Endothermic-exothermic combined reactor systems and associated methods

Abstract

A reactor system and associated processes are disclosed. The reactor system comprises an outer tube and an inner tube arranged together to form an annulus. The annulus between the inner and outer tubes is in fluid communication with the inner tube at one end. The inner tube or the second reactor may contain a catalyst for an exothermic reaction, and the annulus or the first reactor may contain a catalyst for an endothermic reaction. In this way, reactants can be injected into one end of the annulus, undergo an endothermic reaction heated by the exothermic reaction, and at least some of the intermediates can exit the annulus into the inner tube to undergo the exothermic reaction. The reactor may comprise a solid removal system. The disclosed system may enable a continuous process for carbon emissions mitigation into permanent solid carbon.

Description

Endothermic-Exothermic Combined Reactor Systems and Associated MethodsRELATED APPLICATIONS

[0001] This application claims priority from U.S. Provisional Application 63 / 605,293 filed on December 1 , 2023 and entitled, “Endothermic-Exothermic Combined Reactor System and Associated Methods”, the contents of which are hereby incorporated in their entirety.TECHNICAL FIELD

[0002] The invention relates to processes and associated catalysts for carrying out combinations of exothermic and endothermic reactions for producing hydrogen, light hydrocarbons, and solid carbon from light hydrocarbons and CO2. The invention also relates to a reactor system comprising two reactor compartments or two reactors in series for carrying out such processes to minimize heat losses and improve overall heat efficiency while carrying out the selected pair reactions.BACKGROUND

[0003] The rising levels of CO2 and other greenhouse gases (GHG) in the atmosphere have accelerated significant environmental and climate-related challenges. The escalating GHG emissions have sparked urgent environmental and climate-related concerns globally [1].

[0004] The global community has set ambitious targets to curb GHG emissions. These goals involve reducing or eliminating emissions from existing technologies or developing new technologies that can effectively reduce emissions [1 -4].

[0005] Graphite is a highly desirable form of carbon due to its electrical conductivity, thermal stability, and lubricating properties. Traditional methods for graphite production often require high- temperature processes, specialized catalysts, or complex reactor systems.

[0006] CO2 reforming reactions require a significant amount of energy and additional hydrogen. Numerous initiatives are underway to enhance process conditions and optimize reactor designs to minimize the energy demand of reforming processes [3-5].

[0007] Autothermal reactors are designed to operate efficiently by simultaneously combining exothermic and endothermic reactions without needing external heat transfer equipment or limiting their need. Several forms of autothermal reactors include fixed-bed reactors, fluidized-bed reactors, and membrane reactors [4,5].

[0008] Fluidized bed autothermal reactors suspend the catalyst particles in the reactant flow, ensuring efficient mixing and heat transfer. Membrane reactors incorporate selective membranes that facilitate the separation of products, allowing simultaneous reactions and product separation, enhancing overall efficiency. Additionally, autothermal operation can be achieved using direct heat transfer and contact between hot streams and endothermic reactors [4,5,7-10].

[0009] In fixed-bed autothermal reactors, reactants pass through a stationary catalyst bed where exothermic and endothermic reactions occur. However, continuous operation by circulating theendothermic reaction product to the exothermic reactor is still challenging, primarily when solid products like carbon are formed [4-7].

[0010] Hydrogen is produced chiefly through steam reforming of natural gas worldwide, which releases large amounts of CO2 and necessitates the development of a hydrogen production method that can significantly minimize GHG emissions [1 ,10].

[0011] The global steam reforming process occurs over two sequential steps: steam reforming and water gas shift reaction, during which methane, ethane, and propane are converted into CO2 and Hydrogen in excess water. The first step is steam reforming, during which hydrocarbons like methane turn into syngas, primarily composed of H2 and CO. The process requires a catalyst and high temperatures and pressures, usually above 750°C and 30 bars, along with steam and the hydrocarbon feedstock

[0011] .

[0012] In the water gas shift (WGS) reaction, CO reacts with water to produce CO2 and additional hydrogen. A catalyst usually facilitates this reaction, and by adjusting the operating conditions, the WGS reaction can be controlled to yield more hydrogen and carbon dioxide.

[0013] The overall reaction is known as global steam reforming. This energy-demanding reaction emits a large amount of CO2 per Hydrogen produced. Current systems implement complicated separation techniques to separate CO2 produced from the exhaust gases and store it in ecological reservoirs, which is costly and can lead to detrimental effects in the future.

[0014] The emissions associated with hydrogen production are estimated at 11-13 kg of CO2 eq. / kg of hydrogen. The process emission resulting from the reaction is around half the total carbon emissions associated with hydrogen production from natural gas through steam reforming. A considerable part of emissions is related to the heat needed to vaporize water into steam [11-14]. In addition, water is used in steam reforming and other processes for producing hydrogen, leading to higher pressure on the limited freshwater supply [1 , 2].

[0015] Carbon emissions greatly influence the visibility of emerging hydrogen production technologies. Assessing the carbon emissions generated by new processes is crucial when planning for hydrogen as a future clean fuel. An optimum process can be developed by substantially reducing the carbon emissions linked to hydrogen production through reaction products or energy supply [1 , 2],

[0016] Several patent documents disclose modified low-emission hydrogen production methods. However, these patents focused on modified NG steam reforming methods to reduce energy demand throughout the process and increase hydrogen production yield by modifying the design, catalyst, or capturing and storing the produced CO2 [15-17].

[0017] Several patent documents disclose methane pyrolysis to produce hydrogen at temperatures higher than 1000°C or using a catalyst to run methane cracking at 600°C, significantly reducing the produced carbon quality and preventing continuous operation [18,19]. Operating at ahigh-temperature range will increase the capital and operating costs due to the limitations imposed on material selection at high-temperature operation and energy demand.

[0018] Several patent documents disclose that employing renewable energy to produce hydrogen leads to lower utility emissions [20,21]. However, no patented process significantly reduces CO2 emissions generated during hydrogen production from NG or provides a method that significantly reduces energy demands for hydrogen production and allows continuous operation while generating solid carbon.

[0019] The dry reforming of methane (DRM) uses CO2 and methane to produce syngas containing CO and hydrogen. The temperature required for this reaction is usually around 700°C or higher, and the hydrogen produced is associated with large amounts of CO2 emissions due to significant energy demands and CO emissions from the process. The energy demand per one mole of methane is 260.5 kJ / mol. CO is generated as a byproduct along with hydrogen, regarded as a greenhouse gas (GHG) and a hazardous poison gas

[0022] .

[0020] The challenges associated with the DRM process have limited its application on a commercial scale as a hydrogen production pathway.

[0021] GHGs affect the environment and the global economy, leading to unpredictable weather and environmental changes. Developing technology for recycling CO2 into higher hydrocarbons and valuable chemicals will help maintain the environmental balance and will help achieve the world’s sustainability goals in 2030 and 2050 [3,23].

[0022] Several processes and designs were developed and patented to utilize and convert CO2 into hydrocarbons using hydrogenation reactions or by converting CO2 to syngas. Then, the syngas can generate hydrocarbons through the Fisher-Tropsch process [24-26]. Using hydrogen to convert CO2 is usually associated with carbon emissions during hydrogen production. At the same time, the Fisher-Tropsch process utilizes hydrogen within the syngas, which requires a pre-step to form syngas. The pre-step is an endothermic reaction leading to a high carbon footprint for the process

[0027] .

[0023] However, these processes are not widely adopted due to the need for hydrogen, low yield, and high operating temperatures. CO2 conversion processes demand substantial energy and hydrogen to drive chemical reactions. In addition, solid carbon may be produced during these processes, leading to blockages, tremendous pressure drop across the reactor, and process termination. Harnessing advanced technologies and innovative methodologies is crucial in optimizing these processes, ensuring energy efficiency, lowering energy demand, and reducing the environmental footprint

[0028] .

[0024] Critical factors like hydrogen demand, utility costs, and the permanence of carbon sequestration heavily influence the viability of emerging CO2 conversion technologies. Converting CO2 into solid carbon can be used to mitigate carbon emissions permanently. The absence of acommercially viable CO2 conversion technology can be attributed to the substantial requirement for hydrogen, which entails significant carbon emissions and high energy demands [27,28]. These challenges make it difficult to implement existing processes widely [27,28].

[0025] CO2 is a stable molecule, and CO2 reforming requires considerable energy input. DRM, or reactions between CO2 and paraffins, can be used to reform CO2 and produce a syngas mixture. However, due to the endothermic nature of these reactions, these reactions are not considered economically and environmentally feasible. Combining these reactions with exothermic reactions to minimize the net energy demand is important to implement these processes on an industrial scale. Additionally, one of the most critical factors in assessing CO2 mitigation processes is the permanence of the mitigation; forming solid carbon represents an ideal method of permanent mitigation of CO2.

[0026] Propylene, also known as propene, is a critical raw material in the petrochemical industry. Several industrial processes produce propylene, including steam and catalytic cracking of hydrocarbons conducted around 49 atm. The two methods are limited by low yield and conversion rates and are distinguished by high carbon emissions, around 6 and 9 kg of CO2 eq. / kg of propylene, respectively

[0029] .

[0027] Alternatively, propylene can be produced at a higher yield and conversion through the oxidative dehydrogenation of propane with CO2 (ODPC) by reacting propane with CO2 to produce propylene, H2O, and CO

[0030] . The ODPC is an endothermic reaction requiring significant energy input and may lead to substantial net carbon emissions.SUMMARY

[0028] In accordance with the present disclosure, there is provided a reactor system comprising: an outer tube having an outer tube axis; and an inner tube comprising an inner first end and an inner second end and having an inner tube axis, the inner tube being thermally conductive and being located within the outer tube such that the inner and outer tube axes are aligned with each other, wherein the inner and outer tubes create an annulus between the inner and outer tubes, the annulus comprising an annulus first end and an annulus second end, and wherein the annulus second end is in fluid communication with the inner first end.

[0029] The inner tube may comprise a catalyst for catalyzing an exothermic reaction, and the annulus comprises a catalyst for catalyzing an endothermic reaction.

[0030] The catalyst for catalyzing an exothermic reaction may be formed from the material of the inner tube.

[0031] The catalyst used for endothermic reaction may be in the form of a catalyst bed.

[0032] The catalyst for catalyzing an endothermic reaction may be arranged around an inner wall of the inner tube (e.g., on the inner wall).

[0033] The catalyst for catalyzing an endothermic reaction may be a catalyst for Dry Reforming of Methane. The catalyst for catalyzing the endothermic reaction may comprise a transition metal, an alkali earth metal, and a lanthanide metal mounted on a support.

[0034] The support may be inert.

[0035] The support may comprise one or more of: alumina, Y-alumina, 0-alumina, a-alumina, inert ceramic, and silica.

[0036] The catalyst for catalyzing the exothermic reaction may comprise a transition metal.

[0037] At least one product of the endothermic reaction may be a reactant in the exothermic reaction.

[0038] The catalyst used for endothermic reaction may catalyze a reaction between methane and carbon dioxide to produce carbon monoxide and hydrogen.

[0039] The catalyst used for endothermic reaction may catalyze a reaction between propane and carbon dioxide to produce carbon monoxide, propylene, and water.

[0040] The catalyst used for endothermic reaction may catalyze a reaction between paraffins and carbon dioxide to produce carbon monoxide, olefins, hydrogen, and water.

[0041] The catalyst used for endothermic reaction may catalyze a reaction to produce carbon dioxide and solid carbon from carbon monoxide.

[0042] The catalyst used for exothermic reaction may catalyze a reaction between hydrogen and carbon monoxide to produce solid carbon and water.

[0043] The catalyst used for endothermic reaction may catalyze a reaction between propane and carbon monoxide to produce solid carbon, water, and hydrogen.

[0044] The catalyst used for endothermic reaction may catalyze a reaction between propane and carbon monoxide to produce solid carbon, water, and propylene.

[0045] The catalyst used for endothermic reaction may catalyze a reaction between propane and carbon monoxide to produce solid carbon and water.

[0046] The annulus second end may be adjacent to the inner first end.

[0047] The reactor system may comprise a tubular hydrogen separation membrane positioned within and along the length of the annulus.

[0048] The inner tube may house a solid removal system. In some embodiments, the inner tube and solid removal system may be combined with a non-tubular outer reactor, or a stand-alone reactor without being placed within an outer reactor.

[0049] The solid removal system may comprise an auger arranged along the length of the inner tube.

[0050] According to a further aspect, there is provided a process for producing hydrogen within the reactor system comprising one or more inner tubes and one or more annuli, each inner tube being surrounding by a said annulus, the process comprising: injecting reactants into a first end of a said annulus such that the reactants flow through the said annulus towards a second end and are converted to one or more endothermic products in an endothermic reaction, and directing at least a portion of the products from the endothermic reaction in the outer tube or the first reactor to a first end of said inner tube or a second reactor such that the portion of the endothermic products flow through the said inner tube towards a second end of the inner tube and are converted to products in an exothermic reaction.

[0051] The reactants may comprise carbon dioxide and a light hydrocarbon.

[0052] The products (of the endothermic and / or exothermic reactions) may comprise solid carbon.

[0053] The products (of the endothermic and / or exothermic reactions) may comprise hydrogen.

[0054] The process may comprise directing at least a portion of the unreacted reactants from the exit of the annulus second end to the inner first end such that the unreacted reactants flow through the inner tube towards the inner second end and are converted to products in an exothermic reaction.

[0055] The process may comprise separating hydrogen produced in one or more of the induced reactions.

[0056] According to a further aspect, there is provided a process for refining paraffins and CO2 to produce a mixture of olefins, hydrogen, and carbon.

[0057] The process may comprise a combination of one or more exothermic reactions and one or more endothermic reactions.

[0058] According to a further aspect, there is provided a process for producing propylene within the reactor system comprising one or more inner tubes and one or more annuli, each inner tube being surrounded by a said annulus, the process comprising: injecting reactants into the first end of a said annulus such that the reactants flow through the said annulus towards a second end and are converted to one or more endothermic products in an endothermic reaction and directing at least a portion of the products from the endothermic reactions to the first end of said inner tube such that the portion of the products from the endothermic reactions flow through the said inner tube towards a second end of the inner tube and are converted to exothermic products in an exothermic reaction.

[0059] According to a further aspect, there is provided a method for activating a reactor surface to produce graphite-type materials comprising:providing a reactor surface comprising iron (e.g., made of carbon steel, stainless steel, or ceramic with an iron-containing coating); passing an oxygen-containing gas over the reactor surface at temperatures between 450°C to 750°C to expose catalytically active iron atoms.

[0060] In the ceramic case, there may be a previously added coating of an active iron compound on the surface of the ceramic, which is activated for producing the active catalyst for producing graphite. With ceramic, a layer of catalyst (or catalyst precursor) may be added through coating techniques or other catalyst application methods based on the type of ceramic material.

[0061] The method may comprise activating the internal surface by chemical etching or coating with an iron salt, followed by thermal activation.

[0062] The reactor surface may be the inner wall of a tubular reactor.

[0063] The reactor surface may be made of ceramic, and the internal surface is coated with an iron-based active phase.

[0064] The method may comprise introducing a carbon-containing gas into the reactor under controlled temperature and pressure conditions to induce graphite formation on the catalytically active iron atoms.

[0065] The carbon-containing gas may be selected from the group consisting of methane, ethane, propane, natural gas, ethylene, carbon dioxide, and carbon monoxide.

[0066] According to a further aspect, there is provided a process for producing C4 hydrocarbon, the process comprising reacting propane in the presence of a catalyst to produce C4 hydrocarbon and solid carbon.

[0067] The C4 hydrocarbon may comprise one or more of butene, isobutylene, isobutane and butane.

[0068] The catalyst may comprise one or more of: molybdenum carbide; nickel and cerium oxides.

[0069] According to a further aspect, there is provided a A reactor system comprising: an outer container having a container inlet; and an inner tube comprising an tube inlet and a tube outlet, the inner tube being thermally conductive, wherein a first reactor is formed between the inner tube and the outer container and a second reactor volume is inside the inner tube, and wherein the first and second reactors are in fluid communication.

[0070] The tube inlet may be positioned within the container away from the container inlet.

[0071] Tthe tube may pass through a wall of the container.

[0072] The first reactor may comprise a first catalyst for catalysing an endothermic reaction, and the second reactor comprises a second catalyst for catalysing an exothermic reaction.

[0073] The reactor system may comprise a solid removal system for removing solids from the first reactor.

[0074] According to a further aspect, there is provided a reactor system comprising: a tube with inner walls comprising a catalyst for converting gaseous reactants into a solid product; and a solid removal system configured to scrape the inner walls to remove solid product attached to the inner walls.

[0075] The solid removal system may comprise an auger extending along the length of the tube.

[0076] In accordance with the present disclosure, there is provided a reactor for handling a combination of endothermic and exothermic reactions where a solid product is generated.

[0077] The reactor may comprise two concentric tubes. The endothermic reaction may occur in the outer tube (e.g., in the annulus) and the exothermic reaction may occur in the inner tube (reactor). The outer tube may be considered as a first reactor. The inner tube may be considered as a second reactor.

[0078] The inner tube may have openings such that products from the outer tube may pass from the annulus to the inner tube.

[0079] The feed stream may enter the annulus (reactor) from the bottom and moves upward across a catalytic bed to catalyze the endothermic reaction.

[0080] The product from the endothermic reactions may enter the inner tube (reactor) from the top through openings connecting the outer tube (e.g., the annulus) and the inner tube. This allows the gas to flow freely into the inner tube (reactor) and ensures optimal stream distribution as it enters.

[0081] The inner tube may facilitate the exothermic reaction, generating heat to eliminate or minimize the energy demand of the endothermic reaction.

[0082] The inner tube may be an active material, an activated material or alloy. The inner tube may be a vessel decorated with an active catalyst for the exothermic reaction where solids can deposit on the active catalyst on the wall.

[0083] The inner tube may house a solid removal system to continuously remove solid products formed during the exothermic reaction, where the inner tube (reactor) vessel plays a role as a self- supporting catalyst for the exothermic reaction.

[0084] In accordance with the present disclosure, there is provided a process for producing solid carbon allotropes products and low-emissions hydrogen from a gas comprising CO2 and natural gas.

[0085] The inner and outer tube axes may be aligned with each other.

[0086] In the outer tube (e.g., in the annulus), the inlet stream may be converted into a mixture of CO and H2 using a catalytic agent.

[0087] The stream containing CO from the annulus (reactor) may react in the inner tube (reactor) to form solid carbon allotropes using a catalytic agent.

[0088] The net reaction produces solid carbon allotropes and hydrogen, in addition to other hydrocarbons like olefins.

[0089] In accordance with the present disclosure, there is provided a process for producing olefins, hydrogen, water, and solid carbon allotropes products from a gas comprising CO2 and paraffins.

[0090] In the annulus (reactor), the inlet stream may be converted into a mixture of CO, H2, and olefins using a catalytic agent.

[0091] The products from the annulus (reactor) may react in the inner tube (reactor) with paraffins to form solid carbon allotropes using a catalytic agent.

[0092] The net reaction may produce water, hydrogen, and solid carbon allotropes, in addition to other hydrocarbons like olefins.

[0093] In accordance with the present disclosure, there is provided a reactor vessel that can be employed as a self-supporting catalyst.

[0094] The reactor vessel (tube) may comprise a metallic, carbonaceous, or ceramic material or alloy that is activated or coated with an active catalyst for the intended reaction to act as a catalyst for the intended reaction, allowing the continuous operation of many reactions, including reactions where solids are produced.

[0095] The catalyst used for endothermic reaction may be in the form of a catalyst bed. The catalyst used for exothermic reaction may be arranged around an inner wall of the inner tube.

[0096] The catalyst used for endothermic reaction may be a catalyst for Dry Reforming of Methane (DRM) having a transition metal, an alkali earth metal and a lanthanide metal mounted on a support.

[0097] The support may be inert. The support may not react any of the reactants or products in the endothermic reaction.

[0098] The support may comprise one or more of: y-alumina, 0-alumina, a-alumina, inert ceramic, and silica.

[0099] The catalyst used for exothermic reaction may comprise a transition metal.

[0100] At least one product of the endothermic reaction (e.g., carbon monoxide) may be a reactant in the exothermic reaction.

[0101] The catalyst may catalyze an endothermic reaction between methane and carbon dioxide to produce carbon monoxide and hydrogen.

[0102] The catalyst may catalyze an endothermic reaction between an alkane (e.g. propane) and carbon dioxide to produce carbon monoxide, an alkene (e.g., propene) and water.

[0103] The catalyst may catalyze an exothermic reaction to produce carbon dioxide and solid carbon from carbon monoxide.

[0104] The catalyst may catalyze an exothermic reaction between an alkane (e.g. propane) and carbon monoxide to produce solid carbon, water and hydrogen.

[0105] The catalyst may catalyze an exothermic reaction between an alkane (e.g. propane) and carbon monoxide to produce solid carbon, water and an alkene (e.g. propene).

[0106] The catalyst may catalyze an exothermic reaction between an alkane (e.g. propane) and carbon monoxide to produce solid carbon and water.

[0107] The annulus second end may be adjacent to the inner first end.

[0108] The reactor system may comprise a tubular hydrogen separation membrane positioned within and along the length of the annulus. The outer tube may comprise a hydrogen separation membrane. The outer tube may be a hydrogen separation membrane.

[0109] The inner tube may house or contain a solid removal system. The system may allow continuous formation and removal of solids during the reaction.

[0110] By incorporating a solid removal tool for solids removal in a continuous operation mode, like Auger, Drill bits, Rotary Brushes and Scrapers, Pigs, Swaps, and Rodder Systems.

[0111] The outer tube can be made of stainless steel, Inconel, ceramic, or other inert materials for the described processes and can withstand the temperature range of 400-700°C. The inner tube can be made of active material like low carbon steel or other metallic alloy tubes, carbon tubes, activated tubes, or ceramic tubes decorated with active catalysts for the reaction occurring inside the tube. The outer side of the inner tube faces the endothermic reaction catalyst zone (1003). It may be passivated using an inert coating or inserting the inner tube into another passive tube, like ceramic or Inconel tube, to eliminate any catalytic contribution of the inner tube towards the endothermic reaction.

[0112] In another embodiment, the inner tube can be designed in a dual-tube configuration by having an active alloy like steel on the inner side of the tube and a passive (e.g., inert) alloy like Inconel on the outer side of the tube.

[0113] In accordance with the present disclosure, there is provided a process for utilizing CO2 emissions to convert the emissions into solid carbon products:

[0114] The process may have a net CO2 consumption, which entirely fixates CO2 emissions.

[0115] It will be appreciated by those skilled in the art that such an endo-exo combined reactor system, such as the one presented in this disclosure, may be used to carry out a range of other different endothermic and exothermic reaction combinations.

[0116] For example, the reactor system may employ a combination of Dry Reforming of Methane (DRM) and the Boudouard Reaction (BR). Within the DRM process, methane and CO2 react over a catalytic bed to yield syngas (carbon monoxide and hydrogen). This produces syngas with an H2 / CO molar ratio of 1. DRM, being inherently endothermic, demands a continuous energy input. This may be provided by the exothermic Boudouard Reaction after hydrogen separation or throughthe CO hydrogenation reaction. In other embodiments, the generated CO may be reacted with paraffinic compounds (e.g., CsHs) into carbon, CO2 and / or water. Hydrogen may also be produced in the exothermic and / or endothermic reactions.

[0117] In another embodiment, when converting CO2 into solid carbon allotropes and higher hydrocarbons, CO2 may be reacted with paraffinic compounds (e.g., CsHs) within the outer reactor tube over a catalytic bed, yielding CO, water, and olefins (alkenes) like C3H6 (propene). Endothermic processes such as these can be used to produce C3H6 while mitigating CO2, requiring a continuous energy supply.

[0118] The generated CO may then be used in an exothermic reaction, in another embodiment, with paraffins (e.g., CsHs), producing solid carbon allotropes, hydrogen, olefin (C3H6), and water. In this way, the CO2 reaction with paraffins like C3H8 can be employed to produce propylene (propene) with low carbon emissions.

[0119] In another embodiment, the CO reacts with paraffins, exemplified by C3H8, producing solid carbon allotropes and water. In the context of this disclosure, the reactions described in relation to propane may be applicable to other light paraffins. Light paraffins may include saturated hydrocarbons up to C6 (hexane) or C7 (heptane).

[0120] In a further embodiment, CO is converted to CO2 and solid carbon over the catalyst layer coating the inner reactor tube or the second reactor.

[0121] In another embodiment, CO2 can be converted into solid carbon allotropes using a combination of endothermic reactions like DRM or ODPC with an exothermic reaction forming solid carbon allotropes.

[0122] In another embodiment, the described reactor design can be used to perform reactions where the solid product is generated in a continuous mode by using an active reactor vessel and by employing a solid removal system inside the reactor.

[0123] In many of these reactions, the exothermic reaction generates solid carbon allotropes. In the present technology, an internally designed solid removal system may be used to remove carbon buildup on the reactor walls, ensuring continuous operation. Consequently, this process mitigates methane and CO2 emissions by transforming methane and CO2 into hydrogen, higher hydrocarbons, and solid carbon allotropes.

[0124] This disclosure relates to the use of a reaction vessel as a self-supporting catalyst to carry out the Boudouard reaction, CO hydrogenation, and reactions between CO and olefins (e.g., CsHs) to form a solid carbon product. The reactor where these exothermic reactions are performed can be an active metallic alloy vessel, activated metallic alloy vessel, carbon-steel vessel, or a vessel coated with a thin layer of active phase for these reactions.

[0125] In another embodiment, the inner tube (reactor) can be used to house the endothermic reaction, while the annulus (reactor) can be used for the exothermic reaction.

[0126] According to a further embodiment, there is provided a process comprising: injecting reactants into a first end of a said annulus such that the reactants flow through the said annulus towards a second end and are converted to one or more endothermic products in an endothermic reaction, and directing at least a portion of the endothermic products to a first end of a said inner tube such that a portion of the endothermic products flow through the said inner tube towards a second end of the inner tube and are converted to exothermic products in an exothermic reaction.

[0127] The reactants may comprise carbon dioxide and a light hydrocarbon.

[0128] The endothermic and / or exothermic products may comprise solid carbon.

[0129] The endothermic and exothermic products may comprise hydrogen.

[0130] The process may comprise directing at least some of the unreacted reactants from the exit the annulus second end to the inner first end such that the unreacted reactants flow through the inner tube towards the inner second end and are converted to products in an exothermic reaction.

[0131] The process may comprise separating hydrogen produced in one or more of the exothermic and endothermic reactions.

[0132] According to a further embodiment, there is provided a process for producing solid carbon allotropes from light hydrocarbons and CO2 mixture.

[0133] The process may comprise: performing an endothermic reaction in which one or more reactants are converted to one or more endothermic products, wherein the one or more reactants comprise light hydrocarbons and carbon dioxide, and the one or more endothermic products comprise carbon monoxide, and performing an exothermic reaction in which the one or more endothermic products are converted into one or more exothermic products, wherein the one or more products comprise solid carbon.

[0134] The endothermic reaction may convert one or more endothermic reactants into one or more endothermic products. The exothermic reaction may convert one or more exothermic reactants into one or more exothermic products.

[0135] The one or more endothermic products may comprise hydrogen. The hydrogen may be separated.

[0136] The one or more exothermic products may comprise carbon dioxide. The carbon dioxide exothermic product may be recycled as a said reactant.

[0137] The endothermic and / or exothermic products comprise an olefin.

[0138] The process can generate solid carbon allotropes in a continuous mode, leading to an economical path for large-scale production of solid carbon products, which can be used further in several carbon applications, for instance, graphite for car batteries.

[0139] The described reactor may be used to carry out reactions and / or reaction combinations summarized in Tables 1-3 below.

[0140] In the annulus (reactor) or the first reactor, endothermic reactions take place depending on the feed stream. CO2 reacts with methane or paraffins to generate carbon monoxide, hydrogen, water, and olefins, as shown in Table 1 .

[0141] Table 1 : Examples of possible endothermic reactions

[0142] In the inner or second tube (reactor), carbon monoxide reacts with itself to form carbon or reacts with H2 to produce carbon and water, following the reactions in Table 2.

[0143] Table 2: Possible combinations of exothermic reactions in the innertube (reactor) following Reaction (1) in the annulus (reactor)

[0144] Reaction (3) will be the only reaction taking place when hydrogen is separated from Reaction (1) products and only pure CO is sent to the inner or second tube (reactor), forming a solid carbon. In a mixture of CO and hydrogen, multiple reactions can occur, including those described by Reactions (3) and (4), which may lead to the formation of solid carbon. This carbon forms due to the simultaneous progression of both reactions.

[0145] In the inner tube (reactor), CO may react with propane to produce carbon and water, following the Reactions (5)-(7) in Table 3. In a mixture of CO and propane, multiple reactions can occur, including those described by Reactions (3)-(7), which may lead to the formation of solid carbon. This carbon forms due to the simultaneous progression of both reactions.

[0146] Table 3: Possible combinations of exothermic reactions in the innertube (reactor) followingReaction (2) in the annulus (reactor)

[0147] The described reactor allows the conduction of several processes using catalysts through several combinations of endothermic (Reactions (1) and (2)) and exothermic reactions (Reactions (3)-(7)). The reactor may employ a combination of catalytic materials and process conditions that facilitate the conversion of CO2 into a range of compounds, including carbon-neutral fuels, chemicals, and solid materials.

[0148] The reactor may combine Reaction (1) with one or more exothermic Reactions (3)-(4) in Table 2. The reactor may combine Reaction (2) with one or more of the exothermic Reactions (3)- (7) in Tables 2 and 3. Additionally, the process may combine Reaction (1) or Reaction (2) with one or more of exothermic Reactions (3)-(4) in Table 2 and / or Reactions (5)-(7) in Table 3.

[0149] Reaction (1 , Dry Reforming of Methane (DRM) may use a DRM catalyst. The DRM catalyst may have a transition metal (Ni, W, Fe, Co, Mn or mixtures thereof), an alkali earth metal (Mg, Ca, Sr, Ba or mixtures thereof), and a lanthanide metal (La, Ce, Nd, Gd or mixtures thereof) supported over alumina, silica, silica-alumina, titania, clays or combinations thereof, and an inner reactor tube or the second reactor coated with a transition metal like Fe, Mn, Ni or Co as a catalyst, carbon, or made of an alloy that is active for these reactions.

[0150] Oxidative dehydrogenation of propane with CO2 (ODPC) may use an ODPC catalyst. The ODPC catalyst may have a transition metal (Ni, W, Fe, Co, Mn or mixtures thereof), an alkali earth metal (Mg, Ca, Sr, Ba or mixtures thereof), and a lanthanide metal (La, Ce, Nd, Gd or mixtures thereof) supported over alumina, silica, silica-alumina, titania, clays or combinations thereof, and an inner reactor tube or the second reactor coated with a transition metal like Fe, Mn, Ni or Co as a catalyst, or made of an alloy that is active for these reactions.

[0151] For instance, several catalysts were developed and tested previously for DRM and ODPC, including molybdenum carbide and a catalyst composed of non-noble metal, an alkaline earth metal, and a rare earth metal [33-35].

[0152] The inner or second tube (reactor) may be a metal tube containing more than 75% iron content or a metal alloy tube containing more than 75% iron content activated or modified using heat treatment, catalyst activation processes, or alkaline or acidic chemical etchings. In addition, the tube may be coated with a thin layer of an active catalyst for the reactions shown in Tables 2 and 3.

[0153] The inner or second tube (reactor) may be a metallic tube containing the following metals: Fe, Mn, Ni, or Co, and / or carbon tube that can be activated or modified using heat treatment, catalyst activation processes, or alkaline or acidic chemicals. In addition, the tube may be coated or decorated with an active catalyst for the reactions shown in Tables 2 and 3, using several methods available for loading the catalyst on support or tubes.

[0154] The inner tube may be coated with a catalyst like Fe, Ni, Mn, Co, or mixtures thereof that catalyze the Boudouard reaction (Reaction 3) or Reactions (4)-(7) in Tables 2 and 3 or acombination of these reactions to produce solid carbon and CO2. Coating the interior of the inner tube may make it easier to remove the produced solid carbon without removing the catalyst. The inner tube can also be a refractory ceramic tube made of alumina, silica, or similar tubes and coated with a thin layer of an active metal catalyst, as described above, for the desired reaction.

[0155] A catalyst for the Boudouard reaction (BR) may contain Fe, Ni, Mn, Co, or mixtures thereof to support CO conversion into solid carbon allotropes and CO2.

[0156] A catalyst for Reactions (4) - (7) in Tables 2 and 3 may contain Fe, Ni, Mn, Co, or mixtures thereof to support CO conversion into solid carbon allotropes, hydrogen, propylene, and water.

[0157] The inner tube may be loaded with solid catalysts to catalyze Reactions (3)-(7) in a batch operation mode or other reactions to form other hydrocarbons using the mixture produced through Reactions (1) and (2) or by combining endothermic and exothermic reactions; for instance, the following reactions may take place:2C3H6« 2CH4+ C2H4+ 2C AH298=-137.6 kJ / mol (8)2C2H4« C4H8AH298=-121.7 kJ / mol (9)4CH4+ C2H42C4H10AH298=-259.4 kJ / mol (10)

[0158] The catalysts may be used for Reactions (3)-(10), including a transition metal (Ni, W, Fe, Co, Mn or mixtures thereof), an alkali earth metal (Mg, Ca, Sr, Ba or mixtures thereof), and a lanthanide metal (La, Ce, Nd, Gd or mixtures thereof) supported over alumina, silica, silica-alumina, titania, clays or combinations thereof.

[0159] The catalysts used for DRM or ODPC for hydrogen production, propylene production, or CO2 utilization (Reactions (1) and (2)) may contain other active phases, including transition metals like Fe, W, Mn, and Co; alkaline earth metals like Ca, Sr, and Ba; and lanthanide metals like La, Nd, Sm, and Gd. The catalyst may be active at temperatures below 650°C (or below 620°C), significantly reducing the energy demand to maintain the DRM reaction, which usually occurs above 700°C [33,34],

[0160] Also disclosed is a process for converting and mitigating CO2 to produce valuable hydrocarbons and olefins like olefins, hydrogen, water, and CO by reacting CO2 with paraffins to produce olefins, hydrogen, water, and CO. The produced CO forms solid carbon through Reactions (3)-(7) in Tables 2 and 3 to generate solid carbon, water, and energy. Olefins can be further converted into other hydrocarbons following Reactions (8)-(10) to create solid carbon and energy. The reaction product can be optimized by manipulating the catalyst and the process parameters.

[0161] Also disclosed is a process for producing solid carbon allotropes from CO2 and natural gas or paraffin through Reactions (1)-(2), then the products are used to create solid carbon allotropes through Reactions (3)-(7) or a combination of these reactions. The combinations of Reactions (1) and / or (2) with one of the Reactions (3)-(7) or a combination of these reactions will mitigate CO2 emissions into permanent solid carbon allotropes that can be used in several applications withminimum energy demand without adding hydrogen demand. High-temperature or low-temperature may be used to separate the hydrogen or propylene produced in Reactions (1) and (2) if the process is directed to produce solid carbon allotropes through Reaction (3) in addition to hydrogen or propylene [36-43]; for instance, a high-temperature membrane may be used to separate hydrogen [36-39],

[0162] In the context of this disclosure, paraffins may be taken to mean saturated hydrocarbons (i.e ., alkanes), and olefins may be taken to mean unsaturated hydrocarbon compounds containing at least one carbon-to-carbon double-bond (i.e., alkenes).

[0163] Also disclosed is a reactor design that combines endothermic and exothermic reactions to minimize energy demand and heat losses, allowing solid products continuously. It uses two concentric tubes with direct looping from one tube to another without employing external tubes or connections.

[0164] Also disclosed is a reactor design that combines endothermic and exothermic reactions to minimize energy demand and heat losses. It uses two tubes in series with direct looping from one tube to another, with or without internal or external separation technologies between the two tubes, like high-temperature membranes, low-temperature membranes, pressure separation techniques, temperature separation techniques, and chemical separation techniques. This design may employ in-situ or external separation methods for collecting hydrogen or propylene.

[0165] Additionally, the described processes can be conducted in two separate reactors connected in series, where the first reactor houses the endothermic reaction, and the second tube houses the exothermic reaction. This design may employ in-situ or external separation methods for collecting hydrogen or propylene. An external heat exchanger or a heating medium can transfer heat from the exothermic reactor to the endothermic reactor.

[0166] The system may comprise a solid removal system in the inner reactor tube or the second reactor. Using a solid removal system removes carbon deposited through Reactions (3)-(7) in Tables 2 and 3, where carbon is deposited on the active reactor wall. The inner tube or the second reactor vessel or part of it is used as a catalyst for Reactions (3)-(7).

[0167] The system may comprise a solid removal system for reactions that may generate solid carbon allotropes or other solids produced through chemical reactions where the reaction vessel can be activated to catalyze the reaction. Combining the solid removal system with a water trap, cyclones, or wet filters to collect the produced solid carbon allotropes can be collected at the exit. Several solid collection methods can be used to collect the produced solids.

[0168] Also disclosed is a catalyst that can be used for the dry reforming of methane or oxidative dehydrogenation of propane with CO2 at a low-temperature range within 500-600°C at a reasonable reaction rate. Conducting the DRM / ODPC reaction in combination with an exothermic reaction like Reactions (3)-(7) or a combination of these reactions to reduce the energy demand.

[0169] Several materials may be used as the tube material for the outer reactor tube or first reactor, including Inconel, Hastelloy, high carbon stainless steel, other inert stainless-steel alloys, inert heat conductive ceramic tubes, any other inert metallic tubes, or other tubes covered with inert or catalyst layer.

[0170] The inner tube may be a metallic tube made of materials that are active catalysts, like steel, carbon, and other metallic alloys that can be activated for Reactions (3)-(7) and / or covered with an active catalytic phase. In addition, the inner or second reactor tube may be made of heat-conductive ceramic tubes covered with a (thin) catalyst layer. The thickness of this layer may range from 0.1 pm to 5 mm, which is related to the required process and the coating / catalyst application method.

[0171] The inert lower layer added under the catalyst in the annulus, or first reactor, may be a- alumina, other alumina support, inert ceramic, silica, or other inert heat sink materials like carborundum.

[0172] The solid removal system may comprise a mechanical removal system, such as one or more of: augers, drills, brushes, pigging, scrapping, pistons, and blades. In addition, several other removal methods can be employed using gas, ultrasonic, chemical, vacuum, flushing, sonic / acoustic, electrostatic, magnetic, robotic, laser, microwave, agitation, and / or abrasive removal.

[0173] The inner tube may be used without the solid removal system as an empty reactor tube to remove the solid product when operated in batch mode for combining reactions, as included in Tables 1-3. In addition, a solid catalyst can be added inside the inner or second reactor tube to promote another catalytic reaction that does not include solid formation, for instance, Reactions (9) and (10).

[0174] The reactor may comprise two concentric tubes where the endothermic reaction takes place in the outer reactor tube, and the exothermic reaction occurs inside the inner reactor tube. Alternatively, the reactor design can be modified using two tube reactors in series with a heat exchanger inside or outside the reactor assembly to conduct the reactions in Tables 1-3 by combining endothermic and exothermic reactions.

[0175] The reactor design for housing any combination of these reactions in Tables 1-3 can be two concentric tubes or two reactors in series. In the first or outer reactor tube, DRM or the reaction of CO2 and propane or other paraffins (Reactions (1) and or (2)) in Table 1) occurs. While in the inner reactor tube or the second reactor, one or a combination of Reactions (3)-(7) in Tables 2 and 3 is conducted.

[0176] For producing hydrogen and solid carbon allotropes, the following reaction combinations can be used, including DRM with either the exothermic BR reaction (Reaction (3)), paraffins (Reactions (5)-(7) in Table 3), or a combination of these reactions by providing a substoichiometric amount of paraffins. The net process will produce hydrogen and solid carbon allotropes in additionto energy, significantly reducing the energy needed for the DRM reaction, producing hydrogen at a lower carbon footprint compared to steam reforming while producing high-quality solid carbon. In this process configuration, hydrogen can be separated using the widely available high or low- temperature methods inside the outer reactor or by treating the product stream from the first reactor to collect hydrogen before the inner tube or the second reactor to prevent hydrogen consumption in exothermic reactions with CO (Reaction 4).

[0177] For CO2 conversion, producing solid carbon allotropes and propylene, the following reaction combinations may be used, including CO2 reaction with propane or other paraffins (Reaction (2) in Table 1) with either exothermic Boudouard reaction (Reaction (3) in Table 2), CO hydrogenation reaction (Reaction (4) in Table 2), the exothermic reaction of CO and paraffins (Reactions (5)-(7) in Table 3), or a combination of these reactions by providing a substoichiometric amount of paraffins.

[0178] For producing propylene and solid carbon allotropes, the following reaction combinations can be used, including ODPC with one of the exothermic reactions (Reactions (3)-(7) in Tables 2 and 3) or a combination of these reactions. The net process will produce propylene and solid carbon allotropes in addition to energy, significantly reducing the energy needed for the ODPC reaction, producing propylene at a lower carbon footprint while producing high-quality solid carbon. In this process configuration, propylene can be separated using high- or low-temperature methods widely available for collecting propylene.

[0179] For CO2 mitigation and solid carbon formation, the following reaction combinations may be used, including CO2 reaction with methane, ethane, propane, or other paraffins (Reactions (1) and (2) in Table 1) with either exothermic Boudouard reaction (Reaction (3) in Table 2), CO hydrogenation reaction (Reaction (4) in Table 2), the exothermic reaction of CO and paraffins (Reactions (5)-(7) in Table 3), or a combination of these reactions by providing a substoichiometric amount of paraffins.

[0180] The described processes may be conducted continuously by installing a solid removal system in the active or activated inner reactor tube in the case of having the two concentric tube designs or in the second reactor in the case of two reactors in a series. In addition, these processes can be conducted in batch mode without using the auger by running the unit until the inner or second reactor is completely plugged.

[0181] The outer and inner reactor tubes or the first and second reactors for the reactions’ combinations may be covered with active catalyst layers for the processes or reactions mentioned in this disclosure.

[0182] Also disclosed is using a combination of Reaction (1) in Table 1 with one of the exothermic reactions (Reactions (3) and Reactions (5)-(7) in Tables 2 and 3) or a combination of thesereactions to produce hydrogen and solid carbon. This process may generate hydrogen at a lower carbon footprint than current processes for producing hydrogen at a minimum energy demand.

[0183] Also disclosed is using a combination of Reaction (2) in Table 1 with one of the exothermic reactions (Reactions (3)-(7) in Tables 2 and 3) or a combination of these reactions to produce propylene and solid carbon. This process may generate propylene at a lower carbon footprint than current processes for producing propylene at a minimum energy demand.

[0184] Also disclosed is the use of combinations of Reactions (1) and (2) in Table 1 with Reactions (3)-(7) or a combination of these reactions to mitigate and utilize carbon emissions to convert CO2 to solid carbon allotropes.

[0185] The outer reactor tube or the first reactor may be made of inert material or alloy, such as, for instance, Inconel or Hastelloy, not limited to them. Also, poor heat-conductive or heat-insulator material like ceramic should be used for the outer reactor tube or the first reactor, or the outer reactor tube or the first reactor should be covered with a catalyst layer instead of using a catalyst bed.

[0186] The first tube or the first reactor design may be either a tube, several tubes like a radiator where the exothermic reaction reactants can be disturbed, a corrugated tube, several corrugated tubes, or other tube designs.

[0187] The inner tube design or the second reactor may be either a tube, several tubes like a radiator where the exothermic reaction reactants can be disturbed, a corrugated tube, several corrugated tubes, or other tube designs.

[0188] Also disclosed is the running of carbonization and other solid formation reactions that produce solid carbon allotropes or solid products in a continuous mode in a reactor with a solid removal system.

[0189] The reactor design of two reactor tubes combination may be several concentric tubes inside each other, like a tube-in-tube -reactor, where the consecutive tubes are layers of endothermic and exothermic reactors where heat is transferred from exothermic layer or reactor to endothermic layer or reactor.

[0190] The reactor design of two reactor combinations may be a group of several two concentric tubes; each outer tube and inner tube represent a combination of endothermic and exothermic reactors. Combinations of these tubes are placed inside a container, minimizing heat losses to the environment.

[0191] The reactor design of a two-reactor combination may comprise a collection of multiple tubes, with each tube accommodating the endothermic reactor nestled within a single reactor housing the exothermic reaction, resembling a heat exchanger design.

[0192] The reactor design of two tubes (reactors) may comprise two tubes (reactors) in series where the first tube houses the endothermic reaction while the second tube houses the exothermicreaction. Products may be separated using high-temperature or low-temperature separation systems inside or outside the reactor vessels.

[0193] A solid removal system may be used inside the reactor, which houses the carbon formation reactions. This reactor with the solid removal system can be used in combination with reactor housing Reactions (1) and / or (2) or independently to conduct solid formation reactions in a continuous mode where the reactor vessel plays a role in catalyzing the reaction.

[0194] The inner tube (reactor) may act as a catalytic agent for the reaction that occurs in the tube (reactor) by utilizing a suitable alloy for fabricating the inner tube or the second reactor; combined with the solid removal system, solid formation reactor may take place in a simple reactor design.

[0195] Hydrogen may be separated in situ by employing several available high-temperature membranes or low-temperature separation methods [36-38]. This design allows hydrogen collection through the DRM reaction in combination with the Boudouard reaction to convert CO into carbon, leading to hydrogen production with no process emissions. Using high-temperature membranes maximizes methane conversion through DRM.

[0196] Conducting CO2 utilization in a reactor that houses a combination of endo- and exothermic reactions to minimize the energy needed for CO2 utilization and conversion reactions.

[0197] Any source of renewable energy (solar, wind, nuclear, for instance) may provide the energy needed for the process, eliminating associated carbon emissions leading to low-carbon fuels, chemicals, carbon, and hydrogen.

[0198] The process allows conducting the equivalent of methane cracking or methane pyrolysis at a low-temperature range (<1000°C) demand while producing high-quality carbon [1 ,36]. Combining Reactions (1) and (3), the net process is equivalent to methane cracking or pyrolysis at low temperatures in a continuous mode compared to high temperatures used usually in the actual methane pyrolysis [1 ,19].

[0199] The process may comprise circulating the DRM or ODPC products directly to the inner reactor tube without external looping, minimizing heat losses significantly.

[0200] The outer reactor tube or first reactor tube may be heated (e.g., through electricity, using a furnace or heating tape as an external heating source). The external heating source is used initially to initiate the reaction and increase the catalytic bed temperature to the desired value.

[0201] The reacting gases may enter the outer or first reactor tube from the bottom, going through a heat sink bed like alumina, which provides the heat necessary to heat the gases to the desired temperature, then the catalyst bed, where the endothermic reaction occurs. The produced gases may leave the outer or first reactor tube from the top, going through openings at the top of the inner reactor tube or connection tubes to the second reactor tube, where the spontaneous exothermic reaction will occur.

[0202] In another embodiment, the reacting gases may enter the outer or first reactor tube from the bottom, going directly through the catalyst bed, where the endothermic reaction occurs.

[0203] The exothermic reaction releases the energy needed to sustain the endothermic reaction and solid carbon allotropes with no or minimum energy demand from an external heat source. To prevent blocking or plugging the inner or second reactor tube due to solid carbon allotropes accumulation, a solid removal system may be placed inside the inner reactor tube or second reactor to remove any layers of carbon formed on the reactor walls, which will be collected by gravity, pushing down, pushing up, using the solid removal system in any configuration, for instance, vertically, horizontally, and inclined within the reactor through a collection system placed below or connected to the reactor.

[0204] The solid removal system in the reactor may maintain continuous operation and prevent any pressure buildup inside the system due to solid carbon allotropes buildup. The moving parts used in the solid removal system, like the auger, are controlled by a motor, which can move back and forth to help recover the produced carbon. The motor can rotate the auger to dislodge produced carbon from the walls of the inner tube.

[0205] The carbon may be removed from the bottom of the inner tube when the reactor is operated in an upright position. In this way, gravity helps bring the dislodged solid to where it can be removed from the reactor system using a solid collection system.

[0206] The solid removal tool in the solid removal system in a continuous operation mode may be one of these tools or a combination of them, like Auger, Drill bits, Rotary Brushes and Scrapers, Pigs, Swaps, and Rodder Systems in an activated tube described in the previous point.

[0207] The exhaust gas stream components may be separated to recycle unreacted gases and to collect the produced desired gases like hydrogen or olefins like, for instance, propylene. The reactor may comprise a high-temperature membrane outlet connected to a collection system to store the produced pure hydrogen or propylene.

[0208] The total energy provided to the system can be determined based on the desired conversion and yields in each reaction. In addition, the heat released or absorbed by each reactor and the heat losses to the environment will affect the net energy demand or generation. Several temperature and pressure gauges may be placed inside and around the reactor system. The inlet flow is controlled through mass flow controllers.

[0209] During operation, heat is added from external sources to increase the catalyst bed temperature to the required level and initiate the endothermic reaction in the outer or first reactor tube. As the reaction starts, the product will react inside the inner or second reactor tube, generating the final product and a large amount of energy exchanged with the endothermic reaction, reducing or eliminating the external energy demand according to the reaction combinations and the desired conversion level.

[0210] The outer tube may be formed from an inert metallic made of Inconel, Hastelloy, high carbon stainless steel, other inert stainless-steel alloys, inert heat conductive ceramic tubes, any other inert metallic tubes, or other tubes covered with an active catalyst for this reaction. The inner reactor tube, or the second reactor, is a metallic tube made of an active catalyst phase, activated metallic alloy tube, active carbon-based tube, or covered with an active catalytic phase. In addition, the inner reactor tube can be made of heat-conductive ceramic tubes covered with a catalyst.

[0211] The pairing of two reactor tubes may take the form of concentric tubes nested within each other, resembling a tube-in-tube reactor configuration. Here, the successive tubes serve as layers, housing both endothermic and exothermic reactors, facilitating heat transfer from the exothermic layer or reactor to the endothermic layer or reactor. The reactor may operate as a multi-channel stack arranged in a circular configuration. The tubes are assembled to form a stack, and the reactants traverse through dedicated channels directed to both the exothermic and endothermic layers.

[0212] The reactor may comprise a combination of several concentric tube pairs, each outer tube and inner tube representing a combination of endothermic and exothermic reactors. Combinations of these tubes are placed inside a container, minimizing heat losses to the environment.

[0213] The reactor may comprise two-reactor combinations comprising of a collection of multiple tubes, with each tube accommodating the endothermic reactor nestled within a single reactor housing the exothermic reaction, resembling a heat exchanger design.

[0214] The reactor may comprise two reactors (tubes) connected in series.

[0215] The inner tube may comprise one or more of: a single tube, a smooth tube, multiple tubes, and a corrugated tube. The transverse cross-section of the inner tube may be rounded, ovoid, or circular.

[0216] The outer tube may comprise one or more of: a single tube, a smooth tube, multiple tubes, and a corrugated tube. The transverse cross-section of the inner tube may be rounded, ovoid, or circular.

[0217] The products may include low-emission hydrogen, hydrocarbons, water, and solid carbon allotropes. Several in situ or downstream units are used to condense and separate the gases, solid carbon allotropes, water, and hydrocarbons. The produced hydrogen is collected and stored for further use.

[0218] The first separation method may be implemented using high-temperature membranes to separate hydrogen in the outer or the first reactor tube. Then, the product stream will go through a carbon collection unit employing a water trap followed by a wet filter to remove any carbon or char particles. Then, a separation unit may be used to recover unreacted components to be recycled back into the reactor. The separation unit could be a membrane separation unit, pressureadsorption, cryogenic, or amine separation; for instance, high-temperature membranes and other separation techniques were used in previous art [36-39].

[0219] The separation system may comprise a cyclone followed by a wet filter, water trap, and other gas separation techniques.

[0220] The reactor system may be two regular reactors in series housing any combination of endothermic or exothermic reactions discussed herein.

[0221] By implementing a solid removal system, the reactors can house reactions that may result in carbon deposition in continuous operation mode followed by an external separation system like a cyclone.

[0222] The present technology provides a method for producing graphite-like carbon by modifying the internal surfaces of the reactor vessel. The reactor vessel may be carbon steel, stainless steel, other metallic tubes, carbon tubes, and / or ceramic to act as a catalyst for carbon deposition. The surface modification involves pre-treatment and activation processes, which create catalytic sites that enhance the growth of graphite-type carbon from a gaseous carbon-containing feedstock. The catalytic sites may comprise iron and / or carbon (e.g., from steel). In some embodiments, the graphite-like material is formed with the help of a structural modifier surface growth by the physical force exercised by blades on the surface of a carbon layer that is being formed; like for instance, with an auger.

[0223] In one embodiment, the internal surface of the reactor vessel is pre-treated with an oxygencontaining gas at a high temperature to oxidize the surface and expose active metal atoms. These exposed active metal atoms act as nucleation sites, catalyzing the formation of graphite-type carbon during subsequent carbon deposition reactions.

[0224] In an embodiment of the method, surface etching of the metal surface can be enhanced by cyclic / repeated oxidation (as for instance by using O2 diluted in He) and reduction reactions (H2 diluted in Ar) at relatively low temperatures (around 500°C for 1 to 2 hours).

[0225] Alternatively, or in addition to the oxidation treatment, the internal surface may be chemically etched or coated with a solution or a melt of an active metal salt. This salt is subsequently activated by thermal or chemical means to produce a catalytically active layer, further enhancing the surface’s ability to facilitate graphite formation.

[0226] In another embodiment, a ceramic or non-active metallic tube is used as the reactor material. A thin coating of a metal-based active phase is applied to the tube's internal surface. Under appropriate reaction conditions, this coating acts as a catalyst for converting carbon- containing gases into graphite-type carbon.

[0227] The thermal or chemical modifications applied to the tube’s surface are designed to facilitate the rearrangement of metal atoms in such a way that they become catalytically active for the selective growth of graphite. Unlike other carbon structures, such as nanotubes or nanofibers,the process favors the growth of graphite-like flakes, which form in a layered and organized manner. This outcome is achieved by optimizing the surface treatment to ensure that the metal atoms organize into a phase that promotes the graphitization process.

[0228] This disclosure relates to a process where CO2 can be converted economically and without external energy demand by reacting CO2 with light hydrocarbons to produce syngas, hydrogen, and olefins. The produced syngas mixture can be converted into solid carbon through an exothermic reaction using the reactor design presented hereafter.

[0229] This disclosure relates to a process where hydrogen can be produced without process emissions by coupling endothermic and exothermic reactions to allow the high-temperature methane pyrolysis process to continuously occur at lower temperatures (500-600°C) while producing solid carbon products.

[0230] This disclosure relates to a process where ODPC can be combined with an exothermic reaction in the reactor system to produce propylene through the ODPC endothermic reaction, followed by an exothermic reaction where solid carbon allotropes are produced by the reaction between CO and propane or through consuming CO in Boudouard reaction (BR) to form carbon. Combining the endothermic and exothermic reactions within the described reactor will significantly reduce the energy demand of ODPC. Additionally, this process leads to net consumption of CO2, further reducing carbon emissions in the atmosphere.

[0231] This disclosure relates to an autothermal reactor design that allows for efficient heat transfer between exothermic and exothermic processes. In addition, the reactor design allows the formation of solid products in a continuous mode by employing a solid removal system and activating the reactor vessel to act as a self-supporting catalyst for the process under operation.

[0232] The introduction of this reactor system offers a practical and feasible solution. The reactor and processes presented in this technology allow economical and effective mitigation of carbon emissions while producing valuable market commodities. In addition, it enables hydrogen production with low carbon emissions by combining endothermic and exothermic reactions.

[0233] The reactor system presented here may minimize GHG emissions by utilizing GHGs as raw materials, thereby contributing to the global efforts to mitigate GHGs while generating valuable compounds and industrial intermediates like solid carbon allotropes, hydrogen, and olefins.

[0234] This technology seeks to simplify graphite production by utilizing common reactor tube materials — such as carbon steel, stainless steel, or ceramic — and modifying their surfaces by chemical and / or thermal treatment in the presence of an oxidative atmosphere to induce catalytic activity, thereby facilitating the formation of graphite-like carbons under more moderate conditions as described in the Autothermal Auger Reactor (AAR) configurations of the present technology.

[0235] This disclosure relates to a process that can generate hydrogen without producing any CO2 within the process, significantly reducing GHG emissions. In addition, the energy needed forconducting the process will be considerably reduced by combining the endothermic and exothermic reactions within the developed autothermal reactor design. The reactor design described hereafter allows the production of hydrogen and solid carbon allotropes in a continuous mode with minimum energy demand. This peculiar process results in an equivalent overall methane pyrolysis without operating at a high-temperature range. This process takes place at 500-600°C, and no carbon is deposited on the solid catalyst bed.

[0236] A process is necessary to minimize the DRM energy demand by developing a more active catalyst that enables conducting the process at a lower temperature range with a reasonable hydrogen yield without the typical deactivation that previous art DRM catalysts suffer and combining the process with an exothermic reaction, which can reduce the energy demand significantly.

[0237] According to a further aspect, there is provided a process for producing solid carbon comprising: performing an endothermic reaction in which one or more reactants are converted to one or more products, wherein one or more reactants comprise light hydrocarbons and carbon dioxide, and one or more products from endothermic reactions comprise carbon monoxide, and performing an exothermic reaction in which one or more products from the endothermic reactions are converted into one or more products from the exothermic reactions, wherein one or more products comprise solid carbon.

[0238] One or more products from the endothermic reactions may comprise hydrogen and the hydrogen may be separated before the products from the endothermic reaction are reacted in the exothermic reaction zone.

[0239] One or more products from the exothermic reactions may comprise carbon dioxide, which may be recycled as a said reactant.

[0240] The products from the endothermic and exothermic reactions may comprise an olefin.

[0241] The inner tube may be impermeable to gas.

[0242] The inner tube may have a thermal conductivity of at least 10 W m-1K-1.

[0243] According to a further aspect, there is provided a method of using the reactor system as described herein, wherein the method comprises carrying out an exothermic reaction in the annulus and an endothermic reaction in the inner tube.BRIEF DESCRIPTION OF THE DRAWINGS

[0244] In the Detailed Description section below, one or more embodiments are described in relation to the attached figures. These embodiments are intended to provide a better understanding of the technology, how the technology may be put into practice, and to demonstrate some of the advantages of the technology. The drawings are not necessarily to scale, emphasis instead beingplaced upon illustrating the principles of various embodiments of the technology. Similar reference numerals indicate similar components.Figure 1 is a schematic of a first embodiment of the reactor system.Figure 2 is a schematic of a variant of the first embodiment of Figure 1.Figure 3 is a schematic diagram of a second embodiment with a solid removal system.Figure 4 is a schematic of the second embodiment being used to convert methane and carbon dioxide into solid carbon and water.Figure 5 is a schematic of the second embodiment being used to convert propane and carbon dioxide into carbon, water, and propylene.Figure 6 is a schematic diagram of the second embodiment with a hydrogen separator.Figure 7 is a schematic diagram of the second embodiment with a hydrogen separator.Figure 8 is a schematic diagram of a further embodiment for non-solid reactions (i.e., relating only to gas and / or liquid reactants and products).Figure 9 is a schematic diagram showing how the embodiment of Figure 8 can be used to convert propane and carbon dioxide to isobutylene.Figure 10 is a schematic of a further embodiment with a solid removal system.Figure 11 is a schematic of the inner tube and solid removal system being used independently.Figure 12 is a schematic of the embodiment of Fgure 10 being used to convert carbon dioxide and hydrocarbons into a solid product.Figure 13 is a schematic where the tube and solid removal system is positioned outside the first reactor.Figure 14 is a further embodiment of the reactor with multiple inner tubes.Figure 15 is a schematic of the process system is monitored and controlled.Figure 16 is x-ray diffraction data of produced graphite containing embedded iron oxide.Figure 17 is x-ray diffraction data of produced graphite containing embedded iron carbide.Figure 18 is different stages of the inner tube in which the catalyst is built up, the solid is produced and then removed.Figure 19 is a graph of the expected equilibrium fraction of CO and CO2 in a binary mixture.Figure 20 is a graph showing the power utilization reduction achieved through the heat exchange between the hot gases flowing in the inner tube and the cold inlet gases to the outer tube.Figure 21 is a graph showing how power consumption reduces after flow to the inner tube is enabled for a first set of reactions.Figure 22 is a further graph showing how power consumption reduces after flow to the inner tube is enabled for a second set of reactions.Figure 23 is a further graph showing how power consumption reduces after flow to the inner tube is enabled for a third set of reactions.Figure 24 is a graph of the typical composition as a function of operating temperature at the exit of the inner tube when producing C4 hydrocarbons.Figure 25 is a schematic of a control system for controlling a reactor system.Figure 26-27 are SEM images of the produced carbon.Figure 28 is a graph showing the composition of the produced solid carbon allotropes as explored using the EDS technique.Figure 29 is a photograph of the produced solid carbon.Figure 30 is a graph showing three temperature programmed oxidation profiles and associated temperature profile.DETAILED DESCRIPTIONIntroduction

[0245] This disclosure relates to an endo-exo combined reactor systems and processes which may be used for hydrogen production with low carbon emission. The systems may employ a combination of Dry Reforming of Methane (DRM) and the Boudouard Reaction (BR) and / or a reaction of CO produced during DRM with paraffins or hydrogen to form solid carbon allotropes and mitigate CO2 used in DRM.

[0246] In addition, a process for mitigating and converting CO2 from diverse sources into valuable chemical products is disclosed. CO2 conversion is achieved by reacting CO2 and paraffins to produce CO, water, and olefins like propylene. CO can then be converted to solid carbon allotropes through Boudouard reaction, CO hydrogenation, CO reaction with paraffins, or a combination of these reactions, as practiced in Example 1 (see Examples section below).

[0247] The reactor design features two concentric tubes forming two reactors in series, where the outer or first reactor formed in the annulus between the two tubes facilitates an endothermic reaction, and the inner or second reactor facilitates an exothermic reaction. The outer or first reactor may be equipped with high-temperature hydrogen-permeable membranes to separate hydrogen or propylene throughout the catalyst bed in the outer or first reactor. Alternatively, separation can also be achieved using lower temperature range techniques outside the reactor.

[0248] Also, this disclosure relates to a reactor design may support the continuous operation of reactions resulting in the formation of solid products where the reactor vessel is used as a self- supporting catalyst, and the reactor houses a solid removal system that is employed to allow continuous removal and collection of solid products.

[0249] The reactor allows reactions where solids can be formed continuously utilizing the reactor vessel or a part of the reactor vessel as a self-supporting catalyst. These described processes or combinations of reactions may generate hydrogen, olefins, and solid carbon allotropes by converting light hydrocarbons and CO2 into CO, olefins, and hydrogen in endothermic reactions followed by exothermic reactions to produce solid carbon allotropes (e.g., including one or more of graphite, graphene and amorphous carbon). This technology offers an efficient, low-energy method for using carbon emissions to produce low-emission hydrogen, olefins, and solid carbon allotropes while utilizing CO2.

[0250] Performing an endothermic reaction in the first compartment of a vessel and performing an exothermic reaction in the second compartment of the same vessel. In this technique, the vessel may function as an autothermal reactor by allowing heat generated in the exothermic reaction to pass from the first compartment to the second compartment to provide heat for the endothermic reaction.

[0251] Another aspect of the present technology relates to graphite-type carbon materials and, more particularly, to producing graphite in carbon steel, stainless steel, other metallic tubes, carbon tubes, or ceramic tube reactors. The technology involves surface modification of the internal walls of the tube to enhance catalytic activity for the formation of graphite-type carbon under controlled reaction conditions. By applying thermal or chemical treatments to activate or load the reactor vessel with active phase, the reactor’s internal surface is engineered to exhibit catalytic properties conducive to the growth of graphitic carbon. These treatments promote the diffusion and reorganization of active metallic atoms within the tube’s structure, forming an active surface capable of catalyzing organized graphite layers.

[0252] During the reactions, solid carbon allotropes may be formed as a product, which may be removed using a solid removal system. In certain embodiments, an outer annulus facilitates the endothermic reaction, and an inner tube accommodates the exothermic reaction. The annulus may be equipped with high-temperature hydrogen-permeable membranes or high-temperature propylene-permeable membranes to separate hydrogen or propylene throughout the catalyst bed in the annulus. Hydrogen or propylene separation can be achieved using a lower temperature range outside the reactor if two reactors in series are used or by separating and circulating the gases back to the inner tube (reactor).

[0253] Various aspects will now be described with reference to the figures. Simulation and experimental data associated with these described aspects are listed in Examples section below. For the purposes of illustration, components depicted in the figures are not necessarily drawn to scale. Instead, emphasis is placed on highlighting the various contributions of the components to the functionality of various aspects. A number of possible alternative features are introduced during the course of this description. It is to be understood that, according to the knowledge and judgmentof persons skilled in the art, such alternative features may be substituted in various combinations to arrive at different embodiments of the present disclosure.First Embodiment of Reactor

[0254] One aspect of this disclosure relates to a reactor design for taking light hydrocarbons and carbon dioxide as initial reactants and producing solid carbon. Some embodiments may also generate hydrogen and / or olefins (alkenes). This technology also provides a pathway for converting CO2 into useful fuels and chemicals like solid carbon allotropes and light hydrocarbons. Example 1 shows the simulation results of the processes practiced in the described reactor (see the Examples section below for more details).

[0255] Figures 1 and 2 show variants of an embodiment of the reactor system. The reactor comprises: an outer tube 1001 and having an outer tube axis; and an inner tube 1002 comprising an inner first end and an inner second end 1006 and having an inner tube axis, the inner tube being thermally conductive and being located within the outer tube such that the inner and outer tube axes are aligned with each other, wherein the inner and outer tubes create an annulus between the inner and outer tubes, the annulus comprising an annulus first end and an annulus second end, and wherein the annulus second end is in fluid communication with the inner tube’s first end.

[0256] In this embodiment, a catalyst 1003 (e.g., in the form of pellets) is added in the outer tube and supported by a catalyst supporting plate 1009.

[0257] In this way, the reactor system comprises two concentric tubes forming two reaction zones connected in series. One reactor zone is in the annulus, and another reactor zone is within the inner tube. The reactor design facilitates the heat transfer between the endothermic and exothermic reactions, significantly minimizing the energy needed to conduct the process. In operation, the heat flows from the exothermic reactor to the endothermic reactor.

[0258] As shown in Figures 1 and 2, the flow within the annulus is in the opposite direction to the flow within the inner tube.

[0259] In addition, the hot gases from the endothermic reactor flow into the exothermic reactor (e.g., without additional heat), as shown in Figures 1 and 2, where the gases circulate from 1001 to 1002 through an open-ended tube design (Figure 1) or through holes (Figure 2) designed to control the flow between the two reactors. The heat transfer from 1002 to 1001 occurs due to the exothermic reaction in zone 1005, which generates heat to compensate for the energy demand for the endothermic reaction in zone 1003. Additionally, the hot gases leaving the inner tube (zone 1006) may be used to heat the low-temperature feedstock entering the reactor (zone 1007).

[0260] As exemplified by Example 2, in some use cases, inert gas circulation may also be used to reduce the reactor system’s power utilization by using the gases to transfer heat between the endothermic and exothermic reactors. In these ways the heat generated through the exothermic reaction may reduce the power utilization required for the endothermic reaction.

[0261] In this particular embodiment, the endothermic reaction occurs in the outer tube 1001 within the annulus, and the exothermic reaction occurs inside the inner reactor tube 1002. In other embodiments, the reactor system can be designed using two reactors in series provided with a heat exchanger inside or around the reactor assembly.

[0262] For some combinations of endothermic and exothermic reactions, the autothermal reactor system can also house endothermic and exothermic processes in combination where no solid products are produced. The two reactors (tubes) may house a catalyst bed suitable for each reaction.

[0263] For some combinations of endothermic and exothermic reactions, the reactor can house endothermic and exothermic processes operating in a full autothermal mode without external heat sources or with partial autothermal operation where an external heat source may be needed. In addition, the reactor can handle energy-neutral processes where certain temperature levels must be maintained, and the described reactor design is used to improve heat integration and reduce heat transfer losses.

[0264] In some embodiments, the two reactors or tubes can be used as a two-concentric tube design with internal membrane separation or external separation techniques. In addition, the two tubes (reactors) can be connected in series with internal membrane separation or external separation techniques positioned between the two tubes, with the aim of conducting one of the processes described in this disclosure.

[0265] Other embodiments may employ different metallic tubes or reactor vessels for conducting the processes in this technology, including but not limited to austenite alloy tubes, low iron tubes, nickel non-inert-containing tubes, activated metallic tubes, carbon-steel tubes, tubes coated with active catalyst phase, and other metallic tubes active for these processes described by Reactions (3)-(7).

[0266] The described reactor may facilitate reactions where the solid product is expected to form continuously (e.g., without employing fluidized or moving bed reactors). The reactor tube itself may be a self-supporting active catalyst phase for the reaction taking place. In some embodiments, the material of the reactor tube may be a catalyst, or the material may be activated for catalyst activation. The catalyst activation processes may include but are not limited to thermal treatment, hydrogen reduction, oxidation, wet impregnation, dry impregnation, gelation, spray coating, active phase deposition, other coatings techniques, or etching with alkaline or acidic chemicals.The Second Embodiment with a Solid Removal System

[0267] In a related embodiment, Figure 3 shows the reactor system with two concentric tubes and solid removal system 3001 inside the inner reactor tube, which, in this case, comprises an auger. This design is a modification of the design presented in Figures 1 and 2 by placing a solid removal system in the inner tube.

[0268] The auger, in this case, formed from a continuous helical flighting (or flight). The carbon removal system comprises edges which lie adjacent to the wall of the inner tube, such that when they are moved, they can dislodge any produced solids which are attached to the inner wall of the tube. In addition, there is a continuous flow path which allows fluid flow through the inner tube even when the carbon removal system is in place. The auger may also be used to impel the solids towards the outlet where the solids can be collected. In this embodiment, the exhaust gas and the carbon leave the reactor assembly at the bottom through an outlet at the second end of the inner tube.

[0269] In other embodiments, solid removal may be effected through several methods, including mechanical removal like auger, drill, brushes, pigging, scrapping, pistons, and blades. In addition, several other removal methods can be employed using gas, ultrasonic, chemical, vacuum, flushing, sonic / acoustic, electrostatic, magnetic, robotic, laser, microwave, agitation, and / or abrasive removal.

[0270] This reactor design can be used for generating solid products from a reaction where solids can be generated from a reaction catalyzed by the reactor vessel or part of it, and the solids are collected using the solid removal system in a batch or continuous operation mode, as reported in Example 3.

[0271] More generally, a solid removal system may comprise edges that lie adjacent to the wall of the inner tube, such that when they are moved, they can dislodge any produced solids that are attached to the inner wall of the tube, as shown in Figure 3.

[0272] It will be appreciated that the solid removal system may provide a continuous flow path that allows fluid (and gases in particular) to flow through the inner tube even when the solid removal system is in place and when it is in operation. This may be provided by, for example, the helical path between the auger flighting, gaps between blades, gaps between brush bristles, or holes in a piston.

[0273] The auger may also be used to impel the solids towards the outlet where the solids can be collected. In this embodiment, the exhaust gas and the carbon leave the reactor assembly at the bottom through an outlet at the second end in zone 3003 of the inner tube 1002.

[0274] In some embodiments, the solid removal system can be combined with an active tube for a reaction where solid formation occurs. It can be either combined with another reactor or used separately by passing reactants into a single tube (reactor) provided with a solid removal system.In contrast, the tube or reactor vessel is a catalytically active or activated tube for the reaction taking place.

[0275] In some embodiments, the reactor design presented in Figure 3 can be used to produce solid carbon allotropes, for example, using a combination of DRM in the outer tube or the endothermic reactor and the hydrogenation reaction in the inner tube or the exothermic reactor, as shown in Figure 4. The net process will convert CO2 and CF into solid carbon allotropes and water. As noted above, other reaction combinations may be used in other use cases to also produce solid carbon allotropes. The same solid removal systems may be used for these other use cases also.

[0276] In some embodiments, the reactor design presented in Figure 3 can be used to produce solid carbon allotropes using a combination of ODPC in the outer tube or the endothermic reactor and Reactions (5)-(7) in the inner tube or the exothermic reactor, as shown in Figure 5. The net process will convert CO2 and propane into solid carbon allotropes, propylene, hydrogen, and water.

[0277] It will be appreciated that, in some embodiments, the solid removal system may be used in a tube reactor designed to produce a solid product. That is, the solid removal system may be employed even in reactor systems without an exothermic reactor.Hydrogen and Solid Carbon Production

[0278] As shown in Figures 6-7, the reactor system in Figures 1-3 can be adapted for use in the production of hydrogen.

[0279] This may be achieved using a natural gas feedstock (e.g., methane) by combining Reaction 1 in the annulus, dry reforming of methane (DRM - an endothermic process), with combinations of the exothermic reactions, the Boudouard reaction (Reaction (3)) and the hydrogenation reaction (Reaction (4)) when the product from the outer tube or first reactor is circulated directly to the inner tube or second reactor. Hydrogen produced through the DRM is partially used through Reaction (4), and the unreacted hydrogen exits the inner tube and can be separated and collected, as in Example 4.

[0280] In another use case, the reactor system in Figures 1-3 may be used in the production of hydrogen from natural gas (e.g., methane) by combining Reaction (1), the dry reforming of methane (DRM - an endothermic process), with one or a combination of the Boudouard reaction (Reaction (3)) or the reaction of CO with paraffins (Reactions (5)-(7)).

[0281] Produced hydrogen (regardless of the specific reactions used) may be separated using low or high-temperature separation methods from within the outer reactor and / or from the first reactor product stream, as in Example 5.

[0282] Using the reactor of Figures 6 and 7, the endothermic dry reforming of methane (DRM) reaction is performed in annulus 1003 between the outer and inner tubes, and the exothermic Boudouard reaction takes place in the inner reactor tube within zone 1005.

[0283] After separating the hydrogen, the remaining carbon-containing products (e.g., methane, propane, ethane, natural gas, ethylene, carbon dioxide, and / or carbon monoxide) can be reacted to produce solid carbon using catalytically active sites on the internal surface of inner tube. The carbon-producing reactions may be carried out at temperatures ranging from 400°C to 700°C and at pressures of 1 to 10 bar (100-1 ,000 kPa). The catalytically active sites may be generated by activating the material of the inner tube.

[0284] The catalytically active sites on the internal surface of the tube promote the decomposition of the carbon-containing gas, leading to the formation of graphite-type carbon and generating the energy needed to minimize the energy demand for DRM. In addition, a solid removal system can be placed within the activated tube (reactor) to run the process continuously.

[0285] Figures 6 and 7 show that the overall process converts methane to hydrogen and solid carbon allotropes; however, within that process, carbon dioxide is generated as a product in the exothermic Boudouard reaction and recycled to be used as a reactant in the endothermic dry reforming of methane (DRM) reaction. In such cases, CO2 is employed as a gaseous catalyst to facilitate the reforming of the stable CP molecule,

[0286] The overall reaction is methane cracking into hydrogen and solid carbon allotropes, as shown below:

[0287] Dry reforming of methane - DRM

[0027] CH4+ CO22CO + 2H2AH298 = 247 kJ / mol (1 )

[0288] Boudouard reaction - BR

[0032] 2CO CO2+ C AH298 = -172 kJ / mol (3)

[0289] Overall reaction (Methane cracking) [1]CH4^ C + 2H2AH298 = 75 kJ / mol (11)

[0290] In some embodiments, rather than having a distinct catalyst layer, the inner reactor tube wall may be made of material that is active for (i.e., catalyzes) the exothermic reaction, like carbon steel or austenite alloy. The catalyst for the endothermic reaction to form solid carbon is the inner wall of zone 1002. In other embodiments, the material of the tube wall may be activated to provide the catalytically active sites.

[0291] Hydrogen can be separated using low-temperature separation technology (zone 6001) or a high-temperature separation method, like a high-temperature membrane (zone 7001), and CO is circulated to the inner tube or the second reactor. The low temperature separation technology may operate at less than 150°C (e.g., and greater than 0°C). The high temperature separation technology may operate in the range of 150-650°C.

[0292] In Figures 6 and 7, which is a schematic representation of the reactions taking place within the reactor. The annulus 1003 holds a catalyst bed (e.g., comprising catalyst in the form of pellets)for the endothermic reaction, and the inner tube 1002 facilitates the exothermic reaction. In this embodiment, the catalyst is a layer of active catalyst applied on the inner reactor tube walls.

[0293] A catalyst bed is effective where the reactants and the products of a reaction are all in the gas phase. A layer of active catalyst may be advantageous when one of the products in the reaction is a solid, as it may facilitate easier separation of the solid product from the catalyst.

[0294] In some embodiments, rather than have a distinct catalyst layer, the inner reactor tube may be made of material that is active for (i.e., catalyzes) the exothermic reaction, like carbon steel.

[0295] A solid removal system 3001 , as shown in Figure 3, may be used to remove solid carbon allotropes produced within the walls of the tube, removing the carbon and allowing continuous operation.

[0296] A catalyst for the endothermic reaction in zone 1003 may comprise an upper layer composed of catalyst particles prepared by impregnating a mixture of a transition metal, an alkaline earth metal, and a lanthanide metal, for instance, Ni-Mg-Ce. The catalyst may be mounted on a support, e.g., comprising a y-alumina layer and a lower layer made of a-alumina, other alumina support, inert ceramic, and / or silica. The catalyst bed may comprise inert heat sink materials to act as a heat sink to collect the excess heat for heating the inlet gases. The catalyst layer in this embodiment is supported by a catalyst-supporting plate 1009, as shown in Figure 3. The catalystsupporting plate may be gas permeable (e.g., a mesh with a mesh size smaller than the catalyst pellet size).

[0297] The outer tube 1001 , in this case, is made of inert material or alloy like Inconel or Hastelloy to prevent any interaction with the reactants and carbon deposition on the reactor walls, minimizing the plugging problems that are observed with CO2 and hydrocarbon reactions or other metallic tubes that can be covered internally with appropriate inert coating. The inner tube’s external surface adjacent to the exothermic reaction may also be formed of inert material or comprise an inert coating (e.g., on the exterior of the inner tube to avoid catalyzing unwanted reactions in the annulus).

[0298] In this embodiment, the reaction within the annulus 1003 is configured to occur in a temperature range of 400-700°C.

[0299] In this embodiment, the inner reactor tube or the second reactor tube is covered with a layer of catalyst containing Fe, Mn, Ni, or Co. In this case, this layer converts CO produced within the DRM reaction to solid carbon allotropes and CO2. In other embodiments, the inner reactor tube or the second reactor is made of an active material like carbon steel. As shown in Figures 6 and 7, the flow within the annulus 1003 is in the opposite direction to that in the inner tube 1002. That is, the first end of the annulus 1003, where the reactants are circulated, is adjacent to the inner tube’s second end or outlet, where the fluid products of the second reaction are removed. Likewise, thesecond annulus end is positioned adjacent to the first inner 1002 tube end to allow the unseparated intermediates to move between the annulus and enter the inner tube.

[0300] The energy generated in inner tube 1002 provides heat to the endothermic reaction in annulus 1003, ensuring reduced energy demand for the overall process. The heat flows from inner tube 1002 to annulus 1003 through the inner reactor walls or a heat exchange medium from the first reactor to the second reactor. The solid carbon allotropes deposited on the inner reactor’s walls are removed using a solid removal system 3001 , enabling the continuous operation of the reaction.

[0301] In one embodiment, the hydrogen separation from the DRM reaction can be achieved through external separation techniques. Figure 6 shows the DRM products circulated outside the reactor system at the top of 1001 into an external separation system that can operate at a low- temperature range to separate hydrogen from the exit stream, with or without separating the unreacted CO2 and CH4, then the stream is sent back into the inner tube 1002 where solid carbon is formed. The separation system is represented by zone 6001 .

[0302] As shown in Figure 7, hydrogen can be separated along the length of the annulus 1003 using high-temperature membranes 7001 . The membrane separates hydrogen from the reacting mixture. In this case, this creates two annuli where the endothermic reaction takes place: a reaction annulus between the inner tube 1002 and membrane 7001 and an annulus between the membrane and the outer tube of the reactor.

[0303] This process can be conducted to produce hydrogen in two separate reactors by employing two reactors in series with low or high-temperature separation methods to collect hydrogen and unreacted CO2 if needed. The second reactor can be an activated reactor with a solid removal system for continuous operation. Alternatively, the second reactor can be an activated tube without an auger or a fixed bed reactor with a solid catalyst for batch operation.

[0304] In some embodiments, the produced carbon monoxide intermediate can be converted into solid carbon allotropes and carbon dioxide following Reaction (3) or through a reaction with hydrogen or paraffins following one or a combination of the exothermic Reactions (4)-(7). The solid removal system removes the produced carbon within the inner tube. The temperature within the inner tube for Reactions (3)-(7) may be around 500°C (e.g., 400-600°C).

[0305] In other use cases, the described processes include hydrogen production using DRM in combination with one of the exothermic Reactions (3)-(7) or a combination of these reactions by providing a substoichiometric amount of paraffins. The process can be conducted continuously by using a solid removal system in the inner reactor, in the case of two concentric tube reactors, or in the second reactor, in the case of two reactors in series, to remove any solid carbon deposits. In another embodiment of this disclosure, this process can be conducted in batch mode without using a solid removal system by running the unit until the inner tube is plugged.

[0306] In another embodiment, the second reactor (inner tube) can be used separately following or inside a conventional steam methane reforming (SMR) unit where syngas is produced or following or inside any other processes where syngas is produced like reverse water gas shift reactions, low-temperature steam reforming combined with SMR and DRM. For example, the syngas produced in SMR contain a molar ratio of 3 / 1 H2 / CO. Several high-temperature or low- temperature separation techniques can be used to separate the excess hydrogen. The stream can be directed to utilize the CO-hydrogen mixture or pure CO through Reactions (3)-(7) to produce solid carbon allotropes and energy to sustain the endothermic SMR reaction.

[0307] Examples 4 and 5 show that the allotropic solid formation can be achieved while controlling the hydrogen production levels, starting with a CO to hydrogen ratio close to 1 as in example 4 (Reactions (3) and (4)) and to pure CO through the Boudouard reaction (Reaction (3)) resembling a complete collection of hydrogen through the well-developed low and high-temperature methods. This can provide flexibility in operating the described reactor system by manipulating several hydrogen separation levels.

[0308] Several separation processes are available to separate hydrogen and propylene from DRM or ODPC mixtures. These separation methods, like high-temperature membranes, low-temperature membranes, Pressure swing adsorption, and several other methods (34-39), can be used in situ or outside the reactor to separate hydrogen or propylene.

[0309] The separation of these products enables using the described reactor design to produce hydrogen or propylene. Then, the remaining stream after separation can be directed to the inner tube or second reactor to conduct Reaction (3) in case of DRM or Reactions ((3) and (5)-(7)) in case of ODPC. Several separation techniques are patented and used on industrial-scale applications for separating hydrogen and propylene in low and high-temperature ranges (34-42).

[0310] Several studies showed that high-temperature membranes positively affect the DRM reaction's conversion and selectivity by pushing the conversion beyond the thermodynamic limits and reducing the chances of the reverse water gas shift reaction. The recovery of hydrogen or propylene through the high-temperature membrane can be boosted by increasing the pressure difference across the membrane. That is, the separation can be improved by increasing the back pressure inside the reactor and / or by reducing the pressure at the gas outlet. For example, the recovery of hydrogen can be improved using a vacuum pump to increase the pressure drop across the high-temperature membrane

[0043] . A calculation using the average characteristics of the commercial high-temperature membrane showed that 70-80% of the produced hydrogen can be collected as pure hydrogen when the reactor system operates at 5 psig back pressure.

[0311] In one embodiment, an external separation system can be developed to separate hydrogen or propylene and CO2 or other undesired reactants like methane in the second reactor [39-43].

[0312] In another embodiment, the second reactor after separation can be a fixed bed reactor where carbon is deposited on a regular solid catalyst, and the carbon and catalyst can be collected in a batch or continuous mode if a reactor like a fluidized bed is used as the second reactor. In addition, a battery of reactors can be used by alternating the flow between the reactors to allow time for carbon and catalyst discharge.Light Hydrocarbons and Solid Carbon Production

[0313] In addition to hydrogen production, this disclosure relates to a process to convert carbon dioxide into useful hydrocarbons and solid carbon allotropes through a reaction with paraffins (alkanes). In addition, this technology may facilitate a process that can also be used to generate propylene (propene) at low carbon emissions while mitigating CO2, similar to what was presented in Figures 6 and 7 for hydrogen production. The reactants, in these use cases, are CO2 and paraffins (alkanes, e.g., CsHa); the products include olefins (alkenes) like propylene (propene), water, hydrogen, and solid carbon allotropes. As with the hydrogen production reactions described above, the overall process for propylene involves combining an endothermic reaction (e.g., Reaction (2)) with one or more of the exothermic reactions in Tables 2 and 3 (Reactions (3)-(7)). These reactions can be carried out in a reactor system like that shown in Figure 3.

[0314] Like the process shown in Figures 6 and 7, the overall process of CO2 conversion comprises a CO2 reaction with paraffins to produce olefins and solid carbon allotropes over two steps.

[0315] In this embodiment, the first step takes place in the annulus (the first reaction zone 1003) and comprises reacting CO2 with paraffins to form olefins, CO, and water (Reaction (2)) over a catalytic bed. In a subsequent second step, the produced CO intermediate reacts with paraffins (Reactions (5)-(7)) to form carbon or undergoes the Boudouard reaction in the second reaction zone (e.g., within the inner tube), generating heat to at least partially compensate for the energy needed for the endothermic CO2 and paraffin reactions in the annulus (Reactions (5)-(7)). As before, heat passes from the exothermic reaction to the endothermic reaction via the thermally conductive inner tube wall.

[0316] The net reaction products are water, solid carbon, hydrogen, and olefins, which are widely used industrial intermediates in several industries; experimental results are reported in Example 6 below.

[0317] As shown above, CO2 and paraffins can be converted into CO and olefins like propylene (propene) (Reaction (2)). CO can be converted into solid carbon using a combination of the Boudouard reaction (Reaction (3)) and / or by adding hydrogen according to Reaction (4).

[0318] The reaction between CO2 and paraffin (propane in this case) requires 165 kJ / mol, while the CO reaction with paraffin to obtain carbon, water, and hydrogen will produce 27 kJ / mol, so the required heat of the overall reaction is 138 kJ / mol, as shown in the reactions below:C3H8+ CO2 CO + CsHe + H2O AH298= 165 kJ / mol (2)C3H8+ CO 4C + H2O + 3H2AH298=-27 kJ / mol (5)

[0319] In another use case, the reaction between CO2 and paraffin requires energy of 165 kJ / mol, while the CO reaction with paraffin to obtain carbon, water, and olefin will produce 7 kJ / mol, so the required heat of the overall reactions is 158 kJ / mol, as shown in the reactions below:C3H8+ CO2CO + C3H6+ H2O AH298= 165 kJ / mol (2)C3H8+ CO C + H2O + C3H6AH298=-7 kJ / mol (6)

[0320] In another use case, the reaction between CO2 and paraffin requires an energy of 165 kJ / mol, while the CO reaction with paraffin to obtain carbon and water will produce 408 kJ / mol, as shown in the reactions below:C3H8 + CO2 CO + C3H6 + H2O AH298= 165 kJ / mol (2)C3H8+ 4CO 7C + 4H2O AH298=-408 kJ / mol (7)

[0321] In another embodiment, the endothermic dry reforming of methane (DRM) reaction is performed in the annulus 1003, and the exothermic reaction for capturing the produced CO by reacting CO with paraffins takes place in the inner reactor tube.

[0322] The reaction between CO and paraffins (e.g., CsHs) takes place in the inner reactor following a combination of Reactions (5)-(7).

[0323] It will be appreciated that, for each of the examples listed above, other paraffins may be used in place of propane (e.g., saturated hydrocarbons up to C6 or C7, but the specific reaction enthalpies will be different).

[0324] Another embodiment is related to the conversion of CO2 using a combination of two reactions. The first reaction is the reaction of CO2 with paraffins to produce CO, water, and olefins. After separating the olefins, CO reacts with paraffins to produce solid carbon, hydrogen, olefins, and water. Also, CO could be converted to solid carbon and CO2 through the exothermic Boudouard reaction (BR) or CO hydrogenation reaction.

[0325] In another embodiment, the endothermic reaction of CO with paraffin is performed in the annulus 1003, and the exothermic reaction for capturing the produced CO into solid carbon takes place in the inner tube 1002, like what is shown in Figures 6 and 7. CO capture is achieved through the exothermic reaction of CO with paraffins.

[0326] These reactions, and those listed in Tables 1-3, represent some embodiments of possible reactions that can be implemented in the reactor system for producing hydrogen or CO2 conversion with olefin (e.g., propylene or propene) production. Corresponding reactions may also be used to produce other olefins (e.g., unsaturated hydrocarbons up to C6 or C7).

[0327] Propylene and solid carbon production are achieved by exposing the products from ODPC reaction after separating propylene to a modified tube to a carbon-containing gas, such as methane, propane, ethane, natural gas, ethylene, carbon dioxide, and carbon monoxide, at temperatures ranging from 400°C to 700°C and at pressures of 1 to 10 bar. The catalytically active sites on the internal surface of the tube promote the decomposition of the carbon-containing gas, leading to the formation of graphite-type carbon and generating the energy needed to minimize the energy demand for ODPC. In addition, a solid removal system can be placed within the activated tube to run the process continuously.

[0328] Like the reactor design shown in Figure 3, the reactor for propylene production comprises two concentric tubes 1001 , 1002 where the endothermic reaction will take place over the catalyst placed in the annulus 1003, and the exothermic reaction will take place in the inner or second reactor tube 1002 covered with a layer of catalyst or activated to improve the yield and selectivity, similar to what is shown in Figured 6 and 7. The exothermic reaction in the inner or second reactor tube partially provides the heat needed to sustain the endothermic reaction. The solid removal system is placed in the inner reactor tube or second reactor tube to remove the solid carbon allotropes accumulated on the reactor walls.

[0329] In another embodiment, the propylene separation from the ODPC reaction can be achieved through external separation techniques. As shown in Figure 6, the ODPC products are circulated outside the reactor system at the top of 1001 into an external separation system (zone 6001) that can operate at a low-temperature range to separate propylene from the exit stream, with or without separating the uncreated CO2 and C3H8, then the stream is sent back into the inner tube 1002 where solid carbon is formed according to one or a combination of Reactions (3)-(7).

[0330] Similar to what is shown in Figure 7, propylene can be separated along the length of the annulus 1003 using high-temperature membranes 7001. The membrane separates the propylene from the reacting mixture. In this case, this creates two annuli: a reaction annulus where the endothermic reaction takes place between the inner tube 1002 and membrane 7001 , and an annulus between the membrane and the outer tube of the reactor.

[0331] This process can be conducted by employing two reactors in series with low or high- temperature separation methods to collect propylene. The second reactor can be an activated reactor with a solid removal system for continuous operation. Alternatively, the second reactor can be an activated tube without an auger or a fixed bed reactor with a solid catalyst for batch operation.

[0332] Combining Reaction (2) with any of the exothermic Reactions (3)-(7) in the developed reactor will result in CO2 mitigation and production of propylene while minimizing energy demand for Reaction (2) and eliminating hydrogen demand for CO2 mitigation. This process can mitigate CO2 emissions while creating industrially applicable products like olefins at low energy demand. The combination of these reactions takes place at a temperature range of 500-610°C.

[0333] This process can be conducted in batch mode without using the solid removal system by running the unit until the inner or second reactor is completely plugged.

[0334] In one of the embodiments, the reactor design presented in Figures 1 and 2 can be modified to handle a combination of endothermic and exothermic reactions where each reaction requires the presence of a solid catalyst. As shown in Figures 8 and 9, the catalyst in the inner tube or exothermic reactor is placed in zone 8001 . The design can be used to improve heat transfer and energy utilization, where a process may combine exothermic and endothermic reactions without forming solid products.

[0335] In other embodiments, the produced mixture from Reaction (2) can generate several hydrocarbons by placing an active catalyst in the inner tube (reactor), similar to Figure 8 and reported in Example 7. This process can generate several chemicals using the product generated in Reaction (2); for example, if the paraffin used in Reaction (2) is propane, several hydrocarbons can be produced in the inner or second tube (reactor) as follows:2C3H6« 2CH4+ C2H4+ 2C AH298=-137.6 kJ / mol (8)2C2H4« C4H8AH298=-121.7 kJ / mol (9)4CH4+ C2H42C4H10AH298=-259.4 kJ / mol (10)Solid Production

[0336] In addition to hydrogen and olefins (alkenes), the reactor design and processes can be employed to facilitate reactions in which solid products can be produced continuously while the reactor vessel or part of it can be used as a catalyst for the solid formation reaction. Embodiments of these reactors are shown in Figures 10-13. These use cases are related to Examples 8, 9, and 10.

[0337] Figure 10 shows the reactor system, which can be used to activate an inlet feedstock to an outer tube. The active intermediates are converted into a solid product, and the solid products can be collected using solid removal system 1011. In this case, like the embodiment of Figure 3, the solid removal system comprises an auger.

[0338] In one of the embodiments, the inner reactor can be used as a single reactor for conducting reactions where the solid formation is expected while using the reactor vessel or part of it as a catalyst to support the solid formation reaction, as shown in Figure 11 . An example of this process may include placing the activated reactor vessel with the solid removal system after steam methane reforming (SMR) unit where syngas is produced to utilize the produced syngas to form solid carbon. Additionally, this single reactor, presented in Figure 11 , can placed in combination with other units, producing a mixture that can be used to generate solids over the activated reactor vessel. One example of these processes is combining a low-emission steam reforming process with the DRM process to produce a mixture of syngas

[0034] .

[0339] The solid carbon allotropes can be produced using Reactions (1) or Reaction (2) to generate CO. Subsequently, CO can be converted through Reactions (3)-(7). Using paraffins, CO2 can be converted into CO in zone 1001 , for example, following Reactions (1) or (2), producing CO, the raw material needed to mitigate carbon emissions in the described reactor and processes. CO is converted to solid carbon in zone 1002, following Reactions (3)-(7) as an example. However, other paraffins can be used, like Reactions (1) or (2), to produce CO in Zone 1001 , while in Zone 1002, CO is converted by reacting with paraffins like Reactions (5)-(7). The solid carbon product is formed over the active reactor vessel and removed continuously by the solid removal system (zone 1011).

[0340] In one of the embodiments, the described processes provide excellent flexibility where carbon can be produced solely through Reaction (3) or combined with other products through Reactions (4)-(7).

[0341] In one of the embodiments, a solid removal system (zone 1011) can be added to the inner tube (reactor) or the second reactor to allow the continuous formation of carbon by employing the tube or reactor vessel to catalyze the carbon formation.

[0342] In one of the embodiments, the formation of solid carbon can be performed within zone 1002 without employing a solid removal system (zone 1011).

[0343] In one of the embodiments, the described reactor system and processes may be targeting only carbon formation by circulating products in the outer tube (zone 1001) or the first reactor to the inner tube (zone 1002) or the second reactor, for example, hydrogen and CO from Reaction (1). For instance, carbon formation may occur following a Reaction (4). In another embodiment, hydrogen (or propylene from Reaction (2)) can be separated to form carbon through Reaction (3) or Reactions (5)-(7) by adding additional propane.

[0344] In one of the embodiments, separation techniques can be employed to separate hydrogen or propylene inside the reactor (zone 1001) or outside the reactor system and circulate only CO to the inner tube to form carbon using only the Boudouard reaction (Reaction (3)).

[0345] In one of the embodiments, combining the endothermic reaction where CO is produced with exothermic reactions to produce carbon in two concentric tubes or two tubes in series to reduce or eliminate the need for additional energy demand.

[0346] The solid removal system can be mounted from one or two sides for vertical or horizontal reactors. The solid removal system can be used with sharp edges designed to control the shape of the solid carbon particles, or a piston-type or brush-type system is expected to generate more fines.

[0347] As an example, an auger used for the removal of carbon deposits from the inner walls of a reactor would typically consist of a helical screw or spiral blade mounted on a rotating shaft. This auger could be inserted into the inner tube or the second reactor, where solid carbon builds up onthe walls. As the auger rotates, the helical blade scrapes or brushes against the walls, dislodging and removing the accumulated carbon deposits in the tangential, radial, or longitudinal directions.

[0348] The solid removal system can be designed using an auger, Drill bits, Rotary Brushes and Scrapers, pistons, Pigs, Swaps, and Rodder Systems in an activated tube as described previously, where the reactor vessel or part of it is activated to catalyze the reaction where solids are produced. As an example of the solid removal system, an auger was used with a diameter of 0.375” with Tapered Square / Round shank type and open spiral flute bit style. The auger has a right-hand flute direction and a screw point style tip. The auger was controlled by a motor with a variable speed of 1-20 rpm. The outer diameter of the auger may be the same as the inner diameter of the inner tube. The auger may rotate about an axis which is coaxial with the inner tube axis. The inner tube may be in the form of a circular cylinder.

[0349] In other embodiments the auger diameter may be smaller than the inner diameter of the inner tube. The auger may migrate around the inner surface of the inner tube to remove solids from the entire surface of the tube. During this migration, the auger may also be rotating about its own axis (the auger axis).

[0350] The auger may cut the produced carbon in flake form while keeping a continuous flow of the gases from the outer tube without extensive increase in the pressure across the reactor. Other solid removal systems can be used to produce fine carbon particles. However, if the reactor can operate in a batch mode to form a solid product, the inner tube or the second reactor can be used without the solid removal system to create the solid products across the inner tube diameter until the tube is completely blocked.CO2 Mitigation

[0351] In addition to hydrogen and propylene with carbon formation processes, the described reactor design and processes can be used to mitigate CO2; previously described methods provide an efficient method for permanent mitigation of CO2 with minimum or no energy demand while requiring no hydrogen. This embodiment is related to Example 10. Figure 12 shows the process of CO2 mitigation, where CO2 can react with hydrocarbons to form an active gas mixture, which can be later used in the inner tube to form solid carbon deposited on the active reactor vessel. The formed carbon is removed and collected by the solid removal system 3001 .

[0352] CO2 can react with paraffin in the outer tube (zone 1001) or the first reactor to form hydrogen and CO; for example, in Reaction (1), methane and CO2 react in the DRM catalyst (zone 1003 to create syngas, which is a mixture of CO and hydrogen. In the inner tube (zone 1002) or second reactor, CO and hydrogen form solid carbon allotropes following Reactions (3) or (4), mitigating CO2 into a permanent high-demand commodity.

[0353] Additionally, CO2 can react with paraffins in zone 1001 to form CO, olefins, and hydrogen; the olefins and hydrogen can be separated. Then, the CO stream is circulated across the inner tube (zone 1002) to form solid carbon allotropes following Reaction (3).

[0354] In one embodiment, CO2 can be utilized in a reaction with light hydrocarbons to produce CO. After separating byproducts like hydrogen and olefins, CO is converted into solid carbon allotropes through Reaction (3). This provides an efficient process to mitigate CO2 emissions permanently as solid carbon.

[0355] In one embodiment, the described reactor can be used to mitigate carbon emissions by converting CO2 into solid carbon allotropes and other chemicals in a continuous mode by employing a solid removal system (zone 3001) and using an active or activated inner tube or second reactor.

[0356] In one embodiment, the described reactor can mitigate CO2 into solid carbon allotropes and other chemicals by combining and exchanging the heat from an exothermic process to an endothermic process across the inner tube wall, represented by the heat transferred 1008. The quality and characterization of the produced solid carbon allotropes are detailed in Examples 11- 14.

[0357] In one embodiment, the described processes can mitigate CO2 by combining endothermic and exothermic reactions where solid carbon can be formed in a continuous mode using a solid removal system in an active or activated reactor vessel.

[0358] In one embodiment, the CO2 mitigation process can be conducted by combining two different reactions in two reactors connected in series. Figure 13 shows the described reactor system where the first reactor is used to activate the inlet mixture, combining CO2 to generate a gas mixture that can be used in the second reactor containing the solid removal system to produce solid carbon allotropes over the activated reactor vessel. The heat exchange between each reactor may be achieved using several heat exchange processes, such as employing a heat exchanger for direct heat transfer between the reacting and exit streams or running a heat transfer medium in each reactor.

[0359] In one of the embodiments, carbon can be produced using a mixture of CO and hydrogen or CO and propane, as shown in Reaction (4) and Reactions (5)-(7).

[0360] Solid carbon allotropes are generated by exposing a modified tube to a carbon-containing gas, such as methane, propane, ethane, natural gas, ethylene, carbon dioxide, and carbon monoxide. These reactions may occur at temperatures ranging from 500°C to 800°C and at pressures of 1 to 10 bar. The decomposition of the carbon-containing gas may be promoted using catalytically active sites on the internal surface of the tube.Other Reactor Configurations

[0361] The described processes and reactions can be conducted in several configurations in the described reactor system; each configuration represents an option for running these combinations of processes and reactions.

[0362] In one embodiment, the reactor system shown in Figure 3 can be designed using two separate reactors in series, as shown in Figure 13, where heating and cooling jackets are employed using a heat transfer medium that can be circulated from the hot exothermic reactor to the endothermic reactor or by using heat transfer media.

[0363] Both these configurations allow the endothermic reaction like DRM or ODPC over a catalyst in a first reactor (in the annulus in Figure 3) and the exothermic reactions (Reactions (3)- (7)) in a second reactor (in the inner tube in Figure 3). A low-temperature external separation system or high-temperature internal separation method can be employed to separate the hydrogen or propylene, and CO with or without other products or unreacted first reactor feed is directed to the inner or the second reactor (zone 1005 in Figure 3), where solid carbon is formed.

[0364] As shown in Figure 13, the described processes can also be conducted in two different reactors connected in series, where the heat is transferred from the exothermic reactor comprised of the solid removal system to the endothermic reactor using an external heat exchanger, and / or where direct heat exchange is achieved between the hot exit stream from the exothermic reactor to the cold inlet stream for the endothermic reactor.

[0365] In one embodiment, the described reactor system can be used in multiple-tube configurations by developing a reactor system combining several endothermic and exothermic reactors in large, well-insulated vessels for conducting processes discussed previously. Figure 14 shows a large container where several endothermic and exothermic reactors are placed to conduct a process of endothermic and exothermic reactions, and heat can be transferred with high efficiency in a well-insulated container. This embodiment also comprises augers as solid removal systems in each of the reactor tubes in which solids are produced.

[0366] This configuration is one of the possible ways to scale up the unit for industrial-scale application, in addition to unit scaling out or scaling up by increasing the diameter and height of the reactor system.Other Options

[0367] In other embodiments, the design shown in Figures 2 and 3, with or without a solid removal system, can be reconfigured by conducting the endothermic reaction in the inner tube where the solid catalyst bed 1003 is placed and the produced gases are directed to the outer tube designed with or without a solid removal system where the exothermic reaction occurs.

[0368] In other embodiments, the proposed reactor design shown in Figure 3 can be used for conducting liquid reactions, including a combination of endothermic and exothermic reactionswhere solid products are produced in the inner reactor or the second reactor where the catalyst vessel acts as the catalyst for the solid formation reaction, as in Figure 13.

[0369] In other embodiments, the reactor and processes can be scaled up for industrial use by adding multiple reactors in series or using a recycling ratio. This involves circulating an additional amount of the reactants in each reactor after separation. The recycling ratio or the number of reactors in a series can be determined based on the operating conditions and the desired conversion.Control and downstream system

[0370] The unit is fully automated to maintain full control to monitor and maintain full control of energy input, temperature, and pressure, as shown in Figure 15. This figure shows an example of the full unit where the described processes and reactor can be employed.

[0371] As shown in figure 15, a gas supply 3031 is fed to the reactor unit or system 3032 (e.g., the reactor systems as described in the present disclosure). The reactor converts the reactants in from the gas supply into solid products and gaseous products. The gas products are collected in the produced gas collection 3037. The solid products are fed to a collecting vessel / separator 3033 and then a further division of solid products and residual gases are separated. The solid prouduct is then collected in a producted solids collection 3035, and the separated gases are either collected or recycled 3036.

[0372] As shown in Figure 25, the reactor system 10 may be connected to a control system 121 via a number of sensors (e.g., pressure gauges (PG), temperature indicators (Tl), flow sensors, gas sensors), controllers, and control elements (e.g., heaters, temperature indicator controllers (TIC), pumps, valves). These elements include PGs 106, 107, 108 and 1 10, TICs 102, 107, 108 and TIs 100 and 101.

[0373] The controllers allow the system to monitor, adjust and maintain the reaction conditions by monitoring the pressure and temperatures at various points within the reactor system (e.g., flow rate and / or pressure at the first and second ends of the annulus, and first and second ends of the inner tube, and the temperatures within the annulus and inner tube). In response to these monitored variables, the system may adjust the heating supplied to the reactor system, and the flow rates and / or pressures of the various reactants.

[0374] Although the technology has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the invention as understood by those skilled in the art.

[0375] Several units can be used in combination after the reactor to collect the solid carbon allotropes and recycle the unreacted gases back into the reactor system, including the separationof hydrogen or propylene. Hydrogen or propylene separation can be achieved by employing a high- temperature membrane inside the outer tube or the first reactor or by using external separation techniques like low-temperature membranes or other common separation techniques.

[0376] Several unit operation techniques can be used for collecting solid carbon allotropes, including water traps, cyclones, wet filters, and other standard solid collection technologies used in industry.Reactor Vessel or Tube Activation

[0377] The active surface generated through the described tube modification method can vary depending on the exact nature of the treatment, in addition to varying process conditions and the feedstock gas used in the process for generating the solid carbon allotropes (Reactions (3)-(7)), may lead to varying the quality of the produced graphite according to needs. For instance, the resulting graphite may contain embedded iron oxide (as shown in the XRD data in Figure 16 and Table 4) or iron carbide (as shown in the XRD data in Figure 17 and Table 5), depending on the interaction between the surface and the feedstock gases. Alternatively, in some cases where the graphite layers grow extensively, the final product may consist of highly pure graphite with minimal residual catalyst.

[0378] Table 4. Crystalline phases present in the magnetic graphite obtained in Example 12.

[0379] Table 5. Crystalline phases present in the graphite obtained in Example 13

[0380] In certain embodiments of the present disclosure, as shown in Figure 18 integrating a solid removal system is critical in enhancing the organization and alignment of the graphitic flakes produced during the process.

[0381] Stage A represents the first step where the surface of the reactor is modified by adding a source of oxygen to oxidize the upper atomic layers of the tube producing the active iron oxide.

[0382] Stage B is a second procedure to enhance the activity of the already oxidized iron catalyst.

[0383] Stage C is the beginning of the passing of the carbon gas source to produce the graphite layers on the surface of the self-supported catalyst.

[0384] Stage D is a pictorial representation of the growth of the graphite layer of the present technology.

[0385] Stage E represents the continuous formation and removal of the produced carbon in a continuous mode by the use of the solid removal system of the described technology.

[0386] The solid removal system, which may employ a mechanical setup such as an auger or similar blade-based mechanism, functions by applying controlled mechanical forces to the growing graphite layers. As the carbon removal apparatus engages with the graphite surface, it facilitates both the formation and extraction of carbon to promote the orderly orientation of the graphitic flakes. The shape and the design of the auger or other solid removal methods may affect the final form of the collected carbon graphitic material.

[0387] The mechanical interaction between the blades of the solid removal system and the graphite layers induces a directional alignment of the growing graphitic structures. Specifically, the rubbing or scraping action of the blades against the nascent graphite surface helps to direct the stacking and organization of the carbon layers. This mechanical influence can mitigate the random, disordered growth typical of uncontrolled carbon deposition, thus producing more uniformly structured graphite flakes.

[0388] Furthermore, the carbon removal setup serves a dual function by enhancing the graphitization process and ensuring the continuous removal of excess carbon. This prevents the over-accumulation of disorganized carbon structures and allows for a more refined, high-quality graphite product. Depending on the carbon removal apparatus's specific design and operational parameters, such as gas flow, pressure, and temperature, the system can be optimized to produce graphite with superior morphological characteristics.

[0389] This type of embodiment introduces a synergistic mechanical intervention that assists in removing carbon and actively contributes to graphitic flakes controlled growth and orientation. The result is a more refined, structured graphite material with potential applications in advanced technologies where the precise organization of carbon layers is critical to performance.

[0390] This process holds potential for industrial applications in which controlled graphite growth or other solid products are desired, particularly for producing high-quality graphite flakes. By leveraging the inherent properties of iron as a catalyst and manipulating its distribution on the surface of the tube through precise thermal and chemical treatments, the method allows for the tailored production of graphite carbon, opening new possibilities for materials engineering and carbon-based technologies at a lower cost.Detailed Description of the Tube Activation:Materials of Construction:

[0391] The reactor tube may contain carbon steel, stainless steel, other metallic tubes, carbon tubes, or ceramic materials. For example, carbon-steel and stainless-steel tubes have a natural iron (and carbon) content, which can be exposed or enhanced to catalyze graphite formation. While lacking inherent catalytic properties, ceramic tube can be modified with an applied catalytic layer (e.g., containing iron).Surface Pre-treatment:

[0392] The internal surface of carbon-steel or stainless-steel reactor (e.g., the inner tube) is treated with an oxygen-containing gas (e.g., air, O2, O3, CO, CO2, or water vapor). This may be carried out at a temperature ranging from approximately 450°C to 750°C. This treatment selectively oxidizes the surface, exposing iron, which remains an active catalytic site for subsequent reactions.

[0393] Optionally, chemical etching can be performed using acid or base solutions (e.g., hydrochloric acid or sodium hydroxide) to increase surface roughness and expose more iron atoms, improving catalytic activity.

[0394] The thermal etching of the surface may be enhanced by repeated cycles of oxidation (for example, by using O2 diluted in an inert gas such as He) and reduction reactions (for instance, using H2 diluted in an inert gas such as Ar). These cycles may be carried out at relatively low temperatures (For example, around 500°C for 1 to 2 hours).Iron Salt Coating and Activation:

[0395] An aqueous or non-aqueous solution of an iron salt (e.g., iron chloride, iron nitrate) is applied to the internal surface of the tube. The addition can be accomplished by conventional impregnation / deposition / coating techniques or by using a developed specialized skid to anchor suitable particles. The coated tube is then dried and subjected to thermal activation at temperatures between 300°C and 700°C, reducing the iron salt to catalytically active iron particles that facilitate graphite-like carbon formation, as detailed in Example 14.

[0396] It will be appreciated that adding a iron-containing coating is an optional step if iron is present in the tube material. That is, for iron-containing tubes, adding a coating is an alternative way of providing iron for the catalyst. For non-iron-containing tubes (e.g., ceramic or other non- metallic tubes), iron salt coating is one way of providing the iron for producing the catalyst.

[0397] This treatment can be applied before the pretreatment described above when it may be convenient to enhance the amount of iron on the surface of the tube in a faster way.Tube Modification:

[0398] For reactor vessels which are not catalytically active (e.g., formed from ceramic), the surface may be coated with an iron-based active phase using deposition techniques such as spraycoating, dip coating, or chemical vapor deposition (CVD). The addition may be accomplished by conventional impregnation / deposition / coating techniques or by using a developed specialized skid to anchor suitable particles. The coating may consist of iron oxides or iron-containing compounds that are subsequently activated to their catalytic state through thermal or chemical treatment. Other tube activation and catalyst loading:

[0399] Other reactor materials, including metallic, non-metallic, ceramic or catalytically inert materials, can be activated by loading an active metallic phase using several methods commonly used for preparing supported catalysts like wet impregnation, dry impregnation, deposition, electro / electroless plating, and other coating techniques.Reaction Conditions:

[0400] The production of graphite is achieved by exposing the activated reactor surface (e.g., the modified tube surface) to a carbon-containing gas, such as methane, propane, ethane, natural gas, ethylene, carbon dioxide, and carbon monoxide, at temperatures ranging from 500°C to 800°C and at pressures of 1 to 10 bar. The catalytically active sites on the internal surface of the reactor tube promote the decomposition of the carbon-containing gas, leading to the formation of graphite-type carbon.Graphite Formation and Recovery:

[0401] The graphite-type carbon deposits on the internal surface of the reactor tube can be collected continuously or periodically, as described previously. The morphology and crystallinity of the graphite-type carbon can be controlled by adjusting reaction parameters such as temperature, gas composition, and residence time. The graphite-type product may be used in various applications, including batteries, conductive materials, and lubricants.Advantages

[0402] The present technology may provide several advantages.

[0403] Versatility and design: The reactor’s design allows for conducting several catalyzed chemical reactions and producing a diverse array of compounds, including but not limited to low- carbon emission hydrogen, solid carbon allotropes, and petrochemicals.

[0404] Continuous solid formation: The reactor may be equipped with a solid removal system. So, this reactor can create solid carbon allotropes continuously by using a solid removal system inside the reactor to remove the deposited carbon.

[0405] Autothermal operation: The reactor design allows efficient heat transfer by combining endothermic and exothermic reactions in a modular-confined design. This provides an efficient method for reducing the energy demand of several endothermic reactions, allowing the production of low-carbon hydrogen, solid carbon allotropes, and petrochemicals.

[0406] Low carbon hydrogen production: The described reactor and process can generate hydrogen at lower carbon emissions than conventional steam reforming or new methane pyrolysis processes. The reactor design and the developed process will significantly minimize energy demand by combining endothermic and exothermic reactions. In addition, the process operates at a lower temperature range (500-600°C) and low pressures (1-2 bars) compared to a regular steam reforming process (>750°C; >30 bars) or >1000°C in case of methane pyrolysis with the need of a molten metal bed.

[0407] Low carbon propylene production: The described reactor and process can generate propylene at lower carbon emissions than conventional steam and catalytic cracking of hydrocarbon processes through the ODPC process. The reactor design and the developed process will significantly minimize energy demand by combining endothermic and exothermic reactions. In addition, the process operates at a lower pressure range (1-2 bar) compared to regular steam and catalytic cracking of hydrocarbons (>49 bars).

[0408] Additionally, propane reforming through ODPC is an efficient route to produce several olefins like ethene, propene, and iso-butene, providing a method for creating these high-demand chemicals at low energy demand by combining endothermic and exothermic reactions.

[0409] Efficient CO2 mitigation: The described reactor and carbon conversion process can facilitate the conversion of CO2 into a range of high-demand compounds to mitigate CO2 or permanent mitigation of CO2 into solid carbon allotropes with minimum energy demand and without adding hydrogen. Some of the processes described in the present disclosure can mitigate CO2 into permanent sequestration to solid carbon allotropes with no or minimum energy demand while producing hydrogen and other valuable chemicals.

[0410] Solid carbon allotropes formation process: The described reactor and processes represent an efficient method for producing high-quality solid carbon with minimum energy demand; the produced solid carbon is highly demanded for several applications, such as graphite in car batteries, adsorption, intermediate chemicals, and construction materials.

[0411] Minimum energy demand: The developed reactor and processes combine endothermic and exothermic reactions in a reactor design similar to a tube and shell design or two-series reactors with proper heat transfer. Combining endothermic and exothermic reactions significantly minimizes energy demand for hydrogen and propylene production and / or CO2 mitigation.

[0412] Scalability: The developed reactor system provides a hydrogen and propylene production and / or CO2 mitigation reacting system design with low operating cost and energy demand. The reactor’s scalable design enables the implementation of this design across various industrial scales.

[0413] Solid removal system: This disclosure describes a method for solid carbon allotropes or other solids removal that enables continuous operation for several reactions where solids areformed. The solid removal system prevents carbon accumulation, allowing continuous operation without implementing complicated and costly reactors like fluidized or moving bed reactors. Several methods can be employed to remove solid deposits.

[0414] Tube catalyst: This disclosure describes a method for utilizing the reactor vessel or tube as a self-supporting catalytic agent to promote the reactions by employing metallic alloy tubes, activated metallic alloy tubes, tubes coated with active catalysts, and carbon steel tubes.

[0415] Innovative and highly active catalysts: The catalysts used in this technology are active and selective for CO2 conversion and hydrogen production by improving the active phase characteristics, leading to improved selectivity and yield.

[0416] Renewable Energy Integration: Renewable energy sources can be integrated into the reactor’s operation, ensuring that the energy used for performing these processes is environmentally friendly and energy efficient, which can further reduce the carbon footprint. The reactor’s efficient design minimizes energy demand, making it well-suited for integration with low- efficiency renewable energy sources.

[0417] The method described allows for using standard industrial tube materials as both reactor and catalyst, reducing the complexity and cost of the graphite-type carbon production process.

[0418] The pre-treatment and activation techniques are simple and scalable, enabling continuous or batch production of graphite-type materials, and can be performed at relatively low temperatures (around 500°C).

[0419] Using a ceramic tube with a catalytic coating offers a versatile alternative for high- temperature operations where a metallic tube may be unsuitable.

[0420] The ability to control the surface properties and catalytic activity ensures high-quality graphite production with tunable characteristics.Examples

[0421] While the principles of the technology have been described in connection with preferred embodiments, it should be understood that these simulation and experimental data are provided by way of example only and are not intended to limit the scope of the invention.Example 1 : Simulation and modeling results

[0422] Thermodynamic and process simulations showed that the described reactor and system can efficiently convert CO2 to hydrogen, olefins, and solid carbon allotropes while minimizing the energy demand needed for DRM or ODPC reactions.

[0423] The results show that hydrogen, propylene, and solid carbon allotropes formed have a negative carbon footprint. Hydrogen can be produced through a net process similar to the methane cracking or pyrolysis process in a continuous mode in a temperature range of 500-600°C.

[0424] An example of the modeling and pre-experimental analysis is shown in Figure 19; different reaction pathways were studied to understand the visibility and optimum operating conditions of the described processes. Figure 19 shows the thermodynamic modeling regarding the expected equilibrium fraction of CO and CO2 in a binary mixture. The results indicated that the lower temperature range (< 500°C) favors CO conversion into CO2 and solid carbon allotropes.

[0425] The following examples describe the observations collected during experimental testing of the reactor design with different processes.Example 2: Power consumption and reduction associated with power generation from Reactions (3)-(7)

[0426] The heat exchange between the endothermic and exothermic reactions across the inner tube (reactor) walls was demonstrated through the power consumption of the heating tape, which provides heat to sustain the reaction in the annulus (reactor). In these examples, the reactor system was tested using a heating tape of 520 watts, and the power utilization is reported based on the ratio of the actual wattage usage to the maximum wattage available by the hating tape. 40-50% power reduction of the heating tape utilization was observed when the exothermic reactions occurred using the activated inner tube relevant to the power utilization consumed to sustain the endothermic reaction (Reactions (1) or (2)) using an inert metallic tube. The exothermic reactions occurred by replacing the inert inner tube with an austenite alloy tube, as shown in Figure 3 (Zone 1002).

[0427] Figure 20 shows the power utilization reduction achieved through the heat exchange between the hot gases flowing in the inner tube and the cold inlet gases to the outer tube. This figure illustrates a comparison between the power utilization for the case of flowing Nitrogen through the outer tube annulus to exit from the top of the exit tube and the case of flowing the Nitrogen from the outer tube to the inner tube through the openings at the top of the inner tube, at 500°C and 5 psi. The power saving in the second case was around 0.6% as a function of the maximum power of the heating tape. This is attributed to the heat exchange between the hot gases leaving the bottom of the inner tube and the inlet cold gases entering the bottom of the outer tube.

[0428] As an example of the temperature variation between the inner and outer tube during testing DRM / ODPC in the outer tube with an exothermic reaction (Reactions (3)-(7)) in the inner tube, a temperature difference of around 15-20°C was observed between the inner and outer tube temperature allowing the heat to flow from the inner tube to the outer tube catalyst bed (zone 1003). The measurements of circulating the DRM and ODPC reacting gases without using catalysts (replacing the catalyst bed in zone 1003 with alumina) confirmed that the heating tape was used by around 39.5% to maintain an average temperature of 560°C in zone 1003. Most of the power utilization was attributed to heat losses to the environment and poor insulation. The heat losses tothe environment can be reduced significantly using well-insulated or jacketed reactors. The power utilization needed to increase the temperature of the inlet stream (250 ml / min of Cl- and 300 ml / min CO2) from room temperature to 560°C is 1 .5%, while 38% of the heating tape utilization is attributed to the heat losses to the environment.

[0429] The power needed for the DRM conversion for a flow rate of 250 ml / min of CH4 and 300 ml / min CO2 was 4% of the heating tape utilization for 44% conversion of CH4, while the power saving was around 1 .8% generated from Reactions (3) and (4). The calculation shows that the heat generated was expected to reduce the power utilization by only 1 % in this example, attributed to a 35% CO conversion in the inner tube. However, the additional 0.8% power saving is attributed to the heat transfer from the hot gases leaving the inner tube to the cold gases entering the outer tube. This reduction is around 45% compared to the power needed for the DRM reaction under tested conditions. A maximum of 50% power reduction was observed at 54% CH4 conversion and 50% CO conversion.

[0430] Power utilization reduction was observed due to the carbonization of a mixture of hydrogen and CO at an average operating temperature of 560°C at 5 psig following Reaction (4); the operating temperature was measured as an average temperature in the axial direction across the DRM catalyst bed in the outer tube, as shown in Figure 21 .

[0431] A power utilization reduction of around 1.5-2% was observed when the described reactor combined the endothermic ODPC reaction (Reaction (2) and the exothermic reactions between CO and propane (Reactions (3)-(7)), as shown in Figure 22.

[0432] Figure 22 shows the drop in power utilization while running the ODPC reaction (Reaction(2) due to the exothermic reactions (Reactions (3)-(7)), which reduced power utilization by around 1.7%. The average temperature in zone 1003 was 554°C at 5 psig; the observed conversion was 67% of C3H8 through the ODPC reaction, while CO conversion through Reactions (3)-(7) was 50%.Example 3: Continuous operation of the described reactor for different processes

[0433] The combination of the DRM process and the CO hydrogenation process was conducted continuously for 400 hrs.

[0434] The combination of the ODPC process and the reactions between CO and propane (Reactions (5)-(7)) was run for 150 hrs continuously.

[0435] The exothermic reaction, considering separating hydrogen from the DRM mixture through conducting the Boudouard reaction, was performed for 100 hrs continuously.

[0436] This indicates that these processes can be operated on a continuous basis.Example 4: Results from conducting DRM (Reaction (1)) and the combination of Reactions(3) and (4)

[0437] For DRM only, the typical dry-based molar composition of the gases leaving the DRM catalyst zone (starting from a 1.2 CO2 / CH4 mixture at 540°C) was: 20% H2, 26% CO, 23% CH4, and 31 % CO2, which was equivalent to 39% CH4 conversion using an inert inner tube (reactor). A catalyst containing nickel-ceria supported over alumina, as shown in patent application WO2023178418

[0034] , was used in the DRM reaction zone.

[0438] At 560°C, using a mixture of CO2 and CH4 with a molar ratio of 1 .2 CO2 to CH4 and a total flowrate of 550 ml / min, a maximum molar conversion of 54% was achieved in the annulus (reactor), while in the inner tube (reactor), 50% CO molar conversion was observed producing solid carbon allotropes materials. A catalyst containing nickel-ceria supported over alumina, as shown in patent application WO2023178418

[0034] , was used in the DRM reaction zone.

[0439] An austenite alloy tube was used as an inner tube, and carbon was generated from a mixture of CO and H2, CO and propane, and pure CO. The carbon formation in a mixture containing CO and H2 originated through Reactions (3) and (4). The analysis indicated that each reaction (from Reactions (3) and (4)) forms around 50% by mass of the produced solid carbon allotropes.

[0440] For DRM and Reactions (3) and (4), the typical dry-based molar composition of the gases leaving the inner tube (starting from a 1.2 CO2 / CH4 mixture at 543°C) was 19% H2, 25% CO, 24% CH4, and 32% CO2, which was equivalent to 50% CH4 molar conversion in the DRM zone and a 48% molar conversion of CO in the inner tube reactor being an austenite alloy inner tube (reactor). A higher conversion was observed in the DRM zone due to the heat generated in the inner tube, which improved the overall heat efficiency of the system. A catalyst containing nickel-ceria supported over alumina, as shown in patent application WO2023178418

[0034] , was used in the DRM reaction zone.

[0441] As an example of data recording using the automated control system, Figures 22 and 23 illustrate the temperature across the ODPC / ODPC catalytic bed in the outer tube and the power utilization reductions because of the exothermic reaction occurs in the inner tube as a function of time. These measurements in Figure 23 were collected at 565°C and 5 psig within the DRM catalyst zone.

[0442] Table 7: A typical composition of the exit stream at 560°C and 5 psi using an inlet stream of 300 ml / min of CO2 and 250 ml / mi

[0443] It was observed that the reverse water gas shift reaction might play a role in consuming hydrogen, while adding a high-temperature Pd membrane in the DRM section to remove hydrogen can significantly improve the DRM yield and reduce the extent of the reverse water gas shift reaction

[0033] . It was observed that achieving Reactions (3) and (4) in combination with DRM in the outer tube or Reactions (5)-(7) in combination with the ODPC reaction in the outer tube has improved the catalyst bed performance due to the presence of two heat sources: the external heating source and the heat generated through the exothermic reaction in the inner tube, which keeps the catalyst bed temperature in the outer tube consistent with no significant temperature drop due to the endothermic reactions (Reaction (1)-(2)).Example 5: Results for conducting Reaction (3) in the inner tube to resemble using the described configurations for producing hydrogen

[0444] An example of the experimental setup while testing CO conversion was that the inlet feed was added to the inner tube directly, or the outer tube was filled with alumina particles. At 560°C, using a mixture of CO and N2 with a molar ratio of 0.25 CO / N2, a CO conversion of 54% was achieved in the inner tube (reactor); the only reaction products were CO2 and carbon solid allotropes, following the Boudouard reaction (Reaction (3)).

[0445] A typical composition of the exit stream while CO conversion through Boudouard reaction (Reaction (3)) using an inlet mixture of 80% N2 and 20% CO at 125 ml / min, while the outer tube was at 560°C and 5 psig, 100 ml / min N2, 11.5 ml / min CO, and 6.75 ml / min, which is equivalent to 54% CO molar conversion.

[0446] An example of the results observed while conducting Reaction (3) is using a mixture of 80% N2 and 20% CO to study the possibility of forming carbon from CO only, as in Reaction (3).

[0447] Solid carbon allotropes were formed and deposited over the inner tube walls, and then the solid carbon was collected using the auger. The formation of the carbon from CO only, as in Reaction (3), was observed over the non-activated inner tube; however, activation has improved the conversion significantly. For all other exothermic reactions (Reactions (4)-(7)), no solid carbon was formed with the non-activated plain tube. The only gaseous product was CO2, which indicates that only Reaction (3) occurred. An example of the results observed using the mixture of 80% N2 and 20% CO is shown below in Table 8.

[0448] Additionally, two series-system reactors can employ low-temperature separation technologies to produce hydrogen and solid carbon allotropes. Alternatively, the syngas mixture containing a mixture of CO and H2 can be circulated without separating the two concentric tube designs or the two tubes in series design to produce solid carbon, leading to a net CO2 mitigation.Example 6: Results from conducting ODPC (Reaction (1)) and the combination of Reactions (3)-(7)

[0449] An example of the metallic tube used as the inner reactor was a carbon steel tube having > 99% iron content with a carbon content of 0.08-0.13 wt.%, in addition to other impurities. The carbon steel tube was activated and used as a catalyst for the exothermic reactions (Reactions (3)- (7)), as indicated by zone 1002. An example of the carbon steel tube tested was 0.5” outer diameter with a thickness of 0.049”. An example of the outer tube used in this work was a 316 stainless steel tube. The inner surface of the outer tube and the outer surface of the inner tube were covered with an inert coating to prevent any catalytic contributions towards the DRM or ODPC reactions occurred in the annulus between the outer and inner tube (zone 1003).

[0450] At 554°C, using a mixture of CO2 and C3H8 with a molar ratio of 1 .2 CO2 to C3H8, a molar conversion of 67% of CO2 and C3H8 was achieved in the annulus (reactor), while in the inner tube (reactor), 50% CO molar conversion was observed producing carbon solid allotropes.

[0451] Hydrogen can be separated in the annulus (reactor) using a high-temperature membrane [8-10]. A hydrogen-free mixture was passed to the inner tube, producing solid carbon allotropes in the inner tube through Reaction (3). So, the net process was used to produce hydrogen and solid carbon allotropes.

[0452] Produced propylene can be separated in the annulus (reactor) using a high-temperature membrane. A propylene-free mixture was passed to the inner tube, producing solid carbon allotropes in the inner tube through Reaction (3). So, the net process was used to produce propylene and solid carbon allotropes.

[0453] The typical (average) molar-based conversion of CO2 and C3H8 at 575°C and 5 psig: 19 and 60%, respectively, compared to around 32 and 15% in the absence of Reactions (3)-(7).

[0454] The typical inlet stream was 300 ml / min of CO2 and 250 ml / min of C3H8. The higher C3H8 conversion observed in the presence of Reactions (3)-(7) is attributed to the additional heat generated in these exothermic reactions and using CsHa as a reactant, while CO2 conversion drop is attributed to the generation of additional CO2 through Reaction (3). The carbon produced was estimated at 170 mg / min.Example 7: Conducting Reaction (2) in combination with Reactions (8)-(10)

[0455] If a proper catalyst is used in the inner tube instead of producing carbon, the ODPC catalyst zone product stream can generate iso-butene. A 5-10% iso-butene was observed using the GC when a molybdenum carbide catalyst (as the one shown in patent U.S. 10,265,685 B2

[0035] ) was used. Molybdenum carbide catalyst (as the one shown in patent U.S. 10,265,685 B2

[0035] ) or a catalyst containing nickel-ceria supported over alumina (as the one shown in patent application WO 2023 / 178,418

[0034] ) were used. The typical composition as a function of operating temperature at the exit of the second tube is shown in Figure 24. The content of U.S. 10,265,685 and WO 2023 / 178,418 are hereby incorporated by reference in its entirety [34,35].

[0456] Figure 24 shows the composition at the inner tube exit using an inlet feed containing 250 ml / min C3H8 and 300 ml / min CO2 as a function of the average operating temperature using a molybdenum carbide catalyst.

[0457] Additionally, two series-system reactors can employ low-temperature separation technologies to produce propylene and solid carbon allotropes. The carbon emissions of the produced carbon may range between 0 to -2 kg of CO2 eq. for each kg of solid carbon allotrope produced.

[0458] Carbon mitigation was achieved by converting CO2 into solid carbon allotropes, such as graphite and carbon black. The experimental results indicated that 50% of the CO2 fed to the reactor was converted to solid carbon allotropes within the operating range of 500-560°C and a back pressure of 5 psi.

[0459] This process can be used to convert paraffins and CO2 into a mixture of olefins, hydrogen, and carbon; propane was used as an example of paraffins conversion through this process in addition to methane.Example 8: Reactor configurations and solid removal system

[0460] As an example of the solid removal system, an auger was used with a diameter of 0.375” with Tapered Square / Round shank type and open spiral flute bit style. The auger has a right-hand flute direction and a screw point style. The auger was controlled by a motor with a variable speed of 1-20 rpm.

[0461] The solid removal system was developed using an auger and motor. The auger was made of coated stainless-steel operating at an RPM of 5-20. The auger generated carbon flakes and carbon fines particles.

[0462] An example of the experimental setup and the catalytic bed used in this work: 20 gm of alumina forming a bed of 4 cm height are placed over the catalyst holding ring (zone 1009), then a DRM / ODPC catalyst bed was placed over the alumina bed. The alumina bed acts as a heat sink for the heat generated in the inner reactor and provides heat for the cold gases going in the DRM / ODPC catalytic bed. The DRM / ODPC catalyst bed was a 22 gm of catalyst forming a bed of 5 cm height. The temperature was measured in different locations, including at the top and bottom of the catalyst bed. The operating temperature was the average of the top and bottom temperatures across the catalyst bed. The reactor may be heated through a heating tape applied to the outside of the outer tube.

[0463] A typical example of the outer and inner reactors was a 1 .25” stainless steel tube and 0.5” carbon steel tube with different thicknesses; the holes on the inner tube for gas circulation to the inner tube were 1 / 16-1 / 8” holes distributed evenly on the tube perimeter. A typical example of a solid removal system was an auger made of coated steel and controlled by a motor connected through the top reactor flange. In this example, this reactor design can produce around 95 gm / day of solid carbon and 24 gm / day of hydrogen at a DRM average temperature of 560°C, using a mixture of 300 ml / min CO2 and 250 ml / min CH4.Example 9: Solid removal design method

[0464] This auger system can be designed to efficiently recover and transport solid products deposited on activated reactor vessels, preserving solid product quality and allowing free gas flow. Key design factors include mechanical configuration, operational parameters, and material properties to optimize solid product scraping and system efficiency. In this example, the auger design, as an example of a solid removal system, to scrape graphite produced by combining Reaction (1) with Reactions (3) and (4) at an average temperature of 560°C in zone 1003 and 5 psig, using a flow rate of 250 ml / min CH4 and 300 ml / min CO2 is illustrated.

[0465] Auger Description and Design: The pitch and diameter of the auger are crucial for efficient graphite removal, smooth material flow, and effective gas-catalyst interaction. The pitch of the screw (distance between threads) should be optimized to allow solid material to move efficiently without clogging while allowing gas to flow around the material without excessive pressure buildup.

[0466] Pitch: Typically, 1 to 1.5 times the diameter, ensuring proper graphite transport. A larger pitch promotes faster removal, while a smaller pitch allows controlled flake formation.

[0467] Flow Path: Incorporating a helical path with gradual transitions in the screw diameter can aid in moving solid graphite particles while preventing gas flow restrictions.

[0468] Screw Diameter: The auger diameter is an essential parameter to control the quality of the produced graphite. A larger screw diameter allows faster scrapping of the produced graphite. In comparison, a smaller screw diameter allows accumulation of the produced graphite, increasing the carbon content significantly in the scraped graphite.

[0469] Capacity: The material flow capacity of the auger is calculated using the following equation:(12)Where, Q = Capacity of the auger (in3per unit time),Ds= Outer diameter of the auger (inches), d = Shaft diameter (inches),P = Pitch (inches), n = RPM (rotations per minute).

[0470] Helix Angle: The helix angle of an auger screw, typically 20-30 degrees, controls material transport speed, with smaller angles providing slower, more precise movement for processes like graphite removal, while larger angles increase transport speed. The auger's helix angle and pitch are related to the screw diameter according to the following equation:Where, 0S= Helix angle,P = Pitch (inches),Ds= The screw diameter (inches).

[0471] Clearance and Heat Expansion: The auger and reactor tube clearance must be optimized to effectively control graphite quality and buildup while allowing enough space for thermal expansion at the operating temperature range. The auger's thermal expansion is calculated using the following equation:AT? = erf? AT (14)Where, AT? = Change in radius, a = Coefficient of thermal expansion,L= Original Radius,AT = Temperature Change.

[0472] Vibration and Concentricity: The auger's velocity (RPM) can induce vibration if it approaches the critical speed, leading to eccentric rotation or lateral movement. The critical speed (Nc) at which resonance occurs can be mitigated by adding support bearings along the auger length to provide concentricity and minimize lateral movement. The critical speed is calculated using the following equation:Where, Nc= Critical Speed (RPM),L = Length of the auger (in inches),E = Young's modulus of the material (psi), p = Material density (lb / in3).

[0473] Mechanical Operating Parameters: The auger speed is an essential factor affecting how quickly and efficiently graphite is removed. The optimal auger speed for removing graphite deposits is typically between 10 and 100 RPM, depending on the consistency of the graphite, flow rate requirements, and reactor design.

[0474] Low RPM (10-50): This speed is more suitable for slow, controlled scraping in environments with minimal graphite buildup. High RPM (60-100): This is optimal for reactors with higher graphite accumulation, where faster removal is needed to maintain reactor efficiency.

[0475] Metallurgy: The auger must be designed using materials such as Inconel, Hastelloy, or steels with appropriate passivated coatings to enhance resistance to corrosion, high temperatures, and reactive gases like hydrogen, methane, propane, and carbon monoxide. Thermal expansion prevents dimensional changes that could destabilize the graphite flake removal process or affect flake quality, ensuring consistent scraping efficiency and reliable operation under varying temperatures. More details about the actual augers used in the present technology were given earlier in Example 8.

[0476] Range of Optimum Operating Conditions and Parameters

[0477] Temperature and Pressure: The process's optimal operating conditions are 400-650°C and 0 to 5 bar (gauge pressure).

[0478] Auger Speed (RPM): The optimal auger speed for removing graphite deposits is typically between 10 and 100 RPM, depending on the consistency of the graphite, flow rate requirements, and reactor design.

[0479] Pitch: A pitch between 2-30 mm.

[0480] Auger Length: The auger length must be sufficient to ensure that graphite is transported effectively out of the reactor without clogging.

[0481] Helix Angle: The helix angle should be between 20 and 30 degrees, balancing material flow, scraping efficiency, and gas flow within the auger.

[0482] Auger and Reactor Wall Clearance: The clearance between the auger blade and inner pipe wall should be 3% to 30% of the auger diameter to ensure proper graphite scraping.

[0483] When optimized, these parameters will help in an effective auger system operation for removing carbon deposits from activated reactor vessels, enhancing both reactor performance and longevity.Example 10: Carbon mitigations of described processes

[0484] Net carbon mitigation indicated by CO2 overall conversion varied significantly according to the process conditions, inlet stream, and catalyst. The maximum molar CO2 mitigation was 46% in a process combining DRM and Reactions (3) and (4).

[0485] The carbon emissions of the produced solid carbon allotropes may range between 0 to -2 kg of CO2 eq. for each 1 kg of solid carbon produced.Example 11 : Solid carbon characterization

[0486] Several forms of solid carbon allotropes were observed during the characterization of the produced solid carbon, including graphite, carbon black, and graphene; however, graphite-like was the most abundant form found in the solid carbon product. The formed carbon was found in several sizes, including large flakes (>200pm), small flakes (10-200pm), and small carbon aggregates in graphitic structure (<200pm), as shown in Figure 26-27. Figure 28 shows the composition of the produced solid carbon allotropes as explored using the EDS technique.

[0487] A typical composition of the solid carbon product: 82-97% C, 2-14% Fe, and 1-4% O. The composition can be controlled by manipulating the residence time, the precursor, the reactor design, and the solid removal system.

[0488] The characterization results of solid carbon allotropes samples produced through the combination of the DRM (Reaction (1)) and carbon formation (Reactions (3) and (4)) are shown below in Table 9:

[0489] Figure 29 shows one of the samples of the solid carbon allotropes flakes during the combination of Reaction (1) in the outer tube and Reactions (3) and (4) in the inner tube to produce solid carbon allotropes using a CO2 / CH4 molar ratio of 1.2 at 560°C and 5 psi with a total inlet flowrate of 550 ml / min.

[0490] The BET surface area analysis of the produced carbon showed that the surface area of the solid carbon formed during a combination of the DRM reaction and the CO hydrogenation reaction was in the range of 190-250 m2 / g. The solid carbon formed during a combination of theODPC reaction and the CO reaction with propane (Reactions (3)-(7)) was in the range of 100-210 m2 / g.

[0491] The characterization results of solid carbon samples produced through the combination of the ODPC (Reaction (2)) and carbon formation (Reactions (3)-(7)) are shown below in Table 10:

[0492] The BET surface area of the formed solid carbon during the Boudouard reaction (Reaction (3)) was in the range of 74-94 m2 / g, indicating control over the properties of the solid carbon that was produced. The characterization results of solid carbon allotropes samples produced through the Reaction (3) are shown below in Table 11 :Example 12: Tube activation method

[0493] The procedure to activate the inner tube to produce carbon through Reactions (3)-(7) will be described below using a carbon-steel tube as an example. The activation method included ex- situ and in-situ methods. The detailed method is explained in Examples 12-14. The activation method described in this patent application was able to switch the reactor vessel or part of it to act as a catalyst for Reactions (3)-(7), where solid carbon allotropes were obtained. One commonly used example was the activated carbon steel and a solid removal system described by the auger in Examples 8 and 9, at a back pressure of 5 psig and an operating temperature of 560°C within the DRM catalyst zone (1003).Example 13: Detailed activation method

[0494] As described in Example 12, the carbon steel tube was initially activated by heating the tube to 500°C for 12 hours under oxidative conditions to ensure the migration of iron particles to the inner tube surface. To assess the catalyst activation on the tube surface by applying the above- mentioned thermal procedure: Temperature programmed Reduction (TPR) (up to 500°C) in the presence of H2 diluted in Ar, followed by Temperature programmed oxidation (TPO) using O2 diluted in He (up to 460°C) was performed in cycles.

[0495] Each TPR experiment was followed by a TPO measurement to assess the effect of oxidation. It was seen that H2 uptake in successive TPR experiments increased after every oxidation step carried out at 460°C (Table D; Run No 1 to 3). In Table 12, TPR1 shows the H2 uptake of Carbon Steel without any thermal treatment. This Carbon steel was then oxidized using diluted O2 in He up to 460°C. The second TPR experiment, followed by the oxidation step (TPO- 1), showed a dramatic increase in H2 uptake, indicating the exposition of more iron that can take hydrogen. This H2 uptake increased almost 100 times (TPR-3) when the carbon steel sample underwent a second oxidation cycle (TPO-2). This showed that each successive oxidation increased the presence of activated iron oxide on the surface, as evidenced by increased H2 uptake, as shown in Table 12.

[0496] Table 12: Successive Temperature programmed oxidation profiles of the treated tube of Examples 13 and 14.Example 14: Alternative preparation method

[0497] Carbon steel was chemically etched / activated using melted Fe(NO)3.9H2O as follows: 0.1662 g of Fe(NO)3.9H2O was melted at 60°C and used to coat, with a simple layer, a 1.0782 g piece of carbon steel. After coating the carbon steel with the melted salt, the total weight of the piece of carbon steel increased to 1.1206 g. The coated carbon steel was placed in a porcelain capsule and an oven to dry it at 100°C for 3 hours and then to calcine it at 400°C for 6 hours with a ramp of 5°C / min. After the calcination and cooling down, the coated and thermally treated piece weighed 1 .0883 g, which implies an increase of weight of 0.94 wt.%. This sample was then reduced at 500°C using H2 diluted in Ar.

[0498] A protocol similar to the carbon-steel piece of Example 13 was applied to the coated piece in Example 14 to reduce and oxidize the material. The results are shown in Table 12 (runs 4 to 6), and the TPO profiles for each cycle are shown in Figure 30, where the successive temperatureprogrammed oxidation profiles can be observed. As can be seen from comparing run 1 and run 4 in Table 12, adding the coating increases the first treatment amount of H2 uptake, indicating theexposition of more iron that can take hydrogen. The second and third TPO treatments showed a considerable increase in H2 uptake.

[0499] Textural properties were carried out to analyze the original carbon steel tube and the coated and thermally treated material. The original carbon-steel tube showed a specific surface area of 10 cm2 / g. On the other hand, the coated with Fe-nitrate and thermally treated carbon steel showed a specific surface area of 2490 cm2 / g, which indicated that some rugosity was generated on the surface of the carbon steel, increasing the exposed area by about 250 times because of the applied treatment.Bibliography[1] Amin AM, Croiset E, Epling W. Review of methane catalytic cracking for hydrogen production. International Journal of Hydrogen Energy 2011 ;36:2904-35. https: / / d0i.0rg / l 0.1016 / j.ijhydene.2010.11 .035.[2] Nabgan W, Tuan Abdullah TA, Nabgan B, Jalil AA, Nordin AH, Ul-Hamid A, et al. Catalytic biohydrogen production from organic waste materials: A literature review and bibliometric analysis. International Journal of Hydrogen Energy, 46, 2021 ; 46:30903-25. https: / / d0i.0rg / l 0.1016 / j.ijhydene.2021 .04.100.[3] Wang F, Harindintwali JD, Yuan Z, Wang M, Wang F, Li S, et al. Technologies and perspectives for achieving carbon neutrality. The Innovation 2021 ;2:100180. https: / / d0i.0rg / l 0.1016 / j.xinn.2021 .100180.[4] Brown RC. Process Intensification through Directly Coupled Autothermal Operation of Chemical Reactors. Joule 2020;4:2268-89. https: / / doi.org / 10.1016 / jjoule.2020.09.006.[5] Badakhsh A, Cha J, Park Y, Lee Y-J, Jeong H, Kim Y, et al. Autothermal recirculating reactor(ARR) with Cu-BN composite as a stable reactor material for sustainable hydrogen release from ammonia. Journal of Power Sources 2021 ; 506:230081 . https: / / d0i.0rg / l 0.1016 / j.jpowsour.2021 .230081 .[6] Liu D, Oh S. Direct non-oxidative methane conversion in a catalytic wall reactor. US20210379549A1 , 2021.[7] Ashraf Amin, Review of autothermal reactors: Catalysis, reactor design, and processes, International Journal of Hydrogen Energy, Volume 65, 2024, Pages 271-291 , ISSN 0360-3199, https: / / doi.org / 10.1016 / jJjhydene.2024.03.372.[8] Sagar S, David W, Vemuri B, Tian G. Method and Reactor for Oxidative Coupling of Methane. US20210087121 A1 , 2021.[9] Izrailevich L, Vasilyevna M, Leonidovich T, Vladislavovich I, Vladimirovich M, Vasilyevich P. Methods for producing aromatic hydrocarbons from natural gas and processing unit for implementing same. US11667591 B2, 2023.

[0010] Early S. Process for synthesising methanol. GB2606855B, 2023.

[0011] Banu A, Bicer Y. Review on COx-free hydrogen from methane cracking: Catalysts, solar energy integration and applications. Energy Conversion and Management: X 2021 ; 12:100117. https: / / doi.Org / 10.1016 / j.ecmx.2021 .100117.

[0012] Carapellucci R, Giordano L. Steam, dry and autothermal methane reforming for hydrogen production: A thermodynamic equilibrium analysis. Journal of Power Sources 2020;469:228391 . https: / / doi.org / 10.1016 / j powsour.2020.228391 .

[0013] Howarth RW, Jacobson MZ. How green is blue hydrogen? Energy Science & Engineering 2021 ;9:1676-87. https: / / doi.org / 10.1002 / ese3.956.

[0014] Towards hydrogen definitions based on their emissions intensity. IEA; 2023.

[0015] Allam R. Apparatuses and methods for hydrogen production. US11691874B2, 2023.

[0016] Peng X-D, Zhang Y, Courtney T. Process for H2 and syngas production. EP4140945A1 , 2023.

[0017] You SN, Kim BK, Nam GM. Combined reforming apparatus. US20230107936A1 , 2023.

[0018] Thomson M, Bobicki E. Methods for preparing hydrogen and solid carbon from a gaseous hydrocarbon source using microwaves and / or radio waves. US20230202839A1 , 2023.

[0019] Verykios X, Neophytides S. Catalytic materials for pyrolysis of methane and production of hydrogen and solid carbon with substantially zero atmospheric carbon emissions. US11673803B2, 2023.

[0020] Solomon F, Lourens J, Owen D. Renewable energy hydrocarbon processing method and plant. US20230257263A1 , 2023.

[0021] Bar-Gadda R. Simultaneous generation of electricity and chemicals using a renewable primary energy source. US10758888B1 , 2020.

[0022] A. Ibrahim A, Amin A, S. Al-Fatesh A, Siva Kumar N, Olajide Kasim S, S. Al-Awadi A, et al. Nanosized Ni / SBA-15 Catalysts for CO2 Reforming of CH4. Applied Sciences 2019;9. https: / / d0i.0rg / l 0.3390 / app9091926.

[0023] Chenic A S., Cretu Al, Burlacu A, Moroianu N, Vfrjan D, Huru D, et al. Logical Analysis on the Strategy for a Sustainable Transition of the World to Green Energy — 2050. Smart Cities and Villages Coupled to Renewable Energy Sources with Low Carbon Footprint. Sustainability 2022;14. https: / / doi.org / 10.3390 / su14148622.

[0024] Kothandaraman J, Heldebrant D, Jiang Y, Dagle R. Integrated capture and conversion of CO2 to methanol or methanol and glycol. US10961 173B2, 2021 .

[0025] Chintala T, Ittagunta N, Kotdwala R, Dagani S. Generation of methanol from high ash coal and utilization of methanol for syngas cleaning. IN396062B, 2022.

[0026] Crawford L, Schafer W. Systems and methods for integrated CO2 reuse using vapor compression. US10947486B1 , 2021.

[0027] Arora S, Prasad R. An overview on dry reforming of methane: strategies to reduce carbonaceous deactivation of catalysts. RSC Adv 2016;6:108668-88. https: / / doi.Org / 10.1039 / C6RA20450C.

[0028] Mertens J, Krawec M, Attwal R. Techno-economic metrics of carbon utilisation - Part 1. Decarbonisation Technology 2022:31-8.

[0029] Payne, Alexander & Garcia-Garcia, Guillermo & Styring, Peter. (2023). Production of propane and propene via carbon capture utilisation: comparison of its environmental and economic performance against conventional production methods. Green Chemistry. 25. 10.1039 / D2GC04721 G.

[0030] Florou, A.; Bampos, G.; Natsi, P.D.; Kokka, A.; Panagiotopoulou, P. Propylene Production via Oxidative Dehydrogenation of Propane with Carbon Dioxide over Composite MxOy-TiO2 Catalysts. Nanomaterials 2024, 14, 86. https: / / doi.org / 10.3390 / nano14010086.

[0031] Marktus A. Atanga, Fateme Rezaei, Abbas Jawad, Mark Fitch, Ali A. Rownaghi, Oxidative dehydrogenation of propane to propylene with carbon dioxide, Applied Catalysis B: Environmental, Volume 220, 2018, Pages 429-445, https: / / doi.Org / 10.1016 / j.apcatb.2017.08.052.

[0032] Vilekar, Saurabh & Hawley, Kyle & Junaedi, Christian & Walsh, Dennis & Roychoudhury, Subir & Abney, Morgan & Mansell, James. (2012). Performance Evaluation of Staged Bosch Process for CO2 Reduction to Produce Life Support Consumables. 42nd International Conference on Environmental Systems 2012, ICES 2012. 10.2514 / 6.2012-3555.

[0033] Ahmadi Khoshooei, Milad & Wang, Xijun & Vitale, Gerardo & Formalik, Filip & Kirlikovali, Kent & Snurr, Randall & Pereira-Almao, Pedro & Farha, Omar. (2024). An active, stable cubic molybdenum carbide catalyst for the high-temperature reverse water-gas shift reaction. Science (New York, N.Y.). 384. 540-546. 10.1126 / science.adl1260.

[0034] Monica Bartolini Tiberi, Gerardo Vitale Rojas, Diego Hernan Moreno Gonzalez, Pedro Rafael Pereira Almao, Low Temperature Methane Steam Reforming to Produce Hydrogen, WO2023178418, 2023.

[0035] Gerardo Vitale-Rojas, Pedro Rafael Pereira-Almao, Lante Antonio Carbognani, Maria Josefina Perez Zurita, Ronald Scott Smith, Clementina Sosa, Metallo-silicate catalyst (MSC) compositions, methods of preparation and methods of use in partial upgrading of hydrocarbon feedstocks, U.S. 10,265,685 B2, 2019.

[0036] Nataraj S, Russek S. Utilization of synthesis gas produced by mixed conducting membranes. US61 10979A, 2000.

[0037] Kunho Lee Aadesh Harale Thang Pham Aqil Jamal Ahmad O. Khowaiter, Integrated production of hydrogen, electricity, and heat, US17 / 191992, 2021.

[0038] Oyama S. Ted, Yunfeng Gu, Hydrothermally-stable silica-based composite membranes for hydrogen separation, US7862648B2, 2011.

[0039] Robert E. Buxbaum, High temperature gas purification apparatus, US6168650B1 , 2001.

[0040] Sushil Adhikari, Sandun Fernando Hydrogen Membrane Separation Techniques Industrial & Engineering Chemistry Research 2006 45 (3), 875-881 .

[0041] Sazali, N., Mohamed, M.A. & Salleh, W.N.W. Membranes for hydrogen separation: a significant review. Int J Adv Manuf Technol 107, 1859-1881 (2020).

[0042] A. Sudharshan Reddy, Pooja Sharda, S.P. Nehra, Anshu Sharma, Advanced strategies in MOF-based mixed matrix membranes for propylene / propane separation: A critical review, Coordination Chemistry Reviews, 498, 2024.

[0043] Hang Yin, Alex C.K. Yip, A Review on the Production and Purification of Biomass-Derived Hydrogen Using Emerging Membrane Technologies, Catalysts, 7(10), 2017.

Claims

CLAIMS1 . A reactor system comprising: an outer tube having an outer tube axis; and an inner tube comprising an inner first end and an inner second end and having an inner tube axis, the inner tube being thermally conductive and being located within the outer tube such that the inner and outer tube axes are aligned with each other, wherein the inner and outer tubes form an annulus between the inner and outer tubes, the annulus comprising an annulus first end and an annulus second end, and wherein the annulus second end is in fluid communication with the inner first end.

2. The reactor system according to claim 1 , wherein the inner tube comprises a catalyst for catalyzing an exothermic reaction, and the annulus comprises a catalyst for catalyzing an endothermic reaction.

3. The reactor system according to claim 2, the catalyst for catalyzing an exothermic reaction is formed from the material of the inner tube.

4. The reactor system according to any one of claims 2-3, wherein the catalyst used for endothermic reaction is in the form of a catalyst bed, and wherein the catalyst for catalyzing an endothermic reaction is arranged around an inner wall of the inner tube.

5. The reactor system according to any one of claims 2-4, wherein the catalyst for catalyzing an endothermic reaction is a catalyst for Dry Reforming of Methane, the catalyst for catalyzing the endothermic reaction having a transition metal, an alkali earth metal, and a lanthanide metal mounted on a support.

6. The reactor system according to claim 5, wherein the support is inert.

7. The reactor system according to any one of claims 5-6, wherein the support comprises one or more of: y-alumina, 0-alumina, a-alumina, inert ceramic, and silica.

8. The reactor system according to any one of claims 2-7, wherein the catalyst for catalyzing the exothermic reaction comprises a transition metal.

9. The reactor system according to any one of claims 2-8, wherein at least one product of the endothermic reaction is a reactant in the exothermic reaction.

10. The reactor system according to any one of claims 2-9, wherein the catalyst used for endothermic reaction catalyzes a reaction between methane and carbon dioxide to produce carbon monoxide and hydrogen.11 . The reactor system according to any one of claims 2-10, wherein the catalyst used for the endothermic reaction, catalyzes a reaction between propane and carbon dioxide to produce carbon monoxide, propylene, and water.

12. The reactor system according to any one of claims 2-11 , wherein the catalyst used for the endothermic reaction, catalyzes a reaction between paraffins and carbon dioxide to produce carbon monoxide, olefins, hydrogen, and water.

13. The reactor system according to any one of claims 2-12, wherein the catalyst used for exothermic reaction, catalyzes a reaction to produce carbon dioxide and solid carbon from carbon monoxide.

14. The reactor system according to any one of claims 2-13, wherein the catalyst used for exothermic reaction, catalyzes a reaction between hydrogen and carbon monoxide to produce solid carbon and water.

15. The reactor system according to any one of claims 2-14, wherein the catalyst used for exothermic reaction, catalyzes a reaction between a paraffin and carbon monoxide to produce solid carbon, water, and hydrogen.

16. The reactor system according to any one of claims 2-15, wherein the catalyst used for exothermic reaction, catalyzes a reaction between a paraffin and carbon monoxide to produce solid carbon, water, and an olefin.

17. The reactor system according to any one of claims 2-16, wherein the catalyst used for exothermic reaction, catalyzes a reaction between an paraffin and carbon monoxide to produce solid carbon and water.

18. The reactor system according to any one of claims 1-17, wherein the annulus second end is adjacent to the inner first end.

19. The reactor system according to any one of claims 1-18, wherein the reactor system comprises a tubular hydrogen separation membrane positioned within and along the length of the annulus.

20. The reactor system according to any one of claims 1-19, wherein the inner tube houses a solid removal system.21 . The reactor system according to claim 20, wherein the solid removal system comprises an auger arranged along the length of the inner tube.

22. A process for producing hydrogen within the reactor system comprising one or more inner tubes and one or more annuli, each inner tube being surrounding by a said annulus, the process comprising: injecting reactants into a first end of a said annulus such that the reactants flow through the said annulus towards a second end and are converted to one or more endothermic products in an endothermic reaction, and directing at least a portion of the products from the endothermic reaction in the outer tube or the first reactor to a first end of said inner tube or a second reactor such that the portion of theendothermic products flow through the said inner tube towards a second end of the inner tube and are converted to products in an exothermic reaction.

23. The process according to claim 22, wherein the reactants comprise carbon dioxide and a light hydrocarbon.

24. The process according to any one of claims 22-23, wherein the products comprise solid carbon.

25. The process according to any one of claims 22-24, wherein the products comprise hydrogen.

26. The process according to any one of claims 22-25, wherein the process comprises directing at least a portion of the unreacted reactants from the exit of the annulus second end to the inner first end such that the unreacted reactants flow through the inner tube towards the inner second end and are converted to products in an exothermic reaction.

27. The process according to any one of claims 22-26, wherein the process comprises separating hydrogen produced in one or more of the enothermic and exothermic reactions.

28. A process for refining paraffins and CO2 to produce a mixture of olefins, hydrogen, and carbon.

29. A process for producing olefins within the reactor system comprising one or more inner tubes and one or more annuli, each inner tube being surrounded by a said annulus, the process comprising: injecting reactants into the first end of a said annulus such that the reactants flow through the said annulus towards a second end and are converted to one or more endothermic products in an endothermic reaction and directing at least a portion of the products from the endothermic reactions to the first end of said inner tube such that the portion of the products from the endothermic reactions flow through the said inner tube towards a second end of the inner tube and are converted to exothermic products in an exothermic reaction.

30. A method for activating a reactor surface to produce graphite-type materials comprising: providing a reactor surface comprising iron; passing an oxygen-containing gas over the reactor surface at temperatures between 450°C to 750°C to expose catalytically active iron atoms.

31. The method according to claim 30, wherein the method comprises activating the internal surface by chemical etching or coating with an iron salt, followed by thermal activation.

32. The method according to any one of claims 30-31 , wherein the reactor surface is the inner wall of a tubular reactor.

33. The method according to any one of claims 30-32, wherein the reactor surface is made of ceramic, and the internal surface is coated with an iron-based active phase.

34. The method according to any one of claims 30-33, wherein the method comprises introducing a carbon-containing gas into the reactor under controlled temperature and pressure conditions to induce graphite formation on the catalytically active iron atoms.

35. The method according to claim 34, wherein the carbon-containing gas is selected from the group consisting of methane, ethane, propane, natural gas, ethylene, carbon dioxide, and carbon monoxide.

36. A process for producing C4 hydrocarbon, the process comprising reacting propane in the presence of a catalyst to produce C4 hydrocarbon and solid carbon.

37. The process according to claim 36, wherein the C4 hydrocarbon comprises one or more of butene, isobutylene, isobutane and butane.

38. The process according to any one of claims 36-37, wherein the catalyst comprises one or more of: molybdenum carbide; nickel and cerium oxide.

39. A reactor system comprising: an outer container having a container inlet; and an inner tube comprising a tube inlet and a tube outlet, the inner tube being thermally conductive, wherein a first reactor is formed between the inner tube and the outer container and a second reactor volume is inside the inner tube, and wherein the first and second reactors are in fluid communication.

40. The reactor according to claim 39, wherein the tube inlet is positioned within the container away from the container inlet.

41. The reactor according to claim 39-40, wherein the tube passes through a wall of the container.

42. The reactor according to claim 39-41 , wherein the first reactor comprises a first catalyst for catalyzing an endothermic reaction, and the second reactor comprises a second catalyst for catalyzing an exothermic reaction.

43. The reactor according to any one of claims 39-42, wherein the reactor system comprises a solid removal system for removing solids from the first reactor.

44. A reactor system comprising: a tube with inner walls comprising a catalyst for converting gaseous reactants into a solid product; and a solid removal system configured to scrape the inner walls to remove solid product attached to the inner walls.

45. The reactor system according to claim 44, wherein the solid removal system comprises an auger extending along the length of the tube.

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