Patent Application
20150111018
Not applicable.
Current methods and materials for capturing CO2 and H2S from an environment suffer from numerous limitations, including low selectivity, limited sorption capacity, high sorbent costs, and stringent reaction conditions. The present disclosure addresses these limitations.
In some embodiments, the present disclosure pertains to methods of capturing a gas from an environment. In some embodiments, the methods include a step of associating the environment with a porous carbon material. In some embodiments, the associating results in sorption of gas components to the porous carbon material. In some embodiments, the sorbed gas components include at least one of CO2, H2S, and combinations thereof.
In some embodiments, the environment in which gas capture occurs is a pressurized environment. In some embodiments, the environment includes, without limitation, industrial gas streams, natural gas streams, natural gas wells, industrial gas wells, oil and gas fields, and combinations thereof.
In some embodiments, the sorbed gas components include CO2. In some embodiments, the sorption of the CO2 to the porous carbon material occurs selectively over hydrocarbons in the environment. In some embodiments, the CO2 is converted to poly(CO2) within the pores of the porous carbon materials. In some embodiments, the porous carbon material has a CO2 sorption capacity of about 50 wt % to about 200 wt % of the porous carbon material weight.
In some embodiments, the sorbed gas components include H2S. In some embodiments, the H2S is converted within the pores of the porous carbon materials to at least one of elemental sulfur (S), sulfur dioxide (SO2), sulfuric acid (H2SO4), and combinations thereof. In some embodiments, the formed elemental sulfur becomes impregnated with the porous carbon material. In some embodiments, captured H2S remains intact within the porous carbon material. In some embodiments, the porous carbon material has a H2S sorption capacity of about 50 wt % to about 300 wt % of the porous carbon material weight.
In some embodiments, the sorbed gas components include CO2 and H2S. In some embodiments, the sorption of H2S and CO2 to the porous carbon material occurs at the same time. In some embodiments, the sorption of CO2 to the porous carbon material occurs before the sorption of H2S to the porous carbon material. In some embodiments, the sorption of H2S to the porous carbon material occurs before the sorption of CO2 to the porous carbon material.
In some embodiments, the methods of the present disclosure also include a step of releasing captured gas components from the porous carbon material. In some embodiments, the releasing occurs by decreasing the pressure of the environment or heating the environment. In some embodiments, the releasing of sorbed CO2 occurs by decreasing the pressure of the environment or placing the porous carbon material in a second environment that has a lower pressure than the environment where CO2 capture occurred. In some embodiments, the releasing of sorbed H2S occurs by heating the porous carbon material. In some embodiments, the releasing of the CO2 occurs before the releasing of the H2S.
In some embodiments, the methods of the present disclosure also include a step of disposing the released gas. In some embodiments, the methods of the present disclosure also include a step of reusing the porous carbon material after the releasing to capture additional gas components from an environment.
In some embodiments, the porous carbon material utilized for gas capture includes a plurality of pores. In some embodiments, the porous carbon material includes, without limitation, protein-derived porous carbon materials, carbohydrate-derived porous carbon materials, cotton-derived porous carbon materials, fat-derived porous carbon materials, waste-derived porous carbon materials, asphalt-derived porous carbon materials, coal-derived porous carbon materials, coke-derived porous carbon materials, asphaltene-derived porous carbon materials, oil product-derived porous carbon materials, bitumen-derived porous carbon materials, tar-derived porous carbon materials, pitch-derived porous carbon materials, anthracite-derived porous carbon materials, melamine-derived porous carbon materials, and combinations thereof.
In some embodiments, the porous carbon material includes asphalt-derived porous carbon materials. In some embodiments, the porous carbon material is carbonized. In some embodiments, the porous carbon material is reduced. In some embodiments, the porous carbon material is vulcanized. In some embodiments, the porous carbon material includes a plurality of nucleophilic moieties. In some embodiments, the nucleophilic moieties include, without limitation, oxygen-containing moieties, sulfur-containing moieties, metal-containing moieties, metal oxide-containing moieties, metal sulfide-containing moieties, nitrogen-containing moieties, phosphorous-containing moieties, and combinations thereof.
In some embodiments, the porous carbon materials have surface areas ranging from about 2,500 m2/g to about 3,000 m2/g. In some embodiments, the plurality of pores in the porous carbon material comprises diameters ranging from about 1 nm to about 10 nm, and volumes ranging from about 1 cm3/g to about 3 cm3/g. In some embodiments, the porous carbon material has a density ranging from about 0.3 g/cm3 to about 4 g/cm3.
Additional embodiments of the present disclosure pertain to the porous carbon materials used for gas capture. Further embodiments of the present disclosure pertain to methods of making the porous carbon materials of the present disclosure.
It is to be understood that both the foregoing general description and the following detailed description are illustrative and explanatory, and are not restrictive of the subject matter, as claimed. In this application, the use of the singular includes the plural, the word “a” or “an” means “at least one”, and the use of “or” means “and/or”, unless specifically stated otherwise. Furthermore, the use of the term “including”, as well as other forms, such as “includes” and “included”, is not limiting. Also, terms such as “element” or “component” encompass both elements or components comprising one unit and elements or components that comprise more than one unit unless specifically stated otherwise.
The section headings used herein are for organizational purposes and are not to be construed as limiting the subject matter described. All documents, or portions of documents, cited in this application, including, but not limited to, patents, patent applications, articles, books, and treatises, are hereby expressly incorporated herein by reference in their entirety for any purpose. In the event that one or more of the incorporated literature and similar materials defines a term in a manner that contradicts the definition of that term in this application, this application controls.
Environmental and health concerns have been linked to carbon dioxide (CO2) and hydrogen sulfide (H2S) emission sources, such as industrial power plants, refineries and natural gas wells. Therefore, efficient CO2 and H2S capture from flue gases or other high pressure natural gas wells has been a primary approach in mitigating environmental and health risks. For instance, aqueous amine solvents and membrane technologies have been utilized for CO2 capture. In addition, solid sorbents such as activated carbon, zeolites and metal organic frameworks have been utilized as alternative materials for capturing CO2.
However, many of the aforementioned technologies suffer from numerous limitations. For instance, many CO2 and H2S capture technologies that utilize aqueous amine solutions are highly inefficient due to the high energy requirements for regeneration (e.g., 120° C.-140° C.). Moreover, many of the aqueous amine solutions lack selectivity for CO2 over other gases, such as CH4. Furthermore, the corrosive nature of aqueous amine solutions and their high regeneration temperatures make them further unsuitable for many gas capture applications, such as offshore use.
Solid CO2 sorbents have shown many advantages over conventional separation technologies that utilize aqueous amine solvents. For instance, solid CO2 sorbents have been shown to capture CO2 under high pressure. Moreover, many solid CO2 sorbents have lower regeneration energy requirements, higher CO2 uptake capacities, selectivity over hydrocarbons, and ease of handling. Moreover, solid CO2 sorbents have shown lower heat capacities, faster kinetics of sorption and desorption, and high mechanical strength. In addition, solid CO2 sorbents have been utilized to capture and release CO2 without significant pressure and temperature swings.
However, a limitation of many solid CO2 sorbents is the cost of production. Many solid CO2 sorbents are also unable to compress and separate CO2 from the sorbents in an efficient manner. Moreover, the H2S sorption capacities of many solid CO2 sorbents have not been ascertained. Therefore, a need exists for the development of more effective and affordable CO2 and H2S sorbents. A need also exists for more effective methods of utilizing such sorbents to capture CO2 and H2S from various environments.
In some embodiments illustrated in FIG. IA, the present disclosure pertains to methods of capturing a gas from an environment. In some embodiments, the method includes associating the environment with a porous carbon material (step 10) to result in sorption of gas components (e.g., CO2, H2S, and combinations thereof) to the porous carbon material (step 12). In some embodiments, the methods of the present disclosure also include a step of releasing the gas components from the porous carbon material (step 14). In some embodiments, the methods of the present disclosure also include a step of reusing the porous carbon material after the release of the gas components (step 16). In some embodiments, the methods of the present disclosure also include a step of disposing the released gas components (step 18). In some embodiments, the porous carbon material includes asphalt derived porous carbon materials.
As set forth in more detail herein, the gas capture methods and porous carbon materials of the present disclosure have numerous embodiments. For instance, various methods may be utilized to associate various types of porous carbon materials with various environments to result in the capture of various gas components from the environment. Moreover, the captured gas components may be released from the porous carbon materials in various manners.
Environments
The methods of the present disclosure may be utilized to capture gas from various environments. In some embodiments, the environment includes, without limitation, industrial gas streams, natural gas streams, natural gas wells, industrial gas wells, oil and gas fields, and combinations thereof. In some embodiments, the environment is a subsurface oil and gas field. In more specific embodiments, the methods of the present disclosure may be utilized to capture gas from an environment that contains natural gas, such as an oil well.
In some embodiments, the environment is a pressurized environment. For instance, in some embodiments, the environment has a total pressure higher than atmospheric pressure.
In some embodiments, the environment has a total pressure of about 0.1 bar to about 500 bar. In some embodiments, the environment has a total pressure of about 5 bar to about 100 bar. In some embodiments, the environment has a total pressure of about 25 bar to about 30 bar. In some embodiments, the environment has a total pressure of about 100 bar to about 200 bar. In some embodiments, the environment has a total pressure of about 200 bar to about 300 bar.
Gas Components
The methods of the present disclosure may be utilized to capture various gas components from an environment. For instance, in some embodiments, the captured gas component includes, without limitation, CO2, H2S, and combinations thereof. In some embodiments, the captured gas component includes CO2. In some embodiments, the captured gas component includes H2S. In some embodiments, the captured gas component includes CO2 and H2S.
Association of Porous Carbon Materials with an Environment
Various methods may be utilized to associate porous carbon materials of the present disclosure with an environment. In some embodiments, the association occurs by incubating the porous carbon materials with the environment (e.g., a pressurized environment). In some embodiments, the association of porous carbon materials with an environment occurs by flowing the environment through a structure that contains the porous carbon materials. In some embodiments, the structure may be a column or a sheet that contains immobilized porous carbon materials. In some embodiments, the structure may be a floating bed that contains porous carbon materials.
In some embodiments, the porous carbon materials are suspended in a solvent while being associated with an environment. In some embodiments, the solvent may include water or alcohol. In some embodiments, the porous carbon materials are associated with an environment in pelletized form. In some embodiments, the pelletization can be used to assist flow of the gas component through the porous carbon materials.
In some embodiments, the associating occurs by placing the porous carbon material at or near the environment. In some embodiments, such placement occurs by various methods that include, without limitation, adhesion, immobilization, clamping, and embedding. Additional methods by which to associate porous carbon materials with an environment can also be envisioned.
Gas Sorption to Porous Carbon Materials
The sorption of gas components (e.g., CO2, H2S, and combinations thereof) to porous carbon materials of the present disclosure can occur at various environmental pressures. For instance, in some embodiments, the sorption of gas components to porous carbon materials occurs above atmospheric pressure. In some embodiments, the sorption of gas components to porous carbon materials occurs at total pressures ranging from about 0.1 bar to about 500 bar. In some embodiments, the sorption of gas components to porous carbon materials occurs at total pressures ranging from about 5 bar to about 500 bar. In some embodiments, the sorption of gas components to porous carbon materials occurs at total pressures ranging from about 5 bar to about 100 bar. In some embodiments, the sorption of gas components to porous carbon materials occurs at total pressures ranging from about 25 bar to about 30 bar. In some embodiments, the sorption of gas components to porous carbon materials occurs at total pressures ranging from about 100 bar to about 500 bar. In some embodiments, the sorption of gas components to porous carbon materials occurs at total pressures ranging from about 100 bar to about 300 bar. In some embodiments, the sorption of gas components to porous carbon materials occurs at total pressures ranging from about 100 bar to about 200 bar.
The sorption of gas components to porous carbon materials can also occur at various temperatures. For instance, in some embodiments, the sorption of gas components to porous carbon materials occurs at temperatures that range from about 0° C. (e.g., a sea floor temperature where a wellhead may reside) to about 100° C. (e.g., a temperature where machinery may reside). In some embodiments, the sorption of gas components to porous carbon materials occurs at ambient temperature (e.g., temperatures ranging from about 20-25° C., such as 23° C.). In some embodiments, the sorption of gas components to porous carbon materials occurs below ambient temperature. In some embodiments, the sorption of gas components to porous carbon materials occurs above ambient temperature. In some embodiments, the sorption of gas components to porous carbon materials occurs without the heating of the porous carbon materials.
Without being bound by theory, it is envisioned that the sorption of gas components to porous carbon materials occurs by various molecular interactions between gas components (e.g., CO2 or H2S) and the porous carbon materials. For instance, in some embodiments, the sorption of gas components to porous carbon materials occurs by at least one of absorption, adsorption, ionic interactions, physisorption, chemisorption, covalent bonding, non-covalent bonding, hydrogen bonding, van der Waals interactions, acid-base interactions, and combinations of such mechanisms. In some embodiments, the sorption includes an absorption interaction between gas components (e.g., CO2 or H2S) in an environment and the porous carbon materials. In some embodiments, the sorption includes an ionic interaction between the gas components in an environment and the porous carbon materials. In some embodiments, the sorption includes an adsorption interaction between the gas components in an environment and the porous carbon materials. In some embodiments, the sorption includes a physisorption interaction between the gas components in an environment and the porous carbon materials. In some embodiments, the sorption includes a chemisorption interaction between the gas components in an environment and the porous carbon materials. In some embodiments, the sorption includes a covalent bonding interaction between the gas components in an environment and the porous carbon materials. In some embodiments, the sorption includes a non-covalent bonding interaction between the gas components in an environment and the porous carbon materials. In some embodiments, the sorption includes a hydrogen bonding interaction between the gas components in an environment and the porous carbon materials. In some embodiments, the sorption includes a van der Waals interaction between the gas components in an environment and the porous carbon materials. In some embodiments, the sorption includes an acid-base interaction between the gas components in an environment and the porous carbon materials. In some embodiments, the sorption of gas components to porous carbon materials occurs by adsorption and absorption.
CO2 Sorption
In some embodiments, the sorption of gas components to porous carbon materials includes the sorption of CO2 to the porous carbon materials. In some embodiments, the sorption of CO2 to porous carbon materials occurs at a partial CO2 pressure of about 0.1 bar to about 100 bar. In some embodiments, the sorption of CO2 to porous carbon materials occurs at a partial CO2 pressure of about 5 bar to about 30 bar. In some embodiments, the sorption of CO2 to porous carbon materials occurs at a partial CO2 pressure of about 30 bar.
Without being bound by theory, it is envisioned that CO2 sorption may be facilitated by various chemical reactions. For instance, in some embodiments, the sorbed CO2 is converted to poly(CO2) within the pores of the porous carbon materials. In some embodiments, the poly(CO2) comprises the following formula: —(O—C(═O))n—, where n is equal to or greater than 2. In some embodiments, n is between 2 to 10,000. In some embodiments, the formed poly(CO2) may be further stabilized by van der Waals interactions with the carbon surfaces in the pores of the carbon materials. In some embodiments, the formed poly(CO2) may be in solid form.
In some embodiments, the sorption of CO2 to the porous carbon materials occurs selectively. For instance, in some embodiments, the sorption of CO2 to the porous carbon materials occurs selectively over hydrocarbons in the environment (e.g., ethane, propane, butane, pentane, methane, and combinations thereof). In further embodiments, the molecular ratio of sorbed CO2 to sorbed hydrocarbons in the porous carbon materials is greater than about 2. In additional embodiments, the molecular ratio of sorbed CO2 to sorbed hydrocarbons in the porous carbon materials ranges from about 2 to about 5. In additional embodiments, the molecular ratio of sorbed CO2 to sorbed hydrocarbons in the porous carbon materials is about 3.5.
In more specific embodiments, the sorption of CO2 to porous carbon materials occurs selectively over the CH4 in the environment. In further embodiments, the molecular ratio of sorbed CO2 to sorbed CH4 (nCO2/nCH4) in the porous carbon materials is greater than about 2. In additional embodiments, nCO2/nCH4 in the porous carbon materials ranges from about 2 to about 5. In more specific embodiments, nCO2/nCH4 in the porous carbon materials is about 3.5.
In some embodiments, sorption of CO2 to porous carbon materials occurs selectively through poly(CO2) formation within the pores of the porous carbon materials. Without being bound by theory, it is envisioned that poly(CO2) formation within the pores of the porous carbon materials can displace other gas components associated with the porous carbon materials, including any physisorbed gas components and hydrocarbons (e.g., methane, propane, and butane). Without being bound by further theory, it is also envisioned that the displacement of other gas components from the porous carbon materials creates a continual CO2 selectivity that far exceeds various CO2 selectively ranges, including the CO2 selectivity ranges noted above.
In some embodiments, the covalent bond nature of poly(CO2) within the pores of the porous carbon materials can be 100 times stronger than that of other physisorbed entities, including physisorbed gas components within the pores of the porous carbon materials. Therefore, such strong covalent bonds can contribute to the displacement of the physisorbed gas components (e.g., methane, propane and butane).
H2S Sorption
In some embodiments, the sorption of gas components to porous carbon materials includes the sorption of H2S to the porous carbon materials. In some embodiments, the sorption of H2S to porous carbon materials occurs at a partial H2S pressure of about 0.1 bar to about 100 bar. In some embodiments, the sorption of H2S to porous carbon materials occurs at a partial H2S pressure of about 5 bar to about 30 bar. In some embodiments, the sorption of H2S to porous carbon materials occurs at a partial H2S pressure of about 30 bar.
Without being bound by theory, it is envisioned that H2S sorption may be facilitated by various chemical reactions. For instance, in some embodiments, sorbed H2S may be converted within the pores of the porous carbon materials to at least one of elemental sulfur (S), sulfur dioxide (SO2), sulfuric acid (H2SO4), and combinations thereof. In some embodiments, the aforementioned conversion can be facilitated by the presence of oxygen. For instance, in some embodiments, the introduction of small amounts of oxygen into a system containing porous carbon materials can facilitate the conversion of H2S to elemental sulfur. In some embodiments, the oxygen can be introduced either continuously or periodically. In some embodiments, the oxygen can be introduced from air.
In some embodiments, the captured H2S is converted by catalytic oxidation to elemental sulfur at ambient temperature. Thereafter, further oxidation to SO2 and H2SO4 occurs at higher temperatures.
In some embodiments, nitrogen groups of porous carbon materials may facilitate the conversion of H2S to elemental sulfur. For instance, in some embodiments illustrated in the schemes in
In some embodiments, the porous carbon material becomes impregnated with the sulfur derived from captured H2S to form sulfur-impregnated porous carbon materials. In some embodiments, the formation of sulfur-impregnated porous carbon materials may be facilitated by heating. In some embodiments, the heating occurs at temperatures higher than H2S capture temperatures. In some embodiments, the heating occurs in the absence of oxygen. In some embodiments, the sulfur impregnated porous carbon material can be used to efficiently capture CO2 by the aforementioned methods.
In some embodiments, the sorption of H2S to porous carbon materials occurs in intact form. In some embodiments, the sorption of H2S to porous carbon materials in intact form occurs in the absence of oxygen.
CO2 and H2S Sorption
In some embodiments, the sorption of gas components to porous carbon materials includes the sorption of both H2S and CO2 to the porous carbon materials. In some embodiments, the sorption of H2S and CO2 to the porous carbon material occurs at the same time.
In some embodiments, the sorption of CO2 to the porous carbon material occurs before the sorption of H2S to the porous carbon material. For instance, in some embodiments, a gas containing CO2 and H2S flows through a structure that contains porous carbon materials (e.g., trapping cartridges). CO2 is first captured from the gas as the gas flows through the structure. Thereafter, H2S is captured from the gas as the gas continues to flow through the structure.
In some embodiments, the sorption of H2S to the porous carbon material occurs before the sorption of CO2 to the porous carbon material. For instance, in some embodiments, a gas containing CO2 and H2S flows through a structure that contains porous carbon materials (e.g., trapping cartridges). H2S is first captured from the gas as the gas flows through the structure. Thereafter, CO2 is captured from the gas as the gas continues to flow through the structure.
In some embodiments, the porous carbon materials that capture H2S from the gas include nitrogen-containing porous carbon materials, as described in more detail herein. In some embodiments, the porous carbon materials that capture CO2 from the gas include sulfur-containing porous carbon materials that are also described in more detail herein.
Release of Captured Gas
In some embodiments, the methods of the present disclosure also include a step of releasing captured gas components from porous carbon materials. Various methods may be utilized to release captured gas components from porous carbon materials. For instance, in some embodiments, the releasing occurs by decreasing the pressure of the environment. In some embodiments, the pressure of the environment is reduced to atmospheric pressure or below atmospheric pressure. In some embodiments, the releasing occurs by placing the porous carbon material in a second environment that has a lower pressure than the environment where gas capture occurred. In some embodiments, the second environment may be at or below atmospheric pressure. In some embodiments, the releasing occurs spontaneously as the environmental pressure decreases.
The release of captured gas components from porous carbon materials can occur at various pressures. For instance, in some embodiments, the release occurs at or below atmospheric pressure. In some embodiments, the release occurs at total pressures ranging from about 0 bar to about 100 bar. In some embodiments, the release occurs at total pressures ranging from about 0.1 bar to about 50 bar. In some embodiments, the release occurs at total pressures ranging from about 0.1 bar to about 30 bar. In some embodiments, the release occurs at total pressures ranging from about 0.1 bar to about 10 bar.
The release of captured gas components from porous carbon materials can also occur at various temperatures. In some embodiments, the releasing occurs at ambient temperature. In some embodiments, the releasing occurs at the same temperature at which gas sorption occurred. In some embodiments, the releasing occurs without heating the porous carbon materials. Therefore, in some embodiments, a temperature swing is not required to release captured gas components from porous carbon materials.
In some embodiments, the releasing occurs at temperatures ranging from about 30° C. to about 200° C. In some embodiments, the releasing is facilitated by also lowering the pressure.
In some embodiments, the releasing occurs by heating the porous carbon materials. For instance, in some embodiments, the releasing occurs by heating the porous carbon materials to temperatures between about 50° C. to about 200° C. In some embodiments, the releasing occurs by heating the porous carbon materials to temperatures between about 75° C. to about 125° C. In some embodiments, the releasing occurs by heating the porous carbon materials to temperatures ranging from about 50° C. to about 100° C. In some embodiments, the releasing occurs by heating the porous carbon materials to a temperature of about 90° C.
In some embodiments, heat for release of gas components from porous carbon materials can be supplied from various sources. For instance, in some embodiments, the heat for the release of gas components from a porous carbon material-containing vessel can be provided by an adjacent vessel whose heat is being generated during a gas sorption step.
In some embodiments, the release of captured gas components from an environment includes the release of captured CO2 from porous carbon materials. Without being bound by theory, it is envisioned that the release of captured CO2 from porous carbon materials can occur by various mechanisms. For instance, in some embodiments, the release of captured CO2 can occur through a depolymerization of the formed poly(CO2) within the pores of the porous carbon materials. In some embodiments, the depolymerization can be facilitated by a decrease in environmental pressure. In some embodiments, the releasing of the CO2 occurs by decreasing the pressure of the environment or placing the porous carbon material in a second environment that has a lower pressure than the environment where CO2 capture occurred.
In some embodiments, the release of captured gas components from an environment includes the release of captured H2S from porous carbon materials. In some embodiments, the captured H2S is released in intact form.
In some embodiments, H2S is released from porous carbon materials by heating the porous carbon materials. In some embodiments, H2S is released from porous carbon materials by heating the porous carbon materials to temperatures that range from about 50° C. to about 200° C. In some embodiments, H2S is released from the porous carbon materials by heating the porous carbon materials to temperatures between about 75° C. to about 125° C. In some embodiments, H2S is released from the porous carbon materials by heating the porous carbon materials to temperatures between about 50° C. to about 100° C. In some embodiments, H2S is released from the porous carbon materials by heating the porous carbon materials to a temperature of about 90° C.
In some embodiments, the release of captured H2S can occur through conversion of H2S to at least one of elemental sulfur (S), sulfur dioxide (SO2), sulfuric acid (H2SO4), and combinations thereof. In some embodiments, elemental sulfur is retained on the porous carbon material to form sulfur-impregnated porous carbon materials. In some embodiments, the sulfur-containing porous carbon material can be discarded through incineration or burial. In some embodiments, the sulfur-impregnated porous carbon material can be used for the reversible capture of CO2.
In some embodiments, the release of captured gas components can occur in a sequential manner. For instance, in some embodiments where the sorbed gas components include both CO2 and H2S, the releasing of the CO2 occurs by decreasing the pressure of the environment or placing the porous carbon material in a second environment that has a lower pressure than the environment where CO2 capture occurred. In some embodiments, the releasing of the H2S occurs by heating the porous carbon material (e.g., at temperatures ranging from about 50° C. to about 100° C.). In some embodiments, the releasing of the CO2 occurs before the releasing of the H2S. In some embodiments, the releasing of the H2S occurs before the releasing of the CO2. In some embodiments, the releasing of H2S occurs in an environment that lacks oxygen.
Disposal of the Released gas
In some embodiments, the methods of the present disclosure also include a step of disposing the released gas components. For instance, in some embodiments, the released gas components can be off-loaded into a container. In some embodiments, the released gas components can be pumped downhole for long-term storage. In some embodiments, the released gas components can be vented to the atmosphere. In some embodiments, the released gas components include, without limitation, CO2, H2S, SO2, and combinations thereof.
Reuse of the Porous Carbon Material
In some embodiments, the methods of the present disclosure also include a step of reusing the porous carbon materials after gas component release to capture more gas components from an environment. In some embodiments, the porous carbon materials of the present disclosure may be reused over 100 times without substantially affecting their gas sorption capacities. In some embodiments, the porous carbon materials of the present disclosure may be reused over 1000 times without substantially affecting their gas sorption capacities. In some embodiments, the porous carbon materials of the present disclosure may be reused over 10,000 times without substantially affecting their gas sorption capacities.
In some embodiments, the porous carbon materials of the present disclosure may retain 100 wt % of their CO2 or H2S sorption capacities after being used multiple times (e.g., 100 times, 1,000 times or 10,000 times). In some embodiments, the porous carbon materials of the present disclosure may retain at least 98 wt % of their CO2 or H2S sorption capacities after being used multiple times (e.g., 100 times, 1,000 times or 10,000 times). In some embodiments, the porous carbon materials of the present disclosure may retain at least 95 wt % of their CO2 or H2S sorption capacities after being used multiple times (e.g., 100 times, 1,000 times or 10,000 times). In some embodiments, the porous carbon materials of the present disclosure may retain at least 90 wt % of their CO2 or H2S sorption capacities after being used multiple times (e.g., 100 times, 1,000 times or 10,000 times). In some embodiments, the porous carbon materials of the present disclosure may retain at least 80 wt % of their CO2 or H2S sorption capacities after being used multiple times (e.g., 100 times, 1,000 times or 10,000 times).
Porous Carbon Materials
Various porous carbon materials may be utilized to capture gas from an environment. In some embodiments, the present disclosure pertains to the porous carbon materials that are utilized to capture gas from an environment.
Carbon Sources
The porous carbon materials of the present disclosure may be derived from various carbon sources. For instance, in some embodiments, the porous carbon material includes, without limitation, protein-derived porous carbon materials, carbohydrate-derived porous carbon materials, cotton-derived porous carbon materials, fat-derived porous carbon materials, waste-derived porous carbon materials, asphalt-derived porous carbon materials, coal-derived porous carbon materials, coke-derived porous carbon materials, asphaltene-derived porous carbon materials, oil product-derived porous carbon materials, bitumen-derived porous carbon materials, tar-derived porous carbon materials, pitch-derived porous carbon materials, anthracite-derived porous carbon materials, melamine-derived porous carbon materials, and combinations thereof.
In some embodiments, the porous carbon materials of the present disclosure include asphalt-derived porous carbon materials. In some embodiments, the porous carbon materials of the present disclosure include coal-derived porous carbon materials. In some embodiments, the coal source includes, without limitation, bituminous coal, anthracitic coal, brown coal, and combinations thereof.
In some embodiments, the porous carbon materials of the present disclosure include protein-derived porous carbon materials. In some embodiments, the protein source includes, without limitation, whey protein, rice protein, animal protein, plant protein, and combinations thereof.
In some embodiments, the porous carbon materials of the present disclosure include oil product-derived porous carbon materials. In some embodiments, the oil products include, without limitation, petroleum oil, plant oil, and combinations thereof.
In some embodiments, the porous carbon materials of the present disclosure include waste derived porous carbon materials. In some embodiments, the waste can include, without limitation, human waste, animal waste, waste derived from municipality sources, and combinations thereof.
The porous carbon materials of the present disclosure may also be in various states. For instance, in some embodiments, the porous carbon material is carbonized. In some embodiments, the porous carbon material is reduced. In some embodiments, the porous carbon material is vulcanized.
Nucleophilic Moieties
In some embodiments, the porous carbon materials of the present disclosure include a plurality of nucleophilic moieties. In some embodiments, the porous carbon materials of the present disclosure may contain various arrangements of nucleophilic moieties. In some embodiments, the nucleophilic moieties are part of the porous carbon material. In some embodiments, the nucleophilic moieties are embedded within the porous carbon materials. In some embodiments, the nucleophilic moieties are homogenously distributed throughout the porous carbon material framework. In some embodiments, the nucleophilic moieties are embedded within the plurality of the pores of the porous carbon materials.
In some embodiments, the nucleophilic moieties include, without limitation, primary nucleophiles, secondary nucleophiles, tertiary nucleophiles and combinations thereof. In some embodiments, the nucleophilic moieties include, without limitation, oxygen-containing moieties, sulfur-containing moieties, metal-containing moieties, metal oxide-containing moieties, metal sulfide-containing moieties, nitrogen-containing moieties, phosphorous-containing moieties, and combinations thereof.
In more specific embodiments, the nucleophilic moieties include phosphorous-containing moieties. In some embodiments, the phosphorous containing moieties include, without limitation, phosphines, phosphites, phosphine oxides, and combinations thereof.
In some embodiments, the nucleophilic moieties include nitrogen-containing moieties. In some embodiments, the nitrogen-containing moieties include, without limitation, primary amines, secondary amines, tertiary amines, nitrogen oxides, pyridinic nitrogens, pyrrolic nitrogens, graphitic nitrogens, and combinations thereof. In more specific embodiments, the nitrogen containing moieties include nitrogen oxides, such as N-oxides.
In some embodiments, the nitrogen-containing moieties include from about 1 wt % to about 15 wt % by weight of the porous carbon material. In some embodiments, the nitrogen-containing moieties include from about 2 wt % to about 11 wt % by weight of the porous carbon material. In some embodiments, the nitrogen-containing moieties include from about 5 wt % to about 9 wt % by weight of the porous carbon material. In some embodiments, the nitrogen-containing moieties include from about 8 wt % to about 11 wt % by weight of the porous carbon material. In some embodiments, the nitrogen-containing moieties include about 9 wt % by weight of the porous carbon material.
In some embodiments, the nucleophilic moieties include sulfur-containing moieties. In some embodiments, the sulfur-containing moieties include, without limitation, primary sulfurs, secondary sulfurs, sulfur oxides, and combinations thereof.
In some embodiments, the nucleophilic moieties include nitrogen-containing moieties and sulfur-containing moieties. In some embodiments, the nitrogen-containing moieties and sulfur-containing moieties induce CO2 capture by poly(CO2) formation. In some embodiments, the nitrogen-containing moieties induce H2S capture by facilitating oxidation of H2S.
Surface Areas
The porous carbon materials of the present disclosure may have various surface areas. For instance, in some embodiments, the porous carbon materials of the present disclosure have surface areas that range from about 1,000 m2/g to about 3,000 m2/g. In some embodiments, the porous carbon materials of the present disclosure have surface areas that range from about 2,500 m2/g to about 3,000 m2/g. In some embodiments, the porous carbon materials of the present disclosure have surface areas that range from about 2,500 m2/g to about 2,900 m2/g. In more specific embodiments, the porous carbon materials of the present disclosure have surface areas that include at least one of 2,200 m2 g−1, 2,300 m2/g, 2,600 m2/g, 2,800 m2/g, or 2,900 m2 g−1.
Porosities
In some embodiments, the porous carbon materials of the present disclosure include a plurality of pores. In addition, the porous carbon materials of the present disclosure may have various porosities. For instance, in some embodiments, the pores in the porous carbon materials include diameters between about 1 nanometer to about 5 micrometers. In some embodiments, the pores include macropores with diameters of at least about 50 nm. In some embodiments, the pores include macropores with diameters between about 50 nanometers to about 3 micrometers. In some embodiments, the pores include macropores with diameters between about 500 nanometers to about 2 micrometers. In some embodiments, the pores include mesopores with diameters of less than about 50 nm. In some embodiments, the pores include micropores with diameters of less than about 2 nm.
In some embodiments, the pores include diameters that range from about 1 nm to about 10 nm. In some embodiments, the pores include diameters that range from about 1 nm to about 3 nm. In some embodiments, the pores include diameters that range from about 5 nm to about 100 nm.
In some embodiments, the porous carbon materials have a uniform distribution of pore sizes. In some embodiments, the uniform pore sizes are about 1.3 nm in diameter.
The pores of the porous carbon materials of the present disclosure may also have various volumes. For instance, in some embodiments, the pores in the porous carbon materials have volumes ranging from about 1 cm3/g to about 10 cm3/g. In some embodiments, the pores in the porous carbon materials have volumes ranging from about 1 cm3/g to about 3 cm3/g. In some embodiments, the pores in the porous carbon materials have volumes ranging from about 1 cm3/g to about 1.5 cm3/g. In more specific embodiments, the plurality of pores in the porous carbon materials have volumes of about 1.1 cm3/g, about 1.2 cm3/g, or about 1.4 cm3/g.
Densities
The porous carbon materials of the present disclosure may also have various densities. For instance, in some embodiments, the porous carbon materials of the present disclosure have densities that range from about 0.3 g/cm3 to about 10 g/cm3. In some embodiments, the porous carbon materials of the present disclosure have densities that range from about 0.3 g/cm3 to about 4 g/cm3. In some embodiments, the porous carbon materials of the present disclosure have densities that range from about 1 g/cm3 to about 3 g/cm3. In some embodiments, the porous carbon materials of the present disclosure have densities that range from about 1 g/cm3 to about 2.5 g/cm3. In some embodiments, the porous carbon materials of the present disclosure have densities that range from about 2 g/cm3 to about 3 g/cm3. In more specific embodiments, the porous carbon materials of the present disclosure have densities of 1.8 g/cm3, 2 g/cm3, or 2.2 g/cm3.
CO2 Sorption Capacities
The porous carbon materials of the present disclosure may also have various sorption capacities. For instance, in some embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity that ranges from about 10 wt % to about 200 wt % of the porous carbon material weight. In some embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity of about 50 wt % to about 200 wt % of the porous carbon material weight. In some embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity of about 50 wt % to about 100 wt % of the porous carbon material weight. In some embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity of about 100 wt % to about 200 wt % of the porous carbon material weight. In more specific embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity of about 120 wt % to about 130 wt % of the porous carbon material weight.
In further embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity of about 0.5 g to about 2 g of CO2 per 1 g of porous carbon material. In some embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity of about 1 g to about 2 g of CO2 per 1 g of porous carbon material. In some embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity of about 1.2 g to about 1.3 g of CO2 per 1 g of porous carbon material.
In further embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity of about 0.6 g to about 2.0 g of CO2 per 1 g of porous carbon material. In some embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity of about 1 g to about 1.2 g of CO2 per 1 g of porous carbon material. In some embodiments, the porous carbon materials of the present disclosure have a CO2 sorption capacity of about 1.2 g of CO2 per 1 g of porous carbon material.
H2S Sorption Capacities
The porous carbon materials of the present disclosure may also have various H2S sorption capacities. For instance, in some embodiments, the porous carbon materials of the present disclosure have a H2S sorption capacity that ranges from about 10 wt % to about 300 wt % of the porous carbon material weight. In some embodiments, the porous carbon materials of the present disclosure have a H2S sorption capacity of about 50 wt % to about 300 wt % of the porous carbon material weight. In some embodiments, the porous carbon materials of the present disclosure have a H2S sorption capacity of about 50 wt % to about 250 wt % of the porous carbon material weight. In some embodiments, the porous carbon materials of the present disclosure have a H2S sorption capacity of about 100 wt % to about 250 wt % of the porous carbon material weight. In more specific embodiments, the porous carbon materials of the present disclosure have a H2S sorption capacity of about 100 wt % to about 150 wt % of the porous carbon material weight.
In further embodiments, the porous carbon materials of the present disclosure have a H2S sorption capacity of about 0.5 g to about 3 g of sulfur from H2S per 1 g of porous carbon material. In some embodiments, the porous carbon materials of the present disclosure have a H2S sorption capacity of about 0.5 g to about 2.5 g of sulfur from H2S per 1 g of porous carbon material. In some embodiments, the porous carbon materials of the present disclosure have a H2S sorption capacity of about 1 g to about 2.5 g of sulfur from H2S per 1 g of porous carbon material. In some embodiments, the porous carbon materials of the present disclosure have a H2S sorption capacity of about 1 g to about 1.5 g of sulfur from H2S per 1 g of porous carbon material.
Physical States
The porous carbon materials of the present disclosure may be in various states. For instance, in some embodiments, the porous carbon materials of the present disclosure may be in a solid state. In some embodiments, the porous carbon materials of the present disclosure may be in a gaseous state. In some embodiments, the porous carbon materials of the present disclosure may be in a liquid state.
Methods of Forming Porous Carbon Materials
In some embodiments, the present disclosure pertains to methods of forming the porous carbon materials of the present disclosure. In some embodiments that are illustrated in
As set forth in more detail herein, various methods may be utilized to carbonize various types of carbon sources. In addition, various methods may be utilized to dope and vulcanize the carbon sources. Likewise, various methods may be utilized to reduce the formed porous carbon materials.
Carbon Sources
Various carbon sources may be utilized to form porous carbon materials. In some embodiments, the carbon sources include, without limitation, protein, carbohydrates, cotton, fat, waste, asphalt, coal, coke, asphaltene, oil products, bitumen, tar, pitch, anthracite, melamine, and combinations thereof.
In some embodiments, the carbon source includes asphalt. In some embodiments, the carbon source includes coal. In some embodiments, the coal source includes, without limitation, bituminous coal, anthracitic coal, brown coal, and combinations thereof. In some embodiments, the carbon source includes protein. In some embodiments, the protein source includes, without limitation, whey protein, rice protein, animal protein, plant protein, and combinations thereof.
In some embodiments, the carbon source includes oil products. In some embodiments, the oil products include, without limitation, petroleum oil, plant oil, and combinations thereof.
Carbonizing
In the present disclosure, carbonization generally refers to processes or treatments that convert a carbon source (e.g., a non-porous carbon source) to a porous carbon material. Various methods and conditions may be utilized to carbonize carbon sources.
For instance, in some embodiments, the carbonizing occurs in the absence of a solvent. In some embodiments, the carbonizing occurs in the presence of a solvent.
In some embodiments, the carbonizing occurs by exposing the carbon source to a carbonizing agent. In some embodiments, the carbonizing agent includes metal hydroxides or metal oxides. In some embodiments, the carbonizing agent includes, without limitation, potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), cesium hydroxide (CsOH), magnesium hydroxide (Mg(OH)2), calcium hydroxide (Ca(OH)2), and combinations thereof. In some embodiments, the carbonizing agent includes potassium hydroxide (KOH). In some embodiments, the carbonizing agent can be a metal oxide. In some embodiments, the metal oxide includes, without limitation, calcium oxide (CaO), magnesium oxide (MgO), and combinations thereof. In some embodiments, the weight ratio of the carbon source to the carbonizing agent varies from about 1:1 to about 1:5. In some embodiments, the weight ratio of the carbon source to the carbonizing agent is about 1:4.
In some embodiments, the carbonizing occurs by grinding the carbon source in the presence of a carbonizing agent. In some embodiments, the grinding occurs in a mortar. In some embodiments, the grinding includes ball milling. In some embodiments, the grinding results in the formation of a homogenous solid powder.
In some embodiments, the carbon source and the carbonizing agent can be mixed in a solvent. In some embodiments, the solvent is evaporated after mixing. In some embodiments, the evaporation is followed by the carbonization of the carbon source at elevated temperature. In some embodiments, the carbon source is the solvent, and the carbonizing agent is added prior to carbonization at elevated temperatures.
In some embodiments, the carbonizing occurs by heating the carbon source at temperatures ranging from about 200° C. to about 800° C. In some embodiments, the heating occurs at temperatures greater than 500° C. In some embodiments, the heating occurs at temperatures of about 500° C. to about 800° C. In some embodiments, the heating occurs at temperatures of about 600° C. to about 700° C.
In some embodiments, the carbonizing occurs in an inert atmosphere. In some embodiments, the inert atmosphere includes a steady flow of an inert gas, such as argon.
Doping
In some embodiments, the methods of the present disclosure also include a step of doping a carbon source with a dopant. In some embodiments, the dopant includes, without limitation, nitrogen-containing dopants, sulfur-containing dopants, heteroatom-containing dopants, oxygen-containing dopants, sulfur-containing dopants, metal-containing dopants, metal oxide-containing dopants, metal sulfide-containing dopants, phosphorous-containing dopants, and combinations thereof.
In some embodiments, the dopant includes nitrogen-containing dopants. In some embodiments, the nitrogen-containing dopants include, without limitation, primary amines, secondary amines, tertiary amines, nitrogen oxides, pyridinic nitrogens, pyrrolic nitrogens, graphitic nitrogens, and combinations thereof. In some embodiments, the nitrogen-containing dopant includes NH3.
In some embodiments, the dopant includes sulfur-containing dopants. In some embodiments, the sulfur-containing dopants include, without limitation, primary sulfurs, secondary sulfurs, sulfur oxides, and combinations thereof. In some embodiments, the sulfur-containing dopants include H2S.
In some embodiments, the dopants include monomers, such as nitrogen-containing monomers. In some embodiments, the monomers are subsequently polymerized.
Doping can occur at various temperatures. For instance, in some embodiments, the doping occurs at temperatures ranging from about 200° C. to about 800° C. In some embodiments, the doping occurs at temperatures ranging from about 600° C. to about 700° C. In some embodiments, the doping occurs at about 650° C. to about 700° C.
Various amounts of dopants may be utilized. For instance, in some embodiments, the weight ratio of the dopant to the carbon source varies from about 0.2:1 to about 1:1. In some embodiments, the weight ratio of the dopant to the carbon source is about 1:1.
Vulcanization
In some embodiments, the methods of the present disclosure also include a step of vulcanizing the carbon source. In some embodiments, the vulcanizing includes exposing the carbon source to a vulcanizing agent. In some embodiments, the vulcanizing agent includes, without limitation, sulfur-based agents, peroxides, urethane cross-linkers, metallic oxides, acetoxysilane, and combinations thereof. In some embodiments, the vulcanizing agent includes, without limitation, tetramethyldithiuram, 2,2′-dithiobis(benzothiazole), and combinations thereof.
Various amounts of vulcanizing agents may be utilized. For instance, in some embodiments, the weight ratio of the vulcanization agent to the carbon source varies from about 5 wt % to about 200 wt % relative to the carbon source.
Reduction
In some embodiments, the methods of the present disclosure include a step of reducing the formed porous carbon material. In some embodiments, the reducing occurs by exposing the formed porous carbon material to a reducing agent. In some embodiments, the reducing agent includes, without limitation, H2, NaBH4, hydrazine, and combinations thereof. In some embodiments, the reducing agent includes H2.
The methods of the present disclosure may be utilized to make bulk quantities of porous carbon materials. For instance, in some embodiments, the methods of the present disclosure can be utilized to make porous carbon materials in quantities greater than about 1 g. In some embodiments, the methods of the present disclosure can be utilized to make porous carbon materials in quantities greater than about 1 kg. In some embodiments, the methods of the present disclosure can be utilized to make porous carbon materials in quantities greater than about 1000 kg.
Advantages
The gas capture methods and the porous carbon materials of the present disclosure provide numerous advantages over prior gas sorbents. For instance, the porous carbon materials of the present disclosure provide significantly higher CO2 and H2S sorption capacities than prior sorbents. Moreover, due to the availability and affordability of the starting materials, the porous carbon materials of the present disclosure can be made in a facile and economical manner in bulk quantities. Furthermore, unlike traditional gas sorbents, the porous carbon materials of the present disclosure can selectively capture and release CO2 and H2S at ambient temperature without requiring a temperature swing. As such, the porous carbon materials of the present disclosure can avoid substantial thermal insults and be used effectively over successive cycles without losing their original CO2 and H2S sorption capacities.
Accordingly, the gas capture methods and the porous carbon materials of the present disclosure can find numerous applications. For instance, in some embodiments, the gas capture methods and the porous carbon materials of the present disclosure can be utilized for the capture of CO2 and H2S from subsurface oil and gas fields. In more specific embodiments, the process may take advantage of differential pressures commonly found in natural gas collection and processing streams as a driving force during CO2 and H2S capture. For instance, in some embodiments, the methods of the present disclosure may utilize a natural gas-well pressure (e.g., a natural gas well pressure of 200 to 300 bar) as a driving force during CO2 and H2S capture. Thereafter, by lowering the pressure back to ambient conditions after CO2 and H2S uptake, the captured gas can be off-loaded or pumped back downhole into the structures that had held it for geological timeframes. Moreover, the gas capture methods and the porous carbon materials of the present disclosure can allow for the capture and reinjection of CO2 and H2S at the natural gas sites, thereby leading to greatly reduced CO2 and H2S emissions from natural gas streams.
In some embodiments, the methods of the present disclosure can be utilized for the selective release of captured CO2 and H2S. For instance, in some embodiments where a porous carbon material has captured both CO2 and H2S, the lowering of environmental pressure can result in the release of CO2 from the porous carbon material and the retainment of the captured H2S from the porous carbon material. Thereafter, the captured H2S may be released from the porous carbon material by heating the porous carbon material (e.g., at temperatures between about 50° C. to about 100° C.). In additional embodiments where a porous carbon material has captured both CO2 and H2S, the heating of the porous carbon material (e.g., at temperatures between about 50° C. to about 100° C.) can result in the release of the captured H2S and the retainment of the captured CO2. Thereafter, the lowering of environmental pressure can result in the release of CO2 from the porous carbon.
Reference will now be made to more specific embodiments of the present disclosure and experimental results that provide support for such embodiments. However, Applicants note that the disclosure below is for illustrative purposes only and is not intended to limit the scope of the claimed subject matter in any way.
In this Example, Applicants report the preparation and CO2 uptake capacity of microporous carbon materials synthesized from asphalt. Carbonization of asphalt with potassium hydroxide (KOH) at high temperatures (>873 K) yields asphalt-derived porous carbons (A-PC) with Brunauer-Emmett-Teller (BET) surface areas of up to 2800 m2g−1 and CO2 uptake capacities of up to 25 mmol/g at 30 bar and 298 K. Further nitrogen doping of the A-PCs yields active N-doped A-PCs (also referred to as A-NPCs) containing up to 9.3 wt % nitrogen. The A-NPCs have enhanced BET surface areas of up to 2900 m2g−1 and CO2 uptake capacities of up to 1.2 g at 30 bar and 298 K. To the best of Applicants' knowledge, such results represent the highest reported CO2 uptake capacities among the family of activated porous carbon materials. Thus, the porous carbon materials derived from asphalt demonstrate the required properties for capturing CO2 at a well-head during the extraction of natural gas under high pressure.
Asphalt-derived porous carbons (A-PCs) were prepared by carbonization of a molded mixture of asphalt and potassium hydroxide (KOH) at higher temperatures under inert atmosphere (Ar). The treatment of asphalt with KOH was conducted at various temperatures (200° C.-800° C.) and asphalt/KOH weight ratios (varied from 1/1 to 1/5). In addition, the reaction conditions were adjusted and tuned by the CO2 uptake performance of the final porous carbon materials.
In a more specific example, A-PC was synthesized at 700° C. at an asphalt:KOH weight ratio of 1:4. As shown in
Scanning electron microscopy (SEM) images of the A-PCs show porous materials with uniform distribution of the micropores (
Treatment of A-PCs with NH3 at elevated temperatures resulted in N-doped porous carbon materials (A-NPC) (
aEstimated from N2 absorption isotherms at 77 K, where samples were dried at 200° C. for 20 h prior to the measurements.
bCO2 uptake capacity at 23° C.
aCO2 uptake capacity at 23° C.
The surface N-bonding configurations reveal three main nitrogen functional groups in the surface of the carbon framework. As shown in
Further H2 treatment of A-NPCs at 700° C. resulted in formation of reduced A-NPCs (A-rNPC). The elemental composition and the surface area of the A-rNPCs were investigated using XPS (see
Applicants also observed that, as reaction temperatures increased, the relative trend of the pyrrolic nitrogens in A-NPCs increased. However, the opposite was observed for pyridinic nitrogens. These results indicate that pyrolysis temperature during NH3 treatment plays a significant factor in determining the CO2 uptake performance of A-NPCs.
The CO2 uptake capacities of A-PC, A-NPC, and A-rNPC were compared to the CO2 uptake capacities of prior porous carbon materials, including nitrogen containing nucleophilic porous carbons derived from poly(acrylonitrile) (NPCs), sulfur containing porous carbons derived from poly[(2-hydroxymethyl)thiophene (SPCs), commercial activated carbon, and asphalt (the NPCs and SPCs were described previously in PCT/US2014/044315 and Nat Commun., 2014 June 3, 5:3961, doi: 10.1038/ncomms4961). The CO2 uptake capacities were measured by a volumetric method at room temperature over the pressure range of 0-30 bar. The results are shown in
Applicants also observed that volumetric CO2 uptake by A-PC, A-NPC and A-rNPC do not show any hysteresis (data not shown). Such observations suggest that the asphalt-derived porous carbon materials uptake CO2 in a reversible manner. The CO2 uptake capacities at a pressure of 30 bar are summarized in Tables 1 and 2. Such CO2 uptake capacities (i.e., up to 30 mmol/g) are the highest reported CO2 uptake capacities among the activated carbons. Such CO2 uptake capacities are also comparable to the highest CO2 uptake capacities of synthetic metal-organic frameworks (MOFs).
A-rNPC has the highest CO2 uptake performance at 30 bar, although the highest surface is obtained for A-NPC. As Applicants increased the N-doping temperature (from 500° to 800° C.), pyrollic nitrogen starts to decrease in intensity, which is linearly proportional to the CO2 uptake performance of the A-NPCs (see Table 2). Thus, without being bound by theory, Applicants envision that pyrrolic nitrogens play a more significant role in CO2 uptake performance than the bulk nitrogen content of the porous carbon material.
Another key property of the activated carbon materials is the CO2/CH4 selectivity. In order to evaluate the CO2/CH4 selectivity of A-PC, A-NPC and A-rNPCs, Applicants compared CH4 uptake performances with SPC, activated carbon, and ZIF-8 sorbents over the 0-30 bar pressure range at 23° C.
The molar ratios of sorbed CO2 and CH4 (νCO2/νCH4) were estimated as the ratios of the amount of absorbed gases at 30 bar. The measured νCO2/νCH4 for A-rNPC was found to be about 3.5. This value was compared to values for SPC (2.6), activated carbon (1.5) and ZIF-8 (1.9).
In addition, the isosteric heat of absorption of CO2 and CH4 on the surfaces of A-PC, A-NPC and A-rNPC were calculated using low pressure CO2 sorption isotherms at 23° C. and 80° C. The measured value was found to be about 27 kJ/mol.
This Example pertains to the further production and characterization of A-NPCs, A-SPCs, A-rNPCs, and A-NSPCs. In addition, this Example pertains to the use of the aforementioned carbon materials for the capture of both CO2 and H2S.
Asphalt carbon sources were ground with KOH in a mortar. The weight ratio of KOH to the asphalt carbon source was from about 1:3 to about 1:4. The homogeneous powder was heated at 500-800° C. under Ar atmosphere for 1 hour. This was followed by filtration and washing with 10 wt % HCl(aq) and copious amounts of DI water until the extracts were neutral. The filtered sample was then dried at 110° C. until a constant weight was obtained. The above steps produced A-PC.
A-NPC was prepared by annealing the A-PC at 700° C. for 1 hour under an NH3-containing atmosphere. A-rNPC was prepared by further reduction of A-NPC with 10 wt % H2 at 700° C. for 1 hour. A-SPC was prepared by exposing the A-PC to a sulfur source and annealing the sulfur impregnated A-PC at 650° C. for 1 hour. A-NSPC was prepared by annealing the produced A-SPC for 1 hour under an NH3-containing atmosphere to yield A-NSPC.
Next, the produced porous carbon materials were characterized and tested for uptake of CO2 and H2S. The results are summarized in Table 3.
In order to characterize the H2S uptake capacities of the porous carbon materials, the porous carbon materials were first dried at 120° C. for 1 hour under vacuum (0.05 Torr). Next, the porous carbon material was treated with H2S under an air flow for 1 hour. The amount of sulfur retained on the porous carbon material was measured by thermogravimetric analysis (TGA).
After H2S uptake and air oxidation to S, A-rNPC was further characterized by TEM EDS elemental mapping. As shown in
The H2S uptake of A-rNPC was also measured under different conditions, including inert or oxidative conditions. The results are summarized in
Without being bound by theory, it is envisioned that, as a result of the basic functional groups on the surface of A-NPCs and A-rNPCs, and as a result of the pH values of A-NPCs (pH=7.2) and A-rNPCs (pH=7.5), the porous carbon materials of the present disclosure can capture H2S by an acid-base reaction, where an amine group on the porous carbon abstracts a proton from H2S to yield the ammonium salts and hydrogen monosulfide anions according to the following scheme:
R3N (where R is the carbon scaffold or a proton)+H2S→R3NH+ or R2SH++HS−
In this case, the equilibrium constant (keq) is ˜1000 based on the pKa values of the starting materials (H2S) and products (ammonium species). As a result of the reaction of HS− ions with O2 from air introduced in the carbon support, the captured H2S produces sulfur products such as S, SO2 and H2SO4. The catalytic oxidation of H2S on A-NPC, A-rNPC and A-PC can proceed at room temperature by air oxidation.
Applicants also observed that nitrogen doping doubles the H2S capturing capacity of the porous carbon materials (
The CO2 uptake capacities of the porous carbon materials were also evaluated. As shown in
As shown in
In this Example, Applicants provide exemplary schemes for the synthesis of porous carbon materials.
Carbon sources suitable for use in the present disclosure are mixed with a vulcanization agent and heated to 180° C. for 12 hours in accordance with the following scheme:
Carbon source+vulcanization agent→porous carbon material
The weight ratio of the vulcanization agent to the carbon source varied from 5 wt % to 200 wt % relative to the carbon source. The vulcanized carbon source obtained was then treated with KOH, as described in Example 2.1.
Carbon sources suitable for use in the present disclosure are mixed with a vulcanization agent and elemental sulfur and heated to about 180° C. for 12 h in accordance with the following scheme:
Carbon source+vulcanization agent+elemental sulfur→porous carbon material
The weight ratio of the vulcanization agent to the carbon source varied from 5 wt % to 200 wt % relative to the carbon source. The obtained vulcanized carbon source was then treated with KOH as described in Example 2.1.
Carbon sources suitable for use in the present disclosure are mixed with a vulcanization agent, elemental sulfur, and KOH in accordance with the following scheme:
Carbon source+vulcanization agent+KOH→porous carbon material
The homogeneous powder is then heated at 600˜800° C. under Ar atmosphere for 1 hour. This is followed by filtration with 10 wt % HCl(aq) and copious amounts of DI water. The weight ratio of the vulcanization agent was chosen from 5 wt % to 200 wt % additive relative to the carbon source. The weight ratio of KOH to the carbon source varied from 1 to 3.
Carbon sources suitable for use in the present disclosure are mixed with a vulcanization agent, elemental sulfur, and KOH in accordance with the following scheme:
Carbon source+vulcanization agent+elemental sulfur+KOH→porous carbon material
The homogeneous powder is then heated at 600˜800° C. under Ar atmosphere for 1 hour. This is followed by filtration with 10 wt % HCl(aq) and copious amounts of DI water. The weight ratio of the elemental sulfur to the carbon source varied from 0.2 to 1. The weight ratio of the vulcanization agent to the carbon source varied from 5 wt % to 200 wt % relative to the carbon source. The weight ratio of KOH to the carbon source was chosen from 1 to 3.
In summary, Applicants have demonstrated in Examples 1-3 the first successful synthesis of microporous active carbons with uniform distribution of pores sizes from asphalt. Applicants subsequently activated the asphalt derived porous carbon materials with nitrogen functional groups. By changing the reaction conditions, the porous carbon materials can possess variable surface areas and nitrogen contents. The CO2 and H2S uptake capacities of the asphalt-derived porous carbon materials are higher than other porous carbon materials. Additionally, many of the porous carbon materials derived from asphalt exhibit greater CO2:CH4 selectivity than other porous carbon materials. Furthermore, as summarized in Table 4, the carbon sources of the present disclosure are much more affordable than the carbon sources utilized to make other porous carbon materials.
Without further elaboration, it is believed that one skilled in the art can, using the description herein, utilize the present disclosure to its fullest extent. The embodiments described herein are to be construed as illustrative and not as constraining the remainder of the disclosure in any way whatsoever. While the embodiments have been shown and described, many variations and modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims, including all equivalents of the subject matter of the claims. The disclosures of all patents, patent applications and publications cited herein are hereby incorporated herein by reference, to the extent that they provide procedural or other details consistent with and supplementary to those set forth herein.
This application claims priority to U.S. Provisional Patent Application No. 61/865,323, filed on Aug. 13, 2013; and U.S. Provisional Patent Application No. 62/001,552, filed on May 21, 2014. The entirety of each of the aforementioned applications is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61865323 | Aug 2013 | US | |
| 62001552 | May 2014 | US |
