A ce-doped zeolite supported noble metal catalyst, and a preparation method and application thereof

Abstract

The application discloses a Ce-doped zeolite-supported noble metal catalyst and a preparation method and application thereof. The Ce-doped zeolite-supported noble metal catalyst comprises a carrier, an active component and an auxiliary component. The active component is a palladium species, the auxiliary component is a Ce species, and the carrier is a zeolite. The palladium species accounts for 0.5-2 wt.% of the total mass of the Ce-doped zeolite-supported noble metal catalyst. The Ce species accounts for 0.1-5 wt.% of the total mass of the Ce-doped zeolite-supported noble metal catalyst. The Ce-doped zeolite-supported noble metal catalyst is used for catalytic hydrogenation saturation reaction of naphthalene, and the particle size of palladium in the zeolite-supported noble metal catalyst and the acidity of the carrier surface are regulated by introducing the second metal Ce. The Ce-doped zeolite-supported noble metal catalyst has high catalytic activity, high selectivity of decalin and high stability.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology and relates to a catalyst for the hydrogenation saturation reaction of naphthalene, particularly a Ce-doped zeolite-supported noble metal catalyst and its preparation method and application. Background Technology

[0002] With increasing energy demand and growing environmental awareness, the fuel industry is facing increasingly stringent environmental regulations and fuel specifications. However, both coal tar and crude oil contain large amounts of polycyclic aromatic hydrocarbons (PAHs), making them unsuitable for direct use as clean fuels. High PAH content in diesel fuel not only leads to poor combustion quality, reduced fuel quality, and environmental pollution, but also releases large amounts of carcinogens, threatening human health. Catalytic hydrodearomatization (HDA) of fuels is key to solving these problems. Furthermore, catalytic hydrogenation of PAHs can not only improve the cetane number and quality of fuels, but also produce many high-value-added products. Naphthalene, a typical PAH, is present in 8%–12% of diesel fuel produced in refineries and petrochemical plants, and is often selected as a probe molecule for studying the catalytic hydrogenation mechanisms of PAHs. However, the large π-bonds in naphthalene make its structure very stable, and the stable double bonds are difficult to break. Therefore, developing highly efficient catalysts for deep hydrogenation saturation of naphthalene is of great significance.

[0003] Supported catalysts are widely used in the catalytic hydrogenation of polycyclic aromatic hydrocarbons (PAHs). Their catalytic performance is influenced not only by the properties of the supporting metal itself, but also significantly by the structure and acidity of the support. It has been reported that a large specific surface area and appropriate pore structure on the support not only facilitate metal loading and dispersion but also promote mass transfer and diffusion between reactants and products. Furthermore, a support with appropriate acidity promotes deep hydrogenation saturation of naphthalene. Currently, catalysts used for the catalytic hydrogenation of PAHs mainly fall into two categories: noble metal catalysts and non-noble metal catalysts. Noble metal catalysts (Pt, Pd, Ru, Rh, etc.) not only exhibit high activity for deep hydrogenation of naphthalene but also provide mild reaction conditions, maintaining good catalytic performance even at low temperatures. Non-noble metal catalysts (Ni, Mo, Co, etc.) are inexpensive and exhibit good sulfur and nitrogen resistance; however, they generally suffer from lower hydrogenation degrees, poorer activity and stability, and require harsh high-temperature and high-pressure reaction conditions. To obtain deeply hydrogenated saturated products, noble metal catalysts are often used.

[0004] Patent CN113976167A describes a dual-solvent method for preparing a Pd / HY catalyst. By altering the water content, the placement, particle size, and dispersion of the metal particles are controlled. Using dichloromethane and water as solvents, the Pd / HY catalyst is prepared by evaporation-induced aggregation of the metal precursor Pd(OAc)₂. By changing the water content of the dual-solvent system, the ratio of the metal precursor occupying micropores to mesopores in the Pd / HY catalyst is precisely adjusted. Based on this, excellent catalytic performance is obtained under relatively mild reaction conditions. The prepared Pd / HY catalyst exhibits high activity and high selectivity for decahydronaphthalene in the saturated hydrogenation reaction of naphthalene, with a decahydronaphthalene yield exceeding 98%.

[0005] Patent CN113368885A improves catalytic efficiency and noble metal utilization by pretreating and modifying the support and then doping it with phosphorus, achieving deep hydrogenation saturation of polycyclic aromatic hydrocarbons with relatively low noble metal loading. Specifically, mesoporous channels are constructed on HY molecular sieves using an alkali treatment method, resulting in good metal dispersion after palladium loading. Subsequently, phosphorus doping is applied to the catalyst to improve its acidity and the electronic state of the active metal, thereby enhancing both the catalytic performance and stability of the catalyst.

[0006] In summary, due to the high price and scarcity of precious metals, industrial production is difficult. Therefore, there is a desire to further improve their catalytic performance while using as little precious metal as possible. Furthermore, zeolite-supported precious metal catalysts obtained through traditional impregnation methods suffer from drawbacks such as excessively strong support acidity and weak metal-support interaction. This makes hydrogenation saturated products prone to ring-opening cracking or isomerization, leading to the loss and aggregation of active metals, thus reducing the deep hydrogenation saturation efficiency of polycyclic aromatic hydrocarbons. However, if the support acidity is too weak, resulting in low hydrogenation of naphthalene, the support acidity is difficult to adjust appropriately. In addition, existing precious metal catalysts experience aggregation and leaching of precious metal particles after use, leading to poor catalyst stability and short service life.

[0007] Therefore, it is desirable to prepare catalysts with high catalytic activity, high selectivity for decahydronaphthalene, and high stability by modifying the support while loading a small amount of noble metal through a simple preparation method. This invention aims to solve the above problems. Summary of the Invention

[0008] This invention aims to overcome the shortcomings of existing technologies. In the catalytic hydrogenation saturation reaction of naphthalene, the catalytic activity of zeolite-supported noble metal catalysts is low, the selectivity of decahydronaphthalene is low, and the stability is poor. This invention introduces a second metal, Ce, to regulate the particle size of palladium and the acidity of the support surface in the zeolite-supported noble metal catalyst. The Ce-doped zeolite-supported noble metal catalyst exhibits high catalytic activity, high selectivity of decahydronaphthalene, and high stability in the catalytic hydrogenation saturation reaction of naphthalene.

[0009] To improve catalytic performance, this invention employs a simple wet impregnation method to modify and regulate the synthesis of zeolite-supported noble metal catalysts by introducing a second metal, Ce. By doping with an appropriate amount of Ce, the particle size and dispersion of the supported metal, the surface acidity of the support, and the interaction between the metal and the support are significantly improved and regulated. This facilitates hydrogen dissociation, spillover, and adsorption of aromatics, thereby further enhancing the deep hydrogenation saturation efficiency of naphthalene. Furthermore, after three cycles of experiments, it was demonstrated that the stability and reusability of the catalyst doped with an appropriate amount of Ce were significantly improved. This is likely because the Ce species acts as an anchoring agent for the supported active metal, allowing the active metal particles to be stably loaded on the support, thus inhibiting the aggregation and leaching of the active metal particles.

[0010] The technical solution adopted in this invention is as follows:

[0011] The first aspect of this invention provides a Ce-doped zeolite-supported noble metal catalyst, comprising a support, an active component, and an auxiliary component, wherein the active component is a palladium species, the auxiliary component is a Ce species, and the support is zeolite; the palladium species accounts for 0.5 to 2 wt.% of the total mass of the Ce-doped zeolite-supported noble metal catalyst; and the Ce species accounts for 0.1 to 5 wt.% of the total mass of the Ce-doped zeolite-supported noble metal catalyst.

[0012] Preferably, the palladium species has a particle size of 1.91–2.87 nm.

[0013] A second aspect of this invention provides a method for preparing the Ce-doped zeolite-supported noble metal catalyst described in the first aspect of this invention, comprising the following steps:

[0014] (1) Weigh out a cerium source and dissolve it in deionized water by ultrasonication to obtain a first solution. Weigh out a palladium source and dissolve it in deionized water by ultrasonication to obtain a second solution. Mix the first solution and the second solution to obtain a mixed solution.

[0015] (2) Add the carrier and the mixed solution obtained in step (1) into a container and stir. After the mixture is stirred, the resulting suspension is filtered and washed. Then the filter cake is dried and ground to obtain the catalyst precursor.

[0016] (3) The catalyst precursor obtained in step (2) is calcined and reduced to obtain Ce-doped zeolite-supported noble metal catalyst.

[0017] Preferably, in step (1), the cerium source is selected from cerium nitrate and the palladium source is tetraamminepalladium nitrate.

[0018] Preferably, in step (1), the ultrasonic frequency is 20-130 kHz and the ultrasonic treatment time is 1-10 min.

[0019] Preferably, in step (2), the carrier is selected from HY zeolite.

[0020] Preferably, in step (2), the stirring temperature is room temperature, the stirring time is 6 to 24 hours, the drying temperature is 60 to 120°C, and the drying time is 6 to 12 hours.

[0021] Preferably, in step (3), the calcination conditions are: calcination temperature of 400-600℃, calcination time of 2-6h, and heating rate of 1-3℃ / min during calcination; the reduction conditions are: reduction atmosphere of hydrogen, hydrogen flow rate of 60-100mL / min, reduction temperature of 200-600℃, reduction time of 1-6h, and heating rate of 1-3℃ / min during reduction.

[0022] A third aspect of the present invention provides a Ce-doped zeolite-supported noble metal catalyst as described in the first aspect of the present invention, wherein the Ce-doped zeolite-supported noble metal catalyst is used in the hydrogenation saturation reaction of naphthalene to improve the selectivity and stability of decahydronaphthalene.

[0023] This invention involves simultaneously adding different amounts of Ce and Pd sources to a round-bottom flask during the synthesis of the catalyst precursor, and then stirring and impregnating them with a support. After drying, high-temperature calcination, and hydrogen reduction, zeolite-supported noble metal catalysts with varying Ce doping levels are prepared. By doping with an appropriate amount of Ce, even with doubled reactant concentration, a yield of over 99% decahydronaphthalene can still be obtained, and three cycle experiments show that the stability of the catalyst with appropriate Ce doping is also significantly improved. This is attributed to the fact that after appropriate Ce doping, the average particle size of Pd supported on the catalyst is further reduced to 1.91 nm, the interaction between the metal and the support is further enhanced, and Ce mainly exists in the weakly basic oxide CeO2 state, effectively reducing the strong acidity of the HY support, inhibiting further ring-opening cracking and isomerization of the hydrogenation saturated products, and enhancing the anchoring effect of the support on metal Pd, thereby improving the stability and reusability of the catalyst.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention prepares a zeolite-supported noble metal catalyst with a palladium particle size of 1.91 to 2.87 nm by introducing a second metal Ce to regulate the particle size of palladium and the acidity of the support surface in the zeolite-supported noble metal catalyst.

[0026] 2. After doping with an appropriate amount of Ce, the average particle size of Pd loaded on the catalyst is further reduced to 1.91 nm, thereby ensuring that more active sites are exposed with a lower palladium loading. Therefore, the Ce-doped zeolite-supported noble metal catalyst of this invention has higher catalytic activity. Even with a reactant concentration of 3.34 mg / mL naphthalene in a tridecane solution (usually the reaction concentration is investigated at 1.67 mg / mL), a yield of more than 99% decahydronaphthalene can still be obtained.

[0027] 3. In the Ce-doped zeolite-supported noble metal catalyst of this invention, Ce mainly exists in the form of the weakly basic oxide CeO2, which effectively reduces the strong acidity of the HY support and inhibits further ring-opening cracking and isomerization of the hydrogenation saturated product, thereby improving the selectivity of decahydronaphthalene. The Pd-0.8Ce / HY catalyst of this invention achieves a yield of up to 99.35% for decahydronaphthalene.

[0028] 4. The appropriate amount of Ce doping in this invention enhances the anchoring effect of the support on metal Pd, improving the stability and reusability of the catalyst. After three cycles of experiments, the yield of decahydronaphthalene by the Pd-0.8Ce / HY catalyst of this invention decreased from 99.35% to 80.23%, but the selectivity for decahydronaphthalene remained relatively high, indicating that the catalyst maintains high stability and reusability during the rigorous reaction and recovery process.

[0029] In this invention, the zeolite-supported noble metal catalyst is modified by introducing a second metal, Ce, thereby reducing the size of the active metal particles, improving the dispersion of the active metal, adjusting the surface acidity of the support, and enhancing the interaction between the metal and the support. Furthermore, after three cycles of testing, the catalyst with appropriate Ce doping further anchors the supported metal, preventing the loss and aggregation of metal particles, and enhancing the catalyst's stability and reusability.

[0030] The key points of this invention are summarized as follows: This invention introduces a second metal, Ce, to modify the zeolite-supported noble metal catalyst. During the preparation of the catalyst precursor, the zeolite support, Pd source, and Ce source are simultaneously doped and impregnated. The catalyst with appropriate Ce doping achieves a further improvement in the hydrogenation saturation efficiency of naphthalene. Under high reactant concentrations, with 0.8 wt% Ce doping, the prepared Pd-0.8Ce / HY catalyst can still completely convert naphthalene, with a yield of 99.35% for decahydronaphthalene; while the undoped catalyst only achieves a yield of 30.18% for decahydronaphthalene. This is attributed to the smaller Pd particle size (1.91 nm) on the catalyst after appropriate Ce doping, further improving metal dispersion, resulting in more metal active sites and thus further improving the catalytic hydrogenation saturation efficiency. The CeO2 loading also reduces the acidity of the support, further suppressing the hydrogenation cracking side reactions. Furthermore, three cycles of experiments were conducted on the Pd-0Ce / HY and Pd-0.8Ce / HY catalysts. The results showed that the Pd particle size on the Pd-0.8Ce / HY catalyst did not change significantly and maintained a high degree of dispersion. This indicates that the catalyst with appropriate Ce doping exhibits strong interaction between Pd and Ce species, thereby anchoring the Pd particles and enabling them to be stably supported on the support, inhibiting Pd particle aggregation and leaching. Attached Figure Description

[0031] Figure 1 TEM images of different catalysts and their particle size distributions are shown, where (a) and (b) are Comparative Example 1, (c) and (d) are Example 3, and (e) and (f) are Example 4.

[0032] Figure 2 The yields of decahydronaphthalene for different catalysts;

[0033] Figure 3 The product analysis results are shown for the naphthalene hydrogenation reaction under different catalysts;

[0034] Figure 4 NH3-TPD spectra of different catalysts;

[0035] Figure 5 The images show TEM images and particle size distributions of different catalysts after three cycles, where (a) and (b) are Comparative Example 1, and (c) and (d) are Example 3. Detailed Implementation

[0036] The present invention will be further described below through embodiments, but is not limited to these embodiments. Experimental methods not specifically described in the embodiments generally use conventional conditions and conditions described in manuals, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified.

[0037] The specific steps of the method described in this invention are as follows:

[0038] The synthesis of Pd / HY catalysts with different Ce doping amounts is taken as an example.

[0039] (1) Synthesis of catalyst precursor. First, 500 mg of HY zeolite was weighed and added to a 50 mL round-bottom flask. Different amounts of cerium nitrate were weighed and dissolved in 5 mL of deionized water by ultrasonication. Then, a certain amount of Pd(NH3)4(NO3)2 was weighed and dissolved in 5 mL of deionized water by ultrasonication. Next, 10 mL of a mixed solution of Pd(NH3)4(NO3)2 and cerium nitrate was added to the round-bottom flask simultaneously, and the mixture was stirred continuously at room temperature for 12 h. The mixture was then filtered to obtain a filter cake, which was dried in a forced-air oven at 120 °C for 12 h.

[0040] (2) Calcination and Reduction. The ground and dried samples were placed in a muffle furnace and calcined at 500℃ for 4 hours at a rate of 2.5℃ / min. Then, they were placed in an atmosphere furnace with a hydrogen flow rate of 100 mL / min and a temperature of 400℃ for 4 hours at a rate of 2.5℃ / min to obtain Pd-xCe / HY catalysts with different Ce doping amounts, where x represents the mass fraction of Ce doping (x = 0, 0.3, 0.5, 0.8, 1.0). The theoretical Pd loading of the catalyst was 1.0 wt%.

[0041] Specifically:

[0042] Example 1: Pd / HY with varying Ce doping concentration (Ce doping concentration of 0.3 wt%)

[0043] 500 mg of HY zeolite was weighed and added to a 50 mL round-bottom flask. 4.2 mg of cerium nitrate was weighed and dissolved in 5 mL of deionized water by ultrasonication. Then, 14 mg of Pd(NH3)4(NO3)2 was weighed and dissolved in 5 mL of deionized water by ultrasonication. Next, 10 mL of a mixed solution of Pd(NH3)4(NO3)2 and cerium nitrate was added to the round-bottom flask, and the mixture was stirred continuously at room temperature for 12 h. The solid product was then filtered, washed three times with deionized water, and dried in an oven at 120 °C for 12 h. The dried sample was calcined in air at 500 °C for 4 h at a heating rate of 2.5 °C / min. Subsequently, it was reduced in hydrogen at 400 °C for 4 h at a heating rate of 2.5 °C / min to obtain the target catalyst Pd-0.3Ce / HY. The average particle size of the palladium particles was 2.65 ± 0.42 nm.

[0044] Example 2: Pd / HY with varying Ce doping concentration (Ce doping concentration is 0.5 wt%)

[0045] The specific implementation conditions were similar to those in Example 1, but the amount of cerium nitrate added was 6.9 mg, and the other preparation steps were the same, resulting in Pd-0.5Ce / HY. The average particle size of the palladium particles was 2.35 ± 0.31 nm.

[0046] Example 3: Pd / HY with varying Ce doping concentration (Ce doping concentration of 0.8 wt%)

[0047] The specific implementation conditions were similar to those in Example 1, but the amount of cerium nitrate added was 11.1 mg, and the other preparation steps were the same, resulting in Pd-0.8Ce / HY. TEM images are shown below. Figure 1 As shown in (c) and (d), the palladium particles are uniformly dispersed on the support, with an average particle size of 1.91 ± 0.37 nm.

[0048] Example 4: Pd / HY with varying Ce doping concentration (Ce doping concentration is 1.0 wt%)

[0049] The specific implementation conditions were similar to those in Example 1, but the amount of cerium nitrate added was 13.9 mg, and the other preparation steps were the same, resulting in Pd-1.0Ce / HY. TEM images are shown below. Figure 1 As shown in (e) and (f), the palladium particles are relatively uniformly dispersed on the support, with an average particle size of 2.87 ± 0.67 nm.

[0050] Example 5: Pd / HY with altered Ce doping order (Ce doping first, then Pd doping)

[0051] 500 mg of HY molecular sieve was weighed and placed in a round-bottom flask. 5 mL of cerium nitrate aqueous solution (2.22 mg / mL) was added and stirred with the support for 12 h. Then, 5 mL of tetraamminepalladium nitrate aqueous solution was added for impregnation for 12 h (2.8 mg / mL), yielding a precursor with Ce-doped followed by Pd impregnation. The precursor was then filtered to obtain a filter cake, which was dried in a forced-air oven at 120 °C for 12 h. The sample was ground, calcined in a muffle furnace at 500 °C for 4 h, and then reduced in a hydrogen atmosphere furnace at 400 °C for 4 h, with a heating rate of 2.5 °C / min, thus obtaining the Pd-0.8Ce / HY catalyst with Ce-doped followed by Pd.

[0052] Example 6: Pd / HY with altered Ce doping order (Pd first, then Ce)

[0053] The specific implementation conditions are similar to those in Example 5, but 5 mL of tetraamminepalladium nitrate aqueous solution is first added to the support and stirred for 12 h, and then 5 mL of cerium nitrate aqueous solution is added to it and impregnated for another 12 h. The other preparation steps are the same, that is, Pd-0.8Ce / HY catalyst with Pd doping followed by Ce doping is obtained.

[0054] Example 7: Preparation of Ce-doped Pd / HY catalyst (Ce doping amount 0.8 wt%) by equal volume impregnation method

[0055] First, 500 mg of HY support was dried in a forced-air oven at 120 °C for 12 h to remove water from the molecular sieve. The dried HY molecular sieve was then placed in a cylindrical crucible. 14 mg of tetraamminepalladium nitrate and 11.1 mg of cerium nitrate were weighed and added to 700 μL of deionized water for ultrasonic dissolution. This solution was then slowly added dropwise to the HY molecular sieve using a pipette, with thorough and timely stirring using a spatula until the molecular sieve was completely impregnated. The mixture was then left to stand at room temperature for 12 h. Next, the sample was dried in a forced-air oven at 120 °C for 12 h. The dried sample was then ground and calcined in a muffle furnace at a rate of 2.5 °C / min to 500 °C for 4 h. The calcined sample was then ground again and placed in an atmosphere furnace for reduction at 200 °C under a hydrogen atmosphere for 2 h, with a heating rate of 2.5 °C / min and a hydrogen flow rate of 60 mL / min. This yielded the Pd-0.8Ce / HY catalyst prepared by the equal-volume impregnation method. The theoretical content of Pd is 1.0 wt%, and the theoretical content of Ce is 0.8 wt%.

[0056] Example 8: Preparation of Ce-doped Pd / HY catalyst (Ce doping amount 0.8 wt%) by dual solvent method

[0057] First, weigh 500 mg of HY molecular sieve and dry it in an oven at 120 °C for 12 h to ensure the molecular sieve is water-free. Weigh 10.5 mg of palladium acetate and add it to a round-bottom flask, then add 10 mL of dichloromethane and stir. Next, weigh 11.1 mg of cerium nitrate and dissolve it in 88 μL of deionized water by sonication. Slowly add this solution dropwise to the dried molecular sieve and stir evenly with a spatula. At this point, the water content of the HY molecular sieve is 15 wt%. Add the carrier, which is uniformly mixed with the Ce precursor, to dichloromethane containing 1.0 wt% palladium acetate and stir at room temperature for 12 h. After stirring, filter the solution through an organic filter membrane and dry the resulting solid in a forced-air oven at 120 °C for 12 h. Then, calcine it in a muffle furnace at 500 °C for 4 h, with a heating rate of 2.5 °C / min. Finally, the ground and calcined sample was placed in an atmosphere furnace and reduced at 400℃ for 4 hours, with a heating rate of 2.5℃ / min and a hydrogen flow rate of 100mL / min. This yielded the Pd-0.8Ce / HY catalyst prepared by the dual-solvent method.

[0058] Comparative Example 1: Pd-0Ce / HY (undoped Ce)

[0059] The specific implementation conditions were similar to those in Example 1, but HY zeolite (500 mg) was directly dissolved in 10 mL of Pd(NH3)4(NO3)2 aqueous solution (1.403 mg / mL), without Ce source doping, and stirred at room temperature for 12 h. TEM images are shown below. Figure 1 As shown in (a) and (b), the palladium particles are not dispersed uniformly on the support, with an average particle size of 3.25 ± 0.42 nm.

[0060] Example 9: Naphthalene hydrogenation saturation reaction under catalysts with different Ce doping concentrations

[0061] The catalysts obtained in Examples 1, 2, 3, 4, and Comparative Example 1 were applied to the catalytic hydrogenation saturation reaction of naphthalene. The catalytic activity of the Pd-xCe / HY catalyst for naphthalene hydrogenation saturation was tested in a 100 mL steel autoclave. The reaction solvent was n-tetane (30 mL), and the internal standard was n-hexadecane (100 μL). Naphthalene (50 mg) and catalyst (100 mg) were added to the autoclave. The reaction mixture was stirred at 600 rpm, and after the autoclave was heated to a reaction temperature of 200 °C, hydrogen gas was introduced to pressurize the reaction to a reaction pressure of 4 MPa. After reacting for 1 h, the autoclave was cooled to room temperature, and the pressure was reduced to atmospheric pressure for sampling.

[0062] Detailed reaction results of naphthalene hydrogenation catalyzed by different Pd-xCe / HY catalysts are shown in Table 1. On the undoped Ce Pd / HY catalyst, the conversion of naphthalene was 99.87%, with a selectivity for decahydronaphthalene of only 30.22% and a selectivity for cracking products of 1.33%. In contrast, the conversion of naphthalene on catalysts doped with appropriate amounts of Ce was higher than 99%, indicating higher activity, and the selectivity for cracking products was significantly reduced, not exceeding 0.6%. This shows that the addition of appropriate amounts of Ce effectively suppressed ring-opening cracking and isomerization side reactions, and improved the deep hydrogenation saturation efficiency. The yield of decahydronaphthalene on the Pd-xCe / HY catalyst is shown in Table 1. Figure 2 As shown, a volcano-like trend was observed with increasing Ce doping concentration. The highest yield of decahydronaphthalene (99.35%) was observed on the Pd-0.8Ce / HY catalyst with 0.8 wt% Ce doping, while the yield on the undoped Pd / HY catalyst was only 30.18%. The experimental results indicate that appropriate Ce doping to the Pd / HY catalyst can effectively improve its catalytic performance.

[0063] Example 10: Naphthalene hydrogenation saturation reaction under catalysts with different Ce doping sequences

[0064] The specific implementation conditions were similar to those in Example 9, but the catalysts used in the reaction were those in Examples 3, 5, 6, and Comparative Example 1. The product analysis results for the naphthalene hydrogenation reaction under each catalyst are shown in Table 2. It can be found that, during the catalyst precursor preparation process, the catalyst prepared by simultaneously doping with Pd and Ce exhibited the best catalytic performance. Simultaneous impregnation with Pd and Ce resulted in the best deep hydrogenation saturation effect for naphthalene, achieving a yield of 99.16% for decahydronaphthalene. Only simultaneous impregnation with Pd and Ce could achieve a good synergistic effect.

[0065] Example 11: Naphthalene hydrogenation saturation reaction under catalysts prepared by different methods

[0066] The specific implementation conditions are similar to those in Example 9, but the catalysts used in the reactions are those in Examples 3, 7, and 8. The product analysis results of the naphthalene hydrogenation reaction under each catalyst are shown in Table 3. As can be seen from the table, the catalyst prepared by the excess impregnation method has the best effect on the deep hydrogenation of naphthalene, with a naphthalene conversion rate of 99.89% and a yield of over 99% for decahydronaphthalene. In contrast, the catalysts prepared by the equal-volume impregnation method and the dual-solvent method have very low yields of decahydronaphthalene and poor deep hydrogenation saturation effects, with yields of only 33.86% and 21.40%, respectively. Therefore, the excess impregnation method is used to prepare the catalyst.

[0067] Example 12: Three-cycle naphthalene hydrogenation experiment with catalysts doped with appropriate amounts of Ce and those without Ce doping

[0068] The catalyst was recovered by high-speed centrifugation. First, it was washed three times with n-tetane to remove reactants and products, then washed three times with ethanol to remove n-tetane. After centrifugation, the catalyst was dried in a vacuum oven at 60°C for 12 hours for use in the next cycle. The specific implementation conditions were similar to those in Example 9, but the catalysts used were those in Example 3 and Comparative Example 1. The product analysis results for the naphthalene hydrogenation reaction under each catalyst are as follows: Figure 3 As shown in the figure, after three cycles, the yield of decahydronaphthalene by the undoped Ce Pd-0Ce / HY catalyst decreased from 30.18% to 2.70%, with almost no decahydronaphthalene formed, indicating poor catalyst stability and reusability. In contrast, the yield of decahydronaphthalene by the Pd-0.8Ce / HY catalyst decreased from 99.35% to 80.23%, while maintaining relatively high selectivity for decahydronaphthalene, demonstrating that the catalyst maintains high stability and reusability under strict reaction and recovery processes.

[0069] Experimental data show that, using the excess impregnation method and sequentially doping Pd and Ce, the catalyst exhibits the best catalytic performance with a Ce doping amount of 0.8 wt%, maintaining a yield of over 99% for decahydronaphthalene even at higher reactant concentrations. This is likely because, with appropriate Ce doping, the size of the Pd loaded on the catalyst is further reduced to 1.91 nm, and the metal dispersion is further improved. TEM images of the Ce-doped catalyst before the reaction are shown below. Figure 1 As shown; and Ce mainly exists in the weakly basic oxide CeO2 state, which effectively reduces the strong acidity of the HY support, inhibits further cracking and isomerization of saturated products, and enhances the anchoring effect of the support on metal Pd. The acidity of the support after doping with an appropriate amount of Ce is as follows. Figure 4 As shown in the figure. Furthermore, three-cycle experiments indicate that the stability of the catalyst doped with an appropriate amount of Ce is significantly improved. The Pd particle size after the reaction with the appropriately doped Ce catalyst shows no significant change compared to before the reaction. TEM images of the catalyst after the reaction are shown in the figure. Figure 5 As shown.

[0070] Table 1. Hydrogenation reaction data of naphthalene on different Pd-xCe / HY catalysts.

[0071]

[0072] Table 2. Data on naphthalene hydrogenation reactions on catalysts with different Ce doping sequences.

[0073]

[0074] Table 3. Data on naphthalene hydrogenation reactions on Pd-0.8Ce / HY catalysts synthesized by different methods.

[0075]

[0076] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. The application of a Ce-doped zeolite-supported noble metal catalyst in the saturated hydrogenation of naphthalene to prepare decahydronaphthalene, characterized in that, The Ce-doped zeolite-supported noble metal catalyst comprises a support, an active component, and an auxiliary component. The active component is a palladium species, the auxiliary component is a Ce species, and the support is HY zeolite. The palladium species accounts for 0.5–2 wt.% of the total mass of the Ce-doped zeolite-supported noble metal catalyst; the Ce species accounts for 0.1–5 wt.% of the total mass of the Ce-doped zeolite-supported noble metal catalyst. The palladium species have a particle size of 1.91–2.87 nm; The method for preparing the Ce-doped zeolite-supported noble metal catalyst includes the following steps: (1) Weigh out a cerium source and dissolve it in deionized water by ultrasonication to obtain a first solution. Weigh out a palladium source and dissolve it in deionized water by ultrasonication to obtain a second solution. Mix the first solution and the second solution to obtain a mixed solution. (2) Add the carrier and the mixed solution obtained in step (1) into a container and stir. After the stirring is completed, filter and wash the resulting suspension. Then dry and grind the resulting filter cake to obtain the catalyst precursor. (3) The catalyst precursor obtained in step (2) is calcined and reduced to obtain Ce-doped zeolite-supported noble metal catalyst.

2. The application according to claim 1, characterized in that, In step (1), the cerium source is selected from cerium nitrate and the palladium source is tetraamminepalladium nitrate.

3. The application according to claim 1, characterized in that, In step (1), the ultrasonic frequency is 20-130 kHz; the ultrasonic treatment time is 1-10 min.

4. The application according to claim 1, characterized in that, In step (2), the stirring temperature is room temperature, the stirring time is 6 to 24 hours, the drying temperature is 60 to 120°C, and the drying time is 6 to 12 hours.

5. The application according to claim 1, characterized in that, In step (3), the calcination conditions are: calcination temperature of 400-600℃, calcination time of 2-6h, and heating rate of 1-3℃ / min during calcination; the reduction conditions are: reduction atmosphere of hydrogen, hydrogen flow rate of 60-100mL / min, reduction temperature of 200-600℃, reduction time of 1-6h, and heating rate of 1-3℃ / min during reduction.

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