Catalyst for selective oxidation of cyclohexanone to produce adipic acid and preparation method and application thereof

Abstract

The application discloses a catalyst for preparing adipic acid by selective oxidation of cyclohexanone and a preparation method and application thereof. The catalyst is prepared by modifying manganese salt with organic carboxylic acid. The preparation method comprises the following steps: dissolving manganese salt in a mixed solution of ethanol and deionized water, stirring until uniform, adding organic carboxylic acid for dissolution, stirring for 12 hours or more, drying, and calcining under N2 atmosphere. The application of the catalyst for preparing adipic acid by selective oxidation of cyclohexanone comprises the following steps: mixing the catalyst, acetic acid and cyclohexanone, heating to a reaction temperature, continuously introducing oxygen and pressurizing, starting the reaction, cooling to room temperature after the reaction is completed, and obtaining the product. The catalyst has good hydrothermal stability, is convenient to filter and separate, has good recycling performance, and has the advantages of stable and controllable preparation method, good reproducibility, high selectivity of adipic acid and clean and pollution-free production process.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation, specifically to a catalyst for the selective oxidation of cyclohexanone to adipic acid, its preparation method, and its application. Background Technology

[0002] Adipic acid (AA) is a six-carbon dicarboxylic acid with the molecular formula C6H12O. 10O4, a white crystalline powder, odorless, is an aliphatic diacid with significant applications. It can undergo salt formation, esterification, and aminoacylation reactions. Adipic acid can also undergo condensation reactions with diamines and diols to produce high-molecular-weight polymers. Adipic acid applications are broadly categorized into nylon and non-nylon applications: In nylon products, it is mainly used to manufacture nylon 66 salt (approximately 75%), which is then used in the condensation polymerization of nylon 66 salt to produce nylon 66 resin and nylon 66 fiber. In non-nylon applications, it is primarily used to produce polyester polyols, which in turn produce polyurethane products such as polyurethane synthetic leather resins, polyurethane shoe sole resins, thermoplastic polyurethane (TPU), polyurethane adhesives, polyurethane rubber, and polyurethane foam. It can also be used to manufacture polyvinyl chloride (PVC), the third most widely produced synthetic plastic polymer in the world. In addition, adipic acid has wide applications in pharmaceuticals, fragrances, pesticides, coatings, food, adhesives and dyes (see [1] Cui Xiaoming. Current status and development prospects of adipic acid market at home and abroad [J]. Fine and Specialty Chemicals, 2013, 21(1):6-16. and [2] Yang Yansong, Jian Jian, You Kuiyi et al. Research progress on synthetic adipic acid process [J]. Chemical Industry Progress, 2013, 32(11):2638-2643.). There are many ways to produce adipic acid: adipic acid is prepared from cyclohexene, adipic acid is prepared from cyclohexanone, adipic acid is prepared from cyclohexane, and adipic acid is prepared from renewable resources such as starch or cellulose (currently under research). The global annual production of AA exceeds 3 million tons and is growing at a rate of 3-5% per year. It is estimated that by 2025, the global AA market will exceed US$8 billion (see [3] Skoog E, Shin JH, Saez-Jimenez V, et al. Biobased adipic acid - The challenge of developing the production host [J]. Biotechnology advances, 2018, 36(8): 2248-2263. and [4] Adipic Acid Market Size Worth $8.0 Billion By 2024 CAGR 4.7%. [cited 2020 Jan 22]. and [5] Bart JCJ, Cavallo S. Transiting from adipic acid to bioadipic acid. 1, Petroleum-based processes [J]. Industrial & Engineering Chemistry Research, 2015, 54(1): 1-46.). In recent years, researchers have been dedicated to the study of green synthesis processes for adipic acid, and novel catalysts have become a research hotspot.Common catalysts include heteropolyacids and heteropolyacid salts, tungstic acid and tungstates, molecular sieve catalysts, supported catalysts, and other novel catalysts (see [6] Ren Shuiying, Xie Zhengfeng, Xie Xiaopeng, et al. Clean method for catalytic oxidation synthesis of adipic acid [J]. Progress in Chemistry, 2009, 21(4):663-671. and [7] Di Dapeng, Lü Jie, Lou Yang, et al. Adipic acid production process technology and research progress [J]. Refining & Chemical Industry, 2013, 24(5):10-12.). Given the increasing demand for AA and the desire to reduce its negative environmental impact, much effort has been made to develop more sustainable processes. The focus of work on petroleum-based feedstocks is on NO. x Mitigation strategies and non-NO generation x The AA substitution route. Cyclohexanone is an intermediate product of cyclohexane oxidation. Industrially, cyclohexanone is usually oxidized with nitric acid to produce adipic acid (industrial process shown in attached figure). Figure 1 While cyclohexanone oxidation can achieve a conversion rate of up to 90% and a selectivity of about 70% for adipic acid, it also releases a large amount of toxic gases such as nitrogen oxides, which seriously pollutes the environment. Furthermore, concentrated nitric acid is highly corrosive and causes severe corrosion to equipment. Clean oxidation of cyclohexanone has always been a research hotspot in industry.

[0003] An environmentally friendly method for the oxidation of cyclohexanone (Y. Usui, A green method of adipicacid synthesis: organic solvent-and halide-free oxidation of cycloalkanones with 30% hydrogen peroxide. Green Chem. 2003, 5, 373-375.) has been developed, which can convert cyclohexanone to adipic acid at 90°C. This process uses H₂WO₄ as a catalyst, reacting with 3.3 moles of 30% hydrogen peroxide (H₂O₂) in a halide and organic solvent. H₂WO₄ acts as a pre-catalyst in the reaction, but it is easily further oxidized by H₂O₂ to generate water-soluble H₂ [WO(O₂)₂(OH)₂]. Notably, this heterogeneous reaction exhibits higher activity under solvent-free conditions. When solvents such as tert-butanol and dioxane are used, their presence significantly reduces the efficiency of the conversion of cyclohexanone to adipic acid, with yields of 31% and 52%, respectively. This method uses H₂O₂ as an oxidant, which is costly and poses certain safety risks.

[0004] CN104276937 discloses a technique for extracting adipic acid and C-5 dicarboxylic acid from the byproducts of cyclohexane oxidation. This technique involves separating the oil and water in the cyclohexane oxidation solution using wash water, concentrating the wash water, and then obtaining the target compounds through nitric acid oxidation and cooling crystallization. However, this method is only applicable to cyclohexane oxidation solutions that do not use acetic acid as a solvent. It utilizes the extraction capacity of water to concentrate organic matter in the oil phase and recovers byproducts through oxidation. This method requires the use of nitric acid and places high demands on the materials used in the equipment. Furthermore, it cannot effectively separate and utilize tar-like impurities in the system.

[0005] CN102850205B discloses a zinc-modified titanium-silicon molecular sieve catalyst for the production of 1,2-cyclohexanediol and adipic acid during the oxidation of cyclohexene. The preparation process is simple, as the catalyst can be obtained by calcining a zinc compound with a heteroatom molecular sieve. Under mild conditions, using hydrogen peroxide as the oxidant, adipic acid can be synthesized efficiently. However, this method uses organic solvents such as methanol, acetone, and acetonitrile during the production process, which may have negative environmental impacts.

[0006] The production technology of adipic acid needs further improvement; production efficiency needs to be increased and production costs need to be reduced. Using H2O2 as an oxidant seems environmentally friendly, but in reality, the water produced after the hydrogen peroxide reaction dissolves with the reactants, requiring significant industrial investment to separate the water. Furthermore, H2O2 is a vigorous oxidant, making the reaction rate difficult to control and even posing a risk of explosion. Using nitric acid as an oxidant not only places high demands on the materials and quality of the equipment but also produces NO... x The subsequent processing costs are high; using ozone (O3) as a green oxidant has resulted in a high adipic acid yield, which does meet the requirements of being environmentally friendly and having less pollution. However, ozone is not cheap and is difficult to implement in industrial production.

[0007] Therefore, there is an urgent need to develop high-performance heterogeneous catalysts that can reduce catalyst separation difficulties, increase their service life, and ensure high adipic acid yield. Simultaneously, molecular oxygen should be selected as the oxidant to avoid NO generated from concentrated nitric acid. x And the high cost of H2O2 or other oxidants. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a catalyst for the selective oxidation of cyclohexanone to prepare adipic acid, its preparation method and application. The catalyst has good hydrothermal stability, good recycling performance, stable, controllable and reproducible preparation method, high selectivity for adipic acid, and clean and pollution-free production process.

[0009] The technical solution adopted by the present invention to solve its technical problem is that a catalyst for the selective oxidation of cyclohexanone to prepare adipic acid is selected, and a manganese salt modified carbon material is used. The carbon material is an organic carboxylic acid, and the catalyst is expressed as x%Mn / C, where x% is the mass ratio of metallic manganese to organic carboxylic acid.

[0010] Furthermore, x% is 5% to 9%. It can be any one of 5%, 6%, 7%, 8%, or 9%.

[0011] Furthermore, the manganese salt is selected from at least one of manganese acetate, manganese acetylacetone, manganese oxalate, and manganese chloride.

[0012] Furthermore, the selected organic carboxylic acids are chosen from one or more of phthalic acid, isophthalic acid, terephthalic acid, pyromellitic acid, adipic acid, citric acid, and salicylic acid. Studies have shown that the carboxylic acids selected in this invention are all polycarboxylic acids, containing two or more carboxyl groups, which facilitate coordination with manganese ions in manganese salts. Their relatively long carbon chains can serve as templates to guide the formation of carbon materials, forming ordered structures through intermolecular interactions.

[0013] A method for preparing a catalyst for the selective oxidation of cyclohexanone to adipic acid includes the following steps:

[0014] The manganese salt is dissolved in a mixed solution of ethanol and deionized water and stirred until homogeneous. Then, an organic carboxylic acid is added and dissolved, and the mixture is stirred for more than 12 hours. After drying, it is calcined under a N2 atmosphere to obtain the final product.

[0015] Furthermore, the amount of the mixed solution of ethanol and deionized water should be sufficient to dissolve both the manganese salt and the organic carboxylic acid.

[0016] Furthermore, the ethanol and deionized water mixture is a solution in which ethanol and deionized water are mixed in a 1:1 volume ratio. Studies have shown that when ethanol and deionized water are in a 1:1 ratio, the polarity of the solution is conducive to the uniform mixing of manganese salt and polycarboxylic acid.

[0017] Furthermore, the drying temperature is 70–100°C. Drying removes ethanol and deionized water. Too low a drying temperature can lead to incomplete drying, leaving solution residue in the resulting solid powder that affects catalyst structure formation. Too high a drying temperature can cause the polycarboxylic acid to recrystallize into needle-like crystals, ultimately resulting in an uneven catalyst. The drying time is preferably 4–8 hours, more preferably 6 hours.

[0018] Furthermore, the calcination temperature is 300℃~600℃. If the calcination temperature is too low, the coordination between carboxylic acid anions and manganese ions is incomplete, resulting in the manganese ions not being stably anchored on the surface of the carbon material, ultimately affecting the activity of the catalyst in the reaction; if the temperature is too high, the formed ordered structure is easily destroyed. An inert gas, N2, is used as a protective gas to ensure that the structure of the carbon material is not damaged by the high temperature.

[0019] Furthermore, the calcination heating rate is 4-6℃ / min (preferably 5℃ / min). If the heating rate is too slow, the coordination between the carboxylic acid anions and manganese ions will be incomplete, resulting in the manganese ions not being stably anchored on the surface of the carbon material, ultimately affecting the activity of the catalyst in the reaction; if the heating rate is too fast, it will easily destroy the formed ordered structure.

[0020] Furthermore, the calcination time is 4–8 hours. If the calcination time is too short, the coordination between the carboxylic acid anions and manganese ions will be incomplete, resulting in the manganese ions not being stably anchored on the surface of the carbon material, ultimately affecting the activity of the catalyst in the reaction; if the calcination time is too long, the formed ordered structure will be easily destroyed.

[0021] The application of catalysts in the selective oxidation of cyclohexanone to adipic acid, specifically the method of selectively oxidizing cyclohexanone to adipic acid using catalysts, involves the following steps:

[0022] The catalyst, acetic acid, and cyclohexanone are mixed, heated to the reaction temperature, and oxygen is continuously introduced and pressurized to start the reaction. After the reaction is completed, the mixture is cooled to room temperature to obtain the final product.

[0023] Furthermore, the mass ratio of catalyst, acetic acid, and cyclohexanone is 0.5-2:10-30:100 (preferably 1:20:100). The presence of trace amounts of acetic acid reduces the reaction energy barrier and accelerates the reaction rate during the enol transformation of cyclohexanone. Too little or too much acetic acid will decrease the selectivity of adipic acid, as will too little or too much catalyst.

[0024] Furthermore, oxygen is continuously introduced and pressurized, with the reaction pressure being 0.5–0.8 MPa.

[0025] Furthermore, the reaction temperature is 60–80°C (preferably 65–75°C).

[0026] Furthermore, the reaction time is 4–10 h (preferably 5–8 h).

[0027] Furthermore, stirring is maintained throughout the entire reaction process, from the addition of materials to the end of the reaction, at a stirring speed of 300–600 r / min.

[0028] Recycling of catalysts for the selective oxidation of cyclohexanone to adipic acid:

[0029] After filtration, the catalyst in the reaction solution is washed with deionized water and anhydrous ethanol to remove organic matter from its surface. After drying, it is recalcined under N2 atmosphere using the same calcination conditions as in the catalyst preparation method to obtain the catalyst (the resulting catalyst is denoted as Rz-x%Mn / C, where z is the number of catalyst cycles, which can be 2, 3, 4, 5, etc.). New reactants can be added and reacted under the same conditions.

[0030] The beneficial effects of this invention are:

[0031] The catalyst provided by this invention involves uniform mixing of manganese salt and organic carboxylic acid during impregnation to ensure sufficient contact. Subsequently, during calcination, the carboxyl groups (-COOH) in the organic carboxylic acid molecules undergo deprotonation to form carboxylate anions (COO-). The oxygen atoms in these carboxylate anions form coordinate bonds with the manganese ions in the manganese salt, i.e., Mn-O bonds. This coordination firmly anchors the manganese ions to the carbon material framework, forming a stable composite catalyst with good catalytic activity for the reaction. Molecular oxygen can be used as an oxidant to oxidize cyclohexanone to adipic acid in one step.

[0032] The Mn / C heterogeneous catalyst of this invention has advantages such as good hydrothermal stability, easy separation, and good recyclability. The preparation method is stable, controllable, reproducible, and exhibits high selectivity for adipic acid. The production process generates no waste and is clean and pollution-free. The catalyst of this invention has good hydrothermal stability, maintaining its structural stability and catalytic activity under high temperature and high pressure conditions. The heterogeneous catalyst is easy to filter and separate, has good recyclability, and the preparation method is stable, controllable, and reproducible. It also exhibits high selectivity for adipic acid and a clean, pollution-free production process. Attached Figure Description

[0033] Figure 1 This is a typical industrial process for producing adipic acid by oxidizing cyclohexanone with nitric acid. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments.

[0035] Unless otherwise stated, all percentages mentioned in this specification refer to percentages by mass.

[0036] In the actual production of adipic acid by selective oxidation of cyclohexanone, the selectivity of the target product adipic acid is given priority. The higher the selectivity of adipic acid, the easier the subsequent separation and the lower the cost.

[0037] Example 1:

[0038] The application of the catalyst in the selective oxidation of cyclohexanone to adipic acid in this embodiment is a method for selectively oxidizing cyclohexanone to adipic acid using a catalyst. The operation steps are as follows:

[0039] 0.20 g of 5% Mn / C catalyst, 20 g of cyclohexanone, and 4 g of acetic acid were added to the reactor, and then O2 was introduced three times to remove air. When the reaction temperature reached 70°C, O2 was pressurized to 0.6 MPa with stirring (stirring speed of 500 r / min throughout the reaction). After 8 hours of reaction, the gas supply was stopped, and the reactor was placed in a cold water bath to cool to room temperature.

[0040] The reaction product was completely dissolved in anhydrous ethanol and transferred to a volumetric flask to adjust the volume. Qualitative analysis was then performed using gas chromatography-mass spectrometry (Shimadzu QP2010 GC-MS), and quantitative analysis was performed using high performance liquid chromatography (Agilent 1200 HPLC).

[0041] The preparation method of the 5% Mn / C catalyst:

[0042] 1.115 g of manganese acetate tetrahydrate was added to a mixed solution consisting of 30 mL of ethanol and 30 mL of deionized water, and stirred until homogeneous. Then, 5 g of phthalic acid was added to dissolve the mixture, and after stirring for 12 h, it was dried at 90 °C for 6 h. The resulting catalyst powder was calcined at 400 °C (calcination heating rate of 5 °C / min) for 5 h under a N2 atmosphere to obtain the final product.

[0043] In this embodiment, the cyclohexanone conversion rate was 31.2% and the adipic acid selectivity was 92.4%.

[0044] Example 2: The steps and parameters in this example are the same as in Example 1, except that the catalyst is 6% Mn / C. The cyclohexanone conversion rate in this example is 29.4%, and the adipic acid selectivity is 87.6%.

[0045] The preparation method of the 6% Mn / C catalyst:

[0046] 1.338 g of manganese acetate tetrahydrate was added to a mixed solution consisting of 30 mL of ethanol and 30 mL of deionized water, and stirred until homogeneous. Then, 5 g of phthalic acid was added to dissolve the mixture, and after stirring for 12 h, it was dried at 90 °C for 6 h. The resulting catalyst powder was calcined at 400 °C (calcination heating rate of 5 °C / min) for 5 h under a N2 atmosphere to obtain the final product.

[0047] Example 3: The steps are the same as in Example 1, except that the catalyst is 7% Mn / C. In this example, the cyclohexanone conversion rate is 29.7% and the adipic acid selectivity is 84.6%.

[0048] The preparation method of the 7% Mn / C catalyst:

[0049] 1.561 g of manganese acetate tetrahydrate was added to a mixed solution consisting of 30 mL of ethanol and 30 mL of deionized water, and stirred until homogeneous. Then, 5 g of phthalic acid was added to dissolve the mixture, and after stirring for 12 h, it was dried at 90 °C for 6 h. The resulting catalyst powder was calcined at 400 °C (calcination heating rate of 5 °C / min) for 5 h under a N2 atmosphere to obtain the final product.

[0050] Example 4: The steps are the same as in Example 1, except that the catalyst is 9% Mn / C. In this example, the cyclohexanone conversion rate is 28.4% and the adipic acid selectivity is 83.5%.

[0051] The preparation method of the 9% Mn / C catalyst:

[0052] 2.007 g of manganese acetate tetrahydrate was added to a mixed solution consisting of 30 mL of ethanol and 30 mL of deionized water, and stirred until homogeneous. Then, 5 g of phthalic acid was added to dissolve the mixture, and after stirring for 12 h, it was dried at 90 °C for 6 h. The resulting catalyst powder was calcined at 400 °C (calcination heating rate of 5 °C / min) for 5 h under a N2 atmosphere to obtain the final product.

[0053] Example 5: The steps are the same as in Example 1, except that the calcination temperature in the catalyst preparation method is 300°C. In this example, the cyclohexanone conversion rate is 26.1% and the adipic acid selectivity is 75.2%.

[0054] Example 6: The steps are the same as in Example 1, except that the calcination temperature in the catalyst preparation method is 500°C. In this example, the cyclohexanone conversion rate is 35.6% and the adipic acid selectivity is 85.6%.

[0055] Example 7: The steps are the same as in Example 1, except that the calcination temperature in the catalyst preparation method is 600°C. In this example, the cyclohexanone conversion rate is 46.4% and the adipic acid selectivity is 76.7%.

[0056] Comparative Example 1: The steps are the same as in Example 1, except that the calcination temperature in the catalyst preparation method is 700°C. In this example, the cyclohexanone conversion rate is 39.7% and the adipic acid selectivity is 61.9%.

[0057] Example 8: The steps are the same as in Example 1, except that the organic carboxylic acid used to prepare the catalyst is adipic acid. In this example, the cyclohexanone conversion rate is 30.6% and the adipic acid selectivity is 87.0%.

[0058] Example 9: The steps are the same as in Example 1, except that the organic carboxylic acid used to prepare the catalyst is isophthalic acid. In this example, the cyclohexanone conversion rate is 47.9% and the adipic acid selectivity is 71.3%.

[0059] Example 10: The steps are the same as in Example 1, except that the organic carboxylic acid used to prepare the catalyst is terephthalic acid. In this example, the cyclohexanone conversion rate is 46.5% and the adipic acid selectivity is 70.2%.

[0060] Example 11: The steps are the same as in Example 1, except that the organic carboxylic acid used to prepare the catalyst is trimesic acid. In this example, the cyclohexanone conversion rate is 43.8% and the adipic acid selectivity is 69.1%.

[0061] Example 12: The steps are the same as in Example 1, except that the organic carboxylic acid used to prepare the catalyst is citric acid. In this example, the cyclohexanone conversion rate is 36.2% and the adipic acid selectivity is 78.2%.

[0062] Example 13: The steps are the same as in Example 1, except that the organic carboxylic acid used to prepare the catalyst is salicylic acid. In this example, the cyclohexanone conversion rate is 39.0% and the adipic acid selectivity is 69.5%.

[0063] Comparative Example 2: The steps are the same as in Example 1, except that the organic carboxylic acid used to prepare the catalyst is glutaric acid. In this example, the cyclohexanone conversion rate is 29.5% and the adipic acid selectivity is 48.0%.

[0064] Example 14: The steps are the same as in Example 1, except that the manganese salt used to prepare the catalyst is manganese oxalate. In this example, the cyclohexanone conversion rate is 34.4% and the adipic acid selectivity is 71.2%.

[0065] Example 15: The steps are the same as in Example 1, except that the manganese salt used to prepare the catalyst is manganese acetylacetone. In this example, the cyclohexanone conversion rate is 32.3% and the adipic acid selectivity is 86.6%.

[0066] Comparative Example 3: The steps are the same as in Example 1, except that the manganese salt used to prepare the catalyst is manganese nitrate. In this example, the cyclohexanone conversion rate is 23.6% and the adipic acid selectivity is 32.9%.

[0067] Example 16: The steps are the same as in Example 1, except that the manganese salt used to prepare the catalyst is manganese chloride. In this example, the cyclohexanone conversion rate is 14.9% and the adipic acid selectivity is 69.8%.

[0068] Comparative Example 4: The steps are the same as in Example 1, except that the reaction pressure is 0.4 MPa. In this example, the cyclohexanone conversion rate is 22.6% and the adipic acid selectivity is 58.9%.

[0069] Example 17: The steps are the same as in Example 1, except that the reaction pressure is 0.5 MPa. In this example, the cyclohexanone conversion rate is 26.8% and the adipic acid selectivity is 68.3%.

[0070] Example 18: The steps are the same as in Example 1, except that the reaction pressure is 0.8 MPa. In this example, the cyclohexanone conversion rate is 31.1% and the adipic acid selectivity is 87.3%.

[0071] Comparative Example 5: The steps are the same as in Example 1, except that the reaction pressure is 1.0 MPa. In this example, the cyclohexanone conversion rate is 38.4% and the adipic acid selectivity is 57.6%.

[0072] Example 19: The steps are the same as in Example 1, except that the reaction temperature is 65°C. In this example, the cyclohexanone conversion rate is 25.0% and the adipic acid selectivity is 84.8%.

[0073] Example 20: The steps are the same as in Example 1, except that the reaction temperature is 75°C. In this example, the cyclohexanone conversion rate is 32.3% and the adipic acid selectivity is 88.8%.

[0074] Example 21: The steps are the same as in Example 1, except that the reaction temperature is 60°C. In this example, the cyclohexanone conversion rate is 16.5% and the adipic acid selectivity is 78.5%.

[0075] Example 22: The steps are the same as in Example 1, except that the reaction temperature is 80°C. In this example, the cyclohexanone conversion rate is 32.5% and the adipic acid selectivity is 72.2%.

[0076] Example 23: The steps are the same as in Example 1, except that the reaction time is 5 hours. In this example, the cyclohexanone conversion rate is 13.6% and the adipic acid selectivity is 82.4%.

[0077] Example 24: The steps are the same as in Example 1, except that the reaction time is 6 hours. In this example, the cyclohexanone conversion rate is 15.0% and the adipic acid selectivity is 86.5%.

[0078] Example 25: The steps are the same as in Example 1, except that the reaction time is 7 hours. In this example, the cyclohexanone conversion rate is 22.9% and the adipic acid selectivity is 88.8%.

[0079] Example 26: The steps are the same as in Example 1, except that the reaction time is 9 hours. In this example, the cyclohexanone conversion rate is 32.3% and the adipic acid selectivity is 76.6%.

[0080] Example 27: The steps are the same as in Example 1, except that the reaction time is 10 hours. In this example, the cyclohexanone conversion rate is 35.0% and the adipic acid selectivity is 74.2%.

[0081] Example 28: The steps are the same as in Example 1, except that the catalyst is R2-5%Mn / C. In this example, the cyclohexanone conversion rate is 30.1% and the adipic acid selectivity is 90.4%.

[0082] In Example 1, after filtering the catalyst in the reaction solution, the organic matter on the catalyst surface was washed away with deionized water and anhydrous ethanol. After drying, it was recalcined under N2 atmosphere under the same calcination conditions as in the catalyst preparation method to obtain the catalyst (the obtained catalyst is denoted as R2-5%Mn / C). New reactants can be added and reacted under the same conditions.

[0083] Example 29: The steps are the same as in Example 1, except that the catalyst is R3-5%Mn / C. In this example, the cyclohexanone conversion rate is 30.1% and the adipic acid selectivity is 90.4%.

[0084] After filtration, the catalyst R2-5%Mn / C in the reaction solution is washed with deionized water and anhydrous ethanol to remove organic matter from the catalyst surface. After drying, it is recalcined under N2 atmosphere under the same calcination conditions as in the catalyst preparation method to obtain the catalyst (the resulting catalyst is denoted as R3-5%Mn / C). New reactants can be added and the reaction can be carried out under the same conditions.

[0085] Example 30: The steps are the same as in Example 1, except that the catalyst is R4-5%Mn / C. In this example, the cyclohexanone conversion rate is 30.6% and the adipic acid selectivity is 90.3%.

[0086] After filtration, the catalyst R3-5%Mn / C in the reaction solution is washed with deionized water and anhydrous ethanol to remove organic matter from the catalyst surface. After drying, it is recalcined under N2 atmosphere under the same calcination conditions as in the catalyst preparation method to obtain the catalyst (the resulting catalyst is denoted as R4-5%Mn / C). New reactants can be added and the reaction can be carried out under the same conditions.

[0087] Example 31: The steps are the same as in Example 1, except that the catalyst is R8-5%Mn / C. In this example, the cyclohexanone conversion rate is 29.4% and the adipic acid selectivity is 90.8%.

[0088] The catalyst R7-5%Mn / C in the reaction solution was recycled 7 times, filtered, and the organic matter on the catalyst surface was washed away with deionized water and anhydrous ethanol. After drying, it was calcined again under N2 atmosphere under the same calcination conditions as in the catalyst preparation method to obtain the catalyst (the obtained catalyst is denoted as R8-5%Mn / C). New reactants can be added and the reaction can be carried out under the same conditions.

Claims

1. An application of a catalyst for the selective oxidation of cyclohexanone to adipic acid, characterized in that, The operating steps are as follows: The catalyst, acetic acid, and cyclohexanone are mixed, heated to the reaction temperature, and oxygen is continuously introduced and pressurized to start the reaction. After the reaction is completed, the mixture is cooled to room temperature to obtain the final product. The catalyst for the selective oxidation of cyclohexanone to adipic acid uses a manganese salt-modified carbon material, wherein the carbon material is an organic carboxylic acid, and the catalyst is expressed as x%Mn / C, where x% is the mass ratio of metallic manganese to organic carboxylic acid; x% is 5-9%; The manganese salt is selected from at least one of manganese acetate, manganese acetylacetone, manganese oxalate, and manganese chloride; The selected organic carboxylic acids are selected from one or more of phthalic acid, isophthalic acid, terephthalic acid, trimesic acid, adipic acid, citric acid, and salicylic acid; The method for preparing the catalyst for the selective oxidation of cyclohexanone to adipic acid includes the following steps: The manganese salt is dissolved in a mixed solution of ethanol and deionized water and stirred until homogeneous. Then, an organic carboxylic acid is added and dissolved, and the mixture is stirred for more than 12 hours. The solution is then dried and calcined under a N2 atmosphere at a temperature of 300℃ to 600℃ to obtain the final product.

2. The application of the catalyst for the selective oxidation of cyclohexanone to adipic acid according to claim 1, characterized in that, In the preparation method of the catalyst, the amount of the mixed solution of ethanol and deionized water is sufficient to dissolve both manganese salt and organic carboxylic acid; and / or the mixed solution of ethanol and deionized water is a solution in which ethanol and deionized water are mixed in a volume ratio of 1:

1.

3. The application of the catalyst for the selective oxidation of cyclohexanone to adipic acid according to claim 1 or 2, characterized in that, In the preparation method of the catalyst, the drying temperature is 70~100℃; and / or the drying time is 4-8 hours.

4. The application of the catalyst for the selective oxidation of cyclohexanone to adipic acid according to claim 1 or 2, characterized in that, In the preparation method of the catalyst, the calcination heating rate is 4-6℃ / min; and / or the calcination time is 4-8h.

5. The application of the catalyst for the selective oxidation of cyclohexanone to adipic acid according to claim 1, characterized in that, The mass ratio of catalyst, acetic acid, and cyclohexanone is 0.5-2:10-30:100; and / or oxygen is continuously introduced and pressurized, with a reaction pressure of 0.5-0.8 MPa.

6. The application of the catalyst for the selective oxidation of cyclohexanone to adipic acid according to claim 5, characterized in that, The mass ratio of catalyst, acetic acid, and cyclohexanone is 1:20:

100.

7. The application of the catalyst for the selective oxidation of cyclohexanone to adipic acid according to claim 1 or 2, characterized in that, The reaction temperature is 60~80℃; and / or the reaction time is 4~10 h; and / or the stirring is maintained throughout the entire reaction process from the addition of materials to the end of the reaction, with a stirring speed of 300~600 r / min.

8. The application of the catalyst for the selective oxidation of cyclohexanone to adipic acid according to claim 7, characterized in that, The reaction temperature is 65~75℃.

9. The application of the catalyst for the selective oxidation of cyclohexanone to adipic acid according to claim 7, characterized in that, The reaction time is 5-8 hours.

10. The application of the catalyst for the selective oxidation of cyclohexanone to adipic acid according to claim 1 or 2, characterized in that, Recycling of catalysts for the selective oxidation of cyclohexanone to adipic acid: After filtration of the catalyst in the reaction solution, the organic matter on the surface of the catalyst is washed away with deionized water and anhydrous ethanol. After drying, the catalyst is calcined again under N2 atmosphere under the same calcination conditions as in the catalyst preparation method.

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