Gas-liquid bubbling bed reactor, reaction system, and method for synthesizing carbonate esters

Abstract

The present invention discloses a gas-liquid bubbling bed reactor comprising a liquid distributor, a gas distributor located below the liquid distributor, a catalyst bed layer, a catalyst support plate, and an optional blocking screen. The reactor is provided with a gas outlet at the top, a feed port connected to the liquid distributor, a gas inlet connected to the gas distributor, and an outlet at the bottom. The present invention also provides a reaction system including a gas-liquid bubbling bed reactor as a main reactor and a side reactor. The system and method of the present invention specifically address problems in carbonate synthesis, such as low conversion, gas binding in the circulating pump, unstable operation, and low yield of electronic-grade products. The present invention is applicable to related industrial production.

Description

Detailed Description of the Invention

[0001] [Technical Field] The present invention relates to a gas-liquid bubbling bed reactor, more specifically a gas-liquid bubbling bed reactor for synthesizing carbonates; a reaction system; and a method for synthesizing carbonates using said reaction system, more specifically a method for synthesizing carbonates using alkylene oxide and carbon dioxide.

[0002] [Background technology] Carbonates are compounds in which some or all of the hydrogen atoms of the two hydroxyl groups (-OH) in a carbonic acid molecule have been replaced with alkyl groups. In the presence of a strong acid, carbonates decompose into carbon dioxide and alcohol.

[0003] Carbonates can be used in many ways: dimethyl carbonate can be used as a methylating agent; dimethyl pyrocarbonate can be used as a preservative; polycarbonate can be used as a polymeric material; ethylene carbonate and propylene carbonate can be used as polar solvents.

[0004] Taking carbonate as an example, there are three main synthetic methods in the prior art: the phosgene method, the transesterification method, and the addition method of alkylene oxide and carbon dioxide.

[0005] The phosgene process refers to the preparation of carbonates by reacting alcohols or phenols with phosgene. This process was commonly used to prepare carbonates in the past. However, because phosgene is highly toxic and causes serious environmental pollution, this process has been banned in developed countries. Therefore, this process is gradually being replaced by other less polluting methods.

[0006] The transesterification method refers to the preparation of carbonates by the transesterification of dialkyl carbonates and alkanediols. The key to this method is to find a suitable catalyst. However, the raw materials used in this method are relatively expensive, and the catalyst efficiency is relatively low.

[0007] The alkylene oxide and carbon dioxide addition process refers to a process in which alkylene oxide and carbon dioxide react with each other in the presence of a catalyst to produce carbonate. This reaction is exothermic and volume-reducing, and low temperature and high pressure are preferred for this reaction. The reaction system mainly includes homogeneous catalyst systems and heterogeneous catalyst systems. The selection of the catalyst is also key to the smooth progress of this reaction.

[0008] Currently, the energy crisis is becoming more serious, and the rational use of carbon dioxide is essential for the sustainable development of energy conservation. Carbon dioxide is used as a raw material for carbonate synthesis, which has good practical significance. There are two systems for preparing carbonate by reacting alkylene oxide with carbon dioxide: homogeneous and heterogeneous. The development of the homogeneous system is somewhat limited due to problems such as difficult product separation and the large amount of catalyst required. The heterogeneous method has relatively good industrial value because it is advantageous for separating the reaction product from the catalyst, and the catalyst can be easily regenerated and recycled multiple times.

[0009] CN106588862A discloses a process and system for purifying ethylene carbonate, employing a continuous rectification column and a batch rectification column, respectively. First, a crude product is passed through the continuous rectification column, with light components removed overhead and heavy components removed at the bottom. The purified product is then extracted through a side line and passed through a batch rectification column, with light components removed overhead and ethylene carbonate product extracted through a side line. During production operation of the technical process, ethylene carbonate in the removed light components is not recovered, resulting in a low product yield.

[0010] CN102675276A discloses an automatically controlled, stable, and continuous production process for ethylene carbonate. The control center collects data measured by sensors, including flow speed, flow rate, concentration, pressure, temperature, etc., through a data feedback circuit, then integrates the data and transmits it to an effector through a command output circuit to control the on-off, flow speed, and flow rate of a high-pressure metering pump, thereby achieving the goal of balanced, continuous production. However, this production process uses a homogeneous catalyst, which has significant limitations.

[0011] When producing carbonate using existing gas-liquid reactors, problems such as insufficient reaction of raw materials and low conversion efficiency still remain. In addition, carbon dioxide must be introduced into the reactor as a reactant, and the introduction of carbon dioxide can result in gas binding of the pump. Furthermore, the introduction of gas in a gas-liquid reaction causes large fluctuations in the liquid level, making it difficult to accurately determine the actual liquid level in the reactor using a conventional level gauge. This can easily lead to a "full tank" state, which can adversely affect the reaction operation. All of these factors affect the conversion rate of the reactants, and further affect the yield, purity, etc. of the final synthesized carbonate.

[0012] Summary of the Invention The inventors of the present invention have conducted extensive research and found that the above technical problems in the prior art can be solved by using the gas-liquid bubbling bed reactor of the present invention, and that the above technical problems in the prior art can be solved by using the reaction system of the present invention. Furthermore, the inventors of the present invention have also found a process for producing carbonate.

[0013] Specifically, the present invention provides the following technical solutions:

[0014] According to one aspect of the present invention, there is provided a gas-liquid bubbling bed reactor comprising a liquid distributor, a gas distributor located below the liquid distributor, a catalyst bed layer, a catalyst support plate, and an optional blocking screen, wherein the gas outlet is provided at the top of the reactor, the reactor is provided with a feed port connected to the liquid distributor, a gas inlet connected to the gas distributor, and a discharge port at the bottom, and preferably the catalyst bed is loaded with a heterogeneous catalyst.

[0015] According to one aspect of the present invention, there is provided a reaction system comprising the gas-liquid bubbling bed reactor of the present invention and a side reactor, wherein the inlet of the side reactor is connected to the outlet of the gas-liquid bubbling bed reactor, the side reactor is preferably a fixed bed reactor, and the gas space of the gas-liquid bubbling bed reactor is preferably connected to the gas space of the side reactor.

[0016] According to one aspect of the present invention, there is provided a method for synthesizing carbonate using the gas-liquid bubbling bed reactor according to the present invention described above, comprising the steps of mixing an alkylene oxide and a first carbon dioxide gas with a recycle stream from the reactor and sending the resulting mixture to a liquid distributor of the reactor via the feed port; sending a second carbon dioxide gas to the gas distributor of the reactor via a gas inlet; and mixing the upwardly moving second carbon dioxide gas with a downwardly moving stream to react in the presence of a catalyst to obtain a carbonate-containing liquid stream, wherein the catalyst is preferably heterogeneous.

[0017] According to one aspect of the present invention, there is provided a method for synthesizing the above-mentioned carbonate according to the present invention, comprising the steps of: cooling the carbonate-containing liquid stream in a cooler and then dividing it into a first stream and a second stream; the first stream as a recycle stream passes through a circulation pump, a mixer, and a dissolver and continuously enters the feed port of the gas-liquid bubbling bed reactor; introducing an alkylene oxide into the mixer and mixing it with the recycle stream; introducing a first carbon dioxide gas into the dissolver and mixing it with the recycle stream; and introducing a second carbon dioxide gas into the gas distributor of the gas-liquid bubbling bed reactor; mixing the upwardly moving second carbon dioxide gas with the downwardly moving liquid phase stream and reacting them in the presence of a catalyst to obtain a carbonate-containing liquid stream, preferably a heterogeneous catalyst; and introducing the second stream into the side reactor to continue the reaction and produce a carbonate.

[0018] [Effects of the Invention] According to the gas-liquid bubbling bed reactor and the method for synthesizing carbonate using the gas-liquid bubbling bed reactor of the present invention, carbon dioxide gas can be sufficiently dissolved in the recycle stream, thereby shortening or eliminating the time for carbon dioxide dissolution in the reactor, improving the conversion efficiency of carbon dioxide and alkylene oxide, shortening the reaction time, and improving the yield of carbonate. As a result, carbonate can be produced efficiently and in a high yield, and a high-purity carbonate product can be obtained. Furthermore, the gas-liquid bubbling bed reactor of the present invention can also avoid gas binding to the circulation pump caused by carbon dioxide gas.

[0019] The reaction system according to the present invention and the method for synthesizing carbonate using this reaction system can effectively prevent gas binding of carbon dioxide to the circulation pump while maintaining the excellent effects of the gas-liquid reactor according to the present invention described above, suppress the impact on productivity due to overflow in the bubbling bed reactor, and improve the yield of carbonate. Furthermore, the reaction system according to the present invention can solve the problem of backmixing during the reaction process in the gas-liquid bubbling bed, thereby enabling sufficient conversion of alkylene oxide materials and increasing the yield of carbonate.

[0020] Furthermore, the reaction system according to the present invention and the method for synthesizing carbonate using this reaction system allow the crude carbonate product to be continuously rectified in two columns (a light-removal column and a heavy-removal column). Most of the electronic-grade product is obtained from the top and side of the heavy-removal column, and the light and heavy components are further purified in the batch column. This not only improves the yield of carbonate, but also improves the purity of various grades of carbonate.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a system for synthesizing carbonates according to the present invention.

[0022] FIG. 2 is a schematic diagram of a separation unit for the synthesis of carbonates according to the present invention.

[0023] The parts in the figure are as follows:

[0024] [Table 1]

[0025] Detailed Description of the Invention Reference will now be made in detail to the embodiments of the present invention, but it should be understood that the scope of the present invention is not limited by these embodiments, but rather is defined by the appended claims.

[0026] When used herein to introduce a material, substance, process, step, apparatus, element, or the like using expressions such as "known to those skilled in the art," "prior art," or synonyms thereof, the subject matter introduced by such prefixes is intended to include those that are conventionally applied in the art at the time of filing of this application, as well as those that may not be as commonly applied today but are known in the art as being suitable for similar uses.

[0027] In the context of this specification, unless explicitly described, any undescribed elements or matters can be directly applied to those known in the art without any modifications. Furthermore, any embodiment described in this specification can be freely combined with one or more other embodiments described in this specification, and the resulting technical solutions or technical ideas are considered to be part of the original disclosure or original record of the present invention, and should not be considered as new content not disclosed or anticipated in this specification, unless a person skilled in the art believes that the combination is unreasonable.

[0028] The present invention provides a gas-liquid bubbling bed reactor comprising a liquid distributor, a gas distributor located below the liquid distributor, a catalyst bed layer, a catalyst support plate, and an optional blocking screen. In the gas-liquid bubbling bed reactor, a gas outlet is provided at the top of the reactor, a feed port connected to the liquid distributor, a gas inlet connected to the gas distributor, and a discharge port is provided at the bottom, and the catalyst bed is preferably loaded with a heterogeneous catalyst.

[0029] In the present invention, the gas-liquid reaction is not limited to the case where the starting materials are required to be in the gas phase and the liquid phase. The gas-liquid reaction means that the reaction is carried out in a gas-liquid mode, for example, a reaction in which one of the reactants is in the gas phase and the other of the reactants is in the liquid phase. The gas-liquid reactor according to the present invention is preferably used for the preparation of carbonates, particularly preferably for the preparation of carbonates by the addition method of alkylene oxide and carbon dioxide in the presence of a heterogeneous catalyst.

[0030] The gas-liquid bubbling bed reactor of the present invention is provided with a catalyst bed layer, which acts as a catalyst in the catalyst bed in the bubbling reaction to enhance contact between the gas phase, liquid phase, and solid phase. The reaction is carried out so that the internal temperature of the catalyst bed layer is uniform, thereby improving the conversion rate of alkylene oxide.

[0031] More specifically, in the gas-liquid bubbling bed reactor of the present invention, a gas outlet is provided at the top, a feed port and a gas inlet are provided in the reactor, and a discharge port is provided at the bottom of the reactor, with the gas inlet being located lower than the feed port.

[0032] In particular, the gas outlet at the top of the reactor is used for discharging gaseous substances in the reaction stream. Here, the top of the reactor does not mean that the gas outlet must be located on the upper wall of the reactor, but may mean that it may be located at a position on the side wall close to the top of the reactor (as long as it is located above the reaction liquid level), for example, at a position on the side wall of the reactor as close to the top of the reactor as possible.

[0033] The feed ports are used to supply liquid streams (e.g., reactants and reaction recycle streams) and may be located on the sidewall of the reactor or at the top of the reactor, preferably on the sidewall of the reactor.

[0034] The gas inlet is used to supply a gas stream (e.g., carbon dioxide). By locating the gas inlet below the feed inlet, sufficient mixing of the gas-liquid stream can be achieved after the gas stream enters the reactor. The gas inlet can be located on the side wall of the reactor or at the bottom of the reactor. The gas inlet can also be preferably located on the side wall of the reactor below the feed inlet.

[0035] The outlet at the bottom of the reactor is used to discharge the reaction product stream and the recycle stream. Here, the bottom of the reactor does not mean that the outlet must be located at the bottom wall of the reactor, but may mean that the outlet may be located at a position on the side wall near the bottom of the reactor (as long as it is located below the reaction liquid level), for example, at a position on the side wall of the reactor as close to the bottom of the reactor as possible.

[0036] In the gas-liquid bubbling bed reactor of the present invention, a liquid distributor connected to the feed port and a gas distributor connected to the gas inlet are arranged below the liquid distributor. The purpose of arranging both the gas distributor and the liquid distributor is to achieve sufficient contact between the gas stream and the liquid stream.

[0037] In one embodiment of the present invention, the liquid distributor is located at the top of the reactor and can be exposed above the reaction liquid level during the reaction or can be submerged and hidden below the reaction liquid level.

[0038] In one embodiment of the present invention, the gas distributor is located in the center or bottom of the reactor, and when the reaction is carried out, the gas distributor is submerged and hidden below the reaction liquid level.

[0039] In the gas-liquid bubbling bed reactor according to the present invention, a catalyst bed layer is also arranged, and the catalyst bed layer is used to support a heterogeneous catalyst for the reaction. In the reaction of alkylene oxide with carbon dioxide, a homogeneous catalyst or a heterogeneous catalyst can be used, but the use of a heterogeneous catalyst is preferred.

[0040] In one embodiment of the present invention, a catalyst support plate is disposed in the reactor to support the catalyst bed, and the catalyst support plate can effectively prevent carbon dioxide from entering the circulation pump, thereby avoiding gas binding of the circulation pump.

[0041] The catalyst support plates are preferably made from stainless steel, may be in the form of a grid or wire mesh, and may be arranged in a planar or non-planar configuration.

[0042] In one embodiment of the present invention, an isolation screen may be placed in the reactor, which is located at the top of the reactor higher than the catalyst bed to prevent the solid catalyst entrained during gas release from blocking the pipeline.

[0043] In one embodiment of the present invention, the reactor may further include a liquid inlet. The liquid inlet is used to reflux the reactant stream obtained by condensing the gaseous material discharged from the gas outlet. The liquid inlet may be located at the top of the reactor or at the side wall of the reactor. The liquid inlet is preferably located on the side wall of the reactor.

[0044] In one embodiment of the present invention, the gas distributor is preferably tubular. The use of the tubular distributor ensures a passage for gas upflow and liquid downflow, reducing the pressure drop across the bed.

[0045] In one embodiment of the present invention, a stirring device may be provided in the gas-liquid bubbling bed reactor. The stirring device may be any stirring device known in the art, as long as it does not impair the effects of the present invention.

[0046] In one embodiment of the present invention, the gas-liquid bubbling bed reactor further comprises: a circulation pump located between the outlet and the supply port of the reactor; a mixer located between the circulation pump and the supply port of the reactor and having a reactant inlet; and a dissolver located between the mixer and the supply port of the reactor and having a reactant gas inlet, wherein the circulation pump, the mixer, and the dissolver are continuously connected by a pipeline.

[0047] In one embodiment of the present invention, the gas-liquid bubbling bed reactor further comprises a cooler located on the pipeline for the recycle flow from the outlet to the feed inlet of the reactor. The cooler is used to cool the reaction system in the reactor. The cooler is preferably located on the pipeline between the outlet of the reactor and the circulation pump.

[0048] In one embodiment of the present invention, the circulation pump is provided with an inlet and an outlet, the inlet is connected to the outlet of the reactor, and the outlet is connected to the inlet of the mixer. In one embodiment of the present invention, when a cooler is located between the outlet of the reactor and the circulation pump, the cooler is provided with an inlet and an outlet, the inlet is connected to the outlet of the reactor, and the outlet is connected to the inlet of the circulation pump.

[0049] In one embodiment of the present invention, the mixer comprises a feed port, a discharge port, and a reactant inlet, the feed port is connected to the discharge port of the circulation pump, the discharge port is connected to the feed port of the dissolver, and the reactant inlet is used to receive the reactant raw materials.

[0050] In one embodiment of the present invention, the dissolver comprises a feed port, a discharge port, and a reactant gas inlet, the feed port is connected to the discharge port of the mixer, the discharge port is connected to the feed port of the reactor, and the reactant gas inlet is used to receive the reactant gas.

[0051] In one embodiment of the present invention, chemical engineering loading methods known in the art can be used in dissolvers and mixers to increase turbulent mixing.

[0052] In the present invention, the dissolver is installed downstream of the circulation pump, which can prevent gas binding of the circulation pump by gas and avoid unstable operation problems caused by gas binding during the reaction process. Furthermore, by placing a cooler before the circulation pump, gas binding of the circulation pump can be further prevented.

[0053] When the gas-liquid bubbling bed reactor according to the present invention is used to synthesize carbonate from carbon dioxide and alkylene oxide, the alkylene oxide is introduced at the inlet of the mixer and a portion of the carbon dioxide is introduced at the inlet of the dissolver.

[0054] When synthesizing carbonate from carbon dioxide and alkylene oxide, the reaction between carbon dioxide and alkylene oxide is a dissolution reaction, and the dissolution process is the controlling step for the entire reaction. When a bubbling reactor is simply used, the reaction time is relatively long. Furthermore, carbon dioxide dissolves in both carbonate and alkylene oxide, and its solubility in carbonate can reach a concentration of 10 to 20% by mass. Furthermore, when preparing carbonate using the gas-liquid bubbling bed reactor of the present invention, a portion of the carbon dioxide gas is sufficiently dissolved in the recycle stream by a dissolver before the carbon dioxide enters the reactor. As a result, the carbon dioxide content in the recycle stream is increased, thereby reducing or eliminating the dissolution time of carbon dioxide in the reactor and improving the reaction conversion rate, which can reach 99% or more. In addition, in the present invention, a dissolver is installed downstream of the mixer. This can increase the dissolution of carbon dioxide in the solute (alkylene oxide), thereby increasing the carbon dioxide concentration in the recycle stream entering the reactor, thereby further increasing the reaction conversion rate.

[0055] According to one embodiment of the present invention, the gas-liquid bubbling bed reactor further comprises a condenser connected to the gas outlet of the reactor, which is used to condense the gaseous material from the reactor and reflux the liquid material obtained by condensing through the liquid inlet of the reactor into the bubbling bed reactor.

[0056] In one embodiment of the present invention, the condenser comprises a gas inlet, a gas outlet, and a liquid outlet, the gas inlet being connected to the gas outlet of the reactor, and the liquid outlet being connected to the liquid inlet of the reactor.

[0057] According to another aspect of the present invention, there is provided a method for synthesizing carbonates using the gas-liquid bubbling bed reactor according to the present invention, the method comprising the steps of: mixing the alkylene oxide and the first carbon dioxide gas with a recycle stream from the reactor and passing the resulting mixture through the feed port to a liquid distributor of the reactor; delivering a second carbon dioxide gas to a gas distributor of said reactor via a gas inlet; mixing the upwardly moving second carbon dioxide gas with the downwardly moving stream for reaction in the presence of a catalyst to obtain a carbonate-containing liquid stream.

[0058] In one embodiment of the present invention, the recycle stream flowing out of the outlet of the reactor flows through a cooler and a circulation pump, then in a mixer, it is mixed with alkylene oxide introduced from an inlet of the mixer, then in a dissolver, it is mixed with the first carbon dioxide introduced from an inlet of the dissolver, and then it enters the liquid distributor of the reactor through a feed port.

[0059] In one embodiment of the present invention, the gaseous material from the reactor is passed into a condenser for gas-liquid separation, and the resulting liquid is returned to the gas-liquid bubbling bed reactor via a liquid inlet.

[0060] In one embodiment of the present invention, the distribution ratio between the first carbon dioxide gas and the second carbon dioxide gas is (1 to 50):(50 to 99), preferably (10 to 50):(50 to 90), based on the total mass of carbon dioxide introduced into the reactor.

[0061] In one embodiment of the present invention, a solvent may or may not be used in the initial preparation of the carbonate. Various carbonates can be used as the solvent, and preferably the solvent is the same as the carbonate to be prepared. After the start of the preparation, the prepared carbonate itself can be used as the reaction solvent. During the preparation process, new solvent can be added separately, or the prepared carbonate can be used directly as the reaction solvent without adding new solvent.

[0062] In the present invention, the recycle stream refers to a stream from a bubbling bed reactor containing a reaction solvent, reaction raw materials, reaction intermediates, reaction products (which may be a reaction solvent), etc. In the present invention, when the reactant stream is circulated outside the main reactor, the composition of the recycle stream changes depending on the temperature change and the introduction of alkylene oxide and carbon dioxide as reactants. The composition of the recycle stream is not intended to limit the present invention.

[0063] In the present invention, the alkylene oxide may be, but is not limited to, ethylene oxide, 1,2-propylene oxide, 1,3-propylene oxide, butylene oxide, or the like.

[0064] In one embodiment of the present invention, in the method for synthesizing carbonate described above, the catalyst used in the bubbling bed reactor is heterogeneous, and the ratio of the density of the catalyst to the density of the reactant (a liquid mixture of alkylene oxide and carbonate) is 0.3 to 2, preferably 0.5 to 1.5. As the type of catalyst, a conventionally used catalyst such as a resin-based catalyst can be used.

[0065] The density of the catalyst is close to that of the reactants, so that the catalyst is in suspension during gas-liquid mixing and reaction. This is beneficial to the gas distribution within the reactor. If the catalyst density is too high, the gas distributor will be enveloped by the catalyst, and the catalytic reaction will be less effective.

[0066] The catalyst most commonly used in the industry for synthesizing carbonate from alkylene oxide and carbon dioxide is a homogeneous catalyst. Therefore, the catalyst is present in both the recycle stream and the reaction product. Therefore, after the reaction, the catalyst must be separated and recycled, which increases the process complexity and operational difficulty. The present invention employs a heterogeneous catalyst and directly separates the catalyst from the reactants and reaction product in the reactor. This avoids the need for additional equipment and the energy consumption required for subsequent separation of the catalyst. Furthermore, by placing a catalyst bed layer in the reactor of the present invention, the contact between the three phases of the catalyst—gas, liquid, and solid—in the catalyst bed can be enhanced. The reaction is carried out so that the internal temperature of the catalyst bed layer is uniform, thereby improving the conversion rate of alkylene oxide.

[0067] In one embodiment of the present invention, the bubbling bed reactor is regulated and controlled by a cooler through the removal of external circulating heat. The temperature of the catalyst bed is controlled by the circulation rate of the circulation pump. The recirculation rate, on a mass basis, is 10 to 100 times the alkylene oxide feed rate.

[0068] The gas from the top of the reactor is accompanied by a small amount of alkylene oxide and carbonate. Carbonate easily crystallizes and precipitates at temperatures below 40°C, causing blockage of pipelines and / or valves. Therefore, in the present invention, the gas from the top of the bubbling bed reactor is condensed by a condenser and then discharged from the gas absorption device through a gas pressure regulator. The condensation temperature is 40°C or higher.

[0069] In one embodiment of the present invention, the molar ratio of alkylene oxide to carbon dioxide in the reaction is within a range commonly used in the art, and for example, the molar ratio of carbon dioxide to alkylene oxide may be 1:1 to 10:1, and preferably 1:1 to 2:1.

[0070] In one embodiment of the present invention, the temperature, pressure, etc. for reacting the alkylene oxide with carbon dioxide may be those commonly used in the art. For example, the reaction pressure may be 1 to 10 MPa (gauge pressure), and the reaction temperature may be 80 to 300°C.

[0071] In another aspect of the present invention, there is provided a reaction system comprising the above-described gas-liquid bubbling bed reactor according to the present invention (also referred to as a main reactor in the present invention) and a side reactor, wherein the feed inlet of the side reactor is connected to the outlet of the gas-liquid bubbling bed reactor.

[0072] In one embodiment of the present invention, the side reactor may be a reactor commonly selected in the art, as long as it is capable of completing the reaction of the reactants (e.g., carbon dioxide and alkylene oxide) in the reaction stream. Since gaseous reactants do not need to be introduced into the side reactor, the side reactor does not need to have a reaction gas inlet. In one embodiment of the present invention, the side reactor is preferably a fixed-bed reactor.

[0073] In one embodiment of the present invention, there is no need to introduce fresh (additional) reactants into the side reactor.

[0074] In one embodiment of the present invention, the supply port of the secondary reactor is connected to a position between the outlet of the main reactor and the circulation pump via a connecting pipeline. In one embodiment of the present invention, if the main reactor is equipped with a cooler, the supply port of the secondary reactor is connected to a position between the cooler of the main reactor and the circulation pump via a connecting pipeline.

[0075] In one embodiment of the present invention, the side reactor has a gas outlet at its top, a discharge port at its bottom, and a feed port connected to the discharge port of the main reactor. Here, the term "gas discharge port at the top of the side reactor" does not mean that the gas discharge port must be located on the top wall of the side reactor, but rather means that it may be located on a position on the side wall close to the top of the side reactor (as long as it is located above the reaction liquid level), for example, as close to the top of the side reactor as possible. The term "discharge port at the bottom of the side reactor" does not mean that the discharge port must be located on the bottom wall of the side reactor, but rather means that it may be located on a position on the side wall close to the bottom of the side reactor (as long as it is located below the reaction liquid level), for example, as close to the bottom of the side reactor as possible. The feed port of the side reactor may be located on the side wall or the top of the reactor, preferably on the side wall of the reactor.

[0076] Due to countercurrent contact between gas and liquid in the main reactor, there is a backmixing step during the reaction process, which results in incomplete conversion of the stream (e.g., a stream containing alkylene oxide). Therefore, the present invention does not require the introduction of new (additional) reactants (e.g., carbon dioxide, alkylene oxide) into the side reactor. However, the present invention allows saturated dissolved reactants (e.g., carbon dioxide, alkylene oxide) in the reaction product from the main reactor to continue reacting in the side reactor in a manner similar to plug flow. This can further improve the conversion of the reactants.

[0077] On the other hand, when synthesizing carbonate from carbon dioxide and alkylene oxide using the reaction system of the present invention, after carbon dioxide is introduced into the reactor, the liquid level fluctuates significantly due to the influence of concentration differences. It is difficult to accurately determine the actual liquid level in the reactor using a traditional level gauge, and therefore, it can easily reach a "full" state. Therefore, in a preferred embodiment of the present invention, the outlet of the main reactor is connected to the inlet of the secondary reactor via a pipeline. This allows the main and secondary reactors to be connected in series, communicating the gas phase spaces of the two reactors, and allowing the liquid from the main reactor to flow into the secondary reactor in an overflow manner. At this time, the position of the inlet of the secondary reactor is not lower than the packed height of the catalyst bed layer in the main reactor or higher than the height of the liquid distributor of the main reactor.

[0078] In one embodiment of the present invention, the main reactor and the secondary reactor are connected in series, their gas phase spaces are connected, and the liquid from the main reactor enters the secondary reactor in an overflow manner. In one embodiment of the present invention, the position of the feed port of the secondary reactor is not lower than the packed height of the catalyst bed layer of the main reactor and not higher than the height of the liquid distributor of the main reactor.

[0079] In one embodiment of the present invention, the gas outlet of the secondary reactor is connected to the above-mentioned condenser. More specifically, the condenser is used to condense the gaseous material from the secondary reactor and reflux the condensed liquid material into the primary reactor through the liquid inlet of the primary reactor.

[0080] In one embodiment of the present invention, the gas inlet of the condenser is connected to the gas outlet of the secondary reactor. The gas from the top of the secondary reactor is accompanied by a small amount of alkylene oxide and carbonate. Carbonate easily crystallizes and precipitates at temperatures below 40°C, causing blockage of pipelines and valves. In this invention, the gas from the top of the secondary reactor is condensed by the condenser and then discharged from the gas absorption device via a gas pressure regulator. The condensation temperature is 40°C or higher.

[0081] According to one embodiment of the present invention, the reaction system further comprises a separation unit connected to the outlet of the side reactor.

[0082] In one embodiment of the present invention, the separation unit comprises: a flash unit having a feed inlet connected to the outlet of the side reactor; a lights removal column having a feed inlet connected to the outlet of the flash unit; a heavies removal column having a feed inlet connected to the outlet of the lights removal column; a batch column whose feed inlets are connected to the liquid outlets of the lights removal column and the heavies removal column;

[0083] In one embodiment of the present invention, the flash device is preferably selected from a flash drum, a flash column, and a film evaporator, and may be a conventional flash device in the art that operates continuously at atmospheric pressure or negative pressure. The flash device is preferably heated by a coil pipe or a jacket, and the heating temperature is 110 to 160°C.

[0084] In one embodiment of the present invention, the light removal column, the heavy removal column, and the batch column can all be conventional light removal columns, heavy removal columns, and batch columns in the art.

[0085] In one embodiment of the present invention, the light-end removal column can be a conventional light-end removal column in the art. The operating pressure of the light-end removal column is 0 to 5 KPa, and the column bottom temperature is less than 160°C, preferably less than 150°C. The light-end removal column is operated continuously.

[0086] In one embodiment of the present invention, the heavies removal column can be a conventional heavies removal column in the art. The operating pressure of the heavies removal column is 0 to 5 KPa, and the column bottom temperature is less than 160°C, preferably less than 150°C. The heavies removal column is operated continuously. In one embodiment of the present invention, the product can be removed from a side line of the heavies removal column as needed.

[0087] In one embodiment of the present invention, the light components obtained from the light removal column and the heavy removal column, and the column bottom liquid of the heavy removal column, respectively, enter a batch column for further separation. The light components are obtained from the top of the column, and the heavy components are obtained from the bottom of the column. The batch column can be a conventional batch column in the art, and its operating pressure is 0 to 5 KPa, and the column bottom temperature is less than 160°C, preferably less than 150°C. The batch column is operated in a batch mode.

[0088] The structural configuration and packing material selection of the separation unit are designed based on the premise of minimizing the pressure drop in the separation system and the temperature at the bottom of the column.

[0089] On the other hand, the present invention provides a method for synthesizing carbonates using the reaction system according to the present invention described above, comprising the following steps: cooling the carbonate-containing liquid stream in a cooler and then dividing the stream into a first stream and a second stream; said first stream as a recycle stream passes through a circulation pump, a mixer, and a dissolver and continuously enters said feed inlet of said gas-liquid bubbling bed reactor (also known in the present invention as a primary reactor); adding alkylene oxide to said mixer and mixing with said recycle stream; adding a first carbon dioxide gas to the dissolver and mixing with the recycle stream; a second carbon dioxide gas entering the gas distributor of the gas-liquid bubbling bed reactor; mixing the upwardly moving second carbon dioxide gas with the downwardly moving liquid phase stream and reacting them in the presence of a catalyst to obtain a carbonate-containing liquid stream; and introducing the second stream into the side reactor to continue the reaction and produce carbonate.

[0090] In one embodiment of the present invention, the method for synthesizing carbonate further comprises the step of introducing the gaseous materials from the main reactor and the side reactor into a condenser to perform gas-liquid separation, and returning the resulting liquid to the main reactor via a liquid inlet.

[0091] In one embodiment of the present invention, fresh (additional) carbon dioxide and alkylene oxide as feedstocks are not passed to the side reactor, and heat is preferably removed by a jacket and / or coil pipe, and the reaction product of the side reactor is a catalyst-free crude carbonate product.

[0092] In the present invention, in the method for synthesizing carbonate using the reaction system according to the present invention, the distribution ratio between the first carbon dioxide gas and the second carbon dioxide gas is (1-50):(50-99), preferably (10-50):(50-90), based on the total mass of carbon dioxide introduced into the main reactor.

[0093] In the method for synthesizing carbonate using the reaction system according to the present invention described above, the recycle stream refers to a stream from the main reactor containing the reaction solvent, reaction raw materials, reaction intermediates, reaction product (which may be the reaction solvent), etc. In the present invention, when the reactant stream is circulated outside the main reactor, the composition of the recycle stream changes depending on the temperature change and the introduction of alkylene oxide and carbon dioxide as reactants. The composition of the recycle stream is not intended to limit the present invention.

[0094] In the method for synthesizing carbonate using the reaction system according to the present invention described above, the alkylene oxide may be ethylene oxide, 1,2-propylene oxide, 1,3-propylene oxide, butylene oxide, or the like, but is not limited to these.

[0095] In one embodiment of the present invention, in the method for synthesizing carbonate described above, the catalyst used in the main reactor is heterogeneous, and the ratio of the density of the catalyst to the density of the reactant (a liquid mixture of alkylene oxide and carbonate) is 0.3 to 2, preferably 0.5 to 1.5. As the type of catalyst, a conventionally used catalyst such as a resin-based catalyst can be used.

[0096] The density of the catalyst is close to that of the reactants, so that the catalyst is in suspension during gas-liquid mixing and reaction. This is beneficial to the gas distribution within the reactor. If the catalyst density is too high, the gas distributor will be enveloped by the catalyst, and the catalytic reaction will be less effective.

[0097] In one embodiment of the present invention, the method for synthesizing carbonate further comprises a step in which the crude carbonate product obtained from the side reactor enters a separation unit, the method comprising the steps of: treating said crude carbonate product in a flash unit to produce a liquid stream and a gas, said gas being discharged; feeding said liquid stream obtained from the flash unit into a lights removal column for processing to obtain a column overhead light component and a bottoms liquid; charging the bottoms from the lights removal column into a heavies removal column for processing to produce column overhead lights, electronic grade carbonate, high grade carbonate, and a mixture of carbonate and heavy components, or for processing to produce lights, electronic grade carbonate, and a mixture of carbonate and heavy components; and feeding the light components obtained from the light removal column and the heavy removal column, and the bottoms obtained from the heavy removal column, into a batch column to produce light components, high-grade carbonate, electronic-grade carbonate, and heavy components.

[0098] In one embodiment of the present invention, the flash device is preferably selected from a flash drum, a flash column, and a film evaporator, and may be a conventional flash device in the art that operates continuously at atmospheric pressure or negative pressure. The flash device is preferably heated by a coil pipe or a jacket, and the heating temperature is 110 to 160°C.

[0099] In one embodiment of the present invention, the light-end removal column can be a conventional light-end removal column used in the art. The operating pressure of the light-end removal column is 0 to 5 KPa, and the column bottom temperature is less than 160°C, preferably less than 150°C. The light-end removal column is operated continuously. The overhead light components of the light-end removal column include diols and their homologues.

[0100] In one embodiment of the present invention, the heavy-end removal column can be a conventional heavy-end removal column in the art. The operating pressure of the heavy-end removal column is 0 to 5 KPa, and the column bottom temperature is less than 160°C, preferably less than 150°C. The heavy-end removal column is operated continuously. The column top light components of the heavy-end removal column include diol and carbonate. Electronic-grade carbonate is recovered from a side line above the feed position, high-grade carbonate is recovered from a side line below the feed position, and heavy components are recovered from the column bottom, or a mixture of carbonate and heavy components is recovered directly from the column bottom.

[0101] In one embodiment of the present invention, the light components obtained from the light removal column and the heavy removal column, and the column bottom liquid from the heavy removal column, are each entered into a batch column for further separation. The light components, high-grade carbonate, and electronic-grade carbonate are obtained from the top of the column, and the heavy components are obtained from the bottom of the column. The batch column can be a conventional batch column in the art, and its operating pressure is 0 to 5 KPa, the column bottom temperature is less than 160°C, preferably less than 150°C, and it is operated in a batch mode.

[0102] The structural configuration and packing material selection of the separation unit are designed based on the premise of minimizing the pressure drop in the separation system and the temperature at the bottom of the column.

[0103] More specifically, the process flow of the system for synthesizing carbonates according to the present invention is described as follows: The feed alkylene oxide is metered in terms of flow rate and mixed with the recycle stream of the main reactor, then entering the liquid distributor of the main reactor; part of the feed carbon dioxide is dissolved in the recycle stream of the main reactor at a controlled flow rate, and another part is sent to the gas distributor of the main reactor at a controlled flow rate. The reaction heat of the main reactor is removed by external circulation cooling, and the reaction product is sent to the side reactor in an overflow manner to continue the reaction. The gas phase spaces of the main reactor and the side reactor are connected, the gas phase product is condensed by a condenser and discharged through gas phase pressure control, and the condensate is returned to the main reactor; the reaction product of the side reactor is sent to the next separation system. Here, the reaction product first passes through a flash tank, and the resulting non-condensable gas is sent for treatment. The resulting liquid phase is sent to a light-end removal column to obtain heavy components. The heavy components are sent to the heavies removal column from the bottom or through a side line of the lights removal column for further separation; a mixture of high-grade carbonate and heavy components is obtained from the bottom of the heavies removal column, or high-grade carbonate is obtained below the feed point of the heavy removal column and a mixture of carbonate and heavy components is obtained from the column bottom, and an electronic-grade carbonate product useful for power lithium batteries is obtained from a side line; the light components obtained from the lights removal column and the heavy removal column and the column bottoms obtained from the heavy removal column are sent to a batch column for further processing, and the column overhead non-condensable gas is sent for processing. Further products such as high-grade carbonate and electronic-grade carbonate can be obtained from the top of the column or by liquid cut-off from a side line.

[0104] The method of the present invention provides an electronic grade carbonate product with a yield of 70% or more, preferably 85% or more. The method of the present invention specifically solves problems in carbonate synthesis, such as low conversion, gas binding in the circulating pump, unstable operation, and low yield of electronic grade products. The present invention can be applied to related industrial production.

[0105] [Example] The present invention will be further described below through examples, but the present invention is not limited to these examples.

[0106] Example 1 100 kg / h of ethylene oxide was metered into the main reactor at a flow rate and mixed with the recycle stream from the main reactor. The flow rate of the raw carbon dioxide was controlled, with 5 kg / h dissolved in the recycle stream from the main reactor and 115 kg / h sent to the gas distributor of the main reactor. A tubular gas distributor was used. The pressure of the main reactor was 1.5 MPa, the temperature was 100°C, the circulation rate was 3000 kg / h, and the reactor temperature rise was 40°C. The reaction product was sent to the side reactor in an overflow manner to continue the reaction. The operating conditions of the side reactor were the same as those of the main reactor. The temperature rise was less than 10°C. The gas phase spaces of the main and side reactors were connected, and the gas phase product was condensed to 45°C using an external condenser. It was discharged via gas phase pressure control, and the condensate was refluxed to the main reactor. The EO conversion in the main reactor was above 85%.

[0107] The reaction product from the side reactor contained 99% ethylene carbonate, 0.5% ethylene glycol, 0.3% diethylene glycol, and 0.2% other homologues. The product was sent to the next separation system. First, the product was sent to a flash column. The flash column employed a packing material, the type of packing was BX500, and the packing height was 3 m. The flash column operated at atmospheric pressure and was heated with steam. The column bottom temperature was controlled at 160 °C. After flash separation, the resulting non-condensable gas was sent for treatment, and the resulting liquid phase was sent to the light-end removal column. The operating pressure of the light-end removal column was controlled at 5 kPa, and the column bottom temperature was controlled at 160 °C. The column bottom liquid from the light-end removal column was sent to the heavy-end removal column for further separation. The operating pressure of the heavy-end removal column was controlled at 5 kPa, and the column bottom temperature was controlled at 160 °C. High-grade ethylene carbonate was obtained from the bottom of the heavy-end removal column. Electronic-grade ethylene carbonate product useful for power lithium batteries was recovered only from the sideline. The light components obtained from the light-removal column and the heavy-removal column, as well as the column bottoms obtained from the heavy-removal column, were sent to a batch column for further processing. The batch column was operated at 5 kPa, and the column bottoms temperature was controlled at 160°C. The non-condensable gases at the top of the column were sent for processing, and further products such as high-grade ethylene glycol carbonate and electronic-grade ethylene glycol carbonate could be obtained from the column top or the sideline liquid. The packing type for the light-removal column, heavy-removal column, and batch column was BX500, and the packing height was 12 m.

[0108] The separation yielded electronic grade products with yields of ≥70%, purity of ≥99.99%, and color of ≤10, while the high grade products had yields of ≥25%, purity of ≥99.95%, and color of ≤20.

[0109] Example 2 This example was the same as Example 1, except that the flow rate of the feed carbon dioxide was controlled, 20 kg / h of which was dissolved in the recycle stream of the main reactor, and 115 kg / h of which was sent to the gas distributor of the main reactor. The temperature rise in the side reactor was ≦6°C. The EO conversion in the main reactor was ≧87%, and the ethylene carbonate content in the reaction product of the side reactor was ≧95%.

[0110] Through the separation process, the electronic grade product had a yield of ≥70%, a purity of ≥99.99%, and a color of ≤10, while the high grade product had a yield of ≥25%, a purity of ≥99.95%, and a color of ≤20.

[0111] Example 3 This example was identical to Example 1, except that the pressure of the main reactor was 2.0 MPa, the temperature was 80°C, the circulation rate was 4000 kg / h, and the temperature rise of the reactor was 25°C. The EO conversion rate of the main reactor was ≥ 90%, and the content of ethylene carbonate in the reaction product of the side reactor was ≥ 95%.

[0112] Through the separation process, the electronic grade product had a yield of ≥70%, a purity of ≥99.99%, and a color of ≤10, while the high grade product had a yield of ≥25%, a purity of ≥99.95%, and a color of ≤20.

[0113] Example 4 This example was identical to Example 1, except that the batch column operating pressure was 1 kPa, the column bottom temperature was ≦155°C, the packing type was CY900, the packing height was 12 m, the column overhead lights were discharged and recovered, and the sideline or / and column bottoms were returned to the lights removal column.

[0114] Through the separation process, the electronic grade product had a yield of ≥70%, a purity of ≥99.99%, and a color of ≤10, while the high grade product had a yield of ≥28%, a purity of ≥99.95%, and a color of ≤20.

[0115] Example 5 This example was identical to Example 1, except that the flash device was a flash drum, the operating pressure was 10 kPa, and the temperature was controlled at 120°C. The light-ends removal column and batch column had an operating pressure of 3 kPa, a column bottom temperature of 155°C or less, packing type CY700, and a packing height of 15 m. The condensers of the above-mentioned rectification columns were all internally located at the top of the rectification column, and a film evaporator was used at the bottom of the column, implementing circulation.

[0116] Through the above separation, the electronic grade product had a yield of ≥75%, a purity of ≥99.99%, and a color index of ≤10, and the high grade product had a yield of ≥23%, a purity of ≥99.95%, and a color index of ≤20.

[0117] Example 6 This example was the same as Example 1, except that the flow rate of the feed carbon dioxide was controlled, with 15 kg / h of it dissolved in the recycle stream of the main reactor and 100 kg / h of it sent to the gas distributor of the main reactor. The pressure of the main reactor was 2.0 MPa, the temperature was 80°C, the circulation rate was 5000 kg / h, and the temperature rise of the reactor was 15°C. The EO conversion rate of the main reactor was ≥ 95%, and the ethylene carbonate content in the reaction product of the side reactor was ≥ 99.5%.

[0118] Flash column, operating pressure: 0.5 kPa, column bottom temperature: ≦150 °C, packing type: BX500, packing height: 4 m; Light-end removal column, operating pressure: 0.5 kPa, column bottom temperature: ≦150°C, packing type: CY900, packing height: 18 m; Heavy-end removal column, operating pressure: 0.5 kPa, column bottom temperature: ≦150°C, packing type: CY900, packing height: 18 m; Batch column, operating pressure: 0.5 kPa, column bottom temperature: ≦150°C, packing type: CY900, packing height: 10 m, the light components were cut off and the concentrated ethylene carbonate was returned to the light removal column.

[0119] The condensers of the above rectification columns were all internally arranged at the top of the rectification columns, and membrane evaporators were used at the bottom of the columns to implement circulation.

[0120] Through the above separation, the electronic grade product had a yield of ≥85%, a purity of ≥99.99%, and a color index of ≤10, and the high grade product had a yield of ≥13%, a purity of ≥99.95%, and a color index of ≤20.

[0121] Example 7 This example was the same as Example 1, except that the raw materials were propylene oxide and carbon dioxide, which reacted to produce propylene carbonate. The PO conversion in the main reactor was ≥ 85%, and the propylene carbonate content in the reaction product of the side reactor was ≥ 95%.

[0122] The flash unit was a flash drum, with an operating pressure of 10 kPa and a temperature of 120°C. The light-end removal column and batch column had an operating pressure of 1 kPa, a column bottom temperature of ≦160°C, packing material type CY700, and a packing height of 20 m. The condensers for the above rectification columns were all internally located at the top of the rectification column, and a film evaporator was used at the column bottom, providing circulation.

[0123] The separation yielded electronic grade products with yields of ≥70%, purity of ≥99.99%, and color of ≤10, while the high grade products had yields of ≥25%, purity of ≥99.5%, and color of ≤30.

[0124] Example 8 This example was the same as Example 1, except that carbon dioxide was introduced using a mixer with a flow rate controlled at 84 kg / h (i.e., 70%) and a gas distributor with a flow rate controlled at 36 kg / h (i.e., 30%). EO conversion in the primary reactor decreased due to reduced carbon dioxide dissolution in the primary reactor. EO conversion in the primary reactor was ≥ 80%, and the temperature increase in the secondary reactor was 10°C.

[0125] Comparative Example 1 This example was the same as Example 1, except that instead of introducing carbon dioxide through a mixer, all carbon dioxide was passed through the reactor gas inlet and introduced into the main reactor through a gas distributor, resulting in a 3% decrease in EO conversion in the main reactor. The temperature increase in the side reactor was 10°C.

[0126] Any reference to any numerical value herein includes all values ​​in one-unit increments from the lowest value to any highest value, provided that there is a gap of at least two units between any lowest and any highest value. For example, if a quantity of a component is listed, or if a process variable such as temperature, pressure, or time has a value between 50 and 90, it means that numerical values ​​such as 51 to 89, 52 to 88, . . . , 69 to 71, and 70 to 71 are specifically recited herein. For non-integer values, 0.1, 0.01, 0.001, or 0.0001 may be considered as one unit, as appropriate. These are merely specifically designated examples. Similarly, in this application, all possible combinations of numerical values ​​between the recited lowest and highest values ​​are considered disclosed.

[0127] It should be noted that the above embodiments are intended to illustrate the present invention and not to limit it. While the present invention has been described with reference to exemplary embodiments, it should be understood that the terms used therein are terms of description and explanation, rather than terms of limitation. The present invention may be modified within the above-described scope of the invention specified, and may be modified without departing from the scope and spirit of the invention. While the invention described herein refers to particular methods, materials, and embodiments, it is not intended to be limited to the particular examples disclosed herein; rather, the invention may extend to all other methods and applications having the same functionality. [Brief explanation of the drawings]

[0128] [Figure 1] FIG. 1 is a schematic diagram of a system for synthesizing carbonates according to the present invention. [Figure 2]FIG. 2 is a schematic diagram of a separation unit for the synthesis of carbonates according to the present invention.

Claims

1. A gas-liquid bubbling bed reactor comprising a liquid distributor, a gas distributor located below the liquid distributor, a catalyst bed layer, a catalyst support plate, and an isolation screen, wherein a gas outlet is provided at the top of the reactor, the reactor is provided with a feed port connected to the liquid distributor, a gas inlet connected to the gas distributor, and a discharge port at the bottom, and the catalyst bed is loaded with a heterogeneous catalyst; a circulating pump located between the outlet and the supply inlet of the reactor; a mixer located between the circulating pump and the supply inlet of the reactor and having a reactant inlet; and a dissolver located between the mixer and the supply inlet of the reactor and having a reactant gas inlet, wherein the circulating pump, the mixer, and the dissolver are continuously connected by a pipeline.

2. 2. The reactor of claim 1, wherein the liquid distributor is located at the top of the reactor, the gas distributor is located at the middle or bottom of the reactor, the isolation screen is located above the catalyst bed, and the gas distributor is a tubular distributor.

3. 3. The reactor of claim 1 or 2, further comprising a cooler located on the pipeline of the recycle flow from the outlet to the feed inlet of the reactor, the cooler being located on the pipeline between the outlet of the reactor and the circulation pump.

4. 4. The reactor of claim 3, further comprising a condenser connected to the gas outlet of the reactor, the gas inlet of the condenser being connected to the gas outlet of the reactor and the liquid outlet of the condenser being connected to the liquid inlet of the reactor.

5. 5. A reaction system comprising the gas-liquid bubbling bed reactor and a side reactor according to claim 4, wherein the supply port of the side reactor is connected to the outlet of the gas-liquid bubbling bed reactor, the side reactor is a fixed bed reactor, and the gas space of the gas-liquid bubbling bed reactor is in communication with the gas space of the side reactor.

6. 6. The reaction system according to claim 5, wherein the secondary reactor is provided with a gas outlet at its top and a discharge port at its bottom, the gas outlet being connected to the condenser, the secondary reactor is not provided with a reaction gas inlet, the supply port of the secondary reactor is connected to a position between the cooler and the circulation pump of the bubbling bed reactor according to claim 4, and the position of the supply port of the secondary reactor is lower than the packed height of the catalyst bed layer of the gas-liquid bubbling bed reactor and not above the height of the liquid distributor of the gas-liquid bubbling bed reactor.

7. 7. The reaction system according to claim 5 or 6, further comprising a separation unit connected to the outlet of the side reactor.

8. 8. The reaction system according to claim 7, wherein the separation unit comprises: a flash unit having a feed inlet connected to the outlet of the side reactor; a lights removal column having a feed inlet connected to the outlet of the flash unit; a heavy removal column having a feed inlet connected to the outlet of the lights removal column; and a batch column having feed inlets connected to the lights removal column and the liquid outlets of the heavy removal column.

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