Supported metal oxide catalyst, preparation method and application thereof, and method for producing hydrogen through ammonia decomposition

Abstract

The invention relates to the field of catalysts, in particular to a supported metal oxide catalyst, a preparation method and application thereof and a method for producing hydrogen through ammonia decomposition, the supported metal oxide catalyst comprises a carrier and active components, the active components comprise precious metal and transition non-precious metal, the average particle size of the active components is 1-2 nm, and the average particle size of the active components is 1-2 nm. The carrier is selected from at least one of alkaline earth metal oxide and lanthanide metal oxide. The catalyst disclosed by the invention is particularly suitable for ammonia decomposition hydrogen production reaction, and has the advantages of good reaction activity, capability of reducing reaction temperature and the like.

Description

Technical Field

[0001] The invention relates to the field of catalysts, and in particular to a supported metal oxide catalyst, a preparation method and application thereof, and a method for producing hydrogen by decomposing ammonia. Background Art

[0002] With the intensification of environmental pollution and energy crisis, hydrogen energy has attracted widespread attention as an efficient and clean new energy. However, hydrogen energy has a low volume density and is difficult to liquefy, which leads to many technical challenges in its storage and transportation, limiting its widespread application. On-site hydrogen production using hydrogen storage bodies is considered to be an effective way to solve the above problems. To date, hydrogen storage technologies such as high-pressure hydrogen storage, liquefied hydrogen storage, solid adsorption hydrogen storage, and chemical hydrogen storage have made great progress. Compared with other hydrogen storage technologies, chemical hydrogen storage has the advantages of large hydrogen storage capacity, safety and reliability, and low cost, making it one of the most promising technologies in the field of hydrogen storage.

[0003] Ammonia is an excellent chemical hydrogen storage body. It not only has the characteristics of high hydrogen content (mass fraction of 17.75%), easy liquefaction (0.8MPa, 298K), easy storage and transportation, and no production of harmful impurities such as COx, but also has mature production technology, large supply and low cost.

[0004] It can be seen that ammonia decomposition hydrogen production technology is a low-cost, efficient, clean portable in-situ hydrogen production technology with great application prospects. The development of ammonia as a hydrogen storage body is expected to solve the technical problems of traditional high-pressure hydrogen storage and transportation. Summary of the invention

[0005] The object of the present invention is to provide a supported metal oxide catalyst which has fine active component grains, good reaction activity, can reduce the reaction temperature of ammonia decomposition to produce hydrogen, and has low cost.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a supported metal oxide catalyst on the one hand, which includes a carrier and an active component, the active component includes a noble metal and a transition non-noble metal, the average particle size of the active component is 1-2nm, and the carrier is selected from at least one of alkaline earth metal oxides and lanthanide metal oxides.

[0007] The second aspect of the present invention provides a method for preparing a supported metal oxide catalyst, which comprises: step S1: mixing a solvent, a carrier precursor, a noble metal and a transition non-noble metal precursor to form a metal salt solution; step S2: mixing the metal salt solution and a precipitant solution to form a suspension with a pH value of 9-14, then performing a co-precipitation reaction, aging, centrifuging, drying and roasting the reaction slurry after the reaction; the precipitant is a mixture of ammonia water and urea.

[0008] The third aspect of the present invention provides a supported metal oxide catalyst prepared by the preparation method of the present invention.

[0009] The fourth aspect of the present invention provides use of the catalyst of the present invention in catalytic decomposition.

[0010] A fifth aspect of the present invention provides a method for producing hydrogen by decomposing ammonia, the method comprising: decomposing an ammonia raw material to produce hydrogen in the presence of the catalyst of the present invention.

[0011] The supported metal oxide catalyst provided by the present invention has good reaction activity, fine active component grains, and an average particle size of 1-2nm, which can reduce the reaction temperature of ammonia decomposition to produce hydrogen and improve the reaction efficiency. In addition, the catalyst of the present invention has the advantages of low loading amount of precious metal active components, large specific surface area, etc.

[0012] The catalyst preparation method of the present invention has an active component with a smaller grain size, and the nano-grain combination of noble metal and transition non-noble metal is uniformly dispersed on the surface of the metal oxide carrier, thereby having the advantage of a large specific surface area, being suitable for ammonia decomposition hydrogen production reaction, being able to optimize the adsorption and desorption process of ammonia molecules and nitrogen-containing intermediates on the active center, improving the reaction efficiency, and reducing the reaction temperature; the method of the present invention has a low loading amount of the noble metal active component, can reduce costs, has a simple process, does not require a template agent, has good repeatability, and is easy to industrialize.

[0013] The catalyst of the present invention is particularly suitable for the reaction of producing hydrogen by decomposing ammonia, and has the advantages of good reaction activity and the ability to reduce the reaction temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 TEM image of the supported metal oxide catalyst prepared in Example 1;

[0015] Figure 2 This is a HAADF-STEM image of the active component of the supported metal oxide catalyst prepared in Example 1;

[0016] Figure 3 HAADF-STEM image of the supported metal oxide catalyst support prepared in Example 1

[0017] Figure 4 The XRD pattern of the supported metal oxide catalyst prepared in Comparative Example 1;

[0018] Figure 5 TEM image of the supported metal oxide catalyst prepared in Comparative Example 1;

[0019] Figure 6 This is the TEM image of the supported metal oxide catalyst prepared in Comparative Example 4. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0021] The present invention provides a supported metal oxide catalyst, the supported metal oxide catalyst comprises a carrier and an active component, the active component comprises a noble metal and a transition non-noble metal, the average particle size of the active component is 1-2nm, preferably 1-1.5nm, and the carrier is selected from at least one of an alkaline earth metal oxide and a lanthanide metal oxide. The supported metal oxide catalyst having the above characteristics has fine active component grains and good reaction activity, and can be applied to ammonia decomposition to produce hydrogen and can also reduce the reaction temperature of ammonia decomposition to produce hydrogen.

[0022] According to a preferred embodiment of the present invention, based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.1-10wt% in terms of oxide, and the loading amount of the transition non-noble metal is 10-60wt%; preferably, based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.15-5wt% in terms of oxide, and the loading amount of the transition non-noble metal is 20-40wt%; more preferably, based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.15-2wt% in terms of oxide, and the loading amount of the transition non-noble metal is 20-35wt%; further preferably, based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.25-0.35wt% in terms of oxide, and the loading amount of the transition non-noble metal is 22-28wt%. The catalyst having the above preferred technical features can improve the reaction activity and has a low loading amount of the noble metal, and can reduce the cost.

[0023] In the present invention, the catalysts having the aforementioned composition can achieve the purpose of the present invention, and the composition of the active components thereof can be selected in a wide range, which is exemplified below, but does not limit the scope of the present invention.

[0024] According to a preferred embodiment of the present invention, the noble metal is selected from at least one of ruthenium, platinum and palladium.

[0025] According to a preferred embodiment of the present invention, the transition non-noble metal is selected from at least one of copper, iron, cobalt and nickel.

[0026] The catalyst having the above-mentioned preferred technical characteristics is composed of metals with strong and weaker nitrogen binding strengths, respectively, which can accelerate the adsorption and desorption process of reaction intermediates and products and improve reaction activity.

[0027] In the present invention, the supported metal oxide catalyst having the above characteristics can achieve the purpose of the present invention. The range of the carrier type can be selected from a wide range. The following exemplary description is given, but the scope of the present invention is not limited thereto. According to a preferred embodiment of the present invention, the carrier is MgO and / or CeO 2 , preferably MgO. The catalyst having the above preferred technical features can form a strong metal-support interaction and improve the reaction activity.

[0028] The supported metal oxide catalysts having the above characteristics can achieve the purpose of the present invention. There is no special requirement for their specific surface area. The following is an exemplary description, but it does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the specific surface area of ​​the catalyst is 200-400cm 2 / g, preferably 300-400cm 2 / g, more preferably 340-380cm 2 The catalyst having the aforementioned preferred technical features is beneficial for providing more anchoring sites for the active metal and enhancing the reaction activity.

[0029] The supported metal oxide catalysts having the above characteristics can achieve the purpose of the present invention. There is no special requirement for the preparation method thereof. The following exemplary description is given, but the scope of the present invention is not limited thereby. According to a preferred embodiment of the present invention, the present invention provides a method for preparing a supported metal oxide catalyst, and the preparation method comprises:

[0030] Step S1: mixing a solvent, a carrier precursor, a noble metal and a transition non-noble metal precursor to form a metal salt solution;

[0031] Step S2: mixing the metal salt solution and the precipitant solution to form a suspension with a pH value of 9-14, and then performing a coprecipitation reaction, and aging, centrifuging, drying and calcining the reaction slurry after the reaction;

[0032] The precipitant is a mixture of ammonia water and urea.

[0033] The catalyst preparation method of the present invention has an active component with a smaller grain size, and the nano-grain combination of noble metal and transition non-noble metal is uniformly dispersed on the surface of the metal oxide carrier, thereby having the advantage of a large specific surface area, being suitable for ammonia decomposition hydrogen production reaction, being able to optimize the adsorption and desorption process of ammonia molecules and nitrogen-containing intermediates on the active center, improving the reaction efficiency, and reducing the reaction temperature; the method of the present invention has a low loading amount of the noble metal active component, can reduce costs, has a simple process, does not require a template agent, has good repeatability, and is easy to industrialize.

[0034] In the present invention, solutions of different concentrations need to be prepared as needed. If the type of solvent is not specifically specified, water is used as the solvent by default, and solutions of different concentrations can be prepared by adjusting the amount of water added; this is well known to those skilled in the art, and the specific operation is not repeated here.

[0035] In the present invention, when preparing the metal salt solution, there are no special requirements for the order of adding the components and the operation method. For example, the carrier precursor and the non-precious metal precursor can be added to a solvent such as water, and then the precious metal precursor solution is added dropwise. This is one embodiment of the experiment, but the present invention is not limited to this embodiment. Any order and operation method that can obtain the metal salt solution is allowable.

[0036] In the present invention, there is no special requirement for the form of raw materials for preparing the metal salt solution, as long as a uniform and stable metal salt solution is obtained. The raw materials are selected according to their chemical properties and actual needs. For example, the carrier precursor of the present invention can be solid, the transition non-noble metal precursor can be solid, and the noble metal precursor can be liquid.

[0037] Each contact / mixing step and other steps can be carried out under dynamic conditions, which is a well-known technique in the art and will not be described in detail here. For example, the heating step of the present invention can be carried out under stirring, thereby improving the heating efficiency.

[0038] In the present invention, the pH value of the suspension can be measured by a pH meter; this is well known to those skilled in the art, and the specific operation will not be described in detail here.

[0039] In the present invention, the precipitant solution can achieve the purpose of the present invention as long as it meets the above requirements, and its concentration and dosage can be selected in a wide range, which is exemplified below, but does not limit the scope of the present invention.

[0040] According to a preferred embodiment of the present invention, the molar ratio of ammonia to urea is 1-3:1, for example 1:1, 1.5:1, 2:1, 2.5:1, 3:1.

[0041] According to a preferred embodiment of the present invention, the total concentration of ammonia and urea is 1-3 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L.

[0042] The use of the above-mentioned preferred precipitant solution can obtain active components with smaller crystal sizes, and the specific surface area of ​​the obtained catalyst is greatly increased.

[0043] In the present invention, as long as the precipitant solution meets the above requirements, the purpose of the present invention can be achieved. The following exemplary description is not intended to limit the scope of the present invention. According to a preferred embodiment of the present invention, the precipitant solution contains acetone, and the concentration of acetone is 10-20wt%. The above preferred precipitant solution can obtain active components with smaller grain sizes, and the combination of nano-crystals of noble metals and transition non-noble metals in the catalyst is uniformly dispersed on the surface of the metal oxide carrier; and the specific surface area of ​​the obtained catalyst is greatly increased.

[0044] In the present invention, there are no special requirements for the sources and types of the carrier precursor of the metal salt solution, the precursor of the noble metal, and the precursor of the transition non-noble metal. The following are exemplified, but the scope of the present invention is not limited thereby.

[0045] According to one embodiment of the present invention, in the metal salt solution, the carrier precursor includes a nitrate and / or chloride of at least one of an alkaline earth metal oxide and a lanthanide metal oxide, preferably magnesium nitrate and / or cerium nitrate, and more preferably magnesium nitrate.

[0046] According to one embodiment of the present invention, in the metal salt solution, the noble metal precursor includes a nitrate and / or chloride of at least one of ruthenium, platinum and palladium.

[0047] According to one embodiment of the present invention, in the metal salt solution, the transition non-noble metal precursor includes a nitrate and / or chloride of at least one of copper, iron, cobalt and nickel.

[0048] The use of the above-mentioned preferred metal salt solution can obtain active components with smaller grain sizes, and at the same time, the nano-grain combination of noble metal and transition non-noble metal in the catalyst is evenly dispersed on the surface of the metal oxide carrier; and the specific surface area of ​​the obtained catalyst is greatly improved.

[0049] In the present invention, the solvent of the metal salt solution may be selected from a wide range. According to a preferred embodiment of the present invention, the solvent of the metal salt solution is selected from water.

[0050] In the present invention, there is no special requirement for the amount of the carrier precursor, the noble metal precursor and the transition non-noble metal precursor in the metal salt solution. The following exemplary description is given, but the scope of the present invention is not limited thereto. According to a preferred embodiment of the present invention, the amount of the carrier precursor, the noble metal precursor and the transition non-noble metal precursor in the metal salt solution is such that: based on the total amount of the catalyst carrier, in terms of oxide, the loading amount of the noble metal is 0.1-10wt%, and the loading amount of the transition non-noble metal is 10-60wt%; preferably, based on the catalyst Based on the total amount of the catalyst carrier, the loading amount of the precious metal is 0.15-5wt% in terms of oxide, and the loading amount of the transition non-precious metal is 20-40wt%; more preferably, based on the total amount of the catalyst carrier, the loading amount of the precious metal is 0.15-2wt% in terms of oxide, and the loading amount of the transition non-precious metal is 20-35wt%; further preferably, based on the total amount of the catalyst carrier, the loading amount of the precious metal is 0.25-0.35wt% in terms of oxide, and the loading amount of the transition non-precious metal is 22-28wt%.

[0051] In the present invention, the pH value of the coprecipitation reaction can be selected in a wide range, which is exemplified below, but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the pH value is 10-12.

[0052] In the present invention, the coprecipitation temperature can be selected in a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the coprecipitation temperature is 20-80°C, preferably 50-70°C.

[0053] In the present invention, the coprecipitation time can be selected in a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the coprecipitation time is 2-10 hours, preferably 5-7 hours.

[0054] In the present invention, the aging temperature has a wide optional range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the aging temperature is 50-70°C.

[0055] In the present invention, the aging time has a wide range of selectable times, which are described below by way of example only, but are not intended to limit the scope of the present invention. According to a preferred embodiment of the present invention, the aging time is 14-16 hours.

[0056] In the present invention, there is no special requirement for the pH value at the centrifugation endpoint. The following is an exemplary description, but the scope of the present invention is not limited thereto. According to a preferred embodiment of the present invention, centrifugation is stopped when the pH of the centrifugal supernatant is 7-7.5.

[0057] In the present invention, there is no particular limitation on the drying conditions, and conventional drying conditions in the art can achieve the purpose of the present invention.

[0058] In the present invention, the roasting temperature can be selected in a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the roasting temperature is 350-600°C, preferably 550-600°C.

[0059] In the present invention, the roasting time can be selected in a wide range, which is exemplified below but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the roasting time is 1-7h, preferably 4-5h.

[0060] In the present invention, the rate of heating to the roasting temperature can be selected in a wide range, which is exemplified below, but does not limit the scope of the present invention. According to a preferred embodiment of the present invention, the rate of heating to the roasting temperature is 2-10°C / min, preferably 2-5°C / min.

[0061] The present invention provides a catalyst prepared by the method of the present invention. The catalyst prepared by the method of the present invention has an active component with a smaller grain size, and a combination of nano-crystals of a noble metal and a transition non-noble metal is uniformly dispersed on the surface of a metal oxide carrier, thereby having the advantage of a large specific surface area, being suitable for ammonia decomposition hydrogen production reaction, being able to optimize the adsorption and desorption process of ammonia molecules and nitrogen-containing intermediates on the active center, improving the reaction efficiency, and reducing the reaction temperature; the method of the present invention has a low loading amount of the noble metal active component, can reduce costs, has a simple process, does not require a template agent, has good repeatability, and is easy to industrialize.

[0062] The present invention provides application of the catalyst of the present invention in catalytic decomposition to produce hydrogen.

[0063] The catalyst of the present invention is particularly suitable for the ammonia decomposition hydrogen production reaction, and can optimize the adsorption and desorption process of ammonia molecules and nitrogen-containing intermediates on the active center, improve the reaction efficiency, and reduce the reaction temperature. Based on this, the present invention provides a method for ammonia decomposition hydrogen production, which comprises: in the presence of the activated catalyst of the present invention, decomposing an ammonia raw material for hydrogen production reaction.

[0064] In the present invention, there is no special requirement for the reaction conditions of ammonia decomposition to produce hydrogen, and the commonly used reaction conditions of ammonia decomposition to produce hydrogen can be applied to the present invention. The following is an exemplary description, but the scope of the present invention is not limited thereby.

[0065] According to a preferred embodiment of the present invention, the gas pressure of the ammonia decomposition hydrogen production reaction is 0-300 kPa.

[0066] According to a preferred embodiment of the present invention, the reaction temperature of the ammonia decomposition reaction to produce hydrogen is 420-600°C, preferably 450-470°C.

[0067] According to a preferred embodiment of the present invention, the mass space velocity of the ammonia decomposition hydrogen production reaction is 30000-60000mlg -1 h -1 .

[0068] According to a preferred embodiment of the present invention, the ammonia raw material for the ammonia decomposition hydrogen production reaction is ammonia gas.

[0069] In the present invention, there is no special requirement for the reaction time of ammonia decomposition to produce hydrogen, and any conventional reaction time in the art can be applied to the present invention and can be selected according to actual needs. For example, the reaction time of ammonia decomposition to produce hydrogen is 6-8h.

[0070] In the present invention, there is no special requirement for the mass ratio of the catalyst to the quartz sand in the ammonia decomposition hydrogen production reaction. The conventional mass ratio in the art can be applied to the present invention and can be selected according to actual needs. For example, the mass ratio of the catalyst to the quartz sand in the ammonia decomposition hydrogen production reaction is 1:(6-10).

[0071] In the present invention, there is no special requirement for the activation reaction conditions of the catalyst, and commonly used activation reaction conditions can be applied to the present invention. The following is an exemplary description, but the scope of the present invention is not limited thereby.

[0072] According to a preferred embodiment of the present invention, the activation gas is hydrogen and argon, preferably, the hydrogen content is 5-15v%, and the argon content is 85-95v%.

[0073] According to a preferred embodiment of the present invention, the activation temperature is 25-600°C.

[0074] According to a preferred embodiment of the present invention, the activation time is 2-6 hours.

[0075] According to a preferred embodiment of the present invention, the rate of heating to the activation temperature is 3-8°C / min.

[0076] In the present invention, there is no special requirement for the activation step of the catalyst. For example, 10v% hydrogen and 90v% argon can be passed through the tube at room temperature (25°C) for 20 minutes to exhaust the air in the tube, and then the temperature is increased from room temperature (25°C) to 350°C at a heating rate of 5°C / min, and then the temperature is continued to be increased to 460°C for subsequent ammonia decomposition and hydrogen production activity test.

[0077] The present invention will be described in detail by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0078] If no specific experimental steps or conditions are specified in the examples and comparative examples, the conventional experimental steps or conditions described in the literature in the art can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be purchased commercially.

[0079] In the embodiments and comparative examples,

[0080] The average particle size of the active components of the catalyst was calculated by STEM;

[0081] The specific surface area of ​​the catalyst was measured by the BET method. The specific test conditions were as follows: using a fully automatic specific surface area and porosity analyzer, the sample was pretreated at 150 °C and vacuum for 12 h before the adsorption test;

[0082] In the present invention, the XRD pattern of the catalyst is measured by Rigaku X-ray diffractometer;

[0083] In the present invention, the TEM image of the catalyst was measured by a JEOL high-resolution transmission electron microscope (JEM-2100);

[0084] In the present invention, the HAADF-STEM image of the catalyst is measured by Spectra 300S / TEM.

[0085] In the ammonia decomposition hydrogen production activity test, the ammonia conversion rate is calculated by the following formula:

[0086] Ammonia conversion rate (%) = (inlet ammonia concentration - outlet ammonia concentration) / inlet ammonia concentration × 100%;

[0087] The composition of the outlet gas after the ammonia decomposition hydrogen production reaction was analyzed by gas chromatography.

[0088] In the embodiments and comparative examples,

[0089] Table 1 shows the particle size distribution and specific surface area of ​​the catalysts in the examples and comparative examples;

[0090] Table 2 shows the test conditions and ammonia conversion rates in the examples and comparative examples.

[0091] Example 1

[0092] 5.128g of magnesium nitrate and 0.778g of nickel nitrate were weighed and dissolved in 50ml of deionized water, and 2.8ml of ruthenium chloride solution with a concentration of 2.5mg / ml was added dropwise to the solution, and the mixture was mixed to obtain a metal salt solution; a precipitant solution formed by mixing ammonia water and urea (the total concentration of ammonia and urea was 3mol / L, and the molar ratio of ammonia and urea was 2:1) was added to the metal salt solution until a suspension with a pH of 10 was formed; a coprecipitation reaction was then carried out at 70°C. The reaction time is 6 hours; the reaction slurry is aged at 60°C for 16 hours, the product obtained after aging is centrifuged and washed until the pH of the centrifugal supernatant is 7, the washing is stopped, the separated solid is dried, the dried sample is placed in a muffle furnace, heated to 550°C and roasted for 4 hours, the heating rate during the process is 4°C / min, and after cooling to room temperature, a supported metal oxide catalyst (the loading amount of nickel oxide is 22.82wt%, and the loading amount of ruthenium oxide is 0.32wt%) can be obtained. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1. Figure 1 This is the TEM image of the supported metal oxide catalyst, which shows the obvious hexagonal nanostructure of magnesium oxide and the uniform particle size of the catalyst; Figure 2 This is the HAADF-STEM image of the active components of the supported metal oxide catalyst. The tiny metal particles of the active components can be seen relatively clearly, and the bright spots represent metal atoms. Figure 3 This is the HAADF-STEM image of the supported metal oxide catalyst carrier. It can be seen that the catalyst carrier is distributed relatively evenly.

[0093] Ammonia decomposition hydrogen production activity test

[0094] A fixed bed microreactor was used to test the activity of ammonia decomposition and hydrogen production. The feed gas was NH 3 , the air velocity is 40000mL / (g·min). The loading amount of the activated catalyst is 50mg, the proportion of quartz sand is 450mg, the reaction temperature is 460℃, the reaction pressure is 200kPa, and the sample is taken after 7 hours of reaction to analyze the outlet gas composition. The reaction conditions and test results in Example 1 are shown in Table 2. It can be seen from Table 2 that the conversion rate of ammonia in Example 1 is 98.0%.

[0095] Example 2

[0096] 5.365g magnesium nitrate and 0.825g nickel nitrate were weighed and dissolved in 50ml deionized water, and 2.8ml palladium dichloride solution with a concentration of 2.5mg / ml was added dropwise to the solution, and the mixture was mixed to form a metal salt solution; a precipitant solution formed by mixing ammonia water and urea (the total concentration of ammonia and urea was 2mol / L, and the molar ratio of ammonia and urea was 1:1) was added to the metal salt solution until a suspension with a pH of 11 was formed; a coprecipitation reaction was then carried out at 60°C for 6h; the reaction slurry was aged at 60°C for 16h, the product obtained after aging was centrifuged and washed until the pH of the centrifugal supernatant was 7, and the washing was stopped, the separated solid was dried, the dried sample was placed in a muffle furnace, heated to 550°C and roasted for 4h, the heating rate during the process was 5°C / min, and the supported metal oxide catalyst (the loading amount of nickel oxide was 23.13wt%, and the loading amount of palladium oxide was 0.33wt%) was obtained after cooling to room temperature. TEM images and Figure 1 Similarly, the particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0097] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0098] Example 3

[0099] 5.128g magnesium nitrate and 0.778g ferric nitrate were weighed and dissolved in 50ml deionized water, and 3.2ml ruthenium chloride solution with a concentration of 2.5mg / ml was added dropwise to the solution, and the mixture was mixed to obtain a metal salt solution; a precipitant solution formed by mixing ammonia water and urea (the total concentration of ammonia and urea was 1mol / L, and the molar ratio of ammonia and urea was 3:1) was added to the metal salt solution until a suspension with a pH of 12 was formed; a coprecipitation reaction was then carried out at 50°C. The reaction time is 8 hours; the reaction slurry is aged at 60°C for 16 hours, the product obtained after aging is centrifuged and washed until the pH of the centrifugal supernatant is 7, the separated solid is dried, the dried sample is placed in a muffle furnace, heated to 600°C and roasted for 5 hours, the heating rate during the process is 4°C / min, and after cooling to room temperature, a supported metal oxide catalyst (the loading amount of iron oxide is 27.84wt%, and the loading amount of ruthenium oxide is 0.28wt%) can be obtained. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0100] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0101] Example 4

[0102] The method of Example 1 is followed, except that acetone is added to the precipitant solution of ammonia and urea, and the concentration of acetone is 15 wt %. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0103] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0104] Example 5

[0105] The method of Example 1 is followed, except that the molar ratio of ammonia to urea is 4:1. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0106] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0107] Example 6

[0108] The method of Example 1 was followed, except that the total concentration of ammonia and urea was 4 mol / L. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0109] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0110] Example 7

[0111] The catalyst (the loading amount of nickel oxide is 45.91wt% and the loading amount of ruthenium oxide is 0.32wt%) was prepared according to the method of Example 1, except that the amount of nickel nitrate was 1.565g. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0112] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0113] Example 8

[0114] The method of Example 1 is followed, except that the suspension with pH = 10 is changed to the suspension with pH = 9. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0115] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0116] Example 9

[0117] The catalyst (the loading amount of nickel oxide is 15.64wt%, and the loading amount of ruthenium oxide is 0.22wt%) was prepared according to the method of Example 1, except that 5.128g of magnesium nitrate was changed to 5.128g of cerium nitrate. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0118] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0119] Example 10

[0120] The catalyst (with a nickel oxide loading of 15.64 wt % and a ruthenium oxide loading of 0.22 wt %) was prepared according to the method of Example 1, except that 5.128 g of magnesium nitrate was changed to 5.128 g of cerium nitrate, and the suspension solution with a pH of 10 was changed to a suspension solution with a pH of 9. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0121] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0122] Embodiment 11

[0123] The catalyst (with a nickel oxide loading of 15.64 wt % and a ruthenium oxide loading of 0.22 wt %) was prepared according to the method of Example 1, except that 5.128 g of magnesium nitrate was changed to 5.128 g of cerium nitrate, and the suspension solution with a pH of 10 was changed to a suspension solution with a pH of 11. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0124] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0125] Example 12

[0126] The catalyst (with a nickel oxide loading of 15.64 wt % and a ruthenium oxide loading of 0.22 wt %) was prepared according to the method of Example 1, except that 5.128 g of magnesium nitrate was changed to 5.128 g of cerium nitrate, and the suspension solution with a pH of 10 was changed to a suspension solution with a pH of 12. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0127] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0128] Comparative Example 1

[0129] The catalyst (with a nickel oxide loading of 22.82 wt%) was prepared according to the method of Example 1 except that no ruthenium trichloride solution was added. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1. Figure 4 This is the XRD diagram of the supported metal oxide catalyst, where obvious magnesium oxide and nickel oxide crystal phases can be seen with distinct signals. Figure 5 This is a TEM image of a supported metal oxide catalyst. It can be seen that the catalyst is piled up in the form of small nanoparticles with some agglomeration, but the catalyst is relatively uniform as a whole.

[0130] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0131] Comparative Example 2

[0132] The catalyst (with a nickel oxide loading of 22.82 wt%) was prepared by the method of Example 1, except that no ruthenium chloride solution was added and the suspension with a pH of 10 was changed to a suspension with a pH of 11. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0133] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0134] Comparative Example 3

[0135] The catalyst (with a nickel oxide loading of 15.64 wt%) was prepared by following the method of Example 1, except that 5.128 g of magnesium nitrate was changed to 5.128 g of cerium nitrate, no ruthenium chloride solution was added, and the suspension solution with a pH of 10 was changed to a suspension solution with a pH of 11. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0136] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0137] Comparative Example 4

[0138] The catalyst (with a nickel oxide loading of 15.64 wt%) was prepared by following the method of Example 1, except that 5.128 g of magnesium nitrate was changed to 5.128 g of cerium nitrate, no ruthenium chloride solution was added, and the suspension solution with a pH of 10 was changed to a suspension solution with a pH of 12. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1. Figure 6This is a TEM image of a supported metal oxide catalyst. It can be seen that the catalyst is piled up in the form of small nanoparticles with some agglomeration, but the catalyst is relatively uniform as a whole.

[0139] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0140] Comparative Example 5

[0141] The method of Example 1 was followed, except that the precipitant was changed from ammonia water and urea to sodium hydroxide, the concentration of the precipitant solution was 3 mol / L, and the pH of the formed suspension remained unchanged to prepare a catalyst (the loading amount of nickel oxide was 22.82 wt%, and the loading amount of ruthenium oxide was 0.32 wt%). The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0142] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0143] Comparative Example 6

[0144] The method of Example 1 was followed, except that the precipitant solution was ammonia water (concentration was 3 mol / L), and the pH of the formed suspension remained unchanged, to prepare a catalyst (with a nickel oxide loading of 22.82 wt %, and a ruthenium oxide loading of 0.32 wt %). The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0145] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0146] Comparative Example 7

[0147] According to the method of Example 1, the difference is that a precipitant solution formed by mixing sodium hydroxide and urea (the total concentration of sodium hydroxide and urea is 3 mol / L, and the molar ratio of sodium hydroxide to urea is 2:1) is added to the metal salt solution, and the pH of the formed suspension remains unchanged, and a catalyst (the loading amount of nickel oxide is 22.82wt%, and the loading amount of ruthenium oxide is 0.32wt%) is prepared. The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0148] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0149] Comparative Example 8

[0150] The method of Example 1 was followed, except that 5.128 g of magnesium nitrate was replaced by 5.128 g of aluminum nitrate nonahydrate. A catalyst was prepared (the loading amount of nickel oxide was 45.65 wt %, and the loading amount of ruthenium oxide was 0.64 wt %). The particle size distribution of the active metal in the catalyst and the specific surface area of ​​the catalyst are shown in Table 1.

[0151] According to the test method for the hydrogen production activity by decomposition of ammonia in Example 1, the reaction conditions and test results are shown in Table 2.

[0152] Table 1

[0153]

[0154]

[0155] Table 2

[0156] Reaction temperature (℃) Conversion rate (%) Example 1 460 98.0 Example 2 460 97.5 Example 3 460 97.8 Example 4 460 99.5 Example 5 460 82.5 Example 6 460 80.6 Example 7 460 83.7 Example 8 460 90.2 Example 9 460 85.6 Example 10 460 84.0 Embodiment 11 460 84.3 Example 12 460 85.5 Comparative Example 1 460 61.6 Comparative Example 2 460 57.2 Comparative Example 3 460 55.6 Comparative Example 4 460 49.6 Comparative Example 5 460 44.3 Comparative Example 6 460 48.5 Comparative Example 7 460 42.8 Comparative Example 8 460 75.36

[0157] It can be seen from the examples and comparative data that by forming active components with smaller grain sizes and larger specific surface areas, and by evenly dispersing the combination of precious metals and transition non-precious metal nanoparticles on the surface of the metal oxide carrier, the reaction temperature of ammonia decomposition to produce hydrogen can be reduced and the reaction efficiency can be improved.

[0158] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A supported metal oxide catalyst, characterized in that: The supported metal oxide catalyst comprises a carrier and an active component, wherein the active component comprises a noble metal and a transition non-noble metal, the average particle size of the active component is 1-2 nm, and the carrier is selected from at least one of an alkaline earth metal oxide and a lanthanide metal oxide.

2. The catalyst according to claim 1, wherein Based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.1-10wt% in terms of oxide, and the loading amount of the transition non-noble metal is 10-60wt%; Preferably, based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.15-5wt% and the loading amount of the transition non-noble metal is 20-40wt% in terms of oxide; More preferably, based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.15-2 wt % and the loading amount of the transition non-noble metal is 20-35 wt % in terms of oxide; Further preferably, based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.25-0.35 wt % and the loading amount of the transition non-noble metal is 22-28 wt % in terms of oxide; and / or The noble metal is at least one selected from ruthenium, platinum and palladium; and / or The transition non-noble metal is selected from at least one of copper, iron, cobalt and nickel; and / or The average particle size of the active component is 1-1.5 nm; and / or The carrier is MgO and / or CeO2, preferably MgO; and / or The specific surface area of ​​the catalyst is 200-400 cm 2 / g, preferably 300-400cm 2 / g, more preferably 340-380cm 2 / g.

3. A method for preparing a supported metal oxide catalyst, characterized in that: The preparation method comprises: Step S1: mixing a solvent, a carrier precursor, a noble metal and a transition non-noble metal precursor to form a metal salt solution; Step S2: mixing the metal salt solution and the precipitant solution to form a suspension with a pH value of 9-14, and then performing a coprecipitation reaction, and aging, centrifuging, drying and calcining the reaction slurry after the reaction; The precipitant is a mixture of ammonia water and urea.

4. The method according to claim 3, wherein: In the precipitant solution, The molar ratio of ammonia to urea is 1-3:1; and / or The total concentration of ammonia and urea is 1-3 mol / L; and / or The precipitant solution contains acetone, and the concentration of acetone is 10-20wt%; and / or The carrier precursor comprises a nitrate and / or chloride of at least one of an alkaline earth metal oxide and a lanthanide metal oxide, preferably magnesium nitrate and / or cerium nitrate, more preferably magnesium nitrate; and / or The noble metal precursor includes a nitrate and / or chloride of at least one of ruthenium, platinum and palladium; and / or The transition non-noble metal precursor includes a nitrate and / or chloride salt of at least one of copper, iron, cobalt and nickel; and / or The solvent is selected from water.

5. The method according to claim 3 or 4, wherein: The amounts of the carrier precursor, the noble metal precursor and the transition non-noble metal precursor are such that: Based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.1-10wt% and the loading amount of the transition non-noble metal is 10-60wt% in terms of oxide; Preferably, based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.15-5wt% and the loading amount of the transition non-noble metal is 20-40wt% in terms of oxide; More preferably, based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.15-2 wt % and the loading amount of the transition non-noble metal is 20-35 wt % in terms of oxide; More preferably, based on the total amount of the catalyst carrier, the loading amount of the noble metal is 0.25-0.35 wt % and the loading amount of the transition non-noble metal is 22-28 wt % in terms of oxide.

6. The method according to any one of claims 3 to 5, wherein: The reaction conditions of the coprecipitation include: pH 10-12; and / or The temperature is 20-80°C, preferably 50-70°C; and / or The time is 2-10 hours, preferably 5-7 hours.

7. The method according to any one of claims 3 to 6, wherein: The aging conditions include: The temperature is 50-70°C; and / or Time is 14-16h; and / or The conditions for the calcination include: The temperature is 350-600°C, preferably 550-600°C; and / or The time is 1-7h, preferably 4-5h; and / or The rate of heating to the calcination temperature is 2-10°C / min, preferably 2-5°C / min.

8. The catalyst obtained by the method according to any one of claims 3 to 7.

9. Use of the catalyst according to any one of claims 1, 2 or 8 in catalytic decomposition to produce hydrogen.

10. A method for producing hydrogen by decomposing ammonia, characterized in that: The method comprises: decomposing an ammonia raw material to produce hydrogen in the presence of an activated catalyst as claimed in any one of claims 1, 2 or 8; Preferably, the conditions for the ammonia decomposition hydrogen production reaction include: Air pressure is 0-300 kPa; and / or The reaction temperature is 420-600°C, preferably 450-470°C; and / or Mass space velocity 30000-60000ml g -1 h -1 .

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