Carbon-coated nickel-neodymium alloy catalyst with core-shell structure as well as preparation method and application of carbon-coated nickel-neodymium alloy catalyst

Abstract

The invention discloses a core-shell structure carbon-coated nickel-neodymium alloy catalyst as well as a preparation method and application thereof, and relates to the technical field of catalysts. The preparation method comprises the following steps: dispersing a soluble nickel salt, a soluble neodymium salt, glucose and titanium dioxide in a mixed solvent of water and ethylene glycol, carrying out a heating reaction, and roasting the product of the heating reaction to obtain the core-shell structure carbon-coated nickel-neodymium alloy catalyst. According to the core-shell structure carbon-coated nickel-neodymium alloy catalyst disclosed by the invention, nano titanium dioxide is taken as a substrate, and directional regulation and control of adsorption and desorption behaviors of reactants on the surface of the catalyst are realized by finely regulating and controlling electronic microenvironments of nickel and neodymium active centers. The reaction path is effectively guided to proceed in an expected direction, so that the synthesis efficiency of the high-carbon alcohol is remarkably enhanced. Experimental results show that the catalyst has excellent catalytic performance in an ethanol water phase coupling reaction, the yield of C4 and higher alcohols can reach 61.1%, and the selectivity can reach 98.8%.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a core-shell structured carbon-coated nickel-neodymium alloy catalyst, its preparation method, and its application. Background Technology

[0002] In the fine chemical industry, high-carbon alcohols with chain lengths from C4 to C18 play a crucial role. Their molecular structures possess both hydrophilic and hydrophobic properties, providing an ideal framework for constructing high-performance surfactants, thereby enabling precise control over the interfacial behavior and colloidal stability of formulation systems. Furthermore, these alcohols are also widely used as environmentally friendly green solvents in extraction, crystallization, and emulsification processes in the fragrance, pharmaceutical, and food industries. Taking hexanol (C6) and heptanol (C7) as examples, the former serves as a precursor in plasticizer synthesis, while the latter acts as an intermediate in fragrance synthesis, fully demonstrating their significant application value as multifunctional carriers.

[0003] In the synthesis of higher alcohols, Guerbet-catalyzed condensation reactions have become a research hotspot due to their outstanding atom economy. This reaction is essentially a continuous catalytic process encompassing three key steps: first, the alcohol molecule undergoes dehydrogenation to form an aldehyde intermediate; subsequently, this intermediate undergoes Claisen condensation at a basic catalytic site to form an α,β-unsaturated aldehyde; finally, this unsaturated aldehyde is further hydrogenated to form a saturated alcohol product. It is noteworthy that the efficiency of the initial dehydrogenation and final hydrogenation steps largely depends on the electronic structure characteristics of the metal active center. Currently, mainstream catalytic systems mostly employ platinum group metals such as ruthenium (Ru) and rhodium (Rh). Although they can achieve condensation efficiencies of over 80%, they still face two major challenges: first, the noble metal components are prone to leaching during the reaction, resulting in insufficient catalyst cycle stability (typically, the activity decreases by more than 40% after three uses); second, the high cost of platinum group metals, accounting for more than 65% of the total catalyst cost, limits their industrial application.

[0004] Nickel-based catalysts are considered ideal candidates to replace precious metal catalysts due to their abundant natural resources (crustal reserves of 1.3 × 10⁴ ppm) and tunable electronic properties. However, their practical application in the Guerbet reaction still faces technical bottlenecks. For example, under reaction conditions above 200°C, nickel is prone to sintering, which triggers competitive methanation side reactions, ultimately severely inhibiting the effective growth of the carbon chain and resulting in low yields of C₄⁺ higher alcohols. Therefore, it is essential to develop a high-performance nickel-based catalyst for the Guerbet reaction that can effectively improve the yield of C₄⁺ higher alcohols. Summary of the Invention

[0005] The purpose of this invention is to provide a core-shell structured carbon-coated nickel-neodymium alloy catalyst, its preparation method, and its application, in order to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention is a method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: dispersing soluble nickel (Ni) salt, soluble neodymium (Nd) salt, glucose and titanium dioxide (TiO2) in a mixed solvent of water and ethylene glycol, heating and reacting, and then calcining the product of the heated reaction to obtain the core-shell structured carbon-coated nickel-neodymium alloy catalyst (abbreviated as NiNd@C-TiO2 core-shell structure catalyst).

[0007] This invention utilizes a solvothermal method to prepare a core-shell structured carbon-coated nickel-neodymium alloy catalyst. By leveraging the reducing properties and high polarity of the solvent (ethylene glycol) at high temperatures, three key steps are simultaneously achieved: first, the reduction and alloying of nickel and neodymium ions; second, the carbonization of glucose and its direct coating onto the exterior of the nickel-neodymium alloy; and third, the in-situ, uniform anchoring of the generated carbon-coated nickel-neodymium alloy nanoparticles onto the surface of pre-dispersed TiO2 particles. This process forms a multi-level composite structure of "core (NiNd), shell (C), and support (TiO2)," where the in-situ growth of the carbon-coated nickel-neodymium alloy nanoparticles and TiO2 particles leads to stronger chemical interactions, which are crucial for improving the catalyst's catalytic efficiency, stability, and potential metal-support synergistic catalytic effect. Simultaneously, the solvothermal environment is conducive to the generation of uniformly sized and well-dispersed nickel-neodymium alloy nanoparticles, potentially yielding unique morphologies (such as regular spherical shapes), which are difficult to achieve using simple precursor pyrolysis methods.

[0008] In the aqueous-phase synthesis of higher alcohols from ethanol (i.e., the selective coupling of ethanol to higher alcohols), this invention designs and constructs a NiNd@C-TiO2 core-shell structure catalyst. In this design, the alloying of Ni and Nd aims to achieve a key multifunctional synergistic effect: Ni, as the main active center for the dehydrogenation / hydrogenation reaction, is responsible for the activation of ethanol and the hydrogenation of the final product; while the introduction of the rare earth element Nd, with its strong oxygen affinity, effectively regulates the electron density of Ni through electron transfer to Ni (Nd→Ni), inducing it to form a moderately electron-deficient state (Ni δ). +This optimizes the catalyst's activation ability for the CH / OH bonds of the reactants. Simultaneously, Nd sites strongly adsorb and stabilize oxygen-containing intermediates such as acetaldehyde, and synergistically with the hydroxyl acid sites on the adjacent TiO2 surface, greatly promoting the crucial aldol condensation (CC coupling) step. Furthermore, the addition of Nd acts as a structural promoter, inhibiting the sintering of Ni nanoparticles during the reaction and improving the overall stability of the catalyst. Therefore, the synergistic effect of Ni and Nd constructs a functionally complementary network of active sites at the nanoscale, enabling the efficient execution of the "dehydrogenation-condensation-hydrogenation" tandem reaction, ultimately leading to high activity and selectivity for higher alcohol products.

[0009] Furthermore, this invention achieves precise control of the catalytic system by designing a TiO2 support with a well-defined crystalline phase. This support provides atomic-level precise anchoring of the active metal, ensuring high interfacial stability and effectively suppressing the migration, ripening, and aggregation of active components. The hydroxyl groups on the TiO2 surface play a crucial role in regulating the hydrophilicity and hydrophobicity of the interface, optimizing mass transfer kinetics and significantly suppressing side reactions. The main and direct source of the surface hydroxyl groups is TiO2. However, the carbon shell encapsulation and Nd doping jointly regulate the density, distribution, and acidity of these hydroxyl groups, thereby optimizing the catalyst's activity and selectivity for ethanol coupling reactions (involving complex steps such as dehydrogenation, aldol condensation, and hydrogenation). Through the synergistic promotion of this series of interfacial engineering techniques, the hydrogen spillover effect is enhanced, the dehydrogenation energy barrier is significantly reduced, and the directional reconstruction of reactant adsorption modes drives the reaction pathway to preferentially select for the formation of higher alcohols, ultimately achieving a systematic leap in product yield.

[0010] Meanwhile, the core-shell structure of this catalyst is the core of its high performance, with advantages manifested in its excellent stability and resistance to sintering. The nickel-neodymium alloy core is the active center of the CC coupling. The carbon (C) shell encasing the surface of the nickel-neodymium alloy acts as a robust liner of a "nanoreactor," physically isolating and anchoring the metal nanoparticles, effectively preventing their migration, aggregation, or sintering deactivation during high-temperature reactions, thus ensuring the long-term effectiveness of the active sites. In addition, a tight heterogeneous interface is formed between the core (NiNd), shell (C), and support (TiO2), initiating significant interfacial electron transfer. The electron-rich carbon shell and Nd with strong oxygen affinity can jointly donate electrons to the TiO2 support, regulating the acidity of its surface hydroxyl groups (-OH) and the concentration of oxygen vacancies. This electron modification capability allows the catalyst surface to precisely adsorb / activate ethanol molecules and stabilize key aldehyde intermediates, thereby efficiently promoting the coupling pathway.

[0011] Furthermore, the volume ratio of the water to the ethylene glycol is 1:1.

[0012] Optionally, the soluble nickel salt includes nickel nitrate or nickel acetate; the soluble neodymium salt includes neodymium nitrate or neodymium chloride.

[0013] Furthermore, the molar ratio of the soluble nickel salt to the soluble neodymium salt is 0.5-4:1.

[0014] Furthermore, the mass of the glucose is equal to the total mass of the soluble nickel salt and the soluble neodymium salt (i.e., by mass ratio, glucose:(soluble nickel salt + soluble neodymium salt) = 1:1).

[0015] Furthermore, the mass of the titanium dioxide is equal to the total mass of the soluble nickel salt and the soluble neodymium salt (i.e., by mass ratio, titanium dioxide:(soluble nickel salt + soluble neodymium salt) = 1:1).

[0016] Furthermore, the heating reaction is carried out at a temperature of 200°C for 10-14 hours.

[0017] Preferably, the heating reaction takes 12 hours.

[0018] Furthermore, the calcination treatment is carried out at a temperature of 400-650℃, preferably 550℃, for a time of 1-3 hours.

[0019] Optionally, after dispersing the soluble nickel salt, soluble neodymium salt, glucose, and titanium dioxide in a mixed solvent of water and ethylene glycol, the process further includes an ultrasonic treatment for 30 minutes.

[0020] Optionally, after the heating reaction is completed, the process further includes steps of cooling, centrifugation, washing, and drying.

[0021] Preferably, the calcination process is carried out under an inert atmosphere.

[0022] The second technical solution of the present invention: a core-shell structured carbon-coated nickel-neodymium alloy catalyst prepared by the preparation method of the core-shell structured carbon-coated nickel-neodymium alloy catalyst as described above.

[0023] The third technical solution of the present invention: the application of the above-mentioned core-shell structure carbon-coated nickel-neodymium alloy catalyst in the catalytic aqueous-phase synthesis of higher alcohols from ethanol.

[0024] Furthermore, the step of catalytic synthesis of higher alcohols from aqueous ethanol includes: mixing ethanol, water, sodium hydroxide and the above-mentioned core-shell structured carbon-coated nickel-neodymium alloy catalyst as a reaction system, heating under a hydrogen atmosphere to carry out a carbon-carbon coupling reaction, and then centrifuging to separate the aqueous phase and the oil phase, the resulting oil phase being the higher alcohol.

[0025] Furthermore, the higher alcohol is an alcohol with 4 to 16 carbon atoms (referred to as C4+ higher alcohol).

[0026] Furthermore, the mass ratio of the ethanol, the water, the sodium hydroxide, and the core-shell carbon-coated nickel-neodymium alloy catalyst is 5:5:0.88:0.2.

[0027] Furthermore, the conditions for the carbon-carbon coupling reaction include: a reaction temperature of 230°C, an initial hydrogen pressure of 0.1 MPa, a stirring rate of 1500 rpm, and a reaction time of 6 hours.

[0028] The present invention discloses the following technical effects: The core-shell carbon-coated nickel-neodymium alloy catalyst of this invention uses nano-titanium dioxide as a substrate (i.e., support) and nickel-neodymium alloy as the active component. By precisely controlling the electronic microenvironment of the nickel and neodymium active centers, the adsorption and desorption behavior of reactants on the catalyst surface can be directionally controlled. This effectively guides the reaction pathway in the desired direction, thereby significantly enhancing the synthesis efficiency of higher alcohols. In addition, the carbon shell coating on the surface of the nickel-neodymium alloy effectively prevents the nickel-neodymium alloy from migrating, agglomerating, or sintering and deactivating during high-temperature reactions, ensuring the long-term effectiveness of the active sites. Experimental results show that this catalyst exhibits excellent catalytic performance in the aqueous coupling reaction of ethanol, with a yield of 61.1% and a selectivity of 98.8% for C4 and above (i.e., C4+) higher alcohols. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments 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 these drawings without creative effort.

[0030] Figure 1 XRD patterns of the Ni1Nd1@C-TiO2 catalyst prepared in Example 1 and the Ni1Nd1@C catalyst prepared in Comparative Example 1.

[0031] Figure 2 The image shows an HRTEM image of the Ni1Nd1@C-TiO2 catalyst prepared in Example 1.

[0032] Figure 3 The image shows the HRTEM image of the Ni1Nd1@C catalyst prepared in Comparative Example 1. Detailed Implementation

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0035] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0036] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0037] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0038] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0039] In the following embodiments, comparative examples and test examples of the present invention, if room temperature is involved, it specifically refers to 20-30 ℃.

[0040] All raw materials used in the following embodiments, comparative examples and test examples of this invention are common commercially available products. Among them, the titanium dioxide powder is nano-sized titanium dioxide P25 (anatase type).

[0041] Example 1 A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, neodymium nitrate, glucose, and titanium dioxide powder in a mixed solvent of water and ethylene glycol (wherein, the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, the molar ratio of nickel nitrate to neodymium nitrate is 1:1, the mass of glucose is equal to the total mass of nickel nitrate and neodymium nitrate, the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and neodymium nitrate, and the volume ratio of nickel nitrate to the mixed solvent is 1g:10mL), and sonicate for 30 minutes to ensure thorough dispersion, thereby obtaining a mixed suspension; S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-neodymium alloy catalyst, denoted as Ni1Nd1@C-TiO2.

[0042] Example 2 A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, neodymium nitrate, glucose, and titanium dioxide powder in a mixed solvent of water and ethylene glycol (wherein, the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, the molar ratio of nickel nitrate to neodymium nitrate is 0.5:1, the mass of glucose is equal to the total mass of nickel nitrate and neodymium nitrate, the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and neodymium nitrate, and the volume ratio of nickel nitrate to the mixed solvent is 1g:10mL), and sonicate for 30 minutes to ensure thorough dispersion, thereby obtaining a mixed suspension; S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-neodymium alloy catalyst, denoted as Ni. 0.5 Nd1@C-TiO2.

[0043] Example 3 A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, neodymium nitrate, glucose, and titanium dioxide powder in a mixed solvent of water and ethylene glycol (wherein, the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, the molar ratio of nickel nitrate to neodymium nitrate is 2:1, the mass of glucose is equal to the total mass of nickel nitrate and neodymium nitrate, the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and neodymium nitrate, and the volume ratio of nickel nitrate to the mixed solvent is 1g:10mL), and sonicate for 30 minutes to ensure thorough dispersion, thereby obtaining a mixed suspension; S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-neodymium alloy catalyst, denoted as Ni2Nd1@C-TiO2.

[0044] Example 4 A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, neodymium nitrate, glucose, and titanium dioxide powder in a mixed solvent of water and ethylene glycol (wherein, the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, the molar ratio of nickel nitrate to neodymium nitrate is 3:1, the mass of glucose is equal to the total mass of nickel nitrate and neodymium nitrate, the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and neodymium nitrate, and the volume ratio of nickel nitrate to the mixed solvent is 1g:10mL), and sonicate for 30 minutes to ensure thorough dispersion, thereby obtaining a mixed suspension; S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-neodymium alloy catalyst, denoted as Ni3Nd1@C-TiO2.

[0045] Example 5 A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, neodymium nitrate, glucose, and titanium dioxide powder in a mixed solvent of water and ethylene glycol (wherein, the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, the molar ratio of nickel nitrate to neodymium nitrate is 4:1, the mass of glucose is equal to the total mass of nickel nitrate and neodymium nitrate, the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and neodymium nitrate, and the volume ratio of nickel nitrate to the mixed solvent is 1g:10mL), and sonicate for 30 minutes to ensure thorough dispersion, thereby obtaining a mixed suspension; S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-neodymium alloy catalyst, denoted as Ni4Nd1@C-TiO2.

[0046] Example 6 Same as Example 1, except that the roasting temperature in step S4 is 450°C.

[0047] Example 7 Same as Example 1, except that the roasting temperature in step S4 is 500°C.

[0048] Example 8 Same as Example 1, except that the roasting temperature in step S4 is 600°C.

[0049] Example 9 Same as Example 1, except that the roasting temperature in step S4 is 650°C.

[0050] Comparative Example 1 A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, neodymium nitrate and glucose in a mixed solvent of water and ethylene glycol (wherein, the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, the molar ratio of nickel nitrate to neodymium nitrate is 1:1, the mass of glucose is equal to the total mass of nickel nitrate and neodymium nitrate, and the volume ratio of nickel nitrate to the mixed solvent is 1g:10mL), and sonicate for 30 minutes to ensure full dispersion, thereby obtaining a mixed suspension; S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell carbon-coated nickel-neodymium alloy catalyst, denoted as Ni1Nd1@C.

[0051] Comparative Example 2 A method for preparing a core-shell structured carbon-coated nickel catalyst, comprising the following steps: S1. Disperse nickel nitrate, glucose, and titanium dioxide powder in a mixed solvent of water and ethylene glycol (wherein, the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, the mass of glucose is equal to the mass of nickel nitrate, the mass of titanium dioxide powder is equal to the mass of nickel nitrate, and the volume ratio of nickel nitrate to the mixed solvent is 1:10), and sonicate for 30 minutes to ensure full dispersion, thereby obtaining a mixed suspension. S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel catalyst, denoted as Ni@C-TiO2.

[0052] Comparative Example 3 A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, neodymium nitrate, citric acid, and titanium dioxide powder in a mixed solvent of water and ethylene glycol (wherein, the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, the molar ratio of nickel nitrate to neodymium nitrate is 1:1, the mass of citric acid is equal to the total mass of nickel nitrate and neodymium nitrate, the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and neodymium nitrate, and the volume ratio of nickel nitrate to the mixed solvent is 1g:10mL), and sonicate for 30 minutes to ensure thorough dispersion, thereby obtaining a mixed suspension; S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell carbon-coated nickel-neodymium alloy catalyst, denoted as Ni1Nd1@C. N -TiO2.

[0053] Comparative Example 4 A method for preparing a core-shell structured carbon-coated nickel-bismuth alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, bismuth nitrate (Bi(NO3)3), glucose and titanium dioxide powder in a mixed solvent of water and ethylene glycol (wherein, the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, the molar ratio of nickel nitrate to bismuth nitrate is 1:1, the mass of glucose is equal to the total mass of nickel nitrate and bismuth nitrate, the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and bismuth nitrate, and the volume ratio of nickel nitrate to the mixed solvent is 1g:10mL), and sonicate for 30 minutes to ensure full dispersion, thereby obtaining a mixed suspension; S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-bismuth alloy catalyst, denoted as Ni1Bi1@C-TiO2.

[0054] Comparative Example 5 A method for preparing a core-shell structured carbon-coated nickel-cerium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, cerium nitrate (Ce(NO3)3), glucose and titanium dioxide powder in a mixed solvent of water and ethylene glycol (wherein, the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, the molar ratio of nickel nitrate to cerium nitrate is 1:1, the mass of glucose is equal to the total mass of nickel nitrate and cerium nitrate, the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and cerium nitrate, and the volume ratio of nickel nitrate to the mixed solvent is 1g:10mL), and sonicate for 30 minutes to ensure full dispersion, thereby obtaining a mixed suspension; S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-cerium alloy catalyst, denoted as Ni1Ce1@C-TiO2.

[0055] Comparative Example 6 A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, neodymium nitrate, glucose and titanium dioxide powder in water (wherein, the molar ratio of nickel nitrate to neodymium nitrate is 1:1, the mass of glucose is equal to the total mass of nickel nitrate and neodymium nitrate, the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and neodymium nitrate, and the volume ratio of nickel nitrate to water is 1g:10mL), and sonicate for 30 minutes to ensure full dispersion, thereby obtaining a mixed suspension; S2. Transfer the mixed suspension to a high-pressure reactor lined with polytetrafluoroethylene, seal it, and place it in an oven to react at 200°C for 12 hours; S3. After the reaction is complete and cooled to room temperature, the solid product is separated by centrifugation and washed repeatedly with deionized water and ethanol to remove impurities. Then, it is dried under vacuum at 80°C. S4. The dried powder was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-neodymium alloy catalyst, denoted as Ni1Nd1@C-TiO2-H2O.

[0056] Comparative Example 7 A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, glucose and titanium dioxide powder in a mixed solvent of water and ethylene glycol (wherein the volume ratio of water to ethylene glycol in the mixed solvent is 1:1, and the volume ratio of nickel nitrate to the mixed solvent is 1g:10mL), and stir to form a homogeneous solution; S2. Add neodymium nitrate to the homogeneous solution obtained in step S1 and stir at 30°C for 2 hours (wherein, the molar ratio of nickel nitrate to neodymium nitrate is 1:1, the mass of glucose is equal to the total mass of nickel nitrate and neodymium nitrate, and the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and neodymium nitrate), and dry to obtain the precursor; S3. The precursor was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-neodymium alloy catalyst, denoted as Ni1Nd1@C-TiO2-1.

[0057] Comparative Example 8 A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, citric acid and titanium dioxide powder in water (wherein the ratio of nickel nitrate to water is 1g:10mL), and stir to form a homogeneous solution; S2. Add neodymium nitrate to the homogeneous solution obtained in step S1 and stir at 30°C for 2 hours (wherein, the molar ratio of nickel nitrate to neodymium nitrate is 1:1, the mass of citric acid is equal to the total mass of nickel nitrate and neodymium nitrate, and the mass of titanium dioxide powder is equal to the total mass of nickel nitrate and neodymium nitrate), and dry to obtain the precursor; S3. The precursor was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-neodymium alloy catalyst, denoted as Ni1Nd1@C-TiO2-2.

[0058] Comparative Example 9 A method for preparing a core-shell structured carbon-coated nickel-bismuth alloy catalyst, comprising the following steps: S1. Disperse nickel nitrate, citric acid and titanium dioxide powder in water (wherein the ratio of nickel nitrate to water is 1g:10mL), and stir to form a homogeneous solution; S2. Add bismuth nitrate to the homogeneous solution obtained in step S1 and stir at 30°C for 2 hours (wherein, the molar ratio of nickel nitrate to bismuth nitrate is 1:1, the mass of citric acid is equal to 47.3% of the total mass of nickel nitrate and bismuth nitrate, and the mass of titanium dioxide powder is 29.4% of the total mass of nickel nitrate and bismuth nitrate), and dry to obtain the precursor; S3. The precursor was calcined at 550°C for 2 hours under a nitrogen atmosphere to obtain a core-shell structured carbon-coated nickel-bismuth alloy catalyst, denoted as Ni1Bi1@C-TiO2-1.

[0059] Test Example 1 Characterization data: Figure 1 The X-ray diffraction (XRD) spectra of the Ni1Nd1@C-TiO2 catalyst prepared in Example 1 and the Ni1Nd1@C catalyst prepared in Comparative Example 1 are shown. It can be seen that the catalyst prepared in Example 1 exhibits obvious titanium dioxide diffraction peaks in the XRD spectrum, with sharp peak shapes; while the diffraction peaks of elemental nickel have lower intensity and larger peak widths, indicating that the active metals nickel and neodymium are effectively loaded on the titanium dioxide support and exhibit good dispersion. In contrast, no characteristic titanium dioxide diffraction peaks were detected in the catalyst prepared in Comparative Example 1, and its elemental nickel diffraction peaks were sharp, indicating that the nickel species have a high degree of crystallinity and poor dispersion.

[0060] Figure 2 Here is a high-resolution transmission electron microscope (HRTEM) image of the Ni1Nd1@C-TiO2 catalyst prepared in Example 1. Figure 3The image shows a high-resolution transmission electron microscope (HRTEM) image of the Ni1Nd1@C catalyst prepared in Comparative Example 1. It can be seen that the Ni1Nd1@C-TiO2 catalyst exhibits a regular, near-ellipsoidal particle morphology (mainly formed by TiO2), with small carbon-coated NiNd alloy nanoparticles dispersed on its surface. These nanoparticles have clear boundaries and good dispersion, without obvious agglomeration or fusion. This indicates that the introduction of the TiO2 support provides sufficient anchoring sites for the carbon-coated NiNd alloy nanoparticles, effectively suppressing agglomeration and Ostwald ripening effects, thus maintaining a uniform particle size for the active components. Furthermore, the carbon shell structure on the NiNd alloy surface not only provides stable physical support but also further enhances the exposure of active sites by increasing the specific surface area. In contrast, the Ni1Nd1@C catalyst exhibits a clear agglomeration trend, with blurred particle boundaries and fusion forming irregular cluster structures. This phenomenon leads to uneven particle size distribution of the active components, with significant particle growth in localized areas. This aggregation significantly reduces the exposure rate of active sites, hindering contact between the reaction substrate and the active sites, thus adversely affecting catalytic efficiency.

[0061] Test Example 2 Catalytic performance test: The catalysts prepared in each example or comparative example were added to a 70 mL high-pressure reactor and co-catalyzed with a homogeneous base to produce higher alcohols via carbon-carbon coupling of ethanol. Specifically, 5 g of ethanol, 5 g of water, 0.88 g of sodium hydroxide, and 0.2 g of catalyst were mixed as the reaction system and placed in the high-pressure reactor. After verification of the seal, high-purity hydrogen was introduced to replace the air in the reaction system. The reaction was then carried out at 230 °C, an initial hydrogen pressure of 0.1 MPa, and a stirring rate of 1500 rpm for 6 hours. After the reaction, the reaction system was allowed to cool to room temperature, and the gas phase was collected using a gas bag. The liquid phase product was removed from the reactor. The liquid and solid phase catalysts were separated by centrifugation and filtration. After standing, the liquid phase naturally separated into an oil phase and an aqueous phase. The gas phase product, aqueous phase, and oil phase were qualitatively and quantitatively analyzed by gas chromatography. The results showed that the main product in the oil phase was C4+ higher alcohols, which were mainly composed of alcohols with 4 to 16 carbon atoms. Specific analytical results are shown in Table 1.

[0062] Table 1 Note: In the table, C-mol% refers to the percentage based on the number of moles of carbon atoms.

[0063] As shown in Table 1, by systematically adjusting key synthesis parameters such as the molar ratio of soluble nickel salts to neodymium salts and the carbonization temperature, the core-shell carbon-coated nickel-neodymium alloy catalysts prepared in Examples 1-9 exhibited good catalytic performance in the carbon-carbon coupling reaction of ethanol and can be used for the synthesis of higher alcohols. Among them, the catalyst prepared in Example 1 showed the best catalytic performance, with high levels of ethanol conversion, organic phase product yield, selectivity of C4+ higher alcohols in the liquid phase product, and C4+ higher alcohol yield. Compared with Example 1, Comparative Example 1, which did not introduce a titanium dioxide support, lacked effective structural support and a metal dispersion medium, resulting in significant aggregation of the active components nickel and neodymium in the carbon matrix. This led to significantly lower performance in several key indicators, specifically a 66.1% decrease in C4+ higher alcohol yield, a 20.9% decrease in ethanol conversion, and a 31.7% decrease in organic phase yield. Furthermore, compared to Example 1, Comparative Example 2 omitted the addition of neodymium metal; Comparative Example 3 replaced the carbon source with citric acid instead of glucose; Comparative Examples 4-5 replaced neodymium metal with other metal elements; Comparative Example 6 changed the solvent system; Comparative Example 7 changed the preparation method from hydrothermal reaction to impregnation; Comparative Example 8 replaced the carbon source with citric acid while adjusting the preparation method; and Comparative Example 9 replaced neodymium metal with other metal elements, replaced the carbon source with citric acid, and adjusted the preparation method and the amount of each component. The catalytic effect of Comparative Examples 1-9 was not as good as that of Example 1.

[0064] The reason why the catalytic performance of the catalyst decreased after replacing glucose with citric acid as the carbon source may be that glucose has stronger reducing properties and a milder carbonization process compared to citric acid. Glucose molecules are rich in hydroxyl groups, allowing for dehydration and polymerization reactions at lower temperatures, generating a reducing atmosphere that helps reduce metal ions to metals or alloys under relatively mild conditions. While citric acid also has reducing properties, its three carboxyl groups make it prone to intramolecular dehydration to form anhydrides when heated, potentially leading to a more vigorous reaction and greater challenges in controlling the size and morphology of metal particles. Secondly, glucose more readily forms a uniform and dense carbon coating layer. During pyrolysis, glucose undergoes melting, polymerization, and carbonization stages, a characteristic that facilitates the formation of a continuous and complete amorphous carbon layer on the surface of metal particles, effectively preventing core agglomeration. Citric acid, due to its molecular structure, tends to decompose more directly during carbonization, resulting in a thinner or less uniform carbon layer, making it more difficult to control the integrity and thickness of the coating.

[0065] Through microstructure analysis and catalytic performance evaluation, the core role of the TiO2 support in enhancing catalyst performance was clarified. The introduction of TiO2 not only provides a high specific surface area anchoring substrate for NiNd alloy nanoparticles, effectively inhibiting particle agglomeration and Ostwald ripening, and ensuring high dispersion and stability of active sites, but also regulates the electronic structure of the active components through strong metal-support interaction (SMSI), optimizing the adsorption and activation barriers of reaction intermediates. This synergistic effect of structure and electronic effects enables Ni1Nd1@C-TiO2 to exhibit superior activity, selectivity, and cycle stability in catalytic reactions, significantly outperforming Ni1Nd1@C samples without TiO2 support. In summary, the TiO2 support is not only the physical support for achieving efficient dispersion of active components, but also a key element in regulating the electronic effects at the catalyst interface and enhancing the catalytic process, providing important theoretical and experimental basis for designing high-performance supported alloy catalysts.

[0066] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a core-shell structured carbon-coated nickel-neodymium alloy catalyst, characterized in that, The process includes the following steps: dispersing soluble nickel salt, soluble neodymium salt, glucose and titanium dioxide in a mixed solvent of water and ethylene glycol, heating and reacting, and then calcining the product of the heated reaction to obtain the core-shell structured carbon-coated nickel-neodymium alloy catalyst.

2. The preparation method of the core-shell structured carbon-coated nickel-neodymium alloy catalyst as described in claim 1, characterized in that, The volume ratio of water to ethylene glycol is 1:

1.

3. The preparation method of the core-shell structured carbon-coated nickel-neodymium alloy catalyst as described in claim 1, characterized in that, The molar ratio of the soluble nickel salt to the soluble neodymium salt is 0.5-4:

1.

4. The preparation method of the core-shell structured carbon-coated nickel-neodymium alloy catalyst as described in claim 1, characterized in that, The mass of the glucose is equal to the total mass of the soluble nickel salt and the soluble neodymium salt.

5. The method for preparing the core-shell structured carbon-coated nickel-neodymium alloy catalyst as described in claim 1, characterized in that, The mass of the titanium dioxide is equal to the total mass of the soluble nickel salt and the soluble neodymium salt.

6. The method for preparing the core-shell structured carbon-coated nickel-neodymium alloy catalyst as described in claim 1, characterized in that, The heating reaction is carried out at a temperature of 200°C for 10-14 hours.

7. The method for preparing the core-shell structured carbon-coated nickel-neodymium alloy catalyst as described in claim 1, characterized in that, The roasting process is carried out at a temperature of 400-650℃ for 1-3 hours.

8. A core-shell structured carbon-coated nickel-neodymium alloy catalyst prepared by the method described in any one of claims 1-7.

9. The application of the core-shell structured carbon-coated nickel-neodymium alloy catalyst as described in claim 8 in the catalytic aqueous-phase synthesis of higher alcohols from ethanol.

10. The application of the core-shell structured carbon-coated nickel-neodymium alloy catalyst as described in claim 9 in the catalytic aqueous-phase synthesis of higher alcohols from ethanol, characterized in that, The steps for catalytic synthesis of higher alcohols from aqueous ethanol include: mixing ethanol, water, sodium hydroxide, and the core-shell structured carbon-coated nickel-neodymium alloy catalyst as described in claim 8 as a reaction system, heating under a hydrogen atmosphere to carry out a carbon-carbon coupling reaction, and then centrifuging to separate the aqueous phase and the oil phase, with the resulting oil phase being the higher alcohol.

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