Monolithic nickel-based catalyst as well as preparation and application thereof

Abstract

The invention relates to the technical field of ammonia decomposition processes, in particular to an integral nickel-based catalyst as well as preparation and application thereof. The preparation method comprises the following steps: uniformly mixing urea, ammonium salt and a rare earth salt aqueous solution to obtain a mixed solution; and putting the pretreated foamed nickel into the mixed solution, carrying out hydrothermal reaction, and calcining to obtain the monolithic nickel-based catalyst. The monolithic nickel-based catalyst provided by the invention has the advantages of good activity, good stability, easiness in molding, easiness in filling, no need of high-temperature pre-reduction and the like in use, the preparation method is simple, and no active nickel precursor except foamed nickel needs to be added in the preparation process; the method is suitable for industrial production and has practical value and application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonia decomposition processes, and particularly to an integral nickel-based catalyst and its preparation and application. Background Art

[0002] Currently, hydrogen energy, as a typical representative of clean energy, has become a key point in energy transformation. However, hydrogen has a relatively low volumetric energy density and is a flammable gas that is difficult to liquefy. There are many safety and technical problems to be overcome in storing hydrogen using high-pressure containers and hydrogen storage materials. Ammonia (NH3) is considered an excellent hydrogen storage medium and has the following advantages: (1) Compared with other hydrogen carriers (such as methanol, ethanol, etc.), NH3 has a higher hydrogen content (17.8 wt%); (2) Different from pure hydrogen, NH3 is easily liquefied at 0.8 MPa (293 K), which is convenient for transportation and storage; (3) The decomposition of NH3 to produce hydrogen is a carbon-free process, thus avoiding the emission of harmful carbon-containing gases. From a safety perspective, the flammability range of NH3 in air is relatively narrow (16 - 25 vol%), while that of hydrogen is very wide (4 - 75 vol%), and NH3 concentrations exceeding 5 ppm can be easily detected by smell. The process of producing hydrogen through catalytic ammonia decomposition is relatively safe.

[0003] Among the catalysts for ammonia decomposition to produce hydrogen, nickel-based catalysts are the most promising and effective catalyst components in ammonia decomposition reactions due to their relatively high catalytic activity, low price, and high stability. However, in the prior art, methods of improving catalyst activity by combining loading promoters through means such as high-temperature heat treatment, chemical corrosion, or electrochemical corrosion usually require high-temperature pre-reduction in a reducing atmosphere to achieve a relatively high ammonia conversion rate of the catalyst, and the operation is relatively cumbersome. Therefore, it is crucial to provide a catalyst that can directly be used for highly efficient catalytic ammonia decomposition to produce hydrogen.

[0004] Chinese Patent CN116159568A discloses an integral nano-sheet nickel-based ammonia decomposition catalyst for ammonia decomposition to produce hydrogen. Through solvothermal and hydrothermal methods, nickel hydroxide and nickel terephthalate were successfully grown on a nickel foam carrier. Finally, it was reduced in a hydrogen-nitrogen mixed gas atmosphere at 300 - 900 °C for 1 - 12 hours to obtain the integral nano-sheet nickel-based ammonia decomposition catalyst. However, the nickel-based ammonia decomposition catalyst prepared by this method requires adding an active nickel precursor other than nickel foam during the preparation process, and requires long-time reduction under high-temperature conditions, and the catalyst preparation and use processes are relatively complex.

[0005] Therefore, it is crucial to provide a technical solution that can solve the above technical problems. Summary of the Invention

[0006] To solve the above problems, the object of the present invention is to provide a monolithic nickel-based catalyst and its preparation and application. First, urea, ammonium salt and rare earth salt aqueous solution are mixed evenly to obtain a mixed solution; then the pretreated nickel foam is placed in the mixed solution, and after hydrothermal reaction, it is calcined to obtain the monolithic nickel-based catalyst. The monolithic nickel-based catalyst provided by the present invention has the advantages of good activity, good stability, easy shaping, easy loading, and no need for high-temperature pre-reduction during use, and its preparation method is simple, and no active nickel precursor other than nickel foam needs to be added during the preparation process; it is suitable for industrial production and has practical value and application prospects.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] The first object of the present invention is to provide a preparation method of a monolithic nickel-based catalyst, comprising the following steps:

[0009] (S1) Mix urea, ammonium salt and rare earth salt aqueous solution evenly to obtain a mixed solution;

[0010] (S2) Place the pretreated nickel foam in the mixed solution prepared in step (S1), and after hydrothermal reaction, it is calcined to obtain the monolithic nickel-based catalyst.

[0011] In an embodiment of the present invention, in step (S1), the ammonium salt is selected from one or more of ammonium fluoride, ammonium chloride or ammonium nitrate;

[0012] The rare earth salt is selected from one or more of lanthanum chloride, lanthanum nitrate, lanthanum carbonate, lanthanum sulfate, lanthanum oxalate, cerium chloride, cerium nitrate, cerium carbonate, cerium sulfate, cerium oxalate, praseodymium chloride, praseodymium nitrate, praseodymium carbonate, praseodymium sulfate, praseodymium oxalate, yttrium chloride, yttrium nitrate, yttrium carbonate, yttrium sulfate or yttrium oxalate.

[0013] In an embodiment of the present invention, the molar ratio of urea, ammonium salt and rare earth salt aqueous solution is 7.8-8.2:7.8-8.2:3.8-4.2;

[0014] Preferably, the molar ratio of urea, ammonium salt and rare earth salt aqueous solution is 2:2:1.

[0015] In an embodiment of the present invention, in step (S2), the pretreated nickel foam is prepared by the following method:

[0016] Place the nickel foam in an acid solution for cleaning, and then perform post-treatment to obtain the pretreated nickel foam.

[0017] In an embodiment of the present invention, the post-treatment is to wash with deionized water and anhydrous ethanol respectively and then perform drying treatment.

[0018] In one embodiment of the present invention, the acid solution is selected from one of hydrochloric acid, sulfuric acid, hydrofluoric acid or nitric acid.

[0019] In one embodiment of the present invention, in step (S2), during the hydrothermal reaction, the temperature is 80 - 180 °C and the time is 3 - 12 h.

[0020] In one embodiment of the present invention, in step (S2), during the calcination process, the temperature is 300 - 400 °C and the time is 2 - 4 h.

[0021] In one embodiment of the present invention, during the calcination process, the temperature is 350 °C and the time is 3 h.

[0022] The second object of the present invention is to provide a monolithic nickel-based catalyst prepared by the above method.

[0023] The third object of the present invention is to provide an application of the monolithic nickel-based catalyst in the catalytic decomposition of ammonia to produce hydrogen.

[0024] The fourth object of the present invention is to provide a method for catalytic decomposition of ammonia to produce hydrogen using a monolithic nickel-based catalyst, comprising the following steps:

[0025] Using the above monolithic nickel-based catalyst to catalyze the decomposition of ammonia to prepare hydrogen,

[0026] Or, subjecting the above monolithic nickel-based catalyst to high-temperature reduction and then catalyzing the decomposition of ammonia to prepare hydrogen.

[0027] In one embodiment of the present invention, during the decomposition process, the temperature is 450 - 650 °C.

[0028] In one embodiment of the present invention, during the high-temperature reduction process, the reducing atmosphere is hydrogen, the heating rate is 5 - 10 °C / min, the reduction temperature is 450 - 550 °C, and the holding time is 1.5 - 2.5 h.

[0029] In one embodiment of the present invention, during the high-temperature reduction process, the heating rate is 10 °C / min, the reduction temperature is 500 °C, and the holding time is 2 h.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) In the monolithic nickel-based catalyst of the present invention, a suitable rare earth salt is added, and the surface of the nickel foam is modified using rare earth elements. The rare earth elements reduce the particle size of nickel, significantly improving the catalytic performance of the thermal catalytic decomposition of ammonia to produce hydrogen.

[0032] (2) The monolithic nickel-based catalyst provided by the present invention has the advantages of good activity, good stability, easy shaping, easy loading, and no need for high-temperature pre-reduction during use. Moreover, its preparation method is simple, and no active nickel precursor other than nickel foam needs to be added during the preparation process; it is suitable for industrial production and has practical value and application prospects.

[0033] (3) The monolithic nickel-based catalyst of the present invention has good thermal conductivity, making the temperature of the catalyst bed more uniform, and high permeability, greatly reducing the bed pressure drop. At the same time, the stable structure inhibits the surface agglomeration and shedding of the active components during the catalytic process. In the stability test, it can stably catalyze the ammonia decomposition to hydrogen reaction and has good thermal stability. Description of the Drawings

[0034] Figure 1 It is the scanning electron microscope image (SEM image) of nickel foam and the monolithic nickel-based catalyst in Example 1;

[0035] Figure 2 It is the X-ray diffraction pattern (XRD pattern) of nickel foam and the monolithic nickel-based catalyst in Example 1;

[0036] Figure 3 It is the stability test diagram of the monolithic nickel-based catalyst prepared in Example 1 for catalytic ammonia decomposition to hydrogen. Detailed Embodiments

[0037] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0038] In the following embodiments, unless otherwise specified, the reagents used are commercially available reagents, and the detection means and methods used are conventional detection means and methods in the art.

[0039] Example 1

[0040] This example provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0041] (S1) Ten pieces of nickel foam with a thickness of 1.5 mm and a diameter of 6 mm and 110 PPI (Pores Per Inch) (whose SEM image is as shown in Figure 1 A and whose XRD spectrum is as shown in Figure 2 ) are placed in 20 mL of 0.1 M HCl solution for 10 minutes, and then the nickel foam is taken out and washed once with deionized water and anhydrous ethanol respectively. After washing, it is dried (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: nickel foam material without other impurities;

[0042] (S2) 4 mmol of lanthanum nitrate is added to 35 mL of deionized water and mixed evenly to obtain a lanthanum nitrate solution;

[0043] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence, and mix evenly to obtain a mixed solution;

[0044] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal reactor, then place it in an oven, heat it to 120 °C for hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain a monolithic nickel-based catalyst (its SEM image is as shown in Figure 1 Figure B, and its XRD pattern is as shown in Figure 2 Figure).

[0045] It can be found through Figure 1 that the surface of the nickel foam is a smooth three-dimensional porous structure ( Figure 1 Figure A), the surface of the monolithic nickel-based catalyst is a coral-like structure, and the active nickel is anchored on the surface of the nickel foam ( Figure 1 Figure B).

[0046] It can be found through Figure 2 that the catalyst has three prominent diffraction peaks at 2θ values of 44.5°, 51.8° and 76.4°, corresponding to the (111), (200) and (220) planes of face-centered cubic (fcc) nickel respectively. These diffraction peaks are consistent with the standard diffraction card of nickel (JPCDS 04-0850). Compared with the diffraction peaks of the untreated nickel foam, the intensities of the three diffraction peaks at 44.5°, 51.8° and 76.4° are weakened, indicating that the particle size of nickel in the monolithic nickel-based catalyst is smaller than that of nickel in the nickel foam. The XRD results show that the monolithic nickel-based catalyst with a smaller nickel particle size is successfully prepared in this example.

[0047] Example 2

[0048] This example provides a monolithic nickel-based catalyst reduced at high temperature, which is prepared by the following method:

[0049] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm and a diameter of 6 mm and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min, then take out the nickel foam, wash it once with deionized water and anhydrous ethanol respectively, and perform drying treatment (temperature is 80 °C, time is 12 h) after washing to obtain pretreated nickel foam: nickel foam material without other impurities;

[0050] (S2) Add 4 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0051] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0052] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it to 80 °C for hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h; then heat it from room temperature to 500 °C at a rate of 10 °C / min in a pure hydrogen atmosphere and keep it for 2 h to obtain an integrated nickel-based catalyst after high-temperature reduction.

[0053] Example 3

[0054] This example provides an integrated nickel-based catalyst, which is prepared by the following method:

[0055] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm and a diameter of 6 mm of 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min, then take out the nickel foam, wash it once with deionized water and anhydrous ethanol respectively, and perform a drying treatment (temperature is 80 °C, time is 12 h) after washing to obtain pretreated nickel foam: nickel foam material without other impurities;

[0056] (S2) Add 4 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0057] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0058] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it to 80 °C for hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain an integrated nickel-based catalyst.

[0059] Example 4

[0060] This embodiment provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0061] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm, a diameter of 6 mm, and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min. Then take out the nickel foam and wash it once with deionized water and once with absolute ethanol respectively. After washing, perform a drying treatment (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: a nickel foam material without other impurities;

[0062] (S2) Add 4 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0063] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0064] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, raise the temperature to 100 °C and carry out a hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and once with ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and calcine it from room temperature to 350 °C at a rate of 2 °C / min for 3 h to obtain the monolithic nickel-based catalyst.

[0065] Example 5

[0066] This embodiment provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0067] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm, a diameter of 6 mm, and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min. Then take out the nickel foam and wash it once with deionized water and once with absolute ethanol respectively. After washing, perform a drying treatment (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: a nickel foam material without other impurities;

[0068] (S2) Add 4 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0069] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0070] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it to 140 °C for hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain a monolithic nickel-based catalyst.

[0071] Example 6

[0072] This example provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0073] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm and a diameter of 6 mm and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min, then take out the nickel foam, wash it once with deionized water and anhydrous ethanol respectively, and after the washing is completed, perform a drying treatment (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: nickel foam material without other impurities;

[0074] (S2) Add 4 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0075] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0076] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it to 160 °C for hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain a monolithic nickel-based catalyst.

[0077] Example 7

[0078] This example provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0079] (S1) Immerse 10 pieces of nickel foam with a thickness of 1.5 mm, a diameter of 6 mm, and 110 PPI (Pores Per Inch) in 20 mL of 0.1 M HCl solution for 10 min. Then take out the nickel foam and wash it once with deionized water and once with absolute ethanol respectively. After washing, perform a drying treatment (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: a nickel foam material without other impurities;

[0080] (S2) Add 4 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0081] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0082] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it up to 180 °C for a hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and once with ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain a monolithic nickel-based catalyst.

[0083] Example 8

[0084] This example provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0085] (S1) Immerse 10 pieces of nickel foam with a thickness of 1.5 mm, a diameter of 6 mm, and 110 PPI (Pores Per Inch) in 20 mL of 0.1 M HCl solution for 10 min. Then take out the nickel foam and wash it once with deionized water and once with absolute ethanol respectively. After washing, perform a drying treatment (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: a nickel foam material without other impurities;

[0086] (S2) Add 4 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0087] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0088] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it to 120 °C for hydrothermal reaction for 6 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain a monolithic nickel-based catalyst.

[0089] Example 9

[0090] This example provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0091] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm and a diameter of 6 mm and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min, then take out the nickel foam, wash it once with deionized water and anhydrous ethanol respectively, and after the washing is completed, perform a drying treatment (temperature is 80 °C, time is 12 h) to obtain pretreated nickel foam: nickel foam material without other impurities;

[0092] (S2) Add 4 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0093] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0094] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it to 120 °C for hydrothermal reaction for 8 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain a monolithic nickel-based catalyst.

[0095] Example 10

[0096] This example provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0097] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm, a diameter of 6 mm, and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min. Then take out the nickel foam and wash it once with deionized water and once with absolute ethanol respectively. After washing, conduct a drying treatment (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: nickel foam material without other impurities;

[0098] (S2) Add 4 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0099] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0100] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it to 120 °C for hydrothermal reaction for 10 h; after the reaction, wash it once with deionized water and once with ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain a monolithic nickel-based catalyst.

[0101] Example 11

[0102] This example provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0103] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm, a diameter of 6 mm, and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min. Then take out the nickel foam and wash it once with deionized water and once with absolute ethanol respectively. After washing, conduct a drying treatment (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: nickel foam material without other impurities;

[0104] (S2) Add 4 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0105] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0106] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it to 120 °C for hydrothermal reaction for 12 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain a monolithic nickel-based catalyst.

[0107] Example 12

[0108] This example provides a method for preparing a monolithic nickel-based catalyst, which is prepared by the following method:

[0109] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm and a diameter of 6 mm and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min, then take out the nickel foam, wash it once with deionized water and anhydrous ethanol respectively, and perform a drying treatment (temperature is 80 °C, time is 12 h) after the washing to obtain pretreated nickel foam: nickel foam material without other impurities;

[0110] (S2) Add 4 mmol of cerium nitrate to 35 mL of deionized water and mix well to obtain a cerium nitrate solution;

[0111] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the cerium nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0112] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it to 120 °C for hydrothermal reaction for 12 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain a monolithic nickel-based catalyst.

[0113] Comparative Example 1

[0114] This comparative example provides a catalyst, which is nickel foam with a thickness of 1.5 mm, a diameter of 6 mm and 110 PPI (without any treatment).

[0115] Comparative Example 2

[0116] This comparative example provides a method for preparing a nickel-based catalyst, which is prepared by the following method:

[0117] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm, a diameter of 6 mm, and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min. Then take out the nickel foam and wash it once with deionized water and once with absolute ethanol respectively. After washing, perform a drying treatment (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: nickel foam material without other impurities;

[0118] (S2) Add 4 mmol of nickel nitrate to 35 mL of deionized water and mix well to obtain a nickel nitrate solution;

[0119] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the nickel nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0120] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal reactor, then place it in an oven, heat it to 120 °C for hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and once with ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain an integrated nickel-based catalyst.

[0121] Comparative Example 3

[0122] This comparative example provides a method for preparing a nickel-based catalyst, which is prepared by the following method:

[0123] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm, a diameter of 6 mm, and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min. Then take out the nickel foam and wash it once with deionized water and once with absolute ethanol respectively. After washing, perform a drying treatment (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: nickel foam material without other impurities;

[0124] (S2) Add 4 mmol of iron nitrate to 35 mL of deionized water and mix well to obtain an iron nitrate solution;

[0125] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride to the iron nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0126] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal reactor, then place it in an oven, heat it to 120 °C for hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and calcine it from room temperature to 350 °C at a rate of 2 °C / min for 3 h to obtain a monolithic nickel-based catalyst.

[0127] Example 13

[0128] This example provides a method for catalytic ammonia decomposition to hydrogen using a monolithic nickel-based catalyst, which includes the following steps:

[0129] Load the catalysts (10 pieces each) prepared in Examples 1-12 and Comparative Examples 1-3 into a fixed-bed reactor (quartz tube with an inner diameter of 6 mm) to catalyze the decomposition of ammonia to produce hydrogen;

[0130] Among them, during the catalytic reaction process, the raw material gas is high-purity ammonia, and the flow rate is 30 mL·min -1 , and the space velocity is 4245 h -1 , and the reaction pressure is atmospheric pressure. The whole reaction is a continuous dynamic process, and the reaction products enter a gas chromatograph equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID) for sampling and analysis. The experimental results are shown in Table 1.

[0131] The ammonia decomposition conversion rate of the present invention is calculated according to the following formula:

[0132]

[0133] Among them, is the conversion rate of NH3; is the total amount of ammonia in the raw material gas; is the amount of unreacted ammonia.

[0134] Table 1 Experimental results

[0135]

[0136]

[0137] As shown in Table 1, Examples 1 and 2 have a relatively high catalytic ammonia decomposition efficiency, which can be higher than 95% at 600 °C. The corresponding optimal technical solution is as follows: during the hydrothermal reaction process, the temperature is 120 °C and the time is 3 h. The preparation process in Example 2 is relatively complex, and under high temperature conditions, the catalytic ammonia decomposition activities of the catalysts prepared in Examples 1 and 2 are comparable; the activities of Examples 1 and 12 are significantly higher than that of Comparative Example 1, indicating that rare earth elements play an auxiliary role in the catalyst preparation process; the activity of Example 1 is significantly higher than that of Example 12, indicating that lanthanum in rare earth elements is better than cerium. The activity of Example 1 is significantly higher than that of Comparative Example 1, indicating that lanthanum in rare earth elements effectively modifies the nickel foam. The activity of Example 1 is significantly higher than that of Comparative Examples 2 and 3, indicating that the modification effect of lanthanum in rare earth elements on nickel foam is better than that of transition metals nickel and iron.

[0138] Example 14

[0139] This example provides a method for catalytic ammonia decomposition to hydrogen using a monolithic nickel-based catalyst, which includes the following steps:

[0140] Load the monolithic nickel-based catalyst prepared in Example 1 into a fixed-bed reactor to catalyze the decomposition of ammonia to prepare hydrogen;

[0141] Among them, during the catalytic reaction process, the raw material gas is high-purity ammonia, and the flow rate is 30 mL·min -1 , the space velocity is 4245 h -1 , the reaction pressure is atmospheric pressure, the temperature is 600 °C, the time is 100 h, and three points are measured every 2 h to take the average value to complete the stability test. The test results are as Figure 3 shown.

[0142] Through Figure 3 it can be found that after 100 h of reaction, the reaction activity of the monolithic nickel-based catalyst prepared in Example 1 at 600 °C still remains stable, and there is no obvious downward trend, indicating that this monolithic nickel-based catalyst has excellent catalytic stability.

[0143] Example 15

[0144] This example provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0145] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm and a diameter of 6 mm and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min, then take out the nickel foam, and wash it once with deionized water and anhydrous ethanol respectively. After the washing is completed, perform a drying treatment (temperature is 80 °C, time is 12 h) to obtain pretreated nickel foam: nickel foam material without other impurities;

[0146] (S2) Add 3.8 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0147] (S3) Add 7.8 mmol of urea and 8.2 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0148] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal reactor, then place it in an oven, heat it to 120 °C for hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 350 °C at a rate of 2 °C / min for calcination for 3 h to obtain a monolithic nickel-based catalyst.

[0149] Example 16

[0150] This example provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0151] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm and a diameter of 6 mm and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min, then take out the nickel foam, wash it once with deionized water and anhydrous ethanol respectively, and perform drying treatment (temperature is 80 °C, time is 12 h) after washing to obtain pretreated nickel foam: nickel foam material without other impurities;

[0152] (S2) Add 4.2 mmol of lanthanum nitrate to 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0153] (S3) Add 8.2 mmol of urea and 7.8 mmol of ammonium fluoride to the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0154] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal reactor, then place it in an oven, heat it to 120 °C for hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 300 °C at a rate of 2 °C / min for calcination for 4 h to obtain a monolithic nickel-based catalyst.

[0155] Example 17

[0156] This example provides a monolithic nickel-based catalyst, which is prepared by the following method:

[0157] (S1) Place 10 pieces of nickel foam with a thickness of 1.5 mm, a diameter of 6 mm, and 110 PPI (Pores Per Inch) into 20 mL of 0.1 M HCl solution for 10 min. Then take out the nickel foam and wash it once with deionized water and once with absolute ethanol respectively. After washing, conduct a drying treatment (temperature: 80 °C, time: 12 h) to obtain pretreated nickel foam: a nickel foam material without other impurities;

[0158] (S2) Add 4 mmol of lanthanum nitrate into 35 mL of deionized water and mix well to obtain a lanthanum nitrate solution;

[0159] (S3) Add 8 mmol of urea and 8 mmol of ammonium fluoride into the lanthanum nitrate solution prepared in step (S2) in sequence and mix well to obtain a mixed solution;

[0160] (S4) Place the pretreated nickel foam prepared in step (S1) into the mixed solution prepared in step (S3), seal it in a hydrothermal autoclave, then place it in an oven, heat it up to 120 °C for hydrothermal reaction for 3 h; after the reaction, wash it once with deionized water and once with ethanol respectively, then dry the washed sample in an oven at 80 °C for 12 h, and then place the sample in a muffle furnace and heat it from room temperature to 400 °C at a rate of 2 °C / min for calcination for 2 h to obtain a monolithic nickel-based catalyst.

[0161] The monolithic nickel-based catalysts prepared in Examples 15 to 17 have basically the same performance as the monolithic nickel-based catalyst prepared in Example 1.

[0162] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art within the scope of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A preparation method of an integral nickel-based catalyst, characterized in that, It includes the following steps: (S1) Mix urea, ammonium salt and rare earth salt aqueous solution to obtain a mixed solution; (S2) Place the pretreated nickel foam into the mixed solution prepared in step (S1), and obtain the monolithic nickel-based catalyst after hydrothermal reaction and calcination.

2. The preparation method of an integral nickel-based catalyst according to claim 1, characterized in that, In step (S1), the ammonium salt is selected from one or more of ammonium fluoride, ammonium chloride or ammonium nitrate; The rare earth salt is selected from one or more of lanthanum chloride, lanthanum nitrate, lanthanum carbonate, lanthanum sulfate, lanthanum oxalate, cerium chloride, cerium nitrate, cerium carbonate, cerium sulfate, cerium oxalate, praseodymium chloride, praseodymium nitrate, praseodymium carbonate, praseodymium sulfate, praseodymium oxalate, yttrium chloride, yttrium nitrate, yttrium carbonate, yttrium sulfate or yttrium oxalate.

3. The preparation method of an integral nickel-based catalyst according to claim 2, wherein, The molar ratio of urea, ammonium salt and rare earth salt aqueous solution is 7.8-8.2:7.8-8.2:3.8-4.

2.

4. The preparation method of an integral nickel-based catalyst according to claim 1, characterized in that, In step (S2), the pretreated nickel foam is prepared by the following method: Place the nickel foam in an acid solution for cleaning, and obtain the pretreated nickel foam after post-treatment.

5. The preparation method of an integral nickel-based catalyst according to claim 1, characterized in that, In step (S2), during the hydrothermal reaction, the temperature is 80-180 °C and the time is 3-12 h.

6. The preparation method of an integral nickel-based catalyst according to claim 1, characterized in that, In step (S2), during the calcination process, the temperature is 300-400 °C and the time is 2-4 h.

7. An integral nickel-based catalyst, characterized in that, Prepared by the method according to any one of claims 1-6.

8. Use of the monolithic nickel-based catalyst according to claim 7 in catalytic ammonia decomposition for hydrogen production.

9. A method for catalytic ammonia decomposition to produce hydrogen using an integral nickel-based catalyst, characterized in that, It includes the following steps: Use the monolithic nickel-based catalyst according to claim 7 to catalyze the decomposition of ammonia to obtain hydrogen, or, perform high-temperature reduction on the monolithic nickel-based catalyst according to claim 7 and then catalyze the decomposition of ammonia to obtain hydrogen.

10. A method for catalytic ammonia decomposition to produce hydrogen using an integral nickel-based catalyst according to claim 9, characterized in that, During the decomposition process, the temperature is 450-650 °C.

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