Atomic-scale dispersed Pt-Ga bimetallic catalysts, their preparation methods and applications

Abstract

The application relates to the technical field of supported bimetallic catalyst preparation, in particular to an atomic-level dispersed Pt-Ga bimetallic catalyst and a preparation method and application thereof. The preparation method of the atomic-level dispersed Pt-Ga bimetallic catalyst comprises the following steps: mixing nano-alumina and a gallium nitrate ethanol solution, water-bath heating and stirring, and then evaporating the solvent; calcining the obtained precursor material, and then performing reduction oxidation treatment to obtain Ga / Al2O3; adding Ga / Al2O3 powder into a platinum acetylacetone ethanol solution, water-bath heating and stirring, and then evaporating the solvent; and calcining the obtained precursor material to obtain the atomic-level dispersed Pt-Ga bimetallic catalyst. The preparation method of the atomic-level dispersed Pt-Ga bimetallic catalyst provided by the application disperses the metal of the prepared catalyst at an atomic level, the atomic utilization rate is high, and the synergistic effect between the bimetals is greatly enhanced.

Description

Technical Field

[0001] This invention relates to the field of supported bimetallic catalyst preparation technology, specifically to atomically dispersed Pt-Ga bimetallic catalysts, their preparation methods, and applications. Background Technology

[0002] Propylene (C3H6) is one of the most important basic chemical raw materials in the petrochemical industry, widely used in the production of important chemical products such as polypropylene, acrylonitrile, propylene oxide, cumene, and acrylic acid. With the rapid development of the global economy, especially the rapid growth in demand for plastic products in emerging markets, the market demand for propylene continues to rise. Traditional propylene production mainly relies on naphtha cracking and refinery byproducts, but these processes have limited propylene yields and are highly susceptible to fluctuations in crude oil prices. Therefore, developing efficient and low-cost propylene production technologies has become an important research direction in the petrochemical industry. Propane dehydrogenation to propylene (PDH) technology has advantages such as abundant raw material sources, simple process flow, and high product yield, and has received widespread attention in recent years.

[0003] The core of PDH technology is the development of efficient and stable catalysts. Currently, the most studied catalyst systems include Cr-based, V-based, Pt-based, and Ga-based catalysts. Among them, Ga-based and Pt-based catalysts have attracted widespread attention due to their excellent dehydrogenation performance. Pt possesses excellent dehydrogenation activity, effectively promoting the breaking of the CH bond in propane molecules; while Ga species can improve propylene selectivity and suppress side reactions such as deep dehydrogenation and cracking by modulating the electronic structure and surface acidity of the catalyst. Combining Ga and Pt to form bimetallic catalysts holds promise for combining the advantages of both. However, research on the atomic-level dispersion of existing Pt-Ga bimetallic catalysts is still in its early stages, facing challenges such as poor dispersibility of Ga species on the support and difficulties in controlling the interaction between Ga and Pt. This not only limits the maximization of active sites but also affects the overall performance of the catalyst. To achieve effective synergistic effects between Pt and Ga atoms, a precise and controllable synthesis method needs to be developed, enabling Pt and Ga atoms to be uniformly distributed on the support surface while maintaining good electronic interactions.

[0004] Zhang, T., Pei, C., Sun, G., et al. Angew. Chem. Int. Ed., 2022, 134, e202201453. reported an xPt-3Ga2O3 / Al2O3 catalyst that exhibited excellent synergistic catalytic performance in the propane dehydrogenation to propylene reaction. However, this catalyst was synthesized by an impregnation method, and the metals Pt and Ga existed in the form of nanoparticles, resulting in poor dispersion and difficulty in achieving precise coordination of Pt and Ga at the atomic level. Lee, S., Kwon, HC, Jeong, J., et al. J. Am. Chem. Soc., 2025, 147, 6480-6491. reported a Pt-Ga bimetallic catalyst prepared by an impregnation method, which could maximize the utilization of noble metals by controlling the Pt / Ga ratio. HAADF-STEM analysis showed that there was no Ga distribution near Pt and Pt existed in a two-dimensional sheet with a single atom thickness. However, the preparation method of this catalyst requires calcination at 750°C and reduction at 580°C in an H2 atmosphere. The high processing temperature and energy consumption, as well as certain operational risks, make it unsuitable for large-scale industrial production. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an atomically dispersed Pt-Ga bimetallic catalyst, in which Ga is dispersed in an atomic cloud-like manner and Pt is dispersed in a single-atom form, which greatly enhances the synergistic effect between the two metals and improves the activity and selectivity of the catalyst.

[0006] Another objective of this invention is to provide a method for preparing an atomically dispersed Pt-Ga bimetallic catalyst, which effectively improves the dispersion of the metal, significantly enhances the atomic utilization of Pt, and reduces production costs.

[0007] A third objective of this invention is to provide an application of an atomically dispersed Pt-Ga bimetallic catalyst in the propane dehydrogenation to propylene reaction, wherein the space velocity is 4.5 × 10⁻⁶ when the Pt loading is 0.02 wt.% and the reaction temperature is 450 °C. 4 mL·g -1 cat ·h -1 It can achieve a propane conversion rate of 21% and a propylene selectivity of nearly 100%, demonstrating excellent catalytic performance.

[0008] This invention is achieved using the following technical solution:

[0009] The method for preparing the atomically dispersed Pt-Ga bimetallic catalyst includes the following steps:

[0010] (1) Dissolve gallium nitrate in anhydrous ethanol and stir to form a gallium precursor solution;

[0011] (2) Add alumina powder to gallium precursor solution, heat in water bath, cool the solvent by circulation, and then evaporate the solvent under water bath conditions to obtain precursor material;

[0012] (3) The precursor material was calcined in air to obtain gallium oxide-supported nano-alumina material;

[0013] (4) The material obtained in step (3) is heated under a nitrogen atmosphere, then reduced by 10% H2 / N2 reducing gas, then purged with N2 gas, and then calcined with air to obtain Ga / Al2O3 catalyst.

[0014] (5) Dissolve platinum acetylacetonate in anhydrous ethanol to obtain a platinum precursor solution;

[0015] (6) The catalyst obtained in step (4) is immersed in a platinum precursor solution diluted with anhydrous ethanol, heated in a water bath, and the solvent is evaporated under water bath conditions to obtain Pt-Ga bimetallic precursor material.

[0016] (7) The material obtained in step (6) is calcined to obtain Pt-Ga / Al2O3 bimetallic catalyst material; wherein the loading of Ga is 1-10 wt.% and the loading of Pt is 0.01-0.1 wt.%.

[0017] In step (1), the molar ratio of anhydrous ethanol to gallium nitrate is: (0.28 × 10⁻⁶) / (2π ... 3 -1.12×10 3 ):1.

[0018] In step (3), the heating rate during calcination is 2-5℃ / min.

[0019] In step (4), the temperature after heating is 500-600℃, the heating rate is 2-5℃ / min, the reduction time is 0.5-1h, the calcination time is 1-2h, and the gas flow rate is 15-30mL / min.

[0020] The concentration of the platinum precursor solution in step (5) is 0.25-1 mg / mL.

[0021] In step (6), the amount of platinum precursor solution used is 0.2-1 mL, and the volume ratio of anhydrous ethanol to platinum precursor solution is (29-74):1. The ratio of Pt content in the platinum precursor solution to the mass of added alumina is 1×10⁻⁶. -4 -1×10 -3 .

[0022] In step (7), the heating rate during calcination is 2-5℃ / min, and the gas flow rate is 15-30mL / min.

[0023] The water bath heating temperature is 50-70℃, and the continuous stirring time is 2-6 hours.

[0024] The atomically dispersed Pt-Ga bimetallic catalyst is prepared using the above-described method for preparing atomically dispersed Pt-Ga bimetallic catalysts.

[0025] The atomically dispersed Pt-Ga bimetallic catalyst is used in the propane dehydrogenation to propylene reaction. The steps are as follows: the atomically dispersed Pt-Ga bimetallic catalyst is loaded into a fixed-bed reactor, and a reaction gas is introduced under atmospheric pressure at a space velocity of 9 × 10⁻⁶. 3 -3.6×10 5 mL·g cat -1 ·h -1 Under these conditions, propane dehydrogenation to propylene reaction is carried out, and the catalyst does not need to be reduced and pretreated under H2 atmosphere before the reaction.

[0026] The method for preparing the atomically dispersed Pt-Ga bimetallic catalyst includes the following steps:

[0027] (1) Dissolve gallium nitrate in a certain amount of anhydrous ethanol and stir to form a clear gallium precursor solution;

[0028] (2) Add alumina powder to gallium nitrate ethanol solution, and circulate and stir for 2-6 hours under water bath conditions of 50-70℃. Then evaporate the solvent under water bath conditions of 50-70℃ to obtain the precursor material.

[0029] (3) The precursor material was calcined in air at 450-550℃ for 2h to obtain gallium oxide-supported nano-alumina material;

[0030] (4) After the gallium oxide-supported nano-alumina material is heated to 500-600℃ in a nitrogen atmosphere, it is reduced by 10% H2 / N2 mixed gas for 1h, then purged with N2 gas, and then calcined with air for 1h to obtain Ga / Al2O3 catalyst.

[0031] (5) Dissolve platinum acetylacetonate in anhydrous ethanol to obtain a clear platinum precursor solution;

[0032] (6) Take a certain amount of platinum precursor solution, dilute it with anhydrous ethanol, immerse the above Ga / Al2O3 catalyst in the platinum precursor solution, and perform cyclic cooling and continuous stirring for 2-6 hours under the condition of 50-70℃ water bath. Then evaporate the solvent under the condition of 50-70℃ water bath to obtain Pt-Ga bimetallic precursor material.

[0033] (7) The Pt-Ga bimetallic precursor material was calcined in air at 450-550℃ for 2h to obtain the Pt-Ga / Al2O3 bimetallic catalyst material; wherein the loading of Ga was 1-10wt.% and the loading of Pt was 0.01-0.1wt.%.

[0034] In step (2), the alumina used is commercially available γ-Al2O3 or nano-alumina synthesized as disclosed in patent CN117138784A, with the second type of nano-alumina being preferred.

[0035] The preparation method of nano-alumina is as follows: 180 mL of deionized water is added to a 250 mL beaker. 3.3760 g of aluminum nitrate and 7.2072 g of urea are weighed and dissolved in the water to form a mixed solution. The solution is heated in a boiling water bath at 100 °C with stirring for 16 h, then cooled to room temperature and allowed to stand for 16 h. After filtration and washing, the solution is dried in an oven at 110 °C to obtain ammonium aluminum carbonate. The obtained ammonium aluminum carbonate is placed in a tube furnace and calcined at 600 °C for 12 h in a dry air atmosphere with a flow rate of 50 mL / min to obtain nano-alumina.

[0036] Specifically, the preparation method of the atomically dispersed Pt-Ga bimetallic catalyst includes the following steps:

[0037] (1) Measure 15-30 mL of anhydrous ethanol into a round-bottom flask, add a certain amount of gallium nitrate, and stir continuously until a clear solution is obtained.

[0038] (2) Weigh 0.5-2g of nano-alumina carrier and add it to the above gallium nitrate solution. Under the condition of 50-70℃ water bath, perform circulating cooling and continuous stirring for 2-6h. Then transfer the solution to a beaker and heat it in a 50-70℃ water bath to evaporate the ethanol solvent to obtain the precursor material.

[0039] (3) After drying the precursor material at 80°C, place it in a tube furnace and heat it from room temperature to 450-550°C at 2-5°C / min and hold for 2 hours to obtain gallium oxide-loaded nano-alumina material.

[0040] (4) After pressing the above sample into tablets and sieving, place it in a fixed bed reactor, heat it to 500-600℃ at 2-5℃ / min under a nitrogen atmosphere and hold it for 10-30min, reduce it with 10% H2 / N2 mixed gas for 1h, then purge it with N2 gas for 10-30min, and then calcine it with dry air for 1h to obtain Ga / Al2O3 catalyst;

[0041] (5) Dissolve a certain amount of platinum acetylacetonate in anhydrous ethanol and stir continuously to obtain a clear platinum precursor solution. Make up to 50 mL and the Pt ion concentration is 0.25-1 mg / mL.

[0042] (6) Take a certain amount of platinum precursor solution, dilute it with anhydrous ethanol, impregnate the above Ga / Al2O3 catalyst in the platinum precursor solution, and perform circulating cooling and continuous stirring for 2-6 hours under the condition of 50-70℃ water bath. Then transfer the solution to a beaker, heat it in a 50-70℃ water bath to evaporate the ethanol solvent, and obtain Pt-Ga bimetallic precursor material.

[0043] (7) Place the Pt-Ga bimetallic precursor material in a tube furnace and heat it from room temperature to 450-550℃ at 2-5℃ / min and hold for 2h to obtain Pt-Ga / Al2O3 bimetallic catalyst material, wherein the loading of Ga is 1-10wt.% and the loading of Pt is 0.01-0.1wt.%.

[0044] In the preparation of the atomically dispersed Pt-Ga bimetallic catalyst of this invention, anhydrous ethanol is used as the metal precursor solvent. Steps (2) and (6) of this invention employ a water bath temperature controlled at 50-70℃ and a time controlled at 2-6 hours to ensure that Ga and Pt ions are fully dispersed on the support surface. The preparation process is green and pollution-free, and is suitable for using any ethanol-soluble metal salt as a precursor for the active metal. This catalyst exhibits excellent propane dehydrogenation to propylene activity.

[0045] This invention uses nano-alumina with a large specific surface area as a carrier, and its surface has a large number of aluminum hydroxyl groups, which can anchor metal ions and facilitate the dispersion of active metals Ga and Pt.

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] (1) The Pt-Ga bimetallic catalyst prepared by the method of the present invention has Ga dispersed in an atomic cloud-like manner and Pt dispersed in a single-atom form, which greatly enhances the synergistic effect between the two metals and improves the activity and selectivity of the catalyst.

[0048] (2) The Pt-Ga bimetallic catalyst prepared by the method of the present invention effectively improves the metal dispersion, significantly enhances the atomic utilization of Pt, and reduces the production cost.

[0049] (3) The Pt-Ga bimetallic catalyst prepared in this invention was applied to the propane dehydrogenation to propylene reaction. When the Pt loading was 0.02 wt.% and the reaction temperature was 450 °C, the space velocity was 4.5 × 10⁻⁶. 4 mL·g -1 cat ·h -1 It can achieve a propane conversion rate of 21% and a propylene selectivity of nearly 100%, demonstrating excellent catalytic performance. Attached Figure Description

[0050] Figure 1 The infrared absorption spectra of nano-Al2O3 used in Examples 1-7 and γ-Al2O3 used in Comparative Examples 1-4 are shown.

[0051] Figure 2 The XRD patterns are those of the Pt-Ga bimetallic catalysts prepared in Examples 1-4 of this invention.

[0052] Figure 3 High-angle annular dark-field scanning transmission spectrum (A) and EDS elemental analysis spectrum (BE) of the 0.02Pt-8Ga / Al2O3 catalyst prepared in Example 2 of this invention.

[0053] Figure 4 The activity diagram of the 0.02Pt-8Ga / Al2O3 catalyst prepared in Example 2 of this invention for catalyzing the dehydrogenation of propane to propylene at different temperatures is shown.

[0054] Figure 5 High-angle annular dark-field scanning transmission spectrum (A) and EDS elemental analysis spectrum (BE) of the 0.1Pt-8Ga / Al2O3 catalyst prepared in Example 4 of this invention. Detailed Implementation

[0055] To make the objectives and technical solutions of this invention clearer, the invention will be further described in detail below.

[0056] The preparation method of nano-alumina is as follows: 180 mL of deionized water is added to a 250 mL beaker. 3.3760 g of aluminum nitrate and 7.2072 g of urea are weighed and dissolved in the water to form a mixed solution. The solution is heated in a boiling water bath at 100 °C with stirring for 16 h, then cooled to room temperature and allowed to stand for 16 h. After filtration and washing, the solution is dried in an oven at 110 °C to obtain ammonium aluminum carbonate. The obtained ammonium aluminum carbonate is placed in a tube furnace and calcined at 600 °C for 12 h in a dry air atmosphere with a flow rate of 50 mL / min to obtain nano-alumina.

[0057] Example 1

[0058] The method for preparing the atomically dispersed Pt-Ga bimetallic catalyst includes the following steps:

[0059] (1) Measure 15 mL of anhydrous ethanol into a round-bottom flask, add 0.2087 g of gallium nitrate, and stir continuously until a clear solution is obtained.

[0060] (2) Weigh 0.5g of nano-alumina carrier and add it to the above gallium nitrate solution. Under the condition of 60℃ water bath, perform circulating cooling and continuous stirring for 2h. Then transfer the solution to a beaker and heat it under the condition of 60℃ water bath to evaporate the ethanol solvent while continuously stirring to obtain the precursor material.

[0061] (3) After drying the precursor material in an oven at 80°C, place it in a tube furnace and heat it from room temperature to 550°C at 2°C / min for 2 hours to obtain gallium oxide-loaded nano-alumina material.

[0062] (4) After pressing the above sample into tablets and sieving, place it in a fixed bed reactor. Under a nitrogen atmosphere, heat the sample to 550℃ at 2℃ / min and hold for 20min. Then reduce it with 10% H2 / N2 mixed gas for 1h. After purging with N2 gas for 20min, calcine it with dry air for 1h. The gas flow rate is 30mL / min. Ga / Al2O3 catalyst is obtained.

[0063] (5) Dissolve 0.0260g of platinum acetylacetonate in anhydrous ethanol and stir continuously to obtain a clear platinum precursor solution. Make up to 50mL and the Pt ion concentration is 0.25mg / mL.

[0064] (6) Take 0.2 mL of platinum precursor solution, add 14.8 mL of anhydrous ethanol to dilute, impregnate the above Ga / Al2O3 catalyst in the platinum precursor solution, and perform circulating cooling and continuous stirring for 2 h under 60℃ water bath conditions. Then transfer the solution to a beaker, heat it in a 60℃ water bath to evaporate the ethanol solvent, and obtain Pt-Ga bimetallic precursor material.

[0065] (7) After drying the Pt-Ga bimetallic precursor material at 80°C, place it in a tube furnace and pass dry air at a gas flow rate of 15 mL / min. Raise the temperature from room temperature to 550°C at 2°C / min and hold for 2 hours to obtain 0.01Pt-8Ga / Al2O3 bimetallic catalyst material, in which the loading of Ga is 8 wt.% and the loading of Pt is 0.01 wt.%.

[0066] Example 2

[0067] The method for preparing the atomically dispersed Pt-Ga bimetallic catalyst includes the following steps:

[0068] (1) Measure 15 mL of anhydrous ethanol into a round-bottom flask, add 0.2087 g of gallium nitrate, and stir continuously until a clear solution is obtained.

[0069] (2) Weigh 0.5g of nano-alumina carrier and add it to the above gallium nitrate solution. Under the condition of 60°C water bath, perform circulating cooling and continuous stirring for 4h. Then transfer the solution to a beaker and heat it under the condition of 60°C water bath to evaporate the ethanol solvent while continuously stirring to obtain the precursor material.

[0070] (3) After drying the precursor material in an oven at 80°C, place it in a tube furnace and heat it from room temperature to 550°C at 2°C / min for 2 hours to obtain gallium oxide-loaded nano-alumina material.

[0071] (4) After pressing the above sample into tablets and sieving, place it in a fixed bed reactor. Under a nitrogen atmosphere, heat the sample to 550℃ at 2℃ / min and hold for 20min. Then reduce it with 10% H2 / N2 mixed gas for 1h. After purging with N2 gas for 20min, calcine it with dry air for 1h. The gas flow rate is 30mL / min. Ga / Al2O3 catalyst is obtained.

[0072] (5) Dissolve 0.0520g of platinum acetylacetonate in anhydrous ethanol and stir continuously to obtain a clear platinum precursor solution. Make up to 50mL and the Pt ion concentration is 0.5mg / mL.

[0073] (6) Take 0.2 mL of platinum precursor solution, add 14.8 mL of anhydrous ethanol to dilute it, and impregnate the above Ga / Al2O3 catalyst in the platinum precursor solution. Under the condition of 60℃ water bath, perform circulating cooling and continuous stirring for 4 h. Then transfer the solution to a beaker, heat it in a 60℃ water bath to evaporate the ethanol solvent, and obtain Pt-Ga bimetallic precursor material.

[0074] (7) After drying the Pt-Ga bimetallic precursor material at 80°C, place it in a tube furnace and pass dry air at a gas flow rate of 15 mL / min. Raise the temperature from room temperature to 550°C at 2°C / min and hold for 2 hours to obtain 0.02Pt-8Ga / Al2O3 bimetallic catalyst material, in which the loading of Ga is 8 wt.% and the loading of Pt is 0.02 wt.%.

[0075] The nano-alumina used in this embodiment, such as Figure 1 As shown, the infrared absorption spectrum of the sample is in the range of 3200-3700 cm⁻¹. -1 The presence of strong absorption peaks within the specified range indicates that the nano-alumina possesses a large number of aluminum hydroxyl groups; the synthesized 0.02Pt-8Ga / Al2O3 bimetallic catalyst, such as Figure 2 As shown, no diffraction peaks were observed in the XRD pattern, proving that Ga and Pt are well dispersed on the support surface; the synthesized 0.02Pt-8Ga / Al2O3 bimetallic catalyst, as Figure 3 As shown, in the synthesized catalyst, Ga is dispersed in an atomic cloud-like structure, while Pt exists in the form of single atoms. The 0.02Pt-8Ga / Al₂O₃ bimetallic catalyst prepared in this example is used in the propane dehydrogenation to propylene reaction, as shown... Figure 4 As shown, with the increase of reaction temperature, the conversion rate of propane first increases and then remains constant, while the selectivity of propylene gradually decreases. At a reaction temperature of 550℃, the conversion rate of propane is 41.6% and the selectivity of propylene is 99.1%, demonstrating excellent catalytic performance.

[0076] Example 3

[0077] The method for preparing the atomically dispersed Pt-Ga bimetallic catalyst includes the following steps:

[0078] (1) Measure 30 mL of anhydrous ethanol into a round-bottom flask, add 0.4174 g of gallium nitrate, and stir continuously until a clear solution is obtained.

[0079] (2) Weigh 1g of nano-alumina carrier and add it to the above gallium nitrate solution. Under the condition of 60°C water bath, perform circulating cooling and continuous stirring for 6h. Then transfer the solution to a beaker and heat it under the condition of 60°C water bath to evaporate the ethanol solvent while continuously stirring to obtain the precursor material.

[0080] (3) After drying the precursor material in an oven at 80°C, place it in a tube furnace and heat it from room temperature to 550°C at 2°C / min for 2 hours to obtain gallium oxide-loaded nano-alumina material.

[0081] (4) After pressing the above sample into tablets and sieving, place it in a fixed bed reactor. Under a nitrogen atmosphere, heat the sample to 550℃ at 2℃ / min and hold for 20min. Then reduce it with 10% H2 / N2 mixed gas for 1h. After purging with N2 gas for 20min, calcine it with dry air for 1h. The gas flow rate is 30mL / min. Ga / Al2O3 catalyst is obtained.

[0082] (5) Dissolve 0.0520g of platinum acetylacetonate in anhydrous ethanol and stir continuously to obtain a clear platinum precursor solution. Make up to 50mL and the Pt ion concentration is 0.5mg / mL.

[0083] (6) Take 0.8 mL of platinum precursor solution, add 29.2 mL of anhydrous ethanol to dilute, impregnate the above Ga / Al2O3 catalyst in the platinum precursor solution, and perform cyclic cooling and continuous stirring for 6 h under 60 °C water bath conditions. Then transfer the solution to a beaker, heat it in a 60 °C water bath to evaporate the ethanol solvent, and obtain Pt-Ga bimetallic precursor material.

[0084] (7) After drying the Pt-Ga bimetallic precursor material at 80°C, place it in a tube furnace and pass dry air at a gas flow rate of 20 mL / min. The temperature is increased from room temperature to 550°C at 2°C / min and held for 2 hours to obtain 0.04Pt-8Ga / Al2O3 bimetallic catalyst material, in which the loading of Ga is 8 wt.% and the loading of Pt is 0.04 wt.%.

[0085] Example 4

[0086] The method for preparing the atomically dispersed Pt-Ga bimetallic catalyst includes the following steps:

[0087] (1) Measure 30 mL of anhydrous ethanol into a round-bottom flask, add 0.4174 g of gallium nitrate, and stir continuously until a clear solution is obtained.

[0088] (2) Weigh 1g of nano-alumina carrier and add it to the above gallium nitrate solution. Under the condition of 60°C water bath, perform circulating cooling and continuous stirring for 6h. Then transfer the solution to a beaker and heat it under the condition of 60°C water bath to evaporate the ethanol solvent while continuously stirring to obtain the precursor material.

[0089] (3) After drying the precursor material in an oven at 80°C, place it in a tube furnace and heat it from room temperature to 550°C at 2°C / min for 2 hours to obtain gallium oxide-loaded nano-alumina material.

[0090] (4) After pressing the above sample into tablets and sieving, place it in a fixed bed reactor. Under a nitrogen atmosphere, heat the sample to 550℃ at 2℃ / min and hold for 20min. Then reduce it with 10% H2 / N2 mixed gas for 1h. After purging with N2 gas for 20min, calcine it with dry air for 1h. The gas flow rate is 30mL / min. Ga / Al2O3 catalyst is obtained.

[0091] (5) Dissolve 0.1040 g of platinum acetylacetonate in anhydrous ethanol and stir continuously to obtain a clear platinum precursor solution. Make up to 50 mL and the Pt ion concentration is 1 mg / mL.

[0092] (6) Take 1 mL of platinum precursor solution, add 29 mL of anhydrous ethanol to dilute, immerse the above Ga / Al2O3 catalyst in the platinum precursor solution, circulate and cool under a 60°C water bath and stir continuously for 6 h, then transfer the solution to a beaker, heat it in a 60°C water bath to evaporate the ethanol solvent, and obtain Pt-Ga bimetallic precursor material.

[0093] (7) After drying the Pt-Ga bimetallic precursor material at 80°C, place it in a tube furnace and pass dry air at a gas flow rate of 30 mL / min. Raise the temperature from room temperature to 550°C at 2°C / min and hold for 2 h to obtain 0.1Pt-8Ga / Al2O3 bimetallic catalyst material, wherein the loading of Ga is 8 wt.% and the loading of Pt is 0.1 wt.%.

[0094] The 0.1Pt-8Ga / Al2O3 bimetallic catalyst synthesized in this embodiment, such as Figure 5 As shown, Ga is dispersed in an atomic cloud on the synthesized catalyst, while Pt exists not only in the form of single atoms, but also in the form of nanoparticles, indicating that when the Pt loading is 0.1 wt.%, some Pt ​​atoms agglomerate.

[0095] Example 5

[0096] The method for preparing the atomically dispersed Pt-Ga bimetallic catalyst includes the following steps:

[0097] (1) Measure 20 mL of anhydrous ethanol into a round-bottom flask, add 0.5217 g of gallium nitrate, and stir continuously until a clear solution is obtained.

[0098] (2) Weigh 1g of nano-alumina carrier and add it to the above gallium nitrate solution. Under the condition of 60°C water bath, perform circulating cooling and continuous stirring for 4h. Then transfer the solution to a beaker and heat it under the condition of 60°C water bath to evaporate the ethanol solvent while continuously stirring to obtain the precursor material.

[0099] (3) After drying the precursor material in an oven at 80°C, place it in a tube furnace and heat it from room temperature to 550°C at 2°C / min for 2 hours to obtain gallium oxide-loaded nano-alumina material.

[0100] (4) After pressing the above sample into tablets and sieving, place it in a fixed bed reactor. Under a nitrogen atmosphere, heat the sample to 550℃ at 2℃ / min and hold for 20min. Then reduce it with 10% H2 / N2 mixed gas for 1h. After purging with N2 gas for 20min, calcine it with dry air for 1h. The gas flow rate is 30mL / min. Ga / Al2O3 catalyst is obtained.

[0101] (5) Dissolve 0.0520g of platinum acetylacetonate in anhydrous ethanol and stir continuously to obtain a clear platinum precursor solution. Make up to 50mL and the Pt ion concentration is 0.5mg / mL.

[0102] (6) Take 0.2 mL of platinum precursor solution, add 14.8 mL of anhydrous ethanol to dilute it, and impregnate the above Ga / Al2O3 catalyst in the platinum precursor solution. Under the condition of 60℃ water bath, perform circulating cooling and continuous stirring for 4 h. Then transfer the solution to a beaker, heat it in a 60℃ water bath to evaporate the ethanol solvent, and obtain Pt-Ga bimetallic precursor material.

[0103] (7) After drying the Pt-Ga bimetallic precursor material at 80°C, place it in a tube furnace and pass dry air at a gas flow rate of 15 mL / min. Raise the temperature from room temperature to 550°C at 2°C / min and hold for 2 hours to obtain 0.02Pt-10Ga / Al2O3 bimetallic catalyst material, in which the loading of Ga is 10 wt.% and the loading of Pt is 0.02 wt.%.

[0104] Example 6

[0105] The method for preparing the atomically dispersed Pt-Ga bimetallic catalyst includes the following steps:

[0106] (1) Measure 20 mL of anhydrous ethanol into a round-bottom flask, add 0.2608 g of gallium nitrate, and stir continuously until a clear solution is obtained.

[0107] (2) Weigh 1g of nano-alumina carrier and add it to the above gallium nitrate solution. Under the condition of 60°C water bath, perform circulating cooling and continuous stirring for 4h. Then transfer the solution to a beaker and heat it under the condition of 60°C water bath to evaporate the ethanol solvent while continuously stirring to obtain the precursor material.

[0108] (3) After drying the precursor material in an oven at 80°C, place it in a tube furnace and heat it from room temperature to 550°C at 2°C / min for 2 hours to obtain gallium oxide-loaded nano-alumina material.

[0109] (4) After pressing the above sample into tablets and sieving, place it in a fixed bed reactor. Under a nitrogen atmosphere, heat the sample to 550℃ at 2℃ / min and hold for 20min. Then reduce it with 10% H2 / N2 mixed gas for 1h. After purging with N2 gas for 20min, calcine it with dry air for 1h. The gas flow rate is 20mL / min. Ga / Al2O3 catalyst is obtained.

[0110] (5) Dissolve 0.0520g of platinum acetylacetonate in anhydrous ethanol and stir continuously to obtain a clear platinum precursor solution. Make up to 50mL and the Pt ion concentration is 0.5mg / mL.

[0111] (6) Take 0.2 mL of platinum precursor solution, add 14.8 mL of anhydrous ethanol to dilute it, and impregnate the above Ga / Al2O3 catalyst in the platinum precursor solution. Under the condition of 60℃ water bath, perform circulating cooling and continuous stirring for 4 h. Then transfer the solution to a beaker, heat it in a 60℃ water bath to evaporate the ethanol solvent, and obtain Pt-Ga bimetallic precursor material.

[0112] (7) After drying the Pt-Ga bimetallic precursor material at 80°C, place it in a tube furnace and pass dry air at a gas flow rate of 15 mL / min. Raise the temperature from room temperature to 550°C at 2°C / min and hold for 2 h to obtain 0.02Pt-4Ga / Al2O3 bimetallic catalyst material, in which the loading of Ga is 4 wt.% and the loading of Pt is 0.02 wt.%.

[0113] Example 7

[0114] The method for preparing the atomically dispersed Pt-Ga bimetallic catalyst includes the following steps:

[0115] (1) Measure 20 mL of anhydrous ethanol into a round-bottom flask, add 0.1304 g of gallium nitrate, and stir continuously until a clear solution is obtained.

[0116] (2) Weigh 2g of nano-alumina carrier and add it to the above gallium nitrate solution. Under the condition of 60°C water bath, perform circulating cooling and continuous stirring for 4h. Then transfer the solution to a beaker and heat it under the condition of 60°C water bath to evaporate the ethanol solvent while continuously stirring to obtain the precursor material.

[0117] (3) After drying the precursor material in an oven at 80°C, place it in a tube furnace and heat it from room temperature to 550°C at 5°C / min for 2 hours to obtain gallium oxide-loaded nano-alumina material.

[0118] (4) After pressing the above sample into tablets and sieving, place it in a fixed bed reactor. Under a nitrogen atmosphere, heat the sample to 550℃ at 5℃ / min and hold for 20 min. Then reduce it with 10% H2 / N2 mixed gas for 1 h. After purging with N2 gas for 20 min, calcine it with dry air for 1 h. The gas flow rate is 15 mL / min. Ga / Al2O3 catalyst is obtained.

[0119] (5) Dissolve 0.0520g of platinum acetylacetonate in anhydrous ethanol and stir continuously to obtain a clear platinum precursor solution. Make up to 50mL and the Pt ion concentration is 0.5mg / mL.

[0120] (6) Take 0.2 mL of platinum precursor solution, add 14.8 mL of anhydrous ethanol to dilute it, and impregnate the above Ga / Al2O3 catalyst in the platinum precursor solution. Under the condition of 60℃ water bath, perform circulating cooling and continuous stirring for 4 h. Then transfer the solution to a beaker, heat it in a 60℃ water bath to evaporate the ethanol solvent, and obtain Pt-Ga bimetallic precursor material.

[0121] (7) After drying the Pt-Ga bimetallic precursor material at 80°C, place it in a tube furnace and pass dry air at a gas flow rate of 15 mL / min. Raise the temperature from room temperature to 550°C at 2°C / min and hold for 2 h to obtain 0.02Pt-4Ga / Al2O3 bimetallic catalyst material, in which the loading of Ga is 1 wt.% and the loading of Pt is 0.02 wt.%.

[0122] Comparative Example 1

[0123] The difference between this comparative example and Example 1 is that the nano alumina in step (2) is replaced with γ-Al2O3 (CAS: 1344-28-1) from Shanghai McLean Biochemical Technology Co., Ltd., while the other preparation steps are the same.

[0124] Comparative Example 2

[0125] The difference between this comparative example and Example 2 is that the nano alumina in step (2) is replaced with γ-Al2O3 (CAS: 1344-28-1) from Shanghai McLean Biochemical Technology Co., Ltd., while the other preparation steps are the same.

[0126] Comparative Example 3

[0127] The difference between this comparative example and Example 3 is that the nano alumina in step (2) is replaced with γ-Al2O3 (CAS: 1344-28-1) from Shanghai McLean Biochemical Technology Co., Ltd., while the other preparation steps are the same.

[0128] Comparative Example 4

[0129] The difference between this comparative example and Example 4 is that the nano alumina in step (2) is replaced with γ-Al2O3 (CAS: 1344-28-1) from Shanghai McLean Biochemical Technology Co., Ltd., while the other preparation steps are the same.

[0130] Comparative Example 5

[0131] Steps (1)-(4) of this comparative example are the same as those in Example 3, and Ga / Al2O3 catalyst is prepared with a Ga loading of 8 wt.%.

[0132] Comparative Example 6

[0133] The comparative method for preparing a single-atom-scale dispersed monometallic Pt / Al2O3 catalyst includes the following steps:

[0134] (1) Dissolve 0.0520g of platinum acetylacetonate in anhydrous ethanol and stir continuously to obtain a clear platinum precursor solution. Make up to 50mL and the Pt ion concentration is 0.5mg / mL.

[0135] (2) Take 0.2 mL of platinum precursor solution, add 14.8 mL of anhydrous ethanol to dilute, weigh 0.5 g of nano alumina and impregnate it in the platinum precursor solution, circulate and cool it in a water bath at 60 °C and stir continuously for 4 h, then transfer the solution to a beaker, heat it in a water bath at 60 °C to evaporate the ethanol solvent, and obtain the single metal Pt precursor material.

[0136] (3) After drying the single metal Pt precursor material at 80°C, place it in a tube furnace and pass dry air at a gas flow rate of 15 mL / min. Raise the temperature from room temperature to 550°C at 2°C / min and hold for 2 hours to obtain 0.02Pt / Al2O3 single metal catalyst material, in which the loading of Pt is 0.02wt.%.

[0137] Comparative Example 7

[0138] This comparative example uses the traditional impregnation method to prepare Pt-Ga bimetallic catalysts:

[0139] (1) Weigh 0.2087g of gallium nitrate and dissolve it in 10mL of H2O. Then add 0.5g of nano-alumina and stir continuously for 4h to obtain a mixture.

[0140] (2) After drying the mixture in an oven at 80°C, it was placed in a tube furnace and heated from room temperature to 550°C at 2°C / min and held for 2 hours to obtain gallium oxide-loaded nano-alumina material.

[0141] (3) Dissolve 0.0520g of platinum acetylacetonate in deionized water and stir continuously to obtain a clear platinum precursor solution. Make up to 50mL and the Pt ion concentration is 0.5mg / mL.

[0142] (4) Take 0.2 mL of platinum precursor solution, add 14.8 mL of anhydrous ethanol to dilute, immerse the material obtained in step (2) in the platinum precursor solution, stir continuously for 4 h, and then put it in an 80℃ oven to dry, and obtain Pt-Ga bimetallic precursor material.

[0143] (5) The Pt-Ga bimetallic precursor material was placed in a tube furnace and dry air was passed through it at a gas flow rate of 15 mL / min. The temperature was increased from room temperature to 550℃ at 2℃ / min and held for 2h to obtain 0.02Pt-8Ga / Al2O3-IMP bimetallic catalyst material, in which the loading of Ga was 8 wt.% and the loading of Pt was 0.02 wt.%.

[0144] The catalysts prepared in the above examples and comparative examples were subjected to propane dehydrogenation to propylene activity tests according to the following steps: 0.075-0.2 g of Pt-Ga bimetallic catalyst was weighed and placed in a quartz tube reactor (inner diameter 4 mm, outer diameter 8 mm). Inert argon gas was introduced at a flow rate of 30 mL / min. The heating furnace was heated from room temperature to 450 °C at a rate of 2 °C / min and maintained for 1 h. Then, the reaction gas was switched to a ratio of V(C3H8) / V(N2) = 5%:95%, with a flow rate of 30-90 mL / min. The heating furnace was raised to different reaction temperatures, and after reacting for 15 min, the reaction products were detected. The reaction products were analyzed online in a gas chromatograph equipped with a flame ionization detector (FID).

[0145] The test data for Examples 1-7 and Comparative Examples 1-7 are shown in Table 1.

[0146] Table 1 Test data for Examples 1-7 and Comparative Examples 1-7

[0147]

[0148] Comparing the activity evaluation results of Examples 1-4 and Comparative Examples 1-4, it can be seen that compared with commercially available alumina, the Pt-Ga bimetallic catalyst supported on nano-alumina with a large specific surface area and abundant aluminum hydroxyl groups exhibits better performance in catalytic dehydrogenation of propane to propylene. Comparing the activity evaluation results of Example 2 and Comparative Examples 5-6, compared with single-metal Ga / Al2O3 and Pt / Al2O3, the atomically dispersed Pt-Ga bimetallic catalyst of the present invention shows a significant improvement in activity, with its catalytic performance being 7.5 times that of the sum of single-metal catalysts, demonstrating a strong intermetallic synergistic catalytic effect. Comparing the activity evaluation results of Example 2 and Comparative Example 7, it can be seen that compared with the traditional impregnation method, the atomically dispersed Pt-Ga bimetallic catalyst prepared by the present invention has better catalytic activity. This is attributed to the good dispersion of the active metal on the catalyst prepared by the present invention, which greatly improves the atomic utilization rate of the noble metal Pt. Comparing the activity evaluation results of Example 2 and Example 4, it can be seen that when the Pt loading increases from 0.02 wt.% to 0.1 wt.%, the catalyst activity decreases. This is because when the Pt loading is high, some atoms will agglomerate and form nanoparticles, which in turn affects the catalytic performance.

Claims

1. A method for preparing an atomically dispersed Pt-Ga bimetallic catalyst, characterized in that, The method comprises the following steps: (1) dissolving gallium nitrate into anhydrous ethanol to form a gallium precursor solution; (2) adding nano-alumina powder into the gallium precursor solution, performing water bath heating, and evaporating the solvent under water bath condition to obtain a precursor material; (3) calcining the precursor material in air to obtain a gallium oxide loaded nano-alumina material; (4) heating the material obtained in step (3) under nitrogen atmosphere, then passing 10% H2 / N2 reducing gas to reduce, then passing N2 gas to purge, and then calcining in air to obtain a Ga / Al2O3 catalyst; (5) dissolving platinum acetylacetonate into anhydrous ethanol to obtain a platinum precursor solution; (6) immersing the catalyst obtained in step (4) into the platinum precursor solution diluted by anhydrous ethanol, performing water bath heating, and evaporating the solvent under water bath condition to obtain a Pt-Ga bimetallic precursor material; (7) calcining the material obtained in step (6) to obtain a Pt-Ga / Al2O3 bimetallic catalyst material; wherein the loading amount of Ga is 1-10 wt.%, and the loading amount of Pt is 0.01-0.1 wt.%. In step (3), the heating rate during calcination is 2-5 ℃ / min, and the calcination temperature is 450-550 ℃. In step (4), the temperature after heating is 500-600 ℃, the heating rate is 2-5 ℃ / min, the reduction time is 0.5-1 h, the calcination time is 1-2 h, and the gas flow rate is 15-30 mL / min.

2. The method of claim 1, wherein the method is characterized by: The molar ratio of anhydrous ethanol to gallium nitrate in step (1) is: (0.28 x 10 3 -1.12 x 10 3 ):

1.

3. The method of claim 1, wherein the method is characterized by: The concentration of the platinum precursor solution in step (5) is 0.25-1 mg / mL.

4. The method of claim 1, wherein the method is characterized by: The amount of the platinum precursor solution in step (6) is 0.2-1 mL, and the volume ratio of anhydrous ethanol to the platinum precursor solution is (29-74):

1.

5. The method of claim 1, wherein the method is characterized by: In step (7), the heating rate during calcination is 2-5 ℃ / min, and the gas flow rate is 15-30 mL / min.

6. The method of claim 1, wherein the method is characterized by: The water bath heating temperature is 50-70 ℃, and the continuous stirring time is 2-6 h.

7. An atomically dispersed Pt-Ga bimetallic catalyst characterized in that, The atomic-level dispersed Pt-Ga bimetallic catalyst is prepared by the method of any one of claims 1-6.

8. Use of the atomically dispersed Pt-Ga bimetallic catalyst according to claim 7, characterized in that, The application relates to a method for preparing propylene by dehydrogenation of propane, which comprises the following steps: loading an atomically dispersed Pt-Ga bimetallic catalyst into a fixed bed reactor, feeding reaction gas under normal pressure, and carrying out the dehydrogenation of propane under the conditions of a space velocity of 9x10 3 -3.6x10 5 mL.g cat -1 .h -1 The catalyst does not need to be reduced under H2 atmosphere before the reaction.

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