A method for preparing cyclohexylamine by catalytic reductive amination of phenol

Abstract

The application discloses a method for preparing cyclohexylamine by catalytic reduction and amination of phenol, which takes lignin-derived phenol as raw material, takes ammonia as ammonia source, takes water as solvent, and is prepared by reaction in a hydrogen atmosphere under the action of a supported bimetallic multifunctional catalyst. The catalyst takes SAPO-5 as a carrier, and effective active ingredients include oxides of ruthenium and manganese. The method for preparing cyclohexylamine is green and environmentally friendly, has low production cost, high product yield, high catalyst activity and recycling, and has obvious industrial production advantages.

Description

Technical Field

[0001] This invention relates to the fields of biomass resource utilization and cyclohexylamine synthesis, specifically to a method for preparing cyclohexylamine by phenol-catalyzed reductive amination. Background Technology

[0002] Cyclohexylamine is an important organic chemical raw material and fine chemical intermediate, mainly used in pharmaceuticals, pesticides, rubber industry, and electronic materials industry, with broad application prospects. Currently, the main preparation processes for cyclohexylamine include aniline catalytic hydrogenation, cyclohexanol gas-phase ammoniation, and cyclohexanone catalytic ammonolysis. The most commonly used process is the aniline hydrogenation reduction method. However, this process uses aniline, a non-renewable petrochemical resource, and its high price affects the production cost of cyclohexylamine. Therefore, developing green, sustainable, and efficient cyclohexylamine preparation processes is crucial and urgent for achieving sustainable development in the chemical industry.

[0003] This invention utilizes phenol as a raw material to directly prepare cyclohexylamine via catalytic reductive amination. The phenol used can be obtained from lignin, a renewable biomass resource, through depolymerization and conversion. This raw material is renewable and cheaper than aniline. The production of cyclohexylamine via catalytic reductive amination of phenol not only reduces production costs but also possesses green and sustainable characteristics. Summary of the Invention

[0004] To address the aforementioned technical problems in the existing technology, the purpose of this application is to provide a method for the catalytic reduction amination of phenol to prepare cyclohexylamine. The present invention provides an environmentally friendly method for the efficient synthesis of cyclohexylamine from lignin-derived phenol and ammonia via reduction amination under hydrogen conditions, using a supported bimetallic multifunctional catalyst. The reaction process is green, requires a small amount of catalyst, and has a high product yield.

[0005] A method for preparing cyclohexylamine by catalytic reductive amination of lignin-derived phenol, specifically comprising: using phenol, a lignin derivative of Formula I, as the starting material, reacting it in water under the action of a supported bimetallic multifunctional catalyst and in an atmosphere of ammonia and hydrogen; and after the reaction, obtaining cyclohexylamine of Formula II through post-treatment, as shown in the following reaction formula:

[0006]

[0007] The supported bimetallic multifunctional catalyst comprises a SAPO-5 molecular sieve support and an active ingredient supported on the support; the active ingredient comprises ruthenium metal and manganese oxides, with the manganese oxide being MnO. x It indicates a mixture containing MnO and MnO2.

[0008] This invention utilizes ruthenium in the supported bimetallic multifunctional catalyst to provide hydrogenation active sites; the manganese oxide provides certain Lewis acidic sites, which is beneficial for the reductive amination of phenol, and also provides certain basic sites, which is beneficial for the adsorption of phenol; the SAPO-5 support provides certain acidic sites and offers a large specific surface area and pore volume, allowing ruthenium and manganese to be uniformly and highly dispersed on the support, thereby improving the activity of the supported bimetallic multifunctional catalyst; the SAPO-5 support surface has numerous mesopores, which can promote mass transfer diffusion and adsorption of the effective active components. The catalyst prepared by this invention has a high specific surface area, high activity, good selectivity, high metal dispersion, and high product yield, and the catalyst can be recycled, thereby significantly reducing production costs.

[0009] Furthermore, in the supported bimetallic multifunctional catalyst, the molar ratio of ruthenium to manganese is 4:1 to 1:8, preferably 1:1 to 4.

[0010] A suitable molar ratio of ruthenium and manganese exhibits a good interaction, resulting in excellent catalytic performance. If the manganese content is too low, there are insufficient acid-active sites on the catalyst, affecting the selective hydrogenation and amination of phenol. If the manganese content is too high, manganese species will coat the ruthenium particles, thus affecting the activity of the ruthenium sites and hindering the reductive amination of phenol.

[0011] Furthermore, the Ru loading of the supported bimetallic multifunctional catalyst is 0.5–5 wt.%.

[0012] When the ruthenium loading in the catalyst is too low, there are insufficient active sites in the catalyst, resulting in incomplete reaction and very low product yield. However, when the ruthenium loading is too high, the catalyst cost will increase, and too many active sites in the catalyst will easily lead to over-hydrogenation and other side reactions. In addition, when the ruthenium loading is too high, the metal components on the catalyst surface will aggregate, reducing the utilization of metal atoms.

[0013] Furthermore, the mass ratio of phenol to the supported bimetallic multifunctional catalyst is 1:0.01 to 0.4, preferably 1:0.1 to 0.36.

[0014] If the amount of catalyst used in the reaction is too low, the reaction will be incomplete; however, if the amount of catalyst used is too high, the active sites of the catalyst will become saturated with the substrate, and the reaction cost will increase.

[0015] Furthermore, the reaction solvent is water, and the volume of the solvent used is 3-20 mL / g based on the mass of phenol, preferably 5-10 mL / g.

[0016] Using too little or too much solvent is detrimental to the reaction. If the volume of solvent is too small, the concentration of phenol and reaction products will be too high or they will not be completely dissolved, resulting in a long reaction time and a low yield. If the volume of solvent is too high, the solution concentration will be reduced, reducing the collision between molecules, which will slow down the reaction rate and reduce the product yield.

[0017] Furthermore, the ammonia gas pressure is 0.1–0.5 MPa, the hydrogen gas pressure is 0.2–5 MPa, and the reaction is carried out at a temperature of 100–200°C for 4–28 hours.

[0018] Furthermore, the preferred ammonia pressure is 0.3 MPa, the hydrogen pressure is 2 MPa, the reaction temperature is 120–180 °C, and the reaction time is 16–24 h.

[0019] Further, the preparation method of the supported bimetallic multifunctional catalyst is as follows: A hydrothermal synthesis method is used, with aluminum isopropoxide as the aluminum source, phosphoric acid as the phosphorus source, tetraethyl orthosilicate as the silicon source, and triethylamine as the template agent, to prepare a silica-aluminophosphate molecular sieve SAPO-5 support. The SAPO-5 support is completely immersed in a mixed aqueous solution of ruthenium and manganese salts. After impregnation, it is dried at 80–150°C, and finally reduced by a reducing gas at 150–400°C to obtain the supported bimetallic multifunctional catalyst. The specific steps are as follows:

[0020] Take a clean beaker, add aluminum isopropoxide and water, and stir for 3 hours to completely dissolve the aluminum isopropoxide. Add tetraethyl orthosilicate (TEOS) dropwise while stirring, and stir the mixture further for 1 hour. Add phosphoric acid (85 wt.% in H2O) dropwise while stirring, and continue stirring for 1 hour. Add triethylamine (TEA) dropwise while stirring, and stir vigorously for 1 hour to produce a white gel (molar ratio Al:Si:P:TEA:H2O = 1:0.2–0.4:0.8–1.2:0.5–1.0:35–45, preferably 1:0.3:1:0.8:40–45). Transfer the gel to a hydrothermal synthesis reactor and react at 180–220 °C for 8–30 hours. Then recover the solid product from the hydrothermal reactor, wash five times with water until the washings are neutral, and filter. Dry at 100 °C, and finally calcine in a muffle furnace at 550 °C for 12 hours to obtain a white crystalline solid, SAPO-5. Weigh out calculated amounts of ruthenium and manganese salts, add a small amount of water to fully dissolve them, and prepare a bimetallic solution. Take calculated amounts of the SAPO-5 molecular sieve support and slowly add it to the bimetallic solution while stirring to ensure uniform mixing. Add an appropriate amount of distilled water to bring the solution to a saturated, slightly moist state, and then sonicate for 10 minutes to ensure uniform mixing of the metal and support. Impregnate at room temperature for 8–30 hours, dry at 80–150°C, and finally reduce with a reducing gas at 150–400°C to prepare the supported bimetallic multifunctional catalyst RuMn / SPAO-5.

[0021] Furthermore, the ruthenium salt is ruthenium trichloride; the manganese salt is either manganese acetate or manganese nitrate; and the reducing gas is hydrogen.

[0022] The present invention has the following advantages and effects compared with the prior art:

[0023] (1) Compared to the expensive commercially available SAPO-5, this invention provides a stable SAPO-5 in a cost-effective manner. Furthermore, the preparation method of SAPO-5 significantly affects the specific surface area, pore size, pH, and other physicochemical properties of the final SAPO-5, thus influencing catalyst activity. The mesoporous structure of the silica-aluminophosphate molecular sieve SAPO-5 in this invention facilitates mass transfer and provides numerous acidic sites on the catalyst surface, promoting the reductive amination reaction. The large specific surface area of ​​the SAPO-5 support facilitates the high dispersion of metals Ru and Mn. In addition, the addition of phosphorus promotes the formation of phosphorus-metal bonds, significantly improving catalyst stability.

[0024] (2) The catalyst is easily prepared by loading metal Ru and a second metal Mn onto SAPO-5 via a simple impregnation method. Metal Ru exhibits high hydrogenation activity; the oxide of the second metal Mn, MnO... xIt possesses strong Lewis acidity and a certain degree of basicity, which is beneficial for the reductive amination of phenol. Furthermore, the addition of Mn facilitates the dispersion of metallic Ru, resulting in smaller, more uniform metal particle size and higher catalyst activity. MnO x The presence of certain oxygen vacancies facilitates the adsorption of phenol and helps stabilize Ru metal. Highly dispersed Ru and MnO x The synergistic effect of the SAPO-5 support results in high catalyst activity, good selectivity for the target product, and a high yield of cyclohexylamine, reaching over 90%.

[0025] (3) The present invention uses water as a reaction solvent, which is not only green and environmentally friendly but also reduces production costs and meets the requirements of industrial production.

[0026] (4) The catalyst provided by the present invention can be recycled and reused, the amount of catalyst used is small, the cost is reduced, and it is suitable for industrial production. Attached Figure Description

[0027] Figure 1 The X-ray power diffraction (XRD) patterns of RuMn(1:4) / SAPO-5 catalyst, RuMn(1:1) / SAPO-5 catalyst, Ru / SAPO-5 catalyst and SAPO-5 support with Ru loading of 3 wt.% prepared in this invention are compared.

[0028] Figure 2 The comparison results of N2 adsorption-desorption isotherms and pore size distribution of RuMn(1:4) / SAPO-5 catalyst with Ru loading of 3wt.% prepared in this invention, Ru / SAPO-5 catalyst and SAPO-5 support;

[0029] Figure 3 The RuMn(1:4) / SAPO-5 catalyst with a Ru loading of 3 wt.% prepared according to the present invention and

[0030] Comparison of NH3-TPD spectra of Ru / SAPO-5 catalysts. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] SAPO-5 was synthesized using a hydrothermal synthesis method, with the following specific steps: 4.126 g of aluminum isopropoxide was slowly added to 14.5 g of deionized water under stirring, and the mixture was further stirred for 3 hours. 1.26 g of tetraethyl orthosilicate (TEOS) was added dropwise under stirring, and the mixture was further stirred for 1 hour. 2.306 g of phosphoric acid (85 wt.% in H₂O) was added dropwise under stirring, and stirring continued for 1 hour. 1.652 g of triethylamine (TEA) was added dropwise under stirring, and the mixture was vigorously stirred for 1 hour to produce a white gel (molar ratio Al:Si:P:TEA:H₂O = 1:0.3:1:0.8:40). The gel was transferred to a hydrothermal synthesis reactor lined with polytetrafluoroethylene (PTFE), and hydrothermally synthesized at 200 °C for 24 hours. The solid product was then recovered from the hydrothermal reactor, washed five times with water until the washings were neutral, and then filtered. The product was dried at 100°C and then calcined in a muffle furnace at 550°C for 12 hours to obtain a white crystalline solid, SAPO-5.

[0033] The RuMn / SAPO-5 catalyst was prepared by an equal-volume impregnation method. Taking a RuMn(1:4) / SAPO-5 catalyst with a Ru loading of 3 wt.% (a molar ratio of Ru to Mn of 1:4) as an example: 0.079 g of RuCl3·3H2O was weighed and placed in a crucible. 0.29 g of C4H6MnO4·4H2O and 1 ml of distilled water were added, and the mixture was sonicated to dissolve both completely. 0.97 g of SAPO-5 was weighed and slowly added to the above solution. The mixture was sonicated for 10 min to ensure uniform mixing of the metal and the support. The mixture was then impregnated at room temperature for 24 h and dried at 100 °C for 10 h. Finally, it was reduced with hydrogen at 300 °C for 3 h to obtain Ru-MnO. x (1:4) / SAPO-5 catalyst, labeled as RuMn(1:4) / SAPO-5 catalyst.

[0034] In addition, the preparation methods of catalysts with different Mn doping amounts are the same as those for the RuMn(1:4) / SAPO-5 catalyst, with the only difference being the amount of C4H6MnO4·4H2O added.

[0035] Figure 1Comparison of X-ray power diffraction (XRD) patterns of RuMn(1:4) / SAPO-5 catalyst, RuMn(1:1) / SAPO-5 catalyst, Ru / SAPO-5 catalyst, and SAPO-5 support prepared for embodiments of the present invention. The samples showed good matching with typical AFI-type structures. Characteristic peaks belonging to the SAPO-5 phase were observed at 7.3°, 12.8°, 14.7°, 19.6°, 20.9°, 22.3°, 24.6°, 25.8°, 28.9°, 30.0°, 33.5°, 34.5°, 36.9°, and 37.6°. When Ru and Mn were added, the XRD patterns of the samples were similar to those of the SAPO-5 support, indicating that the introduction of the metals did not disrupt the structure of the SAPO-5 support. No phase diffraction peaks related to Ru and Mn were observed, indicating that the Ru and Mn phases were well dispersed on the catalyst.

[0036] Figure 2 Comparative results of N2 adsorption-desorption isotherms and pore size distributions for RuMn(1:4) / SAPO-5 catalysts with a Ru loading of 3 wt.%, Ru / SAPO-5 catalysts, and SAPO-5 support. The N2 adsorption capacity on Ru / SAPO-5 and RuMn(1:4) / SAPO-5 catalysts is reduced compared to the support alone. All samples exhibit distinct H4-type hysteresis loops across the entire P / P0 range. At higher relative pressures, the N2 adsorption-desorption curves show a hysteresis of 0.4–0.9 in the P / P0 range, corresponding to the characteristics of mesoporous molecular sieves with type IV isotherms. Figure 2 The SAPO-5 carrier obtained in this embodiment of the invention has an average pore size of 12.4 nm and a specific surface area of ​​170.5 m². 2 ·g -1 .

[0037] Figure 3Comparison of NH3-TPD spectra of RuMn(1:4) / SAPO-5 catalyst with a Ru loading of 3 wt.% and Ru / SAPO-5 catalyst. Based on the temperature range of ammonia desorption, acidic sites can be subdivided into weak (T < 300°C), moderate (T = 300-500°C), and strong (T > 500°C). Both samples exhibited multiple NH3 desorption peaks, which can be attributed to weak and moderately strong acids, respectively. The low-temperature desorption peaks at <200°C likely correspond to NH3 adsorbed at weakly acidic sites originating from surface silanol groups. The high-temperature peaks above 300°C indicate the presence of moderately strong acidic sites associated with Al-OH and Al-OH-Si groups on the catalyst surface and in the catalyst structure. Notably, with the addition of Mn, the moderately strong acid desorption and desorption peaks shift significantly to higher temperatures, and their intensity also increases significantly. This indicates that the acidity of the catalyst increases with the addition of Mn in the sample. Ru-MnO x Suitable acidity in the SAPO-5 catalyst is beneficial for the reductive amination of phenol to prepare cyclohexylamine.

[0038] Comparative Example 1:

[0039] 0.5 g (5.3 mmol) of phenol was placed in a beaker and dissolved in 3 mL of water. The solution was then transferred to a 25 mL high-pressure reactor. 0.179 g of Ru with a 3 wt.% loading of Ru / SAPO-5 catalyst was added. The reactor was purged with nitrogen five times, followed by continuous ammonia purging and stirring for 20 min to ensure the ammonia was fully dissolved in the water. The pressure of ammonia in the reactor was maintained at 0.3 MPa. Then, 2 MPa of H2 was introduced, and the reaction was carried out at 140 °C for 24 hours to obtain cyclohexylamine. The conversion rate of phenol was 100%, and the yield of cyclohexylamine was 100%.

[0040] Example 1

[0041] Take 0.5 g (5.3 mmol) of phenol and place it in a beaker. Add 3 mL of water to dissolve it. Transfer the solution to a 25 mL high-pressure reactor and add 0.179 g of Ru-MnO4 with a loading of 3 wt.%. x The reactor was prepared with a SAPO-5 catalyst (Ru and Mn in a molar ratio of 1:4, i.e., RuMn(1:4) / SAPO-5 catalyst). Nitrogen gas was purged five times, followed by continuous ammonia gas introduction and stirring for 20 minutes to ensure the ammonia was fully dissolved in the water. The ammonia pressure was maintained at 0.3 MPa. Then, hydrogen gas was introduced at a pressure of 2.0 MPa, the reaction temperature was set at 140℃, and the reaction was carried out for 24 hours to obtain cyclohexylamine. The conversion rate of phenol was 100%, and the yield of cyclohexylamine was 100%.

[0042] Example 2:

[0043] Take 0.5 g (4 mmol) of guaiacol and place it in a beaker. Add 3 mL of water to dissolve it. Transfer the solution to a 25 mL high-pressure reactor and add 0.136 g of Ru-MnO with a loading of 3 wt.%. x The reactor was prepared using a SAPO-5 catalyst (Ru:Mn in a molar ratio of 1:4). Nitrogen gas was purged five times, followed by continuous ammonia gas introduction and stirring for 20 minutes to ensure complete ammonia dissolution in the water. The ammonia pressure was maintained at 0.3 MPa. Hydrogen gas was then introduced at a pressure of 2.0 MPa, and the reaction temperature was set at 200°C for 24 hours to produce cyclohexylamine. The conversion rate of guaiacol was 100%, and the yield of cyclohexylamine was 91.5%.

[0044] Examples 3-5:

[0045] Other operations are the same as in Example 1, except that the Ru / Mn molar ratio is changed and the reaction time is shortened to 4 hours, as shown in Table 1.

[0046] Table 1

[0047]

[0048] Examples 6-8:

[0049] Other operations are the same as in Example 1, except that the reaction temperature is changed, and the following reaction results are obtained (Table 2):

[0050] Table 2

[0051]

[0052] Examples 9-11:

[0053] Other operations are the same as in Example 1, except that the reaction time is changed, and the following reaction results are obtained (Table 3):

[0054] Table 3

[0055]

[0056] Examples 12-16:

[0057] Other operations are the same as in Example 1, except that the number of times the catalyst is recycled is changed, and the following reaction results are obtained (Table 4):

[0058] Table 4

[0059] Example Catalyst repetition count Phenol conversion rate (%) Cyclohexylamine yield (%) 12 1 100 100 13 2 100 99.4 14 3 100 98.4 15 4 100 96.5 16 5 100 95.6

[0060] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for preparing cyclohexylamine by phenol-catalyzed reductive amination, characterized in that, Cyclohexylamine was prepared by reacting phenol as a raw material and ammonia as an ammonia source in a reaction solvent under a hydrogen atmosphere and with the action of a supported bimetallic multifunctional catalyst. The supported bimetallic multifunctional catalyst includes a silica-aluminophosphate molecular sieve SAPO-5 support and an effective active component supported on the SAPO-5 support. The effective active component includes oxides of Ru metal and Mn. The molar ratio of ruthenium to manganese is 1:4; the loading of metallic Ru is 0.5~5 wt.%; The reaction solvent is water, and the volume of the reaction solvent is 3~20 mL / g based on the mass of the substrate. The reaction conditions were: ammonia pressure 0.3 MPa, hydrogen pressure 2 MPa, reaction temperature 120~160 °C, and reaction time 16~24 h. The preparation method of the SAPO-5 carrier is as follows: A hydrothermal synthesis method is used, with aluminum isopropoxide as the aluminum source, phosphoric acid as the phosphorus source, tetraethyl orthosilicate as the silicon source, and triethylamine as the template agent to prepare the aluminosilicate phosphate molecular sieve SAPO-5 carrier. The above four raw materials are placed in a beaker, water is added, and the mixture is stirred thoroughly. The mixture is then poured into a hydrothermal reactor and reacted at 180-220 °C for 8-30 h. After the reaction, the mixture is washed, filtered, and dried. Finally, it is calcined in a muffle furnace at 500-600 °C for 8-12 h to obtain the SAPO-5 carrier.

2. The method for preparing cyclohexylamine by catalytic reductive amination of phenol as described in claim 1, characterized in that, The mass ratio of phenol to the supported bimetallic multifunctional catalyst is 1:0.01~0.

4.

3. The method for preparing cyclohexylamine by catalytic reduction amination of phenol as described in claim 2, characterized in that, The mass ratio of phenol to the supported bimetallic multifunctional catalyst is 1:0.1~0.

36.

4. The method for preparing cyclohexylamine by catalytic reductive amination of phenol as described in claim 1, characterized in that, The volume of the reaction solvent used is 5-10 mL / g based on the mass of the substrate.

5. The method for preparing cyclohexylamine by catalytic reductive amination of phenol as described in claim 1, characterized in that, In the preparation of the SAPO-5 carrier, the molar ratio of aluminum source, silicon source, phosphorus source, triethylamine and water is 1: 0.2~0.4: 0.8~1.2: 0.5~1.0: 35~45.

6. The method for preparing cyclohexylamine by catalytic reductive amination of phenol as described in claim 5, characterized in that, In the preparation of the SAPO-5 carrier, the molar ratio of aluminum source, silicon source, phosphorus source, triethylamine and water is 1: 0.3: 1: 0.8: 40~45.

7. The method for preparing cyclohexylamine by catalytic reductive amination of phenol as described in claim 1, characterized in that, The preparation method of the supported bimetallic multifunctional catalyst is as follows: SAPO-5 support is completely immersed in a mixed aqueous solution of ruthenium salt and manganese salt, ultrasonically mixed evenly, then impregnated at room temperature for 8-30 h, dried at 80-150 °C after impregnation, and finally reduced by passing a reducing gas at 150-400 °C to obtain the supported bimetallic multifunctional catalyst.

8. The method for preparing cyclohexylamine by catalytic reductive amination of phenol as described in claim 7, characterized in that, The ruthenium salt is ruthenium trichloride, the manganese salt is manganese acetate or manganese nitrate, and the reducing gas is H2.

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