CN111589453B - Preparation method of biomimetic catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild condition - Google Patents
Preparation method of biomimetic catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild condition Download PDFInfo
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 102
- 239000003054 catalyst Substances 0.000 title claims abstract description 57
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 51
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 36
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 34
- 239000001257 hydrogen Substances 0.000 title claims abstract description 34
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 30
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 15
- 230000003592 biomimetic effect Effects 0.000 title claims description 27
- 238000002360 preparation method Methods 0.000 title claims description 15
- 230000003197 catalytic effect Effects 0.000 claims abstract description 51
- 239000002131 composite material Substances 0.000 claims abstract description 51
- 239000011664 nicotinic acid Substances 0.000 claims abstract description 22
- 238000006243 chemical reaction Methods 0.000 claims abstract description 18
- 239000002041 carbon nanotube Substances 0.000 claims abstract description 15
- 238000000034 method Methods 0.000 claims abstract description 11
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 127
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 58
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 56
- 238000010438 heat treatment Methods 0.000 claims description 41
- 239000007789 gas Substances 0.000 claims description 35
- 229910052786 argon Inorganic materials 0.000 claims description 29
- 238000001035 drying Methods 0.000 claims description 27
- 239000011259 mixed solution Substances 0.000 claims description 21
- 239000010453 quartz Substances 0.000 claims description 21
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 21
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 14
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 14
- 239000012153 distilled water Substances 0.000 claims description 14
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 claims description 14
- 238000010521 absorption reaction Methods 0.000 claims description 11
- 238000003756 stirring Methods 0.000 claims description 11
- 239000006185 dispersion Substances 0.000 claims description 10
- 238000005406 washing Methods 0.000 claims description 10
- 238000001816 cooling Methods 0.000 claims description 8
- 238000005470 impregnation Methods 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 7
- 230000001590 oxidative effect Effects 0.000 claims description 7
- 229920006395 saturated elastomer Polymers 0.000 claims description 7
- 238000007873 sieving Methods 0.000 claims description 7
- 238000002791 soaking Methods 0.000 claims description 7
- 239000007787 solid Substances 0.000 claims description 7
- 239000000243 solution Substances 0.000 claims description 7
- 238000001354 calcination Methods 0.000 claims description 6
- 238000010298 pulverizing process Methods 0.000 claims description 6
- 230000007935 neutral effect Effects 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract description 49
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 12
- 229910021393 carbon nanotube Inorganic materials 0.000 abstract description 12
- 230000007246 mechanism Effects 0.000 abstract description 9
- 230000004913 activation Effects 0.000 abstract description 8
- 238000010494 dissociation reaction Methods 0.000 abstract description 7
- 230000005593 dissociations Effects 0.000 abstract description 7
- 230000008569 process Effects 0.000 abstract description 7
- 238000004178 biological nitrogen fixation Methods 0.000 abstract description 6
- 229910052723 transition metal Inorganic materials 0.000 abstract description 6
- 150000003624 transition metals Chemical class 0.000 abstract description 6
- 230000004888 barrier function Effects 0.000 abstract description 5
- 238000005984 hydrogenation reaction Methods 0.000 abstract description 4
- 229910052742 iron Inorganic materials 0.000 abstract description 4
- 230000002195 synergetic effect Effects 0.000 abstract description 3
- 230000003647 oxidation Effects 0.000 abstract description 2
- 238000007254 oxidation reaction Methods 0.000 abstract description 2
- 230000033116 oxidation-reduction process Effects 0.000 abstract description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 abstract 2
- 239000000969 carrier Substances 0.000 abstract 2
- 229910052593 corundum Inorganic materials 0.000 abstract 1
- 229910001845 yogo sapphire Inorganic materials 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 21
- 238000012360 testing method Methods 0.000 description 16
- 238000003786 synthesis reaction Methods 0.000 description 14
- 239000012495 reaction gas Substances 0.000 description 12
- 230000015572 biosynthetic process Effects 0.000 description 11
- 238000001179 sorption measurement Methods 0.000 description 6
- 108090000790 Enzymes Proteins 0.000 description 4
- 102000004190 Enzymes Human genes 0.000 description 4
- 241000282326 Felis catus Species 0.000 description 4
- 238000006555 catalytic reaction Methods 0.000 description 4
- 238000013329 compounding Methods 0.000 description 4
- 229910000510 noble metal Inorganic materials 0.000 description 4
- 241000894007 species Species 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000005303 weighing Methods 0.000 description 4
- 238000009620 Haber process Methods 0.000 description 3
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 3
- 238000007210 heterogeneous catalysis Methods 0.000 description 3
- 239000000543 intermediate Substances 0.000 description 3
- 229910052707 ruthenium Inorganic materials 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910001309 Ferromolybdenum Inorganic materials 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- 102000008857 Ferritin Human genes 0.000 description 1
- 108050000784 Ferritin Proteins 0.000 description 1
- 238000008416 Ferritin Methods 0.000 description 1
- 102000010750 Metalloproteins Human genes 0.000 description 1
- 108010063312 Metalloproteins Proteins 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 108010020943 Nitrogenase Proteins 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000007036 catalytic synthesis reaction Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 150000004678 hydrides Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000009790 rate-determining step (RDS) Methods 0.000 description 1
- 239000012048 reactive intermediate Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
Classifications
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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
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/85—Chromium, molybdenum or tungsten
- B01J23/88—Molybdenum
- B01J23/882—Molybdenum and cobalt
-
- B01J35/394—
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/04—Preparation of ammonia by synthesis in the gas phase
- C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst
- C01C1/0411—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst characterised by the catalyst
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Abstract
The invention discloses an artificial bionic catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions, which takes carbon nano tubes and alumina as composite carriers and iron as active components, wherein the active components are dispersed in the composite carriers in the form of atomic clusters or monoatomic atoms to form a unique Fe/CNTs-Al2O3 catalytic microreactor, the Fe in a low oxidation state is taken as an electronic library to adjust charge transfer in the whole process, and the Fe and Co-Mo have synergistic effect to simulate a high-efficiency oxidation-reduction mechanism of biological nitrogen fixation in nature, so that the activation energy barrier of nitrogen is effectively reduced by combining a bionic hydrogenation mechanism, the BEP relation limitation of a traditional heterogeneous catalytic transition metal surface direct dissociation mechanism is broken through, and the synthetic ammonia reaction can be driven under mild conditions.
Description
Technical Field
The invention relates to a preparation method of a catalyst, in particular to a preparation method of a biomimetic catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions.
Background
The Haber-Bosch process is the mainstream process for industrially producing ammonia at present, a fused iron type catalyst is mostly used in the process of producing ammonia by utilizing nitrogen and hydrogen by using the traditional Haber-Bosch process, although the preparation process is mature and has low preparation cost, the process requires severe operating conditions of high temperature (300-550 ℃) and high pressure (15-25 MPa), consumes 1-2% of energy supply in the world every year, and releases a large amount of greenhouse gas (1.87 tons of carbon dioxide are generated per ton of ammonia prepared). The second generation ruthenium-based ammonia synthesis catalyst can reduce the reaction temperature and pressure of ammonia synthesis to a certain extent, but ruthenium-based catalyst is a noble metal and has higher cost, thus preventing wide industrial popularization and application of the ruthenium-based catalyst.
In the traditional heterogeneous thermal catalysis, a transition metal catalyst is mostly utilized to catalyze nitrogen and hydrogen to synthesize ammonia, and the rate-limiting step is N 2 Direct dissociation activation of the molecule, but very stable due to the nitrogen-nitrogen triple bond (bond energy 946 kJ. Mol) -1 )，N 2 Is quite difficult to activate and is subject to
–Evans–Polanyi(BEP) limitation of the relationship, N 2 There is a contradiction between the molecular activation barrier and the adsorption energy of reactive intermediate species. When N is present 2 When the activation energy of the molecule is small, the adsorption energy of the intermediate species is strong; when the adsorption of the intermediate species is weak, N 2 The activation energy of the molecule is again high, which results in a volcanic-type curve for the activity of the ammonia synthesis reaction on the transition metal. An ideal ammonia synthesis catalyst should balance the energy relationship between the two, near the top of the volcano-type curve, and even if such a catalyst is found, it still requires relatively high temperatures and pressures to overcome N simultaneously 2 Activation energy of (2) and adsorption energy of the intermediate species. Recently, chen et al have developed a series of TM-LiH double-active center ammonia synthesis catalysts by introducing LiH as a second active center, and the ammonia synthesis activity of the composite catalysts does not present a volcano-type curve, which shows that the addition of hydride avoids the energy restriction relationship on a transition metal catalyst; li and the like in Fe 3 /θ-Al 2 O 3 And Rh 1 Co 3 the/CoO (011) cluster is taken as a catalytic center, the synthesis of ammonia is realized by a hydrogen assisted dissociation mechanism similar to enzyme catalysis, and N adsorbed on an active site 2 Is first hydrogenated to NNH, N 2 * Dissociation is NNH * The dissociation is replaced by a lower barrier that can be driven under mild thermodynamic conditions.
In nature, the nitrogen-fixing microorganisms can utilize nitrogen-fixing enzymes in organisms to fix N under mild conditions 2 Efficient reduction to NH 3 The biological nitrogen fixation accounts for more than 60% of the total fixed nitrogen in the atmosphere. The most abundant and characteristic nitrogenase is a molybdenum-dependent enzyme formed by the synergy of two indispensable metalloproteins, electron-donating ferritin (Fe-) and catalytic ferromolybdenum (MoFe-), which activates N 2 The molecular properties are derived from the efficient redox cycling of Fe (II) and Fe (III) on the Mo-Fe-S-C cluster of the ferromolybdenum cofactor, through N 2 The bound adsorption of (a) achieves hydrogenation rather than dissociative adsorption as in the Haber-Bosch process. Biological nitrogen fixation is not limited by the high-temperature high-pressure catalytic conditions of heterogeneous thermocatalytic ammonia synthesis, and N is reduced by preferentially combining a hydrogenation mechanism 2 And avoids the limitation of BEP relation, and makes the synthetic ammonia reactShould be able to work efficiently under mild conditions. However, the amount of biological nitrogen fixation in nature is very small, and the requirement of human production and life can not be met.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a preparation method of a biomimetic catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions, which effectively reduces the activation energy barrier of nitrogen, breaks through the BEP relation limitation of the traditional heterogeneous catalysis transition metal surface direct dissociation mechanism, enables the ammonia synthesis reaction to be driven under mild conditions, enables the active phase Fe to reach the atomic level dispersion level, forms a catalytic microreactor with a composite carrier, obviously improves the performance of the biomimetic catalyst, reduces the temperature and pressure of the traditional ammonia synthesis process, and reduces the energy consumption and pollution of the ammonia synthesis industry.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention relates to an artificial bionic catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions, which comprises the following steps:
step one, co-Mo/Al 2 O 3 Preparation of the catalytic carrier:
(1) Industrial pure gamma-Al 2 O 3 Pulverizing, sieving with 12-16 mesh sieve, heating the sieved sample at 800 deg.C for 4 hr to convert to delta (theta) -Al 2 O 3 ；
(2) First, 5g of phase-inverted delta (. Theta) -Al was taken 2 O 3 Placing in 50mL beaker, adding 10mL distilled water, soaking in 60 deg.C water bath for 40min to make delta (theta) -Al 2 O 3 Absorbing water, cooling to 25 deg.C, pouring out unabsorbed water, measuring the volume of poured water and recording as V, and calculating delta (theta) -Al 2 O 3 The saturated water absorption capacity of (A) is:
then, analytically pure Co (NO) 3 ) 2 ·6H 2 O and analytically pure (NH) 4 ) 6 Mo 7 O 24 ·4H 2 Dissolving O in (10-V) mL, and steamingPreparing mixed solution in distilled water, ultrasonically treating the mixed solution by using an ultrasonic cleaner until solid components are completely dissolved, and adding 5g of delta (theta) -Al subjected to phase inversion into the mixed solution 2 O 3 Stirring under infrared lamp baking until the solution is completely impregnated with the transformed delta (theta) -Al 2 O 3 In (d), delta (. Theta) -Al after impregnation 2 O 3 Drying in an oven at 100-120 ℃ to obtain unreduced Co-Mo/Al 2 O 3 A catalytic support;
(3) Mixing Co-Mo/Al 2 O 3 The catalytic carrier is placed in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and in a mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99%, the flow ratio of the two gases is controlled to be Ar: h 2 =80:20 mL/min-50, heating to 500-550 ℃ at the speed of 5-10 ℃/min to reduce Co-Mo/Al 2 O 3 Catalyzing the carrier for 1-3 h to obtain reduced Co-Mo/Al 2 O 3 A catalytic support;
step two, CNTs-Al 2 O 3 Preparing a composite carrier:
(1) Reducing the Co-Mo/Al 2 O 3 Placing the catalytic carrier in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and continuously heating to 550-750 ℃ in the mixed atmosphere of the hydrogen and the argon in the first step at the same flow ratio as that in the first step, wherein the heating rate is 5-10 ℃/min;
(2) Introducing acetylene gas with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and simultaneously closing argon; at C 2 H 2 And H 2 The flow ratio of (A) is 10-100 2 O 3 Growing CNTs on a catalytic carrier in a catalytic manner, and stopping introducing acetylene gas into the horizontal tubular resistance furnace after the reaction is finished;
(3) Continuously introducing mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and controlling the flow ratio of the two gases to be Ar: h 2 20 mL/min-50, rapidly heating to 700-800 ℃ in the atmosphereCNTs 1-3 h, then reducing the temperature to 20-25 ℃ under the protection of the mixed atmosphere, and preparing the CNTs-Al 2 O 3 A composite carrier;
(4) CNTs-Al 2 O 3 15-30% of H for composite carrier 2 O 2 Oxidizing for 6h, washing the treated sample to be neutral, drying in a drying oven at 60-80 ℃ to obtain the purified and modified CNTs-Al 2 O 3 A composite carrier;
step three, fe/CNTs-Al 2 O 3 Preparing a biomimetic catalyst:
(1) Taking 0.5000-5.0000 g FeCl 3 Dissolving in 30mL of analytically pure acetone, and adding the purified and modified CNTs-Al 2 O 3 The composite carrier is stirred for 24 to 48 hours at the temperature of between 20 and 25 ℃ to load Fe, and the CNTs-Al after the Fe is loaded 2 O 3 Filtering the composite carrier sample, washing with water, and slowly drying in a drying oven at 60-80 ℃;
(2) Drying the CNTs-Al loaded with Fe 2 O 3 Placing a composite carrier sample in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and controlling the flow ratio of two gases to be Ar: h 2 20 mL/min-50 mL/min, the heating rate is 5-10 ℃/min, the temperature is gradually increased to 350-750 ℃, then the calcination is carried out for 6-8 h, and then the temperature is reduced to 20-25 ℃ under the protection of the mixed atmosphere, so as to prepare Fe/CNTs-Al with atomic-level dispersion 2 O 3 A biomimetic catalyst.
Compared with the prior art, the invention has the following advantages:
(1) The invention adopts a biological nitrogen fixation mechanism to realize the unification of heterogeneous catalysis and enzyme catalysis. The low oxidation state non-noble metal Fe is used as an electronic library to adjust charge transfer in the whole process, the high-efficiency oxidation reduction cycle of biological nitrogen fixation in nature is simulated by the synergistic effect of the Fe and Co-Mo, the activation energy barrier of nitrogen is effectively reduced by a bionic combination hydrogenation mechanism, the BEP relation limitation of a traditional heterogeneous catalysis transition metal surface direct dissociation mechanism is broken through, the reaction can be driven under a mild thermodynamic condition, and therefore the temperature and the pressure of the traditional Haber-Bosch ammonia synthesis process are remarkably reduced under the condition of no external light and electricity, and the ammonia synthesis reaction can be carried out under a mild condition.
(2) The invention realizes the atomic-level dispersion of the non-noble metal active phase Fe. Composite carrier CNTs-Al 2 O 3 The unique electronic confinement environment ensures that metal particles in the bionic catalyst are not easy to grow up, effectively avoids particle aggregation, and can also keep the stability of the particles in the bionic catalyst at higher temperature, thereby better resisting sintering, and the active phase Fe effectively keeps an atomic-level dispersion state, so that the bionic catalyst has excellent synthetic ammonia activity.
(3) The invention constructs a unique catalytic microreactor. CNTs-Al with macroscopic molding and microscopic adjustment 2 O 3 Is a composite carrier, takes the non-noble metal Fe dispersed in atomic level as an active phase to form Fe/CNTs-Al 2 The O catalysis micro-reactor realizes the bionic high-efficiency catalytic synthesis of ammonia under mild conditions by utilizing the synergistic effect of the unique electronic confinement environment of the micro-reactor and the size effect of atomic-scale Fe.
Detailed Description
The present invention will be described in detail with reference to specific examples.
The invention relates to an artificial bionic catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions, which comprises the following steps:
step one, co-Mo/Al 2 O 3 Preparation of the catalytic carrier:
(1) Industrial pure gamma-Al 2 O 3 Crushing and sieving with 12-16 mesh sieve. Heating the screened sample at 800 ℃ for 4h to convert the phase into delta (theta) -Al 2 O 3 。
(2) First, 5g of phase-inverted delta (. Theta) -Al was taken 2 O 3 Placing in 50mL beaker, adding 10mL distilled water, soaking in 60 deg.C water bath for 40min to make delta (theta) -Al 2 O 3 Absorbing water, cooling to 25 deg.C, pouring out unabsorbed water, measuring the volume of poured water and recording as V, and calculating delta (theta) -Al 2 O 3 The saturated water absorption capacity of (A) is:
then, analytically pure Co (NO 3 ) 2 ·6H 2 O and analytically pure (NH) 4 ) 6 Mo 7 O 24 ·4H 2 Dissolving O in (10-V) mL of distilled water to obtain a mixed solution, treating the mixed solution with ultrasonic wave until the solid component is completely dissolved, and adding 5g of phase-inverted delta (theta) -Al into the mixed solution 2 O 3 And continuously stirring under the baking of an infrared lamp until the solution is completely immersed into the delta (theta) -Al after phase inversion 2 O 3 In (d), delta (. Theta) -Al after impregnation 2 O 3 Drying in an oven at 100-120 ℃ (usually for 24-46 h) to obtain unreduced Co-Mo/Al 2 O 3 A catalytic carrier.
(3) Mixing Co-Mo/Al 2 O 3 The catalytic carrier is placed in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and in a mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99%, the flow ratio of the two gases is controlled to be Ar: h 2 =80:20 mL/min-50, heating to 500-550 ℃ at the speed of 5-10 ℃/min to reduce Co-Mo/Al 2 O 3 Catalyzing the carrier for 1 to 3 hours to obtain reduced Co-Mo/Al 2 O 3 A catalytic carrier.
Step two, CNTs-Al 2 O 3 Preparing a composite carrier:
(1) Reducing the Co-Mo/Al 2 O 3 And (3) placing the catalytic carrier in a constant temperature area of a quartz tube of the horizontal tube type resistance furnace, and continuously heating to 550-750 ℃ in the mixed atmosphere of the hydrogen and the argon in the first step at the same flow ratio as that in the first step, wherein the heating rate is 5-10 ℃/min.
(2) And (3) introducing acetylene gas with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and closing argon. At C 2 H 2 And H 2 The flow ratio of (A) is 10 2 O 3 And (3) catalytically growing Carbon Nano Tubes (CNTs) on the catalytic carrier, and stopping introducing acetylene gas into the horizontal tubular resistance furnace after the reaction is finished.
(3) Continuously introducing mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and controlling the flow ratio of the two gases to be Ar: h 2 And (2) 20-50 mL/min, rapidly heating to 700-800 ℃ in the atmosphere for 1-3 h to generate CNTs, and then reducing to 20-25 ℃ in the mixed atmosphere for protection to prepare CNTs-Al 2 O 3 And (3) a composite carrier.
(4) CNTs-Al 2 O 3 15-30% of H for composite carrier 2 O 2 Oxidizing for 6h, washing the treated sample to neutrality, drying in an oven at 60-80 ℃ (usually for 24-48 h) to obtain the purified and modified CNTs-Al 2 O 3 And (3) a composite carrier.
Step three, fe/CNTs-Al 2 O 3 Preparing a biomimetic catalyst:
(1) Taking 0.5000-5.0000 gFeCl 3 Dissolving in 30mL of analytically pure acetone, and adding the purified and modified CNTs-Al 2 O 3 The composite carrier is stirred for 24 to 48 hours at the temperature of between 20 and 25 ℃ to load Fe, and the CNTs-Al after the Fe is loaded 2 O 3 And filtering the composite carrier sample, washing with water, and slowly drying in an oven at 60-80 ℃ (usually for 24-48 h).
(2) The dried CNTs-Al loaded with Fe 2 O 3 Placing a composite carrier sample in a constant-temperature area of a quartz tube of a horizontal tube type resistance furnace, and controlling the flow ratio of two gases to be Ar: h 2 20 mL/min-50, the heating rate is 5-10 ℃/min, the temperature is gradually increased to 350-750 ℃, then the calcination is carried out for 6-8 h, and then the temperature is reduced to 20-25 ℃ under the protection of the mixed atmosphere, so as to prepare the Fe/CNTs-Al with atomic-level dispersion 2 O 3 A biomimetic catalyst.
Example 1
Step one, co-Mo/Al 2 O 3 Preparation of the catalytic carrier:
(1) Industrial pure gamma-Al 2 O 3 Pulverizing, and sieving with 12 mesh sieve. The screened sample was heated at 800 ℃ for 4h to phase convert to delta (theta)-Al 2 O 3 。
(2) First, 5g of phase-inverted delta (. Theta) -Al was taken 2 O 3 Placing in 50mL beaker, adding 10mL distilled water, soaking in 60 deg.C water bath for 40min to make delta (theta) -Al 2 O 3 Absorbing water, cooling to 25 deg.C, pouring out unabsorbed water, measuring the volume of poured water and recording as V, and calculating delta (theta) -Al 2 O 3 The saturated water absorption capacity of (A) is:
then 1.0000g of analytically pure Co (NO) was weighed out 3 ) 2 ·6H 2 O and 1.0000g analytically pure (NH) 4 ) 6 Mo 7 O 24 ·4H 2 Dissolving O in (10-V) mL of distilled water to obtain a mixed solution, treating the mixed solution with ultrasonic wave until the solid component is completely dissolved, and adding 5g of phase-inverted delta (theta) -Al into the mixed solution 2 O 3 Stirring under infrared lamp baking until the solution is completely impregnated with the transformed delta (theta) -Al 2 O 3 In (d), delta (. Theta) -Al after impregnation 2 O 3 Drying in an oven at 100 ℃ for 24h to obtain unreduced Co-Mo/Al 2 O 3 A catalytic carrier.
(3) Mixing Co-Mo/Al 2 O 3 The catalytic carrier is placed in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and in a mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99%, the flow ratio of the two gases is controlled as Ar: h 2 =80:20mL/min, heating to 500 ℃ at the speed of 5 ℃/min to reduce Co-Mo/Al 2 O 3 Catalyzing the carrier for 1h to obtain reduced Co-Mo/Al 2 O 3 A catalytic carrier.
Step two, CNTs-Al 2 O 3 Preparing a composite carrier:
(1) Reducing the Co-Mo/Al 2 O 3 And (3) placing the catalytic carrier in a constant temperature area of a quartz tube of the horizontal tube type resistance furnace, and continuously heating to 550 ℃ in the mixed atmosphere of the hydrogen and the argon in the first step at the same flow ratio as that in the first step, wherein the heating rate is 5 ℃/min.
(2) And (3) introducing acetylene gas with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and simultaneously closing argon. At C 2 H 2 And H 2 The flow ratio is 10: reacting for 10min under the reaction atmosphere of 100mL/min, and obtaining the reduced Co-Mo/Al 2 O 3 CNTs are catalytically grown on the catalytic carrier, and acetylene gas is stopped from being introduced into the horizontal tubular resistance furnace after the reaction is finished.
(3) Continuously introducing hydrogen and argon mixed atmosphere with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and controlling the flow ratio of the two gases to be Ar: h 2 And (2) =80, heating to 700 ℃ rapidly in the atmosphere for 1h, heating the generated CNTs for 1h, and then reducing to 20 ℃ in the mixed atmosphere for protection to prepare the CNTs-Al 2 O 3 And (3) compounding a carrier.
(4) CNTs-Al 2 O 3 15% of H for composite carrier 2 O 2 Oxidizing for 6h, washing the treated sample to be neutral, and drying in a 60 ℃ oven for 24h to obtain the purified and modified CNTs-Al 2 O 3 And (3) a composite carrier.
Step three, fe/CNTs-Al 2 O 3 Preparing a biomimetic catalyst:
(1) Accurately weighing 0.5000g of FeCl 3 Dissolving in 30ml of analytically pure acetone, and adding purified and modified CNTs-Al 2 O 3 Stirring the composite carrier at 20 ℃ for 24h to load Fe, and carrying out the Fe-loaded CNTs-Al 2 O 3 The composite carrier sample was filtered out and washed with water, and then slowly dried in an oven at 60 ℃ for 24h.
(2) Drying the CNTs-Al loaded with Fe 2 O 3 Placing a composite carrier sample in a constant-temperature area of a quartz tube of a horizontal tube type resistance furnace, and controlling the flow ratio of two gases to be Ar: h 2 =80:20mL/min, the heating rate is 5 ℃/min, the temperature is gradually increased to 350 ℃, then the mixture is calcined for 6h, and then the temperature is reduced to 20 ℃ under the protection of the mixed atmosphere, so that the Fe/CNTs-Al with atomic-level dispersion is prepared 2 O 3 A biomimetic catalyst.
For the Fe/CNTs-Al prepared in this example 2 O 3 Performing synthetic ammonia activity test on the bionic catalyst:
2mg of Fe/CNTs-Al prepared in the present example was taken 2 O 3 The biomimetic catalyst is placed in a synthetic ammonia activity testing device, activated for 3 hours at 200 ℃ by reaction gas in an isothermal zone range of reaction, and then stabilized for 3 hours under testing conditions. The test conditions were: the temperature is 300 ℃, the pressure is 8MPa, and the reaction gas N 2 ：H 2 =1:3 (volume ratio), space velocity 12000h -1 The ammonia concentration in the outlet reaction gas was measured to be 237.3mmol g by chemical absorption cat -1 h -1 And the synthetic ammonia activity of the bionic catalyst is not obviously reduced after the bionic catalyst is stably operated for 72 hours. The atomic-scale artificial bionic catalyst prepared by the invention has excellent performance, and the activity and the stability of the synthetic ammonia are higher under mild conditions.
Example 2
Step one, co-Mo/Al 2 O 3 Preparation of the catalytic carrier:
(1) Industrial pure gamma-Al 2 O 3 Pulverizing, and sieving with 14 mesh sieve. Heating the screened sample at 800 deg.C for 4h to convert to delta (theta) -Al 2 O 3 。
(2) First, 5g of phase-inverted delta (. Theta) -Al was taken 2 O 3 Placing in 50mL beaker, adding 10mL distilled water, soaking in 60 deg.C water bath for 40min to make delta (theta) -Al 2 O 3 Absorbing water, cooling to 25 deg.C, pouring out unabsorbed water, measuring the volume of poured water as V, and calculating delta (theta) -Al 2 O 3 The saturated water absorption capacity of (A) is:
then 2.0000g of analytically pure Co (NO) was weighed out 3 ) 2 ·6H 2 O and 1.0000g analytically pure (NH) 4 ) 6 Mo 7 O 24 ·4H 2 Dissolving O in (10-V) mL of distilled water to obtain a mixed solution, treating the mixed solution with ultrasonic wave until the solid component is completely dissolved, adding 5g of the mixed solution, and phase-convertingDelta (theta) -Al of 2 O 3 And continuously stirring under the baking of an infrared lamp until the solution is completely immersed into the delta (theta) -Al after phase inversion 2 O 3 In (d), delta (. Theta) -Al after impregnation 2 O 3 Drying in an oven at 110 ℃ for 32h to obtain unreduced Co-Mo/Al 2 O 3 A catalytic carrier.
(3) Mixing Co-Mo/Al 2 O 3 The catalytic carrier is placed in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and in a mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99%, the flow ratio of the two gases is controlled to be Ar: h 2 =70:30mL/min, heating to 520 ℃ at the speed of 7 ℃/min to reduce Co-Mo/Al 2 O 3 Catalyzing the carrier for 2 hours to obtain reduced Co-Mo/Al 2 O 3 A catalytic carrier.
Step two, CNTs-Al 2 O 3 Preparing a composite carrier:
(1) Reducing the Co-Mo/Al 2 O 3 And (3) placing the catalytic carrier in a constant-temperature area of a horizontal tube type resistance furnace quartz tube, and continuously heating to 650 ℃ in the mixed atmosphere of the hydrogen and the argon in the first step at the same flow ratio as that in the first step, wherein the heating rate is 7 ℃/min.
(2) And introducing acetylene gas with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and closing argon. At C 2 H 2 And H 2 The flow ratio is 30: reacting for 30min under the reaction atmosphere of 100mL/min, and obtaining the reduced Co-Mo/Al 2 O 3 CNTs are catalytically grown on the catalytic carrier, and acetylene gas is stopped from being introduced into the horizontal tubular resistance furnace after the reaction is finished.
(3) Continuously introducing hydrogen and argon mixed atmosphere with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and controlling the flow ratio of the two gases to be Ar: h 2 And (4) heating the CNTs for 2h at the temperature of 750 ℃ rapidly in the atmosphere of 30mL/min, and then cooling the CNTs to 23 ℃ in the mixed atmosphere for preparation of the CNTs-Al 2 O 3 And (3) a composite carrier.
(4) CNTs-Al 2 O 3 20% of H for composite carrier 2 O 2 Oxidizing for 6h, washing the treated sample to be neutral, and drying in an oven at 70 ℃ for 32h to obtain the purified and modified CNTs-Al 2 O 3 And (3) compounding a carrier.
Step three, fe/CNTs-Al 2 O 3 Preparing a biomimetic catalyst:
(1) Accurately weighing 1.0000g FeCl 3 Dissolving in 30ml of analytically pure acetone, and adding purified and modified CNTs-Al 2 O 3 Stirring the composite carrier at 23 ℃ for 32h to load Fe, and carrying out the Fe-loaded CNTs-Al 2 O 3 The composite support sample was filtered, washed with water and then placed in an oven at 70 ℃ to dry slowly for 32h.
(2) Drying the CNTs-Al loaded with Fe 2 O 3 Placing a composite carrier sample in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and controlling the flow ratio of two gases to be Ar: h 2 =70:30mL/min, the heating rate is 7 ℃/min, the temperature is gradually increased to 550 ℃, then the calcination is carried out for 7h, and then the temperature is reduced to 23 ℃ under the protection of the mixed atmosphere to prepare the Fe/CNTs-Al with atomic-level dispersion 2 O 3 A biomimetic catalyst.
For the Fe/CNTs-Al prepared in this example 2 O 3 Performing synthetic ammonia activity test on the bionic catalyst:
2mg of Fe/CNTs-Al prepared in this example were taken 2 O 3 The biomimetic catalyst is placed in a synthetic ammonia activity testing device, activated for 3 hours at 200 ℃ by reaction gas within the isothermal zone of the reaction, and then stabilized for 3 hours under the testing condition. The test conditions were: the temperature is 300 ℃, the pressure is 8MPa, and the reaction gas N 2 ：H 2 =1:3 (volume ratio), space velocity 12000h -1 The concentration of ammonia in the outlet reaction gas was 998.6mmol g as measured by chemical absorption cat -1 h -1 And the synthetic ammonia activity of the bionic catalyst is not obviously reduced after the bionic catalyst is stably operated for 72 hours. The atomic-scale artificial biomimetic catalyst prepared by the invention has excellent performance, and has higher activity and stability of synthetic ammonia under mild conditions.
Example 3
Step one, co-Mo/Al 2 O 3 Preparation of the catalytic carrier:
(1) Industrial pure gamma-Al 2 O 3 Pulverizing, and sieving with 16 mesh sieve. Heating the screened sample at 800 deg.C for 4h to convert to delta (theta) -Al 2 O 3 。
(2) First, 5g of phase-inverted delta (. Theta) -Al was taken 2 O 3 Placing in 50mL beaker, adding 10mL distilled water, soaking in 60 deg.C water bath for 40min to make delta (theta) -Al 2 O 3 Absorbing water, cooling to 25 deg.C, pouring out unabsorbed water, measuring the volume of poured water and recording as V, and calculating delta (theta) -Al 2 O 3 The saturated water absorption capacity of (A) is:
then 3.0000g of analytically pure Co (NO) was weighed out 3 ) 2 ·6H 2 O and 1.0000g analytically pure (NH) 4 ) 6 Mo 7 O 24 ·4H 2 Dissolving O in (10-V) mL of distilled water to obtain a mixed solution, treating the mixed solution with ultrasonic wave until the solid component is completely dissolved, and adding 5g of phase-inverted delta (theta) -Al into the mixed solution 2 O 3 Stirring under infrared lamp baking until the solution is completely impregnated with the transformed delta (theta) -Al 2 O 3 In (d), delta (. Theta) -Al after impregnation 2 O 3 Drying in an oven at 120 ℃ for 40h to obtain unreduced Co-Mo/Al 2 O 3 A catalytic carrier.
(3) Mixing Co-Mo/Al 2 O 3 The catalytic carrier is placed in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and in a mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99%, the flow ratio of the two gases is controlled to be Ar: h 2 =60:40mL/min, heating to 530 ℃ at the rate of 8 ℃/min to reduce Co-Mo/Al 2 O 3 Catalyzing the carrier for 2.5h to obtain reduced Co-Mo/Al 2 O 3 A catalytic carrier.
Step two, CNTs-Al 2 O 3 Preparing a composite carrier:
(1) After reductionCo-Mo/Al 2 O 3 And (3) placing the catalytic carrier in a constant temperature area of a quartz tube of the horizontal tube type resistance furnace, and continuously heating to 700 ℃ in the mixed atmosphere of the hydrogen and the argon in the first step at the same flow ratio as that in the first step, wherein the heating rate is 8 ℃/min.
(2) And introducing acetylene gas with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and closing argon. At C 2 H 2 And H 2 The flow ratio is 50: reacting for 50min under the reaction atmosphere of 100mL/min, and obtaining the reduced Co-Mo/Al 2 O 3 CNTs are catalytically grown on the catalytic carrier, and acetylene gas is stopped from being introduced into the horizontal tubular resistance furnace after the reaction is finished.
(3) Continuously introducing a hydrogen and argon mixed atmosphere with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and controlling the flow ratio of the two gases to be Ar: h 2 And (2) quickly raising the temperature to 780 ℃ in the atmosphere for heating the generated CNTs for 2.5h, and then reducing the temperature to 24 ℃ in the mixed atmosphere for protection to prepare CNTs-Al 2 O 3 And (3) a composite carrier.
(4) CNTs-Al 2 O 3 The composite carrier uses 25 percent of H by mass fraction 2 O 2 Oxidizing for 6h, washing the treated sample to neutrality, and drying in an oven at 80 ℃ for 40h to obtain the purified and modified CNTs-Al 2 O 3 And (3) compounding a carrier.
Step three, fe/CNTs-Al 2 O 3 Preparing a biomimetic catalyst:
(1) Accurately weighing 3.0000g FeCl 3 Dissolving in 30ml of analytically pure acetone, and adding purified and modified CNTs-Al 2 O 3 Stirring the composite carrier at 24 ℃ for 40h to load Fe, and carrying out the Fe-loaded CNTs-Al 2 O 3 The composite carrier sample was filtered, washed with water, and then slowly dried in an oven at 80 ℃ for 40h.
(2) Drying the CNTs-Al loaded with Fe 2 O 3 Placing a composite carrier sample in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and controlling the flow ratio of two gases to be A in a mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99 percentr：H 2 =60:40mL/min, the heating rate is 8 ℃/min, the temperature is gradually increased to 650 ℃, then the calcination is carried out for 8h, and then the temperature is reduced to 24 ℃ under the protection of the mixed atmosphere to prepare the Fe/CNTs-Al with atomic-scale dispersion 2 O 3 A biomimetic catalyst.
For the Fe/CNTs-Al prepared in this example 2 O 3 Performing synthetic ammonia activity test on the bionic catalyst:
2mg of Fe/CNTs-Al prepared in this example were taken 2 O 3 The biomimetic catalyst is placed in a synthetic ammonia activity testing device, activated for 3 hours at 200 ℃ by reaction gas within the isothermal zone of the reaction, and then stabilized for 3 hours under the testing condition. The test conditions were: the temperature is 300 ℃, the pressure is 8MPa, and the reaction gas N 2 ：H 2 =1:3 (volume ratio), space velocity 12000h -1 The concentration of ammonia in the outlet reaction gas was 563.5mmol g as measured by chemical absorption cat -1 h -1 And the synthetic ammonia activity of the bionic catalyst is not obviously reduced after the bionic catalyst is stably operated for 72 hours. The atomic-scale artificial biomimetic catalyst prepared by the invention has excellent performance, and the activity and stability of the synthetic ammonia are both higher under mild conditions.
Example 4
Step one, co-Mo/Al 2 O 3 Preparation of the catalytic carrier:
(1) Industrial pure gamma-Al 2 O 3 Pulverizing, and sieving with 16 mesh sieve. Heating the screened sample at 800 deg.C for 4h to convert to delta (theta) -Al 2 O 3 。
(2) First, 5g of phase-inverted delta (. Theta) -Al was taken 2 O 3 Placing in 50mL beaker, adding 10mL distilled water, soaking in 60 deg.C water bath for 40min to make delta (theta) -Al 2 O 3 Absorbing water, cooling to 25 deg.C, pouring out unabsorbed water, measuring the volume of poured water and recording as V, and calculating delta (theta) -Al 2 O 3 The saturated water absorption capacity of (A) is:
then 5.0000g of analytically pure Co (NO) was weighed out 3 ) 2 ·6H 2 O and 10000g analytically pure (NH) 4 ) 6 Mo 7 O 24 ·4H 2 Dissolving O in (10-V) mL of distilled water to prepare a mixed solution, treating the mixed solution with ultrasonic waves by using an ultrasonic cleaner until solid components are completely dissolved, and adding 5g of phase-converted delta (theta) -Al into the mixed solution 2 O 3 Stirring under infrared lamp baking until the solution is completely impregnated with the transformed delta (theta) -Al 2 O 3 In (d), delta (. Theta) -Al after impregnation 2 O 3 Drying in an oven at 120 ℃ for 48h to obtain unreduced Co-Mo/Al 2 O 3 A catalytic carrier.
(3) Mixing Co-Mo/Al 2 O 3 The catalytic carrier is placed in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and in a mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99%, the flow ratio of the two gases is controlled as Ar: h 2 =50:50mL/min, heating to 550 ℃ at the speed of 10 ℃/min to reduce Co-Mo/Al 2 O 3 Catalyzing the carrier for 3 hours to obtain reduced Co-Mo/Al 2 O 3 A catalytic carrier.
Step two, CNTs-Al 2 O 3 Preparing a composite carrier:
(1) Reducing the Co-Mo/Al 2 O 3 And (3) placing the catalytic carrier in a constant temperature area of a quartz tube of the horizontal tube type resistance furnace, and continuously heating to 750 ℃ in the mixed atmosphere of the hydrogen and the argon in the first step at the same flow ratio as that in the first step, wherein the heating rate is 10 ℃/min.
(2) And introducing acetylene gas with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and closing argon. At C 2 H 2 And H 2 The flow ratio is 100: reacting for 60min under the reaction atmosphere of 100mL/min, and obtaining the reduced Co-Mo/Al 2 O 3 CNTs are catalytically grown on the catalytic carrier, and acetylene gas is stopped from being introduced into the horizontal tubular resistance furnace after the reaction is finished.
(3) Continuously introducing a hydrogen and argon mixed atmosphere with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and controlling the flow ratio of the two gases to be Ar: h 2 =50 ml/min, rapidly raise temperature to 800 ℃ under this atmosphere plusCNTs (carbon nanotubes) are thermally generated for 3h, and then the temperature is reduced to 25 ℃ under the protection of the mixed atmosphere to prepare CNTs-Al 2 O 3 And (3) compounding a carrier.
(4) CNTs-Al 2 O 3 The composite carrier uses 30 percent of H by mass fraction 2 O 2 Oxidizing for 6h, washing the treated sample to neutrality, and drying in an oven at 80 ℃ for 48h to obtain the purified and modified CNTs-Al 2 O 3 And (3) a composite carrier.
Step three, fe/CNTs-Al 2 O 3 Preparing a biomimetic catalyst:
(1) Accurately weighing 5.0000g FeCl 3 Dissolving in 30ml of analytically pure acetone, and adding purified and modified CNTs-Al 2 O 3 Stirring the composite carrier at 25 ℃ for 48h to load Fe, and carrying out the Fe-loaded CNTs-Al 2 O 3 The composite support sample was filtered, washed with water, and then slowly dried in an oven at 80 ℃ for 48h.
(2) Drying the CNTs-Al loaded with Fe 2 O 3 Placing a composite carrier sample in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and controlling the flow ratio of two gases to be Ar: h 2 =50:50mL/min, the heating rate is 10 ℃/min, the temperature is gradually increased to 750 ℃, then the calcination is carried out for 8h, and then the temperature is reduced to 25 ℃ under the protection of the mixed atmosphere to prepare the Fe/CNTs-Al with atomic-level dispersion 2 O 3 A biomimetic catalyst.
For Fe/CNTs-Al prepared in this example 2 O 3 Performing synthetic ammonia activity test on the bionic catalyst:
2mg of Fe/CNTs-Al prepared in this example were taken 2 O 3 The biomimetic catalyst is placed in a synthetic ammonia activity testing device, activated for 3 hours at 200 ℃ by reaction gas within the isothermal zone of the reaction, and then stabilized for 3 hours under the testing condition. The test conditions were: the temperature is 300 ℃, the pressure is 8MPa, and the reaction gas N 2 ：H 2 =1:3 (volume ratio), space velocity 12000h -1 The concentration of ammonia in the outlet reaction gas was 219.2mmol g as measured by chemical absorption cat -1 h -1 To stably transportAfter the line 72h, the synthetic ammonia activity of the biomimetic catalyst is not obviously reduced. The atomic-scale artificial bionic catalyst prepared by the invention has excellent performance, and has higher activity and stability of synthetic ammonia under mild conditions.
From the experimental results, the biomimetic catalyst prepared by the method has excellent performance, high ammonia synthesis activity and stability under mild conditions, and ideal effect of catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions.
The method of the present invention has been described in detail with reference to the above embodiments, but the present invention is not limited to the above embodiments, and the experimental conditions and method can be flexibly changed without departing from the scope of the present invention. Therefore, the patent and protection scope of the present invention should be subject to the appended claims.
Claims (1)
1. An artificial bionic catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions is characterized in that: the method comprises the following steps:
step one, co-Mo/Al 2 O 3 Preparation of the catalytic carrier:
(1) Industrial pure gamma-Al 2 O 3 Pulverizing, sieving with 12-16 mesh sieve, heating the sieved sample at 800 deg.C for 4 hr to convert to delta (theta) -Al 2 O 3 ；
(2) First, 5g of phase-inverted delta (. Theta) -Al was taken 2 O 3 Placing in 50mL beaker, adding 10mL distilled water, soaking in 60 deg.C water bath for 40min to make delta (theta) -Al 2 O 3 Absorbing water, cooling to 25 deg.C, pouring out unabsorbed water, measuring the volume of poured water and recording as V, and calculating delta (theta) -Al 2 O 3 The saturated water absorption capacity of (A) is:
then, analytically pure Co (NO) 3 ) 2 ·6H 2 O and analytically pure (NH) 4 ) 6 Mo 7 O 24 ·4H 2 Dissolving O in (10-V) mL of distilled water to obtain a mixed solution, treating the mixed solution with ultrasonic wave until the solid component is completely dissolved, and adding 5g of phase-inverted delta (theta) -Al into the mixed solution 2 O 3 Stirring under infrared lamp baking until the solution is completely impregnated with the transformed delta (theta) -Al 2 O 3 In (d), delta (. Theta) -Al after impregnation 2 O 3 Drying in an oven at 100-120 ℃ to obtain unreduced Co-Mo/Al 2 O 3 A catalytic support;
(3) Mixing Co-Mo/Al 2 O 3 The catalytic carrier is placed in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and in a mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99%, the flow ratio of the two gases is controlled to be Ar: h 2 =80:20 mL/min-50 mL/min, heating to 500-550 ℃ at the speed of 5-10 ℃/min, and reducing Co-Mo/Al 2 O 3 Catalyzing the carrier for 1 to 3 hours to obtain reduced Co-Mo/Al 2 O 3 A catalytic support;
step two, CNTs-Al 2 O 3 Preparing a composite carrier:
(1) Reducing the Co-Mo/Al 2 O 3 Placing the catalytic carrier in a constant temperature area of a quartz tube of the horizontal tube type resistance furnace, and continuously heating to 550-750 ℃ in the mixed atmosphere of the hydrogen and the argon in the first step at the same flow ratio as that in the first step, wherein the heating rate is 5-10 ℃/min;
(2) Introducing acetylene gas with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and simultaneously closing argon; at C 2 H 2 And H 2 The flow ratio of (A) is 10-100 2 O 3 Growing CNTs on a catalytic carrier in a catalytic manner, and stopping introducing acetylene gas into the horizontal tubular resistance furnace after the reaction is finished;
(3) Continuously introducing mixed atmosphere of hydrogen and argon with the mass percent purity of 99.99% into the horizontal tubular resistance furnace, and controlling the flow ratio of the two gases to be Ar: h 2 =80Rapidly heating to 700-800 ℃ to generate CNTs for 1-3 h, then reducing to 20-25 ℃ under the protection of the mixed atmosphere to prepare CNTs-Al 2 O 3 A composite carrier;
(4) CNTs-Al 2 O 3 15-30% of H for composite carrier 2 O 2 Oxidizing for 6h, washing the treated sample to be neutral, drying in a drying oven at 60-80 ℃ to obtain the purified and modified CNTs-Al 2 O 3 A composite carrier;
step three, fe/CNTs-Al 2 O 3 Preparing a biomimetic catalyst:
(1) Taking 0.5000-5.0000 g FeCl 3 Dissolving in 30mL of analytically pure acetone, and adding the purified and modified CNTs-Al 2 O 3 The composite carrier is stirred for 24 to 48 hours at the temperature of between 20 and 25 ℃ to load Fe, and the CNTs-Al after the Fe is loaded 2 O 3 Filtering the composite carrier sample, washing with water, and slowly drying in a drying oven at 60-80 ℃;
(2) Drying the CNTs-Al loaded with Fe 2 O 3 Placing a composite carrier sample in a constant temperature area of a quartz tube of a horizontal tube type resistance furnace, and controlling the flow ratio of two gases to be Ar: h 2 20 mL/min-50, the heating rate is 5-10 ℃/min, the temperature is gradually increased to 350-750 ℃, then the calcination is carried out for 6-8 h, and then the temperature is reduced to 20-25 ℃ under the protection of the mixed atmosphere, so as to prepare the Fe/CNTs-Al with atomic-level dispersion 2 O 3 A biomimetic catalyst.
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