CeO2 nanorod catalyst with defect porous structure, preparation method of CeO2 nanorod catalyst and application of CeO2 nanorod catalyst in dimethyl carbonate synthesis reaction
By preparing CeO2 nanorod catalysts with defective porous structures and exposing specific crystal surfaces and active sites, the problem of insufficient activity and selectivity of existing catalysts in the synthesis of dimethyl carbonate by CO2 and methanol is solved, and a highly efficient and stable catalytic effect is achieved.
Patent Information
- Application Number
- CN202510435487.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-08
- Publication Date
- 2025-08-22
AI Technical Summary
The existing catalysts have low activity, poor selectivity, and insufficient stability in the direct synthesis of dimethyl carbonate by CO2 and methanol, making it difficult to overcome the limitations of thermodynamic equilibrium and the influence of water.
A two-step hydrothermal method was used to prepare CeO2 nanorod catalyst with defective porous structures. By exposing low-index and high-index crystal planes, the Ce3+-OV-Ce3+-OL structure was formed, which was used as the adsorption activation site of CO2 and methanol to improve the catalytic performance.
High activity, high selectivity and stable dimethyl carbonate synthesis was achieved, excellent catalytic performance, and good stability was maintained in multiple cycle tests.
Smart Images
Figure CN120515401A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to a CeO2 nanorod catalyst with a defective porous structure and a preparation method and application thereof, belonging to the field of fine chemicals. Background Art
[0002] Dimethyl carbonate is a green chemical with significant demand in applications such as lithium battery solvents, polycarbonate engineering plastics, green coatings, and gasoline and diesel additives, exceeding 1.5 million tons per year. Currently, dimethyl carbonate is synthesized using the following methods: phosgene, transesterification, urea alcoholysis, methanol oxidative carbonylation, CO esterification, and direct synthesis from CO2 and methanol.
[0003] The direct synthesis method of CO2 and methanol uses CO2 and methanol as raw materials to directly react to produce dimethyl carbonate. It has gradually attracted attention in recent years. It has the following advantages: 1) the raw materials are cheap and easy to obtain; 2) the reaction is simple, and dimethyl carbonate can be directly obtained in one step; 3) the production is green and safe, the raw materials are non-toxic or low-toxic, and the reaction process is not prone to explosion.
[0004] Highly active, selective, and stable catalysts are key to the direct synthesis of dimethyl carbonate from CO₂ and methanol. Key technical challenges in this route include thermodynamic equilibrium limitations, difficulty in CO₂ activation, and the influence of water produced by the reaction on the reaction equilibrium. Currently reported catalysts generally produce suboptimal dimethyl carbonate yields without the use of a dehydrating agent.
[0005] Therefore, in order to overcome the above-mentioned defects of the prior art, a highly active, highly selective and stable catalyst was prepared, and this invention is proposed. Summary of the Invention
[0006] According to a first aspect of the present application, a CeO2 nanorod catalyst having a defective porous structure is provided. The catalyst has a defective porous nanorod morphology; in addition to exposing low-index crystal faces, its surface also exposes high-index crystal faces.
[0007] A CeO2 nanorod catalyst with a defective porous structure, wherein the CeO2 nanorod catalyst has a defective porous nanorod morphology;
[0008] The apparent dimensions of the nanorods are 50 to 250 nm in length and 7 to 12 nm in diameter.
[0009] Optionally, the CeO2 nanorod catalyst has a cubic fluorite CeO2 structure.
[0010] Optionally, the surface of the CeO2 nanorod catalyst is rich in Ce 3+ -O V -Ce 3+ -OL structure.
[0011] Optionally, the surface exposed crystal planes of the CeO2 nanorod catalyst include low-index crystal planes;
[0012] The low-index crystal plane is at least one of (111), (110) and (100) crystal planes.
[0013] Optionally, the surface exposed crystal planes of the CeO2 nanorod catalyst further include high-index crystal planes;
[0014] The high-index crystal plane is a (311) crystal plane.
[0015] Optionally, the surface exposed crystal planes of the CeO2 nanorod catalyst are (111), (110), and (311) crystal planes.
[0016] According to a second aspect of the present application, a method for preparing a CeO2 nanorod catalyst having a defective porous structure is provided. The method employs a two-step hydrothermal process. The first hydrothermal step provides a CeO2 nanorod-shaped precursor. The second hydrothermal step results in the appearance of defective pores on the CeO2 catalyst surface, which in turn rearranges the CeO2 surface and alters the exposed crystal faces.
[0017] The preparation method of the CeO2 nanorod catalyst comprises:
[0018] S1: mixing the cerium source solution and the precipitant solution, aging, and then transferring to a hydrothermal kettle for hydrothermal treatment, separation, and drying to obtain a precursor in the shape of CeO2 nanorods;
[0019] S2: dissolving a CeO2 nanorod-shaped precursor in water, placing the precursor in a hydrothermal kettle for hydrothermal treatment, separating, drying, and calcining to obtain the CeO2 nanorod catalyst having a defective porous structure.
[0020] Optionally, in step S1, the cerium source is selected from at least one of cerium chloride, cerium nitrate, and cerium acetate;
[0021] The precipitant is selected from at least one of potassium hydroxide, sodium hydroxide and sodium phosphate.
[0022] Optionally, in step S1, the temperature of the hydrothermal treatment is 100-180° C., and the time of the hydrothermal treatment is 12-48 hours.
[0023] Optionally, in step S2, the temperature of the hydrothermal treatment is 100-180° C., and the time of the hydrothermal treatment is 12-48 hours.
[0024] Optionally, in step S2, the temperature of the hydrothermal treatment is 140°C.
[0025] Optionally, in step S1, the cerium source solution is an aqueous solution of cerium nitrate hexahydrate, and the cerium ion concentration is 0.0625 mmol / ml.
[0026] Optionally, in step S1, the precipitant solution is an aqueous solution of sodium hydroxide with a concentration of 6.25 mmol / ml.
[0027] Optionally, in steps S1 and S2, aging, separation, drying and roasting can be performed by conventional means in the art.
[0028] Specifically, in step S1, aging is performed by standing at room temperature for 0.5 hours, separation is performed by centrifugation at a speed of 3000 to 5000 rpm, and drying is performed by vacuum drying at 60° C. for 6 to 12 hours.
[0029] In step S2, the separation method is suction filtration, the drying method is vacuum drying at 60° C. for 6 to 12 hours, and the calcination temperature is 600° C. for 1 to 4 hours.
[0030] As a preferred embodiment, the preparation method comprises:
[0031] (1) adding a cerium source into ultrapure water for dissolution and / or dispersion; adding a precipitant into ultrapure water for dissolution and / or dispersion;
[0032] (2) adding the cerium solution to the precipitant solution, stirring thoroughly for 2 h at room temperature and then standing for 0.5 h to obtain system I; the pH of system I is >7;
[0033] (3) transferring the system I obtained in step (2) to a hydrothermal reactor and subjecting it to hydrothermal treatment at high temperature to complete the first hydrothermal treatment; and obtaining a precursor in the shape of CeO2 nanorods after separation and drying;
[0034] (4) adding the CeO2 nanorod-shaped precursor obtained in step (3) to ultrapure water and stirring at room temperature for 2 h to obtain system II; the pH of system II is 7;
[0035] (5) Transferring the system II obtained in step (4) to a hydrothermal reactor and subjecting it to hydrothermal treatment at high temperature, thereby completing the second step of hydrothermal treatment; and obtaining the catalyst after separation, drying, and calcination.
[0036] According to the third aspect of the present application, a method for directly synthesizing dimethyl carbonate from CO2 and methanol is provided. The above-mentioned defective porous CeO2 nanorod catalyst has a defective porous structure, and its surface is rich in active Ce 3+ -O V -Ce 3+ -O LThe structure serves as an adsorption activation site for CO2 and methanol, which is beneficial for the catalytic synthesis of dimethyl carbonate. It has the advantages of good catalytic performance, high selectivity and stability.
[0037] A method for directly synthesizing dimethyl carbonate from CO2 and methanol comprises the following steps:
[0038] The catalyst and methanol are placed in a reactor, CO2 is introduced, and the mixture is reacted under stirring to prepare dimethyl carbonate;
[0039] The catalyst is selected from at least one of the above-mentioned CeO2 nanorod catalysts with defective porous structure.
[0040] Optionally, the amount of the catalyst used is 1-2 mg / ml.
[0041] Specifically, the mass of the added catalyst was 17 mg, and the volume of pure methanol was 10 ml.
[0042] Optionally, the injection pressure of CO2 is 3-5 MPa, the reaction temperature is 120-180°C, and the reaction time is 0.5-3 h.
[0043] Preferably, the pressure of CO2 injected into the reactor is 3-5 MPa, and before that, the air in the reactor is first removed using CO2.
[0044] Specifically, the reaction temperature is 160° C., and the reaction time is 2 h.
[0045] The beneficial effects of this application include:
[0046] The CeO2 nanorod catalyst with defective porous structure provided by the present application has active CeO2 on its surface. 3 + -O V -Ce 3+ -O L The structure serves as an adsorption activation site for CO2 and methanol, which is beneficial for the catalytic synthesis of dimethyl carbonate. It has the advantages of good catalytic performance, high selectivity and stability. BRIEF DESCRIPTION OF THE DRAWINGS
[0047] Figure 1 The CeO2-TH-x (x represents the temperature of the second hydrothermal treatment / °C) series catalysts and CeO2-rich O V Powder X-ray diffraction pattern of the precursor;
[0048] Figure 2 The nanorod-like morphology of CeO2-TH-140 in Example 3 (left) and the surface-exposed high-index (311) crystal plane (right) are shown under high-resolution transmission electron microscopy.
[0049] Figure 3 The space-time yield and selectivity of each catalyst in Example 4 for the direct synthesis of dimethyl carbonate from CO2 and methanol;
[0050] Figure 4 These are the results of five cycle stability tests of the CeO2-TH-140 catalyst in Example 4. DETAILED DESCRIPTION
[0051] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.
[0052] Unless otherwise specified, the reagents and raw materials in the examples of this application were purchased through commercial channels.
[0053] Unless otherwise specified, conventional methods were used for testing, and instrument settings were those recommended by the manufacturer.
[0054] Example 1 Catalyst Cerium Precursor CeO2-Rich O V Preparation of CeO2-TH-x
[0055] Weigh 20g of NaOH and 2.171g of Ce(NO3)3·6H2O and dissolve them in 70ml and 10ml of ultrapure water, respectively. Add the cerium solution to the sodium hydroxide solution at room temperature and stir thoroughly for 2h, then age and let it stand for 0.5h. Transfer the obtained purple mixed slurry to a hydrothermal kettle and keep it under hydrothermal conditions at 100℃ for 24h. After the temperature of the hydrothermal kettle drops to room temperature, centrifuge at 4000rpm. Wash the obtained product with ultrapure water and anhydrous ethanol three times by centrifugation, and then vacuum dry at 60℃ for 9h to obtain the cerium precursor CeO2-rich O V .
[0056] Weigh 0.2g of cerium precursor and disperse it in 80ml of ultrapure water and stir it at room temperature for 2h. Transfer the mixed slurry to a hydrothermal kettle and keep it under hydrothermal conditions at different temperatures for 24h. Use suction filtration to wash the obtained yellow-white product with ultrapure water and anhydrous ethanol, and vacuum dry it at 60°C overnight. Finally, place the product in an air atmosphere and calcine it at 600°C in a tubular furnace for 1h, controlling the heating rate to 2°C / min. The synthesized series of catalysts are named CeO2-TH-x (x represents the different temperatures during the second hydrothermal treatment, x = 100, 120, 140, 160, 180°C).
[0057] Example 2 Structural Characterization of Catalyst
[0058] Powder X-ray diffraction of each catalyst was carried out using a Rigaku Miniflex 600 X-ray diffractometer with a Cu Kα radiation source. like Figure 1 As shown, CeO2-rich O V Both CeO2-TH-x catalysts have cubic fluorite CeO2 structure.
[0059] Example 3 Catalyst Cerium Precursor CeO2-Rich O V Determination of the relative proportion of exposed crystal planes and oxygen vacancies on the surface of CeO2-TH-x
[0060] The exposed crystal faces on the catalyst surface were measured using FEI-Talos-F200X high-resolution transmission electron microscopy (HRTEM). Figure 2 As shown, the CeO2-TH-140 catalyst is a nanorod-like structure (left), and its surface shows exposed high-index (311) crystal planes (right).
[0061] Oxygen vacancies in the catalyst (O V ) and Ce 3+ The X-ray photoelectron spectroscopy (XPS) was measured using an Escalab 250Xi equipped with an Al monochromatic source (Al Kα = 1486.6 eV) as an excitation source. The results are shown in Table 1.
[0062] Table 1
[0063]
[0064]
[0065] Example 4 Evaluation of Catalytic Performance of Direct Synthesis of Dimethyl Carbonate from CO2 and Methanol
[0066] 17 mg of catalyst and 10 ml of methanol were weighed and placed in a sealed 30 ml micro-autoclave. At room temperature, the air in the autoclave was first purged with high-purity CO2. Then, CO2 was injected into the autoclave to a pressure of 3.5 MPa. Dimethyl carbonate (DMC) was synthesized at 160°C, 2 hours, and 700 rpm. The product was analyzed using an Agilent 8860 gas chromatograph.
[0067] The space-time yield of DMC was calculated according to the following method:
[0068]
[0069] The DMC space-time yields of each catalyst are shown in Table 2. Figure 3The selectivity of DMC in each evaluation test was above 99%, indicating that the catalyst has good DMC selectivity. For the CeO2-TH-140 catalyst, the feed amount, pressure, reaction time and other conditions were kept unchanged, and only the reaction temperature was changed. The DMC space-time yield at different temperatures is shown in Table 3. At a reaction temperature of 160°C, the DMC yield was the highest, reaching 23.1 mmol·g -1 ·h -1 , after 5 cycles of testing ( Figure 4 ), its performance still remains at 22.2~23.1mmol·g -1 ·h -1 , indicating that the CeO2-TH-140 catalyst has good stability.
[0070] Table 2
[0071]
[0072]
[0073] Table 3
[0074]
[0075] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A CeO2 nanorod catalyst with a defective porous structure, characterized in that: The CeO2 nanorod catalyst has a defective and porous nanorod morphology; The apparent dimensions of the nanorods are 50 to 250 nm in length and 7 to 12 nm in diameter.
2. The CeO2 nanorod catalyst according to claim 1, characterized in that The CeO2 nanorod catalyst has a cubic fluorite CeO2 structure.
3. The CeO2 nanorod catalyst according to claim 1, characterized in that The surface of the CeO2 nanorod catalyst is rich in Ce 3+ -O V -Ce 3+ -O L structure.
4. The CeO2 nanorod catalyst according to claim 1, characterized in that The surface exposed crystal planes of the CeO2 nanorod catalyst include low-index crystal planes; The low-index crystal plane is at least one of (111), (110) and (100) crystal planes; Preferably, the surface exposed crystal planes of the CeO2 nanorod catalyst further include high-index crystal planes; The high-index crystal plane is a (311) crystal plane; Preferably, the crystal planes exposed on the surface of the CeO2 nanorod catalyst are (111), (110), and (311) crystal planes.
5. The method for preparing the CeO2 nanorod catalyst according to any one of claims 1 to 4, characterized in that: The preparation method comprises: S1: mixing the cerium source solution and the precipitant solution, aging, and then transferring to a hydrothermal kettle for hydrothermal treatment, separation, and drying to obtain a precursor in the shape of CeO2 nanorods; S2: dissolving a CeO2 nanorod-shaped precursor in water, placing the precursor in a hydrothermal kettle for hydrothermal treatment, separating, drying, and calcining to obtain the defective porous CeO2 nanorod catalyst.
6. The preparation method according to claim 5, characterized in that In step S1, the cerium source is selected from at least one of cerium chloride, cerium nitrate, and cerium acetate; The precipitant is selected from at least one of potassium hydroxide, sodium hydroxide and sodium phosphate.
7. The preparation method according to claim 5, characterized in that In step S1, the temperature of the hydrothermal treatment is 100 to 180° C., and the time of the hydrothermal treatment is 12 to 48 hours; Preferably, in step S2, the temperature of the hydrothermal treatment is 100 to 180° C., and the time of the hydrothermal treatment is 12 to 48 hours; Preferably, in step S2, the temperature of the hydrothermal treatment is 140°C.
8. A method for directly synthesizing dimethyl carbonate from CO2 and methanol, characterized in that: The following steps are involved: The catalyst and methanol are placed in a reactor, CO2 is introduced, and the mixture is reacted under stirring to prepare dimethyl carbonate; The catalyst is selected from at least one of the CeO2 nanorod catalysts with a defective porous structure according to any one of claims 1 to 4.
9. The method according to claim 8, characterized in that The dosage of the catalyst is 1-2 mg / ml.
10. The method according to claim 8, characterized in that The injection pressure of CO2 is 3-5 MPa, the reaction temperature is 120-180°C, and the reaction time is 0.5-3 h.