One-step process for the production of hydrocarbons from carbon dioxide
20240059978 ยท 2024-02-22
Assignee
Inventors
- Robert Schuetzle (Sacramento, CA, US)
- Dennis Schuetzle (Grass Valley, CA, US)
- Anja Rumplecker Galloway (San Rafael, CA, US)
- Orion Hanbury (Sacramento, CA, US)
- Harold Wright (Menomonee Falls, WI, US)
Cpc classification
International classification
C10G2/00
CHEMISTRY; METALLURGY
Abstract
The present invention are new and improved processes and catalysts that can efficiently facilitate the direct carbon dioxide conversion reaction with hydrogen to hydrocarbons in a single reactor at temperatures less than 450 C. and more preferably at temperatures from 250 C. to 325 C. Carbon dioxide is utilized from stationary sources or from direct air capture. Hydrogen is produced by the electrolysis of water using renewable or low carbon electricity.
Claims
1. A process for the production of hydrocarbons comprising: a. mixing a first feed stream comprising CO.sub.2 with a second feed stream comprising renewable H.sub.2 to produce a CO.sub.2 reactor feed stream; b. feeding the CO.sub.2 reactor feed stream into a CO.sub.2 conversion reactor, wherein the CO.sub.2 conversion reactor comprises two catalysts, thereby producing a reactor product stream comprising C.sup.5+ hydrocarbons, H.sub.2O and unreacted H.sub.2, CO and CO.sub.2.
2. The process of claim 1, wherein the reactor product stream is subjected to a separation step, producing a purified product stream comprising liquid product and a gas-phase product, wherein the liquid product comprises C.sup.5+ hydrocarbons and the gaseous product comprises C.sup.1-C.sup.5 hydrocarbons, CO.sub.2, H.sub.2O, CO and H.sub.2.
3. The process of claim 1, wherein the H.sub.2 in the second feed stream is produced from the electrolysis of H.sub.2O using renewable or low-carbon electric power.
4. The process of claim 1, wherein the CO.sub.2 in the first feed stream is captured from stationary sources or ambient air.
5. The process of claim 1 wherein the CO.sub.2 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 separately heated to between 310 C. and 320 C. and subsequently mixed at a volume/volume ratio between 3.0 and 5.0 before input into the CO.sub.2 conversion reactor.
7. The process of claim 5, wherein one catalyst in the CO.sub.2 conversion reactor is an endothermic catalyst, wherein the endothermic catalyst comprises 0.05-10 weight percent copper impregnated on a copper aluminate spinel or titanium oxide, and wherein the catalyst has a surface area greater than 10 m.sup.2/g.
8. The process of claim 5, wherein one catalyst in the CO.sub.2 conversion reactor is an exothermic catalyst, wherein the exothermic catalyst comprises magnetite, and wherein the magnetite comprises between 94 weight percent and 99.9 weight percent Fe.sub.3O.sub.4 and between 50 ppm and 500 ppm of a precious metal.
9. The process of claim 5, wherein one catalyst in the CO.sub.2 conversion reactor is an exothermic catalyst, and wherein the exothermic catalyst comprises between 99 weight percent and 99.9 weight percent Fe.sub.3O.sub.4, and wherein the catalyst has been impregnated with between 1 ppm and 2,000 ppm of gold.
10. The process of claim 5, wherein there is a first catalyst and a second catalyst in the CO.sub.2 conversion reactor, 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 CO.sub.2 reactor feed stream, and wherein the heat generated from the exothermic catalyst is used to heat the endothermic catalyst, and wherein the step of producing the product stream using the endothermic and exothermic catalysts is isothermal.
11. The process of claim 2, wherein the reactor product stream is fed to a product processing unit that separates the liquid products from the gas-phase products.
12. The process of claim 11, wherein the gas-phase products are recycled back into the isothermal catalytic reactor, thereby producing additional C.sup.5+ hydrocarbon products.
13. The process of claim 11, wherein the H.sub.2 in the second feed stream is produced from the electrolysis of H.sub.2O using renewable or low-carbon electric power, and wherein the gas-phase products are mixed with oxygen generated from the electrolysis to provide an oxygenated mixture, and wherein the oxygenated mixture if fed into an oxyfuel combustor to produce additional CO.sub.2 and CO, and wherein the additional CO.sub.2 and CO is recycled back into the isothermal catalytic reactor to produce additional liquid C.sup.5+ hydrocarbon products.
14. The process of claim 12, wherein the conversion efficiency of CO.sub.2 to liquid hydrocarbon products is between 30 percent and 95 percent.
15. The process of claim 13, wherein the conversion efficiency of CO.sub.2 to liquid hydrocarbon products is between 30 percent and 95 percent.
16. The process of claim 1, wherein the CO.sub.2 conversion reactor is a fixed bed catalytic reactor.
17. The process of claim 1, wherein one of the catalysts in the CO.sub.2 conversion reactor comprises natural magnetite impregnated with 0.10-10.0 weight percent of copper.
18. The process of claim 1, wherein one of the catalysts in the CO.sub.2 conversion reactor comprises synthetic magnetite impregnated with 0.10-10.0 weight percent of copper.
19. The process of claim 17, wherein the natural magnetite impregnated catalyst maintains an operating temperature by the production of steam on the outside of reactor tubes.
20. The process of claim 18, wherein the synthetic magnetite impregnated catalyst maintains an an operating temperature by the production of steam on the outside of reactor tubes.
21. The process of claim 17, wherein the natural magnetite impregnated catalyst maintains an operating temperature using a hot oil system on the outside of reactor tubes.
22. The process of claim 18, wherein the synthetic magnetite impregnated catalyst maintains an operating temperature using a hot oil system outside of reactor tubes.
23. The process of claim 17, wherein the CO.sub.2 reactor feed stream is diluted with additional H.sub.2 in excess of the stoichiometric ration.
24. The process of claim 18, wherein the CO.sub.2 reactor feed stream is diluted with additional H.sub.2 in excess of the stoichiometric ratio.
25. A process for the production of hydrocarbons comprising: a. mixing a first feed stream comprising CO.sub.2 with a second feed stream comprising renewable H.sub.2 to produce a CO.sub.2 reactor feed stream; b. feeding the CO.sub.2 reactor feed stream into a CO.sub.2 conversion reactor, wherein the CO.sub.2 conversion reactor is a multi-tubular fixed bed reactor, and wherein the CO.sub.2 conversion reactor comprises two catalysts, wherein one of the catalyst comprises Fe.sub.3O.sub.4 impregnated with copper, thereby producing a reactor product stream comprising C.sup.5+ hydrocarbons, H.sub.2O and unreacted H.sub.2, CO and CO.sub.2.
26. The process of claim 25, wherein the multi-tubular fixed bed reactor uses hot oil to maintain a constant temperature.
27. The process of claim 26, wherein the ratio of H.sub.2/CO.sub.2 in the reactor feed stream is between 2.75 and 4.25.
28. The process of claim 27, wherein there is a conversion rate of CO.sub.2, and wherein the conversion rate is between 30 percent and 45 percent, and wherein there is a selectivity of product production, and wherein the selectivity of product production for C5+ hydrocarbons is between 50 percent and 70 percent.
29. The process of claim 28, wherein the other catalyst comprises copper aluminate spinel.
30. The process of claim 29, wherein the process is operated at a space velocity between 2,000 hr.sup.1 and 4,000 hr.sup.1.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0022]
[0023]
DETAILED DESCRIPTION OF THE INVENTION
[0024] Hydrocarbons refer to a class of organic chemical compounds composed only of the elements carbon and hydrogen. The hydrogen atoms are attached to the carbon atoms in many different configurations. Hydrocarbons are classified as either aliphatic or aromatic. Aliphatic hydrocarbons are classified as alkanes, alkenes, and alkynes. Aromatic hydrocarbons are classified as arenes, which contain a benzene ring as a structural unit, or non-benzenoid aromatic hydrocarbons which lack a benzene ring as a structural unit.
[0025] C.sub.1-C.sub.5 Hydrocarbons refer to hydrocarbons that contain between 1 carbon atom and 5 carbon atoms.
[0026] C.sub.2-C.sub.5 Hydrocarbons refer to hydrocarbons that contain between 2 carbon atom and 5 carbon atoms.
[0027] C.sub.5+ Hydrocarbons refer to hydrocarbons that contain 5 or more carbon atoms.
[0028] Renewable Electric Power refers to an energy source that is not fossil carbon-based and may include solar, wind, biomass, geothermal, landfill gas, wave, tidal and thermal ocean technologies. Although nuclear energy itself is a renewable energy source, the material used in nuclear power plants is not unless the spent nuclear fuel is recyclable. At this point in time, about 96% of spent nuclear fuel in reactors is recycled.
[0029] Low-Carbon Electric Power refers to electricity produced with substantially lower greenhouse gas emissions than conventional fossil fuel power generation.
[0030] Precious metals refer to rare, naturally occurring metallic chemical elements of high economic value. Precious metals include gold, silver, platinum, palladium, ruthenium, rhodium, osmium, and iridium.
[0031] Natural Magnetite refers to a naturally occurring iron oxide mineral. It is composed primarily of Fe.sub.3O.sub.4 with minor amounts of precious metals. It is the most magnetic of all the naturally occurring minerals on EarthIt is a natural magnet. Magnetite-rich black sands are commonly encountered in gold mining operations. Precious metals often occur in magnetic concentrates as discrete mineral grains, as inclusions in magnetite, and as diffused atoms. in the magnetite lattice. The precious metal content may vary from a few ppm to 1,500 ppm, depending upon the mineral source.
[0032] Synthetic Magnetite refers to the impregnation of synthetic Fe3O4 with up to 1,500 ppm of various precious metals followed by calcining up to about 2,100 F.
[0033] Electrolyzers consist of an anode and a cathode separated by an electrolyte. Different electrolyzers function in slightly different ways. Different electrolyzer designs that use different electrolysis technology that are used include alkaline electrolysis, polymer electrolyte membrane (PEM) electrolysis, solid oxide electrolysis, high temperature electrolysis and other emerging types of electrolysis.
[0034] The products from the electrolyzer are a stream comprising hydrogen called stream 3 in
[0035] In
[0036] Captured CO.sub.2 which is converted into useful products such as fuels (e.g., synthetic natural gas, diesel fuel, gasoline blend stocks, jet fuel, other) and chemicals (e.g., solvents, olefins, alcohols, aromatics, polymers (for textiles, packaging, structural materials, etc., and others), displace fuels and chemicals produced from fossil sources such as petroleum and natural gas, lowering the total net emissions of CO.sub.2 into the atmosphere. This is what is meant by low carbon, very low carbon, zero carbon, or negative carbon fuels and chemicals.
[0037] The CO.sub.2 stream that comes from industrial or biological process, or is captured from the atmosphere, or that is available from a commercial CO.sub.2 pipeline is not generally pure CO.sub.2. These available CO.sub.2 streams from industrial facilities or pipelines can include sulfur containing compounds from none to 2000 parts per million by weight and contain hydrocarbons from none to 10 volume percent. Purification of the CO.sub.2 including the removal of sulfur containing compounds and hydrocarbons is necessary to avoid issues with downstream processing. After purification, the purified CO.sub.2 is suitable for the generation of low carbon or zero-carbon fuels and chemicals as per the invention.
[0038] At least a portion of the stream 3 comprising hydrogen is blended with the stream 5 comprising CO.sub.2 to produce a stream 6 or CO.sub.2C Reactor feed stream. The ratio of H.sub.2/CO.sub.2 is from 2 to 6, or preferably from 3 to 4. The CO.sub.2 and hydrogen in stream 6 are reacted to products in a CO.sub.2C reactor shown as Unit 2 in
CO.sub.2+H.sub.2CO+H.sub.2O (H.sub.298=+42.1 kJ/mole) Eq. 1
CO+3H.sub.2CH.sub.4+H.sub.2O (H.sub.298=206.1 kJ/mole) Eq. 2
nCO+(2n+1)H.sub.2.fwdarw.C.sub.nH.sub.(2n+2)+nH.sub.2O (H.sub.298=165 kJ/(mol CO)) Eq. 3
The first reaction, Eq. 1, is the Reverse Water Gas Shift reaction. At standard temperature, the reaction is endothermic and in other processes requires much higher temperatures than the preferred CO.sub.2C reactor temperatures. The second reaction, Eq. 2, is the methanation reaction where CO and hydrogen gas are reacted to produce methane and water. Methanation is very exothermic as can be seen with the high negative enthalpy of reaction. The third reaction, Eq. 3, is the desired Fischer-Tropsch (F-T) reaction. The F-T reaction is also very exothermic.
[0039] Catalyst is used in the CO.sub.2C reactor to facilitate the chemical reactions. Various catalysts can be used in the CO.sub.2C reactor. Catalysts include multiple components of different functionality. Catalysts may be monofunctional, bifunctional or multifunctional formulations comprising 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 Ni.sub.2Mg unsupported solid solution catalyst, Mg/Mg-aluminate catalyst, Rhodium on gamma alumina, CuFeO.sub.2, FeCo/K/Al.sub.2O.sub.3, In.sub.2O.sub.3/HZSM-5, NaFe.sub.3O.sub.4/HZSM-5, FeNa, NaFe.sub.2O.sub.4/HMCM-22, Fe.sub.2O.sub.3, Co.sub.6/MnO.sub.4, ZnCr/Hy, FeZnZr/HZSM-5, FeMnK, and other catalysts as shown in the review paper of Tan et al (2022) or in Yao et al (2020).
[0040] The product from the CO.sub.2C reactor is shown as stream 7 in
[0041] In one embodiment, the CO.sub.2 conversion in the CO.sub.2C reactor is less than about 90%, and the unreacted CO.sub.2 is removed prior to further processing after the water and C.sub.5+ hydrocarbon removal. CO.sub.2 removal from the stream can be done by any number of available techniques. The removal methods include the use of physical solvents. Physical solvents include refrigerated methanol that is used in the Rectisol process and the Solexol process that uses dimethyl ethers of polyethylene glycol to capture the CO.sub.2 from the gas stream. Other means include the use of membranes selective for CO.sub.2 removal. Another means for CO.sub.2 removal is to use aqueous solutions of alkylamines (referred to as amines) to chemically capture the CO.sub.2. The amine contactor captures the CO.sub.2 in the solution. The overhead of the amine contactor is the CO.sub.2 free gas and the amine solution with the CO.sub.2 is heated in an amine regenerator where the CO.sub.2 is released, and the amine aqueous solution is recycled back to the contactor. Various amines can be used such as diethanolamine (DEA), monoethanolamine (MEA), methyl-diethanolamine (MDEA), and Diisopranolamine (DIPA).
[0042] The CO.sub.2 stream recovered from the CO.sub.2 capture unit is shown as Stream 11 in
[0043] In one embodiment, the CO.sub.2C hydrocarbon product stream comprises n-alkanes with carbon numbers from 6 to 23 that is fed to an CO.sub.2C separation unit where at least three product fractions are produced. The CO.sub.2C separation is any separation process such as absorption, adsorption, filtration, or distillationor a combination of those processes. Distillation is a preferred separation process. The light CO.sub.2C separation product comprises n-alkanes with carbon numbers, between 5 and 9. The medium CO.sub.2C separation product comprises n-alkanes from carbon numbers between 9 and 15.
[0044] The heavy CO.sub.2C separation product comprises n-alkanes with carbon numbers between 16 and 23. Hydrocarbons produced in the CO.sub.2C reactor are represented (collectively) as Stream 9 in
[0045] In one embodiment of the invention, the CO.sub.2C reactor is a mix of two different catalysts that can produce hydrocarbons from mixtures of CO.sub.2 and H.sub.2.
[0046] The first catalyst, catalyst #1, is a CO.sub.2 hydrogenation catalyst that has a CO.sub.2 conversion efficiency of about 25% and a high CO selectivity (>90%) at 300 C. with an H.sub.2/CO.sub.2 feed ratio of about 3.0-3.5/1.0, a pressure of 250-350 psig, and a space velocity of 2,000-3,000 hr.sup.1. This is an endothermic catalyst (H.sub.298=+40 kJ/mole) which requires the input of heat.
[0047] The second catalyst, Catalyst #2, can be any F-T catalyst that is capable of producing hydrocarbons at 300 C. Iron based catalysts are well known to be active for F-T at this temperature. One particularly useful catalyst is a magnetite-based catalyst that operates in the same temperature range of catalyst #1 (300 C.). This is an exothermic catalyst (H.sub.298=200 kJ/mole of CO which produces hydrocarbons from the CO and H.sub.2 formed from catalyst #1. This catalyst operates with a H.sub.2/CO feed ratio of about 1.5-2.0/1.0, a pressure of 250-350 psi, and a space velocity of 2,000-3,000 hr.sup.1.
[0048] The first and second catalyst are mixed in a ratio and physical proximity such, that the exothermic heat from catalyst #2 is directly transferred to the adjacent endothermic catalyst #1. It is estimated that the ratio of catalysts #1 and #2 should be 4-5 to 1 for the catalyst bed to remain isothermal and for there to be enough CO available for catalyst #2 from catalyst #1. The catalytic reactor is held under adiabatic conditions by using sufficient insulation and heat to keep the bed at 300 C.
[0049] Catalyst #1 can be any suitable CO.sub.2 hydrogenation catalyst. Since titanium oxide has the highest surface acidity of any catalyst substrate, TiO.sub.2 is preferred as the substrate for catalyst #1. Zirconium oxide also has a high surface acidity, but lower than that of titanium oxide.
[0050] The impregnation of certain metals on the support of catalyst #1, such as Cu, on TiO.sub.2 will increase the reaction rate. The CO.sub.2 conversion should be about 25% at about 2,000-3,000 hr.sup.1 space velocity with a high CO selectivity and minimal CH.sub.4 formation at 300 C.
[0051] Since the CO produced by catalyst #1 is generated quickly, a highly efficient oligomerization (chain propagating) catalyst (catalyst #2) needs to be mixed with or placed in tandem (close proximity) with the hydrogenation catalyst, catalyst #1. In addition, this chain propagating catalyst needs to operate efficiently at 300 C.
[0052] In one embodiment, magnetite or iron-based catalysts are used for catalyst #2. Depending upon the source, natural magnetite contains from about 50 to 1,500 ppm of precious metals and may be used as the catalyst. In another embodiment, a synthesized magnetite or iron catalyst is used with the desired promoters incorporated into the catalyst which may include precious metals. The precious metals in the magnetite significantly increases the production of H.Math. radicals from H.sub.2, which reduces the probability of free radical chain propagation and thereby decreases the formation of higher molecular weight hydrocarbons species.
[0053] In one embodiment of the invention, the CO.sub.2C reactor is a multi-tubular fixed bed reactor. The inner reactor tubes are filled with a mixture of steam and water. The reaction heat is removed through the production of steam in the shell of the reactor. The inner diameter of the tubes is between 18 and 50 mm. The tubes are filled with catalyst particles. The catalyst particle size is optimized to optimize the tradeoff between conversion and pressure drop across the reactor. This small diameter of the reactor tubes means that as the feed gas reacts on the catalyst, the heat must be transferred from no more than 9 to 25 mm (one-half of the diameter of the tube) to the heat transfer surface. Outside of the tubes, the mixture of steam and water allow heat transfer primarily through nucleation in the vaporization of the liquid water to steam. The water comes from a steam drum. Boiler Feed Water (BFW) is fed to the steam drum and circulates the system. The pressure of the steam system sets the temperature of the steam/water mixture. The pressure of the steam ranges from 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. As such, saturated steam from 1000 to 1200 psig is an ideal cooling fluid for the CO.sub.2C reaction that occurs at 300 C. Typically, water is fed from the steam drum to the water entrance to reactor shell and a mixture of about 50% steam and 50% water is at the steam exit of the reactor shell back to the steam drum.
[0054] In one embodiment, heat transfer is done with a hot oil system. Oil as a working fluid is pumped to the reactor shell. Heat is transferred from the tubes to the oil raising the temperature of the oil. The rate of oil circulation 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, refrigerated water, or propylene glycol or other suitable materials can be used in the cold side of the external heat exchanger to reduce the temperature of the hot oil back to the desired reactor shell inlet temperature. The cooled hot oil is then pumped back to the reactor shell. Several suitable oils have working temperatures that are useful for this service including Therminol XP, Therminol 55, Therminol SP, Therminol 59, or any equivalent or similar oil working fluid.
[0055] In one embodiment, the catalyst inside the CO.sub.2C reactor can be diluted with other, non-reactive solids. Dilution of the catalyst aids in the heat transfer so that the rate of exothermic heat generation per unit volume is less and as such the local temperature rise is less. Suitable diluents include alumina, silicon carbide, spinels, or other refractory materials. Silicon carbide has one advantage as its thermal conductivity is higher and as such could transfer heat from the exothermic heat generation at a higher rate. However, any non-catalytically active material can be used as the diluent.
[0056] In one embodiment, metal partitions can be placed inside the CO.sub.2C reactor tubes prior to the addition of the catalyst such that from the center of the tube to the wall of the tube there are metal pathways or connections. This aids in heat transfer since the high thermal conductivity of the metal increases the rate of heat transfer from the hot center of the tube to the cooled tube walls.
[0057] In one embodiment of the invention, the feed gas to the CO.sub.2C reactor can be diluted with non-reactive gases. Feed gas dilution aids in heat transfer and temperature control in several ways. It reduces the reaction heat generated per unit time per unit volume. It also adds additional mass flow rate that acts as a heat sink. Various dilution gases can be used. The ideal dilution gas is easily separable from the reactor effluent. Low pressure steam can be used as a diluent gas feed to the CO.sub.2C reactor. As the reactor effluent is cooled, the condensed steam can easily be removed from the effluent by a knockout vessel or separator and since steam is a reaction product, the design change involves just increasing the size of the separator.
[0058] In one embodiment, the CO.sub.2C reactor is a series of adiabatic reactors or reactor beds. Each reactor bed length or residence time is set such that the maximum conversion that can occur keeps the bed temperature rise to a preset temperature rise of no more than 50 C., preferable less than 25 C., more preferably less than 10 C. Catalyst and feed gas dilution can also be used to keep the temperature rise to the preset limit. 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 1200 psig. This cools the reactor effluent to a temperature similar to the previous bed inlet temperature. The cooled effluent is then fed to a subsequent bed. The total number of beds is chosen to get the desired overall CO.sub.2 conversion. Optionally, additional hydrogen or hydrogen and CO.sub.2 can be added to the subsequent bed feed gas.
[0059] In one embodiment, the heat transfer and heat management in the reactor are controlled using sequential H.sub.2 injection. The initial H.sub.2/CO.sub.2 ratio is below stoichiometric for the net reaction. This keeps the CO.sub.2 conversion low, and the temperature rise in the reactor bed low. H.sub.2 at a temperature substantially below the reactor bed temperature is added at the end of the bed. The cold H.sub.2 lowers the overall gas temperature to about the previous bed inlet temperature. The additional hydrogen with the previous bed CO.sub.2 reacts in the subsequent bed. In essence, the conversion is spread (stretched) over a longer effective bed depth (or bed number), reducing the amount of heat generated per reactor area or volumemaking the heat removal more manageable. The number of reactor beds and cold hydrogen additions sets the overall CO.sub.2 conversion.
[0060] In one embodiment, the CO.sub.2C reactor is operated at low CO.sub.2 conversion but with high overall gas recycle. This allows the temperature in the reactor bed to be controlled and the temperature rise within the acceptable range. The space velocity or residence time in the reactor bed is high such that conversion is low. Gas dilution and catalyst dilution can be used to aid in the control of the temperature. The per pass CO.sub.2 conversion is kept below 30%, preferably below 20%, more preferably below 10%. The reactor effluent is fed to the Product Processing Unit where the water in the effluent is removed by cooling and separation and the unreacted CO.sub.2 and H.sub.2 are removed and compressed and recycled and blended with the fresh feed to the CO.sub.2C reactor.
EXAMPLE 1
[0061] In this example, which has been performed, two different catalysts were mixed in the CO.sub.2C reactor. Catalyst #1 was an improved high-surface area copper aluminate (CuAl.sub.2O.sub.4) spinel impregnated with 0.055.0 wt % Cu that had been formed into pellets and calcined. Catalyst #2 was a natural magnetite-based catalyst that has been pressed into pellets and calcined. The catalysts were placed in close proximity to each other in the reactor. Catalyst #1 operates endothermally (requires heat) whereas catalyst #2 operates exothermally (produces heat).
[0062] These catalysts were mixed in specified ratios so that they operate isothermally throughout the catalytic reactor. H.sub.2 produced from the electrolysis of water using renewable or low carbon electricity was mixed with captured CO.sub.2.
[0063] Since the catalysts in the catalytic reactor operated under or near isothermal conditions, CO.sub.2C reactor design can be chosen from one of many isothermal reactors currently available including a multi-tubular fixed bed reactor.
[0064] The H.sub.2 and CO.sub.2 were individually heated to the desired temperature of about 315 C. and mixed in specific ratios before introduction into the catalytic reactor.
[0065] Details on the production and composition of catalyst #1 and catalyst #2 are as follows.
[0066] Catalyst #1 was a copper aluminate (CuAl.sub.2O.sub.4) spinel that was formed from mixing a mixture of copper salt and high surface area gamma-alumina powder in which enough extra copper was added such that the resulting catalyst was a copper aluminate spinel in which 0.05-5.0 wt % copper was distributed on the spinel. The copper salts may include copper acetate, copper nitrate, or other copper water-soluble salts. The mixture was then formed into tablets at high pressure. These tablets were calcined at about 950 C. which forms the CuAl.sub.2O.sub.4 spinel. The resulting CuAl.sub.2O.sub.4 catalyst had a BET surface area greater than 10 m.sup.2/g, preferably a surface area of greater than 25 m.sup.2/g, and more preferably a surface area greater than 50 m.sup.2/g.
[0067] An alternative approach for the production of the catalyst is to dissolve copper acetate in water and enough solution is added to the copper aluminate spinel to produce 0.0510.0 wt % of Cu impregnated on the copper aluminate (CuAl.sub.2O.sub.4) spinel.
[0068] This CuCuAl.sub.2O.sub.4 catalysts converted CO.sub.2/H.sub.2 mixtures with about a 25% CO.sub.2 conversion and a CO selectivity greater than 90% at 300 C. and at a CO.sub.2/H.sub.2 molar feed ratio of 3.5/1.0 and at a space velocity of 3,000 hr.sup.1 and a pressure of 300 psi (Table 3).
TABLE-US-00001 TABLE 3 The Effect of Space Velocity for the CO.sub.2 Conversion to CO for Catalyst #1 at 300 C. Space Velocity (hr.sup.1) % CO.sub.2 Conversion to CO 3,000 25 6,000 23 12,000 20 30,000 11 40,000 6
[0069] Catalyst #2 was a magnetite catalyst that is based upon natural occurring magnetite which is found in select areas of North America. This natural magnetite which contains small amounts of precious metals is typically a side product of gold mining. The magnetite is formed into tablets at high pressure. These tablets are then calcined at about 950 C. In this example, the composition of the magnetite was Fe.sub.3O.sub.4 (94.4%) with Al.sub.2O.sub.3 (3.2%), TiO.sub.2 (1.8%), CuO (0.22%), MnO (0.17%), MgO (0.10%), and about 850 ppm of precious metals. In another embodiment, the catalyst was synthesized generally to achieve the desired composition. The precious metals in order of abundance are Au, Ag, Pt, and Pd. These precious metals were widely dispersed in 100-250 Angstrom clusters throughout the Fe.sub.3O.sub.4 matrix, and they were primarily distributed on the surfaces of the magnetite crystals. The surface area of the magnetite catalyst was 3-4 m.sup.2/g with pores in the 10-100 Angstrom (1-10 nanometer) size range. The magnetite catalyst was reduced with H.sub.2 at 300 C. in the catalytic reactor.
[0070] The effect of temperature on the performance of the magnetite catalyst (catalyst #2) in an oligomerization reaction such as a Fischer-Tropsch reaction is summarized in Table 4. The production of C.sub.5+ hydrocarbons was about 39% with the remaining carbon containing products (CH.sub.4, CO.sub.2, C.sub.2-C.sub.5 hydrocarbons and C.sub.24+ hydrocarbons) accounting for the other 61% at 300 C. When this exothermic catalyst is coupled in a short length scale with the endothermic catalyst, catalyst #1, the result is a direct conversion for CO.sub.2 and hydrogen to hydrocarbons. In this example, hydrogen was produced from the electrolysis of water. Additionally, oxygen was produced by the electrolyzer.
[0071] Catalyst #1 catalyzes an endothermic reaction (about +50 kJ/mole) which requires heating and catalyst #2 catalyzes an exothermic reaction (about 175 kJ/mole) which produces heat. Catalyst #1 and catalyst #2 were mixed in the proper proportions such that the heat produced from catalyst #2 was used to heat catalyst #1. Therefore, the masses of the first and second catalyst were adjusted such that the catalytic reactor operates isothermally at about 300 C. Based upon the thermodynamics, the mass ratio of catalyst #1/catalyst #2 of 3.0-5.0/1.0 provided a nearly thermal balance in the catalytic reactor.
[0072] Since there were 3-5 times more catalyst #1 than catalyst #2, more CO was produced than can be used by catalyst #2 even though the conversion efficiency of CO.sub.2 to CO is only about 25% for catalyst #1.
[0073] Although catalyst #2 produces CO.sub.2, the first catalyst converts the CO.sub.2 to additional CO. As a result, the composition of the products from the two catalysts in the catalytic reactor averaged 20% CH.sub.4, 24% C.sub.2-C.sub.5 and 56% C.sub.6-C.sub.24 for three passes. In addition, some CO.sub.2, CO, and H.sub.2 was present in the tail-gas.
[0074] In this example, the CO.sub.2 C reactor effluent was cooled. The water was removed by a water knockout. The C.sub.5+ hydrocarbons were condensed and separated. After the C.sub.5+ hydrocarbons were condensed and collected, the remaining CO.sub.2 and C.sub.1-C.sub.5 in the tailgas (44% total) were recycled by being sent to an oxyfuel combustor where the hydrocarbon and any remaining hydrogen and other combustible material were converted to additional CO.sub.2 through the use of oxygen produced in the electrolysis unit. The CO.sub.2 was then used as recycled feed to the catalytic CO.sub.2C reactor. Therefore, after about 3 recycle loops, more than about 90% of the CO.sub.2 carbon was converted to C.sub.5+ hydrocarbons. The product produced a mixture of hydrocarbons. Up to 30 vol % of the liquid products consisted of C.sub.3-C.sub.11 alpha-olefins and hydroxy-alkanes (alcohols) depending on the reactor operating conditions. The remainder of the liquid products consisted of C.sub.5-C.sub.24 normal alkanes, with a minor fraction of iso-alkanes.
[0075] The CH.sub.4, C.sub.2-C.sub.5, CO and H.sub.2 in the tail gas can be used as energy for the process, or it may be converted using oxy-combustion to produce additional CO.sub.2 and CO.
[0076] The oxyfuel combustor used in this example works in the following way. CO.sub.2 was mixed with oxygen as oxidant for the combustor. The fuel to the combustor is the CO.sub.2C effluent that comprises CO.sub.2, H.sub.2, and the C.sub.1-C.sub.5 fraction produced by the CO.sub.2C reactor. The combustion products were water and CO.sub.2. The combustion products are cooled, and the water is removed. The CO.sub.2 was recirculated and blended with the oxygen to produce the oxidant stream for the combustor. Alternatively, the CO.sub.2 can be blended with the feed to the CO.sub.2C reactor.
TABLE-US-00002 TABLE 4 The Effect of Temperature on Performance of the Natural Magnetite Catalyst with 0.22 wt. % CuO (H.sub.2/CO = 2.0/1.0; P = 391 psi; SV = 3,200 hr.sup.1 CO Conversion Product Selectivity (%) T F. ( C.) (%) CH.sub.4 CO.sub.2 C.sub.5C.sub.24 C.sub.2C.sub.5 C.sub.24+ 380 (193) 9 10.8 3.3 73.5 6.2 6.2 410 (210) 21 11.5 7.1 65.1 11.8 4.5 435 (224) 32 11.8 13.1 58.8 12.9 3.4 450 (232) 38 12.3 16.4 54.6 14.1 2.6 470 (243) 43 12.6 19.3 51.6 14.2 2.3 550 (288) 63 13.7 26.5 41.1 16.6 2.1 570 (300) 68 14.1 27.5 39.1 17.0 2.3 600 (315) 74 14.2 28.1 38.8 16.9 2.0
EXAMPLE 2
[0077] In this example, which has been performed, two catalysts were used in the CO.sub.2C reactor. Catalyst #1 consists of Cu impregnated on a high surface area titanium oxide (TiO.sub.2) substrate (e.g., CuTiO.sub.2) instead of the copper aluminate. Catalyst #2 is the same as previously described in Example 1.
[0078] Catalyst # 1 was prepared by wet impregnation. The copper salt was suspended in a solvent. The high-surface TiO.sub.2 substrate was added to the solution. The solvent was removed by evaporation so that the copper is deposited on the support. The mixture was then formed into tablets at high pressure. These tablets were calcined at about 950 C. which formed the CuTiO.sub.2 catalyst. The resulting CuTiO.sub.2 catalyst had a BET surface area greater than 10 m.sup.2/g, preferably a surface area of greater than 25 m.sup.2/g, and more preferably a surface area greater than 50 m.sup.2/g.
[0079] An alternative approach to produce the catalyst is to dissolve copper acetate in water and enough solution is added to the copper CuTiO.sub.2 to produce 0.05-10.0 wt % of Cu impregnated on the CuTiO.sub.2 material.
[0080] The CO.sub.2C reactor was operated as shown in Example 1 and results in more than about 90% of the CO.sub.2 carbon converted to C.sub.5+ hydrocarbons after recycling. The product produced a mixture of hydrocarbons. Up to 30 vol % of the liquid products consisted of C.sub.3-C.sub.11 alpha-olefins and hydroxy-alkanes (alcohols) depending on the reactor operating conditions. The remainder of the liquid products consisted of C.sub.5-C.sub.24 normal alkanes, with a minor fraction of iso-alkanes.
[0081] The CH.sub.4, C.sub.2-C.sub.5, CO and H.sub.2 in the tail gas can be used as energy for the process, or it may be converted using oxy-combustion to produce additional CO.sub.2 and CO.
EXAMPLE 3
[0082] In this example, which has been performed, the catalyst in the CO.sub.2C reactor used the Fe.sub.3O.sub.4 (magnetite) catalyst that has been impregnated with 0.1-10.0 wt. % copper. The reactor was a multi-tubular fixed bed reactor using hot oil to help maintain a constant catalyst temperature. The H.sub.2/CO.sub.2 in the feed to the CO.sub.2C reactor was 3.0-4.0, pressure was 250-350 psi, and the reactor is operated at 300 C. The CO.sub.2 conversion is 38% with a CH.sub.4 selectivity of 10.4%, C.sub.2-C.sub.5 selectivity of 27.7% and C.sub.5+ selectivity of 61.9%. The CO.sub.2C reactor effluent comprises'a mixture of hydrogen, CO, CO.sub.2, C.sub.1-C.sub.5 hydrocarbons, and C.sub.5+ hydrocarbons. Downstream of the CO.sub.2C reactor, a large fraction of the C.sub.5+ hydrocarbons were condensed to a liquid via a cooling water exchanger and a knockout vessel and sent to product storage. The remaining stream of H.sub.2, CO, CO.sub.2, C.sub.1-C.sub.2 was sent to a CO.sub.2 removal unit, typically an amine unit, where the CO.sub.2 was removed. The CO.sub.2 rich stream was compressed and recycled to the inlet of the CO.sub.2C reactor. Additional hydrogen was fed to the reactor to maintain the H.sub.2/CO ratio in the feed at 3.0-4.0. The CO, H.sub.2 and C.sub.1-C.sub.5 stream were additionally separated and used as plant fuel gas, converted to additional CO.sub.2 and CO, or sold as a fuel product.
REFERENCES
[0083] Landau et al., AU 2015203898 B2 (2015).
[0084] National Academy of Sciences, Chemical Utilization of CO.sub.2 into Chemicals and Fuels, Gaseous Carbon Waste Streams Utilization: Status and Research Needs, National Academies Press, Washington D.C. (2019).
[0085] Pan, et al., Enhanced Ethanol Production Inside Carbon Nanotube Reactors Containing Catalytic Particles, Nature Materials, Volume 6 (2007).
[0086] Shen et al., Identifying the Roles of Ce.sup.3+OH and CeH in the Reverse Water-Gas Shift Reaction Over Highly Active Ni-doped CeO.sub.2 Catalyst, Xi'an Key Laboratory Functional Organic Porous Materials, School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an 710129, China (2022).
[0087] Tan, et al., Current Developments in Catalytic Methanation of Carbon DioxideA Review, Frontiers in Energy Research (2022).
[0088] Wang et al., High Performance M.sub.aZrO.sub.x (M.sub.a=Cd, Ga) Solid-Solution Catalysts for CO.sub.2 Hydrogenation to Methanol, State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China (2019).
[0089] Wang et al., One-Step Plasma-Enabled Catalytic Carbon Dioxide Hydrogenation to Higher Hydrocarbons: Significance of Catalyst-Bed Configuration, Green Chemistry (2021).
[0090] Wei et al., Catalytic Hydrogenation of CO.sub.2 to Isoparaffins over Fe-Based Multifunctional Catalysts, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China (2018).
[0091] Williamson et al., N-Doped Fe@CNT for Combined RWGS/FT CO.sub.2 Hydrogenation, ACS Sustainable Chemical Engineering (2019).
[0092] Yao, et al, Transforming Carbon Dioxide into Jet Fuel Using an Organic Combustion-Synthesized FeMnK Catalyst, Nature Communications, 11, 6395 (2020).