Fullerene modified copper-zinc catalyst, preparation method and application thereof

Abstract

The application provides a fullerene modified copper-zinc catalyst and a preparation method and application thereof, wherein a fullerene-imidazole base dispersion liquid, a copper-zinc solution and a precipitant are mixed, a solid phase is collected, and a catalyst precursor is obtained; the catalyst precursor is subjected to calcination-reduction treatment, and a fullerene modified copper-zinc catalyst is obtained; the calcination-reduction treatment comprises the following steps: after being heated to a calcination temperature at a heating rate of 3-10 DEG C / minute in an inert atmosphere, the temperature is kept for 2-5 hours for calcination; after the atmosphere is switched to a reduction atmosphere, the temperature is kept for 2-5 hours for reduction; the temperature for calcination is 300-450 DEG C, and the temperature for reduction is 300-450 DEG C. In the catalyst, the fullerene serves as an electron buffer, can inhibit the polycondensation and disproportionation side reactions of n-butyl aldehyde under liquid phase high-temperature conditions, and can significantly improve the selectivity of n-butyl alcohol while ensuring the conversion rate of n-butyl aldehyde.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a fullerene-modified copper-zinc catalyst, its preparation method, and its application. Background Technology

[0002] n-Butanol, as an important basic chemical raw material, is mainly used in the production of plasticizers such as butyl acrylate, butyl acetate, and dibutyl phthalate. It can also be used as a solvent, dehydrating agent, and extractant, showing broad application prospects. Currently, the mainstream industrial production process involves the hydroformylation of propylene with syngas to obtain n-butyraldehyde, followed by hydrogenation reduction to obtain n-butanol. In the n-butyraldehyde hydrogenation step, compared to the traditional gas-phase hydrogenation process (which requires pre-vaporization of raw materials, produces more byproducts, and has higher energy consumption), liquid-phase hydrogenation has advantages such as lower energy consumption, shorter process, and simpler process, and is gradually gaining attention.

[0003] However, existing n-butyraldehyde liquid-phase hydrogenation catalysts still suffer from the following technical drawbacks: First, the catalyst selectivity is low, and side reactions are severe. n-Butyraldehyde is chemically reactive and easily undergoes side reactions such as condensation and disproportionation under high-temperature liquid-phase conditions, generating byproducts such as n-butyl ether and high-boiling-point condensation polymers. Most existing liquid-phase hydrogenation catalysts are inorganic oxide-supported catalysts (the supports are mainly alumina, silica, zinc oxide, activated carbon, etc.). The surface acidity of the inorganic support exacerbates the occurrence of side reactions, leading to a decrease in n-butanol selectivity. Although the acidity is usually neutralized by adding alkaline promoters to the catalyst, this method cannot completely solve the side reaction problem. Second, there is a contradiction between catalyst activity and selectivity. In existing technologies, improving the conversion rate of n-butyraldehyde often comes at the cost of increased side reactions and decreased selectivity; it is difficult to achieve both simultaneously. For example, when using traditional copper-chromium catalysts, although a certain conversion rate can be obtained, the n-butanol selectivity is usually difficult to maintain at an ideal level, resulting in a high content of byproducts in the product, requiring a large amount of steam for distillation separation. Existing studies have attempted to improve selectivity and stability by adding promoters such as Mn to regulate catalyst particle size and increase active sites, but the results are still not ideal.

[0004] To address the shortcomings of the prior art, this invention provides a fullerene-modified copper-zinc catalyst, its preparation method, and its application, in order to alleviate or solve the aforementioned problems. Summary of the Invention

[0005] To address the technical problem of achieving both high n-butyraldehyde conversion and high n-butanol selectivity in the liquid-phase hydrogenation reaction of n-butyraldehyde using commonly used techniques, this invention provides a method for preparing a fullerene-modified copper-zinc catalyst, comprising the following steps: The fullerene-imidazolium dispersion, copper-zinc solution and precipitant were mixed, and the solid phase was collected to obtain the catalyst precursor. The catalyst precursor was subjected to calcination-reduction treatment to obtain a fullerene-modified copper-zinc catalyst. The roasting-reduction process is carried out at a temperature of 300-450℃ and a temperature of 300-450℃.

[0006] Furthermore, the copper-zinc solution contains a metal salt, and the fullerene-imidazolium dispersion contains imidazolium compounds; The molar ratio of the metal salt to the imidazole compound is 1:(2-10); the fullerene-imidazole dispersion contains fullerene, and the mass ratio of the fullerene to the metal salt is (1-20):1000.

[0007] Furthermore, the calcination-reduction process includes: calcining at a heating rate of 3-10℃ / min in an inert atmosphere to the calcination temperature, holding at that temperature for 2-5 hours; then switching to a reducing atmosphere and holding at that temperature for 2-5 hours for reduction.

[0008] Furthermore, the preparation of the fullerene-imidazolium dispersion includes the following steps: A surfactant, a polar organic solvent, a fullerene, and an imidazole compound are mixed to obtain the fullerene-imidazolium dispersion. Alternatively, a polar organic solvent, an aromatic organic compound, a fullerene, and an imidazole compound can be mixed to obtain the fullerene-imidazolium dispersion.

[0009] Furthermore, the surfactant is selected from at least one of cetyltrimethylammonium bromide, polyvinylpyrrolidone, polyethylene glycol 4000, sodium dodecylbenzenesulfonate, and sodium stearate; The imidazole compound is selected from at least one of 2-methylimidazolium, benzimidazole, imidazole, and imidazole-2-carboxaldehyde.

[0010] Furthermore, the polar organic solvent is selected from at least one of methanol, ethanol, and N,N-dimethylformamide; The aromatic organic compound is selected from at least one of m-xylene, toluene, and 1-chloronaphthalene.

[0011] Furthermore, the precipitant is selected from at least one of ammonia, ammonium carbonate, ammonium bicarbonate, and triethylamine.

[0012] This invention provides a fullerene-modified copper-zinc catalyst, prepared by the method described above. The fullerene-modified copper-zinc catalyst comprises a copper-zinc carbon-nitrogen matrix and fullerenes encapsulated in the pores of the matrix; the matrix has a porous carbon-nitrogen framework structure.

[0013] The present invention also provides the application of the fullerene-modified copper-zinc catalyst as described above in the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. The n-butyraldehyde and the fullerene-modified copper-zinc catalyst are hydrogenated under a hydrogen atmosphere. After the reaction is completed, solid-liquid separation is performed, the liquid phase product is collected, and n-butanol is obtained by separation. The fullerene-modified copper-zinc catalyst is a copper-zinc composite material in which fullerene is encapsulated in a porous carbon-nitrogen framework.

[0014] Furthermore, the mass ratio of the fullerene-modified copper-zinc catalyst to the n-butyraldehyde is 0.1-0.5; The hydrogenation reaction is carried out at a pressure of 1.0-1.5 MPa, a reaction time of 45-90 minutes, and a reaction temperature of 130-160℃.

[0015] Compared with the prior art, the present invention has at least the following advantages: In this invention, fullerenes form a stable dispersion with an imidazole compound solution with the assistance of a surfactant. The imidazole compound and metal ions in the copper-zinc solution coordinate to form a zeolite-like imidazole framework (ZIF), during which the fullerene is encapsulated within the pores of the ZIF. After calcination and reduction under specific parameters, the ZIF is transformed into a porous carbon-nitrogen framework, and the fullerene remains stably confined within the framework pores, ultimately yielding a fullerene-modified copper-zinc-carbon-nitrogen catalyst.

[0016] This invention encapsulates fullerenes within the pores of a ZIF-derived porous carbon-nitrogen framework, utilizing the electronic buffering effect of fullerenes to regulate the electronic state of the copper-zinc active components, thereby suppressing side reactions such as polycondensation and disproportionation of n-butyraldehyde under high-temperature liquid-phase conditions.

[0017] The fullerene-modified catalyst prepared using the method of this invention (Example 1, Catalyst 1) achieves a n-butyraldehyde conversion rate of 75.9% and a n-butanol selectivity of 90.6% under reaction conditions of 150°C and 1.3 MPa. In contrast, the traditional copper-zinc catalyst (Catalyst 11) of Comparative Example 1, which does not introduce fullerene and imidazole components, exhibits a n-butyraldehyde conversion rate of only 68.7% and a n-butanol selectivity of only 45.8%. The comparison shows that this invention achieves a significant synergistic effect by increasing selectivity by nearly 45 percentage points while improving conversion rate by approximately 7 percentage points.

[0018] This invention utilizes the porous ZIF structure in the catalyst precursor to encapsulate fullerenes within the framework channels, preventing their decomposition during catalyst calcination. Simultaneously, copper and zinc species are generated in situ and uniformly dispersed on the ZIF-derived carbon-nitrogen framework, minimizing the loss and sintering of active components. Compared to the copper-zinc catalyst prepared by the traditional co-precipitation method in Comparative Example 1, the catalyst of this invention exhibits superior active component dispersion and stability. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a photograph of the catalyst prepared in Example 1 of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0023] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.

[0024] This invention provides a method for preparing a fullerene-modified copper-zinc catalyst, comprising the following steps: S1. Obtain fullerene-imidazolium dispersion, copper-zinc solution, and precipitant.

[0025] In some embodiments, the fullerene-imidazolium dispersion comprises fullerene, imidazolium compounds, and a dispersion medium; the dispersion medium is a combination of a surfactant and a polar organic solvent, or a combination of a polar organic solvent and an aromatic organic compound.

[0026] In some embodiments, the fullerene-imidazolium dispersion is obtained by any of the following methods: Option 1: Mix surfactant, polar organic solvent, fullerene, and imidazole compound to obtain the fullerene-imidazolium dispersion; Option 2: Mix a polar organic solvent, an aromatic organic compound, a fullerene, and an imidazole compound to obtain the fullerene-imidazolium dispersion.

[0027] More specifically, the surfactant is selected from at least one of cetyltrimethylammonium bromide, polyvinylpyrrolidone, polyethylene glycol 4000, sodium dodecylbenzenesulfonate, and sodium stearate.

[0028] More specifically, the polar organic solvent is selected from at least one of methanol, ethanol, and N,N-dimethylformamide; the aromatic organic compound is selected from at least one of m-xylene, toluene, and 1-chloronaphthalene.

[0029] More specifically, the imidazole compound is selected from at least one of 2-methylimidazolium, benzimidazole, imidazole, and imidazole-2-carboxaldehyde.

[0030] In some embodiments, the mixing method may be ultrasonic dispersion, with an ultrasonic time of 10-60 min, to promote uniform dispersion of fullerene in the dispersion medium.

[0031] More specifically, in Scheme 1, the mass ratio of the surfactant to the fullerene can be 0.5-100:1, such as 50-100:1, 60-100:1, or 60-80:1. If the amount of surfactant is too low, the solubilization and coating of the fullerene will be insufficient, and the fullerene will easily agglomerate and float; if the amount is too high, the free surfactant will easily adsorb onto the surface of the subsequently generated zeolite-like imidazole framework material and block the pores, affecting the product performance.

[0032] More specifically, in Scheme 2, the volume ratio of the aromatic organic compound to the polar organic solvent is 0.1-10:1, such as 0.2-10:1 or 0.2-5:1. If the proportion of aromatic organic compound is too low, the dispersion stability of fullerene decreases and it is prone to precipitation; if the proportion of polar organic solvent is too low, phase separation easily occurs when the dispersion is mixed with the copper-zinc solution, affecting the uniformity of the coordination reaction.

[0033] More specifically, the molar ratio of the imidazole compound to the metal ions in the copper-zinc solution is 2-10:1, such as 4-8:1. This ratio ensures that the metal ions are fully coordinated to form a zeolite-like imidazole framework, while avoiding excessive imidazole leading to overly rapid nucleation and disordered framework crystallization.

[0034] In some embodiments, the fullerene-imidazolium dispersion obtained in Scheme 1 may also contain water, i.e., the fullerene-imidazolium dispersion is obtained by mixing a surfactant, a polar organic solvent, water, fullerene, and an imidazolium compound. For example, the volume ratio of the polar organic solvent to water is not less than 0.1, such as 0.2-5.

[0035] It should be noted that the fullerene is a hydrophobic carbon material. When water is used as the solvent only in the fullerene-imidazolium dispersion, the fullerene will float on the water surface and cannot enter the pores of the zeolite-imidazolium framework (ZIF). In Scheme 1, the hydrophilic-hydrophobic amphiphilic structure of the surfactant can form micelles that encapsulate the fullerene, and together with polar organic solvents such as N,N-dimethylformamide, it forms a homogeneous dispersion system for the fullerene, making it easier for the fullerene to enter the ZIF pores. In Scheme 2, the fullerene has good affinity with aromatic organic compounds and can be uniformly dispersed in the system.

[0036] It should also be noted that the role of the polar organic solvent in Scheme 2 is as follows: copper-zinc solutions are usually aqueous or alcoholic systems, which have poor miscibility with aromatic organic compounds. Polar organic solvents, on the other hand, are miscible with both aromatic organic compounds and copper-zinc solutions, and can act as a bridge between the two phases. This allows the fullerene-imidazolium dispersion to form a homogeneous system when mixed with the copper-zinc solution, preventing the precipitation of fullerenes due to sudden changes in the solvent environment. At the same time, it promotes the uniform growth of imidazolium compounds and metal ions in the copper-zinc solution into zeolite-like imidazolium framework materials through coordination.

[0037] S2. Mix the fullerene-imidazolium dispersion, copper-zinc solution and precipitant, collect the solid phase to obtain the catalyst precursor.

[0038] In some embodiments, the copper-zinc solution can be mixed with a precipitant to obtain a copper-zinc precipitate; then the copper-zinc precipitate can be mixed with the fullerene-imidazolium dispersion to obtain a catalyst precursor.

[0039] More specifically, it may include: slowly adding the copper-zinc precipitate dropwise into a fullerene-imidazolium dispersion, followed by stirring and solid-liquid separation to obtain the catalyst precursor. The stirring time may be 1-3 hours.

[0040] More specifically, the stirring process can be carried out at room temperature.

[0041] More specifically, the stirring process can be replaced by a crystallization process; the temperature of the crystallization process can be 80-150℃, and the duration can be 8-24h.

[0042] In other embodiments, the fullerene-imidazolium dispersion may be mixed with a precipitant to obtain a mixed system, and then the mixed system may be mixed with a copper-zinc solution. After the stirring treatment or the crystallization treatment, solid-liquid separation is performed to obtain the catalyst precursor.

[0043] In some embodiments, the copper-zinc solution includes a metal salt.

[0044] More specifically, the metal salt includes copper salts and zinc salts. For example, the copper salt may be selected from copper nitrate and copper acetate, and the zinc salt may be selected from zinc nitrate and zinc acetate.

[0045] More specifically, the molar ratio of the metal salt to the imidazole compound is 1:(2-10).

[0046] More specifically, the mass ratio of the fullerene to the metal salt is (1-20):1000.

[0047] In some embodiments, the precipitant is selected from at least one of ammonia, ammonium carbonate, ammonium bicarbonate, and triethylamine.

[0048] In some embodiments, the molar ratio of copper to zinc in the copper-zinc solution can be 1:1-8.

[0049] In some embodiments, the molar ratio of the precipitant to the metal salt can be 0.5-6:1; more specifically, the molar ratio of the precipitant to the metal salt can be 0.5-5.5:1, 0.5-5:1, 0.5-3:1, or 0.8-1.2:1.

[0050] S3. The catalyst precursor is subjected to calcination-reduction treatment to obtain a fullerene-modified copper-zinc catalyst.

[0051] In some embodiments, the calcination-reduction process includes: calcining at a heating rate of 3-10°C / min in an inert atmosphere to the calcination temperature, holding at that temperature for 2-5 hours; and then switching to a reducing atmosphere and holding at that temperature for 2-5 hours for reduction.

[0052] More specifically, the calcination temperature can be 300-450℃ for 2-4 hours, and the reduction temperature can be 300-450℃ for 2-4 hours.

[0053] For example, the calcination temperature can be 300-400℃, 300-350℃, 350-400℃, or 325-375℃; the reduction temperature can be 300-400℃, 300-350℃, 350-400℃, or 325-375℃.

[0054] For example, the roasting time can be 2.5-3.5 hours.

[0055] More specifically, the inert atmosphere can be a nitrogen atmosphere or an argon atmosphere, and the reducing atmosphere can be hydrogen.

[0056] More specifically, the temperature can be raised to the calcination temperature in an inert atmosphere at a rate of 3-10℃ / min, and then held for 2-5 hours for calcination; then the temperature can be switched to a reducing atmosphere and held for 2-5 hours for reduction.

[0057] In some embodiments, the roasting-reduction process can be carried out in a tube furnace.

[0058] The present invention also provides a fullerene-modified copper-zinc catalyst, which is prepared by the preparation method described above. The fullerene-modified copper-zinc catalyst comprises a copper-zinc carbon-nitrogen matrix and fullerene encapsulated in the pores of the matrix, wherein the matrix has a porous carbon-nitrogen framework structure.

[0059] The present invention also provides the application of the fullerene-modified copper-zinc catalyst prepared by the preparation method described above or the fullerene-modified copper-zinc catalyst described above in the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. n-Butyraldehyde and the fullerene-modified copper-zinc catalyst are added to a reactor and hydrogenation reaction is carried out under a hydrogen atmosphere. After the reaction is completed, solid-liquid separation is performed, and the liquid phase product is collected for gas chromatography analysis. The fullerene-modified copper-zinc catalyst is a copper-zinc composite material in which fullerene is encapsulated in a porous carbon-nitrogen framework. The fullerene acts as an electron buffer to regulate the electronic state of the active component during the catalytic reaction, thereby inhibiting the polycondensation and disproportionation reactions of n-butyraldehyde under high-temperature conditions in the liquid phase.

[0060] In some embodiments, the mass ratio of the fullerene-modified copper-zinc catalyst to the n-butyraldehyde is 0.1-0.5; The hydrogenation reaction is carried out at a pressure of 1.0-1.5 MPa, a reaction time of 45-90 minutes, and a reaction temperature of 130-160℃.

[0061] To facilitate a further understanding of the present invention by those skilled in the art, the following examples are provided: Example 1 S1. Obtain a fullerene-imidazolium dispersion.

[0062] Weigh 300g of deionized water and add 150mL of ethanol, then add 5g of polyvinylpyrrolidone and stir. Next, add 0.08g of fullerene, continue stirring and sonicating for 30 minutes; then add 13.14g of 2-methylimidazole to obtain a fullerene-imidazolium dispersion.

[0063] S2. Mix the fullerene-imidazolium dispersion, copper-zinc solution and precipitant, collect the solid phase to obtain the catalyst precursor.

[0064] Specifically: To obtain a copper-zinc solution, weigh 4.832 g of copper nitrate trihydrate and 5.950 g of zinc nitrate hexahydrate and dissolve them in 50 g of deionized water. After the solids dissolve, add 3.843 g of ammonium carbonate to completely precipitate the solids, thus obtaining a copper-zinc precipitate.

[0065] The copper-zinc precipitate was added to the fullerene-imidazolium dispersion and stirred for 1 hour. The solid precipitate was then collected by filtration. After that, it was dried in an oven at 80°C for 12 hours to obtain the catalyst precursor.

[0066] The molar ratio of metal salts (copper nitrate, zinc nitrate) to imidazole compounds is 1:4, the mass ratio of fullerene to metal salts is 0.0074:1, the molar ratio of copper to zinc is 1:1, and the molar ratio of precipitant to metal salts is 1:1.

[0067] S3. The catalyst precursor is placed in a tube furnace and heated to 350°C at 5°C / min under a nitrogen atmosphere and calcined at this temperature for 3 hours. Then the temperature is maintained and hydrogen is switched to reduce for 3 hours. The catalyst is then cooled to room temperature to obtain catalyst 1.

[0068] The catalyst 1 prepared in this embodiment was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, ratio of n-butyraldehyde to catalyst of 12:2, reaction temperature of 150°C, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0069] In this embodiment, the conversion rate of n-butyraldehyde was 75.9%, and the selectivity of n-butanol was 90.6%.

[0070] Example 2 Catalyst 2 was prepared by replacing 0.08g of fullerene in step S1 of Example 1 with 0.16g, while keeping other steps unchanged.

[0071] The molar ratio of metal salts (copper nitrate, zinc nitrate) to imidazole compounds is 1:4, the mass ratio of fullerene to metal salts is 0.0148:1, the molar ratio of copper to zinc is 1:1, and the molar ratio of precipitant to metal salts is 1:1.

[0072] The catalyst 2 prepared in this embodiment was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, ratio of n-butyraldehyde to catalyst of 12:2, reaction temperature of 150°C, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0073] In this embodiment, the conversion rate of n-butyraldehyde was 75.8%, and the selectivity of n-butanol was 91.8%.

[0074] In this embodiment, based on Example 1, the amount of fullerene was increased from 0.08 g to 0.16 g, while other conditions remained unchanged, to prepare catalyst 2. Under the same reaction conditions, catalyst 2 achieved a n-butyraldehyde conversion rate of 75.8% and a n-butanol selectivity of 91.8%.

[0075] The above results indicate that, within the range of fullerene dosage described in this invention, appropriately increasing the amount of fullerene can further improve the selectivity of n-butanol, while having no significant effect on the conversion rate of n-butyraldehyde. This suggests that the electronic buffering effect of fullerene increases with its content, which is beneficial for suppressing side reactions and improving the selectivity of the target product.

[0076] Example 3 Step S2 in Example 1 was modified as follows: 9.664 g of copper nitrate trihydrate and 11.900 g of zinc nitrate hexahydrate were weighed and dissolved in 50 g of deionized water. After the solid was dissolved, 7.687 g of ammonium carbonate was added to precipitate it completely. The remaining steps remained unchanged to obtain catalyst 3.

[0077] The molar ratio of metal salts (copper nitrate, zinc nitrate) to imidazole compounds is 1:2, the mass ratio of fullerene to metal salts is 0.0039:1, the molar ratio of copper to zinc is 1:1, and the molar ratio of precipitant to metal salts is 1:1.

[0078] The catalyst 3 prepared in this embodiment was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, ratio of n-butyraldehyde to catalyst of 12:2, reaction temperature of 150°C, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0079] In this embodiment, the conversion rate of n-butyraldehyde was 80.5%, and the selectivity of n-butanol was 89.5%.

[0080] In this embodiment, based on Example 1, the amounts of copper and zinc salts were doubled (copper nitrate trihydrate increased from 4.832 g to 9.664 g, zinc nitrate hexahydrate increased from 5.950 g to 11.900 g, and ammonium carbonate was correspondingly doubled), while other conditions remained unchanged, to prepare catalyst 3. Under the same reaction conditions, the conversion rate of n-butyraldehyde of catalyst 3 was increased to 80.5%, and the selectivity for n-butanol was 89.5%.

[0081] The above results indicate that, within the range of metal salt dosage described in this invention, appropriately increasing the loading of copper and zinc active components helps to improve the conversion rate of n-butyraldehyde, while the selectivity of n-butanol remains at a high level (89.5%), indicating that the catalyst structure of this invention can accommodate more active sites without significantly sacrificing selectivity.

[0082] Example 4 Catalyst 4 was prepared by replacing 3.843 g of ammonium carbonate in step S2 of Example 1 with 30 mL of triethylamine, while keeping other steps unchanged.

[0083] The molar ratio of metal salts (copper nitrate, zinc nitrate) to imidazole compounds is 1:4, the mass ratio of fullerene to metal salts is 0.0074:1, the molar ratio of copper to zinc is 1:1, and the molar ratio of triethylamine to metal salts is 5.4:1.

[0084] The catalyst 4 prepared in this embodiment was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150°C, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0085] In this embodiment, the conversion rate of n-butyraldehyde was 74.8%, and the selectivity of n-butanol was 89.1%.

[0086] This embodiment is based on Example 1, except that the precipitant is replaced with triethylamine, while other conditions remain unchanged, to prepare catalyst 4. Under the same reaction conditions, catalyst 4 achieves a butyraldehyde conversion rate of 74.8% and a butanol selectivity of 89.1%.

[0087] The above results show that using organic amine compounds (triethylamine) as precipitants can also achieve good catalytic performance, indicating that the types of precipitants selected in this invention have a certain degree of universality, providing more options for the preparation process.

[0088] Example 5 Catalyst 5 was prepared by replacing 3.843 g of ammonium carbonate in step 2 of Example 1 with 3 mL of 25% concentrated ammonia water, while keeping other steps unchanged.

[0089] The molar ratio of metal salts (copper nitrate, zinc nitrate) to imidazole compounds is 1:4, the mass ratio of fullerene to metal salts is 0.0074:1, the molar ratio of copper to zinc is 1:1, and the molar ratio of precipitant to metal salts is 1:1.

[0090] The catalyst 5 prepared in this embodiment was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150°C, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0091] In this embodiment, the conversion rate of n-butyraldehyde was 72.8%, and the selectivity of n-butanol was 87.7%.

[0092] This embodiment is based on Example 1, except that the precipitant is replaced with ammonia water, while other conditions remain unchanged, to prepare catalyst 5. Under the same reaction conditions, catalyst 5 has a n-butyraldehyde conversion rate of 72.8% and a n-butanol selectivity of 87.7%.

[0093] The above results show that using an inorganic weak base (ammonia) as a precipitant can also achieve considerable catalytic performance, further verifying that the preparation method of the present invention has good adaptability to different types of precipitants.

[0094] Example 6 Modify steps S1 and S2 in Example 1 as follows: Weigh 150 mL of N,N-dimethylformamide, then add 30 mL of toluene solution containing 0.08 g of fullerene, stir and sonicate for 30 minutes; then add 13.14 g of 2-methylimidazole to obtain a fullerene-imidazolium dispersion; add 30 mL of triethylamine to the fullerene-imidazolium dispersion to obtain a mixed system.

[0095] To obtain a copper-zinc solution, weigh 4.832 g of copper nitrate trihydrate and 5.950 g of zinc nitrate hexahydrate and dissolve them in 50 g of deionized water, stirring until the solids dissolve.

[0096] A copper-zinc solution was added to the mixture and crystallized at 120°C for 8 hours. After cooling, the solid precipitate was collected by filtration. The precipitate was then dried in an oven at 80°C for 12 hours to obtain the catalyst precursor; other steps remained unchanged to prepare catalyst 6.

[0097] The molar ratio of metal salts (copper nitrate, zinc nitrate) to imidazole compounds is 1:4, the mass ratio of fullerene to metal salts is 0.0074:1, the molar ratio of copper to zinc is 1:1, and the molar ratio of triethylamine to metal salts is 5.4:1.

[0098] The catalyst prepared in this embodiment was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150°C, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0099] Based on Example 1, this embodiment replaces room temperature stirring with crystallization to prepare catalyst 6. Under the same reaction conditions, catalyst 6 exhibits a 75.1% conversion rate of n-butyraldehyde and a 91.1% selectivity for n-butanol. These results demonstrate that considerable catalytic performance can be obtained using different synthetic methods and solvents for ZIF, further verifying the good adaptability of the preparation method of this invention to various synthetic approaches.

[0100] Example 7 Modify steps S1 and S2 in Example 1 as follows: Weigh 150 mL of N,N-dimethylformamide, then add 50 mL of toluene solution containing 0.08 g of fullerene, stir and sonicate for 30 minutes; then add 18.90 g of benzimidazole to obtain a fullerene-imidazolium dispersion; add 30 mL of triethylamine to the fullerene-imidazolium dispersion to obtain a mixed system.

[0101] To obtain a copper-zinc solution, weigh 4.832 g of copper nitrate trihydrate and 5.950 g of zinc nitrate hexahydrate and dissolve them in 50 g of deionized water, stirring until the solids dissolve.

[0102] A copper-zinc solution was added to the mixture and crystallized at 120°C for 8 hours. After cooling, the solid precipitate was collected by filtration. It was then dried in an oven at 80°C for 12 hours to obtain the catalyst precursor. Catalyst 7 was prepared by maintaining the other steps unchanged. A photograph of catalyst 7 is shown below. Figure 1 As shown.

[0103] The molar ratio of metal salts (copper nitrate, zinc nitrate) to imidazole compounds is 1:4, the mass ratio of fullerene to metal salts is 0.0074:1, the molar ratio of copper to zinc is 1:1, and the molar ratio of triethylamine to metal salts is 5.4:1.

[0104] The catalyst prepared in this embodiment was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150°C, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0105] This embodiment is based on Example 1, but 2-methylimidazole is replaced with benzimidazole and room temperature stirring is replaced with crystallization to obtain catalyst 7. Under the same reaction conditions, the conversion rate of n-butyraldehyde of catalyst 7 is 76.2%, and the selectivity of n-butanol is 92.2%.

[0106] The above results show that other imidazole compounds can also achieve considerable catalytic performance when used as ZIF ligands, further verifying that the preparation method of the present invention has good adaptability to the types of imidazole compounds.

[0107] Example 8 Catalyst 8 was prepared by changing the nitrogen calcination temperature and the hydrogen reduction temperature in step S3 of Example 1 to 400°C, while keeping other conditions unchanged.

[0108] The catalyst prepared in this embodiment was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150°C, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0109] In this embodiment, the conversion rate of n-butyraldehyde was 79.5%, and the selectivity of n-butanol was 70.8%.

[0110] Based on Example 1, this embodiment increases both the nitrogen calcination temperature and the hydrogen reduction temperature from 350°C to 400°C, while keeping other conditions unchanged, to prepare catalyst 8. Under the same reaction conditions, catalyst 8 achieves a n-butyraldehyde conversion rate of 79.5% and a n-butanol selectivity of 70.8%.

[0111] The above results indicate that increasing the calcination and reduction temperatures is beneficial for improving the conversion rate of n-butyraldehyde (from 75.9% to 79.5%), but it significantly impairs the selectivity of n-butanol (from 90.6% to 70.8%). Therefore, the preferred calcination and reduction temperature in this invention is 350°C.

[0112] Example 9 Catalyst 9 was prepared by changing the nitrogen calcination time and the hydrogen reduction time in step S3 of Example 1 to 4 hours, while keeping other conditions unchanged.

[0113] The catalyst prepared in this embodiment was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150°C, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0114] In this embodiment, the conversion rate of n-butyraldehyde was 68.7%, and the selectivity of n-butanol was 83.4%.

[0115] In this embodiment, based on Example 1, the nitrogen calcination time and hydrogen reduction time were both extended from 3 hours to 4 hours, while other conditions remained unchanged, to prepare catalyst 9. Under the same reaction conditions, catalyst 9 achieved a n-butyraldehyde conversion rate of 68.7% and a n-butanol selectivity of 83.4%.

[0116] The above results indicate that extending the calcination and reduction time actually led to a decrease in both the conversion rate of n-butyraldehyde and the selectivity of n-butanol (conversion rate decreased from 75.9% to 68.7%, and selectivity decreased from 90.6% to 83.4%). This is because prolonged calcination and reduction may cause the pore structure of the ZIF-derived carbon-nitrogen framework to collapse, reducing the encapsulation stability of the fullerene. Simultaneously, the copper-zinc active components may experience grain growth and agglomeration under prolonged high-temperature treatment, resulting in a reduction in the number of active sites and an exacerbation of side reactions. Therefore, the preferred calcination and reduction time in this invention is 3 hours.

[0117] Example 10 In Example 1, the nitrogen calcination time in step S3 was changed to 2 hours, the hydrogen reduction time was changed to 2 hours, and other conditions remained unchanged to obtain catalyst 10. The catalyst prepared in this embodiment was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150°C, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0118] In this embodiment, the conversion rate of n-butyraldehyde was 62.5%, and the selectivity of n-butanol was 78.4%.

[0119] In this embodiment, based on Example 1, the nitrogen calcination time and hydrogen reduction time were both shortened from 3 hours to 2 hours, while other conditions remained unchanged, to prepare catalyst 10. Under the same reaction conditions, the conversion rate of n-butyraldehyde of catalyst 10 was 62.5%, and the selectivity of n-butanol was 78.4%.

[0120] The above results indicate that shortening the calcination and reduction times significantly decreased both the conversion rate of n-butyraldehyde and the selectivity of n-butanol (conversion rate decreased from 75.9% to 62.5%, and selectivity decreased from 90.6% to 78.4%). This is because insufficient calcination time leads to incomplete carbonization of the catalyst precursor, an incomplete porous carbon-nitrogen framework structure, and the fullerene may agglomerate due to ineffective encapsulation. Simultaneously, insufficient reduction time results in incomplete reduction of the copper-zinc active components, leading to decreased active Cu... 0 The amount of species generated is insufficient. Therefore, the preferred roasting and reduction time in this invention is 3 hours.

[0121] Comparative Example 1 S1. Weigh 4.832g of copper nitrate trihydrate and 5.950g of zinc nitrate hexahydrate and dissolve them in 250g of deionized water. After the solids are dissolved, add 100g of a solution containing 3.843g of ammonium carbonate at a rate of 50 mL / min while stirring. After the addition is complete, continue stirring for 1 h and then age at 80℃ for 2.5 hours. S2. Place the dried solid material from step 1 into a muffle furnace, raise the temperature to 500°C at 5°C / min in air atmosphere, and calcine at this temperature for 4 hours to obtain the catalyst precursor. S3. The catalyst precursor from step 2 is placed in a tube furnace for reduction. The reduction is carried out at 350°C in a hydrogen atmosphere for 4 hours to obtain catalyst 11.

[0122] The catalyst 11 prepared in this comparative example was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150℃, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0123] In this comparative example, the conversion rate of n-butyraldehyde was 68.7%, and the selectivity of n-butanol was 45.8%.

[0124] In this comparative example, a copper-zinc catalyst (without fullerene, 2-methylimidazole, or ZIF structure) was prepared using a conventional co-precipitation method. The catalyst was calcined in an air-filled muffle furnace at 500°C for 4 hours, followed by reduction in hydrogen at 350°C for 4 hours to obtain catalyst 11. Under the same reaction conditions, the conversion rate of n-butyraldehyde was 68.7%, while the selectivity for n-butanol was only 45.8%.

[0125] Compared to Example 1 (conversion rate 75.9%, selectivity 90.6%), the conversion rate of this comparative example is about 7 percentage points lower, and the selectivity is about 45 percentage points lower. These results indicate that although traditional copper-zinc catalysts possess certain hydrogenation activity in the liquid-phase hydrogenation reaction of n-butyraldehyde, they lack the electron buffering effect of fullerenes and the structural confinement effect of the ZIF-derived carbon-nitrogen framework, thus failing to effectively suppress side reactions such as condensation and disproportionation, resulting in significantly lower selectivity for n-butanol.

[0126] Comparative Example 2 S1. Weigh 4.832g of copper nitrate trihydrate and 8.003g of chromium nitrate nonahydrate and dissolve them in 250g of deionized water. After the solids are dissolved, add 100g of an aqueous solution containing 7.687g of ammonium carbonate at a rate of 50 mL / min while stirring. After the addition is complete, continue stirring for 1 h and then age at 80℃ for 2.5 hours.

[0127] S2. The precipitate dried in step 1 is placed in a muffle furnace and heated to 500°C at 5°C / min in an air atmosphere and calcined at this temperature for 4 hours. Then the calcined solid is placed in a tube furnace for reduction and reduced in a hydrogen atmosphere at 350°C for 4 hours to obtain catalyst 12. Catalyst 12 prepared in this comparative example was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150℃, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0128] In this comparative example, the conversion rate of n-butyraldehyde was 70.8%, and the selectivity of n-butanol was 50.4%.

[0129] In this comparative example, the active component was replaced by copper-chromium instead of copper-zinc, and a copper-chromium catalyst was prepared by the traditional co-precipitation method (without fullerene, 2-methylimidazole, or ZIF structure). Under the same reaction conditions, the conversion rate of n-butyraldehyde was 70.8%, and the selectivity of n-butanol was only 50.4%.

[0130] Compared to Example 1 (conversion rate 75.9%, selectivity 90.6%), the conversion rate of this comparative example is slightly lower, and the selectivity is significantly lower (by approximately 40 percentage points). These results indicate that the chromium-based catalyst has poor ability to suppress side reactions in the liquid-phase hydrogenation of n-butyraldehyde.

[0131] Comparative Example 3 Catalyst 13 was prepared according to Comparative Example 1 in the material published in CN 115532260 A.

[0132] The catalyst 13 prepared in this comparative example was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150℃, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0133] In this comparative example, the conversion rate of n-butyraldehyde was 71.2%, and the selectivity of n-butanol was 40.6%.

[0134] Catalyst 13 (i.e., the control experiment without fullerene) was prepared according to Comparative Example 1 of Publication No. CN 115532260 A. Under the same reaction conditions, the conversion rate of n-butyraldehyde was 71.2%, and the selectivity of n-butanol was only 40.6%.

[0135] Compared to Example 1 (conversion rate 75.9%, selectivity 90.6%), the selectivity of this comparative example is significantly lower than that of Example 1 (by approximately 50 percentage points), and the selectivity data is abnormally low (40.6%). These results indicate that the catalyst prepared in this comparative example is extremely unstable, further verifying the crucial role of fullerene modification in improving the selectivity of n-butanol in this invention—without the electron buffering effect of fullerene, side reactions would dominate.

[0136] Comparative Example 4 Catalyst 14 was prepared by replacing 150 mL of ethanol with 150 mL of deionized water in step S1 of Example 1, while keeping other steps unchanged.

[0137] The catalyst 14 prepared in this comparative example was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150℃, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0138] In this comparative example, the conversion rate of n-butyraldehyde was 65.4%, and the selectivity of n-butanol was 68.9%.

[0139] This comparative example, based on Example 1, replaces 150 mL of ethanol in step S1 with an equal amount of deionized water (i.e., the solvent is entirely water, with no ethanol), while keeping other conditions unchanged, to prepare catalyst 14. Under the same reaction conditions, the conversion rate of n-butyraldehyde is 65.4%, and the selectivity of n-butanol is 68.9%.

[0140] Compared to Example 1 (conversion rate 75.9%, selectivity 90.6%), the conversion rate of this comparative example is about 10 percentage points lower, and the selectivity is about 22 percentage points lower. These results indicate that organic solvents play a crucial role as co-solvents in the preparation system of this invention—organic solvents can adjust solvent polarity, reduce the interfacial tension between the aqueous phase and fullerenes, and promote the uniform dispersion of fullerenes in solution, thereby ensuring that fullerenes are effectively encapsulated during ZIF self-assembly. Without the addition of organic solvents, fullerenes are difficult to disperse uniformly in the aqueous phase, and some fullerenes may exist in an aggregated state, unable to be effectively encapsulated by the ZIF channels, ultimately leading to a significant decrease in catalytic performance.

[0141] Comparative Example 5 Step S2 in Example 1 was modified as follows: 4.832g of copper nitrate trihydrate and 5.950g of zinc nitrate hexahydrate were weighed and dissolved in 50g of deionized water, without adding ammonium carbonate as a precipitant; the remaining steps remained unchanged to obtain catalyst 15.

[0142] The catalyst 15 prepared in this comparative example was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150℃, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0143] In this comparative example, the conversion rate of n-butyraldehyde was 45.2%, and the selectivity of n-butanol was 55.9%.

[0144] This comparative example, based on Example 1, omits the addition of a precipitant (ammonium carbonate) in step S2; that is, the copper and zinc salts are directly dissolved in water without precipitation. The remaining steps remain unchanged, yielding catalyst 15. Under the same reaction conditions, the conversion rate of n-butyraldehyde is only 45.2%, and the selectivity of n-butanol is only 55.9%.

[0145] Compared to Example 1 (conversion rate 75.9%, selectivity 90.6%), the conversion rate of this comparative example is about 30 percentage points lower, and the selectivity is about 35 percentage points lower, resulting in a significant decrease in catalytic performance. These results indicate that the addition of a precipitant is an indispensable key step in the preparation method of this invention—unprecipitated copper-zinc ions cannot form a copper-zinc co-precipitate, and therefore cannot assemble in situ to form the required structure during subsequent mixing with 2-methylimidazole. This leads to the inability to form the ZIF framework, and the fullerene cannot be effectively encapsulated. Both the active component and the fullerene exist in an amorphous aggregate state, resulting in extremely low catalytic activity.

[0146] Comparative Example 6 Replace the 3.834g ammonium carbonate in step S2 of Example 1 with 3.2g sodium hydroxide.

[0147] The catalyst 16 prepared in this comparative example was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150℃, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0148] In this comparative example, the conversion rate of n-butyraldehyde was 62.5%, and the selectivity of n-butanol was 88.7%.

[0149] This comparative example, based on Example 1, replaced the precipitant with sodium hydroxide instead of ammonium carbonate, while keeping other conditions unchanged, to prepare catalyst 16. Under the same reaction conditions, the conversion rate of n-butyraldehyde was only 62.5%, and the selectivity for n-butanol was 88.7%.

[0150] Compared to Example 1 (conversion rate 75.9%, selectivity 90.6%), the conversion rate of this comparative example is about 13 percentage points lower, and the selectivity is slightly lower (by about 2 percentage points). These results indicate that when a strong alkali (sodium hydroxide) is used as a precipitant, copper and zinc ions rapidly form hydroxide precipitates. This excessively rapid precipitation rate leads to poor uniformity of metal ions in the copper-zinc co-precipitate, resulting in a lower conversion rate of n-butyraldehyde. In this invention, ammonium carbonate is preferred as the precipitant, as its hydrolysis produces carbonate ions and slowly releases OH-. - Its characteristics make the precipitation process more gentle and controllable, which is conducive to the formation of uniform copper-zinc coprecipitates, thereby obtaining better catalytic performance.

[0151] Comparative Example 7 Catalyst 17 was prepared by changing the nitrogen calcination temperature and the hydrogen reduction temperature in step S3 of Example 1 to 500°C and keeping other conditions unchanged.

[0152] The catalyst prepared in this comparative example was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150℃, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0153] In this comparative example, the conversion rate of n-butyraldehyde was 77.9%, and the selectivity of n-butanol was 45.8%.

[0154] Based on Example 1, this comparative example increased both the nitrogen calcination temperature and the hydrogen reduction temperature from 350°C to 500°C, while keeping other conditions unchanged, to prepare catalyst 17. Under the same reaction conditions, the conversion rate of n-butyraldehyde was 77.9%, while the selectivity for n-butanol was only 45.8%.

[0155] Compared to Example 1 (conversion rate 75.9%, selectivity 90.6%), the conversion rate of this comparative example was basically the same (slightly higher by 2 percentage points), but the selectivity dropped sharply from 90.6% to 45.8%, a decrease of about 45 percentage points. Compared to Example 8 (400°C, selectivity 70.8%), when the temperature was further increased from 400°C to 500°C, the selectivity dropped sharply from 70.8% to 45.8%. The above results indicate that excessively high calcination and reduction temperatures (500°C) can lead to severe damage or even complete collapse of the fullerene carbon cage structure, resulting in the loss of the fullerene's electron buffering effect; at the same time, the copper-zinc active components sinter and agglomerate at extreme high temperatures, and the number and distribution of active sites deteriorate, leading to side reactions becoming dominant.

[0156] Comparative Example 8 Step S3 in Example 1 is modified as follows: the catalyst precursor is placed in a tube furnace, heated to 350°C at 5°C / min under a nitrogen atmosphere and calcined at this temperature for 3 hours, and then cooled to room temperature to obtain catalyst 18. The catalyst prepared in this comparative example was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150℃, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0157] In this comparative example, the conversion rate of n-butyraldehyde was 1.2%, and the selectivity of n-butanol was 95.8%.

[0158] This comparative example omits the hydrogen reduction step in step S3, based on Example 1. Instead, it only involves calcination under a nitrogen atmosphere (350°C, 3 hours) without hydrogen reduction, followed by cooling to room temperature to obtain catalyst 18. Under the same reaction conditions, the conversion rate of n-butyraldehyde is only 1.2%, and the selectivity for n-butanol is 95.8%.

[0159] Compared to Example 1 (conversion 75.9%, selectivity 90.6%), the conversion rate of this comparative example plummeted from 75.9% to 1.2%, exhibiting almost no hydrogenation activity. This indicates that the copper species in the catalyst without hydrogen reduction are mainly CuO or Cu. 2+ It exists in form, but lacks metallic Cu. 0 The active site cannot effectively catalyze the hydrogenation reaction of n-butyraldehyde. Although the selectivity value appears high (95.8%), this is based on an extremely low conversion rate (1.2%) and is therefore meaningless. The above results indicate that the hydrogen reduction step is an indispensable key step in the preparation method of this invention—only through hydrogen reduction can copper species be fully reduced to metallic Cu. 0 The active phase imparts high efficiency to the catalyst for the hydrogenation of n-butyraldehyde.

[0160] Comparative Example 9 Step S3 in Example 1 is modified as follows: the catalyst precursor is placed in a tube furnace, heated to 350°C at 5°C / min under a nitrogen atmosphere, then reduced by hydrogen for 3 hours, and cooled to room temperature to obtain catalyst 19. The catalyst prepared in this comparative example was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150℃, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0161] In this comparative example, the conversion rate of n-butyraldehyde was 58.7%, and the selectivity of n-butanol was 64.8%.

[0162] This comparative example, based on Example 1, omits the nitrogen-atmospheric calcination step while keeping other conditions unchanged, to prepare catalyst 19. Under the same reaction conditions, the conversion rate of n-butyraldehyde was 58.7%, and the selectivity of n-butanol was 64.8%.

[0163] Compared to Example 1 (conversion rate 75.9%, selectivity 90.6%), the conversion rate of this comparative example is about 17 percentage points lower, and the selectivity is about 26 percentage points lower. These results indicate that when hydrogen reduction is performed directly without heat preservation calcination, the ZIF precursor is reduced before it is fully carbonized, the pore structure of the carbon-nitrogen framework is not fully formed, the fullerene encapsulation effect is poor, and the dispersion of the active component is insufficient, ultimately leading to significantly lower conversion rate and selectivity. This fully demonstrates that the two-step heat treatment sequence and time control—first fully calcining to completely carbonize the ZIF, and then activating it with hydrogen reduction—are the key process features of the technical solution of this invention.

[0164] Comparative Example 10 Step 1 in Example 1 was modified as follows: Weigh 300g of deionized water and add 150mL of ethanol to it, then add 5g of polyvinylpyrrolidone and stir, continue stirring and sonicating for 30 minutes; the remaining steps remain unchanged to obtain catalyst 20.

[0165] The catalyst 20 prepared in this comparative example was applied to the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol. Reaction conditions: liquid-phase reactor, n-butyraldehyde to catalyst ratio of 12:2, reaction temperature of 150℃, reaction pressure of 1.3 MPa, reaction time of 1 hour, and stirring speed of 800 rpm.

[0166] In this comparative example, the conversion rate of n-butyraldehyde was 70.8%, and the selectivity of n-butanol was 59.4%.

[0167] This comparative example, based on Example 1, omits the fullerene in step S1 (i.e., the system contains no fullerene, only ethanol, water, polyvinylpyrrolidone, and 2-methylimidazole), while keeping the rest unchanged, to prepare catalyst 20. Under the same reaction conditions, the conversion rate of n-butyraldehyde was 70.8%, and the selectivity of n-butanol was 59.4%.

[0168] Compared to Example 1 (conversion rate 75.9%, selectivity 90.6%), the conversion rate of this comparative example is slightly lower (by about 5 percentage points), and the selectivity is about 31 percentage points lower. These results indicate that, without the addition of fullerenes, although the catalyst still possesses certain hydrogenation activity (derived from the copper-zinc active component and the ZIF-derived carbon-nitrogen framework), the lack of fullerene's electron buffering effect prevents effective control of the electronic state of the active center, significantly increasing the probability of side reactions (condensation polymerization, disproportionation) and markedly decreasing the selectivity of n-butanol. This verifies the core role of fullerenes as an electron buffer in this invention—a key functional component for improving selectivity.

[0169] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a fullerene-modified copper-zinc catalyst, characterized in that, Including the following steps: The fullerene-imidazolium dispersion, copper-zinc solution and precipitant were mixed, and the solid phase was collected to obtain the catalyst precursor. The catalyst precursor was subjected to calcination-reduction treatment to obtain a fullerene-modified copper-zinc catalyst. The roasting-reduction process is carried out at a temperature of 300-450℃ and a temperature of 300-450℃.

2. The method for preparing the fullerene-modified copper-zinc catalyst according to claim 1, characterized in that, The copper-zinc solution contains metal salts, and the fullerene-imidazolium dispersion contains imidazolium compounds; The molar ratio of the metal salt to the imidazole compound is 1:(2-10); The fullerene-imidazolium dispersion contains fullerene, and the mass ratio of the fullerene to the metal salt is (1-20):1000.

3. The method for preparing the fullerene-modified copper-zinc catalyst according to claim 1, characterized in that, The roasting-reduction process includes: roasting to the roasting temperature in an inert atmosphere at a heating rate of 3-10℃ / min, holding at that temperature for 2-5 hours; then switching to a reducing atmosphere and holding at that temperature for 2-5 hours for reduction.

4. The method for preparing the fullerene-modified copper-zinc catalyst according to claim 2, characterized in that, The preparation of the fullerene-imidazolium dispersion includes the following steps: A surfactant, a polar organic solvent, a fullerene, and an imidazole compound are mixed to obtain the fullerene-imidazolium dispersion. Alternatively, a polar organic solvent, an aromatic organic compound, a fullerene, and an imidazole compound can be mixed to obtain the fullerene-imidazolium dispersion.

5. The method for preparing the fullerene-modified copper-zinc catalyst according to claim 4, characterized in that, The surfactant is selected from at least one of cetyltrimethylammonium bromide, polyvinylpyrrolidone, polyethylene glycol 4000, sodium dodecylbenzenesulfonate, and sodium stearate. The imidazole compound is selected from at least one of 2-methylimidazolium, benzimidazole, imidazole, and imidazole-2-carboxaldehyde.

6. The method for preparing the fullerene-modified copper-zinc catalyst according to claim 4, characterized in that, The polar organic solvent is selected from at least one of methanol, ethanol, and N,N-dimethylformamide; The aromatic organic compound is selected from at least one of m-xylene, toluene, and 1-chloronaphthalene.

7. The method for preparing the fullerene-modified copper-zinc catalyst according to claim 1, characterized in that, The precipitant is selected from at least one of ammonia, ammonium carbonate, ammonium bicarbonate, and triethylamine.

8. A fullerene-modified copper-zinc catalyst, prepared by the method according to any one of claims 1-7, characterized in that, The fullerene-modified copper-zinc catalyst comprises a copper-zinc carbon-nitrogen matrix and fullerenes encapsulated in the pores of the matrix; the matrix has a porous carbon-nitrogen framework structure.

9. The application of the fullerene-modified copper-zinc catalyst as described in claim 8 in the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol, characterized in that, n-Butyraldehyde was hydrogenated with the fullerene-modified copper-zinc catalyst under a hydrogen atmosphere. After the reaction was completed, solid-liquid separation was performed, the liquid product was collected, and n-butanol was obtained by separation. The fullerene-modified copper-zinc catalyst is a copper-zinc composite material in which fullerene is encapsulated in a porous carbon-nitrogen framework.

10. The application of the fullerene-modified copper-zinc catalyst according to claim 9 in the liquid-phase hydrogenation of n-butyraldehyde to prepare n-butanol, characterized in that, The mass ratio of the fullerene-modified copper-zinc catalyst to the n-butyraldehyde is 0.1-0.5; The hydrogenation reaction is carried out at a pressure of 1.0-1.5 MPa, a reaction time of 45-90 minutes, and a reaction temperature of 130-160℃.

Images