent, which is selected from one of the C6-C16 n-alkanes.

2. The method according to claim 1, wherein, The rapid cooling temperature is 0-10℃.

3. The method according to claim 1 or 2, wherein, In the depolymerization and distillation separation steps, the bottom temperature of the column is controlled at 170-190℃, the top temperature is controlled at 41-43℃, the reflux volume ratio is 2:1-6:1, and the operating pressure of the distillation column is gauge pressure -0.1MPa to 0.6MPa.

4. The method according to claim 1 or 2, wherein, In the depolymerization and distillation separation steps, the material residence time is 80-210 min.

5. The method according to claim 1 or 2, wherein, The polymerization inhibitor is selected from at least one of aromatic nitro polymerization inhibitors, quinone polymerization inhibitors, phenolic polymerization inhibitors, and amine polymerization inhibitors.

6. The method according to claim 5, wherein, The polymerization inhibitor is a phenolic polymerization inhibitor.

7. The method according to claim 6, wherein, The polymerization inhibitor is selected from at least one of m-di-tert-butyl-p-cresol, p-tert-butylcatechol, and p-nonylphenol.

8. The method according to claim 5, wherein, The amount of the polymerization inhibitor is 0.001-0.02 parts by weight relative to 100 parts by weight of dicyclopentadiene.

9. An apparatus for preparing cyclopentadiene by depolymerization of dicyclopentadiene, characterized in that, The equipment includes a reactive distillation column (01) and a quenching device (02) mounted on the top of the reactive distillation column. In the reactive distillation column (01), dicyclopentadiene depolymerizes to form cyclopentadiene; The rapid cooling device (02) is used to rapidly cool the depolymerization product of dicyclopentadiene.

10. The device according to claim 9, wherein, The coolant in the quenching device (02) is selected from at least one of sodium chloride aqueous solution, calcium chloride aqueous solution, ethylene glycol aqueous solution, and aqueous solution containing C3-C6 polyols.

11. The use of the apparatus of claim 9 or 10 in the depolymerization of dicyclopentadiene to prepare cyclopentadiene.

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