A highly active and stable CMC-Cu-CeO2-ZnO catalyst, its preparation method and its application

Abstract

This invention belongs to the field of catalyst preparation technology and carbon dioxide resource utilization. Specifically, it discloses a highly active and stable CMC-Cu-CeO2-ZnO catalyst, its preparation method, and its applications. This invention uses ZnO and CeO2 as a composite support, with Cu as the active component. Cu is provided by carboxymethyl cellulose copper as a precursor. The catalyst has an in-situ generated molecular channel structure, and near the Cu active sites, there are in-situ oxygen vacancies formed by the thermal decomposition of carboxymethyl cellulose copper. This invention employs an integrated method of in-situ synthesis of carboxymethyl cellulose copper + hybrid composite + high-temperature calcination, achieving in-situ construction of molecular channels within the catalyst body. It also allows the channels to form a dual spatial and functional coupling with the active sites, oxygen vacancies, and valence states of the active component, fundamentally solving the problem of separation between channel construction and catalyst performance regulation in existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology and carbon dioxide resource utilization, and in particular relates to a highly active and stable CMC-Cu-CeO2-ZnO catalyst, its preparation method and its application. Background Technology

[0002] Human activities, such as the massive combustion of fossil fuels, have released excessive amounts of carbon dioxide into the atmosphere, disrupting the natural carbon cycle and causing a series of environmental problems, including global warming. Coupling CO2 with green hydrogen to convert it into methanol and other basic chemical feedstocks is an effective way to utilize CO2 resources and mitigate the greenhouse effect, while also providing green raw materials for the chemical industry, thus possessing both environmental and economic value. However, the strong chemical inertness of CO2 molecules, the high energy barrier of CO2 hydrogenation to methanol reaction, and thermodynamic limitations make it difficult to simultaneously achieve high CO2 conversion rates and high methanol selectivity. Furthermore, the high humidity environment during the reaction process easily leads to catalyst deactivation, and existing catalysts lack effective activation methods for active sites and oxygen vacancy construction, failing to further reduce the difficulty of CO2 activation, becoming a key bottleneck restricting the industrial application of this technology. Therefore, developing catalysts with high activity, high selectivity, and high stability, and capable of effectively activating CO2 molecules, is the core requirement for breakthroughs in CO2 hydrogenation to methanol technology.

[0003] Copper (Cu)-based catalysts have become the most promising catalyst system for industrial application in the CO2 hydrogenation to methanol reaction due to their excellent reaction performance and low cost. Zinc and cerium oxides are often introduced to form Cu-ZnO-CeO2 composite catalyst systems. However, existing catalysts still have many drawbacks: 1) Cu-based catalysts have complex active site properties, exhibiting high activity in the reverse water-gas reaction, which severely reduces methanol selectivity; 2) In high-humidity reaction environments, Cu active species are prone to oxidative aggregation, leading to a rapid decline in catalyst activity and decreased stability; 3) Existing Cu-based catalysts are mostly prepared using a one-step co-precipitation method, which results in low exposure of active sites and makes it difficult to control the ratio of active sites and valence states of active components, thus failing to optimize reaction performance; 4) Current technologies cannot efficiently construct oxygen vacancies near the active sites of the catalyst, making it difficult to effectively activate CO2 molecules, further lower the reaction energy barrier, and improve CO2 conversion efficiency.

[0004] To address the aforementioned issues, existing technologies attempt to improve the stability of Cu species by utilizing the metal-support interaction of CeO2. However, these methods still fail to resolve the problems of insufficient exposure of active sites and uncontrollable ratios of active components inherent in traditional preparation methods. Furthermore, they do not achieve in-situ construction of oxygen vacancies near the active sites, thus failing to simultaneously achieve high conversion rates, high selectivity, and high catalyst stability in the CO2 hydrogenation to methanol reaction. Therefore, there is an urgent need to develop a novel Cu-ZnO-CeO2-based catalyst preparation method that achieves sufficient exposure of active sites, precise control of the active component ratio, and in-situ construction of oxygen vacancies near the active sites, while simultaneously improving the structural and performance stability of the catalyst. Summary of the Invention

[0005] This invention addresses the problems of existing Cu-ZnO-CeO2-based catalysts for CO2 hydrogenation to methanol, including low methanol selectivity, poor stability, insufficient exposure of active sites, difficulty in controlling the ratio of active components, inability to construct oxygen vacancies near active sites to activate CO2 molecules, and limitations of traditional preparation methods. This invention provides a method for preparing a CMC-Cu-CeO2-ZnO-based catalyst, and also provides the catalyst prepared by this method and its application in CO2 hydrogenation to methanol. This invention achieves the construction of internal molecular channels, sufficient exposure of active sites, precise control of the valence ratio of active components, and in-situ construction of oxygen vacancies near Cu active sites through the in-situ synthesis and decomposition of copper carboxymethyl cellulose. Combined with the metal-support interaction between the ZnO-CeO2 support and Cu species, a CMC-Cu-CeO2-ZnO catalyst with high CO2 conversion, high methanol selectivity, and high stability is obtained, overcoming the technical defects of existing Cu-based catalysts and promoting the industrial application of CO2 hydrogenation to methanol technology.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a highly active and stable CMC-Cu-CeO2-ZnO catalyst, with ZnO and CeO2 as composite supports and Cu as active component, wherein the Cu is provided by carboxymethyl cellulose copper as a precursor, the catalyst has an in-situ generated molecular channel structure, and oxygen vacancies formed by the thermal decomposition of carboxymethyl cellulose copper are present near the Cu active site.

[0007] Another technical solution to be protected by this invention: a method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst, which is carried out according to the following steps:

[0008] Step S1: Preparation of ZnO-CeO2 support precursor: Dissolve zinc source and cerium source in deionized water at a molar ratio of 1:1, stir until completely dissolved, and stir at a speed of 250-350 r / min for 25-35 min under a water bath at 50℃-80℃ until the solid is completely dissolved to obtain Zn-Ce mixed salt solution for later use.

[0009] Step S2: Preparation of carboxymethyl cellulose copper microparticles: 0.8-1.2g of carboxymethyl cellulose and 0.04-0.06mol of copper nitrate are added to 90-100mL of deionized water and stirred in a 50℃ water bath for 60min to form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction, thereby realizing the loading and shaping of Cu precursor;

[0010] Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 350-450 r / min for 2-3 h in a water bath at 50℃-80℃. Then, the metal salt solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7±0.2, so that the Cu precursor is uniformly mixed into the ZnO-CeO2 support precursor to obtain a mixed slurry.

[0011] Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105℃ for 11-13h to remove moisture and obtain a solid precursor. The solid precursor is then placed in a muffle furnace at 400-600℃ and calcined for 3-5h. After calcination, it is naturally cooled to room temperature to finally obtain a porous CMC-Cu-CeO2-ZnO catalyst.

[0012] Furthermore, the zinc source is zinc nitrate, the cerium source is cerium nitrate, and the copper source is copper nitrate.

[0013] Preferably, a method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst is carried out according to the following steps:

[0014] Step S1: Preparation of ZnO-CeO2 support precursor: Dissolve 0.1 mol zinc nitrate and 0.1 mol cerium nitrate in 200 mL deionized water, stir until completely dissolved, and stir at 250 r / min for 25 min under 50℃ water bath conditions until the solid is completely dissolved to obtain Zn-Ce mixed salt solution for later use.

[0015] Step S2: Preparation of carboxymethyl cellulose copper microparticles: Weigh 0.8g of sodium carboxymethyl cellulose and 0.04mol of copper nitrate and add them to 90mL of deionized water. Stir for 60min in a 50℃ water bath to form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction, thereby achieving the loading and shaping of Cu precursor.

[0016] Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 350 r / min for 2 h in a 50℃ water bath. Then, the metal salt solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7 ± 0.2, so that the Cu precursor is uniformly mixed into the ZnO-CeO2 support precursor to obtain a mixed slurry.

[0017] Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105°C for 11 hours to remove moisture and obtain a solid precursor. The solid precursor is placed in a muffle furnace and calcined in air at 400°C for 3 hours. After calcination, it is naturally cooled to room temperature to finally obtain a porous CMC-Cu-CeO2-ZnO catalyst.

[0018] Preferably, a method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst is carried out according to the following steps:

[0019] Step S1: Preparation of ZnO-CeO2 support precursor: Dissolve 0.1 mol zinc nitrate and 0.1 mol cerium nitrate in 200 mL deionized water, stir until completely dissolved, and stir at 350 r / min for 35 min under 80℃ water bath conditions until the solid is completely dissolved to obtain Zn-Ce mixed salt solution for later use.

[0020] Step S2: Preparation of carboxymethyl cellulose copper microparticles: Weigh 1.2g of sodium carboxymethyl cellulose and 0.06mol of copper nitrate and add them to 100mL of deionized water. Stir for 60min in a 50℃ water bath to form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction, thereby achieving the loading and shaping of Cu precursor.

[0021] Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 450 r / min for 3 h in an 80℃ water bath. Then, the metal salt solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7 ± 0.2, so that the Cu precursor is uniformly mixed into the ZnO-CeO2 support precursor to obtain a mixed slurry.

[0022] Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105°C for 13 hours to remove moisture and obtain a solid precursor. The solid precursor is placed in a muffle furnace and calcined in air at 600°C for 5 hours. After calcination, it is naturally cooled to room temperature to finally obtain a porous CMC-Cu-CeO2-ZnO catalyst.

[0023] Preferably, a method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst is carried out according to the following steps:

[0024] Step S1: Preparation of ZnO-CeO2 support precursor: Dissolve 0.1 mol zinc nitrate and 0.1 mol cerium nitrate in 200 mL deionized water, stir until completely dissolved, and stir at 300 r / min for 30 min under 70℃ water bath conditions until the solid is completely dissolved to obtain Zn-Ce mixed salt solution for later use.

[0025] Step S2: Preparation of carboxymethyl cellulose copper microparticles: Weigh 1g of sodium carboxymethyl cellulose and 0.05mol of copper nitrate and add them to 95mL of deionized water. Stir for 60min in a 50℃ water bath to form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction, thereby achieving the loading and shaping of Cu precursor.

[0026] Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 400 r / min for 2.5 h in a 70℃ water bath. Then, the metal salt solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7 ± 0.2, so that the Cu precursor is uniformly mixed into the ZnO-CeO2 support precursor to obtain a mixed slurry.

[0027] Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105°C for 12 hours to remove moisture and obtain a solid precursor. The solid precursor is placed in a muffle furnace and calcined in air at 500°C for 4 hours. After calcination, it is naturally cooled to room temperature to finally obtain a porous CMC-Cu-CeO2-ZnO catalyst.

[0028] Another technical solution to be protected by this invention is: the application of a highly active and stable CMC-Cu-CeO2-ZnO catalyst, wherein the above-mentioned CMC-Cu-CeO2-ZnO catalyst is packed in a fixed-bed reactor, and the CO2 hydrogenation to methanol reaction is carried out under the conditions of H2 / CO2 molar ratio of 3:1, reaction temperature of 200~260℃, and reaction pressure of 2.0~4.0MPa.

[0029] The advantages and positive effects of this invention are:

[0030] 1. Existing methods for preparing porous Cu-based catalysts all follow the "first create pores, then load" approach, which suffers from the same pore structure-related defects as traditional co-precipitation methods: the pore structure is separated from the active phase of the catalyst, making it impossible to achieve in-situ coupling between the pores and active sites and oxygen vacancies. This ultimately leads to low exposure of active sites, poor mass transfer efficiency, and high reaction energy barriers, making it difficult to balance the activity, selectivity, and stability of the catalyst.

[0031] This invention employs an integrated method combining in-situ synthesis of copper carboxymethyl cellulose (CMC), hybridization, and high-temperature calcination. This method enables the in-situ construction of molecular channels within the catalyst bulk, thereby improving mass transfer efficiency and the exposure of active sites. Using CMC as a Cu precursor, CMC decomposes during high-temperature calcination, releasing CO2 and generating molecular channels in situ within the catalyst. This not only facilitates the diffusion and mass transfer of reactants such as CO2 and H2 within the catalyst but also fully exposes the active sites, solving the problem of insufficient active site exposure in catalysts prepared by traditional co-precipitation methods and thus enhancing catalyst reactivity.

[0032] 2. Precisely control the ratio of active components to improve methanol selectivity and CO2 conversion rate: During the high-temperature decomposition of carboxymethyl cellulose copper, the valence ratio of Cu active components can be controlled in situ to improve Cu selectivity and CO2 conversion rate. + / (Cu 0 +Cu + The ratio is as high as 0.61, which is conducive to the formation of key intermediates in the CO2 hydrogenation to methanol reaction, effectively suppresses the occurrence of reverse water gas side reaction, solves the problem of low methanol selectivity of traditional Cu-based catalysts, and achieves a dual improvement of high CO2 conversion rate and high methanol selectivity.

[0033] 3. In-situ construction of oxygen vacancies to activate CO2 molecules and reduce reaction energy barrier: The carbon generated by the high-temperature decomposition of copper carboxymethyl cellulose constructs oxygen vacancies in situ near the Cu active site. The oxygen vacancies can effectively activate chemically inert CO2 molecules, reduce the reaction energy barrier of CO2 hydrogenation to methanol, and further improve the conversion efficiency of CO2, breaking through the technical bottleneck that existing catalysts cannot efficiently activate CO2 molecules.

[0034] 4. Enhanced catalyst stability and significantly improved resistance to moisture deactivation: The strong metal-support interaction between CeO2 and Cu active components can stabilize the electronic structure of Cu species. At the same time, the in-situ constructed oxygen vacancies form a synergistic effect with this interaction, effectively inhibiting the oxidation and aggregation of Cu active species in the high-humidity reaction environment, greatly improving the structural and performance stability of the catalyst, and extending the catalyst's service life. Attached Figure Description

[0035] Figure 1This is a process flow diagram for the preparation of the CMC-Cu-CeO2-ZnO catalyst of the present invention.

[0036] Figure 2 The results are the catalytic performance test results, among which, Figure 2 (a) represents the space-time yield of methanol. Figure 2 (b) shows methanol selectivity.

[0037] Figure 3 The results are TEM characterization results, where, Figure 3 (a) is the present invention. Figure 3 (b) is a catalyst prepared by the traditional coprecipitation method. Detailed Implementation

[0038] To make the objectives, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below.

[0039] A highly active and stable CMC-Cu-CeO2-ZnO catalyst is provided, with ZnO and CeO2 as composite supports and Cu as the active component. Cu is provided by carboxymethyl cellulose copper as a precursor. The catalyst has an in-situ generated molecular channel structure and oxygen vacancies formed by the thermal decomposition of carboxymethyl cellulose copper near the Cu active site.

[0040] This invention is the first to apply carboxymethyl cellulose copper as a Cu precursor in the preparation of CMC-Cu-CeO2-ZnO. Through in-situ synthesis and high-temperature decomposition of carboxymethyl cellulose copper, the in-situ construction of molecular channels within the catalyst and the Cu... + / Cu 0 Precise control of valence ratio and in-situ construction of oxygen vacancies near Cu active sites clearly identify ZnO and CeO2 as the catalyst composite support.

[0041] The preparation method of a highly active and stable CMC-Cu-CeO2-ZnO catalyst according to the present invention will be described in detail below.

[0042] Raw material selection

[0043] The zinc source was zinc nitrate (Zn(NO3)2·6H2O), the cerium source was cerium nitrate (Ce(NO3)3·6H2O), the copper source was copper nitrate (Cu(NO3)2·3H2O), the carboxymethyl cellulose was industrial grade sodium carboxymethyl cellulose, and the deionized water was self-made.

[0044] Example 1

[0045] A method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst, comprising the following steps:

[0046] Step S1: Preparation of ZnO-CeO2 support precursor: Weigh 0.1 mol zinc nitrate and 0.1 mol cerium nitrate according to the molar ratio of Zn:Ce=1:1, add them to 200 mL of deionized water, stir at 250 r / min for 25 min under 50℃ water bath conditions until the solid is completely dissolved to obtain Zn-Ce mixed salt solution for later use;

[0047] Step S2: Preparation of carboxymethyl cellulose copper microparticles: Weigh 0.8g of sodium carboxymethyl cellulose and 0.04mol of copper nitrate and add them to 90mL of deionized water. Stir for 60min in a 50℃ water bath to form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction, thereby achieving the loading and shaping of Cu precursor.

[0048] Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 350 r / min for 2 h in a 50℃ water bath. Then, the metal salt solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7 ± 0.2, so that the Cu precursor is uniformly mixed into the ZnO-CeO2 support precursor to obtain a mixed slurry.

[0049] Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105℃ for 11 hours to remove moisture, yielding a solid precursor. The solid precursor is then placed in a muffle furnace and calcined in air at 400℃ for 3 hours. During calcination, copper carboxymethyl cellulose decomposes, releasing CO2 to form molecular channels. The generated carbon constructs oxygen vacancies in situ near the Cu active sites. Simultaneously, the calcination process achieves Cu... + / Cu 0 With precise control of the molar ratio and natural cooling to room temperature after calcination, a porous CMC-Cu-CeO2-ZnO catalyst was finally obtained.

[0050] Example 2

[0051] A method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst, comprising the following steps:

[0052] Step S1: Preparation of ZnO-CeO2 support precursor: Weigh 0.1 mol zinc nitrate and 0.1 mol cerium nitrate according to the molar ratio of Zn:Ce=1:1, add them to 200 mL of deionized water, stir at 350 r / min for 35 min under 80℃ water bath conditions until the solid is completely dissolved to obtain Zn-Ce mixed salt solution for later use;

[0053] Step S2: Preparation of carboxymethyl cellulose copper microparticles: Weigh 1.2g of sodium carboxymethyl cellulose and 0.06mol of copper nitrate and add them to 100mL of deionized water. Stir for 60min in a 50℃ water bath to form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction, thereby achieving the loading and shaping of Cu precursor.

[0054] Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 450 r / min for 3 h in an 80℃ water bath. Then, the metal salt solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7 ± 0.2, so that the Cu precursor is uniformly mixed into the ZnO-CeO2 support precursor to obtain a mixed slurry.

[0055] Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105℃ for 13 hours to remove moisture, yielding a solid precursor. The solid precursor is then placed in a muffle furnace and calcined in air at 600℃ for 5 hours. During the calcination process, Cu... + / Cu 0 With precise control of the molar ratio and natural cooling to room temperature after calcination, a porous CMC-Cu-CeO2-ZnO catalyst was finally obtained.

[0056] Example 3

[0057] A method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst, comprising the following steps:

[0058] Step S1: Preparation of ZnO-CeO2 support precursor: Weigh 0.1 mol zinc nitrate and 0.1 mol cerium nitrate according to the molar ratio of Zn:Ce=1:1, add them to 200 mL of deionized water, stir at 300 r / min for 30 min under 70℃ water bath conditions until the solid is completely dissolved to obtain Zn-Ce mixed salt solution for later use;

[0059] Step S2: Preparation of carboxymethyl cellulose copper microparticles: Weigh 1g of sodium carboxymethyl cellulose and 0.05mol of copper nitrate and add them to 95mL of deionized water. Stir for 60min in a 50℃ water bath to form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction, thereby achieving the loading and shaping of Cu precursor.

[0060] Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 400 r / min for 2.5 h in a 70℃ water bath. Then, the metal salt solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7 ± 0.2, so that the Cu precursor is uniformly mixed into the ZnO-CeO2 support precursor to obtain a mixed slurry.

[0061] Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105℃ for 12 hours to remove moisture, yielding a solid precursor. The solid precursor is then placed in a muffle furnace and calcined in air at 500℃ for 4 hours. During the calcination process, Cu... + / Cu 0 With precise control of the molar ratio and natural cooling to room temperature after calcination, a porous CMC-Cu-CeO2-ZnO catalyst was finally obtained.

[0062] This invention uses carboxymethyl cellulose copper as a Cu precursor, which is mixed and combined with a ZnO-CeO2 support precursor. When the mixture is calcined and decomposed at high temperature, it releases CO2 gas and generates molecular-level channels in situ inside the catalyst body. The channels are part of the catalyst's own structure, thus realizing the integrated design of channels and the active phase of the catalyst.

[0063] By adjusting the amount of copper carboxymethyl cellulose, the calcination temperature (400-600℃), and the time (3-5h), the pore size, distribution, and connectivity of molecular channels can be precisely controlled, avoiding the problems of channel collapse and uneven distribution in existing technologies, and forming a continuous reactant diffusion path.

[0064] During calcination, the carbon generated from the decomposition of copper in carboxymethyl cellulose constructs oxygen vacancies in situ near the Cu active sites, creating spatial coupling between the molecular channels, oxygen vacancies, and Cu active sites. The channels provide mass transfer pathways for the reactants, and the oxygen vacancies directly activate CO2 molecules within the channels, significantly reducing the reaction energy barrier. Simultaneously, Cu… + / Cu 0 The molar ratio can be precisely controlled. In addition, it can fully expose the active sites inside the catalyst, greatly improving the utilization rate of active sites.

[0065] Catalyst performance testing

[0066] Test results show that: Figure 1 and Figure 3 As shown, this invention uses carboxymethyl cellulose copper (CMC-Cu) as a precursor and achieves the reconstruction of the catalyst's microstructure through an integrated process of in-situ synthesis and high-temperature calcination. TEM characterization results show that, compared to... Figure 3(b) Cu-CeO2-ZnO catalysts prepared by the traditional co-precipitation method exhibit severe particle agglomeration and structural densification, such as Figure 3 (a) The CMC-Cu-CeO2-ZnO catalyst prepared in this invention exhibits a loose and porous network structure. This is attributed to the in-situ volatilization of the CMC polymer framework during thermal decomposition, which forms molecular channels, effectively inhibits the sintering and agglomeration of active components at high temperatures, significantly improves the specific surface area of ​​the catalyst and the mass transfer efficiency of reactants, and provides a superior structural basis for highly active reactions.

[0067] The XPS characterization data in Table 1 further reveal the significant optimization of the electronic chemical states on the surface of the catalyst of this invention. The data show that the Cu on the surface of the catalyst of this invention... + / (Cu 0 +Cu + The ratio was as high as 0.614, far exceeding the control sample's 0.407, while the O2 ratio, which characterizes oxygen vacancy concentration, was also significantly higher. II / (O II +O I The ratio increased from 0.619 to 0.760. This confirms that the in-situ carbon species generated by the thermal decomposition of CMC not only construct physical channels but also induce the generation of oxygen vacancies and stabilize Cu. + Active species. This inside-out electronic structure regulation solves the technical problems of unstable regulation of the valence state of active sites and easy annihilation of oxygen vacancies in existing technologies.

[0068]

[0069] The 0.5 g CMC-Cu-CeO2-ZnO catalyst prepared above was packed into a fixed-bed microreactor, and the performance of CO2 hydrogenation to methanol reaction was tested. The reaction conditions were: temperature 240℃, pressure 3.0MPa, and H2:CO2 molar ratio 3:1.

[0070] Combination Figure 2 The catalytic performance test results show that the synergistic optimization of the above-mentioned structure and chemical properties directly translates into superior catalytic performance. Within the entire temperature range of 190-290℃, the methanol space-time yield and selectivity of the catalyst of this invention are significantly better than those of conventional catalysts, especially at 270℃ where the methanol space-time yield approaches 175 mg / g. cat. / h. This proves that the present invention has successfully achieved spatial and functional dual coupling of pore structure, oxygen vacancy concentration and valence state of active components, fundamentally overcoming the defect of phase separation between pore construction and performance regulation in traditional catalysts, and exhibiting excellent activity and selectivity in CO2 hydrogenation to methanol.

[0071] This invention addresses the core defects of existing Cu-based catalysts by abandoning the traditional co-precipitation method and proposing an integrated preparation approach of "precursor hybridization + in-situ pore construction + precise valence state control + in-situ oxygen vacancy construction". It combines the structural characteristics of carboxymethyl cellulose with the performance requirements of Cu-based catalysts, utilizes the carbon from the copper decomposition of carboxymethyl cellulose to construct oxygen vacancies in situ to activate CO2 molecules, and enhances stability by combining the metal-support interaction between CeO2 and Cu. This achieves a synergistic improvement in the catalyst's high activity, high selectivity, and high stability in the CO2 hydrogenation to methanol reaction.

[0072] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A highly active and stable CMC-Cu-CeO2-ZnO catalyst, characterized in that: Using ZnO and CeO2 as composite supports and Cu as the active component, the Cu is provided by carboxymethyl cellulose copper as a precursor. The catalyst has an in-situ generated molecular channel structure and oxygen vacancies formed by the thermal decomposition of carbon from carboxymethyl cellulose copper near the Cu active site.

2. A method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst, characterized in that: Follow these steps: Step S1: Preparation of ZnO-CeO2 support precursor: Dissolve zinc source and cerium source in deionized water at a molar ratio of 1:1, and stir at 250-350 r / min for 25-35 min under water bath conditions of 50℃-80℃ until the solid is completely dissolved to obtain Zn-Ce mixed salt solution for later use. Step S2: Preparation of carboxymethyl cellulose copper microparticles: Add 0.8-1.2g of carboxymethyl cellulose and 0.04-0.06mol of copper nitrate to 90-100mL of deionized water, stir for 60min in a 50℃ water bath, and form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction to achieve loading and shaping of Cu precursor; Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 350-450 r / min for 2-3 h in a water bath at 50℃-80℃. Then, the solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7±0.2, so that the Cu precursor is uniformly mixed into the ZnO-CeO2 support precursor to obtain a mixed slurry. Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105℃ for 11-13h to remove moisture and obtain a solid precursor. The solid precursor is then placed in a muffle furnace at 400-600℃ and calcined for 3-5h. After calcination, it is naturally cooled to room temperature to finally obtain a porous CMC-Cu-CeO2-ZnO catalyst.

3. The method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst according to claim 2, characterized in that: The zinc source is zinc nitrate, and the cerium source is cerium nitrate.

4. The method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst according to claim 3, characterized in that: Follow these steps: Step S1: Preparation of ZnO-CeO2 support precursor: Dissolve 0.1 mol zinc nitrate and 0.1 mol cerium nitrate in 200 mL deionized water, stir at 250 r / min for 25 min in a 50 °C water bath until the solid is completely dissolved to obtain a Zn-Ce mixed salt solution for later use. Step S2: Preparation of carboxymethyl cellulose copper microparticles: Weigh 0.8g of sodium carboxymethyl cellulose and 0.04mol of copper nitrate and add them to 90mL of deionized water. Stir for 60min in a 50℃ water bath to form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction, thereby achieving the loading and shaping of Cu precursor. Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 350 r / min for 2 h in a 50℃ water bath. Then, the solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7 ± 0.2, so that the Cu precursor is uniformly hybridized into the ZnO-CeO2 support precursor to obtain a mixed slurry. Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105°C for 11 hours to remove moisture and obtain a solid precursor. The solid precursor is placed in a muffle furnace and calcined in air at 400°C for 3 hours. After calcination, it is naturally cooled to room temperature to finally obtain a porous CMC-Cu-CeO2-ZnO catalyst.

5. The method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst according to claim 3, characterized in that: Follow these steps: Step S1: Preparation of ZnO-CeO2 support precursor: Dissolve 0.1 mol zinc nitrate and 0.1 mol cerium nitrate in 200 mL deionized water, and stir at 350 r / min for 35 min under 80℃ water bath conditions until the solid is completely dissolved to obtain Zn-Ce mixed salt solution for later use. Step S2: Preparation of carboxymethyl cellulose copper microparticles: Weigh 1.2g of sodium carboxymethyl cellulose and 0.06mol of copper nitrate and add them to 100mL of deionized water. Stir for 60min in a 50℃ water bath to form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction, thereby achieving the loading and shaping of Cu precursor. Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 450 r / min for 3 h in an 80℃ water bath. Then, the solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7 ± 0.2, so that the Cu precursor is uniformly mixed into the ZnO-CeO2 support precursor to obtain a mixed slurry. Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105°C for 13 hours to remove moisture and obtain a solid precursor. The solid precursor is placed in a muffle furnace and calcined in air at 600°C for 5 hours. After calcination, it is naturally cooled to room temperature to finally obtain a porous CMC-Cu-CeO2-ZnO catalyst.

6. The method for preparing a highly active and stable CMC-Cu-CeO2-ZnO catalyst according to claim 3, characterized in that: Follow these steps: Step S1: Preparation of ZnO-CeO2 support precursor: Dissolve 0.1 mol zinc nitrate and 0.1 mol cerium nitrate in 200 mL deionized water, stir at 300 r / min for 30 min under 70℃ water bath conditions until the solid is completely dissolved to obtain Zn-Ce mixed salt solution for later use; Step S2: Preparation of carboxymethyl cellulose copper microparticles: Weigh 1g of sodium carboxymethyl cellulose and 0.05mol of copper nitrate and add them to 95mL of deionized water. Stir for 60min in a 50℃ water bath to form carboxymethyl cellulose copper microparticles through in-situ synthesis reaction, thereby achieving the loading and shaping of Cu precursor. Step S3, Hybridization: The carboxymethyl cellulose copper microparticles prepared in step S2 are added to the Zn-Ce mixed salt solution and stirred at 400 r / min for 2.5 h in a 70 °C water bath. Then, the solution and 40 mL of 1.0 mol / L Na2CO3 are simultaneously added to 200 mL of distilled water using a peristaltic pump to maintain a pH of 7 ± 0.2, so that the Cu precursor is uniformly mixed into the ZnO-CeO2 support precursor to obtain a mixed slurry. Step S4, Drying and Calcination: The mixed slurry from step S3 is placed in a forced-air drying oven and dried at 105°C for 12 hours to remove moisture and obtain a solid precursor. The solid precursor is placed in a muffle furnace and calcined in air at 500°C for 4 hours. After calcination, it is naturally cooled to room temperature to finally obtain a porous CMC-Cu-CeO2-ZnO catalyst.

7. The application of a highly active and stable CMC-Cu-CeO2-ZnO catalyst, characterized in that: The catalyst of claim 1 is loaded into a fixed-bed reactor, and the CO2 hydrogenation to methanol reaction is carried out under the conditions of H2 / CO2 molar ratio of 3:1, reaction temperature of 200~260℃ and reaction pressure of 2.0~4.0MPa.

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