Method for preparing caprolactone

Abstract

The invention belongs to the technical field of chemical synthesis, and particularly relates to a method for preparing caprolactone, in particular to a method for continuously preparing caprolactone. The method comprises the following steps: (1) mixing a peroxy acid synthesis solution containing an acidic catalyst with a stabilizer which is a nitrogen-containing alkaline compound and has lone pair electrons on an N atom; and (2) respectively inputting cyclohexanone and the mixed solution obtained in the step (1) into a microreactor to carry out a first reaction, and then introducing a product obtained by the first reaction into a tubular reactor to carry out a second reaction. By adopting the method for preparing the caprolactone, the stability and safety of the reaction can be improved, meanwhile, the conversion rate of the cyclohexanone is increased, the conversion rate of the cyclohexanone is 99.5% or above, and the selectivity of the prepared caprolactone is gt; the content is 99.5%.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, in particular to a method for preparing caprolactone, and in particular to a method for continuously preparing caprolactone. Background Art

[0002] ε-caprolactone is an important organic synthesis intermediate. The main method for industrial production of ε-caprolactone at present is cyclohexanone oxidation, and the peroxyacid oxidation of cyclohexanone is one of the most common and effective methods. At present, the industry is all kettle process, and the reaction exotherm is large, difficult to control, and production accidents occur frequently. There are also patents for using microreactors to carry out full-process production technology. For example, CN104370873A mixes hydrogen peroxide aqueous solution and formic acid aqueous solution, then adds catalyst and stabilizer to prepare a mixed solution, then cyclohexanone and the above-mentioned mixed solution are pumped into a microchannel modular reaction device for reaction, and the reaction products are separated to obtain the target product caprolactone. CN103539770A discloses a method using cyclohexanone as the starting reaction raw material, using peracetic acid generated by the reaction of hydrogen peroxide and acetic anhydride as an oxidant, and continuously completing processes such as peracid preparation and cyclohexanone oxidation in a microchannel reactor system. The peracetic acid synthesized by CN104370873A and CN103539770A is a water-containing material, which causes hydrolysis of caprolactone during the synthesis process of caprolactone, resulting in substandard products, short reaction residence time, and low cyclohexanone conversion rate. CN113429376B discloses a method for the continuous synthesis of caprolactone, which uses cyclohexanone as a raw material and directly uses hydrogen peroxide as an oxidant. In the presence of a catalyst, caprolactone is prepared by continuous oxidation reaction in a microchannel reactor. The method uses a ferrous complex of disalicylicaldehyde ethylenediamine Schiff base, and the reaction system contains water, resulting in low cyclohexanone conversion rate and caprolactone selectivity. Summary of the Invention

[0003] The present invention addresses the shortcomings of the prior art process for producing caprolactone by peroxyacid oxidation of cyclohexanone, which suffers from rapid reaction speed and high heat release in the early stages, leading to uncontrolled reaction and a high risk of reaction failure, slow reaction speed and long reaction time in the later stages, and extremely unstable processes. Furthermore, residual acidic catalyst in the peroxyacid solution often results in low caprolactone synthesis rate and selectivity. The method proposes a method for producing caprolactone. The method first pretreats a peroxyacid synthesis solution containing an acidic catalyst with a specific stabilizer. The pretreated solution is then mixed with cyclohexanone and reacted sequentially in a microreactor and then a tubular reactor. The method of the present invention provides a stable and highly safe process for producing caprolactone, with a cyclohexanone conversion rate of 99.5% and a caprolactone selectivity greater than 99.5%.

[0004] The present invention provides a method for preparing caprolactone, which comprises the following steps:

[0005] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0006] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction.

[0007] Preferably, the molar ratio of the acidic catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1-10, more preferably 1:3-4.

[0008] 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.

[0009] Preferably, in step (1), the mixing conditions include: temperature of -20 to 10°C, and residence time of 0.5 to 10 hours.

[0010] Preferably, the method further comprises: passing the product obtained from the second reaction into a tank reactor for a third reaction.

[0011] Preferably, the molar ratio of the cyclohexanone to the peroxy acid in the mixed solution is 1:0.9-1.2.

[0012] Preferably, in step (2), the conditions of the first reaction include: a temperature of 20 to 80° C. and a residence time of 1 to 100 s.

[0013] Preferably, in step (2), the conditions of the second reaction include: temperature of 35 to 80° C., and residence time of 0.2 to 2 h.

[0014] Preferably, the microreactor is selected from a sheet-type microchannel reactor, a heart-type microreactor, an umbrella-type microreactor, a T-type microreactor or a Y-type microreactor.

[0015] Preferably, the micromixer is an interdigital micromixer or a separation-recombination micromixer.

[0016] Preferably, the conditions of the third reaction include: temperature of 40-80° C., and residence time of 0.2-5 h.

[0017] Preferably, the content of the acidic catalyst in the peroxyacid synthesis solution is 0.05 to 2% by weight.

[0018] Preferably, the content of peroxyacid in the peroxyacid synthesis solution is 8 to 35% by weight.

[0019] Preferably, the peroxyacid synthetic solution further contains one or more of an organic acid, a water-carrying agent and hydrogen peroxide.

[0020] Preferably, the content of the organic acid is 20 to 40% by weight.

[0021] Preferably, the content of the water-carrying agent is 20 to 40% by weight.

[0022] Preferably, the content of the hydrogen peroxide is 0 to 10% by weight.

[0023] Preferably, the acidic catalyst is selected from one or more of boric acid, metaboric acid, sulfuric acid, nitric acid, isopoly acid and heteropoly acid. More preferably, the isopoly acid is selected from one or more of decatungstic acid, heptatungstic acid, octamolybdic acid and dodecamolybdic acid. Further preferably, the heteropoly acid is selected from one or more of phosphomolybdic acid, phosphotungstic acid and silicotungstic acid.

[0024] Preferably, the peracid in the peracid synthesis solution is selected from one or more of peroxyformic acid, peroxyacetic acid, peroxypropionic acid and peroxybenzoic acid.

[0025] Preferably, the organic acid is selected from one or more of formic acid, acetic acid, benzoic acid and m-chlorobenzoic acid.

[0026] Preferably, the water-carrying agent 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, cyclohexane, benzene and acetonitrile.

[0027] In the method of the present invention, a peroxyacid synthesis solution containing an acidic catalyst is first pretreated with a specific stabilizer to reduce the H + The concentration is adjusted to improve the stability of the synthetic solution. The pretreated solution is then mixed with cyclohexanone for reaction in a microreactor. The rapid heat extraction function of the microreactor can prevent the early stage of the peroxyacid oxidation reaction from getting out of control, thereby improving the stability and safety of the early stage reaction. Finally, the product obtained in the microreactor is passed into a tubular reactor for reaction. The tubular reactor cuts and drains the fluid to maintain the mixed liquid, which can accelerate the reaction speed in the later stage of the peroxyacid oxidation, extend the reaction residence time, and improve the reaction efficiency, so that the conversion rate of cyclohexanone is greater than 99.5%, and the selectivity of the finally prepared caprolactone is greater than 99.5%. In a preferred embodiment, the product obtained in the tubular reactor can also be passed into a kettle reactor for reaction, and the aging reaction therein is utilized to improve the conversion rate of the raw material. DETAILED DESCRIPTION

[0028] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0029] The endpoints of the ranges and any values ​​disclosed herein 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 endpoints of each range, the endpoints of each range and 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 to be specifically disclosed herein.

[0030] The present invention provides a method for preparing caprolactone, which comprises the following steps:

[0031] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0032] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction.

[0033] In the method of the present invention, in a specific embodiment, the acidic catalyst is capable of releasing H + Protonic acid, for example, can be selected from one or more of boric acid, metaboric acid, sulfuric acid, nitric acid, isopoly acid and heteropoly acid. In this article, the isopoly acid is a transition metal oxo acid formed by condensation of the same oxyacid radical ion, and in a preferred embodiment, the isopoly acid is selected from one or more of decatungstic acid, heptatungstic acid, octamolybdic acid and dodecamolybdic acid. In this article, the heteropoly acid is a polymetallic oxo acid formed by condensation of different types of oxyacid radical ions, and in a preferred embodiment, the heteropoly acid is selected from one or more of phosphomolybdic acid, phosphotungstic acid and silicotungstic acid.

[0034] In the method of the present invention, in a preferred embodiment, the content of the acid catalyst in the peroxyacid synthesis solution is 0.05 to 2% by weight.

[0035] In the method of the present invention, in a specific embodiment, the peracid in the peracid synthesis solution is selected from one or more of performic acid, peracetic acid, perpropionic acid and perbenzoic acid.

[0036] In the method of the present invention, in a preferred embodiment, the content of peroxyacid in the peroxyacid synthesis solution is 8 to 35% by weight.

[0037] In the method of the present invention, the peroxyacid synthetic solution containing an acidic catalyst is obtained by reacting hydrogen peroxide and an organic acid in the presence of a catalyst. In a specific embodiment, the peroxyacid synthetic solution further contains an organic acid, a water-carrying agent, and hydrogen peroxide. In a preferred embodiment, the organic acid content is 20 to 40% by weight.

[0038] In the method of the present invention, in a preferred embodiment, the content of the water-carrying agent is 20 to 40% by weight.

[0039] In the method of the present invention, in a preferred embodiment, the content of the hydrogen peroxide is 0 to 10% by weight.

[0040] In the method of the present invention, in a specific embodiment, the organic acid can be a conventional choice in the art. In a preferred embodiment, the organic acid is selected from one or more of formic acid, acetic acid, benzoic acid and m-chlorobenzoic acid.

[0041] In the method of the present invention, in a specific embodiment, the water-carrying agent is selected from one or more of ethyl acetate, propyl acetate, isobutyl acetate, propyl propionate, isopropyl propionate, ethyl propionate, butyl acetate, n-ethane, methylene dichloride, cyclohexane, benzene, and acetonitrile. In a preferred embodiment, the water-carrying agent is selected from one or more of ethyl propionate, methylene dichloride, cyclohexane, and benzene.

[0042] Due to some defects in the peroxyacid oxidation process, the acid catalyst usually remains in the produced peroxyacid synthesis solution. In order to reduce or eliminate the H + In order to reduce the negative impact on the synthesis of caprolactone, the present invention uses a nitrogen-containing basic compound with a lone pair of electrons on the N atom as a stabilizer to pretreat the peroxyacid synthesis solution.

[0043] In the method of the present invention, in a specific 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. In a preferred embodiment, the stabilizer is selected from one or more of pyridine, ethylamine, cyclohexylamine, and aniline.

[0044] In order to make H +To achieve better elimination effects, it is necessary to control the ratio of the acidic catalyst to the stabilizer in the peroxyacid synthesis solution. In the method of the present invention, in a specific embodiment, the molar ratio of the acidic catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1 to 10. In a preferred embodiment, the molar ratio of the acidic catalyst to the stabilizer in the peroxyacid synthesis solution is 1:3 to 4, for example, 1:3, 1:3.5, or 1:4.

[0045] In order to improve the synthesis efficiency of caprolactone, so that the cyclohexanone conversion rate is greater than 99.5% and the caprolactone selectivity is greater than 99.5%, in the method of the present invention, in a specific embodiment, in step (1), the mixing conditions include: a temperature of -20 to 10°C, for example, -20°C, -10°C, 0°C, 5°C or 10°C; 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 mixed solution obtained by mixing in step (1) is -1 to 3.

[0047] In the method of the present invention, in a specific embodiment, in step (2), the molar ratio of the cyclohexanone to the peracid in the mixed solution is 1:0.9 to 1.2, for example, it can be 1:0.9, 1:1.0, 1:1.1 or 1:1.2.

[0048] In the reaction process of peroxyacid oxidation of cyclohexanone to prepare caprolactone, the early reaction speed is fast and the heat release is large. Therefore, it is necessary to quickly mix the materials and quickly remove the heat to prevent the reaction from getting out of control and improve the mass transfer and heat transfer capacity. In the method of the present invention, in a specific embodiment, in step (2), the cyclohexanone and the mixed solution obtained in step (1) are respectively input into a microreactor or a micromixer for a first reaction. In the specific operation process, the feed comprises two raw material feeding devices, including a storage tank, a pipeline and a pump. The two feed pumps are connected to the microreactor, and the cyclohexanone and the mixed solution are respectively input into the microreactor or micromixer through the storage tank, the pipeline and the two feed pumps.

[0049] In the method of the present invention, in a specific embodiment, the microreactor or micromixer is a microreactor or micromixer having heat extraction and mixing functions, and capable of rapidly removing reaction heat.

[0050] In the method of the present invention, in a preferred embodiment, the microreactor is selected from a sheet-type microchannel reactor, a heart-type microreactor, an umbrella-type microreactor, a T-type microreactor or a Y-type microreactor.

[0051] In the method of the present invention, in a preferred embodiment, the micromixer is an interdigital micromixer or a separation-recombination micromixer.

[0052] In order to better mix the materials, quickly remove the reaction heat, improve the safety of the process, and make the subsequent reaction of preparing caprolactone more efficient, so that the cyclohexanone conversion rate is greater than 99.5% and the caprolactone selectivity is greater than 99.5%, it is necessary to reasonably control the reaction process of peroxyacid and cyclohexanone in a microreactor or micromixer. In the method of the present invention, in a specific embodiment, in step (2), the conditions of the first reaction include: a temperature of 20 to 80°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C; a residence time of 1 to 100s, for example, 1s, 2s, 5s, 10s, 20s, 50s, 90s or 100s.

[0053] During the reaction process of peroxyacid oxidation of cyclohexanone to prepare caprolactone, the reaction speed in the later stage is slow, and therefore, it is necessary to improve the reaction speed and efficiency in the later stage. In the method of the present invention, in a specific embodiment, the product obtained in the first reaction is passed into a tubular reactor.

[0054] In the method of the present invention, in a specific embodiment, the tubular reactor cuts and drains the fluid to achieve the purpose of maintaining the mixed liquid. Specifically, the tubular reactor can be an empty tube or a tubular reactor with internal components.

[0055] In the method of the present invention, in a specific embodiment, the microreactor or micromixer is connected in series with the tubular reactor to achieve a continuous operation process, which is suitable for industrial production. At the same time, each reactor is independently temperature controlled.

[0056] In order to improve the reaction speed and the efficiency of caprolactone synthesis, so that the cyclohexanone conversion rate is greater than 99.5% and the caprolactone selectivity is greater than 99.5%, it is necessary to reasonably control the reaction process in the tubular reactor. In the method of the present invention, in a specific embodiment, in step (2), the conditions of the second reaction include: a temperature of 35 to 80°C, for example, 35°C, 45°C, 55°C, 65°C, 75°C or 80°C; and a residence time of 0.2 to 2 hours, for example, 0.2h, 0.3h, 0.33h, 0.5h, 1h, 1.5h or 2h.

[0057] In order to improve the conversion efficiency of cyclohexanone, so that the cyclohexanone conversion rate is greater than 99.5% and the caprolactone selectivity is greater than 99.5%, in the method of the present invention, in a specific embodiment, the product obtained in the tubular reactor is passed into a tank reactor for a third reaction. Specifically, the tubular reactor and the tank reactor are connected in series. At the same time, an overflow mode or one-in-use and one-in-standby mode can be adopted to ensure the continuity of operation. In this article, "overflow mode" refers to the tank reactor adopting a bottom-in and top-out mode, with materials flowing in and out at the same time; "one-in-use and one-in-standby mode" refers to two tank reactors.

[0058] In the method of the present invention, in a specific embodiment, the conditions of the third reaction include: temperature of 40 to 80° C., and residence time of 0.2 to 5 h.

[0059] According to a first embodiment of the present invention, the method for preparing caprolactone comprises the following steps:

[0060] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0061] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction.

[0062] According to a second embodiment of the present invention, the method for preparing caprolactone comprises the following steps:

[0063] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0064] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained from the first reaction is introduced into a tubular reactor for a second reaction; the molar ratio of the acidic catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1 to 10.

[0065] According to a third embodiment of the present invention, the method for preparing caprolactone comprises the following steps:

[0066] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0067] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction; the molar ratio of the acidic catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1 to 10; and 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.

[0068] According to a fourth embodiment of the present invention, the method for preparing caprolactone comprises the following steps:

[0069] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0070] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction; the molar ratio of the acidic catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1 to 10; the stabilizer is selected from one or more of methylamine, ethylamine, ethylenediamine, triethylamine, trimethylamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline; in step (1), the mixing conditions include: a temperature of -20 to 10°C and a residence time of 0.5 to 10 hours.

[0071] According to a fifth embodiment of the present invention, the method for preparing caprolactone comprises the following steps:

[0072] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0073] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction; the molar ratio of the acidic catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1-10; the stabilizer is selected from one or more of methylamine, ethylamine, ethylenediamine, triethylamine, trimethylamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline; in step (1), the mixing conditions include: a temperature of -20-10°C and a residence time of 0.5-10h; and the molar ratio of the cyclohexanone to the peroxyacid in the mixed solution is 1:0.9-1.2.

[0074] According to a sixth embodiment of the present invention, the method for preparing caprolactone comprises the following steps:

[0075] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0076] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction; the molar ratio of the acidic catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1-10; the stabilizer is selected from one or more of methylamine, ethylamine, ethylenediamine, triethylamine, trimethylamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline; in step (1), the mixing conditions include: a temperature of -20-10°C and a residence time of 0.5-10h; the molar ratio of the cyclohexanone to the peroxyacid in the mixed solution is 1:0.9-1.2; in step (2), the conditions for the first reaction include: a temperature of 20-80°C and a residence time of 1-100s.

[0077] According to a seventh embodiment of the present invention, the method for preparing caprolactone comprises the following steps:

[0078] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0079] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction; the molar ratio of the acid catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1 to 10; the stabilizer is selected from methylamine, ethylamine, ethylenediamine, triethylamine, trimethylamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbamide, ...ethylamine, ethylenediamine, triethylamine, trimethylamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carb One or more of azole and quinoline; in step (1), the mixing conditions include: temperature of -20 to 10°C, residence time of 0.5 to 10 hours; the molar ratio of cyclohexanone to the peroxy acid in the mixed solution is 1:0.9 to 1.2; in step (2), the conditions for the first reaction include: temperature of 20 to 80°C, residence time of 1 to 100 seconds; in step (2), the conditions for the second reaction include: temperature of 35 to 80°C, residence time of 0.2 to 2 hours.

[0080] According to an eighth embodiment of the present invention, the method for preparing caprolactone comprises the following steps:

[0081] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0082] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction; the molar ratio of the acid catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1 to 10; the stabilizer is selected from one or more of methylamine, ethylamine, ethylenediamine, triethylamine, trimethylamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline; in step (1), the mixing conditions include: the temperature is -2 0-10°C, with a residence time of 0.5-10h; the molar ratio of the cyclohexanone to the peroxy acid in the mixed solution is 1:0.9-1.2; in step (2), the conditions for the first reaction include: a temperature of 20-80°C, and a residence time of 1-100s; in step (2), the conditions for the second reaction include: a temperature of 35-80°C, and a residence time of 0.2-2h; the microreactor is selected from a sheet-type microchannel reactor, a heart-type microreactor, an umbrella-type microreactor, a T-type microreactor or a Y-type microreactor, and the micromixer is an inner interdigital micromixer or a separation and recombination micromixer.

[0083] According to a ninth embodiment of the present invention, the method for preparing caprolactone comprises the following steps:

[0084] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0085] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction; the molar ratio of the acid catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1 to 10; the stabilizer is selected from one or more of methylamine, ethylamine, ethylenediamine, triethylamine, trimethylamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline; in step (1), the mixing conditions include: a temperature of -20 to 10°C, a residence time of 0.5 to 10h; the cyclohexanone and the stabilizer are mixed. The molar ratio of the peroxy acid in the mixed solution is 1:0.9-1.2; in step (2), the conditions for the first reaction include: a temperature of 20-80° C. and a residence time of 1-100 s; in step (2), the conditions for the second reaction include: a temperature of 35-80° C. and a residence time of 0.2-2 h; the microreactor is selected from a sheet-type microchannel reactor, a heart-type microreactor, an umbrella-type microreactor, a T-type microreactor or a Y-type microreactor, and the micromixer is an inner interdigital micromixer or a separation and recombination micromixer; the content of the acidic catalyst in the peroxy acid synthetic solution is 0.05-2% by weight, and the content of the peroxy acid in the peroxy acid synthetic solution is 8-35% by weight.

[0086] According to a tenth embodiment of the present invention, the method for preparing caprolactone comprises the following steps:

[0087] (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing basic compound with a lone pair of electrons on the nitrogen atom;

[0088] (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction; the molar ratio of the acid catalyst to the stabilizer in the peroxyacid synthesis solution is 1:1-10; the stabilizer is selected from one or more of methylamine, ethylamine, ethylenediamine, triethylamine, trimethylamine, urea, ethanolamine, isopropylamine, tert-butylamine, aniline, benzylamine, cyclohexylamine, pyridine, lutidine, pyrrole, indole, acridine, carbazole and quinoline; in step (1), the mixing conditions include: a temperature of -20-10°C and a residence time of 0.5-10h; the molar ratio of the cyclohexanone to the peroxyacid in the mixed solution is 1:0.9-1.2; in step (2), the conditions for the first reaction are The method comprises the following steps: a temperature of 20 to 80° C. and a residence time of 1 to 100 seconds; in step (2), the conditions for the second reaction include: a temperature of 35 to 80° C. and a residence time of 0.2 to 2 hours; the microreactor is selected from a sheet-type microchannel reactor, a heart-type microreactor, an umbrella-type microreactor, a T-type microreactor or a Y-type microreactor, and the micromixer is an inner interdigital micromixer or a separation and recombination micromixer; the content of the acidic catalyst in the peroxyacid synthetic solution is 0.05 to 2% by weight, and the content of the peroxyacid in the peroxyacid synthetic solution is 8 to 35% by weight; the peroxyacid synthetic solution further contains one or more of an organic acid, a water-carrying agent and hydrogen peroxide, the content of the organic acid is 20 to 40% by weight, the content of the water-carrying agent is 20 to 40% by weight, and the content of the hydrogen peroxide is 0 to 10% by weight.

[0089] 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 operating processes, but the scope of protection of the present invention is not limited to the following examples.

[0090] 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.

[0091] Sheet-type microchannel reactor: manufacturer is Shandong Haomai Machinery Manufacturing Co., Ltd., model is RFHS4020AG.

[0092] Internal interdigital micromixer: manufacturer: Institutfür Mikrotechnik Mainz GmbH, model: HPIMM-SS.

[0093] Separation and recombination type micro mixer: the manufacturer is Institutfür Mikrotechnik Mainz GmbH, the model is CPMM-R300-SS.

[0094] Y-type microreactor: The inner diameter is 0.8 mm, and the minimum angle formed is 90°.

[0095] Tubular reactor: The interior is filled with internal components or small balls.

[0096] Test Case

[0097] The detection method for cyclohexanone and caprolactone refers to HG / T 5618-2019. Gas chromatography with a flame ionization detector (FID) is used during testing. The recommended column is a flexible quartz capillary column coated with 20M polyethylene glycol. The column temperature is set to 80°C initially for 2 minutes, then ramped at a rate of 10°C / min to a final temperature of 220°C for 45 minutes. The vaporizer temperature is set to 250°C. The detector temperature is set to 250°C. The split ratio is 40:1. The injection volume is 0.2 μL.

[0098] Cyclohexanone conversion rate:

[0099] 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%;

[0100] Caprolactone selectivity:

[0101] 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 ).

[0102] Example 1

[0103] (1) 100 g of a peroxy acid synthetic solution containing 22% peroxypropionic acid, 38% ethyl propionate, 39% propionic acid, and 1% sulfuric acid was mixed with 3.16 g of pyridine at −10° C. and reacted for 5 h;

[0104] (2) 24 g of cyclohexanone and the mixed solution obtained in step (1) were respectively introduced into a sheet-type microchannel reactor through two feed pumps, and the reaction was allowed to continue for 90 seconds at 35° C. The reaction product was then introduced into a tubular reactor having an inner diameter of 20 cm and filled with 6 mm glass beads connected in series with the sheet-type microchannel reactor, and the reaction was allowed to continue for 20 minutes at 60° C. Finally, the product obtained in the tubular reactor was introduced into a tank reactor connected in series with the tubular reactor, and the reaction was allowed to continue for 1 hour at 60° C. to obtain caprolactone. Measurement and calculation showed that the conversion rate of cyclohexanone was 99.9%, and the selectivity of caprolactone was 99.8%.

[0105] Example 2

[0106] The method of Example 1 was followed, except that pyridine was replaced by quinoline, and the molar ratio of sulfuric acid to quinoline was 1:1. The method specifically comprised the following steps:

[0107] (1) 100 g of a peroxy acid synthetic solution containing 22% peroxypropionic acid, 38% ethyl propionate, 39% propionic acid, and 1% sulfuric acid was mixed with 1.32 g of quinoline at −10° C. and reacted for 5 h;

[0108] (2) 24 g of cyclohexanone and the mixed solution obtained in step (1) were respectively introduced into a sheet-type microchannel reactor through two feed pumps, and the reaction was allowed to continue for 90 seconds at 35° C. The reaction product was then introduced into a tubular reactor having an inner diameter of 20 cm and filled with 6 mm glass beads connected in series with the sheet-type microchannel reactor, and the reaction was allowed to continue for 20 minutes at 60° C. Finally, the product obtained in the tubular reactor was introduced into a tank reactor connected in series with the tubular reactor, and the reaction was allowed to continue for 1 hour at 60° C. to obtain caprolactone. Measurement and calculation showed that the conversion rate of cyclohexanone was 99.8%, and the selectivity of caprolactone was 99.7%.

[0109] Example 3

[0110] The method of Example 1 was followed, except that pyridine was replaced with ethanolamine, and the molar ratio of sulfuric acid to ethanolamine was 1:10. The method specifically included the following steps:

[0111] (1) 100 g of a peroxy acid synthetic solution containing 22% peroxypropionic acid, 38% ethyl propionate, 39% propionic acid, and 1% sulfuric acid was mixed with 6.22 g of ethanolamine at −10° C. and reacted for 5 h;

[0112] (2) 24 g of cyclohexanone and the mixed solution obtained in step (1) were respectively introduced into a sheet-type microchannel reactor through two feed pumps, and the reaction was allowed to continue for 90 seconds at 35° C. The reaction product was then introduced into a tubular reactor having an inner diameter of 20 cm and filled with 6 mm glass beads connected in series with the sheet-type microchannel reactor, and the reaction was allowed to continue for 20 minutes at 60° C. Finally, the product obtained in the tubular reactor was introduced into a tank reactor connected in series with the tubular reactor, and the reaction was allowed to continue for 1 hour at 60° C. to obtain caprolactone. Measurement and calculation showed that the conversion rate of cyclohexanone was 99.9%, and the selectivity of caprolactone was 99.7%.

[0113] Example 4

[0114] The method of Example 1 was followed, except that pyridine was replaced with aniline and the mixing conditions in step (1) were changed. Specifically, the following steps were included:

[0115] (1) 100 g of a peroxy acid synthetic solution containing 22% peroxypropionic acid, 38% ethyl propionate, 39% propionic acid, and 1% sulfuric acid was mixed with 3.16 g of aniline at 10° C. and reacted for 1 h;

[0116] (2) 24 g of cyclohexanone and the mixed solution obtained in step (1) were respectively introduced into a sheet-type microchannel reactor through two feed pumps, and the reaction was allowed to continue for 90 seconds at 35° C. The reaction product was then introduced into a tubular reactor having an inner diameter of 20 cm and filled with 6 mm glass beads connected in series with the sheet-type microchannel reactor, and the reaction was allowed to continue for 20 minutes at 60° C. Finally, the product obtained in the tubular reactor was introduced into a tank reactor connected in series with the tubular reactor, and the reaction was allowed to continue for 1 hour at 60° C. to obtain caprolactone. Measurement and calculation showed that the conversion rate of cyclohexanone was 99.8%, and the selectivity of caprolactone was 99.7%.

[0117] Example 5

[0118] The method of Example 1 is followed, except that the composition of the peroxyacid synthetic solution is different. Specifically, the following steps are included:

[0119] (1) 100 g of a peroxy acid synthetic solution containing 10% peroxypropionic acid, 39.95% ethyl propionate, 40% propionic acid, 0.05% nitric acid, and 10% hydrogen peroxide was mixed with 0.63 g of pyridine at −10° C. and reacted for 5 h;

[0120] (2) 10.8 g of cyclohexanone and the mixed solution obtained in step (1) were respectively introduced into a sheet-type microchannel reactor through two feed pumps, and the reaction was allowed to continue for 2 seconds at 35° C. The reaction product was then introduced into a tubular reactor having an inner diameter of 20 cm and filled with 6 mm glass beads connected in series with the sheet-type microchannel reactor, and the reaction was allowed to continue for 20 minutes at 60° C. Finally, the product obtained in the tubular reactor was introduced into a tank reactor connected in series with the tubular reactor, and the reaction was allowed to continue for 1 hour at 60° C. to obtain caprolactone. Measurement and calculation showed that the conversion rate of cyclohexanone was 99.7%, and the selectivity of caprolactone was 99.7%.

[0121] Example 6

[0122] The method of Example 1 was followed, except that the sheet-type microchannel reactor was replaced with an internal interdigital micromixer. The conditions for the first reaction were adjusted to: a reaction temperature of 80°C and a residence time of 1 second. Measurements and calculations revealed a cyclohexanone conversion of 99.6% and a caprolactone selectivity of 99.7%.

[0123] Example 7

[0124] The method of Example 1 was followed, except that the sheet-type microchannel reactor was replaced with a Y-type microreactor. The conditions for the first reaction were adjusted to: a reaction temperature of 20°C and a residence time of 50 seconds. Measurement and calculation revealed a cyclohexanone conversion of 99.6% and a caprolactone selectivity of 99.7%.

[0125] Example 8

[0126] The method of Example 1 was followed, except that the reaction in the autoclave reactor was not carried out. Measurement and calculation showed that the conversion of cyclohexanone was 99.6% and the selectivity of caprolactone was 99.8%.

[0127] Example 9

[0128] The method of Example 1 was followed, except that the conditions of the second reaction were adjusted to: reaction temperature of 35° C. and residence time of 2 h. Measurement and calculation showed that the conversion of cyclohexanone was 99.6% and the selectivity of caprolactone was 99.8%.

[0129] Example 10

[0130] The method of Example 1 was followed, except that the conditions of the second reaction were adjusted to: reaction temperature of 80° C., residence time of 0.3 h. Measurement and calculation showed that the conversion of cyclohexanone was 99.6%, and the selectivity of caprolactone was 99.7%.

[0131] Example 11

[0132] The method of Example 1 was followed, except that the molar ratio of sulfuric acid to pyridine was adjusted to 1:15. Measurement and calculation showed that the conversion of cyclohexanone was 99.6%, and the selectivity of caprolactone was 99.6%.

[0133] Comparative Example 1

[0134] The method of Example 1 was followed, except that pyridine was replaced by ethanol. Measurement and calculation showed that the conversion of cyclohexanone was 98.5% and the selectivity of caprolactone was 75.6%.

[0135] Comparative Example 2

[0136] The method of Example 1 was followed, except that step (1) was omitted and the peroxyacid synthesis solution was directly reacted with cyclohexanone. Measurement and calculation showed that the conversion rate of cyclohexanone was 97.6% and the selectivity of caprolactone was 60.3%.

[0137] Comparative Example 3

[0138] The method of Example 1 was followed, except that in step (2), cyclohexanone and the mixed solution obtained in step (1) were introduced into a tubular reactor for reaction, and then the product obtained in the tubular reactor was introduced into a tank reactor for reaction. Measurement and calculation showed that the conversion of cyclohexanone was 98.6%, and the selectivity for caprolactone was 95.1%.

[0139] Comparative Example 4

[0140] The method of Example 1 was followed, except that in step (2), the product obtained in the sheet-type microchannel reactor was directly fed into the tank reactor for reaction. Measurement and calculation showed that the conversion of cyclohexanone was 99.1%, and the selectivity of caprolactone was 93.2%.

[0141] Comparative Example 5

[0142] The method of Example 1 was followed, except that in step (2), cyclohexanone and the mixed solution obtained in step (1) were first introduced into a tubular reactor for reaction, the product obtained in the tubular reactor was then introduced into a sheet-type microchannel reactor for reaction, and the product obtained in the sheet-type microchannel reactor was then introduced into a tank reactor for reaction. Measurement and calculation showed that the conversion of cyclohexanone was 99.6%, and the selectivity for caprolactone was 98.4%.

[0143] Table 1

[0144] Conversion rate of cyclohexanone / % Caprolactone selectivity / % Example 1 99.9 99.8 Example 2 99.8 99.7 Example 3 99.9 99.7 Example 4 99.8 99.7 Example 5 99.7 99.7 Example 6 99.6 99.7 Example 7 99.6 99.7 Example 8 99.6 99.8 Example 9 99.6 99.8 Example 10 99.6 99.7 Example 10 99.7 99.6 Example 11 99.6 99.6 Comparative Example 1 98.5 75.6 Comparative Example 2 97.6 60.3 Comparative Example 3 98.6 95.1 Comparative Example 4 99.1 93.2 Comparative Example 5 99.6 98.4

[0145] As can be seen from Table 1, the method of the present invention is used to prepare caprolactone, and the process is stable and safe. The conversion rate of cyclohexanone is greater than 99.5%, and the selectivity of the obtained caprolactone is greater than 99.5%.

[0146] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing caprolactone, characterized in that: The method comprises the following steps: (1) mixing a peroxyacid synthesis solution containing an acidic catalyst with a stabilizer, wherein the stabilizer is a nitrogen-containing alkaline compound with a lone pair of electrons on the nitrogen atom; (2) Cyclohexanone and the mixed solution obtained in step (1) are respectively introduced into a microreactor or a micromixer for a first reaction, and then the product obtained in the first reaction is introduced into a tubular reactor for a second reaction.

2. The method according to claim 1, characterized in that The molar ratio of the acid catalyst to the stabilizer in the peroxyacid synthesis solution 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 any one of claims 1 to 3, characterized in that: In step (1), the mixing conditions include: temperature of -20 to 10°C and residence time of 0.5 to 10 hours.

5. The method according to any one of claims 1 to 4, characterized in that: The method further comprises: introducing the product obtained from the second reaction into a kettle reactor for a third reaction.

6. The method according to any one of claims 1 to 5, characterized in that: The molar ratio of the cyclohexanone to the peracid in the mixed solution is 1:0.9-1.

2.

7. The method according to any one of claims 1 to 6, characterized in that: In step (2), the conditions of the first reaction include: temperature of 20 to 80° C. and residence time of 1 to 100 s.

8. The method according to any one of claims 1 to 7, characterized in that: In step (2), the conditions of the second reaction include: temperature of 35 to 80° C. and residence time of 0.2 to 2 h.

9. The method according to any one of claims 1 to 8, characterized in that: The microreactor is selected from a sheet-type microchannel reactor, a heart-type microreactor, an umbrella-type microreactor, a T-type microreactor or a Y-type microreactor; Preferably, the micromixer is an interdigital micromixer or a separation-recombination micromixer.

10. The method according to claim 5, characterized in that The conditions of the third reaction include: temperature of 40-80° C. and residence time of 0.2-5 h.

11. The method according to any one of claims 1 to 10, characterized in that: The content of the acid catalyst in the peroxyacid synthesis solution is 0.05 to 2% by weight; Preferably, the content of peroxyacid in the peroxyacid synthetic solution is 8 to 35% by weight.

12. The method according to any one of claims 1 to 11, characterized in that: The peroxyacid synthetic solution also contains one or more of an organic acid, a water-carrying agent and hydrogen peroxide; Preferably, the content of the organic acid is 20 to 40% by weight; Preferably, the content of the water-carrying agent is 20 to 40% by weight; Preferably, the content of the hydrogen peroxide is 0 to 10% by weight.

13. The method according to any one of claims 1 to 12, characterized in that: The acidic catalyst is selected from one or more of boric acid, metaboric acid, sulfuric acid, nitric acid, isopolyacids and heteropolyacids; Preferably, the isopoly acid is selected from one or more of decatungstic acid, heptungstic acid, octamolybdic acid and dodecamolybdic acid; Preferably, the heteropoly acid is selected from one or more of phosphomolybdic acid, phosphotungstic acid and silicotungstic acid.

14. The method according to claim 12, characterized in that The peracid in the peracid synthetic solution is selected from one or more of peroxyformic acid, peroxyacetic acid, peroxypropionic acid and peroxybenzoic acid; Preferably, the organic acid is selected from one or more of formic acid, acetic acid, benzoic acid and m-chlorobenzoic acid; Preferably, the water-carrying agent 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, cyclohexane, benzene and acetonitrile.