CN113171798B - Heterogeneous iron catalyst, preparation method thereof and process for preparing 2-methyl-1, 4-naphthoquinone by catalysis - Google Patents

Abstract

The invention relates to a heterogeneous iron catalyst, a preparation method thereof and a process for catalytically preparing 2-methyl-1,4-naphthoquinone. The catalyst is characterized in that 4,4 bipyridine is connected with two 3-chloroacetylacetones through a quaternary ammonium salt reaction, and a carbonyl oxygen atom is connected with a ferric ion through a coordination bond to form a skeleton structure. The preparation steps include: under an inert gas atmosphere, 4,4-bipyridine and 3-chloroacetylacetone are synthesized to obtain 4,4-bipyridine diacetylacetonate ion ligand, and then heated and stirred in a solvent with ferric salt A heterogeneous iron catalyst is obtained after the reaction. A process method for synthesizing 2-methyl-1,4-naphthoquinone by catalyzing the oxidation of 2-methylnaphthalene with the complex material as a catalyst. The preparation method of the catalyst is simple, the catalyst has good stability, and the catalyst is easy to recycle and reuse. The process condition of the catalyzed oxidation of 2-methylnaphthalene to synthesize 2-methyl-1,4-naphthoquinone is mild and suitable for industrial production.

Description

A kind of heterogeneous iron catalyst and its preparation method and catalytic preparation of 2-methyl-1,4-naphthalene Quinone Process

technical field

The invention relates to a heterogeneous iron catalyst, a preparation method thereof and a process for catalytically preparing 2-methyl-1,4-naphthoquinone.

Background technique

2-methyl-1,4-naphthoquinone (2-MNQ for short) is the earliest used vitamin K3, and it is also an important intermediate for the synthesis of various vitamin K. The compound has anticoagulant effect and can effectively activate anticoagulant factors in organisms; it can also be used as an additive to promote the growth and development of livestock; it is also the most important fat-soluble antioxidant in biological systems, which can promote high-energy compounds in the human body Metabolism, at the same time has the effect of diuresis, enhance liver detoxification function. There are many ways to prepare 2-MNQ, mainly including direct oxidation and indirect oxidation. Direct oxidation methods include 2-methylnaphthalene (Phys.Chem.Chem.Phys., 2015, 17, 23413--23422), 2-methyl-1-hydroxynaphthalene (RSC Advances, 2016, 16, 12717), 2-Methyl-1-methoxynaphthalene (Tetrohedron Lett, 2005, 46, 1091) etc. as raw material reaction pathway; relatively few processes using indirect oxidation method, such as diene synthesis reaction (KINETICS AND CATALYSIS, MAR2020, 61,2,276-282), etc.

In recent years, someone used lanthanum-doped MCM-41 as a catalyst to oxidize 2-methylnaphthalene to 2-methyl-1,4-naphthoquinone in liquid phase (Catalysis Communications 49(2014)10–14), although the substrate High conversion rate (95.8%), but poor selectivity (69.3%), and lanthanum is a precious rare earth element, the price is higher, and simultaneously for organisms, lanthanum has a greater toxic effect.

Among various preparation methods, the synthesis route using 2-methylnaphthalene as raw material is the simplest. Oxidants include peracetic acid, hydrogen peroxide, or chromic anhydride. In the choice of oxidizing agent, the oxidizing agent made of chromium is used to catalyze the oxidation of 2-methylnaphthalene (Med.Chem.Comm, 2014, 5,923; Tetrahedron, 1980, 36,123;) The final conversion rate obtained is 42-65 %, but in the reaction process, the production of chromium-containing waste water and chromium-containing solid waste has caused serious pollution to the environment, making it unsuitable for industrial applications. Therefore, the preparation of green, stable and reusable catalysts is of great importance to the industry needs are especially important.

At present, there are relatively few reports on the catalytic oxidation of 2-methylnaphthalene using iron (Chem. Eur. J. 2010, 16, 10300–10303; J. Org. Chem. 1997, 62, 673-678), but the catalyst cannot be recovered.

Contents of the invention

The object of the present invention is to provide a kind of heterogeneous iron catalyst in order to improve the deficiency of prior art, another object of the present invention is to provide the preparation method of above-mentioned catalyst, and another object of the present invention is to provide a kind of utilizing above-mentioned catalyst to catalyze preparation 2 - Process of methyl-1,4-naphthoquinone. Aiming at the existing problems of large amount of catalyst used, low reaction efficiency, and serious environmental pollution, the present invention provides a green and environmentally friendly method for preparing 2-methanol by oxidation of 2-methylnaphthalene, with mild reaction conditions, high reaction yield, low catalyst amount, and A new approach to the base-1,4-naphthoquinone.

The technical scheme of the present invention is: a heterogeneous iron catalyst, which is characterized in that 4,4 bipyridyl and two 3-chloroacetylacetones are connected through a quaternary ammonium salt reaction, and the carbonyl oxygen atom and the ferric ion are connected through a coordination bond Connected to form a skeleton structure, its structural formula is:

The present invention also provides a method for preparing the above-mentioned heterogeneous iron catalyst, and its specific steps are as follows: under an inert atmosphere, heat 4,4-bipyridine and 3-chloroacetylacetone in acetone (the amount is enough to ensure the dissolution) , after stirring the synthesis reaction, the resulting product obtained (4,4 bipyridyl diacetylacetonate ion ligand) double ion ligand after rotary evaporation, washing, and vacuum drying, and the double ion ligand and ferric salt are under an inert atmosphere. After heating and stirring in a solvent for reaction, the precipitate is filtered, washed and vacuum-dried to obtain a heterogeneous iron catalyst.

Preferably, the molar ratio of 4,4-bipyridine to 3-chloroacetylacetone is 1:(1.8～2.5); the ferric salt is iron nitrate (Fe(NO ₃ ) ₃ ), iron sulfate ( One of Fe ₂ (SO ₄ ) ₃ ) or ferric chloride (FeCl ₃ ). Preferably, the inert atmosphere is nitrogen or argon.

Preferably, the heating temperature for the synthesis of the diionic ligand is 30-50° C., and the synthesis reaction time is 5-15 h. Preferably, the solvent used in the washing step of the post-treatment of the diionic ligand is n-hexane, diethyl ether or ethyl acetate.

Preferably, the temperature of the heating reaction between the iron salt and the diionic ligand is 30-60° C.; the reaction time is 6-10 h; :(2.5-3.5). Preferably, the solvent for the reaction of the iron salt with the diionic ligand is methanol or ethanol.

The present invention also provides a process for synthesizing 2-methyl-1,4-naphthoquinone by catalytic oxidation of 2-methylnaphthalene using the above-mentioned heterogeneous iron catalyst. Naphthalene, an oxidant and a catalyst are reacted at a specific reaction temperature of 10-60 degrees for 1-10 hours to obtain the product 2-methyl-1,4-naphthoquinone. Finally, the catalyst is separated by centrifugation, and the catalyst can be reused after being washed and dried with acetonitrile.

Preferably the above-mentioned organic solvent is acetonitrile; the consumption of the catalyst is that the consumption of metal Fe in the catalyst is 5%-10% of the substance amount of 2-methylnaphthalene; the oxidizing agent is hydrogen peroxide, and the consumption of the oxidizing agent is substrate 2 - 3-9 times the amount of the substance of methylnaphthalene.

Beneficial effect:

The catalyst provided by the invention has simple preparation method, good stability and high activity. The catalyst has relatively high activity and high selectivity for preparing 2-methyl-1,4-naphthoquinone from 2-methylnaphthalene, is easy to recycle and reuse, and has the advantages of green and environmental protection, and is very suitable for industrial production.

Detailed ways

Example 1:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 30°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A1.

Relevant characterization of 4,4 bipyridine diacetylacetonate ion compound: FT-IR (v/cm1): 816,947, 1381.5, 1505.6, 2357.7, 3025.4, 3384.6, 3443.9

Elemental analysis (mass fraction): C: 48.3%; N: 11.3%; O: 32.2%; Fe: 3.7%

¹ HNMR:8.74(4H,s),7.69(4H,s),2.06(2H,s),0.03(12H,s)

¹³ CNMR:24.5(4C,s),25.9(4C,s),37.0(2C,s),52.0(4C,s),98.7(2C,s),206.0(4C,s)

The characterization of the catalysts of the following other examples is the same as above.

Example 2:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 40°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A2.

Example 3:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash three times with ether, remove ether by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A3.

Example 4:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 60°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A4.

Example 5:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 6 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A5.

Embodiment 6:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 8 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A6.

Embodiment 7:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 12 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. It was washed three times with ethyl acetate, and the ethyl acetate was removed by rotary evaporation and vacuum-dried for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A7.

Embodiment 8:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. Weigh 0.162g (1mmol) of anhydrous ferric chloride and dissolve it in 10ml of methanol, and add 1.2g (3mmol) of the above-prepared ligand. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A8.

Embodiment 9:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 50°C to obtain catalyst A9.

Example 10:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. Weigh 0.4g (1mmol) of ferric nitrate nonahydrate and dissolve it in 10ml of methanol, and add 1.2g (3mmol) of the ligand. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 60°C to obtain catalyst A10.

Example 11:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. Weigh 0.4g (1mmol) of ferric nitrate nonahydrate and dissolve it in 10ml of methanol, and add 1.2g (3mmol) of the ligand. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 70°C to obtain catalyst A11.

Example 12:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:1.8 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A12.

Example 13:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2.5 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. Weigh 0.4 g (1 mmol) of ferric nitrate nonahydrate and dissolve it in 10 ml of ethanol, and add 1.2 g (3 mmol) of the ligand prepared above. Under argon atmosphere, stir at 50°C for 8h, filter, wash with ethanol, and dry under vacuum at 80°C to obtain catalyst A13.

Example 14:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.19993 g (0.5 mmol Fe ₂ (SO ₄ ) ₃ ) of anhydrous ferric sulfate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A14.

Example 15:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 5ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A15.

Example 16:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 15ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A16.

Example 17:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 1:2 (molar ratio) in 20ml of acetone, heat and stir at 50°C under an argon atmosphere for 10 hours, and remove the acetone by rotary evaporation after cooling to room temperature Then wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum-dry for future use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A17.

Example 18:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 30°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A18.

Example 19:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 40°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A19.

Example 20:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 5 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A20.

Example 21:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 15 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A21.

Example 22:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.0 g (2.5 mmol) of the ligand prepared above was added. Under nitrogen atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A22.

Example 23:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.4 g (3.5 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 8h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A23.

Example 24:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 6h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A24.

Example 25:

Dissolve 4,4-bipyridine and 3-chloroacetylacetone in 10ml of acetone at a ratio of 1:2 (molar ratio), heat and stir at 50°C under an argon atmosphere for 10 hours, and then remove the acetone by rotary evaporation after cooling to room temperature. Wash with n-hexane three times, remove n-hexane by rotary evaporation and vacuum dry for later use. 0.4 g (1 mmol) of ferric nitrate nonahydrate was weighed and dissolved in 10 ml of methanol, and 1.2 g (3 mmol) of the ligand prepared above was added. Under argon atmosphere, stir at 50°C for 10h, filter, wash with methanol, and dry under vacuum at 80°C to obtain catalyst A25.

Example 26: The prepared catalyst was used in the preparation of 2-methyl-1,4-naphthoquinone.

In a 25ml autoclave, add 1mmol 2-methylnaphthalene, 3mmol hydrogen peroxide, 1ml acetonitrile and catalyst A1, and the amount of catalyst is 62mg (the addition of Fe is 5%=1mmol2-methylnaphthalene*5%), tighten Autoclave lid. Place it in a kettle jacket at 30°C and heat it for 5 hours. After the reaction is over, take out the autoclave from the kettle jacket and let it cool down to room temperature, extract with ether, and detect the conversion rate of 2-methylnaphthalene and 2-methylnaphthalene by gas chromatography. Selectivity of methyl-1,4-naphthoquinone. Finally, the catalyst is filtered and washed with ether, and can be reused after drying. The reaction formula is as follows:

Catalysts A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23, A24, A25 The process is consistent with the process flow of A1, and the reaction results are listed in the following table:

Except following difference, all the other are identical with embodiment case 26, and temperature of reaction is as follows (the catalyzer that uses is A7):

temperature 2-Methylnaphthalene conversion rate 2-Methyl-1,4-Naphthoquinone Selectivity 20°C 15.3% 94% 40℃ 20.7% 96% 50℃ 12.4% 82%

Except following difference, all the other are identical with embodiment case 26, and reaction time is as follows (catalyst that uses is A10):

time (h) 2-Methylnaphthalene conversion rate 2-Methyl-1,4-Naphthoquinone Selectivity 1 6.8% 98% 2 12.4% 95% 3 18.9% 97% 4 23.7% 93% 6 25.7% 95% 8 25.73% 90% 10 25.9% 89%

Except following difference, all the other are identical with embodiment case 26, and hydrogen peroxide amount is as follows (catalyst that uses is A11):

Hydrogen peroxide 2-Methylnaphthalene conversion rate 2-Methyl-1,4-Naphthoquinone Selectivity 6mmol 26.2% 93% 9mmol 26.7% 95%

Except following difference, all the other are identical with embodiment case 26, the addition of metal Fe (for example: the addition of Fe is 5%=1mmol2-methylnaphthalene*5%) in the catalyst is as follows (the catalyst that uses is A13):

The amount of Fe added 2-Methylnaphthalene conversion rate 2-Methyl-1,4-Naphthoquinone Selectivity 6% 25.8% 91% 7% 25.7% 97%

The recovery and use of catalyst A3 is as follows:

Claims (9)

1. a heterogeneous iron catalyst is characterized in that 4, 4-bipyridine and two 3-chloroacetylacetone are connected through quaternary ammonium salt reaction, carbonyl oxygen atoms and ferric ions are connected through coordination bonds to form a framework structure, and the structural formula is as follows:

2. a process for preparing a heterogeneous iron catalyst according to claim 1, comprising the specific steps of: and under the inert atmosphere, heating and stirring 4, 4-dipyridine and 3-chloroacetylacetone in acetone for synthesis reaction, and performing rotary evaporation, washing and vacuum drying on the obtained product to obtain a double-ion ligand, heating and stirring the double-ion ligand and ferric salt in a solvent for reaction under the inert atmosphere, and filtering, washing and vacuum drying the precipitate to obtain the heterogeneous iron catalyst.

3. The method according to claim 2, wherein the molar ratio of 4, 4-bipyridine to 3-chloroacetylacetone is 1 (1.8-2.5); the ferric salt is ferric nitrate.

4. The method of claim 2, wherein the inert atmosphere is nitrogen or argon.

5. The method according to claim 2, wherein the heating temperature for the synthesis of the zwitterionic ligand is 30-50 ℃ and the time for the synthesis reaction is 5-15h.

6. The method according to claim 2, characterized in that the solvent used in the washing step of the post-treatment of the zwitterionic ligand is n-hexane, diethyl ether or ethyl acetate.

7. The method according to claim 2, characterized in that the temperature of the heating reaction of the iron salt with the di-ionic ligand is 30-60 ℃; the reaction time is 6-10h; the molar ratio of iron atoms of ferric salt to the double-ion ligand in the reaction of ferric salt and double-ion ligand is 1 (2.5-3.5).

8. The method according to claim 2, characterized in that the solvent for the reaction of the iron salt with the di-ionic ligand is methanol or ethanol.

9. A process for synthesizing 2-methyl-1, 4-naphthoquinone by catalyzing and preparing 2-methylnaphthalene by using the heterogeneous iron catalyst of claim 1, which comprises the following specific steps: adding 2-methylnaphthalene, an oxidant and a catalyst into an organic solvent, and reacting for 3-10 hours at 20-40 ℃ to obtain a product 2-methyl-1, 4-naphthoquinone; wherein the organic solvent is acetonitrile; the dosage of the catalyst is 5% -10% of the dosage of the metal Fe in the catalyst which is the material of 2-methylnaphthalene; the oxidant is hydrogen peroxide, and the dosage of the oxidant is 3-9 times of the dosage of the substrate 2-methylnaphthalene.