A post-treatment and devolatilization system and method for the production of polycyclohexylene carbonate.

Abstract

This invention discloses a post-processing and devolatilization system and method for the production of polycyclohexane carbonate (PCHC), belonging to the field of polymer devolatilization technology. This invention uses a precipitant to treat the PCHC polymer solution, and uses a solid-liquid separator to extrude the crude PCHC polymer, discharging the precipitate phase. This removes a large amount of polymer monomers, avoiding direct flash devolatilization, significantly reducing energy consumption, and also avoiding the high-temperature process of flash devolatilization, resulting in PCHC polymers with better color. Furthermore, the oil phase collected from chromatography and the liquid collected from devolatilization cooling are combined and then subjected to a pretreatment section for polymer monomer dehydration and purification, achieving monomer recycling. The aqueous phase collected from chromatography can be recycled multiple times to collect the metal catalyst, allowing for further metal recovery. This solves a series of problems such as high metal residue and poor product quality in metal catalyst products.

Description

Technical Field

[0001] This invention belongs to the field of polymer devolatilization technology, specifically relating to a post-processing and devolatilization system and method for the production of polycyclohexane carbonate. Background Technology

[0002] Carbon dioxide is non-toxic and widely available, originating from waste products generated during countless industrial production processes. With the massive emission of carbon dioxide, the "greenhouse effect" continues to intensify, leading to a general rise in global temperatures.

[0003] The development and utilization of carbon dioxide to prepare chemical materials has always been a hot topic of global interest. Polycyclohexane carbonate (PCHC), a ring-opening copolymer of carbon dioxide and cyclohexane oxide, not only has good biodegradability but also a high glass transition temperature, making it the most important CO2-based polymer after PPC.

[0004] Currently, the main processes for preparing PCHC are solution polymerization and bulk polymerization. The products after polymerization often contain volatiles such as solvents, unreacted monomers, and oligomers. Depending on the conversion rate of the polymerization reaction, the volatile content can generally reach 10% to 80%. Different applications of polymer products have different requirements for devolatilization. Typically, the volatile content of the polymer needs to be reduced to several thousand ppm or even tens of ppm. The energy consumption of the devolatilization process often accounts for more than 60% of the total energy consumption. Therefore, the post-treatment of polymerization reactants and the devolatilization process are second only to the reaction process in importance.

[0005] Industrially, for polymers with a volatile content greater than 20%, flash devolatilization is typically used first. When the volatile content is below 20%, a combination of foaming and diffusion devolatilization is employed. Before flash devolatilization, the polymer is preheated to provide the latent heat of vaporization required for flash evaporation. Simultaneously, low pressure is applied to the flash tank to increase the driving force for phase equilibrium, thereby allowing the volatiles to separate from the polymer. During flash devolatilization, the polymer viscosity is usually low, and the mass transfer efficiency is relatively high. However, due to the large amount of material flashed, the required latent heat of vaporization is also significant.

[0006] When the volatile matter content of a polymer decreases from approximately 20% to around 5%, the primary process is foaming devolatilization, which is achieved through the formation, growth, movement, deformation, aggregation and merging, and rupture of bubbles within the polymer. Diffusion devolatilization, on the other hand, reduces the volatile matter content from 5% to the ppm level. At this point, the polymer viscosity is very high, and devolatilization mainly relies on the diffusion of volatile matter. Increasing the specific surface area of ​​the polymer and renewing its flow state can improve the devolatilization effect.

[0007] Various systems and methods for removing volatiles have been published both domestically and internationally, depending on the polymerization system. Most existing polymer volatile removal systems and methods in the industry directly employ multi-stage heating flash evaporation, such as patents CN 114437253A and CN 114369181A. While patent CN 116351088A includes an initial flash evaporation system, a static volatile removal system, and a dynamic volatile removal system, 95% of the volatiles are removed in the flash evaporation and static volatile removal systems. The static volatile removal system contains a heater, essentially making it a heated flash evaporator. Flash evaporation itself is energy-intensive, and for high-viscosity polymers, poor flowability, large liquid film thickness, low diffusion rate, and high mass transfer resistance lead to low volatile removal efficiency, incomplete volatile removal, and large residues. For heat-sensitive polymers, the long residence time and slow surface renewal easily cause coking and yellowing during polymerization.

[0008] Patent CN 112898551A proposes adding hot water to the devolatilization reactor for devolatilization. This method can only be used for low-boiling-point monomers, has poor applicability, and the monomers are not completely removed. Small molecular weight oligomers cannot be removed, resulting in low monomer recovery rate and poor product quality.

[0009] For the preparation of polymer PCHC, there are two types of catalysts: metal and non-metal. Currently, some preparations are made using metal catalysts, which results in metal residues in the product, affecting its color and polluting the soil after degradation. Summary of the Invention

[0010] In order to overcome the shortcomings of the prior art, the present invention aims to provide a post-processing and devolatilization system and method for the production of polycyclohexane carbonate, which solves the technical problems of wide volatile range of PCHC reactive polymers, high energy consumption of traditional devolatilization processes, inability to perform deep devolatilization, large metal residues in products with metal catalysts, and poor product quality.

[0011] To achieve the above objectives, the present invention employs the following technical solution:

[0012] This invention discloses a post-processing and devolatilization system for the production of polycyclohexane carbonate, including a precipitation tank, a solid-liquid separator, a dynamic devolatilizer, and a chromatography tank;

[0013] The outlet of the precipitation vessel is connected to the inlet of the solid-liquid separator; the outlet of the solid-liquid separator is connected to the inlets of the dynamic devolatilizer and the chromatography unit, respectively; the outlets of the chromatography unit and the dynamic devolatilizer are combined and then connected to the pretreatment section of the polymer monomers.

[0014] The outlet of the dynamic devolatilizer is also connected to the product collection device; the outlet of the chromatography unit is also connected to the inlet of the precipitation vessel.

[0015] Furthermore, the outlet of the solid-liquid separator includes a crude PCHC polymer outlet and a liquid phase outlet; the outlet of the dynamic devolatilizer includes a PCHC polymer product outlet and a devolatilized gas phase outlet; and the outlet of the chromatography unit includes an aqueous phase outlet and an oil phase outlet.

[0016] Furthermore, the crude PCHC polymer outlet of the solid-liquid separator is connected to the inlet of the dynamic devolatilizer, and the liquid phase outlet of the solid-liquid separator is connected to the inlet of the chromatography unit.

[0017] The gas phase outlet of the dynamic devolatilizer and the oil phase outlet of the chromatography unit are combined and connected to the pretreatment section of the polymer monomer; the PCHC polymer product outlet of the dynamic devolatilizer is connected to the product collection device.

[0018] The aqueous phase outlet of the chromatography apparatus is also connected to the inlet of the precipitation vessel.

[0019] Furthermore, after the gas phase outlet of the dynamic devolatilizer and the oil phase outlet of the chromatography are combined, a condenser, a buffer tank and a second drain pump are sequentially installed on the pipeline connecting to the pretreatment section of the polymer monomer.

[0020] A first discharge pump is also installed on the pipeline connected to the inlet of the precipitation vessel at the aqueous phase outlet of the chromatography apparatus.

[0021] Furthermore, the precipitation vessel is equipped with a stirring device; the outer wall of the precipitation vessel is provided with a jacket.

[0022] Furthermore, the solid-liquid separator may be centrifugal, pressure filter, or screw type.

[0023] Furthermore, the types of dynamic devolatilizers include screw type, scraper film type, horizontal disc ring type, or horizontal kneading type.

[0024] Furthermore, the chromatography system is configured as a single-stage or multi-stage series system; the chromatography system is equipped with an accelerated oil-water separation device.

[0025] This invention also discloses a method for using the post-treatment and devolatilization system for the production of the above-mentioned polycyclohexane carbonate, including the following steps:

[0026] The PCHC polymer solution and precipitant are introduced into the inlet of the precipitation vessel for precipitation, and then enter the solid-liquid separator for separation to obtain crude PCHC polymer and liquid phase.

[0027] The crude PCHC polymer obtained flows out of the outlet of the solid-liquid separator and is fed into the dynamic devolatilizer for devolatilization to obtain PCHC polymer product and devolatilized gas phase;

[0028] The obtained liquid phase flows out from the outlet of the solid-liquid separator and is fed into a chromatography unit for chromatography to obtain an aqueous phase and an oil phase.

[0029] The obtained PCHC polymer product flows out from the outlet of the dynamic devolatilizer and enters the product collection device; the obtained devolatilized gas phase flows out from the outlet of the dynamic devolatilizer, is condensed, and merges with the oil phase discharged from the chromatograph, and enters the pretreatment section of the polymer monomer for recycling.

[0030] The obtained aqueous phase flows out of the chromatograph outlet and is recycled into the precipitation tank.

[0031] Furthermore, the precipitant is water.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention discloses a post-processing and devolatilization system for the production of polycyclohexane carbonate (PCHC). The PCHC polymer solution is treated with a precipitant, and the crude PCHC polymer is extruded through a solid-liquid separator, discharging the precipitate phase. This removes a large amount of polymer monomers, avoiding direct flash devolatilization, significantly reducing energy consumption, and also avoiding the high-temperature process of flash devolatilization, resulting in a better-colored PCHC polymer. Furthermore, the oil phase collected from chromatography and the liquid collected from devolatilization cooling are combined and then purified by a polymer monomer pretreatment section for dehydration and impurity removal, enabling monomer recycling. The aqueous phase collected from chromatography can be recycled multiple times to collect the metal catalyst, allowing for further metal recovery. This solves a series of problems such as high metal residue and poor product quality in metal catalyst products.

[0034] The present invention also discloses a method for the above-mentioned system, which uses a dynamic devolatilizer to further devolve the crude PCHC polymer separated by precipitation, which can effectively reduce the residue of polymer monomers and low molecular weight oligomers and improve the quality of PCHC polymer products. At the same time, both the polymer monomers after chromatography separation and the polymer monomers after deep devolatilization are sent to the PCHC polymer raw material pretreatment section for reuse, which increases the recycling of polymer monomers and effectively improves the monomer recovery rate.

[0035] Furthermore, water is preferred as the precipitant because it is inexpensive, readily available, and immiscible with the PCHC polymer monomer cyclohexane oxide, allowing for easy chromatographic separation. Chromatographic separation is energy-free, further reducing energy consumption in post-processing. Additionally, when metal catalysts are used in polymerization, using water for precipitation effectively reduces catalyst residue in the product, avoiding the influence of the catalyst during subsequent processing and storage. It also makes catalyst recovery possible (metals in the water can be extracted through evaporation or other methods). Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the post-processing and devolatilization system for the production of polycyclohexane carbonate according to the present invention.

[0037] Wherein: 1-precipitation vessel; 2-solid-liquid separator; 3-dynamic devolatilizer; 4-chromatographic separator; 5-first discharge pump; 6-condenser; 7-buffer tank; 8-second discharge pump; 9-product collection device. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0040] like Figure 1 As shown, this invention discloses a post-processing and devolatilization system for the production of polycyclohexane carbonate, including a precipitation vessel 1, a solid-liquid separator 2, a dynamic devolatilizer 3, and a chromatography unit 4; the outlet of the precipitation vessel 1 is connected to the inlet of the solid-liquid separator 2; the crude PCHC polymer outlet of the solid-liquid separator 2 is connected to the inlet of the dynamic devolatilizer 3, and the liquid phase outlet of the solid-liquid separator 2 is connected to the inlet of the chromatography unit 4; the devolatilized gas phase outlet of the dynamic devolatilizer 3 and the oil phase outlet of the chromatography unit 4 converge and are connected to the pretreatment section of the polymer monomer; the PCHC polymer product outlet of the dynamic devolatilizer 3 is connected to the product collection device 9; the aqueous phase outlet of the chromatography unit 4 is also connected to the inlet of the precipitation vessel 1. The gas phase outlet of the dynamic devolatilizer 3 and the oil phase outlet of the chromatography 4 are connected to the pretreatment section of the polymer monomer via a pipeline, which is then equipped with a condenser 6, a buffer tank 7, and a second drain pump 8. A first drain pump 5 is also installed on the pipeline connected to the inlet of the aqueous phase outlet of the chromatography 4 precipitation vessel 1.

[0041] In this process, a PCHC polymer solution is precipitated in a precipitation vessel 1 using a precipitating agent to precipitate crude PCHC polymer. The precipitation vessel 1 is equipped with a stirring device (stirring device). The outer wall of the precipitation vessel 1 is provided with a jacket. The stirring device ensures that the precipitating agent and the PCHC polymer solution are fully mixed. The jacket is circulated with cooling water to control the temperature of the precipitation vessel. The precipitating agent is preferably water, and the volatile content of the PCHC polymer is in the range of 5%-80%.

[0042] The PCHC polymer solution that has undergone precipitation is extruded and discharged in the solid-liquid separator 2. The solid-liquid separator is not limited to centrifugal, pressure filter, screw, etc.

[0043] The crude PCHC polymer is further deeply devolatilized in the dynamic devolatilizer 3 to meet product requirements; the dynamic devolatilizer is not limited to screw type, scraper film type, horizontal disc ring type, horizontal kneading type, etc.

[0044] In the chromatography unit 4, the liquid phase discharged from the solid-liquid separator is separated into aqueous phase and oil phase. After separation, the precipitant (aqueous phase) and polymer monomer (oil phase) can be recycled. The chromatography unit 4 can be set to one stage or multiple stages, and the chromatography unit is equipped with a coalescer and other devices to accelerate oil-water separation.

[0045] The gas phase discharged from the dynamic devourer 3 is condensed, recovered, and recycled.

[0046] The oil phase collected by chromatography and the gas phase discharged from the dynamic devolatilizer 3 are condensed and collected into liquid, which is then dehydrated and purified in the polymer monomer pretreatment section to achieve monomer recycling.

[0047] When using metal catalysts, the aqueous phase collected by chromatography can be recycled multiple times to collect the metal catalyst, and further metal recovery can be considered.

[0048] Example 1

[0049] The post-treatment and devolatilization system for the production of the above-mentioned polycyclohexane carbonate includes the following steps:

[0050] The PCHC polymer solution is injected into precipitation vessel 1, and a certain amount of precipitating agent is added to precipitation vessel 1. Cooling circulating water is circulated into the jacket, and stirring is started to ensure that the precipitating agent and PCHC polymer solution are fully mixed and homogeneous. The precipitating agent causes the PCHC polymer to precipitate in the mixed solution. The precipitating agent is water, and the mass ratio of the precipitating agent to the PCHC polymer solution is 0.5-10. The stirring speed of the precipitation vessel is 100-600 rad / min, and the cooling temperature of the precipitation vessel is controlled at 30-60℃.

[0051] The PCHC polymer solution after precipitation is then fed into solid-liquid separator 2, where the liquid phase is squeezed out and the crude PCHC polymer is sent to downstream dynamic devolatilizer 3, while the discharged liquid phase is sent to downstream chromatograph 4.

[0052] The crude PCHC polymer undergoes further deep devolatilization in the dynamic devolatilizer 3, reducing the volatile components in the PCHC polymer to below 1000 ppm, and further to below 100 ppm; the operating temperature of the dynamic devolatilizer is 60-200℃, and the operating pressure is 0.2-90 kPaA.

[0053] The liquid phase in the chromatography unit 4 is a mixed solution of precipitant water and PCHC polymer monomer cyclohexane oxide. The mixed solution will be chromatographically separated in the chromatography unit 4. The aqueous phase in the lower layer of the chromatography unit 4 will be sent back to the precipitation tank for recycling through the first discharge pump 5. The oil phase in the upper layer of the chromatography unit 4 will be sent to the raw material pretreatment section of the PCHC polymer monomer, and will be recycled as a reaction raw material after pretreatment such as dehydration and impurity removal. The operating temperature of the chromatography unit 4 is 20-50℃.

[0054] The gas phase discharged by the dynamic devolatilizer 3 during the deep devolatilization process will be condensed and recovered by the condenser 6. The recovered liquid phase will be stored in the buffer tank 7 and periodically sent to the pretreatment section of the PCHC polymer monomer by the second drain pump 9 for recycling.

[0055] Preferably, a PCHC polymer solution with a 30% conversion rate and a precipitant are added to precipitation vessel 1, controlling the mass ratio of the precipitant to the PCHC polymer solution to be 8. Circulating water is introduced, stirring is started, and the precipitation temperature is controlled at around 30°C, with a stirring rate of 350 rad / min, to ensure thorough mixing and precipitation reaction. The polymer solution after precipitation is sent to a twin-screw solid-liquid separator for extrusion, where the liquid phase is removed, and the solid phase is sent to a twin-screw extruder for further deep devolatilization. The operating pressure of the twin-screw extruder is around 0.65 kPaA, and the operating temperature is around 180°C. After devolatilization, the PCHC polymer product is obtained, with a volatile content of 158 ppm.

[0056] Preferably, a PCHC polymer solution with a 60% conversion rate and a precipitating agent are added to precipitation vessel 1, controlling the mass ratio of the precipitating agent to the PCHC polymer solution to be 5. Circulating water is introduced, stirring is started, and the precipitation temperature is controlled at approximately 40°C, with a stirring rate of 150 rad / min to ensure thorough mixing and precipitation reaction. The polymer solution after precipitation is sent to a centrifugal filter to remove the liquid phase, and the solid phase is sent to a twin-screw extruder for further deep devolatilization. The twin-screw extruder operates at a pressure of approximately 2 kPaA and a temperature of approximately 160°C. After devolatilization, the PCHC polymer product is obtained, with a volatile content of 423 ppm.

[0057] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for using a post-processing and devolatilization system for the production of polycyclohexylene carbonate, characterized in that, The post-processing and devolatilization system for the production of polycyclohexane carbonate includes a precipitation vessel (1), a solid-liquid separator (2), a dynamic devolatilizer (3), and a chromatography unit (4). The outlet of the precipitation vessel (1) is connected to the inlet of the solid-liquid separator (2); the outlet of the solid-liquid separator (2) is connected to the inlets of the dynamic devolatilizer (3) and the chromatography unit (4) respectively; the outlet of the chromatography unit (4) and the outlet of the dynamic devolatilizer (3) are combined and connected to the pretreatment section of the polymer monomer. The outlet of the dynamic devolatilizer (3) is also connected to the product collection device (9); the outlet of the chromatography unit (4) is also connected to the inlet of the precipitation vessel (1); The usage method includes the following steps: The PCHC polymer solution and precipitant are introduced into the inlet of the precipitation vessel (1) for precipitation, and then enter the solid-liquid separator (2) for separation to obtain crude PCHC polymer and liquid phase; The crude PCHC polymer obtained flows out from the outlet of the solid-liquid separator (2) and is fed into the dynamic devolatilizer (3) for devolatilization to obtain PCHC polymer product and devolatilized gas phase; The obtained liquid phase flows out from the outlet of the solid-liquid separator (2) and is fed into the chromatography unit (4) for chromatography to obtain an aqueous phase and an oil phase; The obtained PCHC polymer product flows out from the outlet of the dynamic devolatilizer (3) and enters the product collection device (9); the obtained devolatilized gas phase flows out from the outlet of the dynamic devolatilizer (3), condenses and merges with the oil phase discharged from the chromatography unit (4), and enters the pretreatment section of the polymer monomer for recycling. The aqueous phase obtained flows out of the outlet of the chromatograph (4) and is recycled into the precipitation tank (1); The precipitant is water.

2. The method of using the post-processing and devolatilization system for the production of polycyclohexane carbonate according to claim 1, characterized in that, The outlet of the solid-liquid separator (2) includes a crude PCHC polymer outlet and a liquid phase outlet; the outlet of the dynamic devolatilizer (3) includes a PCHC polymer product outlet and a devolatilized gas phase outlet; the outlet of the chromatography unit (4) includes an aqueous phase outlet and an oil phase outlet.

3. The method of using the post-processing and devolatilization system for the production of polycyclohexane carbonate according to claim 2, characterized in that, The crude PCHC polymer outlet of the solid-liquid separator (2) is connected to the inlet of the dynamic devolatilizer (3), and the liquid phase outlet of the solid-liquid separator (2) is connected to the inlet of the chromatography unit (4). The gas phase outlet of the dynamic devolatilizer (3) and the oil phase outlet of the chromatography unit (4) are connected to the pretreatment section of the polymer monomer after they converge; the PCHC polymer product outlet of the dynamic devolatilizer (3) is connected to the product collection device (9). The aqueous phase outlet of the chromatography unit (4) is also connected to the inlet of the precipitation vessel (1).

4. The method of using the post-processing and devolatilization system for the production of polycyclohexane carbonate according to claim 3, characterized in that, After the gas phase outlet of the dynamic devolatilizer (3) and the oil phase outlet of the chromatography (4) converge, a condenser (6), a buffer tank (7) and a second drain pump (8) are sequentially installed on the pipeline connected to the pretreatment section of the polymer monomer. A first discharge pump (5) is also installed on the pipeline connecting the aqueous phase outlet of the chromatography vessel (4) and the inlet of the precipitation vessel (1).

5. The method of using the post-processing and devolatilization system for the production of polycyclohexane carbonate according to claim 1, characterized in that, The sedimentation vessel (1) is equipped with a stirring device; the outer wall of the sedimentation vessel (1) is provided with a jacket.

6. The method of using the post-processing and devolatilization system for the production of polycyclohexane carbonate according to claim 1, characterized in that, The solid-liquid separator (2) can be centrifugal, pressure filter or screw type.

7. The method of using the post-processing and devolatilization system for the production of polycyclohexane carbonate according to claim 1, characterized in that, The types of dynamic devourers (3) include screw type, scraper film type, horizontal disc ring type or horizontal kneading type.

8. The method of using the post-processing and devolatilization system for the production of polycyclohexane carbonate according to claim 1, characterized in that, The chromatography unit (4) is configured in a single or multi-stage series configuration; the chromatography unit (4) is equipped with an accelerated oil-water separation device.

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