A highly selective catalyst Ni-TiO2-P25 and its preparation method and its application in the selective hydrogenation of p-chloronitrobenzene by photothermal synergistic catalysis in a heterogeneous system

Abstract

The present invention relates to a highly selective catalyst Ni-TiO2-P25, a preparation method thereof, and an application of a photothermal synergistic catalytic selective hydrogenation of p-chloronitrobenzene in a heterogeneous system, belonging to the field of catalytic hydrogenation. The catalyst uses nickel acetate tetrahydrate as a nickel source and P25-type TiO2 as a carrier. Active metal Ni is loaded on the P25-type TiO2 by an impregnation method, and the catalyst is placed in a tubular furnace for hydrogen reduction to obtain the catalyst Ni-TiO2-P25. The Ni-TiO2-P25 catalyst with a loading of 3.5% has excellent catalytic performance. When the photocurrent density is 0.4W / cm ‑1 Under full-spectrum irradiation, 50 mg of catalyst, 2 g of p-chloronitrobenzene, a hydrogen pressure of 3 MPa, a temperature of 80°C, and a reaction time of 3.5 hours, the conversion rate reached 100%, and the selectivity reached over 99.9%. This preparation method is simple, low-cost, has a fast catalytic hydrogenation rate, high selectivity for the target product, and is easy to separate, showing promising industrial prospects.

Description

Technical Field

[0001] The present invention belongs to the field of catalytic hydrogenation, and specifically relates to a highly selective catalyst Ni-TiO2-P25 and a preparation method thereof, as well as an application of the catalyst in the photothermal synergistic catalytic selective hydrogenation of p-chloronitrobenzene to p-chloroaniline in a heterogeneous system. Background Art

[0002] p-Chloroaniline (p-CAN), also known as 4-chloroaniline, has the chemical formula C6H6ClN. As an important organic chemical raw material and organic intermediate, p-chloroaniline has broad and important applications in fine chemicals such as pesticides, pharmaceuticals, and dyes. With the continuous expansion of domestic and international markets in recent years, the application prospects of p-chloroaniline are becoming increasingly broad.

[0003] p-Chloroaniline is produced by the reduction of p-chloronitrobenzene. These methods primarily include non-hydrogen reduction, catalytic hydrogenation, and photocatalytic reduction. However, the traditional non-hydrogen reduction method has significant environmental and energy impacts in its production. Catalytic hydrogenation, using hydrogen as a reducing agent, produces high-quality products with high yields, simple post-processing, and environmental friendliness. Furthermore, photocatalytic reduction produces p-chloronitrobenzene through electron reduction. Photocatalysis, which converts abundant solar energy into chemical energy, dates back to 1972, when Fujishima and Honda first reported that illumination of an n-type semiconductor TiO2 electrode resulted in the decomposition of water to produce hydrogen and oxygen. Upon exposure to specific light, electrons in the valence band of the photocatalyst absorb energy and transition to the conduction band, creating a redox potential, thereby reducing the nitro group of p-chloronitrobenzene. Photocatalytic reduction utilizes light as its energy source, resulting in low energy consumption and an environmentally friendly, safe, and green catalytic process. However, photocatalysis suffers from suboptimal catalytic efficiency and low light utilization.

[0004] Catalysts based on precious metals such as Pt, Pd, Ru, and Ir are recognized as highly effective hydrogenation catalysts for nitro compounds, demonstrating excellent stability and catalytic activity. However, due to their high catalytic activity, they can also catalyze the hydrogenolysis of CX (X = F, Cl, Br, I) while simultaneously catalyzing the hydrogenation of nitro compounds, leading to dehalogenation reactions. This not only reduces reaction selectivity but also poisons the catalyst, reducing its activity and lifespan. The resulting HCl can also corrode equipment and pose a safety hazard. For example, the Pd@SiO2 catalyst prepared by Hu Yibo et al. exhibits good activity and stability for the selective hydrogenation of p-chloronitrobenzene, but the selectivity for the target product is low. The Au / TiO2 catalyst prepared by Corma et al. selectively reduces nitro groups to amino groups in the presence of multiple functional groups, but its high price limits its application.

[0005] The catalytic activity and stability of non-precious metals such as Co, Ni, Cu and Fe are still inferior to those of precious metals such as Pt, Pd and Ru, but they have the advantages of being abundant on earth, easy to obtain and low in cost. Beller et al. prepared Co oxide-N / C catalyst, which can selectively catalyze the hydrogenation of halonitrobenzenes, but the reaction conditions are relatively harsh. The catalyst Cu / SiO2 prepared by Masazumi and his team has relatively mild reaction conditions, but its activity is very low, with a TOF value of only 0.02h -1 Combining thermal catalysis and photocatalysis, using both as driving forces and complementing the shortcomings of a single catalytic system, effectively solves the above problems. The combination of light energy and thermal energy not only solves the problem of low conversion efficiency of single photocatalysis, but also overcomes the limitation of high energy consumption of single thermal catalysis, and makes the catalytic activity of non-precious metal-based catalysts even better.

[0006] Supported catalysts consist of two components: a carrier and an active center. The carrier, as the catalyst's foundational structure, primarily supports and disperses the active components. Impregnation is a common catalyst preparation method and an effective way to load the active components onto the carrier. This method significantly reduces the difficulty and cost of catalyst manufacturing. The overall process is simple and rapid, and holds considerable research and application value.

[0007] In summary, catalytic hydrogenation is the best method for preparing p-chloroaniline. Therefore, the development of supported non-precious metal-based catalysts capable of photothermal synergistic catalysis for the efficient and green preparation of p-chloroaniline is of great significance in industrial production. Summary of the Invention

[0008] To address the aforementioned issues with existing catalytic hydrogenation technologies, the present invention aims to provide a highly selective Ni-TiO2-P25 catalyst, its preparation method, and its application in the selective hydrogenation of p-chloronitrobenzene in a heterogeneous system using a photothermal catalytic system. This preparation method offers low cost, rapid catalytic hydrogenation rates, high selectivity for the target product, and ease of separation, demonstrating broad industrial potential.

[0009] To achieve the above objectives, the present invention adopts the following technical solutions.

[0010] One of the purposes of the present invention is to provide a highly selective catalyst Ni-TiO2-P25, wherein Ni is loaded on a P25 type TiO2 carrier, wherein the loading amount of Ni is 3 to 5 wt% of the catalyst.

[0011] In a further preferred embodiment of the present invention, the loading amount of Ni is 3.5 wt % of the catalyst.

[0012] For the Ni-TiO2-P25 catalyst, P25 is the crystal form of TiO2. TiO2 (P25) is composed of 80% anatase and 20% rutile by mass, and is a mixed crystal type of nano-TiO2. The method of expressing the Co loading amount is directly abbreviated as 3-5% in the subsequent content of this article, and its meaning is the same as the 3-5wt% recorded in this article.

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

[0014] (1) Using P25 TiO2 as the carrier, heat and stir on a hot plate to ensure uniform heating;

[0015] (2) Using nickel acetate tetrahydrate as the nickel source and uniformly heated P25-type TiO2 as the carrier, an unreduced catalyst Ni-TiO2-P25 was prepared by an impregnation method;

[0016] (3) The unreduced catalyst Ni-TiO2-P25 was placed in a tubular furnace in a hydrogen atmosphere for heating and reduction, cooled naturally to room temperature, and then introduced into a mixed gas of O2 / Ar for passivation to obtain the reduced catalyst Ni-TiO2-P25.

[0017] According to a further preferred embodiment of the present invention, in step (1), the temperature of the heating plate is between 85°C and 95°C.

[0018] According to a further preferred embodiment of the present invention, in step (3), the heating temperature in the tube furnace is 500°C.

[0019] According to a further preferred embodiment of the present invention, in step (3), the heating time in the tube furnace is 2 hours.

[0020] According to a further preferred embodiment of the present invention, in step (3), the volume fraction of O2 is 10%.

[0021] In a further preferred embodiment of the present invention, in step (3), the time for introducing the mixed gas is 20 minutes.

[0022] The method of the present invention for selective hydrogenation of p-chloronitrobenzene using the highly selective catalyst Ni-TiO2-P25 in a heterogeneous system using photothermal synergy is as follows:

[0023] (1) Select a stainless steel photothermal reactor and insert a polytetrafluoroethylene liner;

[0024] (2) Weighing the prepared Ni-TiO2-P25 catalyst into a photothermal reactor, then weighing p-chloronitropropane and dissolving it in methanol solvent, ultrasonically dispersing it evenly, and then placing the mixed solution into the photothermal reactor;

[0025] (3) After sealing the photothermal reactor, flush it with hydrogen at a pressure of 1.0 MPa three times, maintain the hydrogen pressure at 1.0 MPa at room temperature, and check the airtightness of the photothermal reactor;

[0026] (4) Turn on a 300W full-spectrum xenon lamp and maintain a photocurrent density of 0.4W / cm -1 , heat the photothermal reactor to 80°C, continue to introduce hydrogen to 3.0 MPa, and maintain the temperature and pressure in the photothermal reactor for 3.0-3.5 hours;

[0027] (5) After the reaction is completed, turn off the xenon lamp first, wait for the photothermal reactor to cool to room temperature, open the gas valve, and release hydrogen until the pressure is 0 to complete the reaction process.

[0028] The present invention also aims to provide the application of a highly selective catalyst Ni-TiO2-P25 in a heterogeneous system for the photothermal synergistic selective hydrogenation of p-chloronitrobenzene. When the conversion rate of the 3.5% Ni-TiO2-P25 catalyst is 100%, the selectivity of p-chloroaniline is greater than 99%.

[0029] By adopting the above technology, compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1) The present invention adopts an impregnation method to prepare a highly selective catalyst Ni-TiO2-P25, which uses a non-precious metal as the active phase and P25-type TiO2 as the carrier, greatly reducing the cost of raw materials, and the preparation process is simple, low in energy consumption, and environmentally friendly;

[0031] 2) The catalyst Ni-TiO2-P25 prepared by the present invention has a high efficiency of photothermal synergistic catalytic selective hydrogenation of p-chloronitrobenzene to p-chloroaniline when the Ni loading is 3.5%. The specific conditions are: when the photocurrent density is 0.4W / cm -1 Under the reaction conditions of hydrogen pressure 3MPa, temperature 80℃, reaction 3.5h and catalyst 50mg, when the conversion rate of 2g of p-chloronitrobenzene was 100%, the selectivity reached more than 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the X-ray diffraction analysis diagram of 3.5% Ni-TiO2-P25 catalyst;

[0033] As can be seen from the figure, compared with the JCPDS standard data of anatase and rutile phase titanium dioxide, it can be observed that TiO2 is still composed of mixed crystals of anatase and rutile types. In addition, the characteristic peaks of metallic Ni can be observed at 44.5°(111), 51.8°(200) and 76.4°(220), and no obvious NiO characteristic diffraction peaks are detected, indicating that the Ni in the catalyst is basically reduced to metallic Ni.

[0034] Figure 2 5μm and 2μm SEM images of 3.5% Ni-TiO2-P25 catalyst;

[0035] As can be seen from the figure, the surface of the 3.5% Ni-TiO2-P25 catalyst is uneven and is composed of many small particles stacked together.

[0036] Figure 3 This is the UV-visible diffuse reflectance spectrum of 3.5% Ni-TiO2-P25 catalyst;

[0037] As can be seen from the figure, the absorption peak of the 3.5% Ni-TiO2-P25 catalyst is divided into two parts. The first part is below approximately 385nm, indicating strong UV absorption, and the second part is between 400-700nm, indicating significant absorption in the visible light region. Compared to P25 TiO2, which only absorbs UV light, the addition of Ni broadens its light response area and absorption range, enhancing its absorption capacity. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0039] The present invention uses different Ni contents loaded on P25-type TiO2 as examples and Ni loaded on other crystalline TiO2 as comparative examples to test the application in the catalytic hydrogenation of p-chloronitrobenzene. The performance test steps are as follows:

[0040] The performance test was conducted in a 100mL stainless steel photothermal reactor with a polytetrafluoroethylene liner. 50mg of the catalyst 3% Ni-TiO2-P25 was weighed into the photothermal reactor, followed by 2.0g of p-chloronitrobenzene and 30mL of methanol. The p-chloronitrobenzene was dissolved in methanol, ultrasonically dispersed, and the mixture was placed in the photothermal reactor. After sealing the reactor, it was flushed three times with hydrogen (1MPa), the hydrogen pressure was increased by 1MPa at room temperature, and the airtightness was checked. After checking the airtightness, the magnetron speed was adjusted to 500rpm, and the xenon lamp was turned on to maintain a photocurrent density of 0.4W / cm -1When the temperature of the photothermal reactor is raised to 80°C, hydrogen is introduced until the pressure reaches 3 MPa, and the timer is started. After the reaction has lasted for 3 hours, the xenon lamp is turned off. After cooling to room temperature, the gas valve of the photothermal reactor is opened and hydrogen is released until the pressure reaches 0 MPa.

[0041] After filtering the reaction solution, 0.4 μL was aspirated using a microinjection needle and injected into a gas chromatograph. The gas chromatograph flow rate was set at 40-60 mL / min for hydrogen, 260-300 mL / min for air, and 2-4 mL / min for carrier gas. The injection temperature was set at 280.0°C, the column oven temperature at 130.0°C, and the FID temperature at 280.0°C. The catalyst conversion to p-chloronitrobenzene and the selectivity for p-chloroaniline were calculated by gas chromatography using n-dodecane as the internal standard.

[0042] In addition, the effects of anions and non-precious metals with different loadings on catalytic performance were studied through examples, so as to detect the performance and parameters of the product and determine the optimal performance of the product.

[0043] Example 1: Application test of 3% Ni-TiO2-P25 in catalytic hydrogenation of p-chloronitrobenzene

[0044] The Ni-TiO2-P25 catalyst loaded with metal Ni catalyst obtained in this example, with a loading of 3%, was tested in the catalytic hydrogenation of p-chloronitrobenzene:

[0045] At the full spectrum of 300W xenon lamp, the photocurrent density is 0.4W / cm -1 Under the reaction conditions of hydrogen pressure 3MPa, temperature 80℃, reaction time 3h, catalyst 50mg, and p-chloronitrobenzene 0.5g, the catalyst conversion rate was 28.7% and the selectivity of p-chloroaniline was 97.3%.

[0046] Example 2: Application Test of 3.5% Ni-TiO2-P25 in Catalytic Hydrogenation of p-Chloronitrobenzene

[0047] The Ni-TiO2-P25 catalyst loaded with metal Ni on the P25-type TiO2 obtained in this example, with a loading of 3.5%, was tested in the catalytic hydrogenation of p-chloronitrobenzene:

[0048] At the full spectrum of 300W xenon lamp, the photocurrent density is 0.4W / cm -1 Under the reaction conditions of hydrogen pressure 3MPa, temperature 80℃, reaction time 3h, catalyst 50mg, and p-chloronitrobenzene 0.5g, the catalyst conversion rate was 30.0%, and the selectivity for p-chloroaniline was 98.3%. When the reaction time was further extended to 3.5h, the catalyst conversion rate reached 100%, and the selectivity for p-chloroaniline was >99%.

[0049] Example 3: Application test of 4% Ni-TiO2-P25 in catalytic hydrogenation of p-chloronitrobenzene

[0050] The Ni-TiO2-P25 catalyst loaded with metal Ni obtained in this example, with a loading of 4%, was tested in the catalytic hydrogenation of p-chloronitrobenzene:

[0051] At the full spectrum of 300W xenon lamp, the photocurrent density is 0.4W / cm -1 Under the reaction conditions of 3MPa hydrogen pressure, 80℃ temperature, 3h reaction, 50mg catalyst and 0.5g p-chloronitrobenzene, the catalyst conversion rate was 37.7% and the selectivity of p-chloroaniline was 92.0%.

[0052] Example 4: Application Test of 5% Ni-TiO2-P25 in Catalytic Hydrogenation of p-Chloronitrobenzene

[0053] The Ni-TiO2-P25 catalyst loaded with metal Ni obtained in this example, with a loading of 4%, was tested in the catalytic hydrogenation of p-chloronitrobenzene:

[0054] At the full spectrum of 300W xenon lamp, the photocurrent density is 0.4W / cm -1 Under the reaction conditions of 3MPa hydrogen pressure, 80℃ temperature, 3h reaction, 50mg catalyst and 0.5g p-chloronitrobenzene, the catalyst conversion rate was 14.6% and the selectivity of p-chloroaniline was 91.3%.

[0055] Comparative Example 1: Application Test of 3.5% Ni-TiO2-R in Catalytic Hydrogenation of p-Chloronitrobenzene

[0056] The rutile TiO2-loaded metal Ni catalyst obtained in this comparative example, Ni-TiO2-R with a loading of 3.5%, was tested in the catalytic hydrogenation of p-chloronitrobenzene:

[0057] At the full spectrum of 300W xenon lamp, the photocurrent density is 0.4W / cm -1 Under the reaction conditions of 3MPa hydrogen pressure, 80℃ temperature, 3h reaction, 50mg catalyst and 0.5g p-chloronitrobenzene, the catalyst conversion rate was 2.2% and the selectivity of p-chloroaniline was 71.0%.

[0058] Comparative Example 2: Application Test of 3.5% Ni-TiO2-A in Catalytic Hydrogenation of p-Chloronitrobenzene

[0059] The anatase TiO2-loaded Ni catalyst obtained in this comparative example, Ni-TiO2-A with a loading of 3.5%, was tested in the catalytic hydrogenation of p-chloronitrobenzene:

[0060] At the full spectrum of 300W xenon lamp, the photocurrent density is 0.4W / cm -1 Under the reaction conditions of 3MPa hydrogen pressure, 80℃ temperature, 3h reaction, 50mg catalyst and 0.5g p-chloronitrobenzene, the catalyst conversion rate was 4.5% and the selectivity of p-chloroaniline was 81.3%.

[0061] Through examples, we investigate the effects of anions and different non-precious metal loadings on catalytic performance. We test and obtain product performance and parameters, and analyze and determine the optimal performance. The following table shows products obtained under different conditions, their performance test results, comparative cases, and an analysis of the product's performance and effectiveness.

[0062] Table 1: Effect of different crystal forms of TiO2 on activity

[0063]

[0064] Reaction conditions: catalyst 50 mg, p-chloronitrobenzene 2 g, methanol 30 mL, temperature 80 °C, hydrogen pressure 3 MPa, reaction time 1 h, 300 W xenon lamp full spectrum, photocurrent density 0.4 W / cm -1 .

[0065] As can be seen from Table 1, different crystal forms of TiO2 as carriers have a great influence on the activity. Using P25 type TiO2 as a carrier can significantly improve the activity of the catalyst and the selectivity for p-chloroaniline.

[0066] Table 2: Effect of Ni loading and reaction time on catalytic activity

[0067]

[0068] Reaction conditions: catalyst 50 mg, p-chloronitrobenzene 2 g, methanol 30 mL, temperature 80 °C, hydrogen pressure 3 MPa, reaction time 1 h, 300 W xenon lamp full spectrum, photocurrent density 0.4 W / cm -1 .

[0069] a Reaction time 3.5h

[0070] As can be seen from Table 2, different Ni loadings have a great influence on the catalyst activity. When the metal loading content ranges from 3% to 5%, the conversion rate of p-chloronitrobenzene and the selectivity of p-chloroaniline first increase and then decrease, showing a volcano-shaped trend. The conversion rate reaches a maximum of 37.7% at a loading of 4%, and the selectivity reaches a maximum of 98.3% at a loading of 3.5%. After all conversions are completed, the selectivity is greater than 99.9%.

[0071] Table 3: Effect of metal anions on catalytic activity

[0072]

[0073] Reaction conditions: catalyst 50 mg, p-chloronitrobenzene 2 g, methanol 30 mL, temperature 80 °C, hydrogen pressure 3 MPa, reaction time 1 h, 300 W xenon lamp full spectrum, photocurrent density 0.4 W / cm -1 .

[0074] As can be seen from Table 3, the anions in the metal salts have a great influence on the activity of the catalyst. When the loading amount is 3.5% and the precursor is nickel acetate tetrahydrate, the catalyst activity is significantly higher than that of catalysts with other nickel salts as precursors.

[0075] Table 4: Effect of different metal loadings on reaction activity

[0076]

[0077]

[0078] Reaction conditions: catalyst 50 mg, p-chloronitrobenzene 2 g, methanol 30 mL, temperature 80 °C, hydrogen pressure 3 MPa, reaction time 1 h, 300 W xenon lamp full spectrum, photocurrent density 0.4 W / cm -1 .

[0079] As can be seen from Table 4, the loading of different metals has a great influence on the activity of the catalyst. When the precursor is nickel acetate tetrahydrate, the catalyst activity is significantly higher than that of the catalyst loaded with other non-precious metals.

[0080] Table 5: Effect of light on reaction activity

[0081]

[0082] Reaction conditions: catalyst (3.5% Ni-TiO2-P25) 50 mg, p-chloronitrobenzene 2 g, methanol 30 mL, temperature 80°C, hydrogen pressure 3 MPa, reaction time 1 h.

[0083] As can be seen from Table 5, when light is added to the reaction, the conversion rate and selectivity are significantly improved under the above experimental conditions, indicating that light plays a promoting role in the reaction in this reaction system.

[0084] The above description is only part of the embodiments of the present invention and is not intended to limit the present invention. All equivalent changes and modifications made based on the content of the present invention are within the scope of protection of the present invention.

Claims

1. Application of a highly selective catalyst Ni-TiO2-P25 in a heterogeneous system for photothermal catalytic selective hydrogenation of p-chloronitrobenzene, characterized in that: In the catalyst, Ni is loaded on P25-type TiO2, wherein the loading amount of Ni is 3-5 wt% of the catalyst.

2. The use according to claim 1, characterized in that The specific preparation steps of the highly selective catalyst Ni-TiO2-P25 are as follows: (1) Using P25 TiO2 as the carrier, heat and stir on a heating plate to ensure uniform heating; (2) Using nickel acetate tetrahydrate as the nickel source and P25 type TiO2 as the support, the unreduced catalyst Ni-TiO2-P25 was prepared by impregnation method; (3) The unreduced catalyst Ni-TiO2-P25 was placed in a tubular furnace in a hydrogen atmosphere for heating and reduction, cooled naturally to room temperature, and then introduced into a mixed gas of O2 / Ar for 20 min for passivation to obtain Ni-TiO2-P25.

3. The use according to claim 2, characterized in that In the step (1), the temperature of the heating plate is between 85°C and 95°C.

4. The use according to claim 2, characterized in that In the step (3), the heating temperature in the tube furnace is 500°C.

5. The use according to claim 2, characterized in that In the step (3), the heating time of the catalyst in the tube furnace is 2 hours.

6. The use according to claim 2, characterized in that In step (3), the volume fraction of O2 in the mixed gas is 10%.

7. The use according to claim 1, characterized in that The Ni loading in the catalyst was 3.5 wt % of the catalyst.

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