Preparation method and application of a porous bimetallic oxide loaded Ru monatomic and nanoparticle coexisting catalyst

Abstract

The application belongs to the technical field of photo-assisted catalytic CO2 hydrogenation, and particularly relates to a porous bimetallic oxide loaded Ru monatomic and nanoparticle coexisting catalyst as well as a preparation method and application thereof. The catalyst has two active sites of Ru monatomic and Ru nanoparticle, the Ru nanoparticle serves as an H2 adsorption and dissociation site, and can migrate the dissociated H atom to the monatomic Ru site for the next reaction. The addition of CeO2 can improve the basicity of the catalyst, increase the CO2 adsorption site, and improve the dispersion of the metal species and the heat sintering resistance of the catalyst, thereby improving the stability of the catalyst. Therefore, the catalyst shows excellent photo-assisted catalytic CO2 hydrogenation performance due to the synergistic effect of the Ru monatomic and Ru nanoparticle.

Description

Technical Field

[0001] This invention belongs to the field of photo-assisted catalytic CO2 hydrogenation technology, specifically a method for preparing and applying a porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] CO2 resource utilization technologies have received widespread attention, among which photocatalytic CO2 hydrogenation has gradually become a research hotspot because it can use solar energy to convert CO2 into low-carbon compounds with industrial added value. Currently, photocatalytic CO2 hydrogenation still faces bottlenecks such as low conversion rate, poor product selectivity, and low light energy utilization. Therefore, developing efficient catalytic materials remains a pressing challenge in this field.

[0004] Recently, single-atom catalysts have attracted widespread attention in the field of photo-assisted catalytic CO2 hydrogenation due to their well-defined active sites, ultra-high metal atom utilization, and unique electronic structure. However, because single atoms lack metal-metal bonds, H2 must undergo heterolytic dissociation, which presents a higher barrier than homolytic dissociation, thus limiting the hydrogenation activity of single atoms. Furthermore, the loading of active metal is also limited to prevent the aggregation of single atoms, which would reduce catalytic activity. Introducing metal nanoparticles into single-atom systems has proven to be an effective method to improve catalytic activity. Moreover, the synergistic catalytic effect between single atoms and metal nanoparticles shows great potential in improving catalytic activity and product selectivity.

[0005] However, there is currently no single-atom and nanoparticle coexisting catalyst that can achieve high conversion and high selectivity in the photo-assisted catalytic hydrogenation of CO2 at relatively low reaction temperatures and atmospheric pressures. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention provides a porous bimetallic oxide-supported Ru single-atom and nanoparticle coexistence (Ru 1+NPs Preparation method and application of the catalyst. In this catalyst, Ru nanoparticles serve as H2 adsorption and dissociation sites, allowing dissociated H atoms to migrate to single-atom Ru sites for further reactions. The addition of CeO2 improves the catalyst's basicity and increases the number of CO2 adsorption sites. It also enhances the dispersion of metal species and improves the catalyst's heat resistance to sintering, thereby increasing its stability. Thanks to the synergistic effect of Ru single atoms and Ru nanoparticles, this catalyst exhibits excellent photo-assisted catalytic CO2 hydrogenation performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A first aspect of the present invention provides a porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst, comprising:

[0009] Porous CeO2 / Al2O3 support;

[0010] The porous CeO2 / Al2O3 support is loaded with Ru 1+NPs .

[0011] The Ru 1+NPs The / CeO2 / Al2O3 catalyst includes Ru 1+NPs Active sites and porous CeO2 / Al2O3 support, Ru 1+NPs It is dispersed on a porous CeO2 / Al2O3 support.

[0012] In some embodiments, the molar ratio of ruthenium salt, cerium salt, and aluminum salt is 0.05-0.2:0.5-2:2.5-10.

[0013] In some embodiments, the Ru nanoparticles have a size of 1-2.5 nm, the CeO2 particles have a size of 20-100 nm, and the CeO2 / Al2O3 support has a pore size of approximately 10-15 nm.

[0014] A second aspect of the present invention provides a method for preparing a porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst, comprising:

[0015] Ruthenium salt, cerium salt, aluminum salt, organic compound and organic solvent were uniformly mixed and RuCeAlLDH precursor was synthesized by solvothermal method;

[0016] The RuCeAl LDH was calcined in an inert atmosphere to obtain Ru. 1+NPs / CeO2 / Al2O3 composite material.

[0017] Traditional preparation methods typically involve first preparing a metal oxide, then impregnating the surface of the metal oxide with a noble metal salt, and finally calcining to obtain the desired catalyst. However, a one-step hydrothermal method can uniformly disperse noble metal ions into the matrix material, resulting in a more uniform elemental distribution.

[0018] In some embodiments, the ruthenium salt is one or more of ruthenium acetate, ruthenium acetylacetone, and ruthenium chloride;

[0019] In some embodiments, the cerium salt is cerium nitrate;

[0020] In some embodiments, the aluminum salt is aluminum nitrate;

[0021] In some embodiments, the organic compound is urea;

[0022] In some embodiments, the organic solvent is methanol.

[0023] In some embodiments, the ratio of the amounts of the ruthenium salt, cerium salt, aluminum salt, organic compound, and organic solvent is 0.05-0.2 mmol: 0.5-2 mmol: 2.5-10 mmol: 5-20 mmol: 15-80 mL.

[0024] In some embodiments, the solvothermal synthesis conditions are a temperature of 120-170°C and a reaction time of 10-20 h.

[0025] In some implementations, the RuCeAl LDH precursor is calcined in a tube furnace.

[0026] In some preferred embodiments, the calcination temperature is 400-500℃ and the calcination time is 1-3h.

[0027] In a second aspect, the present invention provides the application of the above-described catalyst and / or the catalyst prepared by the above-described method in photo-assisted catalytic CO2 hydrogenation.

[0028] In some embodiments, the catalytic conditions are: a 300W xenon lamp as the light source, a wavelength of 200-1100nm, and a light intensity of 1.8-3.0W·cm⁻¹. -2 The CO2 flow rate was 4 mL / min, the H2 flow rate was 16 mL / min, the reaction temperature was 170-250℃, and the reaction apparatus was a gas-phase flow reactor.

[0029] Beneficial effects of the present invention

[0030] (1) The photo-assisted catalytic CO2 hydrogenation technology used in this invention can convert CO2 into CH4 at a lower reaction temperature (170-250℃) and normal pressure, which greatly avoids the excessive energy consumption and safety problems caused by the high temperature and high pressure of traditional thermocatalytic reactions.

[0031] (2) Ru 1+NPs The / CeO2 / Al2O3 catalyst exhibited superior performance compared to Ru1 / CeO2 / Al2O3 and Ru1 / CeO2 / Al2O3 catalysts. NPs The catalytic activity of the / CeO2 / Al2O3 catalyst is attributed to the synergistic effect of Ru single atoms and nanoparticles.

[0032] (3) Ru 1+NPsThe / CeO2 / Al2O3 catalyst exhibited an excellent CH4 production rate of 121.2 mmol g under 250 °C (catalyst temperature) and light irradiation. cat -1 h -1 The selectivity was 93.4%, and the CO2 conversion rate was 60.6%.

[0033] (4) The RuCeAl LDH precursor was prepared by a one-step solvothermal method, and then calcined to obtain Ru. 1+NPs The / CeO2 / Al2O3 catalyst method is simple and easy to operate.

[0034] (5) The addition of CeO2 can improve the alkalinity of the catalyst and increase the adsorption sites of CO2. At the same time, it can also improve the dispersibility of metal species and improve the catalyst's resistance to sintering.

[0035] (6) The catalytic system has mild reaction conditions, is easy to operate, saves energy, and does not produce excess harmful substances during the production process. It is green and environmentally friendly and helps to realize industrial production.

[0036] (7) The processing method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0037] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0038] Figure 1 It is Ru prepared in Example 1 1+NPs TEM and HRTEM images of / CeO2 / Al2O3.

[0039] Figure 2 The Ru prepared in Example 1, Comparative Example 1, and Comparative Example 2 1+NPs / CeO2 / Al2O3, Ru1 / CeO2 / Al2O3 and Ru NPs XRD pattern of the / CeO2 / Al2O3 catalyst.

[0040] Figure 3 The Ru prepared in Example 1, Comparative Example 1, and Comparative Example 2 1+NPs / CeO2 / Al2O3, Ru1 / CeO2 / Al2O3 and Ru NPs The curve showing the rate of CH4 production from CO2 hydrogenation via photo-assisted catalysis using a CeO2 / Al2O3 catalyst as a function of reaction temperature.

[0041] Figure 4 The Ru prepared in Example 1, Comparative Example 1, and Comparative Example 2 1+NPs / CeO2 / Al2O3, Ru1 / CeO2 / Al2O3 and Ru NPs The curve showing the change in CO2 conversion rate with reaction temperature during the photo-assisted catalytic CO2 hydrogenation reaction using the / CeO2 / Al2O3 catalyst.

[0042] Figure 5 It is Ru prepared in Example 1 1+NPs Comparison of CO2 hydrogenation performance of / CeO2 / Al2O3 catalyst under darkness and light.

[0043] Figure 6 It is Ru prepared in Example 1 1+NPs Comparison of CO2 hydrogenation performance of / CeO2 / Al2O3 catalyst under different light intensities.

[0044] Figure 7 It is Ru prepared in Example 1 1+NPs Stability testing of the / CeO2 / Al2O3 catalyst. Detailed Implementation

[0045] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0046] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0047] Example 1

[0048] (1) Add 0.1 mmol of ruthenium acetate, 1 mmol of cerium nitrate, 5 mmol of aluminum nitrate and 10 mmol of urea to 30 mL of methanol solution and stir until dissolved;

[0049] (2) Transfer the mixed solution from step (1) to a reaction vessel, keep it at 150°C for 12 hours, then centrifuge and wash the product, and dry it at 70°C to obtain RuCeAl LDH.

[0050] (3) The prepared RuCeAl LDH was placed in a muffle furnace and calcined at 450°C for 2 hours under a hydrogen atmosphere to obtain Ru. 1+NPs / CeO2 / Al2O3 catalyst.

[0051] Figure 1 It is Ru prepared in Example 1 1+NPsTEM and HRTEM images of / CeO2 / Al2O3. The TEM and HRTEM images show that CeO2 particles are anchored on Al2O3, while Ru single atoms and Ru nanoparticles are uniformly dispersed on the CeO2 / Al2O3 surface. Simultaneously, lattice fringes with an interplanar spacing of 0.20 nm correspond to the (101) crystal planes of Ru, indicating the successful preparation of / CeO2 / Al2O3. 1+NPs / CeO2 / Al2O3 composite material.

[0052] Figure 5 It is Ru prepared in Example 1 1+NPs A comparison of the CO2 hydrogenation performance of the / CeO2 / Al2O3 catalyst under darkness and light. Figure 5 As can be seen, the CH4 generation rate under light conditions is higher than that under dark conditions, indicating that the introduction of light can significantly improve catalytic activity.

[0053] Figure 6 It is Ru prepared in Example 1 1+NPs A comparison of the CO2 hydrogenation performance of the / CeO2 / Al2O3 catalyst under different light intensities. Figure 6 As can be seen, the CH4 production rate gradually increases with the increase of light intensity, indicating that there is a positive correlation between light intensity and CO2 hydrogenation performance, further demonstrating that light irradiation can enhance catalytic activity.

[0054] Figure 7 It is Ru prepared in Example 1 1+NPs Stability testing of the / CeO2 / Al2O3 catalyst. From Figure 7 As can be seen, during the 35-hour reaction, the yield and selectivity of CH4 did not decrease significantly, indicating that Ru 1+NPs The / CeO2 / Al2O3 catalyst exhibits excellent catalytic stability.

[0055] Comparative Example 1

[0056] (1) Add 0.1 mmol of ruthenium acetate, 1 mmol of cerium nitrate, 5 mmol of aluminum nitrate and 10 mmol of urea to 30 mL of methanol solution and stir until dissolved;

[0057] (2) Transfer the mixed solution from step (1) to a reaction vessel, keep it at 150°C for 12 hours, then centrifuge and wash the product, and dry it at 70°C to obtain RuCeAl LDH.

[0058] (3) The prepared RuCeAl LDH was placed in a muffle furnace and calcined at 300°C for 2 hours under a hydrogen atmosphere to obtain the Ru1 / CeO2 / Al2O3 catalyst.

[0059] Comparative Example 2

[0060] (1) Add 0.1 mmol of ruthenium acetate, 1 mmol of cerium nitrate, 5 mmol of aluminum nitrate and 10 mmol of urea to 30 mL of methanol solution and stir until dissolved;

[0061] (2) Transfer the mixed solution from step (1) to a reaction vessel, keep it at 150°C for 12 hours, then centrifuge and wash the product, and dry it at 70°C to obtain RuCeAl LDH.

[0062] (3) The prepared RuCeAl LDH was placed in a muffle furnace and calcined at 600℃ for 3 hours under a hydrogen atmosphere to obtain Ru. NPs / CeO2 / Al2O3 catalyst.

[0063] Figure 2 The Ru prepared in Example 1, Comparative Example 1, and Comparative Example 2 1+NPs / CeO2 / Al2O3, Ru1 / CeO2 / Al2O3 and Ru NPs XRD pattern of the / CeO2 / Al2O3 catalyst. From Figure 2 The XRD patterns of all three catalysts show CeO2 diffraction peaks, indicating that Al2O3 in these catalysts is in an amorphous state. However, the characteristic peaks of Ru species are not visible in the XRD patterns of these three catalysts, which may be due to the small particle size and high dispersion of Ru species.

[0064] Figure 3 The Ru prepared in Example 1, Comparative Example 1, and Comparative Example 2 1+NPs / CeO2 / Al2O3, Ru1 / CeO2 / Al2O3 and Ru NPs The curve showing the rate of CH4 production from CO2 hydrogenation via photo-assisted catalysis using a CeO2 / Al2O3 catalyst as a function of reaction temperature. Figure 3 As can be seen from this, compared to Ru1 / CeO2 / Al2O3 and Ru NPs / CeO2 / Al2O3, Ru 1+NPs / CeO2 / Al2O3 exhibited superior catalytic performance, with a CH4 production rate of 121.2 mmol g under 250 °C and light irradiation. cat -1 h -1 The selectivity was 93.4%, indicating a synergistic effect between Ru single atoms and Ru nanoparticles.

[0065] Figure 4 The Ru prepared in Example 1, Comparative Example 1, and Comparative Example 2 1+NPs / CeO2 / Al2O3, Ru1 / CeO2 / Al2O3 and Ru NPsThe curve showing the change in CO2 conversion rate with reaction temperature during the photo-assisted catalytic CO2 hydrogenation reaction using a CeO2 / Al2O3 catalyst. Figure 4 As can be seen from this, Ru 1+NPs / CeO2 / Al2O3 exhibits a higher CO2 conversion rate across the entire temperature range, reaching 60.6% at 250℃ under illumination.

[0066] Photo-assisted catalytic CO2 hydrogenation test:

[0067] The photo-assisted catalytic CO2 hydrogenation experiment was conducted in a fluidized bed reaction system. The catalytic conditions were: a 300W xenon lamp as the light source, wavelength of 200-1100 nm, and light intensity of 1.8 W·cm⁻¹. -2 The CO2 flow rate was 4 mL / min, the H2 flow rate was 16 mL / min, and the reaction temperature was 170-250℃. 50 mg of catalyst was weighed and thoroughly mixed with 1.2 g of quartz sand, then placed in a transparent quartz tube. The quartz tube was placed in a heating furnace, and CO2 and H2 were introduced. The light source was turned on, and the concentration data of CO2 and products were obtained using an online gas chromatograph. The photo-assisted catalytic hydrogenation activity of different catalysts was then compared. Among them, Ru... 1+NPs The / CeO2 / Al2O3 catalyst exhibited the best CO2 hydrogenation activity, with a CH4 production rate of 121.2 mmol g under 250 °C and light irradiation. cat -1 h -1 The photothermal catalytic performance of different catalysts for CO2 hydrogenation, from highest to lowest, is as follows: Ru 1+NPs / CeO2 / Al2O3>Ru NPs / CeO2 / Al2O3>Ru1 / CeO2 / Al2O3.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst, characterized in that, include: Ruthenium salt, cerium salt, aluminum salt, urea and organic solvent were uniformly mixed, and RuCeAl LDH precursor was synthesized by solvothermal method; The RuCeAl LDH was calcined in an inert atmosphere to obtain Ru. 1+NPs / CeO2 / Al2O3 composite material.

2. The method for preparing the porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst as described in claim 1, characterized in that, The ruthenium salt is one or more of ruthenium acetate, ruthenium acetylacetone, and ruthenium chloride; Alternatively, the cerium salt is cerium nitrate; Alternatively, the aluminum salt is aluminum nitrate; Alternatively, the organic solvent may be methanol.

3. The method for preparing the porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst as described in claim 1, characterized in that, The ratio of the amounts of ruthenium salt, cerium salt, aluminum salt, urea, and organic solvent is 0.05-0.2 mmol: 0.5-2 mmol: 2.5-10 mmol: 5-20 mmol: 15-80 mL.

4. The method for preparing the porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst as described in claim 1, characterized in that, The conditions for the solvothermal synthesis are a temperature of 120-170 °C and a reaction time of 10-20 h.

5. The method for preparing the porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst as described in claim 1, characterized in that, The calcination temperature is 400-500 ℃, and the calcination time is 1-3 h.

6. The porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst prepared by the preparation method according to any one of claims 1-5, characterized in that, include: Porous CeO2 / Al2O3 support; The porous CeO2 / Al2O3 support is loaded with Ru 1+NPs .

7. The porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst as described in claim 6, characterized in that, The size of Ru nanoparticles is 1-2.5 nm, the size of CeO2 particles is 20-100 nm, and the average pore size of CeO2 / Al2O3 support is 10-15 nm.

8. The application of the porous bimetallic oxide-supported Ru single-atom and nanoparticle coexisting catalyst prepared by the preparation method according to any one of claims 1-5 in photo-assisted catalytic CO2 hydrogenation.

9. The application according to claim 8, characterized in that, The catalytic conditions were as follows: a 300 W xenon lamp as the light source, a wavelength of 200-1100 nm, and a light intensity of 1.8-3.0 W·cm⁻¹. -2 The CO2 flow rate was 4 mL / min, the H2 flow rate was 16 mL / min, the reaction temperature was 170-250 ℃, and the reaction apparatus was a gas-phase flow reactor.

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