A single-atom alloy catalyst of copper silicate supported Pt, and a preparation method and application thereof

Abstract

This invention discloses a single-atom alloy catalyst of copper silicate supported on Pt, its preparation method, and its application. Copper silicate with different copper loadings is used as a support, and a small amount of platinum is loaded as an active component. The mass percentage of Pt is 0.025-0.15%, and the mass percentage of Cu is 0-15%. In the preparation of copper silicate, a combination of ammonia stripping and hydrothermal method is used to obtain green copper silicate powder. After impregnating the green copper silicate powder with the Pt precursor, it is left to stand at room temperature overnight, and then heated and dried. The obtained catalyst precursor is reduced at high temperature in a fixed-bed reactor to obtain a PtCuSiO3 catalyst. This catalyst has high activity and stability, and its preparation is simple and easy to carry out on a large scale.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a catalyst precursor for the conversion of copper silicate-supported Pt into a high-temperature sintering-resistant single-atom alloy catalyst, its preparation method, and its application in the oxygen-free dehydrogenation of low-chain alkanes to olefins (taking the oxygen-free dehydrogenation of propane to propylene as an example). Background Technology

[0002] Propylene is one of the world's most important petrochemical raw materials, enabling the large-scale production of various high-value chemicals and intermediates (such as polymers and oxygen-containing compounds), including the three major synthetic materials (plastics, synthetic rubber, and synthetic fibers), polypropylene, and propylene oxide. However, like hydrogen, propylene's high reactivity prevents it from existing as a natural resource on its own; therefore, it must be synthesized from other raw materials, almost entirely derived from fossil fuels (oil, coal, and natural gas). To date, propylene has primarily been produced in refineries, such as through steam cracking (SC) and fluid catalytic cracking (FCC) of naphtha, diesel, or other petroleum byproducts. However, these processes were developed for producing other products, such as aromatics and gasoline, resulting in low selectivity for propylene. The boom in plastics production during the 1970s-1990s, driven by various technologies and economics, coincided with rising oil prices, rendering traditional propylene production processes unsuitable for future large-scale demand from both a scale and economic perspective. Meanwhile, the emergence of hydraulic fracturing technology in the early 21st century, enabling the production of inexpensive shale gas, spurred the industrialization of propylene-specific technologies with higher propylene selectivity, such as propane dehydrogenation (PDH) and methanol-to-propylene (MTP). PDH technology, in particular, saw its output increase from 5 million tons in 2010 (5% of total production) to 13.5 million tons in 2020 (12% of total production). Simultaneously, other technologies specifically for olefin production, such as methanol-to-olefins (MTO) and olefin conversion technology (OCT), experienced similar development (each technology currently accounting for approximately 5% of production).

[0003] Propane dehydrogenation (PDH) is a highly economical process for propylene production, driven by the significant propylene supply-demand gap and the substantial price difference between propane and propylene (approximately $600-800 / ton). Consequently, several commercial propylene production processes have been developed. With the rapid development of PDH processes, dehydrogenation technologies and catalysts have been extensively developed and updated. In recent years, several technologies, including Catofin, Oleflex, FBD-4, PDH, STAR, ADHO, FCDh, and K-PROt, have been commercialized and are rapidly emerging. Among these, Catofin and Oleflex are two of the most widely used PDH technologies globally. The Catofin process comprises four main parts: propane dehydrogenation to propylene reaction, reactor evacuation, product recovery, and refining units. This process utilizes a chromium oxide / alumina catalyst with a chromium oxide content greater than 18% by mass. It operates in a fixed-bed reactor using a hydrocarbon-hot air circulation system, reacting at 650°C and 0.5 bar, achieving a propylene selectivity exceeding 87%. Honeywell UOP's Oleflex process converts propane to propylene via thermocatalytic dehydrogenation in a moving-bed reactor, using a fully recoverable PtSn alumina catalyst. The process begins by introducing pretreated C3 LPG feedstock into a propane dehydrogenator. Butane or heavy components are discharged from the bottom of the dehydrogenator, while the gas discharged from the top is fed into the C3 Oleflex unit to produce propylene-rich liquid and hydrogen-rich gaseous products. Hydrogen purified by pressure swing adsorption (PSA) can be discharged directly or used as fuel in the unit. Meanwhile, the Oleflex dehydrogenation unit can be easily integrated into downstream product conversion processes to produce high-octane alkylated oils or isobutylene dimers, which are then hydrogenated to produce high-octane isooctane. This combination of processes is known as UOP indirect alkylation (InAlk). TM The process involves two catalysts that suffer severe deactivation due to carbon buildup, requiring regeneration. Furthermore, cadmium is highly toxic and environmentally harmful, while the scarcity of the precious metal platinum severely limits the development of propane dehydrogenation processes. The emergence of single-atom alloy Pt-based catalysts holds promise for achieving dehydrogenation of low-carbon alkanes.

[0004] Supported metal nanoparticle catalysts, as the mainstream of heterogeneous catalyst development, are widely used in various modern chemical industrial catalytic reactions and clean energy technologies represented by fuel cells. In heterogeneous catalytic reactions, the performance of the catalytic system is related to the size of the metal nanoparticles, which directly affects the specific surface area of ​​the catalytic active sites, the proportion of different atomic types on the particle surface, and the strength of the interaction between the nanoparticles and the support. Nanoparticles responsible for catalytic reactions often undergo sintering (the sintering mechanism is particle migration and aggregation or Austronescent ripening) due to prolonged exposure to high reaction temperatures, leading to catalyst deactivation. High-temperature catalytic reactions, such as propane dehydrogenation, often require reaction temperatures of 550-620℃ to overcome the energy barrier (ΔH) of oxygen-free propane dehydrogenation. 298K =124.3 kJ / g·mol), thus achieving a relatively ideal propylene formation rate. Therefore, from both an academic and practical chemical production perspective, improving the anti-sintering ability of catalysts loaded with nanoparticles is extremely important. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art, focusing on solving the technical problem of sintering deactivation of existing PtCu single-atom alloy catalysts in the high-temperature propane dehydrogenation reaction due to the excessively low copper Taman temperature. This invention provides a method for converting a copper silicate-supported Pt catalyst precursor into a high-temperature sintering-resistant single-atom alloy catalyst, its preparation method, and its application in propane dehydrogenation. This catalyst exhibits high activity, high stability, and extremely low precious metal content in the high-temperature propane dehydrogenation reaction. The single-atom alloy nanoparticles are not easily sintered, thus stabilizing the propylene yield.

[0006] The technical objective of this invention is achieved through the following technical solution.

[0007] A single-atom alloy catalyst of copper silicate supported on Pt is disclosed. Copper silicate is used as the support, with copper silicate accounting for 100% by mass, platinum accounting for 0.025-0.15% by mass, and Cu accounting for 7-10% by mass. The Pt-supported copper silicate is used as a precursor and subjected to hydrogen pre-reduction treatment at 580-780℃. Some or all of the copper is reduced and precipitated from the copper silicate framework to form copper nanoparticles. Pt atoms are highly dispersed in single-atom form on the surface of the copper nanoparticles to form PtCu single-atom alloy nanoparticles, which are then supported on the support (i.e., layered SiO2 support).

[0008] Preferably, based on the mass of the copper silicate support in the catalyst, the mass percentage of Pt is 0.1-0.15%, and the mass percentage of Cu is 7%.

[0009] Preferably, the hydrogen pre-reduction treatment is carried out at 650-680°C.

[0010] The preparation method of the above catalyst is carried out according to the following steps:

[0011] Step 1: Immerse copper silicate in a platinum precursor solution to load platinum onto copper silicate.

[0012] In step 1, the platinum precursor solution is chloroplatinic acid.

[0013] In step 1, the platinum precursor solution is impregnated into copper silicate powder and left to stand at room temperature (20-25 degrees Celsius) for 10-12 hours, followed by drying at 60-90 degrees Celsius for 6-18 hours.

[0014] Step 2: The copper silicate treated in Step 1 is pre-reduced to obtain a copper silicate-supported Pt sintering-resistant single-atom alloy catalyst; a hydrogen atmosphere is used and the pre-reduction temperature is 580-780℃.

[0015] In step 2, the pre-reduction is carried out using a tubular reactor or a fixed-bed reactor.

[0016] In step 2, the pre-reduction temperature is 650-680℃.

[0017] In step 2, the pre-reduction treatment temperature is maintained for 0.5-5 hours to achieve the pre-reduction effect, preferably 1-3 hours.

[0018] In step 2, an inert protective gas (such as nitrogen, helium or argon) is first introduced, and the temperature is raised to the pre-reduction temperature. Then hydrogen is introduced and the pre-reduction temperature is maintained to carry out pre-reduction. The heating rate is 5-10 degrees Celsius per minute.

[0019] The application of the catalyst of the present invention in the dehydrogenation of propane to propylene, namely a method for the dehydrogenation of propane to propylene, wherein the method uses the above-mentioned PtCu single-atom alloy catalyst supported on copper silicate, and is carried out according to the following steps:

[0020] (1) The PtCu single-atom alloy catalyst supported on copper silicate is pressed into granular catalyst with a mesh size of 20-40 mesh.

[0021] (2) The obtained granular catalyst was loaded into a fixed-bed reactor, nitrogen gas was introduced, and the temperature was raised to the pretreatment temperature of 580-780℃; hydrogen gas was introduced for pretreatment, and the pre-reduction treatment temperature was maintained for 0.5-5h, followed by cooling to the reaction temperature of 520-600℃; the reactor was then introduced for reaction, wherein the molar ratio of hydrogen to propane was 0-2, nitrogen gas was used as the equilibrium gas, the total gas velocity was kept constant, and the space velocity of propane was 1-5h. -1 .

[0022] Preferably, the pre-reduction temperature in step (2) is 650-680℃.

[0023] Preferably, the molar ratio of hydrogen to propane in step (2) is 1:1.

[0024] Preferably, the reaction space velocity based on propane in step (2) is 4.5–4.7 h⁻¹. -1 .

[0025] Since the PtCu single-atom alloy catalyst supported on copper silicate may be further oxidized after catalyst tableting, it is first pretreated with hydrogen for reduction after being loaded into the reactor, and then the propane dehydrogenation reaction is carried out. To avoid catalyst oxidation, a mixture of hydrogen and propane is preferred. Alternatively, it can be stored in an inert protective atmosphere after preparation and pretreated with hydrogen for reduction before loading and use to achieve better catalytic effect.

[0026] Compared with existing technologies, the catalyst of this invention supports a PtCu single-atom alloy on a copper silicate support, which has a high specific surface area and mesoporous channels, which is beneficial to the uniform distribution of active components and the diffusion of gas molecules. Using a small amount of Pt as the active component (0.025%-0.15%, compared to over 0.3% in industrial Pt-based catalysts), the Pt content in the catalyst is reduced, lowering the catalyst cost. Pt forms a PtCu single-atom alloy with Cu, with Pt mainly dispersed in single-atom form on the surface of Cu particles. This significantly improves the atomic utilization rate of Pt and promotes the desorption of propylene, suppressing side reactions such as C / C bond breaking and deep dehydrogenation, thus greatly enhancing the catalyst's activity and selectivity. The copper silicate support has strong Cu-SiO2 metal support interaction and a unique layered structure, significantly suppressing the sintering problem of the PtCu single-atom alloy during pre-reduction and high-temperature catalytic reaction, thus greatly improving the catalyst's stability. The catalyst of this invention uses a combination of ammonia stripping hydrothermal method to prepare the support and impregnation method to prepare the catalyst. The raw materials are readily available, the process is simple, and the reproducibility is high, making it of significant industrial value. The catalyst of this invention is suitable for use in a hydrogen-containing atmosphere and exhibits good performance in the dehydrogenation of propane to propylene. The catalyst is placed in a fixed-bed apparatus for the propane dehydrogenation reaction, with a reaction atmosphere ratio of C3H2O. 8: With an H2:N2 ratio of 7:7:36, the propane conversion rate can reach over 42% under high temperature conditions, the propylene selectivity can reach over 90%, and it also has good stability.

[0027] Table 1. Comparison of the performance of the copper silicate-supported PtCu single-atom alloy of the present invention with that of previously reported Pt-based catalysts.

[0028] Attached Figure Description

[0029] Figure 1 The activity test graphs (propane conversion, propylene selectivity, and propylene formation rate) of the PtCu single-atom alloy catalysts supported on copper silicate prepared using Examples 1, 2, and 5 of the present invention are shown.

[0030] Figure 2 This is a performance comparison chart of specific activity and deactivation rate between the copper silicate-supported PtCu single-atom alloy catalyst (0.1Pt7CuSiO3-680R) prepared in Example 1 of this invention and the reported Pt-based propane dehydrogenation catalyst.

[0031] Figure 3 The image shows the HR-TEM microstructure test results of the PtCu single-atom alloy catalyst supported on copper silicate of the present invention, and a statistical diagram of particle size comparison with the PtCu single-atom alloy catalyst (0.1Pt7Cu / SiO2-IM) prepared by co-impregnation method.

[0032] Figure 4 The image shows the in-situ Raman spectrum of the PtCu single-atom alloy catalyst supported on Pt by copper silicate according to the present invention.

[0033] Figure 5 The image shows the in-situ XPS spectrum of the PtCu single-atom alloy catalyst supported on Pt by copper silicate according to the present invention.

[0034] Figure 6 The in-situ XRD patterns and particle size distributions of the PtCu single-atom alloy catalyst supported on copper silicate and the PtCu single-atom alloy catalyst prepared by the co-impregnation method are shown in the present invention.

[0035] Figure 7 This is an in-situ carbon monoxide diffuse reflectance Fourier transform infrared (CO-DRIFTS) test image of the PtCu single-atom alloy catalyst supported on copper silicate according to the present invention.

[0036] Figure 8 The images show spherical aberration electron microscopy and in-situ carbon monoxide diffuse reflectance Fourier transform infrared (CO-DRIFTS) images of the PtCu single-atom alloy catalyst supported on copper silicate of the present invention. Detailed Implementation

[0037] The present invention will be further described in detail below through specific embodiments, which will enable those skilled in the art to have a more comprehensive understanding of the present invention.

[0038] Example 1—In the preparation of copper silicate, a combination of ammonia distillation and hydrothermal method was used. The preparation of copper silicate was carried out with reference to relevant literature on copper silicate preparation: 1. J. Am. Chem. Soc. 2012, 134, 13922-13925; 2. Angew. Chem. Int. Ed. 2021, 60, 15344-15347.

[0039] (1) 5.000g of amorphous fumed silica was suspended and dispersed in 175mL of deionized water and stirred for 15 minutes.

[0040] (2) Mix 1.3300g of Cu(NO3)2·3H2O with 45mL of ammonia water, and add the copper ammonia complex dropwise to the solution obtained in step (1). At the same time, the pH value of the solution is 11. Stir the mixed solution at room temperature for 6h.

[0041] (3) Evaporate the ammonia from the dark blue solution obtained in step (2) at 80°C until the pH value is 6-7;

[0042] (4) Transfer the blue sol obtained in step (3) to a hydrothermal reactor and maintain the hydrothermal reaction at 190°C for 30 hours;

[0043] (5) After the hydrothermal reactor cools down to room temperature, the solution in the reactor is centrifuged and the precipitate is washed 3 times. The precipitate is dried at 80°C for 12 hours and then calcined at 550°C for 4 hours to obtain green copper silicate powder.

[0044] (6) Dissolve 0.0021 g of chloroplatinic acid in 2 mL of deionized water, immerse the Pt precursor solution in 1 g of green copper silicate powder obtained in step (5), let it stand at room temperature for 12 h, and then dry it at 80 °C for 12 h.

[0045] (7) The PtCuSiO3 catalyst prepared in step (6) is pressed into 20-40 mesh granular catalyst.

[0046] (8) The tableted PtCuSiO3 granular catalyst was loaded into a fixed-bed reactor, and nitrogen gas was introduced to raise the temperature to the pretreatment temperature of 680°C; hydrogen gas was introduced for pretreatment, and the temperature was maintained at 680°C for 1 hour; the temperature was then lowered to the reaction temperature of 580°C, and the propane mass hourly space velocity was 4.7 h⁻¹. -1 Switch to the reaction gas, in which the molar ratio of hydrogen to propane is 1:1, and the equilibrium gas is nitrogen.

[0047] Catalyst activity is expressed as propane conversion, propylene selectivity, and deactivation rate. Propylene selectivity and deactivation rate are calculated using the following formula:

[0048] Selectivity:

[0049] Conversion rate:

[0050] Deactivation rate:

[0051] Among them, [F C3H8 ] in The volumetric flow rate of propane at the reactor inlet, [F] C3H8 ] out [F] C3H6 ] out X represents the gas volume flow rates of propane and propylene at the reactor outlet, respectively. initial and X final The values ​​represent the propane conversion rates at the initial stage of the reaction and after 6 hours, respectively.

[0052] The reaction products C3H6, C2H6, C2H8, and CH4 were analyzed online using a GC-2060 gas chromatograph from Shanghai Ruimin Instruments Co., Ltd., with a TCD thermal conductivity detector and TDX01 and 5A molecular sieve columns. XRD characterization was performed using a Bruke D8 ADVANCE X-ray diffractometer with a Cu target and Kα (60kV, 80mA). The XPS characterization instrument was a K-Alpha+ X-ray photoelectron spectrometer from Thermo Scientific, with an Al target (hν = 1486.6 eV) as the X-ray source. The Raman characterization instrument was a LabRAM HR Evolution laser confocal Raman spectrometer from HORIBA. The TEM characterization instrument was a FEI Tecnai G2 F20, and the HAADF-STEM characterization instrument was a JEM-ARM200F.

[0053] As attached Figure 1 and 2 As shown, the catalyst of the present invention operates continuously at 580°C. Comparing the performance of catalysts prepared at different reduction temperatures (580R, i.e., 580 degrees Celsius; 680R, i.e., 680 degrees Celsius; 780R, i.e., 780 degrees Celsius), the PtCu single-atom alloy catalyst supported on copper silicate (0.1Pt7CuSiO3-680R, i.e., a catalyst for hydrogen reduction at 680 degrees Celsius, with a platinum mass percentage of 0.1% and a copper mass percentage of 7%) prepared in Example 1 of the present invention exhibits the best catalytic performance and stability. At 580°C, the C3H8 conversion reaches 42%, the C3H6 selectivity is 93%, and the specific active site is 2.21s. -1 The inactivation rate was 0.018 h. -1The catalyst outperforms most of the currently reported noble metal Pt-based catalysts, and the comparative data are listed in Table 1. When the catalyst 0.1Pt7CuSiO3-680R was continuously operated at 580℃ for more than 30 hours, it still maintained good catalytic performance, with the C3H8 conversion rate reaching 42% and the C3H6 selectivity reaching 93%. That is, the application of the catalyst of this invention in the propane dehydrogenation reaction can produce a mixed gas of propane, propylene, hydrogen, methane, ethane and ethylene.

[0054] As attached Figure 3 As shown, the copper silicate-supported Pt-Cu single-atom alloy catalyst of the present invention (e.g.) Figure 3 The HR-TEM microstructure test results of the PtCu single-atom alloy catalyst (0.1Pt7Cu / SiO2-IM) prepared by co-impregnation method are shown in the figure. The catalyst was prepared by impregnation of silicon dioxide in platinum and copper precursor solutions, followed by hydrogen reduction. The loading ratio of platinum and copper was consistent with that in this embodiment. Figure 3 The particle size statistics diagrams in Figures ab) show the magnified HRTEM microstructure and elemental distribution of the PtCu single-atom alloy catalyst supported on copper silicate. This clearly shows that there is a large interfacial area between the copper nanoparticles and the support. Compared with 0.1Pt7Cu / SiO2-IM, there is a stronger interaction and a unique layered structure between Cu and SiO2 in 0.1Pt7CuSiO3. These factors may be the reason why this catalyst can inhibit the growth of PtCu nanoparticles on the support surface as the reduction temperature increases.

[0055] In-situ Raman scattering is a powerful tool for characterizing nanoscale Cu oxides, and is therefore used to study the chemical structure of surface Cu species in supports and catalysts. For example... Figure 4 As shown, the Raman spectrum of pure SiO2 exhibits three types of peaks: the first type is at 439 cm⁻¹. -1 The first is a strong and broad peak centered at ω1, belonging to the symmetric stretching mode of SiO2; the second is located at 486 (D1 peak) and 605 cm⁻¹. -1 The defect peak (D2 peak) belongs to the symmetrical tensile vibration modes of the four-ring and three-ring quadruple rings of isolated SiO2 tetrahedra; the third type is at 810 cm⁻¹. -1 The SiO2 intrinsic peak (ω3 mode) is centered. After introducing Cu species via the AEM synthesis scheme, the Cu species in the 0.1Pt7CuSiO3 catalyst precursor showed a peak at 591 cm⁻¹. -1 It exhibits a unique Raman peak, unlike the peak value (630 cm⁻¹) of crystalline bulk CuO. -1This indicates that Cu species exist in a divalent state and are highly dispersed in the support, showing good agreement with the XPS results. After reduction of the catalyst at different temperatures, the Raman peaks of the divalent Cu species completely disappeared, but they belong to the second-order 2Γ. 12- Raman-enabled excitation modes of Cu + -O species characteristic peak (227cm) -1 ) appears, such as Figure 4 As shown, as the pretreatment temperature increases from 580℃ to 680℃, Cu + The Raman peak intensity of the -O species increased significantly, but decreased with further increases in temperature to 780 °C, consistent with the results of in-situ CO-DRIFTS and quasi-in-situ XPS. As mentioned above, Cu NPs on the surface... + The increased amount of -O-Si may be a key reason for particle stability.

[0056] Cu LMM Auger spectroscopy is used to distinguish Cu + and Cu 0 The result is as follows Figure 5 As shown, the kinetic energy (KE) peak at 917.8 eV represents metallic Cu, while the KE peak at 913.3 eV belongs to Cu. + Therefore, this further proves that Cu + It can still exist under a reducing atmosphere at extremely high temperatures. Furthermore, based on semi-qualitative analysis of XPS spectra, the Cu in the 0.1Pt7CuSiO3-680R sample... + / Cu 0 The ratio was 66.2%, significantly higher than the 42.2% of 0.1Pt7CuSiO3-580R and 43.7% of 0.1Pt7CuSiO3-780R. This trend is consistent with the CO-DRIFTS results. Therefore, combining the results of electron microscopy, quasi-in-situ XPS, and in-situ CO-DRIFTS, it can be concluded that the 0.1Pt7CuSiSiO3-680R catalyst produces Cu during the high-temperature reduction process. + This species plays a crucial role in stabilizing PtCu SAA nanoparticles in a high-temperature environment and in observing the phenomenon of semi-coating of the nanoparticles.

[0057] As shown in the in-situ XRD ( Figure 6Part a) shows typical XRD peaks of Pt supported on copper silicate, with no obvious peaks of Pt crystals, proving that Pt is a single atom or monodisperse. Compared with 0.1Pt7Cu / SiO2-IM, the 0.1Pt7CuSiO3 sample developed in this application exhibits a completely different particle growth model. For the 0.1Pt7CuSiO3 sample, under a hydrogen atmosphere, as the temperature increases, Cu species in copper silicate undergo reduction and growth, thus a weak diffraction peak of Cu(111) can be detected at 380℃. Considering that 380℃ is very close to the Taman temperature of copper, although layered copper silicate cannot inhibit the growth of nanoclusters and / or ultra-small nanoparticles, it can effectively inhibit the further growth of nanoparticles. This conclusion can be drawn from the fact that Cu nanoparticles remain stable with increasing temperature.

[0058] Furthermore, the size of copper nanoparticles was calculated using the Scherrer equation X-ray broadening technique. Figure 6 (Part b). As the temperature increased from 380℃ to 680℃, the Cu particle size in 0.1Pt7CuSiO3 slowly increased from 7.97 nm to 8.90 nm, and the particle size remained unchanged at 680℃ for 2 h without significant growth. This is likely a combined result of the unique layered structure of copper silicate and the strong interaction between Cu and SiO2. Furthermore, the Pt loading was far below the XRD detection limit, so no diffraction peaks of Pt species could be detected. However, for the 0.1Pt7Cu / SiO2-IM sample prepared by co-impregnation with SiO2 as the support, CuO nanoparticles derived from the decomposition of copper nitrate hydrate were first observed at 230℃. As the temperature increased to 280℃, Cu2O, as a reducing intermediate phase, appeared with weak diffraction peaks, and Cu nanoparticles appeared with a size of approximately 12.6 nm. Furthermore, when the reduction temperature exceeds 480℃, Cu nanoparticles grow rapidly from 15.5 nm to 33.3 nm, indicating that the weak interaction between Cu and SiO2 cannot inhibit the growth of Cu nanoparticles.

[0059] like Figure 7 As shown, deconvolution analysis of the recorded spectra was performed using the Gaussian peak fitting method, revealing that Cu on the 0.1Pt7CuSiO3 catalyst at different reduction temperatures... 0 and Cu + The relative proportions of species vary. They appear at 2125-2113, 2105-2099, and 2093-2089 cm. -1 The three peaks are attributed to CO adsorption on Cu. + Cu at the upper and step sites 0 Cu at the terrace site 0 Through Cu + With two types of Cu0 Relative intensity analysis of species revealed that when the pretreatment temperature was increased from 580℃ to 680℃, Cu + The percentage of sites increased from 19.9% ​​to 28.8%, indicating that Cu + The absolute quantity also increased. Then, as the temperature was further increased to 780℃, Cu + The percentage gradually decreased to 17.7%. As mentioned above, a large amount of Cu exists on the surface of Cu nanoparticles. + -O-Si species may be a key factor in particle stability.

[0060] The presence of isolated Pt atoms can be demonstrated using AC-HAADF-STEM and CO-DRIFTS. Due to the difference in Z-contrast between Pt and Cu, single Pt atoms present on the surface of Cu nanoparticles can be well distinguished. Figure 8 The images show spherical aberration electron microscopy and in-situ carbon monoxide diffuse reflectance Fourier transform infrared (CO-DRIFTS) images of the PtCu single-atom alloy catalyst supported on copper silicate of the present invention. Figure 8 Parts a and b show that individual, brighter Pt atoms are highly dispersed on Cu(111) and Cu(200) crystal planes with different lattice spacings (0.21 nm for Cu(111) and 0.18 nm for Cu(200)). Furthermore, the inset in the upper right corner shows the atomic arrangement on the PtCu SAA surface, clearly revealing that the signal intensity of a single Pt atom is stronger than that of a Cu atom, indicating that Pt is well dispersed in Cu NPs in a single-atom state. In-situ Fourier transform infrared spectroscopy using CO as a molecular probe has been widely used to analyze the local environment of various metallic Pt species. To clearly distinguish the overlapping peaks between CO-Cu and CO-Pt species, the CO-DRIFTS spectrum of the catalyst was recorded at 200 °C to make CO-Cu 0 Complete desorption occurs after purging in an inert gas. Despite this, due to the low electron density of Cu... + Enhanced the σ-feedback interaction of CO at 2120 cm⁻¹ -1 CO-Cu centered + The peak did not completely disappear, but the observation of Pt species remained unaffected. For example... Figure 8 As shown in section c, 0.1Pt7CuSiO3-580R and 0.1Pt7CuSiO3-680R appear at 2036 cm⁻¹. -1 The peak centered at 2083 cm⁻¹ is the same as the peak position of linearly bonded carbon monoxide on isolated Pt atoms in the metallic state. However, for the 0.1Pt₇CuSiO₃-780R sample, due to the reduction of Pt atoms at a temperature higher than Pt's Tammann temperature (approximately 703 °C), this peak is absent, and another peak appears at 2083 cm⁻¹.-1 The peak centered on [the target peak] was not observed on 0.1Pt7CuSiO3-580R and 0.1Pt7CuSiO3-680R. -1 The nearby absorption peaks, which are the elution peaks of CO adsorbed on two adjacent Pt atoms, indicate that there is no dimer Pt or platinum cluster.

[0061] Example 2:

[0062] The preparation was carried out using the method of Example 1, the only difference being that the pre-reduction treatment temperature in step (8) was 580°C, the C3H8 conversion rate was 34%, and the C3H6 selectivity was 90%.

[0063] Example 3:

[0064] The preparation was carried out using the method of Example 1, the only difference being that the pre-reduction treatment temperature in step (8) was 630°C, the C3H8 conversion rate was 34%, and the C3H6 selectivity was 89%.

[0065] Example 4:

[0066] The preparation was carried out using the method of Example 1, the only difference being that the pre-reduction treatment temperature in step (8) was 730°C, the C3H8 conversion rate was 35%, and the C3H6 selectivity was 81%.

[0067] Example 5:

[0068] The preparation was carried out using the method of Example 1, the only difference being that the pre-reduction treatment temperature in step (8) was 780°C, the C3H8 conversion rate was 18.5%, and the C3H6 selectivity was 83%.

[0069] Example 6:

[0070] The preparation was carried out using the method of Example 1, the only difference being that the reaction temperature in step (8) was 550°C, the C3H8 conversion rate was 27%, and the C3H6 selectivity was 91%.

[0071] Example 7:

[0072] The preparation was carried out using the method of Example 1, the only difference being that the reaction temperature in step (8) was 600°C, the C3H8 conversion rate was 55%, and the C3H6 selectivity was 77%.

[0073] Adjusting the relevant process parameters according to the present invention's technical solution can achieve the preparation of PtCu single-atom alloy catalysts supported on copper silicate. Testing has shown that these catalysts exhibit performance essentially consistent with those of the present invention. The present invention has been described above as exemplary. It should be noted that any simple modifications, alterations, or other equivalent substitutions that can be made by those skilled in the art without creative effort, without departing from the core of the present invention, fall within the protection scope of the present invention.

Claims

1. A copper silicate monatomic alloy catalyst supported with Pt, characterized by, With copper silicate at 100% mass, platinum at 0.025-0.15% mass, and Cu at 7-10% mass, Pt-loaded copper silicate as a precursor is subjected to hydrogen pre-reduction treatment at 650-680℃. Copper nanoparticles are reduced and precipitated from the copper silicate framework to form Cu+-O-Si, and Pt atoms are highly dispersed on the surface of copper nanoparticles in the form of single atoms to form PtCu single-atom alloy nanoparticles, which are then loaded on a carrier; the copper silicate is layered copper silicate.

2. The single-atom alloy catalyst of copper silicate supported Pt according to claim 1, characterized in that, Based on the mass of copper silicate in the catalyst, the mass percentage of Pt is 0.1-0.15%, and the mass percentage of Cu is 7%.

3. A method for preparing a single-atom alloy catalyst of copper silicate supported Pt, characterized by, Follow these steps: Step 1: Immerse copper silicate in a platinum precursor solution to load platinum onto the copper silicate; the copper silicate is layered copper silicate. Step 2: The copper silicate treated in Step 1 is pre-reduced to obtain a copper silicate-supported Pt sintering-resistant single-atom alloy catalyst. A hydrogen atmosphere is used, and the pre-reduction temperature is 650-680℃, which is maintained for 0.5-5 hours.

4. The method of claim 3, wherein the method is characterized by, In step 1, the platinum precursor solution is chloroplatinic acid.

5. The method for preparing a single-atom alloy catalyst of copper silicate supported on Pt according to claim 3, characterized in that, In step 2, maintain the pre-reduction treatment temperature for 1-3 hours.

6. The method for preparing a single-atom alloy catalyst of copper silicate supported on Pt according to claim 3, characterized in that, In step 2, an inert protective gas is first introduced, the temperature is raised to the pre-reduction temperature, and then hydrogen is introduced and the pre-reduction temperature is maintained to carry out pre-reduction. The heating rate is 5-10 degrees Celsius per minute.

7. The method for preparing a single-atom alloy catalyst of copper silicate supported on Pt according to claim 6, characterized in that, The inert protective gas is nitrogen, helium, or argon.

8. The application of a copper silicate-supported Pt single-atom alloy catalyst as described in any one of claims 1-2 in the propane dehydrogenation to propylene, characterized in that, After being loaded into the reactor, hydrogen pretreatment and reduction are carried out first, followed by propane dehydrogenation reaction. The pretreatment and reduction temperature is 650-680℃.

9. The application according to claim 8, characterized in that, The reaction temperature is 520-600℃, and a mixture of hydrogen and propane is used as raw material. The molar ratio of hydrogen to propane is 0-2, but not 0. Nitrogen is used as the equilibrium gas, and the total gas velocity is kept constant. The reaction space velocity based on propane is 1-5h-1.

10. The application according to claim 8, characterized in that, The reaction temperature is 520-600℃, using a mixture of hydrogen and propane as raw materials, with a molar ratio of hydrogen to propane of 1:1, and nitrogen as the equilibrium gas. The total gas velocity is kept constant, and the space velocity of propane is 4.5-4.7 h⁻¹.

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