NH4CoF3 catalyst, its preparation method and application

Abstract

The application discloses an NH4CoF3 catalyst and a preparation method and application thereof, and the catalyst is prepared by the following steps: preparing Co3O4 through a hydrothermal method, and etching the Co3O4 through NH4F in a tube furnace at low temperature. The preparation method is simple, and raw materials are cheap and easy to obtain. The prepared catalyst is used in a limonene selective oxidation limonene-1,2-epoxide reaction under the condition that molecular oxygen is used as an oxidant and no solvent is used, and the catalyst exhibits good catalytic performance and stability. The catalytic system meets the requirements of green chemical industry and sustainable development.

Description

TECHNICAL FIELD

[0001] The application relates to an NH4CoF3 catalyst and a preparation method and application thereof, and belongs to the technical field of catalyst preparation. BACKGROUND

[0002] Limonene is a common natural terpene, and oxidation thereof generates many oxidation products, such as limonene-1,2-epoxide, carvone, perillyl alcohol and the like. The limonene-1,2-epoxide can be copolymerized with carbon dioxide to prepare a bio-based polycarbonate, which is expected to replace the traditional petroleum-based route and has extremely high application value and broad prospects.

[0003] In many studies on the preparation of limonene-1,2-epoxide from limonene oxidation, limonene is subjected to homogeneous oxidation in the presence of various metal complexes as catalysts. Although the homogeneous catalysts can more easily provide reactive sites, these catalysts are difficult to separate, have fast activity deactivation, and recycling is still a challenge. On the other hand, traditional oxidation is carried out with a stoichiometric amount of oxidizing agent, such as permanganate, Dess-Martin reagent or active dimethyl sulfoxide reagent. These methods need to use relatively expensive oxidizing agents, lack selectivity, generate metal waste and use non-green halogenated solvents. From the economic and environmental points of view, they are not sustainable and need to be improved. SUMMARY

[0004] The application aims to overcome the deficiencies in the prior art and provide an NH4CoF3 catalyst and a preparation method and application thereof. A preparation method of a heterogeneous catalyst for limonene solvent-free oxidation to prepare limonene-1,2-epoxide is provided. The catalyst is used for limonene solvent-free oxidation to prepare limonene-1,2-epoxide, can efficiently and selectively oxidize limonene under relatively mild reaction conditions, and has no obvious change in catalytic effect after repeated use for many times.

[0005] To achieve the above-mentioned purposes, the technical scheme adopted by the application is as follows:

[0006] In a first aspect, the application provides a preparation method of an NH4CoF3 catalyst, which comprises: dissolving Co(NO3)2.6H2O in a mixed solution of methanol and benzyl alcohol, uniformly mixing and placing in a hydrothermal kettle for heating to obtain a precipitate;

[0007] The precipitate is washed and dried, and Co3O4 is prepared by calcination.

[0008] The Co3O4 and NH4F are calcined in a nitrogen-filled environment to obtain the NH4CoF3 catalyst.

[0009] Further, Co(NO3)2·6H2O is dissolved in a mixed solution of methanol and benzyl alcohol, and the concentration of the cobalt nitrate is 0.0652-0.1087 mol / L;

[0010] Further, the volume ratio of methanol to benzyl alcohol in the mixed solution is 20:3.

[0011] Further, the mass ratio of Co3O4 to NH4F is 1:4-1:6.

[0012] Further, the method comprises placing Co3O4 and NH4F in the same porcelain boat, and the porcelain boat is placed in a tube furnace filled with nitrogen for calcination; the Co3O4 is placed downstream of the porcelain boat, and the NH4F is placed upstream of the porcelain boat.

[0013] In a second aspect, the application provides an NH4CoF3 catalyst prepared according to any of the above-mentioned preparation methods.

[0014] In a third aspect, the application provides an application of the NH4CoF3 catalyst in a reaction for selectively oxidizing limonene to prepare limonene-1,2-epoxide.

[0015] Further, the NH4CoF3 catalyst, limonene and isobutyraldehyde are added to a high-pressure reaction kettle, molecular oxygen is introduced, and the target product limonene-1,2-epoxide is obtained after a certain reaction temperature and pressure for a certain period of time.

[0016] Further, the catalyst is used in an amount of 0.008-0.025 g / mL based on the volume of limonene.

[0017] Further, the molar ratio of limonene to isobutyraldehyde is 1:1.25-1:1.75.

[0018] Further, the reaction temperature of the high-pressure reaction kettle is 20-40℃, the reaction time is 3-5 h, and the reaction pressure is 0.1-0.3 MPa.

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] A preparation method of an NH4CoF3 catalyst, which is first prepared into Co3O4 by a hydrothermal method, and then fluorinated by NH4F in a tube furnace, the raw materials are cheap and easy to obtain, and the preparation method is simple;

[0021] The prepared NH4CoF3 catalyst is used in a reaction for oxidizing limonene to prepare limonene-1,2-epoxide, the catalytic system is simple, the catalytic effect does not change obviously after repeated use for many times, the reaction effect is good, and the application prospect is good. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The cycle effect diagram of the NH4CoF3 catalyst prepared in the embodiment 1 of the present application for limonene oxidation.

[0023] Figure 2 The XRD pattern of the NH4CoF3 catalyst prepared in the embodiment 1 of the present application and the Co3O4 catalyst prepared in the comparative example 1 of the present application.

[0024] Figure 3 The SEM image of the NH4CoF3 catalyst in the embodiment 1 of the present application.

[0025] Figure 4 The SEM image of the Co3O4 catalyst in the comparative example 1 of the present application. DETAILED DESCRIPTION

[0026] The present application will be further described in conjunction with the accompanying drawings, and the following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0027] The present application provides a preparation method of NH4CoF3 catalyst, comprising:

[0028] Dissolving Co(NO3)2·6H2O in a mixed solution of methanol and benzyl alcohol, uniformly mixing and placing in a hydrothermal kettle for heating to obtain a precipitate;

[0029] Washing and drying the precipitate, and preparing Co3O4 by calcination;

[0030] Placing Co3O4 and NH4F in the same porcelain boat, placing Co3O4 in the downstream of the porcelain boat and placing NH4F in the upstream of the porcelain boat, and placing the porcelain boat in a nitrogen-filled tube furnace for calcination to prepare NH4CoF3 catalyst.

[0031] The concentration of the cobalt nitrate solution is 0.0652-0.1087 mol / L, the volume ratio of methanol to benzyl alcohol in the mixed solution is 20:3, and the mass ratio of Co3O4 to NH4F is 1:4-1:6.

[0032] The specific implementation process comprises: dissolving Co(NO3)2·6H2O in a mixed solution of methanol and benzyl alcohol, stirring, and then placing the obtained solution in a hydrothermal kettle, and solvothermal treatment at 150-200℃ for 24-48h in an oven. After the liquid is cooled to room temperature, the precipitate is washed with deionized water and anhydrous ethanol for multiple times, the obtained precipitate is dried, and then calcination is carried out at 200-400℃ for 1-3h to obtain Co3O4 catalyst. Then, Co3O4 and NH4F are placed in the same porcelain boat, and the porcelain boat is placed in a nitrogen-filled tube furnace, and calcination is carried out at 200-400℃ for 1-3h to obtain NH4CoF3 catalyst.

[0033] Example 1

[0034] Dissolve 4.0 mmol Co(N03)2-6H20 in a mixed solution of 40 mL methanol and 6 mL benzyl alcohol, and stir for 0.5 h;

[0035] Transfer the mixed solution into a 100 mL hydrothermal kettle, and hydrothermal treatment at 180 °C for 36 h in an oven. After the hydrothermal kettle is cooled to room temperature, suction filtration is performed, and the precipitate is washed with deionized water and anhydrous ethanol for multiple times;

[0036] Dry the washed precipitate in an 80 °C oven for 12 h, and then calcine at 300 °C under an air atmosphere for 2 h to obtain a Co304 catalyst;

[0037] Place 0.1 g of Co304 and 0.5 g of NH4F in the same boat, with NH4F placed upstream of the boat and Co304 placed downstream of the boat, and then transfer to a tube furnace, and calcine at 200 °C for 2 h under a nitrogen atmosphere to obtain a NH4CoF3 catalyst. As shown in FIG. 1, the XRD pattern of the NH4CoF3 catalyst prepared in this example includes a Figure 2 SEM image thereof. Figure 3

[0038] The prepared catalyst is used for a limonene selective oxidation reaction to prepare limonene-1,2-epoxide, and the specific steps are as follows:

[0039] Add 0.10 g of the NH4CoF3 catalyst, 40 mmol of limonene, and 60 mmol of isobutyraldehyde into a high-pressure reaction kettle. After purging the reactor with oxygen for 3 times, seal the reactor and heat to the required temperature of 30 °C under constant stirring;

[0040] Introduce oxygen into the reactor until the pressure reaches 0.2 MPa, and after 4 h of reaction, the product is quantitatively analyzed by gas chromatography.

[0041] Gas chromatography analysis of this example found that the conversion rate of limonene reached 59.5%, and the selectivity of limonene-1,2-epoxide reached 77.5%.

[0042] In addition, in order to test the recycling performance of the catalyst, the used catalyst is washed with ethanol, and then dried at 80 °C for 12 h before being used for the next test. It is found that after 4 cycles of use, the conversion rate of limonene decreases from 59.5% to 55.3%, and the selectivity of limonene-1,2-epoxide increases from 77.5% to 80.9%, and the catalytic activity does not change significantly. The effect of 4 cycles is shown in FIG. 2. Figure 1

[0043] Comparative Example 1 ​​

[0044] A Co304catalyst was prepared under the same conditions as Example 1 except that NH4F was not added, and the catalytic performance was tested under the same conditions as Example 1. The results showed that the conversion of limonene was 38.6% and the selectivity of limonene-1, 2-epoxide was 80.6%.

[0045] As shown in FIG. 1, the XRD pattern of the Co304catalyst prepared in Example 1, Figure 2 Figure 4 FIG. 2 is a SEM image of the Co304catalyst prepared in Example 1.

[0046] Comparative Example 2

[0047] The catalytic performance was tested under the same conditions as Example 1 except that no catalyst was added. The results showed that the conversion of limonene was 19.0% and the selectivity of limonene-1, 2-epoxide was 67.6%.

[0048] Example 2

[0049] The preparation method was the same as Example 1 except that the amount of NH4F added was 0.4 g, and the catalyst was still NH4CoF3. Under the same conditions except for the amount of NH4F added, the conversion of limonene was 58.6% and the selectivity of limonene-1, 2-epoxide was 78.3%.

[0050] Example 3

[0051] The preparation method was the same as Example 1 except that the amount of NH4F added was 0.6 g, and the catalyst was still NH4CoF3. Under the same conditions except for the amount of NH4F added, the conversion of limonene was 59.7% and the selectivity of limonene-1, 2-epoxide was 79.8%.

[0052] Example 4

[0053] Example 1 was repeated except that 0.05 g of NH4CoF3catalyst was added to the reaction kettle. Under the same conditions except for the amount of NH4F added, the conversion of limonene was 46.8% and the selectivity of limonene-1, 2-epoxide was 79.9%.

[0054] Example 5

[0055] Example 1 was repeated except that 0.15 g of NH4CoF3catalyst was added to the reaction kettle. Under the same conditions except for the amount of NH4F added, the conversion of limonene was 61.2% and the selectivity of limonene-1, 2-epoxide was 76.7%.

[0056] Example 6 ​

[0057] Example 1 was repeated, except that the limonene oxidation temperature was 20°C. Under otherwise identical reaction conditions, the conversion of limonene was 40.2% and the selectivity of limonene-1,2-epoxide was 85.1%.

[0058] Example 7

[0059] Example 1 was repeated, except that the limonene oxidation temperature was 40°C. Under otherwise identical reaction conditions, the conversion of limonene was 64.8% and the selectivity of limonene-1,2-epoxide was 70.1%.

[0060] Example 8

[0061] Example 1 was repeated, except that the limonene oxidation reaction time was 3h. Under otherwise identical reaction conditions, the conversion of limonene was 30.5% and the selectivity of limonene-1,2-epoxide was 80.6%.

[0062] Example 9

[0063] Example 1 was repeated, except that the limonene oxidation reaction time was 5h. Under otherwise identical reaction conditions, the conversion of limonene was 60.9% and the selectivity of limonene-1,2-epoxide was 78.6%.

[0064] Example 10

[0065] Example 1 was repeated, except that the limonene oxidation reaction pressure was 0.1 MPa. Under otherwise identical reaction conditions, the conversion of limonene was 44.2% and the selectivity of limonene-1,2-epoxide was 80.4%.

[0066] Example 11

[0067] Example 1 was repeated, except that the limonene oxidation reaction pressure was 0.3 MPa. Under otherwise identical reaction conditions, the conversion of limonene was 59.9% and the selectivity of limonene-1,2-epoxide was 78.4%.

[0068] Example 12

[0069] Example 1 was repeated, except that the molar ratio of limonene to isobutyraldehyde was 1:1.25. Under otherwise identical reaction conditions, the conversion of limonene was 34.4% and the selectivity of limonene-1,2-epoxide was 80.4%.

[0070] Example 13

[0071] Example 1 was repeated, except that the amount of limonene and isobutyraldehyde was 1:1.75. Under the same reaction conditions, the conversion rate of limonene was 62.6%, and the selectivity of limonene-1,2-epoxide was 71.5%.

[0072] From the above examples and comparative examples, the following conclusions can be drawn:

[0073] (1) As can be seen from the comparative examples, the catalytic performance of the NH4CoF3 catalyst is higher than that of Co3O4, and also higher than that without adding a catalyst, indicating that the NH4CoF3 catalyst has good catalytic performance.

[0074] (2) When the mass ratio of Co3O4 and NH4F is 1:4 to 1:6, NH4CoF3 can be prepared, and the catalytic performance of the obtained NH4CoF3 catalyst remains basically unchanged.

[0075] (3) When the amount of catalyst increases from 0.05 g to 0.10 g, the conversion rate of limonene significantly increases, because the increase in the amount of catalyst leads to an increase in the active sites of the reaction. When the amount of catalyst continues to increase from 0.10 g to 0.15 g, the conversion rate of limonene does not significantly increase, and the selectivity of limonene-1,2-epoxide slightly decreases. Therefore, 0.10 g of catalyst is preferred.

[0076] (4) When the reaction temperature increases from 20°C to 30°C, the conversion rate of limonene increases with the increase of the reaction temperature. However, when the temperature reaches 40°C, the conversion rate increases, but the yield of limonene-1,2-epoxide is lower than that at 30°C. Therefore, 30°C is preferred as the reaction temperature.

[0077] (5) When the reaction time is between 3 h and 4 h, the conversion rate of limonene increases with the increase of time. When the reaction time is between 4 h and 5 h, the conversion rate does not significantly increase. Therefore, 4 h is preferred as the optimal reaction time.

[0078] (6) When the O2 pressure increases from 0.1 MPa to 0.2 MPa, the conversion rate increases with the increase of pressure. However, when the pressure is 0.3 MPa, the conversion rate does not significantly increase with the increase of pressure. Therefore, 0.2 MPa is the optimal reaction pressure.

[0079] (7) When the molar ratio of limonene to isobutyraldehyde increases from 1:1.25 to 1:1.50, the conversion rate of limonene significantly increases. However, the amount of isobutyraldehyde is not the more the better. When the ratio of limonene to isobutyraldehyde increases from 1:1.50 to 1:1.75, the yield of limonene-1,2-epoxide decreases. Therefore, the ratio of limonene to isobutyraldehyde of 1:1.50 is the optimal reaction condition.

[0080] (8) After the cycle test of the catalyst, it is found that the catalytic activity of the NH4CoF3 catalyst does not change obviously after being used for 4 times, and the catalyst has good stability.

[0081] In conclusion, the application provides a new catalyst for selectively oxidizing limonene to limonene-1,2-epoxide without solvent.

[0082] The application discloses an NH4CoF3 catalyst and a preparation method and application thereof. The catalyst is prepared into Co3O4 through a hydrothermal method, and then is fluorinated in a tube furnace through NH4F, raw materials are cheap and easy to obtain, and the preparation method is simple. The NH4CoF3 catalyst prepared by the application is used in a reaction of selectively oxidizing limonene to limonene-1,2-epoxide with molecular oxygen as an oxidant, and good catalytic performance is shown.

[0083] The above is only the preferred embodiment of the application, and it should be pointed out that for ordinary skilled persons in the art, some improvements and modifications can be made without departing from the technical principles of the application, and these improvements and modifications should also be considered as the protection scope of the application.

Claims

1. A method for preparing an NH4CoF3 catalyst, characterized by, The application relates to a preparation method of a NH4CoF3 catalyst and a preparation method of limonene-1,2-epoxide. Co(NO3)2.6H2O is dissolved in a mixed solution of methanol and benzyl alcohol, the solution is uniformly mixed and placed in a hydrothermal kettle for heating to obtain a precipitate; The precipitate is washed and dried, and Co3O4 is prepared by calcination; The Co3O4 and NH4F are placed in a nitrogen-filled environment for calcination to obtain the NH4CoF3 catalyst.

2. The production method according to claim 1, characterized by, Co(NO3)2.6H2O is dissolved in a mixed solution of methanol and benzyl alcohol, the concentration of the cobalt nitrate is 0.0652-0.1087 mol / L, the volume ratio of methanol to benzyl alcohol in the mixed solution is 20:3, and the mass ratio of the Co3O4 to NH4F is 1:4-1:

6.

3. The production method according to claim 1, characterized by, The method comprises placing the Co3O4 and NH4F in the same porcelain boat, placing the porcelain boat in a nitrogen-filled tube furnace for calcination, placing the Co3O4 downstream of the porcelain boat, and placing the NH4F upstream of the porcelain boat.

4. An NH4CoF3 catalyst characterized in that, The preparation method is prepared according to any one of claims 1-3.

5. Use of NH4CoF3 catalyst according to claim 4, characterized in that, The application is used in a reaction for selectively oxidizing limonene to prepare limonene-1,2-epoxide.

6. Use of NH4CoF3 catalyst according to claim 4, characterized by the fact that it is used in the presence of a reducing agent. The application comprises adding the NH4CoF3 catalyst and limonene and isobutyl aldehyde into a high-pressure reaction kettle, and introducing oxygen to prepare limonene-1,2-epoxide.

7. Use according to claim 6, characterized in that, The amount of the NH4CoF3 catalyst is 0.008-0.025 g / mL based on the volume of limonene.

8. Use according to claim 6, characterized in that, The molar ratio of the limonene to isobutyl aldehyde is 1:1.25-1:1.

75.

9. Use according to claim 6, characterized in that, The reaction temperature of the high-pressure reaction kettle is 20-40 DEG C, the reaction time is 3-5 h, and the reaction pressure is 0.1-0.3 MPa.

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