Lanthanum nickelate ammonia synthesis catalyst and preparation method and application thereof
Through the preparation method of lanthanum nitriate synthesis ammonia catalyst, hydrogen reduction is used to generate CaH2-LaNiO3-x catalyst, which solves the problem of long activation time of synthesis ammonia in the prior art, and achieves faster ammonia synthesis rate and higher catalytic performance. In industrial applications.
Patent Information
- Application Number
- CN202411489828.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-24
- Publication Date
- 2025-01-03
AI Technical Summary
The existing ammonia synthetic catalysts have a long activation time during the ammonia synthesis process, resulting in a low ammonia synthesis rate and lack of effective methods for improving.
The preparation method of lanthanum nitrate synthesized ammonia catalyst is adopted. By mixing nickel nitrate, lanthanum nitrate and citric acid in water and calcining it, then calcining it without contact with the hydride, hydrogen reduction is used to generate CaH2-LaNiO3-x catalyst, forming Uniform nanoparticle catalyst to improve catalytic activity.
It significantly accelerates the ammonia synthesis rate, improves catalytic performance, and reduces the activation time of the ammonia synthesis process, and is suitable for industrial applications.
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Figure CN119236958A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of synthetic ammonia, and in particular to a lanthanum nickelate catalyst for synthesizing ammonia, and a preparation method and application thereof. Background Art
[0002] There are many methods for preparing supported metal nanoparticle catalysts, including physical mixing, physical or chemical vapor deposition, deposition precipitation and wet chemical impregnation. However, the above methods can only achieve the synthesis of ammonia, and there is no further in-depth research on improving the synthesis rate.
[0003] In order to further reduce the activation time required for the ammonia synthesis process, so that the central metal of the ammonia synthesis catalyst can be dissolved faster, and the ammonia synthesis rate can be accelerated, it is an urgent problem to be solved in this field. Summary of the invention
[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a lanthanum nickelate catalyst for synthesizing ammonia and a preparation method and application thereof.
[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:
[0006] The present invention provides a method for preparing a lanthanum nickelate catalyst for synthesizing ammonia, comprising the following steps:
[0007] (1) mixing nickel nitrate, lanthanum nitrate, citric acid and water, and then heating and calcining them in sequence to obtain lanthanum nickelate;
[0008] (2) The lanthanum nickelate and hydride are mixed and calcined to obtain the lanthanum nickelate ammonia synthesis catalyst.
[0009] Preferably, the mass ratio of nickel nitrate, lanthanum nitrate and citric acid in step (1) is 0.5-1.5:0.5-1.5:2.5-3.5;
[0010] The mass volume ratio of the nickel nitrate and water is 1-3 g:20-30 mL.
[0011] Preferably, the heating temperature in step (1) is 80-90° C. and the heating time is 2-3 h.
[0012] Preferably, the calcination temperature in step (1) is 700-850° C. and the calcination time is 8-20 h.
[0013] Preferably, the hydride in step (2) is calcium hydride and / or barium hydride;
[0014] The mass ratio of lanthanum nickelate to hydride in step (2) is 1:4-6.
[0015] Preferably, the heating rate of the calcination in step (2) is 5 to 15° C. / min.
[0016] Preferably, the target temperature of the calcination in step (2) is 250-300°C;
[0017] The insulation time after reaching the target temperature is 24 to 168 hours.
[0018] The present invention also provides a lanthanum nickelate ammonia synthesis catalyst prepared by the preparation method of the lanthanum nickelate ammonia synthesis catalyst.
[0019] The invention also provides application of the lanthanum nickelate ammonia synthesis catalyst in ammonia synthesis.
[0020] The present invention also provides a method for synthesizing ammonia, wherein the lanthanum nickelate ammonia synthesis catalyst is placed in a mixed gas of nitrogen and hydrogen to synthesize ammonia;
[0021] The molar ratio of nitrogen to hydrogen is 1:2-4; the flow rate of the mixed gas is 50-75 r / min;
[0022] The amount of the lanthanum nickelate catalyst for synthesizing ammonia is 75-120 mg;
[0023] The synthesis temperature is 350-510° C. and the pressure is 3-6 MPa.
[0024] The present invention provides a method for preparing a lanthanum nickelate catalyst for ammonia synthesis, comprising the following steps: (1) mixing nickel nitrate, lanthanum nitrate, citric acid and water, and then heating and calcining in sequence to obtain lanthanum nickelate; (2) mixing lanthanum nickelate and hydride and calcining to obtain the lanthanum nickelate catalyst for ammonia synthesis. The present invention uses lanthanum nitrate, nickel nitrate and citric acid to mix in water, heat and stir to obtain a gel, dry and calcine to obtain lanthanum nickelate powder, and then heat the compound with hydride without contact, and hydrogen is reduced in the process to obtain a perovskite catalyst for ammonia synthesis CaH2-LaNiO after the reduction of calcium hydride and hydrogen release. 3-x In this catalyst system, the sintering-resistant catalyst is synthesized by precipitating nanoparticles in a reducing atmosphere, and uniform and catalytically active nanoparticle catalysts are produced on the surface, which can accelerate the ammonia synthesis rate and improve the catalytic performance of ammonia synthesis. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 X-ray diffraction patterns of the uncalcined catalyst, the catalyst in Example 1, and the catalysts with three different calcination times;
[0026] Figure 2 The performance test results of the uncalcined catalyst, the catalyst in Example 1 and the catalysts with three different calcination times are shown in FIG. DETAILED DESCRIPTION
[0027] The present invention provides a method for preparing a lanthanum nickelate catalyst for synthesizing ammonia, comprising the following steps:
[0028] (1) mixing nickel nitrate, lanthanum nitrate, citric acid and water, and then heating and calcining them in sequence to obtain lanthanum nickelate;
[0029] (2) The lanthanum nickelate and hydride are mixed and calcined to obtain the lanthanum nickelate ammonia synthesis catalyst.
[0030] In the present invention, the mass ratio of nickel nitrate, lanthanum nitrate and citric acid in step (1) is preferably 0.5-1.5:0.5-1.5:2.5-3.5, more preferably 0.6-1.4:0.6-1.4:2.6-3.4, and more preferably 0.8-1.2:0.8-1.2:2.8-3.2.
[0031] In the present invention, citric acid plays the role of complexation and pH adjustment.
[0032] In the present invention, the mass volume ratio of the nickel nitrate and water is preferably 1-3 g: 20-30 mL, more preferably 1.5-2.5 g: 22-28 mL, and more preferably 1.8-2.2 g: 24-26 mL.
[0033] In the present invention, nickel nitrate, lanthanum nitrate, citric acid and water are mixed and fully dissolved and then heated.
[0034] In the present invention, the heating temperature in step (1) is preferably 80-90°C, more preferably 82-88°C, and more preferably 84-86°C; the heating time is preferably 2-3h, more preferably 2.2-2.8h, and more preferably 2.4-2.6h; the rotation speed is preferably 800-1200rpm, more preferably 850-1150rpm, and more preferably 900-1100rpm.
[0035] In the present invention, the purpose of heating is to form a gel.
[0036] In the present invention, the obtained gel is dried to remove moisture to obtain a powder block; the drying temperature is preferably 70 to 80°C, more preferably 72 to 78°C, and more preferably 74 to 76°C.
[0037] In the present invention, the obtained powder mass is calcined.
[0038] In the present invention, the calcination temperature in step (1) is preferably 700-850°C, more preferably 750-800°C, and more preferably 770-780°C; the calcination time is preferably 8-20h, more preferably 10-18h, and more preferably 13-15h.
[0039] In the present invention, pure phase lanthanum nickelate can be generated under specific calcination conditions, avoiding the generation of impurities such as lanthanum oxide.
[0040] In the present invention, the obtained lanthanum nickelate is ground into powder and calcined in step (2).
[0041] In the present invention, the hydride in step (2) is calcium hydride and / or barium hydride.
[0042] In the present invention, the mass ratio of the lanthanum nickelate to the hydride in step (2) is preferably 1:4-6, more preferably 1:4.5-5.5, and more preferably 1:4.8-5.2.
[0043] In the present invention, lanthanum nickelate and hydride are calcined without contact. In a certain space, lanthanum nickelate is placed on the surface of aluminum foil and suspended in the space; hydride is placed at the bottom. During the calcination process, the hydride will generate hydrogen, which is used to reduce lanthanum nickelate, thereby generating a lanthanum nickelate ammonia synthesis catalyst; during the entire calcination process of step (2), lanthanum nickelate and hydride are not in direct contact.
[0044] In the present invention, the vacuum degree of the calcination in step (2) is 100%, the vacuum pump is pumped to negative pressure, maintained for 5 minutes, and the spray gun is closed to complete the creation of vacuum conditions.
[0045] In the present invention, the heating rate of the calcination in step (2) is preferably 5 to 15°C / min, more preferably 6 to 14°C / min, and more preferably 8 to 12°C / min.
[0046] In the present invention, the target temperature of the calcination in step (2) is preferably 250-300°C, more preferably 260-290°C, and even more preferably 270-280°C.
[0047] In the present invention, the heat preservation time after reaching the target temperature is preferably 24 to 168 hours, more preferably 48 to 144 hours, and even more preferably 72 to 120 hours.
[0048] The present invention also provides a lanthanum nickelate ammonia synthesis catalyst prepared by the preparation method of the lanthanum nickelate ammonia synthesis catalyst.
[0049] The invention also provides application of the lanthanum nickelate ammonia synthesis catalyst in ammonia synthesis.
[0050] The present invention also provides a method for synthesizing ammonia, wherein the lanthanum nickelate ammonia synthesis catalyst is placed in a mixed gas of nitrogen and hydrogen to synthesize ammonia.
[0051] In the present invention, the molar ratio of nitrogen to hydrogen is preferably 1:2-4, more preferably 1:2.5-3.5, and more preferably 1:2.8-3.2; the flow rate of the mixed gas is preferably 50-75 r / min, more preferably 55-70 r / min, and more preferably 60-65 r / min.
[0052] In the present invention, the usage of the lanthanum nickelate catalyst for ammonia synthesis is preferably 75 to 120 mg, more preferably 80 to 115 mg, and even more preferably 90 to 105 mg.
[0053] In the present invention, the synthesis temperature is preferably 350-510°C, more preferably 400-450°C, more preferably 420-430°C; the pressure is preferably 3-6 MPa, more preferably 4-5 MPa, more preferably 4.4-4.6 MPa.
[0054] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.
[0055] Example 1
[0056] 1 g of nickel nitrate, 1 g of lanthanum nitrate and 2.5 g of citric acid were dissolved in 20 mL of water to obtain a mixed solution; the mixed solution was stirred at 80° C. and 800 rpm for 2.5 h to obtain a gel; the gel was dried at 70° C. to constant weight to obtain a powder block; the powder block was calcined at 750° C. for 12 h, and ground to obtain lanthanum nickelate powder.
[0057] 50 mg of lanthanum nickelate powder was wrapped in aluminum foil and sealed in a pyrex tube. 250 mg of calcium hydride was placed at the bottom of the tube. The temperature was raised to 280 °C at a rate of 10 °C / min in a vacuum and calcined at this temperature for 24 h to obtain a lanthanum nickelate catalyst for ammonia synthesis, which was recorded as CaH2-LaNiO. 3-x 1 day.
[0058] Example 2
[0059] 1.5 g of nickel nitrate, 1 g of lanthanum nitrate and 3.4 g of citric acid were dissolved in 30 mL of water to obtain a mixed solution; the mixed solution was stirred at 900 rpm at 85° C. for 3 h to obtain a gel; the gel was dried at 80° C. to constant weight to obtain a powder block; the powder block was calcined at 750° C. for 20 h, and ground to obtain lanthanum nickelate powder.
[0060] 50 mg of lanthanum nickelate powder was wrapped in aluminum foil and sealed in a pyrex tube, 200 mg of calcium hydride was placed at the bottom of the tube, the temperature was raised to 280°C at a rate of 10°C / min in a vacuum, and calcined at this temperature for 48 hours to obtain a lanthanum nickelate ammonia synthesis catalyst.
[0061] The same method as in Example 1 was used to change the calcination time in step (2) to 72 h, 120 h and 168 h to obtain different catalysts. The catalyst calcined for 72 h was denoted as CaH2-LaNiO 3-x 3 days; the catalyst with calcination time of 120h is recorded as CaH2-LaNiO 3-x 5 days; the catalyst with calcination time of 168h is recorded as CaH2-LaNiO 3-x 7 days; the uncalcined catalyst, the catalyst in Example 1 and the above three catalysts with different calcination times were subjected to X-ray diffraction analysis, and the results were as follows Figure 1 As shown, from Figure 1 It can be seen that the lanthanum nickelate ammonia synthesis catalyst reduced by calcium hydride showed characteristic peaks of nickel oxide and metallic nickel, which further accelerated the dissolution of the metal and formed active sites.
[0062] The uncalcined catalyst, the catalyst in Example 1 and three catalysts with different calcination times were tested for performance. The test conditions were as follows: the reaction pressure was 5 MPa, the hydrogen and nitrogen were mixed in a molar ratio of 3:1, and the mixed gas flow rate was 60 mL / min. The ammonia synthesis rate of the two ammonia synthesis catalysts was compared at reaction temperatures of 400°C, 425°C, 450°C, 475°C, and 500°C. The test results are shown in FIG. Figure 2 As shown in the figure, in the temperature range of 400-475℃, its ammonia synthesis activity is higher than that of CaH2-LaNiO 3-x When we use hydride reduction to treat the sample, the activation time is greatly improved compared with the untreated LaNiO3, and the reaction becomes easier to carry out, which also provides application prospects for industrial practical applications. The catalyst provided by the present invention can further reduce the reaction of the synthetic ammonia process and make the reaction easier to occur.
[0063] As can be seen from the above embodiments, the present invention provides a method for preparing a lanthanum nickelate catalyst for ammonia synthesis, comprising the following steps: (1) mixing nickel nitrate, lanthanum nitrate, citric acid and water, and then heating and calcining in sequence to obtain lanthanum nickelate; (2) mixing lanthanum nickelate and hydride and calcining to obtain the lanthanum nickelate catalyst for ammonia synthesis. The present invention uses lanthanum nitrate, nickel nitrate and citric acid to mix in water, heat and stir to obtain a gel, dry and calcine to obtain lanthanum nickelate powder, and then heat the compound with hydride without contact, and hydrogen is reduced in the process to obtain a perovskite catalyst for ammonia synthesis CaH2-LaNiO after the reduction of calcium hydride and hydrogen release. 3-xIn this catalyst system, the sintering-resistant catalyst is synthesized by precipitating nanoparticles in a reducing atmosphere, and uniform and catalytically active nanoparticle catalysts are produced on the surface, which can accelerate the ammonia synthesis rate and improve the catalytic performance of ammonia synthesis.
[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for preparing a lanthanum nickelate catalyst for ammonia synthesis, characterized in that: It includes the following steps: (1) mixing nickel nitrate, lanthanum nitrate, citric acid and water, and then heating and calcining them in sequence to obtain lanthanum nickelate; (2) The lanthanum nickelate and hydride are mixed and calcined to obtain the lanthanum nickelate ammonia synthesis catalyst.
2. The method for preparing a lanthanum nickelate catalyst for ammonia synthesis according to claim 1, characterized in that: The mass ratio of nickel nitrate, lanthanum nitrate and citric acid in step (1) is 0.5-1.5:0.5-1.5:2.5-3.5; The mass volume ratio of the nickel nitrate and water is 1-3 g:20-30 mL.
3. The method for preparing a lanthanum nickelate catalyst for ammonia synthesis according to claim 1 or 2, characterized in that: The heating temperature in step (1) is 80-90° C. and the heating time is 2-3 hours.
4. The method for preparing a lanthanum nickelate catalyst for ammonia synthesis according to claim 3, characterized in that: The calcination temperature in step (1) is 700-850° C. and the calcination time is 8-20 hours.
5. The method for preparing the lanthanum nickelate catalyst for ammonia synthesis according to claim 1 or 4, characterized in that: The hydride in step (2) is calcium hydride and / or barium hydride; The mass ratio of lanthanum nickelate to hydride in step (2) is 1:4-6.
6. The method for preparing a lanthanum nickelate catalyst for ammonia synthesis according to claim 5, characterized in that: The heating rate of the calcination in step (2) is 5 to 15°C / min.
7. The method for preparing a lanthanum nickelate catalyst for ammonia synthesis according to claim 6, characterized in that: The target temperature of calcination in step (2) is 250-300°C; The insulation time after reaching the target temperature is 24 to 168 hours.
8. The lanthanum nickelate ammonia synthesis catalyst prepared by the method for preparing the lanthanum nickelate ammonia synthesis catalyst according to any one of claims 1 to 7.
9. Use of the lanthanum nickelate ammonia synthesis catalyst according to claim 8 in synthesizing ammonia.
10. A method for synthesizing ammonia, characterized in that: Placing the lanthanum nickelate catalyst for ammonia synthesis as claimed in claim 8 in a mixed gas of nitrogen and hydrogen to synthesize ammonia; The molar ratio of nitrogen to hydrogen is 1:2-4; the flow rate of the mixed gas is 50-75 r / min; The amount of the lanthanum nickelate catalyst for synthesizing ammonia is 75-120 mg; The synthesis temperature is 350-510° C. and the pressure is 3-6 MPa.