Cu-Zn2SiO4 catalyst, preparation method and application

Abstract

The invention relates to the technical field of catalytic preparation of methanol, in particular to a Cu-Zn2SiO4 catalyst as well as a preparation method and application thereof. The preparation method of the Cu-Zn2SiO4 catalyst comprises the following steps: uniformly mixing a copper source and a zinc source in an ethanol solution, adding a silicon source and an alkali source into the mixture, stirring to form initial gel, and carrying out hydrothermal crystallization reaction to prepare the Cu-Zn2SiO4 catalyst. The silicon source, the zinc source and the alkali source react to form a stable zinc silicate framework, Cu particles are anchored in the framework to limit movement and migration of the Cu particles, the sintering phenomenon caused by reduction of surface energy under the reaction condition is avoided, meanwhile, reduction of Cu < 2 + > can be hindered to a certain extent, the proportion of Cu < 2 + > in the CuZn-based catalyst is increased, and the CuZn-based catalyst has a good application prospect. The number of active sites of the catalyst is maintained, and the problems that in the prior art, a CuZn-based catalyst is prone to inactivation, and the utilization rate of Cu atoms is low are solved.

Description

Technical Field

[0001] This invention relates to the field of catalytic methanol production technology, specifically to a Cu-Zn2SiO4 catalyst, its preparation method, and its application. Background Technology

[0002] Methanol, as a hydrogen-containing liquid fuel, can be used as a direct substitute for fossil fuels or as a highly efficient and clean fuel additive due to its unique physicochemical properties. More importantly, methanol can be produced through various pathways. Among them, carbon dioxide hydrogenation to methanol technology not only effectively utilizes hydrogen energy but also converts carbon dioxide generated in industrial processes into valuable chemicals, achieving the recycling of carbon resources. This is of great significance for mitigating the greenhouse effect and promoting sustainable development. Therefore, carbon dioxide hydrogenation to methanol technology, as a key pathway integrating carbon dioxide resource utilization and carbon emission reduction, is receiving increasing attention and importance.

[0003] In the carbon dioxide hydrogenation to methanol technology route, catalyst selection and design are crucial, directly affecting reaction efficiency and product selectivity. Among numerous catalyst systems, CuZn-based catalysts stand out due to their unique electronic synergistic effect and moderate CO2 adsorption and activation capacity, becoming a current research hotspot in the field of catalysis. CuZn-based catalysts are typically composed of copper (Cu), zinc (Zn), and possible promoters. By precisely controlling the proportions of each component and the preparation process, the surface structure and electronic properties of the catalyst can be optimized, thereby achieving efficient adsorption and activation of CO2 molecules.

[0004] Although CuZn-based catalysts exhibit excellent catalytic performance in the CO2 hydrogenation to methanol reaction, their industrial application still faces significant challenges, the most prominent of which is the sintering phenomenon of Cu nanoparticles under reaction conditions. At the reaction temperature, due to the decrease in surface energy, Cu nanoparticles tend to reduce their total surface energy through migration and aggregation—a process known as sintering. Sintering leads to a significant increase in the particle size of the active metal and a sharp decrease in the specific surface area, thereby reducing the number of active sites on the catalyst and drastically reducing its catalytic activity.

[0005] Therefore, how to effectively suppress the sintering of Cu nanoparticles, improve the stability and deactivation resistance of catalysts, and enhance the atomic utilization of Cu have become key scientific issues and technological challenges in the current research on CuZn-based catalysts. Summary of the Invention

[0006] To address the problems of easy deactivation and low Cu atom utilization in existing CuZn-based catalysts, this invention provides a Cu-Zn2SiO4 catalyst, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for preparing a Cu-Zn2SiO4 catalyst, comprising: The copper source and zinc source are added to the ethanol solution and mixed thoroughly to obtain a mixed reaction solution; Add a silicon source and an alkali source to the mixed reaction solution, stir, and obtain an initial gel; The initial gel was subjected to a hydrothermal crystallization reaction to obtain a Cu-Zn2SiO4 catalyst.

[0008] Optionally, the copper source is copper nitrate and / or copper acetate; the zinc source is zinc nitrate and / or zinc acetate.

[0009] Optionally, the molar ratio of copper source, zinc source, water and ethanol in the mixed reaction solution is (0.05-0.5):1:(50-200):(10-100).

[0010] Optionally, the silicon source is silica aerosol or silica sol, and the alkali source is urea or ammonia.

[0011] Optionally, the molar ratio of zinc source to silicon source is (0.5-5):1, and the molar ratio of zinc source to alkali source is (0.5-5):1.

[0012] Optionally, the method for obtaining the Cu-Zn2SiO4 catalyst by subjecting the initial gel to a hydrothermal crystallization reaction is as follows: The initial gel was subjected to hydrothermal crystallization at 100–130°C for the first time, and then heated to 170–200°C for the second hydrothermal crystallization. After cooling to room temperature, it was filtered, washed, and dried to obtain the Cu-Zn2SiO4 catalyst.

[0013] Optionally, the time for the first hydrothermal crystallization is 1 to 24 hours, and the time for the second hydrothermal crystallization is 48 to 96 hours.

[0014] Optionally, the drying method is as follows: heat to 100-200℃ at a rate of 1-3℃ / min and maintain for 6-8 hours to obtain Cu-Zn2SiO4 catalyst.

[0015] A Cu-Zn₂SiO₄ catalyst was prepared using the method described above. The Cu-Zn₂SiO₄ catalyst, based on the mass of copper, was prepared at a reaction temperature of 220℃, a reaction pressure of 3 MPa, and a space velocity of 6000 mL g⁻¹. cat -1 h -1 Under the given conditions, the space-time yield of methanol reached 49.6 mmol g after the reaction stabilized. Cu -1 h -1The selectivity reached 99%; the reaction temperature was 250℃, the reaction pressure was 3MPa, and the space velocity was 6000 mL g / L. cat -1 h -1 Under the given conditions, the space-time yield of methanol reached 64.0 mmol g after the reaction stabilized. Cu -1 h -1 The selectivity rate is 70%.

[0016] The applications of the above-mentioned Cu-Zn2SiO4 catalyst in the hydrogenation of CO2 to methanol include: Using Cu-Zn2SiO4 catalyst as the catalyst, the temperature was first raised to 280–320℃, and hydrogen was pretreated for 1–3 h. Then, CO2 and H2 were introduced at a molar ratio of (1:1) to (1:6), with the reaction pressure controlled at 2.0–5.0 MPa, the reaction temperature at 200–300℃, and the space velocity at 5000–15000 mL g. cat -1 h -1 The reaction yields methanol.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing a Cu-Zn2SiO4 catalyst. The method involves uniformly mixing a copper source and a zinc source in an ethanol solution, then adding a silicon source and an alkali source and stirring to form an initial gel. Following a hydrothermal crystallization reaction, the silicon source reacts with the alkali source and interacts with the copper and zinc sources to form a stable zinc silicate framework, anchoring Cu particles within this framework and restricting their movement and migration. At the reaction temperature, even if Cu particles tend to decrease their surface energy, the zinc silicate framework prevents them from freely approaching and aggregating, thus avoiding sintering. Simultaneously, the anchoring of Cu particles within the zinc silicate framework can, to a certain extent, hinder Cu... 2+ The reduction of Cu in CuZn-based catalysts enhances Cu content. 2+ By maintaining the proportion of active sites in the catalyst, more active sites are available for reactant reaction, thereby improving the reaction rate and conversion rate. This method is simple, requires no complex equipment or harsh reaction conditions, and facilitates the continuous industrial production of this catalyst.

[0018] This invention also provides a Cu-Zn2SiO4 catalyst prepared by the above method, wherein the catalyst, based on the mass of copper, is reacted at a temperature of 220°C, a pressure of 3 MPa, and a space velocity of 6000 mL g. cat -1 h -1 Under the given conditions, the space-time yield of methanol reached 49.6 mmol g after the reaction stabilized. Cu -1 h-1 The selectivity reached 99%; the reaction temperature was 250℃, the reaction pressure was 3MPa, and the space velocity was 6000 mL g / L. cat -1 h -1 Under the given conditions, the space-time yield of methanol reached 64.0 mmol g after the reaction stabilized. Cu -1 h -1 With a selectivity of 70%, this catalyst can generate more methanol per unit time and per unit catalyst mass, effectively improving methanol production efficiency. At the same time, at 220℃, the methanol selectivity of 99% can make the purity and yield of the generated methanol higher, providing a more reliable catalyst selection for the industrial application of carbon dioxide hydrogenation to methanol technology.

[0019] The application of the Cu-Zn2SiO4 catalyst in the production of methanol by CO2 hydrogenation can effectively improve the production efficiency of methanol, as the Cu-Zn2SiO4 catalyst has higher reactivity and selectivity. It can also improve the purity and yield of methanol, reduce the subsequent separation and purification steps, and reduce the production cost, making the CO2 hydrogenation to methanol technology more economically feasible and environmentally friendly. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation method of a Cu-Zn2SiO4 catalyst according to the present invention.

[0021] Figure 2 The images show XRD patterns of the catalysts prepared in Example 1 and Comparative Examples 1-3 before and after participating in the catalytic reaction; wherein, a is the XRD pattern of the catalysts prepared in Example 1 and Comparative Examples 1-3 before participating in the catalytic reaction, and b is the XRD pattern corresponding to a after participating in the catalytic reaction.

[0022] Figure 3 The images show SEM images and corresponding elemental energy dispersive spectroscopy (EDS) of the catalysts prepared in Example 1 and Comparative Examples 1-3 of this invention.

[0023] Figure 4 The above are FT-IR comparison images of the catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention.

[0024] Figure 5 Cu 2p of the catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention 3 / 2 XPS diagram.

[0025] Figure 6 This is a comparison graph showing the performance of the catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention over time. Detailed Implementation

[0026] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0027] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0028] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0029] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0030] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0031] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0032] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0033] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0034] See Figure 1 This invention discloses a method for preparing a Cu-Zn2SiO4 catalyst, comprising: S1: Add the copper source and zinc source to the ethanol solution and mix them evenly to obtain a mixed reaction solution. The molar ratio of copper source, zinc source, water and ethanol in the mixed solution is (0.05~0.5):1:(50~200):(10~100), more preferably (0.1~0.3):1:(100~120):20. Preferably, the copper source is copper nitrate trihydrate (Cu(NO3)2·3H2O) or copper acetate monohydrate (Cu(CH3COO)2·H2O), and the zinc source is zinc nitrate hexahydrate (Zn(NO3)2·6H2O) or zinc acetate dihydrate (Zn(CH3COO)2·2H2O).

[0035] S2: Add the silicon source and the alkali source to the mixed reaction solution, stir, and obtain the initial gel, specifically: Add silicon source and alkali source to the mixed reaction solution at a molar ratio of zinc source to silicon source of (0.5-5):1 and a molar ratio of zinc source to alkali source of (0.5-5):1, and stir for 6-12 hours to obtain an initial gel; preferably, the molar ratio of zinc source to silicon source is (0.8-1.4):1 and the molar ratio of silicon source to alkali source is (0.5-2):1; preferably, the silicon source is silica aerosol (SiO2) or silica sol, and the alkali source is urea or ammonia, more preferably urea.

[0036] S3: The initial gel was subjected to a hydrothermal crystallization reaction to obtain a Cu-Zn2SiO4 catalyst, specifically: The initial gel is subjected to hydrothermal crystallization at 100–130°C for the first time, followed by a second hydrothermal crystallization at 170–200°C. After cooling to room temperature, the gel is filtered, washed, and dried to obtain the Cu-Zn2SiO4 catalyst. Preferably, the time for the first hydrothermal crystallization is 1–24 h, and the time for the second hydrothermal crystallization is 48–96 h. More preferably, the temperature for the first hydrothermal crystallization is 120–130°C, and the time for the first hydrothermal crystallization is 20–24 h. The temperature for the second hydrothermal crystallization is 170–180°C, and the time for the second hydrothermal crystallization is 72–96 h. Preferably, the drying process is a programmed temperature rise process, and the catalyst does not need to be calcined after drying. The specific drying method is to raise the temperature to 100–200°C at a rate of 1–3°C / min and hold it for 6–8 h to obtain the Cu-Zn2SiO4 catalyst.

[0037] This method involves uniformly mixing copper and zinc sources in an ethanol solution, then adding silicon and alkali sources and stirring to form an initial gel. Following a hydrothermal crystallization reaction, the silicon and alkali sources react and interact with the copper and zinc sources, forming a stable zinc silicate framework. This framework anchors Cu particles, restricting their movement and migration. At the reaction temperature, even if Cu particles tend to decrease their surface energy, the zinc silicate framework prevents them from freely approaching and aggregating, thus avoiding sintering. Simultaneously, it can, to a certain extent, hinder Cu... 2+ The reduction of Cu in CuZn-based catalysts enhances Cu content. 2+ The proportion of [amount] maintains the number of active sites in the catalyst.

[0038] This invention also provides a Cu-Zn₂SiO₄ catalyst, prepared using the above-described method for preparing Cu-Zn₂SiO₄ catalysts; based on the mass of copper, the Cu-Zn₂SiO₄ catalyst is prepared at a reaction temperature of 220℃, a reaction pressure of 3MPa, and a space velocity of 6000 mL g⁻¹. cat -1 h -1 Under the given conditions, the space-time yield of methanol reached 49.6 mmol g after the reaction stabilized. Cu -1 h -1 The selectivity reached 99%; the reaction temperature was 250℃, the reaction pressure was 3MPa, and the space velocity was 6000 mL g / L. cat -1 h -1 Under the given conditions, the space-time yield of methanol reached 64.0 mmol g after the reaction stabilized. Cu -1 h -1 With a selectivity of 70%, this catalyst can generate more methanol per unit time and per unit catalyst mass, effectively improving methanol production efficiency. Furthermore, at 220℃, its 99% methanol selectivity ensures higher purity and yield of the generated methanol, providing a more reliable catalyst option for the industrial application of carbon dioxide hydrogenation to methanol technology.

[0039] Applications of Cu-Zn2SiO4 catalysts in CO2 hydrogenation to methanol include: Using Cu-Zn2SiO4 catalyst as the catalyst, the temperature was first raised to 280–320℃, and hydrogen was pretreated for 1–3 h. Then, CO2 and H2 were introduced at a molar ratio of (1:1) to (1:6), with the reaction pressure controlled at 2.0–5.0 MPa, the reaction temperature at 200–300℃, and the space velocity at 5000–15000 mL g. cat -1 h -1 The reaction yields methanol.

[0040] Example 1 According to the stoichiometric ratio, 0.0024 mol Cu(NO3)2·3H2O and 0.024 mol Zn(CH3COO)2·2H2O were added to an ethanol solution prepared by 85 mL of deionized water and 45 mL of anhydrous ethanol, and mixed thoroughly to obtain a mixed reaction solution; wherein the molar ratio of copper nitrate, zinc acetate, water and ethanol was 0.1:1:200:50. According to the molar ratio of zinc acetate dihydrate to silica aerosol of 1:1 and the molar ratio of zinc acetate dihydrate to urea of ​​1:1, 0.024 mol SiO2 and 0.024 mol urea were added to the mixed reaction solution and stirred for 12 h to obtain the initial gel. The initial gel was added to a high-pressure reactor and first hydrothermally crystallized at 130℃ for 12 h. Then, the temperature was raised to 170℃ and crystallized for another 72 h. After cooling to room temperature, the mixture was filtered, washed until neutral, and dried at 150℃ for 7 h at a rate of 2℃ / min to obtain the Cu-Zn2SiO4 catalyst, denoted as Cu-Zn2SiO4-1.

[0041] Comparative Example 1 According to the stoichiometric ratio, 0.0024 mol Cu(NO3)2·3H2O and 0.024 mol Zn(CH3COO)2·2H2O were added to an ethanol solution prepared by 85 mL of deionized water and 45 mL of anhydrous ethanol, and mixed thoroughly to obtain a mixed reaction solution; wherein the molar ratio of copper nitrate, zinc acetate, water and ethanol was 0.1:1:200:50. According to the molar ratio of zinc acetate dihydrate to silica aerosol of 1:1 and the molar ratio of zinc acetate dihydrate to urea of ​​1:1, 0.024 mol SiO2 and 0.024 mol urea were added to the mixed reaction solution and stirred for 12 h to obtain the initial gel. The initial gel was added to a high-pressure reactor and crystallized at 170℃ for 72 h. After cooling to room temperature, it was filtered, washed until neutral, and dried at 150℃ for 7 h with a heating rate of 2℃ / min to obtain the Cu-Zn2SiO4 catalyst, denoted as Cu-Zn2SiO4-2.

[0042] Comparative Example 2 According to the stoichiometric ratio, 0.0024 mol Cu(NO3)2·3H2O and 0.024 mol Zn(CH3COO)2·2H2O were added to an ethanol solution prepared by 85 mL of deionized water and 45 mL of anhydrous ethanol, and mixed thoroughly to obtain a mixed reaction solution; wherein the molar ratio of copper nitrate, zinc acetate, water and ethanol was 0.1:1:200:50. With a molar ratio of zinc acetate dihydrate to silica aerosol of 1:1, 0.024 mol SiO2 was added to the mixed reaction solution and stirred for 12 h to obtain the initial gel. The initial gel was added to a high-pressure reactor and first hydrothermally crystallized at 130℃ for 12 h. Then, the temperature was raised to 170℃ and crystallized for another 72 h. After cooling to room temperature, the mixture was filtered, washed until neutral, and dried at 150℃ for 7 h with a temperature increase of 2℃ / min. The resulting Cu-Zn2SiO4 catalyst was denoted as Cu-Zn2SiO4-3.

[0043] Comparative Example 3 0.0024 mol Cu(NO3)2·3H2O and 0.024 mol Zn(CH3COO)2·2H2O were added to 85 mL of deionized water and mixed thoroughly to obtain a mixed reaction solution; the molar ratio of copper nitrate, zinc acetate, and water was 0.1:1:200. According to the molar ratio of zinc acetate dihydrate to silica aerosol of 1:1 and the molar ratio of zinc acetate dihydrate to urea of ​​1:1, 0.024 mol SiO2 and 0.024 mol urea were added to the mixed reaction solution and stirred for 12 h to obtain the initial gel. The initial gel was added to a high-pressure reactor and first hydrothermally crystallized at 130℃ for 12 h. Then, the temperature was raised to 170℃ and crystallized for another 72 h. After cooling to room temperature, the mixture was filtered, washed until neutral, and dried at 150℃ for 7 h at a rate of 2℃ / min to obtain the Cu-Zn2SiO4 catalyst, denoted as Cu-Zn2SiO4-4.

[0044] To further illustrate the beneficial effects of the present invention, XRD tests were performed on the catalysts prepared in Example 1 and Comparative Examples 1-3 before and after their catalytic reaction. The results are shown in [reference needed]. Figure 2 ,from Figure 2As can be seen from Figure a, the diffraction peaks at 2θ = 22.1°, 25.6°, 31.5°, 34.0°, 38.8°, 48.8°, and 65.6° perfectly match the characteristic diffraction peaks of Zn2SiO4 (PDF#72-1856) in the 2θ = 20°–80° range in the standard PDF card; this indicates that the support crystal structure is intact and has not undergone structural distortion due to the introduction of Cu. The corresponding crystal plane indices are (300), (110), (113), (410), (223), (333), and (173). In addition, the diffraction peaks observed in all samples at 2θ = 43.3°, 50.4°, and 74.0° are consistent with the characteristic diffraction peaks of metallic Cu (PDF#70-3038) in the 2θ = 20°–80° range in the standard PDF card, and the peak positions have not shifted. The corresponding crystal plane indices are (111), (200), and (220). The above results indicate that Cu exists as an independent crystalline phase, possibly dispersed as nanoparticles on the surface of Zn₂SiO₄. The Cu-Zn₂SiO₄ catalysts prepared in Example 1 all successfully constructed Cu-Zn₂SiO₄ composite structures. The characteristic diffraction peaks of Zn₂SiO₄ (PDF#72-1856) and Cu (PDF#70-3038) in the 2θ=20°~80° range of the samples in Comparative Examples 1-2 are consistent with those of Zn₂SiO₄ (PDF#72-1856) and Cu (PDF#70-3038) in the standard PDF card, and the peak positions did not shift. This indicates that the catalysts prepared in Comparative Examples 1-2 of this invention have a Cu-Zn₂SiO₄ structure. However, the catalyst prepared in Comparative Example 3 did not show any Zn₂SiO₄ diffraction peaks, indicating that the addition of ethanol is crucial for the formation of a stable Zn₂SiO₄ structure. Figure 2 As can be seen from b, the catalyst prepared in Example 1 of this invention showed a slight decrease in peak intensity but no change in peak position after the reaction, indicating a stable structure. In Comparative Example 2, most of the Zn2SiO4 peaks disappeared, and the Cu peak was significantly enhanced. This indicates that the Zn2SiO4 structure of Comparative Example 2 without the addition of an alkaline source was unstable after the reaction, suggesting that ethanol and alkaline source have an irreplaceable synergistic inducing effect on the formation of active sites.

[0045] See Figure 3 The catalysts prepared in Example 1 and Comparative Examples 1-3 were subjected to SEM and surface scanning energy dispersive spectroscopy. The results showed that the prepared catalysts had clear particle boundaries, uniform size, and interconnected structures. Before the reaction, Cu and Zn2SiO4 formed a composite structure in Example 1 and Comparative Examples 1-3, and the Cu and Zn particles were uniformly dispersed; this was consistent with the XRD characterization results.

[0046] See Figure 4 FT-IR tests were performed on the catalysts prepared in Example 1 and Comparative Examples 1-3. The results showed that at 1609 cm⁻¹... -1 The absorption peak at 1021 cm⁻¹ is attributed to the vibration of the Zn-OH bond. -1The absorption peak at 1021 cm⁻¹ is attributed to the vibration (stretching vibration) of the Cu-O-Si bond. Specifically, the absorption peaks in Examples 1 and Comparative Example 1 at 1021 cm⁻¹ are... -1 There is a relatively obvious Cu-O-Si peak at this position, while no obvious absorption peak was observed at this position in Comparative Example 2 and Comparative Example 3. Therefore, Cu-O-Si bonds may be absent or present in very small amounts in these two samples.

[0047] See Figure 5 XPS tests were performed on the catalysts prepared in Example 1 and Comparative Examples 1-3. It should be noted that 932.5-932.8 eV in the figures corresponds to zero-valent Cu and monovalent Cu ions, denoted as Cu. 0 / Cu + 934.45-935.2 eV corresponds to divalent Cu ions, denoted as Cu. 2+ It can be seen that Cu in each catalyst 0 / Cu + With Cu 2+ Coexistence, and Cu in different samples 2+ The proportion of all Cu species (Cu) 2+ The Cu content varies, and the order from largest to smallest is: Example 1 > Comparative Example 1 > Comparative Example 2 > Comparative Example 3. Among them, the catalyst prepared in Example 1 has a higher Cu content. 2+ Cu has the highest value, at 27.3%. (Combined) Figure 4 The infrared spectrum shows that the catalyst prepared in Example 1 has a wavelength of 1021 cm⁻¹. -1 The intensity of the Cu–O–Si characteristic peak at this location is significantly higher than that in other comparative examples, indicating a strong interaction between Cu species and the silicon-based support surface. This promotes the retention of some Cu species in a high valence state (Cu… 2+ Therefore, it can be inferred that Cu in higher valence states... 2+ It exists in the form of CuSiO3. Figure 2 The XRD characterization showed only peaks for Cu, CuO, Zn₂SiO₄, and SiO₂, indicating that CuSiO₃ may be distributed in a highly dispersed state without any peaks. These results demonstrate that anchoring Cu particles within this zinc silicate framework not only restricts the movement and migration of Cu particles but also, to some extent, hinders Cu flow by forming CuSiO₃. 2+ The reduction of Cu in CuZn-based catalysts enhances Cu content. 2+ The proportion of Cu ensures the number of exposed active sites on the catalyst, allowing more active sites to be available for reactant reaction and improving Cu content. 2+ This improves utilization rate, thereby ensuring the reaction efficiency and conversion rate of the catalytic reaction.

[0048] To further illustrate the beneficial effects of the Cu-Zn2SiO4 catalyst of this invention, experiments were conducted in a fixed-bed reactor under specific conditions of temperature, pressure, space velocity, and CO2 / H2 feed ratio to catalyze the hydrogenation of CO2 to methanol using the Cu-Zn2SiO4 catalyst. The product distribution was analyzed using gas chromatography. The specific procedures are as follows: The catalysts prepared in Example 1 and Comparative Examples 1-3 were pressed into tablets at 10 MPa and then granulated to 20-40 mesh to obtain the respective catalyst particles.

[0049] 0.5 g of catalyst particles were packed into a quartz tube, which was then placed into a fixed-bed reactor. The reactor was heated to 300 °C, and reduction pretreatment was carried out in an H2 atmosphere with an H2 space velocity of 2400 mL g. cat -1 h -1 After 6 hours of reduction, the reactor was cooled to 220°C, and a mixture of H2, CO2, and N2 with a volume ratio of 72:24:4 was introduced at a gas hourly space velocity (GHSV) of 6000 mL g / L. cat -1 h -1 The reaction pressure was increased to 3 MPa, and the reaction proceeded for 42 hours (at a temperature of 220°C). The reactor temperature was then lowered to 250°C, and the reaction was continued for at least 48 hours (at 250°C). The reaction products were analyzed online using gas chromatography to calculate the CO2 conversion rate and product selectivity. The test results are shown in the table below. Figure 6 (It should be noted that: the CO2 conversion rate, methanol selectivity, CO selectivity, and STY in the table refer to the values ​​after the reaction has stabilized, that is, the values ​​at the end of the reaction temperature range of 220℃ or 250℃; the Cu content in the table is the mass percentage of Cu in the catalysts of the examples and comparative examples after inductively coupled plasma atomic emission spectrometry testing.)

[0050] Combining the above table with Figure 6 It is evident that the Cu-Zn2SiO4 catalyst of this invention, by constructing a zinc silicate structure, promotes the dispersion of Cu and Zn, greatly enhancing the utilization rate of metal atoms in the catalyst. Based on the mass of Cu, the space-time yield for CO2 hydrogenation to methanol reaches 64.0 mmol g at 250°C. Cu -1 h -1 The traditional commercial catalyst Cu / ZnO / Al2O3 catalyst (36.7 mmol g) Cu -1 h -1The efficiency of this Cu-Zn2SiO4 catalyst is 1.74 times that of the standard catalyst. Furthermore, by constructing a zinc silicate structure to inhibit Cu particle sintering, the long-term stability of the catalyst is greatly improved, and no deactivation is observed during a 100-hour CO2 hydrogenation to methanol reaction. Figure 6 It can be seen that the catalyst prepared in Example 1 is effective at 250°C, 3 MPa, and 6000 mL g. cat -1 h -1 Under the specified conditions, the space-time yield of methanol reached a maximum of 64.0 mmol g. Cu -1 h -1 The methanol selectivity reached 70%; the highest space-time yield of methanol in the reaction temperature range of 220℃ was 49.6 mmol g. Cu -1 h -1 The methanol selectivity reached 99%. Its high activity and selectivity are attributed to the successful construction of the Cu-Zn2SiO4 synergistic catalytic system by stepwise hydrothermal and composite additive strategies. Its high activity, high selectivity and stability are due to the dual advantages of atomic-level dispersion of Cu species and structural stability of zinc silicate support, providing a new route for low-temperature and high-efficiency CO2 to methanol production.

[0051] By comparison Figure 6 A comparison of the catalytic performance of the catalysts in Example 1 and Comparative Examples 1-3 reveals that, under the same reaction conditions, the methanol space-time yield (STY) from highest to lowest is: Example 1 > Comparative Example 1 > Comparative Example 2 > Comparative Example 3. Figure 5 Cu 2+ The trend of Cu variation is consistent, indicating that Cu 2+ The species is conducive to promoting the hydrogenation of CO2 to methanol.

[0052] Example 2 Copper nitrate and zinc acetate were added to the ethanol solution according to the specified amount and mixed evenly to obtain a mixed reaction solution; wherein the molar ratio of copper nitrate, zinc acetate, water and ethanol was 0.2:1:100:20. Add silica sol and urea to the mixed reaction solution according to the molar ratio of zinc acetate to silica sol of 0.8:1 and the molar ratio of zinc acetate to urea of ​​0.8:1, and stir for 8 hours to obtain the initial gel. The initial gel was added to a high-pressure reactor and first hydrothermally crystallized at 120℃ for 24h. Then, the temperature was raised to 200℃ and crystallized for another 48h. After cooling to room temperature, the mixture was filtered, washed until neutral, and dried at 1℃ / min to 100℃ for 8h to obtain the Cu-Zn2SiO4 catalyst, denoted as Cu-Zn2SiO4-5.

[0053] Example 3 Copper nitrate and zinc acetate were added to the ethanol solution according to the specified amount and mixed evenly to obtain a mixed reaction solution; wherein the molar ratio of copper nitrate, zinc acetate, water and ethanol was 0.5:1:150:100. Add silica sol and urea to the mixed reaction solution according to the molar ratio of zinc acetate to silica sol of 0.5:1 and the molar ratio of zinc acetate to urea of ​​0.5:1, and stir for 10 hours to obtain the initial gel. The initial gel was added to a high-pressure reactor and first hydrothermally crystallized at 120℃ for 20h. Then, the temperature was raised to 180℃ and crystallized for another 80h. After cooling to room temperature, the mixture was filtered, washed until neutral, and dried at 3℃ / min to 200℃ for 6h to obtain the Cu-Zn2SiO4 catalyst, denoted as Cu-Zn2SiO4-6.

[0054] Example 4 Copper nitrate and zinc acetate were added to the ethanol solution according to the specified amount and mixed evenly to obtain a mixed reaction solution; wherein the molar ratio of copper nitrate, zinc acetate, water and ethanol was 0.05:1:50:10. Add silica sol and urea to the mixed reaction solution according to the molar ratio of zinc acetate to silica sol of 0.5:1 and the molar ratio of zinc acetate to urea of ​​0.5:1, and stir for 12 hours to obtain the initial gel. The initial gel was added to a high-pressure reactor and first hydrothermally crystallized at 100℃ for 24h. Then, the temperature was raised to 170℃ and crystallized for another 96h. After cooling to room temperature, the mixture was filtered, washed until neutral, and dried at 150℃ for 7h with a heating rate of 2℃ / min. The resulting Cu-Zn2SiO4 catalyst was denoted as Cu-Zn2SiO4-7.

[0055] Example 5 Copper acetate and zinc nitrate were added to the ethanol solution according to the specified amount and mixed evenly to obtain a mixed reaction solution; wherein the molar ratio of copper acetate, zinc nitrate, water and ethanol was 0.5:1:200:100. According to the molar ratio of zinc nitrate to silica aerosol of 5:1 and the molar ratio of zinc nitrate to ammonia water of 5:1, silica aerosol and ammonia water were added to the mixed reaction solution and stirred for 12 hours to obtain the initial gel. The initial gel was added to a high-pressure reactor and first hydrothermally crystallized at 130℃ for 24 hours. Then, the temperature was raised to 190℃ and crystallized for another 90 hours. After cooling to room temperature, the mixture was filtered, washed until neutral, and dried at 1℃ / min to 100℃ for 8 hours to obtain the Cu-Zn2SiO4 catalyst, denoted as Cu-Zn2SiO4-8.

[0056] Example 6 Copper acetate and zinc nitrate were added to the ethanol solution according to the specified amount and mixed evenly to obtain a mixed reaction solution; wherein the molar ratio of copper acetate, zinc nitrate, water and ethanol was 0.4:1:100:80. According to the molar ratio of zinc nitrate to silica aerosol of 3:1 and the molar ratio of zinc nitrate to ammonia water of 3:1, silica aerosol and ammonia water were added to the mixed reaction solution and stirred for 12 hours to obtain the initial gel. The initial gel was added to a high-pressure reactor and first hydrothermally crystallized at 120℃ for 24h. Then, the temperature was raised to 180℃ and crystallized for another 90h. After cooling to room temperature, the mixture was filtered, washed until neutral, and dried at 1℃ / min to 120℃ for 8h to obtain the Cu-Zn2SiO4 catalyst, denoted as Cu-Zn2SiO4-9.

[0057] Example 7 Copper acetate and zinc nitrate were added to the ethanol solution according to the specified amount and mixed evenly to obtain a mixed reaction solution; wherein the molar ratio of copper acetate, zinc nitrate, water and ethanol was 0.2:1:110:20. According to the molar ratio of zinc nitrate to silica aerosol of 1.4:1 and the molar ratio of zinc nitrate to ammonia of 1.4:1, silica aerosol and ammonia were added to the mixed reaction solution and stirred for 8 hours to obtain the initial gel. The initial gel was added to a high-pressure reactor and first hydrothermally crystallized at 120℃ for 20h. Then, the temperature was raised to 180℃ and crystallized for another 72h. After cooling to room temperature, the mixture was filtered, washed until neutral, and dried at 120℃ for 8h with a heating rate of 2℃ / min. The resulting Cu-Zn2SiO4 catalyst was denoted as Cu-Zn2SiO4-10.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for preparing a Cu-Zn2SiO4 catalyst, characterized in that, include: The copper source and zinc source are added to the ethanol solution and mixed thoroughly to obtain a mixed reaction solution; Add a silicon source and an alkali source to the mixed reaction solution, stir, and obtain an initial gel; The initial gel was subjected to a hydrothermal crystallization reaction to obtain a Cu-Zn2SiO4 catalyst.

2. The method for preparing the Cu-Zn2SiO4 catalyst according to claim 1, characterized in that, The copper source is copper nitrate and / or copper acetate; the zinc source is zinc nitrate and / or zinc acetate.

3. The method for preparing the Cu-Zn2SiO4 catalyst according to claim 1, characterized in that, The molar ratio of copper source, zinc source, water and ethanol in the mixed reaction solution is (0.05~0.5):1:(50~200):(10~100).

4. The method for preparing the Cu-Zn2SiO4 catalyst according to claim 1, characterized in that, The silicon source is silica aerosol or silica sol, and the alkali source is urea or ammonia.

5. The method for preparing the Cu-Zn2SiO4 catalyst according to claim 1, characterized in that, The molar ratio of zinc source to silicon source is (0.5-5):1, and the molar ratio of zinc source to alkali source is (0.5-5):

1.

6. The method for preparing the Cu-Zn2SiO4 catalyst according to claim 1, characterized in that, The method for obtaining the Cu-Zn2SiO4 catalyst by subjecting the initial gel to a hydrothermal crystallization reaction is as follows: The initial gel was subjected to hydrothermal crystallization at 100–130°C for the first time, and then heated to 170–200°C for the second hydrothermal crystallization. After cooling to room temperature, it was filtered, washed, and dried to obtain the Cu-Zn2SiO4 catalyst.

7. The method for preparing the Cu-Zn2SiO4 catalyst according to claim 6, characterized in that, The time for the first hydrothermal crystallization is 1 to 24 hours, and the time for the second hydrothermal crystallization is 48 to 96 hours.

8. The method for preparing the Cu-Zn2SiO4 catalyst according to claim 6, characterized in that, The drying method is as follows: the temperature is increased to 100-200℃ at a rate of 1-3℃ / min and maintained for 6-8 hours to obtain Cu-Zn2SiO4 catalyst.

9. A Cu-Zn2SiO4 catalyst, characterized in that, The Cu-Zn₂SiO₄ catalyst was prepared using the method described in any one of claims 1-8; based on the mass of copper, the Cu-Zn₂SiO₄ catalyst was prepared at a reaction temperature of 220°C, a reaction pressure of 3 MPa, and a space velocity of 6000 mL g. cat -1 h -1 Under the given conditions, the space-time yield of methanol reached 49.6 mmol g after the reaction stabilized. Cu -1 h -1 The selectivity reached 99%; the reaction temperature was 250℃, the reaction pressure was 3MPa, and the space velocity was 6000 mL g / L. cat -1 h -1 Under stable conditions, the space-time yield of methanol reached 64.0 mmol g. Cu -1 h -1 The selectivity rate is 70%.

10. The application of the Cu-Zn2SiO4 catalyst according to claim 9 in the hydrogenation of CO2 to methanol, characterized in that, include: Using Cu-Zn2SiO4 catalyst as the catalyst, the temperature was first raised to 280–320℃, and hydrogen was pretreated for 1–3 h. Then, CO2 and H2 were introduced at a molar ratio of (1:1) to (1:6), with the reaction pressure controlled at 2.0–5.0 MPa, the reaction temperature at 200–300℃, and the space velocity at 5000–15000 mL g. cat -1 h -1 The reaction yields methanol.

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