CN118002183A - Aluminum nitride-based catalyst with local core-shell island structure, preparation method and application - Google Patents
Aluminum nitride-based catalyst with local core-shell island structure, preparation method and application Download PDFInfo
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- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 title claims abstract description 114
- 239000003054 catalyst Substances 0.000 title claims abstract description 104
- 239000011258 core-shell material Substances 0.000 title claims abstract description 51
- 238000002360 preparation method Methods 0.000 title claims description 11
- 229910052751 metal Inorganic materials 0.000 claims abstract description 79
- 239000002184 metal Substances 0.000 claims abstract description 79
- 239000002245 particle Substances 0.000 claims abstract description 33
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 20
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical group O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000006243 chemical reaction Methods 0.000 claims description 35
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 33
- 239000012266 salt solution Substances 0.000 claims description 32
- 239000002243 precursor Substances 0.000 claims description 29
- 239000000843 powder Substances 0.000 claims description 25
- 238000000034 method Methods 0.000 claims description 23
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 17
- 238000010438 heat treatment Methods 0.000 claims description 17
- 239000001257 hydrogen Substances 0.000 claims description 17
- 229910052739 hydrogen Inorganic materials 0.000 claims description 17
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 16
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 16
- 238000001035 drying Methods 0.000 claims description 16
- 229910052757 nitrogen Inorganic materials 0.000 claims description 10
- 230000009467 reduction Effects 0.000 claims description 10
- 229910052759 nickel Inorganic materials 0.000 claims description 9
- 230000015572 biosynthetic process Effects 0.000 claims description 8
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 8
- 239000001569 carbon dioxide Substances 0.000 claims description 8
- 239000007789 gas Substances 0.000 claims description 8
- 238000005470 impregnation Methods 0.000 claims description 8
- LAIZPRYFQUWUBN-UHFFFAOYSA-L nickel chloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].[Cl-].[Ni+2] LAIZPRYFQUWUBN-UHFFFAOYSA-L 0.000 claims description 8
- GFHNAMRJFCEERV-UHFFFAOYSA-L cobalt chloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].[Cl-].[Co+2] GFHNAMRJFCEERV-UHFFFAOYSA-L 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 238000003786 synthesis reaction Methods 0.000 claims description 5
- UXKHAVNKHLIMGP-UHFFFAOYSA-K trichlororhodium hexahydrate Chemical compound O.O.O.O.O.O.[Rh](Cl)(Cl)Cl UXKHAVNKHLIMGP-UHFFFAOYSA-K 0.000 claims description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- 239000011261 inert gas Substances 0.000 claims description 4
- 238000006057 reforming reaction Methods 0.000 claims description 4
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- MPTQRFCYZCXJFQ-UHFFFAOYSA-L copper(II) chloride dihydrate Chemical compound O.O.[Cl-].[Cl-].[Cu+2] MPTQRFCYZCXJFQ-UHFFFAOYSA-L 0.000 claims description 3
- CNFDGXZLMLFIJV-UHFFFAOYSA-L manganese(II) chloride tetrahydrate Chemical compound O.O.O.O.[Cl-].[Cl-].[Mn+2] CNFDGXZLMLFIJV-UHFFFAOYSA-L 0.000 claims description 3
- 229910052703 rhodium Inorganic materials 0.000 claims description 3
- 239000010948 rhodium Substances 0.000 claims description 3
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 239000010949 copper Substances 0.000 claims description 2
- 229940044631 ferric chloride hexahydrate Drugs 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- NQXWGWZJXJUMQB-UHFFFAOYSA-K iron trichloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].Cl[Fe+]Cl NQXWGWZJXJUMQB-UHFFFAOYSA-K 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 239000011572 manganese Substances 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 229910052799 carbon Inorganic materials 0.000 abstract description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 22
- 230000008021 deposition Effects 0.000 abstract description 13
- 229910044991 metal oxide Inorganic materials 0.000 abstract description 7
- 150000004706 metal oxides Chemical class 0.000 abstract description 7
- 238000005245 sintering Methods 0.000 abstract description 5
- 239000000969 carrier Substances 0.000 abstract description 3
- 239000011248 coating agent Substances 0.000 abstract description 3
- 238000000576 coating method Methods 0.000 abstract description 3
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- 230000000694 effects Effects 0.000 description 10
- 230000003197 catalytic effect Effects 0.000 description 9
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- 238000012512 characterization method Methods 0.000 description 7
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 6
- 238000001354 calcination Methods 0.000 description 6
- 239000006185 dispersion Substances 0.000 description 6
- 238000011056 performance test Methods 0.000 description 6
- 239000010453 quartz Substances 0.000 description 6
- 229920006395 saturated elastomer Polymers 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 238000001179 sorption measurement Methods 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 238000005303 weighing Methods 0.000 description 6
- 238000002347 injection Methods 0.000 description 5
- 239000007924 injection Substances 0.000 description 5
- 238000012546 transfer Methods 0.000 description 4
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000006460 hydrolysis reaction Methods 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- 239000002105 nanoparticle Substances 0.000 description 3
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 3
- 238000001016 Ostwald ripening Methods 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 150000003841 chloride salts Chemical class 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
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- WOSISLOTWLGNKT-UHFFFAOYSA-L iron(2+);dichloride;hexahydrate Chemical compound O.O.O.O.O.O.Cl[Fe]Cl WOSISLOTWLGNKT-UHFFFAOYSA-L 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 239000002082 metal nanoparticle Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- AOPCKOPZYFFEDA-UHFFFAOYSA-N nickel(2+);dinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O AOPCKOPZYFFEDA-UHFFFAOYSA-N 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 1
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- 150000001722 carbon compounds Chemical class 0.000 description 1
- 239000012018 catalyst precursor Substances 0.000 description 1
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- 125000001309 chloro group Chemical class Cl* 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 150000004696 coordination complex Chemical class 0.000 description 1
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- 230000001939 inductive effect Effects 0.000 description 1
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- 238000012423 maintenance Methods 0.000 description 1
- 229910001510 metal chloride Inorganic materials 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
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- 238000006386 neutralization reaction Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
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- 150000003839 salts Chemical class 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000002411 thermogravimetry Methods 0.000 description 1
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Abstract
The invention provides an aluminum nitride-based catalyst with a local core-shell island structure, and belongs to the field of catalysts. The catalyst comprises an aluminum nitride carrier and a plurality of core-shell island structures distributed on the aluminum nitride carrier, wherein the plurality of core-shell island structures do not completely cover the surface of the aluminum nitride carrier; the core-shell island structure comprises a core and a shell layer coated outside the core; the inner core is a metal active component, and the shell layer is aluminum oxide. The catalyst structure of the invention forms a shell island structure on part of the aluminum nitride carrier, inhibits active metal component particles from sintering by coating metal component particles with fixed-point metal oxides, and provides high-efficiency heat conduction on the surfaces of the rest aluminum nitride carriers, thereby realizing high heat utilization rate, high stability and carbon deposition resistance, and being further suitable for the field of methane dry reforming.
Description
Technical Field
The invention belongs to the field of catalyst preparation, and particularly relates to an aluminum nitride-based catalyst with a local core-shell island structure, a preparation method and application thereof.
Background
Carbon capture, utilization and storage (CCUS) technology will play an important role in achieving carbon neutralization goals as one of the few solutions to heavy industrial emissions and carbon removal from the atmosphere. Methane Dry Reforming (DRM) converts CO 2 and CH 4 simultaneously to valuable synthesis gas (H 2 +co), where the extra CO 2 is also eliminated. However, the strong endothermic nature of the DRM reaction requires metal nanoparticles with high thermal conductivity, mechanical strength, and resistance to sintering at high temperatures (> 700 ℃).
The carbon deposit resistance of Ni-based catalysts is generally studied from two directions: (1) a carbon deposition-carbon elimination dynamic equilibrium strategy; (2) The formation and growth mechanism of carbon species, i.e. modulation of Ni particle surface geometry and electronic structure. Numerous studies have shown that reducing Ni particle size is a very effective way to achieve this mechanism. Carbon deposition must be formed on a relatively large metallic Ni surface. However, under the high temperature reaction conditions of the DRM process, the smaller Ni nanoparticles are extremely easy to undergo migration agglomeration and Ostwald ripening (Ostwald ripening), and sinter to form larger Ni particles, which aggravate carbon deposition of the catalyst. It has now been found that nickel-based aluminum nitride catalysts can stabilize Ni nanoparticles at smaller sizes through an alumina layer at high temperatures. However, oxidation of the aluminum nitride surface will cause oxygen to be dissolved into the AlN lattice to form aluminum vacancy defects, which will result in increased phonon scattering, reduced mean free path, and reduced thermal conductivity, thereby impeding the temperature distribution of the bed.
A very large non-uniform temperature distribution field accelerates the carbon formation of the nickel-based catalyst. Carbon deposition can reduce activity and disrupt catalyst geometry. In order to improve the heat transfer efficiency, some novel catalysts have been developed, but there are problems of low heat utilization efficiency, durability, or high cost. Therefore, it is very necessary to develop a DRM catalyst having a fixed-point core-shell island structure that has high thermal conductivity, high activity and stable structure.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide an aluminum nitride-based catalyst with a local core-shell island structure and high thermal conductivity, a preparation method and application thereof. The aluminum nitride-based catalyst forms a core-shell structure around only the active metal, the surface of the inactive metal is free of an aluminum oxide layer, and the surface of the inactive metal is still an aluminum nitride surface. The aluminum nitride-based catalyst with a local fixed-point core-shell island structure is formed, and the problems of active metal sintering and carbon deposition of the traditional supported oxide catalyst and the problem of reduction of the heat conductivity of an aluminum nitride carrier caused by an aluminum oxide shell layer are solved. To achieve the above and other related objects, the present invention is achieved by the following technical solutions:
The invention provides an aluminum nitride-based catalyst with a local core-shell island structure, which comprises an aluminum nitride carrier and a plurality of core-shell island structures distributed on the aluminum nitride carrier, wherein the plurality of core-shell island structures do not completely cover the surface of the aluminum nitride carrier; the core-shell island structure comprises a core and a shell layer coated outside the core; the inner core is a metal active component, and the shell layer is metal oxide.
In order to stabilize the maintenance of the metal component nano particles at a smaller size in the prior art, the metal oxide almost even completely coats the whole surface of the aluminum nitride carrier, so that the thermal conductivity is reduced, and the temperature distribution of the bed layer is hindered. The catalyst structure of the application forms a shell island structure on part of the aluminum nitride carrier, inhibits active metal component particles from sintering by coating metal component particles with metal oxide at fixed points, and provides high-efficiency heat conduction on the surfaces of the rest aluminum nitride carriers, thereby realizing high heat utilization rate, high stability and carbon deposition resistance.
In some preferred examples, the metal active component is selected from the group consisting of one or more of nickel, cobalt, iron, rhodium, copper, manganese. Preferably, the metal active component is selected from nickel or cobalt.
Specifically, the source of the metal active component is derived from a metal salt solution, such as nickel chloride hexahydrate, cobalt chloride hexahydrate, iron chloride hexahydrate, rhodium chloride hexahydrate, copper chloride dihydrate, manganese chloride tetrahydrate, and the like.
In some preferred examples, the metal active component comprises 0.2 to 5wt.% of the total mass of the catalyst, maintaining the above-described ratio of metal active component ensures the catalytic performance of the catalyst. The metal active component may comprise 0.2 to 0.5wt.%, 0.5 to 1wt.%, 1 to 1.5wt.%, 1.5 to 2.5wt.%, 2.5 to 3.5wt.%, 3.5 to 4.5wt.%, or 4.5 to 5wt.% of the total mass of the catalyst.
In some preferred examples, the particle size of the metal active component is 5 to 30nm, and the particle size of the metal active component is kept small to ensure the catalytic performance, and the catalyst carbon deposition is not easily caused. The particle size of the metal active component may be 5 to 10nm, 10 to 15nm, 15 to 20nm, 20 to 25nm or 25 to 30nm.
In some preferred examples, the metal active component has a dispersity in the catalyst of from 5 to 10%, for example from 5 to 8% or from 8 to 10%, as measured by conventional methods, for example by hydrogen pulse characterization. The metal oxide is only coated on the outer part of the metal active component, and the metal oxide layer ensures that the metal nano particles are stabilized at a smaller size. The surface of the aluminum nitride carrier without the metal active component is still exposed so as to maintain high-efficiency heat conduction, thereby realizing high heat utilization rate, high stability and carbon deposit resistance of the catalyst.
The second aspect of the invention provides a preparation method of an aluminum nitride-based catalyst with a local core-shell island structure, which comprises the following steps:
1) Providing aluminum nitride powder, and preparing an aluminum nitride carrier;
Specifically, the particle size of the aluminum nitride powder is 40-1000 nm, and the aluminum nitride powder is directly purchased and sold in the market, wherein the particle size is selected from 40-100 nm, 100-200 nm, 200-300 nm, 300-500 nm, 500-700 nm or 700-1000 nm.
More specifically, aluminum nitride powder is treated for 1 to 5 hours at a temperature of between 100 and 200 ℃ to obtain an aluminum nitride carrier. The treatment temperature can be 100-120 ℃, 120-140 ℃, 140-160 ℃ or 160-200 ℃. The treatment time can be 1-2 h, 2-3 h, 3-4h or 4-5 h.
2) Providing a metal salt solution of a metal active component, and adding the metal salt solution into the aluminum nitride carrier in the step 1) to obtain a precursor A;
Specifically, the metal salt solution is selected from one or a combination of a plurality of nickel chloride hexahydrate, cobalt chloride hexahydrate, ferric chloride hexahydrate, rhodium chloride hexahydrate, copper chloride dihydrate and manganese chloride tetrahydrate. Preferably, the metal salt solution is selected from nickel chloride hexahydrate, cobalt chloride hexahydrate, iron chloride hexahydrate or rhodium chloride hexahydrate.
And in particular, the mass concentration of the metal salt solution is 0.01-0.2 g/ml, the reasonable concentration of the metal salt solution is kept, and the structure and the performance of the core-shell island aluminum nitride-based catalyst are ensured. The mass concentration of the metal salt solution may be 0.01 to 0.05g/ml, 0.05 to 0.1g/ml, 0.1 to 0.15g/ml or 0.15 to 0.2g/ml.
The method for adding the metal salt solution into the aluminum nitride carrier is carried out by adopting an equal volume impregnation method, and the metal salt solution is slowly dripped into the aluminum nitride carrier until saturation.
And then, specifically, adding the metal salt solution into the aluminum nitride carrier in the step 1), and drying at 110-140 ℃ for 1-3 hours to obtain the precursor A. The drying may not be performed or the drying may be performed at 110 to 140℃for 1 hour or less, and the specific temperature may be 110 to 120℃or 120 to 130℃or 130 to 140 ℃.
3) Roasting the precursor A in the step 2) to obtain a precursor B;
specifically, the calcination is performed under the protection of inert gas. Preferably, the inert gas is selected from at least one of Ar, N 2, or He.
More specifically, the maximum temperature of the calcination is 350 to 550 ℃, and may be 350 to 400 ℃, 400 to 450 ℃, 450 to 500 ℃, or 500 to 550 ℃.
More specifically, the calcination is maintained at the highest temperature for 1 to 5 hours, which may be 1 to 2 hours, 2 to 3 hours, 3 to 4 hours, or 4 to 5 hours.
And then specifically, the roasting adopts gradient heating, the heating speed is 2-10 ℃/min, and the heating speed can be 2-3 ℃/min, 3-5 ℃/min, 5-8 ℃/min or 8-10 ℃/min.
The inventor experiments prove that the metal chloride salt solution directly treats the aluminum nitride carrier, and the fixed-point core-shell island structure is realized by inducing the partial hydrolysis of the aluminum nitride surface through the chloride salt crystallization water. Namely, the crystallization water of the chlorine salt is difficult to decompose in the process of burning the catalyst, so that a chlorinated metal complex is formed, and a local Al 2O3 shell island is formed around the metal. Eventually, an alumina protective layer is formed only outside the metal active component supported on the aluminum nitride carrier. The temperature and time of calcination have important influence on the formation of the catalyst structure, and the aluminum nitride-based catalyst with good catalytic performance and a core-shell island structure can be prepared by adopting the embodiment.
4) And (3) reducing the precursor B in the step (3) to obtain the aluminum nitride-based catalyst with the local core-shell island structure.
Specifically, the reduction is performed under a mixed gas of hydrogen and nitrogen; preferably, the hydrogen accounts for 5-20% of the volume of the mixed gas, and can be 5-10%, 10-15% or 15-20%.
More specifically, the temperature of the reduction is 600 to 800 ℃, and may be 600 to 700 ℃ or 700 to 800 ℃.
More specifically, the time for the reduction is 0.5 to 2 hours, and may be 0.5 to 1 hour, 1 to 1.5 hours, or 1.5 to 2 hours.
It is noted that the reduction is carried out under the above-described optimum reduction conditions, and reference is of course made to conventional methods for reducing a catalyst precursor.
A third aspect of the invention provides the use of the catalyst of the first aspect or the catalyst prepared by the method of preparation of the second aspect in a methane and carbon dioxide reforming reaction.
In a fourth aspect the invention provides a process for the preparation of synthesis gas by reforming reaction of methane and carbon dioxide, the process comprising: methane and carbon dioxide are carried out in the presence of the catalyst of the first aspect or the catalyst prepared by the preparation method of the second aspect.
Specifically, the molar ratio of methane to carbon dioxide is (0.5-2): 1, and the molar ratio is adjusted according to the requirement of the synthesis gas.
More specifically, the reaction temperature is 600 to 950 ℃, for example 600 to 700 ℃, 700 to 800 ℃, or 800 to 950 ℃.
Still more specifically, the reaction pressure is from 0 to 30bar, for example from 0bar, from 0 to 10bar, from 10 to 20bar or from 20 to 30bar.
More specifically, the reaction time is 100 to 1000 hours, for example, 100 to 200 hours, 200 to 300 hours, 300 to 400 hours, 400 to 500 hours, 500 to 600 hours, 600 to 800 hours, or 800 to 1000 hours.
The invention has the technical effects including but not limited to the following:
1) The catalyst structure of the invention forms a shell island structure on part of the aluminum nitride carrier, inhibits active metal component particles from sintering by coating metal component particles with metal oxide at fixed points, and provides high-efficiency heat conduction on the surfaces of the rest aluminum nitride carriers, thereby realizing high heat utilization rate, high stability and carbon deposition resistance.
2) The invention has less synthesis steps and little pollution of industrial wastewater, and can be produced and used in large scale.
3) The invention adopts metal salt crystallization water to induce the partial hydrolysis of the aluminum nitride surface to prepare the aluminum nitride-based catalyst with fixed-point core-shell, thereby realizing the complete utilization of metal salt solution.
Drawings
FIG. 1 is a transmission electron microscope image of the core-shell island aluminum nitride based catalyst obtained in example 3 before reaction.
FIG. 2 shows the particle size distribution of the core-shell island aluminum nitride based catalyst obtained in example 3 before and after the reaction.
FIG. 3 is a schematic diagram of heat transfer for a prior art and core-shell island aluminum nitride based catalyst according to the present application.
FIG. 4 is a graph showing the reactivity of the core-shell island aluminum nitride-based catalyst obtained in example 3.
FIG. 5 is an in situ thermogravimetric analysis of the comparative aluminum nitride based catalyst and core shell island aluminum nitride based catalyst obtained in examples 2 and 3, respectively, during calcination.
FIG. 6 shows the bed distribution during the reaction of the core-shell island aluminum nitride based catalyst obtained in example 3.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
[ Example 1]
The structure of the aluminum nitride-based catalyst with the core-shell island structure of the example is shown in an electron microscope image of fig. 1 or a schematic diagram of fig. 3.
Specifically, the catalyst comprises an aluminum nitride carrier and a plurality of core-shell island structures distributed on the aluminum nitride carrier, wherein the plurality of core-shell island structures do not completely cover the surface of the aluminum nitride carrier. The core-shell island structure comprises a core and a shell layer coated outside the core, wherein the core is a metal active component, and the shell layer is alumina.
Taking the schematic diagram of fig. 3 as an illustration of the heat transfer of the aluminum oxide fully coated aluminum nitride support of the prior art and the aluminum nitride based catalyst of the core-shell island structure of the present application.
Referring to the left graph of fig. 3, the nickel-based aluminum nitride catalyst and aluminum oxide layer in the prior art are obtained through water treatment, and the obtained aluminum oxide layer coats the whole aluminum nitride surface. Because the encapsulation of the alumina layer will cause oxygen to be solid-dissolved into the aluminum nitride lattice to form aluminum vacancy defects, which will result in increased phonon scattering, reduced mean free path, and a consequent reduction in thermal conductivity, thereby impeding the temperature distribution of the bed. The aluminum nitride-based catalyst with the core-shell island structure only forms an aluminum oxide layer outside the supported metal active component (particularly adopts a metal salt solution to realize positioning induction so as to form a local core-shell island structure on an aluminum nitride carrier). Referring to the right view of fig. 3, the aluminum oxide layer outside the metal active component provides heat protection so that the metal active component is not easily sintered and agglomerated, thereby reducing carbon deposition of the catalyst, while the aluminum nitride carrier part not carrying the metal active component is free of the aluminum oxide layer, thereby not affecting the thermal conductivity of the aluminum nitride carrier.
[ Example 2]
1) Weighing 10g of active aluminum nitride fine powder, and drying at 120 ℃ for 3 hours to obtain an aluminum nitride carrier, wherein the average particle size of the active aluminum nitride fine powder is about 500 nm; 2) Then, 10g of nickel nitrate hexahydrate was weighed and 100ml of water was added to prepare a metal salt solution. Then slowly dripping the metal salt solution into the aluminum nitride carrier by adopting an equal volume impregnation method, fully stirring until powder adsorption is saturated, and drying at 130 ℃ for 2 hours to obtain the precursor A. 3) And under the atmosphere of N 2, heating to 400 ℃ at a heating rate of 5 ℃/min, and keeping the temperature for 2 hours to obtain a precursor B. 4) And then reducing the precursor B for 1h at 700 ℃ in a mixed atmosphere of hydrogen (10 v%) and nitrogen (90 v%) to obtain the core-shell island aluminum nitride-based catalyst. The dispersion degree of the active metal Ni is found to be 5% through a hydrogen pulse characterization test.
The catalysts described above were tested for catalytic activity: 100mg of catalyst is put into a fixed bed quartz tube reactor for catalyst performance test, the ratio of CH 4 to CO 2 in the injection molar quantity is 1:1, the reaction temperature of the catalyst is 800 ℃, the reaction is carried out at normal pressure, after 50h of reaction, the conversion rates of CH 4 and CO 2 are respectively kept at 80% and 82%, the activity of the catalyst is obviously reduced, a large amount of carbon is formed, and the growth degree of Ni particles is large.
[ Example 3]
1) Weighing 10g of active aluminum nitride fine powder, drying at 120 ℃ for 3 hours to obtain an aluminum nitride carrier, wherein the average particle size of the active aluminum nitride fine powder is 500 nm; 2) Then, 10g of nickel chloride hexahydrate was weighed and 100ml of water was added to prepare a metal salt solution. Then slowly dripping the metal salt solution into the aluminum nitride carrier by adopting an equal volume impregnation method, fully stirring until powder adsorption is saturated, and drying at 130 ℃ for 3 hours to obtain a precursor A. 3) And under the atmosphere of N 2, heating to 400 ℃ at a heating rate of 5 ℃/min, and keeping the temperature for 2 hours to obtain a precursor B. 4) And then reducing the precursor B for 1h at 700 ℃ in a mixed atmosphere of hydrogen (10 v%) and nitrogen (90 v%) to obtain the core-shell island aluminum nitride-based catalyst. The dispersion degree of the active metal Ni is 9% through the hydrogen pulse characterization test.
Referring to fig. 1, in the transmission electron microscope image before the catalyst reaction, core-shell islands coated with an alumina shell are uniformly distributed on an aluminum nitride carrier, the particle size of Ni is about 12nm, and the thickness of the alumina shell is about 2nm.
The catalysts described above were tested for catalytic activity: 100mg of catalyst is put into a fixed bed quartz tube reactor for catalyst performance test, the ratio of CH 4 to CO 2 in the injection molar quantity is 1:1, the reaction temperature of the catalyst is 800 ℃, the reaction is carried out under normal pressure (1 bar), after the reaction is carried out for 100 hours, the conversion rates of CH 4 and CO 2 are respectively kept at 85% and 90%, the catalyst activity is stable, no carbon deposit is generated, and the Ni particle size is almost not grown.
Referring to fig. 2, the particle size of the prepared core-shell island aluminum nitride-based catalyst is about 10.5nm, and the particle size after catalytic reaction is about 11.17nm. As can be seen from the particle size distribution before and after the reaction of FIG. 2, ni particles hardly grow.
It can be seen from fig. 5 that the equimolar nickel nitrate hexahydrate and nickel chloride hexahydrate differ in decomposition rate during the catalyst calcination. The crystal water of nickel chloride is difficult to decompose, so that nickel chloride complex is formed, and a local core-shell island is formed around nickel.
From fig. 6, it is found that after nickel metal is supported by self-hydrolysis of nickel chloride precursor crystal water, a core-shell island-type catalyst is formed, and the temperature distribution conditions of the catalyst and the pure aluminum nitride without nickel metal are consistent, which shows that the heat transfer performance of the catalyst is almost completely consistent with that of the pure aluminum nitride without loss.
[ Example 4]
1) Weighing 10g of active aluminum nitride fine powder, drying at 120 ℃ for 3 hours to obtain an aluminum nitride carrier, wherein the average particle size of the active aluminum nitride fine powder is 500 nm; 2) Then, 10g of nickel chloride hexahydrate was weighed and 100ml of water was added to prepare a metal salt solution. Then slowly dripping the metal salt solution into the aluminum nitride carrier by adopting an equal volume impregnation method, fully stirring until powder adsorption is saturated, and drying at 110 ℃ for 3 hours to obtain the precursor A. 3) And under the atmosphere of N 2, heating to 550 ℃ at a heating rate of 5 ℃/min, and keeping the temperature for 2 hours to obtain a precursor B. And then reducing the precursor B for 1h at 700 ℃ in a mixed atmosphere of hydrogen (10 v%) and nitrogen (90 v%) to obtain the core-shell island aluminum nitride-based catalyst. The dispersion degree of the active metal Ni is 9% through the hydrogen pulse characterization test.
The catalysts described above were tested for catalytic activity: 100mg of catalyst is put into a fixed bed quartz tube reactor for catalyst performance test, the ratio of CH 4 to CO 2 in the injection molar quantity is 1:1, the reaction temperature of the catalyst is 800 ℃, the reaction is carried out at normal pressure, after 100h of reaction, the conversion rate of CH 4 and CO 2 are respectively kept at 80% and 84%, the catalyst activity is stable, no carbon deposition is generated, and the Ni particle size is almost not grown.
[ Example 5]
1) Weighing 10g of active aluminum nitride fine powder, drying at 120 ℃ for 3 hours to obtain an aluminum nitride carrier, wherein the average particle size of the active aluminum nitride fine powder is 800 nm; 2) Then, 10g of cobalt chloride hexahydrate was weighed and 100ml of water was added to prepare a metal salt solution. Then slowly dripping the metal salt solution into the aluminum nitride carrier by adopting an equal volume impregnation method, fully stirring until powder adsorption is saturated, and drying at 140 ℃ for 1h to obtain the precursor A. 3) And under the atmosphere of N 2, heating to 400 ℃ at a heating rate of 5 ℃/min, and keeping the temperature for 2 hours to obtain a precursor B. 4) And then reducing the precursor B for 1h at 700 ℃ in a mixed atmosphere of hydrogen (10 v%) and nitrogen (90 v%) to obtain the core-shell island aluminum nitride-based catalyst. The dispersion degree of the active metal Co is found to be 8% through a hydrogen pulse characterization test.
The catalysts described above were tested for catalytic activity: 100mg of catalyst is put into a fixed bed quartz tube reactor for catalyst performance test, the ratio of CH 4 to CO 2 is 1:1, the reaction temperature of the catalyst is 800 ℃, the reaction is carried out under normal pressure, after 100h of reaction, the conversion rates of CH 4 and CO 2 are respectively kept at 82% and 88%, the catalyst activity is stable, no carbon deposition is generated, and the Co particle size is almost not grown.
[ Example 6]
1) Weighing 10g of active aluminum nitride fine powder, drying at 120 ℃ for 3 hours to obtain an aluminum nitride carrier, wherein the average particle size of the active aluminum nitride fine powder is 100 nm; 2) Then, 1g of rhodium chloride hexahydrate was weighed and 100ml of water was added to prepare a metal salt solution. Then slowly dripping the metal salt solution into the aluminum nitride carrier by adopting an equal volume impregnation method, fully stirring until powder adsorption is saturated, and drying at 130 ℃ for 2 hours to obtain the precursor A. 3) And under the atmosphere of N 2, heating to 400 ℃ at a heating rate of 5 ℃/min, and keeping the temperature for 2 hours to obtain a precursor B. And then reducing the precursor B for 1h at 700 ℃ in a mixed atmosphere of hydrogen (10 v%) and nitrogen (90 v%) to obtain the core-shell island aluminum nitride-based catalyst. The dispersion degree of the active metal rhodium is found to be 10% through a hydrogen pulse characterization test. The catalysts described above were tested for catalytic activity: 100mg of catalyst is put into a fixed bed quartz tube reactor for catalyst performance test, the ratio of the injection mole of CH 4 to CO 2 is 1:1, the reaction temperature of the catalyst is 800 ℃, the reaction is carried out at normal pressure, after 100h of reaction, the conversion rate of CH 4 and CO 2 are respectively kept at 92% and 95%, the activity of the catalyst is stable, no carbon deposition is generated, and the Ru particle size is almost not grown.
[ Example 7]
1) Weighing 10g of active aluminum nitride fine powder, drying at 120 ℃ for 3 hours to obtain an aluminum nitride carrier, wherein the average particle size of the active aluminum nitride fine powder is 50 nm; 2) Then, 10g of nickel chloride hexahydrate was weighed and 100ml of water was added to prepare a metal salt solution. Then slowly dripping the metal salt solution into the aluminum nitride carrier by adopting an equal volume impregnation method, fully stirring until powder adsorption is saturated, and drying at 130 ℃ for 2 hours to obtain the precursor A. 3) And under the atmosphere of N 2, heating to 400 ℃ at a heating rate of 5 ℃/min, and keeping the temperature for 2 hours to obtain a precursor B. And then reducing the precursor B for 1h at 700 ℃ in a mixed atmosphere of hydrogen (10 v%) and nitrogen (90 v%) to obtain the core-shell island aluminum nitride-based catalyst. The dispersion degree of the active metal is 9% through the hydrogen pulse characterization test.
The catalysts described above were tested for catalytic activity: 100mg of catalyst is put into a fixed bed quartz tube reactor for catalyst performance test, the ratio of CH 4 to CO 2 in the injection molar quantity is 1:1, the reaction temperature of the catalyst is 800 ℃, the reaction is carried out under 5bar pressure, after the reaction is carried out for 100 hours, the conversion rate of CH 4 and CO 2 are respectively kept at 65% and 70%, the catalyst activity is stable, no carbon deposition is generated, and the Ni particle size is almost not grown.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (10)
1. The aluminum nitride-based catalyst with the local core-shell island structure is characterized by comprising an aluminum nitride carrier and a plurality of core-shell island structures distributed on the aluminum nitride carrier, wherein the plurality of core-shell island structures do not completely cover the surface of the aluminum nitride carrier;
the core-shell island structure comprises a core and a shell layer coated outside the core; the inner core is a metal active component, and the shell layer is aluminum oxide.
2. The aluminum nitride-based catalyst with a local core-shell island structure according to claim 1, which comprises at least one of the following technical characteristics:
a) The metal active component is selected from one or a combination of a plurality of nickel, cobalt, iron, rhodium, copper and manganese;
b) The metal active component accounts for 0.2 to 5 weight percent of the total mass of the catalyst;
c) The particle size of the metal active component is 5-30 nm;
d) The dispersity of the metal active component in the catalyst is 5-10%.
3. A preparation method of an aluminum nitride-based catalyst with a local core-shell island structure comprises the following steps:
1) Providing aluminum nitride powder, and preparing an aluminum nitride carrier;
2) Providing a metal salt solution of a metal active component, and adding the metal salt solution into the aluminum nitride carrier in the step 1) to obtain a precursor A;
3) Roasting the precursor A in the step 2) to obtain a precursor B;
4) And (3) reducing the precursor B in the step (3) to obtain the aluminum nitride-based catalyst with the local core-shell island structure.
4. A method according to claim 3, wherein step 1) comprises at least one of the following technical features:
1a) The grain diameter of the aluminum nitride powder is 40-1000 nm;
1b) Aluminum nitride powder is treated for 1 to 5 hours at the temperature of between 100 and 200 ℃ to obtain the aluminum nitride carrier.
5. A method according to claim 3, wherein step 2) comprises at least one of the following technical features:
2a) The metal salt solution is selected from one or a combination of a plurality of nickel chloride hexahydrate, cobalt chloride hexahydrate, ferric chloride hexahydrate, rhodium chloride hexahydrate, copper chloride dihydrate and manganese chloride tetrahydrate;
2b) The mass concentration of the metal salt solution is 0.01-0.2 g/ml;
2c) The method for adding the metal salt solution into the aluminum nitride carrier is carried out by adopting an equal volume impregnation method;
2d) And (3) adding the metal salt solution into the aluminum nitride carrier in the step (1), and drying at 110-140 ℃ for 1-3 h to obtain the precursor A.
6. A method according to claim 3, wherein step 3) comprises at least one of the following technical features:
3a) Roasting is carried out under the protection of inert gas; preferably, the inert gas is selected from at least one of Ar, N 2, or He;
3b) The highest temperature of roasting is 350-550 ℃, and the roasting is kept for 1-5 h at the highest temperature;
3c) The roasting adopts gradient heating, and the heating speed is 2-10 ℃/min.
7. A method according to claim 3, wherein step 4) comprises at least one of the following technical features:
4a) The reduction is carried out under the mixed gas of hydrogen and nitrogen; preferably, the volume of the hydrogen accounts for 5-20% of the mixed gas;
4b) The reduction temperature is 600-800 ℃;
4c) The reduction time is 0.5-2 h.
8. Use of the catalyst according to claim 1 or 2, or the catalyst obtained by the preparation method according to any one of claims 3 to 7, in methane and carbon dioxide reforming reactions.
9. A method of producing synthesis gas from a methane and carbon dioxide reforming reaction, the method comprising: reacting methane with carbon dioxide in the presence of a catalyst according to claim 1 or 2 or a catalyst obtainable by a process according to any one of claims 3 to 7.
10. The method of claim 9, comprising at least one of the following features:
a) The mole ratio of methane to carbon dioxide is (0.5-2) 1
B) The reaction temperature is 600-950 ℃;
C) The reaction pressure is 0-30 bar;
d) The reaction time is 100-1000 h.
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