Production device and production method of nanocarbon

Abstract

To provide a production device and a production method of nanocarbon which can grow nanocarbon at a high yield on a substrate having a surface of a catalyst layer by a chemical vapor deposition process even without a special configuration.SOLUTION: A production device of nanocarbon which brings raw material gas including hydrocarbon into contact with a substrate having a surface of a catalyst layer in a reactor to thereby produce nanocarbon on the substrate by a chemical vapor deposition process includes: the reactor which supplies the raw material gas from an upper end side and discharges gas from a lower end side after reaction by the chemical vapor deposition process; a plurality of substrates which is placed in the reactor; a substrate placement surface on which the substrates are placed; and a raw material gas supply part which supplies the raw material gas. The substrates are placed on the substrate placement surface so as to face one another, with a gas jet axis of the raw material gas supply part being sandwiched therebetween. The substrates are placed at a slant angle of 10 to 85° degrees relative to the jet axis.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for producing nanocarbon. [Background technology]

[0002] Carbon nanotubes (hereinafter also abbreviated as CNTs) have attracted attention as functional carbons with applications such as structural reinforcement and electrical conductors. Various methods for producing CNTs have been researched and proposed, including arc discharge, laser ablation, and chemical vapor synthesis. Among these, chemical vapor synthesis involves contacting a hydrocarbon-containing source gas with a substrate having a catalyst layer on its surface in a reactor, thereby growing nanocarbons on the substrate.

[0003] The apparatus or method for producing nanocarbon by chemical vapor synthesis includes: (1) An apparatus comprising: a substrate holder that is loaded into a reactor along the axial direction, has a mechanism that can engage with the outer edge of one half of a substrate, and holds a plurality of substrates in a parallel arrangement along the axial direction; the engagement mechanism of the substrate holder is configured to tilt the plurality of substrates with respect to a plane perpendicular to the flow direction of the raw material gas in the reactor (Patent Document 1); (2) an apparatus in which the nozzle outlet is opposed to a catalyst support surface, and raw material gas is sprayed from the nozzle toward the catalyst support surface, whereby the raw material gas hits the catalyst support surface from the outlet, reverses, and then flows around the nozzle in the opposite direction to the catalyst support surface; and The following have been reported: (1) a method for growing carbon nanotubes from a catalyst-supported surface (Patent Document 2); (2) a manufacturing method in which raw material gas and catalytically active substances are diffused through an aggregate of grown and aligned carbon nanotubes and brought into contact with a catalyst-coated surface (Patent Document 3); (3) an apparatus equipped with a reactive gas injection section that injects a reactive gas that reduces carbon solids adhering to the inside of an exhaust pipe by causing a chemical reaction with the raw material gas (Patent Document 4); and (5) a manufacturing method including a growth step in which a substrate has a corrugated shape and raw material gas is injected in the depth direction of the corrugated grooves of the substrate from multiple injection ports arranged opposite the substrate (Patent Document 5). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-145317 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-126318 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-47178 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-219316 [Patent Document 5] Japanese Patent Application Laid-Open No. 2013-173639 Summary of the Invention [Problem to be solved by the invention]

[0005] In the device described in Patent Document 1, the substrate is inclined with respect to the plane perpendicular to the flow direction of the source gas, but the multiple substrates are arranged in parallel in the axial direction, resulting in an insufficient yield of nanocarbon per substrate. In the devices described in Patent Documents 2 to 4, the source gas is arranged perpendicular to the substrate, resulting in an insufficient yield of nanocarbon. In the device described in Patent Document 5, a special corrugated substrate is installed, resulting in uneven growth of nanocarbon. Therefore, an object of the present invention is to provide a nanocarbon manufacturing apparatus and manufacturing method that can grow nanocarbon with high yield on a substrate having a catalyst layer on its surface by chemical vapor deposition without requiring a special structure. [Means for solving the problem]

[0006] Therefore, the inventors conducted various studies on the flow of raw material gas and found that if multiple substrates having a catalyst on their surfaces are placed on a substrate mounting surface at an inclination angle of 10 to 85° with respect to the raw material gas injection axis of the raw material gas supply unit, so that they face each other across the raw material gas injection axis, and the raw material gas is supplied to the multiple substrates from above, the raw material gas will remain on the substrates and can be convected beyond the top of the substrates, dramatically improving the yield of nanocarbon grown on the substrates, and thus completed the present invention.

[0007] That is, the present invention provides the following [1] to [6]. [1] A nanocarbon manufacturing apparatus that generates nanocarbon on a substrate by chemical vapor deposition by contacting a raw material gas containing hydrocarbon with a substrate having a catalyst layer on its surface in a reactor, a reaction furnace into which the source gas is supplied from an upper end side and into which a gas resulting from a reaction by a chemical vapor deposition method is discharged from a lower end side; a plurality of the substrates placed in the reaction furnace; a substrate placement surface on which the substrates are placed; and a source gas supply unit that supplies the source gas; A nanocarbon manufacturing apparatus characterized in that the multiple substrates are placed on a substrate placement surface so as to face each other across the gas injection axis of the raw material gas supply section, and the multiple substrates are placed at an inclination angle of 10 to 85° with respect to the injection axis. [2] The nanocarbon manufacturing apparatus according to [1], wherein the substrate has a catalyst layer on both sides. [3] The nanocarbon manufacturing apparatus according to [1] or [2], wherein the substrate is an alloy substrate containing at least iron and chromium. [4] A method for producing nanocarbon, comprising contacting a raw material gas containing hydrocarbon with a substrate having a catalyst layer on its surface in a reactor, thereby producing nanocarbon on the substrate by chemical vapor deposition, a substrate mounting surface for mounting the substrate thereon; and a source gas supply unit for supplying the source gas; A method for producing nanocarbon, wherein the raw material gas is supplied to a plurality of substrates placed on a substrate placement surface so as to face each other across the raw material gas injection axis at an inclination angle of 10 to 85° with respect to the raw material gas injection axis of the raw material gas supply part, and the raw material gas is allowed to stagnate on the substrates and convect beyond the top of the substrates. [5] The method for producing nanocarbon according to [4], wherein the substrate has a catalyst layer on both sides. [6] The method for producing nanocarbon according to [4] or [5], wherein the substrate is an alloy substrate containing at least iron and chromium. [Effects of the Invention]

[0008] According to the present invention, raw material gas is supplied to multiple substrates placed on a substrate mounting surface facing each other across the raw material gas injection axis at an inclination angle of 10 to 85° with respect to the raw material gas injection axis. As a result, the raw material gas stagnates on the multiple substrates and convects over the top of the substrates, resulting in efficient growth of nanocarbon on the multiple substrates and a dramatic improvement in nanocarbon yield. [Brief explanation of the drawings]

[0009] [Figure 1] A schematic diagram of the reactor is shown. [Figure 2] FIG. 1 is a schematic diagram showing an example of installation of two substrates on a substrate installation surface. [Figure 3] 1A and 1B are a schematic front view (left) and a schematic top projection view (right) showing an example of installation of two substrates on a substrate installation surface. [Figure 4] FIG. 1 is a schematic diagram showing an example of installation of three substrates on a substrate installation surface. [Figure 5] 1A and 1B are a schematic front view (left) and a schematic top projection view (right) showing an example of installation of three substrates on a substrate installation surface. DETAILED DESCRIPTION OF THE INVENTION

[0010] One aspect of the present invention is a nanocarbon production apparatus that produces nanocarbon on a substrate having a catalyst layer on its surface by chemical vapor deposition by bringing a raw material gas containing hydrocarbons into contact with the substrate in a reactor. Specifically, the apparatus includes a reactor into which the source gas is supplied from the upper end side and which discharges gas after the reaction by chemical vapor deposition from the lower end side, a plurality of the substrates placed in the reactor, a substrate placement surface on which the substrates are placed, and a source gas supply unit which supplies the source gas, The nanocarbon manufacturing apparatus is characterized in that the plurality of substrates are placed on a substrate placement surface so as to face each other across the gas injection axis of the raw material gas supply unit, and the plurality of substrates are placed at an inclination angle of 10 to 85° with respect to the injection axis.

[0011] <Nanocarbon> Nanocarbon in the present invention refers to carbon of nanometer size, and specific examples include carbon nanotubes (CNTs), carbon nanofibers, graphene, fullerenes, etc. According to the present invention, nanocarbon including CNTs can be produced in a short time with high yield.

[0012] <Reactor> As shown in FIG. 1, the reactor is a container in which multiple substrates are placed and nanocarbon is produced by chemical vapor deposition, and is equipped with a chamber capable of accommodating the substrates and a heater. The chamber is not particularly limited as long as it can withstand the reaction temperature for producing nanocarbon (700 to 1000°C). For example, quartz glass or the like can be used. The reactor also has a source gas supply unit inside, which sprays the source gas toward the substrates. It also has a substrate mounting surface on which the substrates are placed.

[0013] <Source gas> The source gas is a gas containing a hydrocarbon. A chain or cyclic hydrocarbon, an unsaturated hydrocarbon, or the like can be used as the hydrocarbon, and there is no particular limitation thereon. However, from the viewpoint of reactivity, ethylene and acetylene are preferred. Furthermore, as the hydrocarbon-containing gas, hydrogen, argon, nitrogen, or the like is preferably used in addition to hydrocarbons. Furthermore, in order to promote the production of nanocarbon, it is preferred that the gas contains a small amount of water vapor, carbon monoxide, carbon dioxide, oxygen, or a compound containing an oxygen atom, such as an alcohol such as ethanol or a ketone such as acetone.

[0014] <Substrate> The substrate in the present invention is not particularly limited as long as it has a catalyst layer on its surface capable of decomposing hydrocarbons, but an alloy substrate is preferred. A wide variety of alloys used as heat-resistant alloys can be used as the alloy substrate. In particular, it is preferred that the substrate contains a metal that can act as a catalyst for decomposing hydrocarbons to produce carbon (nanocarbon). Specifically, it is preferred that the substrate contains one or more metals selected from the group consisting of Fe, Ni, Cu, Pt, Au, Ru, Pd, and Rh. In particular, for industrial CNT production, it is preferred that the substrate contain Fe and / or Ni, and it is particularly preferred that the substrate contain Fe. In order to ensure good dispersion of the catalytic metal, it is preferable that the catalyst contains, in addition to the catalytic metal, one or more metals capable of forming a passivation layer selected from the group consisting of Al, Ti, Cr, Mg, Si, Mn, and Mo. In particular, it is preferable that the catalyst contains Cr. Examples of such alloys include various SUS stainless steels, nickel alloys such as nichrome, various Inconels, invar, permalloy, etc. Among these, SUS304, 316, 310S, 410S, and Inconel 600 and 601 are preferred.

[0015] <Installation of the board> The substrates in the present invention are placed on a substrate placement surface in a reactor. As shown in Figures 2 to 5, two or more substrates are placed on the placement surface so that they face each other across the injection axis of the gas supply unit, and are placed at an inclination angle of 10 to 85° with respect to the injection axis. If the inclination angle is less than 10°, the supply of source gas to the gap between the substrates is insufficient, making it impossible to obtain a sufficient yield of nanocarbon. On the other hand, if the inclination angle is greater than 85°, the source gas supplied between the substrates quickly flows to the bottom of the reaction tube, and the supply of source gas to the backside of the gap between the substrates is insufficient, making it impossible to obtain a sufficient yield. The inclination angle is preferably 20 to 80°, more preferably 30 to 70°. In addition, when there is only one substrate, even if the substrate is set at an inclination angle of 10 to 85°, the source gas quickly flows to the bottom of the reaction tube after being supplied to the substrate, and therefore a high yield cannot be obtained. By arranging multiple substrates as described above, the source gas remains on the multiple substrates and convects over the top of the substrates, causing nanocarbon to grow on both sides of the multiple substrates, dramatically improving the yield of nanocarbon. Here, the phrase "two or more substrates are placed facing each other" does not only mean that they are completely opposite to each other, but also includes cases where the angle or surface is partially misaligned, as in the case of the three substrates below.

[0016] The substrate may have a flat plate shape or a curved plate shape, and may have a shape that is narrow at the bottom and wide at the top. The number of substrates may be two or more, and may be two as shown in Figures 2 and 3, or three substrates arranged around the ejection axis (Figures 4 and 5), or four or more substrates arranged facing each other around the ejection axis. The substrate mounting means may be configured so that the source gas remains above the substrates and convects over the substrates, and may be configured so that the substrates are spaced apart from each other on the substrate mounting surface, as shown in Figures 2 and 3, or so that the lower portions of the substrates are in contact with the substrate mounting surface. Furthermore, as shown in Figures 4 and 5, the substrates may be mounted on the mounting surface so that the substrates face each other across the injection axis of the gas supply unit. If the substrate has a curved surface, it is set so that the angle between the tangent plane at the center of the curved surface and the injection axis is an inclination angle of 10 to 85°.

[0017] <Nanocarbon manufacturing method> Another aspect of the present invention is a method for producing nanocarbon, which comprises contacting a raw material gas containing hydrocarbon with a substrate having a catalyst layer on its surface in a reactor, thereby producing nanocarbon on the substrate by chemical vapor deposition. Specifically, the apparatus includes the substrate, a substrate mounting surface on which the substrate is mounted, and a source gas supply unit that supplies the source gas, The method for producing nanocarbon is characterized in that the raw material gas is supplied to a plurality of substrates placed on a substrate mounting surface so as to face each other across the raw material gas injection axis at an inclination angle of 10 to 85° with respect to the raw material gas injection axis of the raw material gas supply unit, and the raw material gas is allowed to stagnate on the substrates and convects over the substrates, as will be described in detail below.

[0018] A source gas containing hydrocarbons is supplied from a source gas supply unit at the upper end of the reactor. The hydrocarbons contained in the source gas are not particularly limited, but from the viewpoint of reactivity, chain or cyclic hydrocarbons or unsaturated hydrocarbons are preferred, with ethylene and acetylene being particularly preferred. Furthermore, in addition to hydrocarbons, hydrogen, argon, nitrogen, and the like are preferably used as the source gas. Furthermore, in order to promote the production of nanocarbons, it is preferable for the source gas to contain a small amount of water vapor, carbon monoxide, carbon dioxide, oxygen, or a compound containing an oxygen atom, such as an alcohol such as ethanol or a ketone such as acetone.

[0019] As shown in Figures 3 and 5, the source gas is supplied to multiple substrates placed on a mounting surface, facing each other across the source gas injection axis, at an inclination angle of 10 to 85° with respect to the source gas injection axis of the source gas supply unit. The source gas is supplied to the substrate mounting surface or below the substrate mounting surface and then remains on the substrate. It then convects toward the top of the substrate, convects from the top of the substrate toward the bottom of the reactor, and is discharged from the bottom exhaust unit to the outside of the reactor. In this case, if a substrate having a catalyst layer on both sides is used, the source gas that has reached the back side of the substrate reacts with the catalyst layer on the back side, producing nanocarbon on the back side of the substrate as well. This further increases the nanocarbon yield per unit area of ​​substrate. The substrate is heated to a reaction temperature at which hydrocarbons are decomposed to produce nanocarbons by an external heater, etc. The reaction temperature is preferably 500 to 1000°C, more preferably 700 to 900°C. [Example]

[0020] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0021] Examples 1 to 3 and Comparative Examples 1 to 2 The alloy substrate used was a SUS304 substrate (25 x 2 mm) with a 2B finish on both sides. It was ultrasonically cleaned in acetone for 40 minutes and then in ethanol for 20 minutes before use in the test. This alloy substrate was subjected to pickling treatment by immersing it in an acidic solution of 100 ml of nitric acid and 1.85 g of sodium fluoride for 5 minutes. After immersion, it was ultrasonically cleaned in distilled water for 15 minutes and then in acetone for 5 minutes. It was then subjected to thermal oxidation treatment at 850°C for 1 hour in a box-type electric furnace with a dry air flow rate of 2 L / min. It was then subjected to reduction treatment at 600°C for 1 hour with a hydrogen and argon mixed gas (90% hydrogen, 10% argon) flow rate of 4 L / min, yielding a catalytically active alloy substrate. This alloy substrate was placed in a reactor, and a mixed gas containing hydrocarbons (ethylene 5%, carbon dioxide 5%, hydrogen 75%, argon 15%) was supplied at 2 L / min. The reaction was carried out at 780°C for 30 minutes, producing nanocarbons (including CNTs) on the alloy substrate. As shown in Figures 2 and 3, two alloy substrates were placed facing each other across the axis of the reactive gas injection, with a V-shape and a gap of approximately 2 mm between the lower parts, and tests were conducted with different tilt angles. The test results are shown in Table 1.

[0022] [Table 1]

[0023] As shown in Table 1, if chemical vapor deposition reaction is carried out in a reactor equipped with a substrate as in the present invention, the yield of nanocarbon is dramatically improved.

Claims

1. A nanocarbon manufacturing apparatus for producing nanocarbon on a substrate having a catalyst layer on its surface by chemical vapor deposition by bringing a raw material gas containing hydrocarbon into contact with the substrate in a reactor, a reaction furnace into which the source gas is supplied from an upper end side and into which a gas resulting from a reaction by a chemical vapor deposition method is discharged from a lower end side; a plurality of the substrates placed in the reaction furnace; a substrate placement surface on which the substrates are placed; and a source gas supply unit that supplies the source gas; A nanocarbon manufacturing apparatus characterized in that the multiple substrates are placed on a substrate placement surface so as to face each other across the gas injection axis of the raw material gas supply section, and the multiple substrates are placed at an inclination angle of 10 to 85° with respect to the injection axis.

2. 2. The nanocarbon manufacturing apparatus according to claim 1, wherein the substrate has catalyst layers on both sides.

3. 3. The nanocarbon manufacturing apparatus according to claim 1, wherein the substrate is an alloy substrate containing at least iron and chromium.

4. A method for producing nanocarbon by bringing a raw material gas containing hydrocarbon into contact with a substrate having a catalyst layer on its surface in a reactor, thereby producing nanocarbon on the substrate by chemical vapor deposition, comprising: a substrate mounting surface for mounting the substrate thereon; and a source gas supply unit for supplying the source gas; A method for producing nanocarbon, characterized in that the raw material gas is supplied to a plurality of substrates placed on a substrate placement surface so as to face each other across the raw material gas injection axis at an inclination angle of 10 to 85° with respect to the raw material gas injection axis of the raw material gas supply part, and the raw material gas is allowed to stagnate on the substrates and convect beyond the top of the substrates.

5. The method for producing nanocarbon according to claim 4, wherein the substrate has a catalyst layer on both sides.

6. 6. The method for producing nanocarbon according to claim 4, wherein the substrate is an alloy substrate containing at least iron and chromium.

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