CN103071532A - Catalyst for preparing cyclohexanone through catalytic oxidation of cyclohexanol and preparation method thereof - Google Patents

Abstract

The invention discloses a high-efficiency catalyst for preparing cyclohexanone by catalytic oxidation of cyclohexanol and a preparation method thereof. The catalyst is a coordination polymer of monovalent copper, and the molecular formula of the coordination polymer is CuL, wherein L For 4,5 dicyanoimidazole. The preparation method of the catalyst: accurately weigh the soluble copper salt and dissolve it in acetonitrile, and add the solution to the bottom of a glass tube with one end sealed, then add tetrabutylammonium bromide aqueous solution to form a solution a; Dicyanoimidazole is dissolved in a mixed solvent of alcohol and nitrobenzene to form solution b; slowly add solution b to the upper part of solution a, vacuumize, and then seal the other end with an alcohol torch. Put the sealed glass tube into an oven, react for a period of time, and then slowly drop to room temperature to obtain the finished target catalyst. The catalyst can not only greatly improve the conversion rate of cyclohexanol, but also obviously improve the selectivity of cyclohexanone, and the catalyst can be reused.

Description

Catalyst for preparing cyclohexanone by catalytic oxidation of cyclohexanol and preparation method thereof

technical field

The invention belongs to the technical field of catalysis, and in particular relates to a catalyst for preparing cyclohexanone by catalytic oxidation of cyclohexanol and a preparation method thereof.

Background technique

Cyclohexanone is an important organic chemical raw material, widely used in coatings, synthetic rubber, medicine and other fields. Cyclohexanone is an important intermediate for the synthesis of adipic acid, caprolactam, nylon and other fine chemicals; and it is used as an important solvent in various fields, such as paints, organic phosphorus pesticides, grease, rubber and dyes. .

At present, there are two main methods for preparing cyclohexanone from cyclohexanol: dehydrogenation of cyclohexanol and oxidation of cyclohexanol. The dehydrogenation of cyclohexanol to prepare cyclohexanone is mainly in the gas phase, at 1.0-3.5Mpa, 220-450°C, adding various catalysts, such as the CuO series catalyst M/CuO/ZnO, M/CuO/ SiO ₂ M=Pd, Pt, Ru; the low-temperature copper-based dehydrogenation catalyst reported by CN1381434A is mainly based on copper metal or oxide, adding palladium or/and platinum metal or metal oxide and selected from zinc, magnesium , calcium, strontium, barium, silicon, aluminum, chromium, manganese, zirconium or titanium metal or oxide; CN101757923A reported CuO/ZnO/Al ₂ O ₃ three-way catalyst, CN102247854A reported CuO/ZnO/ZrO ₂ catalyst . This type of reaction is carried out under gas-phase conditions, and since the gas-phase dehydrogenation reaction is a volume-enlarged reaction, the requirements for the reaction equipment are relatively high, and the internal pressure of the reactor needs to be lowered in time. Therefore, it is necessary to explore a reaction method with lower equipment requirements.

The oxidation of cyclohexanol is mainly through the addition of an oxidizing agent and a catalyst to effectively convert cyclohexanol into cyclohexanone. Traditional oxidants such as chromium trioxide, potassium permanganate, potassium dichromate, etc. Although such oxidants are highly oxidizing and can oxidize various substrates, they are highly corrosive and toxic and will cause equipment corrosion. Products A series of problems such as post-processing difficulties and environmental pollution. Later, it was developed to use green oxidants such as oxygen, hydrogen peroxide, etc. as oxidants, but these oxidants need to be matched with better catalysts to effectively improve the conversion rate of cyclohexanol and the yield of cyclohexanone. A sexual catalyst is very necessary. Sato, K et al. used 3%-30% H ₂ O ₂ as the oxidant, sodium tungstate dihydrate as the catalyst, and trioctylmethylammonium bisulfate as the phase transfer catalyst to successfully realize cyclohexene in an organic-water two-phase system. The alcohol was oxidized to cyclohexanone with very good conversion and selectivity. However, phase transfer catalysts are very expensive, which is not conducive to large-scale use, and organic solvents will also cause serious pollution (J.Am.Chem.Soc.1997, 119, 12386-12387). CN1793099A patent reports that H ₂ O ₂ is used as oxidant, and phosphorus molybdovanadate heteropolyacid salt (Q _3+x PMo _12-x V _x O ₄₀ , X=1～3, Q represents quaternary ammonium salt cation or MH ₄ ⁺ ) as a catalyst to oxidize cyclohexanone with cyclohexanol in an organic solvent, but the conversion efficiency of cyclohexanol is low (the highest is 79%), and the entire oxidation reaction is completed in an organic solvent, so the pollution is serious.

Contents of the invention

In order to solve the problems of low catalytic activity of the catalyst used in the above-mentioned prior art, low conversion rate of cyclohexanol, and serious pollution, the invention provides a high-efficiency catalyst for catalytic oxidation of cyclohexanol and a preparation method thereof. Not only can the conversion rate of cyclohexanol be greatly improved, but also the selectivity of cyclohexanone can be obviously improved, and the catalyst can be reused.

The technical solution adopted by the present invention to solve the above problems:

The invention discloses a catalyst for preparing cyclohexanone by catalytic oxidation of cyclohexanol. The catalyst is a coordination polymer of monovalent copper. The molecular formula of the coordination polymer is CuL, wherein L is 4,5 dicyanoimidazole.

The preparation method of the catalyst comprises the following steps: accurately weighing soluble copper salt and dissolving it in acetonitrile, adding the solution to the bottom of a reaction vessel with one end sealed, and then adding tetrabutylammonium bromide aqueous solution to form solution a; Dissolve the ligand 4,5 dicyanoimidazole in a mixed solvent of alcohol and nitrobenzene to form solution b; slowly add solution b to the upper part of solution a, vacuumize, and then seal the other end of the reaction vessel; seal the Put the reaction container into an oven, react for 2-5 days, and then slowly lower to room temperature to obtain yellow blocky crystals or powder, which is the finished product of the target catalyst.

In the preparation method, the soluble copper salt can be one of copper perchlorate, copper nitrate, copper acetate, copper chloride and copper sulfate.

In the preparation method, in the mixed solvent of alcohol and nitrobenzene, the alcohol used may be one of methanol, ethanol, isopropanol and cyclohexanol.

In the preparation method, the reaction temperature may be 80-120°C.

Application of the above monovalent copper complex in the catalytic oxidation of cyclohexanol to prepare cyclohexanone;

The monovalent copper coordination polymer can be used as a catalyst for the catalytic oxidation of cyclohexanol to prepare cyclohexanone. The amount of catalyst used is: 1.5 mg of catalyst is used in 10 ml of cyclohexanol. Described catalytic experiment process: add cyclohexanol 50ml, catalyzer 7.5mg in the 100 milliliter three-neck flasks with reflux condenser, thermometer, air guide tube, slowly pass into air in the air guide tube, water bath control reaction temperature is 80 ℃, reacted for 5 hours under stirring, and the reaction product was monitored by gas chromatography.

The beneficial effects of the present invention are that the present invention provides a high-efficiency catalyst for the catalytic oxidation of cyclohexanol, which can not only greatly improve the conversion rate of cyclohexanol, but also significantly improve the selectivity, and the preparation of the catalyst is simple and the yield is high, which is beneficial to production.

Description of drawings

Figure 1: Crystal channel diagram of the target catalyst CuL (L=4,5 dicyanoimidazole);

Figure 2: Gas chromatogram of pure cyclohexanol;

Fig. 3: No catalyst is added, only the gas chromatogram of cyclohexanol passing through oxygen;

Figure 4: Adding a catalyst, the gas chromatogram of cyclohexanol after being catalyzed and oxidized;

Figure 5: Gas chromatogram of pure cyclohexanone.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments.

Example 1

Accurately weigh 50 mg of copper perchlorate and dissolve it in 4 ml of acetonitrile, and add the solution to the bottom of glass tube A with one end sealed, then add 20 drops of 1 mg/ml tetrabutylammonium bromide aqueous solution to form solution a; , 5 dicyanoimidazole (20mg) was dissolved in a mixed solvent of cyclohexanol and nitrobenzene 6ml (v/v=1:1) to form solution b; slowly add solution b to the upper part of solution a, vacuumize, and then Seal the other end of the glass tube A with an alcohol blowtorch to prevent the solvent from evaporating. Put the sealed glass tube A into an oven, react at 100 degrees Celsius for 3 days, and then slowly lower it to room temperature to obtain yellow blocky crystals or powder, which is the finished product of the target catalyst. The structure of the target catalyst has been determined by single crystal X-rays. The diffractometer was used for analysis, and the analysis results are shown in Figure 1, and the corresponding crystal data are shown in Table 1.

The crystal data of table 1 target catalyst

Example 2

The difference between embodiment 2 and embodiment 1: the reaction temperature is 80 degrees centigrade, and the reaction time is 5 days.

Example 3

The difference between Example 3 and Example 1: The mixed solvent is methanol and nitrobenzene (1:1, V/V).

Example 4

The difference between embodiment 4 and embodiment 1: copper perchlorate is replaced by copper nitrate.

Example 5

The monovalent copper coordination polymer can be used as a catalyst for the catalytic oxidation of cyclohexanol to prepare cyclohexanone. The amount of catalyst used is: 1.5 mg of catalyst is used in 10 ml of cyclohexanol. Described catalytic experiment process: add cyclohexanol 50ml, catalyzer 7.5mg in the 100 milliliter three-neck flasks with reflux condenser, thermometer, air guide tube, slowly pass into air in the air guide tube, water bath control reaction temperature is 80 ℃, reacted for 5 hours under stirring. The reaction product was monitored by gas chromatography. The conversion rate of cyclohexanol reaches 100%, and the yield of cyclohexanone reaches 94.16%. The gas chromatography of pure cyclohexanol (Fig. 2) shows that the peak appears at the time t of 9.831 seconds; under the reaction conditions of no catalyst and only oxygen, the reaction product is characterized by gas chromatography, and it is found that a similar pure cyclohexanol also appears at 9.808 seconds. The peaks of cyclohexanol (Figures 3, 4, 5), we believe that cyclohexanol is difficult to be oxidized in the absence of catalyst. In the reaction system with the presence of catalyst, the gas chromatogram of the reaction product showed a peak at 11.060 seconds, which was similar to that of pure cyclohexanone (10.372).

It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should belong to the protection scope of the appended claims of the present invention.

Claims (5)

1. one kind is used for the catalyst that the cyclohexanol catalytic oxidation prepares cyclohexanone, it is characterized in that described catalyst is the monovalence copper coordination polymer, and the molecular formula of this Coordination Polymer is CuL, and wherein L is 4,5 dicyano imidazoles.

2. according to the preparation method of the described 1 described catalyst of right, it is characterized in that, may further comprise the steps:

Accurately the mantoquita of weighing solubility is dissolved in the acetonitrile, and solution is joined the reaction container bottom of an end closure, then adds the tetrabutyl phosphonium bromide aqueous ammonium, forms solution a; Part 4,5 dicyano imidazoles are dissolved in the mixed solvent of pure and mild nitrobenzene, form solution b; Solution b is slowly added the top of solution a, vacuumize, then with the other end sealing of reaction vessel; The reaction vessel of sealing is put into baking oven, reacted 2-5 days, then slowly drop to room temperature, obtain yellow bulk crystals or powder, i.e. target catalyst finished product.

3. according to right described 2 described preparation methods, it is characterized in that what described soluble copper salt can be in cupric perchlorate, copper nitrate, copper acetate, copper chloride, the copper sulphate is a kind of.

4. according to right described 2 described preparation methods, it is characterized in that, described pure and mild nitrobenzene mixed solvent, used alcohol can be a kind of in methyl alcohol, ethanol, isopropyl alcohol, the cyclohexanol.

5. according to right described 2 described preparation methods, it is characterized in that described reaction temperature can be 80～120 ℃.

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