A method for the liquid-phase selective oxidation of toluene to prepare benzaldehyde and benzyl alcohol

Abstract

This invention proposes a method for the liquid-phase selective oxidation of toluene to prepare benzaldehyde and benzyl alcohol, comprising the following steps: preparing MnO x The catalyst is UiO-66, followed by a liquid-phase oxidation reaction of toluene. This invention employs a solvothermal method to prepare MnO. x The / UiO-66 catalyst, after calcination, is used as a solvent-free and additive-free green oxidant in the liquid-phase selective oxidation reaction of toluene to prepare high-value-added products such as benzyl alcohol and benzaldehyde. By optimizing process conditions such as reaction temperature, reaction time, catalyst dosage, and reaction oxygen pressure, efficient conversion of toluene and highly selective synthesis of target products are achieved under mild conditions.

Description

Technical Field

[0001] This invention relates to the field of liquid-phase catalytic oxidation technology of toluene, and more specifically to a method for the selective liquid-phase oxidation of toluene to prepare benzaldehyde and benzyl alcohol. Background Technology

[0002] The activation of the CH bond in organic compounds and their selective catalytic oxidation is one of the fundamental pathways for preparing high-value-added oxygen-containing compounds (such as alcohols, aldehydes, and carboxylic acids). Toluene, as the most representative organic compound among alkyl aromatics, can yield three oxygen-containing organic compounds—benzyl alcohol, benzaldehyde, and benzoic acid—through the selective catalytic oxidation of its side-chain methyl group (-CH3). Benzyl alcohol, benzaldehyde, and benzoic acid are important chemical raw materials, widely used in the synthesis of compounds for fragrances, pesticides, pharmaceutical intermediates, plastic additives, preservatives, and common resin plasticizers. With the rapid development of the food, pharmaceutical, and fine chemical industries, their industry status has been significantly enhanced.

[0003] Common process routes for preparing benzaldehyde and benzyl alcohol from toluene include chlorination hydrolysis, photocatalysis, indirect electrochemical oxidation, toluene photocatalysis, gas-phase oxidation of toluene, and liquid-phase oxidation of toluene. In the chlorination hydrolysis method, toluene reacts with chlorine under ultraviolet or blue light irradiation, resulting in the chlorination of the methyl group on the toluene side chain to obtain benzyl chloride (benzyl chloride). Benzyl chloride is then saponified and hydrolyzed to produce benzaldehyde. Benzyl trichloride, a byproduct, reacts with sodium carbonate and hydrochloric acid to prepare benzoic acid. This process has low cost, but the presence of chlorine in the process not only leads to equipment corrosion but also environmental pollution, and the chlorine content in the final product greatly limits its application.

[0004] While chlorination hydrolysis offers advantages such as ease of operation, low cost, and controllable reaction parameters, the highly corrosive nature of chlorine gas leads to severe equipment corrosion, increasing production and maintenance costs. Furthermore, the reaction generates byproducts like hydrogen chloride, causing significant pollution. The inevitable presence of chlorine in the final product limits its application in fields with stringent chlorine content requirements, such as food additives, pharmaceutical intermediates, and high-end fragrances. With the deepening of green chemistry concepts and the rapid development of MOF (Metal-Oxide-Factory) catalytic materials, coupled with the numerous advantages of liquid-phase selective oxidation of toluene, developing an environmentally friendly, highly selective, and chlorine-free MOF-based liquid-phase selective catalytic oxidation system for toluene has become a research hotspot in the green synthesis of benzyl alcohol and benzaldehyde, aiming to meet market demands for high-quality benzaldehyde and benzyl alcohol.

[0005] Photocatalysis is a reaction in which light energy generates photoelectrons on a semiconductor catalyst, thereby promoting the reaction. Compared with traditional thermochemical methods, photocatalysis readily generates highly reactive free radicals, which can promote some challenging reactions (such as the activation of C(sp3)-H bonds) under mild conditions.

[0006] The indirect electrochemical oxidation process mainly involves the transfer of electrons between the reactants and electrodes through a reaction medium at room temperature and pressure to obtain the target product. This method yields benzaldehyde with high purity, good selectivity, high energy utilization, and simple control. However, the catalyst has low activity, short lifespan, high energy consumption, and high cost, making it difficult to achieve industrial-scale production.

[0007] The photocatalytic reaction of toluene involves the photocatalytic activation and oxidation of the CH bonds in the toluene side chain to prepare the target product. This method offers mild reaction conditions, high atom utilization, environmental friendliness, and high selectivity for the target product. However, the separation efficiency of currently available catalytic materials is relatively low, meaning that heterogeneous photocatalytic organic oxidation reactions are still in their early stages. Furthermore, the activation of toluene in the initial stage of the reaction requires high-energy photons, resulting in low energy utilization, low catalytic activity, short lifespan, and immature technology, making industrial-scale production difficult.

[0008] The gas-phase oxidation of toluene involves the oxidation reaction of toluene with an oxidant over a solid catalyst at a high temperature of 350℃-550℃. This method achieves a high toluene conversion rate, but the main product is benzoic acid, with lower levels of benzyl alcohol and benzaldehyde. Furthermore, the reaction is difficult to control and is prone to deep oxidation, producing carbon dioxide and carbon monoxide.

[0009] The liquid-phase oxidation of toluene involves the selective oxidation of toluene at a reaction temperature below 200°C and under a certain oxygen pressure, ultimately yielding benzyl alcohol, benzaldehyde, and benzoic acid. The reaction temperature of liquid-phase oxidation is higher than the boiling point of toluene (110.6°C), and it is carried out under a certain oxygen pressure, which compresses oxygen, keeping toluene in a liquid state. This method offers high product selectivity, good safety, and minimal waste. Therefore, the liquid-phase oxidation of toluene is highly suitable for industrial production.

[0010] Existing liquid-phase catalytic oxidation systems for toluene still have significant shortcomings, such as dependence on solvents or auxiliaries, high preparation costs, harsh reaction conditions, and difficulty in achieving both toluene conversion and selectivity for benzaldehyde and benzyl alcohol. Summary of the Invention

[0011] The purpose of this invention is to provide a method for the liquid-phase selective oxidation of toluene to prepare benzaldehyde and benzyl alcohol, using a solvothermal method to prepare MnO. x The / UiO-66 catalyst, using molecular oxygen as a green oxidant under solvent-free and additive-free conditions, can be applied to the liquid-phase selective oxidation reaction of toluene to prepare benzyl alcohol and benzaldehyde, achieving a balance between toluene conversion and selectivity of benzaldehyde and benzyl alcohol.

[0012] The technical solution of this invention is implemented as follows: One aspect of the present invention provides a method for the liquid-phase selective oxidation of toluene to prepare benzaldehyde and benzyl alcohol, comprising the following steps: Step 1: Catalyst Preparation Weigh out zirconium tetrachloride and manganese acetate, dissolve them in N,N-dimethylformamide solvent, add terephthalic acid and formic acid, and stir to mix them evenly. It was then transferred to a polytetrafluoroethylene hydrothermal reactor and subjected to a solvothermal reaction under heating conditions. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the resulting precipitate was washed several times with anhydrous ethanol, dried in an oven, and calcined at 300°C in air to obtain MnO. x / UiO-66 catalyst, ready for use; Step 2: Liquid-phase oxidation reaction of toluene Weigh out MnO x The UiO-66 catalyst was placed in a magnetically stirred reactor, a magnetic stir bar was added, and toluene was then added to the reactor. After introducing O2 into the reactor to displace the air inside, the magnetically stirred reactor is sealed, and a constant stirring speed and reaction temperature are set. When the actual temperature inside the magnetically stirred reactor is 20°C lower than the preset reaction temperature, O2 is continuously introduced to raise the temperature to the preset temperature, and the reaction time is started. After the reaction is complete, allow the magnetically stirred reactor to cool naturally to room temperature, then turn on the magnetically stirred reactor and weigh the entire system. Centrifugation was used to separate the solid and liquid phases, and gas chromatography was used to perform qualitative and quantitative analysis of each component in the reaction solution.

[0013] Furthermore, in the zirconium tetrachloride and manganese acetate, the molar ratio of Zr to Mn is 10:0.8 to 10:1.2.

[0014] Furthermore, in step one, the stirring time is 25 min-35 min.

[0015] Furthermore, in step one, the reaction temperature is 120℃~130℃, and the reaction time is 12 h~14 h.

[0016] Furthermore, in step two, the reaction temperature is 160℃~200℃, and the reaction time is 1 h~3 h.

[0017] Furthermore, the MnO x The ratio of UiO-66 catalyst to toluene is 0.1:21 to 0.2:21.

[0018] Furthermore, in step two, the oxygen pressure is 0.6 MPa to 1.4 MPa.

[0019] Another aspect of the present invention provides MnO x The preparation method of / UiO-66 catalyst includes the following steps: Weigh out zirconium tetrachloride and manganese acetate, dissolve them in N,N-dimethylformamide solvent, add terephthalic acid and formic acid, and stir to mix them evenly. It was then transferred to a polytetrafluoroethylene hydrothermal reactor and subjected to a solvothermal reaction under heating conditions. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the resulting precipitate was washed several times with anhydrous ethanol, dried in an oven, and calcined at 300°C in air to obtain MnO. x / UiO-66 catalyst.

[0020] The present invention also provides MnO x The / UiO-66 catalyst was prepared by the above method.

[0021] The present invention has the following beneficial effects: 1. This invention provides a method for the liquid-phase selective oxidation of toluene to prepare benzaldehyde and benzyl alcohol, using a solvothermal method to prepare MnO. x The / UiO-66 catalyst, using molecular oxygen as a green oxidant under solvent-free and additive-free conditions, can be applied to the liquid-phase selective oxidation reaction of toluene to prepare benzyl alcohol and benzaldehyde, achieving a balance between toluene conversion and selectivity of benzaldehyde and benzyl alcohol.

[0022] In the embodiments of this invention, toluene conversion is high, and the selectivity of benzaldehyde and benzyl alcohol is high. This invention achieves efficient toluene conversion and highly selective synthesis of the target product under mild conditions by optimizing process conditions such as reaction temperature, reaction time, catalyst dosage, and reaction oxygen pressure, while maintaining low preparation cost.

[0023] 2. In this embodiment of the invention, MnO is prepared using a solvothermal method. x The MnO-66 catalyst was characterized by XRD, FT-IR, TGA, UV-IS DRS, and other methods to analyze its crystal structure, functional group composition, thermal stability, and electronic structure, proving that MnO x / UiO-66 was successfully synthesized. (UiO-66 was synthesized using MnO-66.) x Using UiO-66 as a catalyst, its catalytic activity and reaction effect in a liquid-phase selective oxidation system of toluene were investigated. The results showed that MnO obtained by calcination at 300℃... x / UiO-66(MnO x / UiO-66) exhibits good catalytic performance. In a solvent-free, additive-free, green reaction system using molecular oxygen as the oxidant, the effects of reaction temperature, reaction time, catalyst dosage, and reaction oxygen pressure on the liquid-phase oxidation of toluene were systematically investigated. The results showed that the optimal reaction effect was achieved under the following conditions: toluene dosage of 21.0 g, reaction temperature of 180℃, reaction time of 2.0 h, catalyst dosage of 0.1 g, and reaction oxygen pressure of 1.0 MPa. Under these conditions, the toluene conversion rate reached 4.6%, and the selectivity for benzaldehyde and benzyl alcohol products was 67.3% and 25.6%, respectively. This process offers advantages such as good catalytic effect, simple catalyst preparation, small particle size, large specific surface area, and a green and environmentally friendly reaction system, showing broad application prospects.

[0024] 3. In the embodiments of the present invention, MnO is used. x UiO-66 was used as a catalyst for the selective heterogeneous oxidation of toluene in the liquid phase. Manganese-doped UiO-66 (MnO4) was prepared by a solvothermal method. x The catalyst UiO-66 was used for the liquid-phase selective oxidation of toluene to prepare high-value-added benzaldehyde and benzyl alcohol. The effects of physical mixing of UiO-66, MnO2, MnO2, and UiO-66, as well as MnO2, were compared. x / UiO-66 catalyst, found that MnO calcined at 300℃ x / UIO-66 has the best catalytic effect.

[0025] 4. In the embodiments of the present invention, MnO is used. x Using UiO-66 (Zr:Mn molar ratio = 10:0.8) as a catalyst, toluene as a raw material, and oxygen as a green oxidant, a solvent-free and additive-free liquid-phase oxidation reaction was carried out in a magnetically stirred reactor. After the reaction, the catalyst was separated by centrifugation, and the supernatant was analyzed by gas chromatography to calculate the toluene conversion and product selectivity.

[0026] 5. In this embodiment of the invention, Mn is added to the catalyst formulation. Its main function is to act as an active component, which improves the catalytic activity of UiO-66. There is a synergistic catalytic effect between Zr and Mn, which further enhances the effect of liquid-phase oxidation of toluene.

[0027] 6. In the embodiments of the present invention, the process adopts solid-liquid heterogeneous catalysis, and the separation after reaction is simple. In five consecutive repeatable experiments, it is shown that the catalyst has good reusability and good stability, and has the potential for further industrial application.

[0028] 7. The embodiments of the present invention provide a simple process with high toluene conversion and selectivity for the target product, and the developed MnO xThe / UiO-66 green catalytic system provides a low-cost and efficient non-precious metal catalytic pathway for the selective liquid-phase oxidation of aromatics to prepare high-value-added aldehydes and alcohols, which is of certain significance for promoting the development of the fine chemical industry. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 MnO in the embodiments of the present invention x / UiO-66 catalyst preparation process diagram.

[0031] Figure 2 MnO in the embodiments of the present invention x / Infrared spectrum of UiO-66 catalyst.

[0032] Figure 3 MnO in the embodiments of the present invention x XRD pattern of UiO-66 catalyst.

[0033] Figure 4 MnO in the embodiments of the present invention x / UiO-66 catalyst TGA diagram.

[0034] Figure 5 MnO in the embodiments of the present invention x / UiO-66 catalyst UV-Vis DRS diagram.

[0035] Figure 6 MnO in the embodiments of the present invention x / UiO-66 catalyst stability experiment diagram. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] UiO-66, as a zirconium-based metal-organic framework material, possesses advantages such as large specific surface area, regular pore structure, and tunable active sites, making it an ideal carrier for constructing highly efficient heterogeneous catalytic systems. Transition metal Mn is widely available and inexpensive, and exhibits excellent catalytic performance in activating both the CH bonds of toluene side chains and molecular oxygen.

[0038] Through extensive experiments, the inventors of this application discovered that incorporating the active component Mn into the UiO-66 framework structure can effectively enhance catalytic activity and stability, providing a new approach for developing green and efficient toluene oxidation catalysts.

[0039] The embodiments of the present invention employ a solvothermal method to prepare MnO. x / UiO-66 post-calcination catalyst, under solvent-free and additive-free conditions, uses molecular oxygen as a green oxidant and applies it to the liquid-phase selective oxidation reaction of toluene to prepare high-value-added products such as benzyl alcohol and benzaldehyde. By optimizing process conditions such as reaction temperature, reaction time, catalyst dosage and reaction oxygen pressure, efficient conversion of toluene and highly selective synthesis of target products are achieved under mild conditions.

[0040] This invention provides a method for the liquid-phase selective oxidation of toluene to prepare benzaldehyde and benzyl alcohol, comprising the following steps: Step 1: Catalyst Preparation The present invention employs a solvothermal method to prepare this type of catalyst, and the specific steps are as follows: Weigh 0.5 g of zirconium tetrachloride and 0.04 g of manganese acetate (Zr:Mn molar ratio = 10:0.8), dissolve them in 80 mL of N,N-dimethylformamide solvent, add 0.4 g of terephthalic acid and 6.0 g of formic acid, and stir for 25-35 min to mix thoroughly. Then transfer the mixture to a polytetrafluoroethylene hydrothermal reactor and carry out a solvothermal reaction at 120℃-130℃ for 12-14 h. After the reaction, cool to room temperature, centrifuge, wash the precipitate several times with anhydrous ethanol, dry it in an 80℃ oven, and calcine it at 300℃ in air to obtain the catalyst MnO. x / UiO-66, for backup.

[0041] Step 2: Liquid-phase oxidation reaction of toluene The liquid-phase catalytic oxidation of toluene was carried out in a magnetically stirred reactor. A precise amount of solid catalyst was weighed and placed in the reactor, a magnetic stir bar was added, and then a certain amount of toluene was added. O2 was introduced into the reactor to displace the air, and the high-pressure reactor was sealed. A constant stirring speed and a set reaction temperature were established. When the actual temperature inside the reactor was 20°C lower than the preset reaction temperature, O2 was continuously introduced to raise the temperature to the preset temperature, and the reaction time was started. After the reaction was completed, the reactor was allowed to cool naturally to room temperature, the reactor was opened, and the entire system was weighed. Centrifugation was used to separate the solid and liquid phases, and gas chromatography was used for qualitative and quantitative analysis of the components in the reaction solution.

[0042] The following are specific embodiments. Example 1

[0043] Step 1: Accurately weigh 0.5 g zirconium tetrachloride and 0.04 g manganese acetate (Zr:Mn molar ratio = 10:0.8), dissolve them in 80 mL of N,N-dimethylformamide solvent, add 0.4 g terephthalic acid and 6.0 g formic acid, and stir for 30 min to mix thoroughly. Then transfer the mixture to a polytetrafluoroethylene hydrothermal reactor and carry out a solvothermal reaction at 120℃ for 12 h. After the reaction is complete, cool to room temperature, centrifuge, wash the precipitate several times with anhydrous ethanol, dry it in an 80℃ oven, and calcine it at 300℃ in air to obtain the catalyst MnO. x / UiO-66; Step 2: The liquid-phase catalytic oxidation reaction of toluene was carried out in a magnetically stirred reactor. 0.1 g of MnO was weighed... x The UiO-66 catalyst was placed in a reactor, a magnetic stirrer was added, and 21.0 g of toluene was added. O2 was then introduced into the reactor to displace the air. The high-pressure reactor was then sealed, and O2 was introduced again. A constant stirring speed and a set reaction temperature were established. The reaction was carried out at 180℃ for 2.0 h (when the actual temperature inside the reactor was 20℃ lower than the preset reaction temperature, 1.0 MPa of O2 was continuously introduced to raise the temperature to the preset temperature, and the reaction time was started). After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The reactor was then opened, and the entire system was weighed. Solid-liquid phase separation was achieved by centrifugation, and the components in the reaction solution were quantitatively analyzed by gas chromatography.

[0044] The experimental results show that the toluene conversion rate in Example 1 was 4.6%, and the selectivity of benzaldehyde and benzyl alcohol products was 67.3% and 25.6%, respectively.

[0045] Example 2

[0046] Same as Example 1, except that the Zr:Mn molar ratio is 10:0.6.

[0047] Example 3

[0048] Same as Example 1, except that the Zr:Mn molar ratio is 10:1.0.

[0049] Example 4

[0050] Same as Example 1, except that the Zr:Mn molar ratio is 10:1.2.

[0051] Example 5

[0052] Same as Example 1, except that the Zr:Mn molar ratio is 10:1.4.

[0053] Example 6

[0054] Same as Example 1, except that the reaction temperature in step two is 160°C.

[0055] Example 7

[0056] Same as Example 1, except that the reaction temperature in step two is 170°C.

[0057] Example 8

[0058] Same as Example 1, except that the reaction temperature in step two is 190°C.

[0059] Example 9

[0060] Same as Example 1, except that the reaction temperature in step two is 200°C.

[0061] Example 10

[0062] Same as Example 1, except that the reaction time in step two is 1.0 h.

[0063] Example 11

[0064] Same as Example 1, except that the reaction time in step two is 1.5 h.

[0065] Example 12

[0066] Same as Example 1, except that the reaction time in step two is 2.5 h.

[0067] Example 13

[0068] Same as Example 1, except that the reaction time in step two is 3.0 h.

[0069] Example 14

[0070] Same as Example 1, except that: MnO x / UiO-66 catalyst dosage: 0.02 g.

[0071] Example 15

[0072] Same as Example 1, except that: MnO x / UiO-66 catalyst dosage: 0.05 g.

[0073] Example 16

[0074] Same as Example 1, except that: MnO x / UiO-66 catalyst dosage: 0.15 g.

[0075] Example 17

[0076] Same as Example 1, except that: MnO x / UiO-66 catalyst dosage: 0.20 g.

[0077] Example 18

[0078] Same as Example 1, except that the oxygen pressure is 0.6 MPa.

[0079] Example 19

[0080] Same as Example 1, except that the oxygen pressure is 0.8 MPa.

[0081] Example 20

[0082] Same as Example 1, except that the oxygen pressure is 1.2 MPa.

[0083] Example 21

[0084] Same as Example 1, except that the oxygen pressure is 1.4 MPa.

[0085] Comparative Example 1 Same as Example 1, except that no catalyst was used.

[0086] Comparative Example 2 Same as Example 1, except that UiO-66 is a catalyst.

[0087] Comparative Example 3 Same as Example 1, except that MnO2 is used as the catalyst.

[0088] Comparative Example 4 Same as Example 1, except that MnO2 and UiO-66 are ground and mixed evenly to serve as a catalyst.

[0089] The following are the experimental data for the examples and comparative examples: 1) Catalyst screening

[0090] 2) Effect of different Zr:Mn molar ratios in the catalyst on the liquid-phase oxidation of toluene

[0091] 3) Effect of different reaction temperatures on the liquid-phase oxidation of toluene

[0092] 4) Effect of different reaction times on the liquid-phase oxidation of toluene

[0093] 5) Effect of different catalyst dosages on the liquid-phase oxidation of toluene

[0094] 6) Effect of different reaction oxygen pressures on the liquid-phase oxidation of toluene

[0095] The comparative experiments above show that the catalyst MnO from Example 1 was used. x / UiO-66 showed the highest toluene conversion rate, far exceeding that of comparative examples 1-4. The selectivity of benzaldehyde and benzyl alcohol products was 67.3% and 25.6%, respectively, indicating high selectivity for both benzaldehyde and benzyl alcohol.

[0096] In summary, the catalyst formulation and the process for the liquid-phase selective oxidation of toluene to prepare high-value-added benzyl alcohol and benzaldehyde, as described in the above embodiments, are innovative and advanced. (1) A reasonable zirconium-manganese ratio was adopted, which reduced the production cost and achieved the best matching of the performance of each component, resulting in good catalytic activity.

[0097] (2) A mild liquid-phase selective oxidation method was adopted, which reduced heat loss, saved costs, and ensured a good toluene conversion rate and selectivity of benzaldehyde and benzyl alcohol.

[0098] (3) A solid-liquid heterogeneous catalytic system without solvents and additives is adopted, which is simple to handle after reaction and has good catalyst stability; and oxygen is used as a green oxidant, avoiding the use of high-risk chemical reagents such as hydrogen peroxide as oxidants.

[0099] In summary, the embodiments of the present invention provide a preparation method that is simple in process, has a good toluene conversion rate, and high selectivity for benzaldehyde and benzyl alcohol, making it suitable for industrial production.

[0100] The above provides a detailed description of a method for the selective oxidation of toluene in the liquid phase to prepare benzaldehyde and benzyl alcohol. The principles and implementation methods of the present invention are explained in this paper. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the liquid-phase selective oxidation of toluene to prepare benzaldehyde and benzyl alcohol, characterized in that, Includes the following steps: Step 1: Catalyst Preparation Weigh out zirconium tetrachloride and manganese acetate, dissolve them in N,N-dimethylformamide solvent, add terephthalic acid and formic acid, and stir to mix them evenly. It was then transferred to a polytetrafluoroethylene hydrothermal reactor and subjected to a solvothermal reaction under heating conditions. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the resulting precipitate was washed several times with anhydrous ethanol, dried in an oven, and calcined at 300°C in air to obtain MnO. x / UiO-66 catalyst, ready for use; Step 2: Liquid-phase oxidation reaction of toluene Weigh out MnO x The UiO-66 catalyst was placed in a magnetically stirred reactor, a magnetic stir bar was added, and toluene was then added to the reactor. After introducing O2 into the reactor to displace the air inside, the magnetically stirred reactor is sealed, and a constant stirring speed and reaction temperature are set. When the actual temperature inside the magnetically stirred reactor is 20°C lower than the preset reaction temperature, O2 is continuously introduced to raise the temperature to the preset temperature, and the reaction time is started. After the reaction is complete, allow the magnetically stirred reactor to cool naturally to room temperature, then turn on the magnetically stirred reactor and weigh the entire system. Centrifugation was used to separate the solid and liquid phases, and gas chromatography was used to perform qualitative and quantitative analysis of the components in the reaction solution.

2. The method for preparing benzaldehyde and benzyl alcohol by liquid-phase selective oxidation of toluene according to claim 1, characterized in that, In the zirconium tetrachloride and manganese acetate, the molar ratio of Zr to Mn is 10:0.8 to 10:1.

2.

3. The method for preparing benzaldehyde and benzyl alcohol by liquid-phase selective oxidation of toluene according to claim 1, characterized in that, In step one, the stirring time is 25 min-35 min.

4. The method for preparing benzaldehyde and benzyl alcohol by liquid-phase selective oxidation of toluene according to claim 1, characterized in that, In step one, the reaction temperature is 120℃~130℃ and the reaction time is 12 h~14 h.

5. The method for preparing benzaldehyde and benzyl alcohol by liquid-phase selective oxidation of toluene according to claim 1, characterized in that, In step two, the reaction temperature is 160℃~200℃ and the reaction time is 1 h~3 h.

6. The method for preparing benzaldehyde and benzyl alcohol by liquid-phase selective oxidation of toluene according to claim 1, characterized in that, The MnO x The ratio of UiO-66 catalyst to toluene is 0.1:21 to 0.2:

21.

7. The method for preparing benzaldehyde and benzyl alcohol by liquid-phase selective oxidation of toluene according to claim 1, characterized in that, In step two, the oxygen pressure is 0.6 MPa to 1.4 MPa. 8.MnO x The preparation method of / UiO-66 catalyst is characterized by, Includes the following steps: Weigh out zirconium tetrachloride and manganese acetate, dissolve them in N,N-dimethylformamide solvent, add terephthalic acid and formic acid, and stir to mix them evenly. It was then transferred to a polytetrafluoroethylene hydrothermal reactor and subjected to a solvothermal reaction under heating conditions. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, and the resulting precipitate was washed several times with anhydrous ethanol, dried in an oven, and calcined at 300°C in air to obtain MnO. x / UiO-66 catalyst. 9.MnO x / UiO-66 catalyst, characterized in that, It is prepared by the preparation method described in claim 8.

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