A two-dimensional catalyst of cerium-zirconium solid solution loaded with nickel, a preparation method and application thereof

Abstract

The application provides a cerium-zirconium solid solution supported nickel two-dimensional catalyst, a preparation method and application thereof. The application uses citric acid as a template, metal salts as precursors, forms a uniform cerium-zirconium solid solution supported nickel two-dimensional catalyst through high-temperature expansion and air annealing, the catalyst has a nanosheet structure, and is expressed as Ni / Zr 0.5 Ce 0.5 O2. The Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst is applied to hydrogen production through ammonia cracking, at 250 DEG C, the hydrogen production rate is about 9.25 mmol g ‑1 mim ‑1 , which is higher than that of a noble metal catalyst reported at present, and the catalyst has excellent thermal stability; it is shown that the support structure of the solid solution catalyst can promote ammonia cracking activity at low temperature. The preparation method is simple, the obtained catalyst has high ammonia cracking activity, strong stability and uniform composition, and provides a new way and new idea for application of a non-noble metal catalyst to the field of hydrogen production through ammonia cracking at low temperature.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a two-dimensional catalyst of cerium-zirconium solid solution loaded with nickel, a preparation method and application thereof. BACKGROUND

[0002] Hydrogen energy is considered as an important strategic choice for addressing climate change, replacing fossil energy and building a zero-carbon society due to its characteristics of being clean, efficient, low-carbon and flexible. However, due to the low bulk density and difficulty in liquefaction of hydrogen, storage and transportation face a series of technical obstacles, which limit its wide application. Ammonia is an excellent hydrogen carrier (17.8wt%) with the characteristics of easy liquefaction (0.8MPa, 298K) and easy storage and transportation, which can easily overcome the challenges faced by hydrogen storage and transportation. Moreover, ammonia does not produce CO x and other harmful impurities in the process of producing hydrogen, and the ammonia production technology is mature, with large supply and low cost.

[0003] Nowadays, ammonia decomposition for hydrogen production technology is a low-cost, efficient and clean portable hydrogen production method with great application prospect, and has been committed to developing efficient catalysts for the reaction. At present, the catalyst based on noble metal ruthenium is the best catalytic system for ammonia decomposition at low temperature; however, the price of ruthenium is high, the reserves are scarce, and the use cost is high, which limits its large-scale commercial application. Therefore, in recent years, exploring cheap, high-activity and stable catalysts to meet the demand of low-cost catalytic system has attracted widespread attention. In this regard, nickel-based catalyst has been proved to have excellent NH3 cracking activity, and its performance is better than that of other non-noble metal-based catalysts. However, the existing non-noble metal nickel-based catalysts have low activity when catalyzing ammonia cracking for hydrogen production at low temperature, and cannot achieve the performance comparable to noble metal catalysts under the condition of less than 400℃. This is because the physical and chemical properties and performance of nickel-based catalysts depend largely on the properties of the carrier and the synthesis process. SUMMARY

[0004] The purpose of the present application is to provide a two-dimensional catalyst of cerium-zirconium solid solution loaded with nickel, a preparation method and application thereof, so as to solve the problem of low activity of existing non-noble metal catalysts under low temperature conditions.

[0005] The present application is realized in this way:

[0006] A two-dimensional catalyst of cerium-zirconium solid solution loaded with nickel, which is a single tetragonal phase, and its expression is Ni / Zr 0.5 Ce 0.5 O2, the Ni / Zr 0.5 Ce 0.5 O2 catalyst is a two-dimensional nanosheet, single-phase tetragonal solid solution structure.

[0007] The Ni / Zr0.5 Ce 0.5 The O2 catalyst is prepared by using citric acid as a template, expanding at high temperature to obtain a catalyst precursor with highly uniform dispersion of elements, and then air annealing to obtain a two-dimensional solid solution catalyst, which has the performance of efficiently catalyzing ammonia cracking to produce hydrogen at low temperature.

[0008] The solid solution catalyst is a single-phase catalyst in which cerium-zirconium solid solution supports nickel, the solid solution structure enhances the interaction between the support and the active metal and the stability of the catalyst, and the highly dispersed nickel forms a single-phase structure to provide more active sites, so the solid solution catalyst is one of the most potential candidates for a low-temperature ammonia cracking hydrogen production catalyst.

[0009] In combination Figure 1 The preparation of the high-activity low-temperature ammonia cracking hydrogen production solid solution two-dimensional catalyst provided by the application comprises the following steps:

[0010] (1) A certain amount of citric acid and nickel, cerium and zirconium metal salts are dissolved in deionized water, and stirred uniformly to form a mixed solution.

[0011] (2) A certain amount of nitric acid and ethylenediamine solution is added dropwise to the mixed solution in step (1) and stirred uniformly, and after the solution is stable, ammonia water is added dropwise while stirring the mixed solution until the pH value of the mixed solution is about 6.

[0012] (3) The mixed solution in step (2) is placed on a heating stirring table and stirred at 80℃ and 300 revolutions per minute for 5-7 hours to obtain a sol-like solid, and then dried in a blast drying oven at 80℃ for 24 hours to obtain a gel-like solid solution.

[0013] (4) The gel-like solid obtained in step (3) is expanded at high temperature to obtain a catalyst precursor.

[0014] (5) The catalyst precursor obtained in step (4) is placed in a muffle furnace, heated to 400℃ at a heating rate of 5℃ / min in an air environment and kept for 3 hours, and then naturally cooled to room temperature to obtain a solid solution two-dimensional catalyst.

[0015] Preferably, the high-temperature expansion in step (4) refers to placing the gel-like solid obtained in step (3) into a quartz tube, and then placing the quartz tube on a tube furnace which has been heated to 400℃, and the gel-like solid will instantaneously expand from room temperature to 400℃, and then kept for 3 hours and then naturally cooled to room temperature.

[0016] Preferably, in step (1), the nickel, cerium and zirconium metal salts are corresponding nitrate hydrates.

[0017] Preferably, in step (1), the mass ratio of the nitrate hydrate of nickel to the sum of the nitrate hydrates of zirconium and cerium is 4.8:100; the atomic ratio of zirconium to cerium is 1:1.

[0018] The application discloses a two-dimensional nanosheet solid solution catalyst prepared by the method, and specifically represents Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst, Zr is doped into the crystal lattice structure of CeO2, and a cubic phase fluorite structure cerium-zirconium solid solution is formed, but the Ni / Zr 0.5 Ce 0.5 O2 catalyst has a Raman diffraction spectrum image that has characteristics of a tetragonal phase, which cannot be achieved by others. The catalyst has a solid solution structure, uniform element distribution, single phase, nanosheet shape and tetragonal structure.

[0019] The application further discloses the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst. 0.5 Ce 0.5 O2 two-dimensional catalyst is applied to hydrogen production by ammonia cracking, and specifically, the activity of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst is tested by heating in ammonia and argon mixed gas. The results show that the hydrogen production rate of the Ni / Zr -1 min -1 O2 two-dimensional catalyst reaches 9.25 mmol g -1 min -1 O2 two-dimensional catalyst has excellent thermal stability.

[0020] The application has the following advantages:

[0021] 1) The two-dimensional catalyst (namely, the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst) of the cerium-zirconium solid solution loaded with nickel prepared by the application has a solid solution structure, highly dispersed component elements and single phase, and provides a large number of active sites for the ammonia cracking reaction.

[0022] 2) The equipment for preparing the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst only needs an oven, a tube furnace and a muffle furnace, and has the advantages of phase stability, simple equipment and low cost compared with other methods for preparing solid solution materials.

[0023] 3) The Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst prepared by the application can make the hydrogen production rate of ammonia cracking reach 9.25 mmol g -1 mim -1, which exceeds the performance of noble metal catalysts, provides a new idea for the design and synthesis of non-noble metal-based ammonia cracking catalysts at low temperatures, and has potential for industrial ammonia cracking hydrogen production applications.

[0024] 4) The Ni / Zr 0.5 Ce 0.5 The preparation method of the CeO2 two-dimensional catalyst has expansibility, and the proportion of cerium and zirconium can be changed to prepare cerium-zirconium solid solution carriers with different proportions, and other metal elements (such as lanthanum) can be further changed to form a solid solution structure combined with cerium oxide. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a preparation flowchart of the present application.

[0026] Figure 2 is a morphology and element distribution map of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst obtained in Example 1.

[0027] Figure 3 is a nitrogen adsorption-desorption curve of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst obtained in Example 1.

[0028] Figure 4 is an X-ray diffraction image of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst obtained in Example 1.

[0029] Figure 5 is an HRTEM image of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst obtained in Example 1.

[0030] Figure 6 is a Raman diffraction spectrum image of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst obtained in Example 1.

[0031] Figure 7 is a thermal catalytic ammonia cracking hydrogen production performance graph of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst obtained in Example 1.

[0032] Figure 8 is a thermal catalytic ammonia cracking hydrogen production stability test performance graph of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst obtained in Example 1. DETAILED DESCRIPTION

[0033] The specific embodiments of the present application will be described in detail below with reference to the examples.

[0034] Example 1

[0035] In combination Figure 1 , the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst in this example was synthesized as follows:

[0036] (1) 5 g of citric acid and 0.33 mmol of nickel, 2.3 mmol of cerium, and 2.3 mmol of zirconium nitrate hydrate were dissolved in 10 mL of deionized water, stirred uniformly to form a mixed solution.

[0037] (2) 2.5 mL of nitric acid and 1 mL of ethylenediamine solution were added dropwise to the mixed solution and stirred uniformly, and after the solution was stable, ammonia water was added dropwise while stirring the mixed solution until the pH value of the mixed solution was about 6.

[0038] (3) The mixed solution was placed on a heating stirring table at 80°C and stirred at 300 revolutions per minute for 5-7 hours to obtain a sol-like solid, and then dried in a blast drying oven at 80°C for 24 hours to obtain a gel-like solid solution.

[0039] (4) The gel-like solid was placed in a quartz tube protected by Ar, and the quartz tube was placed in a tube furnace heated to 400°C. The gel-like solid instantaneously expanded at high temperature, and then maintained at 400°C for 3 hours, and then naturally cooled to room temperature to obtain a catalyst precursor.

[0040] (5) The catalyst precursor was placed in a muffle furnace, heated to 400°C at a temperature rising rate of 5°C / min in an air environment, and maintained for 3 hours, and then naturally cooled to room temperature to obtain a cerium-zirconium solid solution loaded with nickel two-dimensional catalyst, i.e., Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst.

[0041] The morphology and element analysis test was performed on the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst prepared in this example, and the results are shown in Figure 2 . Figure 2 In the figure, (a) is the morphology of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst, and (b) is the EDS mapping image. It can be seen from Figure 2 that the Ni / Zr 0.5 Ce 0.5 O2 is a two-dimensional solid solution structure, and each component element is highly dispersed to present a single phase, and no particle aggregation phenomenon is observed.

[0042] The Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst prepared in this example was subjected to nitrogen adsorption-desorption test, and the results are shown in Figure 3 According to Figure 3 the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst, the specific surface area of the catalyst was 140.24 m 2 g -1 .

[0043] The Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst prepared in this example was subjected to XRD, electron microscopy and Raman test, and the results are shown in Figure 4-6 . Figure 4 is the X-ray diffraction pattern of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst, Figure 5 is the HRTEM image of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst, Figure 6 is the Raman diffraction spectrum image of the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst. From Figure 4 it can be seen that the XRD pattern of the Ni / Zr 0.5 Ce 0.5 O2 sample presents the cubic fluorite structure of CeO2, and no characteristic peaks belonging to tetragonal zirconia or cubic zirconia are detected, proving the formation of cerium-zirconium solid solution. According to Figure 5 the HRTEM image shows the high crystalline structure of the solid solution, corresponding to the d = 0.32 ± 0.01 nm of the (111) crystal plane of the cubic fluorite structure of CeO2, and the lattice spacing also confirms the solid solution structure. From Figure 6 it can be understood that the shoulder of the Ni / Zr 0.5 Ce 0.5 O2 sample near 473 cm -1 may be caused by the vibration of the tetragonal phase or the F2g mode, and the characteristics belonging to the tetragonal phase are observed.

[0044] Example 2

[0045] The Ni / Zr 0.5 Ce 0.5O2 two-dimensional catalyst weighing 20 mg was placed in a quartz tube, and then placed in a tube furnace. Argon-ammonia mixed gas was passed into the reaction system at a flow rate of 120 mL / min to start the reaction, wherein the flow rate of argon was 80 mL / min, and the flow rate of ammonia was 40 mL / min. Each temperature point was kept for 30 min, and after the catalyst was stabilized, the gas composition was detected by a gas chromatograph. The performance of the test is shown in Table 1. Figure 7 As shown in Table 1, the hydrogen production rate of Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst reached 9.25 mmol g -1 min -1 . Figure 8 As shown in Table 1, the hydrogen production rate of Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst reached 9.25 mmol g - 1 min -1 around, and it can be seen that its performance is stable.

[0046] The Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst prepared in the application was compared with existing non-noble metal catalysts in terms of hydrogen production by ammonia cracking, as shown in Table 1.

[0047] Table 1 Comparison of hydrogen production performance of Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst of the application and existing catalysts

[0048] catalyst Temperature (℃) H2yield (mmol / g / min) literature Ni / Zr 0.5 Ce 0.5 O2]]> 250 9.25 The present invention Co SA / CeO2]] 450 29.09 [1] Ni SA / CeO2]] 300 3.544 [2] 20Co / La-MgO 450 13.24 [3] Ni / MWCNTs 450 1.46 [4]

[0049] As can be seen from Table 1, the Ni / Zr 0.5 Ce 0.5 O2 two-dimensional catalyst prepared in the application can achieve a relatively high hydrogen production rate at a lower temperature (250℃) for hydrogen production by ammonia cracking, overcoming the problem of higher required temperature for non-noble metal catalysts in the prior art.

[0050] In summary, the application discloses a universal preparation method for preparing a two-dimensional nanometer catalyst of cerium-zirconium solid solution loaded with nickel using citric acid as a template. The catalyst is applied to an ammonia cracking reaction for hydrogen production, and the non-noble metal-based catalyst can catalyze ammonia cracking at low temperature and has excellent performance.

[0051] The above is disclosed in the preferred embodiments of the present application, but is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solutions of the present application, and such changes or modifications are equivalent to equivalent embodiments, which are within the scope of the technical solutions.

[0052] The documents listed in Table 1 in the detailed description part of the present application are as follows:

[0053] [1] Xie Fei. Study on hydrogen production from ammonia decomposition and optimization of photothermal conversion device. [D]. Baoding: Hebei agricultural university, 2022.

[0054] [2] Yaguang Li, Qingqing Guan, Guangyao Huang, et al. Low Temperature Thermal and Solar Heating Carbon-Free Hydrogen Production from Ammonia Using Nickel Single Atom Catalysts. [J]. Advanced Energy Materials, 2022, 12, 2202459.

[0055] [3] Hu Xiu-Cui, Wang Wei-Wei, Jin Zhao, et al. Transition metal nanoparticles supported

[0056] MgO as catalysts for hydrogen production via catalytic decomposition of ammonia [J]. Journal of Energy Chemistry, 2019, 38: 41-49.

[0057] [4] Zhang Hui, Alhamed Yahia Abobakor, Kojima Yoshitsugu, et al. Structure and catalytic properties of Ni / MWCNTs and Ni / AC catalysts for hydrogen production via ammonia decomposition [J]. International journal of hydrogen energy, 2014, 39(1): 277-287.

Claims

1. A two-dimensional catalyst of ceria-zirconia solid solution supported nickel, characterized in that, The catalyst is a single tetragonal phase with the formula Ni / Zr 0.5 Ce 0.5 O2, Ni / Zr 0.5 Ce 0.5 The O2catalyst is a two-dimensional nanosheet solid solution structure; The preparation method of the two-dimensional catalyst of cerium-zirconium solid solution loaded with nickel comprises the following steps: a. Dissolving citric acid and metal salts of nickel, cerium and zirconium in deionized water, stirring uniformly to form a mixed solution; b. Adding nitric acid and ethylenediamine dropwise to the mixed solution of step a and stirring uniformly, and then adding ammonia water dropwise until the pH value of the mixed solution is 6 after the solution is stable; c. Placing the mixed solution of step b on a heating stirring table and stirring at 80℃ for 5-7h to obtain a sol-like solid; d. Drying the sol-like solid in a blast drying oven to obtain a gel-like solid; e. Placing the gel-like solid in a quartz tube, placing the quartz tube in a tube furnace at 400℃, instantaneously expanding the gel-like solid, then keeping at 400℃ for 3h, and then naturally cooling to room temperature to obtain a catalyst precursor; f. Placing the catalyst precursor in a muffle furnace, heating to 400℃ under air environment and keeping for 3h to obtain the two-dimensional catalyst of cerium-zirconium solid solution loaded with nickel.

2. A method for preparing a two-dimensional catalyst of ceria-zirconia solid solution supported nickel, characterized by, comprises the following steps: a. Dissolving citric acid and metal salts of nickel, cerium and zirconium in deionized water, stirring uniformly to form a mixed solution; b. Adding nitric acid and ethylenediamine dropwise to the mixed solution of step a and stirring uniformly, and then adding ammonia water dropwise until the pH value of the mixed solution is 6 after the solution is stable; c. Placing the mixed solution of step b on a heating stirring table and stirring at 80℃ for 5-7h to obtain a sol-like solid; d. Drying the sol-like solid in a blast drying oven to obtain a gel-like solid; e. Placing the gel-like solid in a quartz tube, placing the quartz tube in a tube furnace at 400℃, instantaneously expanding the gel-like solid, then keeping at 400℃ for 3h, and then naturally cooling to room temperature to obtain a catalyst precursor; f. Placing the catalyst precursor in a muffle furnace, heating to 400℃ under air environment and keeping for 3h to obtain the two-dimensional catalyst of cerium-zirconium solid solution loaded with nickel.

3. The method for preparing a two-dimensional catalyst of cerium-zirconium solid solution loaded nickel according to claim 2, characterized in that: In step d, the sol-like solid is dried in a blast drying oven at 80℃ for 24h to obtain a gel-like solid.

4. The method for preparing a two-dimensional catalyst of cerium-zirconium solid solution loaded nickel according to claim 2, wherein: In step e, Ar protective gas is introduced into the quartz tube.

5. The method for preparing a two-dimensional catalyst of cerium-zirconium solid solution loaded nickel according to claim 2, characterized in that: In step f, the heating rate is 5℃ / min.

6. The method of claim 2, wherein the ceria-zirconia solid solution supported nickel two-dimensional catalyst is prepared by the steps of: In step c, the stirring rate is 300r / min.

7. The use of the two-dimensional catalyst of cerium-zirconium solid solution loaded with nickel of claim 1 or the two-dimensional catalyst of cerium-zirconium solid solution loaded with nickel prepared according to the method of any one of claims 2-6 in a low-temperature ammonia cracking hydrogen production reaction.

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