A renewable high-activity Pt / CeO2-Al2O3@SiO2 catalyst, a preparation method and application thereof

Abstract

The application discloses a renewable high-activity Pt / CeO2-Al2O3@SiO2 catalyst and a preparation method and application thereof, and relates to the technical field of catalysts. The method comprises the following steps: firstly, preparing a CeO2-Al2O3 composite carrier through a hydrothermal synthesis method; then, loading metal Pt onto the carrier by using an impregnation method; finally, taking tetraethyl orthosilicate as a silicon source, depositing silicon onto the surface of the Pt / Al2O3 catalyst to form the Pt / CeO2-Al2O3@SiO2 catalyst, the loading amount of Pt in the catalyst is 1.5 wt.%, the molar ratio of Ce / Al is 1 / 10, and the added amount of Si is 0.5-1.5 wt.%. The catalyst is effectively prevented from sintering and leaching of the metal Pt in the multiple regeneration processes through the strong interaction between the carrier and the metal and the synergistic physical coating effect of the surface SiO2; the catalyst maintains stable activity after 10 regeneration cycles in the methylcyclohexane dehydrogenation reaction.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a renewable, highly active Pt / CeO2-Al2O3@SiO2 catalyst, its preparation method, and its applications. Background Technology

[0002] The global transition to a sustainable energy system has significantly intensified the exploration of efficient hydrogen storage and transportation technologies. Hydrogen, as a clean and renewable energy carrier, has demonstrated enormous potential in the deep decarbonization process of transportation, industry, and other sectors. However, its storage and transportation face challenges such as low energy density and high safety requirements, prompting the industry to actively explore alternative technological routes.

[0003] Liquid organic hydrogen carriers (LOHCs) have become a promising solution due to their high hydrogen storage capacity, compatibility with existing fossil fuel infrastructure, and ease of operation. Among them, methylcyclohexane (MCH) has become a research focus due to its high theoretical hydrogen storage capacity (approximately 6.22 wt%), low toxicity, and reversible toluene (TOL) hydrogenation-methylcyclohexane dehydrogenation cycle. Methylcyclohexane dehydrogenation is the core step in LOHC-based hydrogen storage systems. This process not only efficiently releases hydrogen but also allows the regenerated toluene to be reused in subsequent hydrogenation cycles. However, methylcyclohexane dehydrogenation is a strongly endothermic reaction, requiring high-temperature conditions and highly efficient catalysts to achieve high conversion rates and high toluene selectivity.

[0004] In catalyst development, Pt, Pd, and Ni-based catalysts have long been widely used in the dehydrogenation reaction of methylcyclohexane. Among them, the Pt / Al₂O₃ catalyst, with its excellent CH bond activation ability and low C / C bond cleavage tendency, is considered one of the optimal catalyst systems and has been extensively studied. However, in the continuous dehydrogenation reaction of methylcyclohexane, carbon deposits inevitably form and cover the active sites, leading to catalyst deactivation. Frequent replacement or refilling of fresh precious metal catalysts significantly increases the application cost of liquid hydrogen storage technology. Therefore, to fully utilize the value of precious metal catalysts and avoid repeated refilling, developing a catalyst system with high stability, high dehydrogenation efficiency, and recyclability has become an urgent technical challenge. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for preparing a renewable, highly active Pt / CeO2-Al2O3@SiO2 catalyst.

[0006] The second objective of this invention is to provide a highly active Pt / CeO2-Al2O3@SiO2 catalyst prepared by the above-described method.

[0007] A third objective of this invention is to provide the application of the above-mentioned renewable and highly active Pt / CeO2-Al2O3@SiO2 catalyst in the catalytic dehydrogenation of methylcyclohexane.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: One aspect of the present invention provides a method for preparing a regenerable, highly active Pt / CeO2-Al2O3@SiO2 catalyst, comprising the following steps: (1) Aluminum salt, cerium salt and urea are added to water and mixed to obtain mixed solution A. The mixed solution A is placed in a high pressure vessel for hydrothermal reaction. After cooling to room temperature, the precipitate is washed, dried and calcined to obtain CeO2-Al2O3 composite carrier. (2) The CeO2-Al2O3 composite support obtained in step (1) is added to an impregnation solution containing platinum precursor, ultrasonically mixed, then vacuum impregnated and dried, and then calcined to obtain Pt / CeO2-Al2O3 catalyst. (3) The Pt / CeO2-Al2O3 catalyst obtained in step (2) is mixed with ethanol and 25% to 28% ammonia water under continuous stirring to obtain mixed solution B; tetraethyl orthosilicate is mixed with ethanol to obtain mixed solution C, and mixed solution C is added to mixed solution B by injection pump. After thorough stirring, the precipitate is washed, dried and calcined to obtain Pt / CeO2-Al2O3@SiO2 catalyst.

[0009] Preferably, in step (1), the temperature of the hydrothermal reaction is 100°C. o C, the hydrothermal reaction time is 48 hours; the drying temperature is 100°C. o C, the drying time is 12h; the calcination temperature is 500℃, and the calcination time is 4h.

[0010] Preferably, in step (2), the mass ratio of the CeO2-Al2O3 composite support to the volume ratio of the impregnation solution containing the platinum precursor is 1 g: 4 mL; the drying temperature is 100 °C. o C, drying time is 12h; the calcination temperature is 400℃, calcination time is 4h; vacuum impregnation is 12h.

[0011] Preferably, in step (1), the aluminum salt is aluminum nitrate and the cerium salt is cerium nitrate; the concentrations of the aluminum salt, cerium salt, and urea in the mixed solution A are 644 mg / mL, 75 mg / mL, and 928 mg / mL, respectively; in step (2), the platinum precursor is chloroplatinic acid hexahydrate and the concentration of the impregnation solution containing the platinum precursor is 10 mg / mL.

[0012] Preferably, in step (3), the ratio of Pt / CeO2-Al2O3 catalyst, ethanol, and ammonia in mixed solution B is 3g:400mL:20mL; the mass ratio of tetraethyl orthosilicate to Pt / CeO2-Al2O3 catalyst is 1:(12-30); the concentration of tetraethyl orthosilicate in mixed solution C is 0.5-1.25g / L, and the injection pump rate is 40μL / min.

[0013] Preferably, in step (3), the drying temperature is 100°C. o C, the drying time is 12h; the calcination temperature is 350℃, the calcination time is 2h, and the heating rate is 2. o C / min.

[0014] A second aspect of this invention provides a regenerable, highly active Pt / CeO2-Al2O3@SiO2 catalyst prepared by the above-described method. The catalyst has a layered composite structure with Pt / CeO2-Al2O3 as the core and SiO2 as the shell. The catalyst contains 1.5 wt.% Pt, a Ce / Al molar ratio of 1 / 10, and 0.5-1.5 wt.% Si. In the Pt / CeO2-Al2O3@SiO2 catalyst, Pt and the CeO2-Al2O3 support exhibit strong interactions, and SiO2 provides excellent physical coating. Even after multiple regeneration cycles, Pt remains highly dispersed.

[0015] A third aspect of the present invention also provides the application of the above-mentioned regenerable, highly active Pt / CeO2-Al2O3@SiO2 catalyst in the catalytic dehydrogenation of methylcyclohexane. When used as a catalyst for the dehydrogenation reaction of methylcyclohexane, it can maintain excellent dehydrogenation activity and stability during continuous regeneration cycles.

[0016] The specific application process is as follows: the catalyst is compressed into tablets and then crushed into small particles of 40-60 mesh; 50 mg of the crushed Pt / CeO2-Al2O3@SiO2 catalyst (40-60 mesh) is diluted with 0.5 g of quartz sand (40-60 mesh) and placed in the isothermal section of the reactor tube (diameter = 8 mm); before the reaction, the sample is heated at 400°C. o C was reduced in a stream of H2 (30 ml / min) and Ar (30 ml / min) for 2 h; after reduction pretreatment, the catalyst was cooled to 300 °C in an Ar atmosphere; subsequently, methylcyclohexane was introduced under a carrier gas (Ar) and reacted for 10 h; the feed of Ar and H2 was regulated by a mass flow controller, and the feed of methylcyclohexane was controlled by an injection pump; the resulting product was analyzed online by a gas chromatograph.

[0017] To evaluate the regeneration stability of the catalyst, the spent catalyst was regenerated under an O2 atmosphere. After the methylcyclohexane dehydrogenation test, the catalyst was cooled to room temperature in Ar and then subjected to a 550°C test under a 20% O2 / Ar atmosphere (100 mL / min). o Store at C for 30 minutes, with a heating rate of 5. o The regeneration process is carried out at C / min. After regeneration, the catalyst is cooled to room temperature under an Ar atmosphere, and then the same reduction procedure described above is performed. After reduction, a cyclic dehydrogenation reaction is carried out by introducing a reactant gas mixture (methylcyclohexane / Ar).

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The CeO2-Al2O3 composite support prepared by the hydrothermal synthesis method of this invention exhibits strong interaction with metal Pt, with Pt uniformly distributed on the support. The average size of the metal particles in the catalyst is 1.13 nm. Compared with commonly used Pt / Al2O3 catalysts, the Pt / CeO2-Al2O3 catalyst shows superior catalytic activity in the dehydrogenation of methylcyclohexane. As can be seen from Comparative Examples 1-3, the dehydrogenation rate of the Pt / CeO2-Al2O3 catalyst is 720 mmol / g. Pt / min, greater than the 683 mmol / g of the Pt / Al2O3 catalyst. Pt / min.

[0019] 2. This invention utilizes SiO2 coating on a Pt / CeO2-Al2O3 catalyst. Through physical coating and synergistic strong interaction between the support and the metal, the migration of Pt metal in high-temperature environments is significantly suppressed, allowing the catalyst to maintain metal dispersion during multiple cycles. By applying Comparative Example 7 and Application Example 3, Pt / CeO2-Al2O3@SiO2 maintained similar activity to the fresh catalyst after ten regeneration cycles, while Pt / Al2O3 showed significant deactivation after only three cycles. Attached Figure Description

[0020] Figure 1 The XRD patterns are of the catalysts prepared in Comparative Examples 1-3. Figure 2 The above are XPS images of the catalysts prepared in Comparative Examples 1-3. Figure 3 These are TEM images of the catalysts prepared in Comparative Example 1 and Example 2; Figure 4 The graph shows the results of methylcyclohexane dehydrogenation catalyzed by catalysts with different support types and different Ce / Al molar ratios; Figure 5 The graph shows the results of the dehydrogenation reaction of methylcyclohexane catalyzed by catalysts with different SiO2 coating amounts. Figure 6 The graph shows the results of catalytic dehydrogenation of methylcyclohexane after the catalysts obtained in Comparative Example 1 and Example 2 were recycled and regenerated. Figure 7 These are TEM images of the catalysts obtained in Comparative Example 1 and Example 2 after recycling and regeneration. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0022] Comparative Examples 1-3 varied the types of carriers.

[0023] Comparative Example 1 A method for preparing a Pt / Al2O3 catalyst includes the following steps: (1) Dissolve 6.44g Al(NO3)3·9H2O and 9.28g CO(NH2) in 10mL of deionized water to obtain mixed solution A; place mixed solution A in a 200mL stainless steel autoclave lined with Teflon, and heat at 100°C. o Incubate at C for 48 hours; after cooling to room temperature, wash and filter the precipitate multiple times with deionized water, then at 100°C. o Dry at C for 12 hours, and finally in a muffle furnace at 2 o The heating rate is 500 °C / min. o Calcination at C for 4 h yielded Al2O3 support; (2) Using the impregnation method, 0.5 g of Al2O3 support was added to 2 mL of ethanol solution containing 20 mg H2PtCl6·6H2O and sonicated for 30 min; then the mixed solution was impregnated in a vacuum drying oven for 12 h, and after impregnation, it was dried at 100 °C. o Dry at C for 12 hours, then in air at 400°C. o The target catalyst Pt / Al2O3 was obtained by calcination at C for 4 hours.

[0024] Comparative Example 2 A method for preparing a Pt / CeO2 catalyst, wherein “7.47gCe(NO3)3·6H2O” is used instead of “6.44gAl(NO3)3·9H2O” in Comparative Example 1, and other steps and process parameters are kept consistent with Comparative Example 1.

[0025] Comparative Example 3 A method for preparing a Pt / CeO2-Al2O3 catalyst with a Ce / Al ratio of 10, wherein “6.44g Al(NO3)3·9H2O and 0.75g Ce(NO3)3·6H2O” are used instead of “6.44g Al(NO3)3·9H2O” in Comparative Example 1, and other steps and process parameters are kept consistent with Comparative Example 1.

[0026] Comparative Examples 4-5 are based on Comparative Example 3, with the Ce / Al ratio of the mixed carrier adjusted.

[0027] Comparative Example 4 A method for preparing a Pt / 5CeO2-Al2O3 catalyst with a Ce / Al ratio of 5, wherein “6.44g Al(NO3)3·9H2O and 0.36g Ce(NO3)3·6H2O” are used instead of “6.44g Al(NO3)3·9H2O” in Comparative Example 1, and other steps and process parameters are kept consistent with Comparative Example 1.

[0028] Comparative Example 5 A method for preparing a Pt / 15CeO2-Al2O3 catalyst with a Ce / Al ratio of 15, wherein “6.44g Al(NO3)3·9H2O and 1.12g Ce(NO3)3·6H2O” are used instead of “6.44g Al(NO3)3·9H2O” in Comparative Example 1, and other steps and process parameters are kept consistent with Comparative Example 1.

[0029] The XRD patterns of the catalysts prepared in Comparative Examples 1-3 are as follows: Figure 1 As shown in the figure, the XPS graph is as follows Figure 2 As shown. From Figure 1 It can be seen that Comparative Example 1 exhibits typical Al2O3 crystal diffraction peaks, Comparative Example 2 exhibits typical CeO2 crystal diffraction peaks, and Comparative Example 3 has characteristic peaks of both Al2O3 and CeO2 crystals, indicating that the catalyst exhibits a mixed crystal morphology. Figure 1 The absence of diffraction peaks for metallic Pt or metal oxide PtO indicates that the metal particles in Comparative Examples 1-3 are small or have low loading. Figure 2 It can be seen that, compared with Comparative Example 1, the binding energy of Pt in Comparative Example 2 shows a positive shift, indicating that the metal interacts with the support; compared with the catalyst in Comparative Example 2, the binding energy of Pt in Comparative Example 3 shows the most significant positive shift, which proves that there is a strong interaction between the support and the metal, which is beneficial to the dispersion of Pt and its stability under high temperature conditions.

[0030] Examples 1-2 and Comparative Example 6 are based on Comparative Example 3, coated with SiO2.

[0031] Example 1

[0032] A method for preparing a Pt / CeO2-Al2O3@0.5SiO2 catalyst with a SiO2 coating of 0.5 wt.% includes the following steps: 0.30 g of Pt / CeO2-Al2O3 catalyst prepared in Comparative Example 3, 40 mL of ethanol, and 2 mL of 25%–28% ammonia solution were mixed under continuous stirring to obtain mixed solution B. 10 mg of tetraethyl orthosilicate was mixed with 20 mL of ethanol to obtain mixed solution C. Then, mixed solution C was added to mixed solution B via a syringe pump at a rate of 40 μL / min, and the mixture was stirred vigorously for 12 h. The product was obtained by centrifugation. The product was washed and purified at 100 °C. o After drying at C for 12 hours, it is then placed in a muffle furnace at 2 o The heating rate is 350 °C / min. o The target catalyst Pt / CeO2-Al2O3@0.5SiO2 was obtained by calcination at C for 2 h.

[0033] Example 2

[0034] A method for preparing a Pt / CeO2-Al2O3@1.5SiO2 catalyst with a SiO2 coating of 1.5 wt.% is disclosed, wherein “25 mg tetraethyl orthosilicate” is used instead of “10 mg tetraethyl orthosilicate” in Example 1, and other steps and process parameters are kept consistent with those in Example 1.

[0035] Comparative Example 6 A method for preparing a Pt / CeO2-Al2O3@2.5SiO2 catalyst with a SiO2 coating of 2.5 wt.% is disclosed, wherein “40 mg tetraethyl orthosilicate” is used instead of “10 mg tetraethyl orthosilicate” in Example 1, and other steps and process parameters are kept consistent with those in Example 1.

[0036] The surface elemental XPS semi-quantitative analyses of the catalysts prepared in Examples 1-2 and Comparative Example 6 are shown in Table 1. In Example 1, the Si / Al molar ratio was 3.38%, indicating that the SiO2 coating was relatively loose and difficult to completely cover the catalyst surface. In Example 2, the Si / Al molar ratio was 7.54%, indicating that SiO2 covered the catalyst surface in a very thin layer (<1 nm) and was very tightly packed. This thin SiO2 shell had a material confinement effect on the active metal Pt, preventing its aggregation and deactivation at high temperatures. In Comparative Example 6, the Si / Al molar ratio was 12.01%, indicating that SiO2 covered the catalyst surface in a relatively thick layer (>2 nm). This thick coating was not conducive to substrate adsorption, thus reducing the activity of methylcyclohexane dehydrogenation. TEM images of the catalysts prepared in Comparative Example 1 and Example 2 are shown below. Figure 3 As shown, Comparative Example 1 and Example 2 have similar Pt metal particle sizes, 1.16 nm and 1.13 nm, respectively. ICP analysis of the catalysts prepared in Comparative Example 1 and Example 2 is shown in Table 2, with similar Pt metal loadings of approximately 1.5 wt.%.

[0037] Table 1. XPS semi-quantitative analysis of surface elements of catalysts prepared in Examples 1-2 and Comparative Example 6.

[0038] Table 2. ICP analysis of the catalysts prepared in Comparative Example 1 and Example 2, respectively.

[0039] Application of Comparative Example 1: The Pt / Al2O3 catalyst obtained in Comparative Example 1 was applied to the dehydrogenation reaction of methylcyclohexane.

[0040] The Pt / Al2O3 catalyst obtained in Comparative Example 1 was compressed into tablets and then crushed into small particles of 40-60 mesh. 50 mg of Pt / Al2O3 catalyst (40-60 mesh) was diluted with 0.5 g of quartz sand (40-60 mesh) and placed in the isothermal section of a reactor tube (diameter = 8 mm). Before the reaction, the sample was kept at 400°C. o C was reduced in flowing H2 (30 ml / min) and Ar (30 ml / min) for 2 h; after reduction pretreatment, the catalyst was cooled to 300 °C in an Ar atmosphere; subsequently, the catalyst was tested for 10 h with methylcyclohexane at a flow rate of 30 μL / min under atmospheric pressure with Ar as the carrier gas. The feed of Ar and H2 was regulated by a mass flow controller, and the feed of methylcyclohexane was controlled by a syringe pump. The obtained product was analyzed online by gas chromatography.

[0041] Application Comparative Example 2: The Pt / CeO2 catalyst obtained in Comparative Example 2 was applied to the dehydrogenation reaction of methylcyclohexane, and the application process was the same as that in Comparative Example 1.

[0042] Application Comparative Example 3: The Pt / CeO2-Al2O3 catalyst obtained in Comparative Example 3 was applied to the dehydrogenation reaction of methylcyclohexane, and the application process was the same as that in Comparative Example 1.

[0043] Application Comparative Example 4: The Pt / 5CeO2-Al2O3 catalyst obtained in Comparative Example 4 was applied to the dehydrogenation reaction of methylcyclohexane, and the application process was the same as that in Comparative Example 1.

[0044] Application Comparative Example 5: The Pt / 15CeO2-Al2O3 catalyst obtained in Comparative Example 5 was applied to the dehydrogenation reaction of methylcyclohexane, and the application process was the same as that in Comparative Example 1.

[0045] The results of the dehydrogenation of methylcyclohexane catalyzed by catalysts with different support types and different Ce / Al molar ratios are as follows: Figure 4 As shown, the selectivity for methylcyclohexane was >99.9% for all catalysts, with the Al2O3 supported catalyst exhibiting a dehydrogenation rate of 683 mmol / g.Pt The efficiency of the catalyst was significantly better than that of the CeO2-supported catalyst, achieving a dehydrogenation efficiency of 720 mmol / g / min. Based on this, the dehydrogenation efficiency of the methylcyclohexane catalyst supported on CeO2-Al2O3 with a Ce / Al molar ratio of 10 was further improved to 720 mmol / g. Pt / min. However, the dehydrogenation rates of CeO2-Al2O3 supports with Ce / Al molar ratios of 5 and 15 decreased to 571 and 459 mmol / g, respectively. Pt The catalytic dehydrogenation activity of Pt / CeO2-Al2O3 catalysts with different Ce / Al molar ratios exhibited a volcano-shaped distribution. Experimental results show that a suitable Ce / Al molar ratio can effectively improve the catalyst activity, thereby increasing the dehydrogenation rate.

[0046] Application Comparative Example 6: The Pt / CeO2-Al2O3@2.5SiO2 catalyst obtained in Comparative Example 6 was applied to the dehydrogenation reaction of methylcyclohexane, and the application process was the same as in Comparative Example 1.

[0047] Application Example 1: The Pt / CeO2-Al2O3@0.5SiO2 catalyst obtained in Example 1 was applied to the dehydrogenation reaction of methylcyclohexane, and the application process was the same as in Comparative Example 1.

[0048] Application Example 2: The Pt / CeO2-Al2O3@1.5SiO2 catalyst obtained in Example 2 was applied to the dehydrogenation reaction of methylcyclohexane, and the application process was the same as in Comparative Example 1.

[0049] The results of the dehydrogenation of methylcyclohexane catalyzed by catalysts with different SiO2 coating amounts are as follows: Figure 5 As shown, when the SiO2 coating amount is low (0.5 wt.% and 1.5 wt.%), compared with Comparative Example 6, the methylcyclohexane dehydrogenation rate of the Pt / CeO2-Al2O3@0.5SiO2 and Pt / CeO2-Al2O3@1.5SiO2 catalysts remains unchanged. However, when the SiO2 coating amount increases to 2.5 wt.%, the methylcyclohexane dehydrogenation rate of the Pt / CeO2-Al2O3@2.5SiO2 catalyst decreases significantly to 398 mmol / g. Pt This is because a thicker SiO2 layer reduces the adsorption of methylcyclohexane and increases the activation energy barrier of the reaction.

[0050] Application Example 3: The catalyst from Example 2 was applied to the dehydrogenation reaction of cyclic regeneration of methylcyclohexane.

[0051] To evaluate the regeneration stability of the catalyst, the spent catalyst was regenerated under an O2 atmosphere. After the initial methylcyclohexane dehydrogenation test, the catalyst was cooled to room temperature in Ar and then regenerated at 550 °C under a 20% O2 / Ar atmosphere (100 mL / min).o Store at C for 30 minutes, with a heating rate of 5. o The regeneration process was carried out at C / min. After regeneration, the catalyst was cooled to room temperature under an Ar atmosphere, and then the same reduction procedure as in Comparative Example 1 was performed. After reduction, a cyclic dehydrogenation reaction was carried out by introducing a reactant gas mixture (methylcyclohexane / Ar). The conditions for methylcyclohexane dehydrogenation were the same as in Comparative Example 1.

[0052] Application Comparative Example 7: The catalyst of Comparative Example 1 was applied to the dehydrogenation reaction of cyclic regeneration of methylcyclohexane, and the application process was the same as in Application Example 3.

[0053] Typical Pt / Al₂O₃ catalysts and SiO₂-coated Pt / CeO₂-Al₂O₃ catalysts, after undergoing a recycling process, are then used for the catalytic dehydrogenation of methylcyclohexane, such as... Figure 6 After three regeneration cycles, the Pt / Al2O3 catalyst showed a significant decrease in its activity for the dehydrogenation of methylcyclohexane, with a dehydrogenation rate only 52% of that of the fresh catalyst (Comparative Example 1). However, after 10 cycles, the Pt / CeO2-Al2O3@1.5SiO2 catalyst exhibited almost the same activity as the fresh catalyst (Example 2) for the dehydrogenation of methylcyclohexane. These results demonstrate that, compared to the Pt / Al2O3 catalyst, the Pt / CeO2-Al2O3@1.5SiO2 catalyst possesses superior regeneration stability, maintaining high catalytic dehydrogenation performance even after multiple regeneration cycles.

[0054] Comparative Example 7: Comparative Example 1 was regenerated three times to obtain a 3-cycle Pt / Al2O3 catalyst.

[0055] Example 3: After 10 cycles of regeneration, a 10-ycle Pt / CeO2-Al2O3@1.5SiO2 catalyst was obtained.

[0056] TEM images (particle size distribution maps of embedded Pt metal particles) of the catalysts prepared in Comparative Example 7 and Example 3, respectively, are shown below. Figure 7 As shown, significant metal sintering occurred in the 3-cycle Pt / Al2O3 catalyst, compared to... Figure 3The average Pt particle size increased to 2.29 nm. However, in the 10-cycle Pt / CeO2-Al2O3@1.5SiO2 catalyst, the metal was uniformly dispersed without sintering, and the average Pt particle size remained at around 1.21 nm, similar to that of Pt / CeO2-Al2O3@1.5SiO2. ICP analysis of Comparative Example 7 and Example 3 is shown in Table 3. Comparing Table 2, it can be found that the Pt content in the 3-cycle Pt / Al2O3 catalyst decreased significantly by 0.12 wt.% compared to the fresh Pt / Al2O3 catalyst, while the Pt content in the 10-cycle Pt / CeO2-Al2O3@1.5SiO2 catalyst remained almost unchanged compared to the fresh Pt / CeO2-Al2O3@1.5SiO2 catalyst. This indicates that the strong metal-support interaction between CeO2-Al2O3 and Pt, combined with the physical confinement effect of the SiO2 coating layer, can effectively suppress the sintering and leaching of Pt during the cyclic reaction process, thereby improving the stability of the catalyst; while the sintering and leaching of Pt both lead to a significant decrease in dehydrogenation activity.

[0057] Table 3. ICP analysis of the catalysts prepared in Comparative Example 7 and Example 3, respectively.

[0058] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a renewable, highly active Pt / CeO2-Al2O3@SiO2 catalyst, characterized in that, Includes the following steps: (1) Aluminum salt, cerium salt and urea are added to water and mixed to obtain mixed solution A. The mixed solution A is placed in a high pressure vessel for hydrothermal reaction. After cooling to room temperature, the precipitate is washed, dried and calcined to obtain CeO2-Al2O3 composite carrier. (2) The CeO2-Al2O3 composite support obtained in step (1) is added to an impregnation solution containing platinum precursor, ultrasonically mixed, then vacuum impregnated and dried, and then calcined to obtain Pt / CeO2-Al2O3 catalyst. (3) The Pt / CeO2-Al2O3 catalyst obtained in step (2) is mixed with ethanol and 25% to 28% ammonia water under continuous stirring to obtain mixed solution B; tetraethyl orthosilicate is mixed with ethanol to obtain mixed solution C, and mixed solution C is added to mixed solution B by injection pump. After thorough stirring, the precipitate is washed, dried and calcined to obtain Pt / CeO2-Al2O3@SiO2 catalyst.

2. The method for preparing a renewable, highly active Pt / CeO2-Al2O3@SiO2 catalyst according to claim 1, characterized in that, In step (1), the temperature of the hydrothermal reaction is 100°C. o C, the hydrothermal reaction time is 48 hours; the drying temperature is 100°C. o C, the drying time is 12h; the calcination temperature is 500℃, and the calcination time is 4h.

3. The method for preparing a renewable, highly active Pt / CeO2-Al2O3@SiO2 catalyst according to claim 1, characterized in that, In step (2), the mass ratio of the CeO2-Al2O3 composite support to the volume ratio of the impregnation solution containing the platinum precursor is 1 g: 4 mL; the drying temperature is 100 °C. o C, drying time is 12h; the calcination temperature is 400℃, calcination time is 4h; vacuum impregnation is 12h.

4. The method for preparing a regenerable, highly active Pt / CeO2-Al2O3@SiO2 catalyst according to claim 1, characterized in that, In step (1), the aluminum salt is aluminum nitrate and the cerium salt is cerium nitrate; the concentrations of the aluminum salt, cerium salt, and urea in the mixed solution A are 644 mg / mL, 75 mg / mL, and 928 mg / mL, respectively; in step (2), the platinum precursor is chloroplatinic acid hexahydrate and the concentration of the impregnation solution containing the platinum precursor is 10 mg / mL.

5. The method for preparing a regenerable, highly active Pt / CeO2-Al2O3@SiO2 catalyst according to claim 1, characterized in that, In step (3), the ratio of Pt / CeO2-Al2O3 catalyst, ethanol, and ammonia in mixed solution B is 3g:400mL:20mL; the mass ratio of tetraethyl orthosilicate to Pt / CeO2-Al2O3 catalyst is 1:(12-30); the concentration of tetraethyl orthosilicate in mixed solution C is 0.5-1.25g / L, and the injection pump rate is 40μL / min.

6. The method for preparing a regenerable, highly active Pt / CeO2-Al2O3@SiO2 catalyst according to claim 1, characterized in that, In step (3), the drying temperature is 100°C. o C, the drying time is 12h; the calcination temperature is 350℃, the calcination time is 2h, and the heating rate is 2. o C / min.

7. A renewable, highly active Pt / CeO2-Al2O3@SiO2 catalyst, characterized in that, The catalyst is prepared by any one of claims 1 to 6, and has a layered composite structure with Pt / CeO2-Al2O3 as the core and SiO2 as the shell.

8. The regenerable, highly active Pt / CeO2-Al2O3@SiO2 catalyst according to claim 7, characterized in that, The catalyst has a Pt loading of 1.5 wt.%, a Ce / Al molar ratio of 1 / 10, and an Si addition of 0.5-1.5 wt.%.

9. The application of the renewable, highly active Pt / CeO2-Al2O3@SiO2 catalyst according to claim 7 or 8 in the catalytic dehydrogenation of methylcyclohexane.

10. The application according to claim 9, characterized in that, The specific application process is as follows: The Pt / CeO2-Al2O3@SiO2 catalyst was compressed into tablets and then crushed into 40-60 mesh particles. The crushed Pt / CeO2-Al2O3@SiO2 catalyst was diluted with quartz sand and placed in the isothermal section of the reactor tube. Before the reaction, the Pt / CeO2-Al2O3@SiO2 catalyst was kept at 400°C. o C was reduced in H2 and Ar for 2 hours; After reduction pretreatment, the catalyst was cooled to 300℃ in an Ar atmosphere; then, methylcyclohexane was introduced under Ar carrier gas and reacted for 10 h; the resulting product was analyzed online by gas chromatography; the mass ratio between Pt / CeO2-Al2O3@SiO2 catalyst and quartz sand was 1:10.

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