Methods for hydrogen production

Abstract

The present invention relates to a process for producing hydrogen gas from water, iron-containing coal combustion products, and carbon dioxide or a carbon dioxide precursor. The process is spontaneous, without external heating or electrical installation. The process also provides for the recycling of coal combustion products, such as iron slag or ash, and can also be used for carbon dioxide sequestration.

Description

[Technical Field]

[0001] The present invention relates to a spontaneous process for generating hydrogen gas from water in the presence of iron-containing ash or slag and carbon dioxide (CO2) or a carbon dioxide precursor. [Background technology]

[0002] Hydrogen (H2) is one of the important starting materials used in the chemical industry. Hydrogen is also considered the most promising alternative to fossil fuels in transportation, particularly due to its high energy-to-weight ratio and clean combustion product (water). Today, more than 65 million metric tons of commercial hydrogen are produced, the majority of which uses fossil fuels or biomass in addition to water as a resource. Approximately 95% of production relies on steam methane reforming (SMR) or other methods utilizing fossil fuels. SMR involves mixing superheated steam (H2O) (700°C to 1,100°C) with desulfurized natural gas in a reforming reaction to produce hydrogen and carbon monoxide (CO). The carbon monoxide then interacts with the steam in a water shift reaction to produce hydrogen and carbon dioxide. Overall, steam methane reforming is only 65% ​​to 75% efficient, with a significant portion of the methane remaining unreacted throughout the process. In addition, this process has a large carbon footprint, as the production of 1 kilogram (kg) of hydrogen gas generates approximately 7 kg of carbon dioxide (CO2) emissions.

[0003] European Patent No. 3194331 describes a process for synthesizing hydrogen gas (H2) in a reactor under hydrothermal conditions, comprising (a) metallic iron (Fe 0 ) and / or Fe( IIThe process described includes (b) contacting a compound containing a compound with an aqueous composition having a pH of 6.5 or higher and containing carbonate ions and bicarbonate ions at a total concentration of at least 0.01 M to obtain a reaction mixture, and subjecting the reaction mixture to hydrothermal conditions, and (b) reacting the reaction mixture at a reaction temperature above 120°C and not above 240°C and at a pressure of 1 bar to 70 bar to obtain magnetite and hydrogen gas.

[0004] Patent Publication No. 2004-196581 describes a method for producing hydrogen by reacting water with carbon dioxide in a non-oxidizing atmosphere in the presence of aluminum oxide on which potassium, aluminum, and metallic iron are supported as a metallic iron catalyst.

[0005] Patent Publication No. 2007-031169 describes a method for generating hydrogen, comprising activating a metal to generate hydrogen by applying a mechanical impact or stress of a magnitude capable of twisting, deforming, or breaking a metal or a substance containing a low-valence metal in the presence of water. Also provided is a method for fixing carbon dioxide, comprising introducing and interposing carbon dioxide together with water in the above process and converting the carbon dioxide into a stable metal carbonate.

[0006] Carbon dioxide is one of the most important greenhouse gases (GHGs) in the Earth's atmosphere, with a current global average concentration of 409 volume ppm (0.041 volume%) or 622 mass ppm (0.062 mass%). Human activities emit approximately 30 billion tons of CO2 annually, half of which remains in the atmosphere as GHG and is not absorbed by vegetation and / or the ocean. One of the challenges of the 21st century is to reduce carbon dioxide emissions while simultaneously meeting the increasing energy demands of a continuously growing population and economy. Carbon capture and sequestration (CCS), also known as carbon capture and sequestration, is a process of managing CO2 generated (mainly from combustion waste emitted from large point sources such as fossil fuel power plants), transporting the CO2 to storage locations, and depositing the CO2 in a way that prevents it from re-entering the atmosphere. Post-generation CCS, i.e., the removal of CO2 after combustion, is considered one of the most promising strategies for achieving this objective. However, currently available technologies can increase energy costs by 30% to 70% (Leung et al., Renewable and Sustainable Energy Reviews 39(2014)426-443), and are therefore considered prohibitively expensive, and have not yet been widely implemented.

[0007] The majority of captured CO2 is used for enhanced oil recovery (EOR) to recover additional oil from underground oil fields, resulting in the permanent storage of CO2 in these fields. This use is limited in scope and constrained by the availability of suitable natural resources on Earth and transportation costs. The global market for CO2 reuse (in carbonate aggregates, fuels, concrete, methanol, and polymers) is estimated to reach $700 billion by 2030, utilizing 7 billion metric tons of CO2 per year, representing approximately half of the annual amount of CO2 remaining in the atmosphere due to human activities (or 15% of current global CO2 emissions).

[0008] Michiels et al. (Fuel 160(2015)205-216) describe a carbon dioxide-based hydrothermal process for producing hydrogen gas from water via the oxidation of pure metallic iron powder Fe 0 This process requires the application of a significant amount of external energy and is carried out at a high temperature of 160 °C. This process also requires chemical grade Fe 0 powder as a starting material and produces iron(II,III)-oxide Fe3O4.

[0009] Application Publication No. 2007-075773 describes a system for fixing carbon dioxide by contacting carbon dioxide with metal fine particles, or fine particles of a substance containing a metal component in a lower valence state, or aggregates thereof, in the presence of water, enabling the metal component, carbon dioxide, and water to react with each other, thereby converting carbon dioxide into a carbonate of the metal component in a higher valence state.

[0010] Guan et al. (Green Chemistry 5(2003)630-634) describe the reduction of CO2 on 0-valent Fe 0 and Fe 0 system composite materials in an aqueous solution at room temperature to form H2 and a small amount of CH4. When potassium-promoted Fe 0 system composite materials, Fe 0 -K-Al and Fe 0 -Cu-K-Al are used, the CO2 reduction rate increases and CH4, C3H8, CH3OH, and C2H5OH are produced together with H2. Fresh and used Fe 0 powder after the reaction was analyzed by XPS, XRD, and photoelectron emission yield measurements. The results obtained suggest that in the presence of CO2 as a proton source, 0-valent Fe 0 is easily oxidized to stoichiometrically produce H2, and CO2 is catalytically reduced by the obtained H2 on the Fe 0 system composite to produce hydrocarbons and alcohols.

[0011] Coal combustion products (CCP), also known as coal combustion waste (CCW) or coal combustion residual (CCR), pose a significant environmental problem. While less than 50% is recycled, the majority ends up in landfills, stored in mines, or kept in ash reservoirs at coal-fired power plants. CCP is typically classified into four categories: coal ash, which refers to the accumulation of residues produced during coal combustion; fly ash, which refers to the lighter form of coal ash that floats in the exhaust stack; bottom ash, which refers to the heavier portion of coal ash that settles on the boiler floor; and boiler lag, which refers to molten coal ash. The composition of CCP varies as a result of the coal source and combustion parameters. The main component of CCP is silicon dioxide in the form of silica and quartz, which makes up approximately 50% by weight of CCP. Other components include metal oxides such as calcium oxide, potassium oxide, sodium oxide, aluminum oxide, titanium oxide, and magnesium oxide. Iron(II) oxide, FeO, iron(III) oxide, Fe2O3, and iron(II,III) oxide, Fe3O4 are also typically found in CCPs at concentrations of less than 20% by weight.

[0012] There remains an unmet need for cost-effective hydrogen gas production that does not require investment in external heat, while enabling the use and recycling of CCPs. [Overview of the project]

[0013] The present invention provides a spontaneous process for producing H2, comprising contacting water with iron-containing coal combustion products and a CO2 source. The process is carried out in a reactor without external heating, at a temperature below 100°C, for example, in the range of -30°C to 50°C, including ambient temperature.

[0014] This invention is partly based on the remarkable discovery that H2 can be produced at relatively low temperatures without external heating by reacting water, iron-containing coal combustion products, and carbon dioxide (CO2) or a carbon dioxide generating agent. This process can further be used for recycling coal combustion products and for carbon dioxide capture and storage. While previously known processes have utilized high temperatures and / or zero-valent or low-valent iron to generate hydrogen, the inventors of this invention unexpectedly found that it is possible to produce hydrogen at room temperature while using high-valent iron oxide from coal combustion waste. Hydrogen is produced in high purity, while coal combustion waste can be recycled, thereby providing further beneficial environmental advantages.

[0015] According to a first embodiment, a process for producing H2 is provided, the process comprising the step of contacting water with iron-containing coal combustion products and a CO2 source selected from the group consisting of CO2 and CO2 precursors, thereby producing H2, the process being carried out in a reactor in the absence of external heating.

[0016] In another embodiment, a process is provided for generating H2 and recycling coal combustion products or capturing carbon dioxide, the process comprising contacting water with iron-containing coal combustion products and a CO2 source selected from the group consisting of CO2 and CO2 precursors to generate H2 and recycle coal combustion products or capture carbon dioxide, the process being carried out in a reactor in the absence of external heating.

[0017] In one embodiment, the process is performed without the addition of external electrical energy. In another embodiment, the process is performed without the addition of external energy.

[0018] In some embodiments, the process further includes a step of collecting the generated H2. In other embodiments, the process further includes a step of post-processing the generated H2. In certain embodiments, the post-processing includes at least one of gas separation, filtration, and drying. Each possibility represents a separate embodiment. In further embodiments, the generated H2 has a purity of at least about 85%.

[0019] In certain embodiments, water is in the liquid phase. In various embodiments, water is selected from the group consisting of tap water, seawater, partially purified water, deionized water, distilled water, brackish water, and wastewater. Each possibility represents a separate embodiment.

[0020] In other embodiments, the iron-containing coal combustion products are selected from the group consisting of coal ash, fly ash, bottom ash, boiler lag, and mixtures or combinations thereof. Each possibility represents a separate embodiment. In certain embodiments, the iron-containing coal combustion products originate from power plants, fuel boilers, or cement production. Each possibility represents a separate embodiment. In some embodiments, the power plant or boiler is burned with coal or heavy oil. In some embodiments, the iron-containing coal combustion products include divalent iron oxide, trivalent iron oxide, or combinations thereof. Each possibility represents a separate embodiment. In one embodiment, the iron-containing coal combustion products include trivalent iron oxide. In certain embodiments, the iron-containing coal combustion products include at least one of iron(II) oxide (FeO), iron(II,III) oxide (Fe3O4), and iron(III) oxide (Fe2O3). Each possibility represents a separate embodiment.

[0021] In some embodiments, the iron-containing coal combustion product contains iron oxide ranging from about 2% w / w to about 40% w / w, including all values ​​within the specified range. In other embodiments, the iron-containing coal combustion product contains iron oxide ranging from about 5% w / w to about 30% w / w, including all values ​​within the specified range. In exemplary embodiments, the iron-containing coal combustion product contains less than 25% w / w of iron oxide. In further embodiments, the iron-containing coal combustion product contains silicon dioxide ranging from about 25% w / w to about 75% w / w, including all values ​​within the specified range. In further embodiments, the weight ratio of iron oxide to silicon dioxide in the iron-containing coal combustion product is in the range of about 1:1.5 to about 1:10, including all iterations of the ratio within the specified range.

[0022] In certain embodiments, the process further includes pre-treating the iron-containing coal combustion product before contacting it with water and a CO2 source. In some embodiments, the pre-treatment includes at least one of milling the iron-containing coal combustion product and enriching the iron content in the iron-containing coal combustion product. Each possibility represents a separate embodiment. In certain embodiments, the iron-containing coal combustion product is milled to an average particle size of less than about 100 μm, less than about 75 μm, less than about 50 μm, less than about 25 μm, less than about 10 μm, or even less than about 5 μm. Each possibility represents a separate embodiment. In certain embodiments, the iron-containing coal combustion product is milled to an average particle size in the range of about 1 μm to about 5 μm, or about 3 μm to about 5 μm, including each value within the specified range. In further embodiments, the iron content in the iron-containing coal combustion product is enriched by 10% or more of its original content. In other embodiments, the process further includes pre-treating at least one of the water and the CO2 source before bringing the water, iron-containing coal combustion products, and the CO2 source into contact.

[0023] In additional embodiments, the CO2 source is CO2 gas. In various embodiments, the CO2 gas is derived from at least one of pure industrial CO2, flue gas, CO2 production plants, and atmospheric CO2. Each possibility represents a separate embodiment. In one embodiment, the CO2 source is dry ice. In another embodiment, the CO2 precursor is selected from carbonic acid, carbonates, bicarbonates, and mixtures or combinations thereof. Each possibility represents a separate embodiment.

[0024] In some embodiments, the process is a batch production process. In other embodiments, the process is a continuous production process.

[0025] In various embodiments, the process is carried out at a pH of 6.5 or less. In other embodiments, the process is carried out at a pH of 6 or less. In certain embodiments, the process is carried out at a pH of 5.5 or less. In further embodiments, the process is carried out at a pH in the range of about 4 to about 6, including each value within the specified range. In certain embodiments, the process is carried out at a pH in the range of about 5.7 to about 6, including each value within the specified range. In other embodiments, the process is carried out at a pH of at least 6.5, for example, in the range of about 7 to about 10, including each value within the specified range.

[0026] In one embodiment, the process is carried out at a temperature of 100°C or less. In some embodiments, the process is carried out at a temperature in the range of about -30°C to about 100°C, including each value within the specified range. In other embodiments, the process is carried out at a temperature in the range of about -15°C to about 100°C, including each value within the specified range. In still other embodiments, the process is carried out at a temperature in the range of about -5°C to about 100°C, including each value within the specified range. In certain embodiments, the process is carried out at a temperature in the range of about -5°C to about 80°C, including each value within the specified range. In further embodiments, the process is carried out at a temperature of about -5°C to about 50°C, including each value within the specified range. According to the principles of the present invention, the process does not include external heating. In certain embodiments, the process does not include external cooling.

[0027] In certain embodiments, the process is performed at a pressure of approximately 1 bar to approximately 350 bar, including each value within a specified range. In other embodiments, the process is performed at a pressure of approximately 40 bar to approximately 350 bar, including each value within a specified range. In yet another embodiment, the process is performed at a pressure of approximately 1 bar to approximately 100 bar, including each value within a specified range. In yet another embodiment, the process is performed at a pressure of approximately 100 bar to approximately 350 bar, including each value within a specified range. In an additional embodiment, the process is performed at a pressure of approximately 100 bar to approximately 250 bar, including each value within a specified range.

[0028] In various embodiments, the process is carried out under continuous mixing.

[0029] In some embodiments, the process further includes adding a solidification inhibitor to the reaction. In certain embodiments, the solidification inhibitor is selected from the group consisting of tricalcium phosphate, powdered cellulose, magnesium stearate, sodium ferrocyanide, potassium ferrocyanide, calcium ferrocyanide, calcium phosphate, sodium silicate, silicon dioxide, calcium silicate, magnesium trisilicate, talcum powder, sodium aluminosilicate, potassium aluminum silicate, calcium aluminosilicate, bentonite, aluminum silicate, stearic acid, polydimethylsiloxane, and mixtures or combinations thereof. Each possibility represents a separate embodiment. Since iron-containing coal combustion products typically contain a considerable amount of silicon dioxide, it is intended that the addition of a solidification inhibitor can be avoided or reduced while keeping the process efficient.

[0030] In certain embodiments, the process includes (a) dispersing iron-containing coal combustion products in water, and (b) adding a CO2 source to the dispersion from step (a) to generate a reaction. In other embodiments, the process includes (a) replenishing water with CO2 from a CO2 source, and (b) adding iron-containing coal combustion products to the CO2-replenished water from step (a) to generate a reaction.

[0031] In some embodiments, the process further includes the step of adding an acid to water. In additional embodiments, the process includes (a) dispersing an iron-containing coal combustion product in water, (b) adding hydrochloric acid to the dispersion from step (a), and (c) adding a CO2 source to the dispersion from step (b) to generate hydrogen.

[0032] Further embodiments and the full scope of applicability of the present invention will become apparent from the detailed description given below. However, various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description, so it should be understood that the detailed description and specific examples, while illustrating preferred embodiments of the invention, are given only as examples. [Brief explanation of the drawing]

[0033] The accompanying drawings, included to provide a further understanding of the present invention and incorporated herein as part thereof, illustrate embodiments of the present invention and serve to illustrate the principles of the present invention together with this specification.

[0034] [Figure 1] A schematic diagram of a batch reactor configured for performing a batch process, according to one embodiment of the present invention, is shown. [Figure 2] A schematic diagram of a continuous flow reactor configured for performing a continuous process, according to another embodiment of the present invention, is shown. [Modes for carrying out the invention]

[0035] The following description is provided with all chapters of the invention to enable those skilled in the art to utilize the invention and describes the best mode intended by the inventors practicing the invention. However, since the general principles of the invention are specifically defined to provide compositions and methods, various modifications are adapted so as to remain obvious to those skilled in the art. Any reference numerals used herein and in the claims may serve as an aid to understanding but should not be construed as limiting their scope.

[0036] Disclosing a method for producing hydrogen from a reaction involving carbon dioxide, water, and coal combustion products such as slag or ash containing iron oxide, without supplying external heat or electricity to the reaction, is within the scope of the present invention. Accordingly, the present invention provides a spontaneous process from which hydrogen gas can be obtained. The process further comprises the recycling of iron-containing coal combustion waste and, in some embodiments, provides carbon dioxide capture and storage.

[0037] It is hereby disclosed for the first time that hydrogen production at room temperature can be achieved by using high-valent iron oxide species instead of pure iron metal and zero-valent or low-valent iron-containing particles. Furthermore, high-purity hydrogen production can be achieved even when using iron waste derived from coal combustion procedures in which iron oxide constitutes only a trace component. A further advantage arises from the recycling of iron waste that would otherwise have to be disposed of with ecological costs, resulting in additional environmental benefits. In certain embodiments, the recycling of iron waste involves the production of iron carbonate, iron oxide, or a combination thereof. In some embodiments, the process of the present invention further includes capturing CO2 as a metal complex (e.g., an iron complex), thereby resulting in carbon capture and utilization (CCU) and CO2 sequestration. The use of iron-containing coal combustion product reactants has also shown to accelerate the reaction dynamics by containing a relatively large amount of silicon dioxide, which is useful as a solidification inhibitor.

[0038] According to some aspects and embodiments, a process for producing H2 is provided, which includes mixing water, iron-containing coal combustion products, and a CO2 source selected from the group consisting of CO2 and CO2 precursors or generators in a reactor to induce a spontaneous reaction without the use of external heating or electricity. According to other aspects and embodiments, a process is provided for producing H2 and recycling coal combustion products or capturing carbon dioxide, which includes mixing water, iron-containing coal combustion products, and a CO2 source selected from the group consisting of CO2 and CO2 precursors or generators in a reactor to induce a spontaneous reaction without the use of external heating.

[0039] Where used herein, the term “in the absence of external heating” is intended to describe the delivery of heat to the reaction mixture that is not autoheated during the course of the reaction. Specifically, the reaction in this process is mildly exothermic. Thus, as the reaction proceeds and produces hydrogen gas, the internal temperature in the sealed reactor rises spontaneously. Such a rise in temperature is not considered external heating and is therefore not excluded by the phrases “in the absence of external heating,” “without external heating,” “the process does not involve external heating,” and related phrases. Rather, these phrases are intended to exclude the provision of additional heating from an external source, such as by an electronic heating element or burner. Thus, according to these embodiments, the process lacks heating of the reaction mixture. It should be understood that an intrinsic rise in temperature of the reaction mixture can occur and is not excluded by the phrases “in the absence of external heating,” “without external heating,” “the process does not involve external heating,” and related phrases. Specifically, such an intrinsic rise in temperature may originate, for example, from a change in pressure in the sealed reactor where the reaction takes place, or from energy exerted by the dissolution of substances in water. Specifically, throughout the entire reaction of the process of the present invention, CO2 may be replenished as CO2 gas, which may result in an increase in the pressure inside the reactor. Also, according to the principle of the present invention, H2 gas is generated, which increases the gas pressure inside the reactor. Hydrogen is considered an ideal gas, and the temperature of an ideal gas generally correlates with its pressure. As a result, intrinsic heating, which is not excluded by the above definition, may occur. Furthermore, most dissolution processes are exothermic, meaning that when a solution is formed from the solvent and solute (e.g., from water and carbon dioxide), the temperature may rise. This is additional intrinsic heating, which is not excluded by the above definition. Another factor that may slightly affect the reaction temperature and is not excluded by the above phrase is the mixing, stirring, or blending of the reaction contents. Specifically, these mixing processes may result in a slight increase in temperature due to the kinetic energy they release, but are not considered to provide external heating as defined in the present invention.It should be further understood that the use of reaction catalysts, initiators, or accelerators does not preclude the possibility that the reaction is considered spontaneous, as they accelerate the reaction dynamics but do not affect the net thermodynamics. As used herein, a process is considered a spontaneous process. As used herein, the term “spontaneous process” refers to a process that does not utilize external energy in the form of heating or the application of electric current. In certain embodiments, the process is carried out without the addition of external electrical energy.

[0040] In some embodiments, the process is carried out at a temperature of 100°C or less. According to a particular embodiment, the step of contacting water, iron-containing coal combustion products, and a CO2 source is carried out at a temperature in the range of -30°C to 100°C, including values ​​within a specified range. According to another embodiment, the contact step is carried out at a temperature in the range of -15°C to 100°C, including values ​​within a specified range. According to yet another embodiment, the contact step is carried out at a temperature in the range of -5°C to 100°C, including values ​​within a specified range. According to yet another embodiment, the contact step is carried out at a temperature in the range of -5°C to 80°C, including values ​​within a specified range. According to a particular embodiment, the contact step is carried out at a temperature in the range of -5°C to 50°C, including values ​​within a specified range. According to a particular embodiment, the contact step is carried out at a temperature in the range of 5°C to 50°C, including values ​​within a specified range. According to one embodiment, the process is carried out at a temperature of 100°C or less. According to another embodiment, the process is carried out at a temperature of 95°C or less. According to yet another embodiment, the process is carried out at a temperature of 90°C or less. According to some embodiments, the process is carried out at a temperature of 85°C or lower. According to other embodiments, the process is carried out at a temperature of 80°C or lower. According to further embodiments, the process is carried out at a temperature of 75°C or lower. According to additional embodiments, the process is carried out at a temperature of 70°C or lower. According to certain embodiments, the process is carried out at a temperature of 65°C or lower. According to various embodiments, the process is carried out at a temperature of 60°C or lower. According to some embodiments, the process is carried out at a temperature of 55°C or lower. According to certain embodiments, the process is carried out at a temperature of 50°C or lower.

[0041] In some embodiments and settings, the process involves contacting water and iron-containing coal combustion products with a CO2 source. In other embodiments and settings, the process involves contacting water supplemented with a CO2 source with iron-containing coal combustion products. As detailed herein, in some embodiments, the CO2 precursor may include a combination of two components, such as a carbonate compound or a bicarbonate compound and an acid. Thus, in some embodiments, the process involves contacting water, a first component of the CO2 source, and iron-containing coal combustion products with a second component of the CO2 source. As used herein, the term “contact” is intended to mean bringing together water, iron-containing coal combustion products, and the CO2 source to form a mixture, which may be homogeneous or heterogeneous, each possibility representing a separate embodiment. The term “contact” may further, optionally, mean dispersing, suspending, and / or dissolving the CO2 source and iron-containing coal combustion products in water, accompanied by mixing.

[0042] According to various embodiments, a mixture of iron-containing coal combustion products and water is a viscous suspension. Specifically, it should be understood that increasing the weight ratio of coal combustion products to water increases the solid content, and therefore the viscosity of the suspension should also increase. According to some embodiments, the weight ratio of iron-containing coal combustion products to water is in the range of 1:4 to 100:1, and includes all iterations of ratios within the specified range. For example, the weight ratio of iron-containing coal combustion products to water is in the range of 1:3 to 75:1, 1:2 to 50:1, or 1:1.5 to 25:1, and includes all iterations of ratios within the specified range.

[0043] According to several aspects and embodiments, the processes disclosed herein are carried out in a sealed reactor. As used herein, the term “sealed reactor” refers to a sealed system that allows for the accumulation of gas pressure by at least temporarily isolating the reaction mixture contained therein from the surrounding environment and preventing the substance from leaving its enclosure. It should be understood that a sealed reactor may include openings and / or covers for access to the reaction medium therein, and is not limited to a permanently sealed or enclosed structure. Elements such as covers or ports may provide reversible access to the interior of the reactor so that the sealed feature of the reactor may be limited to its operating period. Reactors may have any shape, including but not limited to cylindrical, cubic, and rectangular, and may be constructed from a variety of materials, including but not limited to metal, plastic, and ceramic. Each possibility represents a separate embodiment. According to certain embodiments, the reactor comprises a mixing mechanism. The mixing mechanism may be based on mechanical, magnetic, ultrasonic, and high-pressure liquid mixers, as known in the art. According to several embodiments, the contents of the reactor are mixed by circulating and / or recirculating the reaction mixture by a continuous or intermittent flow. The flow can be generated by a pump, such as a high-pressure pump, which is functionally associated with the reactor. As detailed above, various mixing procedures do not involve the provision of external energy as defined in this invention.

[0044] According to a particular embodiment, the process is (a) A step of dispersing iron-containing coal combustion products in water, (b) A step of adding a CO2 source to the dispersion of step (a), (c) The step of maintaining the mixture from step (b) in a substantially sealed state in a sealed reactor for a certain period of time.

[0045] According to the principles of the present invention, step (a) may include (a1) dispersing iron-containing coal combustion products in water in an open setting, and (a2) transferring the dispersion from step (a1) to a closed reactor.

[0046] According to other embodiments, step (c) further includes mixing the mixture formed in step (b). According to some embodiments, step (a), in which the iron-containing coal combustion product is dispersed in water, may be carried out in a closed reactor.

[0047] According to further embodiments, a CO2 source and iron-containing coal combustion products are added substantially simultaneously to water in a sealed reactor, and the resulting mixture is maintained in a substantially sealed state within the sealed reactor for a certain period of time. According to some embodiments, the process further includes mixing the mixture formed upon addition.

[0048] According to various embodiments, the process is (a) A process of dispersing a CO2 source in water, (b) A step of adding iron-containing coal combustion products to the dispersion of step (a), (c) The step of maintaining the mixture from step (b) in a substantially sealed state in a sealed reactor for a certain period of time.

[0049] According to some embodiments, step (a) of dispersing a CO2 source in water includes at least partially solubilizing the CO2 source in water. According to some embodiments, step (c) further includes mixing the mixture formed in step (b). According to the principles of the present invention, steps (a) and (b) may be carried out in an open setting or in a closed reactor, each possibility representing a separate embodiment.

[0050] One of the advantages of this process is that it produces hydrogen that can be used as a "green" fuel and can contribute to a cleaner environment compared to the use of fossil fuels, which are typically used today. A further advantage of the present invention is that the hydrogen produced by the present invention is of high purity and substantially free of contaminants unsuitable for fuel and combustion. According to exemplary embodiments, the hydrogen produced by this process is produced with a purity of at least 85%. According to other exemplary embodiments, the hydrogen produced by this process is produced with a purity of at least 90%. It should be understood that "at least 85% purity" means that the total volume of hydrogen produced by this process is at least 0.85 times the total volume of reaction products. According to some embodiments, the volume of hydrogen produced by this process is at least 85% of the total gas volume in the reaction at the end of the process.

[0051] According to one embodiment, the process further includes a step of collecting the generated H2. According to some embodiments, collecting the generated H2 includes delivering the H2 gas to a gas container through a gas pipe. According to other embodiments, the gas pipe extends from a sealed reactor to a gas container. According to additional embodiments, the gas pipe includes a valve configured to allow sealing of the sealed reactor for the duration of the reaction. According to further embodiments, the gas valve is configured to allow the passage of hydrogen gas from the sealed reactor to the gas container, thereby allowing the collection of the generated H2. In certain embodiments, the discharge system includes a valve (such as a reversing valve) fitted with a flame retardant and / or bubbler. In certain embodiments, the reactor and / or container further includes a check valve with a flame arrestor. Verification of hydrogen gas formation can be performed, for example, by using a hydrogen burner, as is known in the art.

[0052] According to several embodiments, the process further includes a step of processing the generated hydrogen gas. According to one embodiment, the processing step is selected from the group consisting of separation and dehumidification. Each possibility represents a separate embodiment. According to another embodiment, the processing includes separating gases other than hydrogen from the formed hydrogen gas. It should be understood that other gases may be present after the completion of the reaction, such as CO2, water vapor, and gases present in the atmosphere or flue gas. Therefore, according to several embodiments, the H2 released from the closed reactor can be passed through a gas separation or filtration system. The filtration system may include, but is not limited to, silica, zeolite, polymer absorbents, perovskite, or nanoporous membrane absorbents that allow the passage of smaller molecules such as H2 while blocking larger molecules such as CO2. According to several embodiments, the filtration system includes a polymer membrane constructed from at least one polymer selected from the group consisting of polyethylene, polyamide, polyimide, cellulose acetate, polysulfone, and polydimethylsiloxane. Each possibility represents a separate embodiment. According to certain embodiments, the post-treatment step includes dehumidification. Therefore, the separated hydrogen gas can be passed through a drying system equipped with a desiccant or hygroscopic agent. According to various embodiments, the desiccant includes silica, zeolite, polymer, or metal-organic framework (MOF), etc. Each possibility represents a separate embodiment. According to some embodiments, the filtration system is functionally connected to a valve. According to other embodiments, the drying system is functionally connected to a valve. An additional post-treatment included within the scope of the present invention is pressurization and / or liquefaction of the generated hydrogen.

[0053] According to certain aspects and embodiments, the process of the present invention utilizes water, iron-containing coal combustion products, and a CO2 source as reactants in the process. Advantageously, the reactants can be obtained from a variety of sources, including waste, without the need for purification, pretreatment, or preprocessing. However, it should be understood that each of the reactants may be purified, pretreated, or preprocessed before being used in the process of the present invention.

[0054] As used herein, “water” refers to any type of aqueous medium, including but not limited to tap water, seawater, partially purified water, deionized water, distilled water, brackish water, and wastewater. Each possibility represents a separate embodiment. According to some embodiments, water is unpurified water. According to certain embodiments, water is in a solid phase, liquid phase, or gas phase. Preferably, water is in a liquid phase, i.e., liquid water.

[0055] As used herein, the term “seawater” refers to brine obtained from the sea or ocean. The ion concentration in seawater is typically between approximately 10,000 ppm and 44,000 ppm, and includes values ​​within the specified range. Common ions in seawater include chloride ions, sodium ions, sulfate ions, magnesium ions, calcium ions, potassium ions, bicarbonate ions, carbonate ions, strontium ions, bromide ions, borate ions, fluoride ions, boron ions, silicate ions, and iodide ions.

[0056] As used herein, the term “brackish water” refers to water that has a higher salinity than fresh water but a lower salinity than seawater. Brackish water typically contains at least 0.5 grams of dissolved salt per liter. The term “brackish water” may also include brine.

[0057] As used herein, the term "deionized water" refers to water from which almost all mineral ions, including cations such as sodium, calcium, iron, and copper, and anions such as chloride and sulfate ions, have been removed. Deionization is a chemical process that uses specially manufactured ion exchange resins, which reduce the amount of minerals by exchanging them for hydrogen and hydroxides.

[0058] As used herein, the term “distilled water” refers to water produced by the process of distillation. Distillation involves boiling water and then condensing the vapors into a clean container, leaving behind solid contaminants.

[0059] As used herein, the term “wastewater” refers to residential, household, commercial, and / or industrial liquid waste containing organic or inorganic substances. Typically, the term is used to define one or more of the following: aqueous waste containing biological substances, such as sewage, rainwater, and household wastewater, such as laundry and / or bathroom waste, also known as sewage. As used herein, the term “wastewater” also encompasses non-biological and inorganic aqueous waste materials, such as water used for cleaning or temperature control of industrial machinery. It should be understood that using wastewater for various purposes is both economically and environmentally beneficial, as this type of water would otherwise require a rigorous purification process for recycling for later use. According to some embodiments, the water used in this process includes wastewater.

[0060] As used herein, the term “iron-containing coal combustion products” includes, but is not limited to, iron-containing coal combustion waste and iron-containing coal combustion residues selected from coal ash, fly ash, bottom ash, boiler lag, heavy oil ash, and mixtures or combinations thereof. Each possibility represents a separate embodiment. Iron-containing coal combustion products may originate from power plants, fuel boilers, or cement production or other industrial thermal processes. Each possibility represents a separate embodiment. Iron-containing coal combustion products may also be produced by the combustion of other heavy fuel oils, such as mazut. Since the chemical composition of coal combustion products (CCPs) varies as a result of the coal source and combustion parameters, the iron-containing coal combustion products used in the processes of the present invention may also vary. Typically, iron-containing coal combustion products contain about 2% to about 40% iron oxide, within the specified range. In other embodiments, iron-containing coal combustion products contain about 5% to about 30% iron oxide, within the specified range. In yet another embodiment, iron-containing coal combustion products contain less than 25% iron oxide. Exemplary content of iron oxide in coal combustion products includes, but is not limited to, about 2%, about 5%, about 7%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, or about 40%, each possibility representing a separate embodiment. It should be understood that the ratios and percentages used herein to define the relative amount of a substance refer to weight ratios and weight percentages. For example, a coal combustion product weighing 100 grams and containing 15 grams of iron oxide and 85 grams of other compounds is considered an iron-containing coal combustion product containing 15% iron oxide. It should be further understood that if the coal combustion product contains several different iron oxides (e.g., Fe in different oxidation states), the total amount of iron oxide should be taken into consideration in the calculation of the percentage. For example, a coal combustion product weighing 100 grams and containing 5 grams of iron(II) oxide (FeO), 5 grams of iron(II,III) oxide (Fe3O4), 10 grams of iron(III) oxide (Fe2O3), and 80 grams of other compounds is considered an iron-containing coal combustion product containing 20% ​​iron oxide.

[0061] As used herein, the term “iron oxide” refers to any compound containing a chemical bond between an Fe atom and an O atom. According to some embodiments, iron oxide includes divalent iron oxide, trivalent iron oxide, or a combination thereof. Each possibility represents a separate embodiment. In one embodiment, iron oxide includes trivalent iron oxide. In some embodiments, iron oxide includes at least one of iron(II) oxide (FeO), iron(II,III) oxide (Fe3O4), iron(III) oxide (Fe2O3), and combinations thereof. According to other embodiments, iron oxide is selected from the group consisting of iron(II) oxide (FeO), iron(II,III) oxide (Fe3O4), iron(III) oxide (Fe2O3), and combinations thereof. In other embodiments, iron oxide is selected from the group consisting of iron(II,III) oxide (Fe3O4), iron(III) oxide (Fe2O3), and combinations thereof.

[0062] Coal combustion products also typically contain silicon dioxide as a major component, in a weight ratio of about 25% to about 75% silicon dioxide, including each value within the specified range. Exemplary amounts of silicon dioxide (either silica or quartz) include, but are not limited to, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, or about 75%, each possibility representing a separate embodiment. In additional embodiments, the ratio of iron oxide to silicon dioxide in iron-containing coal combustion products ranges from about 1:1.5 to about 1:10, including all iterations of the ratio within the specified range. In exemplary embodiments, the weight percentage ratio of iron oxide to silicon dioxide in iron-containing coal combustion products includes ratios of approximately 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, or 1:10, each possibility representing a separate embodiment. Furthermore, coal combustion products typically include, but are not limited to, additional oxides such as TiO2, Al2O3, CaO, MgO, K2O, Na2O, and SO3. The total amount of the aforementioned additional oxides varies, typically ranging from approximately 20% to approximately 50%, and includes each value within the specified range. As examples rather than limitations, the weight percentage of TiO2 ranges from approximately 0.2% to 3%, Al2O3 ranges from approximately 5% to 35%, CaO ranges from approximately 1% to 35%, MgO ranges from approximately 0.1% to 8%, K2O ranges from approximately 0.05% to 4%, Na2O ranges from approximately 0.1% to 3%, and SO3 ranges from approximately 0.1% to 2.5%, including values ​​within the specified ranges. Further trace components of coal combustion products include, but are not limited to, MnO, P2O5, SrO, and ZrO2, with their total amounts typically being less than approximately 5% by weight.

[0063] As detailed herein, coal combustion products may be available in different particle or granular sizes (whether ash or slag) depending on the production. Typically, the reaction of such insoluble solids is facilitated when the solid has a large surface-to-bulk area. Therefore, iron-containing coal combustion products may, according to some embodiments, be provided in the form of granules having at least one dimension that is small / narrow enough to allow for a fast reaction.

[0064] Granularity generally refers to the degree to which a substance or system is composed of identifiable fragments. Granularity can refer to either the degree to which larger entities are subdivided, or the degree to which smaller, indistinguishable groups of entities are bound together or aggregated to form larger, identifiable entities. As used herein, the term “granule” refers to identifiable fragments in a granular material. According to some embodiments, each granule is substantially spherical with a diameter ranging from about 0.1 to about 3 millimeters, and each value within the specified range includes.

[0065] According to some embodiments, the iron-containing coal combustion product comprises three-dimensional granules, at least one of which has dimensions less than 1 centimeter. According to other embodiments, at least one of the iron-containing coal combustion product granules has dimensions less than 0.5 centimeters. According to yet another embodiment, at least one of the iron-containing coal combustion product granules has dimensions less than 0.35 centimeters. According to an additional embodiment, at least one of the iron-containing coal combustion product granules has dimensions less than 0.25 centimeters. According to yet another embodiment, at least one of the iron-containing coal combustion product granules has dimensions less than 0.15 centimeters. According to a particular embodiment, at least one of the iron-containing coal combustion product granules has dimensions less than 0.1 centimeters.

[0066] Iron-containing coal combustion products can be pre-treated before being added to the reactor. In some embodiments, the pre-treatment includes milling or grinding the iron-containing coal combustion products. Typically, the milling or grinding is performed to obtain particles having an average particle size of less than about 100 μm. According to some embodiments, the process further includes the step of milling or grinding the iron-containing coal combustion products into a powder. The milling or grinding can be performed using any suitable method, e.g., milling, crushing, cutting, and any suitable device, e.g., vortex mill, jet mill, conical mill, ball mill, SAG mill, pebble mill, roller press, Boorston mill, VSI mill, tower mill, or a combination thereof. Each possibility represents a separate embodiment. According to certain embodiments, the milling or grinding is performed to obtain particles having an average particle size of less than about 100 μm, less than about 75 μm, less than about 50 μm, less than about 25 μm, less than about 10 μm, or even less than about 5 μm. Each possibility represents a separate embodiment. Currently preferred size ranges include sizes of about 1 μm to about 10 μm, for example, about 1 μm to about 5 μm, or about 3 μm to about 5 μm, including each value within the specified range. According to some embodiments, the milled iron-containing particles have an average particle size in the range of about 0.1 to about 0.9 mm, including each value within the specified range. According to other embodiments, the milled iron-containing particles have an average particle size in the range of about 0.15 to about 0.65 mm, including each value within the specified range. According to further embodiments, at least 50% of the total mass of the milled iron-containing particles consists of particles having an average particle size in the range of about 0.1 to about 0.9 mm. According to some embodiments, at least 60% of the total mass of the milled iron-containing particles consists of particles having an average particle size in the range of about 0.1 to about 0.9 mm. According to other embodiments, at least 65% of the total mass of the milled iron-containing particles consists of particles having an average particle size in the range of about 0.1 to about 0.9 mm. In yet another embodiment, at least 70% of the total mass of the milled iron-containing particles consists of particles having an average particle size in the range of about 0.1 to about 0.9 mm.According to an additional embodiment, at least 75% of the total mass of the milled iron-containing particles consists of particles having an average particle size in the range of about 0.1 to about 0.9 mm. According to some embodiments, at least 50% of the total mass of the milled iron-containing particles consists of particles having an average particle size in the range of about 0.15 to about 0.65 mm. According to another embodiment, at least 60% of the total mass of the milled iron-containing particles consists of particles having an average particle size in the range of about 0.15 to about 0.65 mm. According to yet another embodiment, at least 65% of the total mass of the milled iron-containing particles consists of particles having an average particle size in the range of about 0.15 to about 0.65 mm. According to a further embodiment, at least 70% of the total mass of the milled iron-containing particles consists of particles having an average particle size in the range of about 0.15 to about 0.65 mm. According to an additional embodiment, at least 75% of the total mass of the milled iron-containing particles consists of particles having an average particle size in the range of about 0.15 to about 0.65 mm.

[0067] The inventors of the present invention have surprisingly found that it is possible to produce hydrogen of high purity even when using coal combustion products containing less than 25% by weight of iron oxide, for example, when using slag containing about 5-10% iron oxide. Furthermore, the present invention aims to enrich iron-containing coal combustion products or ground iron-containing coal combustion products with iron oxide. Typically, enrichment is influenced such that the total amount or iron oxide increases by at least 10% of the initial amount, for example, the total amount of iron oxide can increase by at least about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, about 100%, about 150%, about 200%, or more. Each possibility represents a separate embodiment. Enrichment can be carried out by various methods known in the art, including but not limited to beneficiation and leaching. Beneficiation processes include, among others, particle size measurement, density separation, magnetic separation, and floss flotation. Each possibility represents a separate embodiment. Particle and magnetic separation using air classification and / or magnetic sieves is currently preferred due to the magnetic properties of iron. For example, cross-belt and overband magnetic separators are commercially available devices, thereby enabling automated magnetic separation.

[0068] Additional pretreatments that may be performed on coal combustion products include, but are not limited to, washing with washing solutions selected from the group consisting of aqueous solutions, acidic solutions, basic solutions, organic solvents, and combinations thereof. Each possibility represents a separate embodiment. Preferred acidic solutions include, but are not limited to, sulfuric acid, phosphoric acid, hydrochloric acid, acetic acid, and citric acid. Each possibility represents a separate embodiment. Preferred basic solutions include, but are not limited to, sodium hydroxide, potassium hydroxide, and ammonium hydroxide. Each possibility represents a separate embodiment.

[0069] The present invention primarily relates to the production of hydrogen from water, a CO2 source, and iron-containing coal combustion products in the absence of external heating, but it is intended that other high-valence iron sources may be used according to the principles disclosed herein. Accordingly, in some aspects and embodiments, the present invention provides a process for producing H2, the process comprising the step of contacting water, a high-valence iron-containing material, and a CO2 source selected from the group consisting of CO2 and CO2 precursors, thereby producing H2, the process being carried out in a reactor in the absence of external heating. High-valence iron-containing materials include, but are not limited to, iron ores containing magnetite, hematite, goetite, limonite, or siderite, and high-valence iron waste derived from solid industrial waste of water treatment, bauxite processing (red clay), mineral paints, metallurgy, chemical, and mechanical engineering plants (e.g., semiconductor manufacturing), and the steel industry. Each possibility represents a separate embodiment.

[0070] The steel industry typically utilizes iron derived from iron ore mines, ore dressing plants, coal mines, coal washing plants, and coke plants. Each possibility represents a separate embodiment. Typically, steel production involves hot working in the presence of an oxygen-containing gas (e.g., air) that corrodes the steel surface into iron oxide, thereby forming a layer called scale on the surface steel. Iron oxides, including iron(II) oxide, FeO, iron(III) oxide, Fe2O3, and iron(II,III) oxide, Fe3O4, may be used in the processes disclosed herein. According to various embodiments, high-valent iron-containing materials may originate from finishing operations common in pig iron production, steelmaking, rolling, and milling of steel, namely cold rolling, tin plating, galvanizing, and hot rolling. Each possibility represents a separate embodiment.

[0071] According to some embodiments and designs, the CO2 source is CO2. According to other embodiments, the CO2 source is CO2 provided as CO2 gas. It should be understood that under atmospheric conditions, CO2 is in a gaseous state, but under high gas pressure conditions and moderate temperatures, CO2 can be in equilibrium between gas, liquid, and supercritical CO2. It should be further understood that depending on the ambient pressure and temperature, CO2 has different water solubility. Therefore, CO2 provided as CO2 gas can exist in different phases during the reaction, including gas, liquid, supercritical, solid (dry ice), and dispersion in water. Each possibility represents a separate embodiment.

[0072] CO2 provided as CO2 gas has several advantages. Specifically, the use of CO2 gas as a starting material contributes to carbon capture and storage. In this way, in addition to the production of hydrogen which can be used as a “green” fuel and the recycling of coal combustion products, the present invention further provides the additional environmental benefit of CO2 sequestration. The terms “Carbon Capture and Storage” (CCS, also referred to as “Carbon Capture” and “Sequestration”), as used herein, refer to the process of managing generated carbon dioxide, transporting carbon dioxide to a storage location, and depositing carbon dioxide in a place where it does not enter or re-enter the atmosphere. Specifically, CO2 is primarily a combustion waste emitted from large point sources such as fossil fuel power plants. If CO2 is removed from the atmosphere, the process may be alternatively defined as Carbon Dioxide Removal (CDR). Therefore, using CO2 gas in this process and thereby contributing to its capture is an environmental advantage. According to some embodiments, the process includes a step of flowing a gas containing CO2. In other embodiments, the gas flowing step further includes a step of concentrating the CO2. In further embodiments, the process includes a step of capturing atmospheric CO2. In additional embodiments, the process includes a step of flowing CO2 generated by a CO2 source. In some embodiments, the process of the present invention further includes capturing CO2 as an iron complex, thereby resulting in carbon capture and utilization (CCU).

[0073] Importantly, according to some embodiments, the CO2 gas does not need to be of a particular high purity. In processes according to certain embodiments of the present invention, even as little as 0.5% CO2 may be used. Thus, according to some embodiments, various sources of CO2 gas can be used as the CO2 source for this process. According to various embodiments, the process further includes a step of capturing carbon dioxide from the atmosphere. According to other embodiments, the process further includes a step of concentrating carbon dioxide from the atmosphere. According to yet another embodiment, at least part of the CO2 source is CO2 gas provided from power plants, biogas plants, distilleries, refineries, combustion engines, cement plants, ammonia plants, steel plants, and iron and steel plants. Each possibility represents a separate embodiment. According to an additional embodiment, the process further includes a step of decontaminating flue gas and / or concentrating CO2 provided by a CO2 generation plant. According to a further embodiment, at least part of the CO2 source is flue gas containing CO2.

[0074] The term "flue gas" refers to gases released into the atmosphere through a flue, which is a pipe or channel used to transport exhaust gases from a fireplace, oven, furnace, boiler, or steam generator. In many cases, flue gas refers to combustion exhaust gases produced in power plants.

[0075] The use of flue gas as a CO2 source has clear economic and environmental advantages, given that flue gas is a significant cause of air pollution and greenhouse gas emissions, and has faced stringent regulatory measures in recent years.

[0076] According to other embodiments, the process further includes the step of decontaminating the flue gas and / or concentrating the CO2 in the flue gas. Specifically, typical contaminants in such an industrial plant may include sulfur-containing compounds such as sulfur oxides and nitrogen-containing compounds such as nitrogen oxides. In certain embodiments, the CO2 contaminants include metals such as mercury. Known decontamination methods involve, but are not limited to, chemical reaction processes, physical methods, and electrochemical methods. According to other embodiments, the CO2 source is CO2 provided as dry ice.

[0077] It should be understood that the CO2 source in this process is not limited to carbon dioxide gas, but may also be a CO2 precursor containing two reactants that produce carbon dioxide during the reaction. According to some embodiments, the CO2 source is a CO2 precursor or generator. According to various embodiments, the CO2 precursor includes a combination of a carbonate compound or bicarbonate compound and an acid. According to other embodiments, the process further includes contacting the carbonate compound or bicarbonate compound with water and iron-containing coal production products, and adding an acid to the resulting dispersion. According to additional embodiments, the addition of the acid is carried out gradually. According to certain embodiments, the process further includes contacting CO2 with water and iron-containing coal production products, and adding a base to the resulting dispersion. According to some embodiments, the process further includes adding a base to water, and then contacting CO2 with basic water.

[0078] It should be understood by those skilled in the art that CO2 is formed during the chemical reaction between a bicarbonate and an acid. Similarly, bicarbonates may be formed during the chemical reaction between a carbonate and an acid, and these bicarbonates may further react with the acid to form CO2.

[0079] According to some embodiments, the CO2 precursor includes a carbonate selected from the group consisting of calcium carbonate, sodium carbonate, potassium carbonate, iron(II) carbonate, ammonium carbonate, magnesium carbonate, and combinations thereof. Each possibility represents a separate embodiment. The carbonate anion has the chemical formula CO32- It is represented as follows. According to other embodiments, the CO2 precursor includes a bicarbonate selected from the group consisting of calcium bicarbonate, sodium bicarbonate, potassium bicarbonate, iron(II) bicarbonate, ammonium bicarbonate, magnesium bicarbonate, and combinations thereof. Each possibility represents a separate embodiment. The bicarbonate anion has the chemical formula HCO3. - It is represented as follows. According to a further embodiment, the CO2 precursor contains carbonic acid.

[0080] According to certain embodiments, the carbon dioxide concentration in the dispersion formed from the CO2 source, water, and iron-containing coal production product is at least 1%, for example, about 1% to about 50%, and includes values ​​within the specified range. Exemplary percentages include, but are not limited to, about 1%, about 2%, about 3%, about 5%, about 7.5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, or about 50%, each possibility representing a separate embodiment. It will be understood by those skilled in the art that carbonic acid (H2CO3) is formed upon contact between CO2 and water, and the pH drops to less than 7. According to some embodiments, the CO2 source and water are brought into contact before the addition of the iron-containing coal combustion product, resulting in the formation of an aqueous solution of carbonic acid with a pH in the range of about 5.5 to about 6.5, and including values ​​within the specified range. The solution may be prepared in a reactor or pre-prepared in a saturated unit. According to some embodiments, the saturation unit is pre-cooled to a temperature below 10°C. The saturation unit may be a gas addition module, a saturation column, or a pressure pump. Each possibility represents a separate embodiment. If the solution is prepared outside the reactor, a high-pressure pump is used to load the solution into the reactor. Once prepared, the solution is typically kept under pressure. According to some embodiments, the pressure is higher than 1 bar.

[0081] According to various embodiments, when a CO2 source is brought into contact with water, the pressure inside the sealed reactor is in the range of 1 bar to about 350 bar, including each value within the specified range. Typical ranges of pressure inside the sealed reactor include, but are not limited to, about 40 to about 350 bar, about 1 to about 100 bar, about 100 to about 350 bar, or about 100 to about 250 bar, including each value within the specified range. Exemplary pressures include, but are not limited to, about 1, about 5, about 10, about 20, about 50, about 100, about 150, about 200, about 250, or about 300 bar, each possibility representing a separate embodiment. In one embodiment, the pressure inside the sealed reactor is above the ambient pressure. According to some embodiments, the pressure inside the sealed reactor is at least 1 bar.

[0082] In some embodiments, it should be understood that as the reaction proceeds, H2 gas is formed, thereby increasing the internal gas pressure in the sealed reactor. Specifically, in some embodiments, unlike carbon dioxide, which tends to condense into a liquid or solid under high pressure, hydrogen does not share a similar tendency, resulting in a significant increase in pressure within the sealed reactor.

[0083] According to some aspects and embodiments, the reaction period between water, iron-containing coal combustion products, and a CO2 source according to the principle of the present invention is at least 30 minutes, for example, about 30 minutes to about 1 week, and includes values ​​within the specified range. According to some aspects and embodiments, the reaction period between water, iron-containing coal combustion products, and a CO2 source according to the principle of the present invention is at least 60 minutes, for example, about 60 minutes to about 100 hours, and includes values ​​within the specified range. Exemplary periods during which the reaction occurs include, but are not limited to, about 30 minutes, about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 10 hours, about 12 hours, about 15 hours, about 18 hours, about 20 hours, about 22 hours, about 24 hours, about 48 hours, about 72 hours, about 4 days, about 5 days, about 6 days, or about 7 days, each possibility representing a separate embodiment.

[0084] In some embodiments, the process further includes adding glycerin to the reaction.

[0085] The reaction mixture of this process has typically been found to be weakly acidic. In some embodiments, a weakly acidic pH is obtained after dissolving CO2 in water without adding any acid. However, the addition of an acid or base to the reaction mixture is also intended by the present invention. According to some embodiments, the process further includes the step of adding an acid to water. According to other embodiments, the step of adding the acid is performed after the start of the reaction. According to yet another embodiment, the acid is selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, acetic acid, and citric acid. Each possibility represents a separate embodiment. According to some embodiments, the acid includes hydrochloric acid.

[0086] According to some embodiments, the step of adding an acid precedes the step of adding a CO2 source. According to some embodiments, the process includes (a) dispersing iron-containing coal combustion products in water, (b) adding an acid to the dispersion from step (a), and (c) adding a CO2 source to the dispersion from step (b) to generate a reaction and produce hydrogen.

[0087] According to some embodiments, contact between a CO2 source, iron-containing coal combustion products, and water forms an aqueous dispersion having a pH of 6.5 or less. According to various embodiments, the reaction pH is less than 6.5, for example, in the range of about 4 to about 6, including each value within the specified range. Alternatively, the reaction pH may be higher than 6.5, for example, in the range of about 7 to about 10, including each value within the specified range. If basic conditions are desired, the process may further include the addition of a base to the water. According to other embodiments, the step of adding the base is performed after the start of the reaction. According to yet another embodiment, the base is selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonium hydroxide. Each possibility represents a separate embodiment.

[0088] According to some embodiments, the process further includes the step of adding a solidification inhibitor to the reaction mixture. Although not bound by any theory or mechanism of action, the solidification inhibitor promotes hydrogen generation, reduces reaction duration, acts as a dispersant, affects adsorption properties, and prevents aggregation or clamping of iron-containing coal combustion products. Suitable solidification inhibitors within the scope of the present invention include, but are not limited to, tricalcium phosphate, powdered cellulose, magnesium stearate, sodium ferrocyanide, potassium ferrocyanide, calcium ferrocyanide, calcium phosphate, sodium silicate, silicon dioxide, calcium silicate, magnesium trisilicate, talcum powder, sodium aluminosilicate, potassium aluminum silicate, calcium aluminosilicate, bentonite, aluminum silicate, stearic acid, polydimethylsiloxane, and mixtures or combinations thereof. Each possibility represents a separate embodiment. Currently preferred is the use of silicon dioxide in the form of silica, such as fumed silica.

[0089] The solidification inhibitor may be added to a dispersion containing water, iron-containing coal production products, and a CO2 source at a concentration of 1% w / w to 10% w / w, within the specified range. According to certain embodiments, the addition supplements the solidification inhibitor that constitutes part of the iron-containing coal production products. According to some embodiments, the solidification inhibitor is a surfactant having an amphiphilic structure. According to other embodiments, the solidification inhibitor comprises at least one functional group selected from the group consisting of -OH, -COOH, -SOOOH, and salts thereof. Each possibility represents a separate embodiment. According to some embodiments, the solidification inhibitor is selected from the group consisting of silica compounds, fumed silica, and pyrolysis-processed silicon dioxide.

[0090] It should be understood that the addition of cacking inhibitors can be avoided by using iron-containing coal production products that contain a considerable amount of silicon dioxide. Therefore, the aforementioned advantages are already obtained in the absence of external cacking inhibitors. Nevertheless, in some embodiments, such external cacking inhibitors are added.

[0091] While the addition of certain additives, as detailed above, may contribute to specific parameters of the present invention, some implementations of hydrogen production benefit from the absence of additives such as organic compounds. According to some embodiments, the process does not involve the addition of organic compounds. According to other embodiments, the process does not involve the addition of compounds other than water, iron-containing coal combustion products, and CO2 sources.

[0092] According to some embodiments, the processes presented herein may be carried out using a closed reactor typically suited for carrying out reactions involving gas as a product and / or stating material. The reactions may be carried out batch or continuous, each possibility representing a separate embodiment. Specifically, according to some embodiments, the reactions may be carried out as a batch process (e.g., in a batch reactor) to produce separate batches of hydrogen in separate reactions, or as a continuous process using a series of batch reactors or continuous flow reactors for continuous production of hydrogen. Non-limiting examples of conventional reactors in which reactions such as those of the present invention may occur are provided below.

[0093] Refer to Figure 1 here. It is within the scope of the invention that the process is carried out as a batch process for hydrogen production. Figure 1 shows a typical configuration of a system for batch production of hydrogen according to several embodiments. According to these embodiments, the system comprises a reactor 4 for carrying out the reaction, a carbon dioxide tank 1 configured to store the carbon dioxide required for the reaction, and a compressor 2 configured to raise and / or regulate the carbon dioxide gas entering the reactor 4. According to some embodiments, the system further comprises a ball valve 3 configured to regulate the flow of carbon dioxide gas from the carbon dioxide tank 1 to the reactor 4. In this configuration, carbon dioxide is added at the bottom of the reactor and dispersed in the reaction slurry. According to other embodiments, the reactor 4 comprises a gas storage area 6 and an area 5 for an aqueous dispersion. According to further embodiments, the system for batch production of hydrogen further comprises a ball valve and a pressure regulator 7 for determining the pressure inside the reactor 4.

[0094] In some embodiments, the reactor 4 comprises at least one mixing unit (not shown). The reactor should be constructed from a non-reactive material capable of withstanding pressures up to 350 bar. The mixing unit may be based on mechanical, magnetic, ultrasonic, and high-pressure liquid mixers known in the art. In one embodiment, aqueous dispersions are mixed by circulation.

[0095] Refer to Figure 2 here. As presented herein, it is within the scope of the invention that the process is carried out as a continuous (flow) process for hydrogen production, for example, in a reactor 21. The reactor 21 may be constructed from an unreactive material capable of withstanding pressures of 350 bar or more. In some embodiments, the reactor 21 comprises at least one mixing unit 22 which may be active, passive, or static. Each possibility represents a separate embodiment. The active mixing unit 22 may be based on a mechanical, magnetic, ultrasonic, or high-pressure liquid mixer as known in the art, powered by a mechanical or magnetic motor 31. Each possibility represents a separate embodiment. In some embodiments, the mixture in the reactor 21 is mixed by circulation. In other embodiments, the reactor 21 comprises at least one supply / loading opening 23, 24, 25 suitable for the continuous addition of reactants (as solid 33, liquid 34, and / or gas 35), according to some embodiments. In further embodiments, the reactor includes a gas release system 26 with a controller such as a one-way valve 36 or facet.

[0096] In some embodiments, the release system 26 may also include a system for handling the hydrogen gas produced by the reaction. Thus, the system may include a gas separation or filtration system 27 comprising an absorbent, such as silica, zeolite, polymer absorbent, perovskite, or nanoporous membrane, which allows the passage of smaller molecules, such as H2, while blocking larger molecules, such as CO2. Each possibility represents a separate embodiment. In some embodiments, the polymer membrane may be polyethylene, polyamide, polyimide, cellulose acetate, polysulfone, polydimethylsiloxane, or palladium membrane. Each possibility represents a separate embodiment. A pressure swing adsorption system may also be used. The system may also include an additional desiccant or moisture absorption system 28, which may comprise an absorbent, such as silica, zeolite, polymer, or metal-organic structure, but is not limited to these. The treated hydrogen can then be transported via pipe for further use, compression, liquefaction, or storage. The reactor further comprises a system 29 for the removal of the reacted solids and / or liquids.

[0097] As used herein and in the appended claims, the singular forms "a," "an," and "the" encompass multiple references unless the context explicitly indicates otherwise. For example, a reference to "an iron-containing coal combustion product" includes a plurality of coal combustion products. It should be noted that the terms "and" or "or" are generally used to include "and / or" unless the context explicitly indicates otherwise. As used herein, the term "about" means to include a variation of ±10%. [Examples]

[0098] The following embodiments are provided to more fully illustrate specific embodiments of the present invention. However, they should not be construed as limiting the broad scope of the invention. Those skilled in the art can readily devise many variations and modifications of the principles disclosed herein without departing from the scope of the invention.

[0099] Example 1 1,000 g of waste material ("iron slag") from a coal-fired power plant boiler was milled to an average particle size of 3.0 ± 0.5 microns. The elemental composition of the iron slag used is outlined in Table 1 below. 320 ml of water was mixed with the milled iron slag in a 1,000 ml reactor at room temperature (25°C). After mixing, a 13% aqueous solution of hydrochloric acid (Sigma Aldrich) was added to bring the pH to 5. Next, 78 g of carbon dioxide (industrial grade, Sigma Aldrich) was added to the reactor, and a pressure of 50 bar was measured inside the reactor. The reactor was kept sealed for 24 hours. During the reaction, the internal pressure rose to 250 bar and the temperature reached 38°C. No external energy was supplied. The reaction was completed, and 14 g of hydrogen was produced with a purity of 91.7%. [Table 1]

[0100] Example 2 2,500 ml of water was mixed with 3,000 g of iron waste ("iron slag," concentrated using a magnetic belt filter) from a coal-fired power plant in a 10 L reactor at room temperature (25°C). After mixing, 300 g of carbon dioxide (industrial grade, Sigma Aldrich) was added to the reactor, and a pressure of 50 atm was measured inside the reactor. The reactor was kept sealed for 48 hours. During the reaction, the internal pressure rose to 160 atm and the temperature reached 38°C. No external energy was supplied.

[0101] The reaction was completed, and 125g of hydrogen was produced with a purity of 99.75%. Gas analysis revealed that the levels of CO2 and other gases were very low (Table 2). [Table 2]

[0102] Example 3 Example 2 was repeated in a 10 L reactor at room temperature (25°C) using iron waste ("iron slag," concentrated using a magnetic belt filter) from a coal-fired power plant. After mixing, 300 g of carbon dioxide (industrial grade, Sigma Aldrich) was added to the reactor, and a pressure of 50 atm was measured inside the reactor. The reactor was kept sealed for 15 hours. During the reaction, the internal pressure rose to 110 atm. No external energy was supplied.

[0103] The reaction was incomplete, producing 112g of hydrogen with a purity of 90.7%. Gas analysis revealed that the CO2 level at that point was 9.21%, and the levels of other gases were very low (Table 3). [Table 3]

[0104] While specific embodiments of the present invention have been illustrated and described, it will be clear that the present invention is not limited to the embodiments described herein. Numerous modifications, changes, alterations, substitutions, and equivalents will be apparent to those skilled in the art without departing from the spirit and scope of the invention as described in the following claims. This disclosure includes the following aspects: <Aspect 1> H 2 A process for generating, the process comprising water, iron-containing coal combustion products, and CO 2 and CO 2 Selected CO from the group consisting of precursors 2 A process comprising the step of bringing a source into contact with a reactor, thereby generating H2, wherein the process is carried out in a reactor in the absence of external heating. <Aspect 2> The process according to embodiment 1, which is performed at a temperature of 100°C or less. <Aspect 3> The process according to embodiment 1 or 2, which is carried out at a temperature of approximately -5°C to approximately 50°C. <Aspect 4> A process according to any one of embodiments 1 to 3, which is performed without the addition of external electrical energy. <Aspect 5> The generated H 2 The process according to any one of embodiments 1 to 4, further comprising the step of collecting. <Aspect 6> The generated H 2 The process according to any one of embodiments 1 to 5, further comprising a post-processing step. <Aspect 7> The process according to embodiment 6, wherein the post-treatment includes at least one of gas separation, filtration, liquefaction, and drying. <Aspect 8> The generated H 2 The process according to any one of embodiments 1 to 7, wherein the product has a purity of at least about 85%. <Pattern 9> The process according to any one of embodiments 1 to 8, wherein the water is in the liquid phase. <Aspect 10> The process according to any one of embodiments 1 to 9, wherein the water is selected from the group consisting of tap water, seawater, partially purified water, deionized water, distilled water, brackish water, and wastewater. <Aspect 11> The process according to any one of embodiments 1 to 10, wherein the iron-containing coal combustion product is selected from the group consisting of coal ash, fly ash, bottom ash, boiler lag, heavy oil ash, and mixtures or combinations thereof. <Aspect 12> The process according to any one of embodiments 1 to 11, wherein the iron-containing coal combustion product originates from a power plant, a fuel boiler, or cement production. <Aspect 13> The process according to any one of embodiments 1 to 12, wherein the iron-containing coal combustion product includes divalent iron oxide, trivalent iron oxide, or a combination thereof. <Aspect 14> The process according to any one of embodiments 1 to 12, wherein the iron-containing coal combustion product includes iron trivalent oxide. <Aspect 15> The aforementioned iron-containing coal combustion products are iron(II) oxide (FeO), iron(II,III) oxide (Fe 3 O 4 ), and iron(III) oxide (Fe 2 O 3 The process according to any one of embodiments 1 to 12, comprising at least one of the following: <Aspect 16> The process according to any one of embodiments 1 to 15, wherein the iron-containing coal combustion product contains approximately 2% w / w to approximately 40% w / w of iron oxide. <Aspect 17> The process according to embodiment 16, wherein the iron-containing coal combustion product further contains approximately 25% w / w to approximately 75% w / w of silicon dioxide. <Aspect 18> Water, iron-containing coal combustion products, and CO 2 The process according to any one of embodiments 1 to 17, further comprising pre-treating the iron-containing coal combustion product before the step of bringing it into contact with the source. <Aspect 19> The process according to embodiment 18, wherein the pretreatment includes at least one of milling the iron-containing coal combustion product and enriching the iron content of the iron-containing coal combustion product. <Aspect 20> The aforementioned CO 2 The source is CO 2 A process according to any one of embodiments 1 to 19, wherein the gas is used. <Aspect 21> The aforementioned CO 2 The gas is pure industrial CO2. 2 , flue gas, CO 2 Production plant, and atmospheric CO 2 The process according to embodiment 20, which is derived from at least one of the following. <Aspect 22> The aforementioned CO 2 The gas is atmospheric CO2. 2 The process is such that atmospheric CO 2 The process according to embodiment 21, further including isolation. <Aspect 23> The aforementioned CO 2 The process according to any one of embodiments 1 to 19, wherein the source is dry ice. <Aspect 24> The aforementioned CO 2 The process according to any one of embodiments 1 to 19, wherein the precursor is selected from the group consisting of carbonic acid, carbonates, bicarbonates, and mixtures or combinations thereof. <Aspect 25> A batch generation process, as described in any one of embodiments 1 to 24. <Aspect 26> A continuous generation process, as described in any one of embodiments 1 to 24. <Aspect 27> The process according to any one of embodiments 1 to 26, performed at a pH of 6.5 or less. <Aspect 28> A process according to any one of embodiments 1 to 27, performed at a pressure of approximately 1 bar to approximately 350 bar. <Aspect 29> The process according to embodiment 28, which is performed at a pressure of approximately 1 bar to approximately 100 bar. <Aspect 30> The process according to any one of embodiments 1 to 29, further comprising adding a solidification inhibitor to the reactor. <Aspect 31> The process according to embodiment 30, wherein the anti-solidification agent is selected from the group consisting of tricalcium phosphate, powdered cellulose, magnesium stearate, sodium ferrocyanide, potassium ferrocyanide, calcium ferrocyanide, calcium phosphate, sodium silicate, silicon dioxide, calcium silicate, magnesium trisilicate, talcum powder, sodium aluminosilicate, potassium aluminum silicate, calcium aluminosilicate, bentonite, aluminum silicate, stearic acid, polydimethylsiloxane, and mixtures or combinations thereof. <Aspect 32> (a) Dispersing iron-containing coal combustion products in water, and (b) CO 2 A process according to any one of embodiments 1 to 31, comprising adding a source to the dispersion of step (a) to generate a reaction. <Aspect 33> (a)CO 2 CO from the source 2 (b) Replenishing the water with (a) the iron-containing coal combustion products with the CO 2 The process according to any one of embodiments 1 to 31, comprising adding to the water that has been replenished, thereby causing a reaction. <Aspect 34> The process according to any one of embodiments 1 to 33, further comprising the step of adding an acid to the water. <Aspect 35> (a) A step of dispersing the iron-containing coal combustion product in water; (b) A step of adding hydrochloric acid to the dispersion from step (a); (c) CO 2 The process according to embodiment 34, comprising the step of adding a source to the dispersion of step (b) to generate hydrogen. <Aspect 36> CO 2 A process according to any one of embodiments 1 to 35, further comprising capture and storage. <Aspect 37> The process according to any one of embodiments 1 to 36, further comprising recycling the coal combustion products.

Claims

1. H ２ A process for generating CO, wherein the process comprises water, iron-containing coal combustion products, and CO ２ and CO ２ CO selected from the group consisting of precursors ２ By bringing it into contact with the source, H ２ A process comprising the step of generating, the process being carried out in a reactor in the absence of external heating, and the internal pressure of the reactor reaching a value of 40 bar to 350 bar.

2. The process according to claim 1, wherein the reaction period between water, iron-containing coal combustion products, and a CO2 source is at least 60 minutes.

3. The H that is performed or generated without the addition of external electrical energy ２ The process according to claim 1 or 2, further comprising the step of collecting.

4. The generated H ２ The process according to any one of claims 1 to 3, further comprising a post-processing step, wherein the post-processing includes at least one of gas separation, filtration, liquefaction, and drying.

5. The generated H ２ The process according to any one of claims 1 to 4, wherein the water has a purity of at least about 85%, or the water is in the liquid phase, or the water is selected from the group consisting of tap water, seawater, partially purified water, deionized water, distilled water, brackish water, and wastewater, or the iron-containing coal combustion product is selected from the group consisting of coal ash, fly ash, bottom ash, boiler lag, heavy oil ash, and mixtures or combinations thereof, or the iron-containing coal combustion product originates from a power plant, a fuel boiler, or cement production.

6. The iron-containing coal combustion product contains iron(II) oxide, iron(III) oxide, or a combination thereof, or the iron-containing coal combustion product contains iron(III) oxide, or the iron-containing coal combustion product contains iron(II) oxide (FeO), iron(II,III) oxide (Fe3O4), and iron(III) oxide (Fe ２ O ３ ) and includes at least one of them, and the process according to any one of claims 1 to 5.

7. The process according to any one of claims 1 to 6, wherein the iron-containing coal combustion product contains about 2% w / w to about 40% w / w of iron oxide, and the iron-containing coal combustion product further contains about 25% w / w to about 75% w / w of silicon dioxide.

8. Water, iron-containing coal combustion products, and CO ２ The process according to any one of claims 1 to 7, further comprising pre-treating the iron-containing coal combustion product prior to the step of bringing it into contact with a source, wherein the pre-treatment includes at least one of milling the iron-containing coal combustion product and enriching the iron content of the iron-containing coal combustion product.

9. The aforementioned CO ２ The source is CO ２ It is a gas, and the CO ２ The gas is pure industrial CO2. ２ , flue gas, CO ２ Production plant, and atmospheric CO ２ A process according to any one of claims 1 to 8, derived from at least one of the following.

10. The aforementioned CO ２ The source is dry ice, or the CO ２ The process according to any one of claims 1 to 9, wherein the precursor is selected from the group consisting of carbonic acid, carbonates, bicarbonates, and mixtures or combinations thereof.

11. The process according to any one of claims 1 to 10, wherein it is a batch generation process or a continuous generation process.

12. The process according to any one of claims 1 to 11, performed at a pH of 6.5 or less.

13. The process according to any one of claims 1 to 12, further comprising adding a solidification inhibitor to the reactor, wherein the solidification inhibitor is selected from the group consisting of tricalcium phosphate, powdered cellulose, magnesium stearate, sodium ferrocyanide, potassium ferrocyanide, calcium ferrocyanide, calcium phosphate, sodium silicate, silicon dioxide, calcium silicate, magnesium trisilicate, talcum powder, sodium aluminosilicate, potassium aluminum silicate, calcium aluminosilicate, bentonite, aluminum silicate, stearic acid, polydimethylsiloxane, and mixtures or combinations thereof.

14. (a) Dispersing iron-containing coal combustion products in water, and (b) CO ２ Adding the source to the dispersion in step (a) thereby generating a reaction, or (a) CO ２ CO from the source ２ (b) Replenishing the water with (a) the iron-containing coal combustion products of the CO ２ The process according to any one of claims 1 to 13, further comprising the steps of adding to the water that has been replenished, thereby causing a reaction, or further comprising the step of adding an acid to the water.

15. CO ２ The process according to any one of claims 1 to 14, further comprising capture and storage, or further comprising recycling the coal combustion products.

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