A catalyst for the oxidation of naphthenes and a process for its preparation and use

Abstract

The application discloses a catalyst for cycloalkane oxidation and a preparation method and application thereof. A vanadium compound is used as a catalyst, is dispersed in cycloalkane, a reaction system is sealed, stirring is carried out, an oxidant is introduced, a set temperature and pressure are maintained, and stirring reaction is carried out. After the reaction is completed, a reaction liquid is subjected to post-treatment, and a product cycloalkyl alcohol and a cycloalkyl ketone are obtained. The application has the advantages of high selectivity of the cycloalkyl alcohol and the cycloalkyl ketone, low reaction temperature, few by-products, small environmental influence and the like. In addition, the cycloalkyl hydroperoxide has low content and high safety factor, and the application provides a method for synthesizing cycloalkyl alcohol and cycloalkyl ketone through selective catalytic oxidation of cycloalkane, which is efficient, feasible and safe.

Description

TECHNICAL FIELD

[0001] The present application relates to the production process of cycloalkane oxidation, belonging to the field of fine chemical industry. BACKGROUND

[0002] Cycloalkane oxidation reaction mainly generates cycloalkyl ketone and cycloalkyl alcohol. Among them, cyclohexane as a representative of cycloalkane is a cycloalkane with extremely large use amount. The mixture generated by the oxidation of cyclohexane is usually called KA oil (ketone / alcohol oil), which is an important chemical raw material. Most of the KA oil is used to produce nylon 66 and nylon 6 precursors, and can also be used to prepare intermediates of dyes, paints, medicines and other chemicals, and can also be used to prepare rubber anti-aging agents, flavors and fruit mildew-proof agents, etc. The KA oil mixture is easily oxidized to generate adipic acid, which is an important reactant for preparing certain condensation polymers, including polyamide and nylon 66, etc.

[0003] The traditional process for preparing KA oil, i.e. cyclohexanone and cyclohexanol mixture, from cyclohexane oxidation is carried out in two steps. First, cyclohexane is oxidized to prepare an oxidation solution containing cyclohexyl hydroperoxide (CyOOH). The second step is to catalyze the decomposition of CyOOH to obtain KA oil with chromium ion or cobalt ion as homogeneous catalyst. With the restriction of regulations in various countries around the world, the replacement of catalysts such as chromium and cobalt which are harmful to the environment is becoming more and more urgent.

[0004] Most technologies begin to focus on using different types of homogeneous catalysts to catalyze the oxidation of cyclohexane with hydrogen peroxide to prepare KA oil. At present, most efforts are concentrated on the use of molecular sieves, polymers and silica supported transition metal complexes, etc. Although some of these materials show relatively good activity and selectivity for K / A oil, most of them will be deactivated 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, the mass percentage of Au is 1-5%, and the mass percentage of cobalt oxide is 95-99%. The reaction is carried out at 1.5 MPa oxygen pressure and 150℃ for 3h, the conversion rate of cyclohexane reaches 8.5%, and the total selectivity is 91.4%. Patent CN111943808A discloses a method for synergistically catalyzing oxidation of cycloalkane by MOFs PCN-224 (Mn) / Zn (II) salt, PCN-224 (Mn) (0.001%-5%, g / mol) and Zn (II) salt (0.01%-10%, mol / mol) are dispersed in cycloalkane, the reaction system is sealed, stirred and heated to 120℃, oxygen is introduced to 1.0 MPa, and stirred for 8.0h, the conversion rate of cyclohexane is 7.00%, the selectivity of cyclohexanol is 75.58%, and the selectivity of cyclohexanone is 17.49%.

[0006] Although the heterogeneous noble metal catalyst has good cyclohexane oxidation activity, the cost of the catalyst is high, which greatly limits its industrial application prospect. 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 preparing KA oil by oxidizing cyclohexane, using vanadium phosphorus oxide catalyst to catalyze the reaction, and the vanadium phosphorus oxide is prepared by the following method: V205, phosphoric acid and distilled water are reacted at 100-120℃ for 16-24 hours, the obtained solid product is added to isobutyl alcohol solvent, and reacted at 90-130℃ for 16-24 hours to obtain the catalyst precursor, and after activation, the catalyst is obtained. The conversion rate of cyclohexane catalyzed by 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 oxidizing cyclohexane, using vanadium phosphorus oxide catalyst to catalyze the reaction, and the catalyst is prepared by the following method: V205 and phosphoric acid are reacted in aqueous solution environment, the obtained powder product is added to isobutyl alcohol, and reacted at 30-90℃ under normal pressure for 4-8 hours, the solvent is evaporated, and the dry solid is obtained to obtain the catalyst powder; or the catalyst is prepared into a supported type. The vanadium phosphorus oxide catalyst is used in the preparation of cyclohexanol by oxidizing cyclohexane, and a new method for preparing cyclohexanol by oxidizing cyclohexane is provided. By using the method of the present application, the conversion rate of cyclohexane and the selectivity of cyclohexanol are improved; especially the selectivity of cyclohexanone is greatly reduced, high-purity cyclohexanol is obtained, and the cost of separating cyclohexanol and cyclohexanone in industry is reduced. This also shows that vanadium compounds can be used in the catalytic oxidation of cycloalkanes. However, the selectivity of the vanadium phosphorus oxide catalyst is still low, and the activity of the catalyst needs to be further improved. SUMMARY

[0007] The problem to be solved by the present application is that one of the main industrial preparation methods of cyclohexanone is cyclohexane oxidation method. The commonly used in industry is non-catalytic oxidation process, which has the disadvantage of low selectivity of generating cyclohexyl hydroperoxide, and the organic acids such as adipic acid, glutaric acid and succinic acid produced by over-oxidation have adverse effects on the activity of the catalyst for subsequent decomposition reaction, resulting in low molecular yield of cyclohexyl hydroperoxide decomposition reaction to generate cyclohexanone and cyclohexanol, low ketone-alcohol ratio, and increased production cost.

[0008] The purpose of the present application is 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, and to provide a cycloalkane oxidation catalyst and a preparation method and application thereof.

[0009] The main technical scheme of the present application is that the cycloalkane oxidation catalyst comprises at least one vanadium compound selected from the following structures:

[0010] .

[0011] In the present application, the cycloalkane is a cycloalkane containing three or more carbon atoms, and also includes a cycloalkane containing an alkyl substituent.

[0012] In the present application, the preferred cycloalkane is one of cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cyclododecane.

[0013] The present application also provides a preparation method of the catalyst for cycloalkane oxidation, and the preparation steps are: 5-hydroxyquinoxaline, 8-chloro-5-hydroxyquinoxaline, and 8-fluoro-5-hydroxyquinoxaline are respectively reacted with vanadyl acetylacetonate in a hydrocarbon solvent, and after the reaction is completed, the catalyst is obtained by standing and filtering.

[0014] In the preparation method of the catalyst, the hydrocarbon solvent is selected from one of benzene, toluene, xylene, cyclohexane, cyclopentane, n-hexane, and n-pentane; and preferably toluene, cyclohexane, and n-hexane.

[0015] In the preparation method of the catalyst, the reaction temperature is -10°C to 100°C; and preferably 30 to 80°C.

[0016] In the preparation method of the catalyst, the ratio of 5-hydroxyquinoxaline to vanadyl acetylacetonate in the reactants is 1.9:1 to 2.1:1; and preferably the ratio is 2:1.

[0017] In the preparation method of the catalyst, the reaction time can be selected according to the reaction condition, and generally can be selected as 1 to 1800 minutes; and preferably 30 to 600 minutes.

[0018] In the preparation method of the catalyst, the temperature for standing and filtering after the reaction is completed can be selected according to the reactants and products, and generally can be selected as -10°C to 50°C; and preferably 0°C to 25°C.

[0019] In the preparation method of the catalyst, the time for standing and filtering after the reaction is completed can be selected according to the reactants and products, and generally can be selected as 1 to 1200 minutes; and preferably 10 to 600 minutes.

[0020] In the preparation method of the catalyst, the catalyst can be dried by volatilizing the solvent under natural conditions, or dried by baking in an oven.

[0021] The present application also provides the use of a catalyst for the oxidation of a cycloalkane in a process for the preparation of a mixture of an alkyl alcohol and an alkyl ketone from a cycloalkane, wherein the conversion of the cycloalkane is not less than 90%, said process comprising the oxidation of the cycloalkane in a homogeneous phase, catalysed by the vanadium compound, wherein the amount of catalyst is between 0.01% and 0.1% by weight of the total weight of the reaction mixture, and wherein the vanadium compound is dissolved in the liquid phase.

[0022] In the use of the present application, a vanadium compound is used as a catalyst, which is dispersed in a cycloalkane, the reaction system is sealed, the temperature is raised by stirring, an oxidizing agent is introduced, the temperature and pressure are maintained, the reaction is stirred, and after the reaction is completed, the reaction liquid is treated to obtain the products cycloalkyl alcohol and cycloalkyl ketone.

[0023] In the use of the present application, the amount of catalyst is between 0.01% and 0.1% by weight of the total weight of the reaction mixture.

[0024] In the use of the present application, preferably the amount of catalyst is between 0.01% and 0.05% by weight of the total weight of the reaction mixture.

[0025] In the use of the present application, the reaction pressure is between 0.10 and 10 MPa.

[0026] In the use of the present application, preferably the reaction pressure is between 0.10 and 5 MPa.

[0027] In the use of the present application, the stirring rate is between 300 and 1200 rpm.

[0028] In the use of the present application, preferably the stirring rate is between 500 and 1000 rpm.

[0029] In the use of the present application, the reaction time can be determined according to the reactants, and the reaction time is usually between 1 and 600 minutes.

[0030] In the use of the present application, the reaction time can be determined according to the reactants, and the reaction temperature is usually between 0°C and 200°C; preferably the reaction temperature is between 60°C and 180°C.

[0031] In the use of the present application, the oxidizing agent is not particularly limited, and for example, air, oxygen, dimethyl sulfoxide, dibutyl sulfoxide, diphenyl sulfoxide, tetramethylene sulfoxide, or the like can be used. Two or more of these oxidizing agents can be mixed. From the viewpoint of productivity and ease of operation, it is preferable to use air, oxygen, dimethyl sulfoxide, tetramethylene sulfoxide, or a mixture of these oxidizing agents.

[0032] In the present application, preferably the oxidizing agent is oxygen, air, or a mixture thereof in any ratio.

[0033] In the present application, when oxygen is used as the oxidizing agent, the oxygen can also be used in combination with other gases, for example, the oxygen can be used in combination with air or an inactive gas (hydrogen, hydrogen, etc.).

[0034] In the present application, when air or oxygen is used as the oxidizing agent, the method for supplying the air or oxygen is not particularly limited, for example, the following methods can be used: a method in which the gas phase in contact with the reaction solution is replaced with air or oxygen, a method in which the gas phase in contact with the reaction solution is circulated in air or oxygen, a method in which air or oxygen is blown into the reaction solution, and the like.

[0035] Advantages: The method described in the present application has the advantages of high selectivity of cycloalkyl alcohol and cycloalkyl ketone, low reaction temperature, few by-products, and small environmental impact. In addition, the cycloalkyl hydroperoxide content of the present application is low, and the safety factor is high. The present application provides a method for selectively catalytic oxidation of cycloalkane to synthesize cycloalkyl alcohol and cycloalkyl ketone, which is efficient, feasible and safe. DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be further described below in conjunction with examples.

[0037] The following examples will further illustrate the present application, but do not limit the content of the present application. All reagents used in the examples are commercially available chemical pure reagents.

[0038] Example 1

[0039] In a 100 ml flask, 2.9 g (0.02 mol) of 5-hydroxyquinoxaline and 2.6 g (0.01 mol) of vanadyl acetylacetonate were added, 50 ml of cyclohexane was added, the resulting dark green mixture was heated to react for 3 hours to obtain a dark solution. Cool to room temperature, after 3 hours, filter out the solid 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.

[0040] Example 2

[0041] In a 100 ml flask, 3.6 g (0.02 mol) of 8-chloro-5-hydroxyquinoxaline and 2.6 g (0.01 mol) of vanadyl acetylacetonate were added, 70 ml of n-hexane was added, the resulting dark mixture was heated to react for 3.5 hours to obtain a dark solution. Cool to room temperature, after 4 hours, filter out the solid 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.

[0042] Example 3

[0043] In a 100 ml Schlenk flask, 0.33 g (0.002 mol) of 8-fluoro-5-hydroxyquinoxaline and 0.26 g (0.001 mol) of acetylacetonato vanadium oxide were added, 20 ml of toluene was added to obtain a dark mixture, which was heated for 2 hours, after which it was left to stand, cooled to about 0°C, after 0.5 hours the solid was filtered off to obtain a dark product, which was washed with cyclohexane and dried to obtain 0.12 g of dark solid a3, LC-MS (ESI) m / z: 393.1.

[0044] Example 4

[0045] In a 100 ml autoclave lined with polytetrafluoroethylene, 42 g (0.5 mol) of cyclohexane and 0.02% of solid a1 (0.036 g) were added, it was stirred and heated to 140°C, oxygen was introduced (1.0 MPa), it was stirred at 800 rpm for 2 hours. After the reaction was complete, 2 g of triphenylphosphine was added to the reaction mixture, it was stirred at room temperature for 1 hour, a sample was taken for gas chromatography analysis. The conversion of cyclohexane was 6.1%, the selectivity of cyclohexanol was 68%, the selectivity of cyclohexanone was 24%.

[0046] Example 5

[0047] In a 100 ml autoclave lined with polytetrafluoroethylene, 42 g (0.5 mol) of cyclohexane and 0.01% of solid a2 (0.02 g) were added, it was stirred and heated to 180°C, oxygen was introduced (1.0 MPa), it was stirred at 900 rpm for 2 hours. After the reaction was complete, 2 g of triphenylphosphine was added to the reaction mixture, it was stirred at room temperature for 1 hour, a sample was taken for gas chromatography analysis. The conversion of cyclohexane was 6.3%, the selectivity of cyclohexanol was 70%, the selectivity of cyclohexanone was 26%.

Claims

1. A catalyst for the oxidation of cycloalkanes, characterized in that The catalyst is a vanadium compound comprising at least one structure selected from the group consisting of: 。 2. The method of claim 1, wherein the catalyst is prepared by The preparation steps are: 5-hydroxyquinoxaline, 8-chloro-5-hydroxyquinoxaline, 8-fluoro-5-hydroxyquinoxaline respectively reacts with acetylacetone vanadyl in a hydrocarbon solvent, the reaction temperature is 30-80℃, after the reaction is completed, standing and filtering to obtain the catalyst.

3. The production method according to claim 2, characterized by The hydrocarbon solvent is selected from one of benzene, toluene, xylene, cyclohexane, cyclopentane, n-hexane, n-pentane.

4. The production method according to claim 3, characterized by The hydrocarbon solvent is selected from one of toluene, cyclohexane, n-hexane.

5. The production method according to claim 2, wherein The ratio of 5-hydroxyquinoxaline to acetylacetone vanadyl in the reactants is 2:

1.

6. Use of a catalyst for the oxidation of cycloparaffins according to claim 1, characterized in that The method for preparing a mixture of alkyl alcohol and alkyl ketone from cycloalkane, wherein the conversion rate of cycloalkane is not less than 90%, the method comprises oxidizing cycloalkane in a homogeneous phase, and the oxidation is catalyzed by the vanadium compound, wherein the catalyst amount accounts for 0.01%-0.1% of the total weight of the reaction mixture, and wherein the vanadium compound is dissolved in the liquid phase.

7. The catalyst of claim 1 wherein The cycloalkane is a cycloalkane comprising three or more carbon atoms, also including cycloalkanes containing alkyl substituents.

8. The catalyst of claim 7, wherein The cycloalkane is one of cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cyclododecane.

9. The use according to claim 6, characterized in that The catalyst amount accounts for 0.01%-0.05% of the total weight of the reaction mixture.

10. The use according to claim 6, characterized in that The reaction pressure is 0.10-10 MPa, the reaction time is 1-600 minutes, the reaction temperature is 0℃-200℃, and the stirring rate is 300-1200 rpm.

11. Use according to claim 10, wherein The reaction pressure is 0.10-5 MPa, the reaction temperature is 60℃-180℃, and the stirring rate is 500-1000 rpm.

12. The use according to claim 6, characterized in that The oxidant is oxygen, air or any ratio mixture thereof.

Images