Method and device for preparing high-purity dicyclopentadiene by flash depolymerization of dicyclopentadiene

Abstract

The application provides a method and device for preparing high-purity dicyclopentadiene by flash depolymerization of dicyclopentadiene. The method comprises the following steps: step S1, heating dicyclopentadiene to 170-220 DEG C under a pressure of 1.2-2.5 MPa; step S2, reducing the pressure of the dicyclopentadiene liquid treated in step S1 to 0.1-0.3 MPa through a throttle valve, then performing flash depolymerization, and simultaneously removing the gas-phase product; step S3, precooling the gas-phase product removed after flash in step S2, separating and recycling the condensed liquid after precooling, and retaining the gas; step S4, low-temperature crystallization of the gas separated in step S3, conversion of the gas into solid and liquid, then performing solid-liquid separation, and the obtained liquid is dicyclopentadiene. The short residence preheating, flash depolymerization, distributed temperature control separation mode and the graphene-silicon carbide coating on the inner wall of the device reduce the coking risk, reduce the energy consumption, prolong the service life of the equipment, and make up for the shortcomings of the traditional process.

Description

Technical Field

[0001] This invention relates to the field of hydrocarbon preparation, specifically to a method and apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene. Background Technology

[0002] Cyclopentadiene (CPD) is a key intermediate in the synthesis of metallocene catalysts, electronic-grade resins, and specialty rubbers, and its purity directly affects the performance of downstream products. Traditional DCPD depolymerization processes mainly fall into two categories: one is prolonged heating in a batch reactor (≥30 minutes), which easily leads to CPD polymerization, coking, and impurity generation, and is characterized by high energy consumption and low yield; the other is the traditional distillation column process, which uses reboiler heating to depolymerize DCPD in the gas phase and then separates CPD from DCPD using distillation, but suffers from long residence times (≥1 hour), large equipment size, low separation efficiency, and high energy consumption. While existing gas-phase depolymerization processes have shortened residence times, they often rely on high-temperature carrier gases, resulting in complex equipment and high separation costs. Furthermore, some methods use flash evaporation processes that do not consider the differences in physical properties between CPD and DCPD, leading to a decrease in product yield and purity. Moreover, the inner walls of reaction equipment are often made of 316L stainless steel, which is prone to coking and has insufficient corrosion resistance, thus resulting in frequent equipment maintenance and affecting product purity. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method and apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene. By employing short-dwelling preheating, flash depolymerization, and temperature-controlled separation, the product yield and purity are improved. The inner wall of the equipment is coated with a graphene-silicon carbide coating, which further reduces the risk of coking, lowers energy consumption, extends equipment life, and compensates for the deficiencies of traditional processes.

[0004] This invention provides a method for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene, the method comprising the following steps: Step S1: Heating dicyclopentadiene to 170-220°C under a pressure of 1.2-2.5 MPa; Step S2: The dicyclopentadiene liquid treated in step S1 is depressurized to 0.1~0.3 MPa through a throttling valve, and then flash depolymerization is performed, while the gaseous products are removed at the same time. Step S3: Pre-cool the gaseous product removed after flash evaporation in step S2, separate and recover the condensed liquid after pre-cooling, and retain the gas. Step S4: The gas separated in step S3 is crystallized at low temperature, and the gas is converted into solid and liquid. Then, solid-liquid separation is performed, and the liquid obtained is cyclopentadiene.

[0005] Further, step S1 is carried out in a preheater with a heating rate of 40~60℃ / s, and the residence time of the dicyclopentadiene is ≤10 s. The preheater includes a single-rotation heat exchanger or a microwave-assisted preheater.

[0006] Furthermore, the temperature of the flash evaporation treatment is 120~150℃.

[0007] Furthermore, the pre-cooling temperature in step S3 is 42~45℃.

[0008] Furthermore, the temperature for low-temperature crystallization in step S4 is -45 to -60°C.

[0009] Furthermore, the method also includes: Step S5: Melt the solid separated in step S4 and return it to step S1 along with the liquid obtained in step S3.

[0010] According to a second aspect of the present invention, an apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene is provided. The apparatus comprises: a dicyclopentadiene storage device, a preheater, a throttling valve, a flash evaporator, a precooler, a gas-liquid separator, a low-temperature crystallizer, and a solid-liquid separator, sequentially connected by pipelines. A pumping device is provided on the pipelines. The inner walls of both the preheater and the flash evaporator are coated with a graphene-silicon carbide coating, the thickness of which is 50~100 μm.

[0011] Furthermore, the flash evaporator is equipped with a wire mesh demister at the top and a cross-shaped anti-vortex plate and an automatic liquid level control valve at the bottom. The surface of the cross-shaped anti-vortex plate is coated with a graphene-silicon carbide coating with a thickness of 50~100 μm.

[0012] Furthermore, the preheater is selected from a single-rotation heat exchanger or a microwave-assisted preheater.

[0013] Furthermore, the device also includes a circulation pipeline connecting the dicyclopentadiene storage device and the precooler, and the circulation pipeline also connects the dicyclopentadiene storage device and the solid-liquid separator.

[0014] This invention provides a method for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene, which has the following beneficial effects: 1) The method of the present invention adopts short residence time and impurity-free preheating: a high-pressure and high-temperature high-efficiency short-range preheater is used to preheat dicyclopentadiene, and the material residence time is ≤10 seconds, so that dicyclopentadiene remains in a liquid state before the reaction. Compared with the traditional carrier gas heating method, it can eliminate the introduction of impurities by additional media. 2) The method of the present invention adopts a one-step flash depolymerization: liquid dicyclopentadiene is instantaneously flashed into gaseous state and rapidly depolymerized, which can suppress cyclopentadiene polymerization (polymer formation amount ≤0.8%) and coking; 3) The method of the present invention adopts a two-step separation: making full use of the difference in melting and boiling points between cyclopentadiene and dicyclopentadiene, the temperature is controlled stepwise by pre-cooling at 42~45℃ and crystallizing at -45~-60℃, and the two-step separation is carried out in sequence to achieve efficient deep purification, so that the product purity is ≥99.95%, which meets the requirements of electronic grade. 4) The method of the present invention significantly improves production efficiency: compared with the traditional distillation tower process, the time required to produce 50 kg of high-purity cyclopentadiene is reduced by 60% to 80%, and the production efficiency is increased by more than 5 times. 4) The method of the present invention is highly efficient and energy-saving: The present invention recycles the dicyclopentadiene separated in two steps, so that the raw material recycling rate is ≥90% and the energy consumption is reduced by more than 35% compared with the traditional distillation tower process. The energy-saving effect is even more significant when using microwave-assisted preheating process.

[0015] Furthermore, in the apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene according to the present invention, a graphene-silicon carbide composite coating is applied to the high-efficiency short-path preheater, the inner wall of the flash evaporator, and the surfaces of various components of the flash evaporator. This increases the temperature resistance of the apparatus to 500°C and improves the thermal conductivity by at least 5 times. Consequently, the coking rate is reduced by more than 60%, while corrosion resistance is significantly improved, the equipment maintenance cycle is extended to more than 12 months, and the service life is extended by at least 2 times. In addition, the various devices in the apparatus of the present invention are tightly connected, eliminating the need for a large distillation column and a high-temperature carrier gas system. Therefore, the floor space is reduced by more than 75%, and the investment cost is reduced by 40%.

[0016] The method and apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene provided by this invention can directly process industrial-grade dicyclopentadiene (purity ≥95%) without pretreatment, and is suitable for high-end fields such as electronic chemicals and pharmaceutical intermediates. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene according to the present invention.

[0018] 1-Dicyclopentadiene storage equipment; 2-High-efficiency short-range preheater; 3-Flash evaporator with throttling valve; 31-Wire mesh demister; 32-Cross-shaped anti-vortex plate; 4-Precooler; 5-Gas-liquid separator; 6-Low-temperature crystallizer; 7-Solid-liquid separator; 8-Circulation pipeline; 9-Heating facilities; 10-Filtration facilities. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The principles and features of the present invention are described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0020] The first aspect of the present invention provides a method for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene, the method comprising the following steps: Step S1: Dicyclopentadiene is heated to 170-220°C under a pressure of 1.2-2.5 MPa. Specifically, dicyclopentadiene is fed into a high-efficiency short-range preheater at a flow rate of approximately 100-120 kg / h. The heating process takes place in this preheater, where the temperature is rapidly increased to 170-220°C at a heating rate of 40-60°C / s under a pressure of 1.2-2.5 MPa. In some embodiments, the residence time of dicyclopentadiene is ≤10 s. Because dicyclopentadiene is under high pressure during preheating, its boiling point is much higher than its boiling point at room temperature. Therefore, dicyclopentadiene remains in a liquid state at this time. The high-pressure liquid phase and short residence time prevent dicyclopentadiene from depolymerizing, kinetically blocking the polymerization reaction. This ensures that large-scale depolymerization of dicyclopentadiene only occurs after flash vaporization and depressurization.

[0021] Furthermore, in some embodiments, the aforementioned high-efficiency short-range preheater may include a single-rotation heat exchanger or a microwave-assisted preheater. These two types of preheaters can minimize pressure loss during rapid heating and effectively improve the system's heat recovery efficiency and operational stability.

[0022] Next, after preheating the dicyclopentadiene, step S2 is performed. The high-temperature, high-pressure liquid dicyclopentadiene treated in step S1 is depressurized to 0.1~0.3 MPa via a throttling valve, followed by flash depolymerization, while the gaseous product is simultaneously removed. The flash depolymerization temperature is 120~150℃. The preheated dicyclopentadiene, after depressurization via a throttling valve, enters the flash evaporator. Upon depressurization, the high-temperature, high-pressure dicyclopentadiene flashes out low-pressure vapor instantly due to its sensible heat, utilizing pressure energy to drive a phase change. In this step, dicyclopentadiene depolymerizes to form cyclopentadiene, both of which are gaseous. Removing the product from the reaction system at this point effectively avoids the reverse reaction and improves the yield. The gaseous product can be directly gravity-fed to the downstream precooler via the system pressure difference, eliminating the need for a separate pump and avoiding energy consumption.

[0023] Thus, dicyclopentadiene completes its depolymerization after undergoing steps S1 and S2. In step S1, a high pressure of 1.2~2.5 MPa locks the high-temperature dicyclopentadiene in a liquid state, leaving no space for gas phase release. During this process, trace amounts of cyclopentadiene may be generated through cracking, and the cyclopentadiene generated in the high-density liquid phase will instantly undergo reverse dimerization. Furthermore, the residence time in step S1 is ≤10 s. During this process, dicyclopentadiene can only store heat and will not effectively depolymerize, meaning no effective cyclopentadiene is produced.

[0024] Subsequently, in step S2, the heat-stored dicyclopentadiene passes through a throttling valve to achieve isenthalpic pressure reduction. The material passage time is usually around milliseconds. Only a very small amount of dicyclopentadiene depolymerizes, and the vast majority of dicyclopentadiene has not yet depolymerized. In other words, no effective cyclopentadiene will be produced after passing through the throttling valve.

[0025] Next, the regenerated liquid dicyclopentadiene undergoes flash evaporation. During this process, the dicyclopentadiene rapidly transforms into a low-pressure gas phase, followed by effective large-scale depolymerization. Once in the gas phase, the intermolecular distance increases instantaneously, significantly reducing the probability of reverse dimerization. Furthermore, the low-pressure environment favors the forward shift of the depolymerization equilibrium; therefore, flash evaporation is the sole primary reaction zone. Additionally, continuously removing the product and reducing its concentration further promotes the forward shift of the depolymerization reaction, preventing dimerization.

[0026] The method of this invention relies on the sensible heat of the material itself to undergo a phase change during the flash depolymerization stage, eliminating the need for an additional heating source. The entire process only requires the preheating section to provide the heat source, while the cold separation section is equipped with a cold source, achieving high efficiency and energy saving. The isenthalpic cooling during the throttling process reduces the heat load on the flash evaporator. The short dwell time of the preheater, combined with a graphene-silicon carbide hot-spot-free inner wall coating, inhibits the polymerization of reactants into heavy component impurities during the preheating stage, reducing the tendency for fouling on the heat exchange surfaces. During the flash evaporation process, only dicyclopentadiene vaporizes and depolymerizes. A small amount of unreacted dicyclopentadiene and other heavy components such as polymers remain at the bottom of the flash evaporator and are periodically discharged, not carried out with the gaseous products. Thus, unconverted dicyclopentadiene is refluxed, and heavy component impurities are periodically discharged, achieving simultaneous purification of the reaction. Compared with existing preheating gasification cracking processes, this significantly reduces heavy component impurities in the product and improves the purity of cyclopentadiene.

[0027] Furthermore, the method of this invention can reduce the dimerization rate of cyclopentadiene. The low-pressure gas phase significantly dilutes the cyclopentadiene molecules, resulting in a sharp decrease in the bimolecular polymerization rate. This optimizes the overall heat input, relying on the material's own heat storage and pressure difference to drive the phase change. The flash depolymerization section does not require additional heating, resulting in rapid depolymerization. For the above reasons, the reaction process of this invention involves rapid transport of gaseous materials, and the reactants and products coexist with the high-temperature equipment wall and undecomposed dicyclopentadiene for a very short time. The high-temperature reaction section (preheater, flash evaporator) lacks a liquid phase enriched with cyclopentadiene, and there is no high-concentration cyclopentadiene liquid medium, thus lacking the conditions for dimerization. Therefore, the cyclopentadiene generated by the method of this invention is not prone to further polymerization.

[0028] The present invention, through the preheater and flash evaporator coated with graphene-silicon carbide composite coating, which will be described in detail later, can eliminate hot spots on the equipment wall, inhibit polymerization, and avoid liquid phase vortex entrainment, thereby reducing the coking rate of the equipment by more than 60% and extending the maintenance cycle to 12 months.

[0029] In addition, the residence time of dicyclopentadiene should be minimized in the pre-depolymerization steps to avoid polymer formation caused by prolonged preheating; the entire process should be kept in a high-pressure liquid phase state, and the material flow rate should be precisely controlled by a flow control valve. This can not only suppress the polymerization and coking of cyclopentadiene (polymer formation ≤0.8%), but also ensure that the preheater has no additional medium contact, eliminating the risk of impurity introduction.

[0030] As described above, dicyclopentadiene undergoes depolymerization upon entering the flash evaporator due to its sensible heat, generating cyclopentadiene within the flash evaporator. At this point, a mixture of two gaseous phases exists in the flash evaporator: unreacted dicyclopentadiene and the gaseous mixture of the reacted cyclopentadiene. Therefore, after removing the gaseous product (gas mixture), this gaseous mixture needs to be separated. This invention separates these two substances based on their melting and boiling point differences through stepwise temperature control.

[0031] Specifically, in step S3, the gaseous product after flash evaporation in step S2 is pre-cooled, and the condensed liquid after pre-cooling is separated and recovered, while the gas is retained. In some embodiments, the pre-cooling temperature is 42~45°C. The flash vapor enters the precooler and is cooled to 42~45°C. The gaseous mixture of dicyclopentadiene and cyclopentadiene is cooled in the precooler. At this time, because the boiling point of cyclopentadiene is relatively low (approximately 41.5°C) and the pre-cooling temperature is 42~45°C, cyclopentadiene remains in the gas phase, while the boiling point of dicyclopentadiene is relatively high (approximately 170°C). Therefore, dicyclopentadiene condenses into a liquid, forming a gas-liquid mixture of cyclopentadiene and dicyclopentadiene. Subsequently, the dicyclopentadiene in the gas-liquid mixture can be rapidly separated by gravity sedimentation.

[0032] Step S4: The gas separated in step S3 is crystallized at low temperature, converting the gas into a solid and a liquid. Solid-liquid separation is then performed, and the resulting liquid is cyclopentadiene. The temperature for this low-temperature crystallization is controlled between -45 and -60°C. During the low-temperature crystallization process, the remaining cyclopentadiene gas (containing trace amounts of dicyclopentadiene) enters the low-temperature crystallizer and is cooled to -45 to -60°C. Because cyclopentadiene has a low melting point (approximately -97.2°C), it remains in a liquid state, while the remaining dicyclopentadiene has a higher melting point (approximately 33°C). Therefore, the dicyclopentadiene rapidly crystallizes into solid particles, suspended in the liquid cyclopentadiene. Subsequently, the dicyclopentadiene solid is removed by precision filtration or centrifugation to obtain high-purity liquid cyclopentadiene.

[0033] Furthermore, in some embodiments, to improve the utilization rate of raw materials, the method of the present invention further includes step S5, in which the solid separated in step S4 is melted and then refluxed with the liquid obtained in step S3 back to step S1. The liquid dicyclopentadiene separated during the pre-cooling process of step S3 and the dicyclopentadiene separated and melted by low-temperature crystallization in step S4 can be pumped back to step S1 separately or after mixing. This material can be reused, greatly improving the utilization rate of the reaction raw materials.

[0034] Therefore, the method for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene provided in the first aspect of this invention, during the liquid-phase flash depolymerization of dicyclopentadiene, not only ensures a complete depolymerization reaction but also, due to the extremely fast reaction rate, inhibits cyclopentadiene polymerization and coking, resulting in a polymer formation amount ≤0.8%. In the post-processing step, based on the difference in melting and boiling points between dicyclopentadiene and cyclopentadiene, this invention employs a two-step separation method to achieve efficient and deep purification, with a product purity ≥99.95%, meeting electronic grade requirements. Thus, the production efficiency of the method of this invention is significantly improved; compared with traditional distillation column processes, the time required to produce 50 kg of high-purity cyclopentadiene is reduced by 60%~80%, and the production efficiency is increased by more than 5 times.

[0035] According to a second aspect of the present invention, an apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene is provided. For example... Figure 1 As shown, the apparatus of the present invention includes a dicyclopentadiene storage device 1, a preheater 2, a throttling valve 11, a flash evaporator 3, a precooler 4, a gas-liquid separator 5, a low-temperature crystallizer 6, and a solid-liquid separator 7 connected in sequence by pipelines. A pumping device (not shown) is provided on the pipelines. The pumping device may be located, for example, at the outlet of the dicyclopentadiene storage device. The pumping device is used to pump dicyclopentadiene out of the storage device.

[0036] Furthermore, the dicyclopentadiene storage device can be, for example, a storage tank or storage pool, for storing liquid dicyclopentadiene.

[0037] Preheater 2 is a high-efficiency short-range preheater, selected from a single-rotation heat exchanger or a microwave-assisted preheater. When a microwave-assisted preheater is selected, the microwave frequency is set to 2450 MHz or 915 MHz. The high-efficiency short-range preheater 2 is used to preheat dicyclopentadiene, and can rapidly raise the temperature of dicyclopentadiene to 170~220℃ at a heating rate of 50℃ / s.

[0038] For example, a sliding sleeve throttle valve can be selected for the throttle valve 11. The multi-stage pressure reduction design of the sliding sleeve throttle valve can effectively suppress flash cavitation under high pressure differential and protect the valve body. The hard alloy material is erosion-resistant and wear-resistant, which can significantly delay coking and ensure that the valve can operate stably for a long period of time under harsh working conditions, thus ensuring the continuity of the depolymerization process.

[0039] After being depressurized by the throttling valve 11, the dicyclopentadiene enters the flash evaporator 3. The flash evaporator 3 of this invention is equipped with a wire mesh demister 31 at the top and a cross-shaped anti-vortex plate 32 and an automatic liquid level control valve at the bottom. The flash evaporator 3 adopts a vertical cylindrical structure. The rapidly preheated dicyclopentadiene enters the flash evaporator 3 through the throttling valve. The pressure of the dicyclopentadiene drops rapidly, and it quickly flashes into the gas phase while depolymerizing.

[0040] During flash evaporation, gas escapes from the liquid phase at high speed, shearing the liquid surface and forming a large amount of foam carrying mist, which flows out with the gas phase, causing material loss. The wire mesh demister 31 is a passive component installed at the gas phase outlet at the top of the flash evaporator 3. It has no start or stop. When the gas carrying foam / mist passes through the wire mesh, the mist adheres to the wire mesh due to inertia, agglomerates into large droplets, and then falls back into the liquid phase below by gravity, achieving gas-liquid separation. The demisting efficiency is as high as 98% or more.

[0041] The falling droplets settle at the bottom of flash evaporator 3. An automatic level control valve is installed at the bottom of flash evaporator 3. This valve can, for example, use a radar level gauge combined with an interlocking diaphragm valve to control the height of the liquid below. The radar level gauge detects the liquid level in real time, and the signal is transmitted to the control unit to trigger the valve: when the liquid level rises to the upper limit, the valve automatically opens to drain the liquid; when the liquid level drops to the lower limit, the valve automatically closes to stop draining the liquid, operating in a closed-loop automatic manner. When the equipment is fed, draining automatically starts when the liquid level reaches the upper limit; after stopping, the valve remains fully open during the emptying phase, and only automatically opens and closes according to the liquid level threshold during normal operation. The preset liquid level can, for example, be stabilized at 1 / 4 to 1 / 3 of the total equipment height, with the lower limit 200 to 500 mm above the top of the anti-vortex plate and the upper limit at least 300 mm below the wire mesh demister.

[0042] Furthermore, during normal operation, if the liquid level is too low or the flow rate is too fast when the liquid phase is discharged from the bottom outlet, a central vortex will form at the outlet, entraining the gas phase above the liquid surface into the liquid phase, causing entrainment. To avoid the above phenomenon, the flash evaporator 3 of the present invention is also equipped with a cross-shaped anti-vortex plate 32 at the bottom. The cross-shaped anti-vortex plate 32 is a structural component fixedly welded above the liquid phase outlet. It has no start-stop function and works continuously. The cross structure can destroy the rotating flow field formed by the vortex, divide the flow channel to allow the liquid to flow out evenly, and directly block the downward extension of the vortex, thus preventing the gas phase from being entrained by the liquid phase from the root.

[0043] Therefore, the flash evaporator 3 provided by this invention not only enables rapid depolymerization of dicyclopentadiene but also allows for preliminary separation of the gas and liquid phases, improving working efficiency. Furthermore, the inner walls of both the preheater and flash evaporator of this invention are coated with a graphene-silicon carbide coating with a thickness of 50-100 μm. The high thermal conductivity of this composite coating ensures uniform temperature throughout the preheater and flash evaporator, allowing for rapid heating of the preheater without localized overheating. This prevents the repolymerization of cyclopentadiene and avoids coking.

[0044] The composite coating of this invention employs atmospheric plasma thermal spraying, relying on fixed single-layer deposition, layered accumulation, automated uniform coating, and real-time calibration via online eddy current thickness measurement. Combined with standardized spraying parameters and multi-point thickness sampling inspection of the finished product, the coating thickness is stabilized within the 50-100 μm range, with thickness deviation controllable within ±10 μm. The uniform coating thickness ensures the elimination of hot spots on the vessel wall, inhibits polymerization, and effectively reduces coking rate.

[0045] The preheater 2, throttling valve 11, and flash evaporator 3 constitute the reaction system of this invention. Dicyclopentadiene is pumped from a dicyclopentadiene storage device to the preheater 2. In the preheater, the dicyclopentadiene is rapidly heated to 170-220°C under a pressure of 1.2-2.5 MPa. Due to the high pressure, the dicyclopentadiene remains in a liquid phase. After passing through the throttling valve 11, the liquid dicyclopentadiene is rapidly depressurized and sent to the flash evaporator 3. In the flash evaporator 3, the liquid dicyclopentadiene instantly flashes out low-pressure vapor and depolymerizes, generating cyclopentadiene. Because the inner walls of both the preheater 2 and the flash evaporator 3 are coated with a graphene-silicon carbide composite coating, the temperature is uniform throughout the reaction equipment, preventing coking.

[0046] Furthermore, the cyclopentadiene and a small amount of unreacted dicyclopentadiene produced by the above reaction system enter the next stage separation system for separation. The separation system consists of a precooler 4, a gas-liquid separator 5, a low-temperature crystallizer 6, and a solid-liquid separator 7. The gaseous mixture of dicyclopentadiene and cyclopentadiene is cooled in the precooler 4. As mentioned in the first aspect of the invention, dicyclopentadiene and cyclopentadiene are separated in the precooler 4 based on their boiling point difference. Therefore, the precooler 4 of the present invention only needs to provide a precooling temperature of 42-45°C for the gaseous products; its specific form is not particularly limited by the present invention.

[0047] Subsequently, the gas-liquid mixture of cyclopentadiene and dicyclopentadiene enters gas-liquid separator 5. After gas-liquid separation, the separated gaseous cyclopentadiene proceeds to the next purification step. The separated liquid dicyclopentadiene can be further stored for subsequent use.

[0048] The gaseous cyclopentadiene enters the low-temperature crystallizer 6. As mentioned in the first aspect of the present invention, the dicyclopentadiene and cyclopentadiene are separated in the low-temperature crystallizer 6 based on their melting point difference. Since cyclopentadiene has a certain viscosity, the low-temperature crystallizer 6 of the present invention can be a scraper crystallizer, and its surface is coated with a polytetrafluoroethylene anti-stick layer to prevent the adhesion of cyclopentadiene and improve the yield.

[0049] The solid-liquid separator 7 of the present invention can be a precision filter or a centrifugal separator, and the filter element is preferably made of ceramic material, capable of precisely separating solid dicyclopentadiene. Other devices not specifically described in this invention can directly employ corresponding devices commonly used in the art; the present invention does not impose any particular limitation, as long as they can achieve the above-described content.

[0050] In some embodiments of the present invention, the inner walls and flow channel surfaces of the preheater 2 and flash evaporator 3 are coated with a graphene-silicon carbide coating, equipped with high-pressure sealing, flow monitoring, and temperature monitoring modules, and have no additional medium contact structure. The thickness of the graphene-silicon carbide coating is 50~100 μm. This invention employs a reaction device with an inner wall coated with a graphene-silicon carbide composite coating, which, compared to traditional 316L stainless steel equipment, improves temperature resistance, achieving a long-term temperature resistance of 500℃, far exceeding the 170~220℃ preheating temperature and subsequent high-temperature operating requirements of the present invention. The graphene-silicon carbide composite coating has extremely high thermal conductivity, ≥300 W / (m·K), which is 5 times higher than that of traditional 316L stainless steel equipment, enabling rapid and uniform heating of materials. The low surface energy of graphene combined with the high hardness of silicon carbide reduces the coking rate by more than 60%, while also resisting corrosion from trace acidic impurities during the depolymerization of dicyclopentadiene, extending the equipment maintenance cycle to more than 12 months (compared to 3-4 months for traditional 316L stainless steel).

[0051] Furthermore, the surface of the wire mesh demister 31 used in this invention is coated with a polytetrafluoroethylene anti-stick layer, and the surface of the bottom cross-shaped anti-vortex plate 32 is coated with a graphene-silicon carbide coating with a thickness of 50~100 μm. The high thermal conductivity of the composite coating can avoid local overheating and further suppress coking and polymer formation.

[0052] Furthermore, in some embodiments, the apparatus of the present invention further includes a circulation pipeline 8, which connects the dicyclopentadiene storage device 1 and the precooler 4, and also connects the dicyclopentadiene storage device 1 and the solid-liquid separator 7. To prevent coking, the inner wall of the circulation pipeline 8 may be coated with a graphene-silicon carbide composite coating. Additionally, to control the reflux flow rate, a flow regulating valve (not shown in the figure) may be provided in the circulation pipeline 8. The dicyclopentadiene liquid separated in the gas-liquid separator 5 and the dicyclopentadiene solid separated in the solid-liquid separator 7, after melting, can be returned to the dicyclopentadiene storage device and participate in subsequent reactions again. To allow the crystalline dicyclopentadiene to melt, a heating device 9 and a filtration device 10 are provided on the circulation pipeline 8 connecting the dicyclopentadiene storage device 1 and the solid-liquid separator 7. The filter element of the filtration device 10 is coated with an anti-stick coating. The dicyclopentadiene can melt in the heating device 9 and pass through the filtration device 10 to remove impurities before flowing back into the dicyclopentadiene storage device 1. The filtration device 10 can be, for example, a two-stage precision filter (1 μm at the front end and 0.22 μm at the rear end).

[0053] The apparatus for preparing high-purity cyclopentadiene from dicyclopentadiene by flash depolymerization of the present invention employs a graphene-silicon carbide composite coating on the inner walls of the high-efficiency short-path preheater 2 and the flash evaporator 3. This increases the temperature resistance of the apparatus to 500°C and improves the thermal conductivity by at least 5 times, thereby reducing the coking rate by more than 60%. Simultaneously, it significantly improves corrosion resistance, extends the equipment maintenance cycle to more than 12 months, and extends the service life by at least 2 times. Furthermore, the apparatus of the present invention features tightly connected components, eliminating the need for a large distillation column and a high-temperature carrier gas system, thus reducing the floor space by more than 75% and lowering investment costs by 40%.

[0054] The present invention will be described in detail below through examples and comparative examples. It should be noted that all examples and comparative examples aim to produce 50 kg of high-purity cyclopentadiene, the raw material is industrial-grade dicyclopentadiene (purity 98%), the product purity requirement is ≥99.95% (electronic grade standard), and the product yield is calculated based on the dicyclopentadiene feed; the inner walls of the high-efficiency short-path preheater 2 and the flash evaporator 3 are both coated with a 50 μm graphene-silicon carbide composite coating, and other devices are configured according to the description in the second aspect of the present invention. Example 1

[0055] Dicyclopentadiene with a purity of 98% was fed into a single-vortex heat exchanger at a flow rate of 100 kg / h. Under a pressure of 2.0 MPa, the temperature was rapidly increased to 190°C at a heating rate of 50°C / s, with a residence time of 4 s. After heating, the liquid phase of dicyclopentadiene was depressurized to 0.2 MPa through a throttling valve and entered flash evaporator 3 at a flash temperature of 135°C. The gaseous product after flash evaporation was removed and sent to precooler 4 for precooling at a temperature of 43°C. The condensed dicyclopentadiene liquid after precooling was separated and recovered, while the cyclopentadiene gas was retained. The separated cyclopentadiene gas was sent to a low-temperature crystallizer 6 for low-temperature crystallization at -50°C. Most of the gas was converted into liquid (cyclopentadiene), and a very small portion was converted into solid (dicyclopentadiene). Solid-liquid separation was then performed, and the obtained liquid phase was cyclopentadiene. The cyclopentadiene product was collected. The total time to achieve the target yield of 50 kg was 3.2 seconds. h, and test the purity, yield and energy loss of the product.

[0056] Testing revealed that the product had a purity of 99.96%, a yield of 93.5%, and energy consumption was reduced by 38% compared to traditional distillation tower processes. The amount of polymer generated was ≤0.8%. After 12 months of continuous operation, the coking thickness on the inner wall of the equipment was ≤0.1 mm, with no obvious corrosion.

[0057] Example 2 Dicyclopentadiene with a purity of 98% was fed into a microwave-assisted preheater at a flow rate of 120 kg / h. The microwave frequency was set to 2450 MHz. The temperature was rapidly increased to 205 °C at a rate of 55 °C / s under a pressure of 2.2 MPa, with a residence time of 2.5 s. After heating, the liquid phase of dicyclopentadiene was depressurized to 0.18 g / L via a throttling valve. The gaseous product is heated to MPa and then enters flash evaporator 3 at a flash temperature of 138℃. The gaseous product after flash evaporation is removed and sent to precooler 4 for precooling at a temperature of 44℃. The condensed dicyclopentadiene liquid after precooling is separated and recovered, while the cyclopentadiene gas is retained. The separated cyclopentadiene gas is sent to low-temperature crystallizer 6 for low-temperature crystallization at -55℃. Most of the gas is converted into liquid (cyclopentadiene), and a very small portion of the gas is converted into solid (dicyclopentadiene). Solid-liquid separation is then performed, and the obtained liquid phase is cyclopentadiene. The cyclopentadiene product is collected, and the total time to reach the target yield of 50 kg is 2.1 h. The purity, yield, and energy loss of the product are measured.

[0058] Testing revealed that the product has a purity of 99.98%, a yield of 95.8%, and energy consumption is reduced by 42% compared to traditional distillation tower processes. The amount of polymer generated is ≤0.5%, and no impurities are introduced. After 12 months of continuous operation, the inner wall of the equipment shows no corrosion or coking and can be easily cleaned.

[0059] Comparative Example Dicyclopentadiene with a purity of 98% was fed into a packed distillation column (the inner wall of the column bottom was made of 316L stainless steel without a composite coating) at a flow rate of 30 kg / h. The column bottom heating temperature was 180℃, and the top pressure was 0.1 MPa. Dicyclopentadiene was depolymerized in the column bottom for an extended period of 65 min. The obtained gaseous product was condensed at the top of the column, and its reflux ratio was controlled at 3:1 to separate cyclopentadiene and dicyclopentadiene. The distillate from the top of the column was collected in a low-temperature storage tank and further filtered to remove impurities. The total time to achieve the target yield of 50 kg was 11.5 h. The purity, yield, and energy loss of the product were measured.

[0060] Testing revealed that the product purity was 99.85% (not meeting electronic grade standards), the yield was 82.3%, the energy consumption was 1.7 times that of Example 2, and the polymer generation was ≥3.2%. After three months of operation, the coking thickness on the inner wall of the tower reached 1.2 mm, requiring shutdown for cleaning.

[0061] Table 1 below lists the performance metrics of the above-mentioned Examples 1, 2 and comparative examples.

[0062] Table 1

[0063] Based on the above results, it can be seen that the method and apparatus of the present invention can produce cyclopentadiene with high purity, which can meet the requirements of electronic grade, with high yield, high efficiency and deep purification, significantly shortening the production time, increasing efficiency by more than 5 times, reducing the internal coking rate of the equipment by more than 60%, extending the equipment maintenance cycle, increasing service life, reducing the floor space, and reducing investment costs by more than 40%.

[0064] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. The specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A method for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene, characterized in that, The method includes the following steps: Step S1: Heating dicyclopentadiene to 170-220°C under a pressure of 1.2-2.5 MPa; Step S2: The dicyclopentadiene liquid treated in step S1 is depressurized to 0.1~0.3 MPa through a throttling valve, and then flash depolymerization is performed, while the gaseous products are removed at the same time. Step S3: Pre-cool the gaseous product removed after flash evaporation in step S2, separate and recover the condensed liquid after pre-cooling, and retain the gas. Step S4: The gas separated in step S3 is crystallized at low temperature, and the gas is converted into solid and liquid. Then, solid-liquid separation is performed, and the liquid obtained is cyclopentadiene.

2. The method for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene according to claim 1, characterized in that, Step S1 is carried out in a preheater with a heating rate of 40~60℃ / s, and the residence time of the dicyclopentadiene is ≤10 s. The preheater includes a single-rotation heat exchanger or a microwave-assisted preheater.

3. The method for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene according to claim 2, characterized in that, The flash evaporation temperature is 120~150℃.

4. The method for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene according to claim 1, characterized in that, The pre-cooling temperature in step S3 is 42~45℃.

5. The method for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene according to claim 1, characterized in that, The temperature for low-temperature crystallization in step S4 is -45 to -60°C.

6. The method for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene according to claim 1, characterized in that, The method further includes: Step S5: Melt the solid separated in step S4 and return it to step S1 along with the liquid obtained in step S3.

7. An apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene, characterized in that, The apparatus comprises: a dicyclopentadiene storage device, a preheater, a throttling valve, a flash evaporator, a precooler, a gas-liquid separator, a low-temperature crystallizer, and a solid-liquid separator, connected sequentially by pipelines. Pumping equipment is installed on the pipelines. The inner walls of both the preheater and the flash evaporator are coated with a graphene-silicon carbide coating, the thickness of which is 50~100 μm.

8. The apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene according to claim 7, characterized in that, The flash evaporator is equipped with a wire mesh demister at the top and a cross-shaped anti-vortex plate and an automatic liquid level control valve at the bottom. The surface of the cross-shaped anti-vortex plate is coated with a graphene-silicon carbide coating with a thickness of 50~100 μm.

9. The apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene according to claim 7, characterized in that, The preheater is selected from a single-rotation heat exchanger or a microwave-assisted preheater.

10. The apparatus for preparing high-purity cyclopentadiene by flash depolymerization of dicyclopentadiene according to claim 7, characterized in that, The device further includes a circulation pipeline connecting the dicyclopentadiene storage device and the precooler, and the circulation pipeline also connects the dicyclopentadiene storage device and the solid-liquid separator.

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