Method for selectively oxidizing cycloalkane
By using vanadium-based catalysts in the cyclohexanyl oxidation process, the problems of chromium and cobalt catalysts in the prior art are solved, the selectivity of cycloalkyl alcohols and ketones is improved, and the generation of by-products is reduced. High-efficiency catalytic oxidation synthesis of cycloalkanes is achieved.
Patent Information
- Application Number
- CN202310690544.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-12
- Publication Date
- 2024-12-13
AI Technical Summary
The catalysts such as chromium and cobalt used in the existing cyclohexanyl oxidation process are harmful to the environment, and the heterogeneous precious metal catalysts are costly and the homogeneous catalysts are low selectivity, resulting in unsatisfactory yields of cyclohexanone and cyclohexanol. Increased production costs.
The cycloalkanes are catalyzed in homogeneous phase using a vanadium-based catalyst, and oxidized by a vanadium compound catalyst (such as a catalyst prepared by the reaction of 5-hydroxyquinoxaline and vanayl acetylacetonate). The reaction conditions include a catalyst amount of 0.01% to 0.1%. , pressure of 0.10 to 10 MPa, stirring rate of 300 to 1200 rpm and temperature of 60 to 200°C, oxygen or mixture thereof is used as oxidant.
The selectivity of cycloalkyl alcohols and cycloalkyl ketones is improved, the generation of by-products is reduced, and the environmental impact is small, and the safety is high, achieving efficient and feasible selective catalytic oxidation synthesis of cycloalkanes is achieved.
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Abstract
Description
Technical Field
[0001] The invention relates to a production process for cycloalkane oxidation, and belongs to the field of fine chemicals. Background Art
[0002] The oxidation reaction of cycloalkanes mainly produces cycloalkyl ketones and cycloalkyl alcohols. Among them, cycloalkanes represented by cyclohexane are the most widely used cycloalkanes. This mixture produced by the oxidation of cyclohexane is usually called KA oil (ketone / alcohol oil), which is an important chemical raw material. Most KA oils are used to produce nylon 66 and nylon 6 precursors, and can also be used to prepare intermediates for chemicals such as dyes, coatings, and medicines. They can also be used to prepare rubber antioxidants, spices, and fruit mildew inhibitors. KA oil mixtures are easily oxidized to produce adipic acid, which is an important reactant for the preparation of certain condensation polymers, including polyamides and nylon 66.
[0003] The traditional process of cyclohexane oxidation to produce KA oil, a mixture of cyclohexanone and cyclohexanol, is carried out in two steps. First, cyclohexane is oxidized to prepare an oxidation solution containing cyclohexyl hydroperoxide (CyOOH). In the second step, chromium ions or cobalt ions are used as homogeneous catalysts to catalyze the decomposition of CyOOH to obtain KA oil. With the restrictions of regulations in various countries around the world, the demand for replacing environmentally unfavorable catalysts such as chromium and cobalt is becoming more and more urgent.
[0004] Most technologies have initially focused on the preparation of KA oil by catalyzing the oxidation of cyclohexane with hydrogen peroxide using different types of homogeneous catalysts. Currently, most efforts are focused on the use of molecular sieves, polymers, and silica-supported transition metal complexes. Although some of these materials show relatively good activity and selectivity for K / A oil, most of them will experience deactivation and / or metal leaching, which hinders their industrial application.
[0005] For example, patent CN103007978A discloses a supported gold catalyst for cyclohexane oxidation reaction, which is composed of active component Au and carrier cobalt oxide, with Au mass percentage of 1~5% and cobalt oxide mass percentage of 95~99%. The reaction is carried out under 1.5MPa oxygen pressure and 150°C temperature for 3h, and the cyclohexane conversion rate reaches 8.5%, and the total selectivity is 91.4%. Patent CN111943808A discloses a method for the synergistic catalytic oxidation of cycloalkanes by MOFs PCN-224 (Mn) / Zn (II) salts. PCN-224 (Mn) (0.001%~5%, g / mol) and Zn (II) salts (0.01%~10%, mol / mol) are dispersed in cycloalkanes, the reaction system is sealed, the temperature is raised to 120°C with stirring, oxygen is introduced to 1.0 MPa, and the reaction is stirred for 8.0 hours. The cyclohexane conversion rate is 7.00%, the cyclohexanol selectivity is 75.58%, and the cyclohexanone selectivity is 17.49%.
[0006] Although heterogeneous precious metal catalysts have good cyclohexane oxidation activity, the cost of such catalysts is high, which greatly limits their prospects for industrial application. Therefore, researchers have also prepared a variety of homogeneous catalysts. Among them, vanadium compounds can be used as a good catalyst. For example, patent CN109251126 discloses a method for cyclohexane oxidation to produce KA oil, which is catalyzed by a vanadium phosphorus oxide catalyst. The vanadium phosphorus oxide is prepared by the following method: V205, phosphoric acid and distilled water are reacted at 100~120°C for 16~24 hours. The solid product obtained is added to an isobutanol solvent and reacted at 90~130°C for 16~24 hours to obtain a catalyst precursor, which is activated to obtain the catalyst. The conversion rate of cyclohexane using a vanadium phosphorus oxide catalyst reaches 7~8%, and the selectivity of KA oil can reach about 50%. CN109251125 discloses a method for preparing cyclohexanol by oxidation of cyclohexane, wherein the vanadium phosphorus oxygen catalyst is used for catalytic reaction, and the catalyst is prepared by the following method: V205 and phosphoric acid are reacted in an aqueous solution environment, and the obtained powder product is added to isobutanol, and the reaction is carried out at 30-90°C for 4-8 hours under normal pressure, and the solvent is evaporated to dryness, and the solid is dried to obtain a catalyst powder; or the catalyst is made into a supported type. The present invention adopts a vanadium phosphorus oxygen catalyst for cyclohexane oxidation to prepare cyclohexanol, and provides a new method for preparing cyclohexanol by oxidation of cyclohexane. By using the method of the present invention, the conversion rate of cyclohexane and the selectivity of cyclohexanol are improved; in particular, the selectivity of cyclohexanone is greatly reduced, and high-purity cyclohexanol is obtained, which reduces the cost of separating cyclohexanol and cyclohexanone in industry. This also shows that vanadium substances can be used for catalytic oxidation of cycloalkanes. However, the selectivity of this type of vanadium phosphorus oxygen catalyst is still low, and the activity of the catalyst needs to be further improved. Summary of the invention
[0007] At present, one of the main industrial preparation methods of cyclohexanone is the cyclohexane oxidation process. The non-catalytic oxidation process is commonly used in industry, which has the disadvantages of low selectivity for the production of cyclohexyl hydroperoxide, and the organic acids such as adipic acid, glutaric acid, and succinic acid produced by excessive oxidation have an adverse effect on the catalyst activity of the subsequent decomposition reaction, resulting in unsatisfactory molecular yields of cyclohexanone and cyclohexanol produced by the decomposition reaction of cyclohexyl hydroperoxide, low ketone-alcohol ratio, and increased production costs. Solution
[0008] In order to better solve the shortcomings of cyclohexane oxidation technology, reduce the proportion of cyclohexane oxidation by-products, and increase the yield of cyclohexane oxidation products, the inventors have conducted in-depth research and invented a new technology containing vanadium-based catalytic oxidation, which can be used for the catalytic oxidation process of cyclohexane oxidation.
[0009] The present invention is achieved as follows: a method for selective oxidation of cycloalkanes, comprising a method for preparing a mixture of alkyl alcohols and alkyl ketones from cycloalkanes, wherein the conversion rate of cycloalkanes is not less than 90%, the method comprising oxidizing cycloalkanes in a homogeneous phase, catalyzed by the vanadium compound, wherein the amount of the vanadium compound catalyst accounts for 0.01% to 0.1% by weight of the total weight of the reaction mixture, and wherein the vanadium compound is dissolved in the liquid phase.
[0010] Wherein, the vanadium compound comprises at least one compound selected from the following structures:
[0011] In the present invention, the cycloalkane is a cycloalkane containing three or more carbon atoms, and also includes a cycloalkane containing an alkyl substituent.
[0012] In the present invention, the preferred cycloalkane is one of cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane and cyclododecane.
[0013] In the present invention, the amount of the catalyst is 0.01% to 0.1% by weight based on the total weight of the reaction mixture.
[0014] In the present invention, the preferred amount of the catalyst is 0.01% to 0.05% by weight based on the total weight of the reaction mixture.
[0015] In the present invention, the reaction pressure is 0.10-10 MPa.
[0016] In the present invention, the reaction pressure is preferably 0.10 to 5 MPa.
[0017] In the present invention, the stirring rate is 300-1200 rpm.
[0018] In the present invention, the stirring rate is preferably 500-1000 rpm.
[0019] In the present invention, the oxidant is oxygen, air or any mixture thereof.
[0020] In the present invention, the oxidant is not particularly limited, and for example, sulfoxides such as air, oxygen, dimethyl sulfoxide, dibutyl sulfoxide, diphenyl sulfoxide, and tetramethylene sulfoxide can be used. Two or more of these oxidants can be mixed. From the viewpoint of productivity and ease of operation, it is preferred to use air, oxygen, dimethyl sulfoxide, tetramethylene sulfoxide, or a mixture of these oxidants.
[0021] In the present invention, preferred oxidants are oxygen and air.
[0022] In the present invention, when oxygen is used as an oxidant, oxygen can also be mixed with other gases for use, for example, oxygen can be mixed with air or an inert gas (hydrogen, hydrogen, etc.) for use.
[0023] In the present invention, when air or oxygen is used as an oxidant, there is no particular limitation on the method of supplying air or oxygen. For example, the following methods can be used: a method of replacing the gas phase in contact with the reaction solution with air or oxygen, a method of allowing the gas phase in contact with the reaction solution to flow in air or oxygen, a method of blowing air or oxygen into the reaction solution, etc.
[0024] In the present invention, the reaction time can be determined according to the reactants, and the reaction time is usually 1 to 600 minutes.
[0025] In the present invention, the reaction time can be determined according to the reactants, and the reaction temperature is usually 0°C to 200°C; the preferred reaction temperature is 60°C to 180°C.
[0026] In the present invention, the preparation step of the vanadium compound catalyst is: select one of 5-hydroxyquinoxaline, 8-chloro-5-hydroxyquinoxaline, or 8-fluoro-5-hydroxyquinoxaline, and react with acetylacetonyl vanadyl in a hydrocarbon solvent, and filter the reaction to obtain a catalyst after the reaction is completed. Wherein, the hydrocarbon solvent is selected from one of benzene, toluene, xylene, cyclohexane, cyclopentane, n-hexane, and n-pentane; preferably toluene, cyclohexane, and n-hexane. Wherein, the reaction temperature is -10°C to 100°C; preferably 30 to 80°C. Wherein, the ratio of quinoxaline to acetylacetonyl vanadyl in the reactant is 1.9:1 to 2.1:1; preferably the ratio is 2:1. Wherein, the reaction time can be carried out according to the reaction situation, and can generally be selected from 1 to 1800 minutes; preferably 30 to 600 minutes. Wherein, the temperature for standing and filtering after the reaction is completed can be carried out according to the reactants and products, and can generally be selected from -10°C to 50°C; preferably 0°C to 25°C. The time for standing and filtering after the reaction is completed can be determined according to the reactants and products, and can generally be selected to be 1 to 1200 minutes, preferably 10 to 600 minutes. The catalyst can be dried by evaporating the solvent under natural conditions, or dried in an oven.
[0027] Beneficial effects: The method of the present invention has the advantages of high selectivity of cycloalkyl alcohols and cycloalkyl ketones, low reaction temperature, few by-products, and small environmental impact. In addition, the content of cycloalkyl hydroperoxides of the present invention is low and the safety factor is high. The present invention provides an efficient, feasible and safe method for synthesizing cycloalkyl alcohols and cycloalkyl ketones by selective catalytic oxidation of cycloalkanes. Implementation
[0028] The technical scheme of the present invention is further described below in conjunction with the examples. The following examples will further illustrate the present invention, but are not intended to limit the content of the present invention. All reagents used in the examples are commercially available chemically pure reagents. Example
[0029] In a 100 mL flask, add 2.9 g (0.02 mol) of 5-hydroxyquinoxaline and 2.6 g (0.01 mol) of acetylacetonatovanadium, add 50 ml of cyclohexane, and heat the resulting dark green mixture for 3 hours to obtain a dark solution. After cooling to room temperature, filter out the solid after 3 hours to obtain a dark product, wash with a small amount of cyclohexane, and dry the product to obtain 2.7 g of dark solid a1, LC-MS (ESI) m / z: 357.1. Example
[0030] In a 100 mL flask, add 3.6 g (0.02 mol) of 8-chloro-5-hydroxyquinoxaline and 2.6 g (0.01 mol) of acetylacetonatovanadium, add 70 ml of n-hexane, and heat the mixture to react for 3.5 hours to obtain a dark solution. Cool to room temperature, filter out the solid after 4 hours to obtain a dark product, wash with n-hexane, and dry to obtain 3.1 g of dark solid a2, LC-MS (ESI) m / z: 424.9. Example
[0031] In a 100 mL flask, add 0.33 g (0.002 mol) of 8-fluoro-5-hydroxyquinoxaline and 0.26 g (0.001 mol) of acetylacetonatovanadium, and add 20 ml of toluene to obtain a dark mixture, which is heated to react for 2 hours. After completion, the mixture is allowed to stand and cooled to about 0°C. After 0.5 hours, the solid is filtered out to obtain a dark product, which is washed with cyclohexane and dried to obtain 0.12 g of a dark solid a3, LC-MS (ESI) m / z: 393.1. Example
[0032] In a 100mL polytetrafluoroethylene-lined autoclave, add 42g (0.5mol) of cyclohexane and 0.02% of solid a1 (0.036g), stir and heat to 140°C, introduce oxygen (1.0MPa), and stir at 800rpm for 2 hours. After the reaction is completed, add 2g of triphenylphosphine to the reaction mixture, stir at room temperature for 1 hour, and take a sample for gas chromatography analysis. The cyclohexane conversion rate is 6.1%, the cyclohexanol selectivity is 68%, and the cyclohexanone selectivity is 24%. Example
[0033] In a 100mL polytetrafluoroethylene-lined autoclave, add 42g (0.5mol) of cyclohexane and 0.01% of solid a2 (0.02g), stir and heat to 180°C, introduce oxygen (1.0MPa), and stir at 900rpm for 2 hours. After the reaction is completed, add 2g of triphenylphosphine to the reaction mixture, stir at room temperature for 1 hour, and take a sample for gas chromatography analysis. The cyclohexane conversion rate is 6.3%, the cyclohexanol selectivity is 70%, and the cyclohexanone selectivity is 26%. Example
[0034] In a 100mL polytetrafluoroethylene-lined autoclave, add 20g of cyclopentane and 0.01% of solid a1 (0.01g), add 30mL of hydrogen peroxide, stir and heat to 140°C, and stir at 700rpm for 1 hour. After the reaction is completed, add 1.5g of triphenylphosphine to the reaction mixture, stir at room temperature for 1 hour, and take a sample for gas chromatography analysis. The cyclopentane conversion rate is 7.3%, the cyclopentanol selectivity is 77%, and the cyclopentanone selectivity is 17%. Example
[0035] In a 100mL polytetrafluoroethylene-lined autoclave, add 25g of cyclononane and 0.01% of solid a2 (0.015g), add 35mL of hydrogen peroxide, stir and heat to 150°C, and stir at 700rpm for 1.5 hours. After the reaction is completed, add 2.5g of triphenylphosphine to the reaction mixture, stir at room temperature for 1 hour, and take a sample for gas chromatography analysis. The conversion rate of cyclononane is 9.3%, the selectivity of cyclononanol is 82%, and the selectivity of cyclononanone is 14%. Example
[0036] In a 100mL polytetrafluoroethylene-lined autoclave, add 42g of cyclododecane and 0.01% of solid a3 (0.02g), add 70mL of hydrogen peroxide, stir and heat to 160°C, and stir at 600rpm for 2 hours. After the reaction is completed, add 3g of triphenylphosphine to the reaction mixture, stir at room temperature for 1 hour, and take a sample for gas chromatography analysis. The conversion rate of cyclododecane is 6.5%, the selectivity of cyclododecanol is 74%, and the selectivity of cyclododecanone is 20%.
Claims
1. A method for selective oxidation of cycloalkanes, characterized in that A method for preparing a mixture of alkyl alcohols and alkyl ketones from cycloalkanes, wherein the conversion rate of cycloalkanes is not less than 90%; the method comprises oxidizing cycloalkanes in a homogeneous phase, catalyzed by a vanadium compound, wherein the amount of the vanadium compound catalyst is 0.01% to 1% by weight based on the total weight of the reaction mixture, and the vanadium compound is dissolved in the liquid phase.
2. The method according to claim 1, characterized in that The vanadium compound comprises at least one compound selected from the following structures: 。 3. The method according to claim 1, characterized in that The cycloalkane is one of cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane and cyclododecane.
4. The method according to claim 1, characterized in that The amount of the catalyst is 0.05 to 0.50% by weight based on the total weight of the reaction mixture.
5. The method according to claim 1, characterized in that The reaction pressure is 0.10-10 MPa, the reaction time is 1-600 minutes, and the reaction temperature is 0° C.-200° C.
6. The method according to claim 1, characterized in that The stirring speed is 300-1200 rpm.
7. The method according to claim 1, characterized in that The oxidant is oxygen, air or any mixture thereof.
8. The method according to claim 1, characterized in that The preparation steps of the vanadium compound catalyst are: selecting 5-hydroxyquinoxaline, 8-chloro-5-hydroxyquinoxaline, or 8-fluoro-5-hydroxyquinoxaline, reacting with vanadium acetylacetonate in a hydrocarbon solvent, and filtering after the reaction to obtain the catalyst.
9. The method according to claim 9, characterized in that The hydrocarbon solvent is selected from one of benzene, toluene, xylene, cyclohexane, cyclopentane, n-hexane and n-pentane.
10. The method according to claim 9, characterized in that The reaction temperature is -10°C to 100°C.
11. The method according to claim 9, characterized in that The ratio of quinoxaline to vanadium acetylacetonate in the reactants is 1.9:1 to 2.1:1.