Loop reactor system and method for liquid-phase peroxidation of ethylbenzene

Abstract

The invention relates to a loop reactor system and method for liquid-phase peroxidation of ethylbenzene. The loop reactor comprises an ejector, a reaction kettle, a circulating pump and a heat exchanger; the ejector comprises a nozzle cavity provided with a nozzle, a suction section, a mixing section and a diffusion section; circulating liquid is ejected at a high speed by the ejector, a low-pressure area is formed at a nozzle of the ejector, gas is entrained and sucked into the ejector, meanwhile, the gas is broken into tiny bubbles, the bottom end of the ejector extends below the liquid level of the reaction kettle, gas-liquid two phases are mixed by the ejector and then flow into the reaction kettle, and gas-liquid mixed materials and materials in the reaction kettle impact each other to promote gas-liquid mixing and dispersion; materials flow through the heat exchanger through a bottom outlet of the reaction kettle. Multi-stage loop reactors are connected in series, an interstage reaction product is sent to a next-stage reactor through a separation system, air is independently fed by each reactor, and an ethylbenzene raw material and other materials are supplemented from the first stage. The loop reactor has the advantages of being high in efficiency, small in occupied area, simple in structure, stable in control and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production, and in particular relates to a loop reactor system and a method for liquid-phase peroxidation of ethylbenzene. Background Art

[0002] Ethylbenzene hydroperoxide is an important organic chemical raw material. It can be used as an oxidant to participate in a variety of organic synthesis reactions. It can oxidize some compounds containing unsaturated bonds (such as carbon-carbon double bonds, carbon-nitrogen double bonds, etc.). For example, in the propylene oxide and styrene co-production (PO / SM) process, it reacts with propylene to produce propylene oxide and styrene. In the field of polymer chemistry, ethylbenzene hydroperoxide is an important free radical polymerization initiator. For example, in the production process of plastics such as polystyrene, it can initiate the polymerization reaction of styrene monomers. This polymerization reaction is the basis for the manufacture of various plastic products. Polystyrene is widely used in packaging materials, electronic and electrical housings and other products due to its good insulation, transparency and processing properties.

[0003] At present, the reactor used in the industrial production of ethylbenzene hydrogen peroxide is a horizontal multi-stage bubbling reactor, and heat exchange tubes and baffles are arranged in each reactor. U.S. Patents US4066706 and US4262143 disclose a horizontal reactor, which uses baffles to divide the reactor into 5 to 10 areas. The ethylbenzene reaction liquid enters the reactor from one side, passes through each area in turn and is discharged from the other side. The air is blown into the corresponding area from the bottom, and is discharged from the top after contacting with ethylbenzene and reacting. The patent CN101022885A applied by Shell Company is different from the above reactor. The Shell Company reactor uses an axial baffle, and the separated reaction zones are respectively arranged with an air inlet distributor, and a shell and tube heat exchanger is provided below the liquid level of the reactor to transfer heat. However, for the multiphase process of ethylbenzene peroxidation, uniform gas distribution is crucial. In the actual application process of the above reactor, there are still problems such as insufficient gas-liquid mixing, limited mass transfer process, and low reaction efficiency.

[0004] In view of the problems existing in the existing reactors, the patents report a variety of methods to improve the gas-liquid mass transfer effect. Wanhua Chemical Group Co., Ltd. disclosed a multi-stage horizontal stirring gas lift reactor in patent CN107930555B. The reactor is still a horizontal cylinder structure, with multiple baffles arranged in the reactor at intervals in the longitudinal direction, and a guide tube and a stirring device are added in the middle to improve the mixing effect of the reaction raw materials and the circulating mother liquor. Zhejiang Zhiying Petrochemical Technology Co., Ltd. disclosed a horizontal reactor in patent CN113680302B. By setting an internal distribution pipe and a radial baffle, the contact time between air and materials is increased, thereby increasing the yield of ethylbenzene hydrogen peroxide. Changzhou Ruihua Chemical Engineering Technology Co., Ltd. disclosed a vertical bubbling tower reaction system in patent CN111606835A, which realizes the concentration control of ethylbenzene hydrogen peroxide through multi-stage series connection. Sinopec Engineering Construction Co., Ltd. disclosed a multi-stage vertical bubbling tower system in the patent, with a guide tube and a gas distribution pipe arranged inside to control the temperature distribution in the reactor. The stirred and bubble tower reactors reported in the above patents still have problems such as uneven gas distribution, insufficient mixing effect, difficulty in scale-up, and complex structure during the design process.

[0005] The loop reactor is a multiphase reactor that can be used for continuous production. It can achieve uniform breakup and dispersion of bubbles through injection and strengthen the gas-liquid mass transfer process. It has been used in hydrogenation, carbonylation and other reaction processes. However, there are no related reports on the production process of ethylbenzene peroxidation.

[0006] The loop reactor is mainly composed of four parts: an ejector, a reactor, a circulation pump, and an external heat exchanger. The liquid is pressurized and injected into the ejector by the circulation pump. The high-speed flowing liquid phase forms a low-pressure area in the ejector, sucking the gas into it and shearing and breaking it into tiny bubbles. The design of the ejector and reactor is the core. For the peroxidation reaction of ethylbenzene, the reactant itself is unstable, the temperature is high (>160°C), and it is easy to decompose. At the same time, it has the characteristics of deep oxidation, generating other by-products (such as acetophenone, phenylethanol, etc.), which have an adverse effect on subsequent synthesis and separation. How to achieve sufficient gas-liquid contact and effective control of reaction depth, the existing design methods cannot provide guidance. Conventional design methods rely on small-scale experiments and empirical correlations, and the scope of application of the system is limited. The relationship between the key structures of the ejector and reactor and the bubble size and mass transfer coefficient cannot be predicted, and the guidance is not strong, and the amplification effect is inevitable. Summary of the invention

[0007] The purpose of the present invention is to solve the shortcomings of existing reactors for ethylbenzene peroxidation, such as large area occupation, poor reaction effect, unstable control, etc., and to develop a new type of efficient, stable and reliable loop reactor system and method.

[0008] In order to achieve the above-mentioned object, the present invention provides a reaction system and method for preparing ethylbenzene hydrogen peroxide by ethylbenzene peroxidation. The method uses ethylbenzene and air as raw materials, performs peroxidation reaction to synthesize ethylbenzene hydrogen peroxide, and adopts a new loop reactor to strengthen gas-liquid mass transfer, which is specifically reflected in the ejector structure size and reactor structure design, thereby solving the problems of poor gas distribution effect, complex equipment structure, large floor space, high investment, etc. of the existing reactor. Among them, the present invention adopts a loop reactor to prepare ethylbenzene hydrogen peroxide: before the reaction starts, the raw materials, initiator, catalyst, etc. are placed in the reactor of the loop reactor, air is introduced into the loop reactor, the reaction temperature is controlled to be 130-160°C by controlling the circulation volume and the shell heat transfer system, and the reactor pressure is controlled to be 0.1-0.3MPa by the tail gas system.

[0009] The present invention adopts a loop reactor as a reactor for liquid-phase peroxidation of ethylbenzene, breaks the gas into tiny bubbles by means of liquid injection, and greatly increases the contact area of ​​gas-liquid reactants (ethylbenzene and oxygen) through optimized design, thereby increasing the mass transfer rate and avoiding excessive oxidation of ethylbenzene to generate other by-products, thereby improving the overall reaction efficiency.

[0010] The technical solution of the present invention is as follows:

[0011] A loop reactor system for liquid phase peroxidation of ethylbenzene; the loop reactor comprises an ejector, a reactor, a circulating pump and a heat exchanger; the ejector comprises, from top to bottom, a nozzle cavity with a nozzle installed, a suction section, a mixing section and a diffusion section; wherein: the key structural parameters of the ejector include the nozzle diameter Dn, the nozzle angle α, the suction section length Lt from the nozzle to the throat, the mixing section diameter Dt, the mixing section length Lm, the diffusion section length Ld and the diffusion section outlet diameter Dd; wherein: the ratio of the mixing section diameter to the nozzle diameter Dt / Dn is 2 to 4; the nozzle contraction angle α is 20 to 40°; the ratio of the suction section diameter to the mixing section diameter Dc / Dt is greater than 2; the ratio of the suction section length to the mixing section diameter Lt / Dt should be greater than 4; the ratio of the ejector mixing section length to the mixing section diameter Lm / Dt is recommended to be (1 to 3):1.

[0012] The reactor length-to-diameter ratio of the loop reactor is preferably 2-6.

[0013] The number of the injectors is preferably 1 to 6.

[0014] The fluid linear velocity at the injector nozzle of the loop reactor is preferably controlled at 60 to 120 m / s.

[0015] The distance r from the center of the ejector to the center of the reactor, the radius of the reactor is R, and the value of r / R is preferably 0.4 to 0.6.

[0016] The ethylbenzene liquid phase peroxidation reaction adopts a multi-stage loop reactor, and the number of stages of the loop reactor is preferably 2-6.

[0017] The heat exchanger used may be a tube type, plate type or other type of heat exchanger.

[0018] The invention discloses a method for liquid-phase peroxidation of ethylbenzene by using a loop reactor system. Before the reaction starts, raw materials, initiators and catalysts are placed in a reactor of the loop reactor, and air is introduced into the loop reactor; a circulating pump is started to provide power for the circulating liquid in the loop; the circulating liquid is ejected at high speed by an ejector, a low-pressure area is formed at the ejector nozzle, and the gas is sucked in; at the same time, the gas is broken into tiny bubbles, which greatly increases the gas-liquid contact area and promotes the improvement of the gas-liquid mass transfer rate; the bottom end of the ejector extends below the liquid surface of the reactor, and the gas-liquid two-phase is fully mixed by the ejector and flows into the reactor, and the gas-liquid mixed material impacts the material in the reactor, which promotes gas-liquid mixing and dispersion; the material flows through a heat exchanger through the bottom outlet of the reactor to remove heat in time, and the reaction temperature is controlled to be 130-160°C by controlling the circulation volume and the shell cooling water temperature, and the reactor pressure is controlled to be 0.1-0.3MPa.

[0019] In order to control the reaction process, multiple loop reactors are connected in series, and the inter-stage reaction products are sent to the next-stage reactor through a separation system. Air feed is fed to each reactor separately, and ethylbenzene raw material and other materials are added from the first stage.

[0020] For the ethylbenzene peroxidation loop reactor system, the key lies in the ejector structure size design, process parameter setting, ejector quantity and its arrangement in the reactor. The nozzle diameter and angle are directly related to the internal flow field change, and the appropriate flow rate is the premise for determining the gas-liquid mixing effect. The distance from the nozzle to the throat, the throat diameter, and the mixing length are directly related to the bubble size distribution, and how to control the ratio is crucial. The diffusion section provides space for the gas and liquid to mix fully.

[0021] Preferably, the ejector of the loop reactor adopts a throat with a mixing length. The purpose of the mixing section is to achieve uniform mixing of bubbles as much as possible. The ratio of the ejector mixing section length to the mixing section diameter Lm / Dt is recommended to be (1-3):1.

[0022] Preferably, during the ethylbenzene peroxidation reaction, the fluid linear velocity at the injector nozzle of the loop reactor is controlled at 60-120 m / s.

[0023] The relative positions of the ejector and the reactor of the loop reactor are preferably arranged in the following manner, defining the distance r from the center of the ejector to the center of the reactor, the radius of the reactor is R, and the value of r / R should be controlled at 0.4 to 0.6.

[0024] The present invention adopts a loop reactor as a reactor for liquid-phase peroxidation of ethylbenzene, and the reaction temperature is controlled by an external circulation cooler. The heat transfer medium of the cooler can produce low-pressure steam as a by-product or perform direct heat exchange with other materials according to process requirements.

[0025] The present invention uses a multi-stage loop reactor to achieve the conversion rate of ethylbenzene peroxidation process, and effectively controls the reaction process and inhibits the occurrence of side reactions by controlling the structure size and reaction temperature of each stage of the reactor. The number of stages of the loop reactor is preferably 2 to 6.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. The present invention optimizes the design of the ejector and reactor structure of the loop reactor, effectively improving the flow and mass transfer performance in the ethylbenzene peroxidation reactor and effectively improving the overall reaction efficiency.

[0028] 2. The present invention achieves efficient bubble crushing and increases the specific surface area of ​​the gas-liquid interface by adopting the optimal ejector mixing section length.

[0029] 3. The loop reactor uses a circulation pump instead of an electric stirring paddle to provide power, which has higher energy transfer efficiency and less mechanical loss.

[0030] 4. The loop reactor uses an external heat exchanger, whose heat exchange area is not limited. It can provide sufficient heat exchange area according to the required heat exchange amount, and can remove the generated reaction heat in time to avoid excessive temperature affecting the fluid flow state and the generation of reactor hot spots.

[0031] 5. There are no other moving parts in the reactor of the loop reactor, the sealing is good, and the length-to-diameter ratio is not restricted. In addition, the ejector, reactor and heat exchanger are all independent components, making the scale-up process easier to achieve.

[0032] 6. Gas suction no longer relies on compressor delivery, but relies on the entrainment effect of the liquid phase, achieving sufficient gas-liquid mixing with lower energy consumption, effectively saving costs.

[0033] 7. The present invention stipulates the aspect ratio of the reactor, the number and position of the ejectors, thereby achieving more complete mixing of the gas and liquid in the reactor, strengthening the gas-liquid mass transfer process, and improving the reaction rate.

[0034] 8. The use of a loop reactor to produce ethylbenzene hydroperoxide has the advantages of high efficiency, small footprint, simple structure, and stable control. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of a single-stage loop reactor for ethylbenzene peroxidation

[0036] Figure 2Schematic diagram of a two-stage loop reactor for ethylbenzene peroxidation

[0037] Figure 3 for Figure 1 Schematic diagram of the specific structure of the ejector

[0038] Figure 4 for Figure 1 Schematic diagram of the relative positions of the three injectors in the reactor

[0039] Description of serial numbers: 101-primary ejector, 102-primary reactor, 103-primary circulation pump, 104-primary heat exchanger, 105-primary separation system, 106-primary ethylbenzene inlet, 107-primary gas suction chamber, 108-primary circulating liquid inlet, 109-primary nozzle, 110-primary mixing section, 111-primary diffusion section, 112-primary nozzle outlet, 201-secondary ejector, 202-secondary reactor, 203-secondary circulation pump, 204-secondary heat exchanger, 205-secondary separation system;

[0040] Explanation of symbols: Di-circulating liquid inlet diameter, Dn-nozzle diameter, Dc-suction section diameter, α-nozzle angle, Lt-suction section length, Dt-mixing section diameter, Lm-mixing section length, Ld-diffusion section length, Dd-diffusion section outlet diameter. DETAILED DESCRIPTION

[0041] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] like Figure 1 As shown, it is a single-stage loop reactor, and the present invention uses this reactor to carry out the ethylbenzene peroxidation process. The loop reactor mainly includes a primary ejector (101), a primary reactor (102), a primary circulation pump (103) and a primary heat exchanger (104). The ejector is a schematic diagram, and the specific structure is shown in FIG. Figure 3 .

[0043] Before the reaction starts, the raw materials ethylbenzene, initiator, catalyst, etc. are placed in the reactor of the loop reactor, and air is introduced into the loop reactor; the primary heat exchanger (104) used in this patent can be a tubular, plate or other type of heat exchanger.

[0044] For the liquid phase peroxidation reaction of ethylbenzene, the structure of the primary ejector (101) and the primary reactor (102) will have a direct impact on the gas-liquid mixing degree, mass transfer and reaction rate. The preferred ejector and reactor structure schematic diagram is as follows: Figure 3 , Figure 4 shown. Figure 3A specific schematic diagram of the first-stage ejector structure is given in the figure. High-speed liquid is ejected from the center of the first-stage nozzle (109), interacting with the first-stage gas suction chamber (107) to form a suction effect. The mixed gas and liquid enter the first-stage mixing section (110) and the first-stage diffusion chamber (111). The entrance of the mixing section is the throat. The gas and liquid are fully mixed and evenly distributed in the mixing section. Figure 4 A schematic diagram of the relative arrangement of multiple injectors in the primary reactor (102) is given, with multiple nozzles being evenly arranged.

[0045] Example 1

[0046] by Figure 2 Take a two-stage loop reactor system as an example:

[0047] The number of the first-stage ejector (101) is 1, and the specific structural parameters are as follows: the diameter Di of the circulating liquid inlet (108) of the first-stage ejector (101) is 500 mm, the diameter Dn of the first-stage nozzle (109) is 80 mm, the ratio of the mixing section diameter to the nozzle diameter is Dt / Dn=2, the nozzle angle α is 30°, the ratio of the suction section diameter to the mixing section diameter is Dc / Dt=2, the ratio of the suction section length to the mixing section diameter is Lt / Dt is 10:1, the ratio of the ejector mixing section length to the mixing section diameter is Lm / Dt is 2:1, the outlet diameter Dd of the first-stage diffusion section (111) is 450 mm, the fluid linear velocity at the first-stage nozzle (109) of the loop reactor is controlled at 100 m / s, the ejector is arranged at the center of the reactor, and the total volume of the reactor is 350 m 3 , aspect ratio 4:1, the two-stage injector (201) has the same configuration;

[0048] The feed rate of ethylbenzene raw material is 1500 t / h, which is added from the primary reaction system. At the same time, the initiator ethylbenzene hydroperoxide (organic peroxide) is added. The catalyst is not added. The air feed rates of the primary reactor (102) and the secondary reactor (202) are 24 t / h and 32 t / h respectively. When the loop reactor is working, the primary circulation pump (103) is started to provide power for the circulating liquid in the loop. The circulating liquid is sprayed at high speed by the primary ejector (101), and a low-pressure area is formed at the primary nozzle (109), and the gas is sucked in. The bottom end of the ejector extends below the liquid surface of the primary reactor (102), and the gas and liquid phases are fully mixed by the ejector and flow into the primary reactor (102). The material flows through the primary heat exchanger (104) at the bottom outlet of the reactor to remove heat in time, and the reaction temperature is controlled to be stable at 150°C. The pressure of the primary reactor (102) is controlled to be 0.2 MPa. In order to control the reaction process, two-stage loop reactors are connected in series, and the inter-stage reaction products are sent to the next-stage reactor through a separation system.

[0049] The bubble size at the throat center of the first-stage ejector (101) is about 0.4 mm, and the bubble size at the outlet of the first-stage diffusion section (111) is about 0.8 mm. The specific surface area of ​​the gas-liquid interface at the throat center of the first-stage mixing section (110) is about 1400 m -1 , volume mass transfer coefficient is about 15s -1 Under this condition, the content of ethylbenzene hydroperoxide in the liquid product of the secondary reactor (202) is about 3.8 wt%.

[0050] Compared with traditional stirring or bubbling methods, by controlling process conditions, the overall reaction efficiency is comparable, the amount of air added is reduced by more than 15%, and the occupied area is reduced by more than 40%.

[0051] Example 2

[0052] by Figure 2 For example, the number of first-stage ejectors (101) is 3, and the specific structural parameters are as follows: the diameter Di of the circulating liquid inlet (108) of the first-stage ejector (101) is 300 mm, the diameter Dn of the nozzle (109) is 60 mm, the ratio of the mixing section diameter to the nozzle diameter Dt / Dn=3, the nozzle angle α is 30°, the ratio of the suction section diameter to the mixing section diameter Dc / Dt=4, the ratio of the suction section length to the mixing section diameter Lt / Dt is 8:1, the ratio of the ejector mixing section length to the mixing section diameter Lm / Dt is 3:1, the diffusion section (111) outlet Dd is 300 mm, the fluid linear velocity at the ejector nozzle (109) of the loop reactor is controlled at 120 m / s, and the nozzles are arranged according to Figure 4 As shown, the r / R value is 0.5. The total volume of the reactor is 300m 3 , aspect ratio 2:1, and the configuration of the secondary injector (201) is the same.

[0053] The feed rate of ethylbenzene raw material is 1500 t / h, which is added from the primary reaction system. At the same time, the initiator ethylbenzene hydroperoxide (organic peroxide) and the catalyst can be a supported cobalt oxide catalyst. The air feed rates of the primary reactor (102) and the secondary reactor (202) are 24 t / h and 32 t / h respectively. When the loop reactor is working, the primary circulation pump (103) is started to provide power for the circulating liquid in the loop. The circulating liquid is sprayed at high speed by the primary ejector (101), and a low-pressure area is formed at the primary nozzle (109), and the gas is sucked in. The bottom end of the ejector extends below the liquid surface of the primary reactor (102), and the gas and liquid phases are fully mixed by the ejector and flow into the primary reactor (102). The material flows through the primary heat exchanger (104) at the bottom outlet of the reactor to remove heat in time, control the reaction temperature to be stable at 130°C, and the pressure of the reactor (102) is controlled to be 0.2 MPa. In order to control the reaction process, two-stage loop reactors are connected in series, and the inter-stage reaction products are sent to the next-stage reactor through a separation system.

[0054] The bubble size at the throat center of the first-stage ejector (101) is about 0.3 mm, and the bubble size at the outlet of the first-stage diffusion section (111) is about 0.6 mm. The specific surface area of ​​the gas-liquid interface at the throat center of the first-stage mixing section (110) is about 1600 m -1 , volume mass transfer coefficient is about 20s -1 Under this condition, the content of ethylbenzene hydroperoxide in the liquid product of the secondary reactor (202) is about 4.2 wt%.

[0055] Compared with traditional stirring or bubbling methods, by controlling process conditions, the overall reaction efficiency is comparable, the amount of air added is reduced by more than 20%, and the occupied area is reduced by more than 50%.

[0056] Example 3

[0057] by Figure 2 For example, the number of the first-stage ejectors (101) is 6, and the specific structural parameters are as follows: the diameter Di of the ejector circulating liquid inlet (108) is 200 mm, the diameter Dn of the nozzle (109) is 30 mm, the ratio of the mixing section diameter to the nozzle diameter Dt / Dn=4, the nozzle angle α is 20°, the ratio of the suction section diameter to the mixing diameter Dc / Dt=6, the ratio of the suction section length to the mixing section diameter Lt / Dt is 4:1, the ratio of the ejector mixing section length to the mixing section diameter Lm / Dt is 3:1, the diffusion section (111) outlet Dd is 400 mm, the fluid linear velocity at the first-stage nozzle (109) of the loop reactor is controlled at 60 m / s, and the ejectors are arranged according to Figure 4 The reactor is arranged evenly and the r / R value is 0.6. The total volume of the reactor is 400m 3 , aspect ratio 2:1, the secondary injector (201) has the same configuration.

[0058] The feed rate of ethylbenzene raw material is 1500 t / h, which is added from the primary reaction system. At the same time, the initiator ethylbenzene hydroperoxide (organic peroxide) and the catalyst can be a supported cobalt oxide catalyst. The air feed rates of the primary reactor (102) and the secondary reactor (202) are 24 t / h and 32 t / h respectively. When the loop reactor is working, the primary circulation pump (103) is started to provide power for the circulating liquid in the loop. The circulating liquid is sprayed at high speed by the primary ejector (101), and a low-pressure area is formed at the primary nozzle (109), and the gas is sucked in. The bottom end of the ejector extends below the liquid surface of the primary reactor (102), and the gas and liquid phases are fully mixed by the ejector and flow into the primary reactor (102). The material flows through the primary heat exchanger (104) at the bottom outlet of the reactor to remove heat in time, and the reaction temperature is controlled to be stable at 140°C. The pressure of the primary reactor (102) is controlled to be 0.1 MPa. In order to control the reaction process, two-stage loop reactors are connected in series, and the inter-stage reaction products are sent to the next-stage reactor through a separation system.

[0059] The bubble size at the throat center of the first-stage ejector (101) is about 0.4 mm, and the bubble size at the outlet of the first-stage diffusion section (111) is about 0.8 mm. The specific surface area of ​​the gas-liquid interface at the throat center of the first-stage mixing section (110) is about 1200 m -1 , volume mass transfer coefficient is about 10s -1 Under this condition, the content of ethylbenzene hydroperoxide in the liquid phase product (202) of the secondary reactor is about 3.7 wt%.

[0060] Compared with traditional stirring or bubbling methods, by controlling the process conditions, the overall reaction efficiency is comparable, the amount of air added is reduced by more than 10%, and the occupied area is reduced by more than 35%.

[0061] Example 4

[0062] by Figure 2 For example, the number of the first-stage ejectors (101) is 3, and the specific parameters are as follows: the diameter Di of the first-stage ejector liquid phase inlet (108) is 350 mm, the diameter Dn of the first-stage nozzle (109) is 50 mm, the ratio of the mixing section diameter to the nozzle diameter is Dt / Dn=4, the nozzle angle α is 40°, the ratio of the suction section diameter to the mixing section diameter is Dc / Dt=3, the ratio of the suction section length to the mixing section diameter is Lt / Dt is 6:1, the ratio of the ejector mixing section length to the mixing section diameter is Lm / Dt is 4:1, the first-stage diffuser outlet diameter Dd is 400 mm, and the fluid linear velocity at the first-stage nozzle (109) of the first-stage loop reactor is controlled at 120 m / s. The bubble size at the throat center of the first-stage ejector (102) is about 0.35 mm, and the ejectors of the first-stage diffuser (111) are arranged according to Figure 4 As shown, the r / R value is 0.4 and the total volume of the reactor is 300m 3, length-to-diameter ratio 6:1, and the configuration of the secondary injector (201) is the same.

[0063] The feed rate of ethylbenzene raw material is 1800 t / h, which is added from the primary reaction system. At the same time, the initiator ethylbenzene hydroperoxide (organic peroxide) and the catalyst can be a supported cobalt oxide catalyst. The air feed rates of the primary reactor (102) and the secondary reactor (202) are 32 t / h and 40 t / h respectively. When the loop reactor is working, the primary circulation pump (103) is started to provide power for the circulating liquid in the loop. The circulating liquid is sprayed at high speed by the primary ejector (101), and a low-pressure area is formed at the nozzle (109) of the primary ejector, and the gas is sucked in. The bottom end of the ejector extends below the liquid surface of the primary reactor (102), and the gas and liquid phases are fully mixed by the ejector and flow into the primary reactor (102). The material flows through the primary heat exchanger (104) at the bottom outlet of the reactor to remove heat in time, and the reaction temperature is controlled to be stable at 160°C. The pressure of the primary reactor (102) is controlled to be 0.3 MPa. In order to control the reaction process, two-stage loop reactors are connected in series, and the inter-stage reaction products are sent to the next-stage reactor through a separation system.

[0064] The bubble size at the throat center of the first-stage ejector (102) is about 0.25 mm, and the bubble size at the outlet of the first-stage diffusion section (111) is about 0.5 mm. The specific surface area of ​​the gas-liquid interface at the throat center of the first-stage mixing section (110) is about 1800 m -1 , volume mass transfer coefficient is about 25s -1 .

[0065] Under this condition, the content of ethylbenzene hydroperoxide in the liquid phase product (202) of the secondary reactor is about 4.5 wt%;

[0066] Compared with traditional stirring or bubbling methods, by controlling process conditions, the overall reaction efficiency is comparable, the amount of air added is reduced by more than 25%, and the occupied area is reduced by more than 50%.

[0067] The technical solutions disclosed and proposed by the present invention can be realized by those skilled in the art by referring to the contents of this article and appropriately changing the conditions, routes and other links. Although the methods and preparation techniques of the present invention have been described through preferred embodiments, relevant technicians can obviously modify or re-combine the methods and technical routes described herein without departing from the content, spirit and scope of the present invention to achieve the final preparation technology. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention. Matters not covered in the present invention belong to the known technology.

Claims

1. A loop reactor system for liquid phase peroxidation of ethylbenzene; characterized in that: The loop reactor includes an ejector, a reactor, a circulation pump and a heat exchanger; the ejector includes a nozzle cavity with a nozzle installed, a suction section, a mixing section and a diffusion section from top to bottom; wherein: the key structural parameters of the ejector include the nozzle diameter Dn, the nozzle angle α, the suction section length Lt from the nozzle to the throat, the mixing section diameter Dt, the mixing section length Lm, the diffusion section length Ld and the diffusion section outlet diameter Dd; wherein: the ratio of the mixing section diameter to the nozzle diameter Dt / Dn is 2 to 4; the nozzle contraction angle α is 20 to 40°; the ratio of the suction section diameter to the mixing section diameter Dc / Dt is greater than 2; the ratio of the suction section length to the mixing section diameter Lt / Dt should be greater than 4; the ratio of the ejector mixing section length to the mixing section diameter Lm / Dt is (1 to 3):

1.

2. A loop reactor system for liquid phase peroxidation of ethylbenzene as claimed in claim 1; characterized in that: The length-to-diameter ratio of the reactor of the loop reactor is 2-6.

3. A loop reactor system for liquid phase peroxidation of ethylbenzene as claimed in claim 1; characterized in that: The number of injectors is 1 to 6.

4. A loop reactor system for liquid phase peroxidation of ethylbenzene as claimed in claim 1; characterized in that: The linear velocity of the fluid at the ejector nozzle of the loop reactor is controlled at 60-120 m / s.

5. A loop reactor system for liquid phase peroxidation of ethylbenzene as claimed in claim 1; characterized in that, The distance r from the center of the ejector to the center of the reactor, the radius of the reactor is R, and the value of r / R is 0.4 to 0.

6.

6. A loop reactor system for liquid phase peroxidation of ethylbenzene as claimed in claim 1; characterized in that: The liquid phase peroxidation reaction of ethylbenzene adopts a multi-stage loop reactor, and the number of stages of the loop reactor is 2 to 6.

7. A loop reactor system for liquid phase peroxidation of ethylbenzene as claimed in claim 1; characterized in that: The heat exchanger used can be a tube type, plate type or other type of heat exchanger.

8. A method for liquid phase peroxidation of ethylbenzene utilizing the loop reactor system of claim 1, characterized in that: Before the reaction starts, the raw materials, initiator and catalyst are placed in the reactor of the loop reactor, and air is introduced into the loop reactor; the circulation pump is started, and the circulating liquid is ejected at high speed through the ejector, forming a low-pressure area at the ejector nozzle, sucking the gas in, and the gas is broken into tiny bubbles at the same time. The bottom end of the ejector extends below the liquid surface of the reactor, and the gas and liquid are mixed by the ejector and flow into the reactor. The gas-liquid mixed material impacts the material in the reactor to promote gas-liquid mixing and dispersion; the material flows through the heat exchanger at the bottom outlet of the reactor to remove heat, and the reaction temperature is controlled to be 130-160°C by controlling the circulation volume and the shell-side heat transfer system, and the reactor pressure is controlled to be 0.1-0.3MPa by the tail gas system.

9. A method for liquid phase peroxidation of ethylbenzene in a loop reactor system as claimed in claim 8, characterized in that: A multi-stage loop reactor is connected in series, and the inter-stage reaction products are sent to the next-stage reactor through a separation system. Air feed is fed to each reactor separately, and ethylbenzene raw material and other materials are fed in from the first stage.

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