Preparation of a nitrogen-doped carbon-supported cobalt-based catalyst and its application in the hydrogenation of amides to prepare amines

Abstract

The present invention provides a preparation method of a nitrogen-doped carbon-supported cobalt-based catalyst and its application in amide hydrogenation. By reasonably controlling the calcination atmosphere and temperature, a nitrogen-doped carbon-supported cobalt-based catalyst is prepared. Under the action of the nitrogen-doped carbon-supported cobalt-based catalyst, the amide undergoes hydrodeoxygenation reaction in a hydrogen atmosphere at 180-200 °C to obtain fatty amines. The invention uses non-precious metal cobalt as the active metal, which not only has broad application prospects in industrial production, but also has flexibility in reaction conditions and catalyst design, and can be adjusted according to different requirements. The preparation method provided by the present invention has the characteristics of economic efficiency, environmental protection and sustainability, and provides a feasible and scalable solution for the production of amines.

Description

Technical Field

[0001] The present invention relates to the fields of catalyst design and chemical synthesis. Specifically, it relates to the preparation of a nitrogen-doped carbon-supported cobalt-based catalyst and its application in amide hydrogenation. Through the present invention, amines can be prepared from amides under more controllable and efficient conditions, providing a feasible production process for related industries. Background Art

[0002] Organic amines are important compounds for the synthesis of dyes, drugs, agrochemicals, pigments, and polymers. Seeking to develop green and sustainable methods for the production of amines is very important for environmental protection. The main synthetic routes of amines are as follows: (1) direct hydrogenation of nitriles, (2) reduction of nitro compounds, (3) reductive amination of carbonyl compounds such as aldehydes or ketones, (4) amination of alcohols with ammonia or amines, and (5) hydrogenation of amides. Among them, the commonly used method for the production of amines in industry is the amination reaction of alcohols with ammonia or amines. This method requires the addition of extra ammonia or amines, and the products are usually mixtures of different amines, which requires additional post-treatment processes for purification or separation of the products. Amides are important functional groups in amino acid monomers and can be directly extracted from algae or obtained by bio-based acid amination, which enables them to be obtained from renewable biomass. Moreover, the by-product of preparing amines by amide hydrogenation is only water, which has atom economy and environmental friendliness. Considering the availability of amides from biomass and the atom utilization rate of amide hydrogenation, the production of amines by amide hydrogenation is a promising process route. However, the conjugated effect of the lone pair electrons of the N atom in the amide with the carbonyl group makes it the most stable among all carbonyl compounds, resulting in low reactivity, especially towards nucleophilic reactions of the carbonyl group.

[0003] In early studies, Ni, Cu, and Re catalysts were used for the heterogeneous catalytic hydrogenation of amides, but the reaction conditions of such catalysts were relatively harsh (>200 °C, 20 - 30 MPa). In recent years, researchers have mainly developed a series of bimetallic catalysts (noble metals and oxygenophilic metals) for amide hydrogenation. However, due to the high price of noble metals, the cost is relatively high in industrial production (Nat. Commun., 2020, 11, 3893). Therefore, the development of highly efficient and recyclable heterogeneous non-noble metal catalysts for amide hydrogenation is helpful for its further industrial application. Summary of the Invention

[0004] The present invention relates to the preparation of a nitrogen-doped carbon-supported cobalt-based catalyst and its application in amide hydrogenation. Through reasonable design of the supported cobalt catalyst, the efficient and highly selective preparation of aliphatic amines from aliphatic amides is achieved. Specifically, the supported cobalt catalyst of the present invention can achieve efficient conversion of the amide hydrogenation reaction with its unique catalytic performance.

[0005] The preparation of the nitrogen-doped carbon-supported cobalt-based catalyst of the present invention comprises the following steps:

[0006] (1) Uniformly mix 2,4-dihydroxybenzoic acid, ethylenediamine, hexamethylenetetramine, polyoxypropylene polyoxyethylene copolymer, and deionized water. Among them, the mass ratio of 2,4-dihydroxybenzoic acid, ethylenediamine, hexamethylenetetramine, polyoxypropylene polyoxyethylene copolymer, and deionized water is 3.08:0.6:0.934:3.5:80.

[0007] (2) Transfer the above solution to a hydrothermal reaction kettle, and then place it in an oven at 125-135 °C for 3-5 h;

[0008] (3) Wait for the hydrothermal reaction kettle to cool, wash the polymer in it multiple times, and dry it at 50-80 °C for 10-15 h;

[0009] (4) Uniformly mix a cobalt source, ammonia water, and deionized water, and then slowly add the above-dried polymer thereto. After stirring at 45-55 °C for 4-8 h, filter, wash it multiple times, and dry it at 50-80 °C for 10-15 h. Among them, the cobalt source is one or more of cobalt nitrate, cobalt chloride, or cobalt acetate. The mass ratio of the cobalt source, ammonia water, deionized water, and polymer is 0.2-0.6:7.2:32:1.

[0010] (5) Place the dried cobalt precursor in a tubular furnace and calcine it at 500-700 °C for 1-3 h to obtain a nitrogen-doped carbon-supported cobalt-based catalyst. Among them, the calcination atmosphere is a mixed atmosphere of H2 and N2, and the volume fraction of hydrogen is 5%.

[0011] The present invention also provides the application of the cobalt-based catalyst in the hydrogenation of fatty amides to prepare fatty amines. Add the amide and the reaction solvent to a high-pressure reaction kettle, add the catalyst, charge H2 at 1-5 MPa (preferably 3 MPa), and carry out a hydrodeoxygenation reaction at 180-200 °C (preferably 180 °C) for 10-15 h to obtain fatty amines.

[0012] The structural formula of the amide is as follows

[0013]

[0014] R, R1, and R2 are alkanes with C1-C3.

[0015] The reaction solvent is n-octane, cyclohexane, or cyclopentyl methyl ether.

[0016] The beneficial effects of the present invention compared with the prior art:

[0017] The present invention prepares a multiphase nitrogen-doped carbon-supported cobalt-based catalyst through a process of precursor preparation - loading - hydrogen reduction pyrolysis. The active center of the catalyst is inexpensive non-precious metal cobalt, which has an obvious cost advantage over traditional precious metals. In addition, it has good catalytic activity for primary, secondary, and tertiary amides. At the same time, the nitrogen-doped carbon-supported cobalt-based catalyst of the present invention has no component loss during use, and the catalyst is easy to recycle, providing a feasible solution for the industrial production of the process of hydrogenating amides to prepare amines. Description of the Drawings

[0018] Figure 1 It is a transmission electron microscope image of the supported cobalt-based catalyst obtained in Example 1 of the present invention. Detailed Description of the Invention

[0019] Example 1

[0020] Preparation of nitrogen-doped carbon-supported cobalt-based catalyst: 3.08 g of 2,4-dihydroxybenzoic acid, 0.6 g of ethylenediamine, 0.934 g of hexamethylenetetramine, 3.5 g of polyoxypropylene polyoxyethylene copolymer (P123) and 80 mL of deionized water were uniformly mixed. The above solution was transferred to a hydrothermal reaction kettle and then placed in an oven at 130 °C for 4 h. After the hydrothermal reaction kettle cooled, the polymer in it was washed with water several times and dried at 50 - 80 °C for 12 h. 0.4 g of cobalt nitrate hexahydrate, 8 mL of ammonia water (28%) and 32 mL of deionized water were mixed evenly, and then 1 g of the dried polymer was slowly added thereto. After stirring at 50 °C for 4 - 8 h, it was filtered, washed with water several times, and dried at 50 - 80 °C for 12 h. The dried cobalt precursor was placed in a tubular furnace and calcined at 500 °C for 2 h in a 5% H2 / N2 atmosphere to obtain a nitrogen-doped carbon-supported cobalt-based catalyst (Catalyst 1).

[0021] Catalyst evaluation: 0.5 mmol of cyclohexanecarboxamide and 3 mL of cyclopentyl methyl ether were added to a 25 mL high-pressure reaction kettle, 50 mg of Catalyst 1 was added, 3 MPa of H2 was charged, and the reaction was carried out at 180 °C for 6 h. After the reaction ended, cyclohexylmethylamine was obtained. After the reaction solution was filtered, dodecane was used as an internal standard and qualitative analysis was carried out by GC-MS. The results are shown in Table 1.

[0022] The transmission electron microscope image of the nitrogen-doped carbon-supported cobalt-based catalyst is as Figure 1 , it can be seen that cobalt nanoparticles are evenly dispersed on the nitrogen-doped carbon support. At the same time, metallic Co and cobalt oxide CoO coexist on the catalyst surface. The Lewis acidic CoO can activate the C=O bond of the amide, while metallic Co can dissociate hydrogen, and the two cooperate to promote the hydrogenation reaction of the amide.

[0023] Example 2

[0024] Preparation of nitrogen-doped carbon-supported cobalt-based catalyst: 3.08 g of 2,4-dihydroxybenzoic acid, 0.6 g of ethylenediamine, 0.934 g of hexamethylenetetramine, 3.5 g of polyoxypropylene polyoxyethylene copolymer and 80 mL of deionized water were uniformly mixed. The above solution was transferred to a hydrothermal reaction kettle and then placed in an oven at 130 °C for 4 h. After the hydrothermal reaction kettle was cooled, the polymer therein was washed with water multiple times and dried at 50-80 °C for 12 h. 0.4 g of cobalt(II) nitrate hexahydrate, 8 mL of ammonia water (28%) and 32 mL of deionized water were uniformly mixed, and then 1 g of the dried polymer was slowly added thereto. After stirring at 50 °C for 4-8 h, it was filtered, washed with water multiple times, and dried at 50-80 °C for 12 h. The dried cobalt precursor was placed in a tubular furnace and calcined at 600 °C for 2 h in a 5% H2 / N2 atmosphere to obtain a nitrogen-doped carbon-supported cobalt-based catalyst (Catalyst 2).

[0025] Catalyst evaluation: 0.5 mmol of cyclohexanecarboxamide and 3 mL of cyclopentyl methyl ether were added to a 25 mL high-pressure reaction kettle, 50 mg of Catalyst 2 was added, and 3 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, cyclohexylmethylamine was obtained. After the reaction solution was filtered, dodecane was used as an internal standard, and qualitative analysis was carried out by GC-MS. The results are shown in Table 1.

[0026] Example 3

[0027] Preparation of nitrogen-doped carbon-supported cobalt-based catalyst: 3.08 g of 2,4-dihydroxybenzoic acid, 0.6 g of ethylenediamine, 0.934 g of hexamethylenetetramine, 3.5 g of polyoxypropylene polyoxyethylene copolymer and 80 mL of deionized water were uniformly mixed. The above solution was transferred to a hydrothermal reaction kettle and then placed in an oven at 130 °C for 4 h. After the hydrothermal reaction kettle was cooled, the polymer therein was washed with water multiple times and dried at 50-80 °C for 12 h. 0.4 g of cobalt(II) nitrate hexahydrate, 8 mL of ammonia water (28%) and 32 mL of deionized water were uniformly mixed, and then 1 g of the dried polymer was slowly added thereto. After stirring at 50 °C for 4-8 h, it was filtered, washed with water multiple times, and dried at 50-80 °C for 12 h. The dried cobalt precursor was placed in a tubular furnace and calcined at 700 °C for 2 h in a 5% H2 / N2 atmosphere to obtain a nitrogen-doped carbon-supported cobalt-based catalyst (Catalyst 3).

[0028] Catalyst evaluation: 0.5 mmol of cyclohexanecarboxamide and 3 mL of cyclopentyl methyl ether were added to a 25 mL high-pressure reactor, 50 mg of catalyst 3 was added, 3 MPa of H2 was charged, and the reaction was carried out at 180 °C for 6 h. After the reaction was completed, cyclohexylmethylamine was obtained. After filtering the reaction solution, using dodecane as the internal standard, qualitative analysis was carried out by GC-MS. The results are shown in Table 1.

[0029] Example 4

[0030] Preparation of nitrogen-doped carbon-supported cobalt-based catalyst: 3.08 g of 2,4-dihydroxybenzoic acid, 0.6 g of ethylenediamine, 0.934 g of hexamethylenetetramine, 3.5 g of polyoxypropylene polyoxyethylene copolymer and 80 mL of deionized water were uniformly mixed. The above solution was transferred to a hydrothermal reactor and then placed in an oven at 130 °C for 4 h. After the hydrothermal reactor was cooled, the polymer in it was washed with water many times and dried at 50-80 °C for 12 h. 0.2 g of cobalt(II) nitrate hexahydrate, 8 mL of ammonia water (28%) and 32 mL of deionized water were mixed evenly, and then 1 g of the dried polymer was slowly added thereto. After stirring at 50 °C for 4-8 h, filtration was carried out, and it was washed with water many times and dried at 50-80 °C for 12 h. The dried cobalt precursor was placed in a tubular furnace and calcined at 500 °C for 2 h in a 5% H2 / N2 atmosphere to obtain a nitrogen-doped carbon-supported cobalt-based catalyst (catalyst 4).

[0031] Catalyst evaluation: 0.5 mmol of cyclohexanecarboxamide and 3 mL of cyclopentyl methyl ether were added to a 25 mL high-pressure reactor, 50 mg of catalyst 4 was added, 3 MPa of H2 was charged, and the reaction was carried out at 180 °C for 6 h. After the reaction was completed, cyclohexylmethylamine was obtained. After filtering the reaction solution, using dodecane as the internal standard, qualitative analysis was carried out by GC-MS. The results are shown in Table 1.

[0032] Example 5

[0033] Preparation of nitrogen-doped carbon-supported cobalt-based catalyst: 3.08 g of 2,4-dihydroxybenzoic acid, 0.6 g of ethylenediamine, 0.934 g of hexamethylenetetramine, 3.5 g of polyoxypropylene-polyoxyethylene copolymer and 80 mL of deionized water were uniformly mixed. The above solution was transferred to a hydrothermal reaction kettle and then placed in an oven at 130 °C for 4 h. After the hydrothermal reaction kettle was cooled, the polymer in it was washed with water several times and dried at 50-80 °C for 12 h. 0.6 g of cobalt nitrate hexahydrate, 8 mL of ammonia water (28%) and 32 mL of deionized water were mixed evenly, and then 1 g of the dried polymer was slowly added thereto. After stirring at 50 °C for 4-8 h, it was filtered, washed with water several times and dried at 50-80 °C for 12 h. The dried cobalt precursor was placed in a tubular furnace and calcined at 500 °C for 2 h in a 5% H2 / N2 atmosphere to obtain a nitrogen-doped carbon-supported cobalt-based catalyst (Catalyst 5).

[0034] Catalyst evaluation: 0.5 mmol of cyclohexanecarboxamide and 3 mL of cyclopentyl methyl ether were added to a 25 mL autoclave, 50 mg of Catalyst 5 was added, and 3 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, cyclohexylmethylamine was obtained. After the reaction solution was filtered, dodecane was used as an internal standard and qualitative analysis was carried out by GC-MS. The results are shown in Table 1.

[0035] Example 6

[0036] 0.5 mmol of cyclohexanecarboxamide and 3 mL of cyclopentyl methyl ether were added to a 25 mL autoclave, 50 mg of Catalyst 1 was added, and 1 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, cyclohexylmethylamine was obtained. After the reaction solution was filtered, dodecane was used as an internal standard and qualitative analysis was carried out by GC-MS. The results are shown in Table 2.

[0037] Example 7

[0038] 0.5 mmol of cyclohexanecarboxamide and 3 mL of cyclopentyl methyl ether were added to a 25 mL autoclave, 50 mg of Catalyst 1 was added, and 5 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, cyclohexylmethylamine was obtained. After the reaction solution was filtered, dodecane was used as an internal standard and qualitative analysis was carried out by GC-MS. The results are shown in Table 2.

[0039] Example 8

[0040] 0.5 mmol of cyclohexanecarboxamide and 3 mL of n-octane were added to a 25 mL high-pressure reactor. 50 mg of catalyst 1 was added, and 3 MPa of H2 was charged. The reaction was carried out at 160 °C for 6 h. After the reaction was completed, cyclohexanemethylamine was obtained. After filtering the reaction solution, using dodecane as the internal standard, qualitative analysis was carried out by GC-MS. The results are shown in Table 3.

[0041] Example 9

[0042] 0.5 mmol of cyclohexanecarboxamide and 3 mL of cyclohexane were added to a 25 mL high-pressure reactor. 50 mg of catalyst 1 was added, and 3 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, cyclohexanemethylamine was obtained. After filtering the reaction solution, using dodecane as the internal standard, qualitative analysis was carried out by GC-MS. The results are shown in Table 3.

[0043] Example 10

[0044] 0.5 mmol of N-methylpyrrolidone and 3 mL of cyclopentyl methyl ether were added to a 25 mL high-pressure reactor. 50 mg of catalyst 1 was added, and 3 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, N-methylpyrrolidine was obtained. After filtering the reaction solution, using dodecane as the internal standard, qualitative analysis was carried out by GC-MS. The results are shown in Table 4.

[0045] Example 11

[0046] 0.5 mmol of 1-acetylpiperidine and 3 mL of cyclopentyl methyl ether were added to a 25 mL high-pressure reactor. 50 mg of catalyst 1 was added, and 3 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, 1-ethylpiperidine was obtained. After filtering the reaction solution, using dodecane as the internal standard, qualitative analysis was carried out by GC-MS. The results are shown in Table 4.

[0047] Example 12

[0048] 0.5 mmol of caprolactam and 3 mL of cyclopentyl methyl ether were added to a 25 mL high-pressure reactor. 50 mg of catalyst 1 was added, and 3 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, cycloheximine was obtained. After filtering the reaction solution, using dodecane as the internal standard, qualitative analysis was carried out by GC-MS. The results are shown in Table 4.

[0049] Example 13

[0050] 0.5 mmol of N-butyl propanamide and 3 mL of cyclopentyl methyl ether were added to a 25 mL high-pressure reactor. 50 mg of catalyst 1 was added, and 3 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, N-propyl butylamine was obtained. After filtering the reaction solution, using dodecane as the internal standard, qualitative analysis was carried out by GC-MS. The results are shown in Table 4.

[0051] Example 14

[0052] 0.5 mmol of N-acetylmorpholine and 3 mL of cyclopentyl methyl ether were added to a 25 mL high-pressure reactor. 50 mg of catalyst 1 was added, and 3 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, N-ethylmorpholine was obtained. After filtering the reaction solution, using dodecane as the internal standard, qualitative analysis was carried out by GC-MS. The results are shown in Table 4.

[0053] Example 15

[0054] 0.5 mmol of hexanamide and 3 mL of cyclopentyl methyl ether were added to a 25 mL high-pressure reactor. 50 mg of catalyst 1 was added, and 3 MPa of H2 was charged. The reaction was carried out at 180 °C for 6 h. After the reaction was completed, hexylamine was obtained. After filtering the reaction solution, using dodecane as the internal standard, qualitative analysis was carried out by GC-MS. The results are shown in Table 4.

[0055]

[0056]

[0057]

[0058]

[0059] In summary, the nitrogen-doped carbon-supported cobalt-based catalyst of the present invention has been successfully applied to the catalytic hydrogenation of amides to prepare amines in a high-pressure reactor. The loading method adopted in the present invention is simple and efficient. The non-precious metal cobalt used as the active center is cheap and easily available compared with traditional precious metals. In terms of temperature, the catalytic performance shows good adaptability in the range of 180-200 °C, and the catalytic effect is the best especially at 180 °C. For the selection of the solvent, cyclopentyl methyl ether is a better reaction solvent. In addition, the catalyst has good catalytic activity for primary, secondary and tertiary amides, which provides a guarantee for the expansion of reaction substrates.

[0060] The above is only one embodiment of the present invention. Any modifications, equivalent replacements, improvements, etc. to the present invention should be included in the protection scope of the present invention.

Claims

1. Application of a nitrogen-doped carbon-supported cobalt-based catalyst in the hydrogenation of amides to prepare amines, characterized in that: Add the amide and the reaction solvent into a high-pressure reactor, add the catalyst, charge H2 at 1 - 5 MPa, and react at 180 - 200 °C for 10 - 15 h to obtain the fatty amine; The preparation method of the nitrogen-doped carbon-supported cobalt-based catalyst comprises the following steps: (1) Uniformly mix 2,4-dihydroxybenzoic acid, ethylenediamine, hexamethylenetetramine, polyoxypropylene polyoxyethylene copolymer, and deionized water; (2) Transfer the above solution into a hydrothermal reactor, and then place it in an oven at 125 - 135 °C for 3 - 5 h; (3) Wait for the hydrothermal reactor to cool, wash the polymer in it multiple times with water, and dry it at 50 - 80 °C for 10 - 15 h; (4) Mix the cobalt source, ammonia water, and deionized water evenly, then slowly add the above dried polymer into it, stir at 45 - 55 °C for 4 - 8 h, filter, wash it multiple times with water, and dry it at 50 - 80 °C for 10 - 15 h; (5) Place the dried cobalt precursor in a tubular furnace and calcine it at 500 - 700 °C for 1 - 3 h to obtain the nitrogen-doped carbon-supported cobalt-based catalyst.

2. Use of the nitrogen-doped carbon-supported cobalt-based catalyst according to claim 1 in the preparation of amines by hydrogenation of amides, characterized in that: The reaction solvent is n-octane, cyclohexane, or cyclopentyl methyl ether.

3. Use of the nitrogen-doped carbon-supported cobalt-based catalyst according to claim 1 in the preparation of amines by amide hydrogenation, characterized in that: In the preparation of the catalyst, the mass ratio of 2,4-dihydroxybenzoic acid, ethylenediamine, hexamethylenetetramine, polyoxypropylene polyoxyethylene copolymer, and deionized water is 3.08:0.6:0.934:3.5:

80.

4. Use of the nitrogen-doped carbon-supported cobalt-based catalyst according to claim 1 in the hydrogenation of amides to prepare amines, characterized in that: In the preparation of the catalyst, the cobalt source is one or more of cobalt nitrate, cobalt chloride, or cobalt acetate.

5. Use of the nitrogen-doped carbon-supported cobalt-based catalyst according to claim 1 in the hydrogenation of amides to prepare amines, characterized in that: In the preparation of the catalyst, the mass ratio of the cobalt source, ammonia water, deionized water, and polymer is 0.2 - 0.6:7.2:32:

1.

6. Use of the nitrogen-doped carbon-supported cobalt-based catalyst according to claim 1 in the preparation of amines by hydrogenation of amides, characterized in that: In the preparation of the catalyst, the calcination atmosphere is a mixed atmosphere of H2 and N2, and the volume fraction of hydrogen is 5%.

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