CN113332997B - RuCu nano alloy catalyst with finite field structure and application thereof in catalyzing carbon monoxide preferential oxidation reaction - Google Patents
RuCu nano alloy catalyst with finite field structure and application thereof in catalyzing carbon monoxide preferential oxidation reaction Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 41
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 31
- 239000000956 alloy Substances 0.000 title claims abstract description 31
- 229910002091 carbon monoxide Inorganic materials 0.000 title claims abstract description 19
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 18
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 16
- 238000006243 chemical reaction Methods 0.000 claims abstract description 20
- GDVKFRBCXAPAQJ-UHFFFAOYSA-A dialuminum;hexamagnesium;carbonate;hexadecahydroxide Chemical group [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Al+3].[Al+3].[O-]C([O-])=O GDVKFRBCXAPAQJ-UHFFFAOYSA-A 0.000 claims abstract description 18
- 239000002245 particle Substances 0.000 claims abstract description 18
- 229960001545 hydrotalcite Drugs 0.000 claims abstract description 17
- 229910001701 hydrotalcite Inorganic materials 0.000 claims abstract description 17
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 16
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000001257 hydrogen Substances 0.000 claims abstract description 15
- 239000002243 precursor Substances 0.000 claims abstract description 15
- 239000012298 atmosphere Substances 0.000 claims abstract description 7
- 239000002131 composite material Substances 0.000 claims abstract description 7
- SNAAJJQQZSMGQD-UHFFFAOYSA-N aluminum magnesium Chemical compound [Mg].[Al] SNAAJJQQZSMGQD-UHFFFAOYSA-N 0.000 claims abstract description 6
- 238000002360 preparation method Methods 0.000 claims abstract description 6
- 238000002425 crystallisation Methods 0.000 claims abstract description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 15
- 239000007789 gas Substances 0.000 claims description 14
- 230000009467 reduction Effects 0.000 claims description 13
- 239000010949 copper Substances 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 239000012266 salt solution Substances 0.000 claims description 8
- 239000000243 solution Substances 0.000 claims description 8
- 239000011777 magnesium Substances 0.000 claims description 7
- 239000003513 alkali Substances 0.000 claims description 6
- 239000008367 deionised water Substances 0.000 claims description 6
- 229910021641 deionized water Inorganic materials 0.000 claims description 6
- 239000011259 mixed solution Substances 0.000 claims description 6
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 6
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 claims description 4
- 150000001879 copper Chemical class 0.000 claims description 4
- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 claims description 4
- 159000000003 magnesium salts Chemical class 0.000 claims description 4
- 150000003303 ruthenium Chemical class 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 3
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims description 2
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Chemical compound [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 claims description 2
- 230000008025 crystallization Effects 0.000 claims description 2
- 230000005669 field effect Effects 0.000 claims description 2
- 238000005216 hydrothermal crystallization Methods 0.000 claims description 2
- 230000007935 neutral effect Effects 0.000 claims description 2
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 2
- YBCAZPLXEGKKFM-UHFFFAOYSA-K ruthenium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Ru+3] YBCAZPLXEGKKFM-UHFFFAOYSA-K 0.000 claims description 2
- 230000002194 synthesizing effect Effects 0.000 claims description 2
- 239000012670 alkaline solution Substances 0.000 claims 2
- 229910052757 nitrogen Inorganic materials 0.000 claims 1
- 230000003647 oxidation Effects 0.000 abstract description 7
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 abstract description 4
- 239000001569 carbon dioxide Substances 0.000 abstract description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 abstract description 2
- 230000000694 effects Effects 0.000 abstract description 2
- 239000006259 organic additive Substances 0.000 abstract description 2
- 239000003960 organic solvent Substances 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 5
- 239000000446 fuel Substances 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 239000002105 nanoparticle Substances 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 239000012528 membrane Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 230000004075 alteration Effects 0.000 description 2
- 150000001450 anions Chemical class 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 150000001768 cations Chemical class 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000002803 fossil fuel Substances 0.000 description 2
- 239000011229 interlayer Substances 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 238000002161 passivation Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000010926 purge Methods 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- 239000002028 Biomass Substances 0.000 description 1
- 101100348341 Caenorhabditis elegans gas-1 gene Proteins 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229920000742 Cotton Polymers 0.000 description 1
- 229910016553 CuOx Inorganic materials 0.000 description 1
- 101100447658 Mus musculus Gas1 gene Proteins 0.000 description 1
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
- 239000006004 Quartz sand Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000000024 high-resolution transmission electron micrograph Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000520 microinjection Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000011943 nanocatalyst Substances 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 239000012429 reaction media Substances 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
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- 230000002195 synergetic effect Effects 0.000 description 1
Classifications
-
- 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
- B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
- B01J23/8926—Copper and noble metals
-
- 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
- B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
- B01J23/8933—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/894—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
-
- B01J35/393—
-
- B01J35/394—
-
- 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
- C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
- C01B3/56—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids
- C01B3/58—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids including a catalytic reaction
- C01B3/583—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids including a catalytic reaction the reaction being the selective oxidation of carbon monoxide
Abstract
The invention discloses a RuCu nano alloy catalyst with a finite field structure and application thereof in catalyzing carbon monoxide preferential oxidation reaction. The MgCuAlRu quaternary hydrotalcite precursor is synthesized by a double-drop method, and then reduced in a hydrogen atmosphere to obtain the RuCu nano alloy catalyst with a finite field structure. RuCu bimetallic nano alloy particles in the catalyst are uniformly dispersed in a weak-crystallization magnesium-aluminum composite oxide, and the magnesium-aluminum composite oxide has a domain-limiting effect on the RuCu bimetallic nano alloy particles. The catalyst not only improves the conversion rate of preferential oxidation of carbon monoxide, but also greatly improves the selectivity and the reaction stability of carbon dioxide. It is used at 85 deg.C, normal pressure and space velocity for 10-30 hr ‑1 Under the condition, the conversion rate of the preferential oxidation reaction of carbon monoxide is 100 percent, and the selectivity is 75 percent. In addition, the catalyst preparation process does not need to use organic solvents or additives, and the method is simple and environment-friendly.
Description
Technical Field
The invention belongs to the technical field of catalyst preparation, and particularly relates to a RuCu nano alloy catalyst with a finite field structure and application thereof in catalyzing carbon monoxide preferential oxidation reaction.
Background
Hydrogen is a gaseous clean energy source mainly derived from chemical plant emissions, fossil fuel combustion, biomass hydrogen production, fossil fuels and electrolyzed water, with 90% of the hydrogen feedstock coming from the former two ways. However, as a reaction medium for a proton membrane fuel cell, the purity is lower than 100 ppm, and since CO contained in the raw material gas can affect the Pt metal electrode of the main active catalyst of the cell, even if a noble metal or a non-noble metal capable of resisting CO adsorption is added to the Pt electrode, the high concentration of CO can cause the overall operation strength of the fuel cell to be reduced, the efficiency to be reduced, and even irreversible deactivation to be affected.
Therefore, a pretreatment purge operation is performed before the hydrogen fuel is introduced into the proton membrane fuel cell. Hydrogen raw material from factory is reformed by hydrocarbon to make organic matter with low unreacted saturated steam react to generate H 2 O、CO、CO 2 、H 2 、CH 4 And the like. After water gas shift (main reaction: CO+H) 2 O → CO 2 + H 2 ) The CO is reduced to about 1-2% of the gas content. Finally, the obtained cleaner hydrogen raw material is put into a carbon monoxide preferential oxidation reaction (CO-PROX, main reaction CO+O) 2 → CO 2 ) In the process, CO is removed greatly, and the CO concentration bearing standard of the proton membrane fuel cell is achieved. CO-PROX, i.e., carbon monoxide preferential oxidation. The reaction is mainly used for solving the problem of trace CO removal in the PEMFC raw material gas. In order to enable the feed gas after CO removal to meet the requirements of battery use directly, the catalyst chosen must be such that no side reactions (H 2 +O 2 →H 2 O) to completely remove CO on the premise that this occurs.
The catalyst with the finite structure plays an important role in industrial application, and the finite structure can be used for preparing the synergistic effect and the interfacial effect of the active site and the surrounding environment, so that the catalytic activity is improved. Hydrotalcite (LDHs) is a layered double hydroxide of the general formula [ M ] 2+ 1−x M 3+ x (OH) 2 ] x+ [A n− ] x/n ·yH 2 O, where M 2+ And M 3+ Divalent and trivalent metal cations, respectively, on the body ply; a is that n− Is an interlayer anion; x is M 3+ /(M 2+ +M 3+ ) Molar ratio of (2); y is the number of water molecules between layers. LDHs have metal cation exchangeability, interlayer anion type and quantity adjustable property and host-guest interactionThe structure characteristics of the adjustable property and the like provide a good platform for preparing the novel nano catalyst with the limited domain structure by the LDHs.
Disclosure of Invention
The invention aims to provide a RuCu nano alloy catalyst with a finite field structure and application thereof in catalyzing carbon monoxide preferential oxidation reaction.
The method comprises the steps of firstly synthesizing a MgCuAlRu quaternary hydrotalcite precursor by a double-drop method, and then adopting temperature programming reduction in a hydrogen atmosphere to obtain the RuCu nano alloy catalyst with a finite field structure.
The RuCu nano alloy catalyst with the finite field structure has the structure that: ruCu bimetal nano alloy particles are uniformly dispersed and supported in the magnesium-aluminum composite oxide with weak crystallization, and the magnesium-aluminum composite oxide has a finite field effect on the RuCu bimetal nano alloy particles; the catalyst is black powdery substance, and the particle size of single particles is 5-7nm.
The preparation method of the RuCu nano alloy catalyst with the finite field structure comprises the following steps:
(1) Preparing MgCuAlRu quaternary hydrotalcite precursor by a double-dropping method: at room temperature, dropwise adding a mixed salt solution prepared from soluble magnesium salt, soluble aluminum salt, soluble copper salt and soluble ruthenium salt into a four-mouth flask together with an alkali solution, maintaining the pH value of the mixed solution in the four-mouth flask to be 8-10, transferring the mixed solution into a high-pressure hydrothermal kettle after dropwise adding, carrying out hydrothermal crystallization for 12-48h at 100-150 ℃, washing with hot deionized water to be neutral after the reaction is completed, and drying to obtain MgCuAlRu quaternary hydrotalcite precursor;
(2) Reducing the MgCuAlRu quaternary hydrotalcite precursor prepared in the step (1) in a hydrogen atmosphere at a reduction temperature of 450-650 ℃ and a heating rate of 3-8 ℃ and min -1 The reduction time is 2-6h, the temperature is reduced to room temperature after the reduction is completed, and then the RuCu nano alloy catalyst with the limited domain structure is obtained after passivation for 0.5-2h in nitrogen atmosphere.
The soluble magnesium salt, the soluble aluminum salt, the soluble copper salt and the soluble ruthenium salt are magnesium nitrate, aluminum nitrate, copper nitrate and ruthenium chloride respectively.
The alkali solution is sodium hydroxide solution or mixed alkali solution of sodium hydroxide and sodium carbonate.
The molar ratio of Mg to Al in the mixed salt solution is 2-4:1, the molar ratio of Mg to Ru is 30-70:1, and the molar ratio of Cu to Ru is 1:2-2:1.
The RuCu nano alloy catalyst with the finite structure prepared by the method is applied to catalyzing the preferential oxidation reaction of carbon monoxide. The conditions for catalyzing the preferential oxidation reaction of carbon monoxide are as follows: the reactor is filled with the RuCu nano alloy catalyst with the limited domain structure, the reaction temperature is 80-180 ℃, the mixed gas containing CO is introduced, and the reaction airspeed is 10-30h -1 The total reaction pressure is-0.1-0.1 MPa, and the reaction time is 5-60 h.
The RuCu nano alloy catalyst with the finite structure is applied to catalytic ethanol liquid phase oxidation, ethanol gas phase oxidation or water gas conversion reaction.
In the RuCu nano alloy catalyst with lamellar domain-limiting structure, which is prepared by the invention, mgAlO x The RuCu nanometer alloy carrier is a very good carrier, can effectively disperse RuCu nanometer alloy particles, has stronger interaction between transition metal and the carrier, prevents sintering and transition metal loss, and provides reactive sites for reactants; the nano alloy formed by RuCu has the advantages that the electronic structure of Ru can be allocated by the existence of Cu, and the adsorption site of Ru on CO is changed, so that the selectivity and stability of the catalyst are enhanced, the migration phenomenon of Ru in the reduction process is limited by the introduction of Cu, and the RuCu alloy is in a high-dispersion state. The catalyst not only improves the conversion rate of preferential oxidation of carbon monoxide, but also greatly improves the selectivity and the reaction stability of carbon dioxide. It is used at 85 deg.C, normal pressure and space velocity for 10-30 hr -1 Under the condition, the conversion rate of the preferential oxidation reaction of carbon monoxide is 100 percent, and the selectivity is 75 percent. In addition, the catalyst preparation process does not need to use organic solvents or additives, and the method is simple and environment-friendly.
Drawings
FIG. 1 is XRD (a) and SEM (b) patterns of MgCuAlRu-LDHs precursor prepared in example 1.
FIG. 2 is an XRD pattern of MgCuAlRu-LDHs precursor prepared in example 1 and reduced samples at different temperatures in a hydrogen atmosphere.
FIG. 3 is a schematic diagram showing the H of MgAlRu-LDHs, mgCuAlRu-LDHs and MgAlCu-LDHs precursors obtained in example 1 2 -a TPR map.
FIG. 4 is a photograph of a high resolution transmission electron microscope and corresponding particle size distribution plot for each catalyst sample; a. b is a MgCuAlRu-450 ℃ sample, C and d are MgCuAlRu-550 ℃ samples, and e and f are MgCuAlRu-650 ℃ samples.
FIG. 5 is a spherical aberration corrected HADDF-STEM plot of the catalyst obtained in example 1 at a temperature of 550 ℃.
FIG. 6 is a graph showing the results of the preferential oxidation of carbon monoxide using each of the catalysts of application example 1.
Detailed Description
Example 1
A. Weigh Mg (NO) 12.79 g 3 ) 2 ·6H 2 O, al (NO) of 8.25. 8.25 g 3 ) 2 ·9H 2 O and Cu (NO) 3 ) 2 ·6H 2 O was dissolved in 77 mL deionized water and 23. 23 mL molar concentration was added to 0.00250 mol.mL -1 RuCl of (F) 3 Salt solution is prepared into mixed salt solution with the molar ratio of Mg/Al of 3, the molar ratio of Mg/Ru of 50 and the molar ratio of Cu/Ru of 1; 5.49 g sodium hydroxide and 6.06 g sodium carbonate are weighed and added into 130 mL deionized water, and the mixed alkali solution is obtained by ultrasonic dissolution. At room temperature, the mixed salt solution and the mixed alkali solution are respectively dripped into a four-mouth flask filled with 100 mL deionized water through a double-way microinjection pump, and the dripping rate of the salt solution is 20 mL.h -1 The pH value of the mixed solution in the four-neck flask is maintained to be 9.5, and the mixed solution is transferred into a high-pressure hydrothermal kettle after the dripping is completed, and is crystallized at 120 ℃ for 24 h. Then washing with deionized water at about 60deg.C to neutrality, and drying at 80deg.C for 24 h to obtain highly dispersed hydrotalcite precursor MgCuAlRu-LDHs, XRD, SEM shown in figure 1.
B. Placing the MgCuAlRu-LDHs prepared in the step A into a tubular furnace, introducing high-purity hydrogen at normal pressure for reduction, wherein the hydrogen flow rate is 20mL/min, the reduction temperature is set to 450-650 ℃, the reduction time is 4h, and the heating rate is 5 ℃ and min -1 . After the sample is reduced, the temperature is reduced to room temperature and then is changed into N 2 And (5) passivating for 1h, and taking out to obtain catalyst samples at various temperatures.
XRD of hydrotalcite samples treated at different temperatures are shown in figure 2. As can be seen from fig. 2, the characteristic crystal plane peak of hydrotalcite at 450 ℃ disappeared and the hydrotalcite structure destroyed. With the rise of temperature, the composite oxide MgAlO x Appears. FIG. 3 is H of hydrotalcite precursor 2 TPR curve, it can be seen that the addition of Ru promotes the reduction of metallic Cu.
Fig. 4 is a HRTEM image of a reduced sample, showing the change in catalyst particle structure with increasing reduction temperature. FIG. 5 is a HADDF-STEM diagram with spherical aberration correction: a. hydrotalcite in the temperature rising process of 105-150 ℃ and Ru 3+ Reduction to Ru 0 The method comprises the steps of carrying out a first treatment on the surface of the b. In the range of 150-450 ℃, the hydrotalcite can remove OH - 、CO 3 2- And H 2 O gradually forms Ru/CuOx/MgAlOx; c. at 450-550 ℃, ruCu alloy is formed between the bottom of Ru nano particles and reduced Cu simple substance, and RuCu/MgAlOx is formed; d. at 550-650 ℃, cu can be removed from the surfaces of Ru nanoparticles due to the ductility of Cu, part of Cu enters the interior of Ru nanoparticles, and the other part of Cu runs off, so that lattice distortion occurs on the surfaces of Ru nanoparticles, and Ru/Cu/MgAlO occurs x 。
Application example 1
The catalyst evaluation device for preferential oxidation of carbon monoxide adopts a two-in one-out stainless steel tube (l=650 mm, d=27 mm, d=12 mm). Preparing hydrotalcite precursor prepared in the step A of the example 1 of 0.5 g into particles with 40-60 meshes, placing the particles in a tube furnace at a temperature rising rate of 5 ℃ per minute, roasting the particles to 550 ︒ ℃ under hydrogen atmosphere, keeping the temperature at 4h, cooling the particles to room temperature, and replacing the particles with N 2 And (3) performing surface passivation treatment on the catalyst for 1h, wherein the obtained catalyst is filled in the middle part of the catalytic reactor to serve as a catalytic layer, quartz sand with 40-60 meshes is filled on two sides of the catalytic layer to serve as a fixture, and a cotton layer is filled between the layers to isolate the layers. Installing the packed reactor in a fixed bed micro reactor, regulating a pressure reducing valve, a back pressure valve and a bypass valve, and introducing N 2 Purging air on the pipeline and the surface of the catalyst, and checking whether air leakage occurs or not by using a leakage detection needle. Introducing mixed gas1% CO，1% O 2 ，50% H 2 ，N 2 The balance gas) and setting catalytic reaction parameters by a temperature programming device, wherein the reaction temperature is 80-180 ℃ and the reaction time is 5-60 h. The gas flow rate was adjusted to 60 ml/min using a BROOKS mass flow meter, and the pressure was adjusted to atmospheric pressure. During the reaction, each time the temperature is raised by 10 ︒ C, gas is injected into the chromatographic analyzer through the automatic sampler to sample and analyze components, and the reaction result is shown in FIG. 6.
Claims (3)
1. A method for catalyzing a preferential oxidation reaction of carbon monoxide, wherein the method comprises the following specific operating conditions: ruCu nano alloy catalyst with filling limit structure in reactor, reaction temperature is 80-180 ℃, mixed gas containing CO is introduced, and reaction airspeed is 10-30h -1 The total reaction pressure is-0.1-0.1 MPa, and the reaction time is 5-60 h; the volume content of CO in the CO-containing mixed gas is 1 percent, O 2 1% of H 2 50%, N 2 Is balance gas;
the RuCu nano alloy catalyst with the finite field structure has the structure that: ruCu bimetal nano alloy particles are uniformly dispersed and supported in the magnesium-aluminum composite oxide with weak crystallization, and the magnesium-aluminum composite oxide has a finite field effect on the RuCu bimetal nano alloy particles; the catalyst is black powdery substance, and the particle size of single particles is 5-7nm;
the preparation method of the RuCu nano alloy catalyst with the finite field structure comprises the following steps: firstly synthesizing MgCuAlRu quaternary hydrotalcite precursor by a double-drop method, and then adopting temperature programming reduction in hydrogen atmosphere to obtain a RuCu nano alloy catalyst with a finite field structure;
the preparation method of the RuCu nano alloy catalyst with the finite field structure comprises the following specific steps:
(1) Preparing MgCuAlRu quaternary hydrotalcite precursor by a double-dropping method: at room temperature, dropwise adding a mixed salt solution prepared from soluble magnesium salt, soluble aluminum salt, soluble copper salt and soluble ruthenium salt into a four-mouth flask together with an alkali solution, maintaining the pH value of the mixed solution in the four-mouth flask to be 8-10, transferring the mixed solution into a high-pressure hydrothermal kettle after dropwise adding, carrying out hydrothermal crystallization for 12-48h at 100-150 ℃, washing with hot deionized water to be neutral after the reaction is completed, and drying to obtain MgCuAlRu quaternary hydrotalcite precursor;
(2) Reducing the MgCuAlRu quaternary hydrotalcite precursor prepared in the step (1) in a hydrogen atmosphere at a reduction temperature of 450-650 ℃ and a heating rate of 3-8 ℃ and min -1 Reducing for 2-6h, cooling to room temperature after the reduction is completed, and passivating for 0.5-2h in nitrogen atmosphere to obtain the RuCu nano alloy catalyst with the limited domain structure;
the molar ratio of Mg to Al in the mixed salt solution is 2-4:1, the molar ratio of Mg to Ru is 30-70:1, and the molar ratio of Cu to Ru is 1:2-2:1.
2. The method of claim 1, wherein the soluble magnesium salt, soluble aluminum salt, soluble copper salt, soluble ruthenium salt are magnesium nitrate, aluminum nitrate, copper nitrate, ruthenium chloride, respectively.
3. The method according to claim 1, wherein the alkaline solution is sodium hydroxide solution or a mixed alkaline solution of sodium hydroxide and sodium carbonate.
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| Bo Huang，et al."A CO Adsorption Site Change Induced by Copper Substitution in a Ruthenium Catalyst for Enhanced CO Oxidation Activity".Angew. Chem. Int. Ed..2018,第2230 -2235页. * |
| XIA Shuixin，et al."Trivalent metal ions M3+ in M0.02Cu0.4Mg5.6Al1.98(OH)16CO3 layered double hydroxide as catalyst precursors for the hydrogenolysis of glycerol".Chinese Journal of Catalysis.2013,第986-992页. * |
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