CN117696056A - Multi-element doped copper-iron-based catalyst, and preparation method and application thereof - Google Patents
Multi-element doped copper-iron-based catalyst, and preparation method and application thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 68
- IYRDVAUFQZOLSB-UHFFFAOYSA-N copper iron Chemical compound [Fe].[Cu] IYRDVAUFQZOLSB-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 71
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 claims abstract description 23
- 239000000126 substance Substances 0.000 claims abstract description 20
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 19
- 238000005984 hydrogenation reaction Methods 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims abstract description 11
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 3
- 229910052701 rubidium Inorganic materials 0.000 claims abstract description 3
- 239000010949 copper Substances 0.000 claims description 53
- 238000010438 heat treatment Methods 0.000 claims description 48
- 238000006243 chemical reaction Methods 0.000 claims description 47
- 238000003756 stirring Methods 0.000 claims description 44
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 36
- 238000001035 drying Methods 0.000 claims description 32
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 claims description 22
- 238000005303 weighing Methods 0.000 claims description 13
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 claims description 12
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 12
- 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 12
- 229910017604 nitric acid Inorganic materials 0.000 claims description 12
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 11
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 11
- 238000000137 annealing Methods 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 11
- 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 10
- WPFGFHJALYCVMO-UHFFFAOYSA-L rubidium carbonate Chemical compound [Rb+].[Rb+].[O-]C([O-])=O WPFGFHJALYCVMO-UHFFFAOYSA-L 0.000 claims description 10
- 229910000026 rubidium carbonate Inorganic materials 0.000 claims description 10
- 239000002135 nanosheet Substances 0.000 abstract description 13
- 150000001336 alkenes Chemical class 0.000 abstract description 11
- 229910052742 iron Inorganic materials 0.000 abstract description 8
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 238000003786 synthesis reaction Methods 0.000 abstract description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 18
- 239000000243 solution Substances 0.000 description 12
- 239000007789 gas Substances 0.000 description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 239000001301 oxygen Substances 0.000 description 9
- 229910052760 oxygen Inorganic materials 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 230000000630 rising effect Effects 0.000 description 8
- 239000002064 nanoplatelet Substances 0.000 description 7
- 238000012360 testing method Methods 0.000 description 6
- 230000035484 reaction time Effects 0.000 description 5
- 229910052723 transition metal Inorganic materials 0.000 description 5
- 150000003624 transition metals Chemical class 0.000 description 5
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 230000002195 synergetic effect Effects 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 239000012752 auxiliary agent Substances 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241000282326 Felis catus Species 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 150000001335 aliphatic alkanes Chemical class 0.000 description 1
- 150000001722 carbon compounds Chemical class 0.000 description 1
- -1 carbon olefin Chemical class 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000011943 nanocatalyst Substances 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides a multielement doped copper-iron-based catalyst, a preparation method and application thereof. The multielement doped copper-iron-based catalyst is prepared by doping Al and Rb in a copper-iron-based catalyst, and the chemical general formula of the catalyst is as follows: yRb-Al x Cu 2 Fe 4‑x O 4 The method comprises the steps of carrying out a first treatment on the surface of the Wherein, the value of y is 1 to 1.2 percent, and the value of x is 0.05 to 0.6. The high selectivity lower olefin disclosed in the examples of the present invention is 1.2% Rb-Al x Cu 2 Fe 4‑x O 4 The nanosheets have greatly improved lower olefin selectivity compared with the traditional iron-based catalyst, and pass CO for 100h 2 In hydrogenation applications, the selectivity is still maintained above 50%. Compared with the traditional iron-based catalyst, CO 2 The hydrogenation reaction has higher selectivity for olefin synthesis and low cost. The method is environment-friendly, simple and feasible, and provides a more valuable route for green synthesis of the low-carbon olefin.
Description
Technical Field
The invention relates to the technical field of nano materials and catalysts, in particular to a multi-element doped copper-iron-based catalyst, a preparation method and application thereof.
Background
The iron-based catalyst is widely used for CO because of its dual RWGS and FTS reactivity 2 And (3) carrying out hydrogenation to prepare olefin. However, the single iron catalyst has poor activity and stability, and often needs to be added with auxiliary agents to improve the catalytic activity and stability. Among them, transition metal assistants (e.g., zn, cu, mn, co, etc.) play an important role in improving the activity and stability of iron-based catalysts. On one hand, the transition metal can be used as a structural auxiliary agent to improve the stability of the catalyst; on the other hand, the transition metal promoter may improve its reduction and carbonization capabilities and promote adsorption of carbon species during the reaction by changing the electron density of the iron phase. However, the impact of transition metal promoters on the performance of iron-based catalysts remains controversial. Furthermore, there is also a lack of theoretical knowledge about the effect of transition metal promoters on olefin selectivity. Although CO 2 Hydrogenation to produce hydrocarbons is exemplified, but high pressures are typically employed to increase conversion efficiency and overcome the high kinetic barrier of C-C coupling. These have all led to the search for synthetic value-added chemicals, and for a sustainable route, a process for producing hydrocarbons at atmospheric pressure and high conversion is sought.
Disclosure of Invention
The invention aims to provide a multi-element doped copper-iron-based catalyst, a preparation method and application thereof, and the catalyst can realize high-stability and high-selectivity CO at normal pressure 2 Hydrogenation to prepare low-carbon olefin, so as to solve the problem of reverse reaction in the prior synthesis technologyThe problems of high pressure, high cost, low selectivity, low conversion rate and the like are solved, and a sustainable path is provided for synthesizing value-added chemicals.
The invention is realized in the following way:
a multielement doped copper-iron-based catalyst is doped with Al and Rb, and the chemical general formula of the catalyst is as follows: yRb-Al x Cu 2 Fe 4-x O 4 The method comprises the steps of carrying out a first treatment on the surface of the Wherein, the value of y is 1 to 1.2 percent, and the value of x is 0.05 to 0.6.
Preferably, y has a value of 1.2%.
Preferably, x takes a value of 0.1.
The preparation method of the multi-doped copper-iron-based catalyst comprises the following steps:
a. yRb-Al according to the above chemical formula x Cu 2 Fe 4-x O 4 Weighing copper nitrate, ferric nitrate, aluminum nitrate and rubidium carbonate according to the medium element metering ratio, weighing citric acid in addition, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, and then adding ammonia water to adjust the pH value of the solution to 6;
b. continuously heating and stirring the solution obtained in the step a in a heating and stirring table until the solution forms sol gel, and then putting the sol gel into a blast drying oven for drying;
c. and (3) placing the dried sample into a tube furnace for roasting, annealing by a muffle furnace, and finally placing the sample into a fixed bed reaction system to prepare the multielement doped copper-iron-based catalyst.
Preferably, in step b, the reaction temperature is 80℃with stirring and the temperature of the air-drying oven is 80 ℃.
Preferably, in step c, the sample is calcined in a tube furnace, in particular: ar is introduced into the tube furnace, the heating rate is 8 ℃/min, the tube furnace is heated to 400 ℃, and the temperature is kept for 2 hours.
Preferably, in step c, the sample is annealed in a muffle furnace, in particular: and (3) placing the sample into a muffle furnace, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours.
Preferably, in step a, the contents of citric acid, copper nitrate, iron nitrate, aluminum nitrate and rubidium carbonate are 5g, 1.5753g, 0.3751g, 0.0375g and 0.0057g, respectively; nitric acid was added at a level of 2.5mL and ethylenediamine at a level of 1mL.
The invention also provides a multielement doped copper-iron-based catalyst yRb-Al x Cu 2 Fe 4-x O 4 In CO 2 The application of hydrogenation to prepare low-carbon olefin. CO injection in a thermocatalytic reaction system 2 And H 2 (1: 3) the mixture was maintained at 320 ℃ to produce light olefins and to achieve a selectivity of above 60%.
With the existing CO 2 Compared with the hydrogenation multi-carbon technology, most of iron-based catalysts are used for preparing CO 2 The use of pressurized processes in hydrogenation applications to increase conversion efficiency overcomes the high kinetic barrier of C-C coupling does not even allow for increased conversion and yield. The high-selectivity low-carbon olefin provided by the invention is 1.2 percent Rb-Al x Cu 2 Fe 4-x O 4 The nanometer sheet can realize the photo-thermal synergistic catalysis of CO under the normal pressure condition 2 The hydrogenation is carried out to prepare the low-carbon olefin with high conversion rate and high yield, and the low-carbon olefin is an important raw material for synthesizing renewable chemicals and fuels. This is done by CO 2 And green hydrogen energy source to synthesize value-added chemicals, providing a sustainable path, and further reducing greenhouse CO 2 。
The invention has the outstanding advantages that:
(1) The catalyst has the advantages of low-cost and easily-obtained raw materials, and can be prepared in a large scale.
(2) The catalyst obtained by the invention has stable property, the selectivity of the low-carbon olefin is still kept above 50% for 100h, and the service life of the catalyst is greatly prolonged.
(3) The catalyst obtained by the invention can pass through CO 2 The hydrogenation reaction directly obtains the low-carbon olefin, and has high conversion rate and low-carbon olefin yield. CO 2 The conversion rate can reach more than 28 percent, the methane selectivity is as low as 15.6 percent, the low-carbon olefin selectivity is as high as 63.3 percent, the low-carbon olefin ratio is as high as 50, and the low-carbon olefin space-time yield is as high as 368 mu mol g -1 h -1 。
Drawings
FIG. 1 is a block diagram of the preparation of example 11.2％Rb-Al x Cu 2 Fe 4-x O 4 XRD pattern of nanoplatelets.
FIG. 2 is a graph showing the yields of the catalysts obtained in examples 1 to 6 and example 9 at the same reaction time.
FIG. 3 is a graph showing the selectivity of the catalysts obtained in examples 1 to 6 and example 9 at the same reaction time.
FIG. 4 is a 1.2% Rb-Al prepared in example 1 0.1 Cu 2 Fe 3.9 O 4 Yield plot for catalyst reaction for 100 h.
FIG. 5 is a 1.2% Rb-Al prepared in example 1 0.1 Cu 2 Fe 3.9 O 4 Selectivity plot for the catalyst reaction for 100 h.
FIG. 6 is a 1.2% Rb-Al prepared in example 1 0.1 Cu 2 Fe 3.9 O 4 The nanoplatelets were reacted for 6h of TEM.
FIG. 7 is a 1.2% Rb-Al prepared in example 1 0.1 Cu 2 Fe 3.9 O 4 The nanoplatelets were reacted for 100h of TEM.
FIG. 8 is a graph of the performance of different Rb feed ratio catalysts prepared in examples 1, 7 and 8.
FIG. 9 is a 1.2% Rb-Al prepared in example 1 0.1 Cu 2 Fe 3.9 O 4 Yield plot of catalyst without addition of light.
FIG. 10 is a 1.2% Rb-Al prepared in example 1 0.1 Cu 2 Fe 3.9 O 4 Selectivity map for catalyst without addition of light.
FIG. 11 is a 1.2% Rb-Al prepared in example 1 0.1 Cu 2 Fe 3.9 O 4 Catalyst addition yield plot.
FIG. 12 is a 1.2% Rb-Al prepared in example 1 0.1 Cu 2 Fe 3.9 O 4 Selectivity map of catalyst addition.
Detailed Description
The invention aims to solve the problem of CO 2 Hydrogenation is carried out to prepare more effective value-added chemicals, which is CO 2 Hydrogenation to make multiple carbons provides a more efficient method. The present invention will be described in detail with reference to specific embodimentsThe invention is characterized in that.
Example 1 preparation of catalyst 1.2% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 。
The molar ratio is 26:2:3.9:0.1:0.025 respectively weighing citric acid, copper nitrate, ferric nitrate, aluminum nitrate and rubidium carbonate, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, adding ammonia water to adjust pH to be less than 6, continuously heating and stirring in a heating and stirring table until the solution forms sol gel, and putting into a blast drying oven for drying; the reaction temperature was 80℃with stirring and the temperature of the air-blast drying oven was 80 ℃. Roasting by a tube furnace, wherein the tube furnace roasting specifically comprises the following steps: ar gas is injected, after oxygen in the tube is exhausted, the temperature rising speed is 8 ℃/min, and the temperature is raised to 400 ℃ and kept for 2 hours. And then annealing by a muffle furnace, specifically: and (3) placing the sample, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours. Finally, placing the sample in a fixed bed reaction system to obtain 1.2% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 A nano-sheet. 1.2% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 Wherein 1.2% means that the doping mass of Rb is 1.2%, as follows.
1.2% Rb-Al prepared in this example 0.1 Cu 2 Fe 3.9 O 4 The nanoplatelets were subjected to XRD testing and the results obtained are shown in figure 1. XRD patterns in FIG. 1 correspond to Fe 5 C 2 、CuFe 2 O 4 And standard cards of Cu.
Example 2 preparation of catalyst 1.2% Rb-Al 0.05 Cu 2 Fe 3.95 O 4 。
The molar ratio is 26:2:3.95:0.05:0.025 respectively weighing citric acid, copper nitrate, ferric nitrate, aluminum nitrate and rubidium carbonate, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, adding ammonia water to adjust pH to be less than 6, continuously heating and stirring in a heating and stirring table until the solution forms sol gel, and putting into a blast drying oven for drying; the reaction temperature was 80℃with stirring and the temperature of the air-blast drying oven was 80 ℃. Roasting by a tube furnace, wherein the tube furnace roasting specifically comprises the following steps: ar gas is injected, oxygen in the pipe is exhausted, the heating rate is 8 ℃/min, and the temperature risesThe temperature is kept at 400 ℃ for 2 hours. And then annealing by a muffle furnace, specifically: and (3) placing the sample, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours. Finally, placing the sample in a fixed bed reaction system to obtain 1.2% Rb-Al 0.05 Cu 2 Fe 3.95 O 4 A nano-sheet.
Example 3 preparation of catalyst 1.2% Rb-Al 0.3 Cu 2 Fe 3.7 O 4 。
The molar ratio is 26:2:3.7:0.3:0.025 respectively weighing citric acid, copper nitrate, ferric nitrate, aluminum nitrate and rubidium carbonate, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, adding ammonia water to adjust pH to be less than 6, continuously heating and stirring in a heating and stirring table until the solution forms sol gel, and putting into a blast drying oven for drying; the reaction temperature was 80℃with stirring and the temperature of the air-blast drying oven was 80 ℃. Roasting by a tube furnace, wherein the tube furnace roasting specifically comprises the following steps: ar gas is injected, after oxygen in the tube is exhausted, the temperature rising speed is 8 ℃/min, and the temperature is raised to 400 ℃ and kept for 2 hours. And then annealing by a muffle furnace, specifically: and (3) placing the sample, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours. Finally, placing the sample in a fixed bed reaction system to obtain 1.2% Rb-Al 0.3 Cu 2 Fe 3.7 O 4 A nano-sheet.
Example 4 preparation of catalyst 1.2% Rb-Al 0.6 Cu 2 Fe 3.4 O 4 。
The molar ratio is 26:2:3.4:0.6:0.025 respectively weighing citric acid, copper nitrate, ferric nitrate, aluminum nitrate and rubidium carbonate, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, adding ammonia water to adjust pH to be less than 6, continuously heating and stirring in a heating and stirring table until the solution forms sol gel, and putting into a blast drying oven for drying; the reaction temperature was 80℃with stirring and the temperature of the air-blast drying oven was 80 ℃. Roasting by a tube furnace, wherein the tube furnace roasting specifically comprises the following steps: ar gas is injected, after oxygen in the tube is exhausted, the temperature rising speed is 8 ℃/min, and the temperature is raised to 400 ℃ and kept for 2 hours. And then annealing by a muffle furnace, specifically: and (3) placing the sample, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours. Finally, the sample is placed in a fixed bed for reactionObtaining 1.2% Rb-Al in the System 0.6 Cu 2 Fe 3.4 O 4 A nano-sheet.
Example 5 preparation of catalyst Al 0.1 Cu 2 Fe 3.9 O 4 。
The molar ratio is 26:2:3.9:0.1 respectively weighing citric acid, copper nitrate, ferric nitrate and aluminum nitrate, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, adding ammonia water to adjust pH to be less than 6, continuously heating and stirring in a heating and stirring table until the solution forms sol gel, and putting into a blast drying oven for drying; the reaction temperature was 80℃with stirring and the temperature of the air-blast drying oven was 80 ℃. Roasting by a tube furnace, wherein the tube furnace roasting specifically comprises the following steps: ar gas is injected, after oxygen in the tube is exhausted, the temperature rising speed is 8 ℃/min, and the temperature is raised to 400 ℃ and kept for 2 hours. And then annealing by a muffle furnace, specifically: and (3) placing the sample, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours. Finally, placing the sample in a fixed bed reaction system to obtain Al 0.1 Cu 2 Fe 3.9 O 4 A nano-sheet.
Example 6 preparation of catalyst 1.2% Rb-Cu 2 Fe 4 O 4 。
The molar ratio is 26:2:4:0.025 respectively weighing citric acid, copper nitrate, ferric nitrate and rubidium carbonate, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, adding ammonia water to adjust pH to be less than 6, continuously heating and stirring in a heating and stirring table until the solution forms sol gel, and putting into a blast drying oven for drying; the reaction temperature was 80℃with stirring and the temperature of the air-blast drying oven was 80 ℃. Roasting by a tube furnace, wherein the tube furnace roasting specifically comprises the following steps: ar gas is injected, after oxygen in the tube is exhausted, the temperature rising speed is 8 ℃/min, and the temperature is raised to 400 ℃ and kept for 2 hours. And then annealing by a muffle furnace, specifically: and (3) placing the sample, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours. Finally, placing the sample in a fixed bed reaction system to obtain 1.2% Rb-Cu 2 Fe 4 O 4 A nano-sheet.
Example 7 preparation of catalyst 0.6% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 。
The molar ratio is 26:2:3.9:0.1:0.0125 respectively weighing citric acid, copper nitrate, ferric nitrate, aluminum nitrate and rubidium carbonate, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, adding ammonia water to adjust pH to be=6, continuously heating and stirring in a heating and stirring table until the solution forms sol gel, and putting into a blast drying oven for drying; the reaction temperature was 80℃with stirring and the temperature of the air-blast drying oven was 80 ℃. Roasting by a tube furnace, wherein the tube furnace roasting specifically comprises the following steps: ar gas is injected, after oxygen in the tube is exhausted, the temperature rising speed is 8 ℃/min, and the temperature is raised to 400 ℃ and kept for 2 hours. And then annealing by a muffle furnace, specifically: and (3) placing the sample, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours. Finally, the sample is placed in a fixed bed reaction system to obtain 0.6 percent Rb-Al 0.1 Cu 2 Fe 3.9 O 4 A nano-sheet.
Example 8 preparation of catalyst 2.4% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 。
The molar ratio is 26:2:3.9:0.1:0.05 respectively weighing citric acid, copper nitrate, ferric nitrate, aluminum nitrate and rubidium carbonate, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, adding ammonia water to adjust pH to be less than 6, continuously heating and stirring in a heating and stirring table until the solution forms sol gel, and putting into a blast drying oven for drying; the reaction temperature was 80℃with stirring and the temperature of the air-blast drying oven was 80 ℃. Roasting by a tube furnace, wherein the tube furnace roasting specifically comprises the following steps: ar gas is injected, after oxygen in the tube is exhausted, the temperature rising speed is 8 ℃/min, and the temperature is raised to 400 ℃ and kept for 2 hours. And then annealing by a muffle furnace, specifically: and (3) placing the sample, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours. Finally, placing the sample in a fixed bed reaction system to obtain 2.4% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 A nano-sheet.
EXAMPLE 9 preparation of catalyst Cu 2 Fe 4 O 4
The molar ratio is 26:2:4, respectively weighing citric acid, copper nitrate and ferric nitrate, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, adding ammonia water to adjust pH to be=6, and continuously adding in a heating stirring tableHot stirring until the solution forms sol gel, and putting into a blast drying oven for drying; the reaction temperature was 80℃with stirring and the temperature of the air-blast drying oven was 80 ℃. Roasting by a tube furnace, wherein the tube furnace roasting specifically comprises the following steps: ar gas is injected, after oxygen in the tube is exhausted, the temperature rising speed is 8 ℃/min, and the temperature is raised to 400 ℃ and kept for 2 hours. And then annealing by a muffle furnace, specifically: and (3) placing the sample, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours. Finally, placing the sample in a fixed bed reaction system to obtain Cu 2 Fe 4 O 4 A nano-sheet.
Example 10 effect of feed on product yield and selectivity.
The catalysts obtained in examples 1-6 and 9 were placed in a reaction apparatus, respectively, and CO was injected 2 And H 2 (1:3) the mixed gas has volume space velocity of 2400-9600mL h -1 g cat -1 The test temperature was kept at 320℃and the reaction pressure was 0.1MPa for 6 hours. FIG. 2 is a graph of the yields of different samples at the same reaction time, it can be seen that sample 1.2% Rb-Al in example 1 0.1 Cu 2 Fe 3.9 O 4 Methane (CH) 4 ) The yield is the lowest, and the lower olefin (C 2 -C 4 ＝ ) The yield is highest. FIG. 3 shows the selectivity of different samples for the same reaction time, again for sample 1.2% Rb-Al in example 1 0.1 Cu 2 Fe 3.9 O 4 The methane selectivity is the lowest and the low-carbon olefin selectivity is the highest. In other examples, the catalyst showed a tendency to have high methane selectivity and low carbon olefin selectivity.
Example 11, effect of performance test temperature on sample.
The catalysts obtained in example 1 were tested at different temperatures and 50mg of 1.2% Rb-Al were weighed 0.1 Cu 2 Fe 3.9 O 4 The nano-sheets are placed in a reaction system, and after the fixed bed reaction system exhausts air, the volume ratio is 1:3 respectively introducing CO 2 、H 2 The temperature rise test is carried out from 0 ℃, the activity of the sample is poor at 300 ℃, when the temperature reaches 320 ℃, the sample performance reaches the optimum after stabilizing for half an hour, and the temperature is continuously raised to 500 ℃ for stabilizing for half an hourWhen the sample is completely deactivated.
Example 12 effect of reaction time on product yield and morphology.
The catalyst obtained in example 1 was tested for a long period of time and 50mg of 1.2% Rb-Al was weighed 0.1 Cu 2 Fe 3.9 O 4 The nano-sheets are arranged in a reaction system, and after the reaction system is exhausted, the volume ratio is 1:3 respectively introducing CO 2 、H 2 The test was performed once an hour when the heating temperature was stabilized to 320 c, and the reaction was performed for 100 hours. FIG. 4 is 1.2% Rb-Al0. 1 Cu 2 Fe 3.9 O 4 The yield of the nanoplatelet reaction for 100h is shown in FIG. 5 as 1.2% Rb-Al0. 1 Cu 2 Fe 3.9 O 4 Selectivity plot for nanoplatelet reactions 100 h. As can be seen from fig. 4 and 5, methane (CH 4 ) Yield from initial 90.82. Mu. Mol g -1 h -1 Raised to 260.58 mu mol g -1 h -1 The selectivity increased from the initial 15.59% to 33.47%. Lower olefins (C) 2 -C 4 ＝ ) Yield from initial 368.82. Mu. Mol g -1 h -1 Raised to 423.52 mu mol g -1 h -1 The selectivity was reduced from the initial 63.31% to 54.40%, and the selectivity was reduced but the selectivity was reduced, but the lower olefins (C 2 -C 4 ＝ ) Still up to 50% conversion due to methane (CH) 4 ) Increased yields lead to C 5 The selectivity was reduced from the initial 19.85% to 10.54%. CO yield and CO 2 The conversion rates all tend to be stable, being kept around 31% and 27%, respectively.
Fig. 6 is a TEM photograph of a 6-hour test of the product reaction, and fig. 7 is a TEM photograph of a 100-hour test of the reaction, and 1.2% rb-Al0 is observed by comparing the TEM photographs of the 6-hour and 100-hour products. 1 Cu 2 Fe 3.9 O 4 The particle size of the nano-sheet is not greatly changed, the particle size is basically the same, no obvious carbon deposit is found, and the product has good stability and sintering resistance.
Example 13, effect of different feed ratios Rb on product yield and selectivity.
From example 1,7 and 8, respectively, are 1.2% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 、0.6％Rb-Al 0.1 Cu 2 Fe 3.9 O 4 And 2.4% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 The yield and selectivity were tested by adjusting the feed ratio of Rb, and the results are shown in fig. 8. FIG. 8 is a schematic representation of FCAR-5 showing 0.6% Rb-Al of the catalyst of example 7 0.1 Cu 2 Fe 3.9 O 4 FCAR-2 represents the catalyst of example 1, 2% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 FCAR-6 represents the catalyst of example 8, 2.4% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 . As can be seen from FIG. 8, the catalyst prepared in example 7 was 0.6% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 (FCAR-5) methane (CH) 4 ) The yield is higher and is 295.39 mu mol g -1 h -1 The selectivity is high, which is up to 56.97%; lower olefins (C) 2 -C 4 ＝ ) The selectivity was only 34.27%. Catalyst prepared in example 8 2.4% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 (FCAR-6) methane (CH 4 ) The yield is low, namely 56.23 mu mol g -1 h -1 The selectivity is 46.32 percent, and the low-carbon olefin (C 2 -C 4 ＝ ) Yield was 49.36. Mu. Mol g -1 h -1 The selectivity was 40.66%. Comprehensive comparison, catalyst prepared in example 1, 1.2% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 (FCAR-2) has the best performance, and its methane (CH) 4 ) Yield was 111. Mu. Mol g -1 h -1 The selectivity was 16.88, the lower olefins (C 2 -C 4 ＝ ) Yield 354. Mu. Mol g - 1 h -1 The selectivity is as high as 60.98%.
Example 14 photo-thermal synergistic catalysis of 1.2% Rb-Al 0.1 Cu 2 Fe 3.9 O 4 Influence of the yield and selectivity of nanoplatelets.
The catalysts obtained in example 1 were tested under Thermal and light+thermal conditions, respectively, and the results are shown in FIGS. 9 to 12. As can be seen from fig. 9 and 10, in the absence ofThe catalyst has almost no C when no light is added at the same temperature 2+ Is the product of (C), CH 4 Almost no methanol production is prevalent. As can be seen from fig. 11 and 12, when light is added at different temperatures (xenon irradiation), the catalyst is used for a low-carbon olefin (C 2 -C 4 ＝ ) Is significantly increased, while the lower alkane (C) 2 -C 4 0 ) The selectivity is lower, and the photo-thermal synergistic catalytic performance at 176 ℃ reaches the optimal result.
Claims (8)
1. A multi-element doped copper-iron-based catalyst is characterized in that Al and Rb are doped in the copper-iron-based catalyst, and the chemical general formula of the catalyst is as follows: yRb-Al x Cu 2 Fe 4-x O 4 The method comprises the steps of carrying out a first treatment on the surface of the Wherein, the value of y is 1 to 1.2 percent, and the value of x is 0.05 to 0.6.
2. The multi-doped copper-iron-based catalyst according to claim 1, wherein y has a value of 1.2%.
3. The multi-doped copper-iron-based catalyst according to claim 2, wherein x has a value of 0.1.
4. The preparation method of the multi-element doped copper-iron-based catalyst is characterized by comprising the following steps of:
a. according to claim 1 of the general formula yRb-Al x Cu 2 Fe 4-x O 4 Weighing copper nitrate, ferric nitrate, aluminum nitrate and rubidium carbonate according to the medium element metering ratio, weighing citric acid in addition, mixing the weighed substances, adding nitric acid and ethylenediamine, stirring, and then adding ammonia water to adjust the pH value of the solution to 6;
b. continuously heating and stirring the solution obtained in the step a in a heating and stirring table until the solution forms sol gel, and then putting the sol gel into a blast drying oven for drying;
c. and (3) placing the dried sample into a tube furnace for roasting, annealing by a muffle furnace, and finally placing the sample into a fixed bed reaction system to prepare the multielement doped copper-iron-based catalyst.
5. The method of preparing a multi-doped copper-iron-based catalyst according to claim 4, wherein in the step b, the heating and stirring reaction temperature is 80 ℃ and the temperature of a blast drying oven is 80 ℃.
6. The method for preparing the multi-doped copper-iron-based catalyst according to claim 4, wherein in the step c, the sample is baked in a tube furnace, specifically: ar is introduced into the tube furnace, the heating rate is 8 ℃/min, the tube furnace is heated to 400 ℃, and the temperature is kept for 2 hours.
7. The method for preparing the multi-doped copper-iron-based catalyst according to claim 4, wherein in the step c, the sample is annealed in a muffle furnace, specifically: and (3) placing the sample into a muffle furnace, heating to 400 ℃ at a heating rate of 5 ℃/min, and preserving heat for 2 hours.
8. A multi-doped copper-iron-based catalyst according to any one of claims 1 to 3, prepared according to the method of any one of claims 4 to 7, in CO 2 The application of hydrogenation to prepare low-carbon olefin.
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