Preparation method of lanthanum-manganese composite controlled by ionic liquid and application thereof
By using ionic liquid-controlled lanthanum-manganese complex preparation methods, the problems of low product selectivity and low conversion rate in the selective oxidation of cyclohexane were solved, achieving efficient KA oil preparation and reusable catalysts.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INSTITUTE OF PROCESS ENGINEERING CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2022-11-03
- Publication Date
- 2026-06-12
AI Technical Summary
In the existing technology, the catalysts for the selective oxidation of cyclohexane to prepare KA oil have problems such as low product selectivity, low conversion rate and difficulty in catalyst recovery. In addition, traditional heterogeneous catalysts have few exposed active sites on the surface and are difficult to desorb products.
A method for preparing lanthanum-manganese complexes using ionic liquids was employed. This method involves mixing soluble lanthanum salt, soluble manganese salt, ionic liquid, and urea, followed by hydrothermal reaction and calcination to form the lanthanum-manganese complex. The ionic liquid serves as a template and structure directing agent, controlling the specific surface area, crystal phase structure, surface acidity/basicity, and exposure of active sites of the catalyst.
The product selectivity and conversion rate of cyclohexane selective oxidation to KA oil were improved, the catalyst preparation process was simplified, and the catalyst could be reused.
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Figure CN117983296B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical catalysis and relates to a method for preparing lanthanum-manganese complexes controlled by ionic liquids and their applications. Background Technology
[0002] The green oxidation of saturated alkanes to produce high-value oxygen-containing chemicals is an important means to address existing resource scarcity and reduce carbon emissions. Among these methods, the efficient utilization of cyclohexane, obtained by the complete hydrogenation of benzene, has attracted widespread attention. The selective oxidation of cyclohexane to produce cyclohexanol / ketone (KA oil) is an important high-value conversion route. The resulting KA oil serves as a key intermediate in the synthesis of nylon 6 and nylon 66, possessing a broad downstream market and promising development prospects.
[0003] Traditionally, homogeneous catalysts using cobalt or manganese salts are used to catalyze the liquid-phase oxidation of cyclohexane to produce KA oil. The KA oil produced in this process is easily further oxidized to dicarboxylic acids. To reduce byproduct formation, the cyclohexane conversion rate is controlled at 3-5%, and the KA oil selectivity is around 80%. This process suffers from high energy consumption, low product selectivity, and difficulties in catalyst recovery. While recent research has explored heterogeneous catalysts such as single-metal oxides, molecular sieves, and supported catalysts, which have addressed catalyst recovery and utilization to some extent, they still suffer from issues such as limited exposure of active sites on the catalyst surface, difficulty in product desorption from the surface, and easy deep oxidation, resulting in low selectivity for the KA oil oxidation product. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for preparing lanthanum-manganese complexes regulated by ionic liquids and their applications.
[0005] This invention provides a method for preparing lanthanum-manganese complexes regulated by ionic liquids, comprising the following steps:
[0006] A mixture of soluble lanthanum salt, soluble manganese salt, ionic liquid, urea, and water was prepared to obtain a solution. The molar ratio of lanthanum in the soluble lanthanum salt, manganese in the soluble manganese salt, and urea was 1:(0.1–3.0):(1.0–3.0). The concentration of lanthanum in the soluble lanthanum salt was 0.01 mol / L–0.2 mol / L, and the concentration of the ionic liquid was 0.001 g / mL–0.05 g / mL. The anion of the ionic liquid was [Br]. - [Cl] - [HSO4] - [AlCl4] - [NTf2] - At least one of them;
[0007] The mixture was subjected to hydrothermal reaction at a temperature range of 120℃ to 180℃ for 6h to 48h to obtain a solid product.
[0008] The solid product was calcined at a temperature range of 400℃ to 800℃ for 1 h to 10 h to obtain the lanthanum-manganese composite.
[0009] The present invention also provides the application of the lanthanum-manganese complex obtained by the above-described method for preparing lanthanum-manganese complex regulated by ionic liquid in the selective oxidation of cyclohexane.
[0010] This invention provides a method for preparing lanthanum-manganese complexes using ionic liquids. Ionic liquids act as templates and structure-directing agents, influencing the specific surface area and crystal structure of the lanthanum-manganese complex, enabling better adsorption of reactants and desorption of products, thus improving catalytic activity. Furthermore, the introduction of ionic liquids into the preparation of the lanthanum-manganese complex can regulate its surface acidity / basicity, redox capacity, and the exposure of active sites. This lanthanum-manganese complex is used for the selective oxidation of cyclohexane to produce KA oil, improving upon the poor product selectivity and low reactant conversion rates of traditional cyclohexane selective oxidation to KA oil technology. Moreover, this preparation process utilizes ionic liquids for green synthesis of the lanthanum-manganese complex, is simple to prepare, and offers good reusability. Attached Figure Description
[0011] Figure 1 This is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 1;
[0012] Figure 2 Here is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 2;
[0013] Figure 3 Here is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 3;
[0014] Figure 4 Here is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 4;
[0015] Figure 5 This is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 5;
[0016] Figure 6 Here is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 6;
[0017] Figure 7 The image shows a scanning electron microscope (SEM) image of the lanthanum-manganese complex obtained in Example 7.
[0018] Figure 8 Here is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 8;
[0019] Figure 9 The image shows a scanning electron microscope (SEM) image of the lanthanum-manganese complex obtained in Comparative Example 1.
[0020] Figure 10 The image shows a scanning electron microscope (SEM) image of the lanthanum-manganese complex obtained in Comparative Example 2.
[0021] Figure 11 The image shows a scanning electron microscope (SEM) image of the lanthanum-manganese complex obtained in Comparative Example 3.
[0022] Figure 12 The image is a scanning electron microscope image of lanthanum oxycarbonate obtained in Comparative Example 4.
[0023] Figure 13 The image shows a scanning electron microscope (SEM) image of manganese trioxide obtained in Comparative Example 5.
[0024] Figure 14 The X-ray diffraction patterns are of the lanthanum-manganese complexes obtained in Examples 1, 2, and 3, and Comparative Examples 1 and 2. Detailed Implementation
[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0026] This invention provides a method for preparing lanthanum-manganese complexes regulated by ionic liquids and their applications, comprising the following steps:
[0027] S01: Weigh and mix soluble lanthanum salt, soluble manganese salt, ionic liquid, urea, and water to obtain a mixture. The molar ratio of lanthanum in the soluble lanthanum salt, manganese in the soluble manganese salt, and urea is 1:(0.1–3.0):(1.0–3.0). The concentration of lanthanum in the soluble lanthanum salt is 0.01 mol / L–0.2 mol / L, and the concentration of the ionic liquid is 0.001 g / mL–0.05 g / mL. The anion of the ionic liquid is [Br]. - [Cl] - [HSO4] - [AlCl4] - [NTf2] - At least one of them;
[0028] S02: The mixture is hydrothermally reacted at a temperature range of 120℃ to 180℃ for 6h to 48h to obtain a solid product;
[0029] S03: The solid product is calcined at a temperature range of 400℃ to 800℃ for 1h to 10h to obtain the lanthanum-manganese composite.
[0030] Preferably, the ionic liquid cation in step (1) is an imidazole cation, specifically, the ionic liquid is at least one of [Bmim][Br], [Bmim][NTf2], [Bmim][AlCl4], [Emim][HSO4], [Bmim][HSO4], [Hmim][HSO4], and [Omim][HSO4]. More preferably, the ionic liquid is at least one of [Bmim][Br], [Emim][HSO4], [Bmim][HSO4], [Hmim][HSO4], and [Omim][HSO4].
[0031] Preferably, the concentration of the ionic liquid is 0.005 g / mL to 0.02 g / mL, such as 0.005 g / mL, 0.01 g / mL, 0.015 g / mL, 0.02 g / mL, etc. If the concentration of the ionic liquid is lower than 0.005 g / mL, the content of the ionic liquid in the system will be low, and it will not be able to enhance the catalyst. If the concentration of the ionic liquid is higher than 0.02 g / mL, it will cause the catalyst particles to aggregate, reduce the surface active sites, and affect the catalytic activity.
[0032] Preferably, the molar ratio of lanthanum in the soluble lanthanum salt, manganese in the soluble manganese salt, and urea is 1:(0.5-1.5):(1.5-2.5), for example, La:Mn:CO(NH2)2 = 1:0.5:1.5, 1:0.5:2, 1:0.5:2.5, 1:1:1.5, 1:1:2, 1:1:2.5, 1:1.5:1.5, 1:1.5:2, 1:1.5:2.5, etc. If the molar ratio of lanthanum to manganese is less than 1:0.5, the proportion of lanthanum and manganese in the system will be too low, and the active phase cannot be formed. If the molar ratio of lanthanum to manganese is greater than 1:1.5, the crystal form and pH of the catalyst will change significantly, resulting in a decrease in selectivity. If the molar ratio of urea to lanthanum is less than 1.5, the alkaline source in the system is reduced, leading to incomplete precipitation of the metal salt and affecting the crystal form and structure of the catalyst. If the molar ratio of urea to lanthanum is greater than 2.5, the catalytic system is too alkaline, resulting in an accelerated catalyst growth rate, which is not conducive to the formation of nanoparticles. More preferably, the molar ratio of lanthanum in the soluble lanthanum salt, manganese in the soluble manganese salt, and urea is 1:(0.8-1.2):(1.8-2.2).
[0033] Preferably, in the mixture, the concentration of lanthanum in the soluble lanthanum salt is 0.04 g / mL to 0.14 g / mL, for example, 0.04 g / mL, 0.06 g / mL, 0.08 g / mL, 0.1 g / mL, 0.12 g / mL, or 0.14 g / mL. If the concentration is below 0.04 g / mL, more impurities will form, leading to reduced selectivity; if the concentration is above 0.12 g / mL, incomplete precipitation of metal ions will occur, reducing the number of catalytic active sites and affecting catalytic activity.
[0034] As a preferred embodiment of the method described in this invention, step S01 specifically involves: first, mixing a soluble lanthanum salt, a soluble manganese salt, urea, and water, and then adding an ionic liquid and mixing thoroughly. The soluble lanthanum salt is at least one of lanthanum nitrate, lanthanum chloride, and lanthanum acetate, and may contain water of crystallization or be anhydrous. Examples include La(NO3)3·6H2O, LaCl3·7H2O, La(CH3COOH)3·5H2O, and La2(C2O4)3·H2O. It is not limited to the lanthanum sources listed above; other commonly used lanthanum sources in the art that achieve the same effect can also be used in this invention, preferably La(NO3)3·6H2O. The soluble manganese salt is at least one of manganese nitrate, manganese chloride, manganese acetate, and manganese oxalate, and may contain water of crystallization or be anhydrous. Examples of manganese sources include Mn(NO3)2, MnCl2·4H2O, Mn(CH3COOH)2·4H2O, and Mn(C2O4)·2H2O, but are not limited to the manganese sources listed above. Other manganese sources commonly used in the art that can achieve the same effect can also be used in this invention, with Mn(NO3)2 being the preferred one.
[0035] Step S02 specifically involves heating the mixture in a hydrothermal reactor to 120°C–180°C and performing a hydrothermal reaction for 6–48 hours to obtain the reactant.
[0036] Preferably, the hydrothermal reaction temperature is 130℃~170℃, for example, 130℃, 140℃, 150℃, 160℃, 170℃, etc. The hydrothermal reaction time is 12h~36h, for example, 12h, 18h, 24h, 30h, 36h, etc. Further, after the hydrothermal reaction is completed, the mixture is cooled to room temperature, and solid-liquid separation is performed to obtain a solid product. The solid-liquid separation can be achieved using centrifugation, filtration, or other methods.
[0037] Preferably, the calcination in step (3) is carried out in air, and the heating rate is 0.5℃ / min to 4.5℃ / min, for example, 0.5℃ / min, 1.5℃ / min, 2.5℃ / min, 3.5℃ / min, 4.5℃ / min, etc.; the calcination temperature is 400℃ to 600℃, for example, 400℃, 450℃, 500℃, 550℃, 600℃, etc.; the calcination time is 1-5h, for example, 1h, 2h, 3h, 4h, 5h, etc.
[0038] This invention also provides the application of the lanthanum-manganese complex obtained by the above-described method for preparing lanthanum-manganese complex regulated by ionic liquid in the selective oxidation of cyclohexane.
[0039] Preferably, the reaction conditions for the selective oxidation of cyclohexane are: reaction temperature 100℃~160℃, oxygen pressure 0.8MPa~1.5MPa, reaction time 1h~4h, stirring speed 400rpm~800rpm, and the mass ratio of the lanthanum-manganese complex to cyclohexane is 1:(50~150).
[0040] The following specific examples illustrate the preparation method of lanthanum-manganese complexes. The compounds in the examples below can be prepared directly using existing methods. Of course, in other examples, they can also be purchased directly from the market, and are not limited thereto.
[0041] Example 1
[0042] Preparation of LMCO-[Bmim][HSO4] catalyst:
[0043] 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of deionized water were weighed and added to a beaker, and stirred until fully dissolved. 0.5 g of the ionic liquid [Bmim][HSO4] was added to the beaker, and the mixture was stirred vigorously at room temperature for 30 min until fully dissolved. The mixture was transferred to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, sealed, and placed in an oven at 150 °C for 24 h. After the hydrothermal reactor cooled naturally to room temperature, the solid was separated by centrifugation, washed alternately with water and anhydrous ethanol, and then dried in an 80 °C oven for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, the solid was calcined in air at a heating rate of 2.5 °C / min to 500 °C for 2 h, and then ground into powder in an agate mortar.
[0044] Detection:
[0045] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at a reaction temperature of 150 °C, an oxygen pressure of 1.0 MPa, and a stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 8.9%, and the selectivity of KA oil was 90.1%.
[0046] Example 2
[0047] Preparation of LMCO-[Bmim][NTf2] catalyst:
[0048] 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of water were weighed and added to a beaker, and stirred until fully dissolved. 0.5 g of the ionic liquid [Bmim][NTf2] was added to the beaker, and the mixture was stirred vigorously at room temperature for 30 min until fully dissolved. The mixture was transferred to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, sealed, and placed in an oven at 150 °C for 24 h. After the hydrothermal reactor cooled naturally to room temperature, the solid was separated by centrifugation, washed alternately with water and anhydrous ethanol, and then dried in an 80 °C oven for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, the solid was calcined at 500 °C for 2 h in an oxygen atmosphere at a heating rate of 2.5 °C / min, and then ground into powder in an agate mortar.
[0049] Detection:
[0050] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 8.1%, and the selectivity of KA oil was 85.0%.
[0051] Example 3
[0052] Preparation of LMCO-[Bmim][Br] catalyst:
[0053] 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of water were weighed and added to a beaker, and stirred until fully dissolved. 0.5 g of the ionic liquid [Bmim][Br] was added to the beaker, and the mixture was stirred vigorously at room temperature for 30 min until fully dissolved. The mixture was transferred to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, sealed, and placed in an oven at 150 °C for 24 h. After the hydrothermal reactor cooled naturally to room temperature, the solid was separated by centrifugation, washed alternately with water and anhydrous ethanol, and then dried in an 80 °C oven for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, the solid was calcined in air at a heating rate of 2.5 °C / min to 500 °C for 2 h, and then ground into powder in an agate mortar.
[0054] Detection:
[0055] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 ml high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 8.0%, and the selectivity of KA oil was 88.9%.
[0056] Example 4
[0057] Preparation of LMCO-[Emim][HSO4] catalyst:
[0058] 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of water were weighed and added to a beaker, and stirred until fully dissolved. 0.5 g of the ionic liquid [Emim][HSO4] was added to the beaker, and the mixture was stirred vigorously at room temperature for 30 min until fully dissolved. The mixture was transferred to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, sealed, and placed in an oven at 150 °C for 24 h. After the hydrothermal reactor cooled naturally to room temperature, the solid was separated by centrifugation, washed alternately with water and anhydrous ethanol, and then dried in an 80 °C oven for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, the solid was calcined in air at a heating rate of 2.5 °C / min to 500 °C for 2 h, and then ground into powder in an agate mortar.
[0059] Detection:
[0060] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 7.8%, and the selectivity of KA oil was 85.3%.
[0061] Example 5
[0062] Preparation of LMCO-[Hmim][HSO4] catalyst:
[0063] 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of water were weighed and added to a beaker, and stirred until fully dissolved. 0.5 g of the ionic liquid [Hmim][HSO4] was added to the beaker, and the mixture was stirred vigorously at room temperature for 30 min until fully dissolved. The mixture was transferred to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, sealed, and placed in an oven at 150 °C for 24 h. After the hydrothermal reactor cooled naturally to room temperature, the solid was separated by centrifugation, washed alternately with water and anhydrous ethanol, and then dried in an 80 °C oven for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, the solid was calcined in air at a heating rate of 2.5 °C / min to 500 °C for 2 h, and then ground into powder in an agate mortar.
[0064] Detection:
[0065] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 8.6%, and the selectivity of KA oil was 86.7%.
[0066] Example 6
[0067] Preparation of LMCO-[Omim][HSO4] catalyst:
[0068] 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of water were weighed and added to a beaker, and stirred until fully dissolved. 0.5 g of the ionic liquid [Omim][HSO4] was added to the beaker, and the mixture was stirred vigorously at room temperature for 30 min until fully dissolved. The mixture was transferred to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, sealed, and placed in an oven at 150 °C for 24 h. After the hydrothermal reactor cooled naturally to room temperature, the solid was separated by centrifugation, washed alternately with water and anhydrous ethanol, and then dried in an 80 °C oven for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, the solid was calcined in air at a heating rate of 2.5 °C / min to 500 °C for 2 h, and then ground into powder in an agate mortar.
[0069] Detection:
[0070] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 8.6%, and the selectivity of KA oil was 88.4%.
[0071] Example 7
[0072] LMCO-[Bmim][HSO4]
[0073] Weigh 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of water into a beaker and stir until fully dissolved. Add 0.4 g of [Bmim][HSO4] to the beaker and stir vigorously at room temperature for 30 min until fully dissolved. Transfer the mixture to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, seal it, and place it in an oven at 150 °C for 24 h. After the hydrothermal reactor cools naturally to room temperature, the solid is separated by centrifugation, washed alternately with water and anhydrous ethanol, and then dried in an oven at 80 °C for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, calcine the solid at 500 °C for 2 h in air at a heating rate of 2.5 °C / min, and grind the resulting solid into powder in an agate mortar.
[0074] Detection:
[0075] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 7.5%, and the selectivity of KA oil was 87.8%.
[0076] Example 8
[0077] LMCO-[Bmim][HSO4]-0.6g ILs
[0078] Weigh 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 ml of deionized water into a beaker and stir until fully dissolved. Add 0.6 g of [Bmim][HSO4] to the beaker and stir vigorously at room temperature for 30 min until fully dissolved. Transfer the mixture to a 100 ml hydrothermal reactor with a polytetrafluoroethylene substrate, seal it, and place it in an oven at 150 °C for 24 h. After the hydrothermal reactor cools naturally to room temperature, the solid is separated by centrifugation and washed alternately with water and anhydrous ethanol. The collected solid is then dried in an oven at 80 °C for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, calcine the solid at 500 °C for 2 h in air at a heating rate of 2.5 °C / min. Grind the resulting solid into powder in an agate mortar.
[0079] Detection:
[0080] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 ml high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 7.2%, and the selectivity of KA oil was 84.8%.
[0081] Comparative Example 1
[0082] Weigh 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of deionized water into a beaker and stir until fully dissolved. Transfer the mixture to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, seal it, and place it in an oven at 150 °C for 24 h. After the hydrothermal reactor cools naturally to room temperature, the solid is separated by centrifugation, washed alternately with water and anhydrous ethanol, and then dried in an oven at 80 °C for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, calcine it at 500 °C for 2 h in air at a heating rate of 2.5 °C / min, and grind the resulting solid into powder in an agate mortar.
[0083] Detection:
[0084] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 7.0%, and the selectivity of KA oil was 85.4%.
[0085] Comparative Example 2
[0086] Preparation of LMCO-[Bmim][BF4] catalyst:
[0087] 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of water were weighed and added to a beaker, and stirred until fully dissolved. 0.5 g of the ionic liquid [Bmim][BF4] was added to the beaker, and the mixture was stirred vigorously at room temperature for 30 min until fully dissolved. The mixture was transferred to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, sealed, and placed in an oven at 150 °C for 24 h. After the hydrothermal reactor cooled naturally to room temperature, the solid was separated by centrifugation, washed alternately with water and anhydrous ethanol, and then dried in an 80 °C oven for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, the solid was calcined in air at a heating rate of 2.5 °C / min to 500 °C for 2 h, and then ground into powder in an agate mortar.
[0088] Detection:
[0089] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 4.0%, and the selectivity of KA oil was 59.3%.
[0090] Comparative Example 3
[0091] Preparation of LMCO-[Bmim][CH3COOH] catalyst:
[0092] Weigh 0.005 mol La(NO3)2·6H2O, 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of water into a beaker and stir until fully dissolved. Add 0.5 g of the ionic liquid [Bmim][CH3COOH] to the beaker and stir vigorously at room temperature for 30 min until fully dissolved. Transfer the mixture to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, seal it, and place it in an oven at 150 °C for 24 h. After the hydrothermal reactor cools naturally to room temperature, the solid is separated by centrifugation and washed alternately with water and anhydrous ethanol. The collected solid is then dried in an oven at 80 °C for 12 h to obtain the precursor of the lanthanum-manganese complex. Finally, calcine the solid at 500 °C for 2 h in air at a heating rate of 2.5 °C / min. Grind the resulting solid into powder in an agate mortar.
[0093] Detection:
[0094] 0.1 g of lanthanum-manganese composite catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 6.5%, and the selectivity of KA oil was 87.7%.
[0095] Comparative Example 4
[0096] Weigh 0.005 mol La(NO3)2·6H2O, 0.01 mol CO(NH2)2, and 50 mL of water into a beaker and stir until fully dissolved. Add 0.5 g of [Bmim][HSO4] to the beaker and stir vigorously at room temperature for 30 min until fully dissolved. Transfer the mixture to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, seal it, and place it in an oven at 150 °C for 24 h. After the hydrothermal reactor cools naturally to room temperature, the solid is separated by centrifugation, washed alternately with water and anhydrous ethanol, and then dried in an oven at 80 °C for 12 h to obtain the lanthanum oxide precursor. Finally, calcine the precursor in air at a heating rate of 2.5 °C / min to 500 °C for 2 h, and grind the resulting solid into powder in an agate mortar.
[0097] Detection:
[0098] 0.1 g of lanthanum oxide catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at 150 °C, oxygen pressure of 1.0 MPa, and stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 3.6%, and the selectivity of KA oil was 70.0%.
[0099] Comparative Example 5
[0100] Weigh 0.005 mol Mn(NO3)2, 0.01 mol CO(NH2)2, and 50 mL of deionized water into a beaker and stir until fully dissolved. Add 0.5 g of [Bmim][HSO4] to the beaker and stir vigorously at room temperature for 30 min until fully dissolved. Transfer the mixture to a 100 mL hydrothermal reactor with a polytetrafluoroethylene substrate, seal it, and place it in an oven at 150 °C for 24 h. After the hydrothermal reactor cools naturally to room temperature, the solid is separated by centrifugation and washed alternately with water and anhydrous ethanol. The collected solid is then dried in an oven at 80 °C for 12 h to obtain the precursor of manganese oxide. Finally, calcine the solid at 500 °C for 2 h in air at a heating rate of 2.5 °C / min. Grind the resulting solid into powder in an agate mortar.
[0101] Detection:
[0102] 0.1 g of manganese oxide catalyst and 10 g of cyclohexane were weighed and placed in a 100 mL high-pressure reactor for catalyst performance evaluation. The reaction was carried out at a temperature of 150 °C, an oxygen pressure of 1.0 MPa, and a stirring speed of 600 rpm for 2 h. After the reaction was completed, the samples were cooled and analyzed by gas chromatography for cyclohexanol / ketone and liquid chromatography for esters and other byproducts. The conversion rate of cyclohexane was 6.6%, and the selectivity of KA oil was 80.4%.
[0103] Table 1 shows that ionic liquids can modulate the catalytic activity of the lanthanum-manganese complex, and imidazole ionic liquids exhibit higher catalytic effects on the complex than on the single-component compound. The influence of different cation and anion groups on the catalyst was investigated by modifying the cations and anions of the ionic liquids. Specifically, the anion selection for imidazole ionic liquids was [Br]. - [NTf2] - and [HSO4] - At this time, the modification of the catalyst has a greater enhancing effect, simultaneously improving the conversion rate of cyclohexane selective oxidation and the selectivity of KA oil; while choosing [BF4]... - and [CH3COOH] - At the same time, the modification of the catalyst has an inhibitory effect. In addition, when examining the effect of imidazole cations on the lanthanum-manganese complex, it was found that with the increase of the alkyl chain of the ionic liquid cation, the conversion of cyclohexane first increased and then decreased, but the selectivity did not change much.
[0104] Table 1
[0105]
[0106] Figure 1 This is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 1; Figure 2 Here is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 2; Figure 3 Here is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 3;
[0107] Figure 4 Here is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 4; Figure 5 This is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 5; Figure 6 Here is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 6; Figure 7 The image shows a scanning electron microscope (SEM) image of the lanthanum-manganese complex obtained in Example 7. Figure 8 Here is a scanning electron microscope image of the lanthanum-manganese complex obtained in Example 8; Figure 9 The image shows a scanning electron microscope (SEM) image of the lanthanum-manganese complex obtained in Comparative Example 1. Figure 10 The image shows a scanning electron microscope (SEM) image of the lanthanum-manganese complex obtained in Comparative Example 2. Figure 11 The image shows a scanning electron microscope (SEM) image of the lanthanum-manganese complex obtained in Comparative Example 3. Figure 12 The image is a scanning electron microscope image of lanthanum oxycarbonate obtained in Comparative Example 4. Figure 13 This is a scanning electron microscope (SEM) image of manganese trioxide obtained in Comparative Example 5. (From...) Figures 1-13 It can be seen that the anion used is [HSO4]. -The morphology of the lanthanum-manganese complex regulated by the ionic liquid was significantly altered. The catalyst exhibited spherical particles of approximately 100 nm with uniform particle distribution, exposing more active sites. In contrast, the comparative example 1, which did not use the ionic liquid, showed a plate-like stacked structure, with active sites covered, thus affecting catalytic performance.
[0108] Table 2
[0109]
[0110] Figure 14 The X-ray diffraction patterns of the lanthanum-manganese complexes obtained in Examples 1, 2, and 3, and Comparative Examples 1 and 2, further demonstrate that the structure-directing and template effects of ionic liquids can regulate the crystal phase structure of the lanthanum-manganese complexes. When the ionic liquid is [Bmim][Br] or [Bmim][NTf2], the crystal form of the lanthanum-manganese complex is tetragonal La2O2CO3 and cubic Mn2O3; when the ionic liquid is [Emim][HSO4], [Bmim][HSO4], [Hmim][HSO4], or [Omim][HSO4], the crystal form of the lanthanum-manganese complex is hexagonal La2O2CO3 and cubic Mn2O3; when the ionic liquid is [Bmim][BF4], the crystal form of the lanthanum-manganese complex is a mixed crystal form of LaOF, LaF3, and MnCO3.
[0111] Table 2 shows the X-ray diffraction and specific surface area analysis results of the lanthanum-manganese composite. The data demonstrate that the introduction of ionic liquids significantly reduces the crystallite size and increases the specific surface area of the catalyst, providing a favorable foundation for the exposure of active surfaces and the dispersion of active sites. Furthermore, comparing the effects of ionic liquids with different carbon chain lengths on the catalyst structure reveals that as the alkyl chain length increases, the pore size and pore volume of the corresponding catalyst also increase, proving the template effect of ionic liquids in regulating the catalyst process.
[0112] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.
Claims
1. A method for preparing lanthanum-manganese complexes regulated by ionic liquids, characterized in that, The method includes the following steps: A soluble lanthanum salt, a soluble manganese salt, an ionic liquid, urea, and water are weighed and mixed to obtain a mixture. The molar ratio of lanthanum in the soluble lanthanum salt, manganese in the soluble manganese salt, and urea is 1:(0.5~1.5):(1.5~2.5). The soluble lanthanum salt is at least one selected from lanthanum nitrate, lanthanum chloride, and lanthanum acetate. The concentration of lanthanum in the soluble lanthanum salt is 0.1 mol / L~0.2 mol / L. The concentration of the ionic liquid is 0.005-0.02 g / mL, and the anion of the ionic liquid is [Br]. - [Cl] - [HSO4] - [AlCl4] - [NTf2] - At least one of them; The mixture was subjected to hydrothermal reaction at a temperature range of 120℃~180℃ for 6 h~48 h to obtain a solid product. The solid product was calcined at a temperature range of 400℃ to 800℃ for 1 h to 10 h to obtain the lanthanum-manganese composite.
2. The method according to claim 1, characterized in that, The cation of the ionic liquid is an imidazole cation.
3. The method according to claim 1 or 2, characterized in that, The ionic liquid is at least one of [Bmim][Br], [Bmim][NTf2], [Bmim][AlCl4], [Emim][HSO4], [Bmim][HSO4], [Hmim][HSO4], and [Omim][HSO4].
4. The method according to claim 1, characterized in that, The ionic liquid is at least one of [Emim][HSO4], [Bmim][HSO4], [Hmim][HSO4], and [Omim][HSO4].
5. The method according to claim 1, characterized in that, The soluble manganese salt is at least one of manganese nitrate, manganese chloride, manganese acetate, and manganese oxalate.
6. The application of a lanthanum-manganese complex obtained by the method according to any one of claims 1 to 5 in the selective oxidation of cyclohexane.