Preparation method of Pd-Ru synergistic catalyst based on metal-organic framework and its hydrogenation application

Abstract

This invention discloses a method for preparing a Pd-Ru synergistic catalyst based on a metal-organic framework (MOF) and its hydrogenation application. Based on MOF materials, this invention coordinates the hydrolysis of Pd-Ru alloy with tetraethyl orthosilicate in a one-pot process, followed by high-temperature carbonization reduction under a nitrogen atmosphere to synthesize a Pd-Ru synergistic catalyst coated with an MOF: PdRu / C@SiO2. This catalyst can be used for the selective hydrogenation of alkynes to olefins. Compared to pure palladium or pure ruthenium, the catalyst of this invention can effectively reduce the desorption energy of styrene, limiting excessive hydrogenation of styrene, and achieving high conversion (95.3%) and high selectivity (99.4%) of phenylacetylene under mild reaction conditions. Simultaneously, this catalyst exhibits excellent catalytic stability and good versatility, showing promising application prospects.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis, and in particular to a Pd-Ru synergistic catalyst based on a metal-organic framework, its preparation method, and its application in selective hydrogenation. Background Technology

[0002] Selective hydrogenation of alkynes to olefins plays a crucial role in the synthesis of fine chemicals. However, over-hydrogenation is prone to occur during the reaction, inevitably producing byproducts such as alkanes.

[0003] As is well known, the hydrogenation of phenylacetylene (PA) is a simple series process, with the intermediate reaction producing styrene (SM). Styrene is a major raw material in the production of polymer materials such as ABS resin, polystyrene (PS), and styrene-butadiene rubber (SBR). In recent years, many research results have emerged, such as various Pd-based nanocatalysts. However, styrene is further converted into ethylbenzene (EB), a saturated product. Therefore, many scholars have conducted extensive research on the purification and separation of styrene, among which Pd-based nanocatalysts... [1-2] Due to its excellent hydrogenation performance, it is the most commonly used catalyst for the selective hydrogenation of phenylacetylene, but its poor selectivity still leads to over-hydrogenation of phenylacetylene.

[0004] In current applications, Pd nanocatalysts are often improved through modifications to their preparation process or by being combined with other metals, co-catalysts, and other active components to enhance their performance. Recent research has shown... [3] This indicates that Ru exhibits good catalytic activity and maintains a certain degree of selectivity in the catalyst. Building on this, in recent years, researchers have applied the Pd-Ru synergistic catalytic system to the catalytic hydrogenation of phenylacetylene, significantly improving the selectivity for styrene while maintaining a high conversion rate. This catalytic activity is attributed to the synergistic effect of Pd-Ru at a single point, which lowers the desorption energy of styrene and thereby increases the barrier to further hydrogenation of styrene, making the application of the Pd-Ru synergistic catalytic system to the hydrogenation of phenylacetylene possible.

[0005] Metal-organic frameworks (MOFs) are a class of porous materials assembled through the coordination of metal ions with organic matter. [4] Due to their fine, tunable, and uniform pore structure, metal-organic frameworks (MOFs) have become ideal materials for coating the surface of metal nanoparticles, preventing the loss and exfoliation of nanoparticles during reactions. Furthermore, MOF materials possess numerous unsaturated sites, which facilitate substrate adsorption and significantly enhance the catalytic activity of the catalyst. Therefore, metal-organic frameworks are of great significance for catalytic reactions.

[0006] Therefore, there is an urgent need to develop novel catalysts with high selectivity and activity for the selective hydrogenation of alkynes (such as phenylacetylene).

[0007] References

[0008] [1]Sabrina Ballauri,Enrico Sartoretti,et al.Praseodymium doping inceria-supported palladium nanocatalysts as an effective strategy to minimize the inhibiting effects of water during methane oxidation[J].A.Catalysis B:Environmental 320(2023)121898.

[0009] [2]Md.Lutfor Rahman,Mohd Sani Sarjadi,et al.Silica-coated magneticpalladium nanocatalyst for Suzuki-Miyaura cross-coupling[J].A.Journal ofChemistry(2022)15,103983.

[0010] [3]Wenqian Yang, Qinglin Liu, Jun Yang, et al.Ultrafifine PdRuNanoparticles Immobilized in Metal-Organic Frameworks for EfficientFluorophenol Hydrodeflfluorination under Mild Aqueous Conditions[J].CCSChem.2022,4,2276-2285.

[0011] [4]Annemieke Janssen,Yifeng Shi,et al.Separating Growth fromNucleation for Facile Control over the Size and Shape of PalladiumNanocrystals[J].Chemistry-A European 202001626.

[0012] [5]Haiping Li,Tianxing Yang,et al.Synthesis of supported Pdnanocluster catalyst by spontaneous reduction on layered double hydroxide[J].J.of Catalysis 385(2020)313-323.

[0013] [6]Qianqian Xie,Chao Lei,et al.Mesoporous ferrihydrite-supported Pdnanoparticles for enhanced catalytic dehalogenation of chlorinatedenvironmental pollutant[J].J.of Colloid and Interface Science 608(2022)2907-2920.

[0014] [7]Ming Zhang, Chaohai Wang, Chao Liu, et al. Metal-organic framework derived Co3O4 / C@SiO2yolk-shell nanoreactors with enhanced catalytic performance [J]. J.Mater.Chem.A, 2018, 6, 11226. Summary of the Invention

[0015] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a Pd-Ru synergistic catalyst based on a metal-organic framework, its preparation method, and its application in selective hydrogenation.

[0016] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: In its first aspect, the present invention provides a method for preparing a Pd-Ru synergistic catalyst based on a metal-organic framework, comprising the following steps:

[0017] S1. Preparation of Pd-Ru@ZIF-8:

[0018] Pd 2+ Ru 3+ Zn 2+ 2-methylimidazole was mixed in a solvent, stirred and reacted. After the reaction was completed, the mixture was centrifuged and the solid product was collected to obtain Pd-Ru@ZIF-8.

[0019] S2. Pd-Ru@ZIF-8 is coated with silica to prepare PdRu@ZIF-8@SiO2;

[0020] S3. PdRu / C@SiO2, the metal-organic framework-based Pd-Ru synergistic catalyst, is prepared by carbonization and reduction.

[0021] Preferably, step S1 specifically includes:

[0022] S1-1. Add 2.5-10 mg Pd(Acac)2 and 17.5-70 mg Ru(Acac)3 to 10-50 mL of a methanol mixture containing 280-1120 mg Zn(NO3)2·6H2O, mix well, and obtain mixture A.

[0023] S1-2. Add 263-1052 mg of 2-methylimidazole to 10-50 mL of methanol and disperse by ultrasonication to obtain mixture B;

[0024] S1-3. Add mixture B to mixture A and stir for 12-48 hours. After the reaction is complete, collect the solid product by centrifugation, wash with methanol, and dry to constant weight to obtain Pd-Ru@ZIF-8.

[0025] Preferably, step S2 specifically includes:

[0026] The Pd-Ru@ZIF-8 prepared in step S1 was added to an ethanol aqueous solution and mixed evenly. Ammonia, hexadecyltrimethylammonium bromide and tetraethyl orthosilicate were added in sequence and stirred to react. After the reaction was completed, the product was centrifuged and washed, the solid product was collected, dried to constant weight, and ground to obtain PdRu@ZIF-8@SiO2.

[0027] Preferably, step S2 specifically includes:

[0028] Take 10-40g of Pd-Ru@ZIF-8 prepared in step S1 and add it to 10-40mL of an ethanol-water solution composed of ethanol and deionized water in a volume ratio of 1:1. Mix well, add 0.5-2mL of ammonia water with a mass concentration of 25%-28%, and then add 250-1000mg of hexadecyltrimethylammonium bromide. After complete dissolution, add 25-100μL of tetraethyl orthosilicate and stir the reaction for 6-24h. Wash the product with ethanol solution by centrifugation, collect the solid product, dry it at 50-70℃ to constant weight, and grind it to obtain PdRu@ZIF-8@SiO2.

[0029] Preferably, step S3 specifically includes:

[0030] Under a nitrogen atmosphere, the PdRu@ZIF-8@SiO2 prepared in step S2 was first calcined at 200-300℃ for 240-960 min, then heated to 500-700℃ and calcined and reduced at 500-700℃ for 90-360 min, and then cooled to room temperature to obtain PdRu / C@SiO2, which is the metal-organic framework-based Pd-Ru synergistic catalyst.

[0031] Preferably, the preparation method of the Pd-Ru synergistic catalyst based on the metal-organic framework includes the following steps:

[0032] S1. Preparation of Pd-Ru@ZIF-8:

[0033] S1-1. Add 5 mg Pd(Acac)2 and 35 mg Ru(Acac)3 to 25 mL of a methanol mixed solution containing 560 mg Zn(NO3)2·6H2O, mix well, and obtain mixture A.

[0034] S1-2. Add 526 mg of 2-methylimidazole to 25 mL of methanol and disperse by ultrasonication to obtain mixture B;

[0035] S1-3. Add mixture B to mixture A and stir for 24 hours. After the reaction is complete, centrifuge to collect the solid product, wash with methanol, dry at room temperature to constant weight, grind to obtain Pd-Ru@ZIF-8.

[0036] S2. PdRu@ZIF-8 is coated with silica to prepare PdRu@ZIF-8@SiO2:

[0037] Take 20g of Pd-Ru@ZIF-8 prepared in step S1 and add it to 20mL of an ethanol-water solution composed of ethanol and deionized water in a volume ratio of 1:1. Mix well, add 1mL of 25% ammonia water, and then add 500mg of hexadecyltrimethylammonium bromide. After complete dissolution, add 50μL of tetraethyl orthosilicate and stir at room temperature for 12h. The product is washed by centrifugation with ethanol solution, the solid product is collected, dried at 60℃ to constant weight, and ground to obtain PdRu@ZIF-8@SiO2.

[0038] S3, PdRu / C@SiO2 was prepared by carbonization and reduction:

[0039] Under a nitrogen atmosphere, the PdRu@ZIF-8@SiO2 prepared in step S2 was first calcined at 250℃ for 480 min, then heated to 600℃ and calcined and reduced at 600℃ for 180 min, and then cooled to room temperature to obtain PdRu / C@SiO2, which is the metal-organic framework-based Pd-Ru synergistic catalyst.

[0040] In a second aspect, the present invention provides a Pd-Ru synergistic catalyst based on a metal-organic framework, which is prepared by the method described above.

[0041] A third aspect of the present invention provides the application of the Pd-Ru synergistic catalyst described above in the selective hydrogenation of alkynes to olefins.

[0042] Preferably, the alkyne is any one of phenylacetylene, 2-acetylenol, 3-acetylenol, 4-acetylenol, 4-methoxyphenylacetylene, 4-acetylenolaniline, 4-ethylphenylacetylene, 4-acetylenolnitrobenzene, 4-fluorophenylacetylene, 4-chlorophenylacetylene, and 4-bromophenylacetylene.

[0043] Preferably, the application method is as follows:

[0044] Alkynes, ethanol, and Pd-Ru synergistic catalyst were mixed evenly and reacted under H2 atmosphere at 65-85℃ and 0.5-2MPa for 1-4 hours to prepare the corresponding olefins.

[0045] The mass ratio of alkyne:ethanol:Pd-Ru synergistic catalyst is 5-20:0.5-2:0.5-2.

[0046] The beneficial effects of this invention are:

[0047] Based on MOF materials, this invention coordinates the hydrolysis of Pd-Ru alloy and tetraethyl orthosilicate (TEOS) in a one-pot process, and then synthesizes a metal-organic material-coated Pd-Ru synergistic catalyst: PdRu / C@SiO2 by high-temperature carbonization reduction under a nitrogen atmosphere. This catalyst can be used for the selective hydrogenation of alkynes to prepare olefins.

[0048] Compared to pure palladium or pure ruthenium, the catalyst of this invention effectively reduces the desorption energy of styrene, limiting excessive hydrogenation of styrene and achieving high conversion (95.3%) and high selectivity (99.4%) of phenylacetylene under mild reaction conditions. This superior performance is attributed to the synergistic effect of Pd and Ru strongly anchored in the metal-organic framework, and the resulting alloy hinders further hydrogenation of styrene. Furthermore, the catalyst's activity and selectivity remain unchanged after five cycles, demonstrating its excellent catalytic stability. In addition, this catalyst has been applied to the selective hydrogenation of various phenylacetylene derivatives, exhibiting good activity and selectivity, proving its versatility and promising application prospects. This invention provides a novel approach to synergistic catalytic systems based on single-site active sites in the selective hydrogenation of alkynes. Attached Figure Description

[0049] Figure 1A schematic diagram of the synthesis routes for PdRu / C@SiO2 and PdRu@SiO2;

[0050] Figure 2 SEM images of PdRu@ZIF-8@SiO2(a), PdRu@SiO2(b) and PdRu / C@SiO2(c) prepared in Example 1;

[0051] Figure 3 The XRD patterns of PdRu@ZIF-8@SiO2, PdRu@SiO2 and PdRu / C@SiO2 prepared in Example 1 are shown below.

[0052] Figure 4 The N2 adsorption-desorption curves of PdRu@SiO2 and PdRu / C@SiO2 prepared in Example 1 are shown respectively.

[0053] Figure 5 The pore size distribution diagrams are shown for PdRu@SiO2 and PdRu / C@SiO2 prepared in Example 1.

[0054] Figure 6 The FT-IR images are of PdRu@ZIF-8@SiO2, PdRu@SiO2 and PdRu / C@SiO2 prepared in Example 1;

[0055] Figure 7 The results show the effect of the reaction solvent on the selective catalytic hydrogenation performance of phenylacetylene.

[0056] Figure 8 The results show the effect of reaction temperature on the selective catalytic hydrogenation performance of phenylacetylene.

[0057] Figure 9 The test results show the effect of reaction pressure on the selective catalytic hydrogenation performance of phenylacetylene;

[0058] Figure 10 The results of the recycling experiment on the PdRu / C@SiO2 catalyst prepared in Example 1 are shown.

[0059] Figure 11 The results show the effect of reaction time on catalytic performance of the catalyst after the experiment. Detailed Implementation

[0060] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0061] It should be understood that terms such as “having,” “comprising,” and “including” as used in this invention do not exclude the presence or addition of one or more other elements or combinations thereof.

[0062] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0063] 1. The main instruments used in the following embodiments are shown in Table 1.1 below:

[0064] Table 1.1

[0065]

[0066]

[0067] 2. The main chemical reagents used in the following examples are sourced from the following table 1.2:

[0068] Table 1.2

[0069]

[0070]

[0071] 3. Relevant performance characterization methods

[0072] X-ray diffractometer (XRD)

[0073] In this study, X-ray powder diffraction was used to characterize the crystal structure of the catalyst. The test conditions were as follows: incident radiation was Cu-Kα (λ=0.15406nm, 40kV, 40mA), and the test range was 10°–80°.

[0074] Scanning electron microscope (SEM)

[0075] The surface area microstructure of the catalyst was analyzed using field emission scanning electron microscopy (SEM, JEOL-6300F, 5kV).

[0076] N2 adsorption-desorption test

[0077] Before measurement, the sample was degassed under vacuum at 300℃ for 6 hours. Then, the pore diameter distribution and specific surface area of ​​the catalytic system were calculated using the N2 adsorption-desorption test (BET) method. Finally, the pore structure of the catalyst was analyzed using an automated adsorption analyzer.

[0078] Fourier transform infrared spectroscopy (FT-IR)

[0079] Data were acquired using a thermal iS50 infrared spectrometer, with a spectral range of 400-4000 cm⁻¹.-1 .

[0080] Example 1

[0081] A Pd-Ru synergistic catalyst based on a metal-organic framework is prepared by the following steps:

[0082] S1. Preparation of Pd-Ru@ZIF-8:

[0083] S1-1. Add 5 mg Pd(Acac)2 (palladium acetylacetone (II)) and 35 mg Ru(Acac)3 (ruthenium acetylacetone (III)) to 25 mL of a methanol mixed solution containing 560 mg Zn(NO3)2·6H2O, mix well, and obtain mixture A.

[0084] S1-2. Add 526 mg of 2-methylimidazole to 25 mL of methanol and disperse by ultrasonication to obtain mixture B;

[0085] S1-3. Add mixture B to mixture A and stir for 24 hours. After the reaction is complete, a red liquid is obtained. Collect the solid product by centrifugation, wash with methanol, and dry at room temperature to constant weight to obtain Pd-Ru@ZIF-8.

[0086] As a control for subsequent experiments, Pd@ZIF-8 and Ru@ZIF-8 were also prepared. The preparation method for Pd@ZIF-8 was the same as above, except that Ru(Acac)3 was not added and the amount of Pd(Acac)2 added was changed to 40 mg. After the reaction in S1-3 was completed, a pale yellow liquid was obtained. The preparation method for Ru@ZIF-8 was the same as above, except that Pd(Acac)2 was not added and Ru(Acac)3 was changed to 40 mg. 32 Except for changing the amount added to 40mg, the same as above, a dark red solution was obtained after the reaction in S1-3 was completed;

[0087] S2. PdRu@ZIF-8 is coated with silica to prepare PdRu@ZIF-8@SiO2:

[0088] Take 20g of Pd-Ru@ZIF-8 prepared in step S1 and add it to 20mL of an ethanol-water solution composed of ethanol and deionized water in a volume ratio of 1:1. Mix well, add 1mL of 25% ammonia water, and then add 500mg of hexadecyltrimethylammonium bromide. After complete dissolution, add 50μL of tetraethyl orthosilicate and stir at room temperature for 12h. Wash the product with ethanol solution by centrifugation, collect the solid product, dry it at 60℃ to constant weight, and grind it to obtain a white product: PdRu@ZIF-8@SiO2.

[0089] As a control for subsequent experiments, Pd@ZIF-8@SiO2 and Ru@ZIF-8@SiO2 were prepared by replacing Pd-Ru@ZIF-8 with Pd@ZIF-8 and Ru@ZIF-8 respectively, using the same method as above.

[0090] S3, PdRu / C@SiO2 was prepared by carbonization and reduction:

[0091] Under a nitrogen atmosphere, the PdRu@ZIF-8@SiO2 prepared in step S2 was placed in a boat and calcined at 250°C for 480 min. Then, the temperature was raised to 600°C and calcined and reduced at 600°C for 180 min. After cooling to room temperature, PdRu / C@SiO2 was obtained, which is the Pd-Ru synergistic catalyst based on the metal-organic framework.

[0092] As a control for subsequent experiments, Pd@ZIF-8@SiO2 and Ru@ZIF-8@SiO2 were used instead of PdRu / C@SiO2 to prepare two other catalysts: Pd / C@SiO2 and Ru / C@SiO2, following the same method as above.

[0093] In addition, the following three catalysts were prepared for subsequent comparison:

[0094] The PdRu@ZIF-8@SiO2 prepared in step S2 was placed in a crucible and calcined in a muffle furnace at 400°C in air atmosphere for 480 min to obtain a grayish-white powder, labeled as PdO-RuO2@SiO2. Subsequently, the PdO-RuO2@SiO2 was placed in a tube furnace and fully reduced in H2 atmosphere at 300°C to obtain the final PdRu@SiO2. The sample appeared grayish-white.

[0095] Two other catalysts, Pd@SiO2 and Ru@SiO2, were prepared by replacing PdRu@ZIF-8@SiO2 with Pd@ZIF-8@SiO2 and following the same method as above. The samples were all grayish-white.

[0096] Therefore, a total of 6 catalysts were prepared through the above methods: PdRu / C@SiO2, Pd / C@SiO2, Ru / C@SiO2; PdRu@SiO2, Pd@SiO2, and Ru@SiO2. Subsequent experiments were conducted, with the latter 5 catalysts mainly used as comparisons.

[0097] The synthesis routes for PdRu / C@SiO2 and PdRu@SiO2 are as follows: Figure 1 As shown.

[0098] Example 2 Performance Characterization

[0099] 1. Reference Figure 2 The images show SEM images of PdRu@ZIF-8@SiO2 (a), PdRu@SiO2 (b), and PdRu / C@SiO2 (c) prepared in Example 1, respectively. The SEM images show that the prepared PdRu / C@SiO2 sample has a rhombic dodecahedral structure. Magnified SEM images are shown below. Figure 2 (c) Insertion shows that the PdRu / C@SiO2 core is clearly encased in a silica shell. This indicates that the dodecahedral structure was preserved during the high-temperature carbonization process without any damage.

[0100] Reference Figure 3 The XRD patterns of PdRu@ZIF-8@SiO2, PdRu@SiO2, and PdRu / C@SiO2 prepared in Example 1 are shown. All patterns exhibit broad SiO2 diffraction peaks (PDF 29-0085), while no diffraction peaks were observed for single metals Ru, Pd, or PdRu alloys. This is mainly due to the highly dispersed and relatively small size of the nanoparticles. For PdRu@ZIF-8@SiO2, typical ZIF-8 crystal plane diffraction peaks are also present, indicating the formation of a MOF material. Further high-temperature carbonization and reduction of the above materials to obtain PdRu / C@SiO2 resulted in the addition of eight sharp ZnO crystal plane diffraction peaks (PDF 36-1451), demonstrating the presence of a partial organometallic framework after carbonization.

[0101] Reference Figure 4 The figures show the N2 adsorption-desorption curves of PdRu@SiO2 and PdRu / C@SiO2 prepared in Example 1, respectively. Both samples exhibit type IV isotherms and have obvious hysteresis loops, which are typical mesoporous materials. Figure 5 The figures show the pore size distribution of PdRu@SiO2 and PdRu / C@SiO2. A small number of micropores smaller than 2 nm are observed, with mesopores of approximately 5–10 nm dominating. Pores larger than 20 nm correspond to the packing pores between hollow nanocatalysts.

[0102] Table 2.1 Structural characteristics of PdRu@SiO2 and PdRu / C@SiO2

[0103]

[0104]

[0105] Note: a) Pore volume refers to the total pore volume after single-point adsorption; b) Average pore diameter refers to the average pore diameter after BJH adsorption.

[0106] Table 3 shows the BET specific surface area, pore size distribution, and pore volume of the two samples obtained from the BET test results. As can be seen from the table, the BET specific surface area of ​​PdRu@SiO2 is 82.4 m². 2 / g, pore volume 0.08cm 3 The surface area is approximately 7.58 nm, with an average pore size of around 7.58 nm. The BET specific surface area of ​​PdRu / C@SiO2 is 172.4 m². 2 / g, pore volume is 0.13cm 3 The surface area of ​​PdRu / C@SiO2 is approximately 4.68 nm, with an average pore size of about 4.68 nm. This indicates that high-temperature carbonization and reduction can significantly increase the specific surface area of ​​PdRu / C@SiO2, providing more active sites and thus enhancing catalytic activity.

[0107] Figure 6 The FT-IR spectra of PdRu@ZIF-8@SiO2, PdRu@SiO2, and PdRu / C@SiO2 prepared in Example 1 show that they have similar absorption peaks. However, the characteristic peak in the Si-O-Si band appears in the 800-1108 cm⁻¹ band. -1 This further confirms the existence of the SiO2 shell. Furthermore, the characteristic peak in the N / C band appears at 1596 cm⁻¹. -1 Furthermore, compared to PdRu@ZIF-8@SiO2 and PdRu@SiO2, PdRu / C@SiO2 exhibits smaller peak fluctuations, demonstrating that it is a good carbon and nitrogen doped material.

[0108] Example 3: Catalytic performance testing and reaction condition optimization of different catalysts

[0109] Catalyst performance evaluation methods

[0110] In this invention, the selective catalytic hydrogenation performance of the catalyst is evaluated through the reaction of phenylacetylene in a high-pressure reactor. A measured amount of substrate, catalyst, and solvent are added to a 35 mL high-pressure reactor and sealed. The reactor is purged five times with H2 atmosphere until the air is almost completely expelled. Then, H2 is introduced to bring the pressure inside the reactor to 1.0 MPa to test the selective hydrogenation performance of the catalyst. The reactor is stirred at 500 rpm, and timing begins once it reaches and stabilizes at a predetermined temperature. After the reaction time is complete, the reactor is immediately cooled, residual gas is removed, the high-pressure reactor is opened, and the filtered catalyst solution is collected.

[0111] Analytical methods for reaction products

[0112] Quantitative analysis of the liquid products was performed using a 7890B gas chromatograph (FID detector, SE-30 capillary column (30m × 0.32mm, membrane thickness 0.25mm), with nonane as the internal standard). During detection, the injection port temperature was maintained at 250℃, the column oven temperature was initially set at 100℃ and held for 1 min, then increased to 250℃ over a predetermined program for 7.5 min and held at 250℃ for 1 min. Qualitative analysis of the liquid products was performed using gas chromatography-mass spectrometry. Conversion and selectivity were calculated using the following formulas:

[0113]

[0114] 3.1 Catalyst Screening

[0115] Following the above method, different catalysts were placed under the same conditions for the selective catalytic hydrogenation of phenylacetylene. The composition of the final reaction product was analyzed to screen and optimize the relevant catalysts. The reaction conditions were as follows: 5 mL ethanol (solvent), 53 μL phenylacetylene, 5 mg catalyst, reaction temperature 65 °C, reaction pressure 1 MPa, and reaction time 2 h.

[0116] The final results are shown in Table 3.1. Traditional Pd nanocatalysts (Pd@SiO2) exhibit relatively high activity but relatively low selectivity, while Ru nanocatalysts (Ru@SiO2) show high selectivity but low activity. Therefore, in this embodiment, an appropriate amount of Ru was added to the original Pd nanocatalyst to improve selectivity.

[0117] Table 3.1 Screening results of catalytic hydrogenation performance of different catalysts

[0118]

[0119] Research on metal carbon-based materials [7] This indicates that the presence of carbon components can significantly enhance the dispersibility and stability of the catalyst's metal components. Furthermore, the introduction of carbon components can significantly improve molecular conductivity and accelerate electron transfer during the reaction, thereby improving the catalyst's catalytic performance. In the two catalysts prepared in this example, catalyst PdRu@SiO2 has a lower carbon content, while catalyst PdRu / C@SiO2, due to its higher carbon content and the formation of a certain metal-organic framework, should theoretically maintain better catalytic hydrogenation performance. The final catalytic hydrogenation performance screening results confirm this, with catalyst PdRu / C@SiO2 achieving a conversion rate of 95.3% and a selectivity of 99.4% under the same conditions.

[0120] 3.2 Optimization of reaction conditions

[0121] In this embodiment, a series of optimization operations were performed on PdRu / C@SiO2, which had the best catalytic effect, including reaction solvent, reaction temperature, and reaction pressure, to finally obtain the optimal reaction conditions.

[0122] The reaction solvent has a significant impact on the selective catalytic hydrogenation performance of phenylacetylene, as shown in the reaction results. Figure 7 As shown in the reaction conditions (5 mL solvent, 53 μL phenylacetylene, 5 mg catalyst, 65 °C, 1 MPa, 2 h), the reaction results indicate that when ethanol (EtOH) is used as the solvent, the conversion rate of phenylacetylene is 95.3% and the selectivity is 99.4%; when methanol (MeOH) is used as the solvent, the conversion rate of phenylacetylene is 88.2%, but the selectivity decreases to 90.1%; when tetrahydrofuran (THF) is used as the solvent, the conversion rate of phenylacetylene is 100.0%, but the selectivity is only 29.7%; when cyclohexane (CHX) is used as the solvent, the conversion rate of phenylacetylene is 87.5%, and the selectivity is 39.7%; when 1,4-dioxane is used as the solvent, the conversion rate of phenylacetylene is 99.1%, but the selectivity is only 37.8%. Therefore, considering all factors, the catalyst exhibits the best activity when ethanol is used as the solvent.

[0123] Secondly, the effect of reaction temperature on the selective catalytic hydrogenation performance of phenylacetylene was studied, and the reaction results are as follows: Figure 8 The reaction conditions are shown (5 mL ethanol, 53 μL phenylacetylene, 5 mg catalyst, 1 MPa, 2 h). At 25 °C, the conversion rate of phenylacetylene is 24.9%, and the selectivity is 100%. At 45 °C, the conversion rate is only 47.1%, and the selectivity is 100%. At 65 °C, the conversion rate increases to 95.3%, and the overall conversion rate is 99.4%. At 85 °C, the conversion rate increases to 100%, but the selectivity decreases. At 105 °C, the conversion rate remains 100%, but the selectivity is still low. Clearly, the catalyst activity is optimal at 65 °C; therefore, 65 °C is chosen as the optimal reaction temperature for the selective catalytic hydrogenation performance of the catalyst for phenylacetylene.

[0124] Finally, this example investigated the effect of reaction pressure on the selective catalytic hydrogenation performance of phenylacetylene, and the reaction results are as follows: Figure 9The reaction conditions shown are: 5 mL ethanol, 53 μL phenylacetylene, 5 mg catalyst, 65 °C, 2 h. At a pressure of 0.1 MPa, the conversion rate of phenylacetylene is 32.6%, and the selectivity is 100%; at a pressure of 0.5 MPa, the conversion rate is 67.3%, and the selectivity is 100%; at a temperature of 1.0 MPa, the conversion rate increases to 95.3%, and the overall conversion rate is 99.4%; at a pressure of 1.5 MPa, the conversion rate increases to 100%, but the selectivity decreases; at a pressure of 2.0 MPa, the conversion rate remains 100%, but the selectivity is lower. Clearly, the catalyst activity is optimal at 1.0 MPa; therefore, 1.0 MPa is selected as the optimal reaction pressure for the selective catalytic hydrogenation performance of the catalyst for phenylacetylene.

[0125] Figures 7-9 and subsequent Figure 10 In this context, PA Conv. represents the conversion rate of phenylacetylene, SM Sel. represents the selectivity of styrene, and EB Sel. represents the selectivity of ethylbenzene.

[0126] This invention prepares a synergistic catalytic system with Pd-Ru as the active component, and after silicon coating and nitrogen atom hybridization, it is used for the directed catalytic semi-hydrogenation of phenylacetylene to styrene. This invention applies the Pd-Ru synergistic catalytic system to the catalytic hydrogenation of phenylacetylene, significantly improving the selectivity for styrene while maintaining a high conversion rate. This catalytic activity is attributed to the synergistic effect of Pd-Ru at a single point, which lowers the desorption energy of styrene and thereby increases the barrier to further hydrogenation of styrene, making the application of the Pd-Ru synergistic catalytic system to the hydrogenation of phenylacetylene possible.

[0127] Example 4 Stability Analysis Experiment

[0128] Repeatability and stability are important results for evaluating catalyst performance. Therefore, this example presents a cycle-replication experiment on the PdRu / C@SiO2 catalyst, and the results are as follows: Figure 10 As shown (reaction conditions: 5 mL ethanol, 53 μL phenylacetylene, 5 mg catalyst, 65 °C, 1 MPa, 2 h). It can be seen that in multiple reactions, the conversion rate of phenylacetylene reached a maximum of 96.1% and a minimum of 95.3%; its selectivity consistently remained around 98.9%, indicating that the catalyst possesses considerable reproducibility and stability.

[0129] Reaction time is also an important factor affecting catalyst performance. Therefore, this example investigated the effect of reaction time on the catalytic performance of the catalyst after a recycling experiment. The reaction results are as follows: Figure 11As shown (reaction conditions: 5 mL ethanol, 53 μL phenylacetylene, 5 mg catalyst, 65 °C, 1 MPa), after 0.5 h of reaction, the conversion rate of phenylacetylene was 33.7%, and the selectivity was 100%; after 1.0 h of reaction, the conversion rate of phenylacetylene was 57.9%, and the selectivity remained unchanged; after 1.5 h of reaction, the conversion rate of phenylacetylene was 83.8%, and the selectivity remained unchanged; after 2.0 h of reaction, the conversion rate increased to 95.3%, and the selectivity was 99.4%; after 2.5 h of reaction, the conversion rate of phenylacetylene was 100%, but the selectivity decreased to 92.7%. In this example, at multiple time points, the conversion rate of phenylacetylene increased with increasing reaction time, but the selectivity decreased. Therefore, the catalyst still exhibited considerable stability after cyclic reuse experiments, and maintained a high conversion rate and good selectivity even after 2.0 h of reaction.

[0130] Example 5: Universality Experiment of Catalyst

[0131] For catalysts, versatility is also one of the key performance indicators for evaluating their quality. Therefore, this embodiment explored the substrate range of PdRu / C@SiO2, selecting only substrates with high conversion (up to 85%) and good selectivity (up to 80%). Catalytic hydrogenation data for different phenylacetylene compounds on PdRu / C@SiO2 were summarized, and the specific results are shown in Table 5.1. In Table 5.1, the catalytic performance of the hydrogenation reactions of methylphenylacetylene substrates (2-acetylenyltoluene, 3-acetylenyltoluene, and 4-acetylenyltoluene) showed conversion rates all higher than 87%, and the selectivity of the corresponding target product methylstyrene reached over 80%. However, the selectivity of 2-acetylenyltoluene was only 82.9%, which may be related to the substrate structure. Furthermore, the conversion rates for 4-methoxyphenylacetylene, 4-ethynylaniline, and 4-ethylphenylacetylene all reached 100%, with selectivity also reaching 80%. For 4-ethynylnitrobenzene, more stringent reaction conditions were required, achieving 100% conversion with good selectivity of 96.4%. Finally, for 4-fluorophenylacetylene, 4-chlorophenylacetylene, and 4-bromophenylacetylene, increasingly stringent reaction conditions were required, with conversion rates exceeding 90% and selectivity for the target products exceeding 80%. This demonstrates that PdRu / C@SiO2 has broad applicability for the hydrogenation reactions of various phenylacetylene compounds.

[0132] Table 5.1 Substrate expansion for the selective hydrogenation of phenylacetylene compounds catalyzed by PdRu / C@SiO2

[0133]

[0134]

[0135] Note:

[0136] aReaction conditions: 5 mL ethanol, 0.05 mmol substrate, 5 mg catalyst, 105 °C, 1 MPa;

[0137] b Reaction conditions: 5 mL ethanol, 0.05 mmol substrate, 5 mg catalyst, 65 °C, 1 MPa;

[0138] c Reaction conditions: 5 mL ethanol, 0.05 mmol substrate, 5 mg catalyst, 35 °C, 1 MPa;

[0139] d Reaction conditions: 5 mL ethanol, 0.05 mmol substrate, 5 mg catalyst, 85 °C, 1 MPa.

[0140] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A method for preparing a Pd-Ru synergistic catalyst based on a metal-organic framework, characterized in that, Includes the following steps: S1. Preparation of Pd-Ru@ZIF-8: Pd 2+ Ru 3+ Zn 2+ 2-methylimidazole was mixed in a solvent, stirred and reacted. After the reaction was completed, the mixture was centrifuged and the solid product was collected to obtain Pd-Ru@ZIF-8. S2. Pd-Ru@ZIF-8 is coated with silica to prepare PdRu@ZIF-8@SiO2; S3, carbonization and reduction to prepare PdRu / C@SiO2, namely the Pd-Ru synergistic catalyst based on the metal-organic framework; Step S3 is as follows: Under a nitrogen atmosphere, the PdRu@ZIF-8@SiO2 prepared in step S2 was first calcined at 200-300℃ for 240-960 min, then heated to 500-700℃ and calcined and reduced at 500-700℃ for 90-360 min, and then cooled to room temperature to obtain PdRu / C@SiO2, which is the metal-organic framework-based Pd-Ru synergistic catalyst.

2. The method for preparing the Pd-Ru synergistic catalyst based on a metal-organic framework according to claim 1, characterized in that, Step S1 is as follows: S1-1. Add 2.5-10 mg Pd(Acac)2 and 17.5-70 mg Ru(Acac)3 to 10-50 mL of a methanol mixture containing 280-1120 mg Zn(NO3)2·6 H2O, mix well, and obtain mixture A. S1-2. Add 263-1052 mg of 2-methylimidazole to 10-50 mL of methanol and disperse by ultrasonication to obtain mixture B; S1-3. Add mixture B to mixture A and stir for 12-48 hours. After the reaction is complete, collect the solid product by centrifugation, wash with methanol, and dry to constant weight to obtain Pd-Ru@ZIF-8.

3. The method for preparing the Pd-Ru synergistic catalyst based on a metal-organic framework according to claim 1, characterized in that, Step S2 is as follows: The Pd-Ru@ZIF-8 prepared in step S1 was added to an ethanol aqueous solution and mixed evenly. Ammonia, hexadecyltrimethylammonium bromide and tetraethyl orthosilicate were added in sequence and stirred to react. After the reaction was completed, the product was centrifuged and washed, the solid product was collected, dried to constant weight, and ground to obtain PdRu@ZIF-8@SiO2.

4. The method for preparing the Pd-Ru synergistic catalyst based on a metal-organic framework according to claim 3, characterized in that, Step S2 is as follows: Take 10-40g of Pd-Ru@ZIF-8 prepared in step S1 and add it to 10-40 mL of an ethanol-water solution composed of ethanol and deionized water in a volume ratio of 1:

1. Mix well, add 0.5-2 mL of ammonia water with a mass concentration of 25%-28%, and then add 250-1000 mg of hexadecyltrimethylammonium bromide. After complete dissolution, add 25-100 μL of tetraethyl orthosilicate and stir the reaction for 6-24 h. Wash the product with ethanol solution by centrifugation, collect the solid product, dry it at 50-70℃ to constant weight, and grind it to obtain PdRu@ZIF-8@SiO2.

5. The method for preparing the Pd-Ru synergistic catalyst based on a metal-organic framework according to claim 1, characterized in that, Includes the following steps: S1. Preparation of Pd-Ru@ZIF-8: S1-1. Add 5 mg Pd(Acac)2 and 35 mg Ru(Acac)3 to 25 mL of a methanol mixture containing 560 mg Zn(NO3)2·6 H2O, mix well, and obtain mixture A. S1-2. Add 526 mg of 2-methylimidazole to 25 mL of methanol and disperse by ultrasonication to obtain mixture B; S1-3. Add mixture B to mixture A and stir for 24 hours. After the reaction is complete, centrifuge to collect the solid product, wash with methanol, dry at room temperature to constant weight, grind to obtain Pd-Ru@ZIF-8. S2. PdRu@ZIF-8 is coated with silica to prepare PdRu@ZIF-8@SiO2: Take 20g of Pd-Ru@ZIF-8 prepared in step S1 and add it to 20 mL of an ethanol-water solution composed of ethanol and deionized water in a volume ratio of 1:

1. Mix well, add 1 mL of 25% ammonia water, then add 500 mg of hexadecyltrimethylammonium bromide. After complete dissolution, add 50 μL of tetraethyl orthosilicate and stir at room temperature for 12 h. Wash the product with ethanol solution by centrifugation, collect the solid product, dry it at 60℃ to constant weight, grind it, and obtain PdRu@ZIF-8@SiO2. S3, PdRu / C@SiO2 was prepared by carbonization and reduction: Under a nitrogen atmosphere, the PdRu@ZIF-8@SiO2 prepared in step S2 was first calcined at 250 °C for 480 min, then heated to 600 °C and calcined and reduced at 600 °C for 180 min, and then cooled to room temperature to obtain PdRu / C@SiO2, which is the metal-organic framework-based Pd-Ru synergistic catalyst.

6. A Pd-Ru synergistic catalyst based on a metal-organic framework, characterized in that, It is prepared by the method described in any one of claims 1-5.

7. The application of the Pd-Ru synergistic catalyst as described in claim 6 in the selective hydrogenation of alkynes to olefins.

8. The application according to claim 7, characterized in that, in, The alkyne is any one of phenylacetylene, 2-acetylenoltoluene, 3-acetylenoltoluene, 4-acetylenoltoluene, 4-methoxyphenylacetylene, 4-acetylenolaniline, 4-ethylphenylacetylene, 4-acetylenolnitrobenzene, 4-fluorophenylacetylene, 4-chlorophenylacetylene, and 4-bromophenylacetylene.

9. The application according to claim 8, characterized in that, The application method is as follows: Alkynes, ethanol, and Pd-Ru synergistic catalysts were mixed uniformly and reacted under H2 atmosphere at 65-85℃ and 0.5-2MPa for 1-4 hours to prepare the corresponding olefins. The mass ratio of alkyne:ethanol:Pd-Ru synergistic catalyst is 5-20:0.5-2:0.5-2.

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