Method for recovering catalyst triethylamine from ethyl acetoacetate crude product
By using Lewis acid-base reaction and metathesis reaction in crude ethyl acetoacetate, the problem of catalyst failure to recover effectively was solved, and efficient recycling and cost savings were achieved.
Patent Information
- Application Number
- CN202311738221.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-15
- Publication Date
- 2025-06-17
AI Technical Summary
The catalyst triethylamine has not been effectively recovered in the prior art, resulting in waste of raw materials and increased difficulty in treating waste liquid.
The triethylamine salt was generated by adding acid and triethylamine to the low boiling produced by the purification head to produce the Lewis acid-base reaction, followed by the addition of alkali for metathesis reaction, the triethylamine was recovered, and the same extraction and separation process was performed in the residue to further recover the triethylamine.
The catalyst triethylamine is fully recycled, with a recovery rate of more than 96%, saving costs, and the entire recycling process is low energy consumption and has good recycling effect.
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Figure CN120157585A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for recovering the catalyst triethylamine from crude ethyl acetoacetate, belonging to the technical field of chemical engineering. Background Art
[0002] Ethyl acetoacetate, also known as ethyl acetylacetate, with the chemical name ethyl 3-oxobutanoate, is an important organic synthesis raw material. It is a colorless or slightly yellow transparent liquid with a fruity fragrance. It is used in the synthesis of dyes and drugs and is also an important intermediate in other organic syntheses.
[0003] Currently, in the production of ethyl acetoacetate, the crude ethyl acetoacetate product is basically prepared by reacting DK and alcohol under the action of the alkaline catalyst triethylamine, and then rectification is carried out. Since ethyl acetoacetate is prone to decomposition during rectification at high temperatures, an acidic stabilizer is added before rectification to cause partial triethylamine to flocculate, which is beneficial to preventing the decomposition of triethylamine. Then rectification is carried out to prevent decomposition during the rectification process. Finally, the finished product, the head (specifically referring to the liquid containing more low-boiling components that is first rectified from the low-boiling tower during the rectification of crude ethyl acetoacetate), and the residue (specifically referring to the liquid containing more high-boiling and other high-polymer impurities remaining after the finished product ester is produced during the rectification of crude ethyl acetoacetate) are obtained through rectification.
[0004] In the whole process of the traditional process, the recovery and reuse of the triethylamine catalyst are not considered, resulting in waste of raw materials and increasing the difficulty of treating waste liquid.
[0005] Therefore, it is necessary to propose a method for recovering the catalyst triethylamine from crude ethyl acetoacetate. Summary of the Invention
[0006] In the existing production process of ethyl acetoacetate, due to the relatively low boiling point of the triethylamine catalyst, during the rectification process, most of the triethylamine in the crude product is distilled out together with the head and the distilled head is pumped into the head storage tank. After storing a certain amount, the head is rectified and purified to recover part of the triethylamine; the low-boiling components distilled out during the purification of the head contain more triethylamine, but are directly treated as waste liquid. In addition, due to the addition of the acidic stabilizer before rectification, the acid also reacts with part of the triethylamine to form a salt, and the salt remains in the residue after rectification and is not treated and is directly treated as waste liquid.
[0007] For this reason, the purpose of the present invention is to develop a method for recovering the catalyst triethylamine from crude ethyl acetoacetate. The present invention adds an acid to the low-boiling components generated during the purification of the head fraction to carry out a Lewis acid-base reaction with triethylamine in the low-boiling components to form the corresponding triethylamine salt, and then allows it to stand for liquid separation to obtain an aqueous solution of the triethylamine salt; after mixing the aqueous solution of the triethylamine salt, an appropriate amount of base is added thereto to react with the triethylamine salt to generate triethylamine, and triethylamine is separated from the aqueous phase to obtain triethylamine; further, water can be added to the residue obtained by preliminary distillation, and after mixing, it is allowed to stand for liquid separation to also obtain an aqueous solution of the triethylamine salt, and more triethylamine can be further recovered. The present invention can realize the full recycling of the triethylamine catalyst by using simple Lewis acid-base reactions, metathesis reactions, and extraction separation methods, saving costs.
[0008] The present invention provides a method for recovering the catalyst triethylamine from crude ethyl acetoacetate, and the method includes:
[0009] (1) Taking the head fraction after rectifying the crude ethyl acetoacetate, adding an acidic aqueous solution to the low-boiling waste liquid generated during the purification of the head fraction, allowing the acid to carry out a Lewis acid-base reaction with triethylamine to form the corresponding triethylamine salt, and separating the layers to obtain a salt solution of the triethylamine salt;
[0010] (2) Adding an appropriate amount of basic solution to the salt solution of the triethylamine salt to react with the triethylamine salt to generate triethylamine, and separating triethylamine from the aqueous phase to obtain triethylamine.
[0011] In one embodiment, the method further includes: taking the residue after rectifying the crude ethyl acetoacetate, adding water, mixing, and separating the layers to obtain a salt solution of the triethylamine salt;
[0012] In one embodiment, the crude ethyl acetoacetate refers to the crude ethyl acetoacetate prepared by reacting diketene (DK) and ethanol under the action of the basic catalyst triethylamine. The crude ethyl acetoacetate is rectified to obtain the finished product of ethyl acetoacetate, the head fraction, and the residue. Before rectifying the crude ethyl acetoacetate, an acidic stabilizer is added to cause partial flocculation of triethylamine, which can effectively inhibit the decomposition of the crude ester.
[0013] In one embodiment, specifically, the preparation of the crude ethyl acetoacetate: Initially, ethanol and the triethylamine catalyst are fully mixed, wherein triethylamine accounts for about 0.56% (about 0.17% of the total feed amount), then it is laid at the bottom of the kettle, stirring is started, and after gradually heating to above 60 °C, diketene is slowly added dropwise and the reaction starts to generate the crude ethyl acetoacetate.
[0014] In one embodiment, the rectification of the crude ethyl acetoacetate is specifically as follows: First, an acidic stabilizer is added to the crude ethyl acetoacetate to inhibit the decomposition of the ethyl ester during rectification. Then, it passes through a low-boiling-point tower. A certain temperature and vacuum are maintained inside the tower, and a certain reflux ratio is maintained at the top of the tower. The heads are started to be removed. In this step, the low-boiling impurities are removed. After removing the low-boiling components, the crude product is sent to the finished product rectification tower. A certain temperature and pressure are still maintained inside the tower, and the finished product ester is taken out at the top of the tower according to a certain reflux ratio. Finally, the residual liquid remains.
[0015] In one embodiment, the rectification of the crude ethyl acetoacetate is specifically as follows: First, the crude ethyl acetoacetate is transported to the low-boiling-point tower. The vacuum inside the tower is maintained at -90.2 Kpa, heated to 100 °C, the reflux ratio is controlled at about 1, the heads are taken out at the top of the tower, and transported to the heads storage tank; after removing the low-boiling components, the crude product is transported to the finished product tower again. The vacuum inside the tower is maintained at -98.5 Kpa, heated to 105 °C, the reflux ratio is also maintained at 1, and the finished product is taken out at the top of the tower; the remaining residual liquid is transported to the residual liquid storage tank for centralized treatment.
[0016] In one embodiment, the process for purifying the heads is specifically as follows: The heads obtained from multiple batches of rectification are concentrated, and then distilled and purified together through an evaporation tower. A certain temperature and pressure are maintained inside the tower, and most of the low-boiling waste liquid is directly distilled out at the top of the tower. What remains inside the tower is the ethyl acetoacetate product with qualified purity.
[0017] In one embodiment, the purification of the heads is specifically as follows: The heads are transported to the distillation tower. The vacuum inside the tower is maintained at -85 Kpa, heated to 92 °C, the low-boiling components are taken out at the top of the tower. After the low-boiling waste liquid is removed, the purified ethyl acetoacetate finished product is obtained inside the tower.
[0018] In one embodiment, the acidic aqueous solution selected can be an acidic aqueous solution such as HCl, H2SO4, HNO3, etc. that can react with triethylamine to form triethylamine salts. Preferably, it is HCl, which is more likely to form salts with triethylamine and is easier to extract.
[0019] In one embodiment, the H in the acid in the acidic aqueous solution + content is controlled at 0.1 mol / L, and the pH is controlled at about 1.
[0020] In one embodiment, the acidic aqueous solution accounts for more than 38% of the mass of the low-boiling components.
[0021] In one embodiment, the acidic aqueous solution accounts for 38% - 45% of the mass of the low-boiling waste liquid. If the addition amount of the acidic aqueous solution is insufficient, it will cause incomplete reaction of triethylamine in the low-boiling waste liquid, thus affecting the recovery rate of triethylamine.
[0022] In one embodiment, the layering after treatment with the acidic aqueous solution is to stir and then let it stand for layering. Optionally, it is to stir and react for 15 - 25 min, and then let it stand for 50 - 60 min for layering.
[0023] In one embodiment, the mass of water added to the residual liquid is more than 50% of the mass of the residual liquid, optionally 50% - 55%. If the amount of water added to the residual liquid is too small, the stratification boundary will not be obvious during stratification, affecting the recovery rate of triethylamine.
[0024] In one embodiment, water is added to the residual liquid, and after mixing, the stratification is carried out by mixing and standing for 28 - 38 min. Sufficient stratification time can ensure a clear boundary line during stratification, facilitating the recovery of triethylamine.
[0025] In one embodiment, the base added to the salt solution can be NaOH, KOH, Ca(OH)₂, etc., which can react with the triethylamine salt to generate triethylamine. Preferably, it is the strong base NaOH or KOH.
[0026] In one embodiment, for the base added to the salt solution, the concentration of the initially added base solution (OH⁻ content is 0.1 mol / L) is controlled; the pH is controlled to reduce side reactions. Under this condition, it is easier to react to form triethylamine and there will be no excessive hydrolysis.
[0027] In one embodiment, in the aqueous solution of triethylamine salt (m 三乙胺盐 ), an alkali solution (m 碱溶液 ) accounting for 35% - 45% of the total mass of the salt solution is added.
[0028] In one embodiment, after adding the alkali solution, the stratification of triethylamine and the aqueous phase is as follows: stirring and reacting for 25 - 30 min, and then standing for 30 - 35 min for stratification.
[0029] In one embodiment, according to the above method, 96% - 96.5% of the total amount of triethylamine can be recovered. Among them, about 80% of the total amount of triethylamine can be recovered from the head.
[0030] Advantageous effects of the present invention:
[0031] The present invention utilizes simple Lewis acid-base reactions, metathesis reactions, and extraction separation techniques to achieve the recovery of the catalyst triethylamine. Among them, most of the triethylamine can be recovered from the head, and triethylamine can also be recovered from the residual liquid. The total recovery rate of triethylamine can reach more than 96%. The method of the present invention enables the catalyst triethylamine to be fully recycled, effectively saving costs, and the entire recovery process has low energy consumption and good recovery effect. Brief Description of the Drawings
[0032] Figure 1 It is a schematic flow chart for recovering the catalyst triethylamine from the crude ethyl acetoacetate of the present invention.
[0033] Figure 2Another process schematic diagram for recovering the catalyst triethylamine from the crude ethyl acetoacetate of the present invention. Detailed implementation manners
[0034] Test / calculation method for the recovery rate of triethylamine:
[0035] Recovery rate of triethylamine = [(recovery amount of triethylamine in the head + recovery amount of triethylamine in the residue)·wt%] / [feeding amount of triethylamine catalyst in the esterification reaction·wt%] wt1% represents the content of the recovered triethylamine, and wt2% represents the content of the triethylamine catalyst fed in the esterification reaction.
[0036] As Figure 1 shown, it is a process schematic diagram for recovering the catalyst triethylamine from the crude ethyl acetoacetate in an embodiment of the present invention.
[0037] (1) Take the crude ethyl acetoacetate prepared by the reaction of diketene (DK) and ethanol under the action of the basic catalyst triethylamine, and carry out rectification to obtain the finished product of ethyl acetoacetate, the head, and the residue; an acidic stabilizer is added before the rectification of the crude ethyl acetoacetate to flocculate part of the triethylamine, which can effectively inhibit the decomposition of the crude ester;
[0038] (2) The head is concentrated and purified again to recover part of the finished product; a certain amount of low-boiling waste liquid is generated during the purification of the head. An appropriate amount of acidic aqueous solution is used to mix with the low-boiling waste liquid, and the acid and triethylamine undergo a Lewis acid-base reaction to form a triethylamine salt. At this time, the aqueous phase and the organic waste liquid are separated, and the salt solution 1 (aqueous solution of triethylamine salt) and the organic layer 1 are separately obtained;
[0039] The reaction equation for the Lewis acid-base reaction of the acid and triethylamine to form a triethylamine salt is as follows:
[0040]
[0041] (3) In the obtained salt solution, an appropriate amount of basic aqueous solution (such as NaOH) is added to undergo a metathesis reaction with the salt in the water to generate triethylamine. The triethylamine and the aqueous solution are separated, and triethylamine can be recovered; the metathesis reaction equation of the base and the triethylamine salt is as follows:
[0042]
[0043] As Figure 2 shown, it is another process schematic diagram for recovering the catalyst triethylamine from the crude ethyl acetoacetate in an embodiment of the present invention. On Figure 1 this basis, triethylamine is further recovered from the residue.
[0044] Since an acidic auxiliary agent is added to the crude ester before distillation, the auxiliary agent reacts with part of the triethylamine in the crude ester to generate salt, and the salt remains in the residual liquid after distillation; water is added to the residual liquid for extraction and separation, and after extraction and stratification, a salt solution 2 (triethylamine salt solution) and an organic layer 2 are obtained; an alkaline solution can be further added to the salt solution 2 to recover the triethylamine.
[0045] Embodiment 1:
[0046] The triethylamine recovery method of the present embodiment adopts Figure 1 The process described is as follows:
[0047] Step (1): Take crude ethyl acetoacetate. The specific preparation process of crude ethyl acetoacetate is as follows:
[0048] Initially, ethanol and triethylamine catalyst are fully mixed, wherein triethylamine accounts for about 0.56% (accounting for about 0.17% of the total feed amount), and then the mixture is spread on the bottom of the kettle, and stirring is started. After gradually heating to above 60°C, diketene is slowly added dropwise and the reaction is started to generate crude ethyl acetoacetate.
[0049] Step (2): distilling the crude ethyl acetoacetate to obtain most of the ethyl acetoacetate finished product, heads, and residual liquid;
[0050] The distillation process is as follows: first, the crude ethyl ester is transported to a low-boiling tower, the vacuum degree in the tower is maintained at -90.2 Kpa, heated to 100°C, the reflux ratio is controlled at about 1, the heads are taken out from the top of the tower, and transported to the heads storage tank; after the low-boiling tower is taken out, the crude product is transported to the finished product tower, the vacuum degree in the tower is maintained at -98.5 Kpa, heated to 105°C, the reflux ratio is also maintained at 1, and the finished product is taken out from the top of the tower; the remaining residual liquid is transported to the residual liquid storage tank for centralized treatment.
[0051] Step (3): Purify the heads obtained in (2). The specific purification process is: transport the heads to a distillation tower, maintain the vacuum degree in the tower at -85Kpa, heat to 92°C, and discharge low boiling points from the top of the tower. After the low boiling points are discharged, the purified ethyl ester product is obtained in the tower.
[0052] After purification, part of the ethyl acetoacetate product and low-boiling waste liquid are obtained.
[0053] Step (4): adding an acidic aqueous solution to the low-boiling waste liquid obtained in (3) to allow the acid to react with triethylamine to generate a corresponding triethylamine salt by Lewis acid-base reaction, extracting and stratifying to obtain a salt solution 1 of the triethylamine salt;
[0054] The acidic aqueous solution selected is HCl, and the H+ content in the acid is controlled to be 0.1 mol / L; the acidic aqueous solution accounts for 40% of the mass of the low-boiling waste liquid; and the extraction and stratification are first stirred for reaction for 20 minutes, and then allowed to stand for 55 minutes for stratification.
[0055] Step (5): Add an appropriate amount of alkali solution to the obtained salt solution to react with the triethylamine salt to form triethylamine. Triethylamine is layered with water, and then triethylamine can be obtained.
[0056] Among them, the alkali added to the salt solution is NaOH, and the content of OH- in the aqueous solution is controlled to be 0.1 mol / L.
[0057] Add an alkali solution accounting for 40% of the total mass of the salt solution to the aqueous solution of triethylamine salt; for layering, stir and react for 27 min, and then let it stand for 32 min to layer.
[0058] According to the method of this example, 81.3% of the total amount of triethylamine is recovered.
[0059] Example 2:
[0060] The triethylamine recovery method of this example uses Figure 2 the process shown.
[0061] Among them, compared with Example 1, only add step (M) for treating the residual liquid after step (4) to obtain salt solution 2; after combining salt solution 2 and salt solution 1, use the method of step (5) above for treatment.
[0062] Step (M) is specifically: Take the residual liquid obtained in (2), add water, mix and layer to obtain salt solution 2 of triethylamine salt; among them, the mass of water added is 52% of the mass of the residual liquid, and the mixing and layering is to let it stand for 32 min to layer after mixing.
[0063] According to the method of this example, 96.5% of the total amount of triethylamine is recovered.
[0064] Example 3:
[0065] The triethylamine recovery method of this example uses Figure 2 the process shown.
[0066] Compared with Example 2, only make the following changes, and other steps and conditions are the same as those in Example 2:
[0067] The acidic aqueous solution selected in step (4) is H2SO4, and the content of H+ in the acid is controlled to be 0.1 mol / L; the acidic aqueous solution accounts for 38% of the mass of the low-boiling waste liquid; stir and react for 15 min, and then let it stand for 55 min to layer;
[0068] In step (M), the mass of water added to the residual liquid is 55% of the mass of the residual liquid, and the mixing and standing layering time is 35 min;
[0069] In step (5), the base added to the aqueous solution of the salt is KOH, and the OH⁻ content in the aqueous solution is controlled to be 0.1 mol / L; a base solution accounting for 45% of the total mass of the salt solution is added to the aqueous solution of the triethylamine salt. Stir and react for 30 min, and then let it stand for 30 min to separate into layers.
[0070] According to the method of this example, 96.0% of the total amount of triethylamine was recovered.
[0071] Example 4:
[0072] The triethylamine recovery method of this example uses Figure 2 the process shown.
[0073] Compared with Example 2, only the following changes are made, and other steps and conditions are the same as those in Example 2:
[0074] In step (4), the acidic aqueous solution selected is HCl, and the H⁺ content in the acid is controlled to be 0.1 mol / L; the acidic aqueous solution accounts for 45% of the mass of the low-boiling fraction; stir and react for 20 min, and then let it stand for 60 min to separate into layers;
[0075] In step (M), the mass of water added to the residual liquid is 52% of the mass of the residual liquid, and the mixing and standing time for separation into layers is 35 min;
[0076] In step (5), the base added to the aqueous solution of the salt is NaOH, and the OH⁻ content in the aqueous solution is controlled to be 0.1 mol / L; a base solution accounting for 40% of the total mass of the salt solution is added to the aqueous solution of the triethylamine salt. Stir and react for 25 min, and then let it stand for 35 min to separate into layers.
[0077] According to the method of this example, 96.4% of the total amount of triethylamine was recovered.
[0078] Example 5:
[0079] The triethylamine recovery method of this example uses Figure 2 the process shown.
[0080] Compared with Example 2, only the following changes are made, and other steps and conditions are the same as those in Example 2:
[0081] In step (4), the acidic aqueous solution selected is HNO₃, and the H + content is controlled to be 0.1 mol / L; the acidic aqueous solution accounts for 38% of the mass of the low-boiling fraction; stir and react for 15 min, and then let it stand for 50 min to separate into layers;
[0082] In step (M), the mass of water added to the residual liquid is 50% of the mass of the residual liquid, and the mixing and standing time for separation into layers is 28 min;
[0083] In step (5), the base added to the aqueous solution of the salt is Ca(OH)2, which reacts with the triethylamine salt to form triethylamine. The OH- content in the aqueous solution is controlled to be 0.1 mol / L. A base solution accounting for 35% of the total mass of the salt solution is added to the aqueous solution of the triethylamine salt. Stir and react for 25 min, and then let it stand for 30 min to separate layers.
[0084] According to the method of this embodiment, 96.2% of the total amount of triethylamine is recovered.
[0085] Example 6
[0086] Compared with Example 1, only the following changes are made, and other steps and conditions are the same as those in Example 1:
[0087] In step (4), the acidic aqueous solution accounts for 25% of the mass of the low-boiling waste liquid.
[0088] According to this method, 67.2% of the total amount of triethylamine is recovered. Since the amount of acid added is insufficient, part of the triethylamine fails to react with hydrochloric acid to form a salt, resulting in insufficient recovery of triethylamine.
[0089] Example 7
[0090] Compared with Example 1, only the following changes are made, and other steps and conditions are the same as those in Example 1:
[0091] In step (5), the mass of water added to the residual liquid is 35% of the mass of the residual liquid.
[0092] According to this method, 68.1% of the total amount of triethylamine is recovered. Since the water fails to mix fully with the residual liquid, the triethylamine salt in the residual liquid cannot be completely extracted, resulting in a decrease in the final triethylamine recovery rate.
[0093] Example 8
[0094] Compared with Example 1, only the following changes are made, and other steps and conditions are the same as those in Example 1:
[0095] In step (6), a base solution accounting for 30% of the total mass of the salt solution is added to the aqueous solution of the triethylamine salt.
[0096] According to this method, 68.9% of the total amount of triethylamine is recovered. Since the amount of the base solution added is too small, it fails to react fully with the salt in the aqueous solution, resulting in less triethylamine being generated and a decrease in the triethylamine recovery rate.
[0097] The present invention has been disclosed in the above preferred embodiments, but it is not intended to limit the present invention. Any technical solutions obtained by using equivalent substitution or equivalent transformation fall within the protection scope of the present invention.
Claims
1. A method for recovering the catalyst triethylamine from crude ethyl acetoacetate, characterized in that, The method includes: (1) Take the head fraction after rectification of the crude ethyl acetoacetate. Add an acidic aqueous solution to the low-boiling waste liquid generated during the purification of the head fraction, so that the acid reacts with triethylamine in a Lewis acid-base reaction to form the corresponding triethylamine salt, and then separate the layers to obtain a salt solution of the triethylamine salt; (2) In the salt solution of the triethylamine salt, add an appropriate amount of alkaline solution to react with the triethylamine salt to form triethylamine. Triethylamine is separated from the aqueous phase to obtain triethylamine.
2. The method according to claim 1, characterized in that, The method further includes: Take the residue after rectification of the crude ethyl acetoacetate, add water, mix and separate the layers to obtain a salt solution of the triethylamine salt.
3. The method according to claim 1, characterized in that, The acidic aqueous solution accounts for more than 38% of the mass of the low-boiling waste liquid.
4. The method according to claim 1, characterized in that, The base added to the salt solution controls the OH content in the initially added base solution to be 0.1 mol / L; 35% - 45% of the base solution based on the total mass of the salt solution is added to the aqueous solution of the triethylamine salt. - 5. The method according to claim 2, characterized in that, The mass of water added to the residue is more than 50% of the mass of the residue.
6. The method according to claim 1, characterized in that, The crude ethyl acetoacetate refers to the crude ethyl acetoacetate prepared by the reaction of diketene and ethanol under the action of the alkaline catalyst triethylamine.
7. The method according to claim 1, characterized in that, The rectification of the crude ethyl acetoacetate is specifically as follows: First, add an acidic stabilizer to the crude ethyl acetoacetate to inhibit the decomposition of the ethyl ester during rectification, and then pass through a low-boiling tower. Keep a certain temperature and vacuum degree in the tower, keep a certain reflux ratio at the top of the tower, start to take out the head fraction. After removing the low-boiling components, the crude product is fed into the finished product rectification tower. Keep a certain temperature and pressure in the tower, and the finished product ester is taken out at a certain reflux ratio at the top of the tower, and finally the residue remains.
8. The method according to claim 1, characterized in that, The process of purifying the head fraction is specifically as follows: The head fraction obtained by rectification is distilled and purified together through an evaporation tower. Keep a certain temperature and pressure in the tower, and most of the low-boiling waste liquid is directly distilled out at the top of the tower, and the remaining in the tower is the ethyl acetoacetate product with qualified purity.
9. The method according to claim 1, characterized in that, The acidic aqueous solution is any one of HCl, H2SO4, and HNO3; the alkaline solution is any one of NaOH, KOH, and Ca(OH)2.
10. The method according to claim 1, characterized in that, The content of H in the acid in the acidic aqueous solution + is 0.1 mol / L.