Monoatom-loaded cerium oxide nanorod catalyst as well as preparation method and application thereof
By loading single atoms of precious metals onto cerium oxide nanorods, the catalyst addresses the inefficiencies of traditional dimethyl carbonate synthesis, achieving high yield and reduced environmental impact.
Patent Information
- Application Number
- CN202410023882.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-08
- Publication Date
- 2025-07-15
AI Technical Summary
The traditional method of synthesis of dimethyl carbonate has problems such as high energy consumption, serious environmental pollution, low atomic economy and high production costs.
A single-atom-supported cerium oxide nanorod catalyst is used to load noble metal chloride onto cerium oxide nanorods to form unsaturated supported sites, reducing the activation energy of the catalytic reaction and improving the utilization rate of the catalyst.
The direct synthesis of dimethyl carbonate without solvent at low temperature and low pressure is achieved, which improves the reaction yield and catalyst selectivity, reduces production costs, and is environmentally friendly.
Smart Images
Figure CN120305962A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the technical field of organic chemistry, and particularly, to a cerium oxide nanorod catalyst loaded with single atoms, a preparation method thereof, and an application thereof. Background Art
[0002] With the increase in global industrialization and energy consumption, excessive emissions of greenhouse gases have been caused, which in turn exacerbate the greenhouse effect and the global climate continues to deteriorate. Carbon dioxide is the main component of greenhouse gases, and reducing carbon dioxide emissions is regarded as the primary way to solve climate problems. Therefore, the capture, emission reduction, and utilization of carbon dioxide have become urgent problems that need to be solved in society. In the related technologies of carbon dioxide conversion, converting carbon dioxide into organic carbonates, especially dimethyl carbonate, is considered a green and atom-economic way, with broad industrial application prospects.
[0003] Due to its green, low-toxic, and low-volatility characteristics, dimethyl carbonate has received extensive attention in the industrial and chemical fields in recent years. Dimethyl carbonate can be used as a component of the electrolyte solution for lithium-ion batteries and supercapacitors, which helps to improve the performance of the battery, including energy density and charge-discharge efficiency. In addition, dimethyl carbonate can also be used as an intermediate in chemical synthesis for the preparation of various organic compounds, such as polycarbonates, drugs, pesticides, and dyes, etc. Compared with some toxic and harmful solvents, dimethyl carbonate can replace them, thereby improving the environmental friendliness and safety of the synthesis process. However, traditional methods for synthesizing dimethyl carbonate often have problems such as high energy consumption, serious environmental pollution, low atom economy, and high production costs. Summary of the Invention
[0004] In view of this, the present disclosure provides a cerium oxide nanorod catalyst loaded with single atoms, a preparation method thereof, and an application thereof to at least partially solve the above technical problems.
[0005] To solve the above technical problems, the technical solutions provided by the present disclosure are as follows:
[0006] As a first aspect of the present disclosure, a preparation method of a cerium oxide nanorod catalyst loaded with single atoms is provided, including:
[0007] Adding a cerium source solution to an alkali solution and mixing to obtain a mixed solution;
[0008] Transferring the mixed solution to a sealed container for heat treatment to obtain a first suspension;
[0009] Performing a first centrifugation treatment on the first suspension, drying it, and then performing a first calcination treatment to obtain cerium oxide nanorods;
[0010] Put the precious metal chloride into the second suspension containing cerium oxide nanorods to obtain a suspension of cerium oxide nanorods loaded with single atoms;
[0011] After the second centrifugation treatment and drying of the suspension of cerium oxide nanorods loaded with single atoms, a cerium oxide nanorod catalyst loaded with single atoms is obtained through the second calcination treatment.
[0012] According to an embodiment of the present disclosure, putting the precious metal chloride into the second suspension containing cerium oxide nanorods to obtain a suspension of cerium oxide nanorods loaded with single atoms includes:
[0013] Add the cerium oxide nanorods into water, and obtain the second suspension containing cerium oxide nanorods through ultrasonic treatment;
[0014] Add the precious metal chloride into the second suspension, and obtain the suspension of cerium oxide nanorods loaded with single atoms through stirring reaction.
[0015] According to an embodiment of the present disclosure, the temperature of the heat treatment is 90 - 180 °C, the heating rate is 5 - 15 °C / min, and the heating time is 12 - 24 h;
[0016] The rate of the first centrifugation treatment is 8000 - 12000 r / min, and the centrifugation time is 1 - 3 min;
[0017] The temperature of the first calcination treatment is 350 - 750 °C, the heating rate is 2.5 - 15 °C / min, and the calcination time is 2 - 5 h;
[0018] The rate of the second centrifugation treatment is 8000 - 12000 r / min, and the centrifugation time is 20 - 50 s;
[0019] The temperature of the second calcination treatment is 250 - 450 °C, the heating rate is 5 - 10 °C / min, and the calcination time is 1.5 - 5.5 h.
[0020] According to an embodiment of the present disclosure, the pH of the alkali solution is 9.8 - 11.2; the concentration of the cerium source solution is 0.02 - 1 mol / L; the concentration of the precious metal chloride is 0.2 - 10 mmol / L; the concentration of the cerium oxide nanorods in the second suspension is 0.02 - 1 mol / L.
[0021] According to an embodiment of the present disclosure, the cerium source includes any one or more of cerium nitrate, cerium oxalate, and cerium sulfate; the alkali solution includes any one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate; the precious metal chloride includes one or more of platinum chloride, palladium chloride, ruthenium chloride, rhodium chloride, and yttrium chloride.
[0022] As the second aspect of the present disclosure, a cerium oxide nanorod catalyst loaded with single atoms is provided, which is prepared by the above preparation method.
[0023] As the third aspect of the present disclosure, there is provided an application of a ceria nanorod catalyst loaded with single atoms in the catalytic synthesis of dimethyl carbonate, including:
[0024] Disperse the ceria nanorod catalyst loaded with single atoms into methanol to obtain a dispersion solution;
[0025] Transfer the dispersion solution to a container, and introduce carbon dioxide gas into the container under a first preset pressure to purify the gas in the container;
[0026] Seal the container under a second preset pressure, and carry out a catalytic reaction on methanol and carbon dioxide at a preset temperature and the second preset pressure to obtain dimethyl carbonate.
[0027] According to the embodiments of the present disclosure, the addition amount of the ceria nanorod catalyst loaded with single atoms is 0.05 - 0.5 g; the volume of methanol is 20 - 50 mL.
[0028] According to the embodiments of the present disclosure, the first preset pressure is 0.2 - 1 MPa.
[0029] According to the embodiments of the present disclosure, the second preset pressure is 0.1 - 3 MPa; the preset temperature is 80 - 160 °C, and the heating rate is 5 - 10 °C / min; the time of the catalytic reaction is 0.5 - 5 h.
[0030] Based on the above technical solutions, the ceria nanorod catalyst loaded with single atoms, the preparation method and the application provided by the present disclosure provide additional controllable active sites by loading noble metals in the form of single atoms onto ceria nanorods. Specifically, ceria nanorods are obtained by mixing a cerium source and an alkali solution, heating to obtain a suspension, and then calcining. There are unsaturated loading sites on the ceria nanorods. Noble metal chlorides are put into the suspension containing ceria nanorods by an impregnation method, and noble metal single atoms are loaded onto the ceria nanorods through calcination treatment. The active sites on the obtained ceria nanorod catalyst loaded with single atoms can reduce the activation energy of the reaction of methanol and carbon dioxide to form dimethyl carbonate, which is beneficial to improving the utilization rate of the catalyst and thus increasing the reaction yield. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 It is the scanning electron microscope image of the ceria nanorod catalyst loaded with single atoms in Example 1 of the present disclosure;
[0032] Figure 2 It is the scanning electron microscope image of the ceria nanorod catalyst loaded with single atoms in Example 2 of the present disclosure; and
[0033] Figure 3It is the nuclear magnetic resonance hydrogen spectrum analysis chart of the supernatant after the catalytic reaction in Example 3 of the present disclosure. Detailed implementation manners
[0034] To make the objectives, technical solutions and advantages of the present disclosure more clear and understandable, the following further describes the present disclosure in detail with reference to specific embodiments and the accompanying drawings.
[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.
[0036] The terms used herein are merely for describing specific embodiments and are not intended to limit the present disclosure. The terms "including", "comprising" and the like used herein indicate the presence of features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.
[0037] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.
[0038] In the case of using expressions such as "at least one of A, B, and C", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include, but is not limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C).
[0039] The synthesis of dimethyl carbonate by a one-step method is a current research hotspot. Using methanol and carbon dioxide as raw materials and under the action of a catalyst, dimethyl carbonate can be directly synthesized by a one-step method. In addition, in the process of implementing the present disclosure, it is found that single-atom catalysts are a special type of catalyst, in which specific metal catalysts are dispersed on the surface of an inert solid support in the form of single atoms, and have advantages such as highly controllable active sites, strong anti-poisoning properties, and precise catalysis. They have broad application potential in the fields of energy conversion, environmental protection, chemical synthesis, etc., and can achieve more efficient and sustainable catalytic reactions.
[0040] In view of this, the present disclosure provides a cerium oxide nanorod catalyst loaded with single atoms, a preparation method and an application. Specifically, as the first aspect of the present disclosure, a preparation method of a cerium oxide nanorod catalyst loaded with single atoms is provided, including:
[0041] Adding a cerium source solution to an alkali solution and mixing to obtain a mixed solution;
[0042] Transferring the mixed solution to a closed container for heat treatment to obtain a first suspension;
[0043] Performing a first centrifugation treatment on the first suspension and drying, and then obtaining cerium oxide nanorods through a first calcination treatment;
[0044] Putting a noble metal chloride into a second suspension containing cerium oxide nanorods to obtain a suspension of cerium oxide nanorods loaded with single atoms;
[0045] Performing a second centrifugation treatment on the suspension of cerium oxide nanorods loaded with single atoms and drying, and then obtaining a cerium oxide nanorod catalyst loaded with single atoms through a second calcination treatment.
[0046] According to the embodiments of the present disclosure, when using a cerium source and an alkali solution to be mixed and heated to obtain a suspension and then calcined to obtain cerium oxide nanorods, there are a large number of unsaturated loading sites, enabling the noble metal chloride to be evenly dispersed on the nano-cerium oxide catalyst support. Loading the noble metal single atoms onto the surface of the cerium oxide nanorods can provide more controllable active sites for the cerium oxide nanorods by the noble metal single atoms, which can change the traditional cerium oxide-based catalyst, reduce the activation energy for catalytic reactions, and increase the contact between the reactants and the catalyst. Moreover, the preparation method of this catalyst is simple, with low cost and environmental friendliness, and has the application prospect of large-scale production.
[0047] According to the embodiments of the present disclosure, first, solid alkali is added to water to dissolve to obtain an alkali solution, and a cerium source is added to water to dissolve to obtain a cerium source solution. Then, the cerium source solution is added to the alkali solution, and after stirring, a mixed solution is obtained; the mixed solution reacts to obtain a first suspension after heat treatment. Among them, the heat treatment can be carried out in a high-temperature reaction kettle and a polytetrafluoroethylene lining. The solvent ratio of the mixed solution to the lining is 1:1.5 to 1:2, such as 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, etc.; the temperature of the heat treatment is 90 to 180 °C, such as 90 °C, 100 °C, 120 °C, 150 °C, 160 °C, etc.; the heating rate is 5 to 15 °C / min, such as 5 °C / min, 6 °C / min, 8 °C / min, 12 °C / min, 15 °C / min, etc.; the heating time is 12 to 24 h, such as 12 h, 15 h, 18 h, 20 h, 22 h, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.
[0048] According to an embodiment of the present disclosure, after the first centrifugation treatment of the suspension in a centrifuge tube, it is washed 3 times with deionized water and ethanol respectively and then dried. When washing, the volume ratio of the suspension to deionized water or ethanol solution is 1:1 to 1:3, the drying temperature is 40 to 50 °C, and the drying time is 6 to 24 h.
[0049] According to an embodiment of the present disclosure, when performing the first centrifugation treatment, the solvent ratio of the suspension in the centrifuge tube to the centrifuge tube is 1:3 to 1:5, for example, it can be 1:3, 1:3.5, 1:3.9, 1:4.2, 1:4.5, etc.; the rate of the first centrifugation treatment is 8000 to 12000 r / min, for example, it can be 8000 r / min, 9000 r / min, 10000 r / min, 11000 r / min, etc.; the centrifugation time is 1 to 3 min, for example, it can be 1 min, 1.2 min, 1.5 min, 2 min, 2.5 min, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.
[0050] According to an embodiment of the present disclosure, the precipitate obtained after the first centrifugation treatment is placed in a muffle furnace for the first calcination treatment. The temperature of the first calcination treatment is 350 to 750 °C, for example, it can be 360 °C, 400 °C, 480 °C, 560 °C, 680 °C, etc.; the heating rate is 2.5 to 15 °C / min, for example, it can be 3 °C / min, 5 °C / min, 8 °C / min, 10 °C / min, 12 °C / min, etc.; the calcination time is 2 to 5 h, for example, it can be 2 h, 2.5 h, 3 h, 3.6 h, 4.2 h, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.
[0051] According to an embodiment of the present disclosure, the mass of the cerium oxide nanorods obtained during the preparation process is 0.01 to 5000 g, and the morphological size under a transmission electron microscope is about 200 nm.
[0052] According to an embodiment of the present disclosure, putting the precious metal chloride into the second suspension containing cerium oxide nanorods, the obtained cerium oxide nanorod suspension loaded with single atoms includes:
[0053] Adding the cerium oxide nanorods into water, and obtaining the second suspension containing cerium oxide nanorods through ultrasonic treatment;
[0054] Adding the precious metal chloride into the second suspension, and obtaining the cerium oxide nanorod suspension loaded with single atoms through stirring reaction.
[0055] According to an embodiment of the present disclosure, the suspension of cerium oxide nanorods loaded with single atoms is transferred to a centrifuge tube for a second centrifugation process. The ratio of the suspension of cerium oxide nanorods loaded with single atoms to the solvent in the centrifuge tube is 1:5 to 1:7. Among them, the rate of the second centrifugation process is 8000 to 12000 r / min, for example, it can be 8000 r / min, 9000 r / min, 10000 r / min, 11000 r / min, etc.; the centrifugation time is 20 to 50 s, for example, it can be 22 s, 25 s, 36 s, 40 s, 48 s, etc. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.
[0056] According to an embodiment of the present disclosure, the precipitate obtained after the second centrifugation process is washed 3 times with deionized water and ethanol respectively and then dried, and then a second calcination process is carried out to obtain the cerium oxide nanorod catalyst loaded with single atoms. Among them, the drying temperature is 40 to 80 °C, and the drying time is 6 to 12 h; the temperature of the second calcination process is 250 to 450 °C, for example, it can be 250 °C, 280 °C, 320 °C, 360 °C, 420 °C, etc.; the heating rate is 5 to 10 °C / min, for example, it can be 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, etc.; the calcination time is 1.5 to 5.5 h, for example, it can be 1.5 h, 2.5 h, 3.6 h, 4.5 h, 5 h, etc. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable.
[0057] According to an embodiment of the present disclosure, the alkali solution includes any one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate. The pH of the alkali solution is 9.8 to 11.2. For example, the pH can be 10, 10.5, 10.8, 11, etc. However, it is not limited to the listed values, and other unlisted values within this value range are equally applicable. The pH range of the alkali solution defines the concentration range of hydrogen ions in the solution. Within this range, the reaction rate with the cerium source solution is relatively high, which can improve the efficiency of generating the cerium oxide nanorod precursor. The cerium source includes any one or more of cerium nitrate, cerium oxalate, and cerium sulfate. The concentration of the cerium source solution is 0.02 to 1 mol / L. For example, it can be 0.05 mol / L, 0.06 mol / L, 0.08 mol / L, 0.09 mol / L, etc. The cerium source solution within this concentration range can provide more reactants to increase the reaction rate. When the concentration of the cerium source solution is relatively low, the reaction rate may be slow. When the concentration of the cerium source solution reaches a certain threshold, further increasing the concentration may not significantly increase the reaction rate.
[0058] According to an embodiment of the present disclosure, when the volume of the alkali solution can be 0.02 - 5 L, the volume of the cerium source solution can be 0.02 - 5 L. At this volume, the alkali solution and the cerium source solution can be fully mixed using magnetic stirring to facilitate the subsequent reaction.
[0059] According to an embodiment of the present disclosure, the noble metal chloride includes one or more of platinum chloride, palladium chloride, ruthenium chloride, rhodium chloride, and yttrium chloride. The concentration of the noble metal chloride is 0.2 - 10 mmol / L. For example, it can be 0.5 mmol / L, 1.5 mmol / L, 3.6 mmol / L, 5.8 mmol / L, 7.2 mmol / L, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. The noble metal chloride has good uniform dispersibility and can be evenly dispersed on the nano-ceria catalyst support. Selecting the noble metal chloride for loading single atoms on the cerium oxide nanorods can achieve a better loading effect.
[0060] According to an embodiment of the present disclosure, the concentration of cerium oxide nanorods in the second suspension is 0.02 - 1 mol / L. For example, it can be 0.05 mol / L, 0.12 mol / L, 0.28 mol / L, 0.56 mol / L, 0.78 mol / L, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. At this concentration, the solution volume of the second suspension can be 0.02 - 5 L.
[0061] As the second aspect of the present disclosure, a cerium oxide nanorod catalyst loaded with single atoms is provided, which is prepared by the above preparation method.
[0062] According to an embodiment of the present disclosure, the mass of the cerium oxide nanorod catalyst loaded with single atoms prepared by the above method can be 0.01 - 5000 g, and its morphological size under a scanning electron microscope is relatively small, about 200 nm. Among them, the noble metal atoms with atomic scale can provide higher catalytic activity and selectivity, enabling the cerium oxide nanorod catalyst loaded with single atoms to fully utilize the active sites on the surface of the noble metal single atoms, increasing the contact between the reactants and the catalyst, and thus enhancing the rate and effect of the catalytic reaction.
[0063] As the third aspect of the present disclosure, an application of a cerium oxide nanorod catalyst loaded with single atoms in the catalytic synthesis of dimethyl carbonate is provided, including:
[0064] Disperse the cerium oxide nanorod catalyst loaded with single atoms into methanol to obtain a dispersion solution;
[0065] Transfer the dispersion solution to a container, and introduce carbon dioxide gas into the container under a first preset pressure to purify the gas in the container;
[0066] Seal the container under the second preset pressure, and carry out a catalytic reaction on methanol and carbon dioxide under a preset temperature and the second preset pressure to obtain dimethyl carbonate.
[0067] According to an embodiment of the present disclosure, the active sites on the cerium oxide nanorod catalyst supporting single atoms change the adsorption form of carbon dioxide molecules on the catalyst surface, which can reduce the activation energy of the catalytic reaction. At a lower temperature and a lower pressure, without adding other cocatalysts, based on the high selectivity and stability of the catalyst, carbon dioxide and methanol can be directly used to react in a one-step solvent-free method to produce dimethyl carbonate, realizing a high-yield synthesis of dimethyl carbonate.
[0068] According to an embodiment of the present disclosure, dispersing the cerium oxide nanorod catalyst supporting single atoms into methanol to obtain a dispersion solution includes: after adding methanol into a centrifuge tube, adding the cerium oxide nanorod catalyst supporting single atoms into the methanol, and performing ultrasonic treatment at a frequency of 150 - 300 kHz. After ultrasonic treatment for 5 - 30 s, a dispersion solution is obtained. Among them, the volume ratio of the centrifuge tube can be 1:2 - 1:4.
[0069] According to an embodiment of the present disclosure, the dispersion solution can be transferred into a high-pressure reactor. Close the outlet valve of the reactor, introduce pure carbon dioxide gas into the high-pressure reactor at a first preset pressure, then close the inlet valve, and slowly open the outlet valve to discharge the gas. Repeat this gas replacement step 2 - 3 times to ensure that the air or other gases in the high-pressure reactor are completely discharged, thereby purifying the gas in the reactor. Among them, the first preset pressure is 0.2 - 1 MPa, for example, it can be 0.3 MPa, 0.5 MPa, 0.7 MPa, 0.9 MPa, etc. After introducing carbon dioxide again, close the inlet valve and the outlet valve of the high-pressure reactor, and program the temperature of the substances in the reactor to the preset temperature under a closed condition with the second preset pressure for catalytic reaction.
[0070] According to an embodiment of the present disclosure, the second preset pressure is 0.1 - 3 MPa, for example, it can be 0.2 MPa, 0.6 MPa, 1.2 MPa, 1.5 MPa, 1.8 MPa, etc.; the preset temperature is 80 - 160 °C, such as it can be 90 °C, 100 °C, 120 °C, 150 °C, 160 °C, etc.; the heating rate is 5 - 10 °C / min, for example, it can be 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, etc.; the time for the catalytic reaction is 0.5 - 5 h, for example, it can be 0.6 h, 0.8 h, 1.5 h, 2.8 h, 4 h, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.
[0071] According to an embodiment of the present disclosure, the addition amount of the cerium oxide nanorod catalyst loaded with single atoms is 0.05 to 0.5 g, for example, it can be 0.06 g, 0.12 g, 0.28 g, 0.36 g, 0.45 g, etc.; the volume of methanol is 20 to 50 mL, for example, it can be 25 mL, 30 mL, 35 mL, 40 mL, 45 mL, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable. Under this range, the cerium oxide nanorod catalyst loaded with single atoms can be uniformly dispersed in methanol, facilitating the progress of subsequent reactions.
[0072] According to an embodiment of the present disclosure, after the catalytic reaction, the reaction solution is added to a centrifuge tube and centrifuged at a centrifugal speed of 6000 to 8000 r / min for 30 to 60 s, and then the supernatant is collected to obtain the reaction product: dimethyl carbonate, and the mass conversion rate of the obtained dimethyl carbonate relative to methanol is 2.1 to 3.0%.
[0073] In order to make the purpose, technical solutions and advantages of the present disclosure clearer and more definite, the technical solutions and principles of the present disclosure will be further elaborated and explained below through specific embodiments in conjunction with the accompanying drawings. It should be noted that the following specific embodiments are only for illustration, and the protection scope of the present disclosure is not limited thereto.
[0074] The test materials and reagents used in the following embodiments, unless otherwise specified, can all be obtained from commercial channels. For those not specifying specific techniques or conditions in the embodiments, they are all conventional methods and can be carried out according to the techniques or conditions described in the literature in this field or according to the product instructions.
[0075] Example 1
[0076] Prepare a cerium oxide nanorod catalyst loaded with single atoms:
[0077] 1.5 mmol of sodium hydroxide and 0.1 mol of cerium nitrate are respectively added to 50 mL of deionized water and magnetically stirred at rates of 800 r / min and 850 r / min respectively until completely dissolved. After obtaining the alkali solution and the cerium source solution, the cerium source solution is added to the alkali solution at a rate of 0.05 mL / s and magnetically stirred at a rate of 8000 r / min to obtain a mixed solution.
[0078] The mixed solution was then transferred to a 70 mL high-temperature reactor in batches, heated to 180 °C with stirring and reacted for 8 hours to obtain a first suspension; the first suspension was transferred to a centrifuge tube, centrifuged at 8000 r / min, washed 3 times with deionized water and absolute ethanol respectively, placed in a vacuum drying oven and dried at 50 °C for 18 hours, and after grinding, the obtained precursor powder was placed in a muffle furnace and heated to 600 °C at a heating rate of 5 °C / min and calcined for 3 hours to obtain 600 mg of cerium oxide nanorods.
[0079] Subsequently, 600 mg of cerium oxide nanorods were added to 75 ml of deionized water and ultrasonically treated at a frequency of 300 Hz for 40 s to obtain a second suspension; 0.075 mmol of ruthenium chloride was added to the second suspension and magnetically stirred at a speed of 12000 r / min for 4 hours to obtain a suspension of cerium oxide nanorods loaded with single atoms.
[0080] Finally, the suspension of cerium oxide nanorods loaded with single atoms was transferred to a centrifuge tube, centrifuged at a rate of 8000 r / min for 30 s, washed 3 times with deionized water and absolute ethanol respectively, dried in a vacuum drying oven at 55 °C for 16 hours, ground, and then placed in a muffle furnace for programmed heating. After heating to 450 °C at a heating rate of 5 °C / min, it was calcined for 3 hours to obtain cerium oxide nanorods loaded with single atoms.
[0081] The morphology of the cerium oxide nanorods loaded with single atoms was characterized by scanning electron microscopy. Figure 1 This is the scanning electron micrograph of the cerium oxide nanorods loaded with single atoms in Example 1 of the present disclosure. Figure 1 It can be seen that the cerium oxide nanorod catalyst loaded with single atoms prepared by this method is in the shape of nanorods.
[0082] Example 2
[0083] Preparation of cerium oxide nanorod catalyst loaded with single atoms:
[0084] 1 mmol of sodium hydroxide and 0.05 mol of cerium nitrate were respectively added to 100 mL of deionized water and magnetically stirred at a rate of 1000 r / min until completely dissolved. After obtaining an alkali solution and a cerium source solution, the cerium source solution was added to the alkali solution at a rate of 0.1 mL / s and magnetically stirred to obtain a mixed solution.
[0085] The mixed solution was then transferred to a 70 mL high-temperature reactor in batches, heated to 180 °C with stirring and reacted for 12 hours to obtain a first suspension; the first suspension was transferred to a centrifuge tube, centrifuged at 10,000 r / min, washed 3 times with deionized water and absolute ethanol respectively, placed in a vacuum drying oven and dried at 50 °C for 12 hours, and after grinding, the obtained precursor powder was placed in a muffle furnace and calcined at a heating rate of 5 °C / min to 600 °C for 3 hours to obtain 400 mg of cerium oxide nanorods.
[0086] Then, 400 mg of cerium oxide nanorods were added to 50 ml of deionized water and ultrasonically treated for 20 s at a frequency of 150 Hz to obtain a second suspension; 0.05 mmol of ruthenium chloride was added to the second suspension and magnetically stirred at a speed of 12,000 r / min for 2 hours to obtain a suspension of cerium oxide nanorods loaded with single atoms.
[0087] Finally, the suspension of cerium oxide nanorods loaded with single atoms was transferred to a centrifuge tube, centrifuged at a rate of 8,000 r / min for 50 s, washed 3 times with deionized water and absolute ethanol respectively, dried at 50 °C in a vacuum drying oven for 24 hours, and after grinding, placed in a muffle furnace for programmed heating, heated to 450 °C at a heating rate of 7.5 °C / min and calcined for 3 hours to obtain cerium oxide nanorods loaded with single atoms.
[0088] The morphology of the cerium oxide nanorods loaded with single atoms was characterized by scanning electron microscopy. Figure 2 This is the scanning electron micrograph of the cerium oxide nanorods loaded with single atoms in Example 2 of the present disclosure. It can be seen from Figure 2 that the cerium oxide nanorod catalyst loaded with single atoms prepared by this method is in the shape of nanorods.
[0089] Example 3
[0090] Use the cerium oxide nanorod catalyst loaded with single atoms to catalyze the synthesis of dimethyl carbonate:
[0091] Weigh 0.25 g of the ceria nanorod catalyst supporting single atoms prepared in Example 2 above, add it to 50 mL of methanol, and ultrasonically treat it for 30 s at a frequency of 350 kHz. After obtaining a homogeneous dispersion solution, transfer it to a high-pressure reactor; introduce pure carbon dioxide gas into the high-pressure reactor at a pressure of 0.5 MPa, and repeat the gas replacement step 3 times. After purifying the gas in the reactor, introduce high-purity carbon dioxide gas into the high-pressure reactor at a pressure of 2 MPa and then seal the reaction system. Under the condition of magnetic stirring at 600 r / min, heat the high-pressure reactor system to 140 °C at a rate of 5 °C / min for catalytic reaction for 3 hours. Then, centrifuge the reaction solution at 8000 r / min for 30 s to separate the catalyst, collect the supernatant, and obtain dimethyl carbonate. The supernatant also contains unreacted raw material methanol.
[0092] Analyze the collected supernatant by nuclear magnetic resonance hydrogen spectrum. Figure 3 This is the nuclear magnetic resonance hydrogen spectrum analysis diagram of the supernatant after the catalytic reaction in Example 3 of the present disclosure. As Figure 3 shown, using the ceria nanorod catalyst supporting single atoms for thermal catalysis can synthesize dimethyl carbonate by a one-step method, and the chemical reaction selectivity for synthesizing dimethyl carbonate is 100%, and the conversion rate is 3%.
[0093] Comparative Example 1
[0094] Use a traditional ceria catalyst to catalyze the synthesis of dimethyl carbonate:
[0095] Weigh 0.25 g of the traditional ceria catalyst, add it to 50 mL of methanol, and ultrasonically treat it for 30 s at a frequency of 350 kHz. After obtaining a homogeneous dispersion solution, transfer it to a high-pressure reactor; introduce pure carbon dioxide gas into the high-pressure reactor at a pressure of 0.5 MPa, and repeat the gas replacement step 3 times. After purifying the gas in the reactor, introduce high-purity carbon dioxide gas into the high-pressure reactor at a pressure of 2 MPa and then seal the reaction system. Under the condition of magnetic stirring at 600 r / min, heat the high-pressure reactor system to 140 °C at a rate of 5 °C / min for catalytic reaction for 3 hours. Then, centrifuge the reaction solution at 8000 r / min for 30 s to separate the catalyst, collect the supernatant, and obtain dimethyl carbonate. The supernatant also contains unreacted raw material methanol. Using the traditional ceria catalyst for thermal catalysis can also synthesize dimethyl carbonate by a one-step method. The chemical reaction selectivity for synthesizing dimethyl carbonate is 100%, but the conversion rate is relatively low, about 0.34%.
[0096] In the above specific embodiments, the objectives, technical solutions and beneficial effects of the present disclosure have been further described in detail. It should be understood that the above are only specific embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.
Claims
1. A preparation method of a cerium oxide nanorod catalyst loaded with single atoms, comprising: Adding a cerium source solution to an alkali solution and mixing to obtain a mixed solution; Transferring the mixed solution to a sealed container for heat treatment to obtain a first suspension; Performing a first centrifugation on the first suspension and drying, and then performing a first calcination treatment to obtain cerium oxide nanorods; Putting a noble metal chloride into a second suspension containing the cerium oxide nanorods to obtain a cerium oxide nanorod suspension loaded with single atoms; Performing a second centrifugation on the cerium oxide nanorod suspension loaded with single atoms and drying, and then performing a second calcination treatment to obtain a cerium oxide nanorod catalyst loaded with single atoms.
2. The preparation method according to claim 1, wherein, The step of putting the noble metal chloride into the second suspension containing the cerium oxide nanorods to obtain a cerium oxide nanorod suspension loaded with single atoms includes: Adding the cerium oxide nanorods into water and performing ultrasonic treatment to obtain a second suspension containing the cerium oxide nanorods; Adding the noble metal chloride into the second suspension and performing a stirring reaction to obtain a cerium oxide nanorod suspension loaded with single atoms.
3. According to the preparation method of claim 1, wherein, The temperature of the heat treatment is 90 - 180 °C, the heating rate is 5 - 15 °C / min, and the heating time is 12 - 24 h; The rate of the first centrifugation is 8000 - 12000 r / min, and the centrifugation time is 1 - 3 min; The temperature of the first calcination treatment is 350 - 750 °C, the heating rate is 2.5 - 15 °C / min, and the calcination time is 2 - 5 h; The rate of the second centrifugation is 8000 - 12000 r / min, and the centrifugation time is 20 - 50 s; The temperature of the second calcination treatment is 250 - 450 °C, the heating rate is 5 - 10 °C / min, and the calcination time is 1.5 - 5.5 h.
4. According to the preparation method of claim 1, wherein, The pH of the alkali solution is 9.8 - 11.2; The concentration of the cerium source solution is 0.02 - 1 mol / L; The concentration of the noble metal chloride is 0.2 - 10 mmol / L; The concentration of the cerium oxide nanorods in the second suspension is 0.02 - 1 mol / L.
5. According to the preparation method of claim 1, wherein, The cerium source includes any one or more of cerium nitrate, cerium oxalate, and cerium sulfate; The alkali solution includes any one or more of sodium hydroxide, sodium carbonate, and sodium bicarbonate; The noble metal chloride includes one or more of platinum chloride, palladium chloride, ruthenium chloride, rhodium chloride, and yttrium chloride.
6. A cerium oxide nanorod catalyst loaded with single atoms, prepared by using the preparation method according to any one of claims 1 - 5.
7. An application of the cerium oxide nanorod catalyst loaded with single atoms according to claim 6 in the catalytic synthesis of dimethyl carbonate, comprising: Dispersing the cerium oxide nanorod catalyst loaded with single atoms into methanol to obtain a dispersed solution; Transferring the dispersed solution to a container, and introducing carbon dioxide gas into the container under a first preset pressure to purify the gas in the container; Close the container under the second preset pressure, and carry out a catalytic reaction on methanol and carbon dioxide at a preset temperature and the second preset pressure to obtain dimethyl carbonate.
8. According to the application described in claim 7, wherein, The addition amount of the cerium oxide nanorod catalyst loaded with single atoms is 0.05 - 0.5 g; The volume of the methanol is 20 - 50 mL.
9. According to the application described in claim 7, wherein, The first preset pressure is 0.2 - 1 MPa.
10. According to the application described in claim 7, wherein, The second preset pressure is 0.1 - 3 MPa; The preset temperature is 80 - 160 °C, and the heating rate is 5 - 10 °C / min; The time of the catalytic reaction is 0.5 - 5 h.