Use of a highly selective catalyst Cu-ZnO / TiO2-P25 for the synthesis of benzimidazoles in a heterogeneous system

Abstract

The application relates to application of a high-selectivity catalyst Cu-ZnO / TiO2 in synthesis of benzimidazole in a heterogeneous system and belongs to the technical field of catalyst preparation and application. The catalyst is prepared by using zinc nitrate hexahydrate as a zinc source, copper nitrate trihydrate as a copper source and P25 type titanium dioxide as a carrier, loading ZnO and Cu on the titanium dioxide by adopting a step-by-step precipitation method, reducing in a tube furnace by hydrogen, obtaining the catalyst Cu-ZnO / TiO2, and then catalyzing o-phenylenediamine to react to synthesize benzimidazole by taking CO2 as a carbon source and hydrogen as a hydrogen source. The Cu-ZnO / TiO2 catalyst with copper and zinc oxide contents of 5% and 4% respectively has excellent catalytic performance, under the reaction conditions of a CO2 pressure of 2.5 MPa, a hydrogen pressure of 3.5 MPa and a temperature of 180 DEG C, when the conversion rate of o-phenylenediamine is 100%, the selectivity of benzimidazole is greater than 99.9%, and the TOF value is 6.4 h ‑1 . The preparation method is simple, low in cost, high in selectivity when used for catalyzing o-phenylenediamine to react with CO2 and H2 to prepare benzimidazole, and has wide industrialization prospects.

Description

Technical Field

[0001] This invention belongs to the field of non-precious metal catalysts, specifically relating to a highly selective catalyst for the catalytic reaction of o-phenylenediamine and CO in a Cu-ZnO / TiO2 heterogeneous system. 2、 Application of H2 reaction in the synthesis of benzimidazole. Background Technology

[0002] Benzimidazole, with the molecular formula C7H6N2, is a colorless, flaky crystal with a relative molecular weight of 118.14, a melting point of 171℃, and a boiling point of 360℃. It is slightly soluble in water and ether, and readily soluble in ethanol, acid solutions, and strong alkaline solutions. Benzimidazole can be used to prepare imidazole intermediates for fungicides such as imidacloprid and prochloraz, and also for the synthesis of drugs such as vitamin B12 and the preparation of high molecular weight compounds. It is typically synthesized by cyclization of o-phenylenediamine with formic acid. Although significant progress has been made in the synthesis of benzimidazole, from the perspective of green chemistry and sustainable development, developing simple and green synthetic routes using non-precious metal catalysts remains a noteworthy issue.

[0003] o-Phenylenediamine readily cyclizes to benzimidazole under relatively mild conditions via CO2. The first report of this cyclization synthesis of benzimidazole appeared in 2013, when Liu and colleagues used RuCl2 (1,2-bis(diphenylphosphine)ethane)2 catalyst to cyclize o-phenylenediamine to benzimidazole under solvent-free conditions. Hao et al. synthesized benzimidazole from inexpensive and readily available o-nitroaniline and CO2 in the presence of H2 using Au / TiO2 catalysis, achieving very good product yields. Other supported gold catalysts, such as Au / Al2O3 and Au / polyurea, have also been found to promote the reaction, although with reduced efficiency. Saptal et al. designed polymer ionic liquid-supported ruthenium nanoparticles (Ru@PsIL) as a novel catalyst for CO2-catalyzed immobilization of azole compounds. Under the dual catalysis of Ru@PsIL and K2CO3, azole compounds can be synthesized from o-phenylenediamine or o-nitroaniline as raw materials via CO2 and DMAB at room temperature. Khatun et al. embedded copper nanoparticles within a covalent organic framework to design catalysts for the synthesis of azole compounds from CO2. They successfully prepared CuNPs@COF, confining Cu nanoparticles within the pores of a COF material, and used it for the synthesis of benzimidazole, benzothiazole, and benzoxazole derivatives. Compared to other heterogeneous catalyst systems, the developed CuNPs@COF catalyst could convert different aromatic amine reagents into their corresponding products in a shorter reaction time. These examples demonstrate that although significant progress has been made in the synthesis of benzimidazole, developing simple, efficient, and environmentally friendly non-noble metal-based catalysts remains an important research direction.

[0004] In conclusion, developing new non-precious metal-based catalysts for the efficient catalysis of the reaction between CO2 and o-phenylenediamine to prepare benzimidazole is of great significance. Summary of the Invention

[0005] To address the aforementioned problems in existing catalytic synthesis technologies for benzimidazole, the present invention aims to provide a highly selective catalyst, Cu-ZnO / TiO2, for the catalytic synthesis of benzimidazole from o-phenylenediamine with CO2 and H2 in a heterogeneous system. This catalyst has low preparation cost, high conversion rate in catalytic application, and high selectivity for the target product, thus showing promising prospects for industrialization.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] The purpose of this invention is to provide an application of the highly selective catalyst Cu-ZnO / TiO2 in the synthesis of benzimidazole in a heterogeneous system. Using Cu-ZnO / TiO2 as the catalyst and N-methylpyrrolidone as the solvent, it is added to a reaction system of o-phenylenediamine with CO2 and H2 to catalyze the reaction of o-phenylenediamine with CO2 and H2 to generate benzimidazole. The catalytic reaction formula is as follows:

[0008] Preferably, under reaction conditions of CO2 pressure 2.5 MPa, hydrogen pressure 3.5 MPa, and temperature 180 °C, when the conversion rate of o-phenylenediamine is 100%, the selectivity of benzimidazole is greater than 99.9%, and the TOF value is 6.4 h. -1 .

[0009] Preferably, the catalyst is Cu-ZnO / TiO2, where Cu and ZnO are supported on P25 type TiO2, and the loading amount of Cu is 1-9 wt% of the catalyst and the loading amount of ZnO is 2-8 wt% of the catalyst.

[0010] Preferably, the loading of Cu is 5 wt% of the catalyst and the loading of ZnO is 4 wt% of the catalyst.

[0011] In Cu-ZnO / TiO2 catalysts, the loading of Cu and ZnO is expressed as 1-9% and 2-8% in the following text, and their meanings are the same as those of 1-9 wt% and 2-8 wt% as recorded in this text.

[0012] The preparation steps of the above catalyst Cu-ZnO / TiO2 are as follows:

[0013] (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 0.5 h, 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 12 h. The sample was then calcined in a muffle furnace under air atmosphere to obtain ZnO / TiO2 support.

[0014] (2) Add ZnO / TiO2 support and copper nitrate trihydrate to pure water and stir evenly. Place the resulting suspension in a water bath at 50-70 ℃ and stir vigorously. Add precipitant-Na2CO3 solution dropwise to adjust the pH to 8-10. 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 ℃ to dry for 12 h to obtain unreduced Cu-ZnO / TiO2.

[0015] (3) The unreduced catalyst Cu-ZnO / TiO2 was placed in a tube furnace and heated and reduced in a hydrogen atmosphere. It was then naturally cooled to room temperature to obtain Cu-ZnO / TiO2.

[0016] 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.

[0017] Preferably, in step (1), the molar ratio of P25 type TiO2 to zinc nitrate hexahydrate is 3-14:1.

[0018] Preferably, in step (1), the heating rate of the muffle furnace is 5 °C / min, the calcination temperature is 250-450 °C, and the calcination time is 3.5-4.5 h. Since the purpose of calcining the carrier is to obtain a carrier with a rich pore structure, it is important to control the appropriate calcination temperature and time to maintain a stable structure of the carrier.

[0019] Preferably, in step (2), the mass ratio of ZnO / TiO2 support to copper nitrate trihydrate is 2-26:1.

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

[0021] 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 1-3 h.

[0022] The specific steps for synthesizing benzimidazole in a heterogeneous system using the highly selective catalyst Cu-ZnO / TiO2 of the present invention are as follows:

[0023] (1) Select a stainless steel high-pressure reactor and insert a glass container as the reactor liner;

[0024] (2) Weigh the catalyst Cu-ZnO / TiO2 into the high-pressure reactor, then weigh o-phenylenediamine and dissolve it in N-methylpyrrolidone solvent. After ultrasonically dispersing it evenly, place the mixture into the high-pressure reactor.

[0025] (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.

[0026] (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.

[0027] (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.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The catalyst Cu-ZnO / TiO2 of the present invention is prepared by deposition-precipitation method, using non-precious metals as active phase and P25 type TiO2 as support, which greatly reduces the cost of raw materials, and the preparation method is simple, green and environmentally friendly, and has industrialization prospects.

[0030] The 5%Cu-4%ZnO / P25 catalyst prepared by this invention has excellent catalytic performance; under the reaction conditions of CO2 pressure 2.5 MPa, hydrogen pressure 3.5 MPa, temperature 180 ℃, reaction time 0.25 h, and catalyst 100 mg, the selectivity of benzimidazole is greater than 99.9% when the conversion rate of 0.108 g o-phenylenediamine is 100%. Attached Figure Description

[0031] Figure 1 The image shows the XRD pattern of the Cu-ZnO / TiO2 catalyst prepared in Example 3.

[0032] Figure 2 The image shows the time course of the Cu-ZnO / TiO2 catalyst prepared in Example 3.

[0033] Figure 3 The figure shows the stability performance of the Cu-ZnO / TiO2 catalyst prepared in Example 3.

[0034] Figure 4 This is a TEM image of the Cu-ZnO / TiO2 catalyst prepared in Example 3. 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 Cu-ZnO / TiO2 with different proportions of Cu and ZnO loaded on P25 type TiO2 as an example to test the performance and parameters of the product and determine the optimal performance of the product.

[0037] In the following specific examples 1-8, the catalyst was prepared using the following steps:

[0038] (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 support.

[0039] (2) Add ZnO / TiO2 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.

[0040] (3) The unreduced catalyst Cu-ZnO / TiO2 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.

[0041] In terms of the amount of raw materials used, by controlling the molar ratio of P25 type TiO2 to zinc nitrate hexahydrate to 3-14:1, and the mass ratio of ZnO / TiO2 support to copper nitrate trihydrate to 2-26:1, Cu and ZnO can be loaded in the catalyst in different proportions.

[0042] The application test of the catalyst prepared by the above method for the catalytic synthesis of benzimidazole was carried out as follows: The reaction was conducted in a 200 mL stainless steel high-pressure reactor with a glass container inserted as the reactor liner. 100 mg of catalyst was weighed into the high-pressure reactor, followed by 0.108 g of o-phenylenediamine and 20 mL of N-methylpyrrolidone. The o-phenylenediamine was dissolved in N-methylpyrrolidone 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 h 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.

[0043] 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 200–300 mL / min, and carrier gas flow rates of 2–3 mL / min. The injection temperature was set to 280.0 °C, the initial column furnace temperature was set to 150 °C and held for 10 min, then increased to 280 °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 synthesis of benzimidazole from o-phenylenediamine were calculated by gas chromatography.

[0044] Example 1: Synthesis of benzimidazole from o-phenylenediamine catalyzed by 5% Cu-2% ZnO / TiO2

[0045] The catalyst of Example 1 of this invention was tested for its application in the catalytic synthesis of benzimidazole from o-phenylenediamine with CO2 and H2. The performance test conditions and results are as follows:

[0046] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa CO2 pressure, 180 °C temperature, 0.25 h reaction time, 100 mg catalyst, and 0.108 g o-phenylenediamine, the catalyst conversion rate was 18.7%, and the selectivity of benzimidazole was greater than 99.9%.

[0047] Example 2: Synthesis of benzimidazole from o-phenylenediamine catalyzed by 5% Cu-4% ZnO / TiO2

[0048] The catalyst of Example 2 of this invention was tested for its application in the catalytic synthesis of benzimidazole from o-phenylenediamine with CO2 and H2. The performance test conditions and results are as follows:

[0049] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa CO2 pressure, 180 °C temperature, 0.25 h reaction time, 100 mg catalyst, and 0.108 g o-phenylenediamine, the catalyst conversion rate was 34.1%, and the selectivity of benzimidazole was greater than 99.9%.

[0050] Example 3: Synthesis of benzimidazole from o-phenylenediamine catalyzed by 5% Cu-6% ZnO / TiO2

[0051] The catalyst of Example 3 of this invention was tested for its application in the catalytic synthesis of benzimidazole from o-phenylenediamine with CO2 and H2. The performance test conditions and results are as follows:

[0052] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa carbon dioxide pressure, 180 °C temperature, 0.25 h reaction time, 100 mg catalyst, and 0.108 g o-phenylenediamine, the catalyst conversion rate was 23.8%, and the selectivity of benzimidazole was greater than 99.9%.

[0053] Example 4: Synthesis of benzimidazole from o-phenylenediamine catalyzed by 5% Cu-8% ZnO / TiO2

[0054] The catalyst of Example 4 of this invention was tested for its application in the catalytic synthesis of benzimidazole from o-phenylenediamine with CO2 and H2. The performance test conditions and results are as follows:

[0055] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa carbon dioxide pressure, 180 °C temperature, 0.25 h reaction time, 100 mg catalyst, and 0.108 g o-phenylenediamine, the catalyst conversion rate was 15.1%, and the selectivity of benzimidazole was greater than 99.9%.

[0056] Comparative Example 1: 5% Cu / ZnO catalyzed synthesis of benzimidazole from o-phenylenediamine

[0057] The catalytic synthesis of benzimidazole from 5% Cu / ZnO in Comparative Example 1 was tested, and the performance test conditions and results are as follows:

[0058] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa carbon dioxide pressure, 180 °C temperature, 0.25 h reaction time, 100 mg catalyst, and 0.108 g o-phenylenediamine, the catalyst conversion rate was 0.8%, and the selectivity of benzimidazole was greater than 99.9%.

[0059] Comparative Example 2: Synthesis of benzimidazole from o-phenylenediamine catalyzed by 5% Cu / TiO2

[0060] The catalytic synthesis of benzimidazole from phenylenediamine using 5% Cu / TiO2 in Comparative Example 2 was tested, and the performance test conditions and results are as follows:

[0061] Under the reaction conditions of hydrogen pressure 3.5 MPa, carbon dioxide pressure 2.5 MPa, temperature 180 ℃, reaction time 0.25 h, catalyst 100 mg, and o-phenylenediamine 0.108 g, the catalyst conversion rate was 9.1%, and the selectivity of benzimidazole was greater than 99.9%.

[0062] Example 5: Synthesis of benzimidazole from o-phenylenediamine catalyzed by 1% Cu-4% ZnO / TiO2

[0063] The catalyst of Example 5 of this invention was tested for its application in the catalytic synthesis of benzimidazole from o-phenylenediamine with CO2 and H2. The performance test conditions and results are as follows:

[0064] Under the reaction conditions of hydrogen pressure 3.5 MPa, carbon dioxide pressure 2.5 MPa, temperature 180 ℃, reaction time 0.25 h, catalyst 50 mg, and aniline 0.1 g, the catalyst conversion rate was 11.7%, and the selectivity of benzimidazole was greater than 99.9%.

[0065] Example 6: Synthesis of benzimidazole from o-phenylenediamine catalyzed by 9% Cu-4% ZnO / TiO2

[0066] The catalyst of Example 6 of this invention was tested for its application in the catalytic synthesis of benzimidazole from o-phenylenediamine with CO2 and H2. The performance test conditions and results are as follows:

[0067] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa carbon dioxide pressure, 180 °C temperature, 0.25 h reaction time, 100 mg catalyst, and 0.108 g o-phenylenediamine, the catalyst conversion rate was 19.7%, and the selectivity of benzimidazole was greater than 99.9%.

[0068] Example 7: Synthesis of benzimidazole from o-phenylenediamine catalyzed by 5% Cu-4% ZnO / TiO2

[0069] The catalyst in Example 7 of this invention was prepared by reduction at a hydrogen reduction temperature of 200 °C, and then its application in the catalytic synthesis of benzimidazole from o-phenylenediamine with CO2 and H2 was tested. The performance test conditions and results are as follows:

[0070] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa carbon dioxide pressure, 180 °C temperature, 0.25 h reaction time, 100 mg catalyst, and 0.108 g o-phenylenediamine, the catalyst conversion rate was 28.3%, and the selectivity of benzimidazole was greater than 99.9%.

[0071] Example 8: Synthesis of benzimidazole from o-phenylenediamine catalyzed by 5% Cu-4% ZnO / TiO2

[0072] The catalyst in Example 8 of this invention was prepared by reduction at a hydrogen reduction temperature of 400°C, and then subjected to application testing for the catalytic synthesis of benzimidazole from o-phenylenediamine with CO2 and H2. The performance test conditions and results are as follows:

[0073] Under the reaction conditions of 3.5 MPa hydrogen pressure, 2.5 MPa carbon dioxide pressure, 180 °C temperature, 0.25 h reaction time, 100 mg catalyst, and 0.108 g o-phenylenediamine, the catalyst achieved a conversion rate of 31.8% and a selectivity for benzimidazole greater than 99.9%.

[0074] The catalyst prepared in Example 2 was subjected to spectral analysis, electron microscopy, catalytic activity testing, and stability testing. The test results are as follows.

[0075] Figure 1 The XRD patterns of the catalyst prepared in Example 2 before and after the catalytic reaction are shown. The characteristic peaks of P25-type TiO2 are clearly observed, and characteristic peaks belonging to the (100), (002), and (101) crystal planes of ZnO and the (111) crystal plane of Cu can be observed in the spectrum. The XRD patterns of the catalyst prepared in Example 2 before and after the catalytic reaction show almost no change. The size of Cu particles in the catalyst is 5 nm before and after the reaction, indicating that the catalyst has a stable structure and is a recyclable heterogeneous catalyst.

[0076] Figure 2 The figure shows the time course curve of the catalyst prepared in Example 3. As can be seen from the figure, the conversion rates of o-phenylenediamine were 22.5%, 34.1%, 47.5%, 58.1%, 72.3%, 88.7%, 98.7%, and 100.0% at reaction times of 0 h, 0.25 h, 0.5 h, 1 h, 2 h, 4 h, 6 h, and 7 h, respectively. The selectivity of benzimidazole was maintained at more than 99.9% in all cases. It can be concluded that the catalyst prepared in Example 2 has high catalytic activity and selectivity.

[0077] Figure 3 The figure shows the stability performance of the catalyst prepared in Example 3. As can be seen from the figure, the conversion rates of aniline were 34.1%, 34.9%, 34.1%, and 34.0% for the first, second, third, and fourth cycles, respectively, and the selectivity of benzimidazole was greater than 99.9% for all of them. It can be concluded that the catalyst has high stability.

[0078] Figure 4The 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 5 nm.

[0079] The catalytic performance of catalyst products obtained under different conditions for aniline under the same reaction conditions is shown in Table 1.

[0080] Table 1: Effect of different loading amounts on catalytic activity

[0081]

[0082] As can be seen from Examples 1-4 in Table 1, the loading of ZnO has a significant impact on the catalyst activity. When the loading content ranges from 2% to 8%, the conversion selectivity of o-phenylenediamine first increases and then decreases, while the selectivity of benzimidazole is greater than 99.9%. This indicates that the catalytic performance of the catalyst also increases first and then decreases, exhibiting a volcano-shaped trend. When the loading is 4%, the conversion rate reaches a maximum of 34.1% and the selectivity is greater than 99.9%.

[0083] As can be seen from Examples 2, 5 and 6, the loading of Cu still has a significant impact on the catalyst activity. When the loading ranges from 1% to 9%, the conversion selectivity of o-phenylenediamine first increases and then decreases, while the selectivity of benzimidazole is greater than 99.9%. When the loading is 5%, the conversion reaches a maximum of 34.1% and the selectivity is greater than 99.9%.

[0084] As can be seen from Examples 2, 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.

[0085] As can be seen from Examples 2, 7, and 8, 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 at a reduction temperature of 300 °C.

[0086] 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. The application of a highly selective catalyst Cu-ZnO / TiO2 in the synthesis of benzimidazole in a heterogeneous system, characterized in that, Using Cu-ZnO / TiO2 as a catalyst and N-methylpyrrolidone as a solvent, it was added to a reaction system of o-phenylenediamine, CO2 and H2 to catalyze the reaction of o-phenylenediamine with CO2 and H2 to generate benzimidazole; Under reaction conditions of 2.5 MPa CO2 pressure, 3.5 MPa hydrogen pressure, and 180 °C, when the conversion of o-phenylenediamine is 100%, the selectivity of benzimidazole is greater than 99.9%, and the TOF value is 6.4 h. -1 ; The catalyst is Cu-ZnO / TiO2, with Cu and ZnO supported on P25 type TiO2. The Cu loading is 1-9 wt% of the catalyst, and the ZnO loading is 2-8 wt%.

2. The application according to claim 1, characterized in that, The Cu loading is 5 wt% of the catalyst, and the ZnO loading is 4 wt%.

3. The application according to claim 1, characterized in that, The preparation steps of the catalyst Cu-ZnO / TiO2 are as follows: (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 0.5 h, 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 12 h. The sample was then calcined in a muffle furnace under air atmosphere to obtain ZnO / TiO2 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 50-70℃ and stir vigorously. Add precipitant-Na2CO3 solution dropwise to adjust the pH to 8-10. 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℃ for 12 h to obtain unreduced Cu-ZnO / TiO2. (3) The unreduced catalyst Cu-ZnO / TiO2 was placed in a tube furnace and heated and reduced in a hydrogen atmosphere. It was then naturally cooled to room temperature to obtain Cu-ZnO / TiO2.

4. The application according to claim 3, characterized in that, In step (1) of the preparation of the highly selective catalyst Cu-ZnO / TiO2, the mass ratio of P25 type TiO2 to zinc nitrate hexahydrate is 3-14:

1.

5. The application according to claim 3, characterized in that, In step (1) of the preparation of the highly selective catalyst Cu-ZnO / TiO2, 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 application according to claim 3, characterized in that, In step (2) of the preparation of the highly selective catalyst Cu-ZnO / TiO2, the mass ratio of ZnO / TiO2-P25 support to copper nitrate trihydrate is 2-26:

1.

7. The application according to claim 3, characterized in that, In steps (1) and (2) of the preparation of the highly selective catalyst Cu-ZnO / TiO2, the concentration of Na2CO3 solution is 0.1 g / mL.

8. The application according to claim 3, characterized in that, In step (3) of the preparation of the highly selective catalyst Cu-ZnO / TiO2, 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 1-3h.

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