Sn-modified PtCu monatomic alloy catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of supported catalysts, and discloses a supported Sn modified PtCu monatomic alloy catalyst and a preparation method and application thereof.According to the catalyst, a proper amount of Sn is added to promote surface segregation of Pt in PtCu monatomic alloy, and the dispersity of Pt is greatly improved; according to the catalyst, Al2O3, SiO2 or SiO2-Al2O3 composite oxide serves as a carrier, a large amount of Cu and a small amount of Sn serve as auxiliaries, trace Pt serves as an active component, during preparation, an equivalent-volume co-impregnation method is adopted, the carrier is impregnated in a mixed solution of chloroplatinic acid, tin tetrachloride and cupric nitrate, and after drying roasting and high-temperature reduction, the supported Sn modified PtCu monatomic alloy catalyst is obtained. Wherein Pt is dispersed on the Sn-modified Cu nanoparticles in a monatomic form, and the dispersity of Pt is close to 100%. The catalyst disclosed by the invention is suitable for a reaction for preparing olefin through dehydrogenation of low-chain alkane, the dehydrogenation activity is high under a high-temperature condition, the propylene selectivity can reach 95% or above, the stability is good, and the Pt dispersity in the catalyst is close to 100%.

Description

Technical Field

[0001] The present invention belongs to the technical field of supported catalysts, and in particular relates to a Sn-modified PtCu single-atom alloy catalyst and a preparation method thereof, and application of the catalyst in the dehydrogenation of light alkanes to olefins. Background Art

[0002] Precious metals, such as Pt, Rh, and Ir, represented by Group VIII metals, are widely used in heterogeneous catalysis due to their excellent catalytic performance (including activity, selectivity, and stability) in many important industrial reactions. However, the scarcity and high cost of precious metals have driven innovation in precious metal catalysts. Researchers are maximizing the atomic utilization of precious metals to reduce their use and thus reduce catalyst costs. At present, the main strategies for improving the atomic utilization of noble metals include regulating the spatial distribution of noble metal nanoparticles (Maximizing noble metal utilization in solid catalysts by control of nanoparticle location. Science 2022, 377, 204-208), and constructing fully exposed clusters or single-atom structures (Fully exposed metal clusters: fabrication and application in alkane dehydrogenation. ACS Catal. 2022, 12, 12720-12743; Advances in heterogeneous single-cluster catalysis. Nat. Rev. Chem 2023, 7, 754-767). There are inherent defects in the strategy of regulating the spatial distribution of noble metal nanoparticles because the atoms inside the nanoparticles are not fully utilized. Constructing fully exposed clusters or single-atom structures often requires the use of strong metal-support interactions to achieve full exposure of the noble metal. Typically, metal-oxygen ion bonds are formed between noble metal atoms and reducible metal oxides (Well-defined materials for heterogeneous catalysis:from nanoparticles to isolated single-atom sites.Chem.Rev.2020,120,623-682), which results in the noble metal atoms at the metal / oxide interface being in (partial) oxidation state (Structural evolution of atomically dispersed Ptcatalysts dictates reactivity.Nat.Mater.2019,18,746-751). Such catalysts excel in reactions involving oxidants such as water gas shift and CO oxidation.However, on the one hand, the strong metal-support interaction causes a large difference in properties between each noble metal atom; on the other hand, due to the high chemical potential of the noble metal single atom in the (partial) oxidation state, its structure is difficult to stabilize in a high-temperature reducing atmosphere, and is prone to reduction and agglomeration (Enhancement of surface self-diffusion of platinum atoms by adsorbed hydrogen. Nature 1999, 398, 134-136), which limits its application in industrial reactions involving high-temperature reducing atmospheres and requiring metallic catalytic active centers. In addition, although it has been reported that silanol nests in pure silicon microporous molecular sieves can stabilize metallic noble metal single atoms (Stable anchoring of single rhodium atoms by indiumin zeolite alkane dehydrogenation catalysts. Science 2024, 383, 998-1004), the microporous channels of the molecular sieve limit the diffusion of reactants and / or product molecules, resulting in a lower mass transfer efficiency, which limits its application in reactions involving macromolecules. Therefore, unlike the confined structure of microporous molecular sieves, it is very necessary to develop a catalyst in which metallic noble metal single atoms are fully exposed on the open surface.

[0003] Propylene plays an important role in the global petrochemical industry chain. Propane dehydrogenation to propylene technology has a high carbon resource utilization economy and is a key technology for achieving light olefin production. Propane dehydrogenation to propylene is a strongly endothermic reversible reaction that requires a high reaction temperature (500-700°C) to obtain a sufficiently high propane conversion rate. However, high temperature will aggravate the occurrence of side reactions such as cracking, hydrogenolysis and carbon deposition, resulting in a decrease in propylene selectivity and catalyst carbon deposition deactivation. Therefore, during the reaction process, it is particularly important to use a suitable catalyst to selectively accelerate the propane dehydrogenation to propylene reaction and inhibit the occurrence of other side reactions. Currently, there are two main types of industrial propane dehydrogenation catalysts: CrO x Based on and Pt-based catalysts. CrO x The main challenges with Pt-based catalysts are high toxicity, severe coking and deactivation, and frequent regeneration. Pt-based catalysts, on the other hand, are environmentally friendly and offer high propylene selectivity. From 2011 to 2022, 45 of 62 propane dehydrogenation projects worldwide employed Pt-based catalysts using the UOP Oleflex process. However, Pt-based catalysts still face challenges such as high cost, sintering, and carbon deposition and deactivation. Therefore, improving the utilization of Pt atoms in the catalyst, minimizing Pt usage, and reducing catalyst costs are crucial. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the utilization rate of Pt atoms in existing Pt-based catalysts for the dehydrogenation of light alkanes needs to be improved. Provided are a supported Sn-modified PtCu single-atom alloy catalyst, a preparation method thereof, and an application in the dehydrogenation of light alkanes. The catalyst has an ultra-low Pt content, high propylene selectivity, and a low deactivation rate.

[0005] In order to achieve the above-mentioned object of the invention, the present invention is implemented through the following technical solutions:

[0006] According to one aspect of the present invention, a Sn-modified PtCu single-atom alloy catalyst is provided, which uses Al2O3, SiO2 or SiO2-Al2O3 composite oxide as a carrier, Pt as an active component, and Sn and Cu as additives; based on the mass of the carrier, the mass percentage of Pt is 0.01%-0.2%, the mass percentage of Sn is 0.06-0.9%, and the mass percentage of Cu is 5%-20%; the surface of the carrier is uniformly loaded with alloy nanoparticles, and for a single alloy nanoparticle, PtSn heteropolymers and Sn single atoms are dispersed in the Cu nanoparticles; the PtSn heteropolymers are formed by the coordination of Pt single atoms and Sn single atoms, while the remaining Sn that fails to coordinate with Pt exists in the form of Sn single atoms.

[0007] Furthermore, the dispersion of Pt is not less than 90%.

[0008] Preferably, based on the mass of the carrier, the mass percentage of Pt is 0.1%, the mass percentage of Sn is 0.6%, and the mass percentage of Cu is 10%.

[0009] According to another aspect of the present invention, there is provided a method for preparing the above-mentioned Sn-modified PtCu single-atom alloy catalyst, comprising:

[0010] (1) Dissolve H2PtCl6, SnCl4 and Cu(NO3)2 in hydrochloric acid solution according to their mass percentages;

[0011] (2) impregnating Al2O3, SiO2 or SiO2-Al2O3 composite oxide into the solution obtained in step (1), sonicating and drying naturally at room temperature, and then completely drying at 80-120°C;

[0012] (3) reducing the solid obtained in step (2) at 400-600° C. to obtain a Sn-modified PtCu single-atom alloy catalyst supported on Al 2 O 3 , SiO 2 or SiO 2 -Al 2 O 3 composite oxide.

[0013] Optionally, the concentration of the hydrochloric acid solution in step (1) is 0.1-1 mol / L.

[0014] Optionally, the ultrasonication time in step (2) is 0.5-2h.

[0015] Optionally, the natural drying time at room temperature in step (2) is 12-24 hours.

[0016] Preferably, the complete drying temperature in step (2) is 80°C.

[0017] Preferably, the reduction temperature in step (3) is 550°C.

[0018] According to another aspect of the present invention, a method for dehydrogenating light alkanes to olefins is provided, wherein the method uses the aforementioned Sn-modified PtCu single-atom alloy catalyst and is carried out according to the following steps:

[0019] (1) pressing the Sn-modified PtCu single-atom alloy catalyst into a granular catalyst;

[0020] (2) The obtained granular catalyst is loaded into a fixed bed reactor, hydrogen is introduced, and reduction is carried out at 400-600°C; the temperature is adjusted to a reaction temperature of 520-600°C, and reaction gas is introduced to react, wherein the molar ratio of hydrogen to propane in the reaction gas is 0-2:1.

[0021] Preferably, the reaction temperature in step (2) is 550°C.

[0022] Preferably, the molar ratio of hydrogen to propane in step (2) is 1:1.

[0023] Preferably, it is used for dehydrogenation of propane to produce propylene.

[0024] The beneficial effects of the present invention are:

[0025] The catalyst of the present invention supports a Sn-modified PtCu single-atom alloy on an Al2O3, SiO2, or SiO2-Al2O3 composite oxide carrier. A small amount of Pt (0.01%-0.2% compared to 0.3% or higher in commercial Pt-based catalysts) is used as the active component. Compared to commercial PtSn / Al2O3 catalysts, this reduces the amount of Pt used and the catalyst cost. Pt, Sn, and Cu organically combine to form a Sn-modified PtCu single-atom alloy. On the surface of Cu nanoparticles, Pt single atoms coordinate with Sn single atoms to form PtSn heteropolymers. Meanwhile, the remaining Sn that fails to coordinate with Pt is atomically dispersed on the surface of the Cu nanoparticles. The Pt dispersion in the catalyst is no less than 90%. Adding an appropriate amount of Sn to the PtCu single-atom alloy, on the one hand, changes the local coordination environment of the Pt atoms and improves the electronic structure of the Pt atoms, thereby promoting the desorption of propylene while inhibiting the further dehydrogenation of propylene; on the other hand, the "atomic abstraction" effect of Sn is utilized to achieve almost complete exposure of metallic Pt single atoms. This "atomic abstraction" effect stems from the fact that the radius of Sn atoms is larger than that of Cu (140pm>128pm), which causes a large number of Sn atoms to be dispersed on the surface of Cu nanoparticles. At the same time, the strong interaction between Sn and Pt causes the Pt atoms located inside the Cu nanoparticles to segregate to the surface, forming PtSn heteropolymers.

[0026] The catalyst of the invention is prepared by an equal volume co-impregnation method, the raw materials are readily available, the process is simple, the repeatability is high, and it has certain industrial significance.

[0027] The catalyst of the present invention has a good effect on the dehydrogenation of low-carbon alkanes to olefins, has high dehydrogenation activity, can achieve propylene selectivity of more than 95%, and has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a performance comparison chart of the SiO2-supported Sn-modified PtCu single-atom alloy catalyst (PtSnCu / SiO2) and the SiO2-supported PtCu single-atom alloy catalyst (PtCu / SiO2) prepared in Example 1.

[0029] Figure 2 Spherical aberration corrected high-angle annular dark-field scanning transmission electron microscopy images of the SiO2-loaded Sn-modified PtCu single-atom alloy catalyst (PtSnCu / SiO2) and the SiO2-loaded PtCu single-atom alloy catalyst (PtCu / SiO2) prepared in Example 1.

[0030] Figure 3 This is a graph showing the change in Pt dispersion with Sn loading in the SiO2-supported Sn-modified PtCu single-atom alloy catalyst prepared in Examples 5, 9, 10, and 11.

[0031] Figure 4 This is a performance comparison chart of the SiO2-supported Sn-modified PtCu single-atom alloy catalyst prepared in Example 5 and the commercial PtSn / Al2O3 catalyst.

[0032] Figure 5 This is a stability comparison chart of the SiO2-supported Sn-modified PtCu single-atom alloy catalyst (PtSnCu / SiO2) prepared in Example 5 and the commercial PtSn / Al2O3 catalyst. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below through specific examples. The following examples may enable those skilled in the art to have a more comprehensive understanding of the present invention, but are not intended to limit the present invention in any way.

[0034] Example 1:

[0035] (1) Dissolve 0.0021 g of H2PtCl6, 0.0134 g of SnCl4, and 0.2884 g of Cu(NO3)2 in 4 mL of 0.1 mol / L hydrochloric acid solution;

[0036] (2) 1.0000 g of SiO2 was immersed in the above solution, ultrasonicated for 0.5 h, dried at room temperature for 12 h, and completely dried at 100 °C;

[0037] (3) reducing the solid obtained in (2) at 550° C. for 1 h to obtain a PtSnCu / SiO2 catalyst, wherein the mass percentage of Pt, the mass percentage of Sn, and the mass percentage of Cu are 0.1%, 0.6%, and 10%, based on the mass of the carrier;

[0038] (4) pressing the prepared PtSnCu / SiO2 catalyst into 40-60 mesh granular catalyst;

[0039] (5) The pressed PtSnCu / SiO2 granular catalyst was loaded into a fixed bed reactor, and hydrogen was introduced for pretreatment. The temperature was raised to a pretreatment temperature of 550°C and maintained for 1 hour. The reaction temperature was 550°C, and the propane mass space velocity was 4.7h -1 The reaction gas was switched to a reaction gas having a molar ratio of hydrogen to propane of 1:1, a propane concentration of 16%, and nitrogen as the balance gas.

[0040] Example 2:

[0041] The preparation and reaction were carried out using the method of Example 1, except that the mass of copper nitrate (Cu(NO3)2) in step (1) was 0.1442 g; the mass percentage of Cu in the obtained catalyst was 5% based on the mass of the carrier.

[0042] Example 3:

[0043] The preparation and reaction were carried out using the method of Example 1, except that the mass of copper nitrate (Cu(NO3)2) in step (1) was 0.5768 g; the mass percentage of Cu in the obtained catalyst was 20% based on the mass of the carrier.

[0044] Example 4:

[0045] The preparation and reaction were carried out using the method of Example 1, with the only difference being that the mass of H2PtCl6 in step (1) was 0.0002 g, and the mass percentage of Pt in the obtained catalyst was 0.01% based on the mass of the carrier.

[0046] Example 5:

[0047] The preparation and reaction were carried out using the method of Example 1, with the only difference being that the mass of H2PtCl6 in step (1) was 0.0006 g, and the mass percentage of Pt in the obtained catalyst was 0.03% based on the mass of the carrier.

[0048] Example 6:

[0049] The preparation and reaction were carried out using the method of Example 1, with the only difference being that the mass of H2PtCl6 in step (1) was 0.0042 g, and the mass percentage of Pt in the obtained catalyst was 0.2% based on the mass of the carrier.

[0050] Example 7:

[0051] The preparation and reaction were carried out using the method of Example 1, with the only difference being that the mass of SnCl4 in step (1) was 0.0013 g, and the percentage of Sn in the obtained catalyst was 0.06% based on the mass of the carrier.

[0052] Example 8:

[0053] The preparation and reaction were carried out using the method of Example 1, with the only difference being that the mass of SnCl4 in step (3) was 0.0201 g, and the percentage of Sn in the obtained catalyst was 0.92% based on the mass of the carrier.

[0054] Example 9:

[0055] The preparation and reaction were carried out using the method of Example 1, with the only difference being that the mass of H2PtCl6 in step (1) was 0.0006 g, no SnCl4 was added, and the mass percentage of Pt in the obtained catalyst was 0.03% based on the mass of the carrier, and no Sn was contained.

[0056] Example 10:

[0057] The preparation and reaction were carried out using the method of Example 1, with the only difference being that in step (1), the mass of H2PtCl6 was 0.0006 g, the mass of SnCl4 was 0.0065 g, and the mass percentage of Pt in the obtained catalyst was 0.03% and 0.3% based on the mass of the carrier.

[0058] Example 11:

[0059] The preparation and reaction were carried out using the method of Example 1, with the only difference being that in step (1), the mass of H2PtCl6 was 0.0006 g, the mass of SnCl4 was 0.0098 g, and the mass percentage of Pt in the obtained catalyst was 0.03% and the mass percentage of Sn was 0.45% based on the mass of the carrier.

[0060] Example 12:

[0061] The preparation and reaction were carried out using the method of Example 1, with the only difference being that the reduction temperature in step (3) was 400°C.

[0062] Example 13:

[0063] The preparation and reaction were carried out using the method of Example 1, the only difference being that the reduction temperature in step (3) was 600°C.

[0064] Example 14:

[0065] The preparation and reaction were carried out using the method of Example 1, except that the molar ratio of hydrogen to propane in step (5) was 0:1.

[0066] Example 15:

[0067] The preparation and reaction were carried out using the method of Example 1, with the only difference being that the molar ratio of hydrogen to propane in step (5) was 2:1.

[0068] Example 16:

[0069] The preparation and reaction were carried out using the method of Example 1, the only difference being that the reaction temperature in step (5) was 520°C.

[0070] Example 17:

[0071] The preparation and reaction were carried out using the method of Example 1, the only difference being that the reaction temperature in step (5) was 600°C.

[0072] Example 18:

[0073] The preparation and reaction were carried out using the method of Example 1, with the only difference being that in step (2), 1.0000 g of Al2O3 was impregnated in the solution of step (1).

[0074] Example 19:

[0075] The preparation and reaction were carried out using the method of Example 1, with the only difference being that in step (2), 1.0000 g of SiO2-Al2O3 composite oxide (SiO2:Al2O3 mass ratio of 8:2) was impregnated in the solution of step (1).

[0076] For the results of the above examples, the activity data at the initial reaction and 10 hours were used for comparison to examine the effects of different parameters on the catalyst reaction performance. The test conditions and methods are as follows:

[0077] The catalyst activity is expressed as propane conversion, propylene selectivity and deactivation rate, which are calculated as follows:

[0078] Optional:

[0079]

[0080] Conversion rate:

[0081]

[0082] Inactivation rate:

[0083]

[0084] in, represents the volume flow rate of propane at the reactor inlet, represent the gas volume flow rates of propane and propylene at the reactor outlet, respectively, and X initial and X final represent the propane conversion rates at the initial stage of the reaction and after 12 h, respectively.

[0085] Figure 1 The activity test results of the SiO2-supported Sn-modified PtCu single-atom alloy catalyst (PtSnCu / SiO2) and the SiO2-supported PtCu single-atom alloy catalyst (PtCu / SiO2) prepared in Example 1 are shown, including the propane conversion rate and propylene selectivity at the initial stage of the reaction and after 10 hours of reaction. The reaction products were analyzed online by gas chromatography, and the relationship between propane conversion rate and propylene selectivity and time is shown in Figure 2. Figure 1 As shown in the figure, the initial propane conversion rate is 47%, which is 46% after 10 hours, and the deactivation rate is only 0.003h -1 , while the propylene selectivity remained at a high level (>95%). It can be seen that adding an appropriate amount of Sn to PtCu / SiO2 improves the initial propane conversion, propylene selectivity and stability.

[0086] Figure 2The spherical aberration corrected high-angle annular dark field scanning transmission electron microscopy images of the SiO2-supported Sn-modified PtCu single-atom alloy catalyst (PtSnCu / SiO2) and the SiO2-supported PtCu single-atom alloy catalyst (PtCu / SiO2) prepared in Example 1. Figure 2 It can be seen that Pt in PtCu / SiO2 is dispersed in Cu nanoparticles in the form of single atoms, and Pt single atoms and Sn single atoms in PtSnCu / SiO2 form PtSn heteropolymers, which are dispersed in Cu nanoparticles.

[0087] Figure 3 Figure 1 shows the variation of Pt dispersion with Sn content in the SiO2-supported Sn-modified PtCu single-atom alloy catalysts (PtSnCu / SiO2) prepared in Examples 5, 9, 10, and 11. The Pt content and Cu content in the SiO2-supported Sn-modified PtCu single-atom alloy catalysts were fixed at 0.03wt%, 10wt%, and the Sn content increased from 0 to 0.6wt%. Figure 3 It can be seen that with the increase of Sn content, the Pt dispersion gradually increases, and when the Sn content reaches 0.6wt%, the Pt dispersion is close to 100%.

[0088] Figure 4 The activity test diagram of the SiO2-supported Sn-modified PtCu single-atom alloy catalyst (PtSnCu / SiO2) and the commercial PtSn / Al2O3 catalyst at near-equilibrium conversion rate prepared in Example 5. Figure 4 It can be seen that PtSnCu / SiO2 (Pt mass percentage of 0.03%) and commercial PtSn / Al2O3 (Pt mass percentage of 0.3%) achieve close to equilibrium conversion under the same reaction conditions. Catalytic performance test conditions: 40-60 mesh granular catalyst is loaded into a fixed bed reactor, hydrogen is introduced for pretreatment, the temperature is raised to a pretreatment temperature of 520-600℃, and maintained for 1h; the reaction temperature is 520-600℃, and the propane mass space velocity is 3.4h -1 The reaction gas was switched to a reaction gas having a molar ratio of hydrogen to propane of 1:1, a propane concentration of 16%, and nitrogen as the balance gas.

[0089] Figure 5 The activity test diagram of the SiO2-supported Sn-modified PtCu single-atom alloy catalyst (PtSnCu / SiO2) and the commercial PtSn / Al2O3 catalyst prepared in Example 5. Figure 5It can be seen that PtSnCu / SiO2 (Pt content of 0.03% by mass) shows better propane conversion, propylene selectivity and stability than commercial PtSn / Al2O3 (Pt content of 0.3% by mass). Catalytic performance test conditions: 40-60 mesh granular catalyst is loaded into a fixed bed reactor, hydrogen is introduced for pretreatment, the temperature is raised to the pretreatment temperature of 580°C, and maintained for 1 hour; the reaction temperature is 580°C, and the propane mass space velocity is 9.4h -1 The reaction gas was switched to a reaction gas having a molar ratio of hydrogen to propane of 1:2, a propane concentration of 66.7%, and a hydrogen concentration of 33.3%.

[0090] (1) The effect of the mass percentage of Cu (based on the mass of the support in the catalyst) on the reaction activity of the PtSnCu / SiO2 catalyst is shown in Table 1. The reaction conditions are the same as those in Examples 1, 2, and 3.

[0091] Table 1. Effect of different Cu mass percentages on propane dehydrogenation activity

[0092]

[0093] As can be seen from Table 1, when the mass fraction of Cu is between 5-20%, the catalysts exhibit high propylene selectivity and high stability, with an initial propane conversion of 28% and a propylene selectivity of 95-97%. At the same time, the deactivation rate is only 0.003-0.014h -1 Among them, when the mass fraction of Cu is 10%, the stability is optimal and the misfire rate is only 0.003h -1 .

[0094] (2) The effect of the mass percentage of Pt (based on the mass of the support in the catalyst) on the reaction activity of the PtSnCu / SiO2 catalyst is shown in Table 2. The reaction conditions are the same as those of Examples 1, 4, 5, and 6.

[0095] Table 2. Effect of different Pt contents on catalytic activity

[0096]

[0097] As can be seen from Table 2, when the mass fraction of Pt is between 0.01% and 0.2%, the catalysts all exhibit high propane conversion, high propylene selectivity, and high stability. As the mass fraction of Pt gradually increases, the initial propane conversion increases from 18% to 28%, the propylene selectivity remains above 96%, and the deactivation rate first decreases and then increases. Among them, when the mass fraction of Pt is 0.1%, the catalyst performance is the best, with an initial propane conversion of 28% and a propylene selectivity of 96%, while the deactivation rate is the lowest, only 0.003h -1 .

[0098] (III) Effect of Sn mass percentage on the catalytic activity of PtSnCu / SiO2 catalyst, see Table 3. The reaction conditions were the same as in Examples 1, 7, and 8.

[0099] Table 3. Effect of Sn mass percentage on catalytic activity

[0100]

[0101]

[0102] As can be seen from Table 3, when the mass fraction of Sn is between 0.06% and 0.9%, the catalysts all exhibit high propane conversion, high propylene selectivity, and high stability. As the mass fraction of Sn increases from 0.06% to 0.9%, the initial propane conversion remains above 20%, the propylene selectivity remains above 95%, and the deactivation rate first decreases and then increases. When the mass fraction of Sn is moderate, the deactivation rate is the lowest, only 0.003h -1 .

[0103] (IV) Effect of reduction temperature on the catalytic activity of PtSnCu / SiO2 catalyst, see Table 4. The reaction conditions were the same as in Examples 1, 12, and 13.

[0104] Table 4. Effect of reduction temperature on catalytic activity

[0105]

[0106] As can be seen from Table 4, in the temperature range of 400-600 °C, the catalysts all exhibited similar high activity, high selectivity and high stability.

[0107] (V) Effect of the molar ratio of hydrogen to propane on propane dehydrogenation activity, see Table 6. The reaction conditions were the same as in Examples 1, 14, and 15.

[0108] Table 5. Effect of hydrogen to propane molar ratio on propane dehydrogenation activity

[0109]

[0110] As can be seen from Table 5, within the range of hydrogen to propane molar ratio of 0-2, the catalysts all exhibited high propane conversion, high propylene selectivity, and high stability. In addition, with the increase of hydrogen molar ratio, the initial propane conversion gradually decreased and the deactivation rate slowed down. The catalyst performance reached its best when the hydrogen to propane molar ratio was 1:1. At this time, the catalyst misfire rate was the lowest, only 0.003h -1 .

[0111] (VI) Effect of reaction temperature on propane dehydrogenation activity, see Table 6. Reaction conditions were the same as in Examples 1, 16, and 17.

[0112] Table 6. Effect of reaction temperature on propane dehydrogenation activity

[0113]

[0114] Table 6 shows that when the reaction temperature is between 520°C and 600°C, the catalysts exhibit high propane conversion, high propylene selectivity, and high stability. As the reaction temperature increases, the propane conversion increases, while the selectivity and stability gradually decrease. Considering both activity and stability, a moderate reaction temperature is optimal.

[0115] (VII) Effect of support material on propane dehydrogenation activity, see Table 7. Reaction conditions were the same as in Examples 1, 18, and 19.

[0116] Table 7. Effect of support materials on propane dehydrogenation activity

[0117]

[0118] As can be seen from Table 7, despite the different support materials, the catalysts all exhibited high propane conversion, high propylene selectivity, and high stability. When pure SiO2 was used as the support, the initial propane conversion, propylene selectivity, and stability of the catalyst were all optimal.

[0119] 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 above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms of specific changes without departing from the scope of protection of the present invention and the claims. These all fall within the scope of protection of the present invention.

Claims

1. A Sn-modified PtCu single-atom alloy catalyst, with Al2O3, SiO2 or SiO2-Al2O3 composite oxide as support, characterized in that: Pt is used as an active component, and Sn and Cu are used as auxiliary agents. Based on the mass of the carrier, the mass percentage of Pt is 0.01%-0.2%, the mass percentage of Sn is 0.06-0.9%, and the mass percentage of Cu is 5%-20%. The surface of the carrier is uniformly loaded with alloy nanoparticles, and in terms of a single alloy nanoparticle, PtSn heteropolymers and Sn single atoms are dispersed in the Cu nanoparticles. The PtSn heteropolymers are formed by the coordination of Pt single atoms and Sn single atoms, and the remaining Sn that fails to coordinate with Pt exists in the form of Sn single atoms.

2. The Sn-modified PtCu single-atom alloy catalyst according to claim 1, characterized in that: The dispersion of Pt is not less than 90%.

3. The Sn-modified PtCu single-atom alloy catalyst according to claim 1, characterized in that: Based on the mass of the carrier, the mass percentage of Pt is 0.1%, the mass percentage of Sn is 0.6%, and the mass percentage of Cu is 10%.

4. A method for preparing a Sn-modified PtCu single-atom alloy catalyst according to any one of claims 1 to 3, characterized in that: include: (1) Dissolve H2PtCl6, SnCl4 and Cu(NO3)2 in hydrochloric acid solution according to their mass percentages; (2) impregnating Al2O3, SiO2 or SiO2-Al2O3 composite oxide into the solution obtained in step (1), sonicating and drying naturally at room temperature, and then completely drying at 80-120°C; (3) reducing the solid obtained in step (2) at 400-600° C. to obtain a Sn-modified PtCu single-atom alloy catalyst supported on Al 2 O 3 , SiO 2 or SiO 2 -Al 2 O 3 composite oxide.

5. The method for preparing a Sn-modified PtCu single-atom alloy catalyst according to claim 4, characterized in that: The concentration of the hydrochloric acid solution in step (1) is 0.1-1 mol / L.

6. The method for preparing a Sn-modified PtCu single-atom alloy catalyst according to claim 4, characterized in that: The ultrasonication time in step (2) is 0.5-2 h, and the natural drying time at room temperature is 12-24 h.

7. A method for dehydrogenating light alkanes to olefins, characterized in that: The method uses the Sn-modified PtCu single-atom alloy catalyst according to any one of claims 1 to 3 and is carried out according to the following steps: (1) pressing the Sn-modified PtCu single-atom alloy catalyst into a granular catalyst; (2) The obtained granular catalyst is loaded into a fixed bed reactor, hydrogen is introduced, and reduction is carried out at 400-600°C; the temperature is adjusted to a reaction temperature of 520-600°C, and reaction gas is introduced to react, wherein the molar ratio of hydrogen to propane in the reaction gas is 0-2:

1.

8. The method for dehydrogenating light alkanes to olefins according to claim 7, characterized in that: The reaction temperature in step (2) is 550°C.

9. The method for dehydrogenating light alkanes to olefins according to claim 7, characterized in that: The molar ratio of hydrogen to propane in step (2) is 1:

1.

10. The method for dehydrogenating light alkanes to olefins according to claim 7, characterized in that: Used for dehydrogenation of propane to produce propylene.

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