Preparation method and application of Ni / Ba-Nd2O3 catalyst

Abstract

The invention relates to the technical field of hydrogen production through ammonia decomposition, in particular to a preparation method and application of a Ni / Ba-Nd2O3 catalyst. The conventional transition metal-based catalyst is very difficult to realize 90% of ammonia decomposition conversion rate at the temperature of lower than 700 DEG C. In order to solve the problems, the invention provides the preparation method of the Ni / Ba-Nd2O3 catalyst, Nd2O3 is subjected to chemical doping modification by adopting a Ba element to obtain Ba-Nd2O3, and Ba-Nd2O3 is subjected to chemical doping modification by adopting a Ni element to finally obtain Ni / Ba-Nd2O3, the obtained Ni / Ba-Nd2O3 has relatively good catalytic activity for hydrogen production reaction through ammonia gas decomposition, and at the temperature of not more than 700 DEG C (about 600 DEG C), the catalytic activity of the Ni / Ba-Nd2O3 is greatly improved. The catalyst can achieve more than 90% of ammonia decomposition conversion rate.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by decomposing ammonia, and in particular to a preparation method and application of a Ni / Ba-Nd2O3 catalyst. Background Art

[0002] The world is facing the problem of energy depletion and environmental pollution caused by the use of fossil fuels, and there is an urgent need to develop efficient green and clean energy. Hydrogen energy has become the focus of research due to its clean and efficient characteristics. The demand for hydrogen energy is growing rapidly worldwide. However, there are still major difficulties in the storage and utilization of hydrogen. Ammonia, as a hydrogen carrier, has the advantages of high yield, high hydrogen content (17.8wt%), low storage pressure, and long-term storage stability. Catalytic ammonia decomposition can directly provide high-purity hydrogen for proton exchange membrane fuel cells, avoiding poisoning of the Pt electrode in the battery.

[0003] The ammonia decomposition reaction is a reversible reaction. The main reaction steps are the adsorption of NH3 molecules on the catalyst, the continuous desorption of H on the surface of NH3 to form N and H atoms, and finally the formation of N2 and H2 through the recombination adsorption of N and H. At present, the active metals mainly used in the research of ammonia decomposition to produce hydrogen are Ru, Ni, Co, Fe, Mo and other active metals. Ru-based catalysts are expensive and costly. Conventional transition metal-based catalysts are difficult to achieve a 90% ammonia decomposition conversion rate at temperatures below 700°C. Summary of the invention

[0004] The problem in the prior art is that it is difficult for conventional transition metal-based catalysts to achieve a 90% ammonia decomposition conversion rate at a temperature below 700°C. In view of the above problem, the present invention provides a method for preparing a Ni / Ba-Nd2O3 catalyst, which comprises the following preparation steps:

[0005] (1) placing a soluble neodymium salt in deionized water, adjusting the solution to be alkaline with ammonia water, stirring the reaction, vacuum drying the product, and calcining the dried product in an air atmosphere to obtain a Nd2O3 carrier;

[0006] (2) dissolving Ba(NO3)2 in deionized water to obtain a barium nitrate solution, placing the Nd2O3 carrier obtained in step (1) in the barium nitrate solution, immersing and aging the carrier, and then drying the carrier. The dried product is calcined in an air atmosphere to obtain Ba-Nd2O3.

[0007] (3) dissolving a soluble nickel salt in deionized water, then adding a Ba-Nd2O3 carrier thereto, stirring, impregnating, aging, and then drying to obtain a precursor;

[0008] (4) The precursor is calcined in an air atmosphere to obtain Ni / Ba-Nd2O3.

[0009] Preferably, in step (2), the mass ratio of Ba(NO3)2 to Nd2O3 carrier is 0.053-0.095:0.5.

[0010] Preferably, in step (2), the mass ratio of Ba(NO3)2 to Nd2O3 carrier is 0.074:0.5.

[0011] Preferably, the calcination temperature in step (1) is not less than 650°C, the calcination time is not less than 4 hours, and the heating rate is not greater than 5°C·min -1 .

[0012] Preferably, the calcination temperature in step (2) is not less than 700°C, the calcination time is not less than 4 hours, and the heating rate is not greater than 5°C·min -1 .

[0013] Preferably, the immersion and aging time in step (2) is not less than 24 hours.

[0014] Preferably, the immersion and aging time in step (3) is not less than 24 hours.

[0015] Preferably, the calcination temperature in step (4) is not less than 700°C, the calcination time is not less than 4 hours, and the heating rate is not greater than 5°C·min -1 .

[0016] Preferably, the mass ratio of the soluble nickel salt to the Ba-Nd2O3 carrier is 0.52:0.3.

[0017] Preferably, the soluble nickel salt is Ni(NO3)2·6H2O.

[0018] The present invention has the following beneficial effects:

[0019] (1) The Ni / Ba-Nd2O3 obtained in the present invention has a good catalytic effect on the ammonia decomposition hydrogen production reaction. No precious metal active substances such as Ru are used in its preparation process, which has lower costs and better market competitiveness;

[0020] (2) Through research, the present invention found that during the preparation process of Ni / Ba-Nd2O3, the mass ratio of Ba(NO3)2 to Nd2O3 carrier is 0.074:0.5, which has better catalytic activity than other mass ratios of Ba(NO3)2 to Nd2O3 carrier. The obtained 35Ni / 7Ba-Nd2O3 has better catalytic activity for the ammonia decomposition reaction to produce hydrogen. At a temperature of about 600°C, the catalyst can achieve an ammonia decomposition conversion rate of more than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1: NH3 conversion rates of the ammonia decomposition hydrogen production catalysts obtained in Examples 1-3 and Comparative Example 1 when catalyzing ammonia decomposition at different temperatures.

[0022] Figure 2 : The hydrogen generation rates of the ammonia decomposition hydrogen production catalysts obtained in Examples 1-3 and Comparative Example 1 when catalyzing ammonia decomposition at different temperatures.

[0023] Figure 3 : The reaction activation energy required for the ammonia decomposition hydrogen production catalysts obtained in Examples 1-3 and Comparative Example 1 to catalyze the decomposition of ammonia.

[0024] Figure 4 : XRD diffraction patterns of the ammonia decomposition hydrogen production catalysts obtained in Example 2 and Comparative Example 1, respectively.

[0025] Figure 5 : TEM image of the ammonia decomposition hydrogen production catalyst obtained in Example 2. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the examples. However, it should be understood that the following examples are only illustrative of the embodiments of the present invention, and are not intended to limit the scope of the present invention.

[0027] The catalytic activity of the catalysts obtained in the following examples of the present invention for hydrogen production by decomposition of ammonia was tested according to the following steps:

[0028] A quartz tube was used as a reactor. The inner diameter of the quartz tube was 4 mm and the length was 0.5 m. 0.1 g of catalyst was placed in the quartz tube. The temperature of the reactor was then raised to different specified temperatures and kept constant for 30 min. NH3 was then continuously and evenly introduced from one end of the quartz tube and discharged from the other end at a flow rate of 50 mL / min. The gases discharged at different temperatures were collected within the same sampling time and the volume content of NH3 in the product was analyzed using a thermal conductivity detector of a Beifen gas chromatograph. The detector temperature was set to 150 °C. H2 was used as the chromatograph carrier gas with a carrier gas flow rate of 40 mL / min. The chromatographic column used was a special column for amine analysis produced by Shanghai Ouni, and the column temperature was set to 110 °C.

[0029] The ammonia decomposition conversion rate is calculated according to the following formula:

[0030]

[0031] in,

[0032] in, is the NH3 conversion rate, is the total amount of ammonia in the feed gas, is the volume content of unreacted NH3.

[0033] Example 1

[0034] A method for preparing a Ni / Ba-Nd2O3 catalyst is as follows:

[0035] (1) 2 g of Nd(NO3)3·6H2O was placed in 100 mL of deionized water, and ammonia water was slowly added to adjust the solution pH to 10. After stirring for 1 h, the reaction solution was dried at 80°C. The dried product was placed in a muffle furnace and calcined in an air atmosphere to obtain a Nd2O3 carrier. The calcination temperature was 650°C, the calcination time was 4 h, and the heating rate was 5°C·min -1 ;

[0036] (2) 0.053 g Ba(NO3)2 was dissolved in 20 mL deionized water, and 0.5 g Nd2O3 carrier was placed in a barium nitrate solution. After immersion and aging for 24 h, the product was dried. The dried product was placed in a muffle furnace and calcined in an air atmosphere to obtain 5Ba-Nd2O3. The calcination temperature was 700 °C, the calcination time was 4 h, and the heating rate was 5 °C min -1 ;

[0037] (3) 0.52 g of Ni(NO3)2·6H2O was dissolved in 20 mL of deionized water to obtain a nickel nitrate solution, 0.3 g of Ba-Nd2O3 carrier was placed in the nickel nitrate solution, immersed and aged for 24 h, and then dried to obtain a precursor, which was then placed in a muffle furnace and calcined in an air atmosphere at a calcination temperature of 700 °C, a calcination time of 4 h, and a heating rate of 5 °C·min -1 , that is, the catalyst obtained in Example 1 is recorded as 35Ni / 5Ba-Nd2O3.

[0038] Example 2 is the same as Example 1, except that the amount of Ba(NO3)2 added in step (2) of Example 2 is 0.074 g.

[0039] The catalyst obtained in Example 2 is recorded as 35Ni / 7Ba-Nd2O3.

[0040] Example 3 is the same as Example 1, except that the amount of Ba(NO3)2 added in step (2) of Example 3 is 0.095 g.

[0041] The catalyst obtained in Example 3 is recorded as 35Ni / 9Ba-Nd2O3.

[0042] Comparative Example 1

[0043] The preparation method of 35Ni / Nd2O3 is as follows:

[0044] 2g Nd(NO3)3·6H2O was placed in 100mL deionized water, and ammonia water was slowly added to adjust the solution pH to 10. After stirring for 1h, the reaction solution was dried at 80°C. The dried product was placed in a muffle furnace and calcined in an air atmosphere to obtain a Nd2O3 carrier. The calcination temperature was 650°C, the calcination time was 4h, and the heating rate was 5°C·min -1 ;

[0045] 0.52 g of Ni(NO3)2·6H2O was dissolved in 20 mL of deionized water to obtain a nickel nitrate solution. 0.3 g of Nd2O3 carrier was placed in the nickel nitrate solution, immersed and aged for 24 h, and then dried to obtain a precursor. The precursor was then placed in a muffle furnace and calcined in an air atmosphere at a calcination temperature of 700 ° C, a calcination time of 4 h, and a heating rate of 5 ° C·min -1 , and the catalyst 35Ni / Nd2O3 is obtained.

[0046] The ammonia decomposition conversion rate, hydrogen generation rate and reaction activation energy of the catalysts obtained in Examples 1-3 and Comparative Example 1 in the process of hydrogen production by ammonia decomposition are as shown in the attached specification. Figure 1-3 As shown in the test results, 35Ni / 7Ba-Nd2O3 has the best performance. When 35Ni / 7Ba-Nd2O3 catalyzes ammonia decomposition, the NH3 conversion rate reaches 96.8% at 600℃, and the hydrogen generation rate is 32.41mmol gcat -1 min -1 The activation energy of the reaction is 53.6 kJ mol -1 .

[0047] When 35Ni / 5Ba-Nd2O3 catalyzes the decomposition of ammonia, the NH3 conversion rate reaches 92.7% at 600℃, and the hydrogen generation rate is 31.03mmol gcat -1 min -1 The activation energy of the reaction is 60.7 kJ mol -1 .

[0048] When 35Ni / 9Ba-Nd2O3 catalyzes the decomposition of ammonia, the NH3 conversion rate reaches 91.6% at 600℃, and the hydrogen generation rate is 30.68mmol gcat -1 min -1 The activation energy of the reaction is 65.3 kJ mol -1 .

[0049] The XRD diffraction patterns of 35Ni / 7Ba-Nd2O3 and 35Ni / Nd2O3 are shown in the attached manual. Figure 4As shown. The image shows that after Ba-Nd2O3 is loaded with Ni, the characteristic diffraction peaks at 2θ=37.2°, 43.3° and 62.8° correspond to the (111), (200) and (220) crystal planes of NiO, respectively, indicating that Ni is successfully loaded onto Nd2O3 in the form of NiO nanoparticles. In addition to the characteristic diffraction peaks of Nd2O3 and NiO, the Ba-doped catalyst 35Ni / 7Ba-Nd2O3 also clearly shows the diffraction peaks of BaO, indicating that Ba is successfully doped into the molecular structure of the catalyst.

[0050] TEM image of 35Ni / 7Ba-Nd2O3 is attached to the manual. Figure 5 As shown in the image, the catalyst NiO particles are evenly distributed on the carrier Nd2O3. The corresponding HRTEM image clearly shows that the NiO lattice fringe spacing is 0.218nm, belonging to the (200) crystal plane of the NiO crystal, which is consistent with the XRD results.

[0051] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a Ni / Ba-Nd2O3 catalyst, characterized in that: The method comprises the following preparation steps: (1) placing a soluble neodymium salt in deionized water, adjusting the solution to be alkaline with ammonia water, stirring the reaction, vacuum drying the product, and calcining the dried product in an air atmosphere to obtain a Nd2O3 carrier; (2) dissolving Ba(NO3)2 in deionized water to obtain a barium nitrate solution, placing the Nd2O3 carrier obtained in step (1) in the barium nitrate solution, immersing and aging the carrier, and then drying the carrier. The dried product is calcined in an air atmosphere to obtain Ba-Nd2O3. (3) dissolving a soluble nickel salt in deionized water, then adding a Ba-Nd2O3 carrier thereto, stirring, impregnating, aging, and then drying to obtain a precursor; (4) The precursor is calcined in an air atmosphere to obtain Ni / Ba-Nd2O3.

2. The method for preparing a Ni / Ba-Nd2O3 catalyst according to claim 1, characterized in that: In step (2), the mass ratio of Ba(NO3)2 to Nd2O3 carrier is 0.053-0.095:0.

5.

3. The method for preparing a Ni / Ba-Nd2O3 catalyst according to claim 2, characterized in that: In step (2), the mass ratio of Ba(NO3)2 to Nd2O3 carrier is 0.074:0.

5.

4. The method for preparing a Ni / Ba-Nd2O3 catalyst according to claim 1, characterized in that: The calcination temperature in step (1) is not less than 650°C, the calcination time is not less than 4 hours, and the heating rate is not greater than 5°C·min -1 .

5. The method for preparing a Ni / Ba-Nd2O3 catalyst according to claim 1, characterized in that: The calcination temperature in step (2) is not less than 700°C, the calcination time is not less than 4 hours, and the heating rate is not greater than 5°C·min -1 .

6. The method for preparing a Ni / Ba-Nd2O3 catalyst according to claim 1, characterized in that: The soaking and aging time in step (2) is not less than 24 hours.

7. The method for preparing a Ni / Ba-Nd2O3 catalyst according to claim 1, characterized in that: The immersion and aging time in step (3) is not less than 24 hours.

8. The method for preparing a Ni / Ba-Nd2O3 catalyst according to claim 1, characterized in that: The calcination temperature in step (4) is not less than 700°C, the calcination time is not less than 4 hours, and the heating rate is not greater than 5°C·min -1 .

9. The method for preparing a Ni / Ba-Nd2O3 catalyst according to claim 1, characterized in that: The mass ratio of the soluble nickel salt to the Ba-Nd2O3 carrier is 0.52:0.

3.

10. The method for preparing a Ni / Ba-Nd2O3 catalyst according to claim 1, characterized in that: The soluble nickel salt is Ni(NO3)2·6H2O.

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