A continuous photochemical reaction device and application thereof

Abstract

The application discloses a kind of continuous photochemical reaction device and its application, including the first reactor system and the second reactor system that are interconnected, first reactor system includes dynamic mixer and gas-liquid residence equipment, the pressure of organic amine and phosgene reaction is regulated through gas-liquid residence equipment, can improve the phosgene concentration and pressure of cold reaction liquid;The second reactor system includes hot reactor, ejector and heater, the high-pressure cold reaction liquid is used to inject low-pressure hot reaction liquid in hot reactor and heater between ejector and establish high-speed circulation and heat to high temperature, so that hydrochloride and acyl chloride are decomposed into isocyanate.The application realizes the improvement of phosgene concentration of reaction system and the high-speed siphon circulation of reaction heating system by real-time accurate regulation to the pressure of each reaction stage, can greatly extend the operation cycle of reaction system while reducing the generation amount of reaction tar residue.

Description

Technical Field

[0001] This invention relates to the technical field of diisocyanate preparation, and more particularly to a continuous photochemical reaction apparatus and its application. Background Technology

[0002] Currently, the most consumed polyurethane products are rigid polyurethane foam, flexible polyurethane foam, synthetic leather slurry, and coatings. Toluene diisocyanate (TDI) is a preferred material for preparing sponges, coatings, and curing agents, and its global production capacity is continuously increasing. Among existing TDI preparation technologies, liquid-phase phosgenation and gas-phase phosgenation are the most commonly used production processes. The gas-phase phosgenation process requires the high-temperature vaporization of m-toluenediamine (MTDA) before reacting with gaseous phosgene. Toluenediamine is a heat-sensitive substance, and during high-temperature vaporization, it is prone to thermal decomposition, generating numerous byproducts that prevent the reaction system from meeting the requirements for long-term operation. Liquid-phase phosgenation, due to its simplicity and high operational stability, has become the mainstream process route for TDI in the industry. However, due to limitations in reactor mixing and high-temperature treatment, numerous side reactions still occur during the MTDA phosgenation reaction and subsequent TDI distillation and purification, easily generating tar residues mainly composed of ureas, biuret, and carbodiimides. Existing literature studies have shown that tar residue is mainly generated in the photochemical reaction process, and the by-product tar residue of these reactions can easily cause coking and blockage of the reactor and its associated heating equipment after a period of operation, thus forcing a forced shutdown for maintenance.

[0003] To reduce the amount of byproducts generated in the liquid phase phosgenation process and to solve the problem of the reaction system being prone to coking and clogging and unable to operate for a long period of time, the isocyanate industry is making unremitting efforts and attempts to address these issues. Many methods are adopted to improve the reaction yield and reduce the occurrence of side reactions by improving the reactor mixing structure, increasing the ratio of phosgene to polyamine, the ratio of inert solvent to polyamine, and increasing the mixing intensity of phosgene and polyamine.

[0004] Patent CN101583594A discloses a method for producing isocyanates, in which phosgene and amines react through a series of microchannel reactors. These reactors exhibit high flow rates and turbulence intensity, enhancing mixing. However, because phosgene and amines react through slits in this method, the resulting blockages easily clog the micropores, making long-term operation impossible.

[0005] Patent CN202898275U discloses an apparatus for producing toluene diisocyanate using a light solvent. A mixture of toluene diamine and solvent is reacted with phosgene in a static jet reactor under cold conditions. The resulting reaction mixture is then introduced into a photochemical reaction tower for a thermal reaction. Because the hydrochloride solids produced during the reaction have a high content and are difficult to decompose completely, significant scaling and clogging problems easily occur in the internal components of the photochemical reaction tower and the heating equipment in the reboiler.

[0006] Patent CN104755458A discloses a method for preparing isocyanates by reacting amines with phosgene in the liquid phase. This method involves mixing and reacting the amines and phosgene in a tubular reactor, then introducing the mixture into a reaction tower under reduced pressure. The hot reaction tower is heated using a pump-driven forced circulation reboiler. However, the tubular reactor suffers from poor mixing and high byproduct content. Furthermore, the trays or packing in the hot reaction tower are prone to coking and clogging. Additionally, the photochemical reaction system involves numerous moving parts, significantly increasing the likelihood of phosgene leakage.

[0007] In summary, existing technologies offer limited solutions to problems such as poor reaction performance, low product yield, and high tar residue leading to coking and blockage in liquid-phase phosgenation processes. There is a need to develop a highly efficient and continuous photochemical reaction device to improve reaction yield and solve the problem of system blockage, thereby achieving the goal of efficient, safe, and long-term stable operation of the production unit. Summary of the Invention

[0008] To address the aforementioned deficiencies in the prior art, this invention provides a continuous photochemical reaction device and its application. By precisely controlling the pressure at each reaction stage in real time, it achieves an increase in the phosgene concentration of the reaction system and a high-speed siphon circulation of the reaction heating system. This reduces the amount of reaction tar residue generated and significantly extends the operating cycle of the reaction system.

[0009] To achieve the above-mentioned objectives, the first aspect of the present invention provides a continuous photochemical reaction apparatus, comprising a first reactor system and a second reactor system connected by pipelines;

[0010] The first reactor system includes:

[0011] The dynamic mixer M1 is used to provide a place for mixing organic amines and phosgene to carry out the first photochemical reaction. The reacted material I enters the gas-liquid residence device D1.

[0012] The gas-liquid retention device D1 is used for gas-liquid separation of material I to obtain liquid material II and gas material. A pressure adjustment mechanism P1 is provided in the exhaust area of ​​the gas-liquid retention device D1 to adjust the pressure in the first reactor system.

[0013] The second reactor system includes:

[0014] Thermal reactor D2 serves as a site for the second photochemical reaction of the materials inside it;

[0015] The ejector J1 is used to receive high-pressure liquid material II from the gas-liquid residence device D1 and low-pressure material III from the thermal reactor D2. The high-pressure liquid material II drives the ejector to mix the low-pressure material III to form high-speed material IV.

[0016] Heater E1 is used to receive material IV from ejector J1 and heat it. After heating, material V enters thermal reactor D2 for the second photochemical reaction.

[0017] The second aspect of the present invention provides the application of the above-described continuous photochemical reaction apparatus in the preparation of toluene diisocyanate.

[0018] A third aspect of the present invention describes a method for preparing toluene diisocyanate using the aforementioned continuous photochemical reaction apparatus, comprising the following steps:

[0019] 1) Organic amines and phosgene are mixed in dynamic mixer M1 to carry out the first photochemical reaction, and the reacted material I enters the gas-liquid residence device D1;

[0020] 2) Material I undergoes gas-liquid separation in the gas-liquid residence device D1 to obtain liquid material II and gas material. The discharge pressure of the gas material is controlled by the pressure adjustment mechanism P1.

[0021] 3) The high-pressure liquid phase material II from the gas-liquid residence device D1 and the low-pressure material III from the thermal reactor D2 enter the ejector J1. The high-pressure liquid phase material II drives the ejector to mix with the low-pressure material III to form a high-speed material IV.

[0022] 4) Material IV from ejector J1 enters heater E1 for heating, and after heating, material V enters thermal reactor D2 for the second photochemical reaction.

[0023] 5) The product after the reaction in thermal reactor D2 is discharged and purified to obtain toluene diisocyanate.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The continuous photochemical reaction apparatus of this invention includes a first reactor system and a second reactor system interconnected. The first reactor system includes a dynamic mixer M1 and a gas-liquid residence device D1. By regulating the pressure of the reaction between organic amines and phosgene through the gas-liquid residence device D1, the phosgene concentration and pressure of the cold reaction liquid can be increased. The second reactor system includes a thermal reactor D2, an ejector J1, and a heater E1. The ejector J1 uses a high-pressure cold reaction liquid to induce a low-pressure hot reaction liquid to establish a high-speed circulation between the thermal reactor D2 and the heater E1, heating it to a high temperature, causing the hydrochloride and acyl chloride to decompose into isocyanate. The apparatus of this invention has a simple structure, high operational stability, and allows for independent control of the pressure at each reaction stage, effectively reducing the generation of by-product tar residue, while extending the operating cycle of the reaction heating system.

[0026] Other features and advantages of the present invention will be described in detail through the following specific embodiments. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A process flow diagram of a continuous photochemical reaction device provided in an embodiment of the present invention.

[0029] The markings are explained as follows: 1 is the first amine inlet, 2 is the second amine inlet, 3 is the third phosgene inlet, 4 is the material outlet of the dynamic mixer (reacted material I), 5 is the liquid phase material of the gas-liquid residence device (high-pressure liquid phase material II), 6 is the gas phase material of the gas-liquid residence device, 7 is the material of the thermal reactor (low-pressure material III); 8 is the material outlet of the ejector (high-speed material IV), 9 is the material outlet of the heater (heated material V), 10 is the gas phase material of the thermal reactor, and 11 is the reaction product of the thermal reactor.

[0030] M1 is the dynamic mixer of the first reactor system, D1 is the gas-liquid residence device of the first reactor system, D2 is the thermal reactor (thermal reaction vessel) of the second reactor system, J1 is the ejector of the second reactor system, E1 is the heater of the second reactor system, P1 is the pressure adjustment structure of the gas-liquid residence device D1, and P2 is the pressure adjustment structure of the thermal reactor D2.

[0031] Figure 2 This is an internal structural diagram of an injector J1 provided in an embodiment of the present invention.

[0032] The markings are explained as follows: a is the drive-side inlet, b is the ejector-side inlet, c is the internal throat of the ejector, d is the suction chamber, e is the tubular distributor, f is the mixing chamber, g is the diffusion chamber, and h is the outlet of the mixed material. Detailed Implementation

[0033] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0034] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0035] Unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and connections within two components or interactions between two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0036] In existing toluene diisocyanate (TBD) production processes, m-toluenediamine and phosgene typically undergo a cold reaction in a mixer before being directly introduced into a downstream hot reactor or hot reaction tower. Because there is no clear pressure distinction between the cold and hot reaction stages, the pressure of the cold reaction cannot be individually controlled, leading to significant phosgene escape during the cold reaction stage. This results in the intermediate products generated from the amine-phosgene reaction, especially hydrochloride or acyl chloride-hydrochloride, failing to continue reacting to form TDD during the hot reaction stage due to excessively low phosgene concentration, ultimately transforming into tar residue. To address these issues, this invention provides a continuous photochemical reaction apparatus, comprising a first reactor system and a second reactor system connected by pipelines.

[0037] The first reactor system includes:

[0038] The dynamic mixer M1 is used to provide a place for mixing organic amines and phosgene to carry out the first photochemical reaction. The reacted material I enters the gas-liquid residence device D1.

[0039] The gas-liquid retention device D1 is used for gas-liquid separation of material I to obtain liquid material II and gas material. A pressure adjustment mechanism P1 is provided in the exhaust area of ​​the gas-liquid retention device D1 to adjust the pressure in the first reactor system.

[0040] The second reactor system includes:

[0041] Thermal reactor D2 serves as a site for the second photochemical reaction of the materials inside it;

[0042] The ejector J1 is used to receive high-pressure liquid material II from the gas-liquid residence device D1 and low-pressure material III from the thermal reactor D2. The high-pressure liquid material II drives the ejector to mix the low-pressure material III to form high-speed material IV.

[0043] Heater E1 is used to receive material IV from ejector J1 and heat it. After heating, material V enters thermal reactor D2 for the second photochemical reaction.

[0044] Through the above technical solution, the continuous photochemical reaction device of the present invention can regulate the pressure through a gas-liquid residence device during the cold reaction stage of organic amines and phosgene. In particular, it can significantly increase the pressure during the cold reaction stage without affecting the pressure of the hot reaction. On the one hand, a large amount of gaseous phosgene can be liquefied and dissolved in the liquid phase. At the same time, the present invention proposes for the first time to use an ejector to drive the low-pressure hot reaction liquid to establish a siphon circulation between the hot reactor and the heater using the pressure of the cold reaction liquid. This fully mixes and accelerates the cold and hot reaction liquids, forming a mixed fluid with a higher flow rate in the reaction heater tubes. This ensures the phosgene concentration and temperature required for the decomposition of hydrochloride or acyl chloride hydrochloride, which can significantly reduce the amount of by-product tar residue generated and effectively extend the operating cycle of the reaction heating system.

[0045] The principle and process of the first photochemical reaction of the present invention are as follows:

[0046] Taking the phosgenation of m-toluenediamine (MTDA) as an example, organic amines and phosgene are mixed in a dynamic mixer M1, and a rapid cold reaction occurs to generate hydrochloride and acyl chloride.

[0047]

[0048] The principle and process of the second photochemical reaction of the present invention are as follows:

[0049] The products of the first photochemical reaction, hydrochloride and phosgene, continue to react during heating to produce acyl chloride and HCl. The acyl chloride then undergoes a decomposition reaction during heating to produce isocyanate products and HCl. The HCl is discharged from the system in the gas phase.

[0050]

[0051] In this invention, it is understood that before the reaction device is started, some solvent can be introduced into the thermal reactor D2 as its internal material, for example, by supplementing the inert solvent o-dichlorobenzene (ODCB) through the start-up auxiliary pipeline of the thermal reactor D2, to establish the liquid level when the equipment is initially started.

[0052] In some embodiments, organic amines and phosgene are fed separately in the dynamic mixer M1, with separate inlets for organic amines and phosgene.

[0053] Preferably, the present invention provides an ultra-fine atomizing nozzle at the feed inlet on the organic amine side, and the organic amine achieves a rapid mixing reaction with phosgene by a sudden pressure drop at the nozzle.

[0054] In a specific example, the dynamic mixer M1 of the present invention is provided with a first amine inlet 1, a second amine inlet 2 and a third phosgene inlet 3. The first amine inlet 1 or the second amine inlet 2 is arranged at an angle of 45° with the central axis of the dynamic mixer M1. Both the first amine inlet 1 and the second amine inlet 2 are provided with ultra-fine atomizing nozzles.

[0055] Preferably, the size of the ultrafine atomizing nozzle is 2-30mm, and more preferably 3-7mm.

[0056] The matching of the positions of the first amine inlet 1 and the second amine inlet 2, as well as the nozzle size, can improve the dispersion effect of inert solvent and organic amine in dynamic mixer M1, avoid excessively high local concentration of organic amine in the mixer, deteriorate the reaction effect with phosgene, generate urea and other tar residues that clog the reactor nozzles, and extend the operating cycle.

[0057] In some embodiments, the gas-liquid residence device D1 is selected from one of a batch reactor, a tubular reactor, or a gas-liquid separation flash tank.

[0058] In some embodiments, a pressure adjustment mechanism P1 is provided at the top of the gas-liquid retention device D1. The pressure adjustment mechanism automatically adjusts the pressure in the first reactor system in real time, thereby increasing the operating pressure of the cold reaction liquid so that more phosgene cannot escape and dissolves in the reaction liquid in the form of liquid phase, thus achieving a significant increase in the phosgene concentration in the reaction liquid. The pressure adjustment mechanism can be selected from a throttling element with a pneumatic, electric or manual actuator. For example, the pressure adjustment mechanism P1 is an automatic pressure regulating valve or a manual valve connected to the exhaust pipeline of the gas-liquid retention device.

[0059] In some embodiments, the ejector J1 of the second reactor system is a Venturi mixer with a built-in constricted throat and both low-pressure and high-pressure material inlets. The reaction liquid of the first reactor system enters the throat of the ejector from the high-pressure material side (drive side), while the material of the second reactor system enters from the low-pressure material side (ejector side), and then they are mixed in the mixing chamber of the ejector.

[0060] Figure 2 This is an internal structural diagram of an injector J1 provided in an embodiment of the present invention. An internal tubular distributor is added, making it particularly suitable for applications with two or more fluid streams, especially when the pressures of the main and secondary streams are unbalanced. Specifically, the injector J1 has, axially, a suction chamber (with an internal throat), a tubular distributor, a mixing chamber, and a diffusion chamber arranged sequentially, with the material finally flowing out from the outlet. The injector J1 has a drive-side material inlet at one end of the suction chamber and an ejector-side material inlet near the internal throat of the suction chamber; wherein:

[0061] The suction chamber has a built-in constricted throat. High-pressure material entering from the drive side undergoes adiabatic expansion at the throat and forms a negative pressure zone at the throat outlet, which in turn ejects low-pressure material into the ejector to mix with the high-pressure material.

[0062] Adding a tubular distributor to the nozzle throat outlet is mainly used to solve the problem of vibration and severe scouring of the nozzle throat when two or more fluids are fed, due to large fluctuations in the flow rate of the driving fluid.

[0063] The mixing chamber is a zone for further mixing of high-pressure and low-pressure materials, achieving a balance between material pressure and velocity.

[0064] After mixing in the diffusion chamber, the velocity energy of the material is converted into pressure energy, making the pressure of the mixed material higher than the pressure of the ejector fluid, thereby increasing the pressure of the circulating material.

[0065] Figure 2 In the diagram, a is the drive-side inlet, b is the ejector-side inlet, c is the internal throat of the ejector, d is the suction chamber, e is the tubular distributor, f is the mixing chamber, g is the diffusion chamber, and h is the outlet for the mixed material.

[0066] Preferably, the throat diameter of the injector J1 is 20-150 mm, more preferably 30-60 mm. This setting can ensure that the cold reaction liquid and the hot reaction liquid achieve better mixing effect, increase the flow rate of the ejector side suction, and obtain a higher material flow rate.

[0067] In some embodiments, the ejector J1 drives the material mixing of the ejector thermal reactor D2 through the high-pressure reaction liquid of the first reactor system, forming a high-speed material that enters the bottom feed port of the heater E1. The material outlet of the heater E1 is located on the side and is directly connected to the thermal reactor through a pipe. That is, the present invention utilizes high-pressure cold reaction liquid in the ejector to drive low-pressure hot reaction liquid to establish a high-speed siphon circulation in the heater, which increases the flow rate and turbulence of the material in the heater tubes, ensuring the phosgene concentration and temperature required for hydrochloride decomposition.

[0068] In some embodiments, the thermal reactor D2 and heater E1 of the second reactor system are placed vertically in parallel, wherein the heater E1 is either a shell-and-tube heat exchanger or a jacketed tube heat exchanger, wherein a shell-and-tube heat exchanger is preferred.

[0069] In some embodiments, the outer diameter of the heater E1 tubes in the second reactor system is DN10-DN50, preferably DN19-DN25, and the material flow velocity inside the tubes is 1m / s-6m / s, preferably 2-4m / s; the material of the heat exchange tubes is either Hastelloy or a nickel-based alloy. This configuration ensures that the pressure drop of the material in the heater is not too high, avoiding impact on the flow rate of the jet circulation loop and the vaporization rate of the material, and ensuring that the heater tubes are in a highly turbulent state and that there is no scaling during long-term operation.

[0070] In some embodiments, a pressure adjustment mechanism P2 is provided at the top of the thermal reactor D2, and the pressure inside the thermal reactor is adjusted in real time through the automatic action of the pressure adjustment mechanism P2; the pressure adjustment mechanism P2 can be selected from a throttling element with a pneumatic, electric or manual actuator; for example, the pressure adjustment mechanism P2 is an automatic pressure regulating valve or a manual valve connected to the exhaust pipeline of the thermal reactor.

[0071] The present invention also provides a method for preparing toluene diisocyanate using the above-described continuous photochemical reaction apparatus, comprising the following steps:

[0072] 1) Organic amines and phosgene are mixed in dynamic mixer M1 to carry out the first photochemical reaction, and the reacted material I enters the gas-liquid residence device D1;

[0073] 2) Material I undergoes gas-liquid separation in the gas-liquid residence device D1 to obtain liquid material II and gas material. The discharge pressure of the gas material is controlled by the pressure adjustment mechanism P1.

[0074] 3) The high-pressure liquid phase material II from the gas-liquid residence device D1 and the low-pressure material III from the thermal reactor D2 enter the ejector J1. The high-pressure liquid phase material II drives the ejector to mix with the low-pressure material III to form a high-speed material IV.

[0075] 4) Material IV from ejector J1 enters heater E1 for heating, and after heating, material V enters thermal reactor D2 for the second photochemical reaction.

[0076] 5) The product after the reaction in thermal reactor D2 is discharged and purified to obtain toluene diisocyanate.

[0077] In step 1) of this invention, the organic amine is selected from one or more of m-toluenediamine (MTDA), diphenylmethanediamine (MDA), polymethylene polyphenylene polyamine (PMDA), and hexamethylenediamine, and is particularly suitable for the phosgenation reaction of m-toluenediamine (MTDA). The organic amine is preferably m-toluenediamine. An inert solvent is used to mix with the organic amine. The inert solvent is selected from one or more of chlorinated aromatic hydrocarbons, dimethyl carbonate, diethyl carbonate, toluene, and xylene, and is preferably o-dichlorobenzene.

[0078] In a specific example, m-toluenediamine and o-dichlorobenzene are prepared into a mixed solution in a pipe mixer, and then introduced into a dynamic mixer M1 through the first amine inlet 1 and the second amine inlet 2. The mixing temperature of m-toluenediamine and o-dichlorobenzene is 55-100°C, preferably 65-85°C, and the feed pressure is 2.0-6.0 MPaG, preferably 3.0-5.0 MPaG. Controlling the mixing temperature of m-toluenediamine and o-dichlorobenzene is to ensure the complete dissolution of m-toluenediamine and prevent the solidification and precipitation of m-toluenediamine due to excessively low temperature from causing blockage in the feed pipe, mixer, and dynamic mixer. Controlling the feed pressure of m-toluenediamine and o-dichlorobenzene is mainly to ensure the pressure requirements of the reaction.

[0079] In a specific example, a mixed solution containing phosgene and ODCB is introduced into the dynamic mixer M1 through the third inlet 3; wherein the mixing temperature of phosgene and o-dichlorobenzene is 20-80°C, preferably 45-65°C, and the feed pressure is 1.5-4.5 MPaG, preferably 2.0-3.5 MPaG. The reaction process occurring in the first reactor system is a cold reaction; controlling the mixed solution of phosgene and ODCB can improve the cold reaction effect and phosgene concentration, thereby increasing the reaction yield. Controlling the feed pressure of the mixed solution of phosgene and ODCB mainly ensures the pressure requirements of the reaction.

[0080] In step 2) of the present invention, preferably, the gas-liquid residence device D1 controls the discharge pressure of the gas phase material to 1.0-4.0 MPaG, preferably 1.6-3.0 MPaG, through the pressure adjustment mechanism P1. This preferred pressure setting can further reduce the partial pressure of phosgene in the gas phase, prevent phosgene escape, and increase the concentration of phosgene in the liquid phase.

[0081] In step 4) of the present invention, preferably, the pressure of the second reactor system, thermal reactor D2, is controlled by pressure adjustment mechanism P2 to be 0.5-1.0 MPaG, more preferably 0.5-0.75 MPaG, and the reaction temperature is 145-185℃, more preferably 150-165℃. Setting the above temperature and pressure parameters in thermal reactor D2 ensures the conversion rate of hydrochloride and acyl chloride, preventing the formation of tar residue due to incomplete conversion of hydrochloride downstream, which would affect the reaction yield.

[0082] The present invention will be further described below with reference to embodiments and comparative examples. However, the present invention is not limited to the listed embodiments, but should also include equivalent improvements and modifications of the technical solutions defined in the appended claims of the present invention.

[0083] In the embodiments and comparative examples of the present invention, the inert solvent is preferably one or more of chloroaromatic hydrocarbons, dimethyl carbonate, diethyl carbonate, toluene, and xylene, and is more preferably o-dichlorobenzene;

[0084] The raw materials and measurement methods involved in the embodiments and comparative examples of the present invention are described below:

[0085] m-Toluenediamine (MTDA): Sourced from the TDI unit in Fujian Wanhua Industrial Park, an industrial product.

[0086] Phosgene: Sourced from the TDI unit in Fujian Wanhua Industrial Park; an industrial product.

[0087] o-Dichlorobenzene (ODCB): Purchased from Jiangsu Yangnong Chemical Co., Ltd., with a purity greater than 99.95 wt%, industrial grade.

[0088] Analytical method for tar residue content in reaction solution: Accurately weigh 2.0000 g (accurate to 0.0001 g) of the sample to be tested and 1.0000 g (accurate to 0.0001 g) of trichlorobenzene (TCB) into a 15 ml centrifuge tube, add dichloromethane to 12 ml, and perform quantitative analysis using gas chromatography with internal standard method (manufacturer: Agilent 8890). The chromatographic column is HP-5, the single injection volume is 0.4 μL, and the initial temperature of the column oven is 90℃. Then, the temperature is increased to 300℃ according to the program of 5℃ / min and held for 10 min. The detector type is FID detector.

[0089] The TDI reaction yield is calculated using the following formula: TDI reaction yield % = (∑TDI cumulative output / ∑MTDA cumulative feed amount * (122.2 / 174.2)) (The above data are all taken within 72 hours after the feed operation is stable. 122.2 is the molecular weight of MTDA and 174.2 is the molecular weight of TDI).

[0090]

Example 1

[0091] Reference Figure 1-2A mixed solution containing phosgene and ODCB (phosgene concentration 85 wt%) was introduced into dynamic mixer M1 through the third phosgene inlet 3 at 55°C and 3.5 MPaG. A mixed solution of m-toluenediamine (MTDA) and o-dichlorobenzene (ODCB) (amine concentration 25 wt%) was prepared in a pipeline mixer and introduced into dynamic mixer M1 through the first amine inlet 1 and the second amine inlet 2 at 80°C and 4.8 MPaG. After dispersion through ultrafine atomizing nozzles, it was mixed with the phosgene solution and reacted. The reaction mixture containing amine hydrochloride, acyl chloride, ODCB, HCl, and excess phosgene was transported from the discharge port of dynamic mixer M1 to gas-liquid separator D1 (gas-liquid residence equipment) via pipeline. The pressure of the cold reaction was set to 3.0 MPaG through the pressure regulating valve P1 on the gas phase pipeline of the gas-liquid separator. At this time, the corresponding cold reaction temperature was 133°C, and the phosgene concentration in the reaction solution was calculated to be 69 wt%.

[0092] The operating pressure of thermal reactor D2 is controlled to be 0.6 MPaG by pressure regulating valve P2. The high-pressure reaction liquid from the bottom of gas-liquid separator D1 is introduced into the drive side inlet of ejector J1 (throat diameter is 30 mm). The material of thermal reactor D2 is ejected into ejector J1 for mixing and acceleration, and then enters shell-and-tube heater E1. Heater E1 is heated to 160°C with 2.0 MPaG saturated steam. Amine hydrochloride continues to react with phosgene in the thermal reactor to convert into acyl chloride. After heating, acyl chloride decomposes to generate toluene diisocyanate and HCl.

[0093] The reaction liquid sample taken from the outlet of thermal reactor D2 was analyzed by gas chromatography and found to contain 1.8 wt% tar residue. After being pumped to a phosgene removal tower, a solvent removal tower, a tar removal tower, and a TDI refining tower for further distillation and purification, a toluene diisocyanate product with a purity of 99.99 wt% was obtained, and the TDI reaction yield was calculated to be 98.1%.

[0094] After industrial-scale testing, heater E1 underwent 180 days of continuous operation. During the overhaul, the equipment was disassembled and inspected, and no obvious coking or blockage problems were found in the heat exchange tubes.

[0095]

Example 2

[0096] A mixed solution containing phosgene and ODCB (phosgene concentration 83 wt%) was introduced into dynamic mixer M1 through the third inlet 3 at 55°C and 2.0 MPaG. A mixed solution of m-toluenediamine (MTDA) and o-dichlorobenzene (ODCB) (amine concentration 25 wt%) was prepared in a pipeline mixer and introduced into dynamic mixer M1 through the first amine inlet 1 and the second amine inlet 2 at 80°C and 3.0 MPaG. After dispersion through ultrafine atomizing nozzles, the mixture was mixed with the phosgene solution and reacted. The reaction mixture containing amine hydrochloride, acyl chloride, ODCB, HCl, and excess phosgene was transported from the discharge port of dynamic mixer M1 to gas-liquid separator D1 via pipeline. The pressure of the cold reaction was set to 1.6 MPaG through the pressure regulating valve P1 on the gas phase pipeline of the gas-liquid separator flash tank, corresponding to a cold reaction temperature of 95°C. The calculated phosgene concentration in the reaction solution was 49.1 wt%.

[0097] The operating pressure of the thermal reactor is controlled at 0.6 MPaG by the pressure regulating valve P2. The high-pressure reaction liquid from the bottom of the gas-liquid separator D1 is introduced into the drive side inlet of the ejector J1 (throat diameter is 60 mm). The material of the ejector thermal reactor D2 is introduced into the ejector for mixing and acceleration, and then enters the vertical shell-and-tube heater E1. The heater E1 is heated to 160°C with 2.0 MPaG saturated steam. The amine hydrochloride continues to react with phosgene in the thermal reactor to convert into acyl chloride. After heating, the acyl chloride decomposes to generate toluene diisocyanate and HCl.

[0098] The reaction liquid sample taken from the outlet of thermal reactor D2 was analyzed by gas chromatography and found to contain 3.8 wt% tar residue. After being pumped to a dephosgene tower, a desolventizing tower, a detarizing tower, and a TDI refining tower for further distillation and purification, a toluene diisocyanate product with a purity of 99.98 wt% was obtained, and the TDI reaction yield was calculated to be 95.9%.

[0099] After industrial-scale testing, heater E1 underwent 180 days of continuous operation. During the overhaul, the equipment was disassembled and inspected, and it was found that 11% of the heat exchange tubes had coking and blockage problems.

[0100]

Example 3

[0101] A mixed solution containing phosgene and ODCB (phosgene concentration 86 wt%) was introduced into dynamic mixer M1 through the third inlet 3 at 55°C and 2.5 MPaG. A mixed solution of m-toluenediamine (MTDA) and o-dichlorobenzene (ODCB) (amine concentration 23 wt%) was prepared in a pipeline mixer and introduced into dynamic mixer M1 through the first amine inlet 1 and the second amine inlet 2 at 80°C and 3.5 MPaG. After dispersion through ultrafine atomizing nozzles, the mixture was mixed with the phosgene solution and reacted. The reaction mixture containing amine hydrochloride, acyl chloride, ODCB, HCl, and excess phosgene was transported from the discharge port of dynamic mixer M1 to gas-liquid separator D1 via pipeline. The pressure of the cold reaction was set to 2.0 MPaG through the pressure regulating valve P1 on the gas phase pipeline of the gas-liquid separator, corresponding to a cold reaction temperature of 108°C. The calculated phosgene concentration in the reaction solution was 59.5 wt%.

[0102] The operating pressure of the thermal reactor is controlled at 0.6 MPaG by the pressure regulating valve P2. The high-pressure reaction liquid from the bottom of the gas-liquid separator D1 is introduced into the drive side inlet of the ejector (throat diameter of 45 mm). The material of the ejector thermal reactor D2 enters the ejector for mixing and acceleration, and then enters the vertical shell-and-tube heater E1. The heater E1 is heated to 160°C with 2.0 MPaG saturated steam. The amine hydrochloride continues to react with phosgene in the thermal reactor to convert into acyl chloride. After heating, the acyl chloride decomposes to generate toluene diisocyanate and HCl.

[0103] The reaction liquid sample taken from the outlet of thermal reactor D2 was analyzed by gas chromatography and found to contain 3.1 wt% tar residue. After being pumped to a phosgene removal tower, a solvent removal tower, a tar removal tower, and a TDI refining tower for further distillation and purification, a toluene diisocyanate product with a purity of 99.98 wt% was obtained, and the TDI reaction yield was calculated to be 96.6 wt%.

[0104] After industrial-scale testing, heater E1 underwent 180 days of continuous operation. During the overhaul, the equipment was disassembled and inspected, and it was found that 6% of the heat exchange tubes had coking and blockage problems.

[0105]

Example 4

[0106] A mixed solution containing phosgene and ODCB (phosgene concentration 85 wt%) was introduced into dynamic mixer M1 through the third inlet 3 at 55°C and 3.0 MPaG. A mixed solution of m-toluenediamine (MTDA) and o-dichlorobenzene (ODCB) (amine concentration 25 wt%) was prepared in a pipeline mixer and introduced into dynamic mixer M1 through the first amine inlet 1 and the second amine inlet 2 at 80°C and 4.0 MPaG. After dispersion through ultrafine atomizing nozzles, the mixture was mixed with the phosgene solution and reacted. The reaction mixture containing amine hydrochloride, acyl chloride, ODCB, HCl, and excess phosgene was transported from the discharge port of dynamic mixer M1 to gas-liquid separator D1 via pipeline. The pressure of the cold reaction was set to 2.5 MPaG through the pressure regulating valve P1 on the gas phase pipeline of the gas-liquid separator, corresponding to a cold reaction temperature of 124°C. The calculated phosgene concentration in the reaction solution was 64.8 wt%.

[0107] The operating pressure of the thermal reactor is controlled at 0.6 MPaG by the pressure regulating valve P2. The high-pressure reaction liquid from the bottom of the gas-liquid separator D1 is introduced into the drive side inlet of the ejector (throat diameter of 40 mm). The material of the ejector thermal reactor D2 enters the ejector for mixing and acceleration, and then enters the vertical shell-and-tube heater E1. The heater E1 is heated to 160°C with 2.0 MPaG saturated steam. The amine hydrochloride continues to react with phosgene in the thermal reactor to convert into acyl chloride. After heating, the acyl chloride decomposes to generate toluene diisocyanate and HCl.

[0108] The reaction liquid sample taken from the outlet of thermal reactor D2 was analyzed by gas chromatography and found to contain 2.3 wt% tar residue. After being pumped to a phosgene removal tower, a solvent removal tower, a tar removal tower, and a TDI refining tower for further distillation and purification, a toluene diisocyanate product with a purity of 99.99 wt% was obtained, and the TDI reaction yield was calculated to be 97.5%.

[0109] After industrial-scale testing, heater E1 underwent 180 days of continuous operation. During the overhaul, the equipment was disassembled and inspected, and it was found that only 2% of the heat exchange tubes had coking and blockage issues.

[0110]

Example 5

[0111] The difference from Example 1 is that the throat diameter of the injector (J1) is 80 mm. All other parameters remain the same.

[0112] The reaction liquid sample taken from the outlet of thermal reactor D2 was analyzed by gas chromatography and found to contain 4.5 wt% tar residue. After being pumped to a phosgene removal tower, a solvent removal tower, a tar removal tower, and a TDI refining tower for further distillation and purification, a toluene diisocyanate product with a purity of 99.99 wt% was obtained, and the TDI reaction yield was calculated to be 95.1%.

[0113] After industrial-scale testing, when heater E1 underwent 180 days of continuous operation, a major overhaul and disassembly inspection revealed that only 13% of the heat exchange tubes had coking and blockage issues.

[0114]

Example 6

[0115] The difference from Example 1 is that the pressure regulating valve P1 on the gas phase pipeline of the gas-liquid separator D1 is set to a cold reaction pressure of 2.0 MPaG, while all other parameters remain consistent, and the phosgene concentration in the reaction liquid is calculated to be 59.3 wt%. The operating pressure of the hot reactor is controlled at 0.6 MPaG by the pressure regulating valve P2. The high-pressure reaction liquid from the bottom of the gas-liquid separator D1 is introduced into the drive side inlet of the ejector (throat diameter of 30 mm), and the material from the ejector thermal reactor D2 is introduced into the ejector for mixing and acceleration before entering the shell-and-tube heater E1. The heater E1 is heated to 160°C with 2.0 MPaG saturated steam. The amine hydrochloride continues to react with phosgene in the hot reactor to convert into acyl chloride. After heating, the acyl chloride decomposes to generate toluene diisocyanate and HCl.

[0116] The reaction liquid sample taken from the outlet of thermal reactor D2 was analyzed by gas chromatography and found to contain 2.9 wt% tar residue. After being pumped to a phosgene removal tower, a solvent removal tower, a tar removal tower, and a TDI refining tower for further distillation and purification, a toluene diisocyanate product with a purity of 99.99 wt% was obtained, and the TDI reaction yield was calculated to be 97.1%.

[0117] After industrial-scale testing, heater E1 underwent 180 days of continuous operation. During the overhaul, the equipment was disassembled and inspected, and it was found that only 4% of the heat exchange tubes had coking and blockage issues.

[0118]

Example 7

[0119] The difference from Example 1 is that the pressure regulating valve P1 on the gas phase pipeline of the gas-liquid separator D1 is set to a cold reaction pressure of 1.0 MPaG, while all other parameters remain consistent, and the phosgene concentration in the reaction liquid is calculated to be 47.8 wt%. The operating pressure of the hot reactor is controlled to 0.6 MPaG by the pressure regulating valve P2. The high-pressure reaction liquid from the bottom of the gas-liquid separator D1 is introduced into the drive side inlet of the ejector (throat diameter of 30 mm), and the material from the ejector thermal reactor D2 is introduced into the ejector for mixing and acceleration before entering the shell-and-tube heater E1. The heater E1 is heated to 160°C with 2.0 MPaG saturated steam. The amine hydrochloride continues to react with phosgene in the hot reactor to convert into acyl chloride. After heating, the acyl chloride decomposes to generate toluene diisocyanate and HCl.

[0120] The reaction liquid sample taken from the outlet of thermal reactor D2 was analyzed by gas chromatography and found to contain 4.0 wt% tar residue. After being pumped to a phosgene removal tower, a solvent removal tower, a tar removal tower, and a TDI refining tower for further distillation and purification, a toluene diisocyanate product with a purity of 99.99 wt% was obtained, and the TDI reaction yield was calculated to be 95.5%.

[0121] After industrial-scale testing, heater E1 underwent 180 days of continuous operation. During the overhaul, the equipment was disassembled and inspected, and it was found that only 8% of the heat exchange tubes had coking and blockage issues.

[0122] Comparative Example 1

[0123] Using the dynamic mixer M1 described in Example 1, a mixed solution of phosgene and ODCB (phosgene concentration 85 wt%) was introduced into the dynamic mixer M1 through the third inlet 3 at 55°C and 2.5 MPaG. A mixed solution of m-toluene diamine (MTDA) and o-dichlorobenzene (ODCB) (amine concentration 25 wt%) was prepared in a pipe mixer and introduced into the dynamic mixer M1 through the first amine inlet 1 and the second amine inlet 2 at 80°C and 3.0 MPaG. The reaction mixture of amine hydrochloride, acyl chloride, ODCB, HCl, and excess phosgene generated by the reaction of MTDA and phosgene was piped to a conventional stirred thermal reactor. The pressure inside the thermal reactor was controlled at 0.65 MPaG, and the calculated phosgene concentration in the cold reaction liquid was 30.4 wt%. The reaction mixture was heated to 160°C by a steam heating coil built into the thermal reactor, where the amine hydrochloride and acyl chloride continued to decompose to produce toluene diisocyanate and HCl.

[0124] A sample taken from the hot reactor was analyzed by gas chromatography and found to contain 7.2 wt% tar residue. The residue was then pumped to a phosgene removal tower, a solvent removal tower, a tar removal tower, and a TDI refining tower for further distillation and purification to obtain a toluene diisocyanate product with a purity of 99.93 wt%. The calculated TDI reaction yield was 92.5 wt%.

[0125] After industrial-scale testing, the internal temperature of the hot reactor's built-in steam heating coils dropped from 160℃ to 135℃ after 180 days of continuous operation. The test was terminated, and the hot reactor was disassembled and inspected, revealing that 90% of the heat exchange coils had developed scaling and blockage issues.

[0126] Comparative Example 2

[0127] This comparative example uses an apparatus for producing toluene diisocyanate using a light solvent, as disclosed in patent CN202898275U. It employs the dynamic mixer M1 and raw material conditions described in Example 1. A mixed solution of phosgene and ODCB (phosgene concentration 85 wt%) is introduced into the dynamic mixer M1 through the third inlet 3 at 55°C and 2.5 MPaG. A mixed solution of m-toluenediamine (MTDA) and o-dichlorobenzene (ODCB) (amine concentration 25 wt%) is prepared in a pipe mixer and introduced into the dynamic mixer M1 through the first amine inlet 1 and the second amine inlet 2 at 80°C and 3.0 MPaG. The reaction mixture of amine hydrochloride, acyl chloride, ODCB, HCl, and excess phosgene generated from the reaction of MTDA and phosgene is transported via pipeline to the photochemical reaction tower. The pressure of the photochemical reaction tower is controlled at 1.2 MPaG, and the calculated phosgene concentration in the reaction solution is 43.8 wt%. The reaction mixture is heated to 165°C in the reaction tower by a forced circulation reboiler in the tower bottom, and then the amine hydrochloride and acyl chloride continue to decompose to produce toluene diisocyanate and HCl.

[0128] A sample taken from the bottom of the photochemical reaction tower was analyzed by gas chromatography and found to contain 5.5 wt% tar residue. The residue was then pumped to a phosgene removal tower, a solvent removal tower, a tar removal tower, and a TDI refining tower for further distillation and purification to obtain a toluene diisocyanate product with a purity of 99.95 wt%. The calculated TDI reaction yield was 94.3%.

[0129] After industrial-scale testing, the temperature of the photochemical reaction tower dropped from 165℃ to 140℃ after 180 days of continuous operation. The test was terminated, and the reaction tower was disassembled and inspected. It was found that 75% of the heat exchange tubes in the reboiler had coking and blockage problems.

[0130] Comparative Example 3

[0131] The difference from Example 1 is that the gas-liquid separator D1 does not use a pressure regulating mechanism P1, while all other parameters remain the same. In this comparative example, the operating pressure of the hot reactor is controlled at 0.6 MPaG by the pressure regulating valve P2. The gas phase from the gas-liquid separator D1 and the gas phase from the hot reactor merge and enter the subsequent exhaust condensation system. At this time, the corresponding cold reaction temperature is 86°C, and the calculated phosgene concentration in the reaction liquid is 30.1 wt%.

[0132] The high-pressure reaction liquid from the bottom of the gas-liquid separator D1 is introduced into the drive-side inlet of the ejector (throat diameter of 30mm). The material from the ejector thermal reactor D2 enters the ejector for mixing and acceleration before entering the shell-and-tube heater E1. Heater E1 is heated to 160°C with 2.0MPaG saturated steam. The amine hydrochloride continues to react with phosgene in the thermal reactor to convert into acyl chloride. After heating, the acyl chloride decomposes to generate toluene diisocyanate and HCl.

[0133] The reaction liquid sample taken from the outlet of thermal reactor D2 was analyzed by gas chromatography and found to contain 4.8 wt% tar residue. After being pumped to a phosgene removal tower, a solvent removal tower, a tar removal tower, and a TDI refining tower for further distillation and purification, a toluene diisocyanate product with a purity of 99.97 wt% was obtained, and the TDI reaction yield was calculated to be 95%.

[0134] After industrial-scale testing, and following 180 days of continuous operation, a major overhaul and disassembly inspection of the equipment revealed that only 18% of the heat exchange tubes had coking and blockage issues.

[0135] Table 1: Comparison of results between the examples and comparative examples

[0136]

[0137]

[0138] As can be seen from the data in Table 1, compared with Comparative Examples 1-3, Examples 1-7 of the present invention have lower tar residue content in the reaction solution and higher TDI reaction yield; it also shows that the implementation of the present invention can enable the isocyanate reaction heating system to obtain a longer operating cycle.

[0139] Furthermore, a comparison between Examples 1, 6, and 7 shows that by precisely controlling the pressure of the cold reaction through the gas-liquid residence device D1, the effective concentration of phosgene in the cold reaction liquid can be increased (the higher the pressure, the higher the phosgene concentration), ensuring the phosgene concentration required for further heating and decomposition of hydrochloride or acyl chloride hydrochloride to generate isocyanate. As a result, the tar residue content in the reaction liquid is lower, and the TDI reaction yield is higher.

[0140] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are within the spirit and scope of the present invention.

Claims

1. A continuous photochemical reactor apparatus, characterized by, The first reactor system and the second reactor system are connected by a pipeline; The first reactor system comprises: a dynamic mixer (M1) for providing a place for the organic amine to mix with the phosgene for the first photochemical reaction, and the reacted material (I) enters a gas-liquid residence device (D1); The gas-liquid residence device (D1) is used for gas-liquid separation of the material (I), and a liquid-phase material (II) and a gas-phase material are obtained, and a pressure adjusting mechanism (P1) is arranged at an exhaust area of the gas-liquid residence device (D1) for adjusting the pressure in the first reactor system; The second reactor system comprises: a thermal reactor (D2) for providing a place for the material inside to perform the second photochemical reaction; an ejector (J1) for receiving the high-pressure liquid-phase material (II) from the gas-liquid residence device (D1) and the low-pressure material (III) from the thermal reactor (D2), the high-pressure liquid-phase material (II) drives the low-pressure material (III) to mix to form a high-speed material (IV); a heater (E1) for receiving the material (IV) from the ejector (J1) and heating, and the heated material (V) enters the thermal reactor (D2) to perform the second photochemical reaction.

2. The continuous photochemical reactor apparatus of claim 1, wherein, The organic amine and the phosgene are separately fed into the dynamic mixer (M1), and the organic amine side feeding port and the phosgene feeding port are arranged respectively; The organic amine side feeding port is provided with superfine atomizing nozzles, and the organic amine is rapidly mixed with the phosgene through pressure drop at the nozzles.

3. The continuous photochemical reactor apparatus of claim 2, wherein, The organic amine side feeding port of the dynamic mixer (M1) comprises a first amine feeding port (1) and a second amine feeding port (2); The first amine feeding port (1) or the second amine feeding port (2) forms an angle of 45° with the central axis of the dynamic mixer (M1); The first amine feeding port (1) and the second amine feeding port (2) are both provided with superfine atomizing nozzles, and the size of the superfine atomizing nozzles is 2-30 mm.

4. The continuous photochemical reactor of claim 3, wherein, The size of the superfine atomizing nozzles is 3-7 mm.

5. The continuous photochemical reactor apparatus of claim 1, wherein, The gas-liquid residence device (D1) is selected from one of a kettle-type reactor, a tubular reactor or a gas-liquid separation flash tank; The pressure adjusting mechanism (P1) is arranged at the top of the gas-liquid residence device (D1), and the pressure adjusting mechanism (P1) is selected from a throttling element with a pneumatic, electric or manual actuator.

6. The continuous photochemical reactor apparatus of claim 5, wherein, The pressure adjusting mechanism (P1) is a pressure automatic regulating valve or a hand valve in communication with the exhaust pipeline of the gas-liquid residence device (D1).

7. The continuous photochemical reactor of claim 1, wherein, The ejector (J1) of the second reactor system is a Venturi mixer with a low-pressure material side feeding port, a high-pressure material side feeding port, a mixing chamber and an inner built-in necked throat, the material of the first reactor system enters the throat of the ejector from the high-pressure material side feeding port, and the material of the second reactor system enters from the low-pressure material side feeding port, and the two materials are mixed in the mixing chamber of the ejector; The ejector (J1) is sequentially provided with an inner built-in throat suction chamber, a tubular distributor, a mixing chamber and a diffusion chamber along the axial direction, and the material flows out from the outlet; one end of the suction chamber of the ejector (J1) is provided with a driving side material inlet, and the inner built-in throat of the suction chamber is provided with a suction side material inlet; The throat diameter of the ejector (J1) is 20-150 mm.

8. The continuous photochemical reactor apparatus of claim 7, wherein, The throat diameter of the ejector (J1) is 30-60 mm.

9. The continuous photochemical reactor of claim 1, wherein, The thermal reactor (D2) and the heater (E1) of the second reactor system are arranged in parallel in a vertical manner, and the heater (E1) is one of a tube-shell heat exchanger or a jacketed tube heat exchanger; The heater (E1) of the second reactor system has a tube row outer diameter of DN10-DN50 and a tube row inner material flow rate of 1-6 m / s, and the tube row material is any one of nickel-based alloys; A pressure adjusting mechanism (P2) is arranged at the top of the thermal reactor (D2), and the pressure adjusting mechanism (P2) is selected from a throttling element with a pneumatic, electric or manual actuator.

10. The continuous photochemical reactor apparatus of claim 9, wherein, The tube row material is a hastelloy alloy.

11. The continuous photochemical reactor apparatus of claim 9, wherein, The heater (E1) is a tube-shell heat exchanger. The heater (E1) of the second reactor system has a tube row outer diameter of DN19-DN25 and a tube row inner material flow rate of 2-4 m / s. The pressure adjusting mechanism (P2) is an automatic pressure regulating valve or a hand valve in communication with the exhaust pipeline of the thermal reactor.

12. Use of the continuous photochemical reaction device of any one of claims 1-11 in the preparation of toluene diisocyanate.

13. A process for the preparation of toluene diisocyanate using the continuous photochemical reactor according to any one of claims 1 to 11, characterized in that, The method comprises the following steps: 1) mixing the organic amine and the phosgene in the dynamic mixer (M1) to perform a first photochemical reaction, and the reacted material (I) enters the gas-liquid residence device (D1); 2) the material (I) is subjected to gas-liquid separation in the gas-liquid residence device (D1) to obtain a liquid phase material (II) and a gas phase material, and the discharge pressure of the gas phase material is controlled by the pressure adjusting mechanism (P1); 3) the high-pressure liquid phase material (II) of the gas-liquid residence device (D1) and the low-pressure material (III) from the thermal reactor (D2) enter the ejector (J1), the high-pressure liquid phase material (II) drives the low-pressure material (III) to mix to form a high-speed material (IV); 4) the material (IV) from the ejector (J1) enters the heater (E1) to be warmed, and the warmed material (V) enters the thermal reactor (D2) to perform a second photochemical reaction; 5) the product after the reaction of the thermal reactor (D2) is discharged and refined to obtain toluene diisocyanate product.

14. The method for preparing toluene diisocyanate according to claim 13, wherein in step 1), the organic amine and the inert solvent are prepared into a mixed solution in a pipeline mixer, and are introduced into the dynamic mixer (M1) from a first amine feeding port (1) and a second amine feeding port (2); wherein the mixed temperature of the organic amine and the inert solvent is 55-100°C, and the feeding pressure is 2.0-6.0 MPaG; and / or in step 1), the mixed solution containing phosgene and inert solvent is introduced into the dynamic mixer (M1) from a third phosgene feeding port (3); wherein the mixed temperature of the phosgene and the inert solvent is 20-80°C, and the feeding pressure is 1.5-4.5 MPaG; the organic amine is selected from one or more of m-toluene diamine, diphenylmethane diamine, polymethylene polyphenylene polyamine and hexamethylene diamine; and the inert solvent is selected from one or more of chlorinated aromatic hydrocarbon, dimethyl carbonate, diethyl carbonate, toluene and xylene. ​ 15. The process for the preparation of toluene diisocyanate as claimed in claim 14, wherein, The mixture temperature of the organic amine and the inert solvent is 65-85℃, and the feeding pressure is 3.0-5.0MPaG; and / or, The mixture temperature of the phosgene and the inert solvent is 45-65℃, and the feeding pressure is 2.0-3.5MPaG; The organic amine is m-toluenediamine, and the inert solvent is o-dichlorobenzene.

16. The process for the preparation of toluene diisocyanate as claimed in claim 13, wherein, The gas-liquid residence device (D1) throttles the discharge pressure of the gas-phase material to 1.0-4.0MPaG through the pressure adjusting mechanism (P1); and / or, The second reactor system thermal reactor (D2) controls the pressure of the thermal reactor to 0.5-1.0MPaG through the pressure adjusting mechanism (P2), and the reaction temperature is 145-185℃.

17. The process for the preparation of toluene diisocyanate as claimed in claim 16, wherein, The gas-liquid residence device (D1) throttles the discharge pressure of the gas-phase material to 1.6-3.0MPaG through the pressure adjusting mechanism (P1); and / or, The second reactor system thermal reactor (D2) controls the pressure of the thermal reactor to 0.5-0.75MPaG through the pressure adjusting mechanism (P2), and the reaction temperature is 150-165℃.

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