Process for the catalytic dehydrogenation of 1,5-pentanediol to produce delta-valerolactone, catalyst and process for the preparation of the catalyst

Abstract

The present application relates to the field of cyclic lactone production, and particularly relates to a method for producing delta-valerolactone by catalytic dehydrogenation of 1,5-pentanediol, a catalyst and a preparation method of the catalyst. The catalyst is a dehydrogenation-cyclization functional catalyst, and the dehydrogenation-cyclization functional catalyst is composed of CuO / ZnO-Al2O3-La2O3. The active component is CuO, and the composite oxide carrier is ZnO-Al2O3-La2O3. The H2 pressure in the dehydrogenation conversion process is 0.05 MPa, and the temperature is 230-240 DEG C. In the present application, the composite carrier copper-based catalyst is used, and the directional catalytic conversion of 1,5-pentanediol can be realized under the condition that the H2 pressure is 0.05 MPa and the temperature is 230-240 DEG C. The method can be used in continuous gas phase fixed bed reactors and the like, and the efficient catalytic conversion of 1,5-pentanediol is realized. The catalyst has stable properties, a simple separation process and the value of industrial production.

Description

Technical Field

[0001] This invention relates to the field of cyclic lactone production, and more particularly to a method for the catalytic dehydrogenation of 1,5-pentanediol to produce δ-pentanediol, as well as a catalyst and a method for preparing the catalyst. Background Technology

[0002] δ-valerolactone is a cyclic lactone compound with a molecular weight of 100 and a boiling point of 230°C. It is a colorless or pale yellow liquid, slightly soluble in water, miscible with ethanol and ether, and is a high-boiling-point solvent. Due to its widespread presence in biologically and optically active compounds, δ-valerolactone has applications in the pharmaceutical field. It readily polymerizes and can also form polylactides with other compounds, resulting in copolymers with good biocompatibility and biodegradability. In recent years, the biodegradability of its polymers has promoted its widespread application in environmental protection and medicine, making its synthesis as a monomer increasingly important.

[0003] In recent years, many research teams have explored the possibilities of a series of new technologies for the synthesis of δ-valerolactone, as well as new catalyst technologies to improve traditional processes. For example, Chinese patent CN 109651318 describes a new method for the isomerization and addition cyclization of alkyl acetate and propylene oxide to generate δ-valerolactone using lithium phosphate / alumina as a catalyst. At 180-250℃ and ~0.5MPa, alkyl acetate and propylene oxide can be efficiently converted to δ-valerolactone, with a selectivity of approximately 95% (based on propylene oxide). However, this propylene oxide process suffers from problems such as the loss of the active component, lithium phosphate, and complex catalyst preparation, and is currently in the laboratory research stage.

[0004] CN 109956921 describes a novel method for the oxidative cracking of 1,6-hexanediol to prepare δ-valerolactone. Air and / or oxygen are used as the oxygen source, and one or more of the following catalysts are selected: CuO / MnO2, VOx / MnO2, CeOx / MnO2, CoOx / MnO2, and NiO / MnO2. Solvents include acetonitrile, dioxane, tert-butanol, tert-amyl alcohol, toluene, and p-xylene. First, the catalyst, 1,6-hexanediol, and solvent are added to a reactor. Then, the oxidant is slowly introduced at 30-150°C, 0.1-5 MPa, and for 0.5-48 hours, during which hexanediol is oxidatively cracked to δ-valerolactone. This hexanediol oxidative cracking process has drawbacks such as carbon release, low material balance, and the risk of explosion, and is currently in the laboratory research stage.

[0005] CN 111484464 and CN 111548333 report a new method for preparing δ-valerolactone by carbonylation of tetrahydrofuran. Tetrahydrofuran and carbon monoxide are used as raw materials, and small-crystal ZSM-5 or H-MOR type molecular sieves are used as catalysts. 0.5g of catalyst is loaded into a reaction tube with an inner diameter of 10mm and a length of 40cm. The reaction temperature is 90-180℃ and the selectivity for δ-valerolactone is 1-5MPa. The tetrahydrofuran conversion rate is 8-18%, and the selectivity for δ-valerolactone is 94-99%. This tetrahydrofuran carbonylation process suffers from the problem of δ-valerolactone oligomers clogging the molecular sieve pores and is currently in the laboratory stage.

[0006] Chinese patent CN 101157677 describes a method for oxidizing 1,5-pentanediol to δ-valerolactone using a supported nano-Au / TiO2 gold catalyst. In a high-pressure reactor, 10–40 ml of tributyl phosphate as solvent, 0.8 g of 1,5-pentanediol, and 0.188–1.5 g of the supported nano-gold catalyst are added. Air is introduced at 0.8–1.3 MPa, and the temperature is controlled at 80–160 °C. The reaction time is 1–24 hours, yielding a δ-valerolactone selectivity of approximately 42%. This air oxidation process for δ-valerolactone uses molecular oxygen, but the low selectivity and potential safety hazards limit its widespread application.

[0007] Chinese patent CN 103980241 reports a process for catalytic dehydrogenation of 1,5-pentanediol to produce δ-valerolactone. The catalyst consists of 15-35% copper, 0.2-2% silver, 1-5% rare earth elements, and 20-60% support. This process requires first dehydrating 1,5-pentanediol in a drying tower to a water content below 0.05%; then mixing hydrogen with the dried 1,5-pentanediol before introducing it into a vaporizer; finally, under conditions of approximately 0.1 MPa and 230-270°C, 1,5-pentanediol is dehydrogenated to δ-valerolactone. This patented technology adds a dehydration section in the drying tower, increasing equipment investment and operating costs.

[0008] CN 106674173 describes a dehydrogenation catalyst for 1,5-pentanediol and a method for producing δ-valerolactone. The catalyst is prepared by an impregnation method, with layered bimetallic hydroxide-modified alumina as the support and copper as the active component. The support is prepared through the following steps: alumina and an alkaline solution are added to a reactor and held at 70-100°C for 10-48 hours; then, a magnesium nitrate solution is added, the temperature is raised to 110-150°C, and held for 10-48 hours, followed by washing with water, drying, and calcination. Under conditions of 170-250°C, ~0.1 MPa, and a copper-based catalyst, the yield of 1,5-pentanediol to δ-valerolactone reaches approximately 98% or higher. This 1,5-pentanediol dehydrogenation technology has drawbacks, including a long catalyst preparation process and the impregnation method for preparing the copper active component, which can lead to copper sintering.

[0009] BASF's US patent 8466299 B2 reports a gas-phase catalytic dehydrogenation technology for 1,5-pentanediol. Using rare earth elements Ce, Yb, and Lu to modify a CuO / SiO2 catalyst, the conversion of 1,5-pentanediol reaches approximately 99% and the selectivity for δ-valerolactone is approximately 95% under reaction temperatures of 260-350℃ and a pressure of 0.05-1 MPa. However, this 1,5-pentanediol dehydrogenation patent suffers from problems such as high reaction temperature, the presence of copper active components, and a tendency to sinter.

[0010] Currently, the main industrial methods for producing δ-valerol are catalytic dehydrogenation of 1,5-pentanediol and the Baeyer-Villiger reaction of cyclopentanone oxidation. The Baeyer-Villiger oxidation process of cyclopentanone uses peroxide oxidants such as perbenzoic acid and anhydrous peracetic acid. Because the peroxide produces organic acids as byproducts, it requires alkaline post-treatment with sodium hydroxide and sodium carbonate, increasing production costs and environmental pollution. Furthermore, the presence of peroxides poses risks of combustion and explosion, so the Baeyer-Villiger method for producing δ-valerol is rarely used industrially. Additionally, the multi-step petrochemical conversion of cyclopentanone results in high prices and a lack of market competitiveness.

[0011] China is a major agricultural country, accounting for over 90% of the world's furfural production capacity. Industrially, furfural is produced from agricultural and forestry waste such as corn cobs and sugarcane bagasse through hydrolysis and refining.

[0012] Meanwhile, my country has achieved large-scale industrialization of furfural hydrogenation to produce furfuryl alcohol, accounting for over 95% of the world's market share. In 2023, Henan Haosen Biomaterials Co., Ltd. completed and put into operation a new 20,000-ton-capacity furfuryl alcohol hydrogenation plant to produce pentanediol, co-producing several thousand tons of biomass-based 1,5-pentanediol. The market price of 1,5-pentanediol has dropped to a reasonable low level, making the catalytic dehydrogenation of biomass-based 1,5-pentanediol to produce δ-pentanolide a significant price advantage.

[0013] The dehydrogenation of 1,5-pentanediol to δ-valerolactone involves an aldehyde condensation reaction. 1,5-pentanediol is first converted to 5-hydroxypentanal, and the hydroxyl group after condensation is dehydrogenated again to generate δ-valerolactone. The reaction pathway is as follows: Figure 1 As shown.

[0014] On December 22, 2024, a search was conducted in the China Patent Publication Database using "1,5-pentanediol and valproic acid and catalyst and dehydrogenation and copper and zinc and aluminum and lanthanum" as abstract keywords, with the option to allow synonym expansion. No relevant literature was found.

[0015] On December 22, 2024, an abstract search was conducted on CNKI (China National Knowledge Infrastructure) for the keywords "1,5-pentanediol and valproic acid and catalyst and dehydrogenation and copper and zinc and aluminum and lanthanum", but no relevant literature was found.

[0016] On December 22, 2024, a search was conducted on the website of the United States Patent and Trademark Office for the term "1,5-pentanediol with valerolactone with catalysts with dehydrogenation with copper with zinc with aluminum with lanthanum", but no relevant literature was found; the search URL is https: / / ppubs.uspto.gov / pubwebapp / .

[0017] On December 22, 2024, a search was conducted on the Korean Patent Office website for "1,5-pentanediol and valerolactone and catalysts and dehydrogenation and copper and zinc and aluminum and lanthanum", but no relevant literature was found; the search URL was engpat.kipr is.or.kr.

[0018] On December 22, 2024, a search was conducted on WIPO's website https: / / patentscope2.wipo.int / for the term "1,5-pentanediol and valerolactone and catalysts and dehydrogenation and copper and zinc and aluminum and lanthanum", but no relevant literature was found.

[0019] On December 22, 2024, a search was conducted on the website of the Japan Patent Office (https: / / www.jplatpat.inpit.go.jp / ) for the term "1,5-pentanediol and valerolactone and catalysts and dehydrogenation and copper and zinc and aluminum and lanthanum", but no relevant literature was found.

[0020] It is completely different from the concept of this patent. Summary of the Invention

[0021] Purpose of the invention: To provide a more effective method for the catalytic dehydrogenation of 1,5-pentanediol to produce δ-valerolactone, as well as a catalyst and a method for preparing the catalyst. Specific objectives are detailed in the specific embodiments section, which outlines several substantial technical effects.

[0022] To achieve the above objectives, the present invention adopts the following technical solution:

[0023] A catalyst for the dehydrogenation of 1,5-pentanediol to produce δ-valerolactone is characterized in that the catalyst is a dehydrogenation-cyclization functional catalyst, the dehydrogenation-cyclization functional catalyst is composed of CuO / ZnO-Al2O3-La2O3, the active component is CuO, the composite oxide support is ZnO-Al2O3-La2O3, the H2 pressure during the dehydrogenation conversion process is 0.05 MPa, and the temperature is 230-240℃.

[0024] A further technical solution of the present invention is that the dehydrogenation-cyclization functional catalyst has the following components in parts by weight of total catalyst: CuO content is 20-35 parts, ZnO content is 45-60 parts, Al2O3 content is 15-23 parts, and La2O3 content is 2-7 parts, all in wt parts.

[0025] A further technical solution of the present invention is that the content of each component is as follows: CuO content is 22-27%, ZnO content is 50-54%, Al2O3 content is 18-22%, and La2O3 content is 3-5%.

[0026] A method for preparing a catalyst for the dehydrogenation of 1,5-pentanediol to produce δ-valerolactone, characterized in that,

[0027] The co-precipitation method was used to prepare the metal salt solutions of each active component in the required proportions.

[0028] Prepare a precipitant: a mixed alkaline solution of sodium hydroxide / sodium carbonate in a molar ratio of 6;

[0029] Then, under controlled temperature and pH conditions, the metal salt solution and the mixed alkaline solution of sodium hydroxide / sodium carbonate were added dropwise to the precipitation vessel, stirred for 1 hour, heated to 80°C and aged for 20 hours, filtered, washed with water, dried and calcined to obtain the desired dehydrogenation catalyst.

[0030] A further technical solution of the present invention is that the specific catalyst preparation includes the following steps:

[0031] (1) Prepare a 1 mol / L solution of copper nitrate, zinc nitrate, aluminum nitrate and lanthanum nitrate, then stir to dissolve and mix evenly to obtain a uniformly mixed acidic salt solution.

[0032] (2) Prepare a mixed alkali with a sodium hydroxide / sodium carbonate molar ratio of 6:1, and use a solution of about 1 mol / L as a precipitant.

[0033] (3) Add the acid and alkali solutions prepared in (1) and (2) above into the precipitation vessel in a co-current flow to carry out co-precipitation, stirring vigorously, and controlling the precipitation temperature at 40-45℃ and the pH value at ~10. The vigorous stirring refers to: 500r / min in the laboratory; and 100r / min or more in the workshop anchor frame stirring.

[0034] (4) Continue stirring, heat to 80℃, and age for 20 hours.

[0035] (5) Filter and wash to remove residual sodium ions, pH value ~7.

[0036] (6) Dry at 110℃ for 12 hours.

[0037] (7) The catalyst was obtained by calcining at 450°C for 5 hours.

[0038] A further technical solution of the present invention is that the hydrogenation reaction is carried out in a continuous gas-phase fixed-bed reactor.

[0039] A further technical solution of the present invention is that the hydrogenation reaction is carried out in a continuous fixed-bed reactor, wherein the fixed-bed reactor is a tubular fixed-bed reactor.

[0040] A method for the catalytic dehydrogenation of 1,5-pentanediol to produce δ-valerolactone, characterized in that 1,5-pentanediol is dehydrogenated and cyclized to produce δ-valerolactone under the catalytic action of a copper-based catalyst on a composite support.

[0041] The catalyst is a dehydrogenation-cyclization functional catalyst with a composition of CuO / ZnO-Al2O3-La2O3. The active component is CuO, and the composite oxide support is ZnO-Al2O3-La2O3. The H2 pressure during the dehydrogenation conversion process is 0.05 MPa, and the temperature is 230-240℃.

[0042] A method for the catalytic dehydrogenation of 1,5-pentanediol to produce δ-valerolactone, characterized in that,

[0043] The dehydrogenation-cyclization catalyst needs to be reduced and activated before use. The activation steps are as follows: First, 1-15% hydrogen gas is introduced, and the other components are inert gases. The temperature is gradually increased from room temperature to 150°C over 10 hours and kept constant for 2 hours. Then, the temperature is slowly increased to 250°C over 10 hours and kept constant for 5 hours. This process is carried out at atmospheric pressure. Then, the gas is gradually switched to pure hydrogen gas, and the reduction is completed.

[0044] A further technical solution of the present invention is that the reaction conditions for the dehydrogenation process are as follows:

[0045] The H2 pressure is 0.05 MPa, the temperature is 230–240 °C, the liquid hourly space velocity is ~0.1 h⁻¹, and the molar ratio of hydrogen to 1,5-pentanediol is 10–20.

[0046] The present invention, employing the above technical solution, has the following advantages over existing technologies: Due to the use of a composite supported copper-based catalyst, the present invention can achieve the directional catalytic conversion of 1,5-pentanediol under H2 pressure of 0.05 MPa and temperature of 230–240 °C. This method can be used in continuous gas-phase fixed-bed reactors to achieve highly efficient catalytic conversion of 1,5-pentanediol. The catalyst is stable, the separation process is simple, and it has value for industrial production. Attached Figure Description

[0047] To further illustrate the present invention, the following description is provided in conjunction with the accompanying drawings:

[0048] Figure 1 The synthetic route for the dehydrogenation of 1,5-pentanediol to δ-pentanelactone is described. Detailed Implementation

[0049] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0050] This invention provides a method for producing δ-valerolactone, which involves selectively dehydrogenating and cyclizing 1,5-pentanediol under the catalysis of a copper-based catalyst co-precipitated on a composite support to generate δ-valerolactone.

[0051] In the above method, pure 1,5-pentanediol without added solvent is used;

[0052] The method uses a continuous gas-phase fixed-bed reactor to prepare δ-valerolactone.

[0053] The above method for preparing 1,5-pentanediol using a fixed-bed reaction is as follows: First, the copper catalyst on the composite support is reduced for 5 hours at 250°C with a hydrogen-nitrogen mixture. Then, pure 1,5-pentanediol is used to react to generate δ-pentanelactone under the conditions of reaction temperature 220-250°C, pressure ~0.05 MPa, space velocity 0.1, and hydrogen-to-alcohol molar ratio 15.

[0054] Example 1

[0055] First, a 1 mol / L solution of copper nitrate, zinc nitrate, and aluminum nitrate was prepared and stirred until homogeneous, resulting in a mixed acidic solution of metal salts. Then, a 1 mol / L solution of a mixed alkali with a sodium hydroxide / sodium carbonate molar ratio of approximately 6 was prepared as a precipitant. Under vigorous stirring, the acid and alkali solutions were added dropwise to a precipitation vessel in a co-current flow for co-precipitation, controlling the precipitation temperature at 40–45 °C and the pH at approximately 10. The mixture was then aged at 80 °C for 20 hours, filtered, washed, dried at 110 °C for 12 hours, and calcined at 450 °C for approximately 5 hours to obtain a CuO / ZnO-Al₂O₃ catalyst. The total catalyst content was: CuO 22%, ZnO 60%, and Al₂O₃ 18%. The catalyst was labeled Cat1. Reaction results are shown in Table 1.

[0056] Example 2

[0057] First, a 1 mol / L solution of copper nitrate, zinc nitrate, and aluminum nitrate was prepared and stirred until homogeneous, resulting in a mixed acidic solution of metal salts. Then, a 1 mol / L solution of a mixed alkali with a sodium hydroxide / sodium carbonate molar ratio of approximately 6 was prepared as a precipitant. Under vigorous stirring, the acid and alkali solutions were added dropwise to a precipitation vessel in a co-current flow for co-precipitation, controlling the precipitation temperature at 40–45 °C and the pH at approximately 10. The mixture was then aged at 80 °C for 20 hours, filtered, washed, dried at 110 °C for 12 hours, and calcined at 450 °C for approximately 5 hours to obtain a CuO / ZnO-Al₂O₃ catalyst. The total catalyst content was: CuO 25%, ZnO 54%, and Al₂O₃ 21%. The catalyst was labeled Cat₂. The reaction results are shown in Table 1.

[0058] Example 3

[0059] (1) First, prepare a 1 mol / L solution of copper nitrate, zinc nitrate, and aluminum nitrate, and stir to mix evenly to obtain a mixed acidic solution of metal salts. Then, prepare a mixed alkali solution with a sodium hydroxide / sodium carbonate molar ratio of approximately 6, and use approximately 1 mol / L of the solution as a precipitant. Under vigorous stirring, add the above acid and alkali solutions dropwise in parallel to the precipitation vessel for co-precipitation, controlling the precipitation temperature at 40–45℃ and the pH value at approximately 10; heat to 80℃ for aging for 20 hours, then filter, wash, dry at 110℃ for 12 hours, and calcine at 450℃ for approximately 5 hours to obtain a CuO / ZnO-Al2O3 catalyst. The total amount of catalyst is: CuO content 27%, ZnO content 50%, and Al2O3 content 23%. The catalyst is labeled Cat3. The reaction results are shown in Table 1.

[0060] Example 4

[0061] (1) First, prepare a 1 mol / L solution of copper nitrate, zinc nitrate, aluminum nitrate, and lanthanum nitrate, and stir to mix evenly to obtain a mixed acidic solution of metal salts. Then, prepare a mixed alkali solution with a sodium hydroxide / sodium carbonate molar ratio of approximately 6, and use a solution of approximately 1 mol / L as a precipitant. Under vigorous stirring, add the above acid and alkali solutions dropwise in parallel to the precipitation vessel for co-precipitation, controlling the precipitation temperature at 40–45℃ and the pH value at approximately 10; heat to 80℃ for aging for 20 hours, then filter, wash, dry at 110℃ for 12 hours, and calcine at 450℃ for approximately 5 hours to obtain CuO / ZnO-Al2O3-La2O3. The total amount of catalyst is: CuO content 25%, ZnO content 50%, Al2O3 content 22%, and La2O3 content 3%. The catalyst is labeled Cat4. The reaction results are shown in Table 1.

[0062] Example 5

[0063] (1) First, prepare a 1 mol / L solution of copper nitrate, zinc nitrate, aluminum nitrate, and lanthanum nitrate, and stir to mix evenly to obtain a mixed acidic solution of metal salts. Then, prepare a mixed alkali solution with a sodium hydroxide / sodium carbonate molar ratio of approximately 6, and use approximately 1 mol / L of the solution as a precipitant. Under vigorous stirring, add the above acid and alkali solutions dropwise in parallel to the precipitation vessel for co-precipitation, controlling the precipitation temperature at 40–45℃ and the pH value at approximately 10; heat to 80℃ for aging for 20 hours, then filter, wash, dry at 110℃ for 12 hours, and calcine at 450℃ for approximately 5 hours to obtain CuO / ZnO-Al2O3-La2O3. Based on the total amount of catalyst: CuO content is 25%, ZnO content is 52%, Al2O3 content is 17%, and La2O3 content is 6%. The catalyst is labeled Cat5. The reaction results are shown in Table 1.

[0064] Reaction conditions: 50g of catalyst was packed into a fixed-bed reactor. The reaction was first carried out at 250℃ for 5 hours under hydrogen reduction conditions; the reaction pressure was 0.05MPa, the reaction temperature was 240℃, the space velocity was 0.1, and the hydrogen / 1,5-pentanediol molar ratio was 15 under solvent-free conditions. The conversion rate of 1,5-pentanediol and the selectivity of δ-pentanelactone are shown in Table 1. Other major byproducts were n-pentanol and tetrahydropyran.

[0065] Product distribution in Example 1: n-Pentanol 2.1%, Tetrahydropyran 2.7%, δ-Velolactone 95.2%.

[0066] Product distribution in Example 4: n-Pentanol 0.8%, tetrahydropyran 1.1%, δ-valerolactone 98.1%.

[0067] Table 1. Effects of different catalysts on the dehydrogenation of 1,5-pentanediol to δ-pentanolide

[0068]

[0069] Example 6

[0070] From Table 1, the results of the dehydrogenation of 1,5-pentanediol to δ-pentanolide using different catalysts show that the catalyst in Example 4 yielded the best δ-pentanolide yield. Therefore, 50 g of the catalyst from Example 4 was reloaded into a fixed-bed reactor, and the reactor was first reduced with hydrogen at 250°C for 5 hours. Then, under solvent-free conditions with a space velocity of 0.1, a hydrogen / 1,5-pentanediol molar ratio of 15, the effect of reaction temperature on the conversion of 1,5-pentanediol and the selectivity of δ-pentanolide was investigated, as shown in Table 2.

[0071] Table 2. Effect of reaction temperature on the conversion of 1,5-pentanediol and the selectivity of δ-pentanelactone

[0072]

[0073] Table 2 shows the effect of reaction temperature on the conversion rate of 1,5-pentanediol and the selectivity of δ-pentanelactone. It is concluded that under the conditions of reaction pressure of 0.05 MPa, 1,5-pentanediol space velocity of 0.1, and hydrogen / 1,5-pentanediol molar ratio of 15, the reaction temperature range of 230-240℃ yields the highest conversion rate of 1,5-pentanediol and selectivity of δ-pentanelactone.

[0074] Based on the above data, it can be seen that a catalyst composed of 25% CuO / 50% ZnO-22% Al2O3-3% La2O3 on CuO / ZnO-Al2O3-La2O3 dehydrogenation catalyst can achieve highly selective preparation of δ-valerolactone from 1,5-pentanediol with a yield of approximately 98%.

[0075] In summary, this invention, employing a composite supported copper-based catalyst, enables the directed catalytic conversion of 1,5-pentanediol under H2 pressure of 0.05 MPa and temperature of 230–240 °C. This method can be applied to continuous gas-phase fixed-bed reactors and other similar devices to achieve highly efficient catalytic conversion of 1,5-pentanediol. The catalyst exhibits stable properties, a simple separation process, and is valuable for industrial production.

[0076] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0077] In summary, this invention relates to the catalytic dehydrogenation and cyclization of 1,5-pentanediol to δ-valerolactone via a copper-based catalyst supported on a composite support. Using 1,5-pentanediol as a raw material, it is converted to δ-valerolactone via dehydrogenation on a copper-based catalyst, with tetrahydropyran and n-pentanol as byproducts. The dehydrogenation-cyclization catalyst is composed of CuO / ZnO-Al2O3-La2O3, the hydrogenation component is CuO, and the composite oxide support is ZnO-Al2O3-La2O3. The pressure conditions for the dehydrogenation conversion process are: H2 pressure of 0.05 MPa and temperature of 230–240 °C.

[0078] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims.

Claims

1. A catalyst for the dehydrogenation of 1,5-pentanediol to produce δ-valerolactone, characterized in that, The catalyst is a dehydrogenation-cyclization functional catalyst. The composition of the dehydrogenation-cyclization functional catalyst is CuO / ZnO-Al2O3-La2O3, with CuO as the active component and ZnO-Al2O3-La2O3 as the composite oxide support. The dehydrogenation-cyclization functional catalyst has the following components in parts by weight: CuO 20-35 parts, ZnO 45-60 parts, Al2O3 15-23 parts, and La2O3 2-7 parts. All of the above are in parts by weight (wt).

2. The catalyst for the dehydrogenation of 1,5-pentanediol to δ-valerolactone as described in claim 1, characterized in that, The contents of each component are as follows: CuO content is 22-27%, ZnO content is 50-54%, Al2O3 content is 18-22%, and La2O3 content is 3-5%.

3. The method for preparing the catalyst for the dehydrogenation of 1,5-pentanediol to δ-valerolactone as described in claim 1, characterized in that, The solution was prepared by co-precipitation method, firstly by preparing copper nitrate, zinc nitrate, aluminum nitrate and lanthanum nitrate solutions in the required proportions; Prepare a precipitant: a mixed alkaline solution of sodium hydroxide / sodium carbonate in a molar ratio of 6; Then, under controlled temperature and pH conditions, the metal salt solution and the mixed alkaline solution of sodium hydroxide / sodium carbonate were added dropwise to the precipitation vessel, stirred for 1 hour, heated to 80°C and aged for 20 hours, filtered, washed with water, dried and calcined to obtain the desired dehydrogenation catalyst.

4. The method for preparing a catalyst for the dehydrogenation of 1,5-pentanediol to δ-valerolactone as described in claim 3, characterized in that, The specific catalyst preparation includes the following steps: (1) Prepare a 1 mol / L solution of copper nitrate, zinc nitrate, aluminum nitrate and lanthanum nitrate, then stir to dissolve and mix evenly to obtain a uniformly mixed acidic salt solution; (2) Prepare a mixed alkali with a sodium hydroxide / sodium carbonate molar ratio of 6:1, and use a 1 mol / L solution as a precipitant; (3) Add the acid and alkali solutions prepared in (1) and (2) above into the precipitation vessel in a co-current flow for co-precipitation, stir vigorously, and control the precipitation temperature at 40~45℃ and the pH value at ~10; (4) Continue stirring, heat to 80℃, and age for 20 hours; (5) Filter and wash to remove residual sodium ions, pH value ~7; (6) Dry at 110℃ for 12 hours; (7) The catalyst was obtained by calcining at 450°C for 5 hours. 5.

1. A method for the catalytic dehydrogenation of 5-pentanediol to produce δ-valerolactone, characterized in that, Under the catalytic action of the catalyst described in claim 1, 1,5-pentanediol is dehydrogenated and cyclized to produce δ-valerolactone. The dehydrogenation conversion process is carried out at an H2 pressure of 0.05 MPa and a temperature of 230–240 °C.

6. The method for producing δ-valerol by catalytic dehydrogenation of 1,5-pentanediol as described in claim 5, characterized in that, The hydrogenation reaction is carried out in a continuous gas-phase fixed-bed reactor.

7. The method for producing δ-valerate by catalytic dehydrogenation of 1,5-pentanediol as described in claim 6, characterized in that, The hydrogenation reaction is carried out in a continuous fixed-bed reactor, which is a tubular fixed-bed reactor.

8. The method for producing δ-valerolactone by catalytic dehydrogenation of 1,5-pentanediol as described in claim 5, characterized in that, Before use, the dehydrogenation-cyclization catalyst needs to be reduced and activated. The reduction and activation steps are as follows: First, 1~15% hydrogen gas is introduced, and the other components are inert gases. The temperature is gradually increased from room temperature to 150°C over 10 hours and kept constant for 2 hours. Then, the temperature is slowly increased to 250°C over 10 hours and kept constant for 5 hours. This process is carried out at atmospheric pressure. Then, the gas is gradually switched to pure hydrogen gas, and the reduction is completed.

9. The method for producing δ-valerate by catalytic dehydrogenation of 1,5-pentanediol as described in claim 8, characterized in that, The dehydrogenation reaction conditions were: H2 pressure of 0.05 MPa, temperature of 230~240℃, liquid hourly space velocity of ~0.1 h⁻¹, and molar ratio of hydrogen to 1,5-pentanediol of 10-20.

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