阅读说明：本技术 一种ε-己内酯的制备方法及其装置 (Method and device for preparing caprolactone ) 是由 彭叶 刘成 叶宇祥 凌朋悟 于 2020-07-14 设计创作，主要内容包括：本发明涉及ε-己内酯的制备领域,公开了一种ε-己内酯的制备方法及其装置。其中,该方法包括：(I)将氧化剂、带水剂和稳定剂在原料预混罐中混合后经第一脱水塔进行脱水,得到第一产物；(II)将第一产物和酸在第一混合器混合后再在第一固定床反应器中进行第一反应,并将得到的反应产物经第二脱水塔进行脱水,得到第二产物；(III)将所述第二产物与环己酮在第二混合器混合后再在第三固定床反应器进行第二反应,得到粗酯；(IV)精馏得到ε-己内酯。采用该方法制备的ε-己内酯收率高。(The invention relates to the field of preparation of caprolactone, and discloses a method and a device for preparing caprolactone. Wherein, the method comprises the following steps: (I) mixing an oxidant, a water-carrying agent and a stabilizer in a raw material premixing tank, and dehydrating through a first dehydrating tower to obtain a first product; (II) mixing the first product and acid in a first mixer, then carrying out a first reaction in a first fixed bed reactor, and dehydrating the obtained reaction product through a second dehydration tower to obtain a second product; (III) mixing the second product with cyclohexanone in a second mixer, and then carrying out a second reaction in a third fixed bed reactor to obtain crude ester; (IV) rectifying to obtain caprolactone. The caprolactone prepared by the method has high yield.)

1. A method for preparing caprolactone, which is characterized in that the method comprises the following steps:

(I) mixing an oxidant, a water-carrying agent and a stabilizer in a raw material premixing tank (1), and dehydrating the obtained mixture through a first dehydrating tower (2) to obtain a first product;

(II) mixing the first product and acid in a first mixer (3), carrying out a first reaction on the obtained first mixture in a first fixed bed reactor (4), and dehydrating the obtained reaction product through a second dehydration tower (5) to obtain a second product;

(III) mixing the second product with cyclohexanone in a second mixer (6) and subjecting the resulting second mixture to a second reaction in a third fixed bed reactor (8) to obtain a crude ester;

(IV) rectifying the crude ester to obtain caprolactone.

2. The process according to claim 1, wherein, in step (I), the stabilizer is a composite stabilizer, preferably, the stabilizer is selected from at least two of picolinic acid, dipicolinic acid, picoline, lutidine, 8-hydroxyquinoline, tributyl phosphate, and dipicolinic acid;

preferably, the oxidizing agent is hydrogen peroxide; more preferably, the concentration of the oxidant is 10-70%;

preferably, the water-carrying agent is selected from one or more of ethyl acetate, ethyl propionate, methyl propionate, isopropyl acetate and propyl formate;

preferably, the weight ratio of the usage amounts of the oxidant, the water-carrying agent and the stabilizer is 1: (4-15): (0.001-0.02);

more preferably, the weight ratio of the usage amounts of the oxidant, the water-carrying agent and the stabilizer is 1: (6-12): (0.005-0.01).

3. The process of claim 1, wherein, in step (II), the acid is selected from one or more of formic acid, acetic acid, and propionic acid;

preferably, the molar ratio of the amount of said oxidizing agent to said acid is 1: (1-5), preferably 1: (1.5-2.5);

preferably, the conditions of the first reaction include: the temperature is 30-90 ℃, the pressure is-0.1 MPa to 0MPa, and the time is 0.2-3 h;

more preferably, the conditions of the first reaction include: the temperature is 40-90 ℃, the pressure is-0.095 MPa to-0.05 MPa, and the time is 0.5-1 h.

4. The process of claim 1, wherein, in step (III), the molar ratio of the second product to the amount of cyclohexanone is 1: (1-5), preferably 1: (1.5-3);

preferably, the conditions of the second reaction include: the temperature is 30-100 ℃, the pressure is 0MPa to 0.1MPa, and the time is 0.2-2 h;

more preferably, the conditions of the second reaction include: the temperature is 40-90 ℃, the pressure is 0.08MPa to 0.2MPa, and the time is 0.5-1 h.

5. The process of claim 3 or 4, wherein in step (II), the conditions of the first reaction further comprise: the weight hourly space velocity is 0.5-2h^-1Preferably 0.6-1.5h^-1；

Preferably, in step (III), the conditions of the second reaction further comprise: the weight hourly space velocity is 1-3h^-1Preferably 2-2.5h^-1。

6. The method according to any one of claims 1-5, wherein the method further comprises: in step (III), the second product is treated by a second fixed bed reactor (7).

7. The method according to any one of claims 1-6, wherein both the first fixed bed reactor (4) and the second fixed bed reactor (7) are packed with a solid acid catalyst;

preferably, the inner part of the first fixed bed reactor (4) and the periphery of the tubes of the second fixed bed reactor (7) are filled with a heat medium;

preferably, the periphery of the tubes in the third fixed bed reactor (8) is filled with a cold medium;

preferably, the first fixed bed reactor (4) is filled with a molecular sieve catalyst loaded with an active component;

preferably, the third fixed bed reactor (8) is filled with an organic acid synthetic resin catalyst, a zeolite molecular sieve catalyst and a modified microporous silicon catalyst.

8. The device for preparing caprolactone is characterized by comprising a pretreatment system, a reaction system and a rectification system which are connected in sequence;

the pretreatment system comprises a raw material premixing tank (1), a first dehydration tower (2) and a first mixer (3); the first dehydration tower (2) is respectively connected with the raw material premixing tank (1) and the first mixer (3) through a circulating pump;

wherein the reaction system comprises a first fixed bed reactor (4), a second dehydration tower (5), a second mixer (6) and a third fixed bed reactor (8); the first mixer (3) is respectively connected with an acid tank (12) and the first fixed bed reactor (4); the second dehydration tower (5) is respectively connected with the first fixed bed reactor (4) and the third fixed bed reactor (8);

the rectification system comprises a rectification device, and the third fixed bed reactor (8) is connected with the rectification device.

9. The apparatus according to claim 7, wherein the rectification apparatus comprises a first separation column (9), a second separation column (10) and a refining column (11) connected in this order;

preferably, the first separation column (9), the second separation column (10) and the refining column (11) each include a condenser, a reboiler, a condensation tank and a bottom discharge pump.

10. The arrangement according to claim 7, wherein the arrangement further comprises a second fixed bed reactor (7), and the second fixed bed reactor (7) is connected with the first fixed bed reactor (4) and the third fixed bed reactor (8), respectively.

Technical Field

The invention relates to the field of preparation of caprolactone, in particular to a method and a device for preparing caprolactone.

Background

With the enhancement of global environmental protection consciousness, the domestic environmental protection policy is gradually tightened, and increasingly strict requirements on environmental pollution control are also provided. Caprolactone as an important polymer synthesized by monomers is a material which can be completely biodegraded, and is a high-solubility substance when used as a solvent, so that the caprolactone has quite wide application and receives wide attention at home and abroad.

But the synthesis process is relatively complex, and the requirements on production equipment and production safety are high, so that the possibility of large-scale industrialization is limited. The influence of environmental protection policy causes the increase of the demand and the sudden rise of the price, which in turn restricts the application of the caprolactone, but also brings huge space for the development of the caprolactone. At present, caprolactone in China basically depends on import, and the caprolactone forms a restriction on related industries in China.

In the prior art, generally, organic acid is oxidized by hydrogen peroxide in a stirring kettle to prepare peroxy acid, a certain amount of peroxide is stored, and then cyclohexanone and peroxycarboxylic acid are reacted to prepare caprolactone by utilizing the Bayer-Virgo oxidation reaction principle.

CN1071923A discloses a process for producing caprolactone, which comprises using a percarboxylic acid solution prepared by oxidizing an organic carboxylic acid in an organic solvent in the presence of hydrogen peroxide and a boric acid catalyst, and cyclohexanone in such a ratio that 0.04 mole or less of hydrogen peroxide is supplied to the reaction system in an amount of 1 to 1.5 moles of the percarboxylic acid per mole of cyclohexanone and 0.012 mole or less of the boric acid catalyst, and then reacting the above hexanone with the above percarboxylic acid to produce caprolactone. That is, it is proposed to oxidize carboxylic acids having 2 to 4 carbon atoms with hydrogen peroxide under boric acid catalysis to produce percarboxylic acids (reaction while continuously removing water under azeotropic conditions), and then to oxidize cyclohexanone to produce caprolactone. Both percarboxylic acid and hydrogen peroxide have self-decomposition properties, and the use of a single stabilizer is not effective, so that percarboxylic acid is easily decomposed, resulting in a decrease in yield, resulting in a decrease in economy and safety. Boric acid is not separated from the system after the caprolactone is prepared, and a large amount of self-polymerization of the caprolactone is caused in the high-temperature rectification process, so that the product yield is reduced.

CN202786068U discloses a caprolactone preparation reactor formed by serially connecting stirred tanks with heat exchange equipment and a caprolactone purification device formed by serially connecting a plurality of rectifying towers, which are essentially intermittent devices, only reduce the intermittent time and cannot realize the real continuity.

CN103570667A discloses a method for continuously preparing caprolactone, which comprises the steps of continuously oxidizing carboxylic acid solution with hydrogen peroxide in a plurality of stirred tanks with rectifying towers in the presence of boric acid, and continuously introducing the obtained peroxycarboxylic acid and cyclohexanone into a plurality of stirred tanks connected in series for reaction to obtain caprolactone.

CN104003972A discloses a method for preparing caprolactone, which comprises mixing organic acid, hydrogen peroxide, organic solvent, stabilizer and catalyst at normal temperature, continuously stirring, dehydrating, distilling to obtain a product, reacting the product with cyclohexanone, and rectifying to obtain-caprolactone. The method is simple, but does not relate to the problems of separating specific rectification products and keeping the stability of the products, and meanwhile, the method has poor safety and is difficult to realize industrialization.

CN105646433A discloses a process for continuously preparing high-purity caprolactone, which adopts a catalytic rectification technology to carry out reaction in a tower, then uses a stirring reaction kettle as a supplementary means, and finally rectifies the product. The method mentions that the catalytic rectifying tower is filled with strong acid cation exchange resin or perfluorinated sulfonic acid resin in the preparation process. However, the process is questionable because the obtaining of peroxide and the subsequent oxidation reaction cannot use the same catalyst at all from the viewpoint of reaction mechanism. Meanwhile, the catalyst packed in the catalyst rectification column has a problem of handling, so that it can be industrially applied to a low degree.

In conclusion, the research and development of a method for continuously preparing caprolactone is of great significance.

Disclosure of Invention

The invention aims to overcome the problems that caprolactone is easy to self-polymerize in rectification and the yield of caprolactone is low in the method disclosed by the prior art, and provides a method and a device for preparing caprolactone. The product prepared by the method has high purity. The method has high conversion rate of the oxidant and the cyclohexanone and high yield of the prepared caprolactone, and can continuously, safely and efficiently prepare the high-purity caprolactone.

In order to achieve the above object, the present invention provides, in a first aspect, a method for producing caprolactone, wherein the method comprises:

(I) mixing an oxidant, a water-carrying agent and a stabilizer in a raw material premixing tank 1, and dehydrating the obtained mixture through a first dehydrating tower 2 to obtain a first product;

(II) mixing the first product and acid in a first mixer 3, carrying out a first reaction on the obtained first mixture in a first fixed bed reactor 4, and dehydrating the obtained reaction product in a second dehydrating tower 5 to obtain a second product;

(III) mixing the second product with cyclohexanone in a second mixer 6 and subjecting the resulting second mixture to a second reaction in a third fixed bed reactor 8 to obtain a crude ester;

(IV) rectifying the crude ester to obtain caprolactone.

The invention provides a device for preparing caprolactone, wherein the device comprises a pretreatment system, a reaction system and a rectification system which are connected in sequence;

the pretreatment system comprises a raw material premixing tank 1, a first dehydration tower 2 and a first mixer 3; the first dehydration tower 2 is respectively connected with the raw material premixing tank 1 and the first mixer 3 through a circulating pump;

wherein the reaction system comprises a first fixed bed reactor 4, a second dehydration tower 5, a second mixer 6 and a third fixed bed reactor 8; the first mixer 3 is respectively connected with an acid tank 12 and the first fixed bed reactor 4; the second dehydration tower 5 is connected with the first fixed bed reactor 4 and the third fixed bed reactor 8 respectively;

the rectification system comprises a rectification device, and the third fixed bed reactor 8 is connected with the rectification device.

Through the technical scheme, the technical scheme of the invention has the following advantages:

(1) the method of the invention avoids the problems of pollution and difficult separation of impurities caused by the use of the liquid acid catalyst in the prior art;

(2) the method of the invention uses the stabilizer to effectively inhibit the decomposition of the intermediate product and the target product;

(3) the method of the invention adopts the fixed bed type reactor filled with the solid acid catalyst, abandons the use of a stirring kettle, ensures continuous production under the conditions of certain retention time and part of reaction material circulation, and reduces the discharge of waste liquid and the production cost because of the use of the solid acid catalyst.

(4) The method for preparing caprolactone by adopting the device has the advantages of high conversion rate, stable operation, high product yield and continuous production in the whole production process.

Drawings

FIG. 1 is a schematic view of an apparatus for producing caprolactone according to the present invention.

Description of the reference numerals

1-raw material premixing tank 2-first dehydrating tower 3-first mixer

4-first fixed bed reactor 5-second dehydration tower 6-second mixer

7-second fixed bed reactor 8-third fixed bed reactor 9-first separation column

10-second separation tower 11-refining tower 12-acid tank

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a preparation method of caprolactone, which comprises the following steps:

(I) mixing an oxidant, a water-carrying agent and a stabilizer in a raw material premixing tank 1, and dehydrating the obtained mixture through a first dehydrating tower 2 to obtain a first product;

(II) mixing the first product and acid in a first mixer 3, carrying out a first reaction on the obtained first mixture in a first fixed bed reactor 4, and dehydrating the obtained reaction product in a second dehydration tower (5) to obtain a second product;

(III) mixing the second product with cyclohexanone in a second mixer 6 and subjecting the resulting second mixture to a second reaction in a third fixed bed reactor 8 to obtain a crude ester;

(IV) rectifying the crude ester to obtain caprolactone.

Aiming at the problems that peroxide is easily decomposed, caprolactone is easily self-polymerized in rectification and an added stabilizer is difficult to remove in the method disclosed by the prior art, and the problems of low yield of percarboxylic acid, poor safety and low yield of caprolactone; the inventor of the invention finds out through experiments that: the fixed bed type reactor filled with the solid acid catalyst is adopted, so that the problems of pollution and difficult separation of impurities caused by the use of a liquid acid catalyst in the prior art can be solved; in addition, the method for preparing caprolactone by adopting the device of the invention has stable operation in the whole production process, high product purity and continuous production.

According to the invention, the caprolactone (-caprolone) molecule is C₆H₁₀O₂The structural formula is shown as formula (1):

according to the invention, in the step (I), the stabilizer is a composite stabilizer, the stabilizer is at least two selected from picolinic acid, dipicolinic acid, picoline, lutidine, 8-hydroxyquinoline, tributyl phosphate and dipicolinic acid, and the composite stabilizer can reduce decomposition of peroxide and improve safety and economy; in addition, in the present invention, preferably, the stabilizer is selected from two optional stabilizers selected from picolinic acid, dipicolinic acid, picoline, lutidine, 8-hydroxyquinoline, and tributyl phosphate, and the weight ratio of the amounts of the two optional stabilizers in picolinic acid, dipicolinic acid, picoline, lutidine, 8-hydroxyquinoline, and tributyl phosphate is 1: (1-20); the weight ratio of the optional three stabilizers in picolinic acid, dipicolinic acid, picoline, lutidine, 8-hydroxyquinoline, and tributyl phosphate is 1: (1-20): (1-20), more preferably 1: (1-5): (1-6); more preferably, the stabilizer is dipicolinic acid and picoline; wherein the dipicolinic acid may be pyridine 2,5 dicarboxylic acid.

According to the present invention, in the actual production, the stabilizer must be added to the raw material premixing tank 1, which not only ensures the stability of the peroxide as the raw material in the reaction system, but also ensures the stability of the intermediate product in the reactor; and the components are extracted from the top of the first separation tower 9 and the bottom of the refining tower 11 and then returned to the system, so that the content of the components in the stabilizer needs to be analyzed periodically in the raw material mixing tank 1.

In the invention, the compound stabilizer is adopted and added into the raw material premixing tank 1, and the decomposition of the intermediate product and the target product can be effectively inhibited within the specific proportion range, and the whole process is safe.

According to the invention, the oxidizing agent is hydrogen peroxide. In the present invention, the concentration of the oxidizing agent is 10 to 70%, preferably 10 to 50%. Hydrogen peroxide (hydrogen peroxide), formula H₂O₂. Pure hydrogen peroxide is light blue viscous liquid, can be mixed and dissolved with water in any proportion, is a strong oxidant, and is a colorless transparent liquid, and the aqueous solution is commonly called hydrogen peroxide.

In the invention, the water-carrying agent is added while the oxidant is dehydrated, so that the reaction rate can not be reduced while the safety can be ensured.

According to the present invention, the first dehydration column 2 dehydrates the water using the azeotropic action of the oxidizing agent and the water-carrying agent, and in the present invention, the oxidizing agent is concentrated and the water-carrying agent is mixed, so that the concentration of the oxidizing agent is provided and the safety can be ensured to the maximum extent.

According to the invention, the water-carrying agent is selected from one or more of ethyl acetate, ethyl propionate, methyl propionate, isopropyl acetate and propyl formate, and ethyl acetate is preferred.

According to the invention, the weight ratio of the amounts of the oxidant, the water-carrying agent and the stabilizer is 1: (4-15): (0.001-0.02); more preferably, the weight ratio of the usage amounts of the oxidant, the water-carrying agent and the stabilizer is 1: (6-12): (0.005-0.01).

According to the invention, in the step (II), azeotrope of water and the first product is obtained at the top of the first dehydrating tower 2, and is condensed and layered, the water-carrying agent on the upper layer of the phase separator returns to the first dehydrating tower 2, and the water phase on the lower layer is extracted; the mixture of the oxidant and the water-carrying agent in the first dehydration tower 2 is pumped into a first mixer 3 through a pump.

According to the invention, the acid is selected from one or more of formic acid, acetic acid and propionic acid, preferably acetic acid.

According to the invention, the molar ratio of the amounts of said oxidizing agent and said acid is 1 (1-5), preferably 1: (1.5-2.5).

According to a preferred embodiment of the invention, the content of the oxidant (hydrogen peroxide) in the second fixed bed reactor (7) is not more than 1 wt%, preferably 0.06-1 wt%, as confirmed by continuous Chinese-style experiments; when the amount of the caprolactone derivative is too high, self-polymerization of caprolactone is accelerated in the subsequent step. The content of the peroxyacid is not preferably less than 18% by weight, preferably from 18 to 22% by weight, and too high a content may cause an increase in risk.

According to the invention, in practical production, the first mixer 3 mixes three materials.

According to the invention, the conditions of the first reaction comprise: the temperature is 30-90 ℃, the pressure is-0.1 MPa to 0MPa, and the time is 0.2-3 h; more preferably, the temperature is 40-90 ℃, the pressure is-0.095 MPa to-0.05 MPa, and the time is 0.5-1 h.

According to the invention, in step (III), the acid is stored in the acid tank 12. The acid is preheated and then enters a first mixer 3, the acid and the first product are mixed and then enter a first fixed bed reactor 4 filled with a solid acid catalyst, one part of the reacted material is circulated to the first mixer 3, and the other part of the reacted material enters a second dehydration tower 5.

According to the invention, the molar ratio of the second product to the amount of cyclohexanone is 1: (1-5), preferably 1: (1.5-3).

According to the invention, the conditions of the second reaction comprise: the temperature is 30-100 ℃, the pressure is 0MPa to 0.1MPa, and the time is 0.2-2 h; more preferably, the temperature is 40-90 ℃, the pressure is 0.08MPa to 0.2MPa, and the time is 0.5-1 h.

According to the invention, the method further comprises: in step (III), the second product is treated in a second fixed bed reactor 7; preferably, the second fixed bed reactor 7 is packed with the oxidant.

According to the present invention, the first fixed bed reactor 4, the second fixed bed reactor 7 and the third fixed bed reactor 8 are all jacketed solid bed reactors; preferably, the first fixed bed reactor 4 and the second fixed bed reactor 7 are both filled with solid acid catalysts; wherein the solid acid catalysts are respectively filled in the tubes arranged in the first fixed bed reactor 4; in the present invention, the periphery of the tubes in the first fixed bed reactor 4 and the second fixed bed reactor 7 is filled with a heat medium (circulating hot water), so that the reaction temperature can be rapidly raised, and the reaction can be carried out toward the product by controlling the temperature of the hot water; the periphery of the tubes in the third fixed bed reactor 8 is filled with a cold medium (circulating cold water), and the arrangement can effectively draw heat generated by the reaction, control the reaction degree and reduce the decomposition of caprolactone.

According to the invention, the molecular sieve catalyst loaded with active components is filled in the first fixed bed reactor 4 and the second fixed bed reactor 7, wherein the molecular sieve catalyst is filled in the first fixed bed reactor and the second fixed bed reactorThe molecular sieve catalyst loaded with the active component is a carrier and the active component loaded on the carrier, wherein the carrier is selected from B₂O₃/γ-Al₂O₃The active component is one or more of phosphotungstic heteropoly acid and/or boric acid, ZSM-5(H-ZSM-5), a modified β molecular sieve and a modified Y-type molecular sieve.

In the present invention, the first fixed bed reactor 4 and the second fixed bed reactor 7 are filled with molecular sieve catalysts loaded with active components, wherein the first fixed bed reactor 4 is provided with a pump capable of self-circulation, and the second fixed bed reactor 7 is provided with a dehydration tower capable of removing product water. The arrangement can effectively reduce the water content in the second product and ensure that the reaction is carried out towards the direction of the produced product, so that the production can be continuous.

According to the present invention, the third fixed bed reactor 8 is filled with an organic acid synthetic resin catalyst.

Wherein the organic acid synthetic resin catalyst is one of Amberlyst-15, 001 x 7 strong acid styrene cation exchange resin and D001 macroporous strong acid styrene cation exchange resin, and D001 macroporous strong acid styrene cation exchange resin is preferred.

Wherein Amberlyst-15 is a solid acidic catalyst, belongs to ion exchange resin, and is a strong acidic catalyst formed by sulfonating macroporous styrene divinylbenzene copolymer. The detailed parameters are as follows: the total mass exchange capacity is more than or equal to 4.60, and the specific surface area is 30-50m²The pore volume is 0.2-0.4ml/g, and the particle size (0.315-1.25mm) is more than or equal to 96 percent.

Wherein 001 × 7 strong acidic styrene cation exchange resin is prepared by polymerizing styrene-divinylbenzene with sulfonic acid group (-SO) on polymer matrix₃H) The ion exchange resin of (1), styrene-divinylbenzene resin structure, functional group-SO₃H, tan to tan spherical particles. The detailed parameters are as follows: the mass total exchange capacity is more than or equal to 4.80, the uniformity coefficient is 1.6, the sphericity rate after grinding is more than or equal to 90 percent, and the particle size (0.315-1.25mm) is more than or equal to 95 percent.

Wherein D001 macroporous strong acid benzeneVinyl cation exchange resin, styrene-divinylbenzene resin structure, and functional group-SO₃H, light camel opaque spherical particles, other parameters: the mass total exchange capacity is more than or equal to 4.70, and the specific surface area is 35-58m²The pore volume is 0.2-0.4ml/g, and the particle size (0.315-1.25mm) is more than or equal to 95 percent.

According to the present invention, the third fixed bed reactor 8 is filled with the organic acid synthetic resin catalyst and is provided with a self-circulation device, so that the components in the separation column 1 can be maintained stable, which is beneficial to continuous production.

According to the invention, in step (III), the second product, cyclohexanone and unreacted materials are fed into a third fixed bed reactor 8 in a second mixer 6 according to a certain proportion, and part of materials are extracted after reaction and fed into a rectifying device.

In actual production, the residence time of the material (the second product) on the catalyst surface in the fixed bed reactor is measured by the weight hourly space velocity and is defined as 1m in 1h³Volume of material (m) through which the catalyst flows³/(m³H)), i.e., h)^-1。

In the present invention, in step (II), the weight hourly space velocity is from 0.5 to 2h^-1Preferably 0.6-1.5h^-1More preferably 0.6 to 0.8h^-1The initial weight hourly space velocity is 0.5h^-1The circulation ratio is 10, and the circulation amount can be gradually reduced while the space velocity is increased according to the content of the target product.

In the present invention, in step (III), the weight hourly space velocity is 1 to 3h^-1Preferably 2-2.5h^-1Initial weight hourly space velocity of 1h^-1The circulation ratio is 5, and the circulation amount can be gradually reduced while the space velocity is increased according to the content of the target product.

In addition, it should be noted that the "circulation ratio" is the ratio of the flow rate of the material at the outlet of the third fixed-bed reactor returned to the inlet to the partial flow rate of the material to be separated in the separation column 1.

According to the present invention, more preferably, the oxidizing agent is hydrogen peroxide, and the water-carrying agent is ethyl acetate, and in the present invention, the reaction for obtaining peroxyacetic acid by performing the first reaction in the first fixed bed reactor 4 is:

in the present invention, the reaction in the first fixed-bed reactor 4 is endothermic, and the shell side is hot water.

In the present invention, the second reaction to give caprolactone in the third fixed bed reactor 8 is:

in the present invention, the reaction in the third fixed bed reactor 8 is an exothermic reaction, and the shell side is cold water.

In actual production, the circulating water firstly passes through the third fixed bed reactor 8 and then goes to the first fixed bed reactor 4.

In the present invention, the second fixed bed reactor 7 is used as a supplement to the first fixed bed reactor 4, and the purpose is to reduce the content of hydrogen peroxide and ensure the effective proceeding of the subsequent reaction.

In the present invention, the reaction in the second fixed bed reactor 7 is endothermic, and the shell side is hot water.

In actual production, the circulating water firstly passes through the third fixed bed reactor 8 and then goes to the first fixed bed reactor 4 and the second fixed bed reactor 7.

According to the invention, in the step (IV), the material to be rectified enters a first separation tower 9 and a second separation tower 10 in sequence, and a water preparation agent and cyclohexanone are respectively removed; meanwhile, the first separation tower 9 and the second separation tower 10 form a multi-effect rectification system, so that the energy consumption can be effectively reduced.

According to the invention, the material in the tower bottom of the second separation tower 10 enters a refining tower, under certain vacuum and temperature, the light component is firstly separated from the tower top, then caprolactone with the content not less than 99.4 percent is obtained from the tower top, and the heavy component is separated from the tower bottom.

According to the invention, the first separation column 9 is operated at a temperature of between 80 and 130 ℃, preferably between 90 and 120 ℃; the operating pressure is from 1 to 30kPa, preferably from 4 to 25 kPa.

According to the invention, the second separation column 10 is operated at a temperature of 80 to 130 ℃, preferably at a temperature of 100-120 ℃; the operating pressure is from 0.1 to 10kPa, preferably from 0.3 to 5 kPa.

Through strict simulation calculation and a formula experiment, in actual production, the first separation tower 9 and the second separation tower 10 form a double-effect rectifying tower system adopting a concurrent flow process, namely, the tower top steam of the first separation tower 9 is used as a heating medium of a reboiler of the second separation tower 10; the preliminary estimate saves about 38% of energy compared to conventional systems.

According to the invention, the operating temperature of the refining tower 11 is 90-140 ℃, preferably 110-130 ℃; the operating pressure is from 0.5 to 10kPa, preferably from 1 to 8 kPa.

The invention provides a device for preparing caprolactone, wherein the device comprises a pretreatment system, a reaction system and a rectification system which are connected in sequence;

the pretreatment system comprises a raw material premixing tank 1, a first dehydration tower 2 and a first mixer 3; the first dehydration tower 2 is respectively connected with the raw material premixing tank 1 and the first mixer 3 through a circulating pump;

wherein the reaction system comprises a first fixed bed reactor 4, a second dehydration tower 5, a second mixer 6 and a third fixed bed reactor 8; the first mixer 3 is respectively connected with an acid tank 12 and the first fixed bed reactor 4; the second dehydration tower 5 is connected with the first fixed bed reactor 4 and the third fixed bed reactor 8 respectively;

the rectification system comprises a rectification device, and the third fixed bed reactor 8 is connected with the rectification device.

According to the invention, the rectification apparatus comprises a first separation column 9, a second separation column 10 and a refining column 11 connected in series.

According to the present invention, each of the first separation column 9, the second separation column 10 and the refining column 11 includes a condenser, a reboiler, a condensation tank and a column bottom discharge pump.

According to the invention, the apparatus further comprises a second fixed bed reactor 7, and the second fixed bed reactor 7 is connected to the first fixed bed reactor 4 and the third fixed bed reactor 8, respectively.

The method and the device provided by the invention have the advantages of wide raw material selection range, high safety coefficient, less system energy consumption, less discharged waste and capability of realizing industrialized continuous production. Meanwhile, the expanded production can be carried out according to actual production conditions.

The present invention will be described in detail below by way of examples.