Catalyst for preparing adipic acid from cyclohexanone, and preparation method therefor and use thereof

Abstract

The present invention provides a catalyst for preparing adipic acid from cyclohexanone, and a preparation method therefor and a use thereof. The method comprises: (1) preparing a metal salt solution, then adding a dispersing agent and a silane coupling agent into the metal salt solution, and then introducing ammonia gas to obtain a first mixed solution; (2) adding tetrapropylammonium hydroxide and organic amine into the first mixed solution to obtain a second mixed solution; (3) adding a silicon source and a titanium source into the second mixed solution to obtain a sol, and carrying out hydrothermal crystallization on the sol, and performing washing, drying and calcination to obtain catalyst raw powder; and (4) using an organic acid solution to carry out acid treatment on the catalyst raw powder, and carrying out washing, drying and calcination to obtain the catalyst for preparing adipic acid from cyclohexanone. The prepared catalyst is used for preparing adipic acid by means of the reaction of cyclohexanone and an oxidizing agent, has high raw material conversion rate, high product selectivity, long service life and high catalytic activity, and is suitable for large-scale industrial production and preparation of adipic acid.

Description

A catalyst for preparing adipic acid from cyclohexanone and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a catalyst for preparing adipic acid from cyclohexanone, and a preparation method and application thereof. Background Art

[0002] Adipic acid (AA), also known as hexanedicarboxylic acid, commonly known as adipic acid, has a molecular formula of C6H 10 Adipic acid (O4), a white, odorless crystalline powder, is an aliphatic dibasic acid with significant application value. Its primary application in nylon products is in the manufacture of nylon 6,6 salt (complex), which is then used in the polycondensation of nylon 6,6 salt to produce nylon 6,6 resin and nylon 6,6 fiber. Adipic acid is also used in the production of polyester polyols, which in turn produce polyurethane products. It also has a wide range of applications in medicine, fragrances, pesticides, coatings, foods, adhesives, and dyes.

[0003] There are various methods for producing adipic acid, such as using cyclohexene as a raw material to prepare adipic acid, using cyclohexanone as a raw material to prepare adipic acid, using cyclohexane as a raw material to prepare adipic acid, or using renewable resources such as starch or cellulose as a raw material to prepare adipic acid. In recent years, research on the direct oxidation synthesis of adipic acid using hydrogen peroxide as an oxidant and cyclohexanone as a raw material has made certain progress. Relative to cyclohexene and cyclohexanol, cyclohexanone is stable in nature and easy to preserve. It is environmentally friendly to use hydrogen peroxide as an oxidant and is very different from the nitric acid oxidation process for KA oil (a mixture of cyclohexanol and cyclohexanone), thus avoiding the corrosion and pollution problems brought during the nitric acid reaction. However, in this method, most of the catalysts use acidic ligands, which cause a certain degree of corrosion to the equipment, and the durability of the catalyst is poor, resulting in serious loss during use, which is unfavorable for industrialized production. Summary of the Invention

[0004] In response to the deficiencies in the prior art, the present invention discloses a catalyst for preparing adipic acid from cyclohexanone, a preparation method thereof, and an application thereof. The prepared catalyst is used for oxidizing cyclohexanone as a raw material to prepare adipic acid, has high raw material conversion rate and product selectivity, and has a long catalyst service life, and is suitable for large-scale industrial production of adipic acid.

[0005] In order to achieve the above technical objectives, on the one hand, the present invention provides a method for preparing a catalyst for preparing adipic acid from cyclohexanone, the method comprising the following steps:

[0006] (1) preparing a metal salt solution, then adding a dispersant and a silane coupling agent to the metal salt solution, and then introducing ammonia gas to obtain a first mixed solution;

[0007] (2) adding tetrapropylammonium hydroxide and an organic amine to the first mixed solution to obtain a second mixed solution;

[0008] (3) adding a silicon source and a titanium source to the second mixed solution to obtain a glue solution; hydrothermally crystallizing the glue solution, washing, drying, and calcining the solution to obtain a catalyst raw powder;

[0009] (4) The catalyst powder is treated with an organic acid solution, and the catalyst for preparing adipic acid from cyclohexanone is obtained through washing, drying and calcining.

[0010] In the above technical solution, metal oxides are introduced into the molecular sieve as the active component of the catalyst, and a complex is formed by introducing ammonia into the metal salt, and then the complex is slowly and evenly decomposed under heating conditions, and under the action of a dispersant, metal oxide balls with uniform size and morphology and no mutual agglomeration are formed. Furthermore, the above technical solution adds a silane coupling agent to the reaction solution, thereby forming a uniform silicon layer on the surface of the metal oxide, and finally forms a core-shell structure catalyst with metal oxide as the core and molecular sieve wrapped by hydrothermal reaction. The catalyst structure is stable, and the active components are evenly distributed in the core of the catalyst particles and the molecular sieve pores, thereby improving the catalytic activity and product selectivity of the catalyst and improving the service life of the catalyst; further, the above technical solution selectively removes the metal oxide particles not wrapped by the molecular sieve by acid treatment of the catalyst raw powder with an organic acid solution, ensuring the stable progress of the catalytic reaction and further improving the service life of the catalyst; in addition, the core-shell structure can also protect the active site from being contaminated by impurities, further extending the service life of the catalyst.

[0011] It should be noted that the present invention does not limit the order of adding the dispersant and the silane coupling agent to the metal salt solution in step (1).

[0012] The examples and comparative examples of the present invention explore the effects of introducing metal salts, adding dispersants, adding silane coupling agents, passing ammonia gas, and acid treatment on the catalytic activity and service life of the prepared catalysts.

[0013] The metal salt solution is prepared by dissolving a metal salt in water. In a further example of the present invention, the types of cations and anions of the metal salt are optimized. Alternatively, the metal salt solution is prepared by dissolving a metal salt in water, wherein the cations of the metal salt include transition metal cations, and further optionally include one or more of iron ions, cobalt ions, nickel ions, copper ions, manganese ions, vanadium ions, chromium ions, and zinc ions, thereby providing better catalytic activity; further, the anions of the metal salt can be selected from one or more of acetate, citrate, sulfate, nitrate, and chloride ions, thereby improving the efficiency of catalyst preparation by using soluble salts of the metal salt cations used to prepare the metal salt solution.

[0014] In a further example of the present invention, the amount of metal salt, and the amount of dispersant and silane coupling agent in the metal salt solution prepared in step (1) are optimized. Optionally, the mass ratio of the metal salt, dispersant and silane coupling agent used in the metal salt solution prepared in step (1) is 1: (0.001-0.05): (0.005-0.1), preferably 1: (0.005-0.02): (0.01-0.03), so that the metal salt is fully dispersed and stably fixed on the surface of the molecular sieve during the subsequent hydrothermal crystallization process.

[0015] In a further example of the present invention, the amount of metal salt and the amount of ammonia in the metal salt solution prepared in step (1) are optimized. Optionally, the molar ratio of the metal salt to the ammonia is 1:(1-6), preferably 1:(2-3), so that the metal salt and the ammonia are fully complexed.

[0016] In a further example of the present invention, the dispersant may be one or more of polyvinyl pyrrolidone, sulfonated polystyrene, sodium polyacrylate, and sodium carboxymethyl cellulose.

[0017] In a further example of the present invention, the silane coupling agent includes one or more of a vinyl silane coupling agent, a chloroalkyl silane coupling agent, an aminoalkyl silane coupling agent, an epoxyalkyl silane coupling agent, a methacryloyloxyalkyl silane coupling agent, a sulfur-containing hydrocarbon silane coupling agent, a pseudohalogen silane coupling agent and a quaternary ammonium hydrocarbon silane coupling agent, and may further optionally include one or more of KH550, KH570, KH560 and KH792.

[0018] In a further example of the present invention, the type and concentration of the organic acid solution, as well as the conditions for acid treatment were explored respectively. The present invention may optionally use a weak acid for acid treatment to dissolve and remove the metal oxide particles deposited on the surface of the catalyst raw powder, but will not excessively dissolve the metal oxides in the molecular sieve pores. Further optionally, the organic acid solution includes an aqueous solution of one or more of acetic acid, propionic acid, acrylic acid, citric acid, oxalic acid, and benzoic acid. Optionally, the concentration of the organic acid solution is 1% to 10%, preferably 3% to 5%. Optionally, the temperature of the acid treatment is 20 to 100°C, preferably 50 to 80°C; the time of the acid treatment is 10 to 200 minutes. It should be noted that the concentration of the organic acid is mass concentration; after acid treatment, the organic acid remaining on the surface of the molecular sieve will be evaporated in the subsequent calcination operation, and the obtained catalyst will not corrode the equipment during the catalytic process.

[0019] In a further example of the present invention, the type and amount of the organic amine were explored and optimized. Specifically, the organic amine can be one or more of n-butylamine, triethylamine, tri-n-propylamine, n-propylamine, diethylamine, and ethylenediamine; and the mass ratio of tetrapropylammonium hydroxide to the organic amine is 1:(0.02-0.8), preferably 1:(0.3-0.5).

[0020] In a further example of the present invention, the types of the silicon source and titanium source and the amounts of the two are optimized respectively. The silicon source can be selected from one of vapor-phase silicon oxide, ethyl orthosilicate, and silica sol; the titanium source can be selected from one of isobutyl titanate, titanium oxide powder, and titanium tetrachloride. The molar ratio of the silicon source to the titanium source is 1: (0.01 to 0.2), preferably 1: (0.02 to 0.05).

[0021] In a further example of the present invention, the control conditions of hydrothermal crystallization were explored and optimized. Optionally, the temperature of the hydrothermal crystallization is 80-220°C, preferably 150-190°C; the time of the hydrothermal crystallization is 10-120h, preferably 48-84h, so that ammonia can be gradually evaporated, and the morphology of the prepared catalyst is controlled by adjusting the hydrothermal crystallization temperature and time to promote uniform distribution of active sites.

[0022] On the other hand, the present invention provides a catalyst for preparing adipic acid from cyclohexanone prepared by the above preparation method.

[0023] On the other hand, the present invention provides a method for preparing adipic acid, which comprises dissolving cyclohexanone in a solvent and reacting the solvent with an oxidant in the presence of the catalyst for preparing adipic acid from cyclohexanone to produce adipic acid.

[0024] Furthermore, the present invention optimizes the control conditions of the above-mentioned adipic acid preparation method. Optionally, the reaction temperature is 50-120°C, preferably 70-90°C.

[0025] Furthermore, the reaction time can be selected to be 10 to 240 minutes. In actual operation, the reaction is terminated when the concentration of the reactants no longer changes significantly.

[0026] Furthermore, the solvent may be selected from one or more of methanol, ethanol, isopropanol, tert-butanol, formic acid, acetic acid, acetonitrile, and 1,2-dichloroethane.

[0027] Furthermore, the present invention explores and optimizes the amounts of raw materials, solvents, and catalysts. Optionally, the mass ratio of the cyclohexanone, the solvent, and the catalyst for preparing adipic acid from cyclohexanone is 1:(0-10):(0.2-2), preferably 1:(1-3):(0.5-1), thereby achieving better raw material conversion, product yield, and catalyst life.

[0028] Furthermore, the present invention explores and optimizes the type and dosage of the oxidant. Specifically, the oxidant includes one or more of cumene hydroperoxide, tert-butyl hydroperoxide, ethylbenzene peroxide, and hydrogen peroxide. The molar ratio of cyclohexanone to the oxidant is 1:(0.2-2.4), preferably 1:(1.0-1.6), thereby achieving better raw material conversion, product yield, and catalyst life.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The preparation method of the catalyst for preparing adipic acid from cyclohexanone is simple and efficient to operate. The prepared catalyst is used for reacting cyclohexanone with an oxidant to prepare adipic acid, thereby avoiding the pollution and equipment corrosion problems in the existing adipic acid production process. The catalyst has high raw material conversion rate and product selectivity, long catalyst service life, and high catalytic activity, and is suitable for large-scale industrial production of adipic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0032] FIG1 is an electron microscope morphology of the catalyst prepared in Example 1. DETAILED DESCRIPTION

[0033] To facilitate understanding of the present invention, the present invention will be described in more detail below, with preferred embodiments of the present invention provided. However, it should be understood that these embodiments are merely for the purpose of further explanation and are not to be construed as limiting the present invention in any form, i.e., they are not intended to limit the scope of protection of the present invention.

[0034] It should be noted that the conversion rate of cyclohexanone in the embodiments of the present invention is the percentage of the mass of the cyclohexanone raw material participating in the reaction to the mass of the total cyclohexanone raw material; the selectivity of adipic acid = the mass ratio of cyclohexanone produced by the reaction to adipic acid to the mass ratio of the total cyclohexanone participating in the reaction; the theoretical conversion rate = the theoretical mass of cyclohexanone participating in the reaction / the mass of the cyclohexanone raw material * 100%.

[0035] Example 1

[0036] 17.7g of nickel acetate was dissolved in water to form a solution, and then 0.018g of sodium polyacrylate and 0.086g of KH570 silane coupling agent were added. Then 3.4g of ammonia gas was introduced into the solution and stirred to obtain a uniform suspension. 400g of tetrapropylammonium hydroxide and 320g of triethylamine were added to the suspension respectively and stirred to form a uniform liquid. 208g of ethyl orthosilicate and 3.4g of isobutyl titanate were added to the liquid respectively and stirred for 2h to form a uniform colloid. The colloid was placed in a hydrothermal autoclave and crystallized at 80°C for 120h. The obtained solid was washed to neutrality, dried with hot air, and then calcined at 800°C for 6h to obtain the catalyst powder.

[0037] A 10% acetic acid solution was prepared and heated to 100°C. The catalyst powder was added to the acetic acid solution and treated for 10 minutes. The treated catalyst was then separated and cleaned to neutrality, dried with hot air, and calcined at 800°C for 6 hours to obtain a catalyst for preparing adipic acid from cyclohexanone.

[0038] Example 2

[0039] 23.8g of cobalt chloride was dissolved in water to form a solution, and then 1.19g of sodium carboxymethyl cellulose and 2.38g of KH550 silane coupling agent were added. Then 1.7g of ammonia gas was introduced into the solution and stirred to obtain a uniform suspension. 400g of tetrapropylammonium hydroxide and 8g of n-butylamine were added to the suspension respectively and stirred to form a uniform liquid. 120g of fumed silicon oxide and 16g of titanium oxide powder were added to the liquid respectively and stirred for 12h to form a uniform glue. The glue was placed in a hydrothermal autoclave and crystallized at 220°C for 84h. The obtained solid was washed to neutrality, dried with hot air, and then calcined at 300°C for 6h to obtain the catalyst raw powder.

[0040] A 1% citric acid solution was prepared and heated to 50°C. The catalyst powder was added to the citric acid solution and treated for 200 minutes. The treated catalyst was then separated and cleaned to neutrality, dried with hot air, and calcined at 300°C for 6 hours to obtain a catalyst for preparing adipic acid from cyclohexanone.

[0041] Example 3

[0042] 16.1 g of zinc sulfate was dissolved in water to form a solution, and then 0.08 g of polyvinyl pyrrolidone and 0.16 g of KH792 silane coupling agent were added. Then 5.1 g of ammonia gas was introduced into the solution and stirred to obtain a uniform suspension. 400 g of tetrapropylammonium hydroxide and 120 g of tri-n-propylamine were added to the suspension respectively and stirred to form a uniform liquid. 240 g of 30% silica sol and 4.55 g of titanium tetrachloride were added to the liquid respectively and stirred for 8 h to form a uniform gel. The gel was placed in a hydrothermal autoclave and crystallized at 190° C. for 10 h. The obtained solid was washed to neutrality, dried with hot air, and then calcined at 600° C. for 6 h to obtain a catalyst powder.

[0043] A 3% acrylic acid solution was prepared, heated to 20°C, and the catalyst powder was added to the acrylic acid solution for treatment for 100 minutes. The treated catalyst was then separated and cleaned to neutrality, dried with hot air, and calcined at 600°C for 6 hours to obtain a catalyst for preparing adipic acid from cyclohexanone.

[0044] Example 4

[0045] Dissolve 18.1g of manganese citrate in water to form a solution, then add 0.36g of sulfonated polystyrene and 0.54g of KH550 silane coupling agent. Then, introduce 3.4g of ammonia gas into the solution and stir to obtain a uniform suspension. Add 300g of tetrapropylammonium hydroxide and 150g of ethylenediamine to the suspension and stir until a uniform liquid forms. Then, add 120g of fumed silica and 6g of titanium oxide powder to the solution and stir for 12 hours until a uniform gel forms. The gel is placed in a hydrothermal autoclave and crystallized at 150°C for 18 hours. The resulting solid is washed to neutrality, dried with hot air, and calcined at 700°C for 6 hours to obtain the catalyst powder.

[0046] A 5% benzoic acid solution was prepared, heated to 80°C, and the catalyst powder was added to the benzoic acid solution for treatment for 120 minutes. The treated catalyst was then separated and cleaned to neutrality, dried with hot air, and calcined at 700°C for 6 hours to obtain a catalyst for preparing adipic acid from cyclohexanone.

[0047] Comparative Example 1

[0048] 400g of tetrapropylammonium hydroxide and 320g of triethylamine were added to water and stirred until a homogeneous liquid was formed. 208g of ethyl orthosilicate and 3.4g of isobutyl titanate were then added to the liquid and stirred for 2 hours until a uniform gel was formed. The gel was placed in a hydrothermal autoclave and crystallized at 80°C for 120 hours. The resulting solid was washed to neutrality, dried with hot air, and then calcined at 800°C for 6 hours to obtain the catalyst powder.

[0049] Prepare 10% acetic acid solution, heat the acetic acid solution to 100°C, add the catalyst powder into the acetic acid solution and treat for 10 minutes, then separate and clean the treated catalyst to neutrality, dry it with hot air, and calcine it at 800°C for 6 hours to obtain the catalyst.

[0050] Comparative Example 2

[0051] 17.7 g of nickel acetate was dissolved in water to form a solution, and then 0.018 g of sodium polyacrylate was added. Then 3.4 g of ammonia gas was introduced into the solution and stirred to obtain a uniform suspension. 400 g of tetrapropylammonium hydroxide and 320 g of triethylamine were added to the suspension respectively and stirred to form a uniform liquid. 208 g of ethyl orthosilicate and 3.4 g of isobutyl titanate were added to the liquid respectively and stirred for 2 h to form a uniform colloid. The colloid was placed in a hydrothermal autoclave and crystallized at 80 ° C for 120 h. The obtained solid was washed to neutrality, dried with hot air, and then calcined at 800 ° C for 6 h to obtain the catalyst raw powder.

[0052] Prepare 10% acetic acid solution, heat the acetic acid solution to 100°C, add the catalyst powder into the acetic acid solution and treat for 10 minutes, then separate and clean the treated catalyst to neutrality, dry it with hot air, and calcine it at 800°C for 6 hours to obtain the catalyst.

[0053] Comparative Example 3

[0054] 17.7g of nickel acetate was dissolved in water to form a solution, followed by the addition of 0.086g of KH570 silane coupling agent. 3.4g of ammonia gas was then introduced into the solution and stirred to obtain a uniform suspension. 400g of tetrapropylammonium hydroxide and 320g of triethylamine were added to the suspension and stirred until a uniform liquid was formed. 208g of ethyl orthosilicate and 3.4g of isobutyl titanate were then added to the suspension and stirred for 2 hours to form a uniform gel. The gel was then placed in a hydrothermal autoclave and crystallized at 80°C for 120 hours. The resulting solid was washed to neutrality, dried with hot air, and then calcined at 800°C for 6 hours to obtain the catalyst powder.

[0055] Prepare 10% acetic acid solution, heat the acetic acid solution to 100°C, add the catalyst powder into the acetic acid solution and treat for 10 minutes, then separate and clean the treated catalyst to neutrality, dry it with hot air, and calcine it at 800°C for 6 hours to obtain the catalyst.

[0056] Comparative Example 4

[0057] 17.7 g of nickel acetate was dissolved in water to form a solution, and then 0.018 g of sodium polyacrylate and 0.086 g of KH570 silane coupling agent were added. Then 3.4 g of ammonia gas was introduced into the solution and stirred to obtain a uniform suspension. 400 g of tetrapropylammonium hydroxide and 320 g of triethylamine were added to the suspension respectively and stirred to form a uniform liquid. 208 g of ethyl orthosilicate was added to the liquid and stirred for 2 h to form a uniform glue. The glue was placed in a hydrothermal autoclave and crystallized at 80 ° C for 120 h. The obtained solid was washed to neutrality, dried with hot air, and then calcined at 800 ° C for 6 h to obtain the catalyst powder.

[0058] Prepare 10% acetic acid solution, heat the acetic acid solution to 100°C, add the catalyst powder into the acetic acid solution and treat for 10 minutes, then separate and clean the treated catalyst to neutrality, dry it with hot air, and calcine it at 800°C for 6 hours to obtain the catalyst.

[0059] Comparative Example 5

[0060] 17.7 g of nickel acetate was dissolved in water to form a solution, and then 0.018 g of sodium polyacrylate and 0.086 g of KH570 silane coupling agent were added. Then 3.4 g of ammonia gas was introduced into the solution and stirred to obtain a uniform suspension. 400 g of tetrapropylammonium hydroxide and 320 g of triethylamine were added to the suspension respectively and stirred to form a uniform liquid. 208 g of ethyl orthosilicate and 3.4 g of isobutyl titanate were added to the liquid respectively and stirred for 2 h to form a uniform colloid. The colloid was placed in a hydrothermal autoclave and crystallized at 80° C. for 120 h. The obtained solid was washed to neutrality, dried with hot air, and then calcined at 800° C. for 6 h to obtain a catalyst.

[0061] Comparative Example 6

[0062] 17.7 g of nickel acetate was dissolved in water to form a solution, and then 0.018 g of sodium polyacrylate and 0.086 g of KH570 silane coupling agent were added and stirred to obtain a uniform suspension; 400 g of tetrapropylammonium hydroxide and 320 g of triethylamine were added to the suspension respectively, and stirred to form a uniform liquid; 208 g of ethyl orthosilicate and 3.4 g of isobutyl titanate were added to the liquid respectively, and stirred for 2 h to form a uniform glue; the glue was placed in a hydrothermal autoclave and crystallized at 80°C for 120 h; the obtained solid was washed to neutrality, dried with hot air, and then calcined at 800°C for 6 h to obtain the catalyst raw powder.

[0063] A 10% acetic acid solution was prepared and heated to 100°C. The catalyst powder was added to the acetic acid solution and treated for 10 minutes. The treated catalyst was then separated and cleaned to neutrality, dried with hot air, and calcined at 800°C for 6 hours to obtain a catalyst for preparing adipic acid from cyclohexanone.

[0064] In Test Examples 1-4 and Comparative Test Examples 1-7, the catalysts prepared in Examples 1-5 and Comparative Examples 1-6 were used to oxidize cyclohexanone as a raw material to prepare adipic acid.

[0065] Test Example 1

[0066] 98 g of cyclohexanone was dissolved in 1000 g of acetic acid, and 49 g of the catalyst for preparing adipic acid from cyclohexanone obtained in Example 1 was added. Stirring was initiated to form a uniform slurry. The slurry was heated to 50° C., and 1014.2 g of 30% cumene peroxide was gradually added to the slurry to initiate the reaction. The reaction was maintained at this temperature for 240 minutes. The theoretical conversion rate for this test example was 100%. Analysis of the product solution revealed a cyclohexanone conversion rate of 99.70% and a selectivity for adipic acid of 95.71%.

[0067] Test Example 2

[0068] 20 g of the catalyst for preparing adipic acid from cyclohexanone obtained in Example 2 was added to 98 g of cyclohexanone. Stirring was initiated to form a uniform slurry. The slurry was heated to 120°C, and 300 g of 30% tert-butyl hydroperoxide was gradually added to the slurry to initiate the reaction. The reaction was maintained at this temperature for 10 minutes. The theoretical conversion rate for this test example was 50%. Analysis of the product liquid revealed a cyclohexanone conversion of 47.73% and a selectivity for adipic acid of 95.51%.

[0069] Test Example 3

[0070] Dissolve 98g of cyclohexanone in 100g of 1,2-dichloroethane. Add 98g of the catalyst for preparing adipic acid from cyclohexanone obtained in Example 3. Stir until the liquid forms a uniform slurry. Heat the slurry to 70°C, then gradually add 992g of 30% ethylbenzene peroxide to initiate the reaction. Maintain the temperature for 120 minutes. The theoretical conversion rate for this test example is 100%. Analysis of the product liquid revealed a cyclohexanone conversion of 100% and a selectivity for adipic acid of 95.15%.

[0071] Test Example 4

[0072] 98g of cyclohexanone was dissolved in 300g of tert-butyl alcohol. 196g of the catalyst for preparing adipic acid from cyclohexanone obtained in Example 4 was added, and stirring was initiated to form a uniform slurry. The slurry was heated to 90°C, and 181.4g of 30% hydrogen peroxide was gradually added to the slurry to initiate the reaction. The reaction was maintained at this temperature for 240 minutes. The theoretical conversion rate for this test example was 80%. Analysis of the product liquid revealed a cyclohexanone conversion of 79.62% and a selectivity for adipic acid of 96.02%.

[0073] Comparative test example 1

[0074] The raw materials, solvents, oxidants and reaction conditions used in this comparative test example are the same as those in Test Example 1, except that the catalyst used is the catalyst prepared in Comparative Example 1. The theoretical conversion rate of this comparative test example is 100%. After analysis of the product liquid, the cyclohexanone conversion rate is 97.85%, and the selectivity of adipic acid is 53.73%.

[0075] Comparative test example 2

[0076] The raw materials, solvents, oxidants and reaction conditions used in this comparative test example are the same as those in Test Example 1, except that the catalyst used is the catalyst prepared in Comparative Example 2. The theoretical conversion rate of this comparative test example is 100%. After analysis of the product liquid, the cyclohexanone conversion rate is 56.51%, and the selectivity of adipic acid is 62.84%.

[0077] Comparative test example 3

[0078] The raw materials, solvents, oxidants and reaction conditions used in this comparative test example are the same as those in Test Example 1, except that the catalyst used is the catalyst prepared in Comparative Example 3. The theoretical conversion rate of this comparative test example is 100%. After analysis of the product liquid, the cyclohexanone conversion rate is 63.26%, and the selectivity of adipic acid is 66.82%.

[0079] Comparative test example 4

[0080] The raw materials, solvents, oxidants and reaction conditions used in this comparative test example are the same as those in Test Example 1, except that the catalyst used is the catalyst prepared in Comparative Example 4. The theoretical conversion rate of this comparative test example is 100%. After analysis of the product liquid, the cyclohexanone conversion rate is 13.41%, and the selectivity of adipic acid is 2.99%.

[0081] Comparative test example 5

[0082] The raw materials, solvents, oxidants and reaction conditions used in this comparative test example are the same as those in Test Example 1, except that the catalyst used is the catalyst prepared in Comparative Example 5. The theoretical conversion rate of this comparative test example is 100%. After analysis of the product liquid, the cyclohexanone conversion rate is 65.14%, and the selectivity of adipic acid is 90.60%.

[0083] Comparative Test Example 6

[0084] The raw materials, solvents, oxidants and reaction conditions used in the comparative test example are the same as those in Test Example 1, except that the catalyst used is the catalyst prepared in Comparative Example 6. The theoretical conversion rate of the comparative test example is 100%. After analysis of the product liquid, the cyclohexanone conversion rate is 27.78%, and the selectivity of adipic acid is 28.62%.

[0085] It can be seen from the above test examples and comparative test examples that compared with the catalyst in the comparative example, the actual raw material conversion rate in the reaction system of the catalyst prepared by the embodiment of the present invention is closer to the theoretical raw material conversion rate, and the product selectivity is better, reflecting that the catalytic reaction of the catalyst of the embodiment of the present invention runs well and the catalytic efficiency is higher.

[0086] Comparative test example 7

[0087] The raw materials, solvents, catalysts, oxidants, and reaction conditions used in the comparative test example were the same as those in Test Example 1. The difference was that after stirring to obtain a uniform slurry of cyclohexanone and catalyst, the slurry was heated to 150°C, and 181.4 g of 30% hydrogen peroxide was gradually added to initiate the reaction. The reaction was then maintained at this temperature for 60 minutes. The theoretical conversion rate in this comparative test example was 100%. Analysis of the product solution revealed a cyclohexanone conversion rate of 21.33% and adipic acid selectivity of 88.72%.

[0088] The reaction temperature of the adipic acid preparation method of the present invention is 50-120° C., preferably 70-90° C. Combining Test Example 1 and Comparative Test Example 7, it can be confirmed that in the reaction process of preparing adipic acid using cyclohexanone as a raw material, the above temperature range can improve the raw material conversion rate and product selectivity.

[0089] Test Example 5 and Comparative Test Example 8 respectively used the catalyst prepared in Example 1 and the tungstate-containing phase transfer catalyst used in the prior art to oxidize cyclohexanone as a raw material to prepare adipic acid.

[0090] Test Example 5

[0091] This embodiment is used to test the service life of the catalyst. The catalyst life is the reaction time during which the catalyst still maintains 90% of its initial performance during use. Specifically, 146g of adipic acid is dissolved in 300g of tert-butanol, 50g of the catalyst for preparing adipic acid from cyclohexanone obtained in Example 1 is added, and stirring is started to form a uniform slurry. Turn on the heating and keep the slurry temperature stable at 60°C. 0.94g of 30% hydrogen peroxide and 0.42g of cyclohexanone are added to the slurry per minute. At the same time, 1.36g of the liquid phase in the slurry is taken out per minute. A long-term evaluation is carried out to measure the catalyst life. In this test, the raw material conversion rate is 98.56%, the adipic acid selectivity is generally greater than 95.61%, and the life is greater than 1578h.

[0092] Comparative test example 8

[0093] In this comparative test, 146g of adipic acid was dissolved in 300g of tert-butyl alcohol. 25g of phosphotungstic acid and 100g of oxalic acid were added as catalysts. Stirring was initiated until the liquid became uniform. Heating was initiated, maintaining the slurry temperature at a constant 60°C. 0.94g of 30% hydrogen peroxide and 0.42g of cyclohexanone were added to the slurry every minute, while 1.36g of the liquid phase was withdrawn from the slurry every minute. Long-term evaluation was performed, and the catalyst life was measured to be 8 hours.

[0094] Combined with Test Example 5 and Comparative Test 8, it can be confirmed that, compared with the existing adipic acid preparation system using phosphotungstic acid as a catalyst, the catalyst prepared by the preparation method of the catalyst for preparing adipic acid from cyclohexanone of the present invention has a long service life, can reduce production costs and process difficulty, and is suitable for large-scale industrial production.

[0095] It should be noted that the above content is a further detailed description of the present invention in conjunction with specific implementation methods, and the specific implementation of the present invention cannot be considered to be limited to these descriptions; the dimensional data of this embodiment does not necessarily limit the technical solution, but only illustrates one specific working condition. For those skilled in the art of the present invention, simple improvements and modifications can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for preparing adipic acid from cyclohexanone, characterized in that: The following steps are involved: (1) preparing a metal salt solution, then adding a dispersant and a silane coupling agent to the metal salt solution, and then introducing ammonia gas to obtain a first mixed solution; (2) adding tetrapropylammonium hydroxide and an organic amine to the first mixed solution to obtain a second mixed solution; (3) adding a silicon source and a titanium source to the second mixed solution to obtain a glue solution; The glue solution is subjected to hydrothermal crystallization, washing, drying and calcination to obtain catalyst raw powder; (4) The catalyst powder is treated with an organic acid solution, and the catalyst for preparing adipic acid from cyclohexanone is obtained through washing, drying and calcining.

2. The method for preparing a catalyst for preparing adipic acid from cyclohexanone according to claim 1, wherein: The metal salt solution is prepared by dissolving a metal salt in water, wherein the cations of the metal salt include transition metal cations, preferably including one or more of iron ions, cobalt ions, nickel ions, copper ions, manganese ions, vanadium ions, chromium ions, and zinc ions; Preferably, the anion of the metal salt is one or more of acetate, citrate, sulfate, nitrate and chloride.

3. The method for preparing a catalyst for preparing adipic acid from cyclohexanone according to claim 1, wherein: The mass ratio of the metal salt, dispersant and silane coupling agent used to prepare the metal salt solution in step (1) is 1: (0.001-0.05): (0.005-0.1), preferably 1: (0.005-0.02): (0.01-0.03); Preferably, the molar ratio of the metal salt to ammonia is 1:(1-6), preferably 1:(2-3).

4. The method for preparing a catalyst for preparing adipic acid from cyclohexanone according to claim 1, wherein: The dispersant includes one or more of polyvinyl pyrrolidone, sulfonated polystyrene, sodium polyacrylate, and sodium carboxymethyl cellulose; Preferably, the silane coupling agent includes one or more of a vinyl silane coupling agent, a chloroalkyl silane coupling agent, an aminoalkyl silane coupling agent, an epoxyalkyl silane coupling agent, a methacryloyloxyalkyl silane coupling agent, a sulfur-containing hydrocarbon silane coupling agent, a pseudohalogen silane coupling agent and a quaternary ammonium hydrocarbon silane coupling agent.

5. The method for preparing a catalyst for preparing adipic acid from cyclohexanone according to claim 1, wherein: In step (5), the organic acid solution comprises an aqueous solution of one or more of acetic acid, propionic acid, acrylic acid, citric acid, oxalic acid, and benzoic acid; Preferably, the mass concentration of the organic acid solution is 1% to 10%, preferably 3% to 5%; Preferably, the temperature of the acid treatment is 20 to 100° C., preferably 50 to 80° C.; and the time of the acid treatment is 10 to 200 minutes.

6. The method for preparing a catalyst for preparing adipic acid from cyclohexanone according to claim 1, wherein: The organic amine includes one or more of n-butylamine, triethylamine, tri-n-propylamine, n-propylamine, diethylamine, and ethylenediamine; preferably, the mass ratio of the tetrapropylammonium hydroxide to the organic amine is 1:(0.02-0.8), preferably 1:(0.3-0.5).

7. The method for preparing a catalyst for preparing adipic acid from cyclohexanone according to claim 1, wherein: The silicon source includes one or more of fumed silicon oxide, ethyl orthosilicate, and silica sol; Preferably, the titanium source includes one or more of isobutyl titanate, titanium oxide powder, and titanium tetrachloride; Preferably, the molar ratio of the silicon source to the titanium source is 1:(0.01-0.1), preferably 1:(0.02-0.05).

8. The method for preparing a catalyst for preparing adipic acid from cyclohexanone according to claim 1, wherein: The temperature of the hydrothermal crystallization is 80 to 220° C., preferably 150 to 190° C.; the time of the hydrothermal crystallization is 10 to 120 hours, preferably 48 to 84 hours.

9. A catalyst for preparing adipic acid from cyclohexanone prepared by the preparation method according to any one of claims 1 to 8.

10. A method for preparing adipic acid, characterized in that: Cyclohexanone is dissolved in a solvent and reacted with an oxidant in the presence of the catalyst for preparing adipic acid from cyclohexanone as claimed in claim 9 to generate adipic acid.

11. The method for preparing adipic acid according to claim 10, characterized in that: The reaction temperature is 50-120°C, preferably 70-90°C; Preferably, the solvent comprises one or more of methanol, ethanol, isopropanol, tert-butanol, formic acid, acetic acid, acetonitrile, and 1,2-dichloroethane; Preferably, the mass ratio of the cyclohexanone, the solvent and the catalyst for preparing adipic acid from cyclohexanone is 1:(0-10):(0.2-2), preferably 1:(1-3):(0.5-1); Preferably, the oxidant comprises one or more of cumene hydroperoxide, tert-butyl hydroperoxide, ethylbenzene peroxide, and hydrogen peroxide; Preferably, the molar ratio of the cyclohexanone to the oxidant is 1:(0.2-2.4), preferably 1:(1.0-1.6).

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