CN118812394A - Refining process and equipment for synthesizing 1,5-pentanediisocyanate by phosgene method - Google Patents
Refining process and equipment for synthesizing 1,5-pentanediisocyanate by phosgene method Download PDFInfo
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Abstract
The invention provides a refining process and equipment for synthesizing 1, 5-pentanediol by a phosgene method, and relates to the technical field of fine chemical intermediate raw materials. The photochemical liquid after the refining process reaction of the invention is subjected to the steps of phosgene removal, solvent removal, byproduct removal and residue removal in sequence to obtain the 1, 5-pentanediisocyanate product. The equipment comprises a dephosgene tower, a desolventizing tower and a product refining tower. The desolventizing tower comprises a first-stage desolventizing tower and a second-stage desolventizing tower, and steam at the top of the first-stage desolventizing tower and liquid at the bottom of the second-stage desolventizing tower are subjected to heat exchange in a heat exchanger and then flow back; the solvent distilled out by the invention can be recycled to the reaction part in two batches as required, the finished product of the 1, 5-pentanediisocyanate is extracted from the side line of the product refining tower, the byproduct is extracted from the liquid phase at the top of the tower, and the residue is extracted from the bottom of the tower. Has the advantages of energy saving, cost reduction, efficiency improvement and the like.
Description
Technical Field
The invention relates to the technical field of fine chemical intermediate raw materials.
In particular to a refining process and equipment for synthesizing 1, 5-pentanediisocyanate by a phosgene method.
Background
1, 5-Pentanediisocyanate is the first isocyanate based on bio-based synthesis and has good market prospect. Currently, the phosgenation process is generally used industrially to prepare 1, 5-pentanediisocyanate. The process typically reacts excess phosgene with 1, 5-pentanediamine in a solvent environment to produce 1, 5-pentanediisocyanate. In the reaction process, the intermediate of the 1, 5-pentanediisocyanate is easy to generate side reaction to generate 5-chloroamyl isocyanate, the boiling point of the 5-chloroamyl isocyanate is higher than that of common chlorobenzene and o-dichlorobenzene solvents, and the property of the 5-chloroamyl isocyanate is close to that of the 1, 5-pentanediisocyanate, so that the reaction process is required to use a large amount of solvents due to the characteristics of the reaction, and a large amount of solvents are required to be removed in the rectification process; at the same time, a higher reflux ratio is needed to separate the product from the impurity 5-chloroamyl isocyanate; the separation of the final product from the residue also requires substantial steaming of the product. The energy consumption of the product refining process is high, so how to effectively reduce the energy consumption becomes a problem to be solved urgently.
In addition, 1, 5-pentanediisocyanate has the characteristic of easy polymerization at high temperature, which can lead to the reduction of the product yield. The common solution is to add stabilizers to the product, but the isocyanate polymerization problem during the rectification is not solved.
In order to solve the problems, the applicant searches CN114984601a to disclose a device system and a method for separating and refining 1, 5-pentanediisocyanate by a non-phosgene method, a stabilizer is added after a solvent is removed to prevent polymerization of a product, a certain effect is achieved, but polymerization of the product is still possible in the subsequent heavy component removal process, and in addition, the stabilizer is generally required to be used under an inert gas atmosphere, so that the refining difficulty is further increased. CN114133343a discloses a method for purifying isocyanate under high vacuum, which purifies isocyanate under high vacuum, effectively reduces polymerization of products, and improves purity of products to a certain extent, but the purification process is an intermittent process, the residence time of materials in a storage tank is too long, phenomena of polymerization of products and generation of other impurities are easy to occur, and other impurities such as components cannot be separated.
In addition, as disclosed in CN104529824B, in the method for refining 3, 5-dichlorophenyl isocyanate, the solvents containing phosgene and NCO distilled from the first-stage desolventizing tower and the second-stage desolventizing tower are combined and sent to a solvent storage tank to be mixed, and then refined by an additional solvent refining tower for recycling, although the consumption of solvent is reduced, the additional solvent refining tower is added, and equipment, energy consumption and refining flow are increased. The applicant has found in a later study that in this reaction scheme, a part of the solvent is used to prepare the 1, 5-pentanediamine solution and another part is used for phosgene absorption. The solvent for amine preparation has high impurity content requirement, and phosgene, isocyanate group (NCO) and other impurities should be extremely low, otherwise, side reaction with 1, 5-pentanediamine is easy to occur, and the impurity content requirement of the solvent for absorbing phosgene is relatively low. Therefore, the reasonable grading recycling of the solvent can save energy consumption, maximize the utilization of the solvent and reduce the loss of the solvent, and has great significance.
In summary, a high-efficiency refining process is very necessary that can reduce energy consumption, reduce product polymerization, reasonably recycle solvents, effectively separate byproducts and impurities, thereby effectively improving product yield and purity.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a refining process of 1, 5-pentanediol, which has the advantages of small equipment investment, low energy consumption, reasonable and repeated use of solvent and effective prevention of product polymerization.
The aim of the invention is achieved by the following technical measures:
A refining process for synthesizing 1, 5-pentanediisocyanate by a phosgene method is characterized in that: the method comprises the following steps:
A. Removing phosgene;
the photochemical liquid after the reaction is sent from the upper part of the decarbosgene tower, phosgene is extracted from the top of the decarbosgene tower, and crude products after the decarbosgene is extracted from the bottom of the decarbosgene tower;
B. desolventizing;
firstly, delivering the crude product after the dephosgene into a first-stage desolventizing tower, then delivering the crude product containing 50-80% of solvent extracted from the bottom of the first-stage desolventizing tower into a second-stage desolventizing tower, and extracting the crude product containing less than 0.01% of solvent from the bottom of the second-stage desolventizing tower;
The steam at the top of the first-stage desolventizing tower and the liquid at the bottom of the second-stage desolventizing tower are subjected to heat exchange in a heat exchanger and then flow back;
C. separating by-products, main products and residues;
The crude product containing less than 0.01% of solvent is sent into a product refining tower, the side line of the product refining tower is used for extracting 1, 5-pentanediisocyanate finished product, the byproduct is extracted from the tower top, and the residue is extracted from the tower bottom.
A specific optimization scheme is that the solvent extracted from the top of the first-stage desolventizing tower is used for preparing a raw material 1, 5-pentanediamine solution before being recycled to the reaction after heat exchange, and the solvent extracted from the top of the second-stage desolventizing tower is condensed and then used for phosgene absorption.
A specific optimization scheme is that the phosgene removal tower is pressurized, the pressure is 120-250kPaA, the theoretical plate number of the phosgene removal tower is 11-17, the feeding position is 3-6 plates, and the reflux ratio is 0.5-3.
A specific optimization scheme is that the pressure of the phosgene removal tower is 150-200kPaA, and the theoretical plate number of the phosgene removal tower is 13-15; the feeding position is between the 4 th plate and the 6 th plate; the reflux ratio is 0.8-1.5.
A specific optimization scheme is that a first-stage desolventizing tower is operated under pressure, the operating pressure of the first-stage desolventizing tower is 200-300kPaA, the theoretical plate number is 8-15, the feeding position is 5-8 plates, and the reflux ratio is 0.5-3.
A specific optimization scheme is that the operating pressure of the first-stage desolventizing tower is 225-275kPaA, the theoretical plate number is 10-12, and the feeding position is 6-7 plates; the reflux ratio is 0.9-2.
A specific optimization scheme is that the secondary desolventizing tower is operated at low pressure, the operating pressure of the secondary desolventizing tower is 3-10kPaA, the theoretical plate number is 12-20, the feeding position is 3-10 plates, and the reflux ratio is 0.1-2.
A specific optimization scheme is that the operating pressure of the secondary desolventizing tower is 4-7kPaA, the theoretical plate number is 13-16, and the feeding position is 4-8 plates; the reflux ratio is 0.2-1.3.
A specific optimization scheme is that a vertical partition plate is arranged in a product refining tower, the vertical partition plate divides the product refining tower into a feeding side and a discharging side, and the height of the vertical partition plate is positioned in the middle of the product refining tower; the operating pressure of the product refining tower is 1.5-5kPaA, the theoretical plate number is 45-55, the feeding position is 13-17 plates, and the side line extraction position is 20-30 plates.
A specific optimization scheme is that the vertical partition plate divides the product refining tower into a feeding side and a discharging side; the height of the vertical partition plate is 1/3-2/3 of the height of the product refining tower; the operating pressure of the product refining tower is 2-3.5kPaA, the theoretical plate number is 47-53, the feeding position is 14-16 plates, and the side line extraction position is 22-27 plates.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the advantages that:
1. the desolventizing adopts two-stage desolventizing tower operation, has high operation elasticity, can reasonably distribute the load of two towers, and ensures that the rectification operation is more energy-saving and flexible.
2. The tower top steam of the first-stage desolventizing tower is used as reboiling steam of a tower bottom reboiler of the second-stage desolventizing tower, and the tower bottom of the corresponding second-stage desolventizing tower is used as a cooling medium of a tower top condenser of the first-stage desolventizing tower. Can greatly reduce the usage amount of heating media such as steam and cooling media such as cooling water, and reduce the energy consumption of production.
3. The solvent extracted from the top of the first-stage desolventizing tower can be directly used for preparing 1, 5-pentanediamine solution, and the solvent extracted from the top of the second-stage desolventizing tower can be used for phosgene absorption, so that the solvent refining step is omitted, the equipment investment is reduced, and the process flow is simplified.
4. When the product is refined, the product refining tower is a partition tower, the product purity is high, the simultaneous separation of multiple components is realized, and the partition plate is added to divide the rectifying tower into two sides, namely a feeding side and a product side. Pre-separating 5-chloroamyl isocyanate, 1, 5-pentanediisocyanate and residues at the feeding side to ensure that the bottom material of the partition board does not contain light-component 5-chloroamyl isocyanate and the top material of the partition board does not contain heavy-component residues; after the materials enter the product side, the light components are continuously enriched to the tower top and are extracted from the tower top, the heavy components are continuously enriched to the tower bottom and are extracted from the tower bottom, and the products are enriched to the tower and are extracted from the side line position; thus, 5-chloroamyl isocyanate, 1, 5-pentanediisocyanate and residues are respectively extracted from the top, the side line and the bottom of the tower at the product side. The separator is added to enable one complex tower to have the separation function of connecting two simple towers in series, so that the two rectifying towers are rectified step by step, and the front tower product is connected with the next tower for further treatment, but due to the adoption of a common tower bottom reboiler and a tower top condenser, the input of external energy sources is reduced, and heat is allowed to flow and recycle in the tower for mass transfer and heat transfer of materials, so that the separation effect and the energy utilization rate are improved.
5. The product refining tower adopts a partition tower to effectively shorten the rectification flow, reduce the isocyanate side reaction, reduce the energy consumption in the rectification process and reduce the equipment investment. The separation yield of the rectified product 1, 5-pentanediisocyanate reaches more than 99 percent, and the purity of the product 1, 5-pentanediisocyanate reaches more than 99.5 percent.
It is another object of the present invention to overcome the above-mentioned disadvantages of the conventional techniques and to provide a refining apparatus for 1, 5-pentanediisocyanate which reduces energy consumption.
The refining equipment for synthesizing the 1, 5-pentanediisocyanate by a phosgene method is characterized in that: the device comprises a primary desolvation tower, a secondary desolvation tower, a heat exchanger and a buffer tank, wherein a heat exchanger hot fluid inlet is communicated with a tower top outlet of the primary desolvation tower, a heat exchanger hot fluid outlet is communicated with a tower top reflux port of the primary desolvation tower through the buffer tank, a heat exchanger cold fluid inlet is communicated with a tower bottom outlet of the secondary desolvation tower, a heat exchanger cold fluid outlet is communicated with a tower bottom reflux port of the secondary desolvation tower, and a vertical partition plate is arranged in the middle of the tower body of the product refining tower.
In a specific optimization scheme, a phosgene removal tower is provided with a pressurizing device, the theoretical plate number is 11-17, and the feeding position is 3-6 plates; the primary desolventizing tower is provided with a pressurizing device, the theoretical plates of the primary desolventizing tower are 8-15, and the feeding positions of the theoretical plates are 5-8; the second-stage desolventizing tower 3 is provided with a vacuum device, the theoretical plates are 12-20, and the feeding positions are 3-10 theoretical plates; the vertical partition board in the product refining tower divides the product refining tower into a feeding side and a discharging side, the height of the vertical partition board is 1/3-2/3 of the height of the product refining tower, the theoretical plate number of the product refining tower is 45-55, the feeding position is 13-17 plates, and the lateral line extraction position is 20-30 plates.
The invention is further described below with reference to the drawings and the detailed description.
Drawings
FIG. 1 is a schematic diagram of the refining apparatus for synthesizing 1, 5-pentanediisocyanate by the phosgene method.
In the figure: 1-a dephosgene tower; 2-a first-stage desolventizing tower; 3-a secondary desolventizing tower; 4-a product refining tower; a 5-heat exchanger; 6-buffer tank.
Detailed Description
Example 1: as shown in figure 1, the refining process for synthesizing the 1, 5-pentanediisocyanate by a phosgene method comprises the following steps:
A. And (5) removing phosgene.
And delivering the reacted photochemical liquid from the upper part of the phosgene removal tower 1, extracting phosgene from the tower top of the phosgene removal tower 1, and extracting a crude product after the phosgene removal from the tower bottom of the phosgene removal tower 1.
The photochemical liquid after the reaction mainly comprises the following components: 1, 5-pentanediisocyanate, solvent, phosgene, residue and 5-chloroamyl isocyanate impurities. Mixing raw material 1,5 pentanediamine with solvent before reaction to obtain 1,5 pentanediamine solvent; phosgene is mixed with a solvent before or during the reaction to prepare a phosgene solution. Then the phosgenation reaction is carried out by a liquid-phase phosgene method or a gas-phase phosgene method. The reaction solvent is chlorobenzene and/or o-dichlorobenzene, in this example chlorobenzene is selected, and o-dichlorobenzene or a mixture of chlorobenzene and o-dichlorobenzene may be selected.
The phosgene extracted from the top of the decarbonylation tower 1 enters a gas phase phosgene washing device, and the washed phosgene enters a phosgenation reaction stage; and (5) completely refluxing the liquid-phase phosgene.
The crude product after the dephosgene is extracted from the bottom of the dephosgene tower 1 is extracted by a pump and then the solvent is further removed.
The dephosgene tower 1 is pressurized and has the pressure of 120-250 kPaA. The theoretical plate number of the dephosgene tower 1 is 11-17, preferably 13-15; the feeding position is between 3 rd and 6 th plates, preferably between 4 th and 6 th plates; the reflux ratio is 0.5 to 3, preferably 0.8 to 1.5.
B. Desolventizing.
Firstly, delivering the crude product after the dephosgene into a first-stage desolventizing tower 2, then delivering the crude product containing 50-80% of solvent, which is extracted from the bottom of the first-stage desolventizing tower 2, into a second-stage desolventizing tower 3, and then extracting the crude product containing less than 0.01% of solvent from the bottom of the second-stage desolventizing tower 3;
In the solvent removal step, heat exchange is generated between steam at the top of the primary solvent removal tower 2 and liquid at the bottom of the secondary solvent removal tower 3 in the heat exchanger 5, and then reflux is generated. Specifically, steam at the top of the first-stage desolventizing tower is sent into a buffer tank 6 through a pump after heat exchange, one part of the steam is returned into the first-stage desolventizing tower 2 through the pump according to requirements, and the other part of the steam is extracted through the pump for preparing the 1, 5-pentanediamine solvent before reaction.
The solvent rectified by the first-stage desolventizing tower 2 and the second-stage desolventizing tower 3 can be recycled and reused for phosgenation reaction. The NCO content in the solvent extracted from the top of the first-stage desolventizing tower 2 is lower than 0.005%, and the solvent can be directly used for preparing 1, 5-pentanediamine solution, and the NCO content in the solvent extracted from the top of the second-stage desolventizing tower 3 is lower than 1%, so that the solvent can be used for phosgene absorption.
The solvent removing device adopted in the solvent removing step is a two-stage rectifying tower operation, and the flow structure of the two-stage solvent removing tower is modified in the invention, the steam at the top of the first-stage solvent removing tower 2 is used as heating steam of a reboiler at the tower bottom of the second-stage solvent removing tower 3, and the tower bottom of the corresponding second-stage solvent removing tower 3 is used as a refrigerant of a condenser at the top of the first-stage solvent removing tower 2. Can greatly reduce the usage amount of heating media such as steam and cooling media such as cooling water, and reduce the energy consumption of production.
The primary desolventizing tower 2 is a pressurized rectification, the operating pressure is 200-300kPaA, preferably 225-275kPaA, the theoretical plate number is 8-15, preferably 10-12, and the feeding position is 5-8 theoretical plates, preferably 6-7; reflux ratio is 0.5-3, preferably 0.9-2, and the bottom of the tower is used for extracting the mixture with the mass content of the solvent of 50-80%.
The secondary desolventizing tower 3 is operated at a low pressure, the operating pressure is 3-10kPaA, preferably 4-7kPaA, the theoretical plate number is 12-20, preferably 13-16, and the feeding position is 3-10 theoretical plates, preferably 4-8 plates; the mixture having a reflux ratio of 0.1 to 2, preferably 0.2 to 1.3 and a solvent bottom mass content of less than 0.01% is fed to the product refining column 4.
The heat exchanger 5 may be a conventional tube type heat exchanger or a plate-fin type heat exchanger. The heat fluid adopted by the heat exchanger 5 is steam distilled from the top of the first-stage desolventizing tower 2, and the steam needs to be condensed; the cold fluid adopted by the heat exchanger 5 is a low-pressure tower bottom liquid mixed material, and the liquid mixed material needs to be vaporized; in the heat exchanger, the two materials exchange heat, hot material solvent vapor is condensed and then passes through the buffer tank 6, one part of the hot material solvent vapor flows back, and the other part of the hot material solvent vapor is extracted after becoming solvent; part of the cold materials are heated and then vaporized and refluxed to the second-stage desolventizing tower to serve as a bottom vapor phase, a heat source is provided for the whole tower, and the materials which are not vaporized are extracted from the bottom liquid phase and enter a product refining tower 4.
C. The by-products, the main product and the residues are separated.
The crude product containing less than 0.01 percent of solvent is sent to a product refining tower 4, 1, 5-pentanediisocyanate finished product is extracted from the side line of the product refining tower 4, byproducts are extracted from the top of the tower, and residues are extracted from the bottom of the tower.
The product refining column 4 is a dividing wall column. The product refining column 4 includes a partition plate that divides the product refining column 4 into a feed side and a discharge side; the height of the vertical partition plate is 1/3-2/3 of the height of the product refining tower 4.
The operating pressure of the product finishing column 4 is 1.5 to 5kPaA, preferably 2 to 3.5kPaA, the theoretical plate number is 45 to 55, preferably 47 to 53, the feeding position is 13 to 17, preferably 14 to 16, the side offtake position is 20 to 30, preferably 22 to 27.
The purity of the product is up to 99.5% at the side line of the product refining tower 4, the byproduct 5-chloroamyl isocyanate is normally extracted from the tower top, and the residue is extracted from the tower bottom, wherein the residue may be tar which is polymerized and decomposed at high temperature in the isocyanate rectification process or diamine in the vapor phase phosgene method, or urea compound which is generated by the reaction of amine compound and isocyanate compound in the liquid phase phosgene method, and is usually treated as waste solids.
The product refining adopts a partition tower, so that the rectification flow is effectively shortened, the isocyanate side reaction is reduced, the energy consumption in the rectification process is reduced, and the equipment investment is reduced.
In this example, the flow rate of the photochemical liquid after the reaction was 3011kg/h, the concentration of 1, 5-pentanediisocyanate in the product was 20.9%, the chlorobenzene content was 73.2%, the phosgene content was 3.8%, the 5-chloroamyl isocyanate content was 1.5%, and the residue content was 0.5%.
The pressure in the tower 1 of the dephosgene tower is 170 kPaA, the theoretical plate number is 14, the feeding position is 4 th plate, the reflux ratio is 0.6, the liquid phase at the top of the tower is 117kg/h, and the phosgene content at the bottom of the tower is 1000ppm.
The first-stage desolventizing tower has the operating pressure of 250kPaA, the theoretical plate number of 9, 7 plates at the feeding position, the reflux ratio of 2, the tower bottom temperature of 179 ℃, the tower bottom solvent content of 70.4%, the tower top solvent extraction amount of 827kg/h and the phosgene content of 100ppm.
The second-stage desolventizing tower has an operating pressure of 5.8kPaA, a theoretical plate number of 14, 7 plates at a feeding position, a reflux ratio of 1.2, a bottom temperature of 150 ℃, a solvent content of 0.01%, a top recovery of 1377kg/h solvent and an NCO content of 1%.
The vertical partition board of the product refining tower 4 is positioned between the main tower 39 and 19 plates, the operating pressure is 3kPaA, the theoretical plate number is 49, the feeding position is 13 th plate on the feeding side, the lateral line extraction position is 26 pieces of tower plates on the extraction side, the extraction amount is 627kg/h, and the product concentration is 99.5%; 44kg/h of byproduct is taken out from the tower top, and the purity of the byproduct 5-chloroamyl isocyanate is 99.5%; 19kg/h of residue, and 20% of product content in the residue; the total yield of the product in the rectification process is 99.1 percent.
The invention adopts double-effect rectification technology, divides the solvent removal process into a high-pressure tower and a low-pressure tower, and integrates the condensation of the top of the high-pressure tower and the vaporization of the bottom of the low-pressure tower into one heat exchanger 5, thereby realizing the integration of energy and reducing the energy consumption. In addition, the invention integrates the light (impurity-removed 5-chloroamyl isocyanate) and heavy (residue-removed) products, and integrates the two towers of the 5-chloroamyl isocyanate removal tower and the residue-removed tower in a partition tower in the conventional process; compared with the common rectification, the invention reduces a rectification tower, a condenser and a reboiler; the equipment investment is reduced, meanwhile, the light component impurities 5-chloroamyl isocyanate and the product 1, 5-pentanediisocyanate are vaporized and condensed only once in the process, the 5-chloroamyl isocyanate is extracted from the top of the tower, and the product 1, 5-pentanediisocyanate is extracted from the middle side line of the tower, so that the separation of the 5-chloroamyl isocyanate, the 1, 5-pentanediisocyanate and residues is realized in one tower, and the energy is saved.
In addition, in the embodiment, besides the pump is adopted for conveying each liquid, the liquid level difference can be utilized for conveying the liquid by gravity; the gas can also be conveyed by a fan. The flow rate is controlled by the valves of the towers, and a control valve can be additionally added to meet the requirement.
Example 2: the refining process for synthesizing 1, 5-pentanediisocyanate by the phosgene method is different from that of the example 1 in that:
The pressure in the dephosgene tower 1 is 120 kPaA, the theoretical plate number is 11, the feeding position is 3 rd plate, and the reflux ratio is 0.5.
The first-stage desolventizing tower is operated under the pressure of 200kPaA, the theoretical plate number of 8, the feeding position of 5 plates and the reflux ratio of 0.5.
The second-stage desolventizing tower is operated at 3kPaA, the theoretical plate number is 12, the feeding position is 3 plates, and the reflux ratio is 0.1.
The operating pressure of the product refining tower 4 is 1.5kPaA, the theoretical plate number is 45, the feeding position is 13 th plates on the feeding side, and the lateral line extraction position is 20 trays on the extraction side.
The remainder was the same as in example 1.
Example 3: the refining process for synthesizing 1, 5-pentanediisocyanate by the phosgene method is different from that of the example 1 in that:
The pressure in the dephosgene tower 1 is 250 kPaA, the theoretical plate number is 17, the feeding position is 6 th plate, and the reflux ratio is 3.
The first-stage desolventizing tower is operated at 300kPaA, 15 theoretical plates, 8 plates at the feeding position and 3 reflux ratio.
The second-stage desolventizing tower is operated at 10kPaA, the theoretical plate number is 20, the feeding position is 10 plates, and the reflux ratio is 2.
The product refining tower 4 has an operating pressure of 5kPaA, a theoretical plate number of 55, a feeding position of 17 th plates on the feeding side and a lateral line extraction position of 30 plates on the extraction side.
The remainder was the same as in example 1.
Example 4: the refining process for synthesizing 1, 5-pentanediisocyanate by the phosgene method is different from that of the example 1 in that:
the pressure in the dephosgene tower 1 is 150 kPaA, the theoretical plate number is 13, the feeding position is 3 rd plate, and the reflux ratio is 0.8.
The first-stage desolventizing tower is operated under the pressure of 225kPaA, the theoretical plate number of 10, the feeding position of 6 plates and the reflux ratio of 0.9.
The second-stage desolventizing tower is operated at 4kPaA, the theoretical plate number is 13, the feeding position is 4 plates, and the reflux ratio is 0.2.
The product refining column 4 operates at a pressure of 2kPaA, a theoretical plate number of 47, a feeding position of 14 th plates on the feeding side, and a lateral line extraction position of 22 trays on the extraction side.
The remainder was the same as in example 1.
Example 5: the refining process for synthesizing 1, 5-pentanediisocyanate by the phosgene method is different from that of the example 1 in that:
the pressure in the dephosgene tower 1 is 200 kPaA, the theoretical plate number is 15, the feeding position is 6 th plate, and the reflux ratio is 1.5.
The first-stage desolventizing tower is operated at a pressure of 275kPaA, a theoretical plate number of 12, a feeding position of 7 plates and a reflux ratio of 2.
The second-stage desolventizing column was operated at a pressure of 7kPaA, a theoretical plate number of 16, a feed position of 8 plates and a reflux ratio of 1.3.
The product refining column 4 operates at a pressure of 3.5kPaA, a theoretical plate number of 53, a feeding position of 16 th plates on the feeding side, and a lateral line extraction position of 27 plates on the extraction side.
The remainder was the same as in example 1.
Example 6: the refining equipment for synthesizing 1, 5-pentanediol diisocyanate by a phosgene method comprises a dephosgene tower 1, a desolventizing device and a product refining tower 4.
The dephosgene tower 1 comprises a tower body, a reboiler, a condenser and a pressurizing device. The theoretical plate number of the dephosgene tower 1 is 11-17, preferably 13-15; the feeding position is in the 3 rd to 6 th plates, preferably 4 th to 6 th plates.
The gas phase extraction pipeline at the top of the dephosgene tower 1 is communicated with a phosgene washing device.
The desolventizing device comprises a first-stage desolventizing tower 2, a second-stage desolventizing tower 3, a heat exchanger 5 and a buffer tank 6. The hot fluid inlet of the heat exchanger 5 is communicated with the top outlet of the first-stage desolventizing tower 2, the hot fluid outlet of the heat exchanger 5 is communicated with the top reflux mouth of the first-stage desolventizing tower 2 through a buffer tank 6, the cold fluid inlet of the heat exchanger 5 is communicated with the bottom outlet of the second-stage desolventizing tower 3, and the cold fluid outlet of the heat exchanger 5 is communicated with the bottom reflux mouth of the second-stage desolventizing tower 3.
The first-stage desolventizing tower 2 comprises a tower body, a reboiler and a pressurizing device. The theoretical plate number of the first-stage desolventizing tower 2 is 8-15, preferably 10-12; the feeding position is in the 5 th to 8 th theoretical plates, preferably in the 6 th to 7 th plates.
The secondary desolventizing tower 3 comprises a tower body, a condenser and a vacuumizing device. The theoretical plate number of the secondary desolventizing tower 3 is 12-20, preferably 13-16; the feeding position is in the 3 rd to 10 th theoretical plates, preferably in the 4 th to 8 th plates.
The buffer tank 6 is communicated with a solvent treatment device.
The gas phase extraction pipeline at the top of the second-stage desolventizing tower 3 is communicated with a phosgene washing device.
The product refining column 4 comprises a column body, a reboiler, a condenser and a vacuum pumping device. A vertical baffle is arranged in the middle position inside the product refining tower body. The vertical partition divides the product refining column 4 into a feed side and a discharge side; the height of the vertical partition plate is 1/3-2/3 of the height of the product refining tower 4, the theoretical plate number is 45-55, preferably 47-53, the feeding position is 13-17, preferably 14-16, the side line extraction position is 20-30, preferably 22-27.
In addition, the transport of the fluids is also realized by arranging corresponding pumps or by setting a level difference, and the control of the flow rate is also realized by setting a requirement through a valve.
In this example, the theoretical plate number of the dephosgene tower 1 is 14, and the feeding position is 4 th plate. The theoretical plate number of the first-stage desolventizing tower is 9, and the feeding position is the 7 th plate. The number of theoretical plates of the secondary desolventizing tower is 14, and the feeding position is 7 plates. The separator of the product refining column 4 divides the column into a feed side and a discharge side; the vertical partition plate is positioned between the main tower 39 and 19 plates, the theoretical plate number is 49, the feeding position is 13 th plate on the feeding side, and the lateral line extraction position is 26 column plates on the extraction side.
Example 7: the refining apparatus for synthesizing 1, 5-pentanediisocyanate by phosgene method is different from example 6 in that:
The theoretical plate number of the dephosgene tower 1 is 11, and the feeding position is 3 rd plate. The theoretical plate number of the first-stage desolventizing tower 2 is 8, and the feeding position is at the 5 th plate. The theoretical plate number of the second-stage desolventizing tower 3 is 12, and the feeding position is 3 rd plate. The theoretical plate number of the product refining tower 4 is 45, the feeding position is 13 th plates on the feeding side, and the lateral line extraction position is 20 trays on the extraction side.
The remainder was the same as in example 1.
Example 8: the refining apparatus for synthesizing 1, 5-pentanediisocyanate by phosgene method is different from example 6 in that:
The theoretical plate number of the dephosgene tower 1 is 17, and the feeding position is the 6 th plate. The theoretical plate number of the first-stage desolventizing tower 2 is 15, and the feeding position is at the 8 th plate. The theoretical plate number of the second-stage desolventizing tower 3 is 20, and the feeding position is at the 10 th plate. The theoretical plate number of the product refining tower 4 is 55, the feeding position is the 17 th plate on the feeding side, and the lateral line extraction position is the 30 column plates on the extraction side.
The remainder was the same as in example 1.
Example 9: the refining apparatus for synthesizing 1, 5-pentanediisocyanate by phosgene method is different from example 6 in that:
the theoretical plate number of the dephosgene tower 1 is 13, and the feeding position is the 4 th plate. The theoretical plate number of the first-stage desolventizing tower 2 is 10, and the feeding position is at the 6 th plate. The theoretical plate number of the second-stage desolventizing tower 3 is 13, and the feeding position is at the 4 th plate. The theoretical plate number 47 of the product refining tower 4 is that the feeding position is the 14 th plate on the feeding side, and the lateral line extraction position is that the 22 tower plates on the extraction side.
The remainder was the same as in example 1.
Example 10: the refining apparatus for synthesizing 1, 5-pentanediisocyanate by phosgene method is different from example 6 in that:
The theoretical plate number of the dephosgene tower 1 is 15, and the feeding position is the 6 th plate. The theoretical plate number of the first-stage desolventizing tower 2 is 12, and the feeding position is at the 7 th plate. The theoretical plate number of the second-stage desolventizing tower 3 is 16, and the feeding position is 8 th plate. The theoretical plate number of the product refining tower 4 is 53, the feeding position is the 16 th plate on the feeding side, and the lateral line extraction position is the 27 tower plates on the extraction side.
The remainder was the same as in example 1.
The foregoing describes several embodiments of the present invention in detail, but the description is merely a preferred embodiment of the invention and should not be construed as limiting the scope of the invention. All equivalent changes and modifications within the scope of the present invention are intended to be covered by the present invention.
Claims (12)
1. A refining process for synthesizing 1, 5-pentanediisocyanate by a phosgene method is characterized in that: the method comprises the following steps:
A. Removing phosgene;
The photochemical solution after the reaction is sent from the upper part of the phosgene removal tower (1), phosgene is extracted from the top of the phosgene removal tower (1), and crude products after the phosgene removal are extracted from the bottom of the phosgene removal tower (1);
B. desolventizing;
firstly, delivering the crude product after the dephosgene into a first-stage desolventizing tower (2), then delivering the crude product containing 50-80% of solvent, which is extracted from the bottom of the first-stage desolventizing tower (2), into a second-stage desolventizing tower (3), and extracting the crude product containing less than 0.01% of solvent from the bottom of the second-stage desolventizing tower (3);
The steam at the top of the first-stage desolventizing tower (2) and the liquid at the bottom of the second-stage desolventizing tower (3) are subjected to heat exchange in a heat exchanger (5) and then flow back;
C. separating by-products, main products and residues;
the crude product containing less than 0.01 percent of solvent is sent into a product refining tower (4), 1, 5-pentanediisocyanate finished product is extracted from the side line of the product refining tower (4), byproducts are extracted from the top of the tower, and residues are extracted from the bottom of the tower.
2. The refining process for synthesizing 1, 5-pentanediisocyanate by using a phosgene method according to claim 1, wherein the refining process is characterized in that: the solvent extracted from the top of the first-stage desolventizing tower (2) is recycled to the reaction after heat exchange and is used for preparing a raw material 1, 5-pentanediamine solution, and the solvent extracted from the top of the second-stage desolventizing tower (3) is condensed and is used for phosgene absorption.
3. The refining process for synthesizing 1, 5-pentanediisocyanate by using a phosgene method according to claim 1, wherein the refining process is characterized in that: the dephosgene tower (1) is pressurized, the pressure is 120-250kPaA, the theoretical plate number of the dephosgene tower (1) is 11-17, the feeding position is 3-6 plates, and the reflux ratio is 0.5-3.
4. The purification process for synthesizing 1, 5-pentanediisocyanate by a phosgene method according to claim 3, wherein the purification process comprises the steps of: the pressure of the dephosgene tower (1) is 150-200kPaA, and the theoretical plate number of the dephosgene tower (1) is 13-15; the feeding position is between the 4 th plate and the 6 th plate; the reflux ratio is 0.8-1.5.
5. The refining process for synthesizing 1, 5-pentanediisocyanate by using a phosgene method according to claim 1, wherein the refining process is characterized in that: the primary desolventizing tower (2) is operated under pressure, the operating pressure of the primary desolventizing tower (2) is 200-300kPaA, the theoretical plate number is 8-15, the feeding position is 5-8 plates, and the reflux ratio is 0.5-3.
6. The refining process for synthesizing 1, 5-pentanediisocyanate by using a phosgene method according to claim 5, wherein the refining process is characterized in that: the operating pressure of the first-stage desolventizing tower (2) is 225-275kPaA, the theoretical plate number is 10-12, and the feeding position is 6-7 plates; the reflux ratio is 0.9-2.
7. The refining process for synthesizing 1, 5-pentanediisocyanate by using a phosgene method according to claim 1, wherein the refining process is characterized in that: the second-stage desolventizing tower (3) is operated at low pressure, the operating pressure of the second-stage desolventizing tower (3) is 3-10kPaA, the theoretical plate number is 12-20, the feeding position is 3-10 plates, and the reflux ratio is 0.1-2.
8. The refining process for synthesizing 1, 5-pentanediisocyanate by using a phosgene method according to claim 7, wherein the refining process is characterized in that: the operating pressure of the secondary desolventizing tower (3) is 4-7kPaA, the theoretical plate number is 13-16, and the feeding position is 4-8 plates; the reflux ratio is 0.2-1.3.
9. The refining process for synthesizing 1, 5-pentanediisocyanate by using a phosgene method according to claim 1, wherein the refining process is characterized in that: a vertical partition board is arranged in the product refining tower (4), the vertical partition board divides the product refining tower (4) into a feeding side and a discharging side, and the height of the vertical partition board is positioned in the middle of the product refining tower (4); the operating pressure of the product refining tower (4) is 1.5-5kPaA, the theoretical plate number is 45-55, the feeding position is 13-17 plates, and the side line extraction position is 20-30 plates.
10. The refining process for synthesizing 1, 5-pentanediisocyanate by using a phosgene method according to claim 9, wherein the refining process is characterized in that: the vertical partition plate divides the product refining tower (4) into a feeding side and a discharging side; the height of the vertical partition plate is 1/3-2/3 of the height of the product refining tower (4); the operating pressure of the product refining tower (4) is 2-3.5kPaA, the theoretical plate number is 47-53, the feeding position is 14-16 plates, and the side line extraction position is 22-27 plates.
11. The refining equipment for synthesizing the 1, 5-pentanediisocyanate by a phosgene method is characterized in that: including desolventizing tower (1), desolventizing device and product refining tower (4), desolventizing device includes one-level desolventizing tower (2), second grade desolventizing tower (3), heat exchanger (5) and buffer tank (6), heat exchanger (5) hot fluid entry and one-level desolventizing tower (2) top of the tower export UNICOM, heat exchanger (5) hot fluid export and one-level desolventizing tower (2) top of the tower reflux mouth pass through buffer tank (6) UNICOM, heat exchanger (5) cold fluid entry and second grade desolventizing tower (3) bottom of the tower export UNICOM, heat exchanger (5) cold fluid export and second grade desolventizing tower (3) bottom of the tower reflux mouth UNICOM, the middle part is equipped with perpendicular baffle in the product refining tower (4) body of the tower.
12. The refining apparatus for synthesizing 1, 5-pentanediisocyanate by phosgene method according to claim 11, wherein: the dephosgene tower (1) is provided with a pressurizing device, the theoretical plate number is 11-17, the feeding position is 3-6 plates, and the reflux ratio is 0.5-3; the first-stage desolventizing tower (2) is provided with a pressurizing device, the theoretical plates of the first-stage desolventizing tower (2) are 8-15, the feeding positions are 5-8 theoretical plates, and the reflux ratio is 0.5-3; the second-stage desolventizing tower (3) is provided with a vacuum device, the theoretical plates are 12-20, the feeding positions are 3-10 theoretical plates, and the reflux ratio is 0.1-2; the vertical partition board in the product refining tower (4) divides the product refining tower (4) into a feeding side and a discharging side, the height of the vertical partition board is 1/3-2/3 of the height of the product refining tower 4, the theoretical plate number of the product refining tower (4) is 45-55, the feeding position is 13-17 plates, and the lateral line extraction position is 20-30 plates.
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