CN116178174A - Method for purifying hexamethylenediamine with low energy consumption - Google Patents
Method for purifying hexamethylenediamine with low energy consumption Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
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Abstract
The invention provides a method for purifying hexamethylenediamine with low energy consumption, which comprises the following steps: 1) Extracting hexamethylenediamine and impurities from water by using ionic liquid from an aqueous reaction liquid of the hexamethylenediamine reaction system to obtain an extraction mixed liquid; 2) Standing and layering the extraction mixed liquor obtained in the step 1), discharging a water phase as wastewater, wherein an organic phase is a mixture of ionic liquid, hexamethylenediamine and impurities; 3) Separating the organic phase obtained in the step 2), obtaining crude hexamethylenediamine at the top and obtaining ionic liquid at the bottom, and returning to the step 1) for recycling the extractant; 4) And 3) feeding the crude hexamethylenediamine obtained in the step 3) into a bulkhead tower to remove light/heavy component impurities, thereby obtaining a hexamethylenediamine product with the purity of more than 99.9 weight percent. The method of the invention removes water and light and heavy component impurities in the reaction liquid by means of ionic liquid extraction and a partition tower technology, can greatly reduce energy consumption and equipment cost, and creates higher economic benefit.
Description
Technical Field
The invention belongs to the technical field of separation and purification, and particularly relates to a method for purifying hexamethylenediamine with low energy consumption.
Background
Hexamethylenediamine is an important difunctional compound, and contains two reactive functional groups in the molecule, so that various important chemicals can be generated. Hexamethylenediamine is a main raw material for producing polyamide (nylon) fibers and resins, is also a main raw material for producing high-grade polyurethane Hexamethylene Diisocyanate (HDI), and can be used for producing curing agents and crosslinking agents for resins.
The process flow has higher operation flexibility and can reach the purity required in the market, but has the defects of longer process flow, high equipment investment cost, high energy consumption and the like, and the problems that salt enters the crude hexamethylenediamine and blocks a downstream separation system and the like due to the conventional rectification dehydration of the reaction liquid exist.
Patent CN10423623B discloses a depolymerization recovery method of high temperature resistant nylon poly (hexamethylene terephthalamide), sodium hydroxide and water are added into a reaction kettle, after dissolution, crushed nylon PA6T is added to obtain alkaline hydrolysis liquid, the alkaline hydrolysis liquid enters a separation extraction section through a filter, and crude hexamethylene diamine extract and terephthalic acid sodium salt extract are obtained by extraction separation with aromatic hydrocarbon/alcohol mixed extractant. Rectifying the crude hexamethylenediamine extract to obtain an extraction solvent and refined hexamethylenediamine respectively. The technology for recovering hexamethylenediamine in the patent can introduce an extractant with high volatility and toxicity and combustibility in actual industrial production, and the rectification process can be longer and more complicated.
Thus, there remains a need for a new low energy purification process for hexamethylenediamine.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a novel method for purifying hexamethylenediamine with low energy consumption.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
a process for purifying hexamethylenediamine with low energy consumption, comprising the steps of:
1) Extracting hexamethylenediamine and impurities from water by using ionic liquid as an extracting agent from the aqueous reaction liquid of the hexamethylenediamine reaction system to obtain an extraction mixed liquid;
2) Standing and layering the extraction mixed liquor obtained in the step 1), discharging a water phase as wastewater, wherein an organic phase is a mixture of ionic liquid, hexamethylenediamine and impurities;
3) Separating the organic phase obtained in the step 2), obtaining crude hexamethylenediamine at the top and obtaining ionic liquid at the bottom, and returning to the step 1) for recycling the extractant;
4) And 3) feeding the crude hexamethylenediamine obtained in the step 3) into a bulkhead tower, and removing light and heavy component impurities to obtain a hexamethylenediamine product with the purity of more than 99.9 weight percent.
In a specific embodiment, the ionic liquid consists of two parts, namely a cation M+ and an anion N-; the cation M+ is imidazole type cation with double substituent groups; the anion N-is hexafluorophosphate; preferably, two substituent groups in the double substituent groups are different, wherein one substituent group is a C7-C10 straight-chain alkenyl group, and the other substituent group is a C1-C2 alkyl group.
In a specific embodiment, the mass ratio of the ionic liquid as extractant in step 1) to the aqueous reaction liquid exiting from the hexamethylenediamine reaction system is from 0.1 to 3, preferably from 0.3 to 1.
In a specific embodiment, step 1) and step 2) are performed in the same device or in two devices, respectively; preferably, the same equipment is selected from any one of a packing extraction tower, a sieve plate extraction tower, a rotary disk extraction tower, a mixer-settler and a centrifugal extractor; the two devices are a stirring kettle and a split-phase tank respectively.
In a specific embodiment, the pressure at which the crude hexamethylenediamine is separated from the ionic liquid in step 3) is from 1 to 10kPaA, preferably from 3 to 6kPaA.
In a specific embodiment, the apparatus used for separating the crude hexamethylenediamine and the ionic liquid in step 3) is selected from any one of a thin film evaporator, a falling film evaporator, a rising film evaporator, and a rectifying column.
In a specific embodiment, the dividing wall column for separating crude hexamethylenediamine in step 4) comprises: the device comprises a main tower, a condenser, a reboiler and a partition plate;
preferably, the main column is divided into a rectification zone, a stripping zone, a prefractionation zone, a main fractionation zone, and comprises at least one feed stream and at least three discharge streams;
the rectification area is mainly used for removing low-boiling-point components, and the stripping area is mainly used for removing high-boiling-point components;
the at least one feed stream is a crude product stream comprising hexamethylenediamine and the at least three discharge streams are a light component stream comprising a minor amount of hexamethylenediamine, a hexamethylenediamine product stream, a heavy component stream comprising a minor amount of hexamethylenediamine.
In a specific embodiment, the crude product stream comprising hexamethylenediamine enters the intermediate feed plate of the prefractionation zone, the upper and lower portions of the feed plate of the prefractionation zone being in communication;
a light component stream containing a small amount of hexamethylenediamine flows out from the top of the rectification area, and a heavy component containing a small amount of hexamethylenediamine flows out from the bottom of the stripping area;
the hexamethylenediamine product stream flows from the middle discharge plate of the main fractionation zone, and the upper and lower portions of the discharge plate of the main fractionation zone are in communication.
In a specific embodiment, the height of the baffles is determined by the number of trays required for the prefractionation zone and the main fractionation zone; preferably, the dividing wall column is operated at a pressure of from 1 to 10kPaA, preferably from 2 to 5kPaA.
In a specific embodiment, the crude product stream comprising hexamethylenediamine comprises: 0.5-10wt% of 1, 3-diazacyclohexane, aminomethylcyclopentane, light components of aminopropanol, 80-99wt% of hexamethylenediamine, 0.5-10wt% of N-ethylhexyl diamine, heavy components of 2-hexanetriamine;
the hexamethylenediamine product stream comprises: more than 99.9wt% hexamethylenediamine, less than 1000ppmwt of light and heavy component impurities.
Compared with the prior art, the invention has the following beneficial effects:
in the method, the ionic liquid is used as the extractant to separate water from crude hexamethylenediamine, so that salt is left in the water phase, and compared with the conventional rectification dehydration, the method can avoid the high energy consumption caused by the need of distilling water out for rectifying and separating hexamethylenediamine and water, can also avoid the problems that the salt in the water enters the crude hexamethylenediamine to block a downstream separation system and the like, and is also a green extraction process.
The method of the invention combines the bulkhead tower to further separate the extracted organic phase on the basis of extracting the aqueous solution of the hexamethylenediamine by utilizing the ionic liquid, thereby avoiding the defects of long process flow, high equipment investment and high energy consumption of the common rectification process, greatly reducing the energy consumption and the equipment investment cost by adopting the bulkhead tower for rectifying the crude hexamethylenediamine, and reducing the process operation.
Drawings
FIG. 1 is a schematic flow chart of the purification of hexamethylenediamine according to the present invention.
FIG. 2 is a schematic diagram of a purification scheme for hexamethylenediamine according to another embodiment of the present invention.
FIG. 3 is a flow chart of hexamethylenediamine purification according to comparative example 3 of the present application.
Wherein, 1 is an ionic liquid extraction device, 2 is a layering device, 3 is an ionic liquid separation device, 4 is a partition tower, 5 is a reboiler, 6 is a condenser, 7 is a hexamethylenediamine dehydration tower, 8 is a desalination tower, 9 is a light component removal tower, and 10 is a hexamethylenediamine refining tower.
Detailed Description
For a better understanding of the technical solution of the present invention, the method and the device provided by the present invention are further described below with reference to the accompanying drawings, but the present invention is not limited to the embodiments listed, but also includes any other known modifications within the scope of the claims of the present invention.
As shown in fig. 1, the process for purifying hexamethylenediamine according to the present invention comprises: the method comprises the steps that hexamethylenediamine reaction liquid and ionic liquid enter an ionic liquid extraction device 1 together, the ionic liquid extracts crude hexamethylenediamine from water, meanwhile salt is remained in the water, a material flow obtained by the ionic liquid extraction device 1 enters a layering device 2, water-oil two phases are subjected to standing layering in the layering device 2, water phases are discharged as wastewater, oil phases enter an ionic liquid separation device 3, the crude hexamethylenediamine and the ionic liquid are separated in the ionic liquid separation device 3, the obtained ionic liquid is circulated to the ionic liquid extraction device 1, the obtained crude hexamethylenediamine enters a partition tower 4 for refining the hexamethylenediamine, the crude hexamethylenediamine enters a middle feeding plate of a prefractionation area, and the upper part and the lower part of the feeding plate of the prefractionation area are communicated. Light components containing a small amount of hexamethylenediamine are extracted from the top of the rectification area, and heavy components containing a small amount of hexamethylenediamine are extracted from the bottom of the rectification area. The hexamethylenediamine product is extracted from the middle discharging plate of the main fractionating area, and the upper part and the lower part of the discharging plate of the main fractionating area are communicated.
The ionic liquid extraction device 1 and the layering device 2 can be combined into one device or two devices, and the used equipment can be extraction equipment such as a filler extraction tower, a sieve plate extraction tower, a rotary disc extraction tower, a stirring kettle and a phase separation tank, a mixer-settler, a centrifugal extractor and the like.
When the ionic liquid extraction device 1 and the layering 2 can be combined into one device, as shown in fig. 2, the hexamethylenediamine reaction liquid and the ionic liquid enter the ionic liquid extraction device 1, the ionic liquid is used for extracting the crude hexamethylenediamine from water, meanwhile, salt is remained in the water, layering is realized, the salt-containing wastewater obtained from the ionic liquid extraction device 1 is directly discharged, the ionic liquid and crude hexamethylenediamine material flow obtained from the ionic liquid extraction device 1 enter the ionic liquid separation device 3 for rectifying and separating the ionic liquid and the crude hexamethylenediamine, the ionic liquid obtained from the tower bottom of the ionic liquid separation device 3 is returned to the extraction tower for recycling, the crude hexamethylenediamine obtained from the tower top enters the partition tower 4 for refining the crude hexamethylenediamine, the light component is extracted from the tower top of the partition tower 4, the hexamethylenediamine product is extracted from the tower bottom, and the heavy component is extracted from the tower bottom.
The equipment used in the ionic liquid separation device 3 can be distillation equipment such as a thin film evaporator, a falling film evaporator, a climbing film evaporator, a rectifying tower and the like.
Wherein the dividing wall column rectifying apparatus comprises: dividing wall column 4, overhead condenser 6, tower kettle reboiler 5. Wherein the divided wall column 4 comprises: a prefractionation zone (left side of the partition), a main fractionation zone (right side of the partition), a partition, a rectification zone (top packing section), a stripping zone (bottom packing section).
In combination with the device system, the method for purifying hexamethylenediamine with low energy consumption comprises the following steps:
1) Extracting hexamethylenediamine and impurities from water by using ionic liquid as an extracting agent from the aqueous reaction liquid of the hexamethylenediamine reaction system to obtain an extraction mixed liquid;
2) Standing and layering the extraction mixed liquor obtained in the step 1), discharging a water phase as wastewater, wherein an organic phase is a mixture of ionic liquid, hexamethylenediamine and impurities;
3) Separating the organic phase obtained in the step 2), obtaining crude hexamethylenediamine at the top and obtaining ionic liquid at the bottom, and returning to the step 1) for recycling the extractant;
4) And 3) feeding the crude hexamethylenediamine obtained in the step 3) into a bulkhead tower to remove light/heavy component impurities, thereby obtaining a hexamethylenediamine product with the purity of more than 99.9 weight percent.
The invention adopts ionic liquid as extractant to separate water and crude hexamethylenediamine, so that salt is remained in water phase, and then the operations of phase separation, rectification and the like are carried out to obtain high-purity hexamethylenediamine. Ionic liquids are a class of liquids composed of anions and cations that are in a liquid state at or near room temperature. As a novel green solvent, the ionic liquid has the advantages of low melting point, low vapor pressure, incombustibility, good solubility, good thermal stability and designability.
The ionic liquid designed by the invention consists of two parts, namely a cation M+ and an anion N-;
the cation M+ is imidazole type cation with double substituent groups;
the anion N-is hexafluorophosphate.
Wherein two substituent groups in the double substituent groups are different, and one substituent group is C7-C10 straight-chain alkenyl, such as heptenyl, octenyl, nonenyl and the like; the other substituent is C1-C2 alkyl, such as methyl or ethyl; specifically, for example, a 1-octenyl-3-methylimidazole hexafluorophosphate ionic liquid, a 1-heptenyl-3-ethylimidazole hexafluorophosphate ionic liquid, a 1-decenyl-3-methylimidazole hexafluorophosphate ionic liquid, and the like are preferable, but not limited thereto.
The method for preparing the ionic liquid in the present invention is not particularly limited, and reference may be made to the prior art, for example, the following method may be adopted:
taking 1-octenyl-3-methylimidazole hexafluorophosphate as an example, the preparation is carried out in two steps, the first step is to synthesize brominated 1-octenyl-3-methylimidazole ([ C) 8 mim]Br), adding 100g of freshly distilled N-methylimidazole and 300ml of trichloroethane into a round-bottomed flask, dropwise adding 200g of freshly distilled 8-bromo-1-octene at 60 ℃ under strong stirring for more than 2 hours, refluxing at 80 ℃ for about 3 hours after the dropwise addition, separating the ionic liquid by a separating funnel after the reaction phenomenon is that the liquid turns into orange-yellow viscous liquid after the turbidity is firstly, and removing residual solvent and water by vacuum drying at 65 ℃ for 48 hours after washing with trichloroethane for several times to obtain [ C ] 8 mim]Br; second step Synthesis of 1-octenyl-3-methylimidazole hexafluorophosphate 250g sodium hexafluorophosphate (NaPF 6 ) Dissolving in 500mL water, and adding [ C ] obtained in the first step 8 mim]Br, stirring for 36h, then extracting with dichloromethane, washing the organic layer several times with water until AgNO is added dropwise to the removed aqueous phase 3 The solution did not yellow precipitate. The dichloromethane solvent was distilled off first and dried under vacuum at 60℃for 24 hours to remove the residual solvent and water.
In the invention, the interaction of hexamethylenediamine and hydrophobic groups in ionic liquid cations and the hydrogen bonding effect formed by H atoms in organic molecules and F atoms in ionic liquid anions are the main driving forces in the extraction process. The introduction of hydrophobic groups and easily-formed hydrogen bond groups in amine molecules can increase the distribution of hexamethylenediamine in ionic liquids.
The mass ratio of the extractant ionic liquid and the reaction liquid used in the present invention is 0.1 to 3, including, for example, but not limited to, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, preferably 0.3 to 1.
The hexamethylenediamine extraction step in the invention can be completed in one step in the same equipment or can be completed in two steps in two equipment, and the equipment can be extraction equipment such as a packing extraction tower, a sieve plate extraction tower, a rotary disk extraction tower, a stirring kettle and a phase separation tank, a mixer-settler, a centrifugal extractor and the like.
The organic phase obtained by standing and layering the mixed liquid is a mixture of ionic liquid, hexamethylenediamine and impurities, and then the ionic liquid and the crude hexamethylenediamine are separated, wherein the equipment for separation can be distillation equipment such as a thin film evaporator, a falling film evaporator, a rising film evaporator, a rectifying tower and the like. The pressure at which the crude hexamethylenediamine is separated from the ionic liquid is, for example, from 1 to 10kPaA, including, for example, but not limited to, 1kPaA, 2kPaA, 3kPaA, 4kPaA, 5kPaA, 6kPaA, 7kPaA, 8kPaA, 9kPaA, 10kPaA, preferably from 3 to 6kPaA.
The invention adopts the partition tower to purify the hexamethylenediamine, the effect of two distillation towers can be achieved by one distillation tower, and compared with the conventional rectification device for purifying the hexamethylenediamine, the invention has the advantages of less energy consumption and lower equipment cost.
As shown in fig. 1, the divided wall column 4 includes: a main tower 4, a condenser 6, a reboiler 5 and a baffle plate. Wherein the main column 4 is divided into a rectification zone, a stripping zone, a prefractionation zone, a main fractionation zone, and comprises at least one feed stream and at least three discharge streams. Wherein the at least one feed stream is a crude product stream comprising hexamethylenediamine and the at least three discharge streams are a light component stream comprising a minor amount of hexamethylenediamine, a hexamethylenediamine product stream, a heavy component stream comprising a minor amount of hexamethylenediamine.
The crude product stream containing hexamethylenediamine enters the intermediate feed plate of the prefractionation zone, the upper and lower portions of the feed plate of the prefractionation zone being in communication. A light component stream containing a small amount of hexamethylenediamine flows out from the top of the rectification zone, and a heavy component containing a small amount of hexamethylenediamine flows out from the bottom of the stripping zone. The hexamethylenediamine product stream flows from the middle discharge plate of the main fractionation zone, with the upper and lower portions of the discharge plate of the main fractionation zone being in communication. Wherein the height of the partition is determined according to the number of trays required for the prefractionation zone and the main fractionation zone.
The crude product stream containing hexamethylenediamine is, for example: 0.5-10wt% of 1, 3-diazacyclohexane, aminomethylcyclopentane, aminopropanol and other light components, 80-99wt% of hexamethylenediamine, 0.5-10wt% of N-ethylhexyl diamine, 2-hexanetriamine and other heavy components.
The hexamethylenediamine product stream is, for example: more than 99.9wt% hexamethylenediamine, less than 1000ppmwt of light and heavy component impurities.
Among them, the dividing wall column operating pressure is 1 to 10kPaA, including, for example, but not limited to, 1kPaA, 2kPaA, 3kPaA, 4kPaA, 5kPaA, 6kPaA, 7kPaA, 8kPaA, 9kPaA, 10kPaA, preferably 2 to 5kPaA.
The partition tower is divided into a left part and a right part due to the action of the partition plate, the left side of the partition plate is used as a prefractionator, firstly, the light component and the heavy component are prefractionated, the right side of the partition plate is used as a main fractionating tower, and the light component, the heavy component and the product are further separated.
The prefractionation area plays a role of a prefractionation tower in the conventional rectification process, a crude product stream containing hexamethylenediamine enters a middle feeding plate of the prefractionation area, steam from the stripping area and liquid from the rectification area enter the prefractionation area for gas-liquid mass transfer exchange, and steam rich in light components and part of products (hexamethylenediamine) flows out of the top of the prefractionation area and enters the rectification area; the liquid rich in heavy components and a part of the product (hexamethylenediamine) flows out from the bottom of the prefractionation zone and enters the stripping zone.
The main fractionating region plays a role of a main fractionating tower in the conventional rectifying process, the hexamethylenediamine product flow flows out from the middle discharging plate of the main rectifying region, light components and products are mainly separated above the discharging plate of the main fractionating region, and heavy components and products are mainly separated below the discharging plate of the main fractionating region. The steam from the stripping area and the liquid from the rectifying area enter a main fractionating area for gas-liquid mass transfer exchange, wherein the steam rich in light components and a small amount of products (hexamethylenediamine) flows out from the top of a prefractionation area and enters the rectifying area; the liquid rich in heavy components and small amount of product (hexamethylenediamine) flows out from the bottom of the prefractionation area and enters the stripping area.
The steam from the top of the prefractionation area and the top of the main fractionation area both contain light components and products (hexamethylenediamine), enter the bottom of the rectification area, the steam from the rectification area enters a condenser for condensation, one part of condensed liquid is used as reflux and enters the top of the rectification area, thus the light components are separated from the products, and the other part of condensed liquid of the condenser is taken as light components. The vapor entering the bottom of the rectifying area and the reflux liquid entering the top of the rectifying area are subjected to gas-liquid mass transfer exchange, the liquid containing light components and products (hexamethylenediamine) flowing out of the bottom of the rectifying area is divided into two streams which are respectively sent to the prefractionation area and the main fractionation area, and the distribution ratio of the two streams of liquid is required to be controlled in order to achieve the required separation effect, and can be specifically adjusted according to the reflux ratio at two sides of the partition plate.
Liquids from the bottom of the prefractionation zone and the bottom of the main fractionation zone, both containing heavies and product (hexamethylenediamine), enter the top of the stripping zone, a portion of the liquid from the bottom of the stripping zone enters the reboiler to produce steam, and the steam enters the bottom of the stripping zone, thus separating heavies from the product, and another portion of the liquid from the bottom of the stripping zone is withdrawn as heavies. The vapor entering the bottom of the stripping zone and the liquid entering the top of the stripping zone are subjected to gas-liquid mass transfer exchange, and the vapor containing heavy components and product (hexamethylenediamine) exiting the top of the rectifying zone is split into two streams which are sent to the prefractionating zone and the main fractionation zone, respectively, and these two streams are distributed by the inherent pressure drops of the prefractionating zone and the main fractionation zone.
The invention is further illustrated, but not limited, by the following examples.
The main raw material sources of the following examples are as follows:
the hexamethylenediamine reaction liquid comes from a hexamethylenediamine pilot plant reaction unit;
the ionic liquid is prepared by the following preparation process:
1-octenyl-3-methylimidazole hexafluorophosphate, prepared in two steps, the first step is to synthesize brominated 1-octenyl-3-methylimidazole ([ C) 8 mim]Br), 100g of freshly distilled N-methylimidazole and 300ml of trichloroethane were introduced into a round-bottomed flask, 200g of freshly distilled 8-bromo-1 were added dropwise at 60℃with vigorous stirringOctene is added dropwise for more than 2 hours, and then the mixture is refluxed at 80 ℃ for about 3 hours after the addition, the reaction phenomenon is that the mixture turns into orange-yellow sticky liquid after being turbid, the ionic liquid is separated by a separating funnel, and after being washed for a plurality of times by trichloroethane, the mixture is dried in vacuum at 65 ℃ for 48 hours to remove residual solvent and water, thus obtaining [ C ] 8 mim]Br; second step Synthesis of 1-octenyl-3-methylimidazole hexafluorophosphate 250g sodium hexafluorophosphate (NaPF 6 ) Dissolving in 500mL water, and adding [ C ] obtained in the first step 8 mim]Br, stirring for 36h, then extracting with dichloromethane, washing the organic layer several times with water until AgNO is added dropwise to the removed aqueous phase 3 The solution did not yellow precipitate. The dichloromethane solvent was distilled off first and dried under vacuum at 60℃for 24 hours to remove the residual solvent and water.
1-heptenyl-3-ethylimidazole hexafluorophosphate, similar to 1-octenyl-3-methylimidazole hexafluorophosphate, is prepared in two steps, the first step being the synthesis of brominated 1-heptenyl-3-ethylimidazole ([ C) 7 mim]Br), except that the temperature of dropwise adding 7-bromo-1-heptene to a solution of N-methylimidazole and trichloroethane was 55 ℃; the second step of synthesizing 1-heptenyl-3-ethylimidazole hexafluorophosphate is the same as the method for synthesizing 1-octenyl-3-methylimidazole hexafluorophosphate.
1-decenyl-3-methylimidazole hexafluorophosphate, similar to 1-octenyl-3-methylimidazole hexafluorophosphate, is also prepared in two steps, the first step being to synthesize brominated 1-decenyl-3-methylimidazole ([ C) 10 mim]Br), except that the temperature of dropwise adding 10-bromo-1-decene to a solution of N-methylimidazole and trichloroethane was 65 ℃; the second step of synthesizing 1-decenyl-3-methylimidazole hexafluorophosphate is the same as that of synthesizing 1-octenyl-3-methylimidazole hexafluorophosphate.
1-hexenyl-3-ethylimidazole hexafluorophosphate, similar to 1-octenyl-3-methylimidazole hexafluorophosphate, is prepared in two steps, the first step being the synthesis of brominated 1-hexenyl-3-ethylimidazole ([ C) 6 mim]Br), except that the temperature of dropwise adding 6-bromo-1-hexene to a solution of N-ethylimidazole and trichloroethane was 50 ℃; second step of synthesizing 1-hexenyl-3-ethylimidazoleThe method for synthesizing the hexafluorophosphate is the same as that for synthesizing the 1-octenyl-3-methylimidazole hexafluorophosphate.
1-n-butyl-3-methylimidazole tetrafluoroborate is prepared by a method similar to that of 1-octenyl-3-methylimidazole hexafluorophosphate and is prepared in two steps, wherein brominated 1-n-butyl-3-methylimidazole ([ C ] is synthesized in the first step 4 mim]Br), except that the temperature of dropwise adding 4-bromo-N-butane to a solution of N-methylimidazole and trichloroethane was 52 ℃; the second step of synthesizing 1-n-butyl-3-methylimidazole tetrafluoroborate, sodium tetrafluoroborate (NaBF 4 ) Dissolving in water, and adding [ C ] obtained in the first step 4 mim]Br, otherwise, is the same as the method for synthesizing 1-octenyl-3-methylimidazole hexafluorophosphate.
The method for analyzing the hexamethylenediamine content comprises the following steps:
gas chromatography analysis: hydrogen Flame Ionization Detector (FID) main test conditions: chromatographic column: capillary column, column material: fused quartz; column length: 30m, column inner diameter: 0.32mm; carrier gas: nitrogen gas; vaporization chamber temperature: 150 ℃; detector temperature: 200 ℃.
Example 1
Referring to fig. 2, the ionic liquid is 1-octenyl-3-methylimidazole hexafluorophosphate, the hexamethylenediamine reaction liquid and the ionic liquid enter a hexamethylenediamine extraction tower, crude hexamethylenediamine is extracted from water by using the ionic liquid, salt is remained in the water, salt-containing wastewater obtained from the extraction tower is directly discharged, the ionic liquid and crude hexamethylenediamine material flow obtained from the extraction tower enter an ionic liquid recovery tower to separate the ionic liquid and the crude hexamethylenediamine by rectification, the ionic liquid obtained from the tower bottom is returned to the extraction tower for recycling, the crude hexamethylenediamine obtained from the tower top enters a partition tower to refine the crude hexamethylenediamine, light components are extracted from the tower top, hexamethylenediamine products are extracted from the tower bottom, and heavy components are extracted from the tower bottom.
The hexamethylenediamine reaction solution comprises the following components: 82.8% by weight of hexamethylenediamine, 15% by weight of water, 0.6% by weight of light components, 1.6% by weight of heavy components and trace salts, at a feed rate of 1000kg/h and a temperature of 40℃and a pressure of 3barg.
The flow rate of the ionic liquid is 650kg/h.
The flow rate of the product obtained was 749kg/h, the purity of the product was >99.9wt%.
The recovery rate of hexamethylenediamine was 90.4%.
Table 1 below is the plant operating conditions and table 2 is the heat consumption.
Table 1 example 1 operating conditions of the apparatus
Table 2 example 1 heat consumption of apparatus
Example 2
This example is identical to example 1 according to the scheme shown in FIG. 2, except that the ionic liquid used is 1-heptenyl-3-ethylimidazole hexafluorophosphate.
The hexamethylenediamine reaction solution comprises the following components: 80.75wt% hexamethylenediamine, 15wt% water, 1.7wt% light component, 2.55wt% heavy component and trace salt, the feed flow being 1000kg/h, the temperature being 40℃and the pressure being 3barg.
The flow rate of the ionic liquid is 300kg/h.
The flow rate of the product obtained was 719kg/h, and the product purity was >99.9wt%.
The recovery rate of hexamethylenediamine was 89%.
Table 3 below shows the plant operating conditions and Table 4 shows the heat consumption.
TABLE 3 example 2 operating conditions of the apparatus
TABLE 4 example 2 Heat consumption of apparatus
Example 3
This example is identical to example 1 according to the scheme shown in FIG. 2, except that the ionic liquid used is 1-decenyl-3-methylimidazole hexafluorophosphate.
The hexamethylenediamine reaction solution comprises the following components: 83.725% by weight of hexamethylenediamine, 15% by weight of water, 0.425% by weight of light components, 0.85% by weight of heavy components and trace salts, at a feed rate of 1000kg/h and a temperature of 40℃and a pressure of 3barg.
The flow rate of the ionic liquid is 1000kg/h.
The flow rate of the obtained product is 754kg/h, and the purity of the product is more than 99.9wt%.
The recovery rate of hexamethylenediamine was 90%.
Table 5 below shows the plant operating conditions and Table 6 shows the heat consumption.
TABLE 5 example 3 operating conditions of the plant
TABLE 6 example 3 Heat consumption of apparatus
Comparative example 1
This comparative example is identical to example 1 according to the scheme shown in FIG. 2, except that the ionic liquid used is 1-hexenyl-3-ethylimidazole hexafluorophosphate.
The hexamethylenediamine reaction solution comprises the following components: 81.2% by weight of hexamethylenediamine, 15% by weight of water, 1.5% by weight of light components, 2.3% by weight of heavy components and trace salts, at a feed rate of 1000kg/h and a temperature of 40℃and a pressure of 3barg.
The flow rate of the ionic liquid is 1500kg/h.
The flow rate of the obtained product is 652kg/h, and the purity of the product is more than 99.9wt%.
The recovery rate of hexamethylenediamine is 80.2%.
Table 7 below shows the plant operating conditions and Table 8 shows the heat consumption.
Table 7 comparative example 1 plant operating conditions
TABLE 8 comparative example 1 Heat consumption of apparatus
Comparative example 2
This comparative example is identical to example 1 according to the scheme shown in FIG. 2, except that the ionic liquid used is 1-n-butyl-3-methylimidazolium tetrafluoroborate.
The hexamethylenediamine reaction solution comprises the following components: 82.8% by weight of hexamethylenediamine, 15% by weight of water, 0.6% by weight of light components, 1.6% by weight of heavy components and trace salts, at a feed rate of 1000kg/h and a temperature of 40℃and a pressure of 3barg.
The flow rate of the ionic liquid is 650kg/h.
The flow rate of the obtained product is 663kg/h, and the purity of the product is more than 99.9wt%.
The recovery rate of hexamethylenediamine was 80%.
Table 9 below shows the plant operating conditions and Table 10 shows the heat consumption.
Table 9 comparative example 2 plant operating conditions
Table 10 comparative example 2 heat consumption of the apparatus
Comparative example 3
As shown in figure 3, the hexamethylenediamine reaction liquid enters a hexamethylenediamine dehydration tower 7, waste water is discharged from the tower top, and crude hexamethylenediamine is obtained from the tower bottom. The crude hexamethylenediamine enters a desalting tower 8, salt and partial heavy components are discharged from the tower bottom, and crude hexamethylenediamine without salt is obtained from the tower top. The crude hexamethylenediamine without salt enters a light component removal tower 9, the top of the tower is discharged with light components, and the bottom of the tower is provided with hexamethylenediamine containing heavy components. The hexamethylenediamine containing heavy components enters a hexamethylenediamine refining tower 10, the hexamethylenediamine product is obtained at the top of the tower, and the heavy components are discharged from the bottom of the tower.
The hexamethylenediamine reaction solution comprises the following components: 82.8% by weight of hexamethylenediamine, 15% by weight of water, 0.6% by weight of light components, 1.6% by weight of heavy components and trace salts, at a feed rate of 1000kg/h and a temperature of 40℃and a pressure of 3barg.
The flow rate of the obtained product is 748kg/h, and the purity of the product is more than 99.9wt%.
The hexamethylenediamine yield was 90.3%.
Table 11 below shows the plant operating conditions and Table 12 shows the heat consumption.
Table 11 comparative example 3 plant operating conditions
Table 12 comparative example 3 heat consumption of the apparatus
| Apparatus and method for controlling the operation of a device | 1 | 4 | 7 | 10 |
| Heat consumption/KW | 259 | 99 | 885 | 265 |
While the present invention has been described in detail through the foregoing description of the preferred embodiment, it should be understood that the foregoing description is not to be considered as limiting the invention. Those skilled in the art will appreciate that certain modifications and adaptations of the invention are possible and can be made under the teaching of the present specification. Such modifications and adaptations are intended to be within the scope of the present invention as defined in the appended claims.
Claims (10)
1. A process for purifying hexamethylenediamine with low energy consumption, comprising the steps of:
1) Extracting hexamethylenediamine and impurities from water by using ionic liquid as an extracting agent from the aqueous reaction liquid of the hexamethylenediamine reaction system to obtain an extraction mixed liquid;
2) Standing and layering the extraction mixed liquor obtained in the step 1), discharging a water phase as wastewater, wherein an organic phase is a mixture of ionic liquid, hexamethylenediamine and impurities;
3) Separating the organic phase obtained in the step 2), obtaining crude hexamethylenediamine at the top and obtaining ionic liquid at the bottom, and returning to the step 1) for recycling the extractant;
4) And 3) feeding the crude hexamethylenediamine obtained in the step 3) into a bulkhead tower to remove light/heavy component impurities, thereby obtaining a hexamethylenediamine product with the purity of more than 99.9 weight percent.
2. The method of claim 1, wherein the ionic liquid consists of two parts, a cation m+ and an anion N-; the cation M+ is imidazole type cation with double substituent groups; the anion N-is hexafluorophosphate; preferably, two substituent groups in the double substituent groups are different, wherein one substituent group is a C7-C10 straight-chain alkenyl group, and the other substituent group is a C1-C2 alkyl group.
3. The process according to claim 1, wherein the mass ratio of the ionic liquid as extractant in step 1) to the aqueous reaction liquid exiting from the hexamethylenediamine reaction system is from 0.1 to 3, preferably from 0.3 to 1.
4. The method according to claim 1, wherein step 1) and step 2) are performed in the same device or in two devices, respectively; preferably, the same equipment is selected from any one of a packing extraction tower, a sieve plate extraction tower, a rotary disk extraction tower, a mixer-settler and a centrifugal extractor; the two devices are a stirring kettle and a split-phase tank respectively.
5. The process according to claim 1, wherein the crude hexamethylenediamine is separated from the ionic liquid in step 3) at a pressure of 1 to 10kPaA, preferably 3 to 6kPaA.
6. The method according to claim 1 or 5, wherein the equipment used for separating the crude hexamethylenediamine and the ionic liquid in step 3) is selected from any one of a thin film evaporator, a falling film evaporator, a rising film evaporator, and a rectifying column.
7. The process of claim 1, wherein the dividing wall column for separating crude hexamethylenediamine in step 4) comprises: the device comprises a main tower, a condenser, a reboiler and a partition plate;
preferably, the main column is divided into a rectification zone, a stripping zone, a prefractionation zone, a main fractionation zone, and comprises at least one feed stream and at least three discharge streams;
the rectification area is mainly used for removing low-boiling-point components, and the stripping area is mainly used for removing high-boiling-point components;
the at least one feed stream is a crude product stream comprising hexamethylenediamine and the at least three discharge streams are a light component stream comprising a minor amount of hexamethylenediamine, a hexamethylenediamine product stream, a heavy component stream comprising a minor amount of hexamethylenediamine.
8. The process of claim 7 wherein the crude product stream comprising hexamethylenediamine enters a middle feed plate of a prefractionation zone, the upper and lower portions of the prefractionation zone feed plate being in communication;
a light component stream containing a small amount of hexamethylenediamine flows out from the top of the rectification area, and a heavy component containing a small amount of hexamethylenediamine flows out from the bottom of the stripping area;
the hexamethylenediamine product stream flows from the middle discharge plate of the main fractionation zone, and the upper and lower portions of the discharge plate of the main fractionation zone are in communication.
9. The method of claim 7, wherein the height of the baffles is determined based on the number of trays required for the prefractionation and main fractionation zones; preferably, the dividing wall column is operated at a pressure of from 1 to 10kPaA, preferably from 2 to 5kPaA.
10. The method according to any one of claims 7 to 9, characterized in that the crude stream comprising hexamethylenediamine comprises: 0.5-10wt% of 1, 3-diazacyclohexane, aminomethylcyclopentane, light components of aminopropanol, 80-99wt% of hexamethylenediamine, 0.5-10wt% of N-ethylhexyl diamine, heavy components of 2-hexanetriamine;
the hexamethylenediamine product stream comprises: more than 99.9wt% hexamethylenediamine, less than 1000ppmwt of light and heavy component impurities.
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