One-step process for producing hydrocarbons from carbon dioxide

Abstract

The present invention is a new and improved process and catalyst that is effective to promote the reaction of carbon dioxide and hydrogen directly to hydrocarbons in a single reactor at a reaction temperature of less than 450 DEG C and more preferably a temperature of 250 DEG C to 325 DEG C. The carbon dioxide used comes from a fixed source or is directly captured from the air. Hydrogen is generated by electrolyzing water using renewable or low-carbon electricity.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 474,544, filed on August 22, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The technical field of the present invention is a process (or "method") for producing hydrocarbons (including sustainable aviation fuel (SAF) or diesel) from CO2 by using a new low-temperature CO2C reaction in a new direct integrated process for producing hydrocarbons. Background Art

[0004] Increased concentrations of carbon dioxide (CO2) in the global atmosphere are associated with changes in the Earth's climate. The combustion of fossil fuels in various engines and heaters produces atmospheric carbon dioxide. Concerns about climate change have led to major societal changes toward renewable or low-carbon electricity. This has also led to increasing activity to decarbonize the economy.

[0005] Electricity can be used to produce synthetic methane, kerosene, methanol or other chemicals, which can be either gas or liquid, also known as power-to-gas (power-to-gas), power-to-chemicals (power-to-chemicals), or more generally power-to-X (PtX, P2X). Electricity produced using solar, wind or other sustainable sources is often called decarbonized electricity. Fuels and chemicals produced using decarbonized electricity result in low, zero or negative emissions of overall CO2. This raw material (feedstock) distinguishes e-fuels from biofuels, which are mainly produced from biomass, and the biomass used often includes food raw materials or raw materials that have a negative impact on the environment (e.g. rapeseed oil, palm oil, etc.).

[0006] The most advanced process is to convert hydrogen and CO2 produced by electrolysis to produce synthesis gas (a mixture of carbon monoxide and hydrogen) and use the synthesis gas to produce fuels and chemicals. The thermodynamic principles of the RWGS reaction require high temperatures of about 800-900°C at the inlet of the RWGS reactor to drive the reaction. Since the synthesis gas formation reaction is highly endothermic (i.e., a large amount of heat needs to be continuously input), the process often requires large electric heaters with high electricity demand. In addition, the subsequent reaction of synthesis gas to fuel (including one or both of hydrocarbons and / or alcohols) is also highly exothermic-the released reaction heat needs to be continuously removed from the reactor system. Therefore, the most advanced technology requires both input heat in the synthesis gas formation step and heat removal in the synthesis gas conversion step. Although the latter partially offsets the former, the net requirement is to input heat to facilitate the integrated process. In addition, it is of great practical significance that the process management of these two thermal effects brings engineering and operational challenges, which has a detrimental impact on both process efficiency and capital cost requirements.

[0007] Various "power-to-X" (PtX) concepts rely on using renewable or low-carbon electricity to produce hydrogen by electrolysis of water. This hydrogen can be used directly as a final energy carrier, or it can also be converted, for example, into methane, syngas, liquid fuels, electricity or chemicals.

[0008] There has been some limited preliminary work investigating the CO2C reaction to C5 + hydrocarbon.

[0009] Most of the work on the one-step conversion of CO2 to liquid hydrocarbon fuels (usually represented by a single reactor) has focused on the development of catalysts that first produce CO from CO2 by hydrogenation and then react with H2 to form liquid hydrocarbons over the same catalyst or catalysts in tandem (in close physical proximity). Ideally, the two reaction sites would be close enough so that the benefits of heat integration can be realized directly, at least in part.

[0010] To date, most research has focused on the use of iron-based catalysts, which are active in the reverse water gas shift reaction and FT chemistry (National Academy of Sciences, 2019).

[0011] Pan et al. (2007) described the use of Rh catalysts supported on carbon nanotubes in a tubular reaction with a reaction time of about 13 hr. -1The problem with this catalyst is that it cannot be scaled up to commercial scale due to the high catalytic reactor pressure drop, very low space velocity and the production of a complex mixture of oxygenated hydrocarbons that requires extensive post-processing to produce specific products that are viable in the commercial market.

[0012] Wang et al. (2019) described an Fe / ZrO2 catalyst for catalytic CO2 hydrogenation, which mainly produces CH4 and C2-C4 paraffins. The selectivity for producing liquid hydrocarbons is very low.

[0013] Landau et al. (2015) described an iron spinel catalyst containing 20% ​​Fe2O3. The particle size of the catalyst varied from 100 μm to 3.0 mm. This catalyst was tested using a H2 / CO2 ratio of 2.0-3.0 / 1.0 and a very low space velocity of about 2.0 hr -1 ; Temperature is 325-350°C; Pressure is 20-40 atmospheres. The maximum conversion of CO2 is 36%. The selectivity of the products is: CO (13%), CH4 (9%), C2-C5 (44%) and C6-C 27 HC (25%). The olefin / paraffin ratio of C6+ hydrocarbons is about 5 / 1. Since the catalyst is used at a very low space velocity (2.0 hr -1 ) and is therefore not commercially viable.

[0014] Wei et al. (2018) described an iron-based catalyst for the one-step conversion of CO2 to isoparaffins. The CO2 conversion efficiency was only 26%, with a lower selectivity of about 17% for CO. Coke (carbon) deposition within the catalyst micropores caused the isoparaffin yield to decrease rapidly over time.

[0015] Williamson et al. (2019) described the performance of a one-step catalyst consisting of iron nanoparticles deposited on carbon nanotubes. The catalyst was calcined in air at 400°C for 1 hour or 570°C for 40 minutes and activated with H2 at 400°C for 3 hours. The catalyst was tested in a laboratory reactor at 370°C and 221 psi using a 3.0 / 1.0 H2 / CO2 mixture. The average conversion of CO2 was 54%, with selectivities of 30% and 70% for CO and hydrocarbons, respectively. The average composition of the hydrocarbon products was 43% CH4, 55% C2-C4, and 2.0% C5+ hydrocarbons (by mass).

[0016] Wang et al. (2021) described a plasma-enabled one-step catalytic process for converting CO2 to hydrocarbons. They found that the process was able to convert CO2 to hydrocarbons with a conversion rate of up to about 70% and a hydrocarbon selectivity of up to about 45% at temperatures around 250°C. However, only C1-C5 hydrocarbons were produced, and the selectivity for methane and C2-C5 was 65-70% and 30-35%, respectively. The large amount of methane produced limits the practical value of this method.

[0017] Shen et al. (2022) synthesized a nickel-cerium solid solution catalyst and found that it could produce CO with high selectivity (>95%) at 300 °C. However, only 10% of CO2 was converted to CO, and this conversion rate decreased over a period of about 100 hours.

[0018] Yao et al. (2020) synthesized an Fe-Mn-K catalyst for direct conversion of CO2 and H2 mixtures to C5+ hydrocarbons. The catalyst was used for the direct conversion of CO2 and H2 mixtures to C5+ hydrocarbons at a 3 / 1 H2 / CO ratio, 300°C, 150 psi, and 2,400 hr -1 The catalyst was tested at a space velocity of 1.5 %. During the 75-hour test period, CO2 conversion dropped from 37% to 34%, indicating that the catalyst was deactivating. The yield of C5+ hydrocarbons was about 22%.

[0019] The object of the present invention is to utilize new and improved processes and catalysts which are capable of promoting the direct conversion of CO2 (CO2C) to hydrocarbons at temperatures below 450°C, more preferably at temperatures between 250°C and 325°C. Summary of the invention

[0020] The present invention is an improved process for producing low carbon fuels and chemicals using a new improved catalyst capable of performing CO2C reactions at temperatures between 250°C and 325°C.

[0021] In one embodiment, a process for producing hydrocarbons is provided. The process comprises: mixing a first feed stream comprising CO2 with a second feed stream comprising renewable H2 to produce a CO2 reactor feed stream; and feeding the CO2 reactor feed stream to a CO2 conversion reactor, wherein the CO2 conversion reactor comprises two catalysts, thereby producing a CO2 reactor comprising CO2. 5 + Reactor product stream of hydrocarbons, H2O, and unreacted H2, CO and CO2.

[0022] In another embodiment, a process for producing hydrocarbons is provided. The process comprises: mixing a first feed stream comprising CO2 with a second feed stream comprising renewable H2 to produce a CO2 reactor feed stream; and feeding the CO2 reactor feed stream to a CO2 conversion reactor, wherein the CO2 conversion reactor is a multi-tubular fixed bed reactor, and wherein the CO2 conversion reactor comprises two catalysts, one of which comprises Fe3O4 impregnated with copper, thereby producing a CO2 reactor comprising CO2. 5+ Reactor product stream of hydrocarbons, H2O, and unreacted H2, CO and CO2. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A process for converting CO2 and hydrogen into hydrocarbons using a CO2C reactor is shown, wherein the various components are: stream 1 - low-carbon electricity; stream 2 - water; stream 3 - H2; stream 4 - O2; stream 5 - CO2; stream 6 - CO2C reactor feed; stream 7 - CO2C product; stream 8 - a portion of the CO2C product; stream 9 - hydrocarbons; stream 10 - water; stream 11 - CO2 and other cycles to unit 2; unit 1 - electrolyzer; unit 2 - CO2C reactor; unit 3 - product processing unit.

[0024] Figure 2 The CO2C process described in Example 2 is shown, wherein the components are: unit 200 - CO2C reactor; unit 201 - water eliminator; unit 202 - amine contactor; unit 203 - amine regenerator; unit 401 - syngas methanation reactor system; unit 402 - methanation reactor product separator; stream 301 - feed to CO2C Rx; 302 - reactor effluent; 303 - water; 304 - methane, H2, CO2; 305 - methane H2 feed to 401; 306 - CO2; 307 - methanation reactor effluent; 308 - methane; 309 - CO2; 310 - water produced by methanation; 311 - CO2 / amine solution; 312 - amine entering contactor; 313 - medium pressure stream. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hydrocarbons are organic compounds that consist only of carbon and hydrogen. Hydrogen atoms are attached to carbon atoms in many different configurations. Hydrocarbons are divided into aliphatic hydrocarbons and aromatic hydrocarbons. Aliphatic hydrocarbons are divided into alkanes, alkenes and alkynes. Aromatic hydrocarbons are divided into arenes that contain benzene rings as structural units and non-benzene aromatic hydrocarbons that do not have benzene rings as structural units.

[0027] C1-C5 hydrocarbons refer to hydrocarbons containing 1 to 5 carbon atoms.

[0028] C2-C5 hydrocarbons refer to hydrocarbons containing 2 to 5 carbon atoms.

[0029] C 5+ Hydrocarbons refer to hydrocarbons containing 5 or more carbon atoms.

[0030] Renewable electricity refers to energy sources that are not fossil carbon-based and can include solar, wind, biomass, geothermal, landfill gas, wave, tidal and ocean thermal technologies. While nuclear power itself is a renewable energy source, the materials used in nuclear power plants are not, unless the spent nuclear fuel is recyclable. Currently, about 96% of spent nuclear fuel in reactors is recycled.

[0031] Low-carbon electricity is electricity that is generated with significantly lower greenhouse gas emissions than traditional fossil fuel-generated electricity.

[0032] Precious metals refer to rare, naturally occurring metallic chemical elements with high economic value. Precious metals include gold, silver, platinum, palladium, ruthenium, rhodium, osmium and iridium.

[0033] Natural magnetite refers to a naturally occurring iron oxide mineral. It is composed primarily of Fe3O4 and small amounts of precious metals. It is the most magnetic of all naturally occurring minerals on Earth - it is a natural magnet. Magnetite-rich "black sands" are commonly found in gold mining operations. Precious metals are usually found in magnetic concentrates as discrete mineral particles, inclusions in magnetite, and diffuse atoms in the magnetite lattice. Precious metal content can vary from a few ppm to 1500 ppm, depending on the mineral source.

[0034] Synthetic magnetite is impregnated with up to 1,500 ppm of various precious metals in synthetic Fe3O4 and then calcined to about 2,100°F. Figure 1 An integrated process for producing hydrocarbons is shown. Feed stream 1 is low-carbon electricity. Low-carbon electricity includes, but is not limited to, wind power, solar power, nuclear power, biomass power or renewable natural gas power, and hydroelectric power. Feed stream 2 is water. These two feed streams are used in unit 1 (i.e., electrolyzer). In the electrolyzer, water and low-carbon energy are used to produce hydrogen and oxygen. Hydrogen is produced by electrolysis of water.

[0035]

[0036] An electrolyzer consists of an anode and a cathode separated by an electrolyte. Different electrolyzers function slightly differently. Different electrolyzer designs using different electrolysis technologies include alkaline electrolysis, polymer electrolyte membrane (PEM) electrolysis, solid oxide electrolysis, high temperature electrolysis, and other emerging electrolysis types.

[0037] The product from the electrolyser is a stream comprising hydrogen ( Figure 13) and a stream comprising oxygen ( Figure 1 4). The electrolyzer produces green hydrogen because it uses a renewable or low-carbon energy source. Other forms of hydrogen production using renewable or non-renewable energy sources may also be used, including methane pyrolysis, steam reforming of hydrocarbons with or without carbon capture, biomass gasification, reforming of renewable natural gas (RNG), or obtaining hydrogen from geological sources; in each of these alternatives, it may be necessary to purify the stream to produce hydrogen for use in the process.

[0038] exist Figure 1 In the embodiment of the present invention, stream 5 is a stream containing CO2. CO2 has a variety of sources. Power plants that generate electricity using various carbonaceous resources will produce a large amount of CO2. Industrial manufacturing plants that produce ammonia for fertilizers will produce a large amount of CO2. Ethanol plants that convert corn or wheat into ethanol produce a large amount of CO2 through fermentation. Other industrial fermentation processes also produce a large amount of CO2. Urban sewage treatment systems use aerobic and anaerobic digestion of sludge to produce a large amount of CO2. As described herein, the utilization or conversion of CO2 generally involves separating and purifying CO2 from a gaseous stream, in which CO2 is not the only component and is usually not the main component (such as waste gas). Typically, alkylamines are used to remove CO2 from gaseous streams. The alkylamines used in the process include monoethanolamine, diethanolamine, methyldiethanolamine, diisopropylamine (disopropylamine), aminoethoxyethanol or a combination thereof. Metal organic framework (MOF) materials are also used as a means of separating CO2 from dilute streams, which capture CO2 from the stream using chemical adsorption or physical adsorption. Other methods of obtaining concentrated CO2 include chemical looping combustion, in which circulating metal oxide materials capture the CO2 produced during the combustion process. CO2 can also be captured from the atmosphere in what is known as direct air capture (DAC). The process of capturing CO2 usually involves regeneration of the capture material. Alkylamines are usually regenerated by heating with low-pressure steam.

[0039] The captured CO2 that can be converted into useful products such as fuels (such as synthetic natural gas, diesel, gasoline blends, jet fuel, etc.) and chemicals (such as solvents, olefins, alcohols, aromatic compounds, polymers (for textiles, packaging, structural materials, etc.), and others) replaces fuels and chemicals produced from fossil sources (such as oil and natural gas), thereby reducing the overall net emissions of CO2 to the atmosphere. This is what is meant by low-carbon, ultra-low-carbon, zero-carbon, or negative-carbon fuels and chemicals.

[0040] CO2 streams from industrial or biological processes or CO2 streams captured from the atmosphere or CO2 streams available from commercial CO2 pipelines are generally not pure carbon dioxide. These CO2 streams obtained from industrial facilities or pipelines may include sulfur compounds (by weight, ranging from zero to 2000ppm) and contain hydrocarbons (ranging from zero to 10 volume %). In order to avoid problems in downstream processing, it is necessary to purify CO2, including removing sulfur compounds and hydrocarbons. According to the present invention, purified CO2 is suitable for producing low-carbon or zero-carbon fuels and chemicals.

[0041] At least a portion of the stream 3 containing hydrogen is mixed with the stream 5 containing CO2 to produce stream 6 or the CO2C reactor feed stream. The ratio of H2 / CO2 is 2 to 6, or preferably 3 to 4. The CO2 and hydrogen in stream 6 react in the CO2C reactor to form products such as Figure 1 The CO2C reactor is operated at a temperature of 250 to 425°C, more preferably at a temperature of 275 to 350°C, and more preferably at about 300°C. The main reactions that may occur in the CO2C reactor are as follows:

[0042] CO2+H2=CO+H2O (ΔH 298 = +42.1 kJ / mole) Eq.1

[0043] CO+3H2=CH4+H2O (ΔH 298 =-206.1 kJ / mole)Eq.2

[0044] nCO+(2n+1)H2→C n H (2n+2) +nH2O (ΔH 298 =-165 kJ / (mol CO))Eq.3

[0045] The first reaction (i.e., Eq. 1) is the reverse water gas shift reaction. At standard temperature, this reaction is endothermic and requires much higher temperatures than the preferred CO2C reactor temperature in other processes. The second reaction (i.e., Eq. 2) is the methanation reaction of CO and hydrogen to form methane and water. As can be seen from the highly negative reaction enthalpy, the methanation reaction is very exothermic. The third reaction (i.e., Eq. 3) is the ideal Fischer-Tropsch synthesis (FT) reaction. The FT reaction is also very exothermic.

[0046] Catalysts are used in CO2C reactors to promote chemical reactions. A variety of catalysts can be used in CO2C reactors. Catalysts include a variety of components with different functions. Catalysts can be monofunctional, bifunctional, or multifunctional formulations containing many different elements, including nickel, magnesium, aluminum, iron, copper, cobalt, indium, sodium, silicon, manganese, zinc, chromium, rhodium, carbon, cerium, titanium, and zirconium. Specifically, catalysts include unsupported Ni2Mg unsupported solid solution catalysts, Mg / Mg-aluminate catalysts, rhodium on gamma alumina, CuFeO2, Fe-Co / K / Al2O3, In2O3 / HZSM-5, Na-Fe3O4 / HZSM-5, FeNa, Na-Fe2O4 / HMCM-22, Fe2O3, Co6 / MnO4, Zn-Cr / Hy, Fe-Zn-Zr / HZSM-5, Fe-Mn-K, and other catalysts, see the review articles by Tan et al. (2022) or Yao et al. (2020) for details.

[0047] The products from the CO2C reactor are as follows Figure 1 At least a portion of the material stream 7 becomes material stream 8 and is fed to the product processing unit, that is, Figure 1 Unit 3 in the product treatment unit. The product treatment unit can be a combination of various processes that allow separation or additional treatment of the CO2C reactor product stream. Different implementations are possible depending on the products, yields, and selectivities observed in the CO2C reactor. Each reaction that occurs in the CO2C reactor produces water. Therefore, the first step in the product treatment unit is to reduce the temperature of the reactor product stream. This can be achieved by many different means, including heat exchange with a cooler feed stream, heat exchange with another cooler stream, and the use of a cooling water heat exchanger. The purpose of cooling is to reduce the C that may be produced in the CO2C. 5+ Hydrocarbons and / or water condense. As is known to all, C 5+ Hydrocarbons are generally insoluble in water. After the effluent stream has been cooled, a three-phase separator or a continuous two-phase separator can be used. This allows water and C to be separated from the reactor effluent. 5+ .

[0048] In one embodiment, the CO2 conversion in the CO2C reactor is less than about 90%, and the CO2 conversion in the CO2C reactor is less than about 90%. 5+After the hydrocarbons, the unreacted CO2 is removed before further processing. Removing CO2 from the feed stream can be achieved by any number of available technologies. Removal methods include the use of physical solvents. Physical solvents include the Solexol process that uses polyethylene glycol dimethyl ether to capture carbon dioxide from a gas stream and the refrigerated methanol used in the Rectisol process. Other means include the use of membranes that selectively remove carbon dioxide. Another means of removing carbon dioxide is to use an aqueous solution of an alkylamine (amine for short) to chemically capture CO2. The amine contactor captures CO2 in the solution. The top of the amine contactor is a gas without CO2, and the amine solution containing CO2 is heated in an amine regenerator to release CO2, and the amine aqueous solution is recycled back to the contactor. Various amines can be used, such as diethanolamine (DEA), monoethanolamine (MEA), methyldiethanolamine (MDEA) and diisoamylamine (DIPA).

[0049] The CO2 stream recovered from the CO2 capture unit is Figure 1 As shown in the material flow 11. Figure 1 As shown in stream 5 in , this stream is compressed and recovered and mixed with the CO2 feed stream.

[0050] In one embodiment, the CO2C hydrocarbon product stream includes normal alkanes with carbon numbers from 6 to 23, and the product stream is fed to a CO2C separation unit, in which at least three product fractions are produced. CO2C separation is any separation process, such as absorption, adsorption, filtration or distillation, or a combination of these processes. Distillation is a preferred separation process. Light CO2C separation products include normal alkanes with carbon numbers between 5 and 9. Medium CO2C separation products include normal alkanes with carbon numbers between 9 and 15.

[0051] The heavy CO2C separation product contains normal alkanes with carbon numbers between 16 and 23. The hydrocarbons produced in the CO2C reactor are Figure 1 It is represented (collectively) as material stream 9.

[0052] In one embodiment of the present invention, the CO2C reactor is composed of a mixture of two different catalysts and can produce hydrocarbons from a mixture of CO2 and H2.

[0053] The first catalyst (i.e., Catalyst #1) is a CO2 hydrogenation catalyst that is heated at 300°C, a H2 / CO2 feed ratio of about 3.0-3.5 / 1.0, a pressure of 250-350 psig, and 2,000-3,000 hr. -1 At a space velocity of 1.5 Å, the CO2 conversion efficiency is about 25%, with a high selectivity for CO (>90%). This is an endothermic catalyst (ΔH 298 =~+40kJ / mole), heat input is required.

[0054] The second catalyst (i.e., Catalyst #2) can be any FT catalyst capable of producing hydrocarbons at a temperature of 300°C. It is well known that iron-based catalysts are active for FT at this temperature. One particularly useful catalyst is a magnetite-based catalyst, which operates in the same temperature range as Catalyst #1 (300°C). This is an exothermic catalyst (ΔH 298 =~-200 kJ / (mol CO)), hydrocarbons can be produced from CO and H2 formed from catalyst #1. This catalyst operates at a feed ratio of about 1.5-2.0 / 1.0, a pressure of 250-350 psi and 2,000-3,000 hr -1 Work at space speed.

[0055] The mixing ratio and physical proximity of the first and second catalysts are such that the exothermic heat of catalyst #2 is directly transferred to the adjacent endothermic catalyst #1. It is estimated that the ratio of catalyst #1 to catalyst #2 should be 4-5:1 to keep the catalyst bed isothermal and provide enough CO from catalyst #1 for catalyst #2. The catalytic reactor is maintained at a bed temperature of 300°C under adiabatic conditions by using sufficient insulation and heat.

[0056] Catalyst #1 can be any suitable CO2 hydrogenation catalyst. TiO2 is preferred as the matrix for Catalyst #1 because titanium oxide has the highest surface acidity among all catalyst matrices. Zirconia also has a high surface acidity, but lower than titanium oxide.

[0057] Impregnation of certain metals (e.g., Cu on TiO2) on the support of Catalyst #1 will increase the reaction rate. -1 With a space velocity of 1.3 and at 300°C, the CO2 conversion should be about 25%, with high selectivity to CO and minimal CH4 formation.

[0058] Since catalyst #1 produces CO very quickly, an efficient oligomerization (chain propagation) catalyst (catalyst #2) needs to be mixed with or placed in series (close to) the hydrogenation catalyst (catalyst #1). In addition, the chain propagation catalyst needs to work efficiently at 300°C.

[0059] In one embodiment, Catalyst #2 uses magnetite or an iron-based catalyst. Natural magnetite contains about 50 to 1,500 ppm of precious metals, depending on the source, and can be used as a catalyst. In another embodiment, a synthetic magnetite or iron catalyst is used, and the desired promoter, which may include precious metals, is added to the catalyst. The precious metals in the magnetite significantly increase the ability to generate H* radicals from H2, which reduces the probability of free radical chain propagation, thereby reducing the formation of higher molecular weight hydrocarbons.

[0060] In one embodiment of the present invention, the CO2C reactor is a multi-tubular fixed bed reactor. The inner reactor tube is filled with a mixture of steam and water. The heat of reaction is taken away by generating steam in the reactor shell. The inner diameter of the tube is between 18 and 50 mm. The tube is filled with catalyst particles. The catalyst particle size is optimized to achieve the best balance between conversion rate and pressure drop across the reactor. The diameter of the reactor tube is very small, which means that when the feed gas reacts on the catalyst, heat must be transferred to the heat transfer surface from a range of no more than 9 to 25 mm (half the diameter of the tube). Outside the tube, the mixture of steam and water is mainly heat transferred by the nucleation process of liquid water vaporization into steam. Water comes from the steam drum. Boiler feed water (BFW) is fed to the steam drum and circulated in the system. The pressure of the steam system determines the temperature of the steam / water mixture. The pressure range of steam is 200 to 1600 psig. At 1200 psig (82.7 barg), the temperature of saturated steam is 298°C. At 1100 psig (75.8 barg), the temperature of saturated steam is 292°C. At 1000 psig (69.0 barg), the temperature of saturated steam is 285°C. Therefore, saturated steam at 1000 to 1200 psig is an ideal cooling fluid for the CO2C reaction at a temperature of 300°C. Typically, water is fed from a steam drum to the water inlet of the reactor shell, and a mixture of about 50% steam and 50% water is returned to the steam drum at the steam outlet of the reactor shell.

[0061] In one embodiment, heat transfer is accomplished by a hot oil system. Oil as a working fluid is pumped to the reactor shell. Heat is transferred from the tubes to the oil, increasing the temperature of the oil. The circulation rate of the oil is controlled by the pumping rate that sets the heat removal rate. The hot oil leaving the reactor shell is cooled in an external heat exchanger. Cooling water, chilled water, propylene glycol or other suitable materials can be used in the cold end of the external heat exchanger to reduce the temperature of the hot oil to the desired reactor shell inlet temperature. The cooled hot oil is then pumped back to the reactor shell. There are several suitable oil operating temperatures suitable for this service, including Therminol XP, Therminol 55, Therminol SP, Therminol 59 or any equivalent or similar oil working fluid.

[0062] In one embodiment, the catalyst in the CO2C reactor can be diluted with other inactive solids. The dilution of the catalyst helps the transfer of heat, thereby reducing the heat release rate per unit volume and reducing local temperature rise. Suitable diluents include alumina, silicon carbide, spinel or other refractory materials. An advantage of silicon carbide is that it has a high thermal conductivity and can therefore transfer heat from the exothermic generation at a higher rate. Nevertheless, any catalytically inactive material can be used as a diluent.

[0063] In one embodiment, metal baffles may be placed inside the CO2C reactor tubes prior to adding the catalyst so that there are metal channels or connections from the center of the tube to the tube wall. This helps with heat transfer because the high thermal conductivity of metal increases the rate of heat transfer from the hot center of the tube to the cool tube wall.

[0064] In one embodiment of the present invention, the feed gas to the CO2C reactor can be diluted with a non-reactive gas. Feed gas dilution helps heat transfer and temperature control in many ways. It can reduce the heat of reaction generated per unit volume per unit time. It can also add additional mass flow rate and act as a heat sink. Various dilution gases can be used. The ideal dilution gas can be easily separated from the reactor effluent. Low pressure steam can be used as the dilution gas fed to the CO2C reactor. When the reactor effluent is cooled, the condensed steam can be easily separated from the effluent by a knockout vessel or separator, and since steam is a reaction product, the design change can be achieved by simply increasing the size of the separator.

[0065] In one embodiment, the CO2C reactor is a series of adiabatic reactors or reaction beds. The length or residence time of each reactor bed is set so that the maximum conversion that can occur keeps the bed temperature rise at a preset temperature rise of no more than 50°C, preferably less than 25°C, and more preferably less than 10°C. Catalyst and feed gas dilution can also be used to control the temperature rise within a preset range. At the outlet of the reactor bed, the effluent gas is cooled in a heat exchanger that produces high-pressure saturated steam in the range of 1000 to 1200psig. This cools the reactor effluent to a temperature close to the previous bed inlet temperature. The cooled effluent is fed to the next bed. The total number of beds is selected to obtain the desired CO2 total conversion. Optionally, additional hydrogen or hydrogen and CO2 can be added to the feed gas of the subsequent bed.

[0066] In one embodiment, heat transfer and thermal management in the reactor are controlled by continuous injection of H2. The initial H2 / CO2 ratio is lower than the stoichiometric ratio for the net reaction. This results in low CO2 conversion and low temperature rise in the reactor bed. H2 is added at the end of the bed at a temperature much lower than the reactor bed temperature. The cold H2 reduces the overall gas temperature to a temperature similar to the inlet temperature of the previous bed. The additional hydrogen reacts with the CO2 in the previous bed in the subsequent bed. In essence, the conversion is spread (extended) over a longer effective bed depth (or number of beds), thereby reducing the heat generated per reactor area or volume, making heat removal more manageable. The number of reactor beds and the amount of cold hydrogen added determine the overall CO2 conversion.

[0067] In one embodiment, the CO2C reactor is operated at a lower CO2 conversion rate, but the overall gas recovery rate is higher. In this way, the temperature in the reactor bed can be controlled and the temperature rise can be controlled within an acceptable range. The space velocity or residence time in the reactor bed is higher, so the conversion rate is lower. Gas dilution and catalyst dilution can be used to help control the temperature. The CO2 conversion rate per pass is maintained at less than 30%, preferably less than 20%, and more preferably less than 10%. The reactor effluent is fed to a product treatment unit, in which the water in the effluent is removed by cooling and separation, and unreacted CO2 and H2 are removed, compressed and recovered, and mixed with the fresh feed of the CO2C reactor.

[0068] Example 1

[0069] In this implemented example, two different catalysts were mixed in a CO2C reactor. Catalyst #1 was a modified high surface copper aluminate (CuAl2O4) spinel impregnated with 0.05-5.0 wt% copper, pelletized and calcined. Catalyst #2 was a natural magnetite-based catalyst that was pressed into pellets and calcined. The catalysts were placed in close proximity to each other in the reactor. Catalyst #1 worked endothermically (required heat), while Catalyst #2 worked exothermically (generated heat).

[0070] These catalysts are mixed in specific proportions to allow them to work isothermally throughout the catalytic reactor. H2 produced by electrolysis of water using renewable or low-carbon electricity is mixed with the captured CO2.

[0071] Since the catalyst in the catalytic reactor operates under isothermal or nearly isothermal conditions, the design of the CO2C reactor can be selected from a variety of existing isothermal reactors, including multi-tubular fixed bed reactors.

[0072] H2 and CO2 are heated to a desired temperature of about 315°C, respectively, and mixed in a specific ratio before being introduced into a catalytic reactor.

[0073] The production and composition details of Catalyst #1 and Catalyst #2 are as follows.

[0074] Catalyst #1 is a copper aluminate (CuAl2O4) spinel formed by mixing a mixture of a copper salt and a high surface area gamma-alumina powder to which sufficient additional copper is added such that the resulting catalyst is a copper aluminate spinel with 0.05-5.0 wt% copper distributed on the spinel. The copper salt may include copper acetate, copper nitrate or other water soluble copper salts. The mixture is then formed into tablets under high pressure. The tablets are calcined at a temperature of about 950°C to form the CuAl2O4 spinel. The resulting CuAl2O4 catalyst has a BET surface area of ​​greater than 10 m 2 / g, preferably with a specific surface area greater than 25 m 2 / g, and more preferably, the specific surface area is greater than 50 m 2 / g.

[0075] Another method of producing the catalyst is to dissolve copper acetate in water and then add sufficient solution to the copper aluminate spinel to produce 0.05-10.0 wt% copper impregnated on the copper aluminate spinel (CuAl2O4).

[0076] The Cu-CuAl2O4 catalyst was tested at 300°C, a CO2 / H2 molar feed ratio of 3.5 / 1.0, and 3,000 hr -1 The CO2 / H2 mixture was converted at a space velocity of 100 psi and a pressure of 300 psi, with a CO2 conversion of about 25% and a selectivity to CO greater than 90% (Table 3).

[0077] Table 3 - Effect of space velocity on CO2 conversion to CO for catalyst #1 at 300°C

[0078]

[0079] Catalyst #2 is a magnetite catalyst based on naturally occurring magnetite found in parts of North America. This naturally occurring magnetite, which contains small amounts of precious metals, is typically a byproduct of gold mining. The magnetite is formed into tablets under high pressure. The tablets are then calcined at a temperature of about 950°C. In this example, the composition of the magnetite is Fe3O4 (94.4%), Al2O3 (3.2%), TiO2 (1.8%), CuO (0.22%), MnO (0.17%), MgO (0.10%), and about 850 ppm of precious metals. In another embodiment, the catalyst is generally synthesized to achieve the desired composition. The abundance of the precious metals is, in order, Au, Ag, Pt, and Pd. These precious metals are widely dispersed throughout the Fe3O4 matrix in the form of 100-250 angstrom clusters, and they are primarily distributed on the surface of the magnetite crystals. The surface area of ​​the magnetite catalyst is 3-4 m 2 / g, pore size is 10-100 angstroms (1-10 nanometers). In a catalytic reactor, the magnetite catalyst is reduced with H2 at 300°C.

[0080] Table 4 summarizes the effect of temperature on the performance of magnetite catalyst (catalyst #2) in oligomerization reactions (e.g., Fischer-Tropsch reactions). At 300°C, the yield of C5+ hydrocarbons was approximately 39%, and the remaining carbon-containing products (CH4, CO2, C2-C5 hydrocarbons, and C 24+ Hydrocarbons) account for the remaining 61%. When this exothermic catalyst is coupled with an endothermic catalyst (Catalyst #1) at a shorter length scale, the result is the direct conversion of CO2 and hydrogen to hydrocarbons. In this example, the hydrogen is produced by electrolysis of water. In addition, the electrolyzer also produces oxygen.

[0081] Catalyst #1 catalyzes an endothermic reaction (about +50 kJ / mole) that requires heating; Catalyst #2 catalyzes an exothermic reaction (about -175 kJ / mole) that generates heat. Catalyst #1 and Catalyst #2 are mixed in appropriate proportions so that the heat generated by Catalyst #2 is used to heat Catalyst #1. Therefore, the masses of the first and second catalysts are adjusted so that the catalytic reactor operates isothermally at a temperature of about 300°C. According to the principles of thermodynamics, the mass ratio of Catalyst #1 / Catalyst #2 is 3.0-5.0 / 1.0, so that the heat in the catalytic reactor is close to equilibrium.

[0082] Although the conversion efficiency of catalyst #1 from CO2 to CO is only 25%, since the amount of catalyst #1 is 3-5 times that of catalyst #2, more CO is produced than catalyst #2 can utilize.

[0083] While catalyst #2 produces CO2, the first catalyst converts CO2 into additional CO. Therefore, for three passes, the product composition from both catalysts in the catalytic reactor averages 20% CH4, 24% C2-C5, and 56% C6-C 24 In addition, the exhaust gas also contains some CO2, CO and H2.

[0084] In this example, the CO2C reactor effluent is cooled. Water is removed by a water eliminator. 5+ The hydrocarbons are condensed and separated. 5+ After the hydrocarbons are converted to CO2, the remaining CO2 and C1-C5 (44% in total) in the tail gas are sent to an oxyfuel combustor for recycling, where the hydrocarbons and any remaining hydrogen and other combustibles are converted to additional CO2 using the oxygen produced in the electrolysis unit. The CO2 is then used as a circulating feed to the catalytic CO2C reactor. Thus, after about 3 cycles, more than about 90% of the CO2 carbon is converted to C 5+ The resulting product is a hydrocarbon mixture. Depending on the operating conditions of the reactor, up to 30% of the liquid product is composed of C3-C 11 α-olefins and hydroxyalkanes (alcohols). The remaining liquid products consist of C5-C 24 It is composed of ordinary alkanes and a small amount of isoalkanes.

[0085] The CH4, C2-C5, CO and H2 in the tail gas can be used as energy for the process or can be converted using oxyfuel combustion to produce additional CO2 and CO.

[0086] The working principle of the oxygen-fuel burner used in this embodiment is as follows. CO2 is mixed with oxygen as the oxidant of the burner. The fuel of the burner is the CO2C effluent, which contains CO2, H2 and the C1-C5 fractions produced by the CO2C reactor. The combustion products are water and CO2. The combustion products are cooled and the water is removed. CO2 is recycled and blended with oxygen to generate an oxidant stream for the burner. Alternatively, CO2 can also be blended with the feed of the CO2C reactor.

[0087] Table 4 - Effect of Temperature on Catalyst Performance of Natural Magnetite Containing 0.22 wt. % CuO (H2 / CO = 2.0 / 1.0; P = 391 psi; SV = 3,200 hr -1 )

[0088]

[0089] Example 2

[0090] In this implemented example, two catalysts were used in the CO2C reactor. Catalyst #1 consisted of copper (e.g., Cu-TiO2) impregnated on a high surface area titanium oxide (TiO2) matrix, rather than copper aluminate. Catalyst #2 was the same as previously described in Example 1.

[0091] Catalyst #1 was prepared by wet impregnation. A copper salt was suspended in a solvent. A high surface TiO2 matrix was added to the solution. The solvent was removed by evaporation, resulting in the deposition of copper on the support. The mixture was then formed into tablets under high pressure. These tablets were calcined at a temperature of about 950°C to form the Cu-TiO2 catalyst. The resulting Cu-TiO2 catalyst had a BET surface area of ​​greater than 10 m 2 / g, preferably with a surface area greater than 25m 2 / g, preferably with a surface area greater than 50m 2 / g.

[0092] Another method of producing the catalyst is to dissolve copper acetate in water and then add enough of the solution to the copper Cu-TiO2 to produce 0.05-10.0 wt% copper impregnated on the Cu-TiO2 material.

[0093] The operation of the CO2C reactor was as described in Example 1, and as a result, more than about 90% of the CO2 carbon was converted to C after recovery. 5+ The resulting product is a hydrocarbon mixture. Depending on the operating conditions of the reactor, up to 30% of the liquid product is composed of C3-C 11 α-olefins and hydroxyalkanes (alcohols). The remaining liquid products consist of C5-C 24 It is composed of ordinary alkanes and a small amount of isoalkanes.

[0094] The CH4, C2-C5, CO and H2 in the tail gas can be used as energy for the process or can be converted using oxyfuel combustion to produce additional CO2 and CO.

[0095] Example 3

[0096] In this embodiment implemented, the catalyst in the CO2C reactor uses Fe3O4 (magnetite) catalyst impregnated with 0.1-10.0 wt% copper. The reactor is a multi-tubular fixed bed reactor, using hot oil to help maintain a constant catalyst temperature. The H2 / CO2 in the feed of the CO2C reactor is 3.0-4.0, the pressure is 250-350psi, and the reactor is operated at 300°C. The CO2 conversion rate is 38%, the CH4 selectivity is 10.4%, the C2-C5 selectivity is 27.7%, and the C5+ selectivity is 61.9%. The CO2C reactor effluent includes a mixture of hydrogen, CO, CO2, C1-C5 hydrocarbons and C5+ hydrocarbons. In the downstream of the CO2C reactor, most of the C5+ hydrocarbons are condensed into liquids by cooling water exchangers and elimination vessels, and are sent to product storage devices. The remaining H2, CO, CO2, C1-C2 streams are sent to a CO2 removal unit (typically an amine unit), where CO2 is removed. The CO2-rich stream is compressed and recycled to the inlet of the CO2C reactor. Additional hydrogen is fed to the reactor to maintain the H2 / CO ratio in the feed between 3.0 and 4.0. In addition, an additional CO, H2 and C1-C5 stream is separated and used as plant fuel gas, or converted into additional CO2 and CO, or sold as a fuel product.

[0097] References:

[0098] Landau et al. AU 2015203898 B2 (2015).

[0099] National Academy of Sciences, Chemical Utilization ofCO2 into Chemicals and Fuels, Gaseous Carbon Waste Streams Utilization: Status and Research Needs, National Academies Press, Washington DC (2019).

[0100] Enhanced Ethanol Production Inside Carbon Nanotube ReactorsContaining Catalytic Particles by Pan et al., Nature Materials, Volume 6 (2007).

[0101] Identifying the Roles of Ce by Shen et al. 3+-OH and Ce-H in the Reverse Water-Gas Shift Reaction Over Highly Active Ni-doped CeO2 Catalyst, Xi'an Key Laboratory of Functional Organic Porous Materials, School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Shaanxi 710129, China (2022).

[0102] Current Developments in Catalytic Methanation of CarbonDioxide–A Review by Tan, et al., Frontiers in Energy Research (2022).

[0103] Wang et al.’s High Performance M a ZrO x (M a =Cd,Ga)Solid-Solution

[0104] Catalysts for CO2 Hydrogenation to Methanol, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, State Key Laboratory of Catalysis (2019).

[0105] One-Step Plasma-Enabled Catalytic Carbon DioxideHydrogenation to Higher Hydrocarbons: Significance of Catalyst-BedConfiguration, Green Chemistry (2021) by Wang et al.

[0106] Wei et al., Catalytic Hydrogenation of CO2 to Isoparaffins over Fe-Based Multifunctional Catalysts, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, National Laboratory for Clean Energy (2018).

[0107] N-Doped Fe@CNT for Combined RWGS / FT CO2Hydrogenation by Williamson et al., ACS Sustainable Chemical Engineering (2019).

[0108] Yao et al., Transforming Carbon Dioxide into Jet Fuel Using an Organic Combustion-Synthesized Fe-Mn-K Catalyst, Nature Communications, 11, 6395 (2020).

Claims

1. A process for producing hydrocarbons, comprising: a. mixing a first feed stream comprising CO2 with a second feed stream comprising renewable H2 to produce a CO2 reactor feed stream; b. feeding the CO2 reactor feed stream to a CO2 conversion reactor, wherein the CO2 conversion reactor comprises two catalysts, thereby producing a CO2 reactor comprising C 5+ Reactor product stream of hydrocarbons, H2O, and unreacted H2, CO and CO2.

2. The process of claim 1, wherein the reactor product stream is subjected to a separation step to produce a purified product stream comprising a liquid product and a vapor product, wherein the liquid product comprises C 5+ hydrocarbons, and the gaseous products contain C 1 -C 5 Hydrocarbons, CO2, H2O, CO and H2.

3. The process of claim 1, wherein the H2 in the second feed stream is produced by electrolysis of H2O using renewable or low-carbon electricity.

4. The process of claim 1, wherein the CO2 in the first feed stream is captured from a stationary source or ambient air.

5. The process of claim 1, wherein the CO2 conversion reactor is an isothermal catalytic reactor that is insulated to prevent heat loss.

6. The process of claim 5, wherein the first feed stream and the second feed stream are heated to 310°C to 320°C, respectively, and then mixed at a volume / volume ratio of 3.0 to 5.0 before being input into the CO2 conversion reactor.

7. The process of claim 5, wherein one catalyst in the CO2 conversion reactor is an endothermic catalyst, wherein the endothermic catalyst comprises 0.05-10 wt. % copper impregnated on copper aluminate spinel or titanium oxide, and wherein the surface area of ​​the catalyst is greater than 10 m 2 / g.

8. The process of claim 5, wherein one catalyst in the CO2 conversion reactor is an exothermic catalyst, wherein the exothermic catalyst comprises magnetite, and wherein the magnetite comprises 94 wt% to 99.9 wt% Fe3O4 and 50 ppm to 500 ppm of precious metals.

9. The process of claim 5, wherein one catalyst in the CO2 conversion reactor is an exothermic catalyst, and wherein the exothermic catalyst comprises 99 wt% to 99.9 wt% Fe3O4, and wherein the catalyst is impregnated with 1 ppm to 2,000 ppm of gold.

10. The process of claim 5, wherein the CO2 conversion reactor has a first catalyst and a second catalyst, and wherein the first catalyst is an endothermic catalyst and the second catalyst is an exothermic catalyst, and wherein the exothermic catalyst generates heat when reacting with the CO2 reactor feed stream, and wherein the heat generated by the exothermic catalyst is used to heat the endothermic catalyst, and wherein the step of producing a product stream using the endothermic catalyst and the exothermic catalyst is isothermal.

11. The process of claim 2, wherein the reactor product stream is fed to a product processing unit that separates the liquid product from the vapor phase product.

12. A process as claimed in claim 11, wherein the gas phase product is recycled back to the isothermal catalytic reactor to produce additional C 5+ Hydrocarbon products.

13. The process of claim 11, wherein the H2 in the second feed stream is produced by electrolysis of H2O using renewable or low carbon electricity, and wherein the gas phase product is mixed with oxygen produced by the electrolysis to provide an oxygen-containing mixture, and wherein the oxygen-containing mixture is fed to an oxyfuel burner to produce additional CO2 and CO, and wherein the additional CO2 and CO are recycled back to the isothermal catalytic reactor to produce additional liquid C 5+ Hydrocarbon products.

14. The process of claim 12, wherein the conversion efficiency of CO2 to liquid hydrocarbon products is between 30% and 95%.

15. The process of claim 13, wherein the conversion efficiency of CO2 to liquid hydrocarbon products is between 30% and 95%.

16. The process of claim 1, wherein the CO2 conversion reactor is a fixed bed catalytic reactor.

17. The process of claim 1 wherein one of the catalysts in the CO2 conversion reactor comprises natural magnetite impregnated with 0.10-10.0 wt. % copper.

18. The process of claim 1 wherein one of the catalysts in the CO2 conversion reactor comprises synthetic magnetite impregnated with 0.10-10.0 wt. % copper.

19. The process of claim 17, wherein the natural magnetite impregnated catalyst is maintained at operating temperature by generating steam outside the reactor tubes.

20. The process of claim 18, wherein the synthetic magnetite impregnated catalyst is maintained at operating temperature by generating steam external to the reactor tubes.

21. The process of claim 17, wherein the natural magnetite impregnated catalyst utilizes a hot oil system external to the reactor tubes to maintain operating temperature.

22. The process of claim 18, wherein the synthetic magnetite impregnated catalyst utilizes a hot oil system external to the reactor tubes to maintain operating temperature.

23. The process of claim 17 wherein the CO2 reactor feed stream is diluted with additional H2 above the stoichiometric ratio.

24. The process of claim 18, wherein the CO2 reactor feed stream is diluted with additional H2 above the stoichiometric ratio.

25. A process for producing hydrocarbons, comprising: a. mixing a first feed stream comprising CO2 with a second feed stream comprising renewable H2 to produce a CO2 reactor feed stream; b. feeding the CO2 reactor feed stream into a CO2 conversion reactor, wherein the CO2 conversion reactor is a multi-tubular fixed bed reactor, and wherein the CO2 conversion reactor comprises two catalysts, wherein one of the catalysts comprises Fe3O4 impregnated with copper, thereby producing a CO2 conversion reactor comprising C 5+ Reactor product stream of hydrocarbons, H2O, and unreacted H2, CO and CO2.

26. The process of claim 25, wherein the multi-tubular fixed bed reactor is maintained at a constant temperature using hot oil.

27. The process of claim 26, wherein the ratio of H2 / CO2 in the reactor feed stream is between 2.75 and 4.

25.

28. The process of claim 27, wherein there is a conversion of CO2, and wherein the conversion is between 30% and 45%, and wherein there is a selectivity for product production, and wherein the selectivity for C 5+ The selectivity of product production in terms of hydrocarbons is between 50% and 70%.

29. The process of claim 28, wherein the other catalyst comprises copper aluminate spinel.

30. The process of claim 29, wherein the process is carried out at 2,000 hr. -1 Up to 4,000hr -1 Operates at space speeds between.

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