A local core-shell island structure aluminum nitride-based catalyst, a preparation method and application thereof
By forming a local core-shell island structure on an aluminum nitride support, the problem of easy sintering and carbon deposition of Ni-based catalysts in high-temperature DRM reactions has been solved, achieving high thermal conductivity and stability, improving catalyst activity and heat transfer efficiency, and making it suitable for large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GAOLU AIR PROD & CHEM (SHANGHAI) ENERGY TECH
- Filing Date
- 2024-03-04
- Publication Date
- 2026-06-16
AI Technical Summary
Existing Ni-based catalysts are prone to sintering and carbon deposition in high-temperature DRM reactions, leading to decreased thermal conductivity and catalyst deactivation, resulting in low heat transfer efficiency. Furthermore, existing improved catalysts suffer from problems such as low thermal utilization efficiency or high cost.
An aluminum nitride-based catalyst with a local core-shell island structure is used. By forming a localized metal oxide shell on the aluminum nitride support to cover the metal active component, the sintering of the metal is inhibited and the high thermal conductivity of the aluminum nitride support is maintained. The catalyst structure includes a core of metal active component and a shell of metal oxide.
It achieves high thermal conductivity, stability, and anti-coking properties, improves catalyst activity and heat transfer efficiency, reduces catalyst coking, and is suitable for large-scale production.
Smart Images
Figure CN118002183B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst preparation, and particularly relates to an aluminum nitride-based catalyst with a localized core-shell island structure, its preparation method, and its application. Background Technology
[0002] Carbon capture, utilization, and storage (CCUS) technology is one of the few solutions for addressing heavy industrial emissions and removing carbon from the atmosphere. Dry methane reforming (DRM) simultaneously converts CO2 and CH4 into valuable syngas (H2 + CO), in which additional CO2 is also eliminated. However, the highly endothermic nature of the DRM reaction necessitates that metal nanoparticles possess high thermal conductivity, mechanical strength, and sintering resistance for high-temperature operation (>700°C).
[0003] The anti-carbon deposition ability of Ni-based catalysts is usually studied from two directions: (1) the dynamic balance strategy of carbon deposition-carbon elimination; (2) the formation and growth mechanism of carbon species, i.e., the modulation of the surface geometry and electronic structure of Ni particles. A large number of studies have shown that reducing the size of Ni particles is a very effective way to achieve this mechanism. Carbon deposition must be formed on a relatively large metallic Ni surface. However, under the high-temperature reaction conditions of the DRM process, smaller Ni nanoparticles are very prone to migration, aggregation and Ostwald ripening, sintering to form larger Ni particles, which aggravates carbon deposition on the catalyst. Current research has found that Ni-based aluminum nitride catalysts can stabilize Ni nanoparticles at a smaller size through an alumina layer at high temperatures. However, oxidation of the aluminum nitride surface will cause oxygen to dissolve into the AlN lattice to form aluminum vacancy defects, which will lead to increased phonon scattering, reduced mean free path, and decreased thermal conductivity, thereby hindering the temperature distribution of the bed.
[0004] Extremely non-uniform temperature distribution fields accelerate carbon formation in nickel-based catalysts. Carbon deposition reduces activity and damages catalyst geometry. While some novel catalysts have been developed to improve heat transfer efficiency, they still suffer from problems such as low thermal efficiency, low durability, or high cost. Therefore, it is essential to develop a DRM catalyst with a site-fixed core-shell island structure that combines high thermal conductivity, high activity, and structural stability. Summary of the Invention
[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an aluminum nitride-based catalyst with a localized core-shell island structure and high thermal conductivity, its preparation method, and its application. The aluminum nitride-based catalyst forms a core-shell structure only around the active metal; the surface without the active metal has no alumina layer and remains an aluminum nitride surface. This locally localized core-shell island structure in the aluminum nitride-based catalyst solves the problems of active metal sintering and carbon deposition in traditional supported oxide catalysts, as well as the problem of decreased thermal conductivity of the aluminum nitride support due to the alumina shell. To achieve the above and other related objectives, this invention is implemented through the following technical solution:
[0006] The first aspect of the present invention provides an aluminum nitride-based catalyst with a localized core-shell island structure. The catalyst includes an aluminum nitride support and a plurality of core-shell island structures distributed on the aluminum nitride support, wherein the plurality of core-shell island structures do not completely cover the surface of the aluminum nitride support; the core-shell island structure includes a core and a shell layer covering the core; the core is a metal active component and the shell layer is a metal oxide.
[0007] In existing technologies, to stabilize the metal component nanoparticles at a small size, the metal oxide almost completely or even completely coats the surface of the aluminum nitride support, which reduces the thermal conductivity and hinders the temperature distribution of the bed. The catalyst structure of this application forms a shell-island structure locally on the aluminum nitride support. By coating the metal component particles with metal oxide at specific points, the sintering of the active metal component particles is inhibited, while the remaining surface of the aluminum nitride support provides efficient heat conduction, achieving high thermal efficiency, high stability, and resistance to carbon deposition.
[0008] In some preferred embodiments, the active metal component is selected from one or more combinations of nickel, cobalt, iron, rhodium, copper, and manganese. Preferably, the active metal component is selected from nickel or cobalt.
[0009] Specifically, the active metal components are derived from metal salt solutions, such as nickel chloride hexahydrate, cobalt chloride hexahydrate, ferric chloride hexahydrate, rhodium chloride hexahydrate, copper chloride dihydrate, and manganese chloride tetrahydrate.
[0010] In some preferred embodiments, the active metal component accounts for 0.2–5 wt.% of the total catalyst mass. Maintaining this proportion of the active metal component ensures the catalytic performance of the catalyst. The proportion of the active metal component in the total catalyst mass can be 0.2–0.5 wt.%, 0.5–1 wt.%, 1–1.5 wt.%, 1.5–2.5 wt.%, 2.5–3.5 wt.%, 3.5–4.5 wt.%, or 4.5–5 wt.%.
[0011] In some preferred embodiments, the particle size of the metal active component is 5–30 nm. Maintaining a small particle size ensures catalytic performance and reduces the likelihood of catalyst carbon deposition. The particle size of the metal active component can be 5–10 nm, 10–15 nm, 15–20 nm, 20–25 nm, or 25–30 nm.
[0012] In some preferred embodiments, the dispersion of the metal active component in the catalyst is 5–10%, for example 5–8% or 8–10%, determined using conventional methods, such as hydrogen pulse characterization. The metal oxide layer coats only the exterior of the metal active component, ensuring the metal nanoparticles remain stable at a small size. Meanwhile, the surface of the aluminum nitride support, without the metal active component, remains exposed to maintain efficient thermal conductivity, thereby achieving high thermal efficiency, high stability, and resistance to carbon deposition in the catalyst.
[0013] A second aspect of this invention provides a method for preparing an aluminum nitride-based catalyst with a locally core-shell island structure, comprising the following steps:
[0014] 1) Provide aluminum nitride powder and prepare an aluminum nitride carrier;
[0015] Specifically, the aluminum nitride powder has a particle size of 40–1000 nm and can be purchased directly from the market. The particle size can be selected from 40–100 nm, 100–200 nm, 200–300 nm, 300–500 nm, 500–700 nm or 700–1000 nm.
[0016] More specifically, aluminum nitride powder is treated at 100–200°C for 1–5 hours to obtain an aluminum nitride carrier. The treatment temperature can be 100–120°C, 120–140°C, 140–160°C, or 160–200°C. The treatment time can be 1–2 hours, 2–3 hours, 3–4 hours, or 4–5 hours.
[0017] 2) Provide a metal salt solution of the metal active component, and add the metal salt solution to the aluminum nitride support in step 1) to obtain precursor A;
[0018] Specifically, the metal salt solution is selected from one or more combinations of nickel chloride hexahydrate, cobalt chloride hexahydrate, ferric chloride hexahydrate, rhodium chloride hexahydrate, copper chloride dihydrate, and manganese chloride tetrahydrate. Preferably, the metal salt solution is selected from nickel chloride hexahydrate, cobalt chloride hexahydrate, ferric chloride hexahydrate, or rhodium chloride hexahydrate.
[0019] More specifically, the mass concentration of the metal salt solution is 0.01–0.2 g / ml. Maintaining a reasonable metal salt solution concentration ensures the structure and performance of the core-shell island aluminum nitride-based catalyst. The mass concentration of the metal salt solution can be 0.01–0.05 g / ml, 0.05–0.1 g / ml, 0.1–0.15 g / ml, or 0.15–0.2 g / ml.
[0020] More specifically, the method of adding the metal salt solution to the aluminum nitride carrier is to use an equal-volume impregnation method, which involves slowly dripping the metal salt solution into the aluminum nitride carrier until it is saturated.
[0021] More specifically, after the metal salt solution is added to the aluminum nitride support in step 1), it is dried at 110–140°C for 1–3 hours to obtain precursor A. Drying may be omitted, or it may be dried at 110–140°C for less than 1 hour, with specific temperatures including 110–120°C, 120–130°C, or 130–140°C.
[0022] 3) Calcine precursor A from step 2) to obtain precursor B;
[0023] Specifically, the calcination is carried out under an inert gas atmosphere. Preferably, the inert gas is selected from at least one of Ar, N2, or He.
[0024] More specifically, the maximum roasting temperature is 350–550℃, which can be 350–400℃, 400–450℃, 450–500℃, or 500–550℃.
[0025] More specifically, the roasting is maintained at the highest temperature for 1 to 5 hours, which can be 1 to 2 hours, 2 to 3 hours, 3 to 4 hours, or 4 to 5 hours.
[0026] More specifically, the calcination adopts a gradient heating method with a heating rate of 2 to 10 °C / min. The heating rate can be 2 to 3 °C / min, 3 to 5 °C / min, 5 to 8 °C / min, or 8 to 10 °C / min.
[0027] It is worth noting that, through experiments conducted by the inventors, direct treatment of the aluminum nitride support with a metal chloride solution resulted in a site-specific core-shell island structure on the aluminum nitride surface induced by the chloride crystal water. Specifically, during catalyst calcination, the chloride crystal water is difficult to decompose, leading to the formation of metal chloride complexes, which in turn form localized Al₂O₃ shell islands around the metal. Ultimately, an alumina protective layer forms only on the exterior of the metal active component supported on the aluminum nitride support. The calcination temperature and time have a significant impact on the formation of the catalyst structure. Using the above-described implementation scheme, a core-shell island structured aluminum nitride-based catalyst with excellent catalytic performance can be prepared.
[0028] 4) Reduce precursor B from step 3) to obtain a locally core-shell island structured aluminum nitride-based catalyst.
[0029] Specifically, the reduction is carried out under a mixture of hydrogen and nitrogen; preferably, the volume of hydrogen accounts for 5 to 20% of the mixture, which can be 5 to 10%, 10 to 15%, or 15 to 20%.
[0030] More specifically, the reduction temperature is 600–800℃, which can be 600–700℃ or 700–800℃.
[0031] More specifically, the restoration time is 0.5 to 2 hours, which can be 0.5 to 1 hour, 1 to 1.5 hours, or 1.5 to 2 hours.
[0032] It is worth noting that the reduction is optimal under the conditions described above, but conventional catalyst precursor reduction methods can also be used as a reference.
[0033] The third aspect of this invention provides the application of the catalyst of the first aspect or the catalyst prepared by the preparation method of the second aspect in the reforming reaction of methane and carbon dioxide.
[0034] The fourth aspect of the present invention provides a method for preparing syngas by reforming methane and carbon dioxide. The method includes: carrying out the reaction of methane and carbon dioxide in the presence of a catalyst prepared by the first aspect or the preparation method of the second aspect.
[0035] Specifically, the molar ratio of methane to carbon dioxide is (0.5–2):1, which can be adjusted according to the syngas requirements.
[0036] More specifically, the reaction temperature is 600–950°C, for example, 600–700°C, 700–800°C, or 800–950°C.
[0037] More specifically, the reaction pressure is 0–30 bar, for example, 0 bar, 0–10 bar, 10–20 bar, or 20–30 bar.
[0038] More specifically, the reaction time is 100–1000 h, for example 100–200 h, 200–300 h, 300–400 h, 400–500 h, 500–600 h, 600–800 h, or 800–1000 h.
[0039] The present invention has, but is not limited to, the following technical effects:
[0040] 1) The catalyst structure of the present invention forms a shell island structure locally on the aluminum nitride support. The active metal component particles are inhibited by coating the metal component particles with metal oxides at specific points. The remaining surface of the aluminum nitride support provides efficient heat conduction, thereby achieving high heat utilization, high stability and anti-carbon deposition performance.
[0041] 2) This invention has fewer synthesis steps and less industrial wastewater pollution, and can be produced and used on a large scale.
[0042] 3) The invention uses the crystal water of metal salt to induce local hydrolysis on the surface of aluminum nitride to prepare a site-defined core-shell aluminum nitride-based catalyst, thereby achieving complete utilization of the metal salt solution. Attached Figure Description
[0043] Figure 1 This is a transmission electron microscope image of the core-shell island aluminum nitride-based catalyst obtained in Example 3 before the reaction.
[0044] Figure 2 The particle size distribution of the core-shell island aluminum nitride-based catalyst obtained in Example 3 before and after the reaction is shown.
[0045] Figure 3 This is a schematic diagram of heat transfer in the existing technology and the core-shell island aluminum nitride-based catalyst obtained in this application.
[0046] Figure 4 The diagram shows the reaction activity of the core-shell island aluminum nitride-based catalyst obtained in Example 3.
[0047] Figure 5 In-situ thermogravimetric analysis was performed during the calcination of the aluminum nitride-based catalyst and the core-shell island aluminum nitride-based catalyst obtained in Examples 2 and 3, respectively.
[0048] Figure 6 The image shows the bed distribution during the reaction of the core-shell island aluminum nitride-based catalyst obtained in Example 3. Detailed Implementation
[0049] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0050] 【Example 1】
[0051] The structure of the core-shell island structured aluminum nitride-based catalyst in this example can be found in [reference needed]. Figure 1 Electron microscope images or see Figure 3 A schematic diagram.
[0052] Specifically, the catalyst includes an aluminum nitride support and a plurality of core-shell island structures distributed on the aluminum nitride support, wherein the plurality of core-shell island structures do not completely cover the surface of the aluminum nitride support. Each core-shell island structure includes a core and a shell covering the core, wherein the core is a metallic active component and the shell is aluminum oxide.
[0053] by Figure 3 The schematic diagram is used as an example to illustrate the heat transfer between the existing alumina fully coated aluminum nitride support and the core-shell island structure aluminum nitride-based catalyst of this application.
[0054] See Figure 3 The left figure shows that in existing nickel-based aluminum nitride catalysts, the alumina layer is obtained through water treatment, resulting in an alumina layer that covers the entire surface of the aluminum nitride. Because the alumina layer encapsulates the surface, oxygen dissolves into the aluminum nitride lattice, forming aluminum vacancy defects. This leads to increased phonon scattering, a decreased mean free path, and a consequent decrease in thermal conductivity, thus hindering the temperature distribution of the bed. In contrast, the core-shell island structure aluminum nitride-based catalyst of this application forms an alumina layer only on the exterior of the supported metal active component (specifically, by using a metal salt solution to achieve localized induction, thereby forming a localized core-shell island structure on the aluminum nitride support). See also... Figure 3 As shown in the right figure, the alumina layer on the outside of the metal active component provides thermal protection, making it less likely for the metal active component to be sintered and agglomerated, thereby reducing carbon deposition on the catalyst. The aluminum nitride support portion without the metal active component has no alumina layer, thus not affecting the thermal conductivity of the aluminum nitride support.
[0055] 【Example 2】
[0056] 1) Weigh 10g of activated aluminum nitride fine powder with an average particle size of approximately 500nm, and dry it at 120℃ for 3h to obtain an aluminum nitride support; 2) Weigh 10g of nickel nitrate hexahydrate and add 100ml of water to prepare a metal salt solution. Then, using an equal-volume impregnation method, slowly drip the metal salt solution into the aluminum nitride support, stir thoroughly until the powder is saturated with adsorption, and dry at 130℃ for 2h to obtain precursor A; 3) Under a N2 atmosphere, heat to 400℃ at a rate of 5℃ / min and hold at that temperature for 2h to obtain precursor B; 4) Reduce precursor B at 700℃ for 1h under a mixed atmosphere of hydrogen (10v%) and nitrogen (90v%) to obtain a core-shell island aluminum nitride-based catalyst. Characterization tests using hydrogen pulses revealed that the dispersion of active metal Ni was 5%.
[0057] The catalytic activity of the above catalyst was tested: 100 mg of catalyst was placed in a fixed-bed quartz tube reactor for catalyst performance testing. The molar ratio of CH4 to CO2 was 1:1. The catalyst reaction temperature was 800℃ and the reaction was carried out under normal pressure. After 50 h of reaction, the conversion rates of CH4 and CO2 remained at 80% and 82%, respectively. The catalyst activity decreased significantly, a large amount of carbon deposits were formed, and the Ni particles grew to a large extent.
[0058] 【Example 3】
[0059] 1) Weigh 10g of activated aluminum nitride fine powder with an average particle size of 500nm and dry it at 120℃ for 3h to obtain an aluminum nitride support; 2) Weigh 10g of nickel chloride hexahydrate and add 100ml of water to prepare a metal salt solution. Then, using an equal-volume impregnation method, slowly drip the metal salt solution into the aluminum nitride support, stir thoroughly until the powder is saturated with adsorption, and dry at 130℃ for 3h to obtain precursor A; 3) Under N2 atmosphere, heat to 400℃ at a heating rate of 5℃ / min and hold at that temperature for 2h to obtain precursor B; 4) Reduce precursor B at 700℃ for 1h under a mixed atmosphere of hydrogen (10v%) and nitrogen (90v%) to obtain a core-shell island aluminum nitride-based catalyst. Characterization by hydrogen pulse testing revealed that the dispersion of active metal Ni was 9%.
[0060] See Figure 1 Transmission electron microscopy image before catalyst reaction: core-shell islands coated with alumina are uniformly distributed on aluminum nitride support. The particle size of Ni is about 12 nm and the thickness of the alumina shell is about 2 nm.
[0061] The catalytic activity of the above catalyst was tested as follows: 100 mg of catalyst was placed in a fixed-bed quartz tube reactor for catalyst performance testing. The molar ratio of CH4 to CO2 was 1:1. The catalyst reaction was carried out at 800℃ and atmospheric pressure (1 bar) for 100 h. (See reference...) Figure 4 The conversion rates of CH4 and CO2 remained at 85% and 90%, respectively. The catalyst activity was stable, with no carbon deposits and almost no growth in Ni particle size.
[0062] See Figure 2 The prepared core-shell island aluminum nitride-based catalyst had a particle size of approximately 10.5 nm, and the particle size after the catalytic reaction was approximately 11.17 nm. From... Figure 2 The particle size distribution before and after the reaction shows that the Ni particles hardly grew.
[0063] from Figure 5 It can be seen that during catalyst calcination, equimolar amounts of nickel nitrate hexahydrate and nickel chloride hexahydrate decompose at different rates. Because the water of crystallization of nickel chloride is difficult to decompose, it forms a nickel chloride complex, which in turn creates localized core-shell islands around the nickel.
[0064] from Figure 6 It was found that after the nickel metal was supported by the self-hydrolysis of the crystal water of the nickel chloride precursor, a core-shell island catalyst was formed. The bed temperature distribution of the catalyst was consistent with that of pure aluminum nitride without nickel metal support, indicating that the heat transfer performance of the catalyst was almost completely consistent with that of pure aluminum nitride, without any loss.
[0065] 【Example 4】
[0066] 1) Weigh 10g of activated aluminum nitride fine powder with an average particle size of 500nm and dry it at 120℃ for 3h to obtain an aluminum nitride support; 2) Weigh 10g of nickel chloride hexahydrate and add 100ml of water to prepare a metal salt solution. Then, using an equal-volume impregnation method, slowly drip the metal salt solution into the aluminum nitride support, stir thoroughly until the powder is saturated with adsorption, and dry at 110℃ for 3h to obtain precursor A; 3) Under N2 atmosphere, heat to 550℃ at a rate of 5℃ / min and hold at that temperature for 2h to obtain precursor B. Then, reduce precursor B at 700℃ for 1h under a mixed atmosphere of hydrogen (10v%) and nitrogen (90v%) to obtain a core-shell island aluminum nitride-based catalyst. Characterization tests using hydrogen pulses showed that the dispersion of active metal Ni was 9%.
[0067] The catalytic activity of the above catalyst was tested: 100 mg of catalyst was placed in a fixed-bed quartz tube reactor for catalyst performance testing. The molar ratio of CH4 to CO2 was 1:1. The catalyst reaction temperature was 800℃ and the reaction was carried out under normal pressure. After 100 h of reaction, the conversion rates of CH4 and CO2 remained at 80% and 84%, respectively. The catalyst activity was stable, no carbon deposits were formed, and the Ni particle size hardly increased.
[0068] 【Example 5】
[0069] 1) Weigh 10g of activated aluminum nitride fine powder with an average particle size of 800nm and dry it at 120℃ for 3h to obtain an aluminum nitride support; 2) Weigh 10g of cobalt chloride hexahydrate and add 100ml of water to prepare a metal salt solution. Then, using an equal-volume impregnation method, slowly drop the metal salt solution into the aluminum nitride support, stir thoroughly until the powder is saturated with adsorption, and dry at 140℃ for 1h to obtain precursor A; 3) Under N2 atmosphere, heat to 400℃ at a heating rate of 5℃ / min and hold at that temperature for 2h to obtain precursor B; 4) Reduce precursor B at 700℃ for 1h under a mixed atmosphere of hydrogen (10v%) and nitrogen (90v%) to obtain a core-shell island aluminum nitride-based catalyst. Characterization by hydrogen pulse testing revealed that the dispersion of the active metal Co was 8%.
[0070] The catalytic activity of the above catalyst was tested: 100 mg of catalyst was placed in a fixed-bed quartz tube reactor for catalyst performance testing. The CH4 and CO2 injection ratio was 1:1. The catalyst reaction temperature was 800℃ and the reaction was carried out under normal pressure. After 100 h of reaction, the conversion rates of CH4 and CO2 remained at 82% and 88%, respectively. The catalyst activity was stable, no carbon deposits were formed, and the Co particle size hardly increased.
[0071] 【Example 6】
[0072] 1) Weigh 10g of activated aluminum nitride fine powder with an average particle size of 100nm and dry it at 120℃ for 3h to obtain an aluminum nitride support; 2) Weigh 1g of rhodium chloride hexahydrate and add 100ml of water to prepare a metal salt solution. Then, using an equal-volume impregnation method, slowly drip the metal salt solution into the aluminum nitride support, stir thoroughly until the powder is saturated with adsorption, and dry at 130℃ for 2h to obtain precursor A; 3) Under N2 atmosphere, heat to 400℃ at a rate of 5℃ / min and hold at that temperature for 2h to obtain precursor B. Then, reduce precursor B at 700℃ for 1h under a mixed atmosphere of hydrogen (10v%) and nitrogen (90v%) to obtain a core-shell island aluminum nitride-based catalyst. Characterization by hydrogen pulse testing showed that the active rhodium dispersion was 10%. The catalytic activity of the above catalyst was tested: 100 mg of catalyst was placed in a fixed-bed quartz tube reactor for catalyst performance testing. The molar ratio of CH4 to CO2 was 1:1. The catalyst reaction temperature was 800℃ and the reaction was carried out under normal pressure. After 100 h of reaction, the conversion rates of CH4 and CO2 remained at 92% and 95%, respectively. The catalyst activity was stable, no carbon deposits were formed, and the Ru particle size hardly increased.
[0073] 【Example 7】
[0074] 1) Weigh 10g of activated aluminum nitride fine powder with an average particle size of 50nm and dry it at 120℃ for 3h to obtain an aluminum nitride support; 2) Weigh 10g of nickel chloride hexahydrate and add 100ml of water to prepare a metal salt solution. Then, using an equal-volume impregnation method, slowly drip the metal salt solution into the aluminum nitride support, stir thoroughly until the powder is saturated with adsorption, and dry at 130℃ for 2h to obtain precursor A; 3) Under N2 atmosphere, heat to 400℃ at a rate of 5℃ / min and hold at that temperature for 2h to obtain precursor B. Then, reduce precursor B at 700℃ for 1h under a mixed atmosphere of hydrogen (10v%) and nitrogen (90v%) to obtain a core-shell island aluminum nitride-based catalyst. Characterization by hydrogen pulse testing showed that the active metal dispersion was 9%.
[0075] The catalytic activity of the above catalyst was tested: 100 mg of catalyst was placed in a fixed-bed quartz tube reactor for catalyst performance testing. The molar ratio of CH4 to CO2 was 1:1. The catalyst reaction was carried out at 800℃ and 5 bar. After 100 h of reaction, the conversion rates of CH4 and CO2 remained at 65% and 70%, respectively. The catalyst activity was stable, no carbon deposits were formed, and the Ni particle size hardly increased.
[0076] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. The application of a locally core-shell island structured aluminum nitride-based catalyst in the reforming reaction of methane and carbon dioxide, characterized in that, The catalyst includes an aluminum nitride support and a plurality of core-shell island structures distributed on the aluminum nitride support, wherein the plurality of core-shell island structures do not completely cover the surface of the aluminum nitride support. The core-shell island structure includes a core and a shell covering the core; the core is a metallic active component, and the shell is aluminum oxide; The active metal component is selected from one or more combinations of nickel, cobalt, iron, rhodium, copper, and manganese; The active metal component accounts for 0.2~5 wt.% of the total mass of the catalyst.
2. The application of the aluminum nitride-based catalyst with a localized core-shell island structure according to claim 1 in the reforming reaction of methane and carbon dioxide, characterized in that, Includes at least one of the following technical features: a) The particle size of the metal active component is 5~30 nm; b) The dispersion of the metal active component in the catalyst is 5-10%.
3. The application of the aluminum nitride-based catalyst with a localized core-shell island structure according to claim 1 or 2 in the reforming reaction of methane and carbon dioxide, characterized in that, The preparation method of aluminum nitride-based catalysts with localized core-shell island structures includes the following steps: 1) Provide aluminum nitride powder and prepare an aluminum nitride carrier; 2) Provide a metal salt solution of the metal active component, and add the metal salt solution to the aluminum nitride support in step 1) to obtain precursor A; 3) Calcining precursor A from step 2) yields precursor B; 4) Reduce precursor B from step 3) to obtain a locally core-shell island structured aluminum nitride-based catalyst.
4. The application of the aluminum nitride-based catalyst with a localized core-shell island structure according to claim 3 in the reforming reaction of methane and carbon dioxide, characterized in that, Step 1) includes at least one of the following technical features: 1a) The particle size of aluminum nitride powder is 40 ~ 1000 nm; 1b) Aluminum nitride powder is treated at 100~200℃ for 1~5h to obtain aluminum nitride carrier.
5. The application of the aluminum nitride-based catalyst with a localized core-shell island structure according to claim 3 in the reforming reaction of methane and carbon dioxide, characterized in that, Step 2) includes at least one of the following technical features: 2a) The metal salt solution is selected from one or more of nickel chloride hexahydrate, cobalt chloride hexahydrate, ferric chloride hexahydrate, rhodium chloride hexahydrate, copper chloride dihydrate, and manganese chloride tetrahydrate; 2b) The mass concentration of the metal salt solution is 0.01~0.2 g / ml; 2c) The method of adding metal salt solution to aluminum nitride carrier is to use an equal-volume impregnation method; 2d) After the metal salt solution is added to the aluminum nitride support in step 1), it is dried at 110~140℃ for 1~3h to obtain precursor A.
6. The application of the aluminum nitride-based catalyst with a localized core-shell island structure according to claim 3 in the reforming reaction of methane and carbon dioxide, characterized in that, Step 3) includes at least one of the following technical features: 3a) Calcination is carried out under an inert gas atmosphere; the inert gas is selected from at least one of Ar, N2 or He; 3b) The maximum calcination temperature is 350~550℃, and the calcination is maintained at the maximum temperature for 1~5 hours; 3c) The calcination adopts a gradient heating method with a heating rate of 2~10 ℃ / min.
7. The application of the locally core-shell island structured aluminum nitride-based catalyst according to claim 3 in the reforming reaction of methane and carbon dioxide, characterized in that, Step 4) includes at least one of the following technical features: 4a) The reduction is carried out in a mixture of hydrogen and nitrogen; the volume of hydrogen accounts for 5-20% of the mixture. 4b) The reduction temperature is 600~800℃; 4c) The reduction time is 0.5~2h.
8. A method for preparing syngas by reforming methane and carbon dioxide, characterized in that, The method includes reacting methane and carbon dioxide in the presence of a catalyst; The catalyst includes an aluminum nitride support and a plurality of core-shell island structures distributed on the aluminum nitride support, wherein the plurality of core-shell island structures do not completely cover the surface of the aluminum nitride support. The core-shell island structure includes a core and a shell covering the core; the core is a metallic active component, and the shell is aluminum oxide; The active metal component is selected from one or more combinations of nickel, cobalt, iron, rhodium, copper, and manganese; The active metal component accounts for 0.2~5 wt.% of the total mass of the catalyst.
9. The method according to claim 8, characterized in that, Includes at least one of the following technical features: A) The molar ratio of methane to carbon dioxide is (0.5~2):1 B) The reaction temperature is 600~950℃; C) The reaction pressure is 0~30 bar; D) The reaction time is 100~1000h.