A highly active catalyst Cu-ZnO / TiO2-P25, its preparation method, and its application in heterogeneous systems for N-methylated aniline.

Abstract

This invention relates to a highly active catalyst, Cu-ZnO / TiO2-P25, its preparation method, and its application in the N-methylation reaction of aniline with CO2, belonging to the field of catalyst preparation and application technology. The catalyst uses zinc nitrate hexahydrate as the zinc source, copper nitrate trihydrate as the copper source, and P25 as the support. Metals are loaded onto P25 using a stepwise precipitation method, followed by hydrogen reduction in a tube furnace to obtain the catalyst Cu-ZnO / TiO2-P25. This catalyst is then dispersed in a solvent, using CO2 as the carbon source and hydrogen as the hydrogen source, to catalyze the N-methylation of aniline. The Cu-ZnO / TiO2-P25 catalyst with copper and zinc oxide contents of 5% and 5.5%, respectively, exhibits excellent catalytic performance. At a CO2 pressure of 2.5 MPa, a hydrogen pressure of 3.5 MPa, a temperature of 180 °C, and a reaction time of 6 h, the conversion rate of aniline reaches 100%, the yield of N-methylaniline reaches 99.7%, and the TOF value is 5.8 h. ‑1 This preparation method is simple and inexpensive. It can be used to catalyze the N-methylation of aniline with CO2 to produce N-methylaniline with high yield and has broad industrialization prospects.

Description

Technical Field

[0001] This invention belongs to the field of non-precious metal catalysts, specifically relating to a highly active catalyst Cu-ZnO / TiO2-P25, its preparation method, and its application in heterogeneous systems of N-methylaniline to N-methylaniline. Background Technology

[0002] CO2 is an inexpensive, readily available, abundant, and renewable carbon source that can be used as a raw material to produce refined, high-value-added chemicals. It provides a sustainable and economical method for carbon capture and utilization, which is of great significance for achieving carbon neutrality and sustainable development.

[0003] N-Methylaniline, with the molecular formula C7H9N, is a colorless to reddish-brown oily liquid with a relative molecular weight of 107.153, a melting point of -57℃, and a boiling point of 232℃. It is slightly soluble in water but soluble in solvents such as ethanol, ether, and chloroform. N-Methylaniline is an important organic intermediate widely used in dyes, rubber, pesticides, and pharmaceuticals, and is typically synthesized by the N-methylation of aniline with a methylating agent. However, traditional N-methylation methods generally suffer from significant drawbacks, including expensive raw materials, high toxicity, overmethylation, low atom economy, and difficulty in separation. Therefore, the development of efficient and clean N-methylation methods has been a major focus.

[0004] Noble metal catalysts play an important role in N-methylation reactions due to their high activity and mild reaction conditions, and mainly include Pt, Pd, and Au. In recent years, numerous chemists both domestically and internationally have developed many noble metal catalysts with excellent catalytic performance. Kon et al., through the synthesis of Pt and MoO2... x Pt-MoO was prepared by co-loading on TiO2 x The Pt-MoO2 catalyst was applied to the methylation reaction of N-methylaniline with CO2 and H2, achieving a yield of 85% for N,N-dimethylaniline, indicating that Pt-MoO2 catalysts are effective catalysts. xThe / TiO2 catalyst exhibits excellent catalytic performance. This method is the first solvent-free and reusable heterogeneous catalytic system, providing a sustainable and practical approach for the production of tertiary amines. Lin et al. successfully prepared a Pd-ZnO / TiO2 catalyst by dispersing PdZn alloy particles on the TiO2 surface using a deposition-precipitation method, and applied it to the N-methylation reaction of N-methylaniline. Experimental results showed that the catalyst exhibited good catalytic activity and selectivity. Du et al. prepared an Au / Al2O3-VS catalyst, which methylated aromatic and aliphatic amines to the corresponding tertiary amines in excellent yields. This catalytic method is one of the simplest, most efficient, and powerful catalytic methods developed to date, providing new possibilities for developing sustainable processes for the conversion of CO2 into high-value-added chemicals. As can be seen from the above examples, noble metal catalysts possess high activity; however, their high price and limited raw materials restrict their industrial application.

[0005] Non-precious metals Fe, Co, Ni, and Cu are widely used in N-methylation reactions due to their high abundance, high reactivity, and low cost. Garcia proposed a novel method for the selective N-methylation of aliphatic primary and secondary amines using a nickel-phosphine-based catalyst. This reaction utilizes CO2 as the C1 component and PhSiH3 as a reducing agent, yielding the desired N-methylated products in high yield under relatively mild conditions. Tamura prepared a Cu / CeO2 catalyst and applied it to the selective N-methylation of aniline, producing N-methylaniline at 433 K, CO2 pressure of 1 MPa, and hydrogen pressure of 7 MPa, with a TOF of 1.7 h⁻¹. -1 The Cu / TiO2 catalyst prepared by Liu can catalyze the conversion of N-methylaniline to N,N-dimethylaniline under conditions of 453 K, CO2 pressure of 2 MPa, and hydrogen pressure of 4 MPa, with a TOF value of only 1.2 h⁻¹. -1 The examples above demonstrate that non-precious metal catalysts require harsh reaction conditions and exhibit low activity; therefore, there is an urgent need to develop efficient and environmentally friendly non-precious metal-based catalysts.

[0006] In summary, catalytic N-methylation to N-methylaniline is currently the most suitable method for industrial production. Therefore, developing non-precious metal-based catalysts to efficiently catalyze the direct N-methylation of CO2 and aniline to N-methylaniline is of great significance. Summary of the Invention

[0007] To address the aforementioned problems in existing catalytic N-methylation technologies, the present invention aims to provide a highly active catalyst, Cu-ZnO / TiO2-P25, its preparation method, and its application in N-methylating aniline in heterogeneous systems. This preparation method is low-cost, has high conversion rates, and exhibits high selectivity for the target product, demonstrating promising industrialization potential.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] One of the objectives of this invention is to provide a highly active catalyst Cu-ZnO / TiO2-P25, wherein Cu and ZnO are supported on P25 type TiO2, and the loading amount of Cu is 2-8 wt% of the catalyst and the loading amount of ZnO is 1-12 wt% of the catalyst.

[0010] Preferably, the loading of ZnO is 5.5 wt% of the catalyst.

[0011] Preferably, the Cu loading is 5 wt% of the catalyst.

[0012] In Cu-ZnO / TiO2-P25 catalysts, the loading of Cu and ZnO is expressed as 2-8% and 1-12% in the following text, and their meanings are the same as those of 2-8 wt% and 1-12 wt% as recorded herein.

[0013] Another object of the present invention is to provide a method for preparing the highly active catalyst Cu-ZnO / TiO2-P25, the specific steps of which are as follows:

[0014] (1) P25 type TiO2 and zinc nitrate hexahydrate were added to pure water and stirred evenly to obtain a suspension. The suspension was placed in a water bath at 60-80℃ and stirred vigorously. The pH was adjusted to 10-12 by adding precipitant-Na2CO3 solution dropwise. The mixture was stirred for 0.5h, the precipitate was collected, and the pH was washed until it reached 7. The sample was placed in a vacuum drying oven at 60℃ and dried for 12h. Then it was calcined in a muffle furnace in an air atmosphere to obtain ZnO / TiO2-P25 support.

[0015] (2) Add ZnO / TiO2-P25 support and copper nitrate trihydrate to pure water and stir evenly. Place the resulting suspension in a water bath at 50-70℃ and stir vigorously. Add precipitant-Na2CO3 solution dropwise to adjust the pH to 8-10. Continue stirring the resulting mixture for 2 hours. Collect the precipitate formed, wash it until the pH value is 7, and then place it in a vacuum drying oven at 60℃ for 12 hours to obtain unreduced Cu-ZnO / TiO2-P25.

[0016] (3) The unreduced catalyst Cu-ZnO / TiO2-P25 was placed in a tube furnace and heated and reduced in a hydrogen atmosphere at a temperature of 250-450℃ for 1-3 hours. It was then naturally cooled to room temperature to obtain Cu-ZnO / TiO2-P25.

[0017] In the above preparation method, zinc nitrate hexahydrate in step (1) can also be zinc sulfate or zinc chloride, and copper nitrate trihydrate in step (2) can also be copper sulfate or copper chloride, and the resulting technical effects are the same.

[0018] Preferably, in step (1), the molar ratio of P25 type TiO2 to zinc nitrate hexahydrate is 2-27:1.

[0019] Preferably, in step (2), the mass ratio of ZnO / TiO2-P25 support to copper nitrate trihydrate is 3-13:1.

[0020] Preferably, in steps (1) and (2), the concentration of the Na2CO3 solution is 0.1 g / mL.

[0021] Preferably, in step (1), the heating rate of the muffle furnace is 5℃ / min, the calcination temperature is 250-450℃, and the calcination time is 3.5-4.5h. Since the purpose of calcining the carrier is to obtain a carrier with a rich pore structure, it is important to control the calcination temperature and time appropriately to maintain a stable pore structure of the carrier.

[0022] Preferably, in step (2), the heating rate of the tube furnace is 5℃ / min, the reduction temperature in the tube furnace is 200-400℃, and the reduction time is 1.5-2.5h.

[0023] Another objective of this invention is to provide the application of the highly active catalyst Cu-ZnO / TiO2-P25 in the N-methylation of aniline in a heterogeneous system, achieving a yield of 99.7% of N-methylaniline at a 100% aniline conversion rate.

[0024] The specific steps for the N-methylation of aniline with the highly active catalyst Cu-ZnO / TiO2-P25 of the present invention in a heterogeneous system are as follows:

[0025] (1) Select a stainless steel high-pressure reactor and insert a glass container as the reactor liner;

[0026] (2) Weigh the catalyst Cu-ZnO / TiO2-P25 into the high-pressure reactor, then weigh aniline and dissolve it in cyclohexane solvent. After ultrasonically dispersing it evenly, place the mixture into the high-pressure reactor.

[0027] (3) After sealing the reactor, purge it three times with hydrogen gas at a pressure of 1 MPa. Maintain the hydrogen pressure at 1 MPa at room temperature and check the airtightness of the reactor.

[0028] (4) First heat the reactor to 180°C, then continue to introduce hydrogen gas to 3.5 MPa, then introduce carbon dioxide gas to 6 MPa, and maintain the temperature and pressure inside the reactor for 1 hour.

[0029] (5) After the reaction is complete and cooled to room temperature, open the gas valve of the high-pressure reactor to release the gas inside the reactor until the pressure is 0, thus completing the reaction process.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1) The present invention uses a stepwise precipitation method to prepare Cu-ZnO / TiO2-P25, which uses non-precious metals as the active phase and P25 type TiO2 as the carrier, which greatly reduces the cost of raw materials and is green and environmentally friendly.

[0032] 2) The 5% Cu-5.5% ZnO / P25 catalyst prepared by the method of this invention exhibits excellent catalytic performance; under the reaction conditions of CO2 pressure 2.5 MPa, hydrogen pressure 3.5 MPa, temperature 180℃, reaction time 1 h, and catalyst 50 mg, when the conversion rate of 0.1 g aniline is 100%, the yield of N-methylaniline is 99.7%, and the TOF value is 5.8 h. -1 . Attached Figure Description

[0033] Figure 1 The image shows the XRD pattern of the Cu-ZnO / TiO2-P25 catalyst prepared in Example 3.

[0034] Figure 2 The image shows the time course of the Cu-ZnO / TiO2-P25 catalyst prepared in Example 3.

[0035] Figure 3 The figure shows the stability performance of the Cu-ZnO / TiO2-P25 catalyst prepared in Example 3.

[0036] Figure 4 This is a TEM image of the Cu-ZnO / TiO2-P25 catalyst prepared in Example 3. Detailed Implementation

[0037] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0038] This invention uses Cu-ZnO / TiO2-P25 prepared by loading Cu and ZnO on P25 type TiO2 in different proportions as an example to test the performance and parameters of the product and determine the optimal performance of the product.

[0039] In the following specific examples 1-8, the catalyst was prepared using the following steps:

[0040] (1) P25 type TiO2 and zinc nitrate hexahydrate were added to pure water and stirred evenly to obtain a suspension. The suspension was placed in a water bath at 70°C and stirred vigorously. A precipitant-Na2CO3 solution with a concentration of 0.1 g / mL was added dropwise to adjust the pH to 11. The mixture was stirred for 0.5 h, the precipitate was collected, and washed until the pH value was 7. The sample was placed in a vacuum drying oven at 60°C and dried for 12 h. It was then placed in a muffle furnace in an air atmosphere and calcined. The muffle furnace was heated to 350°C at a heating rate of 5°C / min and calcined for 3 h to obtain ZnO / TiO2-P25 support.

[0041] (2) Add ZnO / TiO2-P25 support and copper nitrate trihydrate to pure water and stir evenly. Place the resulting suspension in a water bath at 60°C and stir vigorously. Add 0.1 g / mL Na2CO3 precipitant solution dropwise to adjust the pH to 9. Continue stirring the resulting mixture for 2 h. Collect the precipitate formed, wash it until the pH value is 7, and then place it in a vacuum drying oven at 60°C for 12 h to obtain unreduced Cu-ZnO / TiO2-P25.

[0042] (3) The unreduced catalyst Cu-ZnO / TiO2-P25 was placed in a tube furnace and heated and reduced for 2 hours in a hydrogen atmosphere. The temperature was increased to 300℃ at a heating rate of 5℃ / min and the reduction time was 2 hours. The catalyst was then naturally cooled to room temperature to obtain Cu-ZnO / TiO2-P25.

[0043] In terms of the amount of raw materials used, by controlling the molar ratio of P25 type TiO2 to zinc nitrate hexahydrate to 2-27:1, and the mass ratio of ZnO / TiO2-P25 support to copper nitrate trihydrate to 3-13:1, Cu and ZnO can be loaded in the catalyst in different proportions.

[0044] The application test of the catalyst prepared by the above method for the catalytic N-methylation of aniline was carried out as follows: The reaction was conducted in a 200 mL stainless steel high-pressure reactor with a glass container inserted as a liner. 50 mg of catalyst was weighed into the high-pressure reactor, followed by 0.1 g of aniline and 20 mL of cyclohexane. The aniline was dissolved in the cyclohexane and ultrasonically dispersed. The mixture was then placed into the high-pressure reactor. After sealing the reactor, it was purged three times with hydrogen gas (1 MPa). The hydrogen pressure was increased by 1 MPa at room temperature, and the airtightness was checked. After checking the airtightness, the magnetic rotation speed was adjusted to 550 rpm, and the reactor temperature was raised to 180 °C. Hydrogen gas was then introduced until the pressure reached 3.5 MPa, followed by CO2 until the pressure reached 6 MPa, and timing was started. After 1 hour of reaction, the reactor was cooled to room temperature, and the gas valve of the high-pressure reactor was opened to release the gas until the pressure reached 0 MPa.

[0045] After filtering the reaction solution, 0.4 μL was injected into the gas chromatograph using a micro-syringe. The gas chromatograph used hydrogen flow rate was set to 40–60 mL / min, air flow rate to 200–300 mL / min, and carrier gas flow rate to 2–3 mL / min. The injection temperature was set to 280.0 °C, the initial column furnace temperature was set to 160 °C and held for 10 min, then increased to 220 °C at a rate of 25 °C / min and held for 10 min. The FID temperature was set to 280.0 °C. Using n-dodecane as an internal standard, the conversion and selectivity of the catalysts in different embodiments for the N-methylation of aniline were calculated by gas chromatography.

[0046] Example 1: Application of 5% Cu-1% ZnO / TiO2-P25 catalyzed N-methylation of aniline

[0047] The catalyst of Example 1 of this invention was tested for its application in the catalytic N-methylation of aniline. The performance test conditions and results are as follows:

[0048] Under the reaction conditions of hydrogen pressure 3.5 MPa, CO2 pressure 2.5 MPa, temperature 180℃, reaction time 1 h, catalyst 50 mg, and aniline 0.1 g, the catalyst conversion rate was 42.6%, and the selectivity of N-methylaniline was 98.4%.

[0049] Example 2: Application of 5% Cu-3% ZnO / TiO2-P25 catalyzed N-methylation of aniline

[0050] The catalyst of Example 2 of this invention was tested for its application in the catalytic N-methylation of aniline. The performance test conditions and results are as follows:

[0051] Under the reaction conditions of hydrogen pressure 3.5 MPa, CO2 pressure 2.5 MPa, temperature 180℃, reaction time 1 h, catalyst 50 mg, and aniline 0.1 g, the catalyst conversion rate was 45.9%, and the selectivity of N-methylaniline was 98.5%.

[0052] Example 3: Application of 5% Cu-5.5% ZnO / TiO2-P25 catalyzed N-methylation of aniline

[0053] The catalyst of Example 3 of this invention was tested for its application in the catalytic N-methylation of aniline. The performance test conditions and results are as follows:

[0054] Under the reaction conditions of hydrogen pressure 3.5 MPa, carbon dioxide pressure 2.5 MPa, temperature 180℃, reaction time 1 h, catalyst 50 mg, and aniline 0.1 g, the catalyst conversion rate was 55.8%, and the selectivity of N-methylaniline was 99.3%.

[0055] Example 4: Application of 5% Cu-8.25% ZnO / TiO2-P25 catalyzed N-methylation of aniline

[0056] The catalyst of Example 4 of this invention was tested for its application in the catalytic N-methylation of aniline. The performance test conditions and results are as follows:

[0057] Under the reaction conditions of hydrogen pressure 3.5 MPa, carbon dioxide pressure 2.5 MPa, temperature 180 °C, reaction time 1 h, catalyst 50 mg, and aniline 0.1 g, the catalyst conversion rate was 50.1%, and the selectivity of N-methylaniline was 98.8%.

[0058] Example 5: Application of 5% Cu-12% ZnO / TiO2-P25 catalyzed N-methylation of aniline

[0059] The catalyst of Example 5 of this invention was tested for its application in the catalytic N-methylation of aniline. The performance test conditions and results are as follows:

[0060] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa carbon dioxide pressure, 180 °C temperature, 1 h reaction time, 50 mg catalyst, and 0.1 g aniline, the catalyst conversion rate was 43.1%, and the selectivity of N-methylaniline was 98.4%.

[0061] Comparative Example 1: Application in the N-methylation of aniline catalyzed by 5% Cu / ZnO

[0062] The 5% Cu / ZnO of Comparative Example 1 was subjected to aniline N-methylation testing, and the performance test conditions and results are as follows:

[0063] Under the reaction conditions of hydrogen pressure 3.5 MPa, carbon dioxide pressure 2.5 MPa, temperature 180 °C, reaction time 1 h, catalyst 50 mg, and aniline 0.1 g, the catalyst conversion rate was 15.8%, and the selectivity of N-methylaniline was 98.5%.

[0064] Comparative Example 2: Application in the N-methylation of aniline catalyzed by 5% Cu / TiO2-P25

[0065] The 5% Cu / TiO2-P25 of Comparative Example 2 was subjected to aniline N-methylation testing. The performance test conditions and results are as follows:

[0066] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa carbon dioxide pressure, 180 °C temperature, 1 h reaction time, 50 mg catalyst, and 0.1 g aniline, the catalyst conversion rate was 26.3%, and the selectivity of N-methylaniline was 98.2%.

[0067] Example 6: Application of 2% Cu-5.5% ZnO / TiO2-P25 catalyzed N-methylation of aniline

[0068] The catalyst of Example 6 of this invention was tested for its application in the catalytic N-methylation of aniline. The performance test conditions and results are as follows:

[0069] Under the reaction conditions of hydrogen pressure 3.5 MPa, carbon dioxide pressure 2.5 MPa, temperature 180℃, reaction time 1 h, catalyst 50 mg, and aniline 0.1 g, the catalyst conversion rate was 46.3%, and the selectivity of N-methylaniline was 98.2%.

[0070] Example 7: Application of 8% Cu-5.5% ZnO / TiO2-P25 catalyzed N-methylation of aniline

[0071] The catalyst of Example 7 of this invention was tested for its application in the catalytic N-methylation of aniline. The performance test conditions and results are as follows:

[0072] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa carbon dioxide pressure, 180 °C temperature, 1 h reaction time, 50 mg catalyst, and 0.1 g aniline, the catalyst conversion rate was 48.4%, and the selectivity of N-methylaniline was 98.6%.

[0073] Example 8: Application of 5% Cu-5.5% ZnO / TiO2-P25 catalyzed N-methylation of aniline

[0074] The catalyst in Example 8 of this invention was prepared by reduction at a hydrogen reduction temperature of 200°C, and then subjected to application testing for catalytic N-methylation of aniline. The performance test conditions and results are as follows:

[0075] Under the reaction conditions of hydrogen pressure 3.5 MPa, carbon dioxide pressure 2.5 MPa, temperature 180 °C, reaction time 1 h, catalyst 50 mg, and aniline 0.1 g, the catalyst conversion rate was 47.5%, and the selectivity of N-methylaniline was 98.8%.

[0076] Example 9: Application of 5% Cu-5.5% ZnO / TiO2-P25 catalyzed N-methylation of aniline

[0077] The catalyst in Example 9 of this invention was prepared by reduction at a hydrogen reduction temperature of 400°C, and then subjected to application testing for catalytic N-methylation of aniline. The performance test conditions and results are as follows:

[0078] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa carbon dioxide pressure, 180 °C temperature, 1 h reaction time, 50 mg catalyst, and 0.1 g aniline, the catalyst conversion rate was 52.7%, and the selectivity of N-methylaniline was 99.1%.

[0079] The catalyst prepared in step 3 was subjected to spectral analysis, electron microscopy, catalytic activity testing, and stability testing. The results are as follows.

[0080] Figure 1 The XRD patterns of the catalyst prepared in Example 3 before and after the catalytic reaction are shown. Compared with JCPDS standard data, the characteristic peak of P25 is obvious, and characteristic peaks of the (100), (002), and (101) crystal planes of ZnO and the characteristic peak of the Cu (111) crystal plane can be observed in the spectrum. The XRD patterns of the catalyst prepared in Example 3 before and after the catalytic reaction are almost unchanged. The size of Cu particles in the catalyst before and after the reaction is 4 nm, indicating that the catalyst has a stable structure and is a recyclable heterogeneous catalyst.

[0081] Figure 2 The figure shows the time course diagram of the catalyst prepared in Example 3. As can be seen from the figure, the conversion rates of aniline are 34.7%, 55.8%, 72.4%, 93.1%, and 100.0% at reaction times of 0h, 1h, 2h, 4h, and 6h, respectively. The selectivity of N-methylaniline remains above 98%. It can be concluded that the catalyst prepared in Example 3 has high catalytic activity and selectivity.

[0082] Figure 3The figure shows the stability performance of the catalyst prepared in Example 3. As can be seen from the figure, the conversion rate of aniline was 55.8%, 55.8%, 55.7% and 55.6% when the catalyst was cyclic for the first, second, third and fourth times, respectively. The selectivity of N-methylaniline remained above 98%, which shows that the catalyst has high stability.

[0083] Figure 4 The image shows a TEM image of the catalyst prepared in Example 3. As can be seen from the image, Cu and ZnO are supported on P25 type TiO2, and the Cu particle size is 4 nm.

[0084] The catalytic performance of catalyst products obtained under different conditions for aniline under the same reaction conditions is shown in Table 1.

[0085] Table 1: Effect of different loading amounts on catalytic activity

[0086]

[0087]

[0088] As can be seen from Examples 1-5 in Table 1, the loading of ZnO has a significant impact on the catalyst activity. When the loading content ranges from 1% to 12%, the conversion rate of aniline and the selectivity of N-methylaniline first increase and then decrease, which means that the catalytic performance of the catalyst also first increases and then decreases, showing a volcano-shaped trend. When the loading is 5.5%, the conversion rate reaches the highest of 55.8% and the selectivity is 99.3%.

[0089] As can be seen from Examples 3, 6 and 7, the loading of Cu still has a significant impact on the catalyst activity. When the loading ranges from 2% to 8%, the conversion rate of aniline and the selectivity of N-methylaniline first increase and then decrease. When the loading is 5%, the conversion rate reaches the highest of 55.8% and the selectivity is 99.3%.

[0090] As can be seen from Examples 3, 1, and 2, ZnO and Cu have a synergistic effect on the catalytic performance of the catalyst, which can significantly improve the catalytic performance of the catalyst.

[0091] As can be seen from Examples 3, 8 and 9, the reduction temperature of hydrogen has a significant impact on the performance of the catalyst. As the reduction temperature increases from 200°C to 400°C, the catalytic performance of the catalyst first increases and then decreases. The catalytic performance of the catalyst reaches its maximum when the reduction temperature is 300°C.

[0092] The above description is only a partial embodiment of the present invention and is not intended to limit the present invention. Any equivalent changes and modifications made based on the content of this invention are within the protection scope of this invention.

Claims

1. A highly active catalyst Cu-ZnO / TiO2-P25, characterized in that, Cu and ZnO are loaded on P25 type TiO2, the loading amount of Cu is 5 wt% of the catalyst, and the loading amount of ZnO is 5.5 wt% of the catalyst; The specific steps of the catalyst are as follows: (1) P25 type TiO2 and zinc nitrate hexahydrate are added into pure water and stirred uniformly to obtain a suspension, which is placed into a 60-80 ℃ water bath, and a precipitant-Na2CO3 solution is added dropwise to adjust the pH to 10-12, the obtained mixture is continuously stirred for 0.5 h, the formed precipitate is collected, washed until the pH value is 7, and the obtained sample is placed into a 60 ℃ vacuum drying box for drying for 12 h and calcination in a muffle furnace in an air atmosphere to obtain a ZnO / TiO2-P25 carrier; (2) The ZnO / TiO2-P25 carrier and copper nitrate trihydrate are added into pure water and stirred uniformly, the obtained suspension is placed into a 50-70 ℃ water bath, and a precipitant-Na2CO3 solution is added dropwise to adjust the pH to 8-10, the obtained mixture is continuously stirred for 2 h, the formed precipitate is collected, washed until the pH value is 7, and then placed into a 60 ℃ vacuum drying box for drying for 12 h to obtain an unreduced Cu-ZnO / TiO2-P25; (3) The unreduced catalyst Cu-ZnO / TiO2-P25 is placed into a tube furnace for heating reduction under a hydrogen atmosphere, and naturally cooled to room temperature to obtain Cu-ZnO / TiO2-P25.

2. The highly active catalyst Cu-ZnO / TiO2-P25 according to claim 1, characterized in that, The mass ratio of P25 type TiO2 to zinc nitrate hexahydrate in step (1) is 2-27:

1.

3. The highly active catalyst Cu-ZnO / TiO2-P25 according to claim 1, characterized in that, The mass ratio of the ZnO / TiO2-P25 carrier to copper nitrate trihydrate in step (2) is 3-13:

1.

4. The highly active catalyst Cu-ZnO / TiO2-P25 according to claim 1, characterized in that, In steps (1) and (2), the concentration of the Na2CO3 solution is 0.1 g / mL.

5. The highly active catalyst Cu-ZnO / TiO2-P25 according to claim 1, characterized in that, In step (1), the heating rate of the muffle furnace is 5 ℃ / min, the calcination temperature is 250-450 ℃, and the calcination time is 3.5-4.5 h.

6. The highly active catalyst Cu-ZnO / TiO2-P25 according to claim 1, characterized in that, In step (3), the heating rate of the tube furnace is 5 ℃ / min, the reduction temperature in the tube furnace is 200-400 ℃, and the reduction time is 1-3 h.

7. Use of the highly active catalyst Cu-ZnO / TiO2-P25 according to claim 1 for the N- methylation of aniline in a heterogeneous system, wherein the yield of N-methylaniline is 99.7% at 100% conversion of aniline and the TOF value is 5.8 h -1 .

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