Cyclododecatriene hydrogenation method

Abstract

The invention relates to a cyclododecatriene hydrogenation method, which comprises: in the presence of hydrogen, contacting cyclododecatriene with a hydrogenation catalyst to carry out a hydrogenation reaction, wherein the hydrogenation reaction is sequentially carried out in n stages of slurry bed reactors which are connected in series, and hydrogen partial pressures in the n stages of slurry bed reactors are sequentially reduced along the flowing direction of materials; the hydrogenation catalyst is a heterogeneous catalyst. According to the cyclododecatriene hydrogenation method disclosed by the invention, the raw material conversion rate and the cyclododecene selectivity can be remarkably improved, the reaction time is shortened, the energy consumption and the operation cost are reduced, and industrial batch production is favorably realized.

Description

Technical Field

[0001] This disclosure relates to a method for hydrogenating cyclododecanetriene. Background Technology

[0002] Cyclododecene is an important raw material and synthetic intermediate for the preparation of cyclododecone and its derivatives, such as macrocyclic musk and nylon 12. Currently, the synthesis of cyclododecene mainly involves the hydrogenation reaction of cyclododecanetriene. However, the hydrogenation process of cyclododecanetriene can produce dozens of isomers, derivatives, and cracking products. Improving the selectivity of cyclododecene is crucial for its efficient synthesis. Existing technologies primarily achieve this through catalyst design and process parameter optimization, but the overall production efficiency is low, and the selectivity and yield of cyclododecene are difficult to further improve, failing to meet the demands of large-scale continuous production. Summary of the Invention

[0003] The purpose of this disclosure is to provide a method for hydrogenating cyclododecanetrienes to achieve efficient and highly selective production of cyclododecanes.

[0004] To achieve the above objectives, this disclosure provides a method for hydrogenating cyclododecanetriene, the method comprising: In the presence of hydrogen, cyclododecanetriene is brought into contact with a hydrogenation catalyst to undergo a hydrogenation reaction, yielding cyclododecene. The hydrogenation reaction is carried out sequentially in n-stage slurry bed reactors connected in series, and the hydrogen partial pressure in the n-stage slurry bed reactors decreases sequentially along the flow direction of the reactants; the hydrogenation catalyst is a heterogeneous catalyst.

[0005] Heterogeneous catalysis offers advantages such as easy catalyst recovery and low cost. For the selective hydrogenation of cyclododecanetriene to cyclododecene using heterogeneous catalysis, palladium-based catalysts exhibit superior performance. The literature *Ind. End. Chem. Res.*, 42 (2003), 6-13, investigated the hydrogenation reaction of cyclododecanetriene using an upflow fixed-bed reactor loaded with 0.5% Pd / Al₂O₃ catalyst. By optimizing parameters such as temperature, hydrogen partial pressure, feed rate, and hydrogen flow rate, 90% selectivity for cyclododecene was achieved. However, due to the high exothermic reaction of cyclododecanetriene hydrogenation, the fixed-bed reactor is prone to bed runaway. Patents US3400164, US3400166, and GB19680712 disclose a method for preparing cyclododecane by hydrogenation of cyclododecanetriene using a discontinuous pressure fractionation process. This method uses 5% Pd / C as a catalyst and achieves a cyclododecane selectivity of up to 94%. However, this discontinuous production method involves the separation of slurry and catalyst, requiring the design of a filtration unit after the reaction to obtain the product. Furthermore, the energy consumption is higher than that of continuous production, which is not conducive to industrial production.

[0006] Optionally, the number of stages n in the n-stage slurry bed reactor is 2 to 4.

[0007] Optionally, in the n-stage slurry bed reactor, along the flow direction of the reactants, the hydrogen partial pressure in the first-stage slurry bed reactor is 0.15~0.4 MPa, the hydrogen partial pressure in the second-stage slurry bed reactor is 0.03~0.1 MPa, and when n>2, the hydrogen partial pressure P in the nth-stage slurry bed reactor is... n Satisfying 0.15≤P n / P n-1 ≤0.5.

[0008] Optionally, the reaction time of the reactants in the first-stage slurry bed reactor is 20-60 min, and the reaction time in the second-stage slurry bed reactor is 5-34 min. When n>2, the reaction time in the nth-stage slurry bed reactor is... t n Satisfying 0.2≤ t n / t n-1 ≤1.6.

[0009] Optionally, the temperature of the hydrogenation reaction is 60~180℃.

[0010] Optionally, the slurry bed reactor is a batch reactor and / or a tubular reactor.

[0011] Optionally, the weight ratio of the cyclododecanetriene to the hydrogenation catalyst is 100:(2.5~7).

[0012] Optionally, the hydrogenation catalyst includes a support and an active metal component, wherein the active metal component includes palladium.

[0013] Optionally, the content of the active metal component is 0.1 to 10% by weight, based on the dry weight of the hydrogenation catalyst.

[0014] Optionally, the particle size of the hydrogenation catalyst is 0.1~200µm.

[0015] Through the above technical solution, the hydrogenation method of cyclododecanetriene disclosed herein adopts a multi-stage slurry bed reactor, and the hydrogen partial pressure in the multi-stage slurry bed reactor decreases sequentially. Combined with a heterogeneous hydrogenation catalyst, it can not only significantly improve the feed conversion rate and cyclododecane selectivity, but also greatly shorten the reaction time, reduce energy consumption and operating costs, which is conducive to realizing industrial mass production.

[0016] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of a specific implementation method for hydrogenating cyclododecanetriene.

[0018] Explanation of reference numerals in the attached figures 10—Cyclododecanetriene, 21—First-stage hydrogen, 22—Second-stage hydrogen, 23—Third-stage hydrogen, 30—Cyclododecene, T1—First-stage slurry bed reactor, T2—Second-stage slurry bed reactor, T3—Third-stage slurry bed reactor. Detailed Implementation

[0019] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0020] This disclosure provides a method for hydrogenating cyclododecanetriene, the method comprising: contacting cyclododecanetriene with a hydrogenation catalyst in the presence of hydrogen to carry out a hydrogenation reaction to obtain cyclododecene; wherein the hydrogenation reaction is carried out sequentially in n-stage slurry bed reactors connected in series, and the hydrogen partial pressure in the n-stage slurry bed reactors decreases sequentially along the flow direction of the reactants; the hydrogenation catalyst is a heterogeneous catalyst.

[0021] In industrial applications, the hydrogenation of cyclododecanetrienes often employs fixed-bed reactors, which suffer from poor heat transfer and uneven bed temperature. This disclosure utilizes a multi-stage slurry-bed reactor combined with a step-by-step depressurization reaction method. This avoids the problem of uneven heat distribution within the catalyst bed. Furthermore, as the proportion of cyclododecane in the reactants increases with the reaction, it effectively slows down the rate of further conversion of cyclododecane to cyclododecane, thus preventing over-hydrogenation. This significantly improves the selectivity and yield of cyclododecane and greatly shortens the process time. In addition, the use of a heterogeneous hydrogenation catalyst facilitates the separation of the catalyst from the reaction products and catalyst regeneration, thereby reducing investment costs and making it suitable for industrial applications.

[0022] In this disclosure, the cyclododecanetriene is 1,5,9-cyclododecanetriene, with the English name Cyclododecatriene and CAS number 4904-61-4; the cyclododecene is also known as Cyclododecene, with CAS number 1501-82-2, and can be used as an intermediate in the synthesis of high-value-added materials, such as nylon 12.

[0023] According to this disclosure, cyclododecanetriene and a hydrogenation catalyst are sequentially hydrogenated in n-stage slurry bed reactors connected in series. The reactants obtained from the previous stage slurry bed reactor can be directly introduced into the next stage slurry bed reactor for further hydrogenation without liquid-solid separation. That is, no additional filtration unit is required between adjacent slurry bed reactors, which can effectively reduce energy consumption and equipment investment costs, shorten reaction time, and facilitate industrial-scale mass production.

[0024] The number of stages, n, in the n-stage slurry bed reactor can be adjusted as needed. In one specific embodiment, n can be 2 to 4. Figure 1 A specific embodiment of the hydrogenation reaction of cyclododecanetrienes using a three-stage slurry bed reactor is shown. This disclosure does not impose any particular limitation on the specific form of the slurry bed reactor; reactors commonly used in the art, such as batch reactors and / or tubular reactors, can be used. The batch reactor can be a continuous stirred batch reactor, a gas-induced stirred batch reactor, or these reactors connected in series; the tubular reactor can be a plug flow reactor, a bubble column reactor, or these reactors connected in series.

[0025] Furthermore, in order to improve the gas / liquid / solid three-phase mass transfer in each stage of the slurry bed reactor, thereby increasing the feed conversion rate and cyclododecene selectivity, components for enhancing mass transfer can be installed in each stage of the slurry bed reactor. For example, for a batch reactor, the agitator can be a gas mixing agitator or a multi-bladed disc turbine agitator. For a tubular reactor, turbulence-inducing internal components can also be inserted, such as cross-serrated belts, T-shaped blades, static mixers, paddle-type or brush-type internal components.

[0026] According to this disclosure, the hydrogen partial pressure in the n-stage slurry bed reactor decreases sequentially, meaning that in the flow direction of the reactants, in any two adjacent slurry bed reactors, the hydrogen partial pressure in the preceding reactor is greater than that in the following reactor. In the n-stage slurry bed reactor, the hydrogen partial pressure in each reactor can be dynamically adjusted within a certain range according to the reaction progress, as long as the above-mentioned rule is met. Hydrogen can be introduced into each reactor independently to achieve different hydrogen partial pressures in each reactor. Specifically, the hydrogen partial pressure in each reactor can be independently 0~0.4 MPa.

[0027] The hydrogen partial pressure in each stage of the slurry bed reactor can be gradually reduced in a predetermined manner. In one specific embodiment, in the n-stage slurry bed reactor, along the flow direction of the reactants, the hydrogen partial pressure in the first-stage slurry bed reactor can be 0.15~0.4 MPa, the hydrogen partial pressure in the second-stage slurry bed reactor can be 0.03~0.1 MPa, and when n>2, the hydrogen partial pressure P in the nth-stage slurry bed reactor... n Satisfying 0.15≤P n / P n-1 ≤0.5, for example, in an embodiment where n is 3, the hydrogen partial pressure in the third-stage slurry bed reactor can be 0~0.05MPa; in an embodiment where n is 4, the hydrogen partial pressure in the third and fourth-stage slurry bed reactors can be 0~0.05MPa and 0~0.025MPa, respectively.

[0028] To further improve the feed conversion rate and cyclododecene selectivity, the residence time of the reactants in each stage of the slurry bed reactor can be set according to the reaction progress and the hydrogen partial pressure in each stage of the slurry bed reactor. The reaction time in each stage of the slurry bed reactor can be the same or different. In a preferred embodiment, the reaction time of the reactants in the first stage slurry bed reactor is... t The reaction time in the second-stage slurry bed reactor is 5-34 minutes, and the reaction time in the nth-stage slurry bed reactor is 20-60 minutes. t n Satisfying 0.2≤ t n / t n-1 ≤1.6.

[0029] In an n-stage slurry bed reactor, the reaction temperature of the hydrogenation reaction can be adjusted within a certain range. Specifically, the temperature of the hydrogenation reaction can be 60~180℃, preferably 150~170℃. The reaction temperatures in each stage of the slurry bed reactor can be the same or different. In a preferred embodiment, the reaction temperature in the n-stage slurry bed reactor decreases sequentially along the flow direction of the reactants. For example, in the n-stage slurry bed reactor, along the flow direction of the reactants, the temperature in the first stage slurry bed reactor can be 150~170℃, the temperature in the second stage slurry bed reactor can be 140~160℃, and when n>2, there is no special limitation on the temperature in the third stage slurry bed reactor to the nth stage slurry bed reactor.

[0030] According to this disclosure, the hydrogenation catalyst is a heterogeneous catalyst. Compared with homogeneous catalytic systems, heterogeneous hydrogenation catalysts have advantages such as controllable structure and easy separation and regeneration, which helps to reduce production costs. Specifically, the heterogeneous catalyst can be a metal-supported catalyst and / or a composite oxide catalyst, preferably a metal-supported catalyst.

[0031] In one specific embodiment, the hydrogenation catalyst comprises a support and an active metal component. The support may be activated carbon, a metal oxide (such as one or more combinations of titanium oxide, alumina, zirconium oxide, and silicon oxide), graphene, etc.; the active metal component may include one or more of palladium, platinum, ruthenium, gold, silver, cobalt, and nickel, preferably one or more of palladium, platinum, and ruthenium. Further, based on the dry weight of the hydrogenation catalyst, the content of the active metal component may be 0.1-10% by weight, preferably 0.5-3% by weight.

[0032] In one specific embodiment, the particle size of the hydrogenation catalyst can be 0.1~200µm, preferably 30~180µm. Hydrogenation catalysts with the above particle size range are beneficial to further improve the feed conversion rate and cyclododecene selectivity, while also being easier to separate and regenerate.

[0033] The hydrogenation catalyst can achieve highly selective hydrogenation to cyclododecene even with a small amount. Specifically, the weight ratio of the cyclododecanetriene to the hydrogenation catalyst can be 100:(2.5~7), preferably 100:(3~4.5).

[0034] Figure 1 A specific embodiment according to this disclosure is shown below, in conjunction with... Figure 1 This implementation method will be described in detail. For example... Figure 1 As shown, a three-stage slurry bed reactor is used. Cyclododecanetriene 10 and first-stage hydrogen 21 are introduced into the first-stage slurry bed reactor T1 for hydrogenation reaction. Then, the resulting reactants (first-stage product) and second-stage hydrogen 22 are introduced into the second-stage slurry bed reactor T2 for further reaction. Finally, the resulting reactants (second-stage product) and third-stage hydrogen 23 are introduced into the third-stage slurry bed reactor T3 for further reaction to synthesize cyclododecane.

[0035] The present disclosure will be described in detail below through examples, but it is not intended to limit the present disclosure.

[0036] Example 1 The flowchart of this embodiment is as follows: Figure 1 As shown, a three-stage series tubular reactor (T1, T2, and T3) is used for the hydrogenation reaction of cyclododecanetriene to produce cyclododecene, specifically as follows: Cyclododecanetriene and a 2% by weight Pd / Al₂O₃ catalyst with a particle size of 50 µm (weight ratio 100:4) were blended and injected into T1 along with hydrogen. The mixed reactants discharged from T1 were introduced into T2, with additional hydrogen introduced into T2. The mixed reactants discharged from T2 were introduced into T3, with additional hydrogen introduced into T3. The temperatures in T1, T2, and T3 were 160 °C, 155 °C, and 152 °C, respectively, with hydrogen partial pressures controlled at 0.4 MPa, 0.05 MPa, and 0.02 MPa, respectively, and reaction times of 20 min, 32 min, and 15 min, respectively.

[0037] The composition and content of reactants in the third-stage slurry bed reactor were detected by gas chromatography. The conversion rate and selectivity of cyclododecanetriene were calculated according to the following formula, and the results are shown in Table 1.

[0038] Cyclododecanetriene conversion rate = 1 - (weight percentage of cyclododecanetriene after reaction) / (weight percentage of cyclododecanetriene before reaction) Cyclododecene selectivity = weight percentage of cyclododecene after reaction / conversion rate of cyclododecanetriene Example 2 The hydrogenation reaction of cyclododecanetriene to cyclododecene was carried out according to the method of Example 1, except that the hydrogen partial pressures in T1, T2 and T3 were controlled at 0.2 MPa, 0.06 MPa and 0.03 MPa, respectively, and the reaction times were 45 min, 5 min and 8 min, respectively. The conversion rate and selectivity of cyclododecanetriene are shown in Table 1.

[0039] Example 3 The hydrogenation reaction of cyclododecanetriene to cyclododecene was carried out according to the method of Example 1, except that the hydrogen partial pressures in T1, T2 and T3 were controlled at 0.15 MPa, 0.1 MPa and 0.03 MPa, respectively, and the reaction times were 60 min, 15 min and 10 min, respectively. The conversion rate and selectivity of cyclododecanetriene are shown in Table 1.

[0040] Example 4 The hydrogenation reaction of cyclododecanetriene to cyclododecene was carried out according to the method of Example 1, except that the hydrogen partial pressures in T1, T2 and T3 were controlled at 0.6 MPa, 0.15 MPa and 0.1 MPa, respectively, and the reaction times were 10 min, 35 min and 5 min, respectively. The conversion rate and selectivity of cyclododecanetriene are shown in Table 1.

[0041] Example 5 The hydrogenation reaction of cyclododecanetriene to cyclododecene was carried out according to the method of Example 1, except that the weight ratio of cyclododecanetriene to catalyst was 100:7. The conversion and selectivity of cyclododecanetriene are shown in Table 1.

[0042] Example 6 The hydrogenation reaction of cyclododecanetriene to cyclododecene was carried out according to the method of Example 1, except that the catalyst particle size was 5 µm. The conversion and selectivity of cyclododecanetriene are shown in Table 1.

[0043] Example 7 The hydrogenation reaction of cyclododecanetriene to cyclododecene was carried out according to the method of Example 1, except that the temperature in T1, T2 and T3 was 160°C. The conversion rate and selectivity of cyclododecanetriene are shown in Table 1.

[0044] Example 8 The hydrogenation reaction of cyclododecanetriene to cyclododecene was carried out according to the method of Example 1, except that a batch reactor was used instead of a tubular reactor. The conversion rate and selectivity of cyclododecanetriene are shown in Table 1.

[0045] Comparative Example 1 The hydrogenation of cyclododecanetriene to cyclododecene was carried out in a single-stage tubular reactor. The catalyst and reaction temperature were the same as in Example 1, the reaction pressure was 0.4 MPa, and the reaction time was 80 min. The conversion rate and selectivity of cyclododecanetriene are shown in Table 1.

[0046] Comparative Example 2 Cyclododecanetriene and a 2% (w / w) Pd / Al₂O₃ catalyst with a particle size of 50 µm (w / w ratio 100:4) were placed in a reactor. The reactor was pressurized to 0.34 MPa and heated to 160°C for 31 min. Then, the reaction was carried out at 0.07 MPa for 47 min. Finally, the reaction was carried out at 0.04 MPa for 22 min. The conversion and selectivity of cyclododecanetriene are shown in Table 1.

[0047] Table 1

[0048] As shown in Table 1, the method disclosed herein for the hydrogenation of cyclododecanetriene to cyclododecene can effectively improve the feed conversion rate and the selectivity of the target product cyclododecene.

[0049] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0050] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0051] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for hydrogenating cyclododecanetriene, characterized in that, The method includes: In the presence of hydrogen, cyclododecanetriene is brought into contact with a hydrogenation catalyst to undergo a hydrogenation reaction, yielding cyclododecene. The hydrogenation reaction is carried out sequentially in n-stage slurry bed reactors connected in series, and the hydrogen partial pressure in the n-stage slurry bed reactors decreases sequentially along the flow direction of the reactants; the hydrogenation catalyst is a heterogeneous catalyst.

2. The method according to claim 1, wherein, The number of stages n in the n-stage slurry bed reactor is 2 to 4.

3. The method according to claim 1, wherein, In the n-stage slurry bed reactor, along the flow direction of the reactants, the hydrogen partial pressure in the first-stage slurry bed reactor is 0.15~0.4 MPa, the hydrogen partial pressure in the second-stage slurry bed reactor is 0.03~0.1 MPa, and when n>2, the hydrogen partial pressure P in the nth-stage slurry bed reactor is... n Satisfying 0.15≤P n / P n-1 ≤0.

5.

4. The method according to claim 3, wherein, The reaction time of the reactants in the first-stage slurry bed reactor is 20-60 min, and the reaction time in the second-stage slurry bed reactor is 5-34 min. When n>2, the reaction time in the nth-stage slurry bed reactor is... t n Satisfying 0.2≤ t n / t n-1 ≤1.

6.

5. The method according to claim 1, wherein, The hydrogenation reaction is carried out at a temperature of 60~180℃.

6. The method according to claim 1, wherein, The slurry bed reactor is a batch reactor and / or a tubular reactor.

7. The method according to claim 1, wherein, The weight ratio of the cyclododecanetriene to the hydrogenation catalyst is 100:(2.5~7).

8. The method according to claim 1, wherein, The hydrogenation catalyst includes a support and an active metal component, wherein the active metal component includes palladium.

9. The method according to claim 8, wherein, Based on the dry weight of the hydrogenation catalyst, the content of the active metal component is 0.1 to 10% by weight.

10. The method according to claim 1, wherein, The particle size of the hydrogenation catalyst is 0.1~200µm.

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