Preparation method of surface-functionalized ligand self-assembled coated Pt-based catalyst and application of surface-functionalized ligand self-assembled coated Pt-based catalyst in propane dehydrogenation

Abstract

The invention discloses a preparation method of a surface functionalized ligand self-assembled coated Pt-based catalyst and an application of the surface functionalized ligand self-assembled coated Pt-based catalyst in propane dehydrogenation. The catalyst is prepared by a three-step coupling process of ligand metal chelation, in-situ crystallization and high-temperature reduction. A silane ligand is introduced to carry out self-assembly coating on metal, a metal-ligand electron transfer channel is established, the electron density of the metal surface is improved, the migration and agglomeration phenomena of the metal at high temperature are inhibited, and a steric hindrance protection layer is formed. Under the synergistic effect of sulfydryl (-SH) and siloxy (-OCH3) in the bifunctional ligand, surface passivation of metal nanoparticles and chemical bonding with a substrate (molecular sieve) are achieved at the same time, and the phenomenon that Pt migrates and agglomerates due to high surface free energy in a high-temperature environment for a long time is improved. The Pt-based catalyst prepared by the method shows excellent activity and durability in PDH catalytic reaction, and the synthesis method provides reliable technical support for catalyst performance optimization.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial catalyst preparation, and particularly relates to a preparation method for a surface-functionalized ligand self-assembled coated Pt-based catalyst and its application in propane dehydrogenation. Background Art

[0002] Propylene is the second most important petrochemical raw material in the chemical industry and is widely used in the production of various chemical products. With the continuous expansion of the scale of the downstream industries of propylene, the market demand for propylene is also increasing continuously. The propylene production in the traditional petrochemical industry has become increasingly difficult to meet the production needs.

[0003] In recent years, with the continuous optimization of the propylene production process by enterprises and the emergence of new processes, the propylene production capacity of each enterprise has been significantly improved, and the production of propylene has also continued to increase. The propane direct dehydrogenation to propylene (PDH) process is considered to be one of the most promising methods for future propylene production. First of all, propylene is the main product in this process, and there are fewer by-products, so the total yield of propylene is much higher than that of the traditional propylene production process. Secondly, with the exploitation of shale gas, the supply of propane has increased and its price is lower than that of coal and petroleum, which provides a good development opportunity for propane catalytic dehydrogenation to propylene. At present, the commonly used PDH processes in industrial production are mainly the Oleflex and Catofin processes, which use Pt-based catalysts and Cr-based catalysts respectively. However, as the green economy has become the mainstream direction of the development of the chemical industry, the Cr-based catalysts that obviously cause environmental pollution no longer meet the current development trend, and their application prospects are thus limited. Pt-based catalysts are green catalysts, but problems such as their high cost, easy carbon deposition, and unstable catalytic performance cannot be ignored. Therefore, developing an efficient, stable and low-cost Pt-based catalyst has become the key to promoting the development of PDH technology.

[0004] The PDH reaction is a typical endothermic reaction and is restricted by thermodynamics. The most favorable reaction conditions are high temperature and low pressure environments. In this reaction, propane is directly dehydrogenated to form propylene. Since the reaction is carried out under high temperature conditions, the C-C bond is more easily activated than the C-H bond in this environment. Therefore, in the reaction process, side reactions such as hydrogenolysis, cracking, and hydrogenation are often inevitable. These side reactions will not only reduce the selectivity of propylene, but also cause olefin polymerization at high temperatures, and then form coke. The formed coke will cover the active sites and block the catalyst pores, resulting in a gradual decline in the reaction activity of the catalyst. Therefore, how to inhibit the agglomeration and coking problems of catalytically active metals at high temperatures has always been a difficult point in the PDH reaction.

[0005] In view of the above problems, Patent CN202311839800.8 discloses a single-metal Pt-based catalyst with modified silicon carbide as the carrier. The catalyst uses a simple impregnation method to impregnate the Pt precursor solution on the non-acidic silicon carbide carrier, eliminating the negative effect of acid catalysis, inhibiting side reactions, facilitating the improvement of propylene selectivity, and reducing the amount of carbon deposition. Patent CN202211690361.4 once disclosed a Pt-based catalyst with ZrO2-Al2O3 double oxide as the carrier. The ZrO2-Al2O3 double oxide carrier was prepared by the precipitation crystallization method, and then the Pt-containing solution was impregnated on the carrier by the incipient wetness impregnation method. After drying and calcination, the Pt / ZrO2-Al2O3 catalyst was obtained. The addition of ZrO2 changed the interaction between the product and reactant and the active center, thereby improving the propylene selectivity and carbon deposition resistance ability, and ensuring good reaction stability of the catalyst under high-temperature conditions. Patent CN201810400639.7 discloses a supported nano-Pt catalyst and its preparation method. Using Al2O3 as the carrier and metal Pt as the active component, a nano-sol containing a Pt@CeO2 nano-core-shell structure was prepared. The unique Pt@CeO2 nano-core-shell structure can effectively prevent the aggregation of Pt nano-active components. The above catalysts have been greatly improved in performance compared with the traditional industrial Pt / Al2O3 catalyst in the PDH reaction. However, the catalytic activity and high-temperature stability that a single-metal Pt can bring are limited. In order to find a catalyst with more excellent comprehensive performance, it is necessary to further optimize and innovate on the existing preparation methods. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems of low activity, easy carbon deposition and easy sintering of the existing Pt-based catalysts for propane dehydrogenation to propylene under high-temperature reaction conditions. The formation of a large amount of carbon deposition will cover the active sites or sinter into, resulting in permanent deactivation of the catalyst. The present invention uses a multifunctional organosilane as a ligand, and introduces a promoter metal into the catalyst by the ligand protection method, effectively isolating the Pt active species and inhibiting the generation of side reactions and the migration and aggregation of metal nanoparticles. Under high-temperature conditions, the activity and selectivity are significantly improved compared with traditional Pt-based catalysts, and the metal stability is more excellent, having good industrial application prospects.

[0007] To achieve the above object, the present invention adopts the following technical solutions: A surface-functionalized ligand self-assembled coated Pt-based catalyst, the catalyst uses a molecular sieve as the carrier, and contains active metal Pt, promoter metal and silane ligand, wherein the promoter metal is one of the elements Sn, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge; the catalyst uses a silane ligand to self-assemble and coat Pt and the promoter metal to form a steric hindrance protection layer to inhibit the aggregation of Pt and the promoter metal under high-temperature conditions.

[0008] The preparation method of the above surface-functionalized ligand self-assembled coated Pt-based catalyst specifically includes the following steps: (1) Dissolve the main active metal Pt compound and the promoter metal compound in water respectively, and then add the silane ligand to each and mix and stir fully to obtain an active metal-ligand chelate solution and a promoter metal-ligand chelate solution; (2) Stir the silicon source, the template agent and water to obtain a homogeneous solution, and then add the active metal chelate solution and the promoter metal-ligand chelate solution obtained in step (1), and continue to stir to obtain a homogeneous mixed solution; wherein, based on the content of SiO2 in the silicon source, the molar ratio of the silicon source: the template agent: water: Pt: the promoter metal: the silane ligand is 1: (0.10 - 2.00): (1 - 100.0): (0.0001 - 0.01): (0.0001 - 0.01): (0.0001 - 0.01); (3) Slowly add the above mixed solution into the polytetrafluoroethylene lining of a stainless-steel hydrothermal reactor, then place the stainless-steel crystallization kettle in a high-temperature oven, crystallize statically for a certain time to obtain a crystallized solid product, and obtain a catalyst precursor through centrifugation, washing multiple times and drying.

[0009] (4) Place the catalyst precursor in a fixed-bed reactor and introduce high-purity H2, heat it up to the reduction temperature according to a set heating rate program, keep it at a high temperature for a certain time, and then naturally cool it to room temperature to obtain the surface-functionalized ligand self-assembled coated Pt-based catalyst.

[0010] Further, in step (1), the silane ligand is any one or a mixture of several of 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropylmethyldiethoxysilane.

[0011] Further, in step (1), the main active metal component Pt compound is any one or a mixture of several of Pt(NO3)2(NH3)4 and H2PtCl6·6H2O; Further, in step (2), the silicon source is any one or a mixture of several of silica sol, fumed silica, and tetraethyl orthosilicate.

[0012] Further, in step (2), the template agent is any one or a mixture of several of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide.

[0013] Further, in step (3), the crystallization temperature is 90 - 190 °C, the crystallization time is 9 - 190 h; the drying temperature is 90 - 190 °C, and the drying time is 1 - 90 h.

[0014] Further, the reduction temperature described in step (4) is 100 - 900 °C, the reduction time is 1 - 9 h, and the heating rate is 2 °C·min -1 .

[0015] The present invention also discloses an application method of the above surface-functionalized ligand self-assembled coated Pt-based catalyst in the reaction of propane direct dehydrogenation to propylene. The specific process conditions are as follows: Pack the 20 - 60 mesh granular Pt-based catalyst in the constant temperature zone of a quartz tube fixed-bed reactor with an inner diameter of 12 mm. First, perform pretreatment in an H2 atmosphere at 100 - 800 °C, and then raise the temperature to the reaction temperature of 100 - 800 °C. Under the condition of a pure propane gas flow with WHSV = 4 - 2000 h -1 , carry out the catalytic dehydrogenation reaction.

[0016] The beneficial effects of the present invention are as follows: The present invention introduces promoter metals through a ligand protection method to modulate the interaction force between Pt nanoclusters and promoter metals and their surface electronic structures, so as to achieve the effect of isolating and anchoring Pt active species. Through the synchronous coordination-condensation of bifunctional ligands, an anchoring relationship among the active metal, promoter metal, and support is established. Among them, the mercapto group (-SH) in the ligand forms a covalent bond with the metal, constructing an electron transfer channel. The methoxy group (-OCH3) in the ligand first undergoes hydrolysis to generate a silanol group (-Si-OH), and then forms a Si-O-Si covalent bond with the support through a condensation reaction, realizing the stable combination of the metal and the support through a multi-stage reaction. The formation of chemical bonds prevents the migration of active nanoparticles and inhibits the agglomeration and coking of active metals. Moreover, the doped promoter metals provide electrons to the active metal, resulting in the rearrangement of the surface electrons of Pt. As a result, the surface electron cloud density of Pt decreases. When the electron cloud density is relatively low, the adsorption of the catalyst on coke and propylene molecules weakens, promoting the transfer of coke and the desorption of propylene, and improving the propylene selectivity during the reaction. This bifunctional ligand-mediated Pt-based catalyst exhibits excellent high-temperature conversion rate, selectivity, and anti-coking performance in the propane dehydrogenation reaction. The synthesis method of this catalyst provides reliable technical support for the performance optimization of propane dehydrogenation catalysts and has good industrialization prospects. Description of the Drawings

[0017] Figure 1 It is the X-ray diffraction pattern (XRD) of the catalysts in Comparative Example 1 and Examples 1 to 4.

[0018] Figure 2 It is a comparison chart of the catalytic performance of the catalysts prepared in Comparative Example 1 and Example 1; reaction conditions: temperature 585 °C, 100% C3H8, propane mass hourly space velocity WHSV = 4.72 h -1 .

[0019] Figure 3 Transmission electron microscope image (HADDF-STEM) of the catalyst prepared in Comparative Example 2.

[0020] Figure 4 Transmission electron microscope image (HADDF-STEM) of the catalyst prepared in Example 2. Detailed implementation manners

[0021] For a better understanding of the technical solution of the present invention, the following further describes in detail with specific examples and accompanying drawings, but does not limit the protection scope of the present invention.

[0022] In the described examples, the catalyst is named Pt x M x @S-1, where Pt represents the main active metal component; M represents the promoter metal component; and x represents the organic ligand. For example: The catalyst with both Pt and Mn promoter metals added with ligands is named Pt s Mn s @S-1; The catalyst without ligands added for both Pt and Mn promoters is named PtMn@S-1.

[0023] Comparative Example 1 (1) Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them together in 8 g of deionized water, stir for 3.0 h, and obtain a homogeneous solution after complete dissolution; (2) Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water, stir for 1 h to form a homogeneous solution; (3) Weigh 35 mg of anhydrous SnCl2 and dissolve it in 2.0 g of deionized water, stir for 1 h to obtain a homogeneous Sn-containing solution; (4) Mix the solutions in steps (1), (2) and (3), continue to stir together for 3 h to form a uniform mixed solution, and finally load the above mixed solution into the polytetrafluoroethylene inner lining of a stainless steel hydrothermal autoclave; (5) Place the stainless steel hydrothermal autoclave in an oven, heat from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash, and dry at 100 °C for 12 h, and grind to obtain the PtSn@S-1 catalyst powder precursor.

[0024] (6) Place the PtSn@S-1 catalyst powder precursor in a tubular furnace under a high-purity H2 atmosphere, and heat it to 600 °C at a heating rate of 2 °C·min -1 and maintain for 4 h for reduction to finally obtain the PtSn@S-1 catalyst.

[0025] Comparative Example 2 (1)Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them in 8 g of deionized water. Stir for 3.0 h until a homogeneous solution is obtained after complete dissolution. (2)Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water. Stir for 1 h to form a homogeneous solution. (3)Weigh 34 mg of anhydrous MnCl2 and dissolve it in 2.0 g of deionized water. After high-speed stirring for 1 h, a homogeneous Mn-containing solution is obtained. (4)Mix the solutions in steps (1), (2) and (3), continue to stir together for 3 h to form a homogeneous mixed solution. Finally, put the above mixed solution into the polytetrafluoroethylene liner of a stainless steel hydrothermal autoclave. (5)Place the stainless steel hydrothermal autoclave in an oven, heat it from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash and dry at 100 °C for 12 h to obtain the PtMn@S-1 catalyst powder precursor.

[0026] (6)Place the PtMn@S-1 catalyst powder precursor in a high-purity H2 atmosphere in a tubular furnace, heat it at a heating rate of 2 °C·min -1 to 600 °C and maintain for 4 h for reduction, and finally obtain the PtMn@S-1 catalyst.

[0027] Comparative Example 3 (1)Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them in 8 g of deionized water. Stir for 3.0 h until a homogeneous solution is obtained after complete dissolution. (2)Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water. Stir for 1 h to form a homogeneous solution, then slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and continue to stir for 3.0 h to obtain a homogeneous Pt-containing solution. (3)Weigh 35 mg of SnCl2 and dissolve it in 2.0 g of deionized water. Stir for 1 h to obtain a homogeneous Sn-containing solution. (4)Mix the solutions in steps (1), (2) and (3), continue to stir together for 3 h to form a homogeneous mixed solution. Finally, put the above mixed solution into the polytetrafluoroethylene liner of a stainless steel hydrothermal autoclave. (5)Place the stainless steel hydrothermal autoclave in an oven, heat it from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash and dry at 100 °C for 12 h to obtain the Pt s Sn@S-1 catalyst powder precursor.

[0028] (6)The Pt sThe Sn@S-1 catalyst powder precursor was placed in a tubular furnace under a high-purity H2 atmosphere and heated to 600 °C at a heating rate of 2 °C·min -1 and maintained at this temperature for 4 h for reduction, finally obtaining the Pt s Sn@S-1 catalyst.

[0029] Comparative Example 4 (1) Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them in 8 g of deionized water, stir for 3.0 h, and obtain a homogeneous solution after complete dissolution; (2) Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water, stir for 1 h to obtain a homogeneous Pt-containing solution; (3) Weigh 35 mg of SnCl2 and dissolve it in 2.0 g of deionized water, stir for 1 h to form a homogeneous solution, then slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and continue to stir for 3.0 h to obtain a homogeneous Sn-containing solution; (4) Mix the solutions in steps (1), (2), and (3), continue to stir for 3 h to form a uniform mixed solution, and finally place the above mixed solution into the polytetrafluoroethylene inner lining of a stainless steel hydrothermal autoclave; (5) Place the stainless steel hydrothermal autoclave in an oven, heat it from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash, and dry at 100 °C for 12 h to obtain the PtSn s @S-1 catalyst powder precursor.

[0030] (6) Place the PtSn s @S-1 catalyst powder precursor in a tubular furnace under a high-purity H2 atmosphere and heat it to 600 °C at a heating rate of 2 °C·min -1 and maintain at this temperature for 4 h for reduction, finally obtaining the PtSn s @S-1 catalyst.

[0031] Example 1 (1) Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them in 8 g of deionized water, stir for 3.0 h, and obtain a homogeneous solution after complete dissolution; (2) Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water, stir for 1 h to form a homogeneous solution, then slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and continue to stir for 3.0 h to obtain a homogeneous Pt-containing solution; (3) Weigh 35 mg of SnCl2 and dissolve it in 2.0 g of deionized water. After stirring for 1 h to form a homogeneous solution, slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and continue stirring for 3.0 h to obtain a homogeneous Sn-containing solution; (4) Mix the solutions from steps (1), (2) and (3), and continue stirring together for 3 h to form a uniform mixed solution. Finally, put the above mixed solution into the polytetrafluoroethylene inner liner of a stainless steel hydrothermal autoclave; (5) Place the stainless steel hydrothermal autoclave in an oven, heat it from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash and dry at 100 °C for 12 h to obtain the Pt s Sn s @S-1 catalyst powder precursor.

[0032] (6) Place the Pt s Sn s @S-1 catalyst powder precursor in a high-purity H2 atmosphere in a tubular furnace, and raise the temperature to 600 °C at a heating rate of 2 °C·min -1 and maintain for 4 h for reduction. Finally, obtain the Pt s Sn s @S-1 catalyst.

[0033] Example 2 (1) Weigh 16.48 g of TEOS and 16.24 g of TPAOH respectively and dissolve them in 8 g of deionized water. After stirring for 3.0 h until completely dissolved, obtain a homogeneous solution; (2) Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water. After stirring for 1 h to form a homogeneous solution, slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and stir for 3.0 h to obtain a homogeneous Pt-containing solution; (3) Weigh 34 mg of anhydrous MnCl2 and dissolve it in 2.0 g of deionized water. After stirring for 0.5 h, slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane, and after high-speed stirring for 1 h, obtain a homogeneous Mn-containing solution; (4) Mix the solutions in steps (1), (2) and (3), and continue stirring together for 3 h to form a uniform mixed solution. Finally, put the above mixed solution into the polytetrafluoroethylene inner liner of a stainless steel hydrothermal autoclave; (5) Place the stainless steel hydrothermal autoclave in an oven, heat it from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash and dry at 100 °C for 12 h to obtain the Pt s Mn s @S-1 catalyst powder precursor.

[0034] (6) Place the Pt s Mn s @S-1 catalyst powder precursor in a high-purity H2 atmosphere in a tubular furnace and heat it to 600 °C at a heating rate of 2 °C·min -1 and hold for 4 h for reduction to finally obtain the Pt s Mn s @S-1 catalyst.

[0035] Example 3 (1) Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them in 8 g of deionized water. After stirring for 3.0 h until completely dissolved, a homogeneous solution is obtained; (2) Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water. After stirring for 1 h, a homogeneous solution is formed, and then slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and continue stirring for 3.0 h to obtain a homogeneous Pt-containing solution; (3) Weigh 25 mg of FeCl3·6H2O and dissolve it in 2.0 g of deionized water. After stirring for 0.5 h, slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane, and after high-speed stirring for 1 h, a homogeneous Fe-containing solution is obtained; (4) Mix the solutions in steps (1), (2), and (3), continue stirring together for 3 h to form a homogeneous mixed solution, and finally place the above mixed solution into the polytetrafluoroethylene inner lining of a stainless steel hydrothermal autoclave; (5) Place the stainless steel hydrothermal autoclave in an oven and heat it from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash, and dry at 100 °C for 12 h to obtain the Pt s Fe s @S-1 catalyst powder precursor.

[0036] (6) Place the Pt s Fe s @S-1 catalyst powder precursor in a high-purity H2 atmosphere in a tubular furnace and heat it to 600 °C at a heating rate of 2 °C·min -1 and hold for 4 h for reduction to finally obtain the Pt s Fe s @S-1 catalyst.

[0037] Example 4 (1) Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them in 8 g of deionized water. After stirring for 3.0 h until completely dissolved, a homogeneous solution is obtained; (2) Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water. After stirring for 1 h to form a homogeneous solution, slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and continue stirring for 3.0 h to obtain a homogeneous Pt-containing solution; (3) Weigh 36 mg of CoCl2·6H2O and dissolve it in 2.0 g of deionized water. After stirring for 0.5 h, slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane, and after high-speed stirring for 1 h, obtain a homogeneous Co-containing solution; (4) Mix the solutions in steps (1), (2) and (3), continue stirring together for 3 h to form a homogeneous mixed solution, and finally put the above mixed solution into the polytetrafluoroethylene inner liner of a stainless steel hydrothermal autoclave; (5) Place the stainless steel hydrothermal autoclave in an oven, heat it from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash and dry at 100 °C for 12 h to obtain the Pt s Co s @S-1 catalyst powder precursor.

[0038] (6) Place the Pt s Co s @S-1 catalyst powder precursor in a high-purity H2 atmosphere in a tubular furnace, and raise the temperature to 600 °C at a heating rate of 2 °C·min -1 and maintain reduction for 4 h. Finally, obtain the Pt s Co s @S-1 catalyst.

[0039] Example 5 (1) Weigh 16.48 g of TEOS and 16.24 g of TPAOH respectively and dissolve them in 8 g of deionized water. After stirring for 3.0 h until completely dissolved, obtain a homogeneous solution; (2) Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water. After stirring for 1 h to form a homogeneous solution, slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and continue stirring for 3.0 h to obtain a homogeneous Pt-containing solution; (3) Weigh 36 mg of NiCl2·6H2O and dissolve it in 2.0 g of deionized water. After stirring for 0.5 h, slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane, and after high-speed stirring for 1 h, obtain a homogeneous Ni-containing solution; (4) Mix the solutions in steps (1), (2) and (3), continue stirring together for 3 h to form a homogeneous mixed solution, and finally put the above mixed solution into the polytetrafluoroethylene inner liner of a stainless steel hydrothermal autoclave; (5) Place the stainless - steel hydrothermal reactor in an oven, heat it from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash, and dry at 100 °C for 12 h to obtain the Pt s Ni s @S - 1 catalyst powder precursor.

[0040] (6) Place the Pt s Ni s @S - 1 catalyst powder precursor in a high - purity H2 atmosphere in a tubular furnace, heat it at a heating rate of 2 °C·min -1 to 600 °C and maintain for 4 h for reduction, and finally obtain the Pt s Ni s @S - 1 catalyst.

[0041] Example 6 (1) Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them in 8 g of deionized water, stir for 3.0 h, and obtain a homogeneous solution after complete dissolution; (2) Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water, stir for 1 h to form a homogeneous solution, then slowly add 0.5 g of 3 - mercaptopropylmethyldimethoxysilane and continue stirring for 3.0 h to obtain a homogeneous Pt - containing solution; (3) Weigh 40 mg of CuCl2·2H2O and dissolve it in 2.0 g of deionized water, stir for 0.5 h, then slowly add 0.5 g of 3 - mercaptopropylmethyldimethoxysilane, and after high - speed stirring for 1 h, obtain a homogeneous Cu - containing solution; (4) Mix the solutions in steps (1), (2), and (3), continue stirring for 3 h to form a uniform mixed solution, and finally load the above - mentioned mixed solution into the polytetrafluoroethylene liner of the stainless - steel hydrothermal reactor; (5) Place the stainless - steel hydrothermal reactor in an oven, heat it from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash, and dry at 100 °C for 12 h to obtain the Pt s Cu s @S - 1 catalyst powder precursor.

[0042] (6) Place the Pt s Cu s @S - 1 catalyst powder precursor in a high - purity H2 atmosphere in a tubular furnace, heat it at a heating rate of 2 °C·min -1 to 600 °C and maintain for 4 h for reduction, and finally obtain the Pt s Cu s @S - 1 catalyst.

[0043] Example 7 (1)Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them in 8 g of deionized water, stir for 3.0 h, and obtain a homogeneous solution after complete dissolution; (2)Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water, stir for 1 h to form a homogeneous solution, then slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and continue to stir for 3.0 h to obtain a homogeneous Pt-containing solution; (3)Weigh 31 mg of anhydrous ZnCl2 and dissolve it in 2.0 g of deionized water, stir for 0.5 h, then slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane, and after high-speed stirring for 1 h, obtain a homogeneous Zn-containing solution; (4)Mix the solutions in steps (1), (2), and (3), continue to stir together for 3 h to form a uniform mixed solution, and finally load the above mixed solution into the polytetrafluoroethylene inner liner of a stainless steel hydrothermal autoclave; (5)Place the stainless steel hydrothermal autoclave in an oven, heat it from room temperature to 170 °C and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash, and dry at 100 °C for 12 h to obtain the Pt s Zn s @S-1 catalyst powder precursor.

[0044] (6)Place the Pt s Zn s @S-1 catalyst powder precursor in a high-purity H2 atmosphere in a tubular furnace, heat it to 600 °C at a heating rate of 2 °C·min -1 and maintain for 4 h for reduction, and finally obtain the Pt s Zn s @S-1 catalyst.

[0045] Example 8 (1)Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them in 8 g of deionized water, stir for 3.0 h, and obtain a homogeneous solution after complete dissolution; (2)Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water, stir for 1 h to form a homogeneous solution, then slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and continue to stir for 3.0 h to obtain a homogeneous Pt-containing solution; (3)Weigh 55 mg of anhydrous Ga(NO3)3 and dissolve it in 2.0 g of deionized water, stir for 0.5 h, then slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane, and after high-speed stirring for 1 h, obtain a homogeneous Ga-containing solution; (4) Mix the solutions in steps (1), (2), and (3), and continue stirring together for 3 h to form a homogeneous mixed solution. Finally, transfer the above mixed solution into the polytetrafluoroethylene liner of a stainless-steel hydrothermal autoclave; (5) Place the stainless-steel hydrothermal autoclave in an oven, heat it from room temperature to 170 °C, and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash, and dry at 100 °C for 12 h to obtain the Pt s Ga s @S-1 catalyst powder precursor.

[0046] (6) Place the Pt s Ga s @S-1 catalyst powder precursor in a tubular furnace under a high-purity H2 atmosphere, and heat it to 600 °C at a heating rate of 2 °C·min -1 and hold for 4 h for reduction, finally obtaining the Pt s Ga s @S-1 catalyst.

[0047] Example 9 (1) Weigh 16.48 g of TEOS and 16.24 g of TPAOH and dissolve them in 8 g of deionized water, stir for 3.0 h, and obtain a homogeneous solution after complete dissolution; (2) Weigh 40 mg of H2PtCl6·6H2O and dissolve it in 2.0 g of deionized water, stir for 1 h to form a homogeneous solution, then slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane and continue stirring for 3.0 h to obtain a homogeneous Pt-containing solution; (3) Weigh 44 mg of anhydrous GeCl4 and dissolve it in 2.0 g of deionized water, stir for 0.5 h, then slowly add 0.5 g of 3-mercaptopropylmethyldimethoxysilane, and after high-speed stirring for 1 h, obtain a homogeneous Ge-containing solution; (4) Mix the solutions in steps (1), (2), and (3), and continue stirring together for 3 h to form a homogeneous mixed solution. Finally, transfer the above mixed solution into the polytetrafluoroethylene liner of a stainless-steel hydrothermal autoclave; (5) Place the stainless-steel hydrothermal autoclave in an oven, heat it from room temperature to 170 °C, and maintain static hydrothermal reaction crystallization for 3 days. After the crystallization is completed, cool, centrifuge, wash, and dry at 100 °C for 12 h to obtain the Pt s Ge s @S-1 catalyst powder precursor.

[0048] (6) Place the Pt s Ge s @S-1 catalyst powder precursor in a tubular furnace under a high-purity H2 atmosphere, and heat it to 600 °C at a heating rate of 2 °C·min -1The heating rate was increased to 600 °C and maintained for 4 h for reduction, and finally Pt was obtained. s Ge s @S-1 catalyst.

[0049] The above catalyst was filled in the isothermal zone of a quartz tube fixed-bed reactor with an inner diameter of 12 mm. It was first pretreated in a H2 atmosphere at 550 °C, and then the temperature was raised to 585 °C for the reaction temperature. Under the condition of a pure propane gas flow with WHSV = 4.72 h -1 for catalytic dehydrogenation reaction.

[0050] Table 1 Comparison of catalytic performance of Pt-based catalysts modified with different heteroatoms Note: Reaction temperature 585 °C; Reaction raw material: 100% C3H8; Propane mass hourly space velocity WHSV = 4.72 h -1 Figure 1 XRD patterns of the catalysts in Comparative Example 1 and Examples 1-4 are shown. It can be seen from the figure that the self-assembled coated Pt-based catalyst synthesized with a multifunctional ligand has a regular MFI configuration zeolite structure, and no characteristic diffraction peaks of the main active component Pt, promoter metal M and their oxides are found, indicating that a highly dispersed heteroatom-modified Pt-based catalyst has been successfully synthesized. Figure 2 The PDH performance of the catalysts in Comparative Example 1 and Example 1 is shown. Combining the detailed data in Table 1, it can be found that the catalyst prepared by the new method has significant improvements in both catalytic activity and high-temperature durability. In addition, by comparing the reaction activity data of Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Example 1 and Example 2, it can be further found that in the absence of silane ligand, neither the active metal nor the promoter metal can effectively exert their catalytic and co-catalytic effects. Figure 3 and Figure 4 The HADDF-STEM images of Comparative Example 2 and Example 2 are shown respectively. The results show that under the condition of not changing the content of the active metal, the metal particle size (1.0 - 1.2 nm) of the Pt-based catalyst prepared by the multifunctional ligand self-assembled coating strategy is significantly smaller than that of the PtMn@S-1 catalyst prepared without organic ligand (7.8 - 8.0 nm). The above experimental results fully prove that the Pt-based catalyst prepared based on the multifunctional ligand self-assembled coating strategy has significant advantages in high-temperature PDH catalytic reaction. The synchronous coordination-condensation effect between the metal and the ligand constructs an anchoring relationship among the active metal, the promoter metal and the support, effectively inhibiting the migration and aggregation of Pt nanoclusters under high-temperature conditions. Under the synergistic effect of the metal and the support, the activity and stability of the catalyst under high-temperature conditions are significantly improved.

[0051] The above is only a preferred embodiment of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A surface-functionalized ligand self-assembled coated Pt-based catalyst, characterized in that: The catalyst uses a molecular sieve as a carrier and comprises an active metal Pt element, an auxiliary metal and a silane ligand, wherein the auxiliary metal is one of Sn, Mn, Fe, Co, Ni, Cu, Zn, Ga and Ge elements; the catalyst uses a silane ligand to self-assemble and coat Pt and the auxiliary metal to form a steric hindrance protective layer to inhibit the agglomeration of Pt and the auxiliary metal under high temperature conditions.

2. The preparation method of the surface-functionalized ligand self-assembled coated Pt-based catalyst according to claim 1, wherein The specific steps include: (1) dissolving the main active metal Pt compound and the auxiliary metal compound in water respectively, and then adding the silane ligand to each of them, mixing and stirring them thoroughly to obtain an active metal-ligand chelating solution and an auxiliary metal-ligand chelating solution; (2) Stirring the silicon source, template and water to obtain a uniform solution, then adding the active metal chelate solution and the auxiliary metal-ligand chelate solution obtained in step (1), mixing and stirring to obtain a uniform mixed solution; wherein the silicon source is based on the content of SiO2, and the molar ratio of silicon source: template: water: Pt: auxiliary metal: silane ligand is 1: (0.10-2.00): (1-100.0): (0.0001-0.01): (0.0001-0.01): (0.0001-0.01); (3) slowly adding the mixed solution into a stainless steel hydrothermal autoclave and placing it in a high-temperature oven to obtain a crystallized solid product through static crystallization, and then centrifuging, washing and drying to obtain a catalyst precursor; (4) placing the catalyst precursor in a fixed bed reactor and introducing high-purity H2, heating the reactor to a reduction temperature and maintaining the temperature for a period of time, and then naturally cooling the reactor to room temperature to obtain the surface functionalized ligand self-assembled coated Pt-based catalyst.

3. The preparation method according to claim 2, wherein: In step (1), the silane ligand is any one of 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldiethoxysilane, or a mixture of several thereof.

4. The preparation method according to claim 2, characterized in that: The main active metal component Pt compound in step (1) is any one of Pt(NO3)2(NH3)4 and H2PtCl6·6H2O or a mixture of several thereof.

5. The preparation method according to claim 2, characterized in that: The silicon source in step (2) is any one of silica sol, white carbon black, and ethyl orthosilicate, or a mixture of several of them.

6. The preparation method according to claim 2, characterized in that: The template agent in step (2) is any one of tetramethylammonium hydroxide, tetraethylammonium hydroxide and tetrapropylammonium hydroxide, or a mixture of several of them.

7. The preparation method according to claim 2, characterized in that: In step (3), the crystallization temperature is 90-190° C., and the crystallization time is 9-190 h; the drying temperature is 90-190° C., and the drying time is 1-90 h.

8. The preparation method according to claim 2, characterized in that: The reduction temperature described in step (4) is 100 to 900 °C, the reduction time is 1 to 9 h, and the heating rate is 2 °C·min -1 .

9. The preparation method according to any one of claims 1 to 8 obtains a surface functionalized ligand self-assembled coated Pt-based catalyst.

10. Use of the surface functionalized ligand self-assembled coated Pt-based catalyst as claimed in claim 9 in direct dehydrogenation of propane to propylene.

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