Preparation method of supported noble metal aluminide nanocatalyst and application thereof

Abstract

The application belongs to the field of catalytic new materials and fine chemical technology, and discloses a preparation method and application of a supported noble metal aluminide nanocatalyst. The application provides a new preparation method and catalyst, and can synthesize a supported noble metal aluminide catalytic material with high activity and high selectivity at a lower temperature, which is used for selective hydrogenation reaction. In particular, the application aims to solve the problems of difficult preparation, easy phase mixing, and insufficient selectivity and stability in hydrogenation reaction of the high-activity supported noble metal aluminide nanocatalyst, thereby significantly improving the catalytic effect. The supported noble metal aluminide nanocatalyst prepared by the application can obtain the performance even better than that of a conventional noble metal catalyst at a lower reaction temperature and pressure, the reaction path is clear, the metal ratio range is adjustable, the synthesis result has high repeatability, and the application provides a new high-efficiency and stable catalytic material for selective hydrogenation.

Description

Technical Field

[0001] This invention belongs to the field of new catalytic materials and fine chemical technology, and relates to a method for preparing supported noble metal aluminum compound nanocatalysts and their applications. Background Technology

[0002] In the selective hydrogenation of alkynes to olefins, traditional supported noble metal catalysts such as palladium and platinum, while exhibiting excellent hydrogen dissociation activity, often suffer from low olefin selectivity due to over-hydrogenation. Palladium-based catalysts, in particular, tend to form excessive metal hydride species during the reaction, exhibiting similar adsorption capacities for alkynes and the resulting olefins, leading to further hydrogenation of the target olefin to alkanes and hindering the achievement of high selectivity. To suppress the deep hydrogenation activity of palladium, traditional methods involve modifying its electronic structure or diluting surface active sites, such as introducing poisoning agents (e.g., Pb, S) or constructing alloys with second metals (Cu, Ag, etc.). However, these methods still suffer from problems such as activity loss, residual toxicity, or high costs associated with noble metals.

[0003] In recent years, noble metal intermetallic compounds, due to their long-range ordered atomic arrangement, stable metal ratios, and unique geometric and electronic structures, have exhibited electronic properties and catalytic performance distinct from single metals, and have gradually been regarded as ideal materials for constructing highly selective hydrogenation catalysts. Compared to traditional alloys, intermetallic compounds can precisely control the active centers through electronic and geometric effects, thereby effectively limiting over-hydrogenation reactions. These structurally stable catalytic materials have demonstrated excellent catalytic activity and stability in electrocatalysis, CO methanation, and selective hydrogenation of alkynes and alkynols.

[0004] A study by Armbrüster M, Kovnir K, Behrens M, et al. Pd-Ga Intermetallic Compounds as Highly Selective Semihydrogenation Catalysts[J]. J. Am. Chem. Soc., 2010, 132(42): 14745-14747 reported a route for synthesizing ordered Pd-Ga intermetallic compounds such as Pd2Ga and PdGa via melt recasting and annealing. These materials exhibit excellent ethylene selectivity and reaction stability in the acetylene semihydrogenation reaction. The key lies in the uniform isolation of Pd atoms by Ga atoms in the crystal lattice, thereby suppressing PdH xThis method improves the selectivity of semi-hydrogenation. However, it requires extremely high temperatures, resulting in bulk or large particles that need to be ground before use, and has a low specific surface area. Furthermore, this metallurgical method is energy-intensive, difficult to scale up, and struggles to construct supported catalysts, limiting its further application in practical catalytic systems. Chinese patent CN114678541A ​​discloses a method for in-situ construction of intermetallic compounds in mesoporous carbon supports. This method utilizes ultrasound to promote the mixing and nucleation of noble and transition metal precursors within the support pores, followed by high-temperature annealing to transform them into ordered intermetallic compounds. While this method, combined with support pore size constraints, helps suppress metal particle sintering, the overall process temperature is high and involves numerous steps. High-temperature annealing may cause structural damage to the support and changes in the active phase. Moreover, the stability and universality of this complex process for scale-up remain to be verified. Another study, Han SW, Park H, Han J, et al. PtZn Intermetallic Compound Nanoparticles in Mesoporous Zeolite Exhibiting High Catalyst Durability for Propane Dehydrogenation[J]. ACSCatalysis, 2021, 11(13): 7962-7971, reported a method for loading PtZn alloy nanoparticles onto mesoporous materials constructed from silicon-based MFI zeolite nanosheets using a co-impregnation method, followed by processing to form Pt1Zn1 type intermetallic compound nanoparticles. This material exhibited high stability and high propylene selectivity in propane dehydrogenation. However, this method has certain limitations, such as the complex and costly preparation process of the silicon-based MFI zeolite nanosheets, extremely high requirements for precursor ratios and chemical environment, and poor versatility for other noble metal-non-noble metal systems.

[0005] Main group elements, represented by aluminum, possess strong electron-donating capabilities. Their intermetallic compounds with noble metals have been theoretically and experimentally proven to effectively separate the active sites of noble metals, enhancing their electronic regulation of reaction intermediates and thus significantly improving catalytic performance. However, the preparation of these noble metal intermetallic compounds still faces many challenges, mainly because aluminum has a strong affinity for oxygen and is difficult to reduce. Its spontaneous formation of intermetallic compounds requires overcoming a high thermodynamic energy barrier. A study by Zhang L, Li X, Wang Y, et al. Large-Scale Fabrication of Hollow Pt3Al Nanoboxes and Their Electrocatalytic Performance for HydrogenEvolution Reaction[J]. ACS Sustainable Chemistry & Engineering, 2019, 7(9):8362-8369. reported a method for large-scale preparation of Pt3Al hollow nanobox catalysts with an L12 ordered structure through melt spinning combined with self-template etching. This type of material exhibits excellent electrocatalytic activity and structural stability in the hydrogen evolution reaction (HER) under alkaline conditions. However, its preparation process relies on high-temperature melting and subsequent etching processes, with harsh reaction conditions and complex procedures. Furthermore, the hollow structure is prone to collapse under long-term harsh catalytic conditions, which further limits its practical application.

[0006] Overall, the structural controllability and scalability of noble metal intermetallic compounds in catalytic applications remain unresolved, particularly lacking a universal preparation route that can be constructed in situ under mild conditions while simultaneously providing support constraint, structural stability, and nanoscale controllability. Therefore, there is an urgent need to develop a novel strategy that is simple to operate, operates under mild conditions, and can construct noble metal intermetallic compounds in situ within a supported system to meet practical catalytic requirements such as highly selective hydrogenation.

[0007] In summary, the controllable preparation of supported intermetallic compound nanocatalysts containing noble metals and aluminum under mild conditions, while maintaining high catalytic activity and significantly improving selectivity for olefins in the selective hydrogenation of alkynes, has become a pressing technical problem in this field. Based on this background, the present invention provides a novel supported noble metal aluminum compound nanocatalyst and its preparation method, aiming to overcome the synthesis difficulties and performance limitations of existing technologies. Summary of the Invention

[0008] The technical objective of this invention is to address the prominent problems in existing technologies, such as the difficulty in phase formation and poor catalytic performance of supported noble metal aluminum compounds under mild conditions, by providing a novel preparation method and catalyst. This method enables the synthesis of highly active and selective supported noble metal aluminum compound catalytic materials at lower temperatures for selective hydrogenation reactions. Specifically, this invention aims to solve the problems of difficult preparation, easy miscibility, and insufficient selectivity and stability in hydrogenation reactions of highly active supported noble metal aluminum compound nanocatalysts, thereby significantly improving the catalytic effect.

[0009] The technical solution of the present invention: A method for preparing supported noble metal aluminum compound nanocatalysts, comprising the following steps: (1) Under an inert atmosphere, precious metal chlorides and lithium aluminum hydride are added to an aromatic hydrocarbon solvent that has undergone deep dehydration treatment, and the mixture is heated at 180-220 °C. o Reflux at C for 8-24 hours to obtain a reaction system containing noble metal-aluminum species; (2) Allow the reaction system obtained in step (1) to cool naturally to 80-100°C. o C, under an inert atmosphere, add a carrier and heat at 80-100°C. o C is immersed and stirred for 8-24 hours to load precious metal-aluminum species onto the carrier surface; (3) After separating the slurry obtained in step (2), a black powder is obtained, which is then subjected to 10... -1 -10 -3 Under dynamic vacuum conditions of Pa, at 80-150 o Dry at C for 12-24 hours; (4) The dried product obtained in step (3) is subjected to heating and annealing under dynamic vacuum conditions at a heating rate of 2.5. o C·min -1 Heat to 300-450 degrees Celsius o After being heated to C for 6-12 hours and then naturally cooled, a supported noble metal aluminum compound nanocatalyst was obtained.

[0010] The noble metal aluminum compounds in the supported noble metal aluminum compound nanocatalyst are Al-Pt type binary intermetallic compounds, Al-Pd type binary intermetallic compounds, or Al-Ru type binary intermetallic compounds.

[0011] The aromatic hydrocarbon solvent is selected from one or a mixture of two or more of thallium, ethyltoluene, diethylbenzene, and isopropylbenzene.

[0012] Before use, the aromatic hydrocarbon solvent is dried by combining a calcined and activated molecular sieve with calcium hydride and allowed to stand in an inert atmosphere for no less than 12 hours.

[0013] The precursor of the noble metal chloride is one of platinum chloride, palladium chloride, and ruthenium chloride, and the molar ratio of the noble metal element to lithium aluminum hydride in the precursor containing the noble metal-aluminum species is 1:1-10.

[0014] The carrier is one of carbon carrier, calcium oxide, aluminum oxide, and silicon carbide.

[0015] The carrier is subjected to 600-900 before use. o C. High-temperature drying treatment.

[0016] The entire experimental procedure was conducted in a strictly controlled waterless and oxygen-free environment.

[0017] The theoretical loading of noble metals in the supported noble metal aluminum oxide nanocatalyst is 0.1-10 wt.%.

[0018] A supported noble metal aluminum compound nanocatalyst is used for the selective hydrogenation of alkynes, comprising the following steps: reacting in an alcohol solution with a hydrocarbon concentration of 1-10 wt.% at a temperature of 20-100 °C. o Under conditions of C, reaction pressure of 0.1-3 MPa, and a mass ratio of supported noble metal aluminum oxide nanocatalyst to alkyne compound of 1:5-20, selective hydrogenation reaction is carried out in a hydrogen atmosphere to generate the corresponding olefin compound.

[0019] The alcohol is one of ethanol, methanol, and isopropanol.

[0020] The beneficial effects of this invention are as follows: The supported noble metal aluminum compound catalyst prepared by the above method has the advantages of uniform metal atom mixing, high sample purity, and ease of large-scale preparation; it has the significant advantage of achieving the formation of noble metal intermetallic compound phases under mild conditions, making the active site structure of the catalyst well-defined and controllable, avoiding the problems of side phase formation or noble metal sintering in traditional high-temperature solid-state reactions; the highly dispersed nanoparticles are firmly anchored on the support, greatly improving the specific surface area and active site utilization rate, and the catalyst exhibits high conversion rate and high target product selectivity in low-temperature selective hydrogenation reactions, effectively suppressing the occurrence of excessive hydrogenation side reactions; compared with Pd / Al2O3, the AlPd system significantly inhibits PdH x The formation of species reduces the tendency of styrene to undergo perhydrogenation, exhibiting excellent kinetic selectivity. In summary, the catalyst of this invention achieves performance equal to or even superior to traditional noble metal catalysts at lower reaction temperatures and pressures, with a clear reaction pathway, adjustable metal ratio range, and highly reproducible synthesis results, providing a highly efficient and stable novel catalytic material for selective hydrogenation. Attached Figure Description

[0021] Figure 1 This is the XRD diffraction pattern of the supported noble metal aluminum compound nanocatalyst AlPd / Al2O3; Figure 2 The XRD diffraction pattern of AlPd / Al2O3, a supported noble metal aluminum compound nanocatalyst synthesized using a mixed solution of mesitylene and diethylbenzene as a solvent; Figure 3 The XRD diffraction pattern of AlPd / Al2O3, a supported noble metal aluminum oxide nanocatalyst with varying Pd loading, is shown. Figure 4 The image shows the XRD diffraction pattern of the supported noble metal aluminum compound nanocatalyst AlPt3 / Al2O3. Figure 5 The XRD diffraction pattern is that of a Pd-based sample synthesized without strict dehydration treatment of the Al2O3 support. Figure 6 The XRD diffraction pattern is that of a supported Pd-based sample synthesized without strict dehydration treatment of the diethylbenzene solvent. Figure 7 This is the XRD diffraction pattern of the supported Pd-based sample synthesized without the addition of lithium aluminum hydride reagent; Figure 8 The XRD diffraction pattern of the supported Pd-based sample synthesized by stirring at room temperature for the same time without immersion and stirring at 80 °C is shown. Figure 9 The XRD diffraction pattern of the supported Pd-based sample synthesized by omitting the 180 °C reflux step and completing the reaction by stirring at room temperature for the same amount of time is shown. Detailed Implementation

[0022] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0023] Example 1 Activated alumina was heated to 800°C before use. o Burn the mixture in an argon atmosphere for 2 hours, then transfer it to a glove box for storage after cooling. Add 0.1 g PdCl2 and 0.053 g LiAlH4 to 35 mL of diethylbenzene and heat at 180°C under an argon atmosphere. o Reflux for 8 hours. After reflux, allow it to cool naturally to 80°C. o C, add 1.7 g Al2O3 support at 80 o C was used for impregnation and stirring for 12 hours. After stirring was completed, the slurry was centrifuged to obtain a black palladium-aluminum intermetallic compound precursor.

[0024] The aforementioned precursor was placed in a vacuum tube furnace equipped with a cold trap and subjected to dynamic vacuum (10). -2 Pa) down 120 o Dry at 12°C for 12 hours. After drying, heat the powder to 300°C under dynamic vacuum. oC (heating rate 2.5) o C·min -1 Annealing for 6 hours. After natural cooling, the supported noble metal aluminum oxide nanocatalyst AlPd / Al2O3 was obtained. The XRD diffraction of this sample is as follows: Figure 1 As shown.

[0025] Example 2 Under the same conditions as in Example 1, 35 mL of diethylbenzene was converted into 35 mL of mesitylene solution to obtain the supported noble metal aluminum oxide nanocatalyst AlPd / Al2O3.

[0026] Example 3 Under the same conditions as in Example 1, 35 mL of diethylbenzene was replaced with 35 mL of a mixed solution of mesitylene and diethylbenzene at a volume ratio of 1:1 to obtain the supported noble metal aluminum oxide nanocatalyst AlPd / Al2O3. The XRD diffraction pattern of this sample is as follows: Figure 2 As shown.

[0027] Example 4 Under the same conditions as in Example 1, the addition of Al2O3 support was changed from 1.7 g to 0.56 g, resulting in a supported noble metal aluminum oxide nanocatalyst, AlPd / Al2O3. The XRD diffraction pattern of this sample is as follows: Figure 3 As shown.

[0028] Example 5 Activated alumina was heated to 800°C before use. o Burn the mixture in an argon atmosphere for 2 hours, then transfer it to a glove box for storage after cooling. Add 0.15 g PtCl2 and 0.053 g LiAlH4 to 35 mL of diethylbenzene and heat at 180°C under an argon atmosphere. o Reflux for 12 hours. After reflux, allow it to cool naturally to 80°C. o C, add 1.13 g Al2O3 support at 80 o C was used for impregnation and stirring for 12 hours. After stirring was completed, the slurry was centrifuged to obtain a black platinum-aluminum intermetallic compound precursor.

[0029] The aforementioned precursor was placed in a vacuum tube furnace equipped with a cold trap and subjected to dynamic vacuum (10). -2 Pa) down 100 o Dry at 12°C for 12 hours. After drying, heat the powder to 400°C under dynamic vacuum. o C (heating rate 2.5) o C·min -1 Annealing for 6 hours. After natural cooling, the supported noble metal aluminum oxide nanocatalyst AlPt3 / Al2O3 was obtained. The XRD diffraction of this sample is as follows: Figure 4 As shown.

[0030] Example 6 Activated alumina was heated to 800°C before use. o Burn the mixture in an argon atmosphere for 2 hours, then transfer it to a glove box for storage after cooling. Add 0.1 g RuCl3 and 0.053 g LiAlH4 to 35 mL of diethylbenzene and heat at 220 °C under an argon atmosphere. o Reflux for 8 hours. After reflux, allow it to cool naturally to 100°C. o C, add 1.7 g Al2O3 support to 100 o C was used for impregnation and stirring for 12 hours. After stirring was completed, the slurry was centrifuged to obtain a black ruthenium-aluminum intermetallic compound precursor.

[0031] The aforementioned precursor was placed in a vacuum tube furnace equipped with a cold trap and subjected to dynamic vacuum (10). -2 Pa) down 100 o Dry at 12°C for 12 hours. After drying, heat the powder to 450°C under dynamic vacuum. o C (heating rate 2.5) o C·min -1 Anneal for 6 hours. After natural cooling, the supported noble metal aluminum compound nanocatalyst AlRu / Al2O3 is obtained.

[0032] Example 7 Under the same conditions as in Example 1, the addition of 1.7 g Al2O3 support was replaced with the addition of 1.7 g SiC support to obtain the supported noble metal aluminum oxide nanocatalyst AlPd / SiC.

[0033] Application Example 1 The AlPd / Al2O3 catalyst prepared in Example 1 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o The reaction was carried out at temperature C, pressure 0.2 MPa, and time 1 h. Gas chromatography analysis of the product showed a phenylacetylene conversion of 98.3% and a styrene selectivity of 96.6%.

[0034] Application Example 2 The AlPd / Al2O3 catalyst prepared in Example 2 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. oThe reaction was carried out at temperature C, pressure 0.2 MPa, and time 1 h. Gas chromatography analysis of the product showed a phenylacetylene conversion of 97.8% and a styrene selectivity of 96%.

[0035] Application Example 3 The AlPd / Al2O3 catalyst prepared in Example 3 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o The reaction was carried out at temperature C, pressure 0.2 MPa, and time 1 h. Gas chromatography analysis of the product showed a phenylacetylene conversion of 94.2% and a styrene selectivity of 93.6%.

[0036] Application Example 4 The AlPd / Al2O3 catalyst prepared in Example 4 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o The reaction was carried out at temperature C, pressure 0.2 MPa, and time 1 h. Gas chromatography analysis of the product showed a phenylacetylene conversion of 96.3% and a styrene selectivity of 90%.

[0037] Application Example 5 The AlPt3 / Al2O3 catalyst prepared in Example 5 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o The reaction was carried out at temperature C, pressure 0.2 MPa, and time 1 h. Gas chromatography analysis of the product showed a phenylacetylene conversion of 95.2% and a styrene selectivity of 91.3%.

[0038] Application Example 6 The AlRu / Al2O3 catalyst prepared in Example 6 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o The reaction was carried out at temperature C, pressure 0.2 MPa, and time 1 h. Gas chromatography analysis of the product showed a phenylacetylene conversion of 94% and a styrene selectivity of 89.3%.

[0039] Application Example 7 The AlPd / SiC catalyst prepared in Example 7 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o The reaction was carried out at temperature C, pressure 0.2 MPa, and time 1 h. Gas chromatography analysis of the product showed a phenylacetylene conversion of 95.7% and a styrene selectivity of 93.6%.

[0040] Comparison of experimental results from Examples 1-7 shows that the supported noble metal aluminum oxide nanocatalyst AlPd / Al2O3, synthesized with diethylbenzene as solvent and activated alumina as support, exhibits better catalytic activity and selectivity with a theoretical loading of 3%.

[0041] Application Example 8-15 Application Examples 8 to 15 are practical application cases of the AlPd / Al2O3 catalyst prepared in Example 1. In this series of cases, the catalyst is used for the selective hydrogenation of various alkyne compounds to olefins. The overall reaction conditions are consistent with those in Application Example 1, with only some conditions such as reaction solvent, reaction substrate and reaction time being adjusted. The specific condition adjustment schemes and corresponding reaction results of each application example are summarized in Table 1.

[0042] Table 1

[0043] The reaction results of Examples 10-15 show that regardless of whether the substrate molecule has electron-withdrawing or electron-donating groups, the AlPd / Al2O3 aluminum compound catalyst prepared in Example 1 can efficiently convert it into olefin compounds, demonstrating that the catalyst has excellent versatility.

[0044] Comparing the reaction results of Application Examples 8-9 with Application Example 1, it can be found that the above-mentioned AlPd / Al2O3 supported aluminum catalyst exhibits high catalytic activity in the selective hydrogenation of alkynes to olefins in different alcohol solvents.

[0045] Comparative Example 1 Compared to Example 1, Comparative Example 1 did not undergo rigorous dehydration treatment of the Al2O3 support. The XRD diffraction of this sample is as follows: Figure 5 As shown, no characteristic peaks of Al-Pd intermetallic compounds were detected in the product, indicating that the target aluminum-palladium intermetallic compound catalyst could not be generated under the condition of water and oxygen presence.

[0046] Comparative Example 2 Compared to Example 1, Comparative Example 2 did not undergo rigorous dehydration treatment of the mesitylene solvent. The XRD diffraction of this sample was as follows: Figure 6 As shown, no characteristic peaks of Al-Pd intermetallic compounds were detected in the product, indicating that the target aluminum-palladium intermetallic compound catalyst could not be generated under the condition of water and oxygen presence.

[0047] Comparative Example 3 Activated alumina was heated to 800°C before use. o Burn the mixture in an argon atmosphere for 2 hours, then transfer it to a glove box for storage after cooling. Add 0.1 g of PdCl2 to 35 mL of diethylbenzene and heat at 180°C under an argon atmosphere. o Reflux for 8 hours. After reflux, allow it to cool naturally to 80°C. o C, add 1.7 g Al2O3 support at 80 o C. Impregnate and stir for 12 hours. After stirring, centrifuge to separate the slurry and obtain the black precursor.

[0048] The aforementioned precursor was placed in a vacuum tube furnace equipped with a cold trap and subjected to dynamic vacuum (10). -2 Pa) down 120 o Dry at 12°C for 12 hours. After drying, heat the powder to 300°C under dynamic vacuum. o C (heating rate 2.5) o C·min -1 Annealing for 6 hours. The XRD diffraction of this sample is as follows: Figure 7 As shown.

[0049] Compared to Example 1, Comparative Example 3 did not involve the addition of lithium aluminum hydride reagent during preparation. XRD analysis revealed only weak diffraction peaks of metallic Pd, with no signal of Al-Pd intermetallic compound. This indicates that LiAlH4 reduction aluminization was not used, and the expected aluminum-palladium intermetallic compound did not form in the final product, equivalent to obtaining a conventional Pd / Al₂O₃ catalyst.

[0050] Comparative Example 4 Compared to Example 1, Comparative Example 4 omitted the 80 °C soaking and stirring process, and only required stirring at room temperature for the same time. No obvious Al-Pd intermetallic compound peaks were detected in the XRD pattern of the product. This demonstrates that the target aluminum-palladium intermetallic compound is difficult to form without stirring and soaking at a specific temperature.

[0051] Comparative Example 5 Compared to Example 1, Comparative Example 5 omitted the 180 °C reflux step and completed the reaction by stirring at room temperature for the same amount of time. No obvious Al-Pd intermetallic compound peaks were detected in the XRD pattern of the product. This indicates that the target aluminum-palladium intermetallic compound is difficult to form without a heated reaction.

[0052] Comparative Example 6 Compared to Example 1, Comparative Example 6 changed the reflux step of 180 °C for 8 hours to 150 °C for 8 hours. No obvious Al-Pd intermetallic compound peaks were detected in the XRD pattern of the product. This shows that the target aluminum-palladium intermetallic compound is difficult to form without sufficient heating.

[0053] Comparative Example 7 Compared to Example 1, Comparative Example 7 shortened the dynamic vacuum annealing time by 2 hours. No obvious Al-Pd intermetallic compound peaks were detected in the XRD pattern of the product. This indicates that the target aluminum-palladium intermetallic compound is difficult to form without sufficient annealing.

[0054] Comparative Example 8 Compared with Example 1, Comparative Example 8 had a dynamic vacuum annealing temperature of 300°C after drying. o C increased to 600 o C. No obvious Al-Pd intermetallic compound peaks were detected in the XRD pattern of the product, but strong Pd diffraction peaks were observed. This indicates that excessively high dynamic vacuum annealing temperatures are detrimental to the formation of the target aluminum-palladium intermetallic compound.

[0055] Comparative Application Example 1 The catalyst prepared in Comparative Example 1 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o The reaction conditions were: C, reaction pressure 0.2 MPa, reaction time 1.5 h. Gas chromatography analysis of the product showed a phenylacetylene conversion of 88% and a styrene selectivity of 71%.

[0056] Compared to the near-complete conversion and over 90% styrene selectivity of the catalyst in the example, the comparative catalyst showed a significant decrease in styrene selectivity, demonstrating that the performance of the catalyst prepared from an improperly dried support was severely degraded.

[0057] Comparative Application Example 2 The catalyst prepared in Comparative Example 2 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o C, reaction pressure 0.2 MPa, reaction time 1 h. Gas chromatography analysis of the product showed that phenylacetylene was basically converted, but the styrene selectivity in the product was only about 50%, and most of the hydrogenation product was ethylbenzene.

[0058] Compared to the near-complete conversion and over 90% styrene selectivity of the catalyst in the example, the comparative catalyst showed a significant decrease in styrene selectivity, demonstrating the poor performance of catalysts prepared from solvents that were not rigorously dehydrated.

[0059] Comparative Application Example 3 The catalyst prepared in Comparative Example 3 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o At temperature C, the reaction pressure was 0.2 MPa, and the reaction time was 1 h. Gas chromatography analysis of the product showed that the conversion rate of phenylacetylene was close to 100%, but the selectivity for styrene was only about 30%. Most of the phenylacetylene was excessively hydrogenated to ethylbenzene.

[0060] Compared to the near-complete conversion and over 90% styrene selectivity of the catalyst in the comparative example, the catalyst in this example showed a significant decrease in styrene selectivity, demonstrating that although the conventional palladium catalyst lacking aluminum modulation has high activity, it has extremely poor selectivity for partial hydrogenation.

[0061] Comparative Application Example 4 The catalyst prepared in Comparative Example 4 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o The reaction conditions were: C, reaction pressure 0.2 MPa, reaction time 1 h. Gas chromatography analysis of the product showed that the conversion rate of phenylacetylene was close to 100%, but the selectivity for styrene was only about 60%.

[0062] Compared to the near-complete conversion and over 90% styrene selectivity of the catalyst in the examples, the styrene selectivity of the catalyst prepared in this comparative example was significantly reduced. This result indicates that the catalyst prepared without impregnation and stirring at 80°C performed poorly.

[0063] Comparative Application Example 5 The performance of the catalyst in Comparative Example 5 was evaluated under the same conditions as in Application Example 1. The conversion of phenylacetylene exceeded 90% within 1 hour of reaction, but the styrene selectivity was approximately 40%. Compared to the >90% selectivity of the catalysts in the Example series, the proportion of styrene produced by this catalyst is significantly lower. Analysis suggests that because the preparation process did not involve a high-temperature reaction, very few Al-Pd intermetallic compounds were actually formed in the catalyst, and most of the palladium existed in the metallic state, resulting in insufficient control over the selectivity of phenylacetylene during hydrogenation.

[0064] Comparative Application Example 6 The performance of the catalyst in Comparative Example 6 was evaluated under the same conditions as in Application Example 1. The conversion of phenylacetylene reached 90% within 1 hour of reaction, but the styrene selectivity was approximately 46%. Compared to the selectivity of over 90% for the catalysts in the Example series, this catalyst showed significantly lower styrene selectivity. Analysis suggests that due to insufficient high-temperature reaction during preparation, the actual formation of Al-Pd intermetallic compounds in the catalyst was low, with most palladium remaining in the metallic state. Consequently, the selectivity control for phenylacetylene during hydrogenation was insufficient.

[0065] Comparative Application Example 7 The catalyst prepared in Comparative Example 7 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o The reaction conditions were: C, reaction pressure 0.2 MPa, reaction time 1.5 h. Gas chromatography analysis of the product showed that the conversion rate of phenylacetylene was close to 100%, but the selectivity for styrene was only about 43%.

[0066] The catalyst prepared in the comparative example showed a significant decrease in styrene selectivity, indicating that the catalyst prepared without sufficient annealing has extremely poor selectivity for the semi-hydrogenation of phenylacetylene.

[0067] Comparative Application Example 8 The catalyst prepared in Comparative Example 8 was applied to the selective hydrogenation of phenylacetylene to styrene. 0.6 g of phenylacetylene, 50 ml of ethanol, and 30 mg of catalyst were placed in a 100 ml stainless steel high-pressure reactor equipped with an electric stirrer at 800 rpm. The reaction gas was high-purity hydrogen, and the reaction temperature was 40 °C. o The reaction was carried out at temperature C, pressure 0.2 MPa, and time 3 h. Gas chromatography analysis of the product showed a phenylacetylene conversion of 68% and a styrene selectivity of approximately 78%.

[0068] The catalyst prepared in the comparative example showed a significant decrease in activity and selectivity, indicating that the excessively high temperature of the dynamic vacuum annealing process caused Pd to agglomerate, which was not conducive to improving the selectivity of semi-hydrogenation.

[0069] In summary, the catalysts prepared in each comparative example are far inferior to the Al-Pd (Pt, Ru) intermetallic compound catalysts prepared in the embodiments of the present invention in terms of both hydrogenation activity and selectivity, especially in terms of styrene selectivity.

[0070] Comparing the experimental results of Application Examples 1-8 with Application Example 1, it is clear that without strictly limiting experimental conditions, such as anhydrous and oxygen-free operation throughout the experiment, strict solvent dehydration, use of calcined support, heating and reflux and impregnation stirring at specific temperatures, and dynamic vacuum annealing at specific temperatures, it is impossible to synthesize supported noble metal intermetallic compounds. Furthermore, the resulting catalyst does not possess the selectivity for alkyne selective hydrogenation of AlPd / Al2O3 supported noble metal intermetallic compounds.

Claims

1. A method for preparing supported noble metal aluminum compound nanocatalysts, characterized in that, The steps are as follows: (1) Under an inert atmosphere, precious metal chlorides and lithium aluminum hydride are added to an aromatic hydrocarbon solvent that has undergone deep dehydration treatment, and the mixture is heated at 180-220 °C. o Reflux at C for 8-24 hours to obtain a reaction system containing noble metal-aluminum species; (2) Allow the reaction system obtained in step (1) to cool naturally to 80-100°C. o C, under inert atmosphere, add the carrier and heat at 80-100°C. o C is immersed and stirred for 8-24 hours to load precious metal-aluminum species onto the carrier surface; (3) After separating the slurry obtained in step (2), a black powder is obtained, which is then subjected to 10... -1 -10 -3 Under dynamic vacuum conditions of Pa, at 80-150 o Dry at C for 12-24 hours; (4) The dried product obtained in step (3) is subjected to heating and annealing under dynamic vacuum conditions at a heating rate of 2.

5. o C·min -1 Heat to 300-450 degrees Celsius o After being heated to C for 6-12 hours and then naturally cooled, a supported noble metal aluminum compound nanocatalyst was obtained.

2. The method for preparing supported noble metal aluminum compound nanocatalysts according to claim 1, characterized in that, The noble metal aluminum compounds in the supported noble metal aluminum compound nanocatalyst are Al-Pt type binary intermetallic compounds, Al-Pd type binary intermetallic compounds, or Al-Ru type binary intermetallic compounds.

3. The method for preparing supported noble metal aluminum compound nanocatalysts according to claim 1, characterized in that, The aromatic hydrocarbon solvent is selected from one or a mixture of two or more of thallium, ethyltoluene, diethylbenzene, and isopropylbenzene.

4. The method for preparing supported noble metal aluminum compound nanocatalysts according to claim 1, characterized in that, Before use, the aromatic hydrocarbon solvent is dried by combining a calcined and activated molecular sieve with calcium hydride and allowed to stand in an inert atmosphere for no less than 12 hours.

5. The method for preparing supported noble metal aluminum compound nanocatalysts according to claim 1, characterized in that, The precursor of the noble metal chloride is one of platinum chloride, palladium chloride, and ruthenium chloride, and the molar ratio of the noble metal element to lithium aluminum hydride in the precursor containing the noble metal-aluminum species is 1:1-10.

6. The method for preparing supported noble metal aluminum compound nanocatalysts according to claim 1, characterized in that, The carrier is one of carbon carrier, calcium oxide, aluminum oxide, and silicon carbide.

7. The method for preparing supported noble metal aluminum compound nanocatalysts according to claim 1, characterized in that, The carrier is subjected to 600-900 before use. o C. High-temperature drying treatment.

8. The method for preparing supported noble metal aluminum compound nanocatalysts according to claim 1, characterized in that, The theoretical loading of noble metals in the supported noble metal aluminide nanocatalyst is 0.1-10 wt.%.

9. A supported noble metal aluminum compound nanocatalyst for the selective hydrogenation of alkynes, characterized in that, The steps are as follows: In an alcoholic solution with a hydrocarbon concentration of 1-10 wt.%, the reaction temperature is 20-100 °C. o Under conditions of C, reaction pressure of 0.1-3 MPa, and a mass ratio of supported noble metal aluminum oxide nanocatalyst to alkyne compound of 1:5-20, selective hydrogenation reaction is carried out in a hydrogen atmosphere to generate the corresponding olefin compound.

10. The supported noble metal aluminum oxide nanocatalyst according to claim 9 for catalyzing the selective hydrogenation reaction of alkynes, characterized in that, The alcohol is one of ethanol, methanol, and isopropanol.

Images