System and method for photocatalytic production of tetralin based on reactive distillation

Abstract

The application provides a system and method for photocatalytic production of tetrahydrocycloheptane based on reactive distillation, and relates to the technical field of catalytic chemistry. The system comprises a backpack reactive distillation device, a solvent recovery and product purification column, and multiple heat exchangers. The backpack reactive distillation device comprises a distillation column and N photo reactors connected with the distillation column. The raw material norbornadiene, the side sampling stream of the distillation column, and the circulating stream taken from the bottom of the solvent recovery and product purification column are respectively introduced into each photo reactor from three paths. The reflux stream of the distillation column and the outlet streams of the N photo reactors are introduced into the distillation column. The crude product taken from the bottom of the distillation column is introduced into the solvent recovery and product purification column, the solvent recovery and product purification column separates and purifies tetrahydrocycloheptane and recovers the solvent, and high-efficiency and high-purity preparation of tetrahydrocycloheptane is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalytic chemical technology, in particular to a system and method for photocatalytic production of tetrahydrogenated norbornadiene based on reaction distillation. BACKGROUND

[0002] Norbornadiene is an organic compound, and tetrahydrogenated norbornadiene is the product of the photosensitive cycloaddition reaction of norbornadiene under ultraviolet light. It has a high-tension cage structure and a large density, is a highly efficient rocket propellant and missile attitude control agent, and can be used as an additive to increase the energy density of jet fuel. It is also a good solar energy storage material and has received extensive attention in the field of solar energy storage.

[0003] Traditional tetrahydrogenated norbornadiene preparation methods often involve a reaction followed by distillation, which has problems such as low efficiency, high cost, and serious environmental pollution.

[0004] For example, patent document CN114733460A discloses a high-throughput and low-energy-consumption continuous flow synthesis device for tetrahydrogenated norbornadiene. A fluid delivery device delivers the reaction raw materials. A capillary continuous flow reactor is used for the reaction of the raw materials to generate tetrahydrogenated norbornadiene. The capillary continuous flow reactor is arranged between a high-power panel type UV-LED lamp and a reflector. Tetraethyl Michler's ketone is used as a photosensitizer, and tetraethyl Michler's ketone is dissolved in norbornadiene to form a homogeneous reaction solution. The reaction solution is irradiated by an ultraviolet light source in the capillary continuous flow reactor. After the reaction, the reaction product is separated by rotary evaporation to obtain tetrahydrogenated norbornadiene.

[0005] For example, patent document CN103787819B discloses a continuous preparation method for high-purity tetrahydrogenated norbornadiene. The method uses a reaction-distillation integrated method or a method of first reaction and then distillation. A new composite catalyst obtained by loading an organic photosensitizer on a solid photocatalyst is used. The composite catalyst is blended with or coated on the distillation packing to achieve the integration of reaction and distillation. In the method of first reaction and then distillation, the catalyst and the distillation packing are placed separately.

[0006] Therefore, it is particularly important to develop an environmentally friendly, efficient, low-cost, and simple preparation process. The backpack reaction distillation process has the advantages of simplifying the process, reducing operating costs, achieving continuous production, and saving energy. The present application couples the reactor with the distillation column, simultaneously realizes the production and separation of the product, and can improve the single-pass conversion rate of the reaction. SUMMARY

[0007] To solve the above technical problems, the present application provides a system for photocatalytic production of tetrahydrogenated norbornadiene based on reaction distillation, comprising: a backpack reaction distillation device, a solvent recovery and product purification column, and a plurality of heat exchangers.

[0008] The back-pack reaction distillation device comprises a distillation column and N photo-reactors connected with the distillation column.

[0009] The photo-reactors convert raw norbornadiene into tetrahydro-4, 4, 7, 7- tetramethyl-2, 6-bicycloheptane through photocatalysis, and the outlet stream of the photo-reactors enters the distillation column;

[0010] The crude product taken from the bottom of the distillation column enters the solvent recovery and product purification column through a heat exchanger;

[0011] The solvent recovery and product purification column separates and purifies tetrahydro-4, 4, 7, 7-tetramethyl-2, 6-bicycloheptane, and the circulating stream taken from the bottom of the solvent recovery and product purification column is divided into N streams which enter the N photo-reactors through another heat exchanger.

[0012] Further, the feed into the photo-reactors comprises raw norbornadiene, the side-draw stream of the distillation column, and the stream divided from the circulating stream taken from the bottom of the solvent recovery and product purification column.

[0013] Further, the feed of the distillation column comprises the top reflux stream of the distillation column itself and the outlet stream of the N photo-reactors.

[0014] Further, the photo-reactors are one of a pipe type, a tank type, a fixed bed, a fluidized bed, a trickle bed, and a capillary continuous flow; the N photo-reactors are connected in series or in parallel.

[0015] Further, the feed and discharge of each photo-reactor are continuous processes; the photo-reactor uses a heterogeneous catalyst or a homogeneous catalyst or does not use a chemical catalyst.

[0016] Further, the solvent recovery and product purification column is used for separating and purifying tetrahydro-4, 4, 7, 7-tetramethyl-2, 6-bicycloheptane and recovering solvent, the separated and purified tetrahydro-4, 4, 7, 7-tetramethyl-2, 6-bicycloheptane is taken from the top to obtain purified tetrahydro-4, 4, 7, 7-tetramethyl-2, 6-bicycloheptane, and other components containing the solvent to be recovered are taken from the bottom to form a circulating stream.

[0017] Further, the solvent recovery and product purification column is a separate device or a device coupled with the back-pack reaction distillation device.

[0018] The application also provides a method for producing tetrahydro-4, 4, 7, 7-tetramethyl-2, 6-bicycloheptane through photocatalysis based on reaction distillation, which is realized by the above-mentioned system for producing tetrahydro-4, 4, 7, 7-tetramethyl-2, 6-bicycloheptane through photocatalysis based on reaction distillation, and comprises the following steps:

[0019] Raw norbornadiene, the side-draw stream of the distillation column, and the stream divided from the circulating stream taken from the bottom of the solvent recovery and product purification column enter each photo-reactor from three paths respectively;

[0020] The raw norbornadiene is converted into tetrahydro-4, 4, 7, 7-tetramethyl-2, 6-bicycloheptane through photocatalysis in the photo-reactor, and the outlet stream of the photo-reactor enters the distillation column.

[0021] The overhead reflux stream of the rectification tower itself flows back into the tower in the form of total reflux, the crude product taken out from the bottom of the rectification tower enters the solvent recovery and product purification tower after heat exchange, is separated and purified in the solvent recovery and product purification tower, and the purified tetrahydro-4, 4, 7, 7-tetracycloheptane is obtained, and the circulating stream taken out from the bottom of the solvent recovery and product purification tower is recovered, passes through another heat exchanger, and is divided into N streams which enter the N photoreactors respectively.

[0022] Further, the overhead reflux stream of the rectification tower itself includes raw material norbornadiene, tetrahydro-4, 4, 7, 7-tetracycloheptane and solvent, and the side-draw stream of the rectification tower includes raw material norbornadiene, tetrahydro-4, 4, 7, 7-tetracycloheptane and solvent.

[0023] Further, isomerization occurs in the photoreactor, the raw material norbornadiene molecules absorb ultraviolet light energy to form excited state norbornadiene molecules, and the excited state norbornadiene molecules undergo intramolecular rearrangement to gradually establish the structure of tetrahydro-4, 4, 7, 7-tetracycloheptane.

[0024] Compared with the prior art, the present application has the following beneficial technical effects:

[0025] The purpose of the present application is to provide a system and method for photocatalytic production of tetrahydro-4, 4, 7, 7-tetracycloheptane based on reaction rectification, the system comprising a backpack reaction rectification device, a solvent recovery and product purification tower and a plurality of heat exchangers, the photoreactor of the backpack reaction rectification device produces tetrahydro-4, 4, 7, 7-tetracycloheptane by photocatalytic norbornadiene, and high-purity tetrahydro-4, 4, 7, 7-tetracycloheptane is obtained by separation and purification in the solvent recovery and product purification tower; the method for photocatalytic production of tetrahydro-4, 4, 7, 7-tetracycloheptane based on reaction rectification can realize efficient and high-purity production of tetrahydro-4, 4, 7, 7-tetracycloheptane at low energy consumption and cost. Through the design of photocatalyst and light system, the use of backpack reaction rectification device, the optimization of reaction conditions, the improvement of product yield and purity and the realization of continuous production of tetrahydro-4, 4, 7, 7-tetracycloheptane, the use of the equipment reduces environmental pollution and meets the green and sustainable development requirements of modern chemical production. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0027] Figure 1 The system structure diagram of the present application for photocatalytic production of tetrahydro-4, 4, 7, 7-tetracycloheptane based on reaction rectification;

[0028] Figure 2 The isomerization process schematic diagram in the photoreactor of the present application. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] In the accompanying drawings of specific embodiments of the present invention, in order to better and more clearly describe the working principle of each component in the system and show the connection relationship of each part in the device, only the relative positional relationship between each component is clearly distinguished. It does not constitute a limitation on the signal transmission direction, connection sequence, or size, dimension, and shape of each part within the component or structure.

[0031] like Figure 1 The diagram shows the system structure for the photocatalytic production of tetracycloheptane based on reactive distillation. In the diagram, 1 and 1' represent the feedstock norbornene; 2 and 2' represent the N streams entering the photoreactor, which are divided into the recirculation stream 6; 3 and 3' represent the side-collected streams of distillation column I; 4 and 4' represent the effluent streams from the photoreactor; 5 represents the crude product collected from the bottom of distillation column I; 6 represents the recirculation stream collected from the bottom of solvent recovery and product purification column II; 7 represents the tetracycloheptane collected from the top of solvent recovery and product purification column II; 8 and 8' represent the reflux streams from the top of distillation column I; and N represents the number of photoreactors.

[0032] like Figure 1 As shown, the system for photocatalytic production of tetracycloheptane based on reactive distillation includes: a backpack reactive distillation unit, a solvent recovery and product purification tower II, and multiple heat exchangers.

[0033] In a preferred embodiment, the solvent recovery and product purification tower II can be a separate device or a device coupled with a backpack reactive distillation unit.

[0034] exist Figure 1 Before the raw materials norbornene 1 and 1' enter the photoreactor, before the side sample streams 3 and 3' of distillation column I enter the photoreactor, and before the photoreactor outlet streams 4 and 4' enter distillation column I, heat exchangers may or may not be added, depending on the optimal reaction temperature of the catalyst used in the process.

[0035] Distillation column I and its connected N photoreactors together constitute a backpack reactive distillation apparatus.

[0036] Each photoreactor feed consists of three parts:

[0037] The first is the raw material norbornadiene 1 and 1';

[0038] The second is the side-draw stream 3 and 3' of rectification column I, and the mixture in the side-draw stream 3 and 3' includes the raw material norbornadiene, tetrahydro-4, 4, 7, 7- tetramethyl-2, 6-bicycloheptane, and the solvent. Preferably, in different preparation processes, the mixture in the side-draw stream 3 and 3' can include the added photosensitizer.

[0039] The third is the stream 2 and 2' separated from the recycle stream 6 taken from the bottom of the solvent recovery and product purification column II after passing through the heat exchanger.

[0040] The feed of the rectification column I includes the self overhead reflux stream 8 and 8' of the rectification column I and the N number of outlet streams 4 and 4' of the photoreactor.

[0041] The self overhead reflux stream 8 and 8' of the rectification column I contains the mixture of the raw material norbornadiene, tetrahydro-4, 4, 7, 7- tetramethyl-2, 6-bicycloheptane, and the solvent, and the reflux stream 8 and 8' flows back into the column in the form of total reflux. Preferably, when the mixture in the side-draw stream 3 and 3' includes the added photosensitizer, the self overhead reflux stream 8 and 8' of the rectification column I also contains the photosensitizer, and the crude product 5 taken from the bottom of the rectification column I contains the photosensitizer in addition to the solvent.

[0042] The crude product 5 taken from the bottom of the rectification column I enters the solvent recovery and product purification column II after passing through the heat exchanger. The solvent recovery and product purification column II is used for separating and purifying tetrahydro-4, 4, 7, 7- tetramethyl-2, 6-bicycloheptane and recovering the solvent, specifically, the purified tetrahydro-4, 4, 7, 7- tetramethyl-2, 6-bicycloheptane 7 is taken from the top of the solvent recovery and product purification column II, and the recycle stream 6 taken from the bottom of the solvent recovery and product purification column II containing the solvent to be recovered is separated into the streams 2 and 2' flowing into the N number of photoreactors after passing through the heat exchanger.

[0043] In the solvent recovery and product purification column II, the tetrahydro-4, 4, 7, 7- tetramethyl-2, 6-bicycloheptane with a lower boiling point is taken from the top of the column to obtain the purified tetrahydro-4, 4, 7, 7- tetramethyl-2, 6-bicycloheptane, and other components containing the solvent are taken from the bottom of the column to form the recycle stream, and through the above continuous condensation and vaporization rectification process, the tetrahydro-4, 4, 7, 7- tetramethyl-2, 6-bicycloheptane with high purity is finally obtained.

[0044] In the prior art, when the optimal reaction temperature in the photoreactor does not match the separation temperature in the rectification column, the reaction rectification column cannot be applied to the tetrahydro-4, 4, 7, 7- tetramethyl-2, 6-bicycloheptane production system. However, the backpack reaction process proposed in the present application can prove that under different catalyst types, different catalyst dosages, different reaction temperatures, and especially when the optimal reaction temperature in the photoreactor does not match the separation temperature in the rectification column, the backpack reaction process proposed in the present application can still obtain tetrahydro-4, 4, 7, 7- tetramethyl-2, 6-bicycloheptane with high yield.

[0045]

[0046] In a preferred embodiment, the feeding and discharging of the photoreactor is a continuous process; the N photoreactors can be connected in series or in parallel, where N is 1-10; the volumes of the N photoreactors can be the same or different.

[0047] Photoreactors can take the form of tubular, batch, fixed bed, fluidized bed, trickle bed, capillary continuous flow, etc.

[0048] The photoreactor can use heterogeneous or homogeneous catalysts, or it can be without chemical catalysts.

[0049] The light source can be provided by adding a quartz tube to the photoreactor and placing an ultraviolet light source, a high-pressure mercury lamp, or a UV-LED lamp inside the quartz tube.

[0050] An isomerization reaction occurs within the photoreactor, and the reaction process is as follows: Figure 2 As shown: norbornene molecule ( Figure 2 The structure on the left absorbs ultraviolet light energy emitted by a light source, causing electrons to transition from the ground state to an excited state. Under photoexcitation, one π electron of norbornadiene transitions to the π* orbital, a process that puts the norbornadiene molecule into an excited state. The excited-state norbornadiene molecule undergoes intramolecular rearrangement. The rearrangement process involves the breaking and reforming of double bonds; one double bond breaks, and a new σ bond is formed simultaneously. A three-membered ring and a four-membered ring are formed, gradually establishing the molecular structure of tetracycloheptane. Ultimately, norbornadiene is transformed into tetracycloheptane through the above rearrangement process. Figure 2 (Right side structure).

[0051] This reaction is reversible. The reverse reaction mechanism is as follows: the photocatalyst absorbs light energy and is excited from the ground state to the excited state. The excited-state photocatalyst transfers energy to the tetracycloheptane molecule, causing it to enter the excited state. During this process, the photocatalyst returns to the ground state, while the tetracycloheptane molecule absorbs the energy provided by the photocatalyst. The excited-state tetracycloheptane molecule undergoes bond breakage, usually the breakage of weak carbon-carbon or carbon-hydrogen bonds, leading to the cleavage and rearrangement of the tetracycloheptane ring system. After the breakage, the molecule rearranges to form new carbon-carbon double bonds. Tetracycloheptane generates norbornadiene through this process.

[0052] The valence bond isomerization reaction between norbornene and tetracycloane is one of the most promising systems in solar energy conversion and storage research, storing radiant energy through changes in chemical bonds. This system utilizes the readily available and inexpensive raw material, norbornene, and produces tetracycloane with good stability. The valence bond isomerization between the two produces no side reactions, exhibits high quantum yield, and has a large energy storage capacity, making it a suitable circulating system for forming a mobile phase. Furthermore, it is easily controlled. Many photosensitizers can induce the valence bond isomerization reaction of norbornene to generate tetracycloane, and many catalysts can effectively promote the retro-isomerization of tetracycloane, reverting to norbornene and releasing heat energy.

[0053] The above description is provided as an enabling teaching of the application and is not intended to limit its scope in any way. Any modification of the application in keeping with the spirit thereof that is apparent to those skilled in the art is to be considered within the scope of the application as defined by the appended claims.

Claims

1. A method for the photocatalytic production of tetrahydrogenated norcarane based on reactive distillation, characterized in that, The method comprises the following steps: The raw material norbornadiene, the side-draw stream of the rectifying column, and the stream divided from the circulating stream drawn from the bottom of the solvent recovery and product purification column are respectively introduced into N photo-reactors from three paths, and the outlet streams of the N photo-reactors are all introduced into the rectifying column; Before the side-draw stream is introduced into the N photo-reactors, it is all subjected to heat exchange in heat exchangers, and before the outlet streams of the N photo-reactors are introduced into the rectifying column, they are all subjected to heat exchange in heat exchangers; In the N photo-reactors, isomerization reaction occurs, the raw material norbornadiene molecules absorb ultraviolet light energy to form excited-state norbornadiene molecules, the excited-state norbornadiene molecules undergo intramolecular rearrangement, and the structure of tetrahydro-4-methylphenylalanine is gradually established; N is a positive integer; The self-top reflux stream of the rectifying column is introduced into the column in the form of total reflux, the crude product drawn from the bottom of the rectifying column is introduced into the solvent recovery and product purification column after heat exchange in a heat exchanger, is separated and purified in the solvent recovery and product purification column, and purified tetrahydro-4-methylphenylalanine is obtained, and the circulating stream drawn from the bottom of the solvent recovery and product purification column is recovered, subjected to heat exchange in another heat exchanger, and then divided into N streams which are respectively introduced into the N photo-reactors.

2. The method of claim 1, wherein, The feeding and discharging of the N photo-reactors are continuous processes; and a photosensitizer is added to the side-draw stream.

3. A system for photocatalytic production of tetralin based on reactive distillation, characterized by, The system is used to implement the photo-catalytic production method of tetrahydro-4-methylphenylalanine based on reactive distillation according to claim 1 or 2, and comprises a back-pack reactive distillation device, a solvent recovery and product purification column, and a plurality of heat exchangers; wherein: The back-pack reactive distillation device comprises a rectifying column and N photo-reactors connected to the rectifying column through side-draw streams, and the N photo-reactors are coupled to the rectifying column; the feeding of the photo-reactors comprises the raw material norbornadiene, the side-draw stream of the rectifying column, and the stream divided from the circulating stream drawn from the bottom of the solvent recovery and product purification column; N is a positive integer; and the side-draw stream is subjected to heat exchange in a heat exchanger before being introduced into the N photo-reactors; The N photo-reactors are used to convert the raw material norbornadiene into tetrahydro-4-methylphenylalanine through photo-catalysis, and the outlet streams of the N photo-reactors are all subjected to heat exchange in heat exchangers before being introduced into the rectifying column; The self-top reflux stream of the rectifying column is introduced into the column in the form of total reflux; The crude product drawn from the bottom of the rectifying column is introduced into the solvent recovery and product purification column after heat exchange in a heat exchanger; The solvent recovery and product purification column is used to separate and purify tetrahydro-4-methylphenylalanine and recover solvent, the separated and purified tetrahydro-4-methylphenylalanine is drawn from the top of the solvent recovery and product purification column to obtain purified tetrahydro-4-methylphenylalanine, and the circulating stream drawn from the bottom of the solvent recovery and product purification column is subjected to heat exchange in another heat exchanger and then divided into N streams which are respectively introduced into the N photo-reactors.

4. The system for photocatalytic production of tetrahydrocorannulene based on reactive distillation according to claim 3, characterized in that, The N photo-reactors are one of a tubular reactor, a tank reactor, a fixed bed, a fluidized bed, a trickle bed, and a capillary continuous flow reactor; and the N photo-reactors are connected in series or in parallel.

5. The system for photocatalytic production of tetrahydrocorannulene based on reactive distillation according to claim 3, characterized in that, The feeding and discharging of the N photo-reactors are continuous processes; and a non-homogeneous catalyst, a homogeneous catalyst, or no chemical catalyst is used in the N photo-reactors.

6. The system for photocatalytic production of tetrahydrocorannulene based on reactive distillation according to claim 3, characterized in that, The solvent recovery and product purification column is a separate apparatus or is coupled to the backpack reaction rectification apparatus. The solvent recovery and product purification column is a separate apparatus or is coupled to the backpack reaction rectification apparatus.

Images