CN116966914A - Gamma-ferric oxide catalyst, preparation method and application - Google Patents
Gamma-ferric oxide catalyst, preparation method and application Download PDFInfo
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- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 title claims abstract description 79
- 239000003054 catalyst Substances 0.000 title claims abstract description 68
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 62
- 238000006243 chemical reaction Methods 0.000 claims abstract description 53
- 239000002184 metal Substances 0.000 claims abstract description 27
- 229910052751 metal Inorganic materials 0.000 claims abstract description 27
- 239000013078 crystal Substances 0.000 claims abstract description 26
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 claims abstract description 24
- 238000001035 drying Methods 0.000 claims description 25
- 239000002243 precursor Substances 0.000 claims description 23
- 239000000203 mixture Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 101150003085 Pdcl gene Proteins 0.000 claims description 10
- 239000012696 Pd precursors Substances 0.000 claims description 7
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 6
- 239000012692 Fe precursor Substances 0.000 claims description 6
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 6
- 150000001875 compounds Chemical class 0.000 claims description 6
- 229910052707 ruthenium Inorganic materials 0.000 claims description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 3
- 229910002554 Fe(NO3)3·9H2O Inorganic materials 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 2
- 230000003197 catalytic effect Effects 0.000 abstract description 13
- 230000000694 effects Effects 0.000 abstract description 6
- 230000003993 interaction Effects 0.000 abstract description 3
- 230000001105 regulatory effect Effects 0.000 abstract description 3
- 229910001566 austenite Inorganic materials 0.000 description 54
- 229910052739 hydrogen Inorganic materials 0.000 description 36
- 239000001257 hydrogen Substances 0.000 description 32
- 239000000243 solution Substances 0.000 description 23
- 239000007788 liquid Substances 0.000 description 14
- 238000003756 stirring Methods 0.000 description 12
- 239000008367 deionised water Substances 0.000 description 10
- 229910021641 deionized water Inorganic materials 0.000 description 10
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 239000012300 argon atmosphere Substances 0.000 description 8
- 239000008240 homogeneous mixture Substances 0.000 description 8
- 239000007787 solid Substances 0.000 description 8
- 239000002904 solvent Substances 0.000 description 8
- 125000004429 atom Chemical group 0.000 description 6
- 238000001027 hydrothermal synthesis Methods 0.000 description 5
- 238000005470 impregnation Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 229910052786 argon Inorganic materials 0.000 description 4
- 239000012298 atmosphere Substances 0.000 description 4
- 238000007865 diluting Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 238000009835 boiling Methods 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000007664 blowing Methods 0.000 description 2
- 238000010304 firing Methods 0.000 description 2
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- -1 polytetrafluoroethylene Polymers 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 239000003507 refrigerant Substances 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 239000012488 sample solution Substances 0.000 description 2
- 238000002604 ultrasonography Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 235000015842 Hesperis Nutrition 0.000 description 1
- 235000012633 Iberis amara Nutrition 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 238000000024 high-resolution transmission electron micrograph Methods 0.000 description 1
- 239000012456 homogeneous solution Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
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Abstract
The application discloses a gamma ferric oxide catalyst, a preparation method and application, wherein the gamma ferric oxide catalyst comprises the following components: iron oxide and a metal monoatom, the iron oxide exposing a [440] crystal plane; the metal monoatoms are loaded on the [440] crystal face; wherein the metal monoatoms comprise monoatomic Pt, monoatomic Pd, monoatomic Ir and monoatomic Ru. In the application, the catalyst is treated at 200 ℃, so that the interaction degree between single atoms and the carrier gamma ferric oxide [440] can be effectively regulated, and the reaction performance of the catalyst can be regulated. The prepared normal-para-hydrogen conversion catalyst shows excellent activity and stability. The preparation method of the catalyst is simple and easy to implement, the cost is low, the catalytic conversion efficiency of the normal para-hydrogen is high, the catalytic conversion efficiency can reach 87%, and the equilibrium concentration of the para-hydrogen reaches 45.4-50.4.
Description
Technical Field
The application relates to a gamma ferric oxide catalyst, a preparation method and application thereof, and belongs to the technical field of normal-para-hydrogen conversion.
Background
Liquid hydrogen is an important strategic resource for the development of the aerospace and hydrogen energy industries. With the development of aerospace industry in China, the demand for heavy-duty rockets is increasing increasingly due to the continuous promotion of a lunar exploration fire plan, and the liquid hydrogen demand as the optimal energy source of a heavy-duty rocket liquid hydrogen-liquid oxygen engine is increasing continuously.
The hydrogen molecule is composed of two hydrogen atoms, and there are two states of hydrogen, namely, a positive state and a secondary state, due to the difference in the spin directions of the two hydrogen nuclei. The nuclear spin directions of the orthohydrogen are the same, and the nuclear spin directions of the para-hydrogen are opposite. The composition of the equilibrium hydrogen in the positive and the secondary states is dependent on the temperature, and the concentration ratio of the equilibrium hydrogen in the positive and the secondary states is different at different temperatures. At normal temperature, equilibrium hydrogen is a mixture containing normal and 25% para-hydrogen, known as normal or standard hydrogen: the temperature decreases and the percentage of para-hydrogen increases. For example, the para-hydrogen content is about 51% at the normal boiling point of liquid nitrogen, and can reach 99.8% at the normal boiling point of liquid hydrogen. The spontaneous conversion of the normal and secondary state of hydrogen is very slow, so that in the process of cooling and liquefying hydrogen, if the normal and secondary catalytic conversion of hydrogen is not carried out, the produced liquid hydrogen is normal hydrogen, the liquid normal hydrogen can spontaneously undergo secondary conversion, and finally reaches the equilibrium hydrogen at the corresponding temperature, the normal and secondary conversion of hydrogen is an exothermic reaction, and the heat released during the conversion of the liquid normal hydrogen exceeds the gasification latent heat (447 kJ/kg). For this reason, even if liquid normal hydrogen is stored in an ideal adiabatic vessel, the liquid hydrogen is vaporized as well, and therefore in order to obtain equilibrium hydrogen at the normal boiling point, that is, liquid hydrogen having a para-hydrogen concentration of 99.8%, several stages of forward-para-catalytic conversion must be performed during the liquefaction of hydrogen.
The balance ratio of the normal hydrogen and the para hydrogen in the normal para hydrogen is different at different temperatures, for example, the normal hydrogen is 75 percent, the para hydrogen is 25 percent at normal temperature, the normal hydrogen is 51 percent when the temperature is reduced to 80K, the para hydrogen is 49 percent, the para hydrogen is higher and higher along with the continuous reduction of the temperature, the para hydrogen is 99.8 percent when the liquefaction point of the hydrogen is about 20K, and the normal hydrogen is very slowly converted under the normal condition without the action of a catalyst. The conventional normal-to-para-hydrogen conversion catalysts are all hydrated iron oxide catalysts of the same system, so that a novel normal-to-para-hydrogen conversion catalyst capable of always maintaining high activity and high conversion efficiency is needed.
Disclosure of Invention
The application aims to provide a catalyst for the catalytic conversion of the normal para-hydrogen, which has the characteristics of high activity and high stability for the catalytic conversion reaction of the normal para-hydrogen.
The application aims to provide a preparation method of a catalyst for catalytic conversion of normal para-hydrogen, which has the characteristics of simple operation, strong repeatability and high universality.
According to an aspect of the present application, there is provided a gamma iron oxide catalyst comprising: iron oxide and a metal monoatom, the iron oxide exposing a [440] crystal plane;
the metal monoatoms are loaded on the [440] crystal face;
wherein the metal monoatoms comprise at least one of monoatomic Pt, monoatomic Pd, monoatomic Ir and monoatomic Ru.
Optionally, the metal monoatoms account for 0.1 to 5 weight percent of the gamma ferric oxide catalyst.
Optionally, the metal monoatoms account for any value of 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% or a range between any two of the foregoing.
Optionally, the iron oxide accounts for 95 to 99.9 weight percent of the gamma iron oxide catalyst.
According to another aspect of the present application, there is provided a method for preparing the above gamma iron oxide catalyst, the method comprising:
reacting, drying and roasting a mixture containing a metal monoatomic precursor and ferric oxide to obtain a gamma ferric oxide catalyst;
the ferric oxide is ferric oxide with an exposed [440] crystal face;
the metal monoatomic precursor is selected from at least one of Pt precursor, pd precursor, ir precursor and Ru precursor.
Optionally, the preparation method of the exposed [440] crystal face ferric oxide comprises the following steps:
and (3) adding water, ammonia water and ethanol into the iron precursor compound in sequence in a closed container, reacting I, and drying I to obtain the exposed [440] crystal face ferric oxide.
Alternatively, gamma-iron oxide carriers having exposed [440] crystal planes are prepared by a hydrothermal method, which is as follows:
1) Accurately weigh 1.08g FeCl 3 ·6H 2 O was placed in a clean beaker and 4mL of H was added in sequence 2 O,4mL of ammonia water, 60mL of ethanol, and stirring thoroughly for 30min after 30min of ultrasound. After fully stirring, transferring the mixed solution into a polytetrafluoroethylene hydrothermal reaction kettle liner with the volume capacity of 100mL, and packaging the liner;
2) Then the reaction kettle is transferred to an electrothermal blowing drying oven at 180 ℃ for reaction for 24 hours.
3) After the reaction is finished, naturally cooling to room temperature, centrifuging the sample solution after the hydrothermal reaction, and fully washing with deionized water and ethanol for 3 times respectively. And then placing the washed sample in a drying oven at 80 ℃ for drying to obtain the gamma ferric oxide carrier with the [440] crystal face exposed.
Alternatively, the iron precursor compound is selected from FeCl 3 ·6H 2 O、Fe(NO 3 ) 3 ·9H 2 O、Fe 2 (SO 4 ) 3 ·2H 2 At least one of O.
Optionally, the iron precursor compound: water: ammonia water: the mass volume ratio of the ethanol is as follows: 1-2 g: 2-10 mL: 2-10 mL: 30-100 mL.
Optionally, the mass ratio of the metal monoatomic precursor to the ferric oxide is 0.001-5 g: 0.999-9.5 g.
Alternatively, the Pt precursor is selected from H 2 PtCl 6 、Na 2 PtCl 6 、K 2 PtCl 6 At least one of them.
Optionally, the Pd precursor H 2 PdCl 6 、Na 2 PdCl 6 、K 2 PdCl 6 At least one of them.
Optionally, the Ir precursor H 2 IrCl 6 、Na 2 IrCl 6 、K 2 IrCl 6 At least one of them.
Optionally, the Ru precursor RuCl 3 ·3H 2 O、Ru(NO)(NO 3 ) 3 、Ru 2 Cl 4 (CO) 6 、Ru(Ac) 3 At least one of them.
Optionally, the reaction temperature is 40-85 ℃, and the reaction time is 4-24 hours.
Alternatively, the temperature of the reaction is selected from any value or range of values between any two of 40 ℃, 45 ℃, 50 ℃,60 ℃, 70 ℃, 80 ℃, 85 ℃.
Alternatively, the time of the reaction is selected from any of 4h, 8h, 12h, 16h, 20h, 24h or a range of values between any two of the foregoing.
Optionally, the drying temperature is 60-150 ℃ and the drying time is 4-24 h.
Optionally, the temperature of the drying is selected from any value or range of values between any two of 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 120 ℃, 150 ℃.
Optionally, the drying time is selected from any value of 4h, 8h, 12h, 16h, 20h, 24h or a range of values between any two of the foregoing.
Optionally, the roasting temperature is 200-400 ℃, and the roasting time is 1-10 h.
Optionally, the roasting temperature is 200-300 ℃, and the roasting time is 2-3 h.
Optionally, the firing temperature is selected from any value or range of values between any two of 200 ℃, 250 ℃, 300 ℃, 350 ℃, 400 ℃.
Optionally, the firing time is selected from any of 1h, 2h, 4h, 8h, 10h, or a range of values therebetween.
Optionally, the temperature of the reaction I is 150-250 ℃, and the time of the reaction I is 16-48 h.
Alternatively, the temperature of reaction I is selected from any value or range of values between any two of 150 ℃, 160 ℃, 180 ℃, 200 ℃, 220 ℃, 250 ℃.
Alternatively, the time of reaction I is selected from any of 16h, 18h, 24h, 28h, 30h, 38h, 48h or a range of values between any two of the foregoing.
Optionally, the temperature of the drying I is 50-120 ℃, and the time of the drying I is 2-8 h.
Optionally, the temperature of the drying I is selected from any value or range of values between any two of 50 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 120 ℃.
Optionally, the time of drying I is selected from any value of 2h, 3h, 4h, 5h, 6h, 7h, 8h or a range of values between any two of the foregoing.
According to a further aspect of the present application there is provided the use of the gamma iron oxide catalyst described above in the conversion of normal para-hydrogen.
Optionally, the temperature of the gamma iron oxide catalyst in the normal para-hydrogen conversion is 0K-298K.
Optionally, the temperature of the gamma iron oxide catalyst in the normal para-hydrogen conversion is selected from any of 0K, 15K, 20K, 50K, 100K, 150K, 200K, 250K, 298K or a range of values between any of the above.
The catalyst provided by the application is used for evaluating the catalytic conversion performance of the normal para-hydrogen, and the reaction temperature is 0-100K, preferably 15-80K. Pd/gamma-Fe prepared 2 O 3 [440]The catalyst is used for the catalytic conversion reaction of the normal and secondary hydrogen, the monoatomic active components (Pt, pd, ir and Ru) are highly dispersed, the metal utilization rate is obviously improved, and the activity and the stability of the catalytic conversion reaction of the normal and secondary hydrogen are obviously improved.
The catalyst provided by the application is composed of metal monoatoms including monoatomic Pt, monoatomic Pd, monoatomic Ir and monoatomic Ru, and the monoatomic metal active component is loaded on a carrier through an impregnation method. The catalyst is treated at 200 deg.c to regulate the interaction between monoatoms and gamma ferric oxide 440, so as to regulate the reaction performance of the catalyst. The prepared normal-para-hydrogen conversion catalyst shows excellent activity and stability. The preparation method of the catalyst is simple and easy to implement, the cost is low, the catalytic conversion efficiency of the normal para-hydrogen is high, the catalytic conversion efficiency can reach 87%, and the equilibrium concentration of the para-hydrogen reaches 45.4-50.4.
The application has the beneficial effects that:
the preparation method of the catalyst provided by the application is simple and convenient to operate, reliable in method and beneficial to large-scale production and use. The catalyst provided by the application has the advantages that the monoatomic active components (Pt, pd, ir and Ru) are highly dispersed, and the metal utilization rate is very high. The interaction degree between the metal and the carrier can be effectively regulated through roasting treatment, so that the activity and stability of the catalyst are obviously improved. The catalyst provided by the application is used for the catalytic conversion reaction of the normal and the para-hydrogen, the catalytic conversion efficiency of the normal and the para-hydrogen is high and can reach 87%, and the equilibrium concentration of the para-hydrogen can reach 45.4-50.4.
Drawings
FIG. 1 shows gamma-Fe prepared in example 1 of the present application 2 O 3 [440]HRTEM image of catalyst at 20 nm.
FIG. 2 shows the gamma-Fe prepared in examples 1 to 5 of the present application 2 O 3 [440]，Pt/γ-Fe 2 O 3 [440]，Pd/γ-Fe 2 O 3 [440]，Ir/γ-Fe 2 O 3 [440]，Ru/γ-Fe 2 O 3 [440]XRD pattern of the catalyst.
Detailed Description
The present application is described in detail below with reference to examples, but the present application is not limited to these examples.
Unless otherwise indicated, all starting materials in the examples of the present application were purchased commercially.
In the present application, room temperature means "25 ℃".
In the present application, normal para-hydrogen conversion = product para-hydrogen concentration/starting 75% normal hydrogen +25% para-hydrogen concentration.
1. Pt/gamma-Fe 2 O 3 [440]The catalyst is prepared by adopting an impregnation method, and the specific process is as follows:
1) Taking Pt precursor solution with metal Pt of 0.001-0.5 g, forming 20-150 ml uniform solution in deionized water, adding 0.999-9.5 g gamma-Fe into the solution 2 O 3 [440]The carrier forms a homogeneous mixture, the Pt content of the mixture is 0.1 to 5wt% based on the catalyst and calculated by single atom, and the mixture is gamma-Fe 2 O 3 [440]Of carrier gaugesThe content is 95 to 99.9 weight percent; heating and stirring the formed mixture at 40-85 ℃ until the solvent is evaporated, and drying the obtained solid in a baking oven at 60-150 ℃ for 4-24 hours;
2) Roasting in a tubular furnace at 200-400 deg.c in argon atmosphere for 1-10 hr to obtain exposed [440]]Crystal face gamma ferric oxide loaded Pt single atom catalyst, pt/gamma-Fe 2 O 3 [440]。
The Pt precursor in step 1) adopts H 2 PtCl 6 、Na 2 PtCl 6 、K 2 PtCl 6 One or more of the following; carrier gamma-Fe 2 O 3 Exposed crystal face of [440]]。
The roasting temperature in the step 2) is preferably 200-300 ℃ and the time is 2-3 h.
The reducing atmosphere in the step 2) can be high-purity Ar and H 2 A mixture gas with different proportion with Ar.
2. Pd/gamma-Fe 2 O 3 [440]The catalyst is prepared by adopting an impregnation method, and the specific process is as follows:
1) Taking Pd precursor solution with metal Pd of 0.001-0.5 g in deionized water to form 20-150 ml homogeneous solution, adding gamma-Fe of 0.999-9.5 g into the solution 2 O 3 [440]The carrier forms a homogeneous mixture, the Pd content in terms of single atom based on the catalyst is 0.1-5 wt%, gamma-Fe 2 O 3 [440]The content of the carrier is 95 to 99.9 weight percent; heating and stirring the formed mixture at 40-85 ℃ until the solvent is evaporated, and drying the obtained solid in a baking oven at 60-150 ℃ for 4-24 hours;
2) Roasting in a tubular furnace at 200-400 deg.c in argon atmosphere for 1-10 hr to obtain exposed [440]]Pd monoatomic catalyst supported by gamma ferric oxide of crystal face and Pd/gamma-Fe 2 O 3 [440]。
Step 1) Pd precursor adopts H 2 PdCl 6 、Na 2 PdCl 6 、K 2 PdCl 6 One or more of the following; carrier gamma-Fe 2 O 3 Exposed crystal face of [440]]。
The roasting temperature in the step 2) is preferably 200-300 ℃ and the time is 2-3 h.
The reducing atmosphere in the step 2) can be high-purity Ar and H 2 A mixture gas with different proportion with Ar.
3. Ir/gamma-Fe 2 O 3 [440]The catalyst is prepared by adopting an impregnation method, and the specific process is as follows:
1) Taking Ir precursor solution with metal Pd of 0.001-0.5 g and forming 20-150 ml uniform solution in deionized water, adding 0.999-9.5 g gamma-Fe into the solution 2 O 3 [440]The support forms a homogeneous mixture in which the Ir content in terms of monoatoms is from 0.1 to 5% by weight, based on the catalyst, based on gamma-Fe 2 O 3 [440]The content of the carrier is 95 to 99.9 weight percent; heating and stirring the formed mixture at 40-85 ℃ until the solvent is evaporated, and drying the obtained solid in a baking oven at 60-150 ℃ for 4-24 hours;
2) Roasting in a tubular furnace at 200-400 deg.c in argon atmosphere for 1-10 hr to obtain exposed [440]]Ir monoatomic catalyst supported by gamma ferric oxide of crystal face, ir/gamma-Fe 2 O 3 [440]。
Step 1) Ir precursor adopts H 2 IrCl 6 、Na 2 IrCl 6 、K 2 IrCl 6 One or more of the following; carrier gamma-Fe 2 O 3 Exposed crystal face of [440]]。
The roasting temperature in the step 2) is preferably 200-300 ℃ and the time is 2-3 h.
The reducing atmosphere in the step 2) can be high-purity Ar and H 2 A mixture gas with different proportion with Ar.
4. Ru/gamma-Fe 2 O 3 [440]The catalyst is prepared by adopting an impregnation method, and the specific process is as follows:
1) Taking Pd precursor solution with metal Ru of 0.001-0.5 g and forming 20-150 ml uniform solution in deionized water, adding 0.999-9.5 g gamma-Fe into the solution 2 O 3 [440]The carrier forms a homogeneous mixture, the Ru content in terms of single atoms is 0.1-5 wt% based on the catalyst, and gamma-Fe 2 O 3 [440]The content of the carrier is 95 to 99.9 weight percent; heating and stirring the formed mixture at 40-85 ℃ until the solvent is evaporated to dryness, and drying the obtained solid in a baking oven at 60-150 ℃ for 4-24h；
2) Roasting in a tubular furnace at 200-400 deg.c in argon atmosphere for 1-10 hr to obtain exposed [440]]Ru monoatomic catalyst loaded by gamma ferric oxide of crystal face, ru/gamma-Fe 2 O 3 [440]。
Step 1) Ru precursor adopts RuCl 3 ·3H 2 O、Ru(NO)(NO 3 ) 3 、Ru 2 Cl 4 (CO) 6 、Ru(Ac) 3 One or more of the following; carrier gamma-Fe 2 O 3 Exposed crystal face of [440]]。
The roasting temperature in the step 2) is preferably 200-300 ℃ and the time is 2-3 h.
The reducing atmosphere in the step 2) can be high-purity Ar and H 2 A mixture gas with different proportion with Ar.
Example 1
1) Accurately weigh 1.08g FeCl 3 ·6H 2 O was placed in a clean beaker and 4mL of H was added in sequence 2 O,4mL of ammonia water, 60mL of ethanol, and stirring thoroughly for 30min after 30min of ultrasound. After sufficient stirring, the mixed solution was transferred to a polytetrafluoroethylene hydrothermal reaction kettle liner with a volume capacity of 100mL, and the liner was packaged.
2) Then the reaction kettle is transferred to an electrothermal blowing drying oven at 180 ℃ for reaction for 24 hours.
3) After the reaction is finished, naturally cooling to room temperature, centrifuging the sample solution after the hydrothermal reaction, and fully washing with deionized water and ethanol for 3 times respectively. The washed sample was then dried in a drying oven at 80℃to give an exposure [440]]Crystal face gamma iron oxide carrier (named gamma-Fe 2 O 3 [440]). FIG. 1 shows that the specific exposed crystal plane [440] is produced]gamma-Fe of (2) 2 O 3 In the form of uniform nanoparticles of about 10nm, and gamma-Fe 2 O 3 [440]The size is uniform.
Example 2
Taking H with Pt content of 0.06g 2 PtCl 6 ·6H 2 O solution, diluting with deionized water to 50ml of uniform solution, stirring uniformly, adding 1.94g of gamma-Fe into the solution 2 O 3 [440]The carrier forms a homogeneous mixture; the mixtureThe mixture was heated and stirred at 60 ℃ until the solvent evaporated to dryness, the resulting solid was dried in a 100 ℃ oven for 12h, and then calcined in a tube furnace under an argon atmosphere at 200 ℃ for 2h. Thus obtaining Pt/gamma-Fe 2 O 3 [440]A catalyst.
Example 3
Taking H with Pd content of 0.06g 2 PdCl 6 ·6H 2 O solution, diluting with deionized water to 50ml of uniform solution, stirring uniformly, adding 1.94g of gamma-Fe into the solution 2 O 3 [440]The carrier forms a homogeneous mixture; the mixture was heated and stirred at 60 ℃ until the solvent evaporated to dryness, the resulting solid was dried in a 100 ℃ oven for 12h, and then calcined in a tube furnace under an argon atmosphere at 200 ℃ for 2h. Thus obtaining Pd/gamma-Fe 2 O 3 [440]A catalyst.
Example 4
Taking H with Ir content of 0.06g 2 IrCl 6 ·6H 2 O solution, diluting with deionized water to 50ml of uniform solution, stirring uniformly, adding 1.94g of gamma-Fe into the solution 2 O 3 [440]The carrier forms a homogeneous mixture; the mixture was heated and stirred at 60 ℃ until the solvent evaporated to dryness, the resulting solid was dried in a 100 ℃ oven for 12h, and then calcined in a tube furnace under an argon atmosphere at 200 ℃ for 2h. Obtaining Ir/gamma-Fe 2 O 3 [440]A catalyst.
Example 5
RuCl with Ru content of 0.06g is taken 3 ·3H 2 O solution, diluting with deionized water to 50ml of uniform solution, stirring uniformly, adding 1.94g of gamma-Fe into the solution 2 O 3 [440]The carrier forms a homogeneous mixture; the mixture was heated and stirred at 60 ℃ until the solvent evaporated to dryness, the resulting solid was dried in a 100 ℃ oven for 12h, and then calcined in a tube furnace under an argon atmosphere at 200 ℃ for 2h. Thus obtaining Ru/gamma-Fe 2 O 3 [440]A catalyst.
FIG. 2 shows that the catalyst is incorporated into a carrier gamma-Fe 2 O 3 [440]In contrast, the catalyst after loading single atoms comprises Pt/gamma-Fe 2 O 3 [440]，Pd/γ-Fe 2 O 3 [440]，Ir/γ-Fe 2 O 3 [440]，Ru/γ-Fe 2 O 3 [440]Shows the crystal phase structure which is completely the same as the carrier, and proves that no nano particles exist, and the components such as Pt, pd, ir, ru and the like exist in the form of single atoms in gamma-Fe 2 O 3 [440]And (3) on a carrier.
EXAMPLE 6 n-para-hydrogen conversion reaction
And (3) reacting in a low-temperature Dewar tank, adopting liquid nitrogen as a refrigerant medium when operating in a 77K temperature environment, and controlling the pressure in the liquid nitrogen tank through a back pressure valve on the liquid nitrogen tank to ensure the stability of the refrigerant medium at the 77K temperature. Using the exposure prepared in example 1 [440]]0.5g to 3g of gamma-ferric oxide carrier with crystal face and the catalysts prepared in examples 2 to 5, and the reaction space velocity is 100 mL.H 2 The reaction pressure was 0MPa (normal pressure). The specific reaction conditions are shown in Table 1.
Table 1: experimental example 1 gamma-Fe 2 O 3 [440]And the catalyst prepared in examples 2 to 5 were subjected to para-hydrogen conversion
As can be seen from Table 1, table 1 shows γ -Fe 2 O 3 [440]，Pt/γ-Fe 2 O 3 [440]，Pd/γ-Fe 2 O 3 [440]，Ir/γ-Fe 2 O 3 [440]，Ru/γ-Fe 2 O 3 [440]Catalyst conversion of normal para-hydrogen the normal para-hydrogen conversion of the catalyst is equal to that of pure gamma-Fe 2 O 3 [440]Pt/gamma-Fe compared with the carrier 2 O 3 [440]，Pd/γ-Fe 2 O 3 [440]，Ir/γ-Fe 2 O 3 [440]，Ru/γ-Fe 2 O 3 [440]The catalyst shows various degrees of improvement in the conversion of the normal para-hydrogen.
While the application has been described in terms of preferred embodiments, it will be understood by those skilled in the art that various changes and modifications can be made without departing from the scope of the application, and it is intended that the application is not limited to the specific embodiments disclosed.
Claims (10)
1. A gamma iron oxide catalyst, characterized in that the gamma iron oxide catalyst comprises: iron oxide and a metal monoatom, the iron oxide exposing a [440] crystal plane;
the metal monoatoms are loaded on the [440] crystal face;
wherein the metal monoatoms comprise at least one of monoatomic Pt, monoatomic Pd, monoatomic Ir and monoatomic Ru.
2. The gamma iron oxide catalyst according to claim 1, wherein the metal monoatoms account for 0.1 to 5wt% of the gamma iron oxide catalyst;
the iron oxide accounts for 95 to 99.9 weight percent of the gamma iron oxide catalyst.
3. A method for producing a gamma iron oxide catalyst according to any one of claims 1 to 2, characterized in that the production method comprises:
reacting, drying and roasting a mixture containing a metal monoatomic precursor and ferric oxide to obtain a gamma ferric oxide catalyst;
the ferric oxide is ferric oxide with an exposed [440] crystal face;
the metal monoatomic precursor is selected from at least one of Pt precursor, pd precursor, ir precursor and Ru precursor.
4. A method of preparing an exposed [440] crystal face iron oxide according to claim 3, comprising:
adding water, ammonia water and ethanol into an iron precursor compound in turn in a closed container, reacting I, and drying I to obtain exposed [440] crystal face ferric oxide;
preferably, the iron precursor compound is selected from FeCl 3 ·6H 2 O、Fe(NO 3 ) 3 ·9H 2 O、Fe 2 (SO 4 ) 3 ·2H 2 At least one of O.
5. The method of preparing as claimed in claim 4, wherein the iron precursor compound: water: ammonia water: the mass volume ratio of the ethanol is as follows: 1-2 g: 2-10 mL: 2-10 mL: 30-100 mL.
6. The method according to claim 3, wherein the mass ratio of the metal monoatomic precursor to the iron oxide is 0.001 to 5g: 0.999-9.5 g;
preferably, the Pt precursor is selected from H 2 PtCl 6 、Na 2 PtCl 6 、K 2 PtCl 6 At least one of (a) and (b);
preferably, the Pd precursor H 2 PdCl 6 、Na 2 PdCl 6 、K 2 PdCl 6 At least one of (a) and (b);
preferably, the Ir precursor H 2 IrCl 6 、Na 2 IrCl 6 、K 2 IrCl 6 At least one of (a) and (b);
preferably, the Ru precursor RuCl 3 ·3H 2 O、Ru(NO)(NO 3 ) 3 、Ru 2 Cl 4 (CO) 6 、Ru(Ac) 3 At least one of them.
7. The method according to claim 3, wherein the reaction temperature is 40-85 ℃ and the reaction time is 4-24 hours;
preferably, the drying temperature is 60-150 ℃ and the drying time is 4-24 hours;
preferably, the roasting temperature is 200-400 ℃, and the roasting time is 1-10 h.
8. The preparation method according to claim 4, wherein the temperature of the reaction I is 150-250 ℃, and the time of the reaction I is 16-48 h;
preferably, the temperature of the drying I is 50-120 ℃, and the time of the drying I is 2-8 h.
9. Use of the gamma iron oxide catalyst of any one of claims 1 to 2 in the conversion of normal para-hydrogen.
10. The use according to claim 9, characterized in that the temperature of the gamma iron oxide catalyst in the conversion of normal para-hydrogen is between 0K and 298K.
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