A nickel-nickel aluminum spinel-calcium hexaluminate composite catalyst, a preparation method and application thereof

Abstract

The application provides a nickel-nickel aluminum spinel-calcium hexaluminate composite catalyst and a preparation method and application thereof, and belongs to the technical field of catalytic dry reforming of methane to prepare synthesis gas. The nickel-nickel aluminum spinel-calcium hexaluminate composite catalyst is prepared by adopting a metal salt and organic matter mixed combustion-reduction method, the obtained composite catalyst has a stable layered microstructure, can effectively control nickel in the subsurface layer of the catalyst, makes the metal nickel and the carrier have a strong interaction, and can effectively inhibit the migration and sintering of the metal nickel under high temperature conditions; and the existence of the nickel-nickel aluminum spinel-calcium hexaluminate composite structure in the catalyst can effectively inhibit the generation of carbon deposition, and well plays the catalytic effect. The nickel-nickel aluminum spinel-calcium hexaluminate composite catalyst provided by the application has strong thermal stability and catalytic stability in the high-temperature catalytic dry reforming process of methane, and has good mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of methane catalytic dry reforming for syngas production, and particularly to a nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst, its preparation method, and its application. Background Technology

[0002] Natural gas is not only a power source but also an important chemical feedstock. Using natural gas as a feedstock to produce methanol, formaldehyde, ethylene, hydrogen, and syngas is a crucial pathway for large-scale natural gas chemical production. Natural gas is primarily composed of alkanes, with methane making up a significant portion. Methane catalytic reforming for syngas production mainly includes technologies such as methane steam reforming, methane partial oxidation reforming, and methane carbon dioxide reforming (dry methane reforming). Dry methane reforming can simultaneously convert both methane and carbon dioxide, two greenhouse gases, which helps mitigate the greenhouse effect and reduce air pollution. The carbon monoxide-rich syngas produced by dry methane reforming is suitable as a feedstock for carbonyl synthesis and Fischer-Tropsch synthesis to prepare oxygen-containing compounds such as higher alcohols, facilitating the clean recycling of carbon resources.

[0003] Nickel-based catalysts are considered promising industrial catalysts for methane dry reforming due to their high activity and low cost. Since methane dry reforming is an endothermic reaction, the catalyst needs to operate above 700°C to achieve a considerable conversion rate. The main drawback of nickel-based catalysts is that the active nickel metal is prone to deactivation due to carbon deposition and sintering at high temperatures, leading to a decrease in activity and stability. Carbon deposition is mainly caused by carbon species generated from methane cracking or carbon monoxide dismutation covering the active sites; sintering occurs because the reaction temperature is higher than the Taman temperature of nickel metal, which easily migrates and aggregates at high temperatures, resulting in increased particle size and reduced activity. Current strategies for preparing catalysts with high resistance to carbon deposition and sintering mainly include: utilizing metal-support interactions, utilizing the support structure to "confine" the nickel metal, utilizing oxygen vacancies on the support for carbon removal, and using transition metal or noble metal promoters.

[0004] In recent years, many studies have focused on how to construct nickel-based catalysts with resistance to carbon deposition and sintering at low and high temperatures. Supported catalysts are relatively easy to prepare, and nickel-based catalysts with Al-based supports typically exhibit high initial methane dry reforming activity. However, due to the instability of the support structure and the susceptibility to phase transformation during the reaction, weak interactions lead to deactivation of the catalyst due to carbon deposition and sintering, resulting in a decrease in the number of active sites on the catalyst surface. Therefore, the reaction stability still needs improvement. Summary of the Invention

[0005] In view of this, the present invention aims to provide a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst, its preparation method, and its application. The nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst provided by the present invention exhibits high activity, strong resistance to carbon deposition and sintering, and can efficiently catalyze the dry reforming reaction of methane at high temperatures.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst, comprising the following steps:

[0008] Nickel salt metal precursor, aluminum salt metal precursor, calcium salt metal precursor and organic fuel are mixed to obtain a mixed precursor;

[0009] The mixture precursor was dried and calcined sequentially to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor;

[0010] The nickel-aluminum spinel-calcium hexaaluminate composite precursor was placed in a flowing hydrogen atmosphere and subjected to a reduction reaction to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst.

[0011] Preferably, the mixing method is mixing in a solvent or grinding.

[0012] The solvent is water and / or ethanol;

[0013] The grinding and mixing process is performed by manual grinding or ball mill grinding.

[0014] Preferably, in the mixed precursor, the molar ratio of nickel, aluminum and calcium is 0.2-0.8:12.4-13.6:1.

[0015] Preferably, the organic fuel is one or more of alanine, urea, citric acid, maleic hydrazine, and carbazide;

[0016] The ratio of the amount of the organic fuel to the amount of all metal salt precursors is 1 to 5:1.

[0017] Preferably, the drying temperature is 60–150°C, and the holding time is 0.5–3 hours.

[0018] The roasting temperature is 200–800℃, and the time is 1–12 hours.

[0019] Preferably, the hydrogen flow rate is 10–50 mL / min;

[0020] The reduction reaction is carried out at a temperature of 700–950°C for 1–5 hours.

[0021] This invention provides a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst prepared by the above-described method, wherein the phases of the nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst include Ni, NiAl2O4, and CaAl. 12 O 19 The Ni phase exists in elemental form, and the particle size of the Ni particles is preferably 5–20 nm.

[0022] Preferably, in the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst, nickel accounts for 3 to 10% of the total mass of nickel, aluminum, and calcium.

[0023] This invention provides the application of the above-mentioned nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst in the catalytic dry reforming reaction of methane.

[0024] This invention provides a method for catalytic dry reforming of methane, comprising the following steps:

[0025] Methane and carbon dioxide are continuously fed into a reactor containing the nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst to carry out a dry reforming reaction of methane, yielding product gases carbon monoxide and hydrogen.

[0026] This invention provides a method for preparing a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst, comprising the following steps: mixing a nickel salt metal precursor, an aluminum salt metal precursor, a calcium salt metal precursor, and an organic fuel to obtain a mixed precursor; sequentially drying and calcining the mixed precursor to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor; and placing the nickel-aluminum spinel-calcium hexaaluminate composite precursor in a flowing hydrogen atmosphere to carry out a reduction reaction to obtain the nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst. This invention employs a combustion-reduction method involving a mixture of metal salts and organic matter to prepare a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst. The resulting composite catalyst possesses a stable layered microstructure, effectively controlling the nickel content to be in the subsurface layer of the catalyst. This allows for a strong interaction between metallic nickel and the nickel-aluminum spinel-calcium hexaaluminate composite support, effectively inhibiting the migration and sintering of metallic nickel under high-temperature conditions. Furthermore, the presence of the nickel-nickel-aluminum spinel-calcium hexaaluminate composite structure in the catalyst effectively suppresses carbon deposition, maximizing its catalytic effect. The nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst provided by this invention exhibits strong thermal and chemical stability during high-temperature catalytic dry reforming of methane, maintaining stable operation for over 1000 hours. Its long catalytic lifespan during high-temperature dry reforming of methane effectively inhibits the sintering of metallic nickel and catalyst carbon deposition, demonstrating high activity and stability. The results of the examples show that the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst obtained in this invention has high catalytic activity and stability at a high temperature of 800℃, and its methane conversion rate is 88.3-95.2% and carbon dioxide conversion rate is 82.8-93.1% after 50h.

[0027] Meanwhile, the preparation method provided by this invention is relatively simple and fast, and the raw materials used in the preparation process are readily available and inexpensive, making it easy to achieve industrial-scale mass production. Attached Figure Description

[0028] Figure 1 XRD diagrams of nickel-aluminum spinel-calcium hexaaluminate composite precursors with different nickel contents;

[0029] Figure 2 This is a high-resolution transmission HRTEM image of the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst in Example 1;

[0030] Figure 3 This is a high-resolution transmission HRTEM image of the nickel-nickel-aluminum spinel-alumina composite catalyst in Comparative Example 1.

[0031] Figure 4 The graph shows the stability test results of the catalyst in Example 2 for methane dry reforming catalysis at 800°C.

[0032] Figure 5 The graph shows the stability test results of the catalyst in Example 3 for methane dry reforming catalysis at 800°C.

[0033] Figure 6 The thermogravimetric curve of Example 3 after 300 hours of stability evaluation;

[0034] Figure 7 The image shows the XRD pattern of Comparative Example 3 after calcination. Detailed Implementation

[0035] This invention provides a method for preparing a nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst, comprising the following steps:

[0036] Nickel salt metal precursor, aluminum salt metal precursor, calcium salt metal precursor and organic fuel are mixed to obtain a mixed precursor;

[0037] The mixture precursor was dried and calcined sequentially to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor;

[0038] The nickel-aluminum spinel-calcium hexaaluminate composite precursor was placed in a flowing hydrogen atmosphere and subjected to a reduction reaction to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst.

[0039] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0040] This invention mixes a nickel salt metal precursor, an aluminum salt metal precursor, a calcium salt metal precursor, and an organic fuel to obtain a mixed precursor. In this invention, the nickel salt metal precursor is one or more of nickel chloride, nickel nitrate, and nickel sulfate; the aluminum salt metal precursor is preferably one or more of aluminum isopropoxide, aluminum nitrate, aluminum chloride, and aluminum sulfate; and the calcium salt metal precursor is preferably one or more of calcium nitrate, calcium chloride, and calcium sulfate.

[0041] In this invention, the molar ratio of nickel, aluminum, and calcium elements in the nickel salt metal precursor, aluminum salt metal precursor, and calcium salt metal precursor is preferably x:12+2x:1, where x = 0.2 to 0.8, and more preferably 0.4 to 0.6; that is, the molar ratio of nickel, aluminum, and calcium elements is preferably 0.2 to 0.8:12.4 to 13.6:1, and more preferably 0.4 to 0.6:12.8 to 13.2:1.

[0042] In this invention, the organic fuel is preferably one or more of alanine, urea, citric acid, maleic hydrazine, and carbamate; the molar ratio of the organic fuel to all metal salt precursors is preferably 1–5:1, more preferably 2–4:1. In this invention, the organic fuel serves to achieve uniform intermolecular mixing of the organic fuel and the metal salt precursor, enabling an internally propagating combustion reaction during combustion, promoting phase transformation, and thereby obtaining the target oxide.

[0043] In this invention, the mixing method is preferably mixing in a solvent, or grinding mixing. When the mixing is in a solvent, the mixing specifically involves mixing a nickel salt metal precursor, an aluminum salt metal precursor, a calcium salt metal precursor, an organic fuel, and a solvent. In this invention, the solvent is preferably water and / or ethanol, the water is preferably deionized water, and the ethanol is preferably anhydrous ethanol. In this invention, the mixing time in the solvent is preferably 30 min to 2 h, more preferably 1 to 1.5 h.

[0044] When the mixing is a grinding mixture, the grinding mixture is preferably manual grinding or ball mill grinding. In this invention, the manual grinding time is preferably 30 min to 60 min; in this invention, when ball mill grinding is performed, the ball mill speed is preferably 500 to 2000 rpm, and the time is preferably 1 to 3 h.

[0045] After obtaining the mixture precursor, the present invention sequentially dries and calcines the mixture precursor to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor. In the present invention, the drying is preferably carried out in an oven. In the present invention, the drying temperature is preferably 60–150°C, more preferably 80–120°C; the holding time is preferably 0.5–3 h, more preferably 1–2 h.

[0046] In this invention, the dried product is preferably placed in a crucible and then transferred to a preheated muffle furnace for calcination. In this invention, the calcination atmosphere is preferably air.

[0047] In this invention, the calcination temperature is preferably 200–800°C, more preferably 500–600°C; the calcination time is preferably 1–12 h, more preferably 3–10 h, and even more preferably 5–8 h. In this invention, during the calcination process, the metal is converted into metal oxide, nitrate ions are converted into NO2 gas, chloride ions are converted into Cl2, and sulfate ions are converted into SO2, thereby being removed from the precursor.

[0048] After obtaining the nickel-aluminum spinel-calcium hexaaluminate composite precursor, the present invention places the nickel-aluminum spinel-calcium hexaaluminate composite precursor in a flowing hydrogen atmosphere for a reduction reaction to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst. In the present invention, the flow rate of the hydrogen is preferably 10–50 mL / min, more preferably 20–40 mL / min; the temperature of the reduction reaction is preferably 700–950℃, more preferably 800–900℃, and the duration of the reduction reaction is 1–5 h, more preferably 2–4 h. In the present invention, during the reduction process, the nickel-aluminum spinel in the nickel-aluminum spinel-calcium hexaaluminate composite precursor gradually generates Ni particles during the hydrogen reduction process.

[0049] This invention provides a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst prepared by the above-described method, wherein the phases of the nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst include Ni, NiAl2O4, and CaAl. 12 O 19 .

[0050] In this invention, the Ni phase exists in the form of elemental particles, and the particle size of the Ni particles is preferably 5 to 20 nm.

[0051] In this invention, the nickel element in the nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst preferably accounts for 3-10% of the total mass of nickel, aluminum, and calcium, more preferably 5-8%, that is, Ni / (Ni+Al+Ca) is preferably 3-10%, more preferably 5-8%. The nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst prepared by this invention has a stable layered microstructure, which can effectively control the nickel to be located in the subsurface layer of the catalyst.

[0052] This invention provides the application of the above-mentioned nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst in the catalytic dry reforming reaction of methane.

[0053] This invention provides a method for catalytic dry reforming of methane, comprising the following steps:

[0054] Methane and carbon dioxide are continuously fed into a reactor containing the reduction catalyst to carry out a dry reforming reaction of methane, yielding product gases carbon monoxide and hydrogen.

[0055] In this invention, the volume ratio of methane to carbon dioxide is preferably 1:1; in this invention, the space velocity of the methane and carbon dioxide mixture is 15,000 to 60,000 h⁻¹. -1 More preferably 25,000 to 40,000 hours -1 In this invention, the temperature of the methane dry reforming reaction is preferably 750-850°C, more preferably 800°C.

[0056] The following detailed description, in conjunction with embodiments, illustrates the nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst, its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of this invention.

[0057] Example 1

[0058] The preparation method of the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst adopts the following steps:

[0059] (1) Dissolve 0.116g nickel nitrate, 5.067g aluminum isopropoxide, 0.472g calcium nitrate and 1.632g urea in 20mL deionized water and stir for 30min.

[0060] (2) Dry the metal salt-urea mixture precursor in an oven at 120°C for 3 hours.

[0061] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 700°C for 2 hours to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor with Ni / (Ni+Al+Ca)=3wt%.

[0062] (4) The above nickel-aluminum spinel-calcium hexaaluminate composite precursor was reduced in hydrogen at 900℃ for 1h at a flow rate of 20mL / min to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst with Ni / (Ni+Al+Ca)=3wt%.

[0063] Example 2

[0064] The preparation method of the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst adopts the following steps:

[0065] (1) Dissolve 0.421g nickel sulfate, 10.204g aluminum nitrate, 0.472g calcium nitrate and 29.585g citric acid in 20mL anhydrous ethanol and stir for 1h.

[0066] (2) The metal salt-citric acid mixture precursor was dried in an oven at 60°C for 0.5 h.

[0067] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 500°C for 6 hours to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor with Ni / (Ni+Al+Ca)=10wt%.

[0068] (4) The above nickel-aluminum spinel-calcium hexaaluminate composite precursor was reduced in hydrogen at 950℃ for 2h at a flow rate of 10mL / min to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst with Ni / (Ni+Al+Ca)=10wt%.

[0069] Example 3

[0070] The preparation method of the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst adopts the following steps:

[0071] (1) Mix 0.201g nickel chloride, 6.201g aluminum chloride, 0.438g calcium chloride, 5.084g alanine and 5.135g urea in a ball mill at 2000rpm for 1h.

[0072] (2) The metal salt-alanine-urea mixture precursor was dried in an oven at 150°C for 2 hours.

[0073] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 200°C for calcination for 12 hours to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor with Ni / (Ni+Al+Ca)=6wt%.

[0074] (4) The above nickel-aluminum spinel-calcium hexaaluminate composite precursor was reduced in hydrogen at 700℃ for 5h at a flow rate of 50mL / min to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst with Ni / (Ni+Al+Ca)=6wt%.

[0075] Example 4

[0076] The preparation method of the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst adopts the following steps:

[0077] (1) Dissolve 0.341g nickel nitrate, 9.648g aluminum sulfate, 0.472g calcium nitrate and 7.976g carbazide in 20mL of deionized water and stir for 1.5h.

[0078] (2) Dry the metal salt-carbon hydrazine mixture precursor in an oven at 100°C for 3 hours.

[0079] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 800°C for 1 hour to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor with Ni / (Ni+Al+Ca)=8wt%.

[0080] (4) The above nickel-aluminum spinel-calcium hexaaluminate composite precursor was reduced in hydrogen at 800℃ for 3h at a flow rate of 40mL / min to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst with Ni / (Ni+Al+Ca)=8wt%.

[0081] Example 5

[0082] The preparation method of the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst adopts the following steps:

[0083] (1) Grind 0.199g nickel nitrate, 5.246g aluminum isopropoxide, 0.258g calcium chloride and 8.56g urea manually in a mortar for 1 hour.

[0084] (2) Dry the metal salt-urea mixture precursor in an oven at 130°C for 1 hour.

[0085] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 600°C for 4 hours to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor with Ni / (Ni+Al+Ca)=6wt%.

[0086] (4) The above nickel-aluminum spinel-calcium hexaaluminate composite precursor was reduced in hydrogen at 750°C for 4 h at a flow rate of 30 mL / min to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst with Ni / (Ni+Al+Ca)=6wt%.

[0087] Example 6

[0088] The preparation method of the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst adopts the following steps:

[0089] (1) Dissolve 0.616g nickel sulfate, 19.296g aluminum sulfate, 0.876g calcium chloride and 13.71g maleic hydrazine in 20mL of deionized water and stir for 1h.

[0090] (2) Dry the metal salt-maleic hydrazine mixture precursor in an oven at 120°C for 3 hours.

[0091] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 800°C for 10 h to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor with Ni / (Ni+Al+Ca)=8wt%.

[0092] (4) The above nickel-aluminum spinel-calcium hexaaluminate composite precursor was reduced in hydrogen at 850℃ for 1 h at a flow rate of 40 mL / min to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst with Ni / (Ni+Al+Ca)=8wt%.

[0093] Example 7

[0094] (1) Grind 0.160g nickel nitrate, 9.192g aluminum nitrate, 0.472g calcium nitrate and 15.938g citric acid manually for 30 minutes.

[0095] (2) Dry the metal salt-citric acid mixture precursor in an oven at 100°C for 2 hours.

[0096] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 500°C for 8 hours to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor with Ni / (Ni+Al+Ca)=4wt%.

[0097] (4) The above nickel-aluminum spinel-calcium hexaaluminate composite precursor was reduced in hydrogen at 900℃ for 1.5h at a flow rate of 20mL / min to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst with Ni / (Ni+Al+Ca)=4wt%.

[0098] Example 8

[0099] (1) Stir 0.181g nickel nitrate, 9.519g aluminum nitrate, 0.472g calcium nitrate and 3.368g urea in a ball mill at 500rpm for 3h.

[0100] (2) The metal salt-citric acid mixture precursor was dried in an oven at 130°C for 1.5 h.

[0101] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 300°C for 8 hours to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor with Ni / (Ni+Al+Ca)=5wt%.

[0102] (4) The above nickel-aluminum spinel-calcium hexaaluminate composite precursor was reduced in hydrogen at 900℃ for 2h at a flow rate of 25mL / min to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst with Ni / (Ni+Al+Ca)=5wt%.

[0103] Comparative Example 1

[0104] The preparation method of the nickel-nickel-aluminum spinel-alumina composite catalyst is basically similar to that in Example 1, except that:

[0105] (1) Dissolve 0.085g nickel nitrate, 5.049g aluminum isopropoxide and 1.473g urea in 20mL deionized water and stir for 30 minutes.

[0106] (2) Dry the metal salt-urea mixture precursor in an oven at 120°C for 3 hours.

[0107] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 700°C for 2 hours to obtain a nickel-aluminum spinel-alumina composite precursor with Ni / (Ni+Al)=3wt%.

[0108] (4) The above nickel-aluminum spinel-alumina composite precursor was reduced in hydrogen at 900℃ for 1h at a flow rate of 20mL / min to obtain a nickel-nickel-aluminum spinel-alumina composite catalyst with Ni / (Ni+Al)=3wt%.

[0109] Comparative Example 2

[0110] The preparation method of the nickel-nickel-aluminum spinel-alumina composite catalyst is basically similar to that in Example 2, except that:

[0111] (1) Dissolve 0.378g nickel sulfate, 10.253g aluminum nitrate and 28.285g citric acid in 20mL anhydrous ethanol and stir for 1h.

[0112] (2) The metal salt-citric acid mixture precursor was dried in an oven at 60°C for 0.5 h.

[0113] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 500°C for 6 hours to obtain a nickel-aluminum spinel-alumina composite precursor with Ni / (Ni+Al)=10wt%.

[0114] (4) The above nickel-aluminum spinel-alumina composite precursor was reduced in hydrogen at 950°C for 2 h at a flow rate of 10 mL / min to obtain a nickel-nickel-aluminum spinel-alumina composite catalyst with Ni / (Ni+Al)=10wt%.

[0115] Comparative Example 3

[0116] The preparation method of the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst adopts the following steps:

[0117] (1) Dissolve 0.116g nickel nitrate, 5.067g aluminum isopropoxide, 0.472g calcium nitrate and 1.632g urea in 20mL deionized water and stir for 30min.

[0118] (2) Dry the metal salt-urea mixture precursor in an oven at 60°C for 3 hours.

[0119] (3) The mixture was transferred to a crucible and placed in a muffle furnace preheated to 150°C for 12 hours to obtain a nickel-aluminum spinel-calcium hexaaluminate composite precursor with Ni / (Ni+Al+Ca)=3wt%.

[0120] (4) The above nickel-aluminum spinel-calcium hexaaluminate composite precursor was reduced in hydrogen at 900℃ for 1h at a flow rate of 20mL / min to obtain a nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst with Ni / (Ni+Al+Ca)=3wt%.

[0121] Structural characterization

[0122] XRD patterns of nickel-aluminum spinel-calcium hexaaluminate composite precursors with different nickel contents are shown below. Figure 1 As shown. By Figure 1 It can be seen that the nickel-aluminum spinel-calcium hexaaluminate composite precursors with different nickel contents are all composed of NiAl2O4 and CaAl 12 O 19 It consists of two phases.

[0123] Example 1: High-resolution transmission HRTEM image of the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst is shown below. Figure 2 As shown. By Figure 2 It can be seen that the obtained nickel-nickel aluminum spinel-calcium hexaaluminate catalyst has a layered structure, which can effectively disperse nickel species.

[0124] High-resolution transmission HRTEM image of the nickel-nickel-aluminum spinel-alumina composite catalyst in Comparative Example 1 is shown below. Figure 3 As shown. By Figure 3 It can be seen that the catalyst does not have a layered structure.

[0125] Application Example 1

[0126] The methane dry reforming reaction performance of the nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalysts prepared in Examples 1 and 2 of this invention, as well as the nickel-nickel-aluminum spinel-alumina composite catalysts prepared in Comparative Examples 1 and 2, was tested. The specific experimental results are as follows:

[0127] 0.1 g of catalyst was diluted with 0.35 g of quartz sand and then loaded into a fixed-bed quartz tube reactor. The catalyst was heated to 800 °C under a N2 atmosphere, and then reacted with methane and carbon dioxide gas at a molar ratio of 1:1. The products were analyzed online. The catalyst stability test results are shown in Tables 1 and 2.

[0128] Table 1. Stability test results of catalysts in Example 1 and Comparative Example 1

[0129]

[0130] Table 2. Stability test results of catalysts in Example 2 and Comparative Example 2

[0131]

[0132]

[0133] As shown in Table 1, when the catalysts of Example 1 and Comparative Example 1 prepared by the present invention have the same nickel content, the conversion rates of methane and carbon dioxide in Comparative Example 1 continuously decrease when methane dry reforming is carried out under high temperature conditions; Example 1 can stably and efficiently catalyze the methane dry reforming reaction at high temperature, maintaining a stable conversion rate of methane and carbon dioxide.

[0134] Example 2: Stability test results of the catalyst's performance in methane dry reforming at 800℃ are shown in the figure below. Figure 4 As shown in Table 2 and Figure 4 It can be seen that when the Ni / (Ni+Ca+Al) ratio in the nickel-nickel-aluminum spinel-calcium hexaaluminate composite catalyst is 10 wt%, a stable reactant conversion rate can still be maintained. In contrast, the conversion rate of Comparative Example 2, which has a nickel content of 10 wt%, continuously decreased during the 50-hour lifetime evaluation.

[0135] Application Example 2

[0136] Nickel-nickel aluminum spinel-calcium hexaaluminate composite catalysts with Ni / (Ni+Ca+Al) ratios of 6 wt% and 8 wt% (Examples 3-6) were tested at 800 °C and a space velocity of 30,000 h⁻¹. -1 Stability was evaluated under conditions where the ratio of CH4 to CO2 was 1:1. The evaluation results are shown in Table 3.

[0137] Table 3. Stability test results of catalysts in Examples 3-6

[0138]

[0139]

[0140] As shown in Table 3, the conversion rates of methane and carbon dioxide, as well as the H2 / CO ratio, remained stable during the 50-hour stability test.

[0141] Application Example 3

[0142] Example 3 was subjected to 800°C and a space velocity of 30,000 h⁻¹. -1 Long-term stability was evaluated under conditions where CH4 and CO2 were in a 1:1 ratio.

[0143] The stability test results of the catalyst for methane dry reforming at 800℃ in Example 3 are shown in the figure below. Figure 5 As shown, in Example 3, the methane conversion rate was maintained above 93% and the carbon dioxide conversion rate was maintained at around 92% within 300 hours.

[0144] Figure 6The figure shows the thermogravimetric curve of Example 3 after 300 hours of stability evaluation. It can be seen from the figure that the carbon deposition of the catalyst in Example 3 is very low, indicating that the nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst prepared by the method of the present invention has better anti-carbon deposition performance and high temperature stability.

[0145] Application Example 4

[0146] Examples 7 and 8 were performed at 800°C and a space velocity of 15,000–60,000 h⁻¹. -1 The stability was evaluated under a CH4 to CO2 ratio of 1:1. The evaluation results are shown in Table 4. The results show that the conversion rate varied slightly at different space velocities, but remained stable within 50 h.

[0147] Table 4. Results of different space velocities for catalysts in Examples 7 and 8.

[0148]

[0149]

[0150] Application Example 5

[0151] XRD pattern after calcination of Comparative Example 3 is as follows: Figure 7 As shown, it can be seen that the nickel-nickel aluminum spinel-calcium hexaaluminate phase cannot be formed below the specified calcination temperature.

[0152] Comparative Example 3 was tested at 800℃ and a space velocity of 30,000 h⁻¹. -1 Stability was evaluated under conditions where CH4 and CO2 were in a 1:1 ratio. The evaluation results are shown in Table 5: The catalyst activity of Comparative Example 3 was significantly lower than that of Example 1 catalyst with the same nickel content, and it did not remain stable within 50 h. This indicates that the formation of nickel-nickel aluminum spinel-calcium hexaaluminate compound is crucial for improving the relative reactivity and stability.

[0153] Table 5 shows the stability test results of the catalyst in Comparative Example 3.

[0154]

[0155] Application Example 6

[0156] Example 3 was performed at temperatures of 750°C and 850°C with a space velocity of 30,000 h⁻¹. -1 The reaction was carried out under conditions where the ratio of CH4 to CO2 was 1:1. The evaluation results are shown in Table 6: the higher the temperature, the higher the conversion rate of the reactants. In Example 3, the activity remained stable at 750℃ and 850℃ for 50 h.

[0157] Table 6. Test results of catalyst in Example 3 at different temperatures.

[0158]

[0159]

[0160] In summary, the preparation process of the specific embodiments of the present invention is simple, has low production cost, and is environmentally friendly; the prepared nickel-nickel aluminum spinel-calcium hexaaluminate composite catalyst has high efficiency in resisting sintering and carbon deposition during the high-temperature catalytic dry reforming reaction of methane, which greatly improves the stability of the catalyst.

[0161] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for catalyzing a dry reforming reaction of methane, the method comprising the steps of: continuously inputting methane and carbon dioxide into a reactor containing a nickel-nickel-aluminate spinel-calcium hexaluminate composite catalyst to perform a dry reforming reaction of methane, to obtain product gases carbon monoxide and hydrogen; The phase of the nickel-nickel aluminum spinel-calcium hexaluminate composite catalyst includes Ni, NiAl2O4 and CaAl 12 O 19 The nickel-nickel aluminum spinel-calcium hexaluminate composite catalyst has a stable layered microstructure; in the nickel-nickel aluminum spinel-calcium hexaluminate composite catalyst, the mass percentage of nickel element in the total mass of nickel, aluminum and calcium elements is 5-10%. a preparation method of the nickel-nickel-aluminate spinel-calcium hexaluminate composite catalyst comprising the steps of: mixing a nickel salt metal precursor, an aluminum salt metal precursor, a calcium salt metal precursor, and an organic fuel to obtain a mixture precursor; sequentially performing drying and calcination on the mixture precursor to obtain a nickel-aluminate spinel-calcium hexaluminate composite precursor; placing the nickel-aluminate spinel-calcium hexaluminate composite precursor in a flowing hydrogen atmosphere to perform a reduction reaction, to obtain the nickel-nickel-aluminate spinel-calcium hexaluminate composite catalyst; in the mixture precursor, the molar ratio of nickel, aluminum, and calcium elements is 0.2-0.8:12.4-13.6:1; the organic fuel is one or more of alanine, urea, citric acid, maleic hydrazide, and carbohydrazide; the ratio of the amount of substance of the organic fuel to the amount of substance of all metal salt precursors is 1-5:1; the temperature of the calcination is 200-800°C, and the time is 1-12 h; the temperature of the reduction reaction is 700-950°C, and the time is 1-5 h.

2. The method of claim 1, wherein, in the preparation method of the nickel-nickel-aluminate spinel-calcium hexaluminate composite catalyst, the hydrogen flow rate is 10-50 mL / min.

3. The method of claim 1, wherein, in the preparation method of the nickel-nickel-aluminate spinel-calcium hexaluminate composite catalyst, the hydrogen flow rate is 20-40 mL / min.

4. The method of claim 1, wherein, in the preparation method of the nickel-nickel-aluminate spinel-calcium hexaluminate composite catalyst, the temperature of the reduction reaction is 800-900°C, and the time is 2-4 h.

5. The method of claim 1, wherein, in the preparation method of the nickel-nickel-aluminate spinel-calcium hexaluminate composite catalyst, the mixing method is mixing in a solvent or grinding mixing; the solvent is water and / or ethanol; the grinding mixing is manual grinding or ball mill grinding.

6. The method of claim 1, wherein, in the preparation method of the nickel-nickel-aluminate spinel-calcium hexaluminate composite catalyst, the temperature of the drying is 60-150°C, and the holding time is 0.5-3 h.

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