Apparatus and method for producing graphene and hydrogen

Abstract

A method and apparatus are described for producing graphene from a hydrocarbon feedstock by pyrolysis of hydrocarbons and recovering hydrogen gas, a by-product of pyrolysis that may be present in the hydrocarbon feedstock. The apparatus has an elongated reactor having a first end and a second end, the first end configured to receive a hydrocarbon feedstock, a channel defined between the first end and the second end for conveying a fluid, the fluid being a reaction mixture comprising the hydrocarbon feedstock. The apparatus has an end section attached to the second end, the end section being selectively permeable to hydrogen gas and impermeable to other components of the reaction mixture, and a hydrogen recovery section attached to the second end to receive hydrogen gas from the end section, the hydrogen recovery section being impermeable to hydrogen gas.

Description

[Technical field]

[0001] This application relates generally to the production of graphene by pyrolysis of hydrocarbons. More specifically, this disclosure relates to an apparatus and method for producing graphene by pyrolysis of hydrocarbons, such as methane, in the presence of a catalyst, and separating and recovering the hydrogen by-product. [Background technology]

[0002] Graphene is an allotrope of carbon composed of a single layer of atoms arranged in a two-dimensional lattice. Since its development, graphene has been found to be useful in many areas, including but not limited to water purification, medicine, construction, electronic chips, and quantum computing. Each of these uses typically requires a graphene material to have specific properties that can vary depending on, for example, the length and number of graphene layers that form the graphene material. Summary of the Invention [Problem to be solved by the invention]

[0003] Some existing methods for forming graphene involve the catalytic pyrolysis of hydrocarbons such as methane or natural gas into solid carbon and hydrogen, in which the hydrogen produced is often an unused or unwanted by-product.

[0004] There is an ever-increasing industrial demand for both graphene and hydrogen, and therefore, there is an ongoing need to develop improved methods and apparatus for producing graphene and hydrogen. [Means for solving the problem]

[0005] Provided herein are methods and apparatus for producing graphene by pyrolysis of hydrocarbons from a hydrocarbon feedstock and recovering hydrogen gas, a by-product of the pyrolysis, which may also be present in the hydrocarbon feedstock.

[0006] In one aspect, an apparatus for producing graphene and hydrogen includes: The apparatus includes an elongated reactor, the reactor comprising: a first end and a second end, the first end configured to receive a hydrocarbon feedstock; a channel defined for conveying a fluid between said first end and said second end, said fluid being a reaction mixture comprising said hydrocarbon feedstock; and an end section attached to the second end, the end section being selectively permeable to hydrogen gas and impermeable to other components of the reaction mixture; a hydrogen recovery compartment attached to the second end to receive hydrogen gas from the end compartment, the hydrogen recovery compartment being impermeable to hydrogen gas; An apparatus is provided having the following structure:

[0007] In one embodiment, the reactor further comprises an inlet between the first and second ends for adding catalytic metal particles to the reaction mixture.

[0008] In another embodiment, the reactor is constructed of iron.

[0009] In yet another embodiment, the end sections are constructed from stainless steel.

[0010] In yet another embodiment, the reactor further comprises at least one heating element for heating the reaction mixture within the channel.

[0011] In yet another embodiment, the reactor further comprises a sleeve disposed about the reactor adjacent the at least one heating element, the sleeve being constructed from a hydrogen impermeable material and defining an enclosed space between the sleeve and the reactor.

[0012] In yet another embodiment, the hydrogen impermeable material is a ceramic material.

[0013] In another aspect, a method for producing graphene and hydrogen includes the steps of: The method comprises: introducing a hydrocarbon feed into a first zone of a reactor; heating the first zone to above about 300° C. to decompose the hydrocarbons and produce a reaction mixture containing nascent carbon; introducing the reaction mixture into a second zone of the reactor; heating the second region to above about 1000° C. to react the nascent carbon with catalytic metal particles to produce graphene fibers; extracting hydrogen gas from the reaction mixture, the mixture exiting the second region and contacting a terminal end of the reactor that is coated with a material that is permeable only to hydrogen gas; A method is provided comprising:

[0014] In some embodiments, the reaction mixture includes co-delivered catalytic metal particles.

[0015] In another embodiment, the interior surface of the second region is nucleated with metal particles before the hydrocarbon feed is introduced into the reactor. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view of one embodiment of an apparatus for producing graphene and hydrogen. [Diagram 2] 1 is a cross-sectional view of another embodiment of an apparatus for producing graphene and hydrogen, the apparatus being further configured to control hydrogen content. [Diagram 3] FIG. 1 shows a schematic of a reactor and heating system for producing graphene and hydrogen. [Figure 4] FIG. 1 illustrates a system for producing graphene and hydrogen. [Diagram 5]FIG. 1 illustrates a system for producing graphene and hydrogen. [Figure 6] FIG. 1 illustrates a packed bed reactor for producing graphene and hydrogen. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment will be described with reference to the accompanying drawings.

[0018] Throughout this specification, one or more of the terms "front," "rear," "back," "vertical," "vertically," "horizontal," "horizontally," "top," "bottom," "upward," "downward," "internally," "externally," "up," "down," "right," and "left" are used. It is understood that these terms are not intended to be limiting. These terms are used for convenience and as an aid in describing features described herein, for example, as illustrated in the accompanying drawings.

[0019] Below, methods and equipment are described for producing graphene from a hydrocarbon feedstock by pyrolysis of hydrocarbons and recovering hydrogen gas, a by-product of pyrolysis, that may be present in the hydrocarbon feedstock. As shown below, the production of graphene instead of graphite / carbon black can be facilitated by the introduction of a catalyst in several ways.

[0020] FIG. 1 shows an apparatus, or reactor 10, for the production of graphene and hydrogen. The reactor 10 has a tube 12 that defines a continuous gas passageway 3 between a first end or inlet 1 and a second end or outlet 11 of the tube 12. A feedstock 34, including a hydrocarbon such as methane or natural gas, can flow through the inlet. A furnace 16 is provided around the reactor 10, including a helical electrical resistance heating element 18, to heat a first reaction zone 13 within the tube 12. Similarly, a second furnace 20 is provided around the reactor 10, including a helical electrical resistance heating element 22, to heat a second reaction zone 15 within the tube 12.

[0021] In alternative embodiments, there may be multiple tubes 12 and / or the tubes 12 may define a curved or straight continuous gas passage 3. Although two heating elements (18, 22) and furnaces (16, 20) are shown, the reactor 10 may include any number of heating elements / furnaces (collectively "heating elements"). The heating elements may be of any suitable type, such as, for example, standard, inductive or flame heating elements.

[0022] Heating elements 18 and 22 may be heated to suitable temperatures to create a desired temperature profile within tube 12 to grow graphene fibers. For example, heating elements 18 and 22 may be operated such that tube 12 has a low temperature (e.g., 300° C.) in zone 13 near inlet 1 and a high temperature (e.g., 1000° C.) in zone 15 near outlet 11. The hydrocarbon feedstock 34 may be diluted with other gases, such as hydrogen. The flow rate of feedstock 34 into tube 12 may be adjusted as needed. A higher flow rate of feedstock 34 into tube 12 may produce longer and / or thinner graphene fibers 6. Various elements, primarily metals, may be combined with gas stream 3 in zone 13, for example in the form of organic or inorganic salts.

[0023] In some embodiments, iron pentacarbonyl vapor may be fed into or upstream of zone 13. As the gas passes through heated zone 13, the metal compounds - in this example iron compounds - may decompose to produce iron particles 36, the size of which is exaggerated in Figures 1 and 2 for ease of illustration. As previously mentioned, the metal catalyst compound may be iron, which may hereafter be referred to as the "catalyst."

[0024] The iron particles 36 are entrained with the gas flow and transported through the tube 12 towards the outlet 11. Within the heating zone 15, methane may be decomposed from the natural gas. The resulting nascent carbon may react with the iron particles 36 to produce fine graphene filaments 6. The deposition of additional nascent carbon may thicken the graphene filaments 6 by stacking additional individual filaments on the graphene filaments 6. Once the reaction is complete, the graphene filaments 6 may be collected in any suitable manner. For example, a suitable tool, such as a ring or set of rings configured for insertion into the tube 12, may be used to scrape or knock the graphene off the inner walls of the tube 12. This is also fine.

[0025] The reactor 10 may have an end section 7, which is composed of a material that is permeable to hydrogen gas and substantially or completely impermeable to other gases in the tube 12, such as methane gas or inert gases. The end section 7 may be attached (e.g., threadedly or by welding) to the outlet 11 of the tube 12. During pyrolysis of the hydrocarbon feedstock, hydrogen may pass through the end section 7 (see arrow 19) and enter the hydrogen recovery section 2. The hydrogen recovery section 2 may be composed of a material that is impermeable to hydrogen or has a resistance to the passage of hydrogen, such as a ceramic material or iron. The hydrogen 5 may then be discharged from the recovery section 2 through the outlet 4 and may be further processed or stored (not shown).

[0026] Under certain conditions, such as high heat and / or pressure, tube 12, constructed of iron in this embodiment, may allow some hydrogen to pass through. Thus, if desired, device 10 may include an impermeable (to hydrogen) sleeve 8 disposed around tube 12 and heater 20 to recover any hydrogen that may pass through tube 12. Sleeve 8 may be made of or include a hydrogen impermeable material, such as, for example, a ceramic material or iron. Any number of such sleeves 8 may be installed as required.

[0027] Referring to FIG. 2, the apparatus 10 may further include one or more hydrogen recovery lines 35, constructed of a hydrogen permeable material, such as 304 stainless steel. The lines 35 may be used to remove hydrogen from within the tube 12, providing some control over the hydrogen content within the reactor 10, which may be beneficial for the pyrolysis reaction. Such lines 35 may also enhance turbulence within the tube 12. Increased turbulence may increase the uniformity of the graphene distribution on the walls of the tube 12. Other objects or modifications to the tube 12 may be used to enhance turbulence, alone or in combination with the lines 35. In some embodiments, plasma and / or microwave heating may be used alone or in combination with the heaters mentioned above. In some embodiments, the tube 12 may be constructed of a ceramic material or other material that is impermeable to hydrogen gas. In some embodiments, a device for collecting graphene, such as a cloth or mesh filter, may be placed within the tube 12. In some embodiments, the tube 12 is a tubular iron reactor, and the graphene fibers 6 may be grown on the inner walls of the tube 12, and primarily within region 15. The primary location of growth of the graphene fibers 6 may vary depending on factors such as the dimensions of the tube 12 and the temperature profile therein.

[0028] Various metal particles may be obtained from suitable precursor compounds and used as nuclei for graphene filament formation. For example, iron particles may be formed by evaporating a ferric nitrate solution on a suitable surface and decomposing the resulting iron oxide residue. The effectiveness of nucleation depends, at least in part, on the metal particle size, and therefore the metal particle size (degree of elemental metal coalescence) may be adjusted, for example, depending on the desired graphene filament growth rate and properties. As will be appreciated by those skilled in the art, the dissociation rate and particle formation rate are temperature dependent and may vary depending on the metal precursor used. In general, one or more variables, such as the temperature profile across the tube 12, the dimensions and configuration of the tube 12, the location of introduction of the metal precursor, the type of metal nuclei, and the flow rate of the gas stream, may be adjusted to obtain the desired type of graphene.

[0029] In some embodiments, the fibers may be grown on the inner surface of the tube 12 on which metal nuclei have been deposited. Prior to the initiation of pyrolysis, the inner wall may be nucleated by in-situ decomposition of a metal precursor compound, such as an iron carbonyl compound. In one embodiment, the metal precursor is iron pentacarbonyl, Fe(CO) 5 The iron carbonyl may be injected into a stream of inert gas (e.g., argon) at ambient temperature, which may vaporize the iron carbonyl. The stream of inert gas carries the vapor to the reactor, and the flow rate of the stream may be controlled to achieve a desired dispersion of the iron particles within the tube 12.

[0030] As described below, in some embodiments, the catalyst may react with a stream (102) that is composed primarily of methane gas and may contain small amounts of other hydrocarbon gases, such as ethane, propane, or other gases that are often found in trace amounts in oil field produced gas. Gases added to or contained in the oil field gas include H 2 S, mercaptans, and / or other sulfur-containing compounds. Such sulfur gases are important in the formation of various graphites and graphenes.

[0031] In an embodiment, for example, as shown in FIG. 3 illustrating a reactor system 100, the catalyst is provided as a gas suspension, which may be mixed with a feed stream 102 (which may be referred to as "methane gas" or "methane gas stream") that contains primarily methane gas that has been preheated to 500° C. with a heater (110). The feed stream 102 may be at ambient temperature prior to preheating with the heater 110. Multiple preheaters may be included. A portion of the methane gas stream (i.e., the feed stream 102) may first be diverted through a catalyst solution 118 and bubbled through the liquid, leaving it loaded with the suspended catalyst. A diffuser 116 may be used to bubble the liquid through the liquid catalyst solution 118 in another vessel 108. The combined stream 106 then enters an open reactor 114, where it may be heated to 950 to 1100° C., depending on the catalyst used. A pre-heater 110 (which may be, for example, a resistive, inductive, plasma, microwave, or flame-driven heater) may generate a pre-heated reactor feed 112 that enters an open reactor 114. Graphene nanotubes may be produced within such reactor 114 along with hydrogen, methane, and reaction by-products, and more generally, as the output 120 of the reactor system 100 shown in Figure 3. As previously mentioned, this may optionally include a liquid catalyst recycle in addition to the pre-heater 110.

[0032] Alternatively, the catalyst may be distributed throughout the reactor 114, either alone or in combination with features of the liquid catalyst solution 118. This may be done by attaching metal gratings or in a manner similar to that done with latch rings in distillation columns of various sizes and shapes. If this approach is used, the reactor may be quickly opened and most or all of the catalyst matrix may be easily and / or quickly drained and replaced with new catalyst. In this example embodiment, larger stripes of graphite or graphene may be produced. The operating temperature may be between 950°C and 1050°C.

[0033] The catalyst may also be introduced by wetting the walls of the reactor 114 with a catalyst solution. The reactor 114 is operated at 950 to 1150° C. and the gas feed is preheated to 500° C. before entering the reactor. With this approach, graphite and graphene in mixtures of sizes from 8 cm long to 3-6 microns long may be produced.

[0034] As shown in FIG. 4, the reactor system 100 may be part of a system 300 for producing graphene and hydrogen. The system 300 may have a filtration system 306 that receives the output 120 of the reactor system 100. The filtration system 306 may have one or more filters (e.g., a coarse filter 304 and a fine filter 308) that are progressively finer toward the outlet. The filtration system 306 may be closed as needed and periodically opened to remove graphene therefrom, for example, by shaking or vibration, and an outlet stream of gas may be produced. This gas may contain traces of graphene (312), which may be further filtered, if necessary, using an electrostatic filter 314 and emptied, for example, by periodic shaking or vibration. The substantially or completely graphene-free gas 316 may then be conveyed to a heat exchanger 320, cooled, and a cooled outlet gas 322 containing hydrogen and methane may be produced. The outlet gas may then be conveyed to a filtration system, such as a pressure swing adsorption (PSA) system 324, to produce hydrogen 326, which may be conveyed to storage 330. The PSA system 324 also produces a recycled hydrocarbon feed 328, which may be sent back to the reactor system 100. If necessary, the inlet feed 102 may be heated by a heat exchanger 320 to form a preheated stream 112, which may be combined with the recycle stream 328 to produce a combined recycled preheated stream 113. If necessary, the recycled preheated stream 113 may be further preheated within the reactor system 100.

[0035] As shown, multiple filters may be used to perform the separation of graphene and hydrocarbon / hydrogen gas, starting with a coarse filter, then a finer filter, then another fine filter, and so on until all the carbon solid material is removed. Each coarse filter may retain some of the fine carbon material, and the final filter may be one micron or smaller, and each coarse filter may work in conjunction with another filter or filters, so that while one filter is filtering, the other filter is being washed. The final filter may have a dead area in front of it to allow carbon to settle. If necessary, an electrostatic precipitator separator may be included.

[0036] Once the carbon is removed, the hydrocarbon stream (consisting mainly of methane) and hydrogen gas proceed to either a pressure swing adsorption system, or a membrane separation system where the hydrogen and hydrocarbon gases are separated. The membrane separation system provides hydrogen at or near 99.99% purity, and all other gases may be recycled back. Gas separation systems tend to struggle at high temperatures, so a cooling phase before separation and a heating stage for the recycled hydrocarbon gases before returning them to the reactor feed gas may be provided. Piping may be used for heating and cooling, or the inlet gas may be used to heat the gas exhausted to the reactor. Any remaining heat may be used to heat the original gas feed.

[0037] FIG. 5 shows another example of a system for producing graphene and hydrogen. The system has a hydrocarbon feed 402 (as described above) that is introduced into a fluidized bed reactor 400 containing a metal catalyst through which the feed 402 may produce a mixture (stream 404) of graphene, hydrocarbons, hydrogen, and other by-products. The reactor may alternatively or in combination with a catalytic fluid, contain a catalyst deposited on the reactor walls and / or may have a catalyst in the form of an aerosol mixed with the feed as it enters the reactor 400. The stream 404 then enters a pre-heater 406, which may be heated by any of the means described above and may have an acoustic element, if necessary, to facilitate the passage of the produced solids. A pre-heated stream 408 produced by the pre-heater 406 enters another heater 410, which may have an acoustic element (not shown) to facilitate the passage of the produced solids as described above. The heater 410 may produce a recycle stream of hydrocarbons and hydrogen.

[0038] For brevity and clarity of description, where considered appropriate, reference numerals have been repeated throughout the figures to designate corresponding or similar elements. Additionally, numerous specific details have been described in order to provide a thorough understanding of the embodiments described herein. However, it will be apparent to one skilled in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the described embodiments. Additionally, the description is not intended to limit the scope of the embodiments described herein.

[0039] The examples and corresponding figures used herein are for illustrative purposes only. Different configurations and terminology may be used without departing from the principles expressed herein. For example, components and modules may be added, removed, modified, or arranged in different relationships without departing from these principles.

[0040] The steps or operations in the flowcharts and figures described herein are merely examples. There may be many variations to these steps or operations without departing from the principles described above. For example, steps may be performed in a different order, or steps may be added, deleted, or modified.

[0041] Although the foregoing principles have been described with reference to certain specific embodiments, various modifications thereof, as set forth in the appended claims, will be apparent to those skilled in the art.

Claims

1. An apparatus for producing graphene and hydrogen, the apparatus comprising: an elongated reactor having a first end and a second end, the first end being configured to receive a hydrocarbon feedstock; a channel defined between the first end and the second end for carrying a fluid therebetween, the fluid being a reaction mixture comprising the hydrocarbon feedstock; an end section attached to the second end and selectively permeable to hydrogen gas and impermeable to other components of the reaction mixture; a hydrogen recovery section attached to the second end and configured to receive hydrogen gas from the end section, the hydrogen recovery section being impermeable to hydrogen gas.

2. The apparatus of claim 1, wherein the reactor further comprises an inlet between the first and second ends, the inlet being for adding catalytic metal particles to the reaction mixture.

3. The apparatus of claim 1 or 2, wherein the reactor is made of iron.

4. The apparatus of claim 1 or 2, wherein the end section is made of stainless steel.

5. The apparatus of claim 1 or 2, wherein the reactor further comprises at least one heating element for heating the reaction mixture within the channel.

6. The apparatus of claim 5, further comprising a sleeve disposed around the reactor in the vicinity of the at least one heating element, the sleeve being made of a hydrogen-impermeable material and defining a sealed space between the sleeve and the reactor.

7. The apparatus of claim 6, wherein the hydrogen-impermeable material is a ceramic material.

8. The apparatus of claim 1 or 2, wherein the channel has a catalytic packing in the form of metal beads.

9. The apparatus of claim 8, wherein the metal beads are an iron compound.

10. A method for producing graphene and hydrogen, the method comprising: introducing a hydrocarbon feed into a first region of a reactor; heating the first region to about 300 °C or more to decompose the hydrocarbon and produce a reaction mixture containing nascent carbon; introducing the reaction mixture into a second region of the reactor. ​ ​ ​ ​ ​ heating the second region to about 1000 °C or higher to react the nascent carbon with catalytic metal particles to produce graphene fibers; extracting hydrogen gas from the reaction mixture, the mixture being discharged from the second region and contacting a terminal portion of the reactor coated with a material through which only hydrogen gas can permeate; A method comprising. **Claim 11** The method according to claim 10, wherein the reaction mixture comprises catalytic metal particles co-transported. **Claim 12** The method according to claim 10, wherein the inner surface of the second region is nucleated with metal particles before the hydrocarbon feed is introduced into the reactor. **Claim 13** A method for producing graphene and hydrogen, The method comprises: introducing a hydrocarbon feed into a first region of a reactor; heating the first region to about 300 °C or higher to decompose the hydrocarbon and produce a reaction mixture containing nascent carbon; introducing the reaction mixture into a second region of the reactor; heating the second region to about 1000 °C or higher to react the nascent carbon with catalytic metal particles to produce graphene fibers; extracting hydrogen gas from the reaction mixture, the mixture being discharged from the second region and contacting a terminal portion of the reactor coated with a material through which only hydrogen gas can permeate; A method comprising.

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