PtFe-based intermetallic compound composite material and preparation method and application thereof

Abstract

The invention relates to a PtFe-based intermetallic compound composite material and a preparation method and application thereof, and belongs to the field of inorganic chemical materials. The composite material is formed by infiltrating Pt and Fe element compounds on a SiO2 or SBA-15 carrier and carrying out high-temperature calcination. The technical scheme is characterized in that the raw material proportion, calcining temperature and atmosphere are accurately controlled, and the high-performance composite material is obtained. The material is applied to preparation of propylene through propane dehydrogenation, and efficient conversion is realized at a specific temperature and in a gas atmosphere through a fixed bed reactor. The composite material improves the catalytic activity and selectivity of propane dehydrogenation reaction, provides an efficient and stable catalyst for propylene production, and has industrial application potential.

Description

Technical Field

[0001] The present invention belongs to the field of inorganic chemical materials, and relates to a PtFe-based intermetallic compound composite material, a preparation method thereof and an application thereof. Background Art

[0002] In modern chemical production, platinum-based intermetallic compounds have shown broad application prospects in the catalytic field due to their unique physical and chemical properties. However, there are still many challenges in the practical application of traditional platinum-based compounds, such as poor stability at high temperatures, easy aggregation and inactivation of active sites, and low selectivity to target products. In view of these problems, in recent years, researchers have continuously explored new platinum-based intermetallic compounds as catalysts to improve the catalytic activity and selectivity while extending the service life of the catalyst. Platinum-based intermetallic compounds as catalysts show unique electronic and geometric effects in catalytic reactions due to their definite stoichiometry and ordered crystal structure, thus improving the activity and selectivity of the catalyst.

[0003] Propylene is a basic raw material for the production of industrial commodities such as propylene oxide, polypropylene and acetone. Traditional propylene production technologies, including catalytic cracking and steam cracking, can no longer meet the growing market demand. Propane dehydrogenation has received extensive attention due to its unique advantages of cleanness, high efficiency and high atom utilization rate.

[0004] Propane dehydrogenation is an endothermic chemical reaction, usually carried out under the conditions of 550 °C to 650 °C. In addition to the primary propane dehydrogenation reaction, undesirable side reactions such as hydrogenolysis and isomerization inevitably occur, which will not only reduce the selectivity of propylene, but also shorten the service life of the catalyst due to coking. At present, platinum-based catalysts are widely used in alkane dehydrogenation reactions due to their excellent activity. This is attributed to the ability of platinum to effectively activate the C-H bond, while showing low activity towards the cleavage of the C-C bond, thus reducing side reactions and improving the selectivity of propylene. Adding a promoter to the Pt catalyst has been proven to significantly improve the propane dehydrogenation performance, thus developing a series of alloys such as PtSn, PtGa, PtZn, PtIn. The performance enhancement is generally considered to be due to the presence of the second element dispersing the active sites and improving the propane dehydrogenation performance. Traditional platinum alloys have the characteristics of disordered structures due to the limited enhancement effect of metals and are usually unstable. Intermetallic compounds with an ordered atomic structure enable each metal element to occupy a fixed position in the lattice, providing a definite local coordination environment and uniform atomic arrangement for each element. Compared with traditional platinum alloys, intermetallic compounds provide a higher density of active sites and allow the optimization of active sites by precisely controlling the atomic arrangement and electronic structure, thus improving the propane dehydrogenation performance.

[0005] In the CN109706364A patent, a metal intermetallic compound composite material is disclosed, which includes sulfur-doped mesoporous carbon and a metal intermetallic compound based on Pt, Rh or Ir supported on its surface. By regulating the types and temperatures of metal salt precursors, this composite material synthesizes metal intermetallic compounds with a size less than 5 nm, having the advantages of high utilization rate and low cost. However, although this method has the advantages of universality and easy industrial production, in practical applications, it may still face the problem of insufficient stability of metal intermetallic compounds at high temperatures. Although the size of metal intermetallic compounds is effectively limited by the sulfur-doped mesoporous carbon support in this patent, in high-temperature catalytic reactions, metal intermetallic compounds may still agglomerate due to relatively high surface energy, resulting in a reduction in active sites and a decline in catalytic performance. In addition, although this method has a relatively low cost, the preparation process of sulfur-doped mesoporous carbon is relatively complex, which may affect the efficiency of industrial production.

[0006] The CN113304761A patent provides a PtCu 3 metal intermetallic compound, its preparation method and application as a dehydrogenation catalyst. By introducing Cu as an auxiliary agent, this catalyst effectively reduces the dosage of precious metal Pt and improves the selectivity and stability of propane dehydrogenation reaction. However, under long-term high-temperature reaction conditions, this catalyst may still face changes in the structure of PtCu3 metal intermetallic compounds, such as phase separation or surface segregation, thus affecting catalytic performance.

[0007] The CN114377690A patent provides a PtFe-SiO 2 nano-composite material, its preparation method and application in the direct dehydrogenation reaction of propane. By introducing Fe as an auxiliary agent, this composite material realizes the effective dispersion of Pt sites and improves the selectivity and stability of the catalyst. However, in the preparation process of this catalyst, it is necessary to precisely control the ratio of iron source and platinum source, as well as the temperature and time of steps such as drying, calcination and reduction, which puts forward relatively high requirements for industrial production. In addition, although this catalyst shows excellent performance in the propane dehydrogenation reaction, its sensitivity to reaction conditions may limit its wide application under different process conditions. Summary of the Invention

[0008] In view of this, one of the purposes of the present invention is to provide a PtFe-based metal intermetallic compound composite material, the second purpose is to provide a preparation method of a PtFe-based metal intermetallic compound composite material, and the third purpose is to provide an application of a PtFe-based metal intermetallic compound composite material in the preparation of propylene by propane dehydrogenation.

[0009] To achieve the above purposes, the present invention provides the following technical solutions:

[0010] The present invention provides a PtFe-based intermetallic compound composite material, which is formed by calcining a Pt and Fe element compound on a carrier containing SiO 2 or SBA-15 through high-temperature calcination to obtain a PtFe-based intermetallic compound composite material. The molar mass ratio of Pt to Fe is (1-3):1, and the mass percentage of the carrier to Pt is 2.5 w%.

[0011] Furthermore, the present invention provides a method for preparing a PtFe-based intermetallic compound composite material, and the steps are as follows:

[0012] (1) Disperse the carrier in deionized water, stir evenly to prepare a carrier suspension, dissolve chloroplatinic acid hexahydrate and ferric chloride hexahydrate in deionized water to form a dispersion, dropwise add the dispersion into the carrier suspension, stir and mix evenly, and then perform freeze-drying for 24 hours to obtain a precursor;

[0013] (2) Place the precursor described in step (1) in a tubular furnace, then introduce a gas into the tubular furnace, and then set the holding temperature of the tubular furnace to 450-850 °C. After calcination for 2 hours, a PtFe-based intermetallic compound composite material can be obtained;

[0014] The gas is hydrogen and argon, and the volume ratio is 1:19;

[0015] Preferably, the carrier described in step (1) is SiO 2 or any one of SBA-15;

[0016] Preferably, the molar ratio of chloroplatinic acid hexahydrate to ferric chloride hexahydrate described in step (1) is 1:1 or 3:1;

[0017] Preferably, the heating rate described in step (2) is 5 °C / min;

[0018] Preferably, the flow rate of the gas described in step (2) is 20 sccm;

[0019] Furthermore, the application of the PtFe-based intermetallic compound composite material in the dehydrogenation of propane to prepare propylene.

[0020] Furthermore, a method for preparing propylene by dehydrogenating propane includes the following steps:

[0021] (1) Uniformly mix the PtFe-based intermetallic compound composite material and quartz sand to obtain a mixed powder, and then place the mixed powder in a quartz tube reactor. There is quartz wool for blocking above and below the mixed powder. The mass ratio of the PtFe-based intermetallic compound composite material to quartz sand is 1:30;

[0022] (2) Place the loaded quartz tube reactor described in step (1) into a fixed bed reactor, then continuously introduce a reducing gas mixture at 600 °C for 1 hour, and then introduce a reaction gas, and control the temperature at 550 °C - 600 °C to prepare propylene by propane dehydrogenation;

[0023] Preferably, the volume content of the reducing gas mixture described in step (2) is 5% H 2 , 95% Ar; the volume content of the reaction gas components is 20.02% C 3 H 8 , 19.93% H 2 , 60.05% N 2 ; the heating rate of the fixed bed reactor is 5 °C / min.

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

[0025] The present invention provides a PtFe-based intermetallic compound composite material. During the preparation of this composite material, the synthesis of an intermetallic compound with an ordered atomic arrangement is first determined by regulating the ratio of Pt and Fe elements and the calcination temperature. Among them, changing the calcination temperature regulates the morphology and electronic structure of the support and the nanoparticles supported thereon, and regulating the ratio of Pt and Fe elements regulates the morphology and phase of the formed Pt, Fe intermetallic compound. The obtained composite material has intermetallic compound nanoparticles with an ordered atomic arrangement, thus greatly solving the problems of low density of Pt active sites, and the decrease in propylene selectivity caused by excessive dehydrogenation when this composite material is used as a catalyst, and the performance degradation caused by the instability of the disordered alloy during the reaction process, effectively improving the activity of the catalyst. When the composite material is used as a catalyst for propane dehydrogenation to produce propylene, propane can be converted into a high-value chemical product of propylene, and the selectivity for the reduction product propylene is the highest. By adjusting the reaction temperature of the fixed bed reactor, the selectivity of the catalyst for propylene can be further improved, and the production of propylene can reach up to 97%. This is of great significance for solving the problem of increasing propylene production.

[0026] The composite material provided by the present invention is used in the method for propane dehydrogenation to produce propylene. In this method, quartz sand is used to mix and disperse the catalyst. This mixed powder helps to dilute the catalyst, increase the residence time of the reaction raw materials in the catalyst bed layer, enable the reactants to have more sufficient time to contact the catalyst, thereby improving the reaction efficiency. Quartz sand has high stability and a large specific surface area, and can be used as a support for the catalyst to evenly distribute the catalyst particles and prevent the aggregation of catalyst particles, thereby improving the reaction efficiency and selectivity. Combined with the intermetallic compound propane dehydrogenation catalyst in the present invention, the selectivity for the propane dehydrogenation product propylene can be greatly improved.

[0027] A variety of testing methods show that after calcination by controlling the feed ratio and temperature, compared with pure Pt and pure Fe-based catalysts, the composite material provided by the present invention as a catalyst has the characteristics of atomic ordered arrangement, dispersed reaction active sites, strong stability, and strong anti-coking property. When it is used in propane dehydrogenation to produce propylene, it can effectively improve the selectivity to propylene. Therefore, under the background of the current urgent need to increase the propylene production in the industry, it has great application prospects.

[0028] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. Brief Description of the Drawings

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0030] Figure 1 Pt prepared for Example 1 3 HRTEM, HADDF-STEM, EDS and AC-STEM diagrams of Fe / SBA-15 PtFe intermetallic compound catalyst and PtFe / SBA-15 PtFe intermetallic compound catalyst prepared for Example 3, where (a) is Pt 3 HRTEM diagram of Fe / SBA-15, (b-d) are HADDF-STEM and EDS diagrams of Pt 3 Fe / SBA-15, (e) is AC-STEM diagram of Pt 3 Fe / SBA-15, (f) is HRTEM diagram of PtFe / SBA-15, (g-i) are HADDF-STEM and EDS diagrams of PtFe / SBA-15, (j) is AC-STEM diagram of PtFe / SBA-15;

[0031] Figure 2 Pt prepared for Example 1 3 Fe / SBA-15 PtFe intermetallic compound catalyst, L-Pt prepared for Example 2 3 Fe / SBA-15 PtFe intermetallic compound catalyst, PtFe / SBA-15 PtFe intermetallic compound catalyst prepared for Example 3, Pt prepared for Example 4 3 Fe / SiO 2 X-ray powder diffraction diagrams corresponding to PtFe intermetallic compound catalysts;

[0032] Figure 3For the Pt / SBA-15 prepared in Comparative Example 1, the Pt 3 Fe / SBA-15 PtFe intermetallic compound catalyst, the PtFe / SBA-15 PtFe intermetallic compound catalyst prepared in Example 3, the Pt 3 Fe / SBA-15 PtFe intermetallic compound catalyst after the propane dehydrogenation reaction, the corresponding X-ray photoelectron spectroscopy and ultraviolet-visible absorption spectra of the spent catalyst (Pt 3 Fe / SBA-15 PDH), where (a) is the X-ray photoelectron spectroscopy of Pt / SBA-15, Pt 3 Fe / SBA-15, PtFe / SBA-15 and Pt 3 Fe / SBA-15 PDH, (b) is the ultraviolet-visible absorption spectra of Pt / SBA-15, Pt 3 Fe / SBA-15 and SBA-15;

[0033] Figure 4 For the Pt / SBA-15 prepared in Comparative Example 1, the Pt 3 Fe / SBA-15 PtFe intermetallic compound catalyst, the PtFe / SBA-15 PtFe intermetallic compound catalyst prepared in Example 3, the Pt 3 Fe / SiO 2 PtFe intermetallic compound catalyst, the thermogravimetric analysis and Raman spectra of the spent catalyst after the propane dehydrogenation reaction, where (a) is the thermogravimetric analysis of Pt / SBA-15, Pt 3 Fe / SBA-15, PtFe / SBA-15 and Pt 3 Fe / SiO 2 Thermogravimetric analysis of the spent catalyst after the propane dehydrogenation reaction; (b) is the Raman spectra of Pt / SBA-15, Pt 3 Fe / SBA-15, PtFe / SBA-15 and Pt 3 Fe / SiO 2 Raman spectra of the spent catalyst after the propane dehydrogenation reaction;

[0034] Figure 5 For the Pt 3 Fe / SBA-15 PtFe intermetallic compound catalyst prepared in Example 1, the Pt 3 Fe / SiO 2 PtFe intermetallic compound catalyst, the corresponding STEM images and particle size analysis, where (a) is Pt 3STEM images and particle size analysis of Fe / SBA-15 before and after propane dehydrogenation, (b) is Pt 3 Fe / SiO 2 STEM images and particle size analysis of propane dehydrogenation before and after the reaction;

[0035] Figure 6 It is a bar chart comparing the propane conversion rate and propylene selectivity of propane dehydrogenation using the methods in Examples 6-9 and Comparative Examples 3-4. Detailed implementation manners

[0036] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following examples only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following examples and the features in the examples can be combined with each other.

[0037] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and cannot be understood as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0038] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only for illustrative purposes and cannot be understood as a limitation to the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0039] Example 1

[0040] A preparation method of a PtFe-based intermetallic compound catalyst is as follows:

[0041] (1) Disperse 200 mg of SBA-15 support in 100 mL of deionized water and stir for 3 hours. Then, add 13.258 mg of platinum(IV) chloride hexahydrate and 2.306 mg of iron(III) chloride hexahydrate to 10 mL of deionized water, stir evenly, and then dropwise add the mixed solution to the support suspension while continuously stirring. Then, stir and impregnate for 12 hours and place it in a freeze dryer. After drying, a precursor is obtained;

[0042] (2) Place the precursor described in step (1) in a tubular furnace. Then, introduce a mixed reducing gas into the tubular furnace reactor at a flow rate of 20 sccm. The gas composition is 5% H 2 , 95% Ar. Then, set the holding temperature of the tubular furnace to 850 °C, calcine for 2 hours, and then naturally cool to room temperature to obtain the PtFe-based intermetallic compound catalyst (Pt 3 Fe / SBA-15).

[0043] Example 2

[0044] A method for preparing a PtFe-based intermetallic compound catalyst is as follows:

[0045] (1) Disperse 200 mg of SBA-15 support in 100 mL of deionized water and stir for 3 hours. Then, add 13.258 mg of platinum(IV) chloride hexahydrate and 2.306 mg of iron(III) chloride hexahydrate to 10 mL of deionized water, stir evenly, and then dropwise add the mixed solution to the support suspension while continuously stirring. Then, stir and impregnate for 12 hours and place it in a freeze dryer. After drying, a precursor is obtained;

[0046] (2) Place the precursor described in step (1) in a tubular furnace. Then, introduce a mixed reducing gas into the tubular furnace reactor at a flow rate of 20 sccm. The gas composition is 5% H 2 , 95% Ar. Then, set the holding temperature of the tubular furnace to 450 °C, calcine for 2 hours, and then naturally cool to room temperature to obtain the PtFe-based intermetallic compound catalyst (L-Pt3Fe / SBA-15).

[0047] Example 3

[0048] A method for preparing a PtFe-based intermetallic compound catalyst is as follows:

[0049] (1) Disperse 200 mg of SBA-15 support in 100 mL of deionized water and stir for 3 hours. Then, add 13.258 mg of platinum(IV) chloride hexahydrate and 6.918 mg of iron(III) chloride hexahydrate to 10 mL of deionized water, stir evenly, and then dropwise add the mixed solution to the support suspension while continuously stirring. Then, stir and impregnate for 12 hours and place it in a freeze dryer. After drying, a precursor is obtained;

[0050] (2) Place the precursor described in step (1) in a tube furnace, and then introduce a mixed reducing gas into the tube furnace reactor at a flow rate of 20 sccm. The gas composition is 5% H 2 , 95% Ar. Then set the holding temperature of the tube furnace to 850 °C. After calcining for 2 hours, let it cool naturally to room temperature to obtain the PtFe-based intermetallic compound catalyst (PtFe / SBA-15).

[0051] Example 4

[0052] A preparation method of a PtFe-based intermetallic compound catalyst is as follows:

[0053] (1) Disperse 200 mg of SiO 2 support in 100 mL of deionized water and stir for 3 hours. Then add 13.258 mg of platinum chloride hexahydrate and 2.306 mg of iron chloride hexahydrate to 10 ml of deionized water and stir evenly. Then add this mixed solution dropwise to the support suspension while continuously stirring. Then stir and impregnate for 12 hours and then put it into a freeze dryer. After drying, a precursor is obtained;

[0054] (2) Place the precursor described in step (1) in a tube furnace, and then introduce a mixed reducing gas into the tube furnace reactor at a flow rate of 20 sccm. The gas composition is 5% H 2 , 95% Ar. Then set the holding temperature of the tube furnace to 850 °C. After calcining for 2 hours, let it cool naturally to room temperature to obtain the PtFe-based intermetallic compound catalyst (Pt 3 Fe / SiO 2 ).

[0055] Comparative Example 1

[0056] Prepare a propane dehydrogenation catalyst with platinum supported on SBA-15

[0057] (1) Disperse 200 mg of SBA-15 support in 100 mL of deionized water and stir for 3 hours. Then add 13.258 mg of platinum chloride hexahydrate to 10 ml of deionized water and stir evenly. Then add this solution dropwise to the support suspension while continuously stirring. Then stir and impregnate for 12 hours and then put it into a freeze dryer. After drying, a precursor is obtained;

[0058] (2) Place the precursor described in step (1) in a tube furnace, and then introduce a mixed reducing gas into the tube furnace reactor at a flow rate of 20 sccm. The gas composition is 5% H 2, 95% Ar. Then set the holding temperature of the tube furnace to 850 °C. After calcining for 2 hours, let it cool naturally to room temperature to obtain the PtFe-based intermetallic compound catalyst (Pt / SBA-15).

[0059] Comparative Example 2

[0060] Preparation of a propane dehydrogenation catalyst with iron supported on SBA-15

[0061] (1) Disperse 200 mg of SBA-15 support in 100 mL of deionized water and stir for 3 hours. Then add 6.918 mg of ferric chloride hexahydrate to 10 ml of deionized water and stir evenly. Then add this solution dropwise to the support suspension while continuously stirring. Then stir and impregnate for 12 hours and put it into a freeze dryer. After drying, obtain the precursor;

[0062] (2) Place the precursor described in step (1) in a tube furnace. Then, introduce a mixed reducing gas into the tube furnace reactor at a flow rate of 20 sccm. The gas composition is 5% H 2 , 95% Ar. Then set the holding temperature of the tube furnace to 850 °C. After calcining for 2 hours, let it cool naturally to room temperature to obtain the PtFe-based intermetallic compound catalyst (Fe / SBA-15).

[0063] Figure 1 In (a) is Pt 3 HRTEM image of Fe / SBA-15. The loaded nanoparticles have good crystallinity. The lattice spacing of Pt 3 Fe(200) is 0.193 nm, corresponding to the Pt 3 Fe intermetallic compound. (b - d) are HADDF-STEM and EDS images of Pt 3 Fe / SBA-15. The element distribution of the nanoparticles is uniform, and the particle size is uniform. (e) is the AC-STEM image of Pt 3 Fe / SBA-15. The brighter bright spots in the figure are Pt atoms, and the darker bright spots are Fe atoms, forming a standard Pt 3 Fe intermetallic compound structure. (f) is the HRTEM image of PtFe / SBA-15. The loaded nanoparticles have good crystallinity. The lattice spacing of PtFe(200) is 0.192 nm, corresponding to the PtFe intermetallic compound. (g - i) are HADDF-STEM and EDS images of PtFe / SBA-15. The element distribution of the nanoparticles is uniform, and the particle size is uniform. (j) is the AC-STEM image of PtFe / SBA-15. The brighter bright spots in the figure are Pt atoms, and the darker bright spots are Fe atoms, forming a standard PtFe intermetallic compound structure.

[0064] Figure 2 Pt prepared for Example 1 3 Fe / SBA-15 PtFe intermetallic compound catalyst, L-Pt prepared for Example 2 3 Fe / SBA-15 PtFe intermetallic compound catalyst, PtFe / SBA-15 PtFe intermetallic compound catalyst prepared for Example 3, Pt prepared for Example 4 3 Fe / SiO 2 X-ray powder diffraction patterns corresponding to the PtFe intermetallic compound catalysts. It can be seen from Figure 2 that Pt 3 Fe / SBA-15 and Pt 3 Fe / SiO 2 catalysts both show diffraction peaks consistent with the structure of L12 Pt 3 Fe (ICSD No. 56275). Although the SBA-15 support is composed of SiO 2 , due to its porous molecular sieve nature, its characteristic peaks are weaker compared to the SiO2 support. However, the consistent Pt 3 Fe IMC characteristic peaks indicate the successful loading of Pt 3 Fe IMC on different supports. The superlattice peaks at 23° and 32.75° correspond to the (001) and (110) planes of Pt 3 Fe IMC respectively. The diffraction peaks of the two catalysts on different supports match the superlattice peaks of the standard card, indicating that the particles loaded on different supports form an atomically ordered intermetallic structure. The L-Pt 3 Fe / SBA-15 catalyst synthesized at a lower temperature does not show obvious Pt 3 Fe-IMC peaks, indicating that there is no Pt 3 Fe IMC on the support, and there are clusters formed only by Pt aggregation.

[0065] Figure 3 Pt / SBA-15 prepared for Comparative Example 1, Pt 3 Fe / SBA-15 PtFe intermetallic compound catalyst prepared for Example 1, PtFe / SBA-15 PtFe intermetallic compound catalyst prepared for Example 3, Pt 3 Fe / SBA-15 PtFe intermetallic compound catalyst after the propane dehydrogenation reaction (Pt 3 Fe / SBA-15 PDH) corresponding X-ray photoelectron spectroscopy and ultraviolet-visible absorption spectroscopy diagrams. Among them, (a) is Pt / SBA-15, Pt 3 Fe / SBA-15, PtFe / SBA-15 and Pt 3X-ray photoelectron spectroscopy of Fe / SBA-15 PDH shows that the Pt 4f peaks of the four samples in the range of 71 to 73 eV are attributed to metallic Pt, which is due to PtFe or Pt 3 Pt signals within the Fe IMC. As the proportion of Fe species increases during the catalyst preparation process, the surface particles consist of Pt, Pt 3 Fe, and PtFe. The XPS spectra also follow this pattern, with the Pt 4f peaks shifting to lower binding energies (from 75.47 eV to 75.23 eV for 4f5 / 2 and from 72.09 eV to 71.96 eV, 71.31 eV for 4f7 / 2), which is due to the transfer of electrons from Fe to Pt as the Fe species content in the nanoparticles increases. The catalyst used after PDH shows Pt 4f5 / 2 and 4f7 / 2 peaks at 75.33 eV and 72.02 eV, respectively, with little change compared to before the reaction, indicating that the Pt species on the catalyst surface are relatively stable during the propane dehydrogenation process. (b) UV-visible absorption spectra of Pt / SBA-15, Pt 3 Fe / SBA-15, and SBA-15 show that the absorbance of Pt 3 Fe / BBA-15 and Pt / SBA-15 increases significantly compared to the pure SBA-15 reference sample, which is attributed to the charge transfer between metal and oxygen atoms. Obvious signals are observed at 263 nm for Pt / SBA-15 and Pt 3 Fe / SBA-15 catalysts, and this signal originates from [PtCl 6 2- , indicating that the Pt species are successfully loaded onto the SBA-15 support. Compared to Pt / SBA-15, Pt3Fe / SBA-15 shows an additional peak signal at 250 nm, which is due to the charge transfer between the O p orbital and Fe d electrons, confirming the successful loading of Fe species onto the support in addition to Pt.

[0066] Figure 4 Pt / SBA-15 prepared in Comparative Example 1, Pt 3 Fe / SBA-15 PtFe-based intermetallic compound catalyst prepared in Example 1, PtFe / SBA-15 PtFe-based intermetallic compound catalyst prepared in Example 3, Pt 3 Fe / SiO 2 PtFe-based intermetallic compound catalyst, corresponding thermogravimetric analysis and Raman spectra of the spent catalysts after propane dehydrogenation reaction, where (a) is Pt / SBA-15, Pt 3 Fe / SBA-15, PtFe / SBA-15, and Pt 3 Fe / SiO​2 Thermogravimetric analysis diagram of the spent catalyst after propane dehydrogenation reaction; (b) is Pt / SBA-15, Pt 3 Fe / SBA-15, PtFe / SBA-15 and Pt 3 Fe / SiO 2 Raman spectroscopy diagram of the spent catalyst after propane dehydrogenation reaction. It can be seen from the figure that all catalysts will produce amorphous coke after prolonging the reaction time. Pt 3 Fe / SiO 2 catalyst shows the most obvious signal, highlighting the significant influence of the support on coke formation through propane dehydrogenation, indicating that Pt nanoparticles on SiO 2 tend to accelerate the deactivation rate due to the high selectivity for C-C bond cleavage, resulting in severe coke formation.

[0067] Figure 5 Pt 3 Fe / SBA-15 PtFe-based intermetallic compound catalyst prepared in Example 1, Pt 3 Fe / SiO 2 Corresponding STEM diagram and particle size analysis of the PtFe-based intermetallic compound catalyst. It can be analyzed from the figure that there are significant differences in the size and uniformity of the supported nanoparticles on different supports before and after the reaction. The presence of oversized particles on the catalyst reduces the number of active sites and increases the possibility of coke formation due to sintering, which will have an adverse impact on the performance.

[0068] Example 6

[0069] A method for producing propylene by propane dehydrogenation, the method is as follows:

[0070] (1) Take 50 mg of the catalyst prepared in Example 1 (Pt 3 Fe / SBA-15) and 1500 mg of quartz sand, mix them evenly, grind them thoroughly on an agate mortar to obtain a mixed powder, and then place the mixed powder in the middle of a quartz tube reactor, with quartz wool blocking above and below the mixed powder;

[0071] (2) Place the loaded quartz tube reactor in step (1) in a fixed bed reactor, and then introduce a reducing gas (5% H 2 , 95% Ar) at a flow rate of 20 sccm, then heat from room temperature to 600 °C at a heating rate of 5 °C / min and hold for 1 hour, then cool to 550 °C at a cooling rate of 5 °C / min, and introduce a reaction gas (20.02% C 3 H 8 、19.93% H 2 、60.05% N2 ) is sufficient.

[0072] Example 7

[0073] A method for propane dehydrogenation to propylene is as follows:

[0074] It is different from Example 6 in that the catalyst (Pt 3 Fe / SBA-15) prepared in Example 1 in step (1) is replaced with the catalyst (L-Pt 3 Fe / SBA-15) prepared in Example 2, and the other conditions remain unchanged.

[0075] Example 8

[0076] A method for propane dehydrogenation to propylene is as follows:

[0077] It is different from Example 6 in that the catalyst (Pt 3 Fe / SBA-15) prepared in Example 1 in step (1) is replaced with the catalyst (PtFe / SBA-15) prepared in Example 3, and the other conditions remain unchanged.

[0078] Example 9

[0079] A method for propane dehydrogenation to propylene is as follows:

[0080] It is different from Example 6 in that the catalyst (Pt 3 Fe / SBA-15) prepared in Example 1 in step (1) is replaced with the catalyst (Pt 3 Fe / SiO 2 )), and the other conditions remain unchanged.

[0081] Comparative Example 3

[0082] Propane dehydrogenation is carried out using a propane dehydrogenation catalyst with platinum supported on SBA-15, and the specific method is as follows:

[0083] It is different from Example 6 in that the catalyst (Pt 3 Fe / SBA-15) prepared in Example 1 in step (1) is replaced with the catalyst (Pt / SBA-15) prepared in Comparative Example 1, and the other conditions remain unchanged.

[0084] Comparative Example 4

[0085] Propane dehydrogenation is carried out using a propane dehydrogenation catalyst with iron supported on SBA-15, and the specific method is as follows:

[0086] It is different from Example 6 in that the catalyst (Pt 3Replace the catalyst (Fe / SBA-15) prepared in Comparative Example 1 with (Fe / SBA-15), and keep other conditions unchanged.

[0087] Collect the gaseous products prepared by the methods of Examples 6-9 and Comparative Examples 3-4, and then detect the composition and ratio of the gaseous products by gas chromatography. Plot the ratios corresponding to each component as a Figure 6 bar chart as shown. It can be seen from Figure 6 that when propane dehydrogenation is carried out by the methods of Examples 6-9, the conversion rate of propane is increased, and the propylene selectivity can reach up to 97%. It shows that when Fe element is incorporated into the Pt-based catalyst to form an intermetallic compound, the selectivity to propylene can be effectively improved. This is because the presence of the second element disperses the active sites and improves the propane dehydrogenation performance. Compared with traditional platinum alloys, the intermetallic compound provides a higher density of active sites and allows the optimization of active sites by precisely controlling the atomic arrangement and electronic structure, thereby improving the propane dehydrogenation performance.

[0088] In summary, the present invention provides a preparation method of a PtFe-based intermetallic compound catalyst, its product and its application in propane dehydrogenation to propylene. The intermetallic compound catalyst is obtained by first impregnating the carrier and then calcining at a controlled feed ratio and temperature. A variety of testing methods show that after calcining at a controlled feed ratio and temperature, compared with pure Pt and pure Fe-based catalysts, the catalyst has the characteristics of ordered atomic arrangement, dispersed reaction active sites, strong stability and strong anti-coking property. When it is used in propane dehydrogenation to propylene, it can effectively improve the selectivity to propylene. Therefore, under the background of the current urgent need to increase the propylene production in the industry, it has great application prospects.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. PtFe-based intermetallic compound composite material, characterized in that: The material is a PtFe-based intermetallic compound composite material formed by high-temperature calcination of Pt and Fe element compounds on a carrier containing SiO2 or SBA-15, the molar mass ratio of Pt to Fe is (1-3):1, and the mass percentage of the carrier to Pt is 2.5w%.

2. A method for preparing a PtFe-based intermetallic compound composite material, characterized in that: The steps are as follows: (1) dispersing the carrier in deionized water, stirring evenly to prepare a carrier suspension, dissolving chloroplatinic acid hexahydrate and ferric chloride hexahydrate in deionized water to form a dispersion, adding the dispersion dropwise to the carrier suspension, stirring and mixing evenly, and then freeze-drying for 24 hours to obtain a precursor; (2) placing the precursor described in step (1) in a tube furnace, then introducing gas into the tube furnace, and then setting the insulation temperature of the tube furnace to 450-850° C., and calcining for 2 hours to obtain a PtFe-based intermetallic compound composite material; The gases are hydrogen and argon, with a volume ratio of 1:

19.

3. The preparation method according to claim 2, characterized in that: The carrier in step (1) is any one of SiO2 or SBA-15.

4. The preparation method according to claim 2, characterized in that: The molar ratio of chloroplatinic acid hexahydrate to ferric chloride hexahydrate in step (1) is 1:1 or 3:

1.

5. The preparation method according to claim 2, characterized in that: The heating rate in step (2) is 5°C / min.

6. The preparation method according to claim 2, characterized in that: The flow rate of the gas in step (2) is 20 sccm.

7. Use of the PtFe-based intermetallic compound composite material according to claim 1 in the preparation of propylene by dehydrogenation of propane.

8. A method for preparing propylene by dehydrogenating propane, characterized in that: The following steps are involved: (1) The PtFe-based intermetallic compound composite material and quartz sand are uniformly mixed to obtain a mixed powder, and then the mixed powder is placed in the middle of a quartz tube reactor, and quartz wool is provided above and below the mixed powder for blocking, and the mass ratio of the PtFe-based intermetallic compound composite material to the quartz sand is 1:

30. (2) The loaded quartz tube reactor described in step (1) is placed in a fixed bed reactor, and then the reducing mixed gas is continuously introduced at 600° C. for 1 hour, and then the reaction gas is introduced, and the temperature is controlled at 550° C. to 600° C. to carry out propane dehydrogenation to produce propylene.

9. The method according to claim 8, characterized in that: The volume content of the reducing mixed gas component in step (2) is 5% H2, 95% Ar; the volume content of the reaction gas component is 20.02% C3H8, 19.93% H2, 60.05% N2; the heating rate of the fixed bed reactor is 5°C / min.

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