In-situ carbon-modified Pt composite catalyst, preparation method, and application thereof

Abstract

The present invention belongs to the field of catalytic oxidation technology, and discloses a Pt composite catalyst modified in situ and its preparation method and application. The present invention introduces a Pt precursor into the confined space of SBA-15 and template P123 by solid phase grinding-solution infiltration method, calcines the template in an inert atmosphere, and prepares a carbon-modified Pt loaded SBA-15 catalyst in situ, and the obtained catalyst controls the particle size of Pt nanoparticles using the confinement effect of SBA-15, and in situ modifies carbon species in the SBA-15 pores, greatly improving the hydrophobicity of the catalyst carrier. In addition, the prepared catalyst can achieve a complete oxidation of ethylene for more than 7h at a maximum of 0°C, and after 20h, it can still maintain an astonishing 81.5% ethylene conversion and 71.6% carbon dioxide yield, with excellent catalytic ethylene oxidation performance.

Description

Technical Field

[0001] The present invention relates to the technical field of catalytic oxidation, and in particular to an in-situ carbon-modified Pt composite catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Ethylene, a small molecule VOC, is a hormone that naturally triggers plant maturation and aging. It can be used as a ripening agent in the production and cultivation of fruits and vegetables, but it is also a major factor in their deterioration during storage and transportation. The threshold level for ethylene to promote aging and spoilage in fruits and vegetables is well below 5 ppb, yet in the real world, accumulated ethylene levels consistently exceed 5 ppb. Due to high levels of vehicle exhaust emissions and the natural accumulation of ethylene during plant growth and development, ethylene levels in urban areas can reach 500-700 ppb. This makes fresh fruits and vegetables susceptible to environmental ethylene during storage and transportation, causing rapid spoilage and resulting in food waste. Therefore, removing ethylene from the storage and transportation environment is essential to extend the shelf life of fruits and vegetables.

[0003] Currently, the main methods for ethylene removal include genetic modification, adsorption, direct oxidation, and catalytic oxidation. Genetic modification can inhibit endogenous ethylene production, but it cannot treat exogenous ethylene and cannot fundamentally address product losses caused by exogenous ethylene. Furthermore, genetic modification may affect the quality and taste of fruits and vegetables. Adsorption methods, which utilize adsorbents such as zeolites and carbon-based materials to remove ethylene from the environment through physical or chemical adsorption, have been studied and applied to small packaging bags. However, most adsorption methods suffer from poor selectivity, limited adsorption capacity, and the need for frequent adsorbent replacement, limiting their practical application. Direct oxidation, with potassium permanganate and ozone oxidation being common, can quickly and effectively remove ethylene. However, due to the high toxicity of the oxidants and the generation of unwanted byproducts during the oxidation process, it has been gradually phased out. Catalytic oxidation methods include thermal, photocatalytic, and plasma catalytic oxidation. Traditional thermal catalytic oxidation requires only a catalyst to remove ethylene, but the reaction typically requires temperatures of 200–300°C, making it rarely used for ethylene removal in storage and transportation environments. Photocatalytic oxidation requires the use of a catalyst to absorb ultraviolet radiation, generating electron-hole pairs to oxidize ethylene. However, low quantum efficiency and complex processes make it challenging to implement in practice. Plasma-catalyzed oxidation utilizes a variety of plasma-induced, highly oxidizing species, including fast electrons, free radicals, and ions, to effectively remove ethylene. However, high energy requirements and poor CO2 selectivity remain challenges that need to be addressed in practical applications.

[0004] In 2006, Ahn et al. reported a Au / Co3O4 catalyst prepared by a precipitation deposition method, which lowered the temperature for complete catalytic ethylene oxidation to 190°C. This research gradually aroused people's strong interest in low-temperature catalytic ethylene oxidation and led to a series of research and exploration. Subsequently, Kumar et al. used kinetic formulas to calculate that Pd / SiO2 catalysts can completely oxidize ethylene at 150-200°C. Imanaka et al. also used a wet impregnation method to prepare a 3wt% Pt / Ce 0.64 Zr 0.16 Bi 0.20 O 1.90 / γ-Al2O3 catalyst, achieving complete oxidation of ethylene below 100°C. The temperature at which the 2wt% Au / Co3O4 catalyst prepared by Li et al. completely converted 1050ppm of ethylene was 160°C. It was also found that the ethylene conversion rate was 7.4% at 20°C. Based on this, Ma et al. prepared mesoporous Co3O4 using the nanocasting method, which had higher catalytic activity for ethylene. The (110) crystal face of Co3O4 had a significant effect on ethylene oxidation. 2.5wt% Au / Co3O4 (3D) even had a conversion activity of 76% for 50ppm of ethylene at 0°C. Xue et al. also found that Au / Co3O4 nanorods showed extraordinary catalytic activity, achieving a catalytic conversion of 93.7% for 50ppm of ethylene at 0°C. These studies have successively proved that low-temperature catalytic oxidation of ethylene is possible, and its high efficiency, low cost, mild reaction conditions, and reusable catalysts make it unique in the field of ethylene removal. In recent years, a series of studies published by Fukuoka and his team have shown that Pt-based catalysts have excellent low-temperature catalytic ethylene oxidation capabilities, especially Pt-loaded mesoporous silica materials such as Pt / MCM-41 and Pt / SBA-15. At the same time, they found that physical adsorption of water at low temperatures has a significant effect on the catalytic oxidation performance of ethylene. The hydrophobic Pt / SBA-15 (800) catalyst prepared by high-temperature calcination can maintain a 100% conversion rate for 50 ppm ethylene for more than 1 hour at 0°C, and can still achieve a 45% ethylene conversion rate and a 28% carbon dioxide production rate after 300 minutes. Yang and his team believe that the B acid sites on the catalyst are the active sites for low-temperature catalytic ethylene oxidation. The Ag / ZSM-5 they prepared can maintain a 100% ethylene conversion rate for about 405 minutes for 100 ppm ethylene at 25°C. Recently, they prepared Pt / F-ZSM-5, which combines the acidity and water resistance of the catalyst, extending the initial 100% ethylene conversion rate to 11 hours. Furthermore, Kou et al. discovered that the size of noble metal nanoparticles is also a key factor in regulating the catalytic performance of ethylene oxidation. Compared with Pt / SBA-15 prepared by conventional impregnation, Pt / SBA-15 prepared by utilizing the confinement effect between the template and the mesoporous silica walls has smaller Pt nanoparticles. 5wt% Pt / SBA-15 can achieve complete conversion of 0.32vol% ethylene at 40°C.

[0005] Despite significant breakthroughs in low-temperature catalytic ethylene oxidation, practical storage and transportation environments typically require catalysts to operate at temperatures around 0°C, yet research on catalytic ethylene oxidation at this temperature remains relatively scarce. Furthermore, in addition to catalyst activity for ethylene conversion, catalyst stability, resistance to deactivation, and selectivity for carbon dioxide are equally important, and there remains significant room for improvement. Therefore, addressing these challenges remains a key research direction for low-temperature catalytic ethylene oxidation. Summary of the Invention

[0006] The purpose of the present invention is to provide an in-situ carbon-modified Pt composite catalyst and its preparation method and application, so as to solve the problems of high operating temperature, poor stability and poor resistance to deactivation of existing catalysts when catalyzing ethylene oxidation at low temperature.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing an in-situ carbon-modified Pt composite catalyst, comprising the following steps:

[0009] (1) mixing triblock copolymer P123, ethyl orthosilicate, and hydrochloric acid solution, performing a hydrothermal reaction, and drying to obtain SBA-15 containing a template;

[0010] (2) SBA-15 containing a template, water and a Pt precursor are mixed and impregnated, and then dried in a water bath, ground, calcined and reduced to obtain an in situ carbon-modified Pt composite catalyst.

[0011] Furthermore, in the preparation method of the in situ carbon-modified Pt composite catalyst, the mixing process in step (1) is specifically as follows: mixing the triblock copolymer P123 with the hydrochloric acid solution, stirring at 35-45°C for 2-5 hours until the triblock copolymer P123 is completely dissolved, adding tetraethyl orthosilicate dropwise, and continuing to stir at 35-45°C for 24-30 hours.

[0012] Furthermore, in the preparation method of the in situ carbon-modified Pt composite catalyst, in step (1), the mass ratio of the triblock copolymer P123 to the tetraethyl orthosilicate is 1:2.2~2.3; the concentration of the hydrochloric acid solution is 1.5~2.0 mol / L; the mass volume ratio of the triblock copolymer P123 to the hydrochloric acid solution is 1g:37~38mL.

[0013] Furthermore, in the method for preparing the in-situ carbon-modified Pt composite catalyst, in step (1), the temperature of the hydrothermal reaction is 90-100° C., and the time of the hydrothermal reaction is 48-54 hours.

[0014] Furthermore, in the preparation method of the in situ carbon-modified Pt composite catalyst, in step (2), the Pt precursor is an aqueous solution of H2PtCl6·6H2O, and the concentration of the aqueous solution of H2PtCl6·6H2O is 1g / 80~120mL; the mass of the Pt element contained in the Pt precursor is 1~5% of the mass of the SBA-15 containing the template.

[0015] Furthermore, in the preparation method of the in-situ carbon-modified Pt composite catalyst, in step (2), the mass volume ratio of the template-containing SBA-15 to the water is 0.9 g:20-30 mL; and the mixed impregnation time is 30-40 min.

[0016] Furthermore, in the preparation method of the in-situ carbon-modified Pt composite catalyst, in step (2), the water bath drying temperature is 85-95°C; the grinding time is 30-40 minutes; the calcination is carried out under a protective atmosphere, and the protective atmosphere is nitrogen; the calcination temperature is 600-700°C, and the calcination time is 6-10 hours.

[0017] Furthermore, in the preparation method of the in-situ carbon-modified Pt composite catalyst, in step (2), the calcination heating rate is 1-2°C / min; the reduction is carried out under a hydrogen atmosphere; the reduction temperature is 200-250°C, and the reduction time is 2-4h.

[0018] The present invention also provides an in-situ carbon-modified Pt composite catalyst prepared by the preparation method of the in-situ carbon-modified Pt composite catalyst.

[0019] The present invention also provides an application of an in-situ carbon-modified Pt composite catalyst, wherein the in-situ carbon-modified Pt composite catalyst is used for catalyzing ethylene oxidation.

[0020] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention introduces a Pt precursor into the confined space of SBA-15 and the template P123 by a solid-phase grinding-solution infiltration method, and then calcines the template in an inert atmosphere to prepare a carbon-modified Pt-loaded SBA-15 catalyst in situ. The resulting Pt / C-SBA-15 catalyst uses the SBA-15 confinement effect to control the particle size of Pt nanoparticles while in situ modifying carbon species within the SBA-15 pores, greatly improving the hydrophobicity of the catalyst support. TEM characterization results show that compared with Pt / SBA-15 prepared by the solid-phase grinding-solution infiltration method, Pt / C-SBA-15 with the same Pt ​​loading has a smaller Pt nanoparticle size.

[0022] (2) The Pt / C-SBA-15 catalyst prepared in the present invention can achieve complete oxidation of ethylene for more than 7 hours at 0°C, and can still maintain an astonishing 81.5% ethylene conversion rate and 71.6% carbon dioxide yield after 20 hours. The Pt / C-SBA-15 catalyst prepared in the present invention perfectly combines catalytic ethylene conversion activity, carbon dioxide selectivity and catalyst deactivation resistance, and also provides a new preparation idea for the future preparation of small-particle hydrophobic SBA-15 catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments or the prior art.

[0024] Figure 1 The test results of ethylene conversion and carbon dioxide yield of Application Examples 1 to 3 and Comparative Application Example 1, wherein (a) is a graph showing the change of ethylene conversion and carbon dioxide yield over time in the first 7 hours of Application Examples 1 to 3, (b) is a graph showing the change of ethylene conversion and carbon dioxide yield over time in the 20th hour of Application Examples 1 to 3, (c) is a graph showing the change of ethylene conversion and carbon dioxide yield over time in the first 7 hours of Application Example 2 and Comparative Application Example 1, and (d) is a graph showing the change of ethylene conversion and carbon dioxide yield over time in the 20th hour of Application Example 2 and Comparative Application Example 1;

[0025] Figure 2 The XRD patterns of the Pt catalysts obtained in Examples 1 to 3 and Comparative Example 1 are shown, wherein (a) is 2θ≤5.0° and (b) is 2θ≥10°;

[0026] Figure 3 TEM images of the Pt catalysts obtained in Examples 1 to 3 and Comparative Example 1, wherein (a), (b), and (c) are from Example 1, (d), (e), and (f) are from Example 2, (g), (h), and (i) are from Example 3, and (j), (k), and (l) are from Comparative Example 1; in addition, the histograms included in (a), (d), (g), and (j) are the particle size distribution diagrams of the respective catalysts.

[0027] Figure 4 Elemental C mapping diagrams of the Pt catalysts obtained in Examples 1 to 3 and Comparative Example 1, wherein (a, e) are elemental C mapping diagrams of Example 1, (b, f) are elemental C mapping diagrams of Example 2, (c, g) are elemental C mapping diagrams of Example 3, and (d, h) are elemental C mapping diagrams of Comparative Example 1;

[0028] Figure 5 The N2 adsorption-desorption isotherms and pore size analysis diagrams of the Pt catalysts obtained in Examples 1 to 3 and Comparative Example 1, wherein (a) is the N2 adsorption-desorption isotherm and (b) is the pore size distribution diagram;

[0029] Figure 6 TG-DSC test graphs of the Pt catalysts obtained in Examples 1 to 3 and Comparative Example 1, wherein (a) is a TG analysis graph and (b) is a DSC analysis graph;

[0030] Figure 7 The TPO test graphs of the Pt catalysts obtained in Examples 1 to 3 and Comparative Example 1;

[0031] Figure 8 The activation energy and turnover frequency of the Pt composite catalysts obtained in Examples 1 to 3 and Comparative Example 1, wherein (a) is the activation energy test result, and (b) is the turnover frequency test result;

[0032] Figure 9 The XPS test results of the Pt composite catalysts obtained in Examples 1 to 3 and Comparative Example 1 are shown, wherein (a) is the full XPS spectrum and (b) is the high-resolution spectrum in the Pt4f region;

[0033] Figure 10 The interaction test between the Pt composite catalysts obtained in Examples 1 to 3 and Comparative Example 1 and water is shown in Figure 1, where (a) is the H2O TPD-MS spectrum, (b) is the water absorption point density, (c) is the H2O adsorption-desorption isotherm, and (d) is the dynamic water vapor adsorption analysis diagram.

[0034] Figure 11 The contact angles of the Pt composite catalysts obtained in Examples 1 to 3 and Comparative Example 1 with water, wherein (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4;

[0035] Figure 12 The in-situ FTIR spectra of the Pt composite catalysts obtained in Examples 1 to 3 and Comparative Example 1 are shown, wherein (a) and (b) are from Example 1, (c) and (d) are from Example 2, (e) and (f) are from Example 3, and (g) and (h) are from Comparative Example 1;

[0036] Figure 13 Figure 2 is a model diagram of Pt nanocluster, where (a) is a truncated octahedron, (b) is a decahedron, and (c) is a Pt 79 (O2), (d) is Pt 22 (O2), (e) is Pt 22 (H2O), (f) is Pt 22 (H2O)2, (g) is Pt 79 (H2O)3;

[0037] Figure 14 Diagram of the action mechanism of Pt / C-SBA-15 material and Pt / SBA-15 material. DETAILED DESCRIPTION

[0038] The present invention provides a method for preparing an in-situ carbon-modified Pt composite catalyst, comprising the following steps:

[0039] (1) mixing triblock copolymer P123, ethyl orthosilicate, and hydrochloric acid solution, performing a hydrothermal reaction, and drying to obtain SBA-15 containing a template;

[0040] (2) SBA-15 containing a template, water and a Pt precursor are mixed and impregnated, and then dried in a water bath, ground, calcined and reduced to obtain an in situ carbon-modified Pt composite catalyst.

[0041] In the present invention, the mixing process of step (1) is preferably as follows: the triblock copolymer P123 is mixed with the hydrochloric acid solution, stirred at 35-45° C. for 2-5 hours until the triblock copolymer P123 is completely dissolved, and then ethyl orthosilicate is added dropwise, and the stirring is continued at 35-45° C. for 24-30 hours;

[0042] More preferably, the triblock copolymer P123 is mixed with a hydrochloric acid solution, stirred at 38-42° C. for 2-4 hours until the triblock copolymer P123 is completely dissolved, and then ethyl orthosilicate is added dropwise, and the stirring is continued at 38-42° C. for 24-27 hours;

[0043] More preferably, the triblock copolymer P123 is mixed with a hydrochloric acid solution, stirred at 40° C. for 4 h until the triblock copolymer P123 is completely dissolved, and then ethyl orthosilicate is added dropwise, and stirring is continued at 40° C. for 24 h.

[0044] In the present invention, in step (1), the mass ratio of the triblock copolymer P123 to the tetraethyl orthosilicate is preferably 1:2.2-2.3, more preferably 1:2.25-2.3, and more preferably 1:2.25.

[0045] In the present invention, in step (1), the concentration of the hydrochloric acid solution is preferably 1.5 to 2.0 mol / L, more preferably 1.6 to 2.0 mol / L, and more preferably 1.6 mol / L.

[0046] In the present invention, in step (1), the mass volume ratio of the triblock copolymer P123 to the hydrochloric acid solution is preferably 1 g:37-38 mL, more preferably 1 g:37.5-38 mL, and more preferably 1 g:37.5 mL.

[0047] In the present invention, in step (1), the temperature of the hydrothermal reaction is preferably 90-100°C, more preferably 95-100°C, and more preferably 100°C; the time of the hydrothermal reaction is preferably 48-54h, more preferably 48-51h, and more preferably 48h.

[0048] In the present invention, in step (2), the Pt precursor is preferably an aqueous solution of H2PtCl6·6H2O; the concentration of the aqueous solution of H2PtCl6·6H2O is preferably 1 g / 80-120 mL, more preferably 1 g / 100-120 mL, and more preferably 1 g / 100 mL.

[0049] In the present invention, in step (2), the mass of the Pt element contained in the Pt precursor is preferably 1 to 5% of the mass of the template-containing SBA-15, more preferably 2 to 4%, and even more preferably 3%.

[0050] In the present invention, in step (2), the mass volume ratio of the template-containing SBA-15 to the water is preferably 0.9 g:20-30 mL, more preferably 0.9 g:20-25 mL, and even more preferably 0.9 g:20 mL.

[0051] In the present invention, in step (2), the time for the mixed impregnation is preferably 30 to 40 minutes, more preferably 30 to 34 minutes, and even more preferably 30 minutes.

[0052] In the present invention, in step (2), the temperature of the water bath drying is preferably 85 to 95°C, more preferably 87 to 92°C, and even more preferably 90°C.

[0053] In the present invention, in step (2), the grinding time is preferably 30 to 40 minutes, more preferably 30 to 36 minutes, and even more preferably 30 minutes.

[0054] In the present invention, in step (2), the calcination is preferably carried out under a protective atmosphere, and the protective atmosphere is preferably nitrogen.

[0055] In the present invention, in step (2), the calcination temperature is preferably 600-700°C, more preferably 650-700°C, and more preferably 650°C; the calcination time is preferably 6-10h, more preferably 6-8h, and more preferably 6h.

[0056] In the present invention, in step (2), the heating rate of the calcination is preferably 1-2°C / min, more preferably 1-1.4°C / min, and more preferably 1°C / min.

[0057] In the present invention, in step (2), the reduction is preferably carried out under a hydrogen atmosphere; the reduction temperature is preferably 200-250°C, more preferably 200-225°C, and more preferably 200°C; the reduction time is preferably 2-4h, more preferably 2-3h, and more preferably 2h.

[0058] The present invention also provides an in-situ carbon-modified Pt composite catalyst prepared by the preparation method of the in-situ carbon-modified Pt composite catalyst.

[0059] The present invention also provides an application of an in-situ carbon-modified Pt composite catalyst, wherein the in-situ carbon-modified Pt composite catalyst is used for catalyzing ethylene oxidation.

[0060] In the present invention, the catalytic ethylene oxidation is preferably carried out at 0-20°C, more preferably 0-10°C, and even more preferably 0°C.

[0061] In the present invention, the ratio of the amount of the in-situ carbon-modified Pt composite catalyst to the content of ethylene in the air is preferably 0.3-0.5 g:50 ppm, more preferably 0.4-0.5 g:50 ppm, and even more preferably 0.4 g:50 ppm.

[0062] In the present invention, the in situ carbon-modified Pt composite catalyst is preferably passed through a 20-80 mesh sieve (further preferably a 40-80 mesh sieve, more preferably a 40-60 mesh sieve) before being used in the catalytic oxidation of ethylene, and then pretreated at 120-180°C (further preferably 140-160°C, more preferably 150°C) under a helium flow for 1-4 h (further preferably 2-3 h, more preferably 2 h).

[0063] In the present invention, the flow rate of the helium gas is preferably 10 to 40 mL min -1 , more preferably 20 to 30 mL·min -1 , more preferably 20 mL·min -1 .

[0064] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0065] Example 1

[0066] Example 1 provides a method for preparing an in-situ carbon-modified Pt composite catalyst, comprising the following steps:

[0067] (1) 8 g of triblock copolymer P123 was weighed and added to 300 mL of 1.6 mol / L HCl solution. The mixture was stirred at 40°C for 4 h until P123 was completely dissolved and the entire solution was uniformly milky white. Then, 18 g of tetraethylorthosilicate (TEOS) was added dropwise and stirred at 40°C for 24 h. The stirred reaction solution was transferred to a self-pressurized hydrothermal reactor and reacted at 100°C for 48 h. After cooling, the mixture was filtered, washed with deionized water until neutral, and dried at 80°C to obtain SBA-15 containing a template.

[0068] (2) Weigh 0.9 g of SBA-15 containing the template, add 20 mL of deionized water to disperse evenly, then add 2.389 mL of 1 g / 100 mL H2PtCl6·6H2O solution, soak and stir for 30 min, evaporate to dryness in a water bath at 90 °C, and then grind manually for 30 min. The evaporated and ground material is transferred to a tube furnace and heated to 650 °C at a heating rate of 1 °C / min under N2 atmosphere for calcination for 6 h. After cooling to room temperature, the calcined product is heated to 200 °C under H2 atmosphere for reduction for 2 h to obtain an in situ carbon-modified Pt composite catalyst, which is recorded as 1Pt / C-SBA-15.

[0069] Example 2

[0070] Example 2 provides a method for preparing an in situ carbon-modified Pt composite catalyst, which differs from Example 1 in that the amount of H2PtCl6·6H2O solution added in step (2) is 7.167 mL, and the other conditions are the same as those in Example 1, and is recorded as 3Pt / C-SBA-15.

[0071] Example 3

[0072] Example 3 provides a method for preparing an in situ carbon-modified Pt composite catalyst, which differs from Example 1 in that the amount of H2PtCl6·6H2O solution added in step (2) is 11.945 mL, and the other conditions are the same as those in Example 1, recorded as 5Pt / C-SBA-15.

[0073] Comparative Example 1

[0074] Comparative Example 1 provides a method for preparing a Pt composite catalyst, which differs from Example 1 in that: in step (2), the evaporated and ground material is transferred to a tubular furnace, raised to 300°C and calcined for 2 hours under high-purity air. Other conditions are the same as in Example 1, and are recorded as 3Pt / SBA-15.

[0075] Application Example 1

[0076] Application Example 1 provides an application of an in-situ carbon-modified Pt composite catalyst to catalyze ethylene oxidation in a fixed-bed flow reactor with an inner diameter of about 4 mm:

[0077] The 1Pt / C-SBA-15 catalyst of Example 1 was passed through a 40-60 mesh sieve, 0.4 g of which was placed in a U-shaped reaction tube and heated at 20 mL min -1 The mixture was pretreated at 150 °C for 2 h under helium flow; then the gas mixture (C2H4, 50 ppm; O2, 20%; N2, 5%; He, the balance; the flow rate of the gas mixture was 10 mL min -1 ) at 1500 mL·h -1 ·g -1 The space velocity (SV) was passed into the catalyst bed at 0°C for reaction; after the reaction was completed, the outlet gas was passed into an online gas chromatograph (3420A, equipped with a hydrogen flame ionization detector connected to a porapak-Q column and a nickel catalytic converter) for detection to test the outlet concentrations of C2H4 and CO2.

[0078] Application Example 2

[0079] Application Example 2 provides an application of an in-situ carbon-modified Pt composite catalyst. The difference from Application Example 1 is that the 1Pt / C-SBA-15 catalyst in Example 1 is replaced by the 3Pt / C-SBA-15 catalyst in Example 2, and other conditions remain unchanged.

[0080] Application Example 3

[0081] Application Example 3 provides an application of an in-situ carbon-modified Pt composite catalyst. The difference from Application Example 1 is that the 1Pt / C-SBA-15 catalyst in Example 1 is replaced by the 5Pt / C-SBA-15 catalyst in Example 3, and other conditions remain unchanged.

[0082] Comparative Application Example 1

[0083] Comparative Application Example 1 provides an application of an in-situ carbon-modified Pt composite catalyst. The difference from Application Example 1 is that the 1Pt / C-SBA-15 catalyst in Example 1 is replaced by the 3Pt / SBA-15 catalyst in Comparative Example 1, and other conditions remain unchanged.

[0084] Ethylene conversion = ([C2H4] in -[C2H4] out )×100 / [C2H4] in Formula 1;

[0085] Carbon dioxide production rate = [CO2] out ×100 / 2[C2H4] in Formula 2;

[0086] In Formula 1 and Formula 2, [C2H4] in is the initial concentration of C2H4, [C2H4]out is the outlet concentration of C2H4, [CO2] out is the outlet concentration of CO2.

[0087] The performance test of Pt / C-SBA-15 catalysts with different Pt loadings was completed at 0°C. During the reaction, the outlet gas was collected every 5 minutes to detect the outlet gas composition and calculate the concentration of each gas component. Figure 1 The graph of ethylene conversion and carbon dioxide production over time for the first 7 hours is shown, and the ethylene conversion and carbon dioxide production at the 20th hour are recorded. Figure 1 It can be seen from (a) and (b) that 1Pt / C-SBA-15 can maintain 100% ethylene conversion for 65 minutes at 0°C. After 65 minutes, the ethylene conversion rate decreases rapidly and gradually stabilizes over time. After 20 hours, the ethylene conversion rate is detected to be 20.6%. However, 3Pt / CSBA-15 and 5Pt / CSBA-15 can surprisingly maintain 100% ethylene conversion for more than 7 hours, and can still maintain 81.5% and 52.9% ethylene conversion rates after 20 hours. At the same time, the three catalysts of the embodiment can all detect the stable precipitation of CO2 gas. After 20 hours, the CO2 yields of 1Pt / CSBA-15, 3Pt / CSBA-15 and 5Pt / CSBA-15 are 8.9%, 71.6% and 40.3%, respectively. In order to study the role of carbon species in the catalyst, the present invention also prepared 3Pt / SBA-15 catalyst by a similar method as a comparison, as shown in FIG. Figure 1 As shown in (c) and (d). Compared with 3Pt / C-SBA-15, the ethylene conversion rate of 3Pt / SBA-15 began to decrease at 235 min, and the CO2 evolution rate also had a significant turning point. After 20 h, the ethylene conversion rate and CO2 yield stabilized at 63.3% and 55.3%, respectively. Based on the above observations, it is known that the best sample is 3Pt / C-SBA-15. By comparing it with 3Pt / SBA-15, it is known that the Pt / C-SBA-15 catalyst prepared by the solid phase grinding-solution infiltration method can maximize the use of the confinement effect of SBA-15, control the particle size of Pt nanoparticles, and in situ modify the carbon species to make the catalyst more hydrophobic, thereby achieving the optimal catalytic ethylene oxidation effect.

[0088] The Pt composite catalysts obtained in Examples 1 to 3 and Comparative Example 1 were subjected to XRD testing. The results are as follows: Figure 2 As shown. Figure 2It can be seen that the characteristic diffraction peaks of SBA-15 and Pt nanoparticles were detected in all four Pt composite catalysts. Among them, the characteristic peak positions of 0.96°, 1.56°, and 1.79° correspond to the (100), (110), and (200) crystal planes of SBA-15, respectively. The characteristic peak positions of 39.7°, 46.3°, and 67.6° correspond to the (111), (200), and (220) crystal planes of Pt nanoparticles, respectively. The peaks at 15° to 30° are attributed to the characteristic bulging peak of SBA-15. It is worth noting that the diffraction peak intensity of the (100) crystal plane of SBA-15 on 1Pt / C-SBA-15, 3Pt / C-SBA-15 and 5Pt / C-SBA-15 is much weaker than that of 3Pt / SBA-15. This is mainly due to the presence of carbon species causing lattice mismatch of the (100) crystal plane of SBA-15, which indirectly illustrates the successful modification of carbon species on the Pt / C-SBA-15 catalysts obtained in Examples 1 to 3. In addition, Figure 2 It can also be seen in (b) that Pt / C-SBA-15 with different Pt concentrations exhibits different Pt nanoparticle diffraction peak intensities. At the same time, 3Pt / C-SBA-15 and 3Pt / SBA-15 have almost the same Pt ​​characteristic peak intensities, indicating that 3Pt / C-SBA-15 and 3Pt / SBA-15 have similar Pt contents.

[0089] The Pt composite catalysts obtained in Examples 1 to 3 and Comparative Example 1 were subjected to TEM testing. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that the TEM image shows a clearer microstructure of the four Pt composite catalysts, and the clear microscopic pore structure confirms the successful synthesis of SBA-15, which is consistent with the XRD test results. Moreover, whether it is Pt / C-SBA-15 or Pt / SBA-15, the Pt nanoparticles are well loaded in the pores of SBA-15. This shows that the solid phase grinding-solution infiltration method of the present invention can make good use of the template P123 to disperse the Pt nanoparticles, give full play to the confinement effect of SBA-15, and thus obtain Pt particles with smaller particle size. Facts have proved that the smaller the particle size of the Pt nanoparticles, the higher the dispersion, and the more conducive to the catalytic oxidation of ethylene. The element mapping diagram of C (i.e. Figure 4 ) shows the uniform distribution of C on the surface of Pt / C-SBA-15, which is not visible in the image of Pt / SBA-15. In addition, the present invention also selected about 200 individual Pt nanoparticles of these four Pt composite catalysts for particle size statistics, such as Figure 3(a), (d), (g) and (j). From the particle size distribution statistics, it can be found that the particle size of the Pt particles on the in-situ carbon-modified Pt composite catalysts of Examples 1 to 3 increases with the increase of the Pt loading. Among them, the particle size of the corresponding Pt nanoparticles on 3Pt / CSBA-15 in Example 2 is 4.74nm, while the size of the Pt particles on 3Pt / SBA-15 in Comparative Example 1 is 5.27nm. Therefore, this preparation method of in-situ carbon-modified Pt-loaded SBA-15 catalyst also has a certain positive effect on the size control of Pt nanoparticles.

[0090] In order to confirm the positive effect of the preparation method on the size control of Pt nanoparticles, the present invention conducted specific surface area and pore size analysis on these four Pt composite catalysts. The results are as follows Figure 5 As shown in Table 1, all samples have Type IV isotherms with H1 hysteresis loops at relative pressures of 0.6 to 0.8, indicating that all samples have typical ordered mesoporous structures. Among them, 3Pt / SBA-15 has the largest specific surface area and pore volume, which are 778 m 2 ·g -1 and 1.21cm 3 ·g -1 The specific surface area and pore volume of the catalysts in Examples 1 to 3 are both 550 m 2 ·g -1 and 0.84cm 3 ·g -1 At the same time, Figure 5 The pore size distribution diagram also shows that the catalysts of Examples 1 to 3 have a double peak at 4 to 8 nm, while 3Pt / SBA-15 has a single peak at 4 to 8 nm. These phenomena all indicate that carbon has been successfully modified into the pores of SBA-15. It is worth noting that the average pore diameters of 1Pt / C-SBA-15, 3Pt / C-SBA-15 and 5Pt / C-SBA-15 are between 5.4 and 5.5 nm, while the average pore diameter of 3Pt / SBA-15 reaches 5.95 nm. This result well proves that due to the presence of carbon species, the pore size of carbon-modified SBA-15 is smaller, and thus it is more conducive to the formation of small-sized Pt nanoparticles when loading Pt.

[0091] Table 1. Specific surface area and pore size analysis results of the Pt composite catalysts obtained in Examples 1 to 3 and Comparative Example 1

[0092]

[0093] To accurately determine the amount of Pt metal loaded on each catalyst, as well as the carbon content of the carbon-containing catalysts, the present invention subjected the four Pt composite catalysts to ICP-AES and elemental analysis. The test results are shown in Table 2. The Pt nanoparticle contents loaded on 1Pt / C-SBA-15, 3Pt / C-SBA-15, and 5Pt / C-SBA-15 were 1.52 wt.%, 4.36 wt.%, and 7.26 wt.%, respectively. The Pt content loaded on 3Pt / SBA-15 was 4.37 wt.%, corresponding exactly to that of the 3Pt / CSBA-15 catalyst. The elemental analysis results in Table 2 indicate that the carbon contents of the carbon-containing catalysts of Examples 1 to 3 were 1.14 wt.%, 0.91 wt.%, and 1.34 wt.%, respectively, while no carbon species were detected on 3Pt / SBA-15, which is consistent with the XRD and specific surface area characterization results. Figure 6 TG-DSC, Figure 7 The TPO results also show that 1Pt / C-SBA-15, 3Pt / C-SBA-15, and 5Pt / C-SBA-15 have greater mass loss than 3Pt / SBA-15, and there is a more obvious exothermic process, which further confirms the presence of carbon species. Based on the TEM particle size statistics, the particle dispersion of these four Pt composite catalysts can be calculated using Equation 3:

[0094]

[0095] In formula 3, D is the particle dispersion; C Pt is the specific atomic concentration on the PtNP surface (1.30×10 19 atoms m -2 );M Pt is the molar mass of Pt (195.05 g·mol -1 );N A is Avogadro's constant (6.02×10 23 atoms mol -1 ); ρ is the density of Pt (2.145×10 7 g·m -3 );d(nm) is the average particle size D of Pt in TEM image p .

[0096] Table 2. Elemental analysis results of the Pt composite catalysts obtained in Examples 1 to 3 and Comparative Example 1

[0097]

[0098] The ethylene removal rate in the first 3 minutes of the reaction was selected as the initial reaction activity. The present invention controlled the reactant removal rate within 30%, plotted the Arrhenius curve, and calculated the activation energy. The reaction process at this stage had little effect on the catalyst, and it was approximately believed that the ethylene removal process conformed to a pseudo-first-order kinetic process. The specific reaction conditions were: temperature 0-20°C, catalyst dosage 5mg, and reaction gas composition of 50ppm C2H4, 20% O2, and 5% N 2 、He residue, 10mL·min -1 Gas flow rate, space velocity is 120000mL·h -1 ·g -1 According to the Arrhenius curve, the activation energies of 1Pt / C-SBA-15, 3Pt / C-SBA-15 and 5Pt / C-SBA-15 are as follows: Figure 8 (a) and Table 2. In addition, the turnover frequency (TOF) under this condition is also used to reflect the reaction activity of each catalyst single active site, as shown in Table 2 and Figure 8 As shown in (b), compared with 0.83h of 3Pt / SBA-15 -1 The TOF values ​​of 1Pt / C-SBA-15 and 3Pt / C-SBA-15 reached 0.98h -1 and 1.02h -1 This result directly demonstrates the superiority of this in situ carbon-modified Pt composite catalyst preparation method, which combines the confinement effect of SBA-15 with the simultaneous synthesis of a hydrophobic support, showing excellent catalytic ethylene oxidation ability.

[0099] The XPS test results of the Pt composite catalysts obtained in Examples 1 to 3 and Comparative Example 1 are as follows: Figure 9 As shown, Figure 9 The chemical composition and chemical state of each element on the sample surface are shown. From the full XPS spectra of these four Pt composite catalysts, the peaks of O1s, Si2s and Si2p can be clearly seen. The difference is that the peak of C1s was detected in 1Pt / C-SBA-15, 3Pt / C-SBA-15 and 5Pt / C-SBA-15 samples, but not in 3Pt / SBA-15 sample. The 4f spectrum of Pt shows that for these four Pt composite catalysts, the XPS spectrum can be deconvoluted into two peaks, one of which is located at a lower binding energy position corresponding to Pt4f 7 / 2 level, and the other one at a higher binding energy corresponds to Pt4f 5 / 2 Level. Pt4f 7 / 2 The peak position is concentrated at 70.9~71.2eV, Pt4f 5 / 2 The peak position is concentrated in 74.2~74.5eV, which is consistent with the metal Pt 0The standard peak positions of the four catalysts are close, indicating that the Pt on these four catalysts is loaded on SBA-15 in atomic form.

[0100] In order to clarify how each catalyst interacts with water, the present invention uses H2O TPD-MS to quantify the water adsorption sites on each Pt composite catalyst. The specific test process is detailed below. Figure 10 As shown in (a), all tested Pt composite catalysts exhibited similar water TPD patterns, with water desorption peaks in the range of 180–220 °C. However, it should be noted that 1Pt / C-SBA-15, 3Pt / C-SBA-15, and 5Pt / C-SBA-15 had similar adsorption amounts of water molecules, while 3Pt / SBA-15 adsorbed more water under the same conditions. Figure 10 (b) The water absorption point density data obtained by calculating the integral of the lower area of ​​each TPD curve from 100 to 500 ° C can also intuitively show that compared with Pt / C-SBA-15 with similar carbon content in Examples 1 to 3, Pt / SBA-15 has more water molecule adsorption sites, revealing that the presence of carbon species can significantly improve the overall hydrophobicity of the support and Pt composite catalyst, reduce the affinity level of water molecules and catalysts, thereby avoiding the influence of water molecules on the low-temperature catalytic ethylene oxidation reaction and improving the catalytic activity of the catalyst. Similar characterization results can also be obtained by Figure 10 (c) Dynamic water vapor adsorption analysis (DVS) shows that: the experimental setting temperature of the DVS test is 25℃, the experimental setting humidity gradient is from 0% to 95%, and the humidity interval is 10%. All Pt composite catalyst samples have type-Ⅳ adsorption isotherms with H1 hysteresis loops. Figure 10 (d) Compared with 3Pt / SBA-15, 1Pt / C-SBA-15, 3Pt / C-SBA-15 and 5Pt / C-SBA-15 showed weaker hygroscopicity and affinity with water molecules. In addition, the contact angle test ( Figure 11 ) also showed a similar hydrophilic and hydrophobic performance trend as H2O TPD and DVS. These characterization results collectively illustrate the feasibility and importance of this in situ carbon-modified Pt composite catalyst preparation method for regulating the hydrophobicity of Pt / SBA-15.

[0101] In order to better understand the reaction process, in situ FTIR was used to monitor the species changes on the surfaces of the four Pt composite catalysts in real time. The reaction conditions were adjusted to 25 °C, 800 ppm C2H4, 20% O2, 5% N2 and He balance, as shown in Figure 2. Figure 12 As shown in Figure 2, as the reaction time progressed, characteristic peaks of water molecules appeared simultaneously on 1Pt / C-SBA-15, 3Pt / C-SBA-15, and 3Pt / SBA-15 (v s(OH): 3000~3400cm -1 , δ s (OH): 1640cm -1 ). 3740cm -1 The negative band and v s The broad characteristics of (OH) indicate that the water molecules formed during the oxidation process are mainly stabilized by forming a hydrogen bond network with the Si-OH groups on the surface of SBA-15. It is worth noting that the v s (OH) and δ s The (OH) intensity is significantly weaker than that of 3Pt / SBA-15. No water molecules are even detected on the surface of 5Pt / C-SBA-15. This is consistent with the results of the previous H2O TPD, DVS and contact angle tests, proving that the modified carbon species plays a crucial role in regulating the hydrophobic atmosphere on the catalyst surface. When the reaction proceeds to 30s, the FTIR spectra of 3Pt / C-SBA-15 and 5Pt / C-SBA-15 show a peak at 2070cm -1 A more obvious Pt-CO absorption peak also appeared at 2070 cm -1 The absorption peak at 2040 cm -1 The absorption peak at 2040 cm-1 gradually increases, which is mainly due to the fact that water adsorption near the CO adsorption site will cause the Pt-CO vibration red shift due to electron donation. As the reaction continues, the absorption peak at 2040 cm-1 increases. -1 After the absorption peak at 2070cm reaches its peak, it gradually weakens until it disappears. This is because water molecules gradually occupy the active sites on the catalyst surface, causing the catalyst to eventually deactivate. During the entire reaction process, no Pt-CO absorption peak was found in the FTIR spectrum of 1Pt / C-SBA-15. This may be because the lower Pt loading makes the number of exposed Pt active sites smaller, and it is difficult to monitor the formation of the Pt-CO absorption peak under such high space velocity reaction conditions. No 2070cm -1 The Pt-CO absorption peak at 2040 cm-1 appears only after 60 s. -1 A weak absorption was detected at 3Pt / SBA-15, which indicates that for 3Pt / SBA-15 with strong hydrophilicity, water molecules are more easily adsorbed on its catalyst surface, resulting in rapid catalyst deactivation, and relatively poor activity and stability of the catalyst.

[0102] Taking into account that the adsorption and activation of O2 on the active site is a key step in the oxidation reaction, and the particle size of Pt nanoparticles is crucial for the catalytic oxidation of ethylene, the present invention selected two Pt nanocluster models of different sizes, namely a truncated octahedron (Oh) composed of 79 Pt atoms and a decahedron (Dh) composed of 22 Pt atoms, and performed O2 adsorption energy calculation, Pt-O bond length calculation and Mulliken charge analysis on them, as shown in Table 3. When an O2 is adsorbed on a face vertex of the Oh and Dh nanoclusters, the adsorption energy of O2 is -0.503eV and -1.042eV, respectively, which shows that O2 tends to be adsorbed on smaller-sized Pt nanoclusters. At the same time, according to the principle of minimum energy, the shorter Pt-O bond length (Pt 22 (O2) is Pt 79 (O2) is ) and more charge transfer of adsorbed molecules (Pt 22 (O2) is 0.334, Pt 79 (O2) is 0.153) which also shows that O2 molecules are more stable when adsorbed on smaller-sized Pt nanoclusters. According to the calculation results, compared with 3Pt / SBA-15, 3Pt / C-SBA-15 with a smaller Pt particle size has a stronger affinity with O2, making it easier to form reactive oxygen species and having better catalytic activity in ethylene oxidation. More importantly, when Dh nanoclusters were selected and water molecules were introduced to study the competitive adsorption of O2 and H2O on Pt nanoparticles, it was found that the adsorption energy of a single water molecule on the same vertex Pt atom was -1.851eV, which is much lower than the adsorption energy of a single O2 of -1.042eV. At the same time, Pt 22 The Pt-O bond length of (H2O) is Lower than Pt 22 (O2) Pt 22 The charge transfer between H2O is 0.956, which is higher than that of Pt 22 When there is one more H2O adsorbed on the adjacent Pt atom, the average adsorption energy becomes -1.406eV. When the amount of H2O adsorbed reaches three, the average adsorption energy increases to -1.318eV, which is still lower than that of Pt 22 (O2) is much lower. The average Pt-O bond length and Pt 22The charge transfer between Pt and H2O also shows a similar trend of change. These calculation results all indicate that the affinity of Pt for H2O is much stronger than that for Pt and O2, and the adsorption of H2O on Pt particles is more stable and strong. Corresponding to the aforementioned in situ FTIR observations, the active sites on the catalyst are covered by more and more water molecules as the reaction proceeds, and the catalytic activity gradually decreases. Combined with the activity test and hydrophilic and hydrophobic characterization of the catalyst, it can be seen that Pt / C-SBA-15 has more water-resistant Pt active sites, which enables both 3Pt / C-SBA-15 and 5Pt / C-SBA-15 catalysts to achieve 100% ethylene conversion stability for more than 7 hours, and after 20 hours, 3Pt / C-SBA-15 still has an ethylene conversion rate of 81.5% and a carbon dioxide yield of 71.6%. Such excellent catalytic performance has never been seen in previous research.

[0103] Table 3. O2 adsorption energy, Pt-O bond length, and Mulliken charge analysis of several Pt nanoclusters

[0104]

[0105]

[0106] Figure 14A possible mechanism for the enhanced catalytic stability, ethylene conversion, and carbon dioxide yield of the Pt / C-SBA-15 material was demonstrated. Compared with direct removal of the template P123 in high-purity air, high-temperature calcination and carbonization of P123 in an inert atmosphere can leave a thin carbon layer within the pores of SBA-15. This not only cooperates with the confinement effect of SBA-15 to further restrict the growth of Pt nanoparticles within the pores, but more importantly, this hydrophobic carbon layer significantly reduces the affinity of the support and the catalyst as a whole for water molecules, greatly reducing the negative impact of water molecules on the catalyst during the reaction. Without the modification of the carbon layer, H2O can easily enter the pores of SBA-15 and win the competition with O2 for adsorption on the Pt nanoparticles. H2O continuously occupies the active sites of the catalyst, preventing O2 from being successfully activated on the catalyst surface, reducing catalyst activity, and preventing the reaction from proceeding stably (Scheme 1). When the Pt nanoparticles in the pores are surrounded by a thin layer of carbon, the enhanced hydrophobic atmosphere prevents H2O from being easily adsorbed on its surface. O2 is stably adsorbed on the Pt particles and activated, then combines with ethylene molecules to form CHO through a transition state, which is further decomposed into CO. CO is eventually oxidized to CO2 in a continuous oxidizing atmosphere and precipitated (Scheme 2). It should be noted that some carboxylate by-products are still formed during the entire reaction process, which can be seen from the v detected in the in situ FTIR spectrum of 5Pt / C-SBA-15 without the influence of water peaks. as (COO)(1585cm -1 and 1664cm -1 ) has been proven.

[0107] In summary, the present invention successfully synthesized an in-situ carbon-modified Pt composite catalyst and investigated its catalytic oxidation performance for 50 ppm ethylene at 0°C. According to performance test results, both 3Pt / C-SBA-15 and 5Pt / C-SBA-15 were able to maintain 100% ethylene conversion for more than 7 hours, while 3Pt / C-SBA-15 still had an ethylene conversion of 81.5% and a carbon dioxide yield of 71.6% after 20 hours. In contrast, the ethylene conversion of 3Pt / SBA-15 in Comparative Example 1 only began to decrease after approximately 4 hours, and after 20 hours, the ethylene conversion and carbon dioxide yield stabilized at 63.3% and 55.3%, respectively. This is because the in-situ modified carbon can synergize with the confinement effect of SBA-15 to further limit the growth of Pt nanoparticles, while greatly enhancing the hydrophobicity of the catalyst support and reducing the overall affinity of the catalyst for water molecules. Small-sized Pt nanoparticles can more easily bind to and activate oxygen molecules. More importantly, the hydrophobic atmosphere created by the carbon layer allows oxygen to avoid the adverse effects of physically adsorbed water on low-temperature catalytic oxidation reactions, allowing it to remain adsorbed on the surface of the Pt nanoparticles and be successfully activated, ultimately achieving the goal of stabilizing ethylene oxide. This in situ carbon-modified Pt and SBA-15 composite catalyst exhibits excellent ethylene conversion activity, carbon dioxide selectivity, and resistance to catalyst deactivation. This preparation method opens up a new preparation path for the future design of simple and efficient hydrophobic catalysts.

[0108] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An application of an in-situ carbon-modified Pt composite catalyst, characterized in that: The in-situ carbon-modified Pt composite catalyst is used to catalyze ethylene oxidation; The method for preparing the in-situ carbon-modified Pt composite catalyst comprises the following steps: (1) mixing triblock copolymer P123, ethyl orthosilicate, and hydrochloric acid solution, performing a hydrothermal reaction, and drying to obtain SBA-15 containing a template; (2) SBA-15 containing a template, water and a Pt precursor are mixed and impregnated, and then dried in a water bath, ground, calcined and reduced to obtain an in situ carbon-modified Pt composite catalyst.

2. The use of an in-situ carbon-modified Pt composite catalyst according to claim 1, characterized in that: The mixing process of step (1) is specifically as follows: the triblock copolymer P123 is mixed with the hydrochloric acid solution, stirred at 35-45° C. for 2-5 hours until the triblock copolymer P123 is completely dissolved, and then ethyl orthosilicate is added dropwise, and stirring is continued at 35-45° C. for 24-30 hours.

3. The use of an in-situ carbon-modified Pt composite catalyst according to claim 1 or 2, characterized in that: In step (1), the mass ratio of the triblock copolymer P123 to the tetraethyl orthosilicate is 1:2.2-2.3; the concentration of the hydrochloric acid solution is 1.5-2.0 mol / L; and the mass volume ratio of the triblock copolymer P123 to the hydrochloric acid solution is 1 g:37-38 mL.

4. The use of an in-situ carbon-modified Pt composite catalyst as claimed in claim 3, characterized in that: In step (1), the temperature of the hydrothermal reaction is 90-100° C., and the time of the hydrothermal reaction is 48-54 hours.

5. The use of an in-situ carbon-modified Pt composite catalyst according to claim 2 or 4, characterized in that: In step (2), the Pt precursor is an aqueous solution of H2PtCl6·6H2O, and the concentration of the aqueous solution of H2PtCl6·6H2O is 1g / 80-120mL; the mass of the Pt element contained in the Pt precursor is 1-5% of the mass of the SBA-15 containing the template.

6. The use of an in-situ carbon-modified Pt composite catalyst according to claim 5, characterized in that: In step (2), the mass volume ratio of the template-containing SBA-15 to the water is 0.9 g: 20-30 mL; and the mixed immersion time is 30-40 min.

7. The use of an in-situ carbon-modified Pt composite catalyst according to claim 1, 2 or 6, characterized in that: In step (2), the water bath drying temperature is 85-95° C.; the grinding time is 30-40 min; the calcination is carried out under a protective atmosphere, which is nitrogen; the calcination temperature is 600-700° C., and the calcination time is 6-10 h.

8. The use of an in-situ carbon-modified Pt composite catalyst according to claim 7, characterized in that: In step (2), the heating rate of the calcination is 1-2°C / min; the reduction is carried out under a hydrogen atmosphere; the reduction temperature is 200-250°C, and the reduction time is 2-4h.

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