PROCESS TO CONVERT REDUCED SULFUR SPECIES AND WATER INTO HYDROGEN AND SULFURIC ACID
20220411940 · 2022-12-29
Assignee
Inventors
Cpc classification
Y02P40/18
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
Y02E60/36
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
C25B9/17
CHEMISTRY; METALLURGY
Y02E60/50
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
International classification
C25B9/17
CHEMISTRY; METALLURGY
Abstract
In an aspect, provided herein are methods for producing sulfuric acid and hydrogen gas, the methods comprising steps of: providing sulfur dioxide formed by thermal conversion of a sulfur-containing species; electrochemically oxidizing said sulfur dioxide to sulfuric acid in the presence of water; and electrochemically forming hydrogen gas via a reduction reaction. In some embodiments, the methods comprise a step of thermally converting said sulfur-containing species to said sulfur dioxide. Systems configured to perform these methods are also disclosed herein. Also provided herein are methods and systems for producing sulfuric acid and hydrogen gas by electrochemically forming the sulfuric acid and the hydrogen gas in a mixture comprising a sulfur material, a supporting acid, and water. Also provided herein are methods and systems for producing a cement material.
Claims
1. A method for producing a cement material comprising: (a) reacting a first acid and a first cement precursor to form a second cement precursor; and (b) converting the second cement precursor to a cement material.
2. The method of claim 1, wherein the first cement precursor comprises an element selected from the group consisting of Ca, Si, or Al, or a combination of thereof.
3. The method of claim 1, wherein step (a) is performed in the presence of water as a wet slurry.
4. The method of claim 1, wherein the second cement precursor comprises an element selected from the group consisting of Ca, Si, or Al, or a combination thereof.
5. The method of claim 1, wherein the second cement precursor comprises Ca.
6. The method of claim 1, wherein the first acid is at a concentration of greater than or equal to 20% by mass.
7. The method of claim 1, wherein converting the second cement precursor to a cement material comprises thermally converting the second cement precursor at an appropriate temperature for sintering or thermally decomposing the second cement precursor thereby forming the cement material.
8. The method of claim 7, wherein thermally converting comprises treating at a temperature selected from the range of 500 to 2000° C.
9. The method of claim 7, wherein thermally converting occurs in the presence of an additive.
10. The method of claim 9, wherein the additive comprises silica, alumina, or iron oxide, or a combination thereof.
11. The method of claim 10, wherein the additive comprises silica.
12. The method of claim 11, wherein the cement material comprises one or more silicates.
13. The method of claim 10, wherein the additive comprises alumina and/or iron oxide.
14. The method of claim 1, wherein the cement material comprises CaO.
15. The method of claim 1, wherein the cement material comprises a composite cement material.
16. The method of claim 1, further comprising adding one or more aggregates to the cement material to produce a composite cement material.
17. The method of claim 16, wherein the aggregate comprises sand and gravel and the composite cement material comprises concrete.
18. The method of claim 16, wherein the aggregate comprises fine aggregates and the composite cement material comprises mortar.
19. The method of claim 1, further comprising capturing and storing carbon dioxide (CO.sub.2).
20. The method of claim 19, wherein the captured CO.sub.2 comprises a bicarbonate.
21. A system for producing a cement material comprising: (a) an apparatus configured to react a first acid and a first cement precursor to form a second cement precursor; and (b) an apparatus configured to convert the second cement precursor to a cement material, wherein (a) and (b) are operably connected.
22. The system of claim 21, wherein the apparatus of (b) comprises a heated vessel, wherein the apparatus is configured to thermally convert the second cement precursor to the cement material inside the heated vessel.
23. The system of claim 22, wherein the heated vessel is configured to thermally convert the second cement precursor at a temperature selected from the range of 500 to 2000° C.
24. The system of claim 22, wherein the heated vessel comprises a cement kiln.
25. The system of claim 21, further configured to add one or more additives to the second cement precursor prior to conversion.
26. The system of claim 25, wherein the additive comprises silica, alumina, iron oxide, or any combination of these.
27. The system of claim 26, wherein the additive comprises silica.
28. The system of claim 26, wherein the additive comprises alumina and/or iron oxide.
29. The system of claim 21, further comprising an apparatus configured to capture and store carbon dioxide (CO.sub.2).
30. A system for producing a composite cement material comprising: (a) an apparatus configured to receive a cement material produced by the method of claim 1; and (b) an apparatus configured to combine the cement material with water and aggregates, to form concrete.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
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STATEMENTS REGARDING CHEMICAL COMPOUNDS AND NOMENCLATURE
[0082] In general, the terms and phrases used herein have their art-recognized meaning, which can be found by reference to standard texts, journal references and contexts known to those skilled in the art. The following definitions are provided to clarify their specific use in the context of the invention.
[0083] The terms “thermal conversion” and “thermally converting” refer to the conversion of a first chemical species to a second chemical species via a thermally-activated or thermally-driven process, which may also be referred to as a thermochemical process. An exemplary process for thermal conversion of a chemical species is burning, though thermal conversion processes are not necessarily limited thereto. For example, thermal conversion of sulfur to sulfur dioxide may include burning of the sulfur, such as via a sulfur burner system. Thermal oxidation of a species is a form of thermal conversion of the species. For example, thermal conversion of sulfur to sulfur dioxide may be referred to as thermal oxidation of the sulfur to sulfur dioxide. In some embodiments, thermal conversion may be aided by a catalyst. In some embodiments, thermal conversion does not require a catalyst or is performed without a catalyst. It should be noted that thermal oxidation and electrochemical oxidation are different processes, where thermal oxidation is driven or activated thermally (via heat or burning) and electrochemical oxidation is driven electrochemically (e.g., via applying or withdrawing electrical energy, optionally with the aid of an electrochemical catalyst).
[0084] The term “electrochemical cell” refers to devices and/or device components that convert chemical energy into electrical energy or electrical energy into chemical energy. Electrochemical cells have two or more electrodes (e.g., positive and negative electrodes; e.g., cathode and anode) and one or more electrolytes. An electrolyte may include species that are oxidized and species that are reduced during charging or discharging of the electrochemical cell. Reactions occurring at the electrode, such as sorption and desorption of a chemical species or such as an oxidation or reduction reaction, contribute to charge transfer processes in the electrochemical cell. Electrochemical cells include, but are not limited to, electrolytic cells such as electrolysers and fuel cells. Electrochemical oxidation may occur at the positive electrode, for example, and electrochemical reduction may occur at the negative electrode, for example. Electrochemical oxidation refers to a chemical oxidation reaction accompanied by a transfer of electrical energy (e.g., electrical energy input driving the oxidation reaction) occurring in the context an electrochemical cell. Similarly, electrochemical reduction refers to a chemical reduction reaction accompanied by a transfer of electrical energy occurring in the context an electrochemical cell. A chemical species electrochemically oxidized during charging, for example, may be electrochemically reduced during discharging, and vice versa. The term “electrochemically” or “electrochemical” may describe a reaction, process, or a step thereof, as part of which chemical energy is converted into electrical energy or electrical energy is converted into chemical energy. For example, a product may be electrochemically formed when electrical energy is provided to help the chemical conversion of a reactant(s) to the product proceed.
[0085] The term “elemental sulfur” refers to any one or combination of the allotropes of sulfur, such as, but not limited to, S.sub.7, S.sub.8, S.sub.6, S.sub.12, and S.sub.18, and including crystalline, polycrystalline, and/or amorphous sulfur.
[0086] “RHE” refers to the reference electrode commonly referred to as the reversible hydrogen electrode. “SCE” refers to the reference electrode commonly referred to as the saturated calomel electrode.
[0087] The term “initial hours of operation” refers to the time during which the cell is operational starting from the very first/initial operation, or “turning on,” of the cell. Time during which the cell or system is not being operated (i.e., no electrochemical reduction or oxidation occurring therein, or no electrical energy input or output is occurring) is not included in the initial hours of operation determination.
[0088] In some embodiments, the term “aqueous” refers to a solution where the solvent is water such that other species of the solution, or solutes, are substantially solvated by water. In some embodiments, the term “aqueous” may generally refer to a solution comprising water.
[0089] The term “amending agricultural water” refers to changing or adding something, such as a solute, to agricultural water. For example, acidification of agricultural water by the addition of sulfuric acid, such as a solution including sulfuric acid, to agricultural water. Agricultural water refers to water used for an agricultural purpose, such as irrigation. The term “amending soil” refers to changing or adding something to soil. For example, acidification of soil by the addition of sulfuric acid, such as a solution including sulfuric acid, to soil.
[0090] The term “cement” refers to hydraulic, non-hydraulic, or both hydraulic and non-hydraulic cement, including. An exemplary cement is, but is not limited to, Portland cement. Generally, a cement is a binder material, which, for example, may be mixed with fine aggregate particles (such as to produce mortar for masonry) or with sand and gravel (to produce concrete). According to certain embodiments, cement comprises calcium oxide. Cement may optionally further comprise one or more other materials including, but not limited to, certain silicate(s), SiO.sub.2, certain oxide(s), Fe.sub.2O.sub.3, certain aluminate(s), Al.sub.2O.sub.3, belite, alite, tricalcium aluminate, brownmillerite, A “cement material” refers to a material that is a constituent of cement. For example, CaO is a cement material. A composite cement material may include a plurality of cement materials, such as Portland cement, and/or a cement material and one or more other additive(s) that are not cement materials.
[0091] The term “substantially” refers to a property or condition that is within 20%, within 10%, within 5%, within 1%, or is equivalent to a reference property or condition. The term “substantially equal,” “substantially equivalent,” or “substantially unchanged,” when used in conjunction with a reference value describing a property or condition, refers to a value or condition that is within 20%, within 10%, within 5%, within 1%, within 0.1%, or optionally is equivalent to the provided reference value or condition. For example, a voltage that is substantially 500 mV (or, substantially equivalent to 500 mV) is within 20%, within 10%, within 5%, within 1%, or equal to 500 mV. The term “substantially greater,” when used in conjunction with a reference value or condition describing a property or condition, refers to a value that is at least 2%, at least 5%, at least 10%, or at least 20% greater than the provided reference value or condition. For example, a voltage is substantially greater than 500 mV if the voltage is at least 20% greater than, at least 10% greater than, at least 5% greater than, or at least 1% greater than 500 mV. The term “substantially less,” when used in conjunction with a reference value or condition describing a property or condition, refers to a value or condition that is at least 2%, at least 5%, at least 10%, or at least 20% less than the provided reference value. For example, a voltage is substantially less than 500 mV if the voltage is at least 20% less than, at least 10% less than, at least 5% less than, or at least 1% less than 500 mV.
[0092] In an embodiment, a composition or compound of the invention, such as an alloy or precursor to an alloy, is isolated or substantially purified. In an embodiment, an isolated or purified compound is at least partially isolated or substantially purified as would be understood in the art. In an embodiment, a substantially purified composition, compound or formulation of the invention has a chemical purity of 95%, optionally for some applications 99%, optionally for some applications 99.9%, optionally for some applications 99.99%, and optionally for some applications 99.999% pure.
DETAILED DESCRIPTION OF THE INVENTION
[0093] In the following description, numerous specific details of the devices, device components and methods of the present invention are set forth in order to provide a thorough explanation of the precise nature of the invention. It will be apparent, however, to those of skill in the art that the invention can be practiced without these specific details.
[0094] U.S. Provisional Patent Application No. 62/673,707, filed May 18, 2018, U.S. Provisional Patent Application No. 62/726,858, filed Sep. 4, 2018, and U.S. Provisional Patent Application No. 62/743,652, filed Oct. 10, 2018, are all hereby incorporated by reference in their entirety to the extent not inconsistent herewith.
[0095] Disclosed herein are method and systems for converting water and any sulfur species that is more reduced than sulfuric acid (H.sub.2SO.sub.4) (e.g. hydrogen sulfide (H.sub.2S), elemental sulfur (e.g., S), thiols (R-SH), sulfur dioxide (SO.sub.2), etc.) to hydrogen gas and H.sub.2SO.sub.4.
[0096] Some embodiments of the methods and systems may be described as follows. First, the reduced sulfur species is oxidized (e.g. burned in air) to produce SO.sub.2, optionally via a sulfur burner, and the sulfur dioxide is then captured and may be stored. The SO.sub.2 serves as an input to an electrochemical process where the sulfur dioxide is introduced, such as via bubbling through an aqueous electrolyte, and the sulfur dioxide is then electrochemically converted into H.sub.2SO.sub.4 at the anode and hydrogen (H.sub.2) at the cathode using any power source, including distributed power created onsite or power sourced from the grid. For example, the power source may be a photovoltaic system. The produced H.sub.2 gas produced can then be captured and can be stored for future use or can be oxidized directly in a hydrogen fuel cell as a source of reliable electricity or in a furnace as a source of reliable heat, which can optionally be used directly for concentrating sulfuric acid, could be turned into electricity using a steam turbine, or could be captured and used in another process that requires hydrogen gas (e.g. alkylation in oil refineries, or ammonia production via the Haber-Bosch process). Hydrogen is a versatile clean-burning chemical that can be oxidized for energy generation where the only byproduct is water. Therefore a process that uses energy and sulfuric acid, or anywhere that sulfuric acid is used (or could be used) and energy (heat, electricity, or other) could be sold, could benefit from this synergy. The H.sub.2SO.sub.4 can be stored directly for later use or first concentrated and then stored for later use. If the sulfuric acid is concentrated before storage, the water that results from the purification or oxidation of hydrogen steps can be reused as part of the aqueous electrolyte. A flow diagram of the process and system, according to certain embodiments, is shown in
[0097] In some embodiments, the methods and systems disclosed herein directly produce highly concentrated sulfuric acid. For example, the sulfuric acid produced by the methods and systems disclosed herein, such as sulfuric acid output of the methods or systems, is highly concentrated (e.g., greater than or equal to 80%, or greater than or equal to 89%, or greater than or equal to 93%, or substantially 98%), optionally without requiring a separate concentration step or a concentrator. In some embodiments, the solution in which electrochemical production of sulfuric acid and hydrogen gas is occurring is characterized by a bulk concentration of sulfuric acid that is greater than 0% by mass to less than or substantially equal to 98% by mass, or optionally any concentration therebetween. In some embodiments, for example, the sulfuric acid is not combined with oleum, such as oleum produced via the contact process. In some embodiments, the electrochemically produced sulfuric acid is diluted, such as to a concentration selected from the range of 1% to 10%, for example for agricultural applications.
[0098] The methods and systems disclosed herein can provide lower energy consumption, low CO.sub.2 production hydrogen and sulfuric acid for industrial as well as fuel and energy storage needs, compared to certain conventional approaches. Hydrogen and sulfuric acid are used industrially in diverse ways, and in many cases are both used in the same process.
[0099] The methods and systems disclosed herein can be most useful where both hydrogen and sulfuric acid are used. For example, in fertilizer production, sulfuric acid is used to protonate phosphate rock to make bioavailable phosphoric acid. Hydrogen is used in the fertilizer industry in the Haber-Bosch process to thermochemically make ammonia. Ammonia and phosphoric acid are then combined to make ammonium phosphate fertilizer. Ammonia and sulfuric acid can be directly combined to make ammonium sulfate fertilizer. Currently in fertilizer production, hydrogen is made by steam methane reforming and sulfuric acid is made by the contact process. Because the methods and systems disclosed herein include a single process instead of two processes to make both products, they can to save industries an enormous amount of capital expenditure.
[0100] Both sulfuric acid and hydrogen gas are also used in oil refining where sulfuric acid is used as a catalyst for alkylation and hydrogen is used as a reducing agent to remove sulfur containing compounds from oil and gas in order to produce organic fuels and organic feedstocks for alkylation and other uses. By combining hydrogen and sulfuric acid production, the methods and systems disclosed herein can save oil and gas companies large amounts of money.
[0101] Agricultural industries can use either one or both of sulfuric acid and hydrogen. Sulfuric acid can be used to acidify irrigation water and hydrogen can be used as a clean burning fuel for transportation or electricity generation. Currently farmers either buy sulfuric acid that is produced via the contact process to acidify irrigation water or they buy conventional sulfur burners which burn sulfur to produce SO.sub.2 which is then injected into water to produce sulfurous acid (H.sub.2SO.sub.3). In contrast, the methods and systems disclosed herein can generate sulfuric acid (a stronger acid than sulfurous acid) on-site and on-demand as well as generate hydrogen which can be used as a fuel in vehicles or burned for electricity to power other farm equipment. The methods and systems disclosed herein can be configured at a small scale, or whatever scale is appropriate, to meet the size and needs to any farm. The methods and systems disclosed herein can provide on-demand sulfuric acid and hydrogen gas because the processes can be reliably turned-off and turned-on as needed. In some embodiments, the methods and systems disclosed herein can provide on-demand sulfuric acid and hydrogen gas at least because the processes can be reliably turned-off within a time period of 1 hour and turned-on within a time period of 1 hour. This feature obviates the need for large, dangerous, and expensive sulfuric acid storage tanks, for example, which could be an undesired liability for farms, especially small farms.
[0102] The relevant chemical reactions in the methods and systems disclosed herein include: (i) Thermal Oxidation: SR+O.sub.2.fwdarw.SO.sub.2 (SR is any sulfur species that is more reduced than SO.sub.2, e.g. HS, H.sub.2S, DMS, DMDS, S, S.sub.8); (ii) Electrochemical Oxidation: SO.sub.2+2H.sub.2O.fwdarw.H.sub.2SO.sub.4+2H.sup.++2e.sup.−; and (iii) Electrochemical Reduction: 2e.sup.−+2H.sup.+H.sub.2; yielding a net reaction of (iv) S+O.sub.2+2H.sub.2O.fwdarw.H.sub.2SO.sub.4+H.sub.2.
[0103] The thermal conversion of a sulfur-containing species to sulfur dioxide can be performed without a catalyst. The electrochemical production of sulfuric acid and hydrogen gas can be performed with a catalyst. An exemplary catalyst for the electrochemical processes is, but is not limited to, platinum. Advantages of platinum as a catalyst include needing a very low applied potential relative to other electrochemical hydrogen generating processes (i.e. water splitting).
[0104] In some embodiments, the methods and systems disclosed herein are configured to provide for soil acidification, optionally via including a soil acidification unit, by using the produced sulfuric acid to acidify soil. In some embodiments, the methods and systems disclosed herein are configured to provide for agricultural water acidification, optionally via including a water acidification unit, by using the produced sulfuric acid to acidify agricultural water. For example, a reduced sulfur species (e.g. elemental sulfur) can be burned to form SO.sub.2. SO.sub.2 could then be mixed either in the liquid or vapor phase with water. The SO.sub.2 water mixture can then be put through an electrolyser as described above to make sulfuric acid. The produced sulfuric acid can then be mixed with irrigation water in order to acidify the water. The pH could be estimated or measured iteratively to know how much sulfuric acid needs to be added to the irrigation water. The hydrogen that is cogenerated in this process at the cathode can be saved where it could be used as a fuel or can be used to generate electricity either by burning the hydrogen in a generator or passing it through a fuel cell (e.g., see FIG. 3). If this process is powered with intermittent green energy, such as a photovoltaic system, it can function as an energy storage solution. If the catalysts used in the electrolyser are also capable of oxidizing hydrogen and reducing oxygen (e.g. platinum based cathodes and anodes) then the electrolyser could be used as a fuel cell in a regenerative fuel cell scheme (e.g., see
[0105] A conventional method for soil or water amendment (e.g., acidification) is via sulfur burning. In this process, sulfur is purchased by a farmer and is burned in air using a typically small scale (−75 kg sulfur/day) reactor to create sulfur dioxide which is then bubbled into irrigation water where it produces sulfurous acid. This process has two disadvantages, first it emits smog-causing sulfur dioxide into the atmosphere (>1500 tonnes/yr in California's central valley from this process alone) and second sulfurous acid is a weak acid and is about half as good at acidifying soil as sulfuric acid. Due to pKa's, only one proton is available for acidification using sulfurous acid. Conventionally, where sulfur burner infrastructure does not exist, onsite tanks of sulfuric acid are also used for soil acidification. Sulfuric acid has the advantage of being better at acidifying soils than sulfurous acid (e.g., two protons available for acidification in contrast to sulfurous acid), but conventional means for making sulfuric acid are via the thermocatalytic contact process (see reaction 2, below) which cannot be done onsite (e.g., on the farm) and shipping and handling of sulfuric acid make it at least comparably expensive to use than sulfur burning.
2S+3O.sub.2+2H.sub.2O.fwdarw.2H.sub.2SO.sub.4 ΔG.sup.o=−453 kJ/mol H.sub.2SO.sub.4 (exergonic) Reaction 2:
[0106] The methods and systems disclosed herein can make sulfuric acid using an even smaller reactor than is currently needed for sulfur burning (see reaction 3, below).
[0107] Currently, sulfur burners cost around $30,000 to buy. According to certain embodiments, the systems disclosed herein, can cost around $15,000 to build and because sulfuric acid is a stronger acid than sulfurous acid, the systems disclosed herein can provide around $12,000 in savings on sulfur purchasing per machine per year. The methods and systems disclosed herein also can operate without generating smog-causing sulfur dioxide, and cogenerates clean hydrogen which could generate an additional revenue stream by providing anytime use electricity or a clean transportation fuel onsite. In California alone, the soil acidification market could be up to 3.8 million tonnes of sulfuric acid which would produce enough clean hydrogen to power Bakersfield for ¾ of the year. Farmland across the Western United States and the world need soil acidification so there is significant potential for growth using a small scale reactor model, according to certain embodiments of the methods and systems disclosed herein. All prices are in 2018 USD.
S+O.sub.2+2H.sub.2O.fwdarw.H.sub.2SO.sub.4+H.sub.2 ΔG.sup.o=−233 kJ/mol H.sub.2 (exergonic) Reaction 3:
[0108] See also
EXAMPLE 1: PLATINIZED Ti CATALYST
[0109] Preferably for some embodiments of the methods for producing sulfuric acid and hydrogen gas, a catalyst at the positive electrode, the negative electrode, or both, is platinized Ti. In some embodiments, platinized Ti has substantially equivalent activity to platinum metal and therefore can be a much cheaper alternative to Pt metal as a catalyst. Platinized Ti has the distinct advantage over Pt/C type catalysts of being flame resistant. In some embodiments, other platinized materials may be used as catalysts.
EXAMPLE 2: ANTI SULFUR FOULING
[0110] During electrolysis of a sulfur containing compound (e.g. SO.sub.2, H.sub.2S, elemental sulfur, etc) elemental sulfur can plate out on the positive and/or the negative electrode which can deactivate or decrease the activity of the catalyst. In convention sulfur electrolysis systems a Pt/C catalyst is used and it is very difficult to remove the plated sulfur. Preferably for some embodiments of the methods for producing sulfuric acid and hydrogen gas, a metal based catalyst, such as Pt or platinized Ti, is used as a catalyst which allows removal of plated sulfur, such as via burning off of the sulfur, such with a flame, thereby regenerating the catalyst. Such removal of plated sulfur is difficult or impossible in the case of a Pt/C catalyst because the flame can destroy the carbon matrix.
EXAMPLE 3: A PROCESS TO Co-GENERATE CEMENT OR CaO AND H.SUB.2 .WITH OPTIONAL, BUILT-IN CARBON CAPTURE AND STORAGE
[0111] See also
Background and Current State-of-the-Art
[0112] In 2018 more than 4 billion tonnes of cement were produced via the thermal decomposition and sintering of limestone. In this process Limestone and certain additives such alumina-silicates, fly ash, iron oxides, and others are added to a cement kiln which heats these constituents to a sintering temperature between 1400-2000° C. In this process the CaCO.sub.3 undergoes thermal decomposition to form CaO and CO.sub.2 (eq 1).
[0113] The process was responsible for the production of around 10% of global CO.sub.2 emissions in 2017.
CaCO.sub.3+heat.fwdarw.CaO+CO.sub.2 eq 1
[0114] In a variation of this process called the Mueller Kuehne process (see Ribas, et al., US Pat. No. 5,099,198, which is incorporated herein by reference), gypsum (CaSO.sub.4) and its hydrates may be used instead of limestone because they undergo thermal decomposition below 1450° C. and may proceed according to the following equation (eq 2) which can occur at 1450° C. to make SO.sub.2 and CaO (eq 2). Other additives may also be added to make CaO, SO.sub.2, and other products including or separate from O.sub.2.
CaSO.sub.4+heat.fwdarw.CaO+SO.sub.2+½O.sub.2 eq 2
[0115] This process has been the basis for several large cement plants in the UK which use the cogenerated SO.sub.2 to generate sulfuric acid.
[0116] There is another proposed industrial process called the hybrid sulfur cycle or the Westinghouse process. In the hybrid sulfur cycle, sulfuric acid is electrochemically cogenerated with hydrogen from sulfur dioxide and then heat is used to thermally decompose the acid to regenerate the sulfur dioxide, this is represented by
H.sub.2SO.sub.4+heat.fwdarw.SO.sub.2+H.sub.2O+½O.sub.2 eq 3
SO.sub.2+2H.sub.2O+electricity.fwdarw.H.sub.2+H.sub.2SO.sub.4 eq 4
[0117] Here the net reaction is combined thermochemical and electrochemical water splitting:
H.sub.2O+heat+electricity.fwdarw.H.sub.2+½O.sub.2 eq 5
[0118] While the electrochemistry of this reaction may proceed at lower potentials than pure electrochemical water splitting, the net input of energy is similar. Additionally, in order for this reaction to work, very concentrated sulfuric acid is necessary or typically preferred for this process to be energy efficient, and this is a challenge.
[0119] Disclosed herein are methods to electrochemically generate hydrogen and thermochemically generate cement and SO.sub.2. This process follows the following reactions:
SO.sub.2+2H.sub.2O+electricity.fwdarw.H.sub.2SO.sub.4+H.sub.2 eq 6
H.sub.2SO.sub.4+CaCO.sub.3.fwdarw.CaSO.sub.4+CO.sub.2+H.sub.2O eq 7
CaSO.sub.4+heat.fwdarw.CaO+SO.sub.2+½O.sub.2 eq 2
[0120] The net equation is:
CaCO.sub.3+H.sub.2O+electricity+heat.fwdarw.H.sub.2+CaO+½O.sub.2+CO.sub.2 eq 8
[0121] In a simple form of this reaction, SO.sub.2 gas is dissolved in water and dilute sulfuric acid and hydrogen is made electrochemically. Limestone is added to the dilute sulfuric acid resulting in the precipitation of CaSO.sub.4 and the release or capture for sale or storage of very pure CO.sub.2. CaSO.sub.4 is collected from the bottom of the tank.
[0122] Because the reaction of acid with CaCO.sub.3 results in vigorous bubbling of CO.sub.2, this vigorous bubbling may be used to pressurize produced CO.sub.2 for easy transport or sale.
Advantages of the Disclosed Methods Over the Current State-of-the-Art
[0123] This process has several advantages over current technology. If the source of CaCO.sub.3 is limestone and the heat is generated in the cement kiln then the cement making process is similarly expensive to current industrial cement processes and the hydrogen benefits from very low electricity needs. Additionally, because CaSO.sub.4 readily precipitates from solution and CaCO.sub.3 will react with very dilute H.sub.2SO.sub.4 concentrations, it is not necessary to generate highly concentrated H.sub.2SO.sub.4.
[0124] This process also readily allows for carbon capture and storage by simply changing the ratio of CaCO.sub.3 in the reaction:
SO.sub.2+2H.sub.2O+electricity.fwdarw.H.sub.2SO.sub.4+H.sub.2 eq 6
H.sub.2SO.sub.4+2CaCO.sub.3.fwdarw.CaSO.sub.4+Ca.sup.2++2HCO.sub.3.sup.− eq 9
CaSO.sub.4+heat.fwdarw.CaO+SO.sub.2+½O.sub.2 eq 2
[0125] The net equation is:
2CaCO.sub.3+2H.sub.2O+electricity+heat.fwdarw.H.sub.2+CaO+½O.sub.2+Ca.sup.2++2HCO.sub.3.sup.− eq 10
[0126] In this version, Ca.sup.2++2HCO.sub.3.sup.− can be released into the ocean or any other natural water where it is stored outside of the atmosphere. This because this carbon capture only requires the input of 1 additional CaCO.sub.3 and 1 additional water (both chemicals are very cheap) this process could be incredibly inexpensive.
[0127] Finally, making concentrated sulfuric acid via the hybrid sulfur cycle can be difficult, but because dilute sulfuric acid readily reacts with limestone, the applied potential could be much lower for this reaction as compared to the traditional hybrid sulfur cycle.
[0128] If this reaction were to meet the entire cement demand of the world, then it could make 180 million metric tonnes of hydrogen which would saturate the commodity market and leave the rest to be used for heat. This would have the potential of >15% reduction in global CO.sub.2 emissions.
[0129] Possible variations and modifications of the disclosed methods
[0130] Other variations exclude the electrochemistry and use SO.sub.2 as the acid which allow for carbon capture and storage but do not allow for hydrogen production, for example:
SO.sub.2+H.sub.2O.fwdarw.H.sub.2SO.sub.3 eq 11
H.sub.2SO.sub.3+2CaCO.sub.3.fwdarw.CaSO.sub.3+Ca.sup.2++2HCO.sub.3.sup.− eq 12
CaSO.sub.3+heat.fwdarw.CaO+SO.sub.2 eq 13
[0131] The net equation is:
2CaCO.sub.3+H.sub.2O+heat.fwdarw.CaO+Ca.sup.2++2HCO.sub.3.sup.− eq 14
[0132] This could also be done without carbon capture and storage:
SO.sub.2+H.sub.2O.fwdarw.H.sub.2SO.sub.3 eq 15
H.sub.2SO.sub.3+CaCO.sub.3.fwdarw.CaSO.sub.3+CO.sub.2+H.sub.2O eq 16
CaSO.sub.3+heat.fwdarw.CaO+SO.sub.2 eq 17
[0133] The net equation is:
CaCO.sub.3+heat.fwdarw.CaO+CO.sub.2 eq 18
[0134] Exemplary implementation of certain disclosed embodiments: First acid and hydrogen are cogenerated in an electrochemical reactor. Because limestone readily reacts with any acidic water, and the thermodynamics of making dilute acid are much better than strong acid, then it can be better to make dilute acid (>0.001% H.sub.2SO.sub.4) however acid of any strength would work. If dilute acid is, applied potentials for the electrolyser can be below 1 V at 1 A/cm.sup.2. The hydrogen can be purified as necessary and stored, sold, burned for heat or electricity, or off-gassed. The acid is mixed with the limestone or other source of CaCO.sub.3 and produce CaSO.sub.4 which precipitates from the reaction and is separated from the liquid fraction. The liquid fraction which can contain stored carbon can be reused or disposed of. The solid CaSO.sub.4 is placed in the cement kiln where it is heated to the necessary sintering temperature, the source of heat can be burning hydrogen or some other heat source. The SO.sub.2 outflow from the cement kiln can be trapped in water and used as an electrolyte to regenerate sulfuric acid and hydrogen while the produced cement or CaO could be sold, stored, or used onsite.
[0135] Silica, alumina, iron oxides, and a few other metal oxides can be sintered to the CaO in cement. , alumina, iron oxides, and a few other metal oxides can be present in the starting limestone material.
[0136] CaSO.sub.3 can be thermally decomposed into CaO at a lower temp (<800°C.) than CaCO.sub.3 can be (>800 c) so it is a cheap way to make lime as a commodity chemical.
[0137] The reaction with H.sub.2SO.sub.4 and CaCO.sub.3 can happen with or without water (either as a dry reaction or a wet reaction or a slurry reaction).
[0138] See
[0139] See also
[0140] Disclosed here are methods for performing the following chemistry for producing sulfuric acid and hydrogen gas:
1/X S.sub.x+Y O.sub.2+Z H.sub.2O.fwdarw.H.sub.2SO.sub.4+(Z−1) H.sub.2
[0141] Where X could be any integer from 1 to 8, Y could be 0, ½, 1, and Z could be 1, 2, 3, or 4. One way to write this reaction is:
⅛ S.sub.8+4 H.sub.2O.fwdarw.H.sub.2SO.sub.4+3 H.sub.2
[0142] In certain embodiments, this reaction is performed on a Pt catalyst by melting sulfur at 130° C. and mixing the molten sulfur with a mixture of 60% H.sub.2SO.sub.4 and 40% H.sub.2O by mass which boils at an excess of 150° C. Pt is used as a catalyst and current voltage characteristics are measured, showing substantial current (>10 mA/cm.sup.2) well below the thermodynamic voltage necessary for water splitting (1.23 V vs NHE). A control experiment is also performed where sulfur is not added to the reaction mixture in which case no current is observed below 1.23 V vs NHE.
[0143] Because the molar ratio of H.sub.2:H.sub.2SO.sub.4 is larger than 1:1 this process could provide a source of electrochemical hydrogen and sulfuric acid for many industries that consume much more hydrogen than they do sulfuric acid (i.e. oil refining and fertilizer production).
[0144] See also
STATEMENTS REGARDING INCORPORATION BY REFERENCE AND VARIATIONS
[0145] All references throughout this application, for example patent documents including issued or granted patents or equivalents; patent application publications; and non-patent literature documents or other source material; are hereby incorporated by reference herein in their entireties, as though individually incorporated by reference, to the extent each reference is at least partially not inconsistent with the disclosure in this application (for example, a reference that is partially inconsistent is incorporated by reference except for the partially inconsistent portion of the reference).
[0146] The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments, exemplary embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims. The specific embodiments provided herein are examples of useful embodiments of the present invention and it will be apparent to one skilled in the art that the present invention may be carried out using a large number of variations of the devices, device components, methods steps set forth in the present description. As will be obvious to one of skill in the art, methods and devices useful for the present methods can include a large number of optional composition and processing elements and steps.
[0147] As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to “a cell” includes a plurality of such cells and equivalents thereof known to those skilled in the art. As well, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. It is also to be noted that the terms “comprising”, “including”, and “having” can be used interchangeably. The expression “of any of claims XX-YY” (wherein XX and YY refer to claim numbers) is intended to provide a multiple dependent claim in the alternative form, and in some embodiments is interchangeable with the expression “as in any one of claims XX-YY.”
[0148] When a group of substituents is disclosed herein, it is understood that all individual members of that group and all subgroups, including any isomers, enantiomers, and diastereomers of the group members, are disclosed separately. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included in the disclosure. When a compound is described herein such that a particular isomer, enantiomer or diastereomer of the compound is not specified, for example, in a formula or in a chemical name, that description is intended to include each isomers and enantiomer of the compound described individual or in any combination. Additionally, unless otherwise specified, all isotopic variants of compounds disclosed herein are intended to be encompassed by the disclosure. For example, it will be understood that any one or more hydrogens in a molecule disclosed can be replaced with deuterium or tritium. Isotopic variants of a molecule are generally useful as standards in assays for the molecule and in chemical and biological research related to the molecule or its use. Methods for making such isotopic variants are known in the art. Specific names of compounds are intended to be exemplary, as it is known that one of ordinary skill in the art can name the same compounds differently.
[0149] Certain molecules disclosed herein may contain one or more ionizable groups [groups from which a proton can be removed (e.g., —COOH) or added (e.g., amines) or which can be quaternized (e.g., amines)]. All possible ionic forms of such molecules and salts thereof are intended to be included individually in the disclosure herein. With regard to salts of the compounds herein, one of ordinary skill in the art can select from among a wide variety of available counter ions those that are appropriate for preparation of salts of this invention for a given application. In specific applications, the selection of a given anion or cation for preparation of a salt may result in increased or decreased solubility of that salt.
[0150] Every device, system, combination of components, or method described or exemplified herein can be used to practice the invention, unless otherwise stated.
[0151] Whenever a range is given in the specification, for example, a temperature range, a time range, or a composition or concentration range, a voltage range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure. It will be understood that any subranges or individual values in a range or subrange that are included in the description herein can be excluded from the claims herein.
[0152] All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the invention pertains. References cited herein are incorporated by reference herein in their entirety to indicate the state of the art as of their publication or filing date and it is intended that this information can be employed herein, if needed, to exclude specific embodiments that are in the prior art. For example, when composition of matter are claimed, it should be understood that compounds known and available in the art prior to Applicant's invention, including compounds for which an enabling disclosure is provided in the references cited herein, are not intended to be included in the composition of matter claims herein.
[0153] As used herein, “comprising” is synonymous with “including,” “containing,” or “characterized by,” and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, “consisting of” excludes any element, step, or ingredient not specified in the claim element. As used herein, “consisting essentially of” does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In each instance herein any of the terms “comprising”, “consisting essentially of” and “consisting of” may be replaced with either of the other two terms. The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.
[0154] One of ordinary skill in the art will appreciate that starting materials, biological materials, reagents, synthetic methods, purification methods, analytical methods, assay methods, and biological methods other than those specifically exemplified can be employed in the practice of the invention without resort to undue experimentation. All art-known functional equivalents, of any such materials and methods are intended to be included in this invention. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.