CN117960070A - Device and method for preparing superfine molybdenum nitride powder by reduction and nitridation of gas-phase molybdenum oxide - Google Patents
Device and method for preparing superfine molybdenum nitride powder by reduction and nitridation of gas-phase molybdenum oxide Download PDFInfo
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- GPBUGPUPKAGMDK-UHFFFAOYSA-N azanylidynemolybdenum Chemical compound [Mo]#N GPBUGPUPKAGMDK-UHFFFAOYSA-N 0.000 title claims abstract description 57
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- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- SMWDFEZZVXVKRB-UHFFFAOYSA-N Quinoline Chemical compound N1=CC=CC2=CC=CC=C21 SMWDFEZZVXVKRB-UHFFFAOYSA-N 0.000 description 2
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- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
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- 229910015617 MoNx Inorganic materials 0.000 description 1
- 229910003294 NiMo Inorganic materials 0.000 description 1
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- CAVCGVPGBKGDTG-UHFFFAOYSA-N alumanylidynemethyl(alumanylidynemethylalumanylidenemethylidene)alumane Chemical compound [Al]#C[Al]=C=[Al]C#[Al] CAVCGVPGBKGDTG-UHFFFAOYSA-N 0.000 description 1
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- GICWIDZXWJGTCI-UHFFFAOYSA-I molybdenum pentachloride Chemical compound Cl[Mo](Cl)(Cl)(Cl)Cl GICWIDZXWJGTCI-UHFFFAOYSA-I 0.000 description 1
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Landscapes
- Inorganic Compounds Of Heavy Metals (AREA)
Abstract
The invention discloses a device and a method for preparing superfine molybdenum nitride powder by gas-phase molybdenum oxide reduction nitridation, wherein the device comprises a sublimation zone, a reduction nitridation zone, a cooling deposition zone and a heat source for heating the sublimation zone and the reduction nitridation zone, which are sequentially communicated through a nitrogen pipeline; the reduction nitriding zone adopts a micro-channel reactor with a concentric tube structure, the micro-channel reactor is divided into an outer tube and an inner tube, the outer tube is a nitrogen pipeline, the inner tube is a hydrogen pipeline with one end closed, and pores which are uniformly distributed and are communicated with the nitrogen pipeline are arranged in the radial direction of the surface wall of the hydrogen pipeline in the reduction nitriding zone. The device can realize the integrated molding from industrial MoO 3 to superfine molybdenum nitride powder with uniform granularity, greatly reduces equipment investment and operation cost, reduces the preparation energy consumption of the superfine molybdenum nitride powder, has simple preparation flow, simple and convenient operation and high yield, and can be popularized to industrial large-scale high-efficiency production; the device can be used for preparing the molybdenum nitride powder with ultrafine and uniform particle size.
Description
Technical Field
The invention belongs to the field of preparation of molybdenum nitride materials, and particularly relates to a device and a method for preparing superfine molybdenum nitride powder by reduction and nitridation of gas-phase molybdenum oxide.
Background
Molybdenum nitride materials are a generic term for a variety of molybdenum nitrogen binary compounds. Like aluminum carbide materials, nitrogen atoms are interstitially incorporated into the crystal lattice of metallic molybdenum to form molybdenum nitride. Depending on the number of nitrogen atoms, molybdenum nitride forms a non-metered gap compound that can vary over a range. According to different molybdenum-nitrogen ratios, there are mainly several existing forms such as MoN and Mo 2 N. Molybdenum nitride has a range of excellent properties, its high melting point, high hardness, superconductivity and catalytic properties, which make it widely used in ceramic, capacitor materials and catalytic fields. The catalyst has good catalytic activity in the catalytic reactions of decomposition, hydrodenitrogenation, hydrodesulfurization and the like of synthetic ammonia, and certain performances are close to or superior to those of the traditional noble metal catalyst, so the catalyst is known as a quasi-platinum catalyst, and is a new catalytic material with very rich application prospects.
The solid phase synthesis method is the most traditional and common method for synthesizing molybdenum nitride, and comprises a solid phase double decomposition method, a high-pressure solid phase reaction method, a high-energy ball milling method and the like. Solid phase synthesis refers to a process in which nitrogen-and molybdenum-containing species react only in the solid phase under different temperature, pressure, and process conditions to form molybdenum nitride. By adopting a solid phase double decomposition method, moCl 5 and Ca 3N2 are reacted under the pressure of 57kPa, and gamma-Mo 2 N crystals can be obtained; moO 3 is used to react with ammonium chloride to obtain MoN at a pressure of 20kPa and a temperature of 1500 ℃.
In recent years, with the rapid development of the catalytic field, there is an increasing demand for catalytic activity of catalysts, and catalysts having high catalytic activity with high specific surface area are the targets pursued by scientists. As molybdenum nitride has good surface property and adsorption property, the catalytic performances of hexene hydrogenation, hexane hydrogenolysis, cyclohexane dehydrogenation and the like of the molybdenum nitride are widely studied, and the molybdenum nitride has high catalytic activity on the reactions, and the specific activity of the molybdenum nitride in a stable state can be equivalent to that of Pt and Ru. Studies have shown that the hydrodenitrogenation activity of Mo 2 N on quinoline can be as high as that of the commercial sulfided NiMo/Al 2O3 catalyst. However, in some applications, the catalytic activity of common Mo 2 N has not reached the desired level, which has limited further developments in certain catalytic fields, such as: petroleum field, etc. Thus, ultrafine molybdenum nitrides having higher catalytic activity have been developed. The superfine molybdenum nitride has higher catalytic activity due to larger specific surface area, and is the target pursued by the preparation of molybdenum nitride at the present stage.
The superfine synthesis is the key for improving the catalytic performance of the molybdenum nitride, long-term research is carried out on the synthesis aspect of the superfine molybdenum nitride, and the main synthesis methods formed by the superfine synthesis method include a thermal reduction nitridation method, a program temperature control reaction method, an atomic layer deposition method and the like. The concrete introduction is as follows:
Thermal reduction nitridation: into a stainless steel autoclave were placed 0.006mol (about 1.639 g) of analytical grade anhydrous molybdenum pentachloride, 0.004mol (about 0.214 g) of analytical grade ammonium chloride (excess) and 0.044mol (about 1.012 g) of metallic sodium; after sealing under argon atmosphere, heating at 550 ℃ for 10 hours, and then cooling to room temperature in a furnace; washing the product obtained by the autoclave for a plurality of times by using absolute ethyl alcohol, dilute hydrochloric acid aqueous solution and distilled water to remove impurities; finally, washing with absolute ethyl alcohol three times to remove water, and vacuum drying at 60 ℃ for 12 hours to obtain black powder Mo 2 N. In this experiment, NH 4 Cl decomposed to NH 3 and HCl gas at 338 ℃ or higher with an increase in temperature, so the autoclave pressure was very high; moCl 5、NH3 and metallic sodium can react with each other to generate Mo 2 N at the reaction temperature; the high pressure in the autoclave is beneficial to reducing the reaction temperature and improving the reaction speed. The generated HCl gas is strongly absorbed by sodium metal to generate NaCl and H 2. Thus, the thermal reduction-nitridation reaction can be expressed as:
2MoCl5+NH4Cl+11Na＝Mo2N+11NaCl+2H2
MoCl 5 is used as a raw material in the thermal reduction nitridation method, mo 2 N is prepared by high-temperature heating reduction, but metal Na used in the reaction process belongs to a first-grade water combustion article, has high chemical reaction activity, high storage and use risks and high cost; meanwhile, chlorine is used in the preparation and purification processes of MoCl 5, so that the damage is extremely high; in addition, in the reaction process, the product obtained by the autoclave is required to be washed for multiple times by absolute ethyl alcohol, dilute hydrochloric acid aqueous solution and distilled water so as to remove impurities, the operation flow is complicated, and the impurity removal is incomplete.
A programmed temperature control reaction method: the MoO 3 -containing porcelain boat was placed in a tube furnace, then N 2/H2 mixture was introduced, mo 2 N was obtained at 700 to 750 ℃, and experiments showed that the precursor and temperature had a determining effect on the formation of the final product. The microreactor test was performed as follows: in a tube quartz reactor, approximately 0.4gMoO 3 powder was placed in the middle of the quartz tube, then dried N 2/H2 (3:1) mixed gas was introduced at a flow rate of 60ml/min, heated from room temperature to 700℃or 750℃for 2 hours using different heating rates (5, 10, 50 or 100 ℃/min), and then the tube furnace was cooled to room temperature under a flow of N 2/H2.
The program temperature control reaction method has the advantages of simple operation and no impurity introduced, but the prepared molybdenum nitride particles have poor particle size uniformity and large agglomeration probability among particles, thereby greatly reducing the product quality; this has a very severe effect on the surface activity of molybdenum nitride, directly resulting in a significant difference in its subsequent service properties.
Atomic layer deposition: through atomic layer deposition technology, a molybdenum nitride film is obtained through the reaction of MoCl 5 and NH 3 at the temperature of 350-500 ℃, and the test shows that the molybdenum nitride film is a good diffusion-resistant material. Experiments used a commercial flow-through F120 ALD reactor for deposition on silicon substrates 5cm on a side, with MoCl 5、TaCl5 and TiCl 4 as precursors; controlling MoCl 5 and TaCl 5 to evaporate from an open container in the reactor at 90 ℃, storing TiCl 4 in an external container at a constant temperature of 21 ℃ and entering the reactor by means of electromagnetic valve pulse; introducing NH 3 into the reactor through a mass flowmeter, a needle valve and an electromagnetic valve, and regulating the flow to be 14sccm; the pulse time of MoCl 5 and NH 3 is controlled to be 0.5s and 1.0s respectively, and the MoNx film is deposited at 350-500 ℃.
The atomic layer deposition method can prepare nano-scale molybdenum nitride with extremely fine particle size, but has the advantages of slower deposition speed, high reaction cost and low efficiency, and is not suitable for industrial mass production.
Although the three preparation methods of superfine molybdenum nitride have advanced and applied to a certain extent, the preparation methods still have defects in preparation efficiency, energy consumption, cost and the like, so that the application of the preparation methods in the industrial field is limited.
Disclosure of Invention
The invention aims to provide a device and a method for preparing superfine molybdenum nitride powder by reduction and nitridation of gas-phase molybdenum oxide, which greatly reduce equipment investment and operation cost, are simple and convenient to operate, have high yield and can realize green preparation; meanwhile, the molybdenum nitride powder with ultra-fine and uniform particle size can be prepared by using the preparation method of the device.
In order to achieve the above object, the apparatus of the present invention comprises a sublimation zone, a reduction nitriding zone and a cooling deposition zone for placing high purity solid MoO 3, and a heat source for heating the sublimation zone and the reduction nitriding zone, which are sequentially communicated through a nitrogen gas pipe;
The reduction nitriding zone adopts a microchannel reactor with a concentric tube structure, the microchannel reactor comprises an outer tube connected with a nitrogen pipeline and an inner tube connected with a hydrogen pipeline, the tail end of the inner tube is provided with a closed hydrogen pipeline, and pores communicated with the nitrogen pipeline are uniformly distributed on the surface of the inner tube in the reduction nitriding zone in the radial direction.
And a pressure detection meter is arranged on the nitrogen pipeline at the inlet of the sublimation zone.
The sublimation zone is a quartz tube sublimation bin.
And the nitrogen pipeline communicated with the sublimation zone and the reduction nitriding zone adopts a heat-preserving pipeline.
The cooled deposition zone is provided with a bag house for collecting the reactants.
The tail part of the exhaust pipe of the cloth bag dust collector is provided with a nitrogen-hydrogen separation device connected with a nitrogen pipeline and a hydrogen pipeline.
The heat source is a tube furnace heat source.
The method for preparing the superfine molybdenum nitride powder by adopting the device comprises the following steps:
Step one: placing the high-purity solid MoO 3 into a sublimation zone, using N 2 to replace air in the sublimation zone, and heating the sublimation zone by using a heat source to sublimate the high-purity solid MoO 3;
Step two: when the positive pressure of the sublimation area is more than or equal to 50pa, continuously introducing N 2 to drive the sublimation MoO 3 to enter the reduction nitriding area along a nitrogen pipeline, enabling the sublimation MoO 3 and N 2 to form vertical cross air flow with H 2 uniformly blown out from the fine holes on the surface of the inner tube of the microchannel reactor, enabling the volume ratio of the introduced N 2 to the H 2 to be 3:1, and enabling the sublimation MoO 3 to react in the reduction nitriding area to realize homogeneous reduction-nitridation so as to obtain superfine molybdenum nitride powder with uniform particle size.
The temperature of the first step is 600-1000 ℃.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the invention, through sublimation of MoO 3, gas phase reaction is carried out in the mixed atmosphere of N 2 and H 2, and as the particle size of the gas phase reactant is about 100-200nm, the particle size of nitride generated by reduction nitridation is smaller, so that the preparation of superfine molybdenum nitride is realized.
(2) The reduction nitriding zone adopts the microchannel reactor, the narrow channel shortens the transfer time and the transfer distance of reactants, has strong mass transfer characteristic, greatly shortens the molecular diffusion distance, can achieve radial complete mixing in the millisecond level range, and ensures that sublimation MoO 3 and N 2 are instantly and uniformly mixed with H 2 under the simultaneous air, thereby realizing the preparation of ultrafine molybdenum powder with uniform particle size distribution.
(3) The invention can realize the integrated formation from industrial MoO 3 to superfine molybdenum nitride powder with uniform granularity through homogeneous reduction-nitridation, greatly reduces equipment investment and operation cost, reduces the preparation energy consumption of the superfine molybdenum nitride powder, has simple preparation flow, simple and convenient operation and high yield, and can be popularized to the industrial field for large-scale and high-efficiency production.
(4) Compared with the traditional thermal reduction nitriding method, the method avoids the generation and use of harmful gases such as chlorine and the like, and greatly improves the safety of experiments;
Further, the residual N 2 and H 2 after the reaction is separated and reused by the nitrogen-hydrogen separation device, so that an experimental air source and cost are saved, and the green preparation of the molybdenum nitride is realized.
Drawings
FIG. 1 is a schematic diagram of the structure of the device of the present invention;
FIG. 2 is a front view of a microchannel reactor of the apparatus of the present invention;
FIG. 3 is a left side view of a microchannel reactor of the apparatus of the invention;
FIG. 4 is a top view of a microchannel reactor of the apparatus of the present invention;
Wherein: 1-sublimation zone, 2-reduction nitriding zone, 3-cooling deposition zone, 4-pressure detection meter, 5-solid MoO 3, 6-microchannel reactor, 7-heat source, 8-bag dust collector and 9-nitrogen-hydrogen separation device.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
The device as shown in fig. 1 comprises a sublimation zone 1, a reduction nitriding zone 2 and a cooling deposition zone 3 which are communicated in sequence through a nitrogen pipeline and used for placing high-purity solid MoO 3, and a heat source 7 used for heating the sublimation zone 1 and the reduction nitriding zone 2.
The device is integrally communicated, so that equipment investment and operation cost can be greatly reduced, and the preparation energy consumption of the superfine molybdenum nitride powder is reduced. The pressure detection meter 4 is arranged on the nitrogen pipeline at the inlet of the sublimation zone 1 and is used for accurately monitoring the real-time pressure value of the sublimation zone 1; the sublimation zone 1 can adopt a quartz tube sublimation bin, and the quartz tube has higher pressure resistance, so that the safety and stability of the device in operation can be ensured; the nitrogen pipeline which is communicated with the sublimation zone 1 and the reduction nitriding zone 2 adopts a pipeline with heat preservation performance, so that the heat loss can be reduced, and the operation energy consumption can be reduced; the heat source 7 adopts a tube furnace heat source, and can achieve the effects of uniform heating and accurate temperature control. Further, a cloth bag dust collector 8 for collecting reaction gas is arranged in the cooling deposition area 3, so that the dust collection efficiency is high, fine dust with the particle size of more than 0.3 microns can be collected, and the dust collection efficiency can reach more than 99%; the use is more flexible, the processing air quantity can be from hundreds of cubic meters per hour to hundreds of thousands of cubic meters per hour, and the device can be used as a small unit which is directly arranged near an indoor machine tool, and can also be used as a large dust removal chamber; and finally, the structure is simple, the operation is stable, the initial investment is less (compared with an electric dust collector), and the maintenance is convenient. And the tail part of the exhaust pipe of the cloth bag dust collector 8 is provided with the nitrogen-hydrogen separation device 9 connected with the nitrogen pipeline and the hydrogen pipeline, so that residual gas after the reaction is separated and reused through the nitrogen-hydrogen separation device, the experimental gas source and the cost are saved, and the green preparation of the molybdenum nitride is realized.
As shown in fig. 2,3 and 4, the reduction nitriding zone 2 adopts a micro-channel reactor 6 with a concentric tube structure, the micro-channel reactor 6 is divided into an outer tube and an inner tube, the outer tube is a nitrogen gas pipeline, the inner tube is a hydrogen gas pipeline with one end closed, and pores which are uniformly distributed are arranged on the radial direction of the surface of the hydrogen gas pipeline in the reduction nitriding zone 2. The reduction nitriding zone 2 adopts a micro-channel reactor 6, and because the narrow channel shortens the transfer time and the transfer distance of reactants, the micro-channel reactor has strong mass transfer characteristics, so that the molecular diffusion distance is greatly shortened, the radial complete mixing can be achieved in the millisecond range, and the molybdenum trioxide steam, the hydrogen and the nitrogen are instantaneously and uniformly mixed at the same time, thereby realizing the preparation of the superfine molybdenum powder with uniform particle size distribution.
When the device is used for preparing superfine molybdenum nitride powder, the specific steps are as follows:
Step one: placing the high-purity solid MoO 3 into a quartz tube sublimation bin, replacing air in the quartz tube sublimation bin by using N 2, and starting a heat source of a tube furnace to heat the sublimation bin to 600-1000 ℃ to sublimate the high-purity MoO 3;
Step two: when the pressure detection table 4 detects that the positive pressure of the sublimation bin is more than or equal to 50pa, the air outlet valve is opened to continuously introduce N 2 to drive the sublimation MoO 3 to enter the reduction nitriding zone 2 along the axial direction through the heat-preserving nitrogen pipeline, meanwhile, the temperature of the reduction nitriding zone 2 is kept at the sublimation temperature of MoO 3 under the action of the heat source 7, the sublimation MoO 3 and N 2 form vertical cross air flow with H 2 uniformly blown out from the fine holes on the surface of the inner tube of the microchannel reactor 6, the volume ratio of the introduced N 2 to the introduced H 2 is 3:1, and the uniform reduction-nitridation is realized in the reduction nitriding zone 2 to obtain superfine molybdenum nitride powder with uniform particle size.
Under the pushing action of nitrogen, the superfine molybdenum nitride powder and the mixed gas enter a cloth bag dust collector 8 of the cooling deposition area 3, and after the superfine molybdenum nitride powder is cooled and deposited, the rest mixed gas reaches a nitrogen-hydrogen separation device through an exhaust pipe of the cloth bag dust collector 8 for separation and reutilization.
The gas phase reaction has the advantages that the reaction condition is easy to control, and the product is easy to refine; the key is that the concentration, temperature, time and other parameters of the reactants are accurately controlled in the reaction process; namely, the process is precisely controlled, and the product is precisely controlled. The method takes a gas-phase molybdenum source as a raw material source for gas-phase reduction, and utilizes the characteristics of easy sublimation of MoO 3 at more than 600 ℃ and highest sublimation efficiency at about 900 ℃ to realize sublimation of MoO 3 by heating. And the sublimation quantity and molecular weight of MoO 3 are controlled by the temperature and pressure in the sublimation process, and the sublimated MoO 3 steam is blown off by controlling the flow of nitrogen, so that the stable evaporation of molybdenum trioxide is ensured.
The uniform distribution and reaction of the sublimated MoO 3 and H 2/N2 are realized by a gas uniform distribution method, so that the uniformity of the granularity of the nano-scale molybdenum nitride powder is ensured; the reductive nitridation equation can be expressed as: moO 3+3H2＝Mo+3H2O;4Mo+N2＝2Mo2 N.
Claims (9)
1. The device for preparing superfine molybdenum nitride powder by gas-phase molybdenum oxide reduction and nitridation is characterized by comprising a sublimation zone (1), a reduction and nitridation zone (2) and a cooling and deposition zone (3) which are sequentially communicated through a nitrogen pipeline and used for placing high-purity solid MoO 3, and a heat source (7) used for heating the sublimation zone (1) and the reduction and nitridation zone (2);
The reduction nitriding zone (2) adopts a micro-channel reactor (6) with a concentric tube structure, the micro-channel reactor (6) comprises an outer tube connected with a nitrogen pipeline and an inner tube connected with a hydrogen pipeline, the tail end of the inner tube is provided with a closed hydrogen pipeline, and pores communicated with the nitrogen pipeline are uniformly distributed on the surface of the inner tube positioned in the reduction nitriding zone (2) in the radial direction.
2. The device for preparing superfine molybdenum nitride powder by reducing and nitriding gas-phase molybdenum oxide according to claim 1, wherein a pressure detection meter (4) is arranged on a nitrogen pipeline at the inlet of the sublimation zone (1).
3. The device for preparing superfine molybdenum nitride powder by reducing and nitriding gas-phase molybdenum oxide according to claim 1, wherein the sublimation zone (1) is a quartz tube sublimation bin.
4. The apparatus for preparing ultrafine molybdenum nitride powder by gas-phase molybdenum oxide reduction and nitridation according to claim 1, wherein a nitrogen pipeline connecting the sublimation zone (1) and the reduction and nitridation zone (2) adopts a heat-preserving pipeline.
5. The apparatus for preparing ultrafine molybdenum nitride powder by gas-phase molybdenum oxide reduction nitridation according to claim 1, characterized in that the cooling deposition zone (3) is provided with a bag collector (8) for collecting reactants.
6. The device for preparing superfine molybdenum nitride powder by reducing and nitriding gas-phase molybdenum oxide according to claim 5, wherein a nitrogen-hydrogen separation device (9) connected with a nitrogen pipeline and a hydrogen pipeline is arranged at the tail part of an exhaust pipe of the bag dust collector (8).
7. The apparatus for preparing ultrafine molybdenum nitride powder by reducing and nitriding molybdenum oxide in gas phase according to claim 1, wherein the heat source (7) is a tube furnace heat source.
8. An apparatus for preparing ultrafine molybdenum nitride powder by reduction nitridation of gas-phase molybdenum oxide as defined in any one of claims 1 to 7 and a method for preparing ultrafine molybdenum nitride powder, characterized by comprising the steps of:
Step one: placing the high-purity solid MoO 3 into a sublimation zone 1, using N 2 to replace air in the sublimation zone 1, and heating the sublimation zone 1 by using a heat source 7 to sublimate the high-purity solid MoO 3 5;
Step two: when the positive pressure of the sublimation zone (1) is more than or equal to 50pa, continuously introducing N 2 to drive the sublimation MoO 3 to enter the reduction nitriding zone (2) along a nitrogen pipeline, enabling the sublimation MoO 3 and N 2 to form vertical cross air flow with H 2 uniformly blown out from the fine holes on the surface of the inner tube of the microchannel reactor (6), enabling the introduced volume ratio of N 2 to H 2 to be 3:1, and enabling the sublimation MoO 3 to react in the reduction nitriding zone (2) to realize homogeneous reduction-nitridation so as to obtain superfine molybdenum nitride powder with uniform particle size.
9. The method for preparing ultrafine molybdenum nitride powder by gas-phase molybdenum oxide reduction nitridation of claim 8, wherein the temperature rise in the first step is 600-1000 ℃.
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