WO2019229754A1

WO2019229754A1 - Method of producing hydrogen gas from water in liquid phase

Info

Publication number: WO2019229754A1
Application number: PCT/IL2019/050616
Authority: WO
Inventors: Aharon GIVAN
Original assignee: O-Phy Technologies Ltd.
Priority date: 2018-05-31
Filing date: 2019-05-30
Publication date: 2019-12-05

Abstract

A method of producing hydrogen gas from water in liquid phase is disclosed. The method may include: providing at least one of: CO₂, SO₂ and NO₂ to the water until a predefined level of acidic p H is achieved; providing transition metal powder to the water; exposing the transition metal powder to the acidic water to create chemical reactions between hydronium ions and the transition metal powder; and collecting the hydrogen gas produced in the chemical reaction.

Description

METHOD OF PRODUCING HYDROGEN GAS FROM WATER IN LIQUID PHASE

FIELD OF THE INVENTION

[0001] The invention is directed to a chemical method of production of hydrogen. More particularly, the invention is directed to a chemical method of producing hydrogen from water in liquid phase .

BACKGROUND OF THE INVENTION

[0002] Methods for the production of hydrogen from water are known in the field; however, the known methods require electrolysis and/or high temperatures involving water vapor rather than liquid water, which causes the known methods to be disadvantageous in the industry.

[0003] Therefore, there is a need to provide a useful method for producing hydrogen from liquid water without requiring electrolysis or the use of elevated temperatures. Accordingly, such a method may consume very low amounts of energy, relative to the currently used methods.

SUMMARY OF THE INVENTION

[0004] Aspects of the invention may be related to a method of producing hydrogen gas from water in liquid phase. In some embodiments, the method may include: providing at least one of: C0₂, SO2 and NO2 to the water until a predefined level of acidic pH is achieved; providing transition metal powder to the water; exposing the transition metal powder to the acidic water to create chemical reactions between hydronium ions and the transition metal powder; and collecting the hydrogen gas produced in the chemical reaction.

[0005] In some embodiments, the at least one of: CO2, SO2 and NO2 may be provided in one of: gas phase, liquid phase, solid state, and supercritical fluid. In some embodiments, exposing may include one of: adding the transition metal powder to the water followed by providing at least one of: CO2, SO2 and NO2 to the water; and providing at least one of: CO2, SO2 and NO2 to the water followed by introducing the transition metal powder to the acidic water.

[0006] In some embodiments, the method may further include adding a catalyst to the mixture of transition metal powder and the acidic water. In some embodiments, mixing the transition metal powder with the acidic water is conducted by one of: inserting an entire required amount of the transition metal powder in a single portion, periodically inserting sub-portions of the required amount to the acidic water until the required amount is reached, and continuously adding the metal powder to the acidic water along a predefined time period determined so that the required amount is added within the time period.. In some embodiments, the transition metal powder may include at least one of: iron- based powder, nickel-based powder, magnesium-based powder and zinc-based powder.

[0007] In some embodiments, the water temperature is room temperature. In some embodiments, the water temperature is between 5-35°C. the predefined level of acidic pH is at most 5.65. In some embodiments, the method further includes: removing transition metal solid salts precipitated as final product of the chemical reactions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The subj ect matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanied drawings. Embodiments of the invention are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like reference numerals indicate corresponding, analogous or similar elements, and in which:

[0009] Fig. 1 is graph showing the reduction in pH in water as function of the C0₂ pressure provided to the water;

[0010] Fig. 2 is a diagrammatic representation of a system for producing hydrogen gas from water in liquid phase according to some embodiments of the invention;

[0011] Fig. 3 is a flowchart of a method of producing hydrogen gas from water in liquid phase according to some embodiments of the invention.

[0012] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn accurately or to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity, or several physical components may be included in one functional block or element. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. DETAILED DESCRIPTION OF THE INVENTION

[0013] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well- known methods, procedures, and components, modules, units and/or circuits have not been described in detail so as not to obscure the invention. Some features or elements described with respect to one embodiment may be combined with features or elements described with respect to other embodiments. For the sake of clarity, discussion of same or similar features or elements may not be repeated.

[0014] Throughout this application, unless specifically mentioned otherwise or unless a person skilled in the art would have understood otherwise, the term“about” is considered to cover a range of ±10% of the listed value(s).

[0015] Embodiments of the invention are directed to a method for producing ¾ gas from water in the liquid phase and optionally also in at least partial solid state. A method according to embodiments of the invention may consume very low amount of energy (e.g., mainly for provision and mixing of the various components) and may not require investing any energy in the hydrogen production itself, as oppose to the electrolysis and high-temperature methods of the prior art. In some embodiments, the water may be mixed with at least one of C0₂, SO2 and NO2 in order to decrease the pH of the water. In some embodiments, the CO2, SO2 and NO2 may be introduced into the water in one of: gas phase, liquid phase, dry ice and supercritical fluid. In some embodiments, the acidic water may be mixed with transition metal powder to create chemical reactions between hydronium ions and the transition metal powder. In some embodiments, hydrogen gas produced in the chemical reaction may be collected.

[0016] According to some embodiments, the water may be any type of water including distilled water, sea water, wastewater, including both sewage water and greywater, purified sewage water, tap water and any combination thereof.

[0017] According to some embodiments, the transition metal is selected from iron-based powder, nickel-based powder and the like. In some embodiments, additional transition metals may include aluminum -based powder, zinc -based powder and magnesium -based powder either as pure metals or alloys. [0018] Dissolving at least one of C0₂, SO2 and NO2 in water will reduce the pH of the water due to the formation of an acid, for example, the formation of carbonic acid (H2C03) when adding CO2, as shown below in reactions 1-3.

1. CO2 (gas) ® CO2 (aq) 2. CO2 (aq) + H2O ® H2CO3 (carbonic acid)

3. H2CO3 + H20— > H30⁺+ HCO3

[0019] Similarly dissolving SO2 in the water may result in the formation of sulfurous acid (H2S03) and dissolving NO2 may result in the formation of HNO3.

[0020] Even in room temperature and atmospheric pressure, the pH of CO2 solution in water can reach pH 5.65 when adding 1.5 gram/liter of CO2 (e.g., solubility limit of CO2 in water at R.T). Any additional amount of CO2 (or SO2 or NO2) may further reduce the pH of the water, until the solubility limit of CO2 in water as a function of the temperature of water is reached, forming additional hydronium ions. Increasing the amount of CO2 (or SO2 or NO2) dissolved in the water may be conducted by increasing the pressure of the CO2 (or SO2 or NO2) when provided in gas phase (as shown in the graph of Fig. 1). In some embodiments, increasing the amount of CO2 (or SO2 or NO2) dissolved in the water may be conducted by providing the CO2 (or SO2 or NO2) in a liquid phase and/or provided dry-ice or as a supercritical fluid. Fig. 1 show a linear connection between the log of the pressure of the CO2 provided to the water and the resulted pH level. The higher the pressure the more acidic the water and the lower is the pH.

[0021] When transition metal (e.g., Fe) is exposed to acidic water the following reactions may take place.

4a. 2H₃0⁺ + 2Fe ® 2H₂0 + 2Fe⁺² + H₂ (gas)

4b. 2H₃0⁺ + Fe⁺² ® 2H₂0 + Fe⁺³ + H₂ (gas)

[0022] The dual valency Fe⁺² ion may further be oxidized to become a triple valency Fe⁺³ ion. However, reaction 4b may be too slow, for example, for commercial use, therefore increasing the oxygen level in the solution (e.g., by adding oxygen from an external source) may increase the oxidation of dual valency Fe⁺² ion into triple valency Fe⁺³ ion.

4c. 4H₃0⁺ + 0₂+ 4Fe⁺² ® 4H₂0 + 4Fe⁺³+ 2H₂ (gas) [0023] In some embodiments, if the pH of the solution is kept lower than 3 (e.g., 2) the Fe⁺³ ion may remain dissolved in the water as a complex Fe(H₂0)₆ ⁺³. In pH higher than 3 the Fe⁺³ ion may precipitate as hydroxide Fe(OH)3. Fe(H₂0)₆ ⁺³ is a strong acid having pH of about 1-1.5, therefore forming the complexed Fe(H₂0)₆ ⁺³ ions may cause an autocatalytic process that maintains itself by continuously providing hydronium ions to the water solution, as shown in the consecutive reactions 5a-5c.

5a. Fe(H₂0)₆ ⁺³(aq) + H₂0(l) ® Fe{(H₂0)₅(0H)}⁺² (aq)+ H₃0⁺(aq)

5b. Fe { (H₂0)₅ (OH) } ⁺² (aq) + H₂0(l) ®Fe{(H₂0)₄(0H)₂}⁺(aq) + H₃0⁺(aq)

5c. Fe{(H₂0)₄(0H)₂}⁺(aq) + H₂0(l) ® Fe{(H₂0)₃(0H)₃} + H₃0⁺(aq)

[0024] Although, all reactions 5a-5c contribute hydronium ions, it was found that the most efficient one is reaction 5a reacting the complex Fe(H₂0)₆ ⁺³ with water. The last product of these chain of reactions Fe{( H₂0)₃(0H)₃} does not dissolve in water and precipitate if the pH is higher than 3.

[0025] In some embodiments, even if an autocatalytic process has been achieved, transition metal powder may be added in order to maintain the hydrogen production using reaction 4a and 4b. In some embodiments, at least one of the C0₂, S0₂ and N0₂ and optionally also 0₂ may be further added to support reactions 4a-4c.

[0026] Reference is now made to Fig. 2 which is a diagrammatic representation of a system for producing hydrogen gas from water in liquid phase according to some embodiments of the invention. A system 100 may include a source 110 for providing at least one of C0₂, S0₂ and N0₂. In some embodiments, source 110 may be one of: a pressurized gas tank (e.g., at 60-70 bar), a pipe providing a pressurized gas, a pipe providing powerplant exhaust gasses, a tank providing the C0₂, S0₂ and/or N0₂ in a liquid phase, a source providing dry-ice of C0₂, S0₂ and N0₂ and any combination thereof.

[0027] In some embodiments, when the at least one of C0₂, S0₂ and N0₂ are to be provided in supercritical conditions, source 110 may further include a condenser and a heater for providing the C0₂, S0₂ and N0₂ with supercritical pressure and temperature. In some embodiments, supercritical C0₂ may have a temperature of above 31.1 °C and pressure above 73.9 bar, supper critical S0₂ may have a temperature of above 157.2 °C and pressure above 78.7 bar and supercritical N0₂ may have a temperature of above 37 °C and a pressure of above 70 bar.

[0028] System 100 may include a water source 120. Water source 120 may provide any type of water, for example, distilled water, sea water, waste-water, including both sewage water and greywater, purified sewage water, tap water and any combination thereof. [0029] System 100 may further include transition metal powder source 130. The transition metal may include one of iron based and/or nickel based powders, for example, Ni, Ni-alloys, Fe, Fe-alloys, nickel-based powder, magnesium- based powder and the like. For example, powder may be provided at a particle size of 1 micron - 20 mm. The powder may include, for example, steel, Ni-alloy or cast- iron splinters. In some embodiments, the powder may include pig iron.

[0030] In some embodiments, system 100 may include a reaction vessel 140 to which the at least one of C0₂, SO2 and/or NO2, the water and the transition metal powder may be provided. Reaction vessel 140 may be in flowing connection with sources 110, 120 and 130. Reaction vessel 140 may be a batch reactor, a continuous reactor or a semi-continuous reactor, high pressure reactor and the like. In some embodiments, reaction vessel 140 may include one or more stirrers for stirring all the provided materials. In some embodiments, reaction vessel 140 may include one or more heaters and/or one or more coolers for controlling the temperature of the water inside reaction vessel 140. In some embodiments, reaction vessel 140 may include a bubbler, gas separator or any other device that is configured to mix or separate phases in reaction vessel 140. In some embodiments, reaction vessel 140 may include one or more sensors, for example, a pH sensor 142 and a temperature sensor 144. Additional or alternative sensors such as: a water level sensor, a pressure sensor and the like (not illustrated) may be included in reaction vessel 140. The sensors and any other controllable components of system 100 may be in communication with a controller 180.

[0031] Controller 180, may be any computing platform that may be configured to receive signals from sensors, such as sensors 142 and 144 and control controllable components of sources 110, 120, 130 and vessel 140, such as valves, pumps, condensers, heaters and the like. Controller 180 may include a processing unit and a memory for storing instructions for controlling the controllable components of system 100.

[0032] In some embodiments, system 100 may further include an oxygen source 150 for providing hydrogen to vessel 140. The oxygen may be provided to the water after or during the provision of the at least one of CO2, SO2 and NO2 and the transition metal powder. The oxygen may further oxidize the dual valency Fe⁺² ion to become a triple valency Fe⁺³ ion and thus to increase PH reduction rate and therefore the ¾ production rate, as discussed in detail herein above with respect to reaction 4c. The oxygen source may include a pressurized tank, an oxygen pipe or any other source.

[0033] In some embodiments, system 100 may further include a hydrogen collection unit 160. Hydrogen collection unit 160 may include a separator to separate the hydrogen produced in the process from other gasses in the system, for example, oxygen and at least one of CO2, SO2 and NO2. The separator may be any gas separator known in the art, for example, pressure-based separator, temperature-based separator, vacuum swing adsorption separator, cryogenic distillation separator and the like. In some embodiments, hydrogen collection unit 160 may further include a tank for holding the separated and collected hydrogen. In some embodiments, pressure may be built in reactor to produced ¾ at relatively high pressure (e.g., 200 bar) which substantially may reduce postproduction compression costs as ¾ is commonly stored at high pressure.

[0034] Reference is now made to Fig. 3 which is a flowchart of a method of producing hydrogen gas from water in liquid phase according to some embodiments of the invention. In step 210, at least one of: CO2, SO2 and NO2 may be provided to the water until a predefined level of acidic pH is achieved. As disclosed in reactions 1-3 adding at least one of: CO2, SO2 and NO2 to water may result in decreasing the pH of the water making the water acidic. In some embodiments, the water may be provided to a reactor, such as, reaction vessel 140 from water source 120, for example, at room temperature or at ambient temperature 1-45 °C. In some embodiments, the at least one of: CO2, NO2 and SO2 may be provided to reaction vessel 140 from source 110. In some embodiments, the predefined level of acidic pH may be less than 5.65, for example, 5, 4, 3, 2 or 1.

[0035] In some embodiments, in order to increase the production of hydronium ions (HiCT), and as a result to increase the production of hydrogen, the at least one of: CO2, SO2 and NO2 may be provided as pressurized gases, for example, at a pressure of at least 3 bar, 8, bar, 10 bar, 50 bar, 60 bar 68 bar, 70 bar or more, as illustrated in the graph of Fig. 1. In some embodiments, the gas may further be heated in order to increase the reaction rate (although the solubility of the gas in the water may decrease with the raise in temperature). For example, the gas may be heated to 50-100 °C. For example, about 10 kg/cube of CO2 gas may be provided at a pressure of 68 bar at room temperature.

[0036] In some embodiments, in order to increase the production of hydronium ions the at least one of: CO2, SO2 and NO2 may be provided as supercritical fluids. For example, supercritical CO2 may have a temperature of above 31.1 °C and a pressure of above 73.9 bar, supercritical SO2 may have a temperature of above 157.2 °C and pressure above 78.7 bar, and supercritical NO2 may have a temperature of above 37 °C and pressure above 70 bar.

[0037] In some embodiments, in order to increase the production rate of hydronium ions the at least one of: CO2, SO2 and NO2 may be provided in the liquid phase or in solid state (e.g., dry-ice). Although liquid and dry-ice CO2, SO2 and NO2 have subzero temperatures, controlling the amount of frozen liquid being added may reduce the temperature of the water without complete freezing then, while increasing the solubility of the at least one of C0₂, SO2 and NO2 in the water due to lowering the temperature of the water.

[0038] In some embodiments, when the at least one of: CO2, SO2 and NO2 may be introduced into the water in a solid state (e.g., dry ice), the temperature in proximity to the solid may drop rapidly allowing higher amounts of at least one of: CO2, SO2 and NO2 to be dissolve in the water. In such case areas closer to the solid may have higher concentration of hydronium ions, thus higher hydrogen production rate. Additionally or alternatively, adding the at least one of: CO2, SO2 and NO2 in a solid state may cause partial freezing of the water.

[0039] In step 220, transition metal powder may be provided. For example, transition metal powder from transition metal source 130 may be added to reaction vessel 140. In some embodiments, the transition metal powder may include at least one of: iron-based powder, nickel-based powder, aluminum-based powder, magnesium-based powder, zinc-based powder or any combination thereof. In some embodiments, the transition metal powder may have particle size of at most 50 mm.

[0040] In step 230, the transition metal may be exposed to the acidic water to create chemical reactions between hydronium ions and the transition metal powder. In some embodiments, the transition metal powder may be added to the water followed by providing at least one of: CO2, NO2 and SO2 to the water. Alternatively, the at least one of: CO2, SO2 and NO2 may first be added to the water followed by introducing the transition metal powder to the water. In some embodiments, the transition metal powder may be provided together (substantially simultaneously) with the at least one of: CO2, SO2 and NO2. In some embodiments, mixing the transition metal powder with the acidic water may be conducted by one of: inserting an entire required amount of the transition metal powder in a single portion, periodically inserting sub-portions of the required amount to the acidic water until the required amount is reached, and continuously adding the metal powder to the acidic water along a predefined time period determined so that the required amount is added within the time period. In some embodiments, when reaction vessel 140 is a continuous or semi-continuous reactor, the water, the at least one of: CO2, SO2 and NO2 and the transition metal powder may continuously be provided to the reactor. For example, 3 ton/cube of iron- based powder may be provided to an acidic water having a pH lower than 4. According to some embodiments, the concentration of the transition metal in the water-metal ions mixture may be between about 2.8 gr/liter at PH 1 and 28 x 10 ^{5 65} gr/liter at PH 5.65 (ambient conditions). [0041] In some embodiments, when the at least one of: C0₂, NO2 and SO2 may be introduced into the water in a solid state,“ice cages” of acidic ice may be formed. The“ice cages” may further include the transition metal powder, for example, when the transition metal powder was introduced to the vessel before the solid state C02 was introduced to the water. In some embodiments, the hydrogen production reactions may take place also in solid state inside the“ice cages”.

[0042] According to some embodiments, the acidic water and/or the water- metal mixture may further be mixed with a catalyst. According to some embodiments, the catalyst may be an enzyme, or any other in-organic catalyst configured to catalyzed one or more of reactions 1-5. According to some embodiments, the catalyst is a metalloenzyme. According to some embodiments, the metalloenzyme is carbonic anhydrase or the like. According to some embodiments, the catalyst may be added to the water prior to the addition of the metal, after the addition of the metal, prior to or during the provision of the at least one of: CO2, SO2 and NO2 to the or any combination thereof.

[0043] According to some embodiments, oxygen may further be provided to the water- metal mixture in order to increase the rate of production the triple valent transition metal ion (e.g., reaction 4c.) thus increase the rate of the autocatalytic formation of hydronium ions in reactions 5a-5c. Oxygen may be provided to vessel 140 from oxygen source 150. In some embodiments, the amount of oxygen to be provided may be determined as the maximal amount that may minimize undesired solids (such as rust).

[0044] In step 240, the hydrogen gas produced in the chemical reaction may be collected. For example, collecting unit 160 may collected all the gases from reaction vessel 140 and may further separate the gases to collect the hydrogen. The gas may be separated according to any known method, for example, using pressure aided separation, temperature aided separation, vacuum swing adsorption, cryogenic distillation and the like.

[0045] For example, when adding to water about 10 kg/cube of CO2 gas at a pressure of 68 bar at room temperature and 3 ton/cube of Fe based powder H2 gas is formed and released from the oxidized water-metal mixture at a rate of between about 140 gr/hour to about a few kg/hour.

[0046] In some embodiments, transition metal solid salts precipitated as final product of the chemical reactions may be removed. For example, the products of reaction 5c may be removed from the acidic water mixture. For example, the when using iron-based powder the solid precipitates may be hematite which may be used as raw material for the production of pig iron, thus may fully be recycled. [0047] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently.

[0048] It is appreciated that certain features of the invention may also be provided in combination in a single embodiment. Conversely, various elements of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub combination or as suitable in any other described embodiment of the invention. Further, certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[0049] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

1. A method of producing hydrogen gas from water in liquid phase, comprising:

providing at least one of: C0₂, SO2 and NO2 to the water until a predefined level of acidic pH is achieved;

providing transition metal powder to the water;

exposing the transition metal powder to the acidic water to create chemical reactions

between hydronium ions and the transition metal powder; and

collecting the hydrogen gas produced in the chemical reaction.

2. The method of claim 1, wherein the at least one of: CO2, SC and NO2 is provided in one of: gas phase, liquid phase, solid state, and supercritical fluid.

3. The method of claim 1 or claim 2, wherein, exposing comprises one of:

adding the transition metal powder to the water followed by providing at least one of: CO2, SO2 and NO2 to the water;

providing at least one of: CO2, SO2 and NC to the water followed by introducing the

transition metal powder to the acidic water; and

providing transition metal powder to the water together with the provision of the at least one of: CO2, SO2 and NO2.

4. The method according to any one of claim 1-3, further comprising: adding a catalyst to the mixture of transition metal powder and the acidic water.

5. The method according to any one of claims 1-4, wherein mixing the transition metal powder with the acidic water is conducted by one of: inserting an entire required amount of the transition metal powder in a single portion, periodically inserting sub-portions of the required amount to the acidic water until the required amount is reached, and continuously adding the metal powder to the acidic water along a predefined time period determined so that the required amount is added within the time period.

6. The method according to any one of claims 1-5, wherein the transition metal powder includes at least one of: iron-based powder, nickel-based powder, magnesium-based powder and zinc- based powder.

7. The method according to any one of claims 1-6, wherein the water temperature is room temperature.

8. The method according to any one of claims 1-6, wherein the water temperature is between 5- 35°C.

9. The method according to any one of claims 1-8, wherein the predefined level of acidic pH is at most 5.65.

10. The method according to any one of claims 1-9, further comprising removing transition metal solid salts precipitated as final product of the chemical reactions.