A method for preparing 1,4-naphthoquinone compounds by selective oxidation of aromatic ketones

Abstract

The present invention provides a method for preparing 1,4-naphthoquinone compounds by selective oxidation of aromatic ketones, which is a new method for catalytic oxidation of aromatic ketones to prepare 1,4-naphthoquinone compounds using copper-based and vanadium-based heterogeneous catalytic materials, belonging to the technical field of fine chemicals. This method uses molecular oxygen as the oxidant, and a heterogeneous copper-based and vanadium-based catalytic material to prepare 1,4-naphthoquinone compounds by liquid-phase selective oxidation of aromatic ketones under mild conditions. The Cu-N-C and V-N-C composite materials used therein are obtained by mixing inorganic metal salts with organic nitrogen-containing compounds to obtain a precursor, and calcining in an inert atmosphere at a temperature of 300-800 °C for 0.5-10 h. The method provided by the present invention uses aromatic ketones as raw materials and molecular oxygen as the oxidant, and the catalytic reaction conditions are mild with few pollutants. It is a new route for preparing 1,4-naphthoquinone compounds, with strong practicability and broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of fine chemistry, and particularly relates to a new method for preparing 1,4-naphthoquinone compounds by liquid-phase catalytic selective oxidation reaction using aromatic ketones as raw materials and molecular oxygen as an oxidant. Background Art

[0002] Naphthoquinone compounds are a class of small molecule compounds widely existing in nature and have important application values in production and life. For example, 1,4-naphthoquinone is an important fine chemical intermediate and has wide applications in industries such as pesticides, fungicides, dyes, synthetic rubbers, and resins. 2-Methyl-1,4-naphthoquinone is a key intermediate for synthesizing vitamin K.

[0003] Taking 1,4-naphthoquinone as an example, its typical preparation methods include gas-phase oxidation and liquid-phase oxidation. The gas-phase oxidation method directly oxidizes naphthalene with oxygen in the air under the action of a catalyst to obtain 1,4-naphthoquinone, but the yield of 1,4-naphthoquinone is low, only between 15% and 30%. The traditional liquid-phase oxidation method includes using high-valent heavy metal salts, nitric acid, peroxyacids and other oxidants to oxidize naphthalene, naphthylamine, naphthol compounds to prepare naphthoquinone substances, and the environmental pollution is relatively serious. Chinese Patent (CN102976915 A) mixes 1-naphthylamine with sulfuric acid and stirs to generate ammonium sulfate salt, and the ammonium sulfate salt mixture is oxidized by a suspension formed by mixing MnO2 and sulfuric acid to generate 1,4-naphthoquinone. Chinese Patent (CN 102391091 A) mixes hydrogen peroxide and acetic anhydride in a certain proportion to generate peracetic acid without an acid catalyst, and 1,4-naphthoquinone is prepared by oxidizing α-naphthol with peracetic acid. Yamazaki et al. used chromium trioxide as a catalyst and periodic acid as an oxidant to oxidize naphthalene to 1,4-naphthoquinone in an organic solvent acetonitrile, and the stoichiometric ratio of the substrate, catalyst, and oxidant was 1:0.1:4.2 (Tetrahedron Letters, 2001, 42, 3355-3357). Researchers such as Shi developed a catalytic system with a ruthenium complex and sodium dodecane-1-sulfonate. Under the oxidation of hydrogen peroxide, naphthalene and its halogenated substituents can be converted into 1,4-naphthoquinone in water (Journal of Molecular Catalysis A: Chemical, 2007, 270, 68-75). Researcher Tanoue found that in an acetone solvent, silver oxide and nitric acid as oxidants can catalyze naphthol and its derivatives to obtain 1,4-naphthoquinone, but this system is prone to generating by-products of 1,4-naphthoquinone dimer and is difficult to separate (Tetrahedron, 2002, 58, 99-104). It can be seen that the above methods have many problems such as equipment corrosion, serious pollution or high raw material costs. Industrially, 2-methyl-1,4-naphthoquinone is prepared by using chromium anhydride as an oxidant to oxidize 2-methylnaphthalene in glacial acetic acid, and this process also has problems such as serious pollution of chromium wastewater and waste residue and corrosion of equipment by glacial acetic acid. Therefore, developing a new route and new process for preparing 1,4-naphthoquinone compounds with green and high efficiency has important application backgrounds.

[0004] The present invention uses molecular oxygen as an oxygen source to catalytically selectively oxidize aromatic ketones to 1,4-naphthoquinone compounds under mild liquid-phase oxidation reaction conditions, and develops a new route for preparing 1,4-naphthoquinone compounds. Summary of the Invention

[0005] In view of the above problems, the present invention provides a new method for preparing 1,4-naphthoquinone compounds by oxidizing aromatic ketones using a heterogeneous catalyst in a liquid phase system. This method is a new method for preparing 1,4-naphthoquinone compounds with aromatic ketones as raw materials and molecular oxygen as an oxidant under mild conditions.

[0006] To achieve the above object, the specific technical solution of the present invention is as follows:

[0007] A method for the selective oxidation of aromatic ketones to prepare 1,4-naphthoquinone compounds is a new method for the liquid-phase selective oxidation of aromatic ketones to prepare 1,4-naphthoquinone compounds using a copper-based and vanadium-based heterogeneous catalyst. The method uses aromatic ketones as raw materials and molecular oxygen as an oxygen source, and in an organic solvent, the aromatic ketones are catalytically selectively oxidized in the liquid phase to 1,4-naphthoquinone compounds, and the conversion rate (%) of the aromatic ketones can reach more than 62%; the selectivity (%) of the naphthoquinone compounds can reach more than 70%.

[0008] The specific steps are as follows: Add a catalyst, an aromatic ketone raw material, and an organic solvent to a high-pressure reactor. The feeding amount of the catalyst is 5-40 wt% of the feeding amount of the aromatic ketone, and the amount of the organic solvent used is 1-40 times the mass of the aromatic ketone. Using molecular oxygen as an oxygen source, heat and stir in the temperature range of 60-150 °C, the oxygen partial pressure is 0.1-2 MPa, the reaction duration is 0.2-12 h. After the reaction is completed, cool to room temperature, reduce the pressure to atmospheric pressure, and separate to obtain 1,4-naphthoquinone compounds.

[0009] Furthermore, the aromatic ketone has the structure in the following reaction formula, and the 1,4-naphthoquinone compound has the structure in the following reaction formula:

[0010]

[0011] Among them, R1 is one or more of hydrogen, alkyl, phenyl, -Cl, -Br, -F, -NO2, methoxy, ethoxy, cyano, amino, acetoxy or acetamido; R2 is one or more of hydrogen, alkyl, phenyl, -Cl, -Br, -F, -NO2, methoxy, ethoxy, cyano, amino, acetoxy or acetamido; R1 and R2 may be the same or different.

[0012] Furthermore, the organic solvent used in the catalytic oxidation reaction is one or more of γ-valerolactone, δ-valerolactone, γ-butyrolactone, ε-caprolactone.

[0013] Furthermore, the molecular oxygen in the catalytic oxidation reaction comes from air, oxygen or a gas containing oxygen, and the oxygen partial pressure is 0.1-2 MPa.

[0014] Further, the catalyst is one or more of vanadium pentoxide, vanadium dioxide, vanadium trioxide, vanadium nitride, V-N-C composite material, copper oxide, cuprous oxide, Cu-N-C composite material, preferably V-N-C composite material and Cu-N-C composite material; the preparation steps of the V-N-C and Cu-N-C composite material catalysts are as follows: dissolve the metal source and the nitrogen-containing organic ligand in a solvent, the molar ratio of the metal source to the nitrogen-containing organic ligand is 1:1 - 1:10, heat and stir at 30 - 100 °C for 1 - 12 h and then cool to room temperature, rotary evaporate to remove the solvent, dry in a vacuum drying oven at 30 - 80 °C for 1 - 24 h, fully grind the obtained precursor and then pyrolyze it in an inert gas atmosphere at 300 - 800 °C for 0.5 - 10 h and then cool, and fully grind to obtain the Cu-N-C or V-N-C composite material. The copper source used in the preparation process of the V-N-C and Cu-N-C composite materials is one or more of copper nitrate, copper chloride, copper acetate, copper sulfate and their hydrates, and the vanadium salt is one or more of ammonium metavanadate, ammonium vanadate, sodium metavanadate, sodium vanadate and their hydrates.

[0015] The nitrogen-containing organic ligand is one or more of melamine, dicyandiamide, 1,10-phenanthroline, 2,2'-bipyridine, phthalocyanine, porphyrin, cyanuric acid, hydroxylamine hydrochloride, triethylenediamine, 2-methylimidazole, imidazole, 2-pyridinecarboxamide, 2,6-dipicolinic acid, chitosan, urea.

[0016] In the preparation process of the V-N-C and Cu-N-C composite materials, the solvent used is one or more of water, ethanol, methanol, n-propanol, isopropanol. The inert atmosphere is one or a mixture of more of nitrogen, argon, helium

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) The present invention adopts heterogeneous copper-based and vanadium-based catalytic materials, which can catalyze the molecular oxygen oxidation of aromatic ketones to obtain the corresponding 1,4-naphthoquinone compounds, and has strong practicability and broad application prospects.

[0019] (2) Different from the gas-phase oxidation reaction process using naphthalene as the raw material, the present invention adopts a liquid-phase catalytic oxidation reaction system, and the yield of 1,4-naphthoquinone compounds is relatively high compared with the gas-phase oxidation method.

[0020] (3) Different from the process of using naphthalene, naphthol, 1-naphthylamine, etc. as raw materials to produce 1,4-naphthoquinone compounds in a liquid phase system, the present invention uses aromatic ketones as raw materials to prepare naphthoquinone, expanding the raw material channels and being a new route for preparing 1,4-naphthoquinone compounds. Description of the Drawings

[0021] Figure 1(a) is the scanning electron microscope image of catalyst A in Example 1; Figure 1 (b) is Figure 1 the partial enlarged view of (a).

[0022] Figure 2 is the GC analysis chromatogram of the oxidation product of α - tetrahydronaphthone in Example 1.

[0023] Figure 3 is the preparation flow chart of catalyst B in Example 2.

[0024] Figure 4 is the GC analysis chromatogram of the oxidation product of 2 - methyl - 1 - tetrahydronaphthone in Example 2.

[0025] Figure 5 is the GC analysis chromatogram of the oxidation product of α - tetrahydronaphthone in Example 12. Detailed implementation manners

[0026] The present invention will be described in detail below through examples, but the protection scope of the present invention is not limited to the following description.

[0027] Example 1

[0028] 1. Preparation of catalyst A

[0029] The Cu - N - C catalyst was prepared by using copper nitrate trihydrate and 1,10 - phenanthroline with a molar ratio of (1:2): 3 mmol of copper nitrate trihydrate and 6 mmol of 1,10 - phenanthroline were mixed, and 150 mL of ethanol was added. After heating to 100 °C and stirring for 4 h, it was cooled to room temperature, and the ethanol was removed by rotary evaporation. After vacuum drying at 60 °C for 12 h, this mixture was thoroughly ground and then heat - treated in a nitrogen atmosphere at 400 °C for 1.5 h and then cooled to obtain the Cu - N - C catalyst, denoted as catalyst A.

[0030] 2. Synthesis of 1,4 - naphthoquinone

[0031] 2 mmol of α - tetrahydronaphthone, 10 wt% of catalyst A, and 4 mL of γ - valerolactone were added to the reaction kettle, filled with 0.4 MPa of oxygen, and heated to 120 °C with stirring for 8 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. Sampling was carried out for quantitative analysis of the product. The conversion rate of α - tetrahydronaphthone was 80%, and the selectivity of 1,4 - naphthoquinone was 85%. The reaction results are shown in Table 1.

[0032] Example 2

[0033] 1. Preparation of catalyst B

[0034] The Cu-N-C catalyst was prepared by using copper nitrate and 1,10-phenanthroline in a molar ratio of 1:3: 3 mmol of copper nitrate and 9 mmol of 1,10-phenanthroline were mixed, 150 mL of ethanol was added, and the mixture was heated to 100 °C and stirred for 2 h. After cooling to room temperature, the ethanol was removed by rotary evaporation and vacuum dried at 60 °C for 12 h. The mixture was thoroughly ground and then heat-treated in a nitrogen atmosphere at 400 °C for 0.5 h and then cooled to obtain the Cu-N-C catalyst, denoted as catalyst B.

[0035] 2. Synthesis of 2-methyl-1,4-naphthoquinone

[0036] 2 mmol of 2-methyl-1-tetralone, 20 wt% of catalyst B, and 6 mL of γ-valerolactone were added to a reaction kettle, 0.7 MPa of oxygen was charged, and the temperature was raised to 120 °C with stirring and reacted for 8 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. Sampling was carried out for quantitative analysis of the product. The conversion rate of 2-methyl-1-tetralone was 72%, and the selectivity of 2-methyl-1,4-naphthoquinone was 79%. The reaction results are shown in Table 1.

[0037] Example 3

[0038] 1. Preparation of catalyst C

[0039] The Cu-N-C catalyst was prepared by using copper acetate monohydrate and melamine in a molar ratio of 1:5: 1 mmol of copper acetate monohydrate and 5 mmol of melamine were mixed, 250 mL of ethanol was added, and the mixture was heated to 90 °C and stirred for 4 h. After cooling to room temperature, the ethanol was removed by rotary evaporation and vacuum dried at 60 °C for 12 h. The mixture was thoroughly ground and then heat-treated in a nitrogen atmosphere at 600 °C for 3 h and then cooled to obtain the Cu-N-C catalyst, denoted as catalyst C.

[0040] 2. Synthesis of 2-methyl-1,4-naphthoquinone

[0041] 2 mmol of 3-methyl-1-tetralone, 15 wt% of catalyst C, and 6 mL of γ-valerolactone were added to a reaction kettle, 2.0 MPa of oxygen was charged, and the temperature was raised to 100 °C with stirring and reacted for 6 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. Sampling was carried out for quantitative analysis of the product. The conversion rate of 3-methyl-1-tetralone was 75%, and the selectivity of 2-methyl-1,4-naphthoquinone was 79%. The reaction results are shown in Table 1.

[0042] Example 4

[0043] 1. Preparation of catalyst D

[0044] The V-N-C catalyst was prepared by using ammonium metavanadate and hydroxylamine hydrochloride in a molar ratio of (1:1): 3 mmol of ammonium metavanadate and 3 mmol of hydroxylamine hydrochloride were mixed, 100 mL of isopropanol was added, and the mixture was heated to 90 °C and stirred for 4 h. Then it was cooled to room temperature, the methanol was removed by rotary evaporation, and it was dried under vacuum at 60 °C for 12 h. After thoroughly grinding this mixture, it was heat-treated in a nitrogen atmosphere at 600 °C for 10 h and then cooled to obtain the V-N-C catalyst, denoted as catalyst D.

[0045] 2. Synthesis of 1,4-naphthoquinone

[0046] 4 mmol of α-tetralone, 25 wt% of catalyst D, and 8 mL of γ-butyrolactone were added to a reaction kettle, 1.0 MPa of oxygen was charged, and the temperature was raised to 100 °C with stirring and reacted for 10 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. The sample was taken for quantitative analysis of the product. The conversion rate of α-tetralone was 70%, and the selectivity of 1,4-naphthoquinone was 80%. The reaction results are shown in Table 1.

[0047] Example 5

[0048] 1. Preparation of catalyst E

[0049] The V-N-C catalyst was prepared by using sodium vanadate and cyanuric acid in a molar ratio of (1:4): 2 mmol of sodium vanadate and 8 mmol of cyanuric acid were mixed, 100 mL of water was added, and the mixture was heated to 100 °C and stirred for 4 h. Then it was cooled to room temperature, the water was removed by rotary evaporation, and it was dried under vacuum at 80 °C for 12 h. After thoroughly grinding this mixture, it was heat-treated in a nitrogen atmosphere at 300 °C for 10 h and then cooled to obtain the V-N-C catalyst, denoted as catalyst E.

[0050] 2. Synthesis of 1,4-naphthoquinone

[0051] 3 mmol of 3-methyl-1-tetralone, 40 wt% of catalyst E, and 5 mL of δ-butyrolactone were added to a reaction kettle, 0.1 MPa of oxygen was charged, and the temperature was raised to 150 °C with stirring and reacted for 10 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. The sample was taken for quantitative analysis of the product. The conversion rate of α-tetralone was 78%, and the selectivity of 1,4-naphthoquinone was 80%. The reaction results are shown in Table 1.

[0052] Example 6

[0053] 1. Preparation of catalyst F

[0054] The Cu-N-C catalyst was prepared by using copper acetate and 2-pyridinecarboxamide with a molar ratio of (1:8): 1 mmol of copper acetate was mixed with 8 mmol of 2-pyridinecarboxamide, 200 mL of methanol was added, and the mixture was heated to 60 °C and stirred for 2 h. Then it was cooled to room temperature, the methanol was removed by rotary evaporation, and it was dried under vacuum at 80 °C for 12 h. After thoroughly grinding this mixture, it was heat-treated in a nitrogen atmosphere at 500 °C for 5 h and then cooled to obtain the Cu-N-C catalyst, denoted as catalyst F.

[0055] 2. Synthesis of 2-nitro-1,4-naphthoquinone

[0056] 3 mmol of 2-methyl-1-tetralone, 10 wt% of catalyst F, and 5 mL of ε-caprolactone were added to the reaction kettle, 0.5 MPa of oxygen was charged, and the temperature was raised to 130 °C with stirring and reacted for 10 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. Sampling was carried out for quantitative analysis of the product. The conversion rate of 2-nitro-1-tetralone was 77%, and the selectivity of 2-nitro-1,4-naphthoquinone was 81%. The reaction results are shown in Table 1.

[0057] Example 7

[0058] 1. Preparation of catalyst G

[0059] The Cu-N-C catalyst was prepared by using copper chloride and urea with a molar ratio of (1:4): 1 mmol of copper sulfate was mixed with 4 mmol of 2-methylimidazole, 200 mL of methanol was added, and the mixture was heated to 60 °C and stirred for 12 h. Then it was cooled to room temperature, the methanol was removed by rotary evaporation, and it was dried under vacuum at 50 °C for 12 h. After thoroughly grinding this mixture, it was heat-treated in a nitrogen atmosphere at 700 °C for 2 h and then cooled to obtain the Cu-N-C catalyst, denoted as catalyst G.

[0060] 2. Synthesis of 2-chloro-2,3-dihydro-1,4-naphthoquinone

[0061] 1 mmol of 2-chloro-1,2,3,4-tetrahydro-naphthalen-1-one, 20 wt% of catalyst G, and 2 mL of δ-valerolactone were added to the reaction kettle, 0.3 MPa of oxygen was charged, and the temperature was raised to 100 °C with stirring and reacted for 8 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. Sampling was carried out for quantitative analysis of the product. The conversion rate of 2-chloro-1,2,3,4-tetrahydro-naphthalen-1-one was 70%, and the selectivity of 2-chloro-2,3-dihydro-1,4-naphthoquinone was 74%. The reaction results are shown in Table 1.

[0062] Example 8

[0063] 1. Preparation of catalyst H

[0064] The Cu-N-C catalyst was prepared by using copper sulfate and triethylenediamine in a molar ratio of (1:3): 2 mmol of copper sulfate was mixed with 6 mmol of triethylenediamine, 150 mL of methanol was added, and the mixture was heated to 60 °C and stirred for 1 h. Then it was cooled to room temperature, the methanol was removed by rotary evaporation, and it was dried under vacuum at 50 °C for 12 h. After thoroughly grinding this mixture, it was heat-treated in a nitrogen atmosphere at 300 °C for 4 h and then cooled to obtain the Cu-N-C catalyst, denoted as catalyst H.

[0065] 2. Synthesis of 2-methoxy-1,4-naphthoquinone

[0066] 8 mmol of 2-methoxy-3,4-dihydronaphthalen-1(2H)-one, 15 wt% of catalyst H, and 20 mL of ε-caprolactone were added to a reaction kettle, 0.7 MPa of oxygen was charged, and the temperature was raised to 140 °C with stirring and reacted for 2 h. Then it was cooled to room temperature and the pressure was released. Samples were taken for quantitative analysis of the products. The conversion rate of 2-methoxy-3,4-dihydronaphthalen-1(2H)-one was 65%, and the selectivity for 2-methoxy-1,4-naphthoquinone was 70%. The reaction results are shown in Table 1.

[0067] Example 9

[0068] 1. Preparation of catalyst I

[0069] The Cu-N-C catalyst was prepared by using copper dichloride dihydrate and dicyandiamide in a molar ratio of (1:5): 2 mmol of copper sulfate was mixed with 10 mmol of dicyandiamide, 200 mL of ethanol was added, and the mixture was heated to 50 °C and stirred for 10 h. Then it was cooled to room temperature, the ethanol was removed by rotary evaporation, and it was dried under vacuum at 50 °C for 12 h. After thoroughly grinding this mixture, it was heat-treated in a nitrogen atmosphere at 400 °C for 4 h and then cooled to obtain the Cu-N-C catalyst, denoted as catalyst I.

[0070] 2. Synthesis of 2-bromo-2,3-dihydro-1,4-naphthoquinone

[0071] 3 mmol of 2-bromo-1-tetralone, 5 wt% of catalyst I, and 6 mL of δ-valerolactone were added to a reaction kettle, 0.5 MPa of oxygen was charged, and the temperature was raised to 60 °C with stirring and reacted for 10 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. Samples were taken for quantitative analysis of the products. The conversion rate of 2-bromo-1-tetralone was 70%, and the selectivity for 2-bromo-2,3-dihydro-1,4-naphthoquinone was 73%. The reaction results are shown in Table 1.

[0072] Example 10

[0073] 1. Preparation of catalyst J

[0074] The Cu-N-C catalyst was prepared by using copper nitrate trihydrate and 1,3,5-benzenetricarboxylic acid in a molar ratio of (1:10): 1 mmol of copper sulfate was mixed with 10 mmol of chitosan, 250 mL of ethanol was added, and the mixture was heated to 70 °C and stirred for 6 h. After cooling to room temperature, the ethanol was removed by rotary evaporation and vacuum dried at 70 °C for 12 h. The mixture was thoroughly ground and then heat-treated in a nitrogen atmosphere at 800 °C for 4 h and then cooled to obtain the Cu-N-C catalyst, denoted as catalyst J.

[0075] 2.2-Synthesis of aminonaphthalene-1,4-dione

[0076] 3 mmol of 2-amino-3,4-dihydro-1(2H)-naphthalenone, 20 wt% of catalyst J, and 10 mL of γ-valerolactone were added to a reaction kettle, filled with 0.6 MPa of oxygen, heated to 110 °C with stirring, and reacted for 12 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. Sampling was carried out for quantitative analysis of the product. The conversion rate of 2-amino-3,4-dihydro-1(2H)-naphthalenone was 71%, and the selectivity of 2-aminonaphthalene-1,4-dione was 82%. The reaction results are shown in Table 1.

[0077] Example 11

[0078] 2-Acetoxy-1,4-naphthoquinone synthesis

[0079] Using vanadium trioxide as the catalyst, denoted as catalyst K, 3 mmol of 2-acetoxy-3,4-dihydronaphthalen-1(2H)-one, 10 wt% of catalyst K, and 5 mL of γ-valerolactone were added to a reaction kettle, filled with 0.5 MPa of oxygen, heated to 110 °C with stirring, and reacted for 12 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. Sampling was carried out for quantitative analysis of the product. The conversion rate of 2-acetoxy-3,4-dihydronaphthalen-1(2H)-one was 65%, and the selectivity of 2-acetoxy-1,4-naphthoquinone was 80%. The reaction results are shown in Table 1.

[0080] Example 12

[0081] 1,4-Naphthoquinone synthesis

[0082] Using cuprous oxide as the catalyst, denoted as catalyst L, 3 mmol of 2-nitro-1-tetralone, 15 wt% of catalyst L, and 4 mL of γ-valerolactone were added to a reaction kettle, filled with 0.6 MPa of oxygen, heated to 120 °C with stirring, and reacted for 10 h. Then it was cooled to room temperature and the pressure was reduced to atmospheric pressure. Sampling was carried out for quantitative analysis of the product. The conversion rate of α-tetralone was 62%, and the selectivity of 1,4-naphthoquinone was 71%. The reaction results are shown in Table 1.

[0083] Table 1. Different catalyst compositions and solvents and their respective reaction results

[0084]

[0085] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as provided, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for preparing 1,4-naphthoquinone compounds by selective oxidation of aromatic ketones, characterized in that, The method uses aromatic ketones as raw materials and molecular oxygen as the oxygen source to catalytically oxidize aromatic ketones to 1,4-naphthoquinone compounds in an organic solvent through liquid-phase catalysis. The specific steps are as follows: Add a catalyst, an aromatic ketone raw material, and an organic solvent into a high-pressure reactor. The dosage of the catalyst is 5-40 wt% of the dosage of the aromatic ketone, and the dosage of the organic solvent is 1-40 times the mass of the aromatic ketone. Using molecular oxygen as the oxygen source, heat and stir in the temperature range of 60-150 °C, with an oxygen partial pressure of 0.1-2 MPa and a reaction duration of 0.2-12 h. After the reaction, cool to room temperature, reduce the pressure to atmospheric pressure, and separate to obtain 1,4-naphthoquinone compounds. The molecular oxygen in the catalytic oxidation reaction comes from air, oxygen, or a gas containing oxygen. The catalyst is one or more of vanadium pentoxide, vanadium dioxide, vanadium trioxide, vanadium nitride, V-N-C composite materials, copper oxide, cuprous oxide, and Cu-N-C composite materials.

2. The method for preparing 1,4-naphthoquinone compounds by selective oxidation of aromatic ketones according to claim 1, characterized in that, The aromatic ketone has the structure in the following reaction formula, and the 1,4-naphthoquinone compound has the structure in the following reaction formula: Wherein, R1 is one or more of hydrogen, alkyl, phenyl, -Cl, -Br, -F, -NO2, methoxy, ethoxy, cyano, amino, acetoxy, or acetamido; R2 is one or more of hydrogen, alkyl, phenyl, -Cl, -Br, -F, -NO2, methoxy, ethoxy, cyano, amino, acetoxy, or acetamido; R1 and R2 can be the same or different.

3. The method for preparing 1,4-naphthoquinone compounds by selective oxidation of aromatic ketones according to claim 1, characterized in that, The organic solvent used in the catalytic oxidation reaction is one or more of γ-valerolactone, δ-valerolactone, γ-butyrolactone, and ε-caprolactone.

4. A method for preparing 1,4-naphthoquinone compounds by selective oxidation of aromatic ketones according to claim 1, characterized in that, The oxygen partial pressure of the molecular oxygen in the catalytic oxidation reaction is 0.1-2 MPa.

5. A method for preparing 1,4-naphthoquinone compounds by selective oxidation of aromatic ketones according to claim 1, characterized in that, The catalyst is a V-N-C composite material or a Cu-N-C composite material.

6. A method for preparing 1,4-naphthoquinone compounds by selective oxidation of aromatic ketones according to claim 5, characterized in that, The preparation steps of the V-N-C and Cu-N-C composite material catalysts are as follows: Dissolve a metal source and a nitrogen-containing organic ligand in a solvent, where the molar ratio of the metal source to the nitrogen-containing organic ligand is 1:1-1:

10. Heat and stir at 30-100 °C for 1-12 h, then cool to room temperature. Rotate and evaporate to remove the solvent, and after vacuum drying, fully grind the obtained precursor and pyrolyze it in an inert gas atmosphere at 300-800 °C for 0.5-10 h and then cool. After fully grinding, obtain a Cu-N-C or V-N-C composite material.

7. A method for preparing 1,4-naphthoquinone compounds by selective oxidation of aromatic ketones according to claim 6, characterized in that, The copper source used in the preparation process of the V-N-C and Cu-N-C composite materials is one or more of copper nitrate, copper chloride, copper acetate, copper sulfate, and their hydrates, and the vanadium salt is one or more of ammonium metavanadate, ammonium vanadate, sodium metavanadate, sodium vanadate, and their hydrates; the nitrogen-containing organic ligand is one or more of melamine, dicyandiamide, 1,10-phenanthroline, 2,2'-bipyridine, phthalocyanine, porphyrin, cyanuric acid, hydroxylamine hydrochloride, triethylenediamine, 2-methylimidazole, imidazole, 2-pyridinecarboxamide, 2,6-dipyridinecarboxylic acid, chitosan, and urea.

8. A method for preparing 1,4-naphthoquinone compounds by selective oxidation of aromatic ketones according to claim 1, characterized in that, The conversion rate of the aromatic ketone can reach over 62%; the selectivity of the naphthoquinone compound can reach over 70%.

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