Method for producing solid carbon by reducing carbon dioxide.

(54) Title: METHODS TO PRODUCE SOLID CARBON THROUGH REDUCTION OF CARBON DIOXIDE.

(54) Title: METHOD FOR PRODUCING SOLID CARBON BY REDUCING CARBON DIOXIDE.

(57) Summary

A two-stage reaction procedure includes reacting gaseous carbon dioxide with a reducing agent to form carbon monoxide and water; at least a portion of the water condenses to form a dry tail gas; dry tail gas, with the possible addition of a reducing agent, reacts to convert at least a portion of the carbon monoxide to solid carbon and water; Other methods include reacting a supply gas mixture to form a reaction mixture, condensing water from the reaction mixture to form a dry reaction mixture, mixing the dry reaction mixture with a recirculating gas to form a mixture of catalytic converter supply gas, flow the catalytic converter supply gas mixture through a catalytic converter to form solid carbon and a water-containing tail gas mixture, and flow the tail gas mixture through a heat exchanger.

(57) Abstract

A two-stage reaction process includes reacting gaseous carbon dioxide with a reducing agent to form carbon monoxide and water. At least a portion of the water is condensed to form a dry tail gas. The dry tail gas, with the possible addition of a reducing agent, reacts to convert at least a portion of the carbon monoxide to solid carbon and water. Other methods include reacting a feed gas mixture to form a reaction mixture, condensing water from the reaction mixture to form a dried reaction mixture, mixing the dried reaction mixture with a recirculating gas to form a catalytic converter feed gas mixture, flowing the catalytic converter feed gas mixture through a catalytic converter to form solid carbon and a tail gas mixture containing water, and flowing the tail gas mixture through a heat exchanger.

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PATENT TITLE No. 354529

Headlines):

SEERSTONE LLC

D micilio:

808 East 1910 South, Suite 2, Provo, Utah, 84606, USA

D nomination:

METHODS TO PRODUCE SOLID CARBON BY REDUCING CARBON DIOXIDE.

Classification:

CIP:

C01B32 / Q5; B8 £ B | / O |; | 38 | B | / 8O Β8 ^ Υ30 / 00? Β8 ^ Υ4θ / 0θ '*

CPC:

Inventor (s)

DALLAS YES

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6 ° fraecidt¿ »III y, 26/12 /

MX / a / 2014/01254

Validity:

Date of V * ht £ mien

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In accordance with the article Íte the LeydeUa Propiedeted from the date of presentratífe the soliAri¿te ^ ci &lt;U Who subscribes the present title Ιο4β £ (Official Gazette of the Federation o 25/01/2006, 06/05/2009, 01/06/2010, Ή Regulations of the Mexican Institute M articles 1^or, 3®, 4 °, 5® fraction V subsection a), 12/27/1999, amended on 10/10/2002, 29/0 Deputy Generals, Coordinator, Departmental Directors and other subordinates of the Institute 04/08/2004 and 09/13/2007).

International

2013 the Rtoptedbd Industrial.

Vlgencjj | of twenty years extendable, counted to jll £ | J) M0ner vigerifcs l ^ · dárechos.

2 of the Industrial Property Law 1.4 ^ / 1999, 01/26/2004, 06/16/2005, a), 4^or and 12th sections I and III of / 2004, 07/28/2004 and 09/07/2007); or of Industrial Property (DOF Ac8 * do that delegates powers to the Directors, Divisional Deputy Directors, Coordinators 12/1999, amended on 02/04/2000, 07/29/2004,

This letter is signed with an advanced electronic signature (FIEL), based on articles 7 BIS 2 of the Industrial Property Law; 3 of its Regulations, and 1 section III. 2 section V. 26 BIS and 26 TER of the Agreement establishing the guidelines for the use of the Electronic Payment and Services Portal (PASE) of the Mexican Institute of Industrial Property, in the procedures indicated.

THE DIVISIONAL DIRECTOR OF PATENTS

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(55) 53340700 www.gob.mx/impi

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METHODS FOR PRODUCING SOLID CARBON WUIAN IE OT

REDUCTION OF CARBON DIOXIDE

CLAIM OF PRIORITY

This application claims the benefit of the filing date of the United States Provisional Patent Application with the serial number 61 / 624,723, filed on April 16, 2012, with the title Method for Producing Solid Carbon by Reducing Carbon Oxides [Method to produce solid carbon 10 by reducing carbon oxide], the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD OF THE INVENTION

The embodiments of the description refer to the conversion of a carbon containing raw material to solid carbon and more specifically, to methods for converting mixtures containing carbon monoxide, carbon dioxide or combinations thereof into solid carbon of various morphologies.

BACKGROUND OF THE INVENTION

US Patent Publication No. 2012/0034150 A1,

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ΙΝΓΓΠυΤΟ MUJCANO Tk *¹r »the imoPiWAD v» INDUSTRIAL published on February 9, 2012, the description of which is incorporated herein in its entirety by this reference, describes its background information.

Additional information is described in the following documents, each of these descriptions is incorporated herein in its entirety by this reference:

one. International Application No. PCT / US2013 / 000072 (Representative File No. 3525-P10945.1 PC), filed on the same date as this one for “Methods and Structures for Reducing Carbon Oxides with Non-Ferrous Catalysts” [ Methods and Structures for Reducing Carbon Oxides with Non-Ferrous Catalysts], which claims the benefit of USSN 61 / 624,702, filed April 16, 2012, in the name of Dallas B. Noyes;

2. International Application No. PCT / US2013 / 000076 (Representative File No. 3525-P10946.1 PC), filed on the same date as this for “Methods and Systems for Thermal Energy Recovery from Production of Solid Carbon Materials by Reducing Carbon Oxides ”[Methods and systems for the recovery of thermal energy from the production of solid carbon materials by reducing carbon oxides], claiming the benefit of the USSN [US Patent Serial Number] 61 / 624,573, filed on April 16, 2012, in the name of Dallas B. Noyes;

3. International Application No. PCT / US2013 / 000073 (No.

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IMPI * «> UCANO OF THE INDUSTRIAL PROPERTY representative file 3525-P11001.1 PC), presented in the illlUllitr date that the present for“ Methods and Reactors for Producing Solid Carbon Nanotubes, Solid Carbon Clusters, and Forests ”[Methods and reactors to Produce Solid Carbon Nanotubes, Solid Carbon Clusters, and Forests], which claims the benefit of USSN 61 / 624,753, filed April 16, 2012, in the name of Dallas B. Noyes;

Four. International Application No. PCT / US2013 / 000075 (Representative File No. 3525-P11002.1 PC), filed on the same date as this one for “Methods for Treating an Offgas Containing Carbon Oxides” waste gas containing carbon oxides], which claims the benefit of USSN 61 / 624,513, filed on April 16, 2012, in the name of Dallas B. Noyes;

5. International Application No. PCT / US2013 / 000071 (Representative File No. 3525-P11248.1 PC), filed on the same date as this one for “Methods for Using Metal Catalysts in Carbon Oxide Catalytic Converters”. Using Metal Catalysts in Carbon Oxide Catalytic Converters], which claims the benefit of USSN 61 / 624,848, filed April 16, 2012, in the name of Dallas B.

Noyes;

6. International Application No. PCT / US2013 / 000081 (Representative File No. 3525-P11249.1 PC), filed on the same date as this for “Methods and Systems for Capturing and Sequestering Carbon and for Reducing the Mass of Carbon Oxides in a Waste

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Gas Stream ”[Methods and systems for capturing and sequestering carbon and for reducing the mass of carbon oxides in a waste gas stream], which claims the benefit of USSN 61 / 624,462, filed on April 16, 2012, on behalf Dallas B. Noyes;

7. International Application No. PCT / US2013 / 000078 (representative file number 3525-P11361.1 PC), filed on the same date as this one for “Methods and Systems for Forming Ammonia and Solid Carbón Producís” [Methods and systems to form solid carbon and ammonia products], which claims the benefit of USSN 61 / 671,464, filed on July 13, 2012, in the name of Dallas B. Noyes; and

8. International Application No. PCT / US2013 / 000079 (Representative File No. 3525-P11771 PC), filed on the same date as this for "Carbon Nanotubes Having a Bimodal Size Distribution" [Carbon nanotubes having a distribution bimodal size], which claims the benefit of USSN 61 / 637,229, filed on April 23, 2012, in the name of Dallas B. Noyes.

Solid carbon has numerous commercial applications. These applications include old uses such as uses of carbon black and carbon fibers with a filler material in tires, inks, etc., many uses for various forms of graphite (eg pyrolytic graphite in thermal displays) and emerging applications and Innovative for carbon nanotubes and buckminsterfullerene. Conventional methods

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Say THE PROnSTY O »-w3 ·. (INDMTUAL for the manufacture of various forms of solid carbon typically involves pyrolysis of hydrocarbons in the presence of a suitable catalyst. Hydrocarbons are typically used as the carbon sources because there has been abundant availability and relatively low cost. The use of carbon oxides as the carbon source in the production of solid carbon has not been fully exploited.

Carbon oxides, particularly carbon dioxide, are abundant gases that can be extracted from point source emissions such as exhaust gases from hydrocarbon combustion or some process waste gases. Carbon dioxide can also be removed from the air. Since point source emissions have much higher concentrations of carbon dioxide than air, they are generally inexpensive sources from which carbon dioxide can be harvested. However, the immediate availability of air can provide cost trade-offs by eliminating transportation costs by locally producing solid carbon products from carbon dioxide in the air.

Carbon dioxide is becoming increasingly available and is inexpensive as a by-product of power generation and chemical processes in which an object may be present to reduce or eliminate the emission of carbon dioxide into the atmosphere by capturing and subsequent carbon dioxide sequestration (for example, by injection into a geological formation). For example, the capture and kidnapping of

INSTITUTO MEXMJANC DE LA PROITEDAtJ INDUSTRIAL carbon dioxide is the base for some ecological coal power plants. In current practices, the capture and sequestration of carbon dioxide involves a significant cost.

There is a spectrum of reactions involving carbon, oxygen, and hydrogen where various equilibria have been identified. Hydrocarbon pyrolysis involves equilibria between hydrogen and carbon that promote the production of solid carbon, typically with little or no oxygen present. The Boudouard reaction, also called the carbon monoxide disproportion reaction, is the range of equilibria between carbon and oxygen that favors the production of solid carbon, typically with little or no hydrogen present. The Bosch reaction is within an equilibrium region where all carbon, oxygen, and hydrogen are present under reaction conditions that also favor the production of solid carbon.

The relationship between hydrocarbon pyrolysis, the Boudouard and Bosch reactions can be understood in terms of a CHO equilibrium diagram, as shown in Figure 1. The CH-0 equilibrium diagram in Figure 1 shows several known pathways for solid carbon, including carbon nanotubes (CNTs). Hydrocarbon pyrolysis reactions occur at the equilibrium line connecting H and C and in the region near the left edge of the triangle with the upper left of the dotted lines. Two dotted lines are shown because the transition between the pyrolysis zone and the reaction zone

IMPIO * mexican institute t> E PROPERTY C * »PL INDUSTRIAL from Bosch can change with reactor temperature. Boudouard or carbon monoxide disproportion reactions occur near the equilibrium line connecting O and C (i.e. the right edge of the triangle). The equilibrium lines for various temperatures that traverse the diagram show the approximate regions in which the solid carbon will form. For each temperature, solid carbon can form in the regions above the associated equilibrium line, but generally will not form in the regions below the equilibrium line. Boudouard's reaction zone appears on the right side of the triangle. In this zone, the Boudouard reaction is thermodynamically preferred over the Bosch reaction. In the region between the pyrolysis zone and the Boudouard reaction zone and above a particular reaction temperature curve, the Bosch reaction is thermodynamically preferred over the Boudouard reaction.

CNTs are valuable for their unique material properties, including strength, current carrying capacity, and electrical and thermal conductivity. The bulk use of the CNT stream includes use as an additive for resins in the manufacture of compounds. CNT application research and development is very active, and a wide variety of applications are used or considered. Manufacturing cost has been an obstacle to the widespread use of CNT use.

US Patent No. 7,794,690 (Abatzoglou, et al.) Teaches a dry reforming process for carbon sequestration of an organic material. Abatzoglou describes a process using a catalyst

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IX The iwvsTMAi prohibition. *> E3E 2D carbon sequestration optionally with a dry reforming catalyst —in ——— ιιπι ~ ιι ·· [ΐυ · ιιιιΐι _ — _ íil

3D. For example, Abatzoglou describes a two-stage process for the dry reform of an organic material (eg, methane, ethanol) and CO₂ in a 3D catalyst to form syntheta, in a first stage, followed by carbon sequestration of synthese in a 2D carbon steel catalyst to form CNT and carbon nanofilaments. The 2D catalyst may be an active metal (eg Ni, Rh, Ru, Cu-Ni, Sn-N¡) in a ceramic or non-porous metal support or in an iron-based catalyst (eg steel) in a monolith support. The 3D catalyst may have a similar composition or it may be a compound catalyst (eg Ni / ZrO₂-AI₂O3) on a similar support. Abatzoglou teaches preactivation of a 2D catalyst by passing a stream of inert gas over a catalyst surface at a temperature above its eutectic point to transform iron into its alpha phase. Abatzoglou teaches how to minimize water in the two-stage process or by introducing water at low concentrations (0 to 10% by weight) into a reactive gas mixture during the first dry reforming stage.

BRIEF DESCRIPTION OF THE INVENTION

In some embodiments, a two-stage reaction process includes reacting a first feed mixture having a carbon source with a reducing agent under the conditions of the first reaction.

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to convert at least a part of the first feed mixture into a first product mixture comprising carbon monoxide and water. At least part of the water is condensed from the first product mixture to form a first dry product mixture. The first dry product mixture reacts under the conditions of the second reaction to convert at least a portion of the carbon monoxide in the first dry product mixture to solid carbon and a second product mixture that includes water.

In some embodiments, a method for a two-stage reduction of carbon dioxide includes reacting a feed gas mixture having carbon dioxide and a reducing gas to form a reaction mixture having carbon monoxide and water. A part of the water condenses from the reaction mixture to form a dry product mixture. The dry reaction mixture is mixed with a recirculating gas to form a catalytic converter feed gas mixture. The catalytic converter feed gas mixture flows through a catalytic converter in the presence of a metal to form solid carbon and a catalytic converter tail gas mixture that includes water. The catalytic converter feed gas mixture flows through a heat exchanger to condense some of the water and form the recirculating gas.

In certain embodiments herein, the partial pressure of water in the reaction is regulated by various means, including

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DE LA PROH6DAL INDUSTRIAL recycling and condensation of water to influence, for example, the structure or other aspects of the composition of carbon products produced. The partial pressure of water appears to assist in obtaining certain desired carbon allotropes.

In certain embodiments, a wide variety of inexpensive and readily available catalysts are described, including steel-based catalysts, without the need for catalyst activation before being used in a reaction. Iron alloys, including steel, can contain various iron allotropes, including alpha (austenite) iron, gamma iron, and delta iron. In some embodiments, the reactions described herein advantageously utilize an iron-based catalyst, where the iron is not in an alpha phase. In certain embodiments, an iron-containing stainless steel primarily in the austenitic phase is used as a catalyst.

Catalysts, including an iron-based catalyst (eg, iron, steel wool), can be used without the need for an additional solid support. In certain embodiments, the reactions described herein occur without the need for a metal or ceramic support for the catalyst. Omitting a solid support can simplify reactor setup and reduce costs.

In certain embodiments, a two-stage reaction process to convert carbon dioxide to a solid carbon product includes reacting a first feed mixture that has hydrogen and

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IMPI

WJTTTINO MU1GANO DS LA PAOPUDAD INDUSTRIAL carbon dioxide gas under the conditions of the first reaction to______ convert at least part of the carbon dioxide and hydrogen to carbon monoxide and water and form a first product mixture. At least a part of the water is condensed from the first product mixture to form a first dry product mixture. The first dry product mixture is mixed with a recirculating stream of a second dry product mixture to form a second feed mixture including carbon monoxide. The second mixture reacts under the conditions of the second reaction to convert at least a portion of the carbon monoxide in the second feed mixture to solid carbon and a second gaseous product including water and unreacted gases from the second feed mixture. At least a part of the water in the second gaseous reaction product is condensed to form the second dry product mixture.

BRIEF DESCRIPTION OF THE FIGURES

The features and advantages of the description will become apparent from reference to the following detailed description taken in conjunction with the accompanying figures, in which:

Figure 1 illustrates a CHO equilibrium diagram; and

Figures 2 to 4 illustrate simplified process flow diagrams indicating how the processes in the current description can be performed.

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DETAILED DESCRIPTION OF THE INVENTION

The description includes methods of reacting a carbon source with a reducing agent. The methods can be used to make solid carbon products in various morphologies and to convert carbon oxides to solid carbon and water. Solid carbon products can include graphite (eg, pyrolytic graphite), graphene, carbon black, fibrous carbon, buckminsterfullerene, single-walled CNT, or multi-walled CNT. The type, purity, and homogeneity of the solid carbon products can be controlled by the reaction conditions (time, temperature, pressure, partial pressure of reagents, and / or properties of the catalysts).

The methods use the Bosch reaction to produce solid carbon products by reducing carbon dioxide with any of a variety of reduction gases such as hydrogen or methane in the presence of a catalyst and under optimized reaction conditions for any desired type solid carbon. This catalytic conversion process can be incorporated with a variety of separation technologies, and with a variety of carbon dioxide generation processes.

The methods, generally based on the Bosch reaction, include reactions in the interior region of the phase diagram shown in Figure 1 (i.e. the region between the Boudouard reaction zone and the pyrolysis zone), where the balance can be established between carbon

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solid, the compounds of carbon, hydrogen and oxygen. The central region of Figure 1 has several points that are favorable for the formation of CNT and other forms of solid carbon. The type of solid carbon produced can be selectively controlled through the selection and processing of catalysts, reaction gases, and reaction conditions. Therefore, these methods introduce new avenues for the production of valuable solid carbon products such as CNTs.

The process uses two abundant raw materials, carbon oxides (for example, carbon dioxide, carbon monoxide) and a reducing agent. The reducing agent is preferably a hydrocarbon gas (eg, natural gas, methane, ethane, ethylene, etc.), an alcohol (eg, methanol, ethanol, etc.), hydrogen gas (H₂), or a mixture of these. A hydrocarbon gas can have a dual function, both as an additional carbon source and as the reducing agent for carbon oxide. Sintegas mainly comprises carbon monoxide and hydrogen, and sintegas has both carbon oxide and reducing gas in a mix. Synthesis can be used as all or part of the reaction gas mixture.

The reduction process of this method results in the formation of a solid carbon product and water. Subsequently, the water can be condensed and the latent heat can be extracted for heating purposes, or as part of a low pressure energy extraction cycle. Water can be extracted as a useful co-product, and latent heat μ IMPIg

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The methods described here use carbon dioxide as an economically valuable raw material. In many industrial processes, carbon dioxide is an unwanted waste product and may have associated disposal costs. The use of carbon dioxide as a feedstock in the production of solid carbon can reduce or eliminate disposal costs and can simultaneously convert carbon dioxide into a product that can be sold. Therefore, the methods can be incorporated with fossil fuel combustion processes. Combining the processes described herein with fossil fuel combustion processes may also be beneficial because the formation of solid carbon products by such processes may be more economical than existing sequestration and separation methods.

Carbon dioxide is present in many natural gas tanks at various concentrations, such as concentrations up to 5% by volume, up to 20% by volume, up to 60% by volume or even higher. Other compounds, such as H₂S, SO₂, and other sulfur compounds are generally present in natural gas. The removal of sulfur-containing compounds is generally done at a well site to form sweet gas (i.e., gas with little or no sulfur content). Removing carbon dioxide before natural gas is delivered to a consumer can be effectively accomplished using the techniques described

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at the moment.

The methods described produce solid carbon products such as buckminsterfullerene and carbon nanotubes using carbon oxides as the main carbon source. The methods therefore include catalytic conversion of carbon oxides to solid carbon and water. The methods can use carbon oxides from various sources, such as the atmosphere, combustion gases, process waste gases, well gas, and other natural and industrial sources of carbon oxides. Carbon oxides can be separated from these sources and concentrated as necessary, such as by regeneration and absorption of amines.

Bosch reactions, as described herein, use a reducing agent (eg, hydrogen, a hydrocarbon, etc.) to reduce carbon oxides to solid carbon (eg, graphite, graphene, carbon black, fibrous carbon , buckminsterfullerene, single wall CNT, multiple wall CNT, carbon platelets, nanodiamond, etc.) and water. Reactions can be carried out at temperatures above about 650 ° C, such as above about 680 ° C, in the presence of a catalyst. In the formation of CNT, graphite, or fullerene Οθο, Bosch's reaction of carbon dioxide with hydrogen is slightly exothermic (which produces heat) and occurs with stoichiometry:

CO₂ + 2H₂«-> C (_S) + 2H₂O (Equation 1).

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The formation of the CNTs in Equation 1 releases approximately 24.9 kcal / mol at 650 ° C (ie ΔΗ = -24.9 kcal / mol). The graphite formation in Equation 1 releases approximately 23.8 kcal / mol at 650 ° C. The Ceo fullerene formation in Equation 1 releases approximately 13.6 kcal / mol at 650 ° C. Carbon carbon black formation in Equation 1 is endothermic, consuming approximately 147.5 kcal / mol at 650 ° C (i.e. ΔΗ is +147.5 kcal / mol). Bosch's reactions are reversible; In reverse of Equation 1, solid carbon oxidizes with water to form carbon dioxide and hydrogen in an oxygen exchange reaction.

Bosch reactions are actually two-stage reactions that have a general energy release (i.e. the net reactions are exothermic). In the first stage of the reaction shown in Equation 1, carbon dioxide reacts with hydrogen to create carbon monoxide and water in a reverse water-gas shift reaction:

CO2 + H2 «-> CO + H2O (Equation 2).

Equation 2 is slightly endothermic at 650 ° C, requiring a heat input of around 8.47 kcal / mol (i.e. ΔΗ = +8.47 kcal / mol). In the second stage of the reaction shown in Equation 1, carbon monoxide reacts with hydrogen to form solid carbon and water:

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C0 + H₂«-> C (_S) + H₂0 (Equation 3). ,

Equation 3 can be produced with stoichiometric amounts of reagents, or with CO₂ or H₂ surplus. Equation 3 is exothermic at 650 ° C, which releases 33.4 kcal / mol (1.16 * 10⁴ joules / gram of C (_S)) when CNTs are formed (i.e. ΔΗ = -33.4 kcal / mol). The ΔΗ values ​​for Equation 3 can be calculated for other carbon products by the difference between the ΔΗ value for Equation 1 for that particular carbon product and the ΔΗ value for Equation 2.

The method involves the creation of solid carbon, and in particular, CNTs of different shapes or morphologies from carbon oxides. Carbon oxides can be a product of combustion from a major hydrocarbon, the atmosphere, or some other source. The carbon oxides and a reducing agent can be injected into a reaction zone that has been previously heated to a reaction temperature. The reaction typically occurs in the presence of a catalyst. The catalyst composition and its grain size can affect the morphology of the resulting solid carbon products. The reaction conditions, including the temperature and pressure of the reactor, the residence time of the reaction gases and the grain size of the catalyst can be controlled to obtain solid carbon products with selected characteristics. Product and feed mixes can be passed through one or more condensers to remove excess water and to control pressure

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partial water vapor in the reaction gas mixture. The partial pressure of water is a factor that appears to affect the type and character (for example, morphology) of solid carbon formed, as well as the kinetics of carbon formation.

Carbon activity (A_c) can be used as an indicator of whether solid carbon will form under particular reaction conditions (e.g. temperature, pressure, reagents, concentrations). Without wishing to be limited by any particular theory, carbon activity is believed to be the metric key to determining which solid carbon allotrope is formed. Higher carbon activity tends to result in the formation of

CNT, lower carbon activity tends to result in the formation of graphical forms.

Carbon activity for a reaction that forms solid carbon from gaseous reagents can be defined as the equilibrium reaction constant for the partial pressure of the gaseous products, divided by the partial pressure of the reagents. For example, in the reaction, CO (g) + H₂₍g) C (_S) + H₂O (g), with an equilibrium reaction constant of K, the activity of carbon A_c is defined as K- (P_CoPh2 / Ph2o) · Therefore, A_c is directly proportional to the partial pressures of CO and H₂, and inversely proportional to the partial pressure of H₂O. A P_HHigher 2O tends to inhibit CNT formation. The carbon activity of this reaction can also be expressed in terms of mole fractions and total pressure: Α_ο= Κ · Ρτ (ΥοοΎη2 / Υη2ο), where P7-is the total pressure and Y is the mole fraction

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IMPI of a species. Carbon activity generally varies with temperature because the equilibrium reaction constants generally vary with temperature. Carbon activity also varies with total pressure for reactions in which a different number of moles of gas is produced than are consumed. Mixtures of solid carbon allotropes and morphologies of these can be achieved by varying the catalyst and carbon activity of the reaction gases in the reactor.

Solid carbon can be produced in many different morphologies using the method's carbon oxide reduction process. Some of the solid carbon morphologies that can be produced include graphite (eg pyrolytic graphite), graphene, carbon black, fibrous carbon, buckminsterfullerene, single-walled CNT, multi-walled CNT, platelets, or nanodiamonds.

Suitable reducing agents for the reduction reaction can include hydrogen or hydrocarbon gases. Hydrocarbon gases can provide hydrogen and a part of the carbon. A reducing gas mixture of one or more of the commonly available hydrocarbon gases, such as lower hydrocarbon alkanes (eg, methane, ethane, propane, butane, pentane, and hexane), including those found in natural gas, It can be economical in some applications. In one embodiment, the reducing gas comprises methane and releases heat in an exothermic reaction:

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CO₂ + CH₄^ 2C₍s) + 2H₂O (Equation 4).

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The favorable reaction kinetics for the formation of the desired solid carbon species can be established through the use of suitable catalysts. For example, metals from groups 2 to 15 of the periodic table, such as groups 5 to 10 (for example, nickel, molybdenum, chromium, cobalt, tungsten, vanadium, ruthenium, platinum, iridium, iron, etc.) Actinides, lanthanides, or compounds containing any such metal (eg, iron carbide) can accelerate the reaction rates of any of Equations 1-4. Note that the periodic table may have several groups of numbering systems. As used herein, group 2 is the group that includes Be, group 3 is the group that includes Se, group 4 is the group that includes Ti, group 5 is the group that includes V, the group 6 is the group that includes Cr, group 7 is the group that includes Mn, group 8 is the group that includes Fe, group 9 is the group that includes Co, group 10 is the group that includes Ni, the group 11 is the group that includes Cu, group 12 is the group that includes Zn, Group 13 is the group that includes B, Group 14 is the group that includes C, and Group 15 is the group that includes N. In some embodiments, commercially available metals are used without special preparation. Catalysts can facilitate operations at lower temperatures. In CNT-forming reactions, the highest reaction rates may correspond to CNTs of smaller diameters, and the lowest reaction rates may correspond to

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CNT of larger diameters. ........—

The catalysts can be in the form of nanoparticles or in the form of domains or grains and grain boundaries within a solid material. Catalysts can be selected to have a selected grain size related to a characteristic dimension of a desired diameter of the solid carbon product (for example, a CNT diameter). Catalyst powder can be formed near or in the reaction zone by injecting an aerosol solution, so that after evaporation or a carrier solvent a selected particle size distribution occurs. Alternatively, the powdered catalyst can be entrained into a carrier gas and delivered to the reactor. The process can be configured to produce the selected morphologies of solid carbon product by selecting the catalyst and reaction conditions. In some embodiments, the catalyst can be formed on a substrate or support, such as an inert oxide that does not participate in the reactions. However, the substrate is not necessary; In other embodiments, the catalyst material is an unsupported material, such as a coarse metal or metal particles not connected to another material (for example, loose particles, filings, or shot, such as can be used in a bed reactor. fluidized).

Catalysts can be formed from a wide variety of catalyst precursors. Such catalyst precursors can decompose to form a desired catalyst. The forerunners of

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Decomposition is below the temperature of a reaction zone, so that when the catalyst precursors are introduced into the reaction zone, they decompose to form catalyst particles. The size of the catalyst particles can be controlled through the use of catalyst precursors. That is, by forming catalyst particles in situ, the catalyst particles can be kept smaller and / or more uniform in size than would be possible by other means. The morphology and diameter of CNTs can be controlled by controlling the properties of the catalyst particles.

The catalyst precursors can be mixed and dissolved in water or other solvents to make a solution of the catalyst precursors. The resulting solution can be dried to form the catalyst. In some embodiments, the solution can be sprayed to form an aerosol in a heated chamber, such as by spraying in a gas stream, direct spraying of the solution through a nozzle, electrostatic spraying, dispersing the solution from the surface of a rotary device and combinations thereof. In some embodiments, the catalyst precursors can be burned by removing a catalyst precursor solution on a heated surface, allowing the solvent to evaporate, and then allowing the catalyst precursor to burn. Other methods include creating the catalyst through a high vacuum vacuum sedimentation process (for example,

<img file="MX354529B_D0022.tif" />

IMPI

MEXICAN INSTITUTE DELA FRorUDAP INDUSTRIAL

10-⁶ to 10-⁸ Torr) and high temperatures (for example, 900 ° C to 1,300 ° C). The catalysts can be supplied as metal nanoparticles supported by solid supports by secondary extraction or dispersion. Suitable catalysts are described, for example, in US Patent Application Publication No. 2012/0034150 A1. The catalyst can be mobilized, as in a fluidized bed, or can be fixed in the reactor as gas streams containing carbon through the reactor and react with the catalyst.

The catalyst particles can be nucleation sites from which CNTs grow. Catalyst particles can be domains or grains in a piece of metal material or discrete catalytic metal nanoparticles deposited on an inert substrate (for example, a quartz disk) .The size of CNTs can be proportional to the size of the site of nucleation. The relationship between a catalyst particle size and the diameter of a CNT formed from it can be from about 1.2 to about 1.6. A possible theoretical basis for the correlation of particle size and CNT diameter is described in Nasibulin et al., Correlation Between Catalyst Partióle and Single-walled Carbón Nanotube Diameters, 43 Carbón 2251-57 (2005).

The catalyst can be any metal suitable for the progress of a carbon-forming reaction. Various commercially available grades of nickel, molybdenum, platinum, chromium, cobalt, and tungsten, and alloys thereof can be useful as catalysts. You can use '' i 'F^S &lt;

<img file="MX354529B_D0023.tif" />

various grades of chromium, molybdenum, cobalt, tungsten or nickel containing alloys or superalloys, for example materials commercially available from Special Metáis Corp. of New Hartford, New York under the trade name INCONEL®, or materials commercially available from Haynes International, Inc. of Kokomo, Indiana under the trade name HASTELLOY® (for example, HASTELLOY® B-2, HASTELLOY® B3, HASTELLOY® C-4, HASTELLOY® C-2000, HASTELLOY® C-22, HASTELLOY® C-276, HASTELLOY® G-30, HASTELLOY® N, or HASTELLOY® W). The catalyst may be in solid form, such as plates, cylinders, sediments, spheres of various diameters (for example, as steel shot), or combinations of these .

304 stainless steel appears to catalyze CNT formation over a wide range of temperatures, pressures, and gas compositions. However, the rate of CNT formation on 304 stainless steel appears to be relatively low, so 304 stainless steel can be effectively used as a construction material for process equipment, with minimal deposition on surfaces of these in operations normal. 316L stainless steel, by contrast, appears to catalyze the formation of solid carbon at considerably higher rates than 304 stainless steel, but they can also form various carbon morphologies. Therefore, 316L stainless steel can be used as a catalyst to achieve high reaction rates, but particular reaction conditions can be maintained to control product morphology.

<img file="MX354529B_D0024.tif" />

The catalysts can be selected to include Cr, such as in amounts of about 22% or less by weight. For example, 316L stainless steel contains from about 16% to about 18.5% Cr by weight. The catalysts can also be selected to include Ni, such as in amounts of about 8% or more by weight. For example, 316L stainless steel contains from about 10% to about 14% Ni by weight. The catalysts of these types of steel have authentic phase iron, in contrast to the alpha phase iron used as a catalyst in conventional processes. Because of the good results observed with 316L stainless steel, Ni and / or Cr can have a synergistic effect with Fe.

In one embodiment, the substantially spherical catalyst material can be used in conjunction with a fluidized bed reactor. The morphology of CNTs growing on metal catalysts may depend on the chemistry of the metal catalysts and the way the catalyst is processed. For example, CNT morphology can be related to grain size and the shape of grain contours within the metal. For example, the characteristic size of these characteristics may influence the characteristic diameter of CNTs formed in the presence of such metal catalysts.

The grain size of a catalyst material can at least partially determine the size of the CNT product. Metals with smaller grain sizes can produce CNT with

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smaller diameters. The grain size can be a function of both the chemistry of the metal catalyst and the heat treatment methods where the grains are formed.

The grain size of the metallic crystalline surface can also at least partially determine the size of the CNT product. Grain distribution, including crystal grain size and grain contour, can be controlled by methods known in the art. For example, grain size can be controlled by controlling metal nucleation, such as by grain refining or inoculation. Inoculants to promote nucleation may include titanium, boron, aluminum titanium (AI₃Ti), titanium diboro (T1B2), etc.

In general, the grain structure of a metal surface can be changed with methods known in the art. For example, a metal structure can be heated to a temperature sufficient to recrystallize the metal structure to form multiple randomly oriented grains. Alternatively, the metal can be heat treated or annealed to change the grain structure, grain contour, and grain size. For example, metal can be annealed by heating the metal to a temperature above its recrystallization temperature, holding the temperature for a period of time, then cooling the metal. As another example, the metal can be annealed by heating it for a period of time to allow the grains within the metal microstructure to form new grains by recrystallization.

<img file="MX354529B_D0026.tif" />

Recrystallization is a process in which a metal can be plastically deformed, annealed, or otherwise heat treated. When the metal is heated, the heat treatment affects the growth of the grain in the metal structure. The size of a crystal structure can vary with temperature above the critical temperature and time at that temperature. Additionally, a faster cooling rate of the recrystallization temperature can provide supercooling and a greater number of nucleation sites, thereby producing finer grained metal. Therefore, in one embodiment, the size of the crystal grain and therefore the size of the nanotubes can be controlled by nucleating the catalyst metals, the temperature of the catalyst heat treatment, the period of time that the catalyst metal is above the crystallization temperature and the metal cooling process.

Nucleation of a catalyst can be promoted through the use of pulsed laser light, for example by passing electromagnetic pulses through the catalyst or through the catalyst precursors. This use of laser light can improve the size uniformity of the resulting catalyst nanoparticles.

Oxidation and subsequent reduction of the catalyst surface alter the grain structure and grain contours. Without wishing to be bound by any particular theory, oxidation appears to alter the surface of the metal catalyst in the oxidized areas. The subsequent reduction may

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result in a further alteration of the ^ iiparfirip HpI catalyst.

Therefore, the grain size and grain contour of the catalyst can be controlled by oxidation and reduction of the catalyst surface and by controlling the exposure time of the catalyst surface to reducing gas and oxidation gas. Oxidation and / or temperature reduction can be in the range of about 500 ° C to about 1,200 ° C, from about 600 ° C to about 1,000 ° C, or from about 700 ° C to about 900 ° C. The resulting grain size can range from about 0.1 pm to about 500 pm, from about 0.2 pm to about 100 pm, from about 0.5 pm to about 10 pm, or from about 1.0 pm to about 2.0 p.m. In some embodiments, the catalyst may be an oxidized metal (eg, oxidized steel) that is reduced before or during a reaction that forms solid carbon. Without wishing to be bound by any particular theory, it is believed that removal of the oxides leaves gaps or irregularities in the surface of the catalyst material, and increases the overall surface area of ​​the catalyst material.

In some embodiments, the catalyst can be pulverized or ball mill. Powder from the spray or ball mill process can be collected and sieved to increase uniformity of catalyst particle size. If the catalyst is in powder or particulate form, the catalyst can be brought into the reactor using a carrier gas or a reactive gas. The particulate catalyst can also be used in a fluidized bed reactor. The dynamic action of

IMPI

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Metal catalyst particles within the fluidized bed can continually cause new catalyst surfaces to be exposed as carbon nanotubes form and peel off the catalyst particle surface. The catalyst particles can be configured to increase the surface area of ​​the catalyst in contact with carbon dioxide gases and reducing gases as the reaction proceeds.

Reaction temperatures may depend on the composition of the catalyst or the size of the catalyst particles. Catalyst materials that have small particle sizes tend to catalyze reactions at lower temperatures than the same catalyst materials with larger particle sizes. For example, the Bosch reaction can occur at temperatures in the range of about 400⁰ C at 800 ° C for iron-based catalysts, depending on the particle size and composition and the desired solid carbon product. In general, graphite and amorphous solid carbon form at lower temperatures, and CNTs form at higher temperatures. CNTs can form at temperatures above around 680 ° C. In general, the reactions described herein occur over a wide range of pressures, from near vacuum to pressures of 4.0 MPa (580 psi) or higher. For example, CNTs can form at pressure ranges from about 0.28 MPa (40 psi) to about 6.2 MPa (900 psi). In some embodiments, CNTs can form at

IMPI

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pressures from about 0.34 MPa (50 psi) to about 0.41 MPa (60 psi), or at a pressure of about 4.1 MPa (600 psi). Typically, increasing the pressure increases the reaction rate.

When using a thick solid catalyst, such as a metal catalyst pellet, CNTs may appear to grow in a number of generations. For example, CNTs can form masses, pillows, forests, fibers, piles, etc., as described in US Patent Application Publication No. 2012/0034150 A1.

A wide variety of reactor designs can be used to facilitate the formation and collection of the desired solid carbon products. Aerosol and fluidized bed reactors are suitable for continuous high volume production of solid carbon products.

A fluid wall reactor has the advantages of maintaining the introduction of various substances (catalysts, additional reagents) and of minimizing or eliminating the accumulation of solid carbon products on the walls of the reactor.

In some embodiments, the reactor may be an aerosol reactor in which the catalyst is formed in a gas phase or in which the catalyst is pre-formed and selected for a specific size distribution, mixed in a carrier gas solution, or liquid, and then sprayed into the reactor (eg, by electrospray). The catalyst may then remain distributed in the gas phase or may deposit on solid surfaces in the area of

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MEXICAN INSTITUTE OF THE PROfUDAD

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reaction for the growth phase of the carbon product. The catalyst can subsequently transport the product out of the reaction zone. In another embodiment, one or more reactors can be fluidized bed reactors in which the catalyst or catalyst-coated particles are introduced into the reactor and the solid carbon product is grown on the surface of the particles. Solid carbon can be elutriated in the reactor and carried out of the reactor entangled in the reaction gases, or the catalyst particles can be grown and the solid carbon removed from the surface.

The reactors can be batch reactors in which the catalyst is a fixed solid surface or is placed on a fixed solid surface (for example, catalyst nanoparticles deposited on an inert substrate), where the solid carbon is grown in the catalyst, and the catalyst and solid carbon product are periodically removed from the reactor. Alternatively, reactors can be continuous, where a solid catalyst or a catalyst mounted on a solid substrate passes through a flowing gas stream, the resulting solid carbon product is grown, and the solid surface is reintroduced to the reactor . The solid substrate may be the catalyst material (for example, a solid part of a chromium, molybdenum, cobalt or nickel containing alloy or superalloy) or a surface on which the catalyst is mounted.

In one embodiment, a fluidized bed reactor may be designed to retain the catalyst while allowing the solid CNT product to be entrained in the gas stream and to be thrown out of the zone.

IMPI MEXICAN INSTITUTE OF U INDUSTRIAL PROPERTY!

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of reaction after reaching a desired size. The shape of the reactor, ______ gas flow rates, or the shape and flow rates in combination can control the residence time of the elutriates and the corresponding size of the solid carbon product (such as the length of the carbon nanotubes. ).

In one embodiment, the particles in a fluidized bed reactor are of a substantially uniform diameter. The diameter of the catalyst in the fluidized bed can be chosen based on the particular reactor configuration, the flow rate of the reagents through the reactor, the shape of the catalyst, the density of the catalyst, and the density of the reagent gases and any inert carrier gases. The diameter of the catalyst particles can be chosen to avoid entrainment of the catalyst with the reaction product and also to prevent channeling of the reagents through the bed. A diffuser or sprayer can distribute the gaseous reagents to provide a uniform flow design through the bed particles and limit or prevent the channeling of gases through the bed of the particle.

When the catalyst is a sheet or plate on a manufacturing object, the entire surface of the manufacturing object does not need to be uniformly covered with the carbon product. The carbon deposition area on the solid surface can optionally be limited to one or more regions by masking, or selectively by depositing the catalyst to promote the formation of solid carbon in parts of the

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M THE raOTOiOAD industrial solid surface. ---- Solid carbon products can be collected and separated from the gas stream or from the solid surfaces on which they form, such as by elutriation, centrifugation, electrostatic precipitation or filtration. Techniques for separating the solid product from the gas stream and the catalyst may depend on the type of reactor. For example, the solid carbon product can be grown directly from a gas stream using electrophoretic or thermophoretic harvesters, filters, etc., or by harvesting the elutriates as they exit the reactor.

In one embodiment, a cyclone separator is used to separate and collect the solid carbon product. For a solid catalyst or a catalyst placed on a solid surface, the solid carbon product can be scraped or otherwise worn away from the surface of the solid carrier material. Alternatively, when a solid catalyst is used, the solid carbon product can be rinsed from a surface with a solvent for further processing.

In some cases, it may be beneficial or remove the solid carbon product from the reaction gas mixture before cooling it (for example, by removing the solid carbon product from the reactor through a purge chamber where the reaction gases are displaced by an inert purge gas such as argon, nitrogen, or helium). Purging before cooling helps reduce deposit or growth of undesirable morphologies in the

Mexican BWrrrjTo DE U HOHEDAD INDUSTRIAL desired solid carbon product during the cooling process .______

In aerosol reactors or fluidized beds, the residence time in the growth zone can be controlled by one or more forces (such as the gravitational, electromagnetic or centrifugal force) which counteracts the movement of the gas stream. These forces counterbalance the gas flow to help control residence time, so that the size of the solid carbon product can be controlled.

In another embodiment, the catalysts are introduced into an aerosol reactor by an electrospray process. Coulomb forces separate a suspension or solution containing a catalyst powder into small droplets from which individual particles form. Electrospray helps keep the particles apart so they don't tend to accumulate or merge. Electrospray also tends to charge the resulting carbon particles and make them easier to grow from the aerosol using electrostatic collectors.

In aerosol reactors, the catalyst particles can be sprayed into a carrier fluid or gas to transport them to the reaction zone. The catalyst may be pretreated in a catalyst conditioning process before mixing with the reaction gases. Conditioning of the catalyst by heating in an inert carrier gas can promote the growth of specific chiralities

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INDUSTRIAL CNT single wall. For example, heating catalyst material in a helium environment can promote the growth of CNT chiralities that have metallic properties. One or more substances can be introduced into the reaction zone to modify the physical properties of the desired solid carbon product, either through incorporation into the solid carbon product, or by surface deposition on the solid carbon product.

The physical properties of solid carbon products can be substantially modified by applying additional substances to the surface of the solid carbon. Modifying agents (eg, ammonia, thiophene, nitrogen gas, and / or excess hydrogen) can be added to the reaction gases to modify the physical properties of the resulting solid carbon. Modifications and functionalizations can be made in the reaction zone or after the solid carbon products have been removed.

Some modifying agents can be introduced into the reduction reaction chamber near the end of the solid carbon formation reaction by injecting, for example, a stream of water containing a substance to be deposited, such as a metal ion. Substances can also be introduced as a component of a carrier gas. For example, excess hydrogen can cause hydrogenation of a carbon network in some CNTs, causing CNTs to have semiconductor properties.

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MLXXANO INSTITUTE OF THE INDUSTRIAL PBOHiPAD

Small amounts of substances (eg, sulfur) added to the reaction zone can be catalyst promoters that accelerate the growth of carbon products in the catalysts. Such promoters can be introduced into the reactor in a wide variety of compounds. Such compounds can be selected such that the decomposition temperature of the compound is below the reaction temperature. For example, if sulfur is selected as a promoter for an iron-based catalyst, sulfur can be introduced into the reaction zone as a thiophene gas, or thiophene droplets in a carrier gas. Examples of the sulfur-containing promoters include thiophenes, hydrogen sulfide, heterocyclic sulfide, and inorganic sulfide. Other promoters include lead and bismuth compounds.

In some embodiments, a catalyst particle is removed from the surrounding matrix as a CNT grows, and the catalyst particle can become embedded at one end of the CNT. Therefore, some of the catalyst material can be physically removed during the reaction, and the catalyst may need to be continuously regenerated. The material on which a CNT grows may not be considered a catalyst in the classical sense of the word, but is referred to herein and in the art as a catalyst, because carbon is not believed to react with the material. Also, CNTs may not form at all without the catalyst. In scanning electron microscope images, the ends of the catalyst appear considerably larger (for example, 1.2 to

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1.6 times the diameter) that the tubes growing from ^ We &amp; r-EetauiiíexaQcia may be due to a carbon coating surrounding the catalyst, may indicate a fundamental relationship between the size of the catalyst particle and that of the CNT growing from it, or may be to some other factors or coincidence. Whatever the reason, one way to control the size of CNTs seems to be through controlling the size of the catalyst particle, or the grain size, keeping the catalyst particle size slightly larger than the nanotube size. wanted.

A process for converting a carbon source to a solid carbon product can be advantageously carried out in two or more stages. For example, Figure 2 shows a system 100 that can be used in such a method. A carbon source 102 and a reducing agent 104 enter a first reactor 106. The carbon source 102 may include a feed mixture comprising CO₂ gaseous, CO and / or other carbon-containing compound. Reducing agent 104 can include H₂, a hydrocarbon such as CH₄, or any mixture of these. Carbon source 102 and reducing agent 104 can be combined before entering first reactor 106, or mixed within first reactor 106. In some embodiments, a single source of material (for example, synthase, a mixture of CO and H₂) can serve as the carbon source 102 and reducing agent 104.

The first reactor 106 may be any vessel configured to contain, mix, and / or react the carbon source 102 and the reducing agent 104. For example, the first reactor 106 may be a fluidized bed.

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MHUCANO INSTITUTE Ot LA FWH1OAP INPUfHÜM.

The first reactor 106 can be adapted to provide the conditions under which the carbon source 102 and the reducing agent 104 react to form a product mixture from the first reaction 108. For example, the first reactor 106 may include appropriate means for handling the material, mix, control the temperature, control the pressure, etc. The first reactor 106 may include one or more sensors, controllers, etc., and the conditions within the first reactor 106 may remain constant or may vary during processing. For example, controllers can be configured to maintain selected conditions, as indicated by signals received from one or more sensors.

The first reaction product mixture 108 can include products of the carbon source reaction 102 and reducing agent 104, and one or more of the reagents, such as CO, H₂O, CO₂, etc. In some embodiments, carbon source 102 and reducing agent 104 can react substantially to completion in first reactor 106, consuming one or both of carbon source 102 and reducing agent 104. For example, carbon source 102 may be provided in excess, and reducing agent 104 may be consumed substantially or completely stoichiometrically in first reactor 106. In such embodiments, the product mixture from first reaction 108 may include products (for example, CO and H₂O) and a part of carbon source 102; the product mixture from the first reaction 108 leaving the first reactor 106 may be substantially free of reducing agent 104.

<img file="MX354529B_D0032.tif" />

IMPI

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The product mixture from the first reaction 108 can enter a first separator 110. The first separator 110 can be, for example, a condenser configured to separate a condenser 112 from a product mixture from the first dry reaction 114. Condensate 112 it may include water or other condensable matter formed in the first reactor 106 or otherwise present in the product mixture from the first reaction 108.

The product mixture from the first dry reaction 114 may include gases that do not condense under operating conditions of the first separator 110. For example, the product mixture from the first dry reaction 114 may include CO formed in the first reactor 106 and CO₂ unreacted remnant of carbon source 102.

The product mixture from the first dry reaction 114 may enter a second reactor 116 with one or more of a reducing agent 115 and a recirculated mixture 126.The second reducing agent 115 may include H₂, a hydrocarbon such as CH₄, or any mixture of these. In some embodiments, the second reducing agent 115 may have the same composition as the reducing agent 104 introduced into the first reactor 106.

The second reactor 116 can be any vessel configured to contain, mix, and / or react the product mixture from the first dry reaction 114, the second reducing agent 115 and / or the recirculated mixture 126. For example, the second reactor 116 it can be a fluidized bed. The second reactor 116 can be adapted to provide conditions where the product mixture from the first reaction dries uumvro mjuucano

Dt LA KOFUDAD INDUSTRIAL

114, the second reducing agent 115 and / or the recirculated mixture 126 may react to form the solids 118 and a product mixture from the second reaction 120. For example, the second reactor 116 may include appropriate means for handling the material, mixing, control temperature, control pressure etc. The second reactor 116 may include one or more sensors, controllers, etc., and the conditions within the second reactor 116 may remain constant or may vary during processing. For example, controllers can be configured to maintain selected conditions, as indicated by signals received from one or more sensors.

Solids 118 formed in second reactor 116 can include one or more forms of solid carbon. For example, solids 118 can include graphite (eg, pyrolytic graphite), graphene, carbon black, fibrous carbon, buckminsterfullerene, single-walled CNT, multi-walled CNT, platelets, or nanodiamonds. The type of solid carbon product formed can depend on various parameters of the reaction conditions, such as temperatures, pressures, flow rates, reactive compositions, etc. Solids 118 can be separated from the second reaction product mixture 120 within the second reactor 116 or in another device, by any appropriate separation methods.

The product mixture from the second reaction 120 can include reaction products from the product mixture from the first dry reaction 114, the second reducing agent 115, or the recirculated mixture 126, and one or

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MfcXLGANC INSTITUTE

OF THE PRDf> IDAD C INDfimUAL more of the reagents, such as CO, H₂O, CO₂, H ?. etc. In some embodiments, the product mixture from the first dry reaction 114 and the second reducing agent 115 can react substantially to completion in the second reactor 116, consuming one or both of the product mixture from the first dry reaction 114 and the second reducing agent 115. For example, the product mixture from the first dry reaction 114 can be provided in excess, and the second reducing agent 115 can be consumed substantially or completely stoichiometrically in the second reactor 116. In such embodiments, the product mixture from the second reaction 120 may include products (eg H₂O) and a part of the product mixture from the first dry reaction 114; the product mixture from the second reaction 120 leaving the second reactor 116 can be substantially free of the second reducing agent 115.

The product mixture from the second reaction 120 can enter a second separator 122. The second separator 122 can be, for example, a condenser configured to separate a condenser 124 from the recirculated mixture 126. The condensate 124 can include water or other matter condensable formed in second reactor 116 or otherwise present in the product mixture from second reaction 120. The recirculated mixture 126 can include gases that do not condense under operating conditions of the second separator 122. For example, the recirculated mixture 126 can include CO and / or CO₂ it has not reacted to form solids 118.

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Figure 3 shows another system 140 that can be used in a method of converting gaseous carbon dioxide to solid carbon. Like the system 100 shown in Figure 2, the system 140 includes a first reactor 106, a first separator 110, and a second reactor 116. The first reactor 106 and the first separator 110 can operate substantially as described above with with respect to Figure 2.

The product mixture from the first dry reaction 114 enters the second reactor 116 with one or more of the second reducing agent 115 and a compressed recirculated mixture 158.The second reducing agent 115 may include H₂, a hydrocarbon such as CH₄, or any mixture of these.

The second reactor 116 can be any vessel configured to contain, mix, or react the product mixture of the first dry reaction 114, the second reducing agent 115 and the recirculated mixture 126, for example a fluidized bed. An outlet material 142 from the second reactor 116 can include reagents and / or reaction products, such as solid carbon, CO, H₂O, CO₂, H₂, etc. Exit material 142 can enter a solid separator 144, where solids 146 can be separated from gases 148. For example, solid separator 144 can be a cyclone. Solids 146 removed from gases 148 in solid separator 144 can include one or more forms of solid carbon, such as graphite (eg, pyrolytic graphite), graphene, carbon black, fibrous carbon, buckminsterfullerenes, single wall CNTs, or CNTs with multiple walls.

Gases 148 may include products of the reaction of the

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IMPI iMTrmrro mujcano Of LA PROniDAD INDUSTRIAL product mixture of the first dry reaction 114, of the second reducing agent 115, or of the compressed recirculated mixture 158, and one or more of the reagents. Gases 148 can enter condenser 150. Condenser 150 can be configured to separate condensate 152 from recirculated mixture 154. Condensate 152 can include water or other condensable material formed in second reactor 116 or otherwise present. in gases 148. Recirculated mixture 154 can include gases that do not condense under operating conditions of condenser 150. For example, recirculated mixture 154 includes CO or CO₂which has not reacted to form solids 146. The recirculated mixture 154 can enter a compressor 156. The compressor 156 can produce the compressed recirculated mixture 158 by increasing the pressure of the recirculated mixture 154. The increase in pressure imparted by the compressor 156 can compensate for pressure drops within system 140, such as within second reactor 116, cyclone 144, or condenser 150. Although not shown in Figure 3, system 140 may include one or more additional compressors configured to deliver materials at selected pressures (eg, a compressor configured to compress carbon source 102 and / or reducing agent 104) .

The components of the systems 100, 140 shown and described herein can operate at various temperatures and pressures.

For example, the first reactor 106 or the second reactor 116 can operate at a temperature of at least about 450 ° C, such as a temperature

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IMPI rNsrmno mbugano M LA MOMÉDAT

INOUSTWAL of at least around 650 ° C or a temperature of around 680 ° C to around 700 ° C. The first reactor 106 or the second reactor 116 can operate at a pressure of about 0.28 MPa (40 psi) to about 0.41

60 psi (MPa) or at a pressure of about 600 psi (4.1 MPa). The first separator 110, the second separator 122, the solid separator 144, and the condenser 150 can operate at lower temperatures than the first reactor 106 and / or or the second reactor 116. For example, the first separator 110, the second separator 122, the solid separator 144, and the condenser 150 can operate at temperatures of less than about 100 ° C, less than about 80 ° C, or even less around 50 ° C. In some embodiments, heat can be recovered from one material and transferred to another.

For example, Figure 4 shows a system 200 that has heat recovery characteristics. A carbon source 102 and a reducing agent 104 enter a first heat exchanger 202. The first heat exchanger 202 may be a shell and tube heat exchanger, a plate heat exchanger, a plate heat exchanger and fins, a spiral heat exchanger or any other type of heat transfer apparatus. The first heat exchanger 202 can be configured to operate in a co-current, counter-flow, or cross flow. Carbon source 102 and reducing agent 104 can be combined before entering first heat exchanger 202, within first heat exchanger 202, or after leaving first heat exchanger 202. In the embodiment shown in Figure 4 , the

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IMPI ιχτητυτο Mexican OT> LA MOMÍDAT INDUSTRIAL carbon source 102 and reducing agent 104 are mixed inside the first heat exchanger 202, and a heated reagent mixture 204 leaves the first heat exchanger 202. The heated reagent mixture 204 can be hotter than carbon source 102 or reducing agent 104 entering first heat exchanger 202. For example, the heated reagent mixture 204 may be at a temperature of at least 300 ° C, such as a temperature of at least 500 ° C or a temperature of from about 550 ° C to about 600 ° C. The heated reagent mixture 204 can be at a pressure of about 0.28 MPa (40 psi) to about 0.41

MPa (60 psi) or at a pressure of around 4.1 MPa (600 psi).

The heated reagent mixture 204 enters a first reactor

206, which may be similar to the first reactor 106, as shown and described in Figure 2. That is, the first reactor 206 can be adapted to operate under conditions where carbon source 102 and reducing agent 104 react to form a product mixture from the first reaction 208. The first reactor 206 can be heated to a temperature greater than the temperature of the heated reagent mixture 204 entering the first reactor 206. For example, the first reactor 206 can be heated to a temperature of at least 450 ° C, such as a temperature of at least 650 ° C, or a temperature of from about 680 ° C to about 700 ° C.

The product mixture from the first reaction 208 can leave the first reactor 206 at approximately the same temperature as the operating temperature of the first reactor 206. The product mixture

IMPI

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From the first reaction 208 it returns to the first heat exchanger 202 to recover heat from the product mixture from the first reaction 208. The heat from the product mixture from the first reaction 208 is transferred to carbon source 102 and / or the reducing agent 104. Recovery of the heat in the first heat exchanger 202 reduces the heating load necessary to maintain the first reactor 206 at a selected operating temperature. Therefore, a system 200 having a first heat exchanger 202 as shown in Figure 4 may have lower energy costs than a system without such a first heat exchanger 202.

A mixture of the cooled first reaction product 210 leaves the first heat exchanger 202 at a temperature of less than about 200 ° C, such as at a temperature of less than about

150 ° C, or at a temperature of about 80 ° C to about 120 ° C, and enters a condenser 212. Condenser 212 separates a condensate 214 (for example, liquid water) from a product mixture of the first dry reaction 216 (eg CO, gaseous CO2, etc.) Condenser 212 may be similar to first separator 110, as shown in Figure 2.

Capacitor 212 can operate at a temperature of less than about 100 ° C, less than about 80 ° C, or even less than about 50 ° C. Condenser 212 may include one or more cooling means to control operating temperature. Removing the heat from the first product mixture from the first reaction 208 in the first heat exchanger 202 reduces the cooling load of the₄₇ IMPIg 't / KSTrrUTO MEXICANO

FROM PROPERTY V * moustnal condenser 212 by reducing the temperature of the mixed product gives the first cooled reaction 210. Therefore, the first heat exchanger 202 can reduce the cooling needs of system 200.

The product mixture from the first dry reaction 216 enters a second heat exchanger 218 and can be heated or mixed with a reducing agent 220 or a recirculated mixture 240. The second heat exchanger 218 can be a shell and tube heat exchanger , a plate heat exchanger, a plate and fin heat exchanger, a spiral heat exchanger or any other type of heat transfer apparatus. The second heat exchanger 218 can be configured to operate in a co-current, counter-flow, or cross flow. The product mixture from the first dry reaction 216, the reducing agent 220 and the recirculated mixture 240 can be combined before entering the second heat exchanger 218, inside the second heat exchanger 218, or after leaving the second heat exchanger 218. In the embodiment shown in Figure 4, the product mixture from the first dry reaction 216, the reducing agent 220, and the recirculated mixture 240 are mixed within the second heat exchanger 218, and a second heated reagent mix 222 leaves the second heat exchanger 218. The second heated reagent mix 222 may be hotter than the first dry reaction product mix 216, reducing agent 220 or recirculation mix 240 which enters second heat exchanger 218. For example, heated second reagent mix 222 may

<img file="MX354529B_D0039.tif" />

be at a temperature of at least around snri-PC such as a temperature of at least around 500 ° C or a temperature of around 550 ° C to around 600 ° C. The second heated reagent mix

222 It can be at a pressure of around 0.28 MPa (40 psi) to around 0.41 MPa (60 psi) or at a pressure of around 4.1 MPa (600 psi).

The second heated reagent mixture 222 enters a second reactor 224, which may be similar to the second reactor 116, as shown and described in Figure 2.That is, the second reactor 224 can be adapted to operate under conditions where the components of the second heated reaction mixture 222 react to form solid carbon and other products. The reaction products can leave the second reactor 224 as the product mixture from the second reaction 226. The second reactor 224 can be heated to a temperature greater than the temperature of the second heated reagent mixture 222 entering the second reactor 224. By For example, the second reactor 224 can be heated to a temperature of at least 450 ° C, such as a temperature of at least 650 ° C, or a temperature of from about 680 ° C to about 700 ° C. Heat recovery in second heat exchanger 218 can reduce the heat load required to maintain second reactor 224 at a selected operating temperature. Therefore, a system 200 having a second heat exchanger 218 as shown in

Figure 4 may have lower energy costs than a system without said second heat exchanger 218.

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MEXICAN INSTITUTE

OF THE PROPERTY

INDUSTRIAL

<img file="MX354529B_D0040.tif" />

The product mixture from the second reaction 226 can enter a cyclone 228 and the solids 230 can be separated from gases 232. The gases

232 The second heat exchanger 218 enters and heat can be recovered from the gases 232 and can be transferred to the product mixture from the first dry reaction 216, the reducing agent 220 and / or the recirculated mixture 240. The cooled gases 234 leaving the second heat exchanger 218 enters a second condenser 236, where the condensate 238 is separated from the recirculated mixture 240.

System 200 may include one or more compressors to compensate for the pressure drop within system 200. For example, pressure drop may occur within heat exchangers 202, 218, reactors 206, 224, condensers 212, 236, cyclone 228 and / or controllers, sensors, valves, related pipes, etc.

Separating the process to convert carbon dioxide gas into two or more stages, as shown in Figures 2 through 4, can have several benefits. For example, by thermodynamics or kinetics, a single reactor in which full conversion occurs may be technically difficult or economically impossible for some applications. As described above, the Bosch reaction of carbon dioxide with hydrogen is a two-stage reaction. The first reaction:

CO₂+ H₂«-> CO + H₂O (Equation 2),

MSTTTVTO MEXICANO

FROM INDUSTRIAL PROBITY the reverse gas-water exchange reaction can have a much faster reaction rate than the second reaction. The second reaction:

CO + Η₂θ C (s) + H₂Or (Equation 3), you can control the total reaction rate of the process. By separating the process into two stages, the two reactions can be isolated. The first reactors 106, 206 may be relatively smaller than the second reactors 116, 224, but the first reaction may still occur substantially to completion in the first reactors 106, 206. The smaller reactors may be more economical to produce, maintain and operate.

Furthermore, removal of condensates between the two reactions may allow the second reaction to occur in an environment that has a generally lower concentration of water vapor than could occur in a single reactor. A lower concentration of water vapor can be beneficial because water is a product of both Equation 2 and Equation 3. Therefore, to the extent that the reactions are regulated by thermodynamics (i.e., under equilibrium conditions), lower concentrations of water vapor lead to the completion of the reactions (i.e., to the right). Lower water vapor concentrations may also be beneficial in limiting or preventing the oxidation of metals (for example, from reaction vessels or

KSTrn / To μεχκλλιο PE INDUSTRIAL PROPERTY catalysts). Therefore, a concentration of steam should contribute to the efficiency of the process and to reduce maintenance costs.

A reactor can be coupled with cooling and heating mechanisms to control the temperature of the reactor. For example, a reactor can be configured so that surplus products and reagents are recycled using a cooling mechanism to condense water vapor. The excess products and / or reagents can be reheated and recycled in the reactor. By removing some of the water vapor in the recycled gases, the morphology of the solid carbon formed can be controlled. Changing the partial pressure of water vapor changes the carbon activity of a mixture. The reactor can also be coupled to a carbon collector in which water and unreacted reagents are separated from the carbon products. The separated carbon products are collected and removed from the system.

The methods described herein can be incorporated into energy production, chemical processes, and manufacturing processes in which the combustion of a primary hydrocarbon fuel source is the primary source of heat. The combustion gases resulting from such processes contain carbon oxides that can act as carbon sources for the manufacture of the desired solid carbon product. Methods can be scaled to accommodate many different production capacities so that, for example,

<img file="MX354529B_D0041.tif" />

DUTITUTO

LX to

MEXICAN ____ INDUSTRIAL PROPERTY plants designed with this method in mind will be able to handle carbon dioxide emissions from the combustion processes of a coal power plant or those of an internal combustion engine. For example, the methods can be used to reduce atmospheric carbon dioxide, flue gases, process waste gases, exhaust gases from Portland cement manufacturing, and well gases, or from separate fractions of this.

In another embodiment, the carbon oxides in a source gas mixture are separated from the source mixture and concentrated to form the carbon oxide raw material for the reduction process. The carbon oxides in the source gases can be concentrated through various means known in the art. In yet another embodiment, the catalytic conversion process can be employed as an intermediate stage in a multi-stage energy extraction process where the first stages cool the flue gases to the reaction temperature of the reduction process for product formation. desired solid carbon. The cooled flue gases to the desired reduction reaction temperature can then be passed through the reduction process and can then be passed through additional energy extraction steps.

Coupling this method with a hydrocarbon combustion process for the production of electrical energy has the additional advantage that the hydrogen required for the reduction process can be

MEXνίυ MEXICAN Μ INDUSTRIAL PROPERTY formed by electrolysis of water using pnprgía in hours of demand. The oxygen formed in the electrolysis process can be used as at least a part of the fuel mixture for the combustion process.

When the methods described here are coupled with a combustion or chemical process that uses hydrocarbons, a part of the hydrocarbons in the process can be used as the reducing agent gas. This may include pyrolysis of the hydrocarbons to form a hydrogen gas that is provided as the reducing agent gas. The process of this description can be adapted to various available hydrocarbon sources.

EXAMPLE

Methane gas is mixed with carbon dioxide in a 1: 1 ratio inside a first tube furnace lined with a ceramic material, maintained at around 680 ° C and containing steel wool inside. Methane gas reacts with carbon dioxide gas in the presence of steel wool to form a reaction gas mixture of carbon monoxide, water, and hydrogen. The reaction gas mixture enters a condenser operating at around 50 ° C to remove liquid water from the reaction gas mixture. The dry reaction gas mixture enters a second tube furnace lined with a ceramic material, maintained at

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DE LA MOHEDAL · INDUSTRIAL around 680 ° C and containing steel wool inside. The carbon monoxide and hydrogen in the dry reaction gas mixture react in the presence of steel wool to form single-walled carbon nanotubes and a water-tail gas mixture with a little carbon monoxide and residual hydrogen. Carbon nanotubes collect on the surfaces of steel wool. The tail gas mixture enters a condenser that operates at around 50 ° C to remove liquid water from the tail gas mixture. The dry glue gas mixture is recycled in the second tube furnace.

After the process has continued for a period of time, the gas flow stops, the furnaces and condensers cool to room temperature, and the system is purged with an inert gas. Steel wool is removed from the second tube furnace and carbon nanotubes are physically removed from the steel wool. Any remaining metal on the carbon nanotubes can be removed, if desired, by acid washing.

Although the foregoing description contains specific details, these should not be construed as limiting the scope of the present invention, but as merely providing certain embodiments. Similarly, other embodiments of the invention can be established that do not depart from the scope of the present invention. For example, the features described herein may also be provided with reference to one embodiment in other embodiments.

IMPI msrnvro mukano OF INDUSTRIAL PROPERTY

<img file="MX354529B_D0042.tif" />

described herein. Therefore, the scope of the invention is indicated and limited only by the appended claims and their legal equivalents and not by the foregoing description. All additions, deletions, and modifications to the invention, as described herein, which fall within the meaning and scope of the claims, are encompassed by the present invention.