Method for preparing cyclopentadiene by depolymerizing dicyclopentadiene

Abstract

The invention belongs to the field of preparation of cyclopentadiene, and particularly relates to a method for preparing cyclopentadiene by depolymerizing dicyclopentadiene. The method comprises the following steps: mixing dicyclopentadiene with a diluent, preheating, vaporizing, mixing with high-temperature inert particles, depolymerizing dicyclopentadiene in a riser reactor, and sequentially carrying out gas-solid separation and quenching on the depolymerized product to obtain cyclopentadiene. The reaction temperature is provided by adopting the high-temperature inert particles, the gas-solid fluidized bed heating mode has the advantages of large particle heat capacity, high heat transfer coefficient, uniform temperature, relatively easy operation and the like, the problems of unsatisfactory dicyclopentadiene heating and vaporization and the like in the existing process can be effectively solved, and the coking phenomenon is avoided.

Description

Technical Field

[0001] The invention belongs to the field of preparing cyclopentadiene, and more specifically is a method for preparing cyclopentadiene by depolymerizing dicyclopentadiene. Background Art

[0002] Cyclopentadiene (CPD), as an important by-product of ethylene cracking, is widely used in the preparation of pesticides, rubber, fragrances, curing agents, flame retardants, adamantane, ferrocene, glutaraldehyde, norbornenes, etc. It is an important raw material for the preparation of many series of fine chemicals and has broad application prospects and high economic value.

[0003] Cyclopentadiene (CPD) can be prepared by depolymerization of dicyclopentadiene. The depolymerization process is as follows:

[0004]

[0005] However, during the depolymerization process, problems such as too high temperature, uneven heating, and slow heating will easily lead to the following Diels-Alde reaction between the raw material dicyclopentadiene and the target product cyclopentadiene generated by the reaction:

[0006]

[0007] The occurrence of self-polymerization will lead to the generation of a large amount of tricyclopentadiene (TCPD), which will then cause coking. At the same time, it will also be accompanied by the occurrence of side reactions that can generate other polymers, which will seriously affect the quality and yield of the target product.

[0008] There are two existing mainstream dicyclopentadiene depolymerization methods: liquid phase method and gas phase method. Among them, the liquid phase method process is relatively simple, but there are disadvantages such as low yield, many by-products, and difficult recovery of solvents, and it is mostly used for preparing a small amount of samples in the laboratory. In response to this problem, CN 109704905A adds hydroquinone, o-nitrophenol or aniline as inhibitors during the depolymerization process, and adds n-hexadecane and n-hexane as diluents, which improves the yield and purity of cyclopentadiene to a certain extent, but also brings certain negative effects on the production cost and subsequent separation of dicyclopentadiene. The gas phase method is carried out in a temperature range of 330 to 350 ° C and a short residence time, but due to the high temperature, the material is prone to coking, blocking the reactor, causing a large negative impact on continuous production and operation. In contrast, the gas phase method is more suitable for industrial production due to its higher raw material conversion rate and product yield. However, there is currently no efficient solution to the coking problem. The main reason for the coking phenomenon in the process of preparing cyclopentadiene by depolymerization of dicyclopentadiene is that it is difficult for the raw material dicyclopentadiene to complete the heating, vaporization and reaction process efficiently in a short time. In this process, it is very easy for the cyclopentadiene generated by depolymerization to undergo addition polymerization with the dicyclopentadiene that has not yet been depolymerized. Therefore, seeking a fast and efficient material heating method is an effective means to solve this problem. Summary of the invention

[0009] The object of the present invention is to provide a method for preparing cyclopentadiene by depolymerizing dicyclopentadiene, which can effectively avoid the occurrence of self-polymerization reaction during the depolymerization of raw materials and improve the coking phenomenon in the reactor.

[0010] To achieve the above object, the technical solution adopted by the present invention is:

[0011] A method for preparing cyclopentadiene by depolymerizing dicyclopentadiene comprises: mixing dicyclopentadiene with a diluent, preheating, vaporizing, and mixing with high-temperature inert particles; depolymerizing the dicyclopentadiene in a riser reactor; and obtaining cyclopentadiene by sequentially subjecting the depolymerized product to gas-solid separation and rapid cooling.

[0012] The diluent is water;

[0013] The dosage ratio of dicyclopentadiene to diluent is 0.75-1.2:1.

[0014] The inert particles are Geldart A-type inert particles with a particle size range of 50 to 100 μm; the temperature of the high-temperature inert particles is 300° C. to 600° C.

[0015] The reaction conditions of the riser reactor are: reaction temperature of 300°C to 380°C and residence time of 3 to 12s.

[0016] The riser reactor is a variable diameter structure, the variable diameter position is located between 30% and 50% of the total height of the riser, and the height of the variable diameter part accounts for 40% to 60% of the total height of the riser; the ratio of the riser diameter after the diameter change is (1.0 to 3.0):1.

[0017] Furthermore, after dicyclopentadiene is mixed with the diluent, it is preheated in the heat exchanger 6 and then enters the evaporator 7 for heating and evaporation. The mixed steam contacts and mixes with the high-temperature inert particles in the pre-lifting section dense phase bed 8 at the bottom of the riser reactor, and moves upward together, and depolymerization of dicyclopentadiene is carried out in the variable diameter riser 9.

[0018] The cracking products are initially separated by the ultra-short fast separation device 10 at the upper end of the riser reactor, and the inert particles are returned to the storage bed 15 through the feed leg 11. The multiphase fluid is further separated by the cyclone separator 12, and the gas separated by the cyclone separator 12 is rapidly cooled by the condenser 17 to obtain the product cyclopentadiene.

[0019] After being heated by the heated flue gas 3, the inert particles in the storage companion bed 15 are returned to the pre-elevation section dense phase bed 8 through the circulating inclined pipe 16, thereby realizing the recycling of the inert particles.

[0020] Furthermore, (1) the raw material dicyclopentadiene and the diluent are mixed in a certain ratio, preheated in a heat exchanger, and then heated and evaporated in an evaporator, and then input into the pre-lifting air pipe at the bottom of the riser reactor in the form of mixed steam. The pre-lifting air mixed with dicyclopentadiene and the diluent contacts and mixes with the high-temperature inert particles in the dense phase bed of the pre-lifting section at the bottom of the riser, and moves upward together.

[0021] (2) After being accelerated in the pre-lift section, the multiphase fluid mixed with dicyclopentadiene in the riser moves upward at a uniform speed. After reaching the expansion section of the riser, the flow rate of the multiphase fluid decreases. The expansion design is conducive to prolonging the residence time of dicyclopentadiene in the reactor and improving the conversion rate. In this process, dicyclopentadiene is depolymerized into cyclopentadiene. After the multiphase fluid reaches the end of the riser, most of the inert particles are initially separated through the outlet quick separation and then returned to the storage bed through the material leg. The multiphase fluid that has completed the initial separation and still carries a small amount of inert particles is further separated through a cyclone separator. The mixed gas discharged from the top of the cyclone separator is rapidly cooled by a condenser to obtain the target product cyclopentadiene.

[0022] (3) The inert particles returned to the storage bed are reheated by the flue gas and then return to the bottom of the riser through the circulating inclined pipe, completing the cycle.

[0023] The temperature of the heat exchanger and evaporator device is 90-200℃.

[0024] The pre-lifting gas velocity of the riser is 2-4 m / s, and the flow type of the bottom dense phase bed layer is a turbulent bed.

[0025] The temperature of the condenser heat exchange medium is controlled between -20 and 30°C;

[0026] The feeding method of dicyclopentadiene in the riser reactor is direct feeding, atomizing nozzle feeding, jet feeding, etc.

[0027] The temperature of the heat exchange medium in the storage bed 15 is controlled between 300 and 600°C.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] (1) The present invention combines the process of preparing cyclopentadiene by gas phase depolymerization of dicyclopentadiene with a riser reactor device, which can depolymerize dicyclopentadiene to the target product to the greatest extent possible, thereby improving the yield and purity of cyclopentadiene.

[0030] (2) The present invention realizes the steps of heating and reacting the raw materials through the riser reactor, which can effectively enhance the heat exchange efficiency between the raw materials and the heating medium, shorten the vaporization time, and avoid the coking and adhesion of the raw materials caused by being in a high temperature environment for a long time during the heating process, thereby effectively inhibiting the coking phenomenon in the reactor.

[0031] (3) The present invention uses high-temperature inert particles to provide the reaction temperature. The gas-solid fluidized bed heating method has many advantages such as large particle heat capacity, high heat transfer coefficient, uniform temperature, and relatively easy operation. It can effectively solve the problems of dicyclopentadiene heating and unsatisfactory vaporization in the existing process and avoid the occurrence of coking. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a process flow chart of preparing cyclopentadiene by depolymerization of dicyclopentadiene;

[0033] Among them, 1-dicyclopentadiene, diluent metering mixed feed, 2-pre-lifting air, 3-heating flue gas, 4-waste gas discharge port, 5-discharge port, 6-heat exchanger, 7-evaporator, 8-pre-lifting section dense phase bed, 9-variable diameter lift pipe, 10-ultra-short fast separation device, 11-circulating material leg, 12, 13, 14-cyclone separator, 15-storage bed, 16-circulating inclined tube, 17-condenser. DETAILED DESCRIPTION

[0034] The method of the present invention is further described below by means of the accompanying drawings, but the present invention is not limited thereby. Figure 1 As shown, the process flow of the method is as follows:

[0035] The raw material dicyclopentadiene and the diluent are metered and mixed, and then preheated by the heat exchanger 6 through the pipeline 1 and then enter the evaporator 7 for heating and evaporation, and then input into the pre-lifting air pipe 2 at the bottom of the riser reactor in the form of mixed steam. The pre-lifting air contacts and mixes with the high-temperature inert particles in the dense phase bed 8 of the pre-lifting section, and moves upward together. The multiphase fluid mixed with dicyclopentadiene in the variable diameter riser 9 is accelerated by the pre-lifting section and moves upward at a uniform speed. After reaching the expansion section of the riser, the flow rate of the multiphase fluid decreases. The expansion design is conducive to prolonging the residence time of dicyclopentadiene in the reactor and improving the conversion rate. In this process, dicyclopentadiene is depolymerized into cyclopentadiene. After the multiphase fluid reaches the end of the riser, most of the inert particles are initially separated by the ultra-short quick separation device 10 and then returned to the storage companion bed 15 through the material leg 11 to complete the initial separation. The multiphase fluid still carrying a small amount of inert particles is further separated by the cyclone separator 12. The mixed gas from the top of the cyclone separator is rapidly cooled by the condenser 17 and output from the pipeline 5 as the product cyclopentadiene. The inert particles from the bottom of the cyclone separator return to the storage companion bed 15. After the inert particles in the storage companion bed 15 are reheated by the heated flue gas 3, they are returned to the pre-lifting section dense phase bed 8 from the circulation inclined pipe 16 to realize the recycling of the inert particles. The residual waste gas in the storage companion bed 15 is discharged from the waste gas outlet 4 after dust removal by the primary cyclone separator 13 and the secondary cyclone separator 14.

[0036] The heat exchanger 6 is used to preheat dicyclopentadiene and the diluent; the evaporator 7 is used to heat and vaporize the mixture of dicyclopentadiene and the diluent to obtain a vaporized mixed gas; the riser reactor is used to heat the mixed gas and provide a reaction site so that dicyclopentadiene is depolymerized to generate cyclopentadiene; the cyclone separator 12 is used to remove high-temperature inert particles from the multiphase fluid; the condenser 17 is used to quench the fluid containing the target product; and the storage bed 15 is used to recover and heat the inert particles.

[0037] 6-heat exchanger, 7-evaporator, 8-pre-lifting section dense phase bed, 10-ultra-short fast separation device, 12, 13, 14 cyclone separators are all well-known technologies in the art and are commercially available products.

[0038] Example 1

[0039] Dicyclopentadiene and water are mixed in a ratio of 0.75:1 and are preheated to 90°C through the heat exchanger 6 from the pipeline 1. Then, they are heated to 140°C in the evaporator 7 for evaporation and vaporization. Then, they are input into the pre-lifting air pipe 2 in the form of mixed steam. The pre-lifting air velocity is maintained at 2m / s, and the flow pattern of the bottom dense phase bed is maintained as a turbulent bed. The pre-lifting air will mix with the high-temperature inert particles (the inert particles are Geldart Class A inert particles, with a particle size range of 50 to 100 μm; the temperature of high-temperature inert particles is 300°C) contact and mix, and move upward together, entering the variable diameter riser 9, maintaining the temperature of 300°C in the variable diameter riser 9 (the diameter change position is between 30% and 50% of the total height of the riser, and the height of the diameter change part accounts for 40% to 60% of the total height of the riser; the ratio of the diameter of the riser after the diameter change is 3:1), the reaction residence time is 12s, dicyclopentadiene is depolymerized to cyclopentadiene, and the cracking reaction product condenser 17 is quenched to obtain the product cyclopentadiene, and the temperature of the condenser 17 is 20°C. After the inert particles in the storage bed 15 are heated to 300°C by the heated flue gas 3, they are returned to the dense phase bed 8 of the pre-lifting section by the circulating inclined tube 16, realizing the recycling of the inert particles.

[0040] Subsequent experimental analysis of the obtained product showed that the final cyclopentadiene yield was 97.6% and the purity was 99.3%.

[0041] Example 2

[0042] Dicyclopentadiene and water are mixed in a ratio of 0.9:1 and are preheated to 90°C through the heat exchanger 6 from the pipeline 1. Then, they are heated to 160°C in the evaporator 7 for evaporation and vaporization. Then, they are input into the pre-lifting air pipe 2 in the form of mixed steam. The pre-lifting air velocity is maintained at 3m / s, and the flow pattern of the bottom dense phase bed is maintained as a turbulent bed. The pre-lifting air will mix with the high-temperature inert particles (the inert particles are Geldart Class A inert particles, with a particle size range of 50 to 100 μm; the temperature of high-temperature inert particles is 320°C) contact and mix, and move upward together, entering the variable diameter riser 9, maintaining the temperature of 320°C in the variable diameter riser 9 (the diameter change position is between 30% and 50% of the total height of the riser, and the height of the variable diameter part accounts for 40% to 60% of the total height of the riser; the ratio of the diameter of the riser after the diameter change is 3:1), the reaction residence time is 10s, dicyclopentadiene is depolymerized to cyclopentadiene, and the cracking reaction product condenser 17 is quenched to obtain the product cyclopentadiene, and the temperature of the condenser 17 is 20°C. After the inert particles in the storage bed 15 are heated to 320°C by the heated flue gas 3, they are returned to the dense phase bed 8 of the pre-lifting section by the circulating inclined tube 16, realizing the recycling of the inert particles.

[0043] Subsequent experimental analysis of the obtained product showed that the final cyclopentadiene yield was 98.6% and the purity was 99.5%.

[0044] Example 3

[0045] Dicyclopentadiene and water are mixed in a ratio of 1:1 and preheated to 100°C through the heat exchanger 6 from the pipeline 1. Then, they are heated to 160°C in the evaporator 7 for evaporation and vaporization. Then, they are input into the pre-lifting air pipe 2 in the form of mixed steam. The pre-lifting air velocity is maintained at 3m / s, and the flow pattern of the bottom dense phase bed is maintained as a turbulent bed. The pre-lifting air will mix with the high-temperature inert particles (the inert particles are Geldart Class A inert particles, with a particle size range of 50-100 μm; the temperature of high-temperature inert particles is 340°C) contact and mix, and move upward together, entering the variable diameter riser 9, maintaining the temperature of 340°C in the variable diameter riser 9 (the diameter change position is between 30% and 50% of the total height of the riser, and the height of the variable diameter part accounts for 40% to 60% of the total height of the riser; the ratio of the diameter of the riser after the diameter change is 2:1), the reaction residence time is 8s, dicyclopentadiene is depolymerized to cyclopentadiene, and the cracking reaction product condenser 17 is quenched to obtain the product cyclopentadiene, and the temperature of the condenser 17 is 20°C. After the inert particles in the storage bed 15 are heated to 340°C by the heated flue gas 3, they are returned to the dense phase bed 8 of the pre-lifting section by the circulating inclined tube 16, realizing the recycling of the inert particles.

[0046] Subsequent experimental analysis of the obtained product showed that the final cyclopentadiene yield was 98.9% and the purity was 99.7%.

[0047] Example 4

[0048] Dicyclopentadiene and water are mixed in a ratio of 1.1:1 and are preheated to 100°C through the heat exchanger 6 from the pipeline 1. Then, they are heated to 180°C in the evaporator 7 for evaporation and vaporization. Then, they are input into the pre-lifting air pipe 2 in the form of mixed steam. The pre-lifting air velocity is maintained at 4m / s, and the flow pattern of the bottom dense phase bed is maintained as a turbulent bed. The pre-lifting air will mix with the high-temperature inert particles (the inert particles are Geldart Class A inert particles, with a particle size range of 50 to 100 μm; the temperature of high-temperature inert particles is 360°C) contact and mix, and move upward together to enter the variable diameter riser 9, and keep the temperature in the variable diameter riser 9 (the diameter change position is between 30% and 50% of the total height of the riser, and the height of the diameter change part accounts for 40% to 60% of the total height of the riser; the ratio of the diameter of the riser after the diameter change is 1.5:1) at 360°C, the reaction residence time is 4s, dicyclopentadiene is depolymerized to cyclopentadiene, and the cracking reaction product condenser 17 is quenched to obtain the product cyclopentadiene, and the temperature of the condenser 17 is 20°C. After the inert particles in the storage bed 15 are heated to 360°C by the heated flue gas 3, they are returned to the dense phase bed 8 of the pre-lifting section by the circulating inclined tube 16 to realize the recycling of the inert particles.

[0049] Subsequent experimental analysis of the obtained product showed that the final cyclopentadiene yield was 99.3% and the purity was 99.7%.

[0050] Example 5

[0051] Dicyclopentadiene and water are mixed in a ratio of 1.2:1 and are preheated to 110°C through the heat exchanger 6 from the pipeline 1. Then, they are heated to 200°C in the evaporator 7 for evaporation and vaporization. Then, they are input into the pre-lifting air pipe 2 in the form of mixed steam. The pre-lifting air velocity is maintained at 4m / s, and the flow pattern of the bottom dense phase bed is maintained as a turbulent bed. The pre-lifting air will mix with the high-temperature inert particles (the inert particles are Geldart Class A inert particles, with a particle size range of 50 to 100 μm; the temperature of high-temperature inert particles is 380°C) contact and mix, and move upward together to enter the variable diameter riser 9, and keep the temperature in the variable diameter riser 9 (the diameter change position is between 30% and 50% of the total height of the riser, and the height of the diameter change part accounts for 40% to 60% of the total height of the riser; the ratio of the diameter of the riser after the diameter change is 1.5:1) at 380°C, the reaction residence time is 3s, dicyclopentadiene is depolymerized to cyclopentadiene, and the cracking reaction product condenser 17 is quenched to obtain the product cyclopentadiene, and the temperature of the condenser 17 is 20°C. After the inert particles in the storage bed 15 are heated to 380°C by the heated flue gas 3, they are returned to the dense phase bed 8 of the pre-lifting section by the circulating inclined tube 16 to realize the recycling of the inert particles.

[0052] Subsequent experimental analysis of the obtained product showed that the final cyclopentadiene yield was 99.0% and the purity was 99.8%.

[0053] Comparative Example 1

[0054] When dicyclopentadiene was depolymerized in the gas phase using a conventional commercially available tubular reactor, it was found that coking easily occurred on the inner wall of the tube during the reaction, which led to frequent shutdown of the device and affected the product yield.

[0055] As can be seen from the above, the traditional tubular reactor is wall heating. In order to maintain the temperature in the reaction tube, a higher temperature heat medium is usually required, so that local overheating is formed on the heat exchange surface, so that side reactions are easily formed on the inner wall surface of the reaction tube to form coking. The present invention realizes direct heating and reaction of raw materials by lifting the tube reactor, which can effectively strengthen the heat exchange efficiency between raw materials and heating medium, shorten the vaporization time and reaction time, and avoid the coking and adhesion caused by the raw materials being in a high temperature environment for a long time during the heating process, so as to effectively improve the coking phenomenon in the reactor. At the same time, the present invention adopts high temperature inert particles to provide high temperature reaction conditions, and the gas-solid fluidized bed heating method has many advantages such as large particle heat capacity, high heat transfer coefficient, uniform temperature, and relatively easy operation, which can effectively improve the existing process for heating and vaporizing dicyclopentadiene. Problems such as unsatisfactory, avoid the occurrence of coking phenomenon. During implementation, the reaction unit has been running for more than 300 hours cumulatively, and no coking phenomenon is found in the device. Therefore, the dicyclopentadiene depolymerization process of the present invention is simple in process, has high yield of target product, high purity, obvious improvement of coking effect, and less three wastes.

Claims

1. A method for preparing cyclopentadiene by depolymerization of dicyclopentadiene, characterized in that: Dicyclopentadiene is mixed with a diluent, preheated, vaporized, and then mixed with high-temperature inert particles. The dicyclopentadiene is depolymerized in a riser reactor, and the depolymerization product is separated by gas and solid and rapidly cooled to obtain cyclopentadiene.

2. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 1, characterized in that: The diluent is water; the dosage ratio of dicyclopentadiene to the diluent is 0.75-1.2:

1.

3. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 1, characterized in that: The inert particles are Geldart A-type inert particles with a particle size range of 50 to 100 μm; the temperature of the high-temperature inert particles is 300° C. to 600° C.

4. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 1, characterized in that: The reaction conditions of the riser reactor are: reaction temperature of 300°C to 380°C and residence time of 3 to 12s.

5. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 1, characterized in that: The riser reactor is a variable diameter structure, the variable diameter position is located between 30% and 50% of the total height of the riser, and the height of the variable diameter part accounts for 40% to 60% of the total height of the riser; the ratio of the riser diameter after the diameter change is (1.0 to 3.0):

1.

6. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 1, characterized in that: After dicyclopentadiene and the diluent are mixed, they are preheated in a heat exchanger (6) and then enter an evaporator (7) for heating and evaporation. The mixed steam contacts and mixes with high-temperature inert particles in a pre-lifting section dense phase bed (8) at the bottom of the riser reactor, and moves upward together to depolymerize dicyclopentadiene in a variable diameter riser (9).

7. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 1, characterized in that: The cracking products are initially separated by an ultra-short fast separation device (10) at the upper end of the riser reactor, and the inert particles are returned to the storage companion bed (15) via the feed leg (11). The multiphase fluid is further separated by a cyclone separator (12), and the gas separated by the cyclone separator (12) is rapidly cooled by a condenser (17) to obtain the product cyclopentadiene.

8. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 8, characterized in that: After being heated by the heated flue gas (3), the inert particles in the storage companion bed (15) are returned to the pre-lifting section dense phase bed (8) through the circulating inclined pipe (16), thereby realizing the recycling of the inert particles.

9. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 6, characterized in that: The temperature of the heat exchanger and evaporator device is 90-200℃.

10. The method for preparing cyclopentadiene by depolymerization of dicyclopentadiene according to claim 6, characterized in that: The pre-lifting gas velocity of the riser is 2-4 m / s, and the flow type of the bottom dense phase bed layer is a turbulent bed.

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