CN117816219A - Cobalt-based porous material modified by yttrium oxide, preparation method thereof and application thereof in catalytic ammonia decomposition hydrogen production - Google Patents
Cobalt-based porous material modified by yttrium oxide, preparation method thereof and application thereof in catalytic ammonia decomposition hydrogen production Download PDFInfo
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 107
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 50
- 239000011148 porous material Substances 0.000 title claims abstract description 42
- 238000000354 decomposition reaction Methods 0.000 title claims abstract description 36
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 18
- 239000001257 hydrogen Substances 0.000 title claims abstract description 18
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 18
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 title claims abstract description 16
- 229910017052 cobalt Inorganic materials 0.000 title claims abstract description 15
- 239000010941 cobalt Substances 0.000 title claims abstract description 15
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 title claims abstract description 15
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 230000003197 catalytic effect Effects 0.000 title abstract description 13
- 238000004519 manufacturing process Methods 0.000 title description 7
- 239000003054 catalyst Substances 0.000 claims abstract description 40
- 238000006243 chemical reaction Methods 0.000 claims abstract description 20
- -1 yttrium oxide modified cobalt Chemical class 0.000 claims abstract description 14
- 150000001868 cobalt Chemical class 0.000 claims description 23
- 239000007864 aqueous solution Substances 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 14
- LXBGSDVWAMZHDD-UHFFFAOYSA-N 2-methyl-1h-imidazole Chemical compound CC1=NC=CN1 LXBGSDVWAMZHDD-UHFFFAOYSA-N 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 12
- 150000003746 yttrium Chemical class 0.000 claims description 10
- 150000003839 salts Chemical class 0.000 claims description 8
- QBAZWXKSCUESGU-UHFFFAOYSA-N yttrium(3+);trinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Y+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O QBAZWXKSCUESGU-UHFFFAOYSA-N 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 238000001354 calcination Methods 0.000 claims description 6
- 239000000243 solution Substances 0.000 claims description 6
- 239000012298 atmosphere Substances 0.000 claims description 5
- 239000007789 gas Substances 0.000 claims description 5
- 230000004913 activation Effects 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- QGUAJWGNOXCYJF-UHFFFAOYSA-N cobalt dinitrate hexahydrate Chemical compound O.O.O.O.O.O.[Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O QGUAJWGNOXCYJF-UHFFFAOYSA-N 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 238000010926 purge Methods 0.000 claims description 3
- 238000006722 reduction reaction Methods 0.000 claims description 3
- OBOSXEWFRARQPU-UHFFFAOYSA-N 2-n,2-n-dimethylpyridine-2,5-diamine Chemical compound CN(C)C1=CC=C(N)C=N1 OBOSXEWFRARQPU-UHFFFAOYSA-N 0.000 claims description 2
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 claims description 2
- 229910000361 cobalt sulfate Inorganic materials 0.000 claims description 2
- 229940044175 cobalt sulfate Drugs 0.000 claims description 2
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 claims description 2
- ZBYYWKJVSFHYJL-UHFFFAOYSA-L cobalt(2+);diacetate;tetrahydrate Chemical compound O.O.O.O.[Co+2].CC([O-])=O.CC([O-])=O ZBYYWKJVSFHYJL-UHFFFAOYSA-L 0.000 claims description 2
- 238000013329 compounding Methods 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 229910000347 yttrium sulfate Inorganic materials 0.000 claims description 2
- RTAYJOCWVUTQHB-UHFFFAOYSA-H yttrium(3+);trisulfate Chemical compound [Y+3].[Y+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RTAYJOCWVUTQHB-UHFFFAOYSA-H 0.000 claims description 2
- 230000000052 comparative effect Effects 0.000 description 17
- 230000000694 effects Effects 0.000 description 12
- 238000003795 desorption Methods 0.000 description 5
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 125000004433 nitrogen atom Chemical group N* 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- 238000004873 anchoring Methods 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910000000 metal hydroxide Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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Abstract
The invention provides a cobalt-based porous material modified by yttrium oxide, a preparation method thereof and application thereof in catalyzing ammonia to decompose and prepare hydrogen. The yttrium oxide modified cobalt-based porous material provided by the invention has large specific surface area, more Co reaction active sites, high catalytic ammonia decomposition efficiency and pure ammonia airspeed of 20000h at 550 DEG C ‑1 The highest ammonia decomposition rate can reach 92.3%, and the catalyst has good stability and good application in the field of catalytic ammonia decomposition hydrogen productionThe application prospect is good.
Description
Technical Field
The invention belongs to the technical field of catalysts containing metal or metal oxide or hydroxide, and particularly relates to a cobalt-based porous material modified by yttrium oxide, a preparation method thereof and application thereof in catalyzing ammonia decomposition to prepare hydrogen.
Background
The development and utilization of green hydrogen energy sources with high energy density (143 MJ/kg) can effectively improve the energy crisis and environmental problems caused by the over exploitation of fossil fuels. However, the storage and transportation problems of hydrogen are severely limited to be widely applied due to the great difficulty of hydrogen compression. Considering that ammonia is easily liquefied at normal temperature, is safe to transport, and has a high hydrogen content (17.6 wt%) and a large volume energy density (11.5 MJ/L), hydrogen production by ammonia decomposition is an efficient and feasible method for solving the above-mentioned challenges. However, the decomposition of ammonia is an endothermic reaction, which requires high temperatures to be carried out and consumes a large amount of energy. Research shows that the addition of a suitable catalyst can reduce the reaction activation energy and thus the energy consumption of the ammonia decomposition reaction. Of these, ru-based catalysts are considered to be the best ammonia decomposition catalysts at present, but commercial applications are difficult to achieve due to the high price and scarcity of ruthenium. Therefore, it is highly necessary to develop a non-noble metal catalyst having high economic efficiency and excellent ammonia decomposing performance. Among the many non-noble metal catalysts, co-based catalysts exhibit excellent ammonia decomposition activity, and have great potential in achieving high economy of ammonia decomposition. However, co-based catalysts are rarely mentioned for practical use in ammonia decomposition reactions, probably because they deactivate easily at high temperatures, but also attenuate significantly at low temperatures. It is very significant to develop a cobalt catalyst with high activity and good catalytic stability for producing hydrogen by ammonia decomposition.
Disclosure of Invention
Aiming at the defects in the prior art, the technical problem to be solved by the invention is to provide the yttrium oxide modified cobalt-based porous material, the preparation method and the application thereof in the aspect of catalytic ammonia decomposition hydrogen production, wherein the yttrium oxide modified cobalt-based porous material still has good catalytic ammonia decomposition activity at a lower temperature (about 550 ℃), and has good catalytic stability.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
provided is a cobalt-based porous material modified by yttrium oxide, which is obtained by compounding ZIF-67 (Co) and yttrium oxide, wherein the yttrium oxide has nanometer size and is uniformly distributed on the surface of the ZIF-67 (Co).
According to the scheme, the specific surface area of the yttrium oxide modified cobalt-based porous material is 140-270 m 2 Per gram, the Co content in the yttrium oxide modified cobalt-based porous material is 28 to 31 weight percent, Y 2 O 3 The content of (2) is 2-8wt%.
The invention also discloses a preparation method of the yttrium oxide modified cobalt-based porous material, which comprises the following specific steps:
1) Preparation of ZIF-67 (Co): respectively dissolving 2-methylimidazole and cobalt salt in water to obtain an aqueous solution containing 2-methylimidazole and an aqueous solution containing Co salt, slowly adding the aqueous solution containing 2-methylimidazole into the aqueous solution containing Co salt under the condition of stirring, and stirring for 2-4 hours to obtain a reaction solution containing ZIF-67 (Co);
2) Preparation of a cobalt-based porous material modified by yttrium oxide: mixing the reaction solution containing ZIF-67 (Co) obtained in the step 1) with yttrium salt, reacting under stirring, separating to obtain yttrium salt doped ZIF-67 (Co) after the reaction is finished, and then calcining and reducing the obtained yttrium salt doped ZIF-67 (Co) in sequence to obtain the yttrium trioxide modified cobalt-based porous material.
According to the scheme, the cobalt salt in the step 1) is one of cobalt nitrate hexahydrate, cobalt chloride, cobalt sulfate and cobalt acetate tetrahydrate.
According to the scheme, the molar ratio of the cobalt salt to the 2-methylimidazole in the step 1) is 1:4 to 8.
According to the scheme, the concentration of the aqueous solution containing the 2-methylimidazole in the step 1) is 0.2-0.4 mol/L.
According to the scheme, the concentration of the aqueous solution containing Co salt in the step 1) is 0.045-0.055 mol/L.
According to the scheme, the yttrium salt in the step 2) is one of yttrium nitrate hexahydrate, yttrium chloride and yttrium sulfate, and the mass of the yttrium salt is 0.1-1 times of that of the cobalt salt.
According to the scheme, the reaction conditions of the step 2) are as follows: stirring for 2-4 h at room temperature (15-35 ℃).
According to the scheme, the calcining process conditions in the step 2) are as follows: in an inert atmosphere (Ar or N) 2 ) And then heating to 500-900 ℃ from room temperature at a speed of 1-5 ℃/min, and preserving heat for 1-6 h. Calcination carbonizes the prepared ZIF-67 (Co).
According to the scheme, the reduction reaction conditions in the step 2) are as follows: at H 2 Ar gas mixture (wherein H 2 3-8 vol%) or NH 3 And under the atmosphere, the temperature is raised to 350-650 ℃ from the room temperature at a heating rate of 1-5 ℃/min, and the temperature is kept for 1-3 h. The reduction reaction reduces Co to simple substance.
The invention also provides application of the yttrium oxide modified cobalt-based porous material in hydrogen production by ammonia decomposition.
The specific application method is as follows: putting a cobalt-based porous material modified by yttrium oxide as a catalyst into a fluidized bed reactor, purging argon for 30 minutes to remove impurity gas attached to the catalyst, then heating to 400-600 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h to activate the catalyst, introducing pure ammonia gas after the activation is finished and the temperature is reduced to room temperature, and controlling the pure ammonia gas space velocity to be 5000-40000 h at 400-600 DEG C -1 And catalyzing ammonia to decompose.
According to the yttrium oxide modified cobalt-based porous material provided by the invention, the coating effect of the CN (N-doped C) matrix generated by ZIF-67 pyrolysis obviously improves the dispersion degree of Co, and increases more ammonia decomposition reaction active sites. Test results show that Y 2 O 3 The alkalinity of the catalyst surface is obviously improved through the electron donating effect, the number of alkaline sites on the catalyst surface is increased, and the N atom recombination desorption capacity of the catalyst surface is improved, so that the ammonia decomposition activity of the catalyst at low temperature is improved, and meanwhile, Y is 2 O 3 The catalyst can also play a role in anchoring Co nano particles, can play a role in inhibiting Co nano particles from sintering in the high-temperature reaction process, and improves the stability of the catalyst under the high-temperature reaction condition.
The invention has the beneficial effects that: 1. the inventionThe cobalt-based porous material modified by yttrium oxide has large specific surface area, more Co reaction active sites, high catalytic ammonia decomposition efficiency and pure ammonia airspeed of 20000h at 550 DEG C -1 The highest ammonia decomposition rate can reach 92.3%, and the catalyst has good stability and good application prospect in the field of catalytic ammonia decomposition hydrogen production. 2. The preparation method disclosed by the invention is simple in steps, low in cost and easy to quantitatively produce.
Drawings
FIG. 1 is a graph showing comparison of ammonia decomposition activities of samples prepared in examples 1 to 4 and comparative example 1 according to the present invention;
FIG. 2 is XRD patterns of samples prepared in examples 1-4 and comparative example 1;
FIG. 3 is N of samples prepared in examples 1-4 and comparative example 1 2 -a TPD map;
FIG. 4 is a graph showing the catalytic stability of the samples prepared in examples 1-4 and comparative example 1;
FIG. 5 is a BET plot of samples prepared in examples 1-4 and comparative example 1.
Detailed Description
The present invention will be described in further detail below with reference to the accompanying drawings, so that those skilled in the art can better understand the technical scheme of the present invention.
Example 1
The preparation method of the yttrium oxide modified cobalt-based porous material comprises the following specific steps:
taking 1.455g of cobalt nitrate hexahydrate and 1.92g of 2-methylimidazole to be respectively dissolved in 100mL of deionized water to obtain an aqueous solution containing Co salt and an aqueous solution containing 2-methylimidazole, slowly adding the aqueous solution of 2-methylimidazole into the aqueous solution containing Co salt under the condition of stirring at room temperature, stirring for 2 hours, adding 0.327g of yttrium nitrate hexahydrate into the reaction solution, continuously stirring at room temperature for 2 hours, transferring the reaction solution into a centrifuge tube after stirring, centrifugally washing with deionized water as a solvent (the centrifugal speed is 10000 r/min), drying the obtained product in a baking oven at 60 ℃ for 24 hours after 5 times of centrifugal washing, calcining the dried sample in a tube furnace under argon atmosphere, and heating up to 600 ℃ at the room temperature at the heating rate of 3 ℃/minCalcining at 3 deg.C for 2 hr, reducing the sample in pure ammonia atmosphere, heating to 600 deg.C at 3 deg.C/min, and maintaining for 2 hr to obtain yttrium oxide modified cobalt-based porous material with Co content of 30.8wt%, and Y 2 O 3 The content of (2) was 2% by weight.
Taking 0.1g of the yttrium oxide modified cobalt-based porous material prepared in the embodiment as a catalyst, putting the catalyst into a fluidized bed reactor, purging with argon for 30 minutes to remove impurity gas attached to the catalyst, then heating to 550 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h to activate the catalyst, cooling to room temperature after the activation is finished, introducing pure ammonia (99.9999 vol%) and a pure ammonia airspeed of 20000h at 550 DEG C -1 The reaction was carried out for 1 hour to catalyze the decomposition of ammonia, and the ammonia decomposition rate was 84.7% as measured, and the ammonia was converted into nitrogen and hydrogen.
Example 2
A yttria-modified cobalt-based porous material was prepared in a similar manner to example 1, except that yttrium nitrate hexahydrate was added in an amount of 0.654g.
By the same method as in example 1, the decomposition rate of ammonia at 550℃of the yttria-modified cobalt-based porous material prepared in this example was found to be 86.7%.
Example 3
A yttria-modified cobalt-based porous material was prepared in a similar manner to example 1, except that yttrium nitrate hexahydrate was added in an amount of 0.981g.
By the same method as in example 1, the decomposition rate of ammonia at 550℃of the yttria-modified cobalt-based porous material prepared in this example was measured to be 92.3%.
Example 4
A yttria-modified cobalt-based porous material was prepared in a similar manner to example 1, except that yttrium nitrate hexahydrate was added in an amount of 1.308g.
By the same method as in example 1, the decomposition rate of ammonia at 550℃of the yttria-modified cobalt-based porous material prepared in this example was found to be 83.3%.
Comparative example 1
A cobalt-based porous material was prepared in a similar manner to example 1, except that yttrium nitrate hexahydrate was not added.
0.1g of the samples prepared in examples 1 to 4 and comparative example 1 were placed in a quartz tube, respectively, and high-purity ammonia gas having an inlet gas of 99.9999% and an ammonia gas flow rate of 20000h was taken -1 The catalyst samples were tested for ammonia decomposition rate at different temperatures (400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃) for hydrogen production by catalytic ammonia decomposition for 1 hour, and the test results are shown in Table 1.
TABLE 1
| Example 1 | Example 2 | Example 3 | Example 4 | Comparative example 1 | |
| 400℃ | 5.6％ | 8.5％ | 5.4％ | 4.8％ | 2.7％ |
| 450℃ | 19.0％ | 23.7％ | 20.4％ | 17.3％ | 9.0％ |
| 500℃ | 50.6％ | 56.0％ | 52.3％ | 48.3％ | 29.5％ |
| 550℃ | 84.7％ | 92.3％ | 86.7％ | 83.3％ | 72.3％ |
| 600℃ | 99.7％ | 99.9％ | 98.8％ | 98.4％ | 85.1％ |
Samples prepared according to examples 1-4 and comparative example 1 obtained from the data in Table 1 had an ammonia space velocity of 20000h -1 As can be seen from the comparison of the ammonia decomposition activity at different temperatures (400 ℃, 450 ℃, 500 ℃, 550 ℃ and 600 ℃) and the graph shown in FIG. 1, the catalysts of examples 1-4 have significantly higher ammonia decomposition performance at different temperatures than the catalyst of comparative example 1, indicating Y 2 O 3 The modification of (2) can obviously improve the ammonia decomposition activity of the cobalt catalyst.
FIG. 2 is an XRD pattern of the samples prepared in examples 1-4 and comparative example 1, showing Co diffraction peaks in each spectrumY 2 O 3 Does not appear, indicating Y 2 O 3 The dispersion was very uniform and the particles were small (nanometer scale).
N was performed on the samples prepared in examples 1 to 4 and comparative example 1 2 Programmed temperature adsorption and desorption (N) 2 TPD) experiment, measured N 2 The TPD diagram is shown in fig. 3, from which Y can be seen 2 O 3 The modified catalyst has a more obvious N at high temperature 2 Desorption peak, without doping Y 2 O 3 The catalyst of (2) does not exhibit N 2 Desorption peak, indicating Y 2 O 3 The modification of the catalyst obviously improves the N atom recombination desorption capacity of the catalyst, thereby being beneficial to improving the ammonia decomposition activity of the catalyst.
The samples prepared in examples 1 to 4 and comparative example 1 were tested for catalytic stability and the samples prepared in examples 1 to 4 and comparative example 1 were subjected to ammonia gas space velocity at 550℃for 20000 hours -1 As can be seen from the graph showing that the catalysts prepared in examples 1 to 4 show excellent stability in the 72h reaction, the ammonia decomposing activity of the catalyst is not reduced after the reaction is completed, while the ammonia decomposing activity of the catalyst prepared in comparative example 1 is significantly reduced in the 72h reaction, indicating Y 2 O 3 The modification of (2) significantly improves the stability of the catalyst.
FIG. 5 is a graph showing BET curves of samples prepared in examples 1-4 and comparative example 1, from which it can be seen that all of the BET curves of the samples have hysteresis at both low and high pressures, indicating higher specific surface area of 213.4m for examples 1-4 and comparative example 1, respectively, with higher specific surface area of the mesoporous structure 2 /g，265.1m 2 /g，237.1m 2 /g，146.1m 2 /g and 126.1m 2 /g。
Claims (10)
1. The cobalt-based porous material modified by the yttrium oxide is characterized by being obtained by compounding ZIF-67 (Co) and yttrium oxide, wherein the yttrium oxide has nano-size and is uniformly distributed on the surface of the ZIF-67 (Co).
2. According to the weightsThe yttria-modified cobalt-based porous material according to claim 1, wherein the specific surface area of the yttria-modified cobalt-based porous material is 140-270 m 2 Per gram, the Co content in the yttrium oxide modified cobalt-based porous material is 28 to 31 weight percent, Y 2 O 3 The content of (2) is 2-8wt%.
3. A method for preparing the yttria-modified cobalt-based porous material according to claim 1 or 2, comprising the following specific steps:
1) Preparation of ZIF-67 (Co): respectively dissolving 2-methylimidazole and cobalt salt in water to obtain an aqueous solution containing 2-methylimidazole and an aqueous solution containing Co salt, slowly adding the aqueous solution containing 2-methylimidazole into the aqueous solution containing Co salt under the condition of stirring, and stirring for 2-4 hours to obtain a reaction solution containing ZIF-67 (Co);
2) Preparation of a cobalt-based porous material modified by yttrium oxide: mixing the reaction solution containing ZIF-67 (Co) obtained in the step 1) with yttrium salt, reacting under stirring, separating to obtain yttrium salt doped ZIF-67 (Co) after the reaction is finished, and then calcining and reducing the obtained yttrium salt doped ZIF-67 (Co) in sequence to obtain the yttrium trioxide modified cobalt-based porous material.
4. The method of preparing a yttria-modified cobalt-based porous material according to claim 3, wherein the cobalt salt in step 1) is one of cobalt nitrate hexahydrate, cobalt chloride, cobalt sulfate, and cobalt acetate tetrahydrate; the molar ratio of the cobalt salt to the 2-methylimidazole in the step 1) is 1:4 to 8.
5. The method for preparing a yttria-modified cobalt based porous material according to claim 3, wherein the concentration of the 2-methylimidazole-containing aqueous solution in the step 1) is 0.2-0.4 mol/L; the concentration of the aqueous solution containing Co salt in the step 1) is 0.045-0.055 mol/L.
6. The method for preparing a cobalt-based porous material modified by yttrium oxide according to claim 3, wherein in the step 2), the yttrium salt is one of yttrium nitrate hexahydrate, yttrium chloride and yttrium sulfate, and the amount of the yttrium salt is 0.1-1 times of the amount of the cobalt salt; the reaction conditions of the step 2) are as follows: stirring for 2-4 h at room temperature.
7. The method for preparing a yttria-modified cobalt based porous material according to claim 3, wherein the calcining process conditions in step 2) are as follows: under inert atmosphere, the temperature is raised to 500-900 ℃ from room temperature at a speed of 1-5 ℃/min, and the temperature is kept for 1-6 h.
8. The method for preparing a yttria-modified cobalt based porous material according to claim 3, wherein the reduction reaction conditions in the step 2) are as follows: at H 2 Ar mixture or NH 3 And under the atmosphere, the temperature is raised to 350-650 ℃ from the room temperature at a heating rate of 1-5 ℃/min, and the temperature is kept for 1-3 h.
9. Use of the yttria-modified cobalt-based porous material according to claim 1 or 2 for producing hydrogen by ammonia decomposition.
10. The use of the yttria-modified cobalt-based porous material according to claim 9 for producing hydrogen by ammonia decomposition, wherein the specific application method is as follows: putting a cobalt-based porous material modified by yttrium oxide as a catalyst into a fluidized bed reactor, purging argon for 30 minutes to remove impurity gas attached to the catalyst, then heating to 400-600 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h to activate the catalyst, introducing pure ammonia gas after the activation is finished and the temperature is reduced to room temperature, and controlling the pure ammonia gas space velocity to be 5000-40000 h at 400-600 DEG C -1 And catalyzing ammonia to decompose.
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