Method for hydrogenating quinoline using nitrogen-boron dual-doped carbon nanomaterials as catalyst

Abstract

The invention discloses a method for hydrogenating quinoline using nitrogen-boron dual-doped carbon nanomaterial as a catalyst, comprising the following steps: dispersing boric acid and chitin in an ethanol aqueous solution, refluxing, rotary evaporation, and vacuum drying to obtain a precursor powder; placing the precursor powder in a tube furnace, heating and carbonizing in a nitrogen or argon atmosphere to obtain a black powder, i.e., a nitrogen-boron dual-doped carbon nanomaterial; uniformly dispersing the nitrogen-boron dual-doped carbon nanomaterial in a solvent, adding quinoline and a reducing agent, filling with nitrogen at 180-220°C, stirring, and reacting to obtain 1,2,3,4-tetrahydroquinoline, the invention avoids metal contamination and simplifies product purification. The catalytic reaction efficiency is high, the conversion rate of quinoline is more than 75%, and the selectivity for 1,2,3,4-tetrahydroquinoline is more than 74%.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemical industry, in particular to a method for realizing quinoline hydrogenation by using nitrogen-boron dual-doped carbon nanomaterial as catalyst. Background Art

[0002] 1,2,3,4-tetrahydroquinoline compounds are biologically active skeleton molecules and key intermediates in the production and manufacturing of drugs, alkaloids, agricultural chemicals and other fine chemicals. 1,2,3,4-tetrahydroquinoline compounds are present in some important prescription drugs such as oxaniquine, nicaprol, vilamycin and diclofenac. Therefore, the synthesis of 1,2,3,4-tetrahydroquinoline compounds is very important. At present, the preparation methods of 1,2,3,4-tetrahydroquinoline compounds include catalytic cyclization reaction, Beckmann rearrangement reaction and selective hydrogenation reaction of N-heterocyclic molecules; among them, the method of hydrogenating quinoline (containing N-heterocyclic molecules) to obtain 1,2,3,4-tetrahydroquinoline has become the most important synthesis method due to its advantages of directness, simplicity and high atomic utilization.

[0003] Metal-containing catalysts are currently the most commonly used catalysts for quinoline hydrogenation, including precious metals such as palladium, gold, and ruthenium, and non-precious metals such as cobalt and nickel. However, these catalytic systems are difficult to avoid the problem of metal leaching. The strong coordination between metals and nitrogen atoms may also poison the active sites of the catalyst, thereby reducing the stability of the catalyst. Therefore, it is very important to develop a metal-free catalyst for quinoline hydrogenation.

[0004] Metal-free catalysts have significant advantages such as low cost, good biocompatibility, and strong sustainability, and are ideal alternatives to metal-based catalysts. Carbon is a typical non-metallic material with abundant natural reserves and adjustable atomic / morphological structures. In the past few decades, carbon materials have been used as metal-free catalysts in fields such as electrocatalysis and photocatalysis, but there are still no reports on metal-free catalysts for quinoline hydrogenation. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for hydrogenating quinoline using nitrogen-boron dual-doped carbon nanomaterials as catalysts.

[0006] The present invention adopts the following technical solution:

[0007] The method for hydrogenating quinoline using nitrogen-boron dual-doped carbon nanomaterial as a catalyst comprises the following steps:

[0008] (1) dispersing boric acid and chitosan in an ethanol aqueous solution with a volume concentration of 50% to 80%, stirring under reflux for 4 to 6 hours, rotary evaporating, and vacuum drying at 60 to 80° C. to obtain a precursor powder;

[0009] (2) placing the precursor powder in a tube furnace, heating it to 700-1000° C. at a rate of 1-3° C. / min in a nitrogen or argon atmosphere, and carbonizing it for 1.5-2.5 h to obtain a black powder, i.e., a nitrogen-boron dual-doped carbon nanomaterial;

[0010] (3) uniformly dispersing the nitrogen-boron dual-doped carbon nanomaterial in a solvent, adding quinoline and a reducing agent, and filling with nitrogen at 2-4 MPa,

[0011] The reaction was carried out at 180-220°C with stirring for 10-14 hours to obtain 1,2,3,4-tetrahydroquinoline.

[0012] The ratio of boric acid, chitosan and the ethanol aqueous solution with a volume concentration of 50%-80% is preferably 1g:3-10g:100-150ml.

[0013] Step (3) is preferably as follows: according to proportion, 15-45 mg of the nitrogen-boron dual-doped carbon nanomaterial is uniformly dispersed in 3-10 ml of solvent, 0.25 mmol of quinoline and 0.75-1.5 mmol of reducing agent are added, nitrogen gas is filled at 2-4 MPa, and the reaction is carried out at 180-220° C. with stirring for 10-14 h to obtain 1,2,3,4-tetrahydroquinoline.

[0014] The solvent is preferably water, n-hexane, tetrahydrofuran, acetonitrile or toluene.

[0015] The reducing agent is preferably formic acid, hydrazine hydrate or sodium borohydride.

[0016] Advantages of the present invention

[0017] The present invention uses cheap and readily available chitin and boric acid to obtain nitrogen-boron doped carbon nanomaterials through a pyrolysis carbonization method. In terms of catalyzing quinoline hydrogenation reaction, the catalytic system of the nitrogen-boron doped carbon nanomaterials does not introduce metals and acid-base additives, thereby avoiding metal pollution and simplifying product purification. The catalytic reaction efficiency is high, the conversion rate of quinoline is above 75%, and the selectivity for 1,2,3,4-tetrahydroquinoline is above 74%. The catalyst has good stability and good recycling ability, and no obvious deactivation occurs within 5 cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 XRD patterns of BNC5-X (X=700, 900, 1000).

[0019] Figure 2 This is the full XPS spectrum of BNC5-900.

[0020] Figure 3 It is the loop application performance of BNC5-900. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1

[0023] The preparation method of nitrogen-boron dual-doped carbon nanomaterial comprises the following steps:

[0024] (1) dispersing boric acid and chitosan in an ethanol aqueous solution with a volume concentration of 75%, stirring under reflux for 5 h, rotary evaporating, and vacuum drying at 70° C. to obtain a precursor powder;

[0025] (2) placing the precursor powder in a tube furnace, heating it to 900° C. at a rate of 2° C. / min in a nitrogen atmosphere and carbonizing it for 2 h to obtain a black powder, namely, a nitrogen-boron dual-doped carbon nanomaterial; Figure 1 , Figure 2 .

[0026] The ratio of boric acid, chitin and 75% by volume ethanol aqueous solution is 1 g:5 g:120 ml.

[0027] Example 2

[0028] The preparation method of nitrogen-boron dual-doped carbon nanomaterial comprises the following steps:

[0029] (1) dispersing boric acid and chitosan in an ethanol aqueous solution with a volume concentration of 50%, stirring under reflux for 6 hours, rotary evaporating, and vacuum drying at 60° C. to obtain a precursor powder;

[0030] (2) placing the precursor powder in a tube furnace, heating it to 700° C. at a rate of 1° C. / min and carbonizing it for 2.5 h in an argon atmosphere to obtain a black powder, namely, a nitrogen-boron dual-doped carbon nanomaterial; Figure 1 .

[0031] The ratio of boric acid, chitin and ethanol aqueous solution with a volume concentration of 50% is 1g:3g:100ml.

[0032] Example 3

[0033] The preparation method of nitrogen-boron dual-doped carbon nanomaterial comprises the following steps:

[0034] (1) dispersing boric acid and chitosan in an ethanol aqueous solution with a volume concentration of 80%, stirring under reflux for 4 h, rotary evaporating, and vacuum drying at 80° C. to obtain a precursor powder;

[0035] (2) placing the precursor powder in a tube furnace, heating it to 1000° C. at a rate of 3° C. / min in a nitrogen atmosphere and carbonizing it for 1.5 h to obtain a black powder, namely, a nitrogen-boron dual-doped carbon nanomaterial; Figure 1 .

[0036] The ratio of boric acid, chitin and ethanol aqueous solution with a volume concentration of 80% is 1g:10g:150ml.

[0037] Example 4

[0038] The method for hydrogenating quinoline using nitrogen-boron dual-doped carbon nanomaterial as a catalyst comprises the following steps:

[0039] 30 mg of the nitrogen-boron dual-doped carbon nanomaterial prepared in Example 1 was uniformly dispersed in 7 ml of water, 0.25 mmol of quinoline and 1 mmol of formic acid were added, nitrogen gas was filled at 2 MPa, and the mixture was stirred at 200° C. for 12 h to obtain 1,2,3,4-tetrahydroquinoline. Samples were taken, and after membrane filtration, gas chromatography was used to detect the conversion rate of quinoline and the selectivity of 1,2,3,4-tetrahydroquinoline, which were 91% and 93% respectively.

[0040] The catalyst solid after the reaction was filtered, washed with anhydrous ethanol, dried, and reused in the above reaction for 5 times. Figure 3 .

[0041] Example 5

[0042] The method for hydrogenating quinoline using nitrogen-boron dual-doped carbon nanomaterial as a catalyst comprises the following steps:

[0043] 15 mg of the nitrogen-boron dual-doped carbon nanomaterial prepared in Example 2 was uniformly dispersed in 3 ml of n-hexane, 0.25 mmol of quinoline and 0.75 mmol of hydrazine hydrate were added, nitrogen was charged at 4 MPa, and the mixture was stirred at 180° C. for 14 h to obtain 1,2,3,4-tetrahydroquinoline. Samples were taken, and after membrane filtration, gas chromatography was used to detect that the conversion rate of quinoline was 89% and the selectivity of 1,2,3,4-tetrahydroquinoline was 87%.

[0044] Example 6

[0045] The method for hydrogenating quinoline using nitrogen-boron dual-doped carbon nanomaterial as a catalyst comprises the following steps:

[0046] 45 mg of the nitrogen-boron dual-doped carbon nanomaterial prepared in Example 3 was uniformly dispersed in 10 ml of tetrahydrofuran (acetonitrile or toluene may also be used), 0.25 mmol of quinoline and 1.5 mmol of sodium borohydride were added, nitrogen was filled at 3 MPa, and the mixture was stirred at 220° C. for 10 h to obtain 1,2,3,4-tetrahydroquinoline. Samples were taken, and after membrane filtration, the conversion rate of quinoline and the selectivity of 1,2,3,4-tetrahydroquinoline were detected by gas chromatography, and the results were 93% and 87% respectively.

[0047] The gas chromatography detection conditions of the product are as follows: vaporization chamber 280°C, detector 280°C, initial column temperature 8°C, initial hold for 2 min, heating at 20°C / min to 280°C, and hold for 5 min.

[0048] The blank group (Example 4 without nitrogen-boron dual-doped carbon nanomaterials) was the same as Example 4. Sampling was performed and the conversion rate of quinoline was 18% and the selectivity of 1,2,3,4-tetrahydroquinoline was 66% after membrane filtration using gas chromatography.

[0049] Comparative Example: The nitrogen-boron dual-doped carbon nanomaterial in Example 4 was replaced by activated carbon. The other conditions were the same as in Example 4. Sampling was performed. After membrane filtration, the conversion rate of quinoline was 25% and the selectivity of 1,2,3,4-tetrahydroquinoline was 68% as detected by gas chromatography.

[0050] Quinoline hydrogenation experiment. Experimental data show that in the blank experiment, the conversion rate of quinoline hydrogenation reaction is extremely low and the selectivity is also poor; when activated carbon is used as a catalyst to catalyze the quinoline hydrogenation reaction, the conversion rate of quinoline is also very low.

Claims

1. A method for hydrogenating quinoline using nitrogen-boron dual-doped carbon nanomaterials as a catalyst, characterized in that: The following steps are involved: (1) dispersing boric acid and chitosan in an ethanol aqueous solution with a volume concentration of 50% to 80%, stirring under reflux for 4 to 6 hours, rotary evaporating, and vacuum drying at 60 to 80° C. to obtain a precursor powder; (2) placing the precursor powder in a tube furnace, heating it to 700-1000° C. at a rate of 1-3° C. / min in a nitrogen or argon atmosphere, and carbonizing it for 1.5-2.5 h to obtain a black powder, i.e., a nitrogen-boron dual-doped carbon nanomaterial; (3) The nitrogen-boron dual-doped carbon nanomaterial is uniformly dispersed in a solvent, quinoline and a reducing agent are added, nitrogen gas is filled at 2-4 MPa, and the mixture is reacted at 180-220° C. under stirring for 10-14 h to obtain 1,2,3,4-tetrahydroquinoline; the reducing agent is formic acid, hydrazine hydrate or sodium borohydride.

2. The method according to claim 1, characterized in that The ratio of the boric acid, chitin and the ethanol aqueous solution with a volume concentration of 50%-80% is 1g:3-10g:100-150ml.

3. The method according to claim 1, characterized in that The step (3) is as follows: according to the proportion, 15-45 mg of the nitrogen-boron dual-doped carbon nanomaterial is uniformly dispersed in 3-10 ml of solvent, 0.25 mmol of quinoline and 0.75-1.5 mmol of reducing agent are added, nitrogen gas of 2-4 MPa is filled, and the mixture is reacted at 180-220° C. with stirring for 10-14 hours to obtain 1,2,3,4-tetrahydroquinoline.

4. The method according to claim 1 or 3, characterized in that The solvent is water, n-hexane, tetrahydrofuran, acetonitrile or toluene.

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