A catalyst, a process for its preparation and a process for the oxidation of cyclohexane

Abstract

The application belongs to the technical field of chemical industry, and particularly discloses a catalyst, a preparation method thereof and a method for oxidizing cyclohexane. The catalyst comprises a main catalyst and an auxiliary catalyst. The main catalyst comprises a rare earth compound, and the auxiliary catalyst comprises a copper compound and / or a manganese compound. The catalyst improves the conversion rate of raw material cyclohexane and the selectivity of product adipic acid in the method for preparing adipic acid by oxidizing cyclohexane, reduces the occurrence of side reactions, reduces the burden of separating impurities in the synthetic liquid, and achieves good technical effects.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a catalyst, its preparation method, and a method for cyclohexane oxidation. Background Technology

[0002] Adipic acid is an important basic organic chemical raw material. Its main use is in the production of nylon 66 salt. It can also be used in the production of polyurethane, plasticizers, polyamides, synthetic leather, lubricants, etc.

[0003] Adipic acid is typically derived from the catalytic oxidation of cyclohexane. Cyclohexane is first catalytically oxidized to cyclohexanone and cyclohexanol, then separated, purified, and further oxidized to adipic acid. Existing technologies generally optimize the one-step oxidation of cyclohexane to adipic acid by developing new catalysts. For example, CN110872224A discloses a process for the catalytic oxidation of cyclohexane to adipic acid and a method for preparing an acid-modified sepiolite catalyst. This method uses inexpensive sepiolite ore, which is modified with different inorganic or organic acids, washed with water until neutral, filtered, and dried to obtain the catalyst. This catalyst can be used in the industrial production of one-step oxidation of cyclohexane to adipic acid; however, the selectivity of adipic acid in the process using this catalyst is only a maximum of 62.3%, and further improvement is needed.

[0004] Therefore, providing a new catalyst to improve the conversion rate of cyclohexane and the selectivity of adipic acid in the one-step oxidation of cyclohexane to adipic acid remains a research direction in this field. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the purpose of this invention is to provide a catalyst and its preparation method, as well as a method for cyclohexane oxidation. This catalyst improves the conversion rate of cyclohexane and the selectivity of adipic acid in the method of cyclohexane oxidation to adipic acid, reduces the occurrence of side reactions, alleviates the burden of separating impurities in the synthesis liquid, and achieves better technical results.

[0006] A first aspect of the present invention is to provide a catalyst comprising a main catalyst and a co-catalyst, the main catalyst comprising a rare earth compound and the co-catalyst comprising a copper compound and / or a manganese compound.

[0007] In the above technical solution, the catalyst of the present invention includes a mixed main catalyst and a co-catalyst, wherein the main catalyst includes rare earth compounds and the co-catalyst includes copper compounds and / or manganese compounds.

[0008] According to the present invention, the ratio of the mass of rare earth elements in the catalyst to the total mass of copper and manganese elements has a wide range of possible values. In a preferred embodiment of the present invention, the ratio of the mass of rare earth elements in the catalyst to the total mass of copper and manganese elements is (0.5-10):1, preferably (1-5):1. For example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, or any two of the above values ​​or any ranges and 1.

[0009] According to the present invention, the rare earth compound has a wide range of selection. In a preferred embodiment of the present invention, the rare earth element in the rare earth compound is selected from at least one of the lanthanide rare earth elements, preferably at least one of lanthanum, cerium, praseodymium, neodymium and europium.

[0010] According to the present invention, as long as the rare earth compound can dissolve in a polar protic solvent, such that the rare earth element exists as a metal ion in the polar protic solvent, the catalyst of the present invention will have good technical effects. For example, but not limited to, the rare earth compound is selected from salts or oxides of the corresponding rare earth element; preferably, the rare earth compound is selected from at least one of acetate, hydrochloride, nitrate, sulfate, carbonate and rare earth oxide; more preferably, it is rare earth acetate and / or rare earth metal oxide.

[0011] Common catalysts for the oxidation of cyclohexane to adipic acid are mixtures of cobalt, copper, and manganese salts. However, cobalt is highly toxic. In a preferred embodiment of this invention, the co-catalyst does not contain cobalt. Thus, the catalyst of this invention is cobalt-free, further reducing production costs and improving both economic efficiency and environmental friendliness.

[0012] According to the present invention, the selection range of the copper compound and the manganese compound is relatively wide. In a preferred embodiment of the present invention, the copper compound and the manganese compound are each selected from the salts or oxides of the corresponding metal elements, preferably at least one of acetate, hydrochloride, nitrate, carbonate, sulfate and metal oxide; more preferably acetate and / or metal oxide.

[0013] According to the present invention, the mass ratio of copper to manganese can be selected within a wide range. In a preferred embodiment of the present invention, the mass ratio of copper to manganese is (0.2-5):1, preferably (0.5-2):1. For example, relative to 1 part by mass of manganese, the mass content of copper is 0.5, 1, 1.5, 2, or any two of the above values ​​or any range thereof.

[0014] According to the present invention, preferably, the catalyst is soluble in a polar protic solvent, such that the metal elements in the main catalyst and the co-catalyst exist as metal ions in the polar protic solvent.

[0015] According to the present invention, the range of selection of the polar protic solvent is relatively wide. In a preferred embodiment of the present invention, the polar protic solvent is selected from organic polar protic solvents with 6 or fewer carbon atoms, more preferably acidic compounds with pKa ≥ 3, and even more preferably acetic acid and / or propionic acid.

[0016] A second aspect of the present invention is to provide a method for preparing the catalyst described in the first aspect, comprising the step of mixing a rare earth compound, a copper compound, and a manganese compound.

[0017] According to the present invention, the mixing method in the preparation method of the catalyst can be either to directly mix the raw materials or to disperse or dissolve the raw materials in a liquid before use; either of these methods can achieve the present invention.

[0018] A third aspect of the present invention is to provide the application of the catalyst described in the first aspect in the catalytic oxidation reaction of cyclohexane.

[0019] A fourth aspect of the present invention is to provide a method for oxidizing cyclohexane, the method comprising: reacting an oxygen-containing gas with cyclohexane in the presence of a solvent and a catalyst to generate adipic acid; wherein the catalyst is the catalyst described in the first aspect.

[0020] According to the present invention, the solvent can be selected from a wide range. In a preferred embodiment of the present invention, the solvent is selected from at least one of polar protic solvents. Preferably, the catalyst is soluble in the polar protic solvent, such that the metal elements in the main catalyst and the co-catalyst exist as metal ions in the polar protic solvent. Preferably, the solvent is an organic polar protic solvent with 6 or fewer carbon atoms, more preferably an acidic compound with pKa ≥ 3, and even more preferably acetic acid and / or propionic acid.

[0021] According to the present invention, the mass ratio of cyclohexane to solvent can be selected within a wide range. In a preferred embodiment of the present invention, the mass ratio of cyclohexane to solvent is (0.04-0.5):1, preferably (0.075-0.15):1.

[0022] According to the present invention, the mass ratio of the catalyst to the solvent can be selected within a wide range. In a preferred embodiment of the present invention, the mass ratio of the catalyst to the solvent is (0.0005-0.01):1, preferably (0.001-0.008):1, based on the total mass of all metal elements in the catalyst.

[0023] According to the present invention, the oxygen content in the oxygen-containing gas has a wide selection range. In a preferred embodiment of the present invention, the oxygen content in the oxygen-containing gas is 8-21% by volume, preferably 9-18% by volume. Preferably, the oxygen-containing gas also contains carbon monoxide. More preferably, the volume content of carbon monoxide in the oxygen-containing gas is 0.2% or more, preferably 0.5%-2%.

[0024] According to the present invention, preferably, the oxygen-containing gas includes oxygen, carbon monoxide, and a protective gas; more preferably, the protective gas is nitrogen and / or an inert gas.

[0025] According to the present invention, the feeding method has a wide range of options, allowing for both single-feed and continuous feeding. In a preferred embodiment of the present invention, the method includes contacting the cyclohexane in the reaction system mixture with the oxygen-containing gas under continuous injection.

[0026] In the case of continuous feeding, the ratio of the mass flow rate of the oxygen-containing gas to the flow rate of the reaction system mixture (based on the mass of the solvent) during the reaction process has a wide range of choices. Preferably, the ratio of the mass flow rate of the oxygen-containing gas to the flow rate of the reaction system mixture (based on the mass of the solvent) during the reaction process is (10-30):1.

[0027] In a more preferred embodiment of the present invention, the method includes: first dissolving the catalyst in the solvent to obtain a solution containing the corresponding metal ions, and then adding cyclohexane to react.

[0028] In this invention, the reaction conditions can be selected within a wide range, and preferably, the reaction temperature is 85-115℃.

[0029] In this invention, the pressure conditions of the reaction can be selected within a wide range. Preferably, the reaction pressure is 1-4 MPa.

[0030] In this invention, the reaction time conditions can be selected within a wide range. Preferably, the reaction residence time is 1-6 hours.

[0031] In a more preferred embodiment of the present invention, the reaction conditions include: a reaction temperature of 85-115°C; a reaction pressure of 1-4 MPa; and a reaction residence time of 1-6 h.

[0032] Through the above technical solutions, the present invention obtains a catalyst by using rare earth compounds in combination with copper compounds and / or manganese compounds. The catalyst catalyzes the oxidation reaction of cyclohexane in a preferred homogeneous ionic state of the above metal elements, thereby improving the conversion rate of raw material cyclohexane and the selectivity of product adipic acid in the method of cyclohexane oxidation to prepare adipic acid, reducing the occurrence of side reactions, and alleviating the burden of impurities in the synthesis liquid separation.

[0033] The inventors of this invention, through research and verification, believe that the advantages mentioned above are due to the following: The catalyst in this invention uses rare earth elements in synergistic combination with copper and / or manganese elements. Preferably, the rare earth elements and copper and / or manganese elements are catalyzed in a homogeneous ionic state in the solvent. The synergistic combination of multiple element ions results in higher catalytic activity. At this time, the rare earth elements, combined with copper and / or manganese, exhibit a more significant promoting effect. Therefore, it unexpectedly and significantly improves the conversion rate of cyclohexane and the selectivity of adipic acid in the method of cyclohexane oxidation to adipic acid, reduces the occurrence of side reactions, alleviates the burden of impurities in the synthesis liquid separation, and achieves better technical results. Detailed Implementation

[0034] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0035] The present invention will be further described below through specific embodiments, but the scope of the present invention is not limited to the scope covered by the embodiments. In the following embodiments, the raw materials are all commercially available products. For comparison, the rare earth salts and co-catalyst metal salts in the specific embodiments are all acetates.

[0036] In the following implementations, the mass ratios of the metals involved are all expressed as the mass of the corresponding metal elements.

[0037] In the following examples and comparative examples, high performance liquid chromatography was used to analyze the mass concentration of adipic acid in the reaction solution, and gas chromatography was used to analyze the mass concentration of cyclohexane in the reaction solution.

[0038] The specific calculation methods for cyclohexane conversion and adipic acid selectivity are as follows:

[0039] Cyclohexane conversion rate = (mass of cyclohexane before reaction - mass of cyclohexane after reaction) / mass of cyclohexane before reaction × 100%

[0040] Adipic acid selectivity = (Molar amount of adipic acid produced in the reaction) / (Molar amount of cyclohexane before the reaction - Molar amount of cyclohexane after the reaction) × 100%

[0041] Example 1

[0042] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0043] 1) Take 0.12 kg of catalyst (lanthanum acetate, copper acetate, and manganese acetate, based on the mass of lanthanum + copper + manganese). The mass ratio of lanthanum to (copper + manganese) in the catalyst is 2.8:1, and the mass ratio of copper to manganese is 1.5:1. Dissolve the catalyst in 100 kg of acetic acid, add 10 kg of cyclohexane as a reaction raw material, and mix the above materials to prepare an acetic acid solution.

[0044] 2) Oxygen-containing gas (oxygen volume content 15%, the remainder is nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 20 kg / h. The reactor is heated to a reaction temperature of 90°C and a reaction pressure of 3.0 MPa.

[0045] 3) Acetic acid solution and oxygen-containing gas are continuously fed into the reactor. The feed flow rate of acetic acid solution is 1 kg / h (calculated based on the amount of acetic acid in the solution).

[0046] 4) After 40 hours of reaction, the feed was stopped to end the reaction. The average residence time was calculated to be 3 hours. A sample of the adipic acid oxidation reaction solution was taken and its composition was analyzed using chromatographic instruments (including liquid chromatography and gas chromatography, the same below). The cyclohexane conversion rate and adipic acid selectivity were calculated. The composition of the catalyst, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0047] Example 2

[0048] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0049] 1) Take 0.12 kg of catalyst (lanthanum acetate and copper acetate, calculated by mass of lanthanum + copper), where the mass ratio of lanthanum to copper in the catalyst is 2.8. Dissolve the catalyst in 100 kg of acetic acid, add 10 kg of cyclohexane as a reaction raw material, and mix the above materials to prepare an acetic acid solution;

[0050] 2) Oxygen-containing gas (oxygen volume content 15%, the remainder is nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 20 kg / h. The reactor is heated to a reaction temperature of 90°C and a reaction pressure of 3.0 MPa.

[0051] 3) Acetic acid solution and oxygen-containing gas are continuously fed into the reactor. The feed flow rate of acetic acid solution is 1 kg / h (calculated based on the amount of acetic acid in the solution).

[0052] 4) After 40 hours of reaction, the feed was stopped to end the reaction. The average reaction residence time was calculated to be 3 hours. Samples were taken and the composition of the adipic acid oxidation reaction solution was analyzed. The cyclohexane conversion rate and adipic acid selectivity were calculated. The catalyst composition, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0053] Example 3

[0054] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0055] 1) Take 0.12 kg of catalyst (lanthanum acetate and manganese acetate, calculated as lanthanum + manganese by mass), wherein the mass ratio of lanthanum to manganese in the catalyst is 2.8. Dissolve the catalyst in 100 kg of acetic acid, add 10 kg of cyclohexane as a reaction raw material, and mix the above materials to prepare an acetic acid solution;

[0056] 2) Oxygen-containing gas (oxygen volume content 15%, the remainder is nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 20 kg / h. The reactor is heated to a reaction temperature of 90°C and a reaction pressure of 3.0 MPa.

[0057] 3) Acetic acid solution and oxygen-containing gas are continuously fed into the reactor. The feed flow rate of acetic acid solution is 1 kg / h (calculated based on the amount of acetic acid in the solution).

[0058] 4) The average reaction residence time was calculated to be 3 h. Samples were taken and analyzed to determine the composition of the adipic acid oxidation reaction solution. The cyclohexane conversion rate and adipic acid selectivity were calculated. The catalyst composition, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0059] Example 4

[0060] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0061] 1) Take 0.12 kg of catalyst (lanthanum acetate, copper acetate, and manganese acetate, based on the mass of lanthanum + copper + manganese). The mass ratio of lanthanum to (copper + manganese) in the catalyst is 1:1, and the mass ratio of copper to manganese is 1:1. Dissolve the catalyst in 100 kg of acetic acid, add 10 kg of cyclohexane as a reaction raw material, and mix the above materials to prepare an acetic acid solution.

[0062] 2) Oxygen-containing gas (21% oxygen by volume, the remainder being nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 20 kg / h. The reactor is heated to a reaction temperature of 115°C and a reaction pressure of 1.0 MPa.

[0063] 3) Acetic acid solution and oxygen-containing gas are continuously fed into the reactor. The feed flow rate of acetic acid solution is 2 kg / h (calculated based on the amount of acetic acid in the solution).

[0064] 4) After 40 hours of reaction, the feed was stopped to end the reaction. The average residence time was calculated to be 6 hours. Samples were taken and the composition of the adipic acid oxidation reaction solution was analyzed. The cyclohexane conversion rate and adipic acid selectivity were calculated. The catalyst composition, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0065] Example 5

[0066] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0067] 1) Take 0.12 kg of catalyst (lanthanum acetate, copper acetate, and manganese acetate, based on the mass of lanthanum + copper + manganese). The mass ratio of lanthanum to (copper + manganese) in the catalyst is 5:1, and the mass ratio of copper to manganese is 2:1. Dissolve the catalyst in 100 kg of acetic acid, add 10 kg of cyclohexane as a reaction raw material, and mix the above materials to prepare an acetic acid solution.

[0068] 2) Oxygen-containing gas (8% by volume, the remainder being nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 30 kg / h. The reactor is heated to a reaction temperature of 85°C and a reaction pressure of 4.0 MPa.

[0069] 3) Acetic acid solution and oxygen-containing gas are continuously fed into the reactor. The feed flow rate of acetic acid solution is 1 kg / h (calculated based on the amount of acetic acid in the solution).

[0070] 4) After 40 hours of reaction, the feed was stopped to end the reaction. The average residence time was calculated to be 1 hour. Samples were taken and the composition of the adipic acid oxidation reaction solution was analyzed. The cyclohexane conversion rate and adipic acid selectivity were calculated. The catalyst composition, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0071] Example 6

[0072] The reaction was carried out according to the method of Example 1 to obtain an adipic acid oxidation reaction solution. The difference was that the rare earth elements were replaced with cerium, and the cerium salt, copper salt and manganese salt were replaced with the corresponding metal element chlorides. The specific oxidation process conditions are shown in Table 1. Other parameters not listed are the same as those in Example 1.

[0073] The composition of the adipic acid oxidation reaction solution was analyzed by sampling, and the cyclohexane conversion rate and adipic acid selectivity were calculated.

[0074] The composition of the catalyst, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0075] Example 7

[0076] The reaction was carried out according to the method of Example 1 to obtain an adipic acid oxidation reaction solution. The difference was that the rare earth elements were replaced with neodymium, and the neodymium salt, copper salt, and manganese salt were all replaced with the corresponding metal element sulfates. The specific oxidation process conditions are shown in Table 1. Other parameters not listed are the same as in Example 1.

[0077] The composition of the adipic acid oxidation reaction solution was analyzed by sampling, and the cyclohexane conversion and adipic acid selectivity were calculated. The composition of the catalyst, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0078] Example 8

[0079] The reaction was carried out according to the method of Example 1 to obtain an adipic acid oxidation reaction solution. The difference was that the lanthanum salt, copper salt, and manganese salt were all replaced by the corresponding metal element nitrates, and the mass ratio of lanthanum to (copper + manganese) was 10:1, and the mass ratio of copper to manganese was 0.2:1. The specific oxidation process conditions are shown in Table 1. Other parameters not listed are the same as in Example 1.

[0080] The composition of the adipic acid oxidation reaction solution was analyzed by sampling, and the cyclohexane conversion and adipic acid selectivity were calculated. The composition of the catalyst, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0081] Example 9

[0082] The reaction was carried out according to the method of Example 1 to obtain an adipic acid oxidation reaction solution. The difference was that the lanthanum salt, copper salt, and manganese salt were all replaced by the corresponding metal element oxides, and the mass ratio of lanthanum to (copper + manganese) was 0.5:1, and the mass ratio of copper to manganese was 5:1. The specific oxidation process conditions are shown in Table 1. Other parameters not listed are the same as in Example 1.

[0083] The composition of the adipic acid oxidation reaction solution was analyzed by sampling, and the cyclohexane conversion and adipic acid selectivity were calculated. The composition of the catalyst, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0084] Example 10

[0085] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0086] 1) Take 0.12 kg of catalyst (lanthanum acetate, copper acetate, and manganese acetate, based on the mass of lanthanum + copper + manganese). The mass ratio of lanthanum to (copper + manganese) in the catalyst is 2.8:1, and the mass ratio of copper to manganese is 1.5:1. Dissolve the catalyst in 100 kg of acetic acid, add 10 kg of cyclohexane as a reaction raw material, and mix the above materials to prepare an acetic acid solution.

[0087] 2) Oxygen-containing gas (oxygen volume content 15%, the remainder is nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 20 kg / h. The reactor is heated to a reaction temperature of 90°C and a reaction pressure of 3.0 MPa.

[0088] 3) Acetic acid solution is added to the reactor at once, and oxygen-containing gas is continuously fed into the reactor at a flow rate of 20 kg / h;

[0089] 4) After 3 hours of reaction, the feed was stopped to end the reaction. Samples were taken to analyze the composition of the adipic acid oxidation reaction solution, and the cyclohexane conversion and adipic acid selectivity were calculated. The catalyst composition, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0090] Example 11

[0091] The reaction was carried out according to the method of Example 1 to obtain an adipic acid oxidation reaction solution, except that the oxygen-containing gas consisted of the following composition: 12% oxygen by volume, 1% carbon monoxide by volume, and the remainder being nitrogen.

[0092] The composition of the adipic acid oxidation reaction solution was analyzed by sampling, and the cyclohexane conversion and adipic acid selectivity were calculated. The composition of the catalyst, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0093] Comparative Example 1

[0094] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0095] 1) Take 0.12 kg of catalyst (cobalt acetate, copper acetate, and manganese acetate, based on the mass of cobalt + copper + manganese). The mass ratio of cobalt to (copper + manganese) in the catalyst is 2.8, and the mass ratio of copper to manganese is 1.5. Dissolve the catalyst in 100 kg of acetic acid, add 10 kg of cyclohexane as a reaction raw material, and mix the above materials to prepare an acetic acid solution.

[0096] 2) Oxygen-containing gas (oxygen volume content 15%, the remainder is nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 20 kg / h. The reactor is heated to a reaction temperature of 90°C and a reaction pressure of 3.0 MPa.

[0097] 3) Acetic acid solution and oxygen-containing gas are continuously fed into the reactor. The feed flow rate of acetic acid solution is 1 kg / h (calculated based on the amount of acetic acid in the solution).

[0098] 4) After 40 hours of reaction, the feed was stopped to end the reaction. The calculated reaction residence time was 3 hours. Samples were taken and the composition of the adipic acid oxidation reaction solution was analyzed. The cyclohexane conversion rate and adipic acid selectivity were calculated. The catalyst composition, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0099] Comparative Example 2

[0100] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0101] 1) Take 0.12 kg of catalyst (lanthanum acetate, based on the mass of lanthanum). Dissolve the catalyst in 100 kg of acetic acid, add 10 kg of cyclohexane as a reaction raw material, and mix the above materials to prepare an acetic acid solution;

[0102] 2) Oxygen-containing gas (oxygen volume content 15%, the remainder is nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 20 kg / h. The reactor is heated to a reaction temperature of 90°C and a reaction pressure of 3.0 MPa.

[0103] 3) Acetic acid solution and oxygen-containing gas are continuously fed into the reactor. The feed flow rate of acetic acid solution is 1 kg / h (calculated based on the amount of acetic acid in the solution).

[0104] 4) After 40 hours of reaction, the feed was stopped to end the reaction. The average reaction residence time was calculated to be 3 hours. Samples were taken and the composition of the adipic acid oxidation reaction solution was analyzed. The cyclohexane conversion rate and adipic acid selectivity were calculated. The catalyst composition, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0105] Comparative Example 3

[0106] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0107] 1) Take 0.12 kg of catalyst (copper acetate, based on the mass of copper). Dissolve the catalyst in 100 kg of acetic acid, add 10 kg of cyclohexane as a reaction raw material, and mix the above materials to prepare an acetic acid solution;

[0108] 2) Oxygen-containing gas (oxygen volume content 15%, the remainder is nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 20 kg / h. The reactor is heated to a reaction temperature of 90°C and a reaction pressure of 3.0 MPa.

[0109] 3) Acetic acid solution and oxygen-containing gas are continuously fed into the reactor. The feed flow rate of acetic acid solution is 1 kg / h (calculated based on the amount of acetic acid in the solution).

[0110] 4) After 40 hours of reaction, stop feeding to end the reaction. The calculated reaction residence time is 3 hours. Take samples to analyze the composition of the adipic acid oxidation reaction solution and calculate the cyclohexane conversion rate and adipic acid selectivity.

[0111] The composition of the catalyst, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0112] Comparative Example 4

[0113] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0114] 1) Take 0.12 kg of catalyst (manganese acetate, based on manganese mass). Dissolve the catalyst in 100 kg of acetic acid, add 10 kg of cyclohexane as a reaction raw material, and mix the above materials to prepare an acetic acid solution;

[0115] 2) Oxygen-containing gas (oxygen volume content 15%, the remainder is nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 20 kg / h. The reactor is heated to a reaction temperature of 90°C and a reaction pressure of 3.0 MPa.

[0116] 3) Acetic acid solution and oxygen-containing gas are continuously fed into the reactor. The feed flow rate of acetic acid solution is 1 kg / h (calculated based on the amount of acetic acid in the solution).

[0117] 4) Stop feeding after 40 hours of reaction to end the reaction. The reaction residence time is calculated to be 3 hours. Take a sample to analyze the composition of the adipic acid oxidation reaction solution and calculate the cyclohexane conversion rate and adipic acid selectivity.

[0118] The composition of the catalyst, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0119] Comparative Example 5

[0120] The method for preparing adipic acid by oxidation of cyclohexane includes the following steps:

[0121] 1) Take 0.12 kg of catalyst (which consists of lanthanum acetate, copper acetate, and ferric acetate in a ratio of Cu). 10 The catalyst (Fe5La5), based on the mass of lanthanum, copper, and iron, has a lanthanum to (copper + iron) mass ratio of 0.755:1 and a copper to iron mass ratio of 2.286:1. The catalyst is dissolved in 100 kg of acetic acid, and 10 kg of cyclohexane is added as a reactant. The above materials are mixed to prepare an acetic acid solution.

[0122] 2) Oxygen-containing gas (oxygen volume content 15%, the remainder is nitrogen) is continuously introduced into the oxidation reactor at a flow rate of 20 kg / h. The reactor is heated to a reaction temperature of 90°C and a reaction pressure of 3.0 MPa.

[0123] 3) Acetic acid solution and oxygen-containing gas are continuously fed into the reactor. The feed flow rate of acetic acid solution is 1 kg / h (calculated based on the amount of acetic acid in the solution).

[0124] 4) Stop feeding after 40 hours of reaction to end the reaction. The average residence time of the reaction is calculated to be 3 hours. Take samples to analyze the composition of the adipic acid oxidation reaction solution and calculate the cyclohexane conversion rate and adipic acid selectivity.

[0125] The composition of the catalyst, reaction conditions, and experimental results are listed in Tables 1 and 2, respectively.

[0126] Example 1 and Comparative Example 1 show that replacing cobalt with rare earth elements has a better effect, improving the conversion rate of cyclohexane and the selectivity of adipic acid. Cobalt is very expensive; replacing it with rare earth compounds can also reduce the cost of the catalyst.

[0127] A comparison of Example 2 with Comparative Examples 2 and 3 shows that, comparatively, lanthanum and copper have a good synergistic effect in improving the conversion rate of cyclohexane and the selectivity of adipic acid.

[0128] A comparison of Example 3 with Comparative Examples 2 and 4 shows that, comparatively, lanthanum and manganese have a good synergistic effect in improving the conversion rate of cyclohexane and the selectivity of adipic acid.

[0129] As can be seen from the examples and comparative examples of the present invention, the catalyst of the present invention has significant advantages in improving the conversion rate of cyclohexane and the selectivity of adipic acid. Moreover, compared with the general cobalt-based catalysts, the catalyst of the present invention can reduce the cost of the catalyst, making it more economical and environmentally friendly, and thus having higher industrial application value.

[0130] Table 1

[0131]

[0132] Table 2

[0133]

[0134] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0135] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0136] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0137] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0138] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0139] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. A catalyst comprising a main catalyst and a co-catalyst, wherein the main catalyst comprises a rare earth compound and the co-catalyst comprises a copper compound and / or a manganese compound; The catalyst also contains a polar protic solvent; The metal elements in the main catalyst and the co-catalyst exist as metal ions in a polar protic solvent; the polar protic solvent is selected from organic polar protic solvents with 6 or fewer carbon atoms; The catalyst does not contain Br.

2. The catalyst according to claim 1, characterized in that: The mass ratio of rare earth elements to the total mass of copper and manganese elements in the catalyst is (0.5-10):

1.

3. The catalyst according to claim 1, characterized in that: The mass ratio of rare earth elements to the total mass of copper and manganese elements in the catalyst is (1-5):

1.

4. The catalyst according to claim 1, characterized in that: The rare earth element in the rare earth compound is selected from at least one of the lanthanide rare earth elements; and / or, The rare earth compounds are selected from salts or oxides of the corresponding rare earth elements.

5. The catalyst according to claim 1, characterized in that: The rare earth element in the rare earth compound is at least one selected from lanthanum, cerium, praseodymium, neodymium, and europium; and / or, The rare earth compound is selected from at least one of the following: acetate, hydrochloride, nitrate, sulfate, carbonate, and rare earth oxide of the corresponding rare earth element.

6. The catalyst according to claim 1, characterized in that: The metal element in the co-catalyst does not include cobalt; and / or, The copper compound and the manganese compound are each selected from salts or oxides of the corresponding metal elements; and / or, The mass ratio of copper to manganese is (0.2-5):

1.

7. The catalyst according to claim 1, characterized in that: The copper compound and the manganese compound are each selected from at least one of the following: acetate, hydrochloride, nitrate, carbonate, sulfate, and metal oxide of the corresponding metal element; and / or, The mass ratio of copper to manganese is (0.5-2):

1.

8. The catalyst according to any one of claims 1-7, characterized in that: The polar protic solvent is selected from acidic compounds with pKa ≥ 3.

9. The catalyst according to any one of claims 1-7, characterized in that: The polar protic solvent is acetic acid and / or propionic acid.

10. A method for preparing a catalyst according to any one of claims 1-9, comprising the step of mixing a polar protic solvent, a rare earth compound, a copper compound and / or a manganese compound.

11. The use of a catalyst according to any one of claims 1-9 in the catalytic oxidation reaction of cyclohexane.

12. A method for oxidizing cyclohexane, the method comprising: In the presence of a catalyst, oxygen-containing gas reacts with cyclohexane to produce adipic acid; The catalyst is the catalyst according to any one of claims 1-9.

13. The method according to claim 12, characterized in that: The mass ratio of cyclohexane to the polar protic solvent is (0.04-0.5):1; and / or, The mass ratio of the catalyst to the solvent is (0.0005-0.01):1, based on the total mass of all metal elements in the catalyst.

14. The method according to claim 12, characterized in that: The mass ratio of cyclohexane to the polar protic solvent is (0.075-0.15):1; and / or, The mass ratio of the catalyst to the solvent is (0.001-0.008):1, based on the total mass of all metal elements in the catalyst.

15. The method according to claim 12, characterized in that: The oxygen content in the oxygen-containing gas is 8-21% by volume.

16. The method according to claim 12, characterized in that: The oxygen content in the oxygen-containing gas is 9-18% by volume.

17. The method according to claim 15, characterized in that: The oxygen-containing gas also contains carbon monoxide.

18. The method according to claim 17, characterized in that: The volume content of carbon monoxide in the oxygen-containing gas is 0.2% or more.

19. The method according to claim 17, characterized in that: The volume content of carbon monoxide in the oxygen-containing gas is 0.5%-2%.

20. The method according to claim 17, characterized in that: The oxygen-containing gas includes oxygen, carbon monoxide, and a protective gas.

21. The method according to claim 20, characterized in that: The protective gas is nitrogen and / or an inert gas.

22. The method according to claim 12, characterized in that: The method includes contacting cyclohexane in a reaction mixture with the oxygen-containing gas under continuous injection.

23. The method according to claim 22, characterized in that: During the reaction, the ratio of the mass flow rate of the oxygen-containing gas to the flow rate of the reaction mixture (based on the mass of the solvent) is (10-30):

1.

24. The method according to any one of claims 12-23, characterized in that: The method includes: first dissolving the catalyst in the solvent to obtain a solution containing the corresponding metal ions, and then adding cyclohexane to carry out the reaction; And / or, the conditions for the reaction include: The reaction temperature is 85-115℃; and / or, the reaction pressure is 1-4MPa; and / or, the reaction residence time is 1-6h.

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