A process for the preparation of 2,5-bis(aminomethyl)furan

Abstract

The application discloses a method for preparing 2,5-bis(aminomethyl)furan. The method comprises the following steps: loading 5-hydroxymethylfurfural and ammonia into a reaction kettle loaded with a catalyst, introducing hydrogen into the reaction kettle, and reacting at 150 DEG C to 190 DEG C for 10 to 14 hours to generate 2,5-bis(aminomethyl)furan through a reductive amination reaction; the catalyst is a core-shell structure, and is composed of a silica shell and a metal core; the metal core is metal M, which is Ni or Co; and the molar ratio of the silica to the metal M is 0.1 to 0.3. The application has no by-products, no pollution, less waste, and the conversion rate of 5-hydroxymethylfurfural can reach 99%, the selectivity of 2,5-bis(aminomethyl)furan is 99%, and the green and sustainable production of 2,5-bis(aminomethyl)furan is realized.

Description

Technical Field

[0001] This invention relates to a technology for preparing 2,5-di(aminomethyl)furan, a biomass product, and particularly to a method for preparing 2,5-di(aminomethyl)furan from 5-hydroxymethylfurfural as an initial raw material, and its catalyst. Background Technology

[0002] 2,5-Di(aminomethyl)furan, due to its symmetrical structure and the relatively reactive amino group on the furan ring, is widely used in organic synthesis and pharmaceutical fields. For example, polyamides and polyimides produced from 2,5-di(aminomethyl)furan have high mechanical strength and low coefficients of thermal expansion, comparable to traditional petrochemical products, and play a significant role in the automotive, aerospace, electrical and electronic, and construction industries. 2,5-Di(aminomethyl)furan can also be used as a curing agent for epoxy resins. Hexamethylenediamine, prepared from 2,5-di(aminomethyl)furan through hydrogenolysis, can be used to produce materials such as nylon 66, 1,6-hexamethylenediisocyanate, and nylon 610. 2,5-Di(aminomethyl)tetrahydrofuran, formed by hydrogenation of the C=C bond on the furan ring of 2,5-di(aminomethyl)furan, also has important applications in the aforementioned fields.

[0003] Currently, several methods for synthesizing 2,5-di(aminomethyl)furan have been documented, including: a. First, 5-hydroxymethylfurfural is oxidized to 2,5-dicarboxyfuran, then using Raney Ni as a catalyst and tetrahydrofuran as a solvent, with the pH of the reaction solution adjusted to 5, the 2,5-dicarboxyfuran is reduced and aminationd to 2,5-di(aminomethyl)furan (overall yield 42.6%) (ChemCatChem, 2019, 11 (11), 2649-2656.); b. First, using Ru / Nb2O5 as a catalyst and tetrahydrofuran as a solvent, 5-hydroxymethylfurfural was reduced and aminationd to 5-hydroxymethylfurfuralamine, and then [Ru(CO)ClH(PPh3)3] / Xantphos was used as a catalyst to amination of 5-hydroxymethylfurfuralamine to 2,5-di(aminomethyl)furan (overall yield 89.3%) (Journal of the American Chemical Society, 2017, 139 (33): 11493-11499); c. Using 5-hydroxymethylfurfural as a raw material, CuNiAlO xThe catalyst used 1,4-dioxane as a solvent and a large amount of basic catalytic agent Na2CO3 was added. At 90 °C for 9 h, the aldehyde group was first reduced and aminationd, and then the hydroxyl group was catalytically aminationd at 210 °C for 18 h, finally yielding 2,5-di(aminomethyl)furan (overall yield 85.9%) (RSC Advance, 2019, 9 (66), 38877-38881.). However, these schemes or catalytic systems have disadvantages such as the use of organic solvents, expensive catalysts, low yields, multiple steps, or the inability to recycle the catalyst. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing 2,5-di(aminomethyl)furan. This method uses a core-shell structured non-precious metal catalyst and water as a solvent to directly synthesize 2,5-di(aminomethyl)furan in a one-step catalytic amination reaction from 5-hydroxymethylfurfural in high yield (99%). This invention produces no byproducts, no pollution, and generates minimal waste. The conversion rate of 5-hydroxymethylfurfural reaches 99%, and the selectivity for 2,5-di(aminomethyl)furan is 99%, achieving green and sustainable production of 2,5-di(aminomethyl)furan.

[0005] The technical solution of this invention is as follows:

[0006] A method for preparing 2,5-di(aminomethyl)furan, the method comprising the following steps:

[0007] 5-hydroxymethylfurfural and ammonia were loaded into a reactor containing a catalyst. Hydrogen was introduced into the reactor and the reaction was carried out at 150℃~190℃ for 10-14 h to produce 2,5-di(aminomethyl)furan.

[0008] The mass ratio of 2,5-bis(aminomethyl)furan to catalyst is 5~50:1; the molar ratio of 2,5-bis(aminomethyl)furan to ammonia is 1:30~80; and the hydrogen pressure is 1~3 MPa.

[0009] The catalyst has a core-shell structure, comprising a silica shell and a metal core; wherein the metal core is metal M, which is Ni or Co; and the molar ratio of silica to metal M is 0.1~0.3.

[0010] The diameter of the metal core is 10-15 nm, and the shell thickness is 5-20 nm.

[0011] The concentration of the ammonia solution is 20-40 wt%.

[0012] The method for preparing the catalyst includes the following steps:

[0013] (1) Preparation of metal cores:

[0014] The nitrate of the nuclear metal and polyethylene glycol were added sequentially to distilled water. After stirring the solution for 30-60 min, urea was added to obtain a mixed solution. The mixture was then heated to 80-95 °C and reacted for 10-24 h. The precipitate was collected by centrifugation, washed with ethanol and distilled water, dried, and calcined in air at 400-600 °C for 2-4 h to obtain metal oxide nanoparticles.

[0015] In the mixed solution, the concentration of nuclear metal nitrate is 1-5 wt%, the concentration of polyethylene glycol (PEG-20000) is 2-6 wt%, and the concentration of urea is 2-6 wt%.

[0016] (2) A shell surrounds the metal core:

[0017] Metal oxide nanoparticles were added to anhydrous ethanol and subjected to ultrasonic treatment for 30–60 min. Then, a shell-forming reagent and ammonia were added under ultrasonic conditions to obtain a reaction solution. After the addition was complete, the reaction was continued under ultrasonic conditions for another 30–60 min. The solution was centrifuged, washed with ethanol and distilled water, dried, calcined at 400–600 °C for 2–4 h, and then reduced at 400–600 °C in a H2 atmosphere for 2–3 h to obtain the catalyst.

[0018] The molar ratio of the shell-forming agent to the metal nanoparticles is 0.1 to 0.3, and the shell-forming agent of the catalyst is tetraethyl orthosilicate (at this time, the shell of the catalyst is SiO2).

[0019] The concentration of ammonia in the reaction solution is 1.3-2.6 mol / L; the concentration of metal oxide nanoparticles is 0.2-1 wt%.

[0020] The metal M in the metal core is Ni or Co;

[0021] The thickness and pore size of the catalyst shell are determined by the ratio of oxide shell (shell-forming agent) to metal. The molar ratio of shell-forming agent to metal is 0.1–0.3. As the ratio increases from 0.1 to 0.3 (molar ratio), the shell thickness tends to increase, from 5 nm to 20 nm; the specific surface area and pore size within the shell tend to decrease, with the specific surface area decreasing from 91.64 m². 2 / g decreased to 65.86 m 2 / g, the average pore size decreased from 6.44 nm to 4.88 nm.

[0022] The catalyst is represented by M@SiO2-z, where M represents a metal and z represents the molar ratio of silicon to metal M in the catalyst.

[0023] The essential features of this invention are:

[0024] This invention utilizes 5-hydroxymethylfurfural as a raw material and water as a solvent to synthesize 2,5-di(aminomethyl)furan in a one-step, high-yield manner via catalytic amination using an inexpensive, non-precious metal catalyst. The selected catalyst possesses the following characteristics:

[0025] ① The core-shell structure of the catalyst can prevent the carbonyl group in 2,5-bis(aminomethyl)furan from being directly reduced during the reaction, thereby improving the selectivity of the product; it can also prevent the aggregation of metal active components and improve their lifespan.

[0026] ② By adjusting the thickness of the catalyst shell (i.e., the ratio of oxide shell (shell-forming reagent) to metal), the acidity of the catalyst can be changed, and by adjusting the pore size of the catalyst, the self-coupling reaction of the product 2,5-di(aminomethyl)furan can be prevented, thereby further improving the selectivity of the product.

[0027] ③ Due to the unique curved structure of the silica shell, the charge density on the Ni surface inside the shell is reduced, thereby enhancing the adsorption of ammonia and intermediates on the Ni surface and further enhancing its catalytic activity.

[0028] The beneficial effects of this invention are as follows:

[0029] This invention provides a method for synthesizing 2,5-di(aminomethyl)furan from 5-hydroxymethylfurfural, which overcomes the drawbacks of existing production processes, such as high difficulty, severe environmental pollution, and low yield. Furthermore, the catalyst used in this invention is simple to prepare using conventional methods, and the catalyst shell support and the metal core active component are inexpensive and readily available.

[0030] The catalytic amination reaction of this invention is a low-temperature, low-pressure reaction, which does not require sophisticated reaction equipment and improves the economic feasibility of the reaction. During the catalytic process, there are no byproducts, no pollution, and minimal waste. The conversion rate of 5-hydroxymethylfurfural can reach 99%, and the selectivity for 2,5-di(aminomethyl)furan is 99%. Attached Figure Description

[0031] Figure 1 The image shows a TEM image of the Ni@SiO2-0.2 catalyst obtained in Example 4 (corresponding to the metal core prepared in Example 1, and the catalyst prepared according to Example 4).

[0032] Figure 2 The images shown are TEM images of the catalysts obtained in Examples 3, 4, and 5. Figure 2 In the image, 'a' is a TEM image of the Ni@SiO2-0.1 catalyst obtained in Example 3. Figure 2 In the image, b is a TEM image of the Ni@SiO2-0.2 catalyst obtained in Example 4. Figure 2 In this context, c represents the Ni@SiO2-0.3 catalyst obtained in Example 5;

[0033] Figure 3 The pore size distribution diagrams are for the Ni@SiO2-0.1, Ni@SiO2-0.2, and Ni@SiO2-0.3 catalysts obtained in Examples 3, 4, and 5. Detailed Implementation

[0034] The synthetic route of this invention is shown in the reaction formula below:

[0035] .

[0036] The technical features of the present invention are further illustrated below through examples:

[0037] Example 1: Preparation of NiO nanoparticles

[0038] 2.91 g of Ni(NO3)2·6H2O (0.01 mol) was added to 100 mL of distilled water containing 3.00 g of polyethylene glycol (PEG-20000). After stirring the solution for 30 min, 4.5 g of urea was added, and the mixture was heated to 90 °C and reacted for 24 h. The precipitate was collected by centrifugation, washed with ethanol and distilled water, dried at 100 °C for 10 h, and calcined in air at 400 °C for 4 h to obtain NiO nanoparticles.

[0039] Example 2: Preparation of CoO nanoparticles

[0040] 2.91 g of Co(NO3)2·6H2O (0.01 mol) was added to 100 mL of distilled water containing 3.00 g of polyethylene glycol (PEG-20000). After stirring the solution for 30 min, 4.5 g of urea was added, and the mixture was heated to 85 °C and reacted for 24 h. The precipitate was collected by centrifugation, washed with ethanol and distilled water, dried at 100 °C for 10 h, and calcined in air at 500 °C for 4 h to obtain CoO nanoparticles.

[0041] Example 3: Preparation of Ni@SiO2-0.1 catalyst

[0042] 0.25 g (3.3471 mmol) of NiO nanoparticles (obtained from Example 1) were added to 50 mL of anhydrous ethanol and subjected to ultrasonic treatment for 30 min. Then, in an ultrasonic bath, 0.0697 g (0.3346 mmol) of tetraethyl orthosilicate (corresponding to a molar ratio of 0.1 between the shell-forming agent and the metal core) and 10 mL of NH3·H2O (25 wt%, containing 0.13 mol of ammonia) were added sequentially under ultrasonic treatment (60 min). The mixture was dried at 80 °C for 10 h, calcined at 550 °C for 2 h, and reduced at 550 °C under a H2 atmosphere for 2 h to obtain the Ni@SiO2-0.1 catalyst.

[0043] The catalyst is represented by M@SiO2-z, where M represents a metal and z represents the molar ratio of silicon to metal M in the catalyst.

[0044] The molar amount of the metal nanoparticles is based on the actual content measured by ICP characterization, and the amount of material fed here is the same as the measured amount.

[0045] Example 4: Preparation of Ni@SiO2-0.2 catalyst

[0046] 0.25 g of NiO nanoparticles (obtained from Example 1) were added to 50 mL of anhydrous ethanol and subjected to ultrasonic treatment for 30 min. Then, in an ultrasonic bath, 0.1394 g (i.e., 0.6692 mmol) of tetraethyl orthosilicate (corresponding to a molar ratio of 0.2 between the shell-forming agent and the metal core) and 10 mL of NH3·H2O were added sequentially under ultrasonic treatment (60 min). The mixture was dried at 80 °C for 10 h, calcined at 550 °C for 2 h, and reduced at 550 °C under a H2 atmosphere for 2 h to obtain the Ni@SiO2-0.2 catalyst.

[0047] Example 5: Preparation of Ni@SiO2-0.3 catalyst

[0048] 0.25 g of NiO nanoparticles (obtained from Example 1) were added to 50 mL of anhydrous ethanol and subjected to ultrasonic treatment for 30 min. Then, in an ultrasonic bath, 0.2091 g (i.e., 1.0038 mmol) of tetraethyl orthosilicate (corresponding to a molar ratio of 0.3 between the shell-forming agent and the metal core) and 10 mL of NH3·H2O were added sequentially under ultrasonic treatment (60 min). The mixture was dried at 80 °C for 10 h, calcined at 550 °C for 2 h, and reduced at 550 °C under a H2 atmosphere for 2 h to obtain the Ni@SiO2-0.3 catalyst.

[0049] Example 6: Preparation of Co@SiO2-0.2 catalyst

[0050] 0.25 g of CoO nanoparticles (obtained from Example 2) were added to 50 mL of anhydrous ethanol and subjected to ultrasonic treatment for 30 min. Then, in an ultrasonic bath, 0.1394 g (i.e., 0.6692 mmol) of tetraethyl orthosilicate (corresponding to a molar ratio of 0.2 between the shell-forming agent and the metal core) and 10 mL of NH3·H2O were added sequentially under ultrasonic treatment (60 min). The mixture was dried at 80 °C for 10 h, calcined at 550 °C for 2 h, and reduced at 550 °C under a H2 atmosphere for 2 h to obtain the Co@SiO2-0.2 catalyst.

[0051] Figure 1 The image shows a TEM image of the Ni@SiO2-0.2 catalyst obtained in Example 4 (corresponding to the metal core prepared in Example 1, and then the catalyst prepared according to Example 4); the TEM image shows that the diameter of the metal core is 10-15 nm.

[0052] Figure 2 In the image, 'a' is a TEM image of the Ni@SiO2-0.1 catalyst obtained in Example 3, where the molar ratio of the shell-forming agent to the metal core is 0.1. Figure 2 In the image, b is a TEM image of the Ni@SiO2-0.2 catalyst obtained in Example 4, where the molar ratio of the shell-forming agent to the metal core is 0.2. Figure 2 In the image, 'c' represents the TEM image of the Ni@SiO2-0.3 catalyst obtained in Example 5, where the molar ratio of the shell-forming agent to the metal core is 0.3. From... Figure 2 It can be seen that as the molar ratio of the shell-forming reagent to the metal oxide increases from 0.1 to 0.3 (molar ratio), the shell thickness tends to increase, from 5 nm to 20 nm.

[0053] Figure 3 The figures show the pore size distribution of the catalysts in Examples 3, 4, and 5. In the figures, catalyst Ni@SiO2-0.1 corresponds to Example 3, Ni@SiO2-0.2 corresponds to Example 4, and Ni@SiO2-0.1 corresponds to Example 5. The average pore size values ​​of the corresponding catalysts are listed in Table 1.

[0054] Table 1. Average pore size and specific surface area of ​​Ni@SiO2-z catalyst.

[0055]

[0056] Depend on Figure 3 As shown in Table 1, with the ratio of the shell-forming reagent to the metal core increasing from 0.1 to 0.3 (molar ratio), the specific surface area and pore size in the shell tend to decrease. The specific surface area decreases from 91.64 m². 2 / g decreased to 65.86 m 2 / g, the average pore size decreased from 6.44 nm to 4.88 nm.

[0057] Example 7: Reductive amination of 5-hydroxymethylfurfural

[0058] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of Ni@SiO2-0.1 catalyst (25 mg) obtained in Example 3, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia (5 g, 25 wt%, containing 0.07 mol of ammonia). Before the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2 MPa) and temperature (170 °C) with a stirring rate of 1500 rpm. After 12 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, the selectivity for 2,5-di(aminomethyl)furan was 71%, the selectivity for 5-(aminomethyl)-2-furan-methanol was 6%, the selectivity for 2,5-dihydroxymethylfuran was 13%, and the selectivity for dimerized 2,5-di(aminomethyl)furan was 7%.

[0059] Example 8: Reductive amination of 5-hydroxymethylfurfural

[0060] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of Ni@SiO2-0.2 catalyst (25 mg) obtained in Example 4, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia water (5 g, 25 wt%, containing 0.07 mol of ammonia). Before the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2 MPa) and temperature (170 °C) with a stirring rate of 1500 rpm. After 12 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, the selectivity for 2,5-di(aminomethyl)furan was 91%, and the selectivity for 5-(aminomethyl)-2-furan-methanol was 8%.

[0061] Example 9: Reductive amination of 5-hydroxymethylfurfural

[0062] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of Ni@SiO2-0.3 catalyst (25 mg) obtained in Example 5, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia (5 g, 25 wt%, containing 0.07 mol of ammonia). Prior to the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2 MPa) and temperature (170 °C) with a stirring rate of 1500 rpm. After 12 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, the selectivity for 2,5-di(aminomethyl)furan was 79%, and the selectivity for 5-(aminomethyl)-2-furan-methanol was 20%.

[0063] Example 10: Reductive amination of 5-hydroxymethylfurfural

[0064] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of the Co@SiO2-0.2 catalyst (25 mg) obtained in Example 6, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia (5 g, 25 wt%, containing 0.07 mol of ammonia). Before the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2 MPa) and temperature (170 °C) with a stirring rate of 1500 rpm. After 12 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, the selectivity for 2,5-di(aminomethyl)furan was 37%, and the selectivity for 5-(aminomethyl)-2-furan-methanol was 62%.

[0065] Example 11: Reductive amination of 5-hydroxymethylfurfural

[0066] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of Ni@SiO2-0.2 catalyst (25 mg) obtained in Example 4, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia (5 g, 25 wt%, containing 0.07 mol of ammonia). Before the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2 MPa) and temperature (170 °C) with a stirring rate of 1500 rpm. After 14 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, and the selectivity for 2,5-di(aminomethyl)furan was 99%.

[0067] Example 12: Reductive amination of 5-hydroxymethylfurfural

[0068] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of Ni@SiO2-0.2 catalyst (25 mg) obtained in Example 4, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia (5 g, 25 wt%, containing 0.07 mol of ammonia). Before the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2 MPa) and temperature (160 °C) with a stirring rate of 1500 rpm. After 14 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, and the selectivity for 2,5-di(aminomethyl)furan was 99%.

[0069] Example 13: Reductive amination of 5-hydroxymethylfurfural

[0070] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of Ni@SiO2-0.2 catalyst (25 mg) obtained in Example 4, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia (5 g, 25 wt%, containing 0.07 mol of ammonia). Before the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2 MPa) and temperature (150 °C) with a stirring rate of 1500 rpm. After 14 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, the selectivity for 2,5-di(aminomethyl)furan was 86%, and the selectivity for 5-(aminomethyl)-2-furan-methanol was 13%.

[0071] Example 14: Reductive amination of 5-hydroxymethylfurfural

[0072] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of Ni@SiO2-0.2 catalyst (13 mg) obtained in Example 4, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia (5 g, 25 wt%, containing 0.07 mol of ammonia). Prior to the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2 MPa) and temperature (160 °C) with a stirring rate of 1500 rpm. After 14 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, and the selectivity for 2,5-di(aminomethyl)furan was 99%.

[0073] Example 15: Reductive amination of 5-hydroxymethylfurfural

[0074] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of Ni@SiO2-0.2 catalyst (8 mg) obtained in Example 4, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia (5 g, 25 wt%, containing 0.07 mol of ammonia). Prior to the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2 MPa) and temperature (160 °C) with a stirring rate of 1500 rpm. After 14 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, the selectivity for 2,5-di(aminomethyl)furan was 97%, and the selectivity for 5-(aminomethyl)-2-furan-methanol was 2%.

[0075] Example 16: Reductive amination of 5-hydroxymethylfurfural

[0076] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of Ni@SiO2-0.2 catalyst (6 mg) obtained in Example 4, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia (5 g, 25 wt%, containing 0.07 mol of ammonia). Prior to the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2 MPa) and temperature (160 °C) with a stirring rate of 1500 rpm. After 14 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, the selectivity for 2,5-di(aminomethyl)furan was 85%, and the selectivity for 5-(aminomethyl)-2-furan-methanol was 14%.

[0077] Example 17: Reductive amination of 5-hydroxymethylfurfural

[0078] The reaction was carried out in a 15 mL stainless steel reactor, with the addition of Ni@SiO2-0.2 catalyst (6 mg) obtained in Example 4, 5-hydroxymethylfurfural (0.1261 g, 1 mmol), and ammonia (5 g, 25 wt%, containing 0.07 mol of ammonia). Prior to the reaction, the reactor was purged five times with H2 to replace residual air. Hydrogenation was then carried out at a constant H2 pressure (2.5 MPa) and temperature (160 °C) with a stirring rate of 1500 rpm. After 14 h of reaction, the liquid product was separated from the catalyst and further analyzed by gas chromatography with internal standard. The conversion rate of 5-hydroxymethylfurfural was 99%, the selectivity for 2,5-di(aminomethyl)furan was 74%, the selectivity for 5-(aminomethyl)-2-furan-methanol was 8%, the selectivity for 2,5-dihydroxymethylfuran was 7%, the selectivity for 2,5-dihydroxymethyltetrahydrofuran was 3%, and the selectivity for 5-(aminomethyl)tetrahydro-2-furan-methanol was 5%.

[0079] As can be seen from the above embodiments, the core-shell structure of the Ni-encapsulated silica heterogeneous catalyst used in this invention improves the selectivity of the reductive ammoniation process of 5-hydroxymethylfurfural due to the presence of the silica shell. The core-shell structure of the catalyst prevents the oxidation of metal nanoparticles, increasing catalyst lifetime; it also prevents the direct reduction of the carbonyl group in 2,5-di(aminomethyl)furan during the reaction, improving reaction selectivity. By adjusting the thickness of the catalyst shell to change the catalyst's acidity, and by controlling the catalyst's pore size to prevent the self-coupling reaction of 2,5-di(aminomethyl)furan, the reaction selectivity is further improved. Due to the unique curved structure of the silica shell, the charge density on the Ni surface is reduced, thereby enhancing the adsorption of ammonia and intermediates on the Ni surface, further enhancing its catalytic activity.

[0080] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing 2,5-di(aminomethyl)furan, characterized in that the method comprises the following steps: 5-hydroxymethylfurfural and ammonia were loaded into a reactor containing a catalyst. Hydrogen was introduced into the reactor and the reaction was carried out at 150 ℃~190 ℃ for 10-14 h, resulting in a reduction ammoniation reaction to produce 2,5-di(aminomethyl)furan. in, The mass ratio of 2,5-bis(aminomethyl)furan to catalyst is 5~50:1; the molar ratio of 2,5-bis(aminomethyl)furan to ammonia is 1:30~80; the hydrogen pressure is 1~3 MPa. The catalyst has a core-shell structure, comprising a silica shell and a metal core; wherein the metal core is metal M, which is Ni or Co; and the molar ratio of silica to metal M is 0.1~0.

3. The method for preparing the catalyst includes the following steps: (1) Preparation of metal cores: Metal-core nitrate and polyethylene glycol were added sequentially to distilled water. After stirring the solution for 30-60 min, urea was added to obtain a mixed solution. The mixed solution was then heated to 80-95 °C and reacted for 10-24 h. The precipitate was collected by centrifugation, washed with ethanol and distilled water, dried, and calcined in air at 400 ℃~600 ℃ for 2~4 h to obtain metal oxide nanoparticles. In the mixed solution, the concentration of nitrate in the metal core is 1-5 wt%, the concentration of polyethylene glycol is 2-6 wt%, and the concentration of urea is 2-6 wt%. (2) A shell surrounds the metal core: Metal oxide nanoparticles were added to anhydrous ethanol and subjected to ultrasonic treatment for 30–60 min. Then, a shell-forming reagent and ammonia were added under ultrasonic conditions to obtain a reaction solution. After the addition was complete, the reaction was continued under ultrasonic conditions for 30–60 min. The solution was centrifuged, washed with ethanol and distilled water, dried, calcined at 400 ℃–600 ℃ for 2–4 h, and reduced to a catalyst at 400 ℃–600 ℃ under H2 atmosphere for 2–3 h. The molar ratio of the shell-forming agent to the metal oxide nanoparticles is 0.1 to 0.3, and the shell-forming agent of the catalyst is tetraethyl orthosilicate. The concentration of ammonia in the reaction solution is 1.3–2.6 mol / L, and the concentration of metal oxide nanoparticles is 0.2–1 wt%. The metal M in the metal core is Ni or Co.

2. The method for preparing 2,5-bis(aminomethyl)furan as described in claim 1, characterized in that the diameter of the metal core is 10-15 nm and the shell thickness is 5-20 nm.

3. The method for preparing 2,5-bis(aminomethyl)furan according to claim 1, characterized in that the concentration of the ammonia water is 20-40 wt%.

4. The method for preparing 2,5-di(aminomethyl)furan as described in claim 1, characterized in that, In the catalyst preparation method, as the molar ratio of the shell-forming agent to the metal increases from 0.1 to 0.3, the shell thickness tends to increase, from 5 nm to 20 nm; while the specific surface area and pore size within the shell tend to decrease, with the specific surface area decreasing from 91.64 m². 2 / g decreased to 65.86 m 2 / g, the average pore size decreased from 6.44 nm to 4.88 nm.

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