Application of highly active catalyst Cu-ZnO / TiO2 in the heterogeneous synthesis of 4-[(5-methylhexyl-2-yl)amino]phenol

Abstract

This invention relates to the application of a highly active catalyst, Cu-ZnO / TiO2, in the hydrogenation reaction of p-aminophenol and methyl isopentyl ketone to produce 4-[(5-methylhexyl-2-yl)amino]phenol, belonging to the field of catalyst application technology. This catalyst exhibits excellent catalytic performance, achieving 100% conversion of p-aminophenol and a selectivity of 99.9% for the target product 4-[(5-methylhexyl-2-yl)amino]phenol at a hydrogen pressure of 6 MPa, a temperature of 170℃, and a reaction time of 2 h, demonstrating broad industrialization prospects.

Description

Technical Field

[0001] This invention belongs to the field of application technology of non-precious metal catalysts, specifically relating to the application of a highly selective catalyst Cu-ZnO / TiO2 in a heterogeneous system for the condensation and hydrogenation of p-aminophenol and methyl isopentyl ketone to produce 4-[(5-methylhexyl-2-yl)amino]phenol. Background Technology

[0002] 4-[(5-methylhexyl-2-yl)amino]phenol, as an important fine chemical intermediate, has irreplaceable application value in the fields of antioxidants, ultraviolet absorbers, pharmaceutical intermediates, and high-performance material additives. Especially in high-end coatings and biopharmaceutical synthesis, stringent requirements are placed on its purity and synthesis efficiency. Condensation hydrogenation is currently the core route for synthesizing this type of N-alkylated aromatic amine compound. This reaction process involves multiple coupled reactions of carbonyl addition, dehydration condensation, and hydrogenation reduction, resulting in a complex reaction mechanism. It places extremely high demands on the distribution of active sites, electron transfer capability, and structural stability of the catalyst. Therefore, the performance of the catalyst directly determines the reaction efficiency, target product selectivity, mild reaction conditions, and economic viability for industrial production.

[0003] Currently, reported catalysts for condensation hydrogenation reactions are mainly divided into two categories: noble metal catalysts and non-noble metal catalysts. Among them, noble metal catalysts (such as Pd, Pt, and Rh-based catalysts) have shown certain application potential in this type of reaction due to their excellent hydrogenation activity and catalytic stability. However, these catalysts suffer from problems such as high raw material costs (large fluctuations in the price of noble metals and scarcity of resources), complex preparation processes (requiring high-precision loading and modification), and susceptibility to poisoning and deactivation by impurities in the reaction system. These problems result in high catalytic costs per unit product, which seriously limits their widespread application in large-scale industrial production. Meanwhile, while existing non-precious metal catalysts (such as single Cu-based, Ni-based, Zn-based catalysts and simple composite oxide catalysts) have cost advantages, they generally have significant technical shortcomings in catalyzing the condensation hydrogenation reaction of p-aminophenol and methyl isopentyl ketone: First, their catalytic activity is insufficient, requiring harsh conditions such as high temperature (above 180℃) and high pressure (above 8MPa) to achieve a certain conversion rate, which not only increases energy consumption and equipment wear but also easily triggers side reactions; second, their selectivity for the target product is poor, and side reactions such as excessive alkylation of amino groups, incomplete reduction of carbonyl groups, or hydrogenation of aromatic rings easily occur during the reaction, leading to increased difficulty in product separation and purification and reduced product yield; third, their catalyst stability is poor, and the active components are prone to agglomeration, loss, or oxidation during the reaction, resulting in rapid decay of catalytic performance and difficulty in reusing them; fourth, some non-precious metal catalysts require the use of toxic additives in their preparation, posing environmental hazards. These defects together make it difficult for existing non-precious metal catalysts to meet the actual needs of industrial production for high efficiency, low cost, and green environmental protection, becoming the core technical bottleneck restricting the large-scale synthesis of 4-[(5-methylhexyl-2-yl)amino]phenol.

[0004] As the fine chemical industry transforms towards green, low-cost, and high-efficiency directions, developing a non-precious metal catalyst with simple preparation process, low raw material cost, high catalytic activity, excellent selectivity of target products, and strong structural stability for the condensation hydrogenation reaction of p-aminophenol and methyl isopentyl ketone can not only break through existing technical bottlenecks, significantly improve product yield and production efficiency, and reduce production costs, but also reduce energy consumption and pollutant emissions during the reaction process. This aligns with the industry's green development needs and has broad prospects for industrial application. Summary of the Invention

[0005] To address the aforementioned problems in existing catalytic synthesis of the hydrogenation product of p-aminophenol and methyl isopentyl ketone condensation, the present invention aims to provide an application of a highly active catalyst Cu-ZnO / TiO2 in the heterogeneous system for catalyzing the hydrogenation reaction of p-aminophenol and methyl isopentyl ketone condensation. This application has significant advantages such as good performance and high selectivity. The catalyst is simple to prepare, low in cost, and has 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 active catalyst Cu-ZnO / TiO2 in the heterogeneous system for catalyzing the condensation and hydrogenation reaction of p-aminophenol with methyl isopentyl ketone to prepare 4-[(5-methylhexyl-2-yl)amino]phenol.

[0008] Preferably, in this highly active catalyst, Cu and ZnO are supported on P25 type TiO2, with the Cu loading being 1-9 wt% of the catalyst and the ZnO loading being 1-8 wt%.

[0009] Preferably, in this hydrogenation reaction, the catalyst is 0.05 g, p-aminophenol is 1 mmol, methyl isopentyl ketone is 1 mmol, cyclohexane is 20 mL, the temperature is 160-180 °C, the hydrogen pressure is 5-8 MPa, the reaction time is 1-2 h, the p-aminophenol conversion rate is 42.1-100%, and the target product selectivity is 99.9%.

[0010] Preferably, in this highly active catalyst, the Cu loading is 5 wt% and the ZnO loading is 3.75 wt%.

[0011] Preferably, with 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, a temperature of 170 °C, a hydrogen pressure of 6 MPa, and a reaction time of 2 h, the p-aminophenol conversion rate is 100% and the target product selectivity is 99.9%.

[0012] In the above applications, the preparation steps of this highly active 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 ℃ to dry 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.

[0013] Preferably, in step (1), the mass ratio of P25 type TiO2 to zinc nitrate hexahydrate is 3-14:1.

[0014] Preferably, in step (2), the mass ratio of ZnO / TiO2 support to copper nitrate trihydrate is 2-26:1.

[0015] Preferably, in steps (1) and (2), the concentration of the Na2CO3 solution is 0.1 g / mL.

[0016] 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 2-5 h.

[0017] Preferably, in step (3), the heating rate of the tubular furnace is 5 ℃ / min, the reduction temperature in the tubular furnace is 300℃, the reduction time is 1-3 h, and the hydrogen flow rate is 30 mL / min.

[0018] In the catalytic reaction of this invention, under thermocatalytic conditions, the Cu on the surface of the 5%Cu-3.75%ZnO / TiO2 catalyst... 0 Nanoparticles, acting as catalytic active centers, effectively promote Cu catalysis through the introduction of ZnO. 0 This improves the dispersibility and enhances its adsorption and activation ability for H2. At the beginning of the reaction, the carbonyl group (C=O) in the methyl isopentyl ketone molecule is adsorbed perpendicularly onto Cu via the lone pair electrons of the O atom. 0 Surface, Cu 0 Electrons in the d orbitals feed back into the π orbitals of the C=O antibonding structure, causing the C=O bond to polarize and form Cδ. + –Oδ⁻ significantly enhances the electrophilicity of the carbonyl carbon; simultaneously, the –NH₂ group in the p-aminophenol molecule is weakly adsorbed onto the neighboring Cu atom via the lone pair electrons of the N atom. 0 The adsorbed site, or through hydrogen bonding / π-π stacking interactions, approaches the adsorbed methyl isopentyl ketone, reaching surface adsorption saturation. Subsequently, the adsorbed –NH2 groups interact with the polarized carbonyl carbon (Cδ). + The reaction initiates nucleophilic addition to form an α-hydroxyamine (carbinolamine) intermediate. This intermediate then undergoes rapid intramolecular dehydration under thermal drive to form an imine (C=N) intermediate (Schiff base). This step is a reversible equilibrium reaction, with high temperature and a H2 atmosphere shifting the equilibrium to the right. Simultaneously, H2 molecules react in Cu... 0Homolytic dissociation occurs on the surface, with the H–H bond breaking to generate two surface-adsorbed active hydrogen atoms (Cu–H). Finally, the imine C=N bond in Cu… 0 The surface sequentially receives two Cu–H* active hydrogen atoms: the first H atom attacks the imine carbon atom (C). + The process generates an α-aminoalkyl radical intermediate; the second H atom attacks the nitrogen atom, completing the complete reduction of the C=N bond, and generating the target secondary amine product 4-[(5-methylhexyl-2-yl)amino]phenol. The product then decomposes from Cu... 0 Surface desorption, Cu 0 The active sites are re-exposed and enter the next catalytic cycle.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This invention uses a deposition-precipitation method to prepare Cu-ZnO / TiO2, with non-precious metals as the active phase and P25 type TiO2 as the carrier, which greatly reduces the cost of raw materials. Moreover, the preparation method is simple, green and environmentally friendly, and easy to industrialize.

[0020] 2) The Cu-ZnO / TiO2 catalyst prepared by this invention has excellent catalytic performance. Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C temperature and 6 MPa hydrogen pressure, the conversion rate of p-aminophenol reaches 100% and the selectivity of the target product reaches 100% after 2 h of reaction.

[0021] 3) The catalytic reaction system of the present invention is a heterogeneous system, and the catalyst and reaction products are easy to separate and can be reused, which further reduces production energy consumption and cost. Attached Figure Description

[0022] Figure 1 This is a physical image of the Cu-ZnO / TiO2 prepared in Example 2.

[0023] Figure 2 The image shows an electron microscope image of Cu-ZnO / TiO2 prepared in Example 2.

[0024] Figure 3 The image shows the XRD pattern of Cu-ZnO / TiO2 prepared in Example 2.

[0025] Figure 4 The image shows the time course diagram of the preparation of Cu-ZnO / TiO2 prepared in Example 2. Detailed Implementation

[0026] 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.

[0027] This invention uses Cu-ZnO / TiO2 prepared on P25 type TiO2 with different proportions of Cu and ZnO as examples to test the performance and parameters of the product and determine the optimal performance of the product.

[0028] In the following specific embodiments, the catalyst is prepared using the following steps: (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 the pH was washed until it reached 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. (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. (3) The unreduced catalyst Cu-ZnO / TiO2 was placed in a tube furnace and heated and reduced in a hydrogen atmosphere (hydrogen flow rate 30 mL / min). The temperature was increased to 300 °C at a heating rate of 5 °C / min and the reduction time was 2 h. The catalyst was then naturally cooled to room temperature to obtain Cu-ZnO / TiO2.

[0029] 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.

[0030] The test procedure for the condensation hydrogenation reaction of p-aminophenol and methyl isopentyl ketone catalyzed by the catalyst prepared by the above method is as follows: The reaction was carried out in a high-pressure reactor with a glass container inserted as the reactor liner. 0.05 g of catalyst was weighed into the high-pressure reactor, followed by 1 mmol of p-aminophenol, 1 mmol of methyl isopentyl ketone, and 20 mL of cyclohexane. The p-aminophenol and methyl isopentyl ketone were dissolved in the cyclohexane, stirred until evenly dispersed, and then the mixture was placed into the high-pressure reactor. After sealing the reactor, the airtightness was checked. After checking the airtightness, the reactor temperature was raised to 170 °C, and hydrogen gas was introduced until the pressure reached 6 MPa. The stirring speed was adjusted to 500 rpm, and timing was started. After reacting for 1-2 h, the reactor was cooled to room temperature, and the gas valve of the high-pressure reactor was opened to release the gas inside until the pressure reached 0 MPa.

[0031] After filtering the reaction solution, the sample was aspirated using a micro-injection needle and injected into a gas chromatograph to analyze the content of the reaction products and calculate the conversion rate of the raw materials and the selectivity of the catalyst.

[0032] Example 1: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Example 1 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 1 h reaction time, the catalyst achieved a conversion rate of 68.6% for 4-aminophenol and a selectivity of 99.9% for the target product A.

[0033] Example 2: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Example 2 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a 100% conversion rate of 4-aminophenol and a 99.9% selectivity for the target product A.

[0034] Example 3: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Example 3 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The performance test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, temperature 170 ℃, hydrogen pressure 6 MPa, carbon dioxide pressure 2 MPa, stirring speed 500 rpm, and reaction time 1 h, the catalyst achieved a conversion rate of 27.3% for 4-aminophenol and a selectivity of 99.9% for the target product A.

[0035] Example 4: Hydrogenation reaction of p-aminophenol and methyl isopentyl ketone catalyzed by 5% Cu-1% ZnO / TiO2 The catalyst prepared in Example 4 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a conversion rate of 42.1% for p-aminophenol and a selectivity of 70.8% for the target product.

[0036] Example 5: Hydrogenation reaction of p-aminophenol and methyl isopentyl ketone catalyzed by 5% Cu-5% ZnO / TiO2 The catalyst prepared in Example 4 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a conversion rate of 42.1% for p-aminophenol and a selectivity of 99.9% for the target product.

[0037] Comparative Example 1: 5% Cu / ZnO catalyzed hydrogenation reaction of p-aminophenol with methyl isopentyl ketone The 5% Cu / ZnO prepared in Comparative Example 1 was tested for its application in the catalytic hydrogenation reaction of p-aminophenol with methyl isopentyl ketone. The performance test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a conversion rate of 36.3% for p-aminophenol and a selectivity of 99.9% for the target product.

[0038] Comparative Example 2: 5% Cu / TiO2-catalyzed hydrogenation reaction of p-aminophenol with methyl isopentyl ketone The 5% Cu / TiO2 prepared in Comparative Example 2 was used for catalytic hydrogenation reaction of p-aminophenol with methyl isopentyl ketone. The performance test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a conversion rate of 68.7% for p-aminophenol and a selectivity of 99.9% for the target product.

[0039] Comparative Example 3: 5% Fe / AlO2-catalyzed hydrogenation reaction of p-aminophenol with methyl isopentyl ketone The 5% Fe / AlO2 prepared in Comparative Example 3 was used for application testing in the catalytic hydrogenation reaction of p-aminophenol with methyl isopentyl ketone. The performance test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a conversion rate of 74.7% for p-aminophenol and a selectivity of 92.4% for the target product.

[0040] Example 6: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 1% Cu-3.75% ZnO / TiO2 The catalyst prepared in Example 6 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a conversion rate of 70.1% for p-aminophenol and a selectivity of 99.9% for the target product.

[0041] Example 7: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 9% Cu-3.75% ZnO / TiO2 The catalyst prepared in Example 7 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a conversion rate of 57.3% for p-aminophenol and a selectivity of 99.9% for the target product.

[0042] Example 8: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Example 8 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 160 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a conversion rate of 93.5% for 4-aminophenol and a selectivity of 99.9% for the target product A.

[0043] Example 9: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Example 9 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 180 ℃ temperature, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a 100% conversion rate of 4-aminophenol and a 99.9% selectivity for the target product A.

[0044] Comparative Example 4: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Comparative Example 4 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol with methyl isopentyl ketone. The performance test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 100 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a conversion rate of 23.3% for 4-aminophenol and a selectivity of 99.9% for the target product A.

[0045] Comparative Example 5: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Comparative Example 5 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol with methyl isopentyl ketone. The performance test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 200 ℃ temperature, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a 100% conversion rate of 4-aminophenol and a selectivity of 72.9% for the target product A.

[0046] Example 10: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Example 10 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 5 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a conversion rate of 88.0% for 4-aminophenol and a selectivity of 99.9% for the target product A.

[0047] Example 11: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Example 11 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol and methyl isopentyl ketone. The test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 180 ℃ temperature, 8 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a 100% conversion rate of 4-aminophenol and a 99.9% selectivity for the target product A.

[0048] Comparative Example 6: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Comparative Example 6 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol with methyl isopentyl ketone. The performance test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C temperature, 0 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the conversion rate of p-4-aminophenol by this catalyst was 0%.

[0049] Comparative Example 7: Hydrogenation reaction of p-aminophenol with methyl isopentyl ketone catalyzed by 5% Cu-3.75% ZnO / TiO2 The catalyst prepared in Comparative Example 7 of this invention was tested for its application in the catalytic hydrogenation reaction of p-aminophenol with methyl isopentyl ketone. The performance test conditions and results are as follows: Under the reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 10 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, the catalyst achieved a 100% conversion rate of 4-aminophenol and a 62.4% selectivity for the target product A.

[0050] The catalytic performance of the catalyst products obtained under different conditions for aminophenol under different reaction conditions is shown in Table 1.

[0051] Table 1: Effect of different reaction conditions on catalytic activity

[0052] As can be seen from Examples 1-2 in Table 1, the reaction time has a significant impact on the catalyst activity. Under the conditions of hydrogen pressure of 6 MPa and temperature of 170 °C, as the reaction time is extended from 1 h to 2 h, the conversion rate of p-aminophenol increases from 68.6% to 99.9%, indicating that extending the reaction time is beneficial to the full progress of the reaction and improves the conversion rate.

[0053] As can be seen from Examples 1 and 3, the presence of CO2 gas has a significant impact on the catalytic performance of the catalyst. Under the same reaction time of 1 h and temperature of 170 °C, the conversion rate (68.6%) when there is no CO2 gas in the reaction atmosphere is much higher than the conversion rate (27.3%) when there is CO2 gas in the reaction atmosphere. This indicates that a suitable hydrogen pressure is a key factor in ensuring high selectivity.

[0054] As can be seen from Examples 1, 4, and 5 in Table 1, the loading of ZnO has a significant impact on the catalyst activity. When the loading content ranges from 1% to 5%, the selectivity of 4-[(5-methylhexyl-2-yl)amino]phenol remains at 99.9%. The conversion of p-aminophenol first increases and then decreases, which means that the catalytic performance of the catalyst also increases first and then decreases, showing a volcano-shaped trend. When the loading is 3.75%, the conversion rate is 100% and the selectivity reaches a maximum of 99.9%.

[0055] As can be seen from Examples 2, 6 and 7, the loading of Cu still has a significant impact on the catalyst activity. When the loading ranges from 1% to 9%, the conversion of p-aminophenol first increases and then decreases. When the loading is 5%, the conversion rate is 100% and the selectivity reaches a maximum of 99.9%.

[0056] As can be seen from Examples 2, 1, 2 and 3, ZnO and Cu have a synergistic effect on the catalytic performance of the catalyst, which can significantly improve the catalytic performance of the catalyst.

[0057] As can be seen from Examples 2, 8, 9, and Comparative Examples 4 and 5, when the reaction temperature increases from 160°C to 180°C, the conversion of 4-aminophenol first decreases from 100% and then recovers to 100% conversion. When the temperature is too low or too high, the conversion of 4-aminophenol decreases significantly, and the selectivity of target product A also decreases significantly.

[0058] As can be seen from Examples 2, 10, 11, and Comparative Examples 6 and 7, when the hydrogen pressure in the reaction conditions increases from 5 MPa to 8 MPa, the conversion of 4-aminophenol first decreases from 100%, and then recovers to 100% conversion. When the hydrogen pressure is 0, the conversion of 4-aminophenol drops directly to 0; when the preset pressure is exceeded, the selectivity of target product A decreases significantly.

[0059] In summary, the 5%Cu-3.75%ZnO / TiO2 catalyst prepared in this invention, under the optimal reaction conditions of 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, 170 °C, 6 MPa hydrogen pressure, 500 rpm stirring speed, and 2 h reaction time, can achieve 100% conversion of p-aminophenol and 99.9% selectivity for the target product, demonstrating excellent catalytic performance.

[0060] 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. Application of highly active catalyst Cu-ZnO / TiO2 in the preparation of 4-[(5-methylhexyl-2-yl)amino]phenol by catalyzing the condensation and hydrogenation reaction of p-aminophenol and methyl isopentyl ketone in a heterogeneous system.

2. The application according to claim 1, characterized in that, In this highly active catalyst, Cu and ZnO are supported on P25 type TiO2, with Cu loading at 1-9 wt% and ZnO loading at 1-8 wt%.

3. The application according to claim 2, characterized in that, In this hydrogenation reaction, with 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, a temperature of 160-180 °C, a hydrogen pressure of 5-8 MPa, and a reaction time of 1-2 h, the conversion rate of p-aminophenol was 42.1-100%, and the selectivity of the target product was 99.9%.

4. The application according to claim 2, characterized in that, In this highly active catalyst, the Cu loading is 5 wt% and the ZnO loading is 3.75 wt%.

5. The application according to claim 3 or 4, characterized in that, With 0.05 g catalyst, 1 mmol p-aminophenol, 1 mmol methyl isopentyl ketone, 20 mL cyclohexane, a temperature of 170 °C, a hydrogen pressure of 6 MPa, and a reaction time of 2 h, the conversion rate of p-aminophenol was 100%, and the selectivity of the target product was 99.9%.

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