Pretreatment method for caprolactone preparation raw material liquid and method for preparing caprolactone

Abstract

The invention belongs to the technical field of production of chemical products, and particularly relates to a pretreatment method of a raw material solution for preparing caprolactone and a method for preparing the caprolactone. The method comprises the following steps: a peroxy acid raw material solution containing an acid catalyst is mixed with a stabilizer, the stabilizer is a nitrogen-containing alkaline compound, and an N atom has lone pair electrons. The pretreatment mixed solution obtained by the method provided by the invention reacts with cyclohexanone to prepare caprolactone, and the conversion rate of cyclohexanone can be gt; the selectivity of the prepared caprolactone is gt; the product quality is stable, and the method can be widely applied to the pretreatment process of peroxy acid raw material liquid for preparing caprolactone by oxidizing cyclohexanone.

Description

Technical Field

[0001] The invention relates to the technical field of chemical product production, and in particular to a method for pretreating a raw material liquid for preparing caprolactone and a method for preparing caprolactone. Background Art

[0002] Caprolactone is a new polyester monomer. Its polyester has good biocompatibility and biodegradability. It is widely used in biomedicine, degradable plastics and high value-added packaging materials, such as surgical sutures and orthopedic shape memory fixation materials. Caprolactone synthesis involves harsh process operations such as strong oxidation, and the product purity requirements are high. Currently, only a few companies in the United States, Britain, Japan and other countries produce it, while my country mainly relies on imports. According to the different synthesis processes and raw materials of caprolactone, the synthesis methods include: hexanediol dehydrogenation method, hydroxycaproic acid intramolecular condensation method, adipic acid acidification method and cyclohexanone oxidation method. Considering multiple factors such as raw materials, equipment and catalyst preparation, cyclohexanone oxidation method is currently the most effective method and also the method for industrial production of caprolactone.

[0003] According to the different types of oxidants, the methods for synthesizing caprolactone from cyclohexanone by Baeyer-Villger oxidation mainly include: O2 / air oxidation method, biological oxidation method, H2O2 oxidation method and peroxyacid oxidation method. For the O2 / air oxidation method, oxygen is the most economical and greenest oxidant, but the oxidizing ability of molecular oxygen is insufficient, and aldehyde co-oxidants are often added to achieve it. Due to the low activity of molecular oxygen, the yield of the product is low, and the product is more complex and difficult to separate. Industrial application still needs further research. The key to the biological oxidation method is to find suitable microorganisms or biological enzymes, and the reaction conditions are harsh and difficult to control, which is not suitable for industrial production. In the H2O2 oxidation method, the oxidant H2O2 has limited oxidizing ability and generally needs to be carried out in a buffer or organic solvent. This method requires the introduction of a certain amount of catalyst to improve the reaction activity, but the catalyst is expensive and recycling is also challenging.

[0004] CN110183417A discloses a method for continuously producing caprolactone by catalytic reaction distillation, wherein the method uses the concentration section of a reaction distillation tower to purify hydrogen peroxide, and the purified hydrogen peroxide and the remaining water-carrying agent go down to react with the added cyclohexanone to generate a small amount of caprolactone, and then continue to go down to react with acetic acid to generate peracetic acid and water; the generated water is taken out by the water-carrying agent, and the generated peracetic acid goes up after heat exchange, and reacts with cyclohexanone to generate caprolactone and acetic acid. The process does not mention the use of an acidic catalyst. Although the caprolactone yield is high, the peroxyacid synthesis process has a low yield and a long reaction time if no catalyst is added, and the generated peroxyacid is very easy to decompose, which is not conducive to industrial production.

[0005] The peracid oxidation process is the earliest process used in the synthesis of caprolactone, and is also the main process route currently used in the industrial production of caprolactone. This process uses a mixture of organic acid and hydrogen peroxide, introduces an acidic catalyst and an entrainer, and combines it with a reactive distillation process to prepare a high-yield anhydrous peracid. The prepared peroxyformic acid and peracetic acid can be extracted from the top of the tower through reactive distillation technology due to their low boiling points, so the peracid and the acidic catalyst can be separated and can be directly used in the downstream caprolactone synthesis reaction. However, this process requires more than 85% hydrogen peroxide as an oxidant, and the gas phase mixing of peracid and organic entrainer increases the risk of explosion. Most long-chain or aromatic peracids have low boiling points. The product and the catalyst cannot be separated by the distillation process, so that the acid catalyst usually remains in the peroxyacid raw material liquid. For example, CN115490623A discloses a method for continuous synthesis of anhydrous peroxyacid and caprolactone, in which hydrogen peroxide is mixed with an organic acid and a homogeneous catalyst and then enters a microscale falling film reactor with a water-carrying agent in a certain metering ratio. The water and the water-carrying agent generated by the reaction are separated from the upper part of the reactor with the gas phase, and the liquid phase containing the anhydrous peroxyacid flows out from the bottom of the reactor; and then enters the microreactor with cyclohexanone for caprolactone synthesis. Although this process is a continuous peroxyacid and caprolactone production process, the peroxyacid solution flowing out of the falling film reactor still retains an acid catalyst. If the start-up time is too long, it will be unfavorable for the synthesis of caprolactone. The polymerization of caprolactone will lead to a decrease in yield. This peroxyacid solution is used as a raw material liquid. In the process of oxidizing cyclohexanone to prepare caprolactone, the hydrogen ions ionized are very easy to catalyze the polymerization reaction of caprolactone, resulting in low selectivity of caprolactone and a decrease in yield. If the H + If the concentration is too high, caprolactone product may not even be obtained. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that the acid catalyst usually remains in the peroxyacid raw liquid in the existing peroxyacid oxidation process, which leads to low selectivity and reduced yield of caprolactone when the peroxyacid raw liquid is used to oxidize cyclohexanone to prepare caprolactone, and thus propose a pretreatment method for preparing caprolactone raw liquid and a method for preparing caprolactone. The method uses a specific stabilizer to react with the acid catalyst in the peroxyacid raw liquid, thereby reducing the H + The treated peroxy acid raw material liquid is reacted with cyclohexanone to prepare caprolactone, and a cyclohexanone conversion rate of >97% and a caprolactone selectivity of >90% can be achieved.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present invention proposes a pretreatment method for a raw material liquid for preparing caprolactone, the method comprising: mixing a peracid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound and the N atom has a lone pair of electrons.

[0008] Preferably, the molar ratio of the acidic catalyst to the stabilizer is 1:1-10, more preferably 1:3-4.

[0009] Preferably, the stabilizer is selected from one or more of methylamine, ethylamine, triethylamine, trimethylamine, ethylenediamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline.

[0010] Preferably, the acidic catalyst is selected from one or more of boric acid, metaboric acid, concentrated sulfuric acid, concentrated phosphoric acid, nitric acid and concentrated hydrochloric acid.

[0011] Preferably, the content of the acid catalyst in the peroxyacid raw material solution is 0.05 to 1% by weight.

[0012] Preferably, the content of peroxyacid in the peroxyacid raw material solution is 8 to 35% by weight.

[0013] Preferably, the peroxyacid is selected from one or more of peroxyformic acid, peroxyacetic acid, peroxypropionic acid and peroxybenzoic acid.

[0014] Preferably, the peroxyacid raw material solution further contains one or more of water, hydrogen peroxide, an organic acid and a solvent.

[0015] Preferably, the content of water in the peroxyacid raw material solution is 0 to 3% by weight. More preferably, the content of hydrogen peroxide in the peroxyacid raw material solution is 0 to 3% by weight. Further preferably, the content of organic acid in the peroxyacid raw material solution is 20 to 40% by weight. Further preferably, the content of solvent in the peroxyacid raw material solution is 20 to 60% by weight.

[0016] Preferably, the solvent is selected from one or more of ethyl acetate, propyl acetate, isobutyl acetate, propyl propionate, isopropyl propionate, ethyl propionate, butyl acetate, n-ethane, methylene chloride and acetonitrile.

[0017] Preferably, the organic acid is selected from one or more of formic acid, acetic acid, benzoic acid and m-chlorobenzoic acid.

[0018] Preferably, the mixing conditions include: temperature of -20 to 60°C and residence time of 0.5 to 10 hours.

[0019] A second aspect of the present invention provides a method for preparing caprolactone, the method comprising the following steps:

[0020] (1) pre-treating a peroxyacid raw material liquid containing an acid catalyst, wherein the pre-treatment process is performed according to the method described above;

[0021] (2) The mixed solution obtained by the pretreatment in step (1) is mixed with cyclohexanone to react.

[0022] Preferably, the molar ratio of the peracid in the peracid raw material solution to the cyclohexanone is 0.5 to 2:1.

[0023] Preferably, in step (2), the reaction conditions include: temperature of 30 to 80° C. and time of 0.5 to 5 h.

[0024] Preferably, in step (2), the reaction is carried out in a tank reactor, a tubular reactor or a microchannel reactor.

[0025] According to the method for preparing caprolactone of the present invention, a peroxyacid raw material liquid containing an acidic catalyst is first used as a raw material liquid for preparing caprolactone, and is mixed with a specific alkaline stabilizer for pretreatment to complete a neutralization or complexation reaction between the acidic catalyst and the alkaline stabilizer, and then the pretreated solution is mixed with cyclohexanone to react the peroxyacid therein with the cyclohexanone to generate caprolactone. The method for preparing caprolactone of the present invention can reduce the H in the peroxyacid raw material liquid. + concentration, thereby effectively preventing H + The invention interferes with the synthesis of caprolactone, thereby making the cyclohexanone conversion rate greater than 97% and the prepared caprolactone selectivity greater than 90%, and the product quality is stable. The invention can be widely used in the pretreatment process of the peracid raw material liquid for oxidizing cyclohexanone to prepare caprolactone. DETAILED DESCRIPTION

[0026] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0027] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0028] Due to some defects in the peroxyacid oxidation process, the acid catalyst usually remains in the produced peroxyacid raw material liquid. In order to reduce or eliminate the H +The negative impact on the synthesis of caprolactone, therefore, while ensuring the concentration of peroxyacid, it is necessary to separate or control the content of the acidic catalyst, so as to inhibit the polymerization of caprolactone. Based on this, the inventors propose to use a specific alkaline stabilizer to pre-treat the peroxyacid raw material liquid, so that the acidic catalyst and the stabilizer therein are neutralized or complexed, thereby reducing the H + concentration.

[0029] The first aspect of the present invention provides a pretreatment method for a raw material liquid for preparing caprolactone, the method comprising: mixing a peroxyacid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound with a lone pair of electrons on the N atom.

[0030] In the method of the present invention, in a specific embodiment, the peroxyacid raw material solution contains peroxyacid and an acidic catalyst.

[0031] In the method of the present invention, in a preferred embodiment, the content of the acidic catalyst in the peroxyacid raw material liquid is 0.05-5% by weight, for example, 0.05% by weight, 0.1% by weight, 0.35% by weight, 0.37% by weight, 0.49% by weight, 0.53% by weight, 0.66% by weight, 2% by weight, 4% by weight or 5% by weight. In a more preferred embodiment, the content of the acidic catalyst in the peroxyacid raw material liquid is 0.05-1% by weight.

[0032] In the method of the present invention, in a preferred embodiment, the content of peracid in the peracid raw material solution is 8 to 35 weight%, for example, 8 weight%, 10 weight%, 15 weight%, 22.8 weight%, 23.7 weight%, 24 weight%, 31.9 weight% or 35 weight%.

[0033] In the method of the present invention, in a specific embodiment, the acidic catalyst can be a heteropoly acid, an isopoly acid, a protonic acid, etc. + Acidic compounds. In this article, the heteropoly acid refers to a polyoxometalate formed by condensation of different types of oxygen-containing acid radical ions, such as phosphomolybdic acid, phosphotungstic acid or silicotungstic acid, and the isopoly acid refers to a metal oxometalate formed by condensation of the same type of oxygen-containing acid radical ions, such as decatungstic acid, heptungstic acid, octamolybdic acid or dodecamoylic acid. In a preferred embodiment, the acidic catalyst is selected from one or more of boric acid, metaboric acid, concentrated sulfuric acid, concentrated phosphoric acid, nitric acid and concentrated hydrochloric acid.

[0034] In the method of the present invention, in a specific embodiment, the peroxy acid is an organic carboxylic acid containing a peroxy group. In a preferred embodiment, the peroxy acid is selected from one or more of peroxyformic acid, peroxyacetic acid, peroxypropionic acid and peroxybenzoic acid.

[0035] In the method of the present invention, in a more preferred embodiment, the peroxyacid raw material solution further contains one or more of water, hydrogen peroxide, an organic acid and a solvent.

[0036] In the method of the present invention, in a preferred embodiment, the content of hydrogen peroxide in the peroxyacid raw material solution is 0 to 3 weight %, for example, 0 weight %, 1 weight %, 2.1 weight % or 3 weight %.

[0037] In the method of the present invention, in a preferred embodiment, the content of organic acid in the peracid raw material solution is 20 to 40 weight %, for example, 20 weight %, 22.8 weight %, 24 weight %, 26.3 weight %, 31.9 weight %, 35 weight % or 40 weight %.

[0038] In the method of the present invention, in a preferred embodiment, the content of the solvent in the peracid raw material solution is 20 to 60 weight %, for example, 20 weight %, 35.4 weight %, 39.5 weight %, 51.3 weight %, 53.2 weight % or 60 weight %.

[0039] In the method of the present invention, in a preferred embodiment, the water content in the peroxyacid raw material solution is 0 to 3 weight %, for example, 0.1 weight %, 0.28 weight %, 0.63 weight %, 1 weight %, 2 weight % or 3 weight %.

[0040] In the method of the present invention, in a specific embodiment, the solvent is selected from one or more of ethyl acetate, propyl acetate, isobutyl acetate, propyl propionate, isopropyl propionate, ethyl propionate, butyl acetate, n-ethane, methylene chloride and acetonitrile.

[0041] In the method of the present invention, in a specific embodiment, the organic acid is an organic carboxylic acid. In a preferred embodiment, the organic acid is one or more selected from formic acid, acetic acid, benzoic acid and m-chlorobenzoic acid.

[0042] In the method of the present invention, the amount of the acidic catalyst and the stabilizer should be controlled within a certain range so that when the obtained pre-treated mixed solution and cyclohexanone are used to prepare caprolactone, the cyclohexanone has a high conversion rate and the yield of the obtained caprolactone is high. In a specific embodiment, the molar ratio of the acidic catalyst to the stabilizer is 1:1 to 10, for example, it can be 1:1, 1:1.3, 1:2, 1:3.1, 1:3.8, 1:4.1, 1:5.9, 1:7, 1:8, 1:9 or 1:10. In a preferred embodiment, the molar ratio of the amount of the acidic catalyst to the stabilizer is 1:3 to 4.

[0043] In the method of the present invention, in a specific embodiment, the stabilizer can be a nitrogen-containing organic amine or a nitrogen-containing heterocyclic compound. In a preferred embodiment, the stabilizer is selected from one or more of methylamine, ethylamine, triethylamine, trimethylamine, ethylenediamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline, and the heterocyclics include but are not limited to the heterocyclic compounds introduced above, and may include substitutions in various functional group forms. In a more preferred embodiment, the stabilizer is selected from one or more of pyridine, lutidine, cyclohexylamine and urea.

[0044] In the method of the present invention, in a specific operation process, at room temperature, the stabilizer is added dropwise into the peroxyacid raw material solution for mixing.

[0045] In the method of the present invention, in a specific embodiment, the mixing conditions include: a temperature of -20 to 60°C, for example, -20°C, -15°C, -10°C, -5°C, 0°C, 10°C, 20°C, 40°C or 60°C, and a residence time of 0.5 to 10h, for example, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0046] In the method of the present invention, in a specific embodiment, the pH value of the pre-treated mixed solution obtained after mixing is -1 to 3, for example, it can be -1, 0.5, 1, 2 or 3.

[0047] According to a first embodiment of the present invention, the pretreatment method of the raw material liquid for preparing caprolactone of the present invention comprises: mixing a peracid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound and the N atom has a lone pair of electrons.

[0048] According to a second embodiment of the present invention, the pretreatment method of the raw material liquid for preparing caprolactone of the present invention comprises: mixing a peracid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound and the N atom has a lone pair of electrons; the molar ratio of the acidic catalyst to the stabilizer is 1:1 to 10.

[0049] According to a third embodiment of the present invention, the pretreatment method of the raw material liquid for preparing caprolactone of the present invention comprises: mixing a peracid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound and the N atom has a lone pair of electrons; the molar ratio of the acidic catalyst to the stabilizer is 1:1 to 10; the stabilizer is selected from one or more of methylamine, ethylamine, triethylamine, trimethylamine, ethylenediamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, dimethylpyridine, pyrrole, indole, acridine, carbazole and quinoline.

[0050] According to a fourth embodiment of the present invention, the pretreatment method of the raw material liquid for preparing caprolactone of the present invention comprises: mixing a peroxyacid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound and the N atom has a lone pair of electrons; the molar ratio of the acidic catalyst to the stabilizer is 1:1 to 10; the stabilizer is selected from one or more of methylamine, ethylamine, triethylamine, trimethylamine, ethylenediamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline; the acidic catalyst is selected from one or more of boric acid, metaboric acid, concentrated sulfuric acid, concentrated phosphoric acid, nitric acid and concentrated hydrochloric acid.

[0051] According to a fifth embodiment of the present invention, the pretreatment method of the raw material liquid for preparing caprolactone of the present invention comprises: mixing a peracid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound and the N atom has a lone pair of electrons; the molar ratio of the acidic catalyst to the stabilizer is 1:1 to 10; the stabilizer is selected from one or more of methylamine, ethylamine, triethylamine, trimethylamine, ethylenediamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, dimethylpyridine, pyrrole, indole, acridine, carbazole and quinoline; the acidic catalyst is selected from one or more of boric acid, metaboric acid, concentrated sulfuric acid, concentrated phosphoric acid, nitric acid and concentrated hydrochloric acid; the content of the acidic catalyst in the peracid raw material liquid is 0.05 to 1% by weight, and the content of the peracid in the peracid raw material liquid is 8 to 35% by weight.

[0052] According to a sixth embodiment of the present invention, the pretreatment method for preparing a raw material liquid of caprolactone of the present invention comprises: mixing a peroxyacid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound, and the N atom has a lone pair of electrons; the molar ratio of the acidic catalyst to the stabilizer is 1:1 to 10; the stabilizer is selected from methylamine, ethylamine, triethylamine, trimethylamine, ethylenediamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine , pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline; the acidic catalyst is selected from one or more of boric acid, metaboric acid, concentrated sulfuric acid, concentrated phosphoric acid, nitric acid and concentrated hydrochloric acid; the content of the acidic catalyst in the peroxyacid raw material liquid is 0.05-1% by weight, and the content of the peroxyacid in the peroxyacid raw material liquid is 8-35% by weight; the peroxyacid is selected from one or more of peroxyformic acid, peroxyacetic acid, peroxypropionic acid and peroxybenzoic acid.

[0053] According to a seventh embodiment of the present invention, the pretreatment method of the raw material liquid for preparing caprolactone of the present invention comprises: mixing a peroxyacid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound and the N atom has a lone pair of electrons; the molar ratio of the acidic catalyst to the stabilizer is 1:1 to 10; the stabilizer is selected from one or more of methylamine, ethylamine, triethylamine, trimethylamine, ethylenediamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline; the acidic catalyst is selected from boric acid, metaboric acid, concentrated sulfuric acid, concentrated phosphoric acid, nitric acid and concentrated hydrochloric acid. one or more of the following: the content of the acidic catalyst in the peroxyacid raw liquid is 0.05-1% by weight, and the content of the peroxyacid in the peroxyacid raw liquid is 8-35% by weight; the peroxyacid is selected from one or more of peroxyformic acid, peracetic acid, peroxypropionic acid and peroxybenzoic acid; the peroxyacid raw liquid further contains one or more of water, hydrogen peroxide, an organic acid and a solvent, the content of water in the peroxyacid raw liquid is 0-3% by weight, the content of hydrogen peroxide in the peroxyacid raw liquid is 0-3% by weight, and the content of the organic acid in the peroxyacid raw liquid is 20-40% by weight; the content of the solvent in the peroxyacid raw liquid is 20-60% by weight.

[0054] According to an eighth embodiment of the present invention, the pretreatment method for preparing a raw material liquid of caprolactone of the present invention comprises: mixing a peracid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound and the N atom has a lone pair of electrons; the molar ratio of the acidic catalyst to the stabilizer is 1:1 to 10; the stabilizer is selected from one or more of methylamine, ethylamine, triethylamine, trimethylamine, ethylenediamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, dimethylpyridine, pyrrole, indole, acridine, carbazole and quinoline; the acidic catalyst is selected from one or more of boric acid, metaboric acid, concentrated sulfuric acid, concentrated phosphoric acid, nitric acid and concentrated hydrochloric acid; the content of the acidic catalyst in the peracid raw material liquid is 0.05 to 1% by weight, and the content of the peracid raw material liquid in the peracid raw material liquid is 0.05 to 1% by weight. The content of the peroxy acid is 8 to 35 weight %; the peroxy acid is selected from one or more of peroxyformic acid, peracetic acid, peroxypropionic acid and peroxybenzoic acid; the peroxy acid raw material liquid also contains one or more of water, hydrogen peroxide, an organic acid and a solvent, the content of water in the peroxy acid raw material liquid is 0 to 3 weight %, the content of hydrogen peroxide in the peroxy acid raw material liquid is 0 to 3 weight %, and the content of the organic acid in the peroxy acid raw material liquid is 20 to 40 weight %; the content of the solvent in the peroxy acid raw material liquid is 20 to 60 weight %; the solvent is selected from one or more of ethyl acetate, propyl acetate, isobutyl acetate, propyl propionate, isopropyl propionate, ethyl propionate, butyl acetate, n-ethane, dioxymethane and acetonitrile, and the organic acid is selected from one or more of formic acid, acetic acid, benzoic acid and m-chlorobenzoic acid.

[0055] According to a ninth embodiment of the present invention, the pretreatment method for preparing a raw material liquid of caprolactone of the present invention comprises: mixing a peracid raw material liquid containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound and the N atom has a lone pair of electrons; the molar ratio of the acidic catalyst to the stabilizer is 1:1 to 10; the stabilizer is selected from one or more of methylamine, ethylamine, triethylamine, trimethylamine, ethylenediamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, dimethylpyridine, pyrrole, indole, acridine, carbazole and quinoline; the acidic catalyst is selected from one or more of boric acid, metaboric acid, concentrated sulfuric acid, concentrated phosphoric acid, nitric acid and concentrated hydrochloric acid; the content of the acidic catalyst in the peracid raw material liquid is 0.05 to 1% by weight, and the content of the peracid in the peracid raw material liquid is 8 to 35% by weight; The peroxy acid is selected from one or more of peroxyformic acid, peracetic acid, peroxypropionic acid and peroxybenzoic acid; the peroxy acid raw material liquid also contains one or more of water, hydrogen peroxide, organic acid and solvent, the content of water in the peroxy acid raw material liquid is 0-3% by weight, the content of hydrogen peroxide in the peroxy acid raw material liquid is 0-3% by weight, and the content of organic acid in the peroxy acid raw material liquid is 20-40% by weight; the content of solvent in the peroxy acid raw material liquid is 20-60% by weight; the solvent is selected from one or more of ethyl acetate, propyl acetate, isobutyl acetate, propyl propionate, isopropyl propionate, ethyl propionate, butyl acetate, n-ethane, dioxymethane and acetonitrile, and the organic acid is selected from one or more of formic acid, acetic acid, benzoic acid and m-chlorobenzoic acid; the mixing conditions include: temperature is -20-60°C, and residence time is 0.5-10h.

[0056] A second aspect of the present invention provides a method for preparing caprolactone, the method comprising the following steps:

[0057] (1) pre-treating a peroxyacid raw material liquid containing an acid catalyst, wherein the pre-treatment process is performed according to the method described above;

[0058] (2) The mixed solution obtained by the pretreatment in step (1) is mixed with cyclohexanone to react.

[0059] In the method of the present invention, in a specific embodiment, the molar ratio of the peroxy acid in the peroxy acid raw material liquid to the cyclohexanone is 0.5 to 2:1, for example, it can be 0.5:1, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.41:1 or 2:1. In a preferred embodiment, the molar ratio of the peroxy acid in the peroxy acid raw material liquid to the cyclohexanone is 1 to 2:1

[0060] In the method of the present invention, in step (2), during the specific operation, the cyclohexanone is first stirred at a temperature of 40 to 60° C., and the stirring can be magnetic stirring or mechanical stirring. The stirring conditions include: a stirring speed of 10 to 500 rpm and a stirring time of 0.5 to 10 min. After the stirring is completed, the pretreated mixed solution obtained in step (1) is dripped into the cyclohexanone using a syringe pump. In a preferred case, the dripping flow rate is 0.1 to 10 mL / min, specifically 0.1 mL / min, 0.5 mL / min, 1 mL / min, 5 mL / min or 10 mL / min.

[0061] In the method of the present invention, in a specific embodiment, in step (2), the reaction conditions include: temperature of 30 to 80°C, for example, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, and time of 0.5 to 5h, for example, 0.5h, 1h, 2.5h, 4h or 5h.

[0062] In the method of the present invention, in a specific embodiment, in step (2), the reaction is carried out in a tank reactor, a tubular reactor or a microchannel reactor. Specifically, the tank reactor, the tubular reactor and the microchannel reactor are all conventionally selected models in the art.

[0063] In the method of the present invention, in a specific embodiment, in step (2), the reaction can be a batch reaction or a continuous reaction. In a preferred embodiment, in step (2), to ensure the safety of the reaction, if a batch reaction is adopted, the mixed solution obtained by the pretreatment in step (1) can be added to cyclohexanone.

[0064] The following examples further illustrate the method for preparing caprolactone of the present invention. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0065] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0066] Pyridine: Purchased from: Sinopharm Reagent, product purity>99.9%;

[0067] Cyclohexanone: Purchased from: Sinopharm Reagents, product purity > 99.9%;

[0068] Test Case

[0069] The detection method of cyclohexanone and caprolactone refers to HG / T 5618-2019. A gas chromatograph is used during the test, and the detector is a hydrogen flame ionization detector. The recommended chromatographic column is an elastic quartz capillary column coated with polyethylene glycol 20M. The column temperature is 80℃ for the first time, maintained for 2min, the heating rate is 10℃ / min, and the final temperature is 220℃ for 45min. The vaporization chamber temperature is 250℃. The detector temperature is 250℃. The split ratio is 40:1. The injection volume is 0.2μL.

[0070] Cyclohexanone conversion rate:

[0071] X=(A 环己酮的初始峰面积 -A 反应后结束后环己酮峰面积 ) / A 环己酮的初始峰面积 *100%;

[0072] Caprolactone selectivity:

[0073] S=A 己内酯峰面积 / (A 己内酯峰面积 *C 1校正因子 +A 剩余环己酮峰面积 *C 2校正因子 +A 重组分峰面积 *C 3校正因子 ).

[0074] Example 1

[0075] The method for preparing caprolactone comprises the following steps:

[0076] (1) Weighing 374 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 90 g of peroxypropionic acid, 90 g of propionic acid, 192 g of ethyl propionate, 1.4 g of sulfuric acid, 0.2 g of hydrogen peroxide and 0.4 g of water, at room temperature (25° C.), dripping 4.2 g of pyridine into the peroxyacid raw material solution dropwise, and letting the mixture stand at −20° C. for 6 h to obtain a pretreated mixed solution;

[0077] (2) 96 g of cyclohexanone was weighed and placed in a tank reactor, the temperature was raised to 50° C., and stirred at 100 rpm for 5 min. Then, the pretreated mixed solution obtained in step (1) was slowly added to the cyclohexanone at a flow rate of 0.5 mL / min using a syringe pump, and the mixture was reacted at 50° C. for 5 h, and samples were taken and analyzed every 20 min. According to calculation, the cyclohexanone conversion rate was 99.9%, and the caprolactone selectivity was 99.8%.

[0078] Example 2

[0079] The method of Example 1 is followed, except that in step (1), the molar ratio of sulfuric acid (acidic catalyst) to pyridine (stabilizer) is 1:2. The specific steps are as follows:

[0080] (1) Weighing 282.4 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 90 g of peroxypropionic acid, 90 g of propionic acid, 100 g of ethyl propionate, 1.4 g of sulfuric acid, 0.2 g of hydrogen peroxide and 0.8 g of water, at room temperature (27° C.), dripping 2.26 g of pyridine into the peroxyacid raw material solution dropwise, and letting the mixture stand at −20° C. for 6 h to obtain a pretreated mixed solution;

[0081] (2) 98 g of cyclohexanone was weighed and placed in a tank reactor, the temperature was raised to 50° C., and stirred at 50 rpm for 1 min. Then, the pretreated mixed solution obtained in step (1) was slowly added to the cyclohexanone at a flow rate of 0.5 mL / min using a syringe pump, and the mixture was reacted at 50° C. for 4.5 h, and samples were taken and analyzed every 20 min. According to calculations, the cyclohexanone conversion rate was 99.2%, and the caprolactone selectivity was 97%.

[0082] Example 3

[0083] The method of Example 1 is followed, except that in step (1), the molar ratio of sulfuric acid (acidic catalyst) to pyridine (stabilizer) is 1:10. The specific steps are as follows:

[0084] (1) Weighing 343.6 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 90 g of peroxypropionic acid, 100 g of propionic acid, 150 g of ethyl propionate, 2 g of sulfuric acid, 0.8 g of hydrogen peroxide and 0.8 g of water, at room temperature (22° C.), dripping 11.3 g of pyridine into the peroxyacid raw material solution dropwise, mixing, and standing at 10° C. for 6 h to obtain a pretreated mixed solution;

[0085] (2) 97 g of cyclohexanone was weighed and placed in a tank reactor, heated to 50° C., and stirred at 20 rpm for 15 min. Then, the pretreated mixed solution obtained in step (1) was slowly added to the cyclohexanone at a flow rate of 0.5 mL / min using a syringe pump, and reacted at 50° C. for 5.5 h. Samples were taken and analyzed every 20 min. According to calculation, the cyclohexanone conversion rate was 98.5%, and the caprolactone selectivity was 96.2%.

[0086] Example 4

[0087] The method for preparing caprolactone comprises the following steps:

[0088] (1) Weighing 394.7 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 90 g of peroxypropionic acid, 90 g of propionic acid, 210 g of ethyl propionate, 1.4 g of sulfuric acid, 0.8 g of hydrogen peroxide and 2.5 g of water, at room temperature (25° C.), dripping 3.4 g of pyridine into the peroxyacid raw material solution dropwise, and letting the mixture stand at 0° C. for 2 h to obtain a pretreated mixed solution;

[0089] (2) 70 g of cyclohexanone was weighed and placed in a tank reactor, the temperature was raised to 40° C., and stirred at 250 rpm for 20 min. Then, the pretreated mixed solution obtained in step (1) was slowly added to the cyclohexanone at a flow rate of 0.5 mL / min using a syringe pump, and the mixture was reacted at 40° C. for 60 h, and samples were taken and analyzed every 20 min. After calculation, the cyclohexanone conversion rate was 97.2, and the caprolactone selectivity was 95.3.

[0090] Example 5

[0091] The method for preparing caprolactone comprises the following steps:

[0092] (1) Weighing 375 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 90 g of peroxypropionic acid, 90 g of propionic acid, 192 g of ethyl propionate, 1.4 g of sulfuric acid, 0.8 g of hydrogen peroxide and 0.8 g of water, at room temperature (21° C.), dripping 1.4 g of pyridine into the peroxyacid raw material solution dropwise, and letting the mixture stand at −10° C. for 2 h to obtain a pretreated mixed solution;

[0093] (2) 98 g of cyclohexanone was weighed and placed in a tank reactor, the temperature was raised to 70° C., and stirred at 50 rpm for 30 min. Then, the pretreated mixed solution obtained in step (1) was slowly added to the cyclohexanone at a flow rate of 0.5 mL / min using a syringe pump, and the mixture was reacted at 70° C. for 6 h, and samples were taken and analyzed every 20 min. According to calculation, the cyclohexanone conversion rate was 99.1%, and the caprolactone selectivity was 92%.

[0094] Example 6

[0095] The method of Example 1 is followed, except that the molar ratio of the peroxypropionic acid to the cyclohexanone is 2:1. The specific steps are as follows:

[0096] (1) Weighing 373.6 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 90 g of peroxypropionic acid, 90 g of propionic acid, 192 g of ethyl propionate, 1.4 g of sulfuric acid, 0.1 g of hydrogen peroxide and 0.1 g of water, at room temperature (25° C.), dripping 5.4 g of lutidine into the peroxyacid raw material solution dropwise, and letting the mixture stand at −20° C. for 6 h to obtain a pretreated mixed solution;

[0097] (2) Weigh 49 g of cyclohexanone and place it in a tank reactor, heat it to 50° C., and stir it at 300 rpm for 20 min. Then, use a syringe pump to slowly add the pretreated mixed solution obtained in step (1) to the cyclohexanone at a flow rate of 0.5 mL / min, and react at 50° C. for 3.5 h. Samples are taken and analyzed every 20 min. According to calculation, the cyclohexanone conversion rate is 99.9%, and the caprolactone selectivity is 98.2%.

[0098] Example 7

[0099] The method of Example 1 was followed, except that in step (2), the reaction temperature was 60° C. The specific steps were as follows:

[0100] (1) Weighing 374 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 90 g of peroxypropionic acid, 90 g of propionic acid, 192 g of ethyl propionate, 1.4 g of sulfuric acid, 0.2 g of hydrogen peroxide and 0.4 g of water, at room temperature (25° C.), dripping 4.2 g of pyridine into the peroxyacid raw material solution dropwise, and letting the mixture stand at −20° C. for 6 h to obtain a pretreated mixed solution;

[0101] (2) 96 g of cyclohexanone was weighed and placed in a tank reactor, the temperature was raised to 50° C., and stirred at 100 rpm for 5 min. Then, the pretreated mixed solution obtained in step (1) was slowly added to the cyclohexanone at a flow rate of 0.5 mL / min using a syringe pump, and the mixture was reacted at 50° C. for 5 h, and samples were taken and analyzed every 20 min. According to calculation, the cyclohexanone conversion rate was 99.9%, and the caprolactone selectivity was 98.3%.

[0102] Example 8

[0103] The method for preparing caprolactone comprises the following steps:

[0104] (1) Weighing 187.5 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 90 g of peroxypropionic acid, 90 g of propionic acid and 7.5 g of sulfuric acid, at room temperature (22° C.), dripping 36.28 g of pyridine into the peroxyacid raw material solution dropwise to mix, and standing at −20° C. for 6 h for pretreatment to obtain a pretreated mixed solution;

[0105] (2) Weigh 95 g of cyclohexanone and place it in a tank reactor, heat it to 50° C., and stir it at 300 rpm for 10 min. Use a syringe pump to slowly add the pretreated mixed solution obtained in step (1) to the cyclohexanone at a flow rate of 0.5 mL / min, and react at 50° C. for 6 h. Samples are taken and analyzed every 20 min. According to calculation, the cyclohexanone conversion rate is 99%, and the caprolactone selectivity is 93%.

[0106] Example 9

[0107] The method for preparing caprolactone comprises the following steps:

[0108] (1) Weighing 80 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 76 g of peracetic acid, 2.5 g of sulfuric acid and 1.5 g of hydrogen peroxide, at room temperature (25° C.), dripping 6 g of pyridine into the peroxyacid raw material solution dropwise, and letting the mixture stand at −20° C. for 6 h to obtain a pretreated mixed solution;

[0109] (2) 96 g of cyclohexanone was weighed and placed in a tank reactor, the temperature was raised to 50° C., and stirred at 150 rpm for 10 min. Then, the pretreated mixed solution obtained in step (1) was slowly added to the cyclohexanone at a flow rate of 0.5 mL / min using a syringe pump, and the mixture was reacted at 50° C. for 5 h, and samples were taken and analyzed every 20 min. According to calculation, the cyclohexanone conversion rate was 99.3%, and the caprolactone selectivity was 94%.

[0110] Example 10

[0111] The method of Example 1 was followed, except that pyridine was replaced by cyclohexylamine to obtain caprolactone. According to calculation, the cyclohexanone conversion rate was 99.7%, and the caprolactone selectivity was 99.8%.

[0112] Embodiment 11

[0113] The method of Example 1 was followed, except that urea was used to replace pyridine to obtain caprolactone. According to calculation, the conversion rate of cyclohexanone was 99.6%, and the selectivity of caprolactone was 90%.

[0114] Comparative Example 1

[0115] The method of Example 1 is followed, except that the stabilizer pyridine is replaced by sodium hydroxide. The specific steps are as follows:

[0116] (1) Weighing 374 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 90 g of peroxypropionic acid, 90 g of propionic acid, 192 g of ethyl propionate, 1.4 g of sulfuric acid, 0.2 g of hydrogen peroxide and 0.4 g of water, slowly adding 1.2 g of sodium hydroxide powder to the peroxyacid raw material solution at room temperature (25° C.), and letting the mixture stand at −20° C. for 6 h to obtain a pretreated mixed solution;

[0117] (2) 96 g of cyclohexanone was weighed and placed in a tank reactor, the temperature was raised to 50° C., and stirred at 300 rpm for 3 min, and then the pretreated mixed solution obtained in step (1) was slowly added to the cyclohexanone at a flow rate of 0.5 mL / min using a syringe pump, and the mixture was reacted at 50° C. for 6 h. According to calculation, the cyclohexanone conversion rate was 90.4%, and the caprolactone selectivity was 22.5%.

[0118] Comparative Example 2

[0119] The method of Example 1 is followed, except that step (1) is not performed, and the peroxyacid raw material liquid is directly reacted with cyclohexanone. The specific operation steps are as follows:

[0120] Weigh 380g peroxy acid stock solution and 98g cyclohexanone respectively, wherein the peroxy acid stock solution contains 95g peroxy propionic acid, 90g propionic acid, 192g ethyl propionate (solvent), 1.4g sulfuric acid, 0.8g hydrogen peroxide and 0.8g water, place cyclohexanone in a tank reactor, heat to 50°C, and stir at 200rpm for 10min, use a syringe pump to slowly add the peroxy acid stock solution to cyclohexanone at a flow rate of 0.5mL / min, and react at 40°C for 3.5h, sampling and analysis every 20min. After calculation, the cyclohexanone conversion rate is 99.2, and the caprolactone selectivity is 35%.

[0121] Comparative Example 3

[0122] The method of Example 1 is followed, except that the stabilizer pyridine is replaced by potassium hydroxide. The specific steps are as follows:

[0123] (1) Weighing 374 g of a peroxyacid raw material solution, wherein the peroxyacid raw material solution contains 90 g of peroxypropionic acid, 90 g of propionic acid, 192 g of ethyl propionate, 1.4 g of sulfuric acid, 0.2 g of hydrogen peroxide and 0.4 g of water, at room temperature (25° C.), dripping 1.6 g of potassium hydroxide into the peroxyacid raw material solution dropwise, and letting the mixture stand at −20° C. for 6 h to obtain a pretreated mixed solution;

[0124] (2) 96 g of cyclohexanone was weighed and placed in a tank reactor, heated to 50° C., and stirred at 250 rpm for 5 min. Then, the pretreated mixed solution obtained in step (1) was slowly added to the cyclohexanone at a flow rate of 0.5 mL / min using a syringe pump, and reacted at 50° C. for 4 h. Samples were taken and analyzed every 20 min. According to calculation, the cyclohexanone conversion rate was 92.7, and the caprolactone selectivity was 15.1%.

[0125] The results of cyclohexanone conversion and caprolactone selectivity in Examples 1-11 and Comparative Examples 1-3 are shown in Table 1.

[0126] Table 1

[0127] Cyclohexanone conversion Caprolactone selectivity Example 1 99.9 99.8 Example 2 99.2 97 Example 3 98.5 96.2 Example 4 97.2 95.3 Example 5 99.1 92 Example 6 99.9 98.2 Example 7 99.9 98.3 Example 8 99 93 Example 9 99.3 94 Example 10 99.7 99.8 Embodiment 11 99.6 90 Comparative Example 1 90.4 22.5 Comparative Example 2 99.2 35 Comparative Example 3 92.7 15.1

[0128] As can be seen from Table 1, the method for preparing caprolactone of the present invention can make the cyclohexanone conversion rate>97%, and the prepared caprolactone selectivity>90%. At the same time, the method of the present invention has high safety, short reaction time, stable product weight, and can be widely used in the pretreatment process of peroxyacid raw material liquid for oxidizing cyclohexanone to prepare caprolactone.

[0129] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A pretreatment method for preparing a raw material liquid for caprolactone, characterized in that: The method comprises: mixing a peroxyacid raw material liquid containing an acid catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound, and the nitrogen atom has a lone pair of electrons.

2. The method according to claim 1, characterized in that The molar ratio of the acid catalyst to the stabilizer is 1:1-10, preferably 1:3-4.

3. The method according to claim 1 or 2, characterized in that: The stabilizer is selected from one or more of methylamine, ethylamine, triethylamine, trimethylamine, ethylenediamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline.

4. The method according to claim 1 or 2, characterized in that: The acidic catalyst is selected from one or more of boric acid, metaboric acid, concentrated sulfuric acid, concentrated phosphoric acid, nitric acid and concentrated hydrochloric acid.

5. The method according to any one of claims 1 to 4, characterized in that: The content of the acid catalyst in the peroxyacid raw material liquid is 0.05 to 1 weight %; Preferably, the content of peroxyacid in the peroxyacid raw material solution is 8 to 35% by weight.

6. The method according to any one of claims 1 to 5, characterized in that: The peroxy acid is selected from one or more of peroxyformic acid, peroxyacetic acid, peroxypropionic acid and peroxybenzoic acid.

7. The method according to any one of claims 1 to 6, characterized in that: The peroxyacid raw material solution further contains one or more of water, hydrogen peroxide, an organic acid and a solvent; Preferably, the water content in the peroxyacid raw material solution is 0 to 3% by weight; Preferably, the content of hydrogen peroxide in the peroxyacid raw material solution is 0 to 3% by weight; Preferably, the content of organic acid in the peroxyacid raw material solution is 20 to 40% by weight; Preferably, the content of the solvent in the peroxyacid raw material solution is 20 to 60% by weight.

8. The method according to claim 7, characterized in that The solvent is selected from one or more of ethyl acetate, propyl acetate, isobutyl acetate, propyl propionate, isopropyl propionate, ethyl propionate, butyl acetate, n-ethane, methylene chloride and acetonitrile; Preferably, the organic acid is selected from one or more of formic acid, acetic acid, benzoic acid and m-chlorobenzoic acid.

9. The method according to any one of claims 1 to 8, characterized in that: The mixing conditions include: temperature of -20 to 60° C. and residence time of 0.5 to 10 h.

10. A method for preparing caprolactone, characterized in that: The method comprises the following steps: (1) pretreating a peroxyacid raw material liquid containing an acid catalyst, wherein the pretreatment process is performed according to the method described in any one of claims 1 to 9; (2) The mixed solution obtained by the pretreatment in step (1) is mixed with cyclohexanone to react.

11. The method according to claim 10, characterized in that The molar ratio of the peracid in the peracid raw material liquid to the cyclohexanone is 0.5 to 2:

1.

12. The method according to claim 10 or 11, characterized in that: In step (2), the reaction conditions include: temperature of 30 to 80° C. and time of 0.5 to 5 h.

13. The method according to any one of claims 10 to 12, characterized in that: In step (2), the reaction is carried out in a tank reactor, a tubular reactor or a microchannel reactor.