Metal recovery from coked catalysts.

Abstract

Removal of metals from metal-carbon materials includes contacting the metal-carbon material with hydrogen chloride to obtain a metal chloride in a gas phase and a solid product comprising carbon. Both the metal-carbon material and the solid product may comprise elemental carbon. The metal concentration in the solid product is typically less than 1 wt.%.

Description

[Technical field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of U.S. Patent Application No. 63 / 297,286, entitled "RECLAMATION OF METAL FROM COKED CATALYST," filed January 7, 2022, which is incorporated by reference in its entirety.

[0002] [Federally funded research and development] This invention was made with Government support under Contract DE-AR0001019 awarded by the Advanced Research Projects Administration - Energy, part of the U.S. Department of Energy. The U.S. Government has certain rights in this invention.

[0003] The presently disclosed subject matter provides a process for removing metals encapsulated by carbon without chemically modifying the carbon. Summary of the Invention [Problem to be solved by the invention]

[0004] Metal particles are widely used as catalysts for various chemical reactions. In hydroprocessing, metal particles containing some or all of nickel, iron, cobalt, and other transition metals are commonly exposed to hydrocarbons. One mechanism by which catalysts degrade is that substantially pure elemental carbon precipitates on the metal, completely encapsulating it in a protective shell of carbon that is resistant to chemical attack. This process is called coking. Various strategies have been employed to recover the metal after catalyst deactivation. One strategy is to dissolve the metal in a solution, usually a strong acid that can attack the metal to form a soluble metal salt. However, usually a significant portion of the metal (e.g., 5 at.% or more) is retained, and this portion is highly protected by the carbon shell. Another strategy is to burn the carbon, leaving the metal for reuse. However, this process is generally accompanied by the production of carbon dioxide, a greenhouse gas. Because both strategies are inefficient, it is important to develop new methods of recovering metals that do not generate carbon dioxide as a reaction product. [Means for solving the problem]

[0005] This disclosure relates generally to processes for removing metals from mixtures of metals and carbon, particularly those mixtures where the carbon has been found to encapsulate a portion of the metal without chemically altering the carbon. These processes typically involve exposing the metal and carbon mixture to an atmosphere of hydrogen chloride (HCl) gas at a temperature at or above the boiling point of the metal chloride.

[0006] In one embodiment of this process, a nickel-carbon powder mixture formed by methane pyrolysis is exposed to an atmosphere of flowing HCl at high temperature (e.g., 1000°C). As the HCl flows through the mixture, it reacts with the nickel in the powder mixture, including not only the nickel exposed to the atmosphere, but also the nickel protected by a carbon shell. The reaction product is nickel chloride, which sublimes and is carried by the HCl gas until it reaches a cooler location where it condenses. Metals suitable for this process include nickel, iron, manganese, cobalt, zinc, magnesium, and combinations of two or more of these. The carbon formed by this method can be optionally highly purified and has typically been found to have metal contents of less than 10 ppm by weight.

[0007] Although the disclosed inventive concepts include those defined in the appended claims, it is understood that the inventive concepts can also be defined according to the following embodiments.

[0008] Embodiment 1 is a method for removing metal from a metal-carbon material, comprising the steps of: contacting the metal-carbon material with hydrogen chloride to obtain metal chlorides in a gas phase and a solid product comprising carbon. This is the method.

[0009] Embodiment 2 is the method of embodiment 1, wherein the metal-carbon material comprises particles of metal encapsulated by elemental carbon.

[0010] Embodiment 3 is the method of embodiment 1 or 2, wherein the metal-carbon material is a coked metal-carbon material.

[0011] Embodiment 4 is the method of embodiment 3, wherein the coked metal-carbon material is formed in a hydrotreating reaction catalyzed by a metal.

[0012] Embodiment 5 is the method of embodiment 3, wherein the coked metal-carbon material is formed during a metal-catalyzed synthesis of carbon particles.

[0013] Embodiment 6 is the method of embodiment 5, wherein the carbon particles have an average diameter in the range of about 100 nm to about 50 μm.

[0014] Embodiment 7 is the method of embodiment 5 or 6, wherein the carbon particles are in the form of a carbon aerosol.

[0015] Embodiment 8 is the method of embodiment 5 or 6, wherein the carbon particles comprise carbon nanotubes.

[0016] Embodiment 9 is the method of any one of embodiments 1 to 8, wherein the metal-carbon material comprises a hydrocarbon material.

[0017] Embodiment 10 is the method of any one of embodiments 1 to 9, wherein the temperature of the hydrogen chloride and the metal-carbon material after contact is equal to or higher than the boiling point of the metal chloride.

[0018] An eleventh embodiment is the method of any one of the first to tenth embodiments, further comprising the step of condensing the metal chloride by lowering the temperature of the metal chloride to a temperature below the boiling point of the metal chloride.

[0019] Embodiment 12 is the method of any one of embodiments 1 to 11, wherein the metal concentration in the solid product is less than 1000 ppm by weight, less than 100 ppm by weight, or less than 10 ppm by weight.

[0020] Embodiment 13 is the method of any one of embodiments 1 to 12, wherein the hydrogen chloride is in a gaseous state.

[0021] Embodiment 14 is the method of any one of embodiments 1 to 13, wherein the hydrogen chloride is in a gaseous state.

[0022] Embodiment 15 is the method of embodiment 14, wherein contacting the metal-carbon material with the hydrogen chloride comprises flowing the hydrogen chloride over or through the metal-carbon material.

[0023] Embodiment 16 is the method of any one of embodiments 1-15, wherein the temperature of the hydrogen chloride is at least about 1000°C.

[0024] Embodiment 17 is the method of any one of embodiments 1 to 16, wherein contacting the metal-carbon material with the hydrogen chloride occurs in a reactor.

[0025] Embodiment 18 is the method of embodiment 17, wherein the reactor comprises a tube reactor.

[0026] Embodiment 19 is the method of any one of embodiments 1 to 18, further comprising the step of heating the metal-carbon material.

[0027] Embodiment 20 is the method of embodiment 19, wherein the step of heating the metal-carbon material comprises radiative heating.

[0028] Embodiment 21 is the method of embodiment 20, wherein the radiative heating comprises heating by microwave radiation.

[0029] Embodiment 22 is the method of embodiment 19, wherein the step of heating the metal-carbon material comprises electrical resistance heating.

[0030] Embodiment 23 is the method of embodiment 22, wherein the radiative heating comprises heating with a heating element.

[0031] Embodiment 24 is the method of embodiment 19, wherein the step of heating the metal-carbon material comprises Joule heating.

[0032] Embodiment 25 is the method of embodiment 24, wherein the Joule heating comprises passing an electric current through the metal-carbon material.

[0033] Embodiment 26 is the method of any one of embodiments 1 to 25, wherein the metal-carbon material is disposed on a substrate.

[0034] Embodiment 27 is the method of any one of embodiments 1 to 26, wherein the solid product comprises elemental carbon.

[0035] Although certain aspects of the presently disclosed subject matter have been described herein that are addressed in whole or in part by the presently disclosed subject matter, other aspects will become apparent as the description proceeds, as best described below, when taken in conjunction with the accompanying examples and figures. [Brief description of the drawings]

[0036] [Figure 1] 1 shows a transmission electron micrograph of carbon-encapsulated nickel particles formed by methane pyrolysis. [Diagram 2] 1 shows a transmission electron micrograph of hollow carbon particles formed after exposure of carbon encapsulated nickel particles to hydrogen chloride at 1000° C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Provided herein is a method for removing metals from a material comprising metal and carbon ("metal-carbon material"). The method comprises contacting the metal-carbon material with hydrogen chloride to obtain a solid product comprising metal chlorides in a gas phase and carbon. In some embodiments, contacting the metal-carbon material with hydrogen chloride occurs in a reactor (e.g., a tubular reactor). In some embodiments, the metal-carbon material is provided on a substrate. The substrate can refer to any underlying material or material on which the metal-carbon materials disclosed herein can be contacted with hydrogen chloride or used.

[0038] The metal-carbon materials disclosed herein can be particles of metal encapsulated by elemental carbon. In some embodiments, the metal-carbon materials are coked metal-carbon materials. For example, the metal-carbon materials disclosed herein can be depleted metal catalysts (e.g., from hydrotreating reactions) that are coated (e.g., encapsulated) with carbon (e.g., the coked metal-carbon materials can be deposits in carbonaceous or hydrocarbon chambers on the metal). In some embodiments, the coked metal-carbon materials are formed in hydrotreating reactions catalyzed by metals. In some embodiments, the coked metal-carbon materials are formed during the synthesis of carbon particles catalyzed by metals. The carbon particles can have an average diameter ranging from about 100 nm to about 50 μm. In some cases, the carbon particles are in the form of carbon nanotubes or carbon aerosols. As used herein, the term "hydrotreating" refers to various catalytic processes, including hydrotreating and hydrocracking, for removing, for example, sulfur, oxygen, nitrogen, and metals from hydrocarbon products (e.g., petroleum).

[0039] In some embodiments, the carbon of the metal-carbon material comprises a hydrocarbon group, such as an alkyl group. As used herein, the term "alkyl" refers to substituted or unsubstituted saturated hydrocarbon groups, including straight-chain alkyl groups and branched-chain alkyl groups, which can contain one or more (e.g., 1-25, 1-15, 1-10, 1-5, or 1-3) carbons in the chain.

[0040] The methods disclosed herein may include heating the metal-carbon material to a temperature at or above the boiling point of the metal chloride. In some examples, heating the metal-carbon material may be accomplished by radiative heating (e.g., using microwave radiation), electrical resistance heating (e.g., using a heating element), or Joule heating (e.g., passing an electrical current through the metal-carbon material to heat it).

[0041] In some embodiments, the temperature of the hydrogen chloride and the metal-carbon material after contact is at least about 300° C., at least 700° C., at least 900° C., at least about 1000° C., or at least about 1200° C. In some embodiments, the temperature of the hydrogen chloride and the metal-carbon material after contact is from about 700° C. to about 2000° C., from about 1000° C. to about 1750° C., or from about 1000° C. to about 1600° C. For example, when the metal of the metal-carbon material is nickel and the metal chloride comprises Ni(II)Cl2, the temperature of the hydrogen chloride and the metal-carbon material after contact is at least about 975° C. (the boiling point of Ni(II)Cl2). In some embodiments, the temperature of the hydrogen chloride is at least about 1000° C.

[0042] The methods disclosed herein may include condensing the metal chloride by reducing the temperature of the metal chloride to a temperature below the boiling point of the metal chloride. In some embodiments, the metal chloride may be condensed to a solid or liquid. In some embodiments, the temperature of the metal chloride is reduced to less than about 700° C., less than about 500° C., less than about 100° C., or less than about 50° C.

[0043] The carbon of the solid product may comprise, consist essentially of, or consist of elemental carbon. The solid product may contain less than 3 wt%, less than 2 wt%, less than 1 wt%, less than 0.1 wt%, or less than 0.01 wt% metals. In some embodiments, the metal concentration in the solid product is less than 1000 ppm by weight, less than 100 ppm by weight, or less than 10 ppm by weight.

[0044] In some embodiments, the solid product is substantially free of metals. As used herein, the term "substantially free of" a component(s) provided in the present disclosure is intended to mean that the composition or compound(s) contains less than about 0.1 wt%, or less than about 0.01 wt% (weight percent based on the total weight of the composition or compound(s)), or an insignificant or negligible amount of said component(s), unless otherwise specified.

[0045] The metal of the methods disclosed herein may include nickel, iron, manganese, cobalt, zinc, vanadium, molybdenum, magnesium, aluminum, tungsten, or alloys or compounds thereof. In some embodiments, the metal includes nickel, iron, manganese, cobalt, zinc, magnesium, or alloys or compounds thereof. In some embodiments, the metal includes nickel. In some embodiments, the metal includes iron. In some embodiments, the metal includes manganese. In some embodiments, the metal includes magnesium. In some embodiments, the metal includes cobalt. In some embodiments, the metal includes zinc.

[0046] The hydrogen chloride of the methods disclosed herein can be in a gaseous state. In some embodiments, contacting the metal-carbon material with hydrogen chloride comprises flowing hydrogen chloride over or through the metal-carbon material.

[0047] The presently disclosed subject matter will now be described more fully with reference to the accompanying drawings, in which some, but not all, embodiments of the presently disclosed subject matter are shown. The presently disclosed subject matter may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Indeed, many modifications and other embodiments of the presently disclosed subject matter described herein will come to mind to one skilled in the art to which the presently disclosed subject matter pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the presently disclosed subject matter is not limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims.

[0048] Figure 1 is a transmission electron micrograph of a carbon encapsulated nickel particle 100. Such particles can be formed by different chemical processes in which the nickel particles undergo pyrolysis of hydrocarbons into their constituent elements of hydrogen and carbon. In the particular material shown in Figure 1, the material was formed by pyrolysis of methane, a chemical reaction that produces hydrogen via reaction (1), catalyzed by nickel, iron, cobalt, manganese, and alloys and compounds containing these elements. CH4→C+2H2(1) The activity of catalysts for this reaction tends to decrease over time, necessitating the need to recycle the catalyst. Other forms of encapsulated metal particles include, for example, the metal particle catalysts used in the synthesis of carbon nanotubes. However, the synthesis of carbon nanotubes suffers from the same problems as the pyrolysis of methane, namely that the metal particles eventually become encapsulated in carbon and no longer function efficiently as catalysts.

[0049] As described herein, flowing hydrogen chloride gas over a mixture of spent metal catalysts results in the formation of volatile metal chlorides and separation of the metals from the carbon. The process is believed to involve intercalation of hydrogen chloride through the carbon, formation of metal chlorides, and deintercalation of the metal chlorides from the particles followed by sublimation. Thus, the process can be used to remove metals that form chlorides that are also graphite intercalation compounds. Metals in this category include nickel, iron, manganese, and cobalt.

[0050] FIG. 2 shows a transmission electron micrograph of hollow carbon nanoparticles 200 formed from the material shown in FIG. 1 via the methods described herein. EXAMPLES

[0051] The following examples are included to provide those skilled in the art with guidance for carrying out the embodiments of the subject matter of the present disclosure. In light of this disclosure and the general level of skill of those skilled in the art, those skilled in the art will understand that the following examples are intended to be illustrative only, and that many changes, modifications, and alterations can be adopted without departing from the scope of the subject matter currently disclosed. The synthetic descriptions and specific examples that follow are for illustrative purposes and are not to be construed in any way as limiting the preparation of the compounds of the present disclosure by other methods.

[0052] A sample of nickel-carbon powder containing 10 atomic % nickel was placed in a tube furnace and purged with hydrochloric acid at 1200 °C for 30 min to 2 h. After this time, the reactor was cooled and purged with argon. Nickel chloride sublimates condensed in the tube outside the hot zone. After carbon recovery, electron dispersive spectroscopy showed that the carbon powder contained no detectable metals. Elemental analysis showed that the Ni content was less than 100 ppm by weight.

[0053] Although the present disclosure includes details of certain embodiments, this should not be construed as a limitation on the scope of the subject matter or what may be claimed, but rather as a description of features that may be specific to certain embodiments. Certain features described in the present disclosure in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although previously described features may be described as acting in a particular combination, and may even be initially claimed as such, one or more features from a claimed combination may, in some cases, be excised from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0054] Specific embodiments of the subject matter have been described. Other embodiments, modifications, and permutations of the described embodiments, as will be apparent to those of ordinary skill in the art, are within the scope of the following claims. Although operations may be depicted in a particular order in the drawings or claims, this should not be understood as requiring such operations to be performed in the particular order shown, or sequentially, or that all of the operations depicted be performed (although some operations may be considered optional) to achieve desirable results.

[0055] Accordingly, the exemplary embodiments described above do not define or limit the disclosure, and other changes, substitutions, and alterations are possible without departing from the spirit and scope of the disclosure.

Claims

1. 1. A method for removing metal from a metal-carbon material, comprising the steps of: contacting the metal-carbon material with hydrogen chloride, thereby obtaining a solid product comprising metal chlorides in a gas phase and carbon.

2. The method of claim 1 , wherein the metal-carbon material comprises particles of metal encapsulated by elemental carbon.

3. The method of claim 1 , wherein the metal-carbon material is a coked metal-carbon material.

4. 4. The method of claim 3, wherein the coked metal-carbon material is formed in a metal catalyzed hydrotreating reaction.

5. 4. The method of claim 3, wherein the coked metal-carbon material is formed during a metal-catalyzed synthesis of carbon particles.

6. The method of claim 5, wherein the carbon particles have an average diameter in the range of about 100 nm to about 50 μm.

7. The method of claim 5 , wherein the carbon particles are in the form of a carbon aerosol.

8. The method of claim 5 , wherein the carbon particles comprise carbon nanotubes.

9. The method of claim 1 , wherein the metal-carbon material comprises a hydrocarbon material.

10. 10. The method of claim 1, wherein the temperature of the hydrogen chloride and the metal-carbon material after contacting is at or above the boiling point of the metal chloride.

11. 2. The method of claim 1, further comprising the step of condensing the metal chloride by reducing a temperature of the metal chloride to a temperature below the boiling point of the metal chloride.

12. 10. The method of claim 1, wherein the metal concentration in the solid product is less than 1000 ppm by weight, less than 100 ppm by weight, or less than 10 ppm by weight.

13. 2. The method of claim 1, wherein the metal comprises nickel, iron, manganese, cobalt, zinc, vanadium, molybdenum, magnesium, aluminum, tungsten, or and alloys or compounds thereof.

14. 2. The method of claim 1, wherein the hydrogen chloride is in gaseous form.

15. 15. The method of claim 14, wherein contacting the metal-carbon material with the hydrogen chloride comprises flowing the hydrogen chloride over or through the metal-carbon material.

16. 2. The method of claim 1, wherein the temperature of the hydrogen chloride is at least about 1000°C.

17. 10. The method of claim 1, wherein contacting the metal-carbon material with the hydrogen chloride occurs in a reactor.

18. 20. The method of claim 17, wherein the reactor comprises a tube reactor.

19. 10. The method of claim 1, further comprising the step of heating the metal-carbon material.

20. 20. The method of claim 19, wherein the step of heating the metal-carbon material comprises radiative heating.

21. 21. The method of claim 20, wherein the radiative heating comprises heating by microwave radiation.

22. 20. The method of claim 19, wherein the step of heating the metal-carbon material comprises electrical resistance heating.

23. 21. The method of claim 20, wherein the radiative heating comprises heating by a heating element.

24. 20. The method of claim 19, wherein the step of heating the metal-carbon material comprises Joule heating.

25. 25. The method of claim 24, wherein the Joule heating comprises passing an electric current through the metal-carbon material.

26. The method of claim 1 , wherein the metal-carbon material is disposed on a substrate.

27. 10. The method of claim 1, wherein the solid product comprises elemental carbon.

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