Method for preparing cyclopentene by hydrogenation of cyclopentadiene

Abstract

This invention relates to the field of cyclopentene production, specifically to a method for preparing cyclopentene by hydrogenation of cyclopentadiene. The method includes: (1) contacting cyclopentadiene with hydrogen in the presence of a Ni-based catalyst to obtain a hydrogenation product; (2) separating hydrogen from the hydrogenation product and performing a first distillation to obtain a top distillate with a distillation range below 60°C; (3) performing a second distillation on the top distillate of the first distillation to obtain cyclopentene at the bottom of the distillation column; wherein the Ni-based catalyst contains a support and a Ni active metal component and a metal auxiliary component supported on the support. The technical solution of this invention has the advantages of high purity and high selectivity of the prepared cyclopentene, and can also catalyze the hydrogenation reaction of cyclopentadiene in solvent-free conditions, eliminating the problem of solvent separation and effectively reducing energy consumption in production.

Description

Technical Field

[0001] This invention relates to the field of cyclopentene production, and more specifically to a method for preparing cyclopentene from cyclopentadiene. Background Technology

[0002] Cyclopentene is an important fine chemical raw material, used to prepare high-value-added products such as cyclopentanol, cyclopentanone, glutaraldehyde, bromocyclopentane, and chlorocyclopentane. It is also a major raw material for polycyclic olefin polymers. Currently, cyclopentene is mainly produced through the selective hydrogenation of cyclopentadiene.

[0003] Cyclopentadiene is primarily derived from the C5 fraction, a byproduct of ethylene cracking. Because cyclopentadiene readily undergoes self-polymerization at room temperature to form the more stable dicyclopentadiene, industrial cyclopentadiene is typically stored as a dimer. For use, dicyclopentadiene is simply distilled at atmospheric pressure, collecting the fraction with a top temperature of 40-44°C to obtain cyclopentadiene. The cyclopentadiene molecule contains two reactive double bonds. Under typical hydrogenation conditions, one double bond is first hydrogenated to form cyclopentene. The double bond in the resulting cyclopentene molecule can then undergo further hydrogenation to form cyclopentane. Since the activation energy for the hydrogenation of cyclopentadiene to cyclopentene is slightly lower than that for the hydrogenation of cyclopentene to cyclopentane, at high temperatures, cyclopentadiene is prone to both excessive hydrogenation to cyclopentane and self-polymerization to regenerate dicyclopentadiene. Therefore, only at lower temperatures can the reaction be more effectively contained at the cyclopentene formation stage.

[0004] Cyclopentadiene hydrogenation can be divided into fixed-bed continuous hydrogenation and batch hydrogenation processes. Fixed-bed gas-phase hydrogenation typically involves reactions at temperatures above 100°C. However, this high temperature makes it difficult to control the further hydrogenation of cyclopentene to cyclopentane, which inevitably increases the load on subsequent separation processes. Furthermore, gas-phase hydrogenation requires larger reactor volumes, resulting in higher equipment investment costs. Batch hydrogenation typically uses powdered or small-particle catalysts, which present challenges in separating the catalyst from the product, making it unsuitable for large-scale continuous production. The liquid-phase continuous hydrogenation process for cyclopentadiene, on the other hand, facilitates the separation of reactants and catalysts and effectively saves on equipment costs, making it the preferred technical solution for the hydrogenation of cyclopentadiene to cyclopentane. For example, US3994986, CN1911877, and literature (Petrochemical Technology and Application, 2009, 27, 218) disclose a method for producing cyclopentene by fixed-bed hydrogenation of cyclopentadiene using a supported palladium catalyst, and CN 106673938 discloses the hydrogenation of methyl ethyl ether and diethyl ether solutions containing cyclopentadiene using a nickel-based catalyst. Existing liquid-phase continuous hydrogenation processes for cyclopentadiene suffer from the problems of requiring large amounts of organic solvents during hydrogenation and the difficulty in obtaining the active component of the hydrogenation catalyst (such as palladium). Summary of the Invention

[0005] The purpose of this invention is to overcome the problems in existing cyclopentadiene fixed-bed liquid-phase hydrogenation technology, such as the need for large amounts of organic solvents during the hydrogenation process and the difficulty in obtaining the active components in the hydrogenation catalyst. This invention provides a method for preparing cyclopentene by hydrogenation of cyclopentadiene, which enables the preparation of cyclopentene without the use of solvents, and the active components of the hydrogenation catalyst are inexpensive and readily available.

[0006] To achieve the above objectives, the present invention provides a method for preparing cyclopentene by hydrogenation of cyclopentadiene, the method comprising:

[0007] (1) Cyclopentadiene was contacted with hydrogen in the presence of a Ni-based catalyst to obtain a hydrogenation product;

[0008] (2) After separating hydrogen from the hydrogenation product, the first distillation is carried out to obtain the top distillate of the first distillation with a distillation range of less than 60°C.

[0009] (3) The top distillate of the first distillation is subjected to a second distillation, and cyclopentene is obtained from the bottom of the column;

[0010] The Ni-based catalyst contains a support and a Ni active metal component and a metal auxiliary component supported on the support.

[0011] Preferably, in the Ni-based catalyst, at least a portion of the nickel element exists in the form of elemental nickel and / or nickel carbides.

[0012] Preferably, based on the weight percentage of the Ni-based catalyst, the content of nickel is 0.5-5%, the content of the metal auxiliary component is 0.01-0.2%, the content of carbon is 1-5%, and the balance is the support;

[0013] More preferably, the content of nickel in the Ni-based catalyst is 1.5-4% by weight, the content of metal additive components is 0.02-0.1%, the content of carbon is 1.4-3.8%, and the balance is a support.

[0014] In this invention, preferably, the metal additive component is at least one of Group VIB, Group VIIB, Group IIB and lanthanide transition metal elements; preferably at least one of cerium, zinc, chromium, manganese, silver and europium.

[0015] In a preferred embodiment of the present invention, a Ni-based catalyst composed of an active component nickel, a support, and a metal auxiliary component (preferably europium) is used. Compared with the noble metal Pd catalyst used in the prior art, the catalyst of the present invention has the advantages of low cost and high selectivity for cyclopentene. Furthermore, the present invention can catalyze the hydrogenation reaction of cyclopentadiene under solvent-free conditions.

[0016] This invention utilizes a Ni-based catalyst composed of an active component (nickel), a support, and a metal additive component (preferably europium) to hydrogenate cyclopentadiene. The hydrogenated product is first subjected to a first distillation to remove high-boiling-point components (such as dicyclopentadiene, dihydrodicyclopentadiene, and tetrahydrodicyclopentadiene), and then the top fraction is subjected to a second distillation to remove light components (such as cyclopentane), thereby obtaining a cyclopentadiene product with high purity.

[0017] This invention employs a solvent-free catalytic hydrogenation reaction of cyclopentadiene, eliminating the need for solvent separation and effectively reducing energy consumption in production. Detailed Implementation

[0018] 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.

[0019] This invention provides a method for preparing cyclopentene by hydrogenation of cyclopentadiene, the method comprising:

[0020] (1) Cyclopentadiene was contacted with hydrogen in the presence of a Ni-based catalyst to obtain a hydrogenation product;

[0021] (2) After separating hydrogen from the hydrogenation product, the first distillation is carried out to obtain the top distillate of the first distillation with a distillation range of less than 60°C.

[0022] (3) The top distillate of the first distillation is subjected to a second distillation, and cyclopentene is obtained from the bottom of the column;

[0023] The Ni-based catalyst contains a support and a Ni active metal component and a metal auxiliary component supported on the support.

[0024] In this invention, the Ni-based catalyst contains a support and a Ni active metal component and a metal additive component on the supported support. Preferably, at least a portion of the nickel element exists in the form of elemental nickel and / or nickel carbides.

[0025] The Ni-based catalyst does not require expensive metals (such as palladium) as active components. In the process of hydrogenating cyclopentadiene to prepare cyclopentene, no additional solvent or diluent is needed. Moreover, the catalyst has the advantages of high activity, good selectivity, high reusability, and low deactivation. It can also improve the yield and selectivity of cyclopentene in the hydrogenation of cyclopentadiene to prepare cyclopentene.

[0026] In the above technical solution, at least a portion of the nickel element in the Ni active metal component exists in the form of elemental nickel and / or nickel carbides. This means that the nickel element in the Ni active metal component exists in the form of: entirely in elemental nickel, or entirely in the form of nickel carbides, or partially in the form of elemental nickel or nickel carbides, or partially in the form of both elemental nickel and nickel carbides, with the remaining nickel existing, for example, in the form of nickel oxides.

[0027] To further improve the yield and selectivity of cyclopentene in the hydrogenation of cyclopentadiene, preferably, the content of nickel element is 0.5-5% by weight of the Ni-based catalyst, the content of metal auxiliary component is 0.01-0.2%, the content of carbon element is 1-5%, and the balance is the support.

[0028] In this invention, the content of the metal additive components is calculated as metal elements. A portion of the carbon element exists in the form of nickel carbides, while the remainder exists in the form of elemental carbon.

[0029] To further improve the catalyst lifespan and increase the yield and selectivity of cyclopentane during the hydrogenation of cyclopentadiene, preferably, the content of nickel is 1.5-4% by weight of the Ni-based catalyst, the content of metal auxiliary components is 0.02-0.1%, the content of carbon is 1.4-3.8%, and the balance is the support.

[0030] Testing revealed that the catalyst of this invention does not contain nitrides, and the content of the aforementioned carbon element is equal to the carbon content in nickel carbides and the content of elemental carbon.

[0031] In this invention, the composition of the catalyst is detected by inductively coupled atomic emission spectrometry (ICP-AES) and EDX; elemental nickel is detected by spherical aberration electron microscopy; and nickel carbides are detected by diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and XPS.

[0032] The metal additive component can be selected from a variety of options. For example, the metal additive component can be at least one of Group VIB, Group VIIB, Group IIB and lanthanide transition metal elements.

[0033] Preferably, the metal additive component is at least one selected from cerium, zinc, chromium, manganese, silver, and europium. The metal additive component can be selected from one of cerium, zinc, chromium, manganese, silver, and europium, or multiple components can be selected in combination; europium is the preferred metal additive component.

[0034] The support can be selected from various materials, such as silica, alumina, silica-alumina, and molecular sieves. Preferably, the support is at least one of silica, sepiolite, hydrotalcite, activated carbon, and zeolite. The zeolite is selected from at least one of clinoptilolite, mordenite, chalcogenite, calcareous zeolite, calcium cruciformite, flaky zeolite, turbidite, zeolite, and anticline.

[0035] In this invention, the preparation method of the Ni-based catalyst can be a conventional preparation method in the art. Preferably, the Ni-based catalyst is prepared by a preparation method including the following steps:

[0036] S1. Ni active metal component precursor, metal auxiliary component precursor and auxiliary agent are loaded onto the support by impregnation method, and the catalyst precursor I is obtained after drying.

[0037] S2. Pyrolyze catalyst precursor I in an inert atmosphere to obtain catalyst precursor II;

[0038] S3. Under the reduction reaction conditions where combined nickel is reduced to elemental nickel, catalyst precursor II is brought into contact with a reducing gas.

[0039] This invention introduces an auxiliary agent during the loading of the active metal component and the auxiliary metal component, and employs a process of pyrolysis under an inert atmosphere followed by reduction. This allows the resulting catalyst to reduce the self-agglomeration and coking of cyclopentadiene during its hydrogenation to cyclopentene, thereby improving the catalyst's resistance to gum formation. The catalyst exhibits advantages such as high activity, good selectivity, high reusability, and low deactivation rate. Furthermore, it does not require the addition of additional solvents or diluents during the hydrogenation of cyclopentadiene to cyclopentene, thus minimizing deactivation. Additionally, the method for hydrogenating cyclopentadiene to cyclopentene using this invention, combined with the aforementioned catalyst and a fixed-bed liquid-phase hydrogenation process, achieves high selectivity and yield.

[0040] In step S1, the Ni active metal component precursor can be of various types, as long as it is soluble, the present invention can be realized. As a non-limiting example, the Ni active metal component precursor is selected from at least one of nickel chloride, nickel sulfate, nickel sulfamate, nickel acetate, and nickel nitrate. The metal auxiliary component precursor can be of various types, such as salts containing the metal auxiliary component element, such as nitrates, acetates, hydrochlorides, sulfates, oxalates, etc., or acids or salts containing the metal auxiliary component element in the acid anion, etc., as long as they are soluble, the present invention can be realized. As a non-limiting example, the metal auxiliary component precursor is at least one of cerium chloride, cerium nitrate, cerium acetate, europium chloride, europium nitrate, europium acetate, zinc nitrate, zinc chloride, zinc sulfate, zinc acetate, chromium nitrate, chromium chloride, chromium sulfate, chromium perchlorate, manganese chloride, manganese sulfate, manganese nitrate, manganese acetate, and silver nitrate.

[0041] The solvents used in the impregnation method can be of various types, such as water, acetonitrile, ethanol, etc. In a preferred embodiment of the present invention, water is selected as the solvent.

[0042] The amounts of the Ni active metal component precursor, the metal auxiliary component precursor, the auxiliary agent, and the support can be flexibly adjusted. Preferably, the amounts of the Ni active metal component precursor, the metal auxiliary component precursor, the auxiliary agent, and the support are such that, based on the weight percentage of the Ni-based catalyst, the content of nickel is 0.5-5%, the content of the metal auxiliary component is 0.01-0.2%, the content of carbon is 1-5%, and the balance is the support.

[0043] More preferably, the amounts of the Ni active metal component precursor, the metal auxiliary component precursor, the auxiliary agent, and the support are such that, based on the weight percentage of the Ni-based catalyst, the content of nickel is 1.5-4%, the content of the metal auxiliary component is 0.02-0.1%, the content of carbon is 1.4-3.8%, and the balance is the support.

[0044] Preferably, the adjuvant is selected from at least one of citric acid, bipyridine, ethylenediaminetetraethylamine, acetylsalicylic acid, ethylenediaminetetraacetic acid, aminotriacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, and dihydroxyethylglycine.

[0045] More preferably, the adjuvant is selected from at least one of dipyridine, citric acid and ethylenediaminetetraethylamine.

[0046] In this invention, the molar ratio of the auxiliary agent to Ni can be selected within a wide range. Preferably, the molar ratio of the auxiliary agent to Ni is 1-1.3. Within this preferred range, the yield and selectivity of cyclopentene can be improved in the hydrogenation of cyclopentadiene to prepare cyclopentene, while reducing the selectivity for byproducts such as cyclopentane, dicyclopentadiene, dihydrodicyclopentadiene, and tetrahydrodicyclopentadiene.

[0047] In this invention, the drying in step S1 is used to remove the solvent. Preferably, the drying temperature is 80-120°C.

[0048] In this invention, step S2 pyrolysis is used to decompose the Ni active metal component precursor, metal auxiliary component precursor and auxiliary agent loaded on the support in step S1 into a metal-carbon complex.

[0049] Preferably, the pyrolysis temperature is 450-550℃ and the pyrolysis time is 12-24h.

[0050] In the above technical solution, the inert atmosphere can be either an argon atmosphere or a nitrogen atmosphere, both of which can be achieved by the present invention. Preferably, the inert atmosphere is nitrogen, and preferably, the concentration of nitrogen is 15-35% by volume.

[0051] The reduction reaction conditions for reducing combined nickel to elemental nickel can be flexibly adjusted. Preferably, the reduction reaction conditions include a temperature of 300-400℃ and a time of 1-10h.

[0052] In the above technical solutions, there are various reducing gases. As non-limiting examples, these can be a mixture of an inert gas and hydrogen; a mixture of hydrogen and carbon monoxide; a mixture of hydrogen and methane; or a hydrogen atmosphere. Preferably, the reducing gas is a hydrogen atmosphere, and the hydrogen concentration is 15-35% by volume.

[0053] In this invention, the catalyst can be used directly or after molding. The molding time is not particularly limited; for example, molding can be performed on any one of the catalyst precursor I, catalyst precursor II, and the product obtained after contact with a reducing gas.

[0054] In a preferred embodiment of the present invention, the method further includes drying the product obtained after contacting with a reducing gas. The drying conditions can be selected by those skilled in the art as needed, and will not be elaborated here.

[0055] The catalyst preparation method of the present invention involves only drying after molding, without calcination.

[0056] In a preferred embodiment of the present invention, the catalyst, after reduction, is cooled to room temperature under an inert atmosphere. The inert atmosphere may be a nitrogen atmosphere.

[0057] In this invention, the preparation method of the Ni-based catalyst does not include the calcination process under high temperature (above 500°C or even above 600°C) conditions in an oxygen atmosphere, which is a common step in conventional catalyst preparation.

[0058] In this invention, in step (1), preferably, the contact is carried out in a fixed-bed reactor.

[0059] In this invention, the contact conditions in step (1) preferably include: a reactor inlet temperature of 20-70°C, a reaction pressure of 0.3-2.5 MPa, and a hydrogen mass hourly space velocity of 0.5-2 h⁻¹. -1 The molar ratio of hydrogen to cyclopentadiene is 1-2.

[0060] More preferably, the reactor inlet temperature is 40-60℃, the reaction pressure is 1.5-2MPa, and the hydrogen mass hourly space velocity is 1-1.5h. -1The molar ratio of hydrogen to cyclopentadiene is 1.1-1.3. Within this preferred range, the yield and selectivity of cyclopentene can be improved in the hydrogenation of cyclopentadiene to prepare cyclopentene, while reducing the selectivity for byproducts such as cyclopentane, dicyclopentadiene, dihydrodicyclopentadiene, and tetrahydrodicyclopentadiene.

[0061] In this invention, the Ni-based catalyst and hydrogenation method described herein enable the contact process to be solvent-free. In this invention, "solvent-free" means that no additional solvent-acting medium is added to the reaction system at the start and during the reaction. The reaction solvent can be a conventional reaction solvent in the art, such as any one of benzene, toluene, cyclohexane, ethanol, methanol, tert-amyl alcohol, or tert-butanol.

[0062] In this invention, the preferred conditions for the first distillation in step (2) include: a bottom temperature of 215-255°C, a top temperature of 60-85°C, and a top pressure of 0.50-0.65 MPa. Within these preferred ranges, the yield and selectivity of cyclopentene can be improved in the hydrogenation of cyclopentadiene to prepare cyclopentene, while reducing the selectivity for the byproduct cyclopentane.

[0063] Preferably, the first distillation process is carried out in a first distillation column, which has 10-20 theoretical plates. Within this preferred range, the yield and selectivity of cyclopentene can be improved in the hydrogenation of cyclopentadiene to cyclopentene, while reducing the selectivity for the byproduct cyclopentane.

[0064] In this invention, the preferred conditions for the second distillation in step (3) include: a bottom temperature of 95-120°C, a top temperature of 55-80°C, and a top pressure of 0.45-0.70 MPa. Within these preferred ranges, the yield and selectivity of cyclopentene can be improved in the hydrogenation of cyclopentadiene to prepare cyclopentene, while reducing the selectivity for the byproduct cyclopentane.

[0065] Preferably, the second distillation process is carried out in a second distillation column, which has 60-70 theoretical plates. Within this preferred range, the yield and selectivity of cyclopentene can be improved in the hydrogenation of cyclopentadiene to cyclopentene, while reducing the selectivity for the byproduct cyclopentane.

[0066] Preferably, the cyclopentadiene collected during the second distillation process is recycled to step (1) for hydrogenation.

[0067] In this invention, unless otherwise stated, pressure refers to gauge pressure. Distillation range refers to the boiling point of the oil under standard conditions.

[0068] The product after secondary distillation was analyzed by gas chromatography-mass spectrometry (GC-MASS), and the yield and selectivity of cyclopentene were calculated according to the formula:

[0069]

[0070]

[0071] In this invention, the purity of the extracted cyclopentene is detected by gas chromatography.

[0072] The present invention will be described in detail below through embodiments.

[0073] The product after secondary distillation was analyzed by gas chromatography-mass spectrometry (GC-MASS), and the yield and selectivity of cyclopentene were calculated according to the formula:

[0074]

[0075]

[0076] In this invention, the purity of the extracted cyclopentene is detected by gas chromatography.

[0077] In the following examples, unless otherwise specified, all raw materials used were commercially available. These included Raney nickel (Ni% > 90 wt%, Al < 7 wt%, Mo, Ti, Fe, Cr < 0.1 wt%, activity > 3 ml H2, particle size 40 mesh) and Ni / C catalyst (Ni content 5 wt%); both Raney nickel and Ni / C catalyst were products of Yuehua Chemical.

[0078] In the following embodiments, the hydrogenation step is carried out in a fixed-bed reactor; the first distillation is carried out in a first distillation column (with 15 trays), and the second distillation is carried out in a second distillation column (with 65 trays).

[0079] Example 1

[0080] This embodiment illustrates the preparation of Ni-based catalysts and the method of hydrogenating cyclopentadiene to produce cyclopentene.

[0081] 1. Preparation of Ni-based catalysts

[0082] Prepare an aqueous solution containing 0.5 g of nickel nitrate (Ni(NO3)2) and 0.007 g of cerium nitrate (Ce(NO3)3) and add EDTA as an auxiliary agent to achieve an auxiliary agent / nickel molar ratio of 1.3, resulting in 100 mL of impregnation solution. Add 10 g of SiO2 to the impregnation solution to form a slurry, and then slowly evaporate the water at 80 °C to obtain catalyst precursor I.

[0083] Catalyst precursor I was pyrolyzed at 550°C for 12 hours under a nitrogen atmosphere (nitrogen concentration 30% by volume); the calcined sample was then pressed into tablets and sieved to obtain catalyst precursor II with a mesh size of 30-60.

[0084] Catalyst precursor II was reduced at 350°C for 4 hours in a hydrogen atmosphere. After the catalyst was reduced, it was cooled to room temperature and protected with nitrogen to obtain the Ni-based catalyst.

[0085] The component contents of the Ni-based catalyst are shown in Table 1 after testing.

[0086] 2. Method for the hydrogenation of cyclopentadiene to cyclopentene

[0087] (1) Cyclopentadiene feedstock and hydrogen are continuously passed through a fixed-bed reactor packed with a Ni-based catalyst to obtain the hydrogenation product; wherein the hydrogenation reaction conditions for cyclopentadiene are: reactor temperature of 40℃, reaction pressure of 1.5MPa, and hydrogen mass hourly space velocity of 1.0h. -1 The molar ratio of hydrogen to cyclopentadiene is 1.1.

[0088] (2) After separating hydrogen from the hydrogenated product obtained in step (1), the product is fed into the first distillation column. Heavy impurities are collected from the bottom of the column, and the distillate from the top of the column is used as the feed for the second distillation column. The conditions for the first distillation include: a bottom temperature of 220°C, a top temperature of 70°C, and a top pressure of 0.55 MPa.

[0089] (3) The distillate from the top of the first distillation column in step (2) is fed into the second distillation column. The cyclopentene product is collected from the bottom of the column, and the unreacted light component cyclopentadiene is collected from the top of the column and returned to the recycling reaction in step (1). The conditions for the second distillation include: the bottom temperature of the column is 100°C, the top temperature of the column is 60°C, and the top pressure of the column is 0.48 MPa.

[0090] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0091] Example 2

[0092] This embodiment illustrates the preparation of Ni-based catalysts and the method of hydrogenating cyclopentadiene to produce cyclopentene.

[0093] 1. Preparation of Ni-based catalysts

[0094] Prepare an aqueous solution containing 0.35 g of nickel nitrate (Ni(NO3)2) and 0.002 g of silver nitrate (AgNO3). Mix the solutions and add citric acid as an auxiliary agent to achieve an auxiliary agent / nickel molar ratio of 1.0, resulting in 100 mL of impregnation solution. Add 10 g of SiO2 to the impregnation solution to form a slurry, and then slowly evaporate the water at 70 °C to obtain catalyst precursor I.

[0095] Catalyst precursor I was pyrolyzed at 550°C for 8 hours under a nitrogen atmosphere (nitrogen concentration 30% by volume); the calcined sample was then pressed into tablets and sieved to obtain catalyst precursor II with a mesh size of 30-60.

[0096] Catalyst precursor II was reduced at 400°C for 3 hours in a hydrogen atmosphere. After the catalyst was reduced, it was cooled to room temperature and protected with nitrogen to obtain the Ni-based catalyst.

[0097] The component contents of the Ni-based catalyst are shown in Table 1 after testing.

[0098] 2. Method for the hydrogenation of cyclopentadiene to cyclopentene

[0099] (1) Cyclopentadiene feedstock and hydrogen are continuously passed through a fixed-bed reactor packed with a Ni-based catalyst to obtain the hydrogenation product; wherein the hydrogenation reaction conditions for cyclopentadiene are: reactor temperature of 20℃, reaction pressure of 0.3MPa, and hydrogen mass hourly space velocity of 0.5h. -1 The molar ratio of hydrogen to cyclopentadiene is 1.0.

[0100] (2) After separating hydrogen from the hydrogenated product obtained in step (1), the product is fed into the first distillation column. Heavy impurities are collected from the bottom of the column, and the distillate from the top of the column is used as the feed for the second distillation column. The conditions for the first distillation include: a bottom temperature of 225°C, a top temperature of 78°C, and a top pressure of 0.52 MPa.

[0101] (3) The distillate from the top of the first distillation column in step (2) is fed into the second distillation column. The cyclopentene product is collected from the bottom of the column, and the unreacted light component cyclopentadiene is collected from the top of the column and returned to the recycling reaction in step (1). The conditions for the second distillation include: the bottom temperature of the column is 105°C, the top temperature of the column is 60°C, and the top pressure of the column is 0.45 MPa.

[0102] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0103] Example 3

[0104] This embodiment illustrates the preparation of Ni-based catalysts and the method of hydrogenating cyclopentadiene to produce cyclopentene.

[0105] 1. Preparation of Ni-based catalysts

[0106] A solution containing 1.7 g of nickel nitrate (Ni(NO3)2) and 0.05 g of chromium nitrate (Cr(NO3)3) was prepared. After mixing, the auxiliary agent dipyridine was added to achieve an auxiliary agent / nickel molar ratio of 1.3, yielding 100 mL of impregnation solution. 10 g of SiO2 was added to the impregnation solution to form a slurry, which was then slowly evaporated at 70 °C to obtain catalyst precursor I.

[0107] Catalyst precursor I was pyrolyzed at 450°C for 9 hours under a nitrogen atmosphere (nitrogen concentration 30% by volume); the calcined sample was then pressed into tablets and sieved to obtain catalyst precursor II with a mesh size of 30-60.

[0108] Catalyst precursor II was reduced at 450°C for 2 hours in a hydrogen atmosphere. After the catalyst was reduced, it was cooled to room temperature and protected with nitrogen to obtain the Ni-based catalyst.

[0109] The component contents of the Ni-based catalyst are shown in Table 1 after testing.

[0110] 2. Method for the hydrogenation of cyclopentadiene to cyclopentene

[0111] (1) Cyclopentadiene feedstock and hydrogen are continuously passed through a fixed-bed reactor packed with a Ni-based catalyst to obtain the hydrogenation product; wherein the hydrogenation reaction conditions for cyclopentadiene are: reactor temperature of 70℃, reaction pressure of 2.5MPa, and hydrogen mass hourly space velocity of 2.0h. -1 The molar ratio of hydrogen to cyclopentadiene is 2.0.

[0112] (2) After separating hydrogen from the hydrogenated product obtained in step (1), the product is fed into the first distillation column. Heavy impurities are collected from the bottom of the column, and the distillate from the top of the column is used as the feed for the second distillation column. The conditions for the first distillation include: a bottom temperature of 230°C, a top temperature of 80°C, and a top pressure of 0.6 MPa.

[0113] (3) The distillate from the top of the first distillation column in step (2) is fed into the second distillation column. The cyclopentene product is collected from the bottom of the column, and the unreacted light component cyclopentadiene is collected from the top of the column and returned to the recycling reaction in step (1). The conditions for the second distillation include: the bottom temperature of the column is 120°C, the top temperature of the column is 75°C, and the top pressure of the column is 0.65 MPa.

[0114] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0115] Example 4

[0116] This embodiment illustrates the preparation of Ni-based catalysts and the method of hydrogenating cyclopentadiene to produce cyclopentene.

[0117] 1. Preparation of Ni-based catalysts

[0118] Prepare an aqueous solution containing 1.35 g of nickel nitrate (Ni(NO3)2) and 0.035 g of manganese nitrate (Mn(NO3)2) and add the auxiliary agent bipyridine to make the auxiliary agent / nickel molar ratio 1.3, resulting in 100 mL of impregnation solution. Add 10 g of SiO2 to the impregnation solution to form a slurry, and then slowly evaporate the water at 80 °C to obtain catalyst precursor I.

[0119] Catalyst precursor I was pyrolyzed at 550°C for 10 hours under a nitrogen atmosphere (nitrogen concentration 30% by volume); the calcined sample was then pressed into tablets and sieved to obtain catalyst precursor II with a mesh size of 30-60.

[0120] Catalyst precursor II was reduced at 450°C for 6 hours in a hydrogen atmosphere. After the catalyst was reduced, it was cooled to room temperature and protected with nitrogen to obtain the Ni-based catalyst.

[0121] The component contents of the Ni-based catalyst are shown in Table 1 after testing.

[0122] 2. Method for the hydrogenation of cyclopentadiene to cyclopentene

[0123] (1) Cyclopentadiene feedstock and hydrogen are continuously passed through a fixed-bed reactor packed with a Ni-based catalyst to obtain the hydrogenation product; wherein the hydrogenation reaction conditions for cyclopentadiene are: reactor temperature of 60℃, reaction pressure of 2.0MPa, and hydrogen mass hourly space velocity of 1.5h. -1 The molar ratio of hydrogen to cyclopentadiene is 1.3.

[0124] (2) After separating hydrogen from the hydrogenated product obtained in step (1), the product is fed into the first distillation column. Heavy impurities are collected from the bottom of the column, and the distillate from the top of the column is used as the feed for the second distillation column. The conditions for the first distillation include: a bottom temperature of 220°C, a top temperature of 65°C, and a top pressure of 0.55 MPa.

[0125] (3) The distillate from the top of the first distillation column in step (2) is fed into the second distillation column. The cyclopentene product is collected from the bottom of the column, and the unreacted light component cyclopentadiene is collected from the top of the column and returned to the recycling reaction in step (1). The conditions for the second distillation include: the bottom temperature of the column is 110°C, the top temperature of the column is 75°C, and the top pressure of the column is 0.65 MPa.

[0126] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0127] Example 5

[0128] This embodiment illustrates the preparation of Ni-based catalysts and the method of hydrogenating cyclopentadiene to produce cyclopentene.

[0129] 1. Preparation of Ni-based catalysts

[0130] A solution containing 1.0 g of nickel nitrate (Ni(NO3)2) and 0.016 g of europium nitrate (Eu(NO3)3) was prepared. After mixing, the auxiliary agent bipyridine was added to achieve an auxiliary agent / nickel molar ratio of 1.3, yielding 100 mL of impregnation solution. 10 g of SiO2 was added to the impregnation solution to form a slurry, which was then slowly evaporated at 80 °C to obtain catalyst precursor I.

[0131] Catalyst precursor I was pyrolyzed at 500°C for 8 hours under a nitrogen atmosphere (nitrogen concentration 30% by volume); the calcined sample was then pressed into tablets and sieved to obtain catalyst precursor II with a mesh size of 30-60.

[0132] Catalyst precursor II was reduced at 350°C for 4 hours in a hydrogen atmosphere. After the catalyst was reduced, it was cooled to room temperature and protected with nitrogen to obtain the Ni-based catalyst.

[0133] The component contents of the Ni-based catalyst are shown in Table 1 after testing.

[0134] 2. Method for the hydrogenation of cyclopentadiene to cyclopentene

[0135] (1) Cyclopentadiene feedstock and hydrogen are continuously passed through a fixed-bed reactor packed with a Ni-based catalyst to obtain the hydrogenation product; wherein the hydrogenation reaction conditions for cyclopentadiene are: reactor temperature of 50℃, reaction pressure of 1.8MPa, and hydrogen mass hourly space velocity of 1.3h. -1 The molar ratio of hydrogen to cyclopentadiene is 1.2.

[0136] (2) After separating hydrogen from the hydrogenated product obtained in step (1), the product is fed into the first distillation column. Heavy impurities are collected from the bottom of the column, and the distillate from the top of the column is used as the feed for the second distillation column. The conditions for the first distillation include: a bottom temperature of 210°C, a top temperature of 60°C, and a top pressure of 0.55 MPa.

[0137] (3) The distillate from the top of the first distillation column in step (2) is fed into the second distillation column. The cyclopentene product is collected from the bottom of the column, and the unreacted light component cyclopentadiene is collected from the top of the column and returned to the recycling reaction in step (1). The conditions for the second distillation include: the bottom temperature of the column is 100°C, the top temperature of the column is 60°C, and the top pressure of the column is 0.55 MPa.

[0138] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0139] Example 6

[0140] This embodiment illustrates the method for preparing cyclopentene by hydrogenation of cyclopentadiene according to the present invention.

[0141] Cyclopentene was prepared using the method described in Example 5, except that the material flowed sequentially through a fixed-bed reactor, a second distillation column, and a first distillation column. The first distillation was carried out in the second distillation column, and the second distillation was carried out in the first distillation column. The conditions for the first and second distillations remained unchanged.

[0142] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0143] Example 7

[0144] This embodiment illustrates the method for preparing cyclopentene by hydrogenation of cyclopentadiene according to the present invention.

[0145] The Ni-based catalyst prepared by the method described in Example 4 was used to prepare cyclopentene according to the method described in Example 5.

[0146] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0147] Comparative Example 1

[0148] This comparative example is used to illustrate the method of using the reference catalyst for the hydrogenation of cyclopentadiene to prepare cyclopentene.

[0149] Cyclopentene was prepared using the method of Example 1, with Raney nickel replacing the Ni-based catalyst in Example 4.

[0150] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0151] Comparative Example 2

[0152] This comparative example is used to illustrate the method of using the reference catalyst for the hydrogenation of cyclopentadiene to prepare cyclopentene.

[0153] Cyclopentene was prepared using the method of Example 1, replacing the Ni-based catalyst in Example 5 with a "Ni / C catalyst".

[0154] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0155] Comparative Example 3

[0156] This comparative example is used to illustrate the method of using the reference catalyst for the hydrogenation of cyclopentadiene to prepare cyclopentene.

[0157] Cyclopentene was prepared using the method described in Example 5, except that an equimolar amount of Ni was used instead of Eu in the Ni-based catalyst.

[0158] The component contents of the Ni-based catalyst are shown in Table 1 after testing.

[0159] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0160] Comparative Example 4

[0161] This comparative example is used to illustrate the method of preparing cyclopentene by hydrogenation of cyclopentadiene.

[0162] The preparation of cyclopentene by hydrogenation of cyclopentadiene was carried out using the Ni-based catalyst described in Example 1. The difference was that the hydrogenation product obtained in step (1) was separated into hydrogen gas and then fed into a distillation column. Heavy impurities were collected from the bottom of the column, and the distillate from the top of the column was collected as the product. The distillation conditions were as follows: the bottom temperature was 215°C, the top temperature was 60°C, and the top pressure was 0.50 MPa.

[0163] The purity, selectivity, and yield of cyclopentene were detected and calculated, and the specific results are shown in Table 2.

[0164] Table 1

[0165]

[0166] Table 2

[0167]

[0168]

[0169] As can be seen from the results in Table 2, the Ni catalyst prepared by the present invention can achieve higher cyclopentadiene conversion, higher cyclopentene selectivity and yield.

[0170] With the preferred Ni-based catalyst of this invention, the conversion rate of cyclopentadiene, as well as the selectivity and yield of cyclopentene, can be further improved.

[0171] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing cyclopentene by hydrogenation of cyclopentadiene, characterized in that, The method includes: (1) Cyclopentadiene was contacted with hydrogen in the presence of a Ni-based catalyst to obtain a hydrogenation product; (2) After separating hydrogen from the hydrogenation product, a first distillation is carried out to obtain the top distillate of the first distillation with a distillation range of less than 60°C; (3) The top distillate of the first distillation column is subjected to a second distillation, and cyclopentene is obtained from the bottom of the column; The Ni-based catalyst comprises a support and a Ni active metal component and a metal promoter component supported on the support. In the Ni-based catalyst, at least a portion of the nickel element exists in the form of elemental nickel and / or nickel carbides. Based on the weight percentage of the Ni-based catalyst, the nickel content is 0.5-5%, the metal promoter component content is 0.01-0.2%, the carbon content is 1-5%, and the remainder is the support. The metal promoter component is at least one of Group VIB, Group VIIB, Group IIB, and lanthanide transition metals. The contact process does not involve solvents.

2. The method according to claim 1, wherein, In step (1), the contact conditions include: reactor inlet temperature of 20-70℃, reaction pressure of 0.3-2.5MPa, and hydrogen mass hourly space velocity of 0.5-2 h⁻¹. -1 The molar ratio of hydrogen to cyclopentadiene is 1-2.

3. The method according to claim 2, wherein, The reactor inlet temperature is 40-60℃, the reaction pressure is 1.5-2MPa, and the hydrogen mass hourly space velocity is 1-1.5 h⁻¹. -1 The molar ratio of hydrogen to cyclopentadiene is 1.1-1.

3.

4. The method according to claim 1 or 2, wherein, In step (2), the conditions for the first distillation include: a bottom temperature of 215-255℃, a top temperature of 60-85℃, and a top pressure of 0.5-0.65 MPa.

5. The method according to claim 4, wherein, The first distillation process is carried out in a first distillation column, which has 10-20 theoretical plates.

6. The method according to any one of claims 1-3, wherein, In step (3), the conditions for the second distillation include: a bottom temperature of 95-120°C, a top temperature of 55-80°C, and a top pressure of 0.45-0.7 MPa.

7. The method according to claim 6, wherein, The second distillation process is carried out in a second distillation column, which has 60-70 theoretical plates.

8. The method according to claim 7, wherein, The cyclopentadiene collected from the top of the column during the second distillation process is recycled to step (1) for hydrogenation.

9. The method according to claim 1, wherein, The Ni-based catalyst contains 1.5-4% nickel, 0.02-0.1% metal additives, and 1.4-3.8% carbon by weight, with the remainder being a support.

10. The method according to claim 1, wherein, The metal additive component is at least one of cerium, zinc, chromium, manganese, silver and europium.

11. The method according to claim 1, wherein, The carrier is at least one of silica, sepiolite, porous carbon, hydrotalcite, and zeolite molecular sieve.

12. The method according to claim 1, wherein, The Ni-based catalyst is prepared by a method including the following steps: S1. Ni active metal component precursor, metal auxiliary component precursor and auxiliary agent are loaded onto the support by impregnation method, and the catalyst precursor I is obtained after drying. S2. Pyrolyze catalyst precursor I in an inert atmosphere to obtain catalyst precursor II; S3. Under the reduction reaction conditions where combined nickel is reduced to elemental nickel, catalyst precursor II is brought into contact with a reducing gas.

13. The method according to claim 12, wherein, The amounts of Ni active metal component precursor, metal auxiliary component precursor, auxiliary agent and support are such that, by weight percentage, the content of nickel is 0.5-5%, the content of metal auxiliary component is 0.01-0.2%, the content of carbon is 1-5%, and the balance is support.

14. The method according to claim 13, wherein, The adjuvant is selected from at least one of citric acid, bipyridine, ethylenediaminetetraethylamine, acetylsalicylic acid, ethylenediaminetetraacetic acid, aminotriacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, and dihydroxyethylglycine.

15. The method according to claim 14, wherein, The adjuvant is selected from at least one of bipyridine, citric acid, and ethylenediaminetetraethylamine.

16. The method of claim 14, wherein, The molar ratio of the auxiliary agent to Ni element is 1-1.

3.

17. The method according to any one of claims 12-16, wherein, In step S2, the pyrolysis conditions include: a temperature of 450-550℃, a time of 12-24h, and an inert atmosphere of nitrogen.

18. The method according to any one of claims 12-16, wherein, The reduction reaction conditions include: a temperature of 350-450℃ and a time of 2-8h.

19. The method according to any one of claims 12-16, wherein, The reducing gas is a hydrogen atmosphere with a hydrogen concentration of 15-35% by volume.

20. The method according to any one of claims 12-16, wherein, In step S3, the method further includes drying the product obtained after contacting with a reducing gas.

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