A non-noble metal catalyst Cu-ZnO / TiO2, its preparation method, and its application in the catalytic N-methylation of N-methylaniline in a heterogeneous system.

Abstract

This invention relates to a non-precious metal catalyst Cu-ZnO / TiO2, its preparation method, and its application in catalyzing the N-methylation of N-methylaniline in a heterogeneous system, belonging to the field of catalysis. The catalyst is prepared by sequentially loading ZnO and Cu using a precipitation-deposition method. Anhydrous sodium carbonate is used as the precipitant, zinc nitrate hexahydrate as the zinc source, copper nitrate trihydrate as the copper source, and P25 type titanium dioxide as the support. ZnO and Cu are sequentially loaded onto TiO2, and the catalyst is prepared by hydrogen reduction in a tube furnace. With 50 mg of catalyst, 1 mmol of N-methylaniline, a hydrogen pressure of 4.5 MPa, a carbon dioxide pressure of 1.5 MPa, a temperature of 180 °C, and a reaction time of 24 h, the conversion rate reaches 95.8%, and the selectivity for N,N-dimethylaniline reaches over 99%. This catalyst exhibits excellent catalytic performance, a simple preparation method, low cost, high selectivity for the target product, and easy separation, showing promising industrialization potential.

Description

Technical Field

[0001] This invention belongs to the field of catalysis, specifically relating to a non-precious metal catalyst Cu-ZnO / TiO2 and its preparation method, as well as its application in catalyzing the N-methylation of N-methylaniline to N,N-dimethylaniline in a heterogeneous system. Background Technology

[0002] Carbon dioxide (CO2) is a renewable, low-cost, abundant, and non-toxic C1 resource. Therefore, converting CO2 into high-value-added chemicals has received widespread attention in the fields of green chemistry and synthetic chemistry. Researchers are dedicated to using different catalysts to convert CO2 into methanol, formic acid, cyclic carbonates, urea derivatives, carboxylic acids, and light alkanes. The N-methylation of amines has also attracted significant attention due to its widespread use as an important intermediate in solvents, dyes, surfactants, and pesticides.

[0003] For example, Klankermayer et al. mixed [Ru(triphos)(tmm)] complexes with appropriate amounts of organic acids to effectively catalyze the methylation of secondary and primary aromatic amines using CO2 and H2, yielding the corresponding monomethylated or dimethylated products. Using tetrahydrofuran as a solvent, with a CO2 / H2 ratio of 2 / 4 MPa and at 150 °C, the yields were 70–99%, demonstrating good catalytic performance. Furthermore, Pt-MoO... x / TiO2 catalysts can achieve solvent-free methylation of aliphatic and aromatic secondary amines under CO2 and H2. Beller et al. extended the scope of this reaction to a wide variety of substrates, including aliphatic and aromatic amines, primary and secondary amines, which can be methylated via in-situ catalyst systems composed of triphosphate ligands, Ru(III) precursors, LiCl, or acidic additives. However, homogeneous catalysts are not ideal in terms of reusability and catalyst-product separation. Therefore, the development of efficient heterogeneous catalysts is urgently needed.

[0004] Shi et al. reported heterogeneous CuAlO xDirect N-methylation of amines was achieved using Pd / CuZrO2 catalysts at 3.0 MPa CO2, 6.0 MPa H2, and 160 °C, achieving yields exceeding 96%. Au / Al2O3 and Re / TiO2 catalysts exhibited excellent catalytic performance for the N-methylation of aromatic amines and aliphatic secondary amines with CO2 and H2, with high yields of tertiary amines. Zhao et al. achieved the direct N-methylation of N-methylaniline (MA) with CO2 and H2 using PdGa / TiO2 and PdZn / TiO2 catalysts; the formation of formic acid, an important intermediate, was the rate-determining step of the target reaction. However, the long reaction times (24-48 h) and the high cost of precious metals in these heterogeneous systems limit their industrial application.

[0005] Because Cu-based catalysts are inexpensive, they can be used for the direct N-methylation of amines with CO2 and H2. CuAlO x The catalyst can convert primary and secondary amines into their corresponding N-methyl or N,N-dimethyl products in the presence of CO2 and H2. However, 38 mol% Cu is required relative to the amine. Cu / CeO2 is an efficient heterogeneous catalyst for the direct N-methylation reaction of aniline with CO2 and H2, the rate-determining step of which is the hydrogenation of amino acids formed from aniline and CO2 to ethyl acetate. Furthermore, the Cu / TiO2 catalyst is efficient for the heterogeneous N-methylation reaction of amino acids with CO2 and H2. + and Cu 0 The active site is formaldehyde, which is the reaction intermediate. However, the catalytic performance is not satisfactory. Summary of the Invention

[0006] To address the aforementioned problems in existing catalytic hydrogenation technologies, the present invention aims to provide a non-precious metal catalyst Cu-ZnO / TiO2 and its preparation method, as well as its application in catalyzing the N-methylation of N-methylaniline in a heterogeneous system. This preparation method is low-cost, highly selective, has a fast catalytic rate, and is easy to separate, thus possessing broad industrialization prospects.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] One of the objectives of this invention is to provide a non-precious metal catalyst Cu-ZnO / TiO2, wherein ZnO and Cu are sequentially deposited and supported on P25 type TiO2, wherein the loading amount of ZnO is 0.1-7.5 wt% of the catalyst and the loading amount of Cu is 2.5-7.5 wt% of the catalyst.

[0009] Preferably, the ZnO loading is 3.75 wt% of the catalyst and the Cu loading is 5 wt% of the catalyst.

[0010] In Cu-ZnO / TiO2 catalysts, the loading of Cu and ZnO is expressed as 5% and 3.75% in the following text, and their meanings are the same as those of 5wt% and 3.75wt% as recorded in this text.

[0011] Another objective of this invention is to provide a method for preparing the non-noble metal catalyst Cu-ZnO / TiO2, the specific steps of which are as follows:

[0012] (1) P25 type TiO2 and zinc nitrate hexahydrate were added to pure water and stirred evenly. The resulting suspension was placed in a water bath at 60°C. Then, under vigorous stirring, Na2CO3 solution was added dropwise to adjust the pH to 10. The mixture was stirred for 0.5 h. The precipitate was collected, washed with water 3 times, placed in a vacuum drying oven at 60°C and dried for 12 h. The precipitate was calcined in a muffle furnace to obtain ZnO / TiO support.

[0013] (2) Add ZnO / TiO2 support and copper nitrate trihydrate to pure water and stir evenly. Place the resulting suspension in a water bath at 50°C. Then, under vigorous stirring, add Na2CO3 solution dropwise to adjust the pH to 9. Stir the resulting mixture for 2 hours, collect the precipitate, wash it with water 3 times, and dry it in a vacuum drying oven at 60°C for 12 hours to obtain unreduced Cu-ZnO / TiO2.

[0014] (3) The unreduced Cu-ZnO / TiO2 was placed in a tube furnace and reduced in an H2 atmosphere. It was then naturally cooled to room temperature and then passed through a mixture of O2 / Ar gas for passivation. Finally, the Cu-ZnO / TiO2 catalyst was obtained.

[0015] Preferably, in step (1), the molar ratio of P25 type TiO2 to zinc nitrate hexahydrate is 1:0.0036-0.2741.

[0016] Preferably, in step (2), the mass ratio of ZnO / TiO2 support to copper nitrate trihydrate is 1:0.095-0.285.

[0017] Preferably, in steps (1) and (2), the concentration of the Na2CO3 solution is 100 mg / mL.

[0018] Preferably, in step (1), the heating rate of the muffle furnace is 5℃ / min, the calcination temperature is 350℃, and the calcination time is 4h.

[0019] Preferably, in step (2), the heating rate of the tube furnace is 5℃ / min, the reduction temperature in the tube furnace is 300℃, and the reduction time is 2h.

[0020] Preferably, in step (2), the volume fraction of O2 in the O2 / Ar mixed gas is 0.5%, and the introduction time is 30 min.

[0021] Another object of the present invention is to provide the application of the non-precious metal catalyst Cu-ZnO / TiO2 in catalyzing the N-methylation of N-methylaniline in a heterogeneous system, wherein the catalyst exhibits a selectivity for N,N-dimethylaniline greater than 99% at a conversion of 98.8% of N-methylaniline.

[0022] The method for catalyzing the N-methylation of N-methylaniline using the non-noble metal catalyst Cu-ZnO / TiO2 in a heterogeneous system according to the present invention comprises the following steps:

[0023] (1) Select a stainless steel reactor;

[0024] (2) Weigh the prepared catalyst Cu-ZnO / TiO2 into the reactor, then weigh N-methylaniline and dissolve it in n-octane solvent. After ultrasonic dispersion, put the mixture into the reactor.

[0025] (3) After sealing the reactor, flush it three times with hydrogen gas at a pressure of 1.0 MPa to remove air, and check the airtightness of the reactor.

[0026] (4) Heat the reactor to 180°C, continue to introduce 1.5MPa carbon dioxide and 4.5MPa hydrogen, adjust the rotation speed to 520rpm, and maintain the temperature and pressure inside the reactor for 1-24 hours;

[0027] (5) After the reaction is complete, wait for the reactor to cool to room temperature, open the gas valve, release the mixed gas until the pressure is 0, and the reaction process is complete.

[0028] By employing the above-described technology, the beneficial effects of the present invention compared to the prior art are as follows:

[0029] 1) This invention uses a precipitation-deposition method to prepare a non-precious metal catalyst Cu-ZnO / TiO2, which uses non-precious metal Cu as the active phase, reducing the preparation cost of the catalyst, exposing all active components on the surface of the support, improving the utilization rate of the active components, and resulting in a catalyst with a relatively uniform gold particle size distribution.

[0030] 2) The catalyst Cu-ZnO / TiO2 prepared in this invention has the ability to efficiently catalyze the N-methylation of N-methylaniline to N,N-dimethylaniline when the ZnO loading is 3.75% and the Cu loading is 5%. Specifically, under the reaction conditions of 1.5 MPa carbon dioxide pressure, 8 MPa hydrogen pressure, 180 °C temperature, 24 h reaction time, 20 mL n-octane, and 50 mg catalyst, the conversion rate of 1 mmol of N-methylaniline is 95.8%, and the selectivity reaches more than 99%.

[0031] This paper successfully prepared a Cu-ZnO / TiO2 catalyst and applied it to the direct N-methylation reaction of amines with CO2 and H2. The results showed that the yield of N-methylated amines reached 98.4% under the reaction conditions of 180 °C, 1.5 MPa CO2, 4.5 MPa H2, and 24 h, which is significantly better than that of existing Cu-based catalysts. Attached Figure Description

[0032] Figure 1 X-ray diffraction patterns of catalysts supported on different ZnO;

[0033] As can be seen from the figure, compared with the JCPDS standard data of TiO2, ZnO and elemental Cu, the characteristic peaks of TiO2 are obvious. The (100), (002) and (101) crystal planes of ZnO and the (111) crystal plane of Cu can be clearly observed in the spectrum. It can also be clearly observed that the diffraction peak intensity of Cu decreases with the increase of ZnO loading, indicating that ZnO loading can promote the dispersion of Cu particles. It can be seen that Cu exists in a highly dispersed form.

[0034] Figure 2 The image shows a TEM image of the catalyst 5% Cu-3.75% ZnO / TiO2 in Example 2. Detailed Implementation

[0035] 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.

[0036] This invention uses the preparation of a non-noble metal catalyst Cu-ZnO / TiO2 on P25 type TiO2 as an example, and different metals supported on ZnO or TiO2 as comparative examples. The specific preparation steps are as follows:

[0037] (1) P25 type TiO2 and zinc nitrate hexahydrate were added to pure water and stirred evenly. The resulting suspension was placed in a water bath at 60°C. Then, under vigorous stirring, a Na2CO3 solution with a concentration of 100 mg / mL was added dropwise to adjust the pH to 10. The mixture was stirred for 0.5 h. The precipitate was collected, washed with water three times, and dried in a vacuum drying oven at 60°C for 12 h. It was then calcined in a muffle furnace at 350°C for 4 h with a heating rate of 5°C / min to obtain the ZnO / TiO support.

[0038] (2) Add ZnO / TiO2 support and copper nitrate trihydrate to pure water and stir evenly. Place the resulting suspension in a water bath at 50°C. Then, under vigorous stirring, add Na2CO3 solution with a concentration of 100 mg / mL dropwise to adjust the pH to 9. Stir the resulting mixture for 2 hours, collect the precipitate, wash it with water 3 times, and dry it in a vacuum drying oven at 60°C for 12 hours to obtain unreduced Cu-ZnO / TiO2.

[0039] (3) The unreduced Cu-ZnO / TiO2 was placed in a tube furnace at 300℃ and heated and reduced in H2 atmosphere for 2h. The heating rate of the tube furnace was 5℃ / min. After natural cooling to room temperature, a mixture of O2 / Ar gas was introduced for passivation for 30min, in which the volume fraction of O2 was 0.5%. Finally, Cu-ZnO / TiO2 catalyst was obtained.

[0040] In the embodiments of the present invention, when the molar ratio of P25 type TiO2 to zinc nitrate hexahydrate is 1:0.1370, 1:0.0036, and 1:0.2741, respectively, different loading amounts of carriers 3.75% ZnO / TiO2, 0.1% ZnO / TiO2, and 7.5% ZnO / TiO2 can be obtained.

[0041] In the embodiments of the present invention, when the mass ratio of ZnO / TiO2 support to copper nitrate trihydrate is 1:0.19, 1:0.095, and 1:0.285, catalysts with different loadings, namely 5% Cu-3.75% ZnO / TiO2, 2.5% Cu-3.75% ZnO / TiO2, and 7.5% Cu-3.75% ZnO / TiO2, can be obtained respectively.

[0042] The catalyst of the present invention was tested in the N-methylation reaction of N-methylaniline, and its performance testing steps are as follows:

[0043] Performance testing was conducted in a 100 mL stainless steel reactor. 50 mg of the catalyst Cu-ZnO / TiO2 was weighed into the reactor, along with 1 mmol of N-methylaniline and 20 mL of n-octane. The N-methylaniline was dissolved in the n-octane and ultrasonically dispersed until homogeneous. The mixture was then placed into the reactor. After sealing the reactor, it was flushed three times with hydrogen gas (1 MPa), and the airtightness was checked. After checking the airtightness, the magnetic rotation speed was adjusted to 520 rpm, and the reactor temperature was raised to 180 °C. Then, 1.5 MPa of CO2 and 4.5 MPa of H2 were introduced, and timing was started. After reacting for 1 hour, the reactor was allowed to cool to room temperature. The gas valve was then opened to release hydrogen gas until the pressure reached 0 MPa.

[0044] After filtering the reaction solution, 0.4 μL was injected into the gas chromatograph using a micro-injection syringe. The gas chromatograph used hydrogen flow rates of 40–60 mL / min, air flow rates of 260–300 mL / min, and carrier gas flow rates of 2–4 mL / min. The injection temperature was set to 280.0 °C, the column furnace temperature to 160.0 °C, and the FID temperature to 280.0 °C, with a programmed temperature ramp: initial temperature held for 8 min, then ramped to 220 °C at a rate of 25 °C / min, and held for 10 min. Using n-dodecane as an internal standard, the conversion rate of the catalyst to N-methylaniline and the selectivity for N,N-dimethylaniline were calculated by gas chromatography.

[0045] First, the effect of different ZnO loadings on the performance of the catalyst was studied, and specific implementations are shown in Examples 1-3 and Comparative Examples 1 and 2.

[0046] Example 1: Application test of 5% Cu-0.1% ZnO / TiO2 catalyzed N-methylaniline N-methylation

[0047] The 5% Cu-0.1% ZnO / TiO2 from Example 1 was tested after N-methylation of N-methylaniline:

[0048] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 20.4%, and the selectivity of N,N-dimethylaniline was 99.9%.

[0049] Example 2: Application test of 5% Cu-3.75% ZnO / TiO2 catalyzed N-methylaniline N-methylation

[0050] The 5% Cu-3.75% ZnO / TiO2 of Example 2 was tested after N-methylation of N-methylaniline:

[0051] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 32.9%, and the selectivity of N,N-dimethylaniline was 99.9%.

[0052] Example 3: Application test of 5% Cu-7.5% ZnO / TiO2 catalyzed N-methylaniline N-methylation

[0053] The 5% Cu-7.5% ZnO / TiO2 of Example 3 was tested after N-methylation of N-methylaniline:

[0054] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 22.3%, and the selectivity of N,N-dimethylaniline was 99.9%.

[0055] Comparative Example 1: Application Test of 5% Cu / ZnO Catalyzed N-methylaniline N-methylation. The 5% Cu / ZnO catalyst in Comparative Example 1 was used for the N-methylation of N-methylaniline.

[0056] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 1.2%, and the selectivity of N,N-dimethylaniline was 99.9%.

[0057] Comparative Example 2: Application Test of N-methylation of N-methylaniline Catalyzed by 5% Cu / TiO2

[0058] The 5% Cu / TiO2 obtained in Comparative Example 2 was tested after N-methylation of N-methylaniline:

[0059] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 13.8%, and the selectivity of N,N-dimethylaniline was 99.9%.

[0060] The effects of different oxidizing loads on catalysts were investigated, along with comparative studies of the influence of metal loading on catalytic performance. The performance and parameters of the products were measured and analyzed to determine their optimal performance. The table below shows the performance results and comparative examples of catalyst products obtained under different conditions.

[0061] Table 1: Effect of different zinc oxide loadings on catalyst activity

[0062]

[0063] As can be seen from Table 1, different zinc oxide loadings have a significant impact on activity. The catalyst with 3.75% zinc oxide loading has the highest conversion rate, which is 32.9%. The conversion rate of N,N-dimethylaniline is 99.9%.

[0064] Next, the effect of different Cu loadings on the catalyst performance was studied, with specific implementations shown in Examples 3, 4, 5 and Comparative Example 3.

[0065] Example 4: Application test of 2.5% Cu-3.75% ZnO / TiO2 catalyzed N-methylation of N-methylaniline

[0066] The 2.5% Cu-3.75% ZnO / TiO2 of Example 4 was tested after N-methylation of N-methylaniline:

[0067] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 24.9%, and the selectivity of N,N-dimethylaniline was 99.9%.

[0068] Example 5: Application test of 7.5% Cu-3.75% ZnO / TiO2 catalyzed N-methylation of N-methylaniline

[0069] The 7.5% Cu-3.75% ZnO / TiO2 of Example 5 was tested after N-methylation of N-methylaniline:

[0070] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 28.7%, and the selectivity of N,N-dimethylaniline was 99.9%.

[0071] Comparative Example 3: Application Test of N-methylation of N-methylaniline Catalyzed by 3.75% ZnO / TiO2

[0072] The 3.75% ZnO / TiO2 of Comparative Example 3 was tested after N-methylation of N-methylaniline:

[0073] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C temperature, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 0%.

[0074] The effects of different Cu metal loadings on catalytic performance were investigated using Examples 3, 4, and 5, as well as Comparative Example 3. The performance and parameters of the products were measured, and the optimal performance of the products was determined. The table below shows the results and comparative examples of catalyst products obtained under different conditions.

[0075] Table 2: Effect of different copper loading on activity

[0076]

[0077] As can be seen from Table 2, different Cu loadings have a significant impact on the catalyst activity. The catalyst with 5% Cu loading has the highest conversion rate, which is 32.9%. The conversion rate of N,N-dimethylaniline is 99.9%.

[0078] Then, the effects of different loaded metals on the performance of the catalyst were studied, with specific implementations as shown in Example 3, Comparative Examples 4-6.

[0079] Comparative Example 4: Application Test of N-methylation of N-methylaniline Catalyzed by 5% Fe-3.75% ZnO / TiO2

[0080] The 5% Fe-3.75% ZnO / TiO2 of Comparative Example 4 was tested after N-methylation of N-methylaniline:

[0081] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C temperature, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 1.3%, the selectivity for N,N-dimethylaniline was 0%, and the selectivity for N-methylformylaniline was 99.9%.

[0082] Comparative Example 5: Application Test of N-methylation of N-methylaniline Catalyzed by 5% Co-3.75% ZnO / TiO2

[0083] The 5% Co-3.75% ZnO / TiO2 of Comparative Example 5 was tested after N-methylation of N-methylaniline:

[0084] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C temperature, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 2.2%, the selectivity for N,N-dimethylaniline was 0%, and the selectivity for N-methylformylaniline was 99.9%.

[0085] Comparative Example 6: Application Test of N-methylation of N-methylaniline Catalyzed by 5% Ni-3.75% ZnO / TiO2

[0086] The 5% Ni-3.75% ZnO / TiO2 of Comparative Example 6 was tested after N-methylation of N-methylaniline:

[0087] Under the reaction conditions of 1.5 MPa carbon dioxide pressure, 4.5 MPa hydrogen pressure, 180 °C, 1 h reaction time, 50 mg catalyst, 20 mL n-octane, and 1 mmol N-methylaniline, the catalyst conversion rate was 2.1%, the selectivity for N,N-dimethylaniline was 0%, and the selectivity for N-methylformylaniline was 99.9%.

[0088] By comparatively studying the effect of metal loading on catalytic performance, the performance and parameters of the products were obtained through testing, and the optimal performance of the products was determined through analysis. The table below shows the performance results and comparative cases obtained by testing products under different conditions.

[0089] Table 3: Effect of different metal loadings on activity

[0090]

[0091]

[0092] As can be seen from Table 3, the activity of different oxygen metal supports has a great influence. The catalyst supported by copper metal has the highest conversion rate, which is 35.9%. The conversion rate of N,N-dimethylaniline is 99.9%.

[0093] The study then investigated the effect of reaction time on the catalytic effect of the optimal 5% Cu-3.75% ZnO / TiO2 catalyst on N-methylaniline. The product's performance and parameters were measured at different time points during the catalytic reaction, and the optimal performance was determined through analysis. The table below shows the results obtained by measuring the product and its derivatives at different time points.

[0094] Table 4: Effect of reaction time on catalytic activity

[0095]

[0096] Reaction conditions: 50 mg catalyst, 5% Cu-3.75% ZnO / TiO2, 1 mmol N-methylaniline, 20 mL n-octane, temperature 180℃, carbon dioxide 1.5 MPa, hydrogen pressure 4.5 MPa, reducing atmosphere H2.

[0097] As can be seen from Table 4, the conversion of N-methylaniline is slower in the later stage as the catalytic reaction time increases, with the conversion rate reaching 95.8% after 24 hours and the selectivity of N,N-dimethylaniline reaching 99.9%.

[0098] Finally, the study investigated the effect of the number of catalyst cycles on the catalytic effect. The table below shows the results obtained by testing the product and its products at different cycle counts.

[0099] Table 5: Effect of cycle number on catalytic activity

[0100]

[0101] Reaction conditions: 5% Cu-3.75% ZnO / TiO2 50 mg catalyst, 1 mmol N-methylaniline, 20 mL n-octane, temperature 180℃, carbon dioxide 1.5 MPa, hydrogen pressure 4.5 MPa, reaction time 1 h, reducing atmosphere H2.

[0102] As can be seen from Table 5, the conversion rate of N-methylaniline remained stable with the increase of the number of catalytic cycles, while the selectivity of N,N-dimethylaniline decreased slightly in the third repetition.

[0103] 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 method for preparing a non-noble metal catalyst Cu-ZnO / TiO2, characterized in that, In this non-precious metal catalyst Cu-ZnO / TiO2, ZnO and Cu are sequentially deposited and supported on P25 type TiO2, with ZnO loading ranging from 0.1% to 7.5% and Cu loading ranging from 2.5% to 7.5% of the catalyst. The specific steps for developing the non-precious metal catalyst Cu-ZnO / TiO2 are as follows: (1) P25 type TiO2 and zinc nitrate hexahydrate were added to pure water and stirred evenly. The resulting suspension was placed in a water bath at 60 °C. Then, under vigorous stirring, Na2CO3 solution was added dropwise to adjust the pH to 10. The mixture was stirred for 0.5 h. The precipitate was collected, washed with water 3 times, placed in a vacuum drying oven at 60 °C and dried for 12 h. The precipitate was then calcined in a muffle furnace to obtain ZnO / TiO support. (2) Add ZnO / TiO2 support and copper nitrate trihydrate to pure water and stir evenly. Place the resulting suspension in a water bath at 50 °C. Then, under vigorous stirring, add Na2CO3 solution dropwise to adjust the pH to 9. Stir the resulting mixture for 2 h, collect the precipitate, wash it with water 3 times, and dry it in a vacuum drying oven at 60 °C for 12 h to obtain unreduced Cu-ZnO / TiO2. (3) The unreduced Cu-ZnO / TiO2 was placed in a tube furnace and reduced in an H2 atmosphere. It was then naturally cooled to room temperature and then passed through a mixture of O2 / Ar gas for passivation. Finally, the Cu-ZnO / TiO2 catalyst was obtained.

2. The method for preparing the non-noble metal catalyst Cu-ZnO / TiO2 according to claim 1, characterized in that, In this non-precious metal catalyst Cu-ZnO / TiO2, the ZnO loading is 3.75 wt% and the Cu loading is 5 wt%.

3. The method for preparing the non-noble metal catalyst Cu-ZnO / TiO2 according to claim 1, characterized in that, In step (1), the molar ratio of P25 type TiO2 to zinc nitrate hexahydrate is 1:0.0036-0.2741.

4. The method for preparing the non-noble metal catalyst Cu-ZnO / TiO2 according to claim 1, characterized in that, In step (2), the mass ratio of ZnO / TiO2 support to copper nitrate trihydrate is 1:0.095-0.

285.

5. The method for preparing the non-noble metal catalyst Cu-ZnO / TiO2 according to claim 1, characterized in that, In both steps (1) and (2), the concentration of the Na2CO3 solution is 100 mg / mL.

6. The method for preparing the non-noble metal catalyst Cu-ZnO / TiO2 according to claim 1, characterized in that, In step (2), the heating rate of the muffle furnace is 5 ℃ / min, the calcination temperature is 350 ℃, and the calcination time is 4 h.

7. The method for preparing the non-noble metal catalyst Cu-ZnO / TiO2 according to claim 1, characterized in that, In step (2), the heating rate of the tube furnace is 5 ℃ / min, the reduction temperature in the tube furnace is 300 ℃, and the reduction time is 2 h.

8. The method for preparing the non-noble metal catalyst Cu-ZnO / TiO2 according to claim 1, characterized in that, In step (2), the volume fraction of O2 in the O2 / Ar mixed gas is 0.5%, and the introduction time is 30 min.

9. The application of a non-noble metal catalyst Cu-ZnO / TiO2 prepared by the preparation method according to any one of claims 1 to 2 in catalyzing the N-methylation of N-methylaniline in a heterogeneous system, characterized in that, The catalyst exhibits a selectivity greater than 99% for N,N-dimethylaniline at a conversion rate of 98.8% for N-methylaniline.

Images