A method for preparing lactone by liquid phase dehydrogenation of diol

Abstract

This invention discloses a method for preparing lactones by liquid-phase dehydrogenation of diols, belonging to the field of lactone preparation technology. The invention involves a diol-containing solution undergoing a dehydrogenation reaction under the catalysis of a solid catalyst to obtain lactones. The catalyst comprises a support, an auxiliary agent, and an active component; the active component and the auxiliary agent are supported on the support; the active component is Cu, and the auxiliary agent is at least one selected from Fe, Co, Ni, Mn, Cr, V, Zr, Nb, Mo, W, Re, Zn, Ag, Cd, Ce, La, Pr, In, Sn, and Se. Compared to the cyclohexanone oxidation method, this method offers higher selectivity and easier reaction control. Compared to solvent-free or high-temperature gas-phase dehydrogenation, it yields higher results and is less prone to carbon deposition during the reaction, demonstrating excellent application prospects.

Description

Technical Field

[0001] This invention belongs to the field of lactone preparation technology, and more specifically, relates to a method for preparing lactone by liquid-phase dehydrogenation of diol. Background Technology

[0002] Lactones are aliphatic lactones with significant application value. Plastics obtained through ring-opening polymerization or reacted with other monomers generally possess biodegradability and biocompatibility, and their demand is increasing year by year. For example, ε-caprolactone is a precursor to polycaprolactone biodegradable materials. Hunan Juren Company has already built a 50,000-ton capacity reactor for the reaction of cyclohexanone with peroxypropionic acid to produce caprolactone. This process involves the use of large amounts of peroxides, which have poor safety. Enzymatic catalysis exhibits relatively low reaction efficiency, and homogeneous catalysis currently has low selectivity. Caprolactone can also be produced by oxidizing 1,6-hexanediol using inorganic compounds (such as BaMnO4), molecular oxygen, or hydrogen peroxide as oxidants, but the selectivity is relatively low. Hexanediol dehydrogenation can also produce caprolactone; this route is relatively green, often employing high-temperature gas-phase dehydrogenation, but the yield is currently low. Although the gas-phase high-temperature dehydrogenation reaction of 1,4-butanediol has been industrialized, it cannot be directly extended to the dehydrogenation reactions of pentanediol and hexanediol to prepare lactones (Progress in Chemistry, 2023, 35, 1191-1198). Therefore, there is an urgent need to research and develop a method for one-step liquid-phase dehydrogenation of diols to prepare lactones. Summary of the Invention

[0003] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a method for preparing lactones by one-step liquid-phase dehydrogenation of diols. The method of this invention only requires one-step dehydrogenation reaction to prepare ε-caprolactone, δ-caprolactone, γ-caprolactone, δ-caprolactone, and 1,3-dimethylbutyrolactone from 1,6-hexanediol, 1,5-pentanediol, 1,4-pentanediol, 1,5-hexanediol, and 2,5-hexanediol.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] This invention provides a method for one-step liquid-phase dehydrogenation of diols to prepare lactones. A solution containing a diol undergoes a dehydrogenation reaction under the catalysis of a solid catalyst to obtain lactones. The catalyst includes a support, an auxiliary agent, and an active component. The active component and the auxiliary agent are loaded on the support. The active component is Cu, and the auxiliary agent is at least one selected from Fe, Co, Ni, Mn, Cr, V, Zr, Nb, Mo, W, Re, Zn, Ag, Cd, Ce, La, Pr, In, Sn, and Se.

[0006] Based on the above technical solution, the diol further includes 1,6-hexanediol, 1,5-pentanediol, 1,4-pentanediol, 1,5-hexanediol, and 2,5-hexanediol.

[0007] Based on the above technical solution, the carrier is further defined as one of molecular sieve and oxide, wherein the molecular sieve is one of ZSM5, MCM-41, and SBA-15, and the oxide is at least one of silicon oxide, aluminum oxide, and magnesium oxide.

[0008] Based on the above technical solution, further, the active component accounts for 1 to 50 wt% of the total mass of the catalyst, preferably 5 to 30 wt%, and the auxiliary agent accounts for 1 to 50 wt% of the total mass of the catalyst, preferably 5 to 30 wt%.

[0009] Based on the above technical solution, the catalyst preparation method further includes co-precipitation, excess impregnation, and equal volume impregnation.

[0010] Based on the above technical solution, the steps for preparing the catalyst by co-precipitation method are as follows: dissolve the soluble salt of the active component and the soluble salt of the auxiliary agent in water, add an aqueous solution containing urea, maintain at 100-130℃ for 20-30h, collect the precipitate by centrifugation, wash with water until neutral, dry, calcine at 450-550℃ for 2-10h, then reduce at 250-350℃ for 2-5h in a mixed atmosphere of H2 and N2 with a volume ratio of 1:9-3:7, and passivate in a mixed atmosphere of O2 and N2 with a volume ratio of 1:99-10:90 for 5-10h to obtain the catalyst.

[0011] Based on the above technical solution, the reaction temperature of the dehydrogenation reaction is further 120-220℃, preferably 160-200℃.

[0012] Based on the above technical solution, the reaction pressure of the dehydrogenation reaction is further 1-6 MPa, preferably 3-4 MPa.

[0013] Based on the above technical solution, the reaction atmosphere of the dehydrogenation reaction is at least one of nitrogen, argon, helium, and hydrogen.

[0014] Based on the above technical solution, the concentration of the solution containing diol is further 10-500 mg / mL.

[0015] Based on the above technical solution, the solvent of the solution is further selected from at least one of methanol, ethanol, 1-propanol, isopropanol, n-butanol, 2-butanol, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, tetrahydropyran, 1,4-dioxane, 2,5-dimethyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, acetone, methyl isobutyl ketone, acetonitrile, toluene, xylene, N,N-dimethylamide, N-methylpyrrolidone, dimethyl sulfoxide, and ethyl acetate.

[0016] Based on the above technical solution, the solvent of the solution is further composed of a mixture of ethanol and tetrahydrofuran in a volume ratio of 1:1.

[0017] Based on the above technical solution, the reactor for the dehydrogenation reaction is a high-pressure reactor or a fixed-bed reactor.

[0018] The advantages of this invention over the prior art are as follows:

[0019] 1. The one-step dehydrogenation reaction of this invention has a short reaction path, strong reaction controllability, and high selectivity, which can effectively solve the shortcomings of oxidation reaction which is difficult to control, has low selectivity, and produces many products. Compared with solventless or high-temperature gas phase dehydrogenation, the yield is high and carbon deposits are not easily generated during the reaction.

[0020] 2. Under the condition of complete conversion of reactants, the reaction product of this invention is singular and can be separated from the solvent by distillation.

[0021] 3. The reaction process of this invention is relatively safe and can co-produce hydrogen gas;

[0022] 4. The copper catalyst used in this invention is low in cost, simple to prepare, and has significant prospects for industrial application;

[0023] 5. The reaction raw material 1,6-hexanediol used in this invention can be prepared by catalytic conversion of the biomass derivative 5-hydroxymethylfurfural. Detailed Implementation

[0024] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0025] Analytical methods: An Agilent 7890B high-performance gas chromatograph was used to analyze the products of the alcohol dehydrogenation reaction in liquid chromatography. Quantification was performed using the internal standard method, with dodecane as the internal standard. Test conditions in the examples: DB-2 column, flame ionization detector (FID), hydrogen as carrier gas, constant flow mode, split ratio 100:1, column oven temperature 80℃ (2 min), increased to 250℃ at 30℃ / min (held for 2 min).

[0026] Diol conversion rate = (1 - (amount of diol after reaction / amount of diol before reaction)) × 100%

[0027] Lactone selectivity = (Amount of lactone / (Amount of diol before reaction - Amount of diol after reaction)) × 100%

[0028] Example 1

[0029] CuZnAl catalyst synthesis: Co-precipitation method for synthesizing copper-zinc-aluminum catalyst (copper-zinc molar ratio = 1:1). First, accurately weigh 0.015 mol zinc nitrate hexahydrate, 0.015 mol copper nitrate trihydrate, and 0.01 mol aluminum nitrate nonahydrate and dissolve them in a three-necked flask containing 50 ml of deionized water. Stir thoroughly until completely dissolved. Dissolve 0.05 mol urea in 25 ml of deionized water. Transfer the three-necked flask to an oil bath and heat to 70°C. Slowly add the dissolved urea solution to the three-necked flask, using a condenser for reflux during heating. Continue heating in the oil bath to 110°C and maintain for 2 hours. After heating for 4 hours, the three-necked flask was cooled to room temperature. The solution containing the precipitate was transferred to a centrifuge tube and centrifuged at 8000 rpm to separate the precipitate. The precipitate was washed repeatedly with deionized water until neutral. The washed precipitate was dried in a 70°C oven. The dried precipitate was ground into powder and placed in a muffle furnace and calcined at 500°C for 5 hours at a rate of 3°C / min. The calcined catalyst was placed in a tube furnace and a mixture of H2 / N2 (volume ratio 1:9) was introduced. The temperature was increased to 300°C at a rate of 3°C / min for 3 hours for reduction. After reduction, the temperature was lowered to room temperature and a mixture of oxygen / nitrogen containing 2% O2 was introduced for passivation treatment for 8 hours to obtain the CuZnAl catalyst.

[0030] 100 mg of CuZnAl catalyst, 200 mg of 1,6-hexanediol, and 10 mL of ethanol were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings of air with hydrogen, hydrogen was introduced until the reaction pressure reached 3 MPa. The reaction temperature was set to 160 °C, the rotation speed to 600 rpm, and the holding time to 3 h. The reactor was then started. After the reaction was complete, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated reaction conversion rate was 100%, and the selectivity for ε-caprolactone was 0.

[0031] Example 2

[0032] 100 mg of CuZnAl catalyst, 200 mg of 1,6-hexanediol, and 10 mL of ethylene glycol dimethyl ether were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings of air with hydrogen, hydrogen was introduced until the reaction pressure reached 3 MPa. The reaction temperature was set to 160 °C, the rotation speed to 600 rpm, and the holding time to 3 h. The reactor was then started. After the reaction was completed, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated reaction conversion rate was 23%, and the selectivity for ε-caprolactone was 3%.

[0033] Example 3

[0034] 100 mg of CuZnAl catalyst, 200 mg of 1,6-hexanediol, and 10 mL of solvent (ethanol and N,N-dimethylamide in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings of air with hydrogen, hydrogen was introduced to reach a reaction pressure of 3 MPa. The reaction temperature was set to 160 °C, the rotation speed to 600 rpm, and the holding time to 3 h. The reactor was then started. After the reaction was completed, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated reaction conversion rate was 100%, and the selectivity for ε-caprolactone was 0%.

[0035] Example 4

[0036] 100 mg of CuZnAl catalyst, 200 mg of 1,6-hexanediol, and 10 mL of solvent (ethanol and tetrahydrofuran in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings of air with hydrogen, hydrogen was introduced to reach a reaction pressure of 3 MPa. The reaction temperature was set to 160 °C, the rotation speed to 600 rpm, and the holding time to 3 h. The reactor was then started. After the reaction was completed, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated conversion rate was 42%, and the selectivity for ε-caprolactone was 15%.

[0037] Example 5

[0038] 100 mg of CuZnAl catalyst, 200 mg of 1,6-hexanediol, and 10 mL of solvent (ethanol and tetrahydrofuran in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings of air with hydrogen, hydrogen was introduced to reach a reaction pressure of 3 MPa. The reaction temperature was set to 200 °C, the rotation speed to 600 rpm, and the holding time to 3 h. The reactor was then started. After the reaction was complete, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated conversion rate was 97%, and the selectivity for ε-caprolactone was 43%.

[0039] Example 6

[0040] 100 mg of CuZnAl catalyst, 200 mg of 1,6-hexanediol, and 10 mL of solvent (ethanol and tetrahydrofuran in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings of air with hydrogen, hydrogen was introduced to reach a reaction pressure of 5 MPa. The reaction temperature was set to 200 °C, the rotation speed to 600 rpm, and the holding time to 3 h. The reactor was then started. After the reaction was completed, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated reaction conversion rate was 100%, and the selectivity for ε-caprolactone was 11%.

[0041] Example 7

[0042] 100 mg of CuZnAl catalyst, 200 mg of 1,6-hexanediol, and 10 mL of solvent (ethanol and tetrahydrofuran in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings with nitrogen, hydrogen was introduced to reach a reaction pressure of 5 MPa. The reaction temperature was set at 160 °C, the rotation speed at 600 rpm, and the holding time at 3 h. The reactor was then started. After the reaction was completed and the reactor cooled to room temperature, the gas inside was released, and the supernatant was analyzed by gas chromatography. The calculated conversion rate was 7%, and the selectivity for ε-caprolactone was 78%.

[0043] Example 8

[0044] 100 mg of CuZnAl catalyst, 500 mg of 1,6-hexanediol, and 10 mL of solvent (ethanol and tetrahydrofuran in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings with nitrogen, hydrogen was introduced to reach a reaction pressure of 5 MPa. The reaction temperature was set at 160 °C, the rotation speed at 600 rpm, and the holding time at 3 h. The reactor was then started. After the reaction was completed, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated reaction conversion rate was 2%, and the selectivity for ε-caprolactone was 65%.

[0045] Example 9

[0046] 100 mg of CuZnAl catalyst, 200 mg of 1,5-pentanediol, and 10 mL of solvent (ethanol and tetrahydrofuran in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings with nitrogen, hydrogen was introduced to reach a reaction pressure of 5 MPa. The reaction temperature was set at 160 °C, the rotation speed at 600 rpm, and the holding time at 3 h. The reactor was then started. After the reaction was completed, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated conversion rate was 46%, and the selectivity for δ-pentanolide was 66%.

[0047] Example 10

[0048] 100 mg of CuZnAl catalyst, 200 mg of 1,4-pentanediol, and 10 mL of solvent (ethanol and tetrahydrofuran in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings with nitrogen, hydrogen was introduced to reach a reaction pressure of 5 MPa. The reaction temperature was set at 160 °C, the rotation speed at 600 rpm, and the holding time at 3 h. The reactor was then started. After the reaction was completed, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated conversion rate was 53%, and the selectivity for γ-pentanolide was 86%.

[0049] Example 11

[0050] 100 mg of CuZnAl catalyst, 200 mg of 2,5-hexanediol, and 10 mL of solvent (ethanol and tetrahydrofuran in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings with nitrogen, hydrogen was introduced to reach a reaction pressure of 5 MPa. The reaction temperature was set to 160 °C, the rotation speed to 600 rpm, and the holding time to 3 h. The reactor was then started. After the reaction, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated conversion rate was 21%, and the selectivity for 1,3-dimethylbutyrolactone was 55%.

[0051] Example 12

[0052] CuCoAl catalyst synthesis: Copper-cobalt-aluminum catalyst was synthesized by co-precipitation method (copper-cobalt molar ratio = 1:1). First, 0.015 mol of cobalt nitrate hexahydrate, 0.015 mol of copper nitrate trihydrate, and 0.01 mol of aluminum nitrate nonahydrate were accurately weighed and dissolved in a three-necked flask containing 50 ml of deionized water. The solution was stirred thoroughly until completely dissolved. 0.05 mol of urea was dissolved in 25 ml of deionized water. The three-necked flask was transferred to an oil bath and heated to 70°C. The dissolved urea solution was then slowly added to the three-necked flask. Reflux was performed using a condenser during the heating process. The oil bath was then heated to 110°C and maintained for 2 hours. After heating for 4 hours, the three-necked flask was cooled to room temperature. The solution containing the precipitate was transferred to a centrifuge tube and centrifuged at 8000 rpm to separate the precipitate. The precipitate was washed repeatedly with deionized water until neutral. The washed precipitate was dried in a 70°C oven. The dried precipitate was ground into powder and placed in a muffle furnace and calcined at 500°C for 5 hours at a rate of 3°C / min. The calcined catalyst was placed in a tube furnace and a mixture of H2 / N2 (volume ratio 1:9) was introduced. The temperature was increased to 300°C at a rate of 3°C / min for 3 hours for reduction. After reduction, the temperature was lowered to room temperature and a mixture of oxygen / nitrogen containing 2% O2 was introduced for passivation treatment for 8 hours to obtain the CuZnAl catalyst.

[0053] 100 mg of CuCoAl catalyst, 200 mg of 1,6-hexanediol, and 10 mL of solvent (ethanol and tetrahydrofuran in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings with nitrogen, hydrogen was introduced to reach a reaction pressure of 3 MPa. The reaction temperature was set to 200 °C, the rotation speed to 600 rpm, and the holding time to 3 h. The reactor was then started. After the reaction was complete, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated conversion rate was 93%, and the selectivity for ε-caprolactone was 48%.

[0054] Example 13

[0055] 100 mg of CuCoAl catalyst, 200 mg of 1,5-pentanediol, and 10 mL of solvent (ethanol and tetrahydrofuran in a 1:1 volume ratio) were added to a 25 mL polytetrafluoroethylene (PTFE) liner. 20 mg of dodecane was used as an internal standard. The liner was transferred to a high-pressure reactor. After three purgings with nitrogen, hydrogen was introduced to reach a reaction pressure of 3 MPa. The reaction temperature was set to 200 °C, the rotation speed to 600 rpm, and the holding time to 3 h. The reactor was then started. After the reaction, the reactor was allowed to cool to room temperature, and the gas inside was released. The supernatant was collected and analyzed by gas chromatography. The calculated conversion rate was 99%, and the selectivity for δ-pentanolide was 95%.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for one-step liquid-phase dehydrogenation of diols to prepare lactones, characterized in that, A solution containing a diol undergoes a dehydrogenation reaction under the catalysis of a solid catalyst to yield a lactone. The catalyst consists of a support, an auxiliary agent, and an active component, wherein the active component and the auxiliary agent are supported on the support; the active component is Cu, and the auxiliary agent is Co or Zn. The dehydrogenation reaction temperature is 160-220℃, the dehydrogenation reaction pressure is 1-6 MPa, and the dehydrogenation reaction atmosphere is at least one of nitrogen, argon, helium, and hydrogen. The support is at least one of silicon dioxide, aluminum oxide, and magnesium oxide; the active component accounts for 1-50 wt% of the total mass of the catalyst, and the promoter accounts for 1-50 wt% of the total mass of the catalyst. The catalyst is prepared by coprecipitation, and the steps are as follows: Soluble salts of the active component and soluble salts of the auxiliaries are dissolved in water, an aqueous solution containing urea is added, and the mixture is kept at 100-130℃ for 20-30 hours. The precipitate is collected by centrifugation, washed with water until neutral, dried, calcined at 450-550℃ for 2-10 hours, reduced at 250-350℃ for 2-5 hours in a mixed atmosphere of H2 and N2 with a volume ratio of 1:9-3:7, and passivated in a mixed atmosphere of O2 and N2 with a volume ratio of 1:99-10:90 for 5-10 hours to obtain the catalyst. The diol is 1,6-hexanediol, 1,5-pentanediol, 1,4-pentanediol, 1,5-hexanediol, or 2,5-hexanediol. The concentration of the solution containing the diol is 20 mg / mL; The solvent of the solution is a mixture of ethanol and tetrahydrofuran in a volume ratio of 1:

1.

2. The method according to claim 1, characterized in that, The active component accounts for 5-30 wt% of the total mass of the catalyst, and the promoter accounts for 5-30 wt% of the total mass of the catalyst.

3. The method according to claim 1, characterized in that, The reactor for the dehydrogenation reaction is a high-pressure reactor or a fixed-bed reactor.