A catalyst for synthesis of adipic acid and a preparation method and application thereof

Abstract

The application provides a catalyst for adipic acid synthesis and a preparation method and application thereof. The preparation method comprises the following steps: 1) dissolving tetrapropylammonium hydroxide and an organic amine in water to obtain a first mixed solution; 2) preparing a metal salt solution, adding ammonia water into the metal salt solution to obtain a second mixed solution; 3) adding the second mixed solution, a silicon source and a titanium source into the first mixed solution to obtain a glue solution; the glue solution is hydrothermally crystallized, washed, dried and calcined to obtain catalyst raw powder; 4) performing acid treatment on the catalyst raw powder by using an organic acid solution to obtain acid-treated catalyst raw powder; 5) performing alkali treatment on the acid-treated catalyst raw powder by using a tetrapropylammonium hydroxide solution, and the catalyst for adipic acid synthesis is obtained through washing, drying and calcining. The prepared catalyst is used for the reaction of 1,2-cyclohexanediol and an oxidizing agent to form adipic acid, has high conversion rate and selectivity, is convenient to recover, has long service life and is suitable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, in particular to a catalyst for synthesizing adipic acid and a preparation method and application thereof. BACKGROUND

[0002] Adipic acid, also known as fatty acid, is an important chemical raw material for the preparation of synthetic fibers, mainly used for condensation reaction with other compounds to generate nylon macromolecular polymer. Adipic acid is mainly condensed with hexamethylene diamine to generate nylon 66 in the field of nylon. With the rapid development of adiponitrile industry in China in recent years, the market demand for adipic acid is also expanding. At present, the production process of adipic acid mainly includes cyclohexane method, cyclohexene method, air oxidation method, and peroxide oxidation method.

[0003] The cyclohexane method is the most important method for producing adipic acid in the world. This process uses benzene as raw material to generate cyclohexane through hydrogenation reaction, and then reacts cyclohexane with air to produce a mixture of cyclohexanol and cyclohexanone (KA oil). The alcohol-ketone mixture can be used to produce adipic acid. This process has the advantages of single raw material, mature production technology, low raw material consumption, and low energy consumption, and is the main process method adopted by most adipic acid manufacturers in the world. However, the process is complex, has many by-products, produces more industrial waste pollution, and requires a large amount of nitric acid, which can corrode equipment and produce highly polluting nitrogen oxides.

[0004] The cyclohexene method uses benzene and hydrogen as raw materials. First, benzene is hydrogenated to produce cyclohexene. Then, cyclohexene is hydrated with water to obtain cyclohexanol. Finally, cyclohexanol is oxidized with nitric acid to produce adipic acid. Compared with the cyclohexane method, this process reduces energy consumption and raw material consumption, is safer, produces better quality products, and has higher yield. However, this process still requires a large amount of nitric acid, and the problem of nitrogen oxide pollution still exists.

[0005] The air oxidation method uses air as an oxidant to synthesize adipic acid from cyclohexane. Typically, cobalt salt is used as a catalyst and acetic acid is used as a solvent. Compared with other methods, this method requires a longer residence time of 2-6 hours and has a lower selectivity of only 70-80%. Therefore, this process is still in the development stage and has not been industrialized.

[0006] The hydrogen peroxide method uses hydrogen peroxide as an oxidant and cyclohexene, cyclohexanol, and cyclohexanone as raw materials to obtain adipic acid through one or more steps. Since the use of nitric acid oxidation generates a large amount of nitrogen oxides, developing an environmentally friendly adipic acid production process is an important topic in chemical research. Hydrogen peroxide is an ideal oxidant because it is a green oxidant and the only by-product of the oxidation reaction is water, which has no environmental pollution. This method has the advantages of high adipic acid yield, less by-products, and less pollution.

[0007] The peroxide oxidation method is similar to the hydrogen peroxide method, and is to generate adipic acid through one or more steps by using cyclohexene, cyclohexanol and the like as raw materials, using cumene hydroperoxide, ethylbenzene hydroperoxide, peracetic acid and the like as an oxidant, and under the action of a catalyst. Compared with the industrial method, the method has the advantages of low raw material price, high molecular utilization rate, less three-waste discharge, no generation of nitrogen oxides and the like as pollutants, and the like.

[0008] In the prior art, the hydrogen peroxide method and the peroxide oxidation method for preparing adipic acid mostly use heteropoly acid phase transfer catalysts, such as tungstic acid and no acid salt catalysts and the like. Such catalysts have excellent performance, and can make the comprehensive yield of adipic acid reach more than 90%, but have poor durability and are seriously lost after a certain period of use. Therefore, the performance short board of the catalyst leads to the difficulty of applying the hydrogen peroxide method and the peroxide oxidation method for preparing adipic acid to industrial production. SUMMARY

[0009] In view of the deficiencies in the prior art, the present application discloses a catalyst for adipic acid synthesis and a preparation method and application thereof. The titanium-silicon molecular sieve catalyst prepared by the preparation method is used for catalyzing 1,2-cyclohexanediol and an oxidant to react to form adipic acid. The catalyst has high conversion rate and selectivity, is convenient to recover, has long service life, and is suitable for large-scale industrial production.

[0010] In order to achieve the above technical purposes, on the one hand, the present application provides a preparation method of a catalyst for adipic acid synthesis, comprising the following steps:

[0011] (1) dissolving tetrapropylammonium hydroxide and an organic amine in water to obtain a first mixed solution;

[0012] (2) preparing a metal salt solution, and adding ammonia water to the metal salt solution to obtain a second mixed solution;

[0013] (3) adding the second mixed solution, a silicon source and a titanium source into the first mixed solution to obtain a glue solution; the glue solution is hydrothermally crystallized, washed, dried and calcined to obtain a catalyst raw powder;

[0014] (4) acid treating the catalyst raw powder by using an organic acid solution to obtain an acid-treated catalyst raw powder;

[0015] (5) alkali treating the acid-treated catalyst raw powder by using a tetrapropylammonium hydroxide solution, and washing, drying and calcining to obtain the catalyst for adipic acid synthesis.

[0016] In the above technical solution, in step (2), the metal salt is introduced into the molecular sieve as a catalyst active component, and further by adding ammonia water to the metal salt solution to form a uniform complex solution of the metal salt and ammonia, and then by hydrothermal crystallization with the template tetrapropylammonium hydroxide, the active sites of the metal oxide are uniformly formed and deposited, which significantly improves the selectivity of the reaction. The examples and comparative examples of the present application explore the influence of introducing metal salt and adding ammonia water in the metal salt solution on the catalytic activity and selectivity of the catalyst.

[0017] In addition, in step (4) of the above technical solution, the prepared catalyst raw powder is subjected to acid treatment with an organic acid, which removes the metal oxide particles deposited on the surface of the catalyst raw powder, so that the active sites of the prepared catalyst can be uniformly distributed in the molecular sieve channels, improving the selectivity of the catalyst, and also reducing the deactivation and deactivation of the sites, prolonging the service life of the catalyst.

[0018] Further, for the acid-treated catalyst raw powder, step (5) of the above technical solution uses a tetrapropylammonium hydroxide solution for pore expansion treatment, which effectively eliminates the diffusion limitation of the molecular sieve catalyst, strengthens the stability of the crystal structure, enhances the mass transfer, reduces the diffusion resistance of the reactants and products inside the catalyst, and improves the catalytic performance and service life. The examples and comparative examples of the present application explore the influence of acid treatment and alkali treatment on the catalytic activity, selectivity and service life of the catalyst.

[0019] In further examples of the present application, the type and amount of organic amine in step (1) are optimized. Optionally, the organic amine includes one or more of n-butylamine, triethylamine, tri-n-propylamine, n-propylamine, diethylamine, and ethylenediamine; optionally, the mass ratio of tetrapropylammonium hydroxide to organic amine is 1:(0.02-0.8), preferably 1:(0.3-0.5).

[0020] In further examples of the present application, the metal salt solution is prepared by dissolving a metal salt in water, and the cation of the metal salt can be selected from transition metal cations, and further can include one or more of iron ions, cobalt ions, nickel ions, copper ions, manganese ions, vanadium ions, chromium ions, and zinc ions. The catalyst prepared by doping the above cations has excellent conversion rate, selectivity and catalyst service life in the reaction of catalyzing 1,2-cyclohexanediol and an oxidizing agent to form adipic acid.

[0021] In further examples of the present application, the mass ratio of the metal salt to ammonia water in step (2) is optimized to promote the full complexation of the metal salt and ammonia. Optionally, the molar ratio of the metal salt to ammonia water used to prepare the metal salt solution is 1:(1-10), preferably 1:(4-8). It should be noted that the ammonia gas will be evaporated during the subsequent hydrothermal crystallization process.

[0022] In further examples of the present application, the anion of the metal salt used to prepare the metal salt solution in step (2) is optimized. Optionally, the anion of the metal salt is one or more of acetate, citrate, sulfate, nitrate, chloride, thereby improving the efficiency of catalyst preparation by using a soluble salt of the metal salt cation to prepare the metal salt solution.

[0023] It is noted that the order of execution of steps (1) and (2) in the above technical solution is not limited.

[0024] In further examples of the present application, the type of silicon source is optimized. Optionally, the silicon source includes one or more of fumed silica, tetraethyl orthosilicate, silica sol.

[0025] In further examples of the present application, the type of titanium source is optimized. Optionally, the titanium source includes one or more of isobutyl titanate, titanium oxide powder, titanium tetrachloride.

[0026] In further examples of the present application, the amount of the silicon source and the titanium source is optimized. Optionally, the molar ratio of the silicon source to the titanium source is 1:(0.01-0.2), further preferably 1:(0.02-0.05). The examples of the present application show that the conversion rate, selectivity, and service life of the catalyst prepared in this mass ratio range are excellent.

[0027] In further examples of the present application, the control conditions of the hydrothermal crystallization are explored. 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, thereby gradually evaporating ammonia gas and controlling the morphology of the prepared catalyst by adjusting the temperature and time of the hydrothermal crystallization.

[0028] It is noted that the equipment for hydrothermal crystallization in the present application is not limited, and can be a hydrothermal kettle. Those skilled in the art can select other equipment according to actual use requirements, but the technical solutions formed thereby do not deviate from the basic principles of the present application, and are within the scope of protection of the present application.

[0029] In further examples of the present application, the type of organic acid used in the acid treatment is optimized. The present application can optionally use a weak acid for the acid treatment to dissolve and remove the metal oxide particles deposited on the surface of the catalyst raw powder, but not excessively dissolve the metal oxide in the pores of the molecular sieve. Further optionally, the organic acid solution comprises an aqueous solution of one or more of acetic acid, propionic acid, acrylic acid, citric acid, oxalic acid, benzoic acid; in further examples of the present application, the concentration of the organic acid used in the acid treatment is optimized. Optionally, the concentration of the organic acid solution is 1% to 10%, preferably 3% to 5%; in addition, in further examples of the present application, the control conditions of the acid treatment are optimized. 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 min. It is noted that the concentration of the organic acid solution is the mass concentration.

[0030] It is noted that the present application also includes separating and washing the catalyst raw powder after the acid treatment to neutral.

[0031] The present application further includes, in further examples of the present application, the addition amount of tetrapropylammonium hydroxide to the catalyst raw powder after the acid treatment in the process of the base treatment is optimized. Optionally, the mass ratio of tetrapropylammonium hydroxide to the catalyst raw powder after the acid treatment in step (5) is 1:(1 to 20), preferably 1:(3 to 7). In addition, in further examples of the present application, the control conditions of the base treatment are optimized. Optionally, the temperature of the base treatment is 80 to 220°C, preferably 150 to 190°C; the time of the base treatment is 20 to 80 h, thereby obtaining the catalyst for the synthesis of adipic acid which is porous and has stable crystal structure.

[0032] It is noted that the present application does not limit the equipment used for the base treatment, which can be a hydrothermal kettle, and other equipment can be selected by those skilled in the art according to actual use requirements, and the technical solutions thus formed are within the protection scope of the present application.

[0033] It is noted that the present application also includes separating and washing the solid catalyst from the tetrapropylammonium hydroxide solution after the base treatment to neutral.

[0034] It is noted that the present application does not limit the control conditions of the calcination operation in steps (3) and (5), and the calcination temperature can be optionally 300 to 800°C, and the calcination time can be optionally 6 h.

[0035] In another aspect, the present application provides the catalyst for the synthesis of adipic acid prepared by the preparation method described above.

[0036] In another aspect, the present application provides a method for synthesizing adipic acid, which comprises: dissolving 1,2-cyclohexanediol in a solvent, and reacting with an oxidant in the presence of the catalyst for synthesizing adipic acid to generate adipic acid.

[0037] Further, the present application optimizes the control conditions, the solvent, the oxidant, and the amount of the raw material 1,2-cyclohexanediol, the solvent, the catalyst, and the oxidant in the method for synthesizing adipic acid.

[0038] The reaction temperature of the method for synthesizing adipic acid can be selected as 60-100°C, and further selected as 70-90°C; in this temperature range, the product selectivity and the service life of the catalyst can be improved.

[0039] The reaction time of the method for synthesizing adipic acid can be selected as 30-240 min; in actual operation, when the concentration of the reactant no longer changes significantly, it represents the end of the reaction.

[0040] The solvent can include one or more of methanol, ethanol, isopropanol, tert-butanol, formic acid, acetic acid, acetonitrile, and 1,2-dichloroethane.

[0041] The oxidant can include one or more of cumene hydroperoxide, tert-butyl hydroperoxide, ethylbenzene peroxide, and hydrogen peroxide.

[0042] The mass ratio of the 1,2-cyclohexanediol, the solvent, and the catalyst for synthesizing adipic acid can be selected as 1:(1-10):(0.1-6), and further selected as 1:(4-6):(0.3-1).

[0043] The molar ratio of the 1,2-cyclohexanediol to the oxidant can be selected as 1:(0.2-1), and further selected as 1:(0.5-0.8).

[0044] In another aspect, the present application provides a method for synthesizing adipic acid, which comprises: S1, obtaining 1,2-cyclohexanediol by oxidizing cyclohexene; and S2, dissolving the 1,2-cyclohexanediol in a solvent, and reacting with an oxidant in the presence of the catalyst for synthesizing adipic acid to generate adipic acid.

[0045] It should be noted that the present application does not limit the specific operation of obtaining 1,2-cyclohexanediol by oxidizing cyclohexene and the catalyst used, and a phase transfer catalyst such as a tungsten-containing phase transfer catalyst can be selected to catalyze the oxidation of cyclohexene to obtain 1,2-cyclohexanediol.

[0046] In further examples of the present application, the control conditions, the solvent, the oxidant, and the amount of the raw material 1,2-cyclohexanediol, the solvent, the catalyst, and the oxidant in the method for synthesizing adipic acid are optimized.

[0047] The beneficial effects of the present application are:

[0048] Compared with the prior art, the preparation method of the catalyst for synthesis of adipic acid has simple process and strong operability, the prepared titanium-silicon molecular sieve catalyst can be used for synthesis of adipic acid by peroxide oxidation method, has the advantages of high catalytic activity, high conversion rate and selectivity, long service life and the like, and is suitable for industrialized production of adipic acid in large quantities. BRIEF DESCRIPTION OF DRAWINGS

[0049] The drawings constituting a part of the specification of the present application serve to provide further understanding of the present application, the illustrative embodiments of the present application and the description thereof serve to explain the present application, and do not constitute improper limitation on the present application. In the drawings:

[0050] Figure 1 The electron microscope morphology of the catalyst prepared in Example 1. DETAILED DESCRIPTION

[0051] In order to facilitate the understanding of the present application, the present application will be described more fully below, and preferred embodiments of the present application are given. It should be understood that these embodiments are only used for more detailed description, and should not be understood as limiting the present application in any form, i.e. not intended to limit the protection scope of the present application. Except for the definition, the technical terms used in the following examples have the same meaning as generally understood by those skilled in the art to which the present application belongs. The test reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods, unless otherwise specified, are conventional methods.

[0052] The evaluation method of the related parameters of the catalyst prepared in the embodiments of the present application in the reaction of 1,2-cyclohexanediol and oxidant to adipic acid is as follows:

[0053] The raw material conversion rate is used to represent the actual conversion percentage of the 1,2-cyclohexanediol raw material after reaction; in the embodiments of the present application, the raw material conversion rate = (1,2-cyclohexanediol unreacted mass / 1,2-cyclohexanediol raw material mass)*100%.

[0054] The theoretical conversion rate is used to represent the percentage of conversion of 1,2-cyclohexanediol after the 1,2-cyclohexanediol raw material and the oxidant added in the test example are completely reacted and all adipic acid is generated; in the embodiments of the present application, the theoretical conversion rate = (theoretically reacted cyclohexanediol mass / 1,2-cyclohexanediol raw material mass)*100%.

[0055] The product yield: the ratio of the mass of the actual generated adipic acid to the mass of the 1,2-cyclohexanediol raw material, multiplied by the molecular weight coefficient; in the embodiments of the present application, the product yield = 0.795*generated adipic acid mass / 1,2-cyclohexanediol raw material mass.

[0056] Catalyst life is the reaction time for which the catalyst retains 90% of its initial performance in use.

[0057] Example 1

[0058] Dissolve 200 g of tetrapropylammonium hydroxide and 4 g of ethylenediamine in water respectively, and stir until dissolved. Dissolve 5 g of cobalt acetate in water, add 15 g of concentrated ammonia water, and stir until the solution is clear. Add the clear solution and 40 g of fumed silica, 0.5 g of titanium oxide powder respectively to the mixed solution of tetrapropylammonium hydroxide and ethylenediamine, and stir until a uniform gel solution is formed. Continue to stir the gel solution for 12 h, and transfer the gel solution to an autoclave, and crystallize at 220°C for 120 h. Filter and separate the obtained solid, wash to neutral, and dry with hot air, and then calcine at 800°C for 6 h to obtain catalyst raw powder.

[0059] Prepare a 1% acetic acid solution, heat the acetic acid solution to 100°C, and add the catalyst raw powder to the acetic acid solution for treatment for 200 min, and then separate and wash the acid-treated catalyst to neutral.

[0060] Dissolve 100 g of tetrapropylammonium hydroxide in water to obtain a tetrapropylammonium hydroxide solution, and place 100 g of the acid-treated catalyst raw powder in the tetrapropylammonium hydroxide solution, and stir until a stable slurry is formed. Then transfer the slurry to an autoclave, and treat at 220°C for 80 h. Then separate and wash the treated catalyst to neutral, and dry with hot air, and then calcine at 800°C for 6 h to obtain the catalyst for adipic acid synthesis, i.e. the 1,2-cyclohexanediol oxidation reaction catalyst.

[0061] Example 2

[0062] Dissolve 200 g of tetrapropylammonium hydroxide and 160 g of diethylamine in water respectively, and stir until dissolved. Dissolve 2 g of copper sulfate in water, add 2.3 g of concentrated ammonia water, and stir until the solution is clear. Add the clear solution and 150 g of tetraethyl orthosilicate, 24.5 g of isobutyl titanate respectively to the mixed solution of tetrapropylammonium hydroxide and diethylamine, and stir until a uniform gel solution is formed. Continue to stir the gel solution for 2 h, and transfer the gel solution to an autoclave, and crystallize at 80°C for 48 h. Filter and separate the obtained solid, wash to neutral, and dry with hot air, and then calcine at 300°C for 6 h to obtain 1,2-cyclohexanediol oxidation reaction catalyst raw powder.

[0063] Prepare a 5% citric acid solution, heat the citric acid solution to 80°C, and immerse the catalyst raw powder in the citric acid solution for treatment for 100 min, and then separate and wash the treated catalyst to neutral.

[0064] The 200 g of tetrapropylammonium hydroxide was dissolved in water, 10 g of the acid-treated catalyst precursor was put into the tetrapropylammonium hydroxide solution, and stirred until a stable slurry was formed. The slurry was then transferred into an autoclave, and treated at 80°C for 80 h. The treated catalyst was then separated and washed to neutral, and dried with hot air, and then calcined at 300°C for 6 h to obtain the catalyst for adipic acid synthesis, i.e. the 1,2-cyclohexanediol oxidation reaction catalyst.

[0065] Example 3

[0066] The 200 g of tetrapropylammonium hydroxide and 100 g of tri-n-propylamine were respectively dissolved in water, and stirred until dissolved. The 4 g of iron acetate was dissolved in water, and 14 g of concentrated ammonia was added, and stirred until the solution was clear. The clear solution was added to the mixed solution of tetrapropylammonium hydroxide and tri-n-propylamine, along with 150 g of silica sol with a concentration of 30% and 7.1 g of titanium tetrachloride, and stirred until a uniform gel solution was formed. The gel solution was continuously stirred for 2 h, and then transferred into an autoclave, and crystallized at 190°C for 10 h. The obtained solid was separated by filtration, washed to neutral, and dried with hot air, and then calcined at 700°C for 6 h to obtain the catalyst precursor.

[0067] A 10% oxalic acid solution was prepared, and the oxalic acid solution was heated to 20°C. The 1,2-cyclohexanediol oxidation reaction catalyst precursor was immersed in the oxalic acid solution for 10 min, and then the treated catalyst was separated and washed to neutral.

[0068] The 200 g of tetrapropylammonium hydroxide was dissolved in water, 10 g of the acid-treated catalyst precursor was put into the tetrapropylammonium hydroxide solution, and stirred until a stable slurry was formed. The slurry was then transferred into an autoclave, and treated at 80°C for 80 h. The treated catalyst was then separated and washed to neutral, and dried with hot air, and then calcined at 300°C for 6 h to obtain the catalyst for adipic acid synthesis, i.e. the 1,2-cyclohexanediol oxidation reaction catalyst.

[0069] Comparative Example 1

[0070] The 200 g of tetrapropylammonium hydroxide and 4 g of ethylenediamine were respectively dissolved in water, and stirred until dissolved. The 5 g of cobalt acetate was dissolved in water, and 15 g of concentrated ammonia was added, and stirred until the solution was clear. The clear solution was added to the mixed solution of tetrapropylammonium hydroxide and ethylenediamine, along with 40 g of fumed silica and 0.5 g of titanium oxide powder, and stirred until a uniform gel solution was formed. The gel solution was continuously stirred for 12 h, and then transferred into an autoclave, and crystallized at 220°C for 120 h. The obtained solid was separated by filtration, washed to neutral, and dried with hot air, and then calcined at 800°C for 6 h to obtain the catalyst.

[0071] Comparative Example 2

[0072] Dissolve 200 g of tetrapropylammonium hydroxide and 4 g of ethylenediamine in water with stirring until dissolved. Dissolve 5 g of cobalt acetate in water, add 15 g of concentrated ammonia water, and stir until the solution is clear. Add the clear solution to the mixed solution of tetrapropylammonium hydroxide and ethylenediamine with 40 g of fumed silica and 0.5 g of titanium oxide powder, and stir until a uniform gel solution is formed. Continue stirring the gel solution for 12 h, transfer the gel solution to an autoclave, and crystallize at 220°C for 120 h. Filter and separate the resulting solid, wash to neutrality, and dry with hot air, and then calcine at 800°C for 6 h to obtain a catalyst precursor powder.

[0073] Dissolve 100 g of tetrapropylammonium hydroxide in water, and add 100 g of the catalyst precursor powder to the tetrapropylammonium hydroxide solution with stirring until a stable slurry is formed. Then transfer the slurry to an autoclave, and treat at 220°C for 80 h. Then separate the treated catalyst and wash to neutrality, and dry with hot air, and then calcine at 800°C for 6 h to obtain a catalyst.

[0074] Comparative Example 3

[0075] Dissolve 200 g of tetrapropylammonium hydroxide and 4 g of ethylenediamine in water with stirring until dissolved. Dissolve 5 g of cobalt acetate in water, add 15 g of concentrated ammonia water, and stir until the solution is clear. Add the clear solution to the mixed solution of tetrapropylammonium hydroxide and ethylenediamine with 40 g of fumed silica and 0.5 g of titanium oxide powder, and stir until a uniform gel solution is formed. Continue stirring the gel solution for 12 h, transfer the gel solution to an autoclave, and crystallize at 220°C for 120 h. Filter and separate the resulting solid, wash to neutrality, and dry with hot air, and then calcine at 800°C for 6 h to obtain a catalyst precursor powder.

[0076] Prepare a 1% acetic acid solution, heat the acetic acid solution to 100°C, add the catalyst precursor powder to the acetic acid solution, and treat for 200 min, then separate the treated catalyst and wash to neutrality, and then calcine at 800°C for 6 h to obtain a catalyst

[0077] Comparative Example 4

[0078] Dissolve 200 g of tetrapropylammonium hydroxide and 4 g of ethylenediamine in water with stirring until dissolved. Add 40 g of fumed silica and 0.5 g of titanium oxide powder to the mixed solution of tetrapropylammonium hydroxide and ethylenediamine, and stir until a uniform gel solution is formed. Continue stirring the gel solution for 12 h, transfer the gel solution to an autoclave, and crystallize at 220°C for 120 h. Filter and separate the resulting solid, wash to neutrality, and dry with hot air, and then calcine at 800°C for 6 h to obtain a 1,2-cyclohexanediol oxidation reaction catalyst.

[0079] Comparative Example 5

[0080] The 200 g of tetrapropylammonium hydroxide and 4 g of ethylenediamine were dissolved in water with stirring until dissolved. The 5 g of cobalt acetate was dissolved in water with stirring until uniform. The liquids were added to the mixed solution of tetrapropylammonium hydroxide and ethylenediamine with 40 g of fumed silica and 0.5 g of titanium oxide powder with stirring until a uniform gel was formed. The gel was stirred for 12 h, and the gel was transferred to an autoclave, and crystallized at 220°C for 120 h. The resulting solid was separated by filtration, washed to neutral, and dried with hot air, and calcined at 800°C for 6 h to obtain a catalyst precursor powder.

[0081] A 1% acetic acid solution was prepared, and the acetic acid solution was heated to 100°C. The catalyst precursor powder was added to the acetic acid solution and treated for 200 min, and then the treated catalyst was separated and washed to neutral.

[0082] The 100 g of tetrapropylammonium hydroxide was dissolved in water, and 100 g of the acid-treated catalyst precursor powder was placed in the tetrapropylammonium hydroxide solution, and stirred until a stable slurry was formed. The slurry was transferred to an autoclave, and treated at 220°C for 80 h. Then the treated catalyst was separated and washed to neutral, and dried with hot air, and calcined at 800°C for 6 h to obtain a catalyst.

[0083] Comparative Example 6

[0084] The 200 g of tetrapropylammonium hydroxide and 4 g of ethylenediamine were dissolved in water with stirring until dissolved. The 5 g of cobalt acetate was dissolved in water with stirring until uniform. The liquids were added to the mixed solution of tetrapropylammonium hydroxide and ethylenediamine with 40 g of fumed silica and 0.5 g of titanium oxide powder with stirring until a uniform gel was formed. The gel was stirred for 12 h, and the gel was transferred to an autoclave, and crystallized at 220°C for 120 h. The resulting solid was separated by filtration, washed to neutral, and dried with hot air, and calcined at 800°C for 6 h to obtain a catalyst precursor powder.

[0085] A 1% acetic acid solution was prepared, and the acetic acid solution was heated to 100°C. The catalyst precursor powder was added to the acetic acid solution and treated for 200 min, and then the treated catalyst was separated and washed to neutral.

[0086] The 100 g of tetrapropylammonium hydroxide was dissolved in water, and 100 g of the acid-treated catalyst precursor powder was placed in the tetrapropylammonium hydroxide solution, and stirred until a stable slurry was formed. The slurry was transferred to an autoclave, and treated at 220°C for 80 h. Then the treated catalyst was separated and washed to neutral, and dried with hot air, and calcined at 800°C for 6 h to obtain a catalyst.

[0087] The catalysts prepared in the above-mentioned Examples 1-3 and Comparative Examples 1-7 were respectively used in the reaction of 1,2-cyclohexanediol with an oxidant to form adipic acid in Test Examples 1-3 and Comparative Test Examples 1-9, and the reaction conditions were controlled and the conversion of raw material, the theoretical conversion, the product yield and the service life of the catalyst were detected in the product liquid in different test examples.

[0088] Test Example 1

[0089] 100 g of 1,2-cyclohexanediol was dissolved in 100 g of 1,2-dichloroethane, 10 g of the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Example 1 was added, and the liquid was stirred to form a uniform slurry. The slurry was heated to 60°C, and 300 g of ethylbenzene peroxide with a concentration of 20% was gradually added to the slurry to start the reaction, and the temperature was maintained for 30 min. The theoretical conversion of this test example was 50%, and the analysis of the product liquid showed that the conversion of 1,2-cyclohexanediol was 48.12%, and the selectivity of adipic acid was 94.25%.

[0090] In addition, the service life of the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Example 1 was also tested. Specifically, 100 g of adipic acid alcohol was dissolved in 100 g of 1,2-dichloroethane, 10 g of the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Example 1 was added, and the liquid was stirred to form a uniform slurry. The slurry was heated to 60°C, and 1.32 g of 1,2-cyclohexanediol, 1.66 g of 1,2-dichloroethane and 5 g of ethylbenzene peroxide with a concentration of 20% were added to the slurry every minute, and 7.99 g of liquid phase was taken out from the slurry every minute for long-term evaluation, and the service life of the catalyst was measured to be 2100 h.

[0091] Test Example 2

[0092] 100 g of 1,2-cyclohexanediol was dissolved in 1000 g of acetic acid, 600 g of the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Example 2 was added, and the liquid was stirred to form a uniform slurry. The slurry was heated to 100°C, and 98 g of hydrogen peroxide with a concentration of 30% was gradually added to the slurry to start the reaction, and the temperature was maintained for 80 min. The theoretical conversion of this test example was 100%, and the analysis of the product liquid showed that the conversion of 1,2-cyclohexanediol was 98.65%, and the selectivity of adipic acid was 95.44%.

[0093] In addition, the service life of the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Example 2 was also tested. The catalyst service life test method was the same as that in Test Example 1, and the long-term evaluation showed that the service life of the catalyst was 2338 h.

[0094] Test Example 3

[0095] Example 4 100 g of 1,2-cyclohexanediol was dissolved in 400 g of ethanol, and 100 g of the 1,2-cyclohexanediol oxidation reaction catalyst obtained in Example 3 was added, and stirring was started to form a uniform slurry. The slurry was heated to 90°C, and 87 g of cumene hydroperoxide having a concentration of 30% was gradually added to the slurry to start the reaction, and the temperature was maintained for 240 min. The theoretical conversion rate of this test example was 20%, and the product liquid was analyzed to find that the conversion rate of 1,2-cyclohexanediol was 19.03%, and the selectivity of adipic acid was 97.15%.

[0096] In addition, the service life of the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Example 3 was also tested. The service life of the catalyst was measured to be 2984 h by the same method as in Test Example 1.

[0097] Comparative Test Example 1

[0098] 100 g of 1,2-cyclohexanediol was dissolved in 100 g of 1,2-dichloroethane, and 10 g of the 1,2-cyclohexanediol oxidation reaction catalyst obtained in Comparative Example 1 was added, and stirring was started to form a uniform slurry. The slurry was heated to 60°C, and 300 g of ethylbenzene hydroperoxide having a concentration of 20% was gradually added to the slurry to start the reaction, and the temperature was maintained for 30 min. The theoretical conversion rate of this comparative test example was 50%, and the product liquid was analyzed to find that the conversion rate of 1,2-cyclohexanediol was 41.11%, and the selectivity of adipic acid was 36.73%.

[0099] Comparative Test Example 2

[0100] The raw material, oxidizing agent, solvent, and control conditions used in this comparative test example were the same as in Comparative Test Example 1, except that the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Comparative Example 2 was used. The theoretical conversion rate of this comparative test example was 50%, and the product liquid was analyzed to find that the conversion rate of 1,2-cyclohexanediol was 48.17%, and the selectivity of adipic acid was 83.74%.

[0101] Comparative Test Example 3

[0102] The raw material, oxidizing agent, solvent, and control conditions used in this comparative test example were the same as in Comparative Test Example 1, except that the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Comparative Example 3 was used. The theoretical conversion rate of this comparative test example was 50%, and the product liquid was analyzed to find that the conversion rate of 1,2-cyclohexanediol was 36.05%, and the selectivity of adipic acid was 83.97%.

[0103] Comparative Test Example 4

[0104] The raw material, oxidant, solvent and control conditions used in this comparative test example are the same as those in Comparative Test Example 1, except that the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Comparative Example 4 is used. The theoretical conversion rate of this comparative test example is 50%, and the product liquid is analyzed to obtain a 1,2-cyclohexanediol conversion rate of 37.73% and an adipic acid selectivity of 46.74%.

[0105] Comparative Test Example 5

[0106] The raw material, oxidant, solvent and control conditions used in this comparative test example are the same as those in Comparative Test Example 1, except that the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Comparative Example 5 is used. The theoretical conversion rate of this comparative test example is 50%, and the product liquid is analyzed to obtain a 1,2-cyclohexanediol conversion rate of 33.73% and an adipic acid selectivity of 57.74%.

[0107] Comparative Test Example 6

[0108] The raw material, oxidant, solvent and control conditions used in this comparative test example are the same as those in Comparative Test Example 1, except that the 1,2-cyclohexanediol oxidation reaction catalyst prepared in Comparative Example 6 is used. The theoretical conversion rate of this comparative test example is 50%, and the product liquid is analyzed to obtain a 1,2-cyclohexanediol conversion rate of 41.84% and an adipic acid selectivity of 62.95%.

[0109] Based on the above tests, it can be verified that the actual raw material conversion rate of the test example using the catalyst prepared in Examples 1-3 is closer to the theoretical raw material conversion rate than that of Comparative Test Examples 1-6, reflecting that the catalytic reaction using the catalyst prepared in the present application runs well and is more efficient.

[0110] Comparative Test Example 7

[0111] The raw material, catalyst, oxidant, solvent and control conditions used in this comparative test example are the same as those in Test Example 1, except that the 1,2-cyclohexanediol, 1,2-dichloroethane and catalyst are stirred into a uniform slurry, the slurry is heated to 140°C, 147 g of 30% hydrogen peroxide is gradually added to the slurry to start the reaction, and the temperature is maintained for 80 min. The theoretical conversion rate of this comparative test example is 100%, and the product liquid is analyzed to obtain a 1,2-cyclohexanediol conversion rate of 100% and an adipic acid selectivity of 35.96%.

[0112] It can be verified from Test Example 1 and Comparative Test Example 7 that the temperature in the adipic acid synthesis process is one of the important control parameters, and the reaction temperature can be selected to be 60-100°C, and further selected to be 70-90°C, which can improve the product selectivity and the service life of the catalyst in this temperature range.

[0113] Comparative Test Example 8

[0114] In the comparative test, 146 g of adipic acid was dissolved in 300 g of t-butyl alcohol, 25 g of phosphotungstic acid and 100 g of oxalic acid were added as catalysts, and stirring was started to make the liquid uniform. Heating was started, and the slurry temperature was kept stable at 60°C. 1.88 g of 30% hydrogen peroxide and 0.50 g of cyclohexanediol were added to the slurry every minute, and 1.36 g of liquid phase was taken out of the slurry every minute. Long-term evaluation was carried out, and the catalyst life was measured to be 8 h.

[0115] It can be proved by combining Test Examples 1-3 and Comparative Test 8 that, compared with the existing adipic acid preparation system using phosphotungstic acid as catalyst, the catalyst for the oxidation reaction of 1,2-cyclohexanediol has a longer service life, can reduce production cost and process difficulty in large-scale industrial production, has good economic benefits and market promotion value.

[0116] It should be noted that the above is a further detailed description of the present application in combination with specific embodiments, and the specific implementation of the present application cannot be limited to these descriptions; the size data of the present embodiment does not limit the technical solution, but only shows one specific working condition. For ordinary skilled persons in the technical field to which the present application belongs, some simple improvements and refinements can be made without departing from the concept of the present application, and all of them should be regarded as falling within the scope of protection of the present application.

Claims

1. A process for the preparation of a catalyst for the synthesis of adipic acid, characterized in that, The method comprises the following steps: (1) dissolving tetrapropylammonium hydroxide and an organic amine in water to obtain a first mixed solution; the organic amine is selected from one or more of n-butylamine, triethylamine, tri-n-propylamine, n-propylamine, diethylamine and ethylenediamine; (2) preparing a metal salt solution, and adding ammonia water to the metal salt solution to obtain a second mixed solution; the cation of the metal salt is selected from one or more of iron ions, cobalt ions, nickel ions, copper ions, manganese ions, vanadium ions, chromium ions and zinc ions; (3) adding the second mixed solution, a silicon source and a titanium source to the first mixed solution to obtain a glue solution; The glue solution is hydrothermally crystallized, washed, dried and calcined to obtain a catalyst raw powder; (4) performing acid treatment on the catalyst raw powder by using an organic acid solution to obtain an acid-treated catalyst raw powder; the organic acid solution is selected from an aqueous solution of one or more of acetic acid, propionic acid, acrylic acid, citric acid, oxalic acid and benzoic acid; the mass concentration of the organic acid solution is 1% to 10%; the temperature of the acid treatment in step (4) is 20 to 100°C, and the time of the acid treatment is 10 to 200 minutes; (5) performing alkali treatment on the acid-treated catalyst raw powder by using a tetrapropylammonium hydroxide solution, and washing, drying and calcining to obtain the catalyst for synthesis of adipic acid; the mass ratio of the acid-treated catalyst raw powder to tetrapropylammonium hydroxide in step (5) is 1:(1 to 20); the temperature of the alkali treatment in step (5) is 80 to 220°C, and the time of the alkali treatment is 20 to 80 hours.

2. The process for the preparation of catalysts for the synthesis of adipic acid according to claim 1, characterized by the fact that, The metal salt solution is prepared by dissolving a metal salt in water.

3. The process for the preparation of catalysts for the synthesis of adipic acid according to claim 2, characterized by the fact that, The molar ratio of the metal salt to ammonia water is 1:(1 to 10).

4. The process for the preparation of catalysts for the synthesis of adipic acid according to claim 3, characterized by the fact that, The molar ratio of the metal salt to ammonia water is 1:(4 to 8).

5. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 2 wherein, The anion of the metal salt is one or more of acetate, citrate, sulfate, nitrate and chloride.

6. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 1, wherein, The mass concentration of the organic acid solution is 3% to 5%.

7. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 1 wherein, The temperature of the acid treatment in step (4) is 50 to 80°C.

8. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 1 wherein, The mass ratio of the acid-treated catalyst raw powder to tetrapropylammonium hydroxide in step (5) is 1:(3 to 7).

9. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 1 wherein, The temperature of the alkali treatment in step (5) is 150 to 190°C.

10. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 1 wherein, The mass ratio of the tetrapropylammonium hydroxide to the organic amine in step (1) is 1:(0.3 to 0.5).

11. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 1 wherein, The silicon source includes one or more of fumed silica, tetraethyl orthosilicate and silica sol.

12. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 1 wherein, The titanium source includes one or more of isobutyl titanate, titanium oxide powder and titanium tetrachloride.

13. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 1 wherein, The molar ratio of the silicon source to the titanium source is 1:(0.01 to 0.1).

14. The process for the preparation of catalysts for the synthesis of adipic acid according to claim 13, characterized by the fact that, The molar ratio of the silicon source to the titanium source is 1:(0.02 to 0.05).

15. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 1 wherein, The temperature of the hydrothermal crystallization is 80 to 220°C, and the time of the hydrothermal crystallization is 10 to 120 hours.

16. The process for the preparation of a catalyst for the synthesis of adipic acid according to claim 15, characterized in that, The temperature of the hydrothermal crystallization is 150 to 190°C.

17. The process for the preparation of catalyst for synthesis of adipic acid as claimed in claim 15 wherein, The time of the hydrothermal crystallization is 48 to 84 hours.

18. A catalyst for synthesis of adipic acid, which is prepared by the method of any one of claims 1 to 17.

19. A method of synthesizing adipic acid, characterized by, 1,2-cyclohexanediol is dissolved in a solvent, and reacted with an oxidant in the presence of a catalyst for synthesis of adipic acid as defined in claim 18 to generate adipic acid.

20. The method of adipic acid synthesis of claim 19, wherein, The reaction temperature is 60-100℃.

21. The method of adipic acid synthesis of claim 20, wherein, The reaction temperature is 70-90℃.

22. The method of adipic acid synthesis of claim 19, wherein, The solvent includes one or more of methanol, ethanol, isopropanol, tert-butanol, formic acid, acetic acid, acetonitrile, 1,2-dichloroethane.

23. The method of adipic acid synthesis of claim 19, wherein, The oxidant includes one or more of cumene hydroperoxide, tert-butyl hydroperoxide, ethylbenzene hydroperoxide, hydrogen peroxide.

24. The method of adipic acid synthesis of claim 19, wherein, The mass ratio of the 1,2-cyclohexanediol, the solvent, and the catalyst for synthesis of adipic acid is 1:(1-10):(0.1-6).

25. The method of adipic acid synthesis of claim 24, wherein, The mass ratio of the 1,2-cyclohexanediol, the solvent, and the catalyst for synthesis of adipic acid is 1:(4-6):(0.3-1).

26. The method of adipic acid synthesis of claim 19, wherein, The molar ratio of the 1,2-cyclohexanediol to the oxidant is 1:(0.2-1).

27. The method of adipic acid synthesis of claim 26, wherein, The molar ratio of the 1,2-cyclohexanediol to the oxidant is 1:(0.5-0.8).

28. A method of synthesizing adipic acid, characterized by, The method comprises the following steps: S1, cyclohexene is oxidized to obtain 1.2-cyclohexanediol; S2, the 1.2-cyclohexanediol is dissolved in a solvent, and reacted with an oxidant in the presence of the catalyst as defined in claim 18 to generate adipic acid.

29. The method of adipic acid synthesis of claim 28, wherein, The reaction temperature of the step S2 is 60-100℃, and the reaction time is 30-240 min.

30. The method of adipic acid synthesis of claim 29, wherein, The reaction temperature of the step S2 is 70-90℃.

31. The method of synthesizing adipic acid according to claim 28, wherein, The solvent includes one or more of methanol, ethanol, isopropanol, tert-butanol, formic acid, acetic acid, acetonitrile, 1,2-dichloroethane.

32. The method of synthesizing adipic acid according to claim 28, wherein, The oxidant includes one or more of cumene hydroperoxide, tert-butyl hydroperoxide, ethylbenzene hydroperoxide, hydrogen peroxide.

33. The method of adipic acid synthesis of claim 28, wherein, The mass ratio of the 1,2-cyclohexanediol, the solvent, and the catalyst for synthesis of adipic acid is 1:(1-10):(0.1-6).

34. The method of adipic acid synthesis of claim 33, wherein, The mass ratio of the 1,2-cyclohexanediol, the solvent, and the catalyst for synthesis of adipic acid is 1:(4-6):(0.3-1).

35. The method of synthesizing adipic acid according to claim 28, wherein, The molar ratio of the 1,2-cyclohexanediol to the oxidant is 1:(0.2-1).

36. The method of synthesizing adipic acid according to claim 35, wherein, The molar ratio of the 1,2-cyclohexanediol to the oxidant is 1:(0.5-0.8).

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