CN114100661A - Catalyst for preparing hydrogen by decomposing molybdenum-based ammonia and preparation method thereof - Google Patents
Catalyst for preparing hydrogen by decomposing molybdenum-based ammonia and preparation method thereof Download PDFInfo
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 128
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 60
- 239000003054 catalyst Substances 0.000 title claims abstract description 46
- 239000001257 hydrogen Substances 0.000 title claims abstract description 39
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 39
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 229910052750 molybdenum Inorganic materials 0.000 title claims abstract description 15
- 239000011733 molybdenum Substances 0.000 title claims abstract description 15
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 title claims abstract description 14
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 45
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 15
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 96
- 238000003756 stirring Methods 0.000 claims description 29
- 238000001035 drying Methods 0.000 claims description 25
- 238000006243 chemical reaction Methods 0.000 claims description 19
- 229910000069 nitrogen hydride Inorganic materials 0.000 claims description 17
- 238000005121 nitriding Methods 0.000 claims description 15
- 230000001590 oxidative effect Effects 0.000 claims description 14
- 229910052751 metal Inorganic materials 0.000 claims description 13
- 239000002184 metal Substances 0.000 claims description 13
- 239000012266 salt solution Substances 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 12
- 230000003647 oxidation Effects 0.000 claims description 12
- 239000008367 deionised water Substances 0.000 claims description 11
- 229910021641 deionized water Inorganic materials 0.000 claims description 11
- 239000000243 solution Substances 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 239000012018 catalyst precursor Substances 0.000 claims description 10
- 150000003839 salts Chemical class 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 6
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 5
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 3
- 229910019626 (NH4)6Mo7O24 Inorganic materials 0.000 claims description 2
- 229910017333 Mo(CO)6 Inorganic materials 0.000 claims description 2
- 229910004619 Na2MoO4 Inorganic materials 0.000 claims description 2
- UCYXRZPFJJBQDL-UHFFFAOYSA-N acetic acid;molybdenum Chemical compound [Mo].[Mo].CC(O)=O.CC(O)=O.CC(O)=O.CC(O)=O UCYXRZPFJJBQDL-UHFFFAOYSA-N 0.000 claims description 2
- FAMFOTUVEABHMD-UHFFFAOYSA-N dimolybdenum tetrakis(trifluoroacetate) Chemical group [Mo]#[Mo].OC(=O)C(F)(F)F.OC(=O)C(F)(F)F.OC(=O)C(F)(F)F.OC(=O)C(F)(F)F FAMFOTUVEABHMD-UHFFFAOYSA-N 0.000 claims description 2
- 239000011259 mixed solution Substances 0.000 claims description 2
- 239000011684 sodium molybdate Substances 0.000 claims description 2
- TVXXNOYZHKPKGW-UHFFFAOYSA-N sodium molybdate (anhydrous) Chemical compound [Na+].[Na+].[O-][Mo]([O-])(=O)=O TVXXNOYZHKPKGW-UHFFFAOYSA-N 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 23
- 238000011156 evaluation Methods 0.000 abstract description 10
- 239000002243 precursor Substances 0.000 abstract description 8
- QXYJCZRRLLQGCR-UHFFFAOYSA-N molybdenum(IV) oxide Inorganic materials O=[Mo]=O QXYJCZRRLLQGCR-UHFFFAOYSA-N 0.000 abstract description 7
- 230000003197 catalytic effect Effects 0.000 abstract description 6
- 230000007547 defect Effects 0.000 abstract description 4
- 239000000463 material Substances 0.000 abstract description 3
- 239000002245 particle Substances 0.000 abstract description 3
- 239000000203 mixture Substances 0.000 abstract description 2
- 230000005501 phase interface Effects 0.000 abstract description 2
- 238000003980 solgel method Methods 0.000 abstract description 2
- 239000000843 powder Substances 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 15
- 239000007789 gas Substances 0.000 description 15
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 238000003860 storage Methods 0.000 description 10
- 150000002751 molybdenum Chemical class 0.000 description 9
- 229910000510 noble metal Inorganic materials 0.000 description 8
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 230000000630 rising effect Effects 0.000 description 4
- 239000000446 fuel Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 229910015421 Mo2N Inorganic materials 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000001879 gelation Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 238000010926 purge Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 229910002483 Cu Ka Inorganic materials 0.000 description 1
- 229910017299 Mo—O Inorganic materials 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000006185 dispersion Substances 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
- 239000005329 float glass Substances 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- -1 molybdate ions Chemical class 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titanium dioxide Inorganic materials O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/24—Chromium, molybdenum or tungsten
- B01J23/28—Molybdenum
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/03—Precipitation; Co-precipitation
- B01J37/036—Precipitation; Co-precipitation to form a gel or a cogel
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/12—Oxidising
- B01J37/14—Oxidising with gases containing free oxygen
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
- C01B3/047—Decomposition of ammonia
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
Abstract
The invention belongs to the technical field of catalytic materials, and particularly relates to a catalyst for preparing hydrogen by decomposing molybdenum-based ammonia and a preparation method thereof. The precursor of the catalyst for decomposing molybdenum amino to prepare hydrogen is prepared by adopting a sol-gel method, and the size of the particles of the precursor is adjusted by optimizing preparation parameters to obtain the precursor with proper structure and performance; the precursor is treated by nitridation-oxidation to obtain the catalyst, and Mo is formed after the activity evaluation of ammonia decomposition reaction2N and MoO2A mixture phase ofThe two phases coexist in the catalyst, so that more defect sites and phase interfaces are generated, the number of active sites of the catalyst is increased, and the excellent low-temperature activity of ammonia decomposition is shown.
Description
Technical Field
The invention belongs to the technical field of catalytic materials, and particularly relates to a catalyst for preparing hydrogen by decomposing molybdenum-based ammonia and a preparation method thereof.
Technical Field
The hydrogen energy has the advantages of high energy density, high energy conversion rate, cleanness, environmental protection and the like, and is a core link for constructing a low-carbon society. However, due to the characteristics of low volume energy density, flammability and explosiveness of hydrogen, the storage and transportation cost is high, the intrinsic safety is weak, and the popularization and application of hydrogen are severely restricted. High-pressure gaseous hydrogen storage is a mature hydrogen storage technology at present, but has the problems of high storage and transportation pressure, poor safety, serious dependence on import of hydrogen storage carbon fiber materials and the like, and the pain problem of hydrogen storage and transportation is difficult to effectively solve.
High content of hydrogen (17.6 wt%), easy to liquefy (normal temp. 8 atm), non-combustible (ignition point greater than 650 deg.C) and no COXDischarging; mature technology and storage and transportation cost of ammonia industry (ammonia)<<Hydrogen) and has high intrinsic safety, and is an ideal hydrogen storage carrier. Therefore, the ammonia is used as a hydrogen storage carrier, and the hydrogen is produced by combining ammonia decomposition reaction, so that the development of the hydrogen energy industry is expected to be promoted, and the method has great economic value and practical significance.
The ammonia decomposition reaction is an endothermic reaction, and the increase of the reaction temperature is favorable for improving the conversion rate of ammonia, but has great significance for achieving the purposes of energy saving and consumption reduction and developing a low-temperature and high-efficiency catalyst for producing hydrogen by ammonia decomposition. The Ru-based catalyst has good low-temperature ammonia decomposition performance, but the popularization and application of the noble metal Ru are limited due to the high price of the noble metal Ru; therefore, it is important to develop a non-noble metal-based ammonia decomposition catalyst having good low-temperature performance. The research of domestic ammonia decomposition hydrogen production catalyst begins at the end of 20 th century, is mainly used for preparing high-purity hydrogen and nitrogen, and is applied to float glass industry [ CN1078216 ]]. In 1997, Huangjianming uses NiO, MgO, CaO and TiO2Preparation of mixed oxide Ammonia decomposition catalyst for Coke oven gas purification Process [ CN1217229]. In 1998, the Chinese academy of sciencesReason why aluminum and nickel are active components, Al2O3Or MgO as carrier to prepare high-activity ammonia decomposition catalyst [ CN1245737]. In 2003, Qinghua university and hong Kong Bureau university prepared ammonia decomposition hydrogen production catalyst [ CN1456491 ] by using noble metal and metal nitride with noble metal property as active components and carbon nano tube as carrier]. Catalyst for preparing hydrogen by decomposing low-temperature high-efficiency ammonia at Fuzhou university in recent years [ CN109529865A]Ammonia solid oxide fuel cell [ CN110265688A]Ammonia decomposition hydrogen production reactor [ CN111957271A]Supercharged engine and ammonia fuel hybrid power generation system [ CN112761826A ]]And the detailed research is carried out, and related patents are published for nearly 30, so that the development of a novel hydrogen utilization mode of 'liquid ammonia hydrogen storage, ammonia decomposition hydrogen production and fuel cell' is promoted. However, in general, the low-temperature activity and stability of the current non-noble metal ammonia decomposition hydrogen production catalyst are to be further improved.
Patent CN 110327957 a discloses a method for preparing an ammonia decomposition catalyst, which comprises the following steps: 1) Dissolving a metal salt in deionized water to form a metal salt solution; 2) Adding a chelating agent into the metal salt solution, and stirring to form sol; 3) aging the sol to form a gel; 4) Drying the gel, and roasting to form a catalyst precursor; 5) Nitriding the catalyst precursor to prepare the ammonia decomposition catalyst; but the prepared ammonia decomposition catalyst has the reaction space velocity of 15000 h-1The ammonia decomposition rate is close to the equilibrium conversion rate of the reaction at 800 ℃, the working temperature is higher, and the defects of high energy consumption, insufficient safety and the like exist.
Disclosure of Invention
The invention aims to provide a non-noble metal catalyst with high catalytic activity and good ammonia decomposition effect, and a preparation method and application thereof, and overcomes the defects of low-temperature activity and poor ammonia decomposition effect of the non-noble metal ammonia decomposition catalyst in the prior art.
In order to achieve the purpose, the following technical scheme is adopted:
a preparation method of a catalyst for preparing hydrogen by decomposing molybdenum-based ammonia comprises the following steps:
(1) respectively dissolving metal Mo salt and citric acid in deionized water, and stirring until the metal Mo salt and the citric acid are completely dissolved;
(2) slowly adding the citric acid solution into the Mo salt solution within 5min under the stirring condition;
(3) heating the mixed solution in an oil bath to a certain temperature, and reacting for 24 hours to obtain a gel product;
(4) drying the gel at a certain temperature;
(5) roasting the dried product under certain conditions to obtain a catalyst precursor;
(6) nitriding the catalyst precursor at a certain temperature in a nitrogen-containing atmosphere;
(7) and oxidizing the nitriding product in an oxidizing atmosphere to obtain the catalyst.
In the step (1), the metal Mo salt is Mo2(O2CCF3)4、Mo2(OAc)4、Mo(CO)6、H8MoN2O4、Na2MoO4、(NH4)6Mo7O24•4H2One or more of O;
the molar ratio of the metal Mo salt to the citric acid in the step (1) is 1:1-1: 5;
the oil bath reaction temperature in the step (3) is 50-100 ℃;
the drying temperature in the step (4) is 100-160 ℃, and the drying time is 12-48 h;
the roasting temperature in the step (5) is 300-800 ℃, and the roasting time is 1-8 h;
the nitridation treatment in the step (6) is 500-800 ℃, and the nitridation time is 1-4 h; the nitrogen-containing atmosphere is 10vol% NH3/Ar、50vol% NH3/Ar、75vol% H2/N2、50vol% H2/N2、NH3At least one of;
the oxidation treatment temperature in the step (7) is 500-800 ℃, and the oxidation time is 1-4 h; the oxidizing atmosphere was air and 1vol% O2/Ar、5vol% O2/Ar、10vol% O2At least one of/Ar and pure oxygen;
the technical scheme of the invention has the following advantages:
1. the preparation method of the ammonia decomposition catalyst precursor comprises the following steps of dissolving metal Mo salt in a citric acid solution to form sol; carrying out heat treatment on the sol to form gel; and drying and roasting to obtain the catalyst precursor. The preparation method adopted by the invention is a sol-gel method, and the method is favorable for uniformly dispersing Mo metal ions or molybdate ions in an aqueous solution, and obtaining a precursor with smaller particle size and uniform dispersion through gelation, drying and roasting. The invention can adjust the particle size of the precursor by optimizing the temperature and time in the processes of gelation, drying and roasting, and obtain the precursor with proper structure and performance.
2. The preparation method of the ammonia decomposition catalyst provided by the invention comprises the steps of nitriding the precursor in a nitrogen-containing atmosphere, and roasting in an oxidizing atmosphere. The ammonia decomposition reaction activity of the catalyst precursor is tested after the catalyst precursor is directly nitrided, and only pure-phase Mo is observed in the activity evaluation product2N; the nitrided products were subjected to oxidation treatment in an oxidizing atmosphere (nitriding-oxidizing treatment) and evaluated for ammonia decomposition catalytic performance, and Mo was observed in the activity evaluation products2N and MoO2Two phases. Mo2N and MoO2The formation of the mixture phase enables more defect sites and phase interfaces to be generated in the catalyst, and the number of catalytic active sites of the catalyst is increased, so that the catalyst shows more excellent ammonia decomposition reaction performance, and particularly improves the low-temperature ammonia decomposition reaction performance of the Mo-based catalyst. Specifically, the catalyst prepared by the invention can lead the ammonia decomposition conversion to be close to the equilibrium conversion rate at 650 ℃, and the temperature of the Mo-based catalyst which is not subjected to the nitridation-oxidation treatment and is close to the equilibrium conversion rate is higher than 700 ℃.
Drawings
FIG. 1 is an XRD pattern of samples of example 3 of the present invention and comparative examples 1, 2 and 3 after evaluation of the activity of ammonia decomposition reaction. As can be seen from FIG. 1, Mo was observed in example 32N and MoO2Two phases, whereas comparative examples 1, 2 and 3 only observed pure phase Mo2N。
FIG. 2 is an XRD pattern of the samples of examples 1-5 of the present invention after the evaluation of the ammonia decomposition reaction activity. From Mo in FIG. 12N (200) crystal face and MoO2(020) The intensity ratio of diffraction peak of crystal face is known as (I)(200)/I(020)The ratio is shown in FIG. 1), the change of the oxidation treatment temperature has a significant influence on the mixed phase ratio, wherein Mo is contained in the sample of example 32N/MoO2The ratio is the largest.
FIG. 3 is H of samples of examples 1 to 5 of the present invention2-TPR spectrum. As is evident from the graph, the hydrogen consumption peak of the sample of example 3 shifts to a low temperature, indicating that the Mo-O bond energy is weak and is easily broken, thereby facilitating the formation of Mo2The miscible phase with the highest N content.
Detailed Description
The present invention will be described in more detail by the following examples and comparative examples, but is not limited to these examples.
Example 1:
3.53 g (NH) are weighed4)6Mo7O24•4H2O and 11.52 g of citric acid are respectively dissolved in 50 mL of deionized water, after the O and the citric acid are completely dissolved, the molybdenum salt solution is firstly transferred into a 500 mL beaker, the citric acid solution is slowly added into the beaker within 5min under the stirring of 400-600 r/min, and the stirring is continued for 0.5 h. After stirring, the beaker is transferred into an oil bath kettle at the temperature of 80 ℃, and the oil bath is aged for 24 hours. The beaker is then transferred to an oven at 100 ℃ for drying for 24 h. After the drying is finished, the sample is smashed and ground into fine powder, and the powder is roasted for 5 hours in a muffle furnace at 600 ℃. At 50vol% NH3and/Ar is nitriding gas, temperature programming nitriding is carried out, the temperature is raised from room temperature to 350 ℃ at the speed of 1 ℃/min, and then the temperature is raised to 500 ℃ at the speed of 0.5 ℃/min and kept for 3 h. At 5vol% O2and/Ar is oxidizing gas, carrying out temperature programming oxidation (the temperature rising rate is 5 ℃/min), keeping the temperature at 500 ℃ for 1 h, and carrying out tabletting molding to obtain the product of example 1.
Example 2:
3.53 g (NH) are weighed4)6Mo7O24•4H2O and 11.52 g citric acid were dissolved in 50 g of eachAfter the molybdenum salt solution is completely dissolved in the deionized water, the molybdenum salt solution is transferred into a 500 mL beaker, the citric acid solution is slowly added into the beaker within 5min under the stirring of 400-600 r/min, and the stirring is continued for 0.5 h. After stirring, the beaker is transferred into an oil bath kettle at the temperature of 80 ℃, and the oil bath is aged for 24 hours. The beaker was then transferred to an oven at 140 ℃ for drying for 24 h. After the drying is finished, the sample is smashed and ground into fine powder, and the powder is roasted for 5 hours in a muffle furnace at 300 ℃. At 10vol% NH3and/Ar is nitriding gas, temperature programming nitriding is carried out, the temperature is raised from room temperature to 350 ℃ at the speed of 1 ℃/min, and then the temperature is raised to 600 ℃ at the speed of 0.5 ℃/min and kept for 4 h. With 1vol% O2and/Ar is oxidizing gas, carrying out temperature programming oxidation (the temperature rising rate is 5 ℃/min), keeping the temperature at 550 ℃ for 2 h, and carrying out tabletting molding to obtain the embodiment 2.
Example 3:
3.53 g (NH) are weighed4)6Mo7O24•4H2O and 11.52 g of citric acid are respectively dissolved in 50 mL of deionized water, after the O and the citric acid are completely dissolved, the molybdenum salt solution is firstly transferred into a 500 mL beaker, the citric acid solution is slowly added into the beaker within 5min under the stirring of 400-600 r/min, and the stirring is continued for 0.5 h. After stirring, the beaker is transferred into an oil bath kettle at the temperature of 80 ℃, and the oil bath is aged for 24 hours. The beaker is then transferred to an oven at 150 ℃ for drying for 24 h. After the drying is finished, the sample is smashed and ground into fine powder, and the powder is roasted for 5 hours in a muffle furnace at 500 ℃. By NH3The nitrogen is generated by temperature programming and nitriding, raising the temperature from room temperature to 350 ℃ at the speed of 1 ℃/min, and then raising the temperature to 700 ℃ at the speed of 0.5 ℃/min and keeping the temperature for 2 h. Air is used as oxidizing gas, temperature programming oxidation is carried out (the heating rate is 5 ℃/min), the temperature is kept at 600 ℃ for 4 h, and the embodiment 3 is obtained after tabletting and forming.
Example 4:
3.53 g (NH) are weighed4)6Mo7O24•4H2O and 11.52 g of citric acid are respectively dissolved in 50 mL of deionized water, after the O and the citric acid are completely dissolved, the molybdenum salt solution is firstly transferred into a 500 mL beaker, the citric acid solution is slowly added into the beaker within 5min under the stirring of 400-600 r/min, and the stirring is continued for 0.5 h. After stirring, the beaker is transferred into an oil bath kettle at the temperature of 80 ℃, and the oil bath is aged for 24 hours. Then the beaker is turned into 13Drying in an oven at 0 ℃ for 24 h. After the drying is finished, the sample is smashed and ground into fine powder, and the powder is roasted for 5 hours in a muffle furnace at 800 ℃. At 75vol% H2/N2The nitrogen is generated by temperature programming and nitriding, raising the temperature from room temperature to 350 ℃ at the speed of 1 ℃/min, and then raising the temperature to 700 ℃ at the speed of 0.5 ℃/min and keeping the temperature for 1 h. With 10vol% O2and/Ar is oxidizing gas, temperature programming oxidation is carried out (the temperature rising rate is 5 ℃/min), the temperature is kept at 650 ℃ for 3 h, and the embodiment 4 is obtained after tabletting and forming.
Example 5:
3.53 g (NH) are weighed4)6Mo7O24•4H2O and 11.52 g of citric acid are respectively dissolved in 50 mL of deionized water, after the O and the citric acid are completely dissolved, the molybdenum salt solution is firstly transferred into a 500 mL beaker, the citric acid solution is slowly added into the beaker within 5min under the stirring of 400-600 r/min, and the stirring is continued for 0.5 h. After stirring, the beaker is transferred into an oil bath kettle at the temperature of 80 ℃, and the oil bath is aged for 24 hours. The beaker is then transferred to an oven at 160 ℃ for drying for 24 h. After the drying is finished, the sample is smashed and ground into fine powder, and the powder is roasted for 5 hours in a muffle furnace at 700 ℃. At 50vol% H2/N2The nitrogen is generated by temperature programming and nitriding, and the temperature is raised from room temperature to 350 ℃ at the speed of 1 ℃/min, and then raised to 800 ℃ at the speed of 0.5 ℃/min and kept for 1 h. Pure oxygen is used as oxidizing gas, temperature programming oxidation is carried out (the temperature rising rate is 5 ℃/min), the temperature is kept at 700 ℃ for 4 h, and the embodiment 5 is obtained after tabletting and forming.
Comparative example 1:
3.53 g (NH) are weighed4)6Mo7O24•4H2O and 11.52 g of citric acid are respectively dissolved in 50 mL of deionized water, after the O and the citric acid are completely dissolved, the molybdenum salt solution is firstly transferred into a 500 mL beaker, the citric acid solution is slowly added into the beaker within 5min under the stirring of 400-600 r/min, and the stirring is continued for 0.5 h. After stirring, the beaker is transferred into an oil bath kettle at the temperature of 80 ℃, and the oil bath is aged for 24 hours. The beaker is then transferred to an oven at 150 ℃ for drying for 24 h. After the drying is finished, the sample is smashed and ground into fine powder, and the powder is roasted for 5 hours in a muffle furnace at 500 ℃. By NH3Performing temperature programmed nitridation to obtain nitrified gas, heating from room temperature to 350 deg.C at 1 deg.C/min, and heating at 0.5 deg.C/minKeeping the temperature at 700 ℃ for 2 h, and tabletting to obtain the comparative example 1.
Comparative example 2:
3.53 g (NH) are weighed4)6Mo7O24•4H2O and 11.52 g of citric acid are respectively dissolved in 50 mL of deionized water, after the O and the citric acid are completely dissolved, the molybdenum salt solution is firstly transferred into a 500 mL beaker, the citric acid solution is slowly added into the beaker within 5min under the stirring of 400-600 r/min, and the stirring is continued for 0.5 h. After stirring, the beaker is transferred into an oil bath kettle at the temperature of 80 ℃, and the oil bath is aged for 24 hours. The beaker is then transferred to an oven at 150 ℃ for drying for 24 h. After the drying is finished, the sample is smashed and ground into fine powder, and the powder is roasted for 5 hours in a muffle furnace at 500 ℃. By NH3The nitrogen is generated by temperature programming and nitriding, raising the temperature from room temperature to 350 ℃ at the speed of 1 ℃/min, and then raising the temperature to 700 ℃ at the speed of 0.5 ℃/min and keeping the temperature for 2 h. Air is used as oxidizing gas, temperature programming oxidation is carried out (the temperature raising rate is 5 ℃/min), and the temperature is kept at 600 ℃ for 4 h. 0.1 g of sample is taken and placed in an ammonia decomposition activity evaluation device, the temperature is increased from room temperature to 350 ℃ at the speed of 1 ℃/min, then the temperature is increased to 700 ℃ at the speed of 0.5 ℃/min and kept for 2 h, then the temperature is reduced to 400 ℃, and the activity is directly tested without reduction, and the sample is named as comparative example 2.
Comparative example 3:
3.53 g (NH) are weighed4)6Mo7O24•4H2O and 11.52 g of citric acid are respectively dissolved in 50 mL of deionized water, after the O and the citric acid are completely dissolved, the molybdenum salt solution is firstly transferred into a 500 mL beaker, the citric acid solution is slowly added into the beaker within 5min under the stirring of 400-600 r/min, and the stirring is continued for 0.5 h. After stirring, the beaker is transferred into an oil bath kettle at the temperature of 80 ℃, and the oil bath is aged for 24 hours. The beaker is then transferred to an oven at 150 ℃ for drying for 24 h. After the drying is finished, the sample is smashed and ground into fine powder, and the powder is roasted for 5 hours in a muffle furnace at 600 ℃. By NH3The nitrogen is generated by temperature programming and nitriding, raising the temperature from room temperature to 350 ℃ at the speed of 1 ℃/min, and then raising the temperature to 700 ℃ at the speed of 0.5 ℃/min and keeping the temperature for 2 h. And tabletting and forming to obtain the comparative example 3.
The X-ray powder diffraction analysis is carried out on an X 'pert Pro diffractometer of Panalytic company, the Netherlands, and an X' Celerator detector is adopted, Cu-Ka (lambda = 0.1789 nm) target radiation is carried out, the tube pressure is 45 kV, the tube flow is 40 mA, the scanning step length is 0.0131303 degrees, each step is 20.4 s, and the scanning range is 2 theta = 10-80 degrees.
H2Temperature programmed reduction (H)2TPR) experiments were performed on an AutoChem2920 automated catalyst characterization system from Micrometric corporation, USA. Weighing 50 mg of sample, heating to 200 ℃ at a temperature of 10 ℃/min, purging the sample with inert gas (Ar) for 60 min, cooling to room temperature, and then using 10vol% H2And purging the sample by using the/Ar mixed gas, wherein the flow rate is 30 mL/min, after the TCD base line is stable, heating to 750 ℃ at the speed of 10 ℃/min, and recording the TCD signal intensity.
Activity test conditions: the raw material gas is high-purity ammonia, and the reducing gas is 50% H2Ar, reducing for 3 h at 500 ℃. The gas chromatography carrier gas is H2. Space velocity of 30000 mL ∙ g-1∙h-1And the catalyst activity test temperature zone is 400-700 ℃.
NH for catalyst activity3The conversion is expressed.
NH3Conversion = (1-V)NH3'）/（1 + VNH3') X100%, wherein VNH3' is NH in the reactor outlet gas3Volume percent of (c).
By NH3The conversion rate indicates catalytic activity, and the results of activity evaluation of examples and comparative examples are as follows:
TABLE 1 results of activity evaluation of examples and comparative examples
As is clear from the results of activity evaluation in Table 1, the ammonia decomposition catalysts obtained in examples 1 to 5 were maintained at 600 ℃ and 700 ℃ at a high space velocity (30000 h)-1) The pure ammonia gas has higher ammonia decomposition rate under the condition of raw material gas, and the conversion rate approaches to reaction equilibrium at 650 ℃. Among them, the sample of example 3 has achieved 94.3% ammonia decomposition rate at 600 ℃. Comparing examples 1 to 5 with comparative example 1, it can be seen that the ammonia decomposition activity is significantly improved after the "nitridation-oxidation" treatment; comparative examples 1 to 5 and comparative example 2The ammonia conversion rate of the nitrided samples decreased by the second temperature programming in the ammonia decomposition activity evaluation apparatus, indicating that the "nitriding-oxidizing" treatment is the main reason for the activity improvement of examples 1 to 5; it can be seen from comparison of examples 1 to 5 and comparative example 3 that the "nitriding-oxidizing" treatment is a key factor in the improvement of the ammonia decomposition activity of the catalyst.
Claims (9)
1. A preparation method of a catalyst for preparing hydrogen by decomposing molybdenum-based ammonia is characterized by comprising the following steps: the method comprises the following steps:
(1) respectively dissolving metal Mo salt and citric acid in deionized water, and stirring until the metal Mo salt and the citric acid are completely dissolved;
(2) slowly adding the citric acid solution into the Mo salt solution within 5min under the stirring condition;
(3) heating the mixed solution in an oil bath, and reacting for 24 hours to obtain a gel product;
(4) drying the gel;
(5) roasting the dried product to obtain a catalyst precursor;
(6) nitriding the catalyst precursor in a nitrogen-containing atmosphere;
(7) and oxidizing the nitriding product in an oxidizing atmosphere to obtain the catalyst.
2. The method for preparing a catalyst for ammonia decomposition of molybdenum to produce hydrogen according to claim 1, characterized in that: in the step (1), the metal Mo salt is Mo2(O2CCF3)4、Mo2(OAc)4、Mo(CO)6、H8MoN2O4、Na2MoO4、(NH4)6Mo7O24•4H2And one or more of O.
3. The method for preparing a catalyst for ammonia decomposition of molybdenum to produce hydrogen according to claim 1, characterized in that: the molar ratio of the metal Mo salt to the citric acid in the step (1) is 1:1-1: 5.
4. The method for preparing a catalyst for ammonia decomposition of molybdenum to produce hydrogen according to claim 1, characterized in that: the oil bath reaction temperature in the step (3) is 50-100 ℃.
5. The method for preparing a catalyst for ammonia decomposition of molybdenum to produce hydrogen according to claim 1, characterized in that: the drying temperature in the step (4) is 100-160 ℃, and the drying time is 12-48 h.
6. The method for preparing a catalyst for ammonia decomposition of molybdenum to produce hydrogen according to claim 1, characterized in that: the roasting temperature in the step (5) is 300-800 ℃, and the roasting time is 1-8 h.
7. The method for preparing a catalyst for ammonia decomposition of molybdenum to produce hydrogen according to claim 1, characterized in that: the nitridation treatment in the step (6) is 500-800 ℃, and the nitridation time is 1-4 h; the nitrogen-containing atmosphere is 10vol% NH3/Ar、50vol% NH3/Ar、75vol% H2/N2、50vol% H2/N2、NH3At least one of (1).
8. The method for preparing a catalyst for ammonia decomposition of molybdenum to produce hydrogen according to claim 1, characterized in that: the oxidation treatment temperature in the step (7) is 500-800 ℃, and the oxidation time is 1-4 h; the oxidizing atmosphere was air and 1vol% O2/Ar、5vol% O2/Ar、10vol% O2At least one of/Ar and pure oxygen.
9. Use of a molybdenum-based catalyst prepared according to any one of claims 1 to 8 in an ammonia decomposition hydrogen production reaction.
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| CN115318332A (en) * | 2022-08-30 | 2022-11-11 | 天津派森新材料技术有限责任公司 | Preparation method and application of catalyst for hydrogen production by ammonia decomposition |
| CN114618557B (en) * | 2022-04-01 | 2024-05-03 | 太原理工大学 | Supported molybdenum-based nitrogen carrier suitable for chemical chain synthesis of ammonia and preparation method thereof |
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