Cesium-based bimetallic catalyst, its preparation method and application

Abstract

The application discloses a cesium-based bimetallic catalyst and a preparation method and application thereof, and belongs to the technical field of catalysts. The cesium-based bimetallic catalyst comprises a carrier and cesium and zirconium supported on the carrier; in the preparation, the cesium salt and the zirconium salt are co-dissolved in water, then the carrier is immersed in the obtained solution, and then dried, and then calcined in an air atmosphere at 450-550 DEG C for 2-5 h, and then heated to 300-700 DEG C in a reducing atmosphere, and then kept for 3-5 h, and then obtained. The application develops a kind of heterogeneous catalyst for the process of preparing N-methyl morpholine from methanol and morpholine. The catalyst has high activity, and has activity and selectivity comparable to noble metal catalysts, and can realize efficient synthesis of N-methyl morpholine; moreover, the preparation method is simple, and the requirement for reaction equipment is not high; meanwhile, the catalyst has good stability, can be recycled for dozens of times, and has good industrial prospect.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a cesium-based bimetallic catalyst, its preparation method, and its application. Background Technology

[0002] N-Methylmorpholine, as an organic chemical intermediate, possesses the dual properties of tertiary amine and ether, and has a wide range of applications. It can be used as a catalyst in the production of polyurethane foam and in the synthesis of apocillin, ampicillin, and carboxybenzylpenicillin. It can also be used as a surfactant, extractant, and corrosion inhibitor. Its derivative, N-methylmorpholine oxide, is an ideal spinning solvent for manufacturing Lyocel natural fibers and Newcell synthetic fiber filaments. For these reasons, the current demand for N-methylmorpholine is substantial, making the development of a large-scale preparation process for N-methylmorpholine of great significance.

[0003] The synthesis processes of N-methylmorpholine can be classified according to the raw materials into the morpholine method, the N-methyldiethanolamine method, the diethanolamine method, the diethylene glycol method, and the dichloroethyl ether method. Among them, the N-methyldiethanolamine method has few by-products and high yield, but the raw materials are expensive and difficult to source, and it requires the use of precious metals as catalysts, so it is difficult to industrialize. The diethanolamine method, which reacts with highly toxic dimethyl sulfate, has a yield of 81% to 95%, but it does not meet environmental protection requirements and there are no reports of industrialization. The diethylene glycol method requires three steps, which is complex and requires multiple catalysts, making it difficult to industrialize. The dichloroethyl ether method has difficult raw material sources and generates a large amount of industrial wastewater and waste residue, so it has also not been industrialized.

[0004] Existing methods for synthesizing N-methylmorpholine mainly fall into three categories: one uses morpholine as a starting material; the second synthesizes morpholine intermediates; and the third generates it directly through condensation cyclization reactions, either independently of morpholine intermediates or with external sources. Among these, the morpholine method is considered the most promising route, but it currently faces challenges such as complex catalyst preparation processes and difficulties in catalyst recovery. Summary of the Invention

[0005] In view of the above-mentioned prior art, the present invention provides a cesium-based bimetallic catalyst, its preparation method and application, to solve the problems of difficult preparation, low catalytic efficiency and difficult recovery of catalysts used in the preparation of N-methylmorpholine in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is to provide a cesium-based bimetallic catalyst, comprising a support and cesium and zirconium supported on the support.

[0007] Based on the above technical solution, the present invention can be further improved as follows.

[0008] Furthermore, the cesium loading on the support is 2wt%~30wt%, and the zirconium loading is 5wt%~10wt%.

[0009] Furthermore, the support is at least one of HAP, SiO2, MgO, Al2O3, SBA-15, MCM-41, ZSM-5, ZrO2 and ZnO.

[0010] This invention also discloses a method for preparing the above-mentioned cesium-based bimetallic catalyst, comprising the following steps: S1: Dissolve cesium salt and zirconium salt together in water to obtain a mixed solution; S2: Immerse the carrier in the mixed solution at room temperature for 2-5 hours; S3: Allow the carrier impregnated with the mixed solution to air dry naturally, and then dry it at 90~120 ℃ for 10~16 h; S4: The dried sample was calcined in air at 450~550 ℃ for 2~5 h, and then air-cooled to room temperature to obtain the bimetallic catalyst precursor. S5: The bimetallic catalyst precursor is heated to 300~700 ℃ in a reducing atmosphere and held for 3~5 h to obtain the cesium-based bimetallic catalyst.

[0011] Furthermore, the concentration of cesium salt in the mixed solution is 0.07~0.25 g / mL, and the concentration of zirconium salt is 0.1~0.2 g / mL.

[0012] Furthermore, the cesium salts are CsNO3, CsCl, or CH3COOCs; the zirconium salts are ZrCl4·nH2O, Zr(NO3)4·5H2O, ZrOCl2·8H2O, or ZrO(NO3)2.

[0013] Furthermore, the reducing atmosphere is a mixture of H2 and N2, with the volume content of H2 in the mixture being 10%.

[0014] Furthermore, the heating rate in S5 is 2~5 ℃ / min.

[0015] The present invention also discloses the application of the above-mentioned cesium-based bimetallic catalyst in the catalytic reaction of morpholine and methanol to prepare N-methylmorpholine.

[0016] Furthermore, the preparation of N-methylmorpholine includes the following steps: Morpholine and methanol are mixed at a molar ratio of 0.5 to 10:247, and then a cesium-based bimetallic catalyst is added to the mixture. After stirring, the mixture is reacted at a temperature of 140 to 220 °C for 1 to 6 h in an inert atmosphere to obtain N-methylmorpholine.

[0017] The beneficial effects of this invention are as follows: This invention develops a heterogeneous catalyst for the preparation of N-methylmorpholine from methanol and morpholine. This catalyst exhibits high activity, comparable to noble metal catalysts, enabling the efficient synthesis of N-methylmorpholine. Furthermore, the preparation method is simple and requires minimal reaction equipment. Simultaneously, the catalyst demonstrates good stability, can be cycled dozens of times, and shows promising industrial potential. Attached Figure Description

[0018] Figure 1 The figure shows the results of the cycle performance evaluation of the cesium-based bimetallic catalyst. Detailed Implementation

[0019] This invention discloses a cesium-based bimetallic catalyst, comprising a support and cesium and zirconium supported on the support. The support is at least one selected from HAP, SiO2, MgO, Al2O3, SBA-15, MCM-41, ZSM-5, ZrO2, and ZnO; the loading of cesium on the support is 2wt%~30wt%, and the loading of zirconium is 5wt%~10wt%. The cesium-based bimetallic catalyst is prepared through the following steps: S1: Dissolve cesium salt and zirconium salt together in water to obtain a mixed solution; wherein, the cesium salt is CsNO3, CsCl or CH3COOCs; the zirconium salt is ZrCl4·nH2O, Zr(NO3)4·5H2O, ZrOCl2·8H2O or ZrO(NO3)2; S2: Immerse the carrier in the mixed solution at room temperature for 2-5 hours; S3: Allow the carrier impregnated with the mixed solution to air dry naturally, and then dry it at 90~120 ℃ for 10~16 h; S4: The dried sample was calcined in air at 450~550 ℃ for 2~5 h, and then air-cooled to room temperature to obtain the bimetallic catalyst precursor. S5: The bimetallic catalyst precursor is heated to 300~700 ℃ in a reducing atmosphere and held for 3~5 h to obtain the cesium-based bimetallic catalyst; wherein, the reducing atmosphere is preferably a mixture of H2 and N2, and the volume content of H2 in the mixture is 10%; during heating, the heating rate is controlled to be 2~5 ℃ / min.

[0020] The specific embodiments of the present invention will be described in detail below with reference to examples.

[0021] Example 1 A cesium-based bimetallic catalyst is prepared by the following steps: (1) Add 0.15 g CsNO3 and 0.24 g Zr(NO3)4·5H2O to 2 mL of distilled water and stir until completely dissolved to form a mixed solution; (2) Add 1 g of hydroxyapatite carrier (HAP carrier) to the mixed solution of cesium salt and zirconium salt obtained in step (1) and impregnate for 4 h; (3) Place the HAP carrier impregnated in step (2) in the air to air dry naturally, and then dry it at 100 °C for 12 h; (4) The sample dried in step (3) was calcined in an air atmosphere at 500 °C for 3 h and then cooled to room temperature to obtain a bimetallic catalyst precursor. (5) The bimetallic catalyst precursor was heated to 500℃ in a H2 / N2 mixed atmosphere at a heating rate of 3℃ / min and held for 4 h to obtain a cesium-based bimetallic catalyst, denoted as 10%Cs-5%Zr / HAP-500, where 10% and 5% are the mass percentages of Cs and Zr in the HAP support, respectively; the volume content of H2 in the H2 / N2 mixed atmosphere is 10%.

[0022] Example 2 A cesium-based bimetallic catalyst is prepared by the following steps: (1) Add 0.22 g CsNO3 and 0.24 g Zr(NO3)4·5H2O to 2 mL of distilled water and stir until completely dissolved to form a mixed solution; (2) Add 1 g of hydroxyapatite carrier (HAP carrier) to the mixed solution of cesium salt and zirconium salt obtained in step (1) and impregnate for 4 h; (3) Place the HAP carrier impregnated in step (2) in the air to air dry naturally, and then dry it at 100 °C for 12 h; (4) The sample dried in step (3) was calcined in an air atmosphere at 500 °C for 3 h and then cooled to room temperature to obtain a bimetallic catalyst precursor. (5) The bimetallic catalyst precursor was heated to 500℃ in a H2 / N2 mixed atmosphere at a heating rate of 3℃ / min and held for 4 h to obtain a cesium-based bimetallic catalyst, denoted as 15%Cs-5%Zr / HAP-500; the volume content of H2 in the H2 / N2 mixed atmosphere was 10%.

[0023] Example 3 A cesium-based bimetallic catalyst is prepared by the following steps: (1) Add 0.29 g CsNO3 and 0.24 g Zr(NO3)4·5H2O to 2 mL of distilled water and stir until completely dissolved to form a mixed solution; (2) Add 1 g of hydroxyapatite carrier (HAP carrier) to the mixed solution of cesium salt and zirconium salt obtained in step (1) and impregnate for 4 h; (3) Place the HAP carrier impregnated in step (2) in the air to air dry naturally, and then dry it at 100 °C for 12 h; (4) The sample dried in step (3) was calcined in an air atmosphere at 500 °C for 3 h and then cooled to room temperature to obtain a bimetallic catalyst precursor. (5) The bimetallic catalyst precursor was heated to 500℃ in a H2 / N2 mixed atmosphere at a heating rate of 3℃ / min and held for 4 h to obtain a cesium-based bimetallic catalyst, denoted as 20%Cs-5%Zr / HAP-500; the volume content of H2 in the H2 / N2 mixed atmosphere was 10%.

[0024] Example 4 A cesium-based bimetallic catalyst is prepared by the following steps: (1) Add 0.37 g CsNO3 and 0.24 g Zr(NO3)4·5H2O to 2 mL of distilled water and stir until completely dissolved to form a mixed solution; (2) Add 1 g of hydroxyapatite carrier (HAP carrier) to the mixed solution of cesium salt and zirconium salt obtained in step (1) and impregnate for 4 h; (3) Place the HAP carrier impregnated in step (2) in the air to air dry naturally, and then dry it at 100 °C for 12 h; (4) The sample dried in step (3) was calcined in an air atmosphere at 500 °C for 3 h and then cooled to room temperature to obtain a bimetallic catalyst precursor. (5) The bimetallic catalyst precursor was heated to 500℃ in a H2 / N2 mixed atmosphere at a heating rate of 3℃ / min and held for 4 h to obtain a cesium-based bimetallic catalyst, denoted as 25%Cs-5%Zr / HAP-500; the volume content of H2 in the H2 / N2 mixed atmosphere was 10%.

[0025] Example 5 A cesium-based bimetallic catalyst is prepared by the following steps: (1) Add 0.44 g CsNO3 and 0.24 g Zr(NO3)4·5H2O to 2 mL of distilled water and stir until completely dissolved to form a mixed solution; (2) Add 1 g of hydroxyapatite carrier (HAP carrier) to the mixed solution of cesium salt and zirconium salt obtained in step (1) and impregnate for 4 h; (3) Place the HAP carrier impregnated in step (2) in the air to air dry naturally, and then dry it at 100 °C for 12 h; (4) The sample dried in step (3) was calcined in an air atmosphere at 500 °C for 3 h and then cooled to room temperature to obtain a bimetallic catalyst precursor. (5) The bimetallic catalyst precursor was heated to 500℃ in a H2 / N2 mixed atmosphere at a heating rate of 3℃ / min and held for 4 h to obtain a cesium-based bimetallic catalyst, denoted as 30%Cs-5%Zr / HAP-500; the volume content of H2 in the H2 / N2 mixed atmosphere was 10%.

[0026] The cesium-based bimetallic catalysts obtained in Examples 1-5 were cooled to room temperature and then used to catalyze the reaction of morpholine with methanol to prepare N-methylmorpholine. Specifically, a mixed solution of 10 mL of methanol (approximately 247 mmol) and 100 μL of morpholine (approximately 1 mmol) was added to a batch reactor; then 50 mg of the cesium-based bimetallic catalyst was added, followed by purging the batch reactor with an inert gas (nitrogen), and the reaction was carried out at 200 °C for 4 h; finally, post-treatment was performed according to conventional methods to obtain N-methylmorpholine. The catalytic performance of the cesium-based bimetallic catalysts in Examples 1-5 is shown in Table 1.

[0027] Table 1 Catalytic performance of cesium-based bimetallic catalysts in Examples 1-5 10%Cs-5%Zr / HAP-500 50.1 35.1 70.1 15%Cs-5%Zr / HAP-500 99.3 70.9 71.4 20%Cs-5%Zr / HAP-500 100 86.5 86.5 25%Cs-5%Zr / HAP-500 100 90.5 90.5 30%Cs-5%Zr / HAP-500 100 90.1 90.1 As shown in Table 1, when the Cs loading in the cesium-based bimetallic catalyst increased from 10% to 20%, the morpholine conversion increased from 50.1% to 100%, and the N-methylmorpholine yield increased from 35.1% to 86.5%. This is because appropriately increasing the Cs loading provides more active sites. Further increasing the loading to 25% and 30% maintained the morpholine conversion at 100%, while the N-methylmorpholine yield and selectivity further improved and tended to stabilize. Overall, a Cs loading of 25% is the optimal loading.

[0028] Example 6 A cesium-based bimetallic catalyst is prepared by the following steps: (1) Add 0.37 g CsNO3 and 0.24 g Zr(NO3)4·5H2O to 2 mL of distilled water and stir until completely dissolved to form a mixed solution; (2) Add 1 g of hydroxyapatite carrier (HAP carrier) to the mixed solution of cesium salt and zirconium salt obtained in step (1) and impregnate for 4 h; (3) Place the HAP carrier impregnated in step (2) in the air to air dry naturally, and then dry it at 100 °C for 12 h; (4) The sample dried in step (3) was calcined in an air atmosphere at 500 °C for 3 h and then cooled to room temperature to obtain a bimetallic catalyst precursor. (5) The bimetallic catalyst precursor was heated to 300℃ in a H2 / N2 mixed atmosphere at a heating rate of 3℃ / min and held for 4 h to obtain a cesium-based bimetallic catalyst, denoted as 25%Cs-5%Zr / HAP-300; the volume content of H2 in the H2 / N2 mixed atmosphere was 10%.

[0029] Example 7 A cesium-based bimetallic catalyst is prepared by the following steps: (1) Add 0.37 g CsNO3 and 0.24 g Zr(NO3)4·5H2O to 2 mL of distilled water and stir until completely dissolved to form a mixed solution; (2) Add 1 g of hydroxyapatite carrier (HAP carrier) to the mixed solution of cesium salt and zirconium salt obtained in step (1) and impregnate for 4 h; (3) Place the HAP carrier impregnated in step (2) in the air to air dry naturally, and then dry it at 100 °C for 12 h; (4) The sample dried in step (3) was calcined in an air atmosphere at 500 °C for 3 h and then cooled to room temperature to obtain a bimetallic catalyst precursor. (5) The bimetallic catalyst precursor was heated to 400℃ in a H2 / N2 mixed atmosphere at a heating rate of 3℃ / min and held for 4 h to obtain a cesium-based bimetallic catalyst, denoted as 25%Cs-5%Zr / HAP-400; the volume content of H2 in the H2 / N2 mixed atmosphere was 10%.

[0030] Example 8 A cesium-based bimetallic catalyst is prepared by the following steps: (1) Add 0.37 g CsNO3 and 0.24 g Zr(NO3)4·5H2O to 2 mL of distilled water and stir until completely dissolved to form a mixed solution; (2) Add 1 g of hydroxyapatite carrier (HAP carrier) to the mixed solution of cesium salt and zirconium salt obtained in step (1) and impregnate for 4 h; (3) Place the HAP carrier impregnated in step (2) in the air to air dry naturally, and then dry it at 100 °C for 12 h; (4) The sample dried in step (3) was calcined in an air atmosphere at 500 °C for 3 h and then cooled to room temperature to obtain a bimetallic catalyst precursor. (5) The bimetallic catalyst precursor was heated to 600℃ in a H2 / N2 mixed atmosphere at a heating rate of 3℃ / min and held for 4 h to obtain a cesium-based bimetallic catalyst, denoted as 25%Cs-5%Zr / HAP-600; the volume content of H2 in the H2 / N2 mixed atmosphere was 10%.

[0031] Example 9 A cesium-based bimetallic catalyst is prepared by the following steps: (1) Add 0.37 g CsNO3 and 0.24 g Zr(NO3)4·5H2O to 2 mL of distilled water and stir until completely dissolved to form a mixed solution; (2) Add 1 g of hydroxyapatite carrier (HAP carrier) to the mixed solution of cesium salt and zirconium salt obtained in step (1) and impregnate for 4 h; (3) Place the HAP carrier impregnated in step (2) in the air to air dry naturally, and then dry it at 100 °C for 12 h; (4) The sample dried in step (3) was calcined in an air atmosphere at 500 °C for 3 h and then cooled to room temperature to obtain a bimetallic catalyst precursor. (5) The bimetallic catalyst precursor was heated to 700℃ in a H2 / N2 mixed atmosphere at a heating rate of 3℃ / min and held for 4 h to obtain a cesium-based bimetallic catalyst, denoted as 25%Cs-5%Zr / HAP-700; the volume content of H2 in the H2 / N2 mixed atmosphere was 10%.

[0032] The cesium-based bimetallic catalysts obtained in Examples 6-9 were cooled to room temperature and then used to catalyze the reaction of morpholine with methanol to prepare N-methylmorpholine. Specifically, a mixed solution of 10 mL of methanol (approximately 247 mmol) and 100 μL of morpholine (approximately 1 mmol) was added to a batch reactor; then 50 mg of the cesium-based bimetallic catalyst was added, followed by purging the batch reactor with an inert gas (nitrogen), and the reaction was carried out at 200 °C for 4 h; finally, post-treatment was performed according to conventional methods to obtain N-methylmorpholine. The catalytic performance of the cesium-based bimetallic catalysts in Examples 6-9 is shown in Table 2.

[0033] Table 2 Catalytic performance of cesium-based bimetallic catalysts in Examples 6-9 25%Cs-5%Zr / HAP-300 65.4 55.5 84.9 25%Cs-5%Zr / HAP-400 83.4 74.6 89.4 25%Cs-5%Zr / HAP-500 100 90.5 90.5 25%Cs-5%Zr / HAP-600 100 94.9 94.9 25%Cs-5%Zr / HAP-700 80.4 56.6 70.4 Table 2 shows that the reduction temperature has a significant impact on the activity of the cesium-based bimetallic catalyst. From 300℃ to 600℃, the morpholine conversion gradually increases from 65.4% to 100%, and the N-methylmorpholine yield increases from 55.5% to 94.9%. This is because suitable high temperatures are conducive to the reduction of the active component. When the temperature reaches 700℃, the morpholine conversion drops to 80.4%, and the N-methylmorpholine yield and selectivity also decrease significantly, presumably because the high temperature causes the active component to agglomerate, leading to a reduction in the active component. In conclusion, 600℃ is the optimal reduction temperature for this catalyst.

[0034] Taking the cesium-based bimetallic catalyst 25%Cs-5%Zr / HAP-600 prepared in Example 8 as an example, the effect of reaction temperature on the conversion rate of morpholine was investigated. The specific method was as follows: 10 mL of a mixed solution of methanol (approximately 247 mmol) and 100 μL of morpholine (approximately 1 mmol) was added to a batch reactor; then 50 mg of the cesium-based bimetallic catalyst was added, followed by purging the batch reactor with an inert gas (nitrogen), and the reaction was carried out at 140 °C, 160 °C, 180 °C, and 200 °C for 4 h, respectively; then post-treatment was performed according to conventional methods to obtain N-methylmorpholine. The effect of reaction temperature on the conversion rate of morpholine is shown in Table 3.

[0035] Table 3 Effect of reaction temperature on morpholine conversion, etc. 140 13.9 11.5 82.7 160 99.4 84.9 85.4 180 100 94.9 94.9 200 100 96.5 96.5 As shown in Table 3, the conversion of morpholine and the formation of N-methylmorpholine significantly improved with increasing reaction temperature. At a reaction temperature of 200 °C, the yield and selectivity of N-methylmorpholine reached 96.5%. Therefore, 200 °C was selected as the optimal reaction temperature.

[0036] Taking the cesium-based bimetallic catalyst 25%Cs-5%Zr / HAP-600 prepared in Example 8 as an example, the effect of the amount of cesium-based bimetallic catalyst added on the conversion rate of morpholine was investigated. The specific method was as follows: 10 mL of a mixed solution of methanol (approximately 247 mmol) and 100 μL of morpholine (approximately 1 mmol) was added to a batch reactor; then 20 mg, 30 mg, 40 mg, 50 mg, and 60 mg of the cesium-based bimetallic catalyst 25%Cs-5%Zr / HAP-600 were added respectively. An inert gas (nitrogen) was then introduced into the batch reactor, and the reaction was carried out at 200 °C for 4 h. Afterwards, post-treatment was performed according to conventional methods to obtain N-methylmorpholine. The effect of the amount of cesium-based bimetallic catalyst added on the conversion rate of morpholine is shown in Table 4.

[0037] Table 4. Effect of cesium-based bimetallic catalyst addition on morpholine conversion, etc. 20 45.4 37.7 83.0 30 65.3 55.0 84.2 40 83.3 70.5 84.6 50 100 96.5 96.5 60 100 93.3 93.3 As shown in Table 4, when the catalyst dosage increased from 20 mg to 50 mg, the morpholine conversion increased from 45.4% to 100%, and the N-methylmorpholine yield increased from 37.7% to 96.5%. When the dosage was 60 mg, the yield and selectivity were 93.3%, not significantly different from 50 mg. From an economic perspective, a catalyst dosage of 50 mg is more suitable.

[0038] Taking the cesium-based bimetallic catalyst 25%Cs-5%Zr / HAP-600 prepared in Example 8 as an example, the cycling performance of the cesium-based bimetallic catalyst was investigated. The specific method was as follows: 10 mL of a mixed solution of methanol (approximately 247 mmol) and 100 μL of morpholine (approximately 1 mmol) was added to a batch reactor; then 50 mg of the cesium-based bimetallic catalyst was added, followed by purging the batch reactor with inert gas (nitrogen), and reacting at 200 °C for 4 h; then post-treatment was performed according to conventional methods to obtain N-methylmorpholine. After the reaction was completed, the cesium-based bimetallic catalyst was separated, cleaned, and used in the next synthesis reaction. The results of the cycling performance investigation of the cesium-based bimetallic catalyst are as follows: Figure 1 As shown; from Figure 1 As can be seen, after 15 consecutive recovery operations, the conversion rate of morpholine and the yield of N-methylmorpholine did not decrease significantly, indicating that the catalyst activity was not significantly lost, demonstrating the excellent recycling performance of the catalyst. This shows that the 25%Cs-5%Zr / HAP-600 catalyst has good stability.

[0039] Although specific embodiments of the present invention have been described in detail with reference to examples, they should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of this patent.

Claims

1. Application of cesium-based bimetallic catalyst in the catalytic reaction of morpholine and methanol to prepare N-methylmorpholine, wherein the cesium-based bimetallic catalyst comprises a support and cesium and zirconium supported on the support, wherein the loading of cesium on the support is 15wt%~30wt% and the loading of zirconium is 5wt%~10wt%.

2. The application according to claim 1, characterized in that, The preparation of N-methylmorpholine includes the following steps: Morpholine and methanol are mixed at a molar ratio of 0.5 to 10:247, and then a cesium-based bimetallic catalyst is added to the mixture. After stirring, the mixture is reacted at a temperature of 140 to 220 °C for 1 to 6 h in an inert atmosphere to obtain N-methylmorpholine.

3. The application according to claim 1, characterized in that: The support is at least one of HAP, SiO2, MgO, Al2O3, SBA-15, MCM-41, ZSM-5, ZrO2, and ZnO.

4. The application according to claim 1, characterized in that, The cesium-based bimetallic catalyst was prepared through the following steps: S1: Dissolve cesium salt and zirconium salt together in water to obtain a mixed solution; S2: Immerse the carrier in the mixed solution at room temperature for 2-5 hours; S3: Allow the carrier impregnated with the mixed solution to air dry naturally, and then dry it at 90~120 ℃ for 10~16h; S4: The dried sample was calcined in air at 450~550 ℃ for 2~5 h, and then air-cooled to room temperature to obtain the bimetallic catalyst precursor. S5: The bimetallic catalyst precursor is heated to 300~700 ℃ in a reducing atmosphere and held for 3~5 h to obtain the cesium-based bimetallic catalyst.

5. The application according to claim 4, characterized in that: The concentration of cesium salt in the mixed solution is 0.07~0.25 g / mL, and the concentration of zirconium salt is 0.1~0.2 g / mL.

6. The application according to claim 4 or 5, characterized in that: The cesium salt is CsNO3, CsCl, or CH3COOCs; The zirconium salt is ZrCl4·nH2O, Zr(NO3)4·5H2O, or ZrO(NO3)2.

7. The application according to claim 4, characterized in that: The reducing atmosphere is a mixture of H2 and N2, with the volume content of H2 in the mixture being 10%.

8. The application according to claim 4, characterized in that: The heating rate in S5 is 2~5 ℃ / min.

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