Preparation method of 2-pentyl-2-cyclopentenone

Abstract

The invention provides a preparation method of 2-pentyl-2-cyclopentenone, and belongs to the technical field of organic synthesis. The preparation method comprises the following steps: carrying out a first-stage isomerization reaction on 2-pentylidene cyclopentanone and a first composite catalyst in a first atmosphere to obtain an intermediate, carrying out a second-stage isomerization reaction on the intermediate and a second composite catalyst in a second atmosphere, and controlling the volume ratio of nitrogen to hydrogen in the first atmosphere and the second atmosphere to obtain the 2-pentylidene cyclopentanone. In the first-stage isomerization reaction, the conversion rate of converting 2-pentylidene cyclopentanone into 2-pentyl-2-cyclopentenone is increased, and in the second-stage isomerization reaction, the use amount of hydrogen in the second atmosphere is reduced, the temperature of the second-stage isomerization reaction is increased, generation of by-products is inhibited, and the yield of 2-pentylidene cyclopentanone is increased. Further, the yield and the purity of the 2-pentyl-2-cyclopentenone can be improved. According to the preparation method, the first-stage isomerization reaction and the second-stage isomerization reaction are continuous reactions, intermittent reactions are not needed, and the preparation method is more suitable for industrial application.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for preparing 2-pentyl-2-cyclopentenone. Background Technology

[0002] Methyl dihydrojasmonate belongs to the jasmine family of compounds and possesses a beautiful, fresh aroma. It is one of the important synthetic jasmine fragrances and is highly favored by perfumers. 2-Pentyl-2-cyclopentenone is an important intermediate in the synthesis of methyl dihydrojasmonate.

[0003] Currently, several methods for preparing 2-pentyl-2-cyclopentenone have been reported. For example, a related patent discloses a one-step synthesis method of 2-pentyl-2-cyclopentenone in a high-pressure reactor. This method involves reacting n-pentanal and cyclopentenone in an alkaline solution with a composite catalyst under a mixture of nitrogen and hydrogen. Although this method can synthesize 2-pentyl-2-cyclopentenone in one step, it is a batch reaction, requiring the composite catalyst to be filtered and reused in the post-processing, making the operation cumbersome and resulting in a low yield of 2-pentyl-2-cyclopentenone, which is not conducive to industrial application. Another related patent discloses a method for preparing 2-pentyl-2-cyclopentenone by dehydration isomerization of 2-(1-hydroxyalkyl)-cycloalkane-1-one in the presence of an acid and a platinum group metal catalyst. This method yields >10% of the byproduct 2-pentylcyclopentenone, exhibits poor selectivity, and has a yield of only 80-85%, which is relatively low. Another related patent discloses the reaction of methyl 2-oxocyclopentane carboxylate with bromopentane, followed by a series of post-processing steps to obtain 2-oxo-1-pentylcyclopentane. This method involves a long process route, complex post-processing, and large wastewater generation. It is a batch reaction with low industrial production value and is not suitable for industrial application.

[0004] Therefore, there is an urgent need to provide a method for preparing 2-pentyl-2-cyclopentenone that is highly selective, has a high yield, and can be produced continuously. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing 2-pentyl-2-cyclopentenone that is highly selective, has a high yield, and can be produced continuously.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps:

[0008] 2-Pentylcyclopentanone was mixed with a first composite catalyst and subjected to an isomerization reaction under a first atmosphere to obtain an intermediate; the first atmosphere was a mixture of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen in the first atmosphere was 3 to 15:1.

[0009] The intermediate is mixed with a second composite catalyst and subjected to a two-stage isomerization reaction under a second atmosphere to obtain 2-pentyl-2-cyclopentenone; the second atmosphere is a mixture of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen in the second atmosphere is 12 to 60:1.

[0010] The first composite catalyst and the second composite catalyst independently comprise a phosphorus-modified porous support and a transition metal supported on the phosphorus-modified porous support;

[0011] The temperature of the second-stage isomerization reaction is 20–50°C higher than that of the first-stage isomerization reaction.

[0012] Preferably, the mass hourly space velocity (WHSV) of the 2-pentylcyclopentanone is 0.1–3 h⁻¹. -1 .

[0013] Preferably, the temperature of the first-stage isomerization reaction is 100–200°C; the pressure of the first-stage isomerization reaction is 0.05–1 MPa.

[0014] Preferably, the mass hourly space velocity of the intermediate is 0.1 to 3 h⁻¹. -1 .

[0015] Preferably, the temperature of the two-stage isomerization reaction is 120–220°C, and the pressure of the two-stage isomerization reaction is 0.05–1 MPa.

[0016] Preferably, the transition metal in the first composite catalyst and the transition metal in the second composite catalyst independently include Pd and / or Pt.

[0017] Preferably, the loading of the transition metal in the first composite catalyst and the loading of the transition metal in the second composite catalyst are independently 1 to 10 wt%.

[0018] Preferably, the phosphorus-modified porous support comprises one of phosphorus-modified alumina, phosphorus-modified activated carbon, phosphorus-modified molecular sieve, and phosphorus-modified diatomaceous earth.

[0019] Preferably, the phosphorus content in the phosphorus-modified porous support is 0.5–5 wt%.

[0020] Preferably, the apparatus for the first-stage isomerization reaction and the apparatus for the second-stage isomerization reaction are adiabatic fixed-bed reactors.

[0021] This invention provides a method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps: mixing 2-pentylcyclopentenone with a first composite catalyst and performing a first-stage isomerization reaction under a first atmosphere to obtain an intermediate; the first atmosphere is a mixture of nitrogen and hydrogen, wherein the volume ratio of nitrogen to hydrogen in the first atmosphere is 3-15:1; mixing the intermediate with a second composite catalyst and performing a second-stage isomerization reaction under a second atmosphere to obtain 2-pentyl-2-cyclopentenone; the second atmosphere is a mixture of nitrogen and hydrogen, wherein the volume ratio of nitrogen to hydrogen in the second atmosphere is 12-60:1; the first and second composite catalysts independently comprise a phosphorus-modified porous support and a transition metal supported on the phosphorus-modified porous support; the temperature of the second-stage isomerization reaction is 20-50°C higher than the temperature of the first-stage isomerization reaction. This invention improves the conversion rate of 2-pentylcyclopentanone to 2-pentyl-2-cyclopentenone in the first isomerization reaction by controlling the volume ratio of nitrogen and hydrogen in the first and second atmospheres. This results in approximately 60-80% of 2-pentylcyclopentanone being converted to 2-pentyl-2-cyclopentenone in the first isomerization reaction. In the second isomerization reaction, by reducing the amount of hydrogen in the second atmosphere and increasing the temperature of the second isomerization reaction, the conversion rate is improved while reducing the hydrogenation of 2-pentyl-2-cyclopentenone to 2-pentylcyclopentenone, thus inhibiting the formation of byproducts and improving the selectivity and yield of 2-pentyl-2-cyclopentenone. This invention uses a phosphorus-modified porous support and a transition metal supported on the phosphorus-modified porous support as a first composite catalyst and a second composite catalyst. The transition metal serves as the catalytically active component. Using a phosphorus-modified alumina support avoids the use of strong acids such as hydrobromic acid, eliminates the need for solvents, reduces equipment corrosion, and generates no wastewater, making it a green and environmentally friendly method, more suitable for industrial applications. The preparation method provided by this invention allows for continuous single-stage and two-stage isomerization reactions, eliminating the need for batch reactions and making it suitable for industrial applications. Example results show that the preparation method provided by this invention is a continuous reaction, achieving a conversion rate of >98% for the raw material 2-pentylcyclopentenone and a yield of >95% for 2-pentyl-2-cyclopentenone. Attached Figure Description

[0022] Figure 1 A schematic diagram of the reaction apparatus used in the preparation method provided by the present invention. Detailed Implementation

[0023] This invention provides a method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps:

[0024] 2-Pentylcyclopentanone was mixed with a first composite catalyst and subjected to an isomerization reaction under a first atmosphere to obtain an intermediate; the first atmosphere was a mixture of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen in the first atmosphere was 3 to 15:1.

[0025] The intermediate is mixed with a second composite catalyst and subjected to a two-stage isomerization reaction under a second atmosphere to obtain 2-pentyl-2-cyclopentenone; the second atmosphere is a mixture of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen in the second atmosphere is 12 to 60:1.

[0026] The first composite catalyst and the second composite catalyst independently comprise a phosphorus-modified porous support and a transition metal supported on the phosphorus-modified porous support;

[0027] The temperature of the second-stage isomerization reaction is 20–50°C higher than that of the first-stage isomerization reaction.

[0028] In this invention, 2-pentylcyclopentanone is mixed with a first composite catalyst and subjected to an isomerization reaction under a first atmosphere to obtain an intermediate.

[0029] In this invention, the purity of the 2-pentylcyclopentanone is preferably 95% or higher. This invention does not have a particular limitation on the source of the 2-pentylcyclopentanone; any conventional commercially available product may be used.

[0030] In this invention, the first composite catalyst comprises a phosphorus-modified porous support and a transition metal supported on the phosphorus-modified porous support. This invention uses a phosphorus-modified porous support and a transition metal supported on the phosphorus-modified porous support as the first composite catalyst, with the transition metal serving as the catalytically active component. Using a phosphorus-modified porous support avoids the use of strong acids such as hydrobromic acid, eliminates the need for solvents, reduces equipment corrosion, and generates no wastewater, making it a green and environmentally friendly method, more suitable for industrial applications.

[0031] In this invention, the phosphorus-modified porous carrier preferably includes one of phosphorus-modified alumina, phosphorus-modified activated carbon, phosphorus-modified molecular sieve, and phosphorus-modified diatomaceous earth, and more preferably phosphorus-modified alumina.

[0032] In this invention, the loading of the transition metal in the first composite catalyst is preferably 1 to 10 wt%. As one embodiment of this invention, the loading of the transition metal in the first composite catalyst can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%. In this invention, the loading of the transition metal in the first composite catalyst refers to the mass percentage of the transition metal relative to the mass of the first composite catalyst. By controlling the loading of the transition metal within the above range, this invention can improve the catalytic effect and increase the reaction efficiency of the first-stage isomerization reaction.

[0033] In this invention, the phosphorus content in the phosphorus-modified porous carrier is preferably 0.5–5 wt%; more preferably 1–3 wt%. This invention does not have a specific limitation on the source of the phosphorus-modified porous carrier; conventional commercially available products are acceptable.

[0034] In this invention, the transition metal preferably includes Pd and / or Pt, more preferably Pd. This invention employs the aforementioned first composite catalyst, which can improve catalytic efficiency and the reaction efficiency of a single-stage isomerization reaction. In embodiments of this invention, the first composite catalyst can be a phosphorus-modified alumina support and Pd supported on the alumina, wherein the Pd loading can be 5 wt%, and the phosphorus content in the phosphorus-modified porous support can be 3 wt%, simply referred to as 5% Pd / 3% phosphorus-modified Al2O3.

[0035] In this invention, the space velocity of the 2-pentylcyclopentanone is preferably 0.1 to 3 h⁻¹. -1 In one embodiment of the present invention, the mass hourly space velocity (WHSV) of the 2-pentylcyclopentanone can be 0.1 h⁻¹. -1 0.5h -1 1h -1 2h -1 or 3h -1 .

[0036] The present invention does not specifically limit the method of mixing the 2-pentylcyclopentanone with the first composite catalyst; simply mixing them evenly is sufficient. In an embodiment of the present invention, the method of mixing the 2-pentylcyclopentanone with the first composite catalyst preferably includes: filling the first composite catalyst into a device for a first-stage isomerization reaction to obtain a first-stage isomerization reaction device filled with the first composite catalyst, and introducing 2-pentylcyclopentanone into the first-stage isomerization reaction device filled with the first composite catalyst.

[0037] The present invention does not specifically limit the method of filling the first composite catalyst into the device for a first-stage isomerization reaction; adjustments can be made according to the device used.

[0038] In this invention, the apparatus for the isomerization reaction is preferably an adiabatic fixed-bed reactor. This invention uses an adiabatic fixed-bed reactor, which eliminates external heat exchange and ensures a uniform temperature distribution across the bed cross-section, thus helping to maintain stable reaction conditions and reduce the occurrence of side reactions.

[0039] This invention does not impose any special limitation on the size of the adiabatic fixed-bed reactor; any conventional adiabatic fixed-bed reactor can be used. In an embodiment of this invention, the length of the adiabatic fixed-bed reactor can be 1 m, and the inner diameter can be 25 mm.

[0040] In an embodiment of the present invention, when the isomerization reaction apparatus is an adiabatic fixed-bed reactor, the method for filling the first composite catalyst into the isomerization reaction apparatus can be as follows: the first composite catalyst is loaded into the isothermal section of the adiabatic fixed-bed reactor, with inert ceramic balls above and below the isothermal section, separated by quartz wool in the middle. By using inert ceramic balls and separating the sections with quartz wool, the present invention can ensure that the temperature deviation of the isothermal section is below 1°C, which is beneficial for maintaining a stable temperature range in the isothermal section, reducing the formation of byproducts, and improving the selectivity of the product 2-pentyl-2-cyclopentenone.

[0041] In this invention, the space velocity of the introduced 2-pentylcyclopentanone is preferably 0.1 to 3 h⁻¹. -1 In one embodiment of the present invention, the mass hourly space velocity (WHSV) of the introduced 2-pentylcyclopentanone can be 0.1 h⁻¹. -1 0.5h -1 1h -1 2h -1 or 3h -1 .

[0042] In this invention, the first atmosphere is a mixture of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen in the first atmosphere is 3 to 15:1. As one embodiment of this invention, the volume ratio of nitrogen to hydrogen in the first atmosphere can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, or 15:1. By controlling the volume ratio of nitrogen to hydrogen in the first atmosphere within the above range, this invention is more conducive to the complete conversion of 2-pentylcyclopentanone to 2-pentyl-2-cyclopentenone, thereby improving the conversion rate of 2-pentyl-2-cyclopentenone.

[0043] In this invention, the temperature of the first-stage isomerization reaction is preferably 100–200°C. As one embodiment of this invention, the temperature of the first-stage isomerization reaction can be 100°C, 120°C, 150°C, 160°C, 180°C, or 200°C. In this invention, the pressure of the first-stage isomerization reaction is preferably 0.05–1 MPa. As one embodiment of this invention, the pressure of the first-stage isomerization reaction can be 0.05 MPa, 0.1 MPa, 0.5 MPa, or 1 MPa. By controlling the temperature, time, and mass hourly space velocity of the first atmosphere within the above ranges, this invention enables 2-pentylcyclopentanone to undergo a complete isomerization reaction.

[0044] In this invention, the time for the isomerization reaction is preferably 0.15 to 1 hour, more preferably 0.5 to 1 hour.

[0045] After obtaining the intermediate, the present invention mixes the intermediate with a second composite catalyst and carries out a two-stage isomerization reaction under a second atmosphere to obtain 2-pentyl-2-cyclopentenone.

[0046] In this invention, the second composite catalyst comprises a phosphorus-modified porous support and a transition metal supported on the phosphorus-modified porous support. This invention uses a phosphorus-modified porous support and a transition metal supported on the phosphorus-modified porous support as the second composite catalyst, with the transition metal serving as the catalytically active component. Using a phosphorus-modified porous support avoids the use of strong acids such as hydrobromic acid, eliminates the need for solvents, reduces equipment corrosion, and generates no wastewater, making it a green and environmentally friendly method, more suitable for industrial applications.

[0047] In this invention, the loading of the transition metal in the second composite catalyst is preferably 1-10 wt%. As one embodiment of this invention, the loading of the transition metal in the second composite catalyst can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%. In this invention, the loading of the transition metal in the second composite catalyst refers to the mass percentage of the transition metal relative to the mass of the second composite catalyst. By controlling the loading of the transition metal within the above range, this invention can improve the catalytic effect and increase the reaction efficiency of the two-stage isomerization reaction.

[0048] In this invention, the phosphorus-modified porous support preferably comprises one of phosphorus-modified alumina, phosphorus-modified activated carbon, phosphorus-modified molecular sieve, and phosphorus-modified diatomaceous earth, more preferably phosphorus-modified alumina. In this invention, the transition metal preferably comprises Pd and / or Pt, more preferably Pd. In this invention, the use of the above-mentioned phosphorus-modified porous support and transition metal can improve the catalytic effect and increase the reaction efficiency of the two-stage isomerization reaction. In an embodiment of this invention, the second composite catalyst can be alumina and Pd supported on the alumina, the Pd loading can be 5 wt%, and the phosphorus content in the phosphorus-modified porous support can be 3 wt%, simply referred to as 5% Pd / 3% phosphorus-modified Al2O3.

[0049] In this invention, the space velocity of the intermediate is 0.1 to 3 h. -1 In one embodiment of the present invention, the mass hourly space velocity of the intermediate can be 0.1 h⁻¹. -1 0.5h -1 1h -1 2h -1 or 3h -1 .

[0050] The present invention does not specifically limit the method of mixing the intermediate with the second composite catalyst; as long as they are mixed evenly, it is acceptable. In an embodiment of the present invention, the method of mixing the intermediate with the second composite catalyst preferably includes: filling the second composite catalyst into the apparatus for a two-stage isomerization reaction, and introducing the intermediate into the apparatus for the two-stage isomerization reaction filled with the second composite catalyst.

[0051] The present invention does not specifically limit the method of filling the second composite catalyst into the apparatus for the two-stage isomerization reaction; adjustments can be made according to the apparatus used.

[0052] In this invention, the apparatus for the two-stage isomerization reaction is preferably an adiabatic fixed-bed reactor. This invention uses an adiabatic fixed-bed reactor, which eliminates external heat exchange and ensures a uniform temperature distribution across the bed cross-section, thus helping to maintain stable reaction conditions and reduce the occurrence of side reactions.

[0053] In this invention, the apparatus for the first-stage isomerization reaction and the apparatus for the second-stage isomerization reaction are preferably two-stage adiabatic fixed-bed reactors. This invention uses two-stage adiabatic fixed-bed reactors, enabling the intermediate to undergo a direct second-stage isomerization reaction, making the preparation of 2-pentyl-2-cyclopentenone a continuous reaction.

[0054] In an embodiment of the present invention, when the isomerization reaction apparatus is an adiabatic fixed-bed reactor, the method for filling the isomerization reaction apparatus with the second composite catalyst can be as follows: the second composite catalyst is loaded into the isothermal section of the adiabatic fixed-bed reactor, with inert ceramic balls above and below the isothermal section, separated by quartz wool in the middle. By using inert ceramic balls and separating the sections with quartz wool, the present invention can ensure that the temperature deviation of the isothermal section is below 1°C, which is beneficial for maintaining a stable temperature range in the isothermal section, reducing the formation of byproducts, and improving the selectivity of the product 2-pentyl-2-cyclopentenone.

[0055] In this invention, the second atmosphere is a mixture of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen in the first atmosphere is 12 to 60:1. As one embodiment of this invention, the volume ratio of nitrogen to hydrogen in the second atmosphere can be 12:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, or 60:1. By controlling the volume ratio of nitrogen to hydrogen in the second atmosphere within the above range, this invention is more conducive to the complete conversion of 2-pentylcyclopentanone in the intermediate to 2-pentyl-2-cyclopentenone, and inhibits the hydrogenation of 2-pentyl-2-cyclopentenone to 2-pentylcyclopentenone, thereby improving the conversion rate and selectivity of 2-pentyl-2-cyclopentenone.

[0056] In this invention, the temperature of the two-stage isomerization reaction is 20-50°C higher than that of the one-stage isomerization reaction. Preferably, the temperature of the two-stage isomerization reaction is 120-220°C. In one embodiment, the temperature of the two-stage isomerization reaction can be 120°C, 150°C, 160°C, 180°C, 200°C, or 220°C. Preferably, the pressure of the two-stage isomerization reaction is 0.05-1 MPa. In one embodiment, the pressure of the two-stage isomerization reaction can be 0.05 MPa, 0.1 MPa, 0.5 MPa, or 1 MPa. By controlling the temperature, time, and mass hourly space velocity of the second atmosphere within the above ranges, this invention enables the complete conversion of 2-pentylcyclopentanone in the intermediate to 2-pentyl-2-cyclopentenone and inhibits the hydrogenation of 2-pentyl-2-cyclopentenone to 2-pentylcyclopentenone, thereby improving the conversion rate and selectivity of 2-pentyl-2-cyclopentenone.

[0057] In this invention, the time for the two-stage isomerization reaction is preferably 0.15 to 1 hour, more preferably 0.5 to 1 hour.

[0058] In this invention, the preferred gas flow rate of the mixed gas after the two-stage isomerization reaction is 260–820 mL / min. As one embodiment of this invention, the gas flow rate of the mixed gas after the two-stage isomerization reaction can be 260 mL / min, 300 mL / min, 400 mL / min, 420 mL / min, 500 mL / min, 600 mL / min, 620 mL / min, 700 mL / min, 800 mL / min, or 820 mL / min. By controlling the gas flow rate of the mixed gas after the two-stage isomerization reaction to the above range, this invention enables the product to have a reasonable residence time in the bed, thereby improving the product yield.

[0059] A schematic diagram of the reaction apparatus used in the preparation method provided by the present invention is preferably shown below. Figure 1 As shown. From Figure 1 As can be seen, in this invention, 2-pentylcyclopentenone undergoes a first-stage isomerization reaction with a first composite catalyst in a first-stage adiabatic fixed bed under nitrogen and hydrogen (first atmosphere) to obtain an intermediate. Then, in a second-stage isomerization reaction under nitrogen and hydrogen (second atmosphere), the intermediate undergoes a second-stage isomerization reaction with a second composite catalyst in a second-stage adiabatic fixed bed. The product obtained from the second-stage isomerization reaction is then separated in a high-precision separator, and the product in the product tank is the 2-pentyl-2-cyclopentenone product.

[0060] The preparation method provided by this invention is simple to operate. By controlling the volume ratio of nitrogen and hydrogen in the first and second atmospheres, the conversion rate of 2-pentylcyclopentanone to 2-pentyl-2-cyclopentenone is increased in the first-stage isomerization reaction. Furthermore, in the second-stage isomerization reaction, by reducing the amount of hydrogen in the second atmosphere and increasing the temperature of the second-stage isomerization reaction, the hydrogenation of 2-pentyl-2-cyclopentenone to 2-pentylcyclopentenone is reduced, and the formation of byproducts is suppressed, thereby improving the yield and selectivity of 2-pentyl-2-cyclopentenone. The preparation method provided by this invention allows for continuous first-stage and second-stage isomerization reactions, eliminating the need for batch reactions, making it more suitable for industrial applications.

[0061] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0062] Example 1

[0063] A method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps:

[0064] Two-stage adiabatic fixed-bed reactors were used, each 1m in length and 25mm in inner diameter. The first-stage adiabatic fixed-bed reactor was loaded with 30g of a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3), and the second-stage adiabatic fixed-bed reactor was loaded with 30g of a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). Inert ceramic balls were placed at the top and bottom of the first composite catalyst and separated by quartz wool.

[0065] 2-Pentylcyclopentanone was introduced into an adiabatic fixed-bed reactor and mixed with a first composite catalyst (5% Pd / Al₂O₃). A first-stage isomerization reaction was carried out under a first atmosphere to obtain an intermediate. The first atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen-to-hydrogen volume ratio of 3:1. The temperature of the first-stage isomerization reaction was 120°C, and the mass hourly space velocity (WHSV) of 2-pentylcyclopentanone was 1.0 h⁻¹. -1 The pressure for one stage of the isomerization reaction is 0.2 MPa;

[0066] The intermediate was introduced into a two-stage adiabatic fixed-bed reactor and mixed with a second composite catalyst (5% Pd / Al2O3). A two-stage isomerization reaction was carried out under a second atmosphere to obtain 2-pentyl-2-cyclopentenone. The second atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen to hydrogen volume ratio of 12:1. The temperature of the two-stage isomerization reaction was 140°C, and the mass hourly space velocity (WHSV) of the intermediate was 1 h⁻¹. -1 The pressure of the two-stage isomerization reaction was 0.2 MPa; the gas discharge rate of the mixed gas after the two-stage isomerization reaction was 260 mL / min; the reaction results of the obtained 2-pentyl-2-cyclopentenone are shown in Table 1.

[0067] Example 2

[0068] A method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps:

[0069] Two-stage adiabatic fixed-bed reactors were used, each 1m in length and 25mm in inner diameter. The first-stage adiabatic fixed-bed reactor was loaded with 30g of a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3), and the second-stage adiabatic fixed-bed reactor was loaded with 30g of a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). Inert ceramic balls were placed at the top and bottom of the first composite catalyst and separated by quartz wool.

[0070] 2-Pentylcyclopentanone was introduced into an adiabatic fixed-bed reactor and mixed with a first composite catalyst (5% Pd / Al2O3). A first-stage isomerization reaction was carried out under a first atmosphere to obtain an intermediate. The first atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen-to-hydrogen volume ratio of 3:1. The temperature of the first-stage isomerization reaction was 140°C, and the mass hourly space velocity (WHSV) of 2-pentylcyclopentanone was 1.0 h⁻¹. -1 The pressure for one stage of the isomerization reaction is 0.2 MPa;

[0071] The intermediate was introduced into a two-stage adiabatic fixed-bed reactor and mixed with a second composite catalyst (5% Pd / Al2O3). A two-stage isomerization reaction was carried out under a second atmosphere to obtain 2-pentyl-2-cyclopentenone. The second atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen to hydrogen volume ratio of 12:1. The temperature of the two-stage isomerization reaction was 160°C, and the mass hourly space velocity (WHSV) of the intermediate was 1 h⁻¹. -1 The pressure of the two-stage isomerization reaction was 0.2 MPa; the gas discharge rate of the mixed gas after the two-stage isomerization reaction was 260 mL / min; the reaction results of the obtained 2-pentyl-2-cyclopentenone are shown in Table 1.

[0072] Example 3

[0073] A method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps:

[0074] Two-stage adiabatic fixed-bed reactors were used, each 1m in length and 25mm in inner diameter. The first-stage adiabatic fixed-bed reactor was loaded with 30g of a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3), and the second-stage adiabatic fixed-bed reactor was loaded with 30g of a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). Inert ceramic balls were placed at the top and bottom of the first composite catalyst and separated by quartz wool.

[0075] 2-Pentylcyclopentanone was introduced into an adiabatic fixed-bed reactor and mixed with a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). A first-stage isomerization reaction was carried out under a first atmosphere to obtain an intermediate. The first atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen-to-hydrogen volume ratio of 5:1. The temperature of the first-stage isomerization reaction was 140°C, and the mass hourly space velocity (WHSV) of 2-pentylcyclopentanone was 1.0 h⁻¹. -1 The pressure for one stage of the isomerization reaction is 0.2 MPa;

[0076] The intermediate was introduced into a two-stage adiabatic fixed-bed reactor and mixed with a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). A two-stage isomerization reaction was carried out under a second atmosphere to obtain 2-pentyl-2-cyclopentenone. The second atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen to hydrogen volume ratio of 20:1. The temperature of the two-stage isomerization reaction was 160°C, and the mass hourly space velocity (WHSV) of the intermediate was 1 h⁻¹. -1 The pressure of the two-stage isomerization reaction was 0.2 MPa; the gas discharge rate of the mixed gas after the two-stage isomerization reaction was 420 mL / min; the reaction results of the obtained 2-pentyl-2-cyclopentenone are shown in Table 1.

[0077] Example 4

[0078] A method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps:

[0079] Two-stage adiabatic fixed-bed reactors were used, each 1m in length and 25mm in inner diameter. The first-stage adiabatic fixed-bed reactor was loaded with 30g of a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3), and the second-stage adiabatic fixed-bed reactor was loaded with 30g of a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). Inert ceramic balls were placed at the top and bottom of the first composite catalyst and separated by quartz wool.

[0080] 2-Pentylcyclopentanone was introduced into an adiabatic fixed-bed reactor and mixed with a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). A first-stage isomerization reaction was carried out under a first atmosphere to obtain an intermediate. The first atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen-to-hydrogen volume ratio of 3:1. The temperature of the first-stage isomerization reaction was 140°C, and the mass hourly space velocity (WHSV) of 2-pentylcyclopentanone was 1.0 h⁻¹. -1 The pressure for one stage of the isomerization reaction is 0.2 MPa;

[0081] The intermediate was introduced into a two-stage adiabatic fixed-bed reactor and mixed with a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). A two-stage isomerization reaction was carried out under a second atmosphere to obtain 2-pentyl-2-cyclopentenone. The second atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen to hydrogen volume ratio of 30:1. The temperature of the two-stage isomerization reaction was 160°C, and the mass hourly space velocity (WHSV) of the intermediate was 1 h⁻¹. -1 The pressure of the two-stage isomerization reaction was 0.2 MPa; the gas discharge rate of the mixed gas after the two-stage isomerization reaction was 620 mL / min; the reaction results of the obtained 2-pentyl-2-cyclopentenone are shown in Table 1.

[0082] Example 5

[0083] A method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps:

[0084] Two-stage adiabatic fixed-bed reactors were used, each 1m in length and 25mm in inner diameter. The first-stage adiabatic fixed-bed reactor was loaded with 30g of a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3), and the second-stage adiabatic fixed-bed reactor was loaded with 30g of a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). Inert ceramic balls were placed at the top and bottom of the first composite catalyst and separated by quartz wool.

[0085] 2-Pentylcyclopentanone was introduced into an adiabatic fixed-bed reactor and mixed with a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). A first-stage isomerization reaction was carried out under a first atmosphere to obtain an intermediate. The first atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen-to-hydrogen volume ratio of 5:1. The temperature of the first-stage isomerization reaction was 140°C, and the mass hourly space velocity (WHSV) of 2-pentylcyclopentanone was 1.0 h⁻¹. -1 The pressure for one stage of the isomerization reaction is 0.5 MPa;

[0086] The intermediate was introduced into a two-stage adiabatic fixed-bed reactor and mixed with a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). A two-stage isomerization reaction was carried out under a second atmosphere to obtain 2-pentyl-2-cyclopentenone. The second atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen to hydrogen volume ratio of 30:1. The temperature of the two-stage isomerization reaction was 160°C, and the mass hourly space velocity (WHSV) of the intermediate was 1 h⁻¹. -1 The pressure of the two-stage isomerization reaction was 0.5 MPa; the gas discharge rate of the mixed gas after the two-stage isomerization reaction was 620 mL / min; the reaction results of the obtained 2-pentyl-2-cyclopentenone are shown in Table 1.

[0087] Example 6

[0088] A method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps:

[0089] Two-stage adiabatic fixed-bed reactors were used, each 1m in length and 25mm in inner diameter. The first-stage adiabatic fixed-bed reactor was loaded with 30g of a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3), and the second-stage adiabatic fixed-bed reactor was loaded with 30g of a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). Inert ceramic balls were placed at the top and bottom of the first composite catalyst and separated by quartz wool.

[0090] 2-Pentylcyclopentanone was introduced into an adiabatic fixed-bed reactor and mixed with a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). A first-stage isomerization reaction was carried out under a first atmosphere to obtain an intermediate. The first atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen-to-hydrogen volume ratio of 3:1. The temperature of the first-stage isomerization reaction was 140°C, and the mass hourly space velocity (WHSV) of 2-pentylcyclopentanone was 1.0 h⁻¹. -1 The pressure for one stage of the isomerization reaction is 0.5 MPa;

[0091] The intermediate was introduced into a two-stage adiabatic fixed-bed reactor and mixed with a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). A two-stage isomerization reaction was carried out under a second atmosphere to obtain 2-pentyl-2-cyclopentenone. The second atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen to hydrogen volume ratio of 40:1. The temperature of the two-stage isomerization reaction was 160°C, and the mass hourly space velocity (WHSV) of the intermediate was 1 h⁻¹. -1 The pressure of the two-stage isomerization reaction was 0.5 MPa; the gas discharge rate of the mixed gas after the two-stage isomerization reaction was 820 mL / min; the reaction results of the obtained 2-pentyl-2-cyclopentenone are shown in Table 1.

[0092] Comparative Example 1

[0093] A method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps:

[0094] Two-stage adiabatic fixed-bed reactors were used, each 1m in length and 25mm in inner diameter. The first-stage adiabatic fixed-bed reactor was loaded with 30g of a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3), and the second-stage adiabatic fixed-bed reactor was loaded with 30g of a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). Inert ceramic balls were placed at the top and bottom of the first composite catalyst and separated by quartz wool.

[0095] 2-Pentylcyclopentanone was introduced into an adiabatic fixed-bed reactor and mixed with a first composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). A first-stage isomerization reaction was carried out under a first atmosphere to obtain an intermediate. The first atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen-to-hydrogen volume ratio of 3:1. The temperature of the first-stage isomerization reaction was 120°C, and the mass hourly space velocity (WHSV) of 2-pentylcyclopentanone was 1.0 h⁻¹. -1 The pressure for one stage of the isomerization reaction is 0.2 MPa;

[0096] The intermediate was introduced into a two-stage adiabatic fixed-bed reactor and mixed with a second composite catalyst (5% Pd / 3% phosphorus-modified Al2O3). A two-stage isomerization reaction was carried out under a second atmosphere to obtain 2-pentyl-2-cyclopentenone. The second atmosphere was a mixture of nitrogen and hydrogen, with a nitrogen to hydrogen volume ratio of 3:1. The temperature of the two-stage isomerization reaction was 140°C, and the mass hourly space velocity (WHSV) of the intermediate was 1 h⁻¹. -1 The pressure of the two-stage isomerization reaction was 0.2 MPa; the gas discharge rate of the mixed gas after the two-stage isomerization reaction was 820 mL / min; the reaction results of the obtained 2-pentyl-2-cyclopentenone are shown in Table 1.

[0097] Table 1. Reaction results of Examples 1-6 and Comparative Example 1

[0098]

[0099] As can be seen from Table 1, the preparation method provided by the present invention employs two-stage hydrogenation and controls the volume ratio of hydrogen to nitrogen in the two-stage hydrogenation, which can significantly improve the selectivity and yield of the product, making the conversion rate of raw materials >98% and the yield of the product >95%. Compared with Comparative Example 1, which uses two-stage hydrogenation without controlling the volume ratio of hydrogen to nitrogen, the selectivity and yield of the product are significantly improved. This is because the present invention uses two-stage hydrogenation and controls the volume ratio of hydrogen to nitrogen to suppress the synthesis of by-products, keeping the content of by-products below 3%.

[0100] Furthermore, the preparation method provided by this invention does not require the use of corrosive catalysts such as hydrobromic acid and hydrochloric acid, has low corrosivity to equipment, does not require the use of solvents, generates little wastewater, and is a green and environmentally friendly process that can be continuously produced and has high industrial value.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing 2-pentyl-2-cyclopentenone, comprising the following steps: 2-Pentylcyclopentanone was mixed with a first composite catalyst and subjected to an isomerization reaction under a first atmosphere to obtain an intermediate; the first atmosphere was a mixture of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen in the first atmosphere was 3 to 15:

1. The intermediate is mixed with a second composite catalyst and subjected to a two-stage isomerization reaction under a second atmosphere to obtain 2-pentyl-2-cyclopentenone; the second atmosphere is a mixture of nitrogen and hydrogen, and the volume ratio of nitrogen to hydrogen in the second atmosphere is 12 to 60:

1. The first composite catalyst and the second composite catalyst independently comprise a phosphorus-modified porous support and a transition metal supported on the phosphorus-modified porous support; The temperature of the second-stage isomerization reaction is 20–50°C higher than that of the first-stage isomerization reaction.

2. The preparation method according to claim 1, characterized in that, The mass hourly space velocity (HSV) of the 2-pentylcyclopentanone is 0.1–3 h⁻¹. -1 .

3. The preparation method according to claim 1, characterized in that, The temperature of the first-stage isomerization reaction is 100–200°C; the pressure of the first-stage isomerization reaction is 0.05–1 MPa.

4. The preparation method according to claim 1, characterized in that, The mass hourly space velocity of the intermediate is 0.1–3 h⁻¹. -1 .

5. The preparation method according to claim 1, characterized in that, The temperature of the two-stage isomerization reaction is 120–220°C; the pressure of the two-stage isomerization reaction is 0.05–1 MPa.

6. The preparation method according to claim 1, characterized in that, The transition metals in the first composite catalyst and the second composite catalyst independently include Pd and / or Pt.

7. The preparation method according to claim 1 or 6, characterized in that, The loading of transition metal in the first composite catalyst and the loading of transition metal in the second composite catalyst are independently 1 to 10 wt%.

8. The preparation method according to claim 1 or 6, characterized in that, The phosphorus-modified porous carrier includes one of phosphorus-modified alumina, phosphorus-modified activated carbon, phosphorus-modified molecular sieve, and phosphorus-modified diatomaceous earth.

9. The preparation method according to claim 1 or 6, characterized in that, The phosphorus content in the phosphorus-modified porous support is 0.5–5 wt%.

10. The preparation method according to claim 1, characterized in that, The apparatus for the first-stage isomerization reaction and the apparatus for the second-stage isomerization reaction are adiabatic fixed-bed reactors.

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