Process for the preparation of a hanging tetrahydrodicyclopentadiene in one step

Abstract

The present application relates to a kind of by dicyclopentadiene one-step preparation method of hanging type tetrahydrodicyclopentadiene, comprising: dicyclopentadiene and reaction solvent are added to fixed bed reactor, in the presence of molecular sieve supported metal catalyst, dicyclopentadiene is continuously carried out hydrogenation and isomerization reaction, and is converted into hanging type tetrahydrodicyclopentadiene.This method can be continuously prepared by dicyclopentadiene one-step hanging type tetrahydrodicyclopentadiene, compared with the common hydrogenation first, then isomerization two-step conversion method, process flow is simplified, the demand for device investment is reduced, and only one catalyst can be completed conversion, while reaction condition is mild, and reaction product yield is higher.

Description

Technical Field

[0001] This invention relates to a method for preparing hydrocarbons, specifically a method for preparing tetrahydrodicyclopentadiene. Background Technology

[0002] Dicyclopentadiene (DCPD) is mainly derived from the C5 fraction of petroleum cracking for ethylene production and the light benzene fraction of coal coking. It is a dimer of cyclopentadiene and an important chemical intermediate widely used in the synthesis of unsaturated polyester polymers, the preparation of high-density aviation fuels, and the production of medical materials. Its fully hydrogenated product, bridged tetrahydrodicyclopentadiene (Endo-THDCPD), is a high-performance solid high-density fuel and can be further isomerized into hanging tetrahydrodicyclopentadiene (Exo-THDCPD).

[0003]

[0004] Exo-THDCPD, also known as JP-10, can be used alone or in combination. It has a relatively high density (0.94 g / cm³). -3 Exo-THDCPD has advantages such as a low freezing point (-79℃), high volumetric calorific value (39.4 MJ / L), and low toxicity, making it suitable for use in aviation fuel. The common Exo-THDCPD preparation process involves a two-step conversion: first, DCPD is hydrogenated to produce bridged tetrahydrodicyclopentadiene (Endo-THDCPD), which is then isomerized to Exo-THDCPD. Furthermore, the isomerization process is carried out intermittently using highly toxic and polluting AlCl3 as a catalyst, making continuous production impossible, as described in patent CN 102924216B. This results in low Exo-THDCPD yield and high cost, limiting its large-scale application. Other patents, such as CN 101244978A, disclose methods using solid inorganic acids as isomerization catalysts, which often require two solid-bed reactors and two catalysts—a hydrogenation catalyst and an isomerization catalyst—leading to high equipment investment requirements, the need for two catalysts, and a complex process flow. Summary of the Invention

[0005] This invention addresses the problems of the existing two-step method for preparing tetrahydrodicyclopentadiene from dicyclopentadiene, which involves hydrogenation followed by isomerization, by providing a one-step method for preparing tetrahydrodicyclopentadiene.

[0006] The present invention provides a one-step method for preparing hanging tetrahydrodicyclopentadiene, comprising: adding dicyclopentadiene and a reaction solvent into a fixed-bed reactor, and in the presence of a molecular sieve supported metal catalyst, continuously subjecting dicyclopentadiene to hydrogenation and isomerization reactions to convert it into hanging tetrahydrodicyclopentadiene.

[0007] The reaction temperature is 100℃-200℃, preferably 120℃-160℃.

[0008] The reaction pressure is 0.5MPa-5MPa, preferably 1.0MPa-3.0MPa.

[0009] The mass hourly space velocity is 0.5 h. -1 -5h -1 1 hour preferred -1 -3h -1 .

[0010] The hydrogen-to-hydrogen volume ratio is 400-1600, preferably 600-1200.

[0011] The molecular sieve supported metal catalyst comprises an active metal and a molecular sieve support. The active metal is selected from one or more of Pd, Pt, Ru, Rh, and Ni, with Pd and Pt being preferred. When the active metal is a noble metal such as Pd, Pt, Ru, or Rh, the loading is 0.1% to 5.0%, preferably 0.3% to 0.6%. When the active metal is a non-noble metal, the loading is 2% to 15%, preferably 5% to 10%. The molecular sieve support is preferably a Y-type molecular sieve, such as HY, USY, REHY, NEY, or SSY, with HY, REHY, and USY being preferred.

[0012] The molecular sieve-supported metal catalyst can be prepared using conventional methods, such as equal-volume impregnation or excess-volume impregnation. Specifically, a certain amount of metal precursor solution is prepared according to the metal loading, then impregnated onto the molecular sieve. The solution is allowed to stand at room temperature for at least 6 hours with intermittent stirring. It is then dried at 80°C for at least 12 hours, and then calcined in air at 450°C-550°C for 2-5 hours. The calcined catalyst is then reduced in a reducing atmosphere such as hydrogen at 400°C-550°C for 2-5 hours to obtain the activated catalyst.

[0013] The reaction solvent is a hydrocarbon with a boiling point of 40℃ to 200℃, such as cyclohexane, methylcyclohexane, dichloromethane, etc., preferably C6-C10 hydrocarbons, such as cyclohexane and methylcyclohexane; after dicyclopentadiene is mixed with the reaction solvent, the mass concentration of dicyclopentadiene is 10%-50%, preferably 15%-30%.

[0014] The molecular sieve-supported metal catalyst is a bifunctional catalyst for hydrogenation and isomerization. This catalyst can simultaneously catalyze two reactions: hydrogenation and isomerization. The metal catalyzes the hydrogenation process, while the molecular sieve catalyzes the isomerization process.

[0015] The method of this invention utilizes a hydrogenation-isomerization bifunctional catalyst to simultaneously replace common hydrogenation catalysts and isomerization catalysts, thereby replacing the two-step conversion method of first hydrogenating and then isomerizing dicyclopentadiene. This achieves one-step continuous preparation of hanging tetrahydrodicyclopentadiene, reduces the investment requirements for equipment, lowers operating costs, simplifies the entire process, and at the same time, the reaction conditions are mild and the product yield is high. Detailed Implementation

[0016] The following examples further illustrate specific implementations of the present invention.

[0017] In the following embodiments, the hydro-isomerization bifunctional catalyst was placed in the middle section of a fixed bed. Dicyclopentadiene and the reaction solvent were uniformly premixed in a feed tank and then pumped to the top of the fixed bed reactor. Subsequently, the reaction products flowed out from the bottom of the fixed bed. Hydrogen gas entered the fixed bed reactor from the top of the fixed bed along with the reaction liquid, and the gas flow rate was controlled by a mass flow meter. After the system stabilized for 10 hours, samples were collected for gas chromatography analysis, and the reactant conversion rate and product selectivity were calculated using the area normalization method.

[0018] Examples 1-7 (Influence of different loaded metals)

[0019] The reaction was carried out using a methylcyclohexane solution containing 20 wt% dicyclopentadiene as the raw material; REHY was used as the catalyst support, and the loading amounts of noble metals Pd, Pt, and Ru and non-noble metal Ni are shown in Table 1 below; the reaction temperature was 150 °C, the reaction pressure was 2 MPa, and the mass hourly space velocity was 1 h⁻¹. -1 With a hydrogen-to-hydrogen volume ratio of 1000, the effects of the type and amount of loaded metal on the DCPD conversion and the selectivity of Exo-THDCPD were investigated.

[0020] Table 1

[0021]

[0022]

[0023] The table shows that for the noble metals Pt, Pd, and Ru, Pt and Pd exhibit the best catalytic performance at a loading of 0.3 wt%, with DCPD conversions exceeding 90 wt% and the target product Exo-THDCPD selectivity reaching over 79 wt%. When the Pt loading is reduced to 0.2 wt%, a significant decrease in DCPD conversion is observed, indicating a decline in hydrogenation capacity due to the reduced loading. Increasing the Pt loading to 0.5 wt% results in a slight increase in DCPD conversion, but a slight decrease in Exo-THDCPD selectivity. This indicates that the increased loading enhances hydrogenation capacity, leading to a higher DCPD conversion, but the increased metal loading covers more acidic sites on the molecular sieve, reducing the isomerization capacity of the hydro-isomerization bifunctional catalyst. For the non-noble metal Ni, it was found that with a loading of 5 wt%, the DCPD conversion was 83 wt%, which was weaker than that of Pt and Pd. Furthermore, due to the high loading, more of the REHY acid sites were covered, weakening the isomerization ability and reducing the selectivity of the target product Exo-THDCPD. Increasing the Ni loading to 10 wt% did increase the DCPD conversion, but the isomerization ability was even weaker; therefore, the loading should not be too high.

[0024] Examples 2-10 (Influence of Different Carriers)

[0025] The reaction was initiated using a methylcyclohexane solution containing 20 wt% dicyclopentadiene; Pt was used as the metal element with a loading of 0.3 wt%; and common commercially available REHY, USY, HY, ZSM-5, and Hβ were used as isomerization supports. The reaction temperature was 150 °C, the reaction pressure was 2 MPa, and the mass hourly space velocity (HHSV) was 1 h⁻¹. -1 The effect of support type on DCPD conversion and Exo-THDCPD selectivity was investigated with a hydrogen-to-hydrogen volume ratio of 1000. The results are shown in Table 2.

[0026] Table 2

[0027]

[0028]

[0029] As can be seen from Table 2, compared with Y-type molecular sieves including REHY, USY, and HY, the hydrogenation-isomerization bifunctional catalysts supported by comparative examples D1 ZSM-5 and D2 Hβ have similar hydrogenation capabilities, but their isomerization capabilities are significantly weaker than those of Y-type molecular sieves. This is mainly related to the topological structure of the molecular sieves themselves, including the spatial structure and pore size of the pores.

[0030] Example 3 (Effect of different reaction temperatures)

[0031] The reaction was carried out using a methylcyclohexane solution containing 20 wt% dicyclopentadiene as the raw material; REHY was used as the catalyst support, and Pt was used as the elemental metal with a loading of 0.3 wt%; the reaction pressure was 2 MPa and the mass hourly space velocity was 1 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio was 1000, and the effect of reaction temperature on DCPD conversion and Exo-THDCPD selectivity was investigated. The results are shown in Table 3.

[0032] Table 3

[0033]

[0034] As can be seen from Table 3, when the reaction temperature is below 120℃, the DCPD conversion rate and Exo-THDCPD selectivity are both low. When the reaction temperature reaches 180℃, the by-products increase significantly. Therefore, the reaction temperature should not be too low or too high, and 120℃-160℃ is preferred.

[0035] Example 4 (Effect of different reaction pressures)

[0036] The reaction was carried out using a methylcyclohexane solution containing 20 wt% dicyclopentadiene as the raw material; REHY was used as the catalyst support, and Pt was used as the elemental metal with a loading of 0.3 wt%; the reaction temperature was 150 °C, and the mass hourly space velocity was 1 h⁻¹. -1 The effect of reaction pressure on DCPD conversion and Exo-THDCPD selectivity was investigated with a hydrogen-to-hydrogen volume ratio of 1000. The results are shown in Table 4.

[0037] Table 4

[0038]

[0039] As shown in Table 4, when the reaction pressure is 1 MPa, the DCPD conversion rate is 81 wt%. This is mainly because the reaction pressure is too low at this point to allow for more DCPD conversion. When the reaction pressure is increased to 3 MPa, DCPD has a higher conversion rate, but the selectivity of Exo-THDCPD decreases slightly compared to 2 MPa, while the selectivity of by-products increases slightly. When the reaction pressure is further increased to 4 MPa, the selectivity of Exo-THDCPD decreases further, while the selectivity of ring-opening by-products increases further. This is mainly because increasing the hydrogen pressure is beneficial for the hydrogenation conversion of DCPD, but it also promotes the formation of ring-opening by-products. Therefore, the preferred reaction pressure is 1.0 MPa-3.0 MPa.

[0040] Example 5 (Effect of different mass air velocities)

[0041] A methylcyclohexane solution containing 20 wt% dicyclopentadiene was used as the raw material; REHY was used as the catalyst support; Pt was used as the metal element with a loading of 0.3 wt%; the reaction temperature was 150 °C, the reaction pressure was 2 MPa, and the hydrogen-to-hydrocarbon volume ratio was 1000. The effects of mass hourly space velocity (MHV) on DCPD conversion and Exo-THDCPD selectivity were investigated. The results are shown in Table 5.

[0042] Table 5

[0043]

[0044] As can be seen from Table 5, when the mass hourly space velocity is 0.5 h⁻¹ -1 At this time, the material residence time in the reaction is longer, resulting in a higher DCPD conversion rate, but at the same time, the amount of deep reaction byproducts increases, which affects the selectivity of Exo-THDCPD; when the space velocity is increased to 4.0 h⁻¹, the reaction is more efficient. -1 At that time, due to the significant decrease in material residence time, the DCPD conversion rate decreased to 71%, and the Exo-THDCPD selectivity also decreased to 68%. Therefore, the optimal mass hourly space velocity (MHSV) was 1.0 h⁻¹. -1 -3.0h -1 .

[0045] Example 6 (Effect of different hydrogen-to-hydrogen volume ratios)

[0046] The reaction was carried out using a methylcyclohexane solution containing 20 wt% dicyclopentadiene as the raw material; REHY was used as the catalyst support, and Pt was used as the elemental metal with a loading of 0.3 wt%; the reaction temperature was 150 °C, the reaction pressure was 2 MPa, and the mass hourly space velocity was 1 h⁻¹. -1 The effect of hydrogen-to-hydrogen volume ratio on DCPD conversion and Exo-THDCPD selectivity was investigated. (See Table 6.)

[0047] Table 6

[0048]

[0049]

[0050] As can be seen from Table 6, when the hydrogen-to-hydrocarbon volume ratio is 400, the DCPD conversion rate is low, and the Exo-THDCPD selectivity is also low. When the hydrogen-to-hydrocarbon volume ratio is increased to 1000, both the DCPD conversion rate and the Exo-THDCPD conversion rate increase to a certain extent. When it is further increased to 1600, the effect is not obvious. However, further increasing the hydrogen-to-hydrocarbon ratio will lead to excessive waste of hydrogen and increase costs. Therefore, the hydrogen-to-hydrocarbon volume ratio is preferably 600-1200.

[0051] Example 7 (Effect of different solvents and solvent ratios)

[0052] A 20 wt% dicyclopentadiene reaction solution was prepared using methylcyclohexane, cyclohexane, dichloromethane, and isopropanol as reaction solvents. Different concentrations of dicyclopentadiene reaction solutions were then prepared using methylcyclohexane as the reaction solvent. REHY was used as the catalyst support, and Pt was used as the elemental metal with a loading of 0.3 wt%. The reaction temperature was 150 °C, the reaction pressure was 2 MPa, and the mass hourly space velocity (H₂S₀) was 1 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio was 1000. The effects of different solvents and solvent ratios were investigated. As shown in Table 7.

[0053] Table 7

[0054]

[0055]

[0056] As shown in the table, methylcyclohexane, cyclohexane, and dichloromethane have similar DCPD conversion rates and Exo-THDCPD yields. However, dichloromethane is a chlorine-containing solvent, which may cause certain environmental problems. Isopropanol has a high DCPD conversion rate when used as a solvent, but it does not exhibit isomerization activity. Therefore, methylcyclohexane and cyclohexane are preferred. When the DCPD concentration is reduced, the DCPD conversion rate and Exo-THDCPD selectivity decrease slowly. At the same time, excessively reducing the DCPD concentration will increase the amount of solvent used, which will lead to serious energy consumption problems in the subsequent separation process. When the DCPD concentration is increased, the DCPD conversion rate increases to a certain extent. However, since the hydrogenation process of DCPD is a strongly exothermic process, a certain amount of solvent is needed to remove some of the heat. The DCPD concentration should not be too high, otherwise it will cause local overheating of the catalyst and affect the catalytic activity. Therefore, the preferred DCPD mass concentration is 15wt%-30wt%.

Claims

1. A one-step method for preparing tetrahydrodicyclopentadiene, comprising: Dicyclopentadiene and a reaction solvent are added to a fixed-bed reactor. In the presence of a molecular sieve-supported metal catalyst, dicyclopentadiene undergoes continuous hydrogenation and isomerization reactions to convert into hanging tetrahydrodicyclopentadiene. The molecular sieve-supported metal catalyst is placed in the middle of the fixed bed. Dicyclopentadiene and the reaction solvent are uniformly premixed in a feed tank and then pumped to the upper end of the fixed-bed reactor. Subsequently, the reaction product flows out from the lower end of the fixed bed, and hydrogen gas enters the fixed-bed reactor from the upper end of the fixed bed along with the reaction liquid. The reaction temperature is 100℃-200℃, and the reaction pressure is 0.5MPa-5.0MPa. The active metal of the molecular sieve-supported metal catalyst is selected from one or more of Pd, Pt, and Ru, with a loading of 0.3%-0.6%. The molecular sieve is selected from HY, REHY, and USY molecular sieves.

2. The method according to claim 1, wherein, The reaction solvent is a hydrocarbon with a boiling point of 40℃ to 200℃.

3. The method according to claim 1, wherein, The reaction solvent is a C6-C10 hydrocarbon.

4. The method according to claim 1, wherein, The reaction solvent is selected from cyclohexane and methylcyclohexane.

5. The method according to claim 1, wherein, When dicyclopentadiene is mixed with the reaction solvent, the mass concentration of dicyclopentadiene is 10%-50%.

6. The method according to claim 1, wherein, When dicyclopentadiene is mixed with the reaction solvent, the mass concentration of dicyclopentadiene is 15%-30%.

7. The method according to claim 1, wherein, The loading of active metals is 0.3% to 0.5%.

8. The method according to claim 1, wherein, The reaction temperature is 120℃-160℃.

9. The method according to claim 1, wherein, The reaction pressure is 1.0 MPa-3.0 MPa.

10. The method according to claim 1, wherein, Mass hourly space velocity is 0.5 h. -1 -5h -1 .

11. The method according to claim 1, wherein, Mass air velocity is 1h -1 -3h -1 .

12. The method according to claim 1, wherein, The hydrogen-to-hydrogen volume ratio is 400-1600.

13. The method according to claim 1, wherein, The hydrogen-to-hydrogen volume ratio is 600-1200.

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