A method for synthesizing 2-pentylcyclopentenone and a catalyst used

Abstract

This invention discloses a method for synthesizing 2-pentylcyclopentenone and the catalyst used. The method uses 2-pentylcyclopentenone and hydrogen as raw materials, and performs a hydroisomerization reaction in the presence of a catalyst to obtain 2-pentylcyclopentenone. The catalyst is a supported catalyst and includes a support, an active metal, a rare earth metal oxide, and a modifier. The active metal and rare earth metal oxide are supported on the support. The support includes zinc aluminate with a spinel structure. The modifier contains phosphorus and / or nitrogen. This synthesis method achieves high conversion of 2-pentylcyclopentenone, high selectivity and high purity of the target product 2-pentylcyclopentenone, and the process is relatively simple, suitable for industrial production. The catalyst exhibits high catalytic activity and high stability.

Description

Technical Field

[0001] This invention relates to a method for synthesizing 2-pentylcyclopentenone and the catalyst used therein. Background Technology

[0002] Methyl dihydrojasmonate has an elegant floral scent and is often used in the formulation of jasmine, lily of the valley, tuberose, and oriental fragrances, giving them a delicate and realistic natural floral aroma. The industrial synthesis of methyl dihydrojasmonate primarily uses pentanal and cyclopentanone as starting materials, proceeding through aldol condensation, isomerization, Michael addition, and hydrolytic decarboxylation. The key step is the isomerization of 2-pentylcyclopentanone to 2-pentylcyclopentenone.

[0003] In the process of isomerizing 2-pentylcyclopentanone to 2-pentylcyclopentenone, iodine, hydroiodic acid, and hydrobromic acid are usually used as catalysts. However, this step involves many side reactions, and the post-processing generates a lot of waste.

[0004] Chinese patent 202510740234.8 uses a solid acid catalyst for continuous isomerization of 2-pentylcyclopentanone. Although the yield of the target product is relatively high, the small difference in boiling points between 2-pentylcyclopentanone and 2-pentylcyclopentenone makes subsequent separation difficult, making it hard to obtain a target product with high purity. Chinese patent 202511093102.7 uses a supported catalyst for two-stage continuous hydroisomerization, achieving a final yield of approximately 95%. However, the two-stage hydroisomerization process, with significant differences in temperature and hydrogen content between the two stages, makes industrial implementation of this process challenging.

[0005] The challenge lies in achieving high conversion rates, high selectivity, and high purity of the target product using a relatively simple process. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, this invention provides an improved method for synthesizing 2-pentylcyclopentenone. This method achieves high conversion rates of 2-pentylcyclopentenone and high selectivity for the target product 2-pentylcyclopentenone, and the process is relatively simple and suitable for industrial production.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for synthesizing 2-pentylcyclopentenone involves using 2-pentylcyclopentanone and hydrogen as raw materials, and carrying out a hydroisomerization reaction in the presence of a catalyst to obtain the 2-pentylcyclopentenone. The catalyst is a supported catalyst and includes a support, an active metal, a rare earth metal oxide, and a modifier. The active metal and rare earth metal oxide are supported on the support. The support comprises zinc aluminate with a spinel structure. The modifier contains phosphorus and / or nitrogen.

[0008] In this invention, the modifier may be a compound containing phosphorus and / or nitrogen, or a mixture of compounds containing phosphorus and / or nitrogen.

[0009] In some embodiments, the support is zinc aluminate with a spinel structure. The support may be only zinc aluminate with a spinel structure.

[0010] In some embodiments, the support further includes other supports selected from one or more combinations of alumina, silicon dioxide, titanium dioxide, zirconium dioxide, cerium dioxide, molecular sieves, carbon, and zinc oxide. The support may also be a mixture of spinel-structured zinc aluminate and other supports.

[0011] In some embodiments, the molecular sieve is selected from one or more combinations of ZSM-5 molecular sieve, Y-type molecular sieve, Beta-type molecular sieve, SBA-15 molecular sieve, and MCM-41 molecular sieve.

[0012] In some embodiments, when the carrier further includes other carriers, the zinc aluminate accounts for 20%-50% of the mass of the carrier; preferably 30%-40%. For example, the zinc aluminate may account for 20%, 25%, 30%, 35%, 40%, 45%, and 50% of the mass of the carrier, etc.

[0013] In some embodiments, the carrier is zinc aluminate with a spinel structure; the zinc aluminate is prepared by a method comprising the following steps: a water-soluble aluminum salt, a water-soluble zinc salt, and an alkali are subjected to a precipitation reaction in water, followed by solid-liquid separation to obtain a precipitate solid; the precipitate solid is calcined at 450-750°C to obtain the spinel-structured zinc aluminate. When the calcination temperature is too low, spinel-structured zinc aluminate cannot be formed.

[0014] In some embodiments, the water-soluble aluminum salt is selected from one or more combinations of aluminum nitrate, aluminum nitrate nonahydrate, aluminum sulfate, aluminum acetate, and aluminum acetylacetonate.

[0015] In some embodiments, the water-soluble zinc salt is selected from one or more combinations of zinc nitrate, zinc nitrate hexahydrate, zinc sulfate, zinc acetate, and zinc acetylacetonate.

[0016] In some embodiments, the alkali is selected from one or more combinations of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonia, ammonium bicarbonate, and ammonium carbonate.

[0017] In some embodiments, the solid-liquid separation is selected from filtration and centrifugation.

[0018] In some embodiments, the roasting time is 2-10 hours.

[0019] In some embodiments, the calcination is carried out in an air atmosphere.

[0020] In some embodiments, the carrier may further include other carriers, such as alumina.

[0021] In some embodiments, the support further includes other supports, namely alumina; the support is prepared by a method comprising the following steps: reacting an alumina precursor or alumina, a water-soluble zinc salt, and an alkali in water to form a precipitation reaction, followed by solid-liquid separation to obtain a precipitate solid; calcining the precipitate solid at 450-750 °C to obtain the support. When the calcination temperature is too low, spinel-structured zinc aluminate cannot be formed. The alumina precursor serves as an aluminum source for zinc aluminate, reacting with a water-soluble zinc salt to form a precipitation reaction, which, after calcination, ultimately yields zinc aluminate; conversely, the alumina precursor, after calcination, yields alumina, which serves as part of the support. This method obtains a support containing zinc aluminate through precipitation.

[0022] In some embodiments, the support further includes other supports, such as alumina; the support is prepared by a method comprising the following steps: dissolving a water-soluble zinc salt in water to obtain an impregnation solution; impregnating an alumina precursor or alumina in the impregnation solution, and then calcining at 450-750 °C to obtain the support. This method obtains a support containing zinc aluminate through impregnation.

[0023] In some embodiments, the impregnation is performed under vacuum. The pore structure of the carrier is typically filled with air; in a vacuum environment, the air is extracted, allowing the impregnation liquid to enter these narrow pores more smoothly, thereby improving the loading and uniform distribution of the active component within the pores.

[0024] In some embodiments, the support further includes other supports, namely alumina; the support is prepared by a method comprising the following steps: ball milling a water-soluble zinc salt and an alumina precursor or alumina to obtain a mixture; calcining the mixture at 450-750°C to obtain the support. This method obtains a support containing zinc aluminate by ball milling. During ball milling, the zinc salt and the alumina precursor are thoroughly mixed; during calcination, the zinc salt decomposes into zinc oxide, and the alumina precursor reacts into alumina. At this calcination temperature, zinc oxide and alumina react to form a zinc aluminate support.

[0025] In some embodiments, the temperature of the ball mill is 40-80°C.

[0026] In some embodiments, the ball milling time is 1-6 hours.

[0027] In some embodiments, the alumina precursor is one or more of boehmite, soluble aluminum salt, aluminum sol, and aluminum hydroxide.

[0028] In some embodiments, the water-soluble zinc salt is selected from one or more combinations of zinc nitrate, zinc nitrate hexahydrate, zinc sulfate, zinc acetate, and zinc acetylacetonate.

[0029] In some embodiments, the alkali is selected from one or more combinations of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonia, ammonium bicarbonate, and ammonium carbonate.

[0030] In some embodiments, the solid-liquid separation is selected from filtration and centrifugation.

[0031] In some embodiments, the roasting time is 2-10 hours.

[0032] In some embodiments, the calcination is carried out in an air atmosphere.

[0033] In some embodiments, the carrier further includes other carriers selected from one or more combinations of silicon dioxide, titanium dioxide, zirconium dioxide, cerium dioxide, molecular sieves, carbon, and zinc oxide.

[0034] In some embodiments, the support further includes other supports selected from one or more combinations of silicon dioxide, titanium dioxide, zirconium dioxide, cerium dioxide, molecular sieves, carbon, and zinc oxide. The support is prepared by a method comprising the following steps: in the presence of the other supports, a water-soluble aluminum salt, a water-soluble zinc salt, and an alkali are subjected to a precipitation reaction in water, followed by solid-liquid separation to obtain a precipitate solid; the precipitate solid is then calcined at 450-750°C to obtain the support. That is, the zinc aluminate portion of the support is prepared by precipitation in the presence of other supports, while controlling the calcination temperature. The types of water-soluble aluminum salt, water-soluble zinc salt, and alkali, as well as the solid-liquid separation method, can all be described using the same method as described above for the preparation of pure zinc aluminate.

[0035] In some embodiments, the rare earth metal oxide is selected from one or more combinations of cerium dioxide, zirconium dioxide, lanthanum oxide, and yttrium oxide.

[0036] In some embodiments, the active metal is selected from one or more combinations of Pd, Pt, Ru, Rh, and Ni.

[0037] In some embodiments, during the preparation of the catalyst, the rare earth metal oxide is first loaded onto the support, followed by the loading of the active metal and the modifier. That is, the rare earth metal oxide first modifies the support, forming sites on the support that can subsequently anchor the active metal.

[0038] For loading rare earth metal oxides, conventional precipitation or impregnation methods can be used. In the precipitation method, water-soluble salts of the corresponding rare earth metal elements are precipitated in an alkaline aqueous solution in the presence of a support to generate hydroxides. These hydroxides are then calcined at a certain temperature to dehydrate the hydroxides into rare earth metal oxides, which can then be loaded onto the corresponding support. In the impregnation method, the support is impregnated with an impregnation solution containing water-soluble salts of the corresponding rare earth metal elements, and then calcined at a certain temperature to generate oxides from the salts, thus loading the corresponding rare earth metal oxides onto the support.

[0039] For loading active metals and modifiers, an impregnation method can be used, in which a carrier already loaded with rare earth metal oxides is impregnated with a mixture of the active metal precursor, modifier, and solvent, followed by calcination. In this mixture, the active metal precursor and modifier typically form a complex.

[0040] In some embodiments, the modifier is selected from one or more combinations of triphenylphosphine, tributylphosphine, trioctylphosphine, trihexylphosphine, pyridine, pyrimidine, quinoline, pyrrole, and ethylenediaminetetraacetic acid. Triphenylphosphine, tributylphosphine, trioctylphosphine, and trihexylphosphine all contain phosphorus and are phosphorus ligand compounds, while pyridine, pyrimidine, quinoline, pyrrole, and ethylenediaminetetraacetic acid all contain nitrogen and are nitrogen ligand compounds. When phosphorus ligand compounds are used, the corresponding catalytic effect, such as conversion rate, is better than that of nitrogen ligand compounds, possibly because nitrogen-containing ligands have a stronger adsorption effect on Pd and a more pronounced steric effect.

[0041] In some embodiments, the molar ratio of the modifier and the active metal element in the active metal precursor is 2 to 30:1.

[0042] In some embodiments, the catalyst contains, by weight percentage, 0.05%-20% of an active metal, 0.01%-10% of a rare earth metal oxide, 0.01%-5% of a modifier, and 65%-99.3% of a support. The active metal may be, for example, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 5%, 8%, 10%, 12%, 15%, 18%, and 20%; the rare earth metal oxide may be, for example, 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 1%, 3%, 5%, 8%, and 10%; the modifier may be, for example, 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 1%, 3%, and 5%; and the support may be, for example, 65%, 70%, 75%, 80%, 85%, 90%, 95%, and 99%.

[0043] In some embodiments, the catalyst contains 0.05%-5% active metal, 0.01%-10% rare earth metal oxide, 0.1%-1% modifier, and 84%-99.3% support.

[0044] In some embodiments, the synthesis method is batch-based and includes the following steps: adding the 2-pentylcyclopentanone and the catalyst to a reaction vessel, introducing hydrogen or a mixture of hydrogen and nitrogen into the reaction vessel, and carrying out the hydroisomerization reaction to obtain the 2-pentylcyclopentenone.

[0045] In some embodiments, the mass ratio of the catalyst to 2-pentylcyclopentanone is 1:50~10000.

[0046] In some embodiments, the temperature of the hydroisomerization reaction is 40~200 °C.

[0047] In some embodiments, the pressure of the hydroisomerization reaction is 0-2 MPa. The reaction can be carried out at atmospheric pressure.

[0048] In some embodiments, hydrogen accounts for less than 99% of the volume of the gas mixture. The gas mixture may be predominantly hydrogen or nitrogen.

[0049] In some embodiments, the synthesis method is continuous and includes the following steps: 1) loading the catalyst into a fixed-bed reactor and introducing hydrogen gas into the fixed-bed reactor until the pressure inside the reactor reaches the reaction pressure; 2) heating the fixed-bed reactor to the reaction temperature and continuously introducing the 2-pentylcyclopentenone and hydrogen gas or a mixture of hydrogen and nitrogen gas into the fixed-bed reactor to cause the hydroisomerization reaction, thereby obtaining the 2-pentylcyclopentenone. The catalyst of the present invention can be used in both batch and continuous reactions.

[0050] In some embodiments, the mass hourly space velocity (WHSV) of the 2-pentylcyclopentanone is 0.2 to 20 h⁻¹. -1 .

[0051] In some embodiments, the reaction temperature is 40~200°C.

[0052] In some embodiments, the reaction pressure is 0-2 MPa. The reaction can be carried out at atmospheric pressure.

[0053] In some embodiments, the volume hourly space velocity (VHSV) of the hydrogen gas or the mixture of hydrogen and nitrogen is 1 to 3000 h⁻¹. -1 .

[0054] In some embodiments, hydrogen accounts for less than 99% of the volume of the mixed gas.

[0055] The present invention also provides a catalyst used in the aforementioned synthesis method of 2-pentylcyclopentenone. When used to catalyze the isomerization of 2-pentylcyclopentenone to 2-pentylcyclopentenone, this catalyst achieves high conversion rates, high selectivity and high purity of the target product, and exhibits high catalyst stability.

[0056] The present invention also provides a method for preparing the aforementioned catalyst, the method comprising the following steps: 1) introducing rare earth metal oxides onto the support by precipitation or impregnation followed by calcination to obtain a modified support; 2) mixing an active metal precursor, a modifier, and a solvent to obtain an impregnation solution, and impregnating the modified support into the impregnation solution to obtain a catalyst precursor; 3) reducing the catalyst precursor in the presence of hydrogen to obtain the catalyst.

[0057] When using the precipitation method, the water-soluble salts of the corresponding rare earth metal elements are typically precipitated in an alkaline aqueous solution in the presence of a support to generate hydroxides. These hydroxides are then calcined at a specific temperature to dehydrate them into rare earth metal oxides, which can then be loaded onto the corresponding support. When using the impregnation method, the support is impregnated with an impregnation solution containing water-soluble salts of the corresponding rare earth metal elements, followed by calcination at a specific temperature. This causes the salts to form oxides, which are then loaded onto the support.

[0058] In some embodiments, the active metal precursor is selected from one or more combinations of acetate, chloride, sulfate, and acetylacetonate corresponding to the active metal.

[0059] In some embodiments, the solvent is selected from one or more combinations of methanol, ethanol, isopropanol, acetone, toluene, cyclohexane, and water.

[0060] In some embodiments, the molar ratio of the modifier and the active metal element in the active metal precursor is 2 to 30:1.

[0061] In some embodiments, the preparation method further includes a carrier preparation step: preparing a carrier precursor by precipitation, impregnation or ball milling, and calcining the carrier precursor to obtain the carrier.

[0062] In some embodiments, the reduction temperature is 100-600°C. This reduction step can be carried out in situ on the reactor used to synthesize 2-pentylcyclopentenone, i.e., the reduction is carried out simultaneously with the catalyst, which catalyzes the synthesis of 2-pentylcyclopentenone; alternatively, the reduction can be carried out separately first to prepare the catalyst, which is then loaded into the reactor for use in the synthesis of 2-pentylcyclopentenone.

[0063] Compared with the prior art, the present invention has the following advantages: The synthesis method of the present invention can achieve a high conversion rate of 2-pentylcyclopentanone and a high selectivity of the target product 2-pentylcyclopentenone, and the process is relatively simple and suitable for industrial production.

[0064] The catalyst of this invention has good stability and showed no signs of deactivation after being used 80 times in a batch reaction and after 4000 hours in a continuous reaction. Attached Figure Description

[0065] Figure 1 The X-ray diffraction pattern of the Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst in Example 1 is shown. Figure 2 The figure shows the stability test results of the Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst prepared by precipitation method in Example 1 in the continuous reaction of 2-pentylcyclopentenone isomerization (Application Example 4) for 4000 h. Detailed Implementation

[0066] Existing technologies for synthesizing 2-pentylcyclopentenone via the isomerization reaction of 2-pentylcyclopentenone cannot simultaneously achieve high conversion rates, high selectivity and high purity of the target product. Furthermore, the process is relatively simple and suitable for industrial production.

[0067] To address this, the present invention modifies the catalyst support and active components to achieve the aforementioned effects.

[0068] First, the carrier of this invention contains a zinc aluminate spinel structure. The carrier can be pure zinc aluminate spinel or a mixture thereof with other carriers. The zinc aluminate spinel structure carrier has abundant hydroxyl groups and oxygen vacancies. These sites can anchor active metal species and form hydrogen overflow channels, promoting the migration of hydrogen atoms from the metal to the carrier, thereby improving the conversion rate and selectivity of 2-pentylcyclopentanone.

[0069] Secondly, this invention uses rare earth metal oxides to modify the carrier to form a nano-island structure. The rare earth metal oxides on the carrier nano-island structure have strong metal-carrier interactions and spatial confinement effects with the active metal particles, which can achieve directional anchoring and stabilization of small-sized, highly dispersed metal active centers on the carrier surface, thereby reducing the loss of active metals and improving the conversion rate.

[0070] Finally, this invention employs phosphorus- and / or nitrogen-containing modifiers to modify and coordinate the active metal component. Coordinating the active metal with the modifier facilitates its dispersion on the support, regulates electron density, and promotes electron migration from the active metal to the support through electron-metal-support interactions, further optimizing catalytic performance.

[0071] Using the catalyst of this invention, high conversion rate of catalytic reaction, high selectivity and high purity of target product can be achieved. Moreover, the catalyst has high stability and can be used 80 times in batch reaction and after 4000 hours in continuous reaction without any signs of deactivation.

[0072] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0073] The boehmite used below is an alumina precursor, purchased from Zibo Nuoda Chemical Co., Ltd., which forms alumina after calcination. All other reagents were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0074] Example 1 1) Weigh 1.2 kg of boehmite, 1.04 kg of zinc nitrate hexahydrate, and 5 kg of deionized water, and place them in a reaction vessel. Stir at room temperature for half an hour. Heat the reaction vessel to 50 °C and maintain the internal temperature constant. Add 3 kg of sodium carbonate aqueous solution (molar concentration of 1.5 mol / L) to the reaction vessel using a peristaltic pump to carry out the precipitation reaction. The total feeding time of the sodium carbonate aqueous solution is 6 h. After precipitation, maintain the reaction vessel at 50 °C for aging treatment for 12 h. Filter and wash the material in the reaction vessel until the filtrate shows neutrality. Dry the filter cake in a 100 °C oven and then calcine it in air at 550 °C for 6 h to obtain the support ZnAl2O4-Al2O3. ZnAl2O4 is derived from the reaction and calcination of boehmite, zinc nitrate hexahydrate, and alkali, while Al2O3 is derived from the subsequent calcination process of boehmite. In this step, boehmite serves both as part of the carrier precursor and as one of the reaction raw materials for the zinc aluminate carrier portion.

[0075] 2) Weigh 155 g of cerium nitrate hexahydrate, 1 kg of the previously prepared support ZnAl2O4-Al2O3, and 5 L of deionized water, and place them in a reaction vessel. Stir at room temperature for 30 minutes. Heat the reaction vessel to 50 °C and maintain the internal temperature constant. Add 500 g of sodium carbonate aqueous solution (molar concentration of 1.6 mol / L) to the reaction vessel using a peristaltic pump to carry out the precipitation reaction. The total feeding time of the sodium carbonate aqueous solution is 6 h. After precipitation, maintain the internal temperature at 50 °C for aging treatment for 12 h. Filter and wash the material in the reaction vessel until the filtrate shows neutrality. Dry the filter cake in a 100 °C oven and then calcine it in air at 550 °C for 6 h to obtain the rare earth metal oxide modified support CeO2 / ZnAl2O4-Al2O3.

[0076] 3) Weigh 10.59 g of palladium acetate, 174 g of trioctylphosphine, 50 g of water, and 950 g of acetone, place them in a reaction vessel, and stir at room temperature under a nitrogen atmosphere until fully dissolved to obtain an impregnation solution. Add 1 kg of the rare earth metal oxide-modified support CeO2 / ZnAl2O4-Al2O3 prepared in step 2) to a vacuum reactor, turn on the vacuum pump, and vacuum treat for half an hour. Then close the vacuum valve, add the aforementioned impregnation solution to the vacuum reactor, and rotate the vacuum reactor to allow the support to fully absorb the impregnation solution. Then let it stand for 1 hour.

[0077] 4) Place the impregnated catalyst in a tube furnace and heat-treat it at 450°C for 4 hours under a hydrogen atmosphere to obtain the Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst.

[0078] Inductively coupled plasma atomic absorption spectrometry (ICP) analysis revealed that the prepared Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst contained 12.4% Zn, 41.5% Al, 4.3% Ce (corresponding to 5.3% CeO2), 0.46% Pd, and 0.18% P. The X-ray diffraction (XRD) pattern of this catalyst is shown below. Figure 1As shown, besides the characteristic diffraction peaks of amorphous alumina, characteristic diffraction peaks of ZnAl2O4 were observed at 2θ positions of 31.2°, 36.8°, 47.9°, 56.9°, 59.5°, and 66.7° (JCPDS No. 71-1175). No characteristic diffraction peaks of cerium dioxide or palladium were observed, indicating that cerium dioxide and palladium are highly dispersed on ZnAl2O4-Al2O3. Furthermore, combined with ICP and XRD results, it is known that the mass fraction of ZnAl2O4 in the ZnAl2O4-Al2O3 support is 37%, and the mass fraction of ZnAl2O4 in the Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst is 34.8%. The phosphorus element in the catalyst may exist in the form of trioctylphosphine (which did not undergo thermal decomposition) or in other compounds containing phosphorus.

[0079] In this embodiment, in step 2), cerium nitrate hexahydrate can be replaced with any one of zirconium nitrate, lanthanum nitrate, or yttrium nitrate, while keeping the other conditions unchanged. Catalysts modified with different rare earth metal oxides can be prepared, which are respectively denoted as Pd-P-ZrO2 / ZnAl2O4-Al2O3, Pd-P-La2O3 / ZnAl2O4-Al2O3, and Pd-P-Y2O3 / ZnAl2O4-Al2O3.

[0080] In this embodiment, in step 3), palladium acetate can be replaced with any one of platinum acetate, ruthenium acetate, rhodium acetate, or nickel acetate, while keeping the other conditions unchanged. Catalysts with different active metals can be prepared, which are respectively denoted as Pt-P-CeO2 / ZnAl2O4-Al2O3, Ru-P-CeO2 / ZnAl2O4-Al2O3, Rh-P-CeO2 / ZnAl2O4-Al2O3, and Ni-P-CeO2 / ZnAl2O4-Al2O3.

[0081] Example 2 1) Weigh 2.22 kg of aluminum nitrate nonahydrate, 1.56 kg of zinc nitrate hexahydrate, 1 kg of silicon dioxide, and 5 kg of deionized water, and place them in a reaction vessel. Stir at room temperature for half an hour. Heat the reaction vessel to 50 ℃ and maintain the internal temperature constant. Add 4.5 kg of sodium carbonate aqueous solution (molar concentration of 1.5 mol / L) to the reaction vessel using a peristaltic pump to carry out the precipitation reaction. The total feeding time of the sodium carbonate aqueous solution is 6 h. After precipitation, maintain the reaction vessel at 50 ℃ for aging treatment for 12 h. Filter and wash the material in the reaction vessel until the filtrate shows neutrality. Dry the filter cake in a 100 ℃ oven, and then calcine it in air at 550 ℃ for 6 h to obtain the support ZnAl2O4-SiO2. The mass fraction of ZnAl2O4 in the ZnAl2O4-SiO2 support is 35%.

[0082] 2) Weigh 155 g of cerium nitrate hexahydrate, 1 kg of the previously prepared ZnAl2O4-SiO2 support, and 5 L of deionized water, and place them in a reaction vessel. Stir at room temperature for 30 minutes. Heat the reaction vessel to 50 °C and maintain the internal temperature constant. Add 500 g of sodium carbonate aqueous solution (molar concentration of 1.6 mol / L) to the reaction vessel using a peristaltic pump to carry out the precipitation reaction. The total feeding time of the sodium carbonate aqueous solution is 6 h. After precipitation, maintain the internal temperature at 50 °C for aging treatment for 12 h. Filter and wash the material in the reaction vessel until the filtrate shows neutrality. Dry the filter cake in a 100 °C oven and then calcine it in air at 550 °C for 6 h to obtain the rare earth metal oxide modified support CeO2 / ZnAl2O4-SiO2.

[0083] 3) Weigh 10.59 g of palladium acetate, 174 g of trioctylphosphine, 50 g of water, and 950 g of acetone, place them in a reaction vessel, and stir at room temperature under a nitrogen atmosphere until fully dissolved to obtain an impregnation solution. Add 1 kg of the rare earth metal oxide-modified support CeO2 / ZnAl2O4-Al2O3 prepared in step 2) to a vacuum reactor, turn on the vacuum pump, and vacuum treat for half an hour. Then close the vacuum valve, add the aforementioned impregnation solution to the vacuum reactor, and rotate the vacuum reactor to allow the support to fully absorb the impregnation solution. Then let it stand for 1 hour.

[0084] 4) Place the impregnated catalyst in a tube furnace and heat-treat it at 450°C for 4 hours under a hydrogen atmosphere to obtain the Pd-P-CeO2 / ZnAl2O4-SiO2 catalyst.

[0085] In this embodiment, in step 1), silicon dioxide can be replaced by any one of titanium dioxide, zirconium dioxide, cerium dioxide, activated carbon, molecular sieve ZSM-5, and zinc oxide. With the other conditions unchanged, catalysts supported on different supports can be prepared, which are respectively denoted as Pd-P-CeO2 / ZnAl2O4-TiO2, Pd-P-CeO2 / ZnAl2O4-ZrO2, Pd-P-CeO2 / ZnAl2O4-CeO2, Pd-P-CeO2 / ZnAl2O4-C, Pd-P-CeO2 / ZnAl2O4-ZSM-5, and Pd-P-CeO2 / ZnAl2O4-ZnO. In Pd-P-CeO2 / ZnAl2O4-CeO2, the two CeO2 components have different functions. The CeO2 in the support is used to form and load the ZnAl2O4 support in situ, while the modified oxide CeO2 is dispersed and loaded in the ZnAl2O4 support to form a nano-island structure.

[0086] Example 3 In this embodiment, the support is a pure ZnAl2O4 support, as detailed below: 1) Weigh 4.24 kg of aluminum nitrate nonahydrate, 2.97 kg of zinc nitrate hexahydrate, and 15 kg of deionized water, and place them in a reaction vessel. Dissolve them by stirring at room temperature. Heat the reaction vessel to 50 °C and maintain the internal temperature constant. Add 60 kg of sodium carbonate aqueous solution (molar concentration of 1.6 mol / L) to the reaction vessel using a peristaltic pump to carry out the precipitation reaction. The total feeding time of the sodium carbonate aqueous solution is 6 h. After precipitation, maintain the internal temperature at 50 °C for aging treatment for 12 h. Filter and wash the material in the reaction vessel until the filtrate shows neutrality. Dry the filter cake in a 100 °C oven and then calcine it in air at 550 °C for 6 h to obtain pure ZnAl2O4 support.

[0087] Steps 2), 3), and 4) are basically the same as in Example 1, except that the pure ZnAl2O4 support mentioned above is used to prepare the Pd-P-CeO2 / ZnAl2O4 catalyst.

[0088] Example 4 The carrier preparation process in step 1) of Example 1 is modified as follows: 1) 1.04 kg of zinc nitrate hexahydrate and 1.5 kg of deionized water were placed in a reactor and dissolved by stirring at room temperature to obtain an impregnation solution. 1.2 kg of boehmite was added to a vacuum reactor, the vacuum pump was turned on, and vacuum treatment was carried out for half an hour. Then, the vacuum valve was closed, the aforementioned impregnation solution was added to the vacuum reactor, and the reactor was rotated to allow the carrier to fully absorb the impregnation solution. The mixture was then allowed to stand for 1 hour. The impregnated mixture was dried in an oven at 100 ℃ and then calcined in air at 550 ℃ for 6 h to obtain the carrier ZnAl2O4-Al2O3-impregnation. Impregnation yields a mixture of boehmite and zinc salt, while calcination forms ZnAl2O4-Al2O3 in situ.

[0089] Steps 2), 3), and 4) are basically the same as in Example 1, except that the support is impregnated with the aforementioned ZnAl2O4-Al2O3- to obtain the Pd-P-CeO2 / ZnAl2O4-Al2O3- impregnated catalyst.

[0090] Example 5 The carrier preparation process in step 1) of Example 1 is modified as follows: 1.04 kg of zinc nitrate hexahydrate and 1.2 kg of boehmite were weighed and added to a ball mill for ball milling at 50 ℃ for 2 h. The ball-milled mixture was then dried in an oven at 100 ℃ and calcined in air at 550 ℃ for 6 h to obtain the carrier ZnAl2O4-Al2O3-ball-milled material. Ball milling yields a mixture of boehmite and zinc salt, while calcination forms ZnAl2O4-Al2O3 in situ.

[0091] Steps 2), 3), and 4) are basically the same as in Example 1, except that the support is ZnAl2O4-Al2O3-ball milled as described above, which can produce Pd-P-CeO2 / ZnAl2O4-Al2O3-ball milled catalyst.

[0092] Example 6 The process is essentially the same as in Example 1, except that in step 1), boehmite is replaced with alumina. This alumina serves both as part of the support and as one of the reaction raw materials for the zinc aluminate support portion. The final catalyst obtained is also a Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst.

[0093] Example 7 The process is basically the same as in Example 1, except that in step 3), 174 g of trioctylphosphine is replaced with 37 g of pyridine. The resulting catalyst is a Pd-N-CeO2 / ZnAl2O4-Al2O3 catalyst.

[0094] Comparative Example 1 This comparative example provides a comparative catalyst whose support differs from that of the present invention. Its preparation process is essentially the same as in Example 1, except that the calcination temperature of the filter cake in step 1) is replaced with 400 °C, i.e., the calcination temperature is lowered. At this point, the support ZnAl2O4-Al2O3 cannot be obtained; instead, the support ZnO-Al2O3 is obtained. Steps 2)-4) are then performed on the ZnO-Al2O3 support to obtain the Pd-P-CeO2 / ZnO-Al2O3 catalyst.

[0095] Comparative Example 2 This comparative example provides a catalyst whose support differs from that of the present invention. It directly uses boehmite as the support, and its preparation process is basically the same as in Example 1, except that step 1) is omitted, and steps 2)-4) are performed directly using boehmite as the support. Specifically, the steps are as follows: 1) Weigh 155 g of cerium nitrate hexahydrate, 1 kg of boehmite, and 5 L of deionized water into a reactor and stir at room temperature for 30 minutes. Heat the reactor to 50 °C and maintain the internal temperature constant. Add 500 g of sodium carbonate aqueous solution (molar concentration 1.6 mol / L) to the reactor using a peristaltic pump to initiate the precipitation reaction. The total addition time of the sodium carbonate aqueous solution is 6 h. After precipitation, maintain the reactor at 50 °C for aging treatment for 12 h. Filter and wash the material in the reactor until the filtrate is neutral. Dry the filter cake in a 100 °C oven and then calcine it in air at 550 °C for 6 h to obtain the rare earth metal oxide modified support CeO2 / Al2O3.

[0096] 2) Weigh 10.59 g of palladium acetate, 174 g of trioctylphosphine, 50 g of water, and 950 g of acetone, place them in a reaction vessel, and stir at room temperature under a nitrogen atmosphere until fully dissolved to obtain an impregnation solution. Add 1 kg of the rare earth metal oxide-modified support CeO2 / Al2O3 prepared in step 2) to a vacuum reactor, turn on the vacuum pump, and vacuum treat for half an hour. Then close the vacuum valve, add the aforementioned impregnation solution to the vacuum reactor, and rotate the vacuum reactor to allow the support to fully absorb the impregnation solution. Then let it stand for 1 hour.

[0097] 3) Place the impregnated catalyst in a tube furnace and heat-treat it at 450°C for 4 hours under a hydrogen atmosphere to obtain the Pd-P-CeO2 / Al2O3 catalyst.

[0098] In this comparative example, the pseudoboehmite in step 1) can be replaced with zinc oxide to obtain the Pd-P-CeO2 / ZnO catalyst.

[0099] Comparative Example 3 This comparative example provides a comparative catalyst that does not employ cerium oxide modification. Its preparation process is essentially the same as in Example 1, except that steps 2) and 3)-4) are performed directly after step 1) in Example 1, thus obtaining a cerium oxide-free Pd-P / ZnAl2O4-Al2O3 catalyst.

[0100] Comparative Example 4 This comparative example provides a comparative catalyst that does not employ phosphorus modification. Its preparation process is essentially the same as in Example 1, except that trioctylphosphine is not added in step 3). Steps 1), 2), and 4) are the same as in Example 1, thus obtaining a phosphorus-free Pd-CeO2 / ZnAl2O4-Al2O3 catalyst.

[0101] Comparative Example 5 This comparative example provides a comparative catalyst that uses phosphorus-modified alumina as a support, and its preparation process is as follows: 1) Weigh 0.13 kg of diammonium hydrogen phosphate and 1.2 kg of deionized water into a reactor and stir to dissolve at room temperature to obtain an impregnation solution. Add 1 kg of alumina to a vacuum reactor, turn on the vacuum pump, and vacuum treat for half an hour. Then close the vacuum valve, add the aforementioned impregnation solution into the vacuum reactor, and rotate the vacuum reactor to allow the carrier to fully absorb the impregnation solution. Then let it stand for 1 hour. Place the impregnated mixture in a 100 ℃ oven to dry, and then calcine it in an air atmosphere at 550 ℃ for 6 hours to obtain the phosphorus-modified alumina carrier.

[0102] 2) Weigh 10.59 g of palladium acetate, 50 g of water, and 950 g of acetone, place them in a reaction vessel, and stir at room temperature under a nitrogen atmosphere until fully dissolved to obtain an impregnation solution. Add 1 kg of the aforementioned phosphorus-modified alumina support to a vacuum reactor, turn on the vacuum pump, and vacuum treat for half an hour. Then close the vacuum valve, add the aforementioned impregnation solution to the vacuum reactor, and rotate the vacuum reactor to allow the support to fully absorb the impregnation solution. Then let it stand for 1 hour.

[0103] 3) Place the impregnated catalyst in a tube furnace and heat-treat it at 450°C for 4 hours under a hydrogen atmosphere to obtain the Pd / P-Al2O3 catalyst.

[0104] Application Example 1 This application example provides a hydroisomerization reaction of 2-pentylcyclopentanone, as detailed below: 20 g of catalyst powder and 1200 g of 2-pentylcyclopentanone were added to a stainless steel reactor. After purging the reactor with nitrogen five times, the reactor was heated to 100 °C. Once the temperature stabilized, the pressure inside the reactor was reduced to 0.2 MPa (gauge pressure), and then hydrogen was introduced to maintain the pressure at 0.3 MPa. As the reaction proceeded, 2-pentylcyclopentanone underwent excessive hydrogenation to form 2-pentylcyclopentanone byproducts, causing a drop in the reactor pressure. Therefore, hydrogen was continuously introduced during the reaction to maintain the reactor pressure at 0.28–0.32 MPa. After 5 hours of reaction, the reaction was stopped by cooling. After cooling, the catalyst was separated from the reaction solution by filtration. Quantitative analysis of the reaction solution was performed on an Agilent 7890 gas chromatograph using an HP-INNOWax column and an FID detector. The corresponding conversion rate and selectivity of 2-pentylcyclopentanone were calculated.

[0105] Table 1 shows the reaction results of the catalysts Pd-P-CeO2 / ZnAl2O4-Al2O3 prepared by precipitation method in Example 1, Pd-P-CeO2 / ZnAl2O4 prepared in Example 3, Pd-N-CeO2 / ZnAl2O4-Al2O3 modified by nitrogen in Example 7, Pd-P-CeO2 / ZnO-Al2O3 prepared in Comparative Example 1, Pd-P-CeO2 / Al2O3 and Pd-P-CeO2 / ZnO prepared in Comparative Example 2, Pd-P / ZnAl2O4-Al2O3 prepared in Comparative Example 3, and Pd-CeO2 / ZnAl2O4-Al2O3 prepared in Comparative Example 4 in hydroisomerization.

[0106] As can be seen, the Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst of Example 1 and the Pd-P-CeO2 / ZnAl2O4 catalyst of Example 3, under the above reaction conditions, can achieve a conversion rate of over 99% for 2-pentylcyclopentanone and a selectivity of over 98% for 2-pentylcyclopentenone, exhibiting excellent catalytic activity. However, when the support is replaced with ZnO-Al2O3, Al2O3, or ZnO, both the conversion rate and selectivity of 2-pentylcyclopentanone decrease significantly, indicating that ZnAl2O4 plays a crucial role in the catalyst. This is mainly because, compared to ZnO-Al2O3, Al2O3, and ZnO, ZnAl2O4 has abundant hydroxyl groups and oxygen vacancies. These sites can anchor active metal species and form hydrogen overflow channels, promoting the migration of hydrogen atoms from the metal to the support. This allows the catalyst to adsorb and activate more 2-pentylcyclopentanone, thereby improving the conversion rate and selectivity.

[0107] Comparing Example 1 and Comparative Example 3, it can be seen that when the catalyst is not modified with cerium dioxide, the conversion rate and selectivity also decrease significantly.

[0108] Furthermore, after 20 batches of application, ICP analysis showed that the palladium mass fraction on the Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst in Example 1 was 0.43%, while that in Comparative Example 3 was 0.31%. This indicates that the palladium loss in the former was significantly less than in the latter, meaning that the active metal component was more stable after modification with rare earth metal oxides. This is because there is a strong metal-support interaction and spatial confinement effect between the rare earth metal oxides on the support and the active metal particles, achieving directional anchoring and stabilization of small-sized, highly dispersed metal active centers on the support surface, thereby reducing the loss of active metals and improving conversion rate and selectivity.

[0109] Comparing Example 1 and Comparative Example 4, it can be seen that when Pd does not coordinate with phosphorus ligands during the catalyst preparation process and then undergoes adsorption treatment, the conversion rate and selectivity will be significantly reduced. This is because coordinating the active metal with phosphorus ligands helps the active metal to disperse on the support, regulates the electron density, and can also promote the migration of electrons from the active metal to the support through electron-metal-support interaction, further optimizing the catalytic performance.

[0110] Table 1: Comparison of reaction performance of catalysts prepared in the examples and comparative examples

[0111] Table 2 shows the reaction performance of different supported catalysts in Examples 2 and 6. As can be seen from Table 2, all the supports of this invention can achieve excellent conversion rates and selectivity.

[0112] Table 2: Comparison of reaction performance of catalysts with different supports

[0113] Table 3 shows the reaction performance of different rare earth oxide modified catalysts in Example 1. As can be seen from Table 3, all rare earth oxides of this invention can achieve excellent conversion rates and selectivity.

[0114] Table 3: Comparison of reaction performance of catalysts modified with different rare earth oxides

[0115] Table 4 shows the reaction performance of catalysts with different metal active components in Example 1. As can be seen from Table 4, all the metal active components of this invention can achieve excellent conversion rates and selectivity.

[0116] Table 4: Comparison of reaction performance of different active metal catalysts

[0117] Table 5 shows the reaction performance of the catalysts prepared by different methods in Examples 1, 4, and 5. As can be seen from Table 5, excellent conversion rates and selectivity can be achieved when the corresponding supports are prepared using the various methods of the present invention.

[0118] Table 5: Catalyst Reaction Performance by Different Support Preparation Methods

[0119] Application Example 2 The Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst prepared in Example 1 was reused in the intermittent hydroisomerization reaction of 2-pentylcyclopentanone. Evaluation conditions for the 2-pentylcyclopentanone hydroisomerization reuse reaction: 100 g of catalyst and 200 kg of 2-pentylcyclopentanone were added to a stainless steel reactor. After purging with nitrogen five times, the reactor was heated to 100 °C. After the temperature stabilized, the pressure inside the reactor was reduced to 0.2 MPa (gauge pressure), and then hydrogen was introduced to control the pressure inside the reactor at 0.28~0.32 MPa during the reaction. After 8 hours of reaction, the reaction was stopped by cooling. After cooling, the catalyst was separated from the reaction solution by filtration, and the filtered catalyst was returned to the hydrogenation reactor for reuse. Quantitative analysis of the reaction solution was performed on an Agilent 7890 gas chromatograph using an HP-INNOWax column and an FID detector.

[0120] The results are shown in Table 6. It can be seen that after 80 catalyst reuses, the Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst of Example 1 did not show any signs of deactivation, indicating that the catalyst has excellent activity and stability.

[0121] Table 6: Comparison of Reaction Performance with Different Catalysts

[0122] Application Example 3 Continuous hydrogenation of 2-pentylcyclopentanone was carried out in a fixed-bed reactor (12 mm inner diameter). The reactor was loaded with 30 g of catalyst (the catalyst was crushed after molding, resulting in a particle size of 10-20 mesh and a volume of approximately 24 ml). The temperature was set at 80 °C, and the hydrogen-nitrogen mixed gas flow rate was 12 ml / min (molar ratio of hydrogen to nitrogen was 1:1, and total volume hourly space velocity was 720 h⁻¹). -1 The feed flow rate is 90 g / h (mass hourly space velocity 3 h⁻¹). -1 The reaction was carried out at atmospheric pressure. After the feed was stabilized, samples were taken from the bottom of the apparatus for analysis, and the reaction products were detected by gas chromatography (Gas Chromatograph: Agilent 7820A). Under these reaction conditions, the Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst of Example 1 achieved a conversion of 99.6% for 2-pentylcyclopentenone and a selectivity of 99.5% for 2-pentylcyclopentenone, exhibiting excellent catalytic activity. Its reaction performance was significantly better than that of the Pd / P-Al2O3 catalyst prepared in Comparative Example 5 (which had a conversion of 70.4% and a selectivity of 78.5%).

[0123] Application Example 4 Stability evaluation of 2-pentylcyclopentanone through continuous hydroisomerization: A jacketed stainless steel tube reactor was used, with an outer diameter of 45 mm, an inner diameter of 32 mm, and a length of 4000 mm. The shell medium was hot water. The Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst (cloverleaf shape; diameter 3 mm, length 3-5 mm) from Example 1 was loaded in a quantity of 3 kg (catalyst volume approximately 4 L). The reaction was carried out at atmospheric pressure, at a temperature of 75-80 °C, with a hydrogen-nitrogen mixed gas flow rate of 2 L / min (molar ratio 1:1, volume hourly space velocity 120 h⁻¹). -1 The feed flow rate is 9 kg / h (mass hourly space velocity 3 h⁻¹). -1 ).

[0124] The results are as follows Figure 2 As shown, during the 4000-hour stability test, 2-pentylcyclopentenone was almost completely converted, and the selectivity of 2-pentylcyclopentenone was maintained at around 98%. No signs of catalyst deactivation were observed, indicating that the Pd-P-CeO2 / ZnAl2O4-Al2O3 catalyst prepared in Example 1 has excellent reactivity, product selectivity, and stability.

[0125] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0126] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for synthesizing 2-pentylcyclopentenone, comprising using 2-pentylcyclopentanone and hydrogen as raw materials, and carrying out a hydroisomerization reaction in the presence of a catalyst to obtain the 2-pentylcyclopentenone; characterized in that: The catalyst is a supported catalyst and includes a support, an active metal, a rare earth metal oxide, and a modifier; the active metal and the rare earth metal oxide are supported on the support; the support includes zinc aluminate with a spinel structure; the modifier contains phosphorus and / or nitrogen.

2. The method for synthesizing 2-pentylcyclopentenone according to claim 1, characterized in that: The carrier is zinc aluminate with a spinel structure; or, the carrier may include other carriers selected from one or more combinations of alumina, silicon dioxide, titanium dioxide, zirconium dioxide, cerium dioxide, molecular sieves, carbon, and zinc oxide; preferably, the molecular sieve is selected from one or more combinations of ZSM-5 molecular sieves, Y-type molecular sieves, Beta-type molecular sieves, SBA-15 molecular sieves, and MCM-41 molecular sieves.

3. The method for synthesizing 2-pentylcyclopentenone according to claim 2, characterized in that: When the carrier also includes other carriers, the zinc aluminate accounts for 20%-50% of the mass of the carrier.

4. The method for synthesizing 2-pentylcyclopentenone according to claim 1, characterized in that: The carrier is zinc aluminate with a spinel structure; the zinc aluminate is prepared by a method including the following steps: a water-soluble aluminum salt, a water-soluble zinc salt and an alkali are subjected to a precipitation reaction in water, and a solid precipitate is obtained after solid-liquid separation; the solid precipitate is calcined at 450-750℃ to obtain the zinc aluminate with a spinel structure.

5. The method for synthesizing 2-pentylcyclopentenone according to claim 2, characterized in that: The carrier also includes other carriers, wherein the other carriers are aluminum oxide; Preferably, the carrier is prepared by a method comprising the following steps: precipitating an alumina precursor or alumina, a water-soluble zinc salt, and an alkali in water, followed by solid-liquid separation to obtain a precipitate solid; The precipitate solid is calcined at 450-750℃ to obtain the carrier; Alternatively, the carrier may be prepared by a method comprising the following steps: dissolving a water-soluble zinc salt in water to obtain an impregnation solution; impregnating an alumina precursor or alumina in the impregnation solution, and then calcining at 450-750°C to obtain the carrier; Alternatively, the carrier may be prepared by a method comprising the following steps: ball milling a water-soluble zinc salt and an alumina precursor or alumina to obtain a mixture; calcining the mixture at 450-750°C to obtain the carrier.

6. The method for synthesizing 2-pentylcyclopentenone according to claim 5, characterized in that: The alumina precursor is one or more of the following: boehmite, soluble aluminum salt, aluminum sol, and aluminum hydroxide.

7. The method for synthesizing 2-pentylcyclopentenone according to claim 2, characterized in that: The carrier also includes other carriers, which are selected from one or more combinations of silicon dioxide, titanium dioxide, zirconium dioxide, cerium dioxide, molecular sieves, carbon, and zinc oxide; Preferably, the carrier is prepared by a method comprising the following steps: in the presence of the other carrier, a water-soluble aluminum salt, a water-soluble zinc salt and an alkali are subjected to a precipitation reaction in water, and a precipitate solid is obtained after solid-liquid separation; the precipitate solid is calcined at 450-750°C to obtain the carrier.

8. The method for synthesizing 2-pentylcyclopentenone according to claim 1, characterized in that: The rare earth metal oxide is selected from one or more combinations of cerium dioxide, zirconium dioxide, lanthanum oxide, and yttrium oxide; and / or the active metal is selected from one or more combinations of Pd, Pt, Ru, Rh, and Ni.

9. The method for synthesizing 2-pentylcyclopentenone according to claim 1, characterized in that: In preparing the catalyst, the rare earth metal oxide is first loaded onto the support, followed by the active metal and a modifier; and / or, the modifier is selected from one or more combinations of triphenylphosphine, tributylphosphine, trioctylphosphine, trihexylphosphine, pyridine, pyrimidine, quinoline, pyrrole, and ethylenediaminetetraacetic acid.

10. The method for synthesizing 2-pentylcyclopentenone according to claim 1, characterized in that: The catalyst contains, by weight percentage, 0.05%-20% active metal, 0.01%-10% rare earth metal oxide, 0.01%-5% modifier, and 65%-99.3% support; preferably, the catalyst contains 0.05%-5% active metal, 0.01%-10% rare earth metal oxide, 0.1%-1% modifier, and 84%-99.3% support.

11. The method for synthesizing 2-pentylcyclopentenone according to claim 1, characterized in that: The synthesis method is batch and includes the following steps: adding the 2-pentylcyclopentanone and the catalyst to the reaction vessel, introducing hydrogen or a mixture of hydrogen and nitrogen into the reaction vessel, and carrying out the hydroisomerization reaction to obtain the 2-pentylcyclopentenone.

12. The method for synthesizing 2-pentylcyclopentenone according to claim 11, characterized in that: The mass ratio of the catalyst to 2-pentylcyclopentanone is 1:50~10000; and / or, the temperature of the hydroisomerization reaction is 40~200 °C; and / or, the pressure of the hydroisomerization reaction is 0~2 MPa; and / or, in the mixed gas, hydrogen accounts for less than 99% of the volume percentage of the mixed gas.

13. The method for synthesizing 2-pentylcyclopentenone according to claim 1, characterized in that: The synthesis method is continuous and includes the following steps: 1) loading the catalyst into a fixed-bed reactor and introducing hydrogen into the fixed-bed reactor to make the pressure inside the fixed-bed reactor reach the reaction pressure; 2) heating the fixed-bed reactor to the reaction temperature and continuously introducing the 2-pentylcyclopentenone and hydrogen or a mixture of hydrogen and nitrogen into the fixed-bed reactor to cause the hydrogenation isomerization reaction to obtain the 2-pentylcyclopentenone.

14. The method for synthesizing 2-pentylcyclopentenone according to claim 13, characterized in that: The mass hourly space velocity (HHSV) of the 2-pentylcyclopentanone is 0.2–20 h⁻¹. -1 ; and / or, the reaction temperature is 40~200℃; and / or, the reaction pressure is 0~2 MPa; and / or, the volume hourly space velocity of the hydrogen gas or the mixture of hydrogen and nitrogen gas is 1~3000 h⁻¹. -1 ; and / or, in the mixed gas, hydrogen accounts for less than 99% of the volume percentage of the mixed gas.

15. The catalyst according to any one of claims 1-14.

16. A method for preparing the catalyst according to claim 15, characterized in that: The preparation method includes the following steps: 1) introducing rare earth metal oxides onto the support by precipitation or impregnation followed by calcination to obtain a modified support; 2) mixing an active metal precursor, a modifier, and a solvent to obtain an impregnation solution, and impregnating the modified support into the impregnation solution to obtain a catalyst precursor; 3) reducing the catalyst precursor in the presence of hydrogen to obtain the catalyst.

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