Modified alpha-MnO2 catalyst as well as preparation method and application thereof
By performing ascorbic acid reduction treatment and specific preparation methods on the α-MnO2 catalyst, a modified α-MnO2 catalyst was prepared, which solved the problem of insufficient catalyst performance in the prior art, and achieved efficient limonene oxidation reaction and good cycle performance.
Patent Information
- Application Number
- CN202510100898.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-22
- Publication Date
- 2025-05-06
AI Technical Summary
The prior art is difficult to develop novel catalysts with recyclability, stability, high activity, low cost and easy preparation for selective oxidation of limonene.
By performing ascorbic acid reduction treatment on the α-MnO2 catalyst, a modified α-MnO2 catalyst is prepared, and a specific preparation method, including hydrothermal method and calcination treatment, is adopted to improve the performance of the catalyst.
The modified α-MnO2 catalyst showed high catalytic efficiency in the preparation of limonene-1,2-epoxide reaction of limonene oxide. The conversion rate of limonene reached 85.2%. After 5 cycles, the catalytic activity did not change significantly, and it had good stability and cycling performance.
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Figure CN119929882A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of limonene oxidation reaction, and in particular to a modified alpha-MnO2 catalyst and a preparation method and application thereof. Background Art
[0002] Due to the extensive use of coal, crude oil and natural gas, the greenhouse effect and air pollution are becoming increasingly serious, leading to many environmental problems. Therefore, current research focuses on the development of sustainable and green alternatives to seek new chemical processes to produce fuels and chemicals. Citrus fruits are mainly grown in warm tropical and subtropical regions, with an annual output of more than 100 million tons. During the juice production process, a large amount of citrus peel waste is generated after the pulp is consumed. Citrus peel is a promising raw material that can be converted into fuels and various valuable chemicals, among which limonene is the most common one to be extracted from citrus peel. Importantly, the epoxidation reaction of limonene can produce limonene epoxides, which can be used as building blocks for bio-based polymers, providing a way to reduce dependence on petroleum-based polymers. Although a variety of catalysts have been used for the selective oxidation of limonene, including homogeneous and heterogeneous catalysts, it is still very challenging to develop new catalysts with the characteristics of recyclability, stability, high activity, low cost and easy preparation. Summary of the invention
[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a modified α-MnO2 catalyst and a preparation method and application thereof. The modified α-MnO2 catalyst has the advantages of simple preparation, mild use conditions, strong stability and good cycle performance, and has high catalytic efficiency for the oxidation of limonene to prepare limonene-1,2-epoxide, and has strong application prospects.
[0004] To achieve the above object, the present invention is implemented by adopting the following technical solutions:
[0005] In a first aspect, the present invention provides a modified α-MnO2 catalyst, wherein the modified α-MnO2 catalyst is an α-MnO2 catalyst that has been reduced with ascorbic acid.
[0006] In a second aspect, the present invention provides a method for preparing a modified α-MnO2 catalyst, comprising:
[0007] Add KMnO4 and MnSO4 hydrate into deionized water and stir evenly to obtain a mixed solution;
[0008] The mixed solution is transferred to a hydrothermal kettle for hydrothermal treatment and then the hydrothermal kettle is cooled to obtain a precipitate;
[0009] The precipitate was washed with deionized water and ethanol and then dried to obtain a powder;
[0010] The powder is calcined to obtain an α-MnO2 catalyst;
[0011] The α-MnO2 catalyst is reduced with ascorbic acid to obtain a modified α-MnO2 catalyst.
[0012] Further, it includes: adding KMnO4 and MnSO4 hydrate into deionized water, stirring for 25-35 minutes to form a mixed solution;
[0013] Transfer the mixed solution to a 80-100 mL hydrothermal autoclave, and hydroheat at 150-170 °C for 15-17 h, then cool the autoclave to 25-35 °C to obtain a precipitate;
[0014] The precipitate was washed with deionized water and ethanol, and dried in an oven at 80-100°C for 11-13 h to obtain a powder;
[0015] The powder is calcined in a muffle furnace to obtain an α-MnO2 catalyst, wherein the calcination heating rate is 1-3°C / min, the calcination temperature is 500-700°C, and the calcination time is 1-3 h;
[0016] The α-MnO2 catalyst is reduced with ascorbic acid to obtain a modified α-MnO2 catalyst.
[0017] Furthermore, the mass ratio of the deionized water, KMnO4 and MnSO4 hydrate is (55-65):(0.36-0.39):(0.051-0.084).
[0018] Furthermore, the ascorbic acid concentration is 0.04-0.06 mol / L.
[0019] In a third aspect, the present invention provides an application of a modified α-MnO2 catalyst, wherein the modified α-MnO2 catalyst is the modified α-MnO2 catalyst provided by the present invention, or the modified α-MnO2 catalyst prepared by the preparation method provided by the present invention, and the modified α-MnO2 catalyst is used for the oxidation of limonene to prepare limonene-1,2-epoxide.
[0020] Furthermore, the method for using the modified α-MnO2 catalyst to oxidize limonene to prepare limonene-1,2-epoxide comprises: adding limonene, isobutyraldehyde, acetonitrile and the modified α-MnO2 catalyst into a reactor, introducing oxygen to react, and obtaining limonene-1,2-epoxide.
[0021] Further, the amount of the modified α-MnO2 catalyst is 0.0387-0.1549 g / mL based on the volume of the limonene;
[0022] The volume ratio of the acetonitrile to the limonene is (7.0-8.5):1.
[0023] Further, the reaction temperature is 20-40°C;
[0024] And / or, the reaction time is 1 to 4 h;
[0025] And / or, the reaction pressure is 0.1-0.4 MPa.
[0026] Furthermore, the molar ratio of the limonene to the isobutyraldehyde is 1:(1.25-2.5).
[0027] Compared with the prior art, the present invention has the following beneficial effects:
[0028] The application of the modified α-MnO2 catalyst provided by the present invention is an α-MnO2 catalyst that has been reduced with ascorbic acid. The modified α-MnO2 catalyst is used for the reaction of oxidizing limonene to prepare limonene-1,2-epoxide, has high catalytic efficiency, and the conversion rate of limonene is as high as 85.2%. Compared with no addition of catalyst, the conversion rate of limonene is increased from 10.2% to 85.2%. Compared with the reaction of oxidizing limonene to prepare limonene-1,2-epoxide with a common α-MnO2 catalyst, the conversion rate of limonene is increased from 32.6% to 85.2%.
[0029] The modified α-MnO2 catalyst provided by the present invention has simple preparation, mild use conditions, strong stability, and no obvious change in catalytic activity after being recycled for 5 times, and has good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 XRD patterns of the modified α-MnO2 catalyst provided in the embodiment of the present invention and the α-MnO2 catalyst provided in the comparative example;
[0031] Figure 2 The SEM image of the modified α-MnO2 catalyst provided in the embodiment of the present invention;
[0032] Figure 3 SEM image of the α-MnO2 catalyst provided in an embodiment of the present invention;
[0033] Figure 4 This is a diagram showing the effect of a cycle test of the modified α-MnO2 catalyst provided in an embodiment of the present invention. DETAILED DESCRIPTION
[0034] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.
[0035] Example 1
[0036] The present embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof, specifically, application of the modified α-MnO2 catalyst for the molecular oxygen oxidation of limonene to prepare limonene 1,2-epoxide.
[0037] The preparation method of the modified α-MnO2 catalyst comprises:
[0038] 2.4 mmol KMnO4 and 0.4 mmol MnSO4·H2O were added to 60 mL deionized water and stirred for 30 min to form a mixed solution. The solution was transferred to a 100 mL hydrothermal reactor and hydrothermalized at 160 °C for 16 h. The hydrothermal reactor was then cooled to room temperature and the precipitate was washed with deionized water and ethanol.
[0039] The washed precipitate was dried in an oven at 80 °C for 12 h to obtain a powder, which was then placed in a muffle furnace for calcination at a heating rate of 2 °C / min and maintained at 500 °C for 2 h to obtain an α-MnO2 catalyst.
[0040] The obtained α-MnO2 was then reduced with 0.05 mol / L ascorbic acid and finally dried in an oven at 80 °C for 12 h to obtain a modified α-MnO2 catalyst.
[0041] Figure 1 The XRD patterns of the modified α-MnO2 catalyst and the α-MnO2 catalyst prepared in the present invention correspond to the standard card (PDF No.44-0141), wherein the purple line is the XRD pattern of the modified α-MnO2 catalyst prepared in this example. Figure 2 The SEM image of the modified α-MnO2 catalyst prepared in this example shows that its morphology is a rod-like structure.
[0042] The modified α-MnO2 catalyst prepared in this example is used for the molecular oxygen oxidation of limonene to prepare limonene 1,2-epoxide, and the application method includes:
[0043] 8 mmol limonene, 15 mmol isobutyraldehyde, 10 mL acetonitrile and 0.10 g modified α-MnO2 catalyst were added into a high-pressure reactor, wherein the amount of modified α-MnO2 catalyst was 0.0774 g / mL based on the volume of limonene, and the molar ratio of limonene to isobutyraldehyde was 1:1.875;
[0044] After purging the reactor with oxygen three times, the reactor was sealed and heated to the desired temperature of 30 °C under constant stirring. Oxygen was introduced into the reactor until the pressure reached 0.2 MPa. After reacting for 2 h, the final reaction product was obtained.
[0045] Comparative Example 1
[0046] This comparative example provides an application of an α-MnO2 catalyst, wherein the α-MnO2 catalyst is not treated with ascorbic acid, and other preparation conditions are the same as those in Example 1. The method for using the α-MnO2 catalyst for the molecular oxygen oxidation of limonene to prepare limonene 1,2-epoxide is also the same as that in Example 1.
[0047] Figure 1 The XRD patterns of the modified α-MnO2 catalyst and the α-MnO2 catalyst prepared in the present invention correspond to the standard card (PDF No.44-0141), wherein the green line is the XRD pattern of the α-MnO2 catalyst prepared in this comparative example. Figure 3 The SEM image of the α-MnO2 catalyst prepared in this comparative example shows that its morphology is a rod-like structure.
[0048] Comparative Example 2
[0049] This comparative example provides a reaction of preparing limonene 1,2-epoxide by oxidizing limonene with molecular oxygen. In this comparative example, no catalyst is added during the reaction, and other reaction conditions are the same as those in Example 1.
[0050] Example 2
[0051] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Example 1 is that 0.05 g of modified α-MnO2 catalyst is added to the reactor.
[0052] Example 3
[0053] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Example 1 is that 0.15 g of modified α-MnO2 catalyst is added to the reactor.
[0054] Example 4
[0055] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Example 1 is that 0.20 g of the modified α-MnO2 catalyst is added to the reactor.
[0056] Example 5
[0057] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Embodiment 1 is that the limonene oxidation reaction temperature is 20°C.
[0058] Example 6
[0059] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Example 1 is that the limonene oxidation reaction temperature is 40°C.
[0060] Example 7
[0061] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Example 1 is that the limonene oxidation reaction time is 1 h.
[0062] Example 8
[0063] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. Different from Example 1, the limonene oxidation reaction time is 3 h.
[0064] Example 9
[0065] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Example 1 is that the limonene oxidation reaction time is 4 h.
[0066] Example 10
[0067] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Example 1 is that the limonene oxidation reaction pressure is 0.1 MPa.
[0068] Embodiment 11
[0069] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Example 1 is that the limonene oxidation reaction pressure is 0.3 MPa.
[0070] Example 12
[0071] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Example 1 is that the limonene oxidation reaction pressure is 0.4 MPa.
[0072] Embodiment 13
[0073] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. Different from Example 1, the molar ratio of limonene to isobutyraldehyde is 1:1.25.
[0074] Embodiment 14
[0075] This embodiment provides a modified α-MnO2 catalyst and a preparation method and application thereof. The difference from Example 1 is that the molar ratio of limonene to isobutyraldehyde is 1:2.5.
[0076] The final reaction products prepared in Examples 1 to 14 and Comparative Examples 1 to 2 were quantitatively analyzed by gas chromatography, and the analysis results are shown in Table 1.
[0077] Table 1
[0078] Conversion rate of limonene Selectivity of limonene 1,2-epoxide Example 1 79.1% 77.4% Comparative Example 1 32.6% 85.5% Comparative Example 2 10.2% 82.4% Example 2 71.1% 80.5% Example 3 79.1% 77.4% Example 4 80.2% 76.1% Example 5 63.6% 80.1% Example 6 82.4% 64.0% Example 7 49.1% 80.7% Example 8 81.1% 73.3% Example 9 84.5% 67.2% Example 10 61.4% 85.0% Embodiment 11 82.7% 73.5% Example 12 84.9% 68.2% Embodiment 13 41.5% 79.4% Embodiment 14 85.2% 61.1%
[0079] As shown in Table 1, by comparing and analyzing Example 1, Comparative Example and Comparative Example 2, it can be seen that the catalytic performance of the modified α-MnO2 catalyst provided in Example 1 is higher than that of the α-MnO2 catalyst provided in Comparative Example 1, and is also higher than the case where no catalyst is added, indicating that the modified α-MnO2 catalyst obtained by ascorbic acid reduction treatment has good catalytic performance.
[0080] Combining the analysis results of Examples 1, 2, 3 and 4, it can be seen that when the catalyst dosage increases from 0.05 g to 0.10 g, the conversion rate of limonene is significantly improved. This is because when the catalyst dosage increases, the number of active sites for the reaction increases. When it continues to increase from 0.10 g to 0.15 g, the limonene conversion rate does not increase significantly, and the selectivity of limonene-1,2-epoxide decreases slightly. On the whole, 0.10 g of catalyst should be selected.
[0081] Combining the analysis results of Examples 1, 5 and 6, it can be seen that when the temperature rises from 20°C to 30°C, the conversion rate of limonene increases with the increase of reaction temperature. However, when the temperature reaches 40°C, while the conversion rate increases, the yield of limonene-1,2-epoxide is lower than the yield at 30°C. Taking all factors into consideration, the reaction temperature of 30°C is the optimal reaction parameter.
[0082] Combining the analysis results of Examples 1, 7, 8 and 9, it can be seen that when the reaction time is between 1 h and 4 h, the conversion rate of limonene increases with time, but the increase is slow, so 2 h is the optimal reaction time.
[0083] Combining the analysis results of Examples 1, 10, 11 and 12, it can be seen that as the O2 pressure increases from 0.1 MPa to 0.2 MPa, the pressure increases and the conversion rate increases, but after 0.3 MPa, there is no obvious increase in the conversion rate as the pressure increases, so 0.2 MPa is the optimal reaction pressure.
[0084] Combining the analysis results of Examples 1, 13 and 14, it can be seen that when the molar ratio of limonene to isobutyraldehyde increases from 1:1.25 to 1:2.5, the conversion rate of limonene is significantly improved. However, the amount of isobutyraldehyde is not as much as possible. When the ratio of limonene to isobutyraldehyde increases from 1:1.25 to 1:2.5, the yield of limonene-1,2-epoxide decreases. Taking all factors into consideration, the ratio of limonene to isobutyraldehyde is 1:1.875, which is the best reaction condition.
[0085] In addition, in order to test the recycling performance of the modified α-MnO2 catalyst, the modified α-MnO2 catalyst after the reaction in Example 1 was centrifuged, and after being fully washed with deionized water and ethanol, it was dried at 80 °C for 12 h, and the test and washing were repeated until the modified α-MnO2 catalyst was recycled 5 times, and the product of each reaction was quantitatively analyzed by gas chromatography.
[0086] The analysis results are as follows Figure 4 As shown, after the modified α-MnO2 catalyst was recycled for 5 times, the conversion rate of limonene decreased from 79.1% to 70.6%, and the selectivity of limonene 1,2-epoxide increased from 77.4% to 79.5%. After the cyclic test of the modified α-MnO2 catalyst, it was found that there was no obvious change in the catalytic activity after 5 cycles, indicating that the modified α-MnO2 catalyst has good stability.
[0087] In summary, the present invention proposes an application of a modified α-MnO2 catalyst for the oxidation of limonene to prepare limonene-1,2-epoxide. The modified α-MnO2 catalyst has the advantages of simple preparation, mild use conditions, strong stability and good cycle performance, and has high catalytic efficiency for the oxidation of limonene to prepare limonene-1,2-epoxide, and has strong application prospects.
[0088] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.
Claims
1. A modified α-MnO2 catalyst, characterized in that: The modified α-MnO2 catalyst is an α-MnO2 catalyst that has been reduced with ascorbic acid.
2. A method for preparing the modified α-MnO2 catalyst as claimed in claim 1, characterized in that: include: Add KMnO4 and MnSO4 hydrate into deionized water and stir evenly to obtain a mixed solution; The mixed solution is transferred to a hydrothermal kettle for hydrothermal treatment and then the hydrothermal kettle is cooled to obtain a precipitate; The precipitate was washed with deionized water and ethanol and then dried to obtain a powder; The powder is calcined to obtain an α-MnO2 catalyst; The α-MnO2 catalyst is reduced with ascorbic acid to obtain a modified α-MnO2 catalyst.
3. The method for preparing the modified α-MnO2 catalyst according to claim 2, characterized in that: include: Add KMnO4 and MnSO4 hydrate into deionized water and stir for 25-35 min to form a mixed solution; Transfer the mixed solution to a 80-100 mL hydrothermal kettle, and hydroheat at 150-170 °C for 15-17 h, then cool the hydrothermal kettle to 25-35 °C to obtain a precipitate; The precipitate was washed with deionized water and ethanol, and dried in an oven at 80-100°C for 11-13 h to obtain a powder; The powder is calcined in a muffle furnace to obtain an α-MnO2 catalyst, wherein the calcination heating rate is 1-3°C / min, the calcination temperature is 500-700°C, and the calcination time is 1-3 h; The α-MnO2 catalyst is reduced with ascorbic acid to obtain a modified α-MnO2 catalyst.
4. The method for preparing the modified α-MnO2 catalyst according to claim 2, characterized in that: The mass ratio of the deionized water, KMnO4 and MnSO4 hydrate is (55-65):(0.36-0.39):(0.051-0.084).
5. The method for preparing the modified α-MnO2 catalyst according to claim 2, characterized in that: The ascorbic acid concentration is 0.04-0.06 mol / L.
6. An application of a modified α-MnO2 catalyst, characterized in that: The modified α-MnO2 catalyst is the modified α-MnO2 catalyst as claimed in claim 1, or the modified α-MnO2 catalyst prepared by the preparation method as claimed in any one of claims 2 to 5, and the modified α-MnO2 catalyst is used for the oxidation of limonene to prepare limonene-1,2-epoxide.
7. The use of the modified α-MnO2 catalyst according to claim 6, characterized in that: The method for preparing limonene-1,2-epoxide by using the modified α-MnO2 catalyst to oxidize limonene comprises: adding limonene, isobutyraldehyde, acetonitrile and the modified α-MnO2 catalyst into a reactor, introducing oxygen to react, and preparing limonene-1,2-epoxide.
8. The use of the modified α-MnO2 catalyst according to claim 7, characterized in that: The amount of the modified α-MnO2 catalyst is 0.0387-0.1549 g / mL based on the volume of the limonene; The volume ratio of the acetonitrile to the limonene is (7.0-8.5):
1.
9. The use of the modified α-MnO2 catalyst according to claim 7, characterized in that: The reaction temperature is 20-40°C; And / or, the reaction time is 1 to 4 h; And / or, the reaction pressure is 0.1-0.4 MPa.
10. The use of the modified α-MnO2 catalyst according to claim 7, characterized in that: The molar ratio of the limonene to the isobutyraldehyde is 1:(1.25-2.5).