Method for preparing methyl 3-hydroxybenzoate under catalysis of metal oxygen cluster coordinated monatomic nano-catalyst

Abstract

The invention discloses a method for preparing methyl 3-hydroxybenzoate under the catalysis of a metal oxygen cluster coordinated monatomic nano-catalyst. A catalyst-metal oxygen cluster coordinated monatomic nano-catalyst (the molecular formula of the catalyst can be expressed as MaObX, M can be any one of V, Cr, Nb, Mo, Ta and W, a can be any integer between 1 and 20, b can be any integer between 6 and 70, X can be Mn, Fe, Co, Ni and Cu, and the molecular formula of the catalyst can be expressed as MaObX; the preparation method comprises the following steps: adding methyl 3-hydroxybenzoate (any one of N, N and Zn) into a clean reaction tube, adding 3-hydroxybenzoic acid and methanol into the reactor, fully reacting by using a magnetic stirrer under a certain temperature condition, and separating and purifying to obtain methyl 3-hydroxybenzoate. According to the method, the metal oxygen cluster coordinated monatomic nano-catalyst is adopted to catalyze 3-hydroxybenzoic acid and methanol to prepare methyl 3-hydroxybenzoate, the catalyst has extremely high reaction activity and stability, after the reaction is finished, after a sample is simply treated, the used catalyst can be recycled and reused, the method is environmentally friendly, and the method is suitable for industrial production. The reaction cleanliness is improved, the production and manufacturing cost is reduced, and control and industrial production are easy.

Description

Technical Field

[0001] The invention relates to the technical field of catalysis, in particular to a method for preparing methyl 3-hydroxybenzoate by catalyzing 3-hydroxybenzoic acid and methanol using a metal oxygen cluster coordinated single-atom nanocatalyst. Background Art

[0002] Methyl 3-hydroxybenzoate is widely used in many fields. In organic synthesis, it is an important raw material or intermediate, participating in various chemical reactions to prepare other organic compounds. In addition, due to its antiseptic and antibacterial properties, methyl 3-hydroxybenzoate is also often used as a preservative in food, cosmetics and medicine, effectively extending the shelf life of products and ensuring safety. At the same time, its ester properties also allow it to be used as a fragrance or solvent in certain specific occasions, showing a variety of application value.

[0003] The core difficulty of the esterification synthesis method of methyl 3-hydroxybenzoate disclosed at home and abroad lies in the side reaction of phenolic hydroxyl group and the reversibility of the reaction. The phenolic hydroxyl group of 3-hydroxybenzoic acid is prone to oxidation or condensation (such as the formation of ether byproducts) under acidic or high temperature conditions, resulting in a decrease in product purity; at the same time, the esterification reaction itself is a reversible process, and the generated water needs to be efficiently removed to promote the reaction forward. The traditional process relies on concentrated sulfuric acid as a catalyst. Although it can catalyze the reaction, it causes problems such as equipment corrosion and acidic wastewater pollution, and the post-treatment is complicated (neutralization and washing are required), which further increases the cost. The main problem of the current process is reflected in the contradiction between efficiency and environmental protection. On the one hand, the use of azeotropic dehydration (such as toluene-water azeotropy) can improve the reaction conversion rate, but the introduction of additional solvents leads to complex separation steps and increased energy consumption; on the other hand, high temperature conditions (>80°C) accelerate the reaction, but aggravate the oxidation of hydroxyl groups or intermolecular condensation, forcing the yield to be generally lower than 85%, and multiple recrystallization purification is required. In addition, the non-recyclability of catalysts (such as sulfuric acid) pushes up industrialization costs, while the development of solid acid catalysts still faces technical bottlenecks such as insufficient activity or poor stability.

[0004] In recent years, single-atom catalysts (SACs) have become a hot topic in the field of catalysis due to their maximized atomic utilization and uniform active sites. However, their poor stability (easy migration and aggregation) and insufficient regulation of active sites limit their practical applications. Based on this, the metal oxygen cluster coordination strategy came into being: metal oxygen clusters (such as W6O 19 、Mo6O 24) acts as a ligand to anchor single atoms, forming a stable "cluster-single atom" composite structure. The multidentate coordination ability of metal oxygen clusters can effectively fix single atoms and prevent sintering; its unique electronic structure can also adjust the local coordination environment of single atoms and optimize the adsorption energy of intermediates, thereby improving catalytic activity and selectivity. The rigid skeleton of metal oxygen clusters inhibits the migration of single atoms, especially maintaining structural integrity in high temperature or strong acid-base environments; by changing the composition of oxygen clusters (such as transition metal type, cluster size) or coordination mode, the electronic state of single atom sites can be precisely controlled to adapt to different reactions (such as CO2 reduction, OER, HER); electron transfer channels may be formed between metal oxygen clusters and single atoms to achieve multi-active site synergy and break through the activity bottleneck of traditional SACs. At present, research in this direction focuses on designing new oxygen cluster carriers, analyzing the "cluster-single atom" interface action mechanism, and expanding its application in energy conversion and storage, providing a new paradigm for the development of next-generation efficient catalysts. Summary of the invention

[0005] The present invention discloses a method for preparing methyl 3-hydroxybenzoate by catalysis of a metal oxygen cluster coordinated single atom nanocatalyst. The present invention firstly prepares a catalyst, a metal oxygen cluster coordinated single atom nanocatalyst (the catalyst molecular formula can be expressed as M a O b X, wherein M can be any one of V, Cr, Nb, Mo, Ta, and W, a can be any integer between 1 and 20, b can be any integer between 6 and 70, and X can be any one of Mn, Fe, Co, Ni, Cu, and Zn) is placed in a clean reaction tube, and 3-hydroxybenzoic acid and methanol are added to the above reactor, and a magnetic stirrer is used to fully react under certain temperature conditions, and methyl 3-hydroxybenzoate can be obtained after separation and purification; compared with the traditional method for preparing methyl 3-hydroxybenzoate, the catalyst used in the present invention has extremely high reactivity and stability. After the reaction is completed, the sample can be recycled and reused after simple treatment, which is environmentally friendly, improves the cleanliness of the reaction, reduces the production cost, and is easy to control and industrialize. Technical Solution

[0006] A method for efficiently preparing methyl 3-hydroxybenzoate by using a metal oxygen cluster coordinated single atom nanocatalyst, characterized in that the specific steps are as follows: 1) adding raw materials 3-hydroxybenzoic acid and methanol to a reactor equipped with a catalyst, stirring and reacting at 80-150°C for 1-6 hours, and separating and purifying to obtain methyl 3-hydroxybenzoate. 2) recovering and reusing the catalyst used in step (1), and investigating its catalytic activity. 3) optimizing the reaction conditions and exploring the universality of the reaction substrate.

[0007] The general reaction formula for preparing methyl 3-hydroxybenzoate by using a metal oxygen cluster coordinated single atom nanocatalyst is as follows:

[0008] The catalyst in step 1) of the present invention is characterized in that the catalyst molecular formula can be expressed as M a O b X, wherein M can be any one of V, Cr, Nb, Mo, Ta, and W, a can be any integer between 1 and 20, b can be any integer between 6 and 70, X can be any one of Mn, Fe, Co, Ni, Cu, and Zn, and the amount of the catalyst is preferably 1 mol% to 5 mol%, and 1.5 mol% is optimal; the reaction temperature can be 80 to 150 °C, and the best effect is achieved at 120 °C; the reaction time can be between 1 h and 6 h, and 3 h is optimal.

[0009] In step 2) of the present invention, the catalyst is recovered and recycled. After the reaction is completed, an organic solvent such as ether, ethanol, methanol, etc. can be added to the phase system to precipitate the metal oxygen cluster coordinated single atom nanocatalyst, which is then treated and recovered, and the recovered catalyst is reused for catalytic oxidation of methyl 3-hydroxybenzoate.

[0010] The control variable method is used to screen the reaction solvent, temperature, and amount of catalyst to obtain the optimal reaction conditions.

[0011] Compared with the existing method for preparing methyl 3-hydroxybenzoate, the present invention has the following advantages: low catalyst raw material price, simple preparation process, high product yield, no three wastes, environmental friendliness, etc. The catalyst used is a new catalyst-metal oxygen cluster coordinated single atom nano catalyst, and the metal is any one of common V, Cr, Nb, Mo, Ta, W, Mn, Fe, Co, Ni, Cu, and Zn. The preparation raw materials are cheap and easy to obtain, and after the reaction is completed, the catalyst can be recycled for multiple times after simple treatment, which is very conducive to industrial production, so the invention has potential application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a general reaction formula for preparing methyl 3-hydroxybenzoate by catalyzing a single-atom nanocatalyst coordinated by metal oxygen clusters.

[0013] Figure 2 It is a single-atom nanocatalyst coordinated by metal oxygen clusters (V5O 37 Comparison of infrared spectra before and after cycling (using Ni as an example).

[0014] Figure 3 It is a single-atom nanocatalyst coordinated by metal oxygen clusters (V5O 37Ni as an example) and its XRD comparison after multiple recycling.

[0015] Figure 4 It is a single-atom nanocatalyst coordinated by metal oxygen clusters (V5O 37 Ni as an example) catalyzed preparation of methyl 3-hydroxybenzoate 1 HNMR spectrum.

[0016] Figure 5 It is a single-atom nanocatalyst coordinated by metal oxygen clusters (V5O 37 Crystal structure diagram of methyl 3-hydroxybenzoate prepared by catalysis of Ni (as an example). DETAILED DESCRIPTION

[0017] In order to further explain the present invention in detail, several specific implementation cases are given below, but the present invention is not limited to these examples.

[0018] Example 1: 0.05 g of single-atom nanocatalyst V5O coordinated by vanadium metal oxygen clusters with nickel atoms as active centers was added to a 30 mL clean reaction tube. 37 Ni, 2mmol 3-hydroxybenzoic acid and 2mmol methanol were reacted at 120℃ for 3h. After the reaction, samples were taken for GC-MS analysis, and the esterification rate of the reaction substrate was greater than 91%. After separation and purification, nuclear magnetic resonance and X-ray single crystal diffraction confirmed that the product was methyl 3-hydroxybenzoate.

[0019] Example 2: 0.05 g of single-atom nanocatalyst V6O coordinated by vanadium metal oxygen clusters with copper atoms as active centers was added to a 30 mL clean reaction tube. 39 Cu, 2mmol 3-hydroxybenzoic acid and 2mmol methanol were reacted at 100℃ for 4h. After the reaction, samples were taken for GC-MS analysis, and the esterification rate of the reaction substrate was greater than 96%. After separation and purification, nuclear magnetic resonance and X-ray single crystal diffraction confirmed that the product was methyl 3-hydroxybenzoate.

[0020] Example 3: 0.05 g of single-atom nanocatalyst W coordinated by tungsten metal oxygen clusters with iron atoms as active centers was added to a 30 mL clean reaction tube. 12 O 40 Fe, 2mmol 3-hydroxybenzoic acid and 2mmol methanol were reacted at 135 ℃ for 2 h. After the reaction, samples were taken for GC-MS analysis, and the esterification rate of the reaction substrate was greater than 90%. After separation and purification, nuclear magnetic resonance and X-ray single crystal diffraction confirmed that the product was methyl 3-hydroxybenzoate.

[0021] Example 4: 0.05 g of single-atom nanocatalyst W coordinated by tungsten metal oxygen clusters with copper atoms as active centers was added to a 30 mL clean reaction tube.12 O 42 Cu, 2mmol 3-hydroxybenzoic acid and 2mmol methanol were reacted at 135 ℃ for 2 h. After the reaction, samples were taken for GC-MS analysis, and the esterification rate of the reaction substrate was greater than 97%. After separation and purification, nuclear magnetic resonance and X-ray single crystal diffraction confirmed that the product was methyl 3-hydroxybenzoate.

[0022] Example 5: The reaction steps are the same as those of Example 1, except that the catalyst used is recycled and used for the first time. GC-MS analysis shows that the esterification rate of the reaction substrate is greater than 90%. After separation and purification, nuclear magnetic resonance and X-ray single crystal diffraction confirm that the product is methyl 3-hydroxybenzoate. The catalyst is verified to have structural stability by infrared spectroscopy and XRD.

[0023] Example 6: The reaction steps are the same as those of Example 1, except that the catalyst used is recycled and reused for the second time. GC-MS analysis shows that the esterification rate of the reaction substrate is greater than 87%. After separation and purification, nuclear magnetic resonance and X-ray single crystal diffraction confirm that the product is methyl 3-hydroxybenzoate. The catalyst is verified to have structural stability by infrared spectroscopy and XRD.

[0024] Example 7: The reaction steps are the same as those of Example 1, except that the catalyst used is recycled and used for the third time. GC-MS analysis shows that the esterification rate of the reaction substrate is greater than 85%. After separation and purification, nuclear magnetic resonance and X-ray single crystal diffraction confirm that the product is methyl 3-hydroxybenzoate. The catalyst is verified to have structural stability by infrared spectroscopy and XRD.

[0025] Example 8: The reaction steps are the same as those of Example 2, except that the catalyst used is recycled and used for the third time. GC-MS analysis shows that the esterification rate of the reaction substrate is greater than 91%. After separation and purification, nuclear magnetic resonance and X-ray single crystal diffraction confirm that the product is methyl 3-hydroxybenzoate. The catalyst is verified to have structural stability by infrared spectroscopy and XRD.

[0026] All of the above primary implementations do not set out other forms of implementing this new product and / or new method. Those skilled in the art will use this important information to modify the above content to achieve similar implementations. However, all modifications or changes based on the present invention belong to the rights reserved by the present invention.

[0027] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing methyl 3-hydroxybenzoate by catalytic use of a metal oxygen cluster coordinated single atom nanocatalyst, characterized in that: The specific steps are as follows: 1) Add a metal oxygen cluster coordinated single atom nanocatalyst to a clean reaction vessel, then add raw materials 3-hydroxybenzoic acid and methanol, and fully react under magnetic stirring at 80-150 °C for about 1-6 h. After the reaction, separation and purification can obtain methyl 3-hydroxybenzoate. 2) Recycle the metal oxygen cluster coordinated single atom nanocatalyst used in step (1) and then examine its catalytic activity. 3) Optimize the reaction conditions.

2. The preparation method according to claim 1, characterized in that: In step 1), the metal oxygen cluster coordinated single atom nanocatalyst, the catalyst molecular formula can be expressed as M a O b X, wherein M can be any one of V, Cr, Nb, Mo, Ta, and W, a can be any integer between 1 and 20, b can be any integer between 6 and 70, and X can be any one of Mn, Fe, Co, Ni, Cu, and Zn.

3. The preparation method according to claim 1, characterized in that: In step 1), no reaction solvent is required, the reaction temperature is 80°C to 150°C, and the reaction time is 1 h to 6 h.

4. The preparation method according to claim 1, characterized in that: In step 2), after the reaction is completed, an organic solvent is added to the system, and the metal oxygen cluster coordinated single atom nanocatalyst is precipitated, which is then treated and recovered for reuse. The recovered catalyst can be reused to prepare methyl 3-hydroxybenzoate.

5. The preparation method according to claim 1, characterized in that: In step 3), the reaction temperature, solvent, catalyst and amount of catalyst are screened by controlling variables to obtain the optimal reaction conditions.

6. The preparation method according to claim 1, wherein the catalyst is characterized in that the catalyst molecular formula can be expressed as M a O b X, wherein M can be any one of V, Cr, Nb, Mo, Ta, and W, a can be any integer between 1 and 20, b can be any integer between 6 and 70, X can be any one of Mn, Fe, Co, Ni, Cu, and Zn, and the amount of the catalyst used is 1 mol% to 5 mol%.

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