CN114249655A - Method for separating alkali from hydrogenation product of decanedinitrile - Google Patents
Method for separating alkali from hydrogenation product of decanedinitrile Download PDFInfo
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- CN114249655A CN114249655A CN202111598736.XA CN202111598736A CN114249655A CN 114249655 A CN114249655 A CN 114249655A CN 202111598736 A CN202111598736 A CN 202111598736A CN 114249655 A CN114249655 A CN 114249655A
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
- C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
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- C07—ORGANIC CHEMISTRY
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- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
- C07C209/44—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of carboxylic acids or esters thereof in presence of ammonia or amines, or by reduction of nitriles, carboxylic acid amides, imines or imino-ethers
- C07C209/48—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of carboxylic acids or esters thereof in presence of ammonia or amines, or by reduction of nitriles, carboxylic acid amides, imines or imino-ethers by reduction of nitriles
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- 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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- C07C209/86—Separation
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Abstract
The invention belongs to the technical field of fine chemical products, and particularly relates to a method for separating alkali from a sebacic dinitrile hydrogenation product. The separation method of the present invention comprises: the invention relates to a method for preparing decamethylene diamine, which comprises four steps of ethanol recovery, alkali liquor primary separation, dehydration and alkali liquor secondary separation, wherein the method comprises the steps of separating out a catalyst by a sedimentation filtration method, recovering ethanol by a distillation or batch rectification method, performing two-phase separation by using a decamethylene diamine crude product and a concentrated alkali liquor as different phases and having large density difference, and dehydrating and settling the separated decamethylene diamine crude product to separate a small amount of alkali. Compared with the rectification process, the method has the advantages of low energy consumption, good separation effect, no pipeline valve blockage phenomenon in the production process and strong operability; the separation method disclosed by the invention is adopted to separate the liquid alkali in the hydrogenated products of the sebacic dinitrile, so that the repeatability is good, the alkali residue rate is low, and the average alkali residue rate is less than 20 mg/kg; the liquid caustic soda separated by the method can be reused for a sebacic nitrile hydrogenation process, can be circulated for a plurality of times, and can reduce resource waste.
Description
Technical Field
The invention belongs to the technical field of fine chemical products, and particularly relates to a method for separating alkali from a sebacic dinitrile hydrogenation product.
Background
Decamethylene diamine is a main raw material for synthesizing polyamide engineering plastics and hot melt adhesive, is also used in the industries of clothing, surfactants, epoxy resin and the like, and is a fine chemical intermediate with wide application.
Decamethylenediamine belongs to long carbon chain diamine, and the main production method comprises the following steps: preparing decanedionitrile by ammoniating decanedioic acid, and preparing decanediamine by catalytic hydrogenation of decanedioic acid, wherein the hydrogenation process adopts ethanol as a solvent, raney nickel as a catalyst, and strong bases such as sodium hydroxide and potassium hydroxide as a cocatalyst for batch or continuous production; after the hydrogenation process is finished, firstly rectifying to recover ethanol, and then separating and purifying crude amine by a rectification process, which is worth explaining that the system becomes special due to the strong alkali, if the alkali can not be separated or removed before rectification, tower packing and related valves are easy to block, the rectification residual liquid is greatly increased, and the product yield is obviously reduced (3-12 wt%).
Therefore, strong base in the crude decamethylenediamine system has great influence on the subsequent separation of decamethylenediamine, so that the crude decamethylenediamine before rectification needs to be subjected to dealkalization treatment, such as: when certain domestic enterprises produce the same type of aliphatic amine, a continuous dehydration method is adopted firstly, an alkali-containing mixture is collected at the bottom of a tower, most of amine is evaporated through a decoking tower, and then a concentrated phase and a dilute phase are obtained through centrifugal settling separation, the concentrated phase contains more alkali, the aliphatic amine needs to be further recovered through an extraction method, the dilute phase enters a tar stripping tower to recover the aliphatic amine, however, the process is complex, the steps are complex, tower fillers and pipeline valves are easily blocked in production, the energy consumption is high, the alkali cannot be recycled, and the waste of resources is caused; therefore, in view of the shortcomings of the prior art, it is necessary to develop a method for alkali separation of hydrogenation products.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for separating alkali from a decanedinitrile hydrogenation product. The invention separates the catalyst by a sedimentation filtration method, recovers the ethanol by a distillation or batch rectification method, separates two phases by using the crude decamethylene diamine and the concentrated alkali liquor which are different in phase and have large density difference, and dehydrates and sedimentates the separated crude decamethylene diamine to separate a small amount of alkali. The method has the advantages of simple process, simple and convenient operation, no residue of alkali liquor, reuse of separated alkali liquor, economy and environmental protection.
In order to solve the technical problems, the invention adopts the following technical scheme: a method for separating alkali from a decanedinitrile hydrogenation product comprises the following steps:
(1) ethanol recovery:
recovering ethanol in a decanedionitrile hydrogenation system by adopting a distillation or batch rectification method until the temperature of the system reaches 115-120 ℃;
(2) primary separation of alkali liquor:
conveying the decamethylene diamine mixture subjected to ethanol removal in the step (1) to an alkali-liquid separator, controlling the temperature of the alkali-liquid separator at 65-75 ℃, standing and settling for 40-80 min, and sequentially extracting crude decamethylene diamine at the upper layer and concentrated alkali liquid at the lower layer through a liquid level valve;
(3) and (3) dehydrating:
conveying the crude decamethylene diamine separated in the step (2) to a dehydration kettle, heating by using steam, maintaining the temperature of the system at 100-110 ℃, simultaneously vacuumizing to keep the surface pressure at-0.08 to-0.06 MPa, and stirring for 1-2 hours in the dehydration process;
(4) secondary separation of alkali liquor:
(4.1) extracting a decamethylene diamine crude product: conveying the crude amine obtained after the dehydration in the step (3) to another alkali-liquid separator, standing, settling and separating, controlling the temperature at 65-80 ℃, separating a small amount of alkali from the system in the settling process, settling at the bottom of the separator, and collecting a decamethylene diamine crude product through a liquid level valve after 80-120 min;
(4.2) liquid caustic extraction: accumulating the alkali liquor for many times, and adding a proper amount of water into the alkali liquor for dilution when the alkali liquor is sufficiently large in amount. Because the liquid alkali amount of the secondary separation is very little, the single separation does not need to be extracted, and can be accumulated and separated for a plurality of times, but the alkali liquor of the secondary separation has very little water content and very high viscosity, so the alkali liquor can not be directly extracted, and can be discharged after being diluted by adding a small amount of water.
The distillation final temperature in the ethanol recovery in the step (1) is 115-120 ℃, because: when the final distillation temperature is lower than 115 ℃, a considerable amount of ethanol is easy to remain in the crude decamethylenediamine, the ethanol is dissolved with the decamethylenediamine, water and the ethanol are dissolved mutually, and alkali is easy to dissolve in water and can also dissolve in the ethanol, so that the delamination is not facilitated, and part of alkali can be brought into the crude decamethylenediamine;
the final distillation temperature is higher than 120 ℃, excessive evaporation of water in the crude decamethylene diamine is not beneficial to separation of system alkali liquor, and as the solubility of decamethylene diamine in water is extremely low (within the range of 65-95 ℃), the solubility of strong bases (sodium hydroxide and potassium hydroxide) in water is relatively high, even the bases are mixed and dissolved in any proportion, a proper amount of water is reserved in a decamethylene diamine mixed system, and phase boundary separation is facilitated, so that the purpose of removing alkali from the system is achieved.
Further, the base in the sebacic acid nitrile hydrogenation product is a strong base including sodium hydroxide, potassium hydroxide, lithium hydroxide.
And (3) standing and settling for 40-80 min when the alkali liquor is separated for the first time in the step (2), and controlling the temperature of an alkali liquor separator to be 65-75 ℃. When the temperature is lower than 65 ℃ and is close to the melting point of decamethylenediamine (62-63 ℃), the crude decamethylenediamine system is easy to emulsify, is not beneficial to separation and is difficult to operate. When the temperature is higher than 75 ℃, the solubility of decamethylenediamine in water is relatively increased, which is also unfavorable for system separation. When the temperature is controlled within the range of 65-75 ℃, decamethylene diamine does not have emulsification phenomenon and has extremely low solubility in water, thereby being beneficial to the separation of decamethylene diamine and alkali liquor;
when the settling time is less than 40min, the layered interface is unclear, the two phases are not completely separated, and transition layers are increased; the settling time reaches 80min, the two phases are completely separated, and the time is prolonged without practical significance, so that the standing settling time is 40-80 min.
And further, combining the liquid alkali in the primary separation in the step (2) and the liquid alkali in the secondary separation in the step (4) for hydrogenation catalysis of the sebaconitrile.
Further, a proper amount of interface liquid level is reserved when crude decamethylene diamine and concentrated alkali liquid are extracted in the step (2), so that next separation is facilitated. The appropriate interface liquid level is reserved after the alkali liquor is extracted once because the crude decamethylene diamine phase is an organic phase and the alkali liquor phase is an inorganic water phase system, the two phases are not dissolved and can be separated when standing still, the crude decamethylene diamine product is a light phase and is positioned at an upper layer, the alkali liquor phase is a heavy phase and is positioned at a lower layer, the crude decamethylene diamine phase close to the interface contains relatively more alkali liquor, and the part of the alkali liquor phase close to the interface also contains relatively more crude decamethylene diamine.
After primary separation, the water content in a crude decamethylene diamine system is very low, the crude decamethylene diamine system is a ternary coexisting system which mainly contains decamethylene diamine and simultaneously contains a small amount of alkali liquor, the boiling point of the ternary coexisting system is far higher than that of water, if normal-pressure dehydration needs higher temperature, complete removal cannot be realized even when the temperature is heated to more than 200 ℃, the quality of decamethylene diamine is seriously affected, so negative-pressure dehydration must be adopted, the temperature selection needs to be matched with the pressure, and when the heating temperature is lower than 100 ℃, the required vacuum degree is higher, and the power consumption is high; on the contrary, when the vacuum degree is too low and is less than 0.06MPa, the water in the system is difficult to volatilize; when the heating temperature is higher than 120 ℃, some low-boiling by-products in the crude decamethylenediamine are easy to be distilled out, so the most suitable dehydration conditions are as follows: the surface pressure is-0.08 to-0.06 MPa, and the temperature is maintained at 100 to 110 ℃.
And (3) starting stirring in the ethanol recovery process in the step (1) and the dehydration process in the step (3).
Because the moisture in the crude decamethylene diamine system is very little after the dehydration in the step (3), residual alkali is slowly separated out from the system and is in a viscous flocculent form, the settling speed is very slow, and when the separation settling time is less than 80min, the alkali separation is difficult to complete, so that the crude decamethylene diamine system has alkali residue; when the settling time reaches 120min, the settling is complete, and the settling time is not required to be prolonged. Therefore, the settling time is selected to be 80-120 min before the crude decamethylenediamine is extracted.
And (4) recovering 2-5 wt% of alkali.
Further, the sebacic dinitrile hydrogenation product comprises the following components: decamethylene diamine, an ethanol solution, 0.2-2% of alkali and 10-15% of a catalyst, wherein the mass ratio of decamethylene diamine to the ethanol solution is 1: 0.4-0.6, wherein the content of the catalyst is calculated by wet weight, and the volume fraction of the ethanol solution is 92-95%.
Further, the catalyst is separated by means of sedimentation filtration before the ethanol recovery operation is carried out.
Compared with the prior art, the embodiment of the invention has the following beneficial effects:
(1) under specific process conditions, after ethanol in the hydrogenation product of the decanedinitrile is recovered by a distillation or batch rectification method, most of alkali liquor is separated by adopting a standing, settling and layering method, and a small amount of residual alkali is separated by further dehydrating, standing, settling and separating a crude decanediamine system.
(2) Compared with the rectification process, the method has the advantages of low energy consumption, good separation effect, no pipeline valve blockage phenomenon in the production process and strong operability.
(3) The process provided by the invention for separating the liquid caustic soda from the hydrogenation product of the decanedinitrile has good repeatability and low residual rate of the caustic soda, and the average residual rate of the caustic soda is less than 20 mg/kg.
(4) The liquid caustic soda separated by the method can be reused for a sebacic nitrile hydrogenation process, can be circulated for a plurality of times, and can reduce resource waste.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to the following specific examples.
Example 1
A method for separating alkali from a decanedinitrile hydrogenation product, which comprises the following steps: 1100kg of decamethylenediamine, 1000kg of 95% ethanol, 10kg of sodium hydroxide (A.R) and 130kg of Raney nickel catalyst (wet weight).
Before the alkali liquor is separated, the catalyst is removed by a method of firstly settling and then filtering, and then the mixed system is separated according to the method provided by the invention:
(1) ethanol recovery:
conveying the crude decamethylene diamine mixture to a distillation still, and intermittently recovering ethanol in a decanedionitrile hydrogenation system until the distillation temperature of the system reaches 120 ℃;
(2) primary separation of alkali liquor:
conveying the decamethylene diamine mixture subjected to ethanol recovery in the step (1) to an alkali liquid separator, controlling the temperature at 70 ℃, standing and settling for 60min, sequentially extracting an upper layer of crude decamethylene diamine and a lower layer of concentrated alkali liquid through a liquid level valve, and keeping the upper layer liquid level of 12cm and the lower layer liquid level of 5cm during extraction for next separation;
(3) and (3) dehydrating:
and (3) conveying the crude decamethylenediamine separated in the step (2) to a dehydration kettle, heating by using steam, maintaining the temperature of the system within the range of 100-105 ℃, simultaneously vacuumizing and keeping the negative pressure of-0.08 to-0.075 MPa, and stirring for 1.5 hours in the dehydration process.
(4) Secondary separation of alkali liquor:
(4.1) extracting a decamethylene diamine crude product: and (4) conveying the crude decamethylene diamine dehydrated in the step (3) to another alkali liquid separator, standing, settling and separating to separate a small amount of alkali from the system and settle at the bottom of the separator, controlling the temperature at 75-78 ℃, standing for 90min, and then extracting an upper decamethylene diamine crude product through a liquid level valve.
(4.2) liquid caustic extraction:
because the liquid caustic soda amount of the secondary separation is very little, the separation does not need to be extracted, and the liquid caustic soda can be accumulated for a plurality of times continuously; when the amount is enough, a small amount of water is added for dilution, and then the mixture can be discharged.
And (3) taking the decamethylenediamine crude product after the secondary separation, and determining the content of sodium hydroxide, wherein the obtained result is shown in table 1.
Example 2 (repeatability test)
The method for separating the alkali from the hydrogenated product of the sebacic acid dinitrile adopts the same method and conditions as the method and the conditions in the example 1, and the results are shown in the table 1
Example 3 (repeatability test)
The method for separating the alkali from the hydrogenated product of the sebacic acid dinitrile adopts the same method and conditions as the method and the conditions in the example 1, and the results are shown in the table 1
Example 4 (variation of ethanol recovery temperature outside the scope of the invention as claimed)
A method for separating alkali from a hydrogenated product of sebacic dinitrile is carried out by changing the recovery temperature of ethanol in the step (1) to 105 ℃ and keeping the same conditions as in example 1.
As a result: and (3) conveying the decamethylene diamine mixture after ethanol recovery to an alkali liquid separator, controlling the temperature at 70 ℃, standing and settling for 60min, wherein the interface between a crude amine layer and an alkali liquid layer is unclear, and the lower liquid phase is obviously increased and cannot be separated.
Example 5 (changing the temperature of the primary separation of lye outside the scope of the claimed invention)
A method for separating alkali from a hydrogenated product of decanedionitrile changes the primary separation temperature of alkali liquor in the step (2), the primary separation temperature of alkali liquor is set to 55 ℃, and the other conditions are the same as in the example 1.
As a result: the hydrogenation product system in the primary separator is turbid, has no clear phase boundary and cannot be separated.
Example 6 (varying the dehydration time outside the scope of the invention as claimed)
A process for separating the base from the hydrogenated product of sebacic dinitrile, wherein the dehydration time in step (3) is changed to 40min, and the other conditions are the same as in example 1.
The crude decamethylenediamine after the second separation was taken and the sodium hydroxide content was measured, and the results are shown in table 1.
Example 7 (changing the secondary separation settling time of the lye outside the scope of the claimed invention)
A method for separating alkali from a hydrogenated product of decanedinitrile, which changes the settling time of the secondary separation of alkali liquid in the step (4) to 50min, and the other conditions are the same as in example 1.
The crude decamethylenediamine after the second separation was taken and the sodium hydroxide content was measured, and the results are shown in table 1.
TABLE 1 table of sodium hydroxide content in decamethylenediamine crude product after secondary separation of alkali solution
| Item | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | Example 6 | Example 7 |
| Sodium hydroxide (mg/kg) | 9.2 | 10.9 | 12.0 | Cannot measure | Cannot measure | 61.0 | 35.0 |
| Recovery effect | Qualified | Qualified | Qualified | Can not be separated | Can not be separated | Fail to be qualified | Fail to be qualified |
Note:
the method for measuring the content of sodium hydroxide in crude amine comprises the following steps: extracting the crude amine after alkali separation with water, collecting water phase, and measuring sodium content by ion chromatography.
Evaluation of recovery effect: the content of sodium hydroxide in the crude amine is less than 20mg/kg, which meets the requirements of the next procedure, namely the crude amine is qualified for separation.
From the data comparison of table 1, it can be seen that:
firstly, examples 1 to 3 are repeatability tests of the invention, the sodium hydroxide content in the dealkalized decamethylenediamine is very low, and the results are basically consistent; the separation method is strong in operability, good in repeatability and reliable and stable in process.
② example 4 in the ethanol recovery temperature is lower, the final temperature is 105 ℃, lower than 120 ℃, causes ethanol recovery incomplete, so that during the primary alkali liquor separation, the crude amine layer and the alkali liquor layer interface are not clear，And the lower liquid phase is obviously increased and can not be separated.
③ the temperature of the primary separation of the alkali liquor in the embodiment 5 is controlled to be 55 ℃ and is lower than the melting point of the decamethylene diamine, so the whole hydrogenation product system is turbid in a separator, has no clear phase boundary and can not be separated.
In example 6, the dehydration time was 40min (less than 60 min), and the dehydration was incomplete, so that the crude amine phase had increased alkali residue, as evidenced by the results (61.0 mg/kg).
Fifthly, in the embodiment 7, the secondary separation time of the alkali liquor is 50min (less than 80 min), and the settling time is obviously shorter; the alkali precipitation is flocculent during the secondary separation of the liquid alkali, the viscosity is higher, and the sedimentation speed is slow; when the time was short, the residual amount of the base in the crude amine layer increased (35.0 mg/kg in example 7).
Under specific process conditions, after ethanol in a hydrogenation product of the decanedinitrile is recovered, standing, settling and layering are adopted to separate out most of alkali liquor, and then a crude decanediamine system is further dehydrated, stood, settled and separated out a small amount of residual alkali; simple process, easy operation and extremely low alkali residue.
Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.
Claims (7)
1. A method for separating alkali from a hydrogenation product of decanedinitrile, which is characterized by comprising the following steps:
(1) ethanol recovery:
recovering ethanol in a decanedionitrile hydrogenation system by adopting a distillation or batch rectification method until the temperature of the system reaches 115-120 ℃;
(2) primary separation of alkali liquor:
conveying the decamethylene diamine mixture subjected to ethanol removal in the step (1) to an alkali-liquid separator, controlling the temperature of the alkali-liquid separator at 65-75 ℃, standing and settling for 40-80 min, wherein the upper layer is crude decamethylene diamine, the lower layer is concentrated alkali liquid, and sequentially extracting the crude decamethylene diamine and the concentrated alkali liquid through a liquid level valve;
(3) and (3) dehydrating:
conveying the crude decamethylene diamine separated in the step (2) to a dehydration kettle, heating by using steam, maintaining the temperature of the system at 100-110 ℃, simultaneously vacuumizing to keep the surface pressure at-0.08 to-0.06 MPa, and stirring for 1-2 hours in the dehydration process;
(4) secondary separation of alkali liquor:
(4.1) extracting a decamethylene diamine crude product: conveying the crude decamethylene diamine obtained after dehydration in the step (3) to another alkali liquid separator, standing, settling and separating, controlling the temperature at 65-80 ℃, separating a small amount of alkali from the system in the settling process, settling at the bottom of the separator, standing for 80-120 min, and then extracting a crude decamethylene diamine through a liquid level valve;
(4.2) liquid caustic extraction: when the alkali liquor is accumulated to a certain amount, adding a proper amount of water into the alkali liquor for dilution, and discharging.
2. The method of claim 1, wherein the base in the sebacic acid nitrile hydrogenation product is a strong base comprising sodium hydroxide, potassium hydroxide, lithium hydroxide.
3. The method for separating the alkali from the hydrogenation product of sebacic dinitrile according to claim 1, wherein the liquid alkali obtained by the primary separation in step (2) and the liquid alkali obtained by the secondary separation in step (4) are combined and reused for the hydrogenation catalysis of sebacic dinitrile.
4. The method for separating the alkali from the hydrogenated sebaconitrile product according to claim 1, wherein a proper amount of interface liquid level is reserved when crude sebacenediamine and concentrated alkali liquid are extracted in step (2), so that the next separation is facilitated.
5. The method for separating the alkali from the hydrogenated sebaconitrile product of claim 1, wherein the ethanol recovery in step (1) and the dehydration in step (3) are performed under stirring.
6. The process of claim 1, wherein the catalyst is separated by sedimentation filtration prior to the ethanol recovery operation.
7. The process for separating a base from a sebacic nitrile hydrogenation product according to anyone of claims 1-6, ch a racterized by the fact that the sebacic nitrile hydrogenation product comprises the following components: decamethylene diamine, an ethanol solution, 0.2-2% of alkali and 10-15% of a catalyst, wherein the mass ratio of decamethylene diamine to the ethanol solution is 1: 0.4-0.6, wherein the content of the catalyst is calculated by wet weight, and the volume fraction of the ethanol solution is 92-95%.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109438256A (en) * | 2018-11-13 | 2019-03-08 | 中国化学赛鼎宁波工程有限公司 | A kind of production method and production system of hexamethylene diamine |
| CN110237570A (en) * | 2019-07-18 | 2019-09-17 | 重庆华峰化工有限公司 | A kind of hexamethylene diamine lye separation system |
| CN209555114U (en) * | 2018-11-13 | 2019-10-29 | 中国化学赛鼎宁波工程有限公司 | A kind of production system of hexamethylene diamine |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109438256A (en) * | 2018-11-13 | 2019-03-08 | 中国化学赛鼎宁波工程有限公司 | A kind of production method and production system of hexamethylene diamine |
| CN209555114U (en) * | 2018-11-13 | 2019-10-29 | 中国化学赛鼎宁波工程有限公司 | A kind of production system of hexamethylene diamine |
| CN110237570A (en) * | 2019-07-18 | 2019-09-17 | 重庆华峰化工有限公司 | A kind of hexamethylene diamine lye separation system |
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