Preparation of hollow tubular CeO2 and application of hollow tubular CeO2 in catalysis of CO2 to synthesize dimethyl carbonate
The preparation of hollow tubular CeO2 catalysts by hydrothermal synthesis method solved the problem of unclear catalytic performance of hollow tubular CeO2 in the direct synthesis of dimethyl carbonate by CO2 and methanol, and achieved efficient dimethyl carbonate yield and low-cost production.
Patent Information
- Application Number
- CN202510444674.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2025-07-11
AI Technical Summary
In the prior art, the catalytic performance and structure-effect relationship of hollow tubular CeO2 in the direct synthesis of dimethyl carbonate with CO2 and methanol is unclear, and traditional synthesis methods rely on toxic raw materials, resulting in low yields of DMC.
Preparation of hollow tubular CeO2 catalysts by hydrothermal synthesis method, including reacting urea and cerium nitrate hexahydrate in distilled water, then dissolved with sodium hydroxide and crystallized hydrothermally, followed by calcination or reduction under different atmospheres, for the direct synthesis reaction of CO2 and methanol.
It significantly improves the yield of dimethyl carbonate, provides higher specific surface area and mass transfer efficiency, reduces costs, and meets the needs of green industrial production.
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Figure CN120285969A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical fields of the preparation of industrial catalytic materials and the catalytic conversion of CO2, and specifically relates to the preparation of hollow tubular CeO2 and its application in the catalytic synthesis of dimethyl carbonate from CO2. Background Art
[0002] With the acceleration of the global industrialization process, the greenhouse effect and environmental problems caused by the excessive emission of CO2 have become one of the major challenges faced by mankind. Converting CO2 into high-value-added chemicals (such as dimethyl carbonate, DMC) is an important way to relieve the pressure of carbon emissions and achieve resource utilization. As a green chemical, DMC is widely used in fields such as polycarbonate synthesis, organic methylation reactions, and lithium-ion battery electrolytes. Its traditional synthesis methods rely on toxic raw materials such as phosgene or CO, while the direct synthesis route based on CO2 and CH3OH has attracted much attention due to its 100% atom economy and environmental friendliness.
[0003] CeO2 has been widely used in the reaction of CO2 and methanol to produce DMC due to its both acid and base sites and rich surface defects. However, limited by the thermodynamic equilibrium, the low yield of DMC is a serious problem. To make the reaction proceed efficiently in the direction of synthesizing DMC, highly active catalysts are essential. Controlling the morphology of CeO2 to improve its catalytic performance in the reaction of CO2 and methanol to produce DMC is a current research hotspot. However, there is currently no report on the application of hollow tubular CeO2 in the direct synthesis of DMC from CO2 and methanol, and its catalytic performance and structure-activity relationship are not clear. Summary of the Invention
[0004] The purpose of the present invention is to provide the preparation of hollow tubular CeO2 and its application in the catalytic synthesis of dimethyl carbonate from CO2 to solve the problems raised in the above background art.
[0005] To achieve the above purpose, the present invention provides the following technical solution: The preparation of hollow tubular CeO2, the specific steps are as follows:
[0006] Step 1:
[0007] Dissolve urea and cerium(IV) nitrate hexahydrate in distilled water, react at a certain temperature for several hours, and obtain Ce(OH)CO3 through centrifugation, washing, and drying.
[0008] Step 2:
[0009] Dissolve Ce(OH)CO3 and sodium hydroxide in distilled water, and hydrothermally crystallize to obtain hollow tubular CeO2.
[0010] Step 3:
[0011] The hollow tubular CeO2 is calcined at different temperatures in an air atmosphere and then used for the direct synthesis of dimethyl carbonate from CO2 and methanol;
[0012] Step Four:
[0013] The hollow tubular CeO2 is reduced at different temperatures in a reducing gas (95% Ar: 5% H2) atmosphere and then used for the direct synthesis of dimethyl carbonate from CO2 and methanol;
[0014] As a preferred technical solution of the present invention, the specific preparation steps of the Ce(OH)CO3 described in Step One are as follows: Dissolve urea and cerium(III) nitrate hexahydrate in distilled water, stir vigorously at room temperature, and then transfer the mixed solution to a round-bottom flask and stir and reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, cool to room temperature, obtain the solid product by centrifugation, wash it with distilled water, and finally, dry the product to obtain Ce(OH)CO3.
[0015] As a preferred technical solution of the present invention, the mass ratio of the urea, cerium(III) nitrate hexahydrate, and distilled water is 3.6:1.7:80; the reaction temperature is 60-100 °C, the reaction time is 18-30 h; wash 2-4 times; the drying temperature is 50-90 °C, and the time is 8-16 h.
[0016] As a preferred technical solution of the present invention, the specific preparation steps of the CeO2 described in Step Two are as follows: Take the Ce(OH)CO3 from Step One, add distilled water, then add NaOH, stir vigorously at room temperature for 0.5 h to fully dissolve it and uniformly mix it with Ce(OH)CO3. Transfer the mixed solution to a hydrothermal reaction kettle for hydrothermal synthesis to promote the conversion of Ce(OH)CO3 to CeO2 and form a hollow nanotube structure. After the hydrothermal reaction is completed, cool to room temperature, obtain the solid product by centrifugation, and wash it several times with distilled water and ethanol in turn. Finally, dry the product to obtain hollow nanotube CeO2.
[0017] As a preferred technical solution of the present invention, the mass ratio of the Ce(OH)CO3, NaOH, and distilled water is 2.5:48:400; the reaction temperature is 100-140 °C, the time is 18-30 h; wash 2-4 times; the drying temperature is 80-120 °C, and the time is 16-24 h.
[0018] As a preferred technical solution of the present invention, the calcination temperature described in Step Three is 200-600 °C.
[0019] As a preferred technical solution of the present invention, the reduction temperature described in Step Four is 300-600 °C.
[0020] As a preferred technical solution of the present invention, the dimethyl carbonate described in steps three and four is slightly soluble in water and miscible with organic solvents such as alcohols, ketones, esters, and aromatic hydrocarbons.
[0021] To achieve the above-mentioned another object, the present invention provides the following technical solution: Application of hollow tubular CeO2 in the catalytic synthesis of dimethyl carbonate from CO2, and the conditions of the catalytic reaction are: pressure is 3.0 MPa, temperature is 140 °C, reaction time is 4 h, the addition amount of methanol is 15 mL, and the amount of hollow tubular CeO2 used is 0.1 g.
[0022] The beneficial effects of the present invention are as follows:
[0023] The present invention obtains a hollow tubular CeO2 catalyst by a hydrothermal synthesis method. Compared with the existing nano-particles, cubes, nano-rods and hollow microsphere CeO2 catalysts, the catalyst prepared in the present invention can significantly improve the yield of dimethyl carbonate. At the same time, the preparation method of the catalyst is simple and the cost is low, meeting the requirements of green industrial production. Moreover, due to its unique cavity structure, the hollow tubular CeO2 not only provides a higher specific surface area, but also enhances the mass transfer efficiency and the exposure of reaction active sites. Description of the Drawings
[0024] Figure 1 It is the electron microscope schematic diagram of the present invention;
[0025] Figure 2 It is the X-ray diffraction pattern of the hollow tubular CeO2 catalyst prepared in the examples and comparative examples of the present invention;
[0026] Figure 3 It is the catalytic performance table of the catalysts in the examples and comparative examples of the present invention. Detailed Embodiments
[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0028] Comparative Example 1
[0029] As Figures 1 to 3 shown, the embodiments of the present invention provide the preparation of hollow tubular CeO2, and the specific steps are as follows:
[0030] Step one:
[0031] Dissolve urea and cerium(IV) nitrate hexahydrate in distilled water, react at a certain temperature for several hours, and after centrifugation, washing, and drying, Ce(OH)CO3 is obtained;
[0032] Step 2:
[0033] Dissolve Ce(OH)CO3 and sodium hydroxide in distilled water, and hydrothermally crystallize to obtain hollow tubular CeO2.
[0034] Hollow tubular CeO2 is obtained by hydrothermal synthesis method and used as a catalyst in the direct synthesis of dimethyl carbonate from CO2 and methanol. Compared with the existing CeO2 catalysts in the forms of nanoparticles, cubes, nanorods, and hollow microspheres, it can significantly improve the yield of dimethyl carbonate. At the same time, the preparation method of hollow tubular CeO2 is simple and the cost is low. Its unique cavity structure not only provides a higher specific surface area, but also enhances the mass transfer efficiency and the exposure of reactive sites.
[0035] Among them, the specific preparation steps of Ce(OH)CO3 in Step 1 are as follows: Dissolve urea and cerium(IV) nitrate hexahydrate in distilled water, stir vigorously at room temperature. Subsequently, transfer the mixed solution to a round-bottom flask and stir and reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, cool to room temperature, obtain the solid product by centrifugation, wash it with distilled water. Finally, dry the product to obtain Ce(OH)CO3.
[0036] When stirring vigorously at room temperature, set the stirring time to 0.5 h to ensure that the reactants can be fully mixed.
[0037] Among them, the masses of urea, cerium(IV) nitrate hexahydrate, and distilled water are 3.6 g, 1.70 g, and 80.00 mL respectively; the reaction temperature is 80 °C, the reaction time is 24 h; wash 2 - 4 times; the drying temperature is 70 °C and the time is 12 h.
[0038] Urea, cerium(IV) nitrate hexahydrate, and distilled water need to be strictly proportioned according to the ratio of 3.6:1.7:80. At the same time, during the reaction, it is necessary to ensure that the reaction temperature, reaction time, number of washing times, drying time, and temperature are all within the set range.
[0039] Among them, the specific preparation steps of CeO2 in step 2 are: take Ce(OH)CO3 in step 1, add distilled water, then add NaOH, and stir vigorously at room temperature for 0.5h to make it fully dissolved and evenly mixed with Ce(OH)CO3, transfer the mixed solution to a hydrothermal reactor for hydrothermal synthesis to promote the conversion of Ce(OH)CO3 to CeO2 and form a hollow nanotube structure. After the hydrothermal reaction is completed, cool to room temperature, obtain a solid product by centrifugal separation, and wash it several times with distilled water and ethanol respectively. Finally, the product is dried to obtain hollow nanotube CeO2.
[0040] The purpose of adding distilled water to Ce(OH)CO3 is to fully disperse (Ce(OH)CO3) so as to ensure subsequent mixing.
[0041] Among them, the masses of Ce(OH)CO3, NaOH and distilled water are 0.25g, 4.8g and 40.00mL respectively; the reaction temperature is 120℃ and the time is 24h; washing is 3 times; the drying temperature is 100℃ and the time is 20h.
[0042] During preparation, Ce(OH)CO3, NaOH and distilled water must be mixed thoroughly in a strict ratio of 2.5:48:400.
[0043] The above-mentioned hollow tubular CeO2 is used in the catalytic synthesis of dimethyl carbonate from CO2. The catalytic reaction conditions are: pressure of 3.0 MPa, temperature of 140°C, reaction time of 4 h, methanol addition amount of 15 mL, and hollow tubular CeO2 dosage of 0.1 g.
[0044] The synthesis of dimethyl carbonate using CO2 as raw material can not only realize the resource utilization of CO2, but also reduce the dependence on traditional fossil resources.
[0045] Comparative Example 2
[0046] like Figures 1 to 3 As shown, the embodiment of the present invention provides a method for preparing a hollow tubular CeO2, and the specific steps are as follows:
[0047] Step 1:
[0048] Dissolve urea and cerium nitrate hexahydrate in distilled water, react at a certain temperature for several hours, centrifuge, wash and dry to obtain Ce(OH)CO3;
[0049] Step 2:
[0050] Ce(OH)CO3 and sodium hydroxide were dissolved in distilled water and hydrothermally crystallized to obtain hollow tubular CeO2;
[0051] Step 3:
[0052] The hollow tubular CeO₂ is used in the direct synthesis of dimethyl carbonate from CO₂ and methanol after reduction at different temperatures in a reducing gas (95% Ar: 5% H₂) atmosphere.
[0053] The hollow tubular CeO₂ is obtained by hydrothermal synthesis and used as a catalyst in the direct synthesis of dimethyl carbonate from CO₂ and methanol. Compared with the existing CeO₂ catalysts in the forms of nanoparticles, cubes, nanorods, and hollow microspheres, it can significantly improve the yield of dimethyl carbonate. Meanwhile, the preparation method of the hollow tubular CeO₂ is simple and the cost is low. Its unique cavity structure not only provides a higher specific surface area, but also enhances the mass transfer efficiency and the exposure of reactive sites.
[0054] Among them, the specific preparation steps of Ce(OH)CO₃ in Step 1 are as follows: Dissolve urea and cerium(III) nitrate hexahydrate in distilled water and stir vigorously at room temperature. Subsequently, transfer the mixed solution to a round-bottom flask and stir and reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, cool to room temperature, obtain the solid product by centrifugation, wash it with distilled water, and finally, dry the product to obtain Ce(OH)CO₃.
[0055] When stirring vigorously at room temperature, set the stirring time to 0.5 h to ensure that the reactants can be fully mixed.
[0056] Among them, the masses of urea, cerium(III) nitrate hexahydrate, and distilled water are 3.6 g, 1.70 g, and 80.00 mL respectively; the reaction temperature is 80 °C, the reaction time is 24 h; wash 2 - 4 times; the drying temperature is 70 °C and the time is 12 h.
[0057] Urea, cerium(III) nitrate hexahydrate, and distilled water need to be strictly proportioned according to the ratio of 3.6:1.7:80. Meanwhile, during the reaction, it is necessary to ensure that the reaction temperature, reaction time, number of washing times, drying time, and temperature are all within the set range.
[0058] Among them, the specific preparation steps of CeO₂ in Step 2 are as follows: Take the Ce(OH)CO₃ from Step 1, add distilled water, then add NaOH, and stir vigorously at room temperature for 0.5 h to fully dissolve it and uniformly mix it with Ce(OH)CO₃. Transfer the mixed solution to a hydrothermal reaction kettle for hydrothermal synthesis to promote the conversion of Ce(OH)CO₃ to CeO₂ and form a hollow nanotube structure. After the hydrothermal reaction is completed, cool to room temperature, obtain the solid product by centrifugation, and wash it several times with distilled water and ethanol in turn. Finally, dry the product to obtain hollow nanotube CeO₂.
[0059] The purpose of adding distilled water to Ce(OH)CO3 is to fully disperse (Ce(OH)CO3), so as to ensure the subsequent mixing.
[0060] Among them, the masses of Ce(OH)CO3, NaOH, and distilled water are 0.25 g, 4.8 g, and 40.00 mL respectively; the reaction temperature is 120 °C and the time is 24 h; it is washed 3 times; the drying temperature is 100 °C and the time is 20 h.
[0061] During the preparation, Ce(OH)CO3, NaOH, and distilled water need to be fully mixed strictly according to the ratio of 2.5:48:400.
[0062] Among them, the reduction temperature in step three is 600 °C.
[0063] During the reduction, the reduction time is set to 5 h.
[0064] Among them, dimethyl carbonate in step three is slightly soluble in water and miscible with organic solvents such as alcohols, ketones, esters, and aromatic hydrocarbons.
[0065] The chemical formula of dimethyl carbonate is C3H6O3, which can participate in carbonylation, methylation, methoxylation and other reactions. It is an important organic compound with wide industrial application value.
[0066] The application of the above hollow tubular CeO2 in the catalytic synthesis of dimethyl carbonate from CO2, the conditions of the catalytic reaction are: the pressure is 3.0 MPa, the temperature is 140 °C, the reaction time is 4 h, the methanol addition amount is 15 mL, and the amount of hollow tubular CeO2 used is 0.1 g.
[0067] Synthesizing dimethyl carbonate from CO2 as a raw material can not only realize the resource utilization of CO2, but also reduce the dependence on traditional fossil resources.
[0068] Example 1
[0069] As Figures 1 to 3 shown, the embodiment of the present invention provides the preparation of hollow tubular CeO2, and the specific steps are as follows:
[0070] Step 1:
[0071] Dissolve urea and cerium nitrate hexahydrate in distilled water, react at a certain temperature for several hours, and obtain Ce(OH)CO3 through centrifugation, washing, and drying;
[0072] Step 2:
[0073] Dissolve Ce(OH)CO3 and sodium hydroxide in distilled water, and hydrothermally crystallize to obtain hollow tubular CeO2;
[0074] Step 3:
[0075] The hollow tubular CeO2 is calcined at different temperatures in an air atmosphere and then used for the direct synthesis of dimethyl carbonate from CO2 and methanol.
[0076] The hollow tubular CeO2 is obtained by hydrothermal synthesis and used as a catalyst in the direct synthesis of dimethyl carbonate from CO2 and methanol. Compared with the existing CeO2 catalysts such as nanoparticles, cubes, nanorods, and hollow microspheres, it can significantly improve the yield of dimethyl carbonate. At the same time, the preparation method of the hollow tubular CeO2 is simple and the cost is low. Its unique cavity structure not only provides a higher specific surface area, but also enhances the mass transfer efficiency and the exposure of reactive sites.
[0077] Among them, the specific preparation steps of Ce(OH)CO3 in step one are as follows: Dissolve urea and cerium(III) nitrate hexahydrate in distilled water and stir vigorously at room temperature. Subsequently, transfer the mixed solution to a round-bottom flask and stir and reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, cool to room temperature, obtain the solid product by centrifugation, wash it with distilled water, and finally, dry the product to obtain Ce(OH)CO3.
[0078] When stirring vigorously at room temperature, set the stirring time to 0.5 h to ensure that the reactants can be fully mixed.
[0079] Among them, the masses of urea, cerium(III) nitrate hexahydrate, and distilled water are 3.6 g, 1.70 g, and 80.00 mL respectively; the reaction temperature is 80 °C, the reaction time is 24 h; wash 2 - 4 times; the drying temperature is 70 °C and the time is 12 h.
[0080] Urea, cerium(III) nitrate hexahydrate, and distilled water need to be strictly proportioned according to the ratio of 3.6:1.7:80. At the same time, during the reaction, it is necessary to ensure that the reaction temperature, reaction time, number of washing times, drying time, and temperature are all within the set range.
[0081] Among them, the specific preparation steps of CeO2 in step two are as follows: Take the Ce(OH)CO3 obtained in step one, add distilled water, then add NaOH, stir vigorously at room temperature for 0.5 h to fully dissolve it and mix it evenly with Ce(OH)CO3. Transfer the mixed solution to a hydrothermal reaction kettle for hydrothermal synthesis to promote the conversion of Ce(OH)CO3 to CeO2 and form a hollow nanotube structure. After the hydrothermal reaction is completed, cool to room temperature, obtain the solid product by centrifugation, and wash it several times with distilled water and ethanol in sequence. Finally, dry the product to obtain hollow nanotube CeO2.
[0082] The purpose of adding distilled water to Ce(OH)CO3 is to completely disperse Ce(OH)CO3, so as to ensure the subsequent mixing.
[0083] Among them, the masses of Ce(OH)CO3, NaOH, and distilled water are 0.25 g, 4.8 g, and 40.00 mL respectively; the reaction temperature is 120 °C and the time is 24 h; wash 3 times; the drying temperature is 100 °C and the time is 20 h.
[0084] During the preparation, it is necessary to fully mix Ce(OH)CO3, NaOH, and distilled water strictly according to the ratio of 2.5:48:400.
[0085] Among them, the calcination temperature in step three is 200 °C.
[0086] During the calcination, set the calcination time to 5 h.
[0087] Among them, dimethyl carbonate in step three is slightly soluble in water and miscible with organic solvents such as alcohols, ketones, esters, and aromatic hydrocarbons.
[0088] The chemical formula of dimethyl carbonate is C3H6O3, which can participate in reactions such as carbonylation, methylation, and methoxylation. It is an important organic compound with wide industrial application value.
[0089] The application of the above hollow tubular CeO2 in the catalytic synthesis of dimethyl carbonate from CO2, the conditions of the catalytic reaction are: the pressure is 3.0 MPa, the temperature is 140 °C, the reaction time is 4 h, the methanol addition amount is 15 mL, and the amount of hollow tubular CeO2 used is 0.1 g.
[0090] Synthesizing dimethyl carbonate from CO2 as a raw material can not only realize the resource utilization of CO2, but also reduce the dependence on traditional fossil resources.
[0091] Example 2
[0092] As Figures 1 to 3 shown, the embodiment of the present invention provides the preparation of hollow tubular CeO2, and the specific steps are as follows:
[0093] Step 1:
[0094] Dissolve urea and cerium(IV) nitrate hexahydrate in distilled water, react at a certain temperature for several hours, and obtain Ce(OH)CO3 through centrifugation, washing, and drying;
[0095] Step 2:
[0096] Dissolve Ce(OH)CO3 and sodium hydroxide in distilled water, and hydrothermally crystallize to obtain hollow tubular CeO2;
[0097] Step 3:
[0098] The hollow tubular CeO2 was calcined at different temperatures in an air atmosphere and then used in the direct synthesis of dimethyl carbonate from CO2 and methanol.
[0099] The hollow tubular CeO2 was obtained by hydrothermal synthesis and used as a catalyst in the direct synthesis of dimethyl carbonate from CO2 and methanol. Compared with the existing CeO2 catalysts such as nanoparticles, cubes, nanorods, and hollow microspheres, it can significantly improve the yield of dimethyl carbonate. At the same time, the preparation method of the hollow tubular CeO2 is simple and the cost is low. Its unique cavity structure not only provides a higher specific surface area but also enhances the mass transfer efficiency and the exposure of reactive sites.
[0100] Among them, the specific preparation steps of Ce(OH)CO3 in step one are as follows: Urea and cerium(III) nitrate hexahydrate were dissolved in distilled water and stirred vigorously at room temperature. Subsequently, the mixed solution was transferred to a round-bottom flask and stirred under reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction ended, it was cooled to room temperature, and the solid product was obtained by centrifugation and washed with distilled water. Finally, the product was dried to obtain Ce(OH)CO3.
[0101] When stirring vigorously at room temperature, the stirring time was set to 0.5 h to ensure that the reactants could be fully mixed.
[0102] Among them, the masses of urea, cerium(III) nitrate hexahydrate, and distilled water were 3.6 g, 1.70 g, and 80.00 mL respectively; the reaction temperature was 80 °C, the reaction time was 24 h; it was washed 2 - 4 times; the drying temperature was 70 °C and the time was 12 h.
[0103] Urea, cerium(III) nitrate hexahydrate, and distilled water need to be strictly proportioned according to the ratio of 3.6:1.7:80. At the same time, during the reaction, it is necessary to ensure that the reaction temperature, reaction time, number of washing times, drying time, and temperature are all within the set range.
[0104] Among them, the specific preparation steps of CeO2 in step two are as follows: Take the Ce(OH)CO3 from step one, add distilled water, and then add NaOH. Stir vigorously at room temperature for 0.5 h to fully dissolve it and mix it evenly with Ce(OH)CO3. Transfer the mixed solution to a hydrothermal reaction kettle for hydrothermal synthesis to promote the conversion of Ce(OH)CO3 to CeO2 and form a hollow nanotube structure. After the hydrothermal reaction ends, it is cooled to room temperature, and the solid product is obtained by centrifugation and washed several times with distilled water and ethanol in sequence. Finally, the product is dried to obtain hollow nanotube CeO2.
[0105] The purpose of adding distilled water to Ce(OH)CO3 is to fully disperse Ce(OH)CO3, thereby ensuring subsequent mixing.
[0106] Among them, the masses of Ce(OH)CO3, NaOH and distilled water are 0.25g, 4.8g and 40.00mL respectively; the reaction temperature is 120℃ and the time is 24h; washing is 3 times; the drying temperature is 100℃ and the time is 20h.
[0107] During preparation, Ce(OH)CO3, NaOH and distilled water must be mixed thoroughly in a strict ratio of 2.5:48:400.
[0108] Wherein, the calcination temperature in step three is 300°C.
[0109] During roasting, the roasting time was set to 5h.
[0110] Among them, the dimethyl carbonate in step three is slightly soluble in water and miscible with alcohol, ketone, ester and aromatic organic solvents.
[0111] The chemical formula of dimethyl carbonate is C3H6O3. It can participate in carbonylation, methylation, methoxylation and other reactions. It is an important organic compound with wide industrial application value.
[0112] The above-mentioned hollow tubular CeO2 is used in the catalytic synthesis of dimethyl carbonate from CO2. The catalytic reaction conditions are: pressure of 3.0 MPa, temperature of 140°C, reaction time of 4 h, methanol addition amount of 15 mL, and hollow tubular CeO2 dosage of 0.1 g.
[0113] The synthesis of dimethyl carbonate using CO2 as raw material can not only realize the resource utilization of CO2, but also reduce the dependence on traditional fossil resources.
[0114] Example 3
[0115] like Figures 1 to 3 As shown, the embodiment of the present invention provides a method for preparing a hollow tubular CeO2, and the specific steps are as follows:
[0116] Step 1:
[0117] Dissolve urea and cerium nitrate hexahydrate in distilled water, react at a certain temperature for several hours, centrifuge, wash and dry to obtain Ce(OH)CO3;
[0118] Step 2:
[0119] Ce(OH)CO3 and sodium hydroxide were dissolved in distilled water and hydrothermally crystallized to obtain hollow tubular CeO2;
[0120] Step 3:
[0121] The hollow tubular CeO2 was calcined at different temperatures in air atmosphere and used in the direct synthesis of dimethyl carbonate from CO2 and methanol.
[0122] Hollow tubular CeO2 was obtained by hydrothermal synthesis and used as a catalyst in the direct synthesis of dimethyl carbonate from CO2 and methanol. Compared with the existing CeO2 catalysts in the forms of nanoparticles, cubes, nanorods and hollow microspheres, it can significantly improve the yield of dimethyl carbonate. Meanwhile, the preparation method of hollow tubular CeO2 is simple and low-cost. Its unique cavity structure not only provides a higher specific surface area, but also enhances the mass transfer efficiency and the exposure of reactive sites.
[0123] Among them, the specific preparation steps of Ce(OH)CO3 in step one are as follows: Dissolve urea and cerium(III) nitrate hexahydrate in distilled water and stir vigorously at room temperature. Subsequently, transfer the mixed solution to a round-bottom flask and stir and reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, cool to room temperature, obtain the solid product by centrifugation, and wash it with distilled water. Finally, dry the product to obtain Ce(OH)CO3.
[0124] When stirring vigorously at room temperature, set the stirring time to 0.5 h to ensure that the reactants can be fully mixed.
[0125] Among them, the masses of urea, cerium(III) nitrate hexahydrate and distilled water are 3.6 g, 1.70 g and 80.00 mL respectively; the reaction temperature is 80 °C, the reaction time is 24 h; wash 2 - 4 times; the drying temperature is 70 °C and the time is 12 h.
[0126] Urea, cerium(III) nitrate hexahydrate and distilled water need to be strictly proportioned according to the ratio of 3.6:1.7:80. Meanwhile, during the reaction, it is necessary to ensure that the reaction temperature, reaction time, number of washing times, drying time and temperature are all within the set ranges.
[0127] Among them, the specific preparation steps of CeO2 in step two are as follows: Take the Ce(OH)CO3 obtained in step one, add distilled water, and then add NaOH. Stir vigorously at room temperature for 0.5 h to fully dissolve it and uniformly mix it with Ce(OH)CO3. Transfer the mixed solution to a hydrothermal reactor for hydrothermal synthesis to promote the conversion of Ce(OH)CO3 to CeO2 and form a hollow nanotube structure. After the hydrothermal reaction is completed, cool to room temperature, obtain the solid product by centrifugation, and wash it several times with distilled water and ethanol in sequence. Finally, dry the product to obtain hollow nanotube CeO2.
[0128] The purpose of adding distilled water to Ce(OH)CO3 is to fully disperse Ce(OH)CO3, so as to ensure subsequent mixing.
[0129] Among them, the masses of Ce(OH)CO3, NaOH, and distilled water are 0.25 g, 4.8 g, and 40.00 mL respectively; the reaction temperature is 120 °C and the time is 24 h; it is washed 3 times; the drying temperature is 100 °C and the time is 20 h.
[0130] During the preparation, it is necessary to fully mix Ce(OH)CO3, NaOH, and distilled water strictly according to the ratio of 2.5:48:400.
[0131] Among them, the calcination temperature in Step 3 is 400 °C.
[0132] During the calcination, the set calcination time is 5 h.
[0133] Among them, dimethyl carbonate in Step 3 is slightly soluble in water and miscible with organic solvents such as alcohols, ketones, esters, and aromatic hydrocarbons.
[0134] The chemical formula of dimethyl carbonate is C3H6O3, which can participate in reactions such as carbonylation, methylation, and methoxylation. It is an important organic compound with wide industrial application value.
[0135] The application of the above hollow tubular CeO2 in the catalytic synthesis of dimethyl carbonate from CO2, the conditions of the catalytic reaction are: the pressure is 3.0 MPa, the temperature is 140 °C, the reaction time is 4 h, the methanol addition amount is 15 mL, and the amount of hollow tubular CeO2 used is 0.1 g.
[0136] Synthesizing dimethyl carbonate from CO2 as a raw material can not only realize the resource utilization of CO2 but also reduce the dependence on traditional fossil resources.
[0137] Example 4
[0138] As Figures 1 to 3 shown, the embodiment of the present invention provides the preparation of hollow tubular CeO2, and the specific steps are as follows:
[0139] Step 1:
[0140] Dissolve urea and cerium(IV) nitrate hexahydrate in distilled water, react at a certain temperature for several hours, and obtain Ce(OH)CO3 through centrifugation, washing, and drying;
[0141] Step 2:
[0142] Dissolve Ce(OH)CO3 and sodium hydroxide in distilled water, and hydrothermally crystallize to obtain hollow tubular CeO2;
[0143] Step 3:
[0144] Calcine the hollow tubular CeO2 at different temperatures in an air atmosphere and then use it for the direct synthesis reaction of CO2 and methanol to dimethyl carbonate.
[0145] Hollow tubular CeO₂ was obtained by hydrothermal synthesis and used as a catalyst in the direct synthesis of dimethyl carbonate from CO₂ and methanol. Compared with the existing CeO₂ catalysts in the forms of nanoparticles, cubes, nanorods, and hollow microspheres, it can significantly improve the yield of dimethyl carbonate. Meanwhile, the preparation method of hollow tubular CeO₂ is simple and low-cost. Its unique cavity structure not only provides a higher specific surface area but also enhances the mass transfer efficiency and the exposure of reactive sites.
[0146] Among them, the specific preparation steps of Ce(OH)CO₃ in Step 1 are as follows: Urea and cerium(III) nitrate hexahydrate are dissolved in distilled water and stirred vigorously at room temperature. Subsequently, the mixed solution is transferred to a round-bottom flask and stirred under reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, it is cooled to room temperature, and the solid product is obtained by centrifugation and washed with distilled water. Finally, the product is dried to obtain Ce(OH)CO₃.
[0147] When stirring vigorously at room temperature, the stirring time is set to 0.5 h to ensure that the reactants can be fully mixed.
[0148] Among them, the masses of urea, cerium(III) nitrate hexahydrate, and distilled water are 3.6 g, 1.70 g, and 80.00 mL respectively; the reaction temperature is 80 °C, the reaction time is 24 h; it is washed 2 - 4 times; the drying temperature is 70 °C, and the time is 12 h.
[0149] Urea, cerium(III) nitrate hexahydrate, and distilled water need to be strictly proportioned according to the ratio of 3.6:1.7:80. Meanwhile, during the reaction, it is necessary to ensure that the reaction temperature, reaction time, number of washing times, drying time, and temperature are all within the set ranges.
[0150] Among them, the specific preparation steps of CeO₂ in Step 2 are as follows: Take the Ce(OH)CO₃ from Step 1, add distilled water, and then add NaOH. Stir vigorously at room temperature for 0.5 h to make it fully dissolve and mix uniformly with Ce(OH)CO₃. Transfer the mixed solution to a hydrothermal reactor for hydrothermal synthesis to promote the transformation of Ce(OH)CO₃ into CeO₂ and form a hollow nanotube structure. After the hydrothermal reaction is completed, it is cooled to room temperature, and the solid product is obtained by centrifugation and washed several times with distilled water and ethanol in sequence. Finally, the product is dried to obtain hollow nanotube CeO₂.
[0151] The purpose of adding distilled water to Ce(OH)CO₃ is to completely disperse Ce(OH)CO₃, thereby ensuring subsequent mixing.
[0152] Among them, the masses of Ce(OH)CO3, NaOH and distilled water are 0.25g, 4.8g and 40.00mL respectively; the reaction temperature is 120℃ and the time is 24h; washing is 3 times; the drying temperature is 100℃ and the time is 20h.
[0153] During preparation, Ce(OH)CO3, NaOH and distilled water must be mixed thoroughly in a strict ratio of 2.5:48:400.
[0154] Wherein, the calcination temperature in step three is 500°C.
[0155] During roasting, the roasting time was set to 5h.
[0156] Among them, the dimethyl carbonate in step three is slightly soluble in water and miscible with alcohol, ketone, ester and aromatic organic solvents.
[0157] The chemical formula of dimethyl carbonate is C3H6O3. It can participate in carbonylation, methylation, methoxylation and other reactions. It is an important organic compound with wide industrial application value.
[0158] The above-mentioned hollow tubular CeO2 is used in the catalytic synthesis of dimethyl carbonate from CO2. The catalytic reaction conditions are: pressure of 3.0 MPa, temperature of 140°C, reaction time of 4 h, methanol addition amount of 15 mL, and hollow tubular CeO2 dosage of 0.1 g.
[0159] The synthesis of dimethyl carbonate using CO2 as raw material can not only realize the resource utilization of CO2, but also reduce the dependence on traditional fossil resources.
[0160] Example 5
[0161] like Figures 1 to 3 As shown, the embodiment of the present invention provides a method for preparing a hollow tubular CeO2, and the specific steps are as follows:
[0162] Step 1:
[0163] Dissolve urea and cerium nitrate hexahydrate in distilled water, react at a certain temperature for several hours, centrifuge, wash and dry to obtain Ce(OH)CO3;
[0164] Step 2:
[0165] Ce(OH)CO3 and sodium hydroxide were dissolved in distilled water and hydrothermally crystallized to obtain hollow tubular CeO2;
[0166] Step 3:
[0167] The hollow tubular CeO2 was calcined at different temperatures in air atmosphere and used in the direct synthesis of dimethyl carbonate from CO2 and methanol.
[0168] Hollow tubular CeO₂ was obtained by hydrothermal synthesis and used as a catalyst in the direct synthesis of dimethyl carbonate from CO₂ and methanol. Compared with the existing CeO₂ catalysts in the forms of nanoparticles, cubes, nanorods, and hollow microspheres, it can significantly improve the yield of dimethyl carbonate. Meanwhile, the preparation method of hollow tubular CeO₂ is simple and low-cost. Its unique cavity structure not only provides a higher specific surface area but also enhances the mass transfer efficiency and the exposure of reactive sites.
[0169] Among them, the specific preparation steps of Ce(OH)CO₃ in Step 1 are as follows: Dissolve urea and cerium(III) nitrate hexahydrate in distilled water and stir vigorously at room temperature. Subsequently, transfer the mixed solution to a round-bottom flask and stir under reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, cool to room temperature, obtain the solid product by centrifugation, wash it with distilled water, and finally, dry the product to obtain Ce(OH)CO₃.
[0170] When stirring vigorously at room temperature, set the stirring time to 0.5 h to ensure that the reactants can be fully mixed.
[0171] Among them, the masses of urea, cerium(III) nitrate hexahydrate, and distilled water are 3.6 g, 1.70 g, and 80.00 mL respectively; the reaction temperature is 80 °C, the reaction time is 24 h; wash 2 - 4 times; the drying temperature is 70 °C and the time is 12 h.
[0172] Urea, cerium(III) nitrate hexahydrate, and distilled water need to be strictly proportioned according to the ratio of 3.6:1.7:80. Meanwhile, during the reaction, it is necessary to ensure that the reaction temperature, reaction time, number of washing times, drying time, and temperature are all within the set range.
[0173] Among them, the specific preparation steps of CeO₂ in Step 2 are as follows: Take the Ce(OH)CO₃ obtained in Step 1, add distilled water, and then add NaOH. Stir vigorously at room temperature for 0.5 h to fully dissolve it and uniformly mix it with Ce(OH)CO₃. Transfer the mixed solution to a hydrothermal reactor for hydrothermal synthesis to promote the conversion of Ce(OH)CO₃ to CeO₂ and form a hollow nanotube structure. After the hydrothermal reaction is completed, cool to room temperature, obtain the solid product by centrifugation, and wash it several times with distilled water and ethanol in sequence. Finally, dry the product to obtain hollow nanotube CeO₂.
[0174] The purpose of adding distilled water to Ce(OH)CO₃ is to completely disperse Ce(OH)CO₃, thus ensuring subsequent mixing.
[0175] Among them, the masses of Ce(OH)CO3, NaOH, and distilled water are 0.25 g, 4.8 g, and 40.00 mL respectively; the reaction temperature is 120 °C and the time is 24 h; washing is carried out 3 times; the drying temperature is 100 °C and the time is 20 h.
[0176] During the preparation, the Ce(OH)CO3, NaOH, and distilled water need to be fully mixed strictly in the ratio of 2.5:48:400.
[0177] Among them, the calcination temperature in Step 3 is 600 °C.
[0178] During the calcination, the set calcination time is 5 h.
[0179] Among them, dimethyl carbonate in Step 3 is slightly soluble in water and miscible with organic solvents such as alcohols, ketones, esters, and aromatic hydrocarbons.
[0180] The chemical formula of dimethyl carbonate is C3H6O3, which can participate in reactions such as carbonylation, methylation, and methoxylation. It is an important organic compound with wide industrial application value.
[0181] The application of the above hollow tubular CeO2 in the catalytic synthesis of dimethyl carbonate from CO2, the conditions of the catalytic reaction are: the pressure is 3.0 MPa, the temperature is 140 °C, the reaction time is 4 h, the methanol addition amount is 15 mL, and the amount of hollow tubular CeO2 used is 0.1 g.
[0182] Synthesizing dimethyl carbonate from CO2 as a raw material can not only realize the resource utilization of CO2 but also reduce the dependence on traditional fossil resources.
[0183] Example 6
[0184] As Figures 1 to 3 shown, the embodiments of the present invention provide the preparation of hollow tubular CeO2, and the specific steps are as follows:
[0185] Step 1:
[0186] Dissolve urea and cerium(III) nitrate hexahydrate in distilled water, react at a certain temperature for several hours, and obtain Ce(OH)CO3 through centrifugation, washing, and drying.
[0187] Step 2:
[0188] Dissolve Ce(OH)CO3 and sodium hydroxide in distilled water, and hydrothermally crystallize to obtain hollow tubular CeO2.
[0189] Step 3:
[0190] The hollow tubular CeO2 is reduced at different temperatures in a reducing gas (95% Ar: 5% H2) atmosphere and then used for the direct synthesis reaction of CO2 and methanol to dimethyl carbonate.
[0191] Hollow tubular CeO₂ was obtained by hydrothermal synthesis and used as a catalyst in the direct synthesis of dimethyl carbonate from CO₂ and methanol. Compared with the existing CeO₂ catalysts in the forms of nanoparticles, cubes, nanorods, and hollow microspheres, it can significantly improve the yield of dimethyl carbonate. Meanwhile, the preparation method of hollow tubular CeO₂ is simple and low-cost. Its unique cavity structure not only provides a higher specific surface area but also enhances the mass transfer efficiency and the exposure of reactive sites.
[0192] Among them, the specific preparation steps of Ce(OH)CO₃ in step one are as follows: Dissolve urea and cerium(III) nitrate hexahydrate in distilled water and stir vigorously at room temperature. Subsequently, transfer the mixed solution to a round-bottom flask and stir and reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, cool to room temperature, obtain the solid product by centrifugation, wash it with distilled water, and finally, dry the product to obtain Ce(OH)CO₃.
[0193] When stirring vigorously at room temperature, set the stirring time to 0.5 h to ensure that the reactants can be fully mixed.
[0194] Among them, the masses of urea, cerium(III) nitrate hexahydrate, and distilled water are 3.6 g, 1.70 g, and 80.00 mL respectively; the reaction temperature is 80 °C, the reaction time is 24 h; wash 2 - 4 times; the drying temperature is 70 °C and the time is 12 h.
[0195] Urea, cerium(III) nitrate hexahydrate, and distilled water need to be strictly proportioned according to the ratio of 3.6:1.7:80. Meanwhile, during the reaction, it is necessary to ensure that the reaction temperature, reaction time, number of washing times, drying time, and temperature are all within the set ranges.
[0196] Among them, the specific preparation steps of CeO₂ in step two are as follows: Take Ce(OH)CO₃ from step one, add distilled water, and then add NaOH. Stir vigorously at room temperature for 0.5 h to make it fully dissolve and mix evenly with Ce(OH)CO₃. Transfer the mixed solution to a hydrothermal reactor for hydrothermal synthesis to promote the transformation of Ce(OH)CO₃ into CeO₂ and form a hollow nanotube structure. After the hydrothermal reaction is completed, cool to room temperature, obtain the solid product by centrifugation, and wash it several times with distilled water and ethanol in sequence. Finally, dry the product to obtain hollow nanotube CeO₂.
[0197] The purpose of adding distilled water to Ce(OH)CO₃ is to ensure the safe dispersion of Ce(OH)CO₃, so as to ensure the subsequent mixing.
[0198] Among them, the masses of Ce(OH)CO3, NaOH and distilled water are 0.25g, 4.8g and 40.00mL respectively; the reaction temperature is 120℃ and the time is 24h; washing is 3 times; the drying temperature is 100℃ and the time is 20h.
[0199] During preparation, Ce(OH)CO3, NaOH and distilled water must be mixed thoroughly in a strict ratio of 2.5:48:400.
[0200] Wherein, the reduction temperature in step three is 300°C.
[0201] When restoring, set the restoration time to 5h.
[0202] Among them, the dimethyl carbonate in step three is slightly soluble in water and miscible with alcohol, ketone, ester and aromatic organic solvents.
[0203] The chemical formula of dimethyl carbonate is C3H6O3. It can participate in carbonylation, methylation, methoxylation and other reactions. It is an important organic compound with wide industrial application value.
[0204] The above-mentioned hollow tubular CeO2 is used in the catalytic synthesis of dimethyl carbonate from CO2. The catalytic reaction conditions are: pressure of 3.0 MPa, temperature of 140°C, reaction time of 4 h, methanol addition amount of 15 mL, and hollow tubular CeO2 dosage of 0.1 g.
[0205] The synthesis of dimethyl carbonate using CO2 as raw material can not only realize the resource utilization of CO2, but also reduce the dependence on traditional fossil resources.
[0206] Example 7
[0207] like Figures 1 to 3 As shown, the embodiment of the present invention provides a method for preparing a hollow tubular CeO2, and the specific steps are as follows:
[0208] Step 1:
[0209] Dissolve urea and cerium nitrate hexahydrate in distilled water, react at a certain temperature for several hours, centrifuge, wash and dry to obtain Ce(OH)CO3;
[0210] Step 2:
[0211] Ce(OH)CO3 and sodium hydroxide were dissolved in distilled water and hydrothermally crystallized to obtain hollow tubular CeO2;
[0212] Step 3:
[0213] Hollow tubular CeO2 was reduced at different temperatures in a reducing gas (95% Ar: 5% H2) atmosphere and used for the direct synthesis of dimethyl carbonate from CO2 and methanol.
[0214] Hollow tubular CeO2 was obtained by hydrothermal synthesis and used as a catalyst in the direct synthesis of dimethyl carbonate from CO2 and methanol. Compared with the existing CeO2 catalysts in the forms of nanoparticles, cubes, nanorods, and hollow microspheres, it can significantly improve the yield of dimethyl carbonate. Meanwhile, the preparation method of hollow tubular CeO2 is simple and low-cost. Its unique cavity structure not only provides a higher specific surface area but also enhances the mass transfer efficiency and the exposure of reactive sites.
[0215] Among them, the specific preparation steps of Ce(OH)CO3 in step one are as follows: Dissolve urea and cerium(III) nitrate hexahydrate in distilled water and stir vigorously at room temperature. Subsequently, transfer the mixed solution to a round-bottom flask and stir and reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, cool to room temperature, obtain the solid product by centrifugation, wash it with distilled water, and finally, dry the product to obtain Ce(OH)CO3.
[0216] When stirring vigorously at room temperature, set the stirring time to 0.5 h to ensure that the reactants can be fully mixed.
[0217] Among them, the masses of urea, cerium(III) nitrate hexahydrate, and distilled water are 3.6 g, 1.70 g, and 80.00 mL respectively; the reaction temperature is 80 °C, the reaction time is 24 h; wash 2 - 4 times; the drying temperature is 70 °C, and the time is 12 h.
[0218] Urea, cerium(III) nitrate hexahydrate, and distilled water need to be strictly proportioned according to the ratio of 3.6:1.7:80. Meanwhile, during the reaction, it is necessary to ensure that the reaction temperature, reaction time, number of washing times, drying time, and temperature are all within the set ranges.
[0219] Among them, the specific preparation steps of CeO2 in step two are as follows: Take the Ce(OH)CO3 from step one, add distilled water, and then add NaOH. Stir vigorously at room temperature for 0.5 h to fully dissolve it and uniformly mix it with Ce(OH)CO3. Transfer the mixed solution to a hydrothermal reaction kettle for hydrothermal synthesis to promote the transformation of Ce(OH)CO3 into CeO2 and form a hollow nanotube structure. After the hydrothermal reaction is completed, cool to room temperature, obtain the solid product by centrifugation, and wash it several times with distilled water and ethanol in sequence. Finally, dry the product to obtain hollow nanotube CeO2.
[0220] The purpose of adding distilled water to Ce(OH)CO3 is to completely disperse Ce(OH)CO3, thereby ensuring subsequent mixing.
[0221] Among them, the masses of Ce(OH)CO3, NaOH and distilled water are 0.25g, 4.8g and 40.00mL respectively; the reaction temperature is 120℃ and the time is 24h; washing is 3 times; the drying temperature is 100℃ and the time is 20h.
[0222] During preparation, Ce(OH)CO3, NaOH and distilled water must be mixed thoroughly in a strict ratio of 2.5:48:400.
[0223] Wherein, the reduction temperature in step three is 400°C.
[0224] When restoring, set the restoration time to 5h.
[0225] Among them, the dimethyl carbonate in step three is slightly soluble in water and miscible with alcohol, ketone, ester and aromatic organic solvents.
[0226] The chemical formula of dimethyl carbonate is C3H6O3. It can participate in carbonylation, methylation, methoxylation and other reactions. It is an important organic compound with wide industrial application value.
[0227] The above-mentioned hollow tubular CeO2 is used in the catalytic synthesis of dimethyl carbonate from CO2. The catalytic reaction conditions are: pressure of 3.0 MPa, temperature of 140°C, reaction time of 4 h, methanol addition amount of 15 mL, and hollow tubular CeO2 dosage of 0.1 g.
[0228] The synthesis of dimethyl carbonate using CO2 as raw material can not only realize the resource utilization of CO2, but also reduce the dependence on traditional fossil resources.
[0229] Example 8
[0230] like Figures 1 to 3 As shown, the embodiment of the present invention provides a method for preparing a hollow tubular CeO2, and the specific steps are as follows:
[0231] Step 1:
[0232] Dissolve urea and cerium nitrate hexahydrate in distilled water, react at a certain temperature for several hours, centrifuge, wash and dry to obtain Ce(OH)CO3;
[0233] Step 2:
[0234] Ce(OH)CO3 and sodium hydroxide were dissolved in distilled water and hydrothermally crystallized to obtain hollow tubular CeO2;
[0235] Step 3:
[0236] Hollow tubular CeO2 was reduced at different temperatures in a reducing gas (95% Ar: 5% H2) atmosphere and used for the direct synthesis of dimethyl carbonate from CO2 and methanol.
[0237] Hollow tubular CeO₂ was obtained by hydrothermal synthesis and used as a catalyst in the direct synthesis of dimethyl carbonate from CO₂ and methanol. Compared with the existing CeO₂ catalysts in the forms of nanoparticles, cubes, nanorods, and hollow microspheres, it can significantly improve the yield of dimethyl carbonate. Meanwhile, the preparation method of hollow tubular CeO₂ is simple and low-cost. Its unique cavity structure not only provides a higher specific surface area but also enhances the mass transfer efficiency and the exposure of reactive sites.
[0238] Among them, the specific preparation steps of Ce(OH)CO₃ in step one are as follows: Dissolve urea and cerium(III) nitrate hexahydrate in distilled water and stir vigorously at room temperature. Subsequently, transfer the mixed solution to a round-bottom flask and stir and reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, cool to room temperature, obtain the solid product by centrifugation, wash it with distilled water, and finally, dry the product to obtain Ce(OH)CO₃.
[0239] When stirring vigorously at room temperature, set the stirring time to 0.5 h to ensure that the reactants can be fully mixed.
[0240] Among them, the masses of urea, cerium(III) nitrate hexahydrate, and distilled water are 3.6 g, 1.70 g, and 80.00 mL respectively; the reaction temperature is 80 °C, the reaction time is 24 h; wash 2 - 4 times; the drying temperature is 70 °C, and the time is 12 h.
[0241] Urea, cerium(III) nitrate hexahydrate, and distilled water need to be strictly proportioned according to the ratio of 3.6:1.7:80. Meanwhile, during the reaction, it is necessary to ensure that the reaction temperature, reaction time, number of washing times, drying time, and temperature are all within the set ranges.
[0242] Among them, the specific preparation steps of CeO₂ in step two are as follows: Take Ce(OH)CO₃ from step one, add distilled water, and then add NaOH. Stir vigorously at room temperature for 0.5 h to fully dissolve it and uniformly mix it with Ce(OH)CO₃. Transfer the mixed solution to a hydrothermal reaction kettle for hydrothermal synthesis to promote the conversion of Ce(OH)CO₃ to CeO₂ and form a hollow nanotube structure. After the hydrothermal reaction is completed, cool to room temperature, obtain the solid product by centrifugation, and wash it several times with distilled water and ethanol in sequence. Finally, dry the product to obtain hollow nanotube CeO₂.
[0243] The purpose of adding distilled water to Ce(OH)CO₃ is to completely disperse Ce(OH)CO₃, so as to ensure subsequent mixing.
[0244] Among them, the masses of Ce(OH)CO3, NaOH and distilled water are 0.25g, 4.8g and 40.00mL respectively; the reaction temperature is 120℃ and the time is 24h; washing is 3 times; the drying temperature is 100℃ and the time is 20h.
[0245] During preparation, Ce(OH)CO3, NaOH and distilled water must be mixed thoroughly in a strict ratio of 2.5:48:400.
[0246] Wherein, the reduction temperature in step three is 500°C.
[0247] When restoring, set the restoration time to 5h.
[0248] Among them, the dimethyl carbonate in step three is slightly soluble in water and miscible with alcohol, ketone, ester and aromatic organic solvents.
[0249] The chemical formula of dimethyl carbonate is C3H6O3. It can participate in carbonylation, methylation, methoxylation and other reactions. It is an important organic compound with wide industrial application value.
[0250] The above-mentioned hollow tubular CeO2 is used in the catalytic synthesis of dimethyl carbonate from CO2. The catalytic reaction conditions are: pressure of 3.0 MPa, temperature of 140°C, reaction time of 4 h, methanol addition amount of 15 mL, and hollow tubular CeO2 dosage of 0.1 g.
[0251] The synthesis of dimethyl carbonate using CO2 as raw material can not only realize the resource utilization of CO2, but also reduce the dependence on traditional fossil resources.
[0252] Depend on Figure 2 It can be seen that the samples treated in either air or mixed gas atmosphere all show characteristic peaks of cubic fluorite structure (such as (111), (200), (220), (311)), and no impurities are introduced, indicating that the sample purity is relatively high. Figure 2(a) The peak positions at each temperature did not shift significantly, indicating that the calcination temperature in air atmosphere has little effect on the lattice constant and the lattice structure remains stable. The diffraction peaks of the samples treated at low temperature (100 °C - 300 °C) in air atmosphere are relatively wide with a large full width at half maximum, indicating that the grain size is small and the crystallinity is low during low-temperature calcination; the peak intensity is weak, indicating incomplete crystallization or the presence of surface defects. The high specific surface area of the hollow tubular structure may lead to a relatively high surface energy, inhibiting the complete growth of grains at low temperature. The peak shapes of the samples treated at high temperature (400 °C - 600 °C) in air atmosphere gradually become sharp and the full width at half maximum decreases, indicating that as the temperature increases, the grain size increases and the crystallinity increases significantly. The peak intensity increases significantly, attributed to sufficient atomic diffusion, grain boundary migration promoting defect repair, and the formation of a long-range ordered structure. Therefore, the calcination temperature in air atmosphere significantly affects the grain size and crystallinity of hollow tubular CeO2 by regulating the grain growth kinetics and structural densification. Figure 2 (b) The characteristic peak at a reduction temperature of 400 °C is sharper than that at 300 °C, probably because high-temperature reduction promotes the recrystallization and growth of CeO2 grains. According to the Scherrer formula, the full width at half maximum of the diffraction peak is inversely proportional to the grain size, indicating that the grain size increases and the crystallinity improves under the reduction treatment at 400 °C. The obvious increase in the peak intensity at 600 °C may be due to the fact that during the reduction process by the reducing gas, part of Ce in CeO2 4+ is reduced to Ce 3+ , accompanied by the generation of oxygen vacancies to maintain charge balance. The introduction of oxygen vacancies leads to lattice expansion, changes the interplanar spacing d, and thus affects the Bragg diffraction conditions. Lattice expansion may make the arrangement of the (111) crystal plane more orderly, thereby enhancing its diffraction peak intensity. It is also possible that high-temperature reduction causes surface reconstruction of the material, forming a specific preferred crystal plane orientation. Under the reduction treatment at 600 °C, CeO2 may undergo structural reorganization, making the (111) crystal plane the main exposed plane, thereby enhancing its diffraction peak intensity.
[0253] The catalysts prepared in Comparative Examples 1-2 and Examples 1-8 were used in the direct synthesis of dimethyl carbonate from CO2 and methanol to test the yield (Y DMC (mmol / g cat )) and selectivity (S DMC (%)), and the results are as Figure 3 shown. As the calcination temperature in air atmosphere increases from 200 °C to 600 °C, the yield of dimethyl carbonate shows a trend of first increasing and then decreasing. As in Example 4, when the calcination temperature is 500 °C, the yield of dimethyl carbonate reaches the highest (14.43 mmol / g cat), while at 600 °C (Example 5), the yield of dimethyl carbonate decreased slightly. This indicates that at 500 °C, the structure and performance of the catalyst reached the optimal state. High-temperature calcination helps to form a stable crystal structure and active sites, but too high a temperature may lead to a reduction or inactivation of the active sites. As the reduction temperature in the reducing atmosphere increased from 300 °C to 600 °C, the yield of dimethyl carbonate also showed a trend of increasing first and then decreasing. As in Example 7, when the reduction temperature was 400 °C, the yield of dimethyl carbonate was relatively high (8.22 mmol / g cat ), which indicates that the reduction treatment helps to form more active sites, thereby improving the performance of the catalyst. In Comparative Example 2, the yield of dimethyl carbonate was close to 0, which indicates that the active sites of the catalyst may be destroyed after reduction at 600 °C, and the attachment Figure 2 shows that significant changes occurred in the crystal phase structure of CeO2 after reduction at 600 °C. High-temperature reduction may cause changes in the lattice parameters of CeO2, forming more defects and irregular structures. These structural changes may destroy the active sites of the catalyst, resulting in a decrease in its catalytic performance. Based on the above analysis, the calcination temperature in both air and reducing gas atmospheres has a significant impact on the yield of dimethyl carbonate. When calcined at 500 °C in air atmosphere and reduced at 400 °C in reducing gas atmosphere, the performance of the catalyst is the best, indicating that appropriate calcination and reduction treatments can optimize the structure and surface chemical properties of the catalyst, thereby improving the synthesis efficiency of dimethyl carbonate.
[0254] Under the optimal reaction conditions, such as the catalyst prepared in Example 4, the yield of dimethyl carbonate after the catalytic reaction was 14.43 mmol / g cat , and the selectivity was greater than 99.9%.
[0255] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.
[0256] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. Preparation of hollow tubular CeO2, characterized in that, The specific steps are as follows: Step 1: Dissolve urea and cerium(IV) nitrate hexahydrate in distilled water, react at a certain temperature for several hours, and obtain Ce(OH)CO3 after centrifugation, washing, and drying. Step 2: Dissolve Ce(OH)CO3 and sodium hydroxide in distilled water, and hydrothermally crystallize to obtain hollow tubular CeO2. Step 3: Calcine the hollow tubular CeO2 at different temperatures in an air atmosphere and then use it for the direct synthesis of dimethyl carbonate from CO2 and methanol. Step 4: Reduce the hollow tubular CeO2 at different temperatures in a reducing gas (95% Ar: 5% H2) atmosphere and then use it for the direct synthesis of dimethyl carbonate from CO2 and methanol.
2. The preparation of the hollow tubular CeO2 according to claim 1, wherein: The specific preparation steps of Ce(OH)CO3 described in Step 1 are as follows: Dissolve urea and cerium(IV) nitrate hexahydrate in distilled water, stir vigorously at room temperature. Subsequently, transfer the mixed solution to a round-bottom flask and stir and reflux at a certain temperature for several hours to promote the reaction and the formation of the product. After the reaction is completed, cool to room temperature, obtain the solid product by centrifugation, wash it with distilled water. Finally, dry the product to obtain Ce(OH)CO3.
3. The preparation of the hollow tubular CeO2 according to claim 2, characterized in that: The mass ratio of urea, cerium(IV) nitrate hexahydrate, and distilled water is 3.6:1.7:80; the reaction temperature is 60 - 100 °C, the reaction time is 18 - 30 h; wash 2 - 4 times; the drying temperature is 50 - 90 °C, and the time is 8 - 16 h.
4. Preparation of the hollow tubular CeO2 according to claim 1, characterized in that: The specific preparation steps of CeO2 described in Step 2 are as follows: Take Ce(OH)CO3 from Step 1 and add distilled water, then add NaOH, stir vigorously at room temperature for 0.5 h to fully dissolve it and mix it evenly with Ce(OH)CO3. Transfer the mixed solution to a hydrothermal reaction kettle for hydrothermal synthesis to promote the transformation of Ce(OH)CO3 to CeO2 and form a hollow nanotube structure. After the hydrothermal reaction is completed, cool to room temperature, obtain the solid product by centrifugation, and wash it several times with distilled water and ethanol in turn. Finally, dry the product to obtain hollow nanotube CeO2.
5. The preparation of the hollow tubular CeO2 according to claim 4, characterized in that: The mass ratio of Ce(OH)CO3, NaOH, and distilled water is 2.5:48:400; the reaction temperature is 100 - 140 °C, the time is 18 - 30 h; wash 2 - 4 times; the drying temperature is 80 - 120 °C, and the time is 16 - 24 h.
6. The preparation of the hollow tubular CeO2 according to claim 1, wherein: The calcination temperature described in Step 3 is 200 - 600 °C.
7. The preparation of the hollow tubular CeO2 according to claim 1, characterized in that: The reduction temperature described in Step 4 is 300 - 600 °C.
8. The preparation of the hollow tubular CeO2 according to claim 1, characterized in that: Dimethyl carbonate described in Step 3 and Step 4 is slightly soluble in water and miscible with organic solvents such as alcohols, ketones, esters, and aromatic hydrocarbons.
9. Use of the hollow tubular CeO2 according to any one of claims 1-8 in the catalytic synthesis of dimethyl carbonate from CO2, characterized in that: The conditions for the catalytic reaction are: pressure is 3.0 MPa, temperature is 140 °C, reaction time is 4 h, the addition amount of methanol is 15 mL, and the dosage of hollow tubular CeO2 is 0.1 g.