Supported defective metal carbide for catalytic synthesis of ammonia and method of making same

Abstract

This invention relates to a supported defective metal carbide for catalytic ammonia synthesis and its preparation method. The chemical formula of the supported defective metal carbide of this invention is Tm / MeC. 2V Among them, Tm is a transition metal, and its mass fraction in metal carbides is 0.01–50.0 wt.%; Me includes any one of alkaline earth metals and rare earth metals; C 2V The carbon element contains defect sites. This invention relates to the supported defect metal carbide Tm / MeC. 2V Through large size C 2v Defects activate nitrogen, and transition metal Tm activates hydrogen, achieving synergistic catalysis between the supported metal and the catalyst, thereby improving the reactivity of ammonia synthesis. Furthermore, this invention utilizes transition metals and common alkaline earth metals in the ammonia synthesis catalyst, which is significant for controlling the cost of ammonia production and provides a universal method for using defect carbide support materials suitable for high-performance ammonia synthesis.

Description

Technical Field

[0001] This invention belongs to the field of ammonia synthesis catalyst technology, and relates to a supported defect metal carbide for catalytic ammonia synthesis and its preparation method. Background Technology

[0002] The importance of synthetic ammonia as a cornerstone of modern chemical industry is self-evident. It is not only a key raw material for nitrogen fertilizer production, playing a crucial supporting role in global agricultural production, but also widely used in the manufacture of explosives, dyes, plastics, and various chemical products. The invention and large-scale application of synthetic ammonia technology have greatly alleviated the pressure on global food supply and promoted a leap in agricultural output. Furthermore, with technological advancements, green and efficient production methods for synthetic ammonia are constantly being developed, which is of great significance for promoting sustainable development and reducing environmental pollution. In the context of energy transition, synthetic ammonia is also seen as a potential hydrogen energy carrier, providing new possibilities for the storage and transportation of clean energy. Therefore, synthetic ammonia is not only an indispensable part of traditional industry, but also a key element for future innovation and development in the energy and chemical industries, and its strategic position and economic value will continue to be prominent.

[0003] The catalysts commonly used in industrial ammonia synthesis are primarily multi-component catalysts based on Fe, also known as iron catalysts. Their main component is Fe3O4, and they often contain co-catalysts such as K2O, Al2O3, and CaO. Iron catalysts exhibit the highest activity at 500℃-600℃, which is one of the key reasons why ammonia synthesis reactions are generally carried out at high temperatures. Co-catalysts also play an important role in ammonia synthesis. For example, Al2O3 can form a specific crystal structure with iron oxide, enhancing the catalyst's stability; K2O helps increase the electron density of the active metal in the catalyst, thereby enhancing the activation and adsorption of nitrogen and improving catalyst activity.

[0004] Traditional iron-based catalysts primarily rely on iron sites to simultaneously activate N2 and H2, resulting in high reaction energy barriers and susceptibility to the influence of co-catalysts. Unlike traditional catalysts, defect supports (such as LaN containing N defects) effectively activate N2 through surface nitrogen vacancies (Vn), while supported metal sites are responsible for the dissociation of H2. This "dual active site" mechanism avoids the scaling limitations of traditional iron catalysts, significantly lowering the reaction energy barrier and improving catalytic activity.

[0005] Based on the concept of ammonia synthesis using defect supports, further improving the catalytic activity and reducing the conditions for ammonia synthesis by adjusting the defect structure, while optimizing the ammonia synthesis catalytic process, and obtaining ammonia synthesis catalyst materials with superior performance are problems that urgently need to be solved by those skilled in the art. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a supported defective metal carbide for catalytic ammonia synthesis and its preparation method. The supported defective metal carbide of this invention is Tm / MeC. 2V Through C 2v Defects activate nitrogen gas, and transition metal Tm activates hydrogen gas, achieving synergistic catalysis between the supported metal and the carrier, thereby improving the reactivity of ammonia synthesis. This invention provides a universal method for using defect carbide support materials suitable for high-performance ammonia synthesis.

[0007] The objective of this invention can be achieved through the following methods:

[0008] In a first aspect, the present invention provides a supported defective metal carbide for catalytic ammonia synthesis, the chemical formula of the supported defective metal carbide being Tm / MeC. 2V Among them, Tm is a transition metal, and its mass fraction in metal carbides is 0.01–50.0 wt.%; Me includes any one of alkaline earth metals and rare earth metals; C 2V It is a C element containing defect sites.

[0009] In this invention, if the mass fraction of Tm is too high, it will cover the defects on the MeC2 surface, leading to a decrease in the catalytic ammonia synthesis effect. Preferably, the mass fraction of Tm in the metal carbide is 1.00–20.0 wt.%.

[0010] As one embodiment of the present invention, the Tm element is any one of 3d transition metals, 4d transition metals, and 5d transition metals, including any one of Fe, Co, Ni, Ru, Rh, Pd, and Pt.

[0011] As one embodiment of the present invention, the Me element includes any one of La, Sc, Y, Ce, Ca, Sr, and Ba.

[0012] As one embodiment of the present invention, the C 2V It is obtained by heating carbon (C) in a hydrogen atmosphere.

[0013] Secondly, the present invention provides a method for preparing the supported defect metal carbide, comprising the following steps:

[0014] S1. Mix metal Me hydride or metal Me with carbon to obtain metal carbide powder MeC2;

[0015] S2. Mix metal Tm salt and metal carbide powder MeC2, and heat the mixture under an inert atmosphere to obtain transition metal supported metal carbide Tm / MeC2.

[0016] S3. In a hydrogen atmosphere, the transition metal-supported metal carbide Tm / MeC2 is heated to react, thus obtaining Tm / MeC 2V .

[0017] As one embodiment of the present invention, in step S1, the metal Me hydride includes any one of lanthanum hydride, scandium hydride, yttrium hydride, cerium hydride, calcium hydride, strontium hydride, and barium hydride; the metal Me includes any one of lanthanum metal, scandium metal, yttrium metal, cerium metal, calcium metal, strontium metal, and barium metal.

[0018] As one embodiment of the present invention, in step S1, the processing method includes any one of the physical solid-state method and the electric arc method.

[0019] Furthermore, the specific steps of the physical solid-state method include: mixing metal Me hydride and carbon powder in a molar ratio of 1:1-3 and pressing them into tablets for shaping; calcining them at 600-1000°C for 12-48 hours under an inert gas atmosphere to obtain metal carbide powder MeC2. Preferably, the molar ratio is 1:2.

[0020] Furthermore, the specific steps of the electric arc method include: arc fusing metal Me and carbon blocks at a molar ratio of 1:1-3, and grinding them to obtain metal carbide powder MeC2. A molar ratio of 1:2 is preferred.

[0021] As one embodiment of the present invention, in step S2, the metal Tm salt includes any one of nonacarbonyl diferric, octacarbonyl dicobalt, nickel dicerocene, ruthenium acetylacetonate (III), triruthenium dodecylcarbonyl, rhodium acetylacetonate (III), palladium diacetylacetonate, and platinum acetylacetonate.

[0022] In one embodiment of the present invention, in step S2, the temperature of the heating reaction is 100-600°C and the time is 1-12 hours.

[0023] In one embodiment of the present invention, in step S3, the heating reaction temperature is 200–600°C, and the time is 1–2 hours. If the temperature is too low, hydrogen cannot react with the lattice C of MeC2 to form surface carbon vacancies; while if the temperature is too high, exceeding the conventional reaction temperature, a hydride phase may form on the surface, making it impossible to obtain a structure with carbon vacancies. Furthermore, the present invention can only form vacancies by reacting hydrogen with the carbon on the surface of the metal carbide to produce gaseous hydrocarbons; if other methods are used, defect vacancies cannot be formed.

[0024] Thirdly, the present invention provides an application of the supported defective metal carbide in a chemical loop ammonia synthesis. In the chemical loop ammonia synthesis, N2 and H2 are supplied alternately.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention relates to supported defective metal carbides Tm / MeC 2V Through large size C 2v Defects activate nitrogen gas, and transition metal Tm activates hydrogen gas, achieving synergistic catalysis between the supported metal and the catalyst, thereby improving the reactivity of ammonia synthesis. Furthermore, this invention utilizes transition metals and common alkaline earth metals in the ammonia synthesis catalyst, which is of great significance for controlling the cost of ammonia production.

[0027] 2. This invention utilizes supported defective metal carbides in a chemical looping process (CLAS) to synthesize ammonia through alternating supply of N2 and H2. When N2 is introduced, the catalyst support MeC... 2v The C2 defect provides the optimal defect size for N2 adsorption and activation. When H2 is introduced, the transition metal sites activate H2, which then combines with the N2 adsorbed on the C2 defect via overflow, achieving synergistic and efficient ammonia synthesis. This invention avoids the thermodynamic equilibrium limitations caused by the simultaneous presence of N2 and H2 in conventional thermocatalysis. Furthermore, by alternately supplying N2 and H2, it regenerates large-sized C2 defect sites, solving the problem of insufficient N2 activation caused by the occupation of defect sites by nitrogen-hydrogen intermediates in conventional thermocatalysis, thus significantly improving the ammonia production rate.

[0028] 3. In the preparation method of this invention, metal carbide MeC2 is synthesized using a physical / chemical method, and then transition metal Tm is dispersed on a support to obtain supported metal carbide Tm / MeC2. Finally, hydrogen gas is used to react away the lattice carbon on the carbide surface, forming C2 defect sites (C2). 2V Ammonia is efficiently prepared by alternating the addition of N2 and H2 reaction gases through a chemical chain cycle process. Attached Figure Description

[0029] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0030] Figure 1 XRD patterns of MeC2 powder are shown below; where a is the XRD pattern of powdered BaC2 obtained in Example 1; b is the XRD pattern of powdered SrC2 obtained in Example 2; c is the XRD pattern of powdered CaC2 obtained in Example 3; d is the XRD pattern of powdered LaC2 obtained in Example 4; e is the XRD pattern of powdered CeC2 obtained in Example 5; and f is the XRD pattern of powdered YC2 obtained in Example 6.

[0031] Figure 2 Ni / MeC catalyst 2v SEM images and Ni particle distribution diagrams; where a represents the 10Ni / BaC obtained in Example 1. 2VSEM images and Ni particle distribution diagrams; b is the 10Ni / SrC obtained in Example 2. 2V SEM images and Ni particle distribution diagrams; c shows the 10Ni / CaC obtained in Example 3. 2V SEM images and Ni particle distribution diagrams; d represents the 10Ni / LaC obtained in Example 4. 2V SEM images and Ni particle distribution diagrams;

[0032] Figure 3 Nickel-supported alkaline earth metal carbides (Ni / BaC) 2V ) and nickel-loaded rare earth metal carbides (Ni / LaC 2V High-resolution transmission electron microscope image of Ni / BaC; where a is Ni / BaC 2V High-resolution transmission electron microscope image; b is Ni / LaC 2V High-resolution transmission electron microscope image;

[0033] Figure 4 The diagram shows the catalytic activity and activation energy of metal carbides with defective sites and metal oxides without defective sites in the CLAS process and conventional catalytic methods; where a represents Ni / BaC. 2V Graphs showing the catalytic activity and activation energy of Ni / BaO in the CLAS process and conventional catalytic methods; b represents the catalytic activity and activation energy of Ni / LaC. 2V Catalytic activity and activation energy diagrams compared to Ni / La2O3CLAS process and conventional catalytic methods. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0035] The chemical looping ammonia synthesis (CLAS) process utilizes alternating N2 and H2 supplies for ammonia synthesis. When N2 is introduced, the C2 defects in the catalyst support MeC2 provide the optimal defect size for N2 adsorption and activation. When H2 is introduced, the transition metal sites activate H2, which then combines with the N2 adsorbed on the C2 defects via overflow, achieving synergistic and efficient ammonia synthesis. The CLAS process avoids the thermodynamic equilibrium limitations caused by the simultaneous presence of N2 and H2 in conventional thermocatalysis. Furthermore, by alternating N2 and H2 supplies, it regenerates large-sized C2 defect sites, solving the problem of insufficient N2 activation due to the occupation of defect sites by nitrogen-hydrogen intermediates in conventional thermocatalysis, thus significantly improving the ammonia production rate.

[0036] Example 1

[0037] Example 1 prepared 10.0 wt.% Ni-supported defective barium carbide BaC 2V Material 10Ni / BaC 2V .

[0038] Step 1): Grind and mix 864.0 mg of barium hydride (BaH2) and 149.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800°C for 36 h under an inert gas atmosphere to obtain 1 g of barium carbide (BaC2) powder.

[0039] Step 2): 322.0 mg of nickel dicerocene and 1 g of barium carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under an argon atmosphere and held at that temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported barium carbide Ni / BaC2.

[0040] Step 3) The nickel-loaded barium carbide (Ni / BaC2) was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-loaded defective barium carbide material 10Ni / BaC2. 2V .

[0041] Example 2

[0042] Example 2 prepared 10.0 wt.% Ni-supported defective strontium carbide SrC. 2V Material 10Ni / SrC 2V .

[0043] Step 1): Grind and mix 803.0 mg of strontium hydride (SrH2) and 215.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800 °C for 36 h under an inert gas atmosphere to obtain 1 g of strontium carbide (SrC2) powder.

[0044] Step 2): 322.0 mg of nickel dicerocene and 1 g of strontium carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under an argon atmosphere and held at that temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported strontium carbide Ni / SrC2.

[0045] Step 3) The nickel-supported strontium carbide Ni / SrC2 was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-supported defective strontium carbide material 10Ni / SrC2. 2V .

[0046] Example 3

[0047] Example 3 prepared 10.0 wt.% Ni-supported defective calcium carbide (CaC). 2V Material 10Ni / CaC 2V .

[0048] Step 1): Grind and mix 657.0 mg of calcium hydride (CaH2) and 468.0 mg of carbon powder, compress and shape the mixture into tablets, and then calcine it at 750°C for 24 hours under an inert gas atmosphere to obtain 1 g of calcium carbide (CaC2) powder.

[0049] Step 2): 322.0 mg of nickel dicerocene and 1 g of calcium carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under an argon atmosphere and held at this temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported calcium carbide Ni / CaC2.

[0050] Step 3) The nickel-loaded calcium carbide (Ni / CaC2) was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-loaded defective calcium carbide material 10Ni / CaC2. 2V .

[0051] Example 4

[0052] Example 4 prepared 10.0 wt.% Ni-supported defective lanthanum carbide LaC 2V Material 10Ni / LaC 2V .

[0053] Step 1): 853.0 mg of bulk lanthanum La and 147.0 mg of carbon block were mixed and then melted using an electric arc melting method to obtain 1 g of bulk lanthanum carbide LaC2. The bulk LaC2 was then ground to obtain powdered lanthanum carbide LaC2.

[0054] Step 2): 322.0 mg of nickel dicerocene and 1 g of lanthanum carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under an argon atmosphere and held at this temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported lanthanum carbide Ni / LaC2.

[0055] Step 3) The nickel-supported lanthanum carbide Ni / LaC2 was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-supported defect lanthanum carbide material 10Ni / LaC2. 2V .

[0056] Example 5

[0057] Example 5 prepared 10.0 wt.% Ni-supported defective cerium carbide (CeC). 2V Material 10Ni / CeC 2V .

[0058] Step 1): 854.0 mg of bulk cerium metal Ce and 146.0 mg of carbon block were mixed and then melted by arc melting to obtain 1 g of bulk cerium carbide CeC2. The bulk CeC2 was then ground to obtain powdered cerium carbide CeC2.

[0059] Step 2): 322.0 mg of nickel dicerocene was mixed with 1 g of cerium carbide powder and ground evenly. The mixture was heated to 250 °C under an argon atmosphere and held at that temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported cerium carbide Ni / CeC2.

[0060] Step 3) The nickel-loaded cerium carbide (Ni / CeC2) was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-loaded defective cerium carbide material 10Ni / CeC2. 2V .

[0061] Example 6

[0062] Example 6 prepared 10.0 wt.% Ni-supported defective yttrium carbide (YC). 2V Material 10Ni / YC 2V .

[0063] Step 1): 787.0 mg of bulk yttrium Y and 213.0 mg of carbon block were mixed and then melted using an electric arc melting method to obtain 1 g of bulk yttrium carbide YC2. The bulk YC2 was then ground to obtain powdered yttrium carbide YC2.

[0064] Step 2): 322.0 mg of nickel dicerocene and 1 g of yttrium carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under an argon atmosphere and held at that temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported yttrium carbide Ni / YC2.

[0065] Step 3): The nickel-loaded yttrium carbide Ni / YC2 was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-loaded defect yttrium carbide material 10Ni / YC2. 2V .

[0066] Example 7

[0067] Example 7 prepared 10.0 wt.% Ni-supported defective scandium carbide ScC 2V Material 10Ni / ScC 2V .

[0068] Step 1): 652.0 mg of bulk scandium Sc and 348.0 mg of carbon block were mixed and then melted by arc melting to obtain 1 g of bulk scandium carbide ScC2. The bulk ScC2 was then ground to obtain powdered scandium carbide ScC2.

[0069] Step 2): 322.0 mg of nickel dicerocene and 1 g of scandium carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under an argon atmosphere and held at this temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported scandium carbide Ni / ScC2.

[0070] Step 3) The nickel-loaded scandium carbide Ni / ScC2 was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. Then it was cooled to room temperature to obtain the nickel-loaded defect scandium carbide material 10Ni / ScC2. 2V .

[0071] Example 8

[0072] Example 8 prepared 10.0 wt.% Co-supported defective barium carbide (BaC). 2V Material 10Co / BaC 2V .

[0073] Step 1): Grind and mix 864.0 mg of barium hydride (BaH2) and 149.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800°C for 36 h under an inert gas atmosphere to obtain 1 g of barium carbide (BaC2) powder.

[0074] Step 2): 290.0 mg of cobalt octacarbonyl dicobalt was mixed with 1 g of barium carbide powder and ground evenly. The mixture was heated to 250 °C under an argon atmosphere and held at that temperature for 2 h. Then it was cooled to room temperature to obtain cobalt-supported barium carbide Co / BaC2.

[0075] Step 3) The cobalt-supported barium carbide (Co / BaC2) was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the cobalt-supported defective barium carbide material 10Co / BaC2. 2V .

[0076] Example 9

[0077] Example 9 prepared 10.0 wt.% Fe-supported defective barium carbide BaC 2V Material 10Fe / BaC 2V .

[0078] Step 1): Grind and mix 864.0 mg of barium hydride (BaH2) and 149.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800°C for 36 h under an inert gas atmosphere to obtain 1 g of barium carbide (BaC2) powder.

[0079] Step 2): 351.0 mg of cobalt octacarbonyl was mixed with 1 g of barium carbide powder and ground evenly. The mixture was heated to 250 °C under an argon atmosphere and held at that temperature for 2 h. Then, it was cooled to room temperature to obtain iron-supported barium carbide Fe / BaC2.

[0080] Step 3) The iron-loaded barium carbide Fe / BaC2 was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the iron-loaded defective barium carbide material 10Fe / BaC2. 2V .

[0081] Example 10

[0082] Example 10 prepared 10.0 wt.% Ru-supported defective barium carbide BaC 2V Material 10Ru / BaC 2V .

[0083] Step 1): Grind and mix 864.0 mg of barium hydride (BaH2) and 149.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800°C for 36 h under an inert gas atmosphere to obtain 1 g of barium carbide (BaC2) powder.

[0084] Step 2): 394.0 mg of ruthenium acetylacetone (III) was mixed with 1 g of barium carbide powder and ground evenly. The mixture was heated to 250 °C under an argon atmosphere and held at that temperature for 2 h. Then it was cooled to room temperature to obtain ruthenium-supported barium carbide Ru / BaC2.

[0085] Step 3): The ruthenium-supported barium carbide Ru / BaC2 was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the ruthenium-supported defective barium carbide material 10Ru / BaC2. 2V .

[0086] Example 11

[0087] Example 11 prepared 10.0 wt.% Rh-supported defective barium carbide (BaC).2V Material 10Rh / BaC 2V .

[0088] Step 1): Grind and mix 864.0 mg of barium hydride (BaH2) and 149.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800°C for 36 hours under argon gas to obtain 1 g of barium carbide (BaC2) powder.

[0089] Step 2): 389.0 mg of rhodium(III) acetylacetone was mixed with 1 g of barium carbide powder and ground evenly. The mixture was heated to 250 °C under a hydrogen atmosphere and held at this temperature for 2 h. Then it was cooled to room temperature to obtain rhodium-supported barium carbide Rh / BaC2.

[0090] Step 3): The rhodium-loaded barium carbide (Rh / BaC2) was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the rhodium-loaded defective barium carbide material 10Rh / BaC2. 2V .

[0091] Example 12

[0092] Example 12 prepared 10.0 wt.% Pd-supported defective barium carbide (BaC). 2V Material 10Pd / BaC 2V .

[0093] Step 1): Grind and mix 864.0 mg of barium hydride (BaH2) and 149.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800°C for 36 hours under argon gas to obtain 1 g of barium carbide (BaC2) powder.

[0094] Step 2): 286.0 mg of palladium diacetylacetonate was mixed with 1 g of barium carbide powder and ground evenly. The mixture was heated to 250 °C under a hydrogen atmosphere and maintained at this temperature for 2 h. Then, it was cooled to room temperature to obtain palladium-supported barium carbide Pd / BaC2.

[0095] Step 3) The palladium-supported barium carbide Pd / BaC2 was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the palladium-supported defective barium carbide material 10Pd / BaC2. 2V .

[0096] Example 13

[0097] Example 13 prepared 20.0 wt.% Ni-supported defective barium carbide BaC 2V Material 20Ni / BaC 2V .

[0098] Step 1): Grind and mix 864.0 mg of barium hydride (BaH2) and 149.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800°C for 36 hours under argon gas to obtain 1 g of barium carbide (BaC2) powder.

[0099] Step 2): 644.0 mg of nickel dicerocene and 1 g of barium carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under a hydrogen atmosphere and held at this temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported barium carbide Ni / BaC2.

[0100] Step 3) The nickel-loaded barium carbide (Ni / BaC2) was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-loaded defective barium carbide material 20Ni / BaC2. 2V .

[0101] Example 14

[0102] Example 14 prepared 1.0 wt.% Ni-supported defective barium carbide BaC 2V Material 1Ni / BaC 2V .

[0103] Step 1): Grind and mix 864.0 mg of barium hydride (BaH2) and 149.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800°C for 36 hours under argon gas to obtain 1 g of barium carbide (BaC2) powder.

[0104] Step 2): 32.0 mg of nickel dicerocene and 1 g of barium carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under a hydrogen atmosphere and held at this temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported barium carbide Ni / BaC2.

[0105] Step 3) The nickel-loaded barium carbide (Ni / BaC2) was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-loaded defective barium carbide material 1Ni / BaC2. 2V .

[0106] Example 15

[0107] Example 15 prepared 5.0 wt.% Ni-supported defective barium carbide BaC 2V Material 5Ni / BaC 2V .

[0108] Step 1): Grind and mix 864.0 mg of barium hydride (BaH2) and 149.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800°C for 36 hours under argon gas to obtain 1 g of barium carbide (BaC2) powder.

[0109] Step 2): 161.0 mg of nickel dicerocene and 1 g of barium carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under a hydrogen atmosphere and held at this temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported barium carbide Ni / BaC2.

[0110] Step 3) The nickel-loaded barium carbide (Ni / BaC2) was heated to 400°C in a hydrogen atmosphere and held at that temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-loaded defective barium carbide material 5Ni / BaC2. 2V .

[0111] Example 16

[0112] Example 16 prepared 5.0 wt.% Ni-supported defective strontium carbide SrC. 2V Material 5Ni / SrC 2V .

[0113] Step 1): Grind and mix 803.0 mg of strontium hydride (SrH2) and 215.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800 °C for 36 h under argon gas to obtain 1 g of strontium carbide (SrC2) powder.

[0114] Step 2): 161.0 mg of nickel dicerocene and 1 g of strontium carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under a hydrogen atmosphere and held at this temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported strontium carbide Ni / SrC2.

[0115] Step 3) The nickel-loaded strontium carbide Ni / SrC2 was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-loaded defective strontium carbide material 5Ni / SrC2. 2V .

[0116] Example 17

[0117] Example 17 prepared 5.0 wt.% Ni-supported defective calcium carbide (CaC). 2V Material 5Ni / CaC 2V .

[0118] Step 1): Grind and mix 657.0 mg of calcium hydride (CaH2) and 468.0 mg of carbon powder, compress and shape them, and then calcine them at 750°C for 24 hours under argon gas to obtain 1 g of metal carbide calcium carbide (CaC2) powder.

[0119] Step 2): 161.0 mg of nickel dicerocene and 1 g of calcium carbide powder were mixed and ground evenly. The mixture was heated to 250 °C under a hydrogen atmosphere and maintained at this temperature for 2 h. Then it was cooled to room temperature to obtain nickel-supported calcium carbide Ni / CaC2.

[0120] Step 3) The nickel-loaded calcium carbide (Ni / CaC2) was heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It was then cooled to room temperature to obtain the nickel-loaded defective calcium carbide material 5Ni / CaC2. 2V .

[0121] Example 18

[0122] Example 18 prepared 10.0 wt.% Pt-supported defective barium carbide (BaC). 2V Material 10Pt / BaC 2V .

[0123] Step 1): Grind and mix 864.0 mg of barium hydride (BaH2) and 149.0 mg of carbon powder, compress and shape the mixture, and then calcine it at 800°C for 36 hours under argon gas to obtain 1 g of barium carbide (BaC2) powder.

[0124] Step 2): 201.6 mg of platinum acetylacetonate was mixed with 1 g of barium carbide powder and ground evenly. The mixture was heated to 250 °C under a hydrogen atmosphere and maintained at this temperature for 2 h. Then it was cooled to room temperature to obtain platinum-supported barium carbide Pt / BaC2.

[0125] Step 3): Platinum-supported barium carbide (Pt / BaC2) is heated to 400°C in a hydrogen atmosphere and held at this temperature for 2 hours. It is then cooled to room temperature to obtain platinum-supported defective barium carbide material 10Pt / BaC2. 2V .

[0126] Test Experiment

[0127] To test the feasibility of the MeC2 catalyst synthesis method, the MeC2 catalysts (BaC2, SrC2, CaC2, LaC2, CeC2, YC2) synthesized by the above-mentioned general method were characterized by XRD. Comparison with standard XRD cards confirmed the successful preparation of powdered MeC2 (e.g., BaC2, SrC2, CaC2, LaC2, CeC2, YC2). Figure 1 ).

[0128] To further observe the structural characteristics of the catalyst, the Ni / MeC catalyst was investigated. 2v SEM characterization revealed that Ni particles were uniformly dispersed and loaded onto MeC. 2v The above indicates that the Ni sites are similar in various catalysts (e.g., Figure 2 These catalysts have similar specific surface areas and particle sizes, so the differences in ammonia synthesis performance arise from the role of the carbide support rather than Ni sites.

[0129] To further observe the characteristics of catalyst defect sites, Ni / BaC 2V With Ni / LaC2V High-resolution transmission electron microscopy (TEM) tests were performed on Ni / BaC. 2V ( Figure 3 a)With Ni / LaC 2V ( Figure 3 In b), the original crystal structure of Ba and La atoms relative to the top left corner diagram shows obvious lattice distortion. This is because the formation of C2 defects affects the ordered arrangement of metal atoms.

[0130] To further investigate C in carbide supports 2v The effect of defects in the ammonia synthesis reaction was investigated in the CLAS process at 400 °C and 0.1 MPa, where nickel-supported alkaline earth metal carbides (Ni / BaC) containing defect sites were used. 2V ) and metal oxides without defect sites (Ni / BaO), nickel-supported rare earth metal carbides (Ni / LaC) 2V Compared to metal oxides (Ni / La2O3) that do not contain defect sites, such as... Figure 4 It is known that metal oxides Ni / BaO and Ni / La2O3, which do not contain defect sites, have almost no catalytic activity, while metal carbides Ni / BaC, which contain defect sites, have much less catalytic activity. 2V and Ni / LaC 2V All exhibited high catalytic activity, even reaching 10.1 mmol·g. -1 .h -1 The instruction manual states that the presence of C2 defect vacancies can improve the efficiency of ammonia synthesis.

[0131] To further investigate the differences between the catalyst in the CLAS process and conventional catalytic methods, nickel-supported alkaline earth metal carbides (Ni / BaC) were tested. 2V ) and rare earth metal carbides (Ni / LaC) 2V The reaction rate and activation energy of the reaction are shown in the following figures. Figure 4 As shown, the reaction rate of the CLAS process (alternating hydrogen and nitrogen supply) differs significantly from that of the traditional catalytic method (simultaneous hydrogen and nitrogen supply). The Ni / BaC ratio in the CLAS process... 2V and Ni / LaC 2V Compared to traditional catalytic methods, the ammonia synthesis performance was improved by more than four times, indicating that separate feeding of N2 and H2 is beneficial to ammonia formation. (Regarding Ni / BaC...) 2V Activation energy tests were conducted on the CLAS process and conventional catalytic methods to compare the Ni / BaC ratio in the CLAS process. 2V The activation energy is 27.5 kJ·mol⁻¹. -1 The Ni / BaC ratio is much lower than that in traditional catalytic processes. 2V Activation energy (100.7 kJ·mol⁻¹) -1 ). For Ni / LaC2V Activation energies of the CLAS process and conventional catalytic methods were tested, and the Ni / LaC ratio of the CLAS process was measured. 2V The apparent activation energy (Ea) of the catalyst is as low as 25.6 kJ·mol⁻¹. -1 Compared to traditional catalytic processes, Ni / LaC 2V Apparent activation energy of catalyst (56.2 kJ·mol⁻¹) -1 ) decreased by 54.4% (e.g. Figure 4 The decrease in Ea value during the CLAS process can be attributed to the presence of C2 defect vacancies. These large vacancies promote the adsorption and activation of N2. Combined with the alternating gas supply method of chemical looping, N2 molecules are first adsorbed and activated, and then hydrogenated at both ends of the molecule to form ammonia, which greatly increases the ammonia synthesis rate.

[0132] Ni / LaC 2V The catalyst activity reached 10.1 mmol·g. -1 .h -1 It exceeds the performance of existing catalytic ammonia synthesis methods (such as...). Figure 4 These findings highlight the role of surface vacancies in the CLAS reaction cycle, providing a new catalyst design scheme for efficient ammonia synthesis through the synergistic effect of support vacancies and transition metals.

[0133] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A supported defect metal carbide for catalytic ammonia synthesis, characterized in that, The chemical formula of the supported defective metal carbide is Tm / MeC. 2V Among them, Tm is a transition metal, and the mass fraction of Tm in the metal carbide is 0.01–50.0 wt.%; Me includes any one of the alkaline earth metals and rare earth metals; C 2V It is a C element containing defect sites.

2. The supported defect metal carbide according to claim 1, characterized in that, The Tm element includes any one of Fe, Co, Ni, Ru, Rh, Pd, and Pt; the Me element includes any one of La, Sc, Y, Ce, Ca, Sr, and Ba.

3. The supported defect metal carbide according to claim 1, characterized in that, The C 2V It is obtained by heating carbon (C) in a hydrogen atmosphere.

4. A method for preparing a supported defective metal carbide as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Mix metal Me hydride or metal Me with carbon to obtain metal carbide powder MeC2; S2. Mix metal Tm salt and metal carbide powder MeC2, and heat the mixture under an inert atmosphere to obtain transition metal supported metal carbide Tm / MeC2. S3. In a hydrogen atmosphere, the transition metal-supported metal carbide Tm / MeC2 is heated to react, thus obtaining Tm / MeC 2V .

5. The preparation method according to claim 4, characterized in that, In step S1, the metal Me hydride includes any one of lanthanum hydride, scandium hydride, yttrium hydride, cerium hydride, calcium hydride, strontium hydride, and barium hydride; the metal Me includes any one of lanthanum metal, scandium metal, yttrium metal, cerium metal, calcium metal, strontium metal, and barium metal.

6. The preparation method according to claim 4, characterized in that, In step S1, the processing method includes either the physical solid-state method or the electric arc method; The specific steps of the physical solid-state method include: mixing metal Me hydride and carbon powder in a molar ratio of 1:1-3 and pressing them into tablets for shaping; calcining them at 600-1000℃ for 12-48 hours under an inert gas to obtain metal carbide powder MeC2. The specific steps of the electric arc method include: electric arc fusing metal Me and carbon blocks at a molar ratio of 1:1-3, followed by grinding to obtain metal carbide powder MeC2.

7. The preparation method according to claim 4, characterized in that, In step S2, the metal Tm salt includes any one of nonacarbonyl diferric, octacarbonyl dicobalt, nickel dicerocene, ruthenium acetylacetonate (III), triruthenium dodecylcarbonyl, rhodium acetylacetonate (III), palladium diacetylacetonate, and platinum acetylacetonate.

8. The preparation method according to claim 4, characterized in that, In step S2, the heating reaction is carried out at a temperature of 100–600°C for 1–12 hours.

9. The preparation method according to claim 4, characterized in that, In step S3, the heating reaction is carried out at a temperature of 200–600°C for 1–2 hours.

10. The application of a supported defective metal carbide as described in any one of claims 1-3, or a supported defective metal carbide obtained by the preparation method as described in any one of claims 4-9, in chemical looping synthesis of ammonia.

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