Nanosheet catalyst as well as preparation method and application thereof
By doping nanosheet catalysts with metal element M doping in WO3 lattice and depositing surface of the metal element M, the problem of insufficient CO2 conversion and methanol selectivity in the process of CO2 hydrogenation to methanol is solved, and efficient CO2 conversion and methanol selectivity are achieved.
Patent Information
- Application Number
- CN202510410153.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-02
- Publication Date
- 2025-07-04
AI Technical Summary
During the CO2 hydrogenation process to methanol, the CO2 conversion rate and methanol selectivity are low, and the stability is insufficient.
Using nanosheet catalyst, a nanosheet catalyst is formed by doping metal element M in the WO3 lattice and depositing part of the metal element M on its surface to form a nanosheet catalyst doped with M element. Pressurized hydrothermal crystallization technology is used to promote rapid separation of electron hole pairs and interface charge effect, and improve CO2 conversion and methanol selectivity.
The CO2 conversion rate and methanol selectivity are significantly improved, and the stability and catalytic performance of the catalyst are enhanced.
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Figure CN120243043A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of catalysts, and in particular, to a nanosheet catalyst, a preparation method thereof, and an application thereof. Background Art
[0002] As one of the main greenhouse gases, the excessive emission of carbon dioxide exacerbates the occurrence of the greenhouse effect and causes great harm to the global natural ecological environment. The technology of hydrogenating carbon dioxide to methanol can not only realize the resource conversion of carbon dioxide, help to solve the problem of renewable energy storage, but also achieve carbon dioxide emission reduction and slow down ecological deterioration. Therefore, the synthesis of methanol by hydrogenating CO2 is regarded as an effective way for large-scale resource utilization of CO2. However, due to the chemical inertness of CO2, its efficient conversion to methanol is still extremely challenging.
[0003] When traditional CuZnO catalysts are applied to the hydrogenation of CO2 to methanol, the prominent problems are the difficulty in activating CO2 and the low selectivity of methanol. For example, the Catalysis Research Institute of Zhejiang University prepared a Cu / Mn / Al system catalyst by the co-current coprecipitation method. The total conversion rate of CO2 was 15.8%, the selectivity of methanol was 20.8%, and the single-pass yield of methanol was 4.3%. Xu Yong et al. from East China University of Science and Technology studied the synthesis of methanol by hydrogenating CO2 on a Cu-ZnO-Al2O3 catalyst. The selectivity of methanol was 12.57%. The conversion rate of CO2 on the Cu-ZnO binary catalyst was 18.71%, and the selectivity of methanol was 9.87%. It can be seen that although traditional copper-based catalysts have been widely studied in the CO2 hydrogenation reaction, however, due to their high activity in the reverse water gas shift (RWGS), the selectivity of methanol is low, and due to the water-induced sintering of the active phase, they lack stability.
[0004] Due to its unique planar structure, the low-dimensional sheet structure has physical and chemical properties different from those of traditional bulk materials. In recent years, more and more low-dimensional sheet materials have been widely studied. For example, MoS2 with a nanosheet structure, etc. However, the ability of the nanosheet catalysts in the prior art to improve the CO2 conversion rate and methanol selectivity is limited.
[0005] In view of this, the present invention is specifically proposed. Summary of the Invention
[0006] An object of the present invention is to provide a nanosheet catalyst to solve the technical problem that the ability of the existing catalysts to improve the CO2 conversion rate and methanol selectivity simultaneously is not ideal.
[0007] Another object of the present invention is to provide a preparation method of the nanosheet catalyst, which is simple and easy to operate and environmentally friendly.
[0008] To achieve the above object of the present invention, the following technical solutions are specifically adopted:
[0009] A nanosheet catalyst, the nanosheet catalyst comprising a composite of WO3 and a metal element M, the metal element M being located in the lattice and on the outer surface of the WO3; by mass percentage, the WO3 is 80% to 95%, and the metal element M is 5% to 20%.
[0010] In some embodiments, the metal element M includes at least one of Cu, Zn, and In.
[0011] In some embodiments, the length of the nanosheet catalyst is 500 to 600 nm, and the thickness is 5 to 8 nm.
[0012] A method for preparing a nanosheet catalyst, comprising the following steps:
[0013] Performing a first co-current precipitation and aging on a soluble salt solution of the metal element M and a first alkaline solution to obtain a first system; performing a second co-current precipitation on a soluble tungsten salt solution and a second alkaline solution into the first system to obtain a second system; adding urea to the second system to obtain a third system; performing a hydrothermal crystallization treatment under pressure on the third system, and then collecting the solid matter and performing a calcination treatment.
[0014] In some embodiments, in the soluble salt solution of the metal element M, the metal element M includes at least one of Cu, Zn, and In.
[0015] In some embodiments, each of the first alkaline solution and the second alkaline solution independently includes at least one of sodium carbonate, sodium hydroxide, and ammonia water.
[0016] In some embodiments, in the soluble salt solution of the metal element M, the total metal ion concentration is 0.005 to 0.5 mol / L.
[0017] In some embodiments, in the soluble tungsten salt solution, the metal ion concentration is 0.5 to 5 mol / L.
[0018] In some embodiments, the concentrations of the first alkaline solution and the second alkaline solution are each independently 0.5 to 5 mol / L.
[0019] In some embodiments, the precipitation temperature of the first co-current precipitation is 0 to 5 °C, the pH is 7 to 11, and the aging time is 2 to 8 h.
[0020] In some embodiments, the precipitation temperature of the second co-current precipitation is 40 to 80 °C, and the pH is 8 to 12.
[0021] In some embodiments, the molar ratio of the urea to the metal element M in the soluble salt of the metal element M is 5 to 8.
[0022] In some embodiments, the hydrothermal crystallization treatment under pressure is carried out under the first pressure and heat treatment conditions. The first pressure is 0.5 to 4.0 Mpa, the temperature of the heat treatment is 150 to 200 °C, and the time of the heat treatment is 8 to 36 h.
[0023] In some embodiments, the hydrothermal crystallization treatment under pressure specifically includes: placing the third system in a sealing device, filling nitrogen with a certain pressure until the first pressure, and then putting it into a heating device for heat treatment.
[0024] In some embodiments, the temperature of the calcination treatment is 300 to 600 °C, and the time of the calcination treatment is 10 to 24 h.
[0025] In some embodiments, before the calcination treatment, the solid is dried, and the drying temperature is 80 to 120 °C.
[0026] In some embodiments, after the calcination treatment, it further includes crushing treatment and screening, and screening through a 40-60 mesh sieve.
[0027] In some embodiments, the collection of the solid includes filtration and washing. The liquid-solid ratio of the washing is 50% to 80%, and washing is carried out 3 to 5 times.
[0028] A method for highly selectively preparing methanol by hydrogenating CO2 uses the nanosheet catalyst described above, or the nanosheet catalyst prepared by the preparation method of the nanosheet catalyst described above.
[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0030] (1) In the nanosheet catalyst of the present invention, a small part of the element M is located in the WO3 lattice to form M element doping, thereby promoting the rapid separation of electron-hole pairs in WO3 and improving the CO2 conversion rate; a part of the element M is deposited on the surface of WO3 to enhance the interfacial charge effect, thereby increasing the H dissociation ability and improving the methanol selectivity. In addition, the element M and WO3 are combined in an appropriate ratio, which is more conducive to ensuring the catalytic performance of the nanosheet catalyst.
[0031] (2) In the preparation method of the nanosheet catalyst of the present invention, by adopting hydrothermal crystallization under pressure, a small part of the metal element M is promoted to enter the WO3 lattice to form M element doping, thereby promoting the rapid separation of electron-hole pairs in WO3 and improving the CO2 conversion rate; at the same time, the M metal substance that does not enter the lattice is deposited on the surface of WO3 to enhance the interfacial charge effect, thereby increasing the H dissociation ability and improving the methanol selectivity. The cooperation of the above steps is more conducive to ensuring the catalytic performance of the nanosheet catalyst. Brief Description of the Drawings
[0032] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0033] Figure 1 It is the transmission electron microscopy (TEM) image of the nanosheet catalyst in Example 1 of the present invention. Detailed Embodiments
[0034] The following will describe the implementation solutions of the present invention in detail in combination with the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.
[0035] According to one aspect of the present invention, the present invention relates to a nanosheet catalyst, and the nanosheet catalyst includes a composite of WO3 and a metal element M, and the metal element M is located in the lattice of WO3 and on its outer surface; in terms of mass percentage, WO3 is 80% to 95%, and the metal element M is 5% to 20%.
[0036] In the nanosheet catalyst of the present invention, a small part of the element M is located in the WO3 lattice to form M element doping, thereby promoting the rapid separation of electron-hole pairs in WO3 and improving the CO2 conversion rate; a part of the element M is deposited on the surface of WO3 to enhance the interfacial charge effect, thereby increasing the H dissociation ability and improving the methanol selectivity. In addition, the element M and WO3 are combined in an appropriate ratio, which is more conducive to ensuring the catalytic performance of the nanosheet catalyst.
[0037] In some embodiments, in terms of mass percentage, WO3 is 80% to 95%, including but not limited to 80%, 81%, 83%, 85%, 86%, 87%, 88%, 90%, 92%, 94%, 95%, etc., or the range values between any two of them. In some embodiments, in terms of mass percentage, the metal element M is 5% to 20%, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15, 16%, 17%, 18%, 19% or 20%, etc., or the range values between any two of them.
[0038] In some embodiments, the metal element M includes at least one of Cu, Zn, and In. The metal element M can be any one or a combination of several of the above, such as a combination of Cu and Zn, a combination of Zn and In, or a combination of Cu, Zn, and In. In some embodiments, the metal element M exists in the nanosheet catalyst in the form of an oxide, such as at least one of CuO, ZnO, and InO.
[0039] In some embodiments, the length of the nanosheet catalyst is 500 - 600 nm, such as 500 nm, 510 nm, 520 nm, 530 nm, 540 nm, 550 nm, 560 nm, 570 nm, 580 nm, 590 nm, 600 nm, etc., and the thickness is 5 - 8 nm, such as 5 nm, 5.3 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, etc. The length of the nanosheet catalyst can be tested by scanning electron microscopy.
[0040] According to another aspect of the present invention, the present invention also relates to a method for preparing a nanosheet catalyst, comprising the following steps:
[0041] Performing first co-current precipitation and aging on a soluble salt solution of the metal element M and a first alkaline solution to obtain a first system; performing second co-current precipitation on a soluble tungsten salt solution and a second alkaline solution and adding it into the first system to obtain a second system; adding urea into the second system to obtain a third system; performing hydrothermal crystallization treatment under pressure on the third system, and then collecting the solid matter and performing calcination treatment.
[0042] In the method for preparing the nanosheet catalyst of the present invention, by adopting hydrothermal crystallization under pressure, a small part of the metal element M is promoted to enter the WO3 lattice to form M element doping, thereby promoting the rapid separation of electron-hole pairs in WO3 and improving the CO2 conversion rate; at the same time, the M metal substance that does not enter the lattice is deposited on the surface of WO3, enhancing the interfacial charge effect, thereby increasing the H dissociation ability and improving the methanol selectivity. The functions of urea in the present invention include: 1) adjusting the pH value of the system and providing a suitable crystal growth environment in the subsequent hydrothermal crystallization process; 2) utilizing the selective adsorption effect of urea to promote the crystal growth along a certain crystal plane, thereby forming a nanosheet morphology. The cooperation of the above steps is more conducive to ensuring the catalytic performance of the nanosheet catalyst.
[0043] In some embodiments, the metal element M includes at least one of Cu, Zn, and In, such as a combination of Cu and Zn, a combination of Zn and In, or a combination of Cu, Zn, and In. In some embodiments, the soluble salt solution of the metal element M includes at least one of a nitrate solution and a sulfate solution of M. In the soluble salt solution of the metal element M, the total metal ion concentration is 0.005 to 0.5 mol / L, such as 0.005 mol / L, 0.05 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, or 0.5 mol / L, etc. A soluble salt solution of the metal element M with a suitable concentration can ensure better precipitation formation with the first lye.
[0044] In some embodiments, each of the first lye and the second lye independently includes at least one of sodium carbonate, sodium hydroxide, and ammonia water. The concentrations of the first lye and the second lye are each independently 0.5 to 5.0 mol / L, such as 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 4 mol / L, or 5 mol / L, etc., or a range value between any two of them.
[0045] In some embodiments, in the soluble tungstate solution, the metal ion concentration is 0.5 to 5.0 mol / L, such as 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, etc. A soluble tungstate solution with a suitable concentration is more conducive to the second co-current precipitation.
[0046] In some embodiments, for the first co-current precipitation, the precipitation temperature is 0 to 5 °C, such as 0 °C, 1 °C, 2 °C, 3 °C, 4 °C, 5 °C, etc., the pH is 7 to 11, such as 7, 8, 9, 10, 11, etc., and the aging time is 2 to 8 h, such as 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, or 8 h, etc. The above suitable first co-current treatment conditions cooperate to more effectively ensure the co-precipitation effect of the soluble salt solution of the metal element M and the first lye, which is beneficial to the catalytic performance of the subsequent nanosheet catalyst.
[0047] In some embodiments, for the second co-current precipitation, the precipitation temperature is 40 to 80 °C, such as 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 70 °C, 80 °C, etc., and the pH is 8 to 12, such as 8, 8.5, 9, 9.5, 10, 11, or 12, etc. The above suitable second co-current treatment conditions cooperate to more effectively ensure the co-precipitation effect of the soluble tungstate solution and the second lye, which is beneficial to the catalytic performance of the subsequent nanosheet catalyst.
[0048] In some embodiments, the molar ratio of urea to the metal element M in the soluble salt of the metal element M is 5 to 8, such as 5, 5.5, 6, 6.5, 7, 7.5, or 8.
[0049] In some embodiments, the hydrothermal crystallization treatment under pressure is carried out under the first pressure and heat treatment conditions. The first pressure is 0.5 to 4.0 Mpa, such as 0.5 Mpa, 1 Mpa, 1.5 Mpa, 2 Mpa, 3 Mpa, 3.5 Mpa, or 4 Mpa, etc. The temperature of the heat treatment is 150 to 200 °C, such as 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, etc. The time of the heat treatment is 8 to 36 h, such as 8 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, or 36 h, etc. The present invention adopts appropriate hydrothermal crystallization treatment conditions under pressure, which is more conducive to promoting a small part of the M metal to enter the WO3 lattice to form element M doping, thereby promoting the rapid separation of electron-hole pairs in WO3, increasing the concentration of free electrons, and improving the CO2 conversion rate; the M metal substance that does not enter the lattice is deposited on the surface of WO3, enhancing the interfacial charge effect, thereby increasing the H dissociation ability and improving the methanol selectivity.
[0050] In some embodiments, the hydrothermal crystallization treatment under pressure specifically includes: placing the third system in a sealing device, filling nitrogen with a certain pressure until the first pressure, and then putting it into a heating device for heat treatment. The sealing device includes a high-pressure hydrothermal autoclave. The heating device includes an oven.
[0051] In some embodiments, collecting the solid includes filtration and washing. The washing is carried out with deionized water, and the liquid-solid ratio is 50% to 80%, such as 50%, 60%, 70%, 80%, etc. The washing is carried out 3 to 5 times until the washing liquid is neutral.
[0052] In some embodiments, before the calcination treatment, the solid is dried. The drying temperature is 80 to 120 °C, such as 80 °C, 85 °C, 90 °C, 100 °C, 110 °C, 120 °C, etc. Appropriate drying conditions are used to remove moisture to facilitate the subsequent calcination treatment.
[0053] In some embodiments, the temperature of the calcination treatment is 300 to 600 °C, such as 300 °C, 350 °C, 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, etc. The time of the calcination treatment is 10 to 24 h, such as 10 h, 11 h, 12 h, 15 h, 18 h, 20 h, 24 h, etc. Appropriate calcination conditions can ensure the catalytic performance of the finally obtained catalyst.
[0054] In some embodiments, after the calcination treatment, it further includes crushing treatment and screening, and screening through a 40-60 mesh sieve. A 40-60 mesh catalyst is obtained.
[0055] According to another aspect of the present invention, the present invention also relates to a method for highly selectively preparing methanol by hydrogenating CO2, using the nanosheet catalyst described above, or the nanosheet catalyst prepared by the preparation method of the nanosheet catalyst. The nanosheet catalyst of the present invention is applicable to the reaction of hydrogenating CO2 to methanol, which can improve the CO2 conversion rate and simultaneously improve the methanol selectivity.
[0056] In some embodiments, the catalytic reaction temperature is 300 - 400 °C (such as 300 °C, 310 °C, 320 °C, 330 °C, 350 °C, 360 °C or 400 °C, etc.), and the reaction pressure is 2.0 - 10.0 Mpa (such as 2 Mpa, 3 Mpa, 5 Mpa, 7 Mpa, 10 Mpa, etc.).
[0057] The following will be further explained and illustrated in conjunction with specific examples.
[0058] Example 1
[0059] A preparation method of a nanosheet catalyst includes the following steps:
[0060] Weigh 1.9 g of copper nitrate and dissolve it in 100 mL of deionized water to prepare solution A; weigh 44.6 g of sodium carbonate and 40.0 g of sodium hydroxide, dissolve them in 1 L of deionized water together to prepare solution B; then weigh 13.8 g of sodium tungstate and dissolve it in 100 mL of deionized water to prepare solution C.
[0061] Under an ice-water bath and mechanical stirring, using the co-precipitation method, add solution A and solution B dropwise to a beaker containing 50 mL of deionized water for precipitation, control the pH value at 11.0, age for 2 h to form the first system. Then add solution C and solution B dropwise to the first system for continuous precipitation, control the precipitation temperature at 40 °C and the pH value at 11.5, stir evenly after dropping to obtain the second system, weigh 5.9 g of urea solution and add it to the above second system, stir evenly to form the third system.
[0062] Transfer the third system to an autoclave, pressurize it with N2 to 2 MPa, place it in an oven at 165 °C for hydrothermal treatment for 15 h. After cooling and venting, centrifuge to obtain the solid, add deionized water with a liquid-solid ratio of 80%, wash 5 times, then dry in an oven, and then calcine in air at 500 °C for 18 h, press and crush to 40 - 60 mesh to obtain the Cu-WO3 reverse oxide solid solution catalyst. In the catalyst, by mass percentage, Cu is 10% and WO3 is 90%.
[0063] The TEM image of the catalyst in this example is as Figure 1As shown, it can be seen that the catalyst is in a flaky structure, randomly piled up, and the catalyst grain sizes are uneven, mostly broken flakes. The length of the flakes is in the range of 500 - 600 nm, and the thickness is in the range of 5 - 8 nm.
[0064] Example 2
[0065] A preparation method of a nanosheet catalyst, comprising the following steps:
[0066] Weigh 3.8 g of copper nitrate and dissolve it in 150 mL of deionized water to prepare solution A; weigh 44.6 g of sodium carbonate and 40.0 g of sodium hydroxide, dissolve them together in 1 L of deionized water to prepare solution B; then weigh 13.1 g of sodium tungstate and dissolve it in 80 mL of deionized water to prepare solution C.
[0067] In an ice-water bath and under mechanical stirring, using the co-current coprecipitation method, add solution A and solution B dropwise to a beaker containing 50 mL of deionized water for precipitation, control the pH value at 9.0, and age for 2 h to form the first system. Then add solution C and solution B dropwise in parallel to the first system for continuous precipitation, control the precipitation temperature at 40 °C and the pH value at 11.5, stir evenly after dropping, to obtain the second system. Weigh 6.6 g of urea solution and add it to the above second system, stir evenly to obtain the third system.
[0068] Transfer the third system to an autoclave, pressurize it with N2 to 2 MPa, place it in an oven at 165 °C for hydrothermal treatment for 15 h. After cooling and venting, centrifuge to obtain the solid, add deionized water with a liquid-solid ratio of 80%, wash 5 times, then dry in an oven, and then calcine in air at 450 °C for 15 h, press and crush to 40 - 60 mesh to obtain the Cu-WO3 inverse oxide solid solution catalyst. In the catalyst, by mass percentage, Cu is 10% and WO3 is 90%.
[0069] Example 3
[0070] A preparation method of a nanosheet catalyst, comprising the following steps:
[0071] Weigh 2.9 g of copper nitrate and dissolve it in 120 mL of deionized water to prepare solution A; weigh 44.6 g of sodium carbonate and 40.0 g of sodium hydroxide, dissolve them together in 1 L of deionized water to prepare solution B; then weigh 13.4 g of sodium tungstate and dissolve it in 80 mL of deionized water to prepare solution C.
[0072] In an ice-water bath and under mechanical stirring, using the co-current co-precipitation method, solution A and solution B were dropped into a beaker containing 50 mL of deionized water for precipitation, controlling the pH value at 8.0 and aging for 5 h to form the first system. Then, solution C and solution B were co-currently dropped into the first system for continued precipitation, controlling the precipitation temperature at 80 °C and the pH value at 11.5. After the dropping was completed, it was stirred evenly to obtain the second system. 6.3 g of urea solution was weighed and added to the above-mentioned second system, and after stirring evenly, the third system was obtained.
[0073] The third system was transferred to an autoclave, pressurized with N2 to 0.5 MPa, placed in an oven at 200 °C for hydrothermal treatment for 36 h. After cooling and venting, the solid was centrifuged, 50% deionized water with a liquid-solid ratio was added, washed 5 times, then dried in an oven, and then calcined in air at 500 °C for 15 h, and pressed and crushed to 40 - 60 mesh to obtain a Cu-WO3 inverse oxide solid solution catalyst. In the catalyst, by mass percentage, Cu was 7.5% and WO3 was 92.5%.
[0074] Example 4
[0075] A preparation method of a nanosheet catalyst includes the following steps:
[0076] 9.0 g of zinc nitrate was weighed and dissolved in 300 mL of deionized water to prepare solution A; 25% concentrated ammonia water was used to prepare a 2% ammonia water solution labeled as solution B; 11.7 g of sodium tungstate was weighed and dissolved in 70 mL of deionized water to prepare solution C.
[0077] In an ice-water bath and under mechanical stirring, using the co-current co-precipitation method, solution A and solution B were dropped into a beaker containing 50 mL of deionized water for precipitation, controlling the pH value at 7.0 and aging for 6 h to form the first system. Then, solution C and solution B were co-currently dropped into the first system for continued precipitation, controlling the precipitation temperature at 50 °C and the pH value at 11.5. After the dropping was completed, it was stirred evenly to obtain the second system. 7.8 g of urea solution was weighed and added to the above-mentioned second system, and after stirring evenly, the third system was obtained.
[0078] The third system was transferred to an autoclave, pressurized with N2 to 3 MPa, placed in an oven at 150 °C for hydrothermal treatment for 12 h. After cooling and venting, the solid was centrifuged, 80% deionized water with a liquid-solid ratio was added, washed 5 times, then dried in an oven, and then calcined in air at 500 °C for 15 h, and pressed and crushed to 40 - 60 mesh to obtain a Zn-WO3 inverse oxide solid solution catalyst. In the catalyst, by mass percentage, Zn was 19.5% and WO3 was 80.5%.
[0079] Example 5
[0080] A preparation method of a nanosheet catalyst includes the following steps:
[0081] Weigh 4.1 g of zinc nitrate and dissolve it in 150 mL of deionized water to prepare solution A; prepare a 2% ammonia water solution with 25% concentrated ammonia water and label it as solution B; weigh 13.2 g of sodium tungstate and dissolve it in 80 mL of deionized water to prepare solution C.
[0082] In an ice-water bath and under mechanical stirring, using the co-current coprecipitation method, add solution A and solution B dropwise to a beaker containing 50 mL of deionized water for precipitation, control the pH value at 8.5, age for 3 h, and form the first system. Then add solution C and solution B dropwise in parallel to the first system for continuous precipitation, control the precipitation temperature at 60 °C, the pH value at 9.5, stir evenly after dropping, and obtain the second system. Weigh 6.5 g of urea solution and add it to the above second system, stir evenly to obtain the third system.
[0083] Transfer the third system to an autoclave, pressurize it with N2 to 4 MPa, place it in an oven at 150 °C for hydrothermal treatment for 8 h. After cooling and venting, centrifuge to obtain the solid, add deionized water with a liquid-solid ratio of 60%, wash 5 times, then dry in an oven, and then calcine in air at 500 °C for 15 h, press and crush to 40 - 60 mesh to obtain the Zn-WO3 inverse oxide solid solution catalyst. In the catalyst, by mass percentage, Zn is 9.0% and WO3 is 91.0%.
[0084] Example 6
[0085] A preparation method of a nanosheet catalyst, comprising the following steps:
[0086] Weigh 5.2 g of indium nitrate and dissolve it in 170 mL of deionized water to prepare solution A; weigh 85.0 g of sodium carbonate and dissolve it in 1 L of deionized water and label it as solution B; weigh 11.6 g of sodium tungstate and dissolve it in 70 mL of deionized water to prepare solution C.
[0087] In an ice-water bath and under mechanical stirring, using the co-current coprecipitation method, add solution A and solution B dropwise to a beaker containing 50 mL of deionized water for precipitation, control the pH value at 9.5, age for 5 h, and form the first system. Then add solution C and solution B dropwise in parallel to the first system for continuous precipitation, control the precipitation temperature at 80 °C, the pH value at 9.5, stir evenly after dropping, and obtain the second system. Weigh 7.9 g of urea solution and add it to the above second system solution, stir evenly to obtain the third system.
[0088] Transfer the above-mentioned third system to an autoclave, pressurize it with N2 to 3 MPa, and place it in an oven at 165 °C for hydrothermal treatment for 15 h. After cooling and venting, centrifuge to obtain the solid, add deionized water with a liquid-solid ratio of 60%, wash 5 times, then dry in an oven, and then calcine in air at 500 °C for 15 h, press and crush to 40-60 mesh to obtain an In-WO3 reverse oxide solid solution catalyst. In the catalyst, by mass percentage, In is 20.0% and WO3 is 80.0%.
[0089] Example 7
[0090] A method for preparing a nanosheet catalyst, comprising the following steps:
[0091] Weigh 3.0 g of indium nitrate and 4.2 g of zinc nitrate and dissolve them in 350 mL of deionized water to prepare solution A; weigh 44.6 g of sodium carbonate and 40.0 g of sodium hydroxide and dissolve them in 1 L of deionized water to prepare solution B; then weigh 11.6 g of sodium tungstate and dissolve it in 100 mL of deionized water to prepare solution C.
[0092] In an ice-water bath and under mechanical stirring, using the co-current coprecipitation method, add solution A and solution B dropwise to a beaker containing 50 mL of deionized water for precipitation, control the pH value at 9.5, and age for 5 h to obtain the first system. Then add solution C and solution B dropwise in parallel to the first system for continued precipitation, control the precipitation temperature at 80 °C and the pH value at 9.5, and stir evenly after dropping to obtain the second system. Weigh 35.0 g of urea and add it to the above-mentioned second system, stir evenly to obtain the third system.
[0093] Transfer the third system to an autoclave, pressurize it with N2 to 4 MPa, and place it in an oven at 150 °C for hydrothermal treatment for 15 h. After cooling and venting, centrifuge to obtain the solid, add deionized water with a liquid-solid ratio of 60%, wash 5 times, then dry in an oven, and then calcine in air at 500 °C for 15 h, press and crush to 40-60 mesh to obtain a ZnIn-WO3 reverse oxide solid solution catalyst. In the catalyst, by mass percentage, ZnO is 9%, InO is 11%, and WO3 is 80.0%.
[0094] Experimental Example 1
[0095] Use a 5 mL fixed-bed reactor, the catalyst loading is 1.0 g (using the catalysts in Examples 1 to 7 respectively), diluted with 1.0 g of fine quartz sand, the reducing atmosphere is 5% H2-95% N2, the flow rate is 80 mL / min, the reduction temperature is 350 °C, and the reduction time is 8 h. After the reduction process is completed, use N2 to pressurize to 5.0 MPa, maintain the reaction temperature at 320 °C, and the feed gas space velocity is 24000 h -1, the raw material gas composition is H2 / CO2 = 3.0. After the temperature and pressure are stabilized, the reaction starts. The reaction tail gas product is analyzed by on-line chromatography. The tail gas analysis conditions are as follows: the chromatographic column is Porapak-T, the column temperature is 90 °C, the carrier gas is argon, the flow rate is 25 mL / min, the current is 60 mA. The liquid-phase product is collected by a cold trap, taken out and analyzed by chromatography. The analysis conditions are as follows: the chromatographic column is TDX-01, the column temperature is 160 °C, the carrier gas is argon, the flow rate is 30 mL / min, and the current is 60 mA.
[0096] The test results of the catalysts in each example are shown in Table 1.
[0097] Table 1 Performance test results of the catalysts
[0098]
[0099] Experimental Example 2
[0100] A 5 mL fixed-bed reactor is used. The catalyst used is the catalyst in Example 1, with a filling amount of 1.0 g, diluted with 1.0 g of fine quartz sand. The reduction atmosphere is 5% H2-95% N2, the flow rate is 80 mL / min, the reduction temperature is 350 °C, and the reduction time is 8 h. After the reduction process is completed, the temperature is lowered to 300 °C, and the pressure is flushed to 8.0 MPa with N2. Different reaction temperatures are investigated, and the space velocity of the feed gas is 4000 h -1 , the raw material gas composition is H2 / CO2 = 3.0. After the temperature and pressure are stabilized, the reaction starts. The reaction tail gas product is analyzed by on-line chromatography. The tail gas analysis conditions are as follows: the chromatographic column is Porapak-T, the column temperature is 90 °C, the carrier gas is argon, the flow rate is 25 mL / min, the current is 60 mA. The liquid-phase product is collected by a cold trap, taken out and analyzed by chromatography. The analysis conditions are as follows: the chromatographic column is TDX-01, the column temperature is 160 °C, the carrier gas is argon, the flow rate is 30 mL / min, and the current is 60 mA. The evaluation results of the catalyst at different reaction temperatures are shown in Table 2.
[0101] Table 2 Evaluation results of the catalyst at different reaction temperatures
[0102]
[0103]
[0104] Experimental Example 3
[0105] A 5 mL fixed-bed reactor is used. The catalyst used is the catalyst in Example 4, with a filling amount of 1.0 g, diluted with 1.0 g of fine quartz sand. The reduction atmosphere is 5% H2-95% N2, the flow rate is 80 mL / min, the reduction temperature is 350 °C, and the reduction time is 8 h. After the reduction process is completed, the temperature is lowered to 300 °C, and the pressure is flushed to a certain pressure with N2. Different reaction pressures are investigated, and the space velocity of the feed gas is 24000 h-1 , the raw gas composition is H2 / CO2 = 3.0. After the temperature and pressure are stabilized, the reaction starts. The reaction tail gas product is analyzed by on-line chromatography. The tail gas analysis conditions are as follows: the chromatographic column is Porapak-T, the column temperature is 90 °C, the carrier gas is argon, the flow rate is 25 mL / min, and the current is 60 mA. The liquid-phase product is collected by a cold trap, taken out and analyzed by chromatography. The analysis conditions are as follows: the chromatographic column is TDX-01, the column temperature is 160 °C, the carrier gas is argon, the flow rate is 30 mL / min, and the current is 60 mA. The evaluation results of the catalyst at different reaction pressures are shown in Table 3.
[0106] Table 3 Evaluation results of the catalyst at different reaction pressures
[0107]
[0108] As can be seen from the above, the nanosheet catalyst obtained by the method of the present invention can effectively improve the CO2 conversion rate and at the same time improve the methanol selectivity.
[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A nanosheet catalyst, characterized in that, The nanosheet catalyst includes a composite of WO3 and metal element M, and the metal element M is located in the lattice of WO3 and on its outer surface; by mass percentage, WO3 is 80% - 95%, and the metal element M is 5% - 20%.
2. The nanosheet catalyst according to claim 1, wherein The metal element M includes at least one of Cu, Zn, and In.
3. The nanosheet catalyst according to claim 1, wherein The length of the nanosheet catalyst is 500 - 600 nm, and the thickness is 5 - 8 nm.
4. A method for preparing a nanosheet catalyst, characterized in that, It includes the following steps: Carry out first co-current precipitation and aging on the soluble salt solution of metal element M and the first alkali solution to obtain a first system; Carry out second co-current precipitation on the soluble tungsten salt solution and the second alkali solution into the first system to obtain a second system; add urea to the second system to obtain a third system; carry out pressurized hydrothermal crystallization treatment on the third system, and then collect the solid and carry out calcination treatment.
5. The preparation method of the nanosheet catalyst according to claim 4, characterized in that, It includes at least one of the following features (1) - (5): (1) The metal element M includes at least one of Cu, Zn, and In; (2) Each of the first alkali solution and the second alkali solution independently includes at least one of sodium carbonate, sodium hydroxide, and ammonia water; (3) In the soluble salt solution of the metal element M, the total metal ion concentration is 0.005 - 0.5 mol / L; (4) In the soluble tungsten salt solution, the metal ion concentration is 0.5 - 5 mol / L; (5) The concentrations of the first alkali solution and the second alkali solution are each independently 0.5 - 5 mol / L.
6. The preparation method of the nanosheet catalyst according to claim 4, wherein, It includes at least one of the following features (1) - (2): (1) The precipitation temperature of the first co-current precipitation is 0 - 5°C, the pH is 7 - 11, and the aging time is 2 - 8 h; (2) The precipitation temperature of the second co-current precipitation is 40 - 80°C, and the pH is 8 - 12.
7. The preparation method of the nanosheet catalyst according to claim 4, wherein, The molar ratio of urea to the metal element M in the soluble salt of the metal element M is 5 - 8.
8. The preparation method of the nanosheet catalyst according to claim 4, wherein It includes at least one of the following features (1) - (2): (1) The pressurized hydrothermal crystallization treatment is carried out under the first pressure and heat treatment conditions, the first pressure is 0.5 - 4.0 Mpa, the heat treatment temperature is 150 - 200°C, and the heat treatment time is 8 - 36 h; (2) The pressurized hydrothermal crystallization treatment specifically includes: placing the third system in a sealed device, filling it with a protective gas to the first pressure, and then putting it into a heating device for heat treatment.
9. The preparation method of the nanosheet catalyst according to claim 4, wherein, It includes at least one of the following features (1) - (4): (1) The temperature of the calcination treatment is 300 - 600°C, and the time of the calcination treatment is 10 - 24 h; (2) Before the calcination treatment, the solid is dried, and the drying temperature is 80 - 120°C; (3) After the calcination treatment, it also includes crushing treatment and screening, and screening through a 40 - 60 mesh sieve; (4) The collection of the solid includes filtration and washing, the liquid-solid ratio of the washing is 50% - 80%, and washing is carried out 3 - 5 times.
10. A method for highly selectively preparing methanol by hydrogenating CO2, characterized in that, The nanosheet catalyst is prepared by using the nanosheet catalyst according to any one of claims 1 - 3, or the preparation method of the nanosheet catalyst according to any one of claims 4 - 9.