Composite metal oxides, epsilon-caprolactone, and methods of preparation, use

Abstract

The application discloses a composite metal oxide, epsilon-caprolactone and a preparation method and application thereof. The composite metal oxide is CuO-ZnO-MxOy, M is one or more of Cr elements, Mo elements and Co elements; in the composite metal oxide, according to the total mass of metal elements being 100%, the mass percentage of Cu elements in the total mass of metal elements is 20%-40%, the mass percentage of Zn elements in the total mass of metal elements is 20%-45%, and the balance is M elements; when the M elements contain Cr elements or Co elements, x is 2 and y is 3; when the M elements contain Mo elements, x is 2 and y is 3 or x is 1 and y is 3. The composite metal oxide has good catalytic activity, high conversion rate of reactants and high selectivity of target products; the preparation process is simple and low in cost; and when the composite metal oxide is used for preparing epsilon-caprolactone from 1,6-hexanediol, the reaction condition is mild.

Description

Technical Field

[0001] This invention specifically relates to a composite metal oxide, ε-caprolactone, its preparation method, and its application. Background Technology

[0002] ε-caprolactone (ε-CL) is an important organic synthetic monomer with a wide range of applications, especially in the self-polymerization to synthesize polycaprolactone (PCL) or in copolymerization or blending with other ester monomers to obtain PCL copolymers. PCL is an important aliphatic polyester material and also an important branch of biodegradable plastics. Its excellent biocompatibility, biodegradability, strong hydrophobicity, and excellent drug permeability have made it a hot topic in new material development, and it has found good applications in biomedicine, tissue engineering, and environmental protection. However, due to factors such as raw material sourcing, technical difficulty, technical safety, production costs, and environmental protection, the price of PCL monomer ε-CL is high, and domestic research and industrialization are slow. Therefore, research on the synthesis of PCL monomer ε-CL is of great significance for both scientific research and industrialization.

[0003] Currently, the main methods for synthesizing ε-CL include cyclohexanone oxidation, 1,6-hexanediol liquid-phase catalytic dehydrogenation, and 6-hydroxyhexanoic acid intramolecular condensation. Among these, cyclohexanone oxidation is relatively mature and can be further divided into peroxyacid oxidation, hydrogen peroxide oxidation, and oxygen / air oxidation depending on the oxidation system. However, cyclohexanone oxidation for ε-CL preparation suffers from drawbacks such as high pollution levels and safety risks. The 1,6-hexanediol liquid-phase catalytic dehydrogenation uses Ru or Rh organic complexes as catalysts, but its catalyst preparation is complex, costly, and involves a long product separation process. The 6-hydroxyhexanoic acid intramolecular condensation method uses the fraction of 6-hydroxyhexanoate as raw material, cyclizing the 6-hydroxyhexanoate to obtain ε-CL. However, this method involves numerous separation steps, is complex, and consumes a large amount of energy, making it unsuitable for large-scale production.

[0004] Therefore, it is essential to develop catalysts with high catalytic activity and simple preparation methods for the preparation of ε-caprolactone. Summary of the Invention

[0005] To address the shortcomings of existing catalysts for the preparation of ε-caprolactone, such as complex preparation methods and high costs, this invention provides a composite metal oxide, ε-caprolactone, its preparation method, and its applications. The composite metal oxide of this invention exhibits excellent catalytic activity, improving the conversion rate of reactants and the selectivity of the target product. The preparation method of this composite metal oxide is simple, and in the reaction for preparing ε-caprolactone, it can improve the conversion rate of 1,6-hexanediol and the selectivity of ε-caprolactone, with mild reaction conditions, providing a reference for the industrial production of ε-caprolactone.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0007] This invention provides a composite metal oxide CuO-ZnO-MxOy, where M is one or more of Cr, Mo, and Co elements;

[0008] In the composite metal oxide, based on a total mass of 100% metal elements, the mass percentage of Cu element is 20% to 40% of the total mass of metal elements, the mass percentage of Zn element is 20% to 45% of the total mass of metal elements, and the balance is M element.

[0009] When element M contains Cr or Co, x is 2 and y is 3;

[0010] When the element M contains the element Mo, "x is 2, y is 3" or "x is 1, y is 3".

[0011] The percentage of Cu in the total mass of the metal elements can be 25% to 40%, more preferably 35% to 40%.

[0012] The percentage of the Zn element in the total mass of the metal elements can be 30% to 45%, more preferably 35% to 42%, and even more preferably 40%.

[0013] The mass percentage of element M in the total mass of the metallic elements can be 15-60%, more preferably 18-40%, and even more preferably 20-35%.

[0014] The M element is preferably Cr, Co, Mo, "Cr and Mo" or "Co and Mo".

[0015] When the element M is Cr, Mo, or Co, the percentage of the mass of the element M in the total mass of the metal elements can be 18% to 40%, more preferably 20% to 40%, and even more preferably 20% to 35%.

[0016] When the M element is "Cr and Mo" or "Co and Mo", the mass percentage of the M element in the total mass of the metal elements can be 20% to 40%, preferably 20% to 35%.

[0017] When the M element is "Cr and Mo", the mass ratio of Cr to Mo can be 1:(0.8-2), preferably 1:(1-1.5), and more preferably 15:20.

[0018] When the M element is "Co and Mo", the mass ratio of Co to Mo can be 1:(2-4), preferably 1:(2.5-3.5), and more preferably 1:3.

[0019] The composite metal oxide is preferably CuO-ZnO-Cr2O3, CuO-ZnO-Co2O3, CuO-ZnO-Cr2O3-MoO3 or CuO-ZnO-Co2O3-MoO3.

[0020] When the composite metal oxide is CuO-ZnO-Cr2O3, the mass ratio of Cu, Zn and Cr is preferably (2-3):(2-3):1, for example 40:42:18.

[0021] When the composite metal oxide is CuO-ZnO-Co2O3, the preferred mass ratio of Cu, Zn and Co is (0.3-0.6):(0.8-1.2):1, for example 20:40:40.

[0022] When the composite metal oxide is CuO-ZnO-Cr2O3-MoO3, the preferred mass ratio of Cu, Zn, Cr and Mo is (2-2.5):(1.5-2.5):1:(1-1.5), for example 35:30:15:20.

[0023] When the composite metal oxide is CuO-ZnO-Co2O3-MoO3, the preferred mass ratio of Cu, Zn, Co and Mo is (7-9):(7-9):1:(2-4), for example 40:40:5:15.

[0024] The present invention also provides a method for preparing the composite metal oxide, which includes the following steps:

[0025] A mixed solution containing metal ions and a precipitant are mixed and reacted, aged, and the resulting solid is calcined to obtain the composite metal oxide CuO-ZnO-MxOy.

[0026] The metal ions in the mixed solution include Cu. 2+ Zn 2+ And M ions; M ions are one or more of Cr ions, Mo ions and Co ions.

[0027] The solvent in the mixed solution containing metal ions can be conventional in the art, generally water and / or alcohol solvents. The alcohol solvent can be ethanol and / or ethylene glycol.

[0028] In the mixed solution, the total molar concentration of the metal ions can be conventional in the art, preferably 0.5 to 1.5 mol / L, and more preferably 1 mol / L.

[0029] Prior to the mixing reaction, the mixing method of the mixed solution containing metal ions and the precipitant can be conventional in the art. Preferably, the mixed solution containing metal ions and the precipitant are added dropwise to the reaction vessel respectively.

[0030] Wherein, Cu 2+ It can be provided by a Cu salt conventionally used in the art. The Cu salt may be one or more of copper nitrate, copper chloride, copper acetate and copper sulfate, preferably copper nitrate.

[0031] Wherein, Zn 2+ It can be provided by a Zn salt conventionally used in the art. The Zn salt may be one or more of zinc nitrate, zinc chloride, and zinc acetate, preferably zinc nitrate.

[0032] The Cr ions can be provided by Cr salts conventionally used in the art. The Cr salt can be chromium nitrate and / or chromium chloride, preferably chromium nitrate.

[0033] The Mo ions can be provided by Mo salts conventionally used in the art. The Mo salt can be ammonium molybdate and / or sodium molybdate, preferably ammonium molybdate.

[0034] The Co ions can be provided by Co salts conventionally used in the art. The Co salt can be cobalt nitrate.

[0035] The precipitant can be an inorganic precipitant or urea commonly used in the art.

[0036] The inorganic precipitant can be a hydroxide precipitant or a carbonate precipitant. The hydroxide precipitant can be conventional in the art, preferably sodium hydroxide. The carbonate precipitant can be conventional in the art, preferably sodium carbonate.

[0037] When the precipitant is an inorganic precipitant, it can be added in the form of a precipitant solution in accordance with conventional practices in the art.

[0038] The solvent in the precipitant solution can be conventional in the art, generally water and / or an alcohol solvent, wherein the alcohol solvent is generally ethanol and / or ethylene glycol. The concentration of the precipitant in the precipitant solution can be conventional in the art, preferably 0.5–1 mol / L, more preferably 1 mol / L. The method of adding the precipitant solution can be conventional in the art, generally dropwise addition.

[0039] When the precipitant is an inorganic precipitant, the mixing method can be conventional in the art. The mixing temperature can be conventional in the art, preferably 50–90°C.

[0040] When the precipitant is an inorganic precipitant, the pH value of the system during the mixing process can be conventional in the art, preferably 6-9, more preferably 7.5-8.5, for example 8. The conditions and methods for adjusting the pH value of the system to 6-9 can be conventional in the art, and the pH value of the system can generally be adjusted by controlling the amount and rate of addition of the precipitant.

[0041] When the precipitant is an inorganic precipitant, the titration endpoint can generally be controlled by controlling the pH value of the titration endpoint of the system. The pH value of the titration endpoint can be 6 to 9, preferably 7.5 to 8.5, and more preferably 8.

[0042] When the precipitant is an inorganic precipitant, the aging conditions and methods can be those conventional for this type of operation in the art. The aging temperature can be 50–90°C, preferably 80–90°C, for example 85°C. The aging time can be 1–5 hours, preferably 2 hours.

[0043] When the precipitant is urea, the ratio of the molar amount of the precipitant to the total molar amount of the metal ions can be conventional in the art, preferably (5-10):1.

[0044] When the precipitant is urea, the mixing method can be conventional in the art. The mixing temperature can be conventional in the art, preferably room temperature, for example, 20-30°C.

[0045] When the precipitant is urea, the aging conditions and methods can be those conventional for this type of operation in the art.

[0046] The aging temperature can be 70–100°C, preferably 90°C. The aging time can be 1–5 hours, preferably 3 hours.

[0047] The process typically includes filtration, washing, and drying steps before the roasting operation and after the aging operation.

[0048] The filtration method is preferably vacuum filtration.

[0049] The washing method described herein can be a conventional method for this type of operation in the art.

[0050] The solvent used for washing can be a solvent commonly used in this type of operation in the art, such as water. The purpose of washing is to neutralize the mixture.

[0051] The drying conditions and methods are those conventional for this type of operation in the art. The drying temperature is 100–150°C, preferably 110–120°C. The drying time is 5–15 hours, preferably 10 hours.

[0052] The calcination conditions and methods are those conventional for this type of operation in the art, and are generally carried out in a muffle furnace. The calcination temperature is 350–550°C, preferably 400–550°C, and more preferably 450–520°C. The calcination time is 3–10 hours, preferably 4 hours.

[0053] The roasting operation may be followed by a tableting operation.

[0054] The present invention also provides an application of the aforementioned composite metal oxide as a catalyst in a dehydrogenation reaction.

[0055] The dehydrogenation reaction is preferably the reaction of 1,6-hexanediol in the preparation of ε-caprolactone.

[0056] The present invention also provides a method for preparing ε-caprolactone, which includes the following steps: in a hydrogen atmosphere, under the action of the composite metal oxide as described above, 1,6-hexanediol undergoes a dehydrogenation reaction to obtain ε-caprolactone.

[0057] In this invention, the flow rate of hydrogen can be 50-150 mL / h, preferably 100-120 mL / h.

[0058] In this invention, the flow rate of the 1,6-hexanediol can be 1 to 3 mL / h, preferably 1.5 to 2 mL / h.

[0059] In this invention, the liquid hourly space velocity (LHSV) of the 1,6-hexanediol can be conventional in the art, preferably 1–3 h⁻¹. -1 The space velocity generally refers to the liquid volume of 1,6-hexanediol processed per unit time and per unit volume of the catalyst.

[0060] In this invention, the conditions and methods for the dehydrogenation reaction can be conventional in the art and can generally be carried out in a fixed-bed reactor.

[0061] In this invention, in accordance with conventional art, the 1,6-hexanediol participates in the dehydrogenation reaction in a gaseous state.

[0062] In this invention, the temperature of the dehydrogenation reaction can be the conventional temperature for this type of reaction in the art, preferably 250-350°C, and more preferably 270-300°C.

[0063] In this invention, the pressure of the dehydrogenation reaction can be 0.1 to 2 MPa, preferably 0.1 to 1 MPa.

[0064] In this invention, the mesh size of the composite metal oxide can be conventional in the art, preferably 20-80 mesh, more preferably 20-60 mesh, for example 40-60 mesh.

[0065] In this invention, the composite metal oxide can be subjected to reduction and activation treatment in accordance with conventional methods in the art before use. The reduction and activation treatment preferably includes the following steps: the composite metal oxide undergoes a reduction reaction under the action of a reducing atmosphere.

[0066] The reducing atmosphere can be a hydrogen-containing gas commonly used in the art, preferably hydrogen or a mixture of hydrogen and helium or a mixture of hydrogen and argon.

[0067] The reducing atmosphere may further include one or more of nitrogen, helium, and argon. The volume percentage of hydrogen in the reducing atmosphere may be conventional in the art, preferably 10-100%, more preferably 30-100%.

[0068] Preferably, the reducing atmosphere is 30% hydrogen and 70% argon, the percentages being by volume.

[0069] Preferably, the reducing atmosphere is 10% hydrogen and 90% helium, the percentages being by volume.

[0070] The space velocity of the reducing atmosphere can be a conventional space velocity for this type of operation in the art, preferably 500–2000 h⁻¹. -1 The space velocity of a reducing atmosphere, as conventionally described in the art, generally refers to the volume of the reducing atmosphere passing through a unit volume of the composite metal oxide per unit time.

[0071] The temperature of the reduction reaction can be a conventional temperature for this type of reaction in the art, preferably 220-380°C, more preferably 300-380°C, for example 320-350°C.

[0072] The rate at which the temperature is raised to the reduction reaction temperature can be the conventional heating rate for this type of reaction in the art, preferably 2 to 5 °C / min.

[0073] The reduction reaction time can be the conventional time for this type of reaction in the art, preferably 5 to 10 hours, and more preferably 6 hours.

[0074] The pressure of the reduction reaction can be the conventional pressure for this type of reaction in the art, preferably atmospheric pressure, for example 0.1 MPa.

[0075] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0076] The reagents and raw materials used in this invention are all commercially available.

[0077] The positive and progressive effects of this invention are as follows:

[0078] 1. The composite metal oxide of the present invention has good catalytic activity, which can improve the conversion rate of reactants and the selectivity of target products;

[0079] 2. The preparation process of the composite metal oxide of the present invention is simple, readily available, and low in cost;

[0080] 3. Using 1,6-hexanediol as a reactant, ε-caprolactone is prepared by dehydrogenation under the action of the composite metal oxide of the present invention. The conversion rate of 1,6-hexanediol and the selectivity of ε-caprolactone are high, and the reaction conditions are mild, which can provide a reference for the exploration of industrial production of ε-caprolactone. Detailed Implementation

[0081] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0082] Example 1

[0083] A composite metal oxide CuO-ZnO-Cr2O3 was prepared by co-precipitation method, with a Cu:Zn:Cr ratio of 40:42:18 (mass ratio of the materials). A certain amount of copper nitrate, zinc nitrate, and chromium nitrate were weighed and prepared into a 1 mol / L aqueous solution containing metal ions. Simultaneously, a 1 mol / L sodium carbonate aqueous solution was prepared as a precipitant. A beaker containing 100 mL of deionized water was placed in a water bath at 80 °C with stirring. The aqueous solutions of metal ions and sodium carbonate were added dropwise to the beaker, and the pH value was monitored. The amount and rate of precipitant addition were adjusted to maintain the pH value between 7.5 and 8.5. The resulting precipitate was aged at 85 °C for 2 hours. After filtration and washing, it was dried at 100 °C for 10 hours, calcined in a muffle furnace at 400 °C for 4 hours, pressed into tablets, and sieved to obtain a composite metal oxide CuO-ZnO-Cr2O3 with a mesh size of 40–60 mesh.

[0084] The dehydrogenation reaction of 1,6-hexanediol was carried out in a fixed-bed reactor. The amount of composite metal oxide used was 1.0 mL. Before the reaction, the composite metal oxide was reduced in a reducing atmosphere of 30 mL / min at a temperature of 320 °C and a flow rate of 30 mL / min. The reducing atmosphere was a mixture of hydrogen and argon, with hydrogen accounting for 30% by volume. The reduction reaction time was 5 h. After the reaction, the temperature was lowered to the dehydrogenation reaction temperature of 270 °C, and the flow rate of H2 was switched to 120 mL / min. 1,6-hexanediol was vaporized at 250 °C at a rate of 3 mL / h under 1.0 MPa and then introduced into the reactor. After 2 h of reaction, online gas chromatography analysis of the product showed that the conversion rate of 1,6-hexanediol was 71.3%, and the selectivity of ε-caprolactone was 63.4%.

[0085] Example 2

[0086] A composite metal oxide CuO-ZnO-Cr2O3-MoO3 was prepared by co-precipitation method, with Cu:Zn:Cr:Mo ratio of 35:30:15:20 (mass ratio of feed materials). A certain amount of copper nitrate, zinc nitrate, chromium nitrate, and ammonium molybdate were weighed and prepared into a metal ion aqueous solution with a total molar concentration of 1 mol / L. Simultaneously, a 1 mol / L sodium hydroxide aqueous solution was prepared as a precipitant. A beaker containing 100 mL of deionized water was placed in a water bath at 90 °C, and stirring was started. The metal ion aqueous solution and sodium carbonate aqueous solution were added dropwise to the beaker. The pH value was monitored, and the dropping rate of the precipitant was adjusted to maintain the pH value between 8.0 and 9.0. The resulting precipitate was aged at 90 °C for 2 hours. After filtration and washing, the product was dried at 110℃ for 10 hours, calcined in a muffle furnace at 450℃ for 4 hours, pressed into tablets, and sieved to obtain a composite metal oxide CuO-ZnO-Cr2O3-MoO3 with a mesh size of 20-40 mesh.

[0087] The dehydrogenation reaction of 1,6-hexanediol was carried out in a fixed-bed reactor. The amount of composite metal oxide used was 1.0 mL. Before the reaction, the composite metal oxide was reduced in a reducing atmosphere of 300 °C and 30 mL / min using hydrogen gas for 5 h. After the reaction, the temperature was lowered to the dehydrogenation reaction temperature of 280 °C, and the flow rate of H2 was switched to 50 mL / min. 1,6-hexanediol was vaporized at 250 °C at a rate of 1 mL / h and then introduced into the reactor. After 2 h of reaction, online gas chromatography analysis of the product showed that the conversion rate of 1,6-hexanediol was 69.1%, and the selectivity of ε-caprolactone was 70.6%.

[0088] Example 3

[0089] A composite metal oxide CuO-ZnO-Co2O3 was prepared by urea precipitation, with a Cu:Zn:Co element ratio of 20:40:40 (mass ratio of the materials). A certain amount of copper nitrate, zinc nitrate, and cobalt nitrate were weighed to prepare a metal ion aqueous solution with a total molar concentration of 1 mol / L. At room temperature (20±5℃), urea was added to the metal ion aqueous solution, with a urea molar ratio to the total metal ion molar ratio of 8:1. The mixture of urea and the metal ion aqueous solution was heated from room temperature to 90℃, and the resulting precipitate was aged at 90℃ for 3 hours. After filtration and washing, it was dried at 120℃ for 10 hours, calcined at 520℃ for 3 hours, pressed into tablets, and sieved to obtain a composite metal oxide CuO-ZnO-Co2O3 with a mesh size of 20–40 mesh.

[0090] The dehydrogenation reaction of 1,6-hexanediol was carried out in a fixed-bed reactor. The amount of composite metal oxide used was 1.0 mL. Before the reaction, the composite metal oxide was reduced in a reducing atmosphere of 380 °C and 50 mL / min, which was a mixture of hydrogen and helium, with hydrogen accounting for 10% by volume. The reduction reaction time was 6 h. After the reaction, the temperature was lowered to the dehydrogenation reaction temperature of 350 °C, and the flow rate of H2 was switched to 150 mL / min. 1,6-hexanediol was vaporized at 250 °C at a rate of 2 mL / h and then introduced into the reactor at 2.0 MPa. After 2 h of reaction, online gas chromatography analysis of the product showed that the conversion rate of 1,6-hexanediol was 78.3%, and the selectivity of ε-caprolactone was 48.7%.

[0091] Example 4

[0092] A composite metal oxide CuO-ZnO-Co2O3-MoO3 was prepared by co-current co-precipitation, with a Cu:Zn:Co:Mo ratio of 40:40:5:15 (mass ratio of the materials). A certain amount of copper nitrate, zinc nitrate, cobalt nitrate, and ammonium molybdate were weighed and prepared into a metal ion aqueous solution with a total molar concentration of 1 mol / L. Simultaneously, a 1 mol / L sodium carbonate aqueous solution was prepared as a precipitant. A beaker containing 100 mL of deionized water was placed in a water bath at 60 °C with stirring. The metal ion aqueous solution and sodium carbonate aqueous solution were added dropwise to the beaker. The pH value was monitored, and the dropping rate of the precipitant was adjusted to maintain the pH value between 7.5 and 8.5. The resulting precipitate was aged at 80 °C for 2 hours. After filtration and washing, the product was dried at 100℃ for 10 hours, calcined in a muffle furnace at 400℃ for 4 hours, pressed into tablets, and sieved to obtain a composite metal oxide CuO-ZnO-Co2O3-MoO3 with a mesh size of 20-40 mesh.

[0093] The dehydrogenation reaction of 1,6-hexanediol was carried out in a fixed-bed reactor. The amount of composite metal oxide used was 1.0 mL. Before the reaction, the composite metal oxide was reduced in a reducing atmosphere of hydrogen at a temperature of 350 °C and a flow rate of 50 mL / min for 5 h. After the reaction, the temperature was lowered to the dehydrogenation reaction temperature of 300 °C, and the flow rate of H2 was switched to 100 mL / min. 1,6-hexanediol was vaporized at 250 °C at a rate of 1.5 mL / h and then introduced into the reactor. After 2 h of reaction, online gas chromatography analysis of the product showed that the conversion rate of 1,6-hexanediol was 77.1%, and the selectivity of ε-caprolactone was 65.9%.

Claims

1. A method for preparing ε-caprolactone, characterized in that, It includes the following steps: in a hydrogen atmosphere, under the action of the composite metal oxide CuO-ZnO-MxOy, 1,6-hexanediol undergoes a dehydrogenation reaction to obtain ε-caprolactone; in the composite metal oxide CuO-ZnO-MxOy, M is Cr, Co, "Cr and Mo" or "Co and Mo" elements; In the composite metal oxide, based on a total metal element mass of 100%, the mass percentage of Cu is 25%~40%, the mass percentage of Zn is 20%~45%, and the mass percentage of M is 15%~40%. When element M contains Cr or Co, x is 2 and y is 3; When the element M contains the element Mo, "x is 1 and y is 3".

2. The method for preparing ε-caprolactone according to claim 1, characterized in that, The mass percentage of Cu in the total mass of the metal elements is 35-40%. And / or, the mass percentage of the Zn element in the total mass of the metallic elements is 30% to 45%; And / or, the mass of the M element accounts for 18-40% of the total mass of the metal elements.

3. The method for preparing ε-caprolactone according to claim 2, characterized in that, The Zn element accounts for 35-42% of the total mass of the metallic elements. And / or, the mass of the M element accounts for 20-35% of the total mass of the metal elements.

4. The method for preparing ε-caprolactone according to claim 2, characterized in that, The Zn element accounts for 40% of the total mass of the metal elements.

5. The method for preparing ε-caprolactone according to claim 2, characterized in that, The M element is "Cr and Mo", and the mass ratio of Cr to Mo is 1:(0.8-2).

6. The method for preparing ε-caprolactone according to claim 2, characterized in that, The M element is "Cr and Mo", and the mass ratio of Cr to Mo is 1:(1-1.5).

7. The method for preparing ε-caprolactone according to claim 2, characterized in that, The M element is "Cr and Mo elements", and the mass ratio of Cr to Mo elements is 15:

20.

8. The method for preparing ε-caprolactone according to claim 2, characterized in that, The M element is "Co and Mo", and the mass ratio of Co to Mo is 1:(2-4).

9. The method for preparing ε-caprolactone according to claim 2, characterized in that, The M element is "Co and Mo", and the mass ratio of Co to Mo is 1:(2.5-3.5).

10. The method for preparing ε-caprolactone according to claim 2, characterized in that, The M element is "Co and Mo", and the mass ratio of Co to Mo is 1:

3.

11. The method for preparing ε-caprolactone according to claim 2, characterized in that, The composite metal oxide is CuO-ZnO-Cr2O3, and the mass ratio of Cu, Zn and Cr is (2~3):(2~3):

1.

12. The method for preparing ε-caprolactone according to claim 2, characterized in that, When the composite metal oxide is CuO-ZnO-Cr2O3, the mass ratio of Cu, Zn and Cr is 40:42:

18.

13. The method for preparing ε-caprolactone according to claim 2, characterized in that, The composite metal oxide is CuO-ZnO-Cr2O3-MoO3, and the mass ratio of Cu, Zn, Cr and Mo is (2~2.5):(1.5~2.5):1:(1~1.5).

14. The method for preparing ε-caprolactone according to claim 2, characterized in that, The composite metal oxide is CuO-ZnO-Cr2O3-MoO3, and the mass ratio of Cu, Zn, Cr and Mo is 35:30:15:

20.

15. The method for preparing ε-caprolactone according to claim 2, characterized in that, The composite metal oxide is CuO-ZnO-Co2O3-MoO3, and the mass ratio of Cu, Zn, Co and Mo is (7~9):(7~9):1:(2~4).

16. The method for preparing ε-caprolactone according to claim 2, characterized in that, The composite metal oxide is CuO-ZnO-Co2O3-MoO3, and the mass ratio of Cu, Zn, Co and Mo is 40:40:5:

15.

17. The method for preparing ε-caprolactone according to claim 1, characterized in that, The preparation method of the composite metal oxide CuO-ZnO-MxOy includes the following steps: A mixed solution containing metal ions and a precipitant are mixed and reacted, aged, and the resulting solid is calcined to obtain the composite metal oxide CuO-ZnO-MxOy. The metal ions in the mixed solution include Cu. 2+ Zn 2+ And M ions; M ions are Cr ions, Co ions, "Cr ions and Mo ions" or "Co ions and Mo ions".

18. The method for preparing ε-caprolactone according to claim 17, characterized in that, The solvent in the mixed solution containing metal ions is water and / or an alcohol solvent, wherein the alcohol solvent is ethanol and / or ethylene glycol; And / or, in the mixed solution, the total molar concentration of the metal ions is 0.5~1.5 mol / L; And / or, prior to the operation of the mixing reaction, the mixing method of the mixed solution containing metal ions and the precipitant is to add the mixed solution containing metal ions and the precipitant dropwise into the reaction vessel respectively; And / or, the Cu 2+ Provided by a Cu salt, wherein the Cu salt is one or more of copper nitrate, copper chloride, copper acetate, and copper sulfate; And / or, the Zn 2+ Provided by a Zn salt, wherein the Zn salt is one or more of zinc nitrate, zinc chloride, and zinc acetate; And / or, the Cr ions are provided by a Cr salt, which is chromium nitrate and / or chromium chloride; And / or, the Mo ions are provided by a Mo salt, wherein the Mo salt is ammonium molybdate and / or sodium molybdate; And / or, the Co ions are provided by a Co salt, wherein the Co salt is cobalt nitrate.

19. The method for preparing ε-caprolactone according to claim 18, characterized in that, In the mixed solution, the total molar concentration of the metal ions is 1 mol / L; And / or, the Cu salt is copper nitrate; And / or, the Zn salt is zinc nitrate; And / or, the Cr salt is chromium nitrate; And / or, the Mo salt is ammonium molybdate.

20. The method for preparing ε-caprolactone according to claim 17, characterized in that, The precipitant is an inorganic precipitant or urea.

21. The method for preparing ε-caprolactone according to claim 20, characterized in that, The inorganic precipitant is a hydroxide precipitant or a carbonate precipitant; the hydroxide precipitant is sodium hydroxide; the carbonate precipitant is sodium carbonate.

22. The method for preparing ε-caprolactone according to claim 20, characterized in that, The precipitant is an inorganic precipitant, and the precipitant is added in the form of a precipitant solution; the solvent in the precipitant solution is water and / or an alcohol solvent; the alcohol solvent is ethanol and / or ethylene glycol; the concentration of the precipitant in the precipitant solution is 0.5~1 mol / L; the precipitant solution is added dropwise.

23. The method for preparing ε-caprolactone according to claim 22, characterized in that, The concentration of the precipitant in the precipitant solution is 1 mol / L.

24. The method for preparing ε-caprolactone according to claim 20, characterized in that, The precipitant is an inorganic precipitant, and the mixing temperature is 50~90℃.

25. The method for preparing ε-caprolactone according to claim 20, characterized in that, The precipitant is an inorganic precipitant, and the pH of the system is 6-9 during the mixing process. The conditions and methods for adjusting the pH of the system to 6-9 are to adjust the pH of the system by controlling the amount and rate of addition of the precipitant.

26. The method for preparing ε-caprolactone according to claim 25, characterized in that, During the mixing process, the pH value of the system is 7.5~8.

5.

27. The method for preparing ε-caprolactone according to claim 25, characterized in that, During the mixing process, the pH value of the system is 8.

28. The method for preparing ε-caprolactone according to claim 20, characterized in that, The precipitant is an inorganic precipitant, the aging temperature is 50~90℃, and the aging time is 1~5h.

29. The method for preparing ε-caprolactone according to claim 28, characterized in that, The aging temperature is 80~90℃; And / or, the aging time is 2 hours.

30. The method for preparing ε-caprolactone according to claim 28, characterized in that, The aging temperature is 85°C.

31. The method for preparing ε-caprolactone according to claim 20, characterized in that, The precipitant is urea, and the ratio of the molar amount of the precipitant to the total molar amount of the metal ions is (5~10):

1.

32. The method for preparing ε-caprolactone according to claim 20, characterized in that, The precipitant is urea, and the mixing temperature is room temperature.

33. The method for preparing ε-caprolactone according to claim 32, characterized in that, The mixing temperature is 20-30℃.

34. The method for preparing ε-caprolactone according to claim 17, characterized in that, Before the roasting operation and after the aging operation, the process also includes steps of filtering, washing and drying. The filtration is performed by suction filtration; the solvent used for washing is water; the drying temperature is 100~150℃; and the drying time is 5~15 hours. And / or, the roasting is carried out in a muffle furnace; And / or, the calcination temperature is 350~550℃; And / or, the calcination time is 3~10h; And / or, the roasting operation may further include a tableting operation.

35. The method for preparing ε-caprolactone according to claim 34, characterized in that, The roasting temperature is 400-550℃; And / or, the calcination time is 4 hours.

36. The method for preparing ε-caprolactone according to claim 34, characterized in that, The roasting temperature is 450-520℃.

37. The method for preparing ε-caprolactone according to claim 34, characterized in that, The drying temperature is 110-120℃; And / or, the drying time is 10 hours.

38. The method for preparing ε-caprolactone according to claim 1, characterized in that, The flow rate of the hydrogen gas is 50~150mL / h; And / or, the flow rate of the 1,6-hexanediol is 1~3 mL / h; And / or, the liquid hourly space velocity of the 1,6-hexanediol is 1-3 h⁻¹. -1 ; And / or, the dehydrogenation reaction is carried out in a fixed-bed reactor; And / or, the 1,6-hexanediol participates in the dehydrogenation reaction in a gaseous state; And / or, the temperature of the dehydrogenation reaction is 250~350℃; And / or, the pressure of the dehydrogenation reaction is 0.1~2 MPa.

39. The method for preparing ε-caprolactone according to claim 38, characterized in that, The flow rate of the hydrogen gas is 100~120mL / h; And / or, the flow rate of the 1,6-hexanediol is 1.5~2 mL / h; And / or, the temperature of the dehydrogenation reaction is 270~300℃; And / or, the pressure of the dehydrogenation reaction is 0.1~1 MPa.

40. The method for preparing ε-caprolactone according to claim 1, characterized in that, The composite metal oxide has a mesh size of 20-80 mesh; And / or, the composite metal oxide is subjected to reduction and activation treatment before use.

41. The method for preparing ε-caprolactone according to claim 40, characterized in that, The composite metal oxide has a mesh size of 20 to 60 mesh.

42. The method for preparing ε-caprolactone according to claim 40, characterized in that, The composite metal oxide has a mesh size of 40-60 mesh.

43. The method for preparing ε-caprolactone according to claim 40, characterized in that, The reduction and activation treatment includes the following steps: under the action of a reducing atmosphere, the composite metal oxide undergoes a reduction reaction.

44. The method for preparing ε-caprolactone according to claim 43, characterized in that, The reducing atmosphere is a gas containing hydrogen; And / or, the volume percentage of hydrogen in the reducing atmosphere is 10-100%; And / or, the space velocity of the reducing atmosphere is 500~2000 h⁻¹. -1 ; And / or, the temperature of the reduction reaction is 220~380℃; And / or, the rate of heating to the temperature of the reduction reaction is 2~5℃ / min; And / or, the reduction reaction takes 5 to 10 hours; And / or, the reduction reaction is carried out at atmospheric pressure.

45. The method for preparing ε-caprolactone according to claim 44, characterized in that, The reducing atmosphere further includes one or more of nitrogen, helium and argon; And / or, the volume percentage of hydrogen in the reducing atmosphere is 30-100%; And / or, the temperature of the reduction reaction is 300~380℃; And / or, the reduction reaction takes 6 hours; And / or, the pressure of the reduction reaction is 0.1 MPa.

46. ​​The method for preparing ε-caprolactone according to claim 43, characterized in that, The reduction reaction is carried out at a temperature of 320~350℃.

47. The method for preparing ε-caprolactone according to claim 45, characterized in that, The reducing atmosphere consists of 30% hydrogen and 70% argon, with the percentages being by volume.

48. The method for preparing ε-caprolactone according to claim 45, characterized in that, The reducing atmosphere consists of 10% hydrogen and 90% helium, with the percentages being by volume.