A supported catalyst, its preparation method and application in the catalytic dry reforming reaction of methane and carbon dioxide under high pressure

Abstract

The present invention provides a supported catalyst, a preparation method thereof, and an application thereof in the catalytic dry reforming reaction of methane and carbon dioxide under high pressure, relating to the technical fields of catalysts and methane reforming to syngas. The supported catalyst provided by the present invention comprises a MgAl2O4 support and a metal component supported on the surface of the MgAl2O4 support, wherein the metal component comprises Au particles and a transition metal dispersed on the surface of the Au particles, and the transition metal is Ni or Co. For the supported catalyst provided by the present invention, Au particles are used as the dispersed metal of the active metals Ni and Co, and Ni and Co are highly dispersed on the surface of the Au particles to form a highly dispersed catalyst, effectively reducing the overall area of the active metals. When the supported catalyst is used for catalyzing the high-pressure methane-carbon dioxide dry reforming reaction, it has anti-carbon deposition and anti-sintering properties under high-pressure harsh conditions, and can realize the long-term stable operation of this reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts and methane reforming to syngas, and particularly relates to a supported catalyst, a preparation method thereof, and an application thereof in catalytic dry reforming reaction of methane and carbon dioxide under high pressure conditions. Background Art

[0002] Methane (CH4) is not only the main component of natural gas (including oil and gas fields, coalbed methane, shale gas, and combustible ice, etc.), but also a major greenhouse gas. Converting the two greenhouse gases, CH4 and CO2, into syngas with wide applications simultaneously has prominent advantages such as high resource utilization rate, low energy consumption, and low operating costs. The syngas produced has a low CO / H2 ratio and is suitable as a feed gas for olefin hydroformylation and the production of acetic acid, dimethyl ether, olefins, etc. This conversion process has an attractive prospect, and the main bottleneck problem lies in the instability of the catalyst, which is prone to carbon deposition deactivation and high-temperature sintering.

[0003] The existing research on methane-carbon dioxide reforming (dry reforming, DRM) catalysts and their stability mainly focuses on the reaction conditions at atmospheric pressure. It is necessary to reduce the pressure of the high-pressure raw material gas, and the syngas after the reaction needs to be pressurized before being used in the downstream process. Gas compression is a high-energy-consuming unit operation. Considering that the methane and carbon dioxide raw material gases are mainly stored in high-pressure storage tanks, and the subsequent conversion of the downstream syngas also needs to be carried out in a high-pressure reactor, methane-carbon dioxide reforming under high pressure is more economical. At the same time, high pressure also means higher capacity, smaller gas volume, lower investment and operating costs, and saves the investment in compression equipment. Therefore, the industrial community expects the catalyst to operate at a certain (optimal 7 - 28 atm) pressure, and the recent development trend of methane reforming catalysts is also increasingly inclined to explore how to achieve methane-carbon dioxide reforming under high-pressure reaction conditions.

[0004] While the reforming reaction is taking place, there are also three carbon deposition side reactions, namely methane decomposition, CO disproportionation (Boudouard reaction), and CO hydrogenation, as well as the reverse water-gas shift reaction. Thermodynamic analysis shows that methane decomposition is the main carbon deposition reaction at high temperature and high pressure, and the carbon elimination reaction mainly comes from the reaction of CO2 and H2O with surface carbon. Although pressurization has higher industrial economy, it also poses higher requirements for catalyst design. For endothermic and volume-increasing reforming reactions, it means that the reaction temperature needs to be increased (>800 °C) to achieve sufficient conversion. However, high temperature and high pressure will bring three challenges: (1) Methane non-catalytic gas-phase cracking will occur simultaneously at high temperature. Although methane decomposition can be ignored under atmospheric pressure, the increase in pressure increases the collision probability between gas molecules, improves the rate of non-catalytic cracking to produce carbon deposition precursors (such as acetylene, olefins, and aromatics), and accelerates the carbon deposition on the catalyst surface; (2) Increasing pressure is thermodynamically favorable for carbon deposition and unfavorable for the carbon elimination reaction; (3) For most metal surfaces, methane catalytic dissociation under atmospheric pressure is the rate-determining step in the surface reforming reaction and the carbon deposition process, and the carbon deposition rate shows a first-order relationship with the methane partial pressure. With the increase of reaction temperature and methane partial pressure, the surface carbon deposition rate increases significantly, which easily makes the carbon elimination reaction become the kinetic rate-determining step, resulting in surface carbon accumulation and catalyst deactivation.

[0005] Although there have been a large number of reports on the dry reforming of methane, most of the reported results are based on atmospheric pressure evaluation and related catalytic research. For example, the Calcor process (OIL GAS European Magazine, 2001, 3, 44-46.) has been industrially demonstrated and is mainly used to produce syngas rich in CO. To prevent carbon deposition, an atmospheric pressure process is adopted, and the CO2 concentration in the feed gas is increased. The H2 / CO ratio in the single-pass product can reach 0.43. This makes it necessary to compress the syngas in downstream production, and if the H2 / CO ratio is close to 2, the compression will become more difficult. Other processes are similar. Developing a suitable catalyst to enable the long-term operation of methane dry reforming under high pressure is an urgent need and an important challenge for the resource utilization of methane. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a supported catalyst, its preparation method, and its application in the catalytic dry reforming reaction of methane and carbon dioxide under high-pressure conditions. The supported catalyst provided by the present invention shows excellent anti-carbon deposition performance in the catalytic dry reforming reaction of methane and carbon dioxide under high-pressure conditions and can maintain the reaction stability in a long reaction cycle.

[0007] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0008] The present invention provides a supported catalyst, comprising a MgAl2O4 support and a metal component supported on the surface of the MgAl2O4 support. The metal component includes Au particles and a transition metal dispersed on the surface of the Au particles. The transition metal is Ni or Co. The molar ratio of the transition metal to the Au particles is (0.5 - 5):100, and the mass content of the transition metal in the supported catalyst is greater than 0.006% and less than 0.06%.

[0009] Preferably, the particle size of the supported catalyst is 10 - 300 nm, and the particle size of the transition metal in the supported catalyst is 1 - 50 nm.

[0010] The present invention provides a preparation method of the supported catalyst as described in the above technical solution, comprising the following steps:

[0011] Mix urea, a soluble aluminum salt, a soluble magnesium salt and water for hydrothermal reaction to obtain a precipitate;

[0012] Dry and first calcine the precipitate in sequence to obtain a MgAl2O4 support;

[0013] Mix the MgAl2O4 support with a soluble gold source and water for first impregnation, and then concentrate, dry and second calcine in sequence to obtain a MgAl2O4 support loaded with Au;

[0014] Mix the MgAl2O4 support loaded with Au with a soluble salt of the transition metal and water for second impregnation, and then concentrate, dry and third calcine in sequence to obtain the supported catalyst; both the second calcination and the third calcination are carried out in a reducing atmosphere.

[0015] Preferably, the molar ratio of aluminum element in the urea and the soluble aluminum salt to magnesium element in the soluble magnesium salt is (2 - 4):2:1; the temperature of the hydrothermal reaction is 120 - 140 °C, and the time is 12 - 16 h.

[0016] Preferably, the first calcination includes a first stage and a second stage carried out in sequence. The temperature of the first stage is 400 - 550 °C, and the holding time is 1 - 2 h. The temperature of the second stage is 600 - 900 °C, and the holding time is 6 - 8 h.

[0017] Preferably, the time of the first impregnation is 2 - 5 h; the temperature of the second calcination is 600 - 900 °C, and the holding time is 6 - 8 h.

[0018] Preferably, the time of the second impregnation is 2 - 5 h; the temperature of the third calcination is 600 - 900 °C, and the holding time is 6 - 8 h.

[0019] Preferably, the reducing atmosphere is a mixed gas of hydrogen and argon, and the volume percentage of hydrogen in the mixed gas is 10%.

[0020] The present invention provides the use of the supported catalyst described in the above technical solution or the supported catalyst prepared by the preparation method described in the above technical solution in the catalytic dry reforming reaction of methane and carbon dioxide under high pressure conditions. The pressure of the methane and carbon dioxide dry reforming reaction is 1 to 20 bar, and the temperature is 800 to 900 °C.

[0021] Preferably, in the methane and carbon dioxide dry reforming reaction, the volume ratio of CH4 to CO2 is 1:1, and the space velocity GHSV is 3030 to 30300 scc·gcat -1 ·h -1 .

[0022] The present invention provides a supported catalyst, which includes a MgAl2O4 support and a metal component supported on the surface of the MgAl2O4 support. The metal component includes Au particles and transition metals dispersed on the surface of the Au particles. The transition metal is Ni or Co, and the molar ratio of the transition metal to the Au particles is (0.5 to 5):100. The mass content of the transition metal in the supported catalyst is greater than 0.006% and less than 0.06%. In the supported catalyst provided by the present invention, the Au particles are used as the dispersion metal for the active metals Ni and Co. Ni and Co are highly dispersed on the surface of the Au particles, forming a highly dispersed catalyst, effectively reducing the overall area (Ensemble size) of the active metals Ni and Co. The reduction of the overall area of Ni and Co means the reduction of the number of step sites suitable for carbon deposition, which helps to improve the anti-carbon deposition effect under high temperature and high pressure. When the supported catalyst provided by the present invention is used in the catalytic high-pressure methane-carbon dioxide dry reforming reaction, it has anti-carbon deposition and anti-sintering properties under the harsh conditions of the high-pressure methane-carbon dioxide dry reforming reaction, and can achieve long-term stable operation of this reaction.

[0023] The results of the examples show that the supported catalyst provided by the present invention can stably operate for 100 h under the conditions of the high-pressure (20 bar) methane-carbon dioxide dry reforming reaction, and no whisker-like carbon deposition is found on the catalyst after the reaction. Description of the Drawings

[0024] Figure 1 XRD characterization diagrams of the fresh catalysts Co 0.005 -Au1 / MgAl2O4, Ni 0.005 -Au1 / MgAl2O4 and the fresh catalysts Co / MgAl2O4, Ni / MgAl2O4 of Comparative Examples 1 to 2;

[0025] Figure 2For the fresh catalyst Co in the example 0.005 -Au1 / MgAl2O4, Ni 0.005 -SEM / Mapping (EDS surface scan) images of Au1 / MgAl2O4, Figure 2 where a - h correspond to the fresh catalyst Co 0.005 -Au1 / MgAl2O4 in Example 1, and i - p correspond to the fresh catalyst Ni 0.005 -Au1 / MgAl2O4;

[0026] Figure 3 Under the reaction conditions, for the example Co 0.005 -Au1 / MgAl2O4 (a), Ni 0.005 -Au1 / MgAl2O4 (b) and the comparative catalysts Co / MgAl2O4 (c), Ni / MgAl2O4 (d), Co1 - Au 0.03 / MgAl2O4 (e) and Ni1 - Au 0.03 / MgAl2O4 (f) high - pressure evaluation diagrams;

[0027] Figure 4 For the example catalyst Co 0.005 -Au1 / MgAl2O4, Ni 0.005 -XRD characterization diagrams of Au1 / MgAl2O4 and the comparative catalysts Co / MgAl2O4, Ni / MgAl2O4 after reaction;

[0028] Figure 5 For the example catalyst Co 0.005 -Au1 / MgAl2O4, Ni 0.005 -Thermogravimetric curves (TGA) of Au1 / MgAl2O4 and the comparative catalysts Co / MgAl2O4, Ni / MgAl2O4 after reaction, Figure 5 where (a) is CO2 - TGA and (b) is Air - TGA. Detailed implementation mode

[0029] The present invention provides a supported catalyst, which includes a MgAl2O4 support and a metal component supported on the surface of the MgAl2O4 support. The metal component includes Au particles and transition metals dispersed on the surface of the Au particles. The transition metal is Ni or Co, the molar ratio of the transition metal to the Au particles is (0.5 - 5):100, and the mass content of the transition metal in the supported catalyst is greater than 0.006% and less than 0.06%.

[0030] In the present invention, the molar ratio of the transition metal to the Au particles can be 0.5:100, 1:100, 2:100, 3:100, 4:100 or 5:100; the mass content of the transition metal in the supported catalyst can be 0.01%, 0.02%, 0.03%, 0.04% or 0.05%.

[0031] In the present invention, the particle size of the supported catalyst is preferably 10 - 300 nm, and the particle size of the transition metal in the supported catalyst is preferably 1 - 50 nm.

[0032] In the present invention, the supported catalyst is denoted as M-Au / MgAl2O4 (M = Ni or Co). In the supported catalyst provided by the present invention, Ni and Co serve as active metals, and Au serves as a dispersion metal for Ni and Co (Ni, Co and Au are immiscible). Ni and Co are highly dispersed on the surface of the Au particles, forming a highly dispersed structure, which inhibits the nucleation and growth of carbon deposition on the metal surface, and exhibits excellent anti-carbon deposition and anti-sintering properties under harsh reaction conditions of high temperature and high pressure.

[0033] The present invention provides a method for preparing the supported catalyst described in the above technical solution, comprising the following steps:

[0034] Mix urea, soluble aluminum salt, soluble magnesium salt and water for hydrothermal reaction to obtain a precipitate;

[0035] Dry and first calcine the precipitate in sequence to obtain a MgAl2O4 support;

[0036] Mix the MgAl2O4 support with soluble gold source and water for first impregnation, and then concentrate, dry and second calcine in sequence to obtain a MgAl2O4 support loaded with Au;

[0037] Mix the MgAl2O4 support loaded with Au with the soluble salt of the transition metal and water for second impregnation, and then concentrate, dry and third calcine in sequence to obtain the supported catalyst; both the second calcination and the third calcination are carried out in a reducing atmosphere.

[0038] In the present invention, unless otherwise specified, the raw materials involved are all well-known commercially available products in the art.

[0039] In the present invention, urea, soluble aluminum salt, soluble magnesium salt and water are mixed for hydrothermal reaction to obtain a precipitate.

[0040] In the present invention, the soluble aluminum salt may be Al(NO3)3·9H2O, the soluble magnesium salt may be Mg(NO3)2·6H2O, and the water is preferably deionized water. In the present invention, the molar ratio of urea, aluminum element in the soluble aluminum salt to magnesium element in the soluble magnesium salt is preferably (2 - 4):2:1, and may be 2:2:1, 3:2:1 or 4:2:1; the present invention has no special requirement for the dosage of the water, as long as it can ensure the full dissolution of urea, soluble aluminum salt and soluble magnesium salt, and the amount of added water will not affect the formation of the MgAl2O4 support. In the present invention, the urea provides an alkaline synthesis environment, and the addition of urea affects the dispersion degree of the support in the synthesis. By controlling the molar ratio of urea, aluminum element in the soluble aluminum salt to magnesium element in the soluble magnesium salt within the above range, a pure-phase spinel structure can be obtained, with a large specific surface area and small particle size; while the addition of excessive urea will lead to lattice defects, and insufficient urea will cause Al2O3 to exist in the product. In the examples of the present invention, urea, soluble aluminum salt and soluble magnesium salt are put into a container, and water is added thereto and stirred for 3 h to fully dissolve.

[0041] In the present invention, the temperature of the hydrothermal reaction is preferably 120 - 140 °C, and may be 120, 130 or 140 °C, and the time is preferably 12 - 16 h, and may be 12, 13, 14, 15 or 16 h. In the examples of the present invention, the container containing the mixed solution of urea, soluble aluminum salt, soluble magnesium salt and water is transferred to a polytetrafluoroethylene inner liner, placed in a pressure-resistant reaction kettle, and the hydrothermal reaction is carried out. During the hydrothermal reaction, urea decomposes by heating, generating NH4 + in the solution, providing an alkaline environment in the solution, and Al 3+ , Mg 2+ combine with OH - to form a precipitate. Compared with the conventional ammonia precipitation method under normal pressure, slightly excessive urea can ensure that the solution has an appropriate alkalinity, enabling the added Al 3+ , Mg 2+ to precipitate sufficiently, and no aluminate ion is generated in the solution, ensuring that there is no obvious difference in the chemical composition between the actual product and the target product.

[0042] After the hydrothermal reaction is completed, the present invention preferably cools the obtained reaction solution and stands it for 4 h, and then performs solid-liquid separation and solid-phase washing in sequence to obtain the precipitate. The present invention has no special requirement for the method of solid-liquid separation, and any well-known solid-liquid separation method in the art can be used, such as suction filtration; the solid-phase washing is preferably carried out by rinsing with deionized water multiple times.

[0043] After obtaining the precipitate, the present invention dries and first calcines the precipitate in sequence to obtain the MgAl2O4 support.

[0044] In the present invention, the drying temperature is preferably 90 °C, the time is preferably 24 h, and the drying is preferably carried out in an oven. In the present invention, the dried precipitate is preferably ground into a powder, placed in a SiC crucible, and subjected to a first calcination in a muffle furnace. In the present invention, the first calcination is carried out in an air atmosphere; the first calcination preferably includes a first stage and a second stage carried out in sequence; the temperature of the first stage is preferably 400 - 550 °C, which can be 400, 450, 500 or 550 °C, and the heat preservation time is preferably 1 - 2 h, which can be 1, 1.5 or 2 h; the temperature of the second stage is preferably 600 - 900 °C, which can be 800, 850 or 900 °C, and the heat preservation time is preferably 6 - 8 h, which can be 6, 7 or 8 h; the heating rate from room temperature to the temperature of the first stage, and the heating rate from the temperature of the first stage to the temperature of the second stage are preferably 3 °C / min. In the first stage, the combined water in the product is mainly removed and the remaining urea is decomposed; in the second stage, magnesium oxide and aluminum oxide gradually form a stable spinel structure. After the first calcination is completed, it is cooled to room temperature to obtain a pure-phase MgAl2O4 support.

[0045] The MgAl2O4 support prepared by the present invention has a high specific surface area and no phase separation under the conditions of high-temperature and high-pressure reforming reaction.

[0046] After obtaining the MgAl2O4 support, the present invention mixes the MgAl2O4 support with a soluble gold source and water for a first impregnation, and then successively undergoes concentration, drying and a second calcination to obtain an MgAl2O4 support loaded with Au.

[0047] In the present invention, the soluble gold source can be chloroauric acid (HAuCl4), and the water is preferably deionized water. In the examples of the present invention, the method of mixing the MgAl2O4 support with the soluble gold source and water is: putting the soluble gold source and the MgAl2O4 support into a container and adding water thereto. In the present invention, the time of the first impregnation is preferably 2 - 5 h, which can be 2, 3, 4 or 5 h, and the first impregnation is preferably carried out under stirring conditions.

[0048] In the present invention, the concentration method is preferably rotary evaporation, and the rotary evaporation is preferably a 70°C water bath negative pressure rotary evaporation, which is subject to spin drying; while the concentration, the components can be evenly distributed, and there is also a preliminary drying effect to form a precursor of the target catalyst. In the present invention, the drying temperature is preferably 90°C, the time is preferably 16h, and the drying is preferably carried out in an oven. After the drying, the present invention preferably grinds the obtained product into powder, pours the powder into a SiC crucible, and places it in a tube furnace for the second calcination. In the present invention, the temperature of the second calcination is preferably 600~900°C, which can be 600, 700, 800 or 900°C, the holding time is preferably 6~8h, which can be 6, 7 or 8h, and the heating rate from room temperature to the temperature of the second calcination is preferably 2°C / min; the second calcination is carried out in a reducing atmosphere, and the reducing atmosphere is preferably a mixture of hydrogen and argon, and the volume percentage of hydrogen in the mixture is preferably 10%. During the second calcination process, the Au precursor first removes bound water and further decomposes at high temperature to form Au single substance dispersed on the surface of the MgAl2O4 carrier.

[0049] After the second calcination is completed, the calcined product is preferably cooled and then ground to obtain the Au-loaded MgAl2O4 carrier, which is recorded as Au / MgAl2O4.

[0050] After obtaining the Au-loaded MgAl2O4 carrier, the present invention mixes the Au-loaded MgAl2O4 carrier with the soluble salt of the transition metal and water for a second impregnation, and then sequentially concentrates, dries and thirdly roasts to obtain the supported catalyst.

[0051] In the present invention, the transition metal is Ni or Co, and the soluble salt of the transition metal can be nickel nitrate (Ni(NO3)2), nickel acetate, cobalt nitrate (Co(NO3)2), cobalt acetate. In an embodiment of the present invention, the soluble salt of the transition metal is added in the form of a hydrate; the water is preferably deionized water. In an embodiment of the present invention, the method of mixing the Au-loaded MgAl2O4 carrier with the soluble salt of the transition metal and water is preferably: adding the Au-loaded MgAl2O4 carrier and the soluble salt of the transition metal to a container, and adding water thereto. In the present invention, the time of the second impregnation is preferably 2 to 5 hours, and can be 2, 3, 4 or 5 hours, and the second impregnation is preferably carried out under stirring.

[0052] In the present invention, the concentration method is preferably rotary evaporation, and the rotary evaporation is preferably rotary evaporation under negative pressure in a 70 °C water bath until it is dried; the drying temperature is preferably 90 °C, and the time is preferably 16 h. The drying is preferably carried out in an oven. In the present invention, the temperature of the third calcination is preferably 600-900 °C, which can be 600, 700, 800 or 900 °C, the heat preservation time is preferably 6-8 h, which can be 6, 7 or 8 h, and the heating rate from room temperature to the temperature of the third calcination is preferably 2 °C / min; the third calcination is carried out in a reducing atmosphere, and the reducing atmosphere is preferably a mixed gas of hydrogen and argon, and the volume percentage of hydrogen in the mixed gas is preferably 10%; in the examples of the present invention, the third calcination is carried out in a tubular furnace. During the third calcination, the soluble salt of the transition metal decomposes, and in the reducing atmosphere, the decomposition products are swept away by the reducing atmosphere. At the same time, due to the reducing atmosphere, the active metal is directly reduced to elemental Co or Ni and loaded on Au / MgAl2O4 to form a highly dispersed structure.

[0053] After the third calcination, the present invention preferably cools and grinds the obtained product to obtain the supported catalyst.

[0054] The present invention adopts the stepwise impregnation method. First, Au / MgAl2O4 is prepared, and then the active metal Co or Ni is loaded on Au / MgAl2O4 to form a highly dispersed catalyst M-Au / MgAl2O4 in which Co or Ni is highly dispersed on the surface of Au particles. If direct impregnation (i.e., one-step impregnation) is used, the active metal Co or Ni will be largely wrapped inside by Au, resulting in a significant decrease in catalytic performance. The present invention has no special requirements for the amounts of the MgAl2O4 support and the soluble gold source during the first impregnation, and the amounts of the Au-loaded MgAl2O4 support and the soluble salt of the transition metal during the second impregnation, as long as the catalyst with a molar ratio of the transition metal to Au particles of (0.5-5):100 and a mass content of the transition metal in the supported catalyst greater than 0.006% and less than 0.06% can be prepared.

[0055] The present invention provides the application of the supported catalyst described in the above technical solution or the supported catalyst prepared by the preparation method described in the above technical solution in the dry reforming reaction of methane and carbon dioxide under high pressure conditions.

[0056] In the present invention, the pressure of the dry reforming reaction of methane and carbon dioxide is 1-20 bar, which can be 5, 10, 15 or 20 bar, and the temperature is 800-900 °C, which can be 800, 850 or 900 °C.

[0057] In the present invention, in the dry reforming reaction of methane and carbon dioxide, the volume ratio of CH4 to CO2 is preferably 1:1, and the space velocity GHSV is preferably 3030 - 30300 scc·gcat -1 ·h -1 , and it can be 6060 scc·gcat -1 ·h -1 ; in the dry reforming reaction of methane and carbon dioxide, H2 is preferably introduced to maintain the reduced state of the active components on the catalyst surface. The introduced H2 does not affect the reaction equilibrium, and the volume of H2 is preferably 1% of the total volume of CH4, CO2, and H2.

[0058] In the present invention, the dry reforming reaction of methane and carbon dioxide is a reaction in which methane and carbon dioxide react to produce carbon monoxide and hydrogen.

[0059] The supported catalyst provided by the present invention can maintain the reaction stability during a long reaction cycle in the high-pressure methane-carbon dioxide dry reforming reaction, does not generate carbon deposition, and has excellent anti-carbon deposition performance and stability.

[0060] To further illustrate the present invention, the supported catalyst provided by the present invention, its preparation method, and its application in the catalytic high-pressure dry reforming reaction of methane and carbon dioxide will be described in detail below with reference to examples, but they should not be construed as limiting the scope of protection of the present invention.

[0061] The preparation method of the MgAl2O4 support in each example and comparative example is as follows:

[0062] Weigh urea, Al(NO3)3·9H2O, and Mg(NO3)2·6H2O in a molar ratio of 0.12:0.06:0.03, put them into a beaker, add deionized water and stir for 3 h to fully dissolve; transfer the beaker containing the solution to a polytetrafluoroethylene liner, place it in a pressure-resistant reaction kettle and heat at 140 °C for 14 h, then cool and let it stand for 4 h; filter the mixture in the liner, wash it with deionized water multiple times, pour the precipitate into a watch glass and dry it in an oven at 90 °C for 24 h; after drying, grind it into a powder, put it into a SiC crucible, and place it in a muffle furnace for roasting (in an air atmosphere): roast at 500 °C for 1 h, then continue to heat up to 850 °C and keep roasting for 6 h (heating rate is 3 °C / min), and cool to room temperature to obtain a pure-phase MgAl2O4 support.

[0063] Example 1

[0064] Prepare the supported catalyst Co by the multiple impregnation method 0.005- Au1 / MgAl2O4 (the molar content of Au is 20% based on the total molar amount of Au and MgAl2O4), in the catalyst, Au = 25.7032 wt%, Co = 0.0385 wt%, MgAl2O4 = 74.2584 wt%. The preparation steps are as follows:

[0065] Put 0.7719 g of chloroauric acid (99.9%, Au: 50%) and 1.1139 g of MgAl2O4 support into a beaker, add 100 mL of deionized water and stir for 3 h to fully dissolve; transfer the solution to a 500 mL round-bottom flask, perform rotary evaporation under negative pressure in a 70 °C water bath, after evaporation to dryness, put the flask into an oven at 90 °C and dry for 16 h, scrape the flask and grind the powder; pour the powder into a SiC crucible, place it in a tube furnace, and heat from room temperature to 700 °C at a heating rate of 2 °C / min in a 10 vol.% H2 / Ar atmosphere, hold for 6 h and then cool slowly, grind the product to obtain Au / MgAl2O4.

[0066] Loading metal Co: Add the above product (Au / MgAl2O4) and 0.0025 g of cobalt acetate tetrahydrate (99.5%) into a beaker, add 100 mL of deionized water and stir for 3 h, transfer the solution to a 500 mL round-bottom flask, perform rotary evaporation under negative pressure in a 70 °C water bath, after evaporation to dryness, put the flask into an oven at 90 °C and dry for 16 h, scrape the flask and grind the powder; pour the powder into a SiC crucible, place it in a tube furnace, and heat from room temperature to 700 °C at a heating rate of 2 °C / min in a 10 vol.% H2 / Ar atmosphere, hold for 6 h and then cool slowly, grind to obtain the supported catalyst, namely Co 0.005 - Au1 / MgAl2O4.

[0067] Example 2

[0068] Prepare the supported catalyst Ni by the multiple impregnation method 0.005 - Au1 / MgAl2O4 (the molar content of Au is 20% based on the total molar amount of Au and MgAl2O4), in the catalyst, Au = 25.7032 wt%, Ni = 0.0383 wt%, MgAl2O4 = 74.2585 wt%. The preparation steps are as follows:

[0069] Put 0.7719 g of chloroauric acid (99.9%, Au: 50%) and 1.1139 g of MgAl2O4 support into a beaker, add 100 mL of deionized water and stir for 3 h to fully dissolve; transfer the solution to a 500 mL round-bottom flask, perform rotary evaporation under negative pressure in a 70 °C water bath, after evaporation to dryness, put the flask into an oven at 90 °C and dry for 16 h, scrape the flask and grind the powder; pour the powder into a SiC crucible, place it in a tubular furnace, and heat from room temperature to 700 °C at a heating rate of 2 °C / min in a 10 vol.% H2 / Ar atmosphere, hold for 6 h and cool slowly, grind the product to obtain Au / MgAl2O4;

[0070] Loading metal Ni: Add the above product (Au / MgAl2O4) and 0.0024 g of nickel acetate tetrahydrate (99.9%) to a beaker, add 100 mL of deionized water and stir for 3 h, transfer the solution to a 500 mL round-bottom flask, perform rotary evaporation under negative pressure in a 70 °C water bath, after evaporation to dryness, put the flask into an oven at 90 °C and dry for 16 h, scrape the flask and grind the powder; pour the powder into a SiC crucible, place it in a tubular furnace, and heat from room temperature to 700 °C at a heating rate of 2 °C / min in a 10 vol.% H2 / Ar atmosphere, hold for 6 h and cool slowly, grind to obtain the supported catalyst, namely Ni 0.005 -Au1 / MgAl2O4.

[0071] Comparative Example 1

[0072] Prepare the supported catalyst Ni / MgAl2O4 (the molar content of Ni is 20% based on the total molar amount of Ni and MgAl2O4) by the impregnation method. In the catalyst, Ni = 9.3494 wt% and MgAl2O4 = 90.6506 wt%. The preparation steps are as follows:

[0073] Put 0.5952 g of nickel acetate tetrahydrate (99.9%) and 1.3598 g of MgAl2O4 support into a beaker, add deionized water and stir for 3 h to fully dissolve; transfer the solution to a 500 mL round-bottom flask, perform rotary evaporation under negative pressure in a 70 °C water bath, after evaporation to dryness, put the flask into an oven at 90 °C and dry for 16 h, scrape the flask and grind the powder; pour the powder into a SiC crucible, place it in a tubular furnace, and heat from room temperature to 700 °C at a heating rate of 2 °C / min in a 10 vol.% H2 / Ar atmosphere, hold for 6 h and cool slowly, grind the product to obtain Ni / MgAl2O4.

[0074] Comparative Example 2

[0075] Prepare the supported catalyst Co / MgAl2O4 (the molar content of Co is 20% based on the total molar amount of Co and MgAl2O4) by the impregnation method. In the catalyst, Co = 9.3845 wt% and MgAl2O4 = 90.6155 wt%. The preparation steps are as follows:

[0076] Put 0.5979 g of cobalt acetate tetrahydrate (99.5%) and 1.3592 g of MgAl2O4 support into a beaker, add deionized water and stir for 3 h to fully dissolve; transfer the solution to a 500 mL round-bottom flask, carry out rotary evaporation under negative pressure in a 70 °C water bath, after evaporation to dryness, put the flask into an oven at 90 °C and dry for 16 h, scrape the flask and grind the powder; pour the powder into a SiC crucible, place it in a tubular furnace, and heat it from room temperature to 700 °C at a heating rate of 2 °C / min in a 10 vol.% H2 / Ar atmosphere, hold for 6 h and cool slowly, grind the product to obtain Co / MgAl2O4.

[0077] Comparative Example 3

[0078] Passivated catalyst Ni1-Au 0.03 / MgAl2O4 (based on the total molar amount of Ni and MgAl2O4, the molar content of Ni is 20%), and it is prepared by the multiple impregnation method. In the catalyst, Ni = 9.2622 wt%, Au = 0.9325 wt%, MgAl2O4 = 89.8052 wt%. The preparation steps are as follows:

[0079] Put 0.5897 g of nickel acetate tetrahydrate (99.9%) and 1.3471 g of MgAl2O4 support into a beaker, add deionized water and stir for 3 h to fully dissolve; transfer the solution to a 500 mL round-bottom flask, carry out rotary evaporation under negative pressure in a 70 °C water bath, after evaporation to dryness, put the flask into an oven at 90 °C and dry for 16 h, scrape the flask and grind the powder; pour the powder into a SiC crucible, place it in a tubular furnace, and heat it from room temperature to 700 °C at a heating rate of 2 °C / min in a 10 vol.% H2 / Ar atmosphere, hold for 6 h and cool slowly, grind the product to obtain Ni / MgAl2O4.

[0080] Put 0.0280 g of chloroauric acid (99.9%, Au: 50%) and the above-prepared Ni / MgAl2O4 into a beaker, add 100 mL of deionized water and stir for 3 h to fully dissolve; transfer the solution to a 500 mL round-bottom flask, carry out rotary evaporation under negative pressure in a 70 °C water bath, after evaporation to dryness, put the flask into an oven at 90 °C and dry for 16 h, scrape the flask and grind the powder; pour the powder into a SiC crucible, place it in a tubular furnace, and heat it from room temperature to 700 °C at a heating rate of 2 °C / min in a 10 vol.% H2 / Ar atmosphere, hold for 6 h and cool slowly, grind the product to obtain Ni1-Au 0.03 / MgAl2O4.

[0081] Comparative Example 4

[0082] Passivated catalyst Co1-Au 0.03The Co / MgAl2O4 catalyst (the molar content of Co is 20% based on the total molar amount of Co and MgAl2O4) was prepared by the multiple impregnation method. In the catalyst, Co = 9.2970 wt%, Au = 0.9322 wt%, and MgAl2O4 = 89.7708 wt%. The preparation steps are as follows:

[0083] Put 0.5924 g of cobalt acetate tetrahydrate (99.5%) and 1.3466 g of MgAl2O4 support into a beaker, add deionized water and stir for 3 h to fully dissolve; transfer the solution to a 500 mL round-bottom flask, perform negative pressure rotary evaporation in a 70 °C water bath, after drying, put the flask into an oven at 90 °C and dry for 16 h, scrape the flask and grind the powder; pour the powder into a SiC crucible, place it in a tubular furnace, and heat from room temperature to 700 °C at a heating rate of 2 °C / min in a 10 vol.% H2 / Ar atmosphere, hold for 6 h and cool slowly, grind the product to obtain Co / MgAl2O4.

[0084] Put 0.0280 g of chloroauric acid (99.9%, Au: 50%) and the Co / MgAl2O4 prepared above into a beaker, add 100 mL of deionized water and stir for 3 h to fully dissolve; transfer the solution to a 500 mL round-bottom flask, perform negative pressure rotary evaporation in a 70 °C water bath, after drying, put the flask into an oven at 90 °C and dry for 16 h, scrape the flask and grind the powder; pour the powder into a SiC crucible, place it in a tubular furnace, and heat from room temperature to 700 °C at a heating rate of 2 °C / min in a 10 vol.% H2 / Ar atmosphere, hold for 6 h and cool slowly, grind the product to obtain Co1-Au 0.03 / MgAl2O4.

[0085] The catalysts prepared in the examples and comparative examples were characterized, and the characterization methods are as follows:

[0086] The crystal form characteristics of the catalyst were determined by X-ray diffraction (XRD). XRD (Rigaku D / Max-RC) analysis was performed on the catalyst before and after the reaction. Cu was used to excite Kα rays, 40 kW, 100 mA, λ λ = 1.54178 Å, the test speed was 1 ° / min, and the angular range was 2 θ θ = 10~80°;

[0087] The microscopic surface morphology characteristics of the catalyst were observed by field emission scanning electron microscopy (FE-SEM), and the distribution of metal elements on the catalyst surface was analyzed by energy dispersive X-ray spectroscopy mapping (EDS-mapping). The instrument model was GeminiSEM500. Before measurement, the catalyst needs to be pretreated. The catalyst was completely dispersed with ethanol, dropped onto a silicon wafer, placed in an oven until the ethanol was completely dried, the silicon wafer was transferred to the sample stage, fixed with conductive glue, and the distribution of metal elements and the microscopic morphology were observed with the instrument.

[0088] Figure 1 For the fresh catalyst Co 0.005 -Au1 / MgAl2O4, Ni 0.005 -Au1 / MgAl2O4 and the XRD characterization diagrams of the fresh catalyst Co / MgAl2O4, Ni / MgAl2O4 in the comparative example. It can be Figure 1 seen that the supported catalysts Co 0.005 -Au1 / MgAl2O4, Ni 0.005 -Au1 / MgAl2O4 have obvious Au diffraction peaks, and the Co and Ni diffraction peaks are basically invisible, which is because a very small amount of Co and Ni are monolayer-loaded on the catalyst surface.

[0089] Figure 2 For the fresh catalyst Co 0.005 -Au1 / MgAl2O4, Ni 0.005 -Au1 / MgAl2O4 SEM / Mapping (energy spectrum surface scan) diagrams ( Figure 2 in the pictures in the second column, in b and f, red represents Co, green represents Mg, blue represents Al, and pink represents Au; in j and n, red represents Ni, green represents Mg, blue represents Al, and pink represents Au), Figure 2 where a~h correspond to the fresh catalyst Co 0.005 -Au1 / MgAl2O4 in Example 1, and i~p correspond to the fresh catalyst Ni 0.005 -Au1 / MgAl2O4 in Example 2. It can be Figure 2 seen that the active metals Ni and Co are immiscible with Au but in close contact, and are dispersed on the catalyst surface in a highly dispersed form at the same time. The particle size of the catalyst is 10~300 nm. The particle size of the fresh example catalyst in the XRD spectrum diagram is calculated by the Scherrer formula, and the particle size of Ni or Co is 1~50 nm. Figure 1

[0090] The catalysts prepared in the examples and comparative examples were used in the high-pressure methane-carbon dioxide dry reforming reaction, and high-pressure evaluation was carried out on each catalyst. The reaction conditions were as follows: volume ratio of CH4:CO2 = 1:1 (H2 was introduced simultaneously, and the volume of H2 was 1% of the total volume of CH4, CO2 and H2), 850 °C, 1 - 20 bar, GHSV = 6060 scc·gcat -1 ·h -1 , and the high-pressure evaluation included CH4 conversion rate, CO2 conversion rate and the product H2 / CO ratio. The composition of the outlet gas was analyzed by the normalization method. The calculation method of CH4 conversion rate was as shown in Equation (1), the calculation method of CO2 conversion rate was as shown in Equation (2), and the calculation method of H2 / CO ratio was as shown in Equation (3) (in Equations (1) - (3), "in" represents the feed and "out" represents the product):

[0091] Equation (1),

[0092] Equation (2),

[0093] Equation (3).

[0094] Figure 3 Under the above reaction conditions, for the examples Co 0.005 -Au1 / MgAl2O4(a), Ni 0.005 -Au1 / MgAl2O4(b) and the comparative examples Co / MgAl2O4(c), Ni / MgAl2O4(d), Co1-Au 0.03 / MgAl2O4(e) and Ni1-Au 0.03 / MgAl2O4(f), the high-pressure evaluation diagrams, namely the changes of CH4 conversion rate, CO2 conversion rate and the product H2 / CO ratio with reaction time. It can be seen from Figure 3 that under the conditions of high-pressure methane-carbon dioxide reforming at 20 bar and 850 °C, the initial CH4 conversion rate of Co 0.005 -Au1 / MgAl2O4 in Example 1 was 25.39%, and it decreased to 23.06% after 100 h; the Ni 0.005- The initial methane conversion rate of Au1 / MgAl2O4 was 19.85%, and it decreased to 19.39% after 100 h, without obvious deactivation, showing very excellent stability. Under high-pressure reaction conditions, the initial methane conversion rate of Co / MgAl2O4 in Comparative Example 2 was 62.08%, and it decreased to 35.77% after 100 h; the initial methane conversion rate of Ni / MgAl2O4 in Comparative Example 1 was 52.10%, and it decreased to 20.32% after 100 h, with obvious deactivation and a relatively fast decline rate of the conversion rate. The addition of a small amount of Au as a surface passivation metal in the catalysts of Comparative Example 3 and Comparative Example 4 made Co / MgAl2O4 and Ni / MgAl2O4 have stable and relatively high reaction conversion rates under atmospheric pressure, but they were significantly deactivated under pressurized conditions, and there was a sintering phenomenon in the catalyst particles after the reaction. Due to the influence of the RWGS (reverse water gas shift) reaction, the CO2 conversion rate was higher than the CH4 conversion rate, and the trend of H2 / CO was consistent with that of CH4 and CO2, and less than 1.

[0095] Figure 4 For the catalyst Co in the example 0.005 -Au1 / MgAl2O4, Ni 0.005 - XRD characterization diagrams of Au1 / MgAl2O4, Ni-Au1 / MgAl2O4 after reaction with the comparative catalysts Co / MgAl2O4 and Ni / MgAl2O4. Figure 4 Show the example Ni after the reaction 0.005 -Au1 / MgAl2O4 and Co 0.005 -Au1 / MgAl2O4 still maintained the spinel structure. The methane conversion rate of the comparative catalysts Co / MgAl2O4 and Ni / MgAl2O4 decreased significantly under the high-pressure condition of 20 bar, and the bed pressure drop increased significantly. There were obvious carbon deposition diffraction peaks in their XRD characterization, and the particle size of the active metal increased significantly after the reaction, with a sintering phenomenon.

[0096] Figure 5 For the catalyst Co in the example 0.005 -Au1 / MgAl2O4, Ni 0.005 - Thermogravimetric curves of Au1 / MgAl2O4, Ni-Au1 / MgAl2O4 after reaction with the comparative catalysts Co / MgAl2O4 and Ni / MgAl2O4, Figure 5 where (a) is CO2-TGA and (b) is Air-TGA. Figure 5 Show the example Ni after the reaction 0.005 -Au1 / MgAl2O4 and Co 0.005 -Au1 / MgAl2O4 hardly produced carbon deposition, showing very good anti-sintering and anti-carbon deposition properties.

[0097] The above are only the preferred embodiments of the present invention and do not impose any formal restrictions on the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A supported catalyst, characterized in that The catalyst comprises a MgAl2O4 carrier and a metal component supported on the surface of the MgAl2O4 carrier, wherein the metal component comprises Au particles and a transition metal dispersed on the surface of the Au particles, wherein the transition metal is Ni or Co, and the molar ratio of the transition metal to the Au particles is (0.5-5):100, and the mass content of the transition metal in the supported catalyst is greater than 0.006% and less than 0.06%; The preparation method of the MgAl2O4 carrier comprises the following steps: Mixing urea, a soluble aluminum salt, a soluble magnesium salt and water for hydrothermal reaction to obtain a precipitate; the molar ratio of the aluminum element in the urea and the soluble aluminum salt to the magnesium element in the soluble magnesium salt is (2-4):2:1; The precipitate is dried and calcined in sequence to obtain a MgAl2O4 carrier.

2. The supported catalyst according to claim 1, characterized in that The particle size of the supported catalyst is 10-300 nm, and the particle size of the transition metal in the supported catalyst is 1-50 nm.

3. The method for preparing a supported catalyst according to claim 1 or 2, characterized in that: The following steps are involved: Mixing urea, a soluble aluminum salt, a soluble magnesium salt and water for hydrothermal reaction to obtain a precipitate; the molar ratio of the aluminum element in the urea and the soluble aluminum salt to the magnesium element in the soluble magnesium salt is (2-4):2:1; The precipitate is sequentially dried and first calcined to obtain a MgAl2O4 carrier; The MgAl2O4 carrier is mixed with a soluble gold source and water for a first impregnation, and then concentrated, dried and second calcined in sequence to obtain a MgAl2O4 carrier loaded with Au; The Au-loaded MgAl2O4 carrier is mixed with the soluble salt of the transition metal and water for a second impregnation, and then concentrated, dried and calcined for a third time in sequence to obtain the supported catalyst; the second calcination and the third calcination are both carried out in a reducing atmosphere.

4. The preparation method according to claim 3, characterized in that: The temperature of the hydrothermal reaction is 120-140° C. and the time is 12-16 hours.

5. The preparation method according to claim 3, characterized in that: The first calcination includes a first stage and a second stage which are performed sequentially. The temperature of the first stage is 400-550° C. and the insulation time is 1-2 hours. The temperature of the second stage is 600-900° C. and the insulation time is 6-8 hours.

6. The preparation method according to claim 3, characterized in that: The first impregnation time is 2-5 hours; the second roasting temperature is 600-900° C., and the heat preservation time is 6-8 hours.

7. The preparation method according to claim 3, characterized in that: The second impregnation time is 2-5 hours; the third calcination temperature is 600-900° C., and the heat preservation time is 6-8 hours.

8. The preparation method according to claim 3, 6 or 7, characterized in that: The reducing atmosphere is a mixture of hydrogen and argon, and the volume percentage of hydrogen in the mixture is 10%.

9. Use of the supported catalyst according to claim 1 or 2 or the supported catalyst prepared by the preparation method according to any one of claims 3 to 8 in the dry reforming reaction of methane and carbon dioxide under catalytic high-pressure conditions, wherein the pressure of the dry reforming reaction of methane and carbon dioxide is 5 to 20 bar and the temperature is 800 to 900°C.

10. The use according to claim 9, characterized in that: In the dry reforming reaction of methane and carbon dioxide, the volume ratio of CH4 to CO2 is 1:1, and the space velocity GHSV is 3030~30300scc·gcat -1 ·h -1 .

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