Oxygen vacancy mediated MOx-Co interface double-active-center photo-thermal catalyst and application thereof in preparation of methanol through CO2 hydrogenation

Abstract

The invention discloses an oxygen vacancy mediated MOx-Co interface double-active-center photo-thermal catalyst and application of the oxygen vacancy mediated MOx-Co interface double-active-center photo-thermal catalyst to preparation of methanol through CO2 hydrogenation. A carbon-assisted defect engineering strategy is adopted, and the oxygen vacancy mediated MOx-Co interface double-active-center catalyst is accurately constructed through cooperative treatment of step-by-step impregnation, carbon thermal reduction, selective oxidation and controllable reduction. According to the catalyst, gamma-Al2O3 is used as a carrier, and oxygen vacancy-enriched Co-based nanoparticles (6-8 nm), MOx nanoclusters (1-2 nm), a first auxiliary agent (C) and a second auxiliary agent (K or Na) are loaded; wherein the MOx nanocluster is anchored on the surface of the Co-based nanoparticle through oxygen vacancy chemical bonding to form a stable M-O-Co covalent bond. After the catalyst is reduced, CO2 is efficiently catalyzed to directionally generate methanol through the synergistic effect of an oxygen vacancy and an MOx-Co interface. Under the conditions of 150-200 DEG C, 1-2 MPa and simulated sunlight irradiation, the CO2 conversion rate reaches 36%-42%, the methanol selectivity reaches 63%-75%, the methanol yield reaches up to 19.0 mmol.g <-1 >. H <-1 >, and the activity attenuation rate is smaller than 1% after continuous operation for 100 h.

Description

Technical Field

[0001] This invention belongs to the field of photothermal catalytic CO2 hydrogenation to methanol technology, specifically relating to a method for constructing oxygen vacancy-MO through carbon-assisted defect engineering. x -Co interface synergistic dual active center photothermal catalyst and its application. Background Technology

[0002] Excessive carbon dioxide (CO2) emissions have led to global warming, posing a serious challenge to the ecological environment and sustainable development of human society. CO2 capture, utilization, and storage (CCUS) is a key technological pathway for addressing climate change. Among these, the targeted conversion of CO2 into high-value-added chemicals such as methanol through hydrogenation can both reduce industrial carbon emissions and achieve carbon resource recycling, demonstrating significant environmental and economic value.

[0003] Methanol, as an ideal liquid energy carrier (volume energy density 15.6 MJ / L) and a chemical platform compound, is widely used in the synthesis of basic raw materials such as olefins and dimethyl ether. In recent years, it has also become an alternative fuel for ships and a carrier for hydrogen energy storage and transportation, with market demand continuing to rise. Traditional methanol production relies on the reforming of fossil fuels to produce syngas and then hydrogenating it, resulting in a carbon emission intensity of 1.8 tons over its entire life cycle. CO2 / t 甲醇 The renewable energy-based water electrolysis for hydrogen production coupled with industrial CO2 capture and hydrogenation to synthesize methanol can achieve carbon emission reduction throughout the entire life cycle.

[0004] The production of methanol from CO2 via hydrogenation is constrained by inherent contradictions between thermodynamics and kinetics. Thermodynamic limitation: Low temperatures (<250℃) favor improved methanol selectivity (ΔH). 298k =-49.5 kJ / mol, exothermic reaction; however, CO2 molecules have high chemical stability (C=O bond dissociation energy 750 kJ / mol), and the activation energy barrier is too high at low temperatures, resulting in low conversion rates. Kinetic limitations: Although high temperatures can accelerate the reaction, they will promote the reverse water-gas reaction (RWGS, ΔH) 298k =41.1 kJ / mol (endothermic) dominates, leading to an increase in byproducts such as CO and a decrease in methanol selectivity.

[0005] Traditional thermocatalysis requires operation at 250–500°C and 10–30 MPa, resulting in high equipment investment and operating costs. Existing thermocatalysis research shows that although high selectivity can be achieved under mild conditions through precise control of catalyst structure, CO2 conversion rates are generally below 20% due to thermodynamic and kinetic limitations. For example: The Pd / In₂O₃-ZrO₂ catalyst prepared in CN105498756B showed a methanol selectivity of 74.2% and a CO₂ conversion of only 15.7% under conditions of 4 MPa and 270℃; the Cu-based catalyst (Nat. Catal. 2024, 7, 1199) showed a CO₂ conversion of 4.2±0.5% and a methanol selectivity of 76% under conditions of 250℃ and 3.0 MPa; the CuZn-based catalyst (Nat. Commun. 2024, 15, 2159) showed a CO₂ conversion of 8% and a methanol selectivity of 70% under conditions of 260℃ and 2.8 MPa; the In₂O₃-MnCO₃ catalyst (Nature Commun. 2025, 16:7804) showed a CO₂ conversion of 13.5%, a methanol selectivity of 67.5%, and a methanol yield of 13.5% under conditions of H₂ / CO₂ = 3:1, 4.0 MPa, and 150℃. mmol·g -1 ·h -1 The In2O3 / Al2O3-MgO catalyst reported in CN118847096A only achieved a CO2 conversion rate of 8.6% and a selectivity of 72% at 400℃ and 1.0 MPa. None of these catalysts can meet the dual requirements of conversion rate and selectivity for industrial applications.

[0006] To overcome the above-mentioned thermodynamic-kinetic contradictions, photothermal catalysis technology reduces the activation energy barrier of the reaction by inputting light energy. Theoretically, it can achieve a unity of high conversion rate and high selectivity under medium and low temperature conditions, and has become a research hotspot in this field. However, existing photothermal catalysts still have significant technical bottlenecks: (1) Insufficient oxygen vacancy stability: The concentration of oxygen vacancy generated by traditional reduction methods (such as H2 reduction) is difficult to control precisely, and it is easy to cause catalyst particle sintering under high temperature conditions; although plasma treatment can introduce oxygen vacancy, it is limited to the material surface and the oxygen vacancy stability is poor; doping strategies often lead to lattice distortion, affecting the stability of the material structure. (2) Weak interface synergy effect: Existing technologies have not achieved covalent anchoring of oxygen vacancy and metal oxide interface, resulting in poor interface structure stability, easy phase separation, reduced active sites, and reduced electron transport efficiency. (3) High process cost: For example, although the three-dimensional ordered macroporous nitrogen-doped carbon-supported CoPt catalyst reported by patent CN120346826A has certain photothermal catalytic activity, the methanol selectivity is less than 10%, and it involves precious metals and complex preparation processes, resulting in high cost and difficulty in large-scale application. Summary of the Invention

[0007] To address the problems of low photothermal conversion efficiency, insufficient CO2 activation capacity, poor methanol selectivity, and unsatisfactory stability of traditional catalysts, this invention provides a method for constructing oxygen vacancy-mediated MO through carbon-assisted defect engineering. x -Co interface dual-active-center photothermal catalyst enables the directional conversion of CO2 hydrogenation to methanol under medium and low temperature (150-200℃) and low pressure (1-2 MPa) conditions, while simultaneously achieving high activity, high selectivity and long-term stability.

[0008] The oxygen vacancy-mediated MO provided by this invention x The -Co interfacial dual-active-center photothermal catalyst comprises: a γ-Al₂O₃ support; Co-based nanoparticles with oxygen-rich vacancies on their surface, having a size of 6–8 nm; and MO atoms anchored to the surface of the Co-based nanoparticles via chemical bonding through the oxygen vacancies. x Nanoclusters, the MO x The nanoclusters have a diameter of 1–2 nm and form MO-Co covalent bonds with Co-based nanoparticles; MO x It is at least one of In2O3, ZnO, and MnO; the molar ratio of M to Co is 0.1 to 0.2; the first promoter is selected from C or C and N. Based on 100% catalyst mass, the loading of cobalt is 10% to 30%, and the loading of the first promoter is 0.05% to 1%.

[0009] Furthermore, the catalyst also includes a second promoter, which is selected from at least one of K and Na; the second promoter adjusts the electronic properties of the catalyst surface through electronic modification, thereby optimizing the CO2 activation and intermediate conversion pathway.

[0010] Furthermore, based on the catalyst mass of 100%, the preferred loading of cobalt element is 15% to 20%, the loading of the first auxiliary agent is 0.1% to 0.5%, and the loading of the second auxiliary agent is 0.1% to 0.5%.

[0011] The oxygen vacancy-mediated MO provided by this invention x -Co interfacial dual-active-center photothermal catalyst was prepared by the following steps:

[0012] Step 1: Preparation of oxygen-vacancy-rich Co-C / Al2O3 intermediate

[0013] The first auxiliary precursor and the cobalt source precursor were dissolved in distilled water with a volume equal to the pore volume of the γ-Al2O3 support to form a homogeneous precursor solution. The precursor solution was then immersed in the γ-Al2O3 support, mixed evenly, and vacuum rotary dried at 60–100 °C for 2–15 h. The dried sample was then placed in a tube furnace and carbonized at 420–660 °C for 4–6 h under an inert atmosphere. The carbon generated in situ inhibited the agglomeration of cobalt-based particles through confinement, forming 6–8 nm cobalt-based nanoparticles. Simultaneously, the carbon penetrated into the interstitial spaces of the cobalt-based nanoparticles to form a carburized structure. After naturally cooling to room temperature, the sample was calcined at 300–550 °C for 3–5 h under an oxygen-containing atmosphere to selectively oxidize the carbon and form oxygen vacancies on the surface of the Co-based nanoparticles. The residual carbon species stabilized the oxygen vacancies, resulting in an oxygen-vacancy-rich Co-C / Al2O3 intermediate.

[0014] Step 2: Load MO x Nanoclusters

[0015] will MO x The precursor solution was impregnated with the oxygen-rich vacancy Co-C / Al2O3 intermediate obtained in step 1, and after vacuum drying, it was heated to 380-550℃ at a rate of 2-5℃ / min under an inert atmosphere and calcined at this temperature for 3-5 h to induce MO x Nanoclusters are anchored to the surface of Co-based nanoparticles through oxygen vacancy chemical bonding, forming MO-Co covalent bonds, thus yielding MO. x -Co-C / Al2O3 catalyst precursor.

[0016] Step 3: Loading the second adjuvant

[0017] The catalyst precursor obtained in step 2 was impregnated with the second auxiliary agent precursor solution, dried under vacuum, and then calcined at 380–450 °C at a rate of 2–5 °C / min under an oxygen-containing atmosphere for 3–5 h to obtain K(Na)-MO. x -Co-C / Al2O3 catalyst precursor. This step is omitted when the catalyst does not contain a second promoter.

[0018] Step 4: Molding process

[0019] The catalyst precursor obtained in step 3 was compressed into tablets, crushed, and sieved to 40-60 mesh particles under a pressure of 1.0-1.5 MPa to obtain oxygen vacancy-mediated MO. x -Co interface dual-active-center photothermal catalyst.

[0020] Furthermore, in step 1 above, the γ-Al₂O₃ support has a particle size of 20–100 µm and a specific surface area of ​​200–500 m². 2 / g, pore volume 0.5~5 mL / g, pore size 5~100 nm.

[0021] Furthermore, in step 1 above, the cobalt source precursor is selected from any one of cobalt nitrate, cobalt acetate, cobalt carbonyl, cobalt oxalate, and ZIF-67.

[0022] Furthermore, the first adjuvant precursor mentioned above is selected from at least one of glucose, sucrose, sodium alginate, citric acid, cellulose, urea, melamine, N,N-dimethylformamide, ethylenediamine, amino acids, and dimethylimidazole.

[0023] Furthermore, the aforementioned inert atmosphere is nitrogen or argon, and the oxygen-containing atmosphere is a mixture of nitrogen or argon containing 1% to 5% oxygen by volume.

[0024] Furthermore, in step 2 above, the MO x The precursor is a soluble inorganic salt or organometallic compound corresponding to metal M, wherein MO x The precursor solution is MO x The precursor is a solution of distilled water, ethanol, or isopropanol.

[0025] Furthermore, in step 3 above, the second auxiliary agent precursor is selected from at least one of potassium carbonate, potassium nitrate, sodium carbonate, sodium hydroxide, sodium acetate, sodium oxalate, and sodium citrate.

[0026] The present invention also provides the oxygen vacancy-mediated MO x Applications of the -Co interface dual-active-center photothermal catalyst for the catalytic hydrogenation of CO2 to methanol. Specific application methods are as follows:

[0027] Step 1: Pre-reduction treatment of the catalyst

[0028] The catalyst and quartz sand were mixed at a volume ratio of 1:1 and placed in a fixed-bed reactor. Pre-reduction was carried out at a constant temperature of 350–550 °C for 4–6 h under a reducing atmosphere (pure hydrogen or a mixture of nitrogen or argon containing 5%–10% hydrogen by volume). After pre-reduction treatment, the cobalt valence state included Co. 0 Co 2+ .

[0029] Step 2: Catalytic CO2 hydrogenation to methanol

[0030] After the pre-reduction, a feed gas with an H2 / CO2 volume ratio of 3:1 is introduced into the fixed-bed reactor at a flow rate of 20–60 mL / min for purging for 30 min. The reactor pressure is adjusted to 1.0–2.0 MPa, and the temperature is raised to the reaction temperature of 150–200 °C. A 300 W xenon lamp equipped with an AM 1.5G filter is turned on, with a light intensity of 1.8–2.4 W / cm². 2 The reaction involves the hydrogenation of CO2 to produce methanol.

[0031] The beneficial effects of this invention are as follows:

[0032] 1. This invention employs a carbon-assisted defect engineering strategy, precisely constructing oxygen vacancy-mediated MOs through a synergistic process of carbothermal reduction, selective oxidation, and controlled reduction. x -Co interface dual-active-center photothermal catalyst has the following advantages:

[0033] (1) Precise control of oxygen vacancies: The carbon network formed during the carbonization stage can confine the growth of Co-based nanoparticles, while some carbon atoms infiltrate into the lattice of Co-based nanoparticles; subsequently, through the synergistic effect of controlled oxygen calcination and controlled reduction, a high concentration of oxygen vacancies is generated (XPS measurement, oxygen vacancy concentration O vac / O total (The percentage is 35%–60%). Residual carbon species stabilize oxygen vacancies through electron interactions. Compared to traditional methods such as plasma treatment and chemical etching, this process is simpler and can yield richer and more stable oxygen defect structures.

[0034] (2) Interface covalent anchoring reinforcement: MO x Nanoclusters are anchored to the surface of Co-based nanoparticles through oxygen vacancy chemical bonding, forming stable MO-Co covalent bonds, which improves the interfacial electron transport efficiency and lays the structural foundation for the synergistic effect of dual active centers.

[0035] (3) Green and scalable process: The step-by-step wet impregnation combined with carbon-assisted defect engineering strategy does not require the use of precious metals. The process is simple and controllable, with low cost and good industrial scale-up potential.

[0036] 2. Compared with existing photothermal catalytic CO2 hydrogenation technology, this invention achieves oxygen vacancy-MO through carbon-assisted defect engineering. x The precise synergistic regulation of the dual active centers at the Co interface has the following significant technical effects:

[0037] (1) Significantly improved catalytic performance: After reduction, the high concentration of oxygen vacancies on the surface of the catalyst weakens the C=O bond of CO2 through electron transfer, generating *CO3. 2- Or *HCOO intermediate; MO x The -Co interface acts as an electron channel, promoting H* species migration and photogenerated carrier separation, and catalyzing the hydrogenation of intermediates to methanol. Under reaction temperatures of 150–200 °C, reaction pressures of 1–2 MPa, and xenon lamp irradiation, CO2 conversion reached 28%–42%, methanol selectivity was 56%–75%, and methanol yield reached 19.0 mmol·g. -1 ·h -1 .

[0038] (2) Significantly improved long-term stability: After reduction, the residual carbon species stabilize oxygen vacancies through electronic interactions, inhibiting the sintering of Co nanoparticles; MOx The MO-Co covalent bond structure at the -Co interface enhances structural stability, avoids interfacial phase separation, and results in a catalyst activity decay rate of <1% after 100 hours of continuous operation.

[0039] (3) Enhanced industrial applicability: The stepwise wet impregnation combined with carbon-assisted defect engineering strategy eliminates the need for precious metals and complex equipment; the catalyst forming and pretreatment process is compatible with existing fixed-bed reactors, making operation simple, cost controllable, and easy to scale up.

[0040] In summary, this invention overcomes the technical bottleneck of oxygen vacancy stability and interfacial synergy through a carbon-assisted defect engineering strategy, achieving a balance between activity, selectivity and stability in the photothermal catalytic CO2 hydrogenation to methanol process, and providing a scalable technical solution for the high-value utilization of CO2. Attached Figure Description

[0041] Figure 1 These are X-ray diffraction (XRD) patterns of the catalysts prepared in Examples 2 and 5 and Comparative Examples 1 and 4.

[0042] Figure 2 These are electron paramagnetic resonance (EPR) images of the catalysts prepared in Examples 2 and 5 and Comparative Examples 1, 2 and 6 after pre-reduction.

[0043] Figure 3 The X-ray photoelectron spectroscopy (XPS) O1s spectra of the catalysts prepared in Examples 1, 2, 5 and Comparative Examples 1, 2, 6 after pre-reduction are shown.

[0044] Figure 4 These are transmission electron microscope (TEM) images of the catalysts prepared in Examples 1, 2, and 3 after the reaction, respectively. Figure 4 (a), 4(b), 4(c).

[0045] Figure 5 These are the in-situ diffuse reflectance infrared Fourier transform (operando DRIFTS) spectra of the catalysts in Comparative Example 1 and Example 1 during the catalytic CO2 hydrogenation reaction, respectively. Figure 5 (a) 5(b)

[0046] Figure 6 This is the long-cycle reaction stability test curve of the catalyst in Example 1 catalyzing the hydrogenation of CO2 to methanol according to the method in Application Example 1. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments. It should be noted that all processes not specifically described are operations that can be implemented by those skilled in the art based on existing technology; reagents or instruments whose manufacturers are not specified are considered to be commercially available conventional products.

[0048] Example 1

[0049] Step 1: Preparation of oxygen-vacancy-rich Co-C / Al2O3 intermediate

[0050] Weigh 0.5 g glucose and 1.75 g cobalt nitrate hexahydrate and dissolve them in 2.4 mL distilled water (distilled water volume equal to the pore volume of the support). Stir magnetically at 25±2℃ for 30 min until completely dissolved. Slowly add the resulting solution dropwise to 2.0 g γ-Al2O3 support (particle size 50 µm, specific surface area 400 m² / g, pore volume 1.2 mL / g, pore size 20 nm). After thorough mixing, transfer to a rotary evaporator and vacuum dry at 80℃ for 12 h under a vacuum of -0.09 MPa and a rotation speed of 30 r / min. Place the dried sample in a tube furnace and heat to 500℃ at 3℃ / min in high-purity argon (50 mL / min), and perform isothermal carbothermic treatment for 5 h. After naturally cooling to room temperature, calcine at 300℃ for 4 h under an O2-Ar mixed atmosphere containing 3% oxygen by volume. h, an oxygen-vacancy-rich Co-C / Al2O3 intermediate was obtained (the oxygen vacancy concentration was 56% as measured by XPS).

[0051] Step 2: Loading In2O3 nanoclusters

[0052] 0.23 g of indium nitrate was dissolved in 2.4 mL of distilled water and added dropwise to the intermediate obtained in step 1. After thorough mixing, the mixture was transferred to a rotary evaporator and vacuum dried at 80 °C for 12 h at a vacuum of -0.09 MPa and a rotation speed of 30 r / min. The dried sample was placed in a tube furnace and heated to 400 °C at 3 °C / min in high-purity argon gas (50 mL / min). The temperature was kept constant for 4 h to obtain the In2O3-Co-C / Al2O3 catalyst precursor.

[0053] Step 3: Molding process

[0054] The catalyst precursor obtained in step 2 was pressed into tablets, crushed, and sieved to 40-60 mesh under a pressure of 1.0 MPa to obtain the In2O3-Co-C / Al2O3 catalyst. In this catalyst, based on 100% catalyst mass, the Co element loading is 15%, the C loading is 0.3%, and the In to Co molar ratio is 0.1.

[0055] Example 2

[0056] In step 2 of this embodiment, 0.132 g of zinc acetate dihydrate was used to replace indium nitrate in step 2 of Example 1. The other steps were the same as in Example 1, yielding a ZnO-Co-C / Al2O3 catalyst. In this catalyst, based on 100% catalyst mass, the Co element loading was 15%, the C loading was 0.3%, and the Zn to Co molar ratio was 0.1.

[0057] Example 3

[0058] In step 2 of this embodiment, 0.147 g of manganese acetate tetrahydrate was used to replace indium nitrate in step 2 of Example 1. The other steps were the same as in Example 1, resulting in a MnO-Co-C / Al2O3 catalyst. In this catalyst, based on 100% catalyst mass, the Co element loading was 15%, the C loading was 0.3%, and the molar ratio of Mn to Co was 0.1.

[0059] Example 4

[0060] The In2O3-Co-C / Al2O3 catalyst precursor was prepared according to steps 1 and 2 of Example 1. 0.018 g of K2CO3 was weighed and dissolved in a mixture of 5 mL deionized water and 5 mL ethanol. 2.0 g of the above In2O3-Co-C / Al2O3 catalyst precursor was added, and the mixture was ultrasonically dispersed at room temperature for 30 min. The resulting mixture was transferred to a rotary evaporator and vacuum dried at 80 °C for 12 h. Subsequently, it was calcined at 400 °C for 4 h under an O2-Ar mixed atmosphere containing 3% oxygen by volume to obtain the K-In2O3-Co-C / Al2O3 catalyst precursor. This precursor was pressed into tablets at 1.0 MPa, crushed, and sieved to obtain 40–60 mesh particles to obtain the K-In2O3-Co-C / Al2O3 catalyst. In this catalyst, based on 100% catalyst mass, the Co loading was 15%, the C loading was 0.3%, the K loading was 0.1%, and the In to Co molar ratio was 0.1.

[0061] Example 5

[0062] The ZnO-Co-C / Al2O3 catalyst precursor was prepared according to steps 1 and 2 of Example 2. 0.014 g of Na2CO3 was weighed and dissolved in a mixture of 5 mL deionized water and 5 mL ethanol. 2.0 g of the above ZnO-Co-C / Al2O3 catalyst precursor was added, and the mixture was ultrasonically dispersed at room temperature for 30 min. The resulting mixture was transferred to a rotary evaporator and vacuum dried at 80 °C for 12 h. Subsequently, it was calcined at 400 °C for 4 h under an O2-Ar mixed atmosphere containing 3% oxygen by volume to obtain the Na-ZnO-Co-C / Al2O3 catalyst precursor. This catalyst precursor was pressed into tablets at 1.0 MPa, crushed, and sieved to obtain 40–60 mesh particles to obtain the Na-ZnO-Co-C / Al2O3 catalyst. In this catalyst, based on 100% catalyst mass, the Co element loading was 15%, the C loading was 0.3%, the Na loading was 0.1%, and the Zn to Co molar ratio was 0.1.

[0063] Example 6

[0064] In step 2 of this embodiment, the amount of indium nitrate is increased to 0.458 g, and the other steps are the same as in Example 1, to obtain the In2O3-Co-C / Al2O3 catalyst. In this catalyst, based on 100% catalyst mass, the Co loading is 15%, the C loading is 0.3%, and the In to Co molar ratio is 0.2.

[0065] Comparative Example 1

[0066] The oxygen-vacancy-enriched Co-C / Al2O3 intermediate was prepared according to step 1 of Example 1. The oxygen-vacancy-enriched Co-C / Al2O3 intermediate was then compressed, crushed, and sieved according to step 3 of Example 1 to obtain the Co-C / Al2O3 catalyst.

[0067] Comparative Example 2

[0068] In step 1 of Example 1, without adding glucose, a Co / Al2O3 intermediate is obtained. The Co / Al2O3 intermediate is then tableted, crushed, and sieved according to the method in step 3 of Example 1 to obtain a Co / Al2O3 catalyst.

[0069] Comparative Example 3

[0070] Weigh 2.0 g of γ-Al2O3 support, dissolve 0.23 g of indium nitrate in 2.4 mL of distilled water and slowly add it dropwise to 2.0 g of γ-Al2O3 support. After thorough mixing, transfer to a rotary evaporator and vacuum dry at 80 °C for 12 h at a vacuum of -0.09 MPa and a rotation speed of 30 r / min. After naturally cooling to room temperature, calcine at 300 °C for 4 h in an O2-Ar mixed atmosphere containing 3% oxygen by volume to obtain an In2O3 / Al2O3 intermediate. Compress, crush, and sieve the In2O3 / Al2O3 intermediate according to step 3 of Example 1 to obtain the In2O3 / Al2O3 catalyst.

[0071] Comparative Example 4

[0072] In Comparative Example 3, indium nitrate was replaced with 0.132 g of zinc acetate dihydrate, and the other steps were the same as in Comparative Example 3 to obtain the ZnO / Al2O3 catalyst.

[0073] Comparative Example 5

[0074] In step 1 of Example 1, without the addition of glucose, a Co / Al2O3 intermediate was obtained. Then, In2O3 nanoclusters were loaded according to step 2 of Example 1, and the catalyst was shaped according to step 3 of Example 1 to obtain the In2O3-Co / Al2O3 catalyst.

[0075] Comparative Example 6

[0076] In Comparative Example 5, indium nitrate was replaced with 0.132 g of zinc acetate dihydrate, and the other steps were the same as in Comparative Example 5, to obtain the ZnO-Co / Al2O3 catalyst.

[0077] Comparative Example 7

[0078] In Comparative Example 5, indium nitrate was replaced with 0.147 g of manganese acetate tetrahydrate, and the other steps were the same as in Comparative Example 5, to obtain the ZnO-Co / Al2O3 catalyst.

[0079] Application Example 1

[0080] The catalysts obtained in Examples 1-6 and Comparative Examples 1-7 were used to catalyze the hydrogenation of CO2 to methanol, and the specific methods of use are as follows:

[0081] Step 1: Pre-reduction treatment of the catalyst

[0082] 0.5 g of catalyst was mixed with an equal volume of quartz sand and placed in a fixed-bed reactor (quartz tube inner diameter 8 mm). High-purity hydrogen gas (50 mL·min⁻¹) was introduced under atmospheric pressure. -1 ), at 3℃·min -1 Heat to 400℃ and pre-reduced at a constant temperature for 5 hours.

[0083] Step 2: Catalytic CO2 hydrogenation to methanol

[0084] After the pre-reduction, a feed gas with an H2 / CO2 volume ratio of 3:1 was introduced into the fixed-bed reactor at a total flow rate of 50 mL / min for 30 min. The reactor pressure was adjusted to 1.0 MPa, and the temperature was raised to the reaction temperature of 150℃. A 300 W xenon lamp equipped with an AM 1.5G filter was turned on, with a light intensity of 2.0 W / cm². 2 The reaction was carried out using CO2 hydrogenation to produce methanol. CO and CH4 in the gaseous products were detected by gas chromatography (TDX-01 column + TCD detector); methanol in the liquid products was quantitatively analyzed by gas chromatography (equipped with SOLGEL-WAX column and FID detector). The reaction results are shown in Table 1.

[0085] Table 1. Results of catalyst activity tests

[0086]

[0087] The catalysts obtained in Examples 1-6 and Comparative Examples 1-7, as well as the catalysts after reduction treatment and after catalytic reaction, were characterized structurally. The results are shown in the figure. Figures 1-6 .

[0088] Depend on Figure 1 As shown in the XRD patterns, the catalyst in Comparative Example 1 exhibits a characteristic peak of Co3O4, while the catalyst in Comparative Example 4 exhibits a characteristic peak of ZnO. In Examples 2 and 5, the catalysts exhibit characteristic peaks of both Co3O4 and ZnO, and the second promoter K has no significant effect on the characteristic peaks of Co3O4 and ZnO, indicating that the promoter did not change the main phase structure of the catalyst.

[0089] Depend on Figure 2 The electron paramagnetic resonance (EPR) diagrams shown demonstrate that an oxygen-vacancy-rich catalyst precursor was successfully prepared through a synergistic process of stepwise impregnation, carbothermal reduction, selective oxidation, and controlled reduction. Compared with the carbon-free Comparative Examples 2 and 6, the EPR signal intensity of the catalysts in Examples 2 and 5 was significantly enhanced, further confirming the effectiveness of the carbon-assisted defect engineering strategy in regulating oxygen vacancies.

[0090] Combination Figure 3 The XPS O1s spectrum shown (calculated by peak fitting) indicates that the catalyst prepared by the method of this invention has a high oxygen vacancy content and an oxygen vacancy concentration of O. vac / O total The percentage was 35%–60%, which corroborates the EPR results and confirms the efficient role of carbon-assisted strategies in the construction of oxygen vacancies.

[0091] Figure 4Used to demonstrate Co nanoparticles and MO in the catalyst after a long-cycle 100-hour reaction. x The morphology, size, and nano-interface structure formed by the nanoclusters provide direct evidence of the structural stability of the catalyst in long-cycle reactions. Figure 4 (a) TEM results after the catalyst reaction in Example 1 show that after a long-term reaction of 100 h, the Co particle size on the catalyst is 7.8 ± 1.5 nm, the In2O3 cluster particle size is 1.5 ± 0.5 nm, and the In2O3 is uniformly distributed on the surface of the Co particles. The interface structure is stable, and no particle sintering or In2O3-Co phase separation occurs. Figure 4 (b) TEM results after the catalyst reaction in Example 2 show that after a long-term reaction of 100 h, the Co particle size on the catalyst is 6.6 ± 1.0 nm, the ZnO cluster particle size is 1.7 ± 0.6 nm, ZnO is uniformly distributed on the surface of Co particles, the interface structure is stable, and no particle sintering or ZnO-Co phase separation occurs. Figure 4 (c) TEM results after the catalyst reaction in Example 3 show that after a long reaction period of 100 h, the Co particle size on the catalyst is 6.9±1.4 nm, the MnO cluster particle size is 1.7±0.5 nm, MnO is uniformly distributed on the surface of Co particles, the interface structure is stable, and no particle sintering or MnO-Co phase separation occurs.

[0092] Depend on Figure 5 (a) The operando-Drifts spectrum of the catalyst in Comparative Example 1 shows that CH* species were mainly detected during the reaction (1051 cm⁻¹). -1 2822 cm -1 2946 cm -1 3019 cm -1 ) and HCOO* species (1368 cm -1 1550 cm -1 This suggests that it primarily follows the conversion pathway of formate hydrogenation to CH4, therefore the methanol selectivity is 0. Figure 5 (b) The operando-Drift spectrum of the catalyst in Example 1 shows that CO3* species can be observed on the catalyst surface (1607 cm⁻¹). -1 ), HCOO* species (1356 cm) -1 ) and H3CO* species (1046 cm) -1 This provides evidence that the In2O3-Co interface can significantly improve methanol selectivity by regulating the intermediate conversion pathway (HCOO*→H3CO*→CH3OH), which is consistent with the "oxygen vacancy-MO" proposed in this invention. x The "Co-interface synergistic dual active center" provides key mechanistic evidence for the directed synthesis of methanol.

[0093] Depend on Figure 6 The long-term reaction stability test curve of the catalyst in Example 1 shows that the catalyst of the present invention has an activity decay rate of <1% after running continuously for 100 h under the reaction conditions, indicating that it has excellent long-term stability.

[0094] Application Example 2

[0095] The catalyst obtained in Example 1 was treated using the pre-reduction method described in Application Example 1, and then subjected to catalytic CO2 hydrogenation to methanol reaction. The reaction temperature was adjusted to 200°C, and the other conditions were the same as in Application Example 1. The results showed that the CO2 conversion rate was 42±1.3%, the methanol selectivity was 56±2.1%, and the methanol yield was 15.1±0.4 mmol·g. -1 ·h -1 .

[0096] Application Example 3: The catalyst obtained in Example 1 was treated using the pre-reduction method described in Application Example 1, and then subjected to catalytic CO2 hydrogenation to methanol reaction. The reaction pressure was adjusted to 2.0 MPa, and the other conditions were the same as in Application Example 1. The results showed that the CO2 conversion rate was 40 ± 0.9%, the methanol selectivity was 74 ± 2.0%, and the methanol yield was 19.0 ± 0.3 mmol·g. -1 ·h -1 .

Claims

1. An oxygen-vacancy-mediated MO x -Co interface bi-active site photothermal catalyst characterized by: The catalyst comprises: a γ-Al2O3 carrier; Co-based nanoparticles with oxygen-rich surface vacancies, with a size of 6-8 nm; MO chemically bonded to the Co-based nanoparticles through the oxygen vacancies and anchored on the surface of the Co-based nanoparticles x nanoclusters, the MO x nanoclusters, the MO x The diameter of the nanoclusters is 1-2 nm, and the MO forms a M-O-Co covalent bond with the Co-based nanoparticles; the MO x is at least one of In2O3, ZnO, and MnO; the molar ratio of M to Co is 0.1-0.

2. a first additive selected from C or C and N; a cobalt element loading of 10%-30% and a first additive loading of 0.05%-1%, based on 100% of the mass of the catalyst; The preparation method of the catalyst comprises the following steps: Step 1: preparation of an oxygen-rich vacancy Co-C / Al2O3 intermediate The first additive precursor and the cobalt source precursor are dissolved in distilled water in an equal volume to the pore volume of the γ-Al2O3 carrier to form a uniform precursor solution; the precursor solution is impregnated in the γ-Al2O3 carrier, and after being mixed uniformly, vacuum rotary drying is performed at 60-100 ℃ for 2-15 h, then carbonization treatment is performed at 420-660 ℃ under an inert atmosphere for 4-6 h, and after natural cooling, roasting is performed at 300-550 ℃ under an oxygen-containing atmosphere for 3-5 h to obtain the oxygen-rich vacancy Co-C / Al2O3 intermediate; Step 2: Loading MO x Nanoclusters The MO x The precursor solution is impregnated into the resulting intermediate, vacuum dried, and heated to 380-550°C under an inert atmosphere, and held at temperature for 3-5 hours to obtain MO x -Co-C / Al2O3 catalyst precursor; Step 3: molding treatment The resulting catalyst precursor was pressed into a tablet, crushed and sieved to 40-60 mesh to obtain oxygen vacancy-mediated MO x Co interface bimetallic active center photothermal catalyst.

2. The oxygen-vacancy-mediated MO of claim 1 x A photo-thermal catalyst with dual active sites at Co interface, characterized in that: The catalyst further comprises a second assistant selected from at least one of K and Na, and the loading of the second assistant is 0.05% to 1%; in the preparation method of the catalyst, a process of loading the second assistant is further included after step 2 and before step 3, and the specific process is as follows: a second assistant precursor solution is impregnated into the catalyst precursor obtained in step 2, vacuum dried, heated to 380 to 450 DEG C under an oxygen-containing atmosphere, and then constant temperature calcination is performed for 3 to 5 hours to obtain K(Na)-MO x -Co-C / Al2O3 catalyst precursor.

3. The oxygen-vacancy-mediated MO of claim 2 x - Photocatalyst with dual active sites at Co interface, characterized in that: The cobalt element loading is 15%-20%, the first additive loading is 0.1%-0.5%, and the second additive loading is 0.1%-0.5%, based on 100% of the mass of the catalyst.

4. The oxygen-vacancy-mediated MO of claim 1 x A photo-thermal catalyst with dual active sites at Co interface, characterized in that: In Step 1, the γ-Al2O3 support has a particle size of 20 to 100 µm, a specific surface area of 200 to 500 m 2 / g, a pore volume of 0.5 to 5 mL / g, and a pore diameter of 5 to 100 nm.

5. The oxygen-vacancy-mediated MO of claim 1 x A photo-thermal catalyst with dual active sites at Co interface, characterized in that: In step 1, the cobalt source precursor is selected from any one of cobalt nitrate, cobalt acetate, cobalt carbonyl, cobalt oxalate and ZIF-67, and the first additive precursor is selected from at least one of glucose, sucrose, sodium alginate, citric acid, cellulose, urea, melamine, N,N-dimethylformamide, ethylenediamine, amino acid and dimethylimidazole.

6. The oxygen-vacancy-mediated MO of claim 1 or 2 x A photo-thermal catalyst with dual active sites at Co interfaces, characterized in that: The inert atmosphere is nitrogen or argon, and the oxygen-containing atmosphere is a nitrogen or argon mixed gas containing 1%-5% by volume of oxygen.

7. The oxygen-vacancy-mediated MO of claim 1 x A photo-thermal catalyst with dual active sites at Co interface, characterized in that: In step 2, the MO x The precursor is a soluble inorganic salt or a metal organic compound corresponding to the metal M, the MO x The precursor solution is MO x The precursor is a distilled water or ethanol or isopropanol solution.

8. The oxygen-vacancy-mediated MO of claim 2 x A photo-thermal catalyst with dual active sites at Co interface, characterized in that: The second additive precursor is selected from at least one of potassium carbonate, potassium nitrate, sodium carbonate, sodium hydroxide, sodium acetate, sodium oxalate and sodium citrate.

9. The oxygen-vacancy-mediated MO of claim 1 x Use of a photo-thermal catalyst with dual active sites at the Co interface for the hydrogenation of CO2 to methanol.

10. The oxygen-vacancy-mediated MO of claim 9 x The use of a photo-thermal catalyst with dual active sites at the Co interface for the hydrogenation of CO2 to methanol, characterized in that The method comprises the following steps: Step 1: pre-reduction treatment of the catalyst The catalyst is mixed with quartz sand at a volume ratio of 1:1, and placed in a fixed bed reactor, and pre-reduction is performed at 350-550 ℃ under a reduction atmosphere for 4-6 h; the reduction atmosphere is pure hydrogen or a nitrogen or argon mixed gas containing 5%-10% by volume of hydrogen; Step 2: catalytic CO2 hydrogenation to methanol After the pre-reduction is completed, the raw gas with a volume ratio of H2 / CO2 of 3:1 is introduced into the fixed bed reactor at a flow rate of 20-60 mL / min for 30 min; the pressure of the reactor is adjusted to 1.0-2.0 MPa, and the temperature is increased to the reaction temperature of 150-200 ℃; the 300 W xenon lamp equipped with AM 1.5G filter is turned on, and the light intensity is 1.8-2.4 W / cm 2 , and the CO2 hydrogenation to methanol reaction is carried out.

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