INTEGRATED DIRECT AIR CAPTURE AND CONVERSION TO HYDROCARBONS

Abstract

A multifunctional material may include a solid inorganic sorbent. The multifunctional material may include a metal catalyst component, wherein the solid inorganic sorbent and metal catalyst component are integrated into a single material.

Claims

1. A multifunctional material for integrated capture and catalytic conversion of CO.sub.2, comprising: a solid inorganic sorbent; and a metal catalyst component, wherein the solid inorganic sorbent and metal catalyst component are integrated into a single material.

2. The material of claim 1, wherein the solid inorganic sorbent comprises a carbonate.

3. The material of claim 1, wherein the metal catalyst component comprises iron, cobalt, copper, manganese or any combination of oxides thereof.

4. The material of claim 1, wherein the solid inorganic sorbent comprises group 1 metal carbonates, wherein the solid inorganic sorbent comprises a group 1 metal carbonate comprising K.sub.2CO.sub.3, Na.sub.2CO.sub.3, Li.sub.2CO.sub.3, or a mixture thereof, supported on porous materials comprising Al.sub.2O.sub.3, Carbon, SiO.sub.2 ZrO.sub.2, aluminosilicate zeolites, or a mixture thereof.

5. The material of claim 1, wherein metal catalyst component comprises iron.

6. The material of claim 1, wherein the material is Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3.

7. The material of claim 1, wherein the material has a CO.sub.2 capture capacity in a range of from about 1.5 wt % to about 25 wt % at temperatures in a range of from about ambient temperatures to about 150 C. in the presence of water vapor.

8. The material of claim 1, wherein the material is capable of converting captured CO.sub.2 to (C.sub.1-C.sub.10)hydrocarbyl products upon hydrogenation.

9. The material of claim 8, wherein the (C.sub.1-C.sub.10) hydrocarbyl products comprise olefins, paraffins, or both.

10. The material of claim 1, wherein the material comprises Fe particles range from about 2 wt % to about 50 wt % of the material.

11. The material of claim 1, wherein the material is capable of capturing CO.sub.2 from air containing 350 ppm CO.sub.2 to about 1000 ppm CO.sub.2, as well as from concentrated sources containing about 1 vol % CO.sub.2 to about 30 vol % CO.sub.2.

12. The material of claim 1, wherein the material is capable of converting captured CO.sub.2 to (C.sub.1-C.sub.10)hydrocarbyls at temperatures in a range of from about 250 C. to about 400 C.

13. A method for integrated direct air capture and catalytic conversion of CO.sub.2 to (C.sub.1-C.sub.10)hydrocarbyl products, comprising: contacting a multifunctional material comprising a solid inorganic sorbent and a metal catalyst component with air to capture CO.sub.2; and hydrogenating the captured CO.sub.2 to produce (C.sub.1-C.sub.10)hydrocarbyls.

14. The method of claim 13, wherein the solid inorganic sorbent comprises a carbonate.

15. The method of claim 13, wherein the metal catalyst component comprises iron, cobalt, copper, manganese or any combination of oxides thereof.

16. The method of claim 13, wherein the multifunctional material is Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3.

17. The method of claim 13, wherein the hydrogenation occurs at temperatures in a range of from about 300 C. to about 400 C.

18. The method of claim 13, wherein the (C.sub.1-C.sub.10)hydrocarbyl products comprise olefins, paraffins, or both.

19. The method of claim 13, wherein the air contains about 350 ppm CO.sub.2 to about 1000 ppm CO.sub.2.

20. The method of claim 13, wherein the hydrogenation is performed under a hydrogen pressure in a range of from about 0.5 MPa to about 3 MPa.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0006] The drawings illustrate generally, by way of example, but not by way of limitation, various aspects of the present disclosure.

[0007] FIG. 1A is a graph showing the CO.sub.2 capture profile over K.sub.2CO.sub.3/Fe/C.

[0008] FIG. 1B is a graph showing the hydrogenation profile of the captured CO.sub.2 (at heating rate of 20 C./min)

[0009] FIG. 1C is a graph showing the CO.sub.2 conversion and selectivity of products formed in Region 1 at 320 C.,

[0010] FIG. 1D is a graph showing the comparison of the CO.sub.2 conversion and selectivity of the products formed in Region 2 and 360 C.

[0011] FIG. 2A is a graph showing the comparison of the CO.sub.2 adsorption capacity of K.sub.2CO.sub.3 on various materials pretreated at high temperature under H.sub.2 flow.

[0012] FIG. 2B is a graph showing hydrogenation of the captured CO.sub.2 over K.sub.2CO.sub.3/Fe/C/Al.sub.2O.sub.3.

[0013] FIG. 3A is a graph showing the nitrogen adsorption isotherm of K.sub.2CO.sub.3/Al.sub.2O.sub.3 (also referred as KA), K.sub.2CO.sub.3/Fe/C/Al.sub.2O.sub.3, and Fe/C.

[0014] FIG. 3B is a graph showing the pore size distribution Barrett-Joyner-Halenda (BJH) curves for K.sub.2CO.sub.3/Al.sub.2O.sub.3, and K.sub.2CO.sub.3/Fe/C/Al.sub.2O.sub.3.

[0015] FIG. 4A is a graph showing CO.sub.2 capture and hydrogenation of captured CO.sub.2 using Fe/KA.

[0016] FIG. 4B is a graph showing comparison of the N.sub.2 adsorption isotherm of K.sub.2CO.sub.3/Al.sub.2O.sub.3, Fe/KA-Fresh, and Fe/KA-Spent (after hydrogenation).

[0017] FIG. 4C is a graph showing powder XRD of freshly captured CO.sub.2 and spent Fe/KA.

[0018] FIG. 4D shows physicochemical properties of the Fe/KA material.

[0019] FIG. 5A is a bar graph showing the amount of captured CO.sub.2.

[0020] FIG. 5B is a graph showing hydrogenation of captured CO.sub.2 during the five cycles of FIG. 5A.

[0021] FIG. 6A is a graph showing a comparison of gas-phase hydrogenation at 320 C.

[0022] FIG. 6B is a graph showing a comparison of gas-phase hydrogenation at 360 C.

[0023] FIG. 6C is a graph showing a comparison of XRD of Fe/KA for direct air capture and gas-phase reactions carried out at 1:10 and 1:3 ratios of CO.sub.2/H.sub.2.

[0024] FIG. 7 is a scheme showing a proposed mechanism for the conversion of captured CO.sub.2 to hydrocarbons.

DETAILED DESCRIPTION

[0025] Reference will now be made in detail to certain aspects of the disclosed subject matter, examples of which are illustrated in part in the accompanying drawings. While the disclosed subject matter will be described in conjunction with the enumerated claims, it will be understood that the exemplified subject matter is not intended to limit the claims to the disclosed subject matter.

[0026] Current direct air capture (DAC) approaches require a significant amount of energy for heating CO.sub.2-sorbed materials for regeneration and for compressing CO.sub.2 for transportation purposes. Rationally designing materials offering both capture and conversion functionalities can lead to more energy- and cost-efficient direct air capture and conversion. The instant disclosure provides a single sorbent-catalytic (non-noble metal) material that can be used for the Integrated Direct Air Capture and CATalytic (iDAC-CAT) conversion of captured CO.sub.2 into value-added products.

[0027] Given the increasing CO.sub.2 concentration in the atmosphere, rapid and massive deployment of negative emission technologies (NETs) will be needed to limit global temperature increase to 1.5-2 C. In general, NETs should be large enough to remove several gross tons (Gt) of CO.sub.2 from the atmosphere and in this context, direct air capture is expected to complement other NET options. A variety of sorbents have been investigated for CO.sub.2 capture, including physisorbents such as metal-organic frameworks, zeolites, and activated carbon, as well as chemisorbents such as amine-functionalized adsorbents that commonly contain polyamines. Particularly, chemisorbents are suited for CO.sub.2 capture from ultra-dilute sources such as air due to strong chemical interactions between CO.sub.2 and sorbents. As a result, chemisorbents are the subject of understanding and improving their CO.sub.2 adsorption and desorption processes. However, the economic feasibility of large-scale deployment of current direct air capture systems is uncertain due to high energy input needed for the desorption process (cost estimates are $200-1000/ton CO.sub.2 for direct air capture compared to $36-53/ton CO.sub.2 for coal-derived flue gas). Currently, there are no commercially relevant technologies that can economically produce either value-added fuels and chemicals, or solid products for storage using CO.sub.2 captured from air.

[0028] The CO.sub.2 capture and CO.sub.2 conversion has long been viewed as two independent processes. The direct conversion of captured CO.sub.2 into value-added products (coupled approach) is superior to traditional decoupled CO.sub.2 capture and CO.sub.2 conversion because the coupled approach avoids the energy-intensive sorbent regeneration (CO.sub.2 desorption), compression and transportation steps. New reactive pathways for the CO.sub.2 conversion can be realized in the capture media, leading to higher conversion, selectivity, and reduced cost. For example, typical gas-phase CO.sub.2 hydrogenation to methanol requires high temperatures due to slower kinetics. At high temperature, a competing reactionthe reverse water gas shift reactionis also favored, which reduces the selectivity and consumes valuable H.sub.2. On the other hand, in the amine-based capture medium, CO.sub.2 hydrogenation to methanol followed a nontraditional route for conversion to methanol through a formamide intermediate. This nontraditional low-temperature methanol synthesis route was made possible by the presence of an amine-based capture medium. However, amine-based aqueous/non-aqueous solvents are not suitable for direct air capture application due to high volatility, viscosity, and evaporative loss of water under realistic direct air capture conditions. For direct air capture, solid sorbents have several benefits (over well-studied liquid sorbents) such as increased adsorption capacities, lower regeneration energy penalties, relative ease of handling, and improved recyclability.

[0029] Though the feasibility of integrating capture and conversion processes has been shown with liquid systems, the material design principles are not transferable to solids because unlike liquid systems, the sorbent and catalyst need to be integrated into a single multifunctional material in solids. The solid-state iDAC-CAT approach is limited by the lack of design parameters for this multifunctional material with the cooperative sorbent and catalytic features to perform both capture and conversion. In traditional direct air capture approaches, solid or liquid sorbents with low reaction enthalpy, high capture capacity, and rapid kinetics are preferred. The strong binding of CO.sub.2 via chemisorption is considered a limitation in traditional direct air capture approaches due to regeneration requirements. But in the iDAC-CAT approach, the strong binding can be favorable because the captured CO.sub.2 is undergoing chemical conversion. The strong CO.sub.2 binding can enhance the CO.sub.2 uptake kinetics, which is important for direct air capture application.

[0030] Solid materials with dual functionalities have been used for integrated CO.sub.2 capture and conversion to methane. Most of these materials are composed of sorbents (metal oxides and carbonates) and metal catalysts (such as Ru, Ni, and Rh). In a first step, the sorbent reacts with CO.sub.2 to form bi(carbonate) and in a second step, (bi)carbonate reacts with hydrogen at high temperature (>300 C.) to form methane. Most of these materials also require high temperature for capture, which is not an economical option.

[0031] In this disclosure, different combinations of catalytic components and sorbents are disclosed to develop a single material that can capture CO.sub.2 from the air at ambient conditions and then convert the captured CO.sub.2 into valuable C.sub.2 products such as olefins. Olefins are building blocks to produce fuels, plastics, paints, lubricants, and surfactants. Fe-based catalytic components were incorporated into the sorbent materials to facilitate the formation of CC bonds.

[0032] Generally, direct air capture of carbon dioxide using a carbonate sorbent is a process designed to remove CO.sub.2 directly from the atmosphere. This process begins by drawing air to the sorbent. As an example, air can be drawn in with large fans. The air, containing atmospheric concentrations of CO.sub.2, is then directed through a contactor structure housing the carbonate sorbent.

[0033] In some examples, the ambient air can be supplemented with water (liquid or vapor). Supplementing ambient air with water in direct air capture processes can significantly enhance the efficiency and effectiveness of CO.sub.2 removal. Water plays a role in the chemical reactions involved in carbonate-based direct air capture systems. When ambient air is passed through the contactor containing the carbonate sorbent, the presence of water facilitates the formation of bicarbonate, which is the key step in capturing CO.sub.2. The reaction between CO.sub.2 and the carbonate requires water to form bicarbonate. By ensuring an adequate supply of water, the reaction kinetics can be optimized, potentially increasing the rate and capacity of CO.sub.2 absorption. Additionally, maintaining proper humidity levels in the air stream can prevent the drying out of the sorbent solution, which could otherwise reduce its effectiveness. Water also plays a role in the regeneration process, where heat is applied to release the captured CO.sub.2 and regenerate the carbonate sorbent. Adding water also allows for the direct air capture system to be used in arid environments where the ambient air lacks humidity.

[0034] As the air flows through the contactor, a chemical reaction occurs between the CO.sub.2 and the carbonate solution. This reaction transforms the carbonate into bicarbonate, effectively capturing the CO.sub.2 from the air. The process can be represented by the chemical equation: CO.sub.2+H.sub.2O+CT.sub.2CO.sub.3.fwdarw.2CTHCO.sub.3. As used herein CT refers to the cation of the carbonate. Once the sorbent becomes saturated with CO.sub.2, it undergoes a regeneration process. This typically involves heating the solution, which reverses the absorption reaction and releases concentrated CO.sub.2. The regeneration reaction can be expressed as: 2CTHCO.sub.3.fwdarw.CT.sub.2CO.sub.3+H.sub.2O+CO.sub.2.

[0035] Following regeneration, the released CO.sub.2 can be captured, purified, and compressed for storage or utilization or converted by a catalyst to (C.sub.1-C.sub.10)hydrocarbons described herein. Meanwhile, the carbonate solution can is cooled and recycled back to the contactor for reuse in capturing more CO.sub.2. This process can operate continuously, with air constantly being drawn in and CO.sub.2 being captured and released.

[0036] To achieve perform direct air capture and produce the desired products, a multifunctional material for integrated direct air capture and catalytic conversion of CO.sub.2 is used. The multifunctional material includes a solid inorganic sorbent and a metal catalyst component integrated into a single material.

[0037] The solid inorganic sorbent is formed from a carbonate. The carbonate is at least 95 wt % and more commonly 100 wt % of the solid inorganic sorbent. The carbonate materials that can be used include calcium carbonate and magnesium carbonate as well as sodium carbonate, potassium carbonate, lithium carbonate, ammonium carbonate, and various transition metal carbonates.

[0038] Calcium carbonate primarily exists in two polymorphic forms: calcite and aragonite. Calcite, the more stable form at standard temperature and pressure, crystallizes in the trigonal-rhombohedral crystal system. Its structure consists of alternating layers of calcium ions and carbonate groups. Each calcium ion is coordinated with six oxygen atoms from different carbonate groups, forming a distorted octahedral arrangement. The carbonate groups are planar and oriented perpendicular to the c-axis of the crystal. This structure gives calcite its characteristic rhombohedral cleavage and optical properties.

[0039] Aragonite, the metastable polymorph of calcium carbonate, crystallizes in the orthorhombic system. In this structure, the calcium ions are coordinated with nine oxygen atoms from six different carbonate groups, resulting in a more densely packed arrangement compared to calcite. The carbonate groups in aragonite are slightly distorted from their planar configuration, contributing to the crystal's unique properties.

[0040] Magnesium carbonate, also known as magnesite, typically crystallizes in the trigonal-rhombohedral system, similar to calcite. However, the smaller size of the magnesium ion compared to calcium results in some structural differences. In magnesite, each magnesium ion is coordinated with six oxygen atoms from six different carbonate groups, forming a more regular octahedral arrangement than in calcite. The carbonate groups maintain their planar configuration and are oriented perpendicular to the c-axis of the crystal.

[0041] Both calcium and magnesium carbonates can form hydrated structures. For example, calcium carbonate can form ikaite (CaCO.sub.3.Math.6H.sub.2O) under specific conditions, while magnesium carbonate can form various hydrates such as nesquehonite (MgCO.sub.3.Math.3H.sub.2O) and lansfordite (MgCO.sub.3.Math.5H.sub.2O). These hydrated forms have more complex crystal structures due to the incorporation of water molecules into the crystal lattice.

[0042] Potassium carbonate (K.sub.2CO.sub.3) is a white, hygroscopic salt that forms strongly alkaline solutions in water. Its crystal structure belongs to the monoclinic crystal system, specifically the P21/c space group. In this structure, the potassium ions are coordinated with oxygen atoms from the carbonate groups, forming a three-dimensional network. The carbonate ions in the crystal are planar and arranged in a way that maximizes the separation between the negatively charged oxygen atoms.

[0043] In the context of direct air capture, potassium carbonate serves as an effective sorbent for CO.sub.2 removal from ambient air. When used in direct air capture systems, an aqueous solution of potassium carbonate reacts with atmospheric CO.sub.2 to form potassium bicarbonate (KHCO.sub.3). This reaction can be represented as: K.sub.2CO.sub.3+CO.sub.2+H.sub.2O.fwdarw.2KHCO.sub.3. The process is reversible, allowing for regeneration of the sorbent and release of concentrated CO.sub.2 through heating. Potassium carbonate's high solubility in water, strong alkalinity, and favorable reaction kinetics with CO.sub.2 make it a promising candidate for large-scale direct air capture applications.

[0044] The carbonate or a mixture of the aforementioned carbonates, can be supported on a porous material of mixture of porous materials. Porous materials comprising Al.sub.2O.sub.3, Carbon, SiO.sub.2, ZrO.sub.2, aluminosilicate zeolites, or mixtures thereof are a diverse group of substances with high surface area and internal void spaces. These materials are characterized by their network of interconnected pores, which can vary in size from nanometers to micrometers. Alumina (Al.sub.2O.sub.3) porous materials are widely used as catalysts and adsorbents, known for their high thermal stability and surface acidity. Porous carbon materials, such as activated carbon (AC), have favorable adsorption properties due to their high surface area and tunable pore structure. Silica (SiO.sub.2) porous materials, including mesoporous silica, are valued for their uniform pore sizes and versatility in functionalization. Zirconia (ZrO.sub.2) porous materials offer high chemical and thermal stability, making them suitable for harsh environments. Aluminosilicate zeolites are crystalline materials with well-defined pore structures, widely used in catalysis and molecular sieving. Mixtures of these materials can combine their individual properties to create porous composites with enhanced performance for specific applications, such as gas separation, water purification, or heterogeneous catalysis.

[0045] The pore size and structure of these materials significantly influence their performance for CO.sub.2 capture. Smaller pore sizes, typically in the microporous range (less than 2 nm), are generally more effective for CO.sub.2 adsorption due to stronger interactions between the gas molecules and the pore walls. However, excessively small pores can limit diffusion and accessibility, reducing overall capture efficiency.

[0046] Mesoporous materials (pore sizes 2-50 nm) often provide a balance between adsorption capacity and diffusion kinetics. They allow for faster mass transfer of CO.sub.2 molecules while still maintaining a high surface area for adsorption. The interconnectivity of pores is also crucial, as it affects the accessibility of internal surfaces and the overall capture kinetics.

[0047] The pore structure's uniformity can impact selectivity for CO.sub.2 over other gases. Well-defined pore structures, such as those in zeolites, can act as molecular sieves, preferentially adsorbing CO.sub.2 based on size exclusion principles.

[0048] The metal catalyst is used to synthesize the (C.sub.1-C.sub.10)hydrocarbyl. The metal catalyst can include iron, cobalt, copper, manganese or any combination of oxides thereof. These transition metals are useful as catalysts because of their ability to form multiple oxidation states, coordinate and activate CO.sub.2, H.sub.2 and bicarbonates through their vacant d-orbitals, and stabilize CO.sub.2-derived intermediates. The catalytic process, generally, includes several steps. First, the metal catalyst activates CO.sub.2 by weakening its CO bonds, making the carbon more reactive. Next, the activated CO.sub.2 undergoes reduction, often through electron transfer from the metal catalyst or a reducing agent. Finally, the reduced carbon species couple with another activated carbon to form a CC bond. The specific mechanisms vary depending on the metal and reaction conditions. For instance, iron catalysts often operate through a Fischer-Tropsch-like process, while cobalt catalysts can facilitate reductive dimerization of CO.sub.2 to form oxalate intermediates. Copper catalysts are known for reducing CO.sub.2 to hydrocarbons and alcohols, with CC bond formation occurring through coupling of intermediate species. Manganese complexes have demonstrated the ability to catalyze the reductive coupling of CO.sub.2 to form oxalate and other C2 products. The efficiency and selectivity of these processes can be influenced by factors such as the metal's oxidation state, ligand environment, reaction conditions, and the presence of co-catalysts or promoters. The metal catalyst particles can range from about 2 wt % to about 50 wt % of the material, 20 wt % to about 30 wt %, less than, equal to, or greater than about 2 wt %, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 wt %.

[0049] Captured CO.sub.2 are converted to (C.sub.1-C.sub.10)hydrocarbyl products upon hydrogenation. Suitable examples of (C.sub.1-C.sub.10) hydrocarbyl products include olefins, paraffins, or both. C.sub.1-C.sub.10 olefins and paraffins are important classes of hydrocarbons widely used, for example, in the petrochemical industry. Olefins, also known as alkenes, are unsaturated hydrocarbons containing at least one carbon-carbon double bond. Examples include ethylene (C.sub.2) to decene (C.sub.10), with examples including propylene, butene, and pentene. These compounds are highly reactive due to their double bond, making them valuable feedstocks for producing plastics, synthetic rubbers, and other chemical products.

[0050] Paraffins, also called alkanes, are saturated hydrocarbons with single bonds between carbon atoms. Examples include methane (C.sub.1) to decane (C.sub.10), including compounds like ethane, propane, and butane. Paraffins are less reactive than olefins and are commonly used as fuels, solvents, and in the production of various petrochemicals.

[0051] The material described herein is capable of a high degree of selectivity in the products formed. For example, the material is capable of converting captured CO.sub.2 to (C.sub.1-C.sub.10)hydrocarbyls with a selectivity of at least 10% for C.sub.2-C.sub.4 olefins or paraffins, at least 15%, at least 20%, at least, 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95% for C.sub.2-C.sub.4 olefins or paraffins.

[0052] The disclosed material is capable of converting captured CO.sub.2 to (C.sub.1-C.sub.10)hydrocarbyls at temperatures in a range of from about 250 C. to about 400 C., 330 C. to about 360 C., less than, equal to, or greater than about 250 C., 260, 265, 270, 275, 280, 285, 290, 295, 300, 305, 310, 315, 320, 325, 330, 335, 340, 345, 350, 355, 360, 365, 370, 375, 380, 385, 390, 395, or about 400 C. The concentration of CO.sub.2 in the air contacted with the material can range from about 350 ppm CO.sub.2 to about 1000 ppm CO.sub.2, about 500 ppm CO.sub.2 to about 800 ppm CO.sub.2, less than, equal to, or greater than about, 350 ppm CO.sub.2, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650, 660, 670, 680, 690, 700, 710, 720, 730, 740, 750, 760, 770, 780, 790, 800, 810, 820, 830, 840, 850, 860, 870, 880, 890, 900, 910, 920, 930, 940, 950, 960, 970, 980, 990, or about 1000 ppm CO.sub.2. Additionally, the material is capable of capturing CO.sub.2 from concentrated sources containing about 1 vol % CO.sub.2 to about 30 vol % CO.sub.2, about 5 vol % CO.sub.2 to about 20 vol % CO.sub.2, less than, equal to, or greater than about 1 vol % CO.sub.2, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or about 30 vol % CO.sub.2. The material can have a CO.sub.2 capture capacity in a range of from about 1.5 wt % to about 25 wt %, about 5 wt % to about 20 wt %, less than, equal to, or greater than about 1.5 wt %, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5, 24, 24.5, or about 25 wt % at temperatures in a range of from about ambient temperatures to about 150 C. in the presence of water vapor. Ambient air temperature refers to the temperature of the surrounding air in a given environment, typically measured outdoors and away from direct heat sources. It represents the general temperature conditions of the atmosphere at a specific location and time.

[0053] As demonstrated further in the Examples section, a particularly suitable construction is a potassium carbonate sorbent disposed on an aluminum oxide scaffold having iron particles impregnated thereon. The material can be represented by the formula: Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3.

Examples

[0054] Various aspects of the present disclosure can be better understood by reference to the following Examples which are offered by way of illustration. The present disclosure is not limited to the Examples given herein.

CO.sub.2 Capture Studies Using K.sub.2CO.sub.3/Al.sub.2O.sub.3

[0055] Inorganic chemisorbents are chosen for this because they are more durable and low-cost materials compared to amine-based sorbents for direct air capture. The commonly used inorganic chemisorbents for direct air capture are CaO, MgO, and alkali metal carbonates. Among these sorbents, alkali metal carbonates can perform capture at ambient temperature. To increase the carbonation rate of alkali carbonates, they are usually dispersed on high-surface-area materials such as alumina, Al.sub.2O.sub.3. In this Example, 25 wt % of K.sub.2CO.sub.3/Al.sub.2O.sub.3 was synthesized, characterized, and evaluated at 25 C. at different capture conditions to identify suitable conditions for direct air capture. As-synthesized K.sub.2CO.sub.3/Al.sub.2O.sub.3 was characterized by BET analysis. Type IV isotherms with a characteristic hysteresis loop for both Al.sub.2O.sub.3 and K.sub.2CO.sub.3/Al.sub.2O.sub.3 were realized in the BET analysis, indicating that alumina is mesoporous in nature. Impregnation of K.sub.2CO.sub.3 over alumina resulted in a decrease in both surface area and pore volume of the original support, but the average pore sizes were almost comparable. This implies that smaller sizes of K.sub.2CO.sub.3 filled the pores of the mesoporous alumina, confirming the dispersion of K.sub.2CO.sub.3 over the alumina surface.

[0056] The effect of pretreatment conditions and water vapor content on the capture performance of the sorbent was studied. The K.sub.2CO.sub.3/Al.sub.2O.sub.3 sorbent was first pretreated at 200 C. for 1 h under N.sub.2 flow (100 mL/min.). The material was then cooled to room temperature and pre-saturated with both 0.5 and 1.0 mol % H.sub.2O vapor, followed by introduction of 400 ppm of CO.sub.2. The amount of CO.sub.2/g of sorbent adsorbed during both the experiments was calculated from the molar flow concentration profile of CO.sub.2 versus time. For 0.5 mol % of H.sub.2O, 850 mmol/g of CO.sub.2 was adsorbed, whereas in the case of 1 mol % of H.sub.2O, 770 mmol/g of CO.sub.2 was adsorbed, showing that the 0.5 mol % of H.sub.2O had a slightly higher adsorption capacity.

[0057] Next, CO.sub.2 was co-fed with 0.5 mol % H.sub.2O vapor over the pretreated K.sub.2CO.sub.3/Al.sub.2O.sub.3 and compared with the pre-saturated sample. The water vapor co-fed sample shows the highest sorption capacity of 6.5 wt % compared to the water vapor pretreated samples, which is also visible from the area under the curve for the water vapor co-fed and pretreated. The amount of CO.sub.2 adsorbed by the 25 wt % K.sub.2CO.sub.3/Al.sub.2O.sub.3 sorbent is 6.5 wt % higher than the amount reported in the literature, which are 3.6 wt % for K.sub.2CO.sub.3/Al.sub.2O.sub.3 and 4.1 wt % for K.sub.2CO.sub.3/Al.sub.2O.sub.3-700 (Al.sub.2O.sub.3 heated at 700 C. before K.sub.2CO.sub.3 impregnation).

[0058] X-ray diffraction (XRD) analysis shows the change in phase composition of the K.sub.2CO.sub.3/Al.sub.2O.sub.3 before and after air capture at r.t in the presence of water vapor. For fresh K.sub.2CO.sub.3/Al.sub.2O.sub.3, the main diffraction peaks were attributed to dawsonite, KAlCO.sub.3(OH).sub.2, K.sub.2CO.sub.3, and g-Al.sub.2O.sub.3. The formation of the dawsonite on the fresh samples takes place due to the exposure of as-synthesized K.sub.2CO.sub.3/Al.sub.2O.sub.3 to air. This agrees with the TPD of the fresh material, where the peak at 350 C. is due to the decomposition of the dawsonite.

[0059] Thermal decomposition of the air-captured K.sub.2CO.sub.3 using TPD shows two characteristic peaks within 100-200 C., which is likely due to the decomposition of the species containing bicarbonate, K.sub.2CO.sub.3.Math.2KHCO.sub.3.Math.1.5H.sub.2O, and KHCO.sub.3. This agrees with the XRD diffraction patterns of the air-captured sorbent. The higher-temperature peak is mainly due to the decomposition of the KAlCO.sub.3(OH).sub.2, which was reported to take place between 26 and 320 C.

[0060] K.sub.2CO.sub.3/AC was also synthesized and tested for CO.sub.2 capture because activated carbon was also known to be a suitable support material. Compared to K.sub.2CO.sub.3/Al.sub.2O.sub.3, the capture capacity of K.sub.2CO.sub.3/AC was 1.3 times lower. Due to the superior capture performance of K.sub.2CO.sub.3/Al.sub.2O.sub.3 under the optimized reaction conditions, it was chosen as the sorbent material for the integrated capture and conversion studies.

Conversion of Captured CO.sub.2 to C.sub.1 and C.sub.2Products

[0061] The direct conversion of captured CO.sub.2 from air or concentrated point sources to C.sub.1 products such as methane, methanol, and CO has been demonstrated. However, due to the high energy barrier of CC coupling reactions, conversion of captured CO.sub.2 to C.sub.2+ products is still a challenge. Combining the endothermic reverse water gas shift (CO.sub.2+H.sub.2.fwdarw.CO+H.sub.2O) reaction with the exothermic Fischer-Tropsch (CO+H.sub.2.fwdarw.C.sub.xH.sub.y) reaction has been identified as one of the strategies for converting concentrated streams of CO.sub.2 and H.sub.2 in the gas phase to C.sub.2+ products. Particularly, potassium (alkali metal) modified Fe-based catalysts are known to promote carbon-chain growth in the gas-phase CO.sub.2 hydrogenation reaction. It was hypothesized that by combining the Fe-based catalysts and potassium-based sorbents, the captured CO.sub.2 can be directly converted to C.sub.2+ products, bypassing the energy-intensive CO.sub.2 regeneration and compression steps. To test this, different combinations of iron and K.sub.2CO.sub.3/Al.sub.2O.sub.3 based sorbent-catalytic materials were synthesized and evaluated the capture and conversion performance of these synthesized materials.

A) Fe.sub.2O.sub.3K.sub.2CO.sub.3/Al.sub.2O.sub.3

[0062] A physical mixture of Fe.sub.2O.sub.3 and K.sub.2CO.sub.3 has been demonstrated to be effective at converting CO.sub.2 into C.sub.2-C.sub.4 olefins with a selectivity of about 31% via a tandem mechanism. The addition of K.sub.2CO.sub.3 is used for promoting the formation of CO (via potassium bicarbonate and potassium formate intermediates), which gets converted to olefins and paraffins in the presence of iron oxide and iron carbide phases at 350 C. Based on this, a physical mixture of Fe.sub.2O.sub.3K.sub.2CO.sub.3/Al.sub.2O.sub.3 (Fe.sub.2O.sub.3-KA). The Fe.sub.2O.sub.3-KA was prepared and pretreated at 400 C. under H.sub.2 flow (100 mL/min) for 1 h to convert Fe.sub.2O.sub.3 to Fe nanoparticles. CO.sub.2 capture was performed using 400 ppm of CO.sub.2 (1200 mL/min) with 0.5 mol % of H.sub.2O at 25 C. The capture performance was compared with K.sub.2CO.sub.3/Al.sub.2O.sub.3, which was activated under similar conditions. Under this condition, 100% of the K.sub.2CO.sub.3 was utilized during CO.sub.2 capture in the case of K.sub.2CO.sub.3/Al.sub.2O.sub.3, whereas in the case of Fe.sub.2O.sub.3K.sub.2CO.sub.3/Al.sub.2O.sub.3, only 81% of the K.sub.2CO.sub.3 was utilized in CO.sub.2 capture. High-temperature pretreatment enhanced the capture capacity through the dawsonite decomposition reaction. Then, hydrogenation of the captured CO.sub.2 was performed under hydrogen pressure of 145 psi at 320 C. (hold for 2.5 h) and 360 C. (hold for 2 h) at a ramp rate of 5 C./min under H.sub.2 flow (60 mL/min). This resulted in desorption of CO.sub.2 with no detectable amount of hydrogenated CO.sub.2-derived products. Most of the CO.sub.2 was released at 320 C., suggesting that dawsonite is the major species formed during CO.sub.2 capture.

B) K.sub.2CO.sub.3Fe/C and K.sub.2CO.sub.3Fe/C/Al.sub.2O.sub.3

[0063] The use of potassium-promoter-modified Fe/C catalysts can increase olefin selectivity in CO.sub.2 hydrogenation. Fe/C was synthesized by the hydrothermal method. K.sub.2CO.sub.3/Fe/C was formed by impregnating K.sub.2CO.sub.3 (25 wt %) on the Fe/C catalyst. The synthesized material was pretreated at 400 C. under H.sub.2 flow for 10 h to ensure carbide formation before CO.sub.2 capture and conversion studies. CO.sub.2 capture was performed by following a standard capture procedure. The capture profile is shown in FIG. 1A. In the first 50 min, there was an induction period after which the CO.sub.2 capture breakpoint started. The initial delay could either be due to physical adsorption of the CO.sub.2 occupying the macropores of the materials or because the material surface was not immediately saturated with water vapor, which is necessary to start the carbonation reaction. The total CO.sub.2 captured in 4 hours by this material typically ranges between 600 and 700 mmol/g, which is 2 times lower than that of K.sub.2CO.sub.3/Al.sub.2O.sub.3(Table 1). The reduction of the captured CO.sub.2 was carried out under H.sub.2 flow of 60 mL/min under four different conditions: (1) heating rate of 5 C./min to 320 C. (hold for 2.5 h) and 360 C. (hold for 2 h) at 145 psi, (2) heating rate of 20 C./min to 320 C. (hold for 2.5 h) and 360 C. (hold for 2 h) at 145 psi, (3) heating rate of 5 C./min to 320 C. (hold for 2.5 h) and 360 C. (hold for 2 h) at 73 psi, and (4) heating rate of 5 C./min to 320 C. (hold for 2.5 h) and 360 C. (hold for 2 h) at 289 psi. FIG. 1B shows the hydrogenation results of the captured CO.sub.2. With the increase in temperature, some unreacted CO.sub.2 started to desorb. Along with CO.sub.2, CH.sub.4 also formed and was the highest when the temperature reached 320 C. C.sub.2H.sub.4 and C.sub.2H.sub.6 were also produced at Region 1 (at 320 C., 2.5 h). Further increasing the temperature to 360 C. resulted in additional CH.sub.4 production along with small amounts of ethylene and ethane. There were no detectable amounts of higher olefins or paraffins formed. Increasing the heating rate from 5 to 20 C./min increased the overall conversion of CO.sub.2 to methane along with a slight increase in olefin selectivity (2%) at 320 C. The profile for the time-dependent conversion and yield of products is shown in FIG. 1B. With additional increase in the temperature to 360 C., 74% of the total captured CO.sub.2 was converted to C.sub.1 and C.sub.2 products with 94.4% selectivity to methane, 4.2% selectivity to ethane, and 1.4% selectivity to ethene. This is the first demonstration of the conversion of captured CO.sub.2 (air derived) to C.sub.1 and C.sub.2 based products in the presence of an Fe-based catalyst. Besides the formation of olefins, which are the target products, the production of renewable methane from the captured 400 ppm CO.sub.2 is also a great advantage. This can contribute to an alternative for natural gas, and its direct use in existing infrastructure could result in a lower carbon footprint. Varying the hydrogen pressure for the conversion further improved the selectivity to methane with a decrease in the conversion of the captured CO.sub.2 (FIGS. 1C and 1D).

[0064] A decrease in CO.sub.2 capture with K.sub.2CO.sub.3/Fe/C compared to K.sub.2CO.sub.3/Al.sub.2O.sub.3 is likely due to the smaller surface area of Fe/C (33.16 m.sup.2/g), which results in larger K.sub.2CO.sub.3 particles (Table 1). Lower CO.sub.2 loading could inhibit CC bond formation because there are fewer carbons. To increase the surface area and eventually improve the capture performance, K.sub.2CO.sub.3/Fe/C/Al.sub.2O.sub.3 was synthesized via the wet impregnation method and the adsorption capacity was compared with that of K.sub.2CO.sub.3/Al.sub.2O.sub.3 and K.sub.2CO.sub.3/Fe/C under similar capture conditions. The capture performance was significantly improved after the addition of Al.sub.2O.sub.3. The K.sub.2CO.sub.3/Fe/C/Al.sub.2O.sub.3 captured 1220 mmol/g of CO.sub.2 (vs. 600-700 mmol/g of CO.sub.2 for K.sub.2CO.sub.3/Fe/C) (FIG. 2A). This difference can be explained from the BET results of the support over which K.sub.2CO.sub.3 was impregnated. The BET isotherms of three materials are shown in FIG. 3A. As discussed earlier, dispersion of K.sub.2CO.sub.3 on Al.sub.2O.sub.3 retained the mesoporosity of the support and showed a type IV isotherm despite a decrease in the surface area as shown in Table 1.

[0065] The isotherm of Fe/C is a type II isotherm with no pronounced hysteresis loop, showing that the material is either non-porous or macroporous. The surface area is very low compared to the Al.sub.2O.sub.3 support and has no pores, as shown in Table 1. Therefore, the impregnation of K.sub.2CO.sub.3 could have formed larger particles on Fe/C, leading to lower CO.sub.2 capture. Due to the presence of the Al.sub.2O.sub.3 pores, K.sub.2CO.sub.3 was well dispersed over a mixture of high-surface-area, mesoporous Al.sub.2O.sub.3 and non-porous Fe/C. This led to higher CO.sub.2 capture for K.sub.2CO.sub.3/Fe/C/Al.sub.2O.sub.3 compared to only K.sub.2CO.sub.3/Fe/C, as shown in Table 1.

TABLE-US-00001 TABLE 1 Characterizations of the materials from the N.sub.2 adsorption isotherm. Catalytic Activity Physical Properties C.sub.2-C.sub.4 C.sub.2-C.sub.4 Average CO.sub.2 CH.sub.4 Paraffins Olefins C.sub.5+ SA PV Diameter CO.sub.2 Capture Conv. Sel Sel Sel Sel Materials (m.sup.2/g) (cm.sup.3/g) (nm) (mol/g) (wt %) (%) (%) (%) (%) (%) Fe/C 33.16 0.4008 N/A N/A N/A N/A N/A N/A N/A N/A Al.sub.2O.sub.3 182.4 0.6001 11.4 N/A N/A N/A N/A N/A N/A N/A K.sub.2CO.sub.3/Al.sub.2O.sub.3 99.19 0.3262 10.09 1862 8.2 N/A N/A N/A N/A N/A K.sub.2CO.sub.3/Fe/C .sup.a 600-700 2.6-3.1 30.0 96.8 2.2 1.0 0.0 K.sub.2CO.sub.3/Fe/C .sup.b 41.4 93.9 4.1 2.0 0.0 K.sub.2CO.sub.3/Fe/C/ 29.23 0.2476 8.95 1223 5.4 30.5 83.2 8.6 7.3 0.9 Al.sub.2O.sub.3 .sup.a .sup.a Heating rate at 5 C./min during hydrogenation of captured CO.sub.2, .sup.b heating rate of 20 C./min Pretreatment: H.sub.2 60 mL/min, 400 C., 5 h CO.sub.2 capture: CO.sub.2 400 ppm, 1200 mL/min, H.sub.2O vapor 0.5 mol %, 25 C., 4 h Conversion and selectivity at 320 C. under H.sub.2 flow (60 mL/min) and 145 psi

[0066] With the improvement in the capture performance, the CO.sub.2 captured in K.sub.2CO.sub.3/Fe/C/Al.sub.2O.sub.3 was hydrogenated in situ (FIG. 2B shows the hydrogenation profile of captured CO.sub.2). A comparison of the hydrogenation activities of the K.sub.2CO.sub.3/Fe/C and K.sub.2CO.sub.3/Fe/C/Al.sub.2O.sub.3 is shown in Table 1. Interestingly, the C.sub.2-C.sub.4 olefin selectivity significantly improved to 7.3% in the case of K.sub.2CO.sub.3/Fe/C/Al.sub.2O.sub.3. The improved CC coupled products formation could be because of the relatively high CO.sub.2 loading. In addition, a small amount of C.sub.5+ products (1%) was also detected. Increasing the hydrogenation temperature to 360 C. only improved the conversion and selectivity further to methane. Increased methane formation at higher temperature could be due to less carbon (i.e., captured CO.sub.2) content on the material, which could prevent CC formation.

C) Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3 and FeCO/K.sub.2CO.sub.3/Al.sub.2O.sub.3

[0067] Because the physical mixture of Fe.sub.2O.sub.3K.sub.2CO.sub.3/Al.sub.2O.sub.3 formed no CO.sub.2 hydrogenation products, we prepared Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3 (Fe/KA) and FeCOK.sub.2CO.sub.3/Al.sub.2O.sub.3 (FeCO/KA) (by incipient wetness impregnation of Fe and/or Co salts on K.sub.2CO.sub.3/Al.sub.2O.sub.3) to improve the cooperativity between Fe and K to produce CC products. After pretreating these materials at 400 C. for 5 h under H.sub.2 flow, the CO.sub.2 capture was performed under standard conditions (400 ppm of CO.sub.2, 0.5 mol % of H.sub.2O, 25 C., 4 h). The FeCO/KA captured 1970 mmol/g of CO.sub.2, which is almost similar to K.sub.2CO.sub.3/Al.sub.2O.sub.3 (pretreated at 400 C.), showing that the addition of the catalytic component had no impact on the capture performance. Hydrogenation of the captured CO.sub.2 using FeCO/KA was carried out at two different temperature ramp rates, 5 and 20 C./min. Increasing the heating rate decreased the CO.sub.2 conversion to value-added products with no significant impact on product distribution, as shown in Table 2.

TABLE-US-00002 TABLE 2 Comparison of CO.sub.2 capture and conversion for FeCo/ K.sub.2CO.sub.3/Al.sub.2O.sub.3 and Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3 at 320 C. Heating Rate CO.sub.2 CO.sub.2 C.sub.2-C.sub.4 C.sub.2-C.sub.4 ( C./ Captured Conv. CH.sub.4 Paraffins Olefins min) (mmol/g) (%) Sel(%) Sel (%) Sel (%) FeCo/ 5 1970 21.3 88.3 5.1 6.7 KA 20 1970 12.0 86.8 8.3 4.9 Fe/KA 5 1645 22.4 79.7 8.9 11.4

[0068] The Fe/KA captured 1700 mmol/g of CO.sub.2 at our standard capture conditions. The hydrogenation results are shown in FIG. 4A and Table 2. At 320 C., C.sub.2-C.sub.4 olefins and paraffins started forming accompanied with the formation of CH.sub.4. The highest olefin selectivity of 11.4% was obtained with a CO.sub.2 conversion of 22.4%. The BET isotherm shows that the mesoporosity of the K.sub.2CO.sub.3/Al.sub.2O.sub.3 is still maintained after impregnation of Fe particles (FIG. 4B). Upon impregnating Fe, the surface area decreased from 99.19 (for K.sub.2CO.sub.3/Al.sub.2O.sub.3) to 36.83 m.sup.2/g and the diameter of the mesopores decreased to 6.79 nm, confirming the formation of Fe particles inside the mesopores (FIG. 4D). The average pore size of the spent Fe/KA material (after hydrogenation) increased compared to the fresh material along with slight increase in the pore volume and surface area. This shows that after the hydrogenation, more dispersed particles were formed. This could be due to the formation of Fe.sub.5C.sub.2 and Fe.sub.3O.sub.4 particles during the high-temperature hydrogenation.

[0069] FIG. 4C shows wide-angle XRD of the freshly captured CO.sub.2 and spent Fe/KA. In the fresh sample, diffraction peaks corresponding to KNO.sub.3, dawsonite, and Fe.sub.2O.sub.3 particles were evident. The fresh sample was pretreated at 400 C. under pure H.sub.2 flow for 5 h before air capture in the presence of water vapor. XRD of the CO.sub.2-captured Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3 material shows peaks for KHCO.sub.3 and dawsonite along with some Fe.sub.2O.sub.3 and Fe particles. The Fe particles could form from Fe.sub.2O.sub.3 due to hydrogenation with H.sub.2 at high temperature. The spent (after hydrogenation) Fe/KA shows peaks for Fe.sub.5C.sub.2 along with Fe.sub.3O.sub.4, which were formed during hydrogenation of the captured CO.sub.2. The formation of these dispersed particles resulted in an increase of pore volume and of the average pore size of the material. The formation of the Fe.sub.5C.sub.2 phase shows the carburization of Fe.sub.3O.sub.4 particles.

[0070] The spent Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3 after the first cycle of capture and hydrogenation was reused to study the robustness of these materials. The capture capacity was reduced in the second cycle to 1276 mmol/g (5.6 wt CO.sub.2%) compared to 1645 mol/g (7.4 wt CO.sub.2%) in the first cycle. However, the capture performance was steady in the subsequent third (5.4 wt %), fourth (5.6 wt %), and fifth (5.03 wt %) cycles. The drop in the capture capacity could be because of the presence of K.sub.2O in the fresh Fe/KA, which consumed CO.sub.2 from air to form K.sub.2CO.sub.3. A similar drop in the capture capacity was observed between the first (6.5 wt % CO.sub.2) and second cycles (5.3 wt % CO.sub.2) for K.sub.2CO.sub.3/Al.sub.2O.sub.3(Table S3). However, in this case (K.sub.2CO.sub.3/Al.sub.2O.sub.3), the drop in performance could be because the low-temperature pretreatment conditions (at 200 C. for 1 h) prevented the conversion of dawsonite back to K.sub.2CO.sub.3. Before hydrogenation during the fifth cycle, the CO.sub.2-captured material was purged with N.sub.2 flow for 1 h to quantify physiosorbed CO.sub.2 content. Only trace amounts of CO.sub.2 were released during the N.sub.2 purge, and subsequent hydrogenation showed consistent conversion and selectivity to products, demonstrating that the material is stable for at least five cycles.

[0071] To understand the effect of the CO.sub.2-to-H.sub.2 ratio and reaction temperature on the product distribution and conversion, the gas-phase hydrogenation studies were performed with Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3 using 1:3 and 1:10 ratios of CO.sub.2:H.sub.2. The conversion results for the Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3 at 320 C. and 360 C. are shown in FIG. 6 and Tables 3 and 4. At 320 C., in the case of the 1:10 ratio of CO.sub.2/H.sub.2, the selectivity to C.sub.2-C.sub.4 paraffins was very high compared to direct air capture and 1:3 ratio of CO.sub.2/H.sub.2 studies. The selectivity to C.sub.2-C.sub.4 olefins was not significantly altered by the CO.sub.2/H.sub.2 ratio. In addition to C.sub.1-4 products, C.sub.5+ products were detected by gas chromatography. The reaction temperature played a significant role in hydrogenation product selectivity and CO.sub.2 conversion. The CO.sub.2 conversion was 75% and 51% for 1:10 and 1:3 ratios of CO.sub.2/H.sub.2, respectively, at 360 C. (Table 4). High olefin selectivities (>50%) and O/P (olefin/paraffin) ratios (10) were achieved for a 1:3 ratio of CO.sub.2/H.sub.2 at 360 C.

TABLE-US-00003 TABLE 3 Comparison of hydrogenation of captured CO.sub.2 with gas-phase CO.sub.2 at 320 C. over Fe/KA. CO.sub.2 CH.sub.4 C2-C4 C2-C4 C5+ C5+ Conv. Sel Paraffins Olefins Olefins Paraffins O/P (%) (%) Sel (%) Sel (%) (Sel %) (Sel %) Ratio DAC 22.4 79.7 8.9 11.4 0.0 0.0 1.3 1:10 34.5 34.0 38.0 19.9 8.17 0.0 0.5 1:3 27.1 71.3 7.88 16.9 3.84 0.15 2.1

[0072] The XRD spectra of the spent direct air capture and gas-phase CO.sub.2 hydrogenation materials are shown in FIG. 6C. Fe.sub.3O.sub.4 was observed in all spent materials. The Fe.sub.5C.sub.2 diffraction patterns are more pronounced for the 1:3 CO.sub.2/H.sub.2 reaction compared to the 1:10 CO.sub.2/H.sub.2 reaction. This agrees with the decreased CH.sub.4 selectivity and increased O/P ratio of the 1:3 CO.sub.2/H.sub.2 reaction because both Fe.sub.3O.sub.4 (for the RWGS) and Fe.sub.5C.sub.2 are important for CC formation. Peaks for Fe were also observed in the spent direct air capture material, showing that not all the Fe.sub.2O.sub.3 was converted to Fe for carburization. The formation of the carbide-phase reaction route is as follows: Fe.sub.2O.sub.3.fwdarw.Fe.sub.3O.sub.4.fwdarw.FeO.fwdarw.Fe, and then finally the Fe is carburized to Fe.sub.5C.sub.2.

TABLE-US-00004 TABLE 4 Comparison of hydrogenation of gas- phase CO.sub.2 at 360 C. over Fe/KA. CO.sub.2 CH.sub.4 C2-C4 C2-C4 C5+ C5+ Conv. Sel Paraffins Olefins Olefins Paraffins O/P (%) (%) Sel (%) Sel (%) (Sel %) (Sel %) Ratio 1:10 74.7 49.2 11.8 32.8 5.74 0.0 2.78 1:3 50.9 37.1 5.16 50.9 2.96 1.33 9.86

[0073] The Fourier transform infrared spectroscopy (FTIR) spectrum of the spent direct air capture and gas-phase CO.sub.2 hydrogenation materials were compared. The CH vibrations were seen between 2960-2627 cm.sup.1 corresponding to formate and other bound CH species. The carbonyl vibration of formate was observed at the 1631 cm.sup.1 region. The FeCO interactions were visible in the 1800-2100 cm.sup.1 region, which corresponds to bound CO with different forms of Fe. In addition to formate and CO, there are additional bands visible for carbonates and bicarbonates in the infrared spectrum.

[0074] Based on the selectivity of the products and the XRD and FTIR of the spent samples, the conversion of captured CO.sub.2 to olefins occurs via the direct CO.sub.2 conversion pathway, where the CO.sub.2 is converted to CO via RWGS in the presence of Fe.sub.3O.sub.4. The CO is then converted to olefins following the FTS mechanism in the presence of Fe.sub.5C.sub.2. A proposed pathway has been shown in the scheme of FIG. 7.

[0075] When CO.sub.2 is captured (400 ppm) in the presence of water vapor at room temperature, the K.sub.2CO.sub.3 of Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3 transforms to KHCO.sub.3 and KAlCO.sub.3(OH).sub.2, which forms HCOOK and CO upon hydrogenation catalyzed by Fe.sub.3O.sub.4/K.sub.2CO.sub.3/Al.sub.2O.sub.3. The Fe.sub.3O.sub.4/K.sub.2CO.sub.3/Al.sub.2O.sub.3 is formed from Fe.sub.2O.sub.3/K.sub.2CO.sub.3/Al.sub.2O.sub.3 in the presence of H.sub.2. The Fe.sub.3O.sub.4/K.sub.2CO.sub.3/Al.sub.2O.sub.3 helps further convert CO to *CH species, which undergo CC coupling in the presence of Fe.sub.5C.sub.2 formed in situ during the reaction. From our experimental work, we show that the proximity between the Fe and K on the Al.sub.2O.sub.3 is important for CO.sub.2 activation and conversion to CC products.

[0076] The terms and expressions that have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the aspects of the present disclosure. Thus, it should be understood that although the present disclosure has been specifically disclosed by specific aspects and optional features, modification and variation of the concepts herein disclosed may be resorted to by those of ordinary skill in the art, and that such modifications and variations are considered to be within the scope of aspects of the present disclosure.

Exemplary Aspects.

[0077] The following exemplary aspects are provided, the numbering of which is not to be construed as designating levels of importance:

[0078] Aspect 1 provides a multifunctional material for integrated capture and catalytic conversion of CO.sub.2, comprising: [0079] a solid inorganic sorbent; and [0080] a metal catalyst component, [0081] wherein the solid inorganic sorbent and metal catalyst component are integrated into a single material.

[0082] Aspect 2 provides the material of Aspect 1, wherein the solid inorganic sorbent comprises a carbonate.

[0083] Aspect 3 provides the material of any of Aspects 1 or 2, wherein the metal catalyst component comprises iron, cobalt, copper, manganese or any combination of oxides thereof.

[0084] Aspect 4 provides the material of any of Aspects 1-3, wherein the solid inorganic sorbent comprises group 1 metal carbonates, wherein the solid inorganic sorbent comprises a group 1 metal carbonate comprising K.sub.2CO.sub.3, Na.sub.2CO.sub.3, Li.sub.2CO.sub.3, or a mixture thereof, supported on porous materials comprising Al.sub.2O.sub.3, Carbon, SiO.sub.2 ZrO.sub.2, aluminosilicate zeolites, or a mixture thereof.

[0085] Aspect 5 provides the material of any of Aspects 1-4, wherein metal catalyst component comprises iron.

[0086] Aspect 6 provides the material of any of Aspects 1-5, wherein the material is Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3.

[0087] Aspect 7 provides the material of any of Aspects 1-6, wherein the material has a CO.sub.2 capture capacity in a range of from about 1.5 wt % to about 25 wt % at temperatures in a range of from about ambient temperatures to about 150 C. in the presence of water vapor.

[0088] Aspect 8 provides the material of any of Aspects 1-7, wherein the material is capable of converting captured CO.sub.2 to (C.sub.1-C.sub.10)hydrocarbyl products upon hydrogenation.

[0089] Aspect 9 provides the material of Aspect 8, wherein the (C.sub.1-C.sub.10) hydrocarbyl products comprise olefins, paraffins, or both.

[0090] Aspect 10 provides the material of any of Aspects 1-9, wherein the material comprises Fe particles impregnated on K.sub.2CO.sub.3/Al.sub.2O.sub.3.

[0091] Aspect 11 provides the material of Aspect 10, wherein the Fe particles range from about 2 wt % to about 50 wt % of the material.

[0092] Aspect 12 provides the material of any of Aspects 10 or 11, wherein the Fe particles range from about 20 wt % to about 30 wt % of the material.

[0093] Aspect 13 provides the material of any of Aspects 1-12, wherein the material is capable of capturing CO.sub.2 from air containing 350 ppm CO.sub.2 to about 1000 ppm CO.sub.2.

[0094] Aspect 14 provides the material of any of Aspects 1-12, wherein the material is capable of capturing CO.sub.2 from concentrated sources containing about 1 vol % CO.sub.2 to about 30 vol % CO.sub.2.

[0095] Aspect 15 provides the material of any of Aspects 1-14, wherein the material is capable of converting captured CO.sub.2 to (C.sub.1-C.sub.10)hydrocarbyls with a selectivity of at least 10% for C.sub.2-C.sub.4 olefins or paraffins.

[0096] Aspect 16 provides the material of any of Aspects 1-15, wherein the material is capable of converting captured CO.sub.2 to (C.sub.1-C.sub.10)hydrocarbyls at temperatures in a range of from about 250 C. to about 400 C.

[0097] Aspect 17 provides the material of any of Aspects 1-16, wherein the material is capable of converting captured CO.sub.2 to (C.sub.1-C.sub.10)hydrocarbyls at temperatures in a range of from about 330 C. to about 360 C.

[0098] Aspect 18 provides a method for integrated direct air capture and catalytic conversion of CO.sub.2 to (C.sub.1-C.sub.10)hydrocarbyl products, comprising: [0099] contacting a multifunctional material comprising a solid inorganic sorbent and a metal catalyst component with dilute CO.sub.2 gas streams to capture CO.sub.2; and [0100] hydrogenating the captured CO.sub.2 to produce (C.sub.1-C.sub.10)hydrocarbyls.

[0101] Aspect 19 provides the method of Aspect 18, wherein the solid inorganic sorbent comprises a carbonate.

[0102] Aspect 20 provides the method of any of Aspects 18 or 19, wherein the solid inorganic sorbent comprises a group 1 metal carbonate comprising K.sub.2CO.sub.3, Na.sub.2CO.sub.3, Li.sub.2CO.sub.3, or a mixture thereof, supported on porous materials comprising Al.sub.2O.sub.3, Carbon, SiO.sub.2 ZrO.sub.2, aluminosilicate zeolites, or a mixture thereof.

[0103] Aspect 21 provides the method of any of Aspects 18-20, wherein the metal catalyst component comprises iron, cobalt, copper, manganese or any combination of oxides thereof.

[0104] Aspect 22 provides the method of any of Aspects 18-21, wherein the multifunctional material is Fe/K.sub.2CO.sub.3/Al.sub.2O.sub.3.

[0105] Aspect 23 provides the method of any of Aspects 18-22, wherein the CO.sub.2 capture is performed at temperatures in a range of from about ambient temperatures to about 150 C. in the presence of water vapor.

[0106] Aspect 24 provides the method of any of Aspects 18-23, wherein the hydrogenation occurs at temperatures in a range of from about 300 C. to about 400 C.

[0107] Aspect 25 provides the method of any of Aspects 18-24, wherein the hydrogenation occurs at temperatures in a range of from about 332 C. to about 360 C.

[0108] Aspect 26 provides the method of any of Aspects 18-25, wherein the (C.sub.1-C.sub.10)hydrocarbyl products comprise olefins, paraffins, or both.

[0109] Aspect 27 provides the method of any of Aspects 18-26, further comprising recycling the multifunctional material for multiple cycles of CO.sub.2 capture and conversion.

[0110] Aspect 28 provides the method of any of Aspects 18-27, wherein the dilute CO.sub.2 gas stream is air, which contains about 350 ppm CO.sub.2 to about 1000 ppm CO.sub.2.

[0111] Aspect 29 provides the method of any of Aspects 18-28, wherein the dilute CO.sub.2 stream gas is an industrial flue gas source containing about 1 vol % CO.sub.2 to about 30 vol % CO.sub.2.

[0112] Aspect 30 provides the method of any of Aspects 18-29, wherein the hydrogenation is performed under a hydrogen pressure in a range of from about 0.5 MPa to about 3 MPa.

[0113] Aspect 31 provides the method of any of Aspects 18-30, wherein the hydrogenation is performed under a hydrogen pressure in a range of from about 0.8 MPa to about 1.2 MPa.

[0114] Aspect 32 provides the method of any of Aspects 18-31, wherein the method achieves a selectivity in a range of from about 10% to about 90% for C.sub.2-C.sub.4 olefins.

[0115] Aspect 33 provides the method of any of Aspects 18-32, wherein the method converts at least 20% of the captured CO.sub.2 to C2+ products.

[0116] Aspect 34 provides the method of any of Aspects 18-33, further comprising pretreating the multifunctional material with H.sub.2 at a temperature in a range of about 250 C. to about 450 C. prior to CO.sub.2 capture.

[0117] Aspect 35 provides the method of any of Aspects 18-34, further comprising pretreating the multifunctional material with an H.sub.2/CO gas mixture.

[0118] Aspect 36 provides the method of any of Aspects 18-35, further comprising separating the produced (C.sub.1-C.sub.10)hydrocarbyls using a demethanization tower operated at cryogenic conditions.

[0119] Throughout this document, values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of about 0.1% to about 5% or about 0.1% to 5% should be interpreted to include not just about 0.1% to about 5%, but also the individual values (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement about X to Y has the same meaning as about X to about Y, unless indicated otherwise. Likewise, the statement about X, Y, or about Z has the same meaning as about X, about Y, or about Z, unless indicated otherwise.

[0120] In this document, the terms a, an, or the are used to include one or more than one unless the context clearly dictates otherwise. The term or is used to refer to a nonexclusive or unless otherwise indicated. The statement at least one of A and B or at least one of A or B has the same meaning as A, B, or A and B. In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section. A comma can be used as a delimiter or digit group separator to the left or right of a decimal mark; for example, 0.000,1 is equivalent to 0.0001. All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.

[0121] In the methods described herein, the acts can be carried out in any order without departing from the principles of the disclosure, except when a temporal or operational sequence is explicitly recited. Furthermore, specified acts can be carried out concurrently unless explicit claim language recites that they be carried out separately. For example, a claimed act of doing X and a claimed act of doing Y can be conducted simultaneously within a single operation, and the resulting process will fall within the literal scope of the claimed process.

[0122] The term about as used herein can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range, and includes the exact stated value or range. The term substantially as used herein refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more, or 100%. The term substantially free of as used herein can mean having none or having a trivial amount of, such that the amount of material present does not affect the material properties of the composition including the material, such that about 0 wt % to about 5 wt % of the composition is the material, or about 0 wt % to about 1 wt %, or about 5 wt % or less, or less than or equal to about 4.5 wt %, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.01, or about 0.001 wt % or less, or about 0 wt %.

[0123] The term hydrocarbon or hydrocarbyl as used herein refers to a molecule or functional group that includes carbon and hydrogen atoms. The term can also refer to a molecule or functional group that normally includes both carbon and hydrogen atoms but wherein all the hydrogen atoms are substituted with other functional groups. The term hydrocarbyl refers to a functional group derived from a straight chain, branched, or cyclic hydrocarbon, and can be alkyl, alkenyl, alkynyl, aryl, cycloalkyl, acyl, or any combination thereof. Hydrocarbyl groups can be shown as (C.sub.a-C.sub.b)hydrocarbyl, wherein a and b are integers and mean having any of a to b number of carbon atoms. For example, (C.sub.1-C.sub.4)hydrocarbyl means the hydrocarbyl group can be methyl (C.sub.1), ethyl (C.sub.2), propyl (C.sub.3), or butyl (C.sub.4), and (C.sub.0-C.sub.b)hydrocarbyl means in certain aspects there is no hydrocarbyl group. A hydrocarbylene group is a diradical hydrocarbon, e.g., a hydrocarbon that is bonded at two locations