阅读说明：本技术 一种ε-己内酯的连续合成方法 (Continuous synthesis method of epsilon-caprolactone ) 是由 任磊 杨忠林 金钢 于 2021-06-15 设计创作，主要内容包括：本发明公开了一种连续合成ε-己内酯的方法,以环己酮为原料,以双氧水为氧化剂,在催化剂作用下,在微通道反应器中连续氧化反应制备ε-己内酯。该方法,该方法简单易实施,与传统过氧羧酸工艺相比安全性得到显著提高,具有重要的社会效益及经济效益。(The invention discloses a method for continuously synthesizing epsilon-caprolactone, which takes cyclohexanone as a raw material and hydrogen peroxide as an oxidant to prepare the epsilon-caprolactone through continuous oxidation reaction in a microchannel reactor under the action of a catalyst. The method is simple and easy to implement, the safety is obviously improved compared with the traditional peroxycarboxylic acid process, and the method has important social and economic benefits.)

1. A continuous synthesis method of epsilon-caprolactone is characterized by comprising the following specific implementation steps: cyclohexanone and hydrogen peroxide are used as raw materials and are respectively stored in different raw material tanks, wherein a catalyst is added into the cyclohexanone in advance, two materials are respectively conveyed into a microchannel reactor for reaction, and the reaction materials are subjected to low-temperature quenching collection and treatment.

2. The method according to claim 1, wherein the concentration of hydrogen peroxide is 30-60%.

3. The method of claim 1, wherein the catalyst is ferrous bis-salicylaldehyde ethylene diamine schiff base complex.

4. A process according to claim 1 or 3, characterized in that the catalyst is added in an amount of 1-5% by weight of cyclohexanone.

5. The method of claim 1, wherein the hydrogen peroxide solution is H₂O₂The molar ratio of the cyclohexanone to the cyclohexanone is 3-5.

6. The method of claim 1, wherein the microchannel reactor is a Corning Heart Cell configuration microchannel reactor.

7. The method of claim 6, wherein the microchannel reactor is made of glass or silicon carbide, and the channel characteristic dimension is 1.0 mm; according to the reaction requirement, the reactor is divided into three parts of preheating, reaction and cooling quenching, and the materials are continuously and sequentially passed through the three parts at a preset flow rate by a pump.

8. The method of claim 7, wherein the temperature of the preheating zone and the temperature of the reaction zone are both 40 ℃ to 70 ℃, and the reaction temperature of the temperature-reducing quenching zone is less than-5 ℃.

9. The process according to claim 7, wherein the residence time of the reaction mass in the reaction zone is from 40s to 80 s.

10. The method as claimed in claim 3, wherein the catalyst is a bis-salicylaldehyde ethylene diamine Schiff base prepared from ethylenediamine and salicylaldehyde, and ferrous sulfate is added to prepare a bis-salicylaldehyde ethylene diamine Schiff base ferrous complex.

Technical Field

The invention belongs to the technical field of organic synthesis processes, and introduces a continuous synthesis method of epsilon-caprolactone. In particular to a continuous reaction process method for preparing epsilon-caprolactone by using cyclohexanone as a raw material and hydrogen peroxide as an oxidant and oxidizing the cyclohexanone under the action of a catalyst.

Background

The epsilon-caprolactone is an important polyester monomer, is mainly used for synthesizing poly epsilon-caprolactone, can be copolymerized with various resins or blended and modified, and can improve the glossiness, transparency, anti-sticking property and the like of products. In addition, the bioactive material has good biocompatibility, nontoxicity, degradability and drug permeability, and is mainly used as a bioactive material for regenerating and repairing tissues such as bones, skins, nerves and the like in biomedical engineering. The synthesis of the product has high quality requirement on raw materials, and involves harsh technological operations such as strong oxidation and the like, and the purity requirement of the product is also high. At present, only a few companies in the countries of America, English, Japan, etc. can produce the product. The global epsilon-caprolactone production capacity is about 100kt/a, 70kt of the global epsilon-caprolactone production capacity is directly used for matching production of polycaprolactone, polycaprolactone polyol and the like, and the global epsilon-caprolactone demand gap is more than 20 kt/a. At present, the annual production scale of epsilon-caprolactone in China is 5000t/a, and products mainly depend on import. In recent years, the market demand has been increasing with the increasing use of epsilon-caprolactone. In "China manufacture 2025", the product is listed as one of 18 items of high polymer materials in the important development field of the next decade.

The method for synthesizing caprolactone comprises a cyclohexanone oxidation method, a 1, 6-hexanediol liquid-phase catalytic dehydrogenation method, a 6-hydroxycaproic acid intramolecular condensation method and the like. At present, the cyclohexanone oxidation method production process is generally adopted for industrial production abroad. Cyclohexanone oxidation is further classified as peroxyacid oxidation, H₂O₂Oxidation and molecular oxygen oxidation.

At present, a peroxyacid oxidation method is a main industrial technology, the boston adopts a peroxyacid/hydrogen peroxide oxidation method process to realize 60000t/a industrial production, the xylonite and the Hunan polymeric kernel realize 10000t/a and 5000t/a peroxycarboxylic acid oxidation industrial production respectively, the tomb petrifaction finishes a 200t/a peroxycarboxylic acid oxidation method pilot test, and the 10000t/a process bag is compiled.

In prior art reports, caprolactone is prepared by reacting cyclohexanone with peroxycarboxylic acids, including peroxyacetic acid and peroxypropionic acid, among others.

CN102584775A discloses a method for producing caprolactone, which comprises the steps of separating free water brought in hydrogen peroxide water solution from the top of a stirring reaction kettle with a rectifying tower by an azeotropic rectification method through an organic solvent, reacting the obtained anhydrous hydrogen peroxide solution with acetic anhydride to obtain anhydrous peroxyacetic acid, reacting the anhydrous peroxyacetic acid with cyclohexanone to obtain an epsilon-caprolactone solution, and then carrying out rectification purification to obtain high-purity caprolactone.

CN1071923A proposes the oxidation of cyclohexanone with a percarboxylic acid containing 2 to 4 carbon atoms to produce caprolactone, the desired percarboxylic acid being used in the form of a "percarboxylic acid crude solution" obtained by reacting the corresponding carboxylic acid with hydrogen peroxide in the presence of a boric acid catalyst, the azeotropic conditions being maintained during the process to remove water continuously. In this conventional method, since an acidic catalyst is added, impurities which are difficult to separate, such as hydroxycaproic acid, 5-hexenoic acid, and an oligomer of caprolactone, are inevitably generated, which affects the subsequent purification. How to effectively innovate the process route for preparing the caprolactone, reduce the generation of impurities, reduce the difficulty of separating and purifying products, and be beneficial to industrialized application is the problem to be solved by the prior art.

The research on the synthesis of caprolactone by oxidizing peroxy acid as an oxidant is mature, and the caprolactone oxidizing process is widely applied to large-scale industrial production, but a plurality of potential safety hazards which are difficult to solve exist in actual operation, particularly, the concentration of peroxy acid in the early stage of synthesis and the generation of explosive peroxide with higher concentration in the subsequent purification process are obstacles to the practical application of the process, and the existing process technology adopts an intermittent operation mode to carry out reaction, so that the process parameters are changed greatly, the process is unstable, and the safety risk is increased undoubtedly. Historically, several caprolactone development units have suffered from human casualty accidents through explosion during the production and use of peroxyacids.

The hydrogen peroxide oxidation method is to directly oxidize cyclohexanone into epsilon-caprolactone by using hydrogen peroxide. The selectivity and yield of epsilon-caprolactone in this process are reduced because water results in hydrolysis of the product epsilon-caprolactone. In addition, from the viewpoint of process conditions, the reaction conditions are harsh, a large amount of solvent is generally required to be added, the catalyst is expensive, and the recycling of the catalyst is also challenging.

The continuous synthesis process research of caprolactone is carried out by utilizing the micro-channel reaction technical idea, which is a breakthrough to the conventional batch kettle type oxidation reaction process. Microchannel reaction equipment has a range of properties not found in conventional reactors: the device has the advantages of miniaturized channel size, larger heat exchange specific surface area, excellent mass and heat transfer characteristics, continuous reaction, capability of skipping direct amplification through a step-by-step amplification test, flexible production and high safety performance. Thus, there are advantages over the continuous implementation of highly exothermic reactions such as peracid oxidation using suitable microchannel reaction equipment.

CN103539770B describes a method for synthesizing caprolactone, which comprises the steps of firstly oxidizing acetic anhydride into peroxyacetic acid in microreactors with different structures, and reacting the peroxyacetic acid with cyclohexanone after separation and purification to synthesize caprolactone.

CN104370873A mixing the hydrogen peroxide solution and the formic acid solution, and then adding a catalyst and a stabilizer to prepare a mixed solution; and pumping the cyclohexanone and the mixed solution into a micro-channel modular reaction device respectively for reaction, and separating a reaction product to obtain a target product caprolactone.

CN105566278A pumps acetic anhydride and hydrogen peroxide respectively and simultaneously into the micro-reaction fixed bed device filled with catalyst to react, and mixes the discharged material and cyclohexanone to inject into the micro-channel reactor in the micro-reaction device to react.

CN106279093A is prepared from m-chloroperoxybenzoic acid and ethyl acetate by using a microchannel reaction technology.

Disclosure of Invention

The invention aims to provide a method for continuously synthesizing epsilon-caprolactone.

The invention relates to a method for continuously synthesizing epsilon-caprolactone, which takes cyclohexanone as a raw material and hydrogen peroxide as an oxidant to prepare the epsilon-caprolactone through continuous oxidation reaction in a microchannel reactor under the action of a catalyst.

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In order to achieve the purposes, the invention adopts the main technical scheme that: the continuous epsilon-caprolactone synthesizing process features the specific steps: cyclohexanone and hydrogen peroxide are used as raw materials and are respectively stored in different raw material tanks, wherein a catalyst is added into the cyclohexanone in advance, two materials are respectively conveyed into a microchannel reactor for reaction, and the reaction materials are subjected to low-temperature quenching collection and treatment.

Generally, the concentration of the hydrogen peroxide is 30-60%.

The catalyst is a bis-salicylaldehyde ethylene diamine Schiff base ferrous complex.

The adding amount of the catalyst is 1-5% of the weight of the cyclohexanone.

H in the hydrogen peroxide₂O₂The molar ratio of the cyclohexanone to the cyclohexanone is 3-5.

The microchannel reactor is a microchannel reactor with a Corning Heart Cell structure.

The microchannel reactor is made of glass or silicon carbide, and the characteristic dimension of the channel is 1.0 mm; according to the reaction requirement, the reactor is divided into three parts of preheating, reaction and cooling quenching, and the materials are continuously and sequentially passed through the three parts at a preset flow rate by a pump.

The temperature of the preheating section and the reaction section is 40-70 ℃, and the reaction temperature of the cooling quenching section is less than-5 ℃.

The residence time of the reaction materials in the reaction section is 40-80 s.

The catalyst is characterized in that the disalicylaldehyde-ethylenediamine Schiff base is prepared from ethylenediamine and salicylaldehyde, and ferrous sulfate is added to prepare the disalicylaldehyde-ethylenediamine Schiff base ferrous complex.

The invention has the beneficial effects that: the invention provides a method for preparing caprolactone by directly using hydrogen peroxide as an oxidant through continuous oxidation, which is simple and easy to implement, has obviously improved safety compared with the traditional peroxycarboxylic acid process, and has great social benefit and economic benefit.

Drawings

FIG. 1 is a schematic flow chart of a method according to an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a microchannel reactor in an embodiment.

FIG. 3 is a schematic structural diagram of a microchannel according to an embodiment of the present invention.

Detailed Description

The invention will be further described with reference to specific embodiments and the accompanying drawings.

The technical scheme of the embodiment of the invention (refer to the attached figure 1) is as follows:

1. preparation of the catalyst: in a laboratory, the disalicylaldehyde-ethylenediamine Schiff base is prepared from ethylenediamine and salicylaldehyde, ferrous sulfate is added to prepare a disalicylaldehyde-ethylenediamine Schiff base ferrous complex,

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2. mixing a catalyst and cyclohexanone to obtain a raw material A, adding hydrogen peroxide to obtain another raw material B, pumping the mixture into a microchannel reactor at a set flow rate through a pump, preheating the materials in two modules (01 and 02) respectively, and then feeding the preheated materials into a subsequent module for reaction, wherein the preheating temperature is the same as the temperature of a reaction section, and the reaction modules can be different combinations of modules (03, 03-04, 03-05, 03-06, 03-07 and the like). The preheating and reaction modules are removed, the remaining module is a reaction cooling quenching section, the temperature of the reaction quenching section is lower, and the oxidation reaction is not carried out at the lower temperature, so that the collection of subsequent reaction liquid is facilitated (refer to the attached figure 2).

In the embodiment, the microchannel of the microchannel reactor is a Corning Heart Cell structure microchannel (refer to fig. 3), the material is glass or silicon carbide, and the characteristic dimension of the channel is 1.0 mm.

Example 1

Adding 1mo1 salicylaldehyde (and 240mL 85% ethanol into a 500mL three-necked bottle, stirring by using a stirrer, dropwise adding 34mL0.5mo1 ethylenediamine after dissolving, heating and refluxing for 1h after the addition is finished, cooling to room temperature, filtering out a precipitated light yellow solid, washing by using 60% ethanol, and performing vacuum drying to obtain disalicylaldehyde ethylenediamine Schiff base, weighing 2.5g of disalicylaldehyde diethylamine Schiff base, dissolving in 200mL Dimethylformamide (DMF), heating in a water bath to 60 ℃, dropwise adding 60mL of an aqueous solution containing 8mmol of ferrous sulfate, refluxing for 1h, cooling, performing suction filtration, washing by using 50% ethanol, and performing vacuum drying to obtain a black green solid disalicylaldehyde ethylenediamine Schiff base ferrous complex.

Preparing a catalyst and cyclohexanone into slurry according to a mass ratio of 1:100, setting preheating and reaction temperature to be 40 ℃, setting quenching section temperature to be-5 ℃, setting a reaction module to be 03-06, setting a quenching cooling module to be 07-08, using 30% hydrogen peroxide and H in hydrogen peroxide₂O₂The molar ratio to cyclohexanone was 3 and the reaction residence time was 40 s. The reaction solution was extracted with chloroform at low temperature and analyzed by gas chromatography. The reaction conditions are that the conversion rate of cyclohexanone is 49.7 percent and the selectivity of epsilon-caprolactone is 85.2 percent.

Example 2

The reaction residence time was changed to 80s in the same manner as in example 1. The cyclohexanone conversion rate and the epsilon-caprolactone selectivity of the reaction are 72.1% and 80.6% respectively under the conditions.

Example 3

Preparing a catalyst and cyclohexanone into slurry according to a mass ratio of 5:100, setting the preheating and reaction temperature to be 70 ℃, the temperature of a quenching section to be-5 ℃, the reaction module to be 03-05, the quenching and cooling module to be 06-08, using 60% hydrogen peroxide and H in hydrogen peroxide₂O₂The molar ratio to cyclohexanone was 5 and the reaction residence time was 40 s. The reaction solution was extracted with chloroform at low temperature and analyzed by gas chromatography. The reaction conditions showed that the conversion of cyclohexanone was 93.7% and the selectivity of epsilon-caprolactone was 91.8%.

Example 4

The reaction residence time was changed to 80s in the same manner as in example 3. The reaction conditions are that the conversion rate of cyclohexanone is 95.2 percent and the selectivity of epsilon-caprolactone is 89.2 percent.

Example 5

Preparing a catalyst and cyclohexanone into slurry according to a mass ratio of 3:100, setting preheating and reaction temperature to be 60 ℃, setting quenching section temperature to be-5 ℃, setting a reaction module to be 03-05, setting a quenching and cooling module to be 06-08, using 50% hydrogen peroxide and H in hydrogen peroxide₂O₂The molar ratio to cyclohexanone was 4 and the reaction residence time was 60 s. The reaction solution was extracted with chloroform at low temperature and analyzed by gas chromatography. The reaction conditions are 82.1 percent of cyclohexanone conversion rate and 83.4 percent of epsilon-caprolactone selectivity.

Example 6

The reaction temperature was changed to 50 ℃ and the reaction residence time was changed to 80s in the same manner as in the other conditions of example 5. The reaction conditions are that the conversion rate of cyclohexanone is 77.2 percent and the selectivity of epsilon-caprolactone is 81.4 percent.

Example 7

Preparing a catalyst and cyclohexanone into slurry according to a mass ratio of 4:100, setting the preheating and reaction temperature to be 60 ℃, setting the temperature of a quenching section to be-5 ℃, setting a reaction module to be 03-04, setting a quenching and cooling module to be 05-08, using 60% hydrogen peroxide and H in hydrogen peroxide₂O₂The molar ratio to cyclohexanone was 3.5 and the reaction residence time was 60 s. The reaction solution was extracted with chloroform at low temperature and analyzed by gas chromatography. The reaction conditions showed that the conversion of cyclohexanone was 94.2% and the selectivity of epsilon-caprolactone was 92.8%.