Process for capturing carbon dioxide from air and direct conversion of carbon dioxide into fuels and chemicals

Abstract

The invention relates to processes, catalysts and materials for converting renewable electricity, air and water into low or zero carbon fuels and chemicals by directly capturing carbon dioxide from the atmosphere and converting it into fuels and chemicals using hydrogen produced from electrolysis of water.

Description

Technical Field

[0001] This invention relates to processes, catalysts, and materials for converting renewable electricity, air, and water into low-carbon or zero-carbon fuels and chemicals by directly capturing carbon dioxide from the atmosphere and converting it into fuels and chemicals using hydrogen produced by water electrolysis. Background Technology

[0002] Many industrial and biological processes produce carbon dioxide. Carbon dioxide is typically released into the atmosphere, and global atmospheric carbon dioxide levels have been increasing since the beginning of the Industrial Revolution. Carbon dioxide is considered a major greenhouse gas contributing to global climate change. Reducing carbon dioxide at its sources has been particularly difficult and often unsuccessful. Atmospheric carbon dioxide levels continue to rise. A more desirable approach to dealing with carbon dioxide is to efficiently capture it from ambient air and convert it into useful products such as fuels (e.g., diesel, kerosene, jet fuel, gasoline or gasoline blendstock, or other fuels) and chemicals (methanol, ammonia, solvents, waxes, olefins, or other chemicals) that can replace fuels and chemicals produced from fossil sources (e.g., oil and gas) and thereby reduce total net emissions of carbon dioxide into the atmosphere. This is what low-carbon, ultra-low-carbon, or zero-carbon fuels and chemicals mean.

[0003] Carbon dioxide can be obtained from several sources. Industrial manufacturing plants that produce ammonia for fertilizer from natural gas or coal generate significant amounts of carbon dioxide. Ethanol plants that convert corn or wheat into ethanol generate significant amounts of carbon dioxide. Power plants that generate electricity from natural gas or coal generate significant amounts of carbon dioxide. Natural gas deposits may also contain substantial amounts of carbon dioxide, necessitating the processing of large quantities at some natural gas processing plants. Capturing CO2 for utilization often involves separating carbon dioxide from a flue gas stream or another feed stream where carbon dioxide is not a major component. Alkylamines are used to remove carbon dioxide from flue gas streams. Alkylamines used in this process include monoethanolamine, diethanolamine, methyldiethanolamine, diisopropylamine, aminoethoxyethanol, or combinations thereof. Metal-organic framework (MOF) materials have also been used as a means of capturing carbon dioxide from diluent streams using chemisorption or physisorption to separate carbon dioxide from the stream. Other methods for obtaining concentrated carbon dioxide include chemical looping combustion, in which circulating metal oxide materials capture carbon dioxide produced during the combustion process.

[0004] Carbon dioxide can also be captured from the atmosphere in a process known as direct air capture (DAC). The challenges of capturing carbon dioxide from the air differ from those from flue gas or other sources because the concentration of carbon dioxide in the air is very low, around 415 ppm. Liquid alkylamines do not work well at these low concentrations because the amine loss is typically too high. MOF compounds based on the physical absorption of carbon dioxide typically have too low a carbon dioxide absorption capacity. The publication Sanz-Perez et al., “Direct Capture of CO2 from Ambient Air”, Chem. Rev. 2016, 116, 11840-11876, details the historical development of CO2 direct air capture. Many materials have been tried to capture carbon dioxide from diluted air streams.

[0005] Over the past decade, two main types of materials and processes have been considered the most promising. The first group of promising materials and processes utilizes amine-tethered solid adsorbents. This involves the CO2 capture capability of amines (such as the liquid amines mentioned above), but these types of materials are chemically tethered to a solid. Unlike the metal oxide-based chemisorbents described above, supported amine adsorbents operate under near-ambient conditions and can ideally be regenerated by mild temperature fluctuations. Choi et al., “Application of Amine-Tethered Solid Sorbents for Direct CO2 Capture from Ambient Air”, Environmental Science & Technology, 2011, 45, 2420-2427, describe these materials in detail. However, these chemisorbents require temperature fluctuations to release carbon dioxide and require an inert gas to remove it. In the laboratory, nitrogen, argon, or other inert gases are used. However, commercially, separating the inert gas from the carbon dioxide becomes almost as important a problem as initially capturing it. To overcome the inert gas problem, for some of these supported adsorbents, it has been shown that steam can be used to release carbon dioxide and regenerate the adsorbent. See Wen Li et al., “Steam Stripping for Regeneration of Supported Amine-Based CO2 Adsorbents”, ChemSusChem 2010, 3, 899-903. Techniques developed by GlobalThermostat, as described in US 9,555,365, fall into this general category of methods for DACs.

[0006] The second material and process involves reacting an aqueous metal hydroxide with CO2 from the air to produce a metal carbonate, which is then calcined to release the captured CO2 and regenerate the metal hydroxide. This cycle can be carried out in a series of continuous chemical reactors. This is a technology scaled up by carbon engineering. Their processes are discussed in detail in Keith et al., “A Process for the Capture of CO2 from the Atmosphere”, Joule 2, 1573-1594, August 15, 2018. The carbon dioxide obtained from their processes is cooled from 900°C and compressed to greater than 100 atmospheres for geological sequestration or into CO2 pipelines. A renewable source of hydrogen (H2) can be produced from water via electrolysis.

[0007]

[0008] This reaction uses electricity to split water into hydrogen and oxygen. An electrolyzer consists of an anode and a cathode separated by an electrolyte. Different electrolyzers operate in slightly different ways, primarily due to the different types of electrolyte materials involved.

[0009] However, if water is fed into the system at ambient pressure and temperature and all energy input is provided in electrical form, the theoretical minimum electrical input for each electrolysis technology is 39.4 kWh / kgH2 (HHV of hydrogen). If suitable thermal energy is provided to the system, the required electrical input can be reduced to below 39.4 kWh / kgH2. High-temperature electrolysis, such as PEM steam electrolysis, and particularly solid oxide electrolysis, can have lower operating costs if all energy is provided by electricity, provided the electrolyzer is co-located with a low-cost or waste heat source. (Study on development of waterelectrolysis in the EU Final Report, E4tech Sari with Element Energy Ltd for the Fuel Cells and Hydrogen Joint Undertaking, February 2014). Given the high energy required for electrolysis, the placement of zero-carbon fuel and chemical equipment, as envisioned in this invention, must be located in or near locations with inexpensive renewable electricity.

[0010] Besides electrolysis, important current research also includes using light energy and photocatalysts to split water into hydrogen and oxygen. (Acar et al., Int. J. Energy Res. 2016; 40: 1449-1473).

[0011] Recent developments in liquid organic hydrogen carriers (LOHCs) have demonstrated the ability to react hydrogen with toluene at an electrolysis or water splitting site to produce methylcyclohexane. This methylcyclohexane can then be transported as a liquid to another site where it is dehydrogenated to hydrogen gas, and the liquid toluene is returned to its original location to continue the cycle. See Niermann et al., “Liquid Organic Hydrogen Carries (LOHCs) - Techno-Economic Analysis of LOHCs in a Defined Process Scheme”, EnergyEnviron.Sci. 2019, 12, 290. This development implies the possibility of separating the electrolysis site from the end-user of renewable hydrogen.

[0012] One reaction that has been considered for utilizing carbon dioxide is the Reverse Water Gas Shift (RWGS) reaction.

[0013] CO2 + H2 = CO + H2O

[0014] This reaction converts carbon dioxide and hydrogen into carbon monoxide and water. The reaction is endothermic at room temperature, requiring heat to proceed, and significant carbon dioxide conversion necessitates elevated temperatures and a good catalyst.

[0015] Several catalysts for the RWGS reaction have been disclosed. The main catalysts previously studied were Cu, Pt, or Rh dispersed on metal oxide supports (Daza & Kuhn, RSC Adv. 2016, 6, 49675-49691).

[0016] Using CO (carbon monoxide) from an RWGS reaction and hydrogen from water electrolysis, there is potential to obtain useful products through catalytic hydrogenation of carbon monoxide to hydrocarbons. The mixture of H2 and CO is called snythesis gas (or syngas). Syngas can be used as a feedstock for the production of a wide variety of chemical products, including liquid fuels, alcohols, acetic acid, dimethyl ether, and many others. If H2 can be produced from water and CO from CO2, it is possible to achieve truly net-zero carbon fuels and chemicals if no CO2 or greenhouse gas emissions are generated during the generation of syngas and the conversion of syngas into fuels and chemicals.

[0017] In addition to oxidizing hydrocarbons, the catalytic hydrogenation of CO in light gases, liquids, and waxes, ranging from methane to heavy hydrocarbons (C100 and above), is commonly referred to as Fischer-Tropsch (or FT) synthesis. Conventional low-temperature (<250°C) FT processes primarily produce high wt% (or wt%) FT waxes (C25 and above) from a catalytic conversion process. These FT waxes are then hydrocracking and / or further processed to produce diesel, naphtha, and other fractions. Light hydrocarbons are also produced during this hydrocracking process, which may require additional upscaling to produce viable products. Catalysts typically used for FT are cobalt (Co)-based or iron (Fe)-based catalysts that are also active for water-gas shift (WGS) reactions that lead to the conversion of feedstock carbon monoxide to carbon dioxide. For more details on existing Fischer-Tropsch techniques, see (SSAil, S. Dasappa / Renewable and Sustainable Energy Reviews 58(2016) 267-286).

[0018] Despite extensive prior work on this subject and the global importance of successfully developing these technologies, to date, no good processes, systems, and catalysts have been developed to capture atmospheric carbon dioxide and convert it into useful fuels and chemicals. Better processes, systems, and catalysts are needed. Attached Figure Description

[0019] Figure 1 The entire process of producing fuels and chemicals from renewable electricity, water, and air is shown, and the process can occur in two separate locations.

[0020] Figure 2 Two cycles of direct air capture (DAC) of CO2 using amine-based solid chemisorbents are shown.

[0021] Figure 3 Direct air capture (DAC) of CO2 using a metal hydroxide / carbonate cycle is shown.

[0022] Figure 4 The LOHC process for delivering hydrogen generated at position 1 to position 2 is shown.

[0023] Figure 5 and Figure 6 An integrated and efficient process for converting carbon dioxide, water, and renewable electricity into renewable fuels and chemicals is demonstrated.

[0024] Figure 5 The operation of the reverse water gas conversion system and its support unit is shown.

[0025] Figure 6 A portion of the overall process flow diagram for converting H2 and CO2 into fuels and chemicals is shown. Specifically, Figure 6 A liquid fuel production system is shown, in which CO and H2 react to produce long-chain hydrocarbons that can be used as fuel or chemicals. Summary of the Invention

[0026] This invention relates to processes, catalysts, and materials for converting renewable electricity, air, and water into low-carbon or zero-carbon fuels and chemicals by directly capturing carbon dioxide from the atmosphere and converting it into fuels and chemicals using hydrogen produced from water electrolysis. The process involves converting water into hydrogen in a highly efficient electrolysis unit that uses renewable electricity as its energy source and optionally transfers the hydrogen to a direct air capture (DAC) site via a LOHC system. Hydrogen is used advantageously to improve the efficiency of the DAC system. Carbon dioxide and hydrogen react in an RWGS reactor to carbon monoxide and water, where the heat of reaction is provided by renewable electricity. The catalyst used in the RWGS reactor is a novel solid solution catalyst. The product carbon monoxide and additional hydrogen react in a liquid fuel production reactor to produce fuels and chemicals directly using a novel catalyst. The net product produced is a hydrocarbon with a length of 4 to 24 carbon atoms. Other products can be produced from syngas, including methanol, waxes, ammonia, solvents, other fuels, and chemicals. Detailed Implementation

[0027] This invention relates to several subsystems. Figure 1 The entire process of producing fuels and chemicals from air, water, and renewable electricity is illustrated. The entire process begins with (1) the production of renewable hydrogen from renewable or low-carbon electricity and water via electrolysis; (2) the renewable hydrogen may optionally be stored or transported to a secondary location via a liquid organic hydrogen carrier (LOHC) system; (3) direct air capture (DAC), in which carbon dioxide is captured from the atmosphere, using hydrogen from the electrolysis step to improve the efficiency of the DAC process; (4) an RWGS system to produce CO from CO2; (5) a liquid fuel production (LFP) reactor system in which syngas is converted into hydrocarbons; and (6) an autothermal reformer (ATR) section, which converts the light hydrocarbons (C1-C5) produced in the liquid fuel production (LFP) reactor into hydrogen and carbon monoxide (syngas), and the carbon monoxide is recycled back to the LFP reactor.

[0028] Another aspect of the invention is the use of exhaust gas to ignite the calciner in a direct air capture process. Ideally, the calciner should burn oxygen, using oxygen from the electrolyzer to concentrate CO2 from the calciner for recycling back to the RWGS process.

[0029] according to Figure 1 The electrolysis system produces renewable hydrogen. Water is fed into the electrolysis system. Renewable electricity is used to power the electrolysis system. Hydrogen can be produced by electrolyzing water.

[0030]

[0031] An electrolyzer consists of an anode and a cathode separated by an electrolyte. Different electrolyzers operate in slightly different ways. Different electrolyzer designs can be used, utilizing different electrolysis technologies, including alkaline electrolysis, membrane electrolysis, and high-temperature electrolysis. Alkaline electrolysis is preferred because it is commercially capable of large-scale operations (>1 MW). Different electrolytes can be used, including liquid KOH and NaOH with or without activating compounds. Activating compounds can be added to the electrolyte to improve its stability. Most ionic activators used for the hydrogen evolution reaction consist of ethylenediamine-based metal chloride complexes and Na₂MoO₄ or Na₂WO₄. Different electrocatalysts can be used on the electrodes, including many different combinations of metals and oxides, such as Raney nickel-aluminum, which can be enhanced by adding cobalt or molybdenum to the alloy.

[0032] Several combinations of transition metals, such as Pt₂Mo, Hf₂Fe, and TiPt, have been used as cathode materials and have shown significantly higher electrocatalytic activity than existing electrodes.

[0033] Some electrolyzers are designed to operate at high pressures (e.g., 30-50 bar) and produce hydrogen and oxygen. Pressurized electrolyzers are preferred because they eliminate the energy-intensive syngas compression step. Water at the cathode combines with electrons from an external circuit to form hydrogen and negatively charged oxygen ions. These oxygen ions pass through a solid ceramic membrane and react at the anode to form oxygen and generate electrons for use in the external circuit. In this way, both hydrogen and oxygen are produced in the electrolyzer. In one embodiment, multiple electrolyzers operate in parallel. No electrolyzer operates at 100% energy efficiency, and energy consumption is critical for the economical operation of the facility. Energy consumption in the electrolyzer should be less than 200 MWh / MT of H2 produced, preferably less than 120 MWh / MT, and more preferably less than 60 MWh / MT. For alkaline electrolyzer embodiments, energy consumption will be greater than 39.4 MWh / MT of H2 produced. However, for high-temperature electrolyzer implementations, if waste heat is used to heat the electrolyzer to above ambient temperature, the electricity consumption may be lower than the H2 produced by 39.4 MWh / MT.

[0034] Several different direct air capture (DAC) technologies can be used in this invention. A first embodiment of the DAC technology is based on a solid amine adsorbent. Figure 2 One embodiment of the invention is illustrated. A supported amine adsorbent based on a primary, secondary, or tertiary amine is loaded into a DAC reactor. The amine adsorbent is capable of chemisorbing carbon dioxide from the air passing through the DAC reactor. This causes the carbon dioxide-depleted air stream to exit the DAC reactor. This occurs at near-ambient temperature and pressure. A blower can be used to draw air into the reactor. The pressure drop through the DAC reactor is optimized by loading a solid amine adsorbent into the DAC reactor and by controlling the size of the amine adsorbent.

[0035] At least three classes of usable solid-supported amine adsorbents exist. Class 1 adsorbents consist of a polymer or oxide support (typically silica) on which small amine-containing molecules or polymers are physically loaded. Class 2 adsorbents are based on amines covalently bonded to the surface of a solid support (e.g., via the use of organosilanes). For example, a Class 1 adsorbent is tetraethylenepentamine or diethanolamine impregnated on MCM-41 silica. A typical Class 2 adsorbent is a triamine-grafted, pore-expanded MCM-41, which exhibits good adsorption at low carbon dioxide partial pressures. Class 3 adsorbents are amine-based solid adsorbents described as hyperbranched aminosilica (HAS) materials, synthesized via in-situ ring-opening polymerization of aziridine on a porous support. These adsorbents typically have an amine loading of 2–10 mmol / g; a pore size of 4 nm to 7 nm; and a pore size of 40–600 μm.2 The materials have a BET surface area of ​​0.5 mmol / g and a pore volume of 0.1–0.8 cc / g. These materials work well with humid or dry air under ambient conditions and exhibit carbon dioxide adsorption of 0.5–4.0 mmol / g at a carbon dioxide concentration of approximately 400 ppm. Ideally, the DAC reactor is operated such that approximately 20–50% of the carbon dioxide in the air passing through the DAC reactor is removed. Removing more than 50% of the carbon dioxide is generally undesirable because the adsorbent's ability to capture carbon dioxide is significantly reduced. After the CO2 absorption cycle is complete, the DAC reactor switches to a CO2 release and adsorbent regeneration cycle. In this cycle, hydrogen produced in the electrolyzer is heated to approximately 90–120°C via indirect heat exchange. The hydrogen is passed through the DAC reactor, where the adsorbed carbon dioxide is released and mixed with the carbon dioxide gas. Typically, the amount of hydrogen used results in a hydrogen to carbon dioxide molar ratio of 2.0 mol / mol to 3.0 mol / mol in the gas leaving the DAC reactor. This feed stream becomes… Figure 5 The RWGS feed stream is integrated into the system. This integration significantly improves the efficiency of the DAC system because it eliminates the need for steam and separation.

[0036] The second implementation of DAC technology is based on different process chemistry. Figure 3The embodiment described is illustrated. This process involves capturing carbon dioxide from the air by converting a metal hydroxide into a metal carbonate. Air is passed through an air contactor using a blower. The air contactor contacts the carbon dioxide-loaded air with aqueous KOH. The KOH reacts with the carbon dioxide to produce aqueous K₂CO₃. The aqueous K₂CO₃ is then reacted with solid Ca(OH)₂ in a particle reactor. The K₂CO₃ is converted back to KOH, while the Ca(OH)₂ is converted into solid CaCO₃. Calcium carbonate is fed into a calcining furnace system, where it is converted into CaO. The calcining furnace system is novel as a circulating fluidized bed operating at 50 psig or higher. It is an oxygen-blown circulating fluidized bed system. Oxygen is used as the fluidizing gas at an apparent velocity between 0.25 m / s and 2.5 m / s. Natural gas or other combustible gases are fed into the solid bed via lances, where oxygen and gases react to raise the temperature to 900°C. This results in CaCO3 reacting to CaO + CO2 with a conversion efficiency greater than 90%. Solid CaO is separated from gaseous CO2 in a cyclone separator system. The solid CaO is fed to a Slaker reactor, where it is converted into Ca(OH)2 for use in the particle reactor. The hot, CO2-containing gas is immediately mixed with hydrogen produced in the electrolyzer. Typically, the amount of hydrogen mixed with carbon dioxide results in a hydrogen to carbon dioxide molar ratio of 2.0 mol / mol to 3.0 mol / mol in the gas leaving the DAC reactor system. This feed stream becomes... Figure 5 The RWGS feed stream is integrated into the system. This integration significantly improves the efficiency of the DAC system because it eliminates the need for cooling or compressing carbon dioxide. Since the mixed gas temperature is already above 300°C or even higher, the heating requirements in this implementation are also significantly reduced for RWGS feed.

[0037] Figure 4 A LOHC system according to one embodiment of the invention is shown. The electrolyzer and DAC system can be located in the same physical location. However, it seems possible that the DAC unit would be located at the source of consumption of product fuels and chemicals, while the electrolyzer could be located in an area with ample sunlight, wind, or other renewable or low-carbon resources available for generating renewable electricity to produce hydrogen. In this case, the hydrogen produced by the electrolyzer needs to be transported to a second location. Figure 4 This demonstrates how this can be achieved using a LOHC system. While several different LOHC materials are possible, methylcyclohexane (MHC) appears to be the most promising, as it can be produced by the reaction of toluene with hydrogen. This is in Figure 4The process is completed in a hydrogenation reactor. MHC is a liquid that can be easily fed to position 2, which is different from the electrolyzer position. The MHC can then be dehydrogenated at position 2 to produce hydrogen and toluene. The toluene is then fed back to position 1 to complete the cycle. Dehydrogenation is a catalytic reactor system. Many catalysts can be used, but S-Pt on alumina can be included. The dehydrogenation reaction temperature is between 340-360°C, and the pressure is between 1-30 bar. The MHC conversion rate is greater than 95%, and the hydrogen yield is greater than 95%. The high temperature of the dehydrogenation reactor can be advantageously used in metal hydroxide DAC processes. The hydrogen produced via the dehydrogenation reactor can be mixed with CO2 produced by a calcining furnace to produce a gas stream with a temperature above 400-500°C, which can be used as... Figure 5 The RWGS reactor system shown is fed directly (with some form of additional preheating).

[0038] Figure 5 An RWGS system for producing CO from CO2 is shown. Zero-carbon or ultra-low-carbon fuels and chemicals require that no fossil fuels be burned in the processes that produce them. This means that any feed heating in the integrated process needs to be done either indirectly (through a cross heat exchanger) or via electric heating, where the electricity comes from a zero-carbon or renewable source, such as wind, solar, geothermal, or nuclear power.

[0039] exist Figure 5 Hydrogen and carbon dioxide in feed streams 1 and 2 form a mixed gas (feed stream 3). The H2 / CO2 ratio is between 2.0 and 5.0 mol / mol, more preferably between 3.0 and 4.0 mol / mol. The mixed RWGS feedstock can be heated to a temperature greater than 900℉ in unit 4 via indirect heat exchange. Importantly, this initial temperature rise is achieved without using the direct combustion of carbon-containing gases to provide heat, as using the direct combustion of carbon-containing gases to provide heat would mean that CO2 is produced and could potentially offset the effect of converting CO2 into useful fuels and chemicals.

[0040] The RWGS feed gas, which contains a mixture of H2 and CO2, is heated at least in part in a preheater outside the main reactor vessel to an inlet temperature greater than 1400℉ (feed stream 5), or preferably greater than 1500℉, to produce heated feed gas.

[0041] Figure 5The preheater, shown as unit 4, is electrically heated and raises the temperature of the feed gas to greater than 1400℉, preferably greater than 1500℉, and more preferably greater than 1600℉ via indirect heat exchange. There are many methods to achieve the electrical heating of the feed gas. One method is through an electrically heated radiant furnace. In this embodiment, at least a portion of the feed gas passes through heating coils within the furnace. These heating coils are surrounded by radiant electric heating elements. These elements can be made of a variety of materials. The heating elements can be nickel-chromium alloys. These elements can be rolled strips or wires, or cast into a zigzag pattern. The elements are backed by an insulating steel shell, and ceramic fibers are typically used for insulation. The radiant elements can be divided into multiple zones to provide a controlled heating pattern. Multiple coils and multiple zones may be required to provide heat to the feed gas and produce a heated feed gas. The radiant furnace requires proper design of the heating elements and fluid coils to ensure a good viewing factor and good heat transfer. In another embodiment of the invention, the gas passes directly above the heating element, whereby the gas is heated by convective heat transfer. The power consumption of the radiant furnace should be as low as possible. The power consumption of the radiant furnace is less than 0.5 MWh / MT of CO2 in the feed gas; more preferably less than 0.40 MWh / MT of CO2; and even more preferably less than 0.20 MWh / MT of CO2.

[0042] The heated RWGS feed gas is then fed into the main RWGS reactor vessel (unit 6). The main RWGS reactor vessel has two possible implementations. In a first implementation, the main RWGS reactor vessel is adiabatic or near-adiabatic and designed to minimize heat loss, but no additional heat is added to the main reactor vessel, and the temperature in the main reactor vessel decreases from the reactor inlet to the outlet. In a second implementation, the main RWGS reactor vessel is similarly designed, but additional heat is added to the vessel to maintain an isothermal or near-isothermal temperature distribution within it. Heat can be added to the vessel via internal or external heaters or other means.

[0043] The main RWGS reactor vessel (Unit 6) is a reactor whose length is greater than its diameter. The inlet of the main reactor vessel is smaller than the total diameter of the vessel. The main reactor vessel is a steel vessel. The steel vessel is internally insulated to limit heat loss. Various insulation materials, including castable or pourable refractory linings or insulating bricks, can be used to limit heat loss to the environment. (See Harbison-Walker Handbook of Refractory Practices, 2005) https: / / mha- net.org / docs / Harbison%20Walker%202005%20Handbook.pdf ).

[0044] The catalyst bed is located within the main reaction vessel. The catalyst can be granules, pellets, spheres, trefoil, tetralobes, monoliths, or any other engineered shape designed to minimize pressure drop across the reactor. Ideally, the shape and particle size of the catalyst particles are controlled such that the pressure drop across the reactor is less than 50 psi [345 kPa], more preferably less than 20 psi [138 kPa]. The catalyst particles can have a characteristic size between 1 mm and 10 mm or greater. The catalyst particles are structured materials with an internal surface area greater than 40 m². 2 / g, more preferably greater than 80m 2 / g, preferably with a surface area of ​​100m² 2 / g porous material. Several catalyst materials are possible for catalyzing the RWGS reaction. Previously studied RWGS catalysts are Cu, Pt, or Rh dispersed on a metal oxide support (Daza & Kuhn, RSC Adv. 2016, 6, 49675-49691). We have found that the preferred catalyst is a solid solution catalyst with a transition metal on a metal oxide support.

[0045] The RWGS catalyst used in this process is a high-performance solid solution-based catalyst that is highly versatile and efficient in performing RWGS reactions. The robust solid solution catalyst exhibits high thermal stability up to 1,100 °C, does not form carbon (coking), and is well resistant to contaminants that may be present in the captured CO2 stream.

[0046] This catalyst exhibits high activity at low metal concentrations (0.5-20 wt%), compared to other catalysts that require at least 30 wt% transition metal or other metal support. Furthermore, there is no need to use expensive precious metals to enhance catalyst performance. The manufacturing process of the RWGS catalyst is also important because it produces a unique solid solution phase, a bimetallic crystalline phase, which results in the absence of metal phase segregation. This unique chemical structure leads to enhanced resistance to coking compared to conventional metal-supported catalysts. It also results in enhanced resistance to poisons such as sulfur and ammonia. Moreover, this catalyst exhibits enhanced catalytic activity at a lower surface area compared to monometallic segregated catalyst phases. This catalyst does not require the base promotion needed to inhibit carbon deposition. In the main RWGS reactor vessel, the per-pass conversion of CO2 to CO is typically 60-90%, more preferably 70-90%. If an adiabatic reactor implementation is used, the temperature in the main RWGS reactor vessel will decrease from the inlet to the outlet. The outlet temperature of the main RWGS reactor vessel is 100-200℉ lower than the inlet temperature, more preferably between 105℉ and 160℉ lower. The RWGS weight hourly space velocity (WHSV) is the mass flow rate of RWGS reactants (H2+CO2) per hour divided by the mass of catalyst in the main RWGS reactor bed, and is within 1000hr. -1 With 60,000hr -1 Between, more preferably between 5,000 hours -1 With 30,000hr -1 between.

[0047] The gas exiting the main RWGS reactor is the RWGS product gas (feed stream 7). The RWGS product gas contains carbon monoxide (CO), hydrogen (H2), unreacted carbon dioxide (CO2), and water (H2O). In addition, the RWGS product gas may also contain a small amount of methane (CH4) produced in the main reactor via side reactions.

[0048] At this point in the process, the RWGS product gas can be used in several ways. The product gas can be cooled and compressed and used in downstream processes to produce fuels and chemicals. The RWGS product gas can also be cooled, compressed (in Unit 8), and returned to the preheater and fed back to the main reactor vessel.

[0049] The RWGS product gas can also be reheated in a second electric preheater and fed to a second reactor vessel, where an additional CO2-to-CO conversion can occur, as shown in units 9 and 10. Unit 11 shows optional compression of the syngas before it is fed to the liquid fuel production synthesis step.

[0050] Figure 6 A liquid fuel production (LFP) reactor system is shown. This is also known as a hydrocarbon synthesis step. The LFP reactor converts CO and H2 into long-chain hydrocarbons, which can be used as liquid fuels and chemicals. Syngas (feed stream 12) is blended with recycled syngas to produce LFP reactor feed stream 13 and optionally products from the ATR (unit 19) (feed stream 21), as described below. The blended gas fed into the LFP reactor is shown as feed stream 14. The LFP reactor feed contains H2 and CO. Ideally, the H2 to CO ratio in the feed stream is between 1.9 mol / mol and 2.2 mol / mol.

[0051] The LFP reactor (unit 15) is a multi-tube fixed-bed reactor system. The diameter of each LFP reactor tube can be between 13 mm and 26 mm. The length of the reactor tube is typically greater than 6 meters, more preferably greater than 10 meters. The LFP reactor is typically vertically oriented, with the LFP reactor feed entering at the top of the LFP reactor. However, in some cases, horizontal reactor orientation is possible, and in some cases with height restrictions, setting the reactor at an angle is also advantageous.

[0052] The majority of the length of the LFP reactor tube is filled with LFP catalyst. The LFP catalyst may also be blended with a diluent (e.g., silica or alumina) to facilitate the distribution of the LFP reactor feed within and across the LFP reactor tube. The chemical reaction occurring in the LFP reactor produces LFP product gases containing hydrocarbon products (C4-C5) with a length of 4 to 24 carbons. 24 Hydrocarbons and water. Importantly, the LFP reactor does not produce any significant amounts of CO2. Less than 2% of the CO in the LFP reactor feed should be converted to CO2. Equally important, only a limited amount of carbon monoxide in the LFP reactor feed is converted to hydrocarbons with a carbon number greater than 24. Less than 10% by weight of the hydrocarbon fraction in the LFP product should have a carbon number greater than 24. More preferably, less than 4% by weight of the hydrocarbon fraction in the LFP product should have a carbon number greater than 24.

[0053] As mentioned above, the Fischer-Tropsch (FT) process typically produces hydrocarbon products with lengths ranging from 1 to 100 carbon atoms, most of which are in the wax range (C24+). However, the LFP catalyst used in one embodiment of the invention does not produce heavy hydrocarbons in the same yield as other catalysts used in conventional FT processes.

[0054] In some embodiments of the present invention, the LFP catalyst exhibits insignificant activity for the conversion of CO to CO2 via a water-gas shift reaction. In some embodiments of the present invention, the CO-to-CO2 water-gas shift conversion rate is less than 5% of the CO in the feed. In some embodiments, the LFP catalyst comprises nickel as the active metal. In some embodiments, the LFP catalyst comprises cobalt as the active metal. In some embodiments, the LFP catalyst comprises both cobalt and nickel as active metals. The LFP catalyst is supported on a metal oxide support selected from the group consisting of alumina, silica, titanium dioxide, activated carbon, carbon nanotubes, zeolite, or other support materials or mixtures thereof having sufficient size, shape, pore diameter, surface area, crushing strength, effective particle radius, or similar characteristics.

[0055] The catalyst can have various bladed supports of different shapes with three, four, or five blades, wherein two or more of the blades are longer than the other two shorter blades, and the two longer blades are symmetrical. The distance from the midpoint of the support or the midpoint of each blade is called the effective particle radius, which is the effective particle radius for achieving C4 to C64. 24 An important parameter for the desired selectivity of hydrocarbons. The LFP co-catalyst may include one of the following: cerium, ruthenium, lanthanum, platinum, rhenium, gold, nickel, or rhodium. The LFP co-catalyst is less than 1 wt% of the total catalyst, preferably less than 0.5 wt%, and even more preferably less than 0.1 wt%.

[0056] The LFP catalyst support has a pore diameter greater than 8 nanometers (nm), an average effective particle radius less than 600 micrometers (µm), a crushing strength greater than 3 psi, and a compressive strength greater than 125 m. 2 / g BET surface area. The metal-impregnated catalyst has a metal dispersion of approximately 4%. Several types of supports have been found to enable C4-C 24 Hydrocarbon yield is maximized. These supports include alumina, alumina / silica combinations, activated carbon, carbon nanotubes, and / or zeolite-based supports.

[0057] LFP fixed-bed reactor to enable C4-C 24 Operate in a way that maximizes hydrocarbon yield.

[0058] Alternatively, the LFP fixed-bed reactor uses a conventional FT catalyst that primarily produces wax. In one embodiment, the LFP reactor operates at a pressure between 150 psi and 450 psi. The reactor operates at a temperature range of 350℉ to 460℉, more typically at around 410℉. The FT reaction is exothermic. The reactor temperature inside the LFP reactor tubes is maintained by placing the reactor tube bundle in a heat exchanger in which boiling steam is present on the outside of the LFP reactor tubes. The steam temperature is at a lower temperature than the LFP reaction temperature, so heat flows from the LFP reactor tubes to the lower-temperature steam. The steam temperature is maintained by maintaining the steam pressure. The steam is typically saturated steam.

[0059] The CO conversion rate in the LFP reactor is maintained at a single-pass carbon monoxide conversion rate between 30 mol% and 80 mol%. CO can be recycled for additional conversion or fed to downstream additional LFP reactors. The carbon selectivity for CO2 is minimized to below 4% of the converted CO, more preferably below 1%. The carbon selectivity for C4-C24 hydrocarbons is between 60% and 90%. The product gas from the LFP reactor contains the desired C4-C24 hydrocarbons as well as unreacted carbon monoxide, hydrogen, water, small amounts of C1-C5 hydrocarbons, and small amounts of C24+ hydrocarbons. The desired products are separated from the feed stream by distillation or any other acceptable means. Carbon selectivity is defined as:

[0060]

[0061] Where n is transformed co This refers to the molar flow rate of CO converted in the LFP reactor; n i It is the molar flow rate of the i-th carbon number hydrocarbon produced in the LFP reactor. Carbon selectivity for carbon dioxide is defined as...

[0062]

[0063] Where n co2 This is the molar flow rate of CO2 produced in the LFP reactor. This is ideal for zero-carbon fuel and chemical production processes that start with carbon dioxide as a feedstock.

[0064] The product flows out from the bottom of the reactor. Heavy hydrocarbons (C24+) may be generated, so these products can be removed at the reactor outlet. If the LFP reactor is operated with a catalyst under suitable conditions, there will be little or no heavy hydrocarbons. The main LFP product is the feed stream 16, which is cooled and condensed in unit 17. Unreacted carbon monoxide, hydrogen, and C1-C5 hydrocarbons or tail gas (unit 18) are part of the feed to the autothermal reformer. Figure 6The autothermal reformer (ATR) section (Unit 19) of the process is also shown. In the autothermal reformer (ATR), the ATR hydrocarbon feed consists of carbon monoxide, hydrogen, and C1-C5 hydrocarbons. Autothermal reforming of natural gas, primarily methane (C1), into carbon monoxide and hydrogen has been commercially practiced for many years. See K. Aasberg-Petersen et al. / Journal of Natural Gas Science and Engineering 3 (2011) 423-459.

[0065] The ATR used in this invention is not necessarily conventional, as it is desirable to produce products with high CO content, wherein the ratio of H2 to CO in the product is between 1.9 mol / mol and 2.2 mol / mol, and the CO2 in the product gas is less than 10 mol%. The ATR oxidant feed comprises steam and O2, wherein the O2 is at least partially generated by electrolysis of H2O (feed stream 29). The ATR oxidant feed and ATR hydrocarbon feed are preheated and then reacted in the ATR burner, wherein the oxidant and hydrocarbons are partially oxidized at a temperature in the range of 950-1050°C. The ATR reactor may be divided into three zones: a combustion zone (or burner) in which at least a portion of the ATR hydrocarbon feedstock is completely combusted into H2O and CO2.

[0066] In the hot zone, further conversion occurs through homogeneous gas-phase reactions. These reactions are slower than combustion reactions, such as carbon monoxide oxidation and pyrolysis involving higher hydrocarbons. The main overall reactions in the hot zone are homogeneous gas-phase steam hydrocarbon reforming and shift reactions. In the catalytic zone, the final conversion of hydrocarbons takes place through heterogeneous catalytic reactions, including steam methane reforming and water-gas shift reactions. The composition of the resulting ATR product gas is close to the predicted thermodynamic equilibrium composition. The actual ATR product gas composition is the same as the thermodynamic equilibrium composition, differing by less than 70°C. This is known as the equilibrium approach temperature.

[0067] To keep the amount of CO2 generated in the ATR to a minimum, the amount of steam in the ATR oxidant feed needs to be kept as low as possible, which still results in a low-soot ATR product gas composition close to the equilibrium predicted composition. Typically, the total steam to carbon ratio (mol / mol) in the combined ATR feed (oxidant + hydrocarbon) should be between 0.4 and 1.0, with an optimal value of about 0.6.

[0068] The ATR product exits the ATR catalytic zone at temperatures above 800°C. The ATR product is then cooled to a lower temperature via a waste heat boiler (unit 22), where heat is transferred to generate steam. This steam, along with the low-pressure steam generated by the LFP reactor, can be used to generate electricity.

[0069] Suitable ATR catalysts for catalytic zone reactions are typically nickel-based. RWGS catalysts can be used as ATR catalysts. Other suitable ATR catalysts are nickel or magnesium aluminum spinel (MgAl2O4) on α-phase alumina, with or without a noble metal promoter, wherein the noble metal promoter includes gold, platinum, rhenium, or ruthenium. Spinel has a higher melting point, higher thermal strength, and greater stability than alumina-based catalysts.

[0070] ATR products can be blended with RWGS products and used as feed for LFP reactors. This results in high utilization of the original CO2 to C4 to C24 hydrocarbon products.

[0071] In some implementations, the LFP product gas is unsuitable as a direct feed to the ATR and must undergo pre-reforming. In these cases, the LFP product gas, containing unreacted carbon monoxide, hydrogen, and C1-C5 hydrocarbons, includes the pre-reformer hydrocarbon feed gas. Typically, higher hydrocarbons and carbon oxides in the stream require the use of a pre-reformer, rather than being used directly as the ATR hydrocarbon feed. The pre-reformer is typically an adiabatic reactor. The adiabatic pre-reformer converts the higher hydrocarbons in the pre-reformer feed into a mixture of methane, vapor, carbon oxides, and hydrogen, which is then suitable as the ATR hydrocarbon feed. One benefit of using a pre-reformer is that it allows for the preheating of higher ATR hydrocarbon feeds, which reduces the amount of oxygen used in the ATR. The integrated process obtained as described above results in a high conversion rate of carbon dioxide to C4-C24 hydrocarbon products (stream 24) suitable as fuel or chemicals.

Claims

1. An integrated process for converting a feed stream containing air, electricity, and water into a product stream containing hydrocarbons, the process comprising: a. An electrolysis step, wherein an electrolyzer feed stream containing water is converted into an electrolyzer product stream containing hydrogen and oxygen, wherein at least a portion of the electricity used in the electrolysis step is derived from a renewable source; b. A direct air capture step, wherein air is brought into contact with an adsorbent and carbon dioxide is removed from the air stream; c. A reverse water gas shift step, wherein at least a portion of the hydrogen from the electrolyzer product stream is reacted with a carbon dioxide-containing stream from the direct air capture step to produce a reverse water gas shift product stream containing carbon monoxide. d. A hydrocarbon synthesis step, wherein at least a portion of the hydrogen from the electrolyzer product stream is reacted with a stream containing at least a portion of the reverse water gas shift product stream in a liquid combustion production reactor to produce a hydrocarbon synthesis product stream; e. An autothermal reforming step, wherein at least a portion of the oxygen produced by electrolysis is reacted with one or more feed streams containing unreacted reactants from the hydrocarbon synthesis step. The direct air capture described herein uses a solid-supported amine adsorbent; and The solid-supported amine adsorbent is regenerated using a feed stream containing hydrogen generated in the electrolyzer; and In the direct air capture step, 20-50% of the carbon dioxide in the air passing through the reactor used for the direct air capture step is removed; and The liquid combustion production reactor is a multi-tube fixed-bed reactor system, with each reactor tube having a diameter between 13 mm and 26 mm, a length greater than 6 meters, and filled with a liquid combustion production catalyst blended with silica or alumina; and The amount of carbon monoxide converted into a heavier product than C24 is less than 10%; and The reverse water-gas shift step utilizes a solid solution catalyst with a transition metal on a metal oxide support. This solid solution catalyst has a unique solid solution phase, namely a bimetallic crystalline phase, which results in the absence of metal phase segregation. The support for the liquid combustion catalyst has a pore diameter greater than 8 nanometers, an average effective particle radius less than 600 micrometers, a crushing strength greater than 3 psi, and a compressive strength greater than 125 m. 2 / g of BET surface area.

2. The process according to claim 1, wherein the electrolyzer is in position 1, and the direct air capture is in position 2, and hydrogen from the electrolyzer is delivered from position 1 to position 2 via a LOHC process.

3. The process according to claim 1, wherein the reactor feedstock for the reverse water-gas conversion is heated to at least 1500℉ using an electric radiant furnace, and the reactor vessel is an adiabatic reactor, wherein the reactor outlet temperature is at least 100℉ lower than the reactor inlet temperature.

4. The process according to claim 1, wherein the reactor feed for the reverse water-gas shift has a composition such that the molar ratio of hydrogen to carbon dioxide is 2.5-4.

0.

5. The process according to claim 1, wherein the hydrocarbon synthesis feedstock has a hydrogen to carbon monoxide molar ratio between 1.90 and 2.20, and the C4-C24 selectivity is greater than 70%, and wherein the amount of carbon monoxide converted into a heavier product than C24 is less than 4%.

6. The process according to claim 1, wherein the self-heating reforming step comprises steam as feed, wherein the ratio of steam to carbon is 0.40-1.

00.

7. The process according to claim 6, wherein the catalyst in the autothermal reforming step comprises a solid solution catalyst.

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