Synergistic platinum-based propane dehydrogenation tandem catalytic system, method for preparing and use thereof

Abstract

The application belongs to a supported catalyst, and discloses a synergistic platinum-based propane dehydrogenation cascade catalytic system as well as a preparation method and application thereof, which comprises a first catalytic unit and a second catalytic unit through physical mixing, the first catalytic unit comprises a SiO2 carrier and a Pt-based dehydrogenation active component supported on the surface of the carrier, and the Pt-based dehydrogenation active component is Pt or PtSn; the second catalytic unit comprises an Al2O3 carrier and a functional oxide component supported on the surface of the carrier; and the first catalytic unit and the second catalytic unit are physically mixed through any one of particle mixing and powder mixing. According to the application, the spatial distribution mode of different catalytic units in a reaction system is reasonably designed, the behavior of intermediates and carbon species in a reaction process is effectively controlled while ensuring that the propane dehydrogenation reaction is efficiently carried out, so that the catalyst deactivation is inhibited, and the activity and long-term stability of the propane dehydrogenation reaction are improved.

Description

Technical Field

[0001] This invention pertains to supported catalysts, specifically a platinum-based propane dehydrogenation tandem catalytic system, its preparation method, and its applications. Background Technology

[0002] Propylene is an important basic chemical raw material, widely used in the production of bulk chemicals such as polypropylene, acrylonitrile, and propylene oxide. With the continuous development of the chemical industry, traditional propylene production methods, mainly relying on oil refining byproducts, can no longer meet the ever-growing market demand. Therefore, dedicated propylene production technologies using propane as a raw material have gradually become a key focus of research and industrial application. Among various dedicated propylene production routes, propane dehydrogenation to propylene has attracted widespread attention due to its relatively simple reaction path, wide availability of raw materials, and significant economic differences between propane and propylene. Currently, industrial propane dehydrogenation processes mainly employ Pt-based or chromium-based catalyst systems. Pt-based catalysts are widely used due to their high propylene selectivity. To improve the dehydrogenation performance and stability of Pt-based catalysts, existing technologies typically modify them by introducing additives such as tin, for example, by constructing PtSn alloys or co-supported structures. However, during high-temperature reactions and regeneration processes, these catalysts may still experience metal sintering, structural evolution, and coke accumulation, leading to catalytic activity degradation and insufficient stability.

[0003] On the other hand, besides the dehydrogenation active center, the carbon species generated during the reaction and the reaction microenvironment also have a significant impact on the performance of propane dehydrogenation. A single catalytic structure often struggles to simultaneously meet multiple requirements such as high dehydrogenation activity and coke deposition inhibition. In recent years, tandem catalyst configurations, which spatially separate and synergistically construct catalytic units with different functions, have gradually attracted attention. These systems, by spatially separating the dehydrogenation catalyst and the functional control unit, hold promise for achieving multi-level regulation of the reaction pathway, intermediate behavior, and deactivation process.

[0004] However, existing research on the application of tandem catalysts in propane dehydrogenation remains relatively limited, particularly regarding the systematic design of catalytic systems to rationally construct the synergistic relationship between Pt-based dehydrogenation catalysts and functional oxide regulating units. Therefore, it is necessary to develop a Pt-based propane dehydrogenation synergistic catalyst system based on a tandem catalyst configuration to improve reaction stability and extend catalyst lifetime while maintaining high dehydrogenation activity. Summary of the Invention

[0005] To address the technical problems of existing propane dehydrogenation catalysts being prone to sintering and coking deactivation under high-temperature reaction conditions, and the difficulty in balancing high reactivity and long-term stability, the present invention aims to provide a synergistic platinum-based propane dehydrogenation tandem catalytic system, its preparation method, and its application. By rationally designing the spatial organization of different catalytic units in the reaction system, the behavior of intermediates and carbon species during the reaction process is effectively controlled while ensuring the efficient conduction of the propane dehydrogenation reaction, thereby inhibiting catalyst deactivation and improving the activity and long-term stability of the propane dehydrogenation reaction.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] According to one aspect of the present invention, a synergistic platinum-based propane dehydrogenation tandem catalytic system is provided, comprising a first catalytic unit and a second catalytic unit, wherein the first catalytic unit and the second catalytic unit are physically mixed to form a tandem catalytic system; the first catalytic unit comprises a SiO2 support and a Pt-based dehydrogenation active component supported on the surface of the SiO2 support, wherein the Pt-based dehydrogenation active component is Pt or PtSn; the second catalytic unit comprises an Al2O3 support and a functional oxide component supported on the surface of the Al2O3 support.

[0008] In a tandem catalytic system, the second catalytic unit can participate in the further dehydrogenation conversion of intermediates during the propane dehydrogenation reaction, and synergistically promote the conversion of propane to propylene with the first catalytic unit, thereby improving the overall activity of the propane dehydrogenation reaction. At the same time, the functional oxides in the second catalytic unit are beneficial to regulating the migration behavior of carbon species generated during the dehydrogenation reaction, promoting the transfer of carbon species from metal sites to the support, thereby inhibiting the accumulation of coke at the metal active sites and improving the stability of the catalyst.

[0009] Preferably, the mass ratio of the first catalytic unit to the second catalytic unit is 0.25-10:1.

[0010] Preferably, the mass percentage of Pt is 0.1%-1.0% based on the SiO2 support.

[0011] Preferably, the functional oxide is at least one of SnO2, ZrO2, TiO2, and CeO2.

[0012] Preferably, based on the Al2O3 support, the mass percentage of metal elements in the functional oxide is 0.05%-1.0%.

[0013] Preferably, the first catalytic unit is prepared by impregnating a Pt precursor solution or a Pt-Sn precursor solution onto a SiO2 support and then drying it; the second catalytic unit is prepared by impregnating a metal precursor solution onto an Al2O3 support and then drying and calcining it; the first catalytic unit and the second catalytic unit are physically mixed at a certain mass ratio to obtain a synergistic platinum-based propane dehydrogenation tandem catalytic system.

[0014] Preferably, the first catalytic unit and the second catalytic unit are physically mixed by particle mixing or powder mixing.

[0015] According to another aspect of the present invention, a method for preparing the above-described synergistic platinum-based propane dehydrogenation tandem catalytic system is provided, comprising:

[0016] (1) Prepare Pt precursor solution or Pt-Sn precursor solution, immerse SiO2 support in Pt precursor solution or Pt-Sn precursor solution, sonicate, and dry completely in an oven at 80-100 °C to obtain the first catalytic unit Pt / SiO2.

[0017] (2) Prepare metal precursor solution, immerse Al2O3 support in metal precursor solution, sonicate, dry completely in oven at 80-100 °C to obtain catalyst precursor, calcine at 500-650 °C for 1-4 h to obtain second catalyst unit Sn / Al2O3.

[0018] (3) The first catalytic unit Pt / SiO2 and the second catalytic unit Sn / Al2O3 are mixed in powder form at a mass ratio of (0.25-10):1 and ground to obtain a synergistic platinum-based propane dehydrogenation tandem catalytic system.

[0019] According to another aspect of the present invention, a method for producing propylene from propane by dehydrogenation is provided, wherein the reaction is carried out using the above-described synergistic platinum-based propane dehydrogenation tandem catalytic system.

[0020] Furthermore, including:

[0021] (1) The synergistic platinum-based propane dehydrogenation tandem catalyst system is compressed and crushed to prepare 40-60 mesh granular catalyst;

[0022] (2) The granular catalyst is loaded into a fixed-bed reactor and reduced at 500-700 °C for 0.5-2 h under a hydrogen atmosphere;

[0023] (3) A dehydrogenation reaction is carried out by introducing a propane-containing reaction gas at 500-650℃, wherein the molar ratio of hydrogen to propane is 0-2:1, and the space velocity of propane is 9.4-94 h⁻¹. -1 Nitrogen is used as the balance gas and the total gas volume remains constant.

[0024] The beneficial effects of this invention are:

[0025] This invention constructs a composite synergistic catalytic system composed of Pt-based dehydrogenation catalytic units and functional oxide catalytic units, enabling the two types of catalytic units to form a stable functional division and synergistic effect during the reaction process. Compared with traditional co-supported or alloyed catalysts, this invention avoids the problem of excessive structural coupling or uncontrollable structural evolution of different active components under high-temperature conditions, which is beneficial to maintaining the structural stability and regenerability of Pt dehydrogenation active sites.

[0026] Furthermore, by combining the first catalytic unit and the second catalytic unit within a specific ratio range, the present invention enables the dehydrogenation activity function and the intermediate regulation function to form a dynamic synergy, thereby achieving effective regulation of the generation and transformation behavior of key reaction intermediates and carbon species during the reaction process, thereby improving the overall conversion efficiency and propylene selectivity of the propane dehydrogenation reaction without significantly increasing the complexity of the system structure.

[0027] Furthermore, the synergistic tandem catalytic system of the present invention, through the rational design of component ratios, enables the functional oxide units to regulate the formation of carbon precursors and coke species during the reaction process, thereby reducing the accumulation rate of coke at metal active sites, slowing down the catalyst deactivation process, and significantly improving the stability of the catalyst under high-temperature continuous reaction and regeneration cycle conditions.

[0028] Compared with single Pt-based catalysts or single functional oxide systems, the synergistic tandem catalytic system constructed in this invention exhibits a significant synergistic enhancement effect in terms of activity retention, selectivity control, and anti-coking ability. Its overall performance is superior to the effect of simply adding up the individual components, demonstrating a synergistic advantage of "1+1 is greater than 2". Attached Figure Description

[0029] Figure 1 The results of the activity tests (propane conversion and propylene selectivity) of the synergistic tandem catalytic system with SnO2 as the functional oxide in Example 1 and the control sample are shown.

[0030] Figure 2 The graph shows the relationship between the propylene generation rate of the synergistic tandem catalytic system in Example 1 and the mass ratio of the first catalytic unit to the second catalytic unit. Detailed Implementation

[0031] The present invention will be further described in detail below through specific embodiments. These embodiments will enable those skilled in the art to have a more comprehensive understanding of the present invention, but will not limit the present invention in any way.

[0032] The present invention will be further described in detail below through specific embodiments, in which SnO2 is used as the functional oxide (MO).x The preferred representatives of SnO2 and MO will be described, but the present invention is not limited to SnO2 and MO. x It can be SnO2, ZrO2, TiO2, CeO2, etc. The following examples are intended to enable those skilled in the art to better understand the present invention, but do not limit the invention in any way.

[0033] Example 1:

[0034] (1) Preparation of the first catalytic unit Pt / SiO2: 0.00797 parts by mass of H2PtCl6·(H2O)6 were dissolved in deionized water to obtain a precursor solution. 1.000 g of SiO2 support was immersed in the precursor solution, sonicated for 0.5 h until no dry powder was visible, and completely dried in an ordinary oven at 80°C to obtain the first catalytic unit Pt / SiO2.

[0035] (2) Preparation of the second catalytic unit Sn / Al2O3: 0.0054 parts by mass of SnCl4·(H2O)5 were dissolved in deionized water to obtain a precursor solution. 1.000 g of Al2O3 support was impregnated in the precursor solution and sonicated for 0.5 h until no dry powder was visible. The precursor was completely dried in an ordinary oven at 80°C to obtain a catalyst precursor. The precursor was calcined at 600°C for 2 h to obtain the second catalytic unit Sn / Al2O3.

[0036] (3) The prepared Pt / SiO2 and Sn / Al2O3 powders were mixed at a mass ratio of 1:1 and ground for 0.25 h to obtain a tandem catalytic system with two catalytic units. The mass percentage of Pt in the tandem catalytic system was 0.3% based on the mass of the SiO2 support and the mass percentage of Sn was 0.18% based on the mass of the Al2O3 support.

[0037] (4) Compress the prepared catalyst into 40-60 mesh granular catalyst;

[0038] (5) The tableted granular catalyst was loaded into a fixed-bed reactor, and hydrogen was introduced for reduction pretreatment. The temperature was raised to 600 °C and maintained for 1 h. The reaction temperature was 600 °C, and the reaction was carried out at a propane mass hourly space velocity of 94 h⁻¹. -1 Switch to the reaction gas, in which the molar ratio of hydrogen to propane is 1:1, the concentration of propane in the reaction gas is 16%, and the equilibrium gas is nitrogen.

[0039] The reaction products were analyzed online using gas chromatography. The relationship between propane conversion and propylene selectivity and time is as follows: Figure 1 As shown. By Figure 1 It can be seen that the initial propane conversion rate was 28%, which decreased to 21% after 1 h, and the deactivation rate was 0.380 h. -1Meanwhile, propylene selectivity has remained at a high level (>92%).

[0040] Figure 2 This is a graph showing the propylene formation rate as a function of the mixing mass ratio in the Pt / SiO2 and Sn / Al2O3 powder mixed tandem catalytic system prepared in Example 1. Figure 2 It can be seen that the propylene formation rate increases with the increase of the Sn / Al2O3 ratio, and tends to stabilize in the range of higher Sn / Al2O3 ratios.

[0041] Example 2:

[0042] The preparation and reaction were carried out using the method of Example 1, with the only difference being the preparation of the first catalytic unit PtSn / SiO2 in step (1): 0.00797 parts by mass of H2PtCl6·(H2O)6 and 0.00107 parts by mass of SnCl4·(H2O)5 were dissolved in deionized water to obtain a precursor solution. 1.000 g of SiO2 support was immersed in the precursor solution, sonicated for 0.5 h until no dry powder was visible, and completely dried in an ordinary oven at 80°C to obtain the first catalytic unit PtSn / SiO2.

[0043] Example 3:

[0044] The preparation and reaction were carried out using the method of Example 1, the only difference being that the mass of H2PtCl6 in step (1) was 0.0265g, and the mass percentage of Pt in the resulting tandem catalytic system was 1% based on the mass of the SiO2 support.

[0045] Example 4:

[0046] The preparation and reaction were carried out using the method of Example 1, the only difference being that the mass of H2PtCl6 in step (1) was 0.0027 g, and the mass percentage of Pt in the resulting tandem catalytic system was 0.1% based on the mass of the SiO2 support.

[0047] Example 5:

[0048] The preparation and reaction were carried out using the method of Example 1, the only difference being that the mass of SnCl4·(H2O)5 in step (2) was 0.00107 g, and the resulting tandem catalytic system had a Sn percentage content of 0.05% based on the mass of the Al2O3 support.

[0049] Example 6:

[0050] The preparation and reaction were carried out using the method of Example 1, the only difference being that the mass of SnCl4·(H2O)5 in step (2) was 0.0027 g, and the resulting tandem catalytic system had a Sn percentage of 0.36% based on the mass of the Al2O3 support.

[0051] Example 7:

[0052] The preparation and reaction were carried out using the method of Example 1, the only difference being that the mass of SnCl4·(H2O)5 in step (2) was 0.0027 g, and the resulting tandem catalytic system had a Sn percentage of 1% based on the mass of the Al2O3 support.

[0053] Example 8:

[0054] The preparation and reaction were carried out using the method of Example 1, the only difference being that the calcination temperature in step (2) was 550 °C.

[0055] Example 9:

[0056] The preparation and reaction were carried out using the method of Example 1, the only difference being that the calcination temperature in step (2) was 650 °C.

[0057] Example 10:

[0058] The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (3), Pt / SiO2 and Sn / Al2O3 were physically mixed at a mass ratio of 10:1.

[0059] Example 11:

[0060] The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (3), Pt / SiO2 and Sn / Al2O3 were physically mixed at a mass ratio of 2:1.

[0061] Example 12:

[0062] The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (3), Pt / SiO2 and Sn / Al2O3 were physically mixed at a mass ratio of 1:2.

[0063] Example 13:

[0064] The preparation and reaction were carried out using the method of Example 1, the only difference being that in steps (3) and (4), the powder was not mixed, and Pt / SiO2 and Sn / Al2O3 were first pressed into 40-60 mesh granular catalysts, and then mixed in granular form.

[0065] Example 14:

[0066] The preparation and reaction were carried out using the method of Example 1, the only difference being that in steps (3) and (5), the powder was not mixed. Pt / SiO2 and Sn / Al2O3 were first pressed into 40-60 mesh granular catalysts, and then Pt / SiO2 was placed in the upper layer of the bed and Sn / Al2O3 was placed in the lower layer.

[0067] Example 15:

[0068] The preparation and reaction were carried out using the method of Example 1, the only difference being that in steps (3) and (5), the powder was not mixed. Pt / SiO2 and Sn / Al2O3 were first pressed into 40-60 mesh granular catalysts, and then Pt / SiO2 was placed in the lower layer of the bed and Sn / Al2O3 was placed in the upper layer.

[0069] Example 16:

[0070] The preparation and reaction were carried out using the method of Example 1, the only difference being that the propane mass hourly space velocity in step (5) was 47 h⁻¹. -1 .

[0071] Example 17:

[0072] The preparation and reaction were carried out using the method of Example 1, the only difference being that the molar ratio of hydrogen to propane in step (5) was 2:1.

[0073] Example 18:

[0074] The preparation and reaction were carried out using the method of Example 1, the only difference being that the reduction pretreatment time in step (5) was 0.5 h.

[0075] Example 19:

[0076] The preparation and reaction were carried out using the method of Example 1, the only difference being that the reduction pretreatment time in step (5) was 2 hours.

[0077] Example 20:

[0078] The preparation and reaction were carried out using the method of Example 1, the only difference being that the functional metal oxide in step (2) was TiO2.

[0079] Example 21:

[0080] The preparation and reaction were carried out using the method of Example 1, the only difference being that the functional metal oxide in step (2) was ZrO2.

[0081] Example 22:

[0082] The preparation and reaction were carried out using the method of Example 1, the only difference being that the functional metal oxide in step (2) was CeO2.

[0083] For the results of the above embodiments, the activity data at the initial reaction and 1 h were compared. The test conditions and methods were the same as in Example 1 to examine the influence of different parameters on the catalyst reaction performance.

[0084] (a) The effect of the addition of the second catalytic unit on the activity and stability of the propane dehydrogenation reaction in the tandem catalytic system is shown in Table 1. The reaction conditions are the same as in Examples 1 and 2. In the table, Pt / SiO2 and Sn / Al2O3 are given separately as comparative examples.

[0085] Table 1. Effect of the second catalytic unit on the activity and stability of propane dehydrogenation reaction.

[0086] Example catalyst Initial reaction and propane conversion rate (%) after 1 h propylene selectivity at initial reaction and after 1 h (%) <![CDATA[Deactivation rate (h -1 ).]]> Comparison Sample 1 <![CDATA[Pt / SiO2]]> 13 / 9 79 / 81 0.413 Comparison Sample 2 <![CDATA[Sn / Al2O3]]> 3 / 2 60 / 63 0.415 1 <![CDATA[Pt / SiO2+Sn / Al2O3]]> 28 / 21 92 / 93 0.380 Comparison Sample 3 <![CDATA[PtSn / SiO2]]> 24 / 22 98 / 99 0.111 2 <![CDATA[PtSn / SiO2+Sn / Al2O3]]> 37 / 34 99 / 99 0.130

[0087] As shown in Table 1, when the second catalytic unit Sn / Al2O3 is used alone as a catalyst, its initial propane conversion is only 3%, its propylene selectivity is 60%, and its deactivation rate is relatively high. This indicates that Sn / Al2O3 alone has a limited promoting effect on the propane dehydrogenation reaction, making it difficult to obtain high reactivity and selectivity. In contrast, when Sn / Al2O3 and Pt / SiO2 are physically mixed to construct a synergistic tandem catalytic system, the initial propane conversion of the tandem catalytic system significantly increases from 13% to 28%, the propylene selectivity increases from 79% to 92%, and the deactivation rate decreases from 0.413 h⁻¹. -1 Reduced to 0.380 h -1 This indicates that the introduction of the second catalytic unit significantly improves the activity of propane dehydrogenation while also enhancing the stability of the catalytic system. Further comparison of the PtSn / SiO2 and PtSn / SiO2+Sn / Al2O3 systems reveals that, building upon the already high propylene selectivity and low deactivation rate of the original PtSn / SiO2 system, the introduction of Sn / Al2O3 further increases the initial propane conversion to 37%, while maintaining a stable propylene selectivity of 99%. This demonstrates that the second catalytic unit can exert a stable synergistic promoting effect in systems with different first catalytic units.

[0088] The results above show that Sn / Al2O3 does not play a major role as an independent dehydrogenation catalytic unit. Instead, it coexists with the Pt-based first catalytic unit and, by constructing a physically mixed Pt-based propane dehydrogenation tandem catalytic system, can significantly improve the activity and selectivity of the propane dehydrogenation reaction and positively affect the stability of the tandem catalytic system, demonstrating a clear synergistic effect.

[0089] (ii) The effect of the mass percentage of Pt (based on the mass of SiO2 support) on the activity and stability of the propane dehydrogenation reaction in the tandem catalytic system is shown in Table 2. The reaction conditions are the same as in Examples 1, 3, and 4.

[0090] Table 2. Effects of different Pt mass percentages on the activity and stability of propane dehydrogenation reaction.

[0091] Example Pt mass percentage (%) Initial reaction and propane conversion rate (%) after 1 h propylene selectivity at initial reaction and after 1 h (%) <![CDATA[Deactivation rate (h -1 ).]]> 3 0.1 18 / 13 93 / 93 0.384 1 0.3 28 / 21 92 / 93 0.380 4 1 33 / 23 92 / 94 0.500

[0092] Table 2 shows that, under the same reaction conditions, the propane conversion rate of the tandem catalytic system increases with the increase of the Pt mass percentage in the first catalytic unit, while the propylene selectivity remains at a relatively high level with little change. Meanwhile, the deactivation rate of the tandem catalytic system increases when the Pt content is too high. These results indicate that, within the investigated range, the tandem catalytic system exhibits better performance than a single Pt-based catalyst, and a moderate Pt mass percentage (0.3%) is more beneficial in improving the propane dehydrogenation reaction activity while maintaining the stability of the tandem catalytic system.

[0093] (III) The effect of Sn mass percentage (based on Al2O3 support mass) on the activity and stability of propane dehydrogenation reaction in the tandem catalytic system is shown in Table 3. The reaction conditions are the same as in Examples 1, 5, and 6.

[0094] Table 3. Effects of different Sn contents on the activity and stability of propane dehydrogenation reaction

[0095] Example Sn mass percentage (Sn %) Initial reaction and propane conversion rate (%) after 1 h propylene selectivity at initial reaction and after 1 h (%) <![CDATA[Deactivation rate (h -1 ).]]> 5 0.05 19 / 14 90 / 91 0.365 1 0.18 28 / 21 92 / 93 0.380 6 0.36 29 / 22 93 / 94 0.370 7 1 29 / 23 94 / 95 0.324

[0096] Table 3 shows that, under the same reaction conditions, the mass percentage of Sn in the second catalytic unit affects the propane dehydrogenation performance of the tandem catalytic system. As the Sn content increases from 0.05% to 0.18% and 0.36%, the initial propane conversion of the tandem catalytic system increases from 20% to 28% and 29%, respectively, and the propylene selectivity increases from 90% to 92%-94%. Meanwhile, the deactivation rate of the tandem catalytic system remains at a similar level under different Sn contents. These results indicate that, within the investigated range, appropriately increasing the Sn content in the second catalytic unit is beneficial for improving the propane dehydrogenation activity and propylene selectivity, while maintaining the stability of the tandem catalytic system.

[0097] (iv) The effect of Sn / Al2O3 calcination temperature on the activity and stability of propane dehydrogenation reaction in the tandem catalytic system is shown in Table 4. The reaction conditions are the same as in Examples 1, 8, and 9.

[0098] Table 4. Effect of calcination temperature on the activity and stability of propane dehydrogenation reaction

[0099] Example Firing temperature (°C) Initial reaction and propane conversion rate (%) after 1 h propylene selectivity at initial reaction and after 1 h (%) <![CDATA[Deactivation rate (h -1 ).]]> 8 550 27 / 20 92 / 92 0.391 1 600 28 / 21 92 / 93 0.380 9 650 29 / 22 92 / 93 0.370

[0100] Table 4 shows that, under the same reaction conditions, the calcination temperature of the second catalytic unit, Sn / Al₂O₃, within the range of 550-650℃ has little effect on the propane dehydrogenation performance of the tandem catalytic system. Under different calcination temperatures, the propane conversion and propylene selectivity of the tandem catalytic system show relatively small variations, with the propylene selectivity remaining at a high level of 92%-93%. Simultaneously, the deactivation rates of the tandem catalytic system do not differ significantly. These results indicate that within the investigated calcination temperature range, the calcination temperature of Sn / Al₂O₃ does not significantly affect the reactivity and stability of the tandem catalytic system, and the tandem catalytic system exhibits good adaptability to calcination temperatures of 500-650℃.

[0101] (v) The effect of mixing mass ratio on the activity and stability of propane dehydrogenation reaction in the tandem catalytic system is shown in Table 5. The reaction conditions are the same as in Examples 1, 10, 11, and 12.

[0102] Table 5. Effect of mixing mass ratio on the activity and stability of propane dehydrogenation reaction

[0103] Example <![CDATA[Mixing mass ratio (Pt / SiO2:Sn / Al2O3)]]> Initial reaction and propane conversion rate (%) after 1 h propylene selectivity at initial reaction and after 1 h (%) <![CDATA[Deactivation rate (h -1 ).]]> 10 4 21 / 15 89 / 90 0.425 11 2 26 / 20 92 / 93 0.404 1 1 28 / 21 92 / 93 0.380 12 0.5 29 / 22 92 / 93 0.370

[0104] As shown in Table 5, within the investigated mixing mass ratio range, when the mass ratio of Pt / SiO2 to Sn / Al2O3 was adjusted from 4 to 2, the propane dehydrogenation reaction performance of the tandem catalytic system showed a certain degree of improvement. However, when the mixing mass ratio was further adjusted from 2 to 0.5, the changes in propane conversion, propylene selectivity, and deactivation rate of the tandem catalytic system were relatively small, and the overall reaction performance remained basically stable. These results indicate that in the tandem catalytic system of this invention, stable catalytic performance can be obtained within a wide range of mixing mass ratios, and the tandem catalytic system has good adaptability to mixing ratios.

[0105] (vi) The effect of loading on the activity and stability of propane dehydrogenation reaction in the tandem catalytic system is shown in Table 6. The reaction conditions are the same as in Examples 1, 13, 14, and 15.

[0106] Table 6. Effect of packing method on the activity and stability of propane dehydrogenation reaction

[0107] Example Filling method Initial reaction and propane conversion rate (%) after 1 h propylene selectivity at initial reaction and after 1 h (%) <![CDATA[Deactivation rate (h -1 ).]]> 1 Powder Mixing 28 / 21 92 / 93 0.380 13 Particle Mixing 27 / 20 89 / 90 0.391 14 <![CDATA[Pt / SiO2 is located in the upper layer of the bed]]> 20 / 14 86 / 87 0.404 15 <![CDATA[Pt / SiO2 is located in the lower layer of the bed]]> 19 / 13 85 / 86 0.425

[0108] As shown in Table 6, under the same reaction conditions, both the layered packing and physical mixing tandem catalytic systems can achieve a certain synergistic effect of "1+1>2". However, there are significant differences in the synergistic effect between the two. Among them, the physical mixing methods of powder mixing and particle mixing show higher overall propane conversion and propylene selectivity, and relatively lower deactivation rate, exhibiting better comprehensive reaction performance.

[0109] (vii) The effect of reduction time on the activity and stability of propane dehydrogenation reaction in the tandem catalytic system is shown in Table 7. The reaction conditions are the same as in Examples 1, 18, and 19.

[0110] Table 7. Effect of reduction time on the activity and stability of propane dehydrogenation reaction

[0111] Example Restoration time (h) Initial reaction and propane conversion rate (%) after 1 h propylene selectivity at initial reaction and after 1 h (%) <![CDATA[Deactivation rate (h -1 ).]]> 18 0.5 24 / 19 96 / 97 0.297 1 1 28 / 21 92 / 93 0.380 19 2 28 / 21 92 / 93 0.362

[0112] As can be seen from Table 7, under the same reaction conditions, when the reduction time is extended from 0.5 h to 1 h, the propane conversion rate of the tandem catalytic system is improved; while when the reduction time is further extended to 2 h, the propane conversion rate and propylene selectivity do not change much, and the overall reaction performance remains basically stable.

[0113] (viii) The effect of the molar ratio of hydrogen to propane on the propane dehydrogenation activity and stability of the tandem catalytic system is shown in Table 8. The reaction conditions are the same as in Examples 1 and 16.

[0114] Table 8. Effect of the molar ratio of hydrogen to propane on the activity and stability of propane dehydrogenation reaction.

[0115] Example <![CDATA[H2:C3H8]]> Initial reaction and propane conversion rate (%) after 1 h propylene selectivity at initial reaction and after 1 h (%) <![CDATA[Deactivation rate (h -1 ).]]> 1 1 28 / 21 92 / 93 0.380 16 2 24 / 17 89 / 90 0.408

[0116] As can be seen from Table 8, with the increase of the hydrogen molar ratio, the initial conversion rate of propane gradually decreases and the deactivation rate increases. The performance of the tandem catalytic system reaches its best when the hydrogen to propane molar ratio is 1:1, at which point the deactivation rate is the slowest and the activity is the highest.

[0117] (ix) The effect of propane mass hourly space velocity on the propane dehydrogenation activity and stability of the tandem catalytic system is shown in Table 9. The reaction conditions are the same as in Examples 1 and 17.

[0118] Table 9. Effect of propane mass hourly space velocity on the activity and stability of propane dehydrogenation reaction

[0119] Example Propane mass hourly space velocity (h⁻¹) Initial reaction and propane conversion rate (%) after 1 h propylene selectivity at initial reaction and after 1 h (%) Inactivation rate (h⁻¹) 1 94 28 / 21 92 / 93 0.380 17 47 34 / 26 93 / 94 0.383

[0120] As can be seen from Table 9, as the propane mass hourly space velocity increases, the initial conversion rate of propane gradually decreases, the propylene selectivity remains basically unchanged, and the deactivation rate remains basically unchanged.

[0121] (x) The effect of the type of functional oxide on the propane dehydrogenation activity and stability of the tandem catalytic system is shown in Table 10. The reaction conditions are the same as in Examples 1, 20, 21, and 22.

[0122] Table 10. Effect of functional oxide type on the activity and stability of propane dehydrogenation reaction

[0123] Example Functional oxides Initial reaction and propane conversion rate (%) after 1 h propylene selectivity at initial reaction and after 1 h (%) <![CDATA[Deactivation rate (h -1 ).]]> 1 <![CDATA[SnO2]]> 28 / 21 92 / 93 0.380 20 <![CDATA[TiO2]]> 18 / 14 90 / 91 0.256 21 <![CDATA[ZrO2]]> 19 / 14 90 / 91 0.313 22 <![CDATA[CeO2]]> 19 / 14 90 / 91 0.324

[0124] Table 10 shows that, under the same reaction conditions, the tandem catalytic systems constructed with different functional oxides as the second catalytic unit exhibit significantly different reaction performance characteristics in the propane dehydrogenation reaction. When SnO2 is used as the functional oxide, the tandem catalytic system shows a high initial propane conversion and stable propylene selectivity, while maintaining a moderate deactivation rate, demonstrating superior overall reaction performance. When the functional oxide is replaced with TiO2, ZrO2, or CeO2, the mixed catalytic system can still effectively carry out the propane dehydrogenation reaction, with propylene selectivity remaining above 90%, indicating that different functional oxides can construct stable tandem catalytic systems with the first catalytic unit. However, compared to the SnO2 system, the propane conversion rate of the TiO2, ZrO2, and CeO2 systems is reduced, reflecting differences in the regulation of intermediate behavior and reaction microenvironment by different functional oxides during the reaction process.

[0125] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many specific modifications under the guidance of the present invention without departing from the spirit and scope of the claims, and these modifications all fall within the scope of protection of the present invention.

Claims

1. A synergistic platinum-based propane dehydrogenation tandem catalytic system, characterized in that, The system includes a first catalytic unit and a second catalytic unit, which are physically mixed to form a tandem catalytic system. The first catalytic unit includes a SiO2 support and a Pt-based dehydrogenation active component supported on the surface of the SiO2 support, wherein the Pt-based dehydrogenation active component is Pt or PtSn. The second catalytic unit includes an Al2O3 support and a functional oxide component supported on the surface of the Al2O3 support.

2. The synergistic platinum-based propane dehydrogenation tandem catalytic system according to claim 1, characterized in that, The mass ratio of the first catalytic unit to the second catalytic unit is 0.25-10:

1.

3. The synergistic platinum-based propane dehydrogenation tandem catalytic system according to claim 1, characterized in that, Based on SiO2 support, the mass percentage of Pt is 0.1%-1.0%.

4. The synergistic platinum-based propane dehydrogenation tandem catalytic system according to claim 1, characterized in that, The functional oxide is at least one of SnO2, ZrO2, TiO2, and CeO2.

5. The synergistic platinum-based propane dehydrogenation tandem catalytic system according to claim 1, characterized in that, Based on Al2O3 support, the mass percentage of metal elements in the functional oxide is 0.05%-1.0%.

6. The synergistic platinum-based propane dehydrogenation tandem catalytic system according to claim 1, characterized in that, The first catalytic unit is prepared by impregnating a Pt precursor solution or a Pt-Sn precursor solution onto a SiO2 support and then drying it; the second catalytic unit is prepared by impregnating a metal precursor solution onto an Al2O3 support and then drying and calcining it; the first catalytic unit and the second catalytic unit are physically mixed at a certain mass ratio to obtain a synergistic platinum-based propane dehydrogenation tandem catalytic system.

7. The synergistic platinum-based propane dehydrogenation tandem catalytic system according to claim 1, characterized in that, The first catalytic unit and the second catalytic unit are physically mixed through particle mixing or powder mixing.

8. A method for preparing a synergistic platinum-based propane dehydrogenation tandem catalytic system as described in any one of claims 1-7, characterized in that, include: (1) Prepare Pt precursor solution or Pt-Sn precursor solution, immerse SiO2 support in Pt precursor solution or Pt-Sn precursor solution, sonicate, and dry completely in an oven at 80-100 °C to obtain the first catalytic unit Pt / SiO2. (2) Prepare metal precursor solution, immerse Al2O3 support in metal precursor solution, sonicate, dry completely in oven at 80-100 °C to obtain catalyst precursor, calcine at 500-650 °C for 1-4 h to obtain second catalyst unit Sn / Al2O3. (3) The first catalytic unit Pt / SiO2 and the second catalytic unit Sn / Al2O3 are mixed in powder form at a mass ratio of (0.25-10):1 and ground to obtain a synergistic platinum-based propane dehydrogenation tandem catalytic system.

9. A method for producing propylene by dehydrogenation of propane, characterized in that, The reaction is carried out using the synergistic platinum-based propane dehydrogenation tandem catalytic system as described in any one of claims 1-7.

10. A method for producing propylene from propane by dehydrogenation according to claim 9, characterized in that, include: (1) The synergistic platinum-based propane dehydrogenation tandem catalyst system is compressed and crushed to prepare 40-60 mesh granular catalyst; (2) The granular catalyst is loaded into a fixed-bed reactor and reduced at 500-700 °C for 0.5-2 h under a hydrogen atmosphere; (3) A dehydrogenation reaction is carried out by introducing a propane-containing reaction gas at 500-650℃, wherein the molar ratio of hydrogen to propane is 0-2:1, and the space velocity of propane is 9.4-94 h⁻¹. -1 Nitrogen is used as the balance gas and the total gas volume remains constant.

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