CN115155467B - System and method for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation - Google Patents
System and method for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation Download PDFInfo
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Abstract
The application discloses a system for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation, which comprises a bubble-tower pre-synthesis reactor, a bubble-tower curing reactor, a heat exchanger, a condenser and a flash evaporation container, wherein all the devices are correspondingly connected. The method for synthesizing hexamethylene diisocyanate comprises the steps of sequentially enabling a Hexamethylenediamine (HDA) stream and a phosgene stream subjected to heat exchange through a heat exchanger to pass through a bubble column pre-synthesis reactor and a bubble column curing reactor for reaction, condensing tail gas generated by the reaction through a condenser, and flash evaporating reactants obtained by the reaction through a flash evaporation container to obtain an HDI synthetic liquid, namely the hexamethylene diisocyanate synthetic liquid. Compared with the traditional kettle type liquid phase phosgene method, the method can remarkably improve the mass transfer and heat transfer effects, accelerate the reaction efficiency, improve the reaction conversion rate and improve the purity of the reaction liquid.
Description
Technical Field
The application relates to the field of hexamethylene diisocyanate preparation, in particular to a system and a method for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation.
Background
Hexamethylene Diisocyanate (HDI) is a high-end isocyanate product with increasing demand and has applications in the fields of automobiles, paints, military industry and the like. The current method for producing HDI mainly comprises a liquid-phase phosgene method and a gas-phase phosgene method, and a plurality of related documents are also available.
The gas-phase phosgene method is to gasify the corresponding medium-boiling point and low-boiling point amine, then mix the gasified amine with phosgene through a nozzle with a specific structure, then enter a reactor to perform rapid reaction at high temperature, quench the reaction product obtained after extremely short residence time, and finally perform a purification procedure to obtain the isocyanate product. The gas-phase phosgene method has the advantages of high yield, high yield and the like, and because the carbonized tar is easy to generate in the vaporization process of the amine and the polymerization product of the isocyanate and the amine, the equipment pipeline is blocked and needs to be cleaned periodically; too high temperature has severe requirements on equipment materials and has extremely high technical barriers; the defects cause that the gas-phase phosgene method is difficult to be widely applied, and the isocyanate commonly used for the gas-phase phosgene method synthesis in the industry at present only has few products such as TDI, MDI and the like.
The application relates to a method for synthesizing HDI based on a liquid phase phosgene method. Many reports and applications are related to the liquid phase phosgene method: patent CN101805272a provides a method for synthesizing isocyanate by interfacial phosgenation, which can reduce the influence of byproduct hydrogen chloride on the reaction, but ensures phosgene reflux under the micro negative pressure of the system, increases the load of a condenser, and does not solve the problem of low photochemical efficiency, so that the space-time conversion rate is not substantially improved. Patent CN103360282a provides a method for continuously synthesizing HDI, which uses serial kettle reactors to synthesize, and materials are conveyed between the reaction kettles through overflow, so that the utilization rate of phosgene is improved, but in order to reduce the influence of hydrogen chloride on the conversion rate and selectivity of the reaction, methylchlorosilane is used as a protective agent for protecting amino groups, so that the post-treatment is relatively complex, and the problem of low reaction efficiency still exists. Patent CN104755458A discloses a method for preparing isocyanate by reacting amine and phosgene in liquid phase, the method adopts mixing equipment, a high-pressure residence reactor is connected in series with a reaction tower, the amine and the phosgene are mixed in the mixing equipment in advance and then enter the residence reactor for high-pressure mixing reaction, and the obtained material enters the reaction tower for further reaction to obtain reaction liquid. The method focuses on solving the problem of high separation cost of synthesis tail gas, and is less related to the synthesis of isocyanate.
Traditional kettle type liquid phase phosgene method back mixing is serious, the contact probability of byproduct hydrogen chloride and raw material amine is high, so that a large amount of amine hydrochloride is generated, serious negative influence is caused on reaction efficiency, chlorinated impurities are also generated due to overlong contact time of hydrogen chloride and isocyanate at high temperature, product yield is reduced, and the mass transfer heat exchange requirement of reaction is difficult to meet due to overlarge material viscosity through mechanical stirring, so that local high temperature and impurity enrichment are caused. Therefore, the traditional kettle type liquid phase phosgene method has the defects of low reaction conversion rate, low reaction efficiency, poor mass and heat transfer effect and the like.
Disclosure of Invention
The application provides a system and a method for synthesizing hexamethylene diisocyanate by adopting liquid-phase phosgenation, which solve the problems of poor mass and heat transfer effect, high reaction efficiency and reaction conversion rate and low purity of reaction liquid in the kettle-type liquid-phase phosgene method in the prior art.
In order to solve the technical problems, the application provides a system for synthesizing hexamethylene diisocyanate by liquid phase phosgenation, which comprises:
the device comprises a heat exchanger, a bubble column pre-synthesis reactor, a bubble column curing reactor, a condenser and a flash evaporation container;
the flash evaporation container is provided with a synthetic liquid outlet, one side of the lower part of the bubble tower type curing reactor is communicated with a gas phase feed inlet, a discharge port of the heat exchanger is communicated with a liquid phase feed pipe at the bottom of the bubble tower type pre-synthesis reactor, a first liquid phase discharge port at one side of the upper part of the bubble tower type pre-synthesis reactor is communicated with a liquid phase feed inlet at one side of the upper part of the bubble tower type curing reactor, a second liquid phase discharge port at the bottom of the bubble tower type curing reactor is communicated with a feed inlet of the flash evaporation container, a first gas phase discharge port at the top of the bubble tower type pre-synthesis reactor and a second gas phase discharge port at the top of the bubble tower type curing reactor are communicated with a tail gas inlet of the condenser, a reflux port of the condenser is communicated with a reflux port at one side of the upper part of the bubble tower type curing reactor, and a mixed liquid outlet on the flash evaporation container are communicated with a gas conveying pipeline.
Preferably, the bubble column pre-synthesis reactor comprises a first tower body, a first gas phase discharge port is communicated with the top of the first tower body, a liquid phase feed pipe is communicated with the bottom of the first tower body, an annular gas phase feed pipe is communicated with the bottom of the first tower body, the first liquid phase discharge port is communicated with one side of the upper part of the first tower body, a first liquid catcher is arranged at the top of the inner side of the first tower body, a plurality of hollow gas lift pipes are axially arranged in the first tower body, diffusion holes are formed in the upper end of each hollow gas lift pipe, a disc feeder communicated with the liquid phase feed pipe and the annular gas phase feed pipe is arranged at the bottom of the inner side of the tower body, a baffle plate between the disc feeder and the hollow gas lift pipes is arranged at the inner side of the first tower body, and a jacket under the tower body are sequentially arranged on the outer side wall of the first tower body from top to bottom.
Preferably, the bubble column curing reactor comprises a second tower body, a second gas phase discharge port is communicated with the top of the second tower body, a liquid phase feed port is communicated with one side of the upper portion of the second tower body, a second liquid phase discharge port is communicated with the bottom of the second tower body, a gas phase feed port is communicated with one side of the lower portion of the second tower body, a second liquid catcher is arranged at the top of the inner side of the second tower body, a tower jacket is arranged on the outer side wall of the second tower body, an eccentric airlift tube is axially arranged in the second tower body, and a plurality of annular packing plates are arranged in the second tower body.
Preferably, the upper part of the first tower body is also provided with a first expansion section.
Preferably, the upper part of the second tower body is also provided with a second expansion section.
Preferably, the upper surface of the disc feeder is provided with 3-10 concentric annular gas phase feeding holes communicated with the annular gas phase feeding pipe and a single liquid phase feeding hole communicated with the liquid phase feeding pipe, and the horizontal position of the liquid phase feeding hole is lower than that of the concentric annular gas phase feeding hole.
Preferably, the number of the hollow airlift pipes is 6, and the 6 hollow airlift pipes are arranged in a regular hexagon along the axial direction of the first tower body.
In order to solve the above technical problems, the present application also provides a method for synthesizing hexamethylene diisocyanate by liquid phase phosgenation, corresponding to the system for synthesizing hexamethylene diisocyanate by liquid phase phosgenation, which comprises:
adding a solvent of hexamethylenediamine solution into a bubble column pre-synthesis reactor;
introducing a phosgene stream into the disc feeder through an annular gas-phase feeding pipe, wherein the phosgene stream enters the bubble-column pre-synthesis reactor through a gas-phase feeding hole and diffuses upwards along a hollow airlift pipe;
feeding the HDA stream subjected to heat exchange by a heat exchanger into a disc feeder through a liquid phase feeding pipe, enabling the HDA stream to enter a bubble-column pre-synthesis reactor through a liquid phase feeding hole, and enabling the HDA stream to be upwardly diffused along the hollow airlift pipe to be in contact reaction with the phosgene stream so as to obtain a mixture;
introducing phosgene into the bubble tower curing reactor through a gas phase feed inlet, and enabling the mixture to enter the bubble tower curing reactor to contact and react with the phosgene after sequentially passing through a first liquid phase discharge port and a liquid phase feed inlet to obtain a reactant;
the reactant is discharged out of the bubble tower curing reactor through a second liquid phase discharge port and enters a flash evaporation container for flash evaporation, so that hexamethylene diisocyanate and a gas-liquid mixture are obtained;
and tail gas generated in the reaction process of the bubble-column pre-synthesis reactor and the bubble-column curing reactor respectively enters a condenser through a first gas phase discharge port and a second gas phase discharge port, the condensed solvent and phosgene mixture are refluxed to the bubble-column curing reactor for reuse, and uncondensed gas and the gas-liquid mixture enter a gas conveying pipeline.
Preferably, the solvent of the hexamethylenediamine solution is any one of chlorobenzene, dichlorobenzene and xylene.
Preferably, the HDA stream is a mixed stream of hexamethylenediamine and a solvent, wherein the mass concentration of hexamethylenediamine is 5-15%.
Compared with the prior art, the system for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation provided by the application comprises a bubble-tower pre-synthesis reactor, a bubble-tower curing reactor, a heat exchanger, a condenser and a flash evaporation container, and all the devices are correspondingly connected. The method for synthesizing hexamethylene diisocyanate comprises the steps of sequentially enabling a Hexamethylenediamine (HDA) stream and a phosgene stream subjected to heat exchange through a heat exchanger to pass through a bubble column pre-synthesis reactor and a bubble column curing reactor for reaction, condensing tail gas generated by the reaction through a condenser, and flash evaporating reactants obtained by the reaction through a flash evaporation container to obtain an HDI synthetic liquid, namely the hexamethylene diisocyanate synthetic liquid. Compared with the traditional kettle type liquid phase phosgene method, the method can remarkably improve the mass transfer and heat transfer effects, accelerate the reaction efficiency, improve the reaction conversion rate and improve the purity of the reaction liquid.
Drawings
For a clearer description of the technical solutions of the present application, the drawings that are required to be used in the embodiments will be briefly described, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without making any effort.
FIG. 1 is a schematic diagram of a system for synthesizing hexamethylene diisocyanate by liquid phase phosgenation according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a bubble column pre-synthesis reactor according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a bubble column maturation reactor according to an embodiment of the present application;
FIG. 4 is a schematic view of a disc feeder according to an embodiment of the present application;
FIG. 5 is a schematic view of the position structure of a circular feeder and a hollow airlift pipe according to an embodiment of the present application;
in the figure: 1. a heat exchanger; 02. a bubble column pre-synthesis reactor; 2. a first tower; 2-1, a first liquid trap; 2-3, a jacket is arranged on the tower body; 2-4, a first expansion section; 2-5, a first liquid phase discharge port; 2-6, a hollow airlift pipe; 20-2, diffusion holes; 2-7, a lower jacket of the tower body; 2-8, a disc feeder; 2-81, gas phase feed holes; 2-82, liquid phase feeding holes; 2-9, baffle plates; 2-10, a liquid phase feeding pipe; 2-11, annular gas phase feeding pipe; 2-12, a first gas phase discharge port; 03. a bubble column maturation reactor; 3. a second tower; 3-1, a second gas-phase discharge port; 3-2, a second liquid catcher; 3-3, a liquid phase feed inlet; 3-4, a tower jacket; 3-5, an eccentric airlift pipe; 3-6, a second liquid phase discharge port; 3-7, a gas phase feed inlet; 3-8, a second expansion section; 3-9, annular packing plates; 4. a condenser; 5. a flash vessel; 6. a gas delivery conduit.
Detailed Description
In order to enable those skilled in the art to better understand the technical solutions of the present application, the following description will make clear and complete descriptions of the technical solutions of the embodiments of the present application with reference to the accompanying drawings.
The core of the application is to provide a system and a method for synthesizing hexamethylene diisocyanate by adopting liquid-phase phosgenation, which can solve the problems of poor mass and heat transfer effect, high reaction efficiency, high reaction conversion rate and low purity of reaction liquid in the kettle-type liquid-phase phosgene method in the prior art.
Fig. 1 is a schematic diagram of a system for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation according to an embodiment of the present application, fig. 2 is a schematic diagram of a bubble-column pre-synthesis reactor according to an embodiment of the present application, fig. 3 is a schematic diagram of a bubble-column curing reactor according to an embodiment of the present application, fig. 4 is a schematic diagram of a disk feeder according to an embodiment of the present application, and fig. 5 is a schematic diagram of a position structure of a disk feeder and a hollow airlift tube according to an embodiment of the present application, as shown in fig. 1 to 5.
A system for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation comprises a heat exchanger 1, a bubble column pre-synthesis reactor 02, a bubble column curing reactor 03, a condenser 4 and a flash evaporation container 5; the height to diameter ratio of the bubble column pre-synthesis reactor 02 is 5 to 12, preferably 5 to 8. The height to diameter ratio of the bubble column curing reactor 03 is 8 to 20, preferably 8 to 12.
The flash evaporation vessel 5 is provided with a synthetic liquid outlet, the finally prepared hexamethylene diisocyanate synthetic liquid is discharged from the synthetic liquid outlet, one side of the lower part of the bubbling tower curing reactor 03 is communicated with a gas phase feed port 3-7, the gas phase feed port 3-7 is used for reacting with mixed materials in the bubbling tower curing reactor 03 through phosgene, a discharge port of the heat exchanger 1 is communicated with a liquid phase feed pipe 2-10 at the bottom of the bubbling tower pre-synthesis reactor 02, the heat exchanger 1 is used for exchanging heat of an HDA stream, the heat exchanged HDA stream enters the bubbling tower pre-synthesis reactor 02 through the liquid phase feed pipe 2-10, the HDA stream is actually a mixed stream of hexamethylenediamine and a solvent, and the solvent is any one of chlorobenzene, dichlorobenzene and dimethylbenzene. The first liquid phase discharge port 2-5 on the upper side of the bubble column pre-synthesis reactor 02 is communicated with the liquid phase feed port 3-3 on the upper side of the bubble column curing reactor 03, and the mixture after reaction in the bubble column pre-synthesis reactor 02 enters the bubble column curing reactor 03 through the liquid phase feed port 3-3 after coming out of the first liquid phase discharge port 2-5 and reacts with phosgene in the bubble column curing reactor 03 to obtain a reactant. The second liquid phase discharge port 3-6 at the bottom of the bubble tower curing reactor 03 is communicated with the feed port of the flash evaporation vessel 5, and after the reactant is subjected to flash evaporation treatment in the flash evaporation vessel 5, the HDI synthetic liquid, namely the hexamethylene diisocyanate synthetic liquid, can be obtained. The first gas phase discharge port 2-12 at the top of the bubble column pre-synthesis reactor 02 and the second gas phase discharge port 3-1 at the top of the bubble column curing reactor 03 are both communicated with the tail gas inlet of the condenser 4, the reflux port of the condenser 4 is communicated with the reflux port at one side of the upper part of the bubble column curing reactor 03, and the discharge port of the condenser 4 and the mixed liquid outlet on the flash evaporation container 5 are both communicated with the gas conveying pipeline 6.
In this embodiment, a system for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation, a bubble column pre-synthesis reactor 02 comprises a first column body 2, a first gas-phase discharge port 2-12 is communicated with and arranged at the top of the first column body 2, a liquid-phase feed pipe 2-10 is communicated with and arranged at the bottom of the first column body 2, an annular gas-phase feed pipe 2-11 is communicated with and arranged at the bottom of the first column body 2, a first liquid-phase discharge port 2-5 is communicated with and arranged at one side of the upper part of the first column body 2, a first liquid catcher 2-1 is arranged at the top of the inner side of the first column body 2, and the effect of preventing gas-liquid entrained materials from being flooded into a tail gas pipeline is achieved, so that liquid returns into the first column body 2. A plurality of hollow airlift pipes 2-6 are axially arranged in the first tower body 2, diffusion holes 20-2 are formed in the upper ends of the hollow airlift pipes 2-6, a disc feeder 2-8 communicated with a liquid phase feeding pipe 2-10 and an annular gas phase feeding pipe 2-11 is arranged at the bottom of the inner side of the tower body 2, and the ratio of the diameter of the upper surface of the disc feeder 2-8 to the diameter of the tower of the first tower body 2 is 1:1.2 to 4, preferably 1:1.5 to 2.5.
The disk feeders 2-8 function as: 1) The feeding gas is distributed in a ring shape, so that uneven gas distribution in the bubble-column pre-synthesis reactor 02 is avoided. 2) The turbulence degree of the middle-bottom section of the bubbling tower type pre-synthesis reactor 02 is increased, and the mass transfer effect is enhanced. 3) Is linked with the airlift pipe. The inside of the first tower body 2 is provided with a baffle plate 2-9 positioned between the disc feeder 2-8 and the hollow airlift pipe 2-6, and the outer side wall of the first tower body 2 is sequentially provided with a tower body upper jacket 2-3 and a tower body lower jacket 2-7 from top to bottom.
Preferably, a first expansion section 2-4 is also provided in the upper part of the first tower body 2. The first expansion section 2-4 is actually a part of the first tower body 2, and the main difference is that the radial length of the first expansion section 2-4 is slightly longer than the radial length of the middle section of the first tower body 2. The main functions of the first expansion section 2-4 are as follows: 1) The turbulence degree of gas and liquid above the bubbling tower type pre-synthesis reactor 02 is reduced; 2) The solvent trapped by the first liquid trap 2-1 is sprayed downwards to be in countercurrent contact with the ascending gas-liquid mixture, so that the contact area of the solvent and the ascending gas-liquid mixture is increased by the bubble-column pre-synthesis reactor 02, and the mass transfer and heat exchange effects are facilitated.
Preferably, the upper surface of the disc feeder 2-8 is provided with 3-10 concentric annular gas phase feeding holes 2-81 communicated with the annular gas phase feeding pipe 2-11 and a single liquid phase feeding hole 2-82 communicated with the liquid phase feeding pipe 2-10, and the horizontal position of the liquid phase feeding hole 2-82 is lower than that of the concentric annular gas phase feeding hole 2-81. The radial surface area of the liquid phase feeding holes 2-82 is always larger than the sum of the radial surface areas of all the gas phase feeding holes 2-81, and the latter accounts for 20% -60% of the former.
Preferably, the number of the hollow airlift pipes 2-6 is 6, and the 6 hollow airlift pipes 2-6 are arranged in a regular hexagon along the axial direction of the first tower body 2. The ratio of the single pipe diameter of one hollow airlift pipe 2-6 to the tower diameter of the first tower body 2 is 1:3.5 to 8, preferably 1:4 to 5; the ratio of the single eccentric airlift pipe positioned on the tower body F to the tower diameter of the tower F is 1:1.5-5, preferably 1:2 to 3. The upper ends of the six hollow airlift pipes 2-6 are provided with a plurality of uniformly dispersed diffusion holes 20-2, the aperture ratio is 30% -80%, and the shape of the diffusion holes 20-2 can be one or more of a circle, an ellipse and a polygon; the axial length of the open hole area accounts for 5% -15% of the total length of the hollow airlift pipe 2-6.
In this embodiment, a system for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation, a bubble tower curing reactor 03 comprises a second tower body 3, a second gas-phase discharge port 3-1 is communicated with and arranged at the top of the second tower body 3, a liquid-phase feed port 3-3 is communicated with and arranged at one side of the upper part of the second tower body 3, a second liquid-phase discharge port 3-6 is communicated and arranged at the bottom of the second tower body 3, a gas-phase feed port 3-7 is communicated and arranged at one side of the lower part of the second tower body 3, a second liquid catcher 3-2 is arranged at the top of the inner side of the second tower body 3, a tower jacket 3-4 is arranged at the outer side wall of the second tower body 3, an eccentric gas lift pipe 3-5 is axially arranged in the second tower body 3, and the eccentric moment of the eccentric gas lift pipe 3-5 relative to the second tower body 3 is 0.1R-0.5R and is close to the gas-phase feed port 3-7 at the lower part of the second tower body 3.
A plurality of annular packing plates 3-9 are arranged in the second tower body 3. Preferably, the upper part of the second tower body 3 is also provided with a second expansion section 3-8. The structure and principle of the second expansion section 3-8 are described above with respect to the first expansion section 2-4. The structure and principle of the second liquid trap 3-2 are described above with reference to the first liquid trap 2-1. The annular packing plates 3-9 are horizontally arranged in the second tower body 3, the annular packing plates 3-9 are distributed along the second tower body 3 from top to bottom, 2-6 layers of packing layers are formed, and ceramic saddle rings or ceramic iso-saddle ring packing is adopted. The total height of all the annular packing plates 3-9 accounts for 20% -50% of the height of the second tower body 3.
The application provides a system for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation, which comprises a bubble-tower pre-synthesis reactor, a bubble-tower curing reactor, a heat exchanger, a condenser and a flash evaporation container, wherein all the devices are correspondingly connected. Compared with the traditional kettle type liquid phase phosgene method, the method can remarkably improve mass transfer and heat transfer effects, accelerate reaction efficiency, improve reaction conversion rate and improve purity of reaction liquid.
The above description has been made in detail about an embodiment of a system for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation, and the embodiment of the present application also provides a method for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation corresponding to the above embodiment. Since the embodiments of the system portion and the embodiments of the method portion correspond to each other, the embodiments of the method portion are described with reference to the embodiments of the system portion, and are not described herein.
A method for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation, the system for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation according to any one of the embodiments, comprising the steps of:
s1: a solvent for the hexamethylenediamine solution was added to the bubble column pre-synthesis reactor.
The method comprises the steps that a first tower body of a bubble tower pre-synthesis reactor is filled or semi-filled with a solvent of hexamethylenediamine solution before raw material feeding, wherein the solvent is any one of chlorobenzene, dichlorobenzene and dimethylbenzene; and exchanging heat of the materials in the first tower body to 50-85 ℃ through the upper tower body jacket and the lower tower body jacket outside the first tower body.
S2: and introducing a phosgene stream a into the disc feeder through the annular gas-phase feeding pipe, and allowing the phosgene stream a to enter the bubble-column type pre-synthesis reactor through the gas-phase feeding hole and diffuse upwards along the hollow airlift pipe.
S3: and (3) adding the HDA stream b subjected to heat exchange by the heat exchanger into a disc feeder through a liquid phase feeding pipe, enabling the HDA stream b to enter a bubble column type pre-synthesis reactor through a liquid phase feeding hole, and enabling the HDA stream b to be upwardly diffused along a hollow airlift to contact and react with the photo-air stream a to obtain a mixture c.
In the embodiment of the application, the HDA flow b is a mixed flow of hexamethylenediamine and a solvent, wherein the mass concentration of the hexamethylenediamine is 5-15%. The solvent is as above. The heat of the HDA stream b is exchanged by a heat exchanger before feeding, and the feeding temperature of the HDA stream b after heat exchange is 20-65 ℃, preferably 30-45 ℃. The molar feed of phosgene stream a is 1.2 to 3 times, preferably 1.5 to 2.0 times, the molar feed of HDA stream b. The photo-stream a enters the bubble column pre-synthesis reactor prior to the HDA stream b. The concentration of phosgene stream a in the liquid phase decreases from bottom to top in the first column and the vast majority of phosgene stream a is present in pure liquid form in the lower portion of the first column. The mixture c after reaction in the first tower body is a gas-liquid-solid mixture, wherein the solid content is between 5.0% and 50%.
S4: and (3) introducing phosgene d into the bubble tower curing reactor through a gas phase feed inlet, and enabling the mixture c to enter the bubble tower curing reactor to contact and react with the phosgene d after sequentially passing through a first liquid phase discharge port and a liquid phase feed inlet to obtain a reactant e. The column is filled with solvent before mixture c enters the second column, the solvent being consistent with the solvent filled in the first column. The temperature of the materials in the second tower body is 100-180 ℃. The molar amount of phosgene d fed is 3 to 8 times, preferably 4 to 6 times, the molar amount of HDA stream b fed.
S5: and the reactant e is discharged out of the bubble tower curing reactor through a second liquid phase discharge port and enters a flash evaporation container for flash evaporation, so that an HDI synthetic liquid f and a gas-liquid mixture g are obtained. The operating pressure of the first tower body and the second tower body is respectively selected to be 0.09 Mpa-0.2 Mpa. The operating pressure of the flash vessel is selected to be 0.06Mpa to 0.12Mpa. The gas-liquid mixture g after flash evaporation is a mixed flow containing phosgene, hydrogen chloride, a small amount of solvent and other organic matters; the flash evaporation of the HDI synthetic solution f is a mixed flow containing hexamethylene diisocyanate, solvent, phosgene, hydrogen chloride and a small amount of other organic matters, and the purity of the hexamethylene diisocyanate in the HDI synthetic solution f is more than 96 percent.
S6: the tail gas h generated in the reaction process of the bubble-column pre-synthesis reactor and the bubble-column curing reactor respectively enters a condenser through a first gas phase discharge port and a second gas phase discharge port, the condensed solvent and phosgene mixture i flow back to the bubble-column curing reactor for reuse, and the uncondensed gas j and the gas-liquid mixture g enter a gas conveying pipeline and are required to be separated and recovered in the later stage. The uncondensed gases j are mainly hydrogen chloride, phosgene, small amounts of acidic organic substances.
Example 1
This example is a procedure for the synthesis of hexamethylene diisocyanate using the system provided by the present application. The height-diameter ratio of the bubble column type pre-synthesis reactor 02 is 6; the height-to-diameter ratio of the bubble column curing reactor 03 is 12; six hollow airlift pipes 2-6 positioned on the first tower body 2 are arranged in a regular hexagon along the axial direction, and the ratio of the diameter of a single pipe to the diameter of the first tower body 2 is 1:4, the upper ends of the six hollow airlift pipes 2-6 are provided with round uniformly dispersed diffusion holes 20-2, the aperture ratio is 60%, and the axial length of the aperture area accounts for 13% of the total length of the hollow airlift pipes 2-6; the ratio of the single eccentric airlift pipe 3-5 positioned on the second tower body 3 to the tower diameter of the second tower body 3 is 1:2, eccentric moment 0.2R; the ratio of the diameter R of the upper surface of the disk feeders 2-8 to the diameter of the first tower body 2 is 1:1.8; the circular gas phase feeding holes 2-81 on the disc feeder 2-8 are 8 in number; the horizontal multistage annular packing plates 3-9 positioned on the second tower body 3 are distributed from top to bottom along the second tower body 3, 5 layers of packing layers are adopted, ceramic saddle ring packing is adopted, and the total height of the packing layers is 40% of the height of the second tower body 3; the first tower body 2 is provided with a circular baffle plate positioned between the disc feeders 2 to 8 and the hollow airlift pipes 2 to 6. The gas phase space of the first tower body 2 keeps micro-positive pressure of 0.12Mpa, and the gas phase space of the second tower body 3 keeps micro-negative pressure of 0.095Mpa.
Introducing nitrogen into a system in advance to purge air and moisture in the system, filling o-dichlorobenzene (liquid) serving as a solvent into a bubbling tower type pre-synthesis reactor 02 to a liquid level of 30%, after the heat exchange temperature is stable, the temperature of the solvent in the tower is up to 60 ℃, starting phosgene feeding, the feeding flow is 15.3kg/h, starting to enter a hexamethylenediamine flow (HDA flow b) when stable and uniform bubbling occurs on the liquid level of the solvent, exchanging heat of the prepared 10% hexamethylenediamine-o-dichlorobenzene solution to 35 ℃ through a heat exchanger 1, feeding the solution through a liquid phase feeding pipe 2-10, wherein the feeding flow is 117.3kg/h, and at the moment, the system starts to release a large amount of heat, removing heat through heat exchange of a jacket 2-3 on the tower body outside the first tower body 2 and a jacket 2-7 of the hexamethylenediamine flow and the solvent, so that the system temperature is in a relatively constant state, and starting to feed into a bubbling tower type curing reactor 03 after continuously feeding the liquid level in the first tower body 2 to the liquid phase feeding port 3-3; at this time, the second tower 3 is filled with solvent o-dichlorobenzene to 80% liquid level, the solvent o-dichlorobenzene is over the uppermost annular packing plate 3-9, phosgene is stably fed through the second liquid phase discharge port 3-6 below the second tower 3, the feeding flow is 49kg/h, strong bubbling is formed above the liquid level, the second tower 3 is subjected to heat exchange through the tower jacket 3-4 to the internal material temperature of 140 ℃, the mixture c on the first tower 2, which is discharged through the first liquid phase discharge port 2-5, is a uniform and fine white emulsion, after continuous feeding and replacement of the solvent filled in advance in the second tower 3, a material flow, namely a reactant e, is output from the second liquid phase discharge port 3-6 at the bottom of the second tower 3, the material flow is subjected to phase separation under the pressure of 0.06 through the flash evaporation container 5, a small amount of undegraded carbamoyl chloride is promoted to be decomposed, and finally the material flow, namely the synthesis liquid of the HDI synthesis liquid f is a clear and light color liquid is obtained. The purity of HDI was 97.5% by gas chromatography.
Example 2
This example is used to describe the flow of the system provided by the application for synthesizing hexamethylene diisocyanate. The ratio of the height to the diameter of the bubble column pre-synthesis reactor 02 is 5.5; the height-to-diameter ratio of the bubble column curing reactor 03 is 10; six hollow airlift pipes 2-6 positioned on the first tower body 2 are arranged in a regular hexagon along the axial direction, and the ratio of the diameter of a single pipe to the diameter of the first tower body 2 is 1:4.5, the upper ends of the six hollow gas lift pipes 2-6 are provided with round uniformly dispersed diffusion holes 20-2, the aperture ratio is 45%, and the axial length of the aperture area accounts for 15% of the total length of the hollow gas lift pipes 2-6; the ratio of the single eccentric airlift pipe 3-5 positioned on the second tower body 3 to the tower diameter of the second tower body 3 is 1:2.5, eccentric moment 0.3R; the ratio of the diameter R of the upper surface of the disk feeders 2-8 to the diameter of the first tower body 2 is 1:1.5; 2-81 annular gas phase feeding holes on the disc feeder 2-8 are 6; the horizontal multistage annular packing plates 3-9 positioned on the second tower body 3 are distributed from top to bottom along the second tower body 3, 6 layers of packing layers are adopted, ceramic saddle ring packing is adopted, and the total height of the packing layers is 60% of the height of the second tower body 3; the first tower 2 is provided with a circular baffle located between the disc feeders 2-8 and the hollow airlift pipes 2-6. The gas phase space of the first tower body 2 keeps micro-positive pressure of 0.18Mpa, and the gas phase space of the second tower body 3 keeps micro-positive pressure of 0.013Mpa.
Introducing nitrogen into a system in advance to purge air and moisture in the system, filling solvent chlorobenzene to 30% liquid level in a bubble column pre-synthesis reactor 02 in advance, removing heat through heat exchange of circulating water of an upper jacket 2-3 of a column body and a lower jacket 2-7 of the column body and the hexamethylenediamine stream with the temperature of the system being in a relatively constant state after the temperature of the solvent in the column is stabilized to 70 ℃, starting phosgene feeding, starting to enter the hexamethylenediamine stream when the liquid level of the solvent is stabilized and uniformly bubbled, exchanging heat of the prepared 8% hexamethylenediamine-chlorobenzene solution to 40 ℃ through a heat exchanger 1, feeding through a liquid phase feeding pipe 2-10, and starting to feed into a tower curing reactor 03 after the liquid level in the first column body 2 is continuously fed to a liquid phase feeding port 3-3, wherein the system starts to release a large amount of heat; at this time, the second tower body 3 is filled with solvent chlorobenzene to 80% liquid level, the solvent chlorobenzene is stably fed through the second liquid phase discharge port 3-6 below the second tower body 3, the feeding flow is 49kg/h, strong bubbling is formed above the liquid level, the second tower body 3 exchanges heat to the internal material temperature of 135 ℃ through the tower jacket 3-4, the mixture c on the first tower body 2 through the outlet of the first liquid phase discharge port 2-5 is uniform and fine white emulsion, after continuous feeding and replacement of the solvent filled in advance in the second tower body 3, a material flow, namely a reactant e, is output from the second liquid phase discharge port 3-6 at the bottom of the second tower body 3, the material flow is subjected to phase separation under the pressure of 0.06Mpa through the flash evaporation container 5, a small amount of undegraded carbamoyl chloride is promoted to be decomposed, and finally the material flow, namely the synthesis liquid of the HDI synthesis liquid f is clear and light yellow liquid is obtained. The purity of HDI was 98.6% by gas chromatography.
Comparative example 1
The hexamethylene diisocyanate is prepared by adopting a traditional kettle type phosgene method. Adding 5kg of primer solvent chlorobenzene into a reaction kettle, cooling to 5 ℃, preparing hexamethylenediamine-chlorobenzene solution with mass fraction of 15%, opening the kettle for stirring, simultaneously feeding an amine stream and a phosgene stream into the reaction kettle, wherein the feeding flow rates of the amine stream and the phosgene stream are respectively 20kg/h and 3.5kg/h, the jacket heat exchange ensures that the reaction temperature is 5-15 ℃, and after the cold reaction, feeding the materials into a high-temperature reaction kettle to raise the temperature to 120 ℃ for continuous thermal-optical reaction. After 6 hours of reaction, the obtained synthetic solution has macroscopic floccules, is incompletely clarified, and is taken to be subjected to gas chromatographic analysis, wherein the purity of HDI is 91.1%.
According to the method for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation, provided by the application, a Hexamethylenediamine (HDA) flow and a phosgene flow which are subjected to heat exchange through a heat exchanger sequentially pass through a bubble-column pre-synthesis reactor and a bubble-column curing reactor to react, tail gas generated by the reaction is subjected to condensation treatment through a condenser, and a reactant obtained by the reaction is subjected to flash evaporation through a flash evaporation container, so that an HDI synthetic liquid is obtained, namely the hexamethylene diisocyanate synthetic liquid, and compared with a traditional kettle-type liquid-phase phosgene method, the mass transfer and heat transfer effects can be remarkably improved, the reaction efficiency can be accelerated, the reaction conversion rate can be improved, and the purity of the reaction liquid can be improved.
Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the application pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope of the application being indicated by the following claims.
It is to be understood that the application is not limited to the precise arrangements and instrumentalities shown in the drawings, which have been described above, and that various modifications and changes may be effected without departing from the scope thereof. The embodiments of the present application described above do not limit the scope of the present application.
Claims (8)
1. A system for synthesizing hexamethylene diisocyanate by liquid phase phosgenation, comprising:
a heat exchanger (1), a bubble column pre-synthesis reactor (02), a bubble column curing reactor (03), a condenser (4) and a flash vessel (5);
a synthetic liquid outlet is formed in the flash evaporation container (5), a gas phase feed port (3-7) is formed in one side of the lower part of the bubble column type curing reactor (03) in a communicating manner, a discharge port of the heat exchanger (1) is communicated with a liquid phase feed pipe (2-10) at the bottom of the bubble column type pre-synthesis reactor (02), a first liquid phase discharge port (2-5) at one side of the upper part of the bubble column type pre-synthesis reactor (02) is communicated with a liquid phase feed port (3-3) at one side of the upper part of the bubble column type curing reactor (03), a second liquid phase discharge port (3-6) at the bottom of the bubble column type curing reactor (03) is communicated with a feed port of the flash evaporation container (5), a first gas phase discharge port (2-12) at the top of the bubble column type pre-synthesis reactor (02) and a second gas phase discharge port (3-1) at the top of the bubble column type curing reactor (03) are both communicated with a tail gas inlet of the condenser (4), a back flow port of the condenser (4) is communicated with a back flow port of the flash evaporation container (3) at one side of the upper part of the bubble column type curing reactor (03), and the back flow port of the flash evaporation container (03) is communicated with the liquid outlet (6) is communicated with the liquid outlet of the flash evaporation container (3) at the top of the flash evaporation container;
wherein the bubble tower pre-synthesis reactor (02) comprises a first tower body (2), a first gas phase discharge port (2-12) is communicated with the top of the first tower body (2), a liquid phase feed pipe (2-10) is communicated with the bottom of the first tower body (2), an annular gas phase feed pipe (2-11) is communicated with the bottom of the first tower body (2), a first liquid phase discharge port (2-5) is communicated with one side of the upper part of the first tower body (2), a first liquid catcher (2-1) is arranged at the top of the inner side of the first tower body (2), a plurality of hollow gas lift pipes (2-6) are axially arranged in the first tower body (2), a diffusion hole (20-2) is formed in the upper end of each hollow gas lift pipe (2-6), an annular gas phase feed pipe (2-10) and an annular gas phase feed pipe (2-11) are communicated with the inner side of the first tower body (2), a first liquid collector (2-1) is arranged at the top of the first tower body (2) along the axial direction, a plurality of hollow gas lift pipes (2-6) are arranged between the first gas feed pipes (2-8), the outer side wall of the first tower body (2) is sequentially provided with a tower body upper jacket (2-3) and a tower body lower jacket (2-7) from top to bottom;
the upper surface of the disc feeder (2-8) is provided with 3-10 concentric annular gas phase feeding holes (2-81) communicated with the annular gas phase feeding pipe (2-11), and a single liquid phase feeding hole (2-82) communicated with the liquid phase feeding pipe (2-10), wherein the horizontal position of the liquid phase feeding hole (2-82) is lower than that of the concentric annular gas phase feeding hole (2-81).
2. The system for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation according to claim 1, wherein the bubble column curing reactor (03) comprises a second tower body (3), the second gas-phase discharging port (3-1) is communicated with the top of the second tower body (3), the liquid-phase feeding port (3-3) is communicated with the upper part of the second tower body (3), the second liquid-phase discharging port (3-6) is communicated with the bottom of the second tower body (3), the gas-phase feeding port (3-7) is communicated with the lower part of the second tower body (3), a second liquid catcher (3-2) is arranged at the inner top of the second tower body (3), a tower jacket (3-4) is arranged on the outer side wall of the second tower body (3), an eccentric air lift pipe (3-5) is axially arranged in the second tower body (3), and a plurality of annular fillers (3-9) are arranged in the second tower body (3).
3. The system for synthesizing hexamethylene diisocyanate by liquid phase phosgenation according to claim 1, wherein the upper part of the first tower body (2) is further provided with a first expansion section (2-4).
4. The system for synthesizing hexamethylene diisocyanate by liquid phase phosgenation according to claim 2, wherein the second tower (3) is further provided with a second expansion section (3-8) at the upper part.
5. The system for synthesizing hexamethylene diisocyanate by liquid phase phosgenation according to claim 1, wherein the number of the hollow airlift tubes (2-6) is 6, and 6 hollow airlift tubes (2-6) are arranged in a regular hexagon along the axial direction of the first tower body (2).
6. A process for the synthesis of hexamethylene diisocyanate by liquid phase phosgenation, based on a system for the synthesis of hexamethylene diisocyanate by liquid phase phosgenation according to any one of claims 1 to 5, characterized in that it comprises:
adding a solvent of hexamethylenediamine solution into a bubble column pre-synthesis reactor;
introducing a phosgene stream into the disc feeder through an annular gas-phase feeding pipe, wherein the phosgene stream enters the bubble-column pre-synthesis reactor through a gas-phase feeding hole and diffuses upwards along a hollow airlift pipe;
feeding the HDA stream subjected to heat exchange by a heat exchanger into a disc feeder through a liquid phase feeding pipe, enabling the HDA stream to enter a bubble-column pre-synthesis reactor through a liquid phase feeding hole, and enabling the HDA stream to be upwardly diffused along the hollow airlift pipe to be in contact reaction with the phosgene stream so as to obtain a mixture;
introducing phosgene into the bubble tower curing reactor through a gas phase feed inlet, and enabling the mixture to enter the bubble tower curing reactor to contact and react with the phosgene after sequentially passing through a first liquid phase discharge port and a liquid phase feed inlet to obtain a reactant;
the reactant is discharged out of the bubble tower curing reactor through a second liquid phase discharge port and enters a flash evaporation container for flash evaporation, so that an HDI synthetic liquid and gas-liquid mixture is obtained;
and tail gas generated in the reaction process of the bubble-column pre-synthesis reactor and the bubble-column curing reactor respectively enters a condenser through a first gas phase discharge port and a second gas phase discharge port, the condensed solvent and phosgene mixture are refluxed to the bubble-column curing reactor for reuse, and uncondensed gas and the gas-liquid mixture enter a gas conveying pipeline.
7. The method for synthesizing hexamethylene diisocyanate by liquid phase phosgenation according to claim 6, wherein the solvent of the hexamethylenediamine solution is any one of chlorobenzene, dichlorobenzene and xylene.
8. The method for synthesizing hexamethylene diisocyanate by liquid-phase phosgenation according to claim 7, wherein the HDA stream is a mixed stream of hexamethylenediamine and a solvent, and wherein the mass concentration of hexamethylenediamine is 5% -15%.
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