A method for continuously and stably producing diamondoids

Abstract

The present application relates to a kind of continuous stable production adamantane method.Firstly, bridge type tetrahydrodicyclopentadiene is mixed with reaction solvent uniformly, then it is impurity-removed by pretreatment, and then it flows into from the upper end of fixed bed reactor, and flows out from the lower end;In the fixed bed reactor, hydrogenation catalyst is loaded in the upper end, and isomerization catalyst is loaded in the lower end, by the protection of hydrogenation catalyst in the upper end to isomerization catalyst in the lower end, bridge type tetrahydrodicyclopentadiene can be converted into adamantane, process operation is simple, pollution-free, long-period continuous preparation adamantane can be realized, with actual industrial application prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing fine hydrocarbon chemicals, specifically a method for preparing adamantane. Background Technology

[0002] Adamantane (ADH) is a highly symmetrical polycyclic cage-like hydrocarbon compound with the molecular formula C6H2O. 10 H 16 It has the characteristics of high density, good thermal stability and fat solubility. The hydrogen atoms on its ring can undergo substitution and oxidation reactions, such as halogenation, nitration and sulfonation. It has a wide range of applications in the synthesis of pharmaceutical intermediates, development of new materials, preparation of lubricating oils and high-density liquid fuels.

[0003] Currently, the main methods for synthesizing adamantane include the aluminum trichloride method, molecular sieve method, superacid method, and ionic liquid method. In these methods, adamantane is mainly prepared by isomerization reaction of bridged tetrahydrodicyclopentadiene (endo-THDCPD) as the starting material. The main products involved in the reaction are adamantane and its isomer exo-tetrahydrodicyclopentadiene (exo-THDCPD). The specific reaction process is shown below.

[0004]

[0005] The reaction mechanism for preparing adamantane is an acid-catalyzed carbocation reaction, which requires an acid as a catalyst. During the reaction, olefin intermediates are also generated. Under strong acid catalysis, these olefin intermediates are prone to generating excessive tar-like byproducts, which compete with the formation of adamantane, resulting in low adamantane selectivity and severe material loss. However, when the acid strength used is insufficient or the reaction conditions are too mild, the formation of adamantane cannot be promoted either, resulting in the product mainly being the slightly isomerized tetrahydrodicyclopentadiene, and the adamantane selectivity is also low.

[0006] Among these methods, the aluminum trichloride method is characterized by high conversion rate and high selectivity, with a conversion rate exceeding 95% and a selectivity of up to 50%. The remainder is mainly tar products, making it the current industrial method for producing adamantane. However, this method is a batch process using a reactor, and it suffers from problems such as high toxicity, complex post-treatment, inability to recycle the catalyst, and large tar generation. This results in low overall adamantane production, high cost, and severe pollution, failing to meet the future trend of green and low-carbon chemical engineering. The article "Synthesis of adamantane on commercially available zeolitic catalysts, Applied Catalysis A:General, 2000, 127-132" studied the preparation of adamantane via endo-THDCPD isomerization catalyzed by different molecular sieves. With Hβ as the catalyst, the adamantane yield was 15.9%, but a large amount of tar was generated during the process, resulting in a yield of 60%, which does not have the potential for industrial application. The article "Synthesis of Adamantane on PW / USY Composite Catalyst, Journal of Higher Chemical Engineering, 2007, 127-132" discloses the use of a PW / USY catalyst supported on 10% phosphotungstic acid for the endo-THDCPD isomerization to adamantane, achieving a yield of 28.3%. However, this reaction is carried out in a reactor, and after each reaction, the surface of the PW / USY catalyst is covered with coke, requiring high-temperature calcination regeneration. Frequent regeneration makes continuous production impossible. Therefore, existing published literature has not yet achieved continuous preparation of adamantane, particularly failing to address the problem of catalyst deactivation due to coking. Suitable catalysts and supporting processes need to be developed. Summary of the Invention

[0007] This invention addresses the problem that existing industrial processes cannot continuously and stably produce adamantane by providing a method for continuous, long-term, and stable production of adamantane in a fixed-bed reactor.

[0008] This invention provides a method for the continuous and stable production of adamantane, comprising:

[0009] Bridged tetrahydrodicyclopentadiene and a reaction solvent are passed into a pretreatment reactor containing an adsorbent for pretreatment. The effluent then enters a fixed-bed reactor for hydroisomerization to obtain adamantane. In the fixed-bed reactor, the upper section is loaded with a hydrogenation protectant and the lower section is loaded with an isomerization catalyst. The hydrogenation reaction temperature in the upper section is 120℃-300℃, preferably 151℃-250℃, and more preferably 171℃-220℃. The isomerization reaction temperature in the lower section is 181℃-300℃, preferably 200℃-260℃.

[0010] After the reaction, the suspended tetrahydrodicyclopentadiene and the reaction solvent are separated to obtain adamantane concentrate. After cooling and crystallization, crude adamantane can be obtained. After recrystallization, a high-purity adamantane product can be obtained. The suspended tetrahydrodicyclopentadiene and the reaction solvent can be recycled. The whole process has a high atom utilization rate.

[0011] The bridged tetrahydrodicyclopentadiene can be prepared according to various methods disclosed in the prior art, or it can be commercially available.

[0012] The reaction solvent is a solvent with a boiling point of 40℃ to 300℃, such as cyclohexane, methylcyclohexane, dichloromethane, and bridging tetrahydrodicyclopentadiene, preferably C6-C10 hydrocarbons, such as cyclohexane, methylcyclohexane, and bridging tetrahydrodicyclopentadiene. After mixing with the reaction solvent, the mass concentration of bridging tetrahydrodicyclopentadiene is 10%-80%, preferably 30%-60%.

[0013] The function of the pretreatment reactor is to bring the adsorbent into contact with the reaction solvent, including but not limited to fixed-bed reactors or glass reaction tubes.

[0014] The adsorbent can be activated clay, NaY molecular sieve, activated carbon, etc., with activated clay and NaY molecular sieve being preferred.

[0015] The pretreatment temperature is room temperature to 60℃, the pretreatment pressure is 0.0-0.5 MPa, and the adsorbent space velocity is 0.1-10.0 h⁻¹. -1 Preferably 0.2-1h -1 .

[0016] The hydrogenation protectant is a conventional supported metal hydrogenation catalyst. The active metal is selected from one or more of the noble metals Pd, Pt, Ru, and Rh, and the non-noble metal Ni, preferably Ni, Pd, and Pt. The support is selected from non-acidic supports, such as Al2O3, SiO2, ZrO2, TiO2, CeO2, activated carbon, etc., preferably Al2O3 and SiO2. Based on the total mass of the hydrogenation protectant, the loading of non-noble metals is 1%-40%, preferably 5%-30%, more preferably 10%-20%; the loading of noble metals is 0.1%-10%, preferably 0.2%-5%, more preferably 0.3%-3%.

[0017] The isomerization catalyst is a molecular sieve-supported metal catalyst. The active metal is selected from one or more of the noble metals Pd, Pt, Ru, and Rh, and the non-noble metal Ni, with Pt and Pd being preferred. The molecular sieve is a Y-type molecular sieve, which can be selected from one or more of HY, USY, REHY, NTY, and SSY, with HY, USY, and REHY being preferred. Based on the total mass of the isomerization catalyst, the loading of non-noble metals is 1%-20%, preferably 3%-15%, and more preferably 5%-10%; the loading of noble metals is 0.05%-3%, preferably 0.1%-1.0%, and more preferably 0.2%-0.5%.

[0018] 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℃-120℃ for at least 12 hours, and then calcined in air at 450℃-550℃ for 2-5 hours. The calcined catalyst is then reduced in a reducing atmosphere such as hydrogen at 400℃-550℃ for 2-5 hours to obtain the activated catalyst.

[0019] In a fixed-bed reactor, the system reaction pressure is 0.1 MPa-3 MPa hydrogen, preferably 0.5 MPa-1.0 MPa hydrogen. The mass hourly space velocity (HSV) is 0.5 h⁻¹. -1 -5h -1 0.5h is preferred -1 -2h -1 The hydrogen-to-hydrogen volume ratio is 100-1600, preferably 600-1200.

[0020] In this invention, the role of the hydrogenation protectant is to remove trace amounts of olefins and other impurities and activated hydrogen from the raw material bridged tetrahydrodicyclopentadiene, thereby protecting the isomerization catalyst, inhibiting its coking, and extending its lifespan.

[0021] In this invention, the isomerization reaction is carried out by a metal / molecular sieve supported catalyst. This catalyst has a dual function of isomerization and coking inhibition. By loading metal onto the molecular sieve, the molecular sieve exhibits stable isomerization activity. The metal does not participate in the isomerization reaction, but rather inhibits the formation of coking precursors (olefin intermediates) during the reaction, thereby improving the catalyst lifetime.

[0022] The method of this invention uses bridged tetrahydrodicyclopentadiene as the reaction raw material. By pretreating the raw material and adding a hydrogenation protectant in the fixed-bed stage to protect the isomerization catalyst in the lower stage, the lifespan of the isomerization catalyst and the stability of the process are greatly improved. This method achieves green, continuous and stable preparation of adamantane with a conversion rate of up to 99% and a selectivity of up to 15.9% for the target product adamantane. It produces no tar, has high atom utilization, and can achieve continuous operation for more than 500 hours, showing promising prospects for industrial application. Detailed Implementation

[0023] The present invention provides a method for continuous and stable production of adamantane, comprising: firstly, mixing bridged tetrahydrodicyclopentadiene with a reaction solvent uniformly, and then passing it into a pretreatment reactor, where impurities are removed by adsorption of adsorbents such as activated clay and NaY, and then flowing into and out of a fixed-bed reactor from the upper end to the lower end. In the fixed-bed reactor, a hydrogenation protective agent is loaded in the upper section and separated by an inert material in the middle, and an isomerization catalyst is loaded in the lower section.

[0024] The upper hydrogenation reaction temperature is 120℃-300℃; the lower isomerization reaction temperature is 181℃-300℃. The entire fixed-bed reaction operates at a hydrogen pressure of 0.1MPa-3MPa and a mass hourly space velocity (WHSV) of 0.5h⁻¹. -1 -5h -1 The hydrogen-to-hydrogen volume ratio is 100-1600.

[0025] The inert material can be selected from SiO2, Al2O3, carbon materials, quartz sand, etc., with quartz sand being preferred.

[0026] According to the present invention, bridged tetrahydrodicyclopentadiene and the reaction solvent are uniformly premixed in a raw material tank, and then flowed from the top into a pretreatment reactor containing an adsorbent at room temperature and pressure. After impurity removal, the material flows out from the bottom and is then pumped to the top of a fixed-bed reactor, where it passes together with hydrogen through a reaction bed containing a hydrogenation protectant, inert material, and isomerization catalyst. The reaction product flows out from the bottom of the fixed bed. The product contains bridged tetrahydrodicyclopentadiene, adamantane, and other ring-opening byproducts, which can be separated to obtain adamantane.

[0027] The collected samples were analyzed by gas chromatography, and the reactant conversion rate and product selectivity were calculated using the area normalization method.

[0028] The following examples further illustrate specific implementations of the present invention.

[0029] In the following examples, the bridged tetrahydrodicyclopentadiene was purchased from Beijing Innocare Technology Co., Ltd.

[0030] In the following embodiments, quartz sand is used as an inert material to fill the space between the hydrogenation section and the isomerization section.

[0031] Examples 1-2 (Impact of Pretreatment Method)

[0032] In the pretreatment reactor, a methylcyclohexane solution containing 50 wt% bridged tetrahydrodicyclopentadiene was used as raw material, flowing through a pretreatment reactor packed with different adsorbents at ambient temperature and pressure, with a mass hourly space velocity (WHSV) of 0.5 h⁻¹. -1 The pretreated solution is then pumped into a fixed-bed reactor. In the fixed-bed reactor, a methylcyclohexane solution containing 50 wt% bridged tetrahydrodicyclopentadiene (pretreated with different methods) is used as the feedstock; 20 wt% Ni / SiO2 is used as the hydrogenation catalyst, with a hydrogenation reaction temperature of 200℃; 0.3 wt% Pt / HY is used as the isomerization catalyst, with an isomerization reaction temperature of 220℃. The overall fixed-bed reaction pressure is 0.5 MPa hydrogen, and the mass hourly space velocity (HSV) is 1 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio was 1000. After 50 hours of reaction, samples were taken for analysis to investigate the effect of pretreatment on catalyst activity. The results are shown in Table 1.

[0033] Table 1

[0034]

[0035] Examples 3-9 (Influence of Hydrogenation Protectants)

[0036] In the pretreatment reactor, a methylcyclohexane solution containing 50 wt% bridged tetrahydrodicyclopentadiene is used as raw material. After being premixed evenly, it is then subjected to NaY pretreatment to remove impurities.

[0037] In a fixed-bed reactor, 0.3 wt% Pt / HY was used as the isomerization catalyst, the isomerization reaction temperature was 220 °C, the composition of the hydrogenation protectant and the hydrogenation temperature are shown in Table 2, the reaction pressure was 0.5 MPa hydrogen gas, and the mass hourly space velocity was 1 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio was 1000. After 50 hours of reaction, samples were taken for analysis to investigate the effect of the hydrogenation protectant on the catalyst activity. The results are shown in Table 2.

[0038] Table 2

[0039]

[0040]

[0041] Examples 10-14 (Influence of Heterogeneous Catalysts)

[0042] In the pretreatment reactor, a methylcyclohexane solution containing 50 wt% bridged tetrahydrodicyclopentadiene is used as raw material. After being premixed evenly, it is then subjected to NaY pretreatment to remove impurities.

[0043] In a fixed-bed reactor, 20 wt% Ni / SiO2 was used as the hydrogenation protection catalyst. The reaction temperature was 200 °C, the isomerization temperature was 220 °C, and the composition of the isomerization protection agent is shown in Table 3. The reaction pressure was 0.5 MPa, the hydrogen gas pressure was 1 h⁻¹, and the mass hourly space velocity (WHSV) was 1 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio was 1000. After 50 hours of reaction, samples were taken for analysis to investigate the effect of the isomeric catalyst composition on the catalyst activity. The results are shown in Table 3.

[0044] Table 3

[0045]

[0046] Examples 15-17 (Effect of isomerization reaction temperature)

[0047] Using a methylcyclohexane solution containing 50 wt% bridged tetrahydrodicyclopentadiene as raw material, the mixture was pre-mixed and then pretreated with NaY to remove impurities. 20 wt% Ni / SiO2 was used as the hydrogenation protectant, and the hydrogenation temperature was 200℃. 0.3 wt% Pt / HY was used as the isomerization catalyst. The entire fixed-bed reaction was carried out at a hydrogen pressure of 0.5 MPa and a mass hourly space velocity (WHSV) of 1 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio was 1000. After 10 hours of reaction, samples were taken for analysis to investigate the effect of the isomerization reaction temperature. The results are shown in Table 4.

[0048] Table 4

[0049]

[0050]

[0051] Examples 18-21 (Effect of Reaction Pressure)

[0052] Using a methylcyclohexane solution containing 50 wt% bridged tetrahydrodicyclopentadiene as raw material, the mixture was pre-mixed and then pretreated with NaY to remove impurities. 20 wt% Ni / SiO2 was used as the hydrogenation protectant, and the hydrogenation temperature was 200℃. 0.3 wt% Pt / HY was used as the isomerization catalyst, and the isomerization reaction temperature was 220℃ with a mass hourly space velocity (WHSV) of 1 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio was 1000. After 10 hours of reaction, samples were taken for analysis to investigate the effect of hydrogen pressure on the system reaction. The results are shown in Table 5.

[0053] Table 5

[0054]

[0055] Examples 22-25 (Influence of Mass Hourly Velocity)

[0056] A methylcyclohexane solution containing 50 wt% bridged tetrahydrodicyclopentadiene was used as the raw material. After pre-mixing and homogenization, impurities were removed through NaY pretreatment. 20 wt% Ni / SiO2 was used as the hydrogenation protectant, and the hydrogenation section temperature was 200 °C. 0.3 wt% Pt / HY was used as the isomerization catalyst, and the isomerization section reaction temperature was 220 °C. The entire fixed-bed reaction pressure was 0.5 MPa hydrogen, and the hydrogen-to-hydrocarbon volume ratio was 1000. Samples were taken for analysis after 10 h of reaction to investigate the effect of reaction space velocity. The results are shown in Table 6.

[0057] Table 6

[0058]

[0059] Examples 26-28 (Effect of Hydrogen-to-Hydrogen Volume Ratio)

[0060] Using a methylcyclohexane solution containing 50 wt% bridged tetrahydrodicyclopentadiene as raw material, the mixture was pre-mixed and then pretreated with NaY to remove impurities. 20 wt% Ni / SiO2 was used as the hydrogenation protectant, and the hydrogenation temperature was 200℃. 0.3 wt% Pt / HY was used as the isomerization catalyst, and the isomerization reaction temperature was 220℃. The entire fixed-bed reaction pressure was 0.5 MPa, and the hydrogen gas mass hourly space velocity (HHSV) was 1 h⁻¹. -1 After a 10-hour reaction, samples were taken for analysis to investigate the effect of the hydrogen-to-hydrogen volume ratio. The results are shown in Table 7.

[0061] Table 7

[0062]

[0063] Examples 29-32 (Influence of reaction solvent and raw material mass concentration)

[0064] Using bridged tetrahydrodicyclopentadiene solutions of varying mass concentrations as raw materials, the mixture was pre-mixed and then pretreated with NaY to remove impurities. 20 wt% Ni / SiO2 was used as the hydrogenation protectant, and the hydrogenation section temperature was 200℃. 0.3 wt% Pt / HY was used as the isomerization catalyst, and the isomerization section reaction temperature was 220℃. The entire fixed-bed reaction pressure was 0.5 MPa hydrogen gas, and the mass hourly space velocity (WHSV) was 1 h⁻¹. -1 The hydrogen-to-hydrogen volume ratio was 1000. After 10 hours of reaction, samples were taken for analysis to investigate the effects of different reaction solvents and raw material concentrations. The results are shown in Table 8.

[0065] Table 8

[0066]

[0067] Example 33 (System Stability Test)

[0068] Extending the operating cycle of Example 1 (pretreated with NaY) to 500 hours, we found that the endo-THDCPD conversion rate was 99%, the exo-THDCPD selectivity was 71.2%, the adamantane selectivity was 14.9%, and the ring-opening byproduct selectivity was 13.9%, indicating that the system has good stability, effectively improves the catalyst coking problem, and has industrial application prospects.

Claims

1. A method for the continuous and stable production of adamantane, comprising: Bridged tetrahydrodicyclopentadiene and reaction solvent are passed into a pretreatment reactor containing adsorbent for pretreatment. The effluent is then fed into a fixed-bed reactor for hydroisomerization to obtain adamantane. In the fixed-bed reactor, the upper section is loaded with a hydrogenation protective agent, and the lower section is loaded with an isomerization catalyst. The hydrogenation reaction temperature in the upper section is 120℃-300℃, and the isomerization reaction temperature in the lower section is 181℃-300℃. The adsorbent is selected from activated clay and NaY molecular sieve. The pretreatment temperature is room temperature-60℃, the pretreatment pressure is 0.0-0.5MPa, and the adsorbent space velocity is 0.1-10.0 h⁻¹. -1 The active metal of the hydrogenation protective agent is selected from one or more of the noble metals Pd, Pt, Ru, Rh and the non-noble metal Ni. The support is selected from Al2O3, SiO2, ZrO2, TiO2, CeO2, and activated carbon. The isomerization catalyst is a molecular sieve supported metal catalyst, with the active metal selected from one or more of the noble metals Pd, Pt and the non-noble metal Ni. The molecular sieve is a Y-type molecular sieve selected from HY, USY, REHY, NTY, and SSY. In the fixed-bed reactor, the system reaction pressure is 0.1 MPa-3 MPa hydrogen gas, and the mass hourly space velocity is 0.5 h⁻¹. -1 -5h -1 The hydrogen-to-hydrogen volume ratio is 100-1600, and the reaction solvent is selected from C6-C10 hydrocarbons.

2. The method according to claim 1, wherein, The upper hydrogenation reaction temperature is 151℃-250℃; the lower isomerization reaction temperature is 200℃-260℃.

3. The method according to claim 1, wherein, After the bridged tetrahydrodicyclopentadiene is mixed with the reaction solvent, the mass concentration of the bridged tetrahydrodicyclopentadiene is 10%-80%.

4. The method according to claim 1, wherein, After the bridged tetrahydrodicyclopentadiene is mixed with the reaction solvent, the mass concentration of the bridged tetrahydrodicyclopentadiene is 30%-60%.

5. The method according to claim 1, wherein, The pretreatment reactor is a fixed-bed reactor or a glass reaction tube.

6. The method according to claim 1, wherein, The adsorbent is used to treat space velocities of 0.2-1 h⁻¹. -1 .

7. The method according to claim 1, wherein, The active metal of the hydrogenation protective agent is selected from Ni, Pd, and Pt; the support is selected from Al2O3 and SiO2.

8. The method according to claim 1, wherein, Based on the total mass of the hydrogenation protectant, the loading of non-precious metals is 1%-40%, and the loading of precious metals is 0.1%-10%.

9. The method according to claim 1, wherein, Based on the total mass of the hydrogenation protectant, the loading of non-precious metals is 5%-30%, and the loading of precious metals is 0.2%-5%.

10. The method according to claim 1, wherein, Based on the total mass of the hydrogenation protectant, the loading of non-precious metals is 10%-20%, and the loading of precious metals is 0.3%-3%.

11. The method according to claim 1, wherein, Based on the total mass of the isomerization catalyst, the loading of non-precious metals is 1%-20%, and the loading of precious metals is 0.05%-3%.

12. The method according to claim 1, wherein, Based on the total mass of the isomerization catalyst, the loading of non-precious metals is 3%-15%, and the loading of precious metals is 0.1%-1.0%.

13. The method according to claim 1, wherein, Based on the total mass of the isomerization catalyst, the loading of non-precious metals is 5%-10% and the loading of precious metals is 0.2%-0.5%.

14. The method according to claim 1, wherein, In a fixed-bed reactor, the system reaction pressure is 0.5 MPa-1.0 MPa hydrogen gas.

15. The method according to claim 1, wherein, In a fixed-bed reactor, the mass hourly space velocity is 0.5 h⁻¹. -1 -2h -1 The hydrogen-to-hydrogen volume ratio is 600-1200.

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