Hydrocarbon decomposition catalyst and methods of use and recovery

Abstract

Making a hydrocarbon decomposition catalyst includes contacting ferric chloride and a hydrocarbon reactant at a temperature greater than 320 oC and reducing the ferric chloride to yield a product. The product includes a product gas and the hydrocarbon decomposition catalyst. The hydrocarbon decomposition catalyst includes a multiplicity of particles, and each particle of the multiplicity of particles includes iron and carbon.

Description

Attorney Docket No.: 44807-0498WO1 / JHU18371HYDROCARBON DECOMPOSITION CATALYST AND METHODS OF USE AND RECOVERYCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 749,987 filed on January 27, 2025, which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] This invention relates to synthesizing a catalyst used to decompose hydrocarbons to hydrogen and solid carbon and methods to regenerate the catalyst material.BACKGROUND

[0003] Hydrogen is vital in the production of ammonia and petrochemicals and is seeing increased use in metallurgical processes, transportation, and energy production. Methods of hydrogen production, such as combustion and steam methane reforming (SMR), result in significant carbon dioxide emissions. This environmental impact has spurred a global search for alternate, more sustainable methods of hydrogen production.SUMMARY

[0004] This disclosure describes processes for generating hydrogen from hydrocarbons (e.g., hydrocarbons found to naturally occur in natural gas) via reduction of FeCh by the hydrocarbons. This process results in the production of hydrogen chloride gas, hydrogen, and a solid phase of mixed iron-carbon powder. FeCh can be regenerated from the hydrogen chloride gas produced in the reduction of FeCh by hydrocarbons.

[0005] In a general aspect, making a hydrocarbon decomposition catalyst includes contacting ferric chloride and a hydrocarbon reactant at a temperature greater than 320 °C, and reducing the ferric chloride to yield a product. The product includes a product gas and the hydrocarbon decomposition catalyst. The hydrocarbon decomposition catalyst includes a multiplicity of particles. Each particle includes iron and carbon.

[0006] Implementations of the general aspect may include one or more of the following features.Attorney Docket No.: 44807-0498WO1 / JHU18371

[0007] The temperature can be greater than 925 °C, less than 1500 °C, or both. The product gas can include at least 75 vol% hydrogen gas and less than 20 vol% hydrogen chloride gas. In some implementations, the temperature is greater than 1000 °C, and the product gas further includes some of the hydrocarbon reactant.

[0008] The hydrocarbon decomposition catalyst has a stoichiometric atomic ratio of iron to carbon of 4:3. Some implementations include catalyzing reduction of the hydrocarbon with the decomposition catalyst, thereby increasing a relative content of carbon in the hydrocarbon decomposition catalyst. As the amount of carbon increases, the atomic ratio of iron to carbon decreases from 4:3 to a ratio in a range of 1 : 1 to 1 : 100 (e.g., 1 :5 to 1:50).

[0009] The multiplicity of particles can include at least some agglomerates of the particles. An average particle diameter of particles in the multiplicity of particles can be in a range of 10 microns to 50 microns. The agglomerates of particles can have a fractal morphology. The general aspect can further include grinding the multiplicity of particles to yield an average particle diameter in a range of 1 micron to 10 microns.

[0010] The hydrocarbon reactant can include methane, ethane, propane, butane, higher alkanes, or any mixture thereof. The higher alkanes include alkanes having between 5 and 100 carbon atoms. In some cases, the hydrocarbon reactant includes polyethylene.

[0011] Some implementations include separating the hydrogen gas from the hydrogen chloride gas by bubbling the product gas through water to yield hydrogen gas having a purity greater than 99 vol% and a solution comprising hydrochloric acid. Certain implementations include contacting the hydrocarbon decomposition catalyst with an additional hydrocarbon reactant at a temperature greater than 800 °C, thereby decomposing the additional hydrocarbon reactant to yield carbon and a gaseous mixture comprising hydrogen gas and some of the additional hydrocarbon reactant. The additional hydrocarbon reactant can include methane, ethane, propane, butane, higher alkanes, isomers therefore, or a mixture thereof. In some cases, the additional hydrocarbon reactant includes polyethylene.

[0012] Some implementations include depositing the carbon on the hydrocarbon decomposition catalyst to yield a carbon-enriched hydrocarbon decomposition catalyst. Certain implementations include separating the gaseous mixture and the carbon-enriched hydrocarbon decomposition catalyst. In one example, separating includes filtering.Attorney Docket No.: 44807-0498WO1 / JHU18371

[0013] Some implementations further include electrochemically generating chlorine gas from the hydrochloric acid, contacting the carbon-enriched hydrocarbon decomposition catalyst with the chlorine gas at a temperature greater than the boiling point of ferric chloride to yield iron-depleted hydrocarbon decomposition catalyst and gaseous ferric chloride, and condensing the gaseous ferric chloride by cooling to a temperature below the boiling point of ferric chloride. The iron-depleted hydrocarbon decomposition catalyst typically includes less than 0.5 mol% iron. The temperature greater than the boiling point of ferric chloride can be greater than 305 °C or greater than 900 °C, the temperature below the boiling point of ferric chloride can be less than 300 °C, or some combination thereof.

[0014] The details of one or more embodiments of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.BRIEF DESCRIPTION OF DRAWINGS

[0015] FIG. 1 is a scanning electron microscope (SEM) image of a particle containing iron and carbon produced by methods disclosed herein using natural gas to reduce ferric chloride.

[0016] FIG. 2 is an SEM image of a particle containing carbon produced by methods disclosed herein using chlorine gas to remove iron and regenerate ferric chloride.DETAILED DESCRIPTION

[0017] This disclosure describes processes for generating hydrogen from hydrocarbons (e.g., hydrocarbons that naturally occur in natural gas) by reduction of FeCh by the hydrocarbons. This process results in the products including hydrogen chloride gas, hydrogen, and a solid phase of mixed iron-carbon powder. This disclosure also describes processes for regenerating FeCh from the hydrogen chloride gas produced by the reduction of FeCh by the hydrocarbons.

[0018] The process for generating hydrogen from hydrocarbons described herein occurs most quickly at, but is not limited to, elevated temperatures, typically above 1000 °C, according to the following overall chemical reaction.AH0= 42.9 kI / molCH4(1)Attorney Docket No.: 44807-0498WO1 / JHU18371At temperatures above approximately 400 °C, ferric chloride (FeCh) typically decomposes to ferrous chloride (FeCh) and chlorine gas. However, while the reaction products of (1) include hydrogen gas, no substantive amount of chlorine gas is detected. The solid iron and carbon produced in this reaction are believed to catalyze direct hydrocarbon decomposition as shown below.CH4-> C + 2H2AH° = 76 kJ / molCH4(2)Chlorine gas quickly and exothermically reacts with hydrogen to form hydrogen chloride gas as shown below.AH° = -184 kJ / molH2(3)The specific reaction pathway of (1) is not believed to be known (e.g., whether it proceeds by formation of Ch and FeCh intermediates, or whether FeCh is directly reduced by the hydrocarbon). Regardless, free chlorine gas is not formed (e.g., not formed in any significant amount), and FeCh is reduced by hydrocarbons.

[0019] The iron-carbon solid mixture generated by the reduction of ferric chloride by hydrocarbons is a suitable catalyst for a variety of chemical reactions. One such reaction is the pyrolysis of hydrocarbons to generate hydrogen and solid carbon. The decomposition of methane occurs over both iron and carbon surfaces, although the barrier to methane activation on iron surfaces is significantly lower than on carbon. Carbon formed via methane decomposition is deposited onto the catalyst surface during reaction. This carbon, as well as any exposed iron, acts as a catalyst site for further methane pyrolysis.

[0020] The iron-carbon solid formed by reduction in a gaseous hydrocarbon typically includes iron-carbon particles. At least some of the particles are in the form of agglomerates. The agglomerates can be fractal agglomerates. That is, the agglomerates can exhibit a geometric pattern with self-similarity (e.g., similar patterns at different scales). The particles have an average diameter in a range of about 10 nm to about 50 nm. Agglomerates of the particles can have an average diameter in a range of about 10 microns to about 50 microns. The averageAttorney Docket No.: 44807-0498WO1 / JHU18371diameter of the particles can be assessed by a particle size analyzer (PSA) (e.g., a static light scattering PSA, a laser diffraction PSA, or a dynamic light PSA). Agglomerates of the hydrocarbon decomposition catalyst particles can be reduced in size by grinding to yield an average particle diameter (e.g., average diameter of particle agglomerates) in a range of 1 micron to 10 microns. Any suitable grinding technique can be used to reduce the average particle diameter (e.g., ball milling, hammer milling, attrition milling, dry milling, or wet milling).

[0021] FIG. 1 shows a scanning electron microscope (SEM) micrograph of a particle of ironcarbon produced by the reduction of ferric chloride in natural gas. Parts of the particle are composed of pure carbon 1, or carbon with embedded iron or iron carbide particles 2. The ironcarbon particle can also have separate iron or iron carbide particles 3 on the surface.

[0022] The ratio of carbon and iron in the iron-carbon particles can be controlled by varying the input concentration of iron chloride and hydrocarbon in the reactor, as well as by using the iron-carbon particles for further hydrocarbon decomposition without the presence of any iron chloride. In this case, the agglomerates tend to grow in average diameter, from an initial diameter of 1-5 microns to 50 microns or in some cases larger, and the carbomiron atomic ratio can increase up to 100: 1. The fractal agglomerates tend to break apart easily. As such, the particle diameter can be controlled by mechanical milling. In this way, the average particle diameter of the agglomerates can be reduced to be in a range of 1 micron to 10 microns, while increasing the atomic ratio of carbon to iron in the average composition of the particle.

[0023] Metal chlorides can be regenerated from hydrogen chloride gas produced during the reduction of metal chlorides by hydrocarbons at elevated temperatures. One example includes dissolving the carbon-metal material in a solution of hydrochloric acid produced by dissolving hydrogen chloride gas produced in the reduction reaction in water. The process includes exposing the metal-carbon material to an atmosphere of hydrogen chloride gas above the boiling point of the metal chloride. This procedure can be enhanced by first transforming the hydrogen chloride gas produced in, for instance, reaction (1) into chlorine gas. This can be done by dissolving the hydrogen chloride gas in water and then electrochemically producing chlorine from the solution by methods generally known in the art. By exposing the metal-carbon solids to chlorine gas at temperatures above the boiling point of the metal chloride, the metal reacts with the chlorine to yield a metal chloride, which becomes volatilized, separates from the solid, andAttorney Docket No.: 44807-0498WO1 / JHU18371can be condensed downstream in an atmosphere colder than the boiling point of the metal chloride.

[0024] For the iron-carbon material disclosed herein, the carbon can be purified by transforming the iron in the material to a volatile chloride. Typically, most of the iron can be transformed to iron chloride by exposing the material to chlorine gas at temperatures of 320 -350 °C, just above the boiling point of ferric chloride. To make a pure carbon product, the temperature of the iron-carbon material is heated to a temperature above 923 °C, the boiling point of ferrous chloride, which is formed when chlorine intercalates into the carbon structure at high temperatures. In this case, presumably it is ferrous chloride that evaporates from the carbon-containing material; in practice, the chlorine environment oxidizes the gaseous chloride to ferric chloride as it cools and condenses. FIG. 2 shows an SEM micrograph of a metal-carbon particle such as those in FIG. 1, but after exposure to chlorine gas at 1000 °C for twenty minutes. The particles maintain the overall fractal agglomerate shape of the particles prior to exposure, but buried and surface iron has been removed. Elemental analysis shows that the average iron content in this material is below 1%.

[0025] The recovery of the ferric chloride reagent can be achieved by first filtering the clean carbon material at temperatures above approximately 350 °C (where ferric chloride exists in the gas phase), followed by cooling to condense pure ferric chloride out of the stream of unreacted chlorine gas. In some configurations, pure carbon is recovered from a stationary bed when the reaction is complete, while the ferric chloride is recovered where it has deposited on the cold surfaces outside of the heated reactor.

[0026] A method of making a hydrocarbon decomposition catalyst according to this disclosure includes contacting ferric chloride and a hydrocarbon reactant at a contact temperature greater than 320 °C. As used herein, “contact temperature” refers to a temperature of an interior of the reaction chamber in which a reaction occurs. For example, in this case, the ferric chloride and the hydrocarbon reactant are contacted in an interior of a reaction chamber that is at a temperature greater than 320 °C. In one example, the ferric chloride is provided to the interior of a reaction chamber of a reactor, and the hydrocarbon reactant is provided to the interior of the reaction chamber where it contacts the ferric chloride.

[0027] In some cases, when contacting ferric chloride and a hydrocarbon reactant, a contact temperature is greater than 1,000 °C. In certain cases, the contact temperature is in a range ofAttorney Docket No.: 44807-0498WO1 / JHU18371320 °C to 1 ,500 °C (e.g., equal to or greater than 320 °C and less than or equal to 1 ,500 °C) or 925 °C to 1,500 °C. The contact temperature can be controlled by regulating a temperature in an interior of the reaction chamber in which the contacting occurs. In some examples, a heat exchanger, combustion heater, electric heater, cooling system, cooling chamber, or any combination thereof is used to increase or decrease the temperature of the hydrocarbon reactant provided to the reaction chamber. A temperature of the interior of the reaction chamber can be regulated by an electric heater, a combustion heater, a cooling system, a heat exchanger, or a combination thereof.

[0028] The method of making a hydrocarbon decomposition catalyst further includes reducing the ferric chloride to yield a product including a product gas and the hydrocarbon decomposition catalyst. The method can further include catalyzing reduction of the hydrocarbon with the decomposition catalyst to increase a relative content of carbon in the hydrocarbon decomposition catalyst. The hydrocarbon decomposition catalyst includes a multiplicity of particles, with each particle including iron and carbon.

[0029] The hydrocarbon decomposition catalyst has a stoichiometric atomic ratio of iron to carbon of 4:3. As the amount of carbon increases, the atomic ratio of iron to carbon decreases from 4:3 to a ratio in a range of 1:1 to 1:100 (e.g., 1:5 to 1:50).

[0030] As described herein, making a hydrocarbon decomposition catalyst includes reducing the ferric chloride to yield a product including a product gas and the hydrocarbon decomposition catalyst. The product gas includes hydrogen chloride gas, hydrogen gas, and some of the hydrocarbon reactant (e.g., residual hydrocarbon reactant). In one example, the product gas includes at least 75 vol% hydrogen gas and less than 20 vol% hydrogen chloride gas. In some examples, when the contact temperature is greater than 1,000 °C, the product gas can include hydrogen chloride gas, hydrogen, and some of the hydrocarbon reactant.

[0031] Making the hydrocarbon decomposition catalyst can further include separating the hydrogen gas and hydrogen chloride gas (e.g., by bubbling product gas through water) to yield hydrogen gas having a purity greater than 99 vol% (e.g., greater than 99 vol% H2) and a solution including hydrochloric acid.

[0032] Making a hydrocarbon decomposition catalyst can include contacting the hydrocarbon decomposition catalyst with additional hydrocarbon reactant. Contacting the hydrocarbon decomposition catalyst with additional hydrocarbon reactant can occur in theAttorney Docket No.: 44807-0498WO1 / JHU18371interior of the reaction chamber of the reactor described herein, or in the interior of the reaction chamber of another reactor. The additional hydrocarbon reactant decomposes to yield carbon, a gaseous mixture including hydrogen, and some of the additional hydrocarbon reactant. Some examples include contacting additional hydrocarbon reactants with the hydrocarbon decomposition catalyst at a contact temperature greater than 800 °C, thereby decomposing the additional hydrocarbon reactant. A gaseous mixture including hydrogen and some of the additional hydrocarbon reactant is formed, along with carbon. The additional hydrocarbon reactant can include methane, ethane, propane, butane, higher alkanes or isomers thereof, or any combination thereof. In one example, the additional hydrocarbon includes polyethylene.

[0033] In some cases, the carbon formed by decomposition of the additional hydrocarbon reactant can be deposited on (e.g., disposed on and completely covering or partially covering the surface of) the hydrocarbon decomposition catalyst to yield a carbon-enriched hydrocarbon decomposition catalyst. The carbon-enriched hydrocarbon decomposition catalyst can be separated from the gaseous mixture, for example, by filtering. Any technique suitable to separate the carbon-enriched hydrocarbon decomposition catalyst particles from the gaseous mixture can be used (e.g., gravity settling, mechanical collecting, dry filtering, or wet filtering).

[0034] In some examples, making a hydrocarbon decomposition catalyst can include electrochemically generating chlorine gas from the hydrochloric acid. In one example, chlorine gas is generated from the hydrochloric acid by membrane cell electrolysis.

[0035] In some instances, making a hydrocarbon decomposition catalyst can further include contacting the generated chlorine gas with the carbon-enriched hydrocarbon decomposition catalyst at a contact temperature greater than the boiling point of ferric chloride (e.g., about 315 °C to about 319 °C) to yield iron-depleted hydrocarbon decomposition catalyst and gaseous ferric chloride. Contacting can occur, in certain instances, in the interior of the reaction chamber of the reactor described herein, or in the interior of the reaction chamber of another reactor. The iron-depleted hydrocarbon decomposition catalyst has a lower iron content compared to the hydrocarbon decomposition catalyst before contacting the chlorine gas. In an example, the iron-depleted hydrocarbon decomposition catalyst includes less than 0.5 mol% iron.

[0036] In some embodiments, contacting the generated chlorine gas with the carbon-enriched hydrocarbon decomposition catalyst occurs at a contact temperature of greater than 305 °C. In certain cases, the contact temperature is greater than 900 °C.Attorney Docket No.: 44807-0498WO1 / JHU18371

[0037] Making a hydrocarbon decomposition catalyst, in some instances, can further include condensing the gaseous ferric chloride (e.g., in a condenser or a heat exchanger) by cooling to a temperature below the boiling point of ferric chloride. In one example, the gaseous ferric chloride is condensed by cooling to a temperature of less than 300 °C.EMBODIMENTS

[0038] The following embodiments are non-limiting examples of various embodiments of the present disclosure.

[0039] Embodiment 1 is a method of making a hydrocarbon decomposition catalyst, the method comprising:contacting ferric chloride and a hydrocarbon reactant at a temperature greater than 320 °C; andreducing the ferric chloride to yield a product comprising a product gas and the hydrocarbon decomposition catalyst, wherein hydrocarbon decomposition catalyst comprises a multiplicity of particles and each particle includes iron and carbon.

[0040] Embodiment 2 is the method of embodiment 1, wherein the temperature is greater than 925 °C.

[0041] Embodiment 3 is the method of any one of embodiments 1 or 2, wherein the temperature is less than 1500 °C.

[0042] Embodiment 4 is the method of any one of embodiments 1-3, wherein an atomic ratio of iron to carbon in the hydrocarbon decomposition catalyst is less than 4:3.

[0043] Embodiment 5 is the method of any one of embodiments 1-4, wherein the atomic ratio of iron to carbon in the hydrocarbon decomposition catalyst is in a range of 1 : 1 to 1 : 100.

[0044] Embodiment 6 is the method of any one of embodiments 1-6, wherein the atomic ratio of iron to carbon in the hydrocarbon decomposition catalyst in a range of 1 : 1 to 1:50.

[0045] Embodiment 7 is the method of any one of embodiments 1-6, further comprising catalyzing reduction of the hydrocarbon with the decomposition catalyst, thereby increasing a relative content of carbon in the hydrocarbon decomposition catalyst.

[0046] Embodiment 8 is the method of any one of embodiments 1-7, wherein the multiplicity of particles comprises at least some agglomerates of the particles.Attorney Docket No.: 44807-0498WO1 / JHU18371

[0047] Embodiment 9 is method of any one of embodiments 1-8, wherein an average particle diameter of particles in the multiplicity particles is in a range of 10 microns to 50 microns.

[0048] Embodiment 10 is the method of any one of embodiments 8 or 9, wherein the agglomerates of particles have a fractal morphology.

[0049] Embodiment 11 is the method of any one of embodiments 1-10, further comprising reducing the average diameter of the particles in the multiplicity of particles by grinding the multiplicity of particles to yield an average particle diameter in a range of 1 micron to 10 microns.

[0050] Embodiment 12 is the method of any one of embodiments 1-11, wherein the hydrocarbon reactant comprises methane, ethane, propane, butane, higher alkanes, or any mixture thereof.

[0051] Embodiment 13 is the method of embodiment 12, wherein the higher alkanes include alkanes having between 5 and 100 carbon atoms.

[0052] Embodiment 14 is the method of any one of embodiments 1-13, wherein the hydrocarbon reactant comprises polyethylene.

[0053] Embodiment 15 is the method of any one of embodiments 1-14, wherein the temperature is greater than 1000 °C, and the product gas further comprises hydrogen chloride gas, hydrogen, and some of the hydrocarbon reactant.

[0054] Embodiment 16 is the method any one of embodiments 1-15, wherein the product gas comprises at least 75 vol% hydrogen gas and less than 20 vol% hydrogen chloride gas.

[0055] Embodiment 17 is the method of embodiment 16, further comprising separating the hydrogen gas from the hydrogen chloride gas by bubbling the product gas through water to yield hydrogen gas having a purity greater than 99% and a solution including hydrochloric acid.

[0056] Embodiment 18 is the method of embodiment 17, further comprising contacting the hydrocarbon decomposition catalyst with additional hydrocarbon reactant at a temperature greater than 800 °C, thereby decomposing the additional hydrocarbon reactant to yield carbon and a gaseous mixture including hydrogen and some of the additional hydrocarbon reactant.

[0057] Embodiment 19 is the method of embodiment 18, wherein the additional hydrocarbon reactant comprises methane, ethane, propane, butane, higher alkanes, isomers thereof, or a mixture thereof.Attorney Docket No.: 44807-0498WO1 / JHU18371

[0058] Embodiment 20 is the method of embodiment 18, wherein the additional hydrocarbon reactant comprises polyethylene.

[0059] Embodiment 21 is the method of any one of embodiments 18-20, wherein the carbon is deposited on the hydrocarbon decomposition catalyst to yield a carbon-enriched hydrocarbon decomposition catalyst.

[0060] Embodiment 22 is the method of embodiment 21, further comprising separating the gaseous mixture and the carbon-enriched hydrocarbon decomposition catalyst.

[0061] Embodiment 23 is the method of embodiment 22, wherein the separating comprises filtering.

[0062] Embodiment 24 is the method of any one of embodiments 21-23, further comprising:electrochemically generating chlorine gas from the hydrochloric acid; contacting the carbon-enriched hydrocarbon decomposition catalyst with the chlorine gas at a temperature greater than the boiling point of ferric chloride to yield iron-depleted hydrocarbon decomposition catalyst and gaseous ferric chloride; andcondensing the gaseous ferric chloride by cooling to a temperature below the boiling point of ferric chloride.

[0063] Embodiment 25 is the method of embodiment 24, wherein the iron-depleted hydrocarbon decomposition catalyst comprises less than 0.5 mol% iron.

[0064] Embodiment 26 is the method of any one of embodiments 24 or 25, wherein the temperature greater than the boiling point of ferric chloride is greater than 305 °C.

[0065] Embodiment 27 is the method of embodiment 26, wherein the temperature greater than the boiling point of ferric chloride is greater than 900 °C.

[0066] Embodiment 28 is the method of any one of embodiments 24-27, wherein the temperature below the boiling point of ferric chloride is less than 300 °C.

[0067] Although this disclosure contains many specific embodiment details, these should not be construed as limitations on the scope of the subject matter or on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in this disclosure in the context of separate embodiments can also be implemented, in combination, in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments, separately, or in any suitable sub-combination. Moreover, although previouslyAttorney Docket No.: 44807-0498WO1 / JHU18371described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0068] Particular embodiments of the subject matter have been described. Other embodiments, alterations, and permutations of the described embodiments are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results.

[0069] Accordingly, the previously described example embodiments do not define or constrain this disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of this disclosure.

Claims

Attorney Docket No.: 44807-0498WO1 / JHU18371WHAT TS CLAIMED IS:

1. A method of making a hydrocarbon decomposition catalyst, the method comprising: contacting ferric chloride and a hydrocarbon reactant at a temperature greater than 320 °C; andreducing the ferric chloride to yield a product comprising a product gas and the hydrocarbon decomposition catalyst, wherein the hydrocarbon decomposition catalyst comprises a multiplicity of particles, each particle comprising iron and carbon.

2. The method of claim 1, wherein the temperature is greater than 925 °C.

3. The method of claim 1, wherein the temperature is less than 1500 °C.

4. The method of claim 1, further comprising catalyzing reduction of the hydrocarbon with the decomposition catalyst, thereby increasing a relative content of carbon in the hydrocarbon decomposition catalyst.

5. The method of claim 4, wherein an atomic ratio of iron to carbon in the hydrocarbon decomposition catalyst is less than 4:3.

6. The method of claim 5, wherein the atomic ratio of iron to carbon in the hydrocarbon decomposition catalyst is in a range of 1 : 1 to 1 : 100.

7. The method of claim 6, wherein an atomic ratio of iron to carbon in the hydrocarbon decomposition catalyst is in a range of 1 :5 to 1 :50.

8. The method of claim 1, wherein the multiplicity of particles comprises at least some agglomerates of the particles.

9. The method of claim 8, wherein an average particle diameter of particles in the multiplicity of particles is in a range of 10 microns to 50 microns.Attorney Docket No.: 44807-0498WO1 / JHU1837110. The method of claim 8, wherein the agglomerates of particles have a fractal morphology.

11. The method of claim 8, further comprising reducing an average diameter of the agglomerates of particles by grinding the multiplicity of particles to yield an average particle diameter in a range of 1 micron to 10 microns.

12. The method of claim 1, wherein the hydrocarbon reactant comprises methane, ethane, propane, butane, higher alkanes, or any mixture thereof.

13. The method of claim 12, wherein the higher alkanes include alkanes having between 5 and 100 carbon atoms.

14. The method of claim 1, wherein the hydrocarbon reactant comprises polyethylene.

15. The method of claim 1, wherein the product gas comprises at least 75 vol% hydrogen gas and less than 20 vol% hydrogen chloride gas.

16. The method of claim 15, wherein the temperature is greater than 1000 °C, and the product gas further comprises some of the hydrocarbon reactant.

17. The method of claim 16, further comprising separating the hydrogen gas from the hydrogen chloride gas by bubbling the product gas through water to yield hydrogen gas having a purity greater than 99 vol% and a solution comprising hydrochloric acid.

18. The method of claim 17, further comprising contacting the hydrocarbon decomposition catalyst with an additional hydrocarbon reactant at a temperature greater than 800 °C, thereby decomposing the additional hydrocarbon reactant to yield carbon and a gaseous mixture comprising hydrogen and some of the additional hydrocarbon reactant.Attorney Docket No.: 44807-0498WO1 / JHU1837119. The method of claim 18, wherein the additional hydrocarbon reactant comprises methane, ethane, propane, butane, higher alkanes, isomers therefore, or a mixture thereof.

20. The method of claim 18, wherein the additional hydrocarbon reactant comprises polyethylene.

21. The method of claim 18, wherein the carbon is deposited on the hydrocarbon decomposition catalyst to yield a carbon-enriched hydrocarbon decomposition catalyst.

22. The method of claim 21, further comprising separating the gaseous mixture and the carbon-enriched hydrocarbon decomposition catalyst.

23. The method of claim 22, wherein the separating comprises fdtering.

24. The method of claim 21, further comprising:electrochemically generating chlorine gas from the hydrochloric acid;contacting the carbon-enriched hydrocarbon decomposition catalyst with the chlorine gas at a temperature greater than the boiling point of ferric chloride to yield iron-depleted hydrocarbon decomposition catalyst and gaseous ferric chloride; andcondensing the gaseous ferric chloride by cooling to a temperature below the boiling point of ferric chloride.

25. The method of claim 24, wherein the iron-depleted hydrocarbon decomposition catalyst comprises less than 0.5 mol% iron.

26. The method of claim 24, wherein the temperature greater than the boiling point of ferric chloride is greater than 305 °C.

27. The method of claim 26, wherein the temperature greater than the boiling point of ferric chloride is greater than 900 °C.Attorney Docket No.: 44807-0498 WO 1 / JHU1837128. The method of claim 24, wherein the temperature below the boiling point of ferric chloride is less than 300 °C.

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