Supported partially oxidized Pt / zinc-silicon molecular sieve catalysts, their preparation methods and applications

Abstract

This invention belongs to the field of supported catalyst technology, and discloses a supported partially oxidized Pt / zinc-silicon molecular sieve catalyst, its preparation method, and its application. The catalyst uses a zinc-silicon molecular sieve as a support and combines it with an ion exchange process to construct and maintain partially oxidized Pt active sites within the pores of the zinc-silicon molecular sieve. First, a silicon source, zinc source, water, organic template agent, and alkaline solution are stirred evenly and crystallized to obtain a solid product. After washing, drying, and calcination, a zinc-silicon molecular sieve product is obtained. Then, the zinc-silicon molecular sieve is added to a Pt solution in a specific ratio, heated, stirred, and dried to obtain a solid. Finally, the obtained solid is calcined to obtain a partially oxidized Pt / zinc-silicon molecular sieve. The catalyst obtained by this invention can stably maintain partially oxidized Pt active sites under high-temperature dehydrogenation reaction conditions, improving the activation efficiency of individual Pt sites for propane C–H bonds, thereby achieving effective dehydrogenation reactions under low noble metal loading conditions.

Description

Technical Field

[0001] This invention belongs to the field of supported catalyst technology, specifically, it relates to a supported Pt / zinc-silicon molecular sieve catalyst and its preparation method, as well as its application in propane dehydrogenation. Background Technology

[0002] Light olefins are one of the important basic raw materials in the chemical industry, widely used in the production of fuels, polymers, and various high-value-added chemicals. Developing efficient and controllable catalytic strategies to achieve efficient production and high-value conversion of olefins has become an important research direction in the fields of catalysis and chemical engineering. Among existing olefin production routes, alkane dehydrogenation is considered a direct and atom-economical strategy, utilizing low-carbon alkanes such as propane and ethane to produce high-value-added olefins through catalytic dehydrogenation. This reaction uses saturated alkanes as raw materials, selectively breaking C–H bonds to generate the corresponding olefins, without introducing additional carbon sources, exhibiting clear chemical simplicity and process advantages. Taking propane dehydrogenation as an example, propane dehydrogenation is a strongly endothermic reaction, requiring a high-temperature environment of 500-700℃ to overcome thermodynamic equilibrium limitations. However, high-temperature conditions easily trigger side reactions such as cracking, hydrogenolysis, and carbon deposition, leading to reduced selectivity of the target product and rapid catalyst deactivation. This contradiction highlights the importance of developing high-performance catalyst systems: precise control of active sites is needed to achieve directional propane dehydrogenation while effectively suppressing side reaction pathways. Currently, industrial catalyst systems are mainly divided into CrO2-... x The two main categories are CrO-based and Pt-based, although CrO-based x While catalysts are relatively inexpensive, they pose a risk of heavy metal pollution and have poor resistance to carbon buildup, requiring frequent regeneration. In contrast, Pt-based catalysts have become the mainstream choice due to their environmental friendliness and excellent selectivity.

[0003] The development of platinum-based catalysts: As the mainstream technology carrier in propane dehydrogenation, the performance optimization and active state of Pt have always been a focus of industry attention. However, in a large number of reported Pt-based bimetallic catalytic systems, it has been found that while electron-enriched metallic Pt sites are beneficial for suppressing side reactions and improving propylene selectivity and catalyst stability to some extent, they are often accompanied by a decrease in intrinsic activity of the dehydrogenation reaction. Furthermore, this strategy often requires a high Pt loading to maintain sufficient dehydrogenation activity, resulting in low precious metal utilization efficiency, increased catalyst cost, and limited application potential under conditions of low precious metal usage. This indicates that, under current technological conditions, there is still a certain degree of trade-off between activity, selectivity, and stability in Pt-based catalysts, making it difficult to achieve all three simultaneously. In summary, existing Pt-based propane dehydrogenation catalysts generally suffer from problems such as unclear Pt valence state, low utilization of precious metals, and insufficient stability of active sites under high-temperature conditions. A new catalyst system and its preparation method are needed to effectively control the valence state and structure of Pt active sites while reducing the amount of precious metals used, thereby improving the activation efficiency of individual Pt sites on propane CH bonds and ensuring the effective conduction of the dehydrogenation reaction. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of unclear Pt valence state and low precious metal utilization in existing Pt-based dehydrogenation catalysts. It provides a supported partially oxidized Pt / zinc-silicon molecular sieve catalyst, its preparation method, and its application. This catalyst can stably maintain partially oxidized Pt active sites under high-temperature dehydrogenation reaction conditions, improving the activation efficiency of individual Pt sites for propane C–H bonds, thereby achieving effective dehydrogenation reactions under low precious metal loading conditions.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0006] According to one aspect of the present invention, a supported partially oxidized Pt / zinc-silicon molecular sieve catalyst is provided, wherein the catalyst uses a zinc-silicon molecular sieve as a support and combines an ion exchange process to construct and maintain partially oxidized Pt active sites within the pores of the zinc-silicon molecular sieve.

[0007] Preferably, the catalyst contains 0.001%-0.01% Pt by mass and 1%-6% Zn by mass.

[0008] Preferably, the zinc-silicon molecular sieve is either MFI type or BEA type.

[0009] According to another aspect of the present invention, a method for preparing the above-described supported partially oxidized Pt / zinc-silicon molecular sieve catalyst is provided, comprising:

[0010] (1) Mix the silicon source, zinc source, water, organic stencil agent, and alkaline solution, and stir until homogeneous to form a mixture. The mixture contains SiO2:Zn 2+ :OH - The molar ratio of the two components is 1:(0.02-0.4):(0.01-0.04). The mixture is stirred evenly and crystallized at 150-160℃ to obtain a solid product. The solid product is washed with deionized water until neutral and then dried. Subsequently, it is calcined to remove the template agent to obtain the zinc-silicon molecular sieve product.

[0011] (2) Add the zinc-silicon molecular sieve obtained in step (1) to the Pt solution at a ratio of 1 g / 20 mL-1 g / 100 mL, heat to 80-100℃, stir for 8-24 h, and then dry to obtain a solid; wherein the concentration of the Pt solution is 0.01-0.0001 g Pt / mL H2O;

[0012] (3) The solid obtained in step (2) is calcined at 200-400℃ for 1-2 h to obtain partially oxidized Pt / zinc silicon molecular sieve.

[0013] Preferably, in step (1), the zinc source is at least one of zinc acetate and zinc nitrate.

[0014] Preferably, in step (1), the silicon source is either gaseous silicon dioxide or silica sol.

[0015] Preferably, in step (1), the organic template agent is TEAOH.

[0016] Preferably, in step (1), the alkaline solution is at least one of LiOH and NaOH.

[0017] Preferably, in step (1), the molar ratio of SiO2:organic template agent:H2O in the mixture is 1:0.65:30.

[0018] Preferably, in step (1), the crystallization time is 48-120 hours.

[0019] Preferably, in step (1), the roasting temperature is 550-600°C and the time is 8-10 hours.

[0020] According to another aspect of the invention, an application of a supported partially oxidized Pt / zinc-silicon molecular sieve catalyst is provided for catalytic dehydrogenation of alkanes to olefins.

[0021] Furthermore, it is used to catalyze the dehydrogenation of propane to propylene.

[0022] Furthermore, including:

[0023] (1) The supported partially oxidized Pt / zinc-silicon molecular sieve catalyst is pressed into granular catalyst;

[0024] (2) The granular catalyst obtained in step (1) is loaded into the reactor; the reaction temperature is adjusted to 520-600 °C, and the reaction gas is introduced to carry out the reaction; in the reaction gas: the molar ratio of hydrogen to propane is 0-2:1; nitrogen is the equilibrium gas; the total number of gases is kept constant, and the space velocity of propane is 1-20 h⁻¹. -1 .

[0025] The beneficial effects of this invention are:

[0026] This invention employs a Zn-doped heteroatom molecular sieve framework combined with ion exchange to introduce Pt, resulting in highly dispersed Pt sites within the pores. Furthermore, Pt is stably anchored in a partially oxidized state within the zinc-silicon molecular sieve pores. Compared to conventional alumina-supported or conventional impregnation-based Pt-based dehydrogenation catalysts (with loadings of 0.1%-0.3%), the catalyst of this invention maintains high dehydrogenation activity and propylene selectivity even with lower Pt loadings (0.01%-0.001%), significantly reducing the amount of precious metals used and catalyst cost. Simultaneously, it avoids the problem of increased metal usage due to Pt reduction or agglomeration in traditional systems, further improving the atom utilization efficiency of Pt.

[0027] The catalyst of this invention has a certain degree of adaptability to the type of support structure and is suitable for various zinc-silicon molecular sieve structures such as MFI, BEA, and CHA, which is beneficial for flexible selection and application according to different reactor types and process conditions.

[0028] The catalyst of this invention is prepared by hydrothermal and ion exchange methods, using readily available raw materials, a simple process, and high reproducibility, thus possessing significant industrial value. Furthermore, it does not rely on toxic or environmentally hazardous metal components, avoiding the limitations of traditional CrO4 catalysts. x The environmental and safety hazards associated with basic dehydrogenation catalysts align with the technological trends of green chemistry and sustainable development.

[0029] The catalyst of this invention is suitable for both hydrogen-free and hydrogen-containing atmospheres, and has a good effect on the dehydrogenation of propane to propylene. It has high dehydrogenation activity at high temperature, and the propylene selectivity can reach more than 97%, and it also has good stability. Attached Figure Description

[0030] Figure 1 It is a partially oxidized Pt Propane dehydrogenation activity test results of zinc-silicon molecular sieves (with different Pt loadings): C3H8:N2=8:42, T=550 ºC, WHSV=6.2 h -1 ;

[0031] Figure 2 It is a partially oxidized Pt Propane dehydrogenation activity test results of zinc-silicon molecular sieves (with different Pt loadings): C3H8:N2=8:42, T=550 ºC, WHSV=6.2 h -1 .

[0032] Figure 3 This relates to the relationship between the partially oxidized Pt content and catalytic performance of partially oxidized Pt / zinc-silicon molecular sieves during propane dehydrogenation: the space-time yield of propylene and the propane conversion vary with the partially oxidized Pt content.

[0033] Figure 4 These are XRD patterns of zinc-silicon zeolite molecular sieves (MFI, BEA, CHA) with different Zn loadings (Si:Zn=20, 50, 80).

[0034] Figure 5 The equilibrium conversion of propane at different reaction temperatures and the initial propane conversion of partially oxidized Pt / Zincosilicate-BEA (0.01 wt%), partially oxidized Pt / Zincosilicate-BEA (0.001 wt%), Pt / H-BEA (0.01 wt%), and commercial PtSn / Al2O3 (0.3 wt%) catalysts are shown. Reaction conditions: WHSV = 9.4 h. -1 Alkane / N2 = 8 / 42 mL / min. Detailed Implementation

[0035] 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.

[0036] Example 1

[0037] (1) Mix gaseous silica, zinc acetate, water, TEAOH, and LiOH, and stir until homogeneous to form a mixture. The mixture contains SiO2:TEAOH:H2O:Zn 2+ The molar ratio of LiOH was 1:0.65:30:0.02:0.01. The mixture was stirred evenly and placed in a stainless steel hydrothermal reactor. Crystallization was carried out at 160 °C to obtain a solid product. The solid product was washed with deionized water until neutral and then dried. Subsequently, it was calcined in a muffle furnace at 600 °C for 8-10 h to remove the template agent, obtaining the zinc-silicon molecular sieve product. The mass percentage of Zn was 4 wt% based on the carrier mass.

[0038] (2) The zinc-silicon molecular sieve obtained in step (1) was added to the Pt solution at a ratio of 1 g / 20 mL. The solution was heated to 80°C in a water bath and stirred for 24 h. The solid was then obtained by centrifugation and drying. The concentration of the Pt solution was 0.001 g Pt / mL H2O.

[0039] (3) The solid obtained in step (2) was calcined at 300℃ for 2 h to obtain partially oxidized Pt / zinc-silicon molecular sieve; the mass percentage of Pt was 0.01 wt% based on the mass of the support.

[0040] (4) The prepared partially oxidized Pt / zinc-silicon molecular sieve catalyst is pressed into 20-40 mesh granular catalyst;

[0041] (5) The granular catalyst obtained in step (1) is loaded into a fixed-bed reactor; the reaction temperature is adjusted to 550 °C, and the reaction gas is introduced to carry out the reaction. The mass hourly space velocity of propane is 9.4 h⁻¹. -1 The concentration of propane in the reaction gas is 16%, and the equilibrium gas is nitrogen.

[0042] Example 2:

[0043] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the mass of zinc acetate (Zn(AC)2) in step (1) was 4.44 g; and the mass percentage of Zn in the catalyst was 6.3% based on the mass of the support.

[0044] Example 3:

[0045] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the mass of zinc acetate (Zn(AC)2) in step (1) was 2.22 g; and the mass percentage of Zn in the catalyst was 3.2% based on the mass of the support.

[0046] Example 4:

[0047] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the mass of zinc acetate (Zn(AC)2) in step (1) was 1.11 g; and the mass percentage of Zn in the catalyst was 1.6% based on the mass of the support.

[0048] Example 5:

[0049] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the mass of zinc acetate (Zn(AC)2) in step (1) was 0.89 g; and the mass percentage of Zn in the resulting catalyst was 1.3% based on the mass of the support.

[0050] Example 6:

[0051] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the mass of zinc acetate (Zn(AC)2) in step (1) was 0.44 g; and the mass percentage of Zn in the catalyst was 0.6% based on the mass of the support.

[0052] Example 7:

[0053] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the mass of zinc acetate (Zn(AC)2) in step (1) was 0.28 g; and the mass percentage of Zn in the catalyst was 0.3% based on the mass of the support.

[0054] Example 8:

[0055] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the concentration of Pt solution in step (2) was 0.1 g Pt / mL; and the mass percentage of Pt in the catalyst was 1% based on the mass of the support.

[0056] Example 9:

[0057] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the concentration of the Pt solution in step (1) was 0.01 g Pt / mL; and the mass percentage of Pt in the catalyst was 0.65% based on the mass of the support.

[0058] Example 10:

[0059] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the concentration of the Pt solution in step (1) was 0.005 g Pt / mL; and the mass percentage of Pt in the catalyst was 0.1% based on the mass of the support.

[0060] Example 11:

[0061] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the concentration of Pt solution in step (1) was 0.002 g Pt / mL; and the mass percentage of Pt in the catalyst was 0.05% based on the mass of the support.

[0062] Example 12:

[0063] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the concentration of Pt solution in step (1) was 0.0001 g Pt / mL; and the mass percentage of Pt in the catalyst was 0.001% based on the mass of the support.

[0064] Example 13:

[0065] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that zinc nitrate (Zn(NO3)2) was used as the zinc source in step (1).

[0066] Example 14:

[0067] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the silicon source in step (1) was a silica sol.

[0068] Example 15:

[0069] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that NaOH was used as the alkaline solution in step (1).

[0070] Example 16:

[0071] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that in step (1), the template agent TEAOH was replaced with the template agent TPAOH.

[0072] Example 17:

[0073] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that in step (1), the template agent TEAOH was replaced with the template agent TPABr.

[0074] Example 18:

[0075] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the reaction temperature in step (5) was 520°C.

[0076] Example 19:

[0077] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the reaction temperature in step (5) was 580°C.

[0078] Example 20:

[0079] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the reaction temperature in step (5) was 600°C.

[0080] Example 21:

[0081] The catalyst was prepared and propane dehydrogenation was carried out using the method of Example 1, the only difference being that the crystallization temperature of the zinc-silicon molecular sieve in step (1) was 150°C.

[0082] For the results of the above embodiments, the initial activity data of the reaction were used for comparison. The test conditions and methods were the same as in Example 1 to examine the influence of different parameters on the catalyst reaction performance.

[0083] (a) The effect of Zn mass percentage (based on the mass of the support in the catalyst) on the reactivity of the Pt / zinc-silicon molecular sieve catalyst is shown in Table 1. The reaction conditions are the same as in Examples 1, 2, 3, 4, 5, 6, and 7.

[0084] Table 1. Effect of different Zn mass percentages on propane dehydrogenation activity

[0085] Zn content (%) Initial propane conversion rate (%) Initial propylene selectivity (%) 6.3 21 97 4 29 98 3.2 29 98 1.6 25 98 1.3 18 97 0.6 9 98 0.3 7 98

[0086] To investigate the effect of zinc content on the propane dehydrogenation performance of the Pt / zinc-silicon molecular sieve catalyst, the mass percentage of Zn in the support was systematically varied while keeping other preparation and reaction conditions consistent. The results are shown in Table 1. It can be seen that as the Zn content increased from 0.3% to 1.6%-3.2%, the initial propane conversion of the catalyst significantly increased from 7% to 29%, while the propylene selectivity remained at a high level (97%-98%). When the Zn content was further increased to 6.3%, the propane conversion decreased to 21%, as shown in Table 1. Figure 1 As shown.

[0087] The above results indicate that Zn content affects the actual Pt loading and active site density in the reaction by regulating the number of effective sites in the support available for anchoring Pt species. When the Zn content is too low, there are insufficient sites available for Pt exchange or anchoring, resulting in a low effective Pt loading and limiting overall reaction activity. As the Zn content increases, the number of stably introduced Pt sites increases accordingly, significantly improving propane conversion. However, when the Zn content is too high, it may lead to uneven distribution of Pt species or reduced effective exposure, which is detrimental to further improvement of reaction activity. In summary, a Zn mass percentage range of 1.6%–4% is more conducive to achieving a balance between Pt loading and active site utilization efficiency, thus obtaining superior dehydrogenation performance.

[0088] (ii) The effect of the mass percentage of Pt (based on the mass of the support in the catalyst) on the reactivity of the Pt / zinc-silicon molecular sieve catalyst is shown in Table 2. The reaction conditions are the same as in Examples 1, 8, 9, 10, 11, and 12.

[0089] Table 2. Effect of different Pt contents on catalytic activity

[0090] Pt mass percentage (%) Initial propane conversion rate (%) Initial propane selectivity (%) 0.001 25 98 0.01 29 98 0.05 29 98 0.65 27 97 1 24 96

[0091] From Table 2 and Figure 2 As can be seen, when the mass fraction of Pt is 1%, both the catalyst activity and stability decrease. When the mass fraction of Pt is 0.65%, although the initial activity remains unchanged, the stability decreases. When the mass fraction of Pt is moderate (0.001%-0.05%), the catalyst can achieve both high activity and stability, with an initial propane conversion rate of 28% and a selectivity of 96%.

[0092] As shown in Figure 3, under the condition of constant total Pt loading (0.01 wt%), i.e., Example 1, regulation is achieved through the in-situ evolution of Pt species during the reaction process. With prolonged reaction time and continuous contact with propane, some Pt... δ ⁺ The species are gradually reduced to Pt by the reaction atmosphere. 0 This leads to Pt δ ⁺ / Pt 0 The ratio changed. Performance results show that in the initial stage of the reaction, Pt... δ ⁺ When the proportion is high, both the space-time yield (STY) of propylene and the conversion of propane reach high levels; as the reaction progresses, Pt δ As the content of Pt gradually decreases, the catalytic activity also decreases, indicating that Pt δ ⁺ species are the main active sites in propane dehydrogenation reactions.

[0093] Under the condition that the total load of Pt remains constant, this result indicates that Pt δ ⁺ Sites compared to metallic Pt 0 It exhibits higher intrinsic dehydrogenation activity, thus significantly improving the reaction efficiency per unit Pt. This result further demonstrates that the valence state of Pt is one of the key factors determining catalytic performance.

[0094] (III) The effect of zinc source selection on the reaction activity of Pt / zinc-silicon molecular sieve catalyst is shown in Table 3. The reaction conditions are the same as in Examples 1 and 13.

[0095] Table 3. Effect of different zinc source types on catalytic activity

[0096] Zinc source Initial propane conversion rate (%) Initial propane selectivity (%) Zinc nitrate 29 98 Zinc acetate 29 98

[0097] As shown in Table 3, under the condition of maintaining a consistent Pt loading, the initial conversion and propylene selectivity of the Pt / zinc-silicon molecular sieve catalysts prepared using different zinc sources (zinc nitrate or zinc acetate) in the propane dehydrogenation reaction were basically the same, both exhibiting approximately 29% propane conversion and 98% propylene selectivity. This result indicates that under the synthesis conditions used in this work, the type of zinc source has no significant effect on the initial dehydrogenation performance of the catalyst.

[0098] (iv) The effect of molecular sieve topology on catalyst activity is shown in Table 4. The reaction conditions are the same as in Examples 1, 16, and 17.

[0099] Table 4. Effect of molecular sieve topology type on catalytic activity

[0100] Topology type Initial propane conversion rate (%) Initial propane selectivity (%) Zinc-silicon molecular sieve (MFI) 29 98 Zinc-silicon molecular sieve (BEA) 29 98 Zinc-silicon molecular sieve (CHA) 10 97

[0101] The influence of molecular sieve topology on catalytic performance was investigated, and the XRD characterization results of different topologies are as follows: Figure 4 As shown in Table 4, different zinc loadings did not disrupt the overall structure of the molecular sieve, maintaining the integrity of the framework. A comparative study of different zinc-silicon molecular sieve supports was conducted under the same reaction conditions. It can be seen that when using zinc-silicon molecular sieves with MFI and BEA topologies, the catalysts exhibited high propane conversion (29%) and excellent propylene selectivity (98%) in the initial stage of the reaction. In contrast, while the zinc-silicon molecular sieve with CHA topology also maintained high propylene selectivity (97%), its initial propane conversion was significantly reduced to only 10%. These results indicate that the molecular sieve topology has a significant impact on reaction activity. MFI and BEA molecular sieves with larger channels or three-dimensional interconnected pore structures are more conducive to the diffusion of reactant molecules and the full utilization of active sites, thereby improving propane conversion. Conversely, the small-channel CHA structure may restrict mass transfer of reactants, leading to a decrease in overall activity.

[0102] (v) Effect of reaction temperature on propane dehydrogenation activity, see Table 5. Reaction conditions are the same as in Examples 1, 18, 19, and 20.

[0103] Table 5. Effect of reaction temperature on propane dehydrogenation activity

[0104] Reaction temperature (°C) Initial propane conversion rate (%) Initial propane selectivity (%) 525 12 99 550 28 98 575 40 98 600 45 97

[0105] To investigate the effect of reaction temperature on the propane dehydrogenation performance, the catalytic performance at different reaction temperatures was compared under the same reaction conditions, and the results are shown in Table 6. As the reaction temperature increased from 525 °C to 600 °C, the initial propane conversion gradually increased from 12% to 45%, indicating that increasing the reaction temperature is beneficial for the activation of propane molecules and the dehydrogenation reaction. Meanwhile, the propylene selectivity remained at a high level (97%–99%) throughout the temperature range, but showed a slight decreasing trend at high temperatures, possibly related to the increased probability of side reactions.

[0106] Taking into account factors such as propane conversion, propylene selectivity, and catalyst stability, 550 °C was determined to be the optimal reaction temperature condition within the investigated temperature range, as it can achieve relatively ideal reaction activity while ensuring high selectivity.

[0107] Figure 5 The catalysts prepared in Example 1 and Example 12 of this invention, PtSn / Al2O3 and Pt / H-BEA, are compared. Pt / H-BEA is prepared using the method in Example 1 and used for propane dehydrogenation. The only difference is that the zinc-silicon molecular sieve used in step (2) is a silica-alumina molecular sieve (H-BEA).

[0108] Propane dehydrogenation performance of the catalyst. It can be seen that even with a Pt loading of only about 1 / 30 of the comparative catalyst, the catalyst prepared in this invention can still achieve a similar initial activity level, fully demonstrating its excellent utilization efficiency of active sites.

[0109] 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 supported partially oxidized Pt / zinc-silicon molecular sieve catalyst, characterized in that, The catalyst uses zinc-silicon molecular sieves as a support and combines ion exchange technology to construct and maintain partially oxidized Pt active sites within the pores of the zinc-silicon molecular sieves.

2. The supported partially oxidized Pt / zinc-silicon molecular sieve catalyst according to claim 1, characterized in that, The catalyst contains 0.001%-0.01% Pt by mass and 1%-6% Zn by mass.

3. The supported partially oxidized Pt / zinc-silicon molecular sieve catalyst according to claim 1, characterized in that, Zinc-silicon molecular sieves are one of the MFI type and BEA type.

4. A method for preparing a supported partially oxidized Pt / zinc-silicon molecular sieve catalyst as described in any one of claims 1-3, characterized in that, include: (1) Mix the silicon source, zinc source, water, organic stencil agent, and alkaline solution, and stir until homogeneous to form a mixture. The mixture contains SiO2:Zn 2 + :OH - The molar ratio of the two components is 1:(0.02-0.4):(0.01-0.04). The mixture is stirred evenly and crystallized at 150-160 °C to obtain a solid product. The solid product is washed with deionized water until neutral and then dried. Subsequently, it is calcined to remove the template agent to obtain the zinc-silicon molecular sieve product. (2) Add the zinc-silicon molecular sieve obtained in step (1) to the Pt solution at a ratio of 1 g / 20 mL-1 g / 100 mL, heat to 80-100℃, stir for 8-24 h, and then dry to obtain a solid; wherein the concentration of the Pt solution is 0.01-0.0001 g Pt / mL H2O; (3) The solid obtained in step (2) is calcined at 200-400℃ for 1-2 h to obtain partially oxidized Pt / zinc silicon molecular sieve.

5. The method for preparing a supported partially oxidized Pt / zinc-silicon molecular sieve catalyst according to claim 4, characterized in that, In step (1), the zinc source is at least one of zinc acetate and zinc nitrate, the silicon source is at least one of gaseous silica and silica sol, the organic stencil agent is TEAOH, and the alkaline solution is at least one of LiOH and NaOH.

6. The method for preparing a supported partially oxidized Pt / zinc-silicon molecular sieve catalyst according to claim 4, characterized in that, In step (1), the molar ratio of SiO2:organic template agent:H2O in the mixture is 1:0.65:30; the crystallization time is 48-120 hours.

7. The method for preparing a supported partially oxidized Pt / zinc-silicon molecular sieve catalyst according to claim 4, characterized in that, In step (1), the roasting temperature is 550-600°C and the time is 8-10 hours.

8. The application of a supported partially oxidized Pt / zinc-silicon molecular sieve catalyst as described in any one of claims 1-3, characterized in that, Used for catalytic dehydrogenation of alkanes to produce olefins.

9. The application of the supported partially oxidized Pt / zinc-silicon molecular sieve catalyst according to claim 8, characterized in that, Used to catalyze the dehydrogenation of propane to produce propylene.

10. The application of the supported partially oxidized Pt / zinc-silicon molecular sieve catalyst according to claim 9, characterized in that, include: (1) The supported partially oxidized Pt / zinc-silicon molecular sieve catalyst is pressed into granular catalyst; (2) The granular catalyst obtained in step (1) is loaded into the reactor; the reaction temperature is adjusted to 520-600 °C, and the reaction gas is introduced to carry out the reaction; in the reaction gas: the molar ratio of hydrogen to propane is 0-2:1; nitrogen is the equilibrium gas; the total number of gases is kept constant, and the space velocity of propane is 1-20 h⁻¹. -1 .

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