Synthetic method for preparing high-yield tetraacetylethylenediamine at one time

Abstract

The invention provides a synthesis method for preparing high-yield tetraacetylethylenediamine at one time, which comprises the following steps: S1) taking ethylenediamine and toluene as a base, dropwise adding acetic acid, heating and refluxing at the same time, and dehydrating in a water segregator until no water is generated; s2) adding acetic anhydride and methylbenzene, carrying out low-temperature azeotropy to take out acetic acid, extracting and separating acetic acid from azeotropic liquid through ice water, drying a raffinate phase, then recycling the raffinate phase, carrying out high-temperature reflux reaction for 1 hour, and repeating low-temperature acid extraction and high-temperature reaction for three times respectively; the method has the advantages that the heat supply process and the methylbenzene low-temperature acid extraction process are repeatedly and sectionally implemented, so that the production efficiency is improved, the single yield is improved, the color of the product is better, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a synthesis method for preparing tetraacetylethylenediamine with high yield in a single step. Background Art

[0002] Tetraacetylethylenediamine (TAED) is a highly efficient low-temperature oxygen-based bleaching activator. It is biodegradable and harmless to the environment. It can significantly increase the activity of sodium perborate or sodium percarbonate. It will not affect the functions of silicates, brighteners, enzymes and other detergent aids in various laundry detergent formulas. In addition, as an additive to oxygen-based bleach, tetraacetylethylenediamine can enable oxygen-based bleach to fully exert its unique effects of whitening, brightening, disinfection and sterilization under low temperature conditions. It has good compatibility with various enzymes and other surfactants and is non-toxic. Moreover, tetraacetylethylenediamine can completely react and decompose and release active oxygen at a water temperature of 30-60°C, achieving the effects of energy saving, efficient bleaching and safe washing.

[0003] In the prior art, the synthesis of tetraacetylethylenediamine is mostly based on ethylenediamine, acetic acid, and acetic anhydride as raw materials, and a two-step same-cauldron preparation process is adopted. The first step is mixed reaction dehydration, and the second step is to use a catalyst (Chinese patent CN1463963A), microwave induction (Preliminary study on microwave-induced catalytic synthesis of tetraacetylethylenediamine [J]. Leather Chemical Industry. 2003, (2)), gradient heating and adding acetic anhydride in batches (Chinese patent CN109970589A) and other processes to prepare TAED. However, when ethylenediamine and acetic acid are mixed, the temperature is cooled and controlled, the temperature is raised after mixing, and dehydration is performed after the reaction. This series of operations results in a long process time. Diacetylethylenediamine and acetic anhydride react to generate tetraacetylethylenediamine and acetic acid, but acetic acid will inhibit the reaction, and the effects of the catalyst and microwave are not ideal, so it is necessary to separate acetic acid. However, the reaction requires high temperature to increase the rate and conversion rate, so the only way to separate acetic acid from acetic anhydride is by high-temperature distillation. The high temperature of distillation promotes side reactions, and the conversion rate is slow in the later stage of the reaction, which results in many side reactions, low single product yield (<90%), and dark product color. Summary of the invention

[0004] The invention aims to provide a synthesis method for preparing tetraacetylethylenediamine with high yield in a single time, which is suitable for large-scale industrial production, improves production efficiency, improves single yield and has better product color.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solutions: A synthetic method for preparing tetraacetylethylenediamine with high yield in a single step comprises the following steps: S1) Using ethylenediamine and toluene as the base, adding acetic acid dropwise, diacetylethylenediamine can be generated, and at the same time, the temperature is raised and refluxed in the water separator for dehydration until no water is produced; at this time, the liquids that are heated and refluxed are toluene and water; S2) Add acetic anhydride to generate tetraacetylethylenediamine, and then toluene is azeotropically extracted with acetic acid at low temperature, and the azeotropic liquid is then extracted with ice water to separate the acetic acid, and the raffinate is dried and recycled; The high temperature reflux reaction is performed for 1 hour; at this time, the liquids refluxed at high temperature are acetic acid and acetic anhydride; high temperature reflux means that the temperature is raised to the boiling point of the solvent before the reaction is performed, and the role of high temperature reflux is to accelerate the reaction speed and improve the conversion rate; however, long-term high temperature reflux will promote side reactions, resulting in many side reactions, excessive impurities, and low yields; Low-temperature acid extraction can reduce the high-temperature time of side reactions, so low-temperature acid extraction and high-temperature reflux reaction were repeated three times each; S3) cooling, centrifuging and separating acetic anhydride, and recovering the acetic anhydride for reuse; S4) washing with water and drying to obtain the finished product of tetraacetylethylenediamine, which is the target product.

[0006] Furthermore, the toluene serves as both a water-carrying agent and an acid-carrying agent.

[0007] Furthermore, in step S2), the temperature range of azeotropic removal of acetic acid by toluene is 110-125°C.

[0008] Furthermore, in step S2), the temperature range of azeotropic removal of acetic acid by toluene is 115-120°C.

[0009] Furthermore, in step S2), the temperature range of the high temperature reflux reaction is 140-150°C.

[0010] Furthermore, in step S2), the temperature range of the high temperature reflux reaction is 143-148°C.

[0011] Furthermore, in step S2), the low-temperature acid extraction and high-temperature reflux reaction are repeated in a staged process to advance the reaction.

[0012] Furthermore, in step S2), the azeotropic liquid is circulated externally to separate acetic acid through ice water extraction, and toluene is retained in the external circulation during high-temperature reflux reaction.

[0013] Compared with the prior art, the present invention has the following advantages: The present invention discloses a method for preparing tetraacetylethylenediamine with high yield in a single process. The method improves production efficiency by repeatedly implementing a heating process and a toluene low-temperature acid extraction process in stages, thereby improving the single yield, and the product color is better, which is suitable for large-scale industrial production. Specifically, the yield of tetraacetylethylenediamine obtained by the method of the present invention is greater than 95%; in the process, toluene can be recycled, acetic anhydride can be recovered and reused, and the generated acetic acid can be used as a raw material and a by-product, which greatly improves the added value of the process; wherein, the yield of acetic anhydride recovery and reuse is greater than 97%. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0015] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0016] like Figure 1 The figure shows a schematic diagram of the process of preparing tetraacetylethylenediamine according to the present invention, including the sequence of adding raw materials, the generated intermediate products, the purification process, the recycling and recovery process. Example 1

[0017] Add 100g of ethylenediamine and 300g of toluene to a four-necked flask, stir evenly, and then add 240g of acetic acid to the system through a syringe, and heat and reflux at the same time to dehydrate in a water separator until no water is produced. Add 1088g of acetic anhydride, extract acetic acid from toluene at low temperature, extract acetic acid from the azeotropic liquid with ice water, and then dry the raffinate for recycling. Reflux at high temperature for 1h, and repeat low temperature acid extraction and high temperature reaction three times each. Cool down and centrifuge to separate acetic anhydride. Wash with water and dry to obtain 362.07g of tetraacetylethylenediamine with a yield of 95.28%. Example 2

[0018] Add 100g of ethylenediamine and 300g of toluene to a four-necked flask, stir evenly, and then add 240g of acetic acid (recovered) to the system through a syringe, and heat and reflux to dehydrate in a water separator until no water is produced. Add 1088g of acetic anhydride (including recovery), extract acetic acid from toluene at low temperature, extract acetic acid from the azeotropic liquid with ice water, and dry the raffinate for recycling. Reverse the reaction at high temperature for 1h, and repeat the low temperature acid extraction and high temperature reaction three times each. Cool down and centrifuge to separate acetic anhydride. Wash with water and dry to obtain 369.09g of tetraacetylethylenediamine with a yield of 97.13%. Example 3

[0019] Add 100g of ethylenediamine and 300g of toluene to a four-necked flask, stir evenly, and then drop 240g of acetic acid (recovered) into the system through a syringe, and heat and reflux to dehydrate in a water separator until no water is produced. Add 1088g of acetic anhydride (including recovery), extract acetic acid from toluene at low temperature, extract acetic acid from the azeotropic liquid with ice water, and dry the raffinate for recycling. Reverse the reaction at high temperature for 1h, and repeat the low temperature acid extraction and high temperature reaction three times each. Cool down and centrifuge to separate acetic anhydride. Wash with water and dry to obtain 370.58g of tetraacetylethylenediamine with a yield of 97.52%.

[0020] The above description is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the concept of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A synthetic method for preparing tetraacetylethylenediamine in a single step with high yield, characterized in that The steps include: S1) Using ethylenediamine and toluene as the base, acetic acid is added dropwise to generate diacetylethylenediamine, and the temperature is raised and refluxed to dehydrate in a water separator until no water is produced; S2) acetic anhydride is added to generate tetraacetylethylenediamine, and acetic acid is removed by azeotropic reaction with toluene at low temperature. The azeotropic liquid is then extracted with ice water to separate acetic acid, and the raffinate is dried and recycled; High temperature reflux reaction for 1h; Repeat low-temperature acid extraction and high-temperature reaction three times each; S3) cooling, centrifuging and separating acetic anhydride, and recovering the acetic anhydride for reuse; S4) washing with water and drying to obtain the finished product of tetraacetylethylenediamine, which is the target product.

2. The method for synthesizing tetraacetylethylenediamine in a single step with high yield according to claim 1, characterized in that: The toluene serves as both a water-carrying agent and an acid-carrying agent.

3. The synthetic method for preparing tetraacetylethylenediamine in a single step with high yield according to claim 1 or 2, characterized in that: In step S2), the temperature range of azeotropic removal of acetic acid by toluene is 110-125°C.

4. The method for synthesizing tetraacetylethylenediamine in a single step with high yield according to claim 3, characterized in that: In step S2), the temperature range of azeotropic removal of acetic acid by toluene is 115-120°C.

5. The method for synthesizing tetraacetylethylenediamine in a single step with high yield according to claim 1 or 2, characterized in that: In step S2), the temperature range of the high temperature reflux reaction is 140-150°C.

6. The method for synthesizing tetraacetylethylenediamine in a single step with high yield according to claim 5, characterized in that: In step S2), the temperature range of the high temperature reflux reaction is 143-148°C.

7. The method for synthesizing tetraacetylethylenediamine in a single step with high yield according to claim 1 or 2, characterized in that: In step S2), the reaction is promoted by repeating the low-temperature acid extraction and high-temperature reflux reaction in a staged process.

8. The method for synthesizing tetraacetylethylenediamine in a single step with high yield according to claim 1 or 2, characterized in that: In step S2), the azeotropic liquid is circulated externally to separate acetic acid through ice water extraction, and toluene is retained in the external circulation during high-temperature reflux reaction.

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