Process for the selective hydrogenation of p-nitroacetophenone to p-aminoacetophenone

Abstract

The application provides a method for preparing p-aminoacetophenone by selectively hydrogenating p-nitroacetophenone with a metal Pt and 2D amorphous semiconductor hybrid nanostructure catalyst. The method comprises: under the conditions of a specific solvent, anhydrous methanol, a catalyst Pt / @-TiO2 / MCM-22 and preset hydrogenation reaction conditions, raw material p-nitroacetophenone is subjected to hydrogenation reaction to prepare p-aminoacetophenone, the preset hydrogenation reaction conditions include: a hydrogen pressure of 0.6 MPa to 0.8 MPa, a reaction temperature of 50 DEG C to 70 DEG C and a reaction time of 40 min to 60 min; wherein the content of Pt in the Pt / @-TiO2 / MCM-22 catalyst is 0.07 to 0.2 wt%, TiO2 in the Pt / @-TiO2 / MCM-22 catalyst is a 2D amorphous semiconductor film layer, and the active component Pt is anchored on the TiO2 film layer. The method provided by the application can obtain 100% conversion rate of p-nitroacetophenone and p-aminoacetophenone selectivity under mild reaction conditions, and has the advantages of low active component Pt loading, low catalyst consumption and high catalytic efficiency.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a method for the selective hydrogenation of p-nitroacetophenone to prepare p-aminoacetophenone. Background Technology

[0002] Catalytic hydrogenation is a core process in many industries, with approximately 25% of chemical processes involving at least one catalytic hydrogenation step. As the most widely used reaction in chemical manufacturing, hydrogenation remains one of the most extensive research areas in catalysis. The products of catalytic hydrogenation have wide applications in chemistry, pharmaceuticals, food, coatings, and petrochemical materials, among others. Statistics show that catalysts are used in over 90% of chemical processes.

[0003] In hydrogenation reactions, the most commonly used catalysts are traditional metal catalysts with metals directly supported on a support. Their activity is often affected by the size, dispersion, and morphology of the metal particles, making it difficult to simultaneously achieve high catalytic activity and selectivity. In recent years, three types of catalysts have been developed: oxide-like catalysts, organic-inorganic hybrid catalysts, and single-atom catalysts. Compared with traditional metal catalysts, these catalysts have higher activity and selectivity. Single-atom catalysts, in particular, have high stability, but they still have problems such as low loading and easy aggregation of single atoms. Summary of the Invention

[0004] This invention employs an ultraviolet light-induced reduction method to prepare a Pt / @-TiO2 / MCM-22 catalyst, a hybrid nanostructure of metallic Pt and 2D amorphous semiconductor. The Pt / @-TiO2 / MCM-22 catalyst is then applied to the hydrogenation of p-nitroacetophenone to p-aminoacetophenone. Under mild reaction conditions, 100% conversion and 100% selectivity are achieved. This method offers advantages such as low Pt loading, minimal Pt usage, mild reaction conditions, high catalytic efficiency, and environmental friendliness and energy conservation, demonstrating promising prospects for industrial application.

[0005] To achieve the above objectives, this invention provides a method for the selective hydrogenation of p-nitroacetophenone to p-aminoacetophenone catalyzed by a Pt metal and a 2D amorphous semiconductor hybrid nanostructure catalyst. The method includes: under specific solvent, catalyst, and predetermined hydrogenation reaction conditions, p-nitroacetophenone undergoes a hydrogenation reaction to prepare p-aminoacetophenone. The specific solvent is anhydrous methanol, the catalyst is a Pt / @-TiO2 / MCM-22 catalyst, and the predetermined hydrogenation reaction conditions include: hydrogen pressure... The reaction pressure is 0.6 MPa to 0.8 MPa, the reaction temperature is 50℃ to 70℃, and the reaction time is 40 min to 60 min. The Pt content in the Pt / @-TiO2 / MCM-22 catalyst is 0.07 to 0.2 wt%. In the Pt / @-TiO2 / MCM-22 catalyst, TiO2 is a 2D amorphous semiconductor film layer that is spontaneously spread in the pores of the MCM-22 molecular sieve in a monolayer form, while the active component Pt is anchored on the TiO2 film layer.

[0006] In one specific embodiment, the molar ratio of Pt to p-nitroacetophenone in the Pt / @-TiO2 / MCM-22 catalyst is 0.028%-0.1%.

[0007] In one specific embodiment, the preset hydrogenation reaction conditions include: the hydrogen pressure is 0.6 MPa, the reaction temperature is 50°C, and the reaction time is 40 min.

[0008] In one specific embodiment, the TiO2 content in the composite carrier TiO2 / MCM-22 is 5-20% by mass.

[0009] In one specific embodiment, the Pt content in the Pt / @-TiO2 / MCM-22 catalyst is 0.1 wt%, and the TiO2 content in the composite support TiO2 / MCM-22 is 10% by mass.

[0010] In one specific embodiment, the Pt / @-TiO2 / MCM-22 catalyst is prepared by the following method, including:

[0011] TiO2 was spontaneously spread in a monolayer form within the pores of MCM-22 molecular sieve using the sol-gel method to form a 2D amorphous semiconductor film, thus obtaining the composite carrier TiO2 / MCM-22.

[0012] The Pt / @-TiO2 / MCM-22 catalyst was obtained by anchoring Pt nanoparticles onto the 2D amorphous semiconductor film of the composite support TiO2 / MCM-22 using a photocatalytic reduction method. The Pt nanoparticles, as the active component, have a synergistic effect with the TiO2 semiconductor film.

[0013] In one specific embodiment, the gel sol method is as follows: tetrabutyl titanate and pretreated MCM-22 are stirred evenly and then ultrasonically vibrated. Then, while stirring, distilled water, glacial acetic acid and nitric acid solution are added dropwise, followed by anhydrous ethanol. The mixture is stirred at room temperature until it is evenly mixed, and then heated in a water bath and stirred until it becomes gel-like. The resulting gel-like product is dried and calcined to obtain the composite carrier TiO2 / MCM-22.

[0014] In one specific embodiment, in the gel sol method, the ultrasonic vibration time is 10-20 min, the room temperature stirring time is 30-40 min, the water bath heating temperature is 55-70℃, the water bath heating time is 110-130 min, the drying temperature is 70-90℃, and the calcination temperature is 450℃-600℃.

[0015] In one specific embodiment, the photocatalytic reduction method is as follows: the composite support TiO2 / MCM-22 is dissolved in deionized water, an appropriate amount of anhydrous methanol is added, and the mixture is ultrasonically dispersed evenly. Then, H2PtCl4 solution is added, and ultrasonic vibration is continued for a preset time. The mixture is then placed under an ultraviolet lamp and stirred under light irradiation. The resulting solution is filtered, washed, and vacuum dried to obtain the Pt / @-TiO2 / MCM-22 catalyst.

[0016] In one specific embodiment, in the photocatalytic reduction method, the preset time for ultrasonic oscillation is 10-20 min, the stirring time under light irradiation is 12-16 h, and the vacuum drying temperature is 75-85℃.

[0017] The beneficial effects of the present invention include at least the following:

[0018] The catalyst provided by this invention is a Pt hybrid nanostructure catalyst constructed by assembling metallic Pt nanoparticles and 2D amorphous semiconductor metal oxides on a large specific surface area support. It exhibits a synergistic catalytic effect between metallic Pt nanoparticles (3D) and 2D amorphous semiconductor metal oxides. The strong electronic effect at the interface between metallic Pt nanoparticles and 2D amorphous semiconductor metal oxides demonstrates ultra-high catalytic activity (high conversion rate and high selectivity) when catalyzing the hydrogenation of p-nitroacetophenone under mild conditions, and also has the advantage of low loading.

[0019] 2. The loading of metal oxide was controlled according to the principle of spontaneous monolayer dispersion to form a 2D amorphous semiconductor metal oxide film layer on the surface of the support MCM-22 in a monolayer form (XRD confirmed that it is amorphous, not crystalline). This is equivalent to coating a metal oxide "glue" on a large specific surface area support (such as MCM-22). The results show that the stability is good and the catalyst is stable when reused.

[0020] Third, the typical characteristics of TiO2 semiconductor metal oxides lie in their excellent optical properties and strong photocatalytic activity. For different application targets, the photocatalytic activity can be suppressed or enhanced by modifying the TiO2 particles. MCM-22 is a microporous molecular sieve with a large specific surface area and a regular pore structure, providing more contact interfaces and active sites, enabling the 2D amorphous semiconductor film layer TiO2 to be monolayer dispersed on the surface of the MCM-22 support.

[0021] This invention utilizes a sol-gel method to load TiO2 particles in a monolayer onto a carrier MCM-22 molecular sieve to form a semiconductor film. Palladium nanoparticles are then anchored onto this semiconductor film. Due to the large specific surface area of ​​the MCM-22 molecular sieve, the resulting TiO2 semiconductor film has a large surface area. On one hand, the active component, palladium nanoparticles, exhibit high surface dispersion and small particle size on the TiO2 / MCM-22 composite carrier, resulting in excellent activity. On the other hand, the palladium nanoparticles and the TiO2 semiconductor film demonstrate strong synergistic effects. The use of this catalyst generates an interfacial electronic effect, thereby improving its catalytic performance. Thus, the Pt / @-TiO2 / MCM-22 catalyst provided by this invention, under mild reaction conditions, can achieve higher selectivity and conversion in the hydrogenation of p-nitroacetophenone. The 0.1% Pt / @-10% TiO2 / MCM-22 catalyst, under reaction conditions of 50°C, 40 minutes, and 0.6 MPa hydrogen pressure, achieves 100% selectivity and 100% conversion in the hydrogenation of p-nitroacetophenone.

[0022] Fourth, the catalyst in this invention is applied to the selective hydrogenation reaction of p-nitroacetophenone. Compared with the prior art, it has the advantages of mild reaction conditions, low catalyst dosage, high catalytic activity, and good selectivity, and has good prospects for industrial application. Attached Figure Description

[0023] Figure 1 XRD wide-angle diffraction patterns of the catalysts prepared in Example 1 and Comparative Example 1, and the support MCM-22;

[0024] Figure 2 XRD wide-angle diffraction patterns of crystalline TiO2, support MCM-22, and composite supports in the catalysts prepared in Examples 1 and 5-7;

[0025] Figure 3(a) and Figure 3(b) are TEM images of the catalyst prepared in Comparative Example 1;

[0026] Figure 3(c) shows the particle size distribution of the catalyst prepared in Example 1;

[0027] Figures 3(d) and 3(e) are HRTEM images of the catalyst prepared in Example 1;

[0028] Figure 3(f) is the EDX diagram of the catalyst prepared in Example 1. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. However, the present invention may be implemented in many different ways as limited and covered by the claims.

[0030] Example 1

[0031] 1) Preparation of catalysts:

[0032] (1) Preparation of the composite support TiO2 / MCM-22 in the catalyst:

[0033] 0.4573 mL of tetrabutyl titanate and 1.0 g of pretreated MCM-22 molecular sieve were mixed evenly using the sol-gel method. The mixture was sonicated for 10 min, and while stirring, 0.8 mL of distilled water, 0.7 mL of glacial acetic acid, and 1 drop of nitric acid solution were added dropwise. Then, 10 mL of anhydrous ethanol was added, and the mixture was stirred at room temperature for 30 min until homogeneous. The mixture was then heated in a 60°C water bath with stirring for 2 hours, followed by sonication for 2 hours until a gel-like consistency was reached. The sample was then dried overnight in a vacuum oven at 80°C. Finally, the solid powder was calcined in a muffle furnace at 500°C for 2 hours to obtain a TiO2 / MCM-22 composite support with a TiO2 mass fraction of 10%.

[0034] 10% TiO2 / MCM-22.

[0035] (2) Catalyst preparation:

[0036] 0.739 g of the composite support TiO2 / MCM-22 was dispersed in 100 mL of deionized water, 10 mL of anhydrous methanol was added, and the mixture was ultrasonically dispersed for 10 min. Then, an appropriate amount of H2PtCl4 (0.0074 g / mL) solution was added, and the mixture was ultrasonically vibrated for another 20 min. The solution was then placed under a UV lamp and stirred for 12 h under illumination. The resulting solution was filtered, washed until neutral, and vacuum dried at 80 °C for 12 h to obtain 0.1% Pt / @-10% TiO2 / MCM-22, meaning that the mass content of Pt in the Pt / @-10% TiO2 / MCM-22 catalyst was 0.1%; the mass content of TiO2 in the composite support TiO2 / MCM-22 was 10%.

[0037] 2) Preparation of p-aminoacetophenone by hydrogenation of p-nitroacetophenone: p-nitroacetophenone, 0.1% Pt / @-10% TiO2 / MCM-22 catalyst (molar ratio of Pt to p-nitroacetophenone is 0.042%) and 20 mL of anhydrous methanol were placed in a high-pressure reactor. The hydrogen pressure was set to 0.6 MPa and the reaction temperature to 50 °C. After H2 was introduced to displace the air in the reactor, the H2 valve was closed. When the temperature inside the reactor reached the reaction temperature of 50 °C, H2 was introduced and the stirring was turned on to start the reaction. The reaction time was 40 min. After the reaction was completed, the mixture was cooled, and an appropriate amount of the reaction solution was centrifuged and analyzed by gas chromatography. The analysis results are shown in Table 1.

[0038] Example 2

[0039] Similar to Example 1, except that the mass content of Pt in the Pt / @-TiO2 / MCM-22 catalyst is 0.05%, i.e., 0.05%Pt / @-10%TiO2 / MCM-2.

[0040] Example 3

[0041] Similar to Example 1, except that the mass content of Pt in the Pt / @-TiO2 / MCM-22 catalyst is 0.07%, i.e., 0.07%Pt / @-10%TiO2 / MCM-2.

[0042] Example 4

[0043] Similar to Example 1, except that the mass content of Pt in the Pt / @-TiO2 / MCM-22 catalyst is 0.20%, i.e., 0.20%Pt / @-10%TiO2 / MCM-2.

[0044] Comparative Example 1

[0045] Similar to Example 1, except that Pt / @-TiO2 / MCM-22 does not contain palladium nanoparticles, and the mass content of Pt is 0, i.e., 10% TiO2 / MCM-22.

[0046] Table 1 shows the catalytic reaction results of the catalysts used in Examples 1-4 and Comparative Example 1 when they were used to catalyze the hydrogenation reaction of p-nitroacetophenone.

[0047] Table 1. Results of hydrogenation of p-nitroacetophenone using Pt / @-TiO2 / MCM-22 catalysts with different Pt loadings.

[0048] Example <![CDATA[0.10%Pt / @-10%TiO2 / MCM-]]> 100 100 Example <![CDATA[0.05%Pt / @-10%TiO2 / MCM-]]> 91.75 96.78 Example <![CDATA[0.07%Pt / @-10%TiO2 / MCM-]]> 99 99 Example <![CDATA[0.20%Pt / @-10%TiO2 / MCM-]]> 100 100 Comparative Example <![CDATA[10%TiO2 / MCM-22]]> 89.15 91.75

[0049] Table 1 examines the hydrogenation reaction of p-nitroacetophenone catalyzed by Pt / @-TiO2 / MCM-22 catalysts with different Pt loadings. When the theoretical Pt loading is 0.05 wt%, under the conditions of a reaction temperature of 50 °C, a hydrogen pressure of 0.6 MPa, and a molar ratio of Pt metal nanoparticles to p-nitroacetophenone (n(Pt) / n(p-nitroacetophenone)) = 0.021%, the conversion rate of p-nitroacetophenone is only 91.75%, and the selectivity for p-aminoacetophenone is 96.78% when the chemoselective hydrogenation reaction time is 40 min. When the theoretical Pt metal nanoparticle loading increases to 0.10 wt% (actual loading is 0.0614 wt%), under the same reaction conditions, both the conversion rate of p-nitroacetophenone and the selectivity for p-aminoacetophenone reach 100%, with a TOF of 6267 h⁻¹. -1 Experimental results show that as the number of active Pt metal nanoparticles on the catalyst increases, the amount of H2 that can be activated also increases within the same time frame, thereby promoting the increased conversion rate of the chemoselective hydrogenation reaction of p-nitroacetophenone. Table 1 shows that further increasing the loading of Pt metal nanoparticles does not change the catalytic activity; therefore, under the same conditions, a theoretical loading of 0.1 wt% Pt is optimal.

[0050] Preferably, the mass content of Pt in the Pt / @-TiO2 / MCM-22 catalyst is 0.1-0.2%, and more preferably, the mass content of Pt is 0.1%.

[0051] It should be noted that, unless otherwise specified, the mass content of Pt in the Pt / @-TiO2 / MCM-22 catalyst in this invention refers to the theoretical loading. Measurements show that when the theoretical loading of Pt metal nanoparticles is 0.10 wt%, the corresponding actual loading is 0.0614 wt%.

[0052] It should be noted that in this invention, the amount of catalyst and the amount of p-nitroacetophenone added in different embodiments and comparative examples are the same.

[0053] Example 5

[0054] Similar to Example 1, except that the mass fraction of TiO2 in Pt / @-TiO2 / MCM-22 is 5%, i.e., 0.1%Pt / @-5%TiO2 / MCM-22.

[0055] Example 6

[0056] Similar to Example 1, except that the mass fraction of TiO2 in Pt / @-TiO2 / MCM-22 is 15%, i.e., 0.1%Pt / @-15%TiO2 / MCM-22.

[0057] Example 7

[0058] Similar to Example 1, except that the mass fraction of TiO2 in Pt / @-TiO2 / MCM-22 is 20%, i.e., 0.1%Pt / @-20%TiO2 / MCM-22.

[0059] Comparative Example 2

[0060] Similar to Example 1, except that the mass fraction of TiO2 in Pt / @-TiO2MCM-22 is 0, i.e., 0.1% Pt / MCM-22.

[0061] Comparative Example 3

[0062] Similar to Example 1, except that the mass fraction of MCM-22 in Pt / @-TiO2 / MCM-22 is 0, i.e., 0.1% Pt / TiO2.

[0063] It should be noted that the mass fraction of TiO2 in the above embodiments refers to the mass fraction of TiO2 in the composite support TiO2 / MCM-22. The catalytic reaction results of the catalysts used in Examples 1, 5-7 and Comparative Examples 2-3 for the hydrogenation of p-nitroacetophenone are shown in Table 2.

[0064] Table 2. Results of hydrogenation of p-nitroacetophenone using Pt / @-TiO2 / MCM-22 catalysts with different TiO2 loadings.

[0065]

[0066]

[0067] Table 2 examines the effect of different TiO2 loadings on the catalytic activity of Pt / @-TiO2 / MCM-22. Without TiO2 (Pt / MCM-22), the conversion of p-nitroacetophenone was 59.73%, and the selectivity for p-aminoacetophenone was 87.6%. Increasing the TiO2 loading to 10% resulted in both the conversion and selectivity of p-nitroacetophenone reaching 100%. Further increasing the TiO2 loading did not change the conversion and selectivity of p-nitroacetophenone, both remaining above 99%, indicating that the effect of TiO2 loading within the range of 5 wt% to 20 wt% on the conversion and selectivity of p-nitroacetophenone was minimal.

[0068] Preferably, the optimal loading of TiO2 in the catalyst is 10 wt%. Theoretically, the semiconductor film formed by TiO2 is exactly a single layer loaded in the microporous molecular sieve MCM-22, resulting in the best catalytic activity and lower cost.

[0069] Examples 8A to 8D

[0070] Examples 8A to 8D all used the 0.1% Pt / @-10% TiO2 / MCM-22 catalyst prepared in Example 1. The difference lies in the different hydrogenation reaction conditions. Specifically, the hydrogenation reaction conditions for Example 1 were: hydrogen pressure 0.6 MPa, reaction temperature 50°C, and reaction time 40 min; for Example 8A, the hydrogenation reaction conditions were: hydrogen pressure 0.6 MPa, reaction temperature 30°C, and reaction time 40 min; for Example 8B, the hydrogenation reaction conditions were: hydrogen pressure 0.6 MPa, reaction temperature 50°C, and reaction time 10 min; for Example 8C, the hydrogenation reaction conditions were: hydrogen pressure 0.6 MPa, reaction temperature 50°C, and reaction time 30 min; and for Example 8D, the hydrogenation reaction conditions were: hydrogen pressure 0.5 MPa, reaction temperature 50°C, and reaction time 40 min. The catalytic reaction results of the hydrogenation reaction of p-nitroacetophenone in Examples 1, 8A-8D are shown in Table 3.

[0071] Table 3. Results of hydrogenation of p-nitroacetophenone under different hydrogenation reaction conditions.

[0072]

[0073] Table 3 shows that when the hydrogen pressure is 0.6 MPa and the reaction temperature is 50℃, both the conversion rate of p-nitroacetophenone and the selectivity of p-aminoacetophenone increase with increasing reaction time. When the hydrogen pressure is less than 0.6 MPa and the reaction time is 40 min, the conversion rate of p-nitroacetophenone remains unchanged, while the selectivity of p-aminoacetophenone decreases. When the hydrogen pressure is 0.6 MPa, the reaction time is 40 min, and the reaction temperature is less than 50℃, the conversion rate of nitroacetophenone decreases, but the selectivity of p-aminoacetophenone remains essentially unchanged.

[0074] Therefore, by changing any one of the reaction conditions (temperature, time, or pressure) while keeping the other two conditions constant, and comparing different conditions, the most suitable conditions for the selective hydrogenation of p-nitroacetophenone can be found. The hydrogenation reaction of p-nitroacetophenone catalyzed by the 0.1% Pt / @-10% TiO2 / MCM-22 catalyst achieved 100% conversion of p-nitroacetophenone and 100% selectivity for p-aminoacetophenone under the conditions of a reaction temperature of 50℃, a reaction time of 40 min, and a hydrogen pressure of 0.6 MPa.

[0075] Examples 9A-9D

[0076] Examples 9A to 9D all used the 0.1% Pt / @-10% TiO2 / MCM-22 catalyst prepared in Example 1, and the catalytic hydrogenation reaction conditions were the same. The difference was that the solvents used for the hydrogenation of p-nitroacetophenone to p-aminoacetophenone were not exactly the same. Specifically, the solvent in Example 1 was anhydrous methanol; the solvent in Example 9A was anhydrous ethanol; the solvent in Example 9B was water; the solvent in Example 9C was isopropanol; and the solvent in Example 9D was toluene.

[0077] The catalytic reaction results of the hydrogenation reaction of p-nitroacetophenone in Examples 1 and 9A-9D are shown in Table 4.

[0078] Table 4 Results of hydrogenation reaction of p-nitroacetophenone in different solvents

[0079] Example 1 Anhydrous methanol 100 100 Example 9A Anhydrous ethanol 100 91.14 Example 9B water 100 91.87 Example 9C Isopropanol 100 84.52 Example 9D Toluene 35.62 97.68

[0080] Table 4 shows the effect of 0.1% Pt / @-10% TiO2 / MCM-22 catalyst on the chemoselective hydrogenation performance of p-nitroacetophenone in different reaction media. The comparison results show that toluene as a solvent resulted in the least ideal catalytic effect; anhydrous ethanol, isopropanol, and water as solvents all reduced the selectivity of p-nitroacetophenone; and anhydrous methanol as a solvent produced the best catalytic effect.

[0081] Examples 10A-10G

[0082] Examples 10A to 10G all used the 0.1% Pt / @-10% TiO2 / MCM-22 catalyst prepared in Example 1. The catalytic reaction conditions were the same as in Example 1, except that the number of times the catalyst was used to catalyze the selective hydrogenation reaction of p-nitroacetophenone was increased. The catalytic reaction results of p-nitroacetophenone hydrogenation reaction in Examples 1, 10A to 10G are shown in Table 5.

[0083] Table 5 Results of catalyst usage number on acetophenone hydrogenation

[0084]

[0085] Table 5 shows the experimental results of the reusability of the 0.1% Pt / @-10% TiO2 / MCM-22 catalyst. The specific experimental method is as follows: At 50℃, 0.6 MPa hydrogen pressure, 40 min, and n(Pt):n(p-nitroacetophenone) = 0.042%, the selective hydrogenation of p-nitroacetophenone was catalyzed using the 0.1 wt% Pt / @-10% TiO2 / MCM-22 catalyst. The reaction solution was centrifuged to separate the catalyst from the reaction solution. The recovered catalyst was then washed three times with anhydrous ethanol by centrifugation and dried overnight in a forced-air drying oven at 80℃. A second catalytic hydrogenation reaction was then carried out under the same experimental conditions. The above operation was repeated eight times, and the selectivity of p-nitroacetophenone remained stable (100%). However, starting from the sixth reaction, the conversion rate of p-nitroacetophenone gradually decreased. It is preliminarily speculated that this was due to the loss of Pt, leading to a decrease in conversion rate. Additionally, some substances remained in the pores of the MCM-22 catalyst after washing and drying, causing blockage.

[0086] In summary, this catalyst exhibits relatively good stability.

[0087] As can be seen from the above embodiments, the catalysts with different mass fractions provided by the present invention are all active for the selective hydrogenation reaction of p-nitroacetophenone. Moreover, under the premise of adjusting and changing the catalytic reaction temperature, hydrogen pressure, and reaction time, most catalysts can achieve relatively excellent catalytic activity. The scope of the present invention is not limited to the above embodiments. As long as the mass fraction of the active component of the catalyst and the reaction conditions are well controlled, good results can be achieved for the hydrogenation reaction of p-nitroacetophenone.

[0088] Please see Figure 1 As shown in Figure 3, Figure 1 The XRD wide-angle diffraction patterns of the catalysts prepared in Example 1 and Comparative Example 1, and the support MCM-22 are shown; wherein, the XRD wide-angle diffraction patterns from top to bottom correspond to 0.1%Pt / @-10%TiO2 / MCM-22, 10%TiO2 / MCM-22 and support MCM-22, respectively.

[0089] Figure 2 Wide-angle XRD patterns of crystalline TiO2, support MCM-22, and composite supports in the catalysts prepared in Examples 1 and 5-7.

[0090] Figure 3(a) and Figure 3(b) are TEM images of the catalyst prepared in Example 1; Figure 3(c) is a particle size distribution of the catalyst prepared in Example 1; Figure 3(d) and Figure 3(e) are HR-TEM images of the catalyst prepared in Example 1; Figure 3(f) is an EDX image of the catalyst prepared in Example 1.

[0091] Depend on Figure 1As shown in Figure 3, the pore structure of the support MCM-22 in the catalyst provided in this embodiment of the invention has not changed. TiO2 is loaded on the support MCM-22 in the form of a 2D amorphous semiconductor film, and Pt and TiO2 film have a synergistic effect. A strong electronic effect is generated at the interface between Pt nanoparticles and 2D amorphous TiO2, thereby improving the catalytic activity of the catalyst.

[0092] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions and substitutions can be made without departing from the inventive concept, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for the selective hydrogenation of p-nitroacetophenone to p-aminoacetophenone catalyzed by a metal Pt and a 2D amorphous semiconductor hybrid nanostructure catalyst, characterized in that, The method includes: preparing p-aminoacetophenone by hydrogenation of p-nitroacetophenone as a raw material under specific solvent, catalyst, and preset hydrogenation reaction conditions. The specific solvent is anhydrous methanol, and the catalyst is a Pt / @-TiO2 / MCM-22 catalyst. The preset hydrogenation reaction conditions include: hydrogen pressure of 0.6 MPa to 0.8 MPa, reaction temperature of 50°C to 70°C, and reaction time of 40 min to 60 min. The Pt content in the Pt / @-TiO2 / MCM-22 catalyst is specified. The amount is 0.07~0.2wt%, and the mass content of TiO2 in the composite support TiO2 / MCM-22 is 5~20%. In the Pt / @-TiO2 / MCM-22 catalyst, TiO2 is a 2D amorphous semiconductor film layer. TiO2 is spontaneously spread in the pores of MCM-22 molecular sieve by gel sol method. The active component Pt is anchored on the TiO2 film layer of the composite support by photocatalytic reduction method. Pt nanoparticles have a synergistic effect with TiO2 semiconductor film layer as active component.

2. The method for selective hydrogenation of p-nitroacetophenone to p-aminoacetophenone catalyzed by a metal Pt and 2D amorphous semiconductor hybrid nanostructure catalyst according to claim 1, characterized in that, The molar ratio of Pt to p-nitroacetophenone in the Pt / @-TiO2 / MCM-22 catalyst is 0.00028~0.

001.

3. The method for selective hydrogenation of p-nitroacetophenone to p-aminoacetophenone catalyzed by a metal Pt and a 2D amorphous semiconductor hybrid nanostructure catalyst according to claim 1, characterized in that, The preset hydrogenation reaction conditions include: a hydrogen pressure of 0.6 MPa, a reaction temperature of 50°C, and a reaction time of 40 min.

4. The method for selective hydrogenation of p-nitroacetophenone to p-aminoacetophenone catalyzed by a metal Pt and a 2D amorphous semiconductor hybrid nanostructure catalyst according to claim 1, characterized in that, The Pt content in the Pt / @-TiO2 / MCM-22 catalyst is 0.1 wt%, and the TiO2 content in the composite support TiO2 / MCM-22 is 10%.

5. The method for selective hydrogenation of p-nitroacetophenone to p-aminoacetophenone catalyzed by a metal Pt and a 2D amorphous semiconductor hybrid nanostructure catalyst according to claim 1, characterized in that, The specific gel sol method is as follows: tetrabutyl titanate and pretreated MCM-22 are stirred evenly and then ultrasonically vibrated. Then, distilled water, glacial acetic acid and nitric acid solution are added dropwise while stirring. Anhydrous ethanol is then added and stirred at room temperature until the mixture is uniform. The mixture is then heated in a water bath and stirred until it becomes gel-like. The resulting gel-like product is dried and calcined to obtain the composite carrier TiO2 / MCM-22.

6. The method for selective hydrogenation of p-nitroacetophenone to p-aminoacetophenone catalyzed by a metal Pt and a 2D amorphous semiconductor hybrid nanostructure catalyst according to claim 5, characterized in that, In the sol-gel method, the ultrasonic vibration time is 10-20 min, the stirring time at room temperature is 30-40 min, the water bath heating temperature is 55-70℃, the water bath heating time is 110-130 min, the drying temperature is 70-90℃, and the calcination temperature is 450℃-600℃.

7. The method for selective hydrogenation of p-nitroacetophenone to p-aminoacetophenone catalyzed by a metal Pt and a 2D amorphous semiconductor hybrid nanostructure catalyst according to claim 1, characterized in that, The photocatalytic reduction method is as follows: the composite support TiO2 / MCM-22 is dissolved in deionized water, an appropriate amount of anhydrous methanol is added, and the mixture is ultrasonically dispersed evenly. Then, H2PtCl4 solution is added, and ultrasonic vibration is continued for a preset time. The mixture is then placed under a UV lamp and stirred under light irradiation. The resulting solution is filtered, washed, and vacuum dried to obtain the Pt / @-TiO2 / MCM-22 catalyst.

8. The method for selective hydrogenation of p-nitroacetophenone to p-aminoacetophenone catalyzed by a metal Pt and a 2D amorphous semiconductor hybrid nanostructure catalyst according to claim 7, characterized in that, In the photocatalytic reduction method, the preset time for ultrasonic oscillation is 10-20 min, the stirring time under light irradiation is 12-16 h, and the vacuum drying temperature is 75-85℃.

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